• UTC: 2017-06-28 20:13

  • SPC Jun 28, 2017 2000 UTC Day 1 Convective Outlook
    on June 28, 2017 at 8:06 pm

    SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Wed Jun 28 2017 Valid 282000Z - 291200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM FAR SOUTHEAST NE INTO NORTHERN IL/SOUTHERN WI... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL HIGH PLAINS TO THE MIDDLE/UPPER MS VALLEY... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN ROCKIES TO THE GREAT LAKES... ...SUMMARY... Severe thunderstorms with large hail, wind damage and a few tornadoes are expected across the middle Missouri Valley northeastward into the middle and upper Mississippi Valley. Other more isolated severe storms may occur in the central Plains and northern Rockies. ...Severe-weather threat areas... No changes were needed with the severe-probabilities/categorical severe risk areas, as previous forecast reasoning remains valid with this outlook issuance. ...General thunderstorm areas in the Dakotas and eastern NY... Based on convective/lightning trends in eastern MT, the general thunderstorm line in western ND was shifted a little to the east to indicate some potential for thunderstorms to reach far western ND late this afternoon to early evening. A little more of central SD was added to general thunderstorm potential for later tonight. Meanwhile, much of eastern SD/ND into far northern MN was removed from the general thunderstorm area, given the decrease in thunderstorm potential within an area of midlevel subsidence and/or weaker instability. Farther east, convective trends suggest thunderstorm potential should continue to shift east/northeast away from portions of eastern NY. ..Peters.. 06/28/2017 .PREV DISCUSSION... /ISSUED 1136 AM CDT Wed Jun 28 2017/ ...Middle MO River Valley to middle/upper MS River Valley... Related to last night's MCS, scattered showers/thunderstorms and related prevalent cloud cover continue to progress eastward across eastern portions of MN/IA into WI/northern IL late this morning. This is just ahead of an eastward-moving shortwave trough over MN, with a few other convectively related disturbances/MCVs noted farther south, embedded within a belt of moderately strong mid-level westerlies. A surface low analyzed at 15Z near the MN/SD/ND border vicinity will continue to spread eastward across central MN toward northern WI and the western Upper Peninsula of MI through this evening, while a cold front spreads southeastward across MN/IA/WI. Near and ahead of this cold front, low-level moistening and general air mass recovery will steadily occur this afternoon in the wake of the lingering early-day precipitation and cloud cover, particularly given relatively steep mid-level lapse rates and ample low-level moisture sampled in source-region 12Z observed soundings from Omaha NE and Topeka KS. Increasingly prevalent mid/upper 60s F surface dewpoints will support upwards of 2000-3000 J/kg MLCAPE particularly from southeast NE/northern KS into IA, with somewhat more modest (and uncertain) degree of pre-frontal destabilization farther north into WI/eastern MN owing to early-day cloud cover and some regenerative precipitation this morning across northern IA. While the aforementioned cloud cover/precipitation lingering into midday still casts some uncertainty, it seems most likely that surface-based storms will redevelop just ahead of the front semi-focused along outflow and zones of differential heating across southern/eastern IA and nearby far northern MO and northern IL. Pending adequate destabilization, other potentially severe development may occur by late afternoon in closer proximity to the surface low/front from far eastern MN into western/central WI. Around 40-45 kt of effective shear will support some initial supercells capable of large hail, with a few tornadoes possible as well given the strength of 2-3 km AGL southwesterly winds and related 150-250 m2/s2 0-1 km SRH (with prospective surface-based convection). Eastward-moving clusters should evolve by evening with a related increase in damaging wind potential particularly across southern IA/northern MO into northern IL. ...CO/WY Front Range to northern KS/southern NE... Within a modestly moist environment, widely scattered thunderstorms should develop and spread eastward across the region by late afternoon into evening, including some potential for at least small-scale MCS development this evening. Modest buoyancy and ample vertical shear will support the possibility of sporadic large hail and locally damaging winds into this evening. ...Northern Rockies... Ahead of an amplifying shortwave trough over the northern Intermountain region, modest moisture and a strengthening belt of west-southwesterly mid-level winds should contribute to the possibility of isolated strong to severe storms spanning parts of WY/southern MT and eastern ID/northern UT. Read mor […]

  • SPC Tornado Watch 375 Status Reports
    on June 28, 2017 at 7:55 pm

    WW 0375 Status Updates STATUS FOR WATCH 0375 HAS NOT BEEN ISSUED YET Read mor […]

  • SPC Tornado Watch 375
    on June 28, 2017 at 7:55 pm

    WW 375 TORNADO IA IL MO NE WI 281955Z - 290300Z URGENT - IMMEDIATE BROADCAST REQUESTED Tornado Watch Number 375 NWS Storm Prediction Center Norman OK 255 PM CDT Wed Jun 28 2017 The NWS Storm Prediction Center has issued a * Tornado Watch for portions of Iowa Northwest Illinois Northern Missouri Southeast Nebraska Southwest Wisconsin * Effective this Wednesday afternoon and evening from 255 PM until 1000 PM CDT. * Primary threats include... A few tornadoes possible Scattered large hail and isolated very large hail events to 2.5 inches in diameter possible Scattered damaging wind gusts to 70 mph possible SUMMARY...In the wake of early-day storms, strong to severe thunderstorm development should continue to occur with a steadily moistening and destabilizing air mass. While large hail and damaging winds should be the most common hazards, relatively strong low-level shear and the influence of subtle residual boundaries could yield a few tornadoes through the mid/late afternoon hours into this evening. The tornado watch area is approximately along and 105 statute miles east and west of a line from 40 miles northeast of Waterloo IA to 40 miles southwest of Lamoni IA. For a complete depiction of the watch see the associated watch outline update (WOUS64 KWNS WOU5). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A Tornado Watch means conditions are favorable for tornadoes and severe thunderstorms in and close to the watch area. Persons in these areas should be on the lookout for threatening weather conditions and listen for later statements and possible warnings. && AVIATION...Tornadoes and a few severe thunderstorms with hail surface and aloft to 2.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A few cumulonimbi with maximum tops to 500. Mean storm motion vector 27030. ...Guyer Read mor […]

  • SPC MD 1170
    on June 28, 2017 at 7:50 pm

    MD 1170 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PARTS OF EAST CENTRAL AND SOUTHEAST MINNESOTA INTO WESTERN/CENTRAL WISCONSIN Mesoscale Discussion 1170 NWS Storm Prediction Center Norman OK 0249 PM CDT Wed Jun 28 2017 Areas affected...Parts of east central and southeast Minnesota into western/central Wisconsin Concerning...Severe potential...Watch likely Valid 281949Z - 282145Z Probability of Watch Issuance...80 percent SUMMARY...Thunderstorms are expected to develop and intensify across the region through late afternoon, accompanied by increasing severe weather potential as early as the 4-5 PM CDT time frame. A watch issuance seems probable within the next hour or two. DISCUSSION...Within the warm sector of a sub-1000 mb surface cyclone now migrating across central Minnesota, insolation and low-level moistening beneath modestly steep mid-level lapse rates are contributing to considerable boundary layer destabilization. Mixed layer CAPE now appears on the order of 1000-2000 J/kg, along and south of a warm frontal zone extending east southeast of the low center, and objective analysis suggests that mid-level inhibition is in the process of becoming increasingly negligible. Aided by forcing for ascent associated with a mid-level cyclonic vorticity center, progressing through larger-scale upper troughing now shifting across the upper Mississippi Valley and Upper Midwest, thunderstorms are expected to develop and increase across the region through late afternoon. Initial attempts at this may already be underway near/southeast of the Minneapolis area. Activity seems likely to generally focus and propagate along the warm frontal zone, and may include discrete supercells before possibly growing upscale into an organizing convective system, in the presence of strong deep layer shear. ..Kerr/Guyer.. 06/28/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...GRB...DLH...ARX...MPX... LAT...LON 45929211 45568954 44538940 43579118 43819304 44839393 45929211 Read mor […]

  • SPC MD 1169
    on June 28, 2017 at 7:15 pm

    MD 1169 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR MUCH OF CENTRAL AND SOUTHERN IOWA AND ADJACENT PORTIONS OF NORTHWESTERN ILINOIS...NORTHERN MISSOURI AND SOUTHEASTERN NEBRASKA Mesoscale Discussion 1169 NWS Storm Prediction Center Norman OK 0214 PM CDT Wed Jun 28 2017 Areas affected...Much of central and southern Iowa and adjacent portions of northwestern Ilinois...northern Missouri and southeastern Nebraska Concerning...Severe potential...Watch likely Valid 281914Z - 282115Z Probability of Watch Issuance...80 percent SUMMARY...A rapid increase in thunderstorm activity and intensity appears possible late this afternoon, perhaps as early as the 3-5 pm CDT time frame. The latest trends are being closely monitored for increasing severe weather potential which likely will require a watch issuance. DISCUSSION...Potential convective evolution late this afternoon remains a little unclear, but objective analysis suggests that mid-level inhibition is becoming increasingly negligible across much of the region. This is occurring in response to both continued insolation and low-level moistening, with surface dew points currently increasing through the upper 60s and lower 70s F. Beneath a corridor of modestly steep mid-level lapse rates, associated with a thermal ridge extending east northeast of a plume of warmer and more strongly capping elevated mixed-layer air across the central Plains, moderately large mixed layer CAPE (2000-3000 J/kg) appears to be developing. Given this magnitude of potential instability, in the presence of weakening inhibition, rapid thunderstorm development and intensification appears possible within the next few hours. Forcing for ascent to support initiation, however, remains a bit unclear. Deepening convective development is currently evident along the surface trough axis, to the west of a persistent area of elevated thunderstorm activity now spreading east northeastward across north central Iowa. Additional attempts at deepening convective development also appear ongoing around and east of the Omaha area, beneath a somewhat warmer mid-level environment, in the presence of enhanced lower/mid tropospheric warm advection. As a lingering mid-level speed maximum (associated with larger-scale upper troughing shifting into the Upper Midwest) gradually noses east of the mid Missouri Valley late this afternoon, a general increase in convective development seems probable, in the presence of sufficient vertical shear for supercells, and, eventually, an upscale growing thunderstorm cluster or two. ..Kerr/Guyer.. 06/28/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DVN...DMX...EAX...OAX... LAT...LON 41709558 42559466 42409363 42649219 42179114 40609089 40099460 40599631 41709558 Read mor […]

  • SPC MD 1168
    on June 28, 2017 at 6:40 pm

    MD 1168 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR SOUTHERN MT...CENTRAL/EASTERN ID...NORTHERN WY...FAR NORTHERN UT/NORTHEAST NV Mesoscale Discussion 1168 NWS Storm Prediction Center Norman OK 0139 PM CDT Wed Jun 28 2017 Areas affected...Southern MT...Central/eastern ID...Northern WY...Far northern UT/northeast NV Concerning...Severe potential...Watch unlikely Valid 281839Z - 282115Z Probability of Watch Issuance...20 percent SUMMARY...Thunderstorm clusters capable of isolated hail and strong wind gusts will continue into this afternoon. DISCUSSION...Thunderstorm activity has recently increased across portions of southern MT, eastern ID, and western WY, in conjunction with a low-amplitude upper trough moving through the interior Northwest. As heating continues this afternoon in an environment characterized by relatively steep low-midlevel lapse rates and effective shear of 25-35 kt, thunderstorm coverage is expected to increase, with some weakly rotating cells or organized clusters possible. The strong thunderstorm cluster over currently over the Wind River Range in western WY will likely pose some threat of marginally severe hail and strong wind in the short term, with wind threat potentially extending further east into lower elevations if a sufficiently strong cold pool can become established. Additional redevelopment is likely over eastern ID/southwest MT and also across far northeast NV/northern UT, with eastward-moving clusters resulting in a similar risk of isolated hail/strong wind gusts. In general, the magnitude of the threat is expected to remain too low for watch issuance. ..Dean/Guyer.. 06/28/2017 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...UNR...CYS...BYZ...RIW...TFX...SLC...PIH...MSO... BOI...LKN... LAT...LON 41801277 41561453 43301477 45011483 45651408 46171137 46130834 45610583 44710523 43620525 42560684 42400847 42251013 42061121 41801277 Read mor […]

  • SPC Jun 28, 2017 1730 UTC Day 2 Convective Outlook
    on June 28, 2017 at 5:59 pm

    SPC 1730Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1254 PM CDT Wed Jun 28 2017 Valid 291200Z - 301200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN NEBRASKA AND KANSAS INTO FAR NORTHWEST MISSOURI AND SOUTHWEST IOWA... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK AREA ACROSS MUCH OF NEBRASKA AND KANSAS TO SOUTHERN LOWER MICHIGAN AND NORTHERN OHIO... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE SLIGHT RISK AREA FROM WY AND WESTERN SD AND THE CENTRAL HIGH PLAINS TO WESTERN AND NORTHERN PENNSYLVANIA INTO NEW YORK... ...SUMMARY... Scattered significant severe thunderstorms are most likely Thursday into Thursday evening across the central Plains, with areas of large hail and damaging winds. Isolated strong to severe storms are also possible across the Midwest eastward into western and northern Pennsylvania and New York, and across the central high plains to Wyoming, South Dakota to southwest Minnesota. ...Synopsis... Low-amplitude midlevel shortwave troughs will track east-northeast across the Dakotas and mid MO Valley through the Great Lakes, Midwest to the Northeast States Thursday and Thursday night. Meanwhile, a large-scale midlevel trough, currently tracking equatorward through southwest Canada per water vapor imagery, is expected to move southeast reaching the central Rockies/High Plains by 12Z Friday. A warm front attendant to a midlevel trough shifting east from the upper Great Lakes region should extend from northern Lower MI into southern Ontario. Meanwhile, the IA to the NE and northern KS portion of a trailing cold front from the upper Great Lakes should be the focus for thunderstorm development this forecast period. Additional storms will be possible attendant to surface trough moving east across the Dakotas and a separate cold front advancing south through the northern High Plains. ...Central Plains region... Models continue to suggest the greatest coverage of severe storms Thursday afternoon through Thursday evening should occur across the initial Day 2 Enhanced risk area from eastern portions of NE/KS into southwest IA and far northwest MO. This region will have the greatest juxtaposition of high surface moisture (dew points in the upper 60s to around 70 F) beneath steep midlevel lapse rates (exceeding 8 C/km) and diabatic heating, resulting in moderate instability. Despite some height rises in the wake of an early period midlevel impulse across eastern NE/northeast KS, sufficient deepening of boundary layer moisture and strong surface heating will result in a reduction of MLCINH for thunderstorm development near the aforementioned cold front and any differential heating boundaries from early morning ongoing showers and storms. Height falls ahead of the approaching upstream larger scale northwest U.S. trough will support thunderstorm development Thursday afternoon and evening. Strengthening westerly midlevel winds across the central Plains and south-southwesterly low-level winds into eastern KS/northwest MO suggest strong effective bulk shear will support organized storms including supercells. Large hail, some very large, and a potential tornado threat into southeast NE/northeast KS to southwest IA and northwest MO will be the initial severe hazards. Meanwhile, model-to-model and run-to-run consistencies in the NAM/GFS/ECMWF suggest storms in the central High Plains could evolve into a forward-propagating MCS Thursday night across mainly central and eastern KS, with damaging winds being the primary severe threat, as heights falls and further strengthening of deep-layer winds --- with the approach of the upstream large-scale trough. ...Midwest into western PA and NY... Although a synoptic warm front should be located farther north into northern Lower MI into southern Ontario, a differential heating boundary extending from southern Lower MI through northern IL should be the primary focus for new thunderstorm development Thursday afternoon and evening. The 15% (Slight) and 5% (Marginal) severe-risk areas have been expanded a little northward to include more of northern IL and southern Lower MI, with this change based on model consensus (12Z NAM/GFS and 00Z ECMWF) for the placement of showers and thunderstorms in vicinity of the aforementioned surface boundary. Moderate instability and sufficient bulk shear oriented parallel to the convective initiating boundary suggest line segments with locally strong/damaging winds being the primary threat. Farther northeast, stronger west-southwesterly low-level winds (40-50 kt) from northern PA into NY should result in a threat for damaging winds as storms develop across a destabilizing warm sector Thursday afternoon. ...WY/western SD... Marginal instability combined with forcing for ascent attendant to the larger scale trough moving toward the central Rockies and northern High Plains, and in vicinity of a cold front should allow for afternoon to early evening thunderstorm development. Weak to modest bulk shear should limit the overall severe weather threat, though steep low-level lapse rates could enhance locally strong/damaging winds gusts. ...Eastern SD/southwest MN... Effective bulk shear and forcing for ascent attendant to a midevel shortwave trough moving east across ND/SD during this forecast period should support storm development, with some organized. Greatest severe threat, though a Marginal risk due to weak instability, is possible across eastern SD and southwest MN. ..Peters.. 06/28/2017 Read mor […]

  • SPC Day 2 Fire Weather Outlook
    on June 28, 2017 at 5:38 pm

    SPC Day 2 Fire Weather Outlook Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1236 PM CDT Wed Jun 28 2017 Valid 291200Z - 301200Z The Elevated area has been expanded westward across portions of northern AZ and southern UT, where the latest model guidance indicates 15-20 mph westerly winds combining with RH of 5-12 percent amid dry fuels. No other changes have been made to the ongoing forecast. ..Cohen.. 06/28/2017 .PREV DISCUSSION... /ISSUED 0302 AM CDT Wed Jun 28 2017/ ...Synopsis... An upper-level shortwave trough will move eastward across the central Rockies on Thursday with an enhanced band of westerly flow aloft. At the surface, low pressure will deepen over western Kansas, resulting in an increased pressure gradient across New Mexico. ...Northwestern New Mexico and adjacent areas... A hot, dry airmass will linger over the area on Thursday. As vertical mixing occurs in a deepening boundary layer, afternoon RH values will fall into the single digits and sustained wind speeds will increase to 15-20 mph. Given the dry fuels across the region, elevated fire weather conditions will exist. ...Please see www.spc.noaa.gov/fire for graphic product... Read mor […]

  • SPC Day 1 Fire Weather Outlook
    on June 28, 2017 at 4:45 pm

    SPC Day 1 Fire Weather Outlook Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK 1143 AM CDT Wed Jun 28 2017 Valid 281700Z - 291200Z ...CRITICAL FIRE WEATHER AREA FOR PORTIONS OF UT...EASTERN NV...NORTHERN AZ...NORTHWESTERN NM...WESTERN CO...SOUTHWEST WY... No changes have been made to the ongoing forecast, with elevated and critical wind-driven fire-weather risk and isolated dry-thunderstorm potential affecting portions of a broad region from the southwest states to the central Great Basin and central Rockies. While critical fire-weather conditions will be likely across the entire Critical area, there is particular concern for potentially locally extreme fire behavior, enhanced fire spread, and explosive fire growth across parts of southern UT and northern AZ this afternoon into the evening. The 12Z Las Vegas NV and Flagstaff AZ soundings this morning sampled 90th percentile to near-record (warm) 500-mb temperatures combined with 75th percentile to 90th percentile (enhanced) 500-mb wind speeds -- based upon the SPC sounding climatology. These factors reflect the anomalous combination of substantial mid-tropospheric warmth and enhanced winds. Water vapor imagery depicts subtle disturbances grazing the southern periphery of a broader belt of enhanced midlevel zonal flow across the western states -- locally enhancing the height gradient / winds aloft over some of the driest surface conditions and driest fuels (i.e., across southern UT and northern AZ). The aforementioned soundings indicate 30-40 mph of flow in the midlevels, highlighting the enhanced momentum aloft that will be manifest to some extent at the surface. This will be the result of mixed layers deepening to over 10 kft above ground in some areas -- aided by surface temperatures warming well into the 80s across the higher elevations and into the 90s to near 100F at the lower elevations. In addition to supporting an area of locally enhanced winds -- i.e., 22-25 mph sustained west-southwest winds with gusts of 30-35 mph across southern UT and northern AZ -- the deep vertical mixing will also support minimum RH of 3-8 percent. This anomalous combination of very warm to hot temperatures / very low RH at the base of deep, well-mixed boundary layers / very dry fuels -- and the enhanced boundary-layer and surface winds -- will all exacerbate the critical fire-weather risk in southern UT and northern AZ. ..Cohen.. 06/28/2017 .PREV DISCUSSION... /ISSUED 0257 AM CDT Wed Jun 28 2017/ ...Synopsis... An upper-level shortwave trough will move across the Intermountain West today, enhancing westerly flow aloft over much of the central Great Basin and Southwest. At the surface, low pressure will persist over much of the West with continued hot and dry conditions. ...Arizona...Utah...and adjacent areas... A persistent hot, dry airmass over the area will allow for deep, well-mixed boundary layers yielding afternoon RH values in the single digits for most locations. Deep vertical mixing in the presence of enhanced flow aloft will result in sustained afternoon wind speeds of 20-25 mph across much of northern Arizona and southern Utah, resulting in critical fire weather conditions. For the surrounding elevated fire weather areas, sustained wind speeds are expected to remain just below 20 mph. Despite limited moisture across the region, sufficient instability will develop during the afternoon across portions of northern Utah, southwestern Idaho, southern Wyoming, and northern Colorado to support isolated thunderstorm development. Given the expected high cloud bases and dry sub-cloud layers of these thunderstorms, little precipitation is expected to reach the ground, supporting the potential for isolated dry thunderstorms. ...Southern California mountains and adjacent foothills... Continued low RH coupled with modestly enhanced winds will also prolong elevated fire weather conditions through today across portions of Southern California. ...Please see www.spc.noaa.gov/fire for graphic product... Read mor […]

  • SPC Jun 28, 2017 1630 UTC Day 1 Convective Outlook
    on June 28, 2017 at 4:43 pm

    SPC 1630Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1136 AM CDT Wed Jun 28 2017 Valid 281630Z - 291200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM FAR SOUTHEAST NE INTO NORTHERN IL/SOUTHERN WI... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL HIGH PLAINS TO THE MIDDLE/UPPER MS RIVER VALLEY... ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE NORTHERN ROCKIES TO THE GREAT LAKES... ...SUMMARY... Severe thunderstorms with large hail, wind damage and a few tornadoes are expected across the middle Missouri Valley northeastward into the middle and upper Mississippi Valley. Other more isolated severe storms may occur in the central Plains and northern Rockies. ...Middle MO River Valley to middle/upper MS River Valley... Related to last night's MCS, scattered showers/thunderstorms and related prevalent cloud cover continue to progress eastward across eastern portions of MN/IA into WI/northern IL late this morning. This is just ahead of an eastward-moving shortwave trough over MN, with a few other convectively related disturbances/MCVs noted farther south, embedded within a belt of moderately strong mid-level westerlies. A surface low analyzed at 15Z near the MN/SD/ND border vicinity will continue to spread eastward across central MN toward northern WI and the western Upper Peninsula of MI through this evening, while a cold front spreads southeastward across MN/IA/WI. Near and ahead of this cold front, low-level moistening and general air mass recovery will steadily occur this afternoon in the wake of the lingering early-day precipitation and cloud cover, particularly given relatively steep mid-level lapse rates and ample low-level moisture sampled in source-region 12Z observed soundings from Omaha NE and Topeka KS. Increasingly prevalent mid/upper 60s F surface dewpoints will support upwards of 2000-3000 J/kg MLCAPE particularly from southeast NE/northern KS into IA, with somewhat more modest (and uncertain) degree of pre-frontal destabilization farther north into WI/eastern MN owing to early-day cloud cover and some regenerative precipitation this morning across northern IA. While the aforementioned cloud cover/precipitation lingering into midday still casts some uncertainty, it seems most likely that surface-based storms will redevelop just ahead of the front semi-focused along outflow and zones of differential heating across southern/eastern IA and nearby far northern MO and northern IL. Pending adequate destabilization, other potentially severe development may occur by late afternoon in closer proximity to the surface low/front from far eastern MN into western/central WI. Around 40-45 kt of effective shear will support some initial supercells capable of large hail, with a few tornadoes possible as well given the strength of 2-3 km AGL southwesterly winds and related 150-250 m2/s2 0-1 km SRH (with prospective surface-based convection). Eastward-moving clusters should evolve by evening with a related increase in damaging wind potential particularly across southern IA/northern MO into northern IL. ...CO/WY Front Range to northern KS/southern NE... Within a modestly moist environment, widely scattered thunderstorms should develop and spread eastward across the region by late afternoon into evening, including some potential for at least small-scale MCS development this evening. Modest buoyancy and ample vertical shear will support the possibility of sporadic large hail and locally damaging winds into this evening. ...Northern Rockies... Ahead of an amplifying shortwave trough over the northern Intermountain region, modest moisture and a strengthening belt of west-southwesterly mid-level winds should contribute to the possibility of isolated strong to severe storms spanning parts of WY/southern MT and eastern ID/northern UT. ..Guyer/Dean.. 06/28/2017 Read mor […]

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