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ACUS01 KWNS 130058SWODY1SPC AC 130056Day 1 Convective OutlookNWS Storm Prediction Center Norman OK0756 PM CDT Mon Apr 12 2021Valid 130100Z - 131200Z...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER A PORTION OFSOUTH CENTRAL TEXAS......SUMMARY...A few instances of large hail will remain possible mainly over asmall portion of south central Texas through about 02Z. A few stormscapable of hail might also develop from north central Texas intosoutheast Oklahoma tonight....Central through southwest Texas...A small cluster of supercells that initiated along a cold frontpersists across south central Texas near Llano, though a generaldiminishing trend has already commenced. The shear/instabilityparameter space has been sufficient for supercells with large tovery large hail the main threat. However, increasing convectiveinhibition toward southwest TX (as evidenced by the Del Rio RAOB)and augmented by loss of surface heating suggests storms shouldcontinue a gradual weakening trend....North Central Texas through southeast Oklahoma...A few storms are expected to develop primarily within post-frontalregime from north central TX through southeast OK tonight. The 00ZRAOB from Fort Worth indicated steep lapse rates, but also suggestsconvective inhibition with respect to surface-based parcels willincrease significantly with loss of heating. However, forcing forascent accompanying a series of weak impulses embedded within thezonal flow regime might be sufficient to weaken the cap above thesurface layer where up to 1500 J/kg MUCAPE, 8 C/km mid-level lapserates and sufficient effective bulk shear for updraft rotation couldsupport a threat for a few instances of hail...Dial.. 04/13/2021$$FXUS02 KWBC 122049PMDEPDExtended Forecast DiscussionNWS Weather Prediction Center College Park MD448 PM EDT Mon Apr 12 2021Valid 12Z Thu Apr 15 2021 - 12Z Mon Apr 19 2021...Late-week Central Rockies/High Plains Heavy Snow Threat......Guidance/Predictability Assessment...A highly blocky synoptic pattern will continue through much of themedium range period. The main areas of concern will be related tothe progression/evolution of a couple of upper-level lows--onesliding across the Great Lakes and then off to the east of NewEngland, and another exiting the central Rockies toward theeastern U.S. There is increasing model support for theslow-moving upper low over the Great Lakes to trigger cyclogenesisoff the southern New England coast on Friday before heading out tosea on Saturday. Meanwhile, the upper low exiting the centralRockies should culminate with the highest threat of wet snow onFriday from the central Rockies to the High Plains. There isgeneral model agreement that the system will continue to trackeastward and weaken while heading toward the eastern U.S. thisweekend. There is also good model indication for anothershortwave to dip into the northern Plains from southern Canadalate this week. The ECMWF and CMC generally take it on a moresoutherly track into the central U.S. while the GFS tracks it moretoward the upper Midwest and the Great Lakes. Nevertheless, theGEFS mean was in better agreement with the EC mean and the CMCmean regarding this system.The WPC medium range product suite was primarily derived from ablend of well clustered guidance of the 06 UTC GFS/GEFS mean, 00UTC ECMWF/ECMWF ensemble mean together with some contribution fromthe 00Z CMC/CMC mean. Guidance is in decent agreement, bolsteringforecast confidence. Applied an even blend of the deterministicand ensemble means for days 4-5 (Friday-Saturday); then shiftedblend weights in favor of the ensemble means for days 6/7(Sunday-next Monday) amid growing forecast spread. This acts tomaintain good WPC continuity in an overall forecast scenario thatseems in line with latest guidance....Weather/Hazards Highlights...A closed mean trough/low over the West and lead cold Canadian highpressure (with temp anomalies ~10-20 degrees below normal) thisweek should allow a potentially heavy upslope snow event over theNorth-Central Rockies/High Plains to linger into late week. Somedeformation and terrain enhanced precipitation still remainspossible over parts of the Great Basin. Confidence is alsoincreasing on a moderate rain focus which should gradually shiftinto the Plains Thursday-Friday.Meanwhile, a wavy frontal boundary settles and lingers this periodinto the northern Gulf of Mexico and vicinity to focus severalperiods of moderate to heavy rains over Florida/Gulf Coast/LowerMississippi Valley/Southern Plains through the forecast period.The heavy rain chances appear highest from the central Gulf Coastto the Florida Panhandle this weekend and possibly into Monday asa low pressure wave could form along the front. The central GulfCoast states and vicinity have had much above normal rainfallrecently with continued flooding concerns.Farther north, recent guidance has maintained a stronger and lessprogressive main upper trough/low over the Mid-Atlantic andNortheast Thursday-Friday. Moderate to locally heavy rainfall canbe expected to accompany an associated front and surface low totrack across the region. The possibility of coastal cyclogenesiswill also present some maritime and coastal threats later weekinto the weekend. There may also be some mountain snows over theinterior Northeast as the upper low over the Great Lakes interactswith the developing coastal low.Kong/SchichtelAdditional 3-7 Day Hazard information can be found on the WPCmedium range hazards outlook chart at:https://www.wpc.ncep.noaa.gov/threats/threats.phpHazards:- Heavy rain across portions of the Southeast and the LowerMississippi Valley, Sun-Mon, Apr 18-Apr19.- Heavy rain across portions of the Mid-Atlantic and theNorthFXUS21 KWNC 121751PMDTHRUS Hazards OutlookNWS Climate Prediction Center College Park MD300 PM EDT April 12 2021SYNOPSIS: A strong ridge is forecast to encompass most of Alaska and thewestern CONUS during Week-2. This should result in warm, quiet weatherthroughout those regions. Model guidance forecasts a weak trough over much ofthe East during the week. There is a slight chance that temperatures will becold enough at night to damage sensitive vegetation throughout parts of theeastern U.S.HAZARDSSlight risk of much below normal temperatures from the Central Plains to theOhio Valley, Tue-Fri, Apr 20-23.DETAILED SUMMARYFOR THURSDAY APRIL 15 - MONDAY APRIL 19:https://www.wpc.ncep.noaa.gov/threats/threats.phpFOR TUESDAY APRIL 20 - MONDAY APRIL 26: The GFS and ECMWF ensembles are in goodagreement regarding Week-2. Positive height anomalies are forecast to reachfrom Alaska to the Rockies. Negative height anomalies are forecast to beconcentrated over eastern Canada, with weak troughing expected over the easternU.S. The surface temperature pattern is expected to follow this patternclosely, with above normal temperatures underneath the ridging and below normaltemperatures underneath the troughing.There are some ensemble members that forecast minimum temperatures in theeastern U.S. reaching the bottom 15th percentile during the first four days ofthe forecast period. Some areas in the Central Plains and Ohio Valley couldexperience overnight temperatures near or below freezing, which might damagesensitive vegetation. This pattern is expected to moderate during the laterpart of Week-2 as the associated trough moves out to sea.The warmest temperatures are expected throughout the West Coast, especiallywithin interior California. Daily maximum temperatures are forecast to bewithin their upper 15th percentile, but should not reach our thresholds forhazardous weather. Still, these warm temperatures and dry conditions willexacerbate the ongoing drought conditions throughout the Southwest.FORECASTER: Kyle MacRitchie$$ACUS11 KWNS 122344SWOMCDSPC MCD 122343TXZ000-130115-Mesoscale Discussion 0373NWS Storm Prediction Center Norman OK0643 PM CDT Mon Apr 12 2021Areas affected...portions of southwest into central TexasConcerning...Severe Thunderstorm Watch 93...Valid 122343Z - 130115ZThe severe weather threat for Severe Thunderstorm Watch 93continues.SUMMARY...The severe threat continues across Severe ThunderstormWatch #093. Large hail will be the dominant threat over the next fewhours, with up to 3 inch stones possible with the strongest storms.DISCUSSION...Convection has recently been able to initiate off ofthe near-stationary cold front over the past couple of hours, wherelow-level convergence is strongest and where a localized minimum inMLCINH has been noted. The 20Z DRT observed sounding shows that the8+ C/km mid-level lapse rates plume has advected far enough east,over the front to support ample buoyancy above the convectiveinhibition layer around 850 mb, with the latest RAP PFCs showing2000 J/kg MLCAPE in place. While storms have had a history ofbecoming supercellular immediately after initiation, with up to 2.75inch hail observed, the updrafts have tended to dissipate within anhour of initiation, suggesting that convective inhibition mayconstrain the severe threat to storms closest to the front.Nonetheless, updrafts that continue to develop near the front andmature will have the tendency to produce large hail, with 2-3 inchstones likely with the more intense storms. The severe threat isexpected to gradually wane after sunset, as the loss of daytimeheating will reduce the amount of lift near the front...Squitieri.. 04/12/2021...Please see www.spc.noaa.gov for graphic product...ATTN...WFO...FWD...EWX...SJT...MAF...LAT...LON 29650195 30960101 31579969 31639865 31289807 3079979630129863 29559962 29080023 28990088 29650195