Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/13/20

Area Forecast Discussion
National Weather Service La Crosse WI
1100 PM CDT Wed Aug 12 2020 .SHORT TERM...(This evening through Thursday) Issued at 245 PM CDT Wed Aug 12 2020 Current observations show a well formed cold pool across much of Minnesota from earlier convection. GOES water vapor showing moderate shortwave trough energy over central MN with another smaller scale spin further south, now lifting into eastern MN, both associated with the morning/early afternoon storms. There is still an instability axis running from western IA into North Dakota per SPC meso-a with the eastern edge near I-35. RAP analysis of the low-level moisture transport convergence at 18Z is above the cold pool and fairly weak into central MN. Quite dry lower tropospheric conditions exist over WI...with some 700-850 mb dewpoint depressions of 20C. With the shortwave trough lifting east of instability and into drier stable air, would expect continued downward trend to weather as it shifts east this afternoon. Shortwave ridge building should dominate with RAP showing low-level moisture convergence lifting northward toward northern MN. This is where more convective activity is expected this evening and tonight, which could propagate southeast toward instability based on today`s activity /and Corfidi vectors for Thursday/ and end up affecting western WI into sern MN Thursday. With instability gradient shifting to Miss river by morning, little bumps of lift could cause storms. While the nose of the moisture transport shifts into nrn MN, the eastern edge is still isentropically upgliding along I-35 overnight. Will continue the small storm chances in the northwestern forecast area, roughly KEAU-KMCW, late tonight and Thursday. .LONG TERM...(Thursday night through Wednesday) Issued at 245 PM CDT Wed Aug 12 2020 Thursday Night through Saturday... With large scale ridging developing downstream of the trough over the Pacific Northwest and western Canada, instability will build east over the area through Friday with little tangible signal for storms. Have continued the rain chances in northcentral WI through parts of northeast Iowa until cold frontal passage Friday night. Model guidance is in better consensus now with weekend cold front timing and it continues to signal after midnight Friday night through midday Saturday as the main passage time across the area. This does not favor severe storms or heavier rainfall as it is in the diurnal minimum. With instability growing to the northwest Friday, healthy storms are expected over northern MN and these will shift southeast toward the area and weaken Friday night. There are still some slower model solutions /12.12Z NAM/ that would suggest a slower front timing and storms in southwest WI and far eastern IA Saturday afternoon. Weak wind shear profiles would suggest pulse, spotty severe storms at best should this solution verify. Saturday Night Through Wednesday... Good consensus on a period of pleasant weather with large scale northwest flow, mostly clear skies, and highs in the 70s. The only && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 1100 PM CDT Wed Aug 12 2020 Satellite imagery late this evening has shown an expanding area of clouds across central and southern Minnesota where temps were held down today. Ceilings were a mix of MVFR and VFR and looking at the forecast soundings from the 13.01Z RAP, these clouds should expand into KRST overnight with a period of MVFR ceilings. With winds of 20 to 25 knots in the cloud layer, these should mix out shortly after sunrise with VFR conditions expected into Thursday evening. The RAP suggests there is at least a possibility the MVFR clouds could get as far east as KLSE late tonight and have included a short period to cover this possibility. Otherwise, VFR conditions for KLSE through Thursday night as well. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Baumgardt LONG TERM...Baumgardt AVIATION...04
Area Forecast Discussion
National Weather Service State College PA
1132 PM EDT Wed Aug 12 2020 .SYNOPSIS... A weak cold front will stall out around or just south of the Maryland border through Friday. The presence of this front will lead to a daily chance of thunderstorms, mainly across the south, for the rest of the week. Some of the rain could be heavy along and south of the stalled front. A gradual cooling trend will be seen each day through the end of the week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Flash Flood watch was ended early over the SE corner of CWA as precip died out with sunset. Activity shifted to the SW portion of the CWA this evening, with HREF/HRRR indicating blossoming convection there this evening. Considered a short Flood Watch in this area, but then the HRRR started to back off a bit. Convection did develop, but heavy rains in slow moving tstms remained isolated and were handled with a Flood Advisory. Spotty convection does continue into the late evening, with potential for it to linger for next several hours over the SW and may spread back toward the E. Mrgl/Slight Excessive Rainfall Outlook (ERO) does persist through the night across the southern tier as any convection will be nearly stationary in weak flow. Elsewhere, look for mainly dry conditions across the northern 2/3rds of CWA with clouds diminishing as one moves northward. Dewpoints around 70 in the south drop off to the mid 50s over the north, bringing a refreshingly cool night north of I-80. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Daytime mixing on Thursday should lower dewpoints across the north, but dewpoints look like they could creep up a bit again over southern half keeping mention of showers/tstms in the forecast there. Best chance for heavier rains will continue to be along the southern border and southward during the aftn and evening on Thursday. Temperatures trend a little cooler (right around normal) due to the cloud cover to start the day in the central and south. But, abundant sunshine across the north will help them get 5-10F above normal for the day. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... A stationary boundary draped across the Mason-Dixon line will drive the potential for a few lingering showers overnight on Thursday. A small bubble of surface high pressure is expected to develop on Friday, forcing the stationary front south & bringing relatively tranquil weather to most of the Commonwealth into the weekend. Low pressure off the East Coast may bring a few showers into (where else than) southeast PA on Friday afternoon, but going with the dry solution through Saturday. By Saturday evening, split flow produces a weak broad upper trough over the lingering frontal boundary to our south. This will bring a surge of moisture into the Commonwealth during the day on Sunday. There is still ample uncertainty in the northward extent and amount of rainfall on Sunday with the ECENS trending drier and the GEFS trending wetter, but the GEFS mean produces potential for upwards of an inch of rain to much of central and south central PA Sunday afternoon. The ECENS has trended wetter since 24 hours ago and bolsters confidence in higher PoPs. Will likely need to raise Pops to likely starting in the SW Saturday night and expanding over the entire area Sunday afternoon through Monday evening. The weak surface trough will stick around through Monday before a cold front sweeps through the Commonwealth, marking the end of an unsettled stretch and ushering in cooler and drier weather. The Climate Prediction Center 6-10 temperature outlook favors below normal temperatures in central PA. This will be a welcome relief after a prolonged stretch of warm weather. Additionally, the arrival of high pressure by the middle of next week seems to favor a drier than normal stretch for a little bit. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... Minor adjustments made as of 1130 PM. Still a shower near AOO. Earlier discussion below. 00Z TAFS sent. Southeast flow of high dewpoint air across the southern part of central PA trying to keep a few showers and storms going. Current activity away from the TAF sites. Backed off on low clouds overnight. For Thursday, went VCSH across the south during the afternoon, as the cold front stalls just to our south. This may be the case right into Sunday. Thus the best weather may be across the north at BFD and IPT. Outlook... Fri..Isold-sct t-storms possible mainly srn 1/2. Sat-Sun...Risk of t-storms expands north and west. Mon...Still a chance of showers and storms. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/RXR NEAR TERM...Lambert/RXR SHORT TERM...Lambert/Dangelo LONG TERM...RXR/Banghoff AVIATION...Martin
Area Forecast Discussion
National Weather Service Dodge City KS
557 PM CDT Wed Aug 12 2020 ...Updated Aviation... .SHORT TERM...(This evening through Thursday) Issued at 136 PM CDT Wed Aug 12 2020 Early morning convection that crossed north central and portions of south central Kansas occurred just east of a 700mb 12-16C temperature gradient. This 700mb temperature gradient is forecast to remain nearly stationary through this evening based on the RAP and NAM with 700mb to 500mb lapse rates forecast to be 8C/km or greater which will be located ahead a weak disturbance that appears to be located over northeast Colorado based on WV loop. As this upper wave crosses northern Kansas early tonight am concerned convection developing early tonight in the Hays to Larned areas, especially as the 850mb warm air advection and 850m- 700mb moisture transport begins to improve near and east of this 700mb temperature gradient. Models however are less excited with the chance of precipitation this far west rather it keeps developing convection overnight further east as this warm layer moves slowly into Central Kansas. Models probably are correct with the better chances for convection being further east but given the location of mid level temperature gradient and developing WAA before midnight feel there will be at least a slight chance for thunderstorms near highway 183. On Thursday morning the upper level disturbance will be crossing central Kansas. An upper level trough, located over the Pacific Northwest at 12z Wednesday, will approach the northern and central Rockies during the day on Thursday. This upper level trough will cross the Rockies and move out into the Western High Plains Thursday night which will result in another chance for thunderstorms near the northern edge of the mid level baroclinic zone that is currently forecast to extend from southeast Wyoming to south central Nebraska. The storms that develop ahead of this late Thursday wave are expected to move out into the plains and along this mid level baroclinic zone which could bring some overnight convection to portions of Northern Kansas. At this time however it appears that these storms Thursday night will stay well north of the I-70 corridor and closer to the Nebraska border. Temperatures on Thursday will be a little tricky given the potential for a cool outflow boundary from the overnight convection to spread across parts of western Kansas, much like earlier today. At this time I am unsure just how far west this cooler air will move but even given this uncertainty the highs east of highway 183 should easily end up being 5 to near 10 degrees cooler compared to the highs near the Colorado border. Expect afternoon temperatures to range from near 90 to around 100 degrees. .LONG TERM...(Thursday night through Wednesday) Issued at 136 PM CDT Wed Aug 12 2020 On Friday the upper level trough will cross the northern plains as a surface cold front drops south across Nebraska and attempts to move into northern Kansas. This surface boundary will briefly become stationary Friday night as a weak upper level disturbance embedded in a developing northwest flow approaches northwest Kansas. There will be a chance of evening and overnight thunderstorms near this boundary Friday night but at this time any chance for thunderstorms currently appears to be near and north of the I-70 corridor. Across southwest Kansas which will stay south of the approaching cold front it will be another hot August day with highs in the 95 to near 100 degree range. Early this weekend the upper level trough will move into the Mississippi Valley and an upper level ridge will build across the Western United States. This will place western Kansas in a northwesterly flow over the weekend as several upper level waves embedded in this flow rotate around the upper ridge axis and across the Central Plains. Also over the weekend a cold front will drop south across the Northern Plains and move into southwest Kansas on Sunday. This cold front will move into Oklahoma by early next week as a cool dome of high pressure at the surface drops south out of Canada and into the Upper Mississippi Valley. This cool dome of high pressure at the surface will continue to build south and east early next week which will keep some cooler east to southeast flow advecting into central and western Kansas. Currently based on the temperature trends behind the cold front and the ongoing cool air advecting into Central and portions of Western Kansas early next week the highs from Sunday through Wednesday will be mainly in the 80s. The best chance for precipitation this weekend into early next week will be from Saturday night and Sunday as the cold front drops into southwest Kansas as the upper level trough crosses the Northern and Central Plains. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 555 PM CDT Wed Aug 12 2020 Main weather feature tonight will be the development of low clouds and possible fog for all TAF sites mainly after 08Z and especially around 10-13Z. IFR to LIFR conditions will be possible for all TAF sites and then cloud ceilings should rise after 14-15Z back to VFR status. Thunderstorms are possible during the overnight mainly for central and eastern Kansas but a VCTS is possible around HYS from 04-06Z where the storms initially develop. && .PRELIMINARY POINT TEMPS/POPS... DDC 70 88 67 95 / 0 10 0 10 GCK 67 90 65 94 / 0 0 0 10 EHA 66 96 65 99 / 0 0 0 0 LBL 67 92 66 98 / 0 0 0 0 HYS 70 86 68 92 / 30 0 0 0 P28 72 89 70 94 / 10 10 0 10 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Burgert LONG TERM...Burgert AVIATION...Tatro
Area Forecast Discussion
National Weather Service Goodland KS
527 PM MDT Wed Aug 12 2020 .SHORT TERM...(This evening through Saturday) Issued at 245 PM MDT Wed Aug 12 2020 Tonight...There will be a low chance of thunderstorms this evening with the focus being on Yuma county and locations along the Nebraska/Kansas border area where HRRR suggesting some activity moving in from the northwest around 7 PM MDT moving southeast through the evening then dissipating. Fog is expected to spread northward after midnight. Dense fog is possible per model visibility forecasts and at this time would be primarily along and south of Interstate 70. Low temperatures are expected to range from the upper 50s to low 60s in far eastern Colorado to the low to upper 60s elsewhere. Thursday-Thursday night...morning fog is expected to dissipate by 14z or 15z with a sunny to mostly sunny sky in the afternoon. I`ll be adding a slight chance of thunderstorms to the forecast near the CO/KS border in the afternoon hours through about sunset where low level convergence is maximized along a dry line with a weak disturbance moving through from the northwest. High temperatures are expected to range from the low 90s in Norton and Hill City to near 100 degrees across parts of far eastern Colorado behind the dryline and where 850mb temperatures are near 90 degrees F. Low temperatures are expected to be in the low to mid 60s. Friday-Friday night...presently the forecast is dry. If the GFS model is correct enough moisture in the 700-500mb layer moves close to the northeast corner of the area around 00z-03z to support an isolated thunderstorm mention. High temperatures are expected to be in the low to upper 90s with low temperatures in the low to mid 60s. Saturday...isolated afternoon thunderstorms will be possible as the models bring another weather system (per 700-500mb humidity) through the area from the northwest. East to southeast surface winds will provide for slightly "less hot" conditions with high temperatures in the low to mid 90s. .LONG TERM...(Saturday night through Wednesday) Issued at 203 PM MDT Wed Aug 12 2020 Saturday night will see the storms and showers that formed during the afternoon and evening continue to move east and south throughout the evening and early night hours. Lows are likely to drop to near 60 with winds out of the south around 10 to 15 mph. Winds would be stronger with any storm that remained in the area. Sunday has the upper level high sitting near Utah and Nevada begin to have a ridge extend north into Canada off of it. This will not immediately impact the Tri-State area as we would remain under northwest flow aloft with the potential for shortwave energy to pass through the area. While the area as a whole will see a chance for afternoon and evening storms, the greater chances are likely to be in the southern portion of the area based on guidance. Highs are likely to be in the upper 80s but the GFS is suggesting that temperatures may be a few degrees higher. Will have to see what the conditions are after the storms and front pass through on Saturday. Monday through Wednesday has the upper level pattern near stagnant with the upper high in the same position as Sunday with the ridge moving slowly east over the period. Meanwhile an upper low sits just north of Ontario with a trough that extends slowly south across the period. This will have the area remain in north to northwest flow which will continue to allow shortwaves to pass and add instability. At the surface, a stationary boundary will likely linger in Eastern Colorado and serve as a potential focal point for storm development. With PWAT values near or slightly above normal and 850 dewpoints near 14C, there will be sufficient moisture for storms to develop. Henceforth, each day will likely see a similar pattern of storms developing in Central to Eastern Colorado and moving east across our area during the afternoon and evening. It may be possible for some of these storms to become severe and/or produce heavy rainfall given the instability and moisture present but not enough confidence to forecast it yet. Highs are likely to stay in the mid to upper 80`s during this time period. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 525 PM MDT Wed Aug 12 2020 GLD: IFR-LIFR stratus and/or fog may develop late tonight, mainly in the 10-14Z time frame. Otherwise, VFR conditions will prevail through the TAF period. Light E-ESE winds will prevail this evening -- becoming light/variable overnight -- remaining light/ variable or becoming W-SW at 5-10 knots during the day on Thu. MCK: IFR-LIFR stratus and/or fog may develop late tonight, mainly in the 10-13Z time frame. Otherwise, VFR conditions will prevail through the TAF period. Light ESE-SE winds will prevail this evening -- becoming light/variable overnight. Winds will remain light through mid-afternoon, becoming south at 12-16 knots near the end of the TAF period (late Thu afternoon). && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...99 LONG TERM...KAK AVIATION...VINCENT
Area Forecast Discussion
National Weather Service Lincoln IL
750 PM CDT Wed Aug 12 2020 .SYNOPSIS... Issued at 750 PM CDT Wed Aug 12 2020 Partly cloudy skies are expected across central and east central Illinois into Thursday, with high temperatures rising back into the mid 80s on Thursday. While dry conditions will prevail overnight and Thursday morning, scattered showers and thunderstorms are expected in areas south of I-70 by midday, continuing into the afternoon. && .UPDATE... Issued at 750 PM CDT Wed Aug 12 2020 Isolated but persistent convection that has occurred between Effingham and Flora has finally faded away early this evening. However, the RAP and GFS hint at some isolated convection lingering overnight near Flora, so some small rain chances will be kept in the forecast there. Temperatures are largely on track, and adjustments in the forecast were mainly for sky trends. && .SHORT TERM...(This evening through Thursday) ISSUED AT 316 PM CDT Wed Aug 12 2020 Frontal boundary still sitting over southern IL will remain semi- active through tomorrow and might slowly lift to the north Thursday. However, any convection will be confined to southern IL tonight through Thursday with only a chance of precip expected in southeast IL. A slight chance of precip is possible a little further north of this area, but most of the CWA should be dry through the period. Overnight lows are expected to be in the 60s with afternoon highs, Thursday, rebounding into the middle 80s. && .LONG TERM...(Thursday night through Wednesday) ISSUED AT 316 PM CDT Wed Aug 12 2020 A frontal boundary will be near the CWA through the first part of the extended forecast with the chance of precip still confined to southeast IL for Thur night and Fri. After this, as the pattern becomes more progressive, only a slight chance of precip is expected Sat through Sun. A cold front will then move through the area Sun, with a small chance of precip, though will not be mentioned at this time in the worded forecast. Beyond this, Sun night through Wed, dry weather is expected with temps becoming cooler. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 640 PM CDT Wed Aug 12 2020 The latest surface observations indicate a moisture gradient with higher dew point air from about KMQB-KSPI-KDEC-KDNV and southward. Surface high pressure in Michigan was providing an light easterly flow across central Illinois with the drier air generally north of the I-72 corridor. This should keep the northern TAF sites in VFR conditions through the night and into much of Thursday. Locations with higher moisture levels can expect light fog to develop by daybreak with MVFR visibility from KSPI to KCMI. Lower clouds will also develop around 14-15z, keeping the MVFR conditions across central Il into early afternoon due to the proximity to a weak upper level low in south central IL. Mixing will be limited due to the morning cloud cover and light winds, but increasing surface temperatures should allow cloud bases to climb to VFR levels by 18z in the southern half of Illinois. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Geelhart SYNOPSIS...Geelhart SHORT TERM...Auten LONG TERM...Auten AVIATION...Miller
National Weather Service Jackson KY
1145 PM EDT Wed Aug 12 2020 .UPDATE... Issued at 1145 PM EDT WED AUG 12 2020 Did an update to the forecast mainly to fine tune the sky cover and incorporate the latest obs and trends for the T/Td grids. These updates have been sent to the NDFD and web servers. UPDATE Issued at 755 PM EDT WED AUG 12 2020 23z sfc analysis shows Kentucky is just south of a stalled boundary that is helping to keep the air mass rather soupy. As such, a few showers and storms have been able to sustain themselves mainly in the southeast border counties with Virginia. There remains enough instability to keep the activity going for another couple of hours before they fade out for the bulk of the night per the latest CAMs guidance. These are heavy rain producers, as well, with our co-op observer outside of Whitesburg picking up over two inches in less than an hour. Will update the zones and HWO once the storms finally fade out. Otherwise, the forecast is on track, with temperatures settling back into the upper 70s and lower 80s while dewpoints remain elevated in the low to mid 70s in most spots. The winds have been light and variable away from any storms. The forecast grids were updated to mainly fine tune the PoPs and add in the latest T/Td obs and trends - capturing the extra cooling effect of the storms in the southeast. These updates have been sent to the NDFD and web servers. && .SHORT TERM...(This evening through Thursday night) Issued at 435 PM EDT WED AUG 12 2020 This afternoon, at mid and upper levels, much of the Conus from the MS Valley to the eastern seaboard remained in a weakness between ridging centered near Bermuda and ridging centered near the southern Rockies vicinity. A weak upper level low/upper trough continues to meander near the confluence of the OH and MS Rivers with a couple vort maxes rotating around it across the lower OH Valley and into IN. This upper low/trough is displaced well south of the stronger westerlies nearer to the US/Canadian border and Great Lakes and moving only slowly. Another weak vort/shortwave was east of the area over the Appalachians. A min PW extends from the southern Great Lakes south near the I 75 corridor with PW of 1.5 inches or less per mesoanalysis with PW 1.6 inches plus in the southeast part of the CWA east into the Appalachians while a gradient in PW resides across central KY and nearing the Lake Cumberland Region. Some convection that had developed in the southeast counties has mostly dissipated with additional convection over VA. Near and east of the upper low/trough convection continues to move across portions of IL and central and western KY and TN with a diurnal increase having occurred across these regions. Overall, a relative min in instability is expected to persist through the evening near the PW min with RAP forecasts of MLCAPE generally peaking near or less than 1000 J/kg from the far northwest south near I 75. Meanwhile, MLCAPE is analyzed in the 1000 to 1500 J/kg range over the southeastern counties and in the far west in parts of Pulaski and Wayne counties. SBCAPE is generally analyzed in the 2000 to 2500 J/kg or over these more southeastern locations. Shear remains weak, but low level lapse rates are in the 7 to 8C/km range or some additional pulse type convection could still develop over the next few hours as we move into the evening. Cumulus seems to be stunted a bit as cirrus debris from convection to the southwest moves across the northwest half of the area so the evolution of convection through the evening remains uncertain. Convective allowing models for several runs keep most of the activity through the evening in the southeast. Some (especially recent HRRR runs) do develop more isolated activity further north or west to just south of the Mtn Parkway and east of I 75 as well though they have trended downward and the cumulus trends in those areas would generally support this. For now, we have continued to include slight chance pops to just south of the Mtn Parkway and west to an Estill to Knox to Bell County line. With the PW/moisture gradient near the far southwest and the upper low to the west as well as convection in that direction and the potential for outflows reaching the far southwest, slight pops have been included there for the evening. Convection is generally expected to wane across the region by late evening into the overnight hours. Some convective cloud debris though leads to uncertainty in fog development. In general, fog is expected to be more confined to the valley locations. Considering current dewpoints across the region near the 70 degree mark and lows expected to reach the upper 60s to around 70 degree mark and anticipated light winds, the pattern favors fog. Thursday into Thursday night, the upper low/upper trough over the lower OH Valley will slowly meander closer to eastern KY. The current area of rather high PW to the west of the area should gradually advect into the western and southern portions of the region by late Thursday with PW projected to reach the 1.6 to 2 inch range there by that time with PW remaining 1.5 or less in the northwest. A diurnal increase in convection should occur during the day on Thursday though some convection may linger all the way through Thursday night, especially across the west and south as the mid and upper level system slowly nears. With rather storm movements on Thursday and Thursday evening and the increasing moisture, locally heavy rain cannot be ruled out along with a storm or two with gusty winds. The airmass will remain moist with PW increasing to 1.6 or 1.7 to 2 inches across the area. Temperatures will again be mild on Thursday with highs mainly in the mid and upper 80s or 2 to 3 degree above normal for this time of year. Departures should be a bit greater with the moist airmass in place on Thursday night as dewpoints remain near 70 along with a fair amount of cloud cover. Lows on Thursday night will be near the 70 degree mark. .LONG TERM...(Friday through Wednesday) Issued at 506 PM EDT WED AUG 12 2020 Low pressure is expected to bring a soaking rainfall Friday into Saturday. A cold front follows for early next week, ushering in a cooler and drier late summer air mass. Model agreement is surprisingly good with the overall weather pattern through Tuesday. The latest model suite shows an ~ 594 dam high centered over the Desert Southwest Friday morning while a broad trough, associated with a ~546 dam parent cutoff low near Great Slave Lake, covers the northern US from the headwaters of the Mississippi River to the West Coast. To the east of these systems, the Ohio Valley and Great Lakes will lie within a zone of split flow, with a ridge extending northward into in western Quebec and a trough extending southward to near the Gulf Coast. A weak cutoff low, rotating in the split flow pattern over the lower Ohio Valley early Friday, is expected to slowly meander to the northeast through Saturday. By early next week, the southwestern high strengthens as it retrogrades toward the Great Basin and the deep trough digs into the eastern CONUS, breaking down the split flow pattern and lifting the remnant cutoff low circulation away from the Ohio Valley. The split upper level flow pattern will initially support a quasi-stationary boundary lingering over the region into Saturday evening as a weak low pressure lifts across the area. This system will pull deep moisture northward across the Commonwealth, sending PWATs to near 2 inches within a tall, skinny CAPE and light steering flow environment. This will set the stage for efficient warm rain processes and the potential for hydro issues in areas which receive multiple rounds of heavy convection. The low pressure wave and front finally pull away early Sunday, perhaps allowing for weak surface high pressure and shortwave ridging aloft to nose in Sunday morning. Thereafter, a Canadian cold front, supported by the broad digging trough, will surge SE across the Great Lakes and into the Ohio Valley Sunday night/early Monday. This front quickly looses steam as its parent air mass quickly modifies; even so, 850 temps aloft should still cool off modestly into the 14-16C range by Monday evening as a noticeably drier air mass moves into the area. A reinforcing secondary front could follow late Tuesday into Wednesday. Eastern Kentucky will continue to see warm and muggy conditions Friday into Saturday, along with the threat for showers and storms as that wave of low pressure lifts along the quasi- stationary boundary. There is still some uncertainty with regard to the precip timing and associated cloud cover. The UKMET and ECMWF favor a slower arrival on Friday and linger the precip through much of the day Saturday. On the other hand, the NAM, GFS and Canadian are more progressive, pushing the system through Friday into Friday night followed by the arrival of drier air Saturday. Maintained likely to categorical PoPs on both Friday and Saturday, but this will need to be fine-tuned as the models come into better agreement. Nudged NBM max temps down into the low to mid 80s on both days. However, high temps could easily be capped in the 70s in areas which see persistent cloud cover and shower activity. Some clearing is expected Saturday night/Sunday morning with the surface ridging, but shower and storm chances quickly return later Sunday or Monday with our next cold front. Slightly drier and cooler air arrives by late Monday. A reinforcing shot of cool air could arrive by mid-week. Mostly to partly sunny skies should boost high temps in the low to mid 80s Sunday afternoon ahead of the front and then cool off into the upper 70s and lower 80s for Tuesday. Lows near 70 Friday night will cool off to the upper 50s to low 60s by Tuesday morning. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) ISSUED AT 830 PM EDT WED AUG 12 2020 Isolated to scattered showers and storms will fade out over the first part of the evening. Later some clouds from convection west of the area near a slow moving upper level low will lead to some uncertainty in fog development tonight. The fog should be most prevalent in the river valleys again, generally from 4 to 13z and some IFR or lower is anticipated there, at times. KSJS should be most affected with some IFR conditions probable there per trends with generally MVFR reductions in vis for LOZ, SME, JKL, and SYM. The fog should lift and dissipate from 13 to 14z, with convection possibly developing in the south before the end of the period. The threat of spotty convection will be around all day, but at this point have chosen to not refine the placement and timing for any TAF site potentially affected. Winds through the period will be light and variable. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...JP LONG TERM...GEERTSON AVIATION...JP/GREIF
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
831 PM CDT Wed Aug 12 2020 .UPDATE... Issued at 831 PM CDT Wed Aug 12 2020 Rain cooled air north of the MN River has really put the breaks on the northward movement of the warm front, which remains parked roughly along the Buffalo Ridge. This warm front looks to remain more or less stationary through the night. Most models continue to struggle as they have done all day, but the ones that update more frequently (HRRR and HopWRFs) seem to have at least a slight grasp of what`s happening now. Agree with their idea that scattered showers/storms will continue to develop through the night as weak warm advection up over the warm front/outflow boundary, initiating from an unstable airmass where muCAPE exceeds 3000 j/kg, continues to allow storms to initiate. HRRR/HopWRFs are favoring western WI for seeing this activity through the night, but with showers developing clear back to the MS River in central MN, and the farther southwest location of the warm front, think this activity ends up a bit father west that what the HRRR has been depicting. In the end, continued chance pops from eastern MN into western WI through the night to start with and will update with trends from there. && .SHORT TERM...(This evening through Thursday night) Issued at 300 PM CDT Wed Aug 12 2020 The day began with clusters of showers/thunderstorms over far western MN, ahead of a warm front draped NW-SE over the Dakotas into the Mid-Mississippi River Valley, high pressure over the eastern Great Lakes, and multiple residual outflow boundaries across MN. In addition, rounding the base of a large upper level low over western Canada were several shortwave axes, gradually shifting ESE within a flattening upper level ridge. With PWATs near 1" and surface dewpoints into the mid-60s, a plentifully moist atmosphere was in place for these storms to steadily shift east. As they did and formed into more organized clusters and lines, some put some heavy rain over southwestern and southern MN (in the 2-4") range along with hail up to nickel-sized. Such storms are no longer expected as the precipitation shield has become far enough displaced from the surface front and into a slightly more stable atmosphere. Nevertheless, showers/storms will continue mainly N of I-94 and E of I-35 through this afternoon and evening. As the warm front slowly approaches for tomorrow, isolated/scattered showers are possible through the overnight hours but a drier airmass is expected tomorrow as the area becomes warm-sectored and very likely free from precipitation. As such, PoPs have been lowered for much, if not all, of the WFO MPX coverage area for tomorrow with multiple model solutions indicating no precipitation for tomorrow. There is the caveat that these same models had a very difficult time initializing the precipitation for today but with so many solutions indicating dry conditions for Thursday, have gone with that consensus. Precipitation chances then increase for Thursday night as the cold front trailing the warm sector shifts east through the Dakotas and into northwestern MN by daybreak Friday morning. While the heavier of the precipitation is likely beyond this short-term period, a few isolated stronger storms in far western MN are possible around daybreak. Better chances for severe weather on Thursday can be expected northwest of the WFO MPX coverage area, into northwestern MN and eastern ND. With the area being warm-sectored through Friday night, an associated increase in temperatures and humidity can be expected. Lows both tonight and Thursday night will run in the 60s while highs on Thursday climb to the mid-upper 80s. With dewpoints into the lower 70s Thursday, heat index values will climb to the low 90s area- wide (with some portions of far western MN into the mid 90s.) .LONG TERM...(Friday through Wednesday) Issued at 300 PM CDT Wed Aug 12 2020 Friday through Friday night looks to be fairly active across the coverage area as both the aforementioned cold front along with a potent upper level trough moves across the region. The front will push across MN on Friday then through WI Friday night, moving into MI on Saturday. With PWATs climbing to 1.25" to 1.50", in conjunction with dewpoints into the lower 70s, a rather unstable atmosphere is expected with virtually no capping to halt convective development. with frontal lifting and the trough aloft, the combination will be there for fairly good coverage of rain/thunderstorms across the area Friday through Friday night, with some storms potentially strong to severe shifting west to east. Bulk shear is expected to hit the 40-50kt range with MLCAPE values around 3000 J/kg, both supportive of strong-severe thunderstorms capable of large hail and damaging winds. With the exit of the front on Saturday, a prolonged cooler and drier period is then expected for the first half of next week. Highs will drop back to the 70s with lows back into the 50s, and potentially as low as the upper 40s by the middle of next week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 707 PM CDT Wed Aug 12 2020 Lower than normal confidence this period, with problems abound thanks to the warm front near the upper MN River from west central into south central MN. Models continue to struggle mightily with this setup. This warm front will lift north during this period, but that northward push has been slowed considerably by cool outflow air in the wake of clouds and rain across central MN into western WI. North of the front, it`s beginning to look increasingly likely that MVFR cigs will persist through the night, especially west of I-35. In addition, more thunderstorm development will be possible tonight as we see moist/unstable air continually get lifted up and over the warm front and outflow boundaries. Latest runs of the HRRR/HopWRF are favoring the Twin Cities into western WI for seeing additional TS development tonight. As the warm front pushes north, we will see skies clear out (aside from a diurnal cu field), with winds becoming southerly and gusty. Next round of TS does not look possible until Thu night at the moment. KMSP...With the western tail of the storms continuing to build west/south into weak warm advection and stronger instability, MSP is not out of the woods for seeing additional shra/tsra tonight. Also, it looks like we`ll see clouds remain much of the night to the north of the warm front. Lower confidence on what cloud trends will be though through the night, so went the optimistically vague route for this TAF, though would not be surprised if the sct MVFR level cigs mentioned tonight into Thursday morning become a ceiling. /OUTLOOK FOR KMSP/ Fri...Mainly VFR. Aftn/evening TSRA lkly. Wind SSE 15G25 kts. Sat...VFR. Wind N 5-10 kts. Sun...VFR. Wind NW 15G25 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...None. WI...None. && $$ UPDATE...MPG SHORT TERM...JPC LONG TERM...JPC AVIATION...MPG
Area Forecast Discussion
National Weather Service Shreveport LA
1027 PM CDT Wed Aug 12 2020 .UPDATE... Convection has subsided for now, but a weak shear axis remains in place across our eastern half so cannot completely rule out a few shwrs or even a stray tstm redeveloping through the remainder of tonight. In addition, patchy fog is possible in areas where heavy rainfall fell earlier today so did add patchy fog wording across much of SW Arkansas after midnight. Otherwise, temperatures appear to be on track this evening so no additional forecast updates are needed at this time. /19/ && .PREV DISCUSSION... /issued 726 PM CDT Wed Aug 12 2020/ AVIATION... For the 13/00Z TAF period, all sites begin the period with VFR conditions despite an abundance of convective debris clouds in the wake of a large decaying thunderstorm complex. One lone storm is still noted near the MLU terminal, but expect a downward trend in convection through the rest of this evening and overnight. Clouds will linger with some lower clouds, possibly in the MVFR range, eventually developing after midnight and toward daybreak mainly affecting TXK/ELD along with some patchy fog due to the recent rainfall at these sites. Otherwise, look for VFR conditions to prevail elsewhere with cumulus/altocumulus clouds at/above 5Kft to persist through the remainder of the period with light/varible winds becoming more S/SW on Thursday between 5-10 kts. /19/ PREV DISCUSSION... /issued 301 PM CDT Wed Aug 12 2020/ SHORT TERM.../Tonight through Thursday Night/ For the rest of today...continuing to watch a few lingering showers and thunderstorms from this mornings complex that moved through the northern portions of the area. Short range guidance shows these slowly coming to an end as we head into the evening. Significant cloud cover across the area in association with these showers and thunderstorms have prevented afternoon temperatures from reaching their full potential, with many areas in the 70s this afternoon. That being said, I don`t think anyone will be complaining about the rain, cloudy skies, and cooler temperatures. Main concern heading into tonight will revolve around the ongoing showers and thunderstorms. HREF is hinting that the MCV we saw through the day will continue to push towards the SE into the ArkLaMiss into the overnight hours. Often times these types of situations hit their stride overnight, so this would increase our potential for more heavy rain overnight. Latest HRRR model indicate that the storms will continue to weaken through the evening. Nonetheless will keep PoPs going through the night for the eastern portion of the area. Overnight temperatures will range from the lower 70s to the upper 70s. The cooler temperatures will be in the area that saw the rainfall through the day. The heat is on for Thursday...high pressure aloft will begin to build towards the east and into the area. Temperatures across portions of east Texas will climb into the upper 90s to lower 100s by Thursday afternoon. Mixed with high humidity, heat index values will easily reach the mid 100s for all of east Texas and portions of northwest Louisiana. As a result, a Heat Advisory will go into effect at noon on Thursday for all of our Texas counties, portions of Louisiana and Miller and Lafayette counties in Arkansas. There is a small non zero chance that a few showers or thunderstorms will develop across portions of our eastern area during the afternoon hours on Thursday. /33/ LONG TERM.../Friday through Monday/ The forecast period begins with a model consensus indicating that deep mid-level ridging will be firmly in place across the Desert Southwest with a mid-level trough centered across the Mississippi Valley. The eastern periphery of the ridge will extend into East Texas with the ArkLaTex wedged between the ridge and the trough. The trough will be close enough for the ArkLaMiss to help provide forcing to kick off more diurnally driven showers and thunderstorms there on Friday with changes quickly drying out for the I-49 corridor and westward into East Texas. The trough will edge eastward over the weekend and showers and thunderstorms cannot be ruled out for the ArkLaMiss and central Louisiana each afternoon. Otherwise, a dry and hot forecast is in place for the weekend for southeastern Oklahoma, southwestern Arkansas, northwestern Louisiana, East Texas, and Deep East Texas. On Sunday night, models begin to diverge somewhat with the GFS hinting at a short wave sliding southward and potentially kicking off a mesoscale convective system (MCS) for the area with chances of showers and thunderstorms continuing on Monday. With this in mind, have chance POPs (30-40%) late Sunday afternoon and again on Monday afternoon. For temperatures, highs on Friday will range from the lower 90s in SE OK/SW AR to the upper 90s and even close to triple digits in East Texas and Deep East Texas. The trend will continue to warm as the trough edges eastward with highs range from the mid 90s in SW AR/SE OK to the upper 90s and near triple digits elsewhere over the weekend. With the short wave pushing into the area and increased cloud coverage possible Monday, highs will range from the lower 90s in SE OK/SW AR to the upper 90s in Deep East Texas. Each day at least portions of the forecast area will be near or above heat advisory criteria with heat indices warming into the 105-110F range. /04-Woodrum/ && .PRELIMINARY POINT TEMPS/POPS... SHV 77 96 77 96 / 20 20 10 10 MLU 75 94 75 94 / 40 50 20 30 DEQ 72 94 72 93 / 10 10 10 20 TXK 73 92 74 92 / 20 20 10 20 ELD 71 92 72 92 / 40 20 10 20 TYR 78 100 78 100 / 0 0 0 0 GGG 77 99 77 97 / 10 10 0 10 LFK 77 101 77 100 / 0 10 0 10 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...Heat Advisory from noon to 8 PM CDT Thursday for ARZ070-071. LA...Heat Advisory from noon to 8 PM CDT Thursday for LAZ001>004- 010>012-017-018. OK...None. TX...Heat Advisory from noon to 8 PM CDT Thursday for TXZ096-097- 108>112-124>126-136>138-149>153-165>167. && $$ 19/33/04
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday) Issued at 355 PM CDT Wed Aug 12 2020 20Z water vapor imagery depicts broad mid-level troughing over the Pacific Northwest and southwestern Canada, which is working to flatten the ridge over the southwestern CONUS. A subtle shortwave can be seen between these features in eastern CO moving into KS, which is one of several factors influencing tonight`s forecast. A few very isolated thunderstorms remain possible north of I-70 the rest of the afternoon due to isentropic lift, but the main focus is on storms developing late this evening and especially overnight. The trend in today`s models has been for storms in Nebraska to weaken as they progress eastward this evening with our storms initiating in central KS primarily after midnight, associated with an area of isentropic lift which also happens to be on the northern edge of a modest LLJ. We still have quite a bit of variation between the CAMs as to exactly where storms develop, and especially how far north and east they will spread. The area of greatest likelihood appears to be along and south of a line from Concordia to Manhattan to Emporia, but the latest NAM Nest keeps the entire cluster west of the CWA. Meanwhile earlier runs of the HRRR brought storms as far east as Topeka, while current runs struggle to bring them that far east. Where storms do occur, these will be elevated with 1000-1500 J/kg of CAPE and 20-30 kts of effective bulk shear. This along with steeper mid-level lapse rates could be enough for a few storms to produce damaging wind gusts and perhaps hail. With an increase in Pwat to 1.5-1.75 inches, some locally heavy rainfall is also possible. Some showers and storms linger into east central KS for the morning hours with model guidance generally drying us out by the afternoon. Have dropped high temperatures to the mid to upper 80s across the CWA with cloud cover and rain likely to keep conditions cooler at least to start the day. .LONG TERM...(Thursday night through Wednesday) Issued at 355 PM CDT Wed Aug 12 2020 There is at least some possibility for storms to redevelop Thursday night with strengthening WAA and isentropic lift; however, this has shifted more toward southeastern KS. Based on some model guidance, this could stay entirely south of the CWA or it may barely clip the east central counties. Given the weaker forcing and overall pattern in place, the evolution of this round will really depend on how tonight`s system plays out and we see the type of environment we`re left with and where outflow boundaries end up. After this, there are a couple more chances for storms, one on Friday night into Saturday and another on Saturday night into Sunday ahead of a frontal boundary. This cold front looks to bring cooler and drier conditions into the beginning of next week with high temperatures returning to the 80s through mid-week along with dew points in the low 60s. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 640 PM CDT Wed Aug 12 2020 Light VFR showers end this evening in northeast Kansas with renewed thunderstorm development expected after 06-09Z southwest of a MHK to EMP line. These storms lift northeastward through the early morning, possibly impacting TOP/FOE around sunrise. Conditions in the heavier rain could fall below IFR at times. These storms diminish through the morning. VFR conditions are then expected for the rest of the period with light southeast winds. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Picha LONG TERM...Picha AVIATION...Skow