Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/01/21

Area Forecast Discussion
National Weather Service La Crosse WI
656 PM CDT Sat Jul 31 2021 .SHORT TERM...(This evening through Sunday) Issued at 133 PM CDT Sat Jul 31 2021 A cold front is dropping into our northern forecast area early this afternoon with scattered convection developing along and ahead of it. Under mostly sunny skies for most of the morning, this area has built around 500-1000 J/kg of MLCAPE so far, perhaps up to 1200 J/kg at its peak this afternoon. Isolated convection has been sparking along this boundary since late morning with modest low to mid-level lapse rates. Convective initiation has been slightly suppressed by a bit of CIN in the 800-700mb layer, but this is quickly eroding with continued strong afternoon heating ahead of the boundary. Indeed, coverage along the boundary is quickly increasing, evidenced by a line of growing towering cu on satellite. CAPE profiles in RAP forecast soundings fall into the tall/skinny category, so with limited updraft momentum (and meager deep layer shear for that matter) do expect storm longevity will be limited overall. That said, there could be a few stronger, more prolonged updrafts within this broken line of convection this afternoon that may pose an isolated damaging wind and/or large hail threat into early evening as the front drops south through the area. This fits in line with SPC`s marginal risk for our area into early evening. Waning instability past 7PM should lead to a rapid diminishing trend in lingering convection across our south, with dry conditions heading into the overnight. As for hazy/smoky conditions, the HRRR shows near-surface smoke concentrations at their peak through this afternoon, diminishing a bit in the northerly flow behind the front tonight. There then looks to be marked improvement in both near-surface and vertically- integrated smoke through midday least momentarily. A quieter day on tap for Sunday as surface high pressure builds into the region with cooler conditions / highs in the 70s. Turning even less humid with dewpoints falling into the 50s. With a return to bluer skies, it should make for a very pleasant Sunday afternoon. .LONG TERM...(Sunday night through Saturday) Issued at 133 PM CDT Sat Jul 31 2021 Sunday night through Monday night will feature quiet and seasonably cool conditions, as high pressure migrates from the Northern Plains to the Upper Great Lakes. Will likely continue to deal with smoke with northerly flow aloft, and will have to monitor for more areas seeing impacts to visibilities and air quality with increasing subsidence and lighter winds. The Air Quality Alert continues for MN into Tuesday afternoon. Tuesday there remains a signal in some of the guidance for a backdoor cold front nearing in the wake of passing mid level shortwave. Considerable uncertainty though on extent/location, thus have maintained the slight chance PoPs for some of our northeast service area. Wednesday through Saturday the general theme is a warming trend to around normal, with generally 60s for lows and 80s for highs. Moisture will gradually increase in time with a broad trough developing in the Plains. This along with some ejecting impulses will bring periodic chances for showers and storms, mainly heading into the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 657 PM CDT Sat Jul 31 2021 Currently monitoring a broken line of showers and storms north of KLSE. Timing at KLSE would be about 0130Z. However, at this time the SHRA/TSRA look to be just east of KLSE and for now have left it out of the TAF. The activity should also wane with sunset hours. Will monitor for an update as needed. Northerly flow should scour most/all of the wildfire smoke out of the area by Sunday afternoon, thus MVFR smoke vsbys will be improved at sunrise to VFR. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Kurz LONG TERM...McClure AVIATION...Baumgardt
Area Forecast Discussion
National Weather Service Bismarck ND
925 PM CDT Sat Jul 31 2021 .UPDATE... Issued at 920 PM CDT Sat Jul 31 2021 For this update, decided to extend mention of smoke across the east in the gridded forecast until 07z based on current observations and trends. Otherwise, just blended in the latest observations. UPDATE Issued at 604 PM CDT Sat Jul 31 2021 Not much to report weather wise. Another quiet evening with less smoke at the surface. However, smoke aloft will keep the sky hazy at least through the night. For this update, just blended in the latest observations to the going forecast. && .SHORT TERM...(This evening through Sunday) Issued at 146 PM CDT Sat Jul 31 2021 Latest water vapor imagery shows high amplitude ridge in place over the western CONUS with northwest flow over the Northern Plains and drier air aloft continuing to push southward over ND. Surface analysis shows cold front well south of the state with high pressure nudging into ND from the north. Satellite also shows smoke continuing to advect southward across parts of central and eastern ND. Winds will diminish this evening with lows in the 50s and even some upper 40s north. RAP and HRRR smoke model guidance suggest some improvement overnight, though shows a deeper area of smoke moving from Canada into our northeast CWA, progressing south/southeast. Models indicate this smoke will be mainly aloft, not near the surface. Given the relatively limited impacts on visibility this afternoon so far, will not carry smoke in the forecast overnight. .LONG TERM...(Sunday night through Saturday) Issued at 146 PM CDT Sat Jul 31 2021 A similar pattern continues on Sunday with strong western ridge in place and surface high drifting across the Northern Plains. Expect another dry day with highs in the 80s and light winds. Global models and ensemble products, including WPC cluster analysis, continue to indicate the western ridge will deamplify with some shortwave troughs moving through. This supports an upper level low over the Pacific Northwest by next weekend and a more zonal flow over our region. Current forecast reflects this with chance pops Thu night into Friday with a more pronounced shortwave crossing the region. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 925 PM CDT Sat Jul 31 2021 VFR conditions are mostly expected through the period with generally light winds. Surface smoke across the east will continue through at least the first part of the night which could bring reduced visibility at KJMS (MVFR categories at times). && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...ZH SHORT TERM...JNS LONG TERM...JNS AVIATION...ZH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
844 PM MDT Sat Jul 31 2021 .UPDATE... Issued at 810 PM MDT Sat Jul 31 2021 Flash Flood Watches will be allowed to expire. A few changes were made to the forecast. The biggest was to reduce PoPs overnight tonight and through tomorrow. Basically any chance of showers or storms will be west of the Continental Divide tomorrow. East of the Divide will be too stable with an inversion just above 700 mb likely being too strong to overcome considering the drier air in place. The increased smoke tomorrow will aid in keeping instability down as well. So the burn area flash flood matrix will be moved to "none" over the Calwood and Cameron Peak for Sunday. The HRRR smoke model is showing a lot more smoke moving into the area tomorrow. Smoke was clearly visible on satellite today and surface visibility observations were as low as 3 miles in the panhandle of Nebraska due to smoke. It should be noticeably smokier tomorrow so smoke was added to the forecast. Lastly, moist and hazy air will be in place across the eastern plains tonight leading to the possibility of fog. The best chance for fog will be in southern Weld, Fort Morgan, and Washington counties so fog was added to the forecast there. Fog can`t be ruled out elsewhere but the chance was too low to include it into the forecast. && .SHORT TERM...(This evening through Sunday) Issued at 231 PM MDT Sat Jul 31 2021 ...FLASH FLOOD THREAT REMAINS IN PLACE ALONG THE FRONT RANGE THIS EVENING... Satellite and radar shows fairly widespread but not tremendously intense convection across the mountains and foothills. While maximum rainfall rates have been limited by marginal instability, we have seen some breaks in the clouds and MLCAPE near 500 J/kg now over the Denver metro area. There is also a push of stronger northeast winds now arriving to the Front Range, as evidenced by Cheyenne gusting to around 25 mph. Meanwhile, precipitable water values have climbed to around 1.3 to 1.35 inches along the I-25 Corridor, or above the 99th percentile and approaching near historical highs. Warm cloud depths are around 7000 feet, which is quite impressive for the Front Range so despite the limited instability and rainfall rates so far, we`re not done with this event. Extended periods of moderate to heavy rain are still expected in/near the Front Range this evening. The Palmer Divide may also be setting up for heavy rainfall yet this evening, and that could last as late as midnight. The only revision we`ve made so far is to remove central Weld County from the Flash Flood Watch given the increasing stability there and propensity of convection to push back toward the immediate I-25 Corridor and Foothills. The Palmer Divide and southern foothills could see the threat last until midnight, but that depends on how this still evolves this evening so will adjust the Flash Flood Watch there later if necessary. Overall, the rain threat will shift southward through the course of the evening, but perhaps a few showers may linger over the southern portions of the forecast area into the early morning hours. Sunday will feature drier and more stable conditions. We`ll likely stay capped off across the plains due to warm temps aloft and still relatively cool boundary layer, but mountain areas will still see enough elevated heating to potentially break the cap. The flash flood threat will be decreased by only marginal instability and a slightly drier airmass. High temperatures should respond with a little more sunshine and push into the upper 70s and lower 80s over most of the plains. .LONG TERM...(Sunday night through Saturday) Issued at 231 PM MDT Sat Jul 31 2021 A pronounced change in the weather pattern is forecast to take place by mid-week, effectively splitting the long term forecast period in half. Above normal moisture and heavy rain will be the primary impacts through Tuesday night, with the latter half of the week seeing a warming and drying trend. We`ll start of the day Monday with PWATs near normal values... roughly 0.6-0.8" for the area. However, there should be a gradual moistening through the day. There is still some question as to how unstable the higher terrain can get by the afternoon... but do agree on at least some destabilization west of the divide. The past couple of model cycles have shifted the brunt of the heavy rain axis west a little, but the current forecast solution would still favor heavy rain potential, especially over the East Troublesome and Williams Fork fires. Moisture will continue to slowly drift east on Tuesday, with heavy rain possible once again. As is typical a few days away from an event, there is a fairly large spread in model solutions, but in general there continues to be good agreement in an elevated flash flood threat as well. Moisture will decrease substantially across the area by Wednesday, which will mark the end of a very wet period across our forecast area. Mid-level temperatures will increase with low- level southwesterlies also gradually increasing. This should lead to much lower chances of precipitation (generally dry for I-25, chance PoPs for the high terrain). Temperatures should climb into the upper 80s Thursday and Friday, with low 90s possible for the start of the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 810 PM MDT Sat Jul 31 2021 DEN will be in MVFR for ceilings until roughly around 10Z before clouds disperse. Besides a bit of drizzle, rain is not expected for the rest of the TAF period. There is a slight chance that fog develops to the north of DEN during the early morning hours on Sunday. It does not appear that the fog will move into DEN but there is a non-zero chance it does. Smoke was added to the TAF for tomorrow as a swath of thicker smoke will move in from the north. This could impact slantwise visibility tomorrow. && .HYDROLOGY... Issued at 231 PM MDT Sat Jul 31 2021 Local flash flooding has returned this afternoon, with burn areas most susceptible as peak rainfall rates were near 1 inch per hour. However, we still can`t rule out flash flood concerns in the lower adjacent areas, although instability is limited to MLCAPE around 500 J/kg. That said, all the other parameters are still in place so we`ll continue the Flash Flood Watch until 9 pm. There`s a chance the Watch may need to be extended over the Palmer Divide and southern Foothills. We have cancelled the Watch for Central Weld County which appears to be stabilizing, and the frontal surge should keep the highest coverage in/just west of the I-25 Corridor and Palmer Divide. Despite somewhat more limited rainfall rates around 1 inch per hour with the strongest storms, the persistent nature of the showers and storms will keep the flash flood threat in place. For Sunday, the airmass will dry and stabilize a little. This will reduce the flash flood threat as well as convective coverage. There`s still a small threat, however, given the above normal amounts of moisture residing in the atmosphere. Flash flooding concerns ramp up a bit on both Monday and Tuesday. Better moisture returns to the area, particularly along and west of the divide by Monday afternoon, with long skinny CAPE profiles evident in BUFKIT soundings. WPC has much of our higher terrain in a SLGT excessive rainfall outlook which at this point seems fairly reasonable. Primary areas of concern would be the East Troublesome/Williams Fork burn areas, with a lower threat on the Calwood and Cameron Peak burn areas. Models show the potential for another heavy rain day on Tuesday, but confidence is below average at the moment. Given the amount of moisture available along with very slow storm motions, it does look like a favorable setup. We`ll have to watch the trend for both days closely, especially since there`s been a substantial amount of precipitation over the past few days. && .BOU WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 9 PM MDT this evening for COZ030>041. && $$ UPDATE...Danielson SHORT TERM...Barjenbruch LONG TERM...Hiris AVIATION...Danielson HYDROLOGY...Barjenbruch/Hiris
Area Forecast Discussion
National Weather Service Cheyenne WY
544 PM MDT Sat Jul 31 2021 .SHORT TERM...(This evening through Sunday morning) Issued at 200 PM MDT Sat Jul 31 2021 Challenges with this forecast package deals with rain chances. Still a lot of guidance discrepancy for tonight into Sunday. Currently...Surface front that was on the Colorado Wyoming state line yesterday has slipped well south into southern Colorado today. MCV feature over northeastern Colorado through the morning hours...continues to push southeast into western Kansas this afternoon. Another cold front lays across southern South Dakota into northeast Wyoming into south central Montana this afternoon. MCV has really decreased our rain chances this afternoon. NAMNEST short term guidance has begun to come more in line with the HRRR this afternoon with decreasing chances for showers and storms. 18Z NAM showing PWATS really falling across southeast WYoming and Nebraska Panhandle after 00Z. So do think rain chances come quickly to an end after 00Z. Based our PoP forecast on the HRRR solution with showers coming to an end after 8PM tonight. .LONG TERM...(Sunday through Friday) Issued at 351 AM MDT Sat Jul 31 2021 Passage of cold front through the region early Sunday will usher closer to near-normal temperatures along with limiting moisture spread mainly to the southern elevated terrain in southeast Wyoming in the afternoon. High pressure builds once more across the American Southwest with continued influence over our region with pockets of vorticity advection leading once more to afternoon showers on the Wyoming side. GFS and EURO are bit off by some mileage in location of showers and thunderstorms as moisture is advected into the region. Temperatures to remain slightly above normal with highs reaching into the upper 80s and low 90s east of Laramie Range and from the middle 70s to middle 80s west of the Laramie Range for majority of the extended forecast. Moisture advection ahead of main shortwave Tuesday will allow for widespread precipitation chances on the Wy side mainly along and west of the Laramie Range before spreading further Wednesday into the high plains and the Panhandle. In its wake high pressure builds again into the region drying us out and return back into the 90s for the Panhandle Thursday into the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 538 PM MDT Sat Jul 31 2021 VFR conditions will continue for all TAF sites across southeastern Wyoming. Wildfire smoke will lower visibility levels for all western Nebraska Panhandle sites to MVFR conditions through the TAF period Sunday 0Z. Light winds under 13kts overall for all sites across the region as dry conditions are expected to persist through Sunday morning. Clouds will trend from SCT to BKN for the remainder of the TAF period. && .FIRE WEATHER... Issued at 200 PM MDT Sat Jul 31 2021 Minimal fire weather concerns through the rest of the weekend through the middle of next week as monsoonal moisture remains over the area. Expect afternoon humidity to stay in the low 20 percent range with good overnight recoveries. Begin to dry out Thursday as temperatures begin to warm up quite a bit. Could see critical afternoon humidity west of the Laramie Range Thursday and Friday next week. But winds are expected to be weak at this time. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ SHORT TERM...GCC LONG TERM...WM AVIATION...AW FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Des Moines IA
637 PM CDT Sat Jul 31 2021 .SHORT TERM.../Tonight through Sunday Night/ Issued at 234 PM CDT Sat Jul 31 2021 Confidence: High Clouds linger late this afternoon over the south with the departing cool front and associated area of overnight convection. Subjective surface analysis at 12z shows one front south of Iowa with another weak boundary over central MN moving southeast, along with a third cool front over northeast MN. Low pressure is stacked up over the northern Great Lakes near Lake Superior while high pressure is now beginning to enter the Northern Plains. Aloft, a large gyre at H850 over New England will be merging with a low currently over Hudson Bay. High pressure continues across the west with ridging far north into the Canadian provinces. Cooler temperatures will continue to be slated for the eastern/northeast states while rather hot conditions will rebuild over the west. As the weak boundary over central MN heads south this evening, a few showers and isolated thunderstorms are expected to develop with an area of instability along the boundary. The activity will be mainly diurnal and if it holds together this evening, likley not making it any farther south than the US30 corridor in the northeast. As well as a chance of showers and isolated thunderstorms north, smoke is again showing up in the visible imagery over northwest and north central Iowa. Hazy to smoky skies are reported from Ft. Dodge north to Algona and Estherville and across southern MN as well. Have already added smoke to grids over the north this afternoon. Current HRRR modeling of the smoke has it tracking south with the boundary overnight into southern Iowa by daybreak. Lows tonight will cool most areas and drop into the mid 50s northwest to the lower to mid 60s southeast. There may be only a little break early Sunday, but another large plume of smoke in northern MN now, tied to the third cold front identified this morning, will likely also track south southeast which brings it close to southeast MN by 12-15z tomorrow and should again clip our northeast and eastern counties through at least the morning tomorrow. With the broad area of high pressure and reinforcing cooler H850 temperatures anticipated to arrive and continue for several days, afternoon highs Sunday will cool a bit to the mid to upper 70s with a few lower 80s over the region. Sunday night will also be refreshingly cool with overnight lows in the lower to mid 50s north to the upper 50s southeast. .LONG TERM.../Monday night through Saturday/ Issued at 234 PM CDT Sat Jul 31 2021 Confidence: Medium to High A combination of several waves dropping nearly due south into the large eastern North American trough at H500 and a cyclone in the Gulf of Alaska/North Pacific off the BC Coast through Thursday will result in a more amplified regime with much of the Great Lakes and eastern plains seeing northwest flow aloft through Tuesday. With H850 temperatures struggling to move much higher than the lower to mid teens through Wednesday afternoon, afternoon highs over the region will be rather pleasant in the upper 70s to lower 80s for the first half of the week. Through Wednesday, generally dry conditions can be expected with occasional clouds due to weak system passage and diurnal heating considerations. By mid to late week and into the weekend, the H500 pattern will begin to flatten with a wave approaching the area from the west Thursday into Friday. With increasing warm air advection and moisture, showers and thunderstorms will be on the increase over the area. The precipitation will signal the beginnings of another round of hotter conditions across our area. Despite some significant differences between mid-range model guidance, a conservative increase in H850 temperatures back to a 20 to 23C range by Friday into Saturday will have our area highs pushing back into the upper 80s to lower 90s again. There are hints in both the Euro and GFS solutions that another wave will track through the region about this time, bringing some additional chance for showers and storms. Though there is no real way to predict levels of smoke across the region into late week, the general pattern would suggest that some will still be lingering due to the overall persistent northwest flow through Tuesday and more westerly flow aloft Wed through Saturday. This may have some impact on highs and visibility/haze from time to time. && .AVIATION.../For the 00Z TAFS through 00Z Sunday evening/ Issued at 637 PM CDT Sat Jul 31 2021 The only non-VFR impact of concern will be smoke with periods of MVFR conditions anticipated at all TAF sites, the most lengthy of which will occur at KALO/KDSM/KOTM. Otherwise expect VFR conditions with intermittent smoke aloft through the period, along with little beyond patchy cumulus and generally light NW winds. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...REV LONG TERM...REV AVIATION...Small
Area Forecast Discussion
National Weather Service Quad Cities IA IL
659 PM CDT Sat Jul 31 2021 ...AVIATION UPDATE... .SYNOPSIS... Issued at 207 PM CDT Sat Jul 31 2021 Partly to mostly cloudy skies covered much of eastern Iowa, northwest Illinois and far northeast Missouri early this afternoon, and were left over from a morning MCS. That system was well into southern Illinois as of this writing, and other than some lingering rain showers in west central Illinois conditions have been improving through the late morning and early afternoon. Surface obs in portions of our area extending north and west were also picking up on hints of wildfire smoke, which was building south into the upper Mississippi River Valley thanks to northwesterly flow. Visibilities were reduced to 2 miles in portions of northwest Iowa, where concentrations were more dense. && .SHORT TERM...(This Evening through Sunday) ISSUED AT 207 PM CDT Sat Jul 31 2021 [Key Messages] *Chance of a shower or storm mainly north of Hwy 30 this evening *Sunshine and haze/patchy smoke to close out the weekend [Discussion] Much of eastern Iowa, northwest Illinois and far northeast Missouri will see a dry and quiet end to the weekend, as a renewed surge of northerly flow from a passing cold front and high pressure build into the area. This front will arrive in our northern CWA this evening, and may be accompanied by scattered showers and storms that will develop in response to steepening lapse rates and forcing along the front. There is potential some storms could be strong thanks to favored speed shear and dry air aloft, and steep low-level lapse rates for momentum transfer. Damaging winds and large hail would be the primary concern. Activity will diminish once the sun sets. The Storm Prediction Center has a sliver of a Level 1 (marginal) risk for severe storms north of Highway 20. On Sunday, partly to mostly sunny skies will prevail as the high pressure slowly builds south into the upper Mississippi River Valley. Forecast soundings suggest deep mixing will be occurring in the low-levels, which will have potential to mix a plume of wildfire smoke aloft building south into the Mississippi River Valley down to the surface. Analysis from the HRRR and RAP hint at periods of high surface smoke concentrations during the late morning and early afternoon, before gradually waning during the evening. Those most sensitive to air pollution may be affected, but most will likely experience periods of visibility issues from haze. Below normal temperatures will prevail thanks to the northerly flow. Lows tonight will drop into the upper 50s to low 60s, with PM highs Sunday int the upper 70s to low 80s. A welcomed break from the past week of heat and humidity! .LONG TERM...(Sunday Night through Saturday) ISSUED AT 207 PM CDT Sat Jul 31 2021 Northwest upper level flow between the deepening trough over the eastern U.S. and persistent upper level ridge over the Rockies will provide an extended period of mostly dry and cooler than normal temperatures through at least the middle of next week. The continued trajectory from smoke sources in Canada and the western U.S. will likely provide continued hazy skies and possibly some additional period of smoke or haze at the surface. Sunday night through Wednesday: Surface high pressure will prevail, providing light winds and low humidity, which will slowly increase toward midweek. Isolated afternoon showers cannot be completely ruled out,with steep low level lapse rates, especially Tuesday afternoon under a weak mid level impulse. However, forecast confidence is too low to mention. Temperatures will slowly moderate with daytime highs going from the mid and upper 70s Monday to the lower to mid 80s Wednesday, while the dry air and low dewpoints lead to lows in the 50s to lower 60s. Thursday through Saturday will see a return of at least slight chances for showers and thunderstorms as the upper flow deamplifies to a more zonal configuration with periodic shortwaves. Southerly surface winds and rising heights will bring warmer temperatures, back to near or above normal by the weekend. This will also result in the return of ore typical summer humidity levels. && .AVIATION...(For the 00Z TAFS through 00Z Sunday Evening) ISSUED AT 659 PM CDT Sat Jul 31 2021 MVFR vsbys due to smoke will continue through most of the period. There is some indication of IFR into tomorrow morning, but will hold off on that at the current time. Otherwise light winds and no cig restrictions expected. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ SYNOPSIS...Speck SHORT TERM...Speck LONG TERM...Sheets AVIATION...Gibbs
Area Forecast Discussion
National Weather Service Grand Forks ND
701 PM CDT Sat Jul 31 2021 .UPDATE... Issued at 657 PM CDT Sat Jul 31 2021 Breezy north winds are tapering off this evening with temperatures in the 70s. Smoke continues to loft into the region out of Manitoba and Ontario, with only partial clearing to the east of the Red River Valley. Looking upstream, another plume of wildfire smoke will work towards the area through the evening and early overnight period. && .SHORT TERM...(This afternoon through Sunday night) Issued at 246 PM CDT Sat Jul 31 2021 Periods of smoke continue to impact visibility and air quality across our forecast area. Northerly flow advected a plume of thick smoke into our forecast area with some locations near or less than 1 mile visibility and AQI values within the red category. This initial plume should transition into our southern CWA, while additional smoke moving into the region mainly aloft (some still being reported at the surface). HRRR smoke model shows improving trends in surface smoke concentrations tonight, however as surface winds go light this evening the forming nocturnal inversion may act to trap any lingering smoke near the surface. Smoke models keep most smoke aloft within northerly flow as surface flow is much weaker, however at least some impacts at the surface are possible. Temperatures will tend to be near or even slightly lower based on latest guidance in the upper 70s/lower 80s. Lows tonight may be the coolest with some colder spots in our north-northeast in the upper 40s. .LONG TERM...(Monday through Saturday) Issued at 246 PM CDT Sat Jul 31 2021 Overview... Stop us if you`ve heard this one before, but hot and dry weather is expected across the majority of the long term period. Overall minimally impactful weather is looking likely, although there is a small signal for precipitation to return to the area by late week. The week ahead... An upper level ridge over the western CONUS and trough over the eastern CONUS continue to dictate our weather pattern. The northern Plains are stuck in between these features, and while this would typically be an impetus for a more active weather pattern, the ridge out west is amplified enough to really block any appreciable shortwaves that try to pass through. In conjunction with surface high pressure, weather is expected to remain quiet with incrementally increasing temperatures as the week progresses. Initial highs in the mid 80s on Monday will likely begin to creep up toward the low 90s yet again by midweek. The primary shift in the weather pattern is then expected to occur later in the week as an upper trough over the Gulf of Alaska pushes southward toward the Pacific Northwest. This should act to weaken the upper ridge and catapult the Plains into a zonal to southwesterly flow regime. General ensemble guidance and cluster analysis are all in agreement on this solution, with slight variances with respect to timing and magnitude of the weakening ridge. Otherwise, a potential shift to a more active pattern may be in the cards moving toward the latter half of the week and into the weekend with increasing precipitation potential becoming evident within guidance at this time. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 626 PM CDT Sat Jul 31 2021 VFR to MVFR conditions prevail this evening with smoke remaining in the region. The thickest smoke has moved to our south as north winds persisted through much of the day. For tonight, low level smoke should keep visibility in the 4 to 6 mile range; however, mid to upper level smoke could build back into the area through the overnight hours and into Sunday morning. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Lynch SHORT TERM...DJR LONG TERM...Rick AVIATION...Lynch
National Weather Service Sioux Falls SD
1049 PM CDT Sat Jul 31 2021 .SHORT TERM...(This Evening through Sunday) Issued at 235 PM CDT Sat Jul 31 2021 There are two concerns in the short term forecast. The first concern is the near surface smoke which has been over the region since Thursday. Satellite shows that the smoke rapidly dissipates behind a surface front that is currently near I-90. This front is expected to be south of Sioux City and Storm Lake by early evening. While there will still be smoke aloft moving over the area, the lack of near surface smoke will remove the hazy surface conditions. In addition to clearing smoke out, moisture is pooling along the boundary with an area of cumulus forming near the Iowa and Minnesota border. Soundings show that there is a warm layer around 600 mb and most soundings only have a 1-2 h window where the parcels are warm and moist enough to overcome this warm layer. Due to lapse rates of 6-6.5 C/km, the resultant MLCAPE is generally 500-1000 J/kg. The HRRR depiction of a only a few cells developing seems reasonable given the limited surface convergence and weak upper level forcing. So have only 20-30 PoPs from mid afternoon through sunset for the area. Any storms that develop should dissipate shortly after sunset. With decreasing winds and drier air moving in, lows overnight will be in the 50s. On Sunday, northerly flow and dry air favor efficient mixing. While sustained winds will only be around 10 kts, the boundary layer may mix deep enough to support wind gusts of 20 to 25 mph during the early to mid afternoon. Also expect this will help to warm temperatures to near normal with highs from the upper 70s along the Buffalo Ridge in Minnesota to the mid 80s west of I-29. .LONG TERM...(Sunday Night through Saturday) Issued at 235 PM CDT Sat Jul 31 2021 The early part of the week will continue to be dry and seasonable. Upper level smoke will continue to be across the area. And there is some indication surface smoke may return to the area sometime Sunday night or Monday. Given that smoke is very dependent upon the evolution of fires across portions of Canada, did not add any smoke into the grids at this time. But if smoke moves back in, it may be hard to get rid of until later into Tuesday or even Wednesday when the low level flow turns to the south. So there is the potential for degraded air quality into early next week. Otherwise dry conditions are expected with temperatures generally in the 80s for both days. With high pressure nearby, light winds are expected. For Wednesday through Saturday, both the ECMWF ensemble and NAEFS predict a large scale ridge in the west and trough in the east to begin the period. By next weekend, the ensemble mean goes to a quasi-zonal flow with a low amplitude ridge over the area. While there are strong signals for a gradual warm up late this week and into the weekend, the degree of the warm up remains uncertain. The GEFS is much warmer than the ECMWF and Canadian by late this week. The warmer GEFS may be a result of the model parameterization overestimating surface heating which has been an issue over the plains the last 2-4 years so am favoring temperatures closer to the ECMWF and Canadian solutions. The ECMWF and Canadian ensembles have not been as extreme although highs could reach the 90s west of the James River by Thursday and across the remainder of the forecast area by Friday and Saturday. As for precipitation, models show a low (20%) probability of precipitation Wednesday night and Thursday. The 00Z deterministic models showed more QPF than the 12Z deterministic models and most ensemble members with several members remaining dry. As noted in the previous discussion, shear is limited and the lapse rates remain less than 7 C/km so if thunderstorms develop, severe storms appear unlikely at this time. As the flow transitions to quasi- zonal toward the weekend, predictability decreases as to the timing of waves. While most ensemble members agree there will be some rain over the weekend, the amount of the rain and timing is uncertain. There is also some concern about mid-level capping which could limit coverage of any thunderstorms. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1047 PM CDT Sat Jul 31 2021 Satellite imagery before dusk combined with sfc observations show patchy smoke lingering in the region overnight. Generally expect VFR conditions to prevail late tonight through at least early Sunday with the bulk of the incoming smoke streaming through aloft. North winds will weaken overnight as sfc high pressure builds in. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...NONE. MN...NONE. IA...NONE. NE...NONE. && $$ SHORT TERM...Schumacher LONG TERM...Schumacher AVIATION...BP
Area Forecast Discussion
National Weather Service Goodland KS
639 PM MDT Sat Jul 31 2021 .SHORT TERM...(This evening through Monday night) Issued at 328 PM MDT Sat Jul 31 2021 The primary forecast concern is the continuation of the hazy conditions due to smoke from tonight through Sunday, Sunday night and into Monday morning. The upper ridge continues to amplify over the Rockies and Intermountain region tonight into Sunday before several short wave troughs move slowly through the apex of the upper ridge between Monday and Monday night. At the surface, high pressure over the northern and central plains pushes deeper into the southern plains. Expect any thunderstorms that may develop to stay outside of the forecast area to the west and south in closer proximity to the surface convergent areas near the remaining surface boundaries and along the areas of higher terrain. The Near Surface Smoke concentrations in the HRRR show a gradual dissipation of the smoke through the next couple of days. As a result, the heavy haze seen across the area today following the passage of a cold front last night should be gradually dissipating over the next few days. Expect some near surface re-concentration as the overnight inversion sets up. However, once the surface inversion breaks up with the heating of the day, expect the near surface concentration of smoke to mix out through a larger depth. Unfortunately, the vertically integrated smoke being depicted by the HRRR is showing max concentrations through the day on Sunday before pushing further to the south and west. This would tend to support continued hazy conditions through the remainder of the weekend and into the first part of next week, although near surface smoke concentrations may stay low enough to not create air quality issues for potentially susceptible individuals. Expect temperatures to gradually through through Monday with highs back up around 90 degrees on Monday. .LONG TERM...(Tuesday through Saturday) Issued at 156 PM MDT Sat Jul 31 2021 The extended forecast begins with a ridge over Eastern Montana and a longwave trough extending west to east from the Dakotas to New England and south to the Gulf Coast. Northwest flow aloft remains in place over the Tri-State area. High pressure will be in place over the Baja Peninsula. The pattern remains favorable for daily chance for showers and thunderstorms as a few disturbances move across the region. Given the dry conditions we`ve had in the area for the last week and precipitable water values of 0.8-1.0" across portions of the area, confidence in the potential for isolated flash flooding remains low at this time. Any showers and thunderstorms that do develop on Tuesday and Wednesday will have the potential to produce some gusty winds and much needed rainfall. Tuesday afternoon, the ridge begins to break down, shifting to the east over the area. High temperatures will make it up into the 80s with a few areas flirting with the 90 degree mark. Wednesday, the ridge continues to break down with an embedded shortwave trough moving into the area from the northwest. A few showers and thunderstorms will be possible and high temperatures will once again be in the 80s. An upper ridge moves in from the west on Thursday and Friday with a gradual warming trend possible. Highs are expected to return to the low to mid-90s for most of the region Friday afternoon. All eyes turn to the west Friday as a shortwave trough ejects out of the PAC NW, trekking across Montana and the Dakotas through the day. Models are in slight disagreement with the ECMWF being more aggressive in the forward movement of the trough at this time. Models also show an upper low nearing the Olympic Peninsula late in the forecast period. The system is still nearly a week from reaching shore, so will want to continue to monitor the forecast over the coming days. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 627 PM MDT Sat Jul 31 2021 Reduced visibilities (3-6SM) associated with smoke emanating from wildfires in the western CONUS will affect both terminals through Sunday morning. Otherwise, VFR conditions will prevail. 5-10 knot NNE winds will become variable overnight. Winds will remain light/ variable through the day on Sunday. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...LOCKHART LONG TERM...AW AVIATION...VINCENT
Area Forecast Discussion
National Weather Service North Platte NE
616 PM CDT Sat Jul 31 2021 .SHORT TERM...(This evening through Sunday night) Issued at 347 PM CDT Sat Jul 31 202147 The HRRR near-surface smoke forecast indicates the smoke across wrn and ncntl Nebraska will continue moving south tonight and should be south of the region Sunday morning. Satellite and sfc obs across ND and MN show areas of smoke but visibility is generally 5 miles or greater according to the observations. This smoke could be partially or mostly aloft so no areas of smoke are included in the forecast across wrn and ncntl Nebraska Sunday. A fairly broad area of Canadian sfc high pressure across Manitoba and Saskatchewan this afternoon will build south and be located across the upper Midwest by Monday morning. This high pressure should back into wrn and ncntl Nebraska presenting cooler temperatures and a continued decrease in humidity. By Sunday morning, dew points could be in the upper 40s to mid 50s and they will continue to remain steady or slowly fall Sunday and Sunday night. The temperature forecast leans on the cooler short term model blend plus bias correction. This suggested lows in the 50s tonight and Sunday night with highs in the 80s Sunday. This forecast factors in the effects of smoke aloft which could keep high temperatures a few degrees cooler than the very warm MET and MAV guidance which suggest highs closer to 90. The official forecast is close to the cooler ECM guidance. The MCV and isolated shower activity across swrn Nebraska this afternoon should move south into KS by late evening. Isolated showers are in place along and south of Interstate 80 for a few hours this evening. .LONG TERM...(Monday through Saturday) Issued at 329 PM CDT Sat Jul 31 2021 The models are in good agreement showing an upper level ridge of high pressure across the Rockies this afternoon. The models will carry the associated subtropical moisture west away from Nebraska Sunday through Tuesday presenting dry weather conditions. The moisture plume will return Wednesday with an attendant warm front. This would probably be the best chance for thunderstorms next week. By this time the upper level ridge has flattened and winds aloft have become more zonal. A second wave of moisture will move through Friday. Oddly, the blended model forecast, including WPC, suggested little or no rainfall on these days or any of the next 7 days, for that matter. Later forecasts will need to be examined to determine the rain chances next week. Otherwise, highs in the 80s are in place Monday through Wednesday and this is the result of Canadian high pressure across the Midwest. An approaching long wave trof off the West Coast next week will flatten the ridge and send warmer air across the Rockies and into Nebraska Thursday through Saturday. Highs in the upper 80s and 90s are in place during this time which is consistent with temperatures at h700mb rising to 11C to 15C. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 614 PM CDT Sat Jul 31 2021 In the short term, MVFR conditions are expected due to smoke and haze reducing VIS. Expecting this to clear and make way for VFR conditions into the day tomorrow. Winds will be generally from the northeast at the sfc, under 10 kts. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Sinclair
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
644 PM CDT Sat Jul 31 2021 .SHORT TERM... 206 PM CDT Through Sunday... Skies are a bit hazy this afternoon as some of the wildfire smoke aloft is advected our way ahead of a cold front. Otherwise, the near term attention grabber is an area of thunderstorms that have been increasing in coverage across north-central Wisconsin this afternoon. The storms are along and ahead of a cold front that is working southeastward toward our area tonight. With some warming ahead of the front and colder temperatures aloft in the northwest flow aloft pattern, mixed layer CAPE approaching 1000 J/KG and some lower end shear values should allow storms to continue this afternoon. By the time the front approaches, we will be past the heating of the day which has had some influence on convective coverage to this point. To that end, much of the near term guidance continues to suggest that these storms will likely decrease in coverage this evening and weaken or dissipate. Forecast soundings do depict skinny CAPE values aloft hanging on into the evening hours. Current thinking is there will be a few weakening showers or storms, especially since guidance is a bit slow, and we may not decouple if they arrive a bit quicker. Current timing is about 9 pm into the Chicago area if they hold together. Afterwards, the front should help clear out some of the hazy skies for Sunday. Sunday will feature more sunshine, and we will have a reinforcing shot of northeasterly winds and cooler dewpoint air. These winds will again lead to a period of high swim risk conditions at southern Lake Michigan beaches through Sunday evening. Highs will top out in the 70s with afternoon wind gusts near 20 mph inland, making for a somewhat seasonally cooler day. KMD && .LONG TERM... 243 PM CDT Sunday Night through Saturday... After the dangerous swimming conditions at the beaches on Sunday night, there are no significant weather impact concerns through next week. There`s just a few items of interest, starting off with early season lake effect shower potential Sunday night into Monday. Temperatures will start out below normal with comfortable humidity levels and moderate back to around normal by mid week. Signs are then pointing toward above normal warmth and higher humidity returning next weekend. 850 mb temperatures over southern Lake Michigan will cool down to 9C or even slightly lower toward daybreak Monday. With lake surface temperatures in the lower to mid 70s, this will yield a respectable 850 to lake delta T of nearing 15C. Increasing lake induced equilibrium levels (inversion heights) with several hundred J/kg of CAPE and convergence should generate cloud cover initially and then even some at least isolated to scattered shower activity. Have some concern for isolated thunder, though well above freezing level ELs are only brief and there`s a good amount of mid-level dry air when parameters are maximized. The convergence should shift to the southwest portion of the lake overnight, with low PoPs added downwind into parts of northeast IL and extreme northwest Indiana through Monday morning. Aside from the lake effect, forecasting coolest overnight lows. in quite some time of lower-mid 50s inland of lake effect clouds. A short-wave pivoting in on the western flank of longwave troughing over northeast North America will move overhead Monday afternoon. As this occurs, the convergence axis from the lake will be shifting inland. Expecting a fairly healthy Cu field due to seasonably cool air mass aloft steepening lower level lapse rates. Moisture profiles are fairly meager and ELs generally top out near or below the freezing level, so while some isolated/spotty showers are possible, think they would be on the lighter side. Highs will be 5-10F below normal in primarily mid 70s (locally upper 70s) on Monday, with lower 70s lakeside due to onshore flow. Tuesday through Friday have dry forecasts in the official grids. Can`t rule out some spotty shower/sprinkle activity at times. However, think that splotchy afternoon-early evening QPF on some of the guidance, especially from NCEP, is probably owing to unrealistically high dew points (even when accounting for some crop ET) and instability. Humidity levels will remain in check likely through the work week as temperatures warm back to normal low-mid 80s, so no dog days of August yet. Next week should finally bring a return to very warm to hot and humid conditions, with some variance on the magnitude of the warmth. Opening up of moisture trajectories will allow for the aforementioned more humid conditions and also potentially set the stage for a somewhat more active stretch for the second half of next weekend into the following work week. Low chances for showers/thunder return Saturday-Saturday evening in the official forecast. Castro && .AVIATION... For the 00Z TAFs... Aviation Forecast Concerns: * Isolated SHRA/TSRA over WI may spread into northern IL late this evening, though low coverage/low probability for impact to any particular terminal. * Surface cold front moves through during the pre-dawn hours, with wind shift to the north-northeast. Breezy northeast winds with gusts 15-20 kt Sunday morning/midday. * Hazy skies with smoke from western wildfires this evening/tonight. Minor VFR vis restrictions possible. Early evening surface map shows weak low pressure moving southeast across Lake Huron, with a cold front west-southwest across north central WI into northwest IA. Pool of mid-60s surface dew points ahead of the front was producing some modest instability across WI and northeast IA, where isolated to scattered TSRA have developed this afternoon. While isolated SHRA/TSRA can`t completely be ruled out for the forecast area later tonight as the front approaches, the loss of diurnal heating/instability is expected to result in decreasing coverage and intensity by the time the front approaches late this evening/toward midnight (generally 03-06Z). CAM guidance trends continue to favor a decreasing/weakening scenario and thus will maintain dry TAFs, but will monitor for the need to tactically add a VC mention later this evening. The actual cold frontal boundary looks to move into northern IL and across the terminals in the 07-10Z time frame, with a wind shift to the north-northeast. Winds will likely become a bit gusty (15-20 kts) after sunrise as cooler air pushes in with some patchy MVFR cloud bases also possible. Winds should ease and lingering cu/stratocu bases should rise to VFR in the afternoon. Otherwise in the near term, GOES visible satellite imagery depicts hazy conditions across the region associated with smoke from western wildfires. HRRR near-surface smoke forecasts indicate this will remain in the area into tonight, before north-northeasterly winds clear things out tomorrow. A few sites upstream in eastern IA were reporting some 4-6SM visibility restrictions, and its possible the terminals may see some minor restrictions with low level west winds ahead of the cold front this evening. Ratzer && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Beach Hazards Statement...ILZ006-ILZ103-ILZ104...7 AM Sunday to 7 AM Monday. IN...Beach Hazards Statement...INZ001-INZ002...7 AM Sunday to 7 AM Monday. LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744- LMZ745...7 AM Sunday to 7 AM Monday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Updated for 00Z Aviation Forecast Discussion below.

PREV DISCUSSION... /issued 348 PM CDT Sat Jul 31 2021/ DISCUSSION... Another hot and humid day across the Mid-South. Temperatures are mainly in the mid to upper 90s with dewpoints in the mid 70s. Nearly every location in the Mid-South has a heat index of 105 or greater at this hour, with a few locations at 110 or greater. Current heat products look good with an expiration of 8PM this evening. Latest KNQA radar sweep shows a few isolated storms moving into northern portions of our CWA. Storms have behaved themselves thus far, with wind gusts mainly in the 35 to 45 mph range. These storms are expected to weaken as they trek southeast into our area over the next couple of hours. Behind this activity, there is a cold front that will move into the area tonight. CAMs are consistent with storms moving into our CWA around sundown and persisting through the overnight hours. Activity will be confined mainly to areas north of I-40. The front will get hung up and stall near the Tennessee and Mississippi border tomorrow afternoon. There will finally be a generous push southward tomorrow afternoon, as an upper low drops into the Ohio Valley and northwest flow develops across the region. However, ahead of the front, heat will once again be a concern for portions of north Mississippi. Went ahead and issued another advisory for a row of counties in north Mississippi. Elsewhere, high temperatures are only expected to climb into the low to mid 80s as north winds persist. The front will finally push south tomorrow night. A few strong storms are possible, especially over north Mississippi where the highest instability is. Gusty winds are the main threat. Monday will see a few lingering showers over north Mississippi, but most the region will remain dry. Expect highs in the low to mid 80s and comfortable humidity. Tuesday through Thursday looks to be a beautiful stretch of weather for the region, as an upper low remains overhead. Expect highs in the mid 80s, low humidity, no rain, and north winds. A few mornings could get chilly, yes I said it, with readings in the upper 50s across rural parts of west Tennessee on Tuesday and Wednesday. The rest of the region will see lows in the low to mid 50s. Return flow and upper level ridging return to the region next weekend. This will bring the return of summer conditions. Expect increasing humidity and highs in the 90s. AC3 && .AVIATION... 00Z TAFs Surface cold front remains on track to drop into the Midsouth overnight, most likely 09Z at MEM. Scattered SHRA/TSRA are expected ahead of the cold front - which remains the primary forecast challenge. Just prior to 00Z, Isolated SHRA/TSRA were already noted on radar 60N of JBR, ahead of any of the CAM output. Storm chances at JBR through 03Z- 04Z will depend on convective cold pool organization ahead of the cold front over southeast MO. If this cold pool / convective gust front can become organized, there will be TSRA potential at MEM around 04Z. Otherwise, main TSRA window for MEM will be associated with closer to cold frontal passage after 09Z. PWB && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...Heat Advisory from 10 AM to 8 PM CDT Sunday for Calhoun- Chickasaw-Coahoma-Monroe-Quitman-Tallahatchie-Yalobusha. TN...None. && $$
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EDT Sat Jul 31 2021 .SHORT TERM...(This evening through Sunday) Issued at 224 PM EDT SAT JUL 31 2021 NW flow aloft continues today with a W to NW wind at the sfc across Upper Michigan. There has been some haze and smoke across the Upper Midwest today, including the wern half of the UP, which has limited daytime highs a little bit. Temps are generally in the low to mid 70s across the west and half and 60s across the east where some morning convection has kept cloud cover. Diurnal cu continues to develop as daytime heating continues. Heading into this evening, the latest RAP analysis shows a sfc trof draped across the southern UP into northern WI as enhanced conv has kicked off some thunderstorms west of Shawano. MLCAPE across the central UP is around 500-1000J/kg and mostly confined to the central UP with sfc Tds in the low 50s across the interior west. CAMs continue to suggest some thunderstorm development along this sfc trof into the evening hours, before drifting further south out of the cwa by sunset. While a storm could latch on to this boundary, or a subtle lake breeze boundary in Marquette County locally enhancing the shear, bulk shear values remain around 35 knots, which isn`t too conducive for severe storms. While I am not expecting any severe storms this evening, any storms that do develop will have just a slight chance of bcmg feisty. The chance for any storms will wane quickly after 00Z as reinforcing colder air behind a secondary cold front will shift south across the UP. This will bring some light upslope showers and lower clouds across the northern portion of Upper Michigan. By tomorrow morning, daytime heating should lift out these clouds and cut off any remaining showers early on. By the afternoon, stronger low-level lapse rates behind the front will bring a chance for a few diurnal showers across the central interior portions of the UP, but they would be rather transient in nature. Left this chance out of the fcst for now. .LONG TERM...(Sunday night through Saturday) Issued at 300 PM EDT SAT JUL 31 2021 A mostly quiet long-term period is expected. The large scale pattern will initially continue to be dominated by western U.S. ridging and eastern U.S. troughing. However by the middle of next week, a more potent and more equatorward mid-level short wave will move onshore into the West Coast and begin chipping away at the western CONUS ridge. This means a transition to a more zonal pattern across Canada and the northern tier of the CONUS, albeit with weak flow and perforated by multiple short waves in the flow. There is a good model consensus that one of these waves will reach the Upper Great Lakes late Thursday. Its associated cold front may spark off some showers and thunderstorms, although right now the QPF signal in the GEFS and EPS is somewhat muted. The next wave to impact our area looks like it will be the one that began breaking down the amplified pattern over the West Coast. That one should reach the area by next Saturday or Sunday. Although it`s still far out in time, there is decent model consensus on the timing of this wave and front, and a somewhat more robust QPF signal in the ensemble guidance. We`ll start off the week cool with 850 mb temps only around 7-8 C Sunday night and Monday morning. Therefore, look for lows in the 40s interior and 50s along the lakeshores Sunday night. However by Monday afternoon warmer air will be moving in aloft. Therefore, we`ll be in a warming trend Monday through Thursday, with highs in the upper 70s Monday and then in the low 80s Tuesday and mid 80s Wednesday. On Tuesday, the models all suggest enough moisture and instability returning for lake breeze showers and thunderstorms in the afternoon over the central and south central U.P., albeit with northerly shear that is very weak at generally only 15 kts or less. Thursday looks like the warmest day of the week with GEFS and EPS mean 850 mb temps climbing to around 17 C and 15 C, respectively. A southwesterly LLJ out ahead of the wave will make for a breezy day with additional downslope warming in the favored downslope areas and no Lake Superior lake breeze. Look for highs in the mid to perhaps upper 80s. As for precip chances with the front, that remains a question. The 06z and 12z deterministic GFS runs both have precip only making it into the western U.P. before drying up, and the deterministic EC is similarly bearish. With the front in the area, however, it`s probably best to hold onto the chance POPs the NBM populated with. There will hardly be any cooldown behind the front, with temps on Friday still expected to be in the low 80s. On Saturday, as that stronger wave approaches from the west, the LLJ ahead of it will pump moisture northward into the area leading to a hot and sticky feel with highs in the mid 80s and dew points in the low to mid 60s. When the wave and cold front reach the area, most likely Saturday night, that heat and moisture could set the stage for thunderstorms for much of the area. However with it still being 7 days out there`s still plenty of time for things to change, so won`t get too caught up in the details at this point. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 735 PM EDT SAT JUL 31 2021 Mainly VFR conditions will continue though the evening hours. A cold front is passing through the area early this evening accompanied by isolated showers and thunderstorms, mainly south of the TAF sites. By morning upslope flow proceeding the front will result in MVFR CIGs from KSAW to KIWD along with a few showers around KSAW. Ceilings should lift by mid-afternoon with daytime heating tomorrow. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 224 PM EDT SAT JUL 31 2021 Reinforcing colder air behind a cold front tonight will bring an increase in winds from the N to NW across Lake Superior. A few gusts could approach 30 knots across the central portions of the lake, otherwise most locations will see winds gusting around 25 knots. Winds will remain generally light through the rest of the fcst period, with brief SW winds across the west/central approaching 20 knots Monday night. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JAW LONG TERM...RJC AVIATION...NL MARINE...JAW
National Weather Service Morristown TN
944 PM EDT Sat Jul 31 2021 .UPDATE... EVENING UPDATE. && .DISCUSSION... The main change for the update will be to increase PoPs for central areas overnight. A cluster of thunderstorms has developed quickly over northern Middle TN, tracking E-SE. Projecting its speed forward, it should arrive at our Plateau counties around midnight. Although it will be encountering a less favorable environment with lower MUCAPE, the HRRR shows that should hold together enough to warrant high chance to likely PoPs in the 05-11Z time frame. A threat of gusty winds and hail cannot be ruled out due to decent 0-6 km shear, but with low CAPE that threat appears marginal at best. DGS && .AVIATION... 00Z TAF DISCUSSION. Over the next few hours, haze will be an issue at TYS, reducing vis to around 6SM. Later tonight, an area of showers and thunderstorms is expected to move into the area. Best estimate of timing is between 09-15Z at all sites, and will mention as a PROB30 as there is some uncertainty about whether it will hold together or fall apart before arriving. MVFR conditions will accompany storms, and cigs in that range may linger for a few hours after that. VFR conditions should return by the afternoon. DGS && .PREV DISCUSSION... /ISSUED 303 PM EDT Sat Jul 31 2021/ SHORT TERM...(Today through Sunday)... Key Messages: 1. Warm and dry today, with rain chances increasing tonight and on Sunday. Discussion: Deep nwly flow prevails this afternoon across East TN and southwest VA/NC as broad longwave troughing highlights the upper pattern for much of the central/east CONUS, while at the surface and old frontal axis slows/stalls across central AL/GA, stretching westward into West TN and the Lower OH Valley. With that, expected MCS development is underway with convection tracking southeast across the OH River into western KY over the next few hours, which will eventually make its way as a decaying MCS into the TN Valley region overnight. However, today the weather will remain rain free for all areas with the primary highlights being hazy conditions consequent of the fires out west, as well as rather warm temperatures (upper 80s to lower 90s) and mostly full insolation amidst light nwly flow. Moving into tonight, the OH Valley MCS looks to advect southeast across KY into the Middle/East TN after midnight. Guidance favors some MLCAPE in the region (< 750j/kg) along/north of I40 where the bulk of the CAMs take the remnant convection. However, instability will be a bit high in the southern valley/plateau thus any western flanking cells could survive or strengthen as the entire complex dives southward. With that, will keep pops elevated after midnight, highest chances north of 40, yet holding modest chances southward. As for hazards, all in all shear is rather unimpressive (20-25kts 0- 6km) thus not expecting much in the way of organized convection, other than along any cold pool propagation. Still though, won`t rule out a few strong storms with the possibilty of gusty winds and moderate/heavy rain at times. As for Sunday, the day will kick off amidst the approach of a weak frontal boundary from the north and remnant debris cu/stratocu from the overnight convection across the TN Valley. This should slow warming trends a bit into the afternoon hours with highs only topping out in the low/mid 80s northward, upr 80s southward. Meanwhile, broad ascent is favorable as the right entrance region of the H3 jetmax shifts east across the Central Appalachians, which should combine with the aforementioned frontal intrusion to foster additional convection in the afternoon hours, mainly east of interstate 75. Therefore pops reflect such with low chances westward, high chances to low likely pops eastward. As is the case overnight tonight, flow on Sunday will be rather unidirectional through the profile, however slightly stronger. This combined with more favorable diurnal timing suggests the possibility for deeper updrafts, however still thinking widespread organized strong/severe convection chances are low. CDG LONG TERM...(Sunday night through Saturday)... Key Messages: 1. Near to below normal temperatures expected Monday through Thursday with chances of showers and thunderstorms mainly confined to far eastern portions of the forecast area. 2. Slight warming trend Friday and Saturday with temperatures back to near normal. Discussion: Ensemble and deterministic guidance sources are still in great agreement through much of the extended in showing a mid-upper level trough remaining over the eastern CONUS. At the surface, we will be between high pressure to our north and west and lower pressure riding along the gulf coast. We will remain locked in the base of this troughing through the latter portions of the week with several impulses diving out of the midwest reinforcing the cooler weather expected. Lower pressure to the south will generally keep low-level flow out of the north and east through mid/late week keeping low- level temperatures cooler (850mb T`s in the middle teens), translating to high temperatures in the low to mid 80`s. High pressure begins to lift into the Northeast allowing flow to veer toward the south. Increasing thickness in response to warm air advection will begin a slight warming trend on Friday lasting through the weekend with temperatures rebounding to near normal. While the region will remain in the base of deep layer troughing through the period, low pressure to the south and a northerly low- level wind will keep drier air across the area. Precipitation chances will be confined to the eastern portions of the forecast area. Wednesday and Thursday may provide the better chances of coverage of showers and thunderstorms with a stronger impulse moving across the Tennessee Valley. Yet still, the lack of deeper moisture will keep PoPs capped at chance. Diegan && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 73 89 68 86 66 / 50 50 20 20 10 Knoxville McGhee Tyson Airport, TN 69 84 66 86 64 / 60 50 10 10 10 Oak Ridge, TN 69 84 65 84 63 / 60 40 10 10 10 Tri Cities Airport, TN 66 82 61 83 62 / 60 50 10 10 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$
Area Forecast Discussion
National Weather Service Reno NV
126 PM PDT Sat Jul 31 2021 .SYNOPSIS... Daily thunderstorm chances are in the forecast through this weekend with locally heavy rain. Winds generally light across the region, except gusty in and around thunderstorms. A drier southwest flow will bring decreasing storm chances and a return to typical afternoon breezes next week. Other than the milder weather this weekend, temperatures will remain around average. && .SHORT TERM... Some showers and thunderstorms could continue across the Surprise Valley into northwest NV as a weak mid-level trough and weak cyclonic circulation swings into southeast Oregon. The most recent round of GOES-West imagery shows extensive cloud cover north of Lake Tahoe generally moving northward over northeastern CA/northern NV. South of Lake Tahoe a break in the overall cloud cover extends along the central Sierra to another large batch of mid-level monsoonal moisture working its way northwest into the southern Sierra Front from SOCAL/southern NV. The continued moistening of the mid and high-layer regions will maintain PWAT mostly 0.90" to 1.0 plus over the region as storm development takes advantage of local heating and heightened energy. Stronger more moisture laden storms should remain for the most part south of US 50 this afternoon. But this line will advance north to I80 and east to US95 going into the evening as storm cells move off complex terrain of the eastern Sierra into basin areas of western NV. Stronger storm cells capable of much higher rainfall rates sufficient for localized flash flooding could cause debris flows on area burn scars and rock/mud slides in areas of steep terrain. The highest probability for flash floods still appear to be from Mono County to southern Lyon-Mineral Counties, so the current flash flood watch has been expanded to cover the Numbers and Tamarack burn scars in that area. Storm coverage for the northern Sierra (Plumas to Lake Tahoe) and northern Sierra Front should be more isolated as Hi-Res CAM guidance predicts a bit drier-stable conditions in the wake of the mid-level shortwave that just exited to the north into OR. So flood concerns will remain in those southern areas. For Sunday, plenty of moisture remains over the region for storm production with instability enhanced by increased boundary layer heating that partners with the reduction of cloud coverage over the region. Another upper trough digging into the west coast will shoot energy into the increased upper flow and further elevate forcing, instability, and shear over the region. Added to this mix is a weak zephyr churning up to the lee of the Sierra that could enhance low level convergence/focus. These combined elements could produce more robust storm cores capable of strong outflow winds(40+ mph), small hail, and heavier rain rates. As storms initiate along the eastern Sierra in the afternoon, they will push off into the desert basin areas of western NV and continue into the evening. By Monday, other than a slight chance of thunderstorms near the Oregon border and Mono-Mineral Counties in the afternoon, the atmosphere will be much drier and too stable for widespread storms as the upper flow increases from the southwest. A few shallow buildups may occur along a weak zephyr developing later in the afternoon. Monday will be greeted much clearer skies and abundant daytime sunshine. Afternoon temperatures will quickly rebound to more normal summertime heat as the cooler temps this weekend become a brief footnote in history. -Amanda .LONG TERM...Tuesday through Friday. Tuesday will usher in the return of a drier-more stable summer like weather pattern. High pressure up to now mostly centered over the southern Rockies/Four-Corners region will retrograde west and settle over the southwestern deserts (SOCAL/SRN NV/WRN AZ) An upper ridge axis will extend north-south over the Great Region and increase a southwest upper flow over CA-NV. Ensemble model guidance shows this upper pattern persisting into next week as the upper ridge axis tilts more positive in response to a deepening long-wave trough over the eastern Pacific. Monsoonal moisture will once again be confined mostly over the Four-Corners through this forecast period. Except for the eastward directed shot of energy escorted by an upper trough lifting into northern CA and western NV Wed-Thurs, the region should remain mostly dry with near to slightly above average temperatures through the extended period. This will yield more typical summertime temperatures in the mid-90s for the valleys and a return to our typical zephyr wind pattern. But lets talk a bit about the nuisance shot of energy moving across the region mid-week of the extended period. A shortwave trough will approach CA Wednesday and lift northeast across the northern Sierra and northwest NV later that evening. Forecast soundings show little decoupling of the winds with the surface layer going into the overnight hours. Higher elevation areas north of Lake Tahoe across Lassen and Washoe counties could see gusty conditions lasting into the early morning hours Thursday. Higher uncertainty follows this scenario this far out into the extended forecast period. Therefore new fire starts remain a reasonable possibility as elevated fire weather concerns increase by the middle of next week. A more in- depth discussion is included in the Fire WX section. -Amanda && .AVIATION... Showers and thunderstorms will be the primary impact through the weekend as monsoon moisture remains across the Sierra and western Nevada. There will be more cloud cover today as well as showers along with embedded thunderstorms for the afternoon into the evening. Best chances for showers and thunderstorms will be in Mono/Mineral counties (KHTH-KMMH), with a few isolated storms possible in far NW Nevada near the Oregon border. Terminals in far wester Nevada will see a bit of a west wind kick up this afternoon with 15 - 20 kt gusts possible, which may help to limit the potential for showers/thunderstorms, especially at KRNO. For Sunday, clearer skies in the morning along with enhanced mid-level shear could result in a few stronger thunderstorms. Main aviation hazards today will be periods of moderate to heavy rain with reduced CIGS/VIS, terrain obscuration, and gusty erratic winds. For Sunday, the hazards will also include small to moderate sized hail and a higher potential for strong gusty outflow winds. -Edan && .FIRE WEATHER... Thunderstorms with heavy rain and gusty outflow winds for the afternoons and evenings are in the forecast through Sunday. There is still some potential for widespread showers today with minimal lightning activity. HRRR simulations are showing decent potential for thunderstorms to initiate along the Sierra for the afternoon. Areas north of Interstate 80 are still cloud-covered, so convection in those areas may be hard to come by. Areas of most concern will be recent burn scars, especially south of Highway 50. The Tamarack did have some debris flows and runoff yesterday after the heavy rains. As soils become more saturated from rainfall through the weekend, mud and debris may more readily come loose and impact roadways and fire operations. Plan on another round of wet storms for today as well as Sunday, especially from the eastern Sierra into western NV as low pressure nears the California coast. The stable and drier southwest flow will push into western NV and the Sierra late by Monday with our more typical afternoon and evening breezes of 25-30 mph returning to kick off the week. Simulations continue to highlight gusty winds for Wednesday as a low pressure approaches the west coast. Latest simulations continue to highlight the peak ridge winds arriving Wednesday night into early Thursday morning. Plan on breezier than usual conditions starting Wednesday afternoon and persisting into Thursday with the potential for any holdover fires to become active. -Edan && .REV Watches/Warnings/Advisories... NV...Flash Flood Watch until 11 PM PDT this evening NVZ001>003. CA...Flash Flood Watch until 11 PM PDT this evening CAZ072-073. && $$ For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Riverton WY
952 PM MDT Sat Jul 31 2021 .UPDATE... Issued at 816 PM MDT Sat Jul 31 2021 The flash flood watch has been cancelled based on radar trends, and high resolution models showing little if any significant convection over the next few hours. Did have some flooding in the Kemmerer and Diamondville area earlier this evening. && .SHORT TERM...(This evening through Sunday night) Issued at 316 PM MDT Sat Jul 31 2021 Satellite shows the smoke plume that has been over the area for several days to be in a northwest to southeast orientation across the central portions of the state. This should continue to keep hazy conditions across much of the state today. Look for monsoonal moisture to continue for the afternoon with dewpoints into the 50s and 60s. Current radar shows storms focused over southwestern Wyoming, and this is where most lightning will be this afternoon. SPC Mesoanalysis shows an area of 1 inch of PW centered over central portions of the area with the rest of the area from about 0.7 inches to 1 inch. MUCAPE values range in the 400-600 range as of 21z. There is a sharp cutoff over the eastern and northern parts of the state due to drier air entering here. Strong to severe storms with large hail or damaging winds does not look to be an issue as there is very little shear through the atmospheric column. With steering winds being rather light, storms look to be slow moving, making heavy rain and flash flooding the primary concern through this evening, mainly west of the Divide. For tonight storms look to diminish, but the HRRR shows precipitation lingering along the western and southern borders until around 04Z. For tomorrow (Sunday), an elongated ridge axis will be over Wyoming. This allows for southerly winds to transport monsoonal moisture to areas west of the Divide. Far southwestern Wyoming and the Salt and Wyoming Ranges appear to be the locations most likely to receive additional rain with afternoon thunderstorms. Areas east of the Divide should be significantly drier. Dewpoints are expected to be about 10 degrees lower than yesterday for much of the area with readings in the upper 30s for the central basins to lower 50s in western valleys. The combination of the lower dewpoints and drier air should aid in bringing temperatures up a few degrees tomorrow afternoon. .LONG TERM...(Monday through Saturday) Issued at 316 PM MDT Sat Jul 31 2021 An amplified but narrow longwave ridge sits over the Intermountain West Monday. Within this larger feature a shortwave trough is expected to slide eastward through the ridge, with its axis remaining west of Wyoming. Models have been consistent in depicting this feature over the past several runs. Lift from this mesoscale feature aids in shower and afternoon thunderstorm development over and near the terrain features on the western edge of the state. The drier air in place east of the Divide allows high temperatures to increase to near seasonal normals. On Tuesday the slow-moving shortwave moves far enough east to encourage afternoon convective development east of the Divide. More widespread clouds, showers, and thunderstorms are forecast Tuesday afternoon, and this will keep highs 5 to 8 degrees below average. Surface winds remain light, but in the vicinity of thunderstorms gusts 30 to 40 mph are still possible. A drier period begins Wednesday as the upper level ridge reasserts itself. Heights rise and monsoonal moisture is shunted off to the southeast. After the cooler Tuesday, Wednesday afternoon highs again rise to near normal. A well-defined shortwave trough pushes into the western CONUS Thursday into Friday, and forcing from this wave puts scattered afternoon thunderstorms in the forecast again. In addition to storms, the pressure gradient will tighten ahead of the cold front associated with this wave, so expect breezier conditions for the end of the workweek. && .AVIATION...06Z Issuance Showers and thunderstorms should end overnight. VFR conditions should prevail for the most part through the period. With monsoonal moisture retreating to the west chances of showers and thunderstorms should be confined to the western TAF sites, especially KJAC. However, even here coverage will be much more isolated then the past couple of days. There is a chance that VCFG may form in areas that saw rain, but not enough confidence to include in the forecast. && .FIRE WEATHER... Issued AT 1145 AM MDT Sat Jul 31 2021 Monsoonal moisture is expected to be over the area today, but showers and thunderstorms do not look to be as widespread as recent days, mainly staying west of the Divide. The best possibility for precipitation tomorrow (Sunday) is also west of the Divide. Shower and thunderstorm chances increase area-wide Monday as a weak weather system moves through. Relative humidity levels are expected to stay well above critical thresholds throughout early next week. Today looks to have the highest values due to high dew points in the surface layer. For tomorrow, humidity is highest west of the Divide. Winds look to stay mainly under 10 to 15 mph through early next week, with higher gusts of 25 to 35 mph near showers or thunderstorms. && .RIW WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...Murrell SHORT TERM...Clayton LONG TERM...VandenBoogart AVIATION...Hattings FIRE WEATHER...Clayton
Area Forecast Discussion
National Weather Service Blacksburg VA
1102 PM EDT Sat Jul 31 2021 .SYNOPSIS... Low pressure and a wavy cold front will remain over the Carolinas through Sunday leading to showers and thunderstorms for the region late tonight and Sunday morning. After a dry day on Monday, rain returns Tuesday along with cooler temperatures as the front stalls from eastern Virginia through Georgia. && .NEAR TERM /THROUGH SUNDAY/... As of 1100 PM EDT Saturday... ...Limited Threat for Showers/Thunderstorms Late Tonight/Early Sunday, Otherwise Chance for Showers Tonight/Sunday... Made some more adjustments to the pops overnight to reflect current and model trends. HRRR seems to be doing better than NAMNest at the current time, but trended more toward NAMNest later tonight. SPC has removed the severe threat from all except the extreme eastern parts of the CWA and shifted the general thunder mainly east of a LYH-DAN line as well. I am in agreement with this. As noted earlier, think main threat for thunder/severe is east of our CWA closer to the I-95 corridor. Earlier Near Term Discussion from 750 PM EDT... What is left of an MCS earlier in KY is nothing now but an area of mid/high clouds and a few sprinkles/light showers tracking across the northern parts of our CWA and expanding into central/northern VA. P6SM -RA noted at LWB and here at our office BCB/RNK within the last few hours. Removed thunder from grids for this evening as the air mass is very stable and latest analysis shows very limited CAPE and downslope westerly winds across the region this evening. Extensive mid/high clouds from dissipating MCS have left the CWA with even more stable conditions and little to no CU observed across the region this evening. For the overnight hours, personally am not impressed with the threat for severe weather in our CWA. With the exception of the NAMNest, significant convection developing late tonight/early Sunday generally starts up after 12Z and is just east of our CWA. Granted helicity/shear is impressive for August 1st, but timing is very poor and CAPE is little to none at that hour absent of a low level jet, which is not evident in the wind field at all. In low-level winds are either light and variable or southwest to west, not favorable at all. It is noted that the NAMNest wants to develop stronger convection further west in the 08Z-12Z time frame and often this model is correct, so will need to watch, but leaning toward the less agressive solutions of the other models at this point given the lack of instability and low-level wind field as noted above. Severe threat ramps up quickly toward the I-95 corridor during the late morning/early afternoon so there will likely be severe weather in those areas and as noted a threat for a tornado or two there, but again this should in all probability remain east of the RNK CWA. By afternoon, we are left with downslope/increasing westerly flow and little to no precipitation. Previous Near Term Discussion... As of 230 PM EDT Saturday Potential for severe thunderstorms in the far east late tonight/early Sunday morning Mid level speed max helping to spawn showers and thunderstorms across the Ohio Valley is expected to drift across our forecast area late tonight, increasing the upper level divergence over the region. Meanwhile at the surface, surface winds across the VA/NC Piedmonts have veered to the east/northeast and already starting to note an increase in dew points in this area. The short range deterministic models are in relatively good agreement that a wave of low pressure along the frontal boundary to our south lifts northeast across southeast VA between 09z-12Z Sunday morning. This helps push higher CAPE values into far southeastern portion of our forecast area, and with sfc winds from the southeast in advance of this feature, SREF output is showing over 70% chance of 0-1KM SR Helicity values exceeding 100 m/s2. All of this suggests the potential for damaging winds and even isolated tornadoes in the far east late tonight and the HWO was updated to reflect this. Otherwise, leaned toward the warmer guidance for lows tonight with the increased cloud cover. On Sunday, we transition to a deep west/northwest flow and early in the day the best conditions for severe weather shift east of our area. Upslope clouds will linger across the western slopes, but skies should clear along and east of the Blue Ridge and as a result, pushed up highs a couple of degrees on Sunday. Some widely scattered showers and isolated thunderstorms are still possible with height falls, with the highest POPS placed in the south, closer to the stalled sfc front. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 200 PM EDT Saturday... Cooler Than Normal Temps With Best Shower Threat Tuesday... Models showing the front pushing southward Sunday night with things drying out. Could see some lingering showers across the mountains early Sunday evening. High pressure at the surface builds east across the Mid-Atlantic by Tuesday, while upper trough deepens. Another wave across the South moves along the front Tuesday, and with upper trough sharpening, moisture looks to build back north. Latest models showing a slower trend to ramping pops up til Tuesday, but even then models are in different camps on higher pop placement. The 12z GFS is keeping deeper moisture south across southern and eastern Carolinas, and the NAM is not too far off on this solution but shows a better low level convergence axis over the mountains south of WV. The 00z Euro has a moisture convergent axis extending across southside VA into the Alleghanys, then all models pivot the best threat over the southern and central Appalachians and eastern NC in the afternoon. Have decided to curtail pops a bit, and lowered them to low likely Tuesday afternoon over the far SW CWA with chance pops elsewhere. Confidence is not high enough on where the higher pops will be. Thinking more cloud cover will keep temps a little cooler Tuesday, so kept close to the previous forecast thinking with highs running about 10 degrees below normal. This should limit thunderstorm activity, and not expecting any severe weather this period. Once wave accelerates east late Tuesday should see decreasing pops. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 1224 PM EDT Saturday... Daily Threat of Showers/Storms But Not Widespread... Keeping chance of showers/storms through the period as upper trough cannot move east far enough due to a strong ridge in the western Atlantic. Appears the best zone for convection will stay southeast of us along a front, but southwest flow at the mid levels should allow for moisture to remain around, and with any subtle shortwaves a daily threat for showers and storms will occur. Did cut back on the what National Blend of Models had, and went with a more diurnal max/min for pops with highest chances in the afternoon/lowest in the mornings. The synoptic models are in similar camps to this idea, so overall pops will be less than 50 percent, with lower coverage/driest days looking like Thu-Fri. Temperatures through the period should be just below normal, but heights rising toward Saturday should push temps back to normal, with above normal lows given moisture in the low levels. Forecast confidence in the overall pattern is high, but in where it rains is low. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... As of 755 PM EDT Saturday... VFR Conditions Expected Through Most of the TAF Valid Period... Limited Threat for Showers/Thunderstorms Late Tonight/Sunday Morning... Extensive mid/high clouds spreading across the CWA at this hour from a dissipating MCS that was in KY earlier today. Nothing left of this MCS but BKN-OVC clouds with ceilings in the 080-150 range and a few sprinkles generally north of U.S. 460. VFR conditions should continue throughout the evening at all TAF sites. Low-level air mass is marginally moist with dewpoints mostly in the upper 50s to lower 60s. Fog will not be an issue this evening. Overnight, a strong short wave will round the base of a deepening eastern U.S. trough. Timing of this system brings it through the CWA in the 07Z-15Z time frame from west to east. Scattered showers will likely accompany the trough, but limited deep moisture, downslope westerly flow ahead of and behind the trough, and best dynamics remaining just east of the CWA do not support widespread/definite SHRA/TSRA at the TAF sites at this point. Will readdress later, but for now have only indicated VCSH for LWB and BLF. As noted in the near term section above, threat for thunderstorms and severe weather further east in our CWA late tonight/early Sunday appears limited and have removed mention of VCTS in the LYH and DAN TAFs. Not enough confidence for such at 07-09Z in the morning to include at this point. Will monitor closely for amendments as needed, but main threat for TSRA should be further east toward a DCA-RIC-RDU line. Once the trough moves through, look for west to west-northwest winds at speeds of 6-12kts with low end gusts to 20kts west of the Blue Ridge after daybreak Sunday. SCT-BKN CU/SC in the 030-040 range will likely persist, especially west of the Blue Ridge until at least mid-afternoon Sunday. /Confidence Levels in Forecast Parameters/ - Moderate to High Confidence in Ceilings, - High Confidence in Visibilities, - Moderate to High Confidence in Wind Direction and Speed, - Low Confidence in Thunderstorm Potential. Extended Aviation Discussion... A secondary frontal; system arrives Sunday evening/night, bringing a period of sub-VFR conditions mainly to western areas. Monday will be dry with mostly VFR conditions. During the remainder of the week, the region becomes sandwiched between a plume of tropical moisture anchored just to our east and along the coastal areas and a broad upper trough just to our west. The result for our region will be unsettled conditions with scattered largely diurnally driven showers and thunderstorms increasing through midweek, decreasing somewhat by next weekend. Periods of sub-VFR conditions can be expected and late night/early morning fog will be on the increase as well. However, there will still be substantial periods during the daytime of VFR conditions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS/WP NEAR TERM...PH/RAB SHORT TERM...WP LONG TERM...WP AVIATION...RAB
Area Forecast Discussion
National Weather Service San Angelo TX
657 PM CDT Sat Jul 31 2021 ...New AVIATION... .SHORT TERM... (This evening through Sunday) Issued at 201 PM CDT Sat Jul 31 2021 At this hour, West Central Texas remains under an upper level ridge, providing one last opportunity for relatively benign weather this afternoon. Overnight, skies should remain clear with low temperatures only in the mid 70s. By tomorrow morning, a shortwave trough will rotate southward around the base of the main trough over the Great Lakes. This should help to push a surface cold front into our region by midday. While a few small showers are possible across the Big Country in the morning, it appears the cap will erode by early afternoon. This, along with some help from upper-level dynamics moving into the area, should help to ignite more widespread thunderstorms by late afternoon to early evening, which is supported by both the HRRR and the NAMNest models. The main hazards for this activity will be heavy rainfall and frequent lightning. Otherwise, clouds should increase by early afternoon, with high temperatures generally reaching the upper 80s to low 90s. && .LONG TERM... (Sunday night through next Saturday) Issued at 245 PM CDT Sat Jul 31 2021 The upper level ridge which breaks down over our area will redevelop over the southwestern CONUS in the first half of next week. An upper trough will deepen over much of the eastern half of the country. Associated cold front will continue to sag south across our area Sunday night into Monday. Showers and thunderstorms will be likely along and behind this front, with the more conentrated convective activity closer to the front. With weak steering flow and a moist airmass (precipitable water values 1.5 to 2 inches), heavy rainfall will be possible with a threat for localized ponding of water on roads/minor flooding. With increased cloud cover, temperatures will be cooler Monday with highs expected to be in the mid to upper 80s in most areas. For Tuesday into Wednesday, the higher rain chances will be across the southern part of our area along the I-10 corridor. That area will be closer to a diffuse leftover surface boundary. Diurnally driven isolated or widely scattered showers and thunderstorms will be possible farther north across the central part of our area and south of I-20. Daytime temperatures look to remain below normal with highs Tuesday through Thursday in the upper 80s to lower 90s. A weakness in the height field aloft will remain over our area late in the week. Should have a continued possibility for isolated to scattered diurnally driven showers and thunderstorms, over the area mainly south of I-20. Indications are for temperatures to increase by Friday and Saturday, with highs back into the 90s. && .AVIATION... (00Z TAFS) Issued at 634 PM CDT Sat Jul 31 2021 VFR conditions will continue this evening and overnight across the terminals. A cold front will move into the area on Sunday. Showers and thunderstorms are possible along the front especially after 18Z. Have added VCTS to the TAFS to account for this possibility. && .PRELIMINARY POINT TEMPS/POPS... Abilene 77 90 70 88 / 10 60 70 50 San Angelo 75 95 70 87 / 10 60 70 60 Junction 74 96 71 90 / 5 60 60 70 Brownwood 75 95 71 89 / 5 60 70 60 Sweetwater 75 89 69 86 / 10 60 70 50 Ozona 75 94 71 86 / 5 60 60 60 && .SJT WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...SK LONG TERM....19 AVIATION...42
Area Forecast Discussion
National Weather Service Tucson AZ
227 PM MST Sat Jul 31 2021 .SYNOPSIS...Isolated to scattered showers and thunderstorms continue into this evening. The overall trend in thunderstorm coverage will be less for most of next week and focused south and east of Tucson. High temperatures will trend up to near or slightly above normal by midweek. Better coverage of showers and thunderstorms is possible by next weekend. && .DISCUSSION...A few showers and thunderstorms have managed to develop across the area early this afternoon, mainly over the higher terrain. Some of the cu field, however, looks to be struggling for any meaningful vertical development. This could be due to some weaker mid-level lapse rates as noted via the SPC Mesoanalysis. Otherwise, there seems to be plenty of instability to work with, as SBCAPE values are in excess of 1500 J/kg for most of the area. What seems to be generating these values are temperatures within a degree or two compared to this time Friday, and dewpoints 2-6 degrees higher. Satellite PWAT estimates continue to be sufficient, on the order of 1.2" near the AZ/NM border up to around 1.8" across western Pima and Pinal Counties. The storms that have formed are not moving very quickly due to weak steering flow, and anvils seemed to be getting sheared off above H3. Convection should increase slightly through the afternoon, though the latest HRRR run isn`t terribly excited and the U of A WRFs keep activity mainly east of Tucson. However the NAMNest and other HREF members are a bit more robust with precip continuing through the evening and ending by about 01/03Z or 04Z. Threats remain the same as they have in the past several days, with pockets of heavy rainfall and gusty erratic winds associated with the strongest storms. Additionally, the threat for flash flooding remains due to soil saturation, so expect washes to be quick to react under the heavier cores. For Sunday, the upper ridge slides eastward a bit shunting moisture into NM, resulting in thunderstorms remaining east of Tucson and over the higher terrain. To start the new work week, high pressure tries to establish itself to our south, gradually building and migrating north/northwest through mid-week. We`ll see an increase in daytime temperatures as this occurs, with the low-grade monsoon conditions continuing. Later in the week into next weekend, there is fairly good deterministic and ensemble model agreement that high pressure reorients itself near the Four Corners as low pressure rides over the top through the northern tier of the CONUS. Look for deeper easterly flow to return to southeast AZ, and with it an uptick in shower and thunderstorm coverage as our above-average monsoon season continues. && .AVIATION...Valid through 02/00Z. SCT clouds at 8k-12k ft MSL (locally BKN) and SCT-BKN clouds AOA 18k ft MSL thru 01/05Z, then decreasing clouds. FEW-SCT clouds at 9k-13k ft MSL developing aft 01/17Z thru the end of the forecast period. ISOLD-SCT SHRA/TSRA thru 01/05Z and then again aft 01/19Z. Strong, gusty and erratic wind gusts with TSRA to 40 kts, heavy downpours, and temporary MVFR CIGS/VSBYS. Outside of TSRA outflows, SFC wind will generally remain less than 12 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Isolated to scattered showers and thunderstorms are expected through Sunday, with a downward trend in storm activity Monday through Wednesday when storm chances will mainly be east of Tucson. An upswing in thunderstorm activity is expected going into next weekend. Any thunderstorms that develop will be capable of producing strong, gusty and erratic winds along with locally heavy rainfall. RH values will remain well above critical thresholds the next 7 days. After today, temperatures will be near normal through at least Thursday. 20-foot winds will generally be less than 15 mph when not influenced by thunderstorms. && .TWC WATCHES/WARNINGS/ADVISORIES...None && $$ Carpenter/Zell Visit us on Facebook...Twitter...YouTube...and at
Area Forecast Discussion
National Weather Service Las Vegas NV
1215 PM PDT Sat Jul 31 2021 .SYNOPSIS...Another round of thunderstorms in a high monsoonal moisture environment is expected today, with a Flash Flood Watch still in effect for much of the region through Sunday morning. After another round of thunderstorms over eastern areas of the region on Sunday, drier conditions are expected to move in the beginning of next week and result in several days of drier and warmer conditions through the week. && .SHORT TERM...Today and Tomorrow. Convection has begun a little earlier today compared to yesterday due to better morning clearing and extra support from a northward progressing shortwave disturbance, both at the meso and synoptic scales. This morning`s showers may have played a role in both moistening and providing mid level vorticity to help kick things off this morning as opposed to early in the afternoon. Additionally, some UL divergence over the northern 2/3 of the CWA is kicking in some lifting as well. This feature pushes north through the day with an increasing UL jet positioned over the CO River Valley leaving the region in a favorable location for UL support throughout the rest of the day. Combine this added lifting feature with the very moist environment still in place, topographic lifting, and thin but deep instability, and another day of flash flooding continues for most areas. 12Z HREF and latest runs of the HRRR show this activity waning by nightfall, similar to the last several days of convection. Not sure if this will indeed be the case with the aforementioned lifting still in place by this evening, but we will indeed lose diurnal heating and instability. Additionally, we will begin the downward motion of PWAT as the Pacific shortwave comes onshore and advects mid and upper level dry air into the western zones. As previously mentioned, tomorrow will indeed see lesser overall coverage of storms, favoring the eastern-most zones and areas, but where enough moisture lingers for CI tomorrow, the added mid-level dry air and cooling should enhance lapse rates, mid level dry air entrainment into whatever updrafts develop, and more potential for stronger downdrafts, maybe even hail. While the flash flood threat stays more isolated in nature. Main areas of concern for these threats will be along and east of a line from Hiko, NV to Wikieup, AZ or mainly east of the HWY 93 corridor. .LONG TERM...Next Week. Not much change in the long term expectations. A lull in monsoonal moisture is expected for much of the week and only a meager return in PWAT values is expected by late week and the weekend. That being said, trends continue to be on the drier side in the long range ensembles and NBM as PoPs have decreased for Mohave county and are now nil for the rest of the CWA over the weekend. Yesterday, cluster analysis hinted at this possibility and looks like confidence is gradually increasing that a more significant return of monsoonal moisture may not occur over the next 8-14 days. CPC forecasts indicate a slight favoring for below average precip during this time frame as well. What this drier forecast means is an uptick in potential high temperatures and as such, heat risk values indeed increase mid week briefly before moderating by late week. So above average temperatures look to be the main story impact wise through next week and possibly into the weekend should the drier forecast prevail. && .AVIATION...For McCarran...SCT-BKN clouds mainly above 10kft AGL are expected through the morning hours with thunderstorm activity on the increase in the afternoon hours. Storms in the airport vicinity can be expected mainly after 19z, with gusty and erratic winds likely and brief heavy rainfall possible along with locally reduced CIGS to near 8kft. Storm activity will gradually wane in the evening hours with sct-bkn clouds lingering near 10kft AGL. For the rest of southern Nevada, northwest Arizona and southeast California...A few light morning showers can be expected across the Mojave Desert with bkn-ovc skies around 10kft AGL near KDAG and KEED through around 18z. Scattered thunderstorm activity will be on the increase in the afternoon with storms first favoring the higher terrain then gradually drifting into the adjacent valleys. Pockets of sudden convective turbulence are likely along with locally gusty surface winds. Storms will wane in the evening with SCT-BKN clouds lingering between 8-12kft AGL.&& .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSIONS...TB3 AVIATION...Outler For more forecast information...see us on our webpage: or follow us on Facebook and Twitter