Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/12/21

National Weather Service Wakefield VA
741 PM EDT Tue May 11 2021 .SYNOPSIS... A weak front drops across the region tonight. High pressure builds north of the region through low pressure tracks across the southeast states. High pressure builds over the area Thursday. && .NEAR TERM /THROUGH WEDNESDAY/... As of 740 PM EDT Tuesday... Weak cold front continues to make southward progress this evening. Radar has been rather quiet for our area so far but CAM guidance continues to show the potential for light showers along and ahead of the frontal boundary. Clouds are increasing across the north early this evening. Increasing clouds trend continues tonight, as weak front drops across the local area. HRRR time-lagged/ARW is showing about the worst case scenario of some isolated to widely sct showers dropping (mainly) across the northern neck and eastern shore through the course of this evening. Cannot rule out a quick sprinkle most anywhere over the area this evening, so will throw in a slight chc PoP for most zones north of the NC/VA border by midnight. Temps look to drop off quickly initially, but stabilize with increasing cloud cover late and overnight. Lows in the low to mid 40s NW...mid 40s to near 50 central VA/MD eastern shore and upper 40s to low 50s Hampton Roads/NE NC and VA eastern shore. && .SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 225 PM EDT Tuesday... Cool (modifying) Canadian high pressure builds across the region from the Ohio Valley on Wed, as several weak shortwaves track along the slow moving frontal boundary along and south of our southern CWA. Mostly cloudy/overcast to start the day, with some light overrunning rainfall over the US-58 corridor along and south of the VA/NC border. Overrunning light rain overspreads the southern one-third of the area tomorrow morning, as slow clearing ensues across the north. There will be a gradual trend toward clearing for central and southern tier of counties from midday into the afternoon. Cool again w/ NNE winds and highs from the l-m60s N to the u50s- l60s S. High pressure continues to build into the area Wed night-Thu, and will result in a clearing sky and cool/dry wx. Meanwhile, weak low pressure will move along the stalled front across the Gulf coast region. Early morning lows Thu morning in the l-m40s u40s- around 50F right along the coast. Mainly sunny Thu w/ highs from the m60s to around 70F. Lows Thu night/Friday in the l-m 40s inland, upper 40s to low 50s along the coast. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 200 PM EDT Tuesday... Aforementioned low pressure crossing the deep south toward the SE coast will bring some lingering clouds, especially central and south to begin the day on Friday, and ECMWF does paint in some low QPF...but with the remainder of guidance and NBM nearly dry will keep PoP in silent range for now. Sfc high then builds over the region late Fri through this weekend, eventually sliding offshore into early next weekend. This should translate to slowly moderating temperatures throughout the medium range forecast period. Friday`s highs start out in the upper 60s to lower 70s and by the time we reach the weekend, highs will be in the mid to upper 70s. Early morning low temperatures start out in the upper 40s to lower 50s over the weekend, and then lower to mid 50s as we turn to early next week. Looking ahead, strengthening Bermuda high looks to portend a continuation of the warming trend into the middle of next week, with more typical diurnally-driven convection by the middle of next week. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 740 PM EDT Tuesday... Weak cold front is still progged to drop south this evening and tonight with at least some potential for light showers along and ahead of the front. Clouds are increasing across the northern terminals and these clouds will filter southward with time tonight into Wednesday. Left VCSH at SBY tonight where confidence in seeing some showers is highest. Winds are generally from the south or west ahead of the front but will quickly swing around to the north behind the boundary. Will show northerly winds increasing to ~10 kt with gusts 15-20 kt for a period overnight. Clouds hang on across the south for at least the first half of the daylight hours across the southern terminals with more clearing expected for the northern half of the area. Outlook: Expecting mostly VFR conditions Wednesday into the late week period. Northerly flow continues through Thursday before high pressure builds near the region. && .MARINE... As of 230 PM EDT Tuesday... Front is well south of the area this afternoon with weak surface high pressure right off the coast. Calm marine conditions currently with a light onshore flow. Waves in the bay around a foot and seas 2- 3 ft. A weak boundary moves across the area late tonight and strong high pressure builds in from the NW. Winds become northerly and increase to 15-25 kts with gusts around 30 kts over the Bay, rivers, southern coastal waters, and Currituck Sound. SCA`s go into effect late tonight for these areas and run through Wednesday morning. Winds in the middle and northern coastal waters are expected to remain below SCA criteria. There may be a narrow window of 2-3 hours early Wednesday morning where wind gusts approach 25 kts, but can more than likely be handled with a Marine Wx Statement rather than a SCA. Waves in the bay and seas will increase to 2-4 ft overnight, with some 5 ft seas possible over the southern coastal waters. Winds diminish to 5-15 kts by Wednesday afternoon along with waves subsiding to 1-2 ft and seas 2-3 ft as the pressure gradient relaxes. High pressure and sub-SCA conditions expected from Wednesday afternoon through the remainder of the week and the weekend. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 1 AM to 10 AM EDT Wednesday for ANZ632-634-636>638-658. Small Craft Advisory until 10 AM EDT Wednesday for ANZ630-631- 635. Small Craft Advisory from 1 AM to 1 PM EDT Wednesday for ANZ633. Small Craft Advisory from 1 AM to 7 AM EDT Wednesday for ANZ656. && $$ SYNOPSIS...MAM NEAR TERM...MAM/RHR SHORT TERM...ALB/MAM LONG TERM...MAM AVIATION...MAM/RHR MARINE...CMF
National Weather Service Albany NY
921 PM EDT Tue May 11 2021 .SYNOPSIS... After a chilly and breezy day with hit and miss showers, chances for showers increase later tonight, especially in the higher terrain where rain may even change to snow showers in parts of the Adirondacks and southern Greens. The cool and breezy conditions continue tomorrow with additional scattered showers possible, especially in southern Vermont. High pressure builds in for Thursday providing us with plenty of sunshine and warmer weather. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... UPDATE...00Z sounding was well mixed this evening which kept the wind speeds up through this early evening. A few showers extending from central New York was attempting to make it into the Schoharie Valley. Otherwise, south of the Dacks, skies are mainly clear. This should aid with the boundary layer to decouple before the approach of the upstream cold front. Regional radar depicts the leading edge of the precipitation was dissipating, likely thanks to the dry column per our 00Z sounding. However, trends toward a more moist environment should commence overnight as the threat of showers increases with the frontal movement from the north overnight. As temperatures are rather cool already across the higher terrain per the NY Mesonet, the rain/snow mixture still looks good at this time. So main update was to sky coverage and tweaks to the PoP/Wx grids. Overnight lows look good at the moment and closely resembles the LAV/LAMP guidance. Prev Disc...Once we past peak heating and approach sunset, convectively driven clouds should dissipate and we could see a few hours this evening with mainly clear skies. However, our main trough axis, as depicted on the latest GOES16 water vapor imagery, will swing southeastward from Ontario into the Northeast tonight with cloud coverage and showers increasing in response to the enhance mid- level convergence overlapped with sufficient moisture. Latest high res NAM and HRRR both suggest that the higher terrain areas in the southern Adirondacks, Taconics, southern Greens and Berkshires will likely have the greatest potential of experiencing a period of showers tonight, mainly after 03 UTC through 12 UTC, due to enhanced orographic lift within the continued northwest flow regime. Even still, overall precipitation amounts should only range from a few hundredths up to a tenth of an inch. The trough axis will also enhance cold air advection and temperature profiles in the higher terrain areas look to cool enough to support a mix with or even brief changeover to snow showers. Total accumulations will be minimal and reserved to the higher peaks of the southern Adirondacks and southern Greens less than 1 inch. Otherwise, temperatures tonight fall to mid to upper 30s with low 30s in the higher terrain. Increasing clouds overnight and breezy winds will likely mitigate any frost formation. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Breezy west - northwest flow continues tomorrow in the wake of the trough axis so temperatures will once again be cooler than normal. However, a closed high in the Midwest will be building eastward and northwest flow actually will start to advect in warmer air that will rotating around the periphery of the high. Therefore, temperatures should be a bit milder tomorrow compared to today with highs in the upper 50s to low 60s. Despite strong area of high pressure upstream, we will still will be under the influence of the broad trough which will be gradually exiting in the Canadian Maritimes. Therefore, still expecting partly to mostly sunny morning skies to mix with afternoon clouds as we reach our convective temperature. In addition, high res guidance continues to suggest that some scattered showers develop in response to a secondary trough axis swinging through northern New England but these showers look to impacts areas mainly north/east of Albany including Lake George, Washington County, the northern Taconics, and southern Vermont. BUFKIT profiles show mid-level lapse rates steepen ahead of the approaching trough with some weak instability developing (MUCAPE < 250 J/kg). Therefore, we followed suite with WFO Boston and added in isolated thunderstorms possible for these areas. Skies clear Wednesday night as upstream high pressure gradually builds eastward, allowing the pressure gradient to relax. Winds after midnight should weaken below 5 kts which should promote radiational cooling. With temperatures falling into the low to mid 30s in the higher terrain areas of the southern Adirondacks, eastern Catskills, southern Greens, Taconics and Helderbergs, we introduced patchy frost to the forecast. If confidence increases that frost will develop in areas where the growing season has started, we will issue a frost advisory. Our Hazardous Weather Outlook continues to discuss this potential. Thursday will be a beautiful day. Temperatures finally warm into the mid to upper 60s under plenty of sunshine as the strong area of high pressure upstream continues to track eastward towards our area. Northwest winds will also be lighter, sustained generally only between 5 and 10 kts. Mostly clear skies stay in place overnight as high pressure moves overhead resulting in a seasonably chilly night. Overnight lows drop into the low to mid 40s. && .LONG TERM /FRIDAY THROUGH TUESDAY/... A broad, but weak upper level trough will be located over the region for Friday into the weekend. Although forcing will be somewhat limited, there will be a threat for showers each day, mainly during the afternoon and early evening hours. Activity looks fairly scattered in coverage, so not all locations will see rainfall. There may be some minor amounts of instability in place, so can`t rule out a few rumbles of thunder, but coverage looks too low to include this far out. With a partly to mostly cloudy sky in place, daytime temps should reach near 70 for Friday through Sunday in valley areas. High terrain areas look to reach the low to mid 60s. Overnight lows should mainly be in the 40s, so no threat for any frost/freeze conditions at this time. For early next week, there may be a brief period of some ridging for Sunday night into Monday before the next system approach form the Midwest. The timing/exact track of this next storm is still uncertain, but a period of rain or widespread showers is possible closer to mid-week. Temps will continue to be close to seasonal normals for mid May. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... Clouds are dissipating this evening with the loss of diurnal heating, but they will expand into the area again from north to south at and shortly after midnight as another disturbance rotates in from the north. VFR to high end MVFR levels for a time roughly 09-13Z (slightly longer at KPSF with upslope conditions). A couple of showers cannot be ruled out either as we will place VCSH for KGFL-KPSF-KALB. Cloud bases will rise again to VFR levels after 13-14Z as diurnal heating commences, with SCT-BKN coverage returning once again. Winds will remain around 10 kt tonight from the west-northwest. Winds will shift more to the north/northwest after sunrise Wednesday at around 10-15 kts with gusts near 20kts. Outlook... Tuesday Night: Low Operational Impact. NO SIG WX. Wednesday: Low Operational Impact. Breezy. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: Moderate Operational Impact. Scattered SHRA. Friday Night: No Operational Impact. NO SIG WX. Saturday: Moderate Operational Impact. Scattered SHRA. && .FIRE WEATHER... West to northwest winds will gust to around 25 mph tomorrow... After a chilly and breezy day with hit and miss showers, chances for showers increase later tonight, especially in the higher terrain where rain may even change to snow showers in parts of the Adirondacks and southern Greens. The cool and breezy conditions continue tomorrow with additional scattered showers possible, especially in southern Vermont. High pressure builds in for Thursday providing us with plenty of sunshine and warmer weather. Maximum relative humidity values tonight rise to 80 to 100 percent. Then, relative humidity values drop tomorrow afternoon to a minimum between 35 to 50 percent. Overnight maximum relative humidity values Wednesday night then reach to 85 to 100 percent. Winds tomorrow will be west-northwest once again and rise to 8 to 18 mph with gusts up to 25 mph. Winds then gradually weaken Thursday night and drop below 5 kts. && .HYDROLOGY... Without any appreciable rainfall expected through the end of the work week, river levels are expected to remain steady or gradually fall. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Speciale NEAR TERM...BGM/Speciale SHORT TERM...Speciale LONG TERM...Frugis AVIATION...BGM/Thompson FIRE WEATHER...Speciale HYDROLOGY...Speciale
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
654 PM CDT Tue May 11 2021 .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION...The conv coverage to the north of the RGV is on the increase as the cold front continues sagging southwards toward the region. The latest CAMS guidance continues to crank up the conv over the western counties several hours from now with this conv complex pushing SE through the RGV as the cold front moves slowly into the region increasing the surface convergence. SPC is maintaining a slgt risk for svr conv throughout the night into Wed morning and will continue to reflect this in the 00Z TAF issuance for the RGV. Although the next few hours will likely see VFR conditions prevailing for the area, the aviation conditions will degrade pretty steadily later tonight through Wed morning as the conv moves into the region. Expect MVFR conditions to prevail later tonight with periods of IFR conditions as the stronger conv moves closer to the RGV airports. && .PREV DISCUSSION... /issued 239 PM CDT Tue May 11 2021/ SHORT TERM (Now through Wednesday Night): Heres what we know. There will be a cold front dropping into the CWFA overnight tonight, which will likely bring strong to severe thunderstorms and subsequent beneficial rainfall for much of the area through Wednesday evening. The strongest storms will be capable of producing strong to severe wind gusts, severe hail, as well as torrential rainfall and gusty winds. Most of that stronger activity should clear the area by Wednesday afternoon with any lingering precipitation coming in the form of showers, with perhaps a rumble of thunder or two through Wednesday evening. The shower and storm activity expected through the short term will ultimately keep high temperatures Wednesday afternoon and low temperatures late Wednesday night several degrees below seasonal normals. Heres what we are still pinning down. The timing/onset of convection in the BRO CWFA continues to be a source of uncertainty that is causing this forecaster to have a less than ideal time. Storms could potentially enter the northern edge of Zapata and Jim Hogg counties as early as 9-10 PM per latest HRRR and GFS guidance, around midnight per the NAM 3km and ECMWF solutions, or some time closer to 4-5 AM per the NAM 12km solution. Have targeted the later solutions for this forecast package given recent performances between the models. Regardless, a nocturnal convection event appears likely, which will then spill over into a more prolonged rain event for Wednesday. Pay close attention to updates from your friendly neighborhood Warning and Forecast Office this evening! LONG TERM (Thursday through Tuesday): Rain chances will diminish across deep south Texas Thursday into Thurs night as drier air filters into south Texas in the wake of the 500mb trough across the east-central United States moving eastward. Isolated showers and thunderstorms are progged to develop across portions of the Rio Grande Valley Friday as a weak disturbance in the westerly flow aloft approaches the CWA from the west Fri afternoon. A better chance of showers and thunderstorms is expected across the Rio Grande Valley and northern ranchlands on Saturday as a 500mb shortwave trough across southwest Texas moves eastward and low to mid level moisture increases ahead of the upper level feature. Rain chances are expected to linger through the rest of the weekend before a 500mb shortwave ridge develops across southwest Texas Monday providing subsidence in general across the area. MARINE (Now through Wednesday Night): Generally moderate winds and seas prevail in advance of the overnight front. Showers and thunderstorms can be expected across much of the lower Texas coastal waters for Wednesday which may create localized hazardous conditions. Northeasterly winds then increase behind the front, which will likely push winds into Small Craft Exercise Caution criteria across much of the waters to cap off the short term marine forecast. Thursday through Sunday: Moderate to strong northeast winds will develop across the coastal waters Thursday as high pressure across the eastern United States and low pressure across the western Gulf of Mexico increases the pressure gradient across the northwest Gulf. Winds will veer to the east-northeast and diminish Friday as the surface ridge begins to move eastward and the pressure gradient weakens across the western Gulf. Light to moderate east-northeast winds will veer to the east-southeast and increase slightly Saturday as low pressure develops on the lee side of the Rockies. Winds will veer to the southeast on Sunday with low pressure across New Mexico and a surface ridge across the southeast U.S. extending into the Gulf of Mexico. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 77 78 70 79 / 40 60 20 30 BROWNSVILLE 77 80 69 81 / 40 70 20 40 HARLINGEN 77 79 67 80 / 40 70 20 30 MCALLEN 76 77 67 81 / 60 80 20 30 RIO GRANDE CITY 74 76 66 82 / 70 80 20 30 SOUTH PADRE ISLAND 76 77 72 75 / 40 60 20 30 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ This product is also available on the web at: HTTP://WEATHER.GOV/RGV Short Term/Aviation...60-Speece Long Term/Upper Air...69-Farris/65-Soria
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
1006 PM CDT Tue May 11 2021 .UPDATE... Storms have weakened across our CWA and we have allowed the Severe Thunderstorm Watch to expire. && .PREV DISCUSSION... /ISSUED 917 PM CDT Tue May 11 2021/ UPDATE... The severe threat has ended north and west of I-35 and we have canceled the Severe Thunderstorm Watch across this area. There is still a chance for isolated severe thunderstorms east of I-35 and we will allow the watch to continue. Most remaining convection has weakened and this trend will continue over the next few hours. PREV DISCUSSION... /ISSUED 656 PM CDT Tue May 11 2021/ AVIATION... Short term concern is the ongoing convection across the region. Currently storms in the vicinity of SAT and SSF. Storms will be possible for the next several hours in the San Antonio and Austin areas. Strong gusty winds will be the biggest impact from storms with gusts up to 25 kts possible. Ceilings will also lower to MVFR in storms. Otherwise ceilings will be VFR until later this evening when they will lower to MVFR and later to IFR. Ceilings will stay IFR through the morning Wednesday and lift only to MVFR during the afternoon. At DRT, there may be showers for the next few hours, but otherwise will be VFR. Ceilings will drop to MVFR overnight. There is a chance for TS overnight which could drop conditions to LIFR, but probability is low. PREV DISCUSSION... /ISSUED 347 PM CDT Tue May 11 2021/ UPDATE... We have issued a Severe Thunderstorm Watch most of South Central Texas. Conditions are favorable for the formation of severe thunderstorms capable of producing hail up to two inches, wind gusts up to 70 mph, and a tornado or two. The watch is in effect until 10 pm this evening. PREV DISCUSSION... /ISSUED 251 PM CDT Tue May 11 2021/ SHORT TERM (Tonight through Wednesday Night)... A diffuse frontal boundary from west to east across south-central Texas will eventually push south this evening, likely aided by storms that are expected to increase in coverage and move eastward across the region later this afternoon through the evening hours. At 19z, areas south of the front were mostly sunny with temperatures in the 80s to near 90 and dew points in the 70s, while north of it temperatures were in the 60s and low 70s with some light fog and low stratus. Temperature gradient from La Grange to burnet is nearly 30 degrees! An approaching shortwave is already setting off convective development over the SDB mountain range in Mexico, and some WAA forced elevated storms continue from just east of Sonora northeastward into the DFW metroplex, with some of that activity now into our region from Kerr to Burnet counties although with little thunder until you cross into Lampasas. In addition, a weak convergence axis stretches from north of Bryan, TX to near Gonzales although convective development in our area has been minimal at best. Even in the cool sector, elevated CAPE in excess of 2000 J/kg exists above the inversion with steep lapse rates at mid-levels on the order of 7.8-8C/km. And SBCAPE has been able to build to 2500-4000 J/KG in the warm sector today. Deep layer shear is a little weaker today, but still decent west, with the special DRT sounding this afternoon showing 34 knots 0-6km. As the storms in Mexico slowly enter the area this evening, they will pose the greatest risk for large to very large hail and a very low chance for an isolated tornado south of the front where SRH could briefly increase. Any supercells will likely quickly grow upscale though. HRRR still hones in on some storms east of I-35 along the existing convergence axis this afternoon and isolated severe hail or a brief downburst could be possible there if storms are able to develop which appears 50/50 at best. Storms are likely to grow into a SW/NE oriented quasi-complex through the evening hours and pose a marginal to slight risk of large hail or damaging winds. There is also a low chance for isolated flash flood impacts with rainfall amounts of up to three inches in spots which could occur over already saturated ground. Flash flood guidance is lowest today from San Antonio west and southwest to the Rio Grande so those will be the areas to watch. Severe threat should mostly end by midnight at the latest. Some lingering showers and storms may remain behind the front but coverage should decrease quite a bit after midnight. We have kept some low chances of showers and a few thunderstorms in the forecast through much of Wednesday as some weak isentropic lift in conjunction with weak elevated instability could lead to isolated activity at times, especially near the Rio Grande in the AM. Coverage will be low, and impacts are generally not expected. Skies will remain cloudy through the day, and it will be quite cool for this time of year with highs in the low to mid 60s north and low to perhaps mid 70s south. In fact, Bergstrom will likely flirt with record low maxT tomorrow. Wednesday night lows should fall into the 50s and lower 60s with any remaining shower chances relegated to far southwestern portions of the region overnight, if at all. LONG TERM (Thursday through Tuesday)... A northwest to west flow aloft is forecast to prevail Thursday and Friday. Surface winds are expected to turn from northeast to east on Thursday for most areas with southerly winds returning across the entire area by midday on Friday. A warming trend is on the way with highs in the 70s on Thursday and upper 70s to mid 80s on Friday. Clouds are expected to linger for most of the morning period and scattered mid to late afternoon both Thursday and Friday. Showers and storms return across south central Texas on Saturday as several mid to upper level short waves move from west Texas into central Texas. The activity diminishes late Saturday night through early Sunday morning, however, picks up on Sunday as another short wave traverses across the Southern Plains. The wet period continues into early next week as the parade of short waves continue to push over the area. Better chances for rain come on Tuesday areawide as an upper level system travels across the four corners region and opens as it moves over the Southern Plains. The GFS solution pushes a cold front across the area during that time frame while the ECMWF and CMC models keep a surface southerly flow through the extended forecast. Time will tell. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 62 67 58 75 57 / 70 30 - - 0 Austin Bergstrom Intl Airport 62 68 57 75 56 / 70 30 - - 0 New Braunfels Muni Airport 63 69 59 77 58 / 60 40 - - 0 Burnet Muni Airport 58 65 55 73 56 / 50 20 - 0 0 Del Rio Intl Airport 66 70 63 77 64 / 60 50 20 - - Georgetown Muni Airport 60 66 57 74 56 / 70 30 - 0 0 Hondo Muni Airport 65 71 59 77 59 / 50 30 10 - 0 San Marcos Muni Airport 62 68 57 76 56 / 60 30 - - 0 La Grange - Fayette Regional 65 70 60 77 59 / 60 40 10 - 0 San Antonio Intl Airport 64 70 60 75 59 / 70 30 - - 0 Stinson Muni Airport 64 72 61 77 61 / 60 30 - - 0 && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Short-Term/Aviation...Platt Long-Term...05
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
620 PM MDT Tue May 11 2021 .DISCUSSION...(This Evening Through Tuesday) Issued at 133 PM MDT Tue May 11 2021 19z surface analysis had weak high over the upper Midwest with weak trough from central MT into central WY. Modest return flow over the CWA per southeast winds. Water vapour had weak mean trough from central AB into CO. Multiple embedded shortwave disturbances noted over southeast MT, southern AB, and southern WY/northern CO. 100-400J/kg MLCAPE noted over northeast WY into the Black Hills with well-defined CU field in steep low level lapse rate regime. Best showers currently on the convergence zone just north of the Black Hills, but latest 0.5km visible satellite trends suggest expansion of shra/isolated ts will continue this afternoon, persisting into the early evening hours per HRRR guidance. Wouldn`t be surprised to see some small hail with the strongest cells as well as peppy SHSN over the highest elevations. Activity will wane later this evening as diurnal insolation ceases and boundary layer stabilizes. Lows tonight will be near guidance. Wednesday, mean upper trough shifts slowly eastward in response to upper ridge building into the western CONUS. Better piece of energy over southern AB will slide southeast into the northern plains pushing the surface trough through the CWA. This will be the focus for shra/ts activity given convergence along front and interaction with Black Hills terrain. Generally less than 500J/kg MLCAPE will be available, but small hail still possible. Modestly gusty southerly winds expected ahead of the trough. Temperatures Wednesday will be near guidance. Thursday/Friday, western CONUS upper ridge shifts east and flattens leading to west/northwest flow aloft with embedded shortwaves and weak instability. Diurnally driven shra/ts expected with peak hours diurnally driven during the late afternoon/early evening hours. Temperatures will slowly warm given thermal ridge expansion. The weekend in early next week, upper low will probably break off in the west and then spin into the southwest CONUS. A series of disturbances will affect the CWA with daily chances for showers/storms. Temperatures will be near/slightly above normal. Typical mid-May weather. && .AVIATION...(For the 00Z TAFS Through 00Z Wednesday Evening) Issued At 620 PM MDT Tue May 11 2021 Showers and isolated thunderstorms will continue this evening, mainly across the northern Black Hills. Areas of MVFR conditions (and localized IFR in the Black Hills) are possible with the heavier precipitation. Precipitation will wane early this evening. Otherwise, VFR conditions are expected through the forecast period. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION...Helgeson AVIATION...13