Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/22/21

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
915 PM CDT Wed Jul 21 2021 .UPDATE... Issued at 912 PM CDT Wed Jul 21 2021 An area of thunderstorms that developed across the far southwestern part of the CWA has now begun to dissipate and track southeastward, and looks to be out of the area in an hour or so. The showers over the far east are also on their way out of the CWA, so have removed POPs there for the remainder of the nighttime hours. No changes made to winds or temperatures at this time. && .SHORT TERM...(This Evening through Thursday) Issued at 255 PM CDT Wed Jul 21 2021 Still widely scattered showers/sprinkles occurring over parts of the north central/northeast CWA in response to shortwave energy aloft. The main shortwave drops southeast out of North Dakota influencing more of northeast South Dakota and west central Minnesota tonight. This forcing combined with a 30+ KT low level jet and theta-e ridge should be enough to increase coverage of showers and thunderstorms later tonight through early Thursday morning...mainly east of the James River Valley. Hot, humid conditions will be the concern going into Thursday. As per previous forecasts, held back a couple of degrees on the baseline guidance MaxT output. The forecast has had a slight warm bias, likely due to influence of smoke, and the HRRR vertically- integrated smoke is again hinting at a wide swath of smoke streaming over the region again Thursday afternoon. Dewpoints will be in the 60s pushing apparent temp values to borderline heat advisory criteria. Due to uncertainly of smoke and mixing potential, collaboration with surrounding offices was to hold off on a headline for now. .LONG TERM...(Thursday Night through Wednesday) Issued at 255 PM CDT Wed Jul 21 2021 The extended portion of the forecast will remain relatively unchanged from the previous forecast package. The upper level ridge that`s been in place for quite some time across the western CONUS extending ewd into our region will get flattened somewhat on Friday as an upper level shortwave and frontal boundary push through the Dakotas. This will bring some precip chances to the area with best opportunities for seeing something in locales farthest north. So, not everyone will see rainfall from this system. By early next week, the ridge builds back in and amplifies across the western CONUS once again. Temperatures are only expected to remain well above normal through the entire period. Some areas may stay relatively cooler in the 80s to around 90 during the upcoming weekend, but more widespread 90s look to return next week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) Issued at 623 PM CDT Wed Jul 21 2021 Terminals KABR,KATY,KPIR,KMBG For the most part, VFR conditions will prevail across the area tonight and through the day Thursday. A few scattered showers are possible tonight across parts of the southern and eastern part of the CWA. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Parkin SHORT TERM...Serr LONG TERM...Vipond AVIATION...Parkin
Area Forecast Discussion
National Weather Service Denver/Boulder CO
840 PM MDT Wed Jul 21 2021 .UPDATE... Issued at 826 PM MDT Wed Jul 21 2021 The strength and coverage of the thunderstorms will continue to decrease through the evening. Best coverage the rest of the evening will be south and east of Denver. Lingering showers and thunderstorms in the mountains as well, with some residual showers continuing after midnight. The Flash Flood Watch has been allowed to expire. There are a couple of Flash Flood Warning ongoing, but those will likely be allowed to expire by 915 pm. && .SHORT TERM...(This evening through Thursday) Issued at 142 PM MDT Wed Jul 21 2021 Water vapor continues to show a good plume of monsoon moisture stretching across most of the state, with convection blossoming in the past couple of hours. An 18z sounding launched just west of Fort Collins came in with a precipitable water value of 1.18"... which is a remarkable increase compared to values over the plains yesterday. In the higher terrain both precipitable water (near 1") and 700-500mb specific humidity (~7g/kg) are above the 90th percentile. SPC Mesoanalysis indicates MUCAPE greater than 750 J/kg across the high country, and these two factors have largely led to widespread showers and thunderstorms this afternoon. There has been enough flow aloft... roughly 20kt at 500mb... to keep storms moving just fast enough to avoid heavy precipitation totals across our burn areas. Not much is expected to change over the next few hours, with widespread showers and storms over the high country. Current radar trends and some model guidance does favor areas along and south of I-70 through the evening, but flash flooding will continue to be a concern across all of our burn areas through tonight. Over the plains... the aforementioned sounding near FNL showed very little surface-based instability present, but we should see continued destabilization over the next hour or two and at least a couple of storms developing along the I-25 corridor. The HRRR has continued to delay when this will happen, but there`s enough confidence to have some PoPs into the plains this evening. Briefly heavy rain, lightning, and some gusty winds would be the primary impacts for the urban corridor. Tonight should be fairly quiet, but another round of afternoon storms is expected tomorrow. The best moisture and instability will be pushed back to the west of our forecast area... closer to Grand Junction. This should diminish the heavy rainfall threat a little bit, though there will be continued concerns for the burn areas across our high terrain. WPC has maintained a marginal Excessive Rainfall Outlook for along and west of the divide... and we could see localized flash flooding issues if storms form over the wrong spots. Across the plains, it should remain hot and dry, with highs in the mid 90s. A few showers may attempt the journey off the Foothills, but otherwise no precipitation is expected along and east of I-25. .LONG TERM...(Thursday night through Wednesday) Issued at 142 PM MDT Wed Jul 21 2021 An elongated upper level ridge of high pressure will stretch from Central California across Eastern Colorado Thursday night through Friday as an easterly wave moves west across Southern New Mexico. The plume of monsoonal moisture will continue to circulate around the high with PW`s ranging between 0.75" and 1.00" in the high country. This abundant moisture combined with daytime heating and an upper level disturbance moving across the area will result in scattered to numerous slow moving showers and storms in the high country. Some of the storms will be capable of producing locally heavy rain and flash flooding, especially across the burn areas. Further east across the plains PW`s are also high with values ranging between 1.00" and 1.35" Despite the high moisture values, meager instability along with a mid level cap should result in limited precipitation chances. Over the weekend, the easterly wave over the Desert Southwest tries to cut off the monsoonal flow into the western half of Colorado. This may reduce the flash flood threat in the northern mountains somewhat. However, there could still be pockets of higher PW which could contribute to some stronger storms and locally heavy rainfall. A weak frontal surge progged to move across northeastern Colorado on Saturday may provide a slight upslope component and slightly cooler temperatures on the plains. The NBM is forecasting a max temperature of 89 degrees at DIA on Saturday which would end our 90 degree streak if it verifies. A weaker cap, combined with better instability and some upslope flow may result in a better chance for precipitation on the plains. Early next week, ensembles are showing the upper ridge rebuilding over Colorado which would result in hotter and drier weather across the forecast area. This is vastly different than yesterday`s runs which had shifted the upper high eastward into the Southern Plains States and had the plume of monsoonal moisture flowing into Colorado from the Desert Southwest. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 826 PM MDT Wed Jul 21 2021 South/southwest winds will continue the rest of the night, but should weaken later this evening as the rest of shower activity south of Denver tapers off. VFR the rest of tonight through Thursday afternoon. && .HYDROLOGY... Issued at 826 PM MDT Wed Jul 21 2021 The Flash Flood Watch was allowed to expire at 8 pm this evening. Weakening showers/thunderstorms the rest of this evening. The A Flash Flood Warning will continue over the western half of the East Troublesome burn area until 915 pm mdt this evening, although the thunderstorm activity does look to have shifted south of the warning area. Additional rainfall this evening will be light. Any lingering thunderstorms will diminish this evening, with quiet conditions overnight. Thursday will see a limited threat of burn area flash flooding as the best conditions for heavy rainfall. Monsoon moisture will still be around the area, though it does decrease somewhat slightly compared to today. Models generally show less precipitation, and HREF 6hr maxQPF is not nearly as high as today. However, storm motions are likely to be a bit slower with weaker flow aloft. If slow moving thunderstorms develop over the burn areas, flash flooding would certainly be possible. Stay tuned. On Friday, there will be high levels of moisture in place as precipitable water values increase. Moisture levels may decrease somewhat on Saturday across the northwestern sections of the forecast area. A shortwave trough moving across the region on Friday and upslope flow developing on Saturday will aid in the forcing for storms to form. Scattered storms will form over the burn areas with slow storm motion. Will probably need to upgrade some of the burn areas to an elevated threat on Friday. Sunday and into next week, the chance of storms will decrease with warmer and drier air moving in. The threat for flash flooding will decrease as well. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Cooper SHORT TERM...Hiris LONG TERM...Kalina AVIATION...Cooper HYDROLOGY...Hiris/Cooper
Area Forecast Discussion
National Weather Service Des Moines IA
636 PM CDT Wed Jul 21 2021 .DISCUSSION.../Tonight through Wednesday/ Issued at 212 PM CDT Wed Jul 21 2021 Forecast Highlights: -- Isolated showers or storms northeast through early evening -- Patchy fog possible toward daybreak Thursday -- Summery conditions with hottest days being Saturday and then toward middle of next week -- Not a dry 7 days areawide, but little in the way of high confidence, widespread rainfall over the period Details: The flow over the region remains weak with the 12z KOAX RAOB observing winds at 850, 700, and 500mb somewhere between the 10th and 25th percentile with forecast soundings across central Iowa showing winds below 600mb less than 10 knots. GOES-East imagery shows the jet stream flow entering over the west central US and then moving poleward into Saskatchewan before diving southeastward into the northern Middle Atlantic States. Iowa is in the light northerly or northwesterly flow aloft. At the surface, a weak boundary is stretched from west central Minnesota into southeastern Iowa with winds over western and central Iowa from the southwest and over northeastern Iowa generally from the east. This weak boundary/wind shift has fostered a few isolated showers and there is a wind gust potential if a storm collapses with low bulk shear and downdraft CAPE values between 800 and 900 J/kg per SPC mesoanalysis. This wind shift over our northeast counties is also one ingredient for potential funnel clouds this afternoon and early evening, which includes the area around Waterloo. SPC mesoanalysis is not pinging the non-supercell tornado parameter and is just starting to showing some enhanced stretching potential. However, SPC mesoanalysis is showing 0-3km MLCAPE with 75-100 J/kg presently with it expected to increase per RAP forecast. Further, lapse rates should steep through the afternoon. The showers/storms and any funnel cloud reports will wane early this evening and attention will once again turn to fog development. Most of the fog has been light above 5 miles with isolated pockets of lower visibility and expect that tomorrow morning as well. As for high level smoke that has been creating a hazy sky, the higher concentration of smoke today is over eastern Iowa with lighter concentrations elsewhere in the state. A wave of higher concentration of high level smoke arrives late Thursday afternoon over northwestern Iowa. Highs should still reach well into the 80s to around 90 degrees. A weak surface boundary will approach the state as a mid-level trough moves over central Canada with its southern edge into North Dakota and Minnesota on Friday. Temperatures ahead of this boundary will be a bit higher than Thursday in the 90s in most places with heat index values topping well into the 90s to near 100 degrees. This boundary will foster isolated storms along it, though as it moves toward the Iowa border, it will encounter more of the warm air aloft associated with the ridge. The deterministic global models continue to indicate 700mb temperatures around 11C, which may stunt development into northern Iowa until it cools slightly overnight Friday. The number of ensemble members pointing toward light QPF near the Iowa/Minnesota border is growing with about half of the Canadian members, a third of GFS members, and most ECMWF members signaling this from last night`s 00z run. For now, do not see a reason to deviate from initial NBM guidance and have continue with PoPs over northern Iowa Friday night into early Saturday. This surface boundary will gradually dissolve as it slowly slips southward through the state Saturday into Sunday with whatever is left of this boundary settling near the Iowa/Missouri border by Monday morning. 700mb temperatures should keep the precipitation coverage to a minimum over the weekend, but cannot rule out an isolated storm near the boundary with this shown amongst some ensemble members of the CMC and GFS. Temperatures will be well into the 90s on Saturday with heat index values of 95 to near 105 degrees. Will have to watch this day as it will be near heat headline criteria. Sunday will be slightly less hot over northern Iowa with similar temperatures elsewhere. Deterministic models show varying strengths, but agree that a shortwave trough will be moving into Iowa early next week overtop the ridge. The placement of the boundary and the shortwave will dictate where storms will be located, but chances at this point look highest over southern Iowa Sunday night into Monday. Thereafter, the western US ridge is expected to build toward Iowa with the 500mb ensemble mean of the GEFS and ECMWFEns showing the 594dm height contour building into at least southwest if not southern Iowa by Thursday with the CMCE just south of the state. Chances for any storms would be relegated to any wave coming overtop of the ridge with impact likely over our northeastern or eastern areas, but that is not likely at this point. 850mb temperatures will rise to between 22-24C on Wednesday and 24-26C on Thursday, which will translate to surface temperatures into the 90s and in most cases well into the 90s. The 75th percentile of NBM would push many sites to or above 100 degrees. Heat index values will likely be several degrees either side of 100 given current forecast highs. This heat, combined with ensemble mean rainfall through the middle of next week around half an inch, would not be welcome for ongoing drought conditions. && .AVIATION.../For the 00Z TAFS through 00Z Thursday evening/ Issued at 635 PM CDT Wed Jul 21 2021 Aviation weather continue to be relatively tranquil with widespread VFR conditions for much of the period. There may be some very patchy fog overnight with light southeast to south winds. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...Ansorge AVIATION...Cogil
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1038 PM EDT Wed Jul 21 2021 .SYNOPSIS... Somewhat drier air arrives from the north on Thursday along with more sunshine. Temperatures will rebound to near-normal or even slightly above by late week. Afternoon and evening shower and thunderstorm chances gradually increase again over the weekend. && .NEAR TERM /THROUGH THURSDAY/... As of 1030 PM: The forecast looks on track, so no big changes with the evening update. A smoky haze will likely linger across the North Carolina zones well into the night, with some fog developing in the mountain valleys. A couple of showers linger along the escarpment in Rabun and Oconee counties, but should ash out soon as we become more stable. The next 24 hours look uneventful as we should remain under a dry NW flow that will be inhospitable to deep convection. A sfc high over the Great Lakes/Midwest should nose down into the area tonight, with clear sky and light wind that should be conducive to fog development in the mtn valleys. Low temps will be close to normal. The sfc high moves a bit to the east on Thursday, but should keep the deeper moisture suppressed to the south. Will not rule out an isolated shower over the higher terrain Thursday afternoon, but expect little chance of deep convection east of the Blue Ridge as a low level cap should keep the lid on it. High temps should be a few degrees above normal. The HRRR suggests the smoke plume will remain aloft through the day, so some near-sfc haze could come into play again, but for now this was left out of the fcst. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 120 PM EDT Wednesday...A broad east coast trof will slowly lift and pull northeast thru the period. This will allow a supTrob high to dominate the pattern and keep a rather suppressive regime in place. Frontal forcing will remain south of the FA leaving weak flow thru the column north and not much chance for severe tstms. There will be general thunderstorms possible each afternoon as moist e/ly flow interacts with a destabilizing atmos each day, however, coverage will be limited and favor the higher terrain. The airmass will not change much, so expect smoke-induced hazy conds to continue thru the period. With good insol, max temps will have no problem reaching near normal levels, while mins also hover arnd normal. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 200 PM EDT Wednesday...No major changes were made to the ext fcst. SubTrop ridging will continue to dominate the pattern and keep a low shear and suppressed airmass in place. This will limit convective activity Sun and keep the best chance for pulse storms across the mtns Sun afternoon. Still expect hazy conds to continue as the airmass mixes very little. On Mon, the models agree well with lowering h5 heights and a back door cold front working in from the north. This front will be weakly forced and have limited moisture to work with early on. The front now looks to stall across the fcst area thru Tue, possibly into Wed, while llvl moisture flux increases off the Atl and the GOM. So, the front shud become more active possibly leading to localized hydro issues beginning Tue as PWATS hover arnd 1.75 inches each day. Max and min temps will remain arnd or a little below normal each day as cloud cover and areal precip increases. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... At KCLT and elsewhere: Satellite imagery shows a smoke plume over the area that will move little thru the period. The HRRR shows some increase in near-sfc smoke density late tonight into Thursday, so expect some vsby reduction in HZ possible, especially across the NC sites and near GSP. Confidence is still low on anything lower than VFR. The exception is KAVL, where some BR/HZ may form, as fog develops in the mountain valleys. Similar conditions expected tomorrow, with few-sct high-based cu and isolated showers and perhaps a tstm or two in the high terrain. Coverage looks too low for any TS mention in any of the TAFs. Winds will be light thru the period, shifting around the dial from NW to NE tonight, then SE/SW Thursday aftn. Outlook: Smoke from western wildfires should improve by early Friday. Dry conditions will continue through late week, but with early morning fog or low stratus possible. Diurnal thunderstorm chances will steadily return into the weekend. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 100% High 100% High 100% High 100% KGSP High 100% High 100% High 100% High 100% KAVL High 100% High 93% High 100% High 100% KHKY High 100% High 100% High 100% High 100% KGMU High 100% High 100% High 100% High 100% KAND High 100% High 100% High 100% High 100% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...DEO NEAR TERM...ARK/PM SHORT TERM...SBK LONG TERM...SBK AVIATION...ARK
Area Forecast Discussion
National Weather Service Indianapolis IN
1140 PM EDT Wed Jul 21 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 931 PM EDT Wed Jul 21 2021 Forecast is in good shape. Much of the cumulus are dissipating, but some will likely linger as stratocumulus overnight. Areas of high clouds also continue to move through. In addition, smoke continues across the area, with some stations still reporting 5SM visibility. With the smoke and aforementioned clouds, will continue with a partly cloudy forecast. Some patchy ground fog will also likely develop overnight with light winds, but kept things simple and continued to only mention haze. Not expecting any widespread dense fog. Isolated convection across Illinois is moving south and should remain west of the area. Temperatures look good so no significant changes were needed. && .Short Term...(This evening through Thursday night) Issued at 247 PM EDT Wed Jul 21 2021 Dry weather is expected to continue for several more days as Indiana remains within an area of northwest flow around a broad ridge across the Intermountain West. Visibilities have remained generally between 5 and 7 miles due to smoke moving from fires across the Western United States and Southern Canada through the jet stream to central Indiana. The boundary layer today has been up to around 850mb with a cap above it which has further allowed for smoke aloft to mix to the surface. During the overnight hours, a surface inversion should limit the downward mixing, but expect that to pick up again tomorrow. HRRR vertically-integrated smoke parameters show that estimated smoke density will be not quite as intense tomorrow, so not expecting quite as much impact to surface visibility. Afternoon temperatures and humidity will be fairly reasonable for this time of the year with highs topping out in the low to mid 80s with dew points in the low to mid 60s. The aerosols associated with the smoke may have a minor influence in keeping the temperatures from rising higher. During the late overnight hours Thursday night, can`t rule out a complex of thunderstorms skirting the northern counties as a weak shortwave moves along the ridge. Best chances look to be later in the day on Friday when a plume of moisture associated with the wave moves through. Clouds will also be on the increase ahead of the wave. && .Long Term...(Friday through Wednesday) Issued at 247 PM EDT Wed Jul 21 2021 The long term period begins with an upper low off the coast northeast of Maine, and a broad upper ridge over much of the central U.S. As the long term wears on, the axis of the upper ridge builds back toward the intermountain west before again slowly drifting eastward over the central and northern plains. At the surface, high pressure over the area on Friday begins to slide to the east, allowing the tail end of a cold front to eek through the area Saturday afternoon/Saturday night. Very little reflection of anything in the upper pattern showing up in the surface pattern over central Indiana through at least mid week. Northwesterly to westerly flow aloft will be the rule, with generally southwesterly component flow at the surface to bring more heat and humidity into the area. High temperatures will climb into the upper 80s to lower 90s and heat index values in the upper 90s to low 100s, and possibly higher. Precipitation chances through the long term will mainly be driven by diurnal heating for late afternoon/evening storms, and then by quick hitting shortwaves on northwest flow that prompt MCS development upstream, and these ride the periphery of the ridge then into parts of central Indiana. With this said, the better chances for these more organized ridge riders appears to be north of the forecast area this set of runs, but will have to monitor. Confidence is low in precip at any given time given the overall high pressure pattern and variability in timing of individual shortwaves, but a bit higher for Saturday night with the additional forcing of the cold front. Unlikely that coverage would be more than scattered though. . && .Aviation...(06Z TAF Issuance) Issued at 1140 PM EDT Wed Jul 21 2021 IMPACTS: - Occasional MVFR conditions in smoke/haze/ground fog expected through the night. Locally IFR visibility in fog possible at some sites. - Near MVFR conditions in smoke/haze during the day Thursday. - Light winds veering to the southeast by Thursday afternoon. DISCUSSION: Some stratocumulus will linger through the night. More cumulus will pop up on Thursday. MVFR visibility should become predominant at all sites overnight as some fog develops. Lower visibility is possible at mainly the rural sites. More haze/smoke will keep visibility near MVFR territory on Thursday. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...50 Short Term...White Long Term...CP Aviation...50
Area Forecast Discussion
National Weather Service Marquette MI
647 PM EDT Wed Jul 21 2021 .SHORT TERM...(This evening through Thursday) Issued at 305 PM EDT WED JUL 21 2021 Clear skies are slowly giving way to clouds out west as a shortwave slowly progs southeastward near the WI border. Otherwise, today has been fairly calm, with temperatures already reaching 70F at the office as ridging has limited cloud cover over most of the CWA. This lack of cloud cover and WAA from the Western U.S. have helped temperatures be warmer than yesterday. Winds have been fairly light today, with the lakebreezes from both of the Great Lakes dominating wind speed and direction for much of the area. Precipitation is currently staying west out of our area, but that may change come later tonight as the shortwave continues towards the southeast. Cloud cover is expected to slowly increase from west to east throughout the night, with only the far east expected to have sky conditions less than BKN. Therefore, kept the minimum temperatures from the previous shift, save for lowering the far eastern lows by 2 degrees to account for the lesser amount of cloud cover. Some showers and a rumble of thunder or two could be possible late tonight over the far west near Ironwood as the shortwave slowly brings some precipitation over the area. Other areas in the west and central also have a very small chance of precipitation, but, given that model soundings are showing a decent dry layer that needs to be overcome, I don`t think that any precipitation that falls will make it to the ground (save for maybe over the far west), at least during the overnight hours. Rain chances should improve across the rest of the area Thursday as the air above the ground moistens and another shortwave immediately follows behind the previous one. Thunder also seems possible in the west during the afternoon hours Thursday; however, there shouldn`t be anything that is severe, as instability is fairly weak and bulk shear magnitudes are not too impressive. Temperatures may be a little warmer Thursday than what they are today; while widespread cloud cover is expected across the area, there should be some slight WAA, which, if model guidance is to be trusted, should give us slightly warmer high temperatures Thursday. The HRRR also has haze over the west Thursday, but given the chance of rainfall across the area, decided not to put the haze chances in the grids. .LONG TERM...(Thursday night through Wednesday) Issued at 442 PM EDT WED JUL 21 2021 Models indicate that mid/upper level ridging over western North America will deamplify some during the rest of this week into early next week. The result will be a more progressive flow regime developing along the U.S./Canada border region as a series of shortwaves eject eastward from mean troughing just off the west coast of Canada and bring periodic chances for showers to the Upper Great Lakes late this week into next week. As for temps, near to slightly blo normal temps will trend upward to above normal beginning Fri and continue into next week. There will probably be some hot days in the mix through next week, but the overall progressive flow regime in the vicinity of the U.S./Canada border should prevent any prolonged periods of hot conditions from setting up across Upper MI. The shortwave aiding shower activity over mainly west and south central portions of the cwa on Thu will shift se of the area by Thu night, resulting in showers ending for the most part. Although no apparent shortwave will be approaching during the night, weak isentropic ascent and some instability along the warm front lingering to the sw may still support a few showers/maybe some thunder during the night, mainly over west and south central portions of the cwa. Fri into Sat, attention turns to the shortwave moving along the U.S./Canada border with the associated cold front likely sweeping across the fcst area late Fri night/Sat. Models still have a good signal for shra/tsra with this feature. In addition, models indicate sufficient instability (MUCAPE off NAM soundings generally 1000-1500 J/kg) and deep layer shear (35-40 kts) for severe thunderstorm potential as well. If front is slow enough and hasn`t exited to the se by Sat afternoon, additional shra/tsra will likely develop over the s central/se fcst area in the afternoon where instability could build near 1500 j/kg through the day along the frontal boundary. These storms could also pose a severe risk. PWATs fcst up near 2 inches will also result in locally heavy rain, especially with thunderstorms. Mainly dry weather should then follow Sun/Mon as sfc high pressure builds in behind Saturday`s front. High temps will be in the 80s, but could push 90F on Mon, depending on how quickly WAA develops into the Upper Lakes ahead of the next shortwave/cold front, which is due to move in Tue and will bring the next chc of shra/tsra. Shra/tsra could even linger into Wed from this shortwave/frontal system. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 647 PM EDT WED JUL 21 2021 VFR conditions are expected at KSAW throughout the period and at KCMX and KIWD for most of the period. KCMX and KIWD will go temporarily MVFR late Thu morning into Thu afternoon. Shower chances are small enough to go with VCSH at this time. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 305 PM EDT WED JUL 21 2021 Expect winds generally to be 20 knots or less throughout the period across the lake. The only exception may be Friday night, where southerly winds across the eastern may reach up to 25 knots at most. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...TAP LONG TERM...Voss AVIATION...07 MARINE...TAP
National Weather Service Morristown TN
910 PM EDT Wed Jul 21 2021 .UPDATE... EVENING UPDATE. && .DISCUSSION... No changes to the forecast for this evening update. Main weather story continues to be the smoke/haze lingering around the area overnight and into tomorrow. Surface observations are still reporting decreased visibilities in many areas. Some of that might mix out tonight, but expect another hazy day tomorrow, but hopefully less so than what we saw today. ABM && .AVIATION... 00Z TAF DISCUSSION. Quiet weather expected the rest of the evening with the main aviation concern being smoke/haze from the fires. Most weather stations are picking up on very light haze this evening, and think that smoke will mix out overnight. Should re-intensify tomorrow, but the heaviest smoke will likely be further west in TN. Kept 6SM smoke in the TAFs to hint at haze expected all day, but think that visibilities will hopefully be a bit higher than that most of tomorrow. ABM && .PREV DISCUSSION... /ISSUED 724 PM EDT Wed Jul 21 2021/ SHORT TERM... (Tonight and Thursday)... Haze will continue to be an issue this period as the high pressure ridge over MO/IL today will slowly shift east to IL/IN tomorrow. As a result, a northerly low to midlevel flow will persist, and continue to spread smoke from wildfires in Canada southward. The HRRR near-surface smoke concentrations do appear lower for our area tomorrow, with the highest concentrations shifting to our west over Middle TN. Some haze will be mentioned in the Wx grids for tonight and tomorrow morning, particularly across the northern half, and for the Plateau tomorrow morning. The axis of deformation that has been a focus for convection today across N GA and N AL will push southward tomorrow, taking any chance of showers with it. Dry air aloft and subsidence will result in a dry day tomorrow, with highs in the upper 80s to lower 90s. DGS LONG TERM... (Thursday Night through Wednesday)... Key Messages... 1. Drier conditions to begin the period. Chances of precipitation will gradually increase, especially early next week, as moisture becomes more available and locally heavy rainfall becomes a possibility. 2. Temperatures will continue to increase into the weekend and early next week. Increasing moisture by the end of the weekend will bring very humid and muggy conditions with heat indices approaching the mid to upper 90s for the Valley. Discussion... -Thursday Night through Sunday- An upper level ridge will be located over the Central Plains with a positively tilted trough positioned along the far Northeastern Seaboard to begin the long term period Thursday evening. At this time, H5 heights will be around 5920m. Additionally, PWAT values will be around the 1.3-1.5in range. As a result, relatively drier conditions, sunny skies, and warm temperatures will be the primary theme for the duration of this period. The potential for precipitation will be restricted to the higher elevations and far southern portions of the valley where moisture will be more favorable. By Friday, the surface high pressure will begin to shift east from the Ohio Valley with flow aloft out of the northwest. Models are suggesting a weak shortwave disturbance moving through the area, however, overall subsidence associated with the high pressure and the lacking moisture will again keep PoPs more focused around the southern valley and areas of higher elevation. In far northeast TN and southwest VA, PWAT values may drop as low as 1.0in during late Friday night into Saturday morning. This is approaching the lower 10th percentile according to sounding climatology. For the end of the weekend, the surface high continues to progress towards the eastern seaboard as the flow becomes southeasterly and will aid in providing more moisture into the region overall. The moisture along with temperatures in the low to mid 90s associated with the amplifying upper level ridge will favor more of a typical terrain-driven summer shower and thunderstorm pattern at this time. -Monday through Wednesday- Through the latter part of this long term period, the area will continue to see height rises along with positive thickness advection. However, an amplifying upper level low northeast of the Great Lakes region will bring a cold front through the Ohio Valley at this time. With PWATS approaching 2.0in, better coverage of showers and thunderstorms are looking more probable out ahead of the front, especially on Tuesday. Additionally, increasing dewpoint temperatures will make for more muggy conditions and increasing heat indices. Depending on how the precip coverage plays out, temperatures on Tuesday and Wednesday may be a degree or two cooler than the previous days, although, still very hot. KRS/DH && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 71 92 70 91 71 / 10 10 10 20 0 Knoxville McGhee Tyson Airport, TN 68 90 67 92 69 / 0 10 10 10 0 Oak Ridge, TN 68 91 67 91 68 / 0 10 10 10 0 Tri Cities Airport, TN 62 88 62 90 63 / 0 0 10 10 0 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$
Area Forecast Discussion
National Weather Service Spokane WA
251 PM PDT Wed Jul 21 2021 .SYNOPSIS... Dry and breezy winds this evening will raise concern for wildfires and a Red Flag Warning remains in effect through late evening for much of the Inland Northwest. Thursday and Friday will feature high temperatures in the 80s and low 90s. Above average readings will return this weekend and early next week with highs well into the 90s. && .DISCUSSION... Tonight through Friday: A dry slot on the south side of an upper trough passing over British Columbia will sweep across Central Washington this afternoon before sliding east into the Idaho Panhandle this evening. Drier air and tight west-east pressure gradients will promote breezy to locally windy conditions and low relative humidity this evening with Red Flag Warnings in place for most of Eastern Washington and North Idaho. Ongoing fires will likely become increasingly active into the early evening. HRRR smoke model is showing a LARGE AREA of smoke from fires over the north Cascades and southern BC tracking southeast into northern Washington tonight into Thursday morning. The highest smoke concentrations are projected from Waterville to Coulee City to Spokane/Coeur d`Alene north to the Canadian border including the Methow Valley. Thursday and Friday westerly flow lingers over the area with a continued dry atmosphere leading to low relative humidity, normal temperatures, and locally breezy conditions especially near the Cascade gaps. Smoke models suggest another round of smoke for northern WA Thursday Night into Friday morning, although possibly not penetrating as far south as Thursday morning. JW Saturday and Sunday: Afternoon temperatures in the 90s will return on Saturday. The upper trough helping cool our region down close to average will be replaced by a flat ridge of high pressure on Saturday allowing heat over California and the Great Basin to return to our region. Sunday will be even warmer with mid to upper 90s expected for central Washington, the Okanogan Valley, Lewiston area, and the lowlands of northeast Washington. Our temperature forecast largely assumes that smoke won`t have a significant effect on temperatures which may not be a viable assumption. Winds in the low and mid levels are expected to mainly be westerly this weekend pushing smoke from fires in southwest Oregon and northern California south of our region. However, the increasing size of fires in the upper Methow Valley is concerning. Overall, there should be enough westerly flow to provide decent ventilation across our region, but locations near fires like Winthrop and Omak may experience thick smoke at times. We may also be dealing with some new fires from the lightning that occurred this morning in southeast Washington and the Idaho Panhandle. Hold over fires may perk up in the next few days with occasional breeziness and persistent low humidity. Monday and Tuesday: We will be keeping a close eye on monsoonal moisture over the Great Basin and southern Oregon early next week. At this time, it looks like far southeast Washington and the southern Idaho Panhandle will be the most likely areas for scattered showers. Further north, places like central and northeast Washington look to be under enough dry southwesterly flow to remain free of showers and potential lightning, but we will need to watch this closely. Monday and Tuesday will remain quite warm with widespread 90s for high temperatures. /GKoch && .AVIATION... 18Z TAFS: Thunderstorms have pushed east of the region this morning although still can not rule out a few strikes this morning mainly east of KCOE. A tightening pressure gradient with cold front passage will result in increasing westerly winds through the afternoon and into this evening with gusts of 20-30 kts expected. The winds and dry conditions today will also result in increased fire activity. Established fires in the Methow Valley is expected to produce thick smoke near the Methow Valley State Airport into Omak and possibly Republic and Colville as well. Smoke is expected to push south into Spokane and Coeur d`Alene Thursday morning. Higher altitude smoke moving northward across southeast Washington and into the Idaho Panhandle will also produce hazy skies around KLWS and KPUW. JW && .PRELIMINARY POINT TEMPS/POPS... Spokane 52 83 54 87 56 92 / 0 0 0 0 0 0 Coeur d`Alene 51 82 51 86 54 90 / 0 0 0 0 0 0 Pullman 45 79 47 83 50 87 / 0 0 0 0 0 0 Lewiston 59 89 58 92 61 97 / 0 0 0 0 0 0 Colville 43 84 46 88 48 93 / 0 0 0 0 0 0 Sandpoint 47 81 45 84 49 88 / 0 0 0 0 0 0 Kellogg 55 79 56 82 58 87 / 0 0 0 0 0 0 Moses Lake 49 86 53 90 56 94 / 0 0 0 0 0 0 Wenatchee 56 86 59 90 63 94 / 0 0 0 0 0 0 Omak 54 88 56 92 60 97 / 0 0 0 0 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...Red Flag Warning until 10 PM PDT this evening for Northern and Central Idaho Panhandle (Zone 101). WA...Red Flag Warning until 10 PM PDT this evening for East Washington Okanogan Highlands (Zone 687)-East Washington Okanogan/Methow Valleys (Zone 684). Red Flag Warning until 10 PM PDT this evening for East Washington Palouse and Spokane Area (Zone 674). Red Flag Warning until 10 PM PDT this evening for East Washington Northern Columbia Basin (Zone 673). Red Flag Warning until 10 PM PDT this evening for East Washington Northeast (Zone 686). Red Flag Warning until 10 PM PDT this evening for East Washington North Cascades (Zone 685). Red Flag Warning until 10 PM PDT this evening for East Washington Central Cascade Valleys (Zone 677)-East Washington South Central Cascade Valleys (Zone 676). && $$
Area Forecast Discussion
National Weather Service Norman OK
1018 PM CDT Wed Jul 21 2021 ...New AVIATION... .SHORT TERM... (This evening through Thursday) Issued at 200 PM CDT Wed Jul 21 2021 Retrograding closed upper low passing to our south should have little impact on our weather today. Precipitating diurnal convection is expected to be closer to the track of this system deeper into Texas through the rest of the afternoon. But, for our area diurnal cumulus will be shallow and trapped beneath subsidence inversion evident on 12z Lamont sounding, and model forecast soundings. Visual observations and HRRR smoke model indicate wildfire smoke moving westward across our area in tandem with the aforementioned upper low. The smoke will be shunted more easterly into the Ohio Valley tomorrow, but there will still be a residual ribbon of smoke contracting within a weak shear axis over northern Oklahoma. Still some potential for a red sunset as a result, but maybe less tomorrow than previous days given these synoptic-scale flow changes. This morning, several locations saw mostly minor visibility reductions from radiative fog. The surface high will shift enough that southerly winds will be slightly stronger tonight, probably imitating radiative fog potential some compared to this morning. Moisture advection should be weak at best to start so we should have less fog coverage than this morning. The best chance for some radiative fog will be where winds are lightest in south-central and southeast Oklahoma, but a few patches of light fog can`t be ruled out further northwest into central and northern Oklahoma. Similar considerations tomorrow afternoon with regards to convection, although with slowly increasing moisture and PWAT values that aren`t as far below climo, some isolated weak convection may occur near the Red River. BRB && .LONG TERM... (Thursday night through next Tuesday) Issued at 200 PM CDT Wed Jul 21 2021 By Friday afternoon, deep enough moisture may be present that when coupled with diurnal heating could result in a slightly better chance of isolated showers across southern Oklahoma and north Texas. Coverage will still be quite sparse and weak tropospheric flow will limit convective organization and thus intensity. Through the weekend and into early next week, mean ridging builds across much of the country. The greatest 500-mb height anomalies will be north of us especially into early next week with highest height values near the Kansas/Nebraska border. Although this is a hot pattern, it`s generally not associated with significantly anomalous heat as would be the case with a more south-southwest positioned ridge and enhanced southwesterly downslope in our area. Thus, the most significant heat will be across the northern Plains into the Midwest. We`ll likely reach above normal by mid- late July standards by Sunday, and peak only a few degrees above normal by late week. As of now it appears the combination of these temperatures and humidity levels will keep heat indices below traditional Heat Advisory criteria. Furthermore, southerly winds will persist albeit light. Wet bulb globe temperatures should be highest across south-central and southeast Oklahoma toward midweek due to winds being lighter there. Rain chances will be minimal and generally limited to isolated convection in an increasingly more moist environment especially Saturday and Sunday. This may not be entirely diurnal as moisture magnitudes may be significant enough that even very subtle forcing in the mid levels could force convection into the nocturnal period. BRB && .AVIATION... (06Z TAFS) Issued at 1016 PM CDT Wed Jul 21 2021 VFR conditions expected, although we could see brief and minimal BR toward sunrise, similar to this morning. High altitude smoke will also keep the overall hazy looking skies going, especially across the northern- half of Oklahoma. Otherwise, increasing south winds through the period with gusts around 20KT far western Oklahoma. && .UPPER AIR... Issued at 233 AM CDT Mon Jul 19 2021 No upper air flights are planned at this time. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 68 89 71 91 / 0 0 0 0 Hobart OK 68 90 70 92 / 0 0 0 0 Wichita Falls TX 70 92 73 93 / 0 10 10 10 Gage OK 67 90 69 93 / 0 0 0 0 Ponca City OK 67 89 70 92 / 0 0 0 0 Durant OK 72 91 73 93 / 0 20 10 20 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ SHORT TERM...12 LONG TERM....12 AVIATION...11
National Weather Service Raleigh NC
940 PM EDT Wed Jul 21 2021 .SYNOPSIS... Another weak cold front will move slowly south through the area overnight through early Thursday. This front will then stall just south of the area through Friday before finally pushing into the Deep South over the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 920 PM Wednesday... 00Z surface analysis showed the cold front now pressing south through central VA, with a few associated showers and storms mostly confined to the Tidewater region. The western most radar echoes are not on a trajectory to effect Halifax Co, and there`s no indication from hires guidance that additional westward development is expected as nocturnal stabilization continues. Meanwhile, visibility`s across much of central NC have dropped a little to around 6 miles with haze owing to the arrival of the western wildfire smoke stream across the country. HRRR smoke forecasts suggest some improvement as the front pushes through the area, but the mixing with the weak front will be limited, and the haze should linger and still be noticeable on Thursday. An Air Quality Alert for fine particulates has been issued by NC DENR for all of central NC through midnight Thursday night. Otherwise the overnight forecast is on track with lows in the upper 60s and lower 70s. Despite the frontal passage, lows tonight will be near normal with readings in the upper 60s/around 70. && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... As of 245 PM Wednesday... Surface cold front is progged to stall out across the far southern zones Thursday morning, where it is forecast to remain nearly stationary through Friday. Upstairs, central NC will remain on the back-side of the long wave trough in place across the Eastern US and under the influence of deep NWLY flow. Weak upper impulses embedded in the NW flow will traverse the region. However, given limited moisture availability, rain chances will remain very low and generally in proximity to the stalled sfc front across the far southern counties. Hi-res model guidance indicates that the smoke plume will become increasingly diluted throughout the day. Even still, expect the hazy conditions to persist and spread farther south across central and southern NC. Highs Thursday will range from mid/upper 80s north to lower 90s south. Lows in the mid 60s north to lower 70s south. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... As of 255 PM Wednesday... Upper level ridge over the northern plains on Friday will weaken and shift east over the weekend. At the surface, a front will have moved to our south and a lee trough will have taken place across the Piedmont. Thus, we wont be able to get out of the summertime pattern and will have a slight chance of afternoon showers or storms over the weekend. A cold front will then approach the region Monday into Tuesday. These days will be our best chance of precipitation during the long term with slight to chance PoPs in the current forecast. Uncertainty for Wednesday as we wait and see whether the front retracts or continues off the coast. Temps will be near or just above normal with highs in the upper 80s/low 90s on Friday and Saturday, then increase Sunday and Monday to low/mid 90s then cooling down a tad thanks to the cold front with highs in the upper 80s/low 90s. Lows will be in the upper 60s/low 70s. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... As of 725 PM Wednesday... Areas of smoke associated with wildfires burning in the western US will result in hazy conditions through the TAF period. Vsbys have been hovering around 6SM at GSO and INT this afternoon and have also begun to trend downward at RDU/GSO/INT in the past few hours. We are not expecting VSBYS to fall to MVFR, though with nocturnal stabilization this evening, haze should continue. A weak back-door cold front will move south through the area overnight, which should help to alleviate some of the haze in otherwise continued VFR conditions. HRRR smoke guidance indicates the concentration of smoke over VA will be transported back south across NC early Thursday, so the haziness may redevelop/continue during the day Thursday, and thus the TAFs will still reflect some VFR haze. Looking ahead: Aside from some brief periods of sub-VFR conditions associated with isolated to widely scattered afternoon showers and storms, expect predominately VFR conditions through early next week. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...CBL/Blaes NEAR TERM...Smith SHORT TERM...CBL LONG TERM...CA AVIATION...Smith/CBL
Area Forecast Discussion
National Weather Service Reno NV
320 PM PDT Wed Jul 21 2021 .SYNOPSIS... Smoke and haze from the Dixie and Tamarack fires will produce areas of reduced air quality over the next few days. Temperatures will gradually rise into the weekend with highs pushing above 100 degrees in most lower valleys by Saturday. Thunderstorms may return to the region Sunday through the middle of next week. && .DISCUSSION...through next Wednesday... Smoke Trends: * Sadly, the smoke is not going to go away this week as both the Dixie and Tamarack fires continue to grow in size. However, the amount of smoke from both fires highly depends on fire activity and suppression efforts. Both wildfires have produced extensive pyrocumulus this afternoon, leading to more smoke production. Per the latest HRRR model near-surface smoke guidance, smoke from the Dixie fire looks to spread into west-central Nevada (more towards Lovelock-Fallon) tonight through Thursday night. Smoke from the Tamarack fire looks to continue to push across southern Carson Valley and into southern Lyon, Mineral, and far eastern Mono counties through Thursday. For more detailed information please see our Special Weather Statement. Heating Up into this Weekend: * High pressure will continue to strengthen into the weekend over the region, gradually increasing temperatures near to or above 100 degrees Saturday through Monday for the lower valleys of western Nevada and northeastern California. Morning lows should remain in the mid-60s across western Nevada as dry conditions allow for sufficient radiational cooling. This heat is not too unusual for mid-late July, though some heat-health impacts for sensitive groups or those outdoors for extended periods are expected. Temperatures look to cool next Tuesday and Wednesday as an upper level low approaches the region. Typical Afternoon Breezes: * Slightly enhanced southwesterly afternoon breezes (gusts 20-30 mph) are expected today and Thursday before abating a bit Friday through early next week (gusts around 20-25 mph). With the already dry conditions in place, some isolated 1-3 hour critical fire weather conditions are possible through Thursday. For more information, please see the fire weather section below. Thunderstorm Chances increase Sunday-next Wednesday: * Thunderstorm chances will remain low the next few days as 500 hPa heights increase over the region. A push of monsoon moisture looks to work its way into the Sierra and western Nevada by Sunday. This moisture will increase mid-level instability, which could trigger isolated showers and thunderstorms across Mono and Mineral counties by Sunday afternoon, with chances increasing northward through early next week. Medium range deterministic and ensemble guidance continues to hint at PWATs between 0.75-1.00" Monday into Tuesday which could develop more widespread shower and thunderstorm coverage south of Interstate 80 each day. Localized heavy rainfall due to higher moisture content and slower-moving storms could lead to flash flooding potential early next week. -Johnston && .AVIATION... Visibility will be impacted by smoke from multiple large fires. Haze will impact slantwise visibility for much of eastern CA-western NV. Reduced surface visibility and/or lower smoke ceilings to IFR at times are most likely at KMEV through at least Thursday. Other airports in northeast CA and west central NV (including KSVE-KLOL- KNFL-KHTH) will also experience smoke-related impacts from the large Tamarack and Dixie fires that continue to burn actively. Typical afternoon-evening west to southwest wind gusts of 20-25 kt are expected at the main terminals today and Thursday. -Edan && .FIRE WEATHER... Typically breezy summer afternoon/evening winds for the next several days. Most areas in the Sierra and western Nevada will experience wind gusts in the 20-25 mph range, and some isolated gusts of 30-35 mph will be possible for a few hours each afternoon today and Thursday. For eastern Lassen and northern Washoe counties: Plan for single digit humidity values in the afternoons with poor humidity recovery overnight for the foothill and ridge locations. Can`t rule out a handful of hours with critical conditions due to the breezes and low RH`s the next couple of afternoons, especially across eastern Lassen and northern Washoe counties. For Alpine and Mono counties: Humidity values will be in the 10-15% range this afternoon with southwest gusts mainly around 20-25 mph and up to 30 mph for wind prone canyons. A few afternoon cumulus build ups are possible across eastern Mono into southern Lyon and Mineral counties today, with about a 5-10% chance of a thunderstorm or two for the White Mountains in SE Mono county. High pressure expands and strengthens across the West Friday and into the weekend. Monsoon moisture moves northward into the Sierra late this weekend with thunderstorm chances returning to Mono and Mineral counties. Thunderstorm coverage will continue to spread northward through the week with increasing potential for the Tahoe Basin and into Western Nevada. -Edan && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...
National Weather Service Charleston WV
1018 PM EDT Wed Jul 21 2021 .SYNOPSIS... High pressure crosses through from tonight into the weekend. Moisture increases Sunday. Cold front crosses Monday. && .NEAR TERM /THROUGH THURSDAY/... As of 1015 PM Wednesday... Made a few adjustments to cloud cover as some lower to mid level clouds are developing over portions of the mountains. Also bumped up the temperature at EKN a bit based on the current observation as it is remaining on the warmer side compared to the previous forecast. This may be due to the cloud cover along the mountains as the cloudier skies could be preventing this area from radiating as much, keeping it on the warmer side so far tonight. As of 730 PM Wednesday... Made some adjustments to hourly temperatures to better represent current observations. The last few showers have dissipated this evening as the weak front has crossed the area. Overall, current forecast remains on track. As of 210 PM Wednesday... A cold front crossing through the area will continue to bring a few showers and thunderstorms across the northeast portion of the CWA through the afternoon. Haze is again present courtesy of smoke from wildfires in the western US and Canada, but the HRRR model indicates the highest concentrations will drift south by tonight. High pressure begins building into the area from the northwest tonight and temperatures are expected to lower into the 50s to low 60s across the area. With clearing skies and calm conditions, river valley fog is likely to develop late tonight into early Thursday morning. Thursday is expected to be a rather pleasant and dry day as high pressure continues to strengthen over the area. Temperatures should be slightly lower than normal with highs in the upper 70s to low 80s in the lowlands, and mid 60s to upper 70s in the mountains. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 220 PM Wednesday... Surface high pressure and the absence of any upper level disturbance will promote dry weather conditions Thursday and Friday. Models suggest H500 ripples of vorticity within an upper trough clipping our northeast mountains Friday and Friday night. However, believe the high pressure will prevail, and only few showers will be seen along the eastern mountains during the afternoon hours. Tonight should be pleasant with temperatures generally in the 50s Thursday and Friday nights. It will be hot on Friday, with temperatures ranging from the upper 80s lowlands, into the low 70s higher elevations. Some spots reach 90 degrees Friday afternoon. Saturday will be hotter with highs passing the 91 degree mark across the lowlands, and in the mid to lower 80s higher elevations. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 220 PM Wednesday... Ripples of vorticity riding along northwest flow aloft will try to develop few showers or storms mainly along the mountains on Saturday. Meanwhile at the surface, a weak low pressure system along with its cold front/warm front, will pass north of the area Saturday night and Sunday, but weather should remain relatively dry. Then, a stronger cold front is progged to reach our western counties early Monday morning bringing better chances for showers and thunderstorms. Abundant low level moisture and diurnal heating could allow for showers and storm development. However, with the absence of deep layered shear, believe any convection will be weak, perhaps leading to localized heavy downpours and strong gusty winds. Central guidance reflects above normal temperatures, with very minimal influence from the cold front crossing. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... As of 740 PM Wednesday... VFR conditions start the period this evening as any last isolated showers have dissipated out and some scattered clouds remain over the area. Some haze remains possible at HTS this evening but should move out of the area as much of the hazy conditions from the smoke from the wildfires has moved south of the area. High pressure moves into the area tonight which will allow skies to become more clear, and river valley fog will be possible tonight at most sites. Visibilities are expected to drop into the MVFR range later tonight, further dropping to the IFR/LIFR range for the early morning hours. Any fog that forms tonight will begin to clear out tomorrow morning, giving way to dry, VFR conditions for the day with high pressure in control tomorrow. Northwesterly winds begin in the period at around 5 to 10 KTs with a few sites gusting up around 15 KTs. Winds are then expected to become light to calm tonight, assisting with fog formation overnight. Northerly/northwesterly winds will then pick up again during the day tomorrow at around 5 to 10 KTs. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z FRIDAY... FORECAST CONFIDENCE: High. Medium for fog. ALTERNATE SCENARIOS: Extent and intensity of river valley fog tonight may vary from TAFs. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE THU 07/22/21 UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11 EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07 CRW CONSISTENCY H H H H H H H L L L L L HTS CONSISTENCY H H H H H H H H M M L L BKW CONSISTENCY H H H H H H H L L L L L EKN CONSISTENCY H H H H H M M L L M M L PKB CONSISTENCY H H H H H H H H L L L L CKB CONSISTENCY H H H H H H M L L L L L AFTER 00Z FRIDAY... IFR in early morning valley fog possible through Saturday, and locally in thunderstorms on Sunday. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...ARJ/JLB NEAR TERM...CG/JLB SHORT TERM...ARJ LONG TERM...ARJ AVIATION...CG
Area Forecast Discussion
National Weather Service Blacksburg VA
911 PM EDT Wed Jul 21 2021 .SYNOPSIS... Hazy skies are the result of smoke from the western U.S. and Canadian wildfires. Aside from the haze, mainly dry and seasonal weather expected through the remainder of this week. A cold front will approach the region from the northwest Sunday...crossing the area Monday. This will be our next bonafide opportunity for showers and thunderstorms. && .NEAR TERM /THROUGH THURSDAY/... As of 910 PM EDT Wednesday... Minor adjustments to the forecast tonight for latest temperatures and dew points. Winds have already gone calm in many spots. Winds will be northwesterly and light on Thursday with high pressure building in. Overnight lows should drop into the mid 50s in the mountains to the mid 60s over the piedmonts of NC and VA. As of 600 PM EDT Wednesday... A southward-moving front was in the process of pushing through the forecast area, and has moved through western VA and into eastern VA and parts of NC. Gusty NW winds developed briefly just behind the front. This has helped to clear some of the smoke out from the wildfires to our north, at least in the lower levels. Made a few changes to sky cover, temperatures, and winds for this update. As of 300 PM EDT Wednesday... ...Hazy Skies But Seasonal and Mainly Dry... An air quality alert was issued for VA/ for the increase in smoke particulates. is a great place to check out the latest numbers with respect to area DEQ sensors. Roanoke trended into the unhealthy range prompting the alert. The HRRR smoke model maintains higher concentrations of smoke across the area until a cold front introduces a change in airmass tonight. An air quality alert will also be in effect for North Carolina beginning now and continuing through Thursday, or until such time there is an airmass change from the front. Latest satellite imagery indicates haze covering the entire forecast area. A surface cold front was inbound from the north. There were a few thunderstorms along the front to our northeast, but the airmass over our forecast area is not supportive of deep convention with the exception of maybe areas down to about I-64. Generally running with less than 20 percent chance for areas north of I-64 which means no more than isolated coverage. For the overnight, the front is expected to move south and into the state of North Carolina. This will introduce a northerly wind overnight and into the day Thursday. Post frontal drying is expected with falling dewpoints along with temperatures a degree or two cooler compared to Wednesday. The increase in northerly wind is also expected to advect/push the smoke/haze south and west with times, so anticipating better visibility Thursday...improving from the north. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... As of 200 PM EDT Wednesday... An upper level trough over the Mid Atlantic region and surface high pressure over the area, generally looking for fair weather cumulus to pepper the area Friday. Can not rule out a stray shower in the late afternoon and evening. A warm front will pass over the area Saturday and may bring a few drops of rain along with it. Near normal temperatures expected Friday with upper 70s to mid 80s across the mountains and mid to upper 80s east of the Blue Ridge. Following the warm front, heights gradually increase and so do the temperatures. Highs Saturday will range in the 80s west of the Blue Ridge to low 90s east. Each night, overnight lows will fall into the 60s. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 200 PM EDT Wednesday... Heights continue to increase on Sunday, along with temperatures and humidity. With a lee trough over the piedmont, convergence will help spark scattered afternoon and evening thunderstorms along the eastern slopes of the Blue Ridge into the foothills. An approaching cold front should bring some spotty convection west of the Blue Ridge late into the afternoon going into the evening. Instabilities maybe high enough for a few strong storms. The coverage of strong to severe storms increases on Monday as a cold front is set to move through the region late in the day. This front could jump to the lee trough which would put the piedmont in a higher risk for strong storms. The front should clear the area by Tuesday morning with high pressure hanging around into Wednesday. Temperatures ahead of the front will run warmer than normal with the warmest day being Monday. Following the front, temperatures will fall back towards normal values Tuesday and Wednesday. && .AVIATION /01Z THURSDAY THROUGH MONDAY/... As of 900 PM EDT Wednesday... Smoke/haze had mostly scattered out this evening, at least in the lower levels, as a cold front pushed south. Winds have become light and variable and will remain that way overnight, with a prevailing NW direction once the sun comes up Thursday. Models indicate fog for BLF/LWB/BCB late tonight. Forecast confidence is high for winds and sky cover overnight, but lower for fog development after the frontal passage. Extended Aviation Discussion... VFR through Friday with limited if any threat of showers/storms. A front this weekend will bring an uptick in storm coverage, but still VFR outside any storms. Always a possibility for the late night fog at LWB and perhaps BCB especially this weekend. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...PM NEAR TERM...PM/SH SHORT TERM...RCS LONG TERM...RCS AVIATION...PM
We have mentioned an easterly wave in several forecast discussions
that is expected to move westward across the lower 48 and bring
quite a bit of additional moisture and dynamics into the Desert Southwest this weekend. With each model run, this wave is trending slower. Uncertainty surrounding this wave revolves around both timing and location, which, in turn, provides quite a bit of uncertainty in the PoP forecast. Compared to the previous run, the latest run of the NBM has receded a bit eastward with lower PoPs each afternoon through Sunday than originally anticipated. That said, pop-up convection will continue each afternoon through the weekend favoring Mohave County as well as the higher terrain of Lincoln and Clark counties. [EARLY NEXT WEEK] As the easterly wave moves across Arizona and gets sucked around the monsoonal high, the additional moisture and dynamics that it will bring will result in widespread showers and thunderstorms across the forecast area. Impacts of this easterly wave will begin as early as Sunday evening primarily impacting northwestern Arizona. Flash Flood Watches will be coordinated this week with neighboring offices as our timing confidence increases over the next few days. Impacts look to peak on Monday areawide, with highest chances over Mohave County and the higher elevations of southern Nevada. Primary concern will be flash flooding, though winds in excess of 50 mph are possible with associated outflow. [NEXT WEEK] The easterly wave will dance between an off-shore area of low pressure and the monsoonal high before getting caught in an easterly flow aloft and shooting eastward out of our area. As such, through the week, precipitation chances will be focused in the northern portions of our CWA, returning each afternoon. && .AVIATION...For McCarran...Isolated thunderstorms are expected to continue around the region into the early evening. There is the potential for gusty outflow winds associated with storms that form around the Las Vegas Valley with gusts to 30 kts possible. Otherwise, look for a general south to southwest wind this evening between 10 and 15 kts. Diurnal trends expected overnight. For the rest of southern Nevada, northwest Arizona and southeast California...Isolated thunderstorms expected again today, but mainly confined to Lincoln, Clark, Mohave, and eastern San Bernardino counties. Storms will be capable of producing gusty outflow winds and heavy rain from their direction. Outside of thunderstorm influences, look for winds generally 10 kts or less with diurnal trends. FEW-SCT 140-160 with lower CIGS near storms. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION/AVIATION...Varian For more forecast information...see us on our webpage: or follow us on Facebook and Twitter