Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/05/21

Area Forecast Discussion
National Weather Service Aberdeen SD
837 PM CDT Wed Aug 4 2021 .UPDATE... Issued at 837 PM CDT Wed Aug 4 2021 Some showers/storms moving into north central sd this evening along with showers with the short wave trough in the east leaving the region through the rest the evening. Made adjustments to the weather and pops. UPDATE Issued at 647 PM CDT Wed Aug 4 2021 00z aviation discussion updated below. && .SHORT TERM...(This Evening through Thursday) Issued at 242 PM CDT Wed Aug 4 2021 A line of scattered showers, associated with an upper level trough, continues to track from west to east across the Northern Plains. Very little shear and CAPE to work with, so only general thunder (if any) is expected. Should see clearing skies and light winds through the overnight hours. A weak surface trough lingers across the eastern CWA Thursday. Upper level support is generally lacking however. Models do indicate a shortwave tracking across southern Canada and into parts of North Dakota/Minnesota, but best forcing would remain off to the north. That said, Bufkit soundings show steep low level lapse rates and a few hundred J/KG of CAPE to work with. Additionally, CAMs continue to hint at an isolated shower or thunderstorm across the far eastern CWA. The overall POPs reflect this. Temperatures again trended cooler than normal today, both due to cloud cover and still some lingering high level smoke. HRRR integrated smoke product suggests smoke will be streaming in from the west again Thursday. Stuck with the blended guidance for now, but if smoke is a player, it may need to be adjusted down a degree or two. .LONG TERM...(Thursday Night through Wednesday) Issued at 242 PM CDT Wed Aug 4 2021 The long term period begins on Friday with an upper level ridge sliding across the region ahead of a northern Rockies trough. As the trough approaches the region Friday night, a LLJ should develop over the CWA bringing a chance for showers and thunderstorms. The convection should push northeast of the CWA during the morning hours on Saturday with a period of dry conditions possible. During the afternoon hours, the surface low and associated frontal boundary will begin advancing eastward into a more unstable environment. The surface low and upper level trough could be fairly strong, which combined with some instability and shear could produce a few strong to severe storms, mainly in eastern SD and western MN. The convection should push into MN Sunday morning, with the rest of the long term featuring mostly dry conditions. Some models are showing a frontal boundary clipping north-central SD, with additional pcpn possible early next week. && .AVIATION...(For the 00Z TAFS through 00Z Thursday Evening) Issued at 647 PM CDT Wed Aug 4 2021 Terminals KABR,KATY,KPIR,KMBG VFR conditions are expected through tonight and Thursday at all airports. P6SM light showers from a short wave trough will affect the ATY area early this evening as it moves east. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Mohr SHORT TERM...Serr LONG TERM...SD AVIATION...Mohr
Area Forecast Discussion
National Weather Service Denver/Boulder CO
947 PM MDT Wed Aug 4 2021 .UPDATE... Issued at 925 PM MDT Wed Aug 4 2021 The lone storm that developed over Gilpin and Clear Creek counties has dissipated and no more showers or storms will develop tonight. The only change to the forecast was to expand the area of smoke. The latest HRRR smoke run shows quite a bit of smoke over all of our CWA so I figured it was best to put it in the forecast for the entire area. && .SHORT TERM...(This evening through Thursday) Issued at 232 PM MDT Wed Aug 4 2021 After a prolonged active weather pattern, we`re finally trending back to a warmer, quieter pattern. The trough axis that brought healthy rain totals to much of the state yesterday through the early afternoon today has now exited the area, with subsident northerly flow in its wake. There`s been just enough moisture and instability across the plains... as evidenced by an earlier FNL sounding... to develop some shallow cumulus clouds, but otherwise there`s not much to write home about this afternoon. Fairly quiet conditions are expected through the rest of the evening. There could be an isolated storm or two across the high country and into the southern Foothills/Palmer Divide, but confidence in that panning out is pretty low. Tomorrow`s weather should also be fairly quiet, with a ridge trying to build into the Four Corners region, while a shortwave trough approaches from Oregon. Mid-level temperatures should be about 2-4C warmer than today, meaning highs will likely make a run at 90F for the Denver metro, with low 90s likely for the far eastern plains. The main impacts tomorrow will come from wildfire smoke. HRRR smoke forecasts show increasing near surface and total smoke starting late tonight, with thicker smoke likely by late tomorrow morning. Based on the last time we had forecast near surface smoke concentrations this high, there will likely be some haze/reduced surface visibility to go along with the air quality concerns. .LONG TERM...(Thursday night through Wednesday) Issued at 232 PM MDT Wed Aug 4 2021 Thursday evening will be dry and mostly clear under ridging aloft. RAP-Smoke output suggests that high smoke concentrations from fires across the western states, especially the Pacific Northwest, will linger over northeast Colorado into Friday as smoke builds up under the ridge. The ridge axis will move over Colorado late Thursday and early Friday and northeast Colorado will be on the back end of the ridge by Friday afternoon. Continue to expect high temperatures on Friday back in the mid to upper 90s across the plains, upper 70s to mid 80s in the foothills and mountain valleys, and upper 60s and lower 70s in the mountains. Friday afternoon and evening, there should be an increasing and more zonal flow aloft at the base of an approaching shortwave. Models seem to be coming to a consensus on the track and timing of the shortwave which would bring enough forcing over northeast Colorado coincident with enough instability to support isolated to scattered storms and showers Friday afternoon and evening. About 5 g/kg of specific humidity from the lower to mid levels should be enough moisture for some light precipitation. Forecast soundings are currently showing deep mixing up to around 600 to 550 mb which suggests high based showers producing light precipitation and gusty outflow winds. Aside from the possible convection, increasing flow aloft and deep mixing should mean increasing winds in the high country and some breezy conditions in the afternoon and evening Friday, especially in the northern mountains and North Park. Forecast winds seem to be trending slowly stronger with each run, now with gusts up to the 30 to 40 mph range in that area. The shortwave will move over northeast Colorado late Friday and early Saturday, and a weak front behind it should bring a few degrees of cooling. Saturday afternoon and evening should see more breezy conditions, but weaker afternoon winds than those Friday, and mostly clear skies. Sunday looks like a return to drying, clearing and warming as heights rise again between the exiting shortwave and another coming on shore over the Pacific Northwest. Models continue to show this wave passing farther north without significant impacts for Colorado, and a general lack of moisture and instability anyway. Right now it looks like just some more isolated convection bringing light precipitation early next week, focused on the high terrain. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 925 PM MDT Wed Aug 4 2021 Smoke will impact the terminals through the TAF period as the thickness of smoke is only going to increase. DEN may drop below 6 miles of visibility during the day tomorrow with visibility in the 3 to 4 mile range possible. Winds will be light and will follow normal drainage patterns. No other weather, ceilings or visibility issues. && .HYDROLOGY... Issued at 232 PM MDT Wed Aug 4 2021 Low flash flooding threat for tonight and tomorrow. The area of monsoon moisture has departed the area today, with drier air in place through tomorrow. There could be a few weak thunderstorms this evening and again Thursday afternoon. However, with limited instability and moisture available, any precipitation amounts will be very light. The threat of burn area flash flooding should remain low through early next week due to persistent warm and dry conditions. Isolated to scattered showers in the afternoon and evening Friday should produce light precipitation. The weekend will be mostly clear and dry, followed by more isolated showers bringing light precipitation and low impacts early next week. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Danielson SHORT TERM...Hiris LONG TERM...EJD AVIATION...Danielson HYDROLOGY...Hiris/EJD
Area Forecast Discussion
National Weather Service Dodge City KS
510 PM CDT Wed Aug 4 2021 ...UPDATE TO AVIATION... .SHORT TERM...(This evening through Thursday) Issued at 231 PM CDT Wed Aug 4 2021 GOES-16 water vapor channels have been showing a continued expansion eastward and thickening of mid to high level cloud cover across the western 2/3rd of our area this morning although still a few pockets of diffuse insolation was apparent. This synoptic trough will continue to shift across our region Today and Tonight. The only areas where any sort of surface based convection will probably remains to the north and west of our area (nw KS and NE CO), however a few isolated more elevated storms can`t be ruled out as the trough moves dead center over the DDC area in the evening bringing some weak elevated MUCAPE with it. Nothing suggests severe weather, however until sunset, gusty winds with a stronger storms in the west would`t be ruled out given the steep low level lapse rates. Additionally, as the CAPEs are not high there are decent PWAT values around an inch or higher which may lend itself to a slightly more elevated downdraft potential. As of 2 pm a line of weak thunderstorms has rapidly unzipped just northwest of Syracuse and the HRRR has the best handle of the timing and spatial attributes and would have these initial storms to be unable expand very far eastward as the convection much farther north in NW Kansas push towards Scott City after 00Z. Extensive mid level cloudiness will have an impact on the overnight temperatures, especially across the lower plains eastern sections of our forecast area (warmer lows in the mid to upper 60s). Cooler air advection and longwave radiational cooling behind the trough should ensure cooler temperatures by Thursday morning in the 50s out west. .LONG TERM...(Thursday night through Wednesday) Issued at 239 PM CDT Wed Aug 4 2021 Statistically speaking the chances for rain from about Thursday afternoon through about Tuesday are near zero. The influence of the upper trough bring the hot summer conditions back with downslope higher terrain air overspreading the High Plains region from the Dakotas to the Texas panhandle. DDC ought to reach the 100 degree mark as early as about Saturday if not Friday afternoon. The hot temperatures should plateau through the weekend and persist in to early next week. By Tuesday/Wednesday three major 3 global spectral models drive another synoptic scale 500 mb trough/low center across the Northern Rockies and Northern Plains which should result in some surface response of a surface and mid level front being driven equatorward. These model have varying degrees of precipitation fields across the central Plains, but all seem at least to weaken the intensity of the hot air. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 505 PM CDT Wed Aug 4 2021 VFR conditions will prevail in the vicinity of all TAF sites through early Thursday afternoon. Showers and a few embedded thunderstorms will continue to drift northeast across west central and extreme southwest Kansas through late evening, resulting in possible periodic gusty winds in vicinity of KGCK and KLBL. Otherwise, south-southwest winds 10 to 20kt are expected to subside somewhat after sunset this evening. && .PRELIMINARY POINT TEMPS/POPS... DDC 64 91 65 98 / 20 0 0 0 GCK 59 90 61 98 / 20 0 0 0 EHA 57 90 61 98 / 20 0 0 0 LBL 59 91 62 99 / 10 0 0 0 HYS 64 91 65 98 / 10 10 0 0 P28 67 91 67 98 / 10 10 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Russell LONG TERM...Russell AVIATION...JJohnson
Area Forecast Discussion
National Weather Service Des Moines IA
635 PM CDT Wed Aug 4 2021 .DISCUSSION.../Tonight through Wednesday/ Issued at 407 PM CDT Wed Aug 4 2021 Forecast Highlights: -- Scattered showers and a few non-severe thunderstorms Thursday. -- Warming temperatures into the weekend and early next week. -- Strong to severe storms possible Saturday, details below. TODAY AND TOMORROW: Surface high pressure exited the state of Iowa and pushed into Illinois this morning but high pressure conditions continue today with another dry, mild, and quiet day. High temperatures today will again be below normal for early August in the low 80s. The HRRR smoke products suggest increased concentrations of smoke will be in place aloft moving across western into central Iowa today into tonight and into eastern Iowa overnight. Concentrations at the surface look to be light over northeast and far western Iowa late afternoon into this evening with improvements overnight but increased concentrations aloft again late Thursday into Friday. Moisture returns to the area tonight in tandem with a shortwave trough moving through the state. This will bring the threat for non- severe scattered showers and a few thunderstorms across the area overnight into tomorrow morning with another round of scattered showers and thunderstorms on Thursday afternoon, most likely in central and southern IA. These afternoon showers and thunderstorms are the most likely to bring some measurable precipitation, though not widespread due to the scattered nature of the storms, and still with amounts near to below 0.25 in. Although MUCAPE values look to be around 1500 J/kg tomorrow afternoon, forcing and shear still look fairly weak so still not expecting any severe weather. BEYOND THURSDAY: A thermal ridge builds into the area behind the Thursday system with southerly surface winds ushering WAA into the area and sending temperatures towards the 90s on Friday, Saturday, and Sunday and into the 90s on Monday. Have backed off temperatures slightly on Sunday with some hints of lingering clouds, and possibly some additional showers overnight into Sunday morning in the west and southwest, both of which would decrease high temperatures a bit Sunday. Humidity will build into this weekend and early next week with heat indices on Monday looking to be above 100 in southern Iowa as of current trends. The warm and humid conditions look to persist into early next week as well. Along with the return of the heat into this weekend, storm chances also increase again on Saturday. A surface low pressure will move through Nebraska on Saturday with a surface boundary along the leading edge. As this approaches the state on Saturday, it will be riding a mid-level ridge, in combination with the surface boundary, providing the forcing for strong to severe storms on Saturday. No significant updates since the previous forecast as models still differ on timing and location for the greatest threat of severe weather, with timing in the models varying more in recent runs than in previous runs. The best shear still appears to be post-frontal, but all models do indicate sufficient instability, so we will continue to monitor and provide updates in subsequent forecasts on the shower and possible storm potential Saturday. && .AVIATION.../For the 00Z TAFS through 00Z Thursday evening/ Issued at 635 PM CDT Wed Aug 4 2021 Scattered SHRA/TSRA will affect the terminals at times during the TAF period. The first and most likely period will come overnight into Thursday morning...roughly between 06Z and 15Z depending on the terminal...with periodic MVFR ceilings/visibility possible but probability at any given time too low for more than VCTS in the 00Z TAFs. During the day Thursday additional SHRA/TSRA may occur, but low confidence in location and short duration preclude TAF mention at this range. Prevailing MVFR ceilings may also be possible on Thursday, mainly at MCW/ALO. Expect details to be refined in subsequent TAF issuances. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KCM AVIATION...Lee
Area Forecast Discussion
National Weather Service Grand Junction CO
525 PM MDT Wed Aug 4 2021 .SHORT TERM...(Tonight through Thursday night) Issued at 239 PM MDT Wed Aug 4 2021 The current 500mb high is centered over the NV/CA/AZ triple point with north-northwesterly winds covering the entire CWA. As such, dry northwest flow rolling over top the ridge of high pressure has eroded through what was just recently an exceptionally moist atmospheric profile. Satellite imagery only conveys shallow cumulus puffs atop mountain ranges with just a few isolated clouds showing any vertical extent, near Monarch and Wolf Creek Pass. High terrain along the central and southern Divide have the best chance to wring out precipitation from said convection, while the rest of the region maintains a drying trend. Also, accelerated streamlines across the Western CONUS ridge certainly didn`t take long to infiltrate smoke from PacNW fires across much of Western Colorado and Eastern Utah`s skies. Unfortunately, recent vertically integrated HRRR solutions maintain a thick plume of ppm aloft through the short term period. This may inhibit radiational cooling (especially for the northern half of the CWA), moderating overnight lows. The next low pressure system spinning ashore the NorCal coast will nudge high pressure overhead on Thursday. This shift in ridge axis places the CWA in between two upper level jets and temporarily reduces winds aloft. Expect mostly clear skies across the region, with high temperatures running back above normal. Otherwise, the dry and warming trend continues on Thursday, priming the environment for critical fire weather concerns to resurface during the long term. .LONG TERM...(Friday through Wednesday) Issued at 239 PM MDT Wed Aug 4 2021 The high pressure over the Great Basin will start to flatten Thursday evening as a shortwave trough approaches from the west. By Friday, the ridge will have all but broken down, or at least shifted to the south and east, causing flow to become more southwesterly. Supporting the trough will be a 70kt jet streak and as the trough passes, the gradient will tighten while deep mixing up to 500mb will also bring some stronger winds to the surface. Dewpoints look to decrease so this combination looks to bring some critical fire weather conditions to the region as described below. The best forcing looks to stay just to our north and also weaken very quickly during the day Friday. Hardly any precip is expected with trough passage with maybe a few sprinkles or quick rumble of thunder along the Divide but that looks to be it. High temps will drop a few degrees both Fri and Sat thanks to the cooler air moving in from the north. Previous model runs were indicating the possibility of another monsoonal push next week but latest cluster guidance indicates another trough dropping down from the northwest. While we won`t see any precip because the trough will be too far north, it does like the trough will suppress the high pressure. If this latest solution pans out, the brunt of moisture will make its way into Arizona and New Mexico from Monday through Wednesday and just barely nip our southern zones. Confidence is sorta `meh` at the moment but with the GEFS and EPS getting into better agreement, we`ll take and wait and see approach for the next few runs. The long and short of it...much drier over the next few days with temperatures generally increasing, with a slight cooldown Friday and Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 524 PM MDT Wed Aug 4 2021 Clear sailing over the next 24 hours with mainly clear skies..well except for the smoke layer which is creating hazy conditions but for the most part vsby remains unlimited. && .FIRE WEATHER... Issued at 239 PM MDT Wed Aug 4 2021 A ridge of high pressure sliding overhead through Thursday will result in a warming and drying period. By Friday, a disturbance crossing the Northern Rocky Mountains will enhance winds across much of Eastern Utah and Western Colorado, with a frontal passage anticipated Friday afternoon. As such, widespread critical fire weather conditions resurface. Uncertainty lies in fire weather zones where fuels haven`t been updated since early May. Despite recent monsoonal surge, used the last status entered to determine areas included in Fire Weather Watch. Zones included in the Watch may change if conditions have significantly improved from recent rainfall. Otherwise, meteorological conditions will be met. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...Fire Weather Watch from Friday afternoon through Friday evening for COZ200-202-203. UT...Fire Weather Watch from Friday afternoon through Friday evening for UTZ490. && $$ SHORT TERM...ERW LONG TERM...TGR AVIATION...TGJT FIRE WEATHER...ERW
Area Forecast Discussion
National Weather Service Green Bay WI
1036 PM CDT Wed Aug 4 2021 Updated aviation portion for 06Z TAF issuance .SHORT TERM...Tonight and Thursday Issued at 238 PM CDT Wed Aug 4 2021 Smoke from the wildfires out west continues to plague the forecast area this afternoon, and is expected to impact the area through at least Thursday morning. Cumulus clouds across northeast Wisconsin have generally been fairly flat given the upper level ridging across the western Great Lakes; therefore the weather should be fairly quiet during the evening hours. Lows tonight are expected to be fairly warm; ranging from around 60 across the north, with lower to middle 60s across central and east-central Wisconsin. A weak mid level trough and surface cold front will approach the upper Mississippi Valley on Thursday, which could set off showers and thunderstorms across central and north-central Wisconsin during the afternoon hours. Given the main forcing will be west of the area confidence is not high that we will see much in the way of this activity. The arrival of the low pressure system will turn winds to a southwesterly direction, which should help push the aforementioned wildfire smoke out of the forecast area on Thursday. Highs on Thursday are expected to range from the upper 70s across north-central Wisconsin to 80 to 85 across east- central Wisconsin. .LONG TERM...Thursday Night Through Wednesday Issued at 238 PM CDT Wed Aug 4 2021 Active pattern is expected into early next week as several systems will impact the area. Temperatures should run at or above normal during the period. For Thursday night, the first 500mb trough moves into the western Great Lakes region. The ECMWF has the better forcing with the upper level energy well north and south of the state. The ECMWF has meager rainfall amounts across the forecast area, thus capped rain chances for now in the high end chance category. The upper trough will slide east across the area on Friday. Daytime heating combined with a weak frontal boundary moving across the area will be the focusing mechanism for thunderstorm development. The latest bufkit soundings were a little more robust with CAPE values of 1,500 to 2,500 J/KG. Wetbulb zero heights were around 13,000 feet with 0-6km shear values of 10 to 20 knots. With this in mind, added a mention of stronger storms in the Hazardous Weather Outlook (HWO) Friday afternoon into Friday evening for gusty winds, hail and torrential rainfall. 700mb winds were only around 15 knots, thus storms will be relative slow movers. Could not rule out an isolated severe storm with a wet microburst. July and August are the prime months for these type of events. The storms should end later Friday night. There will be a dry period from late Friday into Saturday. The far northeast appears to have the longest period of dry weather while central Wisconsin will have the shortest due to the closer proximity of the warm front. Convection is expected west of the area and some of this activity could spill into north-central and central Wisconsin before dissipating. The main show will be later Saturday night into Sunday night where there is the potential for stronger storms. There is some timing differences among the models when the upper trough and best forcing with the upper level disturbance moves across the region. Also, the amount of instability available will depend on how much clearing takes places after the Sunday morning showers and storms. From Monday through Wednesday, low confidence in the chances of showers and storms due low confidence in the placement and timing of upper level features moving through the mean flow. && .AVIATION...for 06Z TAF Issuance Issued at 1032 PM CDT Wed Aug 4 2021 Quiet weather with generally good flight conditions is expected overnight, but clouds will increase and lower from west to east and showers and scattered thunderstorms will overspread the area on Thursday. No big changes to the handling of the smoke as the HRRR guidance has been consistent with that aspect of the forecast and will continue to rely on it. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....Kurimski LONG TERM......Eckberg AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
738 PM EDT Wed Aug 4 2021 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 218 PM EDT Wed Aug 4 2021 - Isolated storm risk for late this afternoon - Increased potential storms Friday and into early next week - Warming up with some 90 degree reading possible next week && .DISCUSSION...(This evening through next Wednesday) Issued at 218 PM EDT Wed Aug 4 2021 - Isolated storm risk for late this afternoon Based on SPC Mesoscale Analysis page...through 2 pm we have developed 500 to 1000 J/kg of CAPE across the northern half of the CWA. Visible satellite imagery suggest the smoke may be limiting the convection around Southwest Lower MI. Some increased CU where noted along the lake breeze slightly inland from Lake MI. Enough CAPE is around to support an isolated storm or two...mainly north of a Muskegon to Lansing line. The wind fields are relatively weak so any storms should be slow moving and could lead to very localized heavy rain. - Increased potential storms Friday and into early next week A mid to upper level trough tracks through the Great Lakes region Friday into Friday night. An associated low level jet arrives as well which will advect in abundant moisture and better instability. Thus we will feature higher POPs to for this period given the moisture...lift and instability that will be in place. Deep layer shear is shown to be relatively weak so organized severe weather looks unlikely. Another mid to upper level wave arrives Sunday night into Monday. This feature is shown to be losing amplitude...and should be weakening. However plenty of moisture and instability will be around to support showers and thunderstorms. A southwesterly 25 to 35 knot low level jet is shown as well which should help to increase the low level lift. A stronger mid level wave is shown to be tracking eastward through the Canadian Prairies for the middle of next week. It is possible that this system could send a stronger cold front in our direction by the end of the week. - Warming up with some 90 degree reading possible next week The steady south to southwest flow through the weekend and into early next week will support warming temperatures. Some 90 degree readings are starting to show up in the MOS guidance. Temps at 925 mb are shown to reach 26 deg C Sunday afternoon...with similar values for Tuesday and Wednesday. These values will allow for daytime high temps climbing into the upper 80s to near 90 degrees. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 738 PM EDT Wed Aug 4 2021 The smoke layer will prevail through this forecast period. Based on the HRRR smoke model most of the smoke is below 15000. The smoke seems thickest in the 3000 ft to 10000 ft layer. Otherwise, expect VFR conditions with light winds through Thursday. Like today, cumulus clouds will develop by early afternoon. An isolated shower is not out of the question but should so isolated that it should present little problem to VFR flying Thursday. I put VCSH in the GRR TAF since there is a shower currently near Sand Lake. That shower should be gone by shortly after these TAFs are valid. && .MARINE... Issued at 218 PM EDT Wed Aug 4 2021 One low level jet moves in for later Thursday night into Friday night. Southwest winds from this feature will support building waves...especially north of Grand Haven. We will need to monitor the potential for small craft and beach hazard conditions. A similar setup will exist for Sunday into Sunday night. Given the warm waters and likely high beach populations...we will need to assess the situation closely going forward. For now we will feature 2 to 4 foot waves for these periods. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ SYNOPSIS...MJS DISCUSSION...MJS AVIATION...WDM MARINE...MJS
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1012 PM EDT Wed Aug 4 2021 .SYNOPSIS... A stationary front will remain stalled along the southeast United States coast through early Saturday before dissipating. Meanwhile, the trough situated over the eastern United States will gradually lift northeast. High pressure builds in briefly Friday across the southeast before another trough tracks across the region. Diurnal shower and thunderstorm chances will continue this week but will be somewhat limited by lack of moisture. Friday night into Saturday looks like the best chance for showers and thunderstorms as the trough tracks east across the forecast area. && .NEAR TERM /THROUGH THURSDAY/... As of 10 pm EDT Wednesday: The most recent HRRR runs have finally come around to idea that spotty showers will be possible across the NC foothills through the overnight hours as a vorticity lobe in the base of the upper trough lifts northeast through the region. There will not be much instability to work with, so will generally cap nocturnal PoPs in the isolated range, with any thunder confined to the immediate Blue Ridge escarpment where upslope forcing will be best. Otherwise, showers will dissipate overnight in the southern sections that will be on the NVA side of the passing vort lobe overnight. Considerable overnight clouds will continue with moisture trapped beneath a mid-level inversion in area profiles, and mountain valley low stratus and fog will be possible if enough breaks in the clouds form to permit some measure of radiational cooling. Otherwise, lingering surface high pressure to the north and northeast will provide mostly northeasterly winds through Thursday. This will result in even less moisture in profiles, a drier boundary layer, and with upper support moving off to the east, any PoPs will be limited to the western mountains during peak heating. Max temperatures should rebound at least a category with a bit better insolation. && .SHORT TERM /THURSDAY NIGHT THROUGH SUNDAY/... As of 200 PM EDT Wednesday: The stationary front along the SE CONUS should dissipate early Saturday. Meanwhile, northeast Georgia and the Carolinas will be sandwiched between troughs Thursday night into Friday. A high pressure ridge in the western Atlantic should nudge into the southeastern CONUS Friday. With this synoptic pattern in place at the start of the short term period, moisture should be limited across the CWA as PWAT values remain low Thursday night into most of Friday. Therefore, have capped diurnal showers and thunderstorms to a slight chance to chance during this time frame. The ridge of high pressure extending into the area will be forced to the south and east as a trough approaches from the west Friday evening into Saturday. PWATs increase during this time frame as the trough tracks east towards the forecast area. Both the GFS and ECMWF have come into better agreement in regards of the timing and behavior of the trough this weekend. At this time, Friday night into Saturday looks like the best chance to see showers and thunderstorms from this upper-level trough due to the increased moisture the system brings. Capped PoPs from a high end chance to low end likely across the CWA. Sunday this trough should lift northeast into the northeastern CONUS allowing high pressure in the western Atlantic to build in from the south. In response to this ridge building back into the area, PWATs should slightly decline again Sunday. As a result, capped PoPs across the CWA to a slight chance. Highs Friday and Saturday should be near normal to a few degrees below normal. Sunday highs return to above normal. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... As of 200 PM EDT Wednesday: High pressure could continue to build in across the Southeast Sunday night into Monday. The ECMWF shows this, however the GFS hints at a small area of low pressure forming across the Deep South and tracking into the Carolinas during this time frame. Tuesday into Wednesday remains even more uncertain as models continue to diverge on the overall synoptic pattern. The ECMWF keeps the ridge in place for the second half of the extended period while the GFS has the low dissipating early Tuesday with high pressure retreating east as a trough digs from southern Canada into the northern United States. With model disagreement throughout much of the extended period, decided to keep diurnal shower and thunderstorm chances in the forecast, but capped PoPs to a slight chance to chance. Highs throughout the extended period should be above climo and much warmer compared to what we are seeing now. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... At KCLT and elsewhere: Surface high pressure northeast of the region will maintain light easterly winds across the region. This will permit winds at the foothill and Piedmont TAF sites to toggle between ESE and ENE through the period. Winds will be light to calm at KAVL, but mainly NW early and SE late. Showers have diminished around KAVL this evening and expect all sites to remain dry for the rest of the overnight hours despite the passage of an upper trough axis. Thursday appears to have even less of a chance for showers or thunderstorms, with drier air advecting in, dewpoints mixing out further, and any upper support east of the terminals. Expect mainly SCT to BKN VFR bases through much of the period at 5 to 7 kft with moisture under a nighttime inversion, followed by daytime heating through Thursday. Fog and low stratus will be possible in the fog- prone mountain river valleys overnight, with brief daybreak IFR possible at KAVL. Outlook: More typical summertime diurnal convection will redevelop over the area Friday into the weekend. Fog and low stratus will be possible each morning, particularly for the mtn valleys and areas primed by rainfall from the previous evening. 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 90% High 100% KAVL High 100% Low 56% 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...AP NEAR TERM...HG SHORT TERM...AP LONG TERM...AP AVIATION...HG
Area Forecast Discussion
National Weather Service Gray ME
949 PM EDT Wed Aug 4 2021 .SYNOPSIS... Low pressure will track through southern New England later tonight, before passing through the Gulf of Maine Thursday morning possibly bringing some heavy rain to the coast. An upper level trough will bring more clouds to the region Friday, with high pressure building in at the surface through Saturday. Scattered showers and thunderstorms are possible Saturday night into Sunday as a frontal boundary crosses the region. Ridging will continue to build early to mid next week, with a warmer pattern becoming more established. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... 945 PM Update... Radar and ASOS reports indicate that some light rain shower activity has now reached portions of southern NH but the main precipitation shield is still off to the east over the waters. The latest few runs of the HRRR have trended downward in total QPF as a result of keeping the steadiest and heaviest rainfall both to our south and east with little to no measurable rain reaching ME until around 09Z. As a result, PoPs and QPF were adjusted to account for these trends in both radar imagery and model guidance. Other than some minor tweaks to temperatures, dew points, and sky cover the rest of the forecast remains on track. Previously... 530 PM...Some adjustments, mainly to timing of arrival of rain, more chance pops later this evening in SE NH and coastal, and pushing the heavy potential until after midnight, and more likely, the heaviest will be around and after daybreak. Also adjusted temps a bit, although overall mins a re close to previous forecast, but most of the cooling happens this evening, especially in the S, with temps closer to holding steady later tonight. The HRRR continue to focus the heaviest along or just inland of coastal front, which would keep the heaviest of rain in SE NH and the ME coastal plain. Previously...Satellite imagery this afternoon continued to show plumes of moisture developing off the Mid Atlantic coastline with convection firing along and ahead of a surface area of low pressure which was gradually forming just off the coastline. Radar imagery depicts rainfall off the New England coast, similar to most operational and mesoscale models near term forecasts. Most operational and ensemble model solutions continue to have a significant model to model and run to run discontinuity. This is particularly true with the timing and evolution in the precipitation forecast. There has been an eastward shift in the high precipitation and pop forecasts for tonight, with a couple mesoscale models bucking the trend and keeping heavy rainfall totals along the coast. This disparity remains relatively significant. Out of all the model solutions however, the Euro ensemble mean perhaps would lead to the most consistent forecast. In any case, the forecast remains highly uncertain as any waiver in the track of the surface low and high PWAT axis could shift the focus for heavy rainfall back to the coast and some inland areas. This system appears to be similar to the August 13, 2013 event, however this event is displaced further to the east. After coordination with adjacent offices, will hold off on Flash Flood Watches for now as confidence is not sufficiently high to warrant these headlines. However, short term trends will need to be closely monitored during the overnight hours. Precipitation should advance north during the late evening hours. Patchy fog is possible during the overnight hours as easterly winds begin to bring enhanced moisture off the Gulf of Maine. The cloud cover will make for relatively uniform temperatures from north to south with mid to upper 50s for overnight lows in most areas. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... 12Z models and ensemble solutions suggest a second period of shower activity on Thursday with showers continuing during the morning hours as the upper level low and jet streak crosses the region. Locally heavy rainfall may continue along and near the coastline with the highest totals potentially in the Midcoast region of Maine. Surface dew points will continue to rise across the region as tropical air will remain nearby over the Gulf of Maine. The clouds and shower activity will limit daytime highs to the lower 70s in most areas. The chance for showers will continue to diminish Thursday night as the upper level trough pushes east. Nighttime lows will drop into the mid 50s to lower 60s. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... General pattern in the extended will consist of a sprawling Bermuda High along the Eastern Seaboard through Saturday night before a progressive polar jet becomes reestablished bringing mid-level shortwaves between periods of ridging next week. Overall pattern will support above average temperatures and near normal precipitation with rain chances on Sunday and Tuesday night. All rain ends by daybreak on Friday with zonal flow aloft and ridging at the surface as the Bermuda high becomes dominate along the eastern seaboard. SW return flow will become established with a hot and humid airmass in place as dewpoints surge into the upper 60s with heat index values reaching the mid to upper 80s. Still muggy on Saturday and mostly dry on the coastal plain with chance for afternoon showers and thunderstorms across the interior mountains. Weak surface cold front pushes through on Saturday night into Sunday morning along with a 500mb shortwave trough. This will bring in a slightly cooler airmass, but by no means a big cool down. Shower activity will be more widespread across interior areas. Warm and humid airmass returns for the beginning of next week with the potential for instability showers/thunderstorms. No significant widespread events on the horizon at this time. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... Short Term...VFR conditions early this evening will turn to MVFR later this evening and IFR overnight as a moist airmass moves into the region with the potential for a period of heavy rain through Thursday morning. Conditions will improve later Thursday afternoon. Long Term... High pressure is expected on Friday with no significant impacts to aviation operations expected. Fog could be possible on Friday night leading to IFR conditions. Isolated thunderstorms are possible on Saturday afternoon, but threat is low at coastal aviation terminals. && .MARINE... Short Term...Easterly winds will pick up tonight into Thursday with a few gusts to 20 kt, just below Small Craft Advisory criteria. Winds will switch to the north Thursday night. Seas will gradually be on the increase with a few waves near 5 feet along the outer waters Thursday night. Long Term... High pressure is expected over the coastal waters through this period with predominate flow out of the southwest. Seas and winds will stay below SCA conditions but gusts up to 20kts could be possible this weekend. Pattern will also support the chance for fog and low visibilities at times. && .HYDROLOGY... Much uncertainty continues from model to model and run to run in terms of the QPF in the short term portion of the forecast. There is a consensus that the highest rainfall totals will fall along the coast where an inch or two of rain may fall in about a 12 hour period which remains above flash flood guidance values. These amounts will likely need to be adjusted and modified however as radar and satellite signatures are identified during the overnight hours. Therefore, conditions will still need to be monitored for the possibility of a Flash Flood Watch. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Cempa/Tubbs
Area Forecast Discussion
National Weather Service Key West FL
956 PM EDT Wed Aug 4 2021 .DISCUSSION... A ridge axis currently is extending across the Florida Keys and South Florida, which is supporting gentle breezes across the coastal waters and the island chain. Convection across South Florida and the Keys has mostly dissipated, leaving us with partly to mostly cloudy skies from the remnant upper-level cloud cover that came off earlier convection. This cloud cover will continue to deteriorate and leave us with partly cloudy skies. KBYX is mostly echo-free, with only a few light showers in the Straits of Florida that are rapidly falling apart. The 00Z KEY RAOB recorded a layer of drier air beginning around 890 mb. This, combined with an inversion around the same height, has helped keep any shower activity shallow this evening. Temperatures across the island chain are currently in the lower to mid 80s, with dewpoints in the mid 70s. The ridge axis will shift northward overnight, allowing for another wind surge like we experienced last night with breezes becoming light to moderate. Have nudged PoPs down to a slight chance for tonight, which is in line or even slightly above guidance. Otherwise, the forecast looks to be on track and no other changes are needed. && .MARINE... No watches, warnings, or advisories are in effect for the Florida Keys coastal waters. From synopsis, A ridge axis in the vicinity of the island chain will lift northward into Central Florida over the next several days. East to southeast light breezes will tend to freshen in the overnight to early morning periods, occasionally becoming moderate. Breezes will freshen early next week as the ridge axis broadens and lifts further northward. Near-normal rain and thunder chances are expected tonight through at least Monday. && .AVIATION... Shower activity around airports has diminished in the past hour. However, showers are likely to redevelop along the island chain later this evening between 04-06Z per the HRRR model, and will maintain VCSH at terminals overnight. Additional widely scattered showers are also expected near airports much of the day tomorrow and will continue VCSH, and cannot rule out brief periods of MVFR cigs/vis. Light northeast winds this evening will veer to east then southeast and increase to around 8-9 knots overnight into tomorrow. && .CLIMATE... On this day in 1894, both the daily record low temperature of 68F and the daily record rainfall of 2.74" were recorded in Key West. The low temperature of 68F is also tied for the coldest temperature ever recorded in August. Rainfall records date back to 1871 and temperature records date back to 1872. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...NB Aviation/Nowcasts....Shamburger Data Acquisition.....JAM Visit us on the web at Follow us on Facebook and Twitter at:
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
658 PM CDT Wed Aug 4 2021 .SHORT TERM... 249 PM CDT Through Thursday... With high pressure still in place, mostly quiet conditions are expected to continue overnight into tomorrow. Skies remain hazy from wildfire smoke aloft with scattered afternoon cumulus clouds. A weak lake breeze pushed inland earlier this afternoon but has since slowed its westward progression. Surface dewpoints have remained a bit higher today west of this boundary which has aided in a few spotty showers/sprinkles developing this afternoon. A more persistent shower has since developed along the Cook and Lake County IL border this afternoon along the lake breeze boundary. Expect very spotty showers/sprinkles to be bubble up and down through the afternoon. Any showers that are able to sustain taller updrafts may be able to tap into some marginal instability to produce a rogue lightning strike or two. Will also note that model soundings depict a slightly less subsident airmass than yesterday. Any remaining activity should diminish quickly toward sunset with the loss of diurnal heating. Winds turn light and variable this evening into the overnight hours then trending more southerly early Thursday morning as the surface high shifts to the east. Winds begin to pick up out of the southwest through the daytime hours ahead of our next weather system with temperatures warming into the lower to mid 80s again. Petr && .LONG TERM... 249 PM CDT Thursday Night through Wednesday... The late week into weekend forecast features a pattern transition back to a warmer, more humid, and unsettled pattern. While most forecast periods have chances for precipitation given this pattern, the chances for scattered thunderstorms are a little higher Friday, then again Sunday and Sunday night (could be widespread for a part of that time), before predictability notably drops off early next week. The heat early next week could build to the level of heat index readings exceeding 100F. A slightly positively tilted short wave trough will be very gradually easing its way into the Upper to Mid Mississippi Valley Thursday night and then still lingering over the Lower Great Lakes on Friday. There is little window for deep moisture return on Thursday ahead of this, and instability also lags the elevated warm advection that eases overhead Thursday night. So we just inch in a chance of showers in the forecast Thursday night, especially overnight. Cloud cover looks like it will impact the degree of destabilization on Friday, but how much so is tough to tell yet at this point. Model soundings from the NAM and GFS as well as the end of the RAP support convective temperatures being reached. Considering a slightly cooler pocket of air in the mid- levels with the trough, it probably will not take much for diurnally- assisted scattered thunderstorms. The severe threat looks limited due to marginal deep layer shear and questions on what degree of instability there will be. Looking at the weekend, short wave ridging is forecast to spread at least partially over the area on Saturday. Continued southwest low-level flow will nudge our dew points to around 70, and at least some if not quite a bit of sun will probably offer upper 80s. A few storms could pop on any subtle convergence zones, such as a lake breeze predicted to hug the shore that afternoon. Overall though, some capping is shown and the pattern is not supportive of widespread or long lasting storms (low shear). Sunday looks like the more active day, with a fairly strong neutrally tilted short wave forecast to approach the area and pass over it sometime late Sunday or Sunday night. While the mass field agreement in our area is fairly good for Sunday given it is a ~Day 4 forecast, there are some key disagreements upstream Saturday night with convection and how it may evolve toward or into our area on Sunday. This will be a day and/or night we will have to keep an eye on as the parameter space advertised presently would support a scattered/possibly organized severe threat. Into next week, the confidence drops on convective timing due to low amplitude short waves in quasi-zonal flow. Confidence is higher though on the warm, humid pattern. Both the GFS and ECMWF advertise mid 70s dew points knocking on the door Monday and then into the area Tuesday. With 850 mb temperatures of 20-22C, there is support for 92-94 high temperatures, however the pattern is not favorable to deterministically forecast that especially this many days out with potential for multiple rounds of regional convection. Again forecast heat index readings could near Advisory level (105 in our area) Monday and Tuesday afternoons. MTF && .AVIATION... For the 00Z TAFs... Some random pop-up and short lived showers will linger into the first hour or so of the forecast period, but overall coverage, which was never large to begin with, should continue to decrease with the loss of peak heating. Variable winds near the outflow boundaries will trend southerly through the remainder of the period. There appears to be enough of a gradient tomorrow to keep the lake breeze confined closer to the shore, so for now there are no plans to reflect this at ORD or MDW. Lenning && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Please see the previous forecast discussion below for more details
on the cooldown and eventual return to hot conditions. Keene
&& .AVIATION...For the 05/00Z TAF Cycle...Over the coastal waters, along the coast, and in the coastal valleys...IFR/LIFR ceilings are expected tonight into Thursday morning. Patchy drizzle or intermittent light rain can also occur. MVFR ceilings could occur inland into the Umpqua Valley, including Roseburg, along with a chance of showers Thursday morning. Stratus should lift to MVFR/VFR Thursday afternoon. Over the remainder of the area...VFR conditions will mostly persist tonight through Thursday. However, smoke and haze from area wildfires will result in reduction of visibility to MVFR/local IFR at Medford and Klamath Falls. IFR/LIFR visibility is also possible very near the fires. A disturbance will cause isolated to scattered thunderstorms from northern California to the east side Thursday afternoon and evening. The best chances for these storms will be north and east of Klamath Falls. But, any storms that do occur will have the ability to produce strong wind gusts and hail. -Spilde && .MARINE...Updated 200 PM PDT Wednesday 4 August 2021...Gusty north winds and areas of steep seas will persist through this evening with high pressure offshore and a thermal trough inland. The strongest winds are expected between Port Orford and Gold Beach. Winds will be weaker in the inner waters north of Cape Blanco, but weakest near shore south of Pistol River with a southerly wind reversal. Steep seas linger south of Nesika Beach late tonight into early Thursday morning as winds begin to diminish ahead of a front. Winds and seas will continue to diminish into early Friday. A thermal trough and stronger north winds will return this weekend into early next week. -DW/Petrucelli && .FIRE WEATHER...Updated 825 PM PDT Aug 4 2021...A challenging weather scenario is expected over the next 24-36 hours. The region will quickly transition from hot, very dry, windy with unstable conditions through early Thursday afternoon, to cooler conditions with improving humidities, strong shifting winds and thunderstorm potential Thursday afternoon and evening. During this 24-36 hour period, the weather pattern will shift from high pressure over the Four Corners/Nevada Region with low pressure offshore today to low pressure to the east and a more zonal flow pattern over the region. Increasing winds today were in response to an upper level trough offshore approaching the region, tightening pressure gradients and pushing the thermal trough farther inland. This upper trough will move through the region on Thursday and will result in another critical fire weather day, though critical for different reasons compared to today. Afternoon temperatures will drop by 10 to 20 degrees compared to today`s readings and this will help bring up humidities as well. However, there will be a transition period during the early afternoon where strong winds/low RH result in critical conditions across the East Side and Modoc before the concern transitions to thunderstorms. We`ve upgraded the Fire Weather Watch to a Red Flag Warning, and it`s sort a hybrid product. The first few hours of the Red Flag Warning (it`s valid from noon to 10 pm Thursday) will be for strong winds with low RH, then transition to abundant lightning on dry fuels. This Warning is for FWZ 624, 625 and 285, including the Bootleg Fire. While each zone may not see both abundant lightning and/or strong winds with low RH, there`s no arguing that tomorrow is a critical fire weather day and the wind element is the most concerning. First with the low humidities anticipated during the earlier portion of the day, then with shift in wind direction anticipated during the afternoon (from southwest to west/northwest), to strong gusty and erratic outflow winds with any thunderstorms. Regarding the thunderstorm potential, isolated thunderstorms are certainly possible from the Cascades eastward and across northern California. Scattered coverage seems most likely across FWZs 624 and 625, maybe even into the northern portions of the Modoc. This is where the SREF calibrated thunderstorm guidance highlights a 20-30% chance of thunderstorms across the aforementioned areas, so we have added a slight chance of thunderstorms for those areas. The SPC HREF is also concentrating the strongest convection in these areas. Of course the wildcard in all of this is the concentration of smoke across the region. If thick enough, it can inhibit surface heating thus limiting instability and we`ve also seen smoke be an inhibiting factor in thunderstorm development. However, there are some strong dynamics associated with this trough, and it difficult to ignore this. Therefore, have gone ahead with the abundant lightning on dry fuels for Thursday. && .PREV DISCUSSION... /Issued 516 PM PDT Wed Aug 4 2021/ DISCUSSION... Thick smoke from multiple wildfires continue to cover the region with unhealthy air quality. Because of the thick smoke and unhealthy air quality, the Oregon Department of Environmental Quality has issued and air quality advisory for southern Oregon. The general flow pattern won`t change over the next 24 hours with upper level winds pushing the smoke in from California and low level winds bringing smoke in from the Skyline Ridge Complex into valleys west of the Cascades. With all the thick smoke, expect temperatures 3 to 5 degrees below most model guidance. This was what was observed yesterday across multiple observation stations. By Thursday, an upper level low will traverse the forecast area bringing thunderstorms and a general change of the weather pattern. Convective available potential energy(CAPE) will be around 800 to 1000 J/kg east of the Cascades. With CAPE around these values, we have the potential to see some stronger storms. In addition, the storm prediction center has the east side under a marginal risk for severe weather Thursday afternoon and evening. This is likely due to the potential for some strong wind gusts as storms seem to be over riding a fairly dry airmass. Some of the convective allowing models also show the potential for severe wind gusts east of the Cascades Thursday afternoon. In addition, we feel pretty confident that scattered thunderstorms will develop Thursday afternoon. Some of this is based on the model ensemble probabilities showing a 50% chance of thunder around northern Lake and Klamath Counties. Also, the upper level pattern suggests strong upper level divergence on the eastward flank of the low. The only uncertainty here is how much the smoke will play a role in limiting instability and thunderstorm coverage. We dismissed the role of smoke here since we felt the upper level dynamics will be quite strong. In addition, the smoke appeared thinner over locations east of the Cascades. By morning Friday, it appears a warm front will push into the coast of Oregon. It`s denoted by slightly warmer temperatures and a lot of moisture between 1000 to 500 mb. Some models are predicting spotty precipitation along the coast Thursday night into Friday morning. Even with more warmth and moisture moving in, high temperatures will be in the upper 80`s with some locations hitting the lower 90`s in northern California. With deep north westerly flow from Friday onwards, the antecedent smoke should clear out. However, fresh smoke from the wildfires will then pour in from the north west as deep northerly to northwest flow develops. Temperatures appear to warm up briefly on Saturday before cooling down quickly on Sunday as a cold front moves through. This will help keep temperatures in the 80`s on Sunday into early next week. By Tuesday and Wednesday, temperatures begin to warm up again. -Smith && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning until 10 PM PDT this evening for ORZ623-624. Red Flag Warning from noon to 10 PM PDT Thursday for ORZ616-624-625. CA...Red Flag Warning from noon to 10 PM PDT Thursday for CAZ285. Red Flag Warning until 10 PM PDT this evening for CAZ280>282. Red Flag Warning until 10 PM PDT this evening for CAZ284-285. Pacific Coastal Waters...Small Craft Advisory until 5 AM PDT Thursday for PZZ356-376. $$
National Weather Service Morristown TN
740 PM EDT Wed Aug 4 2021 .UPDATE... FOR 00Z AVIATION. && .UPDATE... EVENING UPDATE. && .DISCUSSION... Isolated to scattered showers will dissipate shortly after sunset. Most locations will remain dry overnight. No significant changes were made to the forecast for tonight during the evening update. && .AVIATION... 00Z TAF DISCUSSION. Isolated showers near CHA will dissipate shortly after sunset. Scattered showers near TRI may linger to around or after midnight. Tomorrow, showers will be confined to the higher elevations in and near the Smoky Mountains. Patchy fog is possible in the early morning hours but confidence is too low to include in TAF. VFR conditions are expected this TAF cycle. McD && .PREV DISCUSSION... /ISSUED 311 PM EDT Wed Aug 4 2021/ SHORT TERM...(Tonight and Thursday) Key Messages: 1. Showers/thunderstorms diminish in coverage this evening, drying out tonight. 2. Warmer and drier Thurs with only very isolated afternoon storms in the far E TN mountains. Discussion: Late Afternoon/Evening... The inverted surface trough that caused the persistent showers in NE TN and SW VA all morning is finally lifting out. Clouds and temps mainly in the low 70`s in these areas has kept instability limited, but farther south, breaks of sunshine have warmed temps into the upper 70`s/low 80`s and led to scattered convection blossoming across much of the S Plateau and SE TN where latest RAP soundings and SPC Mesoanalysis depict SBCAPE of 1000-2000 J/Kg and 1000-1200 joules of MLCAPE. This along with abundant low-level moisture in place, large scale lift beneath a deep eastern CONUS mid/upper trough, and relatively steep mid-level lapse rates around 6 C/Km will continue to support this diurnal convection through the evening. Deep layer shear remains weak at under 25 kts, but the instability and some precip loading owing to seasonably high PWATs of 1.20 to 1.40 inches will support gusty winds and locally torrential rainfall within the strongest cores. Expect the convection to quickly wane after 00Z. Tonight and Thursday... The weather pattern will begin to transition away from the cooler, pleasant conditions of late during this period. The eastern CONUS mid/upper trough will shift toward the east coast tonight with the S Appalachians region becoming increasingly under upper level convergence associated with the left entrance region of a 60 kt H3 jet streak. This downward motion combined with drier air and additional subsidence from a surface high dropping through the Midwest will allow the area to dry out overnight. Skies should go mostly clear over most of the region, but lingering moisture will lead to some cloud cover persisting near the mountains and across NE TN into SW VA. The wet ground and small T/Td depressions will lead to patchy fog, but northeastern areas may not see as much due to the lingering clouds. Lows tonight will dip into the low 60`s with some upper 50`s from the N Plateau into parts of SW VA. For Thurs, a mid/upper shortwave ridge will build into the TN and OH Valleys with the aforementioned surface high moving over the Appalachians. The large scale subsidence and dry air will allow any lingering clouds in eastern areas to quickly diminish in the morning allowing for mostly sunny skies areawide. H85 temps will surge to 15-17 C as the shortwave ridge builds in, and this combined with the sunshine and good mixing will boost highs into the mid/upper 80`s (near normal). Increasing southeasterly low- level flow during the afternoon as an upstream shortwave trough approaches from the MS Valley and the surface high begins to shift E could develop isolated convection in favored upslope areas of the Blue Ridge in western NC, and this could spill into the far E TN mountains, but the rest of the area will stay dry, and any coverage in the mountains will be sparse as dry air mostly wins out. Garuckas LONG TERM...(Thursday Night through Wednesday) Key Messages: 1. Best chance of showers and thunderstorms through the extended will occur Saturday. 2. Near normal temperatures through Saturday. Above normal temperatures by Sunday with continued warming through Tuesday. Discussion: -Thursday Night through Saturday- To start the long term period, an upper level trough will be exiting the area to the east-northeast as very brief ridging moves in behind it. The longwave trough will be positioned so that upper level convergence will cover the majority of the CWA. As a result, locations should remain dry late Thursday evening and overnight with the passing of peak heating. Compared to 12Z model runs from yesterday, the weak amplitude ridging expected Friday looks to move through slightly quicker due to the more progressive manor and higher amplitude of the shortwave energy just upstream of it. With the large scale subsidence not looking to be quite as prominent as before, pulse convection will have a little less dynamics working against it, thus, a slight chance of showers and thunderstorms will be possible late Friday afternoon and evening. However, the higher coverage of showers and thunderstorms still looks to be Saturday as better vorticity will be in place associated with the shortwave moving through the region. The precipitation will continue to keep temperatures in the seasonal normal range on Saturday. -Sunday through Wednesday- By Sunday, the aforementioned shortwave pulse will be moving eastward as ridging starts to build and surface high pressure settles along the TN/NC border. With southerly flow becoming more present at the lower levels, some considerable warm air advection will take place and temperatures will begin to rise a few degrees above normal by Monday and Tuesday. With little synoptic support in the region (i.e. no upper/lower jets, no surface boundaries) the chance of diurnal showers and thunderstorms will largely rely on the strength of the high pressure and overall subsidence within the region. NBM loaded with high end chance PoPs on Tuesday and even some low end likely on Wednesday but knocked them down to low/mid- range chance as the confidence that far out with little to no synoptic support is just not there. KS && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 65 87 69 88 70 / 10 10 10 30 20 Knoxville McGhee Tyson Airport, TN 64 87 67 88 69 / 20 10 0 20 40 Oak Ridge, TN 62 86 66 87 68 / 10 0 0 20 30 Tri Cities Airport, TN 61 84 62 87 66 / 20 10 0 10 30 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$
Area Forecast Discussion
National Weather Service New York NY
1106 PM EDT Wed Aug 4 2021 .SYNOPSIS... Multiple waves of low pressure along a frontal boundary just offshore will impact mainly eastern Long Island and southeast Connecticut overnight. The front will then slowly work east on Thursday as weak high pressure begins to build in from the west. A broad area of high pressure will set up over the area on Friday. A frontal system may pass Saturday night. A warming trend is likely next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Rain chances have been adjusted due to current radar, with much of the rain contained to southeast Connecticut and the Twin Forks of Long Island. Western areas such portions of the Lower Hudson Valley and northeast New Jersey will continue to be dry through late tonight. The combination of a longwave trough from the Great Lakes south to the Gulf coast states will send a series of frontal waves near or just south and east of Long Island and eastern CT tonight into Thursday morning. This combined with a subtropical feed of moisture up the eastern seaboard and PW values near 2 inches raises the concern for heavy showers along with embedded thunderstorms, mainly from late tonight through around daybreak. The best potential for the heavy rain will be across far eastern LI and SE CT, where a Flash Flood Watch has been issued. Global models have come into much better agreement with the 12Z cycle generally focus the axis of heavy rainfall across the watch area. However, the GGEM keeps the axis to the east. The CAM`s have been struggling with the frontal wave location, with the 12Z NAMNest the farthest west and most aggressive with the rainfall, with 2 to 5 inches of rainfall extending as far west as New Haven and western Suffolk Counties. The FV3 is more in line with the watch area, and the HRRR has been varying west to east with the last several runs. While there is not a whole lot of instability, moist adiabatic lapse rates and jet exit region dynamics may be all it takes at this time of year to produce heavy rainfall. Feel fairly confident of 1 to 2 inches in the watch area, but the potential is there for more. At the very lest, expect some minor nuisance, poor drainage flooding. Elsewhere, chances of showers will drop appreciably as one goes west, especially NYC and SW CT. Overcast conditions and easterly winds will keep lows in the 60s, a few degrees below normal. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Widespread morning showers will exit around or shortly after daybreak Thursday. However, with the upper trough lifting out across the area, a few lingering showers will be possible into the afternoon, especially across far easter LI and SE CT. Weak high pressure builds in late Thursday into Thursday night with gradually clearing skies late into the day and through Thursday night. Trended toward the cooler side of the guidance based on Wednesday`s highs and the anticipated cloud cover. Highs will be in the 70s, approaching around 80 across the NY/NJ metro. Lows will be in the lower to mid 60s Thursday night with a few spots around the metro around 70. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... The models were in good agreement in the extended, so the NBM was closely followed with local adjustments. Rising heights will end pcpn chances on Fri so a dry day has been fcst. WAA from the west will produce more August-like wx, with temps warmer than those experienced in over a week. The warmer wx however appears to be locked in for a while now, with generally at or slightly abv normal temps over the weekend. There are chances for shwrs and tstms each aftn/eve over the weekend with the passage of a weak h5 trof. The heat really builds next week as the subtropical ridge expands over the CONUS. The modeling has been really consistent on this. A warm front comes thru on Mon, with perhaps some shwrs and tstms invof the boundary. The NBM may be a bit too cool with highs due to the front being close, but this far out decided not to stray from the blended approach. It would not be surprising to see highs about 5 degrees warmer than currently fcst on Mon based on h85 temps approaching 18C. This pattern will set the stage for air mass tstms Tue and Wed with aftn/eve timing favored. The ECMWF suggests an upr low will provide a brief round of relief towards the end of next week, but the GFS disagrees. This is beyond the actual fcst period anyway, so until then a hot and humid Tue-Wed can be expected. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... A frontal boundary will remain offshore with several waves of low pressure passing along it. VFR for NYC terminals and points north and west through 05Z. For eastern terminals such as KISP, KBDR, KGON; MVFR conditions will continue through the overnight hours. However, there may be some improvement at times through 03Z. Thereafter, moderate to heavy rain may affect KGON which may limit visibilities to 3 to 5 SM at times, mainly from 03Z-07Z. E Winds will shift to the NE after 03Z, and then N around daybreak Thursday. Winds speeds will be 10 kt or less for the most part. There may be occasional gusts to 15 kt for coastal terminals, mainly from 06Z-12Z. Sea breezes could then affect coastal terminals late in the day Thursday. NY Metro (KEWR/KLGA/KJFK/KTEB) TAF Uncertainty... Amendments likely for changing flight categories. .OUTLOOK FOR 00Z FRIDAY THROUGH SUNDAY... .Thu night-Fri...VFR. .Sat-Sun...Mainly VFR. Chance of afternoon showers and thunderstorms. .Monday...VFR Detailed information, including hourly TAF wind component forecasts, can be found at: https:/ && .MARINE... Building seas ahead of an waves of low pressure along an offshore frontal boundary will bring SCA conditions to the ocean tonight. Seas look to range from 4 to 7 ft. These elevated seas should linger into Thursday night. The Small Craft Advisory is now in effect through 6am Friday. A few wind gusts up to 25 kt cannot be ruled out on the ocean tonight as well, although winds may stay closer to 20 kt or less. Elevated ocean seas may linger into Thursday night. Seas on the ocean will gradually subside thru the day on Fri, with all waters falling blw sca lvls by Sat mrng. Winds on the protected waters will be blw 25kt. Winds and seas will mainly be blw sca lvls over the weekend, although waves could flirt with 5 ft at times on the ocean. Winds and seas are expected to remain blw sca lvls Mon and Tue. && .HYDROLOGY... Rainfall amounts of 1 to 3 inches with locally higher amounts are forecast late tonight into Thursday morning across eastern Long Island and southeast Connecticut. Minor urban and poor drainage flooding is possible with a localized risk of flash flooding. Amounts should drop off significantly to the west with only light amounts along and west of the Hudson River corridor. No hydrologic impacts are expected Fri-Wed. && .TIDES/COASTAL FLOODING... There is a high rip current risk for all beaches on Thu, and a moderate risk for Fri. Even though there is no wind component on Thu, 5 ft waves are expected at all beaches, resulting in the high risk. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...Flash Flood Watch through Thursday morning for CTZ008-012. NY...Flash Flood Watch through Thursday morning for NYZ079-081. High Rip Current Risk from 6 AM EDT Thursday through Thursday evening for NYZ075-080-081-178-179. NJ...None. MARINE...Small Craft Advisory until 6 AM EDT Friday for ANZ350-353-355. && $$ SYNOPSIS...DJ/DW NEAR TERM...JP SHORT TERM...DW LONG TERM...JMC AVIATION...JP MARINE...JMC/DW HYDROLOGY...JMC/DW TIDES/COASTAL FLOODING...