Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/14/20

Area Forecast Discussion
National Weather Service Caribou ME
1134 PM EDT Sun Sep 13 2020 .SYNOPSIS... A cold front will cross the area later tonight into Monday. High pressure will settle across the area Monday night into Tuesday, and move south of the area Wednesday. A cold front is expected to move into the region on Thursday and move out of the area by Thursday night. High pressure will build in on Friday. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 11:35 PM Update...Lingering showers with the cold front are very light and spotty so lowered pops to isolated showers with most of the rain east of the area now. Also raised temps a couple degrees, mostly over the north, where cloud cover is preventing cooling. previous discussion Sustained winds of 15-20 mph were gusting at times to 30 mph across the open and higher terrain early this evening. The gusty S winds will continue into the evening and there is potential that some sites could see gusts up to 40 mph early in the evening as a 45 kt llvl jet moves across the region. The model soundings support this setup w/the strongest gusts across northern areas. The pre- frontal trof ahead of the strengthening cold front sweeps across the region this evening w/a broken line of showers. The NAM/GFS and GEM show the best forcing to be across northern border producing rainfall amounts of up to 0.25". The HRRR does point to some embedded heavier showers along the line. The llvl jet and PWs climbing around 1.25 inches lend support for the brief heavy rainfall. Further s into the Houlton and Millinocket region, rainfall amounts fall back to less than 0.15". The Bangor and Bar Harbor will see a brief period of rain w/less than 0.10" expected. This first round of showers will diminish by mid evening as the best forcing pushes on out and winds drop off as the llvl jet pushes off to the east. There is another round of showers expected later tonight w/the arrival of the cold front. Not much rainfall expected w/this round of showers, but cooler temps will accompany the front. Winds will be veering to the SW later in the evening and then to the W overnight w/the cold fropa. The front will tend to slow up some as it moves into the Downeast region Monday morning as it parallels the upper trof. A breezy day on Monday and drier and a bit cooler w/some CAA and a good NW wind. The cold front should finally make it off the coast by early afternoon. The cooler air will be held up some to the slower progression of the front. Thus, daytime temps across the Downeast and coast should be able to warm to around 70 before the gradual cooldown in the afternoon. A look at the momentum transfer indicates potential for gusts to be 30-35 mph in the afternoon w/an increasing NW wind all the way through 15k ft. The strongest winds will be across the nor Therefore, decided to increase the wind speeds on Monday by at least 10 mph from the previous setup. Clouds will be around in the morning, but as drier air continues to work into the region, clearing is expected by the afternoon w/a gradual recover in the temps. Daytime temps will be a few degrees below normal. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY/... High pressure will just be nosing into western Maine Monday night. Much of the CWA will remain in N flow ahead of this high, and thus winds are expected to prevent much widespread frost potential. Dew point temps will drop further than the air mass earlier this week. Confidence for frost would increase if the high was located closer to the region, and if low level winds were lighter. At this time will forecast the greatest potential for frost across the NW North Woods, with some patchy frost possible across lower valleys in northern and central Aroostook. The high will pass to the south of the state Tuesday. West winds will bring in some warmer temps, however any clouds developing across the north will limit highs to the upper 50s and lower 60s. Otherwise dry conditions are expected. Tuesday night will cool a little early, but be highlighted by a weak warm front lifting through the region. Expect a warmer night, and the chance of some light showers across the far north. Behind the warm front, temps Wed will rebound well towards the lower 70s. This southerly flow will feed into a low pressure system passing to the north of Maine. Downeast and along the coast will see a breezy day as warm air advection passes through. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... A cold front will impact the area beginning early Thursday morning, though guidance remains split on the timing of this feature with GFS being on the early side and ECMWF following a bit later Thursday afternoon. Best chance for rain across the region will be during the day on Thursday as the front sweeps southwards. Temperatures will dip behind the front, with lows falling into the lower 40s across the north. Clouds will remain in place during the day on Friday, keeping high temperatures capped in the upper 50s to lower 60s. Skies will clear Friday night, allowing for temperatures to plummet even further with sub-freezing temps possible across the North Woods and lows in the upper 40s along the coast. These falling temperatures will also produce the best chance at frost, especially over the North Woods where winds will be light early Saturday morning. High pressure returns for the weekend, keeping skies clear and low PoP chance. && .AVIATION /04Z MONDAY THROUGH FRIDAY/... NEAR TERM: VFR for northern terminals this evening. KBGR and KBHB will see MVFR cigs w/the lower deck coming in off the Gulf of Maine. This MVFR looks like it will lift n and move into the northern terminals this evening. There could be a brief period of IFR especially across the northern terminals in showers. LLWS w/S winds 10-20 mph this evening w/gusts up to 35 mph. VFR for Monday for all terminals w/WNW winds kicking in. Sustained winds of 10-20 mph w/gusts possibly up to 35 mph. SHORT TERM: Monday night: VFR, light NW wind. Tuesday: VFR, Light W wind. Tuesday night, VFR. Light S wind. Wednesday: VFR, some showers near FVE and CAR. Gusty SW wind. Wednesday night: VFR, possibly lowering to MVFR north. SW wind. Thursday: VFR/MVFR. SW wind becoming W. Thursday Night: MVFR improving to VFR. Light wind becoming NW && .MARINE... NEAR TERM: SCA remains in place for the outer zones. S wind 10-15 kt w/gusts to 25 kt becoming SW toward the early morning hrs on Mon. SW winds becoming W by later Monday afternoon w/similar speeds. The bigger concern will be the wave heights. Seas 2-3 ft this evening building to 4-5 ft by Monday morning w/highest waves over the outer zones. Swells from Hurricane Paulette w/a period of 14-16 seconds will begin to show up during the day on Monday. The could be some rough surf given the longer period swell and waves building to 5-6 ft SHORT TERM: Swell from hurricane Paulette is expected to build seas to 5 to 6 ft on Monday and 6 to 7 ft on Tuesday. Seas may continue above 5 ft through mid- week. Additionally, long period swell of 10-15 seconds is expected through Wednesday. SW Winds will generally be 15-25 kts through this period, increasing again Wednesday behind a warm front, potentially towards Gale. && .TIDES/COASTAL FLOODING... Long-period swell of 10 to 15 seconds will affect the coastal waters tonight through Wednesday with near shore waves building 5 to 6 ft. As Hurricane Paulette tracks well off in the open Atlantic, the incoming swell may generate elevated rip current risk and high surf along the coast Monday into mid-week. Additionally, astronomical high tides are due later this week/weekend. Prevailing wave heights and wave periods will be monitored for any spashover or coastal erosion threat to low lying/susceptible locations. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory from 5 AM Monday to 5 AM EDT Tuesday for ANZ050-051. && $$ Near Term...Duda/Hewitt/LaFlash/MCB Short Term...Cornwell Long Term...AStrauser/Cornwell Aviation...Duda/Hewitt/LaFlash/Cornwell Marine...Duda/Hewitt/LaFlash/Cornwell Tides/Coastal Flooding...
Area Forecast Discussion
National Weather Service Des Moines IA
636 PM CDT Sun Sep 13 2020 ...Aviation Update... .DISCUSSION.../Tonight through Sunday/ Issued at 250 PM CDT Sun Sep 13 2020 No appreciable weather impacts are anticipated through the period, but smoke may affect temps and fog potential into at least tomorrow. There are some features of note nearby, but with limited moisture there is nil associated sensible weather. A baroclinic zone is in place across the northern Plains with the associated surface front from SD into MN and low just east of Pierre. As the upper flow becomes a bit more zonal, the front should ooze south into IA overnight before washing out and/or retreating northward as the theta-e advection and baroclinic zone lift farther north and east Monday. With clear skies, light/variable wind, and lingering low level moisture (dewpoints still in the 50s), expect a repeat of fog development overnight. The question will be how much smoke impacts radiational cooling. GOES-16 channel 1/blue imagery shows this nicely with an initial lobe already into IA, and more widespread coverage over the Dakotas upstream. Recent available RAP and HRRR smoke runs suggest this will expand into IA tonight so there are uncertainties regarding how much this will impact radiational cooling, the degree of fog, and low temps. Little past experience with how smoke affects fog development so confidence is low. Some smoke aloft will linger through tomorrow and may even shade a degree or two off highs, but beyond this there should be nil weather for much of the week with little adequate moisture and lift phasing for much of anything. Mild temps can be expected through Wed, but a dry frontal passage late Wed will drop temps somewhat below normal to end the work week. Although they get to it different ways, most deterministic and ensemble solutions suggest low PoPs at least NW Thu Night, and then also late Sun again NW ahead of a cold front where there is somewhat better model agreement. && .AVIATION.../For the 00Z TAFS through 00Z Monday evening/ Issued at 632 PM CDT Sun Sep 13 2020 VFR conditions are predominantly expected, but may be interrupted by fog development tonight that could develop MVFR/IFR conditions. Main sites of concern would be KALO/KOTM and to a lesser extent KMCW/KDSM/KFOD. Otherwise, light winds will begin to turn southerly and smoke streaming overhead will remain aloft and provide some obscuration. && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Small AVIATION...Curtis
Area Forecast Discussion...UPDATED
National Weather Service Nashville TN
833 PM CDT Sun Sep 13 2020 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Activity has decrease markedly over the last few hours. Just a few light showers is all that remains. Latest Hrrr data supports little if any redevelopment overnight. Sfc high to our north should continue to build in slowly over the next 24 hours. Lower dewpoints are noted across nrn KY and we will finally see some of these slightly lower dewpoints, but probably not until tomorrow afternoon. Therefore, will go ahead and add some patchy fog, but development may be limited to the Plateau. && .AVIATION... 00Z TAF DISCUSSION. Rains have come to an end, but MVFR to IFR conditions still exist at KBNA/KMQY. These should improve in a couple of hours, but with the slow movement of today`s front, look for conditions to worsen at KCSV after 06Z. Northerly winds will be light overnight, but look for the surface pressure gradient to tighten quite a bit tomorrow morning, leading to gusty NE winds throughout the day Monday. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......21 AVIATION........Unger
Area Forecast Discussion
National Weather Service Pocatello ID
120 PM MDT Sun Sep 13 2020 .SHORT TERM...Tonight through Tuesday night. Smoke and haze remain in the forecast through the period. Otherwise, we`ll see high pressure shift slightly to the east tonight and tomorrow, allowing for some stronger southwesterly winds to come into the area. Given the widespread smoke and haze, have dropped high temps a few degrees tomorrow. Cooler temps may inhibit, or at least delay, mixing tomorrow afternoon. This gives a bit of uncertainty to the wind forecast. Strongest winds may be over the Central Mountains tomorrow with gusts to 25 mph possible. Ridging will begin to build back to our west on Tuesday. Hinsberger .LONG TERM...Wednesday through next Sunday. The models are in very good agreement throughout the forecast period holding the upper ridge firmly over the region through early Thursday then translating it east and breaking it down Thursday afternoon though Saturday as the upper low off the NW coast finally rotates inland across the NW states and east of the region by Sunday. As for the details, we should remain dry and seasonably warmer than normal through at least Thursday with smoke filtering into the region from California. By Friday afternoon and continuing into Saturday, the passing upper low should bring enough moisture and instability to the region to support scattered showers and afternoon thunderstorms along with breezy conditions...all of which should help to mitigate any smoke issues. By Sunday, the low shifts well east of the region leaving a mostly dry WNW flow aloft across the area and cooler but normal temperatures. Huston && .AVIATION...VSBY impacts due to wildfire smoke will continue through mid-afternoon with some modest improvements late this afternoon and evening as mixing and venting increase across the region due to diurnal heating. The southwest flow aloft will increase across the region Monday which should help to alleviate most of the VSBY restrictions across the region. Thus we should see a transition from near marginal VFR VIS conditions early this afternoon to VFR conditions through Monday. Huston && .FIRE WEATHER...Critical fire conditions are expected tomorrow afternoon due to winds and RH for zones 475 and 476. Wind gusts to 25 mph are possible in the afternoon, though smoke may reduce daytime heating, which will inhibit mixing. Given the extremely low humidity, Haines indices of 6 and marginal wind gusts, we`ve upgraded to a Red Flag Warning for 18Z to 03Z tomorrow. Winds will increase again on Thursday and Friday as a deep upper trough is expected to approach from the west. Thunderstorms are possible on Friday ahead of the trough. Hinsberger && .AIR STAGNATION...Smoke concentrations will continue to gradually dissipate late this afternoon as thermal mixing helps to ventilate the region. The HRRR and NAAPS smoke concentrations show conditions continuing to improve across most of the area later tonight and Monday as the southwest flow aloft increases across the region. Although the increased southwest flow is expected to bring some relief, it will likely only be temporary as smoke from the California wildfires eventually advects into the region. In fact, the NAAPS guidance shows deteriorating conditions as early as Tuesday afternoon. Huston && .PIH WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from Monday afternoon through Monday evening for IDZ475-476. && $$
Area Forecast Discussion
National Weather Service Reno NV
201 PM PDT Sun Sep 13 2020 .SYNOPSIS... Widespread smoke and haze issues will continue much of this week. Warm temperatures are expected through Thursday then a cold front will drop readings back to near or even below normal for the upcoming weekend. Increased winds could bring fire weather concerns especially Thursday and Friday. A few light showers possible in NE California Friday and Saturday. && .DISCUSSION... Most of the forecast hinges on the progression of quasi-cutoff low currently over NE Pacific Ocean and its progression inland by mid to late week. * Smoke: Well today sure started out nasty with hazardous air quality in many areas. Smoke has been slow to clear from valleys thus far relying mainly on vertical mixing. However, a little bit more SW wind into the evening could allow for more appreciable clearing, at least away from ongoing fires. Smoke models are changing up the scenario some Monday-Tuesday versus the last couple days with increased SW transport winds. Were seeing two distinct plume areas in the models where smoke concentrations are heaviest: one into NE California and far NW Nevada (e.g. Susanville) and another from the E Sierra up into parts of W Nevada (e.g. Mammoth, Carson Valley, Yerington, Fallon). Elsewhere likely to still be somewhat hazy with periods of smoke - low confidence scenario on where boundaries between denser smoke and haze will be. * Wind: Winds will be a little stronger the next few afternoons compared to this past weekend, but where were really watching is Thursday and Friday. Guidance projecting a cold front into the area with stronger S-SW winds for most areas. An appreciable number of ECMWF EPS members showing gusts 30-40 MPH from NE California south along the Sierra Front into the Eastern Sierra both days. Could see localized travel and recreation impacts, along with critical fire weather (see below). The stronger winds could either make the smoke situation in our area worse via long range transport and increasing fire activity - or those winds could thin it out alot. We shall see. Smoke models are only reliable out to 24-36 hours. * Rain: Sorry, but not much luck happening here next 1-2 weeks. The best we can muster: ECMWF/GFS ensemble guidance brings the remnants of a weak-moderate atmospheric river into N California late this week. This could yield a few showers down into parts of NE California Friday-Saturday but precip amounts look to be 0.1 at best. Only 3 out of 52 ECMWF members showing anything above 0.25. Could be a good soaking rain further north into Oregon which would help the fire situation up there. -Chris && .AVIATION... * Areas of dense smoke will continue to impact aviation interests in the region through at least Monday. Based on the latest HRRR Smoke model two major plumes will affect the east side of the Sierra tonight into Monday - Quincy to Susanville (SVE) and Mammoth (MMH) to Yerington and Carson City (CXP). Conditions likely to get into IFR or even LIFR levels in smoke in these areas. * Elsewhere including Reno (RNO) and Tahoe (TRK, TVL) smoke and haze are likely however concentrations do not appear as severe as they were this morning. Probably still a good bet to expect some periods of MVFR in these areas. * The slight increase in SW winds weve seen today will continue into Monday with slightly higher gusts but nothing too impactful. Generally at or below 25 knots for most areas. This could be enough to really mix out the smoke in most areas except near and downwind on ongoing large fires. -Chris && .FIRE WEATHER... ***Increased Confidence in Widespread Critical Fire Conditions This Thursday/Friday*** Changes this forecast cycle: *Cancelled the Fire Weather Watch for the northern Sierra Front for Monday. The Watch for northeast California and northern Washoe County still remains. *Increased winds for Friday, especially along the Sierra ridges. Today through Wednesday will most likely see an uptick in the southwest flow with low humidity and poor overnight recoveries. Recent model guidance shows weaker winds overall during this time and that could be the result due to the smoke impacts. With thick smoke present, thermal gradients will be weaker which in return would dampen the strength of the afternoon winds. With this in mind, we have decided to cancel the Fire Weather Watch for NV zone 420, the northern Sierra Front, for Monday. There could be some localized gusts of up to 30 mph with Sierra ridges remaining gusty into the overnight hours, but widespread critical fire conditions throughout the area is less likely at this time. The Fire Weather Watch remains for CA zones 270, 271, & 278 and NV zone 458 (northeast California and northern Washoe County) for Monday afternoon through the evening thanks to gusty southwest winds and low humidity. These areas look to be the best shot at widespread critical conditions, however, confidence is medium at this time which is why we have left the Watch versus upgrading to a Warning. Expect southwest winds 10-20 mph with possible gusts of up to 30 mph. Higher gusts of up to 35 mph are more likely for wind prone locations as well as for the ridges. Tuesday and Wednesday look similar with zephyr-like breezes each afternoon/evening. Localized critical conditions are possible each day with emphasis on the ridges, northeast California, and northern Washoe County. Forecaster confidence continues to increase in the potential for a widespread critical condition event sometime during the Thursday/Friday timeframe of this week. It`s still early and things could change, for example the overall timing of the gusty southwest winds, but for the most part it looks to be windy thanks to more upper-level support rather than just thermal gradient driven. Therefore, we have increased winds on Friday with the strongest winds along the Sierra Crest (emphasis on Mono and Alpine counties). Even though humidity both daytime and overnight look to increase during this time, the presence of the gusty winds could essentially negate the higher RH. Unfortunately, chances for wetting rains (>0.10") across the region are unlikely at this time. -LaGuardia && .REV Watches/Warnings/Advisories... NV...Dense Smoke Advisory until 11 AM PDT Monday NVZ001>005. Fire Weather Watch from Monday afternoon through Monday evening NVZ458. CA...Dense Smoke Advisory until 11 AM PDT Monday CAZ070>073. Fire Weather Watch from Monday afternoon through Monday evening CAZ270-271-278. && $$ For more information from the National Weather Service visit...
Area Forecast Discussion
National Weather Service Seattle WA
810 PM PDT Sun Sep 13 2020 .SYNOPSIS...Smoke from wildfires will remain an issue into Monday resulting in air quality impacts across the region. A frontal system will bring some showers Monday night and Tuesday. An upper low will slowly move onshore later in the week. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/...Stubborn smoke continues to hang on around most of Western Washington with unhealthy air quality expected to linger into Monday. Surface gradients remain light and this will do little to disperse anything across the lowlands. A broad upper trough offshore will send a weakening frontal system into the region Monday night into Tuesday, but models are backing off considerably with precip chances. The trend now appears that the upper trough offshore will largely stay there until later in the week. Will hold off on making changes to the forecast this evening, but overnight shift may need to scale back precip chances Monday night and Tuesday. 27 Previous discussion...Smoke and air quality continue to be the main issues across the region. Most areas continue to report AQI values in the Very Unhealthy and Hazardous categories. And visibility is mostly limited to less than 2 miles in a combo of smoke and haze. The HRRR model does show total smoke thinning out over western WA with stronger winds aloft (and there`s less smoke offshore). However, mixing and ventilation remain poor and there`s still plenty of smoke trapped near the surface. A frontal system will move inland on Monday (mainly Monday afternoon or Monday night) bringing much needed rain to the region. This, along with a stronger air flow pattern and deeper mixing, will help clean things out (at least for areas west of the Cascades). So improvements are on the way. Moist southwest flow sets up over the Pac NW on Tuesday as a upper level low spins offshore. This brings another period of rain to western WA which will further help our air quality. More smoke on Wednesday? We`re under south flow on Wednesday with light offshore winds as the low continues to spin off the coast. This flow pattern could potentially bring more wildfire smoke (especially from OR and northern CA) into the region. But the extent over western WA is unclear at this time. The smoke should be mostly aloft. We will see better mixing through the period along with additional showers so this should help to limit impacts. 33 .LONG TERM /THURSDAY THROUGH SUNDAY/...Western WA will see additional showers Thu-Sat as the upper low slowly wobbles inland. The air mass is slightly unstable over the Cascades where we may see a slight chance of thunderstorms (near the crest). These showers will be wet, though, and critical fire weather conditions are not expected. Onshore flow will prevail late in the weekend as this system exits. This brings a drier start to next week with temperatures near average. 33 && .AVIATION...Southwest flow aloft continues this evening and into Monday. While PIREPs indicate that smoke layer is beginning to thin from the top, widespread 1/2 to 2 sm visibility continues across nearly all of the lowlands into the evening. With continued weak onshore low-level flow expect lowering MVFR to local IFR ceilings again tonight. An approaching front late Monday will bring increasing mid level clouds and rain chances, but may provide enough mixing to increase visibility late Monday afternoon. KSEA...Visibility remains 1 to 1 1/2 SM this evening with light surface winds. Expect little change tonight with restricted visibility and lowering ceilings through early Monday. Increasing mid clouds late Monday afternoon ahead of front, but increased mixing may lead to better visibility. Cullen && .MARINE...Smoke will reduce visibility - especially over the inland and inner coastal waters into Monday. A frontal system lifts north through the waters on Monday into Tuesday. A surface low will develop west of the waters Tuesday then drift towards the Oregon coast Wednesday and Thursday. Small craft advisory southeast winds may develop Monday night ahead of the front over the coastal waters. Meanwhile, seas will build to around 5 to 7 feet behind the front. Increasing onshore flow on Thursday may bring small craft westerlies to the Central and Eastern Strait of Juan de Fuca Thursday afternoon and evening. Cullen && .HYDROLOGY...The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated as needed until then. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$
Area Forecast Discussion
National Weather Service San Diego CA
200 PM PDT Sun Sep 13 2020 .SYNOPSIS... High pressure aloft will remain in control of the weather over the Southwest much of this week. The center will shift farther south by midweek, which will result in warmer weather here, and should help reduce the areas of smoke and haze. This last full week of Summer will be a warm one, even as onshore flow prevails. A weak sea breeze will moderate afternoon temperatures along the coast each day, with some patchy low clouds and fog possible nights and mornings. Cooler weather will arrive late in the week with an incoming Pacific trough. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... The weather pattern this week will see gradual warming conditions through Wednesday as upper ridging builds over Southern California, followed by gradual cooling late in the week as an upper level trough passes by to the north. Smoke fills the sky again today and is creating very hazy conditions with visibility in the 3-5 mile range across the area. HRRR integrated smoke shows little changes through at least Monday, so we will continue under this very hazy, smoky sky. Visibility could come down some near the coast tonight, but we are not anticipating widespread dense fog. Temperatures will gradually warm through Wednesday as the ridge builds. Heat risk isn`t quite there for headlines, but it will be noticeably hotter through mid week. A day or so of near 110 is possible over the lower deserts with around 100 for the IE and mostly 90s for the high deserts and inland valleys. Cooler at the coast. The extent of smoke will depend on how hot temperatures get. If thick smoke hangs around, which certainly is a possibility, then temps would be a few degrees cooler than forecast. An upper trough will remain situated off the Pacific Northwest and finally move fully inland to our north late this week. This will lower heights and allow for a cooling trend, but no rain here, which is no surprise in September. && .AVIATION... 131945Z...Coastal Areas...A few low clouds with fog will linger at the beaches this afternoon. Coverage will begin to increase after 06Z Mon and spread a few miles inland by 14Z Mon. Bases are likely to be around 500-900 ft MSL, with vis locally 1-3 miles on higher coastal terrain. Partial clearing to the immediate coast expected between 15Z and 17Z Monday. Elsewhere...Widespread smoke with variable thickness will continue through tonight, mainly at/above 5,000 ft MSL, reducing vis down to 4-6 miles for most TAF sites west of the mountains. Smoke reducing vis 3-5 miles at desert TAF sites this morning. Local near-surface smoke will reduce vis down to 2-4 miles in the vicinity of ongoing fires. && .MARINE... No hazardous marine conditions are expected through Thursday. && .FIRE WEATHER... High pressure aloft will hold across the region and strengthen a bit into midweek. This will bring a warming trend, but also some moderation in RH as northwest flow aloft becomes more southeasterly. Winds overall will remain light, except for afternoon sea breezes, which could get gusty locally for a few hours. Relative humidities will only see subtle moderation through Tuesday. The heat will build, peaking Wednesday when daytime highs could be 8-14 degrees above average. Despite the heat, minimum RH values and wind speeds are expected to remain below critical values much of this week. Conditions will gradually cool late this week. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...Gregoria AVIATION/MARINE...PG
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
513 PM MDT Sun Sep 13 2020 .DISCUSSION...(This Evening Through Sunday) Issued at 157 PM MDT Sun Sep 13 2020 Mean upper ridging expected over the western CONUS in most of the period. The Northern Plains will remain on the NE edge of this feature as increasingly active flow persists over southern Canada. This will support an undulating frontal boundary over the region with passing sfc lows. Backdoor cold front has settled further south than expected today, with much cooler conds in the northern third. In addition thick smoke has settled into the region aloft, which has also sig limited insolation keeping temps cooler than if it were clear. Decided to add haze to the forecast through tomorrow, given HRRR vertically int smoke which supports high layer smoke over the region. Approaching low will support increasing southerly flow over the region tonight as a warm front shifts north. Hot day expected Monday as the thermal ridge times over the region at peak heating. Did not raise temps to near abs guidance max, which has worked well since it has dried out, given concerns on the amount of thick some aloft, which could certainly limit temps. Low level smoke is also expected in the far west by afternoon, per HRRR near sfc smoke progs, which will also limit insolation. Expect breezy SW flow should help mechanically mix which should allow temps to rise pretty well. Cool front will shift south Tues with warm but breezy northerly winds. Upper ridge will flatten some toward the middle and end of the week as an upper low pushes into the western CONUS. This will result in more unsettled flow locally, with perhaps increasing chances for showers and thunderstorms if enough low level moisture advects into the region. && .AVIATION...(For the 00Z TAFS Through 00Z Monday Evening) Issued At 513 PM MDT Sun Sep 13 2020 VFR conditions are generally expected tonight and Monday. Hazy skies due to smoke from western US wildfires will persist. Breezy south to southwest winds will develop across northeast WY later tonight and across a good portion of western SD late Monday morning and afternoon. && .FIRE WEATHER... Issued At 157 PM MDT Sun Sep 13 2020 A warm front lifting north on Monday will result in a deeply mixed atmosphere and very dry and breezy southwest winds developing across northeast WY and much of far western SD. Upgraded the fire weather watch to a red flag warning, adding a few zones on the east side. Cold front moves through early Tuesday with elevated to near Red Flag conditions again possible although the window looks to be small. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Red Flag Warning from noon MDT /1 PM CDT/ to 8 PM MDT /9 PM CDT/ Monday for SDZ319>327-329-331>334. WY...Red Flag Warning from noon to 8 PM MDT Monday for WYZ314>318. && $$ DISCUSSION...JC AVIATION...26 FIRE WEATHER...JC