Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/13/20

Area Forecast Discussion
National Weather Service Boston/Norton MA
1016 PM EDT Sat Sep 12 2020 .SYNOPSIS... High pressure provides another night of dry and cool weather. Likewise not as cool Sunday as the ridge weakens and the airmass modifies. Morning clouds will slowly break for sunshine Sunday afternoon. A weakening cold front may bring a few isolated showers Sunday night, although most locations remain dry. High pressure builds in on Monday, allowing for blustery conditions but seasonably cool and dry weather through Tuesday. Moderating trend to temperatures for Wednesday ahead of another cold front for either later Thursday or Friday. High surf from Paulette will likely impact the South Coast early next week especially Tuesday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 1015 PM Update... Dry and quiet weather still expected. Have increased the sky cover across southern New England toward the latest RAP as the 950 hPa RH is doing well with the strato-cu just offshore of Long Island. Expect this to spread in from south to north generally after 2 AM. Have also decreased low temperatures a few more degrees based on current observations as we are a tad bit too warm currently. Should see strong radiational cooling until those clouds move in. Low temperatures in the mid to upper 40s across the interior and the 50s across coastal locations. 725 PM Update: Tranquil conditions continue now just after sundown across Southern New England under governing high pressure ridge. This high will continue to shift further offshore as the night progresses. With it will be a shift in low-level flow to SEly and allow us to tap some of the lower-level moisture evident in nighttime microphysics satellite imagery in the waters south of Nantucket. Should see mainly clear skies with good radiational cooling thru midnight, but by late in the overnight and into the pre- dawn Sunday hrs, an increase in stratocu looks probable as this moisture is drawn landward in the SE flow. RAP-based BUFKIT soundings indicate this moisture is very shallow and related cloudiness may be fairly short-lived but will still linger thru sunrise. Lows still look on track, though radiational cooling may start to level off given the increased cloudiness toward daybreak. Previous discussion... A very pleasant fall evening ahead with 1028 mb high pressure along the Maine coast. Any diurnal cumulus clouds quickly erode yielding clear skies, diminishing winds and with dew pts in the 40s and 50s expect temps to fall quickly with sunset. Although as the high retreats seaward, low level flow (925 mb winds) becomes southeast and begins to advect low level moisture northward in the form of low clouds after midnight from south to north. This will level off temps with lows overnight 45-50, except low to mid 50s in the urban areas and much of the coastline. Thus did not follow the coldest MOS guidance. Instead derived min temps from a blend of MOS guidance. Could have some patchy radiational fog overnight especially in the CT river valley. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... Sunday... Mostly cloudy to overcast to begin the day with low level moisture in the form of strato-cu beneath the subsidence inversion. Mid Sep now so sun angle much lower than just a month or two ago. But with ridge weakening as the day progresses along with sun going to work, clouds will lift and break for sunshine in the afternoon. Airmass slowly modifies with S-SE winds advecting dew pts into the upper 50s and lower 60s by days end. Thus it won`t feel as cool as today. Highs should climb to 70-75 throughout the region. Sunday night... Mid level short wave exiting the Great Lakes into the St Lawrence River Valley deamplifies with time, thus forcing for ascent is weak across MA/CT/RI. As a result only expecting a few spot light rain showers across the region with many locations remaining dry. Mild prefrontal weather with frontal passage holding off until late night or even until sunrise for much of RI and eastern MA. && .LONG TERM /MONDAY THROUGH SATURDAY/... Highlights... * Blustery but clear skies and dry conditions Monday, with seasonably cool temperatures. Less breezy but cooler highs on Tuesday. * Potential for high surf later Monday into Tuesday for ocean exposed beaches due to long-period swell from Paulette. * Continued dry but with moderating temperatures with southwest breezes Wed. * Cold front offers next chance for rain later Thursday or Friday. Details... Monday thru Tuesday Night: After some Monday early-day showers come to an end on the Cape, cold front pushes off the coast. The governing feature will be a broad Canadian anticyclone that ridges into the region Monday mid-morning through Tuesday. It will bring with it a shot of cooler and drier air into Southern New England, with clear skies and fairly strong diurnal temperature ranges (e.g. seasonable days with cooler nights). Highs in the 70s to near 80 Monday with lows in the 40s to low 50s. But on Tuesday highs may struggle to reach 70 degrees under clear skies, with similar lows. Could have some lows in the upper 30s Tuesday night in the typically cooler spots as radiational cooling conditions project to be better (e.g. less wind than Monday). Given strong cold advection steepening low-level lapse rates and boosted by fairly strong 3-hrly pressure rises, expect Mon to be a fairly breezy to blustery day in the post-frontal air mass as the PBL deepens. Strongest NW/N wind gusts out across Cape Cod and the Islands but most areas should see gusts in the 25 to 35 mph range late Monday afternoon into early Monday night, then subsiding a bit into early Tues. Occasional breezes on Tues but a decreasing trend in sustained winds and gusts thru Tues into Tues nite. Though more of a beach/surf-zone hazard, ocean-exposed beaches especially southern waters will be seeing long-period 7` seas associated with sea-swell energy with distant TC Paulette later Mon into Tues. May not be a great beach day Tues with cooler than average temperatures, but nonetheless, later shifts will need to consider a high surf advisory at least for Tues given these surf conditions. Wednesday thru Wednesday Night: High pressure area progresses eastward off the waters of Southern New England. Under full sun, this will lead a period of moderating temperatures under fairly breezy SW winds (gusts mainly 20-25 mph in in the interior and more solid 25 mph gusts across Cape Cod/Islands into the South Coast). 925 mb temps around +16 to +18C and 850 mb temps around the mid-teens C should bring highs back into the mid/ upper 70s to near 80F in spots, with lows mid 50s to lower 60s. Dewpoints start to rise more appreciably into Wed nite but should still fall into the comfortable range (mid-upper 50s commonly). Thursday into Friday Night: This period on the whole looks to offer the next chance for rain, however there`s substantial variation in the 12z NWP on the details regarding how that shakes out. A cold front moving through the more active northern stream is a key feature agreed upon by all the deterministic guidance either later Thursday (GFS/Canadian GEM) or into Friday (ECMWF). Other than the timing differences, the 12z ECMWF, which shows more phasing of northern and southern energy streams, also introduces some question if any of the remnant energy from what is now Tropical Storm Sally may interact with the front. That would lead to a much wetter frontal passage than advertised by the GFS/GEM. So still a lot unresolved but there still remains time to iron these details out. Official forecast will keep chances for showers around later Thursday into Friday. Temperatures should turn near to above normal. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 00z TAF Update: Tonight (thru 12z Sun): High confidence. VFR through at least 06z, then start to see borderline VFR/MVFR ceilings advance landward on SE flow. This may happen as soon as 07z towards the South Coast but better confidence inland after 09-10z. Coverage of these clouds don`t look to be any worse than BKN with bases 030-040. SE winds 4-7 kt. Sunday...Moderate confidence...some uncertainty how quickly ceilings lift from MVFR to VFR. VFR/MVFR the morning but slowly lifting to VFR in the afternoon. Light S to SE wind. Sunday night...high confidence. MVFR/VFR with a few spot showers possible although most terminals may remain dry. Light SW wind becoming NW late with frontal passage. KBOS Terminal...High confidence in TAF. KBDL Terminal...High confidence in TAF. Outlook /Monday through Thursday/... Monday: VFR. Windy with areas of gusts up to 35 kt. Monday Night: VFR. Windy with gusts up to 30 kt. Tuesday: VFR. Breezy. Tuesday Night: VFR. Wednesday through Thursday: VFR. Breezy. && .MARINE... Tonight...high pressure remains over the waters, so quiet boating weather along with dry weather and good vsby. Low clouds after midnight may lower vsby some but overall good vsby. Sunday...high pressure weakens and moves offshore with S-SE winds developing but remaining light. Dry weather and good vsby prevail. Sunday night...Cold front approaches from the west with S-SW winds developing. Increasing low level moisture may yield some patchy fog but will be short lived with frontal passage toward morning with wind shift to the NW. Not much if any shower activity with the front. Outlook /Monday through Thursday/... Monday: Low risk for Small Craft Advisory winds with local gusts up to 30 kt. Seas up to 5 ft. Monday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 10 ft. Tuesday: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 10 ft. Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Wednesday: Winds less than 25 kt. Areas of seas approaching 5 ft. Wednesday Night through Thursday: Winds less than 25 kt. Seas up to 5 ft. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 2 AM EDT Tuesday for ANZ250-254>256. && $$ SYNOPSIS...Nocera/BL/Loconto NEAR TERM...Nocera/BL/Loconto SHORT TERM...Nocera LONG TERM...Loconto AVIATION...Nocera/Loconto MARINE...Nocera/Loconto
Area Forecast Discussion
National Weather Service Houston/Galveston TX
745 PM CDT Sat Sep 12 2020 .SHORT TERM [Tonight through Monday]... Quick update sent for gusty winds and scattered storms in the southeastern most areas. These should dissipate quickly between 830-930 pm. A few of the HRRR runs have highlighted some redevelopment there after after 2 am but for now will follow this uptick with a lull through 7 am. Still looking like a much more active day with storms across the southeastern 2/3rds of the region between noon and 9 pm. 45 && .AVIATION [00Z TAF Issuance]... Storms waning in the short term and will see some MVFR decks possibly after 09z advancing in from the northeast and east though may not reach the TAF sites. Showers should get going around 12-15z near the Galveston/Bolivar/Daisetta area and then expand inland. Primary impacts should hold off until after 18z Sunday with passage of bands of showers and thunderstorms with gusty winds and lowered VISBY. 45 && .PREV DISCUSSION /Issued 308 PM CDT Sat Sep 12 2020/... .LONG TERM [Monday through Sunday]... On Monday, an inverted upper trough will be located over Deep South Texas and a tropical system will be approaching the Mississippi delta. Moisture on the north side of the upper trough will be competing with subsidence on the western periphery of TS/Hurr Sally. At this time, feel Sally will be far enough east to allow moisture to remain over at least the SE half of the region. PW values in both the GFS and NAM reach 2.20 inches with convective temperatures around 90. Subsidence begins to kick in on Tuesday and Wednesday as Sally slowly meanders across the northern Gulf coast. 850 mb temps remain warm and with drying noted in area soundings, MaxT values should still be capable of warming into the lower and possibly mid 90s. By late Wednesday, an upper level trough will develop over West Texas. Some differences between the Canadian, GFS and ECMWF with regard to how deep through trough gets and how quickly it will move across the US. Preferred how the ECMWF initialized and it`s relative consistency and have leaned toward the ECMWF for the end of the week into next weekend. Based on the ECMWF, feel the trough will move slowly across the state and will bring a good chance of showers and thunderstorms both Thursday and Friday. Rain chances will diminish Friday night as the upper level trough axis pushes east and a surface cold front pushes through the area. Upper level ridging will redevelop over the 4 corners region and expand into Texas next weekend. A dry northerly upper and low level flow will develop keeping skies generally clear for next weekend. Drier conditions expected in the wake of the sfc front with sfc dew pts possibly falling into the upper 50`s. 43 .MARINE... Offshore flow will become northeasterly tonight as ridge of high pressure builds to the north. Tropical Storm Sally will track over the warm waters of the Eastern Gulf next few days...likely intensifying to a strong tropical storm...then a hurricane before making landfall somewhere on the coast between SE LA and Wrn FL Panhandle possibly on Tuesday. WNA wave model period fields suggest swells from Sally should could arrive on the TX coast as early as Monday night leading to some increase in surf at that time with swell continuing for at least 24 to 36 hours coming out from this slow moving tropical cyclone. The more direct wind and wave impacts from Sally should remain well to the east of the forecast area as the storm pushes inland mid week. Longer term a good deal of uncertainty. ECMWF brings a fairly impressive cold front from the north with moderate north...then northeasterly flow behind it next Friday and Saturday. Canadian actually brings a tropical system up the coast from the Bay of Campeche at that time. GFS maybe a tad more like the Euro but with a much weaker front. We are leaning slightly toward the ECMWF solution here but again note the uncertainty for Days 6 and Friday and Saturday. 18 && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 72 91 72 91 72 / 0 40 20 30 10 Houston (IAH) 76 95 76 93 76 / 30 60 20 30 20 Galveston (GLS) 81 91 80 91 80 / 40 50 50 30 30 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...None. GM...None. && $$ SHORT TERM...45 LONG TERM...41
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
924 PM CDT Sat Sep 12 2020 .UPDATE... Updated for evening discussion. && .DISCUSSION... There was considerable rain coverage from westward-moving bands of convection this afternoon in association with a tropical wave moving across the northwestern Gulf (not to be confused with Sally). Meanwhile, a stalling front extends from the Midwest into the southern Plains, with associated convection moving eastward into the Mid South and Mississippi River Valley this afternoon. This activity converged over central Mississippi early this evening, with a corridor of stalled convection now extending roughly along the Big Black River. Though much of the convection associated with the tropical wave was more diurnal in nature and has since fallen apart, persisting low level convergence ahead of the surface front overnight along with subtle upper diffluence and forcing will keep scattered showers and a few storms going mainly north of the Natchez Trace. The inherited forecast had a decent handle on this, so only minor tweaks were made to adjust to current trends. /DL/ Prior discussion below: Tonight and Sunday: Scattered to numerous coverage of showers and thunderstorms were noted on local radars this afternoon. This activity will gradually diminish this evening with the loss of daytime heating but the chance for rain will likely continue tonight in our west as a quasi-stationary boundary tries to edge into our CWA. Tropical Storm Sally formed in the eastern Gulf of Mexico earlier this afternoon and will slowly move our way through Sunday. Meanwhile, the closed low over the upper Mississippi valley this afternoon will continue tracking to the northeast across the Great Lakes region tonight while weakening. This departing shortwave trough will help the old quasi-stationary frontal boundary just to our northwest to drift southeast into our CWA later tonight and Sunday. This boundary will become the focus for convection Sunday especially during prime heating. Otherwise, warmer than normal temperatures will continue tonight thanks to our tropical airmass. High temperatures will continue above normal the southeast half of our CWA while temperatures are held closer to normal in our northwest due to the greater rain chances and associated cloud cover. /22/ Sunday night through Friday night: Primary weather concerns in the longer term forecast are associated with Tropical Storm Sally. The official NHC forecast strengthens Sally into a hurricane before making landfall somewhere along the central Gulf Coast early Tuesday. With guidance generally trending stronger with Sally and showing a greater chance for intensification as it approaches land, am a little more concerned for tropical cyclone impacts extending into the ArkLaMiss region, especially for heavy rain and wind in the Tues-Wed time frame over the Pine Belt region. One of the complicating factors will be with motion as steering currents will likely become very weak and the system could slow down once near the coast or inland. Given the potential for a slow-moving tropical system, will go ahead and post a limited flooding graphic. If trends continue, both rainfall/wind threats will need to be highlighted more, and we may ultimately need to issue tropical storm watch/warning for southeast portions of the area. Going later into the week, an upper level trough in the westerlies will likely approach and help to send the remnants of "Sally" out of the area, and this would bring an end to the heavy rain threat. /EC/ && .AVIATION... 00Z TAF discussion: Complicated forecast. Dissipating convection over the region will bring some quick showers and thunder through the next few hours. Overnight...bringing in MVFR/IFR cigs towards dawn, mainly after 09z, but persistence from the prev night has closer to daybreak and shortly thereafter and brief. HRRR guidance is spotty with the IFR cigs... but over a broad area. As a result...blending to the current trend and more widespread precip/increasing BL humidity. && .PRELIMINARY POINT TEMPS/POPS... Jackson 73 89 73 89 / 40 55 4 56 Meridian 73 90 73 88 / 18 33 8 63 Vicksburg 74 89 73 91 / 52 65 3 40 Hattiesburg 72 92 73 88 / 22 39 9 68 Natchez 73 89 73 90 / 35 61 5 44 Greenville 73 86 71 88 / 57 66 3 33 Greenwood 72 87 70 90 / 60 69 3 40 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ DL/22/EC/HJS
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
634 PM CDT Sat Sep 12 2020 .SHORT TERM... (Through Late Sunday Afternoon) Issued at 237 PM CDT Sat Sep 12 2020 Current surface analysis shows a cold front which is nearly stationary draped across Missouri and Illinois from KSGF to near KSTL to KSPI. Short range guidance is in good agreement that this front will continue to drift southeast tonight with scattered to numerous showers and a few thunderstorms ahead of it. Some convection allowing guidance PoPs some fairly hefty storms over southeast Missouri and southern Illinois a little later this afternoon, and the RAP does show 1500-1800 J/Kg MLCAPE in those areas over the next few hours so this is not unreasonable. Additionally, there is a secondary cold front over southeast Nebraska that is diving southeast into Missouri which will link up with the front over our area late tonight and finally push it through. Short range guidance including the RAP and nearly all of the CAMs show weak convection developing along this secondary front as well, so have added in some chance PoPs for this evening over northeast Missouri into west central Illinois. I do not expect any thunder in our area with this line of showers, and all guidance has it dissipating during the late evening. High pressure will build across the Midwest behind the front on Sunday. There may be some lingering fog and low clouds over southeast Missouri and west central Illinois early Sunday morning. It`s possible there may be some fog over northeast Missouri and west central Illinois as well if the aforementioned showers along the secondary front moisten the boundary layer enough. Dense and/or widespread fog does not seem likely though given persistent dry advection. With that in mind, Sunday still looks dry and mild with temperatures peaking out about 3-5 degrees below normal in the mid 70s to around 80. Carney .LONG TERM... (Sunday Night through Next Saturday) Issued at 237 PM CDT Sat Sep 12 2020 Sunday night through Tuesday continue to look tranquil with near normal temperatures as high pressure moves east across the Midwest into the Great Lakes region. Mass fields on the GFS and ECMWF are in good agreement into Tuesday night...but by Wednesday morning things start to fall apart. Over the past few runs, the GFS has been trending closer to the ECMWF with the pattern of a strong cut off low over Hudson Bay during the latter half of the week which develops a long wave trough that digs into the eastern 1/2 of the U.S. This pushes a cold front through the mid Mississippi Valley. The primary difference between the GFS and ECMWF is timing. The GFS is about 24 hours faster than the ECMWF with this process bringing the front into northern Missouri and central Illinois around 00Z Thursday while the ECMWF holds the front back until between 18Z Thursday and 00Z Friday. This of course leads to a huge difference in sensible weather between the two models on Wednesday and Thursday. The GFS shows little if any convergence along the front along and ahead of the front on Wednesday as the last vestiges of the ridge axis from earlier in the week keep the flow light and variable. This leads to a dry FROPA on Wednesday night...and then dry and cool weather Thursday and Friday as high pressure moves across the Midwest and Great Lakes. The slower ECMWF is somewhat warmer and more humid on Wednesday, and then Thursday there is actually some interaction between the approaching cold front and the tropical system it`s advertising to be over the lower Mississippi Valley. This leads to a wet FROPA with convection on Thursday and Thursday night. Additionally, the trough aloft is positively tilted as it moves into the Midwest and Great Lakes Region on Thursday, which digs it further south into the eastern CONUS resulting in a deeper and more persistent upper level long wave, and allows the cool high pressure system behind the front to stay anchored over the Great Lakes and Northeast U.S. longer. Ensemble guidance members show a pretty wide range of temperatures for max/mins for Thursday through Saturday as would be expected in this case. Interestingly, the GEFS temperature spread is very tight wednesday and Wednesday night, and even Thursday isn`t too bad with only a 5 degree spread between first and third quartiles and a. few cold outliers. This lends a degree of confidence in the GFS solution. However the ECMWF ensemble is also pretty sure of itself through Wednesday and the same cool outliers into Thursday. I tend to be more trusting of slower solutions when the pattern includes tropical systems and cut off the slower ECMWF is favored here. Will therefore keep some precip chances and stay warmer on Thursday then go with a dry and cooler Friday and Saturday. Carney && .AVIATION... (For the 00z TAFs through 00z Sunday Evening) Issued at 627 PM CDT Sat Sep 12 2020 A cold front with showers and thunderstorms along it has exited the area over the past few hours. MVFR stratus has largely scattered out across the area, with the exception of portions of south-central Illinois. A secondary front is expected to move through the region late tonight, but is expected to pass through dry with winds veering from the west/southwest to the northwest. There remains some hints at some patchy IFR stratus in northeast Missouri and west-central Illinois late tonight into early Sunday morning. Do not have high confidence in the location nor the coverage of this stratus so left a SCT005 group at KUIN. Fog is likely tonight across parts of southeast Missouri and southwest Illinois, but should stay south and east of the terminals. Therefore, expecting dry/VFR conditions for the terminals with the possible exception of the aforementioned stratus at Quincy. SPECIFICS FOR KSTL: MVFR stratus has scattered out over the past couple of hours and has exited to the east/southeast. Dry/VFR conditions are forecast through Sunday evening with a mostly clear sky. A secondary cold front is forecast to pass through the terminal around 0900 UTC late tonight, but will pass through dry with a wind shift from the west/southwest to the northwest. Gosselin && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1008 PM EDT Sat Sep 12 2020 .SYNOPSIS... High pressure will ridge into the area from the northeast through Sunday while a trough of low pressure remains off the coast. A cold front will cross the area Monday followed by high pressure building in from the northwest through Thursday. Another cold front could approach the area late in the week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... As of 1000 PM Sat...Some drier low level air still trying to filter into the area with Tds falling into the low 60s in the northern tier. Adjusted grids accordingly. KMHX radar shows evidence of a weak low aloft about 50 miles SSE of Cape Lookout that may try and pull shower activity closer to the coast. In fact, a few showers have made it to Core Banks but quickly fall apart as high pressure continues to influence the area. Latest HRRR suggests this will continue overnight, so no changes needed to PoPs. Prev disc...High pressure centered over New England will continue to ridge SW into the Southeast tonight while a coastal trough remains offshore near the Gulf Stream. KMHX radar showing just few spotty light showers across southern section early this afternoon while convection offshore has weakened. Meanwhile, 18Z KMHX sounding shows the subsidence inversion around 850 mb has strengthened and the airmass has become more stable since 12z, MLCAPE down from 750 J/kg to less than 50 J/kg, and doubt any convection will develop across the region this afternoon. Therefore, have lowered PoPs to 20 percent or less, highest southern sections. Continued mostly cloudy and stable tonight with descent moisture remaining below the subsidence inversion. A weak area of low pressure may develop along the coastal trough offshore overnight which could advect a few showers westward toward the coast. The high across inland areas remains strong and the showers should dissipate before penetrating too far inland and will limit mentionable PoPs to the immediate coastal sections. Lows will range from the mid to upper 60s inland to low to mid 70s along the coast. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... As of 3 PM Saturday...High pressure across the area weakens Sunday but upper ridging will continue to bring subsidence aloft serving to limit convection. Still, we could see isolated showers or storms in the afternoon with more sunshine expected allowing for greater instability in the afternoon...MLCAPE peaking around 1000-1500 J/kg. Best chances will be across southern coastal sections where the sea breeze may develop and push inland allowing for best convergence with background northerly flow. High expected in the mid 80s most areas. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... As of 330 AM Sat...A cold front will cross the area Monday, with high pressure building in from the north behind it keeping settled and cooler weather through mid-week as Tropical Cyclone Paulette passes well offshore. The next cold front will bring rain chances back to the forecast late in the week into next weekend. Sunday Night...Mainly dry as isolated shower activity will be confined to the proximity of the coastal trough offshore, with only slight chance showers in the forecast near the beaches. Lows will be near 70 away from the beaches, several degrees above normal. Monday and Monday night...Modest height falls aloft occur in response to troughing developing across the Northeast. At the surface, a cold front force primarily by strong high pressure behind it will push through the Mid-Atlantic and toward eastern NC during the day. Despite the lack of any significant pre- frontal WAA, lingering low level moisture should be sufficient to allow for scattered showers and possibly a few storms to develop Monday afternoon. Most likely frontal timing looks to be later Monday afternoon through Monday evening, with precip chances ending with the passage of the front. Temps continue to be several degrees above normal ahead of the front, with CAA developing quickly behind the front Monday night. Tuesday through Thursday...High pres building in from the NW will lead to dry weather with cooler and noticeably less humid air spreading in. Highs Tue and Wed will be in the upr 70s to lower 80s, with low to mid 80s expected Thu. Will see lows drop to around 60 inland Tue night, than a few degrees warmer Wed night. Friday into the weekend...High pressure slides off the Northeast coast as the next cold front approaches Friday, with deeper moisture returning. Look for unsettled weather Friday into the weekend with increasingly warm and humid conditions. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Short Term /through 00Z Mon/... As of 730 PM Sat...VFR conditions prevail across the terminals this evening with a scattered deck of 2-3 kft. Healthy amount of moisture trapped below a strong frontal inversion will result in lowering and thickening ceilings overnight. Hi-res guidance in good agreement over MVFR conditions developing around 06z for all sites with a corridor of IFR developing around 08-09z, highest probability closer to the tidewater. Inversion keeps hold Sunday morning before beginning to slowly break down mid afternoon as front approaches from the west, and could see some VFR conditions return by mid to late afternoon. Isolated shower or storm is possible in areas that can clear out. Long Term /Sunday night through Wednesday/... As of 330 AM Sat...Ample low level moisture keep the threat for nighttime/early morning stratus and patchy fog Monday. Drier air works in behind front Tue with VFR expected to prevail. && .MARINE... Short Term /through Sunday/... As of 1005 PM...Winds continue to weaken across the waters this evening with weakening high pressure. Let the SCA for Albemarle/Alligator/Roanoke and Croatan expire, and Pamlico and Neuse/Bay rivers will likely follow suit at the top of the hour. Prev disc...The front has pushed south of the waters with strong CAA bringing NE flow around 15-25 kt with gusts up to 30 kt across the waters and seas around 6-9 ft. The winds will gradually diminish tonight as the high to the north weakens and the trough offshore pushes toward the coast with seas subsiding around 4-7 ft. N to NE flow around 10-15 kt expected Sunday with seas only gradually subsiding to 3-6 ft by late afternoon. Long Term /Sunday through Wednesday/... As of 330 AM Sat...Northeast winds remain mainly light and at times become variable as a coastal trough lingers just offshore into Monday. Then, a cold front will cross later Monday, with moderate to breezy northerly flow developing quickly behind it Monday night. Expect winds to only gradually wane through midweek, remaining N/NE as what is expected to become Hurricane Paulette passes well offshore and high pressure ridges inland. Swell from Paulette begins to arrive Monday, with seas building in mainly long period swell through Tuesday, when they will peak around 8-11 ft. The swell will only gradually subside thorough the rest of the week as Paulette turns north the northeastward. SCAs will remain in effect for the coastal waters through duration of the hazardous seas caused by Paulette, which is currently expected to be through at least Wednesday or Thursday. && .TIDES/COASTAL FLOODING... As of 330 AM Sat...Gusty NE winds will develop along the coast Tuesday as strong high pressure builds in from the north. That, combined with increasing long period swell from distant Hurricane Paulette, could result in several threats along the coast. Some wave guidance indicates 8-10 ft seas every 13-15 seconds. Though still several days out, there is potential for coastal flooding, ocean overwash, and rough surf along the coast early to mid next week (especially north of Cape Lookout). Dangerous rip currents will be likely all of next week. Please continue to monitor the threat closely over the next several days. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...Beach Hazards Statement through Sunday evening for NCZ195-196- 199-203>205. MARINE...Small Craft Advisory until 11 PM EDT this evening for AMZ135- 137. Small Craft Advisory until midnight EDT Thursday night for AMZ152-154. Small Craft Advisory until midnight EDT Wednesday night for AMZ150-156-158. && $$ SYNOPSIS...MHX NEAR TERM...SK/MS SHORT TERM...SK LONG TERM...CB AVIATION...CB/MS MARINE...SK/CB TIDES/COASTAL FLOODING...MHX
Area Forecast Discussion
National Weather Service Pocatello ID
130 PM MDT Sat Sep 12 2020 .SHORT TERM...Tonight through Monday night. Satellite imagery shows a widespread area of smoke extending into southwest Idaho. Expect to see that smoke drift eastward overnight as ridging aloft slowly moves to the east. A somewhat stronger southerly flow will return to the region Sunday night. With smoke still present, temperatures may be moderated somewhat, but still expected to be in the mid to upper 80s by Monday. Monday should be a bit breezier with a tighter gradient setting up over the region. Hinsberger .LONG TERM...Tuesday through next Saturday. Models remain in lock step through Thursday as the upper low continues to take shape off NW coast early in the period and the downstream ridge amplifies across the NRN Great Basin Wednesday. We may yet see locally breezy conditions across the CNTRL mountains Tuesday afternoon in the wake of Monday`s ejecting energy from the low off the coast but with the ridge amplifying Wednesday we should return to a lighter wind regime. The ridge axis may work east of the region as early as Thursday if the more progressive operational GFS verifies otherwise Friday is looking like the most likely time frame as the low off the NW coast begins to move onshore opening the door for increased SW flow aloft across the region and a chance of showers and afternoon thunderstorms Friday and Saturday. Huston && .AVIATION...Visible satellite imagery was showing smoke from the Oregon wildfires working into SW Idaho with VIS reduced to 5SM at ONO and 1SM at BKE. For now not anticipating VIS to be reduced any lower than 6SM with HZ at SUN and BYI. VFR conditions should prevail through Sunday. Huston && .FIRE WEATHER...Critically low humidity values will be present tomorrow with poor recovery in the Central Mountains tomorrow night. Near critical fire weather conditions are anticipated on Monday as winds increase with gusts approaching 25 mph. Winds should subside slightly on Wednesday, but humidity will still dip to around 12 to 18 percent across much of the forecast area. A gradual increase in humidity is in store Thursday through Saturday, with wind speeds expected to increase as well. Thunderstorm chances increase Friday night with the approach of a strong upper trough. Hinsberger && .AIR STAGNATION...As high pressure progresses eastward this weekend, smoke from wildfires to our west will track toward Idaho. HRRR Smoke is showing reduced visibilities as early as this evening across Central Idaho and portions of South Idaho. The high continues to track eastward through Idaho Sunday; allowing for reduced visibilities across all of Southeast Idaho. A more southwesterly flow will take over Monday and Tuesday which is likely to bring the northern and central California wildfire smoke into the region; as opposed to the Oregon fire smoke. ND && .PIH WATCHES/WARNINGS/ADVISORIES...None. && $$
National Weather Service Charleston WV
1020 PM EDT Sat Sep 12 2020 .SYNOPSIS... A cold front moves through Sunday and Sunday night. Dry weather returns as the cold front exits Monday. Unsettled weather may return beyond midweek. && .NEAR TERM /THROUGH SUNDAY/... As of 1016 PM Saturday... Made a few more adjustments to POPs for NE KY and SE OH, through midnight. Plenty of rain continues to move northeast across northeast KY and should graze our western CWA for the next several hours. Also made a few tweaks to hourly temps and dewpoints for the rest of tonight. As of 807 PM Saturday... Adjusted POPs for this evening and overnight to align more with latest radar trends and latest near term guidance. Ongoing convection across far NE KY is located along the leading nose of 2" PWATS and also on the eastern edge of greater instability. Latest RAP and HRRR indicate an increase in CINh over the next couple of hours (due to onset of nocturnal cooling) and this should translate to a downward trend of overall convective activity. Later this evening (or more likely during the overnight hours), nocturnal development of primarily showers should occur as a quasi-effective warm front stalls along the Ohio River. Most overnight precip should generally be confined to SE OH and far NE KY, although an isolated brief shower may occur across WV as a southerly llvl strengthens just off the surface. Not expecting a significant flood threat overnight but with a rather deep moisture profile in place across the western CWA, more organized showers overnight could be rather efficient. Thus, isolated high water impacts may occur if heavier rains develop. Minimal changes were made to precip for Sunday. Mainly adjusted timing of precip a bit and capped POPs at 80%. As of 130 PM Saturday... Moisture has been increasing in advance of a cold front, with some PWATs forecast to be over 2 inches in western portions of the forecast area this evening. This will allow for some showers and thunderstorms this afternoon and evening, more likely in eastern Kentucky and southeastern Ohio. While storms will be moving and the ground in relatively dry, will have to watch out for any training storms that could produce excessive rainfall. The cold front will slowly push through Sunday and Sunday night. Expect showers and thunderstorms along and in advance of the front. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 240 PM Saturday... Lingering showers may hang about along the higher terrain Sunday night as the cold front makes its passage into the start of the work week. Drier air then filters in from the aid of high pressure building into the Great Lakes region. This will cause a slight drop in afternoon high temperatures Monday and Tuesday, but we`ll see a difference in diurnal range come Tuesday as we wake up to morning lows in the 50s then rising into the low 80s across the lowlands by the afternoon. Behind the post-frontal stratus Monday morning, skies will remain clear and precip-free through the remainder of the short term. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 245 PM Saturday... The forecast heading into midweek will be dependent upon tropical activity currently evolving in the Gulf of Mexico. At the start of the period, high pressure will still be in place over the Mid-Atlantic region, eliminating much in the way of precipitation. However, upper level trough diving down from Canada will nudge the high eastward and enforce a return pattern regime to set up in the Central Appalachia. This will then allow for aforementioned tropical moisture to glide up into the region and set up unsettled weather beyond midweek. The outskirts of what will likely be the remnants of this tropical feature by this time looks to arrive Wednesday afternoon, mostly confined to the Ohio River Valley. Model solutions are still up in the air for the end of the work week, so opted to maintain central guidance POPs through the remainder of the period. Current WPC depictions for Day 5 through 7 QPF keeps most of the tropical moisture south of our forecast area and over the Mississippi Valley. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... As of 725 PM Saturday... Ongoing convection across NE KY is currently expected to remain far enough to the west of KHTS to preclude any impacts there for early this evening. Elsewhere, VFR should prevail through the evening (exception being at KBKW where flight rules may fluctuate b/w VFR and MVFR). Overnight, shower development is expected to occur across much of SE OH ahead of the next storm system and may approach the OH River Sunday morning. Farther east, VFR should generally prevail, although some fluctuations into MVFR may occur as patches of CIGs develop. Stronger LLVL wind fields should generally preclude significant fog development overnight for most areas. Precip activity is then prog to increase and progress from west to east during the day Sunday as a cold front approaches the region. Nearly all aerodromes should experience SHRA at some point on Sunday, but intensity and associated impacts are a little uncertain. Have carried PROB30 everywhere to account for possibility of reduced VSBYs/CIGs with precip. Iso TSRA also possible, but lack of impactful convection has precluded TS mention at the moment. Most precip should be exiting the region towards the end of the valid 00z TAF period with poorer CIGs expected later Sunday night. SSErly sfc winds around 5 knots tonight, eventually veering more SWrly during the day Sunday. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z MONDAY... FORECAST CONFIDENCE: High tonight. Moderate with Sunday precip. ALTERNATE SCENARIOS: MVFR CIG coverage could be a little greater tonight than what TAFs indicate. Fog may be more of an issue at KEKN overnight. Timing of precip may differ during the day Sunday. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE SUN 09/13/20 UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11 EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H M M M M EKN CONSISTENCY M M M M M L M L M M L L PKB CONSISTENCY H H H H H H H H M H H L CKB CONSISTENCY H H H H H H H H H H H H AFTER 00Z MONDAY... IFR conditions may occur Sunday night. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...RPY/MEK NEAR TERM...RPY/RH SHORT TERM...MEK LONG TERM...MEK AVIATION...RH
Area Forecast Discussion
National Weather Service Seattle WA
812 PM PDT Sat Sep 12 2020 .SYNOPSIS...Smoke from wildfires will remain an issue this weekend and probably into Monday resulting in air quality issues 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 TUESDAY/...Smoke continues to plague the region this evening with widespread visibilities in the 1 to 2 statute mile range. HRRR smoke model output continues to suggest that there will be some gradual improvement by around Sunday evening, but conditions are likely to remain rather static over the next 18 to 24 hours. Low level flow is weaker tonight than yesterday evening and this may complicate the forecast overnight in terms of stratus coverage. Nonetheless, fog imagery does show stratus just offshore with some additional low clouds around the San Juans. With smoke not having the thermal blanket properties of low clouds, the short term forecast may need a slight adjustment for overnight low temperatures. Otherwise, no other forecast adjustments are anticipated. Temperatures remain on the cool side Sunday as plentiful smoke and possible morning clouds will cutback on potential incoming solar radiation significantly. 27 Previous discussion...Smoke and air quality continue to be the main issues across the region. We`re seeing a mix of low level stratus and smoke with visibilities generally less than 2 miles across western WA. Air Quality Index values are mostly Very Unhealthy to Hazardous. Given the flow pattern, abundance of smoke, poor mixing and dry air mass, expect little change in the conditions as we move into Sunday. The smoke is really wreaking havoc on the temperature forecast. Most areas are seeing temps near 60 degrees this afternoon which is a good 10 to 20 degrees cooler than guidance. With persistence in mind, will lower max temps on Sunday. 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. Tuesday will see more rain under moist SW flow. 33 .LONG TERM /WEDNESDAY THROUGH SATURDAY/...We`ll see additional showers in the forecast Wed-Fri as a slow moving upper level low wobbles inland. The air mass will be slightly unstable over the Cascades (in south, diffluent flow) for a slight chance of thunderstorms near the crest. Fortunately, these showers look wet with wetting rains expected. Temperatures will be close to average and RHs will be high to keep the overall fire danger low. This system pushes farther inland over the weekend for drier conditions. 33 && .FIRE WEATHER...Varying degrees of onshore flow with marine layer clouds and high humidity will prevent critical fire weather conditions from developing in the week ahead. There will be a chance of rain or periods of shower activity most days next week and that will allow fuel moisture to recover from the season`s low mark this past week. Smoke and areas of low marine stratus and fog will keep visibility low for now - but that will also maintain the rather stable air mass under the marine inversion. An upper trough will slowly move over the area next week and the air mass will become somewhat unstable again. && .AVIATION...Southwest flow aloft expected tonight into Sunday as upper trough offshore moves closer to the region. Low level flow will remain weak overnight, but onshore flow will increase Sunday afternoon. Stratus will increase along the coast tonight, but inland coverage will be somewhat uncertain in the absence of much onshore flow. Despite this, light surface gradients will do little to help the smoke situation with widespread surface visibilities of 1 to 2 statute miles overnight into at least late morning Sunday. KSEA...Surface visibility in smoke of around a mile or occasionally less to continue through Sunday morning. A shallow stratus layer could develop for a few hours around 12Z Sunday morning, but confidence in this is not high. Surface winds light becoming southerly 6 knots or less toward daybreak. 27 && .MARINE...Continued onshore flow pattern will persist through the weekend. Smoke will reduce visibility over the waters into Sunday, with some improvement from west to east later in the day Sunday. A frontal system will move through the waters Monday into Tuesday with possible small craft advisory winds over portions of the coastal waters and the east entrance to the Strait of Juan de Fuca. Low pressure will develop west of the waters Tuesday and remain through Wednesday. Seas over the coastal waters generally hold 2-4 feet through Monday, but build late Monday night through Tuesday to closer to 5 to 7 feet as the front moves through. 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 Tucson AZ
148 PM MST Sat Sep 12 2020 .SYNOPSIS...High pressure over Nevada will move east into Utah allowing for a downward trend in the smoke over the next few days and a slight upward trend in moisture. The moisture will bring a slight chance of showers and thunderstorms to mainly eastern mountain areas Sunday into Tuesday. Also, temperatures will climb to slightly above normal levels beyond Tuesday. && .DISCUSSION...Dense smoke lingers overhead this afternoon and will through tonight. Due to heating, a bit of that is mixing down to the surface and air quality sensors have shown a gradual upward trend through day. This smoke has stunted our temperature rise and based on latest satellite trends don`t anticipate much change in that for the remainder of the day. So we are looking at highs only about 3 degrees warmer than yesterday and a couple of degrees cooler than the morning forecast. Over the next 24 hours the upper level high over currently Nevada will shift east into the Utah/Colorado area by Sunday night, allowing for more northeasterly flow over SE AZ tomorrow into Monday. This will help to begin thinning the smoke over the area. For Sunday, we have low level easterly flow advecting a bit of moisture into the area, while in the mid-levels there is a bit of an inflection in the ridge over the area with a somewhat unstable thermal profile. All this to say I decided to raise the pops a bit over the area for a slight chance (chance over the White Mtns) of afternoon showers and thunderstorms. The NAM and GFS have been leaning this way the last couple of days and the shorter range UA and HRRR CAMS are also showing a bit of convection. Enough to not ignore, so I didn`t. Should not add up to a stellar day, but there should be a few storms around, primarily over the mountains. Much the same on Monday, with a little less smoke and moisture and with a potentially slightly warmer mid-level temperature profile, a somewhat lessor threat of convection, but not zero. Temperatures will again generally remain in the 90s. Tuesday, just a bit more drying and warming aloft pretty much limiting the storm threat to the Mogollon Rim country. Wednesday onward, the ridge is expected to consolidate more over the area with a trough approaching the west coast, which is good news for many of the wildfires from Washington through Northern California. It will help. The difference for us is that it will dry out the air mass and result in warmer afternoon temperatures, on the order of 5 degrees above normal. This is where Tucson may add a day or two to the 100 or greater high temps more total before temperatures likely settle back a bit next weekend. && .AVIATION...Valid through 14/00Z. Smoke layer mainly aloft will continue thru the forecast period, with some lowering of surface visibility due to smoke/haze. Otherwise, mainly SKC with a FEW-SCT clouds at 8k-12k ft MSL in the higher terrain east of a KFHU to KSOW line thru 13/04Z. SCT-BKN clouds at 8k-12k ft MSL will develop aft 13/17Z, with a chance of -SHRA/-TSRA in the White Mountains NE of KSAD and south/southeast of KTUS. SFC wind generally less than 12 kts thru the forecast period, favoring an ELY/SELY direction tonight and Sunday. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...High temperatures will warm to near normal Sunday through Tuesday and then a couple of degrees above normal the second half of next week. There will be a chance of showers and thunderstorms in the White Mountains Sunday and Monday, with a slight chance of showers and thunderstorms to the south/southeast of Tucson. Drier air moves in Tuesday, with just a slight chance of showers and thunderstorms in the White Mountains. Dry conditions are then expected across southeast Arizona Wednesday through Saturday. 20-ft east/southeast winds will develop tonight and continue through next Friday. Elevated east to southeast winds are expected Monday, persisting into Tuesday in a few locations. && .CLIMATE...Tucson will make a few attempts at on adding to the triple digit high total in 2020 later this coming workweek. Currently standing at 91 days of 100+ highs behind 93 days in 1989 and 99 days in 1994. && .TWC WATCHES/WARNINGS/ADVISORIES... None. && $$ Public...Cerniglia Aviation...Zell Fire Weather....Zell Visit us on Facebook...Twitter...YouTube...and at
Area Forecast Discussion
National Weather Service Las Vegas NV
851 PM PDT Sat Sep 12 2020 .SYNOPSIS...High pressure passing overhead will bring temperatures back to and above seasonal normals. Midweek, a trough will dip down from the Pacific Northwest and bring with it cooler temperatures and breezy winds. As dry conditions persist, this will result in enhanced fire danger. && .UPDATE...Mostly clear and tranquil conditions continue across the forecast area tonight. No changes needed to trends detailed in the previous discussion. -Adair && .PREV DISCUSSION... .DISCUSSION...Today through Friday. A ridge of high pressure will slowly pass over the Desert Southwest through the remainder of the weekend and into next week. Temperatures will continue to climb to at and above seasonal averages. The caveat will be smoke. Yesterday, smoke limited the high temperatures quite a bit. Additionally, the smoke cleared out overnight, so temperatures cooled off more than expected. Manually brought down a few temperatures tomorrow morning, but otherwise, blended NBM with CMCnhBC, the local top performer for minimum temperatures, as well as the previous forecast. Populated HRRR Smoke in the grids, which is indicating mostly clear conditions for the short term. California wildfire smoke is wrapping clockwise around the high pressure, which may allow it to funnel back into southern Nevada, northwestern Arizona and southeastern California tonight into tomorrow. As the high pressure moves eastward and directly over southern Nevada, we will get a brief reprieve of smoke before the high continues eastward out of our area. By midweek, a cut off low will drop down from the Pacific Northwest. It is expected to open up before approaching our region, but nonetheless will bring with it a strong cold front. This cold front is not anticipated to drop temperatures near as much as the last, which dropped us 20-30 degrees over the course of a couple of days. Rather, this cold front will drop temperatures around than 5 degrees, bringing us back to seasonal normals, and will primarily be a wind maker. Due to the continued dry conditions, this will result in an increase in wildfire danger, so outdoor recreation involving sparks or flames will not be recommended. && .FIRE WEATHER...Dry conditions continue, coupled with very dry fuels. Afternoon breezes expected to remain below red flag criteria until about midweek when a cold front will bring with it breezy southerly winds. Critically low fuels and relative humidities with weak overnight recoveries will continue, so enhanced fire danger expected toward the end of next week. && .AVIATION...For McCarran...Low impact weather is expected through the TAF period with light diurnal winds and dry conditions. Smoke will drift over the area at times however it should not be as thick as we have seen the past few days. For the rest of southern Nevada, northwest Arizona and southeast California...In general, expecting typical wind patterns across the region for tonight and Sunday, with winds remaining less than 10kts. The main aviation concern will be smoke impacts from California wildfires. Much of the smoke should remain elevated with limited aviation impacts, except at BIH and down the Owens Valley where occasional surface visibility restrictions from haze are possible Sunday morning. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Varian AVIATION...Nickerson For more forecast information...see us on our webpage: or follow us on Facebook and Twitter