Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/16/20

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
624 PM CDT Tue Sep 15 2020 .UPDATE... Issued at 623 PM CDT Tue Sep 15 2020 Forecast remains on track this evening. No major changes are planned. && .SHORT TERM...(This Evening through Wednesday Night) Issued at 207 PM CDT Tue Sep 15 2020 Fairly quiet pattern is expected to continue across the region through the short range. Western ridge aloft and eastern CONUS trof will only change slightly through Wednesday night. However, that said, energy should retrograde the eastern trof a bit, allowing for a sfc high to move southeast into the Northern Plains, and thus pushing the boundary currently over the region further south into the Central Plains. A cooler airmass behind this front will overspread the region for Wednesday and Thursday. As for the elevated smoke, the HRRR model shows it hanging around through Wednesday. However, near sfc smoke/vsby progs also from the HRRR aren`t too bullish and suggest that sfc high building in later tnt and Wednesday may negate the potential for widespread low level smoke. As for temps, expect generally near to below normal temps as sfc high builds south over the forecast area. 2m temp anomalies indicate as much. .LONG TERM...(Thursday through Tuesday) Issued at 207 PM CDT Tue Sep 15 2020 Trends between yesterday`s and todays long term suggest a drier initial opening to the period, with about a 1024mb high setting up to the northeast and despite northwest flow aloft, NAM BUFKIT suggests only a shallow mid level deck which would be less supportive for any precipitation other then a light sprinkle at most. It will remain dry until the weekend when we see an upper low slowly move across the northern plains. Being on the south side of the system, this gives us another shot at warmth for a few days with chances for some thunder (though GFS MUCAPE values are 500j/kg or less. System track doesn`t really dislodge much cold air either, so start of next week looks mild as well. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening) Issued at 623 PM CDT Tue Sep 15 2020 Terminals KABR,KATY,KPIR,KMBG VFR conditions are generally expected through the period. Elevated smoke may occasionally mix down toward the sfc and affect vsby near KMBG and KPIR tonight. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. && $$ UPDATE...Wise SHORT TERM...TDK LONG TERM...Connelly AVIATION...Wise
Area Forecast Discussion
National Weather Service Bismarck ND
957 PM CDT Tue Sep 15 2020 .UPDATE... Issued at 956 PM CDT Tue Sep 15 2020 For late evening update main change was to increase cloud cover primarily over the north later tonight as some low clouds continue to settle south through southern Saskatchewan/Manitoba. Still some question as to how far south these clouds will settle, but pulled them a ways into the north. UPDATE Issued at 630 PM CDT Tue Sep 15 2020 Quiet weather remains over the area. Only change needed was to increase cloud cover a bit over the north central, but with that said the clouds are probably hard to notice anyhow with the smoke passing through. Updates have been sent. && .SHORT TERM...(This evening through Wednesday) Issued at 130 PM CDT Tue Sep 15 2020 Smoke and resulting temperatures highlight the short term period. Currently, skies were partly to mostly cloudy, although filled with smoke and haze. Tonight, a secondary cold front will drop south from Canada and will increase cloud cover a bit across the north and maybe central late tonight into Wednesday morning before dissipating as the center of the high moves overhead. Quite a bit of sunshine on Wednesday, but again with areas of smoke and haze. Stuck with our guidance for lows tonight and daytime highs Wednesday which were both a bit cooler than previous guidance. We kept the mention of smoke/haze tonight, then mainly west and south central through the day Wednesday as HRRR Smoke modelshows the north and east clearing, but remains confined to the southwest. .LONG TERM...(Wednesday night through Tuesday) Issued at 130 PM CDT Tue Sep 15 2020 Seasonable temperatures and minimal precipitation chances highlight the extended forecast period. Our blended guidance has backed off on the shower chances in the south central late Wednesday night. WPC still has a small area of qpf over the far south central. After coord with neighbors will stick with the given blended guidance and leave out pops. Could be a stray sprinkle or shower, but chances for measurable precip look slim. 12 UTC medium range guidance is all dry. The rest of the work week looks seasonably cool and dry with highs mainly in the 60s to lower 70s. Temperatures warm to around climatological normals through the weekend. A negatively tilted trough lifts from the northern Rockies into the southern Canadian Prairie Provinces Saturday night through Sunday night, bringing small chances for showers and isolated thunderstorms. At this time the blended guidance is advertising generally chance pops north to slight chance south, which seems reasonable for now given the track of the mid and upper level circulation. Once this system exits, dry and seasonable weather is in store for the first couple days of next week, then potentially a chance of light precipitation with a cold front moving through by mid week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 630 PM CDT Tue Sep 15 2020 Areas of MVFR ceilings possible over far northwest and north central North Dakota. At this time it appears that the lower ceilings should stay to the north and east of KXWA and KMOT. As for smoke, at this time it appears that all locations should remain VFR, but will continue to monitor area observations and will amend as needed. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JJS SHORT TERM...TWH LONG TERM...TWH AVIATION...JJS
Area Forecast Discussion
National Weather Service Caribou ME
1100 PM EDT Tue Sep 15 2020 .SYNOPSIS... High pressure will move south of the region tonight into Wednesday. A cold front will push into the region on Thursday and continue south of the area Thursday night. Strong Canadian high pressure will slowly build in Friday into the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... 1045 PM Update... Satl imagery continued to show a combination of high clouds and smoke from the California fires moving into the region. Temps have dropped off but clouds have thickened and lowered. So, thinking is that temps will be capped and should hold steady for the reminder of the night. A warm front was lifting across srn Quebec and will lift north into Maine overnight. Radar did show some light showers but most of this was drying up as it pushed east. RAP/NAM Soundings did show the column to moisten w/moisture working it way down to 5k ft across the nwrn areas. Some lift was noted w/the warm front. So, some showers can be expected across the western areas overnight and move across the northern border by Wednesday morning. Not expecting any accumulation as the lvls remain dry below 5k ft. The latest HRRR confirms this as well. Some tweaking done to the pops to adjust more toward the nw. Hrly temps were modified using the latest obs. Previous Discussion... High pressure dominates through the period as it slides offshore. Clouds with a warm front are moving quickly out of Quebec and will move into the forecast area this evening. This should reduce the prospects of radiational cooling with lows in the low to mid 40s north and mid to upper 40s north. Can`t rule out some light rain in northern Aroostook late tonight into early morning, but can`t foresee more than a maximum of a few hundredths of an inch in the western St John Valley. For Wednesday, clearing will spread northward through the day. Smoke from western fires is expected to remain over the area Wednesday and may have an impact on forecast high temperatures. The warm front will bring nominally moister air into the area, but have generally gone below most guidance on dew points. The biggest feature for tomorrow is the arrival of a strong LLJ at 925 and 850. In spite of a relatively shallow mixing layer, winds along the coast will gust over 30 mph much of the day. Further north, the strong 850mb winds arrive along the western border in the afternoon. The big question will be the amount of heating and depth of mixing layer. Have taken a conservative approach with mention of gusts to 30 to 35 mph in most zones, but less than a deeper mixed layer would yield...or if the LLJ arrives earlier than progged. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... Remaining breezy Wednesday night ahead of an approaching cold front. Much milder with not only a milder airmass, but also good mixing keeping areas from decoupling. Went on warm side of guidance with forecast lows in the 50s. Cold front won`t have much moisture to work with and will be weakening as it moves south through our area on Thursday. Reason for weakening is it`s getting further south and away from the better dynamics...the upper trough and jet to our north which won`t be getting much closer through Thursday. With limited moisture and fairly weak forcing, only expect some showers with the front and precip totals less than one quarter inch, with many areas not even getting a tenth of an inch. Have likely PoPs far north and chance PoPs elsewhere. Good temperature gradient Thursday with highs in the 50s north of front and 70s south of front. Front moves offshore Thursday evening. Looking into Friday, can`t rule out some moisture from remnants of Sally moving into Downeast. Odds favor rain staying offshore, but have 20 PoPs in just in case. Cool with dry air Friday, and highs ranging from the mid 50s north to mid 60s coastal Downeast. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Looking for cool and dry weather to persist Friday night through early in the week. Friday night, upper trough over Quebec digs down into our region. Air too dry for any precip, but we will be seeing a bit more cold advection. Should be enough of a NW breeze to keep temps Friday night from dropping too much. Could be some decoupling the far north. Cool Canadian high pressure over the region for the weekend. Potential for a good freeze for many areas Saturday night and Sunday night. Still some uncertainty on the position of the high pressure and whether we can fully decouple from light winds under the high. High center tentatively looks to be positioned just west of us Saturday night and pretty much over us Sunday night. Definitely the threat of a killing freeze in the north and frost into Downeast. Upper ridge builds a bit for Monday and Tuesday with some moderation in temperatures. Appears to stay dry through Tuesday. However, it is possible toward Tuesday or Wednesday that we could have issues from tropical system Teddy. Most models keep Teddy well to our SE as it passes by, with perhaps just some swell. But there are a few models or ensemble members that bring Teddy NW and into New England or the Canadian Maritimes, with this NW movement coming from Teddy being drawn in by an approaching upper trough from the west. Again, this is not the expected outcome, just a small possibility/high impact scenario that needs to be monitored. && .AVIATION /22Z TUESDAY THROUGH SUNDAY/... NEAR TERM: VFR conditions are expected through the period. Smoke will continue to generate hazy conditions above 5000 ft. SHORT TERM: Wednesday Night...Breezy from the S with mainly VFR except possible MVFR/IFR coastal Downeast. Thursday...Generally VFR, but local MVFR possible in showers. S breeze shifting to the NW. Expect less smoke later Thursday behind the cold front. Thursday Night through Friday Night...NW breeze and VFR. Saturday and Sunday...VFR with light winds. && .MARINE... NEAR TERM: Update...High Surf Advisory was cancelled in collaboration with GYX. Seas have been running 3-4 ft at best w/intermittent swells. SCA remains in place. Southwest winds will strengthen quickly on Wednesday with gusts to 30 kts. These will be some of the stronger winds in months over the waters. The combination of the swell...followed by the winds tomorrow led to a continuous advisory through the period. Shorter period wind waves will be generated by the strong SW winds on Wednesday and will reach up to 5 ft. SHORT TERM: Small craft SW winds continue Wednesday night ahead of the cold front as seas build to a rather impressive 8 feet outside of the inner waters. Conditions gradually ease to below small craft late Thursday. Winds switch offshore Thursday night and the NW wind may approach small craft levels Friday morning before easing as high pressure builds in for the weekend. && .FIRE WEATHER... In coordination with Maine Forest Service (MFS), have issued a Fire Weather Watch for central zones Wednesday afternoon. Afternoon relative humidity is expected to drop towards 35 percent while southwesterly wind gusts exceed 30 mph at times. Downeast zones will have relative humidity above watch criteria, but winds will be gusting over 30 mph in that region too. Also excluded NW Aroostook County due to forecast cloudiness. Smoke aloft from western US fires could reduce temps and mixing depth, but have taken a cautious approach due to the very strong low level jet arriving in the afternoon and the MFS fuels assessment. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...Fire Weather Watch from Wednesday afternoon through Wednesday evening for MEZ002>006-010-011-031-032. MARINE...Small Craft Advisory until 8 AM EDT Thursday for ANZ050>052. && $$ Near Term...Hewitt/MCW
Area Forecast Discussion
National Weather Service Grand Forks ND
904 PM CDT Tue Sep 15 2020 .UPDATE... Issued at 903 PM CDT Tue Sep 15 2020 More clouds are showing up across southern Canada, which should move through the FA late tonight into Wednesday morning. The going forecast is still in good shape. UPDATE Issued at 641 PM CDT Tue Sep 15 2020 Lots of smoke/haze remains high overhead in the cirrus layer, while a fair amount of clouds are also moving from west to east across the FA. Bumped up the evening sky amounts a little more, otherwise no other changes were needed. && .SHORT TERM...(This evening through Wednesday night) Issued at 315 PM CDT Tue Sep 15 2020 Few impacts in the short term with high pressure building into the area over the next 24 hours. Will continue to see high levels of smoke partially obscuring the sun. Will continue to handle this with increased cloud cover for partial sunshine wording in the zones and a mention of haze in the grids. With the passage of a secondary cold front tomorrow morning will see better mixing and the HRRR does indicate the integrated smoke to be pushed south of the area tomorrow. Low level CAA peaks around sunrise with winds decreasing later in the morning into the afternoon as pressure gradient relaxes. NW winds are expected to be around 10 to 20mph with gusts up to 30mph per Bufkit soundings. Temps tomorrow will be much cooler with highs in the 50s and 60s as 925mb drop from 15 to 20C this afternoon to 5 to 10C tomorrow. .LONG TERM...(Thursday through Tuesday) Issued at 315 PM CDT Tue Sep 15 2020 Most impactful weather this period will be frosty mornings and a weekend rain chance. We can also expect to continue to see some level of haze in the upper levels through the week. A dip in the jet stream allows CAA to occur until the weekend, keeping temperatures cooler. NW flow will be present until a low pressure system aloft moves to our north, changing flow in the northern plains to be from the southwest and west through the period. Wednesday night into Thursday morning, temperatures and wind speeds will be conducive for frost development in far northwestern Minnesota. Many areas will drop below freezing, but considering this location had a freeze earlier in the month, impacts will be rather minimal. Temperatures for Thursday will warm up nicely into the upper 50s and low 60s. Friday morning brings another potential chance for frost to develop in the Red River Valley. Temperatures will remain above freezing, but we could see some areas with frost develop. Confidence is high that these locations will be isolated if they do occur. Friday temperatures will stay in the low to mid 60s. Into the weekend, a warming pattern will start to become apparent in the northern plains. We will see some rain this weekend, but confidence is increasing on a trace to 1/4 of an inch of total rainfall being the case. Ensembles are coming to a consensus on keeping it less than a quarter, and on the position of the low pressure system to remain to the north in Canada. Overall, impacts will be low. The rainfall this weekend will mainly be in the form of showers, but an isolated thunderstorm cannot be ruled out. For the beginning of the work week, expect a warming pattern leading to highs in the mid to upper 70s by Tuesday, thanks to southerly winds. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 641 PM CDT Tue Sep 15 2020 At this point, ceilings look to remain VFR throughout. Fairly low wind speeds overnight will quickly pick up on Wednesday morning. Generally expect fairly breezy conditions until mid to late afternoon, when speeds will decrease again. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...Godon SHORT TERM...JK LONG TERM...AK AVIATION...Godon
National Weather Service Hastings NE
722 PM CDT Tue Sep 15 2020 ...Short Term and Aviation Update... .UPDATE... Issued at 722 PM CDT Tue Sep 15 2020 A few comments about Wednesday`s possible smoke "event": After some debate, decided to convert the inherited mention of "haze" in Wednesday`s official forecast to "patchy smoke". Admittedly, this is a bit subjective (and we really won`t know until the front goes through whether the smoke will truly be perceptible at/near the surface), but felt that actually calling it smoke (instead of haze) was more consistent with our "Situation Report" messaging sent to partners (and also posted to the top of our web page) earlier today. Obviously not something we deal with commonly around here (although it does happen at least once every few years), so opinions/practices understandably vary somewhat regarding exactly how to handle the potential for surface near- surface smoke in official forecast products. All other reasoning outlined in the main afternoon discussion below remains very much on track. && .DISCUSSION...(This evening through Tuesday) Issued at 407 PM CDT Tue Sep 15 2020 Upper pattern remains largely unchanged over the last 24 hours with upper ridging dominating the Central Plains as the main belt of westerlies remains well N. H85 temps range from around 14-15C over far SE up to 19-20C over far N/W. As such, sfc temps range from upper 70s to mid 80s from SE to NW. Band of upper smoke that settled into the area yesterday has moved very little and remains firmly over central and southern portions of the CWA. Main change for tonight was to add some patchy fog over far S/SE portions of CWA. Similar to last night, this is where winds will be weakest. Crossover temps aren`t quite as obvious, however, thus only patchy coverage as will likely be limited to low lying areas/valleys. Expect another dry night with lows in the 50s. Upper trough will deepen over S Canada tonight into Wed AM as a 140kt jet streak at H3 noses into Great Lakes by 18Z Wed. This will force a cold front thru south central NE during the AM, and north central KS during aftn. Other than a wind shift to N/NE and pleasant breezes, the potential impact of most interest could end up being an incr in sfc smoke. Thus far, all of the smoke we`ve been seeing has been elevated. However, subsidence behind the front and trajectories from Northern Plains where several obs are already 5-6sm suggests we could see a noticeable incr in smoke closer to the sfc for tmrw. This is indicated by 12Z HRRR surface smoke product. Would expect sfc haze to be most noticeable late morning into aftn as that`s the best combo of mixing and subsidence. Decided to handle this with haze in the grids, and 5sm for TAFs. Not expecting it to be dense enough for HWO mention attm. Temps will be slightly cooler for central and northern areas, but southern areas are still mid 80s. Sfc ridge axis swings thru Wed night into Thu AM. Weaker mixing low level trajectories from Great Lakes region will lead to cooler but still very pleasant temps Thu with highs mid 70s to low 80s. Some models continue to hint at potential for WAA driven weak elevated convection Thu night into Fri AM, mainly over NE portions of CWA. There`s not great model agreement and SREF probs are only 10-30 percent and focused primarily over E have held off on introducing new PoPs. Unless model agreement incr, would like to hold off until within range of hi-res models/HREF to get a better handle on it. May need to add some slgt chc PoPs far NE/E at some point. Temps look to warm a bit into the weekend. Current blend (low to mid 80s) is a bit lower than latest 12Z guidance, which is mid to upper 80s. But either way, expect above normal temps for the upcoming weekend. Appears the next trough and associated cold front has slowed down in latest guidance. As such, PoPs have shifted a period slower and now don`t start until Sun and continue into Mon. With that said, chcs still look pretty limited as the primary upper energy slides well N of the area and sfc moisture looks limited with sfc Tds only low to mid 50s. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday) Issued at 721 PM CDT Tue Sep 15 2020 General overview: Very high confidence in VFR ceiling and dry/precip-free conditions through the period. That leaves POSSIBLE MVFR visibility during the latter half of the period (from western wildfires smoke) and also a fairly pronounced wind shift (behind a passing cold front) as the main issues/challenges. Read on for more regarding both. Possible MVFR visibility from western wildfires smoke: Although confidence is not overly-high regarding how this plays out, upstream obs this evening over the Northern High Plains suggest that at least light visibility reductions in smoke could occur during the day Wednesday behind a passing cold front. For now have gone with a prevailing high-end VFR visibility (6SM FU) during the 14-22Z time frame to capture the most likely time frame for possible near-surface smoke issues, but at least brief MVFR cannot be ruled out. Surface winds: Breezes this evening-overnight will average no more than 6-10KT as direction gradually transitions from southerly to more westerly ahead of an approaching cold front. This front makes its initial passage around 13-14Z, turning breezes northerly. Thereafter, speeds pick up out of the north-northeast especially 16-22Z, during which time sustained speeds around 15KT/gusts 20+KT will be common before starting to ease up late in the afternoon. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ UPDATE...Pfannkuch DISCUSSION...Thies AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Wichita KS
646 PM CDT Tue Sep 15 2020 .SYNOPSIS... Issued at 312 PM CDT Tue Sep 15 2020 Hurricane Sally continues to move north reaching southeast Louisiana, Mississippi, Alabama and Florida today. The latest from the National Hurricane Center focuses the concern with storm surge and flash flooding given the very heavy and significant rainfall anticipated. There is low over the Central/Southern Plains while a front stretching from a trough in Ontario bisects the Northern Plains. The Mountain West has a persistent ridge. Temperatures hovered around 80 across Kansas with variable winds from 5 to 10 mph. With these conditions, it is quite stellar and perfect for any outdoor evening activities. && .SHORT TERM...(This evening through Friday night) Issued at 312 PM CDT Tue Sep 15 2020 Highlights: 1) Highs in the upper 70s to lower 80s 2) Maybe some fog in central KS again tonight-early Wednesday 3) Possible haze from smoke out west - no mention in weather grids right now The ridge off to the west will move its way eastward for the rest of the week. A holding weather pattern should persist with high temperatures ranging from the upper 70s to lower 80s. This will continue the fall like feel in the air. Slightly cooler values are forecast on Thursday but very subtly comparative to Wednesday. Unfortunately no chances for precipitation are expected through this period. Only very minor tweaks were made to the forecast other than the addition of patchy fog tonight. There is the possibility of patchy fog in central Kansas similar to this morning. The HREF and a few other models are suggesting this will occur given the dewpoint depression and light winds. Model presence and occurrence of fog this morning resulted in its insertion across north central Kansas late tonight into early Wednesday. Widespread dense fog is not anticipated, but there could be a slight reduction to the visibility in patchy areas. The HRRR near surface smoke plume model hints at the possibility of smoke/haze moving into central Kansas on Wednesday. Smoke is likely across the Northern Plains and along the Front Range. The signal does not appear to be strong enough to make an impact thus the decision was made to leave out any mention of haze at this time. .LONG TERM...(Saturday through Tuesday) Issued at 312 PM CDT Tue Sep 15 2020 Highlights: 1) Highs around 80 degrees 2) Breezy west of KS Highway 14 Saturday to Monday afternoons 3) Chances for thunderstorms in north central KS Sunday eve - Monday Changes: Timing and chances of precipitation Sunday night-Monday As the ridge keeps its eastward track for the latter part of the week, the next trough will move onshore on Friday. The trough will them move to the Rockies by Saturday night and is expected to track across the Plains Sunday into Monday. There still appears to be a northerly track with this system which would limit the influence to the south. Chances of showers and thunderstorms remain possible Sunday evening into Monday in north central Kansas; a later arrival for precipitation is anticipated based on the current trends. Additionally slight chances have been inserted through Monday. Confidence is not high in any precipitation as indicated with the slight chance wording. Temperatures are expected to stay around 80 degrees throughout this time period. Mixing will create an uptick in the wind speeds during the afternoon hours west of KS Highway 14 from Saturday to Monday. It will just be breezy with sustained speeds around 20 mph. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 641 PM CDT Tue Sep 15 2020 VFR conditions are expected for most of the TAF period. There will be a chance for some MVFR visibilities due to fog in central Kansas tonight. This will mainly affect SLN, RSL and GBD terminals. This fog is not expected to last past sunrise and should give way to VFR conditions around 12Z. The main question for tomorrow will be the potential for smoke to reach the ground in the RSL, GBD terminals. If this occurs, it is expected to be late in the afternoon and should only cause MVFR visibilities. However, ceilings could come down into the MVFR level as well. Metzger && .PRELIMINARY POINT TEMPS/POPS... Wichita-KICT 61 84 61 81 / 0 0 0 0 Hutchinson 58 84 58 80 / 0 0 0 0 Newton 59 83 58 79 / 0 0 0 0 ElDorado 60 83 60 79 / 0 0 0 0 Winfield-KWLD 60 83 60 80 / 0 0 0 0 Russell 55 86 55 80 / 0 0 0 0 Great Bend 55 85 56 79 / 0 0 0 0 Salina 58 86 58 81 / 0 0 0 0 McPherson 57 84 57 79 / 0 0 0 0 Coffeyville 59 84 60 81 / 0 10 0 0 Chanute 60 83 60 80 / 0 10 0 0 Iola 59 83 60 80 / 0 0 0 0 Parsons-KPPF 60 84 61 80 / 0 10 0 0 && .ICT WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...VJP SHORT TERM...VJP LONG TERM...VJP AVIATION...ELM
Area Forecast Discussion...UPDATED
National Weather Service Los Angeles/Oxnard CA
829 PM PDT Tue Sep 15 2020 .SYNOPSIS...15/704 PM. Smoky skies are expected to improve Wednesday and Thursday as a low pressure system approaches from the west. Slight warming is expected Wednesday before a slow cooling trend begins Thursday. Gusty northerly winds are expected in southern Santa Barbara County Thursday and Friday evenings. Below normal temperatures are expected for the weekend and continuing into next week with marine layer clouds returning to coastal areas. && .SHORT TERM (TUE-FRI)...15/827 PM. ***UPDATE*** A strong upper-level ridge combined with weak onshore pressure gradients led to another warm day across the region. Temperatures were quite similar to yesterday with slight warming occuring along the Central Coast. However, many of the interior sections actually cooled around 1-4 degrees thanks to the thick smoke layer from the nearby fires (especially the Bobcat). For tonight, expecting similar cloud cover as last night. Satellite imagery is indicating low clouds pushing into the Central Coast, and will expect these clouds to fill into the Santa Ynez Valley overnight. Due to a shallow marine layer in place, there will likely be patchy dense fog. South of Point Conception should remain cloud-free, but patchy low clouds and fog are possible over coastal areas after midnight. Otherwise, reduced visibilities due to smoke are likely across the region. As for winds, expecting weak sundowner winds across the western portion of the Santa Barbara South Coast. Wednesday will look much the same as today, except with a bit of warming. There will finally be some relief from the smoke as models indicate an upper-level trough approaching the Pacific Northwest that will start to push the upper ridge to the southeast. This will lead to increasing southwesterly flow aloft which will help reduce the smoke cover. If enough smoke can clear, there is a good chance that temperatures will warm up a bit more than forecast. Instead of 1-3 degrees of warming, some areas may see up to 3-5 degrees of warming. Current forecast looks in good shape and not planning any updates. ***From Previous Discussion*** The good news is that the HRRR-Smoke model is showing a significant improvement in the air quality as early as Wednesday morning across Ventura and SB Counties and by afternoon for the western half of LA County. Northern SLO and eastern LA County will continue to have smoke issues through the day and likely into Thursday morning at least, though for the Bobcat fire most of the LA Basin will start improving sooner as southwest flow increases. Assuming the smoke clears as the HRRR shows tomorrow`s temperatures could warm up a few more degrees than currently indicated. Am applying model temperature trends to Wednesday`s forecast which may not quite be enough since the models are not taking into account the smoke impacts into today`s conditions. Under smoke-free conditions tomorrow`s temps would be 1-3 degrees warmer on average over today but that could end up being more like 3-6 degrees or locally higher in some areas where it clears out more tomorrow. As the trough slowly approaches and moves onshore Friday most areas, mainly inland should see a couple degrees of cooling but probably not much change at the coast as onshore gradients really don`t change much through Friday. We`ll start seeing increasing Sundowner winds in srn SB County as early as Wed evening but more so Thu evening and then peaking Fri evening. Winds could be advisory level those last two evenings as not only does the SBA- SMX gradient increase but also the SBA-BFL which tends to indicate a more widespread event than just the western portion. The increase in northerly flow there and across some of the other coastal valleys could lead to some locally warming temperatures and lower humidities, though nothing too significant. The increase in northerly flow across the coastal waters later this week will likely limit stratus formation Friday to srn LA County and possibly some patches along the Central Coast. As mentioned previously models have started to indicate some entrainment of moisture from tropical storm Karina which is weakening but in a favorable position to inject it`s moisture into the trough. So far models have not shown a lot of instability with it but enough to keep a close eye on this as we get closer. Models tend to struggle with these systems so for now confidence is too low to mention thunderstorms in the forecast but do like the idea of increasing mid/high clouds Thu/Fri. At some point if models identify a source for increased instability then some thunderstorm chances may be added. .LONG TERM (SAT-TUE)...15/134 PM. The trough is expected to move into the northern Rockies Saturday and into the northern Plains Sunday. As that happens cooler air will filter into the area and onshore flow will increase. We should see the marine layer returning to most coastal areas and likely the valleys eventually, though possibly delayed a day for srn SB County due to the northerly flow. Daytime highs expected to drop a few degrees below normal by over the weekend and remain that way into at least the middle of next week. && .AVIATION...15/2354Z. At 2300Z at KLAX, the marine layer was 400 feet deep. The top of the inversion was at 1600 feet with a temperature of 29 C. Fairly high confidence in TAFs. There is a 20% chance of LIFR or lower cigs at coastal sites south of Point Conception after 09Z. Visibilities of 2 or 3 SM may be off by a mile at times. KLAX...Fairly high confidence in TAF. There is a 20% chance of 2SM HZ FU 12Z-16Z. There is a slight chance of LIFR cigs after 10Z. High confidence that there will be no east wind component greater than 4 kt. KBUR...High confidence in TAF. There is a 20% chance of 3SM HZ FU 12Z-16Z. && .MARINE...15/826 PM. Overall, moderate confidence in forecast. Winds across the outer waters along the Central Coast to Point Conception did not pan out as gusty as expected, so decided to cancel the Small Craft Advisory. However, there may be some local gusts up to 25 kt through this evening. Otherwise, good confidence in winds and seas remaining below SCA level through Wednesday morning. By the afternoon, there is a 40% chance of widespread SCA level winds across the outer waters to San Nicolas Island, especially the western portion. However, confidence increases by Thursday evening where there is a 60-70% chance of widespread SCA level winds which will likely last through Saturday. There is a 40-50% chance that SCA level winds may bleed into the western portion of the Santa Barbara Channel each afternoon and evening Thursday through Saturday. Patchy dense fog will likely continue over the coastal waters through at least Thursday. An elevated south swell of 3 to 4 feet with a period of 10 to 12 seconds will approach the waters on Wednesday evening and last through at least Thursday night. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && .HAZARD POTENTIAL OUTLOOK (FRI-TUE). Gusty northerly winds are expected in southern SB County Friday night. && $$ PUBLIC...Stewart/MW AVIATION...Stewart MARINE...Stewart SYNOPSIS...MW/Smith
Area Forecast Discussion
National Weather Service Medford OR
856 PM PDT Tue Sep 15 2020 .UPDATE... && .DISCUSSION...With the southerly flow across the region, smoke has improved, except for downwind of the largest fires. Josephine county saw much thicker smoke and temperatures where a good amount lower in Grants Pass and in Medford today. Forecast for tonight looks good and will not headline at this time. However, the areas that the GFS has indicated instability for this afternoon, namely the northern coastal waters up to the northern Oregon coast, did see some thunderstorms develop. The GFS is indicating elevated instability briefly tomorrow afternoon, and will wait until the latest HRRR smoke forecast is in and add a slight chance of thunderstorms to areas where the instability is indicated that are outside of the projected heavier smoke. Sven && .AVIATION...For the 16/00Z TAFs...Over the coastal waters and along the coast...Areas of IFR cigs/vsbys over the waters will move onshore this evening, then back offshore by Wednesday afternoon. By Wednesday evening, most of the offshore cigs will be MVFR, and those MVFR conditions will move back onshore Wednesday evening. There will also be isolated thunderstorms this evening, and isolated showers through Wednesday night. Inland areas from the Cascades west...Wildfire smoke will be the main impact during the TAF period. This will limit visibilities to IFR/LIFR across much of the area, possibly improving to MVFR in some areas Wednesday afternoon and evening. East of the Cascades...VFR conditions will prevail through Wednesday night except for local MVFR vsbys in smoke and haze. It will be breezy through this evening and again Wednesday afternoon and evening. && .MARINE...Updated 800 PM PDT Tuesday 15 September 2020...Relatively calm conditions will continue through much of the week, with light south winds and seas below six feet. A series of weak fronts will move onshore through Friday, bringing periods of light rain. A low pressure center will move into the waters Friday, weakening as it does so. The thermal trough may return towards the end of the weekend, bringing gusty north winds and choppy wind driven seas to areas south of Cape Blanco. && .PREV DISCUSSION... /Issued 315 PM PDT Tue Sep 15 2020/ DISCUSSION...Smoke continues to plague the area this afternoon, although there is some improvement (emphasis on some) compared to yesterday. Visibilities are slightly better across west side valleys, up to 1 mile in Medford compared to 1/4 mile, but a look at satellite shows plenty of smoke in and around the area. Along the coast, conditions have improved even more so where visibilities are up to 10 miles. So as we`ve been saying, change is on the way, but it will be gradual each day until Thursday and Friday. Air quality will remain unhealthy until then and an Air Quality Alert remains in effect for this. The upper level pattern won`t change much until Thursday. Low pressure offshore will linger there and high pressure over the Four Corners Region will be slow to weaken. This will result in very little change to overall conditions for the rest of today through Wednesday. East of the Cascades, gusty south to southwest winds ahead of this trough will continue during the afternoons and evenings. These winds will help to keep smoke impacts less than for west side locations, however, it will continue to be very dry as well. These winds coupled with low relative humidities will result in critical fire weather conditions each afternoon through Thursday. See the Fire Weather Discussion below for more details. Smoky conditions will continue west of the Cascades and east of the Coastal Range. Chances for precipitation remain minimal through Wednesday. Even coastal locations likely won`t see much until late Wedensday. The frontal band that was expected to bring some very light precipitation today, has stalled just offshore and models are very slow to bring it inland. Latest guidance doesn`t bring it onshore until Wednesday morning, and even then it washes out as it does so. Otherwise, conditions inland will be very similar to what`s occurred during recent days. The more appreciable change comes Thursday. The upper level pattern finally begins to shift and the upper low will make it`s way closer to the coast. This is when we expect to see a more noticeable improvement in the smoky conditions for West Side Valleys. It will be breezy for all locations, especially east of the Cascades. This will also be the first chance for measureable precipitation west of the Cascades. Ahead of this trough, instability increases and we`ll be looking for a slight chance of thunderstorms Thursday afternoon and evening. Given the smoke concentration in the area, it`s not likely we`ll see any convection based off surface instability since smoke tends to drastically inhibit convection potential. However, there is elevated instability and smoke is thinner along the higher terrain, so feel there is a better chance for storms to get going along the High Cascades Thursday. Currently we have thunderstorms in the forecast from western Siskiyou County up through Jackson and eastern Douglas counties and along the Cascades. Again, I think smoke will really limit convection potential for areas south Medford and think the better possibilities remain roughly north of Lake of the Woods. We`ll take a look at the high resolution convection allowing models (CAMs) once this time period enters their forecast domain and reevaluate the forecast then. As we head into Friday, the upper low moves overhead and this is when there is the potential for more widespread precipitation and locations east of the Cascades should see some precipitation. It should be noted that we`re not expecting hefty amounts of rain with this system. This is by no means a season ending event, but the lower temperatures, higher humidities, and even minimal precipitation will be helpful with fire fighting efforts. At the very least, we should get a few days reprieve from the extremely smoky conditions and hazardous air quality. Looking at the extended, models indicate a largely zonal flow pattern with the potential for a brief period of weak ridging on Sunday. This pattern should keep temperatures moderated, and no big heat waves are expected in the extended period. The question becomes does the smoke return and if so, how much? It`s difficult to say at this time because much will depend on how the upcoming weather affects the local wildfires. Hopefully these fires receive enough rainfall to really diminish activity. However, be prepared for the potential for smoky conditions to return late weekend into next week. /BR-y AVIATION...For the 15/18Z TAFs...Wildfire smoke will be the main impact during the TAF period. This will limit visibilities to IFR/LIFR across much of the area. Partial smoke improvement can be expected again this afternoon, especially along the coast and east of the Cascades as south to southwest winds continue to scour the region, although West Side valleys are likely to remain MVFR/IFR under inversions. The next concern is gusty winds. Expect these to develop again this afternoon and evening with similar conditions to those of Monday. The strongest wind gusts of 20-30kt will be from the Shasta Valley eastward in northern California to areas east of the Cascades in Oregon. Also, marine layer fog and low stratus, along with some showers ahead of the approaching offshore trough, are likely to cause some issues in the coastal waters and the immediate coast, especially north of Cape Blanco. Some isolated to scattered showers are possible as well. -BPN MARINE...Updated 130 PM PDT Tuesday 15 September 2020...Relatively calm conditions will continue through much of the weekend, with light south winds and sea remaining below 6 feet. Rain will be possible at times due to a low pressure area to the west, which will gradually make its way east and onshore through Thursday. The thermal trough may return towards the end of the weekend, bringing the return of gusty north winds and wind driven seas south of Cape Blanco. -BPN/BR-y FIRE WEATHER...Updated 330 PM PDT Tuesday 15 September 2020... Critical winds and low RH will continue through Thursday as a low to our west slowly moves towards higher pressure. Winds around 700 mb remain around 30 to 35 mph, so we`ll continue to see wind gusts around that range east of the Cascades Wednesday afternoon and again Thursday afternoon. It appears the windiest day will likely be Thursday as an occluded front approaches the shoreline. As this happens, RHs will actually trend higher, yet not enough to exceed the critical thresholds east of the Cascades. The other topic worth talking about are thunderstorms west of the Cascades and in northern California on Friday. Models suggest there is plenty of instability lingering around southern Oregon. However, this is based on plenty of surface heating, which we won`t have because of the smoke. There are some hints that the Cascades will see sufficient surface heating given some of the satellite images today. So the Cascades are the main area of concern on Thursday for thunderstorms. Since there is so much smoke around, we`re only going with a LAL of 2 and don`t anticipate any fire weather watches or red flag warnings to be issued for this lightning event. As the low moves into Oregon, the flow will then come out of the west. This should push most of the smoke eastward. Models still suggest some potential instability in the area on Friday. Probability of thunder is around 20 percent over most of Oregon on Friday. During this weekend, weak off shore flow develops over most of the region. Winds aloft are only around 5 to 10 knots, so there shouldn`t be an issue with extreme fire growth. -Smith && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning from 1 PM to 8 PM PDT Wednesday for ORZ624-625. Fire Weather Watch from Thursday afternoon through Thursday evening for ORZ624-625. CA...Red Flag Warning from 1 PM to 8 PM PDT Wednesday for CAZ284-285. Fire Weather Watch from Thursday afternoon through Thursday evening for CAZ285. Pacific Coastal Waters...None. $$ SBN/SBN/SBN
Area Forecast Discussion
National Weather Service Marquette MI
729 PM EDT Tue Sep 15 2020 .SHORT TERM...(This evening through Wednesday) Issued at 315 PM EDT TUE SEP 15 2020 WV imagery and RAP analysis show wnw mid/upper level flow through southern Canada and through the northern Great Lakes atop a ridge from the central Plains through the Rockies. At the surface, a trough is now over northern MN, which is allowing a weak shortwave to move across the northern half of Lake Superior. Low-level clouds lingered over parts of Upper Michigan this morning and since have slowly cleared out, allowing skies to remain partly cloudy for the rest of the day. Through the afternoon and into tonight, the low move across Lake Superior, resulting in breezy SW winds across Upper Michigan. Stability will still be high enough to limit gusts mainly between 30- 35mph. However, can`t rule out a few isolated gusts near 40 mph thanks to downsloping winds. Will continue the Lakeshore Flood Advisory for Delta and southern Schoolcraft counties as waves will still be between 4-6 feet along Lake Michigan. Weak cold front will drop through Upper Michigan tonight and winds will subside a little but will turn more to the nw. This will mostly be a `dry` cold front as soundings look mostly dry in the lower levels but can`t rule out an isolated shower or two. Will cap PoPs at 25% to cover that. Wednesday, in wake of the front passing, winds will be out of the nw and from previous discussion, some smoke will linger through the day and could reach the sfc either along the front or just behind it. Otherwise, wouldn`t rule out an isolated lake-enhanced shower with CAA coming in but general, expect partly cloudy skies. Have tweaked highs a little lower than previous with CAA moving in and nw flow, expect highs in the upper 50s to low 60s. .LONG TERM...(Wednesday night through Tuesday) Issued at 306 PM EDT TUE SEP 15 2020 Relatively benign longterm forecast ahead as broad troffing and negative height anomalies remain over the Great Lakes period through at least the end of the week. Models show a closed off mid-level low off the Pacific Coast helping keep the troubling ridge locked over the western CONUS as downstream troffing develops over the Great Lakes to start the longterm period. Sfc high pressure drops into the central CONUS Wednesday afternoon along the W to NW flow aloft, which should help keep things on the drier side. Cooler air funnels in Wednesday into Thursday, which should keep temperatures below normal through Saturday. As the closed low over Pacific pushes inland Thursday night, it shifts the western CONUS ridging eastward with it, which should help bring an increase in temps (back closer to normal) to the UP in the latter half of the weekend into the start of next week. Tuesday night into Wednesday, sfc low impacting the region on Tuesday pulls away into Quebec with weak pressure rises keeping things a little windy through the night, especially along the lakeshores. CAMs are suggesting light rain across the Keweenaw and east half of the UP, but model soundings aren`t as keen on the idea, so including some sprinkles across the Keweenaw and some drizzle across the east. Late in the night some CAA increases, which may bring some light rain showers, but moisture is still limited to the sfc. By Wednesday afternoon, 850mb temps fall to near 2C, bringing cooling temps, but moisture is generally too limited for precipitation. The rest of the week into the weekend, models are suggesting blo normal height anomalies bringing temperatures 10 to 15 degrees blo normal, at least through Friday. Widespread frost to freeze chances will be around Wednesday night into Friday as sfc high pressure moves into the region. The next chance for precipitation comes in the second half of the weekend as a shortwave moves through the central CONUS. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 729 PM EDT TUE SEP 15 2020 VFR conditions prevail at the start of the forecast, with lowering ceilings behind a cold front moving through the area. Gusty winds have diminished at KSAW and KIWD, but linger at KCMX, but will diminish in the next hour or two. MVFR cigs develop at all three sites, and will approach IFR at KSAW when the winds go light late this evening with low level moisture pooling along and behind the cold front. There is some concern there could be a brief period of IFR ceilings overnight and will monitor for this for now. VFR conditions return with daybreak, along with some gusty winds. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 315 PM EDT TUE SEP 15 2020 The tightening pressure gradient of an approaching low pressure and strong low level jet will result in near 30kt gusts over mainly the eastern portion of the lake with some gale force gusts being possible, especially for higher platforms. As the gradient relaxes overnight Tuesday and winds become northwesterly, winds should lay down briefly, before they building again to near 30kts Wednesday before falling back below 20 kts late Wednesday night, heading towards the end of the week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Beach Hazards Statement through Wednesday morning for MIZ014. Lakeshore Flood Advisory until 2 AM EDT Wednesday for MIZ013-014. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JH LONG TERM...07 AVIATION...RJT MARINE...JH
National Weather Service Raleigh NC
940 PM EDT Tue Sep 15 2020 .SYNOPSIS... High pressure will remain across the Carolinas tonight and early Wednesday. Then the remnants of Tropical Cyclone Sally will move through the Southeast US Thursday through Friday. && .NEAR TERM /TONIGHT/... As of 940 PM Tuesday... Surface analysis this evening shows high pressure over the Mid Atlantic relinquishing its hold a bit and shift offshore, though ridging still extends well south through the Western Piedmont. 925mb flow is veering to more easterly and will provide some stratus owing to shallow isentropic lift late tonight. Most guidance keeps the bulk of the stratus west of US-1 and perhaps I-95. HRRR runs have shown some light precip in the coastal plain by sunrise, but moisture appears to be in too shallow of a layer and without sufficient lift.Outflow cirrus from Hurricane Sally...currently off the AL coast...will stream across the southern CWA but will not be opaque enough to impact lows, which should reach the 50-58 range, with some upper 40s very possible northern Piedmont (already 54 at Roxboro). && .SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/... As of 306 PM Tuesday... High pressure will still be the main player in the forecast Wednesday morning, although we`ll see a fair amount of cloudiness, both high clouds coming up from Sally and stratus due to easterly low level flow. As the day progresses, most of the HREF members suggest that a band of showers may develop along and INVOF the SE NC coast, then spread inland and across our southern Coastal Plain zones during the early evening. This appears to be in part due to increasing low level SE flow and subsequent convergence on the far NE periphery of Sally, coupled with an old boundary lifting back toward the north. High temps tomorrow will range from 75 to 80, warmest SE, but that may be a bit optimistic (esp across our SE zones) given the increasing clouds and rain chances. For Wednesday night... today`s 12Z models, and particularly the GFS and ECMWF, are in better agreement with when the main rain shield assoc with Sally begins to lift north into our area, but overall have notable differences with how much. Nevertheless, it appears that rain will get underway after 06Z Thursday from south to north. However the rain north of Hwy 64 may hold off until after sunrise Thursday morning. Lows in the 60s. && .LONG TERM /THURSDAY THROUGH TUESDAY/... As of 255 PM Tuesday... An inverted coastal trough will amplify off the Carolina coast on Wednesday. Sally will likely track along this trough/surface boundary Thursday and Friday. There are still some questions with exactly where this boundary will sit and thus the track Sally will take. Models have trended a bit farther west, which would mean more rainfall for central NC. Forecast confidence with respect to the exact track is still somewhat low. As the remnants are moving through the Carolinas Friday/Friday night a cold front and strong Canadian high pressure will be approaching from the northwest. Timing of when the front will move into/through central NC will depend on how quickly Sally moves, but it should do so over the weekend. There will likely be a strong pressure gradient across central NC Saturday as the front and remnants of Sally sit offshore and the high encroaches on it. The result would be strong north- northeasterly winds and cold, dry air advecting into the area. Central NC should remain under the influence of cool high pressure through Tuesday. Based on current model timing, the wettest period for central NC should be Thursday through Friday night. Temperatures are expected to be below to well below normal through the extended period. The coolest period will be over the weekend, when highs will top out in the mid 60s to low 70s and lows will bottom out generally in the upper 40s to mid 50s. Normal highs are upper 70s to low 80s and normal lows are upper 50s to low 60s. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 800 PM Tuesday... VFR to continue through 06Z. Easterly flow will then bring some stratus...most likely MVFR...inland from the coast by 09-12Z. The probability of an extended period of MVFR or lower ceilings is greatest at RWI and FAY, although some guidance only shows an hour or two of MVFR at FAY around 12Z. Confidence is lower at RDU as well. Ceilings will lift through the morning hours but could remain at MVFR through midday in moist easterly flow, while conditions are much more likely to remain VFR at GSO/INT throughout the day. Moisture will increase more rapidly Wednesday evening, especially from the south as rain associated with TC Sally begins to overspread the area. Outlook: A prolonged period of adverse aviation conditions with widespread rain is expected from Wednesday night through Friday. A cold frontal passage will bring VFR conditions back to the area Saturday afternoon and evening. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ NEAR TERM...bls SHORT LONG TERM...KC AVIATION...bls
Area Forecast Discussion
National Weather Service Blacksburg VA
736 PM EDT Tue Sep 15 2020 .SYNOPSIS... High pressure extends southward from New England across the mid-Atlantic, maintaining cool and dry northeasterly windflow. The latest official forecast calls for Hurricane Sally to make landfall near Mobile Bay on Wednesday morning, and then track east across central Georgia and South Carolina, weakening as it progresses. The storm will spread rainfall northward across the mid-Atlantic on Thursday and Friday. && .NEAR TERM /THROUGH WEDNESDAY/... As of 730 PM EDT Tuesday... Very little to change with the forecast package from the afternoon. I did reduce cloud cover slightly, compared to what was originally introduced into the grids, perhaps accounting for the overhead smoke tonight. THat said, little to no clouds are expected overnight, now with the low, stratus clouds finally mixed out which held on through a majority of the day in and around the NRV/Roanoke Valley, to WV. Clear skies, mostly calm winds, and ample dry air aloft with high pressure overhead should allow for decoupling and fog development overnight. As of 115 PM EDT Tuesday... Overnight, mountain clouds are expected to gradually diminish, making for a night of mostly clear skies. Strong radiational cooling in the dry northeasterly flow will allow for what should be the coolest night in a while as temperatures range from the mid/upper 40s across the mountains, to the low 50s across the Piedmont. Expect fog to develop in the mountain river valleys, but should be patchy and localized outside of these areas. The cool high pressure will weaken for Wednesday. With increased sunshine early in the day, again filtered through a veil of smoke aloft, expect slightly warmer temperatures with highs generally in the 70s. High clouds will increase during the afternoon as Sally drifts northeast across the southern half of Alabama. Otherwise, expect dry conditions to persist through the day. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 230 PM EDT Tuesday.... Our full attention goes to Hurricane Sally for late in the week as the exact track of the remnant circulation will have a big impact on our rainfall forecast. The overall synoptic pattern ahead of Sally will favor deep lift in the RR quad of an upper jet, and there will be a good supply of moisture rich high theta-e air being steered into the region from high pressure off the coast, so the table is set for Sally. Now we will just have to see how long it takes Sally to RSVP as weak steering currents are giving models a hard time in determining when Sally will be picked up by the large upper trof swinging through southern Canada. Right now, one possible scenario will have the remnant circulation of Sally being picked up by the upper trof sooner rather than later, with the circulation brushing by the region to the southeast early Friday morning. Another scenario has the circulation lingering quite a bit longer over the southeast US before heading in our direction. Trends in ensemble guidance seem to be leaning toward some of the quicker solutions so will start to shade the forecast in that direction as well, though confidence is not high. The net result will be a forecast that shows precipitation spreading up from the south late Wednesday night and continuing through Thursday. The heaviest precipitation looks to occur on Late Thursday into Thursday night before gradually tapering off later on Friday into Friday night. With the track of Sally combined with orographic effects, expect the heaviest rain will fall south of Route 460, particularly south of the VA/NC border, and from the southern Blue Ridge into the NC mountains where rainfall amounts of roughly 2.5 to 3.5 inches seem reasonable. Amounts look to taper off quickly heading to the north with amounts an inch or less from the I-64 corridor northward. Expect changes in these forecast details as new guidance becomes available. Strong winds associated with the remnants of Sally are not expected across southeast West Virginia, southwest Virginia, or northwest North Carolina. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 230 PM EDT Tuesday.... Much quieter period of weather will be settling into the region for the weekend and into early next week. The remnants of Sally and a cold front will be well east of the area as strong high pressure/Canadian airmass settles in over the eastern third of the CONUS. This will be the main dominating feature for the entire period with no notable rain to speak of. Morning low temperatures this weekend will be some of the coolest since Spring, with some locations possibly dropping into the upper 30s, along with widespread 40s. Comfortable daytime highs in the 60s areawide. Temperatures will begin to moderate by early next week back to near normal. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 730 PM EDT Tuesday... VFR and MVFR conditions are expected overnight. High pressure remains overhead, allowing for a clear, cool night. This will allow for good radiational fog development, which will primarily impact LWB with its proximity to the Greenbrier River. I went ahead and brought LYH and BCB to MVFR conditions in anticipation that they will also be impeded by fog, but with lower confidence at LYH compared to BCB. After fog mixes out tomorrow morning between 13 and 15Z, VFR conditions are expected to remain in play through the remainder of the day as high pressure gradually breaks with Sally`s remnants starting to work toward the region, starting with increasing high clouds late in the forecast period. /Confidence in Forecast Parameters/ Ceilings - High, Visibilities - Moderate, Winds- High, Thunderstorm Threat - None. .Extended Aviation Discussion... Main concern through the period will be the eventual path of Hurricane Sally and its track through the southeastern U.S. Tracks via the ECMWF/NAM are much further south and east than the GFS/Canadian tracks, which would have much more impact on our area. Official track is to keep bulk of heavier rain well south of the CWA, but has kept a bit north from previous forecasts. Northern parts of the CWA could evolve into an in-situ wedge with low clouds, fog, drizzle, and light rain until the system moves east of the area by the weekend. Southern areas would have heavier rainfall. Periods of sub-VFR Thursday- Friday, possibly early Sat. Uncertainty in this forecast period is high at this point. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...NF NEAR TERM...NF/RR SHORT TERM...MBS LONG TERM...BMG/MBS AVIATION...NF/RR
Area Forecast Discussion
National Weather Service San Diego CA
125 PM PDT Tue Sep 15 2020 .SYNOPSIS... High pressure over the southwest states will continue the warming trend through the middle of the week. This will be followed by a slow cooling trend from Friday through early next week, as low pressure to the north moves inland. This will strengthen the onshore flow for Friday into Sunday with periods of gusty southwest to west winds in the mountains and deserts. Patchy night and morning coastal low clouds and fog will increase in coverage for the weekend. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... This afternoon...temperatures are mostly a few degrees higher than at this time yesterday. The mid-level moisture has remained to our east and as a result, no cumulus clouds have developed over the mountains of extreme southwestern California. Patches of low clouds and fog over the coastal waters are moving toward the coast but will likely dissipate, at least until sunset. Overnight, patchy marine layer low clouds and fog could move into the coastal areas but are unlikely to spread much inland. From previous discussion... High pressure over the southwest states will continue slow warming through the middle of the week with high temperatures reaching 5 to locally 10 degrees above seasonal averages. This will be followed by a slow cooling trend through next Monday as a low pressure system to the north moves inland around Friday. This will strengthen the onshore flow for Friday into Sunday, bringing periods of gusty southwest to west winds in the mountains and deserts. With the cooling, high temperatures on Monday will be around average for the mountains and deserts, and a few degrees below average for the valleys and inland coastal areas. There will continue to be some smoke aloft through Wednesday and likely beyond. In general, vertically integrated smoke values will be greater to the north and less to the south and west with smoke aloft today a little less than Monday, continuing to decrease for Wednesday towards the coast and over the coastal waters. The HRRR smoke model continues to show more substantial smoke generation from the El Dorado Fire in the San Bernardino Mountains and the Bobcat Fire in the San Gabriel Mountains each afternoon with the smoke generally spreading toward the north and northeast. The marine layer will remain shallow, with night and morning coastal low clouds and locally dense fog remaining quite patchy through midweek. Toward the weekend, there may some increase in coverage of the night and morning coastal slow clouds and fog and some deepening of the marine layer as the onshore flow strengthens and heights fall. Some mid and higher level remnant moisture from Tropical Storm Karina may be transported northward and across central California around late Thursday and early Friday. This could bring some higher clouds to the north and some afternoon clouds over the mountains, but any precipitation is unlikely for southwestern California. && .AVIATION... 152000Z...Widespread vis 4-7 SM in FU/HZ likely through tomorrow, lowering to 2-6 SM in BR/FU overnight and early Wednesday AM. Upper- level smoke AOA 8,000 ft through the period. Very isolated patches of low clouds with bases 300-700 ft MSL possible offshore and for coast 06Z-17Z tonight. However, impact to terminals is unlikely. && .MARINE... No hazardous marine conditions are expected through Sunday. && .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...PG AVIATION/MARINE...Rodriguez
For frequently asked questions about the Area Forecast Discussion
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
529 PM MDT Tue Sep 15 2020 .DISCUSSION...(This Evening Through Tuesday) Issued at 201 PM MDT Tue Sep 15 2020 Persistent upper level ridge will slowly shift east through the week as an upper level trough builds into the western CONUS. Before that happens, the local region will remain on the northeast edge of the ridge with a wavering frontal boundary. Cool front has settled into the region, with the NE half seeing much cooler conditions. However, temps have been affected heavily region-wide by thick deep layer smoke from western wild fires, which has highly impacted insolation. Smoke will likely impact temps the next several days until perhaps the pattern changes this weekend as the upper trough ejects east. Utilized the HRRR guidance to add smoke and haze to the forecast through tomorrow, which will likely be further added in later periods. Cooler night tonight as easterly upslope flow will persist with a secondary front settling into the region Wed. Much cooler conds expected Wed most areas with easterly flow persisting over the eastern 2/3. Return southerly flow will commence over the far west though, offering warmer temps there. General ESE flow will persist through the end of the week with ridge riding impulses advecting NE of the region. Removed pops Wed night in the NE as forecast models have trended further east and weaker with this impulse and resultant lift. The next chance of precip looks to be Sat as the upper trough ejects into the Northern Plains, albeit precip coverage will be sct to isold at best. Semi-zonal flow supported in model ensembles afterward, with seasonal temps to above average temperatures. && .AVIATION...(For the 00Z TAFS Through 00Z Wednesday Evening) Issued At 527 PM MDT Tue Sep 15 2020 Smoke/haze may lead to some reductions in visibility tonight, but suspect that visibilities will generally remain at 5 miles or better in most locations. As a result, mainly VFR conditions are expected to prevail through the TAF period. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...None. WY...None. && $$ DISCUSSION...JC AVIATION...15
Area Forecast Discussion
National Weather Service Las Vegas NV
151 PM PDT Tue Sep 15 2020 .SYNOPSIS...Areas of smoke and haze will persist at least through Wednesday. A low pressure system will approach the coast on Thursday and then move north of the area Friday and Saturday. This will bring increasing clouds and winds to the area Thursday and Friday, with critical conditions for wildfire spread expected north of Las Vegas. For the weekend, winds are expected to decrease with temperatures dropping back to near normal. && .DISCUSSION...Low pressure well offshore of Oregon was still consolidating this afternoon per water vapor satellite loop, with the eventual kicker system coming across the International Date Line. Meanwhile, Tropical Storm Karina was about 800 miles west of Cabo San Lucas and heading northwest toward cooler waters. Through Wednesday, haze and smoke will remain the primary issues. The worst conditions last night and this morning were in the northern Owens Valley, as smoke got trapped under the nocturnal inversion and advected into Bishop on the nighttime downvalley drainage wind. Similar conditions are likely tonight and Wednesday morning, and the HRRR Smoke model supports this as well. As the aforementioned kicker system rotates through the Aleutians on Thursday, it will nudge the low pressure system into the Oregon coast on Friday and to southern Alberta on Saturday. As it passes north of our area, there will be two main effects Thursday and Friday. First will be increasing southerly winds, which will enhance fire danger. Second will be increasing clouds as the upper level remnants of Karina are pulled into the low. On Thursday, relative humidity will be in the single digits, but winds will be marginal. On Friday, winds will increase, but so will the relative humidity as the remnant moisture from Karina streams overhead. The tie breaker, so to speak, in this scenario is that fuels are historically dry after the very hot and nearly rainless summer. Thus, a Fire Weather Watch has been issued for the Sierra and for areas of southern Nevada north of Las Vegas. As the low pressure system weakens and moves farther away Saturday, winds will diminish and clouds will clear out. Temperatures will come down a few degrees across the area, but remain near or slightly above normal for mid to late September. && .FIRE WEATHER...Dry conditions will continue with extremely dry fuels. A storm system to the north will enhance afternoon winds Thursday and especially Friday. The increasing wind could set up critical conditions for wildfire spread, so a Fire Weather Watch has been issued for the Sierra and for Nevada fire zones north of Las Vegas. && .AVIATION...For McCarran...Easterly winds this afternoon will shift to south southwesterly after sunset, and return to easterly Wednesday afternoon. Speeds should be less than 10 knots the vast majority of the time. A few clouds around 15K feet will persist, along with hazy/smoky conditions aloft. For the rest of southern Nevada, northwest Arizona and southeast California...Hazy and/or smoky conditions will persist across the area at least through Wednesday, with the worst surface conditions likely in the Owens Valley including KBIH in the night and morning hours. Southerly winds around 10 knots gusting up to 20 knots will prevail this afternoon, decreasing around sunset. A few clouds around 15k feet will persist east of a line from the Nevada National Security Site to Baker. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Morgan FIRE WEATHER...Morgan AVIATION...Morgan For more forecast information...see us on our webpage: or follow us on Facebook and Twitter