Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/06/20

Area Forecast Discussion
National Weather Service La Crosse WI
1051 PM CDT Sat Sep 5 2020 .SHORT TERM...(This evening through Sunday) Issued at 214 PM CDT Sat Sep 5 2020 All quiet on the western frontier for now as we await the well- advertised severe weather potential late tonight, mainly west of the Mississippi River. Some fair weather cumulus fields over portions of WI, otherwise a beautiful late-summer Saturday. Only fly in the ointment to enjoying an azure blue sky is the intrusion of another plume of smoke aloft from western wildfires, progressively giving the sky a more milky appearance. Cyclogenesis over the Northern Plains will induce development of a very strong southwesterly low level jet nosing into southeast MN and northeast IA. NAEFS forecast 850mb u-wind percentiles for 12Z Sunday fall completely outside all climatology for early September, giving a feel for the anomalous magnitude of this LLJ. Actual forecast 850mb wind speeds will be on the order of 50+ knots as it noses into the area late tonight. Combined with PWATs of 1.6 to 1.9" (roughly 175-200 percent of normal), moisture transport will be very robust late tonight, focused squarely on our counties west of the MS River. Instability will all be elevated with MUCAPE on the order of 2000- 3000 J/kg. Plenty of low level inhibition will be in place given the unfavorable time of night and strong warm air advection centered around 800mb, but steep mid-level lapse rates will be in play. This lends itself to pretty fat CAPE profiles aloft, definitely favorable for very large hail potential. The setup for large hail will be aided by an abundance of deep layer directional/speed shear of 50 to perhaps 60+ knots supportive of elevated supercells, especially as storms initially develop. Some CAMs, particularly recent HRRR runs, show potential for some semi-discrete cells firing up initially over portions of southeast MN and northeast IA. Latest HREF also paints an area of favorable updraft helicity, especially along and west of US 63, that suggests potential for well-organized, rotating elevated storms. TIMING: CAMs have been in decent agreement with the timing and evolution of this storm complex thanks to a more strongly-forced environment. They generally point to storms erupting near SD/MN border between 9pm-midnight, evolving into a more mature complex with semi-discrete development as they enter our far western counties and approach the MS River between midnight and 4am. This would be the most favorable timeframe for large hail before storms congeal into clusters. Storms are expected to spread east of the MS River roughly after 3am, gradually weakening as they propagate east/southeast, eventually clearing out of our east/southeast counties after daybreak Sunday. THREATS: Main threat expected to be very large hail, potentially 2" or greater in diameter (i.e. hen egg or larger). This is for areas west of the Mississippi River, especially along and west of US-63, including the Rochester area. Not as favorable of a setup for damaging winds given the storms won`t be surface-based, but can`t rule out some localized damaging gusts as storms amalgamate into clusters very late tonight by the time they spread southeast into western WI and far northeast IA. Heavy rainfall also very likely given the quick tropical increase of moisture and deepening warm cloud depths. While this complex should be pretty progressive, hi- res guidance suggests a high probability for a swath of 1-2" of rainfall from southeast MN to far southwest WI. HREF 24hr QPF max indicates potential for localized 3 to 4+" within this broad swath. Will have to monitor potential for localized flash flooding, but not anticipating a large hydro threat overall. The expected heavy rain swath area generally ranges from 25 to 75 percent of normal for rainfall over the last 30 to 60 days, so it should be able to handle even moderate rainfall amounts without much trouble. Only concern would be the more complex terrain areas near MS River. Expect some lingering showers and storms Sunday morning in our south and east. Perhaps some additional development along a band of fgen dropping through our southeast during the afternoon, maybe a few storms on the stronger side. Strong WAA aloft will yield a very warm early September day with highs in the mid 80s to near 90 near and south of I-94, 70s to the north. Also a tad humid, but these warm, muggy conditions will be brief. .LONG TERM...(Sunday night through Saturday) Issued at 214 PM CDT Sat Sep 5 2020 Storms may be ongoing across parts of central into southwest Wisconsin Sunday evening/night as a cold front sweeps through. However, the latest guidance suggests that most of the activity should be mostly further south and east out of the local area by this time. Any storms that may still be ongoing should be on a weakening trend as the loss of daytime heating occurs, though with instability forecast to still be around 1000-1500 J/kg and decent bulk shear, a few stronger storms cannot be ruled out. Northwest/zonal flow aloft then transitions to southwest flow early next week as a split flow pattern sets up. A baroclinic zone looks to develop across a big portion of the country, including the local area. This baroclinic zone will orient itself west to east early on in the week, before transitioning to a more southwest to northeast orientation within the large-scale flow by midweek. This will result in an increased chance of precipitation and much cooler temperatures across the entire area through the entirety of the week. Tuesday and Wednesday look to be the coolest days, with high temperatures likely only reaching the low to mid 50s. The baroclinic zone then gradually shifts east of the area come Thursday, with perhaps a brief break in rain. However, models are in rather decent agreement that a closed low will spin up on the eastern side of the Rockies later in the week and lift northeast through the area, bringing additional chances for precipitation. Exact precipitation amounts during the entire long term period is still a little uncertain, though confidence is increasing that heavy rain will result. In summary, expect a cool and soggy week ahead. && .AVIATION...(For the 06Z TAFS through 06Z Sunday night) Issued at 1051 PM CDT Sat Sep 5 2020 Convection has been developing this evening north of a warm front that extends from southeast South Dakota into northern Missouri. The front did not progress as far north as previously expected and as a result, the main area of convection is expected to stay farther to the southwest. Will likely still see some additional development farther to the north as the strong low level jet gets going and this will have a chance to impact KRST overnight with some MVFR/IFR conditions. With KLSE being farther east, even more questionable how much activity will be around it and have dropped back to just a VCTS for now. All this activity should push to the east early Sunday morning with a short period of MVFR ceilings possible. Otherwise, expect breezy southwest winds with VFR conditions until the cold front comes through late in the afternoon/early evening and swings the winds around to the west. Additional convective development Sunday should be to the southeast of both airports. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Kurz LONG TERM...NMB AVIATION...04
Area Forecast Discussion
National Weather Service State College PA
1129 PM EDT Sat Sep 5 2020 .SYNOPSIS... A weak area of low pressure track across the northern border of Pennsylvania tonight, bringing clouds and a few showers to that part of the state. High Pressure over the upper Great Lakes will build southeast over the region for Sunday and Labor Day, continuing the string of dry and pleasantly warm late Summer weather. On Tuesday, a front will stall out to our west over the Lower Great Lakes as an upper level ridge amplifies along the Mid Atlantic Coast. Mild but occasionally showery conditions are likely during the mid to late week time frame. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... A fast moving clipper, located over western Lk Erie at 00Z, will track along the PA/NY border overnight. Despite limited moisture to work with, scattered showers are noted from southern Ontario into western NY at nose of a 30kt low level jet. 00Z radar returns are lining up pretty well with RAP 850-700mb fgen forcing beneath right entrance of upper level jet streak. This forcing is progged shift east overnight, just grazing the northern tier of Pa between 04Z-08Z. A blend of latest model qpf supports around a tenth of an inch over Warren/Mckean/Potter counties north of route 6 tonight. A weak trailing cold front could make it as far south as a KIPT to KUNV and KIDI early Sunday morning, brining an increase in late night clouds across the central counties, but don`t see any measurable rain reaching as far south as I-80. The far south will remain mostly clear. Low temps early Sunday will be mainly in the 50s, though the perennial cold location across the NW mtns should dip into the upper 40s. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/... Remnants of weak cold front are progged to wash out over central and southern Pa on Sunday. Diurnal heating, combined with enhanced low level convergence and moisture in vicinity of this boundary, could yield a few isolated PM showers across roughly the southeast half of the forecast area. 18Z operational runs and earlier 12Z HREF back up this scenario. Model RH profiles support a mostly to partly sunny Sunday. Mixing to 850mb suggests high temperatures will range from the low 70s over the northwest mountains, to the low and mid 80s across the Lower Susq Valley. A dying cold front will approach northwest Pa late Monday, potentially bringing a few showers over that part of the state. Otherwise, high pressure ridge along the east coast should ensure dry weather over most of central Pa both Monday and Tuesday. Anomalous upper ridge over the western Atlantic is progged to expand westward early next week. GEFS plumes show warming at all levels early next week, with daytime, supporting highs well into the 80s over the entire area by Tuesday. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... An increasingly moist southeast flow, associated with high pressure east of the Canadian Maritimes and a weak low approaching the southeast coast, may yield increasing clouds and a chance of showers as early as Wednesday. By Wed night and Thursday, the bulk of med range guidance suggests low clouds and possible showers across the eastern half of the state. During this time, models show southeast flow, a nearly saturated sfc-850mb layer and evidence of weak surface low lifting up the east coast. Have undercut NBM high temps in favor of the cooler Superblend guidance Wed/Thursday based on the above scenario. Model spread among operational models ramp up considerably late in the week. However, a blend of latest NAEFS/ECENS indicate upper trough and associated cold/occluded front will push across central Pa either Thursday night or Friday. Thus, have kept the chance of showers/possible tstorms during this period, then favor cooler/drier conditions by next Saturday. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... Mainly VFR conditions tonight with a dry air mass in place. VFR expected into tomorrow for most areas, except early tomorrow morning at KBFD where areas of fog could lead to a brief period of MVFR or IFR until sunrise. Outlook... Sun-Tue...VFR conditions expected. Wed-Thu...Scattered showers and low cigs, restrictions possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Lambert/Fitzgerald NEAR TERM...Fitzgerald SHORT TERM...Watson/Fitzgerald LONG TERM...Fitzgerald AVIATION...DeVoir/Travis
Area Forecast Discussion
National Weather Service Des Moines IA
642 PM CDT Sat Sep 5 2020 .UPDATE... Issued at 642 PM CDT Sat Sep 5 2020 Continuing to monitor mesoscale/synoptic trends this evening. HiRes models have been consistent in taking most of the convection into northeast Iowa; though the 18z NAMNest which is usually not the model of choice, has brought the convection farther west into central Iowa later this evening. The current issue remains the moisture axis nearer the sfc along with the slightly slower progression of the warm front to the northeast today. There is a potential that the convection may try to ride back into the boundary tonight with an overall farther west track. Will need to evaluate hourly as evening progresses. Timing generally on track for 04-06z initiation over southwest MN or southeast SD. Once the initiation is set, forecasting the shorter term evolution will have higher confidence. Needless to say, tonight`s forecast is still fluid and may change. && .DISCUSSION.../Tonight through Saturday/ Issued at 233 PM CDT Sat Sep 5 2020 Overview...Hot weather today and tomorrow with storm chances tonight into early Sunday morning will be followed by a cool to chilly and wetter pattern by Monday night into the rest of the week. Details...High pressure over the region today has provided plenty of sunshine and allowed temperatures to reach into the 80s and even low 90s in southwestern Iowa. A stalled boundary well to the southwest of the state will lift northeastward into Iowa this evening aided by strong low level warm air advection on the nose of a ~50 knot, 850mb low level jet. Forecast soundings from a variety of high resolution models show MUCAPE values between 2000 to 3000 J/kg with mid-level lapse rates approaching 8 C/km and strong deep layer shear in excess of 50 knots over southern Minnesota and northern Iowa by this evening. While soundings also indicate a decent surface inversion forming after sunset a few hundred meters above ground level, elevated storm development is likely mid to late this evening over southwestern Minnesota. Once storms develop, they should be able to sustain themselves in the ample instability and shear environment. Hodographs have low level curvature and this may allow for initial (elevated) supercell storm mode. However, as they move into north central and northeastern Iowa overnight, they should begin to congeal and become more linear as they push either southeast or east- southeast near if not more likely after midnight. Corfidi vectors do show more of a southward trajectory, which isn`t shown much in the convective allowing models at this point with recent runs of the HRRR pushing the convection nearly out of our forecast area. If the cold pool can become established, this may allow for strong wind gusts to reach the surface. However, the surface inversion does bring into question whether wind gusts aloft will reach the surface, but the potential is there. Hail will be the other concern given storm mode before the system goes linear with soundings showing plenty of CAPE within the hail growth zone. Bulk shear and 0-1km and 0-3km SRH values are quite high, but thinking is that the inversion and low level inhibition will keep at bay a QLCS tornado risk. The most likely area for severe weather tonight appears to be north and east of an Estherville to Waterloo line. The strongest storms will be east of our central Iowa area of forecast responsibility by sunrise with perhaps lingering weaker storms or showers. In the wake of the precipitation Sunday morning, it will be a hot, steamy, and breezy day ahead of a cold front that will move through much of central Iowa in the afternoon and evening. Temperatures will be in 90s and with dewpoints in the 60s with heat indices pushing the middle 90s to around 100 degrees in most places. The other aspect of tomorrow with be the breezy winds with the tight pressure gradient across the state. Forecast soundings show boundary layer mixing of 3000 to 4000 feet by mid to late morning into the afternoon with with winds at the top of the mixed layer around 40 knots. The higher dewpoints/humidity should mitigate fire weather concerns despite the dry antecedent conditions and the gusty winds. As the front moves into southwestern Iowa--if there is enough convergence--there may be a few storms that develop late in the afternoon. A significant pattern change to cooler and wetter weather is expected next week. The cold front will push south of the state Sunday night and stall over the Ozarks and Ohio Valley into at least the middle of next week setting up a strong baroclinic zone south of the state. Surges of low level thermal lift moving over this boundary into our region will allow for periods of showers from Monday night through late next week. Further aloft, a longwave trough will be sinking over the northern states and eventually a closed low is expected to form and drift eastward over the central Plains passing through Iowa, which will prolong rain chances into late next week. One cautionary note is that there is dry air not far away to the northwest that could push southward and thus push the rain area farther south than currently forecast, but likely not out of Iowa. A broad look at thunder chances next week suggest Monday night into Tuesday holds the most promise for thunder. Temperatures will drop by 20 to 25 degrees from Sunday to Monday and another 15 to 20 degrees from Monday to Tuesday. Highs around 80 degrees are typical for early September, but will be in the 50s Tuesday and Wednesday and 60s Thursday and Friday. && .AVIATION.../For the 00Z TAFS through 00Z Monday/ Issued at 642 PM CDT Sat Sep 5 2020 Main concerns will be convection tonight and strong winds Sunday. Warm front not as progressive as forecast and this may bring convection farther west into the aviation forecast area overnight. Still, the predominant sites affected will be KMCW and KALO with a lesser threat at KFOD and KDSM. The storms are forecast to be elevated but any sfc cold pool development will enhance severe wind gusts. Have added a tempo for VRB25G45kt at KCMW and KALO to reflect the possibility. Will be closely monitoring trends this evening. Also, Sunday shows region wide mixing of 30 to 40kts during day with south southwest winds. LLWS overnight tonight may also pose a challenge for some carriers. /rev && .DMX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...REV DISCUSSION...Ansorge AVIATION...Ansorge
National Weather Service Eureka CA
249 PM PDT Sat Sep 5 2020 .SYNOPSIS...Hot and dry weather will continue across inland northwest California through next week, with record heat possible Sunday and Monday. Coastal areas will be mild to warm with periods of late night and early morning cloudiness but plenty of sun during the day. && .DISCUSSION...High pressure over the Great Basin has shifted back westward over northwest California this afternoon and will continue to build over the NE Pacific through early next week. This will support exceptionally hot and dry conditions across interior locations the next few days as 500 mb heights rise to around 598 dekameters with 850 mb temperatures of 27-30 degrees C by Sunday, which corresponds to interior valley temps of 105-110 degrees F. Guidance has even crept up into the 110-115 range for parts of southern Mendocino and Lake Counties by Sunday, putting several records in jeopardy in the coming days. The Excessive Heat Warning therefore remains on track with no changes. Abundant sunshine is also present along the coast as increasing subsidence and drying have taken their toll on the marine layer. There may be just enough lingering low level moisture to support some patchy overnight and early morning fog along the Redwood Coast, but otherwise plenty of sunshine can be expected in the coming days. This will introduce some difficulty to the temperature forecast as weak onshore flow each afternoon is still expected to provide a moderating influence to coastal temps. Currently calling for temperatures around 70 for Sunday and Monday on the North Coast, but those values could easily go higher if the onshore flow does not materialize as expected. Stay tuned. There is little change in the forecast from Monday night into Tuesday as a potent trough digs southward into the eastern Great Basin/central Rockies late Monday into Tuesday, with an attendant dry frontal passage potentially bringing a period of gustier winds and elevated fire weather concerns to portions of northern California. If anything, run to run consistency lends increasing confidence in this scenario, particularly across portions of Lake County Monday night into Tuesday morning. Refer to the Fire Weather section below for more details. Otherwise, temperatures will slowly trend downward but remain hot through much of next week as high pressure gradually weakens but remains in control over the West Coast. /CB && .AVIATION...Visible satellite imagery shows clear skies across NW California. These conditions will prevail for the next few days as high pressure strengthens aloft. VFR conditions are prevailing for KCEC and KACV. Smoke is expected to return in the evening and impact the visibility at the coastal terminals. Meanwhile, marginal MVFR/IFR vsby are lingering at KUKI due to wildfire smoke during late morning. HRRR smoke guidance is suggesting smoke retreat and vsby improvement during late afternoon, prevailing VFR conditions at KUKI. /ZVS && .MARINE...Northerly winds will continue to increase across the outer waters through Sunday as offshore high pressure strengthens and tightens the pressure gradient. Winds will generate small craft conditions with steeps seas from 6 to 10 ft in the outer waters. Small craft advisory level seas will prevail over the S outer waters through Sunday and for the N outer waters through Monday. In addition, winds will locally gust to 30 kt downwind of Cape Mendocino. /ZVS && .FIRE WEATHER...Few changes to the forecast as hot and dry weather will persist during the next seven days over interior NW CA. Expect light and terrain-driven winds lasting through the weekend. Afternoon humidity values will remain very low across the interior through the weekend, with increasingly poor recoveries and near record heat Sunday and Monday. Potential wind event remains on track from late Monday evening into Wednesday morning along the ridges from Lake County into eastern portions of Mendocino and Trinity Counties. There is no change to the Fire Weather Watch for these areas, with potential for gusty winds as high as 40 mph combined with very low RH values and poor overnight recoveries. Confidence is highest for the Lake County portion of the watch, with more uncertainty for eastern Trinity and Mendocino Counties where the stronger winds could remain farther east. This event will continue to be closely monitored in the coming days. /CB && .EKA WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning until 6 PM PDT Tuesday for CAZ107-108-110- 111-113>115. Fire Weather Watch from Monday evening through Wednesday morning for CAZ264-277-283. Excessive Heat Warning from 11 AM Sunday to 6 PM PDT Tuesday for CAZ102-104>106-112. NORTHWEST CALIFORNIA COASTAL WATERS...Small Craft Advisory from midnight tonight to midnight PDT Monday night for PZZ470. Small Craft Advisory until 6 PM PDT Sunday for PZZ475. && $$ Visit us at Follow us on Facebook and Twitter at: For forecast zone information see the forecast zone map online:
Area Forecast Discussion
National Weather Service Grand Forks ND
1022 PM CDT Sat Sep 5 2020 .UPDATE... Issued at 1012 PM CDT Sat Sep 5 2020 Convection beginning to develop across eastern SD on the nose of low level jet creating convergence within a strongly sheared environment. NAMnest seems to have the location of the convective activity resolved the best amongst CAMs. Most CAMs had activity to the north and east where its actually occurring this evening. Will trim pops back as a result to match the current trends. UPDATE Issued at 657 PM CDT Sat Sep 5 2020 Forecast on track with generally light winds and a warm evening. A few sprinkle or light showers are working across the northern valley from weak warm advection. HRRR runs keeping the strong thunderstorms just south of the CWA initiating in the 11pm to 1am time frame. Will keep an eye on future runs and late evening satellite and position of the LLJ for storm initiation. && .SHORT TERM...(This evening through Sunday night) Issued at 306 PM CDT Sat Sep 5 2020 Shower and thunderstorm chances overnight and then rapidly dropping temperatures and increasing winds will be the main impacts for the period. South to southeasterly winds will continue to pick up overnight as surface high moves further east and the trough gets going to our west. The surface trough axis will move into the Red River Valley overnight, although am not too sure how far north the warm front and instability will make it. There will be a decent low level jet, so it is possible that there could be some showers and thunderstorms moving into our southeastern counties late tonight. CAMs keep most of the strong updraft helicity tracks to our south, which fits with current instability. Cannot completely rule out some strong to severe storms straying into our west central MN counties tonight, but not overly excited about our chances so will continue just a mention in the HWO and leave out of grids. Showers will also impact our more northern areas overnight as a weak shortwave moves out of Canada, but will be minimal in QPF. Tomorrow, an upper low digging into western Ontario will help push a strong cold front into the CWA. With strong cold air advection along the boundary, BUFKIT soundings in northeastern ND are mixing all the way up close to 750mb where gusts close to 40 kts will be possible. Wind advisory criteria will be possible, but some uncertainty as to how far south so will hold off on any headlines for the moment. The strong cold air advection will also cause an early high for part of the CWA, with dropping temperatures behind the boundary in the afternoon. The cold air advection will continue into Sunday night, although increasing cloud cover from a shortwave over the western Plains as well as continued wind will keep temps in the low to mid 40s. .LONG TERM...(Monday through Saturday) Issued at 306 PM CDT Sat Sep 5 2020 The Monday through Friday period is expected to be relatively quiet but cooler than average. Weather related impacts are possible, with frost and possibly freeze conditions Tuesday and Wednesday morning. Post-frontal conditions prevail Monday through Wednesday with potent CAA. A reinforcing shortwave pushes southward Monday afternoon, bringing a chance of showers, mainly from the Devils Lake Basin southeastward to near Fergus Falls. Highs on Monday will only reach the lower to middle 50s with lows Monday night falling into the 30s. Lower 30s are possible for the Devils Lake region. Another day in the lower to middle 50s is expected Tuesday, with temperatures falling once more into the lower to middle 30s. The low 30s readings are expected to be a bit more widespread Tuesday night into Wednesday morning with ensemble values ranging from the upper 20s to near freezing across portions of the region. After a cool start to Wednesday, look for a slight rebound in temperatures, with highs generally in the middle 50s to near 60 degrees. Thursday and Friday, the warming trend continues with highs in the upper 60s to lower 70s. Lows will be in the upper 30s to lower 40s, with a slight chance for showers Friday evening. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 657 PM CDT Sat Sep 5 2020 Winds the primary concern for the period as SE winds turn to the west and eventually NW overnight as a cold front pushes across the area. A period of LLWS is expected overnight also with a few showers and thunderstorms possible, unlikely at any TAF site so no inclusion for now. Wind gusts tomorrow afternoon will be over 30 to 40kts. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. $$ UPDATE...JK SHORT TERM...JR LONG TERM...Lynch AVIATION...JK
Area Forecast Discussion
National Weather Service Gray ME
1046 PM EDT Sat Sep 5 2020 .SYNOPSIS... Outside of an isolated shower chance for the mountains tonight, fair weather with pleasant temperatures and low humidity should prevail through the long holiday weekend. Temperatures and humidity will increase into the middle of next week. The chance for showers will also increase for the second half of the upcoming week. && .NEAR TERM /THROUGH SUNDAY/... 1045 PM...Just some adjustments to push lingering showers into the nrn half of CWA through about 05Z, at which point they should winds down. Also, some adj to Sky/T/Td based on current obs. 715 PM...Put some sprinkle into the wrn half of the CWA tonight, based on HRRR and it`s handling of showers and convection currently over NY, they should weaken given dry airmass but there may be enuf convergence to allow them weaken slowly and work through as sprinkles. Previously...Approaching upper trof and mid level moisture is leading to plenty of diurnal Cu this afternoon. A few of the stronger convective cells are producing showers...and so I have isolated wording mentioned mainly across Nrn zones this afternoon and early evening. These will tend to dissipate with loss of daytime heating. Overnight a weak S/WV trof and passing front may lead to some very light precip. Given plenty of dry air in place I have opted for sprinkles rather than showers...because I do not see any real accumulation occurring overnight. Cloud cover associated with the wave will also keep temps a little warm than last night. && .SHORT TERM /SUNDAY NIGHT/... Lingering trofing aloft and daytime heating will again lead to diurnal Cu increasing. Overall expecting another dry day but cannot entirely rule out a stray shower popping up. Ridging aloft really starts to build in from the E Sun night. That will start weak return flow aloft and keep temps more similar to tonight than some of the recent cooler nights...but should help promote good radiational cooling. && .LONG TERM /MONDAY THROUGH SATURDAY/... The ensemble and deterministic model solutions are in good agreement on the long wave pattern through late next week. We begin the period with an upper ridge along the Pacific coast...and a broad downstream trough across much of the northern tier of the CONUS. Digging Pacific energy quickly carves out a deep trough over the plains states...with rising heights downstream across New England with evolving ridge over the western Atlantic. In the offshore ridge keeps us dry and seasonable to end the long holiday weekend. A cold front will attempt to approach from the Great Lakes Monday night into Tuesday. However...rising heights with the evolving western Atlantic ridge should keep the front stalled to our north and west through at least the end of the work week. The southerly return flow around the offshore high will transport warm and increasingly humid air into the region as we head through next week. For the mid to late week period... daytime heating and a series of weak passing impulses should spawn at least scattered shower and thunderstorm activity each day. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... Short Term...VFR conditions are expected to prevail thru Mon. Valley fog is a little uncertain tonight with expected cloud cover keeping temps from radiating completely. I have added some to the TAFs at HIE and LEB...but happening later than usual due to the clouds. High pressure building in more Sun night makes valley fog a little more likely that night...and LIFR conditions will be possible again at LEB and HIE. Long Term... Wed - Thu...Sct MVFR psb in -SHRA/-TSRA. LCL IFR psb in early morning valley stratus and fog. && .MARINE... Short Term...After the passage of a weak front tonight flow will remain offshore Sun. Gradually high pressure will build in thru Mon...with winds and seas remaining below SCA thresholds. Long Term... Mon...SCA`s psb outside the bays. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ SYNOPSIS... NEAR TERM...Cempa/Legro SHORT TERM...Legro LONG TERM...Schwibs AVIATION... MARINE...
Area Forecast Discussion
National Weather Service Lincoln IL
928 PM CDT Sat Sep 5 2020 .SYNOPSIS... Issued at 310 PM CDT Sat Sep 5 2020 Expect increasing cloud cover tonight as thunderstorms approach portions of central and northern Illinois late tonight. Most of the area south of I-74 should stay dry. There will be another chance for showers and thunderstorms Sunday evening and night north of I-70 as a cold front moves over the area. The front will stall across Illinois for several days bringing periodic chances for showers and storms through midweek. && .UPDATE... Issued at 925 PM CDT Sat Sep 5 2020 A complex of storms is expected to roll into our NW counties toward 4-5 am tonight, reaching near PIA and the IL river basin between 6 and 7 am. The RAP and HRRR are indicating our northern counties will get affected by the squall line/bow echo as it pushes across northern IL. A 30 KT LLJ will help to fuel the squall line late tonight. Some weakening is expected as the LLJ diminishes around sunrise, but we can not rule out some strong winds in our northern counties between 5 am and 8 am as the southern end of the squall line advances to the E-SE. Elevated instability will be around 1300 J/kg when the storms arrive near PIA, but the base of that LFC will be near 8K ft. Damaging winds will have a harder time getting to the surface from that level, but it could still happen in short bursts. Have adjusted the PoPs after midnight to slow them down a bit and keep them generally confined to areas along and N of I-74 for the most part. The break in the storms for Sunday afternoon and early evening will help the atmosphere recharge, as SW winds crank up to 15-25 mph Sunday afternoon. Some stabilization will occur before the storms arrive in our NW counties between 10 pm and midnight. CAMs are showing a weakening trend with that line as it pushes across our N counties, but isolated severe wind/hail could develop. && .SHORT TERM...(This evening through Sunday) ISSUED AT 310 PM CDT Sat Sep 5 2020 A weak frontal boundary is stalling out over portions of central Illinois this afternoon, and will lay out along the I-72 corridor overnight before lifting back north as a warm front. Weather should be generally remain quiet rest of today despite the presence of the front, owing to deep column of dry air over the region and building heights aloft. Upstream, a modest shortwave is digging into Montana early this afternoon and another stronger wave is expected to dig across the Canadian Rockies overnight. A strong low/mid level response is anticipated to take place this evening across the central and northern Plains as surface lows deepen and southwest flow ramps up. A strong low level jet is poised to develop overnight, initially setting up across the mid Missouri Valley with Thunderstorms developing on the nose of the LLJ from central IA into southern MN. These storms are expected to propagate ESE overnight along the instability gradient associated with the aforementioned warm front lifting north across central Illinois. Latest suite of guidance suggest storms may build as far south as roughly the I-74 corridor, though some do keep storms just north of the local forecast area. This initial round of storms would arrive into central Illinois during the predawn or early morning hours Sunday. Expect weakening trends at this point as the LLJ veers and weakens, but cannot completely rule out any strong to severe storms reaching the local area. Surface low will continue to deepen across Ontario through the day Sunday while a cold front pushes southeast across the Upper Midwest and into Illinois late in the evening and overnight. Tightening pressure gradient will result in breezy southwest winds through the day Sunday and will help transport warm and moist air back into the region. Dew points will rise back to around 70F Sunday afternoon with temperatures in the mid to upper 80s. This will coincide with steep mid-level lapse rates advecting overhead. H5-H7 lapse rates of 8.0-8.5C/km will be in place by mid evening contributing to moderately strong MLCAPE of 2000-2500 J/kg across the Illinois River Valley. While instability does weaken with the front passing through the local area overnight, strong boundary layer flow will help overcome this some and keep storms going through the night, albeit with a diminishing severe threat. In addition, deep layer shear across the region will be strong (40-45kt across northern counties) with large cyclonically curved hodographs. 0-3km shear in particularly looks impressive with 30-35kt magnitude expected, again strongest in the north. Storms should develop upstream from eastern IA into southern WI then move SE as they congeal into a line of storms with attendant severe wind threat and QLCS tornado threat. As this line enters portions of central Illinois late in the evening, there will be an ongoing severe threat, but that threat should slowly fade with time and southward extent as storms outrun the stronger shear to the north and instability wanes after sunset. .LONG TERM...(Sunday night through Saturday) ISSUED AT 310 PM CDT Sat Sep 5 2020 A broad upper trough will be in place to start the week, spanning much of the country. A strong shortwave is progged to lift across the Canadian Prairies and James Bay Monday while attendant deepening surface low helps to drive a strong cold front south into portions of the Midwest. Meanwhile, a second potent shortwave digs across British Columbia into the Pacific Northwest eventually closing off and reaching the southern Great Plains late Tuesday. A sharp baroclinic zone will be present between the two shortwaves and this zone is expected to pivot over the Midwest through the first half of the week, then gradually shift east through the latter half of the week. We are starting to see much better model agreement, particularly between the GFS and ECMWF with respect to timing and track of the low. The NAM is also in line at least through the end of its run Tuesday evening. The Canadian model continues to hold onto a slower solution with the progression of the H5 closed low and now is an outlier. Through the first half of the week, temperatures should generally be on the warmer side, with the exception of the Illinois River Valley and areas northwest which will see sharp temperature contrast NW to SE across the area. Thursday and Friday will see the temperatures cooling across the remainder of central Illinois as the colder air gradually spreads east. In general next week, expect temperatures well into the 80s on the warm side of the baroclinic zone, then expect highs only in the 60s on the cool side. There will also be daily precip chances across central Illinois until the front passes through. The best chance will be later Monday through Tuesday as an axis of strong mid level WAA and F-gen develops across the mid to upper Mississippi Valley in response to deepening west coast trough. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 700 PM CDT Sat Sep 5 2020 The gusty westerly winds from this afternoon have diminished with diurnal cooling and decreased mixing. All TAF sites are less than 10KT as of 00z/7pm. High surface pressure will continue to provide clear skies for the major of the overnight. The next issue of concern is a squall line of storms that is projected to roll through S MN through Iowa into NW Illinois by late tonight. The HRRR has the storms timed into PIA around 12z/7am, BMI by 13z and CMI by 14z. There could be strong winds with the gust front. Winds will increase from the SW behind the line of storms, with 15g27kt possible by early afternoon. Another wave of storms is projected for mid to late evening on Sunday, but that is just beyond this TAF period. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Shimon SYNOPSIS...Deubelbeiss SHORT TERM...Deubelbeiss LONG TERM...Deubelbeiss AVIATION...Shimon
Area Forecast Discussion
National Weather Service Marquette MI
821 PM EDT Sat Sep 5 2020 .SHORT TERM...(This evening through Sunday) Issued at 345 PM EDT SAT SEP 5 2020 Latest water vapor imagery and RAP analysis reveals persistent large- scale pattern characterized by anomalously strong western US ridging and broad troughing downstream over the Great Lakes and eastern Canada, resulting in a NW flow from the mid levels to the surface. Shortwave energy rounding the western CONUS ridge over northern BC will be the big player in the weather fcst later this holiday weekend as it deepens a low pressure system over Manitoba and northern Ontario and sends a powerful cold front across the area late Sun into Sun night. Confluent flow ahead of the western CONUS ridge and resultant sfc ridging has yielded mostly sunny skies today. Deep mixing to nearly 6 kft has resulted in widespread nw wind gusts of 20-25 mph with highs mostly in the mid to upper 60s, except for some lower 70s readings south central. Tonight, temps should drop off nicely at first with skies still clear and winds light. However as the night goes on and WAA cloud cover and return flow begins to work in from the west, expect to see temps steady off or even rise slightly, mainly after about 06z. The best isentropic lift and theta-e advection with the next wave look to be delayed until after 12z, so continued the dry fcst for tonight. Sunday...Shortwave now over northern BC will dig through southern Saskatchewan/Manitoba early in the day and then will continue to amplify as it moves into northern Ontario in the afternoon along with its associated rapidly deepening sfc low. During the day, a strengthening 50 kt low-level jet will respond by developing northward across Upper MI and Lake Superior. With the resulting strengthening theta-e advection and advection of elevated instability ne into the fcst area, looks like a good setup for showers/t-storms to develop into Upper MI during the day. With a stable sfc based layer, any storms will be elevated. Latest NAM soundings still showing CAPE of 1000-2000 j/kg for parcels lifted around 800 mb or higher advecting into the area. Most of the other model guidance is lower. As an approximation for effective deep layer shear for the storms, 2-7km shear guidance suggests sufficient shear will be present for organized storms and a large hail risk if the higher cape values materialize. SPC has since included the southern portion of the U.P in a marginal risk for SVR storms on Sunday. Deeper sfc based stable layer should limit potential of strong t-storm winds despite low-level jet increasing to 45-55kt. Will still become a breezy day with 7-9 mb/3 hr pres fall max shifting eastward, n of Lake Superior. East half of the fcst area will be favored for stronger winds and MAV/MET guidance capture this well with sustained winds near 20 and gusts 30-35 mph. Developing strong s winds up Lake MI and subsequent building waves will lead to a high swim risk for the Lake MI beaches of Schoolcraft County on Sun. A lakeshore flood advisory will be needed as well for Delta/Schoolcraft counties for beach erosion/minor flooding during the aftn/evening as waves, especially outside of the Bay of GB build to 8 to 10 feet. .LONG TERM...(Sunday night through Saturday) Issued at 345 PM EDT SAT SEP 5 2020 A cold front will make its way through Upper Michigan Sunday night, bringing showers and thunderstorms across the area early. After the precip moves through the area, expect wind gusts from the w & nw that will bring breezy conditions across the land and high-end gales across the Great Lakes. Temperatures also look to cool to below normal Sunday night as Canadian air moves in behind the front. Temperatures will remain below normal until the middle of the week. Winds will slowly weaken Monday as the day progresses. Precipitation looks to make its way back into Upper Michigan Tuesday, with the greatest amounts in the south and east. Models have the precipitation staying until Thursday; however, the Euro has precipitation occurring in the east until the end of the forecast period. Warm air begins returning to the U.P. Wednesday due to WAA; it will move across the area from east to west. Temperatures look to drop again Saturday as a low pressure from the Great Plains makes its way ne through Upper Michigan; this low pressure looks to move out of the area by Saturday evening. More details on the forecast follow below. Showers and thunderstorms will continue moving through the area Sunday night, particularly in the central and east. Thunderstorms look to have the best chance of occurring in the south central early Sunday night, as there will still be enough energy to get convection going. MUCAPE in the NAM model gets over 3000 J/kg at 00z Monday in the south central , while other models such as the GFS and Euro hint at it only reaching ~1000 J/kg. PWaTs also seem anomalously high with the passage of this cold front; PWaTs are in the top 10% ahead of the cold front boundary according to the NAEFS and ENS. Wind shear looks to be supportive of tilted updrafts, as bulk shear magnitude should be 35+ kts across Upper Michigan. Therefore, the limiting factor for thunderstorm and any possible severe weather development appears to the amount of energy available in the atmosphere. If there is enough energy to get convection, then some strong thunderstorms may be possible as there is ample wind shear and moisture. The primary severe weather threat, if severe weather were to occur, looks to be hail due to the high wind shear, amount of CAPE available, and high precipitable water amounts. The thunderstorm threat looks to quickly diminish Sunday night as the cold front moves east throughout the night, as CAPE looks to sharply decrease due to the lack of diurnal heating. Later Sunday night, CAA will bring strong winds to the sfc as the CAA will allow for mixing with a low-level jet behind the cold front. This mixing will allow for high wind speeds to be brought down to the sfc. Winds gusts from the w and nw look to reach speeds of 40-45 kts on the Great Lakes. Models suggest that the time for the highest wind speeds look to be around 06z-09z, with western Lake Superior reaching the highest winds first. Winds gusts will weaken Monday as the CAA weakens. However, expect breezy conditions to continue until Monday night. We will get a break in the precipitation Monday before getting more for the middle of the week beginning Tuesday. Expect mostly cloudy to overcast skies for the week, as a stationary boundary sets up over Upper Michigan. This will allow a long stretch of continuous precipitation to occur from Tuesday until Thursday. This will also make temperatures cooler in the west and warmer in the east, especially as WAA slowly makes its way back into Upper Michigan from east to west beginning Wednesday. The NBM suggests that the greatest chances for thunderstorms associated with the stationary boundary will occur Wednesday night. Thursday should see the rainfall end, and Friday should remain dry, although have some doubts as Euro seemed to imply continuous rainfall in the east for the whole week. A low pressure system from the Rockies will make its way ne towards the U.P. Saturday, and bring more precipitation and slightly lower temperatures back into the area before leaving Saturday evening. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 820 PM EDT SAT SEP 5 2020 Expect VFR conditions tonight as a ridge passes by to the south. Mid level clouds will spread in from the west late tonight ahead of the next approaching frontal system. South winds will increase during the day on Sunday with gusts of 30 knots during the afternoon. Showers and possible t-storms along with increasing low level moisture will drop cigs to MVFR into the afternoon with even IFR possible at KSAW by late afternoon. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 345 PM EDT SAT SEP 5 2020 The main story is a one-two punch of southerly gales developing Sunday afternoon (east half) transitioning to high-end NW gales to 40-45 kts (across the whole lake) late Sunday night through Monday morning. Have upgraded Gale Watch to Gale Warning for the east half starting Sunday afternoon to cover the southerly gales. By early Monday morning, Gale Watches go into effect for the rest of the open water zones on the lake. The system responsible for these gales continues to trend slightly stronger so additional slight increases in forecast wind speed are possible, especially for the eastern half of the lake early Monday morning. Winds are expected to quickly subside below gale threshold by Monday afternoon and then continue weakening to around 15 kts across the lake for Monday night into Thursday as high pressure builds over the lake. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Beach Hazards Statement until 9 PM EDT this evening for MIZ006. Beach Hazards Statement from 8 AM EDT Sunday through late Sunday night for MIZ014. Lakeshore Flood Advisory from 2 PM Sunday to 2 AM EDT Monday for MIZ013-014. Lake Superior... Gale Warning from noon Sunday to 2 PM EDT Monday for LSZ249>251- 266-267. Gale Watch from late Sunday night through Monday morning for LSZ245>248-265. Gale Watch from late Sunday night through Monday morning for LSZ241>244-263-264. Gale Watch from late Sunday night through Monday morning for LSZ162. Lake Michigan... Gale Warning from 10 AM Sunday to 5 AM EDT Monday for LMZ221-248- 250. && $$ SHORT TERM...Voss LONG TERM...TAP AVIATION...JLB MARINE...Voss
Area Forecast Discussion
National Weather Service San Francisco Bay Area
426 PM PDT Sat Sep 5 2020 .SYNOPSIS...Hot to very hot temperatures are forecast through the rest of this Labor Day weekend, with peak temperatures expected tomorrow and Monday when the warmest interior locations are forecast to exceed 110 F. An Excessive Heat Warning is in effect for interior locations from 11 AM Saturday to 9 PM Monday, the Bay Shoreline (excluding SF) from 11 AM Saturday to 9 PM Monday, and a Heat Advisory is in effect for coastal areas from 11 AM Saturday to 9 PM Monday. Winds will be light through Monday, but gusty offshore winds are possible locally in the hills starting Monday evening. A Fire Weather Watch has also been issued for the North Bay Mountains and East Bay Hills from Monday evening and through Wednesday morning. Warm conditions will persist through much of next week, but temperatures are expected to trend gradually downward from Tuesday onward. && of 02:08 PM PDT Saturday...Fort Ord Profiler shows the marine layer over the Central Coast has all but withered away and appears to be close to doing the same in the Bay Area given the steady uptick in temperatures along the SF Peninsula. Most of SF County started out in the mid-60s this morning, and while the marine layer was able to hold out up until mid-morning, its disappearance resulted in temps making it up into the upper- 70s F in the western side of the city (e.g. Sunset District and Presidio) and hotter temps in the low 90s over the eastern and higher-terrain sides of the City (e.g. the Mission District and Hunter`s Point). Meanwhile in Santa Cruz, sharp 10-15 F temperature gradient exists between the immediate shoreline and highway one due to the geographical influence of the area with respect to onshore flow, which has been light at best. Parts of the interior reached the mid-90s by noon as the the upper- level ridge over the Mountain West made it up to 600 dam 500 hPa, with places like Livermore set to make it into the low 100s later this afternoon. In regards to the strength of the upper-level ridge, only two other times this season have we seen upper-level ridges in the Western US make it up into 600 dam, the most recent of which brought on our Heat Wave on the week of August 14th that was followed by the lightning sequence. As for the tonight, and the rest of the Holiday weekend, expecting poor overnight temperature recoveries across most of the CWA given the state of this stagnant air mass. Overnight lows will only fall to the 60s F along the coast and 70s F in the interior, with our hottest locations observing lows in the 80s F. High confidence for Sunday being the hottest day as a result of the poor overnight temperature recoveries, with widespread 100+ F temps Sunday and Monday across the interior, and upper-90s in near-coastal locations. Far interior locations like Pinnacles and areas in San Benito County may even possibly reach 115-120 F temps on Sunday, with MOS guidance for Paso Robles hinting at the possibility of even seeing a high of 122 F! That`s far from what we can expect along the coast and near-coastal locations, but should be something to consider. Speaking of the coast, it is important to keep in mind that we can expect for there to be sharp temp gradients near the coast (e.g. SF, Santa Cruz). Onshore flow will definitely help keep immediate coastal locations cooler than areas even only a few miles inland, but even a slight decline in that onshore flow could make the difference between busting or not.ust to show potential - take a look at 2017 Labor Day in San Francisco. Onshore flow was completely gone and offshore flow prevailed bringing 106 F to Downtown San Francisco. Smoke has been lingering over our CWA for the last few days and will continue to do so as the inverted vertical temperature profile caps it through this weekend. The light winds won`t help advect much of that smoke either, but thankfully will not have to worry about fanning flames. For detailed particulate forecasts, please refer to the Bay Area Air Quality District. The most immediate fire concern will be with regards to the poor overnight humidity recoveries this holiday weekend, which will essentially erase the aid from the workweek`s 2000 ft marine layer. By Monday evening, a 500 hPa trough will make its way into the Canadian Prairies and rapidly deepen quasi-zonally over the Northern High Plains before digging into the Mountain West. The resulting upper-level pressure gradient will in turn produce a sharp synoptic-scale cold front at the surface that extends over much of the CONUS during the early part of next week. Model uncertainty exists with regards to the exact location of the center of the shortwave axis, with GEFS members placing it over the Colorado Front Range, while the EPS members suggesting a more westward dig into the 4-corners region. Depending on its position, and given that our CWA will lie on the convergent quadrant of the shortwave, expecting a gradual cooldown from Monday onwards. Unfortunately, also expecting an uptick in northeasterly mid-to- upper level flow Monday and into Wednesday. Fire Weather Watch has also been in effect for the last few days for North Bay Mountains and East Bay hills owing to rising concerns about a potential moderate wind event following this heat wave, but no chance for thunderstorms due to a lack of monsoonal moisture. For now, excessive heat warnings are in effect for the interior and Bay shoreline locations, while heat advisory is valid all along the coast. This wind uptick culminated with the poor humidity recoveries are both concerning. Could see N to NE offshore winds in our North Bay Mountains and East Bay hills during that period, with winds gusting to 35-45mph and a max of 50mph in some of our highest elevations. Wind forecast confidence will increase as the latest short-term models come in tonight and going into tomorrow. As the concern draws near the watch will be upgraded to a Red Flag Warning. Santa Cruz Mts may need to be included in the Watch as winds appear to be gusty there as well. Please refer to the fire weather discussion below for a more detailed discussion on the Mon-Wed setup. Looking ahead into the rest of the week, the interior will continue its gradual cooldown while temps along the coast will also return closer to average as the long-range ensembles hint at another, albeit much weaker, PAC ridge centering itself just off the California coast. && .AVIATION...As of 04:26 PM PDT Saturday...for the 00Z TAFs. VFR conditions through the period with mainly clear skies as the marine layer has compressed down to 500-800 ft AGL per profiler data. Satellite still shows some smoke across the region from various wildfires. The latest HRRR smoke forecast does show an increase in near surface smoke tomorrow morning/afternoon depending on location. Expect occasional reduced vis at times due to smoke/haze. Onshore winds this afternoon 10-15 kt will diminish overnight before winds increase again tomorrow afternoon. Vicinity of KSFO...VFR. W/NW winds this afternoon around 15 kt easing overnight. Expect onshore winds to increase again tomorrow afternoon. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR through the period with occasional vis issues due to wildfire smoke/haze. W/NW winds this afternoon 10-15 kt into this evening. && .CLIMATE...Record high temperatures for the Labor Day Weekend .................Sept 5.........Sept 6.........Sept 7 ---------------------------------------------------------------- Santa Rosa......101, 2008......106, 1904......108, 1904 Kentfield.......103, 1950......104, 1923......104, 1923 Napa............100, 2008......106, 1904......110, 1904 Richmond.........96, 2004.......91, 2004.......93, 2015 Livermore.......108, 1950......108, 1904......108, 1904 San Francisco....96, 2004.......92, 1904......100, 1904 SFO..............94, 2004.......94, 2004.......93, 1957 Redwood City.....97, 1983......100, 1958.......99, 1982 Half Moon Bay....83, 1961.......80, 2004.......76, 2013 Oakland Dtown....95, 2008.......95, 1979.......93, 2015 San Jose.........99, 2008......100, 1923......106, 1904 Gilroy..........103, 1988......104, 1977......103, 1977 Santa Cruz.......94, 1941.......98, 2004......108, 1904 Salinas..........97, 2004.......97, 2004.......99, 1957 Monterey.........94, 2004.......94, 2004.......92, 1957 King City.......102, 2004......105, 1928......106, 1936 && of 02:07 PM PDT Saturday...Moderate northwest winds will persist across the northern outer waters through Saturday tonight. Elsewhere, wind speeds will gradually diminish through Sunday. Generally light winds are expected Sunday through Labor Day except for locally gusty winds near the coastal jets. Mixed seas will prevail with a northwest and southerly swell. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...Excessive Heat Warning...CAZ506-507-510>513-516>518-528 Heat Advisory...CAZ006-505-509-530 Heat Advisory...CAZ508-529 SCA...Pt Arena to Pt Reyes 0-10 nm until 9 PM SCA...Pt Arena to Pigeon Pt 10-60 nm until 3 AM && $$ PUBLIC FORECAST: Diaz/RGass AVIATION: AS MARINE: RGass Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Riverton WY
335 PM MDT Sat Sep 5 2020 .SHORT TERM...(This evening through Sunday night) Issued at 1223 PM MDT Sat Sep 5 2020 Hot and dry for the rest of the afternoon. A shortwave trough pulling southeast across central Saskatchewan into southern Manitoba will send a dry cold front southward, east of the Divide Sunday. This front is expected to reach the Divide by 18Z Sunday. Temperatures will be about 5 to 15 degrees colder east, while areas west of the Divide will only be a few degrees cooler. HRRR model keeps the smoky/hazy skies across the area through Sunday. Due to the cooler conditions and the marginal winds, have elected to cancel the fire weather watch for central and northern sections of the forecast area. Otherwise no changes to ongoing red flag warnings. .LONG TERM...(Monday through Saturday) Issued at 1223 PM MDT Sat Sep 5 2020 For many, Labor Day marks the end of summer or at least the end of the summer mentality. This Labor Day will certainly make that true. The cold front Sunday will be the precursor for Monday`s main event. Areas north of the line from Jackson to Lander to Jeffery City will see their high temperature for the day occur before or around noon on Monday then cool the rest of the day. High temperatures Monday will be in the 50s and 60s north and 70s to low 80s south of that line. 700mb temps drop from +10 to +12 Monday morning to -6 to -8 by late Monday afternoon. Precipitation with this system will begin across the north in areas like Cody and Buffalo Monday morning and move southwestward through the day. Precipitation will start as rain and then transition to snow as temps drop Monday afternoon and evening. It is looking likely that winter highlights will be necessary for higher elevations east of the Divide and the Lander foothills. In terms of snow amounts, these remain very uncertain, however, up to a foot in the highest elevations prone to upslope effects is not out of the question. Generally, we are looking at 4 to 8 inches across the Absarokas, Wind Rivers, and Bighorns and 3 to 5 from Lander to Jeffery City to Casper. Everywhere else could see a trace to up to an inch or two. Again, areas prone to upslope effect will see more snow than other areas. The far west will be the least impacted by this system, with only a few flurries expected in the Jackson valley and up to an inch in the western mountains. Across the south, the biggest hazard will be wind-driven snow. Northeast winds will be strong and gusty across most areas with a tight pressure gradient plus post frontal winds. Gusts to 50 or 60 mph will be possible across Sweetwater and southern Lincoln counties Monday evening and Monday night with precipitation falling, so a winter highlight could be possible for these areas as well, though only an inch or two of snow is expected to fall. With the cold front and snow still moving through the area Monday night, only a light frost is expected across the region for Tuesday morning. Precipitation will end from north to south on Tuesday morning and should be out of the region for the most part by Tuesday afternoon. High temperatures behind the cold front will struggle to reach 50 even in the warm valleys, and areas that still have snow on the ground will likely struggle to reach 40. Tuesday night, skies will begin to clear and temps will drop into the mid 20s for many locations. This will lead to a hard freeze for those areas that did not freeze during the cold snap last week. Wednesday, temps begin to rebound a bit and a warming trend looks to continue through the rest of the period. The rest of the period also will remain dry in light NNW flow. So we will see the warm, dry weather returning, but this will be more seasonable warmth as compared to the record warmth that has been occurring over the last few days and humidities will be higher as well. && .AVIATION...(For the 00Z TAFS through 00Z Sunday afternoon) Issued at 1139 AM MDT Sat Sep 5 2020 VFR conditions are expected through the forecast period. Gusty winds will continue across the area through 02Z, then decrease. A weak cold front will move into northern WY after 06Z, with a wind shift to the north or northwest. This front will move through KCOD, KWRL, and KCPR by late morning and move southwest into KRIW and KLND later in the afternoon. Dry weather will continue through the period. Areas of smoke aloft will continue over most of WY and will begin to increase Sunday afternoon. && .FIRE WEATHER... Issued AT 1223 PM MDT Sat Sep 5 2020 A red flag warning remains in effect for all of the area through 8 PM. A weak, dry cold front will push south, east of the Continental Divide Sunday. The fire weather watch for northern and central areas has been cancelled due to the cooler temperatures, lighter winds, and slightly higher relative humidity. However the red flag warning across the west and southwest will remain in effect through Sunday evening. This might need to be expanded into the day Monday. A strong cold front will push through the area Monday into Monday night. Significant precipitation is expected over the east, with lighter amounts west. && .RIW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM MDT Sunday for WYZ277>279-288-289- 414>416. Red Flag Warning until 8 PM MDT this evening for WYZ140-275-276- 280>283-285>287-300. && $$ SHORT TERM...Murrell LONG TERM...Fisher AVIATION...Fisher FIRE WEATHER...Murrell