Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/08/20


Area Forecast Discussion
National Weather Service Denver/Boulder CO
806 PM MDT Mon Sep 7 2020 .UPDATE... Issued at 755 PM MDT Mon Sep 7 2020 A couple different pre-front-cold-fronts came down across the CWA late this afternoon and earlier this evening. The real front is now across the northern CWA border, heading south. Real data indicates that the northeasterlies, from the first front made to the the Cameron Peak Fire. It is already showing signs of "decrease-ment". Its smoke plume has tamed down consierably already. The grids are in pretty good shape with the significant weather change expected. && .SHORT TERM...(This evening through Tuesday) Issued at 348 PM MDT Mon Sep 7 2020 ...SNOW AND RECORD COLD EXPECTED TUESDAY INTO WEDNESDAY... The weather expectations remain unchanged as the north winds ahead of the cold front are now spreading across Weld County and towards the Denver/Boulder metro area. Strengthening north winds should continue through the evening as cold air moves into the state. Fire activity on the Cameron Peak fire remains vigorous to extreme. Warnings and Advisories remain in effect for the mountains, foothills and out onto the plains. Rain on the plains and snow in the mountains should develop by midnight. Rain on the plains will continue through about 6 AM, when temperatures cool enough and the airmass becomes cold enough through the column for precipitation to change over to snow. Mountain areas should see accumulating snow overnight and through the day, but accumulations on the plains will be harder to realize due to warm ground temperatures and air temperatures in the lower 30s. Snow sill fall through the day, but will mostly melt until later tomorrow evening. .LONG TERM...(Tuesday night through Monday) Issued at 348 PM MDT Mon Sep 7 2020 The early winter storm will continue to impact the area Tuesday night and possibly into Wednesday before finally loosening its grip on the forecast area. We would expect mostly snow (perhaps a mix in the far northeast corner) continue into Tuesday night with continued upslope, but gradually weakening QG ascent. Models have excellent agreement on the synoptic positioning of the upper level low settling into the Utah/Arizona border/Four Corners region, but the details on the mesoscale forcing and melting still make this a difficult forecast, as usual for Colorado. Most of the models do have one good batch of precipitation rotating around the upper low and across the Front Range and northeast plains during the evening. Apparently there is a weak embedded short wave kicking out of the upper low, but there is little QG signature or other mesoscale forcing like frontogenesis indicated. There has been reasonable consistency with regard to this feature, so we do think a period of heavier snow is possible during the evening. Snow should continue overnight with overall weak QG lift and upslope, although the intensity will decrease as both of these support mechanisms weaken. Tuesday night will provide the highest chances of meaningful accumulating snowfall across the plains, given loss of any solar insolation and continued cooling of the near surface soil temperatures. We`ll likely see our largest storm impacts in this period as we accumulate heavy, wet snow on trees and elevated surfaces. Thus, we`ll continue to message potential for broken tree limbs and scattered power outages. Snow will continue to taper off Wednesday as we lose our upper level forcing and flow turns deep south/southeasterly. That said, this flow pattern would continue to produce accumulating snow in Park County through much of the day. Total snow accumulations are still very tricky considering the heat ahead of this storm and the amount of melting that will occur, especially during the day tomorrow. The higher elevations of the foothills and mountains should be able to hang onto most of the falling snow as accumulation due to the very cold temps in the teens to mid 20s, while the I-25 Urban Corridor is still a wildcard, and will be through this entire event. We did like the newest HRRR variable snow accumulation product, which shows 8-18 inches with locally higher amounts in the foothills, anywhere from 2-6 inches in the I-25 Corridor (locally higher amounts possible right near the foothills and Palmer Divide). Most of the eastern plains would be lighter in the Trace to 4 inch range, but if the heavier band materializes Tuesday evening then a few spots could get more. The upper level low will eventually fill and most likely kick northeast across the state Thursday and Thursday night. This will likely bring one last round of showers to the mountains with light snow accumulations possible, and a chance of rain showers to the lower elevations. Record low temperatures can be expected Tuesday night, with readings dropping below freezing over most of the plains. If precipitation continued all night, lows could hover near 30-32F, otherwise some upper 20s will occur. If it did drop below 30F in Denver Wednesday morning, it would be the earliest 20s ever recorded, and only four days after our latest 100F ever. Wednesday looks like another cold day with highs on the plains only reaching the 30s. Temperatures will then gradually moderate through the end of the week as ridging and drier westerly flow aloft develops. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 755 PM MDT Mon Sep 7 2020 Northeasterly winds currently, should gradually give way to more due northerly winds at DIA by around 0330Z. Initially, after the front moves through, wind gusts could reach 35-40 knots for a couple of hours. Ceilings should come down into the BKN- OVC020-030 range by 06Z. IFR conditions can be expected at DIA sometime around 12Z Tuesday morning. Snow is expected as the precipitation type from that time on into Wednesday, but it will be unlike for any of the snow to accumulate in runways. && .FIRE WEATHER... Issued at 755 PM MDT Mon Sep 7 2020 The RFW has expired at 02Z. Hopefully, the expected incoming moisture will have a serious impact on reducing our short/medium range fire danger and, perhaps, putting our ongoing fires out. && .BOU WATCHES/WARNINGS/ADVISORIES... Freeze Warning from 6 PM Tuesday to noon MDT Wednesday for COZ038>051. Winter Storm Warning from midnight tonight to noon MDT Wednesday for COZ033>037-041. Winter Weather Advisory from midnight tonight to 6 AM MDT Wednesday for COZ031. Winter Weather Advisory from midnight tonight to noon MDT Wednesday for COZ038>040-042-043-045-046. && $$ UPDATE.........RJK SHORT TERM.....Dankers LONG TERM......Barjenbruch AVIATION.......RJK FIRE WEATHER...RJK
Area Forecast Discussion
National Weather Service El Paso TX/Santa Teresa NM
333 PM MDT Mon Sep 7 2020 .SYNOPSIS... Warmer temperatures today and tomorrow, with slight chances for storms in the higher terrain. A cold front moves in early Wednesday morning, brining widespread rain chances and cooler temperatures. Temperatures will drop to 15 - 20 degrees below normal for the middle of the week. As the moisture slowly moves out towards the end of the week, temperatures remain slow to warm back up and storm chances transition to more convective by the weekend. && .DISCUSSION... .SHORT TERM...Tonight and Tuesday... Storm system starting to move into the northern plains and Rockies today and will be moving south overnight and into Tuesday. Main trough will become cutoff over the Great Salt Lake area by morning and then slowly move to just north of the Four Corners region by 00Z Wed. For the Borderland, expect increasing surface pressure gradient as system deepens and west to southwest winds pick up overnight. This will lead to a mild night with most lowland areas not dropping below the mid 60s with KELP possibly remaining in the mid to upper 70s. There will be a decent moisture tap from the WSW which will bring dew points into the 50s across the south which will lead to a better chance for storms Tuesday afternoon. For Tuesday, with decent moisture in place, even with some mixing out for the afternoon, looks like good instability will result, especially over southwest portion of area. With upper low in place, models indicating weak disturbance moving through southwest flow aloft into western NM during the afternoon. Operational global models not producing much more than some storms over area mountains, but 12Z HRRR out to 00Z Wed indicating good storm coverage by late afternoon over much of the CWA. Went with 20-30 pops lowlands and 30-40 pops mountains for the afternoon. Shear not great with fairly uniform westerly winds winds and little change in speed. Could still see some strong storms though as they move quickly eastward. Also expect cold front to be focus for some storms late in the northeast but moreso going into the evening hours. The west to southwest surface winds of 15-30 mph will allow temperatures to warm again nicely. MET guidance looks out to lunch with highs for Tuesday given the winds and warm start. Even MAV which is 5-15 degrees warmer may not be warm enough in some locations, so went with near 100 around Rio Grande Valley and lower to mid 90s out west and far east. Cold front will likely have an effect at least for lower elevations of Sacs with quickly falling temperatures around Mayhill in the late afternoon. && && .LONG TERM...Wednesday through Tuesday... The story of this period is the approaching coldfront, and for good reason. A quickly approaching upper level low spins above southeastern UT. Global models agree on the center of the low remaining over the eastern UT/AZ border for the first 24 hours of the period. Moving southward with it is a surface coldfront to the east of the upper level system. Up until today, there was good agreement on the timing and magnitude of the front arriving. Newest runs push back the arrival time of the front, now more early Wednesday morning, and stall a majority of the coldest air in eastern NM. Cooler air (850 temps in the teens) will spill into the area Wednesday night still and reach just west of the continental divide by day break Wednesday. These newer model runs show the air mass to be more shallow and a bit warmer once it spills into the area. The moisture with this modified air mass still holds PW values around 1 - 1.25 inches (which is healthy for a cooler air mass such as this one). As left over CAPE is pushed southwest, a few thunderstorms could form along the boundary. Gusty conditions will exist as the front contracts and the pressure gradients meanders back and forth around the continental divide area Wednesday. Temperatures are a bit hard to put an exact number on, however we will see values drop to 15 - 20 degrees below normal. Since we still have a higher sun angle, one break in the clouds could warm the air up significantly. Generally, the air behind this front is cooler, and will give the area a much needed break from the heat, especially if light rain continues on and off throughout the day. Thunderstorms are looking more favorable west of the continental divide with these newer model runs. With a more shallow airmass, clouds could clear up during the day Wed and Thursday. Models hint at the western zones holding onto surface dew points in the low 50s. Paired with the cooler air aloft, this could be a nice set up for some CAPE. Models do show ~700 J/Kg around ELP for this time frame. With organized upper level and lower level winds, we have ~30-40kts 0-6km Bulk shear to work with as well in areas of healthy CAPE. In summary, western areas could see some storm development Wed and Thursday afternoons. The strongest winds look to be Wednesday night in the eastern counties, as the coldfront has a nocturnal push westward. Wind speeds and gusts flirt with advisory criteria, especially along the west slopes of mountains in these areas. Temperatures remain well below normal Thursday and Friday, but slowly warm up. By Friday morning, the upper level low lifts north east from the AZ/UT border. This trajectory will keep most of the strongest upper level winds to our north, keeping our surface winds calm for the end of the week. Due to less invasive upper level westerlies, easterly winds remain at the surface this weekend. A heat low over the AZ desert will help pull in moisture from the east. This added lowlevel moisture will keep temperatures near seasonal, and continue rain chances through the end of the period for the eastern counties. && .AVIATION...18Z TAF CYCLE P6SM FEW-SCT120-150 through period. Isolated -TSRA BKN080-100 possible between 18Z-02Z over area mountains. Winds start out S to SW AOB 12KTS but shifting after 03Z to the W to SW at 10-20KTS. Gusts to 25KTS after 15Z, especially around KDMN and KLRU. && 26 && .FIRE WEATHER... One last day expected for Tuesday of very hot temperatures ahead of an unseasonably strong cold front. Highs will again approach the 100 degree range over some lowland areas, especially southern NM and far West TX near the Rio Grande. West to southwest winds will also be in the 15 to 30 mph range with strongest winds over the south. May have a few hours of near critical conditions south, but there is an increase in low level moisture which should keep relative humidities slightly above critical values where winds are strongest. Cold front moves through western half of area Tuesday night which will bring gusty E to NE winds to the area and a chance for showers and thunderstorms areawide. Much cooler temperatures for Wednesday, especially eastern half of the area behind the front and with strong upper low lingering over the Four Corners region through Thursday. As the low lifts northeast late in the week, temperatures will be rebounding back to near normal by the weekend with a few showers and thunderstorms still possible. && 26-Grzywacz && .PRELIMINARY POINT TEMPS/POPS... El Paso 71 100 58 73 / 0 10 80 50 Sierra Blanca 64 96 54 67 / 0 20 80 50 Las Cruces 66 97 56 70 / 0 20 80 50 Alamogordo 68 99 53 70 / 0 40 80 60 Cloudcroft 51 77 35 50 / 0 40 80 70 Truth or Consequences 66 99 53 66 / 0 30 80 60 Silver City 63 91 54 67 / 0 20 70 70 Deming 68 99 56 73 / 0 20 70 60 Lordsburg 67 98 60 76 / 0 20 50 70 West El Paso Metro 73 102 60 75 / 0 10 80 40 Dell City 64 100 49 65 / 0 20 80 40 Fort Hancock 69 102 60 77 / 0 10 80 50 Loma Linda 68 94 53 65 / 0 20 80 50 Fabens 71 100 60 74 / 0 10 70 50 Santa Teresa 69 99 57 74 / 0 20 80 50 White Sands HQ 69 100 57 71 / 0 20 80 50 Jornada Range 65 99 56 70 / 0 20 80 50 Hatch 66 100 56 71 / 0 20 80 60 Columbus 71 99 60 77 / 0 20 60 50 Orogrande 67 100 55 70 / 0 20 80 50 Mayhill 58 87 38 53 / 0 40 80 70 Mescalero 56 87 37 58 / 0 40 80 70 Timberon 53 84 40 56 / 0 40 80 60 Winston 55 92 42 61 / 0 30 70 70 Hillsboro 63 99 49 68 / 0 30 70 70 Spaceport 64 99 53 69 / 0 30 80 60 Lake Roberts 52 90 48 67 / 0 20 70 70 Hurley 64 94 53 69 / 0 20 70 70 Cliff 61 97 56 74 / 0 20 60 60 Mule Creek 61 92 56 71 / 0 20 60 60 Faywood 64 94 53 68 / 0 30 70 70 Animas 66 98 59 79 / 0 20 40 60 Hachita 65 97 57 77 / 0 20 50 60 Antelope Wells 65 94 59 79 / 10 20 40 60 Cloverdale 63 89 61 75 / 10 20 40 60 && .EPZ WATCHES/WARNINGS/ADVISORIES... NM...None. TX...None. && $$ 26-Grzywacz/31/26
Area Forecast Discussion
National Weather Service Grand Forks ND
1008 PM CDT Mon Sep 7 2020 .UPDATE... Issued at 1004 PM CDT Mon Sep 7 2020 The CU really has pretty much dissipated over the area. This leaves thicker cirrus in the far south but rather thin cirrus or mainly clear sky central and north parts of the fcst area. Not ideal radiational cooling but degree of clearing is allowing temps to drop into the upper 30s to low 40s area wide with pockets of mid 30s. Will leave temp fcst as is and no changes to headlines. Some risk of frost outside of Fargo in areas not in advisory but unclear extent at this time as high clouds still upstream. Short term models indicate some additional clouds dropping south toward morning into far NE ND/NW MN but upstream shows not much in the way of cloud cover up thru the central Interlake region north of Winnipeg. So that remains uncertain. UPDATE Issued at 701 PM CDT Mon Sep 7 2020 The CU is breaking up pretty good attm leaving behind some cirrus, though that is thin in the northern fcst area. Areas of stratocu are in Manitoba though and with high to our west will keep enough of a north-northwest wind tonight and patches of clouds to keep lows 30-38 across the area. Going frost/freeze headlines appear reasonable as HRRR sfc temps indicate the two areas of psbl 32 or lower temps, one larger area in north central ND into parts of the DVL basin and the other in areas near Thief River/Fosston. Will need to monitor cloud trends this evening for any temp adjustements. && .SHORT TERM...(This evening through Tuesday night) Issued at 256 PM CDT Mon Sep 7 2020 Temperatures will be the main concerns for the period. Some light rain over the southwestern CWA as an embedded shortwave rounds the base of the big trough over the north central CONUS. Clouds have continued across most of the area, with stratocu rapidly filling in where it tried to clear out in the north. That stratocu will dissipate this evening, so at least partial clearing across the northern counties is expected. Still a bit of north to northwest winds on the front side of the surface high, so radiational cooling will not be ideal, but there will be continued cold air advection. Given that some spots in our northwestern counties got into the upper 30s even with cloud cover last night, getting down into the low 30s or even upper 20s seems reasonable in our cold spots. Will continue to keep the freeze warning going in northeastern ND and the boggy areas of northwestern MN, with frost advisory in the northern RRV and along the southern edges of the warning. Still uncertain to how cold the southern counties will get due to cloud cover, so will continue to keep them out of any headlines for now. Split flow aloft for tomorrow with the southern branch upper low well to our southwest and the northern branch over our area. Cold air aloft should help develop some decent stratocu again tomorrow, as temps heat into the low to mid 50s. That cu will go away after sunset, and with clearing skies and light winds as the surface high moves into the region, temps will get very cold Tuesday night. Will continue to keep the freeze watch going. .LONG TERM...(Wednesday through Monday) Issued at 256 PM CDT Mon Sep 7 2020 The Wednesday through Sunday time period brings a slight warmup and generally quiet weather to the region. Weather impacts will be minimal, and in association with showers and perhaps some embedded thunderstorms Friday and Saturday. For Wednesday, a cool start in the lower 30s will give way to daytime warming and temperatures in the upper 50s to near 60 degrees. Lows will fall into the upper 30s to low 40s Wednesday night into Thursday morning. At the H5 level, progressive flow will facilitate the development of a cut off low working through the Northern Plains and Upper Midwest Thursday through Saturday. This will give us a chance for showers and scattered thunderstorms from pre-dawn Friday through Saturday evening. At this time, ensemble guidance is a bit divided regarding temperature profiles heading into Saturday and Sunday. The general consensus is bringing another cold front through the area Saturday night into Sunday morning, allowing cooler air to filter into the area as we head into next week.&& .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1228 PM CDT Mon Sep 7 2020 VFR conditions at all TAF sites as stratus moving down from Canada has scattered out at KTVF and KBJI. Precip will stay west and south of the TAF sites this afternoon, with all our airports seeing clouds of 3500 ft and above and somewhat gusty north to northwest winds. Winds will go down a bit this evening and the northern TAF sites should scatter out for a brief period. Could see a repeat of stratus coming off of the Canadian lakes, so have MVFR at KTVF and KBJI for a period again. Other locations should remain VFR. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) Issued at 1228 PM CDT Mon Sep 7 2020 VFR conditions at all TAF sites as stratus moving down from Canada has scattered out at KTVF and KBJI. Precip will stay west and south of the TAF sites this afternoon, with all our airports seeing clouds of 3500 ft and above and somewhat gusty north to northwest winds. Winds will go down a bit this evening and the northern TAF sites should scatter out for a brief period. Could see a repeat of stratus coming off of the Canadian lakes, so have MVFR at KTVF and KBJI for a period again. Other locations should remain VFR. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Freeze Watch from late Tuesday night through Wednesday morning for NDZ006>008-014>016-024-026>030-038-039-049-052>054. Frost Advisory from 3 AM to 9 AM CDT Tuesday for NDZ008-016- 026>030-038-054. Freeze Warning from 3 AM to 9 AM CDT Tuesday for NDZ006-007-014- 015-024. MN...Freeze Watch from late Tuesday night through Wednesday morning for MNZ001>009-013>017-022>024-027>032-040. Frost Advisory from 3 AM to 9 AM CDT Tuesday for MNZ001-002-004- 006-007-009-017-024. Freeze Warning from 3 AM to 9 AM CDT Tuesday for MNZ005-008- 013>016-022-023. $$ UPDATE...Riddle SHORT TERM...JR LONG TERM...Lynch AVIATION...Riddle
Area Forecast Discussion
National Weather Service North Platte NE
649 PM CDT Mon Sep 7 2020 .SHORT TERM...(This evening through Tuesday night) Issued at 322 PM CDT Mon Sep 7 2020 A strong 1040 mb hybrid Pacific-Polar high pressure system has formed across British Columbia. The attendant cold front is advancing south through the Nrn High Plains this afternoon. The high pressure system will drop south through the nrn High Plains tonight and settle across ern WY-nern Colorado by Wednesday morning. The wind forecast uses the short term model blend plus the guidance blend for speeds of around 25 mph tonight and Tuesday. Wind speeds should subside Tuesday evening. The RAP model showed the strongest wind with speeds near 30 mph. H850mb speeds have increased to 50- 55kts in that model increasing the risk of high winds but the sfc gusts in the RAP and HRRR models increase to just 40 to 50 mph. The wind gust forecast uses a blend of the wind regression tool plus the RAP and HRRR models for gusts around 45 mph. The temperature forecast leans on the short term model blend plus bias correction for lows in the 30s to around 40 tonight, 40s Tuesday and upper 20s to upper 30s Wednesday morning. The guidance blend was too cold Wednesday morning. All of the models indicate significant cloud cover will continue Tuesday night blocking any sort of radiational cooling for widespread frost. In fact, given the expected cloud cover, the forecast lows below freezing across northwest Nebraska Tuesday night might be too cool and later forecasts might raise these lows a few degrees. There is little change in the rain and snow forecast. The RAP and HRRR models are changing rain to snow across northwest Nebraska between midnight and 3 am tonight. Snow levels fall to around 4000 feet tonight and to around 3000 feet Tuesday night. The best forcing for accumulating snow will occur late tonight and the RAP model suggested a 1 to 2 hour period of heavy snow across northwest Nebraska. The falling snow aloft will have to overcome the strong sensible heating effects of the warm ground. Given the warm ground with 4 inch soil depth temperatures in the 70s according to the Nebraska State Climate Office, the unadjusted snowfall forecast of amounts 1 inch or less seems appropriate. Isolated thunderstorms are possible across swrn/scntl Nebraska late tonight associated with a southwest oriented low level jet which will steepen lapse rates and build a few hundred J/KG of elevated CAPE. The better thunderstorm chances will likely be south and east across KS and ern Neb. There is also a chance for sporadic lightning with the developing rain and snow across wrn and ncntl Nebraska tonight. The combination of strong lift and negative theta-e lapse rates will support convectively enhanced rain and snow bands, possibly capable of lightning. For now, the forecast focuses on the south for traditional thunderstorm development. .LONG TERM...(Wednesday through Monday) Issued at 322 PM CDT Mon Sep 7 2020 The models are in very good agreement developing a deep upper low across the srn Rockies Tuesday. This upper low should remain nearly stationary Wednesday and begin to lift northeast toward Nebraska Thursday and Friday. Showers are in the forecast Wednesday through Friday with wrn and ncntl Nebraska on the forward or warm air advection side of the upper low. The upper low, which is progged to open up as it lifts northeast, should be north of the region Saturday and the forecast is dry next weekend. Cold sfc high pressure will remain across wrn and ncntl Nebraska Wednesday and Thursday which would be favorable for frost or freeze conditions at night, but the models are in very good agreement keeping skies mostly cloudy and this should block any sort of radiation condition preventing a freeze. Clearing skies are likely Friday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 641 PM CDT Mon Sep 7 2020 Rain will move into the area this evening and stick around the remainder of the forecast period. Some locations across the northern Sandhills will see a rain/snow including KVTN terminal. Most of the accumulating snow will be across the NW Sandhills, west of KVTN, and will generally be less than 1 inch. MVFR and IFR conditions will be possible at both KVTN and KLBF terminal through the forecast period with low cigs moving in this evening across the entire forecast area and sticking around over the next 24 hours. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Gomez
Area Forecast Discussion
National Weather Service Pocatello ID
123 PM MDT Mon Sep 7 2020 .SHORT TERM...Tonight through Wednesday...The cold front is just knocking at the door along the Idaho/Montana border at this time. Gusts exceeding 50 mph are already observed and that is well before peak winds are expected. Little change to the forecast package was made; the timing and strength of the frontal passage remains on track this afternoon and evening. This means winds of 35 to 50 mph with gusts of 55 to 60+ mph. Strongest conditions remain forecast over the Arco Desert and Upper Snake Plain and into areas bordering Idaho/Montana where the northerly winds first enter the state. We will leave our advisories/warnings as is at this time. Blowing dust is possible as well or even likely in some spots, especially in areas where precip does not occur or where very little falls. What is an unknown however is the timing on when conditions would improve. There seems to be indications that these winds would remain strong overnight; which is a good 3 to 9 hours longer than previous models had it going. Not all models agree with this thinking; instead opting to lose some energy with end of sunlight. It feels like a good idea to let the event start and if needed, extend the Wind advisories / warnings if necessary tonight based on observations. A mixture of rain and snow showers remain in the forecast tonight for the Central Mountains, East Idaho and portions of the Snake Plain, all associated with the passing front. Snow accumulations would be light, at an inch or less on area mountain passes with the exception of the Idaho Wasatch Mountains/Bear River Range/Plateau which may very well accumulate a few inches of snow tonight. Bear Lake area, Palisades and Caribou Highlands are most vulnerable to higher rainfall amounts tonight, at around 1/10 to 1/4 inch of rain or a rain/snow mixture. Meanwhile, much colder temperatures are on the way behind the front. Temperatures tomorrow morning at forecast in the mid to upper 30s and while near frost/freeze concerns are possible it will be far to windy to develop any frost on any agriculture across the Snake Plain. The Arco Desert would be susceptible to any frost/freeze concerns tonight temperature wise but there are also 30 mph wind gusts forecast. That said, anyone with a garden growing in the Stanley Basin, Soda Springs or Bear Lake area may very well see a freeze/frost tonight as winds will not be so strong anymore tonight. Tuesday night into Wednesday however, we will issue a freeze warning for the entire growing area Wednesday. We are on the cusp of a hard freeze for the Arco Desert/Upper Snake Plain areas as temperatures will be in the mid to upper 20s; and this may be issued tomorrow or tonight if trends continue this way. Either way, precautions are needed. A closed low will sit to our south tomorrow and Wednesday, allow for persistent northerly flow, at much lighter speeds though with cooler temperatures. There may be a chance for precip along the border of Idaho/Utah at times as moisture rotates around the low but right now chances look low. ND .LONG TERM...Thursday through next Monday...The closed low gradually weakens and pushes to the east and north Thursday into Friday while high pressure continues to build over our area. Look for clear skies and mild temperatures over our area. The weekend and Monday also look very mild under a weak ridge of high pressure. ND && .AVIATION...The big story will continue to be strong winds, especially along and behind the cold front moving through this afternoon and tonight. We are expecting sustained winds of 25-35kts with gusts of 40-50kts possible at IDA, PIH, DIJ and BYI. While not as confident that we will see unusually high gusts at SUN, we will keep gusts to 40kts in the TAF for later this afternoon and evening hours. There will be some showers around, and we have indicated - SHRA or VCSH for all TAF sites. It`s possible we might even snow showers at DIJ right before precipitation tapers off. While not in the forecast, a thunderstorm or two can`t be ruled out. The unusually strong northerly winds in the forecast will eventually die off toward sunrise. However, breezy northeast winds will continue Tuesday. Keyes && .FIRE WEATHER....Current RED FLAG WARNINGS for all areas except the central mountains will remain in place through this evening. In reality, wind gusts will be strong everywhere and likely negate any concerns with rising humidity...including the central mountains during the day and overnight when those humidities really begin to rise. Some gusts will easily exceed 50mph...if not 60mph especially along and behind the front. We are also expecting some showers and MAYBE a thunderstorm or two, but amounts and coverage aren`t expected to be widespread. Stronger winds won`t really wind down until well after midnight, with breezy northerly winds persisting Tuesday. At this point, we aren`t seeing strong enough winds (or at least widespread) where humidity drops into critical territory for another RED FLAG WARNING on Tuesday. Colder temperatures will be around through midweek before high pressure returns and sends temperatures quickly upward. It should be dry for several days behind today`s storm. Keyes && .AIR STAGNATION...Hazy skies do persist this afternoon from wildfires to the west. As a strong cold front pushes air from a northerly direction, the HRRR Smoke model bring smoke from the Lone Star fire in Yellowstone through our area tonight. It`s a bit of an unknown how much of this would mix in in combination with the possible rain and/or snow; therefore we will officially leave it out of the forecasted grids but know that this is a possibility. Aside from this and the unknown of any potential new smoke from new fires in the area; conditions look to clear up tomorrow. ND && .PIH WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 11 PM MDT this evening for IDZ410-413-425- 427. Freeze Warning from 1 AM to 9 AM MDT Wednesday for IDZ051>055. Wind Advisory until 11 PM MDT this evening for IDZ051-055>066- 068>071-074-075. High Wind Warning until 11 PM MDT this evening for IDZ052>054- 067. && $$
Area Forecast Discussion
National Weather Service Portland OR
258 PM PDT Mon Sep 7 2020 .SYNOPSIS...A unusually potent east wind event is ramping up this afternoon. East winds will likely peak later tonight and early Tuesday morning. Extreme fire danger and locally damaging winds are likely. Warm and dry weather appears likely through the end of the week. && .SHORT TERM...Tonight through Thursday...The cooler and dry air mass well into eastern WA/OR this afternoon and is filtering into west of the Cascades. In addition to the strong gusty winds in the Columbia Basin, dew points are a good indicator of the air mass boundary. There dewpoint have dropped into the low 30s. Satellite loop shows clouds developing along the frontal boundary with the leading edge now now approaching the Cascade crest. Rattlesnake Ridge WA is gusting to 74 mph at noon, this is an exposed ridge south of Hanford WA. CIRA Dust and natural color satellite imagery show dust smoke from eastern WA fires drifting toward the west. So hazy skies will be increasing through Tue. Hood River and Skamania, and possibly eastern Multnomah & Clackamas counties may see reduced visibility. With the increasing wind and cold air advection, would not be surprised to see some dust kicked up off Mt. Saint Helens tonight and Tue. Overall the forecast appears on track so no changes to warnings at this time. The KOTH-KGEG pressure gradient switched from positive to negative 17Z and at 21Z at -9.0 mb. Models fairly close with RAP closest to obs. NAM is a couple of millibar too high. The RAP peaks near -23 mb, NAM -21 mb, GFS -21 mb between 3-5 am Tue.BUFR soundings near and surrounding the Gorge - between Mt. Adams and Mt. Hood - show winds ramping up quickly early this evening. The lower level jet at 900 mb or roughly 2500 ft MSL winds plateauing around 2 am at 65-70 kt then subsiding after 6 am Tue.There is no big changes in the models so still looks good for 40 to 60 mph east wind gusts will develop with gusts 60 to 80 mph expected on exposed ridges so High Wind Warning look good. Strong winds will affect areas west of the Gorge to the coast as well affecting the Portland/Vancouver metro area with gusts 40 to 55 mph, but may also see gusts 60-65 mph across the higher terrain like the west hills and areas near the Gorge. Similar winds extend across the north coast range to the higher portions of the north coast zone. In other words, the High Wind Warnings currently in good shape. Fire: A Red Flag Warning continues into Wed across entire forecast area due to a combination of dry fuels, very low humidities, and of course wind. It`s a rare occurrence (likely a first) for Extremely Critical fire category for our area from Storm Prediction Center. Critical fire weather continue into Wed however. Since warm dry conditions continue into Thu so may still see continuation of high fire concerns. But fortunately winds will be considerably weaker. Heat: A Heat Advisory for the central coast into Tue due to the strong offshore flow and resulting downslope warming off the coast range combined with a thermal trough right along the coast. 850 mb temps Tue in that area are around 20-23 C. Wed into Thu the heat shifts inland with some relief for the coast as a southerly wind reversal occurs to bring a shallow marine layer along the coastline. Models differ in the timing but the NAM which usually performs well is showing this development. The south and central Willamette Valley may reach Heat Advisory criteria Wed then expand to include north Willamette Valley/Clark county Thu. .LONG TERM...Thursday night through Monday...More cooling looks likely Fri into Sat with weak onshore flow and lowering 500 mb heights along with weak embedded shortwaves. ECMWF and GEFS ensemble show 850 mb temps gradually lowering into the weekend for continued warm but not hot weather. Shallow morning inversions Fri - Sun may lead to lower somewhat stagnant air for the interior valley with potential for lower air quality. /mh && .AVIATION...The 00Z TAF period is highlighted by an impressive east wind event beginning early this evening and continuing into tomorrow. Offshore flow will begin to strengthen this afternoon with easterly to northeasterly wind gusts between 20 and 35 kt impacting most terminals this evening. Locally stronger wind gusts between 40 and 50 kt will be possible across the Portland/Vancouver metro after 00Z Tuesday. In addition, expect very strong low level wind speed shear on the order of 30 to 60 kt at around 2000 ft across portions of NW Oregon and SW Washington. The easterly winds will also bring upper level smoke and haze into the Willamette Valley from nearby fires. In addition, blowing dust from the Columbia Basin could produce hazy conditions across the northern Valley and Columbia River Gorge this evening. Aside from areas with smoke, skies will be clear. Visibility reductions are not expected at the terminals at this time. Refer to http://weather.gov/zse for detailed regional aviation weather and hazard information. KPDX and APPROACHES...Upper level smoke will continue over the next 24 hours, with increasing offshore flow this afternoon and evening. This offshore wind event will bring very gusty east winds to the terminal beginning late Monday afternoon, with occasional gusts to around 50 kt expected late this evening through tonight. Very strong low level wind shear on the order of 30-50 kt over 1000-2000 feet will likely be present over the terminal for much of the night. -TK/DDH && .MARINE...An unusually strong and impressive offshore wind event is expected to unfold this evening and continue through Tuesday night. Easterly wind gusts between 25 and 30 kt should be widespread across the waters, with a few gusts approaching 35 kt. Pockets of stronger Gale Force wind gusts will be possible downwind of the coastal river gaps such as the mouth of the Columbia River, Tillamook Bay, and Yaquina Bay. This will bring another round of steep, choppy seas as wave heights rise to 7 to 9 ft with a period around 8 seconds. Therefore, a Small Craft Advisory is in effect for all waters through this evening through Tuesday night. Offshore flow should weaken considerably on Wednesday as the surface pressure gradient begins to relax over the waters. This should result in winds falling below advisory thresholds and seas dropping below 5 ft. By late Wednesday, low pressure is forecast to drift off the Oregon coast and bring southerly winds across the waters Thursday into Friday. -TK/DDH && .PQR WATCHES/WARNINGS/ADVISORIES... OR...Red Flag Warning until 8 PM PDT Wednesday for Central Oregon Cascade Foothills-Central Oregon Coast-East Slopes of the Central Oregon Coast Range-Mt. Hood National Forest West of Cascade Crest-North Oregon Cascade Foothills-North Oregon Coast-North Oregon Coast Range-Willamette National Forest-Willamette Valley. High Wind Warning until 1 PM PDT Tuesday for Coast Range of Northwest Oregon-Greater Portland Metro Area-North Oregon Coast-Northern Oregon Cascade Foothills-Northern Oregon Cascades. Heat Advisory until 11 PM PDT Tuesday for Central Coast Range of Western Oregon-Central Oregon Coast-North Oregon Coast. WA...Red Flag Warning until 8 PM PDT Wednesday for Clark County Lowlands-East Willapa Hills-Eastern Gifford Pinchot National Forest Mt Adams Ranger District-Extreme South Washington Cascades and Foothills-South Washington Coast and West Willapa Hills. High Wind Warning until 1 PM PDT Tuesday for Greater Vancouver Area-South Washington Cascade Foothills-South Washington Cascades. PZ...Small Craft Advisory until 5 AM PDT Wednesday for coastal waters from Cape Shoalwater WA to Florence OR from 10 to 60 NM. Small Craft Advisory until 5 AM PDT Wednesday for coastal waters from Cape Shoalwater WA to Florence OR out 10 NM. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland
Area Forecast Discussion
National Weather Service Reno NV
326 PM PDT Mon Sep 7 2020 .SYNOPSIS... Gusty winds develop this afternoon and evening along with much cooler temperatures Tuesday behind a dry cold front. Low temperatures will fall to near or below freezing in Sierra valleys, with 30s in colder lower valleys, Wednesday and Thursday. It is expected to warm back to well above average for the latter part of the week. && .DISCUSSION... Smoke and haze from fires in California continue to engulf the area this afternoon. These conditions look to improve for the Eastern Sierra and western Nevada tonight as a strong dry cold front moves across the region. The HRRR and other high spatial/temporal resolution models are showing a strong burst of wind with the FROPA, which is expected to push into Pershing and Churchill counties by 6- 9 PM. A Blowing Dust Advisory was issued for much of western Nevada this evening into Tuesday morning as 40-50 mph wind gusts are expected to loft dust off the playas and dry lake beds. These winds will bring continued fire weather concerns. For more details, see the Fire Weather discussion below. Behind the strong cold front, temperatures are expected to cool down markedly. Tuesday afternoon`s high temperatures will be at least 15- 25 degrees cooler compared to Monday afternoon`s highs, with highs in the upper-60s to mid-70s expected areawide. Breezy easterly winds are expected Tuesday with the tightened pressure/temperature gradient across our region. Sierra ridgetops could gust over 45-50 mph. Temperatures will remain below normal Wednesday as east- northeast flow continues to usher in cool air. For the latter half of the week, an area of high pressure looks to build into our area, increasing temperatures to above average for this time of year. Afternoon highs will increase into the 80s for Sierra valleys and 90s for lower valleys of northeastern California and western Nevada. With clear skies, morning lows will be chilly in the lower valleys of the Sierra. Light slope driven winds look to make a comeback with dry conditions continuing. -Johnston && .AVIATION... Gusty north-northwest winds are expected this afternoon before a strong dry cold front pushes into the region, generating gusty north- northeast winds late this evening into early Tuesday. With this front passing quickly over the dusty playas and dry lake beds of western Nevada, blowing dust looks to become an issue with reduced visibility to 1/4 to 1/2 mile expected across much of western Nevada. Turbulence will also be possible ahead and behind the front. Easterly flow behind the front will push smoke and haze into central and southern California for the next day or two, which should improve slantwise and near-surface visibility. Calm and quiescent conditions are expected for the latter half of the week as an area of high pressure moves into the region. -Johnston && .FIRE WEATHER... * High Fire Danger continues today and Tuesday even with a significant decrease (20-30 degrees) in temperature. Hot and unstable conditions will dramatically disappear over the next 24-48 hours as a cold front drives through the Great Basin. Plan for gusty winds through Tuesday evening for many areas, as well as extremely dry conditions even overnight. Winds have begun to increase across NE CA and NW NV already this afternoon and will spread across the Sierra and western Nevada through tonight. Peak winds will likely occur during the overnight hours as the cold front passes through Nevada with steady north winds forecast for western NV valleys tonight. Northern Sierra ridge gusts could reach 50+ mph late tonight and Tuesday morning, increasing the threat for critical conditions from the Tahoe Basin northward to Plumas and Lassen counties. Winds should start to diminish late in the day Tuesday, though models have trended higher for winds Tuesday afternoon. Afternoon humidity will drop down to 5-15% and may not recover much above 25- 30% for most of western NV and mid and upper slopes of the Sierra due to the very dry air and gusty winds. Critical fire weather conditions may persist all day Tuesday with east winds impacting the mid slopes and the ridges through Tuesday evening. High pressure returns to the region again mid-late this week with temperatures warming back up into the 80s for the Sierra and 90s for western NV. Winds should be light. Brong/Edan && .REV Watches/Warnings/Advisories... NV...Blowing Dust Advisory until 5 AM PDT Tuesday NVZ001-003>005. Red Flag Warning until 5 AM PDT Tuesday NVZ420-423-429-458. Lake Wind Advisory until 11 AM PDT Tuesday for Washoe Lake in NVZ003. Lake Wind Advisory until 5 AM PDT Tuesday NVZ001. Red Flag Warning until 8 PM PDT Tuesday NVZ421. Lake Wind Advisory from 3 AM to 8 PM PDT Tuesday for Lake Tahoe in NVZ002. Lake Wind Advisory until 5 AM PDT Tuesday NVZ004. CA...Red Flag Warning until 5 AM PDT Tuesday CAZ270-278. Red Flag Warning until 8 PM PDT Tuesday CAZ274. Lake Wind Advisory until 11 AM PDT Tuesday CAZ073. Lake Wind Advisory from 3 AM to 8 PM PDT Tuesday for Lake Tahoe in CAZ072. Red Flag Warning from 5 AM to 8 PM PDT Tuesday CAZ271-272. && $$ For more information from the National Weather Service visit... http://weather.gov/reno