Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/18/23

National Weather Service Bismarck ND
946 PM CST Fri Feb 17 2023 .UPDATE... Issued at 946 PM CST Fri Feb 17 2023 Once again only minor changes were made with this update, mainly blending observed trends and recent guidance into the overnight forecast. HRRR, GLAMP, and NBM guidance has trended to a rather dispersive signal for any fog, and probabilities of formation have fallen to around 20% as of this writing, so we once again held off introducing it to the forecast. Regional 00 UTC RAOBs showed less dry air aloft and stronger winds above the ground than typically associated with radiation fog profiles, too. Radar imagery shows some echoes developing in northeastern MT as midlevel warm air advection begins, but our confidence in these being manifest as any precipitation at the ground is too low to add any chance of that to the forecast at this time, either. UPDATE Issued at 552 PM CST Fri Feb 17 2023 Only minor changes were made with this update cycle. Mixing has begun to subside with the approach of sunset and winds are thus diminishing as expected. The Williston/Williams County radar is showing a few light returns in that area so we have continued a mention of flurries over northwest/north central ND this evening as a weak impulse crosses the area. Otherwise, recent HRRR runs have suggested fog could develop overnight in south central ND, but GLAMP and NBM probabilities of its development are only in the 40% range, so we haven`t added it to the forecast yet. && .SHORT TERM...(This Evening through Saturday night) Issued at 343 PM CST Fri Feb 17 2023 Mild conditions are expected again on Saturday with some very light snow possible Saturday night. In the upper levels this afternoon, a broad longwave trough was located across southern Canada with an open shortwave crossing southern Saskatchewan and Manitoba. The associated surface pressure response has created breezy to windy conditions this afternoon across western and central North Dakota, with a wind shift provided by a kink in the pressure field as winds shift to the northwest while the trough passes. The weak cold air advection associated with this trough will be overtaken by another warm air push on Saturday with 850mb temperatures reaching or exceeding 0 C in southern North Dakota. High temperatures will be mild again in the 30s to lower 40s, but with lighter winds. Light snow will be possible Saturday night as the low associated with the earlier warm air push crosses northern North Dakota but ensemble probabilities of greater than one inch of accumulation are low. .LONG TERM...(Sunday through Friday) Issued at 343 PM CST Fri Feb 17 2023 A pattern change towards much colder temperatures with chances for snow next week highlights the long term forecast period. Modestly cooler temperatures are expected Sunday behind the previous low. Then a clipper moves across the state Sunday night through Monday with accumulating snow more likely across the north and east. Greater than 50% probabilities of one inch or more of snow stretch from northwest North Dakota through the northern James River Valley, maximizing over the Turtle Mountains and north central where higher probabilities of greater than two inches also exist. With this clipper comes increased northwest winds during the day Monday, especially for the western and southern areas of the surface low. The overlap of 850mb winds and cold air advection may allow for surface winds to approach advisory criteria, and even more of an impact, combine with the falling snow to potentially create blowing snow where greater winds and snow coincide. Tuesday begins a period of two sets of snowfall chances. A transition to zonal flow brings a speed max across a tight baroclinic zone on Tuesday, draped from Montana across the Dakotas. There remains moderate model uncertainty regarding the north- south placement of this baroclinic zone and the subsequent axis of accumulating snow with a washed out probability field from the NBM. Then through midweek a more significant western CONUS trough develops with a Colorado low ejecting through the region Wednesday- Thursday. Again the northern extent of potentially heavy snowfall is in question, especially with a surface high building through the Dakotas as it passes. The ensemble signal for heavy snow is more apparent with this low, where greater than 50 percent probabilities of at least 6 inches of snow is across South Dakota through southern Minnesota. That isn`t to say there isn`t room in the ensemble field for heavy snow to shift north into North Dakota but as described by the previous shift, the probabilities favor south of the border or especially south of the North Dakota I-94 corridor. The surface high previously mentioned will also be associated with an Arctic airmass impacting the region Tuesday through Friday. By Wednesday highs should struggle to exceed zero degrees and widespread wind chill hazards look possible each night Wednesday through Friday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday Evening) Issued at 946 PM CST Fri Feb 17 2023 VFR conditions will likely prevail through most of the 00 UTC TAF cycle across most of western and central ND. There`s a low, 20% chance of IFR fog or stratus developing tonight and early Saturday over central ND, but those odds have decreased and so we continue to refrain from including any mention of that in the TAFs. Winds will be light overnight and tend south to southwest mainly around 10 kt on Saturday. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...CJS SHORT TERM...AE LONG TERM...AE AVIATION...CJS
Area Forecast Discussion
National Weather Service Burlington VT
931 PM EST Fri Feb 17 2023 .SYNOPSIS... Light snow tapers off early this evening giving way to a seasonably cold and mostly sunny Saturday. Above normal temperatures return for Sunday into early next week before a cool down mid week. The weather pattern is generally quiet with a couple of weak systems bringing light snow and rain showers before a potential storm system arrives on Thursday. && .NEAR TERM /THROUGH SATURDAY NIGHT/... As of 926 PM EST Friday...Made some additional minor tweaks to pops and temp grids thru midnight. This included continuing chc pops on the east side of the CPV associated with northerly flow, caa, and some enhanced moisture from Lake Champlain. Radar shows several weak streamers that have been impacting the BTV area with vis btwn 3-5sm and just minor snow accumulations. As ridge axis builds into cwa, winds aloft become more westerly and better moisture wl dissipate so anticipate areal coverage to decrease aft midnight. Any lingering snowfall accumulations wl be a dusting to 0.5" at most. Otherwise, did note the new 00z HRRR is dropping parts of the SLV temps to near 0F, so have made a minor lowering of temps acrs this region. Rest of the fcst in good shape this evening. Previous discussion below: Forecast has panned out really well for a multi-faceted storm system, one that has our CWA straddling both the cold and warm sectors. The main message for early this afternoon is that the freezing rain threat is now over, with pretty much the entire area below freezing and changed over to snow. Noted that Springfield in southeast VT is still at 33F as of this writing, but webcams in Mendon show even the southern Greens changed over to snow. We opted to let the Winter Weather Advisories expire for all our zones with only an additional inch of snow accumulation expected. The clearing line now almost all the way to the St Lawrence valley per the visible satellite imagery. For the remainder of this afternoon, snow showers continue especially for the eastern Champlain valley, BTV and the western slopes of the Greens due to blocked flow, with the Froude number remaining in subcritical threshold below 0.5 per the NAM guidance. The additional snow is great news as it provides traction on surfaces that might have frozen over or coated with a thin layer of ice underneath. Winds will also be gusting 25-30 mph out of the northwest as low level lapse rates steepen with the air aloft cooling. It certainly feels a lot more like winter out there with wind chills falling into the single digits and teens after we had a tease of spring over the last few days. Any lingering mountain snow showers will wind down overnight tonight as ridging and drier air move into the region. Clearing skies and subsiding winds along with a bit of fresh snow will allow temperatures to drop into the single digits in many locations, with just the Champlain and lower Connecticut Valleys remaining at or above 10F. H5 ridging moves overhead tomorrow, with its axis shifting to our east by mid/late afternoon. Overall expect it should be a rather nice day with plentiful sunshine, though it could be a bit breezy with increasing south/southwest flow around the back of the high, especially in the St Lawrence and Champlain Valleys due to channeling or Bernoulli effect. Also, the clouds could return for the St Lawrence valley in the afternoon but it stays mostly sunny elsewhere. Otherwise, we will see partly to mostly sunny skies and highs in the upper 20s to mid 30s, which is actually right about where we should be for this time of the year. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 300 PM EST Friday...Quiet weather for Sunday as low level ridging slowly progresses east and offshore. As such, partly sunny skies and nil PoPs look good for now. Southerly flow will set up, boosting temperatures into the upper 30s/lower 40s area wide under partly sunny skies. A broad increase in clouds is expected Sunday night ahead of our next frontal system, but conditions should remain dry. Lows holding mild under continued south flow - mainly 30s. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 300 PM EST Friday...Scattered/numerous rain/snow showers then on tap for Monday/Monday evening with passage of the aforementioned front, with frozen precip favored in elevated terrain during the day, and area wide Monday evening before tapering off under modest cold thermal advection. Any accumulations should be light. A few additional/scattered rain snow showers then possible again on Tue/Wed with the passage of another weak system, the Euro being the most bullish among this morning`s deterministic output. Temperatures remain seasonably mild through this mid week time frame with highs in the mid 30s to lower 40s. Thereafter, a larger system tracking east-northeast from the central states will likely affect the area later next week with the potential for a variety of precipitation types. This morning`s Euro is the coldest with mainly snow, with the GFS/GEM camps on the milder side showing snow transitioning to a mix. Time will tell how this pans out. For now have leaned toward blended national guidance, which leans a bit toward the colder Euro idea. Behind this system, indications suggest a period of colder weather by next weekend. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... Through 18Z Saturday...Mix of MVFR and VFR conditions will trend VFR through 12Z as low clouds gradually scatter. Wrap around snow showers from departing low pressure system should diminish as moisture thins over the next few hours with improving visibilities at SLK and MPV, where occasional IFR visibilities are still possible through 04Z. As a surface ridge continues to build in, northwest winds in the 7 to 14 kt range will diminish overnight. Winds then become southwesterly mainly 5 to 10 kts after 12z, and on the breezy side at MSS and SLK with 20-25 kt gusts after 15z. The favorable fetch of moisture off Lake Ontario could induce enough low level moisture for MVFR ceilings after 18Z, but for now have indicated SCT deck at MSS until confidence increases. Outlook... Saturday Night: VFR. NO SIG WX. Sunday: VFR. NO SIG WX. Sunday Night: VFR. NO SIG WX. Washingtons Birthday: Mainly VFR, with areas MVFR possible. Chance SHRA, Chance SHSN. Monday Night: Mainly VFR, with areas MVFR possible. Chance SHSN. Tuesday: VFR. Chance SHSN, Slight chance SHRA. Tuesday Night: Mainly VFR, with local IFR possible. Slight chance SHSN. Wednesday: VFR. Slight chance SHSN, Slight chance SHRA. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...None. && $$ SYNOPSIS...Chai NEAR TERM...Chai/Taber SHORT TERM...JMG LONG TERM...JMG AVIATION...Chai/Kutikoff
Area Forecast Discussion
National Weather Service Grand Forks ND
950 PM CST Fri Feb 17 2023 .UPDATE... Issued at 949 PM CST Fri Feb 17 2023 Clouds and not much else have been the main impacts from the shortwave that is currently pushing into northern ND. Not much in the way of flurries seen in obs or on web cams, and although there are a few weak radar returns in the far west it seems not much is reaching the ground. Temps have been staying in the teens to 20s, and continue to think readings will stay above zero overnight. UPDATE Issued at 547 PM CST Fri Feb 17 2023 Adjusted cloud cover a bit for current satellite trends, but overall forecast seems on track. Still think we will get some flurries later tonight as a weak clipper pushes into the area. Agree with previous shift that impacts seem minimal. && .SHORT TERM...(This evening through Saturday night) Issued at 228 PM CST Fri Feb 17 2023 Overview: Impacts in the short term are minimal, with the introduction of two systems out of a zonal flow. First moves through tonight, with the second Saturday night into Sunday afternoon. Each brings the chance for some snow. Blowing/drifting snow will be possible, but looks to be on the little to no impact side. Today - Saturday morning: System tracks through southern Canada this afternoon and overnight bringing stronger winds to eastern ND and NW MN. Daytime mixing and temperatures in the 20s to 30s have allowed for some areas to gust up to 30mph on a isolated basis. There is little to no impacts associated with blowing/drifting snow as the snowpack is fairly crusted over. As we loose daytime heating winds will slowly subside, but chances for some flurries or a light snow shower will increase along and north of Highway 200. Chances are low (20-30%), but still noticeable in CAMS and HRRR guidance. Thus, added some flurries Highway 200 northward from 00z through 07z as the system moves through. Little to no impacts are expected from the flurries or breezy conditions. Saturday afternoon - Sunday: Temperatures warm into the 20s to lower 30s Saturday afternoon, with clouds lingering around the area ahead of another system moving in by Saturday night into Sunday. Another clipper translates across the northern plains bringing some breezy north winds and light accumulating snow for areas in eastern ND and NW MN. Winds have the potential to gust up to 35mph during the daylight hours Sunday. Snow accumulations look to remain light, with up to an inch possible for areas along and north of Highway 2. Best chances to see up to an inch will be toward Lake of the Woods. Blowing/drifting snow should be minor in impacts, with some light pillow drifts possible and slight reductions to visibility from the newly falling snow. This looks to be a quick window of breezy winds as by the evening guidance has the winds subsiding ahead of another system moving in by Monday. .LONG TERM...(Sunday through Friday) Issued at 228 PM CST Fri Feb 17 2023 Key Messages: -Light snow and gusty winds will introduce some wintry impacts for much of the region late Sunday into Monday, especially impacting the Monday morning commute. -Much colder air arrives Tuesday - Friday. -While high uncertainty remains, a potentially impactful winter weather system is expected to affect the northern Plains across the middle of the week. Sunday night into Monday System... The next successive shortwave is progged to impact the region late Sunday into Monday. This system looks to pack a little more of a punch than the Saturday night system. Ensemble guidance is beginning to gain more certainty in the surface low position. Over 90% of ensemble guidance is indicating a surface low developing over eastern Montana and traveling within the mean flow into eastern North Dakota and northwestern/west central Minnesota. As a result, there is increasing confidence in a swath of light snow extending across much of the forecast area. Latest NBM probabilities of exceeding 1" of new snow with this system are in the 40-60% range from the I-94/Highway corridor southward, with 70-90% probabilities from I-94 northward toward the international border. There remains a low, 10-15%, chance for probabilities of exceeding 4". As a result, looking at a generalized area of 1-3 inches of new snowfall. Gusty winds out of the north-northwest are also expected to accompany this system. While light, with a new, blowable snowpack likely to fall, blowing and drifting snow will be possible throughout the day on Monday. Otherwise, with winds shifting to a northwesterly direction, stout CAA is expected to work into the region beginning Monday night and lasting through the remainder of the week. Highs in the single digits on either side of zero and lows well below zero will likely result in at least advisory criteria wind chills throughout the week ahead. Regardless, there will be increasing chances for snow from Wednesday into Thursday. Wednesday into Thursday System... After a brief reprieve on Tuesday, an upper level pattern shift will begin to work into the northern Plains. Cluster analysis continues to indicate a deepening upper low building in over the western CONUS. The degree of deepening will have a large bearing on how the flow pattern evolves over the northern Plains. A stronger upper low would yield more southwesterly flow aloft, while a weaker upper low would yield more zonal flow aloft. While subtle, these differences will have a strong determination on eventual storm track and evolution. Latest ensemble guidance hints at an increasing likelihood of the surface low tracking across the central Plains, while the upper low tracks to the north of it. This upper low track looks to introduce wintry impacts to the region as a result. Latest NBM probabilities of exceeding 1" are in the 25-50% range from the international border toward the Highway 200 corridor, and the 60-90% range from the Highway 200 corridor southward (increasing probabilities further southward). Furthermore, NBM probabilities exceeding 4" are in the 50-70% range from the I-94 corridor southward, with still 30-40% probabilities of exceeding 8", lending credence to the idea that there may be higher snowfall totals possible with this system. This does look to be a rather progressive system, but given the strong nature of it, could yield some higher impacts across the region. As a result, will continue to monitor latest trends in ensemble guidance as details become clearer. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 547 PM CST Fri Feb 17 2023 Currently VFR with diminishing winds. Several of the model solutions bring quite low IFR ceilings down into the Red River Valley and western MN, but given upstream obs this seems a bit overdone. Do have ceilings going down to MVFR later tonight into tomorrow morning, but will keep IFR out for now. Winds will continue to drop, eventually shifting to a more southerly direction and picking up to near 10 kts by the end of the period. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...JR SHORT TERM...Spender LONG TERM...Rick AVIATION...JR
Area Forecast Discussion UPDATED
National Weather Service Hanford CA
435 PM PST Fri Feb 17 2023 .Update to Air Quality Issues Section... .SYNOPSIS...Dry conditions will continue across the area through the holiday weekend. Above normal temperatures will return to the area as well. Chances for rain and snow will come in on Tuesday night and Wednesday with much cooler temperatures expected across the area by Wednesday. Unsettled weather with cooler than normal temperatures and showery conditions will prevail next Thursday and Friday. && .DISCUSSION...Central CA is currently under a southerly flow between an upper ridge over the Great Basin and an upper low off the central CA coast near 130W which is currently dropping southward. Satellite imagery is showing high clouds being pulled up northward into our area, but dry air in the lower and mid layers are maintaining dry conditions across our area. SREF is indicating that the offshore low will continue dropping southward to off the Socal coast tonight and further south to off the Baja coast by Saturday. The result of this will be continued dry weather across our area along with more high clouds. While MOS guidance is indicating that minimum temperatures in the San Joaquin Valley tonight will approach the freezing mark, NBM probabilistic guidance is indicating the chances of sub-freezing temperatures in the outlying areas of the San Joaquin Valley on Saturday morning are at 40 percent or less so have decided not to issue a Freeze highlight. Have also noticed the DESI HRRR is showing a continuation of the upper level moisture surge across our area tonight suggesting more high clouds streaming over our area. This will keep likely keep minimum temperatures up by a few degrees from MOS guidance. The SREF is showing the offshore low slowly approaching the Baja coast between Saturday night and Monday night with a ridge axis extending inland into central CA. This will result min a warming trend across our area through the holiday weekend with the latest NBM probabilistic guidance indicating the most of the San Joaquin Valley will have between a 35 and 55 percent chance of temperatures exceeding 70 DEG F on Presidents Day. The offshore low is progged to move inland into northwestern Mexico by next Tuesday as an anomalously cold upper trough drops south ward out of the Gulf of AK and into the PAC NW. This trough will drop further southward into central CA on Tuesday night and Wednesday and bring much cooler temperatures to our area along with chances of precipitation. NBM is indicating that high temperatures on Wednesday in the San Joaquin Valley will generally be in the lower 50s just two days after approaching the 70 DEG F mark. QPF progs are showing the Sierra Nevada will pick up between half an inch and an inch of liquid precipitation between Tuesday night and Wednesday night while the adjacent foothills pick up between a quarter inch and a half inch during the same time frame. Rain shadowing will limit precipitation in the San Joaquin Valley to generally a tenth of an inch or less at most locations. Snow levels are progged to plummet from 5000 to 6000 feet at the onset of the event on Tuesday night to below 1000 feet by late Wednesday night. Another cold trough is progged to drop southward over CA on Thursday and Friday which will maintain below normal temperatures and chances of precipitation across the area through the end of next week. The biggest concern for this period will be with low snow levels is that travel will be impacted over the Sierra foothills and over the major passes in the Tehachapi Mountains between Wednesday and Friday of next week. QPF projections are suggesting that between 3 and 6 inches of new snow could accumulate in Mariposa, Oakhurst and Three Rivers and accumulating snow could also impact the Tehachapi, Lebec and Frazier Park areas. Probabilistic guidance is even indicating a 40 to 50 percent chance of subfreezing minimum temperatures across much of the San Joaquin Valley next Thursday and Friday mornings while precipitation remains very much possible. As a result, freezing precipitation and/or light snow cannot be ruled out for the San Joaquin Valley next Thursday and Friday mornings. However, a lot of spread still exists amongst the medium range ensemble members concerning the exact track of the second trough next week which reduces forecaster confidence for the latter portion of next week. && .AVIATION...VFR conditions will prevail across the central California interior for the next 24 hours. && .AIR QUALITY ISSUES... ISSUED: 02/17/2023 14:15 EXPIRES: 02/18/2023 23:59 On Saturday February 18 2023, Fireplace/Wood Stove Burning Status is: No Burning Unless Registered in Fresno, Kern, Kings, and Madera Counties. Burning Discouraged in Merced and Tulare Counties, and Kern (Greater Frazier Park Area) and Sequoia National Park and Forest. && .CERTAINTY... The level of certainty for days 1 and 2 is medium. The level of certainty for days 3 through 7 is low. Certainty levels include low...medium...and high. Please visit for additional information and/or to provide feedback. && .HNX WATCHES/WARNINGS/ADVISORIES...None. && $$ public/aviation/fire wx...DAS pio/idss...JEB
Area Forecast Discussion
National Weather Service Pocatello ID
120 PM MST Fri Feb 17 2023 .SHORT TERM...Tonight through Sunday. Early afternoon satellite imagery was showing a broad upper ridge across the NE Pacific with a well defined short-wave disturbance riding over the ridge into SW Alaska. Numerical models drive this disturbance SE through British Columbia tonight and into/through the NRN Rockies Saturday afternoon through Sunday afternoon. Current forecast snowfall accumulations for Saturday afternoon through Sunday afternoon fall between the 75th and 90th percentile of ensemble members for that time frame and are satisfying Winter Weather Advisory criteria across a broad swath of the ERN mountains (5-10 inches) and eastern foothills from Pocatello through St Anthony (3-5 inches) in a moderately moist upslope NW flow. Light snowfall is expected to linger into Sunday afternoon and evening as we continue to see moisture streaming over the ridge ahead of the next impactful storm system set to arrive Monday night/Tuesday. You can get all the specifics on that system in the Long Term section below. Temperatures should moderate tonight as clouds overspread the region ahead of the first disturbance and remain seasonably cool through Sunday. Huston .LONG TERM...Sunday night through next Friday. We continue to expect a significant, long-duration winter storm system to impact SE Idaho for much of the upcoming week, with the greatest impacts currently focused in the Mon afternoon through Wed eve timeframe. This complex event will begin as an atmospheric river-supported NW stream of moisture feeding across the nrn Rockies Mon and Tue, transitioning into some sort of closed mid-level low riding down the back/west side of a Canadian parent low and setting up shop near our area Wed, transitioning into the overall associated trough elongating SW toward CA with potentially multiple embedded low pressure centers or at least a split-trough pattern at play Thu and Fri...(so the flavor you should be taking from all this is "long duration shenanigans" and "lots of moving parts"). The 12z suite of long-range deterministic models don`t currently bring the overall trough axis through SE Idaho until sometime Fri or Fri bonafide end to precip chances is foreseen until this happens! (Even then, early signals are another system may be on the heals of this one out toward next weekend.) Confidence is still relatively low in the exact mechanics of many of these moving parts (including tracks and positions), which will have a major impact on resultant timing of heaviest precip, snowfall totals for a given location, and wind. The ECMWF remains noticeably drier overall compared to the wetter GFS (which is also potentially skewing EC-based EFI/SOT values), and while 500mb height cluster analysis isn`t in terrible disagreement Wed, by Thu and Fri multiple scenarios are at play, especially in regard to how far SW the overall trough elongates. We`ll also note that today`s deterministic runs bring the closed mid-level low much closer to/over our CWA compared to yesterday (so things are still changing a bit in the guidance), and that as far as ending this system...all ensemble clusters currently keep the trough axis either over or west of our CWA through at least Fri. We really need to continue monitoring some trends here before getting too specific on exact numbers/details, but a few other useful things on our mind at this juncture: 1) Most of this system will favor heavy snowfall in areas that perform well on deep-layer WNW flow, 2) Warmer high temps in the 40s Mon from Pocatello west across Shoshone, Burley, and Malta would favor rain for the first day of the system and potentially hold accumulations near zero here until Tue, 3) Tue high temps have ticked up a few degrees in the forecast, increasing uncertainty in this same corridor on snow accumulations for day 2 of the event as well, 4) The blowing/drifting snow signal remains solid throughout Mon-Wed with WSW winds gusting 30+ MPH, which would be especially problematic almost everywhere outside of the warmer corridor just discussed until sometime Tue/Tue night, and then everywhere Wed, 5) The overall flavor of this system still looks to target the mntns/highlands near and east of I-15 for the most significant accumulations...potentially measured in feet at least from the passes up into the backcountry, and finally 6) Depending on the exact track of the low, there is some low-confidence potential in a Snake Plain convergence band Wed AM which could enhance snowfall totals in the plain. Right now, the NBM 3-day probability of exceeding 4 inches of snow is 60-90% across ALL of our mntns, and 10-30% for places like Pocatello, Idaho Falls, and Rexburg. We continue to encourage everyone to stay tuned as the forecast evolves over the next few days, and bear in mind that widespread travel impacts will be very possible in the Mon afternoon through Wed eve (if not into Thu) timeframe. We`ll dig into better specifics on timing, accumulations, and winds as the event approaches. Colder temps are likely toward the end of this system Thu-Fri, although perhaps not quite as cold as what we just saw over the past several days. - KSmith && .AVIATION...A departing ridge of high pressure will maintain relative control of our wx through the 18z TAF period (through Sat AM), maintaining dry, partly sunny, VFR conditions with very light winds less than 10kts and just some high clouds drifting through at times. Fog/low stratus potential is low again tonight/Sat AM, with the HRRR once again the most aggressive among the guidance envelope and favoring the Arco Desert region. Thus, have again hinted at this at KIDA with VCFG and SCT005 (we saw very BRIEF issues this this last night/this AM). Sat afternoon/eve, expect a shortwave trough to spread snow across the region, along with a bit more wind initially out of the SW. MVFR cigs/vsbys are likely at most terminals by late afternoon or early eve with this system. - KSmith && .PIH WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 11 AM Saturday to 11 AM MST Sunday for IDZ053-054-058-060-062-063-065-066. Winter Storm Warning from 11 AM Saturday to 11 AM MST Sunday for IDZ064. && $$
Area Forecast Discussion
National Weather Service Phoenix AZ
447 PM MST Fri Feb 17 2023 .UPDATE... Updated Aviation && .SYNOPSIS... High pressure over the Intermountain West will help bring breezy to windy conditions today, especially at higher elevations. As an upper- level ridge builds across our region, a gradual warm up will occur for the weekend. Uncertainty remains regarding our next system for early next week, which will meander off the California Coast for the next several days. A stronger system has a chance to bring gusty winds and an elevated chance for rain Wednesday. && .DISCUSSION... Cool, dry air will stick around today and keep temperatures below normal with highs in the middle to upper 60s. High pressure over the Intermountain West has caused the surface pressure gradient to tighten over Central Arizona creating windy conditions. On the east side of our CWA, for the high terrain areas, a Wind Advisory remains in effect until 3 PM MST today, but it is unlikely that it will be extended as most areas in the original advisory will start to see winds diminish this evening. Latest HRRR runs show some higher terrain areas may continue to see isolated 40 mph gusts tonight. In the lower elevations of South-Central Arizona, winds will not be as strong, but gusts 20-25 mph will last through tonight, especially for areas immediately east of Phoenix. These winds will cause difficult driving conditions at times and some minor impacts can be expected where gusts remain elevated. Heading into the weekend, low-amplitude ridging will bring us a gradual warming trend. The latest NBM and HRRR models show temperatures slightly above normal with highs forecasted in the lower to mid 70s Saturday. It will still be breezy over the higher terrain of our eastern CWA. Probabilities of wind gusts exceeding 30 mph will be >80% through around 08Z before decreasing further. By Sunday, high temperatures will once again be in the low to mid 70s. Mid to high level clouds will move out of the region Saturday morning and conditions will be clear for the remainder of the day. Sunday morning looks to be clear as well until more mid to high clouds spread over the region Sunday afternoon. Looking ahead to next week, ensemble clusters show uncertainty surrounding the timing of our next system. A low pressure center will spin off the West Coast and remain there over the weekend. This system is expected to move over our region beginning early next week. Some clusters show the onset of the system beginning Monday, while others show a Tuesday time frame. Latest NBM forecasts have temperatures remaining slightly above normal for Monday and Tuesday. However, model spread remains due to the uncertainty of the timing of the previously mentioned system. PoPs for this system remain low (5-20%) Mon-Tues. The GFS along with model clusters show a more vigorous trough moving through the Great Basin starting Wednesday. Temperatures associated with this system may run around 10 degrees below normal. As of now, windy conditions are possible across most of South-Central Arizona and Southeast California, along with an increased chance of precipitation (40-70%) for the eastern areas of our CWA. && .AVIATION...Updated at 0000Z. South-Central Arizona including KPHX, KIWA, KSDL, KDVT: Gusty east winds will be the primary weather issue through Saturday morning under periods of thicker high cigs. Just off the surface, E-SE winds at 20-40kts will pick up overnight. KIWA has the highest potential to reach LLWS potential for the TAF. While not as strong Saturday, the east component should prevail well into the late afternoon. Winds turn to southerlies around sunset before becoming light and variable Saturday night. Southeast California/Southwest Arizona including KIPL and KBLH: No major weather issues should exist through Saturday morning under periods of thicker high clouds. At KBLH, north winds will be preferred the majority of the period, becoming southerly Saturday afternoon. At KIPL, there also may be a tendency for directions to back more westerly after sunset. After sunrise winds will be light and variable. && .FIRE WEATHER... Below normal temperatures are expected this morning before a gradual warming trend takes hold this weekend due to building high pressure across the west. Temperatures will be at or above normal by Saturday. Below normal RHs are expected the next few days, generally bottoming out around 15-20 percent each afternoon. Surface wind speeds are expected to increase this morning, bringing breezy conditions to south-central Arizona through this afternoon. Lighter wind speeds will return through the rest of the weekend into early next week. Meanwhile, a low pressure system will meander in the eastern Pacific early this weekend, however there is some uncertainty with regard to if and when impacts and precipitation will next affect the Desert Southwest. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...Worley AVIATION...Macfarlane/Heil FIRE WEATHER...Leffel
Area Forecast Discussion
National Weather Service Pueblo CO
251 PM MST Fri Feb 17 2023 .SHORT TERM...(This evening through Saturday) Issued at 251 PM MST Fri Feb 17 2023 Key Messages: 1) Saturday is looking warmer and breezier for most with increasing cloud cover. 2) Damaging winds are possible for our southern Sangres and the southern I-25 corridor, beginning tomorrow afternoon. Currently.. Water vapor imagery shows us wedged in between three main features that will influence our weather over the next 24 hours. A departing trough is pushing off to our east, with a longwave trough axis to our north. Another low is present off the coast of Baja, California. This leaves us under a ridge of high pressure, with clear skies, warming temperatures and downsloping winds prevailing across much of our forecast area. Most of our plains locations have warmed into the low 30s as of 2pm. Visible satellite imagery reveals a lot of snowpack melting this afternoon as well. Rest of Tonight and Tomorrow.. Downsloping winds will continue to keep temperatures slightly warmer for our banana belt locations tonight, with most of these locations only dropping into the mid and upper 20s. Further east, especially through the Arkansas River Valley, we`ll see lows falling into the teens above zero, with another night of single digits and teens below zero expected for the high country. Tomorrow.. As the ridge breaks down overhead through tomorrow morning, an embedded shortwave trough moves in by tomorrow afternoon. This shortwave trough will interact with the longwave trough north of us, and the low coming onshore over the Baja peninsula throughout the day tomorrow, bringing increasing westerly flow and increasing cloud cover to our area. A combination of cloud cover and existing snowpack will likely keep daytime highs in the mid and upper 50s tomorrow on our plains. Westerly winds start to really ramp up across our southern Sangres tomorrow afternoon, as the jet axis approaches from our southwest. A High Wind Watch has been issued for the southern Sangres and the southern I-25 corridor from tomorrow afternoon until Sunday afternoon. .LONG TERM...(Saturday night through Friday) Issued at 251 PM MST Fri Feb 17 2023 Key Messages: 1. High Wind Watch in effect through 11am on Sunday morning for the southern Sangres, Huerfano, and Las Animas Counties. Wind gusts in excess of 60 mph are possible. 2. Heavier mountain snow possible from Tuesday through Thursday with the potential for snow over the mountain valleys and the plains, though still uncertain. Saturday Night and Sunday: A west to east oriented jet streak moves from south to north positioning itself in a favorable position for mountain wave activity over the southern Sangre de Cristo Mountains and the Spanish Peaks region Saturday evening through Sunday morning. Model sounding show a distinct mountain top inversion with a hint of reverse shear. There are varying outcomes from models with CAMs resolving the mountain wave. The 18z HRRR has an interesting output where it resolves a mountain wave at the beginning of the long term period, but as the night time inversion sets up the winds decrease, then once the inversion dissolves after sunrise on Sunday the strong winds return. The NAMNest on the otherhand keeps the strong winds from the mountain wave continuing through the overnight, then weakening as the inversion breaks but continuing throughout the day on Sunday. So overall, there is still a bit of uncertainty of what will occur, but we do have confidence that a mountain wave will form over the aforementioned region. The intensity and if the winds continue during the overnight will be the main point of uncertainty. There are some signals of a weaker mountain wave forming over western El Paso County, on the lee of the Ramparts, Pikes Peak, and Cheyenne Mountain. This wave would form a little later, after midnight, and wind gusts would be around 40 - 50 mph. Since this isn`t in the most favorable location, since the jet axis is a bit further south, we have excluded this from the High Wind Watch. We`ll keep reevaluating, though. Wind gusts during the late morning and evening will be from the west-northwest gusting from 35 to 45 mph, with the strongest winds on the western portion of the plains. Strong wind over the central mountain are expected on Sunday afternoon as well, which may reach close to High Wind Warning criteria winds. The mountain valleys are expected to have wind gusts around 40 to 45 mph on Sunday as well. Overall, a very windy day for most! Snow showers are expected over the Continental Divide, specifically over the Sawatch Range throughout the day on Sunday, but relatively minor accumulation of around 3 to 6 inches are expected. Low temperatures Sunday morning will be in the teens to 30s over the plains and the single digits to 20s over the mountain valleys, with the coldest temperatures being over the valley floor over the San Luis Valley and upper Rio Grande Valley. Plan on temperatures in the 40s to 50s over the plains and the 30s to 40s over the mountain valleys. I dropped max temperatures by a few degrees to incorporate snowpack, as well. Monday through Friday: We are monitoring the potential for a heavier mountain snow event from early Tuesday through Thursday. A long wave trough over the NW US is expected to interact with a closed low over the desert SW, the resulting model derived outcome from these interactions are a fairly potent SW to NE oriented jet streak funneling Pacific based moisture towards our mountains. These kind of interactions between two dynamic systems are hard to resolve via modeling, so we`ll have to keep an eye out, but we are have higher confidence of this storm occurring since the ensembles are in fair agreement. The EPS and GEFS total QPF through Thursday morning have in excess of 1.0" of liquid falling over the eastern San Juans. A cold front associated with this complex system is being resolved to propagate over the plains at some point on Wednesday, which may bring some snow over the plains, however, the main brunt of the QPF is staying over the NE plains of CO. Cold air is associated with the airmass proceeding the cold front, so some cold days and nights are possible Wednesday and onward. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 251 PM MST Fri Feb 17 2023 VFR conditions are expected at all three TAF sites, KCOS, KPUB, and KALS for the next 24 hours. Mid and upper-level cloud cover will increase through the period. Southerly and southwesterly winds gusting up to 25kt are expected at KALS tomorrow afternoon and evening. Increasing westerly winds are expected for KCOS and KPUB tomorrow as well, especially after 18Z tomorrow afternoon. && .PUB WATCHES/WARNINGS/ADVISORIES... High Wind Watch from Saturday afternoon through Sunday morning for COZ074-075-087-088-094. && $$ SHORT TERM...EHR LONG TERM...SKELLY AVIATION...EHR
...Update to aviation forecast discussion...

.DISCUSSION... Issued at 249 PM CST Fri Feb 17 2023 Key Points: - Very high fire danger Saturday, especially across east central and north central KS - Warm into early next week, some precip chances mid-week Low-amplitude upper ridge is beginning to make its way across the central Plains, leading to a warming trend in temperatures today and into the weekend. A closed low is noted in the eastern Pacific off the CA coast. At the surface, high pressure sits over TX/OK and a more robust low pressure system has developed in Manitoba/Ontario, leaving a trailing front into the northern Plains. The upper ridge quickly moves overhead tonight with a transition to southwest flow as we head into Saturday. Weak perturbations in the flow look to induce a deepening lee sfc trough, which results in a tightening pressure gradient across east central KS overnight and through the day Saturday. A 40-50 kt LLJ is also progged to move into the area during the morning and afternoon, then push east in the evening. Mixing up to 900mb plus the pressure gradient should allow for sustained southwest winds of 20-25mph with gusts of 30- 40mph, strongest along and south of I-70. This is also supported by HREF data. There could be isolated locations that reach wind advisory criteria, so wouldn`t rule out a headline if winds trend higher, but at this time this looks like a marginal concern not widespread enough to warrant a headline. The bigger story will be elevated fire danger as drier air is advected into the area from the southwest. (See fire wx section for further details.) Some high clouds moving in from the southwest could keep high temperatures down slightly, but think the winds should be enough to bring us into the 50s area-wide. A few models are hinting at light QPF in east central KS late afternoon and early evening as well. Think the dry air in the low-levels should prevent this from reaching the ground so have kept a dry forecast, but wouldn`t be surprised to see some virga develop. Sunday sees a transition to mainly zonal upper flow with lighter winds as the sfc trough moves across the area. This weak boundary looks to only have a small effect on temperatures with highs in the upper 40s near the KS/NE border while still reaching the 50s elsewhere. The aforementioned upper low is progged to slowly move into northern Mexico and eventually rotate into the southern CONUS while phasing into the northern stream trough. Precip chances increase Tuesday and more so Wednesday into Thursday, but plenty of uncertainty remains in the evolution of that system. Highs remain in the 50s and 60s until Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) Issued at 510 PM CST Fri Feb 17 2023 VFR conditions will continue in a dry lower troposphere and notable boundary layer mixing through the bulk of this forecast. Low-level jet development suggests at least some gusts will reach the surface through much of the nighttime period and should present more of a turbulence instead of wind shear situation. The stronger winds should reach the surface by 18Z and persist through the end of this forecast. && .FIRE WEATHER... Issued at 249 PM CST Fri Feb 17 2023 This morning`s 12Z sounding from DDC showed a dew point of 6 degrees, and some sfc obs in central and southwest KS have continued to show dew points in the single digits to low teens. Additionally, forecast soundings in our local area indicate very dry air aloft, especially above 900mb. So if we mix to 900mb or perhaps even a bit deeper, this could be problematic for fire weather. The RAP and HRRR are lowest on model guidance regarding RH, but they have generally been handling dew points well, so think those solutions aren`t necessarily far-fetched and shouldn`t be ignored. Have incorporated the 15Z RAP dew points into this forecast package and ended up with RH in the 20-25% range across much of the area. This is still on the low end of guidance, but would not rule out parts of north central KS dropping as low as 10-15% as RAP/HRRR have indicated. If we continue to trend lower on RH with the next forecast cycle, a Red Flag Warning may be needed. Currently, at least expect very high fire danger with 20-25% RH combined with southwest winds gusting 30-40mph. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Picha AVIATION...65 FIRE WEATHER...Picha