Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/02/23

National Weather Service Bismarck ND
934 PM CST Sun Jan 1 2023 .UPDATE... Issued at 922 PM CST Sun Jan 1 2023 03Z satellite and surface observations show a variety of ceiling heights and visibilities with low stratus in the east, stratus at 7k feet in the northwest, and patchy fog developing in the south central. The coverage of fog tonight is still uncertain, forecast soundings don`t really saturate in the lower levels and visibility guidance from the HRRR has backed off on the fog potential. Current forecast includes patchy fog for the forecast area, which seems fair with the current observations and potential. No changes needed with this update. UPDATE Issued at 528 PM CST Sun Jan 1 2023 Fog and stratus remain the forecast concern tonight. High-res visibility guidance produces fog that transitions from west to east as a surface high slides across the state tonight. With the center of the high in transition, how long dense fog persists is uncertain tonight. Will continue the fog potential inherited by the day shift and will adjust as fog develops later this evening. && .SHORT TERM...(This Evening through Monday) Issued at 159 PM CST Sun Jan 1 2023 Low level stratus, along with patchy fog, persists from, along, and east of northwestern ND through the James River Valley. That said, it has shown rapid areal decline over the past few hours and may continue to decrease through the remainder of the afternoon before possibly filling back in this evening. A mid level stratus deck in northeastern Montana may also encroach into the forecast area later this afternoon and evening. Finally, a thin and very translucent layer of high clouds off a west CONUS trough continues infiltrating the CWA, especially the southern half. More organized cloud cover should move into the southern half of the forecast area later tonight and Monday. One question for this evening into Monday morning is fog potential. Guidance suggests patchy fog should develop again this evening, especially in the south central, as winds become light and variable. Besides fog potential, expect mostly dry conditions, light winds, and partly to mostly cloudy skies through the period. Temperatures remain seasonable for this time of the year with lows tonight and Monday night dropping mostly into the single digits above zero, while highs Monday should reach the mid teens to mid 20s. .LONG TERM...(Tuesday through Sunday) Issued at 159 PM CST Sun Jan 1 2023 The extended period looks to be quiet with little going on overall. For the most part, seasonable highs will range from the teens to mid 20s, with the warmest area consistently being the southwest. Lows will be mostly in the single digits above zero. There are hints that the area may begin seeing a warming trend late in the week and into the weekend. However, as a result of fairly progressive and weak flow aloft, uncertainty remains. This uncertainty is illustrated by the latest NBM ensemble guidance which suggests a continued large 25th to 75th percentile range in high temperatures Saturday and Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Monday Evening) Issued at 528 PM CST Sun Jan 1 2023 Fog looks likely to develop tonight and and Monday morning, likely from west to east following the progress of a surface high. How long dense fog may persist is very questionable with how this surface high will move across the state overnight. An expansion of MVFR/IFR stratus, possibly LIFR at times, is also possible, however the coverage and timing of this is uncertain. Overall, ceiling and visibility impacts can be expected at times through Monday morning for most areas of western and central North Dakota. VFR conditions expected after 15Z in the west and 18Z in the central. && .BIS WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...AE SHORT TERM...Telken LONG TERM...Telken AVIATION...AE
Area Forecast Discussion
National Weather Service Denver/Boulder CO
758 PM MST Sun Jan 1 2023 .UPDATE... Issued at 758 PM MST Sun Jan 1 2023 No big changes so far from the latest 00Z models that have come in. The more northerly track still looking to be the correct solution. However, the details for tonight are still unclear. General model consensus is that a wave ahead of the main system will bring a brief period of snow tonight. Most models still show this, but the location and timing are slightly off. The 00Z HRRR shows a very weak version of this wave. To add to the uncertainty with the models is that the HiRes models are already missing the area of precipitation from Pueblo to Colorado Springs to Akron, so tough to buy them the rest of the night. Fine tuned weather type for tonight and Monday. Will stick with the idea the wave will move north across the area and bring a period of snow. After this, the mid levels dry, but lower levels are left saturated. Expect a decent period of freezing drizzle once the snow passes across the Front Range and eastern plains late tonight and Monday morning. Don`t expect the snow to return until Monday afternoon when the low is northeast of the area and wrap snow makes it into the area. Snowfall amount forecast of trace to 4 inches looks on track for the Front Range and eastern plains. Could see a little more over the northeast corner of the state. Will add a little more ice accumulation due to the extended period of freezing drizzle. Up to tenth inch seems possible, not a lot, but plenty to make the roads very slick. Because this, will keep the Winter Weather Advisory in effect even though snowfall will likely fall short of criteria. Also increased the coverage and duration of the fog. Already seeing a good amount of fog and it should continue through at least Monday morning. For the mountains, orographic lift combined with the moist southwest to west flow will bring periods of snow tonight. Then on Monday, lift from the upper level system will bring additional snow. && .SHORT TERM...(This evening through Monday) Issued at 148 PM MST Sun Jan 1 2023 Middle and high cloudiness continue to stream northeastward across the CWA at this time. Snow over the mountains has decreased with just scattered showers remaining now and for the rest this afternoon. Currently, winds across the plains are weak northeasterly to southeasterly. They are southwesterly over the high mountains. The 12Z model runs moved the upper circulation center further north on its path across Colorado on Monday. It is also a bit slower. At 03Z Monday evening, the center is now over the northeastern corner of Colorado. Storm total snowfall progs for this storm continue to decrease on the latest model runs. Left current highlights going all the same. Was also hard pressed to just drop the Watch over the eastern plains, so went with an Advisory for those areas as there will be some snow along with the chance of freezing precipitation. The freezing precipitation could make very slippery driving conditons. For temperatures, Monday`s highs are a bit cooler than current readings are now. .LONG TERM...(Monday night through Sunday) Issued at 148 PM MST Sun Jan 1 2023 Monday night into Tuesday, models are showing the 500 MB low tracking from far Northeastern Colorado into the Upper Midwest. On the back side of this low, generally light snow and breezy conditions are expected to continue across the plains with addition snowfall amounts between a trace and and inch by midnight. The snow should end by midnight with a few snow showers lingering across the far northeastern zones into the early morning hours. Across the high country, periods of light snow are expected to continue through about noon on Wednesday due to a moist westerly flow aloft. As for temperatures, max readings are expected to be some 10 degrees below normal through Wednesday. Dry weather and moderating temperatures are expected on Thursday as upper level high pressure moves across the Rocky Mountain Region. More snow is expected to return to the high country Friday and Friday night as the next upper level shortwave moves across North Central and Northeastern Colorado. At this time, snow accumulations appear to be on the light side due to limited moisture. The plains should remain mostly dry with near normal temperatures. Upper level high pressure is progged to rebuild over Colorado by next weekend with dry weather and seasonable temperatures. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 440 PM MST Sun Jan 1 2023 Fog has just moved into DEN with visibility less than a quarter mile. Expect some minor improvement to begin in the 03-05Z time frame when snow moves in. Before this, freezing drizzle will be possible, though it should be very light. Once the snow moves off after midnight, there will be a good chance the dense fog returns with fzdz. This should continue into Monday morning. The next period of snow moves in around 18Z Monday. Total snowfall for DEN is expected to be up to 3 inches. Freezing drizzle may create more issues though. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until midnight MST Monday night for COZ031-033-034. Winter Weather Advisory until 8 PM MST Monday for COZ035-036- 039>041-045-046. Winter Weather Advisory from midnight tonight to midnight MST Monday night for COZ038-042>044-048>051. && $$ UPDATE...Meier SHORT TERM...RJK LONG TERM....jk AVIATION...Meier
Area Forecast Discussion
National Weather Service Cheyenne WY
455 PM MST Sun Jan 1 2023 .SHORT TERM...(This evening through Tuesday) Issued at 205 PM MST Sun Jan 1 2023 What a start to 2023! KEY MESSAGES: 1) Widespread snowfall amounts of 5 to even 10 inches have been recorded across portions of Carbon and Albany Counties already and we are only 24 hours into this winter storm! 2) Winter Storm Warnings remain in effect for most of southeast Wyoming and the Nebraska panhandle, with the exception of the Laramie Valley where a Winter Weather Advisory is in effect. 3) Generally moderate to high impacts are expected across southeast Wyoming and the Nebraska panhandle due to widespread accumulating snowfall. Portions of the Nebraska panhandle may also experience a brief period Monday morning and afternoon of freezing drizzle which could lead to ice accumulation. DISCUSSION: There are so many aspects of this storm to talk about due to it being such a unique setup, especially for December, but we are only going to hit on a few. TIMING: Snowfall began last night and this morning across portions of southeast Wyoming, the snow briefly lifted for a few hours over portions of far southeast Wyoming, only to pick back up later tonight. For timing, heavily leaned the forecast toward the HRRR due to it picking up the current snowfall better than other HiRes guidance. The time period for the heaviest snowfall across the majority of the eastern portions of the CWA remains to be late tonight through Monday morning as the low drifts northeastward and the strong TROWAL impacts the majority of the CWA, resulting in the likelihood for the heaviest precipitation. HiRes guidance shows this happening mainly between 2 AM and 5 PM Monday. The HRRR shows the snowfall ending in areas west of the Laramie Range between 11 PM Monday and 2 AM Tuesday, then the areas of southeast Wyoming east of the Laramie Range between 2 AM and 5 AM Tuesday, and finally the Nebraska panhandle by 10 AM Tuesday. SNOWFALL AMOUNTS: Forecast snowfall amounts have remained relatively consistent, with the exception of a few minor adjustments here and there. Carbon and Albany counties have experienced the brunt of the storm thus far with accumulations 5 to 10 inches at lower elevations and 30 to 40 inches at the highest peaks in the Snowy and Sierra Madre Ranges. Looking at the forecast after 5 PM today, Carbon and Albany counties could still see an additional 4 to 10 inches before the end of the storm. The exception is the Laramie Valley. Unfortunately due to the downsloping wind direction, Laramie is likely to be shadowed for this event once again. The Valley`s best chance for more snowfall is Monday afternoon when the winds are forecast to shift northward. Converse, Niobrara, Platte, and Goshen counties are forecast to see additional 6 to 12 inches of snowfall from 5 PM today to Monday night. Laramie County is likely to experience a sharp gradient in snowfall amounts from 4 to 6 inches in southern parts of the county to 6 to 8 inches in northern parts of the county. The northern Nebraska panhandle has the greatest potential, especially up near the Pine Ridge where they could see widespread 6 to 12 inches and 12 to 15 inches up on the ridge. There is a great deal of uncertainty in the snowfall totals in Kimball, Morrill, and Cheyenne counties due to the potential for mixed precipitation. Currently in the forecast is 4 to 8 inches of snowfall, but there is potential for freezing drizzle and ice accumulation late this evening and Monday morning/afternoon. As the previous discussion mentioned, the GFS soundings continue to show significant drying aloft later this evening and over night, while the lowest 8k+ feet remains entirely saturated within the 0 to -10 deg C layer. This will limit potential for ice growth in cloud and will likely result in heavy drizzle, with significant ice accretion very possible. Forecast ice accretion remains in the 0.05 to 0.1 inch range, with the highest amounts in Cheyenne county. However, if the freezing drizzle holds on and does not switch over to snowfall, the ice accretion amounts will drastically increase, and snowfall amounts will be slashed. This could lead to more serious impacts, such as downed trees and power lines. TEMPERATURES: Temperatures are forecast to remain relatively moderate until Tuesday thanks to strong warm air advection at the surface from the south and east. The environment is quite warm and moist, especially for December! The dense cloud cover will also help insulate the surface, preventing much diurnal temperature fluctuations. Forecast low temperatures tomorrow morning are in the 20s with high temperatures in the upper 20s to low 30s. Temperatures in the single digits to teens move in late Monday night to early Tuesday morning as the snowpack will help cool the ground and our flow turns northerly, advecting colder air into the area. .LONG TERM...(Tuesday night through Sunday) Issued at 105 PM MST Sun Jan 1 2023 Overview: Long term forecast period looks predominately uneventful, with right at or just slightly above seasonal temperatures. Lingering snowpack and a persistent, cool northwest flow aloft, will help keep temperatures slightly below seasonal normals on Wednesday, before a slow moderation occurs toward the end of the week. Most of the region will see dry conditions, but the mountains could see some lingering light snow showers Wednesday. With weak disturbances aloft some elevated winds will be possible across the wind prone areas, but high winds are unlikely at this time. Heading toward the end of the week, long range models begin to hint at the next weather maker which could bring some more widespread valley precipitation and mountain snows back into the forecast. Discussion: The main discussion point to mention in the long term, is that potential next system by the end of the week. interestingly enough, both the GFS and ECMWF are in fairly good agreement on the longwave ridge/trough/ridge/tough pattern across the entire CONUS. Focusing on SE Wyoming and the Nebraska Panhandle, both models bring in a trough feature with the GFS showing a negatively tilted open trough while the EC has a weak closed low developing across north central Wyoming at the same time. Both solutions move the system NW to SE across the region with some decent 700-500mb moisture content. This would suggest a return of precipitation to the forecast in the form of light valley rain/snow across Carbon and Albany counties and mountain snow. PoP forecast will reflect the NBM output with low end PoPs chances across those areas, while locations along and east of the Laramie Range should remain dry. && .AVIATION...(For the 00Z TAFS through Monday afternoon) Issued at 455 PM MST Sun Jan 1 2023 Brief lull in the snowfall for most areas this evening before activity ramps up again between 03z and 08z tonight. Widespread snow expected for nearly all terminals through Monday morning. Some freezing drizzle and fog possible along the Interstate 80 corridor from KCYS to KSNY late tonight and Monday morning. HAZARDS/WEATHER TRENDS: For now, will concentrate on start times and intensity of snowfall arriving between now and 08z tonight: Expect KRWL to have off and on light to moderate snow through the night and Monday morning, so no changes planned at this time. Might need TEMPO groups to address the variable intensity of the snow however. For most other terminals, Expect snowfall to begin between 03z and 08z from south (KCYS, KSNY) to north (KBFF, KCDR) with a rapid transition to LIFR conditions expected. KLAR will hold onto a southeast or easterly wind, so a local snow shadow is likely with intermittent snowfall and off/on MVFR conditions possible through most of the night tonight. && .FIRE WEATHER... Issued at 105 PM MST Sun Jan 1 2023 Widespread snow & colder temperatures should minimize fire weather concerns for the foreseeable future. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Storm Warning until 11 PM MST Monday for WYZ101-102- 104>111-113-116>119. Winter Storm Warning until 5 PM MST Monday for WYZ103-112-114. Winter Weather Advisory until 5 PM MST Monday for WYZ115. NE...Winter Storm Warning from 5 PM this afternoon to 11 PM MST Monday for NEZ002-003-019>021-054-055-095-096. && $$ SHORT TERM...LK LONG TERM...AW AVIATION...TJT FIRE WEATHER...CLH
Area Forecast Discussion
National Weather Service Dodge City KS
456 PM CST Sun Jan 1 2023 ...|Updated aviation section... .SHORT TERM...(This evening through Monday night) Issued at 1218 PM CST Sun Jan 1 2023 18Z observations are showing a large trough over southern California with a 100-110 kt jet streak from Baja California through northern Kansas and Nebraska which is overspreading widespread high and mid level cloud cover. At the surface a low and frontal boundary are located in the far north Texas panhandle and we have widespread light north to northeast winds. Tonight the surface low and frontal boundary looks to move slightly to the north and as it does so winds will continue to be upsloping with the east to northeast direction. Moist air at the surface will advect ahead of the front and saturate the boundary layer especially after midnight. 850 mb winds will increase after 06Z and we should see an area of fog and drizzle develop across most of southwest Kansas with the exception of the far southwest. HREF probabilities of less than 4 SM being around 50-60% for much of the area towards sunrise as well as the HRRR RH values and surface visibilities being low gives better confidence for areas of fog. The main storm system will be approaching the four corners region by 12Z Monday and the first of the 700 mb shortwave will enter into far southwest Kansas at this time. At this point it looks like the precipitation we see will be mainly from any drizzle we get with the rain potential being more towards the day on Monday. Lows tonight should stay above freezing CWA wide so didn`t see the need to include any freezing drizzle wording. Monday it still looks like models haven`t quite have a handle on the track. GFS run to run continues to have the main center in northeast Colorado. RAP/NAM are a little further south and the latest 12Z Euro is slightly more north than previous runs. CAM models are in pretty good agreement of an area of rain developing along and east of highway 283 after 15Z as the main mid level energy will move into southwest Kansas. I thought the WPC idea of having the highest QPF potential from Scott City to Hays looked good. Elsewhere the dry slot is still also on track for our far southwest zones so it does look like a quick clearing of the fog and low clouds should happen for areas around Liberal to Elkhart with the clearing later in the day for areas from Dodge to Garden City. I kept the low clouds in for much of the day in our northern and eastern zones and hence lowered the high temperatures to the lower to mid 40s. Areas from Liberal to Elkhart will be near 60 and everybody else`s temperatures will be largely factored on how much of the weak insolation can burn off the fog. Monday night the last of the strongest mid level energy should exit into Nebraska and our precipitation should quickly end from south to north during the evening hours. A cold front on the back side of the low will race through northwest Kansas during the evening and southwest Kansas around midnight. This could lead to a brief changeover to snow for areas along the I-70 corridor but accumulations should be a dusting at the most. Winds will also increase as the front passes and lows should fall into the 20s. .LONG TERM...(Tuesday through Sunday) Issued at 155 PM CST Sun Jan 1 2023 Tuesday will be cooler as the winds will be out of the northwest and 850 mb temps range from 0 to -5 (C) and highs in the lower 40s. Cooler temperatures will continue into Wednesday as the long wave trough slowly moves through the central plains. By Thursday we should start a slight warm up as a ridge moves from the Rockies into the central plains. The next system of interest will be coming in Friday night through Saturday with the track currently taking most of the energy to the north. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 454 PM CST Sun Jan 1 2023 VFR conditions will prevail this evening with overcast high clouds. Low clouds and patchy fog will quickly form after midnight reducing visibilities and ceilings to IFR to LIFR. These low clouds and patchy fog will continue into late morning with some clearing tomorrow afternoon. Winds will generally be form the northeast through tomorrow morning then shift to a southerly direction by tomorrow afternoon. && .PRELIMINARY POINT TEMPS/POPS... DDC 37 55 25 43 / 30 40 20 0 GCK 36 52 23 41 / 30 40 20 0 EHA 37 59 25 45 / 20 20 10 0 LBL 37 60 24 44 / 30 30 10 0 HYS 35 47 24 39 / 40 60 40 0 P28 41 56 30 46 / 30 40 10 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Tatro LONG TERM...Tatro AVIATION...Hovorka_42
Area Forecast Discussion
National Weather Service Des Moines IA
530 PM CST Sun Jan 1 2023 ...Updated for the 00z Aviation Discussion... .DISCUSSION.../Tonight through Sunday/ Issued at 339 PM CST Sun Jan 1 2023 Key Messages: - Potential for significant ice over northern Iowa late Monday into Tuesday. - Primarily rain and some rumbles of thunder central and south. Radar imagery as we approach 22z shows some minor returns as a subtle wave percolates through the nearly zonal flow aloft. The weak forcing and poor moisture availability is preventing most, if not all of this precip from reaching the ground at this time. Primary feature of concern at the moment is an amplified trough digging through the Great Basin and into the Four Corners region. Models attempt to generate some light, sporadic QPF early in the day as mid-level waa cranks up ahead of the approaching trough. Expecting much of thus early day precip potential to also succumb to dry air. Showers and perhaps some thunderstorms dramatically increase by late afternoon or evening as the trough emerges into the central Plains as strong, phased kinematic and thermodynamic forcing focuses over the state. Northward moisture fetch strengthens considerably as the trough begins to take on a negative tilt, with the RAP showing as high as 5 to 6+ g/kg spec humidity streaming northward on the 295k surface. While mostly liquid rain is expected central and south, a significant icing event may unfold over portions of northern Iowa where the deep, warm moist air overrides surface temps near to below freezing. Ice accretion efficiency will be limited at times due to moderate rainfall rates, but much of the 12z model suite has painted a swath of 0.25"+ ice accums across northwest and into north central Iowa Monday night. Forecast hedged toward the more consistent Euro solution, but ice accums were pulled a bit further east to match the trends shown in several hi-res models. An Ice Storm Warning was issued for areas most likely to see the heavier ice amounts. Travel impacts and the potential for power outages are a concern. A Winter Weather Advisory borders the warning just to the south where the 0c wet bulb transition likely resides during the evening into the overnight hours, and thus considerable uncertainty on potential icing. The longevity of ice impacts is also in question as warm air continues to be pulled northward and the sfc thermal field pivots around the low. This may bring temps back above freezing as far north as Mason City to Algona by early Tuesday morning, so the end time of the warning/advisory may be need to be adjusted. Dry air begins to wrap around the low by later Monday night into Tuesday morning and erodes a good chunk of the precip over the forecast area. Precip will begin to focus more on an intense deformation zone crossing the SD in southern MN. A few inches of snowfall are possible as it clips our far northwest counties. The upper low continues to weaken and wobble a bit as it occludes Tue night into Wed. This will keep some chances for some light snow around as it interacts with residual moisture over the area. Weather pattern quiets down over the latter days of the work week as the upper low departs and a ridge builds over the central conus. Highs rise from the teens and 20s and Thursday to back into the 20s and 30s, and perhaps 40s south on Friday. Next window for winter precip opens next weekend as models bring another upper low off the Rockies. 12z deterministic models trended more bullish on QPF potential, however ensemble data sets remain much more conservative. Latest NBM init may be a bit behind on expanding mention PoPs over the area, so would anticipate if more widespread chance PoPs are introduced in forthcoming updates. && .AVIATION.../For the 00Z TAFS through 00Z Monday evening/ Issued at 530 PM CST Sun Jan 1 2023 Patchy fog is possible overnight, however current guidance suggests this will remain north of the area so have kept from TAFs for now. Into Monday morning ceilings will drop to MVFR and then to IFR as stratus spreads across the area ahead of the approaching system. Precipitation will expand through the late afternoon, reaching eastern sites just beyond the current TAF period. && .DMX WATCHES/WARNINGS/ADVISORIES... Ice Storm Warning from 6 PM Monday to 6 PM CST Tuesday for IAZ004>007-015>017-023-024-033. Winter Weather Advisory from 6 PM Monday to 6 PM CST Tuesday for IAZ025>028-034>036-044-045. && $$ DISCUSSION...Martin AVIATION...Hagenhoff
National Weather Service Hastings NE
502 PM CST Sun Jan 1 2023 ...AVIATION UPDATE... .DISCUSSION...(This evening through Sunday) Issued at 358 PM CST Sun Jan 1 2023 Key Messages: * Complex and significant winter storm with ice and snow will impact the region Monday into Tuesday. The transition zone from ice/snow to mostly rain will likely reside over the forecast area much of Monday-Monday night. * The Winter Storm Watch has been upgraded to a Winter Storm Warning, with a few counties added on the S/SE side. A Winter Weather Advisory has been issued for the same time frame for a row of counties to the S. Finally, additional counties along NE/KS state line will go into an advisory Monday night. * While uncertainties still abound, which is inherent given sharp transition zone ptype within the forecast area, model spread has lessened and they appear to be converging toward a solution that has been most consistent with the EC ensemble mean. * Finally, it`s important to note that impact timing and severity will vary widely from N/NW to S/SE, with the Tri-Cities likely within the transition zone. Folks with end-of-holiday travel should do so yet today, or tomorrow if heading E/S. Folks traveling N/W should consider waiting until Tue PM or Wed AM. Forecast Details: Primary concerns are in the first 36-48hrs, which is where nearly all forecasting time was spent on. Will start off by saying that model spread has generally decr (as one would expect) over the past 12-24 hrs, though there is still some spread noted, particularly between EC and GFS/GEFS/CMC. With that said, there has been a notable trend in the GFS towards the EC ensemble mean, which is the preferred forecast model for this package. Early runs of extended HRRR/RAP seem to align well with the overall thinking from the EPS. For tonight: Most of the overnight hrs should be fairly quiet. The exception could be over far S/W zones after midnight, where DZ and/or FZDZ may develop. May also be some fog over far S zones by dawn. Models have been trending slower with the onset of impactful pcpn, and felt confident enough in this trend and that 90-95 percent of the headline areas will dry through tonight to push back the start of the Winter Weather products until 12Z. Monday: Again, models have trended a bit slower, but think we`ll see a rapid influx of moisture/pcpn during the AM hrs as low pressure deepens along the High Plains. Strong moisture transport of +2 to +4 std dev PWATs leads me to lean towards solutions with heavier and more widespread QPF for the daytime hrs Mon. EC has been leading the way in this aspect, and see no reason to deviate. The main forecast issue will be pinning down sfc temps. Winds will be backing from E to NE late tonight-Mon AM, and with sfc high sitting to the N and thick cloud cover, think temps will really struggle to rise on Mon. In fact, RAP H925 temps clearly fall throughout the day, with freezing line starting near ODX, but ending up near NE/KS state line by Mon eve. This lead me to favor COLDER sfc temp solutions of the NAMNest/HRRR/RAP, and used some of this data in a blend with NBM. This resulted in a few deg drop in hrly temps and highs. This will make frz rain more of an issue for the daytime hrs, at least for the N third of CWA. The tricky part will be from roughly the Platte River to Hwy 6 corridor as even the colder models hover temps within a degree, or two, either side of freezing...pretty much all day. 12Z HREF shows very little fluctuation in 32F line from near Elwood to GRI to OLU, essentially all day. Incr NErly flow will aid in frz rn accum efficiency, esp. on trees/elevated sfcs., but roads may not be all that bad within this zone, esp. considering the daylight hrs. This could be a situation where N side of GRI sees a couple tenths of ice and HSI receives almost none. Areas S/SE from HSI will likely experience just a cold rain with temps in mid to upper 30s. There could be some convective elements to the pcpn by Mon aftn, but didn`t explicitly include in the forecast. This would actually decr frz rn efficiency due to runoff. Monday night: Expect a gradual transition from RA to FZRA to SN (with perhaps some brief IP mixed in) from W/NW to E/SE during the eve hrs...exactly how far/fast is uncertain. The speed of this transition will go a long way in determining final impacts. EC is generally a bit faster, likely owing to stronger sfc low that moves along I-35 corridor from KS to IA, then stalls...which leads to more frozen pcpn for central part of CWA, and more snow for far W/NW zones. Again, this has been a fairly consistent feature on the EC/EPS, and was generally the preferred forecast solution. The stalling and more intense low to mid level low pressure also lends to more organized wrap-around pcpn and potentially more snowfall for our area. The forecast was trended in this direction, but didn`t go as high as the operational EC runs would suggest. This idea would give mostly fzra/snow by midnight, then mostly snow by 12Z Tue. NE-N winds will be on the incr, which is definitely a concern for what will likely be ice-coated trees and power lines by this time for a majority of our NE zones N of Hwy 6. Would expect some power outages in these areas by dawn Tue AM. Tuesday: Biggest question for this period will be how long does pcpn hang on, as even the lesser favored GFS is all snow by dawn Tue. As mentioned above, EC is generally stronger, more negatively tilted, and thus more efficient at wrapping warm/moist air westward within a TROWAL. Again, didn`t go straight deterministic EC, but felt PoPs AND QPF needed to be incr as even the EPS lingers snow across most of south central Neb. for the AM hrs. Colder air wrapping into the system should also incr SLRs, though probably not much more than 12-13:1. Think most areas N of the state line should see a dusting to 1" 12Z to 18Z Tue, with perhaps some areas around ODX to OLU even 2-3". With Nrly wind gusts around 30-35 MPH, some blowing/drifting snow will likely be an issue for the harder hit areas through the AM hrs. Some blsn may extend beyond midday, but felt comfortable leaving headline end time of 18Z as most areas will be calming down. So to reiterate...confidence is HIGH that at least PORTIONS of the CWA will experience significant ice/snow/wind impacts from this system Mon thru Tue AM. Most likely area for these impacts will be within the Winter Storm Warning area from late Mon AM through Tue AM, though the S tier of counties (like Phelps, Hall, Hamilton, and Polk) may be just barely warm up to delay impacts to Mon eve. These areas were a tough call on advisory vs. warning, and for start time. However, felt best to err on side of caution given potential for post-holiday travel that includes I-80. Significant impacts to travel will occur, and power outages will be possible, esp Mon night into Tue., and esp. N of LXN to OLU line. Confidence in coverage, severity, and timing of impacts decr for areas S of I-80 and N of the state line. Still think enough ice and snow will occur to cause travel issues, but may not be until Mon eve as sun sets and temps cool more solidly below freezing. Travel impacts will likely peak late Mon night thru Tue AM. Unknown if enough ice and wind will occur for power issues in this area. If temps are 1-2 deg cooler during the day Mon, or if wrap around snow is more organized/persistent, then some of the advy may need to be upgraded to a warning. Most areas along/S of the state line will probably remain warm enough to preclude wintry pcpn issues through about 06Z Tue. May see some FZRA/IP late, but quick transition should limit amnts. Some lgt wrap around snw will be possible, but only EC is giving much more than a dusting. Rising temps as pcpn ends Tue should lead to improving conditions by midday Tue, even if some minor ice/snow occurs. The rest of the forecast is dry. Temps will remain cool through midweek, then gradually warm Fri into next weekend. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday) Issued at 453 PM CST Sun Jan 1 2023 A -FZRA event is expected to impact the TAF sites tomorrow morning. I kept EAR in -FZRA during the TAF period as it looks to remain below freezing. GRI is closer to the freezing line and looking at some of the short range models thought the afternoon could warm above 32f allowing for some change over to -RA for a brief time. My confidence in the -RA is low, but it did look like a small possibility... Tomorrow afternoon the ceilings look to drop to LIFR and vis looks to drop also to at least IFR for now. && .GID WATCHES/WARNINGS/ADVISORIES... NE...Winter Weather Advisory from 6 PM Monday to noon CST Tuesday for NEZ077-085-086. Winter Storm Warning from 6 AM Monday to noon CST Tuesday for NEZ039>041-046>049-060>063-072-073. Winter Weather Advisory from 6 AM Monday to noon CST Tuesday for NEZ064-074>076-082>084. KS...Winter Weather Advisory from 6 PM Monday to noon CST Tuesday for KSZ005-006. && $$ DISCUSSION...Thies AVIATION...Beda
Area Forecast Discussion
National Weather Service Goodland KS
458 PM MST Sun Jan 1 2023 .SHORT TERM...(This evening through Tuesday Morning) Issued at 214 PM MST Sun Jan 1 2023 Overcast skies are dominating the area ahead of a potent trough over the Baja Peninsula as this is the main weather maker for the short term period. For this evening, confidence is fairly high in fog and/or some drizzle occurring along and south of Interstate 70. The HRRR, LAMP and RAP have been in great consistency with the development of reduced visibilities, some dense fog may possible. The fog is expected to continue into the morning before the winter weather side of this system comes into play. Guidance continues to struggle with the overall positioning of the system as the 12Z runs were taking it north which favors less precipitation; whereas the 18Z runs are trending it more south again. The NAM and GFS has the low over the NW portion of the area which favors more a wintry mix/freezing rain scenario whereas the HRRR and ECMWF take it further south which favors more accumulating snow. The one hazard that most guidance has increased on is ice accumulation across the area as a result of this I opted to issue a Winter Weather Advisory for all but Greeley, Wichita and Gove counties as they are expected to remain above freezing for the duration of the precipitation. Forecast soundings do show a fairly stout warm nose especially north of I-70. Freezing rain mixing with snow is expected to develop across eastern Colorado late this evening which is what prompted the 06Z start time for the advisory. Into Monday, precipitation is expected to increase in coverage in the form of rain to the south, snow to the north and wintry mix/freezing rain in between. It is unusual to be this close to an event and guidance to continue to vary on solutions. Confidence is high though that wintry weather will occur across the majority of the area. As additional runs of guidance continue to come in it is very possible that an upgrade may be needed for portions of the area. The relative best timing for freezing to occur is overnight tonight and through the morning Monday before the best chance for accumulating snow is Monday afternoon through Tuesday morning. Winds will begin to increase as the system moves off to the east with gusts up to 35 mph possible. This may create some blowing snow in areas with greatest snow depth or it may create extra stress on power poles and trees that have any ice accumulation on them. The heaviest of snow looks to come to an end overnight Monday and into Tuesday morning with the advisory ending at 12Z, although some light wraparound snow does remain possible into Tuesday morning. High temperatures for Monday were lowered to account for overcast skies. Highs look to struggle to get out of the mid 30s for the majority of the area as highs to the south are forecasted to be in the lower 40s. Temperatures into Tuesday morning may need to be lowered some if snow pack does occur across the area. The current forecasted lows for Tuesday morning are in the upper teens to mid 20s across the area. .LONG TERM...(Tuesday through Sunday) Issued at 1215 PM MST Sun Jan 1 2023 Light wraparound snow showers may linger into Tuesday morning for northern parts of the area, otherwise the long term period is dry. Temperatures will be below normal Tuesday and Wednesday under northwest flow aloft with highs in the 30s. Upper ridge then moves across the area on Thursday with temperatures warming into the 40s. Next shortwave trough follows on Friday/early Saturday with models showing only limited, if any, precipitation chances. System is of Pacific origin and temperatures are negligibly impacted. Another ridge builds over the weekend with highs in the 40s and 50s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 326 PM MST Sun Jan 1 2023 **** Update **** Lower ceilings and visibilities have begun moving in from the west already as the air continues to saturate. Have amended KGLD to start the lower visibilities and ceilings now. This was due to surrounding observations and best guest based on manual observation. **** An advancing trough will bring aviation concerns at each site starting this evening as ceilings and visibilities will gradually fall through the evening with IFR being dominant at KGLD around 07Z before a duration of LIFR for the majority of the day Monday. Ceilings will slowly drop at KMCK becoming MVFR around 11Z and then IFR around 14Z. Rain/Freezing Rain/Snow can be expected at each site. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...Winter Weather Advisory from 11 PM MST /midnight CST/ this evening to 5 AM MST /6 AM CST/ Tuesday for KSZ001>004- 013>016-027-028. CO...Winter Weather Advisory from 11 PM this evening to 5 AM MST Tuesday for COZ090>092. NE...Winter Weather Advisory from 11 PM MST /midnight CST/ this evening to 5 AM MST /6 AM CST/ Tuesday for NEZ079>081. && $$ SHORT TERM...Trigg LONG TERM...024 AVIATION...Trigg/KAK
Area Forecast Discussion
National Weather Service Grand Rapids MI
926 PM EST Sun Jan 1 2023 LATEST UPDATE... Update .UPDATE... Issued at 919 PM EST Sun Jan 1 2023 Mainly cloudy skies prevailed across the region at this time. Where the clouds have scattered out...patchy dense fog has formed. Kalamazoo was down to 1/4 mile at last check. Many areas will see fog tonight with some of it locally dense. Given the widespread cloud cover...confidence is not high enough to go with a dense fog advisory...but we will have to watch trends closely. I did update the hazardous weather outlook to mention the potential for localized impacts from the fog tonight. && .DISCUSSION...(This evening through next Sunday) Issued at 323 PM EST Sun Jan 1 2023 - Areas of Fog Overnight and into Monday morning The setup for fog development late tonight looks better than what occurred this morning into early afternoon. Light or calm winds beneath an inversion at 1000 ft combined with low dew point depressions, in some cases zero (RH=100%), should create an environment supportive of at least light fog to form. Some dense fog is also possible mainly south of I-96. The inversion height may be a bit high for more of a widespread dense fog to occur especially further north (ie. GRR-LAN and points north), but the 12z HRRR does show inversion heights closer to 500 ft along I-94. The current thinking is that is where probabilities for dense fog are greater. - Rain Still on Track for Monday Night and Tuesday Numerical models have been unwavering for days with regard to a warm advection rain event Monday night into Tuesday. Yes, as the previous discussion noted, a few thunderstorms are also possible given perhaps 100 J/kg of MUCAPE sneaking into areas south of I-96. Not only is elevated instability possible, but the ECMWF, GFS, and GEM are all showing potential for surface based instability (in January!) south of I-96. That is what happens when surface temperatures push 60F and dew points get into the mid 50s. If we get to 60F at any of our long term climatological stations, that would either tie (at AZO) or break (all the other sites) records for January 3. The upper low that is bringing widespread precipitation to California and the Desert Southwest today will lift to the northeast and deepen over the Midwest. Models are indicating a ~995 mb surface low moving over Iowa by 12z Tuesday, maturing until 18z or so before it begins the occlusion process. A 50-60 kt LLJ will intersect the system`s warm front right over southern Lower Michigan. Model QPF continues to be solidly in the 0.50"-1.00" range for southern Lower MI, highest along I-94. Amounts less than 0.50" are looking more likely north of I-96 and especially near U.S. 10. See the Hydrology section for expected impacts with this rainfall. - Rain Changing to Snow Wednesday with Falling Temperatures The upper low will be slow to depart the region. The 850mb temperatures start dropping below 0C Wednesday afternoon and colder, northeasterly low level flow will begin to overspread the region. We should see temperatures drop below 32F everywhere between 7pm-10pm Wednesday night. Temperatures will continue declining into the teens and low 20s by Thursday morning. Wraparound moisture on the north side of the occluding low will move in from north to south. Model QPF is indicating 0.10"-0.30" of liquid equivalent falling as pure snow. That occurs as an area of 850mb-500mb deformation swings through, particularly as shown by the ECWMF and GEM. Even with the GFS, there is shown to be a deep layer of 925mb-700mb Fn vector convergence setting up especially near and north of I-96 around 00z Thursday, indicating there will be an area where the layer`s thermal gradient is potentially stronger and in general, banded snow is a possibility while this moves through because of frontogenetical forcing. We could easily pick up 1"-3" of snow as this system departs, most of that falling late Wednesday into early Thursday. As a result, the Thursday morning commute could prove to be rather slippery depending on how this takes shape. The 12z ECE ensemble mean snowfall (10:1) shows 1"-3" area wide, with a 30% probability for over 3" north of I-96 and a 10% probability for over 6". So, something to keep in mind for the Thursday morning commute. - Light Snow or a Mix Possible Next Saturday into Sunday Another potent West Coast atmospheric river event will occur mid to late week. Some mid level vorticity with the 500 mb wave approaching the West Coast mid week is shown to break off and head on an eastward trajectory. Models are showing a modest shortwave moving toward the Midwest by the weekend. There are timing and location differences with this feature, not surprising this far out. A weak surface low could form. This may give us a chance for some light snow accumulations or a mix of rain and snow. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 642 PM EST Sun Jan 1 2023 The cloud bases have lifted at most sites with generally MVFR conditions prevailing. There were even some patches where the clouds have scattered out. However as we go through the night...a fairly strong signal for widespread IFR and lower conditions developing exists for all sites. While we will see some slight improvement to the ceilings and visibilities during the day on Monday generally IFR is forecast to prevail into the afternoon for most site. Rain will be approaching from the southwest later in the day...but it looks like it will hold off until Monday night. && .MARINE... Issued at 323 PM EST Sun Jan 1 2023 Some fog is possible overnight and into Thursday morning mainly near and south of Holland. Otherwise, light wave action is expected until later Tuesday into Wednesday. By Wednesday, winds and waves may be hazardous to small craft. && .HYDROLOGY... Issued at 323 PM EST Sun Jan 1 2023 With expected rainfall of generally 0.50"-1.00" Monday night into Tuesday, our 72-hr contingency forecasts for area rivers do not show flood stage being reached on major rivers, even when factoring in the small chance of an overachieving rain event on a larger geographic scale (ie. if well over 1.00" occurs along numerous points within a given basin). However, some significant within bank rises could occur especially on smaller rivers and streams with our current QPF and especially if the event overachieves. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...MJS DISCUSSION...Hoving AVIATION...MJS HYDROLOGY...Hoving MARINE...Hoving
Area Forecast Discussion
National Weather Service Lincoln IL
809 PM CST Sun Jan 1 2023 .SYNOPSIS... Issued at 300 PM CST Sun Jan 1 2023 Areas of fog likely again tonight, some of which may be dense. A strong low pressure system will move through the Midwest this week, resulting in well above normal temperatures across the area through Tuesday, with highs in the mid 50s to low 60s. Widespread showers and scattered thunderstorms move through Monday night into Tuesday. && .UPDATE... Issued at 808 PM CST Sun Jan 1 2023 This evening, a warm front stretches from roughly St Louis east- northeast along the I-70 corridor. Near and north of the front, low stratus and fog is once again expanding north across central Illinois and will remain in place overnight. Fog has the potential to become dense across the area, but this is most likely just north of the front between the I-70 and I-72 corridors. Meanwhile, temp-dewpoints spreads across central Illinois are generally less than 2 degrees area wide. With increasing cloud cover and seasonably high surface dew points, temps will not be able to move much overnight and may even warm a degree or two in a few spots. && .SHORT TERM...(This evening through Monday) ISSUED AT 300 PM CST Sun Jan 1 2023 An active stretch of weather is on tap through Tuesday as strong low pressure system develops over the central Plains on Mon and lifts into the upper Midwest by Tues. Forecast impacts across central IL include: 1) Additional dense fog tonight into Mon 2) Thunderstorms Mon eve into Tues, with a chance for isolated flooding and strong storms, primarily south of I-70. 3) Potentially record-setting warmth A deep upper trough is evident across the western US in water vapor imagery this afternoon, with a baroclinic leaf overspreading the southwestern Plains. As lee cyclogenesis unfolds this evening, a frontal boundary positioned across OK/the Ozarks will lift northward overnight as a warm front. That warm front will be draped across central IL tonight, keeping winds light with little change in temperatures/dewpoints overnight. Another round of at least patchy dense fog is looking likely. Both the deterministic NBM and the latest HRRR show widespread dense fog developing. Probabilistic guidance also favors dense fog, with the HREF showing a 60-80% chance of vis below a half mile across much of the CWA. Similar to today, fog could linger through much of the morning on Mon. The front will continue to lift northward Mon, with a tightening pressure gradient. High-res guidance tries to develop isolated to scattered showers across the southern CWA, in response to WAA, however suspect that height rises aloft in advance of the trough to our west may help stymie shower activity until later in the afternoon. A more widespread push of precip, including a chance for thunderstorms, arrives Mon evening after sunset as warmer, more moist air advects northward into central IL. Guidance continues to show marginal instability in place, with a few hundred J/kg of MUCAPE. A robust LLJ will overspread the area Mon night, with 850mb winds in excess of 65 kts, resulting in substantial low level shear. Despite this, severe t-storms still appear unlikely. Forecast soundings for Mon night show weak, albeit non-zero, sfc-based instability (lowering the tornado threat) and weak mid-level lapse rates (eliminating a hail threat). DCAPE is not particularly high, but any stronger downdrafts may result in vertical momentum transport of the strong LLJ winds to the surface, resulting in isolated strong wind gusts. Will need to keep an eye on any lingering activity across E IL Tues AM, as forecast soundings show the low-level inversion weakening. Not only will that allow storms to more readily mix down stronger LLJ winds, but that may allow weak sfc instability to develop: soundings show about 50 J/kg of 0-3km CAPE, which is not overwhelming, but with high low-level helicity (0- 1 km SRH approaching 400 m2/s2) it would not take much for storms to become frisky. The key takeaway here: it`s more likely than not that storms remain sub-severe in our CWA. However, with such strong low- level shear, it is a setup that demands close attention be paid to any storms that do develop, especially across E IL into Tues AM. PWAT values are expected to push into the 1.25-1.5" range, which would be among the highest ever sampled in central IL in January. Despite these values, fast storm motions, a lack of training storms, and thawed ground should limit the flood potential. Guidance continues to highlight south of I-70 as the axis of heaviest precip from this system, and those areas saw 0.75-1.25" of precip over the weekend. The latest HREF suggests most areas south of I-70 see another 0.75-1.25" of rain, but localized, convectively-driven rainfall totals of up to 2" are possible. Further north, rainfall amounts are most likely to be around 0.5", with localized amounts up to 1". Despite mostly cloudy skies, unseasonably warm to near-record temps will persist through Tues. Highs on Mon will be in the mid 50s to low 60s. As the low pressure approaches from the west Mon night, continued southerly flow will result in temps staying in the 50s across much of the area, which would be record warm lows for Jan 3rd. (The caveat here is that lows may fall enough Tues eve before midnight to prevent records from being set for that calendar day). A cold front will push through on Tues, but before it does, temps are expected to climb into the 60s, nearly 30 degrees above normal for early January. The record warm temps for Jan 3rd are 61F in Peoria, 63F in Springfield, and 65F in Lincoln, and our forecast currently calls for records to be broken in Peoria and Springfield. .LONG TERM...(Monday night through Sunday) ISSUED AT 300 PM CST Sun Jan 1 2023 After a cold front moves through on Tues, much cooler air arrives by Wed. Guidance shows 850mb temps falling from +12C on Tues to around -5C on Wed. Sfc temps will be nearly about 25-30F cooler than Tues, which will result in temps back near typical values for early Jan. As the upper low meanders around the upper Midwest, it may lead to scattered showers, primarily snow showers, Wed afternoon through the overnight into Thurs. The best chance for such showers is across the northern half of the CWA. Little accumulation is expected from this activity, with locations that do see snow likely seeing a dusting or less. NBM probabilities have less than a 20% chance for seeing 1" of snow. Temps are expected to remain seasonable through the remainder of the work week, with highs in the 30s and lows in the 20s. Into the weekend, a slight warmup is possible as upper level ridging shifts over the Midwest ahead of another shortwave. There`s still a good deal of uncertainty in the track/timing of the sfc low associated with that wave, but will need to monitor the precip potential Sat/Sun. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 524 PM CST Sun Jan 1 2023 A warm front stretches from roughly St Louis through Paris, IL this evening and will slowly lift north to near the I-72 corridor by early Monday evening. IFR/LIFR ceilings are expected near and north of the front through the period along with light NE to east winds. Visibility is expected to lower with fog development tonight and could also fall into LIFR category. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Deubelbeiss SYNOPSIS...Erwin SHORT TERM...Erwin LONG TERM...Erwin AVIATION...Deubelbeiss
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
845 PM CST Sun Jan 1 2023 .UPDATE... Issued at 845 PM CST Sun Jan 1 2023 Had updated forecast earlier to introduce/expand areas of fog across parts of northern IL. Most widespread dense fog has been near the IL/WI border region through mid-evening, and had issued a dense fog advisory for those areas earlier. Starting to see some patchy dense fog developing southward into parts of the I-88 corridor at this time, and while webcams generally indicate this is likely somewhat patchy, may need to eventually expand fog advisory farther south. Surface analysis indicates that the weak front which settled across the area late last night/early this morning runs from just south of Pontiac to near Rensselaer as 02Z. Air mass south of this boundary is characterized by temps and dew points in the 40s, while farther north temps and dews were mainly in the mid-30s aside from a few milder spots in the Chicago metro. GOES nighttime microphysics RGB combo shows an extensive stratus layer within the warmer air south of the boundary, while father north patchy low clouds/obscuration were harder to see due to mid-level clouds. Quite a spread in various high-res guidance with respect to fog trends overnight, though the high-res ARW appears reasonable at this point. This would suggest some additional expansion across parts of the I-88 corridor overnight, as well as parts of northwest IN/far southeast cwa. This (and the RAP to some extent) even suggest some erosion of fog across the IL/WI border region during the pre-dawn hours as low level winds turn light north-northeasterly. Based on guidance and obs trends, may need to expand the dense fog advisory southward across the I-88 corridor by late evening if dense fog becomes more widespread, and perhaps farther south/southeast overnight as well. Otherwise, going forecast appears to be in decent shape into Monday morning and no other significant changes were made. Ratzer && .SHORT TERM... Issued at 253 PM CST Sun Jan 1 2023 Through Monday night... Temperatures this evening and overnight will be rather steady thanks to some modest low level WAA and low ceilings in anticipation of the approaching storm system. Meanwhile, a potent, quasi-stationary warm front will be hanging out in central IL tonight before trekking northward into the area on Monday. Lows Monday morning will bottom out near freezing across some of Illinois` northern-most counties while the far southern CWA nearer to the front will hang in the lower 40s. Mid-afternoon temperatures will reach the 40s and lower 50s on Monday. Though once the front begins its progression through the area Monday evening and night, conditions will steadily warm behind it. Some spots in far south may not even drop below 50 before they begin warming through the night eventually tapping into the 60s by Tuesday morning. Areas further north, primarily north of I-90, will be allowed to cool back into the upper 30s prior to the arrival of the front Monday night. However, these areas too will warm overnight with the whole CWA expected to be in the 50s by mid- morning on Tuesday. Meanwhile, areas of dense fog this morning have thinned out across the area, though not completely dissipated. Several spots are still reporting visibilities under 5 miles as of 2PM. This isn`t expected to improve much through the remainder of the day before conditions are expected to worsen tonight. With dewpoints sitting in the upper 30s and lower 40s this afternoon, areas of dense fog are anticipated to redevelop as we cool down into the 30s this evening and overnight. The greatest potential for widespread, dense fog is across and south of the Kankakee River valley where they may see some limited moisture advection take place overnight. Through the day tomorrow, fog may stick around or redevelop across areas along and south of the front as we begin to see that influx of low level moisture. As far as the rain expectations go, there have been a few notable changes among guidance since yesterday`s runs. However, the most notable would be the drop in coverage and overall intensity and a resultant drop in QPF. Best guess as to why this is would be the shift in the track of the LLJ to the southeast. The LLJ was previously expected to just graze the CWA to the southeast, but models are now showing it even further displaced from us now moving through central and southeast Indiana and the higher QPF has followed suit. The NAM keeps the LLJ a bit more local leading to higher QPF, though it has certainly become an outlier among models. The LLJ has also taken some of the moisture with it, though PWAT values are still shown to exceed one inch across just about the whole CWA. As high-res and convective allowing models are now reaching into the brunt of this storm, simulated reflectivity shows the rain coverage may not be quite as widespread as previously thought, or at least the window for truly widespread rain has tightened now that we`ve removed some of our moisture and forcing. Nonetheless, a healthy amount of rain remains in the forecast through Tuesday morning. Latest QPF among guidance shows most of the area receiving roughly 0.5-0.8" of rain. Models and ensemble members with widespread 1"+ totals have become few and far between. Though QPF has dropped a bit, thunder chances are kept alive by the ample low level instability still in play. Not a whole lot has changed on the thunder front, in fact, with about 200-400 J/kg of MUCAPE still expected across most of the area, the higher end of that expected further south in the CWA. Some decent low level shear also presents a low, but non-zero, threat for a couple of strong thunderstorms, with damaging winds being the primary concern. The strong storm threat is mainly a concern south of I-80 where the greatest instability and stronger low level flow can be found. At this point, at least a couple of light, embedded thunderstorms in this area appear probable. The most favorable time for thunderstorms lines up with the expected timeframe of the heavier and most widespread rainfall: roughly the six hour period between 10PM and 4AM. The soaking rain overnight will likely be followed by some scattered showers through much of Tuesday morning with a slight chance for a light thunderstorm or two hanging on into the morning as well. Doom && .LONG TERM... Issued at 220 PM CST Sun Jan 1 2023 Tuesday through Sunday... Key weather messages during the long term period are: * Near-record to record warm high temperatures on Tuesday in tandem with breezy southerly winds * Turning colder with a chance for snow including the possibility of minor accumulation late Wednesday into Thursday. Following Monday night into early Tuesday mornings threat of rain and thunderstorms, a dry slot is expected to race northeastward over the area as the occluding surface low shifts into IA. This is expected to bring an end to the rain threat across the area late Tuesday morning through the afternoon as our area becomes entrenched in the breezy and mild warm sector of this low following the early morning warm frontal passage. Breezy south- southwesterly winds, gusting at times to 30 to 35 mph will set the stage for near record warmth across the area. With 925 mb temperatures forecast at near-record 12C to 13C values and such a warm starting point to Tuesday from the system warm sector, we are feeling confident in mid 60s into the area and possibly even through the Chicago metro (GFS MOS guidance indicates a high of 65 for ORD!). See the Climate Discussion below for more on the record daily warmth that could be reached. The record warmth will come to a quick end into Tuesday night as the systems cold front shifts across the area. Low-level cold advection behind this front will take temperatures sharply down into the 30s Tuesday night, and little to no recovery is expected on Wednesday as the main upper low/trough begins to shift overhead. Temperatures Wednesday will thus be a good 25 degrees colder than they were on Tuesday! Forcing for ascent with the upper low will provide good chances for snow showers in this cooler atmosphere, especially late Wednesday into Thursday. While this does not look to be a large amount of snow for the area, some minor accumulations are possible. A short period of minor lake effect snow may also result on Thursday across parts of northwest Indiana as the winds along the back side of the system turn northerly across Lake Michigan. The weather pattern remains unsettled late week into next weekend as shown by long term guidance. A Pacific-origin wave has some semblance in the forecast late next week, but too early to add much value from a guidance blend-provided chance of rain or snow. KJB/MTF && .CLIMATE... There is a growing signal for highly anomalous warmth for the daytime Tuesday, January 3. Forecast highs are currently slightly above the record daily values shown below: High Years ------------------------ Chicago 60 1950 & 1874 Rockford 57 1998 If 60 is reached, it would be the first January daily high of 60+ since January 29, 2013 for both Chicago (63) and Rockford (62). MTF && .AVIATION... For the 00Z TAFs... Primary aviation concerns through the TAF period are as follows: * Expansion and persistence of ongoing low clouds and fog primarily at RFD/DPA, and possibly ORD/MDW/GYY later tonight * Brief opportunity for improvement from mid-morning to mid- afternoon Monday before low cigs and visbys redevelop in the evening * Potential for a prolonged period of LIFR to IFR cigs/visbys from Monday evening through at least daybreak Tuesday. The Lower Great Lakes are within a low-level pressure col extending to nearly 850mb leading to calm winds and little to no thermal or moisture advection. With stagnant low-level moisture and ever-so-gradually cooling temperatures, fog and low clouds are expected to expand/redevelop this evening as already evident by recent visibility and ceiling trends across north-central Illinois (RFD is reporting a visibility of 1/8 of a mile at press time). Even though forecast soundings show the low-level stable layer becoming more shallow with time, conditions appear unlikely to improve through the next 12 hours owing to the low-level pressure col remaining locked in place. As a result, confidence is relatively high in a prolonged period of LIFR to VLIFR conditions primarily at RFD/DPA. At ORD/MDW/GYY, confidence in low clouds and fog is lower since clouds scattered out earlier this afternoon. Any IFR (or lower) cigs and visbys may be dependent on the ongoing fog near RFD/DPA expanding eastward. For now, opted to go with a persistence forecast for the first 12 hours of the TAF (e.g. VFR) in favor of watching trends for AMDs. At least some opportunity for improvement in conditions at RFD/DPA will exists after sunrise tomorrow morning owing to thermal mixing both beneath and on top of the cloud layers and modest dry advection from gradually-increasing northeasterly winds. However, low-level warm air advection will gradually increase during the afternoon hours as a surface low pressure system materializes in the Plains. As a result, low clouds are expected to redevelop by mid-afternoon and especially early-evening, giving way to IFR and eventually LIFR conditions once again. Drizzle will become increasingly common toward the end of the TAF period as a warm front sharpens to the south of the terminals. An extended period of LIFR to IFR cigs and visbys appears possible from tomorrow evening through at least daybreak Tuesday. Borchardt && .LOT WATCHES/WARNINGS/ADVISORIES... IL...Dense Fog Advisory...ILZ003-ILZ004-ILZ005 until 9 AM Monday. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Memphis TN
836 PM CST Sun Jan 1 2023 ...New UPDATE....UPDATE... Issued at 812 PM CST Sun Jan 1 2023 Evening temperatures across the Midsouth range from the Middle 50s to middle 60s. Dew points are mostly in the low to middle 50s with a light south wind. Widespread, dense fog does not look as likely tonight, but we will need to monitor development, especially near the Alabama State line. Overnight lows should fall into the middle 50s to around 60 degrees. The HRRR has been consistent in the development of some light rain or drizzle late tonight. Rain associated with a longwave trough moving across the Plains should overspread the midsouth early tomorrow. The Storm Prediction Center has included most of the Midsouth in a Slight risk for severe thunderstorms in their day 2 convective outlook. This is a typical high shear, low instability setup that is common this time of year. A 40-50kt low level jet will help usher gulf moisture across the Midsouth featuring dew points in the 60s. A surface low will track to our north and an attendant cold front will approach the Midsouth late tomorrow night or early Tuesday keeping us in the warm sector of the storm most of the day tomorrow and tomorrow night. Our highest chance of strong to severe storms will likely be during the overnight hours as the LLJ develops and shifts over the area. Thermodynamic support may prove to be a major limiting factor. However, enhanced deep-layer flow and 40-50+ kt of effective bulk shear should be sufficient to support supercells. All modes of severe weather are possible, but confidence is not high that we will see any severe storms. Additionally, 2-3 inches of rain could result in localized flooding. Expect clearing conditions from west to East Tuesday with dry and cooler conditions returning by midweek. 30/Sirmon && .SYNOPSIS... Issued at 232 PM CST Sun Jan 1 2023 Mild temperatures and dry conditions are the main story for today. Several locations have climbed into the low to mid 70s this afternoon under mostly sunny skies. Warm and increasingly more humid conditions will funnel into the Mid-South tomorrow morning as a secondary warm front lifts across the region. Showers and thunderstorms will begin tomorrow afternoon with the first round of potentially strong to severe thunderstorms arriving early tomorrow evening. Another round of more widespread convection will roll into the Mid-South around midnight and continue through the overnight hours into Tuesday. A few strong to severe thunderstorms will accompany this line of activity. A minor flooding threat is also possible as rainfall totals will approach 2 to 3 inches for areas along and west of the Mississippi River. Dry and cool conditions will build in behind the exiting system with a return to near normal temperatures through the remainder of the workweek. AC3 && .DISCUSSION... (This evening through next Saturday) Issued at 232 PM CST Sun Jan 1 2023 A great start to 2023 as temperatures are impressively mild this afternoon. Several locations are already in the low to mid 70s under mostly sunny skies. Temperatures are expected to remain mild overnight as WAA continues in advance of a deepening trough over the Rockies. Expect lows to fall only into the low 60s. As WAA strengthens overnight, models are hinting at patchy fog and light drizzle developing overnight and through late tomorrow morning. A leading shortwave embedded in the main trough will lift northeast into the Lower Mississippi Valley tomorrow afternoon. This will kick off the first round of showers and thunderstorms by late afternoon. A marginal severe threat will exist from late afternoon through early evening as a batch of thunderstorms lift northeast along the Mississippi River. A low CAPE and modestly sheared environment could support a few instances of small hail and gusty winds with this activity. By late afternoon the main shortwave will be located over the Central Plains and begin to take on a negative tilt. Decent height falls will occur and steepen lapse rates over the Lower Mississippi Valley. Simultaneously, the LLJ is expected to strengthen and support a more organized severe threat across the Mid-South. A likely broken QLCS will arrive in eastern Arkansas before midnight and sweep across west Tennessee and north Mississippi overnight. Even though shear will increase substantially, MLCAPE will remain at or below 500 J/kg. This will limit the overall threat, but a few instances of damaging wind gusts and embedded circulations look possible given the kinematics in place. The main threat appears to be damaging winds with a secondary threat of short-lived tornadoes and isolated flash flooding. This threat will quickly push through the region by daybreak, exiting northeast Mississippi by mid morning. The current SPC outlooks handle this system well, accounting for both timing and expected intensity of this event. Will continue to advertise the two rounds of storms on messaging platforms and highlight the main threat as damaging wind gusts. The cold front will swing through the region by Tuesday evening. This will knock temperatures back down to near normal for the remainder of the week. Expect dry conditions and cool temperatures to persist each day. Highs will mainly be in the 40s and 50s with lows near freezing each night. The next system looks to arrive next weekend as another cold front enters the region. Thunderstorm chances look low with this system for now. AC3 && .AVIATION... (00Z TAFS) Issued at 621 PM CST Sun Jan 1 2023 VFR conditions this afternoon will gradually deteriorate overnight to MVFR and finally IFR by morning through the period. CIGs may even get down to LIFR intermittently tomorrow morning. Pre-frontal light drizzle should start making its way into the region before any heavier showers; mentioned -DZ at all sites from early morning through the afternoon. -SHRA should start up late afternoon from west to east, with increasing thunderstorm potential later on in the evening. The first wave of stronger convection with TSRA should reach MEM by about 00Z tomorrow, but timing is still inconsistent among CAMs. Winds will stay generally southerly around 6-8kt through the morning, picking up to 10-12kt tomorrow afternoon. As the front gets closer tomorrow, southerly winds and gust potential will increase. We could see gusts up to 30kt at MEM tomorrow evening. LLWS will likely need to be added to at least the extended MEM TAF for the 06Z cycle. Reduced visibilities (MVFR to IFR) due to fog and/or showers/thunderstorms will be possible on and off throughout the day tomorrow, especially at JBR. CAD && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$ PUBLIC FORECAST...JDS AVIATION...CAD
Area Forecast Discussion
National Weather Service Marquette MI
549 PM EST Sun Jan 1 2023 .SHORT TERM...(This afternoon and Tonight) Issued at 135 PM EST SUN JAN 1 2023 As a low pressure over northern Lake Superior leaves into northern Ontario this afternoon and evening, expect low level cloud cover to stay across the area for the most part (save for a break near Lake MI tonight). With delta-Ts getting close to 13C this afternoon into tonight, we could see some weak lake-effect snow/drizzle/freezing drizzle showers set up across the WNW wind snow belts. If drizzle/freezing drizzle occurs, some additional slick spots and icy patches could develop across the roadways; in that case, caution should be heeded for the morning commute Monday. That being said, the latest HRRR soundings show inversion heights getting up to around -10C, so confidence is increasing that we will more than likely see snow rather than drizzle/freezing drizzle this evening and tonight. In addition, CAMs show a couple of convergent bands setting up over the Keweenaw and near the Pictured Rocks National Lakeshore this evening and tonight; if this occurs, it would not be out of the realm of possibility for some isolated spots to get an inch or two of wet snowfall as some moderate snowfall rates could be seen at times underneath these bands. However, confidence is very low as to where the higher snowfall amounts would occur (if they do occur). .LONG TERM...(Monday through Sunday) Issued at 243 PM EST SUN JAN 1 2023 Given that there is still model uncertainty on timing of pcpn with developing Plains storm moving into the Great Lakes region Tue-Wed, have decided to hold off on any WSW headlines for now. Will issue a SPS to highlight the potential for a period of heavy snow on Tue, mainly for west and north central counties and maybe mention some mixed pcpn/icing potential for south central and eastern counties. Broad mid-level ridging downstream from the storm system developing over the southern/central Plains will build across the UP on Monday, resulting in dry conditions. By Monday evening EPS guidance shows a sub-1000mb surface low near the OK Panhandle that tracks northeast to just south of Des Moines, IA by Tuesday morning. Most of the models and EPS mean show the surface low moving slowly north into northern IA on Tuesday as the low occludes, but the vertically stacked low starts moving east Tuesday night. Comma-head stratiform precip will extend north of surface low along and immediately north of the system`s warm front. Precip will be forced by a combination of warm air advection up the sloped frontal surface and frontogenesis acting on the boundary. Ensemble means continue to indicate the area of stratiform precip weakening as it enters our area, but a stripe of QPF >0.50" seems probable across the west-north central UP. The large majority of this QPF should fall between 12z Tue-06z Wed, but precip could start a bit sooner far south and linger longer for the northeast wind lake effect snow belts for north central counties. Model 850 mb thermal fields and model fcst soundings now suggest the threat for any sleet/freezing rain on Tue should stay confined to south central and eastern portions of Upper Mi. Models continue to show a sharp cutoff to northern extent of precip associated with a very dry Canadian ridge north of this system, which could reduce QPF amounts for the northern Keweenaw. ECMWF, and to lesser extent the 12Z NAM, show a smaller area of heavy precip developing near the upper level low late Tuesday night into early Wednesday. While most precip associated with this feature misses us to our south, it could enhance lake effect or shift into our area delaying the end of precip so it should be monitored. Synoptic scale precip should be lifting out by Wednesday morning as the very dry Canadian high pressure ridge begins to sinks south into the Great Lakes region. Models have trended cooler with the air mass behind the low which would result in lake-850 mb delta-Ts now around 15-16C, but the very dry air mass/shallow CBL suggests additional LES on Wednesday should be mostly light. Weak low-level convergence, orographic lifting and favorable positioning of the DGZ within the CBL could compensate for shallow inversion heights to squeeze out an inch or two of fluffy accumulation for higher elevation locations, especially in Marquette and Baraga counties. Canadian ridging moves over the UP by Thursday morning with clearing skies, light winds, and fresh snow cover seem like prime ingredients for temperatures to bottom out across the interior. Raw NBM guidance shows temps approaching 0F across the interior west with 10th percentile guidance a few degrees cooler. Ridging continues Thursday and Friday suggesting clear and chilly nights with sunny and relatively comfortable days. Chances for pcpn next weekend looking less certain as models and ensembles seem to depict a split-flow pattern developing over the Western Great Lakes with perhaps more ridging and drier weather for Upper Mi. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 548 PM EST SUN JAN 1 2023 Conditions will conitnue to be high IFR/low MVFR this period at all sites. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 243 PM EST SUN JAN 1 2023 Generally light southeast winds of less than 20 knots this afternoon into tonight becomes westerly to 20 knots Sun afternoon behind a trough passage before winds diminish blo 20 knots and become light and variable again into Monday. A Plains low moving in next week results in northeast winds increasing to 25-30 knots from Tuesday into Wednesday when gale force gusts to 35 knots are possible. Northeast winds then weaken to 20-25 knots by Wednesday evening then become light and variable blo 20 knots late Wednesday night into Friday as the low moves east and is replaced by a high pressure ridge from the west. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...TAP LONG TERM...Voss AVIATION...07 MARINE...Voss
Area Forecast Discussion
National Weather Service Morristown TN
908 PM EST Sun Jan 1 2023 ...New UPDATE... .UPDATE... Issued at 904 PM EST Sun Jan 1 2023 Forecast for tonight generally looks to be on track. Temperatures are generally running a bit lower than forecast, so will bump most min temps down slightly with this update. Will also tweak sky and hourly temps/dew points. Some fog is already starting to show up, and this will bear monitoring to see how extensive it will become. && .SHORT TERM... (This evening through Monday) Issued at 312 PM EST Sun Jan 1 2023 Key Messages: 1. Clearing skies this evening will lead to patchy dense fog overnight. 2. Additional clouds move in tomorrow ahead of our incoming storm system on Tuesday, a few sprinkles possible across the southern TN Valley late tomorrow afternoon. Discussion: Skies will continue to gradually clear this afternoon and evening. This will allow patchy dense fog to develop overnight as low-level moisture remains across the area. Though it`s possible that dense fog may be more widespread than patchy so will have to closely monitor trends through the night. Overnight lows will be mild with temps in the lower to mid 40s for most areas. Heights begin to rise tomorrow in response to the developing storm system across the Great Plains. With the increasing southwest flow across our area additional clouds begin to move in during the late morning to afternoon hours. So expect a little bit of sunshine after the morning fog burns off but then clouds begin to re-enter through the day. Areas east of I-75 should see more sun compared to areas west of I-75. A few sprinkles are possible late tomorrow afternoon across the southern TN Valley as moisture and upper- level divergence increase across the area. Highs tomorrow should be a few degrees warmer, with max temps ranging from the low to upper 60s. && .LONG TERM... (Monday night through next Sunday) Issued at 312 PM EST Sun Jan 1 2023 Key Messages: 1. A strong storm system will affect the area Tuesday through Wednesday, bringing widespread rainfall, gusty winds, and a few thunderstorms. 2. Strong winds are expected in the Tennessee mountains and nearby foothills early Tuesday morning through the afternoon. 3. A few storms could be strong to severe, especially in southeast Tennessee. 4. Localized flooding is also possible in low-lying and poor drainage areas that see repeated rainfall. Monday Night through Thursday At the start of the period, an increasingly negative trough will be ejecting out of the Rockies with a ~997mb associated surface low. These features will continue to progress northeastward towards Missouri and Iowa with recent height rises and southerly flow producing notable WAA across the eastern U.S. During this time, the surface low will be an open wave with the associated warm front initially south and west of the region and its cold front far to the west. This will all lead to increasing PoPs Tuesday morning. With upper divergence via direct ageostrophic vertical circulation, a strengthening of the 850mb jet to 50 - 60 kts and the MSLP gradient will create gusty winds area-wide. With the most recent model data, the set up for mountain wave winds is lacking in the magnitude of the gradient over the terrain (60 micrometers/km or less). However, a jet of this magnitude with even some enhancement is sufficient for confidence in high winds in the mountains. At this time, it still remains somewhat borderline as to if widespread warning criteria will be met, so no High Wind Watch was issued on this shift. There still remains uncertainty in the timing of convection with the favorable upper-level divergence. The 18Z HRRR brings organized convection into the region by the end of the run with the FV3 painting a similar picture with surface-based convection by the afternoon. However, other mesoscale and global models are still showing a slower progression more towards the evening and overnight hours when dynamics are less favorable. In any case, deep-layer shear values of 50+ kts support organized convection in a linear or discrete form, depending on the exact direction of the flow. This will also be combined with low-level SRH values of 150 to 250 m2/s2, enhanced by the low-level jet. Ultimately, this jet will highlight kinematic-induced damaging winds as the highest concern within any storms. Tornado potential remains uncertain due to these continued disagreements for instability being surface-based on Tuesday. With all of these factors in mind, the last SPC outlook for Day 3 remains in line with the current model guidance. The threat for flooding still remains with indications for a slight increase in overall rainfall totals from the recent update. Most places will still likely be near 2" with northeastern areas likely to see lighter values due to strong downsloping. Also, the latest FFG shows that more than 3" in 6 hours or over 2" in 3 hours would be needed for flash flooding. Nevertheless, a deep warm-cloud layer and potential for multiple rounds of rainfall keep flash flooding concerns, especially Tuesday evening through Wednesday morning. With all of these factors in mind, messaging will be kept largely the same with confidence expected to increase as the HREF moves into the period. By Thursday, notable height falls and passage of the cold front will usher in notably cooler temperatures with a few light sprinkles or flurries possible. Friday through Sunday By the weekend, surface high pressure of 1,030mb or more will be set up across the eastern U.S. with gradual height rises towards the end of the period. This will keep the region dry with moderation on Friday and Saturday with some indications of Pops returning by Sunday. Values were kept at slight chance due to this limited confidence. && .AVIATION... (00Z TAFS) Issued at 521 PM EST Sun Jan 1 2023 The sky has mostly cleared, and it looks like there will be fog development again tonight. Details are still not certain, but right now it looks like CHA will drop to at least MVFR while TYS is expected to drop to at least IFR and at TRI LIFR conditions look likely later tonight. Conditions should improve to VFR during Monday morning all sites, but at CHA it may only improve to MVFR or briefly to VFR before MVFR cigs roll back in. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 47 68 58 69 / 0 10 40 100 Knoxville McGhee Tyson Airport, TN 44 66 53 70 / 0 0 30 100 Oak Ridge, TN 45 64 52 68 / 0 10 30 90 Tri Cities Airport, TN 40 65 49 69 / 0 0 10 80 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...SR LONG TERM....BW AVIATION...
Area Forecast Discussion
National Weather Service Pendleton OR
238 PM PST Sun Jan 1 2023 .SHORT TERM...Tonight through Tuesday night...Overall fairly benign weather continues into Monday morning as impacts remain focused on fog/freezing fog around the Columbia Basin into the foothill areas. It’s worth noting the development of a robust stratus deck combined with modest up-slope flow could facilitate some very light snow shower and/or flurry activity across the east slopes of the Washington Cascades headed through Monday morning as well; low confidence but only minor impacts should this activity occur. Monday afternoon through Tuesday night a series of two rather weak disturbances brings a chance of light snow to the higher elevations, otherwise dry. Tonight into Monday morning the interior Pacific Northwest remains under the influence of a ridge of high pressure with a layer of stratus and patchy fog already in place over the Columbia Basin, the artifact of ample surface moisture, temperature inversion, and subsidence aloft. Due to a high degree of confidence in additional fog formation as depicted by guidance like the HRRR in combination with freezing overnight temperatures, Freezing Fog Advisories have been issued for the Kittitas Valley through the Yakima Valley into the Columbia Basin in addition to the foothills of the Blue Mountains. As the fog and stratus layer deepens overnight, westerly to southwesterly flow between 900-800mb may facilitate the development of light snow shower/flurry activity along the east slopes of the Washington Cascades as well. Guidance varies significantly in whether any of this activity actually develops, but there appears to be the proper forcing/moisture, and enough model consensus to add this slight chance(10-15%) to the forecast. Fortunately, impacts appear very minor should it occur. Monday afternoon the axis of the ridge shifts westward due in-part to an approaching trough, although this feature will be rapidly weakening as it moves onshore into Oregon and Washington. Deterministic and ensemble guidance agree the vast majority of the precipitation associated with the aforementioned feature dives to our south Monday night and Tuesday but are do show some discrepancies in how much is able to make it northward through the CWA. The NBM in particular wants to keep much of the region dry outside of just the Cascade crests, deviating from the consensus of most model systems which paint light snow working through central/northern Oregon, the Cascades, and the eastern Mountains. The forecast was adjusted to match the latter, “wetter” scenario. Overall, impacts don’t appear significant with just light snow amounts expected, the highest of which(1-3 inches) occurs along the crests of the Oregon Cascades; generally less than 0.5-1 inch elsewhere. Tuesday evening a similar, weak upper-level shortwave passes through the inland Pacific Northwest, containing even less moisture compared to the one prior. Any chances for snow likely remain confided to just the Cascade crests for this feature leaving the rest of the region dry. It’ll be worth keeping an eye on any model changes as we get closer and confidence in the exact forcing and available moisture increases. A transitory shortwave ridge preceding the next weather disturbance quickly arrives over the region later Tuesday night into Wednesday morning. Schuldt/99 .LONG TERM...Wednesday through Sunday...The long term is expected to be a somewhat progressive pattern as ridging breaks down across the region, but models remain in disagreement on the tracking of potential troughing and how much we will be affected by it in terms of precipitation. Deterministic guidance expects the following overall pattern: we should remain under dry ridging to begin Wednesday, but a deep upper-level low just offshore will push towards the coastline, bringing a frontal boundary inland into Thursday. This will tighten the pressure gradient and bring breezy winds, but these winds should only reach advisory levels in strength, with gusts to around 40 to 45 mph with moderate confidence (60%). This front is expected to weaken and fall apart while the aforementioned low lifts into the Canadian coastline, keeping the bulk of any precipitation higher elevation in nature. Meanwhile, overall flow will shift to southwesterly, promoting a warming trend that will increase temperatures to above average to end the week. Model divergence increases over the weekend, but at least some form of troughing should continue over the region with mountain snow continuing and possibly low elevation rainfall possible, while another deep upper low begins to approach from the Gulf of Alaska. Comparing ensembles versus the deterministic analysis, clusters show the deep low`s approach during the middle to late portion of next week, with then some form of troughing elongated over the PacNW promoting the southwesterly flow expected to bring warmer temperatures along with possible waves of light to occasionally moderate precipitation. Primary differences are how much energy from the troughing drops further south into California, which could present less precipitation chances for the weekend. Overall, there is moderate confidence in the above average temperatures, around 40-50% at this time, with lower confidence in precipitation and the timing of. Therefore, the NBM blend of a more broad swath of precipitation is the accepted solution currently to account for uncertainty. Goatley/87 && .AVIATION...00Z TAFs...FG/BR will continue to re-develop this evening, affecting ALW/PDT, potentially PSC/YKM as well. CIGs and VSBYs will drop considerably, possibly remaining LIFR overnight. Otherwise, look for lowered stratus ceilings, with MVFR to IFR conditions possible DLS/YKM/PSC, and light winds all sites less than 10kts. Goatley/87 && .PRELIMINARY POINT TEMPS/POPS... PDT 25 32 24 37 / 0 0 10 10 ALW 27 34 24 38 / 0 0 0 10 PSC 27 35 27 37 / 0 0 10 10 YKM 22 32 23 34 / 10 10 10 10 HRI 28 35 27 37 / 0 0 10 10 ELN 19 28 19 30 / 10 10 10 10 RDM 20 33 23 40 / 0 10 20 10 LGD 21 31 21 32 / 0 0 0 10 GCD 18 36 19 37 / 0 0 20 30 DLS 31 37 30 40 / 0 10 20 20 && .PDT WATCHES/WARNINGS/ADVISORIES... OR...Freezing Fog Advisory from 8 PM this evening to noon PST Monday for ORZ044-508. Freezing Fog Advisory until noon PST Monday for ORZ507. WA...Freezing Fog Advisory from 8 PM this evening to noon PST Monday for WAZ028. Freezing Fog Advisory until noon PST Monday for WAZ029. Freezing Fog Advisory until noon PST Monday for WAZ026-027. && $$ SHORT TERM...99 LONG TERM....87 AVIATION...87
Area Forecast Discussion
National Weather Service Pueblo CO
830 PM MST Sun Jan 1 2023 .UPDATE... Issued at 823 PM MST Sun Jan 1 2023 Updated the forecast based on current trends and HRRR guidance. Believe we will see a bit more fog and areas of light drizzle/freezing drizzle east of the mtns/plains interface later tonight and tomorrow morning. Seeder feeder process ongoing at this time in the greater PPR, but mid upper levels fcst to dry out later tonight and upslope will bring low clouds to the general I-25 corridor region, especially areas N of the Raton Mesa. This will bring a better chance of fog and drizzle to the above mentioned areas. I have also bumped up snow amounts a slight bit for the western sections of El Paso county. /Hodanish && .SHORT TERM...(This evening through Monday) Issued at 245 PM MST Sun Jan 1 2023 Key Messages: 1) Moderate to heavy snow expected to continue along the mountains overnight and through tomorrow. 2) Freezing drizzle and light snow possible along the Palmer Divide area, but high uncertainty still exist. 3) Dry in most other locations with overall near seasonal temperatures. Tonight and Tomorrow Synopsis... Active and impactful weather is expected for the southern Colorado region tonight and through Monday. Synoptically, a large trough is expected to dig and wrap up around the four corners region and push off to the northeast over Colorado. This storm system will bring a slug of Pacific moisture along with it, causing heavy snow along the mountains, and possible wintry precipitation along the lower elevations. More details about expected forecast conditions and hazards are discussed below. Tonight... Precipitation: For precipitation, the greatest confidence for precipitation development/maintenance remains over the mountains, valleys, and eastern plains. Both deterministic and ensemble model guidance are in relatively good agreement about moderate to heavy snow persisting over the higher terrain and spreading across the valleys this evening and overnight. As the trough approaches from the west, strong and persistent southwesterly flow will maintain orographic forcing, the strongest of which will be over the San Juan Mountains given better orientation of the winds. With the increasing synoptic forcing and persistent orographic forcing, along with the Pacific moisture advecting over southern Colorado, moderate to heavy snow will continue along the mountains overnight, with the heaviest along the San Juan Mountains. Snowfall rates are likely to be between 1-2 inches per hour overnight along the San Juan Mountains. Across the mountain valleys, such as the San Luis Valley (SLV) and Arkansas River Valley, precipitation is expected to increase this evening as the trough begins to edge its way over western Colorado and help to push precipitation off of the higher terrain. For areas around the Arkansas River Valley, all snow is expected, with light to moderate snowfall amounts expected. The SLV however is expected to mostly experience a rain/snow mix as surface temperatures hover right around and just above freezing for the majority of the night. As temperatures finally drop late in the night/early morning, a transition to mostly snow is expected within the SLV, but precipitation coverage wills start to drop at that time, as the trough starts pushing over and drier air behind the system starts advecting into the region. At lower elevations, drier conditions are expected. As the trough starts pushing over the region, an elevated drier and warmer layer of air will begin to wrap around the eastern periphery of the system. This will limit any major precipitation chances for the plains. With that said though, an isolated rain shower or two will be possible given modest upglide forcing from this elevated layer. The area of greatest uncertainty at this time is along the El Paso County/Palmer Divide areas. Model guidance has struggled with trying to resolve this region and the possible precipitation development along these areas, along with model guidance now starting to trend toward a more disorganized and slower low as compared to previous guidance. Given that model guidance is still struggling to resolve things less then 24 hours out from possible impacts, this is leading to a high-impact-low-confidence- event (HILCE). With all of that said, here are the current thoughts about the evolution of things. As the trough starts to approach and edge its way over Colorado overnight, the aforementioned drier and warmer layer will start to nudge its way further north and over the area of concern. This drier and warmer layer of air will help to limit any major precipitation development just like the eastern plains. However, a shallow cold airmass will slowly drift into the southern Colorado region overnight. As this takes place, winds at the surface will take on a more easterly component and modest surface upsloping will develop along the Palmer Divide region. Given this, shallow precipitation is expected to develop. During the evening/early overnight hours, the warmer layer aloft would be expected to melt any liquid from the precipitation, and light freezing drizzle will be possible given the below freezing surface temperatures. Then progressing through the night, colder, but still drier, air moves in and any precipitation that is present would be expected to transition to light snow. Temperatures... For much of the region, overnight temperatures will remain above average. Like previously alluded to, a weak and shallow cold front will sag southward Sunday evening. This will help to bring in modestly cooler air, but increasing cloud cover will limit the amount of radiational cooling that could take place, and temperatures will not drop as much as they would otherwise. Given this, most across southern Colorado will remain 10-20°F above average for this time of year. Tomorrow... Precipitation: For the day Monday, active weather is expected to continue. The trough is anticipated to be pushing across the Colorado region and begin moving to the northeast throughout the day. This will keep synoptic and orographic forcing in place across southern Colorado, though moisture will start to decrease as drier advects in behind the system. Given this, precipitation along the mountains and valleys will decrease in coverage through much of the day. With that said though, snow, more scattered in nature, is expected to continue along the mountains given the forcing mechanisms in place. As the trough does pass over the region, and lapse rates steepen from cooler air associated with it, modest instability is expected to develop. Given this instability, transient convective snow bands will be possible along the mountains. As for the eastern plains, they will continue to remain dry throughout the day. An isolated shower or two is possible though as the ascent from the dry/warm layer continues over that area. During the later afternoon, as the trough and associated low move to the northeast, surface winds will become more northerly behind the system. These surface winds will lead to more upsloping along the Palmer Divide, and that, along with better synoptic support, will allow for isolated to scattered light snow showers to develop along northern El Paso County. Temperatures: For the daytime, a wide varying set of temperatures are expected. Areas further west will experience more westerly winds and compressional warming. This will lead to slightly above average temperatures across western areas. Across parts of the plains, partially clearing skies will help to warm much of this area to around average for this time of year, with the warmest temperatures in the far southeastern plains, where more clearing is expected from the dry slot. Areas further north in the plains will remain near to slightly below average given the weak cold front and cloud cover hindering any major warming. .LONG TERM...(Monday night through Sunday) Issued at 245 PM MST Sun Jan 1 2023 Key Messages: 1) Chilly Tuesday behind departing system then a warming trend. 2) Pacific storm system brings snow mainly to Continental Divide region around Friday and Sunday into Monday. .Monday night and Tuesday...Latest models runs continue the idea of cyclogenesis in western Kansas Monday evening due to the shortwave, current off the coast of the Baja Peninsula, moving into the region. Some models hint that some light precipitation may move into the eastern plains Monday evening. Currently, amounts look to be light, if any precipitation moves into the the region. On Tuesday, chilly northwest flow develops over the region. Orographics, along with a weak disturbance, will result in some occasional light snow near the Continental Divide region. .Wednesday and Thursday...Shortwave ridge builds into the region. Northwest flow may keep some light snow over the Sawatch range on Wednesday with little if any accumulations. Warming trend develops with highs reaching above seasonal values by Thursday. .Friday through Sunday...Ensemble means have one Pacific trough passing over the region around Friday with another system starting to approach the region on Sunday. The NBM and ensemble means suggest mild weather continuing into the weekend with best chances for snow near the Continental Divide. --PGW-- && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 245 PM MST Sun Jan 1 2023 KALS: Precipitation will be moving off of the mountains this afternoon and entering the vicinity of the terminal by 23Z. A rain/snow mix is expected to set in by about 03Z, with quickly lowering cigs and cool fog limiting visibility at times, bringing things down towards IFR or worse. Precip type switches to snow by about 06Z, and with winds expected to lighten overnight fog is anticipated in the valley through the end of this forecast period. KCOS: The incoming system will become less organized as it passes through, giving us a mixed precipitation bag over the next 24 hours. Showers will move near the TAF site by 03Z, and precipitation will begin as a cool rain/snow mix with quickly lowering cigs and decreases to visibility. Currently, a brief period of FZDZ is expected to pass by the terminal between 08-10Z tonight, before becoming primarily snow. After precipitation ends early tomorrow morning, lingering low stratus and potentially fog/mist will last through the end of this forecast period. KPUB: VFR conditions are generally expected through 24 hours. Some precipitation may drift close to the terminal after about 05Z, which will lower cigs into the MVFR range closer to the end of the forecast period. Winds will be mostly light and should maintain an easterly component throughout && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 5 PM MST Monday for COZ058-059-061- 084. Winter Storm Warning until 5 PM MST Monday for COZ060-066-068. Winter Weather Advisory until 11 AM MST Monday for COZ067-072- 073-075. && $$ UPDATE...HODANISH SHORT TERM...SIMCOE LONG TERM...PGW AVIATION...GARBEROGLIO
Area Forecast Discussion
National Weather Service Raleigh NC
1033 PM EST Sun Jan 1 2023 .SYNOPSIS... High pressure will build across and offshore the South Atlantic states through Monday night. A cold front will approach from the west mid-week. && .NEAR TERM /THROUGH TONIGHT/... As of 1030 PM Sunday... Dense Fog Advisory in Effect through 10 AM Monday for most of central NC... Aloft, a broad ridge centered across Cuba was generating zonal flow across central NC. At the surface, a 1021 mb high off the SC coast was maintaining weak southwesterly flow across our area, with dewpoints in the mid 40s to low 50s. Mostly clear skies were helping temps to quickly lower to the dewpoint temperatures, and with residual moisture across the region, many areas are developing dense fog. A Dense Fog Advisory was issued for portions of the Piedmont and Sandhills for visibility of one-quarter mile or less through 10 am Monday morning. Areas of the Coastal Plain and NE Piedmont may need a Dense Fog Advisory if fog continues to develop across the region. Fog will be slow to clear/lift Monday morning. Overnight temperatures will dip into the mid-40s. && .SHORT TERM /MONDAY AND MONDAY NIGHT/... As of 200 PM Sunday.. Monday will likely start similar to the previous couple days with fog, possibly dense in spots, slowly rising to a low overcast through much of the morning hours. Monday morning an upper level closed-low will be positioned over the Four Corners region assisting in the amplification of a downstream ridge axis over the Southeast. The ridge axis will continue to build over the Mid-Atlantic through Monday before shifting offshore late Monday night into Tuesday. At the surface, broad high pressure will be draped along the Carolina coastline Monday morning before slipping offshore during the afternoon/evening hours as low pressure pushes into the central Plains. The persistent airmass characterized by above normal temperatures and remnant low-level moisture will largely remain through Monday night favoring a redevelopment of fog and very low overcast over much of central NC. The climatologically favored areas will be over the northwest and southern Piedmont where confidence is highest, but patchy fog will likely still be an issue across central NC Monday night into Tuesday morning. Highs will be difficult to pinpoint Monday afternoon with any confidence as locations stuck in the low overcast will likely remain in the 50s while places that can manage to scatter out may shoot up into the mid/upper 60s. The return of southerly flow and redevelopment in low overcast will keep lows in the upper 40s to low 50s (roughly 20 degrees above normal). && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 210 PM Sunday... Tuesday and Wednesday: Medium-range model guidance starting to come into better agreement. Aloft, the mid-Atlantic will be situated between the sub-tropical ridge to the southeast and low to the northwest lifting from the central Plains to the upper MS Valley Tue/Tue night. The ridge will get pushed further east over the Atlantic as the low slowly migrates eastward into the OH Valley with its attendant trough extending south to the Gulf. Gulf moisture advection will increase Wed/Wed night, with the moist axis extending north-northeastward through the Southeast and mid-Atlantic. At the surface, central NC will be situated between high pressure to the east over the Atlantic and the approaching frontal system to the west. A warm front will lift northward through the area on Tue/Tue night ahead of the approaching cold front, though the timing varies between the models. The southeasterly return flow around the high will advect Atlantic moisture into the area Tue/Tue night, ahead of the arrival of the more Gulf moisture immediately ahead of the front Wed/Wed night. A period of some isentropic lift driven rain across the area is possible prior to the warm front lifting through and the rain becoming more convective in nature. The best chance for heavy rain and thunder will be immediately ahead of the front Wed/Wed night. Although fropa timing is not quite solidified, generally the cold front should be through central NC Thu morning. Temperatures will be significantly above average. Expect highs in the mid 60s to mid 70s. Lows in the mid 50s to low 60s Tue night will likely decrease for Wed night in the wake of the front. How much of a decrease will depend on fropa timing, but for now expect lows Wed night in the mid 40s NW to around 50 degrees SE. Thursday and Friday: Aloft, the upper low will swing through the OH Valley and into the mid-Atlantic Thu/Fri, then lift northeast toward the New England coast/northern Atlantic Sat. At the surface, the cold front will continue to progress eastward and well out over the Atlantic Thu through Sat as Canadian high pressure drops south through the Plains then drifts eastward through the Deep South and Southeast, into the mid-Atlantic. Temperatures should decrease to closer to normal by Fri. For the Weekend: Forecast confidence decreases quite a bit, due to model solutions diverging with the track of a trailing upper low/wave. The trailing upper wave/low will track eastward from the northern/central Plains, through the upper/mid MS Valley and into the Great Lakes or OH Valley while a weak ridge progresses eastward through the Southeast and mid-Atlantic. The track of the upper low/wave will impact chances for precipitation over the weekend, so for now will keep the forecast dry until there is better model agreement/consistency. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... As of 730 PM Sunday... 24-hour TAF period: With a moist boundary layer and calm winds as high pressure sits over the region, widespread dense fog and LIFR stratus are expected to develop after midnight tonight across the NW Piedmont (including INT and GSO). Fog is also expected around FAY, but it will likely occur later and confidence in its development there is a bit lower. The lowest chance of fog is in the NE (especially RWI) where high-res guidance (including the RAP, HRRR and GLAMP) shows less fog than before, a trend that is reflected in the latest TAFs. Fog will be slow to lift tomorrow, lingering until the mid to late morning, especially at INT and GSO. Winds will be from the south/southwest tomorrow and light (5 kts or less). Looking beyond 00Z Tuesday: Given no change in the residually moist airmass that will linger across the South Atlantic states, redevelopment of LIFR fog and/or low overcast will likely occur once again Monday night. Strong swly flow and transport of anomalously moist air ahead of a cold front will produce widespread rain/isolated storms and sub-VFR conditions in cntl NC Tuesday night and Wednesday. && .CLIMATE... Record Temperatures for Wednesday January 4: SITE RECORD MAX RECORD HIGH MINIMUM GSO 74/2005 57/1950 RDU 76/2005 58/1950 FAY 77/2004 60/2004 && .RAH WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 10 AM EST Monday for NCZ007-021>025-038>042- 073>077-083>086-088. && $$ SYNOPSIS...MWS/JJT NEAR TERM...JJT SHORT TERM...Swiggett LONG TERM...KC AVIATION...Danco/MWS CLIMATE...RAH
...Update to aviation forecast discussion...

.DISCUSSION... Issued at 206 PM CST Sun Jan 1 2023 - There will be chance of rain Monday with a few thunderstorms into Monday evening. -The rain may change over to a wintery mix of precipitation late Monday night across north central KS before before ending Tuesday morning. Early this afternoon an amplified upper level trough was located across the Western US with the main upper jet digging into the northern Baja CA region. A broad upstream H5 ridge was noted across the southern and central Plains. At the surface an area of low pressure was located along the TX/OK/KS border with a warm front extending east-northeast across southern KS. Tonight through Tuesday: The upper level trough will amplify as it lift northeast out of the southwestern US into the central high Plains. A low-level jet will develop later Tonight and advect residual Gulf Moisture northward into eastern KS Monday morning. As the WAA increases low stratus with areas of drizzle will develop across OK this evening and spread northward into eastern KS through the early morning hours of Monday. As the DCVA increase ahead of the H5 trough axis, combined with anisotropic lift, will cause widespread rain to develop across the eastern counties of the CWA. The warm sector will destabilize enough during the afternoon hours for 200 to 500 J/KG of MUCAPE combined with effective shear over 40 KTS, a few of the elevated thunderstorms may produce small hail Monday afternoon into the early evening across the eastern half of the CWA. At this time the surface based severe thunderstorms will remain southeast of the CWA. High temperatures will reach the mid 50s to lower 60s across the east central KS. The north central counties will only reach the mid to upper 40s as the surface warm front will only lift northwest of an ABI, to MHK, to HIA line. The front will push southeast across the remainder of the CWA as the surface low deepens ans shifts northeast across far northeast KS into northwest MO Monday evening. As the upper low tracks northeast into northern IA by 18Z TUE the precip should lift northeast of the CWA during the early morning hours of Tuesday. The cold air advection may cause temperatures to drop below freezing as the precip exits north central KS, which may cause a wintry mix of rain changing to freezing drizzle and snow. At this time amounts look to be very light but if there is a couple hours of freezing drizzle and snow across the north central KS, then there may be a few slick spots on area roadways Tuesday morning. Total QPF Monday into Monday night will range from 0.4 inches in the far eastern counties to only 0.10 inches in the far southwest counties. Any elevated thunderstorms that develop may provide isolated higher amounts. It will feel cooler on Tuesday as the surface CAA increases and highs only struggle back into the lower to mid 40s across east central KS with mid to upper 30s across north central KS. Tuesday night through Thursday: The upper level trough will amplify as it digs southeast from northern IA into the OH River Valley, then east into the mid Atlantic states. The mid and upper level flow will become northwesterly as a surface ridge of high pressure builds southeast across eastern KS. High temperatures will continue to be cool with lower 30s northeast to the upper 30s across the southern counties of the southern CWA. Thursday night through Sunday: Split flow will develop across the North America, with a northern stream ridge developing across the northern Plains, and the southern stream of the upper level jet will become more zonal. A weak H5 trough will move east cross the central Plains Friday night and I cannot rule out a few showers into Saturday morning. High temperatures will gradually moderate through the 40s by next weekend. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 521 PM CST Sun Jan 1 2023 Have backed off a bit on the onset of limiting conditions and the extent of the limitations at this point based on less humid boundary layer at issuance time and belief the HRRR and RAP are too low with visibilities and influencing blends too extreme. IFR conditions are still expected however for the majority of this forecast. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION...Gargan AVIATION...65
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
703 PM MST Sun Jan 1 2023 .UPDATE... Issued at 656 PM MST Sun Jan 1 2023 00z KUNR sounding depicts a modest dry layer below below 600mb, which as expected, is impeding the progress of precipitation moving northeast out of southeast WY/NE panhandle. Wasted lift, but this is accounted for in the forecast tonight. More concerning is the 00z HRRR trends that tighten the northern edge of the main snow band, suggesting lesser amounts from Spearfish to Philip, including parts of Pennington County. HRRR still shows upslope enhancement over the eastern Foothills, however. The secondary band of strong frontogenesis that occurs over south-central SD Monday night suggests higher snow amounts than current forecast may be needed. Don`t anticipate major changes in the forecast this evening, but will be watching satellite/radar developments as well as how they mesh with the entire 00z suite of guidance. && .DISCUSSION...(This Evening Through Sunday) Issued at 218 PM MST Sun Jan 1 2023 Upper trough crossing the central/southern Rockies this afternoon, will eject into the region, supporting widespread snow across most of the area Monday. Two rounds of LSA and associated precip on track with the first round tonight into Monday, and the main round of lift expected Monday night across scentral SD. The main trend of all hires model data has been to tighten the precip gradient across the FA and shift the heaviest band of snow south in line with the strongest FGEN. This has resulted in slightly lower snowfall totals on the northern end of the precip shield, mainly affecting areas along and north of I90 due to dry air entertainment from a building high to the north. There remains a weak upslope enhancement signature in the eastern BH foothills, but given concerns on dry air, strong sink flow NW of the main FGEN band, unfavorable profiles for efficient crystal production, and weak easterly flow, upslope enhancement is expected to be limited. Hence, Pennington County could potentially struggle to reach warning criteria, esp if strong subsidence develops north of the main FGEN band. The only change to the hazards was to add southern Campbell County to the warning given continued high probs for warning levels from Wright south. First band of snow will shift north Monday with a potential lull/downtrend in snow most areas Monday afternoon. Second/main round of lift per impressive FGEN will push into scentral SD Monday night and support heavy snow over scentral SD. Deep DGZ lift and strong forcing will allow for 1-2 inch (or more) snowfall rates just south of the ll FGEN max with some places expected to see well over a foot there. NW of the FGEN band, snow is expected to be light, potentially stopping in some areas given expected strong subsidence, limiting snow amounts further. Still expecting breezy northerly winds Monday night into Tues over scentral SD, with some blowing snow possible, although not too terrible. Snow will shift east and end Monday night across the area west to east, possibly lingering over scentral SD into Tues morning. Not much cold air behind this system with seasonal temps the remainder of next week and dry conditions until next weekend when another trough is progged to cross the region. && .AVIATION...(For the 00Z TAFS Through 00Z Monday Evening) Issued At 419 PM MST Sun Jan 1 2023 Conditions will deteriorate to MVFR/IFR from southwest to northeast tonight. Widespread MVFR/IFR conditions expected Monday. Snow will spread northeast tonight into Monday with areas IFR/LIFR conditions Monday, especially from the Black Hills to KICR. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory from midnight tonight to midnight MST Monday night for SDZ024-025-072-073. Winter Storm Warning from midnight tonight to 5 AM MST Tuesday for SDZ026-028-031-042>044. Winter Storm Warning until 5 AM MST Tuesday for SDZ027-029-030- 041-074. Winter Weather Advisory from 2 AM Monday to 5 AM MST Tuesday for SDZ032. Winter Storm Warning from 3 AM Monday to noon CST Tuesday for SDZ046-047-049. WY...Winter Weather Advisory from midnight tonight to midnight MST Monday night for WYZ057. Winter Storm Warning until 11 PM MST Monday for WYZ055. Winter Weather Advisory until 11 PM MST Monday for WYZ058. && $$ Update...Helgeson DISCUSSION...JC AVIATION...Helgeson
Area Forecast Discussion
National Weather Service Las Vegas NV
749 PM PST Sun Jan 1 2023 .SYNOPSIS...Rain and snow showers will dissipate tonight as an upper low slowly shifts east away from the area. An active weather pattern will continue through the week keeping temperatures cool and bringing additional chances for precipitation. && .UPDATE...Continuing to deal with the upper level low that has been plaguing the southwest US since last year (haha). Satellite and mesoanalysis through the evening showed a broad area of clouds and precipitation rotating around the center of the low, now likely situated over western Arizona base on cloud circulations. Widespread clouds and showers were noted through the evening in eastern Nevada through southeast California into western Arizona. Further west, it has dried out as the back end of the forcing has moved in and dry northwest flow and upper level subsidence has taken over. The low is expected to slowly move east through the night. This will shift the main area of clouds and precipitation further east as well, albeit slowly. Base don where the better forcing should line up, the highest potential for continued showers overnight will be in western and northern Mohave County. While the heaviest precipitation should be winding down in the next hour or two, will need to watch for residual impacts due to rain in northern Mohave County into northeast Clark County as the ground is saturated and responses in local stream gages have been noted. Additional rainfall may result in minor flooding in spots, especially in the next few hours before the main axis of moisture and forcing moves east of the area. The latest models have slowed down the eastward progression of the low and thus have slowed down the precipitation exiting. Latest trends would suggest that precipitation may continue in northeast Mohave County until about 12Z. Updated precipitation chance for tonight to reflect this trend using the best performing models through the evening. QPF after 10pm should be light with 6-hourly amounts remaining under 0.25 inches at all locations after 06Z tonight. Snow levels will fall to around 3000ft behind the system, but that should be displaced from where precipitation should be ongoing in the warm sector. Snow levels where precipitation is expected should remain around 5000-6000ft through the night, and no changes in the snow amount or impacts were made from the previous forecast with a 1 to 3 inches possible tonight in the terrain of Mohave County and northern Lincoln County. Winds were the other lingering issue with this system through the evening. As the low has slowed down, winds have been able to over perform in Nye, Inyo, and Esmeralda County as well as the Yucca Valley region of San Bernardino County. With continued northerly flow expected in this area through much of the night, and a decent 850mb jet of 30-40KT noted on mesoanalysis and model output, increased winds through this region for the overnight period. Not expecting widespread wind impacts overnight, though some minor wind impacts due to wind gusts up to 40 MPH are possible in Esmeralda and western Nye county through the morning. --Nickerson-- && .Previous Discussion...1245 PM PST Sun Jan 1 2023 .DISCUSSION...Through next Sunday. Wet and white start to the New Year. Still more to come through tonight as current upper low over the area slowly migrates east. Not expecting impactful snowfall or winds to continue overnight so will allow our current products to expire on schedule at 4 pm. Have seen some pockets of heavy rain in the lower Colorado River Valley and southern Mohave County associated with isolated thunderstorms that developed in region of MUCAPE of 100-500 J/KG. Don`t anticipate thunderstorms to persist much past sunset as HRRR indicates CAPE values decreasing across southern Mohave County and shifting east into the Phoenix area. Light rain and snow showers in southern Nevada and eastern California will linger into the evening before dissipating, while it will take much of the night for showers to finally dissipate in Mohave County in an area of subsidence behind exiting trough. After a brief break Monday, fast moving impulse will bring chances for rain/snow to the region mainly Monday night - Tuesday. AR with this feature skirts to our south so precipitation will be light during the period. Ensemble solutions suggest amplification of a stronger ridge over the Great Basin Wednesday ahead of a stronger trough over the eastern Pacific. Those ensembles tending to show core of the energy lifting northeast and weakening as it moves inland. However, AR associated with this trough will impact California/southern Sierra the most with again lighter precipitation amounts making it in the Great Basin and Mojave Desert. May need winter weather headlines in time for the southern Sierra and White Mtns. After another brief break Friday, parade of storms from the Pacific sends another one our way next weekend. Can`t complain as that all important snowpack in the Colorado Basin continues to build. Temperatures will be at or slightly below normal through the period. Intervals of gusty winds possible at times. && .AVIATION...For Harry Reid...A cold front is still expected to push through the Las Vegas Valley this afternoon, likely arriving at the terminal between 2130 and 2230Z. As the front passes, an increase in northwesterly winds and the chance of a few additional light showers continuing into the evening can be expected. CIGs will also likely decrease to around 4kft for a few hours behind the front. Conditions will improve overnight, and lighter winds below 10kts are expected tomorrow morning and afternoon. For the rest of southern Nevada, northwest Arizona and southeast California...While the main band of showers has now moved east of the TAF sites, additional scattered showers will still be possible into this evening at the Vegas Valley and Colorado River Valley sites. A few embedded thundershowers are also possible near KIFP and KEED through late afternoon. Winds at most sites will develop or maintain northerly components this afternoon and evening as a cold front moves across the area. The exception will be KDAG, where westerly winds are forecast to persist. Improving CIGs and decreasing winds are expected overnight and Monday as the storm system shifts to the east. && .SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report any significant weather or impacts according to standard operating procedures. && $$ DISCUSSION...Pierce AVIATION...Planz For more forecast information...see us on our webpage: or follow us on Facebook and Twitter