Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/05/25


Area Forecast Discussion
National Weather Service Denver/Boulder CO
819 PM MST Sat Jan 4 2025 .KEY MESSAGES... - A myriad of winter weather highlights across the mountains and eastern plains, with some light snow, fog, and stratus for the I-25 corridor. - Increasing chances (70-80%) for a accumulating snow event Tuesday morning, impacting the commute from the front range east across the adjacent plains. - Widespread single digit overnight lows expected, 80-90% chances over the eastern plains Monday and Wednesday mornings, low-teens elsewhere. - Windier conditions on Thursday over the plains with gusts upwards of 35-40 MPH. && .UPDATE... Issued at 818 PM MST Sat Jan 4 2025 An upper level low was over sern CO and will continue to move eastward into the Central Plains overnight. A band of moderate to heavy snow was moving across the plains this evening and will gradually exit the far ern plains between 06z and 08z. After 08z, there will be some lingering light snow over the plains but additional accumulations will be on the light side. In the mtns, favorable orographics will continue overnight with periods of snow. Finally, in and near the foothills, areas of freezing fog mixed with very light snow may linger overnight as shallow upslope remains in place. && .SHORT TERM /Through Sunday/... Issued at 157 PM MST Sat Jan 4 2025 Water vapor satellite and RAP mesoanalysis data show the shortwave trough axis has made it to the CO/UT border, and continues to quickly advance eastward this afternoon. Snow showers - if they haven`t started already - should develop over the higher elevations with some brief periods of moderate to heavy snow possible this evening into tonight. Across the plains, there`s still a mix of stratus, freezing fog, freezing drizzle, and some very light snow falling in some places. For the I-25 corridor, our initial temperature forecast from last night was far too optimistic, the morning update was still too optimistic, and I fear that even this current afternoon package is still a bit generous on high temperatures. As of this writing, the high for DEN still stands at 24F, and I would be shocked if we get to 30 this afternoon. The main shortwave trough is expected to deepen and become negatively tilted as it tracks across Colorado into southwestern Kansas tonight. With increasing QG ascent over the region, snow showers should become more widespread, first across the high country and then over the eastern plains. The foothills/I-25 corridor will be in a bit of a gap for this event with the slightly drier NNWerly flow as the main limiting factor. However, there is some potential for a more organized round of freezing fog/freezing drizzle along/east of I-25 this evening where it will be difficult to get cloud tops to get to -10C or cooler. One caveat is there could be some seeder-feeder enhancement that would allow for more light snow than drizzle... but either way it`s a complicated forecast. The snowfall forecast remains a little uncertain over the plains as guidance still does not have a great handle on where the best mid-level frontogenesis sets up tonight. There will likely be a band with 4-6" somewhere in the plains... most likely setting up near FMM/STK/AKO. However, snow will be short-lived tonight as the upper low (and it`s better forcing) quickly move into the Central Great Plains where this will end up being a significant blizzard/ice storm over KS/NE/MO. Tonight will also see some of the colder temperatures of the season, with single digit lows across the plains. Temperatures in the low to mid teens look likely for the plains. Tomorrow won`t feature much of a change, as mountain snow showers continue, while the plains struggle to break free from the persistent stratus deck. On the bright side, BUFKIT soundings look more like stratus than fog, which will be a welcomed change. Temperatures will again be in the 20s for most of the region tomorrow afternoon. && .LONG TERM /Sunday night through Saturday/... Issued at 157 PM MST Sat Jan 4 2025 The first day back to school, Tuesday, and we have snow in the forecast for the front range, figures. Waited all break, all 2.5 weeks(!) for snow for the kiddos and nope. The issue and impact with the Tuesday system isn`t so much that snow is forecasted but the timing of said snow, during the AM commute/rush hours across the front range and adjacent plains. Here is what we have: - Mid and low-level closed low dropping through the Four Corners - Very cold temperatures aloft and at the surface - Moisture! - A few hours of upslope at 700 mb(?) While not looking like a ton of snow, LREF is hinting at a 45-60% chance for at least 2" during the late morning and early afternoon hours on Tuesday from FoCO south towards the Palmer. While that may not seem like a lot, the trend in the probabilities has crept upwards and this is also assuming a 10:1 ratio which we will certainly be higher due to the very cold airmass in place. We should loose the lift and upslope fairly quickly Tuesday afternoon as the main closed low dives into southern AZ and we start to dry aloft Tuesday night. Thereafter the brief bit of snow excitement we turn to the cold. We still look to be on the western fringe of the deepest and coldest airmass through the remainder of the work week. Yes we could see some sloshing of the arctic air works back towards the west, Wednesday may have the best chance before shortwave ridging aloft moves back in. That being said we keep daytime highs just below seasonal averages but overnight low have a decent shot across the CO plains to drop towards 0F Wednesday morning - wind chills into the negative single digits. With the aforementioned shortwave ridging nearby, we have shortwave troughing on Thursday cruising through in our NW flow aloft. While not seeing a lot of moisture with this system we do expect to see an increase in winds across the front range and eastern plains. Right now gusts 35-40 MPH appear to be the higher end at this time. && .AVIATION /00Z TAFS through 00Z Monday/... Issued at 428 PM MST Sat Jan 4 2025 LIFR ceilings will continue thru 06Z and could linger a bit longer thru 09z. Visibility will be mainly in the IFR category, however, may see periods of LIFR thru 03z. Areas of light snow will occur this evening, mainly at DIA and APA. Light snow threat should end between 06z and 08z. Accumulations should be an inch or less. By 09z should see ceilings rise to IFR with visbility in the 3-5sm in fog. Ceilings should then become MVFR in the 12z-15Z period and scatter out by early Sun aftn. Winds will be North or NNE tonight and mainly from the north on Sun. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 3 PM MST Sunday for COZ031-033-034. Winter Weather Advisory until 5 AM MST Sunday for COZ042-044>051. && $$ UPDATE...RPK SHORT TERM...Hiris LONG TERM...Heavener AVIATION...RPK
Area Forecast Discussion
National Weather Service Boston/Norton MA
942 PM EST Sat Jan 4 2025 .SYNOPSIS... Rounding out the remainder of the weekend with dry, blustery, and cold conditions. A mid-Atlantic snowstorm misses us to the south Monday. Cold temperatures, blustery northwest winds and dry weather will prevail for much of the upcoming workweek. High temperatures may run some 10 degrees colder than normal, and be accompanied by below zero wind chills for some during the midweek. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Winds continue to diminish this evening. However, not expecting very good radiational cooling conditions due to abundant cloud cover. Did tweak sky cover and temperatures through the overnight to account for observed trends. Latest HRRR was more bullish on a lake effect snow streamer making it to the Berkshires after midnight. Will continue to monitor this potential overnight. Not looking like much more than a coating along the east slopes of the Berkshires. Previous Discussion... Southern New England is sandwiched between two pressure systems, an area of low pressure near the mouth of the St. Lawrence River and an elongated region of high pressure from south-central Canada to the southern Appalachian Mountains, creating a tight pressure gradient across our region. The rest of this afternoon can continue to expect gusts of 25 to 35 mph, but localized gusts up to 40 mph are not out of the question due to a 850mb jet streak around 55 knots. The jet streak lifts northeast this evening and the depth of the boundary layer compresses down to ~900mb. Still, there is a good amount of wind, albeit less around 20 to 35 knots, weaker gusts overnight around 15 to 25 mph. CAA continues overnight with intermittent cloud cover and elevated winds. Nighttime lows are in the teens, slightly less cold near the coast in the lower and middle 20s. As for any precipitation, cannot rule out rouge snow showers because of the ongoing lake effect activity to the west. Thinking these snow showers are limited areas of northwest Connecticut and western Massachusetts. Do have minor snow accumulations in far northwest Massachusetts of an inch or two for towns 1,000 feet. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... There are not many changes to the overall weather pattern on Sunday, thus we expect a mixture of clouds, below normal temperatures, and breezy winds. Gusts are not as strong, between 20 and 30 mph. With temperatures in the upper 20s and lower 30s, the feel like highs are in the upper teens and low 20s. Dry weather persists, outside of a spot snow flurry in northwestern Massachusetts due to the ongoing lake effect snow to our west. Clear skies for the first-half of the night, but clouds increase form southwest to northeast ahead of an offshore storm that will bring impacts to the Mid-Atlantic. Chilly night ahead with lows in the teens, feel like temperatures in the low single digits. && .LONG TERM /MONDAY THROUGH SATURDAY/... Key Messages: * Dry with below normal temperatures much of next week, to be accompanied by blustery to gusty northwest winds. * Wind chills zero to 10 below zero during the evening hours, 5-10 above zero during the daytime. Coldest periods look to be Tue thru Thurs. * Modifying temps late week, possible storminess next weekend? The upcoming workweek looks to be a great target of opportunity to break for a warmer climate for a few days if you are not someone who enjoys a combo of cold temperatures and gusty winds. Coldest airmass to this point in the winter season settles in over much of the Northeast starting Mon night, transported southward along the western end of a slow-moving upper low over the Canadian Maritimes. This will allow for sustained northerly flow aloft to advect air southward from northern Canada/Arctic Canada, a typical setting for intrusions of very cold air. We won`t see temperatures breaking any cold records, but there is reasonably high confidence in the coldest air yet seen in Southern New England to this point in winter. Coldest air aloft (925 mb temps -12 to -15C) advects in Tue thru Thurs, and it is likely these days stand to be the coldest days in the stretch. For these days, highs may struggle to reach the mid 20s in interior Southern New England. Because we are looking at a rather lengthy period of blustery to gusty northwest winds, low temps may be slow to fall so kept these values close to NBM (single digits to low teens). Will have to contend with wind chills between 5 above zero and 10 below at night though. Will have to reevaluate temperatures in the coming days as we get into the mesoscale model guidance realm but for now it looks as though we fall short of Cold Weather Advisory (the replacement to the previous Wind Chill Advisory, effective as of this winter) criteria. However it will still be quite cold nonetheless with some staying power to it, into late this week. Northwest wind gusts this week should stay just below Wind Advisory levels but Tue and Wed could have gusts in the Berks and Worcester County area in the 35 to 40 mph range. Not as gusty at night but the cold advection should keep some gustiness into the nighttime hours. In terms of precip chances...a well-developed coastal storm expected to impact the Mid-Atlantic region passes well to our south on Monday. Other than some increased cloud cover, and an outside chance (<15%) of flurries or light snow showers over the southern outer waters, no impacts are expected from this system. It is actually a rather lengthy stretch of dry weather to accompany the cold temperatures. Some indication in a few global ensemble NWP members of some storminess evolving sometime next weekend; with a complex interplay of phasing of trough energies involved which are tough to pinpoint inside of 3 days let alone a day 7-8 forecast, it`s still too uncertain if we`ll see any development, but it is something we`ll be monitoring. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... Forecast Confidence Levels: Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Tonight: High confidence. VFR cloud bases. NW winds 15-20 kt with gusts 25-30 kt at BOS/ACK, and around 10-12 kt with gusts to 24 kt elsewhere to start, though gust speeds should ease some toward the 2nd half of the night. Sunday... High confidence. VFR. SCT to BKN low-end VFR ceilings, MVFR ceilings for northern and western MA. WNW wind gusts 20 to 25 knots. Sunday Night... High confidence. VFR. Chance of MVFR ceilings for Cape Cod and Islands with ceilings SCT to BKN at 020 to 030. NW wind 8 to 12 knots, gusting to 20 knots. KBOS TAF...High confidence in TAF. SCT-BKN VFR bases. NW gusts to 30 kt thru about 05z, gusts then ease to under 25 kt before picking up again Sunday mid/late AM. KBDL TAF...High confidence in TAF. SCT-BKN VFR bases. NW winds 10-12 kt with occasional gusts to 20 kt rest of tonight, though gusts up to the mid-20s re-develop Sunday mid/late AM. Outlook /Monday through Wednesday/ Monday: VFR. Breezy. Monday Night: VFR. Windy with local gusts up to 30 kt. Tuesday through Wednesday: VFR. Windy with gusts up to 35 kt. && .MARINE... Forecaster Confidence Levels: Low - less than 30 percent. Medium - 30 to 60 percent. High- greater than 60 percent. Key Messages: * Small Craft Advisory conditions into Sunday Night for most waters. Through Tonight... High confidence. Gusty northwest to west-northwest winds 25 to 35 knots, with higher gusts of 40 knots over the southern outer waters, Block Island Sound and Rhode Island Sound. Strength in gusts ease after midnight, but are up to 30 knots. Seas building 5 to 8 feet offshore and 3 to 6 feet nearshore. Sunday and Sunday Night...High confidence. Prolong northwest to west-northwest winds with gusts during the day near 30 knots, diminishing to less than 25 knots overnight. Seas during the day are 5 to 8 feet offshore and 3 to 6 feet nearshore. Overnight seas diminish 4 to 6 feet offshore and 2 to 5 feet nearshore. It is possible the Small Craft Advisory will need to be extended through Sunday night. Outlook /Monday through Thursday/... Monday: Winds less than 25 kt. Areas of seas approaching 5 ft. Monday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of seas approaching 5 ft. Slight chance of snow. Tuesday: Strong winds with gusts up to 35 kt. Seas up to 5 ft. Freezing spray. Tuesday Night: Strong winds with gusts up to 35 kt. Rough seas up to 9 ft. Freezing spray. Wednesday: Strong winds with gusts up to 35 kt. Rough seas up to 10 ft. Freezing spray. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 1 AM EST Monday for ANZ231>234. Small Craft Advisory until 10 PM EST Sunday for ANZ235-237. Small Craft Advisory until 1 PM EST Monday for ANZ250-254>256. Small Craft Advisory until 7 AM EST Sunday for ANZ251. && $$ SYNOPSIS...Loconto/Dooley NEAR TERM...Belk/Loconto/Dooley SHORT TERM...Dooley LONG TERM...Loconto AVIATION...Loconto/Dooley MARINE...Belk/Loconto/Dooley
Area Forecast Discussion
National Weather Service Des Moines IA
831 PM CST Sat Jan 4 2025 .KEY MESSAGES... - Winter storm approaches the state tonight with snow increasing in the south late. - Heavy snow with very tight snowfall gradient in far southern Iowa on Sunday. Increasing north to northeast winds produce blowing snow as well in the headline areas. - Cold temperatures continue through next week but begin to warm slightly into next weekend. && .UPDATE... Issued at 811 PM CST Sat Jan 4 2025 No changes to the current winter weather headlines over southern Iowa this evening. Light snow is moving into southwest Iowa currently and will lift north through the rest of the evening. The latest cross sections and soundings suggest the light snow may reach Des Moines in the 11 pm to 4 am timeframe and some very light accumulations cold reach as far north as Highway 30 tonight. The is a 1045 mb Arctic High descending south into the North Dakota tonight and as this occurs, it reinforce a ridge south into Nebraska and Kansas later tonight into Sunday morning. The impact for Iowa is this will turn the low level flow and surface winds almost straight north and stream very dry air originating from the high into Iowa from north to south. In fact, dew points in the 10 below to 15 below range will move into northern Iowa later tonight. While those dew points will not reach central or southern Iowa, it gives an idea of how strong the dry air intrusion will be. Therefore, the light snow tonight into central Iowa should begin to erode after 3 am as the dry air surges south and the snow will be suppressed back into far southern Iowa. Will hold with the current snowfall total forecast. Any significant snowfall is still on track to be close to the IA/MO border and southward while the expected sharp snowfall gradient on the north edge occurs in far southern Iowa. && .DISCUSSION... Issued at 252 PM CST Sat Jan 4 2025 Surface ridge axis extends across the forecast area from northwest to southeast early this afternoon. A weakening band of mid level forcing had brought a narrow band of flurries into the southwest third of the forecast area with some brief visibility restrictions. However, upon reaching the surface ridge, the precipitation dissipated rather quickly with the near surface subsidence and associated dry air. Otherwise, the developing winter storm was crossing the Rockies with moisture lifting northward in advance of the system across the Plains. A widespread area of freezing drizzle has developed from Kansas into central Nebraska north of the surface front in northern Oklahoma with expanding travel issues. Isentropic lift expands north and east tonight along with the precipitation. Initially, the precipitation remains a wintry mix with nil saturation within the dendritic zone. Some of this may clip southwest Iowa this evening before deeper saturation occurs within the column leading to all snowfall into Iowa overnight. The northward progression of the precipitation remains checked by the increasing influx of dry near surface air from the strengthening north/northeast winds. This should limit any accumulating snow to along I80 or south during the overnight with some retreat of precipitation to the south toward daybreak as the winds increase. Very strong forcing arrives in the mid-levels on Sunday as the upper system crosses Kansas into Missouri. The highest precipitation rates in southern Iowa will be associated with lift coincident with strong moisture transport north into the system. However, the increasing north to northeast wind also bring much drier air into the northern edge continuing to limit any northward expansion of the precipitation during the day. This will lead to a very sharp gradient of snowfall in northern Missouri/southern Iowa with amounts going from near zero to over a half foot over the length of a county or so. This also means and slight shift to the north or south with the system has potentially big implications for those locations near the gradient. Overall 12Z model runs have remained fairly consistent with the gradient near the Iowa/Missouri border. The HRRR is particularly impressive with the snow gradient within a 20- 25 mile corridor. In general, QPF nudge slightly northward which has nudged amounts up along the Missouri border. Therefore, the warning was expanded to include the entire south row of counties in Iowa with an advisory in the 2nd row just to the north. Even if amounts don`t reach criteria in the south, the increasing winds on Sunday should lead to blowing snow and poor visibilities impacting any travel in the far south. Models have been slightly slower with the exit of the system on Sunday evening and have lingered the snow into the evening with some additional light accumulations. Thereafter, the remainder of the week remains relatively uneventful with below normal temperatures. There may be a system by late in the work week which lifts northeast into the Ohio River Valley which may impact portions of southeast Iowa but there is plenty of time to get a handle on the eventual track of that system. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 528 PM CST Sat Jan 4 2025 VFR conditions are expected to persist over northern Iowa including KMCW/KALO/KFOD. A winter storm that will impact parts of southern Iowa will bring a few periods of light snow to KOTM/KDSM and possibly MVFR or lower cigs later tonight and into Sunday. Northeast winds overnight will increase on Sunday and will be gusty at times. && .DMX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 3 AM CST Monday for IAZ081>086. Winter Storm Warning until 3 AM CST Monday for IAZ092>097. && $$ UPDATE...Donavon DISCUSSION...Cogil AVIATION...Donavon
Area Forecast Discussion
National Weather Service Goodland KS
731 PM MST Sat Jan 4 2025 .KEY MESSAGES... - Winter storm on track to impact the region tonight into Sunday. No significant changes from previous forecast. Heaviest snow (5-9") expected in Norton and Graham counties. Snow accumulations may vary considerably from west to east across the forecast area. - Entire area will see hazardous travel conditions associated with ice and/or snow covered roads. Worst overall conditions expected along and east of Hwy 83, where snow accumulation will be greater and blowing/drifting snow is likely. - Wind chill readings as low as 10 to 15 below zero are expected across the entire area Sunday morning. Similar wind chill readings are expected over a limited portion of the area (east of Hwy 83) Monday morning. - Another chance for precipitation Tuesday, but confidence is low it will happen. && .UPDATE... Issued at 730 PM MST Sat Jan 4 2025 Winds have shifted a bit to the northeast over the past couple hours, especially for locales along/west of Highway 25 into Colorado. Temperatures continue to slowly drop as well. This has allowed precipitation to change over to light snow, and is evident in area obs along/west of Highway 25. While about an hour early compared to going forecast, still on track. Little movement of the surface/850 mb low which currents sits along the OK/TX panhandles. Radar is showing an area of snow moving slowly S and E towards the western periphery of the CWA in Colorado. Will be monitoring this over the next couple hours for any enhancement, that may affect ongoing snow totals. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 255 PM MST Sat Jan 4 2025 ..Winter storm on track to impact the region tonight and Sunday.. This Afternoon: Freezing fog that developed very early this morning persists over the Tri-State area this afternoon.. where temperatures have remained near-steady in the upper teens and lower 20s. Most areas have received 0.10 to 0.25" of rime ice accumulation on the east-facing side of trees.. along with grassy and elevated surfaces. The light/fluffy nature of rime ice precludes the majority of impacts one would expect with glaze ice, the latter being the type of ice associated with freezing drizzle/rain. The presence of a thin/transparent layer of ice on most (or all) roadways, sidewalks and parking lots in northwest Kansas suggests that a period (or periods) of freezing drizzle must have occurred this morning. Freezing fog and occasional/spotty freezing drizzle will likely persist until temperatures fall into the lower-mid teens (-10 to -12C) this evening.. at which point precipitation will transition to flurries or very light snow. Tonight-Sunday: A progressive upper level trough (approaching the 4-Corners early this afternoon) will track ESE across the Rockies (tonight) and Central-Southern Plains (Sunday).. fostering the development and intensification of a mid-latitude cyclone over the Southern Plains. The nascent cyclone, a ~1010 mb low centered over northeast NM at 21Z this afternoon, will intensify as it tracks eastward into central OK (tonight) and toward the KS-OK-MO-AR border (Sunday). Current and recent runs of the GFS, ECMWF, NAM NEST, RAP and HRRR continue to indicate the same general scenario.. [1] greatest snow accumulation (5-10") and impacts in eastern portions of the area, where a tight precipitation gradient will exist.. [2] a minimum in snow accumulation between (roughly) Hwy 385 and Hwy 27.. and [3] a secondary, albeit lower (3-6"), maximum in snow accumulation over portions of the Palmer Divide in Colorado, possibly including far western portions of Kit Carson/Yuma counties. Primary forecast concern revolves around the location of the precipitation gradient in western-central KS. While guidance continues to indicate that the aforementioned gradient will be situated along or just east of Hwy 283, precise details (exactly where) continue to vary from model-to-model and run-to-run. Snow accumulation/impacts in eastern portions of the NWS Goodland county warning area will be exquisitely sensitive to the location of this gradient. For example, if said gradient is ~30 miles further west than presently anticipated, snow accumulations in Norton/Graham counties could approach 8-12".. 30 miles further east.. snow accumulations may only reach 3-6". && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 234 PM MST Sat Jan 4 2025 Cold, more winter like temperatures are expected for the long term part of the forecast. Northwest flow will dominate the weather pattern behind the exiting storm system currently impacting the Tri- State Area. This will keep temperatures cooler than normal. In addition the new snow cover will further serve to keep temperatures cool. Tuesday models indicate a weak upper level short wave trough potentially forming over E CO as another upper level trough deepens over the Four Corners Region. Confidence is low this feature will come to fruition due to it currently being placed just upstream of the developing short wave ridge as the trough to the west deepens. Meanwhile the short wave trough will continue to deepen over the Great Basin and move east over the Plains. The GFS and ECMWF are both in remarkable agreement with this trough given the time range. The concerning feature with this trough is it is resembling split flow. The main low is deepening into Northern Mexico while the northern half of the jet stream is over the Northern Plains. Model consensus is dry, which seems reasonable given the favorable look of splitting around the forecast area. Terms: GFS and ECMWF are global forecast models && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 359 PM MST Sat Jan 4 2025 Much of the forecast period for both terminals (KGLD/KMCK) will see LIFR/VLIFR conditions persist as a slow moving storm system moves across the Oklahoma panhandle. Easterly flow will ensue at both sites through about 05z Sunday, then becoming northeast and eventually northerly by 08z-09z Sunday. There will be gust potential at both sites around 20-30kts from at least 08z-13z, but could linger through midday. For KGLD, ceilings OVC003-007 through 18z w/ 3-6sm in SN/BLSN. Brief 1sm possible 05z-09z. 18z-23z Sunday, conditions improve to MVFR and eventually VFR from 23z onward. For KMCK, ceilings OVC004-005 through 13z Sunday, then MVFR around OVC010-015. Persistent 1-2sm in SN/BLSN expected. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...Winter Weather Advisory until 8 AM MST /9 AM CST/ Sunday for KSZ001-013-027-041. Winter Weather Advisory until 6 PM CST Sunday for KSZ002-003- 014-028-042. Winter Storm Warning until 6 PM CST Sunday for KSZ004-015-016- 029. CO...Winter Weather Advisory until 8 AM MST Sunday for COZ090>092. NE...Winter Weather Advisory until 8 AM MST /9 AM CST/ Sunday for NEZ079-080. Winter Weather Advisory until 6 PM CST Sunday for NEZ081. && $$ UPDATE...JN SHORT TERM...Vincent LONG TERM...99/JTL AVIATION...JN
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
947 PM EST Sat Jan 4 2025 .SYNOPSIS... Cold and quiet before a low pressure system crosses the area late Sunday through early Monday, increasing the chances for rain and wintry precipitation. Cold and dry conditions return Tuesday through the end of the week. && .NEAR TERM /THROUGH SUNDAY/... As of 942 PM Saturday: Surface high pressure remains in control across the region with cold and dry conditions persisting. Mid- and high-level clouds will increase in coverage from the west overnight as an upper wave and attendant surface low slide across the heart of the country. Overnight lows will fall into the teens to mid 20s and the ongoing forecast remains on track with no major changes needed. The surface high slides to the coast Sunday as a frontal system approaches from the west. Mid level moisture increases through the day but low level moisture is slow to increase. An initial shot of precip develops by mid morning across the mountains as frontogenesis and isentropic lift associated with a warm front moving north across the area. Thermal profiles suggest a snow/sleet mix at onset with little to no accumulation. This forcing moves north of the area then deeper moisture and forcing associated with the approaching cold front moves in from the west. A strong warm nose develops with this forcing. There will be enough cold air trapped at the surface for the precip to change to freezing rain for the northern mountains and Blue Ridge area which continues through the afternoon. Some freezing rain will also develop across the higher elevations of the central and southern mountains. Right now, it appears that any ice accretion will be best across the northern mountains and Blue Ridge area, so the Watch will be upgraded to an Advisory across that area. Since the ice is limited in amounts and coverage to the highest elevations of the central and southern mountains, will hold off on and advisory there for now. Elsewhere across the forecast area liquid rain is expected to move in. That said, there could be a quick shot of non-accumulating sleet as often happens as temps wet bulb down then start to warm. Can`t rule out some spotty, brief freezing rain over the SC or NE GA mountains, but again, this would be very brief with only a very light accretion on elevated surfaces. Highs across the area will be around 5 degrees below normal, but not as cold as one might expect with a winter precip event since this will only be an in situ CAD event at worst. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... Key Messages: 1) A Winter Weather Advisory will be in effect for Avery, Mitchell, Yancey, and the escarpment areas of Caldwell, Burke and McDowell counties from Sunday afternoon into Monday afternoon for ice accumulations less than a quarter inch. 2) Cold front brings gusty winds on Monday across most of the area. 3) Colder and drier air moves in Monday night. As of 200 PM Saturday: Picking up Sunday night, a low pressure system continues to move toward the Appalachians and brings a swath of p-types across the area. The main concern for this system is freezing rain. Guidance from the HRRR and HREF suggest a higher probability of ice accumulations along the northern NC mountains, with a few signals in the foothills. Modeled soundings in this area show a typical FZRA profile, with a stout warm nose aloft. At the same time, a surge of warm and moist air from the SW ahead of the front could limit how much of the surface falls below freezing. Further east of the mountains, surface temps are expected to remain above freezing, keep the p-type rain. In the mountains, sfc temps hover near or just below freezing. Given the shallow warm nose to start Sunday night, onset of precip is likely to be sleet and transitions into a mix of rain/FZRA. The latest guidance does increase the probability (30%-60%) of ice accumulations in the 0.01- 0.2" range, with the middle range more likely. These setups are tricky and highly dependent on many factors, including moisture and surface temperatures. A degree or two difference in either direction can make for a very cold rain or higher ice accumulations. Even at this time, there still remains some uncertainty to how these microprocesses will affect the p-types and impact the areas. For these reasons, we will issue a Winter Weather Advisory for portions of the northern NC mountains. By Monday morning, most of the precip should quickly transition to all rain and taper off by the afternoon hours. Currently, the QPF response is between 0.25-75", which doesn`t give the system much to work with and will have a direct impact on both rain and FZRA amounts. The cold front looks to cross the CWA Monday and by Monday evening, stout NW flow aloft brings another chance for a quick burst of snow at the TN/NC border. As colder, drier air starts to filter off, rain chances once again get shunted and makes for a quiet end to a busy period. Gusty winds on Monday as the low level jet ramps up ahead of the front. Temperatures Monday ahead of the front will be the warmest of the week, before crashing again with the Arctic blast afterwards. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... Key Messages 1) A mostly drier pattern for the CWA through the end of the week. 2) Cold temperatures well below normal. As of 215 PM Saturday: Picking up on Tuesday night, colder and drier air continues to be the main story for the extended period. Flow aloft becomes more broad and W/NW through the end of the week. Surface high pressure from Canada spills into the CONUS and becomes reinforced over the CWA, ushering in colder temperatures. A fast moving shortwave could cross the CWA Thursday, but model guidance remains unimpressed and keeps the area dry as the arctic air suppresses much of the moisture. By the end of the period, there could be some return moisture and perhaps precipitation chances, but confidence remains very low at this point. Long range guidance does hint at the potential for another area of low pressure forming off to the west and lifting toward the Carolinas. Both the GFS and EURO show another chance for precipitation by the next weekend. However, it`s at and past Day 7 and therefore, too far out to say what type of weather this system could bring. Additionally, the main concern for the extended is the potential for extremely cold air. Guidance has wind chills in the mountains reaching single and negative values Wednesday night. Will continue to monitor. Daytime highs through the week area cold, a mix of 30s and 40s. && .AVIATION /03Z SUNDAY THROUGH THURSDAY/... At KCLT and elsewhere: VFR conditions will prevail at all terminals through the TAF period. Clouds will gradually increase in coverage through the overnight and into Sunday with overcast skies expected by daybreak across much of the area. Ceilings will also gradually lower, but are expected to remain VFR through the period. Showers will increase in coverage from the west, especially across the mountains, by the afternoon with brief visibility restrictions possible at KAVL. Otherwise, winds will be light and variable with a mean direction generally out of the south/southeast. Outlook: The next chance for widespread restrictions and precipitation will be from Sunday night into Monday as the next frontal system impacts the area. Very gusty NW winds likely develop in the wake of the cold front Mon afternoon/night. Dry conditions return Tuesday and Wednesday but occasional gusty winds are possible. Dry high pressure with light winds expected Thursday. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...Winter Weather Advisory from 1 PM Sunday to 1 PM EST Monday for NCZ033-049-050-501-503-505. SC...None. && $$ SYNOPSIS...CP NEAR TERM...RWH/TW SHORT TERM...CP LONG TERM...CP AVIATION...TW
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
811 PM CST Sat Jan 4 2025 .KEY MESSAGES... - Heavy snow will impact much of central and southeast Illinois late tonight through Sunday night. Storm total accumulations will be greatest along and south of a Beardstown to Paris line where amounts of 8 to 12 inches will be likely. - After the snow comes to an end early Monday morning, a very cold week is ahead. High temperatures will remain in the teens and lower 20s Tuesday through Friday. && .UPDATE... Issued at 810 PM CST Sat Jan 4 2025 Mid evening radar imagery shows some weak mid level echoes overspreading portions of west central Illinois but not seeing any indication this initial area is reaching the surface as of 8pm. 00Z ILX sounding continued to show a layer of fairly dry air from the surface up to around 800mb with strengthening northeasterly boundary layer flow reinforcing this dry air. Looks like precip is reaching the surface in a NW/SE arcing band from northwest and north central Missouri to just west of St Louis. This is expected to spread east overnight and 00Z HRRR begins to spread accumulating snow into central Illinois closer to 12Z Sunday morning. Trimmed back snow accumulations in the 06-12Z time frame as a result of some of the slower trends. Deubelbeiss && .DISCUSSION... Issued at 248 PM CST Sat Jan 4 2025 Afternoon water vapor imagery depicts a potent upper-level trough moving across the Rockies with a deep upper-level low anchored over eastern Canada. How these two features coalesce over the next 24 hours will determine how adverse winter weather impacts will become across central and southeast Illinois. Despite cyclogenesis already underway in the lee of the Rockies and wintry weather spreading across the Plains, there remains plenty of boom-or- bust potential for us here. With that said, we would like to highlight 3 transition zones as this winter storm evolves across the Mid-Mississippi Valley. ------------------------------------------------------------------- Transition 1: (6am - 6pm Sunday) We anticipate the thermal profile to support mostly snow as precip spreads into western Illinois after Midnight. A quick glance at model soundings suggest we will overcome the near-sfc dry layer in areas near and south of a Quincy to Paris line sometime between 2am and 6am. Areas north of this line will hold onto the low-level dry air longer, and in some areas along and north of the I-74/Danville corridor, the onset of wintry precip may not arrive until later Sunday afternoon. Nevertheless, for the areas near and south of a Quincy to Terre Haute line, there appears to be multiple hours of moderate-to- heavy snowfall with strong upward omega/lift stretching through a saturated DGZ. Timing gets a little tricky, but the period between 6am-Noon should support at least 0.5"/hr snowfall rates, while the highest probabilities (30-50% chc) for 1"/hr rates remain confined to areas along and south of I-70 during the morning hours. After about Noon on Sunday, extending through 6pm, we are noting some aggressive warming in the 800-700mb layer, mainly in areas near and south of I-70. This could support a transition to sleet for much of Sunday afternoon, which would eat into snowfall amounts across SE Illinois. On the other hand, areas further north and closer to the I-72/Danville corridor, the thermal profile looks cold enough to support a continuation of snow, with another push of 1"/hr snowfall rates becoming possible (30-50% chc) along this corridor between Noon and 6pm. In summary, areas near and south of I-70 could see between 1-4" of snow between 6am and Noon before transitioning to sleet, while areas a little further north up along the Quincy to Paris zone could see 2-6" between 6am and 6pm. Areas further north near the I-74 corridor may see 0-3" of snow during this same timeframe. -------------------------------------------------------------------- Transition 2: (6pm Sunday - 6am Monday) Model guidance remains in excellent agreement that a mid-level dry slot will work across the state during this timeframe. What this does is rob us of our cloud-ice nuclei, transitioning any snow more toward freezing drizzle. This dry slot will work from the Mississippi River eastward to I-55 between 6pm and Midnight, and then from I-55 eastward to the IL/IN stateline between Midnight and roughly 6am. The net effect will be a lull in snow during this time. The freezing drizzle may also settle ontop of any previously accumulating snowfall, working to compact it and give a public perception of less accumulation. Any crust that forms atop the initial snow layer may also work to mitigate blowing/drifting snow as 30-35 mph northerly wind gusts spread across the region. We will need to closely monitor this period, as it could also cut into our current snowfall forecast. ------------------------------------------------------------------- Transition 3: (6am Monday - Noon Monday) With much colder air spilling into the region on the backside of the departing storm system, our confidence in all snow is perhaps highest during this period. The only questions that remain are how far north the snow shield might spread across the I-74 corridor, as well as any potential for mesoscale banding that could boost snowfall amounts Monday morning. A quick 2-D analysis of banded snow potential suggests that frontogenetic forcing might not be particularly strong Monday morning. Furthermore, it`s difficult to find a clear area where negative EPV is present. Together, this suggests that CSI may not be present to support 1"/hr snowfall rates as this system is departing. What we could maybe expect instead are hearty 0.5"/hr rates spread across most of the region due to strong synoptic ascent. This might only result in an additional 1-4" across the region. And with gusty north winds still in place during this period, we are concerned for reductions in visibility as well as the potential for blowing and drifting snow. -------------------------------------------------------------------- In the wake of our winter storm, a stretch of dry and very cold temperatures will bring its own set of impacts to the region. Confidence in well-below normal temperatures remains high as cross-polar flow disperses some of the coldest weather of the season. Some question remains as to how prolonged the cold snap will be, but confidence is high (at least 60% chance) that overnight wind chill values will fall below zero Tuesday night - Wednesday night. MJA && .AVIATION... (For the 00z TAFs through 00z Sunday Evening) Issued at 549 PM CST Sat Jan 4 2025 Surface ridge axis currently over central Illinois will provide light winds and VFR conditions in the near term. Meanwhile, low pressure will develop over the southern Great Plains overnight and shift across the mid Mississippi Valley Sunday evening. Winds will set up out of the east to northeast in response and increase during the day Sunday with gusts picking up into the 20-25kt range. Snow will be overspreading the area from the south with accompanying MVFR then IFR ceilings. Heavy snow is expected along portions of the I-72 corridor, but will taper off further north at BMI/PIA. Deubelbeiss && .ILX WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 6 AM Sunday to noon CST Monday for ILZ027-029-031-037-038. Winter Storm Warning from midnight tonight to noon CST Monday for ILZ036-040>057-061>063-066>068-071>073. && $$
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
918 PM EST Sat Jan 4 2025 .SYNOPSIS... High pressure will briefly build in by tonight. A strong low pressure system will bring wintry precipitation late Sunday into Monday. Below normal temperatures continue through next week as strong arctic high pressure builds towards the region. && .NEAR TERM /THROUGH SUNDAY/... Residual blustery west-northwesterly winds continue this evening. While the core of the gusts have subsided, recent observations show around 15 to 25 mph gusts remain. This is contributing to wind chills in the single digits to teens. Otherwise, temperatures remain chilly with a band of mid-level wave clouds, mainly north of U.S. 50. Temperatures will drop into the teens to lower 20s tonight for much of the area with single digits in the Alleghenies. Additional Cold Weather Advisories for the high Alleghenies may need to be considered, although winds will be gradually diminishing. The first half of Sunday will be dry and blustery once again, with winds gusting in the 20-25 mph range. A potent area of low pressure will approach the region from the west later in the day, with wintry weather likely beginning by Sunday evening. Forecast highs will generally be in the 30s, with upper teens to 20s for mountain locales. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... Tomorrow evening, attention turns to a system approaching from the west. A closed upper low and associated surface low will track eastward from the Central Plains toward the Mid-Mississippi Valley during the day tomorrow, through the Ohio Valley tomorrow night into Monday, and then overhead Monday night. Warm advection aloft well in advance of the low will start to overrun very cold air in place at low-levels tomorrow evening. Precipitation will break out in association with that warm advection driven ascent, and then gradually spread northeastward over the course of the night. Onset times of precipitation are expected to be around 6-9 PM in the Alleghenies, central Shenandoah Valley, and central Virginia, 9PM-midnight in the northern Shenandoah Valley, DC/Baltimore Metros, and southern Maryland, and after midnight in far northeast Maryland. Precipitation will be all snow at onset, and should pick up in intensity fairly quickly. The strongest push of warm advection/frontogenetic forcing is expected to move through during the second half of the night, leading to the heaviest precipitation rates. Snowfall rates may reach 1-2 inches per hour for a time late Sunday night where the heaviest bands set up. This time period with heavier precipitation rates will linger a bit into Monday morning, with precipitation becoming lighter late Monday morning through Monday afternoon as the strength of the low-level warm advection weakens a bit. The system`s upper level low will move overhead Monday night, potentially leading to a secondary burst of briefly moderate to locally heavy snow. Precipitation will than wind down during the late evening/overnight hours. At this juncture, there is a bimodal distribution in model guidance with respect to the track of the system and resultant precipitation amounts/types. The GFS/NAM, and the CAMs that are driven by GFS/NAM lateral boundary conditions (HRRR/FV3/3km NAM/WRF-ARW/WRF-NSSL) are further north with QPF axis, and would bring significant, warning level amounts of precipitation to the entire forecast area. Individual members within that camp differ with respect to how far north a warm nose aloft would make it. The HRRR and NAM-Nest illustrate that spread with respect to the handling of the warm nose. The 12 and 18z HRRR keep nearly all of the CWA snow for the entire event, while the NAM-Nest works the warm nose northward to roughly I-66/US-50. In the example of the NAM-Nest, locations north of I-66/US-50 would get warning level snowfall (likely in excess of 6 inches), while locations further south would get a few inches of snow, and then sleet and freezing rain on top of that (resulting in warning level impacts). In the HRRR scenario, the entirety of the forecast area would receive warning level snow, with some locations even closing in on a foot of snow. The other half of the bimodal distribution is global models from international modeling suites (the Euro, Canadian, UKMET, and ICON). These models have the QPF max suppressed further to the south, placing it across central Virginia to southern Maryland. In this scenario, locations north of I-66/US-50, and especially north of I- 70 would receive reduced amounts of precipitation, resulting in advisory level snowfall, while locations further south across central VA to southern Maryland would receive warning level snowfall (potentially even closing in on a foot of snow), along with some minimal mixing with sleet or freezing rain. Since all of the above scenarios provide warning level impacts (whether it be from all snow or a mix of snow and sleet/freezing rain) from the I-66/US-50 corridor southward, confidence was high enough to upgrade the Winter Storm Watch to a Winter Storm Warning. Further north (across northern Maryland and portions of the WV Panhandle), the Winter Storm Watch was left in place to account for uncertainty in QPF amounts, since snow in those locations could be either advisory level (2-5"), or warning level (5+") depending on which solution verifies. This area will continue to evaluated, with decisions on advisory versus warning likely being made overnight after 00z guidance is available. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Strong arctic high pressure will build into the region in the wake of the Sunday/Monday winter storm. Aloft, strong troughing remains in place across the northeast CONUS, with several pieces of shortwave energy diving out of the Great Lakes region across our area through Thursday. This will bring repeated reinforcing dry cold fronts across the region. As a result, we will continue a period of well below average temperatures. Highs each day will struggle to get above freezing, aside from southern MD and lows will dip into the teens to low 20s for most. Higher elevation zones will be even colder, subtracting about 10 degrees from all of those values. Wednesday night and Thursday night may be particularly cold as high pressure moves more directly overhead. We could see our typical cold pockets even dip into the single digits overnight, with sub-zero temperatures possible in the high elevation valleys. Each day through Thursday looks to have gusty winds around 15 to 25 mph, which paired with the cold temperatures will make it feel like its in the 20s (at max) through this whole period (well below zero in the mountains). This may necessitate Cold Weather Headlines for an extended timeframe during this time as well in the mountains. Throughout all of this, partly to mostly sunny skies are expected during the day each day. Even with highs below freezing, would expect this to aid in some melting of the snowpack. However, this could lead to significant problems when it comes to roadways as melted snow will repeatedly refreeze overnight for areas that aren`t able to adequately dry out. The aforementioned gusty winds during this period may be able to help aid in that though. Either way, morning commutes will likely be tricky each day through the long term, especially on elevated and/or untreated surfaces. A slight "warm up" occurs Friday, and I use that term very hesitantly because high only jump into the mid 30s (20s to low 30s in the mountains). This is thanks to a brief ridge that moves overhead ahead of a very deep trough building across the central CONUS. This trough will develop an area of low pressure across the deep south, which may move towards the region Friday into Saturday and bring another impactful weather event. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... High pressure gradually builds in by tonight. WNW gusts gradually diminish through the evening, but especially overnight. VFR stratocumulus are largely confined to areas along and north of U.S. 50. VFR conditions continue most of Sunday. Some renewal of 15-20 kt gusts is possible during the afternoon out of the WNW. Wintry precipitation overspreads the forecast area late Sunday into Sunday evening, impacting the terminals from southwest to northwest. This will continue through most of Monday. Though a lull seems likely sometime late Monday morning into early Monday afternoon. Precipitation type will initially be snow at all terminals, and may stay snow at MRB/BWI/MTN. Mixed precipitation is possible farther south, especially at CHO. Snow could be heavy at times with accumulations of 6 to 10 inches in a localized (to be determined) snow band. Breezy NW winds are expected on Tue and Wed with gusts of around 20 to 25 knots expected each afternoon. VFR conditions are expected during this time. && .MARINE... Strong WNW winds continue through Sunday, though gradually diminishing. Small Craft Advisory conditions are expected through Sunday, although interior waterways may drop below criteria tonight. Have added an SCA for all waters through at least Sunday evening, but that will likely need to be extended further in time. Wintry weather is expected to impact the waters beginning Sunday evening through Monday evening. As this low departs, winds will increase Monday afternoon into Monday night. Advisories will become likely, and locations along the bay may approach gale force. SCAs will be likely to continue through mid to late week as a tight pressure gradient resides nearby. Gusts of 20 to 25 knots will be possible over the waters with dry conditions expected. && .TIDES/COASTAL FLOODING... Blowout tides currently being observed may continue for another few low tide cycles given persistent NW/offshore flow. Anomalies gradually come up through the end of the week, but no coastal flooding concerns for the foreseeable future. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Winter Storm Warning from 10 PM Sunday to 1 AM EST Tuesday for DCZ001. MD...Small Craft Advisory until 6 PM EST Sunday for MDZ008. Winter Storm Watch from Sunday evening through late Monday night for MDZ003>006-008-011-502-505>508. Winter Storm Warning from 10 PM Sunday to 1 AM EST Tuesday for MDZ013-014-503-504. Winter Storm Warning from 10 PM Sunday to 6 AM EST Tuesday for MDZ001-501. Winter Storm Warning from 6 PM Sunday to 1 AM EST Tuesday for MDZ016>018. VA...Winter Storm Warning from 10 PM Sunday to 1 AM EST Tuesday for VAZ027>031-053-054-501-505-506-526-527. Winter Storm Warning from 6 PM Sunday to 1 AM EST Tuesday for VAZ025-026-036>040-050-051-055>057-502-504-507-508. Cold Weather Advisory until 6 AM EST Sunday for VAZ503. Winter Storm Warning from 6 PM Sunday to 6 AM EST Tuesday for VAZ503. WV...Winter Storm Watch from Sunday evening through late Monday night for WVZ051>053. Winter Storm Warning from 10 PM Sunday to 1 AM EST Tuesday for WVZ050-055-502-504. Winter Storm Warning from 10 PM Sunday to 6 AM EST Tuesday for WVZ501-503. Winter Storm Warning from 6 PM Sunday to 1 AM EST Tuesday for WVZ506. Cold Weather Advisory until 6 AM EST Sunday for WVZ501-505. Winter Storm Warning from 6 PM Sunday to 6 AM EST Tuesday for WVZ505. MARINE...Small Craft Advisory until 6 PM EST Sunday for ANZ530>543. Winter Storm Watch from Sunday evening through late Monday night for ANZ530. && $$ SYNOPSIS...ADS/CJL NEAR TERM...BRO/CJL SHORT TERM...KJP LONG TERM...CJL AVIATION...ADS/BRO/CJL MARINE...ADS/CJL TIDES/COASTAL FLOODING...LWX