Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/19/22

Area Forecast Discussion
National Weather Service Cleveland OH
1005 PM EST Sun Dec 18 2022 .SYNOPSIS... High pressure will gradually build into the region tonight and Monday. A weak cold front pushes through Wednesday. An expansive and impactful low pressure system will organize over the lower Mississippi Valley in conjunction with a deepening upper level trough that will ultimately bring Arctic air, strong winds, and snow to the region after Thursday through Saturday. && .NEAR TERM /THROUGH MONDAY NIGHT/... Late Evening Update: Cold and quiet across most of the area this evening. Lake effect snow has lifted north of Erie County this a subtle shortwave goes by over the next few hours, a bit of re- invigoration along with a push back onshore is expected, with some potential for very light snow to get into Lake and northern Ashtabula Counties overnight into early Monday as well. Freshened snowbelt QPF and POPs with a heavy lean on the hi-res NAM, RGEM, HRRR and RAP models as they`re capturing current placement of the snow best. Enough juice left for any bands to produce some accumulating snow where they take shape overnight, but not expecting anything heavy. Light lake effect will linger into Monday in Erie County and perhaps along I-90 in extreme northeast Ohio before completely tapering by Monday evening as surface ridging moves right overhead. New accumulations of an inch to locally two may occur through Monday morning in parts of northeastern Erie County, with amounts elsewhere in northern portions of the snowbelt under an inch if any manages to accumulate. Reluctantly continued the LES Warning for Erie County PA until 4 AM Monday with this update as potential does exist for one last push of accumulating snow in parts of the County overnight tonight on top of the locally several inches that fell today, though any additional impacts (including to the Monday AM commute) should admittedly be on the minor side. Previous Discussion: The lake effect remains reluctant to move further onshore due to 250-260 wind directions that are more aligned with the Lake Erie shore line, and there has been a large discrepancy in the snowfall totals between Erie PA under an inch of snow and North East PA. Probably going to come in under criteria but will leave headlines in place with the 00Z-06Z Monday POPs pushing inland a bit with winds turning more westerly and more snow still to come. High pressure will push in from the lower Ohio Valley Monday, and will gradually end the snow in the lake effect zones. Meanwhile, the southwestern portion of the CWA will get into some breaks in the clouds Monday, but temperatures area wide will still have trouble getting above freezing. Will cloud back up quickly into Monday night with mid/upper level moisture from a weak warm front passing south to north just west of the CWA. Largely dry Monday night with the lake effect pretty much finished at that point. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Quiet weather will preclude the much talked about late week storm as surface high pressure centered over the Ohio Valley Tuesday morning moves east by the afternoon allowing a fast moving mid/upper shortwave trough to brush across the northern Great Lakes. This wave will be deamplifying, so its associated weak surface low will pass well north of our region tracking from Lake Superior Tuesday afternoon to east of James Bay by Wednesday. Since the energy and forcing is passing well north and moisture return is minimal, expect the trailing cold front to come through dry Tuesday evening and Tuesday night. H85 temps dip to -6 to -8 C late Tuesday night and Wednesday over Lake Erie in the weak post frontal cold advection as we will be on the southern fringe of a large pool of arctic air building into the northern Plains and northern Great Lakes, but the airmass will be too dry for any lake-effect snow. Surface high pressure returns Wednesday afternoon and quickly exits into New England Wednesday night allowing mid/upper ridging to build over the eastern CONUS ahead of a large, dynamic mid/upper trough diving into the Plains. This will be the makings of the late week storm that I know you want to read about, so more on that below. So to some up the mid week period, dry conditions are expected Tuesday through Wednesday followed by chances for light snow showers increasing from south to north late Wednesday night as warm/moist advection and isentropic ascent develop ahead of the deepening trough to the west. Milder highs Tuesday in the upper 30s will cool a degree or two Wednesday into the mid/upper 30s. Lows both Tuesday and Wednesday nights will be generally in the mid 20s, so quite seasonable for mid week. && .LONG TERM /THURSDAY THROUGH SUNDAY/... All eyes remain on the intense storm system expected to impact the entire Ohio Valley and Great Lakes regions Thursday into the start of the holiday weekend. The main messages, as well as the most certain aspects of this event, continue to be rapidly falling temperatures late Thursday night through Friday leading to rain changing to snow and a flash freeze, damaging winds, and extreme cold, both in terms of actual air temperature and wind chill, that will worsen through the day Friday and Friday night. What is more uncertain is how much snow will fall once the rain changes to snow on Friday with differences in model guidance giving ranges from a few inches to over a foot. It is important to note that no matter how much snow falls on Friday, the damaging winds with this system (likely topping 60 mph given the rapidly intensifying low and extreme cold advection), will blow the snow into drifts and easily create white out conditions. It would only take a few hours of falling snow to realize true blizzard conditions with that wind and the rapidly falling temperatures. When you combine that with dangerous wind chill values worsening as the day wears on, this will be a very dangerous storm no matter what. Those with travel plans on Friday should be flexible and stay tuned to the latest updates. We will transition to lake-effect snow behind the system as it lifts north through Ontario Friday night and Saturday, lingering through Sunday, but uncertainty with wind direction (west vs southwest) makes it impossible to pinpoint if the bands will impact NE Ohio and NW PA or if they will stay in western NY. What is certain is that bitter cold temperatures and dangerous wind chills will continue through the weekend with highs in the teens Saturday and Sunday and lows well into the single digits both nights. Wind chill values may get as low as -15 to -20 early in the weekend. Now for a little more on the evolution of the storm, today`s 12Z model runs have actually reverted back to being out of sync with each other. This is unfortunate because it makes the timing of the rain/snow changeover and the amount of snow we will receive highly uncertain; even more uncertain than 24 hours ago. The big mid/upper trough and associated pool of arctic air, originating in Siberia, digs into the Plains Thursday. As it does, a 160+ knot H3 jet diving into the base of the trough will cause it to tilt strongly negative while cascading into the Midwest Thursday night while will lead to a rapidly deepening surface low somewhere in the vicinity of Indiana or western Ohio. Because the trough axis deepens all the way to the Gulf coast, it will also scoop up additional southern stream energy late Thursday. This will further aid in the deepening process allowing the northern and southern streams to phase over the western Ohio Valley and Great Lakes. This will result in a rare "bombing out" of the surface low to take place right over our area as the mid/upper trough closes off, with the whole system then pinwheeling north through the central Great Lakes Friday and Friday night. It is the bombing out that has us so concerned about damaging winds once the arctic front plows through the area. Most guidance has the low at least reaching the sub 975 mb range as it lifts just north of our region, so this very tight pressure gradient combined the jet energy and intense cold air advection will easily support 60+ mph wind gusts. This will down trees and power lines and result in widespread power outages, which is a worst case scenario given the extreme cold. In terms of the snow, today`s 12Z guidance is making this even more uncertain due to timing and track differences. The new GFS came in a solid 6 hours slower and now phases the system over the Ohio Valley/lower lakes Friday afternoon. This would delay the rain to snow changeover to almost midday Friday, with the heaviest snow potentially not falling until Friday evening. The ECMWF maintains a late Thursday night phasing and keeps the changeover to snow consistent with the Friday morning timing, but it tracks the low across west Michigan which would bring a dry slot into the area after an initial burst of snow, with heavier snow from the trowel not arriving until later in the day. The RGEM is in the middle with timing, but it tracks the low toward the eastern Great Lakes as it bombs out through the day Friday. This solution would give us the most snow but may lessen the winds slightly. Any of these solutions will lead to snow, high winds, and brutal cold developing Friday into Friday night, but the amount of snow that actually falls is the biggest question mark. To summarize, warm air advection ahead of the deepening trough Thursday will warm temps into the upper 30s, so precipitation driven by broad warm/moist advection and isentropic ascent will fall as a rain/snow mix, with rain being the dominant p-type Thursday. Rain will rapidly change to snow late Thursday night or Friday morning, depending on timing of the arctic front, with a burst of snow and flash freeze likely. Winds will steadily increase Thursday night from the SE and become damaging by Friday morning as they veer to the W to SW in the cold advection behind the front. Snow will fill back in at some point Friday morning or afternoon after a lull behind the initial burst, with blizzard conditions possible through the day and extensive blowing/drifting, even though exact snow amounts are in question. Temperatures will fall through the teens Friday afternoon and will continue to fall through the single digits Friday night with dangerous wind chill values. The synoptic snow will transition to pure lake-effect Friday night through Sunday east of Cleveland, but to what extent the main band gets into our region remains unclear. It is possible that a SW component to the wind keeps it mainly over western NY most of the weekend, but lingering wind and arctic cold will keep conditions hazardous. && .AVIATION /00Z Monday THROUGH Friday/... An MVFR stratus deck remains across much of the area as moist low-level cyclonic flow continues across the Great Lakes. High pressure wedging in from the Ohio Valley is trying to bring some clearing towards Mansfield from the southwest and they may scatter out the clouds this evening before re-filling in overnight as a subtle shortwave goes by. Elsewhere, expect the stratus to persist tonight, with cigs probably lowering a bit across the board due to some amount of nocturnal cooling. Expect the MVFR stratus to persist Monday with a gradual scattering out from the west/southwest late in the day. The general rule this time of year is to not expect the stratus to lift/scatter out quicker than expected, so leaned somewhat pessimistic in terms of bringing cigs back to VFR. Lake effect snow has lifted just northeast of ERI this evening, but should sag back in later this evening as winds turn slightly more onshore. Generally not expecting heavy snow, but periods of MVFR and somewhat more intermittent IFR are likely late this evening through early Monday. Activity gradually weakens on Monday, but not expecting cigs to lift to IFR through the end of the TAF period even as vsby improves. Modest west-southwest winds continue through the TAF period, a bit stronger at CLE and especially ERI through Monday. Outlook...Non-VFR possible in minor lake effect Tuesday night. Non-VFR and strong winds expected the end of the week with impactful and expansive low pressure system. && .MARINE... Water levels on the western basin fell close to the critical mark of 6 inches above low water datum this afternoon, but those are starting to come back up now. This should continue through tonight as the winds gradually lessen. W winds will decrease to 15-20 knots tonight with waves subsiding to 5-7 feet on the central and eastern basins. This will give way to lighter 5-10 knot winds by Monday afternoon and waves falling under 3 feet as high pressure builds in. Quiet conditions will then continue on the lake through Wednesday night due to weak pressure gradients. By Thursday, a strong trough and developing low pressure system approaching from the west will start to increase winds on the lake. SE winds will increase to 15-20 knots Thursday afternoon becoming SW late Thursday night and Friday and increasing to Gale force as the low moves north and rapidly bombs out. The high winds will continue through Friday and into Friday night. The low is strong enough that storm force winds are not out of the question Friday. Waves will easily top 10 feet in the central and eastern basins with freezing spray as bitter cold arctic air filters across the region. This will lead to water levels in the western basin likely falling well below low water datum Friday and Friday night. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...Lake Effect Snow Warning until 4 AM EST Monday for PAZ001-002. MARINE...Small Craft Advisory until 10 PM EST Monday for LEZ144>149. && $$ SYNOPSIS...26 NEAR TERM...26/Sullivan SHORT TERM...Garuckas LONG TERM...Garuckas AVIATION...Sullivan MARINE...Garuckas
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
940 PM CST Sun Dec 18 2022 ...New UPDATE... .UPDATE... Issued at 929 PM CST Sun Dec 18 2022 Coastal trough is sharpening along the lower and middle Texas coast this evening. Southeasterly low level flow will continue to advect higher moisture into the coastal region tonight with shower activity expected to increase during the overnight hours. Models depict enough elevated instability will develop toward daybreak for isolated thunderstorms to occur westward into the eastern Brush Country for Monday morning. Latest HRRR shows MUCAPE values up to 500 J/kg in the morning in this region. Added slight chance for thunderstorms to the forecast to the east of a Hebbronville to Tilden line. Also, some concern for stronger storms over the marine areas Monday morning as more unstable air mass will move into the coastal waters ahead of the surface low. HRRR shows MLCAPE values from 1000-1500 J/kg with 0-6 km shear around 50 knots. Could see some strong storms over the coastal waters with the potential for rotation with the stronger low level helicity to the east of the surface low. Adjusted marine forecast to show chance for storms during the morning hours. No changes were made to the current SCA configuration. && .SHORT TERM... (Tonight through Monday night) Issued at 343 PM CST Sun Dec 18 2022 Concur with the GFS/ECMWF that an upper level trough will move across the TX Panhandle/southern Plains tonight/Monday, while another upper system moves across the CWA Monday, both at 500mb. Also the CWA is predicted to be under the RRQ of a 250mb jet streak early Monday. Most recent MSAS depict a weak surface trough near the southern coast. The deterministic runs continue to predict this trough to continue to develop, with the GFS developing it into a closed low adjacent to the coast, while the ECMWF retains the trough and slightly east. Nevertheless, expect upper/surface forcing, increasing moisture to result in mainly scattered to numerous showers tonight through early Monday over the Coastal Plains. Although the predicted thermodynamic soundings preclude surface-based CAPE, will add isolated thunderstorms near the coast/offshore, given that conditions in the vicinity of the surface low may be conducive to thunderstorm activity. Expect precipitation to dissipate from west to east Monday afternoon, as the upper/surface systems move east. Yet, concur with the NAM which maintains overcast conditions through Monday afternoon, which should maintain cool conditions. Decided to lower maximum temperatures Monday below the NBM. Will retain the high risk of rip currents tonight. Will not extend the high risk beyond the current 12z Monday expiration, since the transition, beginning after 12z Monday, in the winds in response to the foregoing eastward moving surface low, which will decrease the rip current risk. && .LONG TERM... (Tuesday through next Saturday) Issued at 343 PM CST Sun Dec 18 2022 Key Messages: -Strong arctic cold front Thursday -Well below freezing temperatures likely Thursday night and Friday night. -Single digit wind chills Friday morning? Between Tuesday and Wednesday there`s not a whole lot to talk about. Northerly surface flow will keep temperatures near or slightly below normal with a fair amount of clouds, especially in the east. A mid level shortwave pushes through on Tuesday, but doesn`t have enough moisture to work with for any notable rain chances. The more interesting part of the forecast starts on Thursday. Usually 5 days out, we`re talking about model model shows one thing and others show another. Or that there are timing differences, but not this time! Consistency has been pretty remarkable with the cold air forecast to move through much of the country in the later half of this week. It`s not very often what the models are showing in the 240+ hour range holds up, but baring any unexpected changes, it looks like it will this time. Mid and upper level trough deepens as it moves into the central US and will usher in the coldest air we`ve seen since February 2021. That said...this situation has some important differences from 2021. First, we`re not expecting precipitation. There may be enough moisture/forcing for some showers over the Gulf of Mexico, but as far as land areas, at times of freezing temperatures, we look dry. Second, daytime temperatures are expected to warm above freezing each day. Yes, it`s going to be cold, but it doesn`t compare to 2021. A cold front will blast through the area (yes, blast looks to be an appropriate verb) Thursday afternoon or evening with strong winds and very cold temps following closely. Temperatures fall from the 60s for highs Thursday into the lower and mid 20s for much of the area by Friday morning...The Victoria Crossroads and portions of the northern Coastal Plains could even fall into the teens assuming skies clear as quickly as expected. The strong winds accompanying these low temperatures will bring dangerously cold wind chills in the teens and possibly single digits for some areas. It`s not out of the question that we may have to issue a wind advisory for islands and coastal portions of counties behind the front with gale conditions in the marine areas a near certainty. High temperatures on Friday could stay in the 30s for much of the area before falling into the 20s once again Friday night. A coastal trough develops into the weekend and will push some moisture into the coastal areas which will a) keep temps from falling as cold near the coast and b) bring the potential for an isolated cold shower by Saturday night into Sunday. Important note...the moisture increase that would lead to these showers should also keep temperatures above freezing. Looking ahead into Christmas day, temperatures will begin to rebound with highs expected back into the upper 40s and 50s. && .AVIATION... (00Z TAFS) Issued at 558 PM CST Sun Dec 18 2022 Good aviation conditions, with VFR ceilings from 5-6 kft across most of south Texas except for high end MVFR ceilings near LRD at this time, will deteriorate tonight as the coastal trough develops. The low level warm air advection will increase this evening leading to ceilings falling through MVFR during the evening hours except for the Victoria Crossroads. Showers will develop over the Coastal Bend after midnight with ceilings falling to IFR over most of south Texas, except for MVFR ceilings for VCT area. LIFR ceilings and IFR vsbys with showers will affect the coastal plains during the early to late morning hours as the low drifts to the northeast along the coast. Isolated thunderstorms may develop within the area of showers over the Coastal Bend between 10-16Z while TSRA will be possible at VCT from 14-18Z. Ceilings will gradually lift to MVFR over the Brush Country by late afternoon, maybe even see some clearing skies for LRD. IFR ceilings and MVFR vsbys will linger over the coastal plains during the afternoon while precipitation activity moves to the east. && .MARINE... Issued at 343 PM CST Sun Dec 18 2022 Continue to expect a coastal trough or closed low to develop along/near the coast tonight/early Monday morning, which should contribute to numerous to scattered showers and isolated thunderstorms. Moderate to strong onshore flow and high seas are expected tonight through Monday morning. Conditions will gradually improve from west to east as the surface low moves east. Extended the Small Craft Advisory to 00z Tuesday for the coastal waters. A moderate to strong north wind will develop Tuesday across the region. Winds become moderate from the east and southeast Wednesday ahead of a strong arctic cold front Thursday. Very strong northerly winds and elevated seas are expected behind the cold front Thursday and Thursday night with gale conditions likely Thursday night through Friday morning. Very cold air will drop temperatures into the 30s for much of the Middle Texas area Thursday night and portions of the area Friday night. && .PRELIMINARY POINT TEMPS/POPS... Corpus Christi 57 61 47 61 / 70 70 0 0 Victoria 49 55 45 59 / 50 80 10 0 Laredo 49 58 47 66 / 50 10 0 0 Alice 52 58 45 63 / 70 50 0 0 Rockport 55 62 47 60 / 70 80 10 0 Cotulla 48 56 45 65 / 50 20 0 0 Kingsville 55 60 47 62 / 70 50 0 0 Navy Corpus 59 64 49 60 / 80 80 10 10 && .CRP WATCHES/WARNINGS/ADVISORIES... TX...High Rip Current Risk until 6 AM CST Monday for TXZ345-442-443- 447. GM...Small Craft Advisory until 6 PM CST Monday for GMZ250-255-270- 275. && $$ SHORT TERM...TMT/89 LONG TERM....PH AVIATION...TMT
Area Forecast Discussion
National Weather Service Des Moines IA
534 PM CST Sun Dec 18 2022 ...Updated for the 00z Aviation Discussion... .DISCUSSION.../Tonight through Sunday/ Issued at 352 PM CST Sun Dec 18 2022 Forecast Highlights: - Quiet tonight into early Monday, warming slightly - Snow expected Monday, which may mix in with some freezing drizzle/rain at times later in the day - Large and impactful system Wednesday/Thursday with many inches of snow possible, windy and arctic cold especially Thursday/Friday GOES Satellite Imagery clearly depicts the recently fallen snow from earlier this week across Iowa, thanks to sunny skies as snow can be seen across central and northern Iowa while the far south/southeast remains bare. A short lived high pressure system continues to pass through the state into the afternoon, with generally chilly conditions as temperatures have struggled to increase much through the day. Despite the cloudless skies, snowpack has helped keep temperatures cooler in the teens north of I-80 and in the 20s further south where there is no influence from any snowpack. Winds remained light out of the northwest which continues to reinforce the cooler air. Quiet conditions are expected to continue this evening, though as low level flow shifts southwesterly this evening into Monday, warm air advection with increasing moisture will bring a return of clouds into the state. Overnight lows are expected to fall into the single digits north and in the teens south. A shortwave traveling northeast from the Desert Southwest later today into the Central Plains Monday is expected to bring the next system to the state. Deterministic models have generally slowed the arrival of precipitation slightly, moving into the state from southwest spreading northeast in the mid to late morning. Recent runs of the GFS and Euro have trended the higher QPF amounts slightly further west than has been seen in earlier runs, which would place the highest totals along and west of I-35 Monday. However the NAM is more consistent placing the higher amounts along central Iowa as has been the trend over the previous runs, which the RAP and HRRR also captures. Overall, QPF amounts have not changed much, with general accumulations in the 0.05 to 0.15 inch range before ending late Monday/early Tuesday. Snowfall accumulations between 1-2 inches are still generally expected at most, with less elsewhere across the state. With some ice introduction lost late Monday into Tuesday across parts of eastern Iowa despite low level saturation per soundings, some freezing drizzle could occur with overall little accumulations. The RAP and HRRR does introduce freezing drizzle Monday afternoon/evening to Tuesday with at least little accums, though the NAM, GFS and Euro remain colder with no ice concerns. Confidence is not very high however and if anything would likely be rather isolated, but will depend on how conditions evolve through the event so will keep an eye on this. For now have continued to mention freezing rain/drizzle in the forecast but little to no ice accumulations at this time. Dry conditions return Tuesday but will come with the passage of a cold front pushing northwest to southeast through the morning into the afternoon. This will bring in the first round of much chillier temperatures with returning northwesterly flow. This frontal passage will however be paired with drier air which will keep conditions otherwise dry for the day into Wednesday morning. Morning lows are expected to fall into the single digits northwest and in the teens further southwest, before topping out in the single digits to teens into the afternoon. A very large and impactful system developing from a deepening trough is expected to pivot into the Northern Great Plains and eventually Upper Midwest by midweek. Deterministic models have trended an earlier arrival of widespread snow in most recent runs, arriving into western Iowa into Wednesday afternoon before spreading east across the state into the evening. The evolution of the system remains a bit more uncertain, as the GFS and NAM depict less robust forcing for widespread heavier QPF amounts Wednesday and Thursday before cyclogenesis forms a closed low further into the Ohio Valley, as the greater moisture content remains further south and east. The Euro however continues to be in better favor of this low pressure system becoming better defined into Thursday over Iowa, with much better forcing and moisture availability. Despite these continuing differences, accumulating snowfall is expected to be widespread and highest Wednesday evening throughout Thursday, with at least a few if not several inches falling before finally exiting the state into Friday. Along with this, a strong signal remains in place for gusty winds Thursday and Friday out of the northwest, with gusts looking to occur around 35 to 40 mph for most areas of the state. This will cause for blowing snow and resulting potential blizzard conditions, leading to additional hazards for travel of any kind. If the wind and snow isn`t enough, dangerously cold air dropping into the region from an arctic airmass will allow for extremely bitter temperatures Wednesday and especially through Thursday and Friday. Morning lows will generally fall into the single digits to teens below zero across the state, with highs only reaching into the just above and below zero. Lowest wind chills in the -20s to -40s are looking likely as well. In summary, the weather is going to be extremely unpleasant and will be hazardous if traveling or going outdoors for longer periods of time. Please plan ahead and consider adjusting travel plans as needed in order to avoid these conditions as much as possible. && .AVIATION.../For the 00Z TAFS through 00Z Monday evening/ Issued at 534 PM CST Sun Dec 18 2022 VFR conditions will prevail through the night and Monday morning, then low ceilings and light snow will spread from into the area from the southwest from around midday into the evening. Have advertised the trend of deteriorating conditions in the 00Z TAFs, however timing and magnitude are estimates at this range and will be refined in later TAF issuances. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...Bury/Donavon AVIATION...Lee
National Weather Service Hastings NE
543 PM CST Sun Dec 18 2022 ...AVIATION UPDATE... .DISCUSSION...(This evening through Sunday) Issued at 230 PM CST Sun Dec 18 2022 Key Messages: * HIGH CONFIDENCE in strong winds and very cold air combining to produce very dangerous wind chill values of -25F to -45F Wednesday night through Friday morning. * MEDIUM HIGH CONFIDENCE in travel impacts due to snow and blowing snow, especially on Thursday. Winds WILL be strong, but there is still some uncertainty regarding snowfall amounts. Currently it looks like at least a couple inches but any snow with those winds will likely impact visibility and cover roadways with snow. * LOW to MEDIUM CONFIDENCE in a light wintry mix of light snow and freezing drizzle east and southeast of the Tri-Cities Monday morning. * Confidence is increasing of a warming trend starting Christmas weekend. Forecast Details: Starting with the first potential impact tonight and into Monday morning, a shortwave trough will move across the area, pulling precipitation northeast through Kansas and eastern Nebraska. Most of this precipitation will remain east and southeast of the forecast area, but model guidance continues to show a chance that our eastern and southeastern counties could get impacted by this system. The timing is still a little questionable especially with the HRRR trying to push this later on in the morning, but most likely from the early morning hours Monday through around noon. Most of this will be in the form of flurries but model guidance and forecast soundings do show a brief period of freezing drizzle potential southeast of the Tri-Cities (meaning ice impacts are NOT currently expected in the Tri-Cities). If freezing drizzle does develop, roads and sidewalks will become slick and the morning commute in those areas will likely be affected (this would be one of those low chance but potentially impactful events). Seeing as most of the model guidance indicates no ice at all, we elected not to issue any advisory at this time...but will be watching it closely. Starting Monday afternoon, high pressure begins to dive into the region from Canada and the northern Plains, and this will lead to a fairly wide temperature gradient within the forecast area. Highs Monday will range from the upper teens north to the mid to upper 30s south. This cold air will deepen Monday night and Tuesday, and breezy north winds Monday night will bring about the first night of widespread below zero wind chills, with values of -5F to nearly -20F Monday night/Tuesday morning. Tuesday night, winds will be lighter and wind chill values will not quite be as cold. The most impactful period of this forecast will be the strong winds and deep Arctic cold temperatures Wednesday night through Friday. In addition, there is increasing confidence in at least a couple of inches of snow with this, so blowing snow is also becoming an increasing concern Wednesday through Friday. The first point of note will be the strong winds and dangerously cold wind chills. Winds will start to increase Wednesday and at the peak of this event Thursday, north winds will be gusting to 40-45 mph Thursday. With the Arctic cold and strong winds, wind chill values will be in the -25F to -45F range Wednesday night THROUGH Friday. Wind chills this low can cause frostbite to unprotected skin in as little as 10-15 minutes, just to give an idea of how quickly these values can be impactful. Now that we have covered wind chill, there is also the snow element to this. There is increasing confidence in at least some snow but amounts are still somewhat uncertain...latest WPC ensemble plumes suggest around 2" to 4" but there are still a few days to nail that down and those numbers could trend either way at this point. Regarding timeframe, latest model guidance indicates this will move in Wednesday morning with the bulk of the snow falling Wednesday evening and overnight, then moving out to the east Thursday morning. With temperatures as cold as they will be, this will be a dry, powdery snow with higher than normal liquid to snow ratios (LSRs). Some of the deterministic models like a ratio in the low 20s:1, but chose to go a bit lower due to the probability of dendritic fracturing in those strong winds. No matter what the LSR or the snowfall amount, any snow that falls will blow around, and it does not help that those are a couple of the busiest travel days just before Christmas. It is too early to be forecasting "blizzard" conditions especially with uncertain snowfall amounts, but the potential is in our minds as we get closer to this event. Keep in mind if traveling that the combination of blowing snow, poor visibility, and bitter cold wind chills could make travel conditions very dangerous very quickly. Once we get past the bitter cold wind chills Wednesday night through Friday, temperatures will start to moderate going into Christmas weekend. High temperatures Saturday will climb into the teens and 20s and by Christmas Day there may even be a few places that make it above freezing. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday) Issued at 538 PM CST Sun Dec 18 2022 VFR conditions until around 08Z then cigs will come down to around MVFR then down further to IFR around sunrise. Cigs will be the main concern this period with MVFR and IFR conditions through part of the overnight and throughout most of tomorrow. Cigs will begin to scatter out tomorrow late afternoon into the early evening. Winds will shift in the next few hours from southeasterly to more easterly then northeasterly overnight then more northerly by midday tomorrow. Speeds will be generally modest at around 5-10 kts. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ DISCUSSION...Hickford AVIATION...Shawkey
National Weather Service Charleston WV
728 PM EST Sun Dec 18 2022 .SYNOPSIS... Snow showers become confined to the mountains tonight, clearing elsewhere. High pressure first half of next week. A strong storm sends arctic air by end of week. && .NEAR TERM /THROUGH MONDAY/... As of 645 PM Sunday... Haven`t had to make too many tweaks to the forecast this evening. Adjusted temperatures and dew points in the grids to reflect current obs. Clearing in the lowlands is right on time as high pressure continues sliding in. Snow showers are going to continue tonight in the mountains. The main ponder is to when these showers will finally taper off and move out. Current guidance is suggesting snow showers to continue throughout the night for Randolph and Pocahontas counties. Canadian model keeps these showers past midnight tonight. GFS and EURO shutting them off before midnight. The RAP Keeps a mountain wave over the mountains of Pocahontas and Randolph tonight which will hold the low clouds overhead and enhance snow shower activity tonight. Certainly thinking it is possible for snow showers to continue through morning for the western facing slopes in these counties. Particularly areas such as Snowshoe, Elkins, Buckhannon, and Clarksburg will see this activity. Not expecting any accumulations past a quick hundredth or tenth though. High pressure will dominate the weather pattern starting tomorrow. Some lingering clouds are possible for the mountains. As of 1230 PM Sunday... Snow showers/flurries gradually taper off from south to north through this evening across the lowlands, persisting into the overnight in the mountains. Channeled vorticity associated with an area of upper level low pressure south of Hudson Bay will lift north out of the region through late this afternoon. Should see a marked decrease in upper level seeder clouds as this occurs which should yield less coverage of snow showers/flurries. Additional cold air stratocumulus is already developing across Ohio as upper level cloudiness clears, and would expect this trend to continue in our area. This will yield continuing isolated/scattered show showers/flurries through late this afternoon/early this evening across the lowlands when surface heating is lost. Additional snow accumulations across the lower elevations will be light, generally less than a tenth of an inch, although any more persistent bands could produce slightly more. In the mountains, upslope enhanced snow showers likely continue through daybreak Monday, although once heating is lost this evening additional accumulations will be minimal. Surface high pressure begins to build in overnight amidst clearing skies. Not expecting a perfect radiational cooling night with light westerly flow continuing into the pre-dawn hours, but would expect better protected low spots to fall to saturation yielding temperatures in the upper teens to lower 20s, especially locations holding onto a little bit of snow cover over grassy surfaces. The main concern overnight will be a potential refreeze, primarily on elevated surfaces such as bridges and overpasses. The modest westerly wind should assist in alleviating some of this concern as it assists in drying surfaces. Monday remains chilly with highs struggling to get out of the mid 30s amidst increasing upper level cloudiness in response to a southern stream system that will otherwise have little impact to our sensible weather. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 210 PM Sunday... High pressure continues to keep the area dry through Wednesday afternoon. With a relatively persistent pattern during this time, highs will climb into the 40s with overnight lows in the 20s. Winds will be generally light under ten mph during this weak pattern. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 210 PM Sunday... A winter storm continues to be the main focus for the extended forecast Thursday night through Saturday as a powerful storm tracks across the plains to the northeastern states. Wednesday night rain and snow showers along with gusty southerly winds are expected to develop as disturbances moves up from the south, ahead of a deepening trough over the plains. Warm air advects across the region early Thursday as the front punches to the north, which will change any snow over rain for the lowlands fairly quickly. The mountains may be slower to change over and could maintain a few pockets of cold air that will keep localized snow, or perhaps a wintry mix including ice pellets. Details on these precipitation types still need refining. There could be a short break in precipitation Thursday afternoon across the lowlands behind the frontal passage; but, a strong cold front quickly follows bringing precipitation challenges areawide Thursday night through Friday. The track of the low is critical on working out the details for precipitation types. All models are in relatively good agreement on arctic air to arriving by mid day Friday. The GFS model continues to be an outlier with the low position, tracking the storm slower and farther south than the ECMWF and Canadian models. The GFS solution would support a longer duration of rain into Friday with snow heavier snow lasting into the evening hours. The populated NBM into the forecast is influenced by the colder model solutions which brings the front/higher chances for accumulating snow through early in the day Friday with scattered chances diminishing from the west overnight. Cold arctic air settling Friday night drops temperatures down into the single digits and lower, which will be the chilliest of the season thus far. North to westerly breezes behind the front will also make temperatures feel even colder into Saturday. && .AVIATION /23Z SUNDAY THROUGH FRIDAY/... As of 700 PM Sunday... Currently, ceilings are raising from southwest to northeast as high pressure moves in. Skies are either clearing or lifting and scattering out. Subsequently, most sites in the lowlands and southern mountains have improved to VFR and will stay that way. EKN is at MVFR and will keep this category most of the night. Clearing will continue overnight except for the northeastern mountains where MVFR/IFR ceilings will be probable through the morning hours tomorrow as upslope continues. Light upslope snow showers at EKN/CKB could persist through early tomorrow morning. Periods of MVFR/IFR visibility are possible in some heavier snow showers. Finally, tomorrow VFR will be widespread at all sites after 15Z tomorrow as high pressure dominates. Decoupling may not be widespread under uniform westerly flow so some passing clouds at 18k-23k feet are possible late tomorrow. Winds this period becoming predominantly more westerly at speeds of 3-8KTs tonight. BKW may keep a more WNW/NNW flow from 4-9KTs before becoming more westerly tomorrow. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z TUESDAY... FORECAST CONFIDENCE: High. ALTERNATE SCENARIOS: Localized heavier snow showers could yield IFR conditions for longer than advertised at CKB/EKN tonight. Improvement to VFR in the mountains tomorrow may vary from forecast. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. UTC 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09 EST 1HRLY 17 18 19 20 21 22 23 00 01 02 03 04 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H H H H H EKN CONSISTENCY H H H H H H H H H H H H PKB CONSISTENCY H M H H H H H H H H H H CKB CONSISTENCY M M H H H H H H H H H H AFTER 00Z TUESDAY... IFR possible in rain and snow early Thursday morning. IFR in snow possible Friday morning. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...KH/JP NEAR TERM...LTC/JP SHORT TERM...KH LONG TERM...KH/JZ AVIATION...LTC