Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/14/22

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
844 PM CST Tue Dec 13 2022 .UPDATE... Issued at 840 PM CST Tue Dec 13 2022 The main band of pcpn has shift up into ND this evening as dry slot overtakes the forecast area. Soundings continue to support patchy fzdz and light snow overnight, but most of the accumulating snows have probably ended for the time being. Overnight lows look fine and relatively mild. && .SHORT TERM...(This Evening through Wednesday Afternoon) Issued at 350 PM CST Tue Dec 13 2022 The main forecast challenges include how heavy the snow (snow rates) will be this afternoon through late this evening with this current band of precipitation moving through, and then whether or not any drizzle/freezing drizzle potential will exist behind this precipitation band tonight into Wednesday with the dry slot that moves through. At 2 PM CST, skies were overcast and a significant band of moderate to heavy snowfall was noted lifting north and west across the CWA. Thunder is mentioned in the forecast across the western forecast zones (west of the James River valley) through late this evening. The classic high end lift/high end forcing signal in RAP model cross sections describing heavy/intense snow bands is showing up right now with this band of precipitation moving through. Add to that some very unstable "cold air instability" values of -EPV* and fully expecting to see this large band of snow evolve to smaller embedded heavier bands of snow, and perhaps even some lightning and thunder. Temperatures have remained nearly steady, generally between 30 and 34 degrees. East winds ranging from 15 to 25 mph with gusts to 35 mph are occurring across the Prairie Coteau into west central Minnesota. Across the Missouri River valley westward, winds are more north or northeast for direction between 10 and 20 mph for the most part. There has been a lot of icing on and east of the Prairie Coteau between last night and early this afternoon (CC on KABR working well to differentiate between freezing rain areas and snow areas since RAP/HRRR output seems to be struggling with the strength of the mid- level WAA warm nose). The consensus, though, remains that the thermal profile should be gradually transitioning from a dominant freezing rain p-type to more of a dominant frozen p-type across the eastern forecast zones by early this evening while this more significant band of precipitation works through the region. Regarding the dry slot that takes over behind this band of precipitation, opted to replace any mention of "rain or freezing rain" and run with "drizzle or freezing drizzle" given there should only be a supercooled stratus layer to work with after the saturation layer aloft goes away. And, that`s presuming the "clear all the way down to the ground" slot of air showing up in satellite imagery over Nebraska doesn`t make an appearance up in this CWA. On Wednesday, the 500hpa low moves from near O`Neill, Nebraska to near Vermilion, South Dakota (so, in other words, very little!!). Will have to keep a watchful eye on the area north and northeast of the 500hpa low center to see if/when the "cold air instability" reduction zone becomes active again on Wednesday. It`s a mixed signal amongst the models whether or not that area becomes active. The 12Z HREF output hints a little bit at the potential for there to be some areas of our southern/eastern forecast zones that see snow rates potentially at or above 0.5in/hr on Wednesday. Did lean on the NBM90th percentile and NBM4.1 (50/50 blend) for the winds/gusts tonight and Wednesday. Seeing some of those stronger winds/gusts spilling over into the west river/MO River valley forecast zones by early Wednesday afternoon. Limited low level thermal advection changes over the next 24 hours. The far western forecast zones should be dropping out of the low 30s and into the 20s from late tonight through the day on Wednesday. No changes planned to the current headlines. Letting the Ice Storm Warning stand on its own until 6PM (would like to see the CC values transition to snow before dropping) and then transition over to a Winter Storm Warning. All the rest of the CWA in a Winter Storm Warning will continue to remain in said Winter Strm Warning. .LONG TERM...(Wednesday Evening through Tuesday) Issued at 350 PM CST Tue Dec 13 2022 Weather conditions will continue to revolve around the ongoing winter storm that will be remaining in the vicinity of the region through the first couple of days of this forecast period. Challenges will continue to be winds and related blowing snow/visibility impacts and p-types initially in the period followed by temperatures toward the end of the term. Starting things off Wednesday night, sfc low pressure and it`s mid/upper level reflection will be situated around the NE/SD/MN/IA border region. This system is progged to shift gradually eastward across IA/MN region during the day Thursday and then eventually into WI and the western Great Lakes region by late Thursday into Friday. Shortwave energy will continue to rotate from east to west/southwest across our FA; around the north and west side of the mid-lvl low Wednesday night through Thursday...and to somewhat of a lesser extent on Thursday night into Friday. So, precip chances will remain relatively high through Thursday night before we see a gradual drawdown in chances during the day Friday. This storm system will continue to lift out to the northeast into Canada and farther away from our area during the course of the weekend. Sfc high pressure will build into our forecast area Saturday into Sunday and prevailing through the end of the period. This will lead to drier, but much colder conditions setting in. Look at the precipitation more closely through the first couple days of the period. There`s still some possibilities that some of our eastern zones will see some pockets of freezing rain or freezing drizzle Wednesday night into Thursday morning. This would especially be the case across the higher elevations of the Prairie Coteau and surrounding areas of northeast SD/west central MN. It`s not expected to be as impactful though as it was in those areas today. The transition to more snow will be the trend across our eastern zones on Thursday and for the remainder of the event through Friday. Additional accumulations of snow will be more probable across eastern zones where another 3 to 6 inches could fall between Wednesday night and Friday. Farther west, from the James Valley through West River zones, precip will be all snow for the duration of the event. We might see more pockets or bands of snow across our western zones versus more widespread activity Thursday into Thursday night. Accumulations will generally be lighter or lower across the west through the end of the event. One of the challenges mentioned above will be wind speeds and the resultant impact they will have when it comes to blowing snow and reduced visibilities. Wednesday night into Friday morning still look to be the window for winds to increase substantially, especially west of the James Valley through West River zones. There will be modest cold air advection starting to take place West River and Missouri Valley areas late Wednesday through Thursday. The gradient tightens noticeably across central SD during this time. Ensemble probabilities of seeing max gusts in excess of 40 kts still remain the highest across portions of the Missouri Valley and southwestern sections of the CWA. So, expecting some impactful conditions in either falling snow or from the blowing around of the fluffier snows that have accumulated on the surface. We`ll have to continue to monitor these trends over the next 24 hours in case a change from current headlines is warranted. Finally, temperatures will remain rather mild through the end of the week. A much colder airmass is expected to advent into our region during the course of the weekend. Well below normal temperatures are expected by early next week. Expecting overnight lows will be well below zero and daytime highs will struggle to make into the single digits to low teens. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening) Issued at 507 PM CST Tue Dec 13 2022 Terminals KABR,KATY,KPIR,KMBG IFR/MVFR cigs are expected through the night. Meanwhile a band of snow will move from south to north over the area this evening before pushing off into ND. Heavy snow in that band could reduce vsbys to 1/4sm or less at times for KMBG/KABR/KATY through mid evening. Improvement is expected thereafter. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...Winter Storm Warning until 6 AM CST /5 AM MST/ Thursday for SDZ003>011-015>023-033>037-045-048-051. MN...Winter Storm Warning until 6 AM CST Thursday for MNZ039-046. && $$ UPDATE...TDK SHORT TERM...Dorn LONG TERM...Vipond AVIATION...TDK
Area Forecast Discussion
National Weather Service La Crosse WI
835 PM CST Tue Dec 13 2022 .UPDATE... Issued at 830 PM CST Tue Dec 13 2022 Main update this evening focuses on the increasing (60-70% chance) of a band of moderate to even heavy snow forming from west of Rochester and lifting northeastward north of Winona and then into western Wisconsin between 08-14Z. The high resolution guidance (RAP/HRRR) have been steadfast that the warm nose along this corridor collapses with the arrival of a second band of precipitation after 06Z. This band is lifting northward through southern Iowa/northern Missouri this evening with multiple lightning strikes noted as it crossed the IA/MO border. The HRRR and RAP forecast profiles both show a token (10-30 J/kg) of upright convection above the dendritic growth zone with very impressive synoptic lift through this corridor as well. All combined, these ingredients point to an intense, albeit brief, period of high snowfall rates within this band where rates of 1-2 inches per hour are possible. The main limiting factor for accumulation will be the warm surface temperatures in the mid-30s. Therefore, the main message with this snow band will be reduced visibilities in heavy snow and accumulating snow on mainly grassy surfaces, though one cannot rule out some impacts to roads for a short period. && .DISCUSSION...(This evening through Tuesday) Issued at 237 PM CST Tue Dec 13 2022 Key Messages: - A complex winter storm will linger through late week, with the highest confidence for wintry impacts, including difficult travel, north of I-94 from multiple rounds of precipitation tonight through early Thursday. Some updates to precip types/amounts remain likely as this system passes. - Much below average temperatures are increasingly likely late this week into next week. Tonight-Friday: Slow-moving, complex winter storm continues A deep, nearly vertically stacked low pressure system continues to spin across the central plains this afternoon. Strong, gusty winds up to 35 to 45 mph will persist into tonight with a tightened pressure gradient and low-level jet just off the surface. Anomalous deep moisture transport (precipitable water exceeding 0.80") will continue to feed north ahead of the low with rain spreading north and east late this afternoon and tonight. Some transient mixed precip could occur south of I-94 but the primary area of concern remains areas north of I-94 where surface temps will likely hover near freezing for a longer period of time. Some differences in the strength of the warm nose aloft exist among models, impacting whether precip tonight is more liquid vs mixed/snow. The greatest risk for freezing rain will occur overnight into early Wednesday, with impacts highly dependent on surface temps/dew points. The NBMv4.1 has continued to increase with 60% probabilities of at least 1/10" of ice at Medford, WI and lower probabilities around 20% for 1/4" inch. If the temps are slightly warmer, the icing threat would be reduced considerably. Likewise, if the thermal profile aloft is a bit cooler, more snow/mixed precip would be likely. Given the marginal temps, expect icing impacts to be most noticeable for elevated surfaces. As warmer air gets wrapped northward on Wednesday, some drizzle may persist behind the main precip band, with a transition to rain/snow for north central Wisconsin. Precip amounts have trended upwards on Wednesday night across central/northern Wisconsin as an embedded shortwave rotates through the broader trough and moisture continues to wrap northward around the low. Depending on the placement of this band, several inches of snow could occur within a deformation band, especially across north-central Wisconsin. The HREF indicates potential for snow rates exceeding 1"/hr in the band Wednesday night, mainly just to the east in northeast Wisconsin. So, potential exists for higher amounts where this band develops. Given the prolonged nature of this event with rounds of precip spread across multiple days, elected to convert the Winter Storm Watch for Clark/Taylor counties into a longer duration advisory through Thursday morning. That said, will have to monitor the potential for heavier snow Wednesday night and impacts tonight/early Wednesday from the mixed precip. High latitude blocking will slow the progression of the large scale trough keeping the region in cyclonic flow aloft with snow showers/flurries at times into the weekend and some relatively light accumulations possible. This Weekend into Next Week: Much Colder A transition to colder weather is likely heading through the weekend and especially into next week as the slow-moving low finally moves east. There is strong ensemble agreement for much below average temps into next week with highs in the single digits/teens by early to middle portions of next week and potential for subzero low temps. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 529 PM CST Tue Dec 13 2022 Main taf concerns are IFR/LIFR conditions at both taf sites through the taf period. Low pressure over the Northern Plains States will continue to wrap lower ceilings and precipitation across the area tonight into Wednesday. Latest metars show MVFR conditions across parts of southeast Minnesota...western Wisconsin and parts of northeast Iowa with lower ceilings/IFR conditions over central Iowa/southwest Minnesota. Ceilings will lower into IFR at both taf sites this evening and to LIFR at RST after 09z. Precipitation at both taf sites should remain all rain through the taf period. However a very brief period of wintry mix...less than an hour...will be possible early in the taf period and any longer duration of wintry mix should be confined over north central Wisconsin. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Winter Weather Advisory until 9 AM CST Thursday for WIZ017-029. Winter Weather Advisory until 6 AM CST Wednesday for WIZ034. MN...Wind Advisory until 9 PM CST this evening for MNZ086-087-094-095. IA...Wind Advisory until 9 PM CST this evening for IAZ008>010-018-019- 029. && $$ UPDATE...Skow DISCUSSION...JM AVIATION...DTJ
Area Forecast Discussion
National Weather Service Green Bay WI
931 PM CST Tue Dec 13 2022 New Information added to update section .UPDATE... Issued at 931 PM CST Tue Dec 13 2022 Do not foresee making significant changes to the forecast and headlines late this evening. Arcing band of precip continues to swing northeast but is running into ample mid-level dry air based on the 00z KGRB sounding. Precip has been most consistently hitting the ground over central WI from Marshfield to Wautoma where a wintry mix has occurred so far this evening. Some of the stronger returns may provide light precip to the Fox Valley, but they probably won`t be strong enough to induce the cooling (wet- bulbing) effect on temps to freezing where icing could become an issue. Otherwise, thermal profiles are setting up for a freezing rain event over central WI late tonight into Wednesday morning when the steadier precip remains expected to arrive. The warm nose aloft continues to surge to the northeast and across the state based on the RAP analysis. Meanwhile, surface wetbulb temps have cooled slightly over north- central and central WI where the freezing line is just south of Wautoma and Wisconsin Rapids. The freezing wetbulb temps may shift slightly north overnight based on the latest trends, but probably not enough to alter forecast ice amounts significantly. The freezing rain will likely peak near the morning commute time over central WI so motorists are urged to exercise caution on their way to work in the morning. && .SHORT TERM...Tonight and Wednesday Issued at 259 PM CST Tue Dec 13 2022 Winter weather headline changes are the main focus in the short- term forecast. Precipitation trends: have slowed down the northeast progression of the precipitation a little bit from the previous forecast. Freezing rain/ice accumulations: Slightly warmer temperatures in Waushara County resulted in a a decrease in freezing rain/icing there tonight. The greatest threat for freezing rain remains focused over Marathon and the northern portions of Wood and Portage counties, where a tenth to quarter inch of icing is expected. However, light ice accumulations are still possible in counties to the north and east of the original advisory. Snow/accumulations: have lowered snow accums tonight into Wednesday, due to mixed precipitation resulting from the warm layer aloft and drying in the mid-levels on Wednesday. Expecting less than an inch of snow tonight, and generally 1 to 2 inches over NC/far NE WI on Wednesday. The heaviest snow is still expected to occur Wednesday night as the band of heavy precipitation and dynamic cooling wipes out any lingering warm layer aloft in the evening. Headline changes: slightly warmer temperatures in Waushara County have resulted in a decreased threat for freezing rain tonight, so the Winter Weather Advisory has been cancelled there. The advisory has been expanded north and east to include Lincoln, Langlade, Menominee, Shawano and Waupaca counties - most of this area should see ice accums of less than a tenth of an inch. The expiration time for the entire advisory area has been extended through midday Wednesday. The Winter Storm Watch was maintained for all previous counties in NC/far NE, but the start time was delayed until noon. The Watch for Door County was not changed, though snow amounts were lowered a little bit. The Watch was expanded farther south into Waupaca, Outagamie, Brown and Kewaunee counties to account for higher snowfall totals of 4 to 6 inches. As mentioned earlier, the warm layer is expected to erode over our southern counties in the mid to late Wednesday evening, leading to the potential for a brief burst of heavy snow when the main band of precipitation moves through overnight. .LONG TERM...Wednesday Night Through Tuesday Issued at 259 PM CST Tue Dec 13 2022 The main concern for the extended period will be the resolution of the wintry system for the end of the work week into the weekend. A secondary concern will be arrival of a round of much colder air behind the system for the end of the weekend into early next week. Precipitation will be ongoing Wednesday evening, with snow to the north and rain across central to east-central Wisconsin. Precipitation will transition to all snow rapidly for the early evening, with mostly snow expected after midnight. Models have generally trended higher with qpf, especially in the hours after midnight through mid Thursday morning. Also suspect the models haven`t fully captured the potential wet bulbing in the early overnight, so brought temperatures down a a little earlier in the evening, which will also increase snow totals. The main result of these changes is an increase of snow total along the Highway 29 corridor. The bulk of the snow will be realized after midnight through Thursday morning, which most of northeast Wisconsin seeing 4 to 6 inches in this 12 hour timeframe, but depending on how quickly the p-type transition is realized, these snow totals could still shift an inch or so in either direction. After the bulk of the precipitation moves through Thursday morning, the low pressure system will continue its slow journey across the region through Saturday afternoon, with on and off scattered showers likely across the region through the period. This may mix into rain at times during the afternoons. Dry conditions then finally return by Saturday afternoon into Sunday. Finally, much colder air will follow behind this system for the end of the weekend into next week. High temperatures are expected to drop into the teens by Monday, with overnight low temperatures likely below zero. && .AVIATION...for 00Z TAF Issuance Issued at 522 PM CST Tue Dec 13 2022 A large, complex storm system will generally bring poor flying conditions to the region thru 00z Thursday. Mainly MVFR/IFR flight conditions are expected through the TAF period. VFR conditions are possible for a several hour period across northeast WI late tonight into Wednesday morning. Otherwise, a band of precip consisting of a wintry mix will mainly impact central WI tonight into early Wednesday. Icing is possible from late tonight through midday Wednesday at AUW/CWA. Precip will spread across the rest of the region on Wednesday bringing a wintry mix to areas northwest of the Fox Valley, and mainly rain to the Fox Valley and Lakeshore areas. 1-3 inches of snow will be possible across areas north of HWY 29 through the day on Wednesday. Strong southeast winds of 15 to 25 knots with gusts to 25 to 35 kts are anticipated late tonight through Wednesday afternoon. Significant LLWS will also overspread the region from west to east tonight into Wednesday morning. && .GRB WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from Wednesday afternoon through Thursday morning for WIZ005-010>013-018>021-030-031-035-036-073-074. Winter Weather Advisory until noon CST Wednesday for WIZ018>020- 030-031-035>037. Winter Storm Watch from Wednesday evening through Thursday morning for WIZ022-037>040. && $$ UPDATE.........MPC SHORT TERM.....Kieckbusch LONG TERM......Uhlmann AVIATION.......MPC
Area Forecast Discussion
National Weather Service Jacksonville FL
832 PM EST Tue Dec 13 2022 ...New UPDATE... .UPDATE... Issued at 830 PM EST Tue Dec 13 2022 The current forecast generally on track with considerable cloudiness over the area as overrunning/isentropic ascent exists aloft and a weak inverted trough continues off the east coast. Not much in the way of any showers along the trough in our forecast area, but showers further south over south and central Florida will head into our area early Wednesday morning as the trough and a warm front lift northward ahead of an approaching cold front, which is still well to our west. For the update, just made minor adjustments to the min temps, but temps for rest of tonight will remain fairly steady or drop a few degrees from this evening. Based on latest guidance and a few runs of the HRRR model, have expanded 20-30 percent shower chances a bit along the coastal counties later tonight and continued into Wednesday morning and early aftn. Northeast surface winds will relax a bit tonight, and some patchy fog possible further inland in northeast Florida as the winds relax there at or below 5 mph. The marine forecast was not changed much with seas nearshore above some of the guidance near 5-7 ft. We have also trended dominate wave periods toward wind waves of 6 seconds or so initially, and then as winds relax in next 6-12 hours, background easterly swells of about 14-15 seconds will be dominate. && .NEAR TERM [Through Wednesday]... Light coastal showers will continue on into the afternoon and then ceasing overnight as light showers enter into southeast Georgia from out of the west with the prevailing flow shifting about to become more uniform out of the southwest. Breezy surface winds will continue to be out of the northeast-east and becoming more mild over inland areas overnight with cloud cover becoming more dense by morning. Coastal areas will still experience slightly gusty southeasterly winds on into Wednesday. High temperatures for today will reach into the 60s and 70s, with cooler temps occurring over southeast Georgia. Overnight low temperatures will drop down into the 50s over most inland areas and in the lower 60s for coastal areas in northeast Florida. .SHORT TERM [Wednesday Night Through Thursday Night]... Showers and storms will be moving through the region late Wednesday night and through much of Thursday as a trough ahead of an advancing cold front crosses over the southeastern states from out of the west. Severe thunderstorms are possible ahead of the fropa, with supercells and a potential for tornadic development. Most likely threat in association with these storms will be damaging wind gusts. Cold dry air will begin to build in behind the front on Thursday night, bringing dry weather and clearing skies over the region by Friday. Temperatures during this period will be above the seasonal average with temps rising up into the upper 70s. Overnight lows for midweek will drop down into the 40s following the passage of the frontal boundary on Thursday. .LONG TERM [Friday Through Tuesday]... Cold air and northwesterly winds will settle in over the region through the weekend with potential for frost formation and a possible freeze Saturday night into Sunday morning. Potential for showers over the southernmost portion of the forecast area, from along the southern edge of the frontal boundary up into areas along the I-10 corridor as it lifts slightly northward before reinforcing southward before early Monday. Temperatures will drop over the course of the weekend with temps dropping to below the seasonal average with temps starting to rise again on Monday. && .AVIATION... (00Z TAFS) Issued at 647 PM EST Tue Dec 13 2022 A mix of VFR and MVFR ceilings are persisting over the area with the MVFR currently existing for JAX, CRG, and VQQ. There may be some ceiling improvement overnight, but periods of MVFR ceilings may return for the early morning hours. A few showers may also develop later tonight and into Wednesday as a warm front lifts northward, with showers mainly affecting SGJ, CRG, and SSI. A low end chance of IFR ceilings for GNV around 10Z-14Z, but not confident in showing this chance at this time. Improving ceilings to VFR for all TAFs on Wednesday after about 15Z-18Z, except for SSI where we kept MVFR in place. Northeast sfc winds about 8-13 kt at 00Z expected to weaken overnight and slowly turn more east-northeast, then east to southeast 7-11 kt by mid to late day Wednesday. && .MARINE... The coastal trough will continue to linger over the local Atlantic waters today then begin to lift northward as a warm front late tonight into Wednesday in advance of an approaching cold front. A pre-frontal line of potentially strong thunderstorms will cross the waters early Thursday morning trailed by the cold front passage Thursday evening. Elevated combined seas will continue Small Craft Advisory conditions over portions of the local waters through late Thursday. High pressure will extend across the Gulf Coast region Friday into Saturday as local winds and combined seas decrease below advisory levels. && .PRELIMINARY POINT TEMPS/POPS... AMG 52 73 64 72 / 10 10 80 90 SSI 57 71 64 75 / 20 20 70 100 JAX 58 76 64 75 / 20 20 70 90 SGJ 63 76 64 75 / 30 30 50 90 GNV 59 79 63 75 / 0 0 70 90 OCF 60 79 65 76 / 10 0 70 90 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...High Rip Current Risk through Wednesday evening for FLZ124-125- 133-138. GA...High Rip Current Risk through Wednesday evening for GAZ154-166. AM...Small Craft Advisory until 4 AM EST Wednesday for AMZ450-452-454. Small Craft Advisory until 1 AM EST Friday for AMZ470-472-474. && $$
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
836 PM CST Tue Dec 13 2022 .UPDATE... Issued at 835 PM CST Tue Dec 13 2022 Widespread rainfall has moved into the northeastern quadrant of Illinois this evening, with the leading edge reaching the lakeshore around 8pm. This swath of steady rainfall will continue lifting to the nne overnight, with a break in precip expected to begin over the next hour to two from the sw CWA into the central CWA. However, still appears another wave of precip will develop from what is beginning to appear across eastern Missouri. Rainfall is forecast to prevail through the morning commute, then taper off to scattered showers tomorrow before redevelopment of widespread rainfall returns tomorrow night. Baker && .SHORT TERM... Issued at 236 PM CST Tue Dec 13 2022 Through Wednesday... The northern extent of the approaching rainfall is beginning to graze the far western CWA as of 2PM. On a north-northeastward track, we`ll have to wait until later this afternoon or even early this evening before this stuff really starts to fill in across the area. While there are still embedded pockets of moderate rainfall, the overall intensity of the rainfall appears to be on a downward trend with areas of 40+ dBZ becoming fewer and further between on radar. Additionally, all of the lightning that this system was producing in Missouri earlier today got left behind as the system progressed northward. The reason being lesser instability aloft as you move toward the CWA. Speaking of, instability is also on a downward trend for this evening and overnight. Whereas the RAP and HRRR were displaying upwards of 200 J/kg of CAPE near 600mb over parts of the southern CWA tonight, that number has now dropped closer to about 50- 100 joules. Now the potential for widespread heavy rain is looking less likely and the thunder potential, slim to none. Nonetheless, with still some instability in place, deep layer saturation, and help from a robust low level jet, a very healthy rainfall can still be expected this evening and overnight. High-res guidance is showing anywhere from around a half an inch to an inch of QPF through daybreak tomorrow. Most of us will wake up to rain continuing tomorrow morning before it begins its departure to the northeast through the latter part of the morning into the afternoon. Some brief, low level dry air advection will put us in a lull for the widespread rainfall tomorrow afternoon with some scattered showers probably still in the area. Tomorrow evening, a second surge of rainfall is expected to move in from the south with the passing of the storm`s occluded front and plenty of upper forcing as the mid-upper level jet max moves over the area. Timing in the onset of this second surge is fairly uncertain, though a few pieces of guidance suggest we could see it move in as early as late tomorrow afternoon. Better chances arrive in the evening, so please refer to the long-term discussion below for more details on that. Meanwhile, winds are beginning to ramp up this afternoon. Increasing winds aloft are not contributing much to gusts down at the surface with the strong inversion in place. Our mixing for the time being is essentially capped at around 925mb. This won`t change much as we head into the evening and overnight. However, winds will continue to build with the surface gradient flow strengthening as the low pressure center inches closer and winds through the shallow mixed layer also increasing. Very late tonight into tomorrow morning will see the strongest winds with gusts to near 40 mph. Breezy conditions will continue tomorrow, though winds will gradually subside through the day. Finally, temperatures will be cooling off briefly this evening before steadily warming overnight as we move into the storm`s warm sector. We will drop as low as the middle 30s this evening and will be back into the lower 40s by sunrise tomorrow. Afternoon highs tomorrow will climb into the upper 40s to near 50 degrees despite the rain and cloud cover. Unfortunately, this is the top of the hill before we begin a steady decline into temperatures more appropriate for winter for the latter half of the week. Doom && .LONG TERM... Issued at 236 PM CST Tue Dec 13 2022 Wednesday night through Tuesday... The key weather messages in the long term are: * Increasing signal for a second round of cold, and at times heavy, rainfall Wednesday night * Brief potential for snow to mix in north of I-90 late Wednesday night/early Thursday morning * Turning colder and blustery through the end of the week with intermittent chances for scattered snow showers. While this looked like an outlier scenario a few days ago, forecast guidance continues to more strongly suggest a second, arguably more vigorous disturbance, blasting northward along the southeastern flanks of our sprawling upper low on Wednesday night. An attendant 125 kt jet streak will deliver intense upper divergence as a core of 120+ m/12 hr height falls spreads across central and northern Illinois. PWAT values will be hanging out near/just under an inch, which is still near the 90th percentile for this time of year, and given the impressive dynamics at play, confident in widespread rainfall developing rapidly through the evening and overnight, and some of this rain will likely be heavy. Would not be surprised to see swaths of additional amounts nearing two inches through Wednesday night (this would be on top of what falls tonight and Wednesday). Contemplated adding a slight chance of thunder to the Wednesday night grids as well with some signs of instability lingering upstairs, but have refrained for the time being. Given the increased QPF amounts, we`ll need to keep an eye on area rivers, with some potential for modest river rises and some instances of mainly minor flooding heading into Thursday. The other development today is an increasing signal for dynamic cooling to play a more central role in possibly transitioning precipitation over to a rain/snow mix or even briefly all snow late Wednesday night/early Thursday morning. Latest GFS and ECMWF are actually pretty close from a thermal profile and forcing standpoint. Intense forcing for ascent acting upon a plume of impressively steep lapse rates (600-400 mb) results in a column that dynamically cools towards and below freezing between roughly midnight and 5 AM, mainly north and east of I-90 or thereabouts. Verbatim, forecast soundings would support a rain/snow mix (ECMWF) or even all snow (GFS) before the dryslot arrives and rapidly transitions any lingering precipitation to a light non-freezing drizzle or showers. For this forecast package, think it`s reasonable to add a bit more snow to the grids in this area. That said, surface temperatures will be very marginal, generally in the mid 30s, which will blunt the potential for travel impacts, and 10:1 and Kuchera snow maps are likely way overdone on any snow accumulations. Have added some light accums in our far northeast, but presently not looking at this being a big deal. Something to keep an eye on though given the magnitude of instability and forcing though. A colder airmass will generally just "spill" into the region (as opposed to a sharp temperature drop) as the cold front swings through on Thursday. Looks like we`ll get a brief break in activity through the morning, but looking for additional precip to develop during the afternoon and evening. While surface temperatures will be above freezing, wetbulb zero heights will be close enough to the surface to support snow showers. By later in the evening and overnight, things look to saturate enough to support some more robust snow showers, and this potential will continue through Friday and Friday evening. The pattern through the end of the week (and even into Saturday) will be supportive of embedded heavier bursts of snow and scattered coatings (perhaps locally over an inch). Have beefed up snow shower wording a bit into Saturday. Otherwise, breezy and colder conditions will prevail into the start of next week. Carlaw && .AVIATION... For the 00Z TAFs... Primary aviation concerns through the next 24 to 30 hours include: * Breezy east to southeast winds with gusts at or above 30kt overnight and 20 to 25 kt throughout the day tomorrow. * Lowering cigs and visibilities through the TAF period including IFR and LIFR at times especially after sunrise tomorrow * Periods of showers through the next 24 to 30 hours * Low (<15%) chance that snow mixes with rain at ORD after 06Z Thursday Currently, a large low pressure system is centered in southwestern Nebraska with arcs of showers extending eastward and into the western Great Lakes. As the low gradually drifts eastward tonight, showers will expand in coverage and move over the terminals. At the same time, east to southeasterly winds will increase in magnitude with gusts of 25 to 35 kt becoming common, highest at RFD. Cigs will gradually lower throughout the night with VFR transitioning to MVFR sometime in the 05-07Z timeframe, and MVFR to IFR toward daybreak. Visibility will also gradually lower with prevailing values in the 3 to 5 mile range by daybreak owing to pockets of drizzle and mist. Much of the same is expected from sunrise tomorrow onward with reduced cigs, visbys, and on-and-off showers. East to southeasterly winds will remain breezy, but gradually lower in magnitude from late morning to early afternoon. Toward evening, a secondary low pressure system is expected to rapidly develop in southern Indiana leading to a "kink" in the low-level pressure field over northern Illinois and northwestern Indiana. As a result, low-level winds should decrease in magnitude markedly during the evening allowing for cigs and visbys to deteriorate (potentially as low as 300-400 feet and 1-2SM, respectively), just as an area of steady rain develops overhead. Visibility may lower further as rain intensity picks up after 00Z. Finally, there appears to be a low (<15%) but growing chance that snow mixes in with rain after 06Z Thursday at ORD. With marginal surface temperatures and a "wet" start, the main threat with snow may end up further reducing visibility rather than sticking on runways. In addition, a lightning strike cannot be ruled out over the next 24 to 30 hours, though the chance of such occurring in the vicinity of any given terminal appears less than 5%. Borchardt && .MARINE... Issued at 236 PM CST Tue Dec 13 2022 ...Gale Warning in effect for the southern Lake Michigan nearshore Tuesday evening through Wednesday afternoon... An approaching storm system is building winds up through the day and will continue to do so this evening and tonight. Gales are expected to arrive by mid-evening with gusts upwards of 45 kt anticipated very late tonight into early Wednesday morning. Gales will persist into the afternoon, though winds will gradually subside throughout the day. Occasional waves to 18 ft are expected along the Illinois nearshore, particularly in zones LM740 and LM741. Indiana nearshore zones will see occasional waves to near 8 ft. Doom && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...Gale Warning...nearshore waters until 3 PM Wednesday. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Nashville TN
738 PM CST Tue Dec 13 2022 ...New UPDATE... .UPDATE... Issued at 731 PM CST Tue Dec 13 2022 Already we are seeing echoes enter West Tennessee as a strong cold front bears down on the Mississippi Valley this evening. The 00Z sounding from OHX shows considerable moistening of the column in the past 24 hrs., but still no instability. Surface pressure gradient has already tightened up considerably in advance of the approaching frontal boundary. The most recent HRRR starts bringing showers across the Tennessee River by 04Z and to the Cumberland Plateau by 10Z. Most of the mid state is in for several hours of rain later tonight and tomorrow, as multiple waves develop before a surface low moves directly across the mid state tomorrow evening. At this time, no forecast changes are planned as the current forecast seems to have a good handle on the progression of this system. && .SHORT TERM... (This afternoon through Thursday Night) Issued at 212 PM CST Tue Dec 13 2022 Primary surface low remains stacked across the central Plains this afternoon. Trailing cold front extends southward through the Arklatex region. Showers are located as far east as eastern AR. Look for rainfall to move in tonight into our western zones by late evening and then overspread the area. 850 mb jet will reach the area late tonight. This feature tends to focus more on far southwestern middle TN where differential speed convergence along the jet is centered most. The stronger forcing down there will set the stage for potential flooding by Wednesday afternoon and evening when the second round of stronger forcing moves through, compliments of the primary frontal boundary. As far as tstm potential goes, we are picking up some elevated instability with 850 mb showalter values close to zero. Total precip amounts look like 1 to 2 inches except in our southwest where around 3 inches looks possible through Wednesday night. For this reason we will go ahead and hoist a flood watch for our far southwest, including Wayne, Lawrence and Giles counties. The watch will be in effect from 18Z Wednesday until 12Z Thursday morning. Note that WPC and Hrrr data has trended downward over the last several runs. Hence, the reason for just a small watch inclusion area. Otherwise, look for clearing skies on Thursday with temperatures returning to more seasonal levels. && .LONG TERM... (Friday through next Tuesday) Issued at 212 PM CST Tue Dec 13 2022 In the extended forecast, looks like a benign and seasonably cold pattern on Friday and through the weekend. Next week sometime, some arctic air will be poised to plunge southward, perhaps. No consequential storm systems are indicated at this time for our area, however. For the extended temperatures, looks like lows in the 20s and highs in the 40s. && .AVIATION... (00Z TAFS) Issued at 559 PM CST Tue Dec 13 2022 CKV/BNA/MQY/CSV...Several admendments possible, especially 14/06Z-14/24Z per fluctuations in ceilings, vsby, and impacts of showers at and in vicinity of terminals. Expect surface winds especially after 14/10Z to gusts up to 25kts with a strong low level atmospheric pressure gradient supporting low level wind shear 40-45kts after 14/10Z. Expecting surface winds to prevail SE-S with sustained winds around 10kts. Can not rule out potential of isolated thunderstorms at terminals or in vicinity, but potential is only marginal and do not believe as of this time a FM prevailing group or vicinity thunderstorm remark warranted. && .PRELIMINARY POINT TEMPS/POPS... Nashville 52 61 41 53 / 80 100 100 0 Clarksville 52 61 38 50 / 100 100 100 0 Crossville 44 53 41 49 / 60 100 100 0 Columbia 53 60 40 53 / 80 100 100 0 Cookeville 48 56 42 50 / 70 100 100 0 Jamestown 44 54 42 48 / 70 100 100 0 Lawrenceburg 53 60 40 53 / 80 100 100 0 Murfreesboro 51 58 41 53 / 70 100 100 0 Waverly 52 60 37 50 / 100 100 100 0 && .OHX WATCHES/WARNINGS/ADVISORIES... Flood Watch from Wednesday afternoon through Wednesday evening for Giles-Lawrence-Wayne. && $$ UPDATE.......Rose SHORT TERM...21 LONG TERM....21 AVIATION.....JB Wright
Area Forecast Discussion
National Weather Service Blacksburg VA
909 PM EST Tue Dec 13 2022 .SYNOPSIS... A large low pressure system over the central United States will push across the east on Wednesday and Thursday, bringing rain for the Mid Atlantic and Carolinas and also winter weather north of I-64. Behind this system colder and windy conditions are expected through the weekend. High pressure and dry weather build in for Monday. && .NEAR TERM /THROUGH WEDNESDAY/... As of 910 PM EST Tuesday... Some of the lower clouds scattered out towards Roanoke this evening as mid and high clouds increased across the area. Elsewhere, stratus remains as moisture is locked under a low level inversion. Current temperature trends indicate maybe a wider valley/ridge split in temperatures than previously expected, so have adjusted overnight lows some. Timing of precipitation beginning in the west around 9-10 AM still looks good. As of 620 PM EST Tuesday... Not many changes to the overnight forecast... Low clouds stuck under inversion may be slow to clear if at all across the New River Valley into the NC mtns. High clouds increasing as well, so look for mostly cloudy to overcast skies overnight. Temperatures drop fast this evening before clouds move in, so kept lows in the mid 20s to lower 30s. Previous discussion... Chance of rain arriving by afternoon... Visible satellite images indicating some erosion and thin of low clouds. Expect some additional breaks for the next couple of hours. The clouds are thin but what doesn`t erode will be around for much of the evening. Otherwise coverage of high clouds will increase and cloud heights will lower overnight. At the surface Virginia and North Carolina will remain entrenched in a deep surface based wedge of cold air. Increasing southwest flow over this layer of colder air will provide strong warm air advection and aide in saturating the air mass from the top down. Will have the probability for light rain starting in the mountains around 10Z/5AM. Similar to the past several days,clouds will limit the spread between high and low temperatures. Will lean toward HRRR and GLAMP guidance for hourly temperatures. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 200 PM EST Tuesday... Confidence is high for rain Thursday, with a period of freezing rain for the higher elevations mainly north of the Roanoke Valley Thursday morning. A deep upper level low (the same one responsible for a northern Plains winter storm) will be in place over the Upper Midwest at the start of this period of the forecast. Shortwave energy rounding the base of this trough will likely induce coastal low development by for the Mid-Atlantic, with moderate to heavy rain for the southern Appalachians, and mixed wintry precip farther north. For our forecast area cold air is lacking for much in the way of wintry precip. There will likely be a period of time early Thursday when temperatures flirt with freezing for the higher elevations...mainly north of the Roanoke Valley, where freezing rain would be of concern, but overall just expecting a cold rain which may be heavy at times Thursday morning. While any small changes in the temperatures could shift the areal coverage of freezing rain for Thursday morning, think the models have a good grasp on warm nose aloft which should limit overall threat for anything extreme for our forecast area. With model temperatures near +5 deg C it will be hard to sustain temperatures below freezing for any length of time. The ground was not froze going into this event, so if there is any icing it should be limited to elevated objects. The best chance of icing will be along the Interstate 64 corridor where a tenth of an inch of ice would be possible on elevated objects, e.g. trees and powerlines. Some freezing rain could stretch southward along the higher elevations surrounding the New and Roanoke River valleys, but icing amounts will likely be less than a tenth of an inch there. The rain is expected to come to an end from west to east Thursday afternoon as the storm evolves and moves up the Mid- Atlantic Coast. Overall QPF (rain totals) for the event are forecast to average between 1 and 2 inches. Attm this does not appear that it will result in any flooding, since the event will be of long duration, but do expect modest rises on area rivers given a mean of 1.50 inches of rain. For Thursday night into Friday, a cold front will cross the region bringing the winds around to the west associated with falling temperatures and breezy conditions. Drier air will begin to work into the region scouring some of the cloud cover. Not impressed with the trajectories for mountain snow showers until later in the weekend. Bottom line, not seeing anything extreme or hazard/headline worthy for Friday. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 200 PM EST Tuesday... Confidence is high for gusty winds and colder temperatures this weekend. Broad upper level trough of low pressure over eastern North America is forecast to persist through the weekend...the forecast area remaining in mainly dry cold west-northwest flow. There is a jet streak that passes south of the area Saturday which may result in a period of mid/upper level clouds, but with no precip. For Sunday, the flow favors more of a northwesterly flavor which may produce more in the way of low level upslope clouds for the mountains, but little or none east of the Blue Ridge. Precip from these clouds would likely be in the form of flurries. Model soundings for BLF/LWB/TNB suggest moisture will be shallow, moisture depth 5kft or less, so not expecting much in the way of measurable precipitation. After the weekend models diverge with respect to details, but overall do not see any extremes. For now keeping things dry with temperatures moderating slightly for mid week. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... As of 615 PM EST Tuesday... High confidence in mainly VFR, though concerned lower cigs may linger longer at BCB through this evening, but trending toward it scattering out with high clouds increasing. Still looking at delayed timing of precip til midday to early afternoon in the mountains reaching perhaps DAN/LYH by end of the taf period. At the moment not seeing any ptype issues at the terminals. Looking for VFR through most of the period but lowering to MVFR to possibly IFR at BLF/LWB/BCB by the end of the taf valid period. Average confidence in ceilings,visibilities, wind and arrival time of rain. Extended Aviation Discussion... A low-level wind shear will increase Wednesday evening as a large storm system approaches. Rain, along with MVFR conditions will spread from west to east across Virginia and North Carolina Wednesday night. Freezing rain is expected north of I-64 late Wednesday night into Thursday morning. Scattered MVFR snow showers may be possible Friday in the mountains. Gusty wind is also expected in the mountains Friday. MVFR clouds will linger in the western upslope areas of the central Appalachians through Sunday. Ceilings will be VFR east of the Blue Ridge. Drier air will arrive for Monday and wind speeds will diminish so VFR conditions are expected. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS/SH/WP SHORT TERM...PM LONG TERM...PM AVIATION...AMS/KK/WP