Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/13/22

National Weather Service Bismarck ND
844 PM CST Mon Dec 12 2022 .UPDATE... Issued at 844 PM CST Mon Dec 12 2022 Dual-polarization radar data and surface webcams indicate snow as a precipitation type along the South Dakota border from near Strasburg to Ellendale, moving north-northwest. The snow generally coincides with an area of cooler cloud tops depicted by 3.9 micron infrared satellite imagery, steep mid level lapse rates, and the nose of a low-level jet. 00Z RAOBs at both Bismarck and Aberdeen showed a dry mid-level layer of air that the increasing forcing for ascent appears to have eroded, at least to some extent, allowing ice crystals aloft to act as seeder feeders through the low-level saturated layer. Recent runs of the HRRR did hint at this potential, but not to the spatial extent it is being observed. A mention of scattered snow showers was added to the forecast from south central into southeast North Dakota for the late evening. Freezing drizzle is still a major concern across all of central and most of western North Dakota. The 00Z Bismarck RAOB shows the near- surface saturated layer extends up to 1.5 km AGL, about 0.5 km greater than had been advertised by deterministic model soundings. No changes to headlines are needed for this update. UPDATE Issued at 624 PM CST Mon Dec 12 2022 Surface observations and webcams show persistent freezing drizzle across much of western and central North Dakota this evening. ASOS ice accretion sensors at Bismarck, Jamestown, Minot, and Dickinson have all reported a few hundredths of an inch over the past few hours. Dense fog also remains an issue, mainly for areas to the south and west of the Missouri River, as well as near the Turtle Mountains. No major changes in forecast messaging are needed for this update. The afternoon Winter Weather Advisory for freezing drizzle in south central and southeast North Dakota has expired, and all other headlines are now in effect. && .SHORT TERM...(This Evening through Tuesday Night) Issued at 312 PM CST Mon Dec 12 2022 Freezing drizzle will remain a threat through the night across much of the central and portions of the west. Snow then begins in earnest overnight into Tuesday morning, lifting from the south to the north out of South Dakota. Western and central North Dakota is currently situated under nearly meridional flow aloft as a closed low and mid level trough digs into the Great Basin region well to our southwest. At the surface, a low continues to deepen over eastern Colorado to the lee of the Rockies under the left exit region of a strong upper level jet. Low level moisture pooling this afternoon and tonight will continue along and in the vicinity of an inverted surface trough, extending north northeast into the Dakotas from the surface low. Given dry mid levels, this will mean periods of light freezing drizzle/mist across much of western and central North Dakota the rest of today through at least Tuesday morning. The most significant icing generally looks to take place across the south central and into the James River Valley where we could see a tenth of an inch or two of accumulation. However, anywhere along and east of the Highway 83 corridor could see ice accumulations leading to significant impacts. Further west, a light glaze to a few hundredths of a inch seems reasonable. Ice potential lessens approaching the Montana border. A strong wave will rotate around the base of the mid level low, ejecting north and approaching southern North Dakota late tonight into Tuesday morning, which should help to gradually moisten the mid levels. The latest suite of CAM runs suggest a transition from freezing drizzle/light freezing rain to snow along the South Dakota border area in the 06z to 12z time frame Tuesday morning depending on how vertical profiles evolve. An initial band of moderate to heavy snow will develop around the border and rotate into portions of central North Dakota by late morning/early afternoon. NAM soundings continue to suggest a possible dry slot and loss of cloud ice behind this band which could mean a brief lull in the snow for some during the early to mid afternoon hours. This could also mean some more freezing drizzle under any dry slot. By later in the afternoon, this dry slot should start to fill in as the main deformation band rotates up from South Dakota, leading to more widespread moderate to heavy snow across much of western and central North Dakota through Tuesday night. While snow will continue well into Wednesday and light snow probably even into Thursday, we can talk about storm totals here in the short term. Forecast totals remain steady with widespread totals of 6 to 14 inches expected with the highest totals generally west and south. Some uncertainty remains however, given potential dry slotting/periodic loss of saturation in the dendritic growth zone. However, it is worth noting that the NBM v4.1 continues to advertise 12 inches of snow or greater in the 50 to 90 percentile range for much of western and central North Dakota. So potential scenarios for an even higher end event are certainly not out of the question. .LONG TERM...(Wednesday through Monday) Issued at 312 PM CST Mon Dec 12 2022 By Wednesday morning, the low kicks up into southeastern South Dakota. As the surface low starts to fill, heavy banding will start to become a bit more disorganized through the day. This will mean more of a transition to periodic light to moderate snow instead of heavy banding (although some transient heavy pockets will remain possible, especially across the west under the weakening deformation band). Portions of the central may also experience some more dry slotting during the day on Wednesday but periodic light snow should continue to rotate around the low in cyclonic flow aloft through Thursday, likely into Friday and maybe even into early Saturday. Only light accumulations are likely in the Thursday through Saturday time frame but winds will increase, leading to some areas of blowing snow. Therefore, an eventual Winter Weather Advisory for blowing snow is possible at some point towards the end of the week after all current headlines expire. The other story will be the next arctic push through the weekend and into next week. Forecast highs on Friday will be in the low to mid teens, the single digits Saturday, closer to zero Sunday and maybe even single digits below zero on Monday. Thus wind chill headlines are also probably on the far horizon around the end of the weekend and into next week. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) Issued at 844 PM CST Mon Dec 12 2022 A winter storm will bring IFR/LIFR conditions to all terminals through the forecast period. Visibility restrictions this evening through much of the night will be primarily driven by freezing drizzle/light freezing rain. The greatest icing concerns are at KJMS. Dense fog is also possible at KDIK this evening. Precipitation will transition to snow late tonight into Tuesday morning, but freezing drizzle could still mix in at times through Tuesday afternoon. Expect LIFR visibility under falling snow for much of the day Tuesday. Northerly winds across western North Dakota and east to northeast winds across central North Dakota will increase to 15-20 kts on Tuesday, gusting near 30 kts. && .BIS WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 6 AM CST Thursday for NDZ001>005- 009>013. Winter Storm Warning until 6 AM CST /5 AM MST/ Thursday for NDZ017>023-025-031>037-040>048-050-051. && $$ UPDATE...AE/Hollan SHORT TERM...ZH LONG TERM...ZH AVIATION...Hollan
Area Forecast Discussion
National Weather Service Dodge City KS
607 PM CST Mon Dec 12 2022 ...Updated for aviation discussion... .SHORT TERM...(This evening through Tuesday night) Issued at 250 PM CST Mon Dec 12 2022 Multiple hazards impacting the area now and through the overnight. First, fog and areas of dense fog will persist in an enhanced dew point/upslope region across the south central Kansas counties , where early afternoon highway cams were showing dense fog. Based on saturated point HRRR forecast soundings and the general HREF trend for visibility at 1/4mi, some areas of dense fog are likely to continue through the evening across Ford, Kiowa and Pratt counties, southward to the OK line and even northward into Hodgeman and Pawnee. The uncertainty in widespread nature will preclude extension of the earlier dense fog advisory. Attention then turns to convection chances and threats this evening. An intense upper jet across the AZ and NM/Mexico border arced into southwest Kansas will lift a sharp PV anomaly max into the SE CO/TX Panhandle and southwest Kansas area through mid evening, juxtaposed across an ever increasingly moist boundary layer noted in SPC 850 moisture transport fields. With the north- south oriented surface based CAPE axis and generally parallel wind field, the convection that may or may not develop in the western counties should become quickly linear. Very skinny CAPE profiles above the surface layer doesn’t support hail, and the qlcs nature could support mesovorices (swaths of wind damage) in the 9pm to midnight time frame. SPC’s 5% Tornado risk outlines the added risk very quick moving mesovotices that may develop. Not all the CAMS are all that keen with the more robust storms in that window, namely the FV3 does support it while many others dry slot the local area. All models have the more widespread showers and storms moving into the eastern counties with a generally lessening surface CAPE with time. PoPs increase significantly west to east and the front should clear out the entire area after about 7z/1AM or so. Beyond the convective risks tonight, the westerly momentum Tuesday morning will lead to strong gusty westerly winds for the entire forecast area, probably falling below the High wind threshold, but at least making for a difficult north – south travel Tuesday morning. .LONG TERM...(Wednesday through Monday) Issued at 250 PM CST Mon Dec 12 2022 We changed up NBM’s winds to the 90th percentile which better supports the weather trends given the pipeline of cold air we`ll be seeing in the coming days. Colder air will limit highs to the 30s over most of the area through the weekend, but more impactful will be the apparent temperatures or wind chills during the overnight and early morning periods. Official forecast calculations for wind chill area commonly in the single digits every morning beginning Wednesday and lasting through the rest of the current long term. Any slight moderation in real temperatures through the weekend will be reinforced by more cold air into early next week. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 603 PM CST Mon Dec 12 2022 Moist southerly winds will result in widespread low MVFR/LIFR/IFR CIGS through 6z. A strong disturbance will approach this evening, with thunderstorms possible between 02 and 7z. These could be severe with high winds. After the cold front passes between 09 and 12z, VFR CIGS will return. Winds will shift to the west and southwest behind the front and become gusty. && .PRELIMINARY POINT TEMPS/POPS... DDC 34 47 21 41 / 60 0 0 0 GCK 30 42 19 39 / 50 0 0 0 EHA 29 46 19 43 / 10 0 0 0 LBL 31 48 19 43 / 20 0 0 0 HYS 35 47 19 37 / 80 10 0 0 P28 42 55 25 43 / 100 10 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Russell LONG TERM...Russell AVIATION...Finch
Area Forecast Discussion
National Weather Service Flagstaff AZ
305 PM MST Mon Dec 12 2022 .SYNOPSIS...Occasional snow showers are forecast for the rest of this afternoon and again Tuesday afternoon. These snow showers may result in quick snow accumulations and hazardous driving conditions on a highly localized scale. Otherwise, the main theme will be unseasonably cold conditions, with widespread single digit temperatures for morning lows on Wednesday. && .DISCUSSION...Our anticipated winter weather episode has unfolded as expected, however, we may not be done with the wintry precipitation just yet. Regional satellite imagery revealed a pair of shortwave troughs rotating around the main longwave feature this afternoon. The lead shortwave trough, across southern California, will eject eastward this afternoon and spread modest ascent across the southern half of the High Country. The region with the greatest chance for additional snowfall this afternoon and tonight will be for locations near and south of the I-40 corridor (PoPs are 20-40%). Areas north of I-40 generally have a less than 10% chance for precipitation. With that in mind, I`ve shaved off the western half of the Winter Weather Advisory (the Kaibab Plateau, Grand Canyon Country, and the Flagstaff area). Farther south and east, ascent will be maximized and the Winter Weather Advisory for central/eastern Rim and White Mountains areas will run through 06 UTC. The most noteworthy changes to the forecast were on Tuesday. Recent runs of the HRRR and HRRR-Time Lagged Ensemble suggest that more pronounced synoptic scale ascent will accompany the second shortwave trough that will dive southward around the back end of the aforementioned longwave feature. This feature is forecast to slide into the area, induce westerly to northwesterly upslope flow during peak heating on Tuesday. Forecast soundings (even from the coarser NWP) indicate a MAUL or moist adiabatic unstable layer with a saturated lower half of the troposphere characterized by nearly 8 C/km lapse rates. With even modest ascent, this will likely be enough to encourage pockets of deeper convection. CAPE values actually approach 100-200 J/kg across portions of the area suggesting a non-zero risk for thunder. As a result, I`ve inserted isolated thunder into the worded forecast and boosted PoPs considerably. The greatest PoPs for Tuesday reside along the SF Volcanic Field, down the Mogollon Rim and into the White Mountains with values ranging between 50 and 80 percent. The North Rim of the Grand Canyon, over to the Black Mesa, and Defiance Plateau have around a 30-50% chance for precipitation. Snow levels will be quite low (around 3,500 feet), so areas such as the LCR may see a few flakes fly. In terms of snowfall amounts, there`s a broad swath of 1 to 7 inches. Areas across the Kaibab Plateau and Central Mogollon Rim could experience 1-3 inches of snow, with the Eastern Rim and White Mountains looking at 3-7 inches of snow. It should be noted, that because of the convective nature of activity, not all locations advertised with mentionable PoPs will experience accumulating snowfall. In fact, snow may be highly localized in spots and as a result, this will result in very rapid changes in driving conditions! By midnight Wednesday, most areas will be clear and with light winds and a fresh snowpack, temperatures will crater. Many locations across the higher terrain will experience Wednesday morning low temperatures in the single digits, with "freezing" conditions all the way down across the Yavapai County deserts. The rest of the outlook period appears cold and the NBM appears to be on track in terms of temperatures---though we may need to nudge things down by a degree or two depending on trends. && .AVIATION...For the 00Z TAF package...Periods of LIFR/IFR conditions are possible through the period. Expect scattered snow showers this evening and again tomorrow afternoon. These convective snow showers may rapidly reduce visibility and lower cloud ceilings, especially along a KGCN-KFLG-KINW line. Mostly VFR conditions are expected elsewhere. Winds stay generally light out of the west-southwest around 10 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Unseasonably cold. Scattered snow showers are expected Tuesday afternoon, before skies clear on Wednesday. Expect west-southwest breezes Tuesday, shifting to west-northwest breezes on Wednesday. Thursday through Saturday...Dry weather prevails and winds stay light. Temperatures broadly 10-15 degrees below average will allow snow cover to persist over the high country. && .FGZ WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 11 PM MST this evening for AZZ016>018-116>118. && $$ PUBLIC...Bain AVIATION...BAJ FIRE WEATHER...BAJ For Northern Arizona weather information visit
National Weather Service Hastings NE
725 PM CST Mon Dec 12 2022 .UPDATE... Issued at 715 PM CST Mon Dec 12 2022 * Dense Fog Advisory has been cancelled. Appears the window for dense fog has passed us for the rest of the evening and overnight. Observational trends have been steady in the 1-3+ range, and hi-res models such as the HRRR (which is already overdoing the fog) suggests gradually improving conditions for the rest of the evening. No other changes to the overnight forecast at this time. Expect convection to incr substantially in the 02-04Z time frame as upper forcing attendent to mid level jet streak noses in from the SW. Still appears greatest severe threat will remain just SW of the CWA, closer to primary MUCAPE plume of 500-1000 J/kg. Nonetheless, with continued moisture advection and steepening mid-upper lapse rates, could still see up to 500-750 J/kg of MUCAPE edge into portions of the area, esp. SW of the Tri-Cities. Elevated instability combined with strong cloud layer shear and cool low level temps could be enough for marginally severe hail with the strongest cores. Stable near-sfc layer should preclude too much of a strong wind threat. While not explicitly shown in the Day 2 severe weather outlook, can`t completely rule out some hail concerns Tue from low-topped convection as the sfc-500mb low becomes deep and vertically stacked over central Neb. Narrow tongue of higher low level theta-e air will wrap W back into the sfc low as it moves from near MCK to LXN and BBW during the daylight hrs. In conjunction with very cold H5 temps of -26 to -28C, expect another small area of MUCAPE of around 500 J/kg to build and move SW to NE through W 2/3rds of CWA. Small hail would be main concern, but if instability trends any higher then could conceivably get some nickels and quarters. High ambient vorticity and cold mid level temps also argue for perhaps some cold air funnel clouds, too. Don`t have high confidence one way or the other, and very maginal sfc temps (likely less than 50F) argue against strong storms... but with the deep low nearly overhead I wouldn`t be shocked if some convection "overachieves" tomorrow, as sometimes happens with intense cold season low pressure systems. Will let night shift evaluate whether these concerns are worthy of further messaging. && .DISCUSSION...(This evening through Monday) Issued at 317 PM CST Mon Dec 12 2022 Key Messages: * Fog persists this afternoon and into the evening. * Rain and thunderstorms expected tonight into Tuesday. There is a marginal risk for severe weather. * Some snow moves from the west/northwest late Tuesday afternoon. Periods of flurries and light snow continuing through Wednesday and even into Thursday morning. * Strong northwest winds (gusts 40-50 MPH) expected Tuesday night through Thursday. * Below-normal temperatures likely through the weekend and most (if not all) of next week. Details: Despite the gusty southeast wind, we`ve actually seen an uptick in dense fog this afternoon as higher dewpoints advect into the area. As such, a Dense Fog Advisory was issued through 9pm. It is possible that this will need to be expanded. This evening, drizzle should transition to more rain showers as we see increasing lift arrive ahead of the upper low. CAMs indicate that the main risk for thunderstorms will be after 8pm (but cannot totally rule some out before that). The best instability (especially in the low levels) is initially well to the southwest of the area. As such, expect that the strongest updrafts will initiate in this area. These may approach our southwestern zones after midnight but will probably be on a weakening trend. Nevertheless, a few strong to marginally storms cannot be ruled out through Tuesday morning given the strong shear and dynamic lift. On Tuesday, the surface low moves through the area. A few thunderstorms are expected to persist through the morning and early afternoon, gradually pushing to the northeast. The severe threat is decreased due to decreasing instability. Rain totals are expected to range from just around a tenth in our southwest to over an inch in parts of central and north-central Nebraska. Temperatures will crash behind the cold front on Tuesday afternoon. Some light snow may push in from the northwest, but most of the area will only see a dusting through Wednesday morning. Far northwestern zones may pick up 1-2". The low moves eastward very slowly through Wednesday, meaning that we will continue to see flurries and light snow over portions of Nebraska through Wednesday and even into Thursday morning. More notable than the snow will be the strong northwest winds (gusts 40-50 MPH) that will persist through Thursday. After this system departs, we will see a much colder pattern continue through the weekend and into next week. Single digit highs and subzero lows are completely possible. There will be spotty chances for light snow, but there is not enough model agreement to really pinpoint any timeframe as particularly concerning at this point. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday) Issued at 545 PM CST Mon Dec 12 2022 Significant weather: LIFR CIGs, MVFR-IFR VSBYs, strong wind, and scattered thunderstorms. Tonight: LIFR CIGs are likely here to stay through the overnight period. VSBY has been, and will continue to be, quite tricky. With that said, appears per ob/model trends that TAF sites may be past the lowest VSBYs and that we`ll be primarily in the 1-4sm range. Will probably oscillate back and forth between IFR and MVFR, but think we`re done with any dense fog. Expect shower, and eventually t-storm, activity to build over the next few hrs, with overall best chances coming in the 03Z-12Z time frame. Can`t rule out some small hail with the strongest cores, but best chc for svr looks to be SW of the terminals. Finally, strong SE winds will continue all night, generally sustained near 20kt, and gusts 30-35kt. Confidence: CIGs/Wind - High, VSBYs - medium. Tuesday: Complex TAF forecast will continue through this period as well. Will start off with continued LIFR CIGs and perhaps a break from steady shwrs/storms. Some model evidence that VSBYs could dip around daybreak as winds back slightly in response to deepening sfc low off to the SW. This slight incr in upslope component could give VSBYs a chc to fall back to around 1sm, but this is uncertain. If VSBYs do drop, don`t think it will be to LIFR levels. The dry slot from the major storm system will wrap into the area around late AM, and provide a distinct, but brief, reprieve from solid IFR CIGs and shwr/storm chcs. However, wrap around flow will quickly bring at least BKN MVFR CIGs and possibly more iso-sct tstm chcs for the aftn hrs. Winds will start off SE, then veer to S and eventually SW with arrival of dry slot around midday, and remain strong - sustained 20-25kt, gusts up to around 35kt. Confidence: Medium. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$ UPDATE...Thies DISCUSSION...Mangels AVIATION...Thies
National Weather Service Wilmington OH
949 PM EST Mon Dec 12 2022 .SYNOPSIS... Dry conditions are expected through Tuesday before rain impacts the Ohio Valley midweek. Temperatures will generally be very close to normal to slightly above normal for the first half of the workweek before trending below normal for the end of the workweek. Unsettled conditions will be possible Friday into the weekend, with some snow showers possible. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Despite surface ridging extending across the Great Lakes and Ohio Valley, stubborn stratocumulus clouds beneath a subsidence inversion continues to plague the region. However, there appears to be some erosion taking place on the southern edge of the cloud deck per latest GOES-16 nighttime microphysics loop. Per latest RAP run, am expecting drier air between 900 mb and 875 mb to gradually nudge its way northward overnight as the flow in this layer turns southeast. Where the low level cloud deck erodes, some high level clouds will take its place above. The process will be slowly going and will continue from south to north into the first part of Tuesday. Lows tonight will be somewhat uniform given easterly flow between 5 and 15 mph. Lows will range from the upper 20s to the lower 30s. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... The influence of surface high pressure begins to wane on Tuesday as a low pressure system ejects into the high Plains from the Rockies. Easterly/southeasterly flow increases through the day and temperatures moderate with upper level ridging building over the region. The most welcome change to the weather pattern on Tuesday is a sharp reduction in low level moisture allowing for temporary clearing of low level cloud cover. Filtered sunshine is expected through the building cirrus with some peeks of blue sky being possible. Forecast highs reach into the 40s. Partial clearing in the cloud cover does not last long since Tuesday night features increasing moisture, cloud cover, and increasing rain chances ahead of the approaching low to the west. Any precipitation that falls late Tuesday night is likely to be rain since increasing WAA aloft shifts the profile well above freezing by the time any chance for precipitation starts. Surface temperatures are also likely to be above freezing by precipitation onset. Forecast lows are near freezing overnight. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Strong low pressure over the central Plains will slowly shift into the upper Midwest from Wednesday through Thursday. Initial shortwave Wednesday morning and its accompanying rain will exit to the northeast by afternoon, leaving a few hour break and lower PoPs. A second stronger shortwave lifts into the region Wednesday night along with a surface low and cold front. The region will be well into the warm sector, so expecting all rain with any precipitation that falls Wednesday night through Thursday. Behind the front colder temperatures advect into the Ohio Valley late Thursday into Friday. At the same time, the core of the mid- level low drifts into the Great Lakes. With the cold air aloft and surface temperatures in the mid to upper 30s Friday afternoon, can`t rule out a few rain/snow showers. Mostly cloudy skies will still be present through Saturday as the mid-level low continues to wobble over the Great Lakes. The low shifts east Sunday so the region may see a few peaks of sunshine at that time. Temperatures will be below seasonal norms from Friday through the end of the extended period on Monday. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... Surface ridging extends from Hudson Bay southward into the Ohio Valley this evening. This ridge axis will gradually move east through the TAF period while a mid level ridge axis moves briefly east into the region. Stubborn low level stratocumulus trapped underneath a subsidence inversion is expected to show some signs of erosion/movement over the next 12 to 18 hours. Before then, MVFR ceilings are expected. The erosion/movement should gradually occur from south to north overnight into the first part of Tuesday. By Tuesday afternoon, any stratocumulus left over near the northern terminals should eventually mix out and dissipate. In its wake will be some high level clouds spilling through the mid level ridge. Winds will generally be from the east between 5 and 10 knots. OUTLOOK...MVFR/IFR conditions likely late Tuesday night into Thursday. MVFR ceilings possible Thursday night into Saturday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Campbell/KC NEAR TERM...Hickman SHORT TERM...Campbell LONG TERM... AVIATION...Hickman
Area Forecast Discussion
National Weather Service Indianapolis IN
937 PM EST Mon Dec 12 2022 .Forecast Update... Issued at 936 PM EST Mon Dec 12 2022 * Evening Update Dry air subsidence in the axis of an approaching ridge is aiding in the erosion of a thick low level cloud layer over the NE half of central Indiana. This should continue over the next several hours, eventually leading to a two part cloud deck; FEW at 3000FT, and a more broad cloud deck above 20000 feet associated with a diffluent upper level jet. Due to a delay in diurnal cooling over NE central Indiana, morning lows have been increased slightly. Otherwise, forecast looks on track, minus a few observational based changes. && .Short Term...(This evening through Tuesday) Issued at 237 PM EST Mon Dec 12 2022 Cloud cover and temperatures remain only concern in this tranquil short term period before large scale pattern change begins to take shape in later periods. High pressure over Great Lakes providing a light easterly flow across central Indiana today. Surprisingly we have seen low perma cloud deck slowly erode this morning over southern and southwest CWA despite easterly flow and strong inversion. Model and ACAR soundings tell the story with a very shallow layer of moisture near inversion that has been eroded today by drier air and subsidence associated with high pressure. HRRR shows this clearing to continue working west and north across western portions of central Indiana, with east to northeast areas likely remaining mostly cloudy. The question is whether enough residual moisture remains to allow clouds to fill back in this evening across the areas that have cleared and what the southern fringe of cloud cover in the north will do. Previous forecast trended toward some clearing tonight and with these observational trends see no reason to deviate from that thinking south and west with support of HRRR. However, will remain more pessimistic in the north and northeast where satellite and observations suggest clouds will linger. Any clearing will be short lived as ridge axis quickly passes and warm air advection begins ahead of next system. Mid and high clouds to spread back in later on Tuesday but deeper moisture and large scale lift ahead of potent short wave remains west so expect the day to be dry. With fewer clouds around and 850mb temps warming to between +5C to +7C in the southwest, expect high temps to respond into 50s there. A bit more uncertainty as you go north and east with uncertainty on cloud cover so trended toward lower to middle 40s with consensus guidance. && .Long Term...(Tuesday night through Monday) Issued at 237 PM EST Mon Dec 12 2022 If you were in search of a pattern change...wait a few days and winter weather will return to the Ohio Valley later this week. But before we dive into the extended pattern change, we have a potent well-developed system poised to impact many areas on the lee-side of the Rockies Tue/Wed. Highlights for the extended: * Periods of rain early Wed through midday...again late Wed into early Thur. * Quick flirt of mild temps in the 50s Wed...enjoy it while it lasts. * Winter knocks at the door Sat...with a wide-open door to close-out the weekend. Tue Night/Wed: As is common with well-developed systems, adjustments to the timing of arrival continues to be refined. Before we look at the upcoming system, we first need to look downstream and the block that is developing across the North Atlantic. This will set the stage for an amplified upstream wave, ie next weather system. Guidance has continued to lean towards more amplification to the heights across the Ohio Valley Tue eve, with persistent diffluent conditions within the lower 3km of the atmosphere. The low-level jet will begin to ramp up, but it doesn`t appear to be the case until after 6Z Wed for Central Indiana. Meridional flow has trended stronger, which is essentially the south to north flow of parcels, and this is supported by the amplification of heights. This should allow a rapid moistening along isentropic surfaces, with parcels likely becoming saturated quickly from southwest to northeast Wed early morning. The axis of deep moisture begins to pivot east around 12Z Wed, which should help to usher in a dry nose in the 925-800mb layer likely helping to diminish the steadier rain coverage marginally. Temps Tue ngt, likely will not budge will hold onto mild air heading into Wed. The challenge for Wed highs temps will depend on cloud cover and precip coverage. But at this time it does appear we can lean slightly warmer, and could see Wed highs touching the low 50s, perhaps in the far south even a few spots could hit 60 briefly. Wed aftn-Thur: There is another jet maxima that points northeast Wed aftn, which could help to lift parcels modestly and re-engage the precip coverage Wed aftn/eve. Given the continued strong meridional flow in the sfc-850mb layer, some better organization to the precip coverage could occur before the trough axis arrives and kicks the rain east. Isallobaric pressure gradient quickly arrives Wed aftn/eve, and depending on mixing heights, we could see gusty conditions develop. Have nudged winds/gusts up and may flirt with higher gusts between 35-40 mph for a period Wed. Guidance continues to fluctuate with timing of the potent 500mb shortwave late Wed to early Thur, which will dictate the back edge to the precip. Dry boundary finally arrives early Thur morning, with temps likely falling throughout the day. Fri-Sun: As was eluded to earlier, Winter will be knocking at the door late this week but especially over the weekend. The 500mb trough axis finally arrives Fri across the Ohio valley, as the thermal trough dives south from the Upper Midwest. Cold air advection will rapidly pour into the Ohio Valley late Fri, being sensed Sat/Sun as temps struggle to push beyond the mid/upr 20s. At the present time, there doesn`t appear to be any lingering northwest flow shortwaves that could trigger light snow. So for now it appears perhaps flurries would be the extent of winter precipitation for the weekend. The deep trough will then linger through the weekend with a continued winter pattern. && .Aviation...(00Z TAF Issuance) Issued at 628 PM EST Mon Dec 12 2022 Impacts: * MVFR ceilings likely at LAF, intermittent at KIND through 03Z * Gusts up to 20kts possible tomorrow afternoon. Discussion: Shallow moisture near a strong inversion leading to thin layer of stratocu clouds that have thinned further and cleared in areas across central Indiana. Satellite shows this trend with drier air and subsidence associated with high pressure slowly eroding cloud deck. There has been a slight trend westward within the eastward winds. But this should erode before impacts are seen at KIND. Still, have left a tempo for BKN025 for the possibility of intermittent MVFR ceilings. VFR conditions expected for the remainder of the TAF period. Gusts up to 20kts are possible tomorrow afternoon. Have only included at KIND and KBMG, with confidence higher at these locations. SE dry air should lead to brief periods of clearing at these locations, increasing PBL mixing. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...Updike Short Term...Lashley Long Term...Beach Aviation...Updike
Area Forecast Discussion
National Weather Service North Platte NE
535 PM CST Mon Dec 12 2022 .SYNOPSIS... Issued at 355 PM CST Mon Dec 12 2022 H5 analysis this morning has a closed low over far northeastern Nevada with a trough extending to a secondary, strong shortwave over southern California. East of this feature, a highly amplified ridge extended from the Ozarks north into western Ontario. West of the western CONUS trough, another highly amplified ridge extended from the eastern Pacific into the Yukon. Current WV imagery has a nice plume of upper level moisture, streaming into the rockies and high plains from northwestern Mexico. At the surface, a lee side trough of low pressure extended from southeastern Wyoming along the front ranges of eastern Colorado. A warm front was present along the Kansas/Nebraska border and a cold front extended from central Wyoming, into southwestern, then north central South Dakota. Southeasterly and easterly winds extended east of the trough across western and north central Nebraska this afternoon. These winds have led to increasing low level moisture across the area overnight with continued low level moisture advection this afternoon. Skies remained cloudy across the area as a shroud of low level clouds continued across the area. Temperatures as of 2 PM CST ranged from 33 at Gordon to 45 degrees at North Platte and Imperial. Key Messages: -A major winter storm is expected to impact the area starting tonight and continuing into Thursday. -Early this evening, there is a threat for severe thunderstorms south of Interstate 80. -Dangerous blizzard conditions are expected for much of the Panhandle, western Sandhills, and portions of northern Nebraska. -Potentially life threatening travel conditions are expected to develop Monday night into Thursday, especially in the Blizzard Warning area. -Ice accumulations of a light glaze to around a tenth of an inch are expected for much of western and north central Nebraska. -Strong northwest wind gusts of 45 to 50 mph, with gusts approaching 60mph will lead to significant blowing and drifting snow. -Much colder temperatures persist into the weekend, with the potential for well below zero wind chills each morning into next week. && .SHORT TERM...(This evening through Thursday) Issued at 355 PM CST Mon Dec 12 2022 A significant storm system will impact western and north central Nebraska over the next 24 to 72 hours with several hazards expected. Synoptically, an upper level low will emerge and deepen over southeastern Colorado overnight. This feature will then track from western Kansas into central Nebraska Tuesday, then will decelerate as it tracks from central Nebraska into southeastern South Dakota Tuesday night through Wednesday night. The low will then track east southeast, finally exiting northern Iowa late Thursday. Strong surface cyclogenesis is currently underway over eastern Colorado. This area of surface low pressure will track slowly east northeast on Tuesday, then north northeast Tuesday night into Wednesday, ending up as an occluded low over sern South Dakota Wednesday into Wednesday evening. The very slow movement of the upper level low and surface low is a result of a blocking ridge of high pressure anchored over the eastern CONUS. As mentioned before, this storm system will be multifaceted with a significant number of hazards over the next 72 hours. With respect to the thunderstorm threat this evening. Surface analysis this afternoon has a nice tongue of 40+ degree dew points extending as far north as Thedford Nebraska. Further south, 50+ degree dew points had pushed into southwestern Kansas this afternoon. With the approach of the H5 low this afternoon, increased instability has led to a band of convective cloudiness over the northern TX panhandle and OK panhandle over the past hour. Looking at the latest NAM12 soln, a tongue of SB capes (750-1000J/KG lifts north into western Kansas this evening. As an area of very steep mid level lapse rates approaches the area of increased CAPE early evening, thunderstorm development appears likely over western Kansas. The latest HRRR lifts this convection into southwestern Nebraska during the 00z-02z time frame. Strong mid level flow and anticipated linear storm structure across southwestern Nebraska may would favor strong winds as the main severe threat. Wouldn`t be surprised if we saw some dime to quarter sized hail with any of the stronger storms given the very steep lapse rates. Storms will continue to track north into the Sandhills this evening, weakening north of I-80. As these showers and embedded thunderstorms lift over the approaching cold front this evening, we will see our greatest threat for freezing precipitation over northwestern portions of the forecast area. ATTM, based on forecast soundings, this appears to be a narrow corridor of light to briefly moderate freezing precipitation this evening into the early overnight hours. Further north of the front, thermal profiles are indicative of snow which may be heavy at times, thanks to the degree of instability and upright/not slantwise lift. Overnight, the cold front will track slowly east, becoming oriented from Ogallala to near Valentine by 12z Tuesday. The surface low will track east northeast across southern Nebraska, occluding over northeastern portions of the forecast area Tuesday afternoon. Strong isentropic lift will continue Tuesday behind the front with deep lift in the dendritic zone noted west of a line from Ogallala to Bassett. Given the degree of mid level lift, am expecting the heaviest snow to fly Tuesday into Tuesday evening. For the most part, the current snowfall forecast was on track with the previous forecast. With some minor changes noted with the surface low track, heavier precipitation was carried east into northeastern portions of the forecast area. This necessitated expansion of the blizzard warning into Keya Paha and Brown counties, and a winter storm warning into Rock, Blaine and Logan counties. In the expanded blizzard area, snow accumulations were increased with up to 10 inches in western Keya Paha and northern Brown counties. In the expanded winter storm warning counties listed above, accumulations of 2 to 6 inches are forecast. I realize this falls short of warning criteria but with expected wind gusts of 50+ MPH, blowing snow will be a major issue. Left Boyd and Holt counties in a watch as the surface low tracks over these counties and will probably limit snow accumulations. Will have the night shift look at this and determine if the forecast low track shifts further east. Snow will linger across northern Nebraska Wednesday night into Thursday as weak mid level isentropic lift lingers. Strong winds will accompany this system and will be an impact through Thursday. With the anticipated snowfall, blowing snow will remain impactful, well after snowfall ends. Current headlines end at 6 AM CT on Thursday morning. Current model trends indicate strong winds persisting well into Thursday with H85 winds of 40+ KTS. If this materializes, we will possibly need to extend, or replace winter headlines for the threat for blowing snow. .LONG TERM...(Thursday night through Monday) Issued at 355 PM CST Mon Dec 12 2022 Upper level low pressure, will remain entrenched over the northern Great Lakes Friday through Saturday. This feature will finally transition east into the eastern Great Lakes Sunday. On its heels, a secondary upper level low and arctic trough, will track south from western Canada into the northwestern CONUS early next week. Cold and mainly dry conditions will persist through Monday with even colder air arriving midweek next week. Highs through Sunday will be in the teens and 20s with single digits to teens for next Monday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 535 PM CST Mon Dec 12 2022 Fairly widespread IFR/LIFR in fog and low or very low ceilings is expected tonight. Rain, showers, snow and isolated thunderstorms are expected to develop later this evening which will continue Tuesday. Some improvement in flight conditions is possible along and south of Interstate 80 Tuesday afternoon where MVFR/IFR ceilings and vsbys may develop. && .LBF WATCHES/WARNINGS/ADVISORIES... Blizzard Warning from midnight CST /11 PM MST/ tonight to 6 AM CST /5 AM MST/ Thursday for NEZ004-005-022>024-035-056-094. Blizzard Warning from 6 AM Tuesday to 6 AM CST Thursday for NEZ006-008. Winter Storm Watch from Tuesday morning through late Wednesday night for NEZ007-010. Winter Storm Warning from 6 AM CST /5 AM MST/ Tuesday to 6 AM CST /5 AM MST/ Thursday for NEZ009-025-026-036-037-057-058. Winter Weather Advisory from 6 AM CST /5 AM MST/ Tuesday to 6 AM CST /5 AM MST/ Thursday for NEZ059-069. && $$ SYNOPSIS...Buttler SHORT TERM...Buttler LONG TERM...Buttler AVIATION...CDC
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
537 PM CST Mon Dec 12 2022 .SHORT TERM... (Through Late Tuesday Night) Issued at 229 PM CST Mon Dec 12 2022 the Mid Mississippi Valley remains under an upper level ridge sandwiched between to long wave troughs over the western Atlantic and the western U.S. The subsidence inversion beneath the ridge has trapped low level moisture over the area which has kept us socked in with low clouds and patchy fog. There has been some drying in southeast Missouri and southern Illinois due to east-southeast low level flow which is pushing somewhat drier air in from the Tennessee Valley, however I think this break in the clouds will be short lived as the next system gets wound up over the Plains. There has been little change to the forecast for tonight through Tuesday. Low pressure will advance into the central Plains by Tuesday afternoon, with a strong low level jet developing ahead of it. Moisture convergence associated with the jet is expected to produce widespread showers and a few thunderstorms which will overspread the area from west to east through the day and into Tuesday evening. All guidance shows widespread precip in response to the moisture convergence and as a mentor of mine said in these situations, "if the entire area doesn`t get some rain, it`s going to miss a darn good chance." Have therefore continued with unconditional PoPs ahead of the front Tuesday afternoon and evening. Latest storm total QPF is for around 0.75 and 1.25 inches, with the lion`s share of that falling Tuesday afternoon and evening. RAP MUCAPE shows a tongue of weak instability creeping up into our forecast area late Tuesday afternoon into the evening ahead of the cold front. Highest values are hovering around 500 J/Kg, but there`s little if any SBCAPE. The latest GFS doesn`t even have 100 J/Kg MUCAPE during that period. This morning`s HREF SBCAPE max has around 100 J/Kg ahead of the front, and mean MUCAPE is likewise around 100 J/Kg. All this means I cannot rule out a few rumbles of thunder, but there seems to be little if any chance the storms could be strong or severe. That being said, the gradient wind ahead of the system will be pretty strong on Tuesday and Tuesday evening. Sustained winds of 15-20kts with gusts of 30-40kts look likely until around 03-06Z Wednesday. Carney .LONG TERM... (Wednesday through Next Monday) Issued at 229 PM CST Mon Dec 12 2022 The stacked closed low will meander across the eastern Plains Wednesday and into the Upper Midwest Thursday. Medium range deterministic guidance stalls the low over Minnesota/Wisconsin through Saturday and then ejects it east across the Great Lakes on Sunday. GEFS and ECE open the low up somewhat more quickly, but the general pattern is the same. West-northwest flow on the west side of the low will bring progressively colder air south from Canada to spread across the Missouri Valley. The cold air won`t really start filtering into our area until Wednesday night so highs Wednesday will be mild in the 50s. However Thursday through Saturday will get progressively colder with highs dropping into the 30s and 40s. Saturday will be the coldest day of the bunch with parts of northern Missouri and west central Illinois struggling to reach 30. Mid teens to low 20s will be the rule for lows. Deterministic guidance shows another fast-moving short wave moving across the Plains into the Mid Mississippi Valley Sunday night into Monday. It gets washed out in the ensembles, and/or masked by the next huge upper low. At any rate, the deterministic guidance prints out some QPF which the NBM picked up on and inserted PoPs Sunday night and Monday. The low chance/slight chance PoPs look reasonable at this time given the movement of the wave so we`ll keep them for now. Temperatures suggest that some of this precip could be a brief wintry mix before warm advection turns the precip to all rain. Carney && .AVIATION... (For the 00z TAFs through 00z Tuesday Evening) Issued at 532 PM CST Mon Dec 12 2022 The clearing trend has worked from southeast to northwest just about reaching sections of central MO. Metro terminals have gone VFR, although broken high clouds continue to stream overhead. MVFR conditions will likely move back in as temperatures cool this evening with all sites under MVFR ceilings around and after 04z. Greatest impacts will stem from an approaching system that will lead to gusty southeast winds from mid-morning Tuesday onward. Ceiling will continue to lower into IFR as rain potential increases through late morning/early afternoon. Reduced visibilities are expected to accompany rainfall through the end of the period. Maples && .PRELIMINARY POINT TEMPS/POPS... Saint Louis 36 55 48 58 / 0 100 100 20 Quincy 35 50 43 52 / 0 100 100 5 Columbia 37 54 41 51 / 20 100 70 0 Jefferson City 37 56 41 53 / 20 100 70 0 Salem 33 52 48 58 / 0 50 100 50 Farmington 33 56 45 57 / 0 100 100 20 && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
952 PM EST Mon Dec 12 2022 .SYNOPSIS... High pressure ridge continues to nose south into the Carolinas through mid week. A strong cold front will then approach the area Wednesday night and Thursday with an excellent chance of appreciable rain. Cold high pressure will build over the area over the weekend. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... As of 950 PM Mon...Cloud cover has quickly eroded over the coastal plain and in response temperatures have already plummeted into the 30s as radiational cooling has taken hold. There are likely colder spots in well sheltered areas. Latest HRRR is capturing temperature trend well and blended some of this in for this update with little effect to the overnight low forecast. Prev disc...A synoptic cold front pushed well offshore to the south of the Carolinas earlier today, with high pressure nosing in from the Great Lakes. Behind the front, satellite imagery reveals a well-defined surface trough pivoting south through the far western Atlantic. While it is very dry aloft, the low- levels are fairly moist within the cyclonic flow around the SFC trough. This is leading to a broad area of low clouds streaming south along, and off, the Mid-Atlantic Coast at this time. Short term guidance have struggled with the western extent of the clouds, which have ended up fairly far inland this afternoon. Some of this is probably diurnally- enhanced, and it appears the extent of clouds will thin some after sunset. That said, the moist confluent flow will continue to support periods of low clouds through tonight, especially east of HWY 17. Consequently, this will have a big impact on temperatures overnight. For areas east of HWY 17, temperatures won`t drop as much as areas to the west. However, if the clouds end up not being as widespread, lows will be colder than currently forecast and vice-versa. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... As of 1200 PM Monday...High pressure will continue to be wedged south from the Great Lakes into the Carolinas on Tuesday. With time, a more significant push of drier low-level air should help to scatter out any lingering low clouds during the day. Given the potential for lingering clouds early in the day, and with a chilly start to the diurnal curve, highs Tuesday may actually be colder than today, despite gradually rising low-level thicknesses. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... As of 330 AM Monday...Cool and dry conditions expected into Wednesday. The next storm system and cold front which will bring next chance of appreciable rain will arrive late Wednesday evening or Thursday. Tuesday night through Wednesday...Reinforcing shortwave troughs rotating around an upper low centered over northern New England will bringing renewed nrly surge and CAA with cool temps continuing, albeit mostly sunny skies with dry high pres ridging in. Brief ridging aloft builds over the area Tuesday night into Wednesday ahead of another upper low across the central plains. Clouds will thicken and lower Wednesday as the system approaches but guidance is a bit slower bringing precip into ENC and expect dry conditions through the afternoon. Highs expected around 50-55 with lows around freezing or lower inland to upper 30s to lower 40 coast. Wednesday Night through Thursday Night...Aforementioned upper low over the Central Plains slides into the western Great Lakes through this period while an attendant strong cold front approaches the area Thursday. Sfc low press develops along the front as it pushes across the Southeast and is progged to track across the coastal plain late Thursday afternoon and evening, which may lead to some marginal destabilization along the coast and continue slight chance of thunderstorms. Stronger forcing and SW flow aloft brings a better feed of moisture from the Gulf of Mexico and expect appreciable rain with this system with 1 to 2+ inches possible. Cool temps continue Wed night with lows generally in the 40s. WAA ahead of the front and sfc low will bring warmer temps Thursday with highs expected around 60-65, warmest along the coast. CAA ramps up behind the departing low Thursday night with lows in the 40s expected. Friday through Sunday...Cyclonic flow continues aloft through the weekend with the upper low remaining centered over the Great Lakes Friday and Saturday before sliding into the northern New England Sunday. A series of shortwave trough will transition through the flow aloft bringing reinforcing shots of CAA but with limited moisture not expecting any precip. Temps near normal Friday with highs in the mid to upper 50s with about 5 degrees of cooling each day Saturday and Sunday. Lows mainly in the mid 30s inland to around 40 coast Friday night with many inland areas likely see sub-freezing temps Saturday night and Sunday night. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... SHORT TERM /through Tuesday/... As of 705 PM Mon...VFR conditions persist at all terminals this evening although periods of MVFR are likely especially for the Outer Banks. Healthy amount of low-level moisture advection continues to sock the Outer Banks in low stratus, which has bounced between MVFR and VFR levels most of the afternoon. Current expectation, following guidance, is a gradual lowering of cigs to a predominant MVFR overnight before returning to a mix of VFR and MVFR tomorrow. Further west over the TAF terminals, cloud cover is beginning to erode and expect only a few clouds. EWN is close enough to the coastal stratus deck that some lower cigs could sneak over the terminal, although no IFR is anticipated. Combination of elevated winds and Td depressions suggest little in the way of fog. After sunrise, VFR conditions prevail with high clouds across all terminals. Lower stratus will continue to plague OBX terminals. Northerly winds continue at 5-10 kt, except 10-15 kt along the coast. LONG TERM /Tuesday night through Friday/... As of 4 AM Monday...High pressure builds through Wednesday with pred VFR conditions expected. A frontal system will approach rtes Wednesday with clouds thickening and lowering throughout the day but should remain VFR into the evening hours. Periods of sub-VFR conditions expected late Wednesday night through Thursday night with precip along and ahead of the cold front and sfc low lifting across the coastal plain. VFR conditions should return Friday and cooler and drier air builds in. && .MARINE... SHORT TERM /through Tuesday/... As of 950 PM Mon...Northerly winds have eased over the sounds this evening as the pressure gradient continues to relax, and opted to drop the SCA slightly early. Dangerous offshore seas continue through the rest of the week. Prev disc...Late this afternoon, seas of 7-9 ft and north winds of 10-20kt are common across the coastal waters. For the sounds and inland rivers, north winds have underperformed some, and have generally held in the 10-15kt range with occasional gusts to 20kt. For the sounds, I`ll hold onto the SCA for another few hours in case there is a bump on the western edge of the modest pressure gradient associated with a surface trough moving south offshore. For the inland rivers, I decided to go ahead and cancel the SCA early given the lower wind speeds that have been observed today. Additionally, that area should be further removed from the tighter gradient located offshore. Modest north winds continue into Tuesday, but will decrease some, even over the coastal waters. LONG TERM /Tuesday night through Friday/... As of 415 AM Monday...SCA conditions will prevail across the coastal waters through the much of the week with a strong low pres system well out in the open Atlantic bringing long period swell and elevated seas to around 6-10 ft much of the period. Nly winds diminish late Tuesday through Wednesday but a strong frontal system will approach the area Wednesday night with a developing low pressure area lifting along the front just west of the waters Thursday evening. Winds to SCA expected to develop Thursday morning in sely flow which veers to sly during the afternoon. There is a potential for a period of Gales late Thursday afternoon and evening just ahead of the low. Winds become wly around 15-25 kt late Thursday night and Friday behind the departing low. && .TIDES/COASTAL FLOODING... As of 330 PM Monday...High Surf Advisories remain in effect for the Outer Banks, now until early Wednesday morning. Powerful swell from distant low pressure systems out in the Atlantic will continue to impact the Outer Banks beaches with wave run up over the next couple of days. As a result, rough surf is expected to continue for east facing area beaches. This will continue to support an elevated risk of minor ocean overwash and beach erosion for the Outer Banks. Main impacts will be felt from Oregon Inlet to Cape Hatteras, with the greatest impacts coming Tuesday. Impacts may also extend to the Northern Outer Banks and Ocracoke Island. Portions of Hwy 12 with vulnerable dune structure may be impacted, mainly during times of high tide. && .MHX WATCHES/WARNINGS/ADVISORIES... NC...High Surf Advisory until 7 AM EST Wednesday for NCZ203>205. MARINE...Small Craft Advisory until 6 AM EST Saturday for AMZ150-152- 154-156-158. && $$ SYNOPSIS...MHX NEAR TERM...RM/MS SHORT TERM...RM LONG TERM...SK/CEB AVIATION...RM/SK MARINE...RM/SK/CEB TIDES/COASTAL FLOODING...MHX
Area Forecast Discussion
National Weather Service Portland OR
239 PM PST Mon Dec 12 2022 .SYNOPSIS...The forecast is highlighted by an extended stretch of dry and cold weather with increasing east winds late in the week as low-level offshore flow strengthens. && .DISCUSSION...Tonight through Sunday night...A few light snow showers were still being observed over the Cascades early Monday afternoon, however the coverage of showers was quickly decreasing as high pressure continues building into the area from the west. As a result, still expecting showers to end completely tonight. The main forecast challenge for tonight is determining the potential for fog development. If cloud cover clears out this evening, then areas of fog are likely to develop as winds will be calm. If cloud cover does not clear out, would only expect patchy fog at best. The latest iteration of the HREF suggests cloud cover will clear out to some degree tonight, but mainly over the southern and central Willamette Valley rather than the northern valley into southwest WA. Sure enough, this is exactly where the HRRR and the RAP depict fog development. Current satellite imagery already shows cloud cover attempting to break up over the southern valley, so this outcome seems very reasonable. Cannot completely rule out fog in the northern valley, but the chance is lowest to the north of Aurora and highest in the Eugene area. Then, a prolonged period of dry weather with gradually cooling temperatures will occur Tuesday through at least Saturday. This is due to what appears to be an omega blocking pattern, as the GEFS/EPS/CMC ensemble mean for 500 mb heights are all showing a quasi-stationary ridge over the Gulf of Alaska being blocked by an upper low to the west and east of this ridge. This synoptic scale setup will result in a prolonged period of northerly flow aloft across WA/OR, allowing for several shots of relatively cold air from Canada to dive southward into the region. This will also result in strengthening offshore flow at the surface, especially on Thursday and Friday when the cold pool east of the Cascades is set to deepen and east winds begin to ramp up. Until then, it is worth mentioning that there are some air stagnation concerns over southwest WA/northwest OR Tuesday night through Wednesday morning. Initially considered issuing an Air Stagnation Advisory for Tuesday night through Wednesday night, but after taking a closer look at GFS/NAM model soundings, have determined that transport winds will be above our 5 kt threshold Wednesday afternoon and then well above that threshold on Thursday and Friday. Air Stagnation Advisories are only issued when mixing heights are below 2000 feet and transport winds are below 5 kt for at least 48 hours straight. Currently, it looks like criteria will only be met for approximately 36 hours, so have decided not to issue an Air Stagnation Advisory. How cold will it get this week? Well, the NBM continues to suggest high temperatures on Tuesday and Wednesday will be in the low to mid 40s, except mid to upper 40s at the coast. Even colder Thursday through Sunday when the NBM is suggesting highs in the mid 30s to around 40 degrees, except mid 40s at the coast. Overnight lows will be significantly colder, with widespread lows in the 20s expected each night beginning Wednesday night. Cannot rule out lows in the upper teens for typical cool spots such as Hillsboro, Battle Ground, and Corvallis. Even colder over the Cascades with lows in the single digits to teens. In addition, breezy east winds on Thursday and Friday will make it feel even colder. Expecting widespread wind chills in the upper teens across the lowlands, except 20s at the coast. Model spread on the NBM 1D Viewer is very small for temperatures, suggesting confidence is high that the cold weather will materialize. Model spread increases drastically Sunday into early next week as models and their ensembles struggle to determine when the omega blocking pattern will break down. A few of the GEFS ensemble members are even hinting at low elevation snow on Sunday, but most members maintain the dry conditions at this time. For now, have left the NBM v4.0 PoPs for Sunday, which seem reasonable at 15-25%. -TK && .AVIATION...00Z TAF preliminary thoughts: Region is squeezed between high pressure to the west and a departing low pressure center to the east. A persistent cloud deck at FL045-055 remains over the area but seems to be more driven by daylight mixing versus other methods.Feel these should somewhat break up with sunset. Isolated MVFR cigs remain across the central Willamette Valley, to include KUAO AND KSLE, but think these will also dissipate with the loss of sun. Then, conditions should remain VFR through roughly 08Z tonight when stable conditions will promote another stratus deck forming. Cigs will initially in the FL015-025 layer with many areas lowering to cigs 005-015. KHIO, KUAO, KEUG, and maybe KSLE will drop to LIFR fog later overnight. Conditions across the board will then change little through 13/18Z given very little wind and minimal daytime mixing. Areas with fog will be very slow to improve but could lift above IFR for a short time Tuesday afternoon. Other areas should improve closer to 20Z. For detailed Pac NW aviation weather information, go online to: KPDX AND APPROACHES...Cigs 015-020 will linger the next couple hours at most. Then expect VFR conds with cigs above FL040 until around 13/08Z when calm stable conditions will promote cigs 020-025 through the Tuesday morning arrivals. /JBonk && .MARINE...Seas have been slow to subside with the inner buoys bouncing between 7 and 10 feet. The peaks have become more spaced out in recent hours, so will keep the SCA in place through 3 PM with the expectation seas will continue to subside and become more consistently below criteria shortly thereafter, if not by then. High pressure and northerly flow over the waters will eventually develop into a thermal low along the SW Oregon coast as higher pressure builds inland. Winds will will eventually become a consistent easterly across the waters Thursday. However, sustained speeds appear to remain 15 kts or less through the forecast. Seas subside further tonight and then remain 5 to 7 ft for the next several days. /JBonk && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 3 PM PST this afternoon for coastal waters from Cape Shoalwater WA to Florence OR out 60 nm. && $$ Interact with us via social media:
Area Forecast Discussion
National Weather Service Pueblo CO
319 PM MST Mon Dec 12 2022 .SHORT TERM...(This evening through Tuesday) Issued at 316 PM MST Mon Dec 12 2022 ...Impactful storm will bring snow, blowing snow, along with strong and gusty winds for portions of southeast Colorado through tomorrow morning... Key messages: 1) Snow and blowing snow will develop over the Palmer Divide late this evening through early tomorrow morning which may result in high impacts to travel over this area. Portions of southern El Paso County and northern Pueblo County could also be impacted. 2) It will become very windy on the backside of this low, with areas that could potentially reach High Wind Warning Criteria during the early morning hours through afternoon tomorrow over the eastern plains. 3) Snow will continue over the high elevations and portions of the central and eastern plains though the afternoon tomorrow with a few additional inches possible. Locally higher amounts can be expected north of the US-50. Detailed discussion: Currently and tonight... Current satellite imagery shows a band of mid and high level clouds advecting in over the region from the baroclinic leaf associated with the major shortwave trough, which continues to propagate towards the region. There have been some strong and gusty SW`ly winds over much of the plains, which as led to some critical fire weather conditions this afternoon over portions of the southern I-25 corridor. These winds will continue to subside into the evening hours over the plains, but remain stronger over the higher elevations. There is very low confidence of thunderstorms initiating over our extreme southeastern portion of the CWA later this evening. If they do, it will likely be right where the current moisture axis is located, in the very southeastern portion of Baca County. There is a very high amount of bulk shear, although higher CAPE values of 1000 J/k or more tend to remain just to the east of the KS/Co border, and most CAM`s keep potential development east of the border with only a few having cells develop right along the border and then racing off to the northeast. That being said, if the moisture axis retorgrades back to the west, there could be a rogue storm could fire right over the very eastern fringes of our CWA between 6 and 9 PM. As the low ejects out over the plains this evening, it will undergo rapid lee-side cyclogenesis, resulting in a tightening of the pressure gradient and will produce very strong winds on the backside of this low as it does. The latest models in recent days have been trending southward where this low pressure center spins up, and now the general consensus appears to be somewhere over northeastern Pueblo County to Kiowa County. The deformation zone will back into the I-25 corridor and as it does, the TROWAL (Trough of Warm Air Aloft) will establish itself. As this does, it will allow for some heavier bands of snow to set up, especially on the northern facing slopes of the Palmer Divide where there will be some upsloping aiding in the development of these bands. With winds increasing to near High Wind Warning criteria for some locations, coupled with the heavier bands of snow, there could be a brief window of near- blizzard like, or near white-out conditions, with treacherous travel possible over portions of the northern I-25 corridor. The latest HRRR also reflects a heavier band developing due to the cyclogenesis over northeastern Pueblo for increased upward vertical motions around the low and higher omega forcing, that will produce a heavier band later this evening over northern Pueblo County and extending into Otero County by around 10 PM and lasting until midnight or shortly thereafter. When looking at soundings for Pueblo, the HRRR tends to bring in more moisture in the lower levels, either from mixing down to the surface from the mid levels or as the trough axis moves over, that results in a very saturated PBL and mist adiabatically up to the 700 mb level for a window of a few hours that convectively induced snow hangs out over Pueblo and Otero Counties. Another element will be possible heavier bands of snow produced by the TROWAL that will make its way over into the I- 25 corridor over southern El Paso County, as some of the high resolution models have been suggesting. Lows will continue to drop into the 20s over the plains, and single digits to teens for high county after passage of the trough. Tomorrow... The TROWAL will continue to produce snow over the Palmer Divide into the early morning hours, while the wrap around moisture over the lower Arkansas River Valley continues to provide so additional snow into the late morning hours. The main story for tomorrow will be the winds on the backside of this low, along with much colder temperatures being advected in. Some of the high resolution models have been depicting winds near High Wind Warning criteria over the eastern portion of Kiowa County and northern portions of Prowers County. If models continue to trend towards stronger winds over this area, the High Wind Watch currently in place may need to be upgraded to a warning for tomorrow afternoon and evening. Snow will continue over the higher terrain, but should let up by the afternoon hours and the wrap around moisture will continue to move east and diminish as the surface low does with clearing skies. With the cold NNW`ly winds over much of the plains, temperatures will only max out in the 30s and low 40s for most locations. In the higher terrain, upper 20s low 30s are expected for the upper Arkansas River Valley and San Luis Valley. Teens and 20s are expected for highs across the rest of the high terrain with even some single digits for the fourteeners. -Stewey .LONG TERM...(Tuesday night through Monday) Issued at 316 PM MST Mon Dec 12 2022 Key Messages: 1. High Wind Watch for Kiowa and Prowers counties late Tuesday night. 2. Winter Weather Advisory for the Sawatch Mountains 8 PM Tuesday until 5 AM Wednesday. Tuesday night into Wednesday... Low pressure system to our Northeast will be making a slow trek to the east, bringing a Northwest flow to our area. The pressure gradients will be a little on the tight side towards the northeast counties in the area. Winds are expected to be gusty with winds 35 to 40 MPH in Prowers and Kiowa Counties. This prompted a High Wind Watch for Tuesday night. The westerly flow will also cause some upsloping in portions of the Continental Divide, which will bring some snow in Lake and Chaffee counties, necessitating continuation of a Winter Weather Advisory from Tuesday night into Wednesday Morning. The area will have a blanket of cloud cover Tuesday night into Wednesday morning, hindering any radiational cooling. This will keep overnight low temperatures in check with lows in the teens and 20s in the plains and single digits to teens in the Mountains and Mountain Valleys. For Wednesday`s highs, downsloping will be occuring along the mountains adjacent to the I-25 Corridor and the Palmer divide. This will keep temperatures just a little above seasonal norms with highs in the 40s in the Plains and 20s and 30s in the Mountains and Mountain Valleys. Thursday and beyond... As the low pressure system to our northeast finally makes its move to the east, there will be more gusty winds in the eastern counties, but certainty not high enough to issue highlights for high winds. The movement of the low will bring a cold front through the area Thursday night into Friday, bringing winds to a more northerly component, and dropping overnight low temperatures and daytime high temperatures close to seasonal norms. The continued influx of cold air will continue into Friday night as lows will drop even lower to below seasonal norms. This should hold through the weekend. As the new work week starts on Monday, a slight warming trend will occur. For next week, a few models are hinting at a deep trough pushing through, and with it a cold front bringing in arctic air crossing the Canadian border, and possibly dipping into our area. If this occurs, there is a possibility of bitter cold temperatures in the area with highs only reaching the teens and lows possibly in the negative single digits or even in the negative teens. This of course is a worst case scenario, but a development definitely worth watching. -Riser && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 316 PM MST Mon Dec 12 2022 VFR conditions are expected to prevail for all TAF sites (KALS, KCOS, and KPUB) throughout the forecast period. Winds will become influenced by the approaching low pressure system at all terminals with a SW`ly direction and gusts up to 29 kts at KALS, and 25 kts at KCOS and KPUB. Wind will eventually shift to the WNW at KALS, and out of the NNW at KCOS and KPUB later this evening after FROPA occurs. This looks to occur around 03Z at KALS and KCOS, and 04Z at KPUB, but could occur slightly sooner at KCOS and KPUB if the cold air descends quicker down the Palmer Divide. This will produce very strong winds for KCOS and KPUB, with gusts as high as 40 kts possible through the early morning hours. -SHSN is expected to begin for KCOS around 07Z, and may also impact the terminal of KPUB, which would reduce VIS down to 5SM and CIGs into MVFR criteria. Some of the lastest CAM models have also been hinting at a heavier convective band of snow developing over KPUB between 03Z and 10Z. VIS could also be further reduced if heavier bands develop, which would be more likely to occur at KCOS, and may drop into IFR criteria if it does. Winds will weaken early tomorrow morning at KALS. Winds will still be very strong and gusty out of the NW at KCOS and KPUB later in the morning tomorrow, yet begin to become somewhat reduced in strength. VCSH could still be present at both KCOS and KPUB through the later part of the morning, towards the end of the forecast period, but should begin to clear out after 18Z. -Stewey && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 5 AM MST Wednesday for COZ058-060. Winter Weather Advisory until 5 PM MST Tuesday for COZ059-061. Winter Weather Advisory until 11 PM MST this evening for COZ066. Winter Storm Warning until 11 PM MST this evening for COZ068. Winter Weather Advisory from 9 PM this evening to 8 AM MST Tuesday for COZ084. Red Flag Warning until 5 PM MST this afternoon for COZ228>230- 232-233-235. High Wind Watch from late tonight through Tuesday evening for COZ095-096-098. && $$ SHORT TERM...STEWARD LONG TERM...RISER AVIATION...STEWARD