Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/02/21

National Weather Service Albany NY
1009 PM EST Mon Feb 1 2021 .SYNOPSIS... A coastal storm will bring a heavy snowfall and blustery conditions to eastern New York and western New England tonight into Tuesday. The storm will be slow to exit our region as light snow and snow showers are expected Tuesday night into Wednesday evening. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Winter Storm Warning: Dutchess, Ulster and Litchfield Counties until 4 pm Tuesday Winter Storm Warning: Eastern Catskills, Capital District, Mohawk Valley, Schoharie Valley, Helderbergs, northern and central Taconics, northern mid Hudson Valley, Hamilton and northern Warren Counties, southern VT and the Berkshires until 7 pm Tuesday Winter Weather Advisory: Washington, northern Saratoga, northern Herkimer and southeast Warren counties until 7 pm Tuesday As of 1005 PM EST...Nor`easter is around 995 hPa based on the latest RAP MSLP analysis and is east/southeast of southern NJ slowly drifting to the east to northeast. The dry slot in the water vapor imagery has punched into eastern CT and RI. The ALY forecast area continues to be in the comma head of the cyclone with an intense mesoscale snow band due to the strong low-level /mid-level FGEN yielding 1-3" per hr snow rates across the eastern Catskills, northern mid Hudson Valley, central and northern Taconics, the eastern Capital Region and southern VT. The snow shield has finally expanded into the west-central Mohawk Valley, Saratoga Region, and the KGFL area. These locations should see the snow continue to pivot in as the band lifts north/northwest. Some downsloping off the south-central Greens may continue to shadow the snow amounts some off the upper Hudson Valley as the anomalous easterly H8500 LLJ jet impacts the region which can be seen nicely on the KENX VWP. Strong upslope continues across the eastern Catskills and Helderbergs with the band as snow totals up to 17.0" have come in from Tannersville. The latest hourly snow depth change from the NYS Mesonet was 2.7"!. Many locations have received 10-16" in the mid Hudson Valley, southern Taconics, southern Berkshires and Litchfield County Connecticut. An additional 2-4" is possible in the mid Hudson Valley/Litchfield County CT before the snow diminishes with the Pivoting band per the CSTAR research. The eastern Catskills could get additional around 8-12" and some snow totals may reach 24-30". Spotty higher amounts. The Capital Region may get another 3-6" with amounts of 2-6" coming in so far, as totals in the 6-12" are possible still. Southern VT in the Berkshires will be in the 8-18" range with the lower amounts in the valley areas of VT. The headlines still look good, as the snow continues to pivot into the central-western Mohawk Valley with 6-12" possible. The eastern Adirondacks could still get 6-10" overnight with 4-8" amounts in the Upper Hudson Valley. Snowfall ratios will generally be near climatology (10-13:1) as per coordination with WPC WWD/QPF branches, there may be a minimum just north of the Capital Region and into Glens Falls and Washington County. Then into the Dacks and Catskills, expectations are additional upslope enhancement so the current headlines look good at this time. Lows generally into the 20s. Wind gusts of 25-35 mph will continues with those higher values into the higher terrain. This will result in some blowing and drifting of the snow into the morning. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY/... The upper low over West Virginia will eventually catch up the near quasi-stationary surface low just to the east of coastal NJ into Tuesday. Deformation/TROWAL axis appears to be setting up over western areas or near I81 corridor as additional episodic light snow/snow showers evolve to the east. As drier air is expected aloft, some mix may occur to the southeast of Albany, however, not enough confidence at this time per the HREF probabilities. Temperatures Tuesday afternoon appear anomalously high on the GFS-MOS as we followed more closely to the NBM/MET guidance. Tuesday night, a pivotal deformation band is expected somewhere over eastern upstate NY. However, vertically stacked low just off the Jersey Shore will become occluded so additional light snow and/or snow showers with upslope areas susceptible for additional light snow accumulations. Winds will remain problematic as well with some blowing and drifting of the snow with mixing layer heights still expected to be at or above 2k feet where 30+kts reside. Overnight lows into the teens and lower half of the 20s. Wednesday, a slow transitional day is expected as either the upper low lingers over Cape Cod or moves northeastward into the Gulf of Maine. This will determine where the deformation axis of snow will persist or impact. As some upslope areas are expected to still experience some additional snow per the Froude number less than 0.5, we will also need to watch the potential for Mohawk-Hudson convergence that could evolve through the day. Additional QPF appears to be at or below two-tenths of an inch as snow ratios will be near climatology. High temperatures into the lower 30s for the Hudson River Valley and mostly 20s elsewhere. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... The upper-level low will slowly push eastward out of the area Wednesday night with any lingering snow showers ending. Partial clearing is expected as well along with a decrease in wind speeds. Low temperatures will dip into the teens to lower 20s. Thursday is shaping up to be a rather nice day as upper-level ridging and surface high pressure builds overhead. A dry day is expected under a partly to mostly sunny sky. High temperatures will range from the mid-20s in the higher elevations to the 30s in the valleys. The next system will move across our region late Thursday night through Friday. The track of the low will be across the Great Lakes into Hudson Bay. The track along with mild enough air in the boundary layer will support a rain/snow mix across some valley areas with mostly all snow across the higher terrain. Lows Thursday night will be mainly in the teens with highs Friday mostly in the 30s. Some lake-effect snow showers will be possible in the wake of this system for Friday night and Saturday before another storm system may approach Sunday into Monday. The evolution of this system will be highly dependent on the interaction between northern and southern stream pieces of upper-level energy, which are highly uncertain this far out. High temperatures over the weekend will be in the 20s and 30s and in the teens and 20s on Monday. Lows each night mainly in the single digits and/or teens. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... The peak of the winter storm impacts with respect to accumulating snow and low vsby expected to occur 00-06Z. During this timeframe, LIFR vsby will be common at KPOU/KPSF/KALB with heavy snow (1/4SM vsby or less) possible at times. Snowfall rates of 1-2 inches per hour are possible. KGFL, on the periphery of the storm, has yet to see snow and it may be toward closer to 02Z before cigs/vsby fall to IFR. The heaviest snow is expected to shift out of KALB/KPOU/KPSF after 06Z, but IFR vsby expected to prevail at all terminals with a mixture of snow and blowing snow. Downsloping winds may briefly result in improving cigs/vsby at KALB/KPSF/KGFL, although confidence is low on this scenario. Snow showers expected to become more spotty during the day Tuesday as a midlevel dry slot kicks in, with conditions improving to MVFR, but light accumulations will likely continue. Winds will be from the north (except northeast at KPSF) at 10-15 kt with gusts of 20-25 kt at times through the TAF period. Low level wind shear conditions are forecast at KPSF through 12Z Tuesday with 45-50 kt winds at 2kft AGL. Outlook... Tuesday Night: High Operational Impact. Likely SN. Wednesday: Moderate Operational Impact. Breezy. Chance of SHSN. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: Low Operational Impact. Slight Chance of SN. Friday: Moderate Operational Impact. Likely RA...SN. Friday Night: Low Operational Impact. Slight Chance of SN. Saturday: No Operational Impact. NO SIG WX. && .HYDROLOGY... No widespread hydrological issues are expected for the week. A coastal storm will bring accumulating snowfall to the area into Tuesday. The storm will be slow to move away from the region so intermittent light snow is expected Tuesday night into Wednesday. Temperatures will be seasonable cold for early February into mid week where ice has built up on rivers and streams, then temperatures are expected to moderate by the end of the week which may result in some snow melt. A low pressure system will impact the region by the end of the week bringing snow and rain to the area. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...Winter Storm Warning until 4 PM EST Tuesday for CTZ001-013. NY...Winter Storm Warning until 7 PM EST Tuesday for NYZ033-038>040- 042-047>054-058>061-063-082. Winter Storm Warning until 4 PM EST Tuesday for NYZ064>066. Winter Weather Advisory until 7 PM EST Tuesday for NYZ032-041- 043-083-084. MA...Winter Storm Warning until 7 PM EST Tuesday for MAZ001-025. VT...Winter Storm Warning until 7 PM EST Tuesday for VTZ013>015. && $$ SYNOPSIS...BGM/Wasula NEAR TERM...BGM/Wasula SHORT TERM...BGM LONG TERM...Rathbun AVIATION...Thompson HYDROLOGY...IAA/BGM
Area Forecast Discussion
National Weather Service La Crosse WI
955 PM CST Mon Feb 1 2021 .SHORT TERM...(Tonight and Wednesday) Issued at 200 PM CST Mon Feb 1 2021 Clouds the main forecast concern for the next few days with stubborn low level deck holding across the region. RAP/NAM doing the best job with the low saturation currently - matching up fairly well with fog/stratus vsby satellite imagery. How quickly the clouds will break up ahead of approaching sfc high is the main question. The NAM slowly erodes the western edge of the deck through the night, holding it along the mississippi river by 12z. The gradually dissipation continues through the day as sfc high moves overhead. The RAP is not as aggressive, nothing really getting into a lot of clearing til later in the day Tue. Mostly, this is in line with when the upper level trough axis starts to press in from the west. Confidence not high in how this plays out, but will lean toward holding clouds longer - more reasonable for setup/time of the year. If you are a groundhog believer - hold out hope those low clouds do stick around for no shadow and an earlier spring. As for temps, the relatively mild start to Feb will continue into mid week with highs mostly in the lower 30s (normals in the upper 20s). .LONG TERM...(Wednesday night through Monday) Issued at 200 PM CST Mon Feb 1 2021 WINTER STORM: Wed night-Thu night ****************** Upper level shortwave still on track to drop from western Canada, across the northern plains, and through the Upper Mississippi River Valley Thu/Thu night. EC/GFS are a bit more south and elongated with this feature now, and bit more punchy. 01.12z NAM a tad faster than the GFS/EC but packs a similar punch. Debatable as to whether there is some influence from bits of energy in the southern stream of the upper level flow. In addition, some hints of 300 mb jet support on Thu, with some QG convergence in the 700:300 mb layer leading the shortwave across the region. Good frontogenetic forcing along the associated cold front, with hints at secondary banding in the 600:700mb layer post the front (deformation region). Confident that widespread pcpn will occur, with questions on amounts and ptype. Looks like a quick hitter though, with the bulk of accumulations coming in a 12 hour window at any particular location. PTYPE: strong warming ahead of the system, with 850 mb +1 to 3 C. West-east running x-sections and Bufkit soundings show fairly uniform warming to the sfc though - which suggests more of a rain/snow question rather than a warm layer/melting-partial melting and freezing rain-sleet question. Not ruling out a short period of wintry mix at this time though - a lot of finer details to sort out as we near Thu. In addition, NAM bufkit soundings suggest there could be a short window of freezing drizzle preceding the heart of the storm (lack of ice in the cloud). Again, something else to consider but not clear cut yet. SNOW AMOUNTS: latest COBB output and various GEFS Plumes and EC ensemble data all favoring amounts from 1-3", 2-4" with minimal if any icing (at this time). Looks like a reasonable place to start. DGZ generally under 100 mb with little threat for inch per hour rates at this time. WINDS: tight pressure gradient post the cold front will ramp up the winds for Thu afternoon/night. GFS the more robust of the models at this time, suggesting wind gusts punching north of 40 mph. EC ensembles trending closer to 30 while the NAM is a touch less. Could be a significant factor with a threat for blowing/drifting snow - dependent on how just much snow falls - and how wet it is. HEADLINES: think Winter Weather Advisories could/will be needed for that mix of accumulating snow, blowing and drifting, along with some wintry mix for good measure. Despite potentially low end amounts of snow for headlines, the variety of impactful winter weather would certainly suffice. BITTER COLD: Sat-Early Next Week ******************* GFS/EC have been in good agreement with dropping a slug of arctic air southward from Canada down across the upper mississippi river valley this weekend, hanging around into the start of the new work week. The GFS had been the more robust of the models, suggesting -30 C 850 mb air would work this far south. Previous EC runs were not as aggressive, but they have been trending this way, with latest deterministic going as cold at -32 C at 850 mb. Good support from ensemble members in both models, although the deterministic GFS continues to be the coldest of all its members. Still, -20 F and colder lows gaining more support, especially for Mon morning. Depending on timing of other features, winds will also be a factor, Suspect wind chill advisories will be needed for some locations Sun- Tue, with values dropping into the lower 30s below zero possible (if not probable). && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 955 PM CST Mon Feb 1 2021 IFR to LIFR ceilings are expected through Tuesday morning at KRST, with MVFR ceilings at KLSE. Some improvement to ceilings is possible by afternoon at both TAF sites. Surface high pressure ridge continues to push into the area tonight, bringing light northerly winds and relatively quiet weather. However, MVFR/IFR stratus continues to remain trapped under a low- level temperature inversion, with plenty of additional stratus upstream. Guidance has continued to trend later with the break up of these clouds Tuesday, though there are still hints that it might try to break apart by afternoon as the surface ridge axis passes overhead and winds turn to southeasterly. That said, there are quite a few clouds on the back side of the ridge at present, so confidence is low that this will occur and will continue to maintain MVFR stratus through the afternoon. There are signals that fog may develop Tuesday evening/night in the southerly flow behind the departing ridge, but opted not to include this in the TAFs until confidence increases. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ SHORT TERM...Rieck LONG TERM....Rieck AVIATION...Lee
National Weather Service Hastings NE
949 PM CST Mon Feb 1 2021 .UPDATE... Issued at 945 PM CST Mon Feb 1 2021 Dense Fog Advisory appears on track, though there are some interesting trends from the HRRR regarding the timing of improving conditions Tue AM. Dense fog is in place across all but the far W and S tiers of counties, but GOES-16 night RGB and area METARs shows steady expansion over past few hrs, so even these areas should get in on the "action" by midnight. Expect widespread 1/4 to 1/2 mile visibility thru at least midnight. After midnight, exact details become a bit more unclear, esp w/ regards to S extent of fog, due to recent trends from the HRRR. Starting with the 22Z run, and continuing in subsequent runs since then, the HRRR has been bringing an end to the dense fog from S to N much sooner, perhaps even as far N as Hwy 6 by dawn per latest runs. However, with fog still expanding and no real change in sfc conditions (i.e. wind speed/dir) expected overnight, not sure I buy this trend just yet. The gap in stratus/fog noted just E of Hwy 81 has been filling over past 30-90 min, and the HRRR is not adequately picking up on this. Also, other data like RAP, SREF, new 00Z HREF, and EXPHRRR, all keep dense fog conditions in place across all but far S/SE through at least mid- morning. Thus, not making any changes to headline, but will brief incoming mid shift on latest HRRR trends. && .DISCUSSION...(This evening through Monday) Issued at 507 PM CST Mon Feb 1 2021 General overview of the entire 7-day forecast: Apologize for the later discussion, as today has admittedly been a challenge trying to juggle/assess focus short-term dense fog concern, mid-term wintry precipitation concerns (mainly Wed night- Thurs), and long-term (mainly weekend) cold air concerns including perhaps our very first true flirtation with Advisory /near- Advisory wind chills this season, at least within northern parts of the CWA. Quick look at the current/recent weather scene as of 430 PM: What a big contrast in weather today from much of western/southwestern CWA which saw quite a bit of sunshine (at least earlier before high clouds increased) and temps reaching well into the 30s/40s, versus much of our central/eastern counties that remained "socked in" under low stratus an/or fog essentially all day with temps not escaping the 20s. In fact, not only did some places not only never let go of fog in general, but they essentially never even let go of DENSE fog, which even in winter is fairly rare to keep around through the entire daylight cycle. In the mid-upper levels, you`d never know we had tricky issues going on down low, because all looks quiet locally thanks to broad ridging dominating the western CONUS, other than the aforementioned high cirrus spilling over the top (that half our CWA can`t even see anyway because of all the low stuff/grunge). Wind-wise, no big issues as afternoon breezes have picked up to only around 10 MPH from the south-southeast. Now looking ahead forecast-wise and briefly covering things in mainly chronological order... This evening-Tuesday daytime (how widespread is dense fog?): Clearly fog (technically freezing fog) and how dense it becomes is the paramount issue. In short, have the entire CWA in a Dense Fog Advisory through Noon Tuesday, with eastern areas (which have been in one throughout the day) just continuing on via extension- in- time, while western areas will officially kick in at 9 PM (for now, but would not be surprised to see some spots need put in effect a bit sooner depending on trends as night falls). While not all areas will see truly dense fog through the ENTIRE run of the valid Advisory, felt that enough areas would see fog issues for enough time to justify the Advisory and let later shifts possibly drop some areas and/or cancel sooner if necessary. But if the latest HRRR is onto anything (and it seemed to perform fairly well last night-today) then most of our CWA will probably get "socked in" at some point overnight into Tues AM, with perhaps our far southwestern counties (Rooks/Osborne) perhaps being among the "least-justified" to be in a long-fuse Advisory compared to other areas. Time will tell, but odds are high that more of the CWA experiences dense to near-dense fog overnight than those areas that do not. Low temps mainly somewhere in the 20s, as clouds of varying heights should keep places from dropping as cold as last night. Tuesday daytime will surely be another battle with fog and how quickly it dissipates, and like today not even sure the noon expiration time will necessarily cut it, especially near/north of I-80. Daytime high temps are a challenge, and if anything were nudged down slightly (maybe not enough), but for now aiming most of the CWA mid-upper 30s with some 40s around the far southern/western fringes. Tues night-Wednesday: Did not get "cute" with details, but blanketed the evening through mid-morning hours with a generic "areas of fog". Based on early HRRR visibility progs though, dense fog should not be as pervasive as tonight, and could in theory improve from southwest-to- northeast as the night wears on and breezes turn a bit more southwesterly. Plenty of uncertainty here though, and we really need to take fog "one night at a time". Temp-wise, Wednesday will "try" to be the overall-warmest day of the week, but so much will depend on cloud trends and obviously the incessant cooling effect of lingering snow cover. For now though, have northern areas climbing to around 40 and far southern/southwest areas around 50. Wednesday night-Thursday: Did not dive into details much here, but the bottom line is that chances are increasing for a quick hit of wintry weather, mainly in the midnight-noon time frame. While this BY NO MEANS looks like the "major winter storm" that it appeared in "model fantasyland" about 4-5 days ago, various models (ECMWF/GFS/NAM) are increasingly keying in on a quick-hit of initially mixed precip (anywhere from rain/light freezing rain/sleet) quickly transitioning to snow before ending from northwest to southeast. PoPs have been raised a bit (perhaps not enough) and now have around 1" of snow accumulation potential north of I-80, with lesser amounts farther south (especially KS). The bottom line is that this may not be a "zero impact" event despite limited amounts, as there could be a period of blowing snow thanks to northwesterly gusts 30+ MPH, and we could be looking at a "flash freeze" of any liquid precip that falls early on in the event. Definitely a period to keep an eye on despite the quick-hitting nature of it. High temps Thursday only aimed upper 20s to low 30s most areas, so surely colder than Wednesday. Friday: Fairly high confidence in a dry day here although could foresee some flurries around in the presence of weak west- northwest flow waves. At least for now, forecast reflects a slight "warm up" back into the 30s most areas/40s south and west. Saturday-Sunday: Plenty of time for details to change, but another trough diving down across the central CONUS looks to bring our coldest air of the winter so far, with highs currently aimed mainly teens to low 20s and lows single digits both above/below zero. Saturday night could feature our first true chance for Wind Chill Advisory values around -20, especially north. Forecast is currently mostly dry, but some slight snow chances are now in for Saturday which might need increased per especially latest ECMWF. Monday: CONSIDERABLE uncertainty at this time range, but perhaps a slight modification in temps with highs trying to get back in the 20s most areas/30s southwest. Also dry for now, but with west- northwest flow around at least some "sneaky" flurries/light snow chances cannot be ruled out. && .AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday) Issued at 550 PM CST Mon Feb 1 2021 Significant wx: Around 18 hrs of IFR/LIFR VSBYs and CIGs Tonight: Conditions never improved much at GRI and latest obs and satellite show fog/stratus already worsening and expanding W. So GRI is likely beginning what looks to be about 18 hrs of 1/4sm and CIGs around 200 ft or less. EAR is currently on the edge, but with the expansion to the W this eve, expect rapidly deteriorating conditions to LIFR over the next 1-3 hrs. Wind will be lgt out of the SE for both sites. Confidence: High. Tuesday: Model data is in pretty good agreement that any meaningful improvement to conditions will probably not occur until close to midday. That`s when at least VSBYs should improve to around 1-2sm, though CIGs will remain LIFR for a few more hrs. Perhaps further improvement arrives by late aftn (best chc at EAR), but exactly how far the fog/stratus errodes remains uncertain. It`s possible both sites could see another round of issues Tue eve-night. Confidence: Medium && .GID WATCHES/WARNINGS/ADVISORIES... NE...Dense Fog Advisory until noon CST Tuesday for NEZ039>041-046>049- 060>064-072>077-082>087. KS...Dense Fog Advisory until noon CST Tuesday for KSZ005>007-017>019. && $$ UPDATE...Thies DISCUSSION...Pfannkuch AVIATION...Thies
Area Forecast Discussion
National Weather Service Jacksonville FL
900 PM EST Mon Feb 1 2021 ...COLD AND BLUSTERY TONIGHT WITH WINDS CHILLS IN THE 20S TOMORROW MORNING... ...GALE FORCE GUSTS OVER THE COASTAL WATERS... .UPDATE... A strong pressure gradient continued this evening between a strong surface low offshore of New England and a ridge settling southward across the Mid-West. Aloft, an upper level trough was still deepening along the US Atlantic Coast, which will continue to deepen the surface low near New England and keep a cold, breezy weather regime in place across the local area through Tuesday. Cloudy skies will continue tonight with wind gusts 15-20 mph well inland to 25-35 mph at times near the Atlantic coast due to about a 4-5 mb pressure gradient in place. The combination of a cold low level airmass funneling over the local area and strong winds will create wind chills in the 20s tomorrow morning, which meets wind chill criteria across NE Florida where a wind chill advisory remains in effect. Recent guidance trended a tad warmer with lows tonight due to lingering clouds with minimum temps ranging in the lower 30s inland to mid/upper 30s toward the coast. A few inland locations across SE GA (west of Highway 301) and NE FL including the Suwannee River Valley may briefly reach freezing around sunrise. Cloud cover will gradually break up through early afternoon after sunrise Tue, with more peaks of sunshine Tue afternoon but a continuation of gusty NW winds and below normal temps with highs only in the 50s (upper 40s for max temps possible for some areas near Altamaha River basin). A more widespread light inland freeze is expected Tue night with less wind and a deeper depth of cold air across the area. && .MARINE... Gusts to gale force will impact the coastal waters tonight through Tuesday. Adjust combined seas down by 1 ft this evening in the forecast based on obs with offshore flow, otherwise forecast on track. Rip Currents: Moderate risk. && .PREV DISCUSSION [633 PM EST]... .NEAR TERM [Tonight through Tuesday]...Strong cold air advection continues as intense low pressure off the NJ coast continues to deepen. A tight pressure gradient will continue the gusty northwest winds overnight. Strong winds will combine with temperatures in the low/mid 30s tonight to produce wind chill temperatures in the mid 20s. Have issued a wind chill advisory for all of ne Fl as criteria(25F) will be reached late tonight and early Tuesday morning. A light freeze is possible in se Ga...with temperatures in the mid 30s across ne Fl. Low wraparound clouds will continue over the area tonight with models showing clearing skies Tuesday morning. Blustery conditions will continue on Tuesday with highs only reaching the lower 50s. .SHORT TERM [Tuesday night through Thursday night]...Tuesday night will be another cold night with winds staying up as the pressure gradient remains tight. A light brief freeze will be possible over se Ga and inland NE Fl but will hold off on a freeze watch as freezing temperatures and duration will be marginal. Winds chills will again drop into the 20s. Dry and cold conditions again for Wednesday as nw winds start to ease with below normal temperatures. Winds will drop off Wednesday night allowing for good radiational cooling. Frost and a light inland freeze expected as surface high pressure settles over the area. Thursday will see a warming trend as the high shifts to our se and winds become sw. Temperatures will return to normal levels. .LONG TERM [Friday Through Monday]...Models in much better agreement during the extended period showing a cold front with rain and possibly thunder Friday and Saturday. Clearing for Sunday and Monday as high pressure builds in from the nw with a drier and colder airmass. .AVIATION... [Through 00Z Wednesday] Low stratus with bases 3-4 kft covered the terminals this evening under brisk NW winds 12-15 kts with consistent gusts near 25 kts. Potential for MVFR restrictions tonight at all terminals as stratus deck lowers with airmass cooling under continued gusty NW winds. Favored HRRR and NBM guidance based on better initialization with low stratus deck and both models advertised gradual improvement in low clouds at SSI by 12z with improvement southward toward JAX/VQQ/CRG through 14z then GNV/SGJ through 16z as drier air trails passage of 925-850 mb troughs. Prevailing VFR conditions are expected by 18z under a continuation of blustery NW winds near 15 kts with gusts near 25 kts. Winds will gradually decouple into tomorrow evening under VFR conditions. .FIRE WEATHER...Cold and breezy conditions will continue through Wednesday. Dispersions will be high on Tuesday and minimum RH values will be near critical values Wednesday afternoon. && .PRELIMINARY POINT TEMPS/POPS... AMG 32 51 30 53 28 / 0 0 0 0 0 SSI 36 53 33 54 35 / 0 0 0 0 0 JAX 35 53 33 56 33 / 0 0 0 0 0 SGJ 36 53 35 56 36 / 0 0 0 0 0 GNV 33 53 32 57 29 / 0 0 0 0 0 OCF 34 55 32 59 30 / 0 0 0 0 0 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Wind Chill Advisory from 4 AM to 9 AM EST Tuesday for Baker- Bradford-Central Marion-Clay-Coastal Duval-Coastal Flagler- Coastal Nassau-Coastal St. Johns-Eastern Alachua-Eastern Marion-Gilchrist-Hamilton-Inland Duval-Inland Flagler- Inland Nassau-Inland St. Johns-Northern Columbia-Putnam- Southern Columbia-Suwannee-Union-Western Alachua-Western Marion. GA...None. AM...Small Craft Advisory from 4 AM to 11 AM EST Wednesday for Waters from Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM-Waters from Fernandina Beach to St. Augustine FL from 20 to 60 NM-Waters from St. Augustine to Flagler Beach FL from 20 to 60 NM. Gale Warning until 4 AM EST Wednesday for Waters from Altamaha Sound GA to Fernandina Beach FL from 20 to 60 NM-Waters from Fernandina Beach to St. Augustine FL from 20 to 60 NM- Waters from St. Augustine to Flagler Beach FL from 20 to 60 NM. Small Craft Advisory until 8 AM EST Wednesday for Coastal waters from Altamaha Sound to Fernandina Beach FL out 20 NM- Coastal waters from Fernandina Beach to St. Augustine FL out 20 NM-Coastal waters from St. Augustine to Flagler Beach FL out 20 NM. &&
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
933 PM CST Mon Feb 1 2021 .UPDATE... Issued at 933 PM CST Mon Feb 1 2021 A dense fog advisory is in place across parts of swrn and ncntl Nebraska overnight. Although conditions are okay right now, dry air and weak winds aloft, strong radiational cooling and reasonable moisture at the low levels should be favorable for the formation of dense fog. The fog forecast follows the short term model blend which is consistent with most of the rapid refresh and mesoscale fog forecasting models. && .SHORT TERM...(This evening through Tuesday night) Issued at 215 PM CST Mon Feb 1 2021 Concern tonight is again the potential for fog. Stratus deck is slowly eroding to the east, but slower than the models anticipated and areas of fog continue along the immediate edge of the stratus from Boyd south through Wheeler county. Time lagged HRRR and RAP slowly work the stratus and fog back to the west tonight. This seems reasonable as south winds advect warmer and relatively moist air northward from KS across remaining snowpack. We`ll have to again watch for the possibility of dense fog on the immediate west edge of the stratus, much like we saw this morning. Will pass this concern along to the incoming evening shift. A leeward surface trough will begin to deepen Tuesday from southwest SD to eastern CO. South winds will continue across much of the Central Plains to the east of the surface trough. The combination of south winds and remaining snowpack will likely help the lower stratus deck and fog to linger through much of the morning, then slowly erode to the east during the afternoon. Feel that areas around Butte/O`Neill/Bartlett won`t see much clearing with clouds possibly lingering all day. Will adjust temperatures accordingly for those areas. For areas across western Nebraska where snowpack has eroded expect a very mild day. H85 temps approach 12C across far western Nebraska, and should see highs reach into the lower 60s and mid 60s where no snow cover exists. .LONG TERM...(Wednesday through Monday) Issued at 215 PM CST Mon Feb 1 2021 On Wednesday, a potent shortwave trough will be digging into the northern Rockies. Surface low pressure will deepen across eastern CO ahead of this feature, with an inverted surface trough extending northeast from the low into western Nebraska and central SD. Lift associated with the shortwave will overspread the area Wednesday night. Meanwhile the surface low will migrate eastward across KS with a strong cold front moving southeast through the area. The GFS and ECMWF have been fairly consistent in developing an FGEN enhanced band of precipitation (post frontal) across portions of western and north central Nebraska. The NAM appears to showing signs of this too in the latest run. Will continue to monitor the model trends, as any snowfall will be accompanied by strong north winds. The next concern will be this weekend. The operational models and ensemble data has been advertising the coldest air of the season to arrive. Broad northwest flow will be in place across the region during this time. A shortwave will move southeast within the flow which will be accompanied by a strong Arctic cold front. There is some potential for at least light snow with this feature, with some model soundings showing favorable snow growth potential and at least some light accumulation. Falling temperatures and strong north winds can also be expected Friday night into Saturday morning with the arrival of the front. Ensemble mean averages low temperatures right near zero across Holt and Boyd counties Saturday night/early Sunday morning. Many members are below zero and so are both the operational GFS and ECMWF. Right now the forecast is for lows to drop below zero with the coldest about -6F or so. Wind chills will be even colder, with readings approaching advisory criteria. A strong 1035mb (per ECMWF) will be centered across the area Sunday, then shifting east Sunday night. Return southerly flow should help to moderate lows Sunday night slightly, but reading still likely dropping to near zero across Boyd/Holt/Wheeler counties. Cold weather will linger into at least the first few days of next week. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 530 PM CST Mon Feb 1 2021 There is a good chance the IFR/LIFR in fog/stratus across cntl Neb this evening will spread west to KLBF tonight and last until late morning Tuesday. IFR/LIFR is likely 05z tonight -21z Tuesday affecting areas along and east of highway 83. && .LBF WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 11 AM CST Tuesday for NEZ010-027>029- 037-038-059-070-071. && $$ UPDATE...CDC SHORT TERM...Taylor LONG TERM...Taylor AVIATION...CDC
Area Forecast Discussion
National Weather Service Louisville KY
852 PM EST Mon Feb 1 2021 .Forecast Update... Issued at 852 PM EST Mon Feb 1 2021 Radar remains mostly quiet this hour, but there are some very light reflectivities (< 10 dBZ) east of I-65 from eastern Jefferson County east to Franklin County and south toward Taylor County. Because saturation in the DGZ decreases west of I-75, any precip reaching the ground could be a freezing mist or brief freezing drizzle. RAP soundings at SDF do show the moist layer up to -9 or - 10 C, so flurries are possible as well. Think that a fast moving mid- level impulse diving SSE (currently near the IL/IN border) is responsible for sufficient lift to produce very light precip. For most, this is likely no more than a mist. But given current temperatures, some very light icing is possible on elevated objects. The primary precip shield is pushing south across northern KY this evening and will continue to spread into the Bluegrass Region. This is a slight western bulge in deep moisture extending up through the DGZ pivoting south across the eastern half of KY. This light snow will continue to move south across KY through the early morning hours of Tue, with wintry impacts most likely near and east of the US-127 corridor. The snow should push almost due south, perhaps pushing slightly SSE with time given prevailing NNW flow over KY. As it stands, the westernmost part of the Winter Weather Advisory should not see much more than flurries. A light coating seems more likely further east, so plan on dropping a row of counties from Washington CO south through Monroe Co. The eastern CWA, especially near and east of US-127, could see quickly deteriorating roads tonight with only light snowfall accumulations. Temperatures are currently in the upper 20s and will slowly fall through the 20s overnight. Some roads could remain slick during the Tue AM commute. && .Short Term...(This evening through Tuesday) Issued at 310 PM EST Mon Feb 1 2021 After a morning of light snow showers that dropped 1-2 inches across the region, KLVX radar is quiet across most of the CWA this afternoon. Latest sfc analysis places the primary sfc low just off the coast of Delaware, with a secondary low over Ohio/West Virginia. Regional mosaic radar reveals the secondary sfc circulation nicely as returns wrap around the circulation over Ohio/West Virginia. While radar is quiet now for most of the LMK CWA, still expecting to see some backbuilding of light snow showers this evening over the Bluegrass and Cumberland regions. Official LEX snowfall for today is up to 2 inches, and with another round of snow for tonight, could see an additional 0.5-1.0 inch accumulation for the LEX area and surrounding counties. Based on the latest snow accumulation guidance, have decided to trim a few counties off the current Winter Weather Advisory that appear to be too far west for any additional impactful snow amounts. After coordinating with JKL/OHX, have also decided to extend the Advisory through 06z tonight. CAMs suggest our eastern CWA won`t see much precip until closer to 00z this evening as another wave of energy spins around the vertically stacked low. Precip chances exit the eastern CWA by early tomorrow morning, but clouds will hold on for areas along the I-65 corridor. Additional snowfall on top of what we received earlier today could recover roads and create slick spots again. Rural roads could be difficult to travel on if left untreated, and any compacted snow could freeze over tonight. Several models, such as the RAP, HRRR, NAM, and HREF, pick up on possibly seeing some lake effect flurries travel from the southern tip of Lake Michigan, down the I-65 corridor and into our region by Tuesday mid-late morning. With the large stacked low off to our east, deep NNW flow and a stream of vorticity extending from the Great Lakes down to Kentucky could be enough to get some flurries despite dry air aloft working in. Skycover guidance from numerous models have picked up on this trend in recent runs and are consistent enough to see a swath of cloud cover over the I-65 area and central KY. It will be interesting to see how this plays out, and would not be surprised to see some flurries tomorrow. For now, not enough confidence to include in the forecast given the amount of dry air advecting in with NW flow, but just worth a mention. Temps for tonight will drop to the low-mid 20s with NW winds of 10 to mph and occasional gusts of 20 to 25 mph. Tomorrow`s temps will be similar to today and struggle to get to the mid 30s with continuous NW flow. .Long Term...(Tuesday night through Monday) Issued at 321 PM EST Mon Feb 1 2021 Tuesday night, surface high pressure and upper ridging, centered over the Plains, begin pushing the system over New England out into the Atlantic. A few lake effect flurries could try to hold into the night, but by Wednesday morning, skies are expected to begin clearing from the west. Clear skies will cover the CWA by around noon, but the sunny weather will be short lived. Thursday begins under cloudy skies as a surface low begins moving east across the Great Lakes with a cold front in tow. The cold front brings in the next round of precipitation, and with the cool morning temperatures, a wintry mix is likely. The change over to all rain is expected by midday. Precipitation is expected to end Friday morning. Again with morning lows, a light wintry mix is possible where precipitation remains. On Friday, behind the front, a weak surface high passes through the region. This will likely allow sunshine to peek through the clouds before a frigid weekend. Over the last 3 runs of the GFS, a Canadian Clipper riding along northwest flow pushes a cold front through the CWA. This is something to watch. Blended temperatures on Saturday reach to either side of 40, but if this clipper materializes, believe much cooler temperatures are possible. Global guidance continues to push temperatures lower for Sunday and with high pressure and clear skies Monday morning, it looks even colder. Single digits are possible (maybe even lower), but for the lowest temperatures, snow would need to be on the ground. The GFS has its clipper system, and the Euro brings precip to the CWA a little later. They both show precipitation and cooler temperatures, but the details remain out of focus. && .Aviation...(00Z TAF Issuance) Issued at 656 PM EST Mon Feb 1 2021 All terminals initializing at MVFR to begin the TAF period, but drier air advecting in from the north overnight may result in variable conditions. Lake-effect clouds struggling to fill in over portions of Indiana may cause HNB to SCT out and go VFR much quicker than anticipated, so will monitor for necessary amendments. SDF should see MVFR clouds SCT out after 05-06z and then return again Tuesday afternoon along with flurries. LEX will see light snow showers develop after 02z and persist through about 07z with an additional coating expected. Vsby dropping into the MVFR range at times is likely in the snow. Snow will wind down at LEX in the early morning hours, with drier air improving conditions after 12z. Winds will remain breezy through the period out of the NNW. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...Winter Weather Advisory until 1 AM EST /midnight CST/ Tuesday for KYZ035>037-039>043-046>049-054>057-064>067-075>078-081- 082. && $$ Update...EBW Short Term...CJP Long Term...KDW Aviation...EBW
Area Forecast Discussion
National Weather Service Sacramento CA
243 PM PST Mon Feb 1 2021 .SYNOPSIS... A winter storm will move across NorCal late tonight into Wednesday with mountain travel impacts expected. Dry weather should return by Thursday and continue through the weekend with periods of increased north to east winds. && .DISCUSSION... Upper level trough is moving onshore this afternoon as seen on visible satellite imagery, bringing the next winter storm to impact interior NorCal. A few light showers have been occurring throughout the day in the mountains and northern Sacramento ahead of the main trough passage. The main moisture plume is currently situated just moving into the CWA with precipitation moving over the Coastal Range and into the western Valley. NAM 3k and HRRR show widespread precipitation slowly moving north to south through the area through the afternoon and evening hours. The heaviest precipitation is expected tonight through tomorrow with light showers lingering through Wednesday along the back side of the trough. Moderate to heavy mountain snow is expected tonight through tomorrow. Around 8 to 18 inches of snow is forecast over the Sierra through the storm. Models show snow remaining north of I-80 this evening, spreading to areas along and south of I-80 after midnight. Snow levels will start out around 5000 to 6000 feet today, falling to 4000 to 4500 feet by tomorrow behind the frontal passage. SREF plumes and NBM continue to suggest around 3 to 8 inches of snow down to Blue Canyon at around 5200 feet. Winter Storm Warning remains in effect from tonight through early Wednesday morning. HREF, NAM 3k, and HRRR indicate periods of moderate to heavy rain possible along the cold front as is moves through the area this evening through the overnight areas. HREF shows only small (10 to 15%) probability of rain rates over 0.5 inch an hour. Therefore, debris flow impacts over burn scars are not expected, though can`t rule out localized flooding or minor slides due to areas of heavier precipitation. Post-frontal scattered Valley showers are expected to continue tomorrow. A slight chance of scattered thunderstorms is also possible in the Sacramento Valley. HREF and NAM indicating CAPE around 200-300 J/kg in the Valley, enough to potentially form a few stronger cells. Main impact with any thunderstorm would be small hail and brief heavy rain with maybe some lightning. HREF indicates rainfall rates should be below 0.5 inch in an hour, so burn scar impacts are also not expected at this time. There are slight discrepancies between GEFS and Euro ENS on the trough placement Wednesday. Euro ENS has the trough slightly farther south which would bring light showers into the Valley Wednesday. GEFS is a bit shallower which would leave shower chances mainly in the mountains. Either way, additional precipitation accumulations would be fairly light. Dry weather returns Thursday as ensembles show the trough pushes to the east and upper level ridging builds over the eastern Pacific. Gusty north to east winds are possible as the ridge builds, though they are not expected to be strong at this time. -HEC && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Ensemble guidance has continued to indicate high pressure over the region will keep Northern California dry though the extended forecast period. High temperatures will generally be a smidge warmer than the seasonal averages for this time of year. The warmest locations will be in the Northern Sacramento Valley with highs reaching into the mid to upper 60s this weekend which is about 5 to 10 degrees above normal for early February. Low temperatures in the Valley will be a little cooler than normal for this time of year with temperatures expected to be in the mid 30s to low 40s. Upper foothill and mountain locations will have low temperatures that are slightly warmer than normal. Locally breezy north to east winds are also possible at times. && .AVIATION... VFR decreasing to MVFR with areas of IFR and LIFR possible with passing shower activity. Snow levels around 4500-6000 feet. Southerly surface winds generally under 15kts with gusts up to 25 possible. && .STO WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from 7 PM this evening to 6 AM PST Wednesday for West Slope Northern Sierra Nevada-Western Plumas County/Lassen Park. && $$