Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/09/20


AREA FORECAST DISCUSSION
National Weather Service Albany NY
948 PM EST Tue Dec 8 2020 .SYNOPSIS... Brisk and chilly conditions will persist into Thursday, before turning warmer with above normal temperatures by the end of the week. A passing disturbance will bring a period of some light accumulating snow showers across the forecast area Wednesday into Wednesday night. Accumulations should generally range from a dusting to 3 inches with locally higher amounts possible in the western Adirondacks and southern Green Mountains. Tranquil weather returns Thursday through Friday. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 948 PM EST...Clouds continue to erode, although there are still patches of mostly cloudy skies over mainly higher terrain areas west/east of the Capital District. Made some minor adjustments to reflect current observations and trends. Partial clearing will persist into the overnight before additional clouds increase from the west late. Latest trends in the guidance (including CAMs) indicate snow showers will develop for areas north/west of the Capital District between 4-6 AM. The rest of this evening will be rather quiet. Clouds will thicken and lower in elevation tonight ahead of a shortwave that will dive southeastward out of Canada tonight. Winds will be out of the west-northwest 5-15 mph through this afternoon before becoming light and variable this evening/tonight. Another cold night is on tab with low temperatures expected to fall into the 20s (teens across the higher elevations). && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... The main weather focus during the short term period will be on the potential for some light accumulating snow across the forecast area Wednesday through Wednesday night. Precipitation type will by and large (spatially and temporally) be snow. The only exception will be in the Hudson Valley where p-types will be a rain/snow mix during the afternoon hours as sfc temperatures are expected to warm into the upper 30s amid southerly winds. Light snow will develop from west to east courtesy of a shortwave that will move over the forecast area tonight through Wednesday. Light snow is expected to begin across our northwest zones (i.e. Herkimer county) between 3-4 am EST and across the Capital District, southern VT and the Berkshires between 5-7am EST Wednesday morning. Delta T values between Lake Ontario and 850 mb will be on the order of 12-13C. This will be sufficient enough for some lake enhancement under a west-northwest flow aloft regime. Lake effect snow will mostly affect our northwestern zones. Some hi-res models such as the HREF HRRR member are indicating that a band of lake effect rain/snow showers could shift southward into western Mohawk Valley, Schoharie Valley into the Capital District Wednesday afternoon into Wednesday evening. Should this materialize, this has the potential to produce at times brief burst of snow potentially worthy of SPS/Special Weather Statements. Will have to monitor these trends. Upslope snow is expected over southern VT into the Berkshires. With snow ratios ranging between 7:1 (valleys) to 13:1 (higher elevations), snow amounts will generally range from a dusting to 3 inches with the higher amounts across the SW Adirondacks of Herkimer County and possibly over the higher terrain of southern VT. Areas across northwestern Herkimer county (adjacent to KBUF`s winter weather advised counties) could see locally higher amounts greater than 3 inches (up to 5 inches). Have opted to not issue a Winter Weather Advisory at this time due to the fact that much of Herkimer county will average around 3 inches of snow (sub-advisory levels). Snow will come to an end by Thursday morning as high pressure builds in from the southwest. Tranquil weather will persist through Friday. High temperatures will moderate across the valleys from the upper 30s Wednesday to the mid 40s on Friday (cooler higher elevations). Low temperatures will mainly be in the 20s Wednesday morning through Friday morning with some teens across the higher elevations Wednesday morning. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The period starts out on Friday with ridging aloft and a southerly low level flow in place, with high pressure positioned off the east coast. This will result in dry conditions with mild temperatures. High temps expected to be around 10 degrees above normal. Dry conditions should prevail through at least Friday night and possible through Saturday morning, as upper ridging remain in place, although it will likely be flattening out somewhat by Saturday. Chances for showers will start to increase later on Saturday and especially Saturday night, as a cyclone tracks northeastward into the south/central Great Lakes region. Moisture flux associated with increasing southerly flow and increasing isentropic lift will result in some showers developing. Forecast confidence decreases Saturday night through Sunday, as the GFS is indicating a stronger primary cyclone, with high pressure positioned well north/east while the ECMWF is depicting a weaker cyclone, with the high positioned closer (south/east of the GFS). The CMC is most similar to the GFS at this time, so not yet ready to completely lean towards any camp just yet and will go with a blend for temperatures, but will lower from the mean NBM values. Low level thermal profiles will have significant implications regarding precip type, as ECMWF would indicate a potential wintry mix across northern and eastern zones, while the GFS/CMC would result in more plain rain. Will mention some rain/snow mix for now, with time to refine the forecast as the guidance comes into better agreement. In wake of the weekend system, seasonable cool and breezy conditions expected for Monday, with a few snow showers possible mainly over the higher terrain. Very low forecast confidence for Monday night thhrough Tuesday, as the ECMWF is showing a strong southern stream storm approaching from the south/west, while the GFS is depicting an innocuous zonal flow pattern with dry conditions. Overall there is a lot of volatility in the weather pattern through early next week. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Low level clouds stuck in place at KALB/KGFL/KPSF, with cigs borderline VFR/MVFR at KALB/KGFL and MVFR at KPSF. However, clouds are slowly scouring out from SW to NE across the area as there are no low level clouds at KPOU. Expecting at least some partial clearing for the rest of the TAF sites later this evening, before additional clouds increase from west to east overnight into early Wednesday morning, ahead of an approaching upper level disturbance. Snow showers will develop from NW to SE and become prevalent between 12Z-15Z at KGFL, KALB, then KPSF. Scattered snow showers may affect KPOU for a short time, but not expected to be widespread there, so will mention PROB30. Will mention MVFR conditions for KGFL/KALB/KPSF at this time, although there is a chance of IFR developing especially at KPSF. Will monitor trends for subsequent TAF issuances. Winds will become light and variable overnight, then shifting to the southwest around 5-10 kt on Wednesday. Outlook... Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: No Operational Impact. NO SIG WX. Friday: No Operational Impact. NO SIG WX. Friday Night: No Operational Impact. NO SIG WX. Saturday: Low Operational Impact. Slight Chance of RA. Saturday Night: Moderate Operational Impact. Chance of RA. Sunday: Moderate Operational Impact. Chance of RA. && .HYDROLOGY... Mainly cool and dry conditions are expected through tonight, with only some light precipitation possible Wednesday into early Thursday, mainly in the form of snow. This will allow river levels to slowly recede. 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...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Evbuoma/JPV NEAR TERM...Evbuoma/JPV SHORT TERM...Evbuoma LONG TERM...JPV AVIATION...JPV HYDROLOGY...Evbuoma/KL/NAS
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
352 PM CST Tue Dec 8 2020 .Discussion... Issued at 351 PM CST TUE DEC 8 2020 Low sun angle and weak flow has made it a struggle to shake low clouds and stratus today. Have seen an improvement through the afternoon hours across central and eastern Missouri, but am a bit concerned that atmosphere was unable to adequately mix out the low level moisture. HRRR has hinted at the potential for fog re- development along and east of highway 63, though there remains some question in terms of density and areal coverage. For now, have added patchy fog mention across eastern Missouri through the overnight, but think fog development would favor low lying areas. Low level jet increases overnight ahead of a subtle cold front that moves through the area tomorrow morning. Behind the front, 925 hpa temperatures cool through the day, and thus have dropped forecast highs on Wednesday a few degrees. With that said, still looks like a very pleasant day for December with 925 hpa temperatures of 11-13 C leading to highs in the lower 60s F. Mild conditions continue into Thursday, but will start trending towards cooler conditions as a boundary approaches from the northwest and becomes oriented more in an east/west fashion Thursday night into Friday. As leading wave in upper trough approaches on Friday, isentropic lift increases to the point where light rain is expected to develop across central Missouri, but will have to keep an eye on far northwestern Missouri. Models are differing on the depth of stratus and lift embedded within, but GFS soundings would suggest the potential for soundings wet bulbing to freezing drizzle. As the cooler air settles southward, could see precipitation mix with and change over to snow Friday night into Saturday as short wave train continues aloft. Once the upper trough works through the area on Sunday, quieter weather is expected early next week with seasonal temperatures. && .Aviation...(For the 18Z TAFS through 18Z Wednesday Afternoon) Issued at 1109 AM CST TUE DEC 8 2020 VFR conditions will slowly spread from west to east through the afternoon hours. Potential for fog to linger through the early afternoon hours across central Missouri. West to southwest winds will prevail through the period. Subtle cold front will work through the area Wednesday morning with flow becoming northwest. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...NONE. MO...NONE. && $$ Update...Kurtz Discussion...BT Aviation...BT
Area Forecast Discussion
National Weather Service Grand Rapids MI
657 PM EST Tue Dec 8 2020 LATEST UPDATE... Aviation .SYNOPSIS... Issued at 330 PM EST Tue Dec 8 2020 - Small chances for very light precipitation tonight - Weekend system has many questions yet - Potential for another weak system early next week && .DISCUSSION...(This evening through next Tuesday) Issued at 330 PM EST Tue Dec 8 2020 -- Small chances for very light precipitation tonight -- A warm front will move into the area tonight with the potential for some very light precipitation. The 18Z HRRR is for the most part dry, but we feel there could be a little light drizzle. This appears to be a non event however as ground temperatures are in the upper 30s and air temperatures will be near to slightly above freezing. The temperatures may end up being slightly warmer than some of the models indicate (a few spots may dip slightly below freezing) due to the fact that winds will be strong and a bit mixy tonight, along with a direction off of Lake Michigan with water temperatures that are in the 40s. Bottom line...we may see a little drizzle tonight, but we are not expecting any of the freezing variety due to the above factors. -- Weekend system has many questions yet -- The main story in the 7 day forecast is the potential for an impactful system over the weekend. The upper systems do not phase well and at best the phasing could be described as disjointed right now. The evolution of multiple upper waves is complex and is 5 days out yet in the forecast. The main players in our weather for the weekend are a cutoff low off the Baja of Mexico, a shortwave trough west of Washington and Oregon over the Pacific and another trough further west south of the Aleutian Island chain of Alaska. So, we have some ground to traverse yet before we start nailing down any details. What we know...1) Models have converged on a low moving through the Great Lakes over the weekend, 2) the exact track of that low is up for considerable debate, 3) as is the depth of the low depending on how the upper waves phase (or not) and 4) there is the potential for some impacts. The operational GFS and ECMWF bring a low up through Indiana and Ohio to near Lake Erie and then off into Ontario. Many of the lows in the ensembles of both models though are tracking over the Lower Peninsula, or a bit further north and west than their deterministic runs. That would be a warmer solution and more in the way of rain. The operational runs would favor a swath of snow through portions of the Southwest Quarter of Lower Michigan. At this point it is probably safe to say that we are looking at the potential of rain and possibly some snow in the Friday through Sunday time frame, but there is just way too much play in the evolution to nail much more down than that. Especially given the range in the forecast and we are talking about the interplay of 2 shortwaves and a cut off low that are all still over the Pacific (one of which is half way across the Pacific). Bottom line...stay tuned as we watch the evolution of this system over the coming days. Accumulating snow is certainly possible, but temperatures both aloft and at the surface are a bit marginal and as stated above there is quite a bit of uncertainty. -- Potential for another weak system early next week -- A weak upper shortwave and associated surface low move through the area next Monday night and Tuesday. At this point it looks like some very small chances for some light rain or snow. We could remain dry as well given what the operational runs of the ECMWF and GFS are showing. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 657 PM EST Tue Dec 8 2020 Widespread MVFR cigs of 1500-2500 ft this evening are expected to trend down to IFR or LIFR late tonight into Wednesday morning, accompanied by some areas of fog as well. Conditions improving Wednesday afternoon, with cigs gradually lifting into MVFR category. Confidence is low however as to whether or not we eventually clear out this persistent stratus deck and go VFR by mid to late afternoon. The best chance of that occurring would be west of LAN and JXN. Southwest sfc winds of 10 to 20 kts this evneing will diminish to around 10 kts and become west later tonight into Wednesday. && .MARINE... Issued at 330 PM EST Tue Dec 8 2020 Small Craft Advisory remains in affect through midday on Wednesday. We are just entering into the period of stronger winds (southwest 20-30 knots) from about 300pm through 300am. Webcams along the lakeshore are already showing rolling whitecaps so we fully expect to see 5-7 footers at the peak later this evening and tonight. Waves and water levels are expected to remain below criteria for the issuance of a Lakeshore Flood headline. Winds and waves will steadily diminish on Wednesday as the winds subside a bit. The next period of potentially higher winds and waves will come into next weekend, most likely on the backside of a low pressure system (Saturday into Sunday). && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 1 PM EST Wednesday for LMZ844>849. && $$ SYNOPSIS...Duke DISCUSSION...Duke AVIATION...Meade MARINE...Duke
Area Forecast Discussion
National Weather Service Jackson MS
842 PM CST Tue Dec 8 2020 .UPDATE... Updated for evening discussion. && .DISCUSSION... Have made some minor updates to the forecast this evening to add in some patchy fog after midnight. Dewpoints are slow to drop, and winds have already gone calm. Though NAMNest is by far the most aggressive, the GFSlamp, HRRR and RAP13 are all trending to more of a patchy fog overnight. Prior discussion below: Tranquil and near seasonal wx conditions continue to prevail over the lower MS Valley this Tue afternoon, under predom sunny skies. A sharp upper trough pattern across much of the ern CONUS is also helping to usher sig drier above H85 into the region, with current temps ranging from the mid 50s NE to the mid 60s SW. Little change in this overall pattern is xpcted thru tonight and into mid week, with lows early Wed from the upper 30s/around 30F, before temps rebound well into the mid 60s later in the day. A gradual warming trend may then develop Wed night into Fri, as the sfc high exits the mid/srn Atlantic Coasts to the east. The latest model suites are then hinting at rain chances coming back to the forecast starting late Fri and continuing into Sat, as an upper low/trough axis quickly lifts NE out of the SW states, while a sfc reflection out of the mid Plains traverses NE thru the Midwest/NE states. This sfc low will quickly pull a cold front ewd thru the Mid South/lower MS Valley areas late Fri thru Sat, with showers developing along/just ahead of the approaching boundary. In fact, some weak instability may develop late Fri night as the front initially moves into the wrn half of the area. This may translate into a few embedded tstms possible within increasing showers. As mentioned, the front will then quickly exit to the east Sat evening, with rainfall tapering off. Overall temps look to trend near/slightly above normal during the first half of the weekend, before cooler air once again spreads into the lower MS Valley from the NW Sun into Mon following the passage of the cold front. && .AVIATION... 00Z TAF discussion: Generally VFR conditions with light and variable winds throughout the TAF pd. Chance for some MVFR/IFR vis, particularly in the southeast before dawn. Have some concerns that there may be more patchy fog elsewhere...but guidance so far is less pervasive. && .PRELIMINARY POINT TEMPS/POPS... Jackson 36 66 39 70 / 0 0 0 0 Meridian 34 66 38 69 / 0 0 0 0 Vicksburg 35 67 41 71 / 0 0 0 0 Hattiesburg 37 68 39 71 / 0 0 0 0 Natchez 38 66 41 70 / 0 0 0 0 Greenville 36 66 40 69 / 0 0 0 0 Greenwood 36 65 40 68 / 0 0 0 0 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ HJS
Area Forecast Discussion
National Weather Service Memphis TN
906 PM CST Tue Dec 8 2020 .UPDATE... We continue to see strong northwest flow aloft across the Mid- South this evening. A strong polar jet is diving southeast across the Great Lakes, spilling abundant mid/high clouds into the OH Valley, but subsidence associated with the subtropical jet along the Gulf coast has been eroding this cloud cover as it approaches. We do anticipate an increase in sky cover overnight, mainly in the northeast half of the CWA and this should help temperatures level out a bit. Otherwise, some areas have already reached forecast minimum temperatures, necessitating a quick update. Min temperatures were lowered mainly across interior west TN where subtle terrain chances allow the colder air to pool. Otherwise, the main forecast issue tonight will be the potential for fog after 06z. We`re already seeing a few sites reporting minor visibility obstructions and that trend should continue. The HREF and HRRRE probabilities are rather high for visibility less than 1 mile across north MS and southwest TN tonight. Patchy fog was continued, but wording may need to be enhanced if trends hold as expected. MJ && .PREV DISCUSSION... /issued 343 PM CST Tue Dec 8 2020/ DISCUSSION... Currently...An upper trough is pushing off the eastern seaboard while upper ridging is building into the southern Plains. Surface high pressure covers the southern U.S. with light and variable winds across the Mid-South. After a chilly start temps have recovered into the 50s with Clarksdale breaking the 60F barrier. Tonight...Main concern is whether fog will develop. Dewpoints have rebounded into the mid and upper 30s and with mostly clear skies and light winds temps will fall to the crossover temp. The HRRR indicates some dense fog developing over parts of the Delta and north MS while the HREF shows higher chances over NE MS and SE west TN. High clouds moving south into the region also add another aspect into the equation. For now will go with patchy fog over most of the area after midnight. Low temps will generally range from 33 to 37 degrees though would not be surprised to see some lows below the freezing mark in the typically colder spots in north MS and west TN. If some dense fog does form in those areas there could be some slick spots. Wednesday and Thursday...Some really nice late fall weather is on tap. Upper ridging will move across the area as light southwest surface flow brings in some mild air. Expect plenty of sunshine with highs well into the 60s and maybe even a 70 possible on Thursday. Friday and Saturday...A large trough will develop over the western U.S. and approach the Mid-South Friday. Most of the Mid-South will squeak out another really nice day on Friday with well above normal temps and some sun before rain chances increase west of the river in the afternoon. Expect numerous to widespread showers and a few thunderstorms Friday night Saturday morning. Instability continues to look meager so severe threat remains low but will be keeping an eye on it. Rain chances will taper off during the day on Saturday from west to east with cooler temps. Saturday night through Sunday night...Models are all over the place Sunday and Monday as they handle the evolution of the upper trough in much different ways. The operational ECMWF cuts off an upper low over the Lower MS Valley while the operational GFS pushes the upper trough through the region and transitions to fast zonal flow with some dry weather for a couple of days. Their respective ensemble systems echo their operational counterparts with the ECMWF ensembles much wetter than the GEFS. The Canadian system is also trending wetter. Pops have been added Saturday night through Sunday night. Monday and Tuesday...Looks like a dry and cool period as either the GFS pans out or the system picked up by the ECMWF and Canadian has moved east. SJM && .AVIATION... 00Z TAFs VFR conds through much of the period. The exception may be light MVFR fog overnight at JBR...MKL..and TUP. Light and variable winds over the next several hours becoming southwest around 4 kts or less around midnight. High clouds will continue to stream in from the north overnight. These clouds should keep fog from becoming too dense overnight. Southwest winds will strengthen to 7-9 kts by late tomorrow morning. AC3 && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$