Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 11/25/20

National Weather Service Albany NY
951 PM EST Tue Nov 24 2020 .SYNOPSIS... High pressure will move east of northern New England overnight, as a weak warm front will be approaching from the south. A period of light snow, mainly along and north of Interstate 90 and Albany, is possible overnight with very light accumulations expected. Warmer air will move back into the region as a storm approaches from the Ohio Valley. Most of this precipitation will fall as rain showers as this system tracks across the region through Thanksgiving Day. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 950 PM EST...A 1032 hPa sfc anticyclone based on the latest RAP is moving east of northern Maine tonight. A weak warm front is approaching from the south and west with a short-wave in the southwest flow aloft. Mid and high clouds are increasing based on the latest GOES IR Imagery over central and eastern NY. These clouds will slow down the radiational cooling where temps have fallen into the teens over the southern Adirondacks and the 20s to lower 30s over the rest of the forecast area based on the latest NYS mesonet observations. Some light snow and rain has begun over western NY and is moving to the east to northeast. The 00Z KALY sounding is very dry with a PWAT of 0.19" and very dry low levels below 435 hPa. The onset of light snow looks to be between 06Z-09Z from the eastern Catskills, Capital Region and Berkshires north and west based on the latest 3-km HRRR. Snow amounts will range from a dusting to a half an inch or so. Thickness and thermal profiles will be cold enough for light snow, we will increased PoPs into the chance and low likely range over the western Dacks and western Mohawk Valley. Amounts appear to be rather light with QPF values generally less than one tenth of an inch. A few half inch amounts or so are possible over the higher terrain with a coating to a few tenths in some of the lower elevations. This will all depend where the column saturates better. The best chance looks like from the I-90 corridor north. Lows will be in the teens to mid and upper 20s but temps should steady or slightly rise in the early to mid morning hours. A south to southeast breeze will increase shortly before daybreak. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... For Thanksgiving Eve, the surface warm front lifts northward initially then becoming quasi-stationary later in the day. As upper low and its surface reflection approach, most of the morning hours should be rather dry (exception would be portions of the Dacks and near Lake George). Chances for precipitation increase once again during the afternoon hours. As this frontal boundary drifts southward, increasing baroclinicity along with persistent warm advection and isentropic lift will reintroduce more wet conditions for most of the region into the afternoon and especially toward sunset. High temperatures into the 40s for most of the CWA, some mid-upr 30s for the Dacks and southern Greens. Wednesday night, consensus favors a rather high PoP for wet conditions as combination of diffluence aloft, warm and moist low level advection and approaching upper low for periods of showers/rain. Thermal profiles suggest mainly rain, some rain/snow mixture for portions of the Dacks and southern Greens. Overnight lows into the 30s, generally above freezing, for the higher terrain with lower 40s for the Capital Region and points southward through the mid-Hudson Valley and NW CT. Thanksgiving Day, this upper low will transverse the region throughout the day. Additional rain showers, drizzle and patchy fog are expected. The best theta-e axis still appears to be just to the southeast of Litchfield County where the heaviest axis of QPF is possible. Furthermore, Showalter values are a little lower this 12Z NCEP Model Suite with values near zero for our southern zones (eastern Ulster, Dutchess and Litchfield Counties). So a rumble of thunder for these areas are possible but appears to limited at this time for inclusion within the forecast (future adjustments are possible). High temperatures ranges from the 40s across the terrain to lower half of the 50s from the Capital Region and into Litchfield County CT. Thanksgiving Night, the upper low tracks east with considerable low level moisture remaining in place. We will keep low chance PoPs through the evening hours as H850 frontal zone slides into the region. Some patchy fog and/or mist is possible with lows generally between 40-45F. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The extended forecast will begin with above normal temperatures and some weak disturbances for late in the week into the holiday weekend. However, the longwave pattern becomes more amplified and a significant storm system may impact the region early next week with moderate to heavy precipitation. Friday...Improving conditions are expected in the wake of the compact, and progressive closed H500 low that moves east of New England early in the day. Sfc high pressure ridges in from the Mid Atlantic States. Some short-wave ridging may build in for some partial sunshine south and east of the Capital Region. Mid and upper level heights begin to fall late in the day ahead of the next northern stream mid and upper level trough. A few showers tapping lake moisture with the weak warm advection are possible over the western Adirondacks, as the flow backs to the southwest. Max temps will run about 10 degrees above normal with lower to mid 50s in the valleys, and 40s to lower 50s over the hills and mtns. Friday night to Saturday...A cold front and a short-wave trough with limited low-level moisture impacts the ALY forecast area. Clouds increase and the best chance of showers will be across the western Mohawk Valley and western Adirondacks Fri night. A little wet snow may mix in on the onset. Isolated to scattered showers are possible from the northern Catskills, Capital Region, and the Berkshires north and west on Saturday. Depending on the timing of the front, a few snow showers are possible over the western Dacks during the late pm. Temps may also steady or fall during the day. Max temps will be cooler than FRI, but still will be slightly above normal. Highs will be in the mid 40s to lower 50s across the lower elevations, and upper 30s to mid 40s over the higher terrain. Saturday night through Sunday...A fair and tranquil stretch of weather with a sfc high building in from the OH Valley and the Mid Atlantic States. Mid and upper level heights begin to increase late in the day ahead of the northern stream trough. Meanwhile, an vigorous southern stream trough will be lifting northeast out of the southern MS River Valley and Deep Southeast late in the day. Lows Saturday night will be in the 20s to around 30F. Highs will still run above normal with mid and upper 40s in the lower elevations on Sunday and mid 30s to lower 40s over the higher terrain. Sunday night into Monday...The 12Z EC/GFS/CMC and some of the GEFS are showing better agreement with an impressive storm system impacting the region early next week. The question still remains where the exact northern and southern streams phase short-waves. The 12z GFS and CMC are similar with a sfc low forming along the southern and central Appalachians and moving the cyclone over central NY by 00Z/TUE. The 12Z ECMWF has the sfc wave form west of the Appalachians and the full-latitude trough becomes negatively tilted and moves the sfc wave from the OH Valley to east of eastern MI by 00Z/TUE. The bottom line is a deep fetch of Gulf moisture is expected with a strong low-level jet. The water vapor transport will be strong with above normal PWAT values /+1 to +2 STDEVs/ based on the 12Z GEFS. Thermal profiles based on the track favor rain which may be moderate to heavy at times. Windy conditions will also be possible. PoPs were increased to likely values on Monday. Lows will be early on in the upper 20s to lower 30s Sunday night but then rising overnight. Highs on Monday will be in 40s to lower 50s. Monday Night into Tuesday...Depending on the placement of the deepening and intensifying sfc low and its associated frontal boundary periods of rain could persist into Tue. A dry slot may also eventually punch into the region. As the sfc cyclone may deepen to 975-980 hPa over the eastern Great Lakes Region and southeast Ontario. Blustery conditions are also possible and colder air filtering back into the region may yield some higher elevation snowfall. Temps trend back to normal readings Mon night into Tue. A 1 to 2+ inch pcpn event is possible and QPF trends may will be monitored for any potential hydrological issues. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... A warm front will approach the terminals tonight with thickening and lowering clouds and a period of light snow from KALB-KPSF northward. The boundary will continue north in the late morning into the early afternoon. Another upper level disturbance ahead of a warm front over the Ohio Valley will keep it cloudy and increase the chances of showers towards Wednesday night. VFR conditions are expected prior to 08Z-10Z/WED at KPOU/KALB/KPSF/KGFL with thickening and lowering clouds to cigs in the 3.5-6 kft AGL range. Some light snow may impact KALB- KPSF between 08Z-12Z with MVFR cigs/vsbys forming, and a TEMPO group was used here. Further north KGFL will have a period of light snow from 11Z-15Z/WED with MVFR conditions possible. It will take some time to saturate to lower cigs. KPOU we kept VFR with cigs of 3.5-4 kft AGL. A low VFR/high MVFR stratus deck may linger in the late morning into the early afternoon in the wake of the frontal passage. We trended back to VFR cigs mainly 3.5-6 kft AGL by the early pm. Some PROB30 groups were used for a chance of showers with the next disturbance between 21Z/WED to 00Z/THU at KGFL/KPSF. We only placed VCSH groups at KALB/KPOU around 22Z/WED. The winds will become calm or light and variable in direction at 4 kts or less early this evening. They will increase from the east to southeast at 5-10 kts prior to 12Z/WED. South to southeast winds will continue from the late morning into the afternoon at 8-14 kts with some gusts around 20 kts at KALB. LLWS was included from 11Z-15Z at KGFL, as the sfc winds remain light at 5 kts or less as 2 kft AGL winds will be close to 35 kts. Outlook... Wednesday Night: High Operational Impact. Likely SHRA. Thanksgiving Day: High Operational Impact. Likely SHRA. 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 SHRA. Saturday Night: Low Operational Impact. NO SIG WX. Sunday: No Operational Impact. NO SIG WX. && .HYDROLOGY... A warm front will be approaching tonight. A period of light snow, mainly along and north of Interstate 90, is possible overnight with very light accumulations expected. Warmer air will move back into the region as a storm approaches from the Ohio Valley. Most of this precipitation will fall as rain showers as this system tracks across the region through Thanksgiving Day. Total rainfall amounts will generally be a quarter to half inch, which should have little impact on rivers and streams. Dry weather is then expected behind this system for Friday into the weekend. 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...BGM/Wasula NEAR TERM...BGM/Wasula SHORT TERM...BGM LONG TERM...Wasula AVIATION...Wasula HYDROLOGY...Frugis/BGM
Area Forecast Discussion
National Weather Service Dodge City KS
635 PM CST Tue Nov 24 2020 .UPDATE... Issued at 635 PM CST Tue Nov 24 2020 Phase change is proving to be efficient across the western zones, with Garden City reporting snow as of 630 pm, with heavy snow and 1/4 mile visibility at Elkhart. This banded deformation snow will pivot quickly through this evening, and opted to place a widespread 1 inch snow amounts in the grids. Most of this will accumulate rapidly on grassy/elevated surfaces, but roadways will remain wet. Precipitation is expected to be ended around midnight. With rapid clearing and diminishing winds after midnight, temperatures will fall below freezing easily by sunrise Wednesday. Some freezing of water is possible on roadways late tonight. UPDATE Issued at 542 PM CST Tue Nov 24 2020 Still uncertainty in the forecast this evening, even at this late hour. Moderate to heavy rain associated with the warm conveyor belt is slowly exiting the eastern zones. The latest HRRR iterations show a pronounced deformation zone and associated strong precipitation rates pivoting across SW KS over the next 4 hours or so. This process will undoubtedly occur, but exact placement is still waffling, and the thermodynamic profiles are still exactly borderline regarding rain versus very wet snow. Updated grids to put more wet snow in the weather grids this evening, but kept amounts minimal given 1) wet ground, 2) wet snow and 3) very progressive trough and very brief forcing at any one location. Radar and satellite showing the deformation solidifying across the western zones currently. Will need to watch trends and observations closely this evening for phase changes and rapid reductions in visibility. && .SHORT TERM...(This evening through Wednesday) Issued at 150 PM CST Tue Nov 24 2020 Based on radar trends, showers and thunderstorms will spread across southwest Kansas into central Kansas early this evening as a compact upper level shortwave trough upper low shifts eastward out of southwest and central Kansas into eastern Kansas and western Missouri by late tonight. However, the main focus will be for a possible switchover to snow as colder air begins to spill southward into western Kansas in wake of the frontal passage. As it stands now, CAMs and short range models indicate modest H7 frontogenetic banding developing from central Kansas down into portions of southwest Kansas briefly early this evening before quickly weakening. The question will be if cold enough air spreads into the area in conjunction with the increased forcing before it weakens/moves out of the area. Based on QPF fields, potential snowfall accumulations could range anywhere from a few tenths to possibly upward of an inch or so if heavier snow bands develop. Regardless, warmer ground and likely wetter ground due to previous rainfall could hinder snow accumulations of what is already expected to be a wet snow. Additionally, a tightening pressure gradient across western Kansas in wake of the frontal passage this afternoon will allow gusty north winds to develop, persisting through much of the evening. This may lead to brief periods of reduced visibilities due to blowing snow conditions associated with possible heavier snow bands. Snow chances will dwindle west to east late evening through overnight as the upper level storm system quickly lifts northeast into the Upper Midwest. Below freezing temperatures are expected tonight as cold air surges southward through the Western High Plains, pushing the H85 0C isotherm well down into the Oklahoma Panhandle. Look for lows generally down into the 20s(F) tonight, especially in west central and extreme southwest Kansas where cloud cover is likely to lift/scatter out before daybreak. Lee side troughing will quickly develop in eastern Colorado Wednesday behind surface high pressure shifting southeast out of the Southern Rockies into the South Plains of west Texas. This will result in a west-southwesterly downslope flow across western Kansas through much of the day, in turn pulling warmer air back into the area with H85 temperatures pushing up around 5-7C by mid-afternoon. Afternoon highs are expected to reach up into the lower/mid 50s(F) under mostly sunny skies. .LONG TERM...(Wednesday night through Tuesday) Issued at 200 PM CST Tue Nov 24 2020 Drier conditions will prevail through the end of the week as medium range models continue to indicate weak ridging aloft moving east through the Central Plains Wednesday night into Tuesday, giving way to a southwest flow aloft across the Western High Plains. With another round of drier air expected to arrive Thursday in wake of a cold front projected to move through western Kansas by early/mid afternoon, precip chances will remain out of the forecast through at least Friday afternoon. There is relative agreement between the GFS and the ECMWF/GEM of another upper level shortwave trough transitioning across the Northern Plains late Friday with an upper low potentially closing off from the aforementioned trough axis generally across the Desert Southwest. This could set the stage for precip chances possibly returning to portions of southwest Kansas as early as Friday night into early Saturday. A cold frontal passage Thursday will reinforce a cooler air mass stretched across the high plains of western Kansas, likely keeping temperatures near normal with highs expected up into the 50s(F) to possibly a few upper 40s(F). Similar temperatures are forecast through the early part of the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 452 PM CST Tue Nov 24 2020 Poor aviation conditions will continue for about the next 4-5 hours as a strong storm system impacts the terminals. IFR/MVFR stratus will continue this evening along with strong NW winds gusting 30-35 kts. Deformation precipitation, most likely in the form of wet snow, is projected to impact all airports for a few hours this evening. Followed the latest HRRR iterations closely with this, and included TEMPO groups for snow/reduced visibility during the 02-05z Wed time range. After 06z Wed, rapidly improving aviation conditions are expected, with rapid clearing to VFR/SKC and rapidly diminishing NW winds. Strong subsidence will deliver excellent flying weather Wednesday with VFR/SKC and light winds. && .PRELIMINARY POINT TEMPS/POPS... DDC 28 56 29 50 / 100 0 0 0 GCK 26 55 25 49 / 100 0 0 0 EHA 26 57 27 54 / 80 0 0 0 LBL 25 56 26 53 / 100 0 0 0 HYS 27 52 26 49 / 100 0 0 0 P28 33 56 31 56 / 70 0 0 0 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Turner SHORT TERM...JJohnson LONG TERM...JJohnson AVIATION...Turner
Area Forecast Discussion
National Weather Service Goodland KS
410 PM MST Tue Nov 24 2020 .SHORT TERM...(This evening through Wednesday) Issued at 106 PM MST Tue Nov 24 2020 19Z Water Vapor Imagery and RAP analysis indicates closed low circulation moving into the Oklahoma panhandle. At the surface,low was centered in the TX panhandle with inverted trough extending to the northeast along cold front which is well to the south of the CWA. Main forecast concerns will be ongoing precipitation followed by how cold it will get behind tonights system. Initial area of precipitation along H7 frontal zone has shifted to the southern part of the CWA as closed low begins to move onto the plains. This new area of precipitation will likely represent the northern and western extent of precipitation from this point on. As cooler air works southeast expect rain showers to transition to snow showers. While there is some instability present there could be some pockets of more intense precipitation, it is likely that any lingering instability will be used up before a change over to snow, so do not anticipate any significant accumulations. Strong synoptic scale forcing ends quickly after 00z as low moves into eastern Kansas. Skies will clear fairly rapidly tonight and with drier air and decreasing winds, think several locations will fall into the mid teens and have opted to keep forecast near the colder extremes, especially in the west. Weather will be quiet for the rest of the period as southerly return flow redevelops leading to warmer conditions and no precipitation. Warmup will be a bit short lived as next cold front enters the area Wednesday night. .LONG TERM...(Thursday through Monday) Issued at 100 PM MST Tue Nov 24 2020 Thursday... The Tri-State area will be under SW flow aloft through Friday afternoon as the positively-tilted upper level trough continues to move east. A cold front should move across the area Thursday morning from the northwest. There is very little moisture associated with this front, so the area is expected to remain dry for Thanksgiving. The surface low and trough that formed south of the area Wednesday evening is expected to continue east along the Kansas-Oklahoma border. As the low moves east, the models are showing an increase in moisture over the eastern half of the CWA Thursday afternoon. Despite the added moisture, the area should remain dry. The high temperatures are expected to range from the 40s to low 50s. Low temperatures are expected to fall back into the upper teens to mid 20s overnight. Friday... Both the GFS and the ECMWF are continuing to depict the trough finally moving over the CWA throughout the day on Friday; however, now both models are depicting the development of a cut off low as it cross the Colorado Rockies. The ECMWF continues to favor a stronger closed low over the Four Corners region at the base of the deep trough compared to the cut-off low seen with the latest GFS run. As of now, it does not appear that the low will have an impact on the Tri-State area as it stays to the south. At the surface, high pressure is expected to move over the Central Plains, keeping the region dry. Temperatures on Friday are currently expected to range from the 40s to low 50s for highs and low to mid 20s for lows. Saturday... There is quite a bit of uncertainty as the models continue to disagree. The latest GFS shows the cut-off low becoming closed late Saturday/early Sunday morning over the panhandles of TX and OK. The ECMWF remains a slower solution. If either of these solutions actually play out this weekend, majority of the precipitation is expected to occur south of the CWA in southern Kansas. There is a small potential that areas south of US-40 could see some light snow beginning Saturday morning, but confidence is low. As the temperatures rise during the day, the snow should transition into light rain. During the evening hours, rain chances are expected to increase east of Hwy 83. Snow could begin to mix with the rain before becoming all snow Saturday night as the temperatures drop. Very low to no accumulations are expected at this time. Current PoPs are near or less than 20% for Saturday due to a lack of confidence in the track and actual precipitation occurring. Temperatures will be slightly warmer on Saturday, with highs in the 50s and lows in the 20s to low 30s across the area. Sunday... Sunday will be colder due to the frontal passage early Sunday morning from the north. Any left over precipitation from Saturday night, if any occurs, should move out of the area during the morning hours. As the closed low south of the area continues east overnight Saturday/early Sunday morning, a ridge is expected to slowly move over the Tri-State area. Winds could be breezy from the north on Sunday as an upper level trough moves across the Northern Plains and digs into southern Nebraska, creating a tight pressure gradient. The area is expected to remain dry Sunday with highs in the 40s. Low temperatures are expected to range from the upper teens to low 20s. Monday... The Tri-State area is expected to be under the influence of an upper level ridge extending along the Rockies from the western coast of Mexico into central Canada. An area of high pressure at the surface is expected to move into the area throughout the day, keeping us dry. Temperatures are forecasted to reach the upper 40s to lower 50s during the day and cool back into the upper teens and 20s at night. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 408 PM MST Tue Nov 24 2020 VFR conditions forecast for the TAFs. Winds will gradually decline through the evening and turn to the west tonight, then southwest Wednesday. Precipitation will remain well south of the TAF sites. && .GLD WATCHES/WARNINGS/ADVISORIES... KS...NONE. CO...NONE. NE...NONE. && $$ SHORT TERM...JRM LONG TERM...KMK AVIATION...JTL
Area Forecast Discussion
National Weather Service Green Bay WI
952 PM CST Tue Nov 24 2020 New Information added to update section .UPDATE... Issued at 951 PM CST Tue Nov 24 2020 An inverted surface trough will move across southern/central sections of Wisconsin tonight. Visibilities in southwest Wisconsin are already below 1 mile and with parts of central Wisconsin having received 1-3 inches of snow, expect fog to become more widespread overnight. Therefore, have issued a Dense Fog Advisory for Wood, Portage, Waupaca and Waushara Counties until 10 AM Wednesday morning. This advisory may need to be expanded later tonight depending on how bad the fog gets. Have also issued a SPS to cover the fog for the rest of northeast Wisconsin. && .SHORT TERM...Tonight and Wednesday Issued at 236 PM CST Tue Nov 24 2020 The latest RAP analysis and satellite/radar imagery show low pressure centered over the central Plains and broad southwest/south flow ahead of the low into the western Great Lakes. Most of the precip has fallen from central to northeast WI so far today where temperatures are a within a couple degrees on either side of the freezing mark. Thermal profiles continue to warm across the region, but snowfall has been most persistent in the winter weather advisory area, south of Mosinee, and west of the Fox Cities/Oshkosh. Calls to these counties revealed 1-2 inches of snow and slippery roads at midday. Even though thermal profiles continue to warm, heavier precip rates are holding down temps by a degree or two, which is making a big difference in regards to precip types. As a result, will extend the winter weather advisory through 02z, which also serves to cover the evening commute. Forecast concerns continue to revolve around precip trends and possible impacts as low pressure travels south of the region. Tonight...Southwest flow will continue over northeast Wisconsin during the evening as low pressure travels east across Kansas. Northern stream shortwave energy will push deeper mid and upper moisture east of the region by late evening or early overnight, thereby ending widespread precip chances. However, the layer below 750mb will remain nearly saturated until late tonight, which suggests that areas of drizzle and fog will likely persist into the overnight hours. Temps won`t fall much at all tonight, but could see some slippery roads develop if untreated over north- central WI. Under overcast skies, lows ranging from the lower 30s to upper 30s near Lake Michigan. Wednesday...Low pressure will continue to head east over southern Illinois. The northern edge of the comma head of this cyclone will likely pass over east-central WI, where a chance of light rain will persist through the day. Otherwise, after a cloudy and perhaps foggy start, mostly cloudy to overcast conditions should continue through the day. Highs ranging from the upper 30s to middle 40s. .LONG TERM...Wednesday Night Through Tuesday Issued at 236 PM CST Tue Nov 24 2020 Besides monitoring the late weekend system, quiet conditions are anticipated throughout this period. Above normal temperatures are expected for the first portion of this forecast, followed by a surge of colder air early next week. Wednesday evening through Thanksgiving Day...Lingering light precipitation will be coming to an end in east-central Wisconsin Wednesday evening as a surface low pressure system slides into southern Michigan. The precipitation should fall as rain or drizzle as boundary layer temps will be warm enough. Under mostly cloudy skies, low temperatures will range from the upper 20s in north- central Wisconsin to the middle 30s in east-central Wisconsin for Wednesday night. The clouds are expected to continue into Thanksgiving Day with generally quiet conditions and high temps ranging from the upper 30s to middle 40s. A relatively weak surface boundary will sweep across the forecast area Thursday afternoon and evening. With moisture lacking, kept a dry forecast, however, cannot rule out the potential for a few sprinkles. Rest of the extended...After a moisture-lacking upper-level trough moves across the region on Friday, a transition from an upper-level northwest flow to zonal flow will occur into Saturday. Dry conditions and above normal temperatures are anticipated for Friday and Saturday. Sunday into Monday is where the forecast continues to raise plenty of questions. Model guidance is struggling where and when two pieces of energy will phase together. The latest 12z guidance indicates a digging upper-level trough will move over the forecast area Sunday night and begin to phase with a closed low located over the Lower Mississippi Valley/Tennessee River Valley. Although there appears to be some agreement bringing snow showers across far north-central Wisconsin Sunday night and phasing the pieces of energy further to the east on Monday, kept a dry forecast for now, however changes are very likely to occur. Much colder air will fill in as the upper-level trough moves over the region causing below normal temperatures for the beginning of next week. && .AVIATION...for 00Z TAF Issuance Issued at 534 PM CST Tue Nov 24 2020 Poor flying conditions are expected tonight into Wednesday morning as a pair of weak systems move through the region. Widespread IFR/LIFR ceilings/visibilities are forecast tonight/most of Wednesday morning with only modest improvement to low-end MVFR ceilings/VFR visibilities Wednesday afternoon. Most of the precipitation will come to an end this evening, although patchy drizzle or freezing drizzle will be possible later tonight. Wednesday looks dry for most locations, although there is a small chance for light rain over the MTW TAF site Wednesday afternoon. && .GRB WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 10 AM CST Wednesday for WIZ035>037-045. && $$ UPDATE.........Kallas SHORT TERM.....MPC LONG TERM......Hykin AVIATION.......Kallas
Area Forecast Discussion
National Weather Service Grand Rapids MI
1028 PM EST Tue Nov 24 2020 LATEST UPDATE... Update/Marine .SYNOPSIS... Issued at 312 PM EST Tue Nov 24 2020 - Snow north tonight, Rain Wednesday - Fair for Thanksgiving, then a Stormy Weekend? && .UPDATE... Issued at 1029 PM EST Tue Nov 24 2020 The rain/snow line has moved closer to Route 20, and the final band of snow is moving through the area now. The snow should be coming to an end after midnight. Some light rain and drizzle are still possible during the early morning hours. Air temperatures should rise into the mid 30s by morning even in the Route 10 area so that should help road conditions. Travel issues have improved but sections of US-131 north of Cedar Springs and US-127 near and North of Mount Pleasant still have some slow downs. Snow can be seen falling on the MDOT webcams near and north of Route 20. UPDATE Issued at 712 PM EST Tue Nov 24 2020 Overall our forecast is on track. The rain to snow line has recently lifted through the Grand Rapids area. Our dual pole CC curve shows it to be over northern Kent County at 6:45 pm. However it is moving northward fairly quickly. Expect rain or drizzle near and south of I-96 the rest of the night. Meanwhile near Route 10, where our Winter Weather Advisory remains in effect snow is still falling. Looking at our MDOT cameras and highway speeds, seems north of Cedar Springs roads are snow covered on US-131 and speeds are significantly reduced. The situations is similar on US-127 north of Mount Pleasant. Based on radar data and the latest runs of the RAP and HRRR, several more bands of moderate to heavy snow should be expected in the Advisory area through around midnight. After that the lift in DGZ seems to diminish significantly so snowfall rates should decrease significantly. I could see 2 to 4 inches more falling before the snow diminishes around midnight. Also in the 2 am to 4 am time frame the freezing level should be high enough to change whatever is falling to rain. Still roads may remain very slippery through sunrise since temperatures are near to just below freezing up there now and while temperatures should rise above freezing by morning even up there, winds will not be all that strong so it may take awhile for any snow and ice on the roads to melt. && .DISCUSSION...(This evening through next Tuesday) Issued at 312 PM EST Tue Nov 24 2020 -- Snow north Tonight, Rain Wednesday -- We have bumped up snow amounts slightly across the far north where the Winter Weather Advisory is in effect. We expect 2 to 4 inches there with the higher amounts across Osceola and Clare Counties before the snow changes to rain later tonight. Area of isentropic ascent and northward moisture transport will continue to bring rain showers further south overnight. We do not expect any freezing rain as warm air advection will prevent surface temperatures and dew points from falling as rain changes to snow. The surface low moves north on Wednesday with the northern edge of the steady rain moving north through the forecast area in the afternoon. Showers should taper off during the evening as the low departs to the east. -- Fair for Thanksgiving, then a Stormy Weekend? -- Fair weather returns for Thanksgiving Day. Then we will have to watch the potential for storminess developing over the weekend into early next week as a complex pattern develops with split stream flow possibly going towards phasing of a northern stream trough with an upper low over the Southern Plains to Gulf Coast. Lots of ensemble spread here, but increasing support for a deepening low affecting the eastern Great Lakes region during this time. Most of the heavier precip may remain off to the east, but lake effect snow showers are possible in northwest flow late in the weekend or early next week. Another low may follow for Tuesday or Wednesday as an active weather pattern develops in fast west- northwest flow. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 638 PM EST Tue Nov 24 2020 This forecast period will be plagued with mostly IFR conditions through most of the time. All terminals have now changed over to rain from snow as of 2330z. Rain showers will gradually shift to drizzle for most of the night. The IFR is briefly going to VFR at most sites for the next few hours, except KMKG. The low clouds, fog, and drizzle will come back in at all sites later tonight. Then, we expect more widespread steady rainfall to move in by about 18z Wed at all sites. This will keep the IFR-LIFR in over the area through the end of this period. There is some chance it may improve late at the southern sites, but it is too uncertain at this time to mention yet. && .MARINE... Issued at 1029 PM EST Tue Nov 24 2020 I have expunged the Small Craft Advisory as winds and waves are below criteria until your out past the 5 mile point in the near shore. Winds are expected to decrease overnight and so will wave heights. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory until 4 AM EST Wednesday for MIZ037>040- 043>046. LM...None. && $$ UPDATE...WDM SYNOPSIS...Ostuno DISCUSSION...Ostuno AVIATION...NJJ MARINE...WDM
Area Forecast Discussion
National Weather Service Little Rock AR
248 PM CST Tue Nov 24 2020 .SHORT TERM...Tonight Through Thursday Night Main focus remains on a conditional svr wx threat overnight Tues into Wed morning... 1) A cool season high shear-low CAPE (HSLC) svr wx event remains possible over the state late tonight and into early Wed morning. 2) Two rounds of storms will be possible...the first consisting of semi-discrete storms in the warm sector which will maintain the best chance for all svr hazards, including some brief tornadic activity. Another line of thunderstorms is expected to form along the cold front as it sweeps through later Tues night/early Wed morning. 3) Primary caveat...svr wx threat is marginal and very conditional...nocturnal timing keeps the possibility of sfc-based storms persisting questionable but if this condition is met, a few strong storms will be possible, which at times could be severe given the strong parameter space expected. ...Synopsis... A quick glance at mesoanalysis data indicated a progressive upper shortwave trof was located over the OK/TX panhandle, w/ a S/Wrly jet streak of 50+ kts moving over the Natural State. Below, a sfc low w/ strengthening gradient winds was co-located just E of the upper trof, indicating the two have become well in phase. Latest radar data also indicated a broad area of precipitation developing in the warm sector, downstream of the trof where synoptic forcing for ascent is currently maximized. Sfc low over the OK/TX panhandle will remain juxtapositioned w/ upper shortwave, enhancing the sfc mass response. As the upper trof continues to translate Ewrd, lifting slightly to the N/E, the sfc low will follow suit. W/ a strong sfc pres grad in place, Srly sfc winds of 10-15 kts in conjunction w/ low-lvl winds of 40-50 kts b/w H925 and H850 will continue to support a rapid poleward flux of low- lvl moisture resulting in a narrow plume of Td`s in excess of 55F that will extend into the S/Wrn portion of the state by 00Z Wed. ...Tonight... Through Tues evening, strong WAA and moisture transport in conjunction w/ increasing DCVA from the approaching trof will continue to drive scattered showers over the Wrn half of the state ahead of the advancing cold front. CAM guidance continues to suggest messy storm modes, with the potential for semi-discrete cells early on before storm interactions take over and a transition to a linear QLCS occurs. Per the last few synoptic HRRR runs, CI and discrete cells are possible in the warm sector around 00Z this evening near the OK/AR border region, and the following hour to hour runs have remained consistent on this possibility. Following CI, in which storms may be sfc based initially, cooling of the bndry layer will quickly act to stabilize the downstream environment and the persistence of discrete storms comes into question. The development of a strong LLJ w/ 40-50 kt Srly winds as low as H925 may aid in fueling discrete storm maintenance, particularly through elongated hodographs...hi-res guidance is progging a large swath of 0-3 km SRH exceeding 300 m2/s2, however the effective inflow quantities remain questionable given the uncertainty of parcel origins...and increasing low-lvl wind shear...well in excess of 35-40 kts through 0-3 km. Sample fcst soundings around the region following CI certainly show potential for sfc based storms initially, however by 03Z, diurnal stabilization is evident at the sfc, and buoyancy profiles become more elevated in nature. Main takeaway here...if storms develop and stay semi-discrete, while also staying based at the sfc as they progress Ewrd (the biggest condition to be met), all svr wx hazards may be possible...including brief tornadic storms progress through the night. By 06-07Z Wed, the sfc low is expected to be located over the KS/MO border region, and a tailing cold frnt will begin to enter the state from the W. As the frnt encounters the remaining bndry layer moisture, another round of storms is expected to develop along the frnt. The progressive upper trof will keep the frnt movement swift, and the bndry will lkly be through the state by sunrise Wed morning. Storms along the FROPA could become strong and severe at times, w/ damaging winds being the primary svr hazard. ...Wed through Thurs... For the remainder of the short term, a brief period of settled wx will ensue as drier air is flushed in behind the FROPA from Tues night. Through the day Wed, strong winds of 10-15 kts will prevail from the W with gusts up to 20 kts possible, particularly over Ern AR Wed evening. Thanksgiving day will yield a more tranquil pattern as sfc high pressure settles over the fcst area and winds become Srly again. Afternoon temps will remain seasonal w/ morning lows in the upper 30s Wed and mid 40s Thurs. && .LONG TERM...Friday Through Tuesday It`s complicated. Zonal flow aloft will be in place late week with a potent mid-level trough closing off across the Four Corners region by Friday evening. Concurrently, a strong surface ridge will translate across the central Plains and into the Ohio Valley by Sunday. The resulting low- level flow pattern will keep the richest moisture and bulk of warm air advection to our south through the first part of the weekend, although some rain and thunder will be possible over the southern half of the area Friday and Saturday as the Four Corners cyclone approaches and synoptic forcing for ascent increases. Temps will remain above average Friday immediately ahead of the surface ridge with more seasonable temps through the weekend. Saturday into Sunday, the aforementioned closed upper cyclone will dig into the Red River Valley with surface cyclogenesis most favored to our south, potentially as far south as the Gulf Coast. While notable model discrepancies persist, successive model runs continue suggesting a southerly storm track with widespread rain in the Saturday night through Sunday night time frame. Minimal if any instability will be present, so did not include thunder with this activity. Confidence drops dramatically concerning the relative timing of departing moisture to incoming cold air as the system exits late Sunday into Monday. Did retain a small window of snow potential late Sunday night into the pre-dawn hours Monday morning, but again, confidence is very low attm. At most a few flakes may fly over northwestern and northern sections of the state, but significant impacts do not appear likely. The southern upper cyclone will phase with a large and progressive northern stream trough early next week with precip quickly ending over our area, save for isolated rain over far southeast AR, on Monday. Winds and cold air advection will be strong in the wake of this system with well below average temps likely late in the period. Highs Monday and Tuesday may not breach 50 degrees with widespread readings in the 20s by Tuesday morning. If you haven`t pulled out the wool socks and such yet, now may be the time... && .PRELIMINARY POINT TEMPS/POPS... Batesville AR 52 63 39 61 / 90 20 0 0 Camden AR 55 68 37 67 / 80 30 0 0 Harrison AR 44 54 35 61 / 90 10 0 0 Hot Springs AR 51 64 37 63 / 80 10 0 0 Little Rock AR 55 64 39 62 / 80 30 0 0 Monticello AR 60 69 41 65 / 80 50 0 0 Mount Ida AR 48 62 34 63 / 90 10 0 0 Mountain Home AR 47 58 35 61 / 90 10 0 0 Newport AR 53 66 41 60 / 90 30 0 0 Pine Bluff AR 56 68 39 64 / 80 40 0 0 Russellville AR 47 60 35 63 / 90 10 0 0 Searcy AR 51 65 36 62 / 90 30 0 0 Stuttgart AR 57 69 40 64 / 90 40 0 0 && .LZK Watches/Warnings/Advisories...NONE. && $$ Short Term...GREEN / Long Term...COOPER
Area Forecast Discussion
National Weather Service Memphis TN
921 PM CST Tue Nov 24 2020 .UPDATE... We have expanded the area of the Wind Advisory this evening to include all of west TN and more of northern MS through noon Wednesday. Current forecast looks to be on track with winds increasing over the next few hours. Strong to severe storms will be possible tonight as the Storms Prediction Center maintains a Marginal Risk of severe weather tonight going into Wednesday. Strong winds will be the main threat, but the tornado threat is also non zero so we can`t rule out that as a threat overnight as the main line pushes through. && .PREV DISCUSSION... /issued 555 PM CST Tue Nov 24 2020/ UPDATE... Updated to include 00Z Aviation Discussion. PREV DISCUSSION... /issued 308 PM CST Tue Nov 24 2020/ DISCUSSION... Breezy night ahead, with temperatures steady or slowly climbing. Showers and thunderstorms on track to arrive during the pre-dawn hours west of the MS River, one or two storms could reach severe limits they track east through the morning. Midafternoon GOES water vapor imagery showed a closed upper low centered over northeast NM/western TX panhandle. This low will lift to the Kansas City area by sunrise Wednesday. An attendant 50 to 70 kt low level jet will precede the upper low through east AR and lower Ohio River valleys overnight, under diffluent flow aloft. This low level jet will provide a steady supply of moist, marginally unstable air, ahead of a surface cold front over western AR. Showers and thunderstorms will root in this elevated layer, and likely organize along a couple of elevated boundaries oriented SSW to NNE, parallel to the midlevel flow. These one or more broken convective lines will likely consolidate over east AR, as a midlevel speed max/dry slot rounds the base of the upper low toward sunrise. This broken line of showers and storms will lift east of the MS River after 8 AM. Any storms that develop bowing structures will present a damaging wind threat, given the strong environmental wind fields in which they`re embedded. HRRR surface wind potential prog depicts a 40 to 50 kt gradient wind gust potential outside of storms. The bulk of the this stronger wind will remain aloft, but the potential is there, given the surface pressure gradient. A wind advisory has been issued from 10 pm through noon Wednesday for the delta and most of west TN. Limiting factors for a more robust severe weather event tonight include limited chances that storms become rooted in the boundary layer, where directional shear would support more organized storm structures and perhaps mini-supercells. By the time the convective line lifts east of Memphis midmorning Wednesday, the potential for near-surface rooted storms will increase. But by this time, wind fields and low level convergent zones will have weakened, as the midlevel jet max exits to the northeast. Midlevel lapse rates will support a marginal threat for large hail with any isolated storm that remains through midday, along with the gradually decreasing wind threat. To the west, the surface cold front will finally arrive, bringing drier and cooler conditions, as it sweeps across the Midsouth mid/late Wednesday afternoon. Fair and mild weather remain on track for Thanksgiving Day, under south-southwest flow aloft. Today`s 12Z medium range models showed better agreement with the weekend periods. The subtropical jet and stalled frontal boundary will focus ran chances along the gulf coast early Friday, though a weak shortwave may bring some showers into north MS Friday afternoon. Midsouth rain chances increase by early Sunday, ahead of a closed low dropping southeast into the Arklatex. This upper low will kick out Sunday night, just as a high amplitude trof digs almost through the MS River valley. The ECMWF model maintains sufficient wrap-around moisture to support snow showers Monday over west TN Monday morning. The GFS model is dry early Monday, but concurs with the ECMWF`s cold thermal profiles: 850mb temps of -11C and 1000-500mb thickness around 525 dm. Perhaps a brief taste of winter, but too early to be certain at this point. PWB AVIATION... 00Z TAF cycle VFR conditions will be prevalent this evening. However, conditions will deteriorate to MVFR conditions late tonight towards sunrise on Wednesday as showers and thunderstorms approach and move through the area. At this time, the best potential for VCTS appears to be between 06-09Z at JBR, 11-13Z at MEM/MKL, and 12-16Z at TUP. LLWS expected to begin around 03Z at JBR/MEM and spread east to MKL/TUP overnight. The best sustained winds/wind gusts are expected towards and just after sunrise. CJC && .MEG WATCHES/WARNINGS/ADVISORIES... AR...Wind Advisory until noon CST Wednesday for Clay-Craighead- Crittenden-Cross-Greene-Lee AR-Mississippi-Phillips- Poinsett-St. Francis. MO...Wind Advisory until noon CST Wednesday for Dunklin-Pemiscot. MS...Wind Advisory until noon CST Wednesday for Alcorn-Benton MS- Coahoma-DeSoto-Marshall-Panola-Quitman-Tallahatchie-Tate- Tippah-Tunica. TN...Wind Advisory until noon CST Wednesday for Benton TN-Carroll- Chester-Crockett-Decatur-Dyer-Fayette-Gibson-Hardeman- Hardin-Haywood-Henderson-Henry-Lake-Lauderdale-Madison- McNairy-Obion-Shelby-Tipton-Weakley. && $$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
838 PM CST Tue Nov 24 2020 .UPDATE... Issued at 838 PM CST Tue Nov 24 2020 In the end, continued degredation of visibilities along the bubble ridge axis has pushed us to issuing a dense fog advisory for the eastern half or so of our MN forecast area and a row of counties in WI. There are westerly winds pushing east from western MN that have been improving visibilities quite rapidly as the slowly push east, so this advisory will be slowly getting eaten away from the west through the night. In addition, the HRRR and GLAMP show fog filling in from basically Eau Claire to Green Bay, so this may need to be expanded to the east as well. For now, highlighted areas that were in/near the worst conditions at 830 pm and we`ll go from there. && .SHORT TERM...(This evening through Wednesday night) Issued at 155 PM CST Tue Nov 24 2020 Visible satellite imagery shows extensive cloud cover across the region this afternoon. Low pressure located over the southern Plains will slowly lift northeast through the period, with minimal advection or change in airmass across our area as we see only some weak surface ridging move in from the west on Wednesday. This will work to keep plenty of low level moisture and stratus in place across the forecast area. Some improvement will be seen over the west on Wednesday, but most of the area will need to wait until Wednesday night and Thursday for significant clearing. In terms of precipitation, steady rain (mixed with some snow at times this afternoon) will be confined to the far south/southeast portion of the area, closer to the main baroclinic zone and forcing. Drizzle will linger over much of the rest of the area into tonight, and could persist into Wednesday morning (although remained somewhat optimistic for now and only mentioned it through this evening). Patchy freezing drizzle will occur where surface temperatures are near/below freezing, but that should mainly be north of I-94. .LONG TERM...(Thursday through Tuesday) Issued at 155 PM CST Tue Nov 24 2020 No major weather systems are expected in the extended period, or between late this week, and into the early part of next week. A split flow regime will dominate North America with the southern jet stream the most active. Although models continue to support some type of large scale storm system for the eastern of the CONUS, the main impact for our region will be brisk winds and cooler conditions. Even the most western extent of this system will only bring the gusty winds with the bulk of the precipitation across the Great Lakes, and east coast. I cant rule out a few flurries during the onset of the colder air mass late in the weekend, and into early next week, but the lack of deep moisture should preclude anything significant unless the system moves farther to the west. As with most split flow regimes, models dont usually have a good handle on timing and strength of synoptic scale systems. However, based on the strength and consistency of a large scale storm over the eastern of the CONUS, it would be wise to monitor for any changes to the path of this storm and whether it takes a track farther to the west than currently expected. Temperatures will again be problematic due to the storm system in question. But, the persistent quasi-zonal flow out in the west and the main northern jet still mostly in Canada, I would expect to be near or above normal this weekend, and into the first week of December. Typically, temperatures fall quite a bit during this time period with highs dropping into the 20s, and lows in the teens. Currently, the forecast is for highs in the 30s and 40s, with overnight lows in the teens and 20s. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 530 PM CST Tue Nov 24 2020 Main concern is significant degradation in conditions along a baggy pressure trough that we are seeing over central MN. Within this zone of weak flow, expect vis down between 1/4sm and 2sm with cigs under 500 feet. Not expecting much improvement in conditions until light northwest winds become established. We`ll remain within a zone of weak flow through much of the night, so confidence is low in how long these low conditions will linger, though it could be longer than we currently have. For clearing of clouds Wednesday, it`s going to take some time with the light flow in place. We may see some clearing in western MN Tuesday afternoon, but it may not be until Thursday until more substantial clearing occurs across the entire area. KMSP...Given observation trends to the west, dropped cigs/vis at 2z when the baggy trough moves across the Twin Cities. Not out of the question we could see vis down to 1/2sm at MSP overnight. Clearing could happen as early as 19z Wednesday at MSP, though this time of year, it`s usually safer to err on the side of stratus, so that`s what we have done for now. /OUTLOOK FOR KMSP/ Thu...VFR. Wind W 5-10 kts. Fri...VFR. Wind W 5-10 kts. Sat...VFR. Wind SW 5-10 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...Dense Fog Advisory until 8 AM CST Wednesday for Anoka-Benton-Blue Earth-Carver-Chisago-Dakota-Freeborn-Goodhue-Hennepin-Isanti- Kanabec-Le Sueur-McLeod-Meeker-Mille Lacs-Morrison-Nicollet- Ramsey-Rice-Scott-Sherburne-Sibley-Stearns-Steele-Waseca- Washington-Wright. WI...Dense Fog Advisory until 8 AM CST Wednesday for Pepin-Pierce-Polk- St. Croix. && $$ UPDATE...MPG SHORT TERM... LONG TERM...JLT AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
633 PM EST Tue Nov 24 2020 .SHORT TERM...(This evening through Wednesday) Issued at 253 PM EST TUE NOV 24 2020 RAP analysis and GOES water vapor imagery highlight a duel stream/split flow trough axis emanating southward from northern Manitoba. Within this pattern, two main shortwaves have been the focus through the day and will continue to do so through the short term period. The first is a weak mid-level low/shortwave over Manitoba extending southward into the eastern Dakotas. The second, and more vigorous shortwave is currently over the Central Plains. Water vapor imagery highlight nicely the extent of the cloud shield with this southern wave covering most of the Central CONUS. Over Upper Michigan, desipte the widespread radar returns, very little precip has been observed. This indicates the column is taking its sweet time saturating down and helping us miss out on some much desired snow! Some places have recieved some light snow this afternoon, such as our office and KSAW. Through the remainder of the day, the weak shortwave to the west pushes east while the shortwave over the Plains pinches off a closed low and slowly begins its migration toward the northeast, prattling WAA/isentropic lift into the region resulting in continued precip over the region. Overall, wetbulb zero heights and model soundings suggest mostly snow before transitioning over to light rain. QPF amounts look to be light, generally less than 0.20" with the most expected over the south and east. With snow ratios less than 10:1, a wet ~1" or less of snow is expected, mainly away across the central UP and isolated places in the east this evening. As the shortwave to the north helps push much of this out of the way, increasing subsidence late this evening should result in a melioration toward drizzle and then to some patchy fog. With temps expected to hover close to freezing through much of the evening and then cooling some overnight, some freezing fog will be possible. On Wednesday, with high pressure settling over the area atop the trapped low level moisture, expecting a mostly cloudy day. High temps should rebound to near 40F. .LONG TERM...(Wednesday night through Tuesday) Issued at 435 PM EST TUE NOV 24 2020 A shortwave trough will pass to our south Wednesday night into Thursday. Limited forcing aloft should prevent precipitation, but low level saturation lingers in the area through Thursday morning. As a result, low level cloud cover is expected to be widespread and patchy fog or drizzle may occur. There is a possibility of visibilities below 1 mile, but left that out of the grids for now. Lower levels are expected to dry out during the day on Thursday ending the threat for visibility restrictions. A weak cold front is expected to move through Thursday night, bringing a drier air mass and shortwave ridging into the area for Friday and Saturday. This should result in primarily dry weather, but 850mb temperatures decreasing to around -5C may instigate some isolated or weak lake effect snow for westerly belts. Additionally, winds are expected to increase across Lake Superior on Saturday with gusts perhaps approaching gale force near the tip of the Keweenaw. Grids were nudged in that direction accordingly. The next weather system of note is expected on Sunday into Monday, but uncertainty remains high. Northern and southern stream energies are expected to phase across the eastern U.S. during this time frame. Deterministic models have trended toward a slower phase that results in a storm track well to the south of our CWA. However, most operational guidance indicates a deep closed low forming across the eastern U.S. by Monday afternoon before tracking northeast toward Quebec. Deep northerly flow behind this low results in strong cold air advection starting Sunday night. Spread in NBM temperature guidance decreases substantially to between 5-7F on Sunday night through Monday night indicating below average temperatures are likely on Monday. Additionally, NBM guidance indicates several inches of lake effect snow from Sunday night into Tuesday. Deterministic guidance indicates delta Ts could exceed 20C suggesting a potentially signicant period of lake effect snow. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 632 PM EST TUE NOV 24 2020 LIFR ceilings will be the them through most of the TAF period with only minor improvement expected through the day on Wednesday. Intermittent light snow this evening will diminish around midnight. At KCMX and KIWD...ceilings will lower into the IFR range overnight and remain there through most of Wednesday. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 253 PM EST TUE NOV 24 2020 A slow moving low will continue migrating northeast toward the Great Lakes tonight and tomorrow. As it does, southerly winds along the eastern half of the lake could approach 30kts while winds on the western half should remain at or near 20-25kts. As the low lifts, winds will become northwest and conditions will improve to below 20kts across the lake by Wednesday. A weak cold front moving through the lake on Thursday could be preceded by 20-25kt southwesterly winds west of the Keweenaw Peninsula. Otherwise, winds should be around 20kts or less through the week. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JP LONG TERM...- None - AVIATION...MZ MARINE...JP
Area Forecast Discussion
National Weather Service San Francisco Bay Area
559 PM PST Tue Nov 24 2020 .SYNOPSIS...A cold front will sink through the region tomorrow with a slight chance of rain for North Bay Counties. Cold air will slide in behind the front causing overnight lows to drop into the mid 20s to mid 30s. In addition, winds behind the front will increase from out of the Northeast. Along the beaches a long period swell will be impacting shorelines with large breaking surf. Otherwise the Bay Area will remain dry for the next 7 to 10 days. && of 04:16 PM PST Tuesday...Afternoon satellite shows clear skies over the Bay Area and Monterey Bay region. However, skies will cloud over tomorrow as a front approaches the region. While this front will mainly pass dry, this forecast package has introduced a slight chance of rain for portions of North Bay Counties. Any amounts that fall will be limited at best. Behind the front, there will be a short period of possible post frontal showers for North Bay. Otherwise clearing will take place as cold air filters into the region. The cold air mass will really take hold Thanksgiving night through the first part of the weekend before modifying. The main areas of concern are non coastal east-west oriented valleys where the cold air can sink in and remain until a solid air mass change can come mix it out. The other concern is the threat of offshore winds around Thanksgiving. 925 mb winds are showing in the 30-40 kt range which means we could see wind gusts in the hills into the 50 mph range. This by no means is high confidence, but something we need to watch over the next few model runs. In addition, the offshore flow will bring in very dry air by Friday, bringing RH values below 30% in a lot of areas with some dipping into the teens. While fire weather concerns are not high, we are seeing a return of drying trend in the fuels. So far, the rains from a couple weeks back are holding us in a good position. Beyond the weekend look for continued dry conditions right into December. Main changes to the ongoing forecast: introduced slight chance of rain to the forecast for North Bay on Wednesday. Lowered temps by a few degrees from Tday into the weekend. Stay safe everyone! && .AVIATION...As of 5:59 PM PST Tuesday...For the 00z TAFs. It`s VFR except for patchy fog and low clouds /VLIFR-MVFR/ on the coastline. A cold front off the Pacific Northwest is moving southeast 30-35 mph and will move over the forecast area late tonight and early Wednesday morning. Pre-frontal conditions are drier per lower dew point temp trends and the 00z Oakland sounding`s precipitable water value at 0.45". Nonetheless, still expect surface winds converging along the cold front increasing areal coverage of VLIFR-MVFR conditions through the evening, possibly generating spotty light rain tonight to isolated showers in the post frontal air mass Wednesday. Guidance doesn`t show gusty winds tonight or Wednesday, however given the coupling of mid-lower level dynamics, moderate speed and slope of the incoming front winds may briefly pick up to around 25 or 30 mph with frontal passage. Lower level winds will be gusty over the coastal waters with gusty winds overlapping Sonoma, Marin, possibly San Francisco and San Mateo Counties tonight; will see what the 00z WRF model output shows, may need to amend KSTS to include low level wind shear tonight/Wednesday morning. RAP model output also showing potential low level wind shear vicinity KSFO by 16z-17z Wednesday prior to returning diurnal vertical mixing. Drier conditions Wednesday for VFR at the terminals. Vicinity of KSFO...VFR, west to northwest wind 15 knots decreasing to 10 knots late tonight and Wednesday morning. The 18z NAM output shows spotty light rain/drizzle tonight/Wednesday morning KSFO to KOAK to KSJC. Surface winds may briefly become gusty to around 25 mph with frontal passage tonight without a lower level temperature inversion in place. Momentum transfer of gusty NW winds aloft can reach the surface more easily without an inversion and when moderate or strong mid level dynamics accompany a front. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR except KWVI reports 1/4 mile in fog. Expect a mix of VFR with patchy VLIFR-IFR in fog and low clouds on the coastline increasing in coverage and advancing inland tonight. Mixing will lift ceilings and visibilities to MVFR-VFR much later tonight and Wednesday morning with spotty light rain/drizzle possible. VFR forecast Wednesday afternoon and evening. && of 02:31 PM PST Tuesday...Winds out of the northwest prevail with occasional gusts. A front moving over the waters will provide a slight chance for showers, mainly over the northern waters, early Wednesday morning. This front will have increasing winds Tuesday night and into Wednesday morning with stronger gusts, generating steep fresh swell that may be hazardous for small craft vessels. These winds are expected to continue through Thanksgiving. A large long period swell train will arrive between early Wednesday morning and taper off by Friday. Large surf is expected midday Wednesday into midday Thursday and may lead to additional hazards for small craft vessels. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Pt Reyes to Pigeon Pt 0-10 nm from 3 AM SCA...Pigeon Pt to Pt Pinos 0-10 nm from 3 AM SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 3 AM SCA...Pt Arena to Pigeon Pt 10-60 nm from 9 PM SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm && $$ PUBLIC FORECAST: BFG AVIATION: Canepa MARINE: DK Visit us at Follow us on Facebook, Twitter, and YouTube at:
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 300 PM CST Tue Nov 24 2020 The main forecast concerns are precipitation type and amount for the tonight and Wednesday morning periods. Upper air charts from 12Z this morning had the following features of interest. At 300 mb there was a jetstreak of around 100 knots punching northeast from the TX panhandle at strongest 12 hour height falls at that level were around 230 meters at KABQ. At 500 mb height falls were around 100 meters, with the center also near KABQ. At 12Z there probably was not a closed mid tropospheric circulation center, but there appeared to be one as of mid afternoon near the OK panhandle. Mid afternoon surface analysis showed a cold front stretching from MN southward across western IA, far southeast NE and then southwest from there across KS. Our area at 3 pm was kind of between areas of stronger lift. Another area of forcing should bring heavier precipitation back into southeast NE, southwest IA and possibly east central NE later this afternoon, this evening and into tonight. Heaviest amounts should be south of our area though. Some models show elevated frontogenesis below 700 mb and some recent RUC model soundings had some mid level instability. Could possibly see a mix of rain, sleet, snow or small graupel in any isolated thunderstorms that develop. Surprisingly, there is still a fair amount of difference in the model QPF numbers tonight, but at least the 12Z NAM now has much lower values tonight compared to its 12Z run. With the closed low expected to track to just southeast of Kansas City by daybreak Wednesday and then into IL Wednesday afternoon, we will see some some impacts (probably minor) from the northwest edge of the deformation zone. Right now, it should be mostly rain or a rain/snow mix. Confidence on snow amounts is low to moderate. Some minor accumulations appear possible, with a low - but not zero - probability of amounts over an inch. Forecast soundings are right on the edge between a change from rain to snow - and any stronger periods of lift after midnight would favor snow. Light precipitation, possibly drizzle or freezing drizzle, could linger past daybreak Wednesday but should be ending by 9 to 10 am in southwest IA. Then look for dry weather and decreasing clouds from west to east the rest of the day. Highs should only reach back into the lower and mid 40s, with north or northwest winds. Thursday into Tuesday... This period is expected to be mainly dry, with a few disturbances moving through the region. Temperatures should moderate from Thursday to Saturday, reaching into the 50s by Saturday. There will be a cold front pushing through the region Saturday night that could possibly cause a bit of light rain or light snow for southern parts of the area. The 12Z ECMWF is a little more supportive for that, compared to the GFS. The GFS seemed too far south, having no precipitation into KS or MO. Model differences start to increase by Monday and Tuesday, with fairly large variance by Wednesday. We will stay pretty close to the NBM (National Blend of Models) solution from the weekend into early next week, which keeps temperatures cooler than normal Sunday into Tuesday. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 522 PM CST Tue Nov 24 2020 VFR conditions have built in at KOFK, but LIFR and IFR conditions will persist longer at KOMA and KLNK with cigs as low as FL003. VFR conditions will hold off until about 15Z at KLNK and 21Z at KOMA. Stronger northerly winds anticipated overnight. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Miller AVIATION...Nicolaisen
Area Forecast Discussion
National Weather Service Nashville TN
852 PM CST Tue Nov 24 2020 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Cool but windy evening across Middle Tennessee with current temperatures in the upper 40s and 50s. Temps will remain steady or slowly rise overnight thanks to continued WAA. South winds are already gusting up to 30 mph in some areas, and guidance indicates 925mb winds will strengthen further overnight and reach up to 50-60 kts by 12Z as an area of low pressure in the Plains moves into the Midwest. Based on this, have opted to issue a wind advisory for the entire area overnight through midday tomorrow. Once precip moves in from the west tomorrow morning, this may act to strengthen the low level inversion some and thus lower the surface winds, but LLJ will remain quite strong through early afternoon. Severe weather threat for tomorrow remains very conditional and uncertain due to the anticipated morning rain/storms. Some models such as the HRRR continue to move the morning activity out quickly, with showers and storms redeveloping along a narrow instability axis just ahead of the main cold front Wednesday afternoon. Other models show little additional activity after the morning round. If storms are able to develop along the front like the HRRR suggests, a perusal of forecast soundings show a narrow window available of just enough instability (MLCAPE 250-500 J/Kg) in the presence of strong low level wind shear (0-1km SRH of 200-400 m2/s2) for a few severe storms. Main threat would be damaging winds, but a tornado cannot be ruled out with such strong low level shear. A reasonable alternative scenario is that storms are not able to redevelop tomorrow afternoon due to the limited instability, and no strong or severe weather occurs. Adjusted pops based on latest timing of guidance, but no significant changes were made. && .AVIATION... 00Z TAF DISCUSSION. Southerly winds will slowly increase overnight, gusting 20-25 kts or higher by 12z. LLWS will pick up after 00z but primarily after 03z as a 850mb jet strengthens. A strong front will bring SHRA and perhaps a few TS to the terminals late morning thru the afternoon. Timing and development of activity remains uncertain, so leaned toward an earlier arrival of RA/TS. Future TAFs will address this with more certainty. LLWS will conclude around 18z for much of the Mid State, though surface winds could still be gusting 20-25 kts thru 00z Thu. && .OHX WATCHES/WARNINGS/ADVISORIES... Wind Advisory from 3 AM to noon CST Wednesday for Bedford-Cannon- Cheatham-Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson- Fentress-Giles-Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence- Lewis-Macon-Marshall-Maury-Montgomery-Overton-Perry-Pickett- Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-Trousdale-Van Buren-Warren-Wayne-White-Williamson-Wilson. && $$ DISCUSSION......Shamburger AVIATION........Schaper
Area Forecast Discussion
National Weather Service Norman OK
530 PM CST Tue Nov 24 2020 ...New AVIATION... .SHORT TERM... (This evening through Wednesday) Issued at 208 PM CST Tue Nov 24 2020 A complex and rapidly evolving situation is expected today as 1) a dryline mixes eastward into our southwest counties, 2) cold front moves into northwest Oklahoma, 3) Pacific front moves eastward. Both fire weather conditions and severe convection are near term concerns. All this is spawn from progressive closed low now that is now seen clearly in water vapor channel imagery moving into the Texas Panhandle. Latest surface observations show eastward mixing dryline encroaching on our Texas counties. A rapid drop in RH will result, along with momentum transfer with deep mixing supporting at least a brief period of elevated to near-critical fire weather conditions generally southeast of a Sayre to Fredrick to Archer City line through late afternoon. The next concern today is intensifying convection along/near the southeastward moving cold front now across the Panhandles. As strong DPVA/forcing pushes Pacific front eastward, merging with the dryline, convection should tend to consolidate into linear segments and move east. There may be a brief window for quasi-discrete mode in a small corridor ahead of the aforementioned forcing. This is supported by some of the CAM guidance. Although temperatures are not particularly warm and generally cooler that typically seen with severe events, midlevel temperatures are quite cold yielding short but sufficiently broad CAPE profiles for low-top/mini supercells, with a hail threat. Thermal profiles hint at a tendency for larger quantities of smaller hail, particularly if storm cores are numerous and interacting. This could mitigate concerns of significant hail sizes, though isolated 2+ inch sizes cannot be ruled out. Fortunately, the core of the low-level jet will be displaced to the east with latest RAP model data showing more modest low level shear limiting the tornado concerns in northwest Oklahoma. We`ll still need to watch trends closely, however. Keep in mind that with this thermodynamic profile we`ll need to downscale our conceptual model some, with high reflectivity cores not reaching as high and mesocyclones that are smaller/weaker potentially of more concern. Later evolution should be strongly forced within an environment that`s otherwise capped. With overall modest instability and convective vigor not overly impressive, RIJ/surges probably won`t be that substantial and should limit the QLCS tornado threat with eastward extent. Strong flow aloft and momentum transfer should still yield a few severe wind gusts. Southward extent is in question, but at least isolated convection may occur in southern Oklahoma. Later in the night, TROWAL and associated midlevel moistening/ascent may result in a band of light rain traversing northern counties. Thermal profiles are close to supporting snow but currently appear to be all rain. We`ll need to monitor trends closely. Only light/brief precipitation amounts are expected. We increased post-frontal winds tonight through early tomorrow. BRB && .LONG TERM... (Wednesday night through next Monday) Issued at 208 PM CST Tue Nov 24 2020 A brief period of ridging and dry, mild weather will occur Wednesday and Thursday. With the next wave, the northern stream will outpace the southern stream component, leaving a NE/SW oriented shear axis that will traverse the area Friday night through Saturday. Precipitation should generally be relegated to the Texarkana region within deeper moisture and positive precipitable water anomalies. So, the most noticable effect will be from downslope/warm conditions Thursday to post-frontal northwesterly flow and cooler (but near normal) conditions Friday onward. A trend toward deeper more closed low on the southwest end of aforementioned trough has resulted in an increase in precipitation chances Friday night into Saturday as modest deep moisture return occurs. On the northern edge, thermal profiles could be briefly supportive of snow, although impacts are not currently expected. Continued warm advection should transition precipitation to all rain later Saturday. A southeast moving shortwave trough will pass Tuesday, but again a dry column doesn`t appear to support precipitation. Just beyond the forecast period, deterministic and ensemble guidance suggest a trend toward a broad blocking pattern with low predictability in a couple closed lows at our latitude. Details on sensible weather will be refined over the next several days. BRB && .AVIATION... (00Z TAFS) Issued at 529 PM CST Tue Nov 24 2020 Storms should be east of our TAF sites by 04Z, but scattered showers and low ceilings wrapped around the storm system will then move across northern Oklahoma from about 02Z to 09Z. Very low clouds and BR will precede a dryline and surface front, as the front overtakes the dryline, then sweeps rapidly east between 00Z and about 05-06Z, with generally improving conditions behind it. Gusty northwest winds will continue overnight and into tomorrow morning, then winds will diminish during the afternoon under a ridge of high pressure and clear skies. && .PRELIMINARY POINT TEMPS/POPS... Oklahoma City OK 39 57 38 68 / 50 0 0 0 Hobart OK 38 60 39 68 / 10 0 0 0 Wichita Falls TX 41 62 39 75 / 0 0 0 0 Gage OK 33 58 35 60 / 50 0 0 0 Ponca City OK 37 52 34 64 / 80 0 0 0 Durant OK 42 61 38 69 / 30 0 0 0 && .OUN WATCHES/WARNINGS/ADVISORIES... OK...None. TX...None. && $$ SHORT TERM...12 LONG TERM....12 AVIATION...23
Area Forecast Discussion
National Weather Service Topeka KS
932 PM CST Tue Nov 24 2020 .UPDATE... Issued at 932 PM CST Tue Nov 24 2020 The surface low is beginning to lift into east central KS with the upper level low just southeast of DDC. As the system continues to move east, cold air on the back side of the system is expected to change precip into a wintry mix or possibly all snow. Based on the latest HRRR/RAP/NAM, 850MB temps look to stay just above 0C implying that a wintry mix is more likely than a change to all snow. Forecast soundings from the RAP and HRRR only show minor accumulations of snow overnight, I think mainly because temps don`t cool off fast enough and by the time precip changes it soon comes to an end. The disconcerting thing though is the spread amount the models in snow amounts with SREF plums showing the potential for quite a bit more snow accumulations. With surface temps still holding in the mid and upper 30s upstream and soil temps in the middle 40s, think the higher snow amounts from the ensembles is a low probability outcome and plan to keep the forecast as is and monitor trends. && .UPDATE... Issued at 746 PM CST Tue Nov 24 2020 There is a concern for temps to cool enough for mixed precip or a change over to snow within the deformation band of precip tonight. This would likely impact parts of north central KS from Abilene and Minneapolis to Washington and Marysville. The latest HRRR and RAP forecast soundings at KCNK and KMHK show the column cooling with the warm nose falling off to around +0.5C to +1C. This would certainly support a wintry mix of precip developing generally after 10 PM tonight. And if models are off just a little and the cooling more robust, there could be a narrow band of snow develop. The question is will the rate of precip be high enough for accumulations since soil temps from the KState mesonet show the ground is still fairly warm with 2 and 4 inch soil temps in the middle 40s. Additionally the window for mixed precip or snow looks to be only a few hours before the forcing exits and the precip comes to an end. Will be monitoring trends this evening as confidence is marginal due to the warm ground temps. But it is not impossible for a narrow band of accumulating snow tonight. && .DISCUSSION... Issued at 232 PM CST Tue Nov 24 2020 Upper trough axis enters the Panhandle region this afternoon as broad mid to low level moisture advects northeast along and ahead of it. Temps today have remained steady, if not increased a few degrees given the insulated cloud cover and scattered showers in the area. Initial showers have been slow to materialize over northeast Kansas, likely attributing to the optimal lift associated with a lead upper wave focused over southeast Kansas. Latest radar scans in the past hour however, are showing enhanced echos building from southwest KS into portions of central KS. Expectations for this afternoon and evening are mostly the same in terms of rain showers expanding and spreading northeastward as the upper trough axis matures over southern Kansas. Latest forecast profilers are a bit more robust with the elevated instability from the HRRR, HREF, and RAP exhibiting up to 1000 J/KG of MUCAPE between 20Z and 06Z. Decent curvature seen on forecast hodographs suggest adequate bulk shear values to allow for an isolated severe storm to develop, especially along and south of I-35. Latest few runs from the HRRR would suggest a line of stronger storms to develop in southwest KS before reaching portions of east central KS during the early evening. Hail would be the primary hazard with any stronger storms. In addition to the stronger storm threat, also expanded the mention of general thunder further north, encompassing most of the forecast area from late afternoon through the evening. The cold front swiftly translates southeast across northeast Kansas overnight, bringing most of the precip to an end by Wednesday morning. Increased winds behind the front as both the RAP and HRRR are consistent with an impressive pressure gradient, resulting in wind gusts in upwards of 40 mph through Wednesday morning. Concern for accumulating snow is less than previous forecast given the overall short term models trending further south and east with the deformation zone axis, closer to areas where temps remain above freezing for a longer period. There is also some uncertainty on how quickly freezing temps reach the CWA as most of the short term guidance drops to freezing as precip is ending, with the exception of the NAM. Regardless, confidence is moderate for rain to transition to a light wintry mix within the deformation band that impacts central and portions of northeast KS before diminishing early Wed. morning. I am not expecting widespread impacts, but there is a possibility for a few slick spots during the AM commute with any accumulations being less than 1 inch. Gusty northwest winds sustain through early Wednesday afternoon as cloud cover diminishes from west to east. Persistent cold air advection limits highs to the middle 40s. Clear skies Wednesday night allows temps to drop into the upper 20s before weak southerly flow returns on Thanksgiving Day, boosting temps into the upper 50s under sunny skies and light winds. Extended forecast is overall dry and seasonable in terms of temps with highs ranging from the upper 40s to lower 50s Friday through Sunday. Mornings low are generally near 30 degrees. Maintained slight pops for the southern half of the CWA Saturday night and Sunday as a closed upper low tracks east over the southern plains. Latest runs exhibit a slight shift southward from the Canadian, closer to the GFS solution which would leave the area dry. 12Z ECMWF however maintains the upper low track bringing a light rain and snow mix to portions of the area. && .AVIATION...(For the 00Z TAFS through 00Z Thursday) Issued at 501 PM CST Tue Nov 24 2020 With the strongest forcing beginning to impact the area, think precip will become more widespread with CIGS falling below 1000 FT in spite of the current obs. There could be a brief period of mixed precip on the tail end Wednesday morning. This is forecast to come to an end by mid morning. However the MVFR CIGS are likely to stick around for much of the day for TOP and FOE with skies clearing sooner for MHK. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Wolters DISCUSSION...22 AVIATION...Wolters