Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/02/18

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
624 PM CST Sat Dec 1 2018 .UPDATE... Issued at 619 PM CST Sat Dec 1 2018 Made some adjustments to pops and snow totals based on current observations and latest hi-res model guidance. Inch an hour accumulation rates are occurring in southern Deuel county, so still may need to upgrade them to a warning. However, radar shows a gap in precip that will reach the area in another few hours. Will need to see if the wave of precip behind that makes it far enough west to really increase accumulation potential. All models except the RAP top out the area at 5 to 6 inches. The RAP is significantly higher at 7 to 10. Removed all counties from WSW except Lyman. Warning amounts only possible in the bootheel and the far southern edge of the county now. Kept Hand and Buffalo in an advisory though advisory amounts only look possible on the eastern or southeastern edges of Hand. && .SHORT TERM...(This Evening through Sunday) Issued at 254 PM CST Sat Dec 1 2018 A winter storm impacting the region over the next 12 to 24 hours will produce a challenging forecast. The biggest issue is snowfall amounts along the I90 corridor, and over our southeastern portion of the CWA. The CWA has seen little snowfall as of 20Z. Webcams and a few reports indicate light accumulating snowfall in the far western portion of Stanley and Jones County. Am very concerned the current winter storm warning for Buffalo, Lyman, and Jones County will not verify, with significantly less snowfall expected. The RAP models still suggests near winter storms level snowfall in extreme southern Lyman county, which maybe overdone when compared to the HRRR and 18Z NAM. Snowfall amounts in our far southeastern CWA, mainly Deuel county is also rather challenging. A narrow band of moderate to heavy snow is currently rotating northwest across southeastern SD and southern MN. The band should reach the CWA within the next few hours. With an upslope wind component, wouldn`t be surprised to see enhanced snowfall amounts. The RAP model has been very consistent with showing 8 plus inches occurring in Deuel Co, with 6 inches possible in parts of Grant, Codington, and Hamlin. The latest 18Z NAM is showing something similar. Did increase snowfall amounts for now, but will maintain the current winter weather advisory. Drier air pushing into the Missouri River will cause the loss of prob ice, resulting in a period of freezing drizzle. Low stratus and fog can be expected tonight through Sunday morning as well. The dry air should encompass the entire CWA before 18Z Sunday with no pcpn expected Sunday afternoon. .LONG TERM...(Sunday Night through Saturday) Issued at 254 PM CST Sat Dec 1 2018 A large area of high pressure is over the region when the period opens. The steering flow aloft becomes northwesterly early on, and the most notable short-wave (clipper system) working through this region in that pattern is progged for Wednesday/Wednesday night. For now, most of the precipitation-producing forcing/lift with the mid- week system is north/east of this CWA, but there is expected to be an uptick in northwest winds immediately behind the system heading into Wednesday night. Low level thermal progs and NAEFS table temp anomalies support below climo normal conditions for much of the period, with high temperatures in the 20s to perhaps low 30s Monday through Wednesday, but then things look to cool down Thursday through Saturday into the teens and 20s. && .AVIATION...(For the 00Z TAFS through 00Z Sunday Evening) Issued at 525 PM CST Sat Dec 1 2018 Mainly IFR conditions are expected through tonight with some improvement to MVFR Sunday morning. Snow will continue to rotate into KATY this evening and overnight before tapering off early Sunday morning. Gusty northerly winds will persist through the period. && .ABR WATCHES/WARNINGS/ADVISORIES... SD...Winter Weather Advisory until 6 AM CST Sunday for SDZ037-051. Winter Storm Warning until 6 AM CST Sunday for SDZ048. Winter Weather Advisory until 9 AM CST Sunday for SDZ020>023. MN...None. && $$ UPDATE...Wise SHORT TERM...SD LONG TERM...Dorn AVIATION...Wise
Area Forecast Discussion
National Weather Service Albany NY
837 PM EST Sat Dec 1 2018 .SYNOPSIS... Another wintry mixture of precipitation including snow, sleet and freezing rain, will occur tonight into Sunday morning. This wintry mix will gradually change over to plain rain through the morning hours Sunday eventually tapering off to rain showers during the afternoon. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... As of 837 PM EST...Large closed off storm system over the Great Plains will be heading towards the Upper Midwest and western Great Lakes for tonight into Sunday morning. Well ahead of this system, isentropic lift ahead of an approaching warm front will allow for a period of steady precipitation across our region, especially for the 2nd half of the overnight hours. Precip is finally starting to reach into the Catskills and mid-Hudson Valley and will continue to overspread the area southwest to northeast later through the evening hours. All areas should be seeing precip by around midnight. Temps have fallen this evening and most areas outside the immediate Hudson Valley are below freezing. With dry air at low levels, dewpoints remains in the 20s across much of the region, which would allow for some wet bulbing effects once precip begins, which may drop temps even further and its even possible temps briefly drop to the freezing mark even in the Albany area itself. Based off the 00z KALY sounding, there is a warm nose aloft around 800 hpa to about 1 C, but lots of dry air was also in place at that level. Wouldn`t be surprised to see precip briefly begin as snow or snow/sleet in many areas before transition to rain or freezing rain based of surface temps. With surface temps so close to freezing, have decided to expand Winter Weather Advisory to include Capital Region and northern parts of the mid Hudson Valley, as a period of mixed precip may make some surfaces slippery late this evening. The 23Z HRRR also agrees with the idea of a several hour period of snow/sleet before going over to rain/freezing rain by later tonight. Any accumulations of snow/sleet will be light mainly a 1/2 inch or less with closer to an inch across portions of the southern Adirondacks and southern Green Mountains. Ice accumulations through 6 am are expected to be around a tenth across the portions of the southern Adirondacks, eastern Catskills, southern Vermont into the northern Berkshires. While across the rest of the advisory area a trace to less than a tenth of an inch are expected. Still, this may make surface rather slick, especially untreated roads, bridges, overpasses, sidewalks, walkways, driveways, stairs, decks, patios, railings, etc. Temperatures will drop this evening with loss of heating as due to evaporative cooling with the onset of the precipitation. They are then expected to stabilize then rise overnight, with the only areas still below freezing by daybreak Sunday across the Adirondacks, southern VT and perhaps the northern Berkshires. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/... Winter Weather Advisory remains in effect for the southern Adirondacks, northern Berkshires and southern Vermont through the morning. By sunrise, freezing rain is expected to be limited to the remaining advisory area as surface temperatures struggle to warm with less than an tenth of an inch of additional ice accumulations expected. By noon, the threat for the freezing rain is expected to be over with the steady rain tapering off to showers during the afternoon from southwest to northeast across the local area. Temperatures are expected to rise into the upper 30s to upper 40s Sunday afternoon. The region will be between storm systems and with no influx of colder air it will be mild Sunday night with lows only in mid 30s to lower 40s. Chances for showers will decrease with mainly fair weather expected overnight except to northwest of the Capital District and across the higher terrain of southern Vermont into the northern Berkshires where lingering chances for showers will persist. Monday will be mild with temperatures expected to be about 10 degrees above normal in the upper 30s to lower 50s as we warm in southwesterly flow ahead of an approaching cold front. Expecting chances for showers mainly along an north of I-90. With the passage of the cold front a colder airmass will be ushered back in with lows Monday night expected to drop into the upper teens to around 30 degrees. Chances for snow showers are expected to linger due to cyclonic and upslope flow. && .LONG TERM /TUESDAY THROUGH SATURDAY/... The extended period begins with improved conditions as high pressure begins ridging into the eastern third of the country from the nation`s mid-section. A clipper system moving into the Great Lakes region and southern Quebec through Friday will result in increasing chances of mainly snow through the mid-week period as even high temperatures remain down in the mid 30s or lower each day. The fast- moving cold front associated with this system will result in a gradual improvement late in the week, but no drastically colder temperatures. Low temperatures will also be fairly consistent day- to-day as lows will be mostly in the mid teens to mid 20s range. The normal low temperatures at Albany in early December are in the mid 20s. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Flying conditions are currently VFR with increasing mid level clouds. However, steady precip is headed towards the area and should arrive across southern areas (KPOU, KPSF, KALB) by 03-04z and reaching KGFL by 06z. Initially, precip will be a mix of rain and sleet for KPOU/KALB and snow and sleet for KPSF/KGFL). There will a changeover to FZRA at KGFL/KPSF which will last through the rest of the overnight. Meanwhile, warming surface temps will allow KALB/KPOU to change to plain rain by 07z. Once precip begins, flying conditions will quickly lower down to IFR for both vsby/cigs and this looks to be in place for the rest of the overnight and into Sunday morning. Steady precip will end by mid to late morning on Sunday, but some showers will continue into the afternoon and the low-level moisture will be trapped in place. While visibility may improve somewhat, flying conditions look to mainly stay IFR due to low ceilings. There could be an improvement back to MVFR by late in the day, although this is rather uncertain. Light winds from an east to northeast direction are expected overnight and into Sunday morning. 2 kft winds will increase to 30-40 kts on Sunday morning from a southeast direction so have included some LLWS for all sites. Surface winds may wind up switching to the south to southeast on Sunday, but will remain rather light. Winds aloft will decrease by Sunday afternoon, as the best low-level jet shifts away from the area. Outlook... Sunday Night: Low Operational Impact. Slight Chance of SHRA. Monday: Moderate Operational Impact. Chance of SHRA. Monday Night: No Operational Impact. NO SIG WX. Tuesday: No Operational Impact. NO SIG WX. Tuesday Night: No Operational Impact. NO SIG WX. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. && .HYDROLOGY... Another widespread precipitation event will occur across the area tonight into Sunday. A wintry mix including snow, sleet and freezing rain will overspread the area this evening. This wintry mix will gradually change over to plain rain through the morning hours Sunday eventually tapering off to rain showers during the afternoon. QPF amounts of 1/2 to about an inch are expected. Flooding is not anticipated at this time. The NERFC river forecasts has only the following river forecast points reaching/exceeding action stage: Williamstown and Eagle Bridge on the Hoosic River. Limited snowmelt will over the higher terrain. It will turn colder this week with frozen precipitation then expected. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...Winter Weather Advisory until 6 AM EST Sunday for CTZ001. NY...Winter Weather Advisory until 6 AM EST Sunday for NYZ032- 038>041-043-047-048-051-054-058-061-063-083-084. Winter Weather Advisory until 4 AM EST Sunday for NYZ049-050- 052-053-059-060. Winter Weather Advisory until noon EST Sunday for NYZ033-042- 082. MA...Winter Weather Advisory until 6 AM EST Sunday for MAZ025. Winter Weather Advisory until noon EST Sunday for MAZ001. VT...Winter Weather Advisory until noon EST Sunday for VTZ013>015. && $$ SYNOPSIS...IAA NEAR TERM...IAA/Frugis SHORT TERM...IAA LONG TERM...ELH AVIATION...Frugis HYDROLOGY...IAA
Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
457 PM MST Sat Dec 1 2018 .SHORT TERM...(This evening through Sunday night) Issued at 230 PM MST Sat Dec 1 2018 Early afternoon water vapor imagery showed an intense mid/upper low centered over northeast KS surrounded by a large precipitation shield encompassing much of the Central Plains into eastern portions of the CWA. Radar, surface obs and webcams indicated the western edge of the snow from eastern Niobrara County WY to Kimball County NE. The steadier, periods of moderate snow were occurring over northern portions of the NE Panhandle. Snow tapered off over the Snowy and Sierra Madre Ranges as indicated by recent SNOTEL obs, and the Winter Weather Advisory was cancelled. Gusty northwest winds up to 35 mph will create areas of blowing snow and poor visibility across the high plains through late afternoon. Recent runs of the HRRR model prog a band of moderate snow to spread westward from the NE Panhandle into portions of east and southeast WY tonight. Snow accumulations of 2 to 4 inches are likely, mainly along the I-25 corridor north of Cheyenne. Snow amounts will taper off further east into the NE Panhandle. Following the WPC guidance for QPF and snow accumulations, lowered totals by 1 to 2 inches. Downgraded the Winter Storm Warning to a Winter Weather Advisory for Niobrara County. The Winter Storm Warning remains in effect through late Sunday morning for North Sioux, Dawes and Box Butte counties NE where four to seven inches are forecast. Two to five inches still on target for counties included in the Winter Weather Advisory. Periods of light snow will persist into Sunday evening west of I-25. Low temperatures tonight will range from the upper teens to mid 20s along and east of I-25 to the single digits to mid teens west of I-25. Lighter winds tonight will keep wind chills in the single digits and teens. High temperatures Sunday will range from the low 20s to low 30s. .LONG TERM...(Monday through Saturday) Issued at 230 PM MST Sat Dec 1 2018 The synoptic scale pattern next week will be dominated by a broad mid/upper trough from the northern Rockies to the eastern CONUS. An energetic northwest flow aloft will promote colder than normal temperatures (700mb temperatures 10 to 14C) and periodic snow showers associated with passing weak shortwaves. The medium range models suggest ridging aloft may put an end to the string of weekend winter weather systems, along with a modest temperature moderation. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 447 PM MST Sat Dec 1 2018 Aviation impacts remain confined to the NE Panhandle this afternoon and early evening with MVFR to IFR ceilings along with light to moderate snow at KCDR and KAIA. Snow coverage has reduced over the past several hours but a new snow band is likely to develop north of KCYS and into the NE Panhandle again this evening and overnight. Will need to monitor how close it comes to KCYS for additional amendments for direct SN mention in TAF. MVFR to LIFR conditions will persist in the NE Panhandle through mid- morning Sunday. Lower ceilings of MVFR to IFR will also likely spread west to KCYS and KLAR Sunday morning as well. Winds will decrease overnight and through Sunday to 10 knots or less. && .FIRE WEATHER... Issued at 326 AM MST Sat Dec 1 2018 No fire weather concerns. Widespread snow is expected over much of the high plains region this weekend, with an appreciable snow pack developing for some areas. Temperatures will trend colder over the next few days, with RH values well outside of critical thresholds. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Weather Advisory until noon MST Sunday for WYZ101-102-107- 108. NE...Winter Storm Warning until noon MST Sunday for NEZ002-003-095. Winter Weather Advisory until noon MST Sunday for NEZ019>021-055- 096. && $$ SHORT TERM...MAJ LONG TERM...MAJ AVIATION...JSA FIRE WEATHER...CLH
Area Forecast Discussion
National Weather Service Grand Rapids MI
1008 PM EST Sat Dec 1 2018 LATEST UPDATE... Update/Marine .SYNOPSIS... Issued at 241 PM EST Sat Dec 1 2018 Periodic rain with a rumble of thunder tonight and a few leftover showers on Sunday, then turning colder with some light snow for the Monday morning commute. Cold for the rest of the week with a clipper bringing some snow on Thursday. && .UPDATE... Issued at 1008 PM EST Sat Dec 1 2018 I made some minor changes to the going forecast, mostly the heaviest rainfall over the NW CWA. I also delayed the temperature rise over the central and northern CWA. Overall there seems to be less rainfall then was forecast by the models. I have trended down the QPF over all but the northwest CWA where it seems the most likely area to see the greatest rainfall. It seems to me the warm front occludes before reaching Grand Rapids which means our temperatures will not really rise much until the occluded front comes through here just before sunrise. There is marginal instability south of I-96 based on MU cape (500 to 750 j/kg). There is strong upper divergence over Eastern Wisconsin and Lake Michigan since that is where the upper jet crosses the low level jet. It is also the right exit region of the upper jet. It is for those reasons the heaviest rain will be over our NW CWA tonight. Actually there will be two bands of convection tonight, the first is lifting through the I-96 area now but the second area, assoicated with the front, will not reach this area until the early morning hours of Sunday. Expect some thunderstorms (mostly near and south of I-96) but there is a deep stable layer so I do not expect much of an issue with severe storms. && .DISCUSSION...(This evening through next Saturday) Issued at 241 PM EST Sat Dec 1 2018 Steady rain is currently pushing through this afternoon with scattered showers and isolated thunderstorms upstream across northern Illinois. HRRR and other hi res models show the bulk of that moving just west of Lower Michigan. We will maintain continuity with the previous forecast and include slight chance of thunder across most of the forecast area this evening. Instability is impressive with total totals in the upper 50s across the southern half of the forecast area. Bulk shear values are not excessive, generally in the 30 knot range and the storms across Illinois have not shown any organization this afternoon. Sfc low moves east Sunday night with colder air on the back side. It still looks like light snow Sunday night as sfc temperatures drop blo freezing so some icy roads could develop by the morning commute. Cold with light snow showers during Tue-Wed. Lake enhanced snow showers pick up on Thursday along with light synoptic snow as clipper moves through. This looks like a potentially widespread 1 to 3 or 2 to 4 inch snow event, followed by lake effect snow showers into the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 644 PM EST Sat Dec 1 2018 IFR conditions will more than likely prevail for all of our TAF sites into the early morning hours of Sunday. An isolated thunderstorm is possible through the night but the odds of it hitting any one taf site are to low to even put VCTS in the TAFs. While there will be showers around from time to time it seems from the Hi Res models it seems to me it will not be raining most of the time. It will be windy till around 06z, then the system gets closer to this area and winds will relaxed some. There will also be low level wind shear till around 06z too, due to the 35 to 45 knot low level jet will be overhead till then. Toward morning at the occluded front comes through I would expect most of our TAF sites to become briefly VFR as the low clouds break out and we should be between rain bands. There could be some fog but typically when this sort of front comes through any fog lifts and clouds break up. Once the cold air starts coming back in by late morning or early afternoon expect scattered rain showers and MVFR cigs. && .MARINE... Issued at 1008 PM EST Sat Dec 1 2018 I continued the Small Craft Advisory until 5 am, since it seems it will take longer for the gusty winds in the Near Shore area so decrease. The large waves will remain off shore due to the east to southeast winds. && .HYDROLOGY... Issued at 1250 PM EST Sat Dec 1 2018 Rainfall amounts ranging from one-half to three-quarters of an inch can be expected throughout the day today and into Sunday as a low pressure system approaches from the southwest. In addition, warmer temperatures in the 40s will help melt much of the snowpack by Monday morning. The combination of rainfall runoff and snowmelt throughout the weekend will lead to rises on nearly all streams and rivers around the area. No significant flooding is expected, however minor overflow is possible for some small to medium sized streams around the area. These areas would include low spots near Sycamore Creek, Looking Glass River, and the Maple River. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 5 AM EST Sunday for LMZ844>849. && $$ UPDATE...WDM SYNOPSIS...Ostuno DISCUSSION...Ostuno AVIATION...WDM HYDROLOGY...ANH MARINE...WDM
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
913 PM EST Sat Dec 1 2018 .SYNOPSIS... A strong low pressure system will remain to our northwest and continue to bring widespread precipitation to the region tonight and early tomorrow. A cold front will then move through the forecast area later tomorrow and stall to our south and east on Monday. Another cold front will arrive Tuesday and push our temperatures back below normal for midweek and beyond. && .NEAR TERM /THROUGH SUNDAY/... As of 900 PM: just did a quick update to the temp trends for the overnight to line up with obs and the latest CONSSHORT. So far, vsbys have been holding steady, if not improving, across most of the area. Plenty of convection across the Deep South seems to be robbing some of the moisture transport, and resulting in diminishing rain/shower coverage. The current PoP trends do show this decreasing trend. Will have to keep an eye on tstms over central TN, closer to the cold front. The last couple of HRRR runs show this activity dying before entering the NC mountains. As of 700 PM: Overall, the forecast looks on track. A stratiform rain shield was seen just exiting the eastern edge of the CWFA, while an area of showers and elevated tstms was affecting the western half of the area. An in-situ wedge is holding tough for now, and should preclude any severe tstms thru the evening. Temps are actually warming a tad around the edge of the wedge, especially from Greenwood to Charlotte. A non-diurnal temp trend will continue thru the night, as the wedge weakens. Still concerned about dense fog potential, but will hold off on any dense fog advisory until vsby come down. Isentropic lift will continue thru the overnight, and won`t totally shut off until tomorrow. MUCAPE is progged to increase over the next 12-15 hours, sufficient enough to mention thunder chances over much of the Piedmont. Heights aloft will fall as the upper trough associated with the Plains low replaces the ridge over the East Coast. Low-level flow veers to southwesterly and warm advection occurs down to the surface. The CAD wedge will become increasingly shallow and temps will begin to increase in a portion of our Piedmont zones as the wedge boundary retreats northward, warming as much as 10 degrees between sunset and sunrise. This warming trend will continue into the day Sunday when highs are expected to be near 70 across the lower elevations. Several guidance sources, including the majority of HREF members, depict SBCAPE creeping into our southeastern CWFA just before dawn, lingering through peak heating Sunday afternoon. Though the LLJ will have pushed north and east of the area by the time this occurs, 0-1 km and 0-3 km shear/helicity still will be strong enough not to ignore. SPC Day 1 outlook now includes a portion of our southern SC/GA counties in the Marginal Risk area for a 5% wind threat; the Day 2 maintains a Marginal Risk southeast of I-85 up through the southern Charlotte metro. Skies are expected to remain overcast over this area almost all day, and if there are any breaks earlier that could result in an uptick that would rapidly increase the severe threat. && .SHORT TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... As of 200 PM EST Saturday: The short term picks up Sunday evening, with maybe a little in the way of lingering pops in our southeast zones, but everything moving out as the strongly occluded front continues to push toward the coast. SW flow aloft will continue as the sharp very positively tilted upper trough works across the Great Lakes slowly. Will certainly see a decrease in temps behind the front, but with SW winds continuing into Monday with a lee trough remaining in place through the afternoon, temps will still be above seasonal normals (kind of nice for a change) by a handful of degrees or so. Winds will shift NW Monday night but lack of deep CAA will keep temps from dropping to normal just yet, hovering just above. A shortwave will push into the mountains Monday evening as the upper trough begins to fill, but with a sharp little cutoff digging down toward the southern Appalachians Tuesday afternoon and evening. This is when the CAA will begin in earnest, with highs Tuesday over 10 degrees colder than those on Monday and (back to) well below seasonal normals. Still a lot of difference in this system but confidence is high enough to continue slight to low chance pops across the mountains. Tuesday night, though, confidence in sensible weather impacts decreases. 12z GFS continues to indicate that some moisture in the NW flow regime as the shortwave moves through will be able to break containment, bringing some showery activity to the Piedmont overnight - and with lows just at or slightly above freezing, could not rule out some flurries or light snow showers. However, operational GFS is certainly an outlier as GEFS plumes not nearly as moist, and ECMWF has the shortwave much more open and a little farther north. Have capped Piedmont pops at 14% and a little too early to warrant mentioning sprinkles/flurries, but will have to continue to reevaluate model guidance in case a quick shot of light snow begins to look more plausible across the Piedmont Tuesday night. Maybe some lingering pops across the mountains at daybreak, but otherwise any moisture would be out of here before sunrise. Colder on Wednesday behind the front, and by this time over 10 degrees below seasonal normals on another cold and blustery day across the area. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... As of 205 PM Saturday: the extended fcst picks up at 00z on Thursday with very broad upper trofing across the Eastern CONUS and lower amplitude upper ridging over the Southwest CONUS. At the start of the period, an embedded upper shortwave will be moving off the Carolina Coast as the broader trof remains over the region. Over the next couple of days, the trof is expected to flatten to some degree as heights gradually rise in response. By the end of the period next Sat, the long-range models diverge quite a bit with the GFS keeping the upper ridge over the region, while the ECMWF brings another embedded upper shortwave to the fcst area. At the sfc, broad high pressure will be spreading across the region to start the period and is expected to linger thru Friday. As we move into Day 7 on Sat, things get more interesting. The models develop a low to our SW and move it towards the CWFA to end the period. The system is expected to still be to our SW at the end of the period, and it`s unclear at this point if there will enough cold air in place to produce much frozen precip outside of the higher terrain. For the time being, most of the snow is confined to the Northern Mtns for Sat. Temps will remain below climatology thru the period. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... At KCLT and elsewhere: LIFR TO IFR conditions at all sites tonight, as an in-situ cold air damming wedge holds on. Precip is becoming more showery in nature, and this along with continued strong southerly flow atop the wedge will allow the wedge to begin to weaken. Guidance generally agrees that as this happens overnight, cigs will lower to around 200 ft and vsby may crater to 1/4 to 1/2sm before daybreak Sunday, especially across the Piedmont sites. In addition to this, elevated convection crossing over the wedge may produce some occasional lightning strikes and variable winds/vsby/cigs. Tried to base mention of TS on the latest high-res guidance, especially the latest HRRR. A cold front will cross the area Sunday aftn, finally scouring out the low clouds and taking convection with it to the east. Winds are generally out of the S or SE to start the TAF, except for NE at the Upstate sites. Then winds will gradually veer as the wedge erodes and the cold front approaches to SW by around 13z, increasing to around 10-12 kts. Some low-end gusts will be possible during the daylight hours Sunday. Outlook: Conditions are expected to continue to improve into Monday. An upper level disturbance pushing through the region Tuesday will support breezy NW winds with showers possible across the mountains. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT High 98% High 86% Med 68% High 91% KGSP High 100% Med 66% Med 69% High 100% KAVL Med 70% Med 64% Low 55% High 100% KHKY Med 75% Med 73% Med 75% High 89% KGMU High 94% Med 69% Low 55% High 89% KAND High 82% Low 59% Low 47% High 91% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...JPT NEAR TERM...ARK/Wimberley SHORT TERM...TDP LONG TERM...JPT AVIATION...ARK
National Weather Service Jackson KY
1032 PM EST Sat Dec 1 2018 .UPDATE... Issued at 1032 PM EST SAT DEC 1 2018 Still watching the two lines of showers and storms. The first one has now shifted into far eastern Kentucky and will move across these areas over the next few hours before exiting to the east. The second line continues to fill in as it approaches the area. This line will move through overnight and have refined pops to capture this line as it moves east overnight using our local timing tool. Still some thunder being reported at times with the current line moving east and the line upstream. Thus, will maintain thunder chances through the overnight hours. It does look like all showers and storms should be to the east by dawn, leaving behind dry conditions for Sunday. UPDATE Issued at 700 PM EST SAT DEC 1 2018 Showers and storms from earlier have all exited the area with dry conditions being observed over much of east Kentucky presently. A complex of showers and storms from Richmond to Lexington will track northeast and clip our Bluegrass counties over the next few hours. Otherwise, we are watching a two developing lines of showers and storms. The first one is southwest of the area and developing to the north rather quickly. This line could develop into east Kentucky by 9 pm. The second line is associated with the occluded front and is presently back across western Kentucky. These two lines will continue to blossom as we head into the overnight hours with jet support increasing. Thus, have gone ahead and increased rain chances to categorical for the area after 9 pm as these lines of showers and storms push on through. Instability remains limited to the east, so thunderstorm potential should drop off as activity moves east overnight. However, for now, will hang onto the thunder chances for our western zones. && .SHORT TERM...(This evening through Sunday night) Issued at 320 PM EST SAT DEC 1 2018 19z sfc analysis shows a deep cyclone over the Central Plains with an elongated warm front stretched east into Kentucky. With this front, scattered to numerous showers are passing through eastern Kentucky this afternoon with a band of thunderstorms developing over south central Kentucky well ahead of the system`s cold front. The pressure gradient is tight through Kentucky keeping the winds up, but still not seeing their full potential most places yet as an inversion appears to be keeping the stronger winds aloft confined to just our higher terrain. However, the more convective nature of the showers and storms moving into western parts of the area could also bring down higher winds so will keep the SPS going for winds of 30 to 40 mph across the area through sunset. The clouds have exhibited some breaks over the east this afternoon - likely helping to increase the instability over the area as temperatures have climbed into the mid 50s to lower 60s while dewpoints are in the low to mid 50s. The models are in good agreement aloft through the short term portion of the forecast. They all depict a closed low over the Central Plains opening up and working into the Ohio Valley on Sunday and into the Great Lakes later that night. The bulk of the energy associated with this low stays north of Kentucky until late in the period. Given the agreement have favored the blended solution as a starting point for the grids with a lean toward the HRRR and NAM12 for details. Sensible weather will feature an active late afternoon and evening as windy conditions aloft may make it to the sfc thanks to showers and possible thunderstorms. Meanwhile, the higher elevations near the Virginia border continue to see some higher gusts thanks in part to a mountain wave component to the winds running just above the sfc. This will move off later this evening while the convection settles down as well, limiting the stronger wind threat. With the area in between the system`s fronts tonight we will probably see a small ridge to valley temperature difference into dawn. On Sunday, sunshine returns with breezy conditions continuing on southwest winds making for another mild day with highs in the mid 60s most places. Clouds return on Sunday night along with winds turning more to the west generating some upslope component enhancing the low cloud formation. Would not be surprised if some sprinkles or drizzle develop late Sunday night, but will leave it out for now. Temperatures into Monday morning should be more uniform than the night before on a CAA pattern. Used the CONSShort and ShortBlend as the starting point for all the grids through the short term with some adjustments to temperatures each night for terrain distinctions. As for PoPs, generally went above the blends until the main boundary moves through late tonight. .LONG TERM...(Monday through Saturday) Issued at 424 PM EST SAT DEC 1 2018 Models are in good agreement to start out the extended portion of the forecast, with a deep southern stream longwave troughing pattern across much of the continental U.S., and SW to NE flow across KY. A shortwave will push southward and lower heights across the state throughout the day Monday, becoming fairly stationary through the day Tuesday. The GFS is much stronger with this system, developing a upper level low, while the ECMWF is just an open wave. Meanwhile, another trough will press southward from Canada, merging the northern stream with the southern stream on Tuesday. During this time the GFS has the above mentioned shortwave maintaining strength as it slowly pushes east of the state by Tuesday night. However, the ECMWF develops another shortwave that tracks just north of the state during the day Wednesday as well. Compared to yesterday, the models go back into surprisingly good agreement by Thursday, with generally zonal flow across the region through at least Friday. Things go awry again as a wave develops and strengthens across the western half of the U.S. and shifts towards the Ohio Valley. Heights begin to lower across the state according to the ECMWF to round out the end of the period, while the GFS keeps a dampened trough across the region. As for sensible weather, a secondary cold front will be moving into the state during the day Monday, but will lose considerable strength and dissipate as it moves across the CWA late in the day. Kept slight to low end chance pops, mainly across the northern and far eastern portion of the CWA as this weakening system moves across. Much colder air near the surface will move in behind this front, despite the WSW flow in the mid/upper levels. Highs on Monday will be some 20 degrees lower than highs on Sunday in many places, generally ranging from the mid 40s in the north, to around 50 in the southeast. The above mentioned discrepancy in waves will move through Tuesday into Wednesday, resulting in the blend having some degree of pops in place across the CWA during this time. Since the GFS has higher pops associated with its upper level low on Tuesday/Tuesday night, the Superblend produced 20 to 30 pops across portion of the CWA. Meanwhile, the ECMWF is much lighter with its system, with the Superblend essentially averaging out the pops just below mentionable criteria. Given the uncertainty on which model is current, generally kept Superblend pops during this time. As the northern flow continues shift southward, colder flow will continue to make its way into the region, with NW flow expected aloft by Tuesday night. Highs on Tuesday will only be in the mid 30s, so precip that falls throughout the afternoon could be a mix of rain and snow, changing over to all snow by Tuesday night. QPF amounts are very low, especially given the lack of continuity between the models, so any accumulations should be light, generally a few tenths of an inch or less, and confined to the far eastern portion of the state. High pressure will move into the state during the day Wednesday, with drier air advecting into the region. This will slowly dissipate clouds throughout the day, and provide maximum radiational cooling with light winds for the overnight. Temperatures will fall into the low 20s across much of the region Wednesday night, especially in the valley locations. Temperatures will then rebound to the low 40s for Thursday afternoon as high pressure remains in place. Another cold front will push through the state during the day Friday. This front will also be weakening as it reaches our region, so there is some question about the extent of precip as it moves across the state, with the GFS keeping us dry and the ECMWF only showing light amounts. Kept with Superblend pops during this time since it is so far out in the period, which only puts low in slight chance pops in during the day on Friday. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) ISSUED AT 700 PM EST SAT DEC 1 2018 Southeast winds will continue at 5 to 10 knots through the evening hours, with strong flow just off the surface supporting a longer period of LLWS. This wind shear will likely last well into the night before the better winds shift off to the east. A front will move through overnight with a slight wind shift to the south expected. Showers and perhaps a few storms will accompany the front as it passes overnight. This could bring a brief window of MVFR conditions to the area tonight. Otherwise, mainly VFR conditions are expected. Gusty winds will likely develop again by Sunday afternoon. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...KAS SHORT TERM...GREIF LONG TERM...JMW AVIATION...KAS
Area Forecast Discussion
National Weather Service Louisville KY
928 PM EST Sat Dec 1 2018 .Forecast Update... Issued at 928 PM EST Sat Dec 1 2018 The forecast is in good shape and no significant updates are needed. A broken line of elevated showers continues to cross central Kentucky at this hour, and may mix down some 30-40mph wind gusts. Overall, though, an inversion around 3kft has been keeping the strongest winds aloft. Shower activity should end across central Kentucky by 2am EST. && .Short Term...(This evening through Sunday) Issued at 305 PM EST Sat Dec 1 2018 As a deep surface and upper low spin over N/NE Kansas this afternoon, the warm conveyer belt well ahead of this system continues to cause scattered to numerous showers and a few embedded thunderstorms over the OH and TN Valleys. For example, a small line of thunderstorms with some CG lightning has been progressing NE over parts of south-central KY the last hour, but is now slowly weakening. Winds associated with this line earlier were still slightly elevated as surface wind speeds were not much different than ambient values across central KY this afternoon. As expected, surface temps this afternoon have been roughly steady in the mid 50s to around 60, although thinning clouds in SW KY has allowed temps there to rise into the mid 60s at this time. Across our area, expect to see temps rise slowly late this afternoon and top out actually during the evening hours as southerly flow continues across the area just off the surface. A couple AMDAR aircraft soundings continue to show a low-level inversion around SDF which has prevented stronger surface wind gusts. However, the inversion is a little weaker over western KY and SW IN allowing surface winds as shown by ASOS and KY Mesonet sites to gust from 20-25 mph. Winds over central KY and southern IN should become a little more gusty later this afternoon and evening as well. As for precip, high-res/convection-allowing models are not consistent in their new term solutions. The latest HRRR continues to show another line or two of convection forming on the western edge of the moist axis over the lower OH Valley and progressing NE over our area late this afternoon and evening. The WRF runs and NAM3 are not as emphatic but still show potential for isolated to scattered convective cells. Instability appears that it will remain largely just elevated meaning locally heavy rain and perhaps small hail in any stronger cores. All precip will push NE this evening, ending last over east-central KY late this evening. Behind it, expect clearing skies overnight as the dry slot works farther NE into our area. Lows by Sunday morning should be in the upper 40s over southern IN and around 50/lower 50s in central KY. On Sunday, expect plenty of sunshine as we remain in a low and mid- level dry slot. The main concern Sunday will be surface winds. With 30-50 kt winds forecast from 925-850 mb and steep low-level lapse rates by late morning and afternoon, S to SW surface winds could gust over 30 mph at times. No wind advisory at this time, but this may have to be considered in later forecasts. Given the sun and gusty winds, afternoon highs Sunday should reach well up in the mid and upper 60s in central KY, possibly a bit cooler over southern IN. .Long Term...(Sunday night through Saturday) Issued at 255 PM EST Sat Dec 1 2018 The large system affecting the short term finally will bring its associated cold front to the Ohio Valley Monday. It looks like it still will not be in a hurry to clear the area, and a few models spit out some precipitation either along or just behind the front. Given the cold air in place, this could end up as mix of rain or snow or drizzle, depending on the depth of the moisture into the colder air aloft. This "marginal" situation could extend through Tuesday, as waves aloft move across the region from the northwest. Midweek "looks" dry for now, but any quick-moving impulses in the weak trough pattern aloft could provied a brief very light precip event. Blended forecast for now keeps the forecast dry, and will lean that way for now. Speaking of quick-hitting, another moisture-starved front looks to move through here some time Thursday. Only have a slight chance for showers in the afternoon. That front may linger close enough to the region to meander back north and affect us for the upcoming weekend, as a southern stream system moves across the Deep South. As is usual this far out, there still are plenty of question marks with this system. Blended forecast will has snow Friday night transitioning to rain or mix during the day. Temperatures generally stay below normal for this period. && .Aviation...(00Z TAF Issuance) Updated at 618 PM EST Sat Dec 1 2018 Low ceilings and scattered thunderstorms will continue to stream rapidly northeastward ahead of a dry slot that is in turn ahead of a strong upper low near MCI this evening. Overnight the low will head northeast into Iowa and will pull the dry slot into southern Indiana and central Kentucky, shutting off the storms and bringing in clear skies. On Sunday the low will fill as it tears northeast to Lake Huron, with low-end MVFR clouds sweeping into the Ohio Valley on cold air advection behind the departing storm system. Winds will be brisk from the south tonight, occasionally gusting over 20kt especially this evening. AMDAR soundings have been showing a sharp low level inversion around 2500-3000 feet at BNA and 4000 feet at SDF which has been keeping the strongest winds off the surface. Tomorrow there should be good mixing with sunshine, especially at BWG and LEX where more sunshine is expected. Winds coming in from the southwest will gust to 30kt. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...13 Short Term...TWF Long Term....RJS Aviation...13
Area Forecast Discussion
National Weather Service Omaha/Valley NE
916 PM CST Sat Dec 1 2018 .UPDATE... Issued at 915 PM CST Sat Dec 1 2018 Made a minor update to increase snow amounts in parts of southwest Iowa where recent RAP and HRRR model runs have shown potential for amounts upwards of 6 inches. Otherwise, nearly stacked low pressure system continued to lift slowly northeast. Main center in the mid levels appeared to be over northwest Missouri, but there were other embedded circulations pivoting counter clockwise around the low. Heavies snow seems to have been across the northern parts of northeast Nebraska based on what reports we have received so far. No other changes except minor tweaks to wind and temperatures. && .SHORT TERM...(Today through Monday) Issued at 333 AM CST Sat Dec 1 2018 This storm system continues to impress with its complexity, and have continued to attempt to adapt the forecast to match up with the latest trends in observational and model data. In terms of what has happened so far, snow amounts range wildly even across areas that have seen persistent snow fall. Melting has played a huge role that seems to be magnified by the rain that fell prior to snow, and also by the relative warmth of the snowflakes that are falling through a fairly deep warm layer above the surface. The end result has been that snowfall predictions seem to have been pretty accurate but some of the snow accumulation amounts on the ground have been on the low end so far, owing to that melting. That said, several reports in the 5-6 inch range have come in to the office, and expect a slow but steady accumulation of additional light to moderate snow in these areas all the way through Sunday. Would like to focus on 3 key areas for the forecast through the rest of Sunday. The first is in far northeast Nebraska where 2-7 inches of snow has fallen by now. There is a strong signal for persistent light to moderate snow over the next 12 hours or so and even into the day on Sunday. Deformation and mid level frontogenesis will remain focused in this area for a prolonged period with very little movement of the overall storm system. Do expect a banded area within this region to total out in the 9-12 inch range by the time its all winding down. The second area of focus is what is expected to be a relatively persistent band of moderate snow extending from around David City and Columbus up through Stanton, Wayne, and West Point. While it may fluctuate west or east of this axis with time, it should remain in the general vicinity and lead to several additional inches of snowfall through tonight before it weakens and dissipates. The third area, and perhaps the biggest change in the forecast is over southeast Nebraska up toward Omaha and into southwest Iowa. It has become increasingly apparent over recent model and observational data that the zone immediately northwest and west of the low will be a focus for moderate precipitation through around sunrise on Sunday. That will lead to a prolonged period of what should be a majority of snow that pivots and focuses in the general Nebraska City and Shenandoah areas. This band will be between 50-100 miles wide for much of its lifetime and at least initially surface temperatures will be warmer than freezing. The difference between this snow and the snow of this morning is that it will fall at night which favors slightly better accumulation but will still experience some melting. At this time have gone with a 2-6 inch prediction and also expanded the advisory across the remainder of the CWA, but will need to closely monitor trends as it is not out of the question that some of these areas could end up exceeding 6 inches by Sunday morning in what is a very delicate forecast of snowfall vs. snowmelt. Sunday into Sunday evening will feature periods of light snow moving across the entire forecast area and gradually coming to an end from northwest to southeast by late in the day. Winds will continue to gust in the 20-30 mph range through the day with cooler temperatures steadily building into the region. .LONG TERM...(Tuesday night through Saturday) Issued at 121 PM CST Sat Dec 1 2018 Snowy conditions may linger through Monday night as this low pressure system drifts off toward the Great Lakes. The bulk of the accumulating snow will end Sunday however some light snow may hang around Sunday night in southeast Nebraska and southwest Iowa. By Monday high pressure begins to build back into the area bringing mainly drier weather and colder temperatures through the week. High temperatures are expected to be mainly in the 20s with lows in the single digits and teens through the longer term period. Wednesday, a few locations in far southeast Nebraska and southwest Iowa may break the freezing mark with highs reaching the mid 30s, however this "warmth" will be short lived mainly 20s returning again by Thursday. A shortwave system on Thursday may bring some light snow to southern parts of Nebraska and Iowa however this will be fast moving which should limit any significant accumulations. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 520 PM CST Sat Dec 1 2018 Expect snow to continue at KOFK with IFR conditions most of the period. Winds may also cause blowing snow there. For KOMA and KLNK, also expect ceilings mainly at or below 1000 feet with mostly visibilities below 3 miles. Some blowing snow is possible, mainly at KLNK. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Winter Weather Advisory until 6 PM CST Sunday for NEZ034-044-045- 050>053-065>068-078-088>093. Winter Storm Warning until 6 PM CST Sunday for NEZ011-012- 015>018-030>033-042-043. IA...Winter Weather Advisory until 6 PM CST Sunday for IAZ043-055-056- 069-079-080-090-091. && $$ UPDATE...Miller SHORT TERM...BLB LONG TERM...HB AVIATION...Miller
Area Forecast Discussion
National Weather Service Nashville TN
550 PM CST Sat Dec 1 2018 .UPDATE... FOR 00Z AVIATION DISCUSSION. && .DISCUSSION... Showers and a few thunderstorms across the area are weakening currently, and are having a tough time staying together this afternoon. 18Z sounding from OHX showing a decent low level inversion, with some elevated CAPE from 850 mb. Also showing some drier air aloft, and with strong 80 knot 0-6km shear, likely having a hard time staying together before that dry air entrains and mixes to dissipate the showers. Short term models and CAMs are hinting at a weak front sneaking through the mid state from 00Z- 06Z this evening, and kicking off some convection out ahead. The HRRR has been the most bullish with this solution, and following suit is the NAMNest and even the hi-res WRF models. Adjusted pops up slightly for this evening to account for the precip, but instability falls off rapidly after 00Z so not sure if there will be much in the way of stronger cells east of I-65. Will continue to monitor for any potential for damaging wind gusts or even some small hail, especially west of I-65 as developing convection utilizes some of the remaining instability. Winds will continue to decrease tonight and through the overnight hours, but pick up again during the day Sunday ahead of the approaching cold front. There wont be a dramatic wind shift during the day tomorrow since winds will remain southwesterly and keep temps warm, but slowly will become westerly Sunday night then northwesterly by Monday. Cold front is more evident with 850mb temps, and cold air will begin working its way southward and eventually have the entire mid state below 0C at 850mb by mid afternoon. Temperatures will be below average through the week as any substantial warming will be absent thanks to the lack of strong southerly flow. Conditions will remain dry Monday, but a slow moving upper trough will continue to keep cold air aloft, and may bring some precip chances during the day Tuesday. Moisture is struggling to show up for this event despite a few hints of QPF between model solutions. Kept most of the mid state dry except for the northern Plateau where some orographic help may be able to squeeze out some moisture for precip. Temps will be cold enough for some snow to mix in, but likely just some light rain chances. Tuesday night may see some flurries over the northern Plateau before dry conditions return for Wednesday and Thursday with upper ridging/northwest flow aloft. On Friday, some shortwave trough activity may kick off some showers during the day, but better precip chances are in store for the weekend as a stronger upper shortwave moves through the area. Models are not lining up yet, of course, but do hint at similar low level solutions and QPF timing. So have chance pops in for Saturday and Sunday. Friday night and Saturday night, temperatures are cold enough for some snow to mix in, but further drops in temperature with next runs will yield more snow. Current lows are in the mid 30s, so still too close to call just yet on snow potential next weekend. Leaned towards the warmer solutions and have mainly rain in during daytime hours, and a rain snow mix during the overnight. && .AVIATION... 00Z TAF DISCUSSION. Scattered showers could impact the terminals during the first 6 hours of the taf period and then vfr conditions will quickly return. A line of showers currently just west of CKV will be the last threat to the terminals. That line will move east of CSV by 08z. Winds will calm to 5-10 kts behind the line. Winds will increase to 10-15 kts with some gusts to 20 kts out of the southwest after 15z. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......Barnwell AVIATION........Reagan
Area Forecast Discussion
National Weather Service New York NY
800 PM EST Sat Dec 1 2018 .SYNOPSIS... High pressure will continue to give way to a storm system over the Mid Mississippi Valley. The associated low will track up into the Great Lakes by Sunday night, sending a warm front through the region on Sunday, followed by a cold front late Monday and Monday night as the low continues into the Canadian Maritimes. High pressure then builds into the region through midweek. An upper level disturbance could produce light wintry weather Thursday night into Friday. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Update this eve mainly reflects more defined pops based on radar and trends in HRRR since it is capturing reality well. Initial band of overrunning WAA rain ahead of a warm front moves across the Tri State Area through 2z, with a brief break before the rain picks up again after midnight as a strengthening low- level jet moves up the coast and enhances thermal forcing. E to SE winds will also pick up through the night as the gradient between the departing high and approaching low tightens across the region. Gusts up to 20 mph will possible at the coast by daybreak. Areas of fog will also develop late as low- level moistures increases and the airmass saturates beneath a strengthening low-level inversion. Lows will be achieved early this evening, in the mid 30s to lower 40s, then slowly rise overnight. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... A moderate rain will mainly fall during the morning hours Sunday along and ahead of a warm front. An isolated thunderstorm also can not be ruled out as instability develops aloft. As the low- level jet translates east by afternoon and the warm front lifts north of the region the rain will transition over to drizzle and may even end all together by early evening. Areas of fog and low clouds could persist into the night. Sunday and Sunday night will be considerably warmer in the warm sector due to a deep-layered SW flow ahead on approaching cold front. Highs Sunday will get into the 50s for most locations and then don`t fall off much overnight. Readings will generally be 8 to 15 degrees above normal. && .LONG TERM /MONDAY THROUGH SATURDAY/... Long term period looks fairly uneventful for a change with NWP in good agreement until mid-late next week. Potent shortwave and associated sfc low pass north of the area on Mon with more sheared mid/upper level energy ahead of the trough axis passing through southern New England Mon night. It will continue to be gusty but warm (mid to upper 50s) on Mon as the departing storm strengthens and high pres builds from the Plains. CAA behind the cold front could also keep gusts into the overnight hours. Moisture appears to be limited, so other than an increase in cloud cover, the passage of a cold front and the upper trough axis Mon night is expected to be dry. There is some weak lift however, so if any light pcpn were to reach the ground, it could be sprinkles or flurries depending on timing. Ridging then builds at the sfc and aloft through the middle of the week. Winds diminish on Tue, especially in the aftn, as the high builds and the gradient relaxes. Dry with below normal temps will be the rule through Thu. Will need to keep an eye on a vigorous shortwave approaching from the Midwest on Wed. Differences in model solutions begin to unfold with this which could influence the remainder of the forecast period. All 12z guidance has this shortwave passing to our south with cyclogenesis occurring off the Mid Atlantic coast. GFS is the fastest and EC is the strongest/earliest with cyclogenesis. However, it is close enough to the local area that it continues to bear watching despite the trend to the south. A weakening shortwave diving out of western Canada then approaches for Thu night/Fri morning. The combination of WAA and the exit region of a 90+ kt jet streak could be enough to produce light QPF across the area. Thermal profiles indicate the boundary layer should still be cold enough for snow showers despite the WAA. Dry weather then returns through Sat as high pres builds from the west. Temps will remain below normal. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... A warm front approaching from the southwest should lift to the north by early Sunday afternoon. Band of light rain moving across the NYC metros and lower Hudson Valley attm accompanied by mainly VFR conds. Cigs after passage of this band have dropped to MVFR at the PHL metros and to IFR north/west, so expect the metros to drop to MVFR as well, then to IFR late tonight into early Sunday morning, and remain that way for most of Sunday as additional rain moves in. It is possible that conds could improve to MVFR sooner than forecast as winds shift from E to S with the warm fropa. There is slight chance of a tstm thunderstorm Sunday morning. Chances too low to reflect in TAF. LLWS possible late tonight into Sunday afternoon at all but KSWF. .OUTLOOK FOR 00Z MONDAY THROUGH THURSDAY... .Sunday night...Slight chance of showers early with MVFR or lower possible, otherwise VFR. .Monday...VFR. WSW-W winds G15-20KT. .Monday night-Tuesday...VFR. NW winds G15-20KT. .Tuesday night-Wednesday...VFR. NE-N winds G15-20KT. .Wednesday night...VFR. .Thursday...VFR. W winds G15-20KT. && .MARINE... The combination of departing high pressure to the north and east and an approaching warm front from the southwest will allow for a strengthening easterly flow overnight, which veers around to the southwest behind a warm frontal passage Sunday. SCA conditions are likely across the ocean waters late tonight through Sunday night, with a shorter window for gusts across the eastern Sound and bays. SCA will likely be needed on the ocean waters, possibly on eastern LI Sound and adjacent bays, through Mon night, possibly Tue morning as a strong W flow becomes NW. As low pres departs and high pres builds from the west winds will diminish with sub-advsy conds then expected until possibly Fri. && .HYDROLOGY... Up to an inch of rainfall is possible tonight through Sunday. Any hydrologic impacts should be minor. No hydrologic concerns are then expected through the end of next week. && .TIDES/COASTAL FLOODING... A coastal flood statement has been issued for portions of the coastline adjacent to western Long Island Sound for the Sunday morning high tide cycle. Easterly winds strengthen ahead of an approaching warm front, producing a surge of 1 1/2 to 2 ft. This will bring water levels close to minor coastal flood benchmarks in a few of the more vulnerable spots. Elsewhere, particularly the vulnerable south shore bay locations of western Long Island, it seems less likely due to the timing of the wind forcing. && .EQUIPMENT... NYC Central Park winds are out of service until further notice. Loss of data is due to a severed cable. Parts are on order. NYC NOAA Weather Radio Station KWO35 (162.55 MHz) will remain off the air for an extended period of time. && .OKX WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. NJ...None. MARINE...Small Craft Advisory from midnight tonight to noon EST Sunday for ANZ330-340-345. Small Craft Advisory from midnight tonight to 6 AM EST Monday for ANZ350-353-355. && $$ SYNOPSIS...24/DW NEAR TERM...DW SHORT TERM...DW LONG TERM...24 AVIATION...Goodman MARINE...24/DW HYDROLOGY...24/DW TIDES/COASTAL FLOODING... EQUIPMENT...
Area Forecast Discussion
National Weather Service Blacksburg VA
853 PM EST Sat Dec 1 2018 .SYNOPSIS... A wedge of high pressure will erode this evening, with steadily warming temperatures overnight tonight. A cold front will move across the area early Sunday. While temperatures will be above normal tonight into Sunday, high pressure across the center of the country will usher in a colder air mass for early next week. && .NEAR TERM /THROUGH SUNDAY/... As of 850 PM EST Saturday... The 00Z RNK sounding shows an impressive low level inversion keeping a cool and moist wedge at the surface. Visibilities have improved at many locations, but will continue to keep the dense fog advisory in place as mesoscale models and SREF indicate visibilities drop, especially east of the Blue Ridge. Considering the strength of the inversion, slowed the rate of warmth overnight, as low level wedge may remain in place longer than earlier forecast as shown by many of the mesoscale models and the latest NAM nest. Also brought down temps a couple of degrees at LYH tomorrow with slower erosion of the wedge. Convective line of storms across eastern TN/KY will have a very difficult time surviving as it leaves the small ribbon of instability as shown on the SPC mesocale analysis page. However, this will likely bring another round of light to moderate rain to the western portion of the forecast area around or after 06z as shown by the ARW-NMM which was one of the few mesoscale models that picked up on this convection. As of 520 PM EST Saturday... The combination of moist ground, rain and drizzle in the area, and a wedge of cool air undercutting the upper-level moisture has contributed to the development of widespread dense fog and drizzle. It pretty much appears like it is going to be one of those nights where much of the CWA is completely socked in with fog, drizzle, and low clouds. Visibilities are near zero in many locations above 2000 feet elevation near the Blue Ridge and also across much of the Piedmont widespread 1/4 to 1/2SM. HRRR suggests little improvement overnight. Perhaps rain areas may move in later, but right now it appears that they will split for the next several hours at least and go north or south of our area. Therefore, have issued a Dense Fog Advisory for all but some far western VA/WV counties until 13Z Sunday. Will continue to monitor to see if an expansion in area or time is needed. As of 251 PM EST Saturday... Stubborn in-situ wedge has surged into northern Carolinas and has led to overall cool temperatures, extensive low clouds with fog at times across essentially the Piedmont, Blue Ridge, foothills into the New and southern Shenandoah Valleys. Fog should begin to become less prevalent as winds increase and become southerly (as opposed to light east). Had issued a SPS for continued fog for the aforementioned areas until 330 PM. Otherwise, a vertically-stacked low centered near Kansas City trails a long tail of warm-advection rain from the Great Lakes, Appalachians into the northern Gulf Coast states. Southern end of this precip shield is affected our southern and eastern counties, and will continue to do so through the first part of the evening. Best chances/highest PoP for steadier rains is from the NC Piedmont through areas along/east of the Virginia Blue Ridge. Have shown a local minimum in PoPs through midnight from the New River Valley/NW North Carolina Mtns westward into southeastern West Virginia through midnight, where dry slot aloft is currently progressing across the Ohio/Tennessee Valleys. These trends are all generally reflected by most of the coarser-res NAM/GFS and the finer resolution NAM-3km and HRRR guidance. Will be areas of mist and fog as well, though visibilities should be higher than current and coverage will tend to be restricted to east of the Blue Ridge into the foothills/Piedmont/Southside. After 06z/2 AM, while the eastern two- thirds of the CWA clear out with lowered PoPs, things get potentially more interesting in western areas, as a number of higher- resolution guidance break out a scattered band of convectively enhanced showers along the cold front/wind shift. This appears to be models keying on the convection occurring near Nashville/Middle TN. Showalter indices drop to around -1 to -2 on the NAM, which suggests elevated instability above stable surface-based conditions. Have included a slight chance of thunder in these western areas between the overnight and pre-dawn hours, and while wind shear is pretty stout low-levels are still much too stable to allow for even gusty convective winds to be transported to the ground. Regarding temperatures, a largely non-diurnal approach was taken and given the way the day has unfolded, it`s quite likely that calendar-day highs occur overnight tonight. As the wedge erodes, 850 mb temperatures rise to +11 to +13C overnight along with increasing dewpoints into the upper 40s to the 50s. Look for early lows in the 40s to low 50s, with most areas reaching the low-mid 50s by early Sunday morning. QPF amounts run from about a quarter to nearly a half-inch. Cold front aloft will continue to be progressing across our eastern two-thirds of the forecast area. This will clear most areas out with lowering PoPs. Greater potential for warming and drying pre-frontal across Southside into the NC foothills/Piedmont leads to a potential threat of thunder here. The milder GFS show surface based CAPEs closer to 800 J/kg in this axis, while the still cooler and more stable NAM shows this instability above stable inversion. Think there is a non-zero threat of stronger cells in a high-shear/very low CAPE environment from Yadkinville to Mount Airy NC northeastward into Southside Virginia tomorrow late morning/early afternoon, particularly if a stability profile more like the GFS materializes. A NAM depiction would lend to less likelihood of stronger convective gusts given the stabler profile. Shear through low levels and deep layer are quite strong, but is mostly straight-line from a hodograph perspective. SPC keeps probabilities of severe weather farther south and east in the Day-2 outlook, with general thunder this far north. There`s still a good deal of uncertainty on the potential, as alluded to, but think it is prudent to raise awareness of stronger thunderstorms from Yadkin County north/east into Southside highlighted in the HWO. Highs will run from the 60s to the low 70s, with potential for low- mid 70s in Southside/NC Piedmont if greater warming can materialize. Forecast confidence is overall moderate to high for the tonight period, but is lower on the potential for thunderstorms tonight and early Sunday as well as on temperatures Sunday. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 254 PM EST Saturday... Cold frontal passage will occur Sunday night into Monday morning bringing low level upslope clouds, mainly in the west. After being spoiled with a warm Sunday, temperatures will begin to trend somewhat cooler on Monday with highs in the 50s for the mountains, and low to mid 60s east. Temps will drop to below normal values for Tuesday with high temps for most in the mountains struggling to get to 40, and mid to high 40s for the foothills and piedmont. Winds will be westerly which will trend to the northwest Monday evening and remain for the duration of the period. Increased upslope flow will cause enough moisture to gather to bring isolated showers to the mountains with snow possible in the higher elevations. Coverage Monday night will be restricted to the farthest western areas however will expand through Tuesday into Tuesday night. By Tuesday night, temps will drop far enough that any precipitation that falls will likely be as snow or at the very least a wintery mix. As of now, precip amounts look to be rather low, therefore any significant accumulating snowfall appears unlikely for all areas, with the exceptions possibly being the typical upslope areas in the NC high country and higher elevations WV. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 254 PM EST Saturday... Forecast models continue to advertise a broad trough over the eastern US through the period which will continue to support below normal high temperatures through the period. Have opted for a model blend as there are several different outcomes as to just how cold it will actually become. Upslope snow showers will begin to taper off Wednesday but will continue to be possible, mainly in the far western areas. A weak disturbance passing through the area on Friday will also promote some additional showers Friday into Friday night. Late in the work week, models are showing a fairly decent low pressure system developing well to the southeast which could entrain enough moisture to bring some impact to the Mid-Atlantic as early as Saturday. Confidence is low at this point on when or what impact this system will have on the forecast area at this point, but will be paying close attention in the coming days. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... As of 645 PM EST Saturday... Poor to very poor flight conditions expected through around 13Z Sunday morning. Classic wedge set up reinforced with light rain and drizzle. Do not expect any erosion of the wedge before daybreak, likely holding in until 13-14Z. However, as the wedge breaks, gusty southwest winds will evolve quickly in its wake, clearing out the low clouds, fog, and drizzle and bringing VFR conditions with unseasonably warm temperatures by afternoon. Periods of light rain will spread across the region overnight into the morning, but no significant rainfall is expected. The bulk of the support for heavier rain showers will remain to our south where the southern stream is focused. Thus, either -RA or -DZ BR/FG in place at all TAF sites overnight/early morning Early Sunday morning, a cold front will begin to approach from the west. May be convective elements/chance of thunder from Blacksburg west between 08-12z but confidence too low to incorporate in the TAF; will mention SHRA in areas that have an outside thunder potential. This front will progress across the Blue Ridge and points east into the Piedmont toward the latter part of the 18z TAF period. Very limited threat of thunder further east, but will not include in the TAFs at this time. Main threat for thunder will be well east and south of our CWA. Winds...east to southeast (northeast at Lynchburg) 4-8 kts will tend to veer to southeast/south this evening. Will see an increased potential for low-level wind shear as south/southeast jet of 40-45 kts affects terminals from Roanoke west. Winds will shift to the southwest with speeds 5-10kts around mid-morning Sunday. /Confidence Levels in Forecast Parameters/ Ceilings - Moderate to High, Visibilities - Moderate to High, Winds - Moderate to High. Extended Aviation Discussion... Cold northwest flow will gradually return through the week and the weather pattern will resemble winter again. Isolated MVFR showers are possible on Monday but most areas dry and VRF with better chance for snow showers in the mountains by late Monday night into Tuesday as push of colder air behind front moves in and winds shift from west to northwest but not especially strong. MVFR snow showers and snow flurries may continue in the northwest mountains on Wednesday. && .EQUIPMENT... As of 400 PM EST Saturday... The KDAN ASOS has been repaired. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Dense Fog Advisory until 8 AM EST Sunday for VAZ011-013>020- 022>024-032>035-043>047-058-059. NC...Dense Fog Advisory until 8 AM EST Sunday for NCZ001>006- 018>020. WV...None. && $$ SYNOPSIS...AL NEAR TERM...AL/PH/RAB SHORT TERM...JR LONG TERM...JR AVIATION...AL/RAB/WP EQUIPMENT...AL/WP