Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/05/18

Area Forecast Discussion
National Weather Service Wilmington OH
1006 PM EST Tue Dec 4 2018 .SYNOPSIS... As an upper level trough moves through the Ohio Valley, occasional light snow will be possible through Wednesday. High pressure will build into the southeastern states on Wednesday night, as a cold front crosses the Ohio Valley on Thursday, bringing another chance of precipitation. && .NEAR TERM /THROUGH WEDNESDAY/... A weak upper level low with embedded energy rotating around its southern periphery will move into the region tonight. As this occurs, steep low level lapse rates will combine with the forcing to produce scattered to likely snow showers, most numerous along and south of the Ohio River. Latest NAM and RAP model runs support the previous thinking, so have gone chance PoPs north with likely PoPs mainly along and south of I-70. Snow accumulations will generally be around a half inch, but some local spots of near an inch can not be ruled out, especially near the Ohio River. An SPS has been issue to cover this scenario, which may impact the morning commute. Though it will remain cloudy, some cold advection will allow temperatures to fall overnight, with min temps in the middle to upper 20s. && .SHORT TERM /WEDNESDAY NIGHT/... As forcing associated with the mid-level low moves east of the ILN CWA on Wednesday, snow showers will fade to flurries, and then fade to dry conditions by early afternoon. Subsidence on the back side of the trough axis will allow for some clearing of the persistent stratocumulus deck, though cloudy conditions were kept around in the forecast a little longer than previously, as these scenarios often seem to take some time to clear up. Aside from some late day clearing, there is little reason to take the over on temperatures, with westerly winds persisting and the coldest 850mb/925mb air moving over the area during the afternoon hours. Max temps will hover within a degree or two on either side of the freezing mark. As high pressure builds into the southeastern states on Wednesday night, the pattern will begin a brief change over the Ohio Valley, with winds shifting to the SSW. Ahead of an approaching cold front (which will be discussed in the Long Term AFD section) models are indicating a wedge of higher theta-e air nosing into the area from SW-to-NE by Thursday morning. Looks like min temps should arrive early on Wednesday night (perhaps around 06Z) with values in the middle 20s, before temperatures begin to rise heading through the rest of the overnight hours. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Mid level short wave energy will move across the southern Great Lakes on Thursday. This will help push an associated cold front southeast across the upper Ohio Valley through the day. An axis of low level convergence along and ahead of the front will lead to an increasing chance of precipitation across the northwest through the morning and then working into the southeast portions of our area through the afternoon. Highs on Thursday will range from the mid 30s in the northwest to the lower 40s in the southeast. Some non diurnal temperatures are also expected on Thursday, particularly across the northwest where they will get into some low level CAA on the back side of the front through the afternoon hours. Across the northwest any precipitation in the morning will likely be snow, before possibly mixing with rain into the afternoon, and then changing back to snow before ending through late afternoon. Farther to the southeast, expect more of a rain/snow mix to rain through the afternoon, before possibly mixing with/changing to snow in the evening, before tapering off as drier air moves in behind the front. Surface high pressure will build east across the southern Great Lakes and upper Ohio Valley Friday into Saturday. This will result in dry but below normal temperatures with highs both days in the low to mid 30s. A developing low pressure system will move across the southeast United States on Sunday before shifting off of the East Coast on Monday. The 12Z deterministic and GEFS continue to keep us on the northern fringe of any pcpn associated with this. Will therefore continue with some lower end pops along and south of the Ohio River later in the weekend and into the day on Monday. Highs Sunday and Monday with be in the mid to upper 30s. It looks like any pcpn that sneaks up into our south would be mainly snow. High pressure build into the Ohio Valley on Tuesday, leading to dry conditions with highs mainly in the 35 to 40 degree range. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... A weak upper level low with embedded energy rotating around its southern periphery will move into the region tonight. As this occurs, steep low level lapse rates will combine with the forcing to produce scattered to likely snow showers, most numerous along and south of the Ohio River. This will allow ceilings to drop back into the MVFR category. Where the most persistent snow showers occur, ceilings will likely drop between 1000 and 2000 feet with visibilities briefly dropping into the IFR category. On Wednesday, upper level low will move east with snow showers tapering off to some flurries before ending. CAA stratocumulus will linger for much of the day with ceilings remaining MVFR. By Wednesday night, cold pool of air centered near 850 mb will shift to the east. WAA and drier air aloft will eventually lift/push stratocumulus deck to the east, returning VFR conditions. OUTLOOK...MVFR conditions are possible Thursday with a mix of rain and snow. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Hatzos/Hickman SHORT TERM...Hatzos LONG TERM...JGL AVIATION...Hickman
National Weather Service Jackson KY
1102 PM EST Tue Dec 4 2018 .UPDATE... Issued at 1100 PM EST TUE DEC 4 2018 A relative lull in the snow shower activity between waves has been affecting much of the region over the past couple of hours. The heaviest snow showers at this point are near the VA border though there has been an increase in reflectivity upstream over central and western KY. The short term model guidance continues to indicate an uptick overnight corresponding to the next mid level wave moving in from the west. Thus snow showers are still expected to impact the Wed morning commute and the Winter Weather Advisory remains in effect. Hourly pops and temperatures, etc. were updated based on the trends noted above and recent observations. UPDATE Issued at 725 PM EST TUE DEC 4 2018 Snow showers continue across northeastern, eastern and southwestern sections of the CWA, but a lull in the activity has moved into the middle of East KY. Temperatures are generally a couple of degrees above freezing in the valleys at this time. Ridges across the coalfields and much of the northwest part of the area are at the freezing mark or just below. The higher ridges, however at 2000 feet and above have dropped below 30. The snow shower activity has been a high snow to liquid ratio event with only a trace recorded here at JKL, but 0.2 inches of snowfall. Within the snow showers, social media reports and webcam imagery from KYTC and others indicates some light accumulations on ridges in the higher elevations during the heavier showers. The dry slow or lull in the activity should spread across the area over the next couple of hours, with guidance suggesting an increase in coverage toward midnight and after when all locations should be at or below freezing. Although this next round of snow may be less than an inch in most areas, impacts to the Wed AM commute are expected as well as overnight travel. Radar trends will be monitored and some fine tuning of lowering pops for a couple of hours prior to midnight may be needed in some locations. Overall, no substantial changes were needed at this time. The main adjustments were to hourly temperatures and dewpoints to reflect recent observation trends which led to slightly lower temperatures particularly for coalfield ridges. && .SHORT TERM...(This evening through Wednesday night) Issued at 325 PM EST TUE DEC 4 2018 19z sfc analysis shows low pressure southeast of the area while northwest wind low level flow and energy moving by aloft are maintaining overcast skies and a good amount of showers across eastern Kentucky this afternoon. Temperatures are generally in the mid 30s keeping the pcpn as a mixture of both rain and snow. The showers are variable in intensity with some brief dustings of snow possible - mainly on the ridges. Meanwhile, dewpoints are running in the low 30s with northwest winds of 5 to 10 mph most places. The models are in good agreement aloft through the short term portion of the forecast. They all depict the Ohio Valley at the heart of a large but fairly shallow trough. Along the base of this, essentially through Kentucky, a stream of mid level energy will pass through keeping good lift over our CWA with an enhancement peak expected around and just after midnight. A final weaker wave then passes through by midday Wednesday followed by rising heights and fast, flat flow into Thursday morning. Given the good model agreement have favored a general blend with a strong lean on the higher resolution near term models like the HRRR and HREF for weather details especially tonight and Wednesday. Sensible weather will feature scattered to numerous rain and snow showers through the first part of the evening before transitioning more toward snow after sunset. Expect the snow to become more expansive through the late evening and overnight for the area with falling temperatures leading to more potential to accumulate - including on the roads. Additionally, much of the time overnight and into Wednesday morning the saturated clouds will be cold enough to reach the favorable dendrite growth zone. Accordingly, have gone ahead and issued a Winter Weather Advisory for the entire CWA through 1 pm Wednesday. The snow will likely be more variable than depicted in the forecast snow fall accumulation maps - due to the showery nature of the snow, some banding, and heavier batches. In general, an inch or less is expected for the western parts of the area with 1 to 2 inches east - highest amounts on the ridges and lower ones in the valleys. Temperatures will settle into the mid to upper 20s by dawn Wednesday with only a small recovery expected during the day as the snow showers come to an end. Look for a colder night into Thursday morning under a brief period of mostly clear skies allowing a ridge to valley temperature split to develop with sheltered spots likely falling to around 20 degrees by dawn Thursday. Used the CONSShort and ShortBlend guidance as the starting point for the grids with some terrain based temperature adjustments - mainly Wednesday night. As for PoPs and QPF: leaned more heavily on the HREF through the first part of the forecast with extra enhancement to the upslope areas. .LONG TERM...(Thursday through Tuesday) Issued at 412 PM EST TUE DEC 4 2018 The northern stream will begin phasing with the southern stream by 12Z on Thursday, with zonal flow expected across the region through the remainder of the work week. Kentucky will still be within the colder northern stream flow, however, with high temperatures steady but below normal in the upper 30s to low 40s Thursday through Saturday as a result. Models are continuing to come into better agreement about an upper level low developing across the southwest U.S. during the day Saturday. The ECMWF is showing the low developing across the SW/Mexico border region Friday evening/night and sustaining as it pushes eastward throughout the weekend. Meanwhile, the GFS shows the closed low developing later (Saturday evening) but being stronger and faster than the ECMWF. The model solutions start to phase again as the system moves over the state during the day Sunday, though the GFS will keep the low slightly farther north and deeper during this time period. This upper level low will then linger across the region through the end of the forecast period. So what will this system mean for sensible weather? There is still quite a bit of uncertainty this far out in the forecast, but generally we can expect widespread precipitation, mainly in the form of snow. Given this is a southern stream system moving northward into our region, we will be in the cold sector of the system. If the GFS pans out (faster and stronger) precip could move into the southern CWA by during the day Saturday. The ECMWF is some 18 hours slower, not moving into the southern CWA until Saturday night. The GFS will pull the precip across the entire CWA and keep widespread pops across the region through Monday. The ECMWF may keep pops across much of the CWA, but could keep some of the northern counties dry given its more southern track. In similar fashion, the deeper nature of the system according to the GFS will favor more QPF. Tried to keep a blend between the two models for the pops/QPF. High temperatures during the daytime hours will generally be in the upper 30s to around 40, but with nightfall temperatures are expected to fall below freezing. This will promote snow overnight switching back to rain during the day. Can`t rule out some mixing ice potential as well if the GFS forecast soundings pan out, but confidence in this is very low given how far out this is in the forecast and the fact that the models are not in good agreement. All things said, based on a blend of the two models, snowfall totals may range from around an inch in the northern CWA to between 5 and 7 inches near the VA border. Some of the highest peaks could see locally higher amounts (Black Mountain has a current forecast of 9 inches). That being said, this is a cumulative total between Saturday and Monday night, and does not take into account the changeover to rain during the day which will likely melt a lot of the snow that accumulated the night before. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) ISSUED AT 715 PM EST TUE DEC 4 2018 Scattered to numerous snow showers will continue to move across the area during the first 12 to 18 hours of the period, before tapering to flurries as upper level disturbances move through the region. With this, MVFR ceilings and VIS are expected with some brief further reductions to IFR in heavier snow showers. Some light accumulations are expected with this activity. Winds will be light and generally out of the west to northwest through the TAF period. && .JKL WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 1 PM EST Wednesday for KYZ044- 050>052-058>060-068-069-079-080-083>088-104-106>120. && $$ UPDATE...JP SHORT TERM...GREIF LONG TERM...JMW AVIATION...JP
Area Forecast Discussion
National Weather Service Louisville KY
1048 PM EST Tue Dec 4 2018 .Forecast Update... Issued at 1048 PM EST Tue Dec 4 2018 Band of snow showers stretching from southern Illinois to west central Kentucky is a bit farther north than earlier expected, and some showers in the band will be moving into counties just north of the previously issued advisory. Reports from the Evansville area indicate roughly half an inch of snow has fallen but that there have no impacts on the roads thus far. However, as temperatures slip into the 20s overnight, some issues may begin to develop by morning commute time farther downstream in central Kentucky. HRRR has been advertising a stripe of accumulating snow from Hancock County to LaRue County. So, after collaborating with PAH, have decided to go ahead and add one tier of counties to the north edge of the western advisory. Issued at 902 PM EST Tue Dec 4 2018 No changes to the current forecast. Light, wet snow has been falling intermittently across the region this evening but road temperatures have been in the middle 30s to middle 40s and air temperatures just above freezing, so no significant impacts as of yet. However temperatures will fall into the 25-30 degree range tonight and there is a band of snow showers extending roughly from Saint Louis to Bowling Green that still needs to move through. So, slick roads will still be a possibility overnight and into Wednesday morning. && .Short Term...(This evening through Wednesday) Issued at 230 PM EST Tue Dec 4 2018 Certainly not the easiest of forecasts this afternoon. Despite temperatures in the mid to upper 30s across most of the region, snow rates across south Kentucky were enough to cause some accidents. Traffic monitoring sites are showing slow downs across many of the county seats down there. Any heavier showers could briefly cause slick spots on roads, thus as we were going to issue an advisory for this evening anyway, decided to go ahead and start it early. The evening advisory comes as several higher-resolution models are pegging several snow showers moving across southern KY tonight. Gentle upslope flow in our east likely will aid shower development as well. Expect less coverage over the Louisville metro and points west/north, but cannot rule out a lonely shower have a streak of 1" snowfall totals in its wake. Will continue that area with an SPS for now. The main wave causing this snow will depart to the east as the day continues Wednesday. Thus will have precip ending by mid morning in the I-65 corridor and then I-75 in the afternoon. Morning lows in the upper 20s look to cause some road issues with the snow on the ground. Afternoon highs will not warm up too much above freezing, if at all in the I-75 corridor. Have the warmest highs well west of I-65, where they have the best chance for some afternoon sunshine. .Long Term...(Wednesday night through Tuesday) Issued at 227 PM EST Mon Dec 4 2018 Relatively dry and calm weather will start out the long term period. Surface flow will switch to the southwest Wednesday night ahead of a cold front. As the cold front approaches the region on Thursday afternoon, light precipitation should develop ahead of it in southern Indiana, and eventually overspread central Kentucky during the evening and overnight hours. Thermal profiles would suggest the precipitation starting out as rain during the daytime, and gradually transitioning to snow as we head into the evening and overnight hours. Moisture looks to be pretty limited ahead of the front, so any snow accumulations overnight should be light. Can`t rule out a few slick spots in central/eastern KY where the snow falls Thursday night. The front looks to clear the region by Friday morning, leaving dry but cold conditions in its wake. The forecast for the weekend continues to look unsettled and potentially wintry, though confidence in the details remain low. Long range guidance continues to show a southern stream trough (currently a 500mb cut-off low west of the CA coast as of writing this) moving across the Gulf Coast States/Southeastern US over the weekend into early next week. The specifics regarding the track and evolution of the upper level fields, thermal profiles, and extent of precipitation continue to vary from model to model. Precipitation that is thrown our way, however, looks to be wintry in nature (snow, sleet, and/or freezing rain) at some point over the weekend and possibly into Monday due to a strong Canadian high over the Midwest that will help keep the cold air locked in place. Those with travel plans this weekend should continue to monitor the forecasts closely in the coming days given the potential for impactful wintry precipitation. && .Aviation...(00Z TAF Issuance) Updated at 624 PM EST Tue Dec 4 2018 An elongated upper level disturbance moving along the length of Kentucky will bring light snow showers to the TAF sites tonight, with BWG likely receiving the brunt of the shower activity. MVFR cigs/vis can be expected in the showers, with some sub-fuel alternate ceilings possible temporarily in the heavier showers. Tomorrow the upper wave will move to the east and surface high pressure will build from the Red River Valley to the Tennessee Valley, resulting in gradually improving flying conditions. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...Winter Weather Advisory until 10 AM EST /9 AM CST/ Wednesday for KYZ023-024-026>028-053-061>064-070>078-081-082. Winter Weather Advisory until 1 PM EST Wednesday for KYZ035>037- 039>043-046>049-054>057-065>067. && $$ Update...13 Short Term...RJS Long Term...DM Aviation...13
Area Forecast Discussion
National Weather Service Marquette MI
543 PM EST Tue Dec 4 2018 .SHORT TERM...(This evening through Wednesday) Issued at 319 PM EST TUE DEC 4 2018 WV imagery and RAP analysis indicated mid/upper level ridging building over the northern Great Lakes with an upstream shortwave trough from Manitoba into the northern plains. At the surface, southwesterly flow was increasing ahead of a trough into the eastern Dakotas. Vis loop showed clearing over much of Upper Michigan with mainly cirrus as daytime mixing has helped scour the remaining stratocu. Tonight, weak 700-300 mb qvector conv, slightly deepening moisture and CAA dropping 850 mb temps to -12C associated with the approaching shortwave from south central Canada and the northern Plains will help boost west-flow LES mainly late tonight across the Keweenaw Peninsula. There is some uncertainty on how quickly the LES will move onshore as the bands mainly just graze the western shoreline of the Keweenaw. However, any accumulations should be light at an inch or less. Radiational cooling should allow temps to drop into the teens before clouds increase again. Wednesday, As winds gradually veer from wsw to west the most favorable low level convergence will also shift to the south through most of northwest Upper Michigan. Deeper moisture moving in during the afternoon will also favor increasing LES intensity. 1-3 inch snow amounts are expected over the Keweenaw but may be locally higher if any stronger bands linger over a particular location. The shortwave trough will be strong enough to bring a chance of light snow even to inland portions of the west by mid to late afternoon. .LONG TERM...(Wednesday night through Tuesday) Issued at 425 PM EST TUE DEC 4 2018 No changes in thinking from previous shift. Still looking at potential for moderate LES in NW wind snowbelts Wed night into Thu. Could see advisory level impacts over the W during this time with moderate accumulations possible and breezy winds near Lake Superior. Even as cooler air to -19C moves over Thu evening into Thu night, inversion heights decrease so impacts shouldn`t be a big issue later Thu into Fri, even as LES continues in the W-NW snowbelts. Lows in the single digits to low teens are expected Thu night and Fri night, with highs in the teens to around 20 on Fri (although winds chills should top out in the single digits to around ten). For Sun on, temperatures will be closer to normal with minimal chances of precip. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 542 PM EST TUE DEC 4 2018 MVFR conditions are expected to persist at IWD through the forecast period and through mid afternoon at CMX before light snow moves in and lowers them to IFR. VFR conditions at SAW will last for about half the period and MVFR for the other half as they will be on the edge of lake effect clouds and snow showers. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 319 PM EST TUE DEC 4 2018 Look for westerly winds of 15-25 knots tonight into Wednesday. There may be some higher gusts near the Keweenaw where terrain convergence enhances the wind. The next chance for stronger northerly winds will arrive late Wed night into Thursday behind a stronger cold front when northwest to north gale force gusts are possible. Northwest to west winds diminish back down to 15-25 knots Thu night into Fri as another high pressure ridge passes through the Upper Great Lakes. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...Titus AVIATION...07 MARINE...JLB