Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/29/17

Area Forecast Discussion
National Weather Service Green Bay WI
457 PM CST Sat Jan 28 2017 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Sunday Issued at 221 PM CST Sat Jan 28 2017 The latest rap analysis and satellite/radar imagery show cyclonic flow through the column over the western Great Lakes early this afternoon. A shortwave trough is moving southeast through this flow over northeast Wisconsin, which is supporting widespread very light snow showers and flurries. The flurries are showing signs of dissipating over western Wisconsin, with some breaks in the overcast occurring from Lincoln County to Duluth. Think this trend will continue for the rest of the afternoon as weak subsidence overcomes a thin saturated layer. The next shortwave is diving south over northern Manitoba, and is poised to arrive late tonight. Light snow shower trends and accumulations are the main forecast concerns. Tonight...The shortwave trough moving across northeast WI this afternoon will exit during the evening. Widespread cloudiness lies upstream, but wonder if some holes could develop, particularly in central and east-central WI, since the saturated layer is relatively thin. After midnight, a channeled vort max will be diving south into the region. Lake effect parameters will improve over western Lake Superior as the wave approaches, generally after 06Z. With favorable trajectories and 850mb temps squarely in the dendritic growth zone, should see lake effect bands intensify through the overnight hours. Could see an inch or two of fluff by sunrise over the northern parts of Vilas county. Some of these snow showers and flurries could also spread southeast into parts of central and northeast WI towards daybreak. Lows in the middle to upper teens. Sunday...The shortwave trough will continue to drop southeast across the state during the morning. Upward motion generated by the wave combined with increasing humidity in the 800-850mb layer and steepening low level lapse rates should result in widespread light snow showers and flurries through mid-afternoon, before drier air arrives from west to east thereafter. Though a small dusting will be possible everywhere, significant accumulations will be primarily confined to Vilas county where 2 to 3 additional inches will be possible in the northwest part of the county. No changes to the winter weather advisory. Highs in the upper teens north to middle 20s southeast. .LONG TERM...Sunday Night Through Saturday Issued at 221 PM CST Sat Jan 28 2017 Latest progs pointing to a clipper type system to track over the state Monday into Tuesday. Contribution with the warm air advection snow Monday may struggle with the initially dry air mass at the onset. However mid level height falls with a trend to a closed surface and or 850 mb low sliding over the north half of the state, may concentrate higher band of snow across the northern half or third of the state. Usually these clippers are more robust with an arctic air mass, but the colder air is lagging behind this system. Weak confluence aloft and a surface ridge building into the western Great Lakes will produce a colder and mainly drier regime for the rest of the week. Lake effect snows possible across the far north in the wake of the clipper system into Tuesday night, otherwise boundary layer winds appear too westerly for the remainder of the week. Air mass does not seem that cold, but later shifts may have to contend with clouds trends with respect to overnight low temperatures and a fresh snow cover. && .AVIATION...for 00Z TAF Issuance Issued at 454 PM CST Sat Jan 28 2017 Some breaks in the low clouds are likely this evening, though expect clouds to become more widespread across the area again later tonight as shortwave embedded in northwest flow approaches the region. Scattered snow showers and flurries will spread across the area late tonight into Sunday morning. Anticipate mainly MVFR conditions, though brief IFR conditions are possible with the heavier snow showers. && .GRB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from midnight tonight to 3 PM CST Sunday for WIZ005. && $$ SHORT TERM.....MPC LONG TERM......TDH AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
931 PM EST Sat Jan 28 2017 LATEST UPDATE... Update/Marine .SYNOPSIS... Issued at 320 PM EST Sat Jan 28 2017 Light lake effect snow showers will continue through the rest of the weekend. A brief period of steadier lake effect snow will affect the lakeshore counties Sunday afternoon and evening. A clipper system will bring potential for accumulating snow across much of our area Monday night and Tuesday. && .UPDATE... Issued at 931 PM EST Sat Jan 28 2017 I increased the snowfall overnight and Sunday west of US-131 based on the QFP forecast from the NAMGND5...the RAP model (numerous runs) and the HRRR and HRRRX (numerous runs). It seems our cold front is slipping south and is creating a frontogenesis area along the boundary were the inland colder air runs into the lake air. Currently (9 pm) the enhanced snow band is from north of Ludington to near Big Rapids. Behind the surface winds turn to the northwest and temperatures have fallen into the lower to to 20s, while ahead of the front winds are west and temperatures are holding in the upper 20s. This band will pivot to be from Hart to GRR by midnight and that will be where the snow showers should be strongest (west of US-131 after midnight). Tomorrow a strong shortwave drops nearly due south over Lake Michigan and increases the inversion heights increase from near 6000 ft around midnight to around 10000 ft Sunday afternoon. The 00z run of the RAP model shows the max lift is nearly dead center in the DGZ Sunday afternoon. All of this should play together to result in 2 to 4 inches of snow with the heaviest amounts from Grand Haven to near the city of Allegan. The surface winds show a convergence band at noon, near I-94 that could bring the snow showers inland along I-94 in the afternoon. The bottom line is stronger snow shower near the lake shore overnight into Sunday afternoon. && .SHORT TERM...(This evening through Monday) Issued at 320 PM EST Sat Jan 28 2017 Fcst concerns involve determining probabilities for lake effect snow showers and potential for any light accumulations. Light lake effect snow showers will continue to develop late this afternoon through tonight aided by some 1000-850 mb convergence and an upper level disturbance which is moving through this afternoon. Isolated patchy freezing drizzle mainly near to see of a line from Lansing to Battle Creek will end late this afternoon. Light wnw flow lake effect snow showers will continue tonight as h8 temps fall to -13 to -15 C by 12Z Sunday. A stronger upper disturbance will bring a period of steadier lake effect snow showers Sunday afternoon and evening. These will be most focused across our lakeshore counties due to fairly light nw winds that will gradually veer more to the nnw by late aftn/eve. Light snow accumulations of 1-3 inches are anticipated across the lakeshore counties with isolated higher amounts near 4 inches possible. Accumulations of only an inch or less are fcst Sunday afternoon through Sunday night near to east of US-131. Thx for extensive coord on no headline decision APX/IWX. Lake effect snow showers will taper off Monday as h8 temps gradually moderate through the day. However light snow associated with the clipper system may move into our nw fcst area as early as mid to late Monday aftn. .LONG TERM...(Monday night through Saturday) Issued at 320 PM EST Sat Jan 28 2017 The main challenge in the long term deals with the risk for impacts with next storm system Monday Night into Tuesday. Confidence continues to grow that at least moderate impacts will occur with this system. An area of snow will be spreading in from the northwest toward the end of the Monday evening commute as a stronger wave of low pressure moves in. South to southwest flow out ahead of this system will tap Lake MI moisture as the atmosphere will be supportive of lake enhance moisture with this system. 925 mb temperatures of -9 to -10 deg C at 18z Mon would be dry adiabatic to the unfrozen Lake MI. This flow typically favors areas north of a Grand Rapids to Holland line for heavier snow. The snow bands then pivot as the flow turns west northwest with the passage of the storm Monday Night into Tuesday. With just the synoptic wave moving through the CWA all areas should see accumulations...but it is where the bands pivot...likely Ottawa...Muskegon...Oceana and Mason counties are likely to see the most snow with 6 or more inches possible. There is some mid level Fgen and instability which could enhance the snow. The Nam did come in with a further north track...which would really limit the impacts...but it looked like the odd model out and was not used. Also the surface temperature could climb above freezing Tuesday morning...especially closer to the lakeshore...which would also limit the hazards. Cyclonic northwest flow then prevails for the remained of the week. This will support lake effect snow showers. Overall the temperature will be trending downward the the arctic airmass slowly filter in from the north. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 710 PM EST Sat Jan 28 2017 Expect snow showers to continue for the next 24 hours and then some. As is typical of lake effect snow showers, they tend to be closer the lake shore overnight and expand inland during the daytime. I would think inland TAF sites like GRR and LAN should be mostly VFR tonight. Also, typical of these events the snow showers are generally north and south of MKG, that too is expected, locations like Holland and South Haven will have heaver snow showers more frequently than MKG. On Sunday a second cold front comes into the area and that increases inversion height and the intensity of the snow showers. Seems we would get one of those I-94 snow bands by afternoon. Which means locations like JXN may have IFR or LIFR snow showers at times but I did not put that in their TAF since I should not be a dominant condition. I would think AZO is the most likely location to get IFR most of the time Sunday. MKG may be in a better location to see the snow showers Sunday afternoon so I did show that in their TAF. Expect for AZO and possibly MKG, we may see many hours of VFR with shore burst of IFR in snow showers into Monday morning. && .MARINE... Issued at 931 PM EST Sat Jan 28 2017 I extended the Small Craft Advisory into Monday morning since the winds support this idea. && .HYDROLOGY... Issued at 133 PM EST Fri Jan 27 2017 Rivers continue to have above normal flows, including some minor out-of-bank flooding. Advisories continue for: the Grand River At Ionia, the Grand River At Lowell, the Looking Glass River Near Eagle, the Maple River At Maple Rapids and the Thornapple River Above Hastings. River levels should slowly fall, as no rain is forecast through next week. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 8 AM EST Monday for LMZ844>849. && $$ UPDATE...WDM SYNOPSIS...Laurens SHORT TERM...Laurens LONG TERM...MJS AVIATION...WDM HYDROLOGY...63 MARINE...WDM
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
939 PM CST Sat Jan 28 2017 .UPDATE... Issued at 939 PM CST Sat Jan 28 2017 Rain showers over central Missouri will continue to move southeast ahead of a mid level vort max. Isolated rain and snow showers will continue overnight into Sunday morning as a series of vort maxes move across the area in northwest flow. Still could be some minor snow accumulations in some of the heavier snow showers. Made only minor adjustments to temperatures. Britt && .SHORT TERM... (Through Late Sunday Afternoon) Issued at 225 PM CST Sat Jan 28 2017 Several disturbances within a NW flow pattern aloft will move across the area tonight and tomorrow, bringing periods of clouds and flurries to parts of MO/IL as well as contributing to the development of a trough over the East Coast. 20z water vapor imagery complemented by RAP 1.5 PVU and local WRF vorticity fields showed two of these disturbances upstream. One disturbance was located over eastern SD and the other was farther north over western MB. The resulting vort max corridor will continue moving SSE into western and central MO tonight. Steep lapse rates, synoptic lift, and some moisture suggest that flurries or light snow showers are possible tonight, especially after 03z. Some locations over northeast and central MO may even see a tenth or two of accumulating snowfall, but only the late night owls or early morning larks are likely to see it before it melts on Sunday morning. A much stronger disturbance was located over the western Hudson Bay this afternoon and will continue diving southward tonight, eventually reaching northern IL/IN tomorrow morning. The stronger lift associated with this feature remains east of the CWA, but a weaker disturbance on its W/SW periphery could support flurries/sprinkles or light snow/rain tomorrow, primarily across SW IL. Low temperatures will be slightly warmer than average tonight and highs will be near average tomorrow across most of the area. Kanofsky .LONG TERM... (Sunday Night through Next Saturday) Issued at 225 PM CST Sat Jan 28 2017 Cyclonic flow aloft will continue into Sunday night with flurries or light snow showers still possible east of the Mississippi River early Sunday evening. Otherwise...expect a mostly cloudy sky initially to become more partly cloudy late Sunday night. Low temperatures are expected to be predominantly in the mid to upper 20s. Did warm up lows several degrees from previous forecast to be more in line with latest MAV/MET guidance mainly due to expected slow fall due to ample cloud cover most of the night. Quick warmup will be in store for Monday as weak ridge axis quickly moves off to the east of the CWA. Strong low-level WAA ahead of a potent clipper transversing the Upper Midwest will help yield high temperatures well above normal for late January. High temperatures are expected to range from the low 40s across far eastern sections of the CWFA to low 50s across portions of central Missouri. Flow pattern aloft will continue to generally be northwesterly through the remainder of the extended but will gradually become more zonal by late next week and early next weekend. Vast majority of the Tuesday - next Saturday timeframe should be dry with near normal temperatures. Two periods of interest for precipitation. The first is Tuesday night/early Wednesday as combination of weak WAA and 850- 700 hPa frontogenesis could produce some light snow. Lack of forcing mechanisms at mid and upper levels along with scant moisture available preclude PoPs however at this time...but could be something to watch. Better chance at widespread light precipitation most likely in the form of snow would be toward next Saturday as weak impulse ejects out of the Rockies into the south- central Plains. Gosselin && .AVIATION... (For the 00z TAFs through 00z Sunday Evening) Issued at 601 PM CST Sat Jan 28 2017 Area of MVFR cloudiness over Iowa will move southeast and reach KUIN and KCOU by mid evening and the St. Louis area terminals around 06Z. These low clouds are expected to remain over the area through at least midday Sunday before ceilings improve to VFR. There will be the chance for isolated snow showers or flurries, but coverage is too difficult to try to time at any of the terminals at this time. West to northwesterly winds will continue through the end of the period. SPECIFICS FOR KSTL: MVFR ceilings will move into the area from the northwest late this evening. The MVFR ceilings will continue through midday Sunday before improving by midday Sunday. There will be isolated snow showers or flurries in the area between 06-18Z, but have not included mention in the TAF at this point as exact timing in the terminal is uncertain. West to northwesterly winds will continue through the end of the period. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Updated for 00Z Aviation Forecast Discussion below.

&& .PREV DISCUSSION... /issued 252 PM CST Sat Jan 28 2017/ DISCUSSION...Water Vapor satellite trends this afternoon indicate an upper level trough over the Eastern United States. A mid-level shortwave trough is located over Missouri this afternoon. Meanwhile, sunny skies prevail across the Mid-South with temperatures as of 2 pm CST in the 40s at most locations. A series of mid-level shortwave troughs embedded within northwest flow aloft will move across the Mid-South and Lower Mississippi Valley tonight and again Sunday morning. A few clouds are possible with the first shortwave and a potential for some light rain and/or snow showers mainly Sunday morning across portions of West Tennessee near the Tennessee River. Not anticipating any significant impacts at this time due to limited moisture and duration of precipitation. The upper level trough will begin to move slightly east with the Lower Mississippi Valley remaining under the influence of northwest flow aloft through the middle of next week. At the surface, another weak front will drop into the region on Tuesday. Long term models diverge towards late next week as the front begins to move slowly back north across the Mid-South. Precipitation chances are anticipated to return but confidence remains low due to significant model run to run differences. CJC && .AVIATION... 00Z TAFs VFR and light winds to prevail for the evening. MKL will be most likely to see MVFR cigs dropping down the back side of a longwave trof over the Ohio Valley on Sunday. A few -SN -RA showers possible at MKL, but suspect a fair amount of this will evaporate in the dry subcloud layer. PWB && .AVIATION... && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Area Forecast Discussion
National Weather Service Miami FL
803 PM EST Sat Jan 28 2017 .UPDATE... The 00Z MFL sounding indicates light northerly flow near the surface with stronger west southwest flow aloft. Moisture had increased in the lower and mid levels, but still noticeably dry above 700 mb. Water vapor imagery shows a plume of moisture stretching south Texas eastward across northern and central Florida then out over the Atlantic. Models continue to prog this moisture belt to sag south and affect our CWA later tonight through Sunday evening. Latest runs of the HRRR and Hi- Res WRF push light to moderate showers ashore from the Gulf starting around 2 or 3 am EST. Have decreased PoPs until this timeframe to account for the delayed arrival of precip. Otherwise, all other variables appear on track. && .PREV DISCUSSION... /issued 703 PM EST Sat Jan 28 2017/ AVIATION... NNW wind around 5 KT overnight will increase to around 10 KT by mid-morning Sunday. VFR conditions will gradually degrade after SHRA and -RA envelop the region around sunrise. Went the conservative approach in terms of delayed onset of restrictions, based on relatively dry low-levels. Still, expect by late morning for MVFR CIGS to overspread the region, likely from NW-SE, like PCPN onset. Could see some IFR conditions to especially early/mid-afternoon, but confidence is too low to mention in TAFs ATTM. Also, could see rain ending/improving conditions toward end of TAF period. PREV DISCUSSION... /issued 449 PM EST Sat Jan 28 2017/ DISCUSSION... Late this afternoon through Sunday: Latest surface analysis shows a stationary front stretching from the Bahamas southwest towards Western Cuba. Cold air advection from the north has led to a much cooler and drier day as compared to yesterday. Dewpoints have already dropped into the upper 30s (northern interior) and 40s elsewhere. Maximum temperatures have struggled to rise into the low 70s. Tonight, global models begin to deepen a long wave trough over the southeast CONUS. As this occurs, warm moist air from Carribean will be drawn northward, up over the aforementioned stationary front. Isentropic ascent will likely help to generate overcast cloud conditions with widespread showers over South Florida. According to the HRRR and Hi-Res WRF, scattered light showers will begin to push onshore from the Gulf by early Sunday morning. By late Sunday morning into early afternoon, light to moderate showers increase in coverage with likely to categorical PoPs now in the grids. Highest probabilities are progged along the east coast metro region. Not expecting much in the way of convective activity, as instability parameters, such as CAPE, are unimpressive. A cool airmass, combined with this thick low/middle level cloud deck, will lead to a very chilly day (by Florida standards). Maximum temperatures on Sunday are only forecast in the upper 50s (northern interior) to lower 60s elsewhere. These values are between 10-15 degrees below normal for this time of year and will be flirting with daily low maximum records. Late Sunday afternoon into Sunday evening, precipitation chances will dwindle as an approaching front pushes the activity eastward and offshore. Sunday night, light winds and drier conditons will allow for temperatures to once again drop down to the 40s and low 50s. Monday through mid-next week: Zonal flow will prevail through mid- week next week. This pattern promote dry and cool conditions across the area. Surface winds will gradually shift from north to northeast as the week progresses. Monday night will be the coldest with lows falling down to near 40 (northern interior) and generally widespread 40s to low 50s elsewhere. Wind chills may drop to the mid 30s near Lake Okeechobee and mid 40s for the east coast metro. Expect a slight warming trend through the work week, with temperatures rising a couple degrees each day. MARINE... Generally light to moderate northerly flow will prevail through Sunday evening. A frontal passage Sunday night will increase these winds to 15-20 KT over the over the waters and small craft should exercise caution. However, waves are should to remain relatively small, mainly below 6 feet. Widespread light to moderate rain will spread over the coastal waters late tonight through Sunday afternoon. By early next week, drier weather will return with winds shifting to the northeast. FIRE WEATHER... RH should increase on Sunday, when a front begins to push over the region. This feature will bring an increase in low level moisture and widespread light to moderate precipitation. Dry and cool northerly flow will return Monday through the middle of next week. && .PRELIMINARY POINT TEMPS/POPS... West Palm Beach 71 48 62 47 / 0 40 80 20 Fort Lauderdale 72 50 63 53 / 0 40 80 20 Miami 74 52 62 53 / 0 50 80 20 Naples 70 53 64 51 / 0 50 70 10 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. GM...None. && UPDATE...27/JT DISCUSSION...27/JT MARINE...27/JT AVIATION...23/SK FIRE WEATHER...27/JT
Area Forecast Discussion
National Weather Service Marquette MI
640 PM EST Sat Jan 28 2017 .SHORT TERM...(This evening through Sunday) Issued at 451 PM EST SAT JAN 28 2017 Water vapor imagery and RAP analysis show a ridge over western N America with a trof over eastern N America. Dropping sse into the trof, one shortwave passed across the area earlier today giving LES a boost, mainly off central and eastern Lake Superior. Sfc trof associated with the shortwave was the focus for heaviest snowfall as it pushed s across nw, central and eastern Upper MI. In the wake of the sfc trof, it has taken awhile for LES to organize, but with 850mb temps steadily dropping, now down to around -17C over the e half of the lake, wind parallel LES bands have rapidly organized in the last couple hrs. Over western Upper MI, LES has been light this aftn under more pronounced deep layer q-vector divergence/subsidence in the wake of the shortwave and a warmer air mass with 850mb temps about 3C higher than over the e half of the lake. Attention now turns to the shortwave currently dropping sse thru northern Manitoba. This wave will track across ne MN/western Lake Superior and WI late tonight and Sunday morning with passage of associated sfc trof veering winds from a northwesterly direction to a more northerly direction. Consistent with previous model runs, models show best deep layer forcing with shortwave passing over western Lake Superior. Although best forcing passes across the w, the eastern half of the fcst area will be deeper into the large scale trof, resulting in deeper moisture up to 12+kft. Over the w, inversion/moisture lift to 8+kft. End result should be similar snow accumulations for both areas. Fcst soundings show the dgz ideally situated in the convective layer with a nice intersection thru the upward motion. With winds not strong to cause fracturing/breaking of dendrites, expect to see high snow-to-water ratios of at least 30 to 1. Wouldn`t be surprised to see it much higher. Snowfall this morning here at the office was running at a 45 to 1 ratio. Setup seems very favorable for heavy snow in a fairly short period of time, heaviest from late tonight into Sun morning. With the wind shift to n or nnw, far western Upper MI (Gogebic/Ontonagon counties) and north central Upper MI (Marquette county eastward) will be favored for heaviest snowfall. 12hr snow amounts may push the 8in/12hr warning threshold for low snow to water ratio snow in a few spots. However, given the lack of other hazards (strong wind/blsn), impacts won`t be significant even if a few spots receive more snow. With less favorable wind direction, snowfall across the Keweenaw will probably total 3-5 inches for the tonight/Sun period. Inversions will fall to around 5kft over the w during Sun as increasing subsidence overspreads the area in the wake of the shortwave. Over the e, moisture/inversion stay up toward 10kft thru the day, supporting continued mdt to perhaps heavy LES at times. Only 2 changes were made to headlines with this fcst issuance. First was to cancel the Baraga advy early. For simplicity and to avoid cancelling and issuing a new advy for Marquette county, current advy was extended thru Sun even though mdt/hvy snowfall does not begin until late tonight/early Sun morning. .LONG TERM...(Sunday night through Saturday) Issued at 308 PM EST SAT JAN 28 2017 The main forecast highlights will be LES coming to an end on Monday ahead of a clipper system progged to drop down across the region Monday into Tuesday. This system will bring widespread system snow to the region, but confidence is not high in how much at this time with models continuing to trend south with the system. Behind the clipper system LES is expecting to linger as northwest flow dominates the upper-air pattern across the Great Lakes Region with colder air coming down from Canada. A brief break or at least lessening of LES is possible towards the end of the week. Sunday night into Monday as 850mb flow backs to the west and southwest as warm air advection increases ahead of the approaching clipper system, this will allow LES to transition from the northwest wind to west wind belts before diminishing through on Monday. Temperatures will warm a few degrees above normal for this time of year given the warm air advection. As the system approaches from the northwest, expect the system snow to fill in from west to east across the area Monday afternoon and possibly linger through early Tuesday morning. Even though there is some uncertainty among the ensembles and deterministic models, the general trends have been for the system to take a more southern track. Therefore, the combination of the GFS/ECMWF at this time looks to be a good starting point. Right now, the models are showing the best lift hugging the Upper Michigan/Wisconsin border with the 850/700mb warm air advection nosed into the region with the left front quadrant tracking just to the south. Amounts from this system look like they may range from 1 to 4 inches of system snow, with the highest probability of seeing 3 to 4 inches being along the Wisconsin border and where lake enhancement looks possible along southwest portions of Lake Superior and northern portions of Lake Michigan. As the system exits the region into Tuesday into Wednesday, expect light LES to linger in the northwest wind snow belts. 850mb temperatures do not look impressive until after another shortwave digs south across the region ushering in much colder 850mb temperatures, around -20C. This will allow for lingering LES to increase in coverage and intensify across the northwest wind snow belts on Wednesday. Given the strong cold air advection, also expect temperatures to drop as well. Overnight lows look like they will easily drop into the single digits and teens at night with teens and 20s during the daytime hours. Thursday into Friday as upper- level subsidence increases and flow backs to the west in response to high pressure dropping southeast across the northern plains, expect LES to diminish in intensity and transition into the west wind snow belts. A few locations may even see a break in the LES, especially across the west. The ECMWF and GFS then dig another shortwave across the area which should favor LES to increase briefly in coverage towards the end of the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 640 PM EST SAT JAN 28 2017 Lake effect snows will continue at all three TAF sites through the forecast as northwesterly winds continue over the region. The heaviest snows are still expected to occur in association with a disturbance passing across the western Great Lakes overnight thru Sunday morning. With the the passage of this feature, expect snowfall rates to increase overnight with a resulting drop in visibilities into the IFR range during the overnight hours and extending into Sunday morning. As the passes by and winds diminish and shift a bit more westerly, cold air advection also diminishes and the intensity of the snow showers weaken as well. Visibilities improve through the afternoon at all three TAF sites with MVFR conditions prevailing by then. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 451 PM EST SAT JAN 28 2017 No gales are expected thru Thu. Nw to n winds of 15-30kt are expected tonight/Sun, strongest over the e half of the lake. Winds will then diminish to under 15kt for a time Sun night/early Mon as high pres ridge passes. As the ridge shifts e and another low pres approaches from the w, southerly winds will increase up to around 25kt for a time Mon aftn/evening over the e portion of the lake. Once the low moves to the e, expect nw winds up to 25kt. Winds will icnrease further, up to 30kt for Wed/Thu as pres gradient tightens ahead of an approaching high pres ridge. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Lake Effect Snow Advisory until 7 PM EST Sunday for MIZ005>007- 085. Lake Effect Snow Advisory from midnight EST /11 PM CST/ tonight to 4 PM EST /3 PM CST/ Sunday for MIZ002-009. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Rolfson LONG TERM...Ritzman AVIATION...RJT MARINE...Rolfson
Area Forecast Discussion
National Weather Service Morristown TN
955 PM EST Sat Jan 28 2017 .DISCUSSION... Latest water vapor and RAP upper air analysis indicating the first in a series of shortwave troughs is beginning to push east across the CWA. This has brought increasing cloudiness and and an overcast layer at about 7000-8000 ft. With dewpoints in the upper teens to low 20s across most of the area, the light returns on radar noted over southeast Kentucky and southwest Virginia are not reaching the ground as pcpn at this time. Forecast is still on track as second in series of shortwaves currently over central Missouri pushes further SE across the area by 12-15Z on Sunday commencing period of light snow mainly across higher elevations of southwest Virginia and Tennessee mountains. As surface temperatures in the valley warm during the afternoon, expect pcpn to transition to rain across central Tennessee Valley while areas closer to Tennesee-Virginia-Kentucky border and locations in the northern Cumberland Plateau may continue to see snow showers throughout the afternoon. Currently, all of southwest Virginia and mountains of east Tennessee remain in a Winter Weather Advisory while remainder of the central and northern Valleys along with the northern Cumberland Plateau are still expected to see accumulations of 2 inches or less. Tweaked temperature grids as cloud cover has held temps up a bit across the central and northern valleys. Additionally tweaked sky grid to account for quicker timing of increasing cloudiness area wide. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 33 44 30 46 / 10 40 20 0 Knoxville McGhee Tyson Airport, TN 33 43 29 41 / 20 70 60 10 Oak Ridge, TN 33 43 29 41 / 20 70 60 10 Tri Cities Airport, TN 27 41 24 36 / 30 70 70 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...Winter Weather Advisory from noon Sunday to noon EST Monday for Blount Smoky Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Unicoi. VA...Winter Weather Advisory from noon Sunday to noon EST Monday for Lee-Russell-Scott-Washington-Wise. && $$
Area Forecast Discussion
National Weather Service Paducah KY
925 PM CST Sat Jan 28 2017 .UPDATE... Issued at 925 PM CST Sat Jan 28 2017 Temperatures have been slower to fall this evening than forecast. The short-term consensus model blend has risen a few degrees since this afternoon. Therefore, temps overnight were raised just a couple degrees, which keeps lows at or above freezing south of a kcgi/kpah/Madisonville line. As far as the precip, some rain has been reported in central Missouri the past couple hours. This is in line with the 00z rap and hrrr, which bring patchy measurable precip across our region through 12z. Pops have been raised a bit tonight, but measurable precip chances are still only 20 to 30 percent. The precip should become mostly snow as boundary layer temps cool overnight. Any accumulations will be less than a half inch, mainly on grassy areas. && .SHORT TERM...(Tonight through Monday night) Issued at 157 PM CST Sat Jan 28 2017 Above average confidence through the short term due to decent model agreement. Other than an increase in low level moisture and resultant deck of low clouds, no precipitation expected through most of this evening. By midnight precipitation in the form of snow showers will begin to move into the far northwestern sections of our CWA as the first of a series of short waves rotating around the back side of an upper low over southeast Canada taps into deeper moisture. Light snow showers will continue from late tonight through mid Sunday morning across all but the far western sections of our CWA with little to no snow accumulation expected. As the day progresses and temperatures warm a bit, the changeover from snow to rain or a mixture thereof is expected to migrate northward through the day. Precipitation may never change over to or mix with rain over the far northeast sections of our CWA Sunday. As temperatures cool Sunday evening, what`s left of upper level energy and moisture may produce light snow showers over the far eastern and northeastern sections of our CWA. Again little to no snow accumulation expected. In the wake of this system, the northern fringes of surface high pressure should be the dominant weather feature on Monday. Monday night a short wave diving southeast out of the northern plains will push/pull a cold front across the CWA but due to a lack of moisture no precipitation is expected. Temperatures through the period within a couple degrees of normal. .LONG TERM...(Tuesday through Saturday) Issued at 157 PM CST Sat Jan 28 2017 The extended forecast period starts out with a upper ridge in the west and trough in the east, putting us in northwest flow. The pressure gradient relaxes during the day as weak sfc high pressure builds into the area behind a dry frontal passage early in the day. The Canadian model still depicts a swath of precipitation arriving Tuesday night in association with weak support aloft, but the GFS/ECMWF not excited about any prospects. Based on collaboration with neighboring offices, decided to drop chances for Tuesday night for now. We should see dry weather for Wednesday as a reinforcing high pressure builds in. A surface frontal boundary will be setup just to our south. Any precipitation associated with this front should stay south. However, models differ on the chances for precipitation Thursday through Friday. The GFS and GFS ensembles continues to indicate decent isentropic lift across the area along with a minor disturbance in the upper flow. Precipitation is produced mainly Thursday afternoon into the evening. This will result in rain to start out and then transitioning to some light snow. The ECMWF is much less robust with the lift and hence precipitation. We see chances on Saturday/Saturday night as well, as the upper pattern becomes more active. However, differences in models this far in the extended period are to be expected, so will maintain just chance type POPs for now. Again, we could be dealing with some light snow at times mainly during the night time hours, as during the day we should be in the 40s in most locations, maybe upper 30s up in the far north. All in all, no big signals right now of anything major with any of these precipitation chances. The latest model data just seems a bit chaotic right now and we need to watch how future runs deal with the latter half of the week and into the weekend. Tuesday will be the warmest day with highs in the upper 40s to lower 50s. Beyond that, we will be sticking in the 40s in most locales for highs for the rest of the week and into the weekend, with upper 30s possible far north. && .AVIATION... Issued at 456 PM CST Sat Jan 28 2017 VFR conditions through 07-10z with increasing mainly high clouds and west winds below 10 kts. Some light snows should develop late tonight and continue Sunday with winds becoming gusty NW and cigs mainly MVFR. The light snows should be in bands / showers and not persistent. But ocnl MVFR vsbys are likely in some areas. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ Update...MY