Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/08/16

Area Forecast Discussion
National Weather Service Binghamton NY
945 PM EST Wed Dec 7 2016 .SYNOPSIS... Lake effect snow showers will develop over NY and far northern PA on Thursday, and become more potent heading into the weekend. && .NEAR TERM /THROUGH THURSDAY/... 930 PM update... In the broad southwest flow ahead of a closed upper low south of James Bay, some vorticity at 500 mb is causing some very light snow in southern Missouri right now. Why mention light snow in MO? Well, as the cut off low moves into far western Ontario by 12Z Thursday, this channeled vorticity sneaks up toward the NY/PA border. The higher resolution guidance such as the HRRR and ARW/NMM continue to show some scattered flurries or very light snow with this between 09Z and 14Z tomorrow. We already had a chance for snow across much of NY but I increased pops toward the NY state line and into northern PA to account for this. Otherwise no big changes to the forecast. We have fielded a few questions on social media about why we lowered snowfall amounts for Thursday night through Friday night. If have a few moments, we made a quick but detailed video on some of the challenges of forecasting lake effect snow. You can see it at The previous AFD is below... 205 PM update... A potent polar air mass will plunge into the base of a trough rotating through the northeastern U.S., activating the lakes early Thursday. We largely followed the lake bands produced by the CMC Regional guidance, as these look realistic in terms of placement and QPF. However, we added in a larger area of light snow surrounding the bands over central NY, as persistent northwest flow should generate light precipitation nearly to the NY/PA border by mid- afternoon. Most NY sites will not make it out of the 20s on Thursday. 1030 AM update... With precipitation moving out and clouds thinning, temperatures are climbing quickly this morning, with several observations already at or above the projected maximums. We raised forecast maximums this afternoon. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... Lake effect snow watches and the warning for Northern Onedia county remain in place. The main change with this update was to lower snowfall amounts as some favorable factors for high amounts of snow are now becoming less favorable. A lake effect band of snow north of our area Thursday evening should impact northern Oneida County through 06Z Friday with a flow between 270/275. Inversion heights are well above 10,000 feet, with a good fetch over lake with moderate instability. The snow growth region is a bit lower than yesterday and the models are still forecasting shear. This may widen the band somewhat but also make it more diffuse. The other question mark is some models are faster with a trof, which would shift our winds into the northwest and sink the band farther south than currently anticipated. We lowered amounts a bit to compensate for some of the concerns above but overall this area remains the most likely area to see signficant snowfall in our area, at this vantage point. Early Friday the trof mentioned above will swing through and disrupt the snow band while moving it south. Eventually a steady 300 to 310 wind flow will set up Friday and Friday night. The inversion heights do lower as expected but they are 2 to 4kft lower than the runs of the models yesterday. In addition while not perfect, the snow growth region is a bit higher than previously thought and the best lift in the atmosphere may not line up as well. Model QPFs remain very low and while not usually at all in reality in lake effect events, with the low QPF and the slightly less favorable conditions just 24 hours removed from yesterday, it was hard to argue in not lowering amounts. The WATCh will remain in place and hopefully we can have more clarity tonight with the 0Z runs. We may be looking at a widespread lake effect advisory area vs. a warning but time will tell. Speaking of an advisory, folks in nothern Cortland, Chenango, Delware and Otsego counties will remain close enough to lake snows that advisory level snows are possible here. We will mention it in the hazardous weather outlook. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... 210 PM update... A persistent trough over the northeastern U.S. will keep the weather stormier than normal, while temperatures remain on the cool side. Lake effect snows will be ongoing Saturday night, with most of the activity migrating north of Oneida County on Sunday. A powerful storm will move up the Ohio Valley on Monday, bringing another round of snow, possibly mixing with rain during the warmest midday hours. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... VFR expected overnight with bkn to ovc mid to high level clouds. The main concern will be the potential for brief heavier snow squalls Thursday at the NY terminals. While the heaviest and steadiest snows will remain well to the north and west of the terminals, two time periods may poise a problem. First between 12Z and 16Z some mvfr cigs to high end ifr vsbys possible at KSYR and KRME in light snow showers. Not expecting vsbys to drop below 1 to 2sm here. After 18Z a band of lake effect snow off Lake Erie will likely be near KITH and perhaps even KBGM. During that time at least mvfr cigs and vsbys will be possible. Confidence was higher the band would be closest at KITH so I included some high end ifr here. It should be noted however that brief vsbys under 1sm are possible in the heaviest of squalls. OUTLOOK... Thursday night -Saturday...Restrictions likely at KSYR in lake- effect snow, with possible restrictions in snow showers/flurries down to KRME, KELM, KITH, and KBGM. KAVP should be mainly VFR. Sunday...Widespread restrictions becoming more likely with a general light snowfall. Monday...restrictions possible in sct. snow showers. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...Lake Effect Snow Watch from Thursday evening through late Friday night for NYZ017-018-036-037. Lake Effect Snow Warning from 11 AM Thursday to 7 AM EST Friday for NYZ009. && $$ SYNOPSIS...DJP NEAR TERM...DJP/Heden SHORT TERM...MLJ LONG TERM...DJP AVIATION...Heden
Area Forecast Discussion
National Weather Service Bismarck ND
905 PM CST Wed Dec 7 2016 .UPDATE... Issued at 859 PM CST Wed Dec 7 2016 Will let the blizzard warning expire as winds have or will diminish below 35 mph although 30 to 35 mph will be common overnight with a few gusts to 40 mph early on. However as the surface trough moves south through the region the band of snow will move south as well and that will help improve the visibilities which are now a half mile or better at many locations in the blizzard area. The RAP model maintains its steady rise in 3hr pressures of 2 mb through the night and that should maintain winds in the 30 to 35 mph range east central. So went with a winter weather advisory through 15z. Also extended the wind chill advisory another set of counties east tonight. UPDATE Issued at 625 PM CST Wed Dec 7 2016 Canadian and NWS radars show the band of snow involved with the blowing and drifting snow is moving south with the surface pressure trough. The RAP model does project 2-3 MB pressure rises every 3 hours across the east half of North Dakota at least through most of the night. This will help to sustain the winds but with the snow tapering off over time the blowing snow will be reduced. So thinking about issuing winter weather advisory after the blizzard warning expires at 9 pm. Will continue to evaluate. Across the south central places like Bismarck will be on the edge of wind chill advisory criteria and will continue to monitor for eastward expansion of the wind chill advisory later this evening. && .SHORT TERM...(This evening through Thursday) Issued at 315 PM CST Wed Dec 7 2016 Blizzard conditions this evening highlight the short term forecast. Did upgrade the Winter Weather Advisory to a Blizzard Warning across north central North Dakota through the James River Valley through 03 UTC this evening. Surface and webcam observations through 21 UTC are confirmed by multiple reports on social media of the redevelopment of near zero visibility this afternoon across the aforementioned areas in blowing snow and lightly falling snow. The LAMP guidance is the preferred source for winds as it is the highest and matches observations the best. This suggests wind gusts in excess of 40kts may continue through 00 UTC, and only decreasing very slowly thereafter. The 12-18 UTC global suites also support lightly falling snow to continue through the evening as well. This all equates to a high likelihood of blizzard conditions continuing into the evening. No changes made to the remainder of the Winter Weather Advisory or the Wind Chill Advisory at this time. .LONG TERM...(Thursday night through Wednesday) Issued at 315 PM CST Wed Dec 7 2016 Dangerous wind chills for much of the period and the potential for accumulating snow on Saturday highlight the extended forecast. The 12 UTC global suites are in good agreement on arctic high pressure across the Northern Plains through Friday night. Dependent on cloud cover, Thursday night into Friday morning may be very cold with the arctic high centered over western and central North Dakota with a large snowpack. Accumulating snow is favored for Saturday across the area north of a surface low forecast to propagate across the central plains. The arctic airmass may rebuild across the area Sunday into next week. Dangerous wind chills are possible at least during the overnight and morning hours nearly each day across portions of western and central North Dakota. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 625 PM CST Wed Dec 7 2016 Low pressure extending from Ontario west into North Dakota will bring widespread gusty winds to 45kts and ifr conditions in areas of blowing snow impacting KJMS through 06z. winds will gradually trend lower after 06z. Otherwise VFR to occasionally MVFR conditions KDIK- KISN- KMOT- KBIS in gusty winds to 35kts and brief areas of blowing snow. && .BIS WATCHES/WARNINGS/ADVISORIES... Wind Chill Advisory until noon CST /11 AM MST/ Thursday for NDZ001>003-009>011-017>021-031>035-040>046. Winter Weather Advisory until 9 AM CST Thursday for NDZ004-005- 012-013-022-023-025-036-037-047-048-050-051. && $$ UPDATE...WAA AVIATION...WAA
Area Forecast Discussion
National Weather Service Denver/Boulder CO
826 PM MST Wed Dec 7 2016 .UPDATE... Issued at 820 PM MST Wed Dec 7 2016 Arctic high pressure moving over the area will bring dry conditions and light winds tonight. A weak east/northeast flow around the high has kept low clouds along the foothills and Palmer Divide. Most of these will dissipate by midnight. Only made minor changes to line up with current trends. && .SHORT TERM...(This evening through Thursday) Issued at 222 PM MST Wed Dec 7 2016 The upper level trough that produced snow across our area is migrating east this afternoon and winds aloft will transition to a dry west northwest flow. At the surface a strong ridge of high pressure will gradually build across Colorado. There is still just enough upslope component and instability within the base of the trough to generate some lingering light snow showers along the north side of the Palmer divide and along the east slopes of the Front Range. Any snow showers should be brief and should diminish this evening as the trough axis moves out of the state and the upslope flow weakens with the building of the surface ridge. Do not expect additional snowfall accumulation this afternoon/evening. Tonight a strong surface ridge of high pressure will build into far NE Colorado with maximum sea level pressure getting to about 1043mb. This will act to weaken the winds across the Plains overnight. Weak winds, clearing skies, and a fresh snow cover will cause already cold temperatures to plummet shortly after sunset area-wide. Expecting minimum temperatures to drop below zero across the Denver metro area for the first time since February 2015. All model blends and most of the deterministic models do not have a good handle on the low temperatures. The bright spots in terms of guidance are the high res models: RAP and HRRR, as well as the ESRL HRRR, all seem to zero in on the really cold min temperatures. For low temperatures tonight have followed the HRRR and RAP closely, which are at least 10 degrees colder than any other blend or deterministic guidance out there. Low temperatures should bottom out in the -5 to -10 range in the Denver metro area, close to -15 in the Platte River Valley, and in the -10 to -20 range in the mountains. Temperatures alone are near wind chill advisory levels across the BOU CWA. However, the only areas expected to have winds above 5-10 mph and exceed advisory criteria should be the far eastern counties. Have hoisted a wind chill advisory for Logan, Washington, Sedgwick, and Phillips counties from 11 PM to 8 AM local time, in line with surrounding offices. Despite the weak winds in the metro area, it will still be exceptionally cold so it will be a good idea to take cold weather precautions for sensitive/vulnerable people and animals. On Thursday temperatures will struggle to hit 20 degrees across the Plains of northeast Colorado given the cold start, snow cover, and presence of the surface high pressure preventing any downslope component to the low level winds. Should remain dry across the Plains and mountains with light winds. .LONG TERM...(Thursday night through Wednesday) Issued at 222 PM MST Wed Dec 7 2016 Continued moisture will flow into the mountains from the WNW through the extended period bringing accumulating snowfall. Thursday night into Friday models show increasing moisture over the mountains with warm air advection moving in with WNW flow aloft. QG increases through the day Friday which will help with snow making properties. Will keep high pops for this period with confidence in some accumulation on Friday...especially for west-facing slopes of the Northern and Central mountains. Will double-down on the previous mention of the need for a possible advisory for zone 31 given current QPF model accumulation amounts. On the plains a lee side low will form at the base of the Foothills keeping the area dry. Downslope winds will heat the plains and help to increase snow melt. Cold air near the surface will take some time to scour out as melting and evaporation will lower temps before they increase so will maintain temps in the 40s with even warmer temperatures possible by Saturday. Friday the jet will start to drop south over the state increasing mountain top winds. Model cross sections show component along values upwards of 50 knots at mountain top level but do not see a distinct stable level with adequate shear that would allow for those winds to make it down into the foothills and plains. For the weekend the upper jet will continue to drop south over the Central mountains increasing winds over the higher terrain. Moisture continues to flow into the mountains increasing snowfall production through the weekend. Elements such as QG instability,shortwave, high levels of moisture and upper jet dynamics could result in a winter storm event in the mountains with high levels of accumulation. The front will move onto the plains by late Saturday bringing some increased moisture and cooler NW flow. This is a quick shot with little accumulation shown at this time...however if surface winds switch just a little more NNE the foothills and western plains could see some light snow so will keep pops in place. For next week the upper level NW flow will continue with multiple embedded shortwaves keeping the orographic snow machine churning. The main difference in the models is the amount of cooler air that makes it onto the plains. With continued NW flow in the synoptic picture I do think that colder arctic air could make it down so keeping temps an average between the two models with some nudging to the cooler side. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) Issued at 820 PM MST Wed Dec 7 2016 VFR conditions will prevail through Thursday evening with light winds. && .BOU WATCHES/WARNINGS/ADVISORIES... Wind Chill Advisory until 8 AM MST Thursday for COZ048>051. && $$ UPDATE...Meier SHORT TERM...Schlatter LONG TERM...Bowen AVIATION...Meier
Area Forecast Discussion
National Weather Service Burlington VT
956 PM EST Wed Dec 7 2016 .SYNOPSIS... An unsettled pattern is expected across the North Country through the end of the week...with occasional snow showers and isolated snow temperatures drop to below normal levels by the weekend. Total snow accumulations of 3 to 6 inches with isolated higher amounts will be possible south of Route 3 in Saint Lawrence County and the northern mountains of Vermont and New York. A dusting to several inches possible in the valleys with periods of hazardous travel possible. && .NEAR TERM /THROUGH THURSDAY NIGHT/... As of 935 PM EST Wednesday......Lake snow advisory continues for Southern Saint Lawrence County mainly south of Route 3 for 4 to 7 inches of snow by Thursday Night... Current forecast remains in good shape with only some subtle tweaks to the chance for precip through the next couple of hours. KTYX is showing a weak band of showers extending off Lake Ontario but Watertown is reporting light rain. Expect as the band lifts further north that it will turn to light snow but there shouldn`t be much accumulation from it. The HRRR and our local WRF models seem to have a good grasp of the precip so I heavily blended that combination into the forecast through midnight. Otherwise no changes to the forecast were needed. Previous Discussion...Forecast challenge will be timing of snow showers and squalls across our region...along with potential impacts and accumulation. Large picture shows closed 5h/7h circulation over the northern Great Lakes with broad southwest flow aloft across the northeast conus. Watching increasing mid level moisture and weak elongated vort over the central/northern plains moving our way for Thursday. This energy and moisture aloft...will combined with cooling thermal profiles to produce occasional snow showers and isolated snow squalls across parts of our region. High resolution models show ingredients coming together with instability...moisture...and favorable southwest aligned flow around 12z Thursday across central Saint Lawrence County. Latest 4km NAM and locally developed BTV 4km shows this band intensifying btwn 15z-21z low level instability increases from surface heating and cooling aloft associated with trof and deeper moisture feed from Lake Ontario. Very difficult to determine organization of band without a sharp convergence line and limited deep layer moisture...but thinking snowfall rates of up to 1 inch per hour are possible. Qpf/snowfall is the greatest from southern Saint Lawrence Valley into the northern mountains of vt near Jay Peak where snow accumulations of 2 to 6 inches are likely with isolated higher amounts. Elsewhere...away from the most persistent lake effect snow shower activity...a dusting to several inches is possible. Have noted high resolution data shows intense omega couplet...along with favorable moisture in snow growth area at BTV around 18z Thursday...along with a quick 0.05 to 0.10 of qpf...which could produce a burst of 1 to 2 inches of snow right before evening commute. This band is progged to shift south and dissipate across central/southern vt by 21z Thursday. Temps mainly in the mid/upper 20s to mid 30s...but falling back into the teens and 20s on Thursday Night. Forecasting these events are difficult with timing and intensity...but something we will watch very closely over the next 12 to 18 hours. Thursday Night...mid/upper level trof deepens with leftover 850 to 500mb moisture in the trof axis. This combined with developing upslope flow and moderate low level cold air advection will produce a period of favorable upslope snow from 03z to 12z Friday. Soundings show good moisture in snow growth region...along with enhance 1000 to 700mb omega across the northern dacks into the central/northern green mountains from near Sugarbush to Stowe to Jay Peak. Have increased pops to likely/cat...including the eastern cpv...associated with some lake champlain moisture enhancement. Expecting a high fluff factor with additional snow accumulations of 2 to 6 inches in the mountains and another inch or so across the eastern champlain valley. Temps drop to near normal for lows ranging from the teens to mid 20s. && .SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/... As of 300 PM EST Wednesday...Work week ends with surface low pressure continuing to pull northeast through the Canadian maritimes while cyclonic mid/upper flow persists across the North Country. Higher elevation upslope snow showers persist through much of Friday on west/northwest flow, with a few more inches of snow possible generally above 1000 feet, but activity will begin to dissipate going into Friday night as surface high pressure builds into the Ohio Valley. Temperatures will be slightly below seasonal normals with highs in the mid/upper 20s to lows mainly in the teens. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 300 PM EST Wednesday...For Saturday and Saturday night aforementioned high pressure builds into the northeast with dry conditions expected. Aloft the mid/upper flow remains out of the west/northwest so despite strong subsidence at the surface, feel we`ll see a good deal of clouds around. Strong cold air advection on the front-side of the high will continue to provide below normal temperatures with highs only in the teens to 20s, and widespread single digits to low teens for lows Saturday night. For Sunday onward, large uncertainty continues to exist with the forecast with increased model differences from the 00z suite in the handling/phasing of energy pulling out of the lee of the Rockies Saturday night. Latest ECMWF and CMC continue to offer a deeper trough with the ECMWF phasing with the northern stream pulling a robust surface low northeast through the Ohio Valley Sunday night and the St. Lawrence and Ottawa Valleys through Monday night. The CMC however does not phase, keeping the surface low more suppressed to the south, and the GFS while it does phase with the northern stream offers a much weaker trough and surface low with little impacts. Your guess is as good as mine as to what happens here, so for now I`ve offered a blended model approach with mid-chances for some light snow. Models do come into better consistency though heading into the middle of next week behind whatever system we get for Monday/Tuesday. The trend here will be towards much colder air with possibly our first arctic outbreak as a deep cold low settles over southern Ontario/Quebec and strong surface high pressure develops over the central CONUS. Coldest air looks to arrive beyond this forecast period though, so stay tuned. && .AVIATION /03Z Thursday THROUGH Monday/... Through 00Z Friday...Overall VFR conditions across the region with KSLK still lingering with MVFR ceilings. Expecting VFR for most locations with short periods of potential MVFR/IFR with brief passing snow showers tomorrow. KSLK should see the worst with possible IFR/LIFR conditions possible on Thursday. Light southerly winds at 05-10 knots overnight should give way to a southwesterly direction tomorrow with the St Lawrence Valley also seeing a gustier 10-20 knots in the afternoon. Outlook 00Z Friday through Monday...Occasional snow showers with a brief snow squall possible btwn 00z-06z Friday...with rapid change in vis/cigs likely in any snow squall. After 00z snow showers become confined mainly to the mountains with ifr conditions lingering at mpv/slk through 12z Friday. Mvfr cigs linger at slk/mpv on Friday with vfr developing Friday night into Sunday. Next system arrives on Sunday afternoon with another widespread light snow event. This system will produce widespread ifr conditions between 18z Sunday into 12z Monday. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...None. NY...Lake Effect Snow Advisory until midnight EST Thursday night for NYZ029. && $$ SYNOPSIS...Taber NEAR TERM...Deal/Taber SHORT TERM...Lahiff LONG TERM...Lahiff AVIATION...Taber/MV
Area Forecast Discussion
National Weather Service Charleston SC
957 PM EST Wed Dec 7 2016 .SYNOPSIS... High pressure will build over the region through mid week. A strong cold front will sweep through the area Thursday night, followed by cooler high pressure filling in over the weekend. Another cold front should push through the area early next week before high pressure returns mid week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Late evening 11-3.9 micrometer satellite imagery and surface observations show stratus continues to expand and thicken. A few sites are already reporting some locally dense fog, which is what RAP soundings have been suggesting for the past several hours. While conditions do not look ideal for widespread stratus build-down yielding significant dense fog overnight, areas of fog, locally dense, look plausible north of the I-16 corridor. Farther south, winds look to increase a bit too much after 2-3 am with the approaching a cold front from the west to support much more than patchy fog. Temperatures have fallen a bit quicker than expected east of a Moncks Corner-James Island line due to nearly ideal radiational conditions. Expect temperatures to level off and then rise shortly as stratus intrudes so have made adjustments in the hourly dewpoint and temperature forecasts to reflect this. Opted to nudge overnight lows up by several degrees for most locations given thermal declines will diminish as stratus thickens. However, still kept temperatures a degree or so cooler than some warmer guidance members would suggest. Further adjustments will be made as the night progresses. Expect dry conditions overnight despite some models generating some very light QPF across the CWFA. Suspect these models are having a hard time resolving the low-stratus and may be erroneously generating light shower activity. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Thursday: A broad mid and upper trough will push east through northeast quad of the nation, sending a an arctic cold front toward the area Thursday, before pushing into the Atlantic early Thursday night. Downslope flow and compressional heating in advance of the front will warm the region into the lower and middle 60s, with the warmest temps near and east of I-95. The cold front will come through dry, with generally no more than scattered-broken layered clouds. A huge 1045 mb arctic high will build from the Great Plains behind the cold front, resulting in modest cold advection into our CWFA Thursday night. The 850 mb 0C isotherm penetrates down into our northern and western counties, enough to cause low temps by Friday morning to fall to the mid and upper 30s most communities aside from the immediate coast. Friday through Saturday: The coldest air mass of the season will encompass southern South Carolina and southeast Georgia as the core of the arctic high shifts east toward the Mississippi Valley Friday and toward the coast of the Carolinas on Saturday. We anticipate full sunshine Friday, with no more than some late day stratocumulus from off the Atlantic in coastal Georgia late Saturday. With this in mind our forecast has leaned heavily in regards to the low level thickness prognosis, which supports max temps both days about 10-12F below normal. Friday night into Saturday morning is still supporting a solid freeze all the way to near the intra-coastal, with a potential for a hard freeze in parts of the northwest tier from inland Berkeley County to Allendale, Screven and Jenkins counties. Often times the models are a little too cold in these types of scenarios, and depending upon how much decoupling transpires and how quickly the synoptic flow veers to northeast will be strong factors in actually how low are temps are by dawn on Saturday. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Cold high pressure will persist into Saturday night with temps dipping into the low/mid 30s away from the coast. By Sunday, high pressure will begin to shift off the Mid-Atlantic Coast while a coastal trough develops along the Southeast Coast. A few showers could drift onshore across Southeast South Carolina and Southeast Georgia, but confidence is too low to mention in the forecast at this time. A low pressure system is then expected to track over the Great Lakes region and Northeast with a southward extending cold front that reaches the area Monday into early Tuesday. Deep moisture should provide chances of showers as fropa occurs across the region. Dry high pressure will then build across the region behind the departing cold front with temps near normal through midweek. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... Stratus will fill back in at the terminals this evening. Expect IFR cigs to return to KCHS by 08z, but current indications are that cigs will remain MVFR at KSAV. Limited cigs to high end IFR and above alternate minimums at KCHS, but there are signals in the latest RAP soundings that a few hours of cigs below alternate minimums may occur. Will need to watch trends before the inclusion of such conditions. VFR will return to both terminals 11-15z, earliest at KSAV, as winds begin to increase ahead of cold front. Winds will shift northwest and become gusty by early-mid afternoon as the cold front shifts offshore. Extended Aviation Outlook: VFR. && .MARINE... Tonight: A weak gradient across the waters will limit winds to 5-10 kt maximum. Seas will range from 1-2 ft. Thursday: A gentle to moderate offshore flow will prevail in advance of the arctic cold front which arrives from the northwest during Thursday night, followed by strong high pressure building from the Great Plains. Modest cold advection and steady isallobaric pressure rises in wake of the cold front will lead to Small Craft Advisory conditions across most of the marine area, but given that it`s still the third period of the forecast we will refrain from hoisting any advisories at this stage. Friday through Saturday: Continental high pressure will cover the local waters late this week, as the center of the high heads east and reaches the coast of North and South Carolina by 00Z Sunday. Winds and seas will remain elevated given favorable fetch and some pinching to the gradient, although the most favorable time for any advisory conditions would be Friday morning during the best cold advection pattern. Sunday through Monday: High pressure slides into the Atlantic Sunday as a coastal trough develops over or near the area, before dissipating by Monday, and gives way to another cold front that approaches late Monday. Winds and seas are forecast to remain below any advisory thresholds early next week. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$
National Weather Service Jackson KY
913 PM EST Wed Dec 7 2016 .UPDATE... Issued at 912 PM EST WED DEC 7 2016 High and mid level clouds moving across the area so far have been too sparse to keep the southeastern Valley locations from decoupling and dropping to around 30 degrees. The top of Black Mtn around 4000 feet MSL has experienced an increase in dewpoints from the single digits above zero to around 20 during the past hour, however, model data and 0Z ILN and BNA RAOB suggests there is still a dry layer between that level and about 7 to 10kft. Models continue to suggest some moistening up of this dry layer as a shortwave approaches overnight, possibly enough to support a few flurries prior to dawn or around dawn falling from this mid deck or high low cloud deck. Upstream over parts of central MO a few flurry or very light snow observations have been noted over the past hour. HRRR and short term models generally keep any very light activity south of the I 64 or the Mtn Parkway and have it diminishing as moisture again 850 to 700 mb moisture decreases after dawn on Thursday. Hourly grids have been freshened up based on recent observations and short term model trends. UPDATE Issued at 730 PM EST WED DEC 7 2016 Some mid and high clouds continue to drift overhead with light generally northwest winds across the area as sfc high pressure begins to build into the region. At upper levels, a closed low was located over Ontario and the Northern Great Lakes region with a couple of shortwaves in west to southwest flow approaching the Lower OH Valley region. As the strongest of these shortwaves nears, models do have an increase in moisture near and below the dendritic growth zone and some omega in that layer later tonight into early on Thursday although the air from about 850 mb to the sfc is progged to remain rather dry. This scenario will be favorable for lowering of the mid clouds toward the 5kft mark at least briefly around sunrise and perhaps a few flurries. This is in line with the previous forecast. Hourly grids have been freshened up based on recent observations and trends with little change overall being necessary at this time. && .SHORT TERM...(This evening through Thursday night) Issued at 245 PM EST WED DEC 7 2016 Upper low north of Lake Superior will continue to move east across Ontario, with trailing upper trough axis over the plains shifting east. At the surface, cold high pressure will continue to nose east into the Ohio Valley. The upper troughing and surface ridging results in colder air working its way into KY, with lows tonight mostly in the upper 20s and highs on Thursday from the mid 30s to around 40, about 10 degrees cooler than today. Even with the trough shifting east, and the surge of colder air, there will be very little moisture available. The outside chance for a few flurries remains in the forecast for late tonight and early Thursday. Thursday night will be even colder than tonight, with lows in the upper teens to lower 20s. Some clouds will affect the northeastern part of the forecast area as a short wave trough swings by to our northeast. The clouds are not expected until late in the night, so temperatures should still fall off quickly in the northeast Thursday evening. If the clouds move in earlier than expected overnight lows would be warmer than current forecast in the northeast. There is still an outside chance for a few flurries in the northeastern part of the forecast area late Thursday night. .LONG TERM...(Friday through Wednesday) Issued at 318 PM EST WED DEC 7 2016 Models struggle right out the gate trying to capture strength and timing of progressive features in a broad mean trough, or nearly zonal flow pattern across the CONUS. First main shortwave disturbance to deal with will track quickly out of the Pacific NW and through the Plains, bearing down on the Ohio Valley region by sometime Sunday, or possibly Sunday night into Monday. The 12Z ECMWF is roughly 18 to 24 hours slower than the 12Z GFS with this first system. The 12Z Canadian keeps the middle ground, showing similar timing to the ECMWF while at the same time finding a way to support the GFS by picking up on some energy into the area a bit earlier on Sunday proper. The second main shortwave system to affect our area, similar to the first with respect to its track will drop into the region at the end of the extended window. The ECMWF is considerably weaker with this shortwave than the GFS but is similar in timing. For sensible weather, temperatures remain seasonably cold to below normal through the entire period. Models are still having difficulty with the details of Sunday`s system and forecaster confidence is low. This system appears to be trending slower overall. As such that may provide enough time for the column to warm so that the bulk of precipitation falls as rain. However, we still can not rule out a little wintry mix at the onset of precipitation. For our second system at the very end of the extended window, there is reasonable agreement that this next system will be colder. Still way too far out to say for sure, but this system may present our first real chance at some accumulating snowfall. Time will tell. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) ISSUED AT 735 PM EST WED DEC 7 2016 VFR conditions should prevail through the period although ceilings might fall to as low as 4 to 6kft for a time between 9Z and 15Z as a shortwave passes and a few flurries would also be possible. Winds will generally be light and variable through tonight, but become westerly by 15Z at 5 to 10 KT. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JP SHORT TERM...SBH LONG TERM...RAY AVIATION...JP
Area Forecast Discussion
National Weather Service Lake Charles LA
945 PM CST Wed Dec 7 2016 .DISCUSSION... Wx map shows cold front moving through the Arklatex this evening. Radar showing patchy light rain developing over Southeast Texas, which will spread east northeast with the flow aloft, gradually filling south and eastward as the cold front moves through the region Thursday. Not much changes in forecast, mainly leaving chance of showers with the frontal passage. No changes to ongoing wind hazards inland and offshore. DML && .PREV DISCUSSION... /issued 523 PM CST Wed Dec 7 2016/ AVIATION...Mostly MVFR conditions are expected this evening, however IFR ceilings will become common as midnight approaches. Scattered to numerous showers will also move through the region reducing vis at times. Ceilings will slowly improve through Thursday. Winds will be north to northeast through the period and very gusty during Thursday. PREV DISCUSSION... /issued 520 PM CST Wed Dec 7 2016/ DISCUSSION... Main update was to trend a bit upward in sustained winds and gusts across the coastal lakes/bays as well as inland locations for most of Thursday with just about every available guidance increasing confidence in a windy day Thursday. Thus it is necessary to issue a wind advisory from 9 am to 6 pm Thursday for portions of Central and Southern Louisiana, and Southeast Texas. With guidance slightly lower for Inland Southeast Texas, did not include them at this time, but this may have to be adjusted if later guidance comes in higher. DML MARINE... Main update was to include Small Craft Advisories for Sabine & Calcasieu Lake, and Vermilion Bay from 6 AM Thursday through 6 AM Friday, which matches well with the ongoing Gale Warning across the 0-60 NM coastal marine zones. DML PREV DISCUSSION... /issued 349 PM CST Wed Dec 7 2016/ DISCUSSION... Under cloudy skies...temperatures were slow to climb out of the mid 50s across the northern areas. We did see some slightly warmer temperatures this afternoon across the southern areas with highs making it into the lower 60s. Southerly winds had yet to materialize which in concert with the thick cloud cover...played a key role in temperatures much cooler than expected. The stationary frontal boundary over the gulf waters never made it back as a warm front. The active weather pattern we have seen over the last week will continue to plaque the area. In the upper levels...a broad trough covered much of the interior part of the country. We do expect a strong cold front to arrive later tonight and sweep into the coastal waters by early Thursday morning. Much colder temperatures are on the way including a chance of showers in the vicinity of the cold front. Much colder canadian air will spill down into the central and southern United states through Friday. Therefore...the arctic blast of cold air will be felt starting Thursday (highs upper 40s to lower 50s) and Friday (highs mid 40s to near 50). Northerly winds tomorrow look to remain below wind advisory criteria except perhaps just near the coastline. Will let the overnight crew decide if we will need a wind advisory for the coastal zones when they get a newer model run. For now...current GFS/NWPS wind grids do not support it. However...the HRRR model does. The next shift folks will look at the newer models and will make the decision later tonight. We do expect the coastal waters will receive much of the stronger winds and therefore will upgrade Gale Watch to Gale Warning for 12Z Thursday to 12Z Friday. This arctic blast of air will bring a freeze to areas north of the I- 10 corridor Thursday night into Friday morning and most all of the area Saturday morning. Temps begin to moderate Saturday afternoon as high pressure shifts east and winds turn southerly in advance of the next cold front...the timing of which the long range models are beginning to come into agreement and therefore expecting another round of rain Sunday and Sunday night with another front sweeping the rain out during the same time period. Expect probability of rain to fall off sharply early Monday as the front sweeps out the moisture. The progressive pattern continues into the middle and latter part of next week as guidance indicates reinforcement of northerly flow Tuesday and then another front swings through on Wednesday. These rapid swings in weather will continue for the foreseeable future. MARINE... A Gale warning is now in effect Thursday morning through Friday morning for coastal waters out 60 NM. Offshore winds behind a cold front pushing through the area Thursday morning will gust to 35- 40 knots and continue through early Friday morning. Seas will be in the 7-9 foot range from 20-60 NM offshore. Winds will moderate during the day Friday. && .PRELIMINARY POINT TEMPS/POPS... AEX 45 47 28 45 / 30 30 10 0 LCH 52 52 34 48 / 40 50 10 0 LFT 51 52 33 48 / 40 50 10 0 BPT 53 54 35 50 / 50 50 10 0 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...Wind Advisory from 9 AM to 6 PM CST Thursday for LAZ029-032-033- 041>045-052>055-073-074. TX...Wind Advisory from 9 AM to 6 PM CST Thursday for TXZ215-216. GM...Gale Warning from 6 AM Thursday to 6 AM CST Friday for GMZ450- 452-455-470-472-475. Small Craft Advisory from 6 AM Thursday to 6 AM CST Friday for GMZ430-432-435. && $$ PUBLIC...04
Area Forecast Discussion
National Weather Service Memphis TN
832 PM CST Wed Dec 7 2016 .DISCUSSION... Arctic air seeping southward into the MId-South region. Meanwhile a 150 kt upper level jet is screaming across the Mid-Mississippi Valley. This feature is helping to create some lift across the region through moisture is very limited. Some light snow/flurries is occurring along the I-44 corridor in Missouri though that band is unlikely to reach the Mid-South. The latest HRRR indicates that some light precip may spread into the region from AR...KLZK 88D beginning to show some light echoes over central AR...over the next few hours. Low levels are fairly dry so at least some of this would probably not reach the ground. As a result precip chances overnight remain low across the Mid-South though we could see a few flakes or sprinkles or a mix of both. Impacts will be minimal. By morning it will feel like winter with lows from the upper 20s north to lower to mid 30s south and a stiff north breeze. Highs will not reach 40 along and north of I-40 on Thursday. SJM && PREV DISCUSSION... /issued 338 PM CST Wed Dec 7 2016/ Low overcast conditions have persisted across much of the Mid- South keeping temperatures in the 40s this afternoon. Surface winds are from the northeast at 5-10 mph. Weak isentropic ascent will continue through sunset, but looks to quickly dissipate this evening. A band of mid-level frontogenesis is progged to develop across the region tonight, juxtaposed with a layer of convective instability (negative EPV). This will provide some mesoscale lift during the overnight period, but moisture will remain limited. Low PoPs were retained for tonight across most of the area. Precipitation is expected to remain all rain across north MS, but may mix with a few snowflakes across the northern half of the CWA. That said, no accumulations are anticipated as most of this precip will either evaporate before reaching the surface or will be too light to measure. Any precipitation that develops overnight is forecast to pull off to the east by sunrise Thursday. Cold advection will continue throughout the day, and should limit the warm-up, despite clearing skies. Afternoon temperatures will range from the mid 30s to around 40 degrees. Winds will be light on Friday, but temperatures will again be rather chilly. Highs are expected to remain in the 30s for the most part. The coldest temperatures so far this season are anticipated Friday and Saturday morning. Low temperatures near 20 degrees are forecast for many areas, and some of the low-lying drainage areas may dip into the mid teens. Southerly flow will Saturday and Saturday night will promote an increase in low-level moisture, preconditioning the environment ahead of the next shortwave trough. This system will bring another chance for rain to the area beginning Saturday night and continuing into early Monday. Rain chances are at/above 60% on Sunday and Sunday night with modest QPF totals. Temperatures should remain sufficiently warm to preclude winter weather concerns. Strong, quasi-zonal flow aloft early next week will keep the door open for another shortwave trough by midweek. Rain chances were included on Wednesday. An accompanying cold front is expected to result in cooler temperatures Wednesday and/or Thursday. Johnson && .AVIATION... 00Z TAF cycle Current MVFR ceilings at KTUP will continue into the overnight hours while there may be a period of MVFR ceilings at KMEM later this evening. Otherwise, VFR conditions should persist for much of the forecast period. Winds will be mainly from the north at 5 to 10 knots for much of the forecast period. ARS && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$
Forecast discussion for Thursday fore earlier today below still
on track...
&& .AVIATION (08/00Z through 09/00Z)... VFR through 06Z for all terminals. Strong agreement in the guidance that we will see fog/low cigs developing north of the I-4 corridor and drifting southward late night. Best potential to see a period of MVFR/IFR vis will be at KLAL. Lower potential but still possible for a brief MVFR/IFR cig to reach KTPA/KPIE between 10-14UTC. General VFR conditions for much of Thursday...with increasing clouds above 5KFT through the day. Further south...increasing clouds through the overnight for KPGD/KFMY/KRSW...but generally above 5KFT...and no significant restrictions expected through TAF period. && .Prev Discussion... /issued 622 PM EST Wed Dec 7 2016/ SHORT TERM (Tonight - Thursday)... The main concern for the first 24 hours of the forecast will be fog development overnight. Low-level moisture will remain plentiful, and surface winds will generally be a light drainage flow. The only question is whether or not increasing cloud cover will curtail radiational cooling. Visible satellite imagery already shows some over-running cloudiness lifting northward from the stationary frontal boundary to our south. Model guidance is in good agreement that this will continue overnight, but there are differences in extent and timing. Areas south of Tampa Bay are the most likely to see too much cloud cover to allow for significant fog overnight. From the Bay area north, clouds will be slower to increase and should allow better radiational cooling. With this in mind, will have patchy fog overnight around the Tampa Bay area, then areas of fog for the Nature Coast. There is also a fair chance that some areas will see dense fog, and advisories may be needed later tonight. Clouds will lower and thicken on Thursday with light rain and showers developing over our southern zones in the morning, then spreading northward into the Tampa Bay area during the afternoon. I don`t expect to see measurable rain make it much farther north than Tampa before sunset. Clouds and rain may keep temperatures a bit lower than currently forecast. LONG TERM (Thursday Night - Wednesday)... A closed upper low sits over central Quebec with troughing extending through the Great Lakes region. The trough moves slowly eastward through Friday and deepens over northern Florida. The upper flow over Florida becomes more zonal on Saturday with a 160 knot jet max over the mid- Atlantic region. On the surface, models are in good agreement with the weather pattern through the weekend. A disturbance develops along a stationary frontal boundary extending over southern Florida and into the Gulf of Mexico. This will bring our highest rain chances through the period with 20-30 POPs from Tampa northward and 40-50 POPs south of Tampa. This boundary moves south of Florida by late Friday as a 1037 MB high pressure center over the central U.S. moves eastward and takes control of the weather over Florida. The gradient between the boundary over southern Florida and strong high pressure up north will produce Small Craft Advisory winds and seas over the coastal waters by Friday morning and lasting through Saturday morning. This will also allow for some of the coolest air we`ve seen this season to advect into the region. The high and low temps on Friday and Saturday will be 6-10 degrees below average for this time of year. The high pushes east over the western Atlantic by Sunday morning, which will cause a veering of the winds to the east- southeast, allowing for the temps to rebound to near normal for Sunday and into next week. On Sunday is when the models begin to diverge. GFS is developing a 1006 MB low pressure system and frontal boundary near the Great Lakes. ECMWF is also developing a system as well, but not nearly as strong keeping it around 1017 MB. The movement is also slower with the ECMWF. Leaning more toward the GFS solution which would bring the front through early Monday, which will prompt our next rain event. Due to the uncertainty at this time, will keep POPs in the 20-40 percent range region wide. High pressure to the north moves southeast and will bring clearing conditions by late Monday into early Tuesday morning. Temperatures next week will be right around average. MARINE... Benign conditions will continue for about another 18-24 hours then northerly winds increase to 20 knots or so behind a cold front beginning late Thursday into Friday. Enhanced northeast flow will continue through Saturday followed by decreasing easterly flow on Sunday as high pressure moves by to our north. Small Craft Advisories will likely be needed by Thursday night. FIRE WEATHER... Very dry air will be in place on Friday with relative humidities falling below 35 percent over portions of the nature coast. Winds could exceed 15 mph, but ERC values are forecast to remain low enough to preclude red flag conditions. && .Preliminary Point Temps/PoPs... TPA 60 73 54 63 / 0 20 30 10 FMY 65 78 59 67 / 10 30 40 30 GIF 57 75 53 63 / 0 10 30 10 SRQ 60 72 56 65 / 0 30 30 10 BKV 50 72 49 61 / 0 10 20 10 SPG 61 72 55 63 / 0 20 30 10 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...None. Gulf waters...None. && $$ UPDATE/AVIATION...MROCZKA PREVIOUS DISCUSSION...JILLSON/WYNN