Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/15/16

Area Forecast Discussion
National Weather Service Wakefield VA
1057 PM EST Wed Dec 14 2016 .SYNOPSIS... A dry cold front crosses the area tonight and ushers in an arctic airmass for Thursday and Friday. Low pressure tracks across the Great Lakes region this weekend. A warm front will move north across the area Saturday with the trailing cold front crossing the region Sunday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Latest surface analysis depicts a ridge axis along the Southeast coast with the approaching Arctic cold front across northern Virginia. Aloft...latest water vapor imagery depicts the associated wave over northern Ohio. Beginning to see an area of light precip and mid level clouds developing over northeast Maryland into southeast Pennsylvania. However, ceilings over the local area remain above 12k feet AGL. Temperatures range from the upper 30`s to low 40`s. A few locales have actually warmed the past few hours thanks to a southwest wind. Trends have slowed slightly with the onset of the Arctic air mass, with the RAP handling the current obs/trends well. Have followed suit and delayed the cold/dry air mass a few hours. The front still progged to drop into the area late tonight, pushing offshore around day break. The upstream air mass will begin to advect into the region late tonight as low level thicknesses drop rapidly. Models still in good agreement with dropping the area of light precip over northeast Maryland southeast into the Delmarva. However, the latest trends keep the best chances for measurable precip north of the Wakefield area. Will keep mention of slight chance to low end chance POPs after midnight. Temperatures will be dropping into the upper 20`s to low 30`s so expect light snow. No accumulation is expected. A dry northwest flow will result in decreasing clouds west to east behind the front. Lows from the low to mid 20`s northwest to the mid 30`s southeast coast. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/... Mostly sunny, blustery and cold Thursday. Strong CAA and falling H85 temps suggest highs peak out around noon with falling readings there after. Highs lwr 30s N/NW to lwr 40s SE coast. Wind chills in the teens and 20s. Clear / very cold Thursday night with slowly diminishing winds west of the Ches Bay. Winds do stay up along the coast. The coldest air of the season expected with lows 10-15...except near 20 at the beaches. Wind chills drop into the single digits most areas except the lower MD ern shore where a wind chill advisory may be needed for values aob zero. Only record low that might be challenged will be at ORF. See climate section below. Ridge axis overhead at 12Z Fri will slowly move east throughout the day. Sunny skies to start with high level clouds in the afternoon ahead of next system. H85 support highs between 30-35, pretty impressive for these parts given no snow cover. Well advertised overrunning event shaping up for late Friday night into early Saturday. Models keep it dry through 06Z with light pcpn breaking out between 06Z-09Z. Thicknesses suggest a wintry mix of snow, sleet and freezing rain to start as the column saturates. Boundary layer temps begin to warm along the SE coast as the high pressure tracks further offshore and winds become SSE. Expect a quick changeover to rain there before 12Z Sat. Despite QPF being only a few hundredths of an inch and given how cold surfaces will be, could very well see a light ice accum mainly along/west of I-95 prior to 12Z and have noted this in the ice accum forecast. Best chance for a minimal snow accumulation will be from Caroline County and the Northern Neck over to the lower MD Eastern Shore where the coldest air aloft will hold on the longest before the changeover to rain. If these forecast trends hold, a winter weather advisory may be needed. Lows in the low-mid 20s except upr 20s-lwr 30s along the coast with temps rising after midnight along the coast. Warm air quickly floods north across the area shortly after 12Z Sat changing all pcpn to rain. Will continue to indicate a mix for a few hour period, but expect most areas to see just plain rain by 15Z, last to go over would be Louisa/Fluvanna counties. Best lift and support for steady pcpn into the aftn will be across the north as the warm front lifts north of the area. Thus, kept chc pops across the south with likely to categorical pops (rain) across the north. Highs Sat from nr 50 to the low 60s SE coast. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... Warm front to lift well NE of the FA Sat night resulting in a drop in PoPs and steady to rising temperatures. Lo pres will be tracking through the ern lakes Sat night...then continue NE along the St Lawrence River Sun...pushing its associated cold front through much of the FA by Sun eve. Starting out mild Sun...then cooling during the afternoon as winds shift to NNW. There will also be an increase in PoPs from NW-SE throughout the day. Colder air will continue to press into the FA Sun night into Mon morning. Models continue to suggest possible wintry mix (mainly IP)...especially NNW 1/2 by 12Z/19 as cold air will initially be shallow. Dry/partial clearing expected NW-SE by Mon afternoon...though will keep chc PoPs invof far SE VA-NE NC. Sfc hi pres builds into the region Mon night through Tue while an area of moisture lingers invof coastal NC. Models push the moisture farther S by Wed. Lows in the m-u40s NW to u50s SE Sat night...but rising. Highs Sun from the u50s NW to the u60s-around 70F SE...though possibly trending cooler NW during the day. Lows Sun night from the u20s NW to the u30s SE. Highs Mon in the m30s NW to the m40s far SE. Low Mon night from the l20s NW to the l30s SE. Highs Tue in the u30s NW to the m40s SE. Highs Wed in the l40s NW to the l50s in coastal NE NC. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... VFR conditions with mostly high clouds movg across the region. An arctic front will move through the region during the overnight. The front will bring some lower ceilings...2500 to 5000 ft...across the Delmarva during the overnight. Winds will pick up behind the front and will gust to 25-40 kt during the day with the strongest gusts in the northern half of the CWA. There is a slight chance of a few snow showers for SBY but did not mention due to lack of confidence. Believe that most precip will remain north of SBY. Outlook: A complex area of low pressure and its associated frontal boundaries will affect the region over the weekend. Some wintry pcpn possible early Sat with rain expected most areas by noon. More showery weather expected Sunday ahead of yet another strong cold front. && .MARINE... Starting out w/ weak sfc hi pres over the waters this afternoon...remaining so this eve. Strong cold front late tonight/Thu morning with strong hi sfc pres building in behind it. Gale warning in effect all waters except rivers for Thu w/ solid 20-30 kt sustained...gusts 35 kt (potential 40 kt nrn ocean waters. SCA elsewhere with gusts up to 25-30 kt expected. Strongest winds will be daytime Thu...slowly subsiding afterwards w/ sfc hi pres becoming centered directly over the area by Fri aftn. Expect waves over the Bay of 3-5 ft Thu/Thu night with 4-6 ft seas over coastal wtrs. Warm front lifts N across the waters Sat w/ increasing SSW winds to at least solid SCA. SSW winds continue (though a tad lower in speed Sun) then become NNW w/ another period of lo level CAA late Sun/Sun night. Possible for a short period of at least gale gusts w/ that arrival of cold air very late in the weekend. && .CLIMATE... Record low min temps for Dec 16th: RIC...1 in 1958 ORF...15 in 1958 SBY...-6 in 1958 ECG...11 in 1958 Record low max temps for Dec 16th: RIC...25 in 1951 ORF...27 in 1901 SBY...26 in 1951 ECG...29 in 1951 && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 4 AM Thursday to 1 AM EST Friday for ANZ635>638. Gale Warning from 7 AM to 7 PM EST Thursday for ANZ630>632-634. Small Craft Advisory from 4 AM Thursday to 4 AM EST Friday for ANZ633. Gale Warning from 7 AM to 10 PM EST Thursday for ANZ650-652- 654-656-658. && $$ SYNOPSIS...JDM NEAR TERM...JDM/SAM SHORT TERM...JDM LONG TERM...ALB AVIATION...JDM/JEF MARINE...ALB CLIMATE...
Area Forecast Discussion
National Weather Service State College PA
1102 PM EST Wed Dec 14 2016 .SYNOPSIS... Arctic air arrives late tonight and Thursday and lasts through Friday. Snow showers and a few heavy squalls will occur tonight and thursday as the front moves through. Lake effect snows will pile up over the northwest and north-central mountains. Wind chills will get very low Thursday into Friday morning. A more significant weather system will bring a variety of precipitation types to central Pennsylvania beginning Friday night and lasting into Sunday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Minor changes made to overnight temps, and the timing of snow showers. Little or no snow is expected SE of the Allegheny Front until around 10-12Z based on the last few runs of the HRRR which coincides well with the NAM and RAP timesections which show the subsidence inversion base shooting up over 5 kft agl. Previous Discussion Below... Well-advertised arctic boundary will enter the northwest by midnight, but will be slowing/losing steam as it presses farther into Central PA overnight as it will become more-parallel to the flow. However, the 25-30unit vort max rolling over the nc mtns will help the front to pack a bit of a punch. This punch will probably be tempered a bit by the lack of surface instability overnight. However, snow showers and a few heavy squalls (snow showers accompanied by gusty winds) will drop 1-3 inches overnight in the northwestern third of the area. After the front goes by there, the flow becomes better-aligned for lake effect. It may be fluffy stuff with very dry air in place. SLRs in the 15:1 or 17:1 range are most likely. QPF is light from the models most likely due to the transitory nature of the bands. Temps drop into the single digits overnight with help from the snow pack already on the ground. The wind will pick up and by morning, some wind chills will be 5 to 15 below. The valley locations should not be all that bad wind-chill wise as the strongest winds should be on the hill tops. However, the wind will blow the fluffy snow around and will make it difficult to keep the roads cleared. The southeast has an interesting forecast for tonight as a very minor jet streak moves overhead and briefly enhances lift over MD and far SErn PA. Have continued to paint chc POPs in the far SE and even hinted at a dusting of snow south of route 30. This feature moves very quickly and no snow should linger into the morning. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/... Active wx continues with multiple headlines. Lake effect snow will continue through the day and into Thursday night in the snow belt. A few bands could stretch quite far into the CWA, so have continued chc POPs into the aftn for the central mtns. Winds will back and shsn will taper off over the Laurels before sunset - perhaps even before 2 or 3 PM. Bands will continue to produce heavy snow for at least the first half of Thursday night with fetch favorable for multi-lake connections to be made. The biggest snow totals will be in NW Warren Co where eventual numbers will be 8-10 inches and perhaps near a foot. Other places will be at the whim of how long the bands linger, but expect a general 2-5 in the nc mtns and perhaps a little less in the Laurels. Again, the winds will be a factor, and have contributed to the issuance of the LES advy and WW advy. Winds will pick up during the day on Thursday - and last much of Thurs night. Wind chills will get into the 5 to 15 below range for many places and the higher elevations and west-facing slopes where the wind will be strongest will get to 15 or 20 below on Thursday night. Have tried to place the ending times of the LES flags at the end of the snow and lowest wind chills Fri AM. The low wind chills may linger into mid- morning before temps warm and winds slacken a bit. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Fair and dry (but very cold) weather is expected to persist Friday and Friday night. However, a moisture-laden storm will likely impact a large chunk of the region (beginning Friday night or Saturday) with snow changing to mixed precip or rain from the SW as a strong and rapidly warming southerly jet overruns the colder surface air (850mb temps may rise as much as 20-25C over a 36hr period from 12z Fri through 00z Sun). Although it`s still too early to give specifics on that storm w/resp to snowfall, both the EC and GEFS do show the parent storm heading NE from the mid Mississippi to the Upper Great Lakes. Since this storm track is so far to the NW, the deep valleys in Central PA could easily trap the cold, sub- freezing air into Saturday afternoon, bringing a slower or only partial changeover further north and east. As trough on back side of this system lifts across the Great Lakes, could see a period of light snow Sat night before high pressure builds in again on Sunday. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... Arctic front pushing through tonight will shift winds to the west northwest, and bring increasingly windy conditions as speeds pick up to 15-25 mph with frequent gusts into the 30s by Thursday. Other notable impacts will be a return to a lake effect snow regime. This will affect KBFD and KJST the most with IFR ceiling reductions in frequent snow showers. KAOO, KUNV and KIPT will drop to MVFR conditions toward morning mainly from ceiling restrictions, with -SHSN being mainly flurries or infrequent showers. KMDT and KLNS will only see ceilings drop to BKN050. Northwest flow and lake snow bands, both depicted by the HRRR and NAM 4km, establish over the northwest/KBFD starting after 07z and in the Laurel Highlands/KJST after 10-12Z. A few heavier snow squalls will be possible into the central mtns Thu morning. Outlook... Thu...MVFR/IFR with frequent snow showers west; MVFR to low VFR ceilings central and east with ocnl snow showers and flurries. Windy with 25-35kt gusts from 280-310. Snow squalls possible. Fri...Decreasing winds. No sig wx. Fri night...Restrictions with light snow becoming likely. LLWS developing. Sat...MVFR/IFR. Wintry mix transitioning to rain from south to north. Increasing winds from the south with LLWS likely into Saturday night. Sun...MVFR/IFR. Rain early...ending as mix/snow. Mon...No sig wx. && .CTP WATCHES/WARNINGS/ADVISORIES... Lake Effect Snow Advisory until 7 AM EST Friday FOR PAZ005-006- 010-011. Lake Effect Snow Warning until 7 AM EST Friday FOR PAZ004. Wind Chill Advisory from 3 PM Thursday to 10 AM EST Friday FOR PAZ012-017-018-024-025-033-034-037-041-042. Winter Weather Advisory until 3 PM EST Thursday FOR PAZ017-024- 033. && $$ Synopsis...Dangelo/Lambert Near Term...Dangelo/Lambert Short Term...Dangelo Long Term...Gartner Aviation...RXR
Area Forecast Discussion
National Weather Service Cheyenne WY
424 PM MST Wed Dec 14 2016 .SHORT TERM...(Tonight - Thursday Night) Issued at 323 PM MST Wed Dec 14 2016 We are still on track for widespread snow across southeast Wyoming and the western Nebraska panhandle tonight. Copious amounts of mid and high level moisture continue to stream into the area late this afternoon courtesy of the Pineapple Express. An impressive 160-170 knot H25 jet streak extends from central Montana southeast through eastern Wyoming, setting up strong upper-level divergence over the I-80 corridor in southeast WY. Low-level warm air advection should increase markedly during the evening/overnight, likely setting the stage for significant overrunning. The latest radar loop shows W-E oriented bands of snow increasing in coverage in response to these mechanisms. Forecast soundings continue to show good potential for excellent dendritic growth in the overrunning layer along w/ quite deep saturation. That said, we expect snow to become heavy but the duration will likely not last long enough for significant snowfall accumulations. Snow should end around sunrise, as the arctic front retreats to the northeast. Winds will increase overnight and could become rather strong over our wind corridors on Thursday. Both the H85 and H7 CAG-CPR gradients climb above 70 meters, but the 850 mb gradient continues to lag behind the 700 mb gradient by 3 hours or so. The H7 gradient first climbs above 70 meters by 06z, so we may see winds markedly at Arlington after midnight tonight w/ stronger winds occurring mid-day Thursday. Bordeaux should eventually reach High Wind Warning criteria per in-house probabilistic guidance and 60 knot H75 flow once surface winds go westerly. The south Laramie Range and adjacent foothills will be extremely windy too, and high wind highlights may eventually be required. Do not believe the 700 mb subsidence will spread far enough east to initiate strong winds in CYS, especially w/ warm advection contributing to a shallow sfc inversion. Warming temperatures are still expected tonight, w/high temperatures in the 40s for many areas on Thursday. The impacts of winter weather tonight are uncertain. The Arlington area will see snow through about 2 AM, but very strong winds might not arrive until closer to sunrise. However, winds should begin to increase by midnight with a few hours of significantly reduced vis in falling/blowing snow. The question is whether or not the Winter Weather Advisory is enough to cover the impacts, but prefer to let the next shift monitor conditions and make that decision since the snow amounts are still uncertain. Although high winds are possible from sunrise and beyond, rapidly warming surface temperatures over night could limit the blowing snow potential. Nonetheless, we have extended the Winter Weather Advisory for ARL until 18z Thursday as hazardous travel has potential to persist. Same story for the I-80 summit. We will maintain a 12z expiration for the remaining winter headlines as blowing snow is not expected to be as impactful. High Wind Warnings may be required on Thursday, but will let the winter threats pass first. .LONG TERM...(Friday - Wednesday) Issued at 323 PM MST Wed Dec 14 2016 Main weather this period will be the winter storm system that will affect the area Friday thru Friday night. Models remain in pretty good agreement with the evolution of the system. Arctic cold front will move south over the CWA Friday morning. Max temperatures over southern parts of the CWA will occur late morning with temperatures falling through the afternoon across the CWA. Overrunning pattern and upslope flow will allow snow to expand across the CWA during the day Friday. Areas close to the Colorado border from roughly Cheyenne to Sidney may not see much snow until Friday evening. Heavier snows still look to be over the mtns and the northern parts of the CWA where over 6 inches a decent bet so the current winter storm watch looks to be in good shape. Snow should be most widespread over the CWA Friday evening then taper off after midnight as much colder and drier air filters down and the main upper trough axis moves by. A few lingering flurries still possible Saturday morning but main story Saturday through Sunday will be the very cold temperatures. After mins below zero Saturday morning highs Saturday will struggle to get above zero in many areas. Still bitterly cold Sunday morning with wind chills likely to become dangerously low in some areas. The cold surface airmass begins to pull out Sunday allowing for warmer temperatures to return through Tuesday. Mainly dry weather expected once the snow ends Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 422 PM MST Wed Dec 14 2016 Snow to become pretty widespread this evening with IFR/LIFR spreading out into the Nebraska Panhandle. Generally followed latest HRRR guidance on onset and dissipation times of IFR/LIFR. There will be an end time to snow from west to east later this evening, generally after 06-07Z across southeast Wyoming as stronger westerly winds kick in. && .FIRE WEATHER... Issued at 238 AM MST Wed Dec 14 2016 No Fire Weather Concerns this week and into the weekend as a series of weather disturbances bring accumulating snowfall to the area through Saturday morning. Bitter cold temperatures and high relative humidities are expected...especially across the High Plains. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...Winter Storm Watch from late Thursday night through late Friday night for WYZ101>105-110-112-114. Winter Weather Advisory until 11 AM MST Thursday for WYZ110-116. Winter Weather Advisory until 5 AM MST Thursday for WYZ103- 105>107-112>115-117>119. NE...Winter Storm Watch from late Thursday night through late Friday night for NEZ002-095. && $$ SHORT TERM...CLH LONG TERM...RE AVIATION...GCC FIRE WEATHER...TJT
Area Forecast Discussion
National Weather Service Grand Forks ND
657 PM CST Wed Dec 14 2016 .UPDATE... Issued at 653 PM CST Wed Dec 14 2016 Winds are diminishing as anticipated and will continue to do more this evening. But with high pressure ridge to our west they will remain up enough to keep wind chills in the advisory range into Thursday. Kept lows the same with likely coldest readings just east of the RRV Fosston-Park Rapids area wh ere temps nearing -10F. Some pesky thin stratocu showing up around Bemidji and Baudette. Overall they will dissipate or move out this evening. && .SHORT TERM...(This evening through Thursday) Issued at 211 PM CST Wed Dec 14 2016 Forecast challenge for tonight will be overnight lows and wind chills. Blustery winds continue across the Devils Lake basin with breezy conditions across much of remaining zones in eastern North Dakota. A shallow adiabatic layer up to about the H900 level should begin to dissipate around 23Z to 00Z, based on the latest HRRR soundings from around the area. This will help winds and any patchy drifting snow taper off but will prevent the sharp drop in temperatures common with the snow pack and early sunset. Will slow down the diurnal curve through about 03Z to 06Z timeframe. Modest cold advection with temps falling into the teens below zero will keep 5 to 10 mph winds throughout the night, however, as the surface high over eastern MT undercuts the valley and moves across SD...keeping a light westerly wind throughout the night. This will keep apparent temperatures in the 25 to 40 below range and no plans to change any headlines. The coldest apparent temps should be after midnight in northwest Minnesota, where winds will be light enough to allow ambient temps to approach 20 below zero. Clear skies will continue thorugh tomorrow morning with increasing clouds in the afternoon, as the next low pressure system begins to develop and move into the plains. Have generally preferred the BCCONSHORTTL today which brings daytime highs just above zero across southeastern ND yet maintains sub zero temperatures across northwest MN. .LONG TERM...(Thursday night through Wednesday) Issued at 211 PM CST Wed Dec 14 2016 The long term starts off with generally zonal flow aloft and a low pressure system developing in the lee of the Rockies in eastern CO. An area of warm air advection producing snow will precede this warm air pushes north into the cold high pressure dominating the region. Snowfall amounts Thursday night in the Wahpeton/Fergus Falls region are expected to be rather light...under a half an inch. As the low moves out of CO and across KS Friday and Friday night and a mid level wave moves through the area...a large area of snow is expected across SD/southern ND and central/southern MN. Currently expecting 2-4 inches across an area south of Fargo and Park Rapids Fri aftn/Fri night. Cold high pressure then fills in behind this low on Saturday and Saturday night. Some of the coldest air of the year will make its way across the Canadian border...with highs expected to range from -14 to -5 F based on the current forecast. Lows Saturday night will be mostly in the 20s below zero. The high moves east into the eastern US by Monday...allowing temps to rebound closer to average by Monday and above average by Tuesday when highs in the mid to upper 20s are expected. The warm up will continue into Wednesday ...with minor precipitation chances expected as well. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 653 PM CST Wed Dec 14 2016 West-northwest winds to continue tonight 8 to 18 kts then turn southerly on Thursday. Some thin stratocu/ice crystals resulting in brief MVFR cigs at Bemidji and surrounding areas early this evening, but for the most part clear tonight with increasing high clouds by Thursday afternoon. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...Wind Chill Advisory until 9 AM CST Thursday for NDZ049-052-053. Wind Chill Advisory until noon CST Thursday for NDZ006>008- 014>016-024-026>030-038-039-054. MN...Wind Chill Advisory until 9 AM CST Thursday for MNZ029>032-040. Wind Chill Advisory until noon CST Thursday for MNZ001>009- 013>017-022>024-027-028. && $$ UPDATE...Riddle SHORT TERM...Speicher LONG TERM...Knutsvig AVIATION...Riddle
Area Forecast Discussion
National Weather Service Huntsville AL
859 PM CST Wed Dec 14 2016 .NEAR TERM...(Tonight) Issued at 859 PM CST Wed Dec 14 2016 An Arctic surface high in the 1035mb range across the South Dakota and Nebraska region was building to the southeast, bringing another shot of very cold air toward this region. Current temperatures near and north of this high were generally near or below zero Fahrenheit from Montana to Lake Superior. Close to home, an area of stratus was moving in a NNW-SSE manner across the region, producing MVFR ceilings (cloud bases < 3000` above the ground) from near Tupelo, across the greater Huntsville area, and the western Cumberland Plateau in Tennessee. Temperatures across this region were in the mid 30s to low 40s, with northerly winds of 5-15 mph. Some higher gusts were being realized as the stratus deck moves by. Changes for tonights forecast were mainly minor timing and cloud coverage this evening. Stayed with more clouds over our northern areas, especially Tennessee as short term guidance suggests more low clouds will affect them before daybreak Thu. Also made minor tweaks to night time lows and wind, with higher winds (and lower apparent temperatures) in the higher terrain. Precautions will be needed for outdoor pets and exposed water pipes, as night time lows fall into the mid 20s, and 5-15 mph winds (gusts to 25 mph in the higher terrain) during most of tonight. .SHORT TERM...(Thursday through Friday) Issued at 315 PM CST Wed Dec 14 2016 The Arctic high settles in on Thursday and with the strong CAA occurring, afternoon highs will only be in the low to mid 30s. It will be a blustery/chilly morning with wind chills remaining in the teens through the morning hours. Winds finally begin to weaken by the afternoon but it will still feel quite cold. The Arctic high will also bring very dry air into the region sending dewpoints into the single digits for the northern half of the area. Decreasing winds and mostly clear skies will allow temps to drop rather quickly Thursday night. NAM/GFS forecast soundings suggest some possible mid and high level clouds moving in early Friday morning ahead of our next system. But believe that this is probably optimistic, given how dry it will be with this Arctic high. With all of that said, decided to knock temps down a couple of degrees across the board for Friday morning with most places in the lower 20s. Our TN counties could see temps drop into the teens. Both of these nights people may want to take some pre-cautionary measures to protect household pipes and ensure you dress warmly as it will feel quite cold Thursday/Friday mornings. The other concern is with the dry air is Fire Wx. The recent rainfall has helped to increase fuel moistures but as we saw with the last shot of dry Arctic air there is still a potential for fire starts. So, extra caution is still advised for any outdoor burning. Especially, during the day Thursday with the increased winds. .LONG TERM...(Friday night through Tuesday) Issued at 315 PM CST Wed Dec 14 2016 Increasingly southerly flow on Friday should help to warm temperatures back up into the mid to upper 40s, as a surface low develops in Colorado and Oklahoma. This surface low should begin to advect increasingly more moist air northeast towards the Tennessee Valley. Strong low level jets (850 and 925 mb) ahead of the surface low and a much more saturated boundary layer develop in response on Friday night over the Tennessee Valley. As a weak shortwave develops ahead of the front Friday night and into Saturday morning, steady light rain development is expected. Lows on Saturday morning should be much warmer as well west of I-65 (lows in the 45 to 50 degree range). East of those areas lows drop into the upper 30s to lower 40s (effect of cold air damming). New model runs converge on this low pushing eastward quickly into the Ohio Valley/eastern Great Lakes region during the afternoon on Saturday. A developing cold front extends southwest from this low into western Tennessee and northern Louisiana. West of I-65, 925 mb winds increase to between 40 and 50 KTS. This should advect much warmer temperatures and moist air into the area by the afternoon/evening hours. By Saturday night, as the front moves into northern Alabama and Southern Middle Tennessee, upper level energy swings eastward and aids in cyclogenesis. This should steepen lapse rates slightly and models show ~ 500 J/KG of elevated CAPE. Abundant shear will be in place as well, but much of this looks linear in nature. However, there may be just enough surface based CAPE and helicity in place Saturday night for an isolated tornado near the MS/AL border. However, confidence is very low. A wind advisory may be needed on Saturday. Very cold air will push into the area behind the front on Sunday. Temperatures could drop to 32-34 degrees in Southern Middle Tennessee/extreme Northwest Alabama by late morning and early afternoon. However, the models diverge on how quickly this pushes eastward. The ECMWF continues to be the quicker moving solution, pushing precipitation east of the area after 15Z. However, the GFS holds onto rainfall through the early afternoon hours, before slowly pushing it east of the area by Sunday evening. Kept a compromise in the forecast, with the POP closer to ECMWF. At this point, think it will end as rain as much drier air quickly moves in behind the front, which exits the area by noon. Went with Superblend through the rest of the forecast due to model divergence as multiple disturbances move through the area. Main takeaway is that it will be a warmer and rainy pattern through Wednesday night. && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 536 PM CST Wed Dec 14 2016 MVFR clouds present north of the region were showing a southward drift per low cloud/fog satellite imagery. Rough timing of these clouds moving southward and output from the RAP suggests that local terminals could be impacted in the early/mid evening. Timing has the clouds reaching KMSL around 15/0200Z, and KHSV an hour later. Right now, stayed with a TEMPO MVFR CIGs, as drier air moving southward should bring VFR CIGs in for the overnight. Winds should continue from the north around 10kt tonight, but increase into the 10-15kt, gusting to 20kt as a reinforcing shot of cold air moves across the region. NNE winds should diminish somewhat late Thur afternoon. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...RSB SHORT TERM...Stumpf LONG TERM...KTW AVIATION...RSB For more information please visit our website at
Area Forecast Discussion
National Weather Service Wilmington OH
855 PM EST Wed Dec 14 2016 .SYNOPSIS... Another last push of arctic air will descend into the area tonight, bringing some gusty winds tonight and continued bitterly cold temperatures through early Friday. A vigorous low pressure system approaching the area late Friday bringing first light snow and then a mix of sleet and freezing rain before changing to rain for Saturday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Winds behind the arctic front have increased slightly stronger than expected and the forecast has been adjusted to reflect this for the next few hours. HRRR timelag temperatures were also showing a cooler air surge by a bit. Did not shave more than a degree or three off of the temperatures tonight but did not cool as much as aforementioned guidance. Thought that the fresh snow would also trend the temps colder than most guidance would support. The increased wind and cooler temperatures necessitated an expansion of the wind chill advisory for almost another tier of counties to the south. Did not include Clermont/Brown in this expansion as the southern halves of them did not reach the -10 criteria and the northern sections only had these apparent temperatures for a brief period in time. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... As the arctic high settles into the area for Thursday, temperatures well below normal. The center of the high passes through the forecast area Thursday night, bringing in some overrunning clouds in the western forecast area. With clouds reaching through the area, radiational cooling scenario not quite as efficient as tonight, and with winds very light, did not meet the minimum 6kt wind criteria for a wind chill advisory for Friday morning. Increasing clouds through the day on Friday with the area under southeast flow. A complex weather scenario late Friday into Friday night, with and initial overrunning snow set up affecting especially the western and northern forecast area bringing light snow. Through the overnight though, very strong warm air advection will warm the mid then low levels, but with the area coming off of an arctic airmass and very cold surface temperatures with a snowpack in place through the northern 2/3 of the forecast area, warming may not occur as quickly as some of the more aggressive solutions like the GFS/ECMWF. It`s interesting to note that the NAM seems to recognize the very cold surface conditions in place, which could make for greater ice accumulations in especially the central and northern forecast area. By daybreak the entire area should succumb to this strong push of warm air with all rain by 12z Saturday. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... With surface low pressure located over Illinois on Saturday morning, the entire ILN forecast area is likely to be within a regime of strong warm / positive theta-e advection, leading to moderate to high confidence in rain as the dominant p-type through Saturday afternoon/evening. While the majority of the warm frontal forcing will be shifting north and northeast of the middle Ohio Valley by Saturday morning, continued strong moisture convergence will lead to patchy/showery precipitation through the day. The situation begins to change again late in the day and during the evening, as the approaching cold front undergoes impressive frontogenesis (strengthening) over the ILN forecast area, in advance of a mid-level wave. Precipitation is expected to become more widespread in the vicinity of this front, with some concerns regarding precipitation type, as the sharp surface cold front may actually undercut the slower-to-modify air in the 850mb/700mb layer. This may result in a period of mixed precipitation, rather than an orderly rain-to-snow switch near the time of the frontal passage. Regardless, the push of cold air will be significant and sharp, bringing temperatures down significantly through Saturday night and into Sunday morning. Models have come in slightly faster with the end of precipitation during the day on Sunday, but with continued strong cold advection, there may be little diurnal rise in temperatures. The coldest air aloft with this air mass is expected to be in place over the region on Monday morning, which may end up as the coldest morning of the extended forecast period. Surface high pressure is expected to settle into the Ohio Valley through Monday, Tuesday, and Wednesday. This will allow for a gradual modification in temperatures, and weak warm advection through the period, under zonal 500mb flow. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... An Arctic front will be crossing the region in the next few hours. Mid level altostratus deck will give way to generally clear skies as the drier air behind the front pushes in. Earlier sct cu/stratocu around 3kft in forecast behind front does not appear to be seen upstream with the drier air winning out. Expect wnw winds to be sustained at 15kt with higher gusts up to 25kt through about daybreak - lasting a bit further into the morning in central Ohio taf sites of KCMH/KLCK. Sustained winds in the cold air will still be 13-15kt through much of the day Thursday but the gusts will subside early. Towards 0z Friday - winds will go slack and cirrostratus or a high altostratus deck will encroach on the region. OUTLOOK...MVFR conditions possible Friday night into Sunday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...Wind Chill Advisory from 2 AM to noon EST Thursday for OHZ046- 055-056-060>065-070>074-077-080. Wind Chill Advisory until 2 PM EST Thursday for OHZ026-034-035- 042>045-051>054. KY...None. IN...Wind Chill Advisory from 2 AM to noon EST Thursday for INZ050- 058-059-066-073-074. && $$ SYNOPSIS...Coniglio NEAR TERM...JDR/Franks SHORT TERM...JDR LONG TERM...Hatzos AVIATION...Franks
Area Forecast Discussion
National Weather Service Louisville KY
943 PM EST Wed Dec 14 2016 .Forecast Update... Issued at 945 PM EST Wed Dec 14 2016 Updated the forecast to increase wind gusts overnight. Upstream obs are still quite breezy with gusts as high as 20-25 mph. The latest soundings indicate our area will be gusty overnight as well. The higher gusts and slightly lower forecast temps for tonight resulted in lower wind chill values. Low temps should range from 8-13 degrees over southern Indiana/north central KY with the lowest wind chills in the -5 to 0 degree range late tonight. Low temps over south central KY will range from 13-19 degrees with lowest wind chills in the 0 to 5 degree range. && .Short Term...(This evening through Thursday night) Issued at 310 PM EST Wed Dec 14 2016 Extensive mid/high-level cloud cover streaking across the Ohio Valley, but low-level moisture is lacking ahead of the secondary Arctic front diving across Illinois and Indiana. This front will push through overnight, and finally could tap enough low-level moisture in a mixy boundary-layer to generate a few bands of flurries. No accums or impacts expected. Winds should stay up enough to keep temps from bottoming out, with most locations reaching mins in the teens. However, those winds will drop wind chills to around zero along and north of I-64. Arctic high pressure will slide by to our north on Thursday, with continued mid/high clouds under a fast upper jet. The cold will hang on as 900mb temps around -16C will limit max temps to the lower/mid 20s, around 20 degrees below normal for mid-December. By Thu night the high will be far enough east to open up weak return flow, so expect a quick drop in temps Thu evening with flat or slowly rising temps after midnight. .Long Term...(Friday through Wednesday) Issued at 315 PM EST Wed Dec 14 2016 ...Very Dynamic Storm System to Affect the Region Friday night through Sunday... Friday will be a transition day with a gradual thickening and lowering of cloud cover as the low levels take all day to saturate. Temps recover noticeably from Thursday`s big chill, but still a solid 10 degrees below climo. POPs really ramp up on Friday evening as the low-level jet sets up ahead of the main low kicking out of the OK/TX Panhandle. Early drop in temps will present precip type issues at onset, with a brief wintry mix possible mainly along and north of the I-64 corridor. Temps will rise significantly overnight, so any issues will be short- lived. Widespread showers expected on Saturday in the warm sector, with just enough moisture and instability for isolated thunder in south-central Kentucky. Some hint that an upper dry slot may cut in, limiting QPF during the day on Sat, with the higher totals now skewed toward Sat night. Surface front swings through on Saturday evening, but another wave riding up behind the front will keep precip chances going through the night and even into Sunday. Biggest challenge is presented by a very sharp drop in temperatures, from Sat afternoon highs around 60 (if not warmer) all the way into the 20s by daybreak Sunday, and the accompanying changeover in precip type. Cold air arrives slowly enough that a freezing rain transition is possible at some point, but it`s still too early to get caught up in multiple P-types. For now will carry a rain-to-snow transition in the official forecast products, but a more general wintry mix mention in our other messaging. Travel impacts are likely for at least some part of the area late Sat night/Sun morning. Low-amplitude pattern aloft through the first half of next week, but Arctic high pressure will keep us dry and cold. Temps gradually recover to climo by Wednesday, but a southern stream system could bring rain chances back into the picture by the end of Day 7. && .Aviation...(0Z TAF Issuance) Issued at 625 PM EST Wed Dec 14 2016 VFR conditions are expected through the TAF period as Arctic high pressure builds into the region. A strong pressure gradient on the east side of the high will result in gusty NW winds tonight. The latest RAP and NAM soundings are in favor of a well mixed boundary layer through the overnight hours which will result in gusts between 16-20 kts at the TAF sites. The pressure gradient should relax after sunrise tomorrow causing gusts to diminish. && .LMK Watches/Warnings/Advisories... IN...None. KY...None. && $$ Update...AMS Short Term...RAS Long Term...RAS Aviation...AMS
Area Forecast Discussion
National Weather Service Medford OR
800 PM PST Wed Dec 14 2016 .UPDATE...No major changes were necessary this evening as the current forecast appears to be on track. Rainfall continues across the area as the cold front begins to push east over the coast and across the forecast area. Standing water and full ditches will continue to be a concern until the rain ends later tonight, and a flood warning continues for Deer Creek at Roseburg. For more information, see the previous discussion below. -BPN && .AVIATION...15/00Z TAF CYCLE...Freezing levels will drop to around 2000 to 3000 feet by midnight. IFR to LIFR conditions are expected to return to most of the west side this evening. east of the Cascades will see mostly MVFR ceilings, but with warmer air moving over the recently heavy snowfall some areas of fog are possible. Ceilings are not expected to rise to vfr over almost all of the region tomorrow. Sven && .MARINE...Updated 800 PM PST Wednesday 14 December 2016...The front has moved through the area and weaker north winds have moved in behind. The fresh south swell generated by the south winds ahead of the upper low are expected to migrate northward through the northern waters this evening and continue through Thursday. North winds will increase some with borderline small craft possible in the southern outer waters late Thursday afternoon and evening. Calmer conditions are expected Friday into next weekend. Very high and very long period swell may possibly move into the waters Tuesday. -Sven/BPN && .PREV DISCUSSION... /Issued 322 PM PST Wed Dec 14 2016/ DISCUSSION...A high-impact winter storm continues to affect Northern California and Southern Oregon with heavy rain at the coast and west of the Cascades, snow east of the Cascades from Chiloquin northward, and some high winds in the Shasta Valley and areas east of the Cascades. A Winter Storm Warning will expire around 4pm as snow levels continue to rise over the Cascades and portions of the East Side. After that time, the most significant impacts will be confined to areas east of the Cascades north of Chiloquin where lingering cold air at the surface will help maintain snow or a mix of snow/rain/freezing rain through the afternoon, potentially changing to all rain this evening, then transitioning back to snow tonight with snow expected through early Thursday morning. We have relied on HRRR surface temperature output to provide an idea on where the freezing temperatures will last the longest and have adjusted based on observations. A Winter Weather Advisory at WSW has been issued to cover this. Snow is also expected to impact the highest elevations of the Cascades through the night, like the Crater Lake Rim. Lower elevations in the mountains will likely receive sub- advisory snow amounts but still expect some snow accumulation in the mountain passes as the cold front moves through quickly Thursday morning. The heavy rain threat continues through Thursday morning, and an Areal Flood Watch has been maintained at FFAMFR to highlight the potential impacts from the rain. We have added most of Jackson County given the already-impressive rainfall received last night and today. Also, we have issued a flood advisory for some areas of the West Side to include the Applegate and Highway 238 and the Illinois Valley area. Models suggest that when the front pushes back to the south tonight, the duration of heavy rain won`t be long-duration, so the threat for flooding does diminish some tonight. Still, rivers and streams are rising sharply this afternoon, and drivers should use caution when traveling in flood-prone areas. -NSK Winds in the short term will be another major concern in the forecast. The strongest winds are expected to be across the Cascades and eastward this afternoon and evening. Current observations indicate that winds are following the forecast well in the Shasta valley as well as in Modoc County, but are slow to increase across the Eastside in Oregon. Winds are still forecast to pick up later this evening, around 4:00 PM PST. They will begin to come down around 7 or 8 PM PST and become lighter after 4 AM PST. While winds are strong, visibilities may be reduced due to rainfall and possible blowing snow. Otherwise, winds will be relatively light for the next few days. Temperatures are going to be the main concern after this system moves out of the area. Although temperatures are going to be heavily moderated due to cloud cover tonight through tomorrow, skies are expected to clear out and this will allow temperatures to plummet, especially across areas which are snow-covered beginning Friday night. West of the Cascades including the coast, temperatures are going to range in the 20s and 30s with a few isolated higher elevation places reaching into the teens. Meanwhile on the Eastside and across Modoc County, temperatures are expected to reach into the teens and single digits. The coldest night will be on Friday night. Guidance is showing frigid temperatures across the Eastside, but the clear skies and cloud cover will likely mean even colder temperatures than what guidance is showing. This means that temperatures will reach near zero and below zero in many locations including Klamath Falls, Lakeview, and Alturas. More northerly places like Chemult may even see temperatures plummeting to negative 10 degrees. West of the cascades, temperatures will remain similar with lows reaching the 20s and 30s with the warmer of these temperatures occurring near the coast. Temperatures will be slow to recover, and will continue the cold trends through the weekend. -Schaaf Saturday through Wednesday...It will be a cold start to the weekend Saturday morning with at least freezing temperatures over the entire area inland from the immediate coast. With mainly clear skies, fresh snow cover, and a 1030 mb surface high parked just to the east, the east side will be quite cold. Lows Saturday morning will be below zero over much of the east side, with lows potentially 10 to 15 degrees below zero over northern Klamath and Lake counties. On Sunday, the GFS shows a weak disturbance bringing some snow showers to the north Cascades and portions of the east side. The ECMWF and GEM show the disturbance much further north and not affecting us at all. It`s worthy of some low pops, but we`ve definitely skewed it toward the drier solutions. Monday should be dry as a weak ridge pokes in over us, but by Tuesday and Wednesday, another system is likely to bring precipitation to our area. All the models show a moderately wet system during this timeframe, but there are some timing differences with the ECMWF being about 12 hours faster than any other model. Snow levels should be high enough (4000 feet plus) that impacts will be mostly in the mountains. However, the east side may see snow in places. -Wright && .MFR WATCHES/WARNINGS/ADVISORIES... OR...High Wind Warning until 10 PM PST this evening for ORZ030-031. Winter Weather Advisory until 10 AM PST Thursday for ORZ030-031. Wind Advisory until 10 PM PST this evening for ORZ030-031. Flood Watch until 4 AM PST Thursday for ORZ021-022-024-026-028. Wind Advisory until 10 PM PST this evening for ORZ029. CA...High Wind Warning until 10 PM PST this evening for CAZ085. Wind Advisory until 10 PM PST this evening for CAZ085. Wind Advisory until 10 PM PST this evening for CAZ084. Flood Watch through Thursday afternoon for CAZ080>083. Flash Flood Watch until 10 PM PST this evening for CAZ080. Flood Watch from 4 AM PST Thursday through Thursday evening for CAZ084-085. Pacific Coastal Waters...Flood Watch until 4 AM PST Thursday for PZZ356. Small Craft Advisory until 10 PM PST this evening for PZZ356-376. $$ BPN/SBN/BMS/NSK
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
955 PM EST Wed Dec 14 2016 .DISCUSSION... MRMS is showing light precip from WV across KY, moving east. Dual- pol from KJKL shows that it is snow, but so far no obs in that area show it reaching the ground. The HRRR and RAP maintain light precip across SW VA and NE TN from 06Z to 08Z, so the current forecast of snow flurries in that area appears on track. Cold front passage in our area will occur between 09Z and 12Z. Winds will increase behind the front but should stay below advisory criteria in the mountains. Forecast low temps in the lower to mid 20s looks on track, but will tweak the hourly temp/dewpt grids for the update. && .MRX WATCHES/WARNINGS/ADVISORIES... NC...None. TN...None. VA...None. && $$ DGS
Area Forecast Discussion
National Weather Service Mount Holly NJ
944 PM EST Wed Dec 14 2016 .SYNOPSIS... A strong cold frontal boundary will move from northeast to southwest across the region tonight. High pressure will then build eastward into the region by Friday and then move offshore by Saturday. A strong low pressure system will develop in the midwest tracking into the Great Lakes. This will be followed by a cold frontal passage by Monday. High pressure will then build eastward toward the region in the Tuesday and Wednesday timeframe with areas of low pressure tracking to our south. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Latest KDIX and KDOX radars showing some light returns over extreme SE PA, and into N and E MD. However, dewpoint depressions are still fairly high, generally from 10 to 20 degrees F, so that precip is evaporating before reaching the ground. This light precip will help to moisten up the atmosphere, so snow will be able to develop later tonight. Latest HRRR continues to indicate a swath of snow across the Delmarva and into S NJ, where around 1" with as much as 2" in banding of snow is possible. This should be a relatively quick shot of snow, generally from around 11 pm to 3 am. Highest snow amounts possible in S NJ. NW winds behind the arctic front will become breezy toward early morning. Forecast lows range from the teens N/W of the Fall Line to the mid 20s along the coast. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Arctic air will make its presence felt on Thursday. The pressure gradient between low pressure over southeastern Canada and high pressure building in from the Midwest states will yield a brisk W-NW winds tomorrow. Steep lapse rates owing to strong CAA in the boundary layer will yield deep mixing of stronger winds aloft down to the surface. We were on the fence about issuing a wind advisory for tomorrow as wind gusts should generally be in the 35-45 mph range. However, forecast soundings (particularly off the GFS) in BUFKIT show the potential for higher gusts to 50 mph if the upper bound values of momentum transfer are realized with deep mixing. Will let later shifts re-evaluate the need for a wind advisory. In addition to the cold and wind, the other concern is for localized snow squalls. The environment becomes conditionally supportive of snow squalls with steep lapse rates in the boundary layer and mid- level moisture streaming in from the Great Lakes. A mean W-NW (300 degrees) wind direction in the boundary layer will direct lake effect moisture toward NE PA and NW NJ (I-78 and I-80 corridors). The BTV snow squall parameter from the NAM/GFS/RAP highlight these areas as being conducive for maintaining snow squalls. Timing is uncertain, but it looks like the first snow bands could reach our northern zones during the morning rush. Even though the threat will be very localized, it could potentially be a high impact on travel; which is why we have kept it in the HWO. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Lengthy long term AFD today, summary listed first then body of long term section. 1. Bitter cold Thursday night with wind chills near or below zero. 2. Potential burst of moderate to heavy snow late Friday night into Saturday morning and uncertainty with changeover timing from south to north. 3. Likely temperature spike Sunday morning before rapidly falling temperatures later Sunday. 4. Prospects for a secondary area of low pressure to keep precipitation going Sunday night, leading to a changeover back to sleet and snow from northwest to southeast. 5. Another cold shot and ensemble signal of another low pressure system at some point Monday through Wednesday. A very active long term period. In the mid levels a predominant staple of the winter season so far is a potent ridge over the Southeastern United States. Teleconnections such as the EPO and WPO will allow for a few shots of very cold air to move southward into the country from Canada as well. In between these features, there will be an extremely active storm track and a surface frontal boundary for the weekend and early next week. Temperature extremes will potentially vary as much as 50 degrees on either side of the boundary leading to more uncertainty than usual. Thursday night and Friday: We could still have a few lingering snow showers or flurries in the northwest flow aided by the higher terrain. These should dwindle down once the steepness of the lapse rates decrease in the evening. The main story will be the cold temperatures which will fall into the single digits or low teens for many as skies clear some. Bufkit soundings show the potential for 35-40 mph gusts with the highest gusts in the evening. This would send wind chills below zero for most of the region and close to advisory criteria in spots. Please refer to our facebook and twitter pages for tips on how to stay safe during the cold. Winds will decrease and temperatures will warm well into the 20`s on Friday as a high pressure system moves over the region making it less harsh overall. Friday night through Saturday night: A high impact wintry event will move through the region. A strong low pressure system will track northeast from the Southern Plains into the midwest. With the high offshore, warm air advection will increase and correspond with a warm front pushing northward. Isentropic lift will combine with increased mid level vertical velocities and frontogenesis forcing leading to the development of precipitation late Friday night and Saturday which is highly probable to become moderate or heavy at times. Wind gusts of 20 mph are possible as well in this timeframe. The precipitation should start everywhere as snow but the warm air advection will be potent (strong LLJ) with the high not in an ideal place to keep cold air around for an extended period. The snow should quickly change to rain Saturday morning across Delmarva and coastal New Jersey south of Atlantic City. Further north the snow will last a few hours longer in the Philadelphia and central New Jersey regions changing over by noon. In Northern New Jersey, the Lehigh Valley and Southern Poconos cold air is likely to hang on throughout most of the day before seeing a changeover to rain. A period of sleet and freezing rain is also probable at many locations in the transition as the mid-levels warm faster than the surface. For some of the valleys north and west, it may be more of a challenge to scour out the low level cold resulting in an extended period of ice. Models are notorious for getting rid of low level cold too quick. One thing that could allow the cold to hang on longer would be the formation of a secondary low off the NJ coastline, which is a possibility shown on some ensemble members. First guess snow totals with a few locations listed for each range. Will likely change based on track and intensity of system in the coming days. Ratios may start out in the 10-15:1 as snow growth looks favorable in the -10 to 20C layer along with the favorable lift described above. 4-6 for Mount Pocono, Wantage, Reading, Allentown and Somerville. 2-4 for Wilmington, Philadelphia, Mount Holly and New Brunswick 1-2 for Dover, Millville northeast into the Pine Barrens Less than an inch is currently expected for Georgetown and Cape May. Temperatures will continue to rise Saturday night in the warm sector. However, the forcing which results in widespread rain and snow Saturday takes a break Saturday night resulting in a dry slot or just some scattered rain showers. An 8-9 Standard deviation spread with the ensembles for temperatures is present in this timeframe, really high uncertainty. Sunday and Sunday night: Another low pressure system will develop along the frontal boundary as additional mid-level energy moves northeast from the southern Plains. A slight majority of ensemble members show a progressive frontal passage, which has been the trend on most of the operational models as well. However a group of ensemble members slow the front with an additional area of low pressure riding northeast along it. That would result in precipitation through Sunday night with the highest amounts south. Regardless, high temperatures will be early in the day with falling temperatures during the day. Temperatures are likely to quickly spike into the 40`s and 50`s but that depends on how entrenched into the warm sector we are. The cold air behind the front will be faster to move in just above surface than further up in the atmosphere. If precipitation continues into Sunday afternoon and evening a change to sleet would occur based on the expected depth of the cold air and then change to snow from northwest to southeast. Additional snow and sleet accumulation could occur with the highest odds for accumulation on the ensembles across Delmarva currently. Monday through Wednesday: Quite a bit of ensemble spread depending on where the front which moves through Sunday stalls. Some members develop additional areas of low pressure with prospects for more wintry precipitation. This included the 12Z/14 operational ECMWF. Other models and ensemble members allow a stronger high pressure system to move into the region with the front far enough offshore to keep us dry. Stuck close to the ensemble blend on temperatures in this timeframe. Pops will be highest in southern portions of the region with colder mid-levels to result in mainly or all snow. Longer term: The mid-level ridge is expected to strengthen across the Eastern United States heading into the holiday travel period along with the EPO and WPO reversing to more of a positive phase. As a result, milder temperatures are favored by the CPC in the 8-14 day period. Although it may remain quite a bit wet as well, further denting the ongoing drought. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Generally a VFR forecast. W winds 5-10 KT initially will increase to 15-20 KT with 25-35 KT gusts after midnight and towards daybreak. A band of snow is expected to develop over the Delmarva and S NJ overnight. This could bring a period of IFR conditions and steadier snows to MIV and ACY for a 2-3 hr period. ILG and PHL may be on the northern fringe of the snow, so impacts will be less. VFR elsewhere overnight. Mainly VFR on Thursday. Breezy W-NW 15 to 25 knots will gust to 30-35 kt during the day. Isolated higher gusts approaching 40 kt are possible. There is still a slight risk of localized snow showers/squalls that could bring brief restrictions to our northwestern TAF sites such as ABE and RDG during the day. OUTLOOK... Thursday night and Friday: Mainly VFR, could be a brief lower restriction in any snow shower or snow flurry activity north. Northwest wind gusts 20-30 knots Thursday night decreasing to under 10 knots and becoming more southerly on Friday. Friday night and Saturday: Celings and visibilities decreasing to IFR or lower with snow developing from south to north. Could be moderate or heavy for a few hours around 12Z Saturday. Gradual change to rain from SE to NW with KMIV and KACY changing over by 14z and PHL by 16z with KABE closer to 18z. Southerly wind gusts increasing to 20 knots on Saturday. Transition may include a brief period of sleet and freezing rain. Saturday night: IFR or lower celings and visibilities, in light rain and patchy fog. Southwest Winds of around 20 knots may prevent widespread fog formation. Sunday and Sunday night: IFR or lower still likely with rain potentially changing to snow from northwest to southeast in the afternoon and evening. Winds shifting to northwest and gusting from 15-25 knots. Monday: More uncertain but improvement to VFR is currently anticipated for most terminals. A chance is present that snow may impact southern terminals with lower restrictions. Northerly wind gusts 10-15 knots. && .MARINE... W-NW winds 10-15 KT with gusts to 20 KT will increase late tonight into Thursday morning behind a cold front. Expect gale force gusts of 35-40 kt to develop shortly before daybreak Thursday and become more numerous during the daytime hours. There could also be locally reduced visibility on Thursday farther offshore with ocean-effect snow bands developing. OUTLOOK... Seas will generally be just above five feet through the outlook period with a lull in the Friday/Friday night time period. Northwesterly wind gusts of 25-30 knots behind a cold front Thursday night then a period of southerly wind gusts Saturday and Saturday night that may approach gale force with warm air advection. Winds still 25 knots on Sunday but shifting to the northwest after a frontal passage. && .CLIMATE... Our first true shot of winter air will move into the region later this week with near record or record cold highs on Thursday and Friday. Low temperatures the morning of the 16th look to stay above record values. Daily record min temperatures (F) December 16th... ACY: 8 1968 PHL: 9 1876 ILG: 5 1910 ABE: 1 1951 TTN: 9 1917 RDG: 5 1917 GED: -7 1958 MPO: -7 1917 Daily record coldest max temperatures (F) for December 15th and 16th... ACY: 22 (1915) and 23 (1916) PHL: 22 (1914) and 22 (1917) ILG: 24 (1904) and 21 (1917) ABE: 22 (1943) and 15 (1951) TTN: 29 (2010) and 29 (2010) GED: 30 (2010) and 26 (2010) RDG: 30 (2010) and 26 (2010) MPO: 19 (2010) and 21 (2010) && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning from 2 AM Thursday to 1 AM EST Friday for ANZ430- 431-450>455. && $$ Synopsis...Gaines Near Term...Klein/MPS Short Term...Klein Long Term...Gaines Aviation...Gaines/Klein/MPS Marine...Gaines/Klein Climate...
Area Forecast Discussion
National Weather Service Raleigh NC
950 PM EST Wed Dec 14 2016 .SYNOPSIS... Weak high pressure will remain overhead tonight, in advance of an arctic cold front that will surge through VA and NC early Thursday. Arctic high pressure will follow and crest over our region on Friday. && .NEAR TERM /TODAY AND TONIGHT/... As of 950 PM Wednesday... Skies have cleared pretty rapidly from the southwest this evening, and will remain mostly clear except for some jet and orographically enhanced cirrus skirting along the NC/VA border. A 1033mb arctic high over the Central Plains will continue to build east tonight, though the associated cold air looks as though it will remain pent up against he western side of the Appalachians until closer to 09- 12, at which time northwest winds and cold advection will begin to pick up. In the meantime, weak pressure gradient in the lee of mountains and good radiational cooling conditions has led to temps quickly falling into the mid and upper 30s. Patchy fog seems plausible, mainly over the coastal plain where dewpoint depressions are low. HRRR soundings suggest fog potential is best between 04Z and 09Z prior to the onset of northwest winds. Overnight lows have been tweaked a little to reflect current trends and rural urban variability...29-35. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... As of 130 PM Wednesday... Brisk NW wind and cold. Strong cold advection in the wake of the arctic cold frontal passage Thu morning will result in mostly clear skies and a brisk NW wind sustained at 15-25 mph with gusts as high as 35 mph during the day (particularly along/east of Hwy 1). Expect highs ranging from the mid 30s NW to mid 40s SE, plus or minus a few degrees depending on precise fropa timing. With Canadian high pressure building over the Mid-Atlantic/Carolinas by 12Z Friday morning, expect very cold overnight lows in the teens to lower 20s, coldest in the N/NW Piedmont where the MSLP gradient will slacken the earliest. -Vincent Friday:Modified Arctic high pressure will be centered over the region to start the day on Friday and will shift east, off the Mid- Atlantic seaboard Friday evening. With the h8 thermal trough lingering over the area, expect another day of frigid temperatures on Friday, with afternoon temperatures struggling to climb above freezing across the northern piedmont and coastal plain, to upper 30s across the south. -CBL && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... As of 350 PM WEDNESDAY... Friday night through Saturday night: Next batch of northern Pacific energy will will lead to re- amplification of the mean trough in place over the Conus and the development of a surface low over the Central Plains on Friday. This low will track northeast through the Middle MS and Ohio Valleys Friday night and Saturday, and then accelerate across the NE and New England by early Sunday. Strong 850mb WAA ahead of the system, fueled by a 50-60kt SWLY LLJ will support a period of overrunning/isentropic lift late Friday night/Saturday morning. Near to sub-freezing temperatures Friday night/early Saturday may support a few wet snowflakes or sleet at precip onset, but will quickly change-over to light freezing rain and then rain from SE to NW between 06 to 15z Saturday as a stout/prominent 10 to 12 C warm nose overspreads the sub-freezing near surface layer. Without a favorably located parent high to supply a steady feed of CAA, the freezing rain/drizzle will be short-lived and a self- limiting process. Additionally, with only 0.10" of liquid-equivalent expected, and all of that not going towards ice accrual, expect a light glaze at best(1/16" or 0.05") across the far NW Piedmont/Triad area where the the longest duration(~6hr) of freezing rain is possible. Lows Friday night in the upper 20s north to lower 30s south. Could see light patchy rain through the afternoon, but once the warm front lifts north through the area by noon Saturday, we could see a lull in rain until Sunday as the front approaches from the west. High temps Saturday will depend on the timing of the warm front lifting north through the area and resultant In-situ CAD erosion across the Piedmont. Highs ranging from mid/upper 40s NW to around 60 SE. Temperatures Saturday evening/night are expected to either hold steady or slowly rise in advance of the front. Sunday through Monday: The southern end of the trailing cold front attendant to the surface low moving through the Canadian maritimes will move slowly east through the area late Sunday afternoon and Sunday night. Forecast models are in fairly good agreement in showing a healthy band of ana-frontal precip with the system, bringing some much needed-widespread rainfall of 0.50-1.0" to central NC. Pre-frontal warm sector highs on Sunday will be mild, ranging from near 60 NW to lower 70s SE. Much cooler behind the front on Monday, and continued cloudy and potentially wet, especially across the east in proximity to the stalled front offshore. Monday night through Wednesday: In response to the development of a closed low over the SW US and resultant continued SWLY flow aloft, the front is forecast to stall off the Southeast Coast through Tuesday. Ana-frontal precip could linger across eastern NC through early Tuesday, but otherwise models have trended drier and cooler as another strong ~1040mb surface high builds into the area from the West. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... As of 740 PM Wednesday.. An upper level disturbance and associated mid level ceilings and virga will continue to move E and offshore this evening, followed by clearing and calm/light and variable winds overnight. Consequent radiational cooling may result in the occurrence of patchy fog in Ern NC, including a small chance at KRWI and KFAY, between 04-10Z. Otherwise, VFR conditions are expected; and an arctic cold front will move SE across the forecast area early Thu, with following blustery NW winds that are expected to gust up to 25 kts Thu afternoon. Outlook: Sub-VFR conditions, and light precipitation, will develop late Fri night and early Sat, and continue at times throughout the weekend, as a storm system approaching from the west interacts with lingering arctic high pressure. The precipitation will likely begin as a period of light freezing rain early Sat, with the highest probability and relative greatest impacts from a light glaze, at Piedmont sites. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...Vincent/Smith SHORT TERM...Vincent/CBL LONG TERM...CBL AVIATION...MWS
Area Forecast Discussion
National Weather Service Charleston WV
1036 PM EST Wed Dec 14 2016 .SYNOPSIS... Cold front crosses tonight, followed by very cold weather Thursday and Friday. Storm system this weekend starts as wintry mix, then becomes all rain. Colder again to start next week. && .NEAR TERM /THROUGH THURSDAY/... As of 1035 PM Wednesday... Burst of snow has indeed developed along I79 corridor over the last hour with some reductions in vsby to 1 mile or less. Have upped the snow accumulation a few tenths along this corridor...still below 1 inch until reaching the high terrain, where an inch or so is possible over the next 3 hours. Things quickly wind down after 06Z as drier air works thru the column. As of 635 PM Wednesday... Forecast generally on track. We are awaiting the arrival of arctic air as the night progresses, with some flurries breaking out. Near term models are continuing to suggest a burst of snow showers across the central mountains in the the 4 to 6Z time frame which may put down a coating. Tweaked hourly temp/wind grids using latest HRRR and Nam as a base. Winds will become gusty as strong CAA ensues overnight, sending wind chill values into the low single digits to below zero by morning. Current headlines still look good, so no changes anticipated this evening with those. As of 335 PM Wednesday... Cold front, just entering IN and western MI this afternoon, charges eastward across the forecast area tonight. The polar/pacific air in place, and the polar/arctic air mass behind it, together with a subtle southwest to northwest wind shift, spells little inflow, and thus little moisture and precipitation with the front itself. However, winds pick up behind the front, strengthening the upslope flow given increased contribution based on both speed and direction. This will lead to snow showers in the mountains, mainly the windward side. With primarily only upslope and good crystal growth, only looking at an inch to an inch and a half accumulation tonight in the most favored higher windward terrain. The snow showers quit Thursday morning as the arctic air is also very dry, but the last flurry will not be gone almost until the last cloud is gone given the very low temperatures Thursday. Guidance has been handling temperatures well in this pattern, and the near term update did not result in much change. Temperatures will be very slow to start recovering Thursday morning, typical of arctic air masses. The combination of low temperatures and the wind will lead to wind chill advisory criteria in the northwest corner of the county warning area, and across the higher terrain. For Perry county, 10 kt winds will drive wind chills to around ten degrees below zero Thursday morning, beginning well before dawn. Have wind gusts up to 25 kts. For the higher terrain, 10 to 25 kt sustained winds, with gusts 25 to 40 kts, will drive wind chills to 10 to 20 below zero, the worst values across the highest terrain, also starting well before dawn Thursday, but lasting through Thursday night. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... As of 345 PM Wednesday... A very cold night expected across the region as we head into Friday morning. For now it appears that cloud cover will not start to increase until early Friday morning so that will allow plenty of time for radiational cooling. Some sites will likely drop below zero in the coldest spots of Pocahontas and Randolph Counties. Elsewhere it is looking like widespread single digits with near zero lows in the Northern Forecast Area. Clouds will be on the increase Friday as moisture begins to return. Strong WAA/overrunning pushing northward Friday night. Cold air will remain entrenched at the surface, however aloft temperatures will climb well above freezing by Midnight. With dewpoints in the teens I would expect evaporational cooling will keep temperatures below freezing across the region into early Saturday morning. A wintry mix or plain freezing rain will be a high probability from I64 northward and there is a could chance locations further south will also see a period of frozen precipitation. Winter weather advisories will probably be need, but due to some uncertainty with how fast surface temperatures will warm we have decided to just continue to highlight in the HWO and hold off any headlines until we get a bit closer to the event. Eventually by mid morning on Saturday the temps should be warm enough everywhere for precipitation to turn to all rain. Light rain will continue through the day with about a quarter of an inch expected. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 345 PM Wednesday... A cold front pushes into the region Saturday night with a heavier shot of rain expected. Colder air filters in behind the front fairly quickly, and rain should turn over to snow early Saturday morning as all guidance is in fairly good agreement with this now. However, how much moisture lags behind the front is where the spread in the guidance increases. Light snow accumulations will be possible for the entire area, but how much will depend on how fast the changeover occurs and if enough moisture lingers behind the front. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... As of 645 PM Wednesday... An arctic front will cross tonight with MVFR stratocu developing along the boundary. This will be brief out across the lowlands, or not even occur at all along the Ohio River. Snow showers are possible in the mountains overnight, with flurries over the lowlands, mainly east of the Ohio River, in the arriving arctic air. There looks to be a 1 to 2 hour window centered on 04Z for a burst of snow in the central mountains, affecting KEKN/KBKW with brief IFR vsby which has been handled with tempo groups. Snow showers, flurries and clouds will break up Friday morning as very dry air moves in. Surface winds will strengthen and become gusty from the west to northwest overnight and remain so on Friday, as the arctic air moves in. Moderate west flow aloft will veer to moderate northwest tonight and remain so on Friday. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY... FORECAST CONFIDENCE: Medium to high. ALTERNATE SCENARIOS: IFR vsby may not materialize in the 4 to 6Z time frame at KEKN/KBKW should expected snow burst not occur. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE THU 12/15/16 UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 EST 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09 CRW CONSISTENCY L H H H H H H H H H H M HTS CONSISTENCY H H H H H H H H H H H M BKW CONSISTENCY M M L M M M H H H H H M EKN CONSISTENCY L L M H H H H H M M M L PKB CONSISTENCY H H H H H H H H M M H M CKB CONSISTENCY H H H H H H H H M M M M AFTER 06Z FRIDAY... IFR possible in mixed wintry precipitation Friday night into Saturday. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...Wind Chill Advisory from 2 AM Thursday to 6 AM EST Friday for WVZ520-522>526. OH...Wind Chill Advisory from 2 AM to noon EST Thursday for OHZ066. KY...None. VA...None. && $$ SYNOPSIS...TRM/MPK NEAR TERM...TRM/30 SHORT TERM...MPK LONG TERM...MPK AVIATION...30