Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/07/18

Area Forecast Discussion
National Weather Service Columbia SC
1038 PM EST Tue Feb 6 2018 .SYNOPSIS... Moisture will be on the increase tonight in an onshore flow on the backside of offshore high pressure and ahead of a cold front approaching from the west. The cold front will move through the area Wednesday evening. High pressure will ridge into the area from the north briefly Thursday. Moisture will increase again Friday ahead of a warm front. The front and associated moisture will be in the area Friday night and Saturday. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Moisture will be on the increase tonight. High pressure off the coast will direct a low-level onshore flow into the region. The models display moisture becoming deep from west to east ahead of a mid-level shortwave trough. The HRRR displayed rain reaching the CSRA around 500 am and Columbia area toward 700 am. Expect little temperature change overnight because of cloudiness. Readings will be near 50. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... Showers will be associated with the front in the area Wednesday. Expect heavy downpours at times associated with moisture advection in a 50-kt h85 jet. The HRRR displayed the heaviest band of showers moving through the area from west to east during the noon to 300 pm time frame. The GFS, ECWMF, and SREF mean support general rain totals of one-half to one inch. Mixing should be limited because of cloudiness and rain but the Bufkit momentum transfer tool and GFS LAMP suggest general gusts of 20 to 25 mph. The high shear indicates a possibility of severe thunderstorms but the chance appears low at this time because of a lack of significant surface-based instability. The NAM and GFS depict surface-based LI values 0 to -1 in the southeast section and stability farther north and west. The front will push east of the area Wednesday night and expect showers will end from west to east. Dry ridging will dominate Thursday. Mixing favored the higher temperature guidance Wednesday night. Used the guidance consensus for the temperature Thursday. && .LONG TERM /FRIDAY THROUGH TUESDAY/... The GFS and ECMWF display a moisture increase Friday with an onshore flow and approaching warm front. The warm front may linger Saturday ahead of a cold front approaching from the west. The models show this slow moving frontal system lingering in the region through Tuesday. The GFS and ECMWF MOS support a wet period with above normal temperatures. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... High confidence for VFR through this evening with restrictions developing after midnight. An approaching cold front will bring mid-level clouds in from the west later this evening. Models indicated ceiling restrictions returning to the terminals after 06Z as low-level moisture increases. Have indicated MVFR conditions at AGS/DNL by 06Z and at CAE/CUB and possible OGB around 09Z. Some fog will also be possible ahead of the front, with rain showers moving in after 12Z. LLWS is possible after 09Z as a low-level southerly jet develops across the region. Light southerly winds overnight will increase to 10 to 15 knots with gusts near 25 knots by late morning. EXTENDED AVIATION OUTLOOK...Restrictions possible through Wednesday night as the cold front crosses the region. Another cold front is expected to bring showers and associated restrictions Friday night through Sunday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...99 LONG TERM...99 AVIATION...99
Area Forecast Discussion
National Weather Service Cleveland OH
1030 PM EST Tue Feb 6 2018 .SYNOPSIS... Low pressure will develop over the lower Mississippi Valley and move across the central Appalachians on Wednesday and off the New England coast on Thursday. High pressure will move to the lower Ohio Valley on Thursday. Another system will approach the area this weekend. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/... Update...Expanded the advisory west one or two counties to roughly the rt-71 corridor based on updated nam, hrrr forecast radar and WPC QPF. Latest HRRR has light to moderate snow moving into the area from the south by 07-08Z and reaching KCLE and KERI by 9-11Z. Heaviest snow still looks favored to develop east, along and west of a surface trough axis which will extend across eastern OH through the YNG area to nwrn PA by 12z. However expect sufficient QPF will spread west from MFD vcnty to the CLE vcnty for several inches of snow late tonight thru Wed morning. Moderate snow should linger across the eastern third of the area through the morning before pulling quickly east during the afternoon. Original...A relatively strong short wave was lifting out from the southwestern states. Unlike recent systems, this one will tap Gulf moisture that accompanies a weak wave lifting out across the southeastern states. This will result in a surface low developing over the lower Mississippi Valley that will track up the Appalachians on Wednesday. There will be a band of light to moderate snow that will develop across the Great Lakes in the divergence/trough aloft on the north side of the jet. Heavier precip will come up into the Ohio Valley and Appalachians. The forecast dilemma is that we stay in between systems for a while tonight and early Wednesday. The Great Lakes snow tonight will clip the Toledo area and will remain light elsewhere. The deeper southern moisture will spread north late tonight with the heavier precipitation clipping the southeast part of the forecast area from the predawn hours into Wednesday afternoon. The GFS remains the more conservative model with respect to QPF which I prefer especially in the area where the deeper moisture does not penetrate. The current advisory looks good. Will add Knox County where they should get 4 or perhaps 5 inches which could end up being their biggest snow of the season. Eastern Erie and Crawford County PA will be borderline between advisory and warning amounts but the folks there are hardy and they can handle a 5-7 inch snowfall over 18 hours with an advisory. If the lake were ice free, I would worry about lake enhancement in the snowbelt including Cleveland but given the ice cover, the contribution should be limited. Some lake effect snow will linger after the system moves east late Wednesday and Wednesday night. The model soundings indicate that it will take until Thursday morning for the subsidence to increase and the inversion to lower. Significant lake effect is not expected but another inch or two or locally three of fluffy snow could accumulate in the snowbelt. Forecast temperatures will generally be below guidance given the Arctic air mass. Temps could really tumble early tonight where there are just some high clouds and winds become light, then probably rise a little later tonight as the clouds thicken. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Area will transition from northwest flow to more zonal, but the active pattern will continue. Thursday will be the break day although a few flurries/light snow showers may still be ongoing across northwest PA. High pressure moves overhead Thursday afternoon. Will go with mid 20s for highs and teens again for lows. The system for Friday into Saturday still leaves much to be desired when it comes to details. A west-east baroclinic zone will set up across the lower Great Lakes for Friday. Broad lift is expected with favorably positioned jet energy developing overhead. Snow aught to break out Thursday night and continue into Friday. Any more moderate snow will likely be confined to a narrow corridor. Latest runs seem to have pushed this a bit more northward along a line from Toledo to Cleveland to Erie. Would be hesitant to push it too far north with a cold lake to overcome and in the absence of a stronger wave. So for now have a 3 to 6 inch swath across the far northern counties for Thursday night/Friday. By Saturday a shortwave is expected to be digging across the Rockies with ridging building across the southeast U.S. We will be close to tapping into better moisture with the southerly flow for Saturday, but also warmer temperatures, and warm advection showery type precip. Guidance temperatures have recently trended warmer and will wait to make too much change to the forecast. Therefore still have below freezing highs for Toledo with near 40 by Canton. && .LONG TERM /SATURDAY THROUGH TUESDAY/... A weak surface low will cut northeast across the Lower Ohio River Valley Saturday night. This will bring snow showers to the area, but there is still uncertainty with how widespread/heavy the snow will be. Some dry air may enter the mid-levels across much of the area Saturday night which would significantly cut into snow amounts. Behind the initial wave of precipitation an upper level trough will provide enough lift for what will likely be a second shot of snow area wide Sunday into Sunday night. A reinforcing shot of cold air will arrive Sunday with lows Sunday night falling into the lower teens. High pressure quickly builds in from the west later Sunday night bringing an end to the snow. This will keep us dry for Monday and Monday night. A warming trend will take place Tuesday as the high shifts off to the east and southerly winds return. && .AVIATION /00Z Wednesday THROUGH Sunday/... Low pressure will move northeast out of the Tennessee Valley this evening across eastern KY overnight. Wednesday the low will continue northeast across West Virginia into Pennsylvania. Conditions MVFR this evening at CAK and YNG but VFR elsewhere. MVFR may lift to a low VFR CIG but expect conditions to quickly drop through MVFR to IFR in light snow across the area between 06Z-10Z as moisture moves in ahead of the low. Conditions will improve to VFR from west to east Wednesday afternoon but some lake effect snow will linger Wednesday night with MVFR and local IFR conditions persisting across extreme northeast OH and northwest PA. OUTLOOK...Non-VFR may develop Friday and continue into the weekend, especially on Sunday. && .MARINE... High pressure will ease east tonight with light winds on the lake. Low pressure will move across the TN and OH Valleys Wednesday bringing northeast winds that will shift to the northwest through the course of the day. High pressure then moves overhead for Wednesday and shifts southeast of the lake for Thursday. A nearly stationary front will park itself in the vicinity of northern OH Friday into Saturday. As it appears now, the front will stay south of the lake and winds will be from the northeast going into and through the weekend. Winds will be under 25 knots through the period. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Winter Weather Advisory from 4 AM to 4 PM EST Wednesday for OHZ011>014-020>023-029>033-037-038-047-089. PA...Winter Weather Advisory from 4 AM to 4 PM EST Wednesday for PAZ001>003. MARINE...None. && $$ SYNOPSIS...Kosarik NEAR TERM...TK/Kosarik SHORT TERM...Oudeman LONG TERM...Mottice AVIATION...TK MARINE...Oudeman
Area Forecast Discussion
National Weather Service State College PA
1104 PM EST Tue Feb 6 2018 .SYNOPSIS... A winter storm will move through the region late tonight and Wednesday. After a brief visit from high pressure Thursday, several weak systems will keep us unsettled from Friday through the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... No changes to current Winter Storm Warnings for heavy snow (north) and snow to ice (south), as well as the Winter Weather Advisories for up to several inches of snow, followed by a change to sleet and freezing rain for several hours Wed afternoon across much of the Central Mountains and Susquehanna River Valley. A wavy frontal system to our south will spawn a storm system over the lower Miss Valley this evening that will race NEWD overnight and Wednesday. Latest timing of precipitation via the RAP and SPC High Res Ensemble shows snow reaching my SWRN counties between 2 and 4 AM Wed, then overspreading much of the rest of the region between 4 and 7 AM. The SPC HREF shows a wedge of warm air also be moving rapidly NE promising to complicate the precip type forecast rather early in the event. It looks like by dawn Wednesday snow will have overspread most if not all of the forecast area with the warm air already having turned things over to sleet/freezing rain over my SWRN counties. Lows will drop back into the mid teens north to mid 20s south. && .SHORT TERM /WEDNESDAY NIGHT THROUGH 6 PM WEDNESDAY/... The bulk of the precip from this upcoming high impact Winter Storm will fall between about 12Z-21Z/7am- 4pm Wed. Models are in good agreement with the low moving to around JST by early afternoon before pressure falls along the coast lead to a rapid center jump to a new storm over or near the NJ coast by nightfall. The storm will then race up through the Bay of Fundy overnight. Continue to lean heavily twd the SPC HREF to time the changeover line of the precip northward into the central mountains and even through the Middle Susq Valley throughout the morning and into the afternoon. The biggest issues will likely arise with the morning commute coinciding with the period of heaviest snow over much of the region from Altoona-State College eastward. Snowfall rates during this period will likely be 1-1.5 inches per hour with vsbys averaging 1/4-1/2 mile. A changeover to sleet/freezing rain will also be advancing north so early travel will certainly be adversely impacted. As it stands now the changeover line will likely surge well into central PA to the north of RT 22 by around lunchtime, and maybe as far north as I-80 by mid afternoon. The storm will wind down rapidly during the second half of the day with the new low expected to be forming rapidly somewhere in the vicinity of Philadelphia by mid/late afternoon. Precipitation will likely just end over eastern areas and taper off to scattered snow showers over the west. Daytime highs will vary from the mid 20s over the NW to around 40 in the SE. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... The storm winds down by Wednesday evening, and behind it a modified arctic airmass will enter the region under broad upper cyclonic flow. Below normal temperatures will return while we become vulnerable to weak shortwaves rippling through the pattern aloft into next weekend. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... MVFR ceilings ongoing over western and central terminals with VFR over the Susq Valley. This will persist into the overnight hours as westerly flow shifts to the S/SE ahead of an approaching winter storm. Expect snow and mixed precipitation to quickly overspread the airspace from southwest to northeast Wednesday morning (around 08z at JST / 10-12z elsewhere) with high confidence in widespread MVFR to IFR conditions quickly developing, along with LLWS as 850mb winds increase to 40-50 mph. Precipitation will start out as snow, but transition to a wintry mix/freezing rain over the south during the morning hours, while northern areas along and north of I-80 remain primarily snow. Precipitation tapers off late Wed afternoon into Wed evening, with westerly winds generating lighter snow showers/continued primarily ceiling restrictions over western/northern areas. Outlook... Wed...Widespread MVFR/IFR in snow and mixed precipitation. LLWS. Thu...Gusty winds/snow showers. MVFR west/north. VFR elsewhere. Fri...Reduced conditions and snow likely over northern 1/3. Sat-Sun...Snow/mixed precipitation likely late Saturday into Sunday. && .CTP WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from 4 AM to 10 PM EST Wednesday for PAZ004>006-010>012-037-041-042-046-051-053. Winter Weather Advisory until 7 PM EST Wednesday for PAZ017>019-024>028-045-049-050-052-056>059-063. Winter Storm Warning until 4 PM EST Wednesday for PAZ033>036. Winter Weather Advisory from 3 AM to 4 PM EST Wednesday for PAZ064>066. && $$ SYNOPSIS...La Corte/Lambert NEAR TERM...La Corte/Lambert SHORT TERM...La Corte LONG TERM...Lambert AVIATION...RXR
Area Forecast Discussion
National Weather Service Quad Cities IA IL
601 PM CST Tue Feb 6 2018 .UPDATE... Issued at 559 PM CST Tue Feb 6 2018 Looking at the weather map the atmosphere was beginning to saturate and snow was developing across sw IA/far nw MO and the se corner of NE. Visibilities were less than a mile in some spots. This snow will continue to spread northeast into the dvn cwa as the evening progresses. I will continue to monitor the situation. && .SYNOPSIS... Issued at 333 PM CST Tue Feb 6 2018 18Z surface data has high pressure over the western Great Lakes and upper Mississippi Valley. Dew points were below zero across the upper Midwest and northern Plains with single digits above and teens running from the Great Lakes into the southern Plains. && .SHORT TERM...(This Evening through Wednesday) ISSUED AT 333 PM CST Tue Feb 6 2018 Through sunset mainly dry conditions will be seen across the area. After sunset, the atmosphere will saturate south of a Galesburg, IL to to Fairfield, IA with snow developing across the area. North of this line saturate will take a little longer but the entire area will see snow tonight. Trends with the RAP indicate strong forcing will act upon the saturated atmosphere this evening from Memphis, MO toward Peoria, IL. This forcing will pivot and turn slightly to the northwest late this evening and overnight. Late tonight the forcing quickly weakens as the upper level disturbance moves into the Great Lakes. Snow will end from west to east with nearly the entire area dry by sunrise Wednesday. Snowfall amounts. Northwest of a Oskaloosa, IA to Dixon, IL line snowfall amounts of under an inch are expected. A band of 3 to 4 inches roughly 60 miles wide should be centered on a line from Memphis, MO to between KC75 and KPNT. Localized 5 inch amounts are possible. In between the previously mentioned areas snowfall amounts of 1 to 3 inches are expected. The current advisory will remain as is. However, any slight northward shift in the heaviest band of snow may require expanding the advisory to the north and west by a tier of counties. On Wednesday, mainly dry and cold conditions will be seen across the area with slowly clearing skies. Temperatures will be well below normal. .LONG TERM...(Wednesday Night through Tuesday) ISSUED AT 333 PM CST Tue Feb 6 2018 Wednesday Night and Thursday Light snow is possible at times late Wednesday night into Thursday as isentropic lift increases downstream of a low amplitude 850mb wave. Confidence is low on areal coverage. For now, only have precipitation chances between 20-40% (highest north of I-80). If models continue with the signal for light snow will have to adjust precipitation chances accordingly. The current forecast has amounts of a trace to a half inch, but they could increase slightly. Highs are forecast from the mid 30s far south to the lower 20s far north. Thursday Night and Friday Main message is another round of accumulating snow is likely for parts of the forecast area, especially on Friday. Once we can gain confidence in the most likely location of the snow band, we will probably have to increase snowfall amounts in a corridor several counties wide. Winter headlines may be needed for this event. Environmental Setup and Model Discrepancies: Persistent elevated warm air advection and increasing low to mid- level frontogenetic forcing beneath the right entrance region of an upper-level jet streak will cause a band of snow to develop across portions of the forecast area. The exact location of the snow band is uncertain and changes to the forecast can be expected. Current forecast snowfall amounts are preliminary. The ECMWF is the furthest north with the heaviest snow across the northern forecast area; other models are favoring the central forecast area. Saturday After possibly a brief break Friday night, yet another round of accumulating snow is likely Saturday into Saturday night as a mid- level trough crosses the Midwest and Western Great Lakes area. Confidence is low regarding the strength of this system. Make sure to keep up with the latest forecast through this week. Sunday On Below normal temperatures continue into early next week. Fresh snow cover and WNW winds are supportive of colder highs on Sunday than what the superblend has so trended toward the colder raw model blend. Models have dry conditions early next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening) ISSUED AT 559 PM CST Tue Feb 6 2018 Conditions will rapidly deteriorate to MVFR and then IFR between this evening as another snow storm moves through the Midwest. KBRL is expected to be impacted significantly by low visibilities and ceilings due to snow. After 12z/07 conditions will slowly improve to MVFR as the storm system moves into the Great Lakes, with MVFR cigs for most of the day on Wednesday. Winds will gradually back to the northwest later tonight into Wednesday with speeds around 10 knots or less. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...Winter Weather Advisory until 6 AM CST Wednesday for Des Moines- Henry IA-Lee-Van Buren. IL...Winter Weather Advisory until 6 AM CST Wednesday for Hancock- Henderson-McDonough-Warren. MO...Winter Weather Advisory until 6 AM CST Wednesday for Clark- Scotland. && $$ UPDATE...Haase SYNOPSIS...08 SHORT TERM...08 LONG TERM...Uttech AVIATION...Haase
Area Forecast Discussion
National Weather Service Sioux Falls SD
556 PM CST Tue Feb 6 2018 .SHORT TERM...(This evening through Wednesday) Issued at 354 PM CST Tue Feb 6 2018 In the near term, warm air advection will continue to shift eastward late this afternoon and evening. Low level saturation has been a real issue with this system, and although areas of light snowfall are occurring and will continue to occur this evening, amounts will be minimal. Expecting snow amounts of just a trace to a dusting, perhaps a bit more here and there east of I 29. Then tonight, a short wave will move southeastward coupled with a strong PV surge, and an associated surface cold front. Nudged up winds over consensus speeds just behind the wind shift itself as pressure rises indicate breezy conditions for a few hours generally along and west of I 29. Concerning lows, readings should moderate from last night`s values. However when the cloud cover clears out is a bit of a question mark. The GFS hangs onto stratus for a lot of the forecast area for much of the night, whereas the RAP and NAM clear things out from about midnight onward. With a northwest wind, and a lack of stratus upstream in western ND and eastern MT, decided to go the more optimistic cloud cover route. That said even if it does clear out late tonight, the atmosphere should be mixed enough through the boundary layer to keep temperatures from plummeting too far. Wednesday looks like a dry day with increasing mid and upper level cloud cover from west to east. Although seasonably cold once again, the winds will be pretty light, especially by afternoon. .LONG TERM...(Wednesday night through Tuesday) Issued at 354 PM CST Tue Feb 6 2018 On Wednesday night, a brief shot of warm air advection aloft and 850mb frontogenesis could produce chances for light snow or flurries primarily across the northeast half of the forecast area. With a fairly dry low layer, measurable snow amounts might be tough to find, however this will be followed by a longer term event late in the week. With arctic high pressure to the north, and low pressure over the southwestern plains, a strong squeeze of air in this area creates a prolonged baroclinic zone, quite strong from 850-700mb. Especially along and north of I 90, low level saturation begins to increase along this zone as Thursday progresses, producing likely pops of snowfall by afternoon for many locations along and north of I 90 except the northern sections of southwest MN. Then on Thursday night, the arctic high will ooze further southward with a strong short wave interacting with the southward moving baroclinic zone. Temperatures aloft rise a bit across our southern zones producing less than efficient temperatures. In fact, there could be a bit of mixed precip right along the Nebraska border Thursday evening. However, just north of this warm air, this also helps instability with highly negative EPV* centered close to I 90 denoting instability aloft close to 600mb above mid level frontogenesis, and the 700-500mb layer is highly saturated. Therefore for Thursday night, boosted QPF amounts in a stripe centered along the I 90 corridor Thursday evening, then across our southern zones late Thursday night. Many areas, except perhaps the Highway 14 corridor in our far north, could receive a quick 2 to 3 inches of snow in that 12 hour period. High pops are justified in our southern zones lingering into Friday morning as the instability aloft shifts southward along the baroclinic zone. There then appears to be a lull in between systems Friday afternoon and evening, with an increase in pops again later Friday night and early Saturday, at least across our southern zones associated with the next short wave. By this time frame, temperatures will be efficient aloft with high snow ratios. All told through the late week to Saturday morning event, many models are pointing at around 0.3 to 0.5 inches of QPF for the southern two thirds of the forecast area, relating to accumulating snowfall of 4 to 8 inches through the entire event. Less amounts are likely along highway 14 however they too should receive some snowfall. Snow amounts at this time only go through the Friday day period and do not include Friday night and Saturday, and of course in the future we will have to watch for banding and will refine where any 6 to 8 inch amounts may or may not occur under that banding. The rest of the forecast Sunday through Tuesday is rather benign with a warmup to temperatures closer to normal early next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 556 PM CST Tue Feb 6 2018 Favorable temperatures and weak lift will make for periods of light snow and flurries early this evening near/east of KFSD/KSUX, but should taper off around TAF sites by 01-02z. Ceilings are likely to depress this evening, dropping into the upper MVFR range around KFSD and KSUX, before breaking out just ahead of advancing cold front. Surface winds could gust briefly to around 25 knots for a couple or three hours behind the boundary, along with another period of potential MVFR ceilings. The remainder of the period will reside in VFR conditions, but a low probability for having ceilings fall back into MVFR levels toward 00z Thu around KHON, along with perhaps the initial occurrence of some snow and reduced visibility. && .FSD WATCHES/WARNINGS/ADVISORIES... SD...None. MN...None. IA...None. NE...None. && $$ SHORT TERM...MJ LONG TERM...MJ AVIATION...Chapman
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
651 PM CST Tue Feb 6 2018 .UPDATE... 651 PM CST Have made a few tweaks to tonight`s pop/wx/snow amount grids to hit the banded snow potential harder late this evening in response to strong mid-level frontogenesis that high-res guidance is in good agreement in developing near and just to the south of I-80 as the evening wears on. Model vertical cross sections through the f-gen band nicely depict the sloped frontal circulation and resultant strong omega on the cool side of the circulation, with NAM and RAP showing significantly negative values of saturated EPV (equivalent potential vorticity), a measure of potential instability (both slant-wise and upright). The fairly impressive instability juxtaposed with the strong mid level f-gen band raise concerns about a window of potential heavy snow late this evening near and especially just south of I-80. Concerned that snowfall rates could briefly reach an inch or so per hour. Have sharpened up the snowfall forecast for tonight with a narrow band of 2-4" now from far southern LaSalle and far northern Livingston county to central/southern Lake Co IN. To the south of this band, snowfall amounts will likely be quite limited and cut back on QPF and pops some far south. Guidance suggests a quick weakening of the f-gen overnight which should allow for a transition from a more focused banded structure more toward a broader area of light snow. Considered issuing a winter weather advisory for the area most likely to see the heaviest snow set-up, but thinking the most likely totals will be in the 2-4" range and while there could be 4-5" totals, confidence is not high in amounts that significant, so plan to defer to day shift`s decision to hold off on an advisory. - Izzi && .SHORT TERM... 200 PM CST Through Wednesday... Another round of snow is on tap for later this evening, and more so overnight. While the bulk of the snow will be done by Wednesday morning, the snow will be ending at the beginning or just prior to the morning commute, so do expect that there will still be some slippery conditions, with even some covered untreated roads by daybreak. See the associated special weather statement and weather stories for more details. National radar mosaic depicts an east-west band of snow across the central Plains extending into Missouri. Out ahead of the main upper level wave across eastern Colorado/western Nebraska is a focused area of increased lift and attached to the main forcing of our snowfall. There is some higher based frontogenesis (i.e frontal strengthening aloft) out ahead of the the main wave that will lift into areas along and south of I-80 this evening, and this should help to erode the lower level dry layers later through the evening. This is the area where some initial banding may occur, and given this signal once saturation does occur snow may briefly be moderate to heavy, up to around half inch per hour rates. This signal weakens a bit and shifts northeastward through the night, so then we generally expect a more typical steady snow to spread into the remainder of the area late this evening into the overnight. Expect generally less than one half inch per hour rates farther north, with this being possible briefly during the overnight hours. There is a deep isothermal layer that will be in place during the peak period of lift, but model guidance for our southern locations depict this layer may be warmer than the best snow growth region. Still there is enough lift to have a mix of some dendritic growth/bigger flakes for a brief time. This dendritic snow signal is a bit better in the more modest QPF axis farther north, which includes the Chicago metro area, . Because of this, expect a nice 2-3" swath of snow, with lighter amounts of 1-2" surrounding this both far north/northwest across the Wisconsin border and far south across central Illinois. While the bulk of the snow will end by daybreak, a northern stream upper trough will rotate through the area Wednesday morning. Forecast soundings depict a shallower moisture layer, but cold lower cloud deck that will be supportive of some flurries or even some light snow showers in the morning, and possibly the early afternoon as low level lapse rates steepen. Model guidance is still supportive of the development of a lake effect snow band over the lake, and some of this will likely get into Lake and Porter county given a decent convergence signal per the NAM, but there is still some uncertainly how long lived this will be. Most guidance shifts the flow to more northwesterly in the afternoon. KMD && .LONG TERM... 300 PM CST Wednesday night through Tuesday... The forecast concerns for the long term are centered on the likelihood of two back-to-back snow events in the Thursday- Saturday period, which could very well result in what will be close to just one longer duration light to moderate accumulating snow. There is a northern CWA emphasis at first in this event and then a shift south at some point either Thursday night or Friday. The second snow system looks to move across the area Friday night into Saturday. It should be stressed that while there has been good consistency in model guidance in some of the spatial footprints of the snow noted above, the focus initially (Thursday- early Friday) is quite narrow and owes to still a fairly high degree of uncertainty, especially on the southern gradient. Being even further out, there obviously is continued notable uncertainty into how the second system will progress across the region as well. Initially Wednesday night could be quite chilly, similar to this morning with lows outperforming and dropping several degrees below zero. However, incoming clouds are expected at some point. Forcing for lift for snow is limited during the day with the frontogenetic circulation being weak, but this is forecast to strengthen into Thursday night as the area is encompassed by a right entrance region to the upper jet. Elevated instability is not pronounced, but it is still too far to gauge a good handle on how that will assist any frontogenesis. Nonetheless, light snow at the least looks to become more persistent by Thursday evening from a west-to-east...possibly slightly sloped southeast. Again emphasis in model solutions and ensembles is for the northern CWA and into Wisconsin to be more impacted by this. An undulation is expected in the baroclinic zone during Friday into Friday night as one or two short wave ripples propagate across. This will dictate placement of snow, and likely some southward progression is expected before a break. Snow accumulations are challenging to say at this juncture, but a stripe of 24-hour totals of 3+ inches by Friday evening look plausible, with a bit more confidence in the northern CWA seeing this given trends. Low-level northeasterly flow will begin to increase on Friday. Some minimal lake enhancement to the synoptic snow is possible, but not looking to be a big factor given forecast shallow inversion heights. The second system is forecast to be from a more amplified strong wave moving across the middle of the country this weekend. Fairly deep moisture (PWATs near one half inch), are forecast ahead of this up to near the residual elevated baroclinic zone. Trends today are for not as much warm air to progress northward in the GFS, so less concerns for freezing rain/sleet, however the potential for widespread moderate accumulating snow does exist. Given the back-to-back nature, continued impacts could be seen for a 48-60 hour period from snow for parts of the area. Behind this system, some of the raw guidance indicates colder temperatures for Sunday, including subzero (maybe well into subzero) for Sunday night over what could be fresh snow cover. MTF && .AVIATION... For the 00Z TAFs... 545 pm...Primary forecast concern is light snow developing late this evening and continuing through sunrise Wednesday morning. Light snow will develop over portions of central IL this evening and lift north across the terminals in the late evening and just after midnight. There still remains some uncertainty for specific start times...but the light snow is expected at gyy first and at rfd last. Timing tweaks will likely be needed with the 03z update this evening. A band of moderate snow is possible and currently expected to remain south of the terminals...perhaps affecting gyy during the early morning hours. This snow is expected to end in the 11z-13z time period with some lingering flurries possible. A second wave will be weakening as it moves across southern WI later Wednesday morning and currently not expecting anything more than flurries. Light easterly winds are possible near the lake this evening but light and variable winds will prevail later this evening into the early overnight...with winds shifting light northwest in the early morning hours. Northwest winds will increase toward 10kts on Wednesday morning and diminish Wednesday evening. Mainly mvfr cigs expected with the snow at the terminals but ifr is possible wherever the moderate snow band sets up. Guidance is suggesting mvfr cigs may continue well into Wednesday afternoon but confidence is low. cms && .MARINE... 304 PM CST No strong signal for any gales through the weekend as the active pattern shifts south of the lake. Some periods of west to northwest winds gusting to 25 kt are probable through midweek. For Friday-Saturday, northeast winds look strong enough to potentially build waves to Small Craft Advisory criteria along the Illinois and Indiana nearshores. MTF && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion
National Weather Service Melbourne FL
843 PM EST Tue Feb 6 2018 .UPDATE... Tonight...High pressure ridge to our north will sink a little to the south, but onshore low level winds will be maintained. This will bring much milder temperatures with lows around 60, except mid 60s along the coast south of Cape Canaveral to the Treasure Coast. The only possible weather hazard will be fog as dew points have risen due to the onshore flow. However, the models show boundary layer winds 10-15 knots through the night. Hence, even though the GFS MOS shows low visibility at 12z over the interior, it only indicates a ceiling at Leesburg. This usually portends shallow patchy fog. The various mesoscale models don`t show much of any fog, except for the local WRF which shows some affecting Lake county. Will leave patchy fog over the interior and coastal Volusia, but would expect any potential for dense fog would be west of Interstate 4. && .AVIATION... Mainly VFR until after 06z. IFR ceilings are possible over interior terminals late tonight, especially west of I-4. Conditions do not look favorable for widespread fog. On Wed, southerly flow 10-12 knots will increase moisture so there will be more clouds but expect VFR ceilings 035-040 AGL. && .MARINE... Tonight/Wednesday...High pressure center will shift away from the eastern seaboard while a ridge axis settles into the waters on Wed. This will cause easterly flow to become southeast tonight and south/southeast on Wed. Currently, speeds are 10-15 knots but marine MOS and the HRRR model show wind speeds bumping up closer to a solid 15 knots across the south half. Seas have been running 2 to 4 feet, which is about a foot lower than what the wave models are forecasting. There is some potential for 15-20 knot winds to develop in the south, so will hold onto the exercise caution statement offshore from the Cape southward, though it looks marginal. && .MLB WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. && $$ FORECASTS...Lascody IMPACT WX...Ulrich
Area Forecast Discussion...UPDATED
National Weather Service Mobile AL
949 PM CST Tue Feb 6 2018 .DISCUSSION...See updated information for land areas below. && .UPDATE...Am letting current package ride. West of KMOB radar is generall dry, but am seeing development on the KLIX radar over NE LA. No changes planned attm. /16 && .PREV DISCUSSION... /issued 540 PM CST Tue Feb 6 2018/ DISCUSSION...See updated information below. UPDATE...Considering latest high resolution NAM12 and HRRR visibility products as well as the latest SREF showing modest probabilities for restrictions to visibility lowering to less than 3 miles tonight, have updated weather grids to mention fog. This is also evident over area bays and sounds. An update to zones and coastal waters forecast was made to mention fog. No other updates. AVIATION... 00Z issuance...Extensive cloud cover with multiple bases continues to spread in from the west along with scattered showers. Cig bases are forecast to lower to LIFR to IFR categories thru the night with some potential of vsby in fog lowering a category or so less in some areas, to VLIFR/LIFR categories. Light east to southeast winds. /10 PREV DISCUSSION... /issued 354 PM CST Tue Feb 6 2018/ NEAR TERM /Now Through Wednesday/...A surface trough from south Texas to northern Alabama will deepen slightly overnight and then shift eastward across the forecast late tonight through Wednesday, with associated cold front passing through the forecast area by late Wednesday afternoon. The southerly low level wind flow will continue to bring increasing moisture into the forecast area ahead of the front. Meanwhile, an upper level shortwave over the central plains will approach the region from the northwest through Wednesday. An upper level jet between 120 to 150 knots will form over the eastern conus ahead of the trough, with the forecast area residing in the right entrance region by noon, enhancing upper level lift. A strengthening low level jet is expected to develop over the forecast area on Wednesday, with bulk layer shear values expected to range from 40 to 50 knots. Mixed layer CAPE values are expected to increase to between 500 to 900 J/kg by noon Wednesday, along with SFC-1km SRH ranging from 250 to 500 M^2/S^2. Strong thunderstorm wind gusts between 40 to 50 mph are possible with the strongest storms just ahead of the cold front, with isolated severe thunderstorm possible. An isolated tornado can not be ruled out during maximum heating in the afternoon north of I-10. Widespread total rainfall amounts through the near term are expected to range from 1.25 inches across the extreme northwest portion of the forecast area, to 0.25 of an inch far southeast. A few places northwest of I-65 could receive between 2 to 3 inches in areas affected by prolonged heavier shower or stronger thunderstorm. /22 SHORT TERM /Wednesday night Through Friday night/...A cold front will move offshore Wednesday night with isolated to scattered showers expected during the evening. A drier and cooler airmass moves in from the north late Wednesday night into Thursday. Highs on Thursday will be in the upper 50s and low 60s. The stalled front will move north as a warm front late Thursday night into Friday, allowing moisture to return to the area. Moisture will continue to deepen across the area through Friday night as an upper trough digs across the southwestern states. Disturbances embedded in the southwest upper flow across the Gulf Coast will maintain a wet pattern for the start of the weekend. /13 LONG TERM /Saturday Through Tuesday/...The wet pattern continues through the extended as upper level southwest flow continues through the weekend. An advancing cold front will only move slowly to the southeast through early next week due to the southwest upper flow. This will maintain large scale lift in a very moist environment, setting the stage for continued rounds of rain through the weekend into early next week. /13 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...None. FL...None. MS...None. GM...None. && $$ This product is also available on the web at:
Area Forecast Discussion
National Weather Service Marquette MI
655 PM EST Tue Feb 6 2018 .SHORT TERM...(This evening through Wednesday) Issued at 300 PM EST TUE FEB 6 2018 Water vapor imagery and RAP analysis show a deep broad trough dominating much of Canada. Core of very low 500mb heights around 465dm remains centered in the vicinity of far northern Hudson Bay. Farther s, broad cyclonic flow now encompasses much of the CONUS. In this cyclonic flow, the next shortwave of interest is currently over northern Saskatchewan and is progged to move across the Upper Great Lakes late tonight and Wed morning. LES will continue off Lake Superior tonight with 850mb temps moderating slightly from -24C to around -20C. As w-nw low-level flow backs sw late today in response to the approach of the Saskatchewan shortwave, LES will be steadily shifting. By late afternoon, LES will have shifted offshore of eastern Upper MI. To the w, LES will become confined to the Keweenaw, perhaps with just a weak dominant band only along the western shore by evening. Although low-level sw winds suggest all LES will be offshore of Upper MI this evening, winds up at 850mb are more westerly. So, a weak dominant LES band may continue to brush the w side of the Keweenaw during the evening. As Saskatchewan shortwave swings into the Upper Lakes late tonight, sending a sfc trough out over Lake Superior, deep layer forcing per q-vector convergence and strengthening low-level convergence will result in an increase in intensity of the LES band along/near the w shore of the Keweenaw. The veering winds will then send this band across the Keweenaw and perhaps into far northern Ontonagon county overnight. Given the ice cover inhibiting normal heat/moisture fluxes off the lake, LES won`t be as heavy as it could be. Accumulations tonight should be in the 1- 3 inch range. Elsewhere, shortwave may be sufficient to generate some flurries across the far w and s central overnight. Increasing/thickening high/mid clouds will help keep temps up tonight, but if cloud cover is only thin this evening, temps could plummet quickly this evening. Interior central locations should be coldest, down to around -10F. After the Canadian shortwave exits e of the western Great Lakes Wed afternoon, synoptic scale forcing will pass east as well. Drying and subsidence behind the shortwave and inversions lowering to 3-4 kft will limit additional snow accumulation into the nw counties. A bit higher inversion heights over the eastern lake and more open water could result in around an inch of snow accumulation over portions of eastern Alger and northern Luce counties on Wed. Temps will remain 10 to 15 degrees below normal for this time of year. Expect lows tonight reaching down into the double digits blo zero at a few of the west and central interior locations with readings closer to zero near the Great Lakes shorelines. Highs on Wed will generally be in the teens. .LONG TERM...(Wednesday night through Tuesday) Issued at 300 PM EST TUE FEB 6 2018 The main forecast concerns through the extended are lake effect snow across the west and northwest wind snow belts and the continued below-normal temperatures through the end of the week, with a gradual warming trend this weekend into early next week as temperatures climb back to normal or above normal next Mon-Tue. Wed night through Friday: Models hint at a weak clipper shortwave moving through the Upper Lakes on Thu which could bring weak enhancement to w-nw lake effect snow late Wed night into Thu morning as 850 temps fall slightly from around -20C to -23/-24c. However, increasing ice coverage over the lake will likely limit lake effect snow accumulations. As winds veer more nw Thu night into early Fri, there may be better chances for lake effect snow accumulation into the counties east of Marquette as low-level convergence is enhanced by land breezes off Ontario. Since there is a bit more open water over eastern Lake Superior, this could allow for 2 to possibly 3" of accumulation into Alger, Luce and northern Schoolcraft counties late Thu night into Fri morning before winds back more westerly Fri afternoon and begin to push les bands offshore. With 850mb temperatures running around -20 to -25C, SLRs could be a bit lower with smaller snowflakes contributing to substantially reduced visibilities within any dominant bands that form. The upcoming weekend into early next week: Lingering lake effect snow should begin to wane in intensity On Sat as surface ridging slides across the region during the first half of the weekend and 850 mb temps rise to -12C to -14C. Another clipper shortwave tracking east across the region on Sunday will bring a brief shot of CAA (850 mb temps down to around -20C) to allow les to return for the w-nw wind snowbelts. This lake effect snow will taper off into the early part of next week as return flow develops out ahead of a shortwave advancing across the northern Plains. With 850mb temperatures progged to climb to -5C to -10C, expect a warm up into the low to mid 20s Monday/Tuesday. How much pcpn we get from this next Northern Plains system is still uncertain and highly dependent on the track and strength of this wave. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 654 PM EST TUE FEB 6 2018 At KCMX, winds will veer enough late tonight to maintain an overwater component that will result in lake effect clouds/shsn and mainly MVFR conditions through the rest of this fcst period. Similarly, at KIWD, a wnw wind component above the sfc layer may also bring in some MVFR lake clouds late tonight into Wednesday morning. However, confidence is lower. At KSAW, VFR conditions will prevail through this fcst period. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 300 PM EST TUE FEB 6 2018 No gales are expected for the remainder of this week. Overall, winds will mostly fall into the 15-25kt range...except for a brief period of 20-30 kt wsw winds late Sun into Sun night as another clipper system approaches from central Canada. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...Voss AVIATION...JLB MARINE...Voss
Area Forecast Discussion
National Weather Service Paducah KY
515 PM CST Tue Feb 6 2018 .UPDATE... Issued at 514 PM CST Tue Feb 6 2018 Added thunder to the forecast for southeast MO into west KY, and the southern tip of IL. Computed RAP li`s (750mb) support this along with lightning strikes into Carter and Ripley counties. Thunder with glazing reported around Fairdealing, MO, with icing now underway in the Poplar Bluff area. CN UPDATE Issued at 501 PM CST Tue Feb 6 2018 Updated for 00z TAFS only. && .SHORT TERM...(Tonight through Thursday night) Issued at 258 PM CST Tue Feb 6 2018 The main concern for tonight continues to be winter hazards. A variety of winter precipitation types is expected. A moist 500 mb shortwave will track east from the Plains tonight. Widespread precipitation is developing across Arkansas and Tennessee this afternoon. This precipitation will spread northeast across our region this evening. A pronounced elevated warm layer will keep snow to a minimum, although some minor accumulations around an inch are expected in parts of southern IL and southwest IN. The primary precip type is still expected to be freezing rain in areas south of a kmdh to kevv line. The 12z model runs generally trended higher with qpf in western KY and parts of se Missouri. This higher qpf overlaps the sub-freezing air in parts of se Missouri. Therefore, icing amounts have been increased to around one-quarter inch there. An upgrade to an Ice Storm Warning has been issued for several counties, mainly in se Missouri. The freezing line will be critical in this event. It appears the freezing line will remain fairly close to the Ohio River and the Missouri Bootheel early tonight. A slow southeast movement of the freezing line is expected late tonight, which should result in a change to freezing rain in much of western KY. The southern Pennyrile region will be the last to change over. A Winter Wx Advisory may be required there for the early morning hours of Wednesday, depending on how quickly the precip moves out. Rainfall amounts in the southern Pennyrile including khop will be over an inch within a 12-hour timeframe. This may cause some localized drainage issues. A Special Wx Statement will be issued for that area for the heavy rainfall, followed by the potential of icy spots early Wednesday. The precip will end early Wed morning across most of our region. North winds will increase to around 15 mph by early Wed morning. This could pose a problem for ice-laden trees, mainly in areas that receive 0.25 inch or more of ice. Skies are expected to clear out on Wednesday. The sunshine should boost temps to around or just above freezing in the afternoon, and winds will diminish gradually after noon. Temps will quickly drop after dark, with lows in the teens Wed night. .LONG TERM...(Friday through Tuesday) Issued at 258 PM CST Tue Feb 6 2018 High pressure to our east will keep our region dry for the end of the work week. South winds around the high will bring moisture north, along with warmer conditions. Models show a cold front sinking south Friday night, colliding with the moisture coming up from the south. Precipitation will move into southern portions of the PAH forecast area late Friday night, spreading north across the entire area Saturday morning. Precipitation will start as snow or a rain/snow mix, gradually becoming all rain from southeast to northwest Saturday morning as temperatures warm into the 40s. Areas of low pressure will move along the front, and rain will continue through Saturday afternoon, changing back over to snow from northwest to southeast Saturday night. Low chances will continue on Sunday, and with north winds bringing colder air into the region, any precipitation in northern portions of the area may just stay a rain/snow mix through the day. High pressure will move over our region for Sunday night into Monday, giving us dry and near seasonal conditions. Models show an area of low pressure over the Great Lakes region Monday night, and GFS shows a trailing cold front giving us precipitation chances late Monday night into Tuesday. Kept possibilities in the chance category due to the ECMWF pretty much keeping the front farther west during that time frame. With colder air in place, any precipitation would be snow or a rain/snow mix late Monday night into Tuesday morning. && .AVIATION... Issued at 501 PM CST Tue Feb 6 2018 Not many changes with previous TAF`s. We go MVFR overnight with freezing or frozen precip for all sites. Also extended the cigs and precip a few hours longer until we approach sunrise. By sunrise we should be out of the precip with VFR cigs. We will likely get rid of cigs after 18z wed. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...Winter Weather Advisory until 6 AM CST Wednesday for ILZ075>078- 080>091-093-094. Ice Storm Warning until 6 AM CST Wednesday for ILZ092. MO...Winter Weather Advisory until 6 AM CST Wednesday for MOZ076-086- 087-100-107-112-114. Ice Storm Warning until 6 AM CST Wednesday for MOZ108>111. IN...Winter Weather Advisory until 6 AM CST Wednesday for INZ081-082- 085>088. KY...Winter Weather Advisory until 6 AM CST Wednesday for KYZ001>008- 010-011-013>016-018>020. && $$ SHORT TERM...MY LONG TERM...RST AVIATION...KH
Area Forecast Discussion
National Weather Service Mount Holly NJ
927 PM EST Tue Feb 6 2018 .SYNOPSIS... High pressure over the Upper Midwest this afternoon will build eastward into the Northeast states tonight. Meanwhile, an area of low pressure will organize over the Gulf States tonight. The low will track northeastward across the central Appalachians Wednesday morning and then into the northern Mid-Atlantic states Wednesday afternoon. A cold front will move through the region Wednesday night after the low passes to our northeast. High pressure builds in from the Midwest on Thursday before moving off the Mid-Atlantic coast Friday. Another low pressure system is expected to lift northeastward through the region this weekend. High pressure returns early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 930 pm update: No updates were necessary to the forecast this evening. Previous discussion below... A cold front has pushed across the area, and will continue to push southward through tonight. High pressure located across the Great Lakes region late today will build eastward and to our north tonight, then across northern New England by daybreak. Our area will remain on the southern edge of the high, which will keep quiet weather for much of the overnight period. Temperatures will cool this evening and overnight, but as clouds increase later in the night, temperatures will likely steady off, and possibly warm a degree or two toward daybreak. An area of low pressure will be developing along this boundary across the Deep South/Gulf Coast this evening, before moving northeastward along the boundary through the Appalachians overnight. Some moisture will be lifting into our area overnight ahead of the storm system, so there could be some light precipitation developing and spreading into the area during the pre-daybreak hours. Temperatures will be cold enough everywhere for all precipitation to start as snow. That will change as we go through the daybreak hours. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... 930 pm update: An analysis of the latest high-resolution model output and the 18Z operational model suite suggests the forecast is generally on track, though uncertainty remains, particularly regarding the timing of precipitation type transitions and resultant influences on storm total snow and ice amounts. There seems to be an additional trend toward warmer solutions, which increases the icing threat in the northern CWA and slightly reduces it south of I-78. However, I am somewhat skeptical. Model sounding analysis (NAM/RAP/HRRR) at KPHL during the morning rush indicates the potential for a couple hours of a wintry mix (primarily freezing rain and sleet) before transition to rain by mid to late morning. There are also indications that locations along/south of the I-76/I-276/I-195 corridors may see a brief break in precipitation before steadier rain moves in during the afternoon (as boundary-layer temperatures warm above freezing). Farther to the north, the transition will be slower, and I cannot help but wonder if models are too fast with the transition in general (especially with Sunday`s event freshly in mind). Though I expect a gradual transition to rain in much of the region south of I-78 by afternoon, the 10-15 degree dew point depressions observed this evening give me some pause. After wet-bulbing cools temperatures down, I think it will be more challenging to warm the near-surface layer as quickly as many of the models are projecting. For example, the latest HRRR has Reading and Allentown at rain by early afternoon. While certainly plausible given the good model agreement with the RAP and 18Z NAM Nest, models were universally too aggressive in warming areas northwest of the Fall Line for Sunday`s event. This requires close monitoring through the event, as a slower transition would prolong the wintry threat in these areas, which is concerning given the forecast precipitation amounts and the implied potential for a decent duration of freezing rain. The warming trend in models would temper snow amounts in the warning area somewhat, but would also increase the icing potential...think of it as a meteorological Hobson`s choice. With all of the above said, think the way to go is to let the forecast ride for now, continue to monitor short-term trends, and adjust as needed. Previous discussion... As we approach and go through the daybreak hours, temperatures at the ground and aloft begin to warm, and a wintry mix begins to take place. We expect a period of snow, sleet, and/or freezing rain to develop for much of the area, before most places warm through the day and change over to all rain. For most of coastal New Jersey and the southern half of our Delware and Maryland counties, we expect the precipitation to be either snow/sleet, or all rain. Surface temperatures are expected to warm above freezing before precipitation starts, so freezing rain is not expected to be a problem there, so we did not issue an advisory there. For areas along the I-95/NJ Turnpike corridor, including Philadelphia and closest suburbs, we expect less than a half inch of snow and a possible glaze of ice from freezing rain. These areas are expected to change over to rain by the mid-late morning hours, so the advisory here ends earlier. For areas along the outer suburbs of Philadelphia and portions of central New Jersey, the wintry mix could last longer, so we could see an inch or two of snow, with a few hundredths of an inch of ice. The advisory ends here during the early afternoon. The precipitation is expected to change over to rain by the early afternoon. Farther north across Berks County, the Lehigh Valley, and portions of northern New Jersey, we could have 2 to 4 inches of snow and up to a tenth of an inch of ice from freezing rain. We have issued an advisory here as well as conditions are not forecast to meet warning criteria before changing to rain as temperatures warm slightly during the afternoon, before dropping again by the evening hours. The advisory here continues through the afternoon and into the evening. Finally, across Carbon/Monroe, PA and Sussex, NJ, we have issued a Winter Storm Warning as we expect upward of 4-7 inches of snow, in addition to up to a tenth of an inch of ice from freezing rain as temperatures aloft warm and create some freezing fain late in the day. Some areas may warm above freezing, but the higher elevations will likely stay below freezing through the event. The warning continues through the afternoon and into the evening. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Wednesday night and Thursday... Low pressure will exit the area and move northeastward into New England. Westerly flow around the backside of the low will allow the cold front to advance eastward through the area. Precipitation will quickly end from west to east during the evening as colder and drier air moves in behind the front. Models indicate the strongest CAA arrives just after the back edge of the precipitation shield progresses through. Accordingly, precipitation may briefly transition to sleet and/or snow at higher elevations in NE PA and NW NJ at the tail end while most other locations will end as rain. Guidance than indicate temperatures dropping rather quickly overnight into the 20s along the I-95 corridor/coastal plain and teens along/west of the Fall Line. While the brisk NW winds (gusts 20-30 mph) will aid in drying, there will likely be standing water (given QPF amounts of 0.75-1.25" verifies) that will freeze overnight as a result of the quick temperature drop. Similar to what happened this past Sunday night-Monday morning after the last round of moderate precipitation, black ice forming on untreated roads and sidewalks will likely impact travel late Wednesday night and Thursday morning. There is even a potential for a more widespread/ hazardous flash freeze in parts of the area, along and especially west of I-95 where the axis heaviest rain and quickest descent to freezing temperatures likely coincide. We will highlight in the HWO the concern for an icy morning commute on Thursday. Winds should gradually weaken during the day on Thursday as high pressure builds in from the west and the pressure gradient relaxes. Temperatures are not expected to rebound much during the day from early morning lows as CAA partially offsets solar heating. Forecast highs are about 8-12 degrees below normal, ranging from the mid 20s in the southern Poconos to the mid 30s along and east of I-95. Thursday night and Friday... High pressure moves off the Mid-Atlantic coast late Thursday night while a cold front approaches from the Ohio Valley-eastern Great Lakes region. This front will likely stall to our north near the PA-NY border on Friday as it gets caught up in zonal steering flow that becomes oriented parallel to the boundary. Light southerly flow south of the front will allow the airmass to moderate with highs in 40s along and S/E of I-95. We will continue to mention a chance of light snow across the far north (I-80) on Friday but with the deeper lift staying to our north, do not expect much in the way of accumulations. Saturday and Sunday... A wet pattern is in store for the weekend as the next storm system forming on the lee side of the Rockies late in the week tracks northeastward from the Southern Plains to the Mid- Atlantic this weekend. The current projected track of this low is similar to tomorrow`s system as well as the past couple of ones but the biggest difference with the upcoming weekend event is the lack of cold air preceding it. Accordingly, the predominate precipitation type should be rain. There is a modest risk that freezing rain and/or sleet occurs at the onset in the coldest spots across the far north (e.g., southern Poconos, far NW NJ). Despite there being timing uncertainty (e.g., when the rain moves in and when it exits the area, there was enough support to go with likely PoPs for Saturday night and Sunday. Monday and Tuesday... High pressure builds into the area. A fast- zonal flow pattern aloft indicates high pressure building in behind the weekend storm system for Monday will be rather progressive and move offshore by Tuesday. Additionally, temperatures will be near or slightly above normal. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR, but CIGs will be developing/lowering to 3000-6000 feet by around 09Z-11Z. Light west to northwest winds will become east or northeast after midnight. Given that the timing of these change in directions is quite uncertain, light and variable winds were included at most TAF sites through the period. Medium confidence. Wednesday...Rapid deterioration early in the morning (11Z-14Z) to MVFR and IFR conditions, with snow likely to persist near/northwest of RDG/ABE during the morning and a wintry mix transitioning to rain elsewhere (very quickly at ILG/ACY/MIV; probably in the 13Z to 15Z time window). Transition at the Philly terminals will likely be in the mid-to-late morning hours (14Z to 17Z). RDG/ABE will likely have a switchover to sleet/freezing rain during the afternoon. Once it sets in, IFR should persist through the day at all TAF sites. LLWS will develop during the afternoon hours, as well. Winds will primarily be east-northeast to east-southeast during the morning but will veer to southwest/west during the afternoon hours. Low confidence, especially with timing of precipitation type transitions. OUTLOOK... Wednesday night...MVFR/IFR with RA early will quickly improve to VFR as rain ends from west to east during the evening. Wind shift from SW to W and then to NW occurs during the evening. NW winds increase to 10-15 kt with gusts to 25 kt. High forecast confidence. Thursday...VFR. NW winds gradually relax during the day. High forecast confidence. Thursday night through Friday night...Mainly VFR. However, there is a potential of sub-VFR conditions at ABE on Friday if snow reaches the terminal but there is low confidence in that happening. Saturday and Sunday...MVFR and IFR conditions possible with rain overspreading the area. High confidence for the occurrence of rain but low confidence in timing of the rain. && .MARINE... 930 pm update: The NAM continues to advertise a brief period of near-gale force gusts in the Atlantic waters late Wednesday afternoon. With very strong winds not far from the surface, it would not take much to generate some brief winds in excess of 34 kts. However, the low-level thermal profile is unfavorable for sufficient mixing, and confidence is too low for issuance of a gale warning. Will continue to monitor. Previous discussion... Sub-Small Craft Advisory conditions are expected to remain across the waters through tonight. However, winds and seas are both expected to build during the day Wednesday and reach advisory levels by the afternoon. So we have kept the advisory in place across the Atlantic Ocean, and expanded it across the Delaware Bay. OUTLOOK... Wednesday night and Thursday morning...SCA that was already in effect for Wednesday night was extended into Thursday morning. There are two potential brief windows of gales: (1) Early Wednesday evening when southerly winds peak and (2) Overnight Wednesday night in occurrence with NW winds surging behind a cold front. Confidence on reaching criteria was too low to issue a Gale Warning. Thursday afternoon through Sunday...No marine headlines are anticipated. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory from 4 AM to 9 PM EST Wednesday for PAZ060>062. Winter Weather Advisory from 4 AM to 2 PM EST Wednesday for PAZ101-103-105. Winter Storm Warning from 4 AM to 9 PM EST Wednesday for PAZ054-055. Winter Weather Advisory from 4 AM to 11 AM EST Wednesday for PAZ070-071-102-104-106. NJ...Winter Weather Advisory from 4 AM to 9 PM EST Wednesday for NJZ007-008. Winter Weather Advisory from 4 AM to 2 PM EST Wednesday for NJZ009-010. Winter Storm Warning from 4 AM to 9 PM EST Wednesday for NJZ001. Winter Weather Advisory from 4 AM to 9 AM EST Wednesday for NJZ013-016>019. Winter Weather Advisory from 4 AM to 11 AM EST Wednesday for NJZ012-015. DE...Winter Weather Advisory from 4 AM to 9 AM EST Wednesday for DEZ001. MD...Winter Weather Advisory from 4 AM to 9 AM EST Wednesday for MDZ008-012. MARINE...Small Craft Advisory from noon Wednesday to noon EST Thursday for ANZ430-431-450>455. && $$ Synopsis...Klein Near Term...CMS/Robertson Short Term...CMS/Robertson Long Term...Klein Aviation...CMS/Klein Marine...CMS/Klein/Robertson