Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 161802 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 102 PM EST Thu Feb 16 2017 .SYNOPSIS... An area of low pressure will continue to intensify as it moves into the Canadian Maritimes tonight and lingers there through Friday. Weak high pressure affects the area Friday into Friday night. An area of low pressure will pass well to our north Saturday night into Sunday, pulling a cold front across our area early Sunday, then another boundary may move into the area later in the day. High pressure affects the area Monday into Tuesday, before moving offshore Tuesday night. && .NEAR TERM /THROUGH TONIGHT/...
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1230 PM ESTF: Everything on track tho temps Delmarva may remain at originally fcst values of 330 am. Pretty cold day. Temps several degrees below normal. Isolated flurries down to near I-95, but usually its difficult to get flurries with a temp-dew spread of 20F+, unless it needs to be squally with that kind of spread to get snow to the ground. Lapse rates are large but not much 12 hr change in stability and no well defined surface trough except northern PA, so am not expecting much except high terrain north of I-80 where it should be slippery at times, especially Poconos-lake effect and cold trough aloft passing sewd. As for the winds, expect the strongest winds to be through early afternoon before the pressure gradient begins to decrease late in the afternoon...near sunset. The mixed layer could be as deep as through 800mb. If this is the case, could see peak gusts up to 35 mph. Tonight..it rapidly clears. Any lake effect cold trough aloft flurries scattered snow showers near and north of I-80 high terrain dries out late at night. Lows near normal with diminishing gustiness. Forecast basis: 50 50 blended 12z/16 GFS/NAM MOS and already posted for the 1230 PM fcst.
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&& .SHORT TERM /FRIDAY/...
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Mostly sunny. Some cirrus at times. Northwest winds half as strong when compared to today and backing to westerly and southwesterly as the afternoon moves along. Max temps near normal. Forecast basis: 50 50 blended 12z/16 GFS/NAM MOS and already posted for the 1230 PM fcst.
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&& .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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A mostly dry forecast for the majority of the extended. On Saturday, a warm front may lift north of the area as low pressure moves across southern tier of Canada. The low passes to our north overnight Saturday into early Sunday. This will bring a couple of cold fronts/surface troughs across the area early Sunday morning and later Sunday afternoon. The airmass is forecast to be relatively dry and there is not much in the way of short waves/vorticity impulses to help create any shower activity. So we`ll keep the forecast dry. High pressure is then expected to affect the area on Monday into Tuesday. Dry weather should continue on Monday, but a warm front may pass to our west on Tuesday as high pressure begins to shift offshore. A couple of short wave/vorticity impulses may cross the area Tuesday through Wednesday which may help create some isolated showers.
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&& .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions will continue at the terminals through the TAF period. Ceilings around 5000 ft today will start to clear out by later this afternoon with mainly clear skies overnight. Some high cirrus will likely be around the region overnight and through much of Friday. Main concern today continues to be the winds. A strong northwest wind will continue through tonight with the higher gusts (27 to 32 kts) dropping off between 22-00Z. Sustained winds around 15 knots will continue through 03-06Z tonight and then winds will drop down to around 10 knots overnight and into early Friday. Winds on Friday will start to turn more to the west southwest, mainly towards the afternoon. OUTLOOK... Friday night-Monday...Generally VFR expected, although MVFR CIGS may be possible during the day if clouds develop. Gusty winds 15-20 knots during the day.
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&& .MARINE...
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Marginal gale in progress Atlantic waters. May extend a few hours into the evening due to a small uptick in momentum transfer forecast for late today into the evening then a downglide from there. Once winds drop below gale conditions on the Atlantic coastal waters, an SCA will be needed. SCA on DE BAY probably will be extended to 12z Friday for the slight uptick in the last gasp cold trough aloft instability momentum transfer. OUTLOOK... Friday...Small Craft Advisory level conditions possible early, then diminishing during the day. Friday night-Monday...Sub Small Craft Advisory conditions expected. Winds may gust around 20 knots at times however.
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&& .CLIMATE...
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Updated 1104 AM Thu Feb 16 and please do not expect any further updates prior to late Friday or Saturday. Projecting widespread top 10 warmest February on record in our forecast area. Confidence: above average. Details below. Seasonal average (DJF) temperature projecting widespread top 14. PHL is projecting #9 warmest, ABE #6 and ACY #12. February: The month as a whole has so far averaged 3.4 to 5.5 degrees above normal through the 15th, except 1.4 above normal at KMPO. There still isn`t any sign of long duration substantially colder than normal air coming this month and in fact some of the guidance is suggesting near record warmth is possible either this weekend and maybe the middle of next week (date and climate location dependent). Just the 7 day period of tomorrow through the 23rd should average close to 10 degrees above normal. The following projection is for Philadelphia with remainder of the area relationship discussed. Using this mornings low of 33 and the NWS forecast through the 22nd (see SFTCTP), and then FTPRHA max/min for PHL D8-11, and the normal the last two days of February (max min of 47/30) we project a monthly average of 41.9 degrees at PHL (2 degrees higher than the current first 15 day average). Normal for February is 35.7 or a projection of 6.2 degrees above normal. This would make February the 2nd warmest in our period of record dating back to 1874. The warmest February on record was 42.2F in 1925. Ninth warmest is 40.1 degrees, so you see that we have 1.7 degrees to give = be wrong, and still enjoy a top 10 warmest February. Average temperatures at all our other climate sites should average at least a degree warmer than what has occurred through the first 15 days. Lack of snow cover is partly to blame and goes in tandem with the primary storm track northwest of our area across the Ohio Valley-Great Lakes this winter (DJF) as evidenced by above normal pcpn fm KY northward into the Great Lakes. Detailing ACY and ABE for February as per PHL data process input. ACY projects #2 warmest at 41.1F with the record being 41.6F in 1890. The 30 normal is 35.3 or a positive departure of nearly 6 degrees. The projection has 1.2 degrees to give on the down side for a #9 rank with the POR back to 1874. ACY climate is subject to radiational cooling which at times may force a colder solution so confidence on ACY maintaining a #2 projection is less than PHL. Still, if the pattern doesn`t change significantly from the outlook of the past two days...it will be a noteworthy top 10 warmest February on record through most of our Mount Holly forecast area. ABE projects 7th warmest with a 36.1 average, or 5.4 degrees above the norm of 30.7. ABE has less room to give on the down side. NOTE: there has been no talk here of even warmer avg temps since climatologically the error would favor this projection being too warm. Finally...PHL for the winter season (DJF) is projecting an average of 39.6 degrees...the 9th warmest DJF in the period of record dating back to 1873-1874. Room to give is 0.4 degrees on the down side to #10 warmest winter. Essentially its going to take all of at least a 1.2 degree warm side error to drop back to #10 warmest seasonal average. While this could happen, am thinking via ensemble guidance that this is unlikely. Projected seasonal rankings for ACY and ABE follow: ABE seasonal average temp projects 34.9 or #6 in the POR back to the winter 1922-23. 0.7 to give to drop out of top 10 so #6 looks pretty solid. ACY seasonal average temp projects to 39.2 or #12 in the POR back to the winter 1873-74. .6 to give to drop back to #14. Split flow = no snow was something I heard in Boston and it seems to apply for the next 10 days as the pattern is devoid of much phasing of the northern and southern streams. Change is ensembled sometime between the 25th and the first week of March with a storm track nearby and a better shot at colder temps and some winter wx. Because of that i hesitate to look at seasonal snowfall records. Allentown current #7 least snowy winter will most likely drop out of the top 10, needing only 1.5" the rest of the way. PHL ILG are already out of the top 10 least snowy.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 PM EST this evening for ANZ450>455. Small Craft Advisory until midnight EST tonight for ANZ430-431. && $$ Synopsis...Robertson Near Term...Drag 101 Short Term...Drag 101 Long Term...Robertson Aviation...Robertson/Meola Marine...Drag/Robertson 101 Climate...101

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