Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 180419 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1119 PM EST Tue Jan 17 2017 .SYNOPSIS...
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Low pressure forming near the New Jersey coast will intensify eastward to the south of Cape Cod Wednesday. High pressure then builds across the Eastern Seaboard Thursday. Weak low pressure will pass through the region this weekend, and then a much larger and stronger system will impact the area early next week.
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&& .NEAR TERM /THROUGH WEDNESDAY/...
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Overnight...light freezing rain and drizzle persists at or above 1000 feet in northern monroe and northern Sussex counties. Otherwise patches of showers drizzle and fog will be occuring in our forecast area. North to northeast wind PA and northern half of Nj while low pressure forms near the s NJ coast with light southwest winds Delmarva and s NJ turning northwest overnight. Wednesday...Mostly cloudy with scattered showers through early afternoon (drizzle north as well) as a sharp trough aloft passes southeast through the mid Atlantic states. Cool north but becoming milder south during the afternoon as skies brighten a bit toward sunset. North winds near and northwest of I78 while a northwest wind becomes gusty 20-25 MPH during the afternoon s NJ and Philly area southward through the Delmarva. Max temps 5 to 10F warmer than normal north and around 10 warmer than normal south.
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&& .SHORT TERM /WEDNESDAY NIGHT/...
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Clearing south though it may remain mostly cloudy north. Temps 10 to 15 degrees above normal. Northwest wind.
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&& .LONG TERM /THURSDAY THROUGH TUESDAY/...
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Overview: The long term period will feature a series of low pressure systems that will bring unsettled weather to much of the Northeast and Mid-Atlantic. This period also features a jet stream that will keep the Arctic air bottled up to the north. Although a series of storm systems will impact the area during this time, they do not have origins from the Arctic, so any cold air that funnels into the Northeast and Mid-Atlantic will generally return temperatures closer to normal. With deep S-SW flow that will dominate the time frame due to a Bermuda high that will set up over the western Atlantic, temperatures will run well above normal, with high temperatures generally 10 degrees above normal, for this time of the year. Although a bit beyond the time frame for this forecast period, the Climate Prediction Center 6-10 day outlook starting on Monday indicates a high probability, 60-70% for NJ and Delmarva and 70-80% for SE PA and the Poconos, of above normal temperatures next week. The high will continue to slowly press east on Thursday, and will be nearly overhead along the East Coast late Thursday night, and then will move offshore on Friday. Skies clear out during the day Thursday, and generally expecting mild conditions with highs in the low to mid 40s across the Poconos, and in the low to mid 50s across the rest of NJ, SE PA, and into the Delmarva. The next system is rather weak and disorganized, and is almost falling apart as it tracks from the Southern Plains and into the Great Lakes and OH Valley. Nonetheless, a weak warm front approaches on Friday afternoon, and some light precip will develop over extreme SW portions of the CWA, generally across SE PA, the Delmarva, and southern NJ in the afternoon, and then light precip spreads to the north and east Friday night as that system lifts northeast through the region. High pressure briefly builds through the region on Saturday, but moves offshore by Sunday as a weak cold front passes through. Conditions should generally be dry, but cannot rule out a few passing showers. Things get interesting for the start of the new work week. A trough moves into the Western U.S. early in the weekend, and then a strong closed H5 low moves into the Southern Plains/Gulf Coast states on Sunday, where a storm system become more organized and developed. This system will lift to the north and east, towards the TN/OH Valleys, Sunday night and Monday, and will slowly work its way through the East Coast Monday through Tuesday. Latest GFS/ECMWF in decent agreement with the overall setup, so feel reasonably confident going with high-end likely PoPs for Sunday night through Monday night, with western portions of the CWA bumped up to low-end categorical. With strong onshore flow ahead of this system, can expect abundant low-level moisture to spread into the region. GFS indicating PWATs around 1.5" during this time, so can expect locally heavy rain from time to time. In addition, GFS indicating an environment with CAPE (less than 100 J/kg) and 850-700MB wind speed 60-65 KT. Cannot rule out a rumble of thunder Monday afternoon, especially south of I-76, but given that it is mid-late January, may be a bit too far to include a mention of thunder on Day 7. But will keep an eye out on it. Lower confidence in the forecast by Tuesday. Models indicating secondary low will develop off the Mid-Atlantic coast, and it remains to be seen how that will impact the Northeast/Mid- Atlantic. Will carry chance PoPs for most of the region, with higher PoPs along the coast. Monday looks to be the warmest, but wettest, day of the period with highs ranging from the 40s across the Poconos to near 60 in the Delmarva. Otherwise, as mentioned above, temperatures will be warm.
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&& .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...IFR conditions with patches of LIFR in stratus/fog/drizzle and scattered showers overnight. Light north - northeast wind except vcnty KACY and KMIV where nearly calm or light southwest wind turns northwest. Wednesday...IFR conditions at sunrise will gradually improve to MVFR cigs during midday with vsby improving to VFR as north to northwest winds gradually increase with northwest gusts vcnty KACY, KPHL, KMIV and KILG of 20-25 kt during the afternoon. Scattered morning showers/drizzle will end early afternoon. Wednesday night...Probably VFR sct-bkn aoa 3500 ft. Light northwest wind. OUTLOOK... Thursday through Friday morning...VFR. Wind speeds should be 10 KT or less during this time. Friday afternoon through Friday night...Sub-VFR conditions in -RA. Saturday through Sunday. Mainly VFR. Few passing showers with brief sub-VFR conditions possible.
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&& .MARINE...
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Short period of SCA northwest wind headline anticipated to be issued 330 am Wednesday for the S NJ and De coasts. OUTLOOK... Thursday through Sunday...Sub-SCA conditions expected. Few passing showers possible on Friday/Friday night. Sunday night through Monday night...Easterly flow 20-30 KT. SCA conditions likely, with gale force winds possible on Monday, mainly on the ocean waters. Rain, possibly heavy at times. Isolated thunderstorms possible Monday afternoon.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...Freezing Rain Advisory until 7 AM EST Wednesday for PAZ055. NJ...Freezing Rain Advisory until 7 AM EST Wednesday for NJZ001. DE...None. MD...None. MARINE...None. && $$ Synopsis...MPS Near Term...CMS/Drag 1118 Short Term...Drag/Iovino 1118 Long Term...MPS Aviation...CMS/Drag/Iovino/MPS 1118 Marine...Drag/Iovino/MPS 1118

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