Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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823 FXUS61 KPHI 290811 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 411 AM EDT Wed Mar 29 2017 .SYNOPSIS... High pressure near Hudson`s Bay will build into our region through Wednesday night. Low pressure moving through the Ohio Valley on Friday will redevelop near the New Jersey coast Friday night and move offshore on Saturday. High pressure will move into the area for Sunday and Monday. Low pressure over the Ohio Valley and its associated fronts will approach our region on Tuesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Early this morning...slow clearing. north to northwest wind 5-15 kt. Today...Partly to mostly sunny with a gusty north to northwest wind 10-25 mph. Max t in PHL today around 62-63F. Slightly above normal max temps. Forecast basis: 50 50 blended 00z/29 GFS/NAM MOS guidance and the EC 2m temps which has 58 in PHL at 2 PM. I usually add 4-5F on a p-m/s day with decently mixing n-w wind. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... Clear or mostly clear skies, a few fragments of sc in the early eve and possibly a little cirrus. Some radiational cooling expected. Light north wind. Normal or slightly below normal mins. Forecast basis: 50 50 blended 00z/29 GFS/NAM MOS guidance. Applied minor 1-2F cooler than guidance adjustments in our 330 AM fcst for tonight. && .LONG TERM /THURSDAY THROUGH TUESDAY/... The primary players during the long term will be two southern stream systems that are expected to impact our region in the Friday-Saturday and Tuesday time frames. The first system may produce 1 to 1.5 inches of rain across portions of the region, especially in the Delaware Valley. While there could be some urban and poor drainage flooding, we do not expect any major impacts on rivers and streams. There is also a consistent signal in the models for mixed precip north of I-80, with sleet and freezing rain the primary concerns, during the Friday night and Saturday morning period. We have mentioned this in the HWO. Looking ahead to early next week, the next system is expected to bring more precip to our region Monday night into Tuesday. This setup looks warmer, given the absence of high latitude blocking, and would favor predominantly rain. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through 12z...Still some leftover IFR/MVFR conds which will be improving to VFR sct clouds by 12z. North to northwest wind 5 to 15 kt. After 12z...VFR sct-bkn near 4000 ft will become VFR clr by 21z. North to northwest wind gusty 20-25 kt. Tonight...VFR with fragments of sc in the evening and maybe some thin cirrus at times. Light north wind. OUTLOOK... Predominantly VFR, except MVFR possible Friday into Saturday. && .MARINE... No headlines through tonight. Northerly flow becomes northwest during the daylight hours with gusts 20 kt. A few gusts 25 kt possible this evening in the NNJ waters when we may need to issue a short fuse SCA, then northerly winds diminishing early Thursday. OUTLOOK... SCA likely Friday into Saturday, with the potential for gale force southeasterly wind gusts Friday night, mainly across the northern NJ waters. Otherwise, sub-SCA. && .TIDES/COASTAL FLOODING... Though astronomical tides will be gradually diminishing through the week now that we are past the new moon, the threat of minor tidal flooding along the NJ and DE Atlantic coasts increases late in the week. This is a result of a low pressure system bringing a prolonged period of onshore flow. The tide of most concern at this point is the high tide on Friday evening/late Friday night. By this tide cycle, it will take a surge of 0.8 to 1.0 feet to reach minor flooding thresholds, which is possible but still uncertain (it will be dependent on how quickly the on shore flow develops and how strong it will be by then). At least one source of guidance shows water levels reaching minor tidal flooding thresholds with the Thursday evening/night high tide, but that seems unlikely as the latest forecast depicts onshore flow either developing right around or just after the time of that high tide. We have mentioned the potential of minor flooding along the northern NJ coast in the HWO, where the threat is greatest during the Friday evening/late Friday night high tide cycle. && .CLIMATE... Mo avg temps March Dep Feb DEP ABE 38.0 -1.1 39.2 +8.5 ACY 41.6 -0.6 43.0 +7.7 ILG 41.7 -1.3 43.1 +8.0 PHL 42.2 -1.3 44.2 +8.5 First of all: This March will be a below normal month for temps.... One of the VERY few the last two years. Second, we appreciate that this is possibly old news, but March temperatures will average colder than the FEB average at all 4 long term climate locations. The last time this occurred, 1984. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Franck Near Term...Drag Short Term...Drag Long Term...Franck Aviation...Drag/Franck Marine...Drag/Franck Tides/Coastal Flooding... Climate...410A is the U.S. government's official web portal to all federal, state and local government web resources and services.