Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251411 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1011 AM EDT Sat Mar 25 2017 .SYNOPSIS... A cold front over the southern tier of New York will sag south across our area this afternoon and evening, becoming nearly stationary just south of Delaware on Sunday. It then returns slowly north as a warm front into our area Monday and Tuesday. Low pressure crosses New Jersey Tuesday evening pulling the front out to sea. Canadian high pressure follows into the northeast United States late Wednesday and Thursday. Low pressure in the nations midsection on Friday develops a warm front toward our area. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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As of mid-morning, broken mid and high-level clouds are moving across the area, with more solid clouds noted north of a frontal boundary roughly along the NY/PA border. Radar shows bands of light precip falling but mostly not reaching the ground. Temperatures range from around 40 in far northern NJ to around 60 in southern DE. This contrast will continue or even increase a bit during today with somewhat greater daytime heating expected over Delmava and southern NJ. The frontal boundary noted above has started to push south into northern NJ and this trend will continue through the afternoon. Increasing clouds and NE winds will limit heating over northern NJ and adjacent PA where afternoon highs are expected to be only in the 50s to low 60s. The chances for light rain or sprinkles will also increase behind the front. Previous discussion below: Mild and dry weather early will be replaced by clouds and higher chances for showers from north to south today. The northern half of the area will have pops >= 50 % today and these tail off to the south. A front will be moving N to S today and cooler air will seep in behind it. Before the front moves thru high temperatures will reach the 50s over the north and mid 70s over Delmarva. Readings will trend downward once the front passes. Models are offering somewhat different solutions with regards to coverage and timing of showers. Confid in precip timing is rather limited.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... The front continues to drop southward across the area and there are better chances for overcast skies and scattered showers along with it. Temperatures will slowly fall through the night reaching the low/mid 30s across the higher elevations to the north and mid 40s over Delmarva. The precipitation could become a little ice at the highest elevations across the southern Poconos late tonight. It appears the the chances will be low enough as to not have to issue an advisory at this point. && .LONG TERM /SUNDAY THROUGH FRIDAY/... **Damp weather will be featured tonight - Tuesday** 500 MB: A strong ridge over the northeast USA Sunday weakens considerably as a southern stream closed low in the Ohio Valley opens up and moves into the northeast on Monday. It is followed by a northern stream short wave in central Canada Tuesday, which intensifies into Quebec Wednesday. The next southern stream short wave should affect our area toward the end of the week. Temperatures: Calendar day averages 5 to 10 degrees above normal Monday, 10 to 15 above normal Tuesday, 5 to 10 degrees above normal Wednesday, near normal Thursday and Friday. Forecast basis: 50 50 blended 00z/25 GFS/NAM MOS Sunday-Monday blended downward with 2m NAM temps, then 00z/25 MEXMOS Monday night-Tuesday and thereafter WPC guidance Tuesday night-Friday. The dailies... Sunday...there may need to be an icing hazard for the Poconos and far northwest NJ (elevations north of I80). Despite warm ground, if rain or drizzle develops as expected, it would glaze on trees/wires, bridges and overpasses first. While qpf amounts would not be heavy, the upslope and misty rain expected could add up to a tenth of an inch of radial icing. Thats a worst case scenario. Elsewhere...much much cooler Sunday afternoon compared to this Saturday afternoon s of I-78 (20-25F cooler). Stratus overcast and chance of a little light rain or drizzle but confidence on rain/drizzle occurrence is average. East to northeast wind may gust 15-20 mph. Monday...East-west front south of Delaware attempts to edge north as a warm front. Not convinced about how far north it can move due to mostly west southwest flow aloft. The boundary layer will be quite moist and there should patchy fog and measurable drizzle/scattered showers in a cool inverted marine layer. Some of the fog could be quite thick, especially elevations, near the waters and along the warm front. I think the cooler NAM should be more accurate, but since there is considerable uncertainty, the forecast result was blended temps between the warmer and cooler model solutions. Tuesday...May be our best chance to warm up...and thin out the murky low level cloudiness. Uncertainty. Also, a short wave should organize low pressure development somewhere in the mid Atlantic states with a batch of showers, especially near the convergence associated with the low center Tuesday evening. In terms of hydrology, given the above normal temperatures through the long term, the snow pack north of I-78 will continue to melt. The model consensus brings additional rainfall amounts of three quarters of an inch to two inches across this area through Tuesday evening. Unless there are significant changes, we expect rises on area streams and rivers, but no flooding concerns at this time. Tides Sunday and Monday sunrise: At this time...expected to remain below advisory threshold but will be monitored. Wednesday...Clearing with north or northwesterly flow. Thursday...Increasing clouds later on. Small chance pcpn arrives Thu night? Friday...Southern stream short wave crossing the lower Mississippi Valley should spread precipitation into our area, mostly rain. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... VFR conditions in most areas early this morning with mostly CI/CS clouds over the area. There could be a few patchy lower clouds or some light fog before dawn, but mostly good weather early today before a front moves thru and brings poorer conditions from N to S. Cigs will decrease as the chcs for rains develop this afternoon and persist into tonight. IFR conditions with rain and fog will arrive over most areas. Timing of the decreases is somewhat uncertain. Winds will shift to E or NE behind the front. The IFR conditions will persist into Sunday morning. OUTLOOK... Sunday and Sunday night...Cigs 500-1500 ft vsby ocnl below 3 mi in patchy rain/drizzle/fog with icing on the ridges of ne PA and nw NJ in layers below 3000 ft MSL. PATCHY LIFR in st/fog/drizzle possible late at night. East northeast flow. Confidence: above average. Monday and Monday night...IFR conditions with periods of rain and drizzle. Patchy LIFR possible. Easterly flow may turn southeast to south Monday afternoon or night vcnty KMIV/KACY/KILG. Confidence: average. Tuesday...IFR conditions to start the day could improve to VFR cigs in the afternoon with a light south to southwest flow? Confidence: below average due to the position uncertainty of the northward moving warm front. Wednesday...Morning MVFR or VFR cigs becoming sct clouds near 4000 ft in the afternoon. Northwest wind gusty 20 kt. Confidence: above average. && .MARINE... Seas continue to slowly decrease on the northern NJ coastal waters. It looks like we will be able to drop the SCA flag for these waters with the 330 issuance. Seas could linger close to 5 ft thru dawn however. At 630 it looks like we will need another SCA flag for tonight and into Sunday with a NE flow behind the front bringing seas back up and gusts also should be around 25 kts. Looks like just the nrn NJ waters will need the SCA for now the Sat night period. Scat showers expected later this afternoon and tonight. OUTLOOK... Sunday-Sunday night...Small Craft Advisory in effect for the NJ waters for combined seas increasing to 5 or 6 feet and scattered gusts 25 kt. Elsewhere, no SCA at this time for the DE waters though this is being monitored. Confidence: average. Monday-Tuesday...Winds may be below advisory levels, but seas could remain elevated, possibly leading to Small Craft Advisory levels for the NJ and De Atlantic waters. Confidence: average. Wednesday...northwest wind...gusty 20 kt. Small chance gusty 25 kt. SCA possible but not likely. Confidence: average. && .CLIMATE... Record high temperatures today March 25 for reference...not impossible to see one or 2 about 2F from record...closest possibilities appear to be ACY GED ACY-79 1963 PHL-82 1910 ILG-80-1939 ABE-77 1988, 1963 TTN-78 1963 GED-79 1959 RDG-81 1910 MPO-72 1939 March monthly average temp: While the negative departures will diminish considerably the next few days...the month as a whole for PHl is currently expected to end up about one half to 1 degree below normal. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 6 AM Sunday to 2 AM EDT Monday for ANZ452-453. Small Craft Advisory from 8 PM this evening to 2 AM EDT Monday for ANZ450-451. && $$ Synopsis...Drag Near Term...AMC/O`Hara Short Term...O`Hara Long Term...Drag Aviation...Drag/O`Hara Marine...Drag/Johnson/Klein/O`Hara Climate...

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