Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 221006 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 606 AM EDT Sun Oct 22 2017 .SYNOPSIS... High pressure generally east of New England through Monday. A strong cold front is forecast to move across our region Tuesday night. Low pressure is expected to develop along the front and should be located over or near New England and southeastern Canada on Wednesday and Thursday. High pressure follows to our south for Friday and Saturday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... There is varying amounts of Ci clouds across the area early this morning. Still enough cooling has occurred for some fog to develop across (mostly) srn NJ attm. Vsbys have dropped to 1-2 mi at a few of the Metar sites. This fog will stick around through just after dawn, before mixing out. Another good weather day is expected with mostly sunny skies and very warm temperatures again. Highs will be in the low/mid 70s in most areas, easily 10 degrees above normal. Humidity levels will be a little higher than Saturday, but still not too noticeable. Winds will be light from the SE or S. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... Low level moisture will continue to slowly increase over the area. Low clouds and areas of fog should develop again Sunday night and become more widespread (than Sat. night). Low temperatures will drop down only to the low 50s north and mid 50s to low 60s south/east. These readings are well above the normal lows for this date. && .LONG TERM /MONDAY THROUGH SATURDAY/...
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** Hazards...possible dense fog Monday morning and then HSLC severe potential Tuesday** The hazards are not yet included in the HWO due to headline/warning confidence is below average. 500MB: -2 to -3 SD troughing develops in the Ohio Valley early and midweek then weakens as it lifts newd negatively tilted through the mid Atlantic states Thursday. Heights rise along the east coast by Saturday as a new -2SD trough develops in the Midwest and Great Lakes region next weekend. Temperatures: Calendar day averages Monday and Tuesday 15 to 18 degrees above normal cooling to around 7 degrees above normal Wednesday, and then near 3 degrees above normal Thursday and Friday then warming to 5 to 10 degrees above normal next Saturday. These departures are solidifying the high likelihood that October will be a top 5 warmest on record, if not record warmest. Forecast basis...Unless otherwise note a 50 50 blend of the 00z/22 GFS/NAM MOS for Monday-Tuesday, then 00z/22 GFS MEX MOS Tuesday night and finally the 05z WPC D4-8 elements of 12 hour pop/max/min temps, and 6 hourly dewpoint, sky, sky and wind. The dailies... Monday...Stratus lifts and thins in the afternoon. More humid. Dewpoint near 60. South to Southeast gust 15 to 20 MPH. PWAT 1.1 inches Monday night - Tuesday...Humid with a south to southeast wind increasingly gusty to 30 mph MPH on Tuesday as dewpoints rise into the upper 60s. Showers should develop Monday night in e PA and Northern New Jersey, chancey elsewhere. Then for Tuesday...bands of showers and iso tstms with potential for a line or line segments of marginally svr storms in the aftn/evening (40-45 kt). MLC of at least 300J appears most favorable in NJ. SHERB value just under 1. PWAT builds to ~ 1.45 inches. Low temperatures Tuesday morning 20-25 degrees above normal (60s) but the midnight LST min temp may not allow a record high min except for PHL/ACY/ABE. Please see the climate section for our likely VULNERABLE potential new record listing. Tuesday night...CFP showers probably end from west to east but there are model hints that low pressure forming on the front to our east may keep the showers going across NJ. PWAT 1.5" in the evening and still 1" or greater NJ/Delmarva 12z Wed. Might have some patchy dense fog late, especially e PA. Wed...Do the showers linger in NJ as low pressure forms just to our east and northeast? Lots of uncertainty. It should dry out in e MD and se PA. West wind. Thu...Trough aloft passage. Coolest daytime high temps of the week! Still lots of clouds and maybe a residual shower. Fri...Dry and milder with height rises. Southwest wind. Sat...Increasing clouds. Milder than Friday as a south wind gusts possibly to 20-25 mph in the afternoon.
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&& .AVIATION /10Z SUNDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. High pressure is moving offshore this morning and the low level moisture is beginning to return to the region. There is some very shallow ground fog across Delmarva and srn NJ attm. This should burn off rather quickly this morning. Another VFR day with only CI clouds expected. Winds will be light and variable this morning and light from the S or SE this afternoon. Tonight...more added moisture will result in more fog and also some ST across the region. The 12Z tafs will have more details with regards to extent of the ST and possible vsby restrictions in fog. OUTLOOK... Monday...IFR or MVFR conditions in stratus/fog Monday morning then VFR sct-bkn near 4000 ft in the afternoon. South to southeast gust 15-20 kt in the afternoon. Monday night through Tuesday evening...Conditions lowering to MVFR and IFR in showers. Isolated thunderstorms and moderate to heavy rain are possible on Tuesday, along with a south wind gusting around 30 knots. There is a small chance for a gust to 45 kt in a thunderstorm Tuesday afternoon. Tuesday night...After 04z/25 cigs generally between 2000-4000 ft in a light west wind. Chance of IFR conds in st/fog. Wednesday...Conditions probably improving to VFR. West wind gust 15 kt. showers possible, especially coastal New Jersey. Thursday...Mainly VFR CIGS. West to northwest wind gusts to 20 kt.
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&& .MARINE...
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High pressure across the waters early today will move further offshore tonight. A fairly quiet day expected with mostly SE winds at 5 to 10 knots. Seas on the ocean 2-3 ft and 1-2 ft across Del Bay. Fair weather today and tonight. OUTLOOK... Monday...No marine headline anticipated. Southeast flow slowly increases. Monday night...SCA Atlantic waters and DE Bay issued for the period 04z/24 onward through Tuesday afternoon. A short period of 35-40 kt southerly gale gusts anticipated in the 19z/24-03z/25 time frame, possibly heavy shower or tstm enhanced. Best chc for gale verification looks like lower DE Bay with a shorter period gale gusts (SMW) for the Atlc waters. For now have kept this simple and the MWW elaborates on the possible Gale. Seas on the Atlantic waters increase to between 7 and 10 feet late Tuesday. Late Tuesday night through Thursday...A Small Craft Advisory will probably be needed on our ocean waters for wave heights of 5 to 6 feet, even as the wind becomes west to northwest around 10 to 20 knots. Also... low pressure developing nearby to our east and northeast may increase the west northwest gusts to 25 kt later Wed or Thu.
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&& .CLIMATE...
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Vulnerable record high minimums Tuesday the 24th. As of this 330 am forecast...we are forecasting records here. However, if the cold front speeds up and a little clearing ensues then the min temp would probably fall just short. Right now the mid shift forecaster has odds favoring record. Elsewhere for now...no other records anticipated. We`ll add locations if we forecast warmer in future forecasts. Allentown 58 1975 Atlantic City 63 2001 Philadelphia 63 1900 Everything else continues on track for top 5 warmest October on record in our forecast area...numbers fluctuating between 1 and 2 warmest for both ABE/PHL. We`ll do the numbers again tomorrow morning.
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&& .EQUIPMENT... 44091 buoy drifted away from its mooring and has since been recovered. Its return to service date is still unknown, though we`ll try to have an answer Monday afternoon. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from midnight Monday night to 6 PM EDT Tuesday for ANZ430-431-450>455. && $$ Synopsis...Drag Near Term...O`Hara Short Term...O`Hara Long Term...Drag 606 Aviation...Drag/O`Hara Marine...Drag/O`Hara Climate...606 Equipment...

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