Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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167 FXUS61 KPHI 170649 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 149 AM EST Fri Nov 17 2017 .SYNOPSIS...
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Low pressure will continue to move into the Canadian Maritimes through Friday, while high pressure briefly builds across the east coast during Friday. Strong low pressure will move across the eastern Great Lakes Saturday, then into New England Saturday night into Sunday. A warm front will lift across the area Saturday, followed by a strong cold front overnight Saturday into early Sunday morning. High pressure will build to our south Monday into Tuesday, before a dry cold front moves across the area Tuesday night. High pressure then builds in later Wednesday into Thursday.
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&& .NEAR TERM /THROUGH TODAY/...
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Early this morning...scattered sprinkles ne PA and NNJ (mainly I-78 north) will eventually dissipate the next couple of hours. the deck of clouds between 2500-4500 feet should also begin drying-receding northwestward by sunrise...certainly more than we anticipated at this time ydy. The wind also has been about 4 kt less than expected ydy aftn and early this morning but its still gusty this morning preventing rad cooling. Today...we expect Mostly sunny, a brisk northwest wind to 25 MPH at times and seasonably cool temps...highs generally in the upper 40s to lower 50s... low or mid 40s Poconos. Forecast basis was a 50 50 blend of the 00z/17 GFS/NAM MOS. I did adjust s DE down from guidance by 3-4F and capped the max T there around 53-54F.
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&& .SHORT TERM /TONIGHT/...
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Mostly clear and a bit chillier than last night with radiational cooling in the countryside. Light northwest wind to start becoming light south toward morning. Forecast basis was a 50 50 blend of the 00z/17 GFS/NAM MOS.
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&& .LONG TERM /SATURDAY THROUGH THURSDAY/...
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The main focus in the extended will be the storm system expected Saturday through Sunday. Otherwise, fairly quiet weather through much of the rest of the extended period. However, as we move into Saturday, strong south to southwest flow begins to develop during the day between the departing high pressure to our south, and an area of low pressure moving through the Ohio Valley and into the eastern Great Lakes. Meanwhile, a warm front is forecast to lift across the area during the day Saturday as well as a short wave/vorticity impulse slides north across the area as well. This is expected to lead to a period of showers during the afternoon, especially along and north of the I-95 corridor. South to southwest winds are expected to increase through the day as well, with gusts reaching 25-35 mph. As we move into Saturday night, a strong cold front is expected to move across the area. Ahead of this front, gusty southwest winds will continue through the night with gusts of 25-35 mph possible. As the front moves through during the overnight, shower chances will be increasing across the area, and move from west to east fairly quickly. There is not much instability forecast, so we do not have thunder in the forecast at this time. However, PW values increase to 1.00-1.25 inches, so there could be some moderate, to occasionally heavy rainfall at times. The cold front is expected to have moved through the area, and either be offshore, or just along the coastal areas of New Jersey and Delaware by around daybreak Sunday. Showers will come to an end behind the cold front, with the exception of possible continued showers in the Poconos as some lake effect streamers may develop. As the strong cold front moves across the area, winds will continue to be gusty, but become west to northwest as it shifts eastward. Wind gusts could reach 35-40 mph at times as the front crosses the area early Sunday, before slowly diminishing during the day. As we go into Sunday night, winds could remain gusty around 20-30 mph and all precipitation is expected to have ceased. The only exception is the possibility for some flurries in the Poconos Sunday evening. High pressure builds to our south Monday into Tuesday. Dry weather is expected Monday through Tuesday, but winds will likely remain gusty around 20-25 mph. A cold front is forecast to move across the area Tuesday night into early Wednesday morning, but it is currently expected to be a dry frontal passage. High pressure is expected to then build across the area later Wednesday into Thursday.
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&& .AVIATION /07Z FRIDAY THROUGH TUESDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Early this morning prior to 12z...VFR sct -bkn clouds aoa 3500 ft. Northwest wind with scattered gusts 20 kt. Today...VFR few clouds aoa 5000 ft. NW wind gusts to around 25 kt through early afternoon, decreasing late in the afternoon. Confidence is very high. Tonight...VFR few clouds aoa 10000 ft with thickening cirrus arriving toward sunrise Saturday and a light northwest wind this evening becomes light south toward morning. Very high confidence. OUTLOOK... Saturday...VFR early, with deteriorating conditions through the day with scattered showers during the afternoon associated with a warm front. Gusty south-southwest winds 20-25 knots. Moderate confidence. Saturday night...IFR conditions likely, with periods of showers associated with a cold front. Gusty southwest winds 30-35 knots possible. Moderate confidence. Sunday...Improving to MVFR, then VFR behind the cold frontal passage. Gusty west-northwest winds 30-35 knots. Moderate confidence. Sunday night...Generally VFR. Gusty northwest winds 25-30 knots. Moderate confidence. Monday...Generally VFR. Gusty west-northwest winds 20-25 knots. Moderate confidence. Monday night-Tuesday...VFR. Winds may gust 15-20 knots during the afternoon Tuesday. Moderate confidence.
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&& .MARINE...
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Gale will be converted to an SCA at 6 AM for the Atlantic waters where isolated gale gusts still possible. DE Bay will convert to an SCA at 330 AM pending one more check of observations. So far this marginal gale has verified 4 of the 8 zones. Winds have been around 4 kt less than expected. After 6 am...SCA everywhere through the day then subsiding nw winds tonight so that no headlines are anticipated for tonight. OUTLOOK... Friday night...Conditions fall below advisory levels. Saturday-Sunday night...An extended period of gale force wind gusts are expected starting Saturday afternoon, then continuing Saturday night through early Sunday night. Conditions likely to lower to Small Craft Advisory levels overnight. Monday-Tuesday...Small Craft Advisory conditions expected to continue into Monday and Tuesday. A brief lull may be possible late Monday into Monday evening.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 AM EST early this morning for ANZ430-431- 450>455.
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&& $$ Synopsis...Robertson 149 Near Term...Drag 149 Short Term...Drag 149 Long Term...Robertson Aviation...Drag/Robertson 149 Marine...Drag/Robertson 149

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