Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 240003 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 803 PM EDT Mon Oct 23 2017 .SYNOPSIS... High pressure located off Nova Scotia this afternoon will continue to lose its influence over our weather. A slow moving cold front extending from the Great Lakes to the eastern Gulf of Mexico will progress to the east and it should pass through our region on Tuesday night. High pressure is expected to nose up from the southwest and south for the second half of the work week. Another cold front from the west is anticipated to arrive on Sunday. Low pressure may develop along the boundary after it moves off the coast. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... The main change to the forecast overnight has been to increase wind gusts through the night, especially for higher elevations across portions of northeast Pennsylvania and northwest New Jersey. We have expanded the Wind Advisory slightly eastward as the winds associated with the low level jet ahead of the cold front may have better potential to mix down to the surface across these more elevated areas. Otherwise, cloudy conditions with increasing chance of showers through the night. A few sprinkles or light showers may occur this evening, before showers become more widespread after midnight. The heaviest showers and possible isolated thunder are expected to begin closer to daybreak Tuesday as a cold front approaches the area from the west. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... The cold front will move slowly across our area on Tuesday. An unseasonably warm and humid airmass will continue. Heavy showers and thunderstorms are likely throughout the day. SPC has placed our region within a slight risk of severe thunderstorms. There is ample shear as well as modest SB CAPE, with damaging winds the primary. But given strong 0-1 km shear and low LCLs, cannot rule out an isolated tornado, especially in association with any Quasi Linear Convective System. In addition, any heavier showers and t-storms will have the potential to tap the stronger winds aloft and produce wind gusts up to around 40 mph. The heaviest rainfall should be confined from the PA Turnpike east to Ocean County and points north, with the main concern being urban and poor drainage flooding. The severe weather and flood threat have been included in the Hazardous Weather Outlook. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... A mid level trough is forecast to drift over the eastern states from Tuesday night into Thursday. Ridging is expected to take place from Thursday night into Saturday before another trough affects the eastern states on Sunday and Monday. A slow moving cold front is expected to extend through our region on Tuesday evening. It should continue moving slowly eastward and it is anticipated to be off the coast on Wednesday morning. Rain is forecast to end gradually from west to east in our region from Tuesday evening into Wednesday. Moderate to heavy rain and a chance of thunder will linger in our eastern counties on Tuesday evening. The clouds and lingering showers associated with the front will likely be slow to move away from our region on Wednesday. It will take the arrival of the axis of the mid level trough on Thursday to finally kick the system well to our east. Surface high pressure from the southwest and south is anticipated to build into our region for Thursday night into Friday night, resulting in some clearing. Another cold front approaching from the west is forecast to bring an increase in cloud cover for Saturday. It is expected to be another slow moving boundary, so we have mentioned a chance of showers for Saturday night, Sunday and Sunday night. The coldest air mass of the season to affect our region is expected to arrive in the wake of the cold front for early next week. Temperatures should not be far from normal for the period from Wednesday through Sunday, then then should begin to fall below normal on Monday. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are beginning to lower early this evening for some areas, and everyone should be MVFR by 03z-06z as scattered showers begin to move into the area. Conditions will continue to deteriorate overnight as showers become heavier toward daybreak Tuesday and continue through the day. There is also a chance of thunderstorms during the day Tuesday, especially for southeast Pennsylvania, New Jersey, Delaware, and Maryland. Southeast winds will gust 20 to 30 knots at all TAF sites tonight into Tuesday, with higher wind gusts are possible in and around thunderstorms. Winds will gradually shift to the south and southwest on Tuesday afternoon, with a gradual improvement to VFR for some areas expected as the front and rainfall move eastward. OUTLOOK... Tuesday night...MVFR and IFR conditions in showers for some areas improving to VFR. Wednesday through Saturday...Mainly VFR. && .MARINE... SCA remains in effect for the Atlantic and Delaware Bay waters through Tuesday. South-southeast winds will gust up to around 30 knots at times. There is the potential for a short period of gale-force gusts for a couple hours around dawn Tuesday morning, then in and around and heavier showers and thunderstorms Tuesday afternoon and evening. Seas will also increase up to 9 feet on the ocean, and 5 feet at the entrance to DE Bay on Tuesday. OUTLOOK... Tuesday night...A Small Craft Advisory is in effect for our ocean waters. We are expecting a south wind around 20 knots becoming west and diminishing around 10 knots. Gusts around 30 knots are possible on Tuesday evening on our ocean waters. Wave heights are anticipated to be 6 to 9 feet on our ocean waters. Wednesday...A Small Craft Advisory is in effect for our ocean waters with wave heights expected to be 4 to 6 feet. Wednesday night through Thursday morning...A Small Craft Advisory may be needed on our ocean waters for wave heights around 5 feet. Winds should be west to northwest around 10 to 15 knots. Thursday afternoon through Saturday...No marine headlines are anticipated. && .HYDROLOGY... Hydro: storm total rainfall Tue-Tue night, generally 1-2" with in excess of 2 inches most favored over NJ. Leaf-clogged drains will enhance the possibility of ponding of water on roadways. && .CLIMATE... Vulnerable record high minimums Tuesday the 24th: Allentown 58 1975 Atlantic City 63 2001 Philadelphia 63 1900 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Wind Advisory from 1 AM to 8 AM EDT Tuesday for PAZ060>062. Wind Advisory until 8 AM EDT Tuesday for PAZ054-055. NJ...Wind Advisory from 1 AM to 8 AM EDT Tuesday for NJZ001-007. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EDT Wednesday for ANZ450>455. Small Craft Advisory until 6 PM EDT Tuesday for ANZ430-431. && $$ Synopsis...Iovino Near Term...Franck/Johnson/Robertson Short Term...Franck Long Term...Iovino Aviation...Franck/Iovino/Robertson Marine...Franck/Iovino Hydrology...Staff Climate...Staff is the U.S. government's official web portal to all federal, state and local government web resources and services.