Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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775 FXUS61 KPHI 241959 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 359 PM EDT Mon Jul 24 2017 .SYNOPSIS...
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A cold front will move slowly south across our region this evening and offshore tonight. A broad high pressure system extending from the Great Lakes into eastern Canada will gradually build southeast into our area through Wednesday. As this high slides offshore late Wednesday, a warm front will move through our region on Thursday, followed by another slow moving cold front on Friday. High pressure is expected to make a return this weekend into the beginning of the work week.
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&& .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Significant thunderstorm wind damage occurred overnight in the Stevensville area of Kent Island in Queen Anne`s County, Maryland. A survey team is on their way to assess the damage and we should have more information on this event later this afternoon. A front will lift across the region and the rains has ended. The back of the boundary will bring more sct tstms to the area later this afternoon. Temperatures today will be very warm with upper 80s and low 90s over the region. Clouds will gradually thin later this morning and into the afternoon. Winds will be mostly S/SE early, then turn SW/W this afternoon. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... System begins to move away and the showers associated with the cold front will end from W to E early tonight. Drier air will begin to arrive N/W and will spread over the rest of the area later Tuesday. Lows will be in the low 70s S/E and low 60s N/W. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
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One mid-level trough exits the east coast Tuesday night, with a brief zonal flow and some short wave ridging for Wednesday, followed by continued troughiness through the end of the long term period. A frontal system in the Thursday thru Friday time frame features the greatest chance of sensible weather, in terms of increased humidity, and the chance for showers and thunderstorms. This front will slow as it moves offshore, and stall to our south through the weekend into early next week, as waves of low pressure traverse it. All of the available guidance keeps our region dry in the Saturday thru Monday period, but lingering cloudiness is possible, especially south Jersey into Delmarva. In addition, if the guidance slows the southward progress of this feature, this could result in a more pessimistic forecast for the aforementioned area. Showers and thunderstorms with heavy downpours and gusty winds are possible Thursday into Friday. It`s still too early to nail down the spatial and temporal details, as the GFS is much more progressive with the front compared to the Euro, so there is low confidence due to the uncertainty. In fact, the GFS event window would be Thursday into Thursday night, with the Euro window is centered on Friday. Nevertheless, effective bulk shear values rise to near 40 knots, while surface-based cape is in excess of 2.0 kJ across portions of the area. In addition, the front slows as it moves trough or area, while Precipitable Water values rise to around 2.0 inches. These indicators point to some potential for strong thunderstorms and heavy rainfall in the Thursday and Friday period, and we have mentioned this in the Hazardous Weather Outlook. Temperature-wise, slightly below normal temperatures on Wednesday rebound to at or slightly above average from Thursday thru Friday. Average to slightly below average temperatures are expected in the post-frontal air mass on Saturday, with a moderation to near normal in the Sunday thru Monday time frame. In fact, Thursday and Friday are shaping up to be the warmest days, with temperatures well into the 80s to near 90. The only exception may be closer to the coast, where a prolonged onshore flow may develop over the weekend into early next week, keeping temperatures cooler. Finally, depending on the extent of the aforementioned onshore flow, astronomical tides are much lower over the weekend into early next week as we move away from the new moon. This should limit the potential for coastal flooding.
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&& .AVIATION /20Z MONDAY THROUGH SATURDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Challenging fcsts for the morning with widespread poor flying conditions across the area and sct showers/downpours and a few tstms too. Overall, expect improvement this morning, but timing in the tafs is low confid with a variety of mesoscale factors affecting conditions. Winds will be mostly SE early, then turn SW/W by late morning. There will probably be more showers/sct tstms this afternoon across the area, again low confid in timing, basically used PROB30s from guidance. Frequent Amds expected. OUTLOOK.... There is some potential for MVFR in low clouds associated with a frontal system from Thursday into Friday. This potential may linger into Saturday in ACY and MIV as the southward progression of the front slows. In addition, any showers or thunderstorms during this time frame may briefly reduce ceilings and visibility`s to IFR. Otherwise, VFR for the remainder of the period.
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&& .MARINE...
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Small Craft Advisory for hazardous seas is in effect for our northern New Jersey coastal waters through 4PM. Seas are at 5 feet and will start to drop through this afternoon. The SCA has been dropped elsewhere. Wind directions have mostly been E or SE on the north side of the front. The front will move northward today and winds will become S or SW behind that. Scattered showers and tstms with locally higher winds and seas around tstms. Showers coverage will diminish later this morning, be a few more tstms possible later this afternoon and into the evening. OUTLOOK... Wednesday through Saturday...A Small Craft advisory may be needed on Thursday and Friday. RIP CURRENTS... A moderate risk for rip currents remains in effect through this evening for the Delaware and New Jersey beaches. A low risk of rip currents is currently expected for the Delaware and New Jersey beaches on Tuesday.
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&& .TIDES/COASTAL FLOODING...
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There is Coastal Flood Advisory in effect for this evening`s high tide along the New Jersey and Delaware coasts. We do not anticipate minor flooding in Delaware Bay. While surface wind turned offshore during on Monday, it is expected to become onshore again this evening, especially along the New Jersey coast. Conditions may be a bit marginal for Delaware.
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&& .EQUIPMENT... Dew point readings at KDOV continue to measure too high compared to surrounding locations and should be treated as unrepresentative of the area. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...Coastal Flood Advisory from 9 PM this evening to 2 AM EDT Tuesday for NJZ012>014-020-022>027. DE...Coastal Flood Advisory from 9 PM this evening to 2 AM EDT Tuesday for DEZ003-004. MD...None. MARINE...Small Craft Advisory for hazardous seas until 6 PM EDT this evening for ANZ450.
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&& $$ Synopsis...Meola Near Term...Meola Short Term...Meola Long Term...Franck Aviation...Franck/Meola Marine...Franck/Meola Tides/Coastal Flooding...Franck Equipment...Staff

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