Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 161729 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 129 PM EDT Mon Apr 16 2018 .SYNOPSIS... The low pressure system that brought storms and a cold front to the Mid Atlantic this morning, will slowly propagate northeast away from the region on Tuesday. Another area of low pressure organizing over the Midwest will propagate towards New England on Thursday. As it does so, our region will first see a warm front, followed quickly by a cold front. Canadian high pressure will move into the area for the weekend. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The steady moderate to heavy rainfall has moved out of the area this morning, therefore the Flash Flood Watch was cancelled. There will remain some residual flooding into this afternoon and evening. Several Flood Warnings and Flood Advisories remain in effect, so please see these statements for the latest updates. A warm front remains in place across basically the I-95 corridor early this afternoon. Its parent low pressure system has now moved to Chester and Lancaster counties in Pennsylvanian. This low will continue to lift across eastern Pennsylvania through the remainder of today, before lifting into New York state through the late afternoon and into this evening. As it does so, it will continue to lift the warm front across the area, as well as pull the cold front across the area as well. As the low lifts north of the area and the fronts move across the area, there will remain a chance for scattered showers and thunderstorms through the afternoon as additional short wave/vorticity impulses move across the area. However, most places this afternoon will remain dry. Winds will remain gusty 20 to 30 mph, with higher gusts reaching 30-40 mph at times into this afternoon. Directions will remain northeast-easterly ahead of the warm front, then become more south-southwesterly behind the warm front, before swinging to west-southwest behind the cold front this afternoon. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... By early this evening, low will be departing to the NE into NY State into New England dragging a final surface trough through the area. In addition, systems` upper low will still be centered near western PA with the broad circulation continuing to spin shortwaves through the area. The upshot of this is that mainly cloudy skies with some continuing scattered showers are likely to affect parts of the area at least into this evening and likely through the overnight across the southern Poconos. In fact as temperatures drop off into the low to mid 30s tonight across the far north, any rain showers will change over to snow showers with continuing cool, gusty, west winds. Temps will be a bit warmer farther south with lows mainly in the upper 30s to low 40s over SE PA through central, S NJ, and the Delmarva. && .LONG TERM /TUESDAY THROUGH SUNDAY/... Made few changes to the long term forecast in order to focus on the ongoing weather tonight. Fair weather is expected from Tuesday night into Wednesday as high pressure arrives across the area. It will be a bit warmer than Monday/Tuesday, but still slightly below normal for mid-April. Highs will generally be in the mid/upper 50s north/west and low/mid 60s south/east. These values will be 2 o 4 degrees below normal. Another low pressure system will approach the area later Wednesday and last into Thursday evening. The system will be progressive, so even though the low is depicted by the models as being rather strong, it will not have large window of opportunity when our area will be in the warm sector, and thus have more moisture for precipitation. We therefore have mostly chc pops in the fcst for Wed night/Thu and slgt chc pops into Thu night. Temperatures will remain mostly at or a little below normal this period. The warmest day will be Thursday (near normal) with mid/upper 50s for highs across the north and low/mid 60s over Delmarva and srn NJ. High pressure from Canada builds in for late this week and into the weekend. Mostly fair weather is expected with a continuation of below normal temperatures. && .AVIATION /17Z MONDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...Conditions remain between MVFR and IFR early this afternoon, and will remain so through much of the remainder of the afternoon. However, by late this afternoon and into this evening, we expect an improving trend to VFR. There will remain a chance for scattered showers during the afternoon hours, with an occasional thunderstorm possible. However, we will not include thunderstorms at this time unless we see them on radar. E/SE winds north of the warm front will shift to SW/W this afternoon as the warm front and low pressure lift north of the area. Winds speeds will be around 10 to 15 knots, with gusts to around 20 to 30 knots for many locations. Potential for some erratic winds/gusts around showers. Moderate confidence. Tonight...mainly VFR. Moderate confidence. Outlook... Tuesday and Wednesday...Mostly VFR conditions are expected. A few showers are possible, primarily for KABE and KRDG, which could lead to brief reductions in the flight category. Moderate confidence. Wednesday night and Thursday...Starting VFR, we may see conditions lower as a warm front lifts through the area and precipitation moves in. However, confidence is low at this time. Thursday night and Friday...Mostly VFR expected behind a cold front that will bring a shift to northwesterly winds and drier conditions. High confidence. && .MARINE... We have extended the Gale Warning for the Delaware Bay and the southern waters adjacent to Delaware, and also keep the Gale Warning in place across the waters adjacent to New Jersey. While many locations are not reaching gale force right now, as the low pressure lifts to the north of the area and the cold front slides through this afternoon, winds will likely increase again to gale force for a period this afternoon. The heaviest and steady rainfall is lifting through the northern half of the New Jersey coastal waters, and behind this rainfall, we expect scattered showers and possibly an occasional thunderstorm through the remainder of the afternoon. Tonight...A relative respite as winds should actually drop below SCA levels this evening before starting to ramp back up again overnight...likely to near or just below SCA levels by early Tuesday. Outlook... Tuesday and Tuesday night...lingering elevated seas are possible on the ocean waters through this time. Otherwise, winds should stay below SCA criteria. Wednesday and Thursday...Winds and seas are expected to be below SCA criteria. Thursday night and Friday...Winds and seas should increase once again and may approach SCA criteria. && .HYDROLOGY... Flash Flood Watch will continue for now as heavy rain moves through the area. Several Flood Advisories and Flood/Flash Flood Warnings are being issued as well. Please see the latest warnings and advisories for the latest information. && .TIDES/COASTAL FLOODING...
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130 PM Update: Coastal Flood Warnings have been allowed to expire for coastal NJ and DE. Most tidal gauges captured minor tidal flooding. However, the severity of flooding was exacerbated by freshwater runoff from the heavy rain that occurred with the morning high tide. The Coastal Flood Warning for the upper Delaware Bay (New Castle, DE and Salem, NJ counties) continues through 2 PM. Reedy Point peaked at only one-tenth inch below moderate threshold with the midday high tide. The Coastal Flood Advisory for the tidal portion of the Delaware River (including Philadelphia and Trenton) was originally only valid through 3 PM but was extended through 5 PM since high tide occurs at Philadelphia just before 3 PM and just after 4 PM at Trenton. A Coastal Flood Advisory was issued for the eastern and northeastern shore of the Maryland Chesapeake Bay for this afternoon and evening. Positive tidal anomalies about both Tolchester and Cambridge tidal gauges have been increasing steadily over the past few hours and has not been particularly well forecast by models. Expect these surge values to remain steady or even start to decrease heading toward the next high tide (just after 5 PM at Cambridge and just after 8 PM at Tolchester Beach) in conjunction with a wind shift from Sly to Wly.
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PA...Coastal Flood Advisory until 5 PM EDT this afternoon for PAZ070-071-106. NJ...Coastal Flood Warning until 2 PM EDT this afternoon for NJZ016. Coastal Flood Advisory until 5 PM EDT this afternoon for NJZ015-017>019. DE...Coastal Flood Warning until 2 PM EDT this afternoon for DEZ001. MD...Coastal Flood Advisory until 11 PM EDT this evening for MDZ008- 012. Coastal Flood Advisory until 9 PM EDT this evening for MDZ015- 019-020. MARINE...Gale Warning until 5 PM EDT this afternoon for ANZ430-431- 450>455.
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&& $$ Synopsis...Johnson Near Term...Fitzsimmons/Robertson Short Term...Fitzsimmons Long Term...Johnson Aviation...Fitzsimmons/Johnson/Robertson Marine...Fitzsimmons/Johnson/Robertson Hydrology... Tides/Coastal Flooding...Klein is the U.S. government's official web portal to all federal, state and local government web resources and services.