Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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290 FXUS61 KPHI 222328 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 628 PM EST Wed Nov 22 2017 .SYNOPSIS... High pressure will begin to build eastward into the region tonight and move over the region Thursday and Friday. This will be followed by a cold frontal passage on Saturday. Another area of high pressure will build into the region for the early part of next week. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Tonight...Becoming mostly clear with diminishing gusts...tho still a breeze in the urban centers and along the coasts where boundary layer instability is greater with the decent cold air advection. Lows 4 to 8 degrees below normal. This forecast was a 50 50 blend of the 12z/22 GFS/NAM MOS. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Sunny with spotty high cloudiness early in the day and then a general deck of waa mid or high clouds arriving from the west northwest late in the day reaching to near I-95 around 6 PM. Light northwest to west wind. Mixing doesn`t look too good so a fairly chilly Thanksgiving day. Highs 6 to 9 degrees below normal. This forecast was a 50 50 blend of the 12z/22 GFS/NAM MOS. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/... Thursday night through Friday night: High pressure will be in place during this period with mostly sunny skies. Temperatures will warm into the 50`s Friday after starting out in the 20`s and 30`s. Friday night has trended warmer with the past few model runs. Light winds will shift to southerly and increase slightly ahead of an approaching cold front with lows generally in the 30`s and low 40`s. Saturday and Saturday night: A cold frontal boundary will move through the area on Saturday. Overall, timing has sped up a few hours on average with the modeling and ensembles. Enough lift and moisture should be present for a few spotty rain showers, primarily in the afternoon hours. Temperatures Saturday morning may be close enough to freezing in the southern Poconos and NW NJ for a freezing rain concern. Right now any precipitation is expected to hold off till mid-morning when it warms well above freezing. Precipitation looks very light, only a few hundredths and this forecast used a SREF/WPC blend. A few southerly wind gusts in the afternoon around 15 mph are possible before the frontal passage. Northwest flow on the backside of the front could also kick off some sprinkles and flurries toward sunrise Sunday that could be enhanced where the elevation is highest (southern Poconos and NW NJ). The 12z 11/22 NAM was discounted given a NW bias tendency in the medium range with low pressure systems. Ensemble guidance continues to show a low pressure will track from the Carolinas northeast out to sea with little to no influence in our area. Sunday through Wednesday: A fairly strong push of cold air advection will occur behind the front. This will lead to another period of more winter like temperatures across the region with stronger northwest winds, gusting perhaps to 25 mph on Sunday. The northwest flow may also allow for some moisture to transport southeast off of the Great Lakes. The moisture could be enhanced by the higher terrain. Highs Sunday and Monday will generally be in the 40`s with overnight lows will be in the 20`s and 30`s. Conditions are expected to clear later Sunday and Monday as the northwest flow weakens and high pressure builds into the region. We should see a fairly quick rebound Tuesday and Wednesday with temperatures into the 50`s as the high pressure system moves offshore. Right now the forecast does hedge above the mean of the ensemble guidance on Tuesday but is closer to the ensemble mean on Wednesday. Some uncertainty is present with the speed of a cold frontal boundary moving toward the area sometime Wednesday or Thursday of next week. For now, we went middle of the road between the GFS and ECMWF with a shower chance for next Wednesday night. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR clearing with northwest wind gusts diminishing. Confidence high. Thursday...VFR clear or some high clouds at times. Northwest to west wind with gusts under 15 kt. Confidence high. OUTLOOK... Thursday night through Friday night: VFR, westerly winds becoming southwesterly but staying at 10 knots or less. High confidence. Saturday and Saturday night: Sub-VFR possible with some scattered showers primarily from 15 to 23Z. Southerly wind gusts 10-15 knots, becoming northwest Saturday night. Medium confidence. Sunday and Sunday night: VFR, a few sprinkles or flurries possible. Northwest winds with gusts from 20-25 knots in the afternoon. Medium confidence. Monday and Monday night: VFR, West winds at or under 10 knots. High confidence. && .MARINE... SCA continues as previously advertised. Gusts near 30 kt this evening. Diminishing wind and waves for Thursday. OUTLOOK... Thursday night through Friday night: Sub-SCA winds and seas. West winds becoming south on Friday with any gusts under 15 knots. Seas lower for a time to around three feet. Medium to high confidence. Saturday and Saturday night: Seas building slightly but staying under 5 feet. Southerly wind gusts 15-20 knots in the afternoon. Winds becoming northwesterly Saturday night. Medium confidence. Sunday and Sunday night: Seas continue to to build slightly close to 5 feet with a increase in northwest wind gusts around 25 knots in the afternoon. Low to medium confidence. Monday and Monday night: West-southwest wind gusts around 15 knots Monday increasing Monday night to around 25 knots late. Seas decrease to below SCA levels but should begin to build up by Tuesday. Medium confidence. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 AM EST Thursday for ANZ450>455. Small Craft Advisory until midnight EST tonight for ANZ430-431. && $$ Synopsis...Gaines Near Term...Drag Short Term...Drag Long Term...Gaines Aviation...Drag/Gaines Marine...Drag/Gaines

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