Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 020239 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 939 PM EST Thu Dec 1 2016 .SYNOPSIS... A strong low pressure system will continue to move slowly through northeastern Canada over the next couple of days keeping a cool northwest flow over our region. High pressure over the Ohio Valley on Saturday will move into the area on Sunday and then will move off to the northeast late Monday. A complex low pressure system will track through the plains into the midwest and impact our weather through the mid week period. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A short wave ridge within the fast westerly flow aloft will settle over the region. As a result, expect the stratocumulus deck to continue to dissipate over the region. Given the pressure gradient, northwest winds will maintain around 10 knots, with less gustiness due to the loss of the daytime boundary layer. Low temperatures will be near normal. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/... As the aforementioned shortwave ridging moves east, another short- wave will approach the northwest late in the day. This will lead to an increase in cloudiness, mainly owing to low-level instability/ moisture transport through the boundary layer, mainly north of I-78. But the model mass fields indicate the deeper moisture and better lift associated with the shortwave remaining to the northwest of this area through the day. The 12Z NAM does generate some flurries over the Poconos, although it is an outlier, as the rest of the guidance suite is void of precip. In addition, the NAM was too far southeast with its QPF on Thursday afternoon over NY/PA. We kept the forecast dry. High temperatures will be near normal, with northwest wind gusts of 20 to 25 mph from late morning into the afternoon. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... Friday night...a shortwave will rotate through the mid level flow and this will keep a northwest flow across our area. Temperatures Friday night will drop down into 30s across the region with some upper 20s in the southern Poconos. Moisture is limited but with the strong northwest flow there may be some flurries that make it into the Poconos late Friday night. Saturday and Sunday...High pressure will start to build towards the region on Saturday, reaching our area on Sunday. For the most part we should remain dry during this time frame. Saturday will be cloudier than Sunday but overall both days make for a decent weekend. The northwest flow will remain and this will keep the temperatures on the cool side, moreso on Sunday than on Saturday. Highs will generally remain in the 40s, near 50s south and in the 30s across the north. Overnight lows both nights will range from the upper 20s to low to mid 30s across the area. Increasing cloudiness arrives in advance of an approaching weakening shortwave. A shortwave arrives Sunday night but enough moisture may be around for some light rain or snow showers. We maintain low pops for Sunday night with the best chances to the north and west of Philadelphia. Monday through Thursday...The surface high starts to weaken as strengthening low pressure near the Gulf of Mexico starts to move to the northeast. The low moves into the Ohio Valley on Tuesday and then splits. The southern low will track just south of our area as it moves off to the east. The northern low tracks northward and into the Great Lakes region. This split system will bring in some more much needed moisture to the region. Precipitation will move in late Monday night into Tuesday morning. As the low moves across Delmarva and offshore, we should see the heavier rain across our southern zones. With cold air in place, there will be a chance for some mixed precipitation or rain changing to snow, mainly north of the I-95 corridor. A cold front will then drop down from the northwest and cross the region Wednesday into Thursday. This feature should bring more steady precipitation to our northern zones, where drought conditions are ongoing. Temperatures are expected to be near normal through through midweek. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions will continue through the TAF period. Lingering mid level clouds (4000 to 6000 ft AGL) will continue to dissipate over the next few hours. Gusty conditions have continued as some of the TAF sites, but still expect wind speeds to diminish overnight, remaining near 10 kt through 15Z, before increasing again with gusts up to 20kt possible tomorrow. OUTLOOK... Friday night through Sunday...mainly VFR conditions are expected. West to northwest winds around 10 to 15 knots expected with gusts up to 25 knots Saturday afternoon. Winds are expected to be less gusty on Sunday. Sunday night through Tuesday...mainly VFR conditions are expected. Rain or snow showers are possible late Sunday night into Monday morning and then again late Monday night and Tuesday. Best chances for precipitation exist to the north and west of KPHL. && .MARINE... On the Delaware Bay and Delaware coastal waters, wind gusts above 20 kt are possible, but should stay just below SCA conditions. On the coastal waters adjacent to NJ, SCA conditions for both winds and seas continues with peak gusts generally between 25 and 30 kt and seas right at 5 feet. Winds and seas should slowly diminish late tonight. Friday...Sub-SCA northwest winds thru the day, then increasing in the evening with gusts up to around 25 knots likely on the ocean waters after 21Z, especially northern NJ. OUTLOOK... Friday night and Saturday...Increasing winds, especially late Friday night, expected as cold air advection takes place over the waters. Strong northwest flow of 20 to 25 knots with gusts up to 30 knots on the ocean. Winds will start to subside late Saturday. Seas will also increase into Saturday but look to remain just below 5 feet. A Small Craft Advisory will likely be needed. There is also a small possibility for same gale force gusts but confidence is low at this time. Sunday and Monday...Sub-advisory conditions are expected on the area waters as high pressure builds into and over the region. Tuesday...a low pressure system will move into the area. Seas will start to build on Tuesday and may exceed 5 feet. A Small Craft Advisory may be needed. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 3 AM EST Friday for ANZ450>453. && $$ Synopsis...Meola Near Term...Franck/Johnson Short Term...Franck Long Term...Meola Aviation...Franck/Johnson/Meola Marine...Franck/Johnson/Meola is the U.S. government's official web portal to all federal, state and local government web resources and services.