Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 010837 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 337 AM EST Thu Dec 1 2016 .SYNOPSIS... Low pressure will be to our north today and tonight before slowly moving into the Canadian Maritimes later Friday into Saturday. High pressure over the Ohio Valley Saturday will move into the Mid Atlantic during Sunday. Meanwhile, areas of low pressure in the Midwest and Plains Tuesday will consolidate into one main storm as it tracks into the Great Lakes later Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Boundary between modified warm air to the north (Wednesdays max temps 10F warmer than normal) and the 15-20F warmer than normal air to the south, never made it past ILG/PHL. it was an overestimation on the northward push on my part. In this case, the combined GFS/EC was a little better on handling the area temps on Wednesday. One more band of showers will race newd through the area between now and 5 am, then it clears with the variable turning southerly flow(except gusty southwest flow 30-35 mph along the coastal plain) shifts to west. After sunrise...a sunny or mostly sunny starts gives way to diurnal caa cloudiness with a bkn deck for a time during midday- afternoon. Gusty west winds of 25-030 mph are expected midday and afternoon. Temps during the day still warmer than normal. The forecast - already posted at 1230 AM - was based on a 50 50 blend of the 00z/01 GFS/NAM MOS, favoring the slightly warmer NAM/ECMWF temps. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Clear or mostly clear skies with diminished wind and some radiational cooling. Lows maybe a couple of degrees warmer than normal. Forecast basis: a 50 50 blend of the 00z/01 GFS/NAM MOS. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... The synoptic setup starts with a closed low to our north that eventually elongates and weakens eastward to the Canadian Maritimes Friday. The southwestern flank of the trough however pivots across the Northeast later Friday into Saturday before shifting east. A rather busy flow regime occurs with several short waves involved. The model guidance has been having trouble in handling the ejection of a Southwestern U.S. upper-level low, corresponding to differences regarding an interaction from the northern stream. As mentioned by WPC, the 00z GFS, UKMET and CMC provide added support for staying a little slower than the 12z ECMWF mean with the ejection of the upper- level low. A deepening trough then in the West results in several surface lows initially Tuesday, however this should consolidate into the Great Lakes Wednesday as one storm. This may turn into a rather potent trough and surface cold front as it shifts eastward. We used a model/continuity blend Friday through Saturday night, then blended in the 00z WPC Guidance. Some adjustments were then made following additional collaboration with our neighboring offices. For Friday through Sunday...An upper-level trough pivots across the area Friday into Saturday then shifts east. Some ridging though arrives Sunday before perhaps a weakening short wave trough arrives Sunday night into Monday. This feature should be on the weak side, and therefore kept some low PoPs going Sunday night. The low-level airmass may remain dry enough to reduce the amount of precipitation that can occur, however this could allow for a bit of snow across the north. It will be chilly during this time frame, with a gusty west-northwest wind especially during the daytime hours. There should be more cloudiness especially across the northern and western areas Friday and Saturday. Some lake effect moisture may allow for a few snow/rain showers or flurries in the Poconos Friday night and Saturday. We are expecting an increase in the clouds during Sunday due to a general weak system arriving. For Monday and Tuesday...This time frame features an amplifying upper-level trough across the West, which will drive some ridging downstream. There is the potential for a lead short wave trough that ejects northeastward from the Gulf coast states well ahead of the main trough. This would toss some precipitation our way Tuesday as high pressure sits to our north. This surface high pressure anchored to our north may provide enough subsidence and low-level dry air to keep precipitation at bay despite a warm front developing to our southwest. There looks to be an overrunning scenario potentially setting up, therefore we will monitor this. Kept Tuesday during the day dry, then brought in some low PoPs northward at night. For Wednesday...A storm system organizes and strengthens into the Upper Great Lakes region. This will push surface high pressure east of New England with a southerly flow of warmer air surging northward. It appears that a warm front will be approaching from the south, with cooler air to its north. There is the potential for some showers due to warm air advection and lift north of the warm front. If enough low-level dry air remains longer, then this could set up a cold air damming scenario north of the warm front. && .AVIATION /09Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through 12z...mixed variable conditions in showers, patches of stratus/fog, becoming vfr CIGS everywhere by 09z. gusty southwest winds 25-30 kt VCNTY KACy through 08z. otherwise light winds tending to briefly become south or southwest before shifting to west and gusty to 20 kt everywhere between 07z-10z subsequent to an eastward moving cold front. After 12z today...VFR sct-bkn aoa 4000 ft. Westerly winds will gust 25-30 kt by 17z. Tonight...VFR clear with sct cirrus possible late. West winds, generally under 10 kt. OUTLOOK... Friday through Sunday...VFR overall. West-northwest winds 10-15 knots with gusts up to 25 knots both Friday and Saturday afternoons, then diminishing Sunday. Sunday night and Monday...Mainly VFR. Some rain or snow showers are possible Sunday night into Monday morning, especially to the north and west of PHL. && .MARINE... Marine dense fog advisory was just cancelled at 120am. Considering a GLW for ANZ450-451 but no decision on that til 3am. Otherwise the SCA continues posted as previously. More at 300 am. OUTLOOK... Friday and Saturday...A cold air advection regime will be in place during this time frame, however steeper lapse rates Saturday should provide better mixing. As a result wind gusts from the northwest up to 30 knots (especially Friday night and Saturday) are anticipated and a Small Craft Advisory looks to be needed. Sunday and Monday...High pressure builds in overall with lighter winds. Therefore, the conditions are forecast to be below Small Craft Advisory criteria. && .CLIMATE... November averaged 1 to 3 degrees above normal throughout our forecast area of responsibility. PHL Nov avg 50.0 or 2.4F above normal. Ranked 14th warmest Nov in the PHL period of record (tied 14). ABE NOV avg 45.9 or 3.2F above normal. Ranked #16 warmest in the ABE period of record. ACY NOV avg 48.3 or 1.5F above normal. Not ranked top 16. Georgetown missed equaling their record high by 2F. No matter the average temperature yesterday at Georgetown DE was 23 degrees above normal. Additionally: Allentown - 1.05 and Trenton-0.95 posted RER daily rainfalls ydy. Atlantic City`s monthly total of 1.08" tied for 13th driest November in the period of record. We will post 24 hour storm totals by 515am. It`s possible our office will compile 2 day storm totals in a PNS late this morning, as time allows. We do know widespread 2-3" amounts occurred to the northwest of Interstate 95. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 3 AM EST Friday for ANZ431-450>455. Small Craft Advisory until 10 PM EST this evening for ANZ430. && $$ Synopsis...Gorse Near Term...Drag Short Term...Drag Long Term...Gorse Aviation...Drag/Gorse Marine...Drag/Gorse Climate...Drag is the U.S. government's official web portal to all federal, state and local government web resources and services.