Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 210814 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 414 AM EDT Sat Apr 21 2018 .SYNOPSIS... High pressure over the Great Lakes builds east today, and eventually moves offshore on Monday. Low pressure over the Gulf Coast states tracks to the east, and slowly impacts the Mid- Atlantic during the mid-week period. Another area of low pressure may affect the area at the end of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Main forecast concern is temperatures this morning, with current temperatures running about 2-4 degrees lower than forecast (locally more), as clear skies and light to calm winds have allowed for nearly ideal radiational cooling conditions. The favorable valleys and rural locations have tanked in the past hour or two temp-wise, with locations in the Pine Barrens already reaching freezing. Upgraded the frost advisory to a freeze warning given these trends (though one may question the effectiveness of such an upgrade so late in the night) for the Pine Barrens and zones north/west of Philadelphia (where temps 32-35 degrees are observed at this time). After this morning`s chill, today should be a nice day, as northwesterly midlevel flow and building surface high pressure allow for dry conditions with temperatures just a little below seasonal averages. Winds should be a little lower today as the surface pressure gradient slackens with the approaching high. A 250-mb jet streak and accompanying vort max should provide some lift in the upper levels to allow for some increasing clouds. These may limit temperatures from climbing a degree or two, and I generally reduced highs by this amount today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... Northwest midlevel flow will continue tonight as a surface ridge remains over the region. Some perturbations in the midlevel flow will approach the region by morning, but there is little lift with these perturbations. Other than some increased mid and upper-level clouds, not expecting much in terms of sensible weather impacts. This means that temperatures will once again be the primary forecast concern. Could see temperatures flirting with freezing again in portions of the area with the growing season underway, but tonight`s environment will be a little less favorable. For one thing, if increased cloud cover is present, some radiation may be re-emitted to the surface (though the height of the clouds will not hamper nocturnal cooling as much as one may anticipate). This will be especially true in the southern CWA, but how far north these clouds persist may prove critical in how far temperatures fall in more susceptible locations such as the Pine Barrens. At this point, way too uncertain/marginal to issue additional frost/freeze products. My suspicion is that no additional products will be necessary. && .LONG TERM /SUNDAY THROUGH FRIDAY/... High pressure over the area Sunday slowly drifts offshore Sunday night, and remains over the western Atlantic Ocean waters through Monday night before drifting offshore on Tuesday. Plenty of sunshine and mild, though temperatures will generally be a few degrees below normal during the day. At night, with clear skies and light winds, radiational cooling conditions will allow for colder conditions in the mountains and in the Pine Barrens of NJ. During this time, low pressure over the Gulf Coast states will slowly track to the east, and will be over the Southeast U.S by Tuesday evening. A warm front just southwest of the region lifts north through the region Tuesday night as the low tracks north along the coast. Though there are rain chances during the day Tuesday lifting from south to north, the best chances will be Tuesday night as the low lifts to the north. The low then slowly works its way north through Wednesday, will be south of Long Island Wednesday night, and departs on Thursday. Although there may be a period on Wednesday where locally heavy rain is possible at times, not expecting a prolonged period of widespread heavy rain with this system. Weak high pressure builds through the region late Friday and Friday night. Another cold front approaches on Saturday. Temperatures during this time will generally be at or below normal levels for most of the week, but temperatures trend warmer towards the end of next week. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR with SCT-BKN high clouds. Northwest winds 5 to 15 kts. High confidence. Tonight...VFR with SCT-BKN high clouds, especially south of PHL. Winds should become light and variable. High confidence. OUTLOOK... Sunday through Monday night...VFR. Generally light winds. High confidence. Tuesday...Generally VFR. Clouds build from south to north. E-SE winds 10-15 kt. Tuesday night through Wednesday...MVFR/IFR in rain and fog. E-NE winds 10-15 kt. && .MARINE... Fair weather and sub-advisory winds/seas are expected through tonight. Northwest winds 10 to 15 kts (possibly gusting to 20 kts or so) this morning will likely switch to southwest this afternoon before switching back to northwest or north tonight. Seas should remain near or below 3 feet. OUTLOOK... Sunday through Tuesday...Tranquil conditions on the waters with sub-SCA conditions. Tuesday night and Wednesday...Rain, fog, and gusty E-NE winds as low pressure impacts the waters. SCA conditions expected. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Freeze Warning until 8 AM EDT this morning for PAZ060-101>104- 106. NJ...Freeze Warning until 8 AM EDT this morning for NJZ012-013-015- 019-020-022-027. Frost Advisory until 8 AM EDT this morning for NJZ016>018-021. DE...Frost Advisory until 8 AM EDT this morning for DEZ001>003. MD...Freeze Warning until 8 AM EDT this morning for MDZ008. Frost Advisory until 8 AM EDT this morning for MDZ012-015-020. MARINE...None. && $$ Synopsis...MPS Near Term...CMS Short Term...CMS Long Term...MPS Aviation...CMS/MPS Marine...CMS/MPS is the U.S. government's official web portal to all federal, state and local government web resources and services.