Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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 201953 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 353 PM EDT Sat May 20 2017 .SYNOPSIS...
-- Changed Discussion --
Canadian high pressure will build down into New England this weekend then pass south of Nova Scotia Monday. Low pressure over the upper Great Lakes on Sunday moves to near James Bay Canada late Monday with its associated cold front crossing the mid Atlantic states Monday night. Weak high pressure follows into the mid Atlantic states Tuesday. Complex low pressure will develop northeastward into the mid and north Atlantic states Wednesday and Thursday. The cold front sweeps off the coast Friday with weak high pressure to follow next Saturday.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
-- Changed Discussion --
Considerable low-/mid-level cloudiness persists over the forecast area this afternoon, although the earlier shower activity has now moved away to the east. With continuing cloud cover and a NE wind off the cool Atlantic, tempertures have been holding about steady in the upper 50s over east PA and lower to mid 60s over NJ and north Delmarva. A southward clearing trend is noted along the northern edge of the clouds over NY. For tonight, high pressure will continue to build in from the north along with somewhat drier air at low-to-mid levels. Partial clearing is expected overnight which should allow overnight temps to fall into the 40s or low 50s in more urban areas.
-- End Changed Discussion --
&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
-- Changed Discussion --
For Sunday, high pressure shifts offshore from New England allowing our low-level flow to veer more to the SE. Some low to mid-level warm advection along with generally less cloudiness should allow afternoon max temps to be a few degrees warmer than today, especially N/W of PHL. A rather sharp shortwv ridge axis at 500 hPa is forecast to move slowly east across the mid-Atlantic during the day. There will be increasing clouds and moisture to our west, but at this time it looks like eastern PA and the rest of the forecast area should remain rain free.
-- End Changed Discussion --
&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
-- Changed Discussion --
500 MB: A ridge along the east coast Sunday slowly weakens this coming week as a large trough evolves in the central United States, which then weakens considerably as it heads to the east coast Thursday and Friday. Temperatures: The 3 day period (17-19) of 10 to 20 degree above normal temperatures numerically compensated for the cold of the 4th-14th and so the first 19 days of the month are near normal (except 2F colder than normal for KMPO). The pattern says that there will be some below normal calendar day chill these next few days but the GEFS and ECEFS have recently shifted to a considerable warming trend beginning Memorial Day weekend that could last the rest of the month. So calendar day averages Monday should be 1 to 3 degrees below normal, near normal Tuesday and then normal to 5 degrees above normal Wednesday through Saturday. Forecast basis: Unless otherwise note: a 50 50 blend of the 12z/20 GFS/NAM MOS Sunday night-Monday night, GFS MEX MOS Tuesday, and thereafter the 15z/20 WPC guidance Tuesday night- Saturday. No change from last night in the expectation of an active but detail uncertain pattern this coming week. The dailies... Sunday night through Monday night...Warm air advection increasing cloud cover Sunday night, then a probable 6 to 12 hour period of showery rains Monday, which should end from west to east Monday evening. PWAT of 1 inch or so Sunday evening increases to 1.75 Inches Monday morning vcnty the Delmarva then the PWAT axis slides east during the afternoon so that PWAT has decreased to near 1.2" by Monday evening and 0.8" early Tuesday. There will be a period or two of heavy showers that will cause pockets of poor drainage street flooding, slowing travel etc but not expecting any flood watch potential. Small chance for a thunderstorm but no blatant signal. South wind Sunday night shifts southwest Monday afternoon then northwest to north late Monday night. Fog could be a hazard in some areas Monday evening-night. Overall confidence: above average. Tuesday...Expect at least one tranquil day on Tuesday before we may start to see the effects of the next low pressure system. Partly sunny north and mostly cloudy south where we have uncertain chance pops for showers . East wind. Confidence: below average on sky cover, rain chances and consequently, max temps. Wednesday through Thursday night...The substantial trough in the nations midsection will bring a period or two of showers and possibly a thunderstorm to our region but odds for a coastal noreaster are decreasing in light of recent ensemble trend`s to rapidly weaken the trough aloft as it moves into the northeast USA Friday. Confidence on details: below average. Friday...should dry out with just a chance of a shower in the I80 region. Improved conditions and abetter chance of warming up. Confidence: average.
-- End Changed Discussion --
&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conditions are expected at all the TAF sites through Sunday. Some BKN to OVC ceilings will likely persist but should be no lower than about 5000 ft. Winds will diminish some overnight but will continue mainly from the E to ENE. No visibility restrictions are expected. Outlook... Sunday night...VFR CIGS to start may deteriorate after 07z/22 to IFR CIGS. South wind. Confidence: above average. Monday...Widespread MVFR and deteriorating to widespread IFR in showery rains/stratus/fog later Monday into Monday evening. South wind shifts southwest late. Confidence: above average. Monday night...MVFR variable LIFR conditions in st/fog/leftover showery rain or drizzle but conditions may improve late at night. Southwest wind shift northwest to north late at night. Confidence: above average. Tuesday...VFR sct-bkn layers aoa 4000 ft except MVFR CIGS possible vcnty KMIV and KILG. East wind. Confidence: above average. Tuesday night...VFR cigs may deteriorate late. Confidence: below avg. Wednesday...A period of MVFR or IFR conds in showers is possible. Timing uncertain. Confidence: below average. Thursday...For now, VFR. Confidence: below average
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
The post cold-front surge resulted in somewhat gusty NE winds today over the forecast waters. This NE flow also built up the seas to 5 to 7 feet over the Atlantic coastal waters, with higher waves off DE where there is a longer fetch. It looks now like winds are beginning to diminish, but the seas will likely remain a bit rough through tonight and into Sunday. The SCA configuration was adjusted some to remove SCA north of Manasquan but extend the time farther south. This is based on current buoy obs as well as forecast wind and waves. Outlook... Sunday night...elevated seas are expected to continue on the DE coastal waters through at least Sunday night. Elevated seas may also develop on the southern NJ coastal waters. For the rest of the area, winds and seas are expected to stay below SCA criteria. Monday...SCA conditions, both seas and winds, are possible Monday into Monday night, primarily along the Atlantic coastal waters. Tuesday and Wednesday...winds and seas are expected to stay below SCA criteria. Rip Currents: A moderate rip risk of rip currents was expected for today at the NJ and DE beaches. A breezy NE wind 15-20 mph with gusts to 30 mph, short-period NE swells and waves of 4 to 5 feet in the surf zone will contribute to this moderate risk. Inputting these values in our in-house regression tool put us very close to a high risk.
-- End Changed Discussion --
&& .PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 2 AM EDT Sunday for ANZ451-452. Small Craft Advisory until 6 PM EDT Sunday for ANZ453>455. Small Craft Advisory until 6 PM EDT this evening for ANZ431.
-- End Changed Discussion --
&& $$ Synopsis...Drag 353 Near Term...AMC 353 Short Term...AMC 353 Long Term...Drag 353 Aviation...AMC/Drag 353 Marine...AMC/Drag 353

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.