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 141407 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 907 AM EST Sat Jan 14 2017 .SYNOPSIS... An inverted trough associated with low pressure over the southeast states will persist near our region through Saturday. High pressure over the Mississippi Valley will move into our area on Sunday and offshore on Monday. Low pressure traversing the Great Lakes sends a warm front through our region on Tuesday, followed by a cold front on Wednesday. An area of high pressure is expected to settle over the Appalachians Thursday into Friday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pressure to the north will move off the New england coast this afternoon. Meanwhile, weak low pressure and a warm front will be south of the area. This weak low and front will try to send some warmer humid air over cooler air at the sfc. A mix of precipitation is expected today, but the later starting times (compared to earlier fcsts) tend to lead us to believe that snow/sleet are favored across the north and sleet and some rain over Delmarva. There is still the possibility for some freezing rain, but the amounts will be very limited and probably restricted to the wrn most areas of the forecast area. We have decided to issue a Winter weather advisory for a small glazing potential at this time for Chester, Cecil and Kent MD. It`s possible that the area could be expanded later. The confidence in p-types is rather limited. The good thing is that with the system being rather weak is that amounts will be light. Snow accumulations will probably only be an inch or so. Roads may become a bit slippery later today, so be prepared for some slower travel across the area. Temperatures today will reach the low 30s over the far north and close to 40 over srn Delaware. No major changes to fcst with this update. Will see where precip is with later update and make any necessary changes at that point. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... The system from the near term will be advancing across the area this evening and it should more offshore tonight. Pops will decrease this evening, but low clouds will remain thru the night. Temperatures will drop into the upper teens/ low 20s over the north and upper 20s/low 30s south. Winds will shift to NW tonight behind the low which will be offshore. The winter weather advisory will be up thru midnight, but may be taken down earlier if the threat for freezing rain is done by then. && .LONG TERM /SUNDAY THROUGH FRIDAY/... The mid-level flow features a shortwave moving southward along the west coast of the U.S. this weekend, lifting a closed low northeast out of the four corners into early next week. Meanwhile, a complex northern stream features several shortwaves near the U.S./Canadian border. The streams remain largely separate with little in the way of phasing, with the development of a slow moving storm system over the Mississippi Valley early next week, moving slowly eastward thru mid-week. This storm system will lift a warm front northward through our area on Tuesday, followed by a cold front on Wednesday. These features will be the primary focus for precipitation during this time frame, including the potential for a wintry mix Monday night into Tuesday morning, and heavy downpours with the frontal passage on Wednesday. There is uncertainty with regard to the timing and extent of wintry precip, although the models have come into better agreement on the timing of the cold frontal passage. A relatively warm period is in store with daily average temperatures above normal during the Sunday thru Friday time frame. Indications are not quite as warm as this past week, thanks to additional mid- latitude blocking over Atlantic Canada, which will suppress heights somewhat. With the anomalous warm pattern over the past week, NWP guidance was biased cold. Given a somewhat similar pattern, went above guidance, especially Tuesday and Wednesday in advance of a cold front. Fair weather is expected Sunday into Monday with an increasingly anticyclonic flow aloft building in high pressure at the surface. We expect ideal radiational cooling conditions Sunday night with high pressure directly overhead. As a result, went several degrees below guidance at the typically colder locations outside of the I-95 corridor. With the approach of a warm front Monday night into Tuesday, an overrunning regime will setup over the region. The lift is fairly weak and dry air at the surface will discourage precip initially. Model soundings already indicate a significant above freezing layer aloft (warm nose) which will favor more sleet over snow, with a changeover to freezing rain. With the lack of warm air advection in the boundary layer and a dry air mass in place, we favored colder model 2-meter temperatures. There is still a lot of uncertainty in terms of the amount of precipitation that can be generated, as well as a dominant p-type, if any. At this time, the area most favored for wintry precip would be northwest of the NJ Turnpike/I-95. Stay tuned. Patchy fog is also possible Tuesday and especially Tuesday night, mainly northwest of the NJ Turnpike/I-95. A fairly robust short-wave will move accompany the cold frontal passage on Wednesday. Expect some heavier downpours as a result, although the front will be progressive enough to limit rainfall amounts only to around a half an inch. In addition, lapse rates approach 6.5 C/Km, along with weak ML CAPE and Showalter values falling to near zero. As a result, cannot rule out some thunder across the region. Fair weather is expected to return for Thursday. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. While clouds will be increasing across the area this morning, VFR conditions are expected for much of the day. Winds will mostly be from the NE to E this morning before becoming somewhat variable and light for the rest of the day. Clouds will lower this afternoon with the approach of a disturbance and MVFR conditions are expected by late afternoon. Light snow possibly mixed with sleet will occur across the area south of KRDG-KTTN. IFR conditions and lower vsbys also south of KRDG-KTTN this evening. Confid in precip types not the best, but amounts will be light. Precip will end this evening, but cigs/vsbys in fog will be slow to improve overnight. OUTLOOK... VFR conditions expected across all the terminals Sunday and Monday. With the approach of a warm front Monday night into Tuesday, there is a strong signal for widespread MVFR conditions during the day on Tuesday continuing into Wednesday. IFR conditions are also possible at times, especially Tuesday night. && .MARINE... Strong high pressure to the north will move offshore today while a disturbance moves by to the south. The pressure gradient will favor N to NE winds this morning, before winds veer to E then SE by afternoon. Winds should continue to veer to SW then W tonight. Winds speeds will be around 10-12 knots early today then decrease a little this afternoon. Winds and seas will remain below SCA criteria thru the period. Light snow/rain expected this afternoon and evening. OUTLOOK... Tranquil conditions across the waters Sunday into Monday with high pressure overhead. A southerly flow will setup over the waters on Monday night into Tuesday in advance of a cold front. Wind gusts may reach Small Craft Advisory criteria Tuesday night into Wednesday. In addition, seas will approach 5 FT. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until midnight EST tonight for PAZ101- 102. NJ...None. DE...None. MD...Winter Weather Advisory until midnight EST tonight for MDZ008- 012. MARINE...None. && $$ Synopsis...Franck Near Term...Nierenberg/O`Hara Short Term...O`Hara Long Term...Franck Aviation...Franck/O`Hara Marine...Franck/O`Hara is the U.S. government's official web portal to all federal, state and local government web resources and services.