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 151027 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 527 AM EST Thu Feb 15 2018 .SYNOPSIS... Some weak disturbances will move across the region today and tonight, then a cold front arrives into our area late tonight. The cold front will settle to our south and east by later Friday. High pressure builds across the region Friday night into Saturday before shifting into the Canadian Maritimes Saturday night. Low pressure is forecast to quickly track south and east of our region Saturday night before moving out to sea Sunday morning. High pressure builds in later Sunday before moving offshore Monday, then a warm front arrives Tuesday followed by a cold front late Wednesday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
Instability burst waa showers are in the process of ending and should end be all done around 12z. Then today...Considerable cloudiness, mostly high south of I78 but low cigs now developing near I78 may not dissipate and so am concerned that temps will not reach max`s up north. Otherwise in the south, stayed close to the prior fcst with also some concern there that max`s may not be reached. Nevertheless, we may be near record at ACY where todays record max is 65 in 1989. Lack of mixing a concern for not realizing MOS potential. Next pulse of waa instability burst may arrive near sundown in parts of e PA. Fcst max temp (18 to 24F above normal) was a blend of continuity and the new warmer MOS guidance s of I78 but used a cooler blend of NAM and prev fcst I80 north. POPS, mostly continuity except a 50 50 blend of the NAM/GFS mos after 21z.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
-- Changed Discussion --
850 speed max 50-60kt near the Mason Dixon line at 06z is part of the driver for rain and some of that rain will be briefly mdt or heavy with qpf values double or triple what occurred early this morning. Used a blend of models and WPC QPF. The HRRRX favors mostly n of PHL early tonight and then slips south late at night. fwiw: The 06z HRRRX sends the first band of rain mostly n of PHL this evening then trails the second band southward over night so that I80 region is basically all done at 11z Friday and the far southern part of our area never receives any rain before sunrise Friday. Temps were a 50 50 blend of the 00z/15 GFS/NAM MOS. MIN temps early this Friday morning (calendar will be 2359EST this Friday night) 27 to 33 F above normal.
-- End Changed Discussion --
&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Summary...Rather mild and wet for a time Friday then drying Friday night and turning colder; snow/wintry mix from late Saturday afternoon into very early Sunday; turning much warmer during the first half of next week. Synoptic Overview...A positively tilted upper-level trough centered in the vicinity of Hudson Bay will shift east some into the weekend. Significant short wave energy though Saturday into Sunday looks to sharpen the southern part of the trough enough to help focus surface low pressure near the Mid-Atlantic, although this is within a progressive flow regime. Late in the weekend and especially during the first half of next week, the pattern becomes more amplified as a significant trough develops in the West with a strengthening ridge in the East. This will open the door for much warmer air to surge across our region starting Tuesday. For Friday...Areas of rain should tend to weaken by later Friday as a cold front settles farther south of our area and the low-level flow becomes a bit more anticyclonic. The precipitation is anticipated to end across the northern areas before the airmass gets cold enough for any mixing or changeover. High pressure then builds eastward and encompasses our region Friday night. Another rather mild day will turn much colder at night along with the eventual start of much drier low-level air. For Saturday and Sunday...The guidance is in good agreement with a stronger short wave sliding east along the southern side of a broad upper-level trough centered near Hudson Bay Canada. This feature may sharpen the trough some as it quickly shifts eastward, however there are still several questions regarding the details. Looks like a precipitation event will occur, however some guidance is a little farther south although some associated ensembles suggest a farther north track. In addition, boundary layer temperatures will be key regarding the extent of snow accumulations as the surface will be warmer leading into this. However, the snow will be falling at night which will help cool the ground and if the intensity of the precipitation is heavier this will also improve the accumulation efficiency. The forecast soundings are rather dry prior to the arrival of the precipitation which would lead to more evaporational cooling. High pressure will be moving into the Canadian Maritimes which would allow some warming, however the initially very dry air may help with wet bulbing and keep the airmass cooler. Overall, temperatures look to be close to freezing where snow occurs and the snow to liquid ratios will be low allowing the snow to be wetter. There looks to be some sort of mixed precipitation zone that meanders some, however this may end up being a rain/snow mix. We did not carry any ice accumulations at this time given the uncertainty. Our first take on snow amounts will post early this morning and we went more conservative given the uncertainty with the thermal fields and even surface temperatures. This translates into a swath of 1-3/2- 4 inches with less farther south across Delmarva and eastward toward the New Jersey Shore. Some guidance, which shows higher QPF, looks to be hinting at a ribbon of enhanced ascent northwest of the surface low as the thermal gradient aloft may tighten for a time allowing for stronger frontogenetic forcing. If this were to occur, an embedded area of heavier rates would result. As of now this is of lower confidence, but cannot be ruled out. In addition, our region is forecast to be within the right entrance region of a potent 250 mb jet Saturday night which would enhance the large scale ascent across the Mid-Atlantic. The flow aloft is progressive therefore this system should be quick moving. As a result, precipitation should end by daybreak Sunday and therefore continued with a dry day Sunday. High pressure looks to quickly start building in Sunday afternoon and night, however the airmass is not forecast to be all that cold following the storm. For Monday and Tuesday...The pattern is forecast to become much more amplified, with a large trough settling in across the West while a ridge strengthens in the East. This will set the stage for another round of warming in the East. As high pressure shifts offshore Monday morning, a return flow sets up along with warm air advection. A warm front at the surface will approach later Monday, and the bulk of the model guidance shows a warm air advection burst producing a swath of showers or a period of rain Monday before lifting northward. This warm front should work northward Tuesday, with possible showers with it. The extent of the showers on Tuesday will depend on the warm air advection push with the northbound warm front. Given the pattern with surface high pressure in the western Atlantic and a ridge aloft, the warm front should be able to lift to our north Tuesday. We continued with a time of chance PoPs, although Monday the PoPs may need to be increased and Tuesday could end up being mostly dry as it warms up quite a bit. For Wednesday...As strong energy slides southeastward from central Canada, the ridge in the East should tend to become flatter with time. This will allow a cold front with a few ripples of low pressure to settle southeastward. This front is currently forecast to cross our area late Wednesday with at least some showers. This should result in another rather warm day, then the cooling process will start to develop in the wake of this front. && .AVIATION /10Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Early this morning...Mostly VFR cigs aoa 5000 ft with vsby briefly near 5 mi in fog . Vcnty KABE/KRDG MVFR/IFR conds in st/fog. Wind mostly light south. Today...VFR cigs, generally aoa 12000 ft. Exception vcnty KRDG/KABE where MVFR or IFR conds in st/fog may only slowly improve to VFR CIGS early afternoon. Southwest wind may gust 15 or 20 kt this afternoon. Tonight...VFR CIGS, probably lowering to MVFR/IFR conditions overnight, especially KABE/KRDG in periods of rain. LLWS possible vcnty KPHL/KILG/KMIV/KACY in the 04z-10z time frame. South to southwest wind. Please see TAFS for details. OUTLOOK... Friday...MVFR/IFR conditions possibly in the morning due to low clouds/fog and some rain. West to northwest winds increase to around 15 knots with gusts to around 25 knots, then diminishing some at night. Moderate confidence. Saturday and Sunday...Conditions should lower to MVFR/IFR as rain/snow or a wintry mix moves across the area Saturday night into very early Sunday. Conditions then return to VFR on Sunday. Low confidence with the timing and precipitation types. Monday...MVFR/IFR possible as showers may arrive from the west. Southwest winds may gust to around 20 knots during the afternoon.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
SCA issued for the ATLC waters later tonight onward as southwest winds gust 20-25 kt and seas build to 5 or 6 ft on the Atlc waters. Warm air (50s) over ssts` around 40 acts to suppress potential gustiness. Elsewhere, a south to southwest wind through tonight...strongest tonight. Fog may develop later today, or more likely tonight on the Atlantic waters, especially NJ and could become a marine hazard. OUTLOOK... Friday...As a cold front settles to our south and east, colder air starts arriving and this strengthens Friday night. Northwest winds will increase with the better chance for gusts to around 25 knots Friday afternoon and evening. Seas will be around 5 feet on the ocean zones. A Small Craft Advisory has been issued through Friday evening for the ocean zones, and from 18z/1pm to 03z/10pm for Delaware Bay. Saturday and Sunday...The conditions are anticipated to below Small Craft Advisory criteria despite low pressure tracking to our south and east. Monday...The conditions are anticipated to be below Small Craft Advisory criteria, however southerly winds will start to increase late.
-- End Changed Discussion --
&& .CLIMATE...
-- Changed Discussion --
Highs may approach record values at Atlantic City today. The current forecast high is in the low to mid 60s both days. All other climate sites are forecasted to be at least five degrees cooler than the record highs today and Friday. February 15th: 65 back in 1989 We may need to post records for next Tuesday and Wednesday as some models have 2meter temps near 70F and records both days are within 3F of 70.
-- End Changed Discussion --
&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from midnight tonight to midnight EST Friday night for ANZ450>455. Small Craft Advisory from 1 PM to 10 PM EST Friday for ANZ430- 431. && $$ Synopsis...Gorse Near Term...Drag 527 Short Term...Drag 527 Long Term...Gorse Aviation...Drag/Gorse 527 Marine...Drag/Gorse 527 Climate...527

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