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 072029 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 329 PM EST Wed Dec 7 2016 .SYNOPSIS... Low pressure in southeastern Canada will move slowly eastward through the end of the week. The strong cold front associated with this low will cross the area on Thursday. Large high pressure will then build in for the early part of the weekend. Then, another area of low pressure will begin to bring precipitation possibly as early as Sunday afternoon or Sunday night, with a cold front crossing the region Monday night or early Tuesday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Remainder of this afternoon...skies should generally brighten with the lower clouds thinning out and clearing near sunset. Isolated nw flow gusts 19 kt as observed. Tonight...we will presume the subsidence inversion dissipates and that so too, the low clouds continue their mid afternoon clearing trend. However, a deck of mid or high clouds should arrive after midnight from the west. light west to northwest wind. Fcst elements are a 50 50 blend of the 12z/7 GFS/NAM MOS. Its possible that there could be isolated frosty fog patches in the countryside in the light boundary layer flow radiational cooling sitn (low confidence of occurrence). Low temps above normal. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Considerable mid and high cloudiness during the morning becoming mostly sunny and breezy during the afternoon with westerly wind gusts expected to increase to 25 mph. This cloud wind sequence in assn with the arrival in the aftn of a ne-sw positive tilt 500 mb trough axis with 12 hr 100-140m hfc overhead. max temps near normal. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... A strong cold front will have crossed the area on Thu and high pres will be building in behind in. Strong nwly flow will result Fri into Sat, making it feel colder. In the nwly flow, there cud be some snow shwrs mainly n on Fri, but otherwise dry wx is expected thru Sun. The aforementioned high pres will move off the coast durg Sun and low pres will then begin to advance twd our region from the w. There are mdl diffs with this sys. The GFS develops a low acrs IA and moves it ewd acrs the Grtlks and into srn Canada. The wmfnt assocd with this low will bring precip to the area beginning Sun aftn, with the cdfnt Mon mrng. The ECMWF develops a much stronger low over the srn plains, and moves it newd int the OH Vly. By Mon AM. Due to the stronger low, it is slower with its motion and the onset and ending time of precip. The ECMWF doesn`t bring much precip before Sun night, with the bulk of the precip on Mon before CFP late Mon. The CMC soln is somewhere in the middle. So, while confidence is lower than average on the actual timing, we do know that precip will develop during the latter half of Sunday and continue for at least the first portion of Monday. Over northern and wrn areas, temps will be cold enough for at least some wintry precip, some of that will be dependent on the track of the low. The ECMWF is also a significantly warmer soln. Most other areas will se all Or mostly rain, but the details on this one will need to be ironed out as we get closer. High pres returns for Tue. Temps look to be below nrml thru most, if not all of the pd. They cud return to close to nrml around Monday, before dropping again with the next CFP. && .AVIATION /20Z WEDNESDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Remainder of this afternoon...mvfr cigs in the process of advecting eastward to leave behind sct clouds aoa 3000 ft. Wind generally northwest with gusts under 20 kt. Tonight...VFR. W-NW winds will be light (under 10 kt). Thursday...VFR multi layered cigs aoa 10000 ft during the morning- midday with chance of an hour of cigs down to near 6000 ft during midday with isolated sprinkles or flurries mainly higher terrain of e PA. Then becoming VFR clear late in the day. Westerly wind increasing, with gusts 22-28 kt during the afternoon as the caa process develops more earnestly. OUTLOOK... Thu night-Sat...Mainly VFR, but some local MVFR psble each mrng. NW wind cud gust wo to 25 kts on Fri. Moderate to High confidence. Sun and Mon...VFR early, lowering to MVFR then IFR by the afternoon and overnight. RA and SN psbl Sun into Mon. Low to Moderate confidence on the timing of precip. && .MARINE... SCA seas has been extended since easterly swells in the wake of last nights short gale are slow to decrease. Guidance continues to lower these swells/seas too fast. Pls see MWW or the CWF. Eventually the seas should subside below the 5 ft sca criteria overnight. Thursday...anticipating the need for a westerly flow cold air advection small craft advisory for many of the waters Thursday afternoon. Have begun the process with a DE Bay SCA. OUTLOOK... Thu night-Sat...SCA conds expected in strong nwly flow. Wind could gust to 25 to 20kts. There is a small chance of gales Thu night into Fri behind the front. Sat night-Sun...Sub-SCA conds are expected, but wind will increase to just below SCA by later Sun. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory for hazardous seas until 4 AM EST Thursday for ANZ452>455. Small Craft Advisory for hazardous seas until 11 PM EST this evening for ANZ450-451. Small Craft Advisory from noon Thursday to 7 AM EST Friday for ANZ430-431. && $$ Synopsis...Nierenberg Near Term...Drag Short Term...Drag Long Term...Nierenberg Aviation...Drag/Nierenberg Marine...Drag/Nierenberg

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