Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 140735 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 235 AM EST Thu Dec 14 2017 .SYNOPSIS... A fast moving low pressure system will move across the area tonight and then offshore Thursday. A ridge of high pressure will build over the area later Thursday through Friday. A low pressure system will move up along the coast Friday night. More high pressure will affect the area much of this weekend. Another few disturbances will be across the area beginning later Sunday and lasting into early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Mesoscale update: Vigorous but fast-moving snow band moved through the southern half of the CWA during the past 3 hours. Snow reports indicate generally 0.5-1.5 inch totals with the band, mostly in about 1-2 hours. Pronounced dry slot has moved into the area generally along/south of I-76/I-295 corridor, and hi-res models show little precip occurring the rest of the night in this area. Meanwhile, precip to the north looks lighter but longer-lasting. For now, will keep current advisory as is given the signal for at least light precip to the north for the next few hours, but the snow looks mostly done Philly southward. Expect slick roads tomorrow morning, but I suspect there will be little additional snow. If current trends continue, portions of the advisory will need to be cancelled early. Grids update: Dew points were way too low (which makes sense given the very sudden snowfall and shallow dry layer), so needed to adjust these upward considerably overnight. Spatial distribution of temperatures is largely based on presence of snow or not, so frequent updates to temps will be required through the night. For now, teens in the Poconos and twenties elsewhere. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TODAY/... Snow tapers off fairly quickly after sunrise Thursday morning, but not before dropping up to 1/2" of additional snowfall across northern zones. Behind strengthening and departing low, west to northwest winds will increase to 15-20 mph with gusts up to 25 mph starting in the late morning hours. The pressure gradient relaxes during the afternoon. Temperatures moderate a bit Thursday afternoon compared to highs today, but will still be below normal. && .LONG TERM /TONIGHT THROUGH WEDNESDAY/... Weak high pressure will be across the Middle Atlantic region Thursday night and Friday. It will bring mostly fair and continued cool weather to the area. Temperatures will remain some 5 to 10 degrees below normal. A quick moving low pressure system will move just off the NJ/DE coastal areas Friday night. This could bring some light precipitation (most likely snow) to parts of SE NJ Friday evening. Overall, confid in this is low however with the system looking disorganized and the trends are to minimize any qpf over the area. We`ll just keep the slgt chc pops for now, with this low and an upper trough crossing the area. Much of the upcoming weekend will be fair, with high pressure building over the area. Sunny weather is expected most of Saturday and much of Sunday before clouds increase later Sunday. Temperatures will still be a little below normal Saturday before moderating back to normal levels Sunday. A few showers are possible Sunday afternoon in a warm advection pattern, but again confid in this is rather low attm, so we`ll just have slgt chc or small chc pops only for this time. A better chc for rains (a some higher elevations snows) will develop Sunday night and last into Monday as a upper trough begin to affect the area. We`ll have chc pops for Sunday night and slgt chc pops for Monday. We`ll carry the low pops into Tuesday as well, with the different models having varying solutions for this period. Most of the precip will be rain with the temperatures Monday and Tuesday having moderated back to above normal by then. A few snow showers across the southern Poconos are possible however. && .AVIATION /08Z THURSDAY THROUGH MONDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...IFR in snow but generally VFR or MVFR (CIGs) in the absence of snow for the rest of the night. Best chances of snow are north of PHL, with most snow probably done at PHL, ILG, MIV, and ACY. Some light snow/flurries should be present for the next couple of hours, so kept some mention here, but improved CIGs/VSBYs considerably from previous TAFs. Winds light/variable, though may see some stronger south/southeast winds at times. Medium confidence. Thursday...Potential for residual MVFR CIGs between 12Z and 15Z, but rapid improvement to VFR is expected. Gusty west or northwest winds will commence 15Z to 22Z for most of the area (speeds 5 to 15 kts with gusts 15 to 25 kts). High confidence. Outlook... Thu night thru Fri...VFR. Fri evening thru Sat morning...Mostly VFR. Few showers psbl. Sat afternoon thru Sunday...Mostly VFR. Sunday night thru Monday...Mostly VFR. Slgt chc showers. && .MARINE... Gales have developed at buoy 44009 this morning, so I have issued a short-fused gale warning for the Delaware coastal waters through noon today. Elsewhere, strong small-craft advisory conditions will exist this morning before a slow diminishing trend occurs this afternoon. Although winds may linger near/slightly above advisory criteria early this evening, not confident enough to extend the advisory at this time. Seas should remain elevated through the day, but as northwest flow develops this afternoon, there should be a diminishing trend this evening. Light snow should continue across the New Jersey coastal waters this morning, with visibility restrictions likely. Fair weather should set in this afternoon and tonight. Outlook... Thu night...SCA conditions early, diminishing. Fair, Fri thru Fri evening...Sub-SCA. Chc rain/snow. Fri night thru Sat...SCA with low end Gale psbl. Chc rain/snow. Sat night thru Sunday...Mostly sub-SCA. Mostly fair. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory until 10 AM EST this morning for PAZ054-055-060>062-070-071-101>106. NJ...Winter Weather Advisory until 10 AM EST this morning for NJZ001-007>010-012-015-017>019. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ430- 431-450>453. Gale Warning until noon EST today for ANZ454-455. && $$ Synopsis...O`Hara Near Term...CMS/MPS Short Term...CMS/MPS Long Term...O`Hara Aviation...CMS/O`Hara Marine...CMS/O`Hara is the U.S. government's official web portal to all federal, state and local government web resources and services.