Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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471 FXUS61 KPHI 140827 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 327 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 AM THIS MORNING/... 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. && .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM 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 NIGHT THROUGH FRIDAY/... The low moves out by erly Sun and high pres builds to the n which will bring dry wx for at least the first part of Mon. Then, low pres will develop over the srn plain and will move newd twd the Grtlks thru Tue. The wmfnt assocd with this low will cross the area Mon night. Precip will develop as erly as Mon aftn (GFS) or hold off until Mon night or Tue (ECMWF and CMC). For now, will keep Mon dry. Pops increase Mon night into Tue. There is genly good agreement wrt this aspect, though the mdls disagree on when and where the precip is most likely to occur. The GFS is also faster in moving the precip out. The cdfnt crosses the area erly Wed in the GFS and then Wed into Thu is dry. In the ECMWF, a secondary low forms on the front, it is, therefore, slower to cross and Wednesday is wet, before fropa Wed night and a dry Thu. The CMC is somewhere in the middle, slower (much) than the GFS but not as slow as the ECMWF. So, for now, will hold some pops thru Wed and see how this develops. Needless to say this is a lower than average confidence fcst. The good news is that temps will be quite warm thru most of the week (after Mon)...well into the 50s in many areas. Therefore, any precip that falls Tue into Wed will be plain rain everywhere. Temps look to be 10-15 degrees above nrml for most of next week!! && .AVIATION /09Z 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... Saturday night...MVFR or IFR conditions especially ceilings. Some light mixed precipitation possible mainly in the evening, with mainly snow/sleet for ABE/RDG/TTN, and snow/sleet/freezing rain possible for the remainder of the TAF sites. Low to moderate confidence. Sunday-Sunday night...Conditions improving to VFR. Moderate to high confidence. Monday-Wednesday...VFR early, lowering to MVFR, then to IFR late Monday night into Tuesday. Chance of precipitation late Monday into Tuesday. A wintry mix possible, mainly north and west early Tuesday, then timing differences develop after that. It is possible conditions could improve on Wednesday. Moderate to high confidence Monday-Tuesday, then low on Wednesday. && .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... Sat-Tue..Sub SCA conds are expected, although winds may gust 15-20 knots at times on Sun. Wed...SCA conds psbl as swly flow increases in advance of cdfnt. Wind cud gust to 25 kts and seas could reach 6 ft. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Winter Weather Advisory from 7 AM this morning to midnight EST tonight for PAZ101-102. NJ...None. DE...None. MD...Winter Weather Advisory from 7 AM this morning to midnight EST tonight for MDZ008-012. MARINE...None. && $$ Synopsis...Franck Near Term...O`Hara Short Term...O`Hara Long Term...Nierenberg Aviation...Nierenberg/O`Hara Marine...Nierenberg/O`Hara

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