855 FXUS61 KPHI 311050 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 650 AM EDT Sun Mar 31 2019 .SYNOPSIS... A cold front will cross the area today while low pressure moves down the saint Lawrence Valley. High pressure from the Ohio Valley will build across the area Monday and then move offshore by Tuesday. A coastal low will develop off the Carolinas Tuesday and then move east of our area Tuesday night and part of wednesday. More high pressure will affect the area Thursday. Another low may bring unsettled conditions for the close of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... No major changes with the 630 AM update. The front is making slower, but steady progress east out of central PA. It should be arriving in the southern Poconos, Lehigh Valley, and Berks County within the next 3 hours. With and just behind the front, a few bands of showers have developed and should continue into our region. As mentioned by the previous shift, they may become more organized over our region thanks to the departing low level jet. However, instability appears to be too meager for much in the way of a lightning threat, especially given the robust inversion which is not expected to dissipate before the front arrives. Speaking of the inversion, it is to blame for the very noticeable smoke across much of central and northern NJ. The smoke is originating from the Spring Hill fire in Burlington County. Thanks to the inversion, dispersion is very poor. However, conditions should improve later this morning, thanks both to the showers as well as the shift to off shore flow behind the front. While the strongest cold air advection is not expected until tonight, there will still be enough cold air advection to result in temperatures being steady or even falling behind the front. Consequently, the calendar day high has likely already been reached for most of the area (current temperatures are in the 60s and 50s). && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... A secondary cold front is expected tonight, which will usher in stronger cold air advection. There is some chance for flurries in the Poconos, but otherwise, this frontal passage looks to be dry. However, one impact of the front overnight is that winds will stay breezy for much if not all of the night. Therefore, wind chill values overnight could be in the teens for much of the region. && .LONG TERM /MONDAY THROUGH SATURDAY/... Monday thru Tuesday...Generally fair weather with below normal temperatures, especially Monday. Highs Monday mostly in the 40s and low/mid 50s for Tuesday. Increasing clouds Tue afternoon as the next system approaches. Tuesday night thru Wednesday...A coastal system will strengthen and move east of our (land) forecast area. Most of the latest guidance suggests that the region will get brushed by the NW edge of the system with some clouds and light rain. Consequently, we have continued with the chc pops across the S/E areas and kept the mention of slgt chc pops elsewhere. It wouldn't take much of a turn for the system to bring a soaking rain to the ern areas, but the trends do not show this yet. The 00Z GFS, in fact, keep measurable QPF offshore. Wednesday afternoon thru Thursday...More high pressure and dry weather expected. Milder with readings around 5 degrees above normal. Thursday night into Saturday...More unsettled conditions expected as a H5 trough and sfc low approach from the west. Look like it may cut up into the Great Lakes and bring a cold front thru Fri or Fri night. Plenty of time to work out the details since there is some model disagreement at this period. High chc pops and a few low likely pops for Fri/Fri night look OK for now. Mild temperatures should prevail and last into next weekend. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Through 18Z...VFR conditions should continue through at least 12Z. Then, expect temporary MVFR conditions as a cold front and showers move in. The cold front should arrive at KRDG and KABE between 13 and 16Z, at the Delaware Valley sites (KPHL, KILG, KTTN, and KPNE) between 14 and 17Z, and KMIV/KACY between 15 and 18Z. Winds will be southerly at 10 to 15 kt until the front arrives, at which point winds will quickly shift to west northwesterly around 15 gusting to 25 kt. After 18Z...Conditions should improve to VFR within a few hours after the front has past. winds will gradually shift to northwesterly and continue gusting as high as 25 kt through the day. Tonight...VFR conditions are expected with northwesterly winds of 10 to 15 kt with gusts of 20 to 25 kt. Outlook... Mon/Mon night/Tue...VFR expected. Increasing clouds Tue. Tue night/Wed morning...Restrictions psbl especially S/E. Chc for rain. Wed afternoon/Thursday...VFR expected. && .MARINE... Expect an abrupt shift to west northwesterly winds late this morning or early this afternoon. With this shift, expect an increase in winds, gusting above 25 kt for much of the afternoon. The strongest winds are expected this evening into the overnight hours. Gale force gusts are becoming increasingly likely for the lower Delware Bay and the nearby coastal waters. Therefore, a gale watch has been issued for these locations. For the rest of the waters, expect northwesterly gusts around 30 kt for much of the night. Outlook... Monday...SCA conditions diminishing. Fair. Monday night/Tue...Sub-SCA. Fair Monday night with a chc for rain Tue. Tue night thru Wednesday night...SCA expected. Chc for rain. Thu/Thu night...Mostly sub-SCA. Fair. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ450>452. Gale Watch from 6 PM EDT this evening through late tonight for ANZ431-453>455. Small Craft Advisory until 6 PM EDT this evening for ANZ453>455. Small Craft Advisory from 2 PM this afternoon to 6 AM EDT Monday for ANZ430. && $$ Synopsis...O'Hara Near Term...Johnson Short Term...Johnson Long Term...O'Hara Aviation...Johnson/O'Hara Marine...Johnson/O'Hara