Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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443 FXUS61 KPHI 221932 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 332 PM EDT FRI JUL 22 2016 .SYNOPSIS... A weak cold front is expected to move into the area late tonight into Saturday. High pressure will build in for Sunday through Tuesday, however another weak front is expected late Monday into Tuesday and will stall nearby Wednesday and Thursday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... 3 PM: We are in the process of issuing an advy/warning/watch to cover the urban corridor and upcoming DNC multi concerns with advy criteria Saturday. Larry-our extended forecaster will detail the concerns Sunday and beyond in the long term section after 330PM. Through 8 or 9 PM: Around 1400J MLC at 21z vcnty TEB-ABE-RDG axis with KI 35+, TT49, SWI -3. 0-6KM bulk shear poor-20-25kt. But the heat, waa and 30kt at 500mb should allow 40-45 kt gusts, "IF" storms can get going. That is the uncertainty. Also appears to be a weak mid lvl cap of around 10C trying to develop late today that could impact the life of any strong thunderstorm cells. pwat 1.75" would also mean poor drainage flooding in a few locations. We are including HRRR in the fcst . Not as confident south of I78 as north where something should get going by 4 or 5 PM. MAX HI today so far through 3PM TTN and WRI 100, 101 KPNE so could have issued down here. This lends added value to our warning/advy for Saturday. Tonight...The wind shift from N38 to the Catskills should initiate convection soon and we just dont know how long and how far southeast. The pops may cover too large an area. Very late in the night though, the wind shift should slide at least partially through the region, possibly getting hung up along the MD border to KACY which would impact tomorrow afternoons weather. After midnight: Fair! Fcst elements were produced using a 50 50 blend of 12z/22 GFS/NAM MOS guidance. Unlikely for much if any fog/haze late at night. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/... Sunny, hot and humid Saturday with HI 100 or greater most areas south and west of KBLM along the I95 corridor. Its also Day1 of an excessive heat warning. While Saturdays values are less than warning criteria, it is probably D2 of mid 90s actual max temps that will likely last into the middle or end of next week. Prolonged literal mid 90s heat will take a toll. If the boundary hangs up near the Mason Dixon line to ACY, then the potential would exist for late afternoon isolated severe thunderstorms Delmarva. Still plenty of instability there with better 0-6km bulk shear. There is a subtle indication in the convergent wind fields for a more sizable are of convection Delmarva and s NJ late Sat. Fcst elements were produced using a 50 50 blend of 12z/22 GFS/NAM MOS guidance. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... A cdfnt will be crossing the area Sat night and there cud be some lingering pops especially early. High pres will build back in on Sun. However both temps and humidity will be a bit lower on Sun, so while it will be hot, it will be a little more bearable. The heat returns with a vengeance on Monday, which at this point looks to be the hottest/most humid day. Heat index values will be in the 105-110 range in the urban corridor. Heat headlines are being modified as follows...for the urban corridor, an excessive heat warning will be issued through Monday, and it may need to be extended for Tuesday. We will likely fall short of criteria on Sunday, but it will still be hot. For Monday, the excessive heat watch will remain in place for the area surrounding the warning (that it was previously in effect for)...basically the entire cwa, outside of the Poconos and Sussex County NJ. Felt excessive heat warning was the best way to go with high impact events in Philadelphia this upcoming week. On Monday, low pres will be movg acrs ern Canada. Its assocd cdfnt will move thru the region and will touch off shwrs/tstms in a very hot and sticky ams. Tue and Wed look genly dry but the front will stall to the s and there cud be some low pops acrs the Delmarva extreme srn NJ. && .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Remainder of this afternoon...VFR sct-bkn aoa 5000 ft with a sw wind gusting 15-20 kt. Anticipating redevelopment of confection near and N of KRDG-KABE-KTTN later today. North-northwest wind gusts to 40-45 kt possible in any tstms ne and e central PA and n 1/2 NJ...mainly near and n of KABE and KTTN. Tonight...VFR with small chance MVFR haze/fog late at night, especially wherever it rained after 21z/22 (today). There may still be some leftover decaying sewd moving evening convection vcnty PHL-ACY as it runs into the capped mid lvl thermal profile. Southwest wind with gusts to 15 kt early shifting to light northwest late at night. Saturday...VFR sct-bkn aoa 5000 ft. Potential for convection may still exist vcnty KILG/KACY/KMIV. Light west northwest wind in the morning turning westerly in the afternoon with gusts 15 to 20 kt. Winds may turn southwest at KMIV and KILG/KACY during the afternoon. OUTLOOK... Sat night-Sun. VFR. High pres. High confidence. Mon-Mon night...Generally VFR. A chance of shra/tsra which may briefly lead to MVFR/IFR. Gusty southwest winds 15-20 knots. Mdt to high confidence. Lower confidence of MVFR/IFR and precip coverage. Tue-Wed...VFR. High confidence. && .MARINE... Today...Southwesterly winds will continue through the day today, increasing this afternoon. For the New Jersey coastal waters, expect gusts above 25 kt to develop by mid afternoon, with seas expected to subsequently increase to 5 feet by this evening. For the Delaware coastal waters and the Delaware Bay, wind gusts above 20 kts are possible, but should stay below SCA criteria. Tonight...Winds and seas should subside before daybreak Saturday. Saturday...Sub small craft advisory conditions anticipated. Max gusts around 20 kt. OUTLOOK... Sat night-Sun...No marine headlines anticipated. Mon-Mon night...SCA conds psbl with increasing wind ahead of approaching cdfnt. Tue-Wed...No marine headlines anticipated. RIP CURRENTS...Added Cape May county to the moderate risk for the formation of dangerous rip currents this afternoon so that all of the NJ coast is now Moderate, while we`ve maintained low risk for the Delaware Beaches. Confidence on how much southerly component is a little below average so the moderate risk may end up low enhanced. Essentially... a 3-4 ft chop driven by gusty southwest wind of 15-20 mph is near parallel to shore. This will create a decent south to north long shore current and could result in some surprisingly strong rip currents by mid afternoon along the NJ shore, when also low tide occurs. Saturday: The probability for the formation of dangerous rip currents is Low. Looking further ahead, with the Atlantic Basin still devoid of tropical storms, the probable risk for the formation of dangerous rip currents should be low this weekend, especially with lighter winds and tendency more of an offshore component. Next Monday the 25th, we might have enough wave height to around 4 feet late in the day and water buildup due to southerly winds, to have a more widespread low enhanced or even moderate risk but confidence on seas building that high is below average. Water temperatures fell about 4 degrees between 6 am and 10 am, implying upwelling. Values were variably down into the mid 60s to lower 70s....colder along the NJ coast. Even colder upwelling may develop Saturday when the wind turns more westerly. && Barring afternoon convective cloud debris, record breaking heat is likely in our forecast area Monday. These records Monday are vulnerably low. Our 330 am grids fcst record warm values of 97 at Philadelphia and Wilmington Monday, 96 Allentown and a record equaling 96 at Reading. Other near record (within 2F) or record warmth can occur on other days, especially the 24th and 26th. Based on 12z guidance we may extend the records to the 28th... if we still are showing rather high modeled 2m temps. There may be a slight warm bias on these modeled 2m temps at extended we are cautious about adding any additional information. 23rd 24th 25th 26th 27th 28th PHL 101-2011 98-2011 96-1899 101-1892 101-1940 100-1941 ABE 99-1955 95-1999 95-1999 98-1940 98-1955 97-1949 ACY 105-2011 100-2011 99-2010 96-2011&1963 99-2005 98-1999 ILG 100-2011 98-2011 96-1987 99-1894 100-1894 101-1894 TTN 104-2011 98-1910 97-1999 99-1892 100-1894 101-1894 GED 104-2011 99-2011 99-2010 97-2012 98-2005 99-1949 RDG 100-2011 96-2010 96-1999 99-1940 98-1955 99-1941 MPO 91-1955 91-1914 90-1999 89-1949 91-1955 93-1949 && .EQUIPMENT... Lewes weather radio is intermittently off the air with an ac replacement needed. We hope to have it going late today. 44009 data has stopped transmitting (batteries failed). It may not be replaced til November. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...Excessive Heat Watch from Monday morning through Monday afternoon for PAZ060>062-101-103-105. Excessive Heat Warning from 11 AM Saturday to 6 PM EDT Monday for PAZ070-071-102-104-106. NJ...Excessive Heat Watch from Monday morning through Monday afternoon for NJZ007>010-012>014-016-020>027. Heat Advisory from 11 AM to 8 PM EDT Saturday for NJZ012>014- 016-020>027. Excessive Heat Warning from 11 AM Saturday to 6 PM EDT Monday for NJZ015-017>019. DE...Excessive Heat Watch from Monday morning through Monday afternoon for DEZ002>004. Heat Advisory from 11 AM to 8 PM EDT Saturday for DEZ002>004. Excessive Heat Warning from 11 AM Saturday to 6 PM EDT Monday for DEZ001. MD...Excessive Heat Watch from Monday morning through Monday afternoon for MDZ008-012-015-019-020. Heat Advisory from 11 AM to 8 PM EDT Saturday for MDZ008-012- 015-019-020. MARINE...Small Craft Advisory until 5 AM EDT Saturday for ANZ450>453. && $$ Synopsis...Nierenberg Near Term...Drag Short Term...Drag Long Term...Nierenberg Aviation...Drag/Nierenberg Marine...Drag/Nierenberg Climate... 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