Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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488 FXUS61 KPHI 230941 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 541 AM EDT Sun Oct 23 2016 .SYNOPSIS... The next cold front will slide through our region late tonight into Monday morning. A high, currently over central Canada will build south towards our region through mid week. A warm front, followed quickly by another cold front is expected in our region at the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... High pres will build in from the s today. As it does, strong low pres will remain in place over ern Canada. The pgrad between these 2 sys will cause gusty nw wind again this aftn, but not as strong as on Sat. Overall, a dry and more pleasant day is in store with high temps mainly in the 50s n and w and 60s elsewhere. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... A weak disturbance will move acrs nrn areas tonight. This feature will bring some showers, but any rain will be over with before daybreak. The vast majority of the guid keeps precip confined to nrn sections, while the ECMWF wants to bring it a bit further s. For now will go with the more nrn soln. && .LONG TERM /MONDAY THROUGH SATURDAY/...
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Monday and Tuesday...models have sped up the development of the northwesterly flow pattern, and thus the cold air advection. Therefore, expect a bit of a cooling trend with highs tomorrow, and then even more pronounced on Tuesday. Monday night begins what will likely be the first of several nights with frost/freeze potential for much of the area where the growing season continues. With another day of cold air advection, and even better radiational cooling conditions, Tuesday night looks to be even colder, with a freeze likely for much of southeastern PA (with the exception of the Philly metro area), and the remainder of NW NJ. the high moves closer, flow shifts more northerly, but still quite cool with highs about 10 degrees below normal. There will be another risk for freeze on Wedensday night. However, unlike Tuesday night, increasing clouds late may somewhat limit radiational cooling. If the clouds come in early enough, this could inhibit frost development. For now, kept a mention of patchy frost for areas with a forecast min of 36 degrees or less, but may have to adjust both the min temp forecast and mention of frost if the trend continues with low and mid level clouds moving in before dawn. Thursday and Friday...Models came into much better agreement with the track of the extra tropical low lifting across the Great Lakes region and into Quebec through this time. However, there remain some timing differences, with the GFS being the more progressive solution, while the ECMWF and CMC are slower. Still, with this track, it looks like a warm front will lift through our region sometime on Thursday. Within the warm sector, we should see increasing chances for precipitation across the region. Then, a cold front should sweep through the region on Friday. Those are the factors that the models agree on. However, the GFS is depicting a mid level short wave trough lifting through the region ahead of the warm front on Thursday morning, providing enough lift for some pre frontal precip. This is significant because GFS model soundings across the Poconos indicate that if this does happen, it could be a rain/snow mix. However, it is a very small chance especially considering that neither the CMC and ECMWF are depicting this and there would be limited opportunity for moisture advection ahead of the front. For now have only mentioned a chance of rain and snow across the Poconos through Thursday morning, before switching precip to all rain. Saturday and Sunday...models are depicting the cold front stalling near or just south of our Delmarva counties. However, this seems unlikely given the upper level northwesterly flow pattern. Thus...have kept the forecast dry beyond Friday.
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&& .AVIATION /10Z SUNDAY THROUGH THURSDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. VFR conds are expected thru the TAF pd, with high pres genly in control. A weak disturbance will move acrs nrn sections tonight and bring some SHRA, but precip shud be light enough that no impacts to cigs or vsbys are expected. Dry conds are expected again by daybreak Monday. A gusty nw wind is expected again this aftn, but it will not be as strong as on Sat. Gusts to 25 kt are psbl, with wind subsiding to 10 kts or less after sunset. Outlook... Monday through Wednesday...mostly VFR conditions expected. Wednesday night and Thursday...ceilings should lower through the overnight hours to MVFR (with possible localized IFR) by mid day Thursday. Visibility restrictions possible with rain showers later in the day. && .MARINE... The gale warning on upper Delaware Bay has been dropped and replaced with a SCA which is in effect until 21Z. For lower Delaware Bay, gusts around gale criteria keep occurring, so the GLW remains and has been extended. The gale warning remains in effect on the Ocean waters. The only change is that zone 453 has been added to the later expiration time. Outlook... Monday and Tuesday...SCA conditions are expected to continue as winds should continue gusting above 25 kt (though seas may drop off below 5 ft. Wednesday and Thursday...winds and seas should stay below SCA criteria. Thursday night...winds could increase above SCA criteria on the coastal waters late. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 PM EDT this evening for ANZ450>452. Gale Warning until noon EDT today for ANZ431-453>455. Small Craft Advisory until 4 PM EDT this afternoon for ANZ430. && $$ Synopsis...Johnson Near Term...Nierenberg Short Term...Nierenberg Long Term...Johnson Aviation...Johnson/Nierenberg Marine...Johnson/Nierenberg is the U.S. government's official web portal to all federal, state and local government web resources and services.