Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 300058 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 858 PM EDT Sat Apr 29 2017 .SYNOPSIS...
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A cold front across the Delmarva will slide south then stall before returning northward into our area as a warm front Sunday night. Low pressure and its associated fronts move toward the Middle Atlantic states later Monday and Monday night. High pressure will build in for the middle of next week. Another low will affect our area towards the end of next week.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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930 PM ESTF: expecting the sfc convergence to increase during the night in the high PWAT air along the front across the Delmarva and expect showers to develop, possibly heavy with maybe isolated thunder. Otherwise, a wind shift to the north and northeast will move from north to south overnight as part two of the cold front works southward. Low temperatures were mostly a MOS/continuity blend and the downward trend was delayed a little. Max temps for ACY PHL Sunday may be occuring at 1 am.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
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The 630 PM Saturday update added chance of sprinkles to much of the area Sunday morning and the 930 PM raised pops slightly and called it isolated showers or scattered sprinkles. The reasoning...some of the models are producing qpf and while there is a generally ely bl flow, there is waa above the inversion (above 900mb) and small sign of a lobe of instability moving newd during the morning that also gives a deep vertical 2 hr wide spike in rh. I wanted to put the uncertainty of a shower in the fcst for Sunday morning. The weather will be rather different Sunday compared to today (Saturday) in the wake of a cold front. This front is expected to clear our entire area before stalling in a west to east orientation. An upper-level ridge axis should be moving across our area, allowing surface high pressure to build to our north and east. This will allow for a northeast low-level flow which should become east and then southeast with time. This will allow for a much cooler airmass to be over our area, enhanced by the flow off the colder ocean waters. While there may be areas of stratocumulus, the cloud bases may lower especially in the afternoon as the flow turns more east and southeast resulting in some increase in the moisture. Overall though, there should be a fair amount of cloudiness across the region during the day. High temperatures were a MOS/continuity blend, then some tweaks were made mostly along the coast.
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&& .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... A weak ridge of high pressure will be across the area during the start of the long range. It will remain in place through Monday before moving to the east. Dry weather is expected Sunday night, then clouds will increase Monday along with the chances for a few showers across the N/W areas Monday afternoon. Temperatures will be above normal with highs Monday in the low 80s over srn NJ and Delmarva while highs will be in the mid/upper 70s across the N/W areas. A low pressure system across the upper Great Lakes Monday morning will move NE across southern Canada through Wednesday. A strong cold front will move across the Middle Atlantic Mon night and into early Tue. There appears to be a decent chc for showers and tstms with this front, so only small changes to the already high pops were made today. We have categorical pops N/W and high Likely S/E. It could be a 1/4 to 1/2 inch rain producer, higher in tstms. On Tuesday, the front will be east of the area, but the lingering upper low aloft will lead us to keep the chc for some showers into the early afternoon. High temps Tue will still be a little above normal S/E but by Wed, readings will be close to normal for early May. A short period for far weather Wed/Wed night with an area of high pressure across the area. Another low will approach Thu and will again bring decent chc for showers and sct tstms (Delmarva) for the end of next week. We have some likely pops for many areas Thu/Thu night and chc pops for Fri/Sat. Temperatures will be near or below normal towards the end of the week. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Tonight...VFR with a few clouds near 5000 feet and cirrus on top. A broken deck of clouds near 5000 ft will form...develop newd into the TAF sites toward 09z/30 and there may be a few showers vcnty KILG. Winds northwest then shifting northeast after 06z/30. Gusts generally under 18 kt. Please see TAFS for the details. Sunday...VFR ceilings may lower to MVFR through the day, however confidence is below avg on timing any lowering to MVFR CIGS. Chance of a morning sprinkle or shower (waa- elevated instability) Northeast winds around 10 knots, becoming east and southeast in the afternoon. OUTLOOK... Sunday night-Monday morning...IFR conds in st/fog and possible drizzle in light moist maritime easterly flow north of a warm front. Mon Afternoon...Mostly VFR expected. Mon night thru Tue...Restrictions with showers especially Mon night. Tue night thru Wed night...Mostly VFR. Patchy morning fog psbl. Thu...Restrictions possible with showers.
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&& .MARINE...
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A cold front has sort of stalled from the vicinity of Cape May NJ westward to the northern part of Chesapeake Bay, there will be a reinforcing of the front from the northeast toward 12z and hat will force it further to the southwest during the day Sunday. There could be a northeast to east wind surge Sunday especially across the northern coastal waters zones, however for now, gusts are below 25 knots. The duration of this does not look long enough and therefore kept seas 4 feet or less. OUTLOOK... Sun night thru Mon morning...Sub-SCA conditions with Patchy fog and possibly some drizzle. Monday afternoon thru Tue night...SCA expected. Showers with sct tstms. Tue night...SCA on the ocean and sub-SCA across Del Bay. Fair. Wed thru Thu...Sub-SCA. Fair thru Wed night then sct showers Thu.
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&& .CLIMATE... RER for the new record high temperature at Georgetown, DE...91 at 241PM was issued. Atlantic City was 1 shy (91). Atlantic City doesn`t normally reach 90 until June 11 although the long term statistical database may be skewed to cooler temperatures closer to the coast. The earliest 90 degree day at Atlantic City occurred April 7, 2010. **Record or number 2 warmest April on record** Presuming our forecast temps these last 30 hrs of April are accurate, we are assured of a top 2 warmest April on record in much of our forecast area. Sunday temps determine record or not. Just Below: April projected within the top April average temps, the normal for April and the period of record (POR). This includes todays (29th) high and low temperatures through 4 PM. Sundays max temps may occur at 1 am and the min temps Sunday evening. PHL normal 54.0 POR 1874 59.5 2017 Projected warmest ever: still could slip .2 degrees. 59.4 1994 58.5 1921 58.4 2010 57.9 1941 ABE normal 49.9 POR 1922 56.8 projecting record and almost cant miss a record. 56.4 1941 54.7 1994 ACY normal 51.7 POR 1874 57.6 projecting record and almost cant miss. 56.3 2010 56.1 2011 && .EQUIPMENT...
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We are aware of the DOV dewpoints being excessively high the past two days and even far too high this evening.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Drag/O`Hara Near Term...Drag 859 Short Term...Drag 859 Long Term...O`Hara Aviation...Drag/O`Hara 859 Marine...Drag/Gorse/O`Hara 859 Climate...859 Equipment...859

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