Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 211941 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 341 PM EDT SUN AUG 21 2016 .SYNOPSIS...
-- Changed Discussion --
A cold front was located just to our west this afternoon. The front will move eastward through the area this evening. High pressure builds into the area Monday and remain over the area through Thursday. The next cold front approaches from the northwest on Friday. The front may dissipate over the area next weekend while the center of high pressure approaches from the Great Lakes.
-- End Changed Discussion --
&& .NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
-- Changed Discussion --
A band of showers and isolated tstms associated with a cold front will cross the area this evening and early overnight. Showers will end from west to east behind this front. We have kept the pops mostly in the categorical range with the activity on radar looking rather solid attm. The best chc for thunder will be over Delmarva this evening. The primary threat with these showers and storms are locally heavy rainfall with 1-2 inches falling in an hour. Poor drainage flooding is possible. Any severe weather threat will be confined to the Delmarva and far southern NJ, where the strongest heating earlier in the afternoon and greatest instability (MLCAPE around 1000 J/kg) reside. Later tonight, skies will clear as drier and cooler air settles in. Lows will drop into the upper 50s/low 60s north and mid/upper 60s over Delmarva. Winds will shift to NW and remain around 5 to 10 mph overnight.
-- End Changed Discussion --
&& .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
-- Changed Discussion --
High pressure will begin to build towards the region Monday. This will be the beginning of a nice stretch of fair weather. The airmass will be cooler and much drier. High temperatures will only reach the 70s across the north and low/mid 80s elsewhere. Dew points will only be in the 40s/50s too...so this will be a big break in the recent stretch of sultry summer weather. Winds will be a bit gusty however with NW winds 10 to 15 mph and gusts around 20 mph.
-- End Changed Discussion --
&& .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
-- Changed Discussion --
Expansive high pressure system will build in from the west Monday night with the center of the high over the area Tuesday and Wednesday. The high will move offshore late Wednesday and retreat into the open waters of the northwest Atlantic Ocean through the end of the week. Southerly return flow around the western periphery of the high will become established along the eastern seaboard during this time. A very quiet stretch of weather is in store for the mid- Atlantic region through Thursday with the high firmly in control. Comfortable outdoor weather conditions can be expected with highs generally in the low 80s Tuesday and mid 80s both Wednesday and Thursday. It will be very dry midweek for August standards with dewpoints in the 50s. The humidity increases a bit by Thursday but it will still be at comfortable levels with dewpoints in the 60s. Each day should also offer plenty of sunshine. The heat and humidity increases further by Friday as a cold front approaches from the west. It doesn`t appear to be excessive heat but highs in the upper 80s to lows 90F and dewpoints near 70F will make it feel muggy again. In general, went a couple of degrees above WPC/Superblend guidance for highs on Friday as they appear to be too cool. The front should provide us with our first perceptible chance of precipitation in the period. However, we continue to advertise very low PoPs. The forecast area will be situated on the northern side of an anticyclone/upper ridge over the Southeast states. In this setup, there is a risk that the subsidence inversion underneath the ridge would put a lid on convective development on Friday, especially the farther south you go. Furthermore, the deeper lift will also be displaced from the front, remaining well to our north as the belt of stronger westerlies associated with the subtropical jet stream resides near the U.S.-Canadian border. The front may stall and then washout in the area or nearby during the weekend as it meets the downstream blocking on the northern periphery of the ridge. Exactly where this happens will determine if our region is positioned on the cool side of the front with highs in the lower 80s or warm side with highs in the lower 90s...or somewhere in between. Leaned toward the warmer range of solutions with the pattern favorable for heat to build underneath the ridge. At this time, it appears that next weekend should be mainly dry. However, if the front stalls over the area and there is still enough residual convergence along it, then an isolated pop-up shower or storm map develop during peak heating.
-- End Changed Discussion --
&& .AVIATION /19Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. A cold front will approach from the west this evening and then pass offshore overnight. A band of lower clouds and showers will accompany the front. There is a chc for thunder as well and we have included tempo groups in most terminals for show the expected conditions should a tstm occur. Winds will be mostly S or SW around 10-15 knots ahead of the front. Winds will shift to W then NW after frontal passage. Skies will clear out behind the front with drier air mixing in behind it. It`s possible that some light fog may develop across srn NJ with the drier air doesn`t make it this far before the boundary layer gets decoupled. I have included some fog in the MIV tafs for this possibility. VFR conditions expected with gusty NW winds up to around 20 knots on Monday. OUTLOOK... Monday night through Thursday night...Mainly VFR and light winds. Friday...Low chance for showers and storms with a cold front approaching from the NW.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Winds and seas slowly increasing this afternoon. An update was made earlier to raise the SCA flag for Del Bay where gusts around 25 kts had developed. We already were advertising SCA conditions for tonight, but decided to raise the SCA flag for the coastal waters earlier and put it into effect with the 330 CWF. Winds will likely gust into the low 20s kt range with the approach of the cold front and the tightening pressure gradient ahead of it. Seas will build to around 4 ft on the ocean and 2-3 ft across Delaware bay. Gusty winds should continue Monday with the arrival of the cooler and drier air. OUTLOOK... Monday night through Thursday...No marine hazards are expected. Friday...Winds and seas below SCA thresholds. The official NHC forecast for Tropical Storm Fiona is for it to track westward and then to weaken as it curves to the north near Bermuda late in the week. We may start to see long period swell arrive in our coastal waters by Friday or next weekend but unless the system becomes much stronger than forecast, seas will still be below 5 ft. RIP CURRENTS... Wind gusts from the southeast this afternoon coupled with wave heights of 3 to 4 feet are enhancing the setup for dangerous rip currents at the beaches. A moderate risk day was assigned to the New Jersey and Delaware beaches today. The probable risk for the development of dangerous rip currents on Monday is low with an offshore wind expected.
-- End Changed Discussion --
&& .PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 7 PM this evening to 11 AM EDT Monday for ANZ452>455. Small Craft Advisory from 7 PM this evening to 6 PM EDT Monday for ANZ450-451 and ANZ430-431.
-- End Changed Discussion --
&& $$ Synopsis...Klein Near Term...O`Hara/Klein Short Term...O`Hara Long Term...Klein Aviation...Klein/O`Hara Marine...Klein/O`Hara

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.