Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 132234 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 634 PM EDT Wed Sep 13 2017 .SYNOPSIS...
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An upper air low pressure system will weaken as it moves across the Middle Atlantic region tonight through Friday. A weak high pressure area will affect the weather for the weekend. Hurricane Jose is expected to remain well offshore this weekend and into early next week. Low pressure and a front from the midwest will arrive over the area later next week.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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The band of rain showers had lifted to the north and northeast of our region by 6:00 PM. We are not anticipating any additional showers before midnight based on the latest guidance. As a result, we have removed them from the forecast. Patchy drizzle will continue this evening in parts of eastern Pennsylvania and New Jersey. The clearing over parts of northeastern Maryland and central and southern Delaware was making slow progress northward this evening. The warm air to our south was riding over the slightly cooler air associated with the low clouds and drizzle. We continue to think that the sky should favor cloudy in eastern Pennsylvania and New Jersey for tonight with the clouds possibly expanding southward as daytime heating ceases. The wind is forecast to be light and variable for tonight with patchy fog developing. Low temperatures should favor the 60s.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/... Irma`s weakening trough aloft passes overhead tomorrow and with a moist boundary layer...this should allow at least one band of showers to cross the area. Instability aloft might allow a thunderstorm. For now...model differences in the instability axis are present, so have favored the GFS and its newd punch of greater instability across DE/NJ late Thursday morning/afternoon. This portion of the forecast was a 50 50 blend of the 12z/13 GFS/NAM MOS. && .LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
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A closed upper air low pressure system, which is what is left over from Irma, will be weakening across the area during the beginning of the long term. The low will diminish into an positively tilted upper trough which will linger across the region into early next week. It will cause showers from Thursday to linger Thursday night and into Friday. Mostly scattered showers are expected with little in the way of organized surface features present. We will carry smaller chances for showers into Saturday and Sunday afternoon as well, but it is not expected to widespread or frequent. Overall, the forecast hasn`t changed too much from earlier. Temperatures for late this week and into the weekend will be a little above normal with upper 70s to low 80s for highs and lows generally in the 60s. Patchy morning fog is expected in rural/river valley areas. Hurricane Jose will spin across the western Atlantic waters into the weekend. It is not presently expected to affect our weather directly, but higher seas and longer period swells may create some hazardous rip currents at beaches. The National Hurricane Center will continue to issue advisories for this system, so consult those for the latest. Remember, we are at the peak of hurricane season, so make sure you have plans just in case. Next week, Jose will likely be moving away from the area, while an upper ridge begins to build across the Eastern U.S. This will contribute to lessening chances for showers and a continuation of temperatures above normal. We will carry a dry fcst for Mon-Wed at this time.
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&& .AVIATION /00Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Conditions are forecast to favor MVFR this evening at KPHL, KILG, KMIV and KACY. They should vary between IFR and MVFR at KPNE, KTTN, KABE and KRDG. The forecast for tonight is one of low confidence. It appears as though conditions will deteriorate as low level moisture remains trapped in our region. We are anticipating a light and variable wind for tonight. Thursday...IFR st/fog may persist through 15z vcnty KABE/KRDG otherwise conditions improving to VFR cigs, but lowering to MVFR conditions in a band or two of showers. slight chc of a tstm. light south to southwest wind. OUTLOOK... Thursday night-Friday morning...Lower CIGS/VSBYS possible with showers and some fog late. Friday afternoon thru Monday...Mostly VFR. Sct afternoon showers. Patchy early morning for with lower VSBYS psbl.
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&& .MARINE...
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No marine headlines through Thursday. Patchy fog possible tonight. Otherwise, leftover showers should end this evening. Long period 3-4 foot se swells continue on the Atlantic waters. OUTLOOK... Thursday night-Friday night...Generally sub Small Craft Advisory conditions expected. Seas forecast to be 3-4 feet. Saturday-Monday...Conditions may reach Small Craft Advisory levels as seas may build to 5 feet. Sct afternoon showers. Rip Currents... This evening...Moderate except added HIGH risk of RC to 3 NJ counties for the remainder of this afternoon...our calculator has no more than moderate risk but a report of lifeguard concern prompted the issuance. Thursday: Moderate risk for the formation of dangerous rip currents. Long- period (10-14 sec) southeasterly swells from Hurricane Jose continue. Looking ahead...a low or moderate risk is expected Friday then larger longer period swells from tropical cyclone Jose should arrives this weekend and we expect moderate or high risk days from Saturday through at least next Tuesday with swells building to 5 to 6 feet and period lengthening to near 15 seconds. Even surfers can suffer injury from wave slam and certainly swimmers are asked to follow lifeguard and other official advice... and in my opinion...in these upcoming conditions its not worth the risk.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...High Rip Current Risk until 9 PM EDT this evening for NJZ024>026. DE...None. MD...None. MARINE...None. && $$ Synopsis...O`Hara Near Term...Iovino Short Term...Drag Long Term...O`Hara Aviation...Drag/O`Hara/Iovino Marine...Drag/O`Hara

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