Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 220643 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 243 AM EDT THU SEP 22 2016 .SYNOPSIS...
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High pressure will continue to build over the region and become established over our area through Friday with the remnants of Julia drifting offshore. A backdoor cold front will then move through the region early Saturday and be followed by another high pressure system building in from the northwest early next week. By the middle of next week, a cold frontal boundary will move toward the region from the west.
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&& .NEAR TERM /THROUGH TODAY/...
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Early this morning...cirrus bands, mostly thin with radiational cooling shallow fog expected by 6 am in parts of e PA and nw NJ. Today...Considerable sunshine with remaining bands of thicker cirrus thinning midday. Max temps 8-13 degrees above normal...greatest positive departure in the northwest portion of our area vcnty KABE and KMPO. light wind becomes east this afternoon around 10 kt with scattered gusts near 15, especially coasts. Forecast a max temp of 86F in PHL and confidence is very high that the max will fall in the range of 85-87F. KABE and KSMQ should be warmest with max temps around 87F, possibly even 88. Forecast basis started with a 50 50 blend of the 00z/22 GFS/NAM MOS.
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&& .SHORT TERM /TONIGHT/...
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Clear or mostly clear with radiational cooling and a few patches of fog possible late at night, the usual countryside suspects of ne PA and nw NJ. Forecast basis started with a 50 50 blend of the 00z/22 GFS/NAM MOS. I did lower that blend by 3-5F to fcst mins in the countryside lower than guidance but within a couple of degrees of the coolest GFS 2m temps (09z) which has widespread 48F Northampton/ Warren and Sussex counties in ne PA and NW NJ.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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Friday through Friday night: High pressure will continue become established across the region on Friday. Some cloudcover ahead of an approaching frontal boundary may keep low temperatures slightly higher Friday night. Friday looks like the last of the anomalous early fall heat for at least a little while with temperatures well into the 80`s. Modeled boundary layer temperatures indicators of surface temperatures match well with MET/MAV and ECMWF statistical guidance. Saturday through Monday night: A cold front will move from northeast to southwest across our region. Our coolest airmass of the season will advect in as another high pressure system dives southeast from Canada. Enough lift and moisture may be present for a temporary increase in cloud cover and isolated showers on Saturday otherwise continued dry conditions. temperatures will be much cooler for the weekend. Some indications in ensemble guidance have a slightly delayed frontal passage which may allow for Saturday to get into the 80`s. However, we will stick with the mean timing of early Saturday with the operational and ensemble guidance for the frontal passage. Much cooler air, a first real taste of fall with lows in the 40`s and 50`s with highs in the 60`s and 70`s. Less spread with temperatures Sunday and Monday with the ensemble guidance. Tuesday through Wednesday: The backdoor frontal boundary coupled with a mid-level ridge to our west look to setup an omega block which will likely slow the approach of the next cold frontal boundary or weaken as it moves east. As is usually the case in the 5-7 day time period uncertainty is present on the exact timing of this feature. The UKMET, CMC and some ensemble data weaken the front before it approaches our area. On the other spectrum, the GFS and GEFS are much faster bringing it through around Tuesday. Given this spread and questions if the front makes it to our area, will keep a dry forecast. Low and high temperatures should slightly warm each day unless the high pressure system sets-up just to our north. In that case an easterly flow could slow the approach of a warmer airmass expected ahead of the next front.
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&& .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Early this morning...VFR bands of cirrus with small chance of MVFR fog KABE/KMIV but not in the TAF due to low confidence. light north wind or calm. Today...VFR bands of cirrus thinning. Wind becoming east northeast around 10 kt this afternoon with scattered gusts around 15 kt. Tonight...VFR but may degrade to areas of ifr or mvfr fog after 06z, vcnty KMIV/KACY and KILG where a little more shallow moisture available. Nearly calm wind. OUTLOOK... Friday through Friday night: VFR.Varibale winds becoming west- southwest but staying under 10 knots. Saturday through Monday: VFR. An isolated shower possibile on Saturday. Northerly winds around 10 knots Saturday afternoon with gusts up to 20 knots then staying under 10 knots Sunday and Monday.
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&& .MARINE...
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A Small Craft Advisory for hazardous is in effect from Noon today to 6 am Friday. Have pulled back a bit on the extensiveness and duration of SCA conditions and converted to Haz seas. Forecast seas are a little less than previous guidance. The 18z GWES prob for >6 ft is southeast of our area, and pulling eastward faster early Friday. We dont have 44009 data to measure seas so we rely on BTHD1. Elsewhere for the Atlantic waters a 2 to 4 foot easterly swell of 11 seconds occasionally 6 seconds through tonight. De Bay a few gusts 20 kt today. Water temperatures continue above normal. OUTLOOK... Waveheights will start in the four to five feet range and should slowly decrease on Friday. GWES guidance indicates a fairly high confidence for seas to reach five feet Thursday night and early Friday. So have issued an SCA which goes through 18z Friday. This ending time may be slightly long but allows for wiggle room if waveheights respond slower, typical of easterly flow. For the weekend into early next week seas and winds are expected to remain below SCA criteria. RIP CURRENTS... There is a moderate risk for the formation of dangerous rip currents along the NJ shore and Delaware Beaches today, mostly driven by a 2-3 foot ese swell of 11 seconds and additional onshore wind wave created by an east northeast wind gusting 15 kt. Swim only in the presence of a lifeguard. Friday...A generally low or low enhanced risk is forecast. Weekend...There is a pretty good chance of a moderate risk for the formation of dangerous rip currents on at least one of the weekend days as a 4 to 5 foot ESE swell from Tropical Cyclone Karl arrives along with a gusty northeast wind.
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&& .CLIMATE...
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We`ll rereview the forecast monthly outcome at 5 am.
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&& .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory for hazardous seas from noon today to 6 AM EDT Friday for ANZ454-455.
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&& $$ Synopsis...Gorse Near Term...Drag 242 Short Term...Drag 242 Long Term...Gaines Aviation...Drag/Gaines 242 Marine...Drag/Gaines 242 Climate...

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