Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231548 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1048 AM EST Thu Feb 23 2017 .SYNOPSIS... A cold front moving through the Great Lakes today will stall just north of our region tonight into Friday, before lifting northward as a warm front Friday night. This will be followed by a strong cold frontal passage on Saturday evening. High pressure will traverse the middle Atlantic Sunday into Monday. A frontal boundary will setup near our region during the early to middle part of next week, and several waves of low pressure are expected move along it. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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The Dense Fog Advisory has been cancelled for the entire area just before 10 AM. Visibilities continue to improve area wide with all ASOS/AWOS sites reporting 1/2SM or above. 15Z visible satellite shows whats left of the stratus deck over far northern Delmarva, southwestern and central NJ and eastern PA (south of I-80). These low clouds will take longer to erode (possibly not until mid afternoon in spots) given the relatively low sun angle right now and a lack of dry air advection. Now that we see the whites of it eyes, it has become evident where the temperature gradient will setup due to differential heating. Max temperatures were adjusted accordingly. The rapid refresh guidance and 12Z NAM was blended with the previous temperature forecast since these newest available models seem to capture the evolution of the stratus erosion better. Forecast highs in the lower to mid 70s in eastern MD, DE and southern NJ will be near record today (a certainty for GED). Despite the cloudy start, there is still a shot at reaching 70F in Philadelphia today since the city is on the southern fringe of the stratus deck and thus should thin sooner. Farther north, the area between I-195/PA Turnpike and I-78 will likely struggle to reach 60F until the low clouds erode this afternoon and then may only max out in the mid 60s. Clear skies north of I-80 will allow temperatures to quickly warm into the 60s before stratocu arrives ahead of a cold front this afternoon.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Our region should be more solidly in the warm air for tonight. As a result, we may see more stratus than fog development except near the water. Nevertheless, we will continue to mention at least some patchy fog for late tonight. Scattered showers may spread across parts of eastern Pennsylvania and northern and central New Jersey. Rainfall amounts should be light, generally a few hundredths of an inch. The wind is forecast to be light for tonight and low temperatures should range from the middle 40s in the Poconos and far northern New Jersey to the lower 50s on the coastal plain. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Active pattern in the Friday thru Wednesday period. Dense fog is possible Friday and Friday night. There is a marginal risk of severe thunderstorms on Saturday. There is also the potential for daily record high temperatures on Friday, especially Delmarva. Temperatures cool to seasonal levels on Sunday. A more zonal flow sets up in the Monday thru Wednesday time frame with additional chances of light precip along with a return to above average temperatures. There is a lot of uncertainty regarding coverage and timing of precip in the early to middle part of next week. Friday will feature a warm front just north of the area, with diffuse shortwave energy moving along it. This will promote the chance for scattered rain showers, mainly north of an I-195 to PA Turnpike line. Given the proximity of a warm front, which may briefly backdoor to the south, we anticipate considerable cloudiness across much of NJ and eastern PA. This is reflected in our temperature grids, and will likely limit record high potential across this area. Further south across Delmarva, we have maintained warmer temperatures (mid-70s), and thus there is a greater potential of setting records across this area. With the nearby frontal boundary, we expect fog through mid- morning Friday and again Friday night. The fog could be dense, and we have continued a mention of this in the HWO. Saturday and Sunday...A strong cold front moves through the region Saturday evening. The synoptic pattern is favorable for a squall/convective line to move through much of the area, and SPC has placed our entire region within a marginal risk of severe thunderstorms in their day 3 convective outlook. Thus, we maintain a chance of thunder in the forecast. Some heavier downpours are also likely, but amounts are expected to be less than one inch. High temperatures on Saturday are expected to fall just shy of daily records. Fair weather is expected for Sunday, with a return to near normal temperatures, and gusty west-northwest winds. Looking ahead to Monday thru Wednesday, several shortwaves will interact with a frontal boundary that sets up near our region, offering additional chances of light precipitation. Details in timing and coverage continues to be low, so the forecast shows a general slight chance of showers during this period. Snow showers are possible Monday and Tuesday nights. We expect temperatures to return to above average levels, generally around 5 to 10 degrees above normal. && .AVIATION /15Z THURSDAY THROUGH MONDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. At 1030 AM...Visibilities continue to improve everywhere with the fog lifting. However, stratus deck has kept CIGs at LIFR or IFR north and west of MIV/ACY. Expect these low clouds to slowly erode generally between 16-19Z: first at ILG, then PHL/RDG/ABE and last at PNE/TTN. IFR or low-end MVFR CIGs will persist until then. VFR conditions are anticipated from mid afternoon and into this evening for most locations. However, convective showers and perhaps an isolated thunderstorm may organize ahead of a cold front this afternoon, possibly reaching RDG-ABE during the late evening or overnight. Then a return of low clouds and fog is expected late tonight. A light southwest and south around 5 kt this morning will increase to 10 kt this afternoon. Gusts at or slightly above 15 kt are likely for the southern (PHL south) mid to late afternoon. The wind is anticipated to become light and variable again for tonight. OUTLOOK.. Friday through Saturday...There is the potential for MVFR/IFR at times, especially Friday night, and again on Saturday with showers and potential thunderstorms ahead of a cold front. Winds out of the south on Saturday could gust up to around 20 knots. Saturday night and Sunday...Becoming VFR Saturday night with gusty west-northwest winds anticipated into Sunday, 25 to 30 knots at times.
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&& .MARINE...
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The Dense Fog Advisory continues for the NJ coastal waters north of Great Egg Inlet through noon. This may need to be extended into this afternoon if the fog bank that is seen on visible satellite is slower to drift farther offshore than our coastal water extends out to (i.e., 20 nm out). A southwest to south flow will continue on the coastal waters of Delaware and New Jersey for today and tonight. Sustained wind speeds should remain less than 15 knots with no gusts in excess of 20 knots. Wave heights on our ocean waters should range from 2 to 4 feet. Waves on Delaware Bay will likely be 2 feet or less. Another round of dense fog may occur over the waters as early as late tonight or early Friday morning. We will consider issuing a marine dense fog advisory sometime this afternoon. OUTLOOK... Dense fog on Friday could potential persist into Saturday across a portion of the waters as anomalously moist air (characterized by dewpoints in the 50s) ahead of a cold front moves atop the colder waters (SSTs still in the low to mid 40s). Sub-SCA conditions are forecast Friday. SCA possible Friday night thru Monday, with period of gales possible on Sunday. Sub- SCA conditions are forecast Tuesday.
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&& .CLIMATE... For reference, here are the high temperature records for Thursday, Friday and Saturday. Location Thursday 2/23 Friday 2/24 Saturday 2/25 ACY 72-1985 75-1985 77-1930 PHL 75-1874 74-1985 79-1930 ILG 72-1985 78-1985 78-1930 ABE 71-1985 76-1985 74-1930 TTN 74-1874 74-1985 76-1930 GED 67-1985/1990 72-1961 76-1975 RDG 72/1932/1922 77-1985 77-1930 MPO 60-1977 60-1984 70-1930 The following monthly and seasonal expectations were recalculated with todays max/min and then the official 330 PM Mount Holly forecast. It is virtually certain that the numbers below will stand and that our forecast area is experiencing a record warm, or at least a 2nd warmest February on record and a top 10 warmest winter. Records date back to the late 19th century. Details below. These values are probably on the lower side of the solutions. February: PHL 43.3. #1 Normal 35.7 Record 42.2-1925 POR 1874 ABE 37.6 #2 Normal 30.7 Record 38.6-1998 POR 1922 ACY 42.2 #1 Normal 35.3 Record 41.6-1890 POR 1874 ILG 42.3 #1 tie Normal 35.1 Record 42.3-1903 POR 1895 Note for ABE: There is a pretty good chance ABE will end up warmer and possibly very close to their monthly temp record. Winter (DJF) PHL 40.1 #7 ABE 35.4 #5 ACY 39.6 #10 ILG 39.1 #6 tie Past two years of monthly average temperatures through February 2017, a summary of above normal months listed below: For ABE: 23 consecutive months of above normal temps! FOR PHL: 22 of the past 23 months have been above normal. For ACY: 19 of the past 23 months have been above normal. For ILG: 17 of the past 23 months have been above normal. (Jan Feb March 2015 was the last time we had significant and persistent below normal monthly temps.) Snow: Atlantic City should/could end up tied for 5th least snowiest February on record. && .PHI WATCHES/WARNINGS/ADVISORIES...
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PA...None. NJ...None. DE...None. MD...None. MARINE...Dense Fog Advisory until noon EST today for ANZ450>452.
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&& $$ Synopsis...Franck Near Term...Klein Short Term...Iovino Long Term...Franck Aviation...Franck/Iovino/Klein Marine...Franck/Iovino/Klein Climate...Drag/Klein

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