Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 221501 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1001 AM EST Wed Feb 22 2017 .SYNOPSIS... High pressure will remain anchored just off the east coast through midweek. A backdoor cold front over New England may approach the area, before moving northward as a warm front Friday into Friday night. Low pressure moving through the Great Lakes region will bring a strong cold front through the area on Saturday. High pressure builds in from the west late in the weekend, before moving offshore early next week, while another warm front approaches the area. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Water vapor satellite imagery subtly captures a weak shortwave trough moving thru the northern Mid Atlantic this morning. This disturbance has resulted in a cloudy start to the day. Additionally, regional radar mosaic showed multiple bands of light rain showers. Kept PoPs below 20 percent with sprinkles across the I-195 corridor and in far southern zones of DE/eastern MD for late this morning. A more organized band of precipitation farther north (along and north of I-80) warranted raising PoPs to introduce light rain showers to the forecast thru the early afternoon. Otherwise, a dry afternoon is in store. Hourly PoP/Weather grids were updated earlier in the morning and sent to the web around 8 AM. Temperatures have been slower to rise so far this morning than previously forecast, likely owing to the overcast skies that have tempered our ability to mix out the nocturnal inversion. Blending our previous forecast with some of the latest rapid refresh guidance resulted in max temperatures that are only a degree or two lower than previous forecast. Therefore, we should be able to warm rather quickly during the afternoon, especially once the cloud cover thins out mid to late afternoon, despite the slow start. The record highs for today are listed in the climate section below. Most locations will fall several degrees short of their record based on our latest projections. However, Mount Pocono may get close their daily record...a forecast high of 56F would tie their daily record.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... The surface high is forecast to begin moving farther out to sea tonight. However, it should keep a light southwest to south surface flow in our region. The increase in low level moisture may result in the development of low clouds and patchy fog late tonight. Temperatures are expected to remain mild for this time of the year. Minimum readings should favor the 40s in northeastern Maryland, Delaware, New Jersey and much of eastern Pennsylvania. && .LONG TERM /THURSDAY THROUGH TUESDAY/... A more active pattern is shaping up for the Thursday thru Tuesday period, with the most impactful weather expected on Saturday in association with a strong cold, preceded by the potential record warmth Thursday into Saturday. In terms of the mid-level pattern, a split flow regime will begin to consolidate as phasing takes place over the upper Mississippi Valley on Saturday. In spite of a couple fast moving shortwave impulses near the area Thursday into Friday, 500 hPa heights will continue to rise, reaching 570 Decameters by Saturday. A more zonal pattern takes hold Sunday night into Tuesday, as temperatures return to near normal for a change. Several shortwave disturbances embedded within the zonal flow will increase chances for generally light precipitation during this time frame. Thursday and 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. In fact, there could be a rumble of thunder both days, especially on Thursday. Also, there is the potential for record highs on both Thursday and Friday. Given the proximity of a backdoor front, which may make it into northern NJ on Friday, in addition to increased cloud cover, record warmth potential is greater on Thursday. Finally, there is the potential for some patchy fog both Thursday and Friday mornings. Saturday and Sunday...Saturday could be an active day as a strong cold front moves through the region. We should be within the warm sector, and the synoptic pattern is favorable for at least a fine line of convection to move through much of the area. Model soundings show a modest shear-low CAPE environment, in addition to negative Showalter indices. While this is still a ways out, there is at least a chance of thunder, and this continues to be reflected in the forecast. In addition, some heavier downpours are possible, with the potential for rainfall amounts to approach one inch, especially closer to the Poconos. Once again, record warmth is possible within the warm sector on Saturday. If the timing of the system holds, fair weather is in store for Sunday, with a return to near normal temperatures, and gusty west-northwest winds. Looking ahead to Monday and Tuesday, several shortwaves will interact with a nearby frontal boundary, offering additional chances of light precipitation. Details in timing and coverage are low at this time, so the forecast reflects a general slight chance of showers during this period. We expect temperatures to continue near average as mentioned earlier. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
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The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Mainly VFR conditions expected through early tonight. However, lower CIGs with stratus detected over Delmarva may spread downstream and briefly result in MVFR CIGS at MIV thru about 17Z. Lower confidence that stratus reaches ACY. Otherwise, CIGs should be above 7 kft today. Decreasing cloud cover is forecast for the mid to late afternoon and into this evening. Increasing low-level moisture late tonight may result in the development of low clouds and some fog. There is the potential for MVFR and IFR conditions at that time. Confidence in the onset and extent of the stratus/fog is low at this time. A light southwest to south wind is anticipated to develop for today at speeds around 4 to 8 knots. The wind should become light and variable at most locations for tonight. OUTLOOK... Thursday...Potential for MVFR/IFR in early morning clouds and fog, otherwise, VFR. Southwest wind gusts to 20 knots possible in the afternoon. Thursday night through Saturday...There is the potential for MVFR/IFR at times, especially Thursday night through Friday night with a warm front nearby, and again on Saturday with showers and potential thunderstorms ahead of a cold front. Winds out of the south on Saturday could gust to at least 20 knots. Saturday night and Sunday...Becoming VFR Saturday night with gusty west-northwest winds anticipated into Sunday.
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&& .MARINE... High pressure located off the Middle Atlantic Coast today should maintain a southwest to south flow over the coastal waters of New Jersey and Delaware for today and tonight. Wind speeds and gusts should remain mostly less than 15 knots. Wave heights on our ocean waters are forecast to range from 2 to 3 feet. Waves on Delaware Bay are anticipated to be 2 feet or less. OUTLOOK... Sub-SCA conditions are forecast Thursday into Friday. SCA possible Friday night into Saturday, with gales possible Saturday night into Sunday. && .CLIMATE... High temperature records for Wednesday-Saturday. Although most of these records will probably remain intact, the greatest potential to break a few of these records will be on Thursday. Wednesday 2/22 Thursday 2/23 Friday 2/24 Saturday 2/25 ACY 68-1991 72-1985 75-1985 77-1930 PHL 68-1997/1974 75-1874 74-1985 79-1930 ILG 69-1997/1974 72-1985 78-1985 78-1930 ABE 68-1974 71-1985 76-1985 74-1930 TTN 66-1997 74-1874 74-1985 76-1930 GED 72-1997 67-1985/1990 72-1961 76-1975 RDG 70-1974 72/1932/1922 77-1985 77-1930 MPO 56-1997 60-1977 60-1984 70-1930 && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Franck Near Term...Klein Short Term...Iovino Long Term...Franck Aviation...Franck/Iovino/Klein Marine...Franck/Iovino Climate...

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