240 FXUS61 KPHI 021915 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 215 PM EST Sun Feb 2 2020 .SYNOPSIS... A weak upper level disturbance will bring a round of light precipitation to the northern half of the area today. High pressure will build across the southeastern US early next week as another low passes well north of the area across eastern Canada. An approaching trough over the Central US will result in a prolonged period of unsettled weather from Tuesday through the end of the week with several systems impacting the region through the period. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... 130-150 kt jet at 250 mb working its way through the region along with strong shortwave energy in the middle layers of the atmosphere. A line of precip, mostly rain south of the Fall Line, although a few wet snowflakes are possible, and mostly snow north and west of the Fall Line, will work its way east through early this evening. This precip seems to be moving quicker than originally thought, as it has already cleared the Delaware valley and Delmarva, and should be offshore by 7-8pm. Most QPF will be light, especially south of the Fall Line. North of the Fall Line, however, the shortwave energy will be slower to depart, so some snow showers will continue through this evening. Around an inch of snow possible, though some spots in the southern Poconos could get up to two inches. After midnight, skies clear out as high pressure begins to build in from the west. 850 mb temps will rise from around 0C to +3C in southern areas, and as a result, overnight lows should be a few degrees warmer than last night. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... Surface high pressure builds in from the south and west on Monday with rising heights and thicknesses. Abundant sunshine on tap along with west winds 10-15 mph with gusts up to 20 mph. In terms of temps, there are some differences between the NAM and the GFS. For Delmarva, both have highs in the lower 60s, however, for southeast Pennsylvania and most of New Jersey, the NAM has highs some 5-7 degrees colder compared to the GFS, and the GFS is similar to the previous forecast. Will go ahead and use the GFS and mix down from the mixing height (around 900 mb or so) and blend with consensus MOS guidance to have highs in the low to mid 60s in Delmarva, mid to upper 50s to around 60 in the Delaware valley and southern New Jersey, and mostly in the mid 50s otherwise except for the southern Poconos, which should be in the mid to upper 40s. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... The long term continues to look like an active period for the region, with multiple upper level disturbances traversing the area. Monday and next Saturday will likely be the only dry days for the entire extended period, with Tuesday through Friday featuring above normal precipitation and temperatures. On Monday, an expansive area of high pressure will build across the eastern United States allowing for mostly sunny skies with highs in the 50s (northern NJ) and 60s (southern DE). Late Monday afternoon cirrus will begin to thicken from the southwest as southern stream energy lifts north. Precipitation will then approach from the southwest as a weak rex block that was located just southwest of California collapses. The demise of the block will come from an upper level low diving south over the west coast late Sunday. This low will then nudge the weak low that was part of the rex northeast. As the low heads northeast Monday evening it will open up washing over the area Tuesday morning. Models are in really good agreement here that this will be the first chance of rain for the area. The wave will then exit the region Tuesday evening with mostly cloudy skies behind. The upper level low that was diving south over the western United States Sunday evening will be slowly heading east over the four corners region Tuesday evening. Unfortunately, it looks like this low will dive to far south and be out of phase with a much stronger low over the Hudson Bay. This means multiple rounds of precipitation appear likely. The first round will be Wednesday in association with a surface cold front. Support for this cold front looks impressive, as an upper level jet streak strengthens over northern New York. This would place the PHI CWA solidly in a RRQ. PWATs ahead of the front are also expected to surge up towards around 1.10". This would be near max values for this time of year. Given the above, have nudged PoPs up for Wednesday. The surface cold front will cross the area Wednesday morning, with temperatures falling during the day. The ECMWF is fastest with the cold front, and brings it through the area early Wednesday morning. The GFS is slowest with front, and waits to push it through the area until Wednesday afternoon. The CMC appears to be a good compromise here (mid Wednesday morning frontal passage). Most of the precipitation should fall as rain with the frontal passage, with a change over to snow on the backside across the higher terrain. Wednesday night into early Thursday morning there will then be a brief break in the precipitation before round two of the precipitation arrives. Early Thursday morning, returns on the radar will again be approaching from the southwest as strong isentropic upglide commences. At the 300 K and 295 K surfaces winds approaching 50 kts on the GFS was noted. Condensation pressure deficits also quickly fall off to zero. The strength of the upglide here is impressive with rain continuing all day Thursday. Across the northern zones, a period of snow changing over to sleet, then freezing rain, and finally rain looks likely. The continued precipitation into the shallow cold dome, will also help to keep temperatures locked into the 30s and 40s for most of the area. The one exception here will be southern Delaware with highs in the 50s. Have lowered highs Thursday, given the above. Thursday night into Friday the low over the central United States will finally swing east and take on a negative tilt. The ECMWF, GFS, and CMC all show slightly different solutions here. The GFS has surface low pressure heading northeast over the coastal plain of NJ. The ECMWF has the low heading northeast towards Ontario. The CMC is a hybrid of the two. Either way, wet weather looks to persist into Friday. The latest run of the GEFS shows a widespread 1 to 2" possible for the Wednesday through Friday period, while the EPS run has totals closer to two inches. Saturday, drier weather will return with another upper level low approaching from the west. && .AVIATION /19Z SUNDAY THROUGH FRIDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR conditions with a few sites still at MVFR restrictions, mainly near MIV and ACY where lower CIGs were found this morning. A narrow band of rain showers will move through the region along a warm front after 18Z, with some snow showers possibly mixing in at RDG, ABE, and TTN. Conditions should begin to improve from southwest to northeast from 22Z through 03Z. Westerly winds turning southwesterly as the precipitation moves eastward from 5 to 10 knots and gusts to 15 knots. Tonight...Mostly VFR conditions expected with a few lingering showers and snow showers across the Poconos and far northern New Jersey. Dry conditions expected across the Philly terminals through the night. Westerly winds from 5 to 10 knots with gusts to 15 knots. Outlook... Monday...VFR conditions expected with southwesterly winds around 5 to 10 knots with gusts up to 20 knots. High confidence. Tuesday...Mainly VFR conditions early with MVFR possibly developing with scattered rain showers, especially late morning to early afternoon. Southwesterly winds around 5 knots. Moderate confidence. Wednesday...Sub-VFR conditions with periods of rain showers. Rain will be heavy at times, with sub-IFR vsby restrictions possible. Southwesterly winds in the morning turning from the north late Wednesday morning. Gusts up to 20 knots possible Wednesday afternoon. Confidence is high on precipitation occurrence, but low on timing. Thursday...Sub-VFR conditions with rain. Easterly winds from 10 to 15 knots. Low confidence. && .MARINE... Today...Sub-advisory conditions expected with westerly winds turning southwesterly from 10 to 15 knots. A few gusts may reach to 20 knots. Seas generally remaining from 2 to 4 feet. Tonight...Sub-advisory conditions expected with westerly winds from 15 to 20 knots. There is a possibility that a few gusts may near 25 knots for a few hours early Monday morning. Seas generally ranging from 2 to 4 feet. Outlook... Tuesday...Sub- SCA conditions are expected with seas 2 to 4 feet. Wednesday...A cold front will cross the waters early Wednesday afternoon, with occasional wind gusts above 25 kts. Seas 3 to 5 feet. Thursday...Winds will increase out of the east with gusts of 20 to 25 kts possible. Seas 3 to 5 feet. The exact track of an area of low pressure will greatly influence the eventual strength of wind gusts and any build up of seas. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Haines Near Term...MPS Short Term...MPS Long Term...Haines Aviation...Davis/Haines Marine...Davis/Haines