903 FXUS61 KPHI 071730 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1230 PM EST Thu Mar 7 2019 .SYNOPSIS... High pressure will continue slowly building into the region from the west through today as a weak wave of low pressure passes north of our area. High pressure moves offshore early Friday then weak low pressure will pass across the Mid-Atlantic later on Friday. High pressure will build from the north into Saturday. Much stronger low pressure is forecast to track across the Great Lakes Sunday with a warm front lifting north into our area Sunday morning. A cold front will follow in the wake of this system late Sunday and again late Monday then high pressure returns through the middle of next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Light snow/flurries continue to develop across the forecast area and have added the mention of them into the gridded forecast. These showers should taper off towards late afternoon. Previous discussion... Made some minor adjustments to the temperature and dew point grids to better reflect the current conditions and trends. Also adjusted the sky cover as clouds have yet to flow back across much of the area this morning but will start to overspread the area through the day. One more short wave trough is expected to dig southeast across the region today before the surface high builds in. In response to the trough, some snow showers could propagate over the region from late morning into the early afternoon. Moisture is quite limited, so not anticipating accumulating snow, but some of the stronger and more isolated snow showers could result in briefly lowered visibilities. We expect to see a modest warming trend today, thanks to some low level downsloping flow. Highs should be in the 20s in the southern Poconos, and in the lower 30s north and west of the Fall Line. For the I-95 corridor, southern NJ, and Delmarva, highs will be in the mid to upper 30s. Though it will be slightly higher than temperatures on Wednesday, this will still be 15 to 20 degrees below normal. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... Surface high will be over the region, resulting in light and variable winds. Increasing clouds are possible late tonight in advance of the next system on Friday. Despite very efficient radiational cooling conditions for at least the first half of the night, temperatures will be 5 to 10 degrees higher than Thursday morning, with lows generally in the teens to mid 20s across the region. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... Summary: There are 2 main rounds of precipitation expected to impact our area Friday through Sunday with a brief period of dry weather expected in between systems. Fair weather will return by the beginning of next week. A weak area of low pressure is expected to pass just to the south of the forecast area Friday afternoon and evening along a stalled frontal boundary. North of the front, moisture and forcing will increase from southwest to northeast throughout the day on Friday yielding increasing cloud cover and eventually precipitation. Precipitation is expected to start later Friday morning or early afternoon from southwest to northeast. As far as precip type, this looks to be a rain/snow mix event (no sleet/freezing rain). Expecting mainly all rain in the far southern part of our Delmarva counties, with a rain/snow transition setting up from about Dover/Cape May northward to the I-95 corridor. The transition to all rain should lift northward by a few dozen miles during the afternoon after the main round of precip arrives. Areas north of I-95 are likely to remain all snow for the entire event. QPF is forecast to be generally 0.10" or less for this event with the higher amounts favored south and west where forcing for accent will be stronger. Given temperatures likely above freezing for most area at precip onset and light QPF, expecting snow totals to remain less than 1" in all areas. Berks and Chester Counties may receive totals a bit higher and closer to the 1" mark. Areas of light snow showers or flurries and perhaps even some drizzle will be possible through the evening hours as the precip tapers. High pressure will build briefly from the north into Saturday yielding fair and tranquil weather with temps just a few degrees below normal. Unfortunately, this dry period will be temporary. A strong low pressure system will be moving across the Great Lakes region late Saturday through Sunday. This will lift a warm front toward the area overnight, before sweeping a cold front across the area during the day Sunday. Forcing will increase across the area as several short wave/vorticity impulses slide across the area north of the warm front and in association with the cold front. The forcing, combined with increasing moisture from the south, will lead to an extended period of rain chances overnight Saturday into Sunday afternoon. Depending on how early the precipitation starts, there will likely be some freezing and/or frozen precipitation overnight Saturday into Sunday morning for portions of eastern Pennsylvania, and northern and central New Jersey before it all changes to rain from south to north by daybreak. There is potential for moderate to locally heavy rainfall, but QPF should remain in the half to one inch range for most so not expecting any widespread flooding concerns. The cold front will move out to sea Sunday night, while the low pressure moves across eastern Canada through Monday. High pressure builds out of the Plains and across the northern Mississippi Valley and into the Great Lakes region Monday through Tuesday. Our area will remain in between the high to our west and the low to our north, which will keep a west to northwest flow across the area Monday into Tuesday. This northwest flow will keep the chance of showers or flurries/sprinkles during the day Monday as an area of enhanced lapse rates and moisture moves across the area along with a fairly potent short wave. High pressure briefly returns into the middle of the week which will bring another period of dry conditions with temps near normal. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today: Mostly VFR conditions are expected. Isolated to scattered flurries with brief MVFR conditions possible through this afternoon. Westerly winds around 8 to 12 knots with gusts around 18 to 20 knots through this afternoon and then dropping off and becoming light and variable. High confidence. Tonight: VFR conditions are expected with light and variable winds. High confidence. Outlook... Friday...Light snow/rain developing with MVFR probable and IFR conditions possible. Light and variable wind becoming SE around 5 kts by late morning. Moderate confidence. Friday night and Saturday...Conditions improving to VFR Friday evening. Light and variable winds becoming N around 5 kts then shifting east on Saturday. Moderate confidence. Saturday night through Sunday...Widespread rain and clouds with IFR conditions expected by Sunday. S wind 10-15 kts shifting west later Sunday afternoon. Moderate confidence. Sunday night through Monday...Conditions improving to VFR. W winds 10-20 kts with gusts up to 25 kts possible, especially during the day Monday. Moderate confidence. && .MARINE... On the Delaware Bay, winds and waves are expected to remain below Small Craft Advisory conditions today and tonight. On the NJ and DE coastal waters, we are currently in a lull with winds, but wind gusts near 25 kt are expected to redevelop around mid day. Therefore, the SCA continues through early this evening. By tonight however, winds and seas should stay below SCA criteria. Outlook... Thursday through Saturday...Sub-SCA conditions are expected through the entire outlook period. Seas are expected to build to 4-5 feet with winds also increasing late Saturday as the next storm system approaches. Sunday and Sunday night...SCA conditions likely developing by Sunday morning. Monday...SCA conditions likely lingering at least through the morning hours with seas and winds diminishing throughout the day. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 7 PM EST this evening for ANZ450>455. && $$ Synopsis...Staarmann Near Term...Johnson/Meola Short Term...Johnson Long Term...Robertson/MPS/Staarmann Aviation...Johnson/Meola/Staarmann Marine...Johnson/Staarmann