Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 061404 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 904 AM EST Sat Mar 6 2021 .SYNOPSIS... A final trough will cross the region on Sunday. Otherwise, surface high pressure and tranquil weather will persist through at least Wednesday. By Thursday, a cold front is expected to approach the region. This front may remain over our near our region through at least Friday. && .NEAR TERM /THROUGH TONIGHT/... This morning we are certainly making the best out of a thin ribbon of moisture rounding the base of an upper level low pressure system that is slowing pulling to the north and west. This should mean that at least through the rest of the morning, there will be some light snow showers or flurries with little in the way of accumulation. This the combination of a high pressure system extending southward into the northern Plains and Great Lakes, and the upper level low over Newfoundland responsible for a modest pressure gradient across the Northeast, which is responsible for our breezy conditions as of late. As a weak surface trough and mid- level shortwave pivot eastward with the aforementioned low to our northeast, high pressure will gradually build into the region through the day and into Sunday with weak cold air advection gradually backing off as well. The good news is that this will relax the pressure gradient as the low begins to gradually fill and pull off towards Greenland. A broken mid-level stratus deck will continue to push through the region as light snow showers gradually taper off to our north and west closer to the lakes on the windward side of the Appalachian crest. Can`t rule out a few flurries across the Poconos and into Sussex County, NJ but no accumulations are expected. Partly cloudy skies will persist through the day with more clearing as we head into the overnight. A rather similar day to Friday, though the weaker winds will result in less of a wind chill with highs in the mid to upper 30s and wind chill values closer to the freezing mark. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... The final of the mid level short wave troughs rotating around the base of the main trough will quickly dig over the region during the day on Sunday. Given the very dry air mass that will still be in place, expect most areas to stay dry. However, given the pattern, expect at least modest rising motion in the mid levels. If the dry layer (which by model soundings look like it will extend up through 700 mb) is shallower or not quite as dry as expected, this trough could be enough for some very light snow showers Sunday morning. At this point, I think the dry air will win out, so have kept the forecast dry for now. Once the mid level trough shifts southeast of our region, the mid level ridge will begin to build east towards our region. Although the more significant warm up won`t occur until we start seeing low level southwesterly flow (beginning late Monday/Monday night), this subtle shift, with the accompanying increasing thicknesses and mid and upper level subsidence, will be enough for temperatures on Monday to be 5 to 10 degrees higher than Sunday. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Overview: Tranquil weather continues through at least Wednesday. A cold front approaching the region Thursday and Friday could bring the next chance for precipitation to the region. Details: Tuesday and Wednesday...both the surface high and mid level short wave ridge shift over (and eventually east of) our region. Consequently, we will see low level southwesterly flow, and significant warm air advection. For both days, expect highs in the 50s and 60s. The good news is that the southwesterly flow should also result in some moisture advection, which should help to limit the fire weather threat somewhat (see fire weather discussion below), but I agree with the previous forecaster that guidance can have a wet and cold bias with this pattern especially during the early transition season. Will be watching the trends over the next several days. Thursday and Friday...A cold front approaches the region. As mentioned by the previous shift, the timing is still uncertain as the front may slow or even stall for a period during this time. However, it still looks like we won`t see the front progress through the area until Friday. On Thursday though, the front may be close enough that the front edge of precipitation in the warm sector (in this case, all rain) will move into portions of our region, mostly north and west of the fall line. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today and tonight...VFR with scattered to broken mid-level clouds through the day. Light snow showers with temporary MVFR restrictions at KRDG and KABE, but these should be on the downturn through the morning. West- northwest winds from 10 to 15 knots with gusts to 20 knots possible. High confidence. Outlook... Sunday...VFR. Northwest wind 5 to 10 kt. High confidence. Monday... VFR. Winds gradually shifting from northwest to west- southwest at 5 to 10 kt. High confidence. Tuesday-Wednesday... VFR. Southwest wind 5 to 10 kt. High confidence. && .MARINE... Cold northwest flow will continue through tonight with winds slowly lessening through the day. Winds are expected to fall below advisory criteria late this morning with the SCA lasting through 10 am. Northwest winds from 15 to 20 knots into the afternoon and lasting through the overnight. Outlook... Winds and seas should stay below SCA criteria Sunday through Wednesday. && .FIRE WEATHER... After dew points in the single digits and northwest winds gusting to 35 mph at times yesterday, we are expecting slight improvement today with west winds gusting from 20 to 25 mph, and minimum RH values ranging from 35 to 40 percent. After collaboration with our state fire partners yesterday, fuels are not expected to be wet enough for a Special Weather Statement to be needed. However, a prolonged dry and breezy period will be in place over the region, so there will be close monitoring for the fire weather threat into next week. At this point, it doesn`t appear that we will reach low humidity criteria coincident with gusty winds, but Monday should have very dry conditions, and Tuesday and Wednesday will be much warmer than normal. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Davis/Johnson Near Term...Davis/Deal Short Term...Johnson Long Term...Johnson Aviation...Davis/Johnson/O`Brien Marine...Davis/Johnson Fire Weather...WFO PHI

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