021 FXUS61 KPHI 101534 AFDPHI Area Forecast Discussion National Weather Service Mount Holly NJ 1034 AM EST Tue Nov 10 2020 .SYNOPSIS... High pressure will shift offshore today. A cold front associated with a low crossing southern Canada is expected to cross our region Wednesday night into Thursday morning. High pressure will briefly build back over the region through the first half of the weekend before a warm front is expected to lift through our region Sunday into Monday. && .NEAR TERM /THROUGH TONIGHT/... Warm moist air across the forecast area early this morning along with relatively calm winds. Surface heating has raised temperatures enough that all fog has dissipated across the region. Winds will begin to increase from 5 to 10 mph from the south-southwest into the afternoon with another pleasantly warm afternoon. Cloud cover will keep us a few degrees cooler than last night. With that, this first forecast with our new 33 county CWA without Cecil County, MD has been issued. Previous discussion... High pressure will push further offshore through tonight, keeping a light southerly flow across the region. With continued strong southwest flow through the mid and upper levels of the atmosphere, we will continue to see warm air spread across the area, giving us yet another day of temperatures well above normal. Highs are expected to rise into the 70s through much of the region with some mid/upper 60s across the higher elevations of the southern Poconos and northwest New Jersey. As we head into the evening, we will start to see the clouds moving in. The increased cloud cover will help to limit radiational cooling and we won't see temperatures fall quite as much as they have the past few nights. Overnight lows will only drop down into the 50s to lower 60s and with dewpoints remaining high, it will feel rather muggy out. Additionally, the winds will drop off and with so much low level moisture around, cannot rule out another night of fog developing, though with the clouds moving and thickening through the night, it will be patchy over widespread areas of fog. As a cold front starts to push in from the west, we could start to see some showers develop ahead of it and entering our western areas towards dawn, though chances will be better as we head into Wednesday. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... The biggest change in this period as compared to yesterday's model runs is that guidance is now depicting a more progressive cold front. Most guidance (with a notable exception of the NAM) depict the front off shore and south of the region by 12Z Thursday. The timing of the rain though hasn't changed too much. For most of the region, the rain should be starting Wednesday afternoon, though it appears likely to start in the Poconos, Berks County, and the Lehigh Valley sometime Wednesday morning. Even with the more progressive front, rain could linger for several hours behind the front as a trailing mid level short wave trough could provide enough lift for rain to continue through the day on Thursday. Although behind the front, expect significant dry air advection, so heavier rain will likely be limited to Wednesday afternoon through late Wednesday night. As for rain amounts, it still appears to be a general 1 to 3 inches across the region, but if the front arrives as early as we are forecasting now, the axis of heaviest rain totals, those above 2 inches, should be shifted southeast where flash flood guidance is highest. Therefore, the risk of flash flooding remains relatively low. None the less, will keep a mention in the HWO as there is a brief window when it will be possible. As with the forecast yesterday, the risk for thunderstorms looks to be quite limited (and confined to areas ahead of the cold front). Thus, have only included a mention for portions of Delmarva and southeastern NJ Wednesday night. On Wednesday, have gone close to a blend of guidance for temperatures as I think the rain and persistent cloud cover should help keep temperatures closer to guidance (as compared to the last several days when we have been well above guidance for Max Temperatures. Even so, much of the region should once again get close or exceed 70 on Wednesday. Given the more progressive solutions with the front, I decreased the forecast for temperatures on Thursday as immediately in the wake of the front there will likely be little diurnal swing in temperatures and we could even have an atypical temperature trend with temperatures remaining steady or even decreasing through the day. && .LONG TERM /FRIDAY THROUGH MONDAY/... Friday...We should start the long term period dry as a surface high builds in. Some guidance is depicting precip on Friday as a mid level short wave trough crosses the region. However, I see little opportunity for moisture recovery by then so aside from a slight chance of lingering showers along the coast, I've kept the forecast dry for now. Despite the cold front on Thursday, temperatures should be slightly above normal, with highs in the 50s to lower 60s. Friday night and Saturday...A reinforcing shot of cold air is expected Friday night. Moisture remains limited so do not expect any precipitation as a result. However, Saturday looks like our best chance to see below normal temperatures in over a week. Favoring a blend of guidance, highs on Saturday are forecast to range from the mid 40s in the Poconos to mid 50s along the coastal plains. Sunday and Monday...the below normal temperatures will be short lived, as by Sunday morning a warm front is expected to lift through the region. Not only will this bring a return to above normal temperatures, but it will also bring another chance for precipitation across the region. Depending on the timing of the warm front (especially just above the boundary layer), there is potential for a cold air damming set up in the southern Poconos and Northwest NJ. If moisture arrives early enough, this set up could result in a period of wintry mix at the start of the precipitation in these areas before changing over to all rain. However, I'm not confident that we will see moisture return that quickly. Therefore, I've stayed close to the previous forecast with only a mention of rain/snow mix in these areas from late Saturday night through mid Sunday morning. Otherwise, precipitation should be all rain. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Today...VFR with increasing high clouds into the afternoon/ Light winds this morning becoming southwest less than 10 knots this afternoon. High confidence on overall pattern but low confidence on timing of improvement. Tonight...VFR conditions expected before dropping to MVFR by around 04-06Z and then to IFR or lower after 09Z. Light south winds. Moderate confidence on overall pattern but low confidence on categorical changes and timing. Outlook... Wednesday...Patchy morning fog with sub-VFR conditions is possible. Otherwise, mostly VFR conditions are expected through mid day. In the afternoon, ceiling and visibility restrictions to MVFR are possible with rain, which could be heavy at times. South- southwesterly winds from 5 to 10 knots with gusts to 15 knots. Moderate confidence on the overall pattern, but low confidence on morning fog and timing details. Wednesday night...MVFR and even IFR ceilings are possible with some visibility restrictions in rain showers. Expect an abrupt shift from southwesterly to northwesterly winds at 5 to 15 kt. Moderate confidence on the overall pattern, but low confidence on the details. Thursday...Conditions should gradually improve to VFR as rain clears out. Northwesterly and northerly winds of 5 to 15 kt. Moderate confidence. Friday...VFR conditions expected. Winds should start northerly at 5 kt, but may become light and variable through the day. Moderate confidence. Saturday...VFR conditions expected with light (less than 10 kt) northwesterly winds. Moderate confidence. && .MARINE... Sub-advisory winds and seas are expected to continue through tonight on the area waters. Southerly winds around 10 to 15 knots. Seas will be between 1 and 3 feet on the ocean, building to around 2 to 4 feet by late tonight. Seas on the Delaware Bay will be around 1 to 2 feet through tonight. Outlook... Wednesday and Wednesday night...A period of SCA conditions (for both winds and seas) are likely, especially on the Atlantic coastal waters. Thursday...Seas should gradually subside below 5 feet through the day. Friday and Saturday...Winds and seas should stay below SCA criteria. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Johnson Near Term...Davis/Meola Short Term...Johnson Long Term...Johnson Aviation...Davis/Johnson/Meola Marine...Davis/Johnson/Meola