textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Updates for frontal passage across the area today.

KEY MESSAGES

1. Fog and low stratus lingers this morning as the backdoor front crawls north ahead of an advancing cold front that will bring a round of showers and thunderstorms.

2. Fire weather conditions possible on Monday and Tuesday.

3. Chilly temperatures Wednesday morning and Thursday morning may affect the beginning of the growing season, where the growing season is currently active.

DISCUSSION

KEY MESSAGE 1...An advancing cold front that will continue to bring showers and perhaps a thunderstorm.

A line of showers and thunderstorms is crossing the forecast area as of the noon hour. Mostly heavy showers, but some lightning across parts of ern PA and into North NJ. No warnings have been issued as of now, and it appears that this will remain the case today. The SPC has a Marginal Risk for severe weather across Delmarva for today. Showers are expected to drop around 0.50-0.75 inches of rain across the region, with areas south and east seeing the best chances for heavier rainfall and thunderstorms. Clouds will diminish from North/West to South/East thru the afternoon. Gusty West winds will develop too with speeds 10 to 15 mph and gusts to around 25 mph at times.

Behind the cold front, temperatures will take a modest fall, with overnight lows expected to dip into the mid 30s to low 40s; areas across the Poconos could reach freezing. WNW winds will also gust to around 15-20 mph for a period overnight.

KEY MESSAGE 2...A slight risk of fire spread is possible on Monday and Tuesday.

A period of fire weather conditions is possible on Monday, but more so on Tuesday as a dry airmass infiltrates the area. MinRH values will be in the 30-40% range across much of the area for Monday afternoon with westerly winds around 10-15 mph and gusts up to 20-25 mph. By Tuesday morning, a secondary cold front is forecast to pass through the region. This will cause dew points to fall into the teens. MinRH values will be in the 25-35% range with northwest winds around 15-20 mph and gusts up to 30-35 mph.

At this time, these conditions do not meet Red Flag Warning criteria on Monday, but will be close on Tuesday. Depending on how dry fuel moisture are across the region, we may need to consider a Special Weather Statement for an increased risk of fire spread. We will be in contact with our partners at a later time to determine if a SPS is warranted.

KEY MESSAGE 3...Chilly temperatures Wednesday morning and Thursday morning may affect the beginning of the growing season, where the growing season is currently active.

Strong Canadian 1040 mb high pressure will settle over New York State on Wednesday morning before shifting off the New England coast by Thursday morning. In wake of a cold front on Tuesday, a reinforcing shot of cold, dry air will arrive Tuesday night and linger into Wednesday night. Low temperatures will fall into the low to mid 20s to low to mid 30s for most locales, with teens in the Poconos by Wednesday morning. Considering that the growing season is now active across portions of the Delmarva, patchy areas of frost are possible. However, with such a dry airmass in place, frost formation may be limited.

Temperatures will be somewhat similar for Thursday morning, but with the high shifting offshore, lows should be a few degrees warmer than Wednesday. With closer dew point depressions expected for Thursday morning, suppose more patchy frost is possible. Will continue to monitor forecast trends and evaluate if any frost headlines may be warranted in the coming days.

AVIATION /16Z SUNDAY THROUGH THURSDAY/

The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas.

This afternoon... Showers and and a few tstms crossing the area attm. CIGs/VSBYs haven't lowered too much with the line with mainly MVFR and a couple short periods of lower. Conditions will improve back to VFR from N/W to S/E this afternoon. Winds West to Northwest at 10 to 15 kts with gusts to 25 kts at times. Moderate confidence.

Sunday night... Except for any lingering showers across southern NJ or Delaware during Sunday evening, mostly VFR is expected. Patchy rural fog possible Monday morning. Moderate confidence.

Outlook...

Monday through Tuesday...VFR. Gusty winds up to 20 kt possible on Monday with gusty winds up to 25-30 kt possible on Tuesday. Otherwise, no significant weather.

Tuesday night through Thursday...VFR. No significant weather expected.

MARINE

SCA conditions through tonight. A cold front will push across the waters this afternoon, shifting winds WNW behind it. There may be a lull in winds immediately behind the front, but winds overnight will ramp back up to 20-25 kts. Seas will stay elevated around 4-6 feet.

Outlook...

Monday through Monday night...No marine headlines expected. Winds generally 20 kt or less and seas of 2-4 feet.

Tuesday...Small Craft Advisory conditions possible with winds gusting around 25 kt.

Tuesday night through Thursday...No marine headlines expected. Winds generally 20 kt or less and seas of 2-4 feet.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ430- 431. Small Craft Advisory until 6 AM EDT Monday for ANZ450>455.