textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Confidence increased in enhanced risk for fire spread on Tuesday.

KEY MESSAGES

1. Increasing concern in fire weather conditions Monday and especially Tuesday as a dry airmass moves overhead. Cannot rule out the need for a Red Flag Warning on Tuesday.

2...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...Increasing concern in fire weather conditions Monday and especially Tuesday as a dry airmass moves overhead. Cannot rule out the need for a Red Flag Warning on 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 as a very dry airmass moves overhead. MinRH values will be in the 20-30% range with northwest winds around 15-25 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. We will be in contact with our partners at a later time to determine if a SPS is warranted and if a Red Flag Warning is needed for Tuesday. While there is high confidence in meteorological conditions being present for a Red Flag Warning, rainfall today up to half an inch may keep fuel moistures high enough on the ground to be the limiting factor. This will depend on what our fire weather partners are seeing on the ground. While we are getting some rain today, most of the area remains in some form of a drought.

KEY MESSAGE 2...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. The growing season is currently active over Delmarva with the exception of New Castle County, DE. There is a decent chance (50-60%) for temperatures at or below freezing on Wednesday morning over Delmarva as skies will be clear and winds light. With a dry airmass overhead though, frost is not really expected even with such cold temperatures. Will need to eventually decide if a Freeze Warning is needed for areas where the growing season is active. The growing season does not expand to a more widespread area until April 11.

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. May need a Frost Advisory on Thursday morning but there is rather high confidence in Wednesday morning being the coldest of this stretch.

A return to more normal temperatures well above freezing comes by Friday morning, continuing at least through the weekend.

Monday

VFR conditions expected with mostly clear skies early then partly cloudy for the afternoon. Winds will generally be West at around 10 knots with some gusts to around 20 knots by late morning and into the afternoon. High confidence.

Outlook...

Monday Night...VFR. No significant weather.

Tuesday...VFR. Wind gusts out of the northwest around 25 to 30 kt.

Tuesday Night through Friday...VFR. No significant weather.

MARINE

Winds and seas will remain up following a cold front passage into the evening. West winds will become 10 to 15 kts with gusts 25 knots at times and seas of 4-6 feet. SCA conditions in the ocean but just below SCA for Delaware Bay. A Small Craft Advisory remains in effect through 6 AM Monday for coastal Atlantic Ocean waters.

Sub-SCA conditions on Monday with westerly winds around 10 knots and gusts around 20 knots. Seas of 2-4 feet.

Outlook...

Monday Night...No marine headlines expected.

Tuesday...SCA conditions likely (70-80%) as wind gusts out of the northwest will be around 25 to 30 kt.

Tuesday Night through Friday...No marine headlines expected.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ450>455.