textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Expired the freeze warning for this morning.

KEY MESSAGES

1. Warmer tonight, but some frost is likely to develop.

2. Elevated risk of rapid fire spread expected today for areas in eastern Pennsylvania north and west of the I-95 corridor. A dry weather pattern continues for the remainder of the week and potentially most of this upcoming weekend.

3. A significant warm up is expected for the early and middle part of next week.

DISCUSSION

KEY MESSAGE 1...Warmer tonight, but some frost is likely to develop.

Temperatures have warmed, and the freeze warning for this morning has been allowed to expire.

For tonight, southerly flow will result in some moderation to the airmass and slightly warmer temperatures. Lows for the most part will remain just above freezing and in the mid 30s, though some more sheltered and rural areas could fall below freezing. A large majority of any freezing temperatures will be in areas where the growing season has not started yet though, so not anticipating any Freeze Warnings for tonight at this time.

However, low dewpoint depressions tonight could result in some frost developing where the growing season is active. With temperatures in the mid 30s, some frost is likely to develop within more rural areas away from the I-95 corridor and away from the coast (where temperatures could be warm enough to preclude frost development). At this point, we will let the current Freeze Warnings ride before making a decision on if any Frost Advisories are needed for tonight, but it would not be a surprise if headlines were needed. With RHs expected to be between 95-100% tonight, some patchy fog cannot be ruled out either.

KEY MESSAGE 2...Elevated risk of rapid fire spread expected today for areas in eastern Pennsylvania north and west of the I-95 corridor. A dry weather pattern continues for the remainder of the week and potentially most of this upcoming weekend.

High pressure moving offshore this morning will result in southerly flow setting up today. This will bring some moisture to a very dry airmass limiting the potential for fire spread over most of the area. However, after some coordination with fire weather partners, conditions on the ground are dry enough over eastern PA to the point where there is some risk for fire spread. Eastern PA also will have the lowest RHs compared to other parts of the area, around 35-45%. RHs will be around 40-50% across the rest of the area, and with light winds, there is little to no risk over NJ, SE PA including Philly, and Delmarva. Will go ahead and issue an SPS later this morning for Carbon/Monroe/Lehigh/Northampton/Berks to cover the fire weather threat.

Light southerly flow continues on Friday, resulting in higher dew points, along with increasing clouds ahead of an approaching front. This combination will generally decrease the risk for fire spread concerns. However, temperatures will warm as well, resulting in some minimum RHs in the 30-40% range, particularly in eastern New Jersey and Delmarva where there may be less cloud coverage and better mixing conditions, so there may still be some limited fire weather concerns.

A cold front will move through the region Friday night. A few light showers may accompany the frontal passage, though as of right now the potential for a wetting rainfall remains low (15% chance or less). Widespread RHs around 25-35% are expected to follow on Saturday with northwest wind gusts potentially increasing to around 20-30 mph. Saturday continues to bear watching for fire weather concerns, as a result.

KEY MESSAGE 3...A significant warm up is expected for the early and middle part of next week.

After a seasonable weekend, a significant warming trend will likely take place across the area early next week. High pressure will initially build back in across the region in the wake of the cold front this weekend, before shifting east and allowing for a prolonged period of return flow. By mid-week, high temperatures could surge well into the 80s across much of the area, with overnight lows only falling into the 60s.

A few weak disturbances could bring a slight chance for a few showers to northern parts of the area Monday night. Otherwise, conditions are expected to remain dry until at least Wednesday, when a cold front may begin to approach the area from the northwest.

AVIATION /13Z THURSDAY THROUGH MONDAY/

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

Through This Morning (16z)...Stratus has developed and continues to increase in coverage and move towards the terminals. Would expect periods of MVFR CIGs at all sites through the morning, mixing out and/or lifting towards the late morning. Winds generally calm but gradually increasing as the morning goes on out of the south/southeast around 5 to 10 kt. Moderate confidence.

This Afternoon...VFR. Winds out of the south/southeast around 10 kt. High confidence.

Tonight...Primarily VFR. Some patchy fog develops, though only have put VSBY restrictions at KACY/KMIV for now. Light winds generally out of the south around 5 kt or less. Low confidence.

Friday...VFR. Southerly winds around 5 to 10 kt. High confidence.

Outlook...

Friday night...Primarily VFR. Brief periods of sub-VFR conditions are possible with a chance of showers, primarily for the Lehigh Valley terminals.

Saturday through Monday...VFR. No significant weather.

MARINE

Tranquil conditions on the waters expected through tonight. Winds out of the east/southeast around 10 kt or less with 2 to 4 foot seas.

Outlook...

Friday through Saturday...SCA conditions possible. Winds under 25 kt. However, seas will increase to 4-6 feet Friday and continue through Saturday.

Saturday night through Sunday night...No marine hazards anticipated. Winds under 25 kt. Seas under 5 feet.

Monday...SCA conditions possible. Southerly winds gusting near 25 kt. Seas increase to 4-6 feet.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...None.