textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Increased fire weather concern for today.

KEY MESSAGES

1. Warm temperatures, low humidity and an afternoon breeze will result in elevated fire weather concerns today.

2. A wave of low pressure will bring widespread rainfall to the region this weekend with seasonably cool temperatures.

DISCUSSION

KEY MESSAGE 1...Warm temperatures, low humidity and an afternoon breeze will result in elevated fire weather concerns today.

High pressure builds both over Hudson Bay in Canada and over the Mid-Atlantic and Southeast today. Winds turn to the west- northwest and will increase to 10 to 15 mph with gusts up to 25 mph in the afternoon. Skies will be sunny after any patchy low clouds and fog burn off, and it will be quite warm with highs in the mid to upper 70s, though some spots along the I-95 corridor and interior portions of Delmarva may top off around 80.

Surface dew points will start out close to 50, then will mix down to the low 40s and even upper 30s with efficient mixing. This results in MinRH values from 25 to 35 percent away from the coasts. Given this, have reached out to fire weather partners regarding any concerns which may justify a special weather statement, but any feedback is likely several hours away.

KEY MESSAGE 2...A wave of low pressure will bring widespread rainfall to the region this weekend with seasonably cool temperatures.

A back door cold front sinks south of the area on Friday as high pressure settles to the north in Canada. A few showers may develop in the afternoon as some mid-level energy embedded in the northwest flow aloft clips the region, but overall conditions look to be mainly dry and cool. Forecast highs on Friday will mainly be in the 60s to around 70, perhaps pushing into the mid 70s near the Eastern Shore of MD. It should be noted that forecast guidance notoriously struggles with back door fronts and it is entirely possible that the front sinks through much faster than currently progged. This would result in much cooler temperatures than what is currently in the forecast.

A low pressure system organizing near the Great Lakes region Friday night will move through the region this weekend. The latest trend has been for the bulk of the rain showers to be Saturday with Sunday trending drier. However, some model guidance does still have some showers lingering on Sunday, so I have kept slight chance to chance PoPs for Sunday. Current rainfall amounts look to total around 0.50- 1.0 inch to the north of Philadelphia and around 0.25-0.50 inches to the south of Philadelphia.

Saturday will be dreary, damp, and cool with highs only in the upper 40s to upper 50s. Some improvement should be expected for Sunday, but it is fully dependent on how quickly our low pressure system exits. For Sunday, temperatures increase into the mid 50s to mid 60s. By early next week, we trend warmer than the weekend. Monday is looking dry with our next system approaching Monday night and bringing rain showers to the area into midweek.

AVIATION /06Z THURSDAY THROUGH MONDAY/

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

Thru 12Z this morning...Mainly VFR. Some patchy low clouds or fog/mist may develop at the terminals other than KPHL, but right now the only TAF which even hints at it is KMIV as confidence is pretty low. Moderate confidence.

Today...Any patchy fog and stratus will lift and dissipate shortly after sunrise, with VFR prevailing. NW winds 5 to 10 kt, increase to 10 to 15 kt with gusts up to 20 kt in the afternoon. Moderate confidence.

Tonight...VFR with mainly some high clouds. Winds shifting to the N but reducing to 5-10 kts. High confidence.

Outlook...

Friday through Friday night...Primarily VFR expected with a chance of rain showers on Friday night.

Saturday through Saturday night...Sub-VFR conditions likely. Rain showers likely, especially Saturday afternoon into Saturday night. Patchy fog possible.

Sunday...VFR expected. A slight chance of rain showers.

Sunday night through Monday...VFR. No significant weather.

Monday night through Tuesday...Sub-VFR conditions possible with rain showers and low clouds.

MARINE

Sub-Small Craft Advisory conditions through tonight. NE winds 5 to 10 kt early become then NW 10 to 15 kt later this morning, then become S in the afternoon behind afternoon sea breezes. Seas overall 2 to 4 feet. Winds shift back to N 5-10 kts tonight.

VSBY restrictions possible in fog, mostly near the coasts, early this morning.

Outlook...

Friday through Friday night...No marine headlines expected. Winds around 5-15 kt with seas of 2-3 feet.

Saturday through Sunday night...SCA conditions likely to develop by Saturday evening. Winds around 15-20 kt with gusts up to 25 kt possible. Seas of 4-7 feet. Rain showers likely.

Monday through Monday night...No marine headlines expected. Winds generally 10-15 kt and seas 2-4 feet.

Tuesday...No marine headlines expected. Winds around 10-15 kt with gusts to 20 kt. Seas of 2-4 feet. Chance for rain showers.

PHI WATCHES/WARNINGS/ADVISORIES

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