textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

1. Warm temperatures, low humidity and breezy conditions will continue to bring elevated fire weather concerns for eastern Pennsylvania today. Friday will be cooler with less wind and higher humidity levels compared to today.

2. Low pressure will pass through the region this weekend with widespread showers and seasonably chilly temperatures.

DISCUSSION

KEY MESSAGE 1...Warm temperatures, low humidity and breezy conditions will continue to bring elevated fire weather concerns for eastern Pennsylvania today. Friday will be cooler with less wind and higher humidity levels compared to today.

High pressure continues to dominate our weather this afternoon as one high center sits to our north over Hudson Bay with another off the southeast coast over the western Atlantic. It will be a bit breezy over the area this afternoon however as diurnal mixing will allow for some slightly stronger winds to mix down. Generally expect northwest winds around 10 to 15 gusting 20 to 25 mph at times. Highs should be mainly in the middle to upper 70s except possibly reaching 80 over portions of SE PA, interior southern NJ, and Delmarva. Coastal areas as well as the Poconos will be a bit cooler.

Surface dew points will mix down to the low 40s and even some 30s with efficient mixing this afternoon. This results in MinRH values from 25 to 35 percent away from the coasts. Given this, we have coordinated with our fire weather partners and issued a Special Weather Statement for eastern PA zones for fire weather concerns. This is in effect until 7 PM.

Winds diminish early this evening with the loss of daytime heating. Otherwise, the high to our north along with low pressure east of the Canadian Maritimes will help drive a backdoor cold front southward through the area overnight into early Friday. This will also bring some increasing cloud cover. For Friday, expect partly to mostly cloudy skies with light NE winds and cooler temperatures compared to today. Highs will be mainly in the 60s to around 70 except cooler near the coast and a bit warmer over our eastern MD counties in Delmarva since this will be closer to the front. The cooler temperatures will result in humidity levels being higher than today along with lighter winds so we don't expect there to be fire weather concerns.

KEY MESSAGE 2...Low pressure will pass through the region this weekend with widespread showers and seasonably chilly temperatures.

High pressure will be settled over eastern Canada, and the base of this high will extend down into the Northeast. As a result, winds will take on an easterly flow starting Friday night, and onshore flow will persist through most of the weekend. This will usher a chilly airmass into the region due to ocean temperatures 50s. High temperatures Saturday and Sunday will be in the 50s with lows in the 40s.

Low pressure will organize and develop over the Great Lakes Friday night and will dive towards the Delmarva Peninsula and the Mid- Atlantic on Saturday before departing throughout the day Sunday. Showers develop Saturday night, and then continues throughout the day Saturday and Saturday night. Will keep chance PoPs for Sunday morning as that low departs.

This all sets up a raw, breezy, wet weekend.

Rainfall totals this weekend, at least from Friday night through Saturday night, will range from 1 to 1.25 inches across the southern Poconos, northern New Jersey, and the Lehigh Valley, and from 1/2 to 1 inch across the Delaware Valley, including Philadelphia, southern New Jersey, and Delmarva. While this may be unpleasant, especially since it will be over the weekend, it is good to remember that this is a beneficial rainfall.

AVIATION /18Z THURSDAY THROUGH TUESDAY/

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

Rest of this afternoon...VFR. NW winds around 10 knots gusting 15 to 20 knots at times. High confidence.

Tonight...VFR with mainly some high clouds. Winds veering to northeast by later this evening but decreasing to around 5 knots. High confidence.

Friday...VFR with some mid and high level cloudiness around at times. Winds generally northeast around 5 to 8 knots expect becoming southeast in the afternoon for ACY and MIV. Moderate confidence.

Outlook...

Friday night...Sub-VFR conds in stratus and SHRA develop late.

Saturday through Saturday night...Sub-VFR conds in SHRA, patchy fog, and low stratus.

Sunday...Lingering sub-VFR conds in SHRA/stratus in the morning. Gradual improvement late.

Sunday night through Monday night...VFR. NSW.

Tuesday...Sub-VFR conds in SHRA/stratus.

MARINE

Sub-Small Craft Advisory conditions through Friday. Winds will generally be around 10 knots or less with seas generally 2 to 4 feet today through Friday.

Outlook...

Friday night...Sub-SCA conditions. VSBY restrictions in showers developing late.

Saturday through Sunday night...SCA conditions will develop on Saturday with 15 to 20 kt winds with 25 to 30 kt gusts and seas 6 to 8 ft. Cannot rule out a few brief gale force gusts, mainly on the New Jersey ocean waters, Sunday afternoon. VSBY restrictions in rain and fog.

Monday through Monday night...SCA conditions, mostly for 5 to 6 ft seas on Monday, Conditions subside to sub-SCA conditions Monday night.

Tuesday...Sub-SCA conditions likely.

PHI WATCHES/WARNINGS/ADVISORIES

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