textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Rainfall totals have lowered a bit. The chance for stronger thunderstorms has lowered.

KEY MESSAGES

1. Low pressure and its associated fronts will cross the area later today and into early Thursday.

2. A storm system tracks close to our area from the south Saturday, bringing a potential for rain.

DISCUSSION

KEY MESSAGE 1...Low pressure and its associated fronts will cross the area later today and into early Thursday.

A deepening upper-level trough/closed low centered across the Upper Great Lakes region today will pivot eastward through Thursday. This will promote a surface low pressure system to form across the Ohio Valley today and move east-northeast overnight. A strong cold front will follow for Thursday morning.

Rains will move out ahead of the low today and chances increase from West to East through the day. There is also a chance for a tstm as milder and slightly unstable air moves in later today along with the low level jet around 40kts. The chances for any strong or severe tstms is low with CAPE values remaining low with the limited surface heating today. The SPC has reduced the areal coverage of the Marginal risk area in our CWA today but it remains just SW our our region.

Overall, storm total rainfall looks to be between 0.25-0.75 inches across our entire region. These totals are lower compared to the previous forecast. If an embedded stronger convective contribution materializes though, then locally higher rainfall totals will be probable. This rain is much needed given the ongoing longer term drought conditions in place. The showers rapidly end early Thursday morning as the cold front and surface low clears our area, with a gusty breeze occurring during Thursday.

KEY MESSAGE 2...A storm system tracks close to our area from the south Saturday, bringing a potential for rain.

As a closed low remains across southeastern Canada over the weekend, a stronger shortwave is forecast to rotate through the base of it from the Ohio Valley to the Mid-Atlantic then offshore. This feature should support surface low development, however the model guidance varies on the placement of this low. Some models and ensembles have this low stronger and farther to the north, which would bring a shield of rain across most of our area. Some other guidance, including the GFS, are weaker and farther south with the surface low. Despite the uncertainty with the location/track of the surface low, given the synoptic setup suggests that whatever system occurs would tend to be a quick mover. Also, given the presence of the closed low, temperatures will be chilly over the weekend (well below average) with Saturday being the coolest. This potential system will continue to be monitored as a more developed and farther north storm track would offer widespread rainfall across the area.

AVIATION /06Z WEDNESDAY THROUGH SUNDAY/

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

Today... VFR conditions mostly but high end MVFR (for CIGS) early today at KRDG. The VFR conditions will continue thru the day with S to SE winds increasing to 10-12 kts this afternoon. Lowering CIGS with showers moving W to E across the region this afternoon. Medium/high confid.

Tonight... sub-VFR with IFR possible. Showers with a small chance for a TSTM. Left Tstms out of the TAFs at 06Z with confid in them occurring low. Improving conditions possible late for KRDG/KABE. Low/medium confid.

Outlook...

Thursday...Sub-VFR conditions possible with some lingering showers early, then VFR. Northwest wind gusts up to 20-25 knots.

Friday...Mainly VFR. West-northwest wind gusts up to 20 knots during the day.

Saturday...A period of sub-VFR and showers possible.

Sunday...Mainly VFR.

MARINE

Sub-SCA conditions expected today and tonight. Winds will be mainly SE 5 to 10 kts this morning then 10 to 15 kts this afternoon and early evening. Winds turn SW then NW between midnight and dawn Thu. Low-end SCA gusts possible, but not certain. Fair today then showers with a chance of a tstm this evening.

Outlook...

Thursday...A period of Small Craft Advisory conditions possible, mainly for seas around 3-5 feet.

Friday through Sunday...The conditions are anticipated to be below Small Craft Advisory criteria.

PHI WATCHES/WARNINGS/ADVISORIES

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