textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Dense Fog Advisory issued for the Coastal waters for tonight. Dense Fog Advisory issued for the coastal areas of NJ and DE for tonight.

KEY MESSAGES

1. Dense fog is expected tonight for mostly the shore areas. Remaining mostly cloudy with continuing chances for showers into Friday.

2. Turning very mild this weekend and early next week along with several chances for showers.

DISCUSSION

KEY MESSAGE 1...Dense fog is expected tonight for mostly the shore areas. Remaining mostly cloudy with continuing chances for showers into Friday.

High pressure sliding by to the north will cause the surface winds will shift more Easterly overnight. The winds will remain light, but the fog currently across the waters will advect inland across the adjacent land areas. Just how far inland remains the tricky question. We'll hoist a Dense Fog Advisory now to get ahead of the expected poor conditions. The upcoming shift can adjust the areas if needed later tonight. Scattered showers will remain near the front across mostly ern PA and NJ tonight and into Thursday morning.

Friday will feature one more day of rather dreary conditions as a back door cold front will have pushed through from the north and east and then remain stalled for a time over Delmarva. Expect mostly cloudy skies with some drizzle and a little light rain possible as low clouds and moisture remain trapped below an inversion. Most of our eastern PA and NJ zones should see highs in the 40s with a trickier forecast over Delmarva since that will be right where the front likely stalls with an associated sharp temperature gradient. Our current forecast for this area has highs mainly in the 50s. However if the front pushes farther south and west, parts of Delaware may not get out of the 40s while if it sets up a bit farther north and east temperatures in Delmarva could get into the 60s.

KEY MESSAGE 2...Turning very mild this weekend and early next week along with several chances for showers.

A much warmer air mass is forecast to overspread our area this weekend and especially early next week. In addition, there will be several opportunities for showers and perhaps a few thunderstorms across the area.

For Friday night into Saturday, high pressure near the coast will shift farther offshore as an area of low pressure lifts northward through the Great Lakes. This will help push the backdoor cold front from Friday back to the north as a warm front on Saturday. However this could take some time to occur so the first half of the day may remain on the dreary and cooler side. Highs should eventually get into at least the low to mid 60s for many areas with low to mid 70s likely over Delmarva. Meanwhile the Poconos and NW NJ will likely see highs in the 50s. A little lingering drizzle will be possible early in the day but otherwise it should be mainly dry until late day when a few showers may start to get into our western zones due to an approaching cold front. There could even be a few rumbles of thunder with these showers.

The aformentioned cold front moves through Saturday night but will tend to weaken and "wash out" as it does so. However it will still likely bring some showers as it moves through but nothing significant in terms of rainfall.

Similarly mild temperatures to Saturday can be expected for Sunday with a mix of sun and clouds. Another disturbance looks to move through along the remnant boundary to our south but most of the precip with this should stay south of area. However we do maintain slight chance to low end chance POPs across portions of Delmarva into southern NJ through Sunday and Sunday night (POPs here generally 20-30 percent).

Mild to warm temperatures continue through at least the first part of next week as strong ridging persists near the east coast. Monday looks to feature sunshine with highs generally in the low to mid 60s. Then for Tuesday and Wednesday highs for many areas could get into the 70s as south/southwest flow looks to strengthen along the east coast as the next low lifts northward to our west. However there are a couple caveats here: 1) This setup could feature a robust sea breeze developing keeping it much cooler near the coast, and 2) There are indications from some models that high pressure over eastern Canada could push a cold front southward into the area which would result in cooler conditions, especially by Wednesday. So this all said, forecast confidence by the middle of next weeks is relatively low. The aformentioned front could also bring the area some showers by later Tuesday into Wednesday.

Thursday

IFR/LIFR early then slow improvement possible. Scattered showers early then more steady rain for the afternoon and evening. Light E/SE winds. Medium confid.

Outlook...

Friday...Sub-VFR conditions due to low clouds and possible fog. A few showers possible.

Saturday...Times of sub-VFR conditions with some showers. Showers more numerous mostly at night with some thunder possible.

Sunday...Conditions may improve to VFR. A few showers still possible.

Monday...Mainly VFR.

MARINE

Winds and seas will remain below SCA conditions tonight and into Thursday. High pressure moving by to the north early tonight and a slow moving front will keep clouds and showers on the waters during the period. Also, with the cold waters and humid airmass, fog is expected to continue and become thicker tonight. A Dense Fog Advisory will be issued for the overnight and into Thursday morning.

Outlook...

Friday...The conditions are anticipated to be below Small Craft Advisory criteria. Fog possible.

Saturday and Sunday...A period of Small Craft Advisory conditions possible late day Saturday into early Sunday.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...Dense Fog Advisory from 6 PM this evening to 10 AM EST Thursday for NJZ013-014-020-022>027. DE...Dense Fog Advisory from 6 PM this evening to 10 AM EST Thursday for DEZ003-004. MD...None. MARINE...Dense Fog Advisory from 6 PM this evening to 10 AM EST Thursday for ANZ430-431-450>455.