textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

The Dense Fog Advisory and Winter Weather Advisories have been allowed to expire.

Marine Dense Fog Advisory and Small Craft Advisory issued for portions of the coastal waters.

KEY MESSAGES

1. Periods of rain and areas of fog will persist into tonight.

2. A significant warm-up is anticipated from mid-week through early next week with several chances for showers.

DISCUSSION

KEY MESSAGE 1...Periods of rain and areas of fog will persist into tonight.

Arctic high pressure is retreating well offshore. Our boundary layer is shifting into a more maritime influence with ENE surface winds. Southwest winds aloft are advecting in much deeper moisture. All of this combined with some broad, weak forcing for ascent in the mid levels are producing our periods of rain into tonight.

Temperatures have risen above freezing across the area, so all Winter Weather Advisories have been allowed to expire. Additional rainfall into tonight will be below a 0.10".

Afternoon/evening high temperatures will be in the mid 30s to low 40s for most. Temperatures nearly steady overnight.

Some breaks of sun on Wednesday, but remaining mostly cloudy with a chance of showers near/south of the Philly metro. Highs mainly in the mid 50s.

KEY MESSAGE 2...A significant warm-up is anticipated from mid- week through early next week with several chances for showers.

A significant warm up is still expected across the region from mid- week extending into early next week. In addition, there will be several opportunities for showers and perhaps a few thunderstorms across the area.

Wednesday night into Thursday, a couple of mid-level impulses look to traverse the region, with a stronger shortwave passing just north of the area Thursday night. At the surface, a warm front will lift northward into the area on Thursday. Ahead of the warm front, widespread rain is expected to develop late Wednesday night. Current PoPs Wednesday night are highest south of I-78, and range from 60- 80%. On Thursday as the front lifts northward, PoPs decrease to 30- 50% for much of Delmarva and southern NJ, with 60-70% elsewhere.

Thursday night as the stronger short wave and an associated weak surface low passes just north of the area, another round of widespread showers is anticipated. Modest elevated instability could allow for a few rumbles of thunder with this activity. Overall, it appears that precipitation amounts Wednesday night through Thursday night will be highest across the northern half or so of the area, where amounts could plausibly exceed 1 inch. Expected QPF diminished fairly quickly with southern extent.

Friday and into the weekend, height rises are expected as ridging expands over the Eastern Seaboard northwestward into portions of the Appalachians. This should lead to quieter weather for a couple of days. Saturday night into Sunday, another upper-level disturbance looks to pass to the north of the area, with a trailing cold front passing through the region. This is expected to bring additional chances for showers and perhaps a few thunderstorms to the region. Beyond Sunday, only a few weak disturbances look to pass through the region, with PoPs generally in the 20-30% range.

Regarding the expected warm up, uncertainty remains for Thursday and Friday, with much higher confidence for Saturday through Tuesday. It looks increasingly likely that the aforementioned front will stall over our area and perhaps begin to sag southward through Thursday and Friday. This may lead to wide range of temperatures across the area. In general, highs north of the front Thursday and Friday look to be in the low to mid 50s, and mid 60s to near 70 south of the front. Lows look to be in the upper 30s to near 40 north of the front and mid 40s to near 50 south of it. Where exactly it sets up is the primary question at this time. Regardless, return flow is expected to commence for the entire area by Saturday, and any cool down with the frontal passage Saturday night into sunday looks fairly minimal. As a result, much warmer temperatures are expected areawide. Highs Saturday through Tuesday are expected to be in the mid-upper 60s across the entire area, with some locations breaching 70. Overnight lows look to be in the upper 40s to mid 50s each night.

AVIATION /03Z WEDNESDAY THROUGH SUNDAY/

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

Tonight...IFR/LIFR in periods of -RA and BR/FG. The -RA looks to move out between 08Z-12Z. Additional drizzle or BR/FG remains possible through around 16Z. Winds settling out of the southwest 5-10 kts for a time, then becoming light and variable. Moderate confidence in details, but high confidence in prevailing IFR conditions.

Wednesday...IFR through around 15Z or so, then improving to VFR by around 18Z for most terminals. For KILG, KMIV, and KACY, conditions look to remain MVFR/IFR beyond 18Z due to low ceilings and reduced visibility from another period of -RA/BR. Northeast winds near 5 kts. High confidence in the general pattern, lower confidence in exact timing of improvements.

Outlook...

Wednesday night through Thursday night...Sub-VFR conditions expected in periods of rain, some thunder is possible Thursday night.

Friday through Saturday...Primarily VFR. Brief periods of sub- VFR conditions can't be ruled out in scattered showers each day.

Saturday night through Sunday...Sub-VFR conditions expected in showers and possible thunderstorms. Conditions will likely improve by late Sunday.

MARINE

East winds shifting south to southwest into tonight near 10-15 kts. Seas 3-5 feet. Winds diminishing and shifting northeast Wednesday. Visibility restrictions to 1 NM or less in rain and fog through tonight.

Marine Dense Fog Advisory and Small Craft Advisory issued for portions of the coastal waters to highlight the threat of 5 foot seas and low visibility.

Outlook...

Wednesday night through Friday...Sub-SCA conditions expected with winds under 25 kt and seas below 5 feet. Visibility restrictions likely at times in periods of rain and perhaps a few thunderstorms Wednesday night through Thursday night.

Friday night through Sunday...SCA conditions possible. Winds are expected to remain below SCA criteria through most of Saturday. By Saturday evening and continuing through Saturday night, southerly winds 10-15 kt with gusts 20-25 kt. Winds will become southwesterly on Sunday and diminish with time. Seas 3-5 feet Friday night, increasing to 4-7 feet Saturday night, and again diminishing to 3-5 feet for Sunday.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Dense Fog Advisory until 6 AM EST Wednesday for ANZ430-431- 450>455. Small Craft Advisory until 1 PM EST Wednesday for ANZ450>455.