textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

No significant changes with this issuance.

KEY MESSAGES

1. A warm front lifts north through the region today, followed by weak low pressure tonight. Widespread wintry precipitation will impact the morning commute this morning before changing to rain.

2. A significant warm-up mid-week and continuing through early next week with several chances for showers.

DISCUSSION

KEY MESSAGE 1...A warm front lifts north through the region today, followed by weak low pressure tonight. Widespread wintry precipitation will impact the morning commute this morning before changing to rain.

Arctic high pressure that was over the area now lies south and east of Cape Cod. Cold air remains over the area with temperatures at or just below freezing. A warm front south of the area will begin to lift to the north early this morning, and this will result in wintry precipitation developing over the area.

For northern Delaware and along the I-95 corridor, precipitation will be a wintry mix of snow and freezing rain this morning, resulting in minimal snowfall and perhaps a glaze of ice. Farther inland, for the Lehigh Valley, northern New Jersey, and the southern Poconos, snow will persist a bit longer before mixing with freezing rain, and eventually changing to plain rain late this morning or around midday. Snowfall totals may be as high as an inch with several hundredths of an inch of ice. Winter Weather Advisories remain in effect for these areas, starting and ending from south to north this morning through midday.

Rain continues throughout the day. Low pressure approaches later this afternoon and passes through the region tonight. Rain tapers off after midnight, skies remain cloudy and fog will develop.

Highs today will be in the 30s to around 40 north and west of the Fall Line, and in the low to mid 40s for southern New Jersey and the Delaware Valley. Highs will be in the upper 40s to low 50s in southern Delmarva. Lows tonight will be just several degrees cooler tonight compared to the highs today.

KEY MESSAGE 2...A significant warm-up mid-week and continuing through early next week with several chances for showers.

A pattern change occurs later this week and right into early next week as a trough aloft develops over the western U.S. and ridging aloft sets up over the eastern U.S. By Friday, the trough out West will dig further south into western Mexico which will allow the ridge over the East to further amplify through the weekend. At the surface, a large Bermuda high will be in control.

As a result, temperatures late this week into early next week are forecast to be as much as 10 to 20 degrees above average. On Wednesday, temperatures will be in the 50s to near 60. The temperature forecast is more complicated for Thursday through Saturday as guidance indicates a front wavering back and forth across our area. The front initially lifts northward on Thursday before stalling then dropping back southward as a backdoor front Friday into Saturday. How far north and south the front makes it each day will lead to significant temperature differences on each side of the boundary. South of the boundary, temperatures will warm into the mid 60s to around 70, with temperatures right around 60 in the vicinity of the front. North of the boundary, temps will be much cooler, in the 40s and 50s. It is quite possible that especially for Friday and Saturday, much of our area could end up being much cooler than currently forecast particularly if a low-level east to northeast wind locks in. For especially Sunday and Monday, the front lifts back north, clearing the area and putting the region firmly back into the warm sector. Highs Sunday and into early next week should mainly be in the 60s and low 70s. Coastal areas though will only be in the 40s and 50s thanks to a cold ocean.

Overall, the large scale pattern does not point to any significant storms occuring. For Wednesday into Saturday, the main feature will be the boundary that meanders north and south from time to time while several weak disturbances transverse along it leading to several chances for showers. A slightly stronger wave moves through Thursday night, where some rumbles of thunder may be possible. All in all, any rainfall will be welcomed considering the ongoing drought conditions. Shower chances continue through the weekend into early next week as the jet stream will be well to our north.

AVIATION /12Z TUESDAY THROUGH SATURDAY/

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

Today...FZRA/SN will change to RA from south to north from 15Z to 17Z, then plain RA. IFR/LIFR conds. E winds around 5 kt, becoming SE late. Moderate confidence.

Tonight...IFR/LIFR in RA/BR, then BR. SW winds around 5 kt.

Outlook...

Wednesday...Sub-VFR conditions and some light rain possible.

Thursday...Sub-VFR conditions probable with some rain showers. Isolated thunder possible.

Friday and Saturday...Times of sub-VFR possible along with some showers, especially later Saturday.

MARINE

Sub-Small Craft Advisory conditions through tonight. East to southeast winds 10 to 15 kt, turning southeast this evening. Seas 3 to 4 feet. Visibility restrictions in rain and fog today through tonight.

Outlook...

Wednesday...Seas may start out around 5 feet on the ocean zones, otherwise these then subside.

Thursday and Friday...No marine headlines expected.

Saturday...Small Craft Advisory conditions possible at night.

PHI WATCHES/WARNINGS/ADVISORIES

PA...Winter Weather Advisory until 11 AM EST this morning for PAZ101>106. Winter Weather Advisory until 9 AM EST this morning for PAZ070- 071. Winter Weather Advisory until 7 PM EST this evening for PAZ054- 055. Winter Weather Advisory until 1 PM EST this afternoon for PAZ060>062. NJ...Winter Weather Advisory until 8 AM EST this morning for NJZ016. Winter Weather Advisory until 3 PM EST this afternoon for NJZ001-007-008. Winter Weather Advisory until 11 AM EST this morning for NJZ009-010-015. Winter Weather Advisory until 9 AM EST this morning for NJZ017>019. DE...Winter Weather Advisory until 8 AM EST this morning for DEZ001. MD...None. MARINE...None.