textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

No significant changes.

KEY MESSAGES

1. An arctic front late Saturday night into Sunday may bring some snow to our northern areas.

2. A couple waves of low pressure may impact the region through the middle of next week with periods of wintry precipitation possible.

3. A significant warm-up is expected late next week.

DISCUSSION

KEY MESSAGE 1...An arctic front late Saturday night into Sunday may bring some snow to our northern areas.

A mild period starts the weekend with highs likely well into the 50s for much of the region Saturday, helping along the snow melt. A cold front will then advance into the region Saturday night, stalling out as it does so. A wave of low pressure then moves eastward to our north during the morning Sunday, producing some spotty showers of rain and snow, especially across the northern areas (Poconos/NW NJ) where a small accumulation is possible. Behind the front, we'll see a return of winter, at least for a day or two, with temps falling below normal again. Highs will be about 5 degrees lower on Sunday across the southern Delmarva, closer to 10 degrees lower across the bulk of the area including metro Philly, but up to 15 degrees lower in the Poconos.

KEY MESSAGE 2...A couple waves of low pressure may impact the region through the middle of next week with periods of wintry precipitation possible.

A cold airmass is forecast to be in place on Monday into Tuesday as arctic high pressure from Canada builds over the Northeast. As of this afternoon, guidance continues to gain agreement that a couple separate systems will pass close to or over the area. The first will come on Monday into Monday evening with the second coming later Tuesday into Wednesday.

Starting with the Monday system, weak low pressure is forecast to track east out of the Tennessee Valley along a stalled frontal boundary. With the strong, arctic high to the north, guidance keeps this system suppressed to the south while tracking off the coast near the Chesapeake region. Suppose a period of light snow may impact the area later Monday, but PoPs have continued to decrease to the 15-30% range. Trends in accumulations with this system continue to decline as well. As this system exits, another disturbance is forecast to ride along this boundary which will then impact the region Tuesday into Wednesday, though timing differences amongst guidance persists. With temperatures gradually warming on Tuesday into Tuesday night as a southerly flow regime sets-up a rain/snow mix may occur at the onset before changing over to plain rain into Tuesday night. PoPs during this period have increased, now in the 60-80% range.

KEY MESSAGE 3...A significant warm-up is expected late next week.

In wake of wintry systems earlier in the week, a significant warm-up is expected starting late next week into next weekend. GEFS and ECENS guidance are in pretty good agreement that positive height anomalies are forecast over the eastern CONUS with troughing over the western CONUS. CPC probabilities suggest that there is a 60-70% chance that temperatures will be above normal. Current forecast highs for late week are in the 50s and 60s.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

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

This afternoon...VFR. Light and variable winds becoming southeast to south-southwest around 5 knots. Moderate confidence.

Tonight...VFR overall. Some fog/low clouds possible late, especially around KPHL/KPNE and areas to the south and east. Southerly winds around 5 knots becoming light and variable to calm. Low confidence.

Saturday...Some fog/low clouds possible to start, otherwise VFR. Light and variable to calm winds, becoming south to southwest 4-8 knots. Low confidence regarding fog/low clouds.

Outlook... Saturday nihgt...VFR.

Sunday...Sub-VFR possible with passing rain and snow showers, with best chance of these conditions occurring across KABE/KRDG/KTTN.

Sunday night through Monday night...VFR most likely, slight chance sub-VFR with small chance of snow.

Tuesday through Wednesday...Sub-VFR likely with brief period of snow changing to mixed precip and then rain by Tuesday night, with rain possibly persisting in Wednesday.

MARINE

The conditions are expected to remain below Small Craft Advisory criteria through Saturday. Some fog and/or low clouds may develop late tonight and linger through Saturday, however this is low confidence. As of now, included a patchy fog mention.

Outlook...

Saturday night through Sunday...mainly below Small Craft Advisory conditions.

Sunday night...SCA conditions possible with northwest winds gusting to 25 kts and waves up to 5 feet.

Monday through Wednesday...sub-SCA likely, but slight chance of snow Monday becomes a chance of snow and rain Tuesday then rain likely Tuesday night into Wednesday, with vsby restrictions becoming likely.

PHI WATCHES/WARNINGS/ADVISORIES

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