textproduct: Philadelphia/Mt Holly

SYNOPSIS

High pressure will move offshore of the Virginia and North Carolina coasts later today into tonight. A couple of dry cold fronts are expected to move across the area Sunday and early Monday, followed briefly by high pressure later Monday. A warm front and subsequent cold front is then forecast to move across the area around Tuesday into early Wednesday, followed briefly by high pressure late Wednesday. A pair of weak disturbances could then affect the area for the end of next week.

NEAR TERM /THROUGH TONIGHT/

Thru dawn, Winds will continue to decrease as high pressure builds in quickly from the Ohio Valley. Temps will mostly be in the 20s with some teens on the Pocono plateau. Winds chills will be in the teens most spots with single digits for Mount Pocono.

Today, Sunny skies are expected with decreasing winds this morning. High pressure arrives across the region early this afternoon then moves off the coast. Winds will switch around from West/Northwest to Southwest by sunset. High temps today will be cool but the sunshine will make it feel better. Highs will be in the upper 30s/low 40s for the S/E areas and low/mid 30s N/W. So, overall, about 4 to 6 degrees below normal.

For tonight, the high pressure system will be offshore and a return flow behind it sets up across the Middle Atlantic. Meanwhile, low pressure advances across southern Canada well to our north. The pressure gradient between these two systems will keep a South to Southwest synoptic flow across our region. Skies will be mostly clear early, but then increasing clouds are expected late. Overnight lows will be milder than the current night with lows dropping to the mid/upper 20s for the NW areas and low 30s for Delmarva, metro Philadelphia and south NJ.

SHORT TERM /SUNDAY THROUGH MONDAY/

A dry cold front moves through early Sunday, with a gusty northwest wind developing. We'll likely see gusts of 25-30 mph during the day with the cold advection behind the front. That said, it actually looks a little milder than Saturday, with highs rebounding into the 40s thanks to better mixing and the warm advection preceding the front itself. A few wraparound snow showers or flurries may make their way into the Poconos, but overall dry conditions should prevail.

Northwest winds continue with cold advection on Sunday night as high pressure very slowly builds eastward from the Ohio Valley. Could still be some flurries in the Poconos, but otherwise dry. Lows drop substantially from Saturday night, with teens Poconos and low-mid 20s elsewhere.

The aforementioned high moves right across the region or just to the south on Monday, with lighter winds. This should also allow for some sunshine, but with the cold advection preceding it, highs will be notably cooler, with 30s for most of the region.

LONG TERM /MONDAY NIGHT THROUGH FRIDAY/

Another system will approach from the west Monday night, crossing the region on Tuesday. This will bring an increasing risk of precip as it passes, with the highest chance being late Monday night into Tuesday morning. With the antecedent cold air mass in place, if precip arrives early enough, it could fall in the form of snow. Chances of this remain near 30-50% and confidence on any accumulation is low due to the uncertainty in the timing of the precip onset and QPF amounts. If the system trends slower and precip moves in a bit later, it could end up being mostly rain outside of the higher terrain of E PA and N NJ. Our forecast include less than 1" of snow for all of our Pennsylvania counties, much of our New Jersey counties, and northern Delaware. A reasonable worst case scenario (something similar to the 00Z GFS) would be around 1-2" of snow as far south as the Philly metro, and perhaps as much as 3-4" in the higher elevations of the Poconos and NW NJ. While the forecast calls for relatively light amounts, we'll have to keep an eye on this period, as the light snowfall could impact the Tuesday morning commute. Lows Monday night will be in the mid 20s to low 30s for most, but temperatures should warm to the low to mid 40s as the system crosses the area on Tuesday. So any snow that does fall early in the morning, it should melt away pretty quickly.

This system has little if any cold air behind it... in fact, temps show moderation. Thus, lows Tuesday night stay in the 30s for most, with highs again in the 40s for Wednesday (Christmas Eve) as another high pressure moves in from the west, this one being more Pacific in origin and weaker than its predecessor.

Mostly clear skies and light winds under said high may allow for some radiational cooling Wednesday (Christmas Eve) night, but a very weak disturbance may bring clouds or even a little light precip for Thursday (Christmas Day) itself. Overall however, the moderating trend will continue, with highs likely approaching or even possibly exceeding 50 degrees.

Uncertainty is still pretty high for Friday (Boxing Day), with questions regarding the speed of passing upper level impulses, but the main theme is mild... with highs likely 50s much of the region and possibly 60+ from Philly south. The main question is whether its accompanied by showers or not.

AVIATION /07Z SATURDAY THROUGH WEDNESDAY/

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

Today... VFR expected with mostly sunny skies. West winds around 10 knots will switch to Southwest by mid afternoon and then continue to back to South late. High confid.

Tonight... VFR continues with mostly just high clouds expected. South winds 5 to 10 knots. LLWS developing with 35 to 40 kts at 020 from the Southwest. Medium/high confid.

Outlook...

Sunday through Monday...VFR. Gusty WNW winds on Sunday.

Monday night into Tuesday...Restrictions possible due to a chance (30-50%) of rain or snow and low clouds. Conditions improving late Tuesday.

Wednesday (Christmas Eve)...VFR. No significant weather.

MARINE

We decided to extend the Gale out several more hours as wind gusts remained at the low-end of the Gale range at expiration time. We'll convert the Gale to SCA by dawn and run it into the morning. Winds and seas look to decrease rather quickly as the strong high builds overhead today. Tonight, we'll be in the return flow behind the high and winds will return to SCA levels overnight. Fair weather today and tonight.

Outlook...

Sunday through Sunday night...Small Craft Advisory conditions likely develop Saturday night and continue into Sunday night as another cold front approaches and then passes through the region.

Monday through Monday night...High pressure passing overhead likely results in conditions below advisory levels.

Tuesday...Another cold front approaching the region brings a return of advisory conditions, with a small risk of gales after the front passes.

Wednesday (Christmas Eve)...Conditions should remain below advisory levels. Fair weather.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Gale Warning until 6 AM EST early this morning for ANZ430-431- 450>455.