textproduct: Philadelphia/Mt Holly

WHAT HAS CHANGED

Snow forecast remains on tap for tonight with the highest totals north of the I-195 and PA Turnpike corridors.

KEY MESSAGES

1. Low pressure moves through the Mid-Atlantic tonight through Monday morning, bringing rain and snow to the area.

2. Above normal temperatures are expected for most of this week and into next weekend.

3.An unsettled pattern takes hold for this week with multiple chances for rain, and potentially some mixed precipitation in the higher elevations of our northern areas.

DISCUSSION

KEY MESSAGE 1...Low pressure moves through the Mid-Atlantic tonight through Monday morning, bringing rain and snow to the area.

Low pressure over the Gulf Coast states tracks east this evening, and will lift towards the Mid-Atlantic by midnight tonight before departing into the Western Atlantic on Monday.

Rain develops on a warm front out ahead of this low in Delmarva, the Delaware Valley, and southern New Jersey late this afternoon/early this evening, and then precipitation lifts to the north and east as the night progresses. For northern areas, there should be enough wet bulbing, at least initially, for snow, and then as the night progresses, enough cold air will wrap around into the area to keep precipitation as all snow. The big question is where the rain/snow line sets up. Based on latest model trends, it looks like that area will be around the I-195 corridor in New Jersey west through Philadelphia and across the PA Turnpike. In this area, and 5 to 10 miles north and south of this area, there will be a mix of rain and snow, while precipitation will be plain rain south of that area, mainly south of a line from Wilmington to Atlantic City.Snow accumulations will generally average a coating to an inch, though locally up to 2 inches is possible in portions of northeast New Jersey. For Delmarva and southern New Jersey, generally 1/4 to 1/2 inch of rain is expected.

High pressure develops over the area on Monday, but a prolonged onshore flow will keep skies cloudy throughout the day. Highs will mostly be in the upper 30s to low 40s, which are still several degrees below normal.

KEY MESSAGE 2..Above normal temperatures are expected for most of this week and into next weekend.

A high pressure system that is moving offshore Tuesday leads to a southwest wind with its return flow and remains offshore into Wednesday. This leads to warm air advection and temperatures trending above normal for this timeframe. Beyond this, multiple systems move through the region allowing for more opportunities for warm air advection keeping above normal temperatures going into next weekend.

For the specifics on temperatures, highs range from the mid 40 to low 50s for much of the area Tuesday through Saturday. Highs on Wednesday through Friday get into the mid to upper 50s with some spots potentially getting to 60 in the southern portion of Delmarva.

In terms of overnight lows, Monday night will feature temperatures in the upper 20s and low 30s. For a large amount of the area, this will likely be the last night with below freezing lows for the remainder of this week. Lows Tuesday night through Friday night look to be mainly in the mid 30s to low 40s.

After over two weeks now with snow on the ground, these warmer temperatures will allow the snowpack to melt quicker.

KEY MESSAGE 3...An unsettled pattern takes hold for this week with multiple chances for rain, and potentially some mixed precipitation in the higher elevations of our northern areas.

During this week and into next weekend, there will be multiple low pressure systems moving through the region. This will lead to multiple rounds of precipitation mainly in the form of rain but some wintry precipitation is possible in the higher elevations of our northern areas at times.

Our first system to move through will be the weakest out of all the systems with much of the area remaining dry. A weak shortwave dives in from the northwest Monday night and moves through the Northeast. This system may be able to result in some light mixed precipitation in our northern areas. An area of slight chance (20%) PoPs have been maintained to show the potential for light precipitation. When mentioning this as light mixed precipitation, it has the potential to include snow, freezing rain/drizzle, and plain rain. Due to the mixed precipitation potential, the timeframe bears watching. Overall though, the light precipitation looks relatively unimpactful given the limited coverage of it.

For the second system, a more notable shortwave moves through. At the surface, there will be a low pressure system near the Midwest that drags a warm front northward on Wednesday which will result in some rain for the area during the day Wednesday into early Wednesday night. Model guidance has trended more in the direction of this being an all rain event for our area. QPF amounts look rather light with NBM Probability of 1 inch or more of QPF being less than 10% for the entire area. However, our area could certainly use some rain and this could be the first measurable rain for some in almost a month or more (given how cold it has been, precipitation type has been all snow). We then stay in the warm sector Thursday into Thursday night with the potential for some isolated rain showers to pass through the area during this timeframe.

Another system arrives towards the end of the week for the Friday into Saturday timeframe. This is another low pressure system originating from the Midwest and moving towards our area. Just like the midweek system, this should mainly be an all rain event for most, if not all of the region given the track of the low. However, if more precipitation comes during the overnight hours, higher elevation areas in the southern Poconos and far northern NJ could see some snow or freezing rain. NBM Probability of QPF over 1 inch is still on the lower side at around 10-20%. The details will be ironed out over the next couple days, especially once the timing comes more into focus.

Beyond this, there is the potential for yet another system towards the end of the weekend but there remains uncertainty with the details of this system as it is at the end of the long term period.

Overall, these systems will bring primarily rain to most of the area, with the potential for mixed precipitation in far northern New Jersey and the southern Poconos depending on timing. One key note with these systems, we are not currently expecting moderate or major impacts. In fact, for most of the region, it will be more of a beneficial rain.

AVIATION /19Z SUNDAY THROUGH FRIDAY/

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

Rest of today...VFR with MVFR conds developing after 22Z. At KRDG/KPNE/KPHL, precip will be RASN, while precip will be SN at KABE, KTTN and RA at KILG, KMIV, KACY. E winds 5 to 10 kt. Moderate confidence.

Tonight...MVFR conds, lowering to IFR by 03Z. At KRDG, KABE, KTTN, precip will be SN. At KPNE, KPHL, KILG, precip will be RASN. At KMIV and KACY, precip will be RA. Precip mostly ends by 09Z, then IFR/LIFR CIGs for the rest of the night. E-NE winds 8 to 12 kt. Moderate confidence.

Monday...IFR CIGs in the morning, slowly lifting to MVFR in the afternoon, and eventually to VFR prior to 00Z Tuesday. NE winds around 10 kt, becoming LGT/VRB late. Moderate confidence.

Outlook...

Monday night...Sub-VFR possible due to low clouds.

Tuesday through Tuesday night...VFR. No significant weather.

Wednesday through Wednesday night...Sub-VFR conditions expected with rain showers and low ceilings moving through.

Thursday through Thursday night...Primarily VFR, though sub-VFR conditions possible in isolated rain showers or low clouds.

Friday...Sub-VFR conditions expected due to rain and low clouds.

MARINE

Sub-Small Craft Advisory conditions on tap for most of tonight. Low pressure passes south of the coastal waters late tonight through Monday morning, and then northeast winds increase to 15 to 20 kt with gusts in excess of 25 kt. Seas build to around 5 feet. Though winds diminish late Monday morning as low pressure departs, seas on the ocean remain elevated through the day. The SCA remains in effect for the ocean for Monday.

VSBY restrictions in rain and/or snow and fog tonight. VSBY restrictions in fog may continue through late Monday morning.

Regarding the river/bay ice...Ice cover continues across many area bay waters and inland estuaries. This includes, but is not limited to the Delaware estuary. On rivers, the ice thickness is enough to cause some restrictions in the flow. Per satellite imagery and ice analysis data, the Delaware River is mostly ice covered from the Delaware Memorial Bridge upstream, to at least Washington Crossing, though we are seeing improvement with warmer temperatures that will only get better with warmer days ahead.

According to latest analysis from the National Ice Center, Delaware Bay is actually mainly ice-free with less than 10% coverage of ice.

The most common ways river ice can break up is either through a thermal or mechanical means. We would like to see temperatures rise into the 40s for a few days, which parts of the region are forecast to get to once again this weekend with some areas getting into the 50s early next week. Significant rainfall, producing river rises, can also break up ice but that is not in the forecast this week.

As a result, ice cover will gradually decline over the next week or so and we are already seeing major improvement in Delaware Bay.

Outlook...

Monday night through Tuesday...A Small Craft Advisory is in effect for all ocean zones. Seas of 5 to 7 feet expected. Winds will be relatively light out of the north and west - around 10 kt or less and then shift to be more out of the southwest during the day Tuesday. Sub-SCA conditions expected on Delaware Bay.

Tuesday night...Lingering 5 foot seas could result in an extension to the Small Craft Advisory on the ocean.

Wednesday through Thursday...Small Craft Advisory conditions possible with seas near 5 feet.

Friday...Small Craft Advisory conditions possible with seas near 5 feet.

EQUIPMENT

KDIX will remain out of service through at least Sunday, February 15.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory from 6 AM Monday to 6 PM EST Tuesday for ANZ450>455.