textproduct: Philadelphia/Mt Holly

SYNOPSIS

A weak high pressure area will extend from the Ohio Valley to Delmarva later today and linger into the weekend. An area of low pressure tracks south of our region Saturday night into early Sunday. High pressure builds in for Monday before shifting offshore into Tuesday. A cold front crosses our area Wednesday.

NEAR TERM /THROUGH TONIGHT/

The cold front and snows from earlier today have cleared the southern potions of our CWA as of 930AM. Drier and colder air are presently sweeping across the Middle Atlantic region as a strong pressure gradient develops between low pressure over eastern Canada and high pressure across the central US. Northwest winds will remain 15 to 20 mph with 25 to 35 mph gusts for most of the day, then winds diminish shortly after sunset with loss of diurnal heating and as the pressure gradient slackens. Highs today will be cold, even for early January, topping off in the upper 20s to low 30s, except for southeast New Jersey and Delmarva, where highs will be in the mid to upper 30s.

An upper trough remains over the Northeast tonight and some more shortwaves will pass through the region. While some flurries are possible, not expecting much more than that. Winds remain elevated, generally around 10 mph with some gusts to 15 mph or so. Those winds, combined with cloudy skies will keep optimal radiational cooling conditions from developing. That said, cold air advection will be underway and lows tonight will be in the teens to low 20s. Wind chills tonight will be in the single digits to low teens.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

Friday is a dry day, although there will be some troughing to the north into Friday which keeps some clouds around. There will be ongoing snow showers to the north associated with the troughing and some lake effect during this time frame as well, which may result in some flurries reaching into the northwest portion of our area. This activity looks limited at this time. Highs on Friday are mainly in the 30s (20s in the Poconos and far northwest New Jersey).

An area of high pressure moves into the Midwest Friday night and eastward into the weekend. This will allow for dry weather Friday night and for most of Saturday. Friday night is mostly clear to partly cloudy. Lows are in the mid teens to low 20s Friday night. Clouds increase through the day Saturday from the south as an area of low pressure develops across the southeast U.S. and travels northeastward. Most of the day is dry Saturday with highs in the 30s for many.

For the time period of Saturday night into early Sunday morning, there will be an upper-level trough moving through the region along with two pieces of upper-level energy with one to the south of the area into Delmarva and one to the north of our area. Generally, the guidance keeps the developing low well to our south. The northern extent of the precipitation shield will depend not just on the track of the surface low, but also dry air northward and if the trough aloft sharpens up a bit more. The latter would involve the southern energy phasing more with the northern energy, and therefore something to watch. Given the continued uncertainty, made no changes from the National Blend of Models (NBM) which paints slight chance to low chance PoPS from about I-95 south and east. As of now, this system looks to be a quick mover as it exits very early Sunday morning.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Summary...Cold conditions, then some milder air starts to arrive Wednesday.

Synoptic Overview...A sharpening upper-level trough pivots across the East Sunday, then a shortwave embedded within the northwest flow aloft crosses the Northeast later Monday into Tuesday and may amplify the trough for a time. Another upper-level trough crosses the Great Lakes region into adjacent Canada Wednesday. At the surface, a cold front looks to cross our area late Tuesday or during Wednesday.

For Sunday and Monday...As the axis of a sharpening upper-level trough pivots across the East Sunday morning, surface low pressure is forecast to track out to sea as it is centered well east of Delmarva. This should result in dry but cold conditions. Surface high pressure then slides across our area Monday but quickly shifts offshore by Monday night. Some warm air advection ahead of a clipper type system in the Great Lakes could produce some light snow late Monday across mainly portions of our northern and western areas. This feature looks weak and moisture starved therefore any snow that would occur, as of now, looks to be rather light.

For Tuesday and Wednesday...Some mid level ridging arrives across our area during Tuesday as the axis of high pressure slides across our region. A trough in the Upper Midwest and Great Lakes will toss a warm front our way, and with return flow become more established, a milder air mass will start to arrive especially by Wednesday ahead of a cold front. The amount of moisture with this front is uncertain, especially given that the main energy may end up lifting well to our north, thus leaving our region within an area of much weaker forcing. Daytime temperatures especially on Wednesday are forecast to top out several degrees above average.

AVIATION /14Z THURSDAY THROUGH MONDAY/

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

Today...VFR conditions with few clouds. W to NW winds 15 to 20 kt with 25 to 30 kt gusts. Moderate/high confidence.

Tonight...VFR. NSW. W winds 5 to 10 kt. High confidence.

Outlook...

Friday and Saturday...VFR.

Saturday night...Mainly VFR, however if a southern system shifts far enough north then a period of sub-VFR conditions along with some light snow will be possible.

Sunday and Monday...VFR.

MARINE

A cold front, which crossed the waters earlier today, will continue east of the waters thru the day. Overall, SCA gusts will predominate today but a few brief, sporadic gale force gusts are possible. Right now. we don't think the gusts will be frequent enough nor widespread enough to warrant a Gale Warning.

Sub-SCA conditions tonight with Fair weather.

Outlook...

Friday through Monday...The conditions are anticipated to be below Small Craft Advisory criteria.

PHI WATCHES/WARNINGS/ADVISORIES

PA...None. NJ...None. DE...None. MD...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ430- 431-450>455.