Marine Weather and Tide Forecast for Cape St. Claire, MD

NEAR TERM /THROUGH SUNDAY/
As of early this afternoon, high pressure is heading east off the Jersey shore while low pressure is over southwestern Indiana heading up the Ohio Valley. A secondary low presssure is starting to develop near Cape Hatteras, and another large high pressure is sitting over the northern High Plains. As we head through tonight, the Ohio Valley low will continue heading east- northeast toward northwestern PA while the coastal system will head north- northeast towards Long Island. Late tonight, the low from the Ohio Valley will dissipate over northern PA while the coastal low takes over and heads northeast up the New England coast. As that system heads away, the high over the northern High Plains will build slowly southeastward into the area.

With a cold and dry air mass currenty in place, light precip aloft so far has mostly evaporated/sublimated before reaching the ground. Exception has been the far south, where light snow and mixed precip has been observed in the Delmarva so far with little impact. However, as the lows approach from both west and south, expect precip to blossom across the region with strong warm advection and difluence developing aloft to support it. The strong warm advection aloft, and easterly winds at the surface, should work on making this a mixed precip system, with initial snow transitioning to sleet/freezing rain in nearly the entire CWA, and to rain from I-95 and points south and east. Freezing rain looks to linger longest across the western Philly suburbs, so continue with highest ice accumulations in this area, possibly up to around a quarter inch, but did drop snowfall amounts a smidge across Philly metro as it looks like the warm air really comes in fast aloft.

Further north, a burst of moderate to heavy snow looks likely after sunset for the Lehigh Valley, Poconos and northern NJ, possibly extending into the northern Philly suburbs and central NJ briefly, before the change to sleet and freezing rain. Where that lingers longest as snow, highest accumulations will be found, with 3-6 inches expected in northernmost NJ, 2-4 inches in the Poconos and the rest of north-central NJ, and 1-2 inches in the Lehigh Valley, northern Philly suburbs and central NJ.
This prolonged period of snow, followed by sleet, should result in less ice accumulation, closer to a tenth of an inch or less.

From I-95 on south and east, a transition to rain looks likely overnight as the easterly flow works some warmer air inland, though this appears to likely be a struggle, and it may fail to change over in Philly until very late in the storm. That said, still expect around a tenth of an inch of ice across the I-95 corridor and interior southern NJ and northern Delmarva. That quickly declines further southeast where oceanic influence should be more dominant, with ice of just a few hundredths of an inch before warming occurs.

The consolidated low pulls out of the area early Sunday, and conditions improve pretty markedly by day's end, with sun returning on a gusty northwest wind. After lows tonight mostly near or below freezing, expect highs Sunday to rebound back to 40 or higher for most of the region, with far southern aras approaching 50 and only areas from about Allentown north likely to stay in the 30s. This should allow any lingering ice to melt for much of the region. The gusty wind will make it feel colder with gusts of 20-30 mph likely.

SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/
Low pressure will be southeast of Cape Cod by Sunday morning and will continue to track out to sea. High pressure builds in from the west, and a tightening pressure gradient will allow for west to northwest winds around 15 mph with 20 to 25 mph gusts to develop. Highs on Sunday will be around the seasonal averages, topping off in the upper 30s to low 40s, though in the mid and upper 40s in southern Delmarva.

High pressure continues to build east Sunday night before passing over the Northeast on Monday and departing Monday night.
Dry conditions on tap with temperatures several degrees below normal. Lows will be in the teens and 20s at night and in the upper 20s in the southern Poconos to the 30s for most of the area and in the low 40s in southern Delmarva on Monday.

LONG TERM /TUESDAY THROUGH SATURDAY/
Unsettled conditions on tap for the Long Term period as several storm systems are gearing up to affect the region.

High pressure will be over the area Tuesday morning before departing by early afternoon. Developing low pressure lifts towards the Mid-Atlantic and moves out to sea Tuesday night.
Although surface temperatures will be at or a few degrees above freezing for most of the area, it will be relatively dry for most of the day with dew points in the teens and low 20s, gradually rising through the day. As a result, there should be enough of a wet bulb effect for temperatures to fall below freezing and for precipitation to be mostly snow, though depending on how far north the low can reach, there may be a rain/snow mix for Delmarva Tuesday afternoon. There also could be a fairly sharp cutoff on the northern extent of the accumulating snow. 08/00Z operational GFS and the CMC seem to have a southern shift with the low, and the 08/01Z NBM showing 40 to 50 percent probability of 4 inches of accumulating snow or more, pretty much across most of the region. This is a tick down from the prior run of the NBM, and may slide south with the next run of the NBM. 08/00Z NAM goes out to 12Z Tuesday, so will need another 24 hours to get a handle on initial potential snow accumulations for the area.

This low will depart late Tuesday night, and then another storm system follows behind it fairly quickly for late Wednesday through Thursday. Based on latest trends, a quick shot of snow is possible throughout starting Wednesday night, but without much of a strong blocking high over eastern Canada, the low looks to take more of a northern track during the day Thursday, allowing snow to mix with and change to rain for all but far northern areas.

High pressure returns to close out the work week. Temperatures will be at or below the seasonal averages for the period.

AVIATION /19Z SATURDAY THROUGH THURSDAY/
The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas...

Through tonight...VFR conditions as of early this afternoon will slide downward after 20Z from southwest to northeast as snow, then sleet and freezing rain, envelops the region.
Expect terminals to be IFR either due to vsby or cigs by around 0Z and likely staying IFR or lower thru tonight as precip from KPHL south and east transitions to plain rain, though icing lingers further northwest. A burst of heavier snow, possibly with vsby below 1/2 mile, is possible for KABE with lower odds at KTTN/KRDG. Further south, mixing with sleet should prevent the excessively low vsby. Precip tapers off late tonight but low cigs linger. Winds southeast winds around 5 kts become easterly this evening and then light and variable overnight. Moderate confidence overall, low confidence in individual details.

Sunday...Improving to VFR after a mostly IFR start as northwest winds increase behind the system, gusting 20-30 kts. Moderate confidence.

Outlook...

Sunday...Lingering sub-VFR conditions Sunday morning will give way to VFR conditions in the afternoon.

Sunday night through Monday night...VFR.

Tuesday through Tuesday night...Sub-VFR conditions in SN, though a RA/SN mix is possible at KACY.

Wednesday...Lingering sub-VFR conditions in the morning, then VFR.

MARINE
No marine headlines are in effect through tonight. Southeast winds around 10-20 kt will become westerly after midnight as low pressure passes on by. A few gusts up to 25 kt possible, but largely should remain below SCA thresholds. Seas around 2-4 feet. Periods of sleet expected early, before changing to plain rain.

Sunday...SCA in effect for wind gusts up to 25 kt on the ocean and on Delaware Bay and for seas on the ocean up to 5 ft.

Outlook...

Sunday night through Monday night...Sub-SCA conditions.

Tuesday through Wednesday...Sub-SCA conditions. VSBY restrictions in snow and/or rain.

PHI WATCHES/WARNINGS/ADVISORIES
PA...Winter Weather Advisory until 6 AM EST Sunday for PAZ060-070- 071-101>104.
Winter Weather Advisory until 6 AM EST Sunday for PAZ054-055- 061-062-105-106.
NJ...Winter Weather Advisory until 6 AM EST Sunday for NJZ016>019.
Winter Weather Advisory until midnight EST tonight for NJZ021.
Winter Weather Advisory until 6 AM EST Sunday for NJZ001- 007>010-012-015.
Winter Weather Advisory until 2 AM EST Sunday for NJZ013-020- 022-027.
DE...Winter Weather Advisory until 6 AM EST Sunday for DEZ001.
Winter Weather Advisory until midnight EST tonight for DEZ002.
MD...Winter Weather Advisory until midnight EST tonight for MDZ012- 015-019-020.
MARINE...Small Craft Advisory from 6 AM to 6 PM EST Sunday for ANZ430- 431-450>455.