Marine Weather and Tide Forecast for Arnold, MD

KEY MESSAGES
- 1) An area of low pressure may impact the area this weekend, but the details remain highly uncertain.

- 2) Relatively mild weather will linger into Wednesday east of the mountains, but colder weather and bouts of upslope wintry precipitation return mid to late week.

DISCUSSION
KEY MESSAGE 1...An area of low pressure may impact the area this weekend, but the details remain highly uncertain.

The 12Z deterministic global models continued to show rather large inconsistencies with their previous runs with respect to the potential storm during the Sun-Sun night period, basically showing the storm missing our area to the south or just too warm for snow.
On the other hand, the ensemble and the AIFS ensemble guidance continue to show some risk of wintry weather to our area, mainly for areas west of the Blue Ridge Mountains. The 12Z EPS showed some clustering with a low pressure center near Cape Hatteras bringing precip to the southern half of the fcst area with the system moving quickly out to sea early Monday while trends in the AIFS ensemble mean showed this system remaining further south than the EPS with a lessening risk of snow. In summary, large uncertainty still looms with respect to the track and whether there will be enough cold air to support snow outside of the mountain areas.

KEY MESSAGE 2...Relatively mild weather will linger into Wednesday east of the mountains, but colder weather and bouts of upslope wintry precipitation return mid to late week.

The brief stretch of mild weather will come to an end over the next 24 to 36 hours following the passage of a cold front.

Not much precipitation is expected east of the Appalachians, though a few showers could still pop up this evening as the front moves by. There is an outside chance (10-15%) of some very spotty and light freezing rain over northeastern Maryland with temperatures hovering near freezing this evening.

A few extra rain showers are possible given some southwest upslope enhancement into the west side of the Appalachians this evening, but even here amounts should be quite light. As the night wears on, however, temperatures fall readily behind the cold front along and west of the Allegheny Front. Forecast soundings show saturated profiles, but only in the lowest 2,000 feet or so above the ground. This, coupled with temperatures just below freezing in this layer, would support a period of upslope freezing drizzle or light freezing rain (lack of ice crystals), perhaps mixed with a little snow at times in any slightly deeper showers that manage to develop heading into Wednesday. Went ahead and issued a Winter Weather Advisory for this threat from late tonight until mid afternoon Wednesday.
Despite air temperatures in the 40s and 50s this afternoon, a lingering snow/ice pack and cold ground temperatures should support some ice accretion. This may result in some slick travel for the Wednesday morning commute, though total amounts are likely hard pressed to exceed 0.10".

In the wake of the cold front on Wednesday, blustery northwest winds will take hold across the region. There is a bit of a signal for some downslope enhancement off the Alleghenies, which could result in some 45-50 mph gusts Wednesday into Wednesday night along and east of the ridgelines. Confidence was too low for an advisory given the marginal nature of the winds in most guidance (plus a downward trend in the 12z HRRR), but have mentioned gusts to 45 mph in the Winter Weather Advisory. For areas near and east of I-81, gusts of 25 to perhaps 40 mph are likely. Downsloping northwest flow will compensate somewhat for cold advection leading to high temperatures near or even slightly above normal, but with colder wind chills than today.
Wave clouds appear likely in this pattern which could result in periods of mostly cloudy skies, though current guidance is not quite yet picking up on these clouds (hence the partly to mostly sunny forecast for the moment - will evaluate in future updates).

As cold advection continues and saturation/inversion heights rise later Wednesday into Thursday, snow should become the predominant precipitation type over the Alleghenies. An inch or two of snow seems plausible, but with a lot of the Great Lakes frozen over the moisture source will be lacking. Am currently anticipating sub-advisory snowfall as a result, though there is the potential for spillover due to FROUDE numbers of 1-2.

The colder airmass will linger through the end of the week, though it will not be nearly as frigid as recent cold spells.

AVIATION /18Z TUESDAY THROUGH SUNDAY/
VFR conditions are expected at the TAF sites through Thursday.
However, some briefly lower CIGs (around FL025) are possible mainly near KMRB from 02Z-08Z. A brief sprinkle or shower can't be ruled out as a cold front crosses tonight, but any CIG/VSBY restrictions should be very brief and spotty. S/SW winds 4-8 kts will switch to W/NW between 04Z-08Z. A period of LLWS is likely this evening with the passage of a warm front. Winds increase on Wednesday with gusts of 20-30 kts likely in the afternoon and into the evening. Elevated winds persist through Thursday.

Relatively light winds Fri and Sat with no flight restrictions expected.

MARINE
South to southwest winds will remain generally light through this evening, though a few gusts of 15-20 kts are possible around southern MD as a warm front lifts through. Winds shift to the west and northwest late tonight and increase Wednesday through Thursday with gusts of 20 to 30 knots likely.

Winds begin to diminish Friday. No SCA conditions expected through Sunday.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Winter Weather Advisory from 3 AM to 3 PM EST Wednesday for MDZ509.
VA...None.
WV...Winter Weather Advisory from 3 AM to 3 PM EST Wednesday for WVZ501-505.
MARINE...Small Craft Advisory from 7 AM Wednesday to 4 PM EST Thursday for ANZ530>543.