Marine Weather and Tide Forecast for Accokeek, MD

KEY MESSAGES
- 1) Dry and milder through Wednesday.

- 2) Much cooler conditions return for Thursday through Saturday, along with chances for precipitation.

DISCUSSION
KEY MESSAGE 1...Dry and milder through Wednesday.

Heights aloft will rebound later today while the pressure gradient relaxes substantially leading to slightly warmer temperatures and noticeable lighter winds this afternoon.

A dry cold front will then cross the area Monday, leading to gusty northwest winds returning. There isn't much of a thermal or moisture gradient/discontinuity with this front, so high temperatures will likely be similar to Sunday when combined with downsloping effects.

Another sfc trough will move across the region Tuesday.
Temperatures will be about 5 to 8 degrees above average as there could be a warming surface wind out of the southwest. Highs will reach the middle 60s to lower 70s with upper 50s to near 60 in the mountains. Lows Tuesday night will drop into the upper 30s to mid 40s. Once the front moves through, a surface high pressure will quickly build into and across the region for Wednesday. This will allow for temperatures to remain above average by a few degrees and the day to be dry. Highs in the middle to upper 60s with middle 50s in the mountains. The high quickly moves east by Wednesday night. Lows mid 30s to mid 40s.
The colder temperatures could support some frost/freeze concerns where the growing season continues mainly east of the Blue Ridge.

KEY MESSAGE 2...Much cooler conditions return for Thursday through Saturday, along with chances for precipitation.

Model guidance is in very good agreement that a very deep trough will dig southward across the Eastern half of the CONUS late in the week. While there's good agreement that a longwave pattern with troughing in the East and ridging in the West will set up, there are still considerable differences with respect to the finer forecast details during that time, with several individual lobes of vorticity interacting and then combining to ultimately dig out the deeper longwave trough.

In terms of sensible weather, clouds will be on the increase on Thursday as the upper trough digs to our west. Despite the increase in cloud cover, temperatures are still forecast to be seasonable, with highs generally in the upper 50s and lower 60s. An area of low pressure is expected to form downstream of the digging trough, but there's still some spread with respect to where exactly it will form and how it will track. Some solutions (such as the 12z Euro) have the low tracking directly overhead on Thursday and then offshore Thursday night into Friday, while others (such as the 12z GFS) have the low forming to our south over the Carolinas and then tracking northeastward toward just east of the Delmarva. In most of these scenarios, precipitation would likely break out in the form of rain across much of the forecast area on Thursday.

In any of the above scenarios colder air will start to filter into the area from the north Thursday night into Friday. Depending on the ultimate track and strength of the low, some locations may transition over from rain to snow Thursday night into Friday. As is often the case, chances for snow will be greater as one goes higher up in elevation and further to the northwest.

If the absolute coldest solutions were to verify, many locations could see their first flakes of the season, although accumulations would still be unlikely at lower elevations with marginal temperatures in place. A more likely scenario is for precipitation to stay all rain at lower elevations with snow mixing in at the higher elevations. The Alleghenies will have the greatest chance for accumulating snow, but even there there's still considerable spread, due to the uncertainty in the finer scale details within the trough and the ultimate track/strength of the low.

Most guidance suggests that precipitation should begin to wind down by late Friday night, but a few solutions keep lingering light precipitation through much of the day Saturday. Either way, temperatures look to remain cool, with highs in the 40s to near 50.

AVIATION /12Z SUNDAY THROUGH THURSDAY/
P6SM SKC and W winds 08g16kt. Some LLWS is possible tonight as sfc winds decouple, but strengthen aloft. Stronger NW winds Mon gusting up to 30 kt. Lighter winds Tue and Wed.

VFR conditions and light winds are expected during the day Wednesday. Winds will turn easterly on Thursday and then eventually northerly Thursday night. VFR conditions are expected through much of the day Thursday along with chances for rain. Sub-VFR conditions appear possible by Thursday night as ceilings start to lower.

MARINE
Winds will continue to diminish through the day today. Have canceled some SCAs where winds have already diminished. Winds strengthen substantially on Monday in the wake of a dry cold front. Have issued new SCAs for Monday, which may need to be extended for some parts of the waters Monday night.

Light and variable winds are expected over the waters on Wednesday. Wind will become easterly on Thursday and then northerly Thursday night. Small Craft Advisory level winds appear possible in northerly flow Thursday night.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 6 PM EST Monday for ANZ530>534- 539>541-543.
Small Craft Advisory from 9 AM to 6 PM EST Monday for ANZ535>538-542.
Small Craft Advisory until 6 AM EST Monday for ANZ537.