Marine Weather and Tide Forecast for Lexington Park, MD

NEAR TERM /UNTIL 6 PM THIS EVENING/
Mid morning update: Cloud cover continues to increase across southwestern portions of the forecast area, with mostly sunny skies further northeast. No changes have been made to the previous forecast
Previous discussion follows

High pressure is positioned over New England this morning. A closed low remains near Louisiana/Mississippi, blocked by ridging to the north and east. Still mainly high clouds across the area for now, with the nearest showers in southwestern Virginia. That will change through the day, as the high slides off the coast and allows moisture to be advected northward.
However, it will be battling residual dry air, so it will take time for anything more than light showers/sprinkles to advance northward...generally late morning/afternoon for locations south of I-66 and evening farther north. However, Baltimore/northeast MD may not see much rain until Tuesday morning being closer to the ridge. The showers and isolated thunderstorms that move into central Virginia today should be intermittent and not produce enough rain to cause any flooding issues. High temperatures today will be dependent on the advance of thicker clouds, but more of the area may reach the upper 70s to near 80 now with the slower onset. The southwestern corner of the CWA will stay in the mid 60s to lower 70s.

SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/
The upper low will begin to pivot to the northeast tonight into Tuesday as ridging moves off the coast and a trough moves into the Intermountain West. This will focus moisture transport into the CWA with precipitable water values in excess of 1.5 inches.
A southeasterly low level flow will enhance lift as it encounters the mountains, especially the Blue Ridge. While some embedded thunderstorms are possible during this period, relatively weak instability may limit instantaneous rainfall rates. However, the long duration of rain will result in average totals of 1 to 4 inches, with the highest amounts likely in the vicinity of the Blue Ridge. While the drought will provide some buffer to flooding, the prolonged period of favorable conditions for heavy rain may ultimately lead to some flooding.
Have issued a Flood Watch for areas bordering the Blue Ridge where the highest totals are expected from this evening through Tuesday evening. While relatively lower totals (and shorter duration of heavier rain) are expected north of the watch, flash flood guidance suggests there may be more susceptibility in this area due to recent rainfall. Future shifts will evaluate whether this balance is enough to warrant an expansion of the watch. Temperatures Tuesday will be muted in the upper 60s/lower 70s. A relative dry slot may reduce shower coverage and intensity by Tuesday evening, although some showers likely continue through the night.

The upper low will be near the central Appalachians Wednesday but slowly opening. A few breaks in the clouds are possible, or at least enough low level drying to support temperatures rising into the 70s. Combined with the approaching trough, some limited instability will be able to develop, leading to widespread showers and some thunderstorms by the afternoon hours.
Precipitable water values will be lower, and QPF forecasts are not too excessive. However, slow moving thunderstorms that move over any sensitive areas that already received heavy rainfall could result in a few additional instances of flooding. Rain chances will likely decrease Wednesday night as instability wanes and the opening trough axis moves overhead.

LONG TERM /THURSDAY THROUGH SUNDAY/
As the ULL becomes sheared out over the Northeast United States Thu, clouds should break over the local area. This will result in milder temperatures Thu (generally upper 70s to low 80s), but will increase instability over the area. Model soundings show more flow than Wed, so storms should move more. Main uncertainty with Thu is coverage, but some showers/thunderstorms appear possible at this time.

By Fri, another ULL will track eastward toward the Great Lakes. At the surface, a notable moisture return will occur from the Gulf of America into the Ohio Valley and Mid-Atlantic Fri into Sat. This will be coupled with some of the warmest temperatures of the spring thus far (mid to upper 80s both days), resulting in modest instability. The combination of low-level moisture, steep low-level lapse rates, steep for the Mid-Atlantic mid-level lapse rates, and strong flow will yield the potential for strong to severe thunderstorms. Depending on timing of cold front, Saturday may be the more active day, or it may be to the south of the area. Will continue to monitor. Regardless, the end of the week could yield a couple days of severe weather. High pressure may briefly move in Sun, but uncertainties with frontal positioning and the next shortwave over the Ohio Valley exist.

AVIATION /14Z MONDAY THROUGH FRIDAY/
Moisture will gradually advect northward today between high pressure moving off the coast and low pressure in the deep south. CHO will be the first to see lower ceilings and rain showers, perhaps by late morning. The remainder of the terminals will see deteriorating conditions late this afternoon or evening. Have been conservative with decreasing ceilings compared to guidance given a trend to slower timing as well as residual dry air. A stray thunderstorm could also affect CHO late this afternoon or evening.

Moderate to locally heavy rain will spread across the area tonight into Tuesday, with CHO expected to have the heaviest rain. IFR conditions likely set in tonight, perhaps lifting to MVFR for a time Tuesday. A few thunderstorms could be embedded by Tuesday afternoon. Shower coverage and intensity should decrease Tuesday night, but IFR to LIFR ceilings will become likely.

Some improvement to MVFR, or even VFR, is possible Wednesday.
However, showers and embedded thunderstorms remain likely, especially during the afternoon and evening. IFR to perhaps LIFR conditions will return Wednesday night as rain tapers off.

Main aviation hazard Thu and Fri will be potential for afternoon showers and thunderstorms. Winds southerly Thu, more southwesterly Fri. Generally light outside of any thunderstorms.

MARINE
High pressure will depart offshore today, resulting in winds becoming southeasterly. Tricky forecast from later this afternoon into tonight as winds increase aloft but mixing may be poor. Some sporadic gusts to 20 kt could occur, especially tonight on the middle bay and lower Potomac. However, confidence is not currently high enough to hoist an advisory.

Winds increase a bit further on Tuesday, with advisories going into effect for all waters. A soaking rain will develop late tonight into Tuesday, which may come with a few thunderstorms, particularly during the second half of Tuesday. Advisories will likely continue into Tuesday night, with some indication of a stronger surge of wind (at least 25 kt) on the southern Maryland waters during the evening. Lighter SE to S winds are forecast Wednesday and Wednesday night, although thunderstorms will be possible again Wednesday afternoon.

Winds likely remain below SCA criteria Thu and Fri. Southerly winds Thu become more southwesterly Fri. Afternoon thunderstorms are possible Thu and Fri afternoon, which could result in gusty winds.

TIDES/COASTAL FLOODING
As a low pressure system slowly approaches through mid week, continued onshore flow will gradually build anomalies. Sensitive shoreline could approach minor tidal flood levels between Tuesday and early Thursday.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Small Craft Advisory from 10 AM to 6 PM EDT Tuesday for MDZ008.
VA...Flood Watch from 8 PM EDT this evening through Tuesday evening for VAZ025>027-029-030-036>040-507-508.
WV...None.
MARINE...Small Craft Advisory from 10 AM to 6 PM EDT Tuesday for ANZ530>532-535-536-538>542.
Small Craft Advisory from 6 AM to 6 PM EDT Tuesday for ANZ533- 534-537-543.