Marine Weather and Tide Forecast for Mayo, MD

KEY MESSAGES
- 1) Hotter conditions return today with potential for severe thunderstorms and strong gradient winds.

- 2) A strong low pressure system could bring the threat for heavy rainfall and thunderstorms late Sunday through Monday.

- 3) An active upper-level pattern could bring continued rain chances through mid-week.

DISCUSSION
KEY MESSAGE 1...Hotter conditions return today with potential for severe thunderstorms and strong gradient winds.

As ripples of energy in the mid-levels move east across our northern zones early this morning, some rain showers will bring some much needed rain to parts of the region through daybreak.
Most of these showers have occurred or are expected to occur across the northern half of the Alleghenies, western and central Maryland, northeastern West Virginia, and northwestern Virginia.

A cold front will drag across the region throughout the rest of today through early Friday. Hotter temperatures than yesterday expected this afternoon with highs in the middle 70s to middle 80s west of the Blue Ridge and highs in the lower to middle 90s east of the Blue Ridge. Heat index values in the mid 90s to perhaps near 100 expected. This heat, combined with effects from increasing humidity and wind shear in all levels could spawn some strong to severe thunderstorms across most of our region. There is some uncertainty as to the area extent of such strong to severe thunderstorms given the most recent nighttime convection, cloud cover, and expected slightly cooler temperatures in the aforementioned zones of our northwestern third of our region. Otherwise, all other areas may be more prone to such strong convection this afternoon into early evening.

Timing of strong to severe thunderstorms seem more probable late morning to mid-afternoon in the northwest and north-central areas, while the afternoon hours seem more legitimate farther east and southeast into the metros and northern half of Virginia. The southeastern zones, including southern Maryland would be more probable later this afternoon and early evening.
The main threats will be damaging wind gusts over 55 mph and large hail. Lightning may also become a big factor with the strongest thunderstorms. Not only will damaging winds be anticipated in strong to severe thunderstorms, but also from a synoptic or gradient viewpoint as well. Winds just above the boundary layer are very strong due to a low-level jet. A Wind Advisory remains in effect throughout the Alleghenies, interior western zones, and the northern Blue Ridge.

The cold front will push southward Thursday night. The front will absorb an area of low pressure to the south, likely originating from Arthur. There is still some spread with how far north additional rain reaches, but some rain chances will linger across the southern half of the area in particular through Friday morning. Skies should clear through the day with lowering humidity and seasonable temperatures.

KEY MESSAGE 2...A strong low pressure system could bring the threat for heavy rainfall and thunderstorms late Sunday through Monday.

After a mainly quiet weekend across the region, there is an increasing signal of active weather returning late Sunday into Monday. Looking aloft first, the key players are a compact upper low dropping southeastward from the Great Lakes as well as an open wave ejecting eastward from the Ohio Valley. The combination of these features will fuel increasing lift across the Mid-Atlantic region.
While the accompanying surface low is more modest in nature compared to the one today/Thursday, it still may feature a 1000-mb surface pressure. Ensemble spread is notable as this low tracks across the Ohio Valley toward the Mason-Dixon Line. Where this low tracks and how quickly the warm sector crosses the local area will drive the degree of instability in the atmosphere. One aspect of the forecast that does appear a bit more certain is anomalous moisture tracking up the Eastern Seaboard on Monday. The heavy rainfall signal is certainly non-zero, but still bears watching as models continue to resolve the more complex details.

KEY MESSAGE 3...An active upper-level pattern could bring continued rain chances through mid-week.

As the early week system drives a cold front offshore early Tuesday, there is a loose ensemble signal of additional unsettled conditions through mid-week. Mid/upper heights begin to build across the Desert Southwest into northwestern Mexico. At the same time, cyclonic flow across south-central Canada begins to dig toward the Midwest and northeastern U.S. Forcing from this trough could again increase shower and thunderstorm chances across the region. At this point, uncertainty is high across the board as shown by the low probabilities for rainfall in the forecast. Temperatures appear seasonable heading into mid-week with a gradual uptick in humidity levels.

AVIATION /06Z THURSDAY THROUGH MONDAY/
A southwest wind gradient increases this morning and could exceed 30 knots at times. There is some uncertainty in convection coverage given the overnight convection into early this morning. This early convection could help to stabilize the atmosphere most of the morning leading into the afternoon.
PROB30 groups have been used due to the combination of low coverage and low confidence. MRB may largely miss out on the potential for stronger storms, but the strongest could produce severe gusts elsewhere. A second round of showers could affect portions of the area tonight into Friday morning, but impacts are uncertain. Skies should gradually clear Friday with gusty northwest winds.

Gusty NW winds around 20-25 kts can be expected Saturday. While VFR conditions are expected for much of Sunday, there is an increasing signal of heavy rainfall and thunderstorms toward the night and into Monday. Depending on how this plays out, restrictions would become more likely. Initial winds on Sunday begin out of the west-southwest before shifting over to southeasterly by the evening/night. A return to westerlies is expected for Monday with gusts increasing to around 15 to 20 knots.

MARINE
Southwest winds are expected to increase through today. This will provide an environment for Small Craft Advisories for portions of the waters by late this afternoon and most waters tonight. High end advisory conditions are likely today as strong low pressure passes to the north. Gale Warnings are in effect for the northern Chesapeake Bay. The strongest gusts will be near the shore as air temperatures rise into the 90s.
Special Marine Warnings may be needed during the afternoon and early evening as scattered strong to severe thunderstorms potentially track over the waters.

There may be a bit of a break in the winds tonight as the front slows down. Marginal Small Craft Advisories may be needed for portions of the waters Friday in northwest flow.

Winds on Saturday will be out of the NW and near SCA criteria in the wake of a secondary cold front. Winds will likely taper off into Saturday evening as they gradually turn out of the south.
Sub-advisory level winds are expected for Sunday before hazardous conditions return to the forecast on Monday. Increasing south to southwesterly winds may lead to Small Craft Advisories across the area waterways.

TIDES/COASTAL FLOODING
An increasing southwesterly flow ahead of a cold front will allow for anomalies to peak early this morning. Several locations may experience minor tidal flooding this morning.
Advisories remain in effect for Annapolis and Havre de Grace, where confidence is currently highest. Annapolis may even approach moderate flood stage.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...Small Craft Advisory until 9 AM EDT this morning for MDZ008.
Gale Warning from 9 AM this morning to 8 PM EDT this evening for MDZ008.
Coastal Flood Advisory until 1 PM EDT this afternoon for MDZ014.
Wind Advisory from 7 AM this morning to 6 PM EDT this evening for MDZ501-502-509-510.
Coastal Flood Advisory from 10 AM this morning to 4 PM EDT this afternoon for MDZ508.
VA...Wind Advisory from 7 AM this morning to 6 PM EDT this evening for VAZ503-504-507.
WV...Wind Advisory from 7 AM this morning to 6 PM EDT this evening for WVZ050-055-501>506.
MARINE...Small Craft Advisory until 9 AM EDT this morning for ANZ530- 531-535-538.
Gale Warning from 9 AM this morning to 8 PM EDT this evening for ANZ530-531-535-538.
Small Craft Advisory until 8 PM EDT this evening for ANZ532>534-536-537-539>543.