Marine Weather and Tide Forecast for Washington, DC

NEAR TERM /THROUGH TONIGHT/
A warm front along the Potomac River will continue to move northeast through the remainder of the day. Low clouds are eroding away along the central Blue Ridge and areas to the north and east. A couple of showers are moving northeast across western Maryland and eastern parts of West Virginia. Additional showers and thunderstorms will develop this afternoon as a shortwave trough pivots across the region. A west to southwest flow should limit widespread convection across the region with a focus mainly east of the Blue Ridge. This is due largely in part to the shortwave pressure trough pivoting through along with it's interaction with any sort of bay/river breeze that may set up later this afternoon. An additional severe threat exists west of the Alleghenies as the cold front works east from the Ohio River Valley. 00z CAM guidance suggest a shorter window for convection this afternoon roughly between 2-7pm (especially east of the Blue Ridge). Scattered multicellular clusters and perhaps a broken line of storms will be the general theme of things this afternoon in regards to radar presentation. MUCAPE values look to sit between 1500-2000 j/kg with 0-6 km shear values running anywhere between 30- 40 kts. Damaging winds will be the primary threat with any storms that form along with localized concerns for flash flooding. For now, holding off on a Flood Watch given the coverage of storms this afternoon. Still may need one especially in and around the Washington DC metro north along I-270 and back across the eastern WV Panhandle where max/mean values from the CAMS paint a solid 1-3 inches of rain with localized bullseye up to 5". FFG in the 3 to 6 hr period in these areas still remains less than 1.50".

More sunshine this afternoon will lead to warmer temperatures behind the warm front. Humidity will increase as well as dewpoint temperatures linger or rise into the lower to middle 70s. Highs this afternoon will push into the upper 80s and low 90s outside the mountains. Heat index values will make it feel like the mid 90s, especially east US-15 as humidity continues to increase across the region.

The lead shortwave trough works eastward late tonight into Thursday as the cold front approaches from the Ohio River Valley. Thunderstorms over the metros will come to an end with a focus on convection back toward the Alleghenies. This convection will slowly dissipate given the lack of instability during the overnight hours. Lows tonight will fall back into the low to mid 70s. Areas of fog are possible especially in locations that did see substantial rainfall as well as in the river valleys.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/
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A strong cold front looks to cross the area Thursday into Friday. The front will bring a widespread risk of severe thunderstorms to the area Thursday afternoon and evening. SPC continues to maintain a (Level 2 out 5) risk for severe weather across the region during this time. CAPE values will increase to around 1500-2000 j/kg with steep low-level lapse rates (7+ C/Km) and moderate bulk shear values of (35-50 kts).This will lead to progressive multicellular clusters line segments , and supercells across the region. The main threat with storms will be damaging winds although large hail and even an isolated tornado cannot be ruled out. The risk for localized flash flooding will also continue due to antecedent conditions and low FFG values below 1-1.5 inches across a large chunk of the forecast area. One wildcard will be the scope of coverage given unidirectional flow aloft. This is especially true the further south and easy you go across the forecast region. We'll continue to monitor this threat as it evolves. High temperatures will rise into the low to mid 90s Thursday afternoon with heat index values in the metros near 100 degrees.

Any convection will come to an end Thursday night with lowering humidity in the wake of the frontal passage. Lows Thursday night will fall back into the low to mid 60s. Areas of fog will remain possible near the water and in the valleys.

Friday looks to be the best day of the next 7 when it comes to temperatures and low humidity. Strong upper level ridging and surface high pressure will build over the eastern CONUS through the weekend. The high and upper level ridge will continue to strengthen each day bringing warming temperatures and eventually more humidity.
FOr Friday, expect highs back in the mid to upper 80s with dewpoints in the 50s and low 60s. Overnight lows Friday night will fall into the upper 50s and low 60s west of the Blue Ridge with mid to upper 60s in the metro areas.

LONG TERM /SATURDAY THROUGH TUESDAY/
Strong upper level ridging builds over the Mid-Atlantic throughout the long term period, leading to dry conditions and warming temperatures. Medium range model progs indicate a likelihood of several days of 90+ degree high temperatures, with some low end potential of hitting 100 particularly early to mid next week (Tuesday-Thursday). Although no large scale troughs or fronts are expected to cross the region, small disturbances rounding the ridge in the hot and increasingly humid airmass could result in a risk for showers and thunderstorms late in the weekend into early next week.
Heat indices will be on the rise as well during this time, with at least a small chance of the first round of heat headlines for the season early next week. Heat indices Monday through Wednesday could near or exceed 100 degrees. Higher elevations won't catch a break either with highs well into the 80s.

AVIATION /14Z WEDNESDAY THROUGH SUNDAY/
IFR to LIFR conditions in terms of ceilings will likely hang on across the corridor terminals through at least 15-16z/11am- noon with a warm front bisecting both the Baltimore/DC airspace.
Conditions will improve back to VFR this afternoon. Temporary sub-VFR drops will be possible at times between 19-23z/2-7pm across terminals east of the Blue Ridge. This is due largely in part to shower and thunderstorm activity that looks to bubble from a shortwave trough pivoting through. Overall coverage will be limited with damaging winds and localized flash flooding once again as the primary concerns.

Prevailing VFR conditions are expected Thursday. Temporary drops to sub-VFR conditions may be possible in thunderstorms especially Thursday afternoon and evening (19-00z/2-8pm). VFR conditions are expected Friday into Saturday with west to northwest winds 5-10 knots becoming south.

VFR conditions are expected throughout much of next week as hot high pressure builds over the region. Winds will remain light generally out of the west and southwest at less than 10kts.

MARINE
Sub- SCA level southerly winds are expected over the waters this afternoon at less than 15kts. An SMW or two cannot be ruled out with scattered showers and thunderstorms during the afternoon and evening hours. Highest coverage for storms this afternoon will be between 3-8pm.

SMWs are possible given thermodynamic and kinematic environment for Thursday in any thunderstorm. SCA conditions likely return with cold frontal passage Thursday into Friday. West to northwest winds are expected Friday into Saturday, becoming southerly Saturday afternoon at generally 10 knots or less.

No marine hazards outside of heat are expected for the remainder of the weekend into early next week.

LWX WATCHES/WARNINGS/ADVISORIES
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.