Sunrise 5:50 AM   Sunset 8:22 PM Moonrise 4:45 PM   Moonset 3:08 AM

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ANZ535 Tidal Potomac From Key Bridge To Indian Head- 636 Am Edt Mon May 20 2024
Today - SE winds 5 kt. Waves less than 1 ft. Tonight - S winds around 5 kt. Waves 1 ft. Tue - S winds around 5 kt. Waves 1 ft. Areas of fog. Vsby 1 to 3 nm. Tue night - S winds 5 kt. Waves less than 1 ft. Wed - S winds 5 to 10 kt. Waves 1 ft. Wed night - S winds 5 kt. Waves less than 1 ft. Thu - W winds around 5 kt. Waves 1 ft or less. A chance of showers and tstms. Fri - W winds around 5 kt. Waves 1 ft or less. A chance of showers. A chance of tstms through the night.
winds and waves higher and visibilities lower in and near tstms.

ANZ500 636 Am Edt Mon May 20 2024
Synopsis for the tidal potomac and md portion of the chesapeake bay -
high pressure will build over the waters through Tuesday. A strong cold front will approach the waters Wednesday into Thursday. This frontal system will settle south of the area by the end of the work week. Small craft advisories may be needed for portions of the waters Wednesday.

FXUS61 KLWX 200739 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 339 AM EDT Mon May 20 2024

SYNOPSIS
High pressure overhead will move offshore through Wednesday. A cold front will approach from the Ohio River Valley Wednesday night, then cross the Mid-Atlantic Thursday. The front will likely stall just to the south, and meander nearby through the upcoming weekend.

NEAR TERM /THROUGH TONIGHT/
Early morning satellite imagery reveals areas of fog, some dense, developing over much of the region. A few patches of stratus were meandering about, as well. This is due to lingering low-level moisture in light onshore flow.

Fog and low clouds should lift a few hours after daybreak, eventually becoming mostly sunny this afternoon. Subsidence beneath high pressure should keep the region dry, with any very low chances for showers likely staying west of the Appalachians.

High temperatures are expected to reach the upper 70s to lower 80s across most of the area today once the sun comes out. Low temperatures tonight are expected to fall into the 50s with some patchy fog or low clouds possible once again overnight.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
High pressure will move offshore Tuesday into Wednesday. Ridging aloft will still be present Tuesday, and this may act to cap convection. However, just enough lift from added terrain circulations could pop a shower or thunderstorm later in the afternoon on Tuesday mainly west of I-81 in eastern WV.

The ridge will begin to break down a bit on Wednesday, but with the main forcing from the incoming trough/cold front still well to the west, convection should remain isolated and generally confined to west of the Blue Ridge late Wednesday afternoon.

LONG TERM /THURSDAY THROUGH SUNDAY/
To the south of a deep upper trough tracking across Quebec will be a series of lower amplitude waves that race toward the Mid- Atlantic region on Thursday. As this occurs, a slow moving cold front is expected to push through the local area by midday into the evening hours. There is fairly strong mid/upper support with a belt of 500-mb west-southwesterlies around 40 to 50 knots.
This is accompanied by ample right entrance region jet dynamics within a jet streak running between 100 to 110 knots. The key parameter that will dictate the degree of severe weather threat is the instability. At this point, even global ensembles are showing around 1,000 to 1,500 J/kg of surface-based CAPE on Thursday. This would be more than adequate to support severe convection given the extent of vertical shear in the profile.
However, as usual, the near to short term trends of cloud cover which inhibits convective potential will need to be monitored ahead of the event. Besides the threat for showers and strong/severe thunderstorms, it should be a very warm day with decent humidity owing to persistent south-southwesterlies.
Forecast highs are in the mid/upper 80s, with heat indices approaching the low 90s. The frontal boundary eventually slides off to the south by Friday morning.

In the wake of this frontal system, temperatures and dew points drop off some to finish out the work week. Shower and thunderstorm chances do return later in the day on Friday as this boundary re-approaches the area from the south. This leads to a period of unsettled conditions heading into the weekend.
The position of this frontal zone and amplitude/strength of disturbances aloft will dictate the degree of threats to the local area. General low-amplitude troughiness persists upstream which would tend to support this semi-active convective pattern.
Daily chances of showers and thunderstorms are shown in the forecast package for this weekend. Temperatures remain fairly close to average for late May standards.

AVIATION /06Z MONDAY THROUGH FRIDAY/
Fog and patchy low stratus will affect most TAF sites through 12-14z this morning. Some fog may be dense, especially for KCHO, KMRB, and KIAD. IFR is likely for all TAF sites until an hour or two after daybreak with light SE flow. Conditions should improve to VFR 14-16z with continued light SE flow. Additional fog or low clouds could develop again mainly after midnight tonight.

Prevailing VFR is expected Tuesday into Wednesday outside of any patchy late night/early morning fog/low clouds with continued light S/SE flow. A shower or thunderstorm could approach KMRB late Wednesday afternoon, but otherwise it should be dry.

A slow moving cold front tracks through the Mid-Atlantic region on Thursday. The threat for showers and thunderstorms will favor periods of sub-VFR conditions. This is accompanied by some degree of severe weather risk given the parameter space at hand.
The area terminals should gradually dry out from west to east during the evening and into the night. Initial west- southwesterly winds will give way to northwesterlies by late Thursday into portions of Friday. This boundary does not stay to the south very long as it returns northward as a warm front.
Ultimately this supports some additional shower and thunderstorm chances into Friday, and thus some possible restrictions.



MARINE
Generally light south to southeast winds are expected through Wednesday, though some channeling/river or bay breeze enhancement is possible during the afternoon and evening each day. This should stay entirely sub SCA through tonight given high pressure moving overhead, with some marginal/sporadic SCA gusts possible late Tuesday afternoon into early evening. By Wednesday afternoon, the gradient tightens a bit with high pressure more firmly offshore, raising the prospects for channeling and SCAs.

Background winds should stay below Small Craft Advisory levels on Thursday on Friday. However, this comes with a caveat as strong to severe thunderstorms may impact the local waters on Thursday, possibly into Thursday night. There is certainly a risk of Special Marine Warnings along with a threat of frequent lightning with any of the convection. As the cold front responsible for this activity settles to the south on Friday morning, winds will be out of the west-northwest. This boundary does return northward as a warm front which may bring additional showers and thunderstorms on Friday.

TIDES/COASTAL FLOODING
Elevated water levels are expected to persist through the middle of the week with persistent light onshore (S/SE) flow. Minor flooding is likely along vulnerable shoreline particularly during the overnight/early morning high tide cycles (the higher of the two astronomically). The higher end of the guidance envelope approaches moderate flooding at Straits Point and Annapolis, but this seems unlikely given the light flow.

Winds turn offshore behind a cold front Thursday, which will cause a subsequent decrease in water levels.

LWX WATCHES/WARNINGS/ADVISORIES
DC...Coastal Flood Advisory until 9 AM EDT this morning for DCZ001.
MD...Coastal Flood Advisory until 7 AM EDT this morning for MDZ014.
Coastal Flood Advisory until 3 AM EDT early this morning for MDZ017.
VA...None.
WV...None.
MARINE...None.

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Chain Bridge
Click for Map
Mon -- 01:04 AM EDT     0.55 feet Low Tide
Mon -- 04:06 AM EDT     Moonset
Mon -- 05:51 AM EDT     Sunrise
Mon -- 07:17 AM EDT     3.27 feet High Tide
Mon -- 02:01 PM EDT     0.54 feet Low Tide
Mon -- 05:42 PM EDT     Moonrise
Mon -- 07:44 PM EDT     2.81 feet High Tide
Mon -- 08:19 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION

Chain Bridge, D.C., Tide feet

Chain Bridge
Click for Map
Mon -- 12:59 AM EDT     0.55 feet Low Tide
Mon -- 04:06 AM EDT     Moonset
Mon -- 05:51 AM EDT     Sunrise
Mon -- 07:12 AM EDT     3.27 feet High Tide
Mon -- 01:56 PM EDT     0.54 feet Low Tide
Mon -- 05:42 PM EDT     Moonrise
Mon -- 07:39 PM EDT     2.81 feet High Tide
Mon -- 08:19 PM EDT     Sunset
Tide / Current data from XTide NOT FOR NAVIGATION

Chain Bridge, one mile below, D.C., Tide feet

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