Sunrise 5:50 AM   Sunset 8:23 PM Moonrise 5:48 PM   Moonset 3:30 AM

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ANZ535 Tidal Potomac From Key Bridge To Indian Head- 733 Am Edt Tue May 21 2024
Today - S winds 5 kt. Waves less than 1 ft. Tonight - S winds 5 to 10 kt. Waves 1 ft. Wed - S winds 5 to 10 kt. Waves 1 ft. Wed night - S winds around 5 kt. Waves 1 ft. Thu - SW winds 5 to 10 kt. Waves 1 ft. Showers likely with a chance of tstms. Thu night - W winds 5 to 10 kt. Waves 1 ft. A chance of showers and tstms. Fri - SW winds around 5 kt. Waves 1 ft or less. A chance of showers. A chance of tstms. Sat - SE winds around 5 kt. Waves 1 ft. Showers likely with a chance of tstms.
winds and waves higher and visibilities lower in and near tstms.

ANZ500 733 Am Edt Tue May 21 2024
Synopsis for the tidal potomac and md portion of the chesapeake bay -
high pressure will build over the waters today. A strong cold front will approach the waters Wednesday into Thursday. This frontal system will settle south of the area Friday before retreating back toward the waters this weekend. Small craft advisories may be needed for portions of the waters Wednesday.

FXUS61 KLWX 210705 AFDLWX

Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 305 AM EDT Tue May 21 2024

SYNOPSIS
High pressure will move offshore through Wednesday. A cold front will approach from the Midwest late Wednesday, then cross the northern Mid-Atlantic Thursday. The front will stall to the north across Pennsylvania keeping the local area in a warm and humid air mass through early next week.

NEAR TERM /THROUGH TONIGHT/
Early morning satellite and surface observations indicate high cirrus tumbling in from the northwest, with an area of low clouds and stratus developing near the Chesapeake Bay. Patches of fog have developed where there are breaks in the high clouds.

Any fog or low clouds should lift by mid morning resulting in a mainly sunny day. Slightly lower heights associated with a weak lead shortwave, coupled with heating and orographic lift could result in a few showers and thunderstorms generally west of the Blue Ridge and south of US-50 mid to late afternoon into this evening. Flow aloft is relatively weak (W 15-20 kts 700-300 hPa, SE 5-10 kts 850 hPa). Although light, the veering nature of the flow could help prop or lock cells to the terrain, with subsequent outflow collisions resulting in only a slow east- southeastward drift. There is a stable layer around 600 hPa in forecast soundings, and this plus a lack of a large scale trigger may inhibit more widespread deeper convection for much of the day. Although storm motion may be slow, any excessive rainfall threat should be mitigated by lower PWs of around 1 inch. Still, isolated totals of 1-2 inches are possible under any slow-moving/repeat storms. CAPE around 1500 J/kg and steepening low-level lapse rates could result in some spotty small hail or gusty winds and frequent lightning.

Any shower and thunderstorm activity should dwindle this evening with additional mid and high level clouds beginning to move in from the west. These clouds may help reduce the threat of more widespread and/or dense fog tonight, but some patchy fog or perhaps marine stratus are possible.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
High pressure at the surface will shift offshore Wednesday into Wednesday night. Meanwhile, a broad area of troughing and associated surface low pressure will trek gradually eastward from the Midwest. This will lead to a period of unsettled weather starting as early as Wednesday afternoon, and lingering through at least Thursday evening.

Deep layer shear is expected to remain weak Wednesday (AOB 20 kts sfc-500 hPa). However, flow will increase subtly later in the day, and heights will begin to come down slightly as well.
This, coupled with above normal temperatures and increasing humidity and instability will lend to a threat of at least widely scattered showers and thunderstorms come afternoon. The threat appears greatest west of I-95 further away from the departing ridge and any associated subsidence. A couple storms could produce a little hail or gusty winds given the increased instability, but the lack of shear will probably keep a more organized or widespread severe weather threat marginal, and relegated to north of US-33/west of US-15 for the most part.

Heights fall more appreciably on Thursday as a surface cold front impinges on the area. Latest guidance times the front favorably with peak heating. The background airmass will be very warm and humid, but cloud debris from previous day's convection over the middle of the country could inhibit more significant CAPE. If higher instability is realized, a more organized threat for strong to severe thunderstorm clusters could develop given the strong surface front and increasing flow/shear aloft in the right entrance region of a seasonably strong upper jet. The threat for strong to severe thunderstorms may be greater south of US-50/I-66 and east of US-15 where the potential for more heating is highest.

Activity should gradually dissipate heading into Thursday night as daytime instability wanes and the front sags south. But, the front's progress will be slow, so the potential of showers may linger well into the night south of US-50/I-66.

LONG TERM /FRIDAY THROUGH MONDAY/

A front will remain generally north of the Pennsylvania Turnpike through early next week keeping the local area in a warm and humid air mass with the risk of almost daily afternoon and early evening showers and thunderstorms. A well defined 700 mb shortwave-trough is fcst to approach the area Fri night with its axis crossing the area around 18Z Saturday. With shear vectors on the weaker side and slow storm motions, storms Fri afternoon and evening may pose a risk of heavy rainfall and flash flooding. Saturday's threat really depends on the timing of that shortwave as it appears the trough axis will be too far east to enhance t-storm activity.

On Sunday, the models show significant 925-850 mb drying under low- mid level ridging, which is likely to keep t-storm activity isolated at best.

On Monday, a potent shortwave-trough and attendant sfc cyclone will move across Ohio and northern Mid-Atlantic. This system could pose a more substantial severe wx threat given strong winds aloft especially if the timing of the frontal passage coincides with peak heating. The latest timing suggests a severe threat during the morning hours, but things could definitely still change between now and next Monday.

AVIATION /06Z TUESDAY THROUGH SATURDAY/
As of early this morning (06Z), IFR stratus was developing near the Chesapeake Bay. This layer will attempt a slow NW drift through daybreak, most likely affecting KMTN/KBWI, with a bit more uncertainty towards KDCA and especially KIAD. High clouds were moving overhead, but there were enough breaks to allow some cooling to near the dew points. This could result in patches of fog through daybreak, as well. VFR should return to all TAF sites by 13-15Z. Any shower or thunderstorm activity this afternoon into this evening should be sparse in coverage and west of the TAF sites. Light south flow is expected.

Some patches of fog or low clouds are possible again overnight tonight into early Wednesday with continued light south flow.
Widely scattered showers and thunderstorms may develop Wednesday afternoon and early evening, especially west of the metros.
Otherwise, VFR is expected through Thursday morning. Sub-VFR conditions are possible with potentially more widespread shower and thunderstorm activity Thursday into Thursday night as a cold front crosses. Winds will shift to northwest.

Isold-sct afternoon t-storms Fri and Sat.

MARINE
Generally light south to southeast flow is expected through Thursday, becoming northwest by Thursday night as a cold front crosses. A brief period of sporadic and marginal SCA-level gusts is possible late this afternoon into this evening, with a bit better chance Wednesday afternoon and evening as high pressure moves offshore. There is a low potential of a shower or thunderstorm approaching the waters Wednesday evening, with a much higher chance Thursday.

SCA conditions possible Fri night across the southern waters in southerly channeling.

TIDES/COASTAL FLOODING

Minor coastal flooding is occurring at Annapolis and expected to occur shortly at DC Waterfront. After this morning's high tide, water levels are expected to recede, but may increase again with tonight's high tide especially at Annapolis.

LWX WATCHES/WARNINGS/ADVISORIES
DC...Coastal Flood Advisory until 9 AM EDT this morning for DCZ001.
MD...Coastal Flood Advisory until 9 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
Tue -- 01:45 AM EDT     0.53 feet Low Tide
Tue -- 04:29 AM EDT     Moonset
Tue -- 05:50 AM EDT     Sunrise
Tue -- 07:55 AM EDT     3.34 feet High Tide
Tue -- 02:48 PM EDT     0.47 feet Low Tide
Tue -- 06:45 PM EDT     Moonrise
Tue -- 08:20 PM EDT     Sunset
Tue -- 08:27 PM EDT     2.80 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION

Chain Bridge, D.C., Tide feet

Chain Bridge
Click for Map
Tue -- 01:40 AM EDT     0.53 feet Low Tide
Tue -- 04:29 AM EDT     Moonset
Tue -- 05:50 AM EDT     Sunrise
Tue -- 07:50 AM EDT     3.34 feet High Tide
Tue -- 02:43 PM EDT     0.47 feet Low Tide
Tue -- 06:45 PM EDT     Moonrise
Tue -- 08:19 PM EDT     Sunset
Tue -- 08:22 PM EDT     2.80 feet High Tide
Tide / Current data from XTide NOT FOR NAVIGATION

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

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Sterling, VA,