Marine Weather Net

Tidal Potomac from Cobb Island MD to Smith Point VA Marine Forecast


TONIGHT

SW
WINDS
5 KNOTS

FRI

SW
WINDS
5 KNOTS

FRI NIGHT

SW
WINDS
5 - 10
KNOTS

SAT

SW
WINDS
5 KNOTS

The Marine Weather Forecast In Detail:
ANZ537 Forecast Issued: 735 PM EDT Thu Jul 18 2019

Tonight...Sw Winds 5 Kt. Waves Less Than 1 Ft. Scattered Showers And Tstms, Mainly This Evening.
Fri...Sw Winds 5 Kt. Waves Less Than 1 Ft.
Fri Night...Sw Winds 5 To 10 Kt. Waves 1 Ft.
Sat...Sw Winds 5 Kt. Waves Less Than 1 Ft.
Sat Night...Sw Winds 5 Kt. Waves Less Than 1 Ft.
Sun...Sw Winds 5 Kt. Waves Less Than 1 Ft. A Chance Of Showers And Tstms.
Sun Night...Sw Winds 5 To 10 Kt. Waves 1 Ft. A Chance Of Showers.
Mon...Nw Winds 5 To 10 Kt. Waves 1 Ft. Tstms Likely. Showers Likely.
Tue...N Winds 5 To 10 Kt. Waves 1 Ft. Showers Likely, Mainly In The Morning. Winds And Waves Higher And Visibilities Lower In And Near Tstms.
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Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
355pm EDT Thu July 18 2019

Synopsis: An upper level disturbance will move into the western Atlantic tonight. High pressure will build over the southeastern United States Friday through the weekend. A cold front approaching from the Great Lakes and Pennsylvania will cross the region early next week.

Near Term - Until 6am Friday Morning
A trough axis remains across the I-95 corridor this afternoon. Daytime heating has permitted nearly 1500 J/kg of MLCAPE to develop, but with little shear. The catalyst for thunderstorms today will be the available instability (which increases toward the Bay), steepening low level lapse rates, high dewpoints, and various disorganized spokes of vorticity embedded within the mid level flow. Given precipitable water near 2.25 inches in the Baltimore-Washington corridor with small MBE vectors, heavy rain will also be a concern. Wet microbursts could result in the most mature storms. The trough axis should reach the Bay by dusk, ending the thunderstorm threat.

Warm and humid tonight with lows in the 70s and patchy fog possible, especially in any areas that receive rain today given decreasing cloud cover

Short Term - 6am Friday Morning Through Saturday Night
Based on latest high-performing temperature/dew point guidance, have gone ahead and hoisted a Heat Advisory for much of the area excluding the higher elevations. Some locations along the I-95 corridor may be borderline for a warning, so it's possible a later shift may need to upgrade. Excessive Heat Watches remain in place for Saturday. A building ridge of high pressure will make that the primary concern, as 850 temps rise to 22-24C. Think that subsidence will mostly prevent storms from developing, but could not rule out a stray shower/thunderstorm from breaking the cap. Do not have confidence in placement or timing, so will be silent on that risk for now.

While the entire period looks hot, Saturday may be the day of greater concern, without the benefit of any real relief at night

Long Term - Sunday Through Thursday
High pressure will shift off the coast as a warm front moves through our region on Sunday. This will place our region in the warm sector ahead of an approaching cold front from the west. This will lead to another hot day with daytime temperatures hovering in the upper 90s to low 100s. These high temperatures will combine with dew point temperatures in the mid to upper 60s and lower 70s to create another day of dangerous heat indexes for most of our region. This means that heat advisories will likely be needed with possibly a excessive heat warning. Thunderstorms and showers will be a concern again during the day due to high CAPE. The better chance for showers and thunderstorms will be later in the day Sunday and into Monday as the cold front approaches and moves through our region. The models have been trending quicker with this frontal passage. This has led to the main threat becoming more flood based compared to severe due to the frontal timing. If the front moves through later on Monday, the risk for severe weather could increase but there remains a lot of uncertainty at this time. The biggest message will be that there will be threat for thunderstorms and showers late Sunday into Monday with an isolated threat for flood and severe weather.

The cold front is expected to move through our region by late Monday and into early Tuesday. The models have been hinting that the boundary may stall over our southern parts of our CWA or just south of our CWA. This would lead to continued chances for showers into Tuesday. Again there remains a lot of uncertainty on this solution. There is good agreement that Tuesday into Wednesday will be much cooler in the low to mid 80s with dew points in the 50s. High pressure will build back into our region for Wednesday

.AVIATION /20Z THURSDAY THROUGH TUESDAY/... Mainly VFR expected through Saturday night. Possible exceptions would be in any thunderstorm that develops this afternoon, or any patchy fog that develops during the overnight/early morning hours. Generally west flow AOB 10 kts expected. Best chance for thunderstorms today appears to be near/east of the Blue Ridge this afternoon, with best fog potential between 8-12Z near outlying terminals or in areas that receive rain this afternoon. The thunderstorm threat is slim to none for Friday and Saturday.

Skies will be mostly clear with some scattered cloud cover. It will continue to be hot and humid with heat indexes above 105 and possibly 110. VFR conditions expected for most of the day Sunday at this time.

Clouds will increase Sunday evening through Monday as a cold front moves through our region. Thunderstorms and showers will be possible. SubVFR conditions will be possible

Marine Discussion
South/west winds 10 kt or less this afternoon, though gusty winds are possible in and near any thunderstorms that develop (which may require SMWs). Winds will remain light through Saturday.

Hot humid conditions expected Sunday and Monday with a southerly flow. Small Craft Advisories may be needed

Climate
The record daily warm low temperature for IAD for July 18th is 74 degrees, set in 2005 and 1969.

As a reference, here are the warm temperature records for Friday through this weekend:

Record Daily High Temperatures July 19 July 20 July 21 DCA 102 (1930) 106 (1930) 104 (1926) BWI 103 (1930) 102 (1930) 104 (1930) IAD 98 (1977) 101 (1980) 101 (1991)

Record Daily Warm Low Temperatures July 19 July 20 July 21 DCA 81 (1930) 82 (2015) 82 (1987) BWI 80 (1942) 80 (1930) 83 (1930) IAD 77 (2013) 75 (2015) 77 (1987)

Highest July Temperatures Highest Max Warmest Low DCA 106 (7/20/1930) 84 (7/24/2011, 7/23/2011, 7/16/1983) BWI 107 (7/10/1936) 83 (7/21/1930) IAD 105 (7/22/2011) 78 (7/24/2010, 7/8/2010)

All-time Highest Temperatures Highest Max Warmest Low DCA 106 (7/20/1930, 8/6/1918) 84 (7/24/2011, 7/23/2011, 7/16/1983) BWI 107 (7/10/1936) 83 (8/5/1930, 7/21/1930, 6/6/1925) IAD 105 (7/22/2011) 79 (8/8/2007)

Longest stretches of consecutive days with high temperatures at or over 100 degrees at IAD: 2 (7/7-8/2012, 7/21-22/2011, 7/6-7/2010, 8/16-17/1997, 7/16-17/1988 and 7/20-21/1980)

Longest stretch of consecutive days with low temperatures at or over 80 degrees at DCA: 5 (7/16-20/2013)

Longest stretch of consecutive days with low temperatures at or over 80 degrees at BWI: 4 (8/8-11/1900)

Temperature records for the Washington DC area have been kept at what is now Ronald Reagan Washington National Airport (DCA) since 1941. Additional temperature records observed downtown extend the period of record back to 1872.

Temperature records for the Baltimore MD area have been kept at what is now Baltimore-Washington International Thurgood Marshall Airport (BWI) since 1950. Additional temperature records observed downtown extend the period of record back to 1872.

Temperature records for the Sterling/Dulles VA area have been kept at what is now Washington Dulles International Airport (IAD) since 1960.

NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories
DC...Heat Advisory from 11am to 9pm EDT Friday for DCZ001. Excessive Heat Watch from Saturday morning through Saturday evening for DCZ001. Excessive Heat Watch from Sunday morning through Sunday evening for DCZ001. MD...Heat Advisory from 11am to 9pm EDT Friday for MDZ003>006-011- 013-014-016>018-502>508. Excessive Heat Watch from Saturday morning through Saturday evening for MDZ003>006-011-013-014-016>018-503>508. Excessive Heat Watch from Sunday morning through Sunday evening for MDZ003>006-011-013-014-016>018-503>508. VA...Heat Advisory from 11am to 9pm EDT Friday for VAZ026>031- 036>040-050>057-501-502-505-506. Excessive Heat Watch from Saturday morning through Saturday evening for VAZ028-030-031-052>057-501-502-505-506. Excessive Heat Watch from Sunday morning through Sunday evening for VAZ028-030-031-052>057-501-502-505-506. WV...Heat Advisory from 11am to 9pm EDT Friday for WVZ050>053-055- 502-504. Excessive Heat Watch from Saturday morning through Saturday evening for WVZ051>053. Excessive Heat Watch from Sunday morning through Sunday evening for WVZ051>053. MARINE...None.