Tidal Potomac from Key Bridge to Indian Head MD Marine Forecast
|Tonight...Sw Winds 5 Kt. Waves Less Than 1 Ft. Scattered Showers And Tstms, Mainly This Evening.|
|Sun...W Winds 5 To 10 Kt. Waves 1 Ft.|
|Sun Night...W Winds Around 5 Kt. Waves 1 Ft. A Chance Of Showers And Tstms.|
|Mon...Sw Winds Around 5 Kt. Waves 1 Ft. Showers And Tstms.|
|Mon Night...W Winds 5 Kt. Waves Less Than 1 Ft. Showers And Tstms Likely.|
|Tue...Nw Winds 5 To 10 Kt. Waves 1 Ft. Showers Likely.|
|Tue Night...Nw Winds 5 Kt. Waves Less Than 1 Ft.|
|Wed...Nw Winds Around 5 Kt. Waves 1 Ft Or Less.|
|Thu...W Winds Around 5 Kt. Waves 1 Ft Or Less. Winds And Waves Higher And Visibilities Lower In And Near Tstms.|
|Area Forecast Discussion|
National Weather Service Baltimore MD/Washington DC
939pm EDT Sat July 20 2019
Synopsis: High pressure will remain over the southeastern United States overnight into Sunday. A cold front will approach from the Great Lakes Sunday and Monday before passing through our area Monday night into Tuesday. High pressure will return for the middle portion of next week.
Near Term - Until 6am Sunday Morning
During the past few hours, we have had a couple of showers develop over Hardy and Hampshire Counties in West Virginia. In that allotted time, these showers materialized into thunderstorms, becoming severe at times as they crossed into and over extreme northern and northeastern Virginia. Currently, there is one severe thunderstorm moving into the northern half of the District of Columbia and could bring winds over 55 mph, lightning, heavy rain and perhaps some hail. Additional showers and thunderstorms are weakening over southern Pennsylvania as they move toward our CWA. Little to no impacts expected with this activity.
Upper-level high pressure will remain overhead tonight, causing very warm and humid conditions to continue. Latest guidance support current low temperatures forecasts...in the 70s for most, lower and middle 80s in downtown Washington and Baltimore. Heat indices for urban areas along the I-95 Corridor may hold in the 90s
Short Term - 6am Sunday Morning Through Monday Night
The ridge will start to break down Sunday, but not til late in the day. In that aspect, Sunday should be similar to Saturday. However, convective complexes across the Great Lakes likely to toss debris clouds toward the Mid Atlantic. In addition, winds likely to become more westerly as heigheights start to lower. That could lead to warmer temperatures but lower humidity. Further, 850 temperatures forecast to be a degree or two lower. Based on latest guidance and very little rainfall relief from this afternoon's activity, we have issued an Excessive Heat Warning and Heat Advisory for a large portion of our CWA on Sunday between 11am and 9pm, similar to Saturday.
The cold front will continue to drop south approaching the Ohio Valley Sunday night, and height falls will continue as a result. A chance of showers and thunderstorms enter the forecast by early afternoon. Have a slow but steady increase in precip potential as the dynamic situation improves Sunday evening and overnight. The potential for damaging wind gusts exists with these thunderstorms.
The cold front still forecast to pass through the Ohio Valley Monday and into our area Monday night. It looks like there will be a pre-frontal trough axis also capable of focusing thunderstorm activity. Lower heigheights and a southwest flow aloft combined with low-level boundary forcing and ample instability will be more than enough to trigger showers and thunderstorms, especially during the afternoon and evening hours. Increased shear profiles along with the high instability suggests that storms will have the chance to be severe. Monday will not be as hot as recent days due to more cloud cover and more coverage of showers and thunderstorms...but that all depends upon how these thunderstorms evolve. There is still the potential for pockets of rapid heating
Long Term - Tuesday Through Saturday
Tuesday's weather will be dependent on the southward progression of the surface front. 12z guidance has trended further south with the initial positioning of the boundary Tuesday morning, placing it over far southeastern portions of our forecast area or even further southeast. As the main trough axis approaches from the northwest, it will drive the frontal boundary further southeast through the day. Shower activity will extend well north of the boundary, but with the front trending more progressive, shower activity should primarily be confined to locations south and east of DC. The trend throughout the day will be for showers to gradually move out of the area, with most locations staying dry during the afternoon hours. It will be much cooler and less humid compared to previous days, with highs in the upper 70s to low 80s and dewpoints dropping through the 60s. Even where conditions remain dry, skies are expected to stay mostly cloudy as the upper trough axis starts to approach from the northwest.
High pressure will build to our west on Wednesday, before eventually becoming centered close to overhead on Thursday and Friday. Mostly sunny skies are expected, with below average temperatures (highs in the low-mid 80s) and humidity levels (dewpoints in the upper 50s to low 60s.
High pressure to the south will likely cause a west to southwest flow through Sunday. Wind speeds should remain below Small Craft Advisory criteria for most areas. Mesoscale guidance suggesting southerly channeling possible again tonight. Signals don't look as strong as yesterday, which didn't pan out to the extent requiring an Advisory. Will raise forecast gusts this evening but keep forecasts below Small Craft Advisory thresholds.
In addition, a stray thunderstorm is not out of the question this evening. There is a better chance (isolated to scattered coverage) for thunderstorms later Sunday afternoon and Sunday night as a cold front approaches. Some storms may produce gusty winds. The cold front will cross the waters Monday night. By that point, precipitation likely to to interfere with mixing processes.
Sub-Small Craft Advisory level winds are expected on Tuesday, along with the potential for some lingering morning showers. Conditions should improve Tuesday afternoon through the middle of the week as high pressure builds in from the west
Here are the warm temperature records for this weekend:
Record Daily High Temperatures July 20 July 21 DCA 106 (1930) 104 (1926) BWI 102 (1930) 104 (1930) IAD 101 (1980) 101 (1991)
Record Daily Warm Low Temperatures July 20 July 21 DCA 82 (2015) 82 (1987) BWI 80 (1930) 83 (1930) IAD 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...Excessive Heat Warning from 11am to 9pm EDT Sunday for DCZ001. MD...Heat Advisory from 11am to 9pm EDT Sunday for MDZ502. Excessive Heat Warning from 11am to 9pm EDT Sunday for MDZ003>006-011-013-014-016>018-503>508. VA...Heat Advisory from 11am to 9pm EDT Sunday for VAZ025>030- 036>040. Excessive Heat Warning from 11am to 9pm EDT Sunday for VAZ031-050>057-501-502-505-506. WV...Heat Advisory from 11am to 9pm EDT Sunday for WVZ050-051-055- 502-504. Excessive Heat Warning from 11am to 9pm EDT Sunday for WVZ052-053. MARINE...None