Baltimore Harbor & Patapsco River Marine Forecast
| This Afternoon...Sw Winds 5 Kt. Waves Flat. |
| Tonight...W Winds 5 Kt. Waves Less Than 1 Ft. A Chance Of Showers And Tstms. |
| Sat...W Winds Around 5 Kt...Becoming S Late. Waves 1 Ft Or Less. A Chance Of Showers And Tstms. |
| Sat Night...W Winds 5 To 10 Kt. Waves 1 Ft Or Less. A Chance Of Showers And Tstms. |
| Sun...S Winds 5 Kt. Waves Less Than 1 Ft. Showers Likely With A Chance Of Tstms. |
| Sun Night...E Winds 5 Kt. Waves Less Than 1 Ft. Showers With A Chance Of Tstms. |
| Mon...E Winds 5 Kt. Waves Less Than 1 Ft. A Chance Of Showers In The Morning, Then Showers Likely With A Chance Of Tstms. |
| Tue...Ne Winds 5 Kt. Waves Less Than 1 Ft. A Chance Of Showers. Winds And Waves Higher And Visibilities Lower In And Near Tstms. |
| Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 235pm EDT Fri July 3 2026 .WHAT HAS CHANGED... Continuing to fine tune heat headlines and storm chances based on latest guidance and observations. Flash flood threat Sunday into Monday is increasing. .KEY MESSAGES... - 1) Extreme heat and humidity continues through the Independence Day holiday weekend with some relief early next week. - 2) An increased risk for severe thunderstorms through the Independence Day holiday weekend. - 3) Increasing concern for the threat of flash flooding both Sunday and Monday afternoon/evening. KEY MESSAGE 1...Extreme heat and humidity continue through the Independence Day holiday weekend with some relief early next week. Record temperatures will continue through much of the upcoming Independence Day holiday weekend. An upper ridge remains parked across a vast portion of the southeastern U.S. into the Tennessee/Ohio Valleys and Mid-Atlantic region. Lower tropospheric temperatures remain very anomalous and record breaking in nature. Extreme Heat Warnings remain in effect through this evening, and again Saturday afternoon and evening due to a combination of near record high temperatures and elevated humidity levels. Winds remain on the lighter side under this expansive dome of high pressure. Skies should stay mostly sunny with any convective threats likely holding off until the evening (see Key Message 2 for more information). Otherwise, it is a literal wash, rinse, and repeat setup heading into Saturday/Independence Day. This does offer a bit of transition in the overall pattern as mid-level heigheights slowly decrease. These subtle height falls will make for a slightly more challenging temperature forecast as convection becomes more active during the core heating hours. How much convection and cloud cover overspread the region could hinder some of the diurnal heating. At this point, the guidance keeps humidity levels plenty high to support additional heat products. Extreme Heat Warnings are in place from 10am until 9pm for areas east of the Blue Ridge. Heat indices again reach the 110 degree mark, slightly higher toward the urban areas and along the Chesapeake Bay. For the Shenandoah Valley, it will be another day of Heat Advisories as heat indices rise to around 100 to 103 degrees. Overall, additional daily temperature records could be broken through Saturday (see the Climate section near the bottom of this discussion). Temperatures drop off a bit into Sunday as convection becomes a larger part of the equation. However, even with forecast highs now in the low/mid 90s, elevated dew points could yield additional heat headlines (i.e., Heat Advisories) on Sunday. KEY MESSAGE 2...An increased risk for severe thunderstorms through the Independence Day holiday weekend. The Storm Prediction Center outlooks through late Sunday paint the picture of an active convective pattern ahead. A Slight Risk for severe thunderstorms is being advertised across portions of the area during this period. Most of the local area (Mid-Atlantic) should remain capped under upper ridging with forcing displaced to the north. However, any storms that develop to the north may make a run at the I-68/I-70 corridor this evening. Some guidance also attempts to develop an isolated thunderstorm or two along the bay breeze or near the Blue Ridge Mountains. As the upper ridge begins to undergo some weakening, the threat of strong to severe thunderstorms will increase through the holiday weekend. While the guidance shows deep-layered westerlies on Saturday, the flow is on the weaker side which would limit the negative influence of this flow on convective development. The likely triggers for diurnal convection will be around mesoscale boundaries like the lee-side trough, as well as bay and river breezes. Multiple days of intense heat and humidity yields somewhat extreme levels of instability (i.e., mixed layer CAPEs (Convective Available Potential Energy - high values indicate potential for severe weather) around 3,000 to 4,000 J/kg in some models). With downdraft CAPE values nearing 1,500 J/kg, significant wind damage is not out of the question with more potent updrafts. While difficult to hone in on timing, multiple rounds cannot be ruled given the degree of instability in the atmosphere. A Slight Risk for severe convection remains across the entire region. The updated Day 3/Sunday outlook also brings another Slight Risk day to the local area. A series of weak to modest perturbations in the flow will work in tandem with an approaching nearby frontal system. The position of remnant outflows, degree of convective debris, and additional development are all questions looming for Sunday's forecast. Despite the uncertainty, the parameters remain favorable for further thunderstorm activity. Additional chances for showers and thunderstorms continue through Tuesday, although the speed at which this weekend's trough tracks south will be critical for these continued chances to materialize. ML guidance shows an upwards chance in thunderstorm & severe potential for Monday, with NCAR's Medium-Range AI NWP (Numerical Weather Prediction) guidance showing a 30%-45% probability in the 00z guidance for Monday afternoon/evening. Synoptic setup in the days beforehand will be critical in understanding the nature & scope of thunderstorms during this period. Temperatures look to potentially drop as this cold front tracks to the south by early Tuesday, although dewpoints will remain elevated for now resulting in continued humid conditions. Nevertheless, heat indices look to potentially dip back into double digits by Tuesday afternoon in the metros. High pressure moves over the region midweek. KEY MESSAGE 3...Increasing concern for the threat of flash flooding through Monday. Outside of the severe potential over the next few days, which is mentioned in detail above, there is growing concern for a flash flood threat. For Independence Day, the threat is much lower, but still not zero. An extremely moist air mass will be in place over the region, so storms will produce prolific rainfall rates for those that do get them. However, as mentioned above, there is a big concern for damaging downbursts, which should actually mitigate the flash flood threat by keeping storms moving. Urban/poor drainage areas will have an isolated flash flood threat, but it will be very situational, hence the marginal risk for excessive rainfall from WPC over the area. Outside of the metro areas, most locations are still very dry due to the ongoing drought, so the flash flood threat is much lower. By Sunday, things start to get a little more concerning, but especially by Monday. As the upper-level ridge continues to buckle, a trough over the Great Lakes will form with a cold front tracking through the region by Monday. Storms on Sunday are likely to trigger ahead of this front and along existing outflow boundaries from Saturday, terrain circulations, and Bay/River breezes. Storms should generally be progressive, but the threat for training increases if any of these existing boundaries line up parallel to the mean flow. A lot of uncertainty with this, as we have to see how Saturday's event unfolds first and see what boundaries are left behind in its wake. By Monday though, the slow-moving frontal boundary drops into our region. This front will be very wavy in nature, but some portion seems likely to line up with the mean low-mid level flow, which is out of the WSW. Training convection is much more likely Monday afternoon. Additionally, several days of convection before Monday could reduce the flash-flood guidance, with some areas becoming more susceptible. Either way, the urban areas are the greatest area of concern, as model guidance wants to hang this front up somewhere nearby. With PWATs (Precipitable Waters) in excess of 2", skinny CAPE profiles, a deep warm cloud layer, and boundary-parallel low-mid level flow, a lot of ingredients are there for a more widespread flash flooding threat. Marine In response to expansive high pressure over the region, winds remain light and well below any hazard thresholds. The weaker flow will yield a series of wind shifts as this ridge reconfigures in time. The bigger issue will be related to convection impacting the waterways. While chances are low, a few storms could approach the northern-most waters later this evening/night. Otherwise, an active weather weekend lies ahead for those out and about for the Independence Day holiday. Special Marine Warnings may be needed at times, particularly during the afternoon/evening hours this weekend. Before going out on the waters, ensure to check the forecast and have multiple ways of receiving hazardous weather information. Wind gusts stay below SCA (Small Craft Advisory) thresholds through Monday afternoon. Winds could potentially approach SCA (Small Craft Advisory) thresholds Monday evening before diminishing again Tuesday. Showers & thunderstorms remain possible over the waters for Monday afternoon & evening, potentially causing erratic winds, lightning, and storm-associated wind gusts. Climate There is a Significant Heat Risk through at least Saturday (Independence Day). The numbers below aren't a forecast, but rather a reference for historical context for comparison. Latest forecast: weather.gov/lwx. A number of daily records have been broken at the local airports the past couple of days (July 1-2). ================================================================== *** ALL-TIME RECORD HIGHS *** ================================================================== Baltimore 107 (set on July 10, 1936) Washington 106 (set on July 20, 1930 + August 06, 1918) Sterling-Dulles Airport 105 (set on July 22, 2011) Baltimore Downtown 108 (set on July 07, 2012 + July 22, 2011) Annapolis 106 (set on August 06, 1918) Hagerstown 105 (set on July 14, 1954) Martinsburg 112 (set on July 11, 1936) Charlottesville 107 (set on September 07, 1954 + 3 other times) ================================================================== *** ALL-TIME RECORD WARM LOWS *** ================================================================== Baltimore 83 (set on August 05, 1930 + 2 other times) Washington 84 (set on July 24, 2011 + 2 other times) Sterling-Dulles Airport 79 (set on August 08, 2007) Baltimore Downtown 88 (set on July 22, 2011 and July 10, 1993) Annapolis 92 (set on July 07, 1994) Hagerstown 86 (set on Jun 15, 1899) Martinsburg 86 (set on July 21, 1930) Charlottesville 85 (set on August 07, 1918) ================================================================== *** JULY MONTHLY RECORD HIGHS *** ================================================================== Baltimore 107 (set on July 10, 1936) Washington 106 (set on July 20, 1930) Sterling-Dulles Airport 105 (set on July 22, 2011) Baltimore Downtown 108 (set on July 07, 2012 + July 22, 2011) Annapolis 105 (set on July 21, 1930 + July 02, 1901) Hagerstown 105 (set on July 14, 1954) Martinsburg 112 (set on July 11, 1936) Charlottesville 107 (set on July 10, 1936 + July 20, 1930) ================================================================== *** JULY MONTHLY RECORD WARM LOWS *** ================================================================== Baltimore 83 (set on July 21, 1930) Washington 84 (set on July 24, 2011 + 2 other times) Sterling-Dulles Airport 78 (set on July 24, 2010 + July 08, 2010) Baltimore Downtown 88 (set on July 22, 2011 + July 10, 1993) Annapolis 92 (set on July 07, 1994) Hagerstown 83 (set on July 24, 2010) Martinsburg 86 (set on July 21, 1930) Charlottesville 84 (set on July 22, 1930) ================================================================== *** DAILY RECORD HIGHS | WARM LOWS *** VALID: July 03 ================================================================== Baltimore 104 (1898) | 80 (1898) Washington 101 (1966 + 2) | 80 (2018) Sterling-Dulles Airport 103 (1966) | 73 (2018 + 2) Baltimore Downtown 102 (1997) | 82 (2018 + 1983) Annapolis 100 (1901) | 84 (1896) Hagerstown 102 (1966) | 76 (2002) Martinsburg 102 (1941 + 1911) | 74 (1980) Charlottesville 100 (1966 + 1954) | 79 (1911) ================================================================== *** DAILY RECORD HIGHS | WARM LOWS *** VALID: July 04 ================================================================== Baltimore 100 (2002 + 2) | 78 (1911) Washington 100 (1919) | 80 (2018 + 2002) Sterling-Dulles Airport 97 (2002 + 1999) | 75 (2018) Baltimore Downtown 101 (2002 + 1990) | 83 (2002) Annapolis 98 (1999) | 81 (2018) Hagerstown 100 (1966 + 1919) | 76 (2018) Martinsburg 103 (1898) | 76 (1999) Charlottesville 100 (2012) | 78 (1919) ----------------------------------------------------------------- Number of Consecutive Days Max Temp >=100 Area (obs site) Records since ------------------------------------------------------------------ Baltimore (BWI) 4 days July 14-17,2024 & July 19-22,1930 Washington (DCA) 4 days July 14-17, 2024 & July 5-8, 2012 Sterling-Dulles (IAD) 2 days July 7-8, 2012, July 21-22, 2011 July 6-7, 2010, July 16-17, 1997 Baltimore Downtown (DMH) 5 days July 3-7, 2010 & July 7-11, 1993 Annapolis (NAK) 1 day July 21, 2019, July 7, 2012, July 22, 2011, June 29, 1959 Hagerstown (HGR) 3 days July 5-7, 2010 Martinsburg (MRB) 6 days June 1-6, 1925 Charlottesville (CHO) 5 days July 4-8, 2012 Period of Record (POR) context... Area (obs site) Records since ------------------------------------------------------------------ Baltimore (BWI) Jan 1872 Washington (DCA) July 1872 Sterling-Dulles Airport (IAD) Jan 1960 Baltimore Downtown (DMH) July 1950 Annapolis (NAK) Jan 1894 Hagerstown (HGR) Jan 1899 Martinsburg (MRB) Jan 1891 Charlottesville (CHO) Jan 1893 NOAA Baltimore MD/Washington DC Office: Watches - Warnings - Advisories DC...Extreme Heat Warning until 9pm EDT this evening for DCZ001. Extreme Heat Warning from 10am to 9pm EDT Saturday for DCZ001. MD...Extreme Heat Warning until 9pm EDT this evening for MDZ004>006-008-011-013-014-016>018-503>508. Extreme Heat Warning from 10am to 9pm EDT Saturday for MDZ004>006-008-011-013-014-016>018-503>508. Extreme Heat Warning until 8pm EDT this evening for MDZ003- 502. Heat Advisory from 10am to 8pm EDT Saturday for MDZ003-502. Heat Advisory until 8pm EDT this evening for MDZ501-509-510. VA...Extreme Heat Warning until 9pm EDT this evening for VAZ036>040-050-051-053>057-501-502-505-506-526-527. Extreme Heat Warning from 10am to 9pm EDT Saturday for VAZ036>040-050-051-053>057-501-502-505-506-526-527. Extreme Heat Warning until 8pm EDT this evening for VAZ027>031. Heat Advisory from 10am to 8pm EDT Saturday for VAZ025>031- 504. Heat Advisory until 8pm EDT this evening for VAZ025-026-503- 504-507-508. WV...Extreme Heat Warning until 8pm EDT this evening for WVZ050>053-055-502-504. Heat Advisory from 10am to 8pm EDT Saturday for WVZ050>053- 055-502-504-506. Heat Advisory until 8pm EDT this evening for WVZ501-503-505- 506. Marine Extreme Heat Warning until 9pm EDT this evening for ANZ530. Extreme Heat Warning from 10am to 9pm EDT Saturday for ANZ530. |
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