503 FXUS61 KLWX 290754 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 354 AM EDT Mon Jun 29 2026 .WHAT HAS CHANGED... We continue to monitor the potential for heat and humidity during the middle to latter portions of the week. && .KEY MESSAGES... - (1) Heat and humidity gradually build across the region early this week. - (2) Potentially extreme heat could persist through the Independence Day weekend, along with a return of showers & thunderstorms. && .DISCUSSION... KEY MESSAGE 1...Heat and humidity gradually build across the region early this week. Low clouds and patchy fog are in place across much of the forecast area early this morning. Any fog will persist through daybreak, but should quickly dissipate after sunrise. Low clouds will also begin to lift and gradually break up over the course of the morning. Conditions are expected to remain dry across the majority of the forecast area today, but a few popup afternoon showers or a brief thunderstorm can't be ruled out west of US-15, especially across the higher terrain. Temperatures are forecast to climb into the mid to upper 80s today, with dewpoints in the upper 60s to lower 70s. Strong upper ridging will gradually build in from the west through Wednesday, with a closed mid-level anticyclone becoming centered over the Central Appalachians by Wednesday. Heat and humidity will continue to build across the region each successive day, with temperatures at lower elevations climbing into the upper 80s to lower 90s on Tuesday, and then upper 90s to around 100 on Wednesday. Dewpoints will increase into the lower 70s to the west of the Blue Ridge on Tuesday, with 60s further east. Lower 70s dewpoints are expected to overspread the majority of the forecast area by Wednesday. Heat indices are forecast to reach into the upper 80s to mid 90s for most on Tuesday, but could approach 100 just in the lee of the Alleghenies from near Cumberland to Petersburg. Heat Advisories may potentially need to be considered for those locations on Tuesday. Heat indices are then forecast to reach 100-110 across all lower elevations on Wednesday. Heat headlines will almost certainly be needed for Wednesday. Conditions are largely expected to remain dry on Tuesday and Wednesday as large scale subsidence increases ahead of the approaching upper ridge axis, but a stray popup afternoon shower or storm can't be ruled out in the mountains. KEY MESSAGE 2...Significant heat risk this week heading into the Independence Day holiday. Upper level ridging will remain centered over the Appalachians potentially through the end of the week, allowing temperatures and humidity to continually increase into the Independence Day holiday weekend. Beginning Thursday, conditions could begin to become an extreme heat risk as defined by the NWS HeatRisk guidance. With widespread dewpoints in the lower 70s due to subtropical high pressure bringing moist air in, air temperatures ranging between the upper 90s-low 100s could cause heat indices approaching 110 in some areas Wednesday through Sunday. Towards the end of this period, a shortwave trough could develop over the Mid-Atlantic Friday and Saturday. This could potentially reintroduce widespread showers and thunderstorms throughout the region, with thunderstorms having the potential to become severe due to the extended heat & humidity. Multiple ML and AI model outputs currently show a 15%-40% probability for severe weather to materialize between Friday July 3rd to Sunday July 5th as this trough moves through. Given all the ongoing outdoor activities across the region during this timeframe, will have to continue to closely monitor the synoptic setup ahead of this time period. Early model guidance suggests that upper-level ridging officially begins to exit the region towards the start of next week, potentially signaling a breakdown in the heat towards the end of the forecast period. && .AVIATION /07Z MONDAY THROUGH FRIDAY/... Patchy fog and some MVFR ceilings linger across portions of the area this morning. Improvement back to VFR conditions is expected shortly after daybreak. Thereafter, VFR conditions are forecast to persist through Wednesday. Winds will be light out of the northeast for much of the day, before turning out of the south later this evening. Winds are expected to remain out of the south on Tuesday, before becoming southwesterly on Wednesday. Prevailing VFR conditions are expected Thursday through Friday morning. Beginning Friday afternoon & evening, thunderstorm chances increase. Should thunderstorms materialize, some could become severe. Intermittent sub-VFR conditions are possible Friday & Saturday as a result, as well as changes in wind speed and direction. && .MARINE... Light and variable winds are expected over the waters through mid-afternoon. Winds then turn southerly this evening, and could briefly near low-end SCA for a few hours. Winds remain southerly for Tuesday and Wednesday, with SCAs likely in southerly channeling each afternoon and evening. Winds stay below SCA thresholds Thursday and through the weekend. Thunderstorm chances over the waters increase Friday and Saturday, which could become severe. Should these conditions materialize, Special Marine Warnings could become necessary. Winds generally flow south to southwesterly Thursday & Friday. && .CLIMATE... There is a significant heat risk this week. The numbers below aren't a forecast, but rather a reference for historical context for comparison. Latest forecast: weather.gov/lwx. ================================================================== *** ALL-TIME RECORD HIGHS *** ================================================================== Baltimore 107 (set on Jul 10, 1936) Washington 106 (set on Jul 20, 1930 + Aug 06, 1918) Sterling-Dulles Airport 105 (set on Jul 22, 2011) Baltimore Downtown 108 (set on Jul 07, 2012 + Jul 22, 2011) Annapolis 106 (set on Aug 06, 1918) Hagerstown 105 (set on Jul 14, 1954) Martinsburg 112 (set on Jul 11, 1936) Charlottesville 107 (set on Sep 07, 1954 + 3 other times) ================================================================== *** ALL-TIME RECORD WARM LOWS *** ================================================================== Baltimore 83 (set on Aug 05, 1930 + 2 other times) Washington 84 (set on Jul 24, 2011 + 2 other times) Sterling-Dulles Airport 79 (set on Aug 08, 2007) Baltimore Downtown 88 (set on Jul 02, 2011 and Jul 10, 1993) Annapolis 92 (set on Jul 07, 1994) Hagerstown 86 (set on Jun 15, 1899) Martinsburg 86 (set on Jul 21, 1930) Charlottesville 85 (set on Aug 07, 1918) ================================================================== *** JULY MONTHLY RECORD HIGHS *** ================================================================== Baltimore 107 (set on Jul 10, 1936) Washington 106 (set on Jul 20, 1930) Sterling-Dulles Airport 105 (set on Jul 22, 2011) Baltimore Downtown 108 (set on Jul 07, 2012 + Jul 22, 2011) Annapolis 105 (set on Jul 21, 1930 + Jul 02, 1901) Hagerstown 105 (set on Jul 14, 1954) Martinsburg 112 (set on Jul 11, 1936) Charlottesville 107 (set on Jul 10, 1936 + Jul 20, 1930) ================================================================== *** JULY MONTHLY RECORD WARM LOWS *** ================================================================== Baltimore 83 (set on Jul 21, 1930) Washington 84 (set on Jul 24, 2011 + 2 other times) Sterling-Dulles Airport 78 (set on Jul 24, 2010 + Jul 08, 2010) Baltimore Downtown 88 (set on Jul 22, 2011 + Jul 10, 1993) Annapolis 92 (set on Jul 07, 1994) Hagerstown 83 (set on Jul 24, 2010) Martinsburg 86 (set on Jul 21, 1930) Charlottesville 84 (set on Jul 22, 1930) ================================================================== *** DAILY RECORD HIGHS | WARM LOWS *** VALID: Jul 01 ================================================================== Baltimore 103 (1901) | 80 (1933 + 1901) Washington 102 (1901) | 79 (1977) Sterling-Dulles Airport 96 (2012) | 72 (2017 + 3) Baltimore Downtown 101 (2012) | 82 (2012) Annapolis 103 (1901) | 79 (1945 + 1901) Hagerstown 100 (1901) | 74 (2017 + 1977) Martinsburg 102 (1933) | 74 (1933) Charlottesville 101 (2012 + 1945) | 78 (1901) ================================================================== *** DAILY RECORD HIGHS | WARM LOWS *** VALID: Jul 02 ================================================================== Baltimore 103 (1901) | 80 (1901) Washington 101 (1898) | 79 (2012 + 1872) Sterling-Dulles Airport 98 (1966) | 75 (2022) Baltimore Downtown 102 (1966) | 84 (2002) Annapolis 105 (1901) | 80 (1901) Hagerstown 100 (1966) | 74 (2018 + 1901) Martinsburg 102 (1933 + 1931) | 75 (1933 + 1901) Charlottesville 100 (1954) | 76 (1910) ================================================================== *** DAILY RECORD HIGHS | WARM LOWS *** VALID: Jul 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) Period of Record (POR) context... Area (obs site) Records since ------------------------------------------------------------------ Baltimore (BWI) Jan 1872 Washington (DCA) Jul 1872 Sterling-Dulles Airport (IAD) Jan 1960 Baltimore Downtown (DMH) Jul 1950 Annapolis (NAK) Jan 1894 Hagerstown (HGR) Jan 1899 Martinsburg (MRB) Jan 1891 Charlottesville (CHO) Jan 1893 && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ DISCUSSION...KJP/SRT AVIATION...KJP/SRT MARINE...KJP/SRT