808 FXUS61 KLWX 290121 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 921 PM EDT Sun Jun 28 2026 .WHAT HAS CHANGED... Scattered showers are moving south over the Alleghenies and central Shenandoah Valley. Occasional downpours accompanying a few of these showers. && .KEY MESSAGES... - (1) A weak frontal boundary will linger across the region through tonight delivering waves of downpours. - (2) Significant heat risk this week heading into the Independence Day holiday. - (3) The threat for strong to severe thunderstorms returns late this week into the Independence Day weekend. && .DISCUSSION... KEY MESSAGE 1...A weak frontal boundary will linger across the region through tonight delivering waves of downpours. Brief downpours could accompany a couple of the showers over the Alleghenies and central Shenandoah Valley overnight. Otherwise, some patchy fog could develop in places overnight. Some fog may be dense. Upper ridging will start to build in from the west on Monday and Tuesday. Largely dry conditions are expected both days, but a stray afternoon shower or thunderstorm could potentially pop up over the higher terrain to the west of the Blue Ridge. Temperatures will gradually start to warm, with highs in the mid to upper 80s on Monday, and then lower 90s on Tuesday. KEY MESSAGE 2...Significant heat risk this week heading into the Independence Day holiday. Increased confidence for a prolonged period of extreme heat and humidity through the Independence Day July 4th holiday weekend. Synoptically, subtropical high pressure and a building upper-level ridge will allow temperatures and humidity values to climb toward record levels over a multi-day period mid to late this week. Temperatures Wednesday through Sunday will be the peak of the dangerous heat with highs for most in the upper 90s and lower 100s. Heat indices each afternoon will run between 102-108 degrees with a few readings around 110 along the immediate I-95 metro corridor, western shore of the Chesapeake Bay/southern MD, and down across the VA Piedmont region. Minimal relief is expected across the mountains with highs in the mid 80s and low 90s and heat indices in the mid to upper 90s as the heat peaks mid to late week. Another concerning aspect of this heat wave is that there will be very little relief at night, with widespread lows in the upper 60s to mid 70s (upper 70s-80 urban areas) Wednesday through Saturday. With that said, looking at major to extreme heat risk across the region during this period. Heat headlines will likely be needed and evaluated as the event gets closer. More at weather.gov/lwx/heat. KEY MESSAGE 3...The threat for strong to severe thunderstorms returns late this week into the Independence Day weekend. As mentioned in Key Message 2, heat is a big concern this week. However, with excessive heat and increasing humidity towards the end of the week, thunderstorms will become a threat towards the end of the week into the weekend. This occurs as the strong upper- level ridge over the region eventually begins to break down and we start to see some ripples of upper-level shortwave energy move nearby. This threat is illustrated by CSU/CIPS/NSSL (15-40 percent probabilities) outlooks along with the Google WxNext AI model which suggest the risk for severe weather during the Thursday July 2nd to Sunday July 5th timeframe. Something we'll continue to monitor in subsequent forecast shifts given all the ongoing outdoor activities across the region. Historically, near record summer heat often ends with widespread strong thunderstorm activity, and latest guidance starts to break down the heat this weekend (July 4) into early next week. && .AVIATION /01Z MONDAY THROUGH FRIDAY/... MVFR ceilings and patchy fog appear possible again tonight. Some fog may be dense. Improvement back to VFR is expected on Monday, with prevailing VFR conditions thereafter through Tuesday. Winds will be light out of the northeast today, light out of the east tomorrow, and then turn out of the south on Tuesday. VFR conditions mainly expected Wednesday through Friday night. Winds south 5 to 10 knots each day. Thunderstorm chances increase by Friday afternoon/evening, a few of which could be strong to severe given the extreme heat and humidity. Sub-VFR conditions will be possible at times in any storms, along with changes in wind speed and direction. && .MARINE... Winds turn light out of the east to northeast overnight into tomorrow, before becoming southerly on Tuesday. Brief near SCA periods of gusts are possible each afternoon and evening. Winds may reach more solid SCA levels in channeled southerly flow Tuesday afternoon/night. Southerly winds around 5 to 10 knots are expected on both Wednesday and Thursday. However, as temperatures drop closer to the water temperatures in the evening/overnight, conditions will be favorable for southerly channeling winds close to 20 knots. SCAs may be needed during the evening/overnight hours each night as this pattern takes hold. Similar conditions are expected on Friday, but with a return of thunderstorm chances. Storms on Friday afternoon, should they develop, could be quite strong to severe. Special Marine Warnings may be needed Friday afternoon/evening as a result. && .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...KLW/DHOF/EST AVIATION...KLW/DHOF/EST MARINE...KLW/DHOF/EST