756 FXUS61 KLWX 300100 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 900 PM EDT Mon Jun 29 2026 .WHAT HAS CHANGED... No major changes were made to the forecast. Will continue to monitor the latest forecast guidance to determine when hazardous heat products will be issued. && .KEY MESSAGES... - (1) Significant heat wave builds through the week. - (2) Potential for severe thunderstorms increases late this week through the weekend. && .DISCUSSION... KEY MESSAGE 1...Significant heat wave builds through the week. Subsidence has larged quelled any discernible shower and thunderstorm threat. The only exception has been across southwestern Highland County owing to some terrain aided enhancement. However, any residual showers have dissipated given the loss of daytime heating. Dry weather and clearing skies with light southeast winds are expected overnight. Lingering low-level moisture could lead to areas of fog southwest of the Potomac River where low-level moisture is expected to be most robust. Low temperatures will drop into the 60s for most of the region. Tuesday... A strong ridge aloft begins to build in earnest on Tuesday, centered over the Ohio River Valley. At the surface, high pressure settles over the East Coast. This marks the start of what may turn out to be the most significant heat wave in over a decade for much of the region (thinking about the heat in 2012). The building ridge and corresponding low-level thermals support high temperatures in the lower 90s. Higher low-level moisture is expected to begin advecting in from the west, and should reach the upper Potomac River Valley (eastern WV, western MD) by peak heating with dew points into the lower 70s pooled in the valleys. This supports heat index values around 100 for a few hours. Have issued a Heat Advisory for this reason. Further east, dry air just above the surface coupled with onshore flow off relatively cooler water is expected to keep high temperatures a degree or two lower with dew points dropping down into the lower to middle 60s. Lower heat indices are forecast as a result, and therefore there are no headlines along or east of I-81 at the moment for Tuesday. Should heating or moisture (or both) trend upwards more quickly, this may have to be re-evaluated. Low temperatures Tuesday night will only drop into the upper 60s to lower 70s as humidity increases areawide. Wednesday... Heights and temperatures increase further on Wednesday, though height rises slow a bit late in the day into the evening especially in the vicinity of northeast MD farthest away from the center of the ridge. SLP patterns show a sharpening lee pressure trough east of the Appalachians along much of the East Coast (roughly near the Blue Ridge Mountains locally). The setup seems favorable Wednesday afternoon for the surface trough and bay breeze to interact, which could spark a thunderstorm or two mainly northeast of the Potomac (farthest from the ridge). Should anything develop, it could be quite strong given high levels of instability. But, most will be dry. Very high instability on Wednesday is due in large part to high low-level moisture content. Dew points/humidity may peak on Wednesday, although air temperatures probably don't peak until Thursday-Friday. The combination of mid to upper 90s air temps and low 70s dew points results in solid Heat Advisory criteria areawide. For this reason, no Extreme Heat Watch (which is a precursor to an anticipated warning-level event) has been issued. If trends in either low-level moisture or temps (or both) come to fruition, this may need to be reconsidered tonight. Either way, it will be quite hot. Thursday through Saturday... The heat peaks late this week into the Independence Day holiday. Trends have been for a slower breakdown of the ridge, which pushes the highest thunderstorm chances into the weekend. Barring widespread convection earlier Friday afternoon, air temps could be similar to Thursday. Dew points will be a bit less on Thursday as slightly drier air aloft works in, but may rebound a bit Friday. Both days may see widespread heat indices well over 100, approaching or exceeding 110 for the I-95 corridor, near the Chesapeake Bay, and into the central Virginia piedmont. Watches would be issued for this once it is within the 60-72 hour lead time window as confidence increases from possible to probable. The chance of thunderstorms increases Saturday as the ridge begins to buckle. This all points toward temps a couple degrees lower but with a potential uptick in humidity, resulting in heat index values that may ultimately be similar to Thursday and Friday. It will also be the fourth day in a row of near or above 100 degree temps, overlapping a holiday, which could be very impactful. Begin preparing now for the heat. Visit the Website weather.gov/safety/heat for preparedness information. Refer to the Climate section below for heat records. KEY MESSAGE 2...Potential for severe thunderstorms increases late this week through the weekend. With the increase in near record heat and humidity comes abundant instability. After building untapped for several days, convection may erupt late in the week as the ridge begins to shift and break down. This begins to happen in a subtle (trending slower) sense Friday, but really gets going this weekend. At the very least, scattered strong to severe thunderstorms with frequent lightning, damaging wind gusts, heavy downpours, and perhaps hail seem plausible. This would probably be centered on the afternoon and evening hours when heat and instability are relatively higher. Shear looks quite low, but if any subtle waves approach the region from the west and northwest between the ridge to the south and the jet stream to the north, this could increase shear and consolidate storms into more widespread clusters. Plan ahead for any outdoor activities this weekend, as they are likely to be interrupted by storms at some point. Given the heat in place, some storms could be quite intense (if they form). From a historical perspective, prolonged near record heat in summer often ends in a period of strong storms. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... VFR conditions are forecast to persist through Wednesday. However, some fog may form especially near MRB/CHO later tonight into Tuesday morning. Winds will be light out of the southeast 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. Afternoon bay breezes may cause more E/SE flow at MTN and possibly BWI. Dry weather is expected through mid week, though a pop up t-storm can't be ruled out near any bay breezes (especially Wednesday). Prevailing VFR conditions are expected Thursday through Friday morning. Beginning Friday afternoon and evening, thunderstorm chances increase. Should thunderstorms materialize, some could become severe. Intermittent sub-VFR conditions are possible Friday into the weekend as a result, as well as changes in wind speed and direction. && .MARINE... Winds turn southerly this evening, and could briefly near low- end SCA for a few hours as they do so. Brief/marginal nature of this threat would be covered with a Marine Weather Statement versus a Small Craft Advisory (SCA). Winds remain southerly for Tuesday and Wednesday, with SCAs in effect Tuesday afternoon and night. Additional SCAs may be needed Wednesday. Winds likely stay below SCA thresholds Thursday and through the weekend. Thunderstorm chances over the waters increase Friday into the weekend, which could become severe. Should these conditions materialize, Special Marine Warnings could become necessary. Winds generally flow south to southwesterly. && .TIDES/COASTAL FLOODING... Increasing southerly flow could cause near minor flooding particularly at Annapolis and possibly Havre de Grace, Bowley's Quarters and Alexandria late tonight into Tuesday. && .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 22, 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 04 ================================================================== 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: Jul 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) 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...Small Craft Advisory from 5 PM Tuesday to 6 AM EDT Wednesday for MDZ008. Heat Advisory from 11 AM to 8 PM EDT Tuesday for MDZ502. VA...None. WV...Heat Advisory from 11 AM to 8 PM EDT Tuesday for WVZ050-055- 502-504-506. MARINE...Small Craft Advisory from 5 PM Tuesday to 6 AM EDT Wednesday for ANZ530-534-539>541-543. Small Craft Advisory from 2 PM Tuesday to 6 AM EDT Wednesday for ANZ531>533. Small Craft Advisory from 5 PM Tuesday to 1 AM EDT Wednesday for ANZ535-538. Small Craft Advisory from 2 PM Tuesday to 1 AM EDT Wednesday for ANZ536-537-542. && $$ DISCUSSION...BRO/DHOF/KJP/SRT AVIATION...DHOF/KJP/SRT MARINE...DHOF/KJP/SRT TIDES/COASTAL FLOODING...DHOF/BRO CLIMATE...DHOF/BRO