978 FXUS61 KLWX 080800 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 400 AM EDT Tue Jul 8 2025 .SYNOPSIS... A cold front will drop closer to the area by this afternoon and will then stall and waver nearby through the weekend. && .NEAR TERM /THROUGH TONIGHT/... There`s a lull in the active weather to start the day, with just some patches of clouds and fog. Ridging at the surface and aloft remains offshore, while a cold front lurks across central PA into central OH. The front will slowly sag toward the area this afternoon, while ripples in the WSW flow aloft will provide additional lift and enhance mid level winds slightly. Expect convection to rapidly develop over the mountains between noon and 2 PM and then progress eastward through the remainder of the afternoon and evening. Moderate to strong instability in the hot and humid airmass will support strong updrafts. While the airmass will be fairly moist with weaker lapse rates, the favorably-oriented 20-25 kt of shear will help organize the storms into clusters, and there will likely be sufficient DCAPE for strong to severe downbursts. This threat is greatest as storms intensify near and east of the Blue Ridge, where SPC has a Slight Risk. Precipitable water values will be around 2 inches east of the Blue Ridge as well, supporting heavy rain rates. While average storm motion should limit residence time of the thunderstorms, there is potential for mergers and backbuilding along outflows. There are also some indications the storms could get "strung out" for a time across southern Maryland, which has had above normal rainfall over the past week. Combined with the more sensitive urban areas, a Flood Watch for flash flooding has been issued from 2 PM until midnight for this area. Today will be the hottest day of the week for a large part of the area with highs in the lower to mid 90s east of I-81. Have expanded the Heat Advisory to include Washington DC and the VA I-95 corridor, as it appears dew points will pool along and east of a subtle surface trough near the fall line. This area will also see the longest period of sunshine before storms arrive, so feel there is a reasonable chance to reach 105 heat index. Elsewhere, heat indices will be in the upper 90s to lower 100s. The second half of tonight will bring the opportunity for fog and/or low clouds in the saturated low level airmass. Lows will range from the upper 60s to mid 70s. && .SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... The weather pattern will get stagnant moving forward as the frontal zone gets stuck between the ridge to the southeast and stronger troughing in Canada. The theme for each day will be similar, with exact details unfolding as the airmass boundary between the warm and humid air to the south and slightly drier air to the north wavers about the Mid Atlantic. Showers and thunderstorms will primarily focus on the afternoon and evening hours each day, with some attendant threat of localized flooding and damaging winds. Of Wednesday and Thursday, Wednesday may be a bit more active as a notable shortwave is forecast to traverse the area during peak heating. Shear may increase with this wave, though there are indications the greatest instability will favor the southern half of the area. We are currently outlooked for Marginal Severe and Slight Excessive Rainfall. CAMS indicate there may be opportunities for greater rainfall totals compared to Tuesday due to the boundary being situated nearby which could promote training. Temperatures may be a few degrees cooler as the ridge is suppressed, but still likely reach the upper 80s and lower 90s. Deep southwest flow looks to bring more cloud cover Thursday, which may keep temperatures a bit cooler and limit instability. Therefore showers and storms may not be quite as intense, but will have to continue to monitor the threats as mentioned above. Overnights will be muggy with some potential for fog and/or low clouds. && .LONG TERM /FRIDAY THROUGH MONDAY/... A front is expected to stall across the region late in the week and through much of the weekend. Upper level energy will ride along the stalled front and be fueled by rich humidity to create several rounds of showers and thunderstorms. Most of the convection will occur during the afternoon and early evening hours. Temperatures will be near average with highs in the middle 80s. && .AVIATION /07Z TUESDAY THROUGH SATURDAY/... The day will start out mostly clear and calm, but expect thunderstorms to erupt this afternoon with fairly widespread coverage. The bigger time window appears to be between 1 and 9 PM from west to east, but tried to keep a 3 hour TEMPO window in the TAF. If storms can organize into clusters, impacts should be less than an hour, but there is some potential for more complicated and erratic storm evolution. Threats will include very heavy rain, frequent lightning, and potential downbursts to 50 kt. Somewhat lower coverage around MRB and CHO makes impacts less certain there, but intense storms are highly likely in the metros. S to SW winds will remain less than 10 kt otherwise. After storms depart, there are indications fog and/or low clouds may form the second half of the night, especially west of the metros. There will be another opportunity for strong to severe thunderstorms with heavy rain Wednesday afternoon and evening. While not totally certain, the more intense storms may be near IAD/DCA and to the south. The pattern remains fairly stagnant the remainder of the week with daily opportunities of mainly afternoon and evening thunderstorms and patchy fog and/or low clouds overnight. Outside of storms, winds generally remain less than 10 kt. && .MARINE... As a cold front approaches today, more widespread coverage of thunderstorms is expected during the afternoon and evening hours today with potential severe downburst winds. This will likely repeat Wednesday, though the highest coverage may be focused across southern Maryland as the front shifts a bit to the south and stalls. Winds should be fairly light out of the south outside of thunderstorms, with outflows likely disrupting opportunities for southerly channeling. Sub-advisory caliber winds are expected for Thursday through Saturday. Gradients remain rather weak with wind direction being dictated by the position of the front and any convective- scale processes. The main hazard will come from gusty thunderstorm winds possible each afternoon and evening. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Heat Advisory from 1 PM this afternoon to 7 PM EDT this evening for DCZ001. Flood Watch from 2 PM EDT this afternoon through this evening for DCZ001. MD...Heat Advisory from 1 PM this afternoon to 7 PM EDT this evening for MDZ008-011-013-014-016>018-508. Flood Watch from 2 PM EDT this afternoon through this evening for MDZ005-006-008-011-013-014-016>018-503>508. VA...Heat Advisory from 1 PM this afternoon to 7 PM EDT this evening for VAZ053>057-527. Flood Watch from 2 PM EDT this afternoon through this evening for VAZ053-054-506-526-527. WV...None. MARINE...Heat Advisory from 1 PM this afternoon to 7 PM EDT this evening for ANZ530. Flood Watch from 2 PM EDT this afternoon through this evening for ANZ530. && $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS LONG TERM...KLW AVIATION...ADS MARINE...ADS