FXUS61 KLWX 181304 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 904 AM EDT Sat Jul 18 2026 .WHAT HAS CHANGED... Early morning thunderstorms have weakened and departed. A zone of subtle lift has been left in its wake. Thunderstorms may develop as early as midday in the vicinity of western Maryland. && .KEY MESSAGES... - 1) Hot and humid conditions with a risk of severe thunderstorms today. - 2) Thunderstorm chances may linger across southern portions of the area as the front stalls to the south Sunday and Monday. - 3) A strong cold front and trough of low pressure may bring severe weather Tuesday and/or Wednesday. && .DISCUSSION... KEY MESSAGE 1...Hot and humid conditions with a risk of severe thunderstorms today. 12Z KIAD RAOB shows plentiful elevated instability in the wake of a warm front. Will have to see where this effective warm front ends up later this morning. Differential heating in the wake of the warm front and earlier storms coupled with the onset of height falls aloft could prompt storms to fire as early as midday in the vicinity of western MD. If that's the case, storms could reach the metros by mid afternoon (3-4pm). Despite the presence of clouds, it won't take much heating to reach convective temperatures given high (and increasing) low- level theta-e. Another thing to note is the flood threat. Individual storm cells will likely be moving given flow aloft, but the flow is oriented parallel to the lifting mechanism (nearby warm front). Back-building cells or clusters (possibly transient HP supercells) as well as multiple rounds are possible. Areas with lower FFG and in complex terrain around western MD would be of particular concern, and may need to consider a watch here especially if multiple rounds materialize. To the east, there may be a hint downsloping/rain shadow, with most model QPFs showing a relative min. Farther to the east, the metro areas are typical more vulnerable to begin with. Here, multiple rounds of storms with some (but not as strong as further west) signal of back-building, as well as a conglomeration of bay/river breezes, outflow, and the nearby warm front, could still result in heavy rainfall. This is another area to be monitored later today. With surface winds turning southerly and winds aloft turning southwesterly, there should be an improvement in smoke and air quality from south to north through the midday hours. Skies may not become completely sunny, but it won't take much to warm up. It will also be very humid with dew points in the lower to mid 70s. Heat index values will likely range from 100-105 east of the Blue Ridge and mid to upper 90s in the lower elevations to the west. A Heat Advisory has been issued for the I-95 corridor from Baltimore southward. This area is expected to have the most heating before storms arrive, and higher dew points will likely remain pooled east of a developing lee trough in this area. With 30+ kt of deep layer shear, the hot and humid airmass will result in substantial instability and a favorable environment for severe thunderstorm development. A primary focus for storm initiation and/or intensification will be the lee trough east of the Blue Ridge. Most CAMs have storms developing in this area by early to mid afternoon. Storms will likely also develop well upstream in the Great Lakes closer to the surface front. What happens in between these features is a bit more uncertain, though additional thunderstorms are certainly possible given the strong upper trough and deepening surface low to the north. Some areas could see multiple rounds. The primary hazard will be damaging winds, with some considerable swaths of damage possible in any sustained supercells or linear segments. Some isolated large hail is possible,but modest mid level lapse rates will be a limiting factor. A tornado is also possible, with the greatest chances in northeast Maryland where low level flow will be more favorable. Frequent lightning and heavy rainfall are likely with any storm. Precipitable water values surge to greater than 2 inches. The flash flood threat appears to be isolated and limited to any areas with localized training or repeating storms, as overall storm motions should be progressive. The QPF signal is highest in northeast MD. A secondary concentration of thunderstorms will develop closer to the cold front near the Great Lakes. Most guidance shows this activity rapidly weakening as it approaches the area during the late evening, with some stronger storms potentially reaching the Allegheny Front. The REFS does show a bit more persistence to these storms however. Either way, there will be a drying trend the second half of the night. KEY MESSAGE 2...Thunderstorm chances may linger across southern portions of the area as the front stalls to the south Sunday and Monday. The cold front will push south through the area Sunday. By the time convection initiates, it may largely be south of the forecast area. However, there is enough uncertainty in the frontal position that the I-64 corridor in central VA could see some thunderstorms on Sunday. The greatest risk for severe thunderstorms remains south of the area. High pressure briefly building to the north will bring cooler temperatures Sunday and Monday. The front will stall temporarily but begin to lift back north Monday into Monday night. Depending how quickly this occurs, some showers and thunderstorms could move back into the area. KEY MESSAGE 3...A strong cold front and trough of low pressure may bring severe weather Tuesday and/or Wednesday. A strong upper trough and cold front will cross the region Tuesday into Wednesday. There still remains uncertainty in timing and placement of upper trough and front, along with coverage of convection each day. It looks as if there will be secondary cold front to follow the first front sometime midday Wednesday into the afternoon. As we get closer in time each day, we will have a better feel for this convective period of time in the middle of the week. SPC outlooks denote roughly at 15% risk Tuesday into Wednesday from west to east, with various ML/AI guidance a tick or two higher than that. Damaging winds will likely be the primary threat with storms, although other hazards cannot be ruled out pending the placement of the trough and ingredients at play. Behind this system will be lower humidity and cooler than normal temperatures for the second half of next week with high pressure returning to the region. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... Smoke continues to reduce visibilities. These conditions should improve from south to north through midday as southerly winds pick up, which could potentially gust to 20 kt this afternoon. Additional thunderstorms are likely this afternoon, especially for the metro terminals. Coverage is a bit more uncertain for CHO and MRB. Timing is also a bit uncertain, and it's not out of the question there could be multiple rounds. Thunderstorms may be strong to severe with strong winds, hail, frequent lightning, and very heavy rain. A possibly weakening line of storms may approach during the late evening as it drops in from the northwest, but it may largely fall apart first. Winds will shift back to the N and NW behind the cold front heading into Sunday. CHO may remain close enough to the front to see more thunderstorms Sunday afternoon. Prevailing VFR conditions are expected Monday, though some guidance has showers and thunderstorms working back northward with a warm front by afternoon or Monday night. Possible sub-VFR conditions on Tuesday into Wednesday. Showers and thunderstorms could push through multiple times. We will monitor the set up as we get past this weekend. Winds southeast to south 5 to 10 knots Tuesday. Winds south to southwest 10 to 15 knots Wednesday. && .MARINE... Southerly winds strengthen by this afternoon in the wake of the warm front. Advisories have been issued from 11 AM to 11 PM for all waters, and lingering for the mid bay through the night. Strong to severe storms are possible this afternoon and evening as well, which may prompt Special Marine Warnings. Leftover storms on Sunday would probably be limited to areas around southern MD, but trends suggest they will form farther to the south. Otherwise winds become northerly in the front's wake, and could result in marginal advisory conditions. Expect sub-SCA level conditions Sunday night into Monday as high pressure builds to the north. Southerly channeling may increase winds by Monday night. SCA conditions due to southerly channeling could occur Tuesday into Wednesday as a storm system and two possible cold fronts push across the region. Winds southeast 10 to 15 knots Tuesday. Winds south 10 to 20 knots gusts higher Wednesday. && .TIDES/COASTAL FLOODING... Increasing southerly flow today and again on Tuesday could lead to water levels approaching minor flood stage, especially at Annapolis. However, current trends suggest levels should fall short of flood stage today/tonight. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Heat Advisory until 7 PM EDT this evening for DCZ001. MD...Small Craft Advisory until 11 PM EDT this evening for MDZ008. VA...Heat Advisory until 7 PM EDT this evening for VAZ053>057-527. WV...Air Quality Alert until midnight EDT tonight for WVZ050-055- 501>504. MARINE...Small Craft Advisory until 11 PM EDT this evening for ANZ530>533-535-536-538>542. Small Craft Advisory until 6 AM EDT Sunday for ANZ534-537-543. && $$ DISCUSSION...ADS/KLW/DHOF AVIATION...ADS/KLW/DHOF MARINE...ADS/KLW/DHOF TIDES/COASTAL FLOODING...LWX