Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
895 FXUS61 KLWX 130118 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 918 PM EDT Sat Jul 12 2025 .SYNOPSIS... High pressure will remain in place offshore through the upcoming week. A weakening cold front will move through on Monday, before stalling out and dissipating. A stronger cold front will approach from the northwest by next weekend. && .NEAR TERM /THROUGH SUNDAY/... A broad linear orientation of showers and strong to severe thunderstorms are aligned from Allegany County Maryland to Augusta County Virginia. This linear convection will move east at 20 to 30 mph over the next couple of hours. The main threat will be torrential rainfall that could lead to flash flooding, lightning, and damaging winds. As midnight arrives, most of this convection should weaken and/or dissipate. A few showers or a thunderstorm could still linger across the Virginia Piedmont or along the Mason-Dixon region. Otherwise, toward the latter half of the night, some patchy fog or low clouds could form in some places. Lows will drop into the upper 60s to middle 70s. A potent shortwave and associated area of low pressure at the surface will track northeastward toward Hudson Bay Sunday. We`ll actually experience slight height rises aloft as this occurs, but the low-level mass response associated with the surface low will lead to increased moisture (PWATs increasing to near or above 2 inches) and low-level convergence. Model guidance is in good agreement that storms will develop along a well-defined surface trough over the Potomac Highlands and Shenandoah Valley during the early to mid afternoon hours. Those storms will then slowly track eastward, reaching the US-15 corridor by around 5 or 6 PM, and then start to weaken as they approach the I-95 corridor around sunset. Model soundings show around 2000-3000 J/kg of MLCAPE, around 600-800 J/kg of DCAPE, 10-15 knots of effective bulk shear, and PWAT values increasing to near 2 inches. The lower DCAPE values may temper the potential for downbursts in storms tomorrow, but the overall higher coverage of storms and higher PWAT values may still make water loaded downbursts possible. SPC currently has much of the area outlooked in a Marginal Risk for severe storms. With PWAT values approaching 2 inches and significant instability present, storms should be capable of producing very heavy rainfall. That coupled with slow storm motions may make flash flooding possible tomorrow as well. WPC has much of the area outlooked in a Slight Risk for Excessive Rainfall tomorrow. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... A decaying cold front associated with Sunday`s system will drop southward into the area on Monday, before eventually stalling out. Various sources of guidance differ with respect to where this boundary will set up, but additional showers and thunderstorms appear likely along and southeast of the boundary within the deepest moisture. Continued heat and humidity will persist Sunday into Monday, with high temperatures around 90, low temperatures around 70, and dewpoints in the low to mid 70s. && .LONG TERM /TUESDAY THROUGH SATURDAY/... An active weather pattern looks to continue through the end of next week, with daily chances for showers and thunderstorms. Mid-level ridging centers over the Carolinas by mid to late week as the axis of the Bermuda High builds toward the southwest Atlantic. The stalled frontal boundary over the area Tuesday lifts north as a warm front. The region then remains in a hot and humid airmass the rest of the week as numerous shortwave troughs traverse overhead. The moist airmass could favor thunderstorms capable of producing heavy downpours and localized flooding. Depending on the location or development of local mesoscale features, there could be some possible strong to severe storms. While uncertain at this time, Tuesday and Wednesday look to have the best chance for that. Highs will be in the upper 80s to low 90s, with heat indices in the low 100s. && .AVIATION /01Z SUNDAY THROUGH THURSDAY/... Showers and thunderstorms should weaken and/or dissipate late this evening into the overnight. Low clouds will move in during the second half of the night tonight, with IFR conditions possible late tonight through the first half of tomorrow morning. Conditions should gradually improve back to VFR by the late morning/early afternoon hours. Coverage of thunderstorms is expected to be much higher tomorrow, with MRB, CHO, IAD, and DCA being the most likely to experience impacts. Storms could potentially weaken or dissipate altogether before reaching BWI and MTN. Showers and thunderstorms may also be possible on Monday, with CHO standing the greatest chance. Winds will be out of the southeast through the day tomorrow, before becoming light and somewhat variable in the vicinity of a decaying cold front on Monday. Daily afternoon to evening showers and thunderstorms are in the forecast through the middle of next week. These storms could produce brief periods of sub-VFR conditions if they move over a terminal. Outside of shower/thunderstorm activity, VFR conditions prevail. && .MARINE... Sub-SCA level southeasterly winds are expected through Sunday, before winds become light and variable on Monday. SMWs in association with thunderstorms may be possible again Sunday afternoon and evening and again on Monday. There is a good chance that storms may decay tomorrow evening before reaching the Bay. Southerly winds around 10 knots prevail Tuesday into Wednesday. Daily afternoon to evening thunderstorms could be a hazard to mariners with gusty winds and lighting strikes likely. Southerly channeling Wednesday night could bring winds near SCA levels over the open waters of the Chesapeake Bay. && .TIDES/COASTAL FLOODING... A prolonged period of southeasterly winds will lead to elevated tidal anomalies over the weekend and into early next week. This carries most of the tidal locations into Action stage, particularly during the higher of the two astronomical high tide cycles. Sensitive locations, such as Annapolis, are forecast to hit Minor stage during the high tide cycle Sunday and Monday mornings. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...KJP NEAR TERM...KLW/KJP SHORT TERM...KJP LONG TERM...KRR AVIATION...KLW/KJP/KRR MARINE...KLW/KJP/KRR TIDES/COASTAL FLOODING...KLW