Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
551 FXUS61 KLWX 251406 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1006 AM EDT Sat May 25 2024 .SYNOPSIS... A frontal boundary will dissipate near the Mason-Dixon Line today. Another boundary settles to the north and remains there through the holiday weekend. Eventually, a much stronger cold front pushes through the region Monday into Monday night. A secondary cold front moves in by mid-week before high pressure builds in late next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Dry/stable conditions observed on 12Z IAD sounding, and a bit less so at PBZ. Some mid and high level clouds are likely much of the day due to upstream convective debris. A few showers and storms may develop due to terrain circulations and lee troughing this afternoon in the mountains, but the greater threat appears to be after 5 PM as potential clusters of storms approach from the upper Ohio Valley in association with a subtle shortwave trough. Instability, shear, and lapse rates are all on the modest end of the spectrum, but a few instances of wind damage and hail can`t be ruled out with more organized structures. There is some uncertainty on whether storms will survive east of the Blue Ridge later this evening, but even if they do they will likely be in a weakening state. Otherwise warm and muggy conditions are expected with highs reaching the mid 80s for most. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/... Model guidance indicate significant height rises through the day Sunday ahead of deepening trough over the western Great Lks. While this should tend to suppress convective development, air mass is expected to become moderately unstable by afternoon with MUCAPE of ~1000 J/kg. Scattered thunderstorm development is possible along a weak pressure trof. Some remnant MCS from the OH Valley may also make it into the area during the overnight hours Sunday night. Memorial Day...Some remnant or decaying convection is possible early in the morning. By afternoon, height falls and strengthening sfc convergence along a deepening sfc trof is expected to result in convective initiation with all modes of severe weather possible before convection tries to evolve into an increasingly organized line. This appears to be the most significant severe wx event so far this convective season. Despite expected relatively fast storm motions, isolated flash flooding is also possible due to multiple rounds of convection. Storms are likely to exit the area by 02Z Tue if not a little sooner than that. && .LONG TERM /MONDAY THROUGH FRIDAY/... CAPE decreases significantly behind the front Monday, though a passing SW trough could bring additional rain showers Tuesday into Wednesday. Does not look like a washout either day with weak sfc high pressure underneath the upper level system. Behind this wave, dew points will fall into 40s come next Thursday with highs in the upper 60s to low 70s. This may be the least humid day until September across the area. Likely remaining dry into Friday before the next system brings the potential for rain showers or thunderstorms next Saturday. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... Best chance for t-storms today is at MRB toward late afternoon or early evening. Looks like any activity moving toward the metro areas later this evening will be in a weakening state, so will be evaluating guidance as to whether a mention needs to be made in the TAFs. Patchy fog is possible late tonight, especially at MRB. Shower and storm coverage is expected to be sparse Sunday with weak high pressure. Widespread showers and thunderstorms expected on Memorial Day with severe thunderstorms likely. Prevailing VFR conditions are likely Tuesday into Wednesday, though a passing shower is possible. Winds will become northwesterly at about 10 kts. && .MARINE... Winds should remain below SCA until Sun night. Isolated t-storms are possible this evening and again late Sunday. Widespread showers and thunderstorms expected on Memorial Day, some of which are likely to be severe and require SMWs. SCAs are likely Monday through Monday night. A passing shower is possible over the waters Tuesday into Wednesday. Winds will be prevailing out of the NW about 10 kts, with gusts up to 15-20 kts during the afternoon hours. && .TIDES/COASTAL FLOODING... Water levels are expected to gradually rise into the weekend given south to southeasterly warm advection. Many tidal sites see their higher of the two high tides reach Action stage. Further increases are likely into Monday/Memorial Day which could lead to some coastal flooding. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...ADS SHORT TERM...LFR LONG TERM...CPB AVIATION...ADS/LFR/CPB MARINE...ADS/LFR/CPB TIDES/COASTAL FLOODING...LFR