Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
554 FXUS61 KLWX 041342 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 942 AM EDT Mon Aug 4 2025 .SYNOPSIS... High pressure near James Bay will gradually build southeastward settling over New England during the middle and latter portions of the week. Meanwhile, a broad area of low pressure is forecast to form during the middle of the week off the coast of the southeastern U.S. before drifting west or northwest toward the coast during the latter part of the week. && .NEAR TERM /THROUGH TONIGHT/... Another cool start early this morning with temperatures in the mid 50s to low 60s. Some of the colder drainage areas along the western Alleghenies observed low temperatures down in the upper 30s and low 40s. This includes Bittinger, MD, Mill Gap, VA, and Bayard, WV to name a few. Dry conditions will continue today as surface high pressure slides into southeast Canada. The high will remain firmly wedged down the eastern face of the Appalachians leading to a continuation of low humidity, light onshore flow, and near normal temperatures. Skies will trend mostly sunny to partly cloudy with stratocumulus bubbling up during the peak heating period. Some high clouds will work in from the south this evening with perhaps a few low clouds and areas of river valley fog south of I-66/US-50 (mainly central VA and Shenandoah Valley) late tonight into early Tuesday morning as onshore flow increases. Confidence in the coverage of low clouds remains low with 12z PWATs per this morning`s soundings at IAD remaining less than an inch. Similar values were noted at PBZ with 1.1" at RNK per 12z soundings. Highs today will push into the low to mid 80s. Mountain and valley locations west of the Blue Ridge will see high in the mid to upper 70s and low 80s. Lows tonight will fall into the upper 50s and low to mid 60s. These values will be a touch warmer from previous nights given the increased high level cloud cover. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Onshore flow is expected to strengthen Wed night into Thu between high pressure over New England and developing low pressure off the southeastern U.S. This is expected to result in low overcast conditions Wed-Wed night with periods of light rain. However, ensemble guidance show uncertainty on how fast the low clouds, drizzle/rain arrive with the fastest solutions showing light rain beginning as early as Tue morning and the slowest solutions delaying the rain until Wed afternoon across central VA and not reaching any further north than I-66. Temps will likely struggle to reach 80 Wed under thick low overcast and onshore flow. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Guidance continues to exhibit a fair amount of forecast spread in the long term. On the synoptic scale, a weak upper trough over the eastern US is expected to potentially become cutoff and weaken further as upper ridging starts to build over the Great Lakes in advance of an upper trough over the Rockies/Northern Plains. At the surface, an area of high pressure is expected to hold strong off the New England coastline, leading to a prolonged period of onshore flow across the Mid-Atlantic states. This should result in continued below normal temperatures, with highs in the upper 70s to mid 80s, and lows in the 60s for most. Conditions look to remain dry for the most part, but a stray afternoon shower or thunderstorm can`t be ruled out. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... VFR conditions look to prevail through this evening. FEW-SCT stratocumulus are possible during the peaking heat period with CIGS around 050-080 KFT. Low clouds begin to increase late tonight across central VA impacting KCHO, then spread northward through the day Tue. Solid low overcast is then expected to persist through mid week and beyond. Expect MVFR cigs Wed along with some passing showers (especially and central and southern VA terminals). Prevailing VFR conditions and easterly winds are expected on both Thursday and Friday. An afternoon shower or thunderstorm can`t be ruled out either day. && .MARINE... Light and variable winds through Wed. Winds begin to strengthen Wed night into Thu with SCA conditions possible. Winds may approach low-end SCA levels within easterly flow on both Thursday and Friday. && .TIDES/COASTAL FLOODING... Caution stages will prevail through mid week. As we approach Full Moon on Sat Aug 9 and onshore flow strengthens, expect the risk of minor coastal flooding to increase again during the second half of the week. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR/EST NEAR TERM...EST SHORT TERM...LFR LONG TERM...KJP AVIATION...LFR/KJP/EST MARINE...LFR/KJP TIDES/COASTAL FLOODING...LFR