Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
147 FXUS61 KLWX 160804 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 404 AM EDT Mon Sep 16 2024 .SYNOPSIS... High pressure to the northeast will begin to retreat today. Meanwhile, low pressure will move into the Carolinas through Tuesday before weakening during the middle of the week. Another low may develop off the coast toward the end of the week, with a backdoor front approaching this weekend. && .NEAR TERM /THROUGH TONIGHT/... Some low clouds will develop this morning, mainly east of I-81. Otherwise, high pressure will keep the area dry into the middle part of this evening. Moisture building up across central Virginia could aid in the development of isolated showers, mainly later this evening and south of I-66. As a low pressure system off of the Southeast U.S. Coast moves inland and toward the northwest, showers could become heavier after midnight and could be accompanied by a rumble of thunder as well across the Virginia Piedmont. Highs today will reach the middle to upper 70s to near 80 for most of the lower elevations. Upper 60s will be more common across the mountains. Lows in the lower to middle 60s tonight with a few lower 50s in the western mountains. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Rain showers and the isolated thunderstorm threat will continue and likely spread north and east during the day Tuesday as the low pressure system moves into the western Carolinas and becomes nearly stationary. Rain showers and isolated thunder could linger Tuesday night through midweek, including the Wednesday night timeframe. Average rain amounts Monday night through Wednesday night could average one half to one inch across the northern 2/3rds of the region, while the southern 1/3rd, including along and east of the Blue Ridge could encounter rain amounts in the one and a half to as much as 3 inches of rain. Local amounts could reach up to 5 or 6 inches of rain depending on the model and the track and movement of the low pressure system. A lot may change within the forecast as the forecast track becomes more apparent. Continue to monitor our forecast locally as well as the National Hurricane Center. && .LONG TERM /THURSDAY THROUGH SUNDAY/... Uncertainty remains high for the extended period due to a blocky upper level pattern. For Thursday and Friday, any remnant of the previous coastal low will be weakened if not dissipated, and the mid/upper low may also weaken and open into a trough. However, secondary low pressure development could take place off the coast. Shower chances will persist through this period thanks to the upper trough, but may be comparably lower Friday as forcing weakens and the trough axis perhaps aligning just east of the area. Temperatures will be near normal. For Saturday and Sunday, ridging will amplify northwest of the area while a trough moves across the Canadian Maritimes. This combination may result in another upper low closing off over the southeast US. At the surface, a backdoor front will push toward the region, but lose definition as it encounters a staunch coastal front along the southeast coast. Strong high pressure over New England may result in a good southward push however. It`s still unclear whether drier air will be able to work into the area behind the front, or if clouds and continued light rain chances persist. Temperatures will trend below normal however. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... Low clouds could reduce ceilings to MVFR status this morning. Brief IFR can`t be ruled out as moisture has increased in the region. MVFR/IFR CIGs likely tonight. Rain moves in Tuesday with IFR ceiling restrictions likely at times. Rain likely continues through Tuesday night before diminishing Wednesday afternoon. Winds will remain E/NE 5-15 kts. With the residual low pressure nearby, expect periods of sub-VFR conditions, particularly on Wednesday. Sub-VFR conditions may continue into Thursday, but there is potential for some improvement as low pressure weakens. Showers will remain possible however. Friday stands a better chance to see VFR conditions and lower rain chances...perhaps even some clearing. && .MARINE... SCA conditions will remain possible this morning, mainly across the southernmost waters, then become increasingly likely tonight into Tuesday morning as gradient tightens in response to approaching coastal low and high pressure to the north. At this time, the risk of gale force winds appears low. As a weakening area of low pressure tracks through the area, winds will be out of the east on Wednesday. Northeasterly winds will continue Thursday and Friday. With a weaker pressure gradient now forecast for Thursday, winds may remain below advisory criteria. The potential for advisories may return Friday depending on low pressure development off the coast. && .TIDES/COASTAL FLOODING... Onshore flow strengthens through Tuesday morning with minor coastal flooding becoming increasingly likely. However, surge guidance has been trending downward, perhaps due to the low remaining farther south and winds a touch weaker and more from a northeasterly direction. Advisories remain in effect but may need adjustments. Moderate flooding is much less likely now. However, between the full moon and continued onshore flow, tide levels will likely remain elevated and near minor flood thresholds much of the week. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until 10 PM EDT Tuesday for DCZ001. MD...Small Craft Advisory until 6 PM EDT Tuesday for MDZ008. Coastal Flood Advisory until 10 PM EDT Tuesday for MDZ014. Coastal Flood Advisory from noon today to 6 PM EDT Tuesday for MDZ016. Coastal Flood Advisory from midnight tonight to 6 PM EDT Tuesday for MDZ018. VA...Coastal Flood Advisory from noon today to 6 PM EDT Tuesday for VAZ057. WV...None. MARINE...Small Craft Advisory until 6 PM EDT Tuesday for ANZ530>532-536- 538>542. Small Craft Advisory until 6 PM EDT Tuesday for ANZ533-534-537- 543. Small Craft Advisory from 2 PM this afternoon to 6 PM EDT Tuesday for ANZ535. && $$ SYNOPSIS...ADS NEAR TERM...KLW SHORT TERM...KLW LONG TERM...ADS AVIATION...ADS/KLW MARINE...ADS/KLW TIDES/COASTAL FLOODING...ADS