Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 230747 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 347 AM EDT Sun Apr 23 2017 .SYNOPSIS... A cold front will stall out over the Carolinas today. Low pressure will develop along the front tonight and it will track toward the Mid-Atlantic Coast Monday and it will remain nearly stationary through Tuesday before finally weakening and moving off to the north and east on Wednesday. A cold front will approach the area Thursday but it will stall out nearby or just to our north for Friday. The cold front may move into the area next weekend. && .NEAR TERM /THROUGH TODAY/... Persistent northerly flow from elongated ridge over the eastern Great Lakes has shunted frontal boundary and deeper moisture south of much of the area this morning. A few showers do remain across central Virginia, but most areas are rain-free. As clouds thinned overnight, areas of fog have developed, mainly from the Blue Ridge/Catoctins west. As low pressure system moves through the southeastern US during the day today, additional rain will break out across portions of the lower Appalachians and try to push northeastward. However, low level dry air will continue filtering southward on northeasterly flow. This will keep most areas dry through much of today. The exception will be parts of central VA where rain will gradually expand through the day, reaching into portions of southern Maryland towards the evening hours. Otherwise, any breaks of sun this morning in northwestern areas will fill back in as dense high clouds move back overhead. High temperatures will range from the mid/upper 50s in central VA to low 60s in northern areas. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... Low pressure system will work towards the SE US coast tonight and move to a position near the NC/SC border on Monday. Rain will continue to overspread the region from south to north tonight and persist through Monday with strong moisture advection. Periods of rain will continue through Monday night, although intensity likely to experience a downtrend later Monday and Monday night as forcing lessens. As the low pressure system then slowly trudges up the Mid- Atlantic coastline, to a position near the Outer Banks/Norfolk by later Tuesday, rain will continue, with an uptick in intensity/coverage likely again. Low pressure will slowly fill and weaken Tuesday night with steady rain tapering off to showers. Additional rain amounts from this morning through Tuesday night expected to range on average from 1-2", with somewhat less in northern/western areas to locally 2-3" south, especially along the eastern facing slopes in Nelson County and along the Blue Ridge. Temperatures during this time period will see limited diurnal change with solid overcast and periods of rain. Highs Monday will hold in the low/mid 50s, possibly nearing 60F on Tuesday. Lows tonight/Mon night from the mid 40s to low 50s. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Cutoff low pressure along the Mid-Atlantic Coast Wednesday morning will finally get drawn into the jet stream and move off to our north and east. Morning clouds and perhaps even a light rain should give way to some sunshine Wednesday afternoon. However...clouds may be stubborn to give way to sunshine across eastern areas depending on how quick the low moves away from the area. Noticeably warmer conditions are expected Wednesday...especially west of the Blue Ridge Mountains where confidence is higher in more sunshine. High pressure will build over the Atlantic for Wednesday night through Friday. A cold front to our west will approach our area Thursday...but it will likely stall out nearby or just to our north as it runs into the blocking high over the Atlantic. Therefore...much warmer and more humid conditions are likely during this time. A few showers and thunderstorms are possible...but coverage may be isolated or scattered due to most of the mid and upper-level forcing remaining well off to the north and west. A backdoor cold front may impact the area next weekend. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... Areas of fog have developed this morning across portions of eastern WV, northern VA, and central/western MD. This is currently affecting the MRB terminal with LIFR conditions, and this will continue through the early morning hours, before improvement after sunrise. Elsewhere, fog not significantly impacting the TAF sites, however some MVFR is possible early this morning at IAD/BWI. Otherwise, mainly VFR is expected today with thickening and lowering high/mid clouds. A few showers will move near CHO this morning, with rain then affecting the site by the afternoon, before gradually spreading northward across all sites this evening and tonight. Conditions will deteriorate as the rain/stratus overspread with MVFR/IFR developing later tonight and on Monday. Rain/stratus and associated reductions expected to continue through at least Tuesday, possibly Tuesday night. Winds will be out of the northeast through the period. Low clouds may impact the terminals Wednesday morning. Conditions should gradually improve later Wednesday. High pressure over the Atlantic will cause southerly winds and mainly VFR conditions for Wednesday night and Thursday. A few showers and thunderstorms are possible Thursday. && .MARINE... SCA conditions being observed early this morning will gradually taper through the first half of the day, with SCA-winds confined to only portions of the central Chesapeake by this afternoon. This will however be a short-lived break as northeasterly winds re- intensify tonight and continue through Tuesday night as coastal low intensifies and slowly moves up the east coast. Low pressure will move away from the waters Wednesday. High pressure over the Atlantic will cause a southerly flow for Wednesday night through Friday. A Small Craft Advisory may be needed for portions of the waters during this time. A few showers and thunderstorms are possible Thursday and Friday...but coverage may be isolated or scattered since forcing will be weak. && .TIDES/COASTAL FLOODING... A persistent onshore flow will continue over the waters through Tuesday. Elevated water levels are expected during this time. Most areas should remain below minor flooding thresholds through the high tide cycle this afternoon. Will have to watch Straits Point...but as of now confidence was not high enough for an advisory since the next tide will be the lower of the two and the onshore flow may lighten up just a bit. The onshore flow will strengthen a bit for tonight through Tuesday. Minor flooding is possible near times of high tide. The flow should gradually turn north Tuesday night into Wednesday as the low moves away from the area. Water levels should decrease during this time. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 11 AM EDT this morning for ANZ531>533-536-537-539>542. Small Craft Advisory from 6 AM to 6 PM EDT Monday for ANZ530- 531-535-536-538>540-542. Small Craft Advisory until 6 PM EDT Monday for ANZ534-543. Small Craft Advisory from 11 PM this evening to 6 PM EDT Monday for ANZ532-533-537-541. && $$ SYNOPSIS...BJL NEAR TERM...MM SHORT TERM...MM LONG TERM...BJL/MM AVIATION...BJL/MM MARINE...BJL/MM TIDES/COASTAL FLOODING...BJL is the U.S. government's official web portal to all federal, state and local government web resources and services.