Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 181840 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 240 PM EDT Mon Sep 18 2017 .SYNOPSIS... Warm high pressure will remain over the eastern United States this week. Meanwhile, Hurricane Jose is expected to track north off the Mid Atlantic coast tonight through Wednesday. Refer to the National Hurricane Center`s website hurricanes.gov for the latest on Jose. && .NEAR TERM /THROUGH TONIGHT/... An upper-level ridge will remain over the eastern United States through tonight while surface high pressure over New England wedges down into the Mid-Atlantic. Breaks of sunshine has allowed for another warm afternoon...but low-level moisture has also cause limited instability underneath the subsidence inversion. An isolated shower cannot be ruled out this afternoon but much of the time should turn out dry. A north to northeast flow is expected tonight as Jose moves north well offshore. The onshore flow will continue to cause high amounts of low-level moisture...which means areas of low clouds and fog are likely overnight as the moisture gets trapped underneath the subsidence inversion. There is a better chance for fog in sheltered valleys west of the Blue Ridge Mountains and there is a better chance for low clouds east of the Blue Ridge Mountains where the onshore flow will be stronger. A few bands of showers from Jose will approach areas near the Bay tonight while other locations remain dry. However...Jose should remain far enough for the steadier rain to remain to our east. Min temps will range from the mid to upper 50s in the colder valleys of the Potomac Highlands to the mid and upper 60s in downtown Washington and Baltimore. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... Jose will pass by well to our east Tuesday before moving well off to our north and east Tuesday night through Wednesday night. Outer bands of showers from Jose will approach areas near and east of Interstate 95 into portions of north-central Maryland Tuesday. The best chance for showers will be near the Bay. Any rain amounts will be light across these areas. Elsewhere...subsidence from a large scale upper-level ridge overhead and behind the tropical system will allow for dry conditions along with some sunshine. Max temps will range from the mid to upper 70s near the Bay where more clouds and possible showers are expected to the lower 80s across most other locations where more breaks of sunshine are expected. Jose will move well off to the north and east Tuesday night while surface high pressure builds overhead. Dry conditions are expected during this time. Another upper-level disturbance will build in from the west later Wednesday into Wednesday night while weak surface high pressure remains overhead. There may be a couple showers across central Virginia into the Potomac Highlands later Wednesday into Wednesday evening...but any instability will be limited so much of the time will be dry. Elsewhere...dry conditions are expected along with more warm conditions. && .LONG TERM /THURSDAY THROUGH MONDAY/... Benign conditions expected in the long term period as upper level ridge/surface high pressure builds over our area Thursday into Monday. Maybe some showers over the ridges, but looking minimal. So, looking at an extended period of dry conditions and high temperatures near 80 of in the low to mid 80s. Remnants of Jose might be lingering off of the Mid- Atlantic/New England coast, away from us, and Maria could be somewhere in the west Atlantic, but it is too early to tell. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... A band of MVFR cigs and isolated showers are expected through 21z across the eastern terminals. Cigs should lift to VFR levels across these areas late this afternoon. Elsewhere...VFR conditions are expected. An onshore flow will lead to more areas of low clouds and fog late tonight into Tuesday morning. An increasing flow may allow for more MVFR conditions vs. IFR conditions across the eastern terminals and that is reflected in the forecast...but confidence is low and IFR conditions are possible. Low clouds and fog will dissipate later Tuesday morning...but a few showers are possible across the eastern terminals. Even across these areas much of the time should turn out dry with the steadier rain remaining off to the east. High pressure will build overhead for Tuesday night through Wednesday night. Patchy fog cannot be ruled out during the overnight and early morning hours. VFR conditions expected Thursday into Saturday with high pressure built into our area. && .MARINE... Jose will move north offshore tonight and pass by well to our east Tuesday before moving off to the north and east Tuesday night through Wednesday. A strengthening gradient will allow for winds to strengthen through tonight into Tuesday. Will continue with the Small Craft Advisory for the middle portion of the Maryland Chesapeake Bay and lower Tidal Potomac River tonight...and all of the waters Tuesday into Tuesday evening. The strongest winds will be across the southern Maryland Chesapeake Bay Tuesday with gusts around 30 knots likely. A Small Craft Advisory remains in effect for the middle portion of the Bay and lower Tidal Potomac River Tuesday night and it may need to be extended Wednesday for portions of the waters. High pressure will build overhead Wednesday night. No small craft advisory expected between Thursday and Saturday due to low wind speeds over our area. && .TIDES/COASTAL FLOODING... An onshore flow has led to elevated water levels around one half to three quarters of a foot above normal. The elevated water levels will continue through Tuesday morning as the onshore flow strengthens. A Coastal Flood Advisory remains in effect for Straits Point in St. Marys county during this time. Water levels will be close to minor flood thresholds in Annapolis and Washington DC during the high tide cycle late tonight into Tuesday morning. Model spread remains high for later Tuesday and Wednesday. Water may be piled up near the Bay from Jose...but a northerly flow should push water out of the Bay. Will continue with elevated water levels in the forecast with caution stages being met...but confidence in forecast is low and minor flooding cannot be ruled out. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory until 4 PM EDT Tuesday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory from midnight tonight to 8 PM EDT Tuesday for ANZ531-539. Small Craft Advisory from 6 AM to 8 PM EDT Tuesday for ANZ530- 535-536-538. Small Craft Advisory until 8 PM EDT Tuesday for ANZ542. Small Craft Advisory until 6 AM EDT Wednesday for ANZ532>534- 537-540-541-543. && $$ SYNOPSIS...BJL NEAR TERM...BJL SHORT TERM...BJL LONG TERM...IMR AVIATION...BJL/IMR MARINE...BJL/IMR TIDES/COASTAL FLOODING...BJL

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.