Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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 101530 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1030 AM EST Sun Dec 10 2017 .SYNOPSIS... A gyre of upper level low pressure over Hudson Bay Canada will send multiple clipper-like systems through the area over the next several days. && .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Cloud coverage has varied this morning across the CWA with a swath of stratocumulus and mountain waves visible on satellite imagery stretching from the panhandle of WV eastward across northern VA and the D.C. metro area. Areas along and north of Interstate 70 in MD have seen skies clear a bit this morning, and across southern portions of our area in central VA. These clouds are in response an upper level shortwave slowly exiting the region and cold air advection. Snow showers have been reported in the far western zones of WV thanks to an upslope component with some minor accumulations. Clouds will continue in those ares mentioned above for the remainder of this morning before clearing out this afternoon, allowing for the sun to make a return. Temperatures will be on the cool side and winds are expected to pick up by early afternoon and become gusty as clouds start to clear. Temperatures today will struggle to breach the 40 degree mark, remaining in the upper 30s for most. A weak shortwave trough will approach the area tonight, bringing an increase in cloud cover, but not much in the way of fanfare in terms of precipitation. The exception would be a few scattered snow showers along the western ridges of the Allegheny Front. Winds will diminish this evening and become light out of the west. Low temperatures will range in the mid-upper 20s, likely toward the higher end of that range in areas where cloud cover remains.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... Another transient surface ridge will traverse the area Monday, the axis of which should be east of the area by midday along for light southerly flow and slightly milder temperatures (a few degrees milder than Sunday). A mostly sunny day seems likely in the wake of the departing Sunday night shortwave. The big wheel of low pressure keeps turning into Tuesday, sending another spoke (shortwave/clipper) towards the area. I think it`s quite possible there is a little more light precipitation than model guidance is explicitly printing out at the moment due to a subtle coupled upper jet, strong mid-level vorticity advection and low-level isentropic upglide. Temperature profiles will still be quite cool, so precipitation type should be wintry, though at the moment cold air appears deep enough to result in snow or sleet as opposed to freezing rain. The highest chances are along and west of the Allegheny Front and near the Mason-Dixon line Monday night into Tuesday. As the trough pivots through, another one fast on its heels catches up and phases with it, resulting in cyclogenesis to our northeast. The tightening pressure gradient behind this low as well as strong cold air advection in the wake of the upper trough will result in strong and gusty northwest winds. Trajectories are favorable for upslope snow showers and squalls and substantial accumulations are possible. The strong winds and very cold air (-12 C or colder at 850 mb) may also result in wind chills well below zero over the ridges of the Allegheny Front as well. Both Winter Weather and Wind Chill Advisories could be required for these areas. Despite the very strong cold air advection, model wind fields suggest winds should stay mostly below Wind Advisory criteria, but it is quite possible gusts over 45 mph may be observed for a time Tuesday into Tuesday night, even at lower elevations. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... Windy and cold Wednesday as an area of high pressure builds in behind a departing storm system. Winds should diminish Wednesday night but temperatures will not modify. They will stay cold. As winds back around from the northwest to the southwest Thursday, temperatures will not be as chilly. There is a chance for snow showers across much of the region Thursday, particularly in the western zones and along the Mason-Dixon region, as the next storm system pivots across the lower Great Lakes region. This chance will linger into Thursday night and Friday as well due to the upper level cold air support behind the surface storm. A modifying area of high pressure is expected to build eastward behind the low pressure system Friday night through Saturday night, bringing milder temperatures and temperate southwesterly breeze. By Sunday, the next threat for precipitation will come with a cold front sagging southward across the region. High temperatures, next weekend, could reach the 50s. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
VFR conditions forecast today across all terminals, and will persist through Monday. Winds will become gusty by this afternoon out of the west, gusting to near 20 knots. Winds will diminish this evening, becoming light and holding on to a westerly component. Light southerly flow AOB 10 kts is expected Monday into Monday night, then gusty NW flow returns Tuesday. Flight restrictions are possible Monday night into Tuesday as a frontal system approaches bringing the potential for lower ceilings or brief visibility restrictions. A wintry mix is possible, most likely north of a line from MRB to MTN Monday night. VFR conditions Wednesday through Thursday night. Any brief snow showers could reduce conditions briefly. Winds northwest 15 knots gusting 20 to 25 knots Wednesday, diminishing Wednesday night, before becoming southwest at 5 to 10 knots Thursday and Thursday night.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Potential exists for gusty winds over the waters today as a cold airmass surges in to the region. Mixing over relatively warmer waters could produce gusts of 20 to 25 knots today. Gusts diminish over near shore waters, but likely persist well into the night over open waters. Winds are then expected to be light on Monday. Southerly channeling is possible ahead of a frontal system Monday night which may require another Small Craft Advisory. Strong northwest flow behind said frontal system will likely necessitate a Gale Warning Tuesday into Wednesday. No marine hazards are expected Thursday.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EST this evening for ANZ530>533-535-536-538>542. Small Craft Advisory until 5 AM EST Monday for ANZ534-537-543.
-- End Changed Discussion --
&& $$ SYNOPSIS...DHOF NEAR TERM...BKF/DHOF SHORT TERM...DHOF LONG TERM...KLW AVIATION...BKF/KLW/DHOF MARINE...BKF/KLW/DHOF

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