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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 180055 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 855 PM EDT Fri Mar 17 2017 .SYNOPSIS... A warm front will move into the area late tonight into early Saturday before a cold front passes through Saturday afternoon. High pressure builds over the area early next week. Another cold front will cross the area on Tuesday. && .NEAR TERM /UNTIL 7 AM SATURDAY MORNING/... Warm frontal precip will continue to push across the region this evening and into tonight, before moving east of the area by morning. Despite the relatively warmer temperatures today, wet- bulb cooling has allowed temperatures to drop into the 30s after precipitation has started. This has led to rain changing to snow across portions of the area, so far mainly from the Blue Ridge west. Have had reports of up to about 2 inches as of 830pm in the higher terrain of the Allegheny Highlands. As warmer air moves in aloft, will see precipitation change over to rain, however lingering cold in the low levels and at the surface will lead to some areas of freezing rain and sleet. This is already being observed west of the Allegheny Front and will push eastward over the next couple of hours. Thus have issued a Winter Weather Advisory for a wintry mix of snow and ice for these locations. Elsewhere, very little impact is expected as rain and some light snow move across. May see a dusting to a couple of tenths of snow accumulate on grassy surfaces across portions of the area north and west of the metros. After main batch of precipitation ends, some lingering light fog, drizzle, and low stratus is likely. Lows will be generally in the 30s to around 40F. && .SHORT TERM /7 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... The warm frontal boundary will remain nearly stationary over the Potomac Highlands into central Virginia and southern Maryland Saturday. Closed upper-level low will track into Pennsylvania and this will cause low pressure to develop along the boundary Saturday afternoon before developing into a coastal low Saturday night. The dry slot should keep most areas dry Saturday morning...with the exception of low clouds/fog and drizzle due to moisture trapped underneath the subsidence inversion. However...as the low pass through our area later Saturday afternoon and begins to develop off the coast...a north to northwest flow will develop. This may mix out any cool air that`s trapped and cause warmer conditions relative to recent days. Max temps will range from the 40s across northern Maryland to the lower and middle 50s near Washington and Baltimore to the lower middle 60s in central Virginia. The warmer air along with unseasonably low 500mb heights from the upper-level low will trigger a few showers Saturday afternoon into Saturday evening. Some showers may even contain small hail if enough instability develops. The upper-level low will pass through our area Saturday night...bringing the chance for a few rain and snow showers. The best chance for snow will be across northeastern Maryland where forcing will be a bit stronger northeast of the upper-level low. Snow may coat the ground across these areas. An upslope flow will cause accumulating snow along and west of the Allegheny Front as well. Winter headlines may be needed for this area. The upper-level low will move away from the area Sunday and a northwest flow will bring drier air to the area along with chilly conditions for this time of year. However...it will not be nearly as cold as recent days. Highs will be in the 40s across most areas to lower and middle 50s in central Virginia. High pressure will build overhead Sunday night...bringing dry and chilly conditions. && .LONG TERM /MONDAY THROUGH FRIDAY/... High pressure over the region Monday will move east to allow for a cold front to sag southward and bring a chance for rain showers Monday night into Tuesday. A second area of high pressure will build southward from the Great Lakes Tuesday night through Thursday night. Drier air and colder temperatures will ensue into the region. High pressure will move to the coast to allow for a return flow to usher in milder air Friday. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/... A warm front will stall out over central Virginia tonight. Low pressure will track along the boundary Saturday before moving off to the east Saturday night. A period of rain and snow is expected this evening and tonight ahead of the warm front. The highest chances for snow will be at MRB/MTN/BWI. Snow may coat the ground near KMRB...but paved surfaces will likely remain wet due to the warm conditions today. Cigs/Vsbys will deteriorate this evening and MVFR conditions expected at all TAF sites late tonight through most of Saturday morning, with potential for IFR. Greatest risk of IFR at MRB/BWI/MTN Saturday morning, where it is included in the forecast. Cigs/vsbys should improve some by Saturday afternoon...but MVFR conditions will persist through much of the day, with IFR even into the afternoon at MRB/BWI/MTN. A few showers are possible Saturday afternoon into Saturday evening. Snow showers are possible Saturday night...especially across the northern terminals. VFR conditions along with north to northwest winds will return for Sunday and Sunday night. Vfr conditions are also expected for Monday. A cold front may impact the terminals Monday night into Tuesday. High pressure will return for the middle portion of next week. && .MARINE... A warm front will stall out near the southern waters tonight into Saturday. A Small Craft Advisory is in effect for middle portions of the Bay and the lower Tidal Potomac tonight into Saturday morning where the gradient will strengthen. Low pressure will pass by to the south Saturday before developing into a coastal low Saturday night. Winds may approach SCA criteria Saturday afternoon...but confidence is not high enough for a headline since cool air trapped underneath the inversion may limit mixing. A Small Craft Advisory is in effect for the waters Saturday night and will likely be needed Sunday through Sunday night. No marine hazards Monday through Tuesday night. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Winter Weather Advisory until 6 AM EDT Saturday for MDZ501. VA...Winter Weather Advisory until 6 AM EDT Saturday for VAZ503-504. WV...Winter Weather Advisory until 6 AM EDT Saturday for WVZ501-503- 505. MARINE...Small Craft Advisory from 11 PM Saturday to 6 AM EDT Sunday for ANZ530>543. Small Craft Advisory until 8 AM EDT Saturday for ANZ532>534- 537-540-541-543. && $$ SYNOPSIS...BJL NEAR TERM...BJL/MM SHORT TERM...BJL LONG TERM...IMR AVIATION...BJL/MM/IMR MARINE...BJL/MM/IMR

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