NWS and I are not in agreement on this one. Immediate Piedmont of Far NW VA and Western MD I could see hitting Winter Storm Criterea from Ice..but I agree with TinkWx (See Forum) on the warmer side of things so I downgraded to a brief mix over to rain most areas.
NWS has a watch out area wide..
Their Discussion
LONG TERM /SATURDAY THROUGH THURSDAY/...
...WINTER STORM WATCH ISSUED FOR ENTIRE CWA FOR THE UPCOMING WEEKEND
STORM THAT WILL PRODUCE A WINTRY MIX OF PRECIPITATION ACROSS THE CWA...
WATER VAPOR IMAGERY INDICATED A POTENT PIECE OF SHORTWAVE ENERGY
MOVING SOUTH FROM THE GREAT BASIN INTO THE FOUR CORNERS AREA EARLY
THIS MORNING. THIS IS THE ENERGY THAT THE MODELS HAVE DEPICTED FOR
DAYS THAT WILL HELP SPAWN SURFACE CYCLOGENESIS NEAR THE GULF
COAST/LOWER MISSISSIPPI VALLEY BY 12Z SATURDAY. THE MODELS CONTINUE
TO SHOW THIS...AND DEEPEN LOW PRESSURE AS IT MOVES TO THE
NORTHEAST INTO THE TENNESSEE VALLEY ON SUNDAY. THEREAFTER...THE
MODELS HAVE TRENDED MORE WEST WITH THE INITIAL LOW...MOVING IT UP
OR EVEN JUST WEST OF THE APPALACHIANS WHILE NEW LOW PRESSURE FORMS
OFF THE MID ATLANTIC COAST BY 12Z SUNDAY...BECOMING A NOR'EASTER.
THE GENERAL SCENARIO IS FOR A STORM TO AFFECT OUR CWA THIS
WEEKEND...HOWEVER THE SPECIFIC DETAILS ASSOCIATED WITH THE
STRENGTH/TRACK/TIMING OF UPPER LEVEL AND SURFACE FEATURES AND
THERMAL PROFILES CONTINUE TO MAKE THIS A VERY CHALLENGING FORECAST.
WHILE THE OPERATIONAL MODELS HAVE TRENDED BOTH SLOWER AND
WARMER...SOME SHORT RANGE ENSEMBLE GUIDANCE IS NOT AS WARM. IN
ADDITION...EVEN IF A WARMER SOLUTION DOES OCCUR...THERE REMAINS THE
RISK FOR A SIGNIFICANT PERIOD OF WINTRY PRECIPITATION ACROSS MUCH OF
THE CWA. THEREFORE...HAVE OPTED TO ISSUE A WINTER STORM WATCH FOR
THE ENTIRE CWA FOR THIS POTENTIALLY HIGH IMPACT EVENT.
EXPERIENCE SAYS THAT THE OPERATIONAL MODELS SOMETIMES DEVELOP
PRECIPITATION TOO SLOWLY...ESPECIALLY WHEN WARM ADVECTION AND
ISENTROPIC LIFT ARE INVOLVED. WARM ADVECTION AND ISENTROPIC LIFT
WILL STRENGTHEN ON SATURDAY...THEREFORE WILL BEGIN PRECIPITATION
SOONER THAN THE OPERATIONAL NAM AND GFS. PRECIPITATION IS EXPECTED
TO BEGIN ACROSS THE SOUTHWEST CWA LATE SATURDAY MORNING...THEN
SPREAD NORTH AND EAST THROUGH SATURDAY AFTERNOON ACROSS THE REST OF
THE CWA. SHORT RANGE ENSEMBLES /INCLUDING NCEP AND CZYS
PRECIPITATION TYPE ALGORITHMS/ HAVE STRONG INDICATIONS THAT INITIAL
PRECIPITATION TYPE WOULD BE SNOW AND/OR SLEET ACROSS THE CWA. SOME
MINOR SNOW/SLEET ACCUMULATION IS POSSIBLE ON SATURDAY...HIGHEST
AMOUNTS FAVORED WEST OF THE BLUE RIDGE. THEN...THE MODELS AND
ENSEMBLES SHOW WARM AIR BEGINNING TO INTRUDE SATURDAY NIGHT. WARM
AIR INTRUSION ALOFT WILL CAUSE A MESSY MIX...MORE THAN LIKELY MORE
SLEET AND FREEZING RAIN ACROSS MUCH OF THE CWA THAN SNOW
ESPECIALLY EAST OF THE MOUNTAINS IF THE MOST RECENT GUIDANCE IS TO
BE BELIEVED. WEST OF THE MOUNTAINS WILL LIKELY HOLD ONTO SNOW THE
LONGEST. QPF SHOULD BE BOUNTIFUL...EVEN IF OUR CWA GETS CAUGHT IN
A RELATIVE MINIMUM OF QPF BETWEEN THE INITIAL LOW TO OUR WEST AND
THE DEVELOPING COASTAL LOW. SUCH QPF HAS THE POTENTIAL TO LEAD TO
SIGNIFICANT AMOUNTS OF WINTRY PRECIPITATION...AND THIS IS
CONSIDERING THE POSSIBILITY THAT MIXED PRECIPITATION COULD EVEN
CHANGE TO RAIN FOR A TIME. THIS IS MOST LIKELY TO OCCUR ACROSS
LOWER SOUTHERN MARYLAND. EXACT AMOUNTS OF EACH TYPE OF
PRECIPITATION WILL NEED TO BE DETERMINED AT A LATER TIME.
MOREOVER...THERE IS STRONG AGREEMENT IN THE MODELS AND ENSEMBLES IN
PRECIPITATION LINGERING LONGER THAN PREVIOUSLY FORECAST.
THEREFORE...HAVE INCREASED POPS FOR SUNDAY. ANY MIXED PRECIPITATION
WOULD LIKELY CHANGE TO SNOW BY SUNDAY AFTERNOON AS THE COASTAL LOW
DOMINATES AND NORTHWEST WINDS DRAW IN COLDER AIR. WITH THE STRENGTHENING
NOR'EASTER...GUSTY WINDS WILL ALSO DEVELOP ON SUNDAY. THERE IS THE
POTENTIAL FOR AT LEAST 45 MPH GUSTS /IF NOT HIGHER/ TO SPREAD
ACROSS THE CWA...SO WIND HEADLINES MAY BE NECESSARY IN THE FUTURE.
ALSO OF IMPORTANCE IS THAT ANY LOCATION THAT RECEIVES ICE
ACCUMULATION ON TREES AND POWERLINES WILL BE MORE VULNERABLE TO
ICE INDUCED DAMAGE WITH WINDS OF THAT MAGNITUDE.
