CWFLWX) AND HAZARDOUS 
WEATHER STATEMENT (WBCHWOLWX).

LONG TERM (FRIDAY NIGHT THROUGH THURSDAY)...
OBSERVATIONS...
500MB HEIGHT/ANOMALY PATTERN DURING THE PAST FIVE DAYS SHOWS SEVERAL 
PACIFIC TROPICAL SYSTEMS MOVED INTO THE NORTH POLE...FORCING A COLD 
AIRMASS TO SINK SOUTH THROUGH CENTRAL CANADA. WATER VAPOR LOOP SHOWS 
A VERY DEEP UPPER LOW CENTERED ACROSS THE UPPER GREAT LAKES...WITH A 
SECOND (CUT-OFF) UPPER LOW OFF THE CALIFORNIA COAST. 12Z SURFACE 
ANALYSIS PLACED A PRIMARY COLD FRONT ALONG THE BLUE RIDGE...WITH A 
SECONDARY COLD FRONT ALONG THE APPALACHIANS. A 1020MB ANTICYCLONE 
DOMINATED THE PLAINS.

MODELS...
THE 12Z NAM (WRF-NMM)/GFS/CANADIAN ALONG WITH THE 00Z EUROPEAN AND 
UKMET WERE INVESTIGATED. THE OPERATIONAL MODELS ARE IN GOOD 
AGREEMENT INTO THE LONG RANGE WITH REGARD TO THE SYNOPTIC SCALE 
PATTERN. THE MODELS SHOW A WEAKENING TREND WITH THE CYCLONE TO THE 
NORTHWEST THROUGH THE WEEKEND...WITH BUILDING HEIGHTS ALLOWING HIGH 
PRESSURE TO BUILD ACROSS THE MID ATLANTIC THIS WEEKEND. THE 
CALIFORNIA CUT-OFF GETS PICKED UP IN THE MEAN FLOW...AND WEAKENS AS 
IT MOVES THE PLAINS AND MID ATLANTIC THROUGH MID WEEK.

ENSEMBLE DATA...
00Z GFS 500MB HEIGHT ENSEMBLES SHOW A -4.5 STANDARD DEVIATION UPPER 
LOW ACROSS THE UPPER MIDWEST AND A -3 STANDARD DEVIATION UPPER LOW 
OFF THE CALIFORNIA COAST. THE UPPER MIDWEST UPPER LOW FILLS WITH THE 
TROUGH AXIS PASSING DURING THE WEEKEND. HEIGHTS RISE DURING THE 
EARLY WORK WEEK AS A TROUGH DEVELOPS ALONG THE WEST COAST. THE 
CALIFORNIA UPPER LOW IS SHOWN TO WEAKEN AND MOVE WITHIN THE MEAN 
FLOW ACROSS THE MID ATLANTIC DURING THE MID WEEK. THERE IS GOOD 
CONSISTENCY INTO DAY 7 WITH THIS PATTERN EVOLUTION (ESPECIALLY 
CONSIDERING THE LARGE PATTERN CHANGE DEPICTED).

THE GFS ENSEMBLE MOS PRODUCT IS CURRENTLY UNAVAILABLE.

FORECAST RATIONALE...
ANOMALOUSLY LOW HEIGHTS AND CLEARING CONDITIONS AS HIGH PRESSURE 
BUILDS INTO THE REGION IS A RECIPE FOR FROST/FREEZE CONDITIONS 
ACROSS A GOOD PORTION OF THE FORECAST AREA THROUGH SUNDAY MORNING. 
WILL TAKE IT ONE NIGHT AT A TIME IN ORDER TO ELIMINATE PREVIOUS 
FREEZES...AND THUS WILL HAVE A MENTION IN THE HAZARDOUS WEATHER 
STATEMENT (WBCHWOLWX).

OPERATIONAL MODELS AND GFS ENSEMBLES ARE IN GOOD AGREEMENT WITH 
REGARD TO PATTERN EVOLUTION DURING THE MEDIUM RANGE. WITH LOWERING 
HEIGHTS ACROSS THE WESTERN CONUS...CALIFORNIA UPPER LOW WILL BE 
PICKED UP WITHIN THE MEAN FLOW. SEVERAL FACTORS INDICATE THAT IT 
WILL BE A HEALTHY QPF EVENT ACROSS THE MID ATLANTIC. FIRST...IT IS A 
SIGNIFICANT PATTERN CHANGE. SECOND...THIS SYSTEM HAS PACIFIC 
ORIGINS...AND A MOISTURE FEED FROM THE GULF COAST/SOUTHEAST ATLANTIC 
WILL BE OPENING UP EARLY NEXT WEEK. FINALLY...IT APPEARS TO BE A 
FAIRLY GOOD ISENTROPIC LIFT SCENARIO WITH THE SURFACE HIGH ACROSS 
NEW ENGLAND.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...FREEZE WARNING FOR MDZ002 FROM 2 AM FRIDAY TO 8 AM FRIDAY.
VA...FREEZE WARNING FOR VAZ021 FROM 2 AM FRIDAY TO 8 AM FRIDAY.
WV...FREEZE WARNING FOR WVZ048>051-054-055 FROM 2 AM FRIDAY TO 8 AM 
     FRIDAY.
MARINE...SMALL CRAFT ADVISORY FOR ANZ530>537 UNTIL 4 AM FRIDAY.
&&

$$