FXUS61 KRNK 251801
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
101 PM EST FRI DEC 25 2009

.SYNOPSIS...
HIGH PRESSURE WAS WEDGED DOWN THE EAST SIDE OF THE APPALACHIANS. 
A LARGE LOW PRESSURE SYSTEM WILL REMAIN OVER THE MID MISSISSIPPI
VALLEY AND WILL PUSH A FRONT EAST ACROSS THE REGION TONIGHT. WEAK
HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT ON SATURDAY BRINGING
DRIER WEATHER.

&&

.NEAR TERM /THROUGH TONIGHT/...
REPORTS FROM AROUND THE AREA INDICATE THAT TEMPS ARE RISING
RAPIDLY AS STRONGER WINDS MIX SOME TO THE SURFACE. WILL PROBABLY
BE ABLE TO CANCEL ANY ICE-RELATED HEADLINES LEFT AROUND NOON
TODAY. PLEASE SEE OUR LSR REPORTS FOR ICE DAMAGE IN THE NC MTNS
AND ALONG THE BLUE RIDGE IN SW VA. THE LLJ IS STILL FORECAST TO BE
EXTREMELY STRONG TODAY. DECIDED THAT IT WAS BEST TO EXTEND THE
HIGH WIND WARNINGS AND ADVISORIES TO 400 PM. IN ADDITION...I HAVE
ALSO EXTENDED THE COVERAGE OF THE ADVISORIES TO INCLUDE ALL OF OUR
CWA THAT HAS HIGHER ELEVATIONS- THINK THAT THEY HAVE A GOOD CHC OF
SEEING THE STRONG WINDS DESPITE THE CAD. FINALLY...WITH RADAR
SHOWING A LONG BAND OF MD-HEAVY RAIN STREAMING NORTHWARD AND THE
BAND MOVING ONLY SLOWLY EAST...THOUGHT IT BEST TO ISSUE A FLOOD
WATCH. THINK THAT RATES WILL NOT BE VERY HIGH...BUT SATELLITE
INDICATES THAT PWATS ARE GREATER THAN AN INCH STREAMING UP THIS
WAY...AND I EXPECT RAINFALL TO BE HEAVIER THAN MODELS ESTIMATE.
1.5 INCHES LIKELY...WHICH MAY CAUSE SMALL STREAMS TO COME OUT OF
THEIR BANKS. THE FLOOD WATCH RUNS THROUGH 400 PM. 

PREVIOUS DISCUSSION...
STILL EXPECT TEMPERATURES TO RISE ABOVE FREEZING IN ALMOST ALL
AREAS AFTER 17Z BUT ENOUGH QPF ALONG THE BLUE RIDGE AND FROM
SOUTHEAST WEST VIRGINIA INTO THE ALLEGHANY HIGHLANDS TO ADD MORE
COUNTIES TO THE ICE STORM WARNING. ALSO HAVE INCREASED ICE TOTALS
ALONG THE SOUTHERN BLUE RIDGE WHERE WARNING WAS ALREADY IN EFFECT.

HAVE EXPANDED THE HIGH WIND WARNING IN THE FAR WESTERN COUNTY
WARNING AREA. ALL MODELS WERE SHOWING 70-80 KNOTS 850 MB WINDS
MOVING FROM THE NORTH CAROLINA MOUNTAINS EARLY TODAY INTO
SOUTHEAST WEST VIRGINIA BY AFTERNOON. 

WIND ADVISORY AND FREEZING RAIN ADVISORIES CONTINUE FOR MUCH OF
THE REST OF THE FORECAST AREA TODAY. MODELS SIMILAR ON THE TIMING
OF THE PRECIPITATION WITH THE BEST LIFT FROM 09-21Z...AND ENDING
FROM SOUTHWEST TO NORTHEAST. 

CHANGED THE PRECIPITATION OVERNIGHT TO FREEZING RAIN IN THE COLD
SPOTS INSTEAD OF SNOW SINCE MOISTURE BECOMES SHALLOW BUT STILL NOT
NEARLY COLD ENOUGH ALOFT FOR CRYSTAL GROWTH. EVEN WITH THE FRONT
COMING THROUGH TONIGHT COLD AIR HOLDS JUST TO THE WEST.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
FRONTAL BOUNDARY WILL PUSH EAST INTO THE ATLANTIC OCEAN SATURDAY.
IN THE WAKE OF THE FRONT...DRIER AND COLDER AIR WILL PUSH ACROSS OUR 
REGION. COLD ADVECTION WILL FILTER INTO THE MOUNTAINS SATURDAY...AND 
FURTHER EAST SATURDAY NIGHT INTO SUNDAY WITH 85H TEMPERATURES AS 
LOW AS -11 DEGREE C IN SOUTHEAST WEST VIRGINIA. KEPT SATURDAY HIGHS 
COLD CLOSE TO ADJMETBC WITH READINGS FROM THE MID 30S IN THE 
NORTHWEST TO AROUND 50 IN THE SOUTHEAST. 

A SURFACE RIDGE TO THE SOUTHWEST NOSES INTO THE WESTERN PORTION OF 
THE AREA WHICH SHOULD HOLD THE DRY WEATHER THROUGH SUNDAY. WITH 
CLOUDS THINNING IN COMBINATION WITH THE DRY AIR AND COLD 
ADVECTION...TEMPERATURES WILL DROP TO AROUND 20 IN THE MOUNTAINS 
WITH THE PIEDMONT SEEING MID 20S FOR SUNDAY NIGHT. 

THE NEXT DISTURBANCE WILL APPROACH THE AREA SUNDAY NIGHT WITH A 
SOUTHWESTERLY FLOW INCREASING MOISTURE IN THE WESTERN ZONES. WINDS 
WILL THEN VEER TOWARD A WEST TO NORTHWEST DIRECTION WHICH WILL 
ENHANCE THE UPSLOPE COMPONENT. INCREASED POPS SUNDAY NIGHT INTO 
MONDAY MORNING. WITH TEMPERATURES BEING WELL BELOW FREEZING...EXPECT 
SNOW SHOWERS ALONG AND WEST OF THE APPALACHIAN MOUNTAINS. AMPLIFIED 
TROUGH OVER THE EAST WILL RESULT IN CHILLY AIR MONDAY WITH 85H 
TEMPERATURES AROUND MINUS 10. PLAYED TEMPERATURES CLOSE TO 
MOSGUIDEBC FOR MONDAY.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AMPLIFIED TROUGH OVER THE EASTERN CONUS DELIVERING A DOSE OF FAIRLY 
CHILLY AIR BY EARLY NEXT WEEK ON BOTH GFS/ECMWF...H85 TEMPS -8 TO 
-12 EARLY MONDAY. TROUGH LIFTS OUT TO THE NORTHEAST SOME BY MID-WEEK 
WITH MORE ZONAL FLOW AND MODERATING TEMPS BY WED. POTENTIAL FOR A 
REINFORCING SHORT-WAVE AND COLDER BY LATER IN THE WEEK WITH GFS 
SUGGESTING A WEAK COASTAL LOW BY FRIDAY WHICH WILL HAVE TO BE 
WATCHED IN LIGHT OF THE TENDENCY THIS YEAR FOR SUCH SYSTEMS TO 
STRENGTHEN AND AMPLIFY. H5 MEAN HEIGHT NEGATIVE ANOMALIES ON THE GFS 
RANGE ANYWHERE FROM 100 TO 150DM THRU MUCH NEXT WEEK SO IT WILL BE 
CHILLY WEEK REGARDLESS...ALTHOUGH THE MUCH COLDER CORE OF AIR 
REMAINS UP OVER NEW ENGLAND PER THE EC MODEL WHICH IS THE PREFERRED 
SOLUTION PER THE NCEP EPD DISCUSSION. AT THIS TIME WILL MAINTAIN LOW 
POPS FOR MUCH OF THE WEEK...ALTHOUGH MTN SNOW SHOWERS POSSIBLE 
MONDAY AS THE COLDER AIR SPILLS EASTWARD COULD PRODUCE SOME SNOW IN 
FAVORED AREAS DEPENDING ON EXACT TRAJECTORIES.  A SPRAWLING RIDGE OF 
COLD SURFACE HIGH PRESSURE ACROSS THE CENTRAL US WILL BUILD EASTWARD 
IN THE EARLY TO MID-WEEK PERIOD WITH THAT POTENTIAL SURFACE LOW 
DEVELOPING OVER THE GULF COAST BY LATER IN THE WEEK...OBVIOUSLY MANY 
OUTCOMES POSSIBLE WITH SOMETHING THAT FAR OUT...BUT RAISED POPS INTO 
THE CHANCE CATEGORY BY NEXT THU/FRI.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
FREEZING RAIN HAS ENDED AT ALL WFO RNK TERMINAL SITES...BUT CIGS
HAVE LOWERED TO IFR EAST OF THE MTNS AT ROA...LYH AND DAN. LOWERED
CIGS ARE ALSO EXPECTED AT BLF AND LWB...BUT THEY WILL BE VARYING
HIGHER AT TIMES THE REST OF THE AFTERNOON. MAIN ISSUE THROUGH 21
TO 22Z WILL BE LLWS. A VERY STRONG LLJ REMAINS OVER THE
AREA...THOUGH SHOULD BE STARTING TO DECREASE IN SPEED REST OF THE
AFTERNOON. HOWEVER...WITH SFC WINDS MAINLY LIGHT AT ALL SITES EXCEPT
FOR BLF...THE SHEAR MAGNITUDE WILL BE GREAT...POSSIBLY UP TO 40
KNOTS IN THE LOWEST 2000 FEET. 

RAIN WILL BE LIFTING NE AWAY FROM THE REGION THIS EVENING...AND
ALL SITES ARE EXPECTED TO DROP TO IFR OR EVEN LIFR WITH A LIGHTER
WIND FLOW AND ABUNDANT LOW LEVEL MOISTURE. THE IFR CONDITIONS WILL
LIKELY HANG ON UNTIL AROUND/AFTER 12Z SATURDAY. VFR CONDITIONS ARE
THEN EXPECTED AT ALL SITES BY 18Z SATURDAY.

THERE WILL BE TYPICAL MVFR TO LOCALIZED IFR RESTRICTIONS
CONTINUING IN THE UPSLOPE AREAS WEST OF THE BLUE RIDGE (KBLF/KLWB)
DUE TO STRATOCUMULUS AND SCATTERED SNOW SHOWERS THROUGH SUNDAY.

&&

.EQUIPMENT...
USE THE WIND OBSERVATION AT ROA WITH CAUTION. AN ERROR HAS BEEN
REPORTED WITH THE WIND SENSOR...IT MAY BE FROZEN. IF THE SENSOR
HAS FROZEN IT WILL CONTINUE TO REPORT A CALM WIND UNTIL THE ICE IS
BROKEN OFF OR THE ICE MELTS OFF THE SENSOR.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR VAZ011>014-
     016>020-022>024-032>035.
     FREEZING RAIN ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR 
     VAZ019-023-024-034-035-045>047.
     HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR VAZ007-009-
     010-015.
     FLOOD WATCH UNTIL 4 PM EST THIS AFTERNOON FOR VAZ032-043-044-
     058.
     ICE STORM WARNING UNTIL 4 PM EST THIS AFTERNOON FOR VAZ020.
NC...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR NCZ002.
     HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR NCZ001-018.
     FLOOD WATCH UNTIL 4 PM EST THIS AFTERNOON FOR NCZ003>006-019-
     020.
WV...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR WVZ044.
     HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR WVZ042-043-
     045.

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS/JJ
SHORT TERM...KK
LONG TERM...PC
AVIATION...AMS/JJ
EQUIPMENT...