006 
FXUS61 KRNK 211734
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1234 PM EST SAT NOV 21 2009

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN IN THE AREA THIS AFTERNOON INTO TONIGHT.
LOW PRESSURE DEVELOPING ACROSS THE GULF COAST STATES WILL IMPACT
OUR WEATHER SUNDAY WHILE HIGH PRESSURE WEDGES DOWN FROM THE
NORTHEAST.

&&

.NEAR TERM /THROUGH TONIGHT/...
SATELLITE LOOP SHOWED HIGH CLOUDS SPREADING EAST ACROSS THE REGION.
THICKNESS VALUES SUPPORT FORECAST HIGHS FOR THIS AFTERNOON FROM THE 
UPPER 40S IN THE NORTHWEST TO THE LOWER 60S IN THE SOUTHEAST. THE 
EXTENT/COVERAGE OF CLOUDINESS MAY EFFECT TEMPERATURES. THE NRN 
STREAM SHORTWAVE MOVING ACROSS THE OHIO VALLEY TODAY. FOR TONIGHT
THE NRN STREAM SHORTWAVE SLIDES SLOWLY INTO THE MID ATLANTIC REGION 
WITH SHORTWAVE RIDGING OCCURRING OVER OUR AREA....WHILE THE TROUGH 
OVER TX SLIDES INTO THE GULF COAST STATES. QUESTION FOR TONIGHT
IS HOW LONG DOES IT TAKE TO SATURATE THE LOW LEVELS OF THE 
ATMOSPHERE ? TREND OF MODELS HAVE BEEN SLOWER WITH THE ARRIVAL OF 
PRECIPITATION. WILL REVIEW 12Z RUNS BEFORE MAKING ADJUSTMENTS IN 
POPS. DECIDED MAKE A FEW MINOR ADJUSTMENTS IN CLOUDS AND
TEMPERATURES.

.PREVIOUS DISCUSSION...

THE 00Z MODELS HAVE CONTINUED TO TREND DRIER THIS RUN WITH THE 
SYSTEM COMING OUT OF THE GULF COASTAL REGION. THE 00Z GFS ATTM...IS 
DOING A BETTER JOB HANDLING THE CS POURING OVER THE REGION AHEAD OF 
THE NRN STREAM TROUGH ACROSS THE MIDWEST. THESE HIGH CLOUDS HAVE 
LIMITED FOG DEVELOPMENT...BUT STILL SHOULD SEE SOME THINNING ACROSS 
THE RIVER VALLEYS SO KEPT SOME PATCHY FOG IN THIS MORNING.

FOR TODAY...THE MAIN FORECAST CHALLENGE WILL BE EXTENT OF CLOUDINESS 
AND EFFECT ON TEMPS. DURING THE LATE FALL MONTHS THE GFS SEEMS TO DO 
A BETTER JOB WITH HIGH CLOUDS IN TERMS OF ITS RH DEPICTION IN THE 
UPPER LVLS...AND THE AMOUNT OF OPAQUENESS IS SOMETIMES 
UNDERESTIMATED. FOR NOW...WITH THE NRN STREAM SHORTWAVE MOVING 
ACROSS THE OHIO VALLEY TODAY THINK THE HIGH CLOUDS WILL  GET SHUNTED 
EAST...WITH SOME LOWER CLOUDS ARRIVING IN THE NWRN CWA...ALTHOUGH 
NOT IMPRESSED WITH THAT ATTM. WITH THIS IN MIND...HAVE RUN WITH A 
MIDDLE OF THE ROAD APPROACH FOR SKY COVER WITH 40-60 PERCENT 
COVERAGE. HIGHS AS SUCH WILL REMAIN CLOSE TO THE PREVIOUS FORECAST 
OF 50S IN THE MTNS TO LOWER 60S OUT EAST...CLOSE TO A MOS BLEND.

TONIGHT...THE NRN STREAM SHORTWAVE SLIDES SLOWLY INTO THE MID 
ATLANTIC STATES WITH SHORTWAVE RIDGING OCCURRING OVER OUR 
CWA....WHILE THE TROUGH OVER TX SLIDES INTO THE GULF COAST STATES. 
HAVE BACKED OFF ON POPS THINKING THAT THE RAIN SHIELD STAYS SOUTH OF 
OUR CWA UNTIL AFTER 12Z SUNDAY. HOWEVER...KEPT THE CHANCE IN THERE 
FOR POTENTIAL OF NRN STREAM SHORTWAVE SLIDING FURTHER EAST. THE E-SE 
FLOW LATE TONIGHT MAY HELP SATURATE THE LOW LVLS OVER THE NC MTNS. 
ALL IN ALL...PRETTY DRY TONIGHT...WITH CLOUDS DECREASING IN THE 
NORTH BUT INCREASING AFTER MIDNIGHT OVER THE SOUTH. LOWS TONIGHT 
WILL REMAIN CLOSE TO MOS...DROPPED A COUPLE DEGREES FROM PREVIOUS 
FORECAST DUE TO SLOWER ARRIVAL OF CLOUDS AND SOME EVAP COOLING 
POTENTIAL WITH VIRGA IN THE SOUTH.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/...
MODELS CONTINUE TRENDING SLOWER...DRIER AND KEEPING HEAVIER RAIN
SE OF THE CWA ON SUNDAY. BECAUSE OF THIS WAS FORCED TO REDUCE AND
SLOW POPS...HOWEVER DID NOT GO AS LOW AS GUIDANCE SINCE MODELS
MAY PROBABLY AGAIN CHANGE DRASTICALLY. ALTHOUGH LOW PRESSURE MOVES
UP THE COAST ON MONDAY...AN UPPER LEVEL DISTURBANCE ENTERING FROM
THE WEST IN ITS WAKE...MAY ALLOW ANOTHER RAIN SHIELD TO DEVELOP
LATER MONDAY. TUESDAY SHOULD PROVIDE AM OPPORTUNITY TO DRY OUT
WITH TEMPS CLOSE TO 60F AGAIN.

&&

.LONG TERM /WEDNESDAY THROUGH FRIDAY/...
ECMWF INDICATES UPPER LEVEL RIDGING APPROACHING THE AREA TUESDAY 
AFTERNOON INTO EARLY WEDNESDAY MORNING...WHILE THE SURFACE WEDGE 
HANGS ON THROUGH THE END OF THE WEEK. IT ALSO SUGGESTS A SURFACE AND 
UPPER LOW PRESSURE SYSTEM DEVELOPING OVER THE MIDWEST AND PUSHING 
TOWARD THE AREA BY MID TO LATE WEEK. HAVE AT LEAST CHANCE TO SLIGHT 
CHANCE OF POPS ACROSS THE COUNTY WARNING AREA THROUGH THE EXTENDED 
PERIOD. WITH THICKNESSES 1000-850MB AND 850-700MB THICKNESSES 
LOWERING BY MID WEEK...THERE COULD BE SOME LIGHT SNOW MIXED WITH 
RAIN IN THE HIGHER ELEVATIONS OF SOUTHEAST WEST VIRGINIA. IN THESE 
SAME AREAS MAINLY ALONG THE RIDGES...SURFACE LOW TEMPERATURES COULD 
ALSO REACH FREEZING OR A FEW DEGREES BELOW.

GFS HAS BEEN HAVING A HARD TIME WITH RUN TO RUN CONSISTENCY IN THE 
EXTENDED. IT HAS BEEN FASTER AND MORE PROGRESSIVE WITH PUSHING THE 
SYSTEMS THROUGH THE FORECAST AREA. DUE TO THIS HAVE LEANED MORE 
TOWARD THE ECMWF AS IT SEEMS TO BE A BIT MORE CONSISTENT IN EACH RUN 
THE PAST FEW DAYS.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH TONIGHT. EXPECT 
VFR CONDITIONS THROUGH THE PERIOD WITH CIRRUS/CS CIGS.

LOW PRESSURE WILL SLIDE NORTHEAST FROM THE GULF COAST STATES INTO THE
SOUTHEAST COASTAL AREA BY TUESDAY. LOOK FOR LOWERING CIGS DURING
THE DAY SUNDAY WITH RAINFALL EXPECTED AT THE TAF SITES BY LATE 
SUNDAY. MODELS SEEM TO BE SLOWING THE RAIN START TIMES DOWN...SO
WITH THAT IN MIND WE MAY NOT SEE SUB VFR CONDITIONS UNTIL SUNDAY
NIGHT INTO MONDAY.

TUESDAY WILL FEATURE IMPROVING CONDITIONS AS THE SFC LOW TRACKS
NORTHEAST UP THE EASTERN SEABOARD WITH HIGH PRESSURE BUILDING OVER
THE MID ATLANTIC FOR MID WEEK.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...PM/WP
NEAR TERM...KK/WP
SHORT TERM...KM/WERT
LONG TERM...REB
AVIATION...KK/WP