FXUS61 KRNK 031122
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
622 AM EST THU DEC 3 2009
.SYNOPSIS...
LOW PRESSURE PASSING WELL NORTH OF THE AREA WILL DRAG A TRAILING
COLD FRONT THROUGH THE REGION THIS MORNING. HIGH PRESSURE SLOWLY
BUILDS IN BEHIND THE FRONT LATER TODAY THROUGH FRIDAY. ANOTHER
AREA OF LOW PRESSURE WILL DEVELOP ALONG THE SOUTHEAST COAST AND
MOVE OFFSHORE THIS WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
INITIAL OCCLUDED BOUNDARY NOW WORKING INTO THE PIEDMONT SHOULD EXIT
EARLY THIS MORNING FOLLOWED BY THE SECONDARY COLD FRONT APPROACHING
THE MOUNTAINS ATTM. FEW SHRA BANDS AHEAD OF THIS FRONT WILL AFFECT
THE FAR WESTERN ZONES THIS MORNING BEFORE THINGS TRANSITION TO MORE
OF A WEAK UPSLOPE REGIME WITH SPOTTY -SHRA WESTERN SLOPES INTO THE
AFTERNOON. SOME OF THIS MAY SPILL TOWARD THE BLUE RIDGE THIS MORNING
OTRW THINKING DRY OUT EAST WITH DOWNSLOPE FLOW DEVELOPING AND MAINLY
CHANCE POPS WEST WHERE MORE CLOUDS LIKELY. WINDS REMAIN GUSTY AND
WITH ANOTHER EARLY MORNING SURGE OF SUBSIDENCE BEHIND THE FROPA WILL
NEED TO ISSUE ANOTHER WIND ADVISORY FOR PARTS OF AT LEAST THE SW AND
PERHAPS FARTHER NORTH ALONG THE BLUE RIDGE. THIS ESPCLY TRUE GIVEN
GUSTINESS AND WET SOIL CONDITIONS AFTER THE HEAVY RAINFALL FROM YDA.
HIGH TEMPS AGAIN TRICKY INITIALLY SINCE WILL BE FALLING TOWARD
FORECAST HIGHS BEHIND THE FRONT EARLY THIS MORNING WITH SOME REBOUND
IN THE EAST THIS AFTERNOON AGAIN PER HEATING/DOWNSLOPE. EXPECT
CLOUDS AND WEAK COLD ADVECTION TO PUT THE LID ON MUCH RISE IN THE
UPSLOPE AREAS SO QUITE A RANGE FROM MID/UPPER 40S FAR WEST TO 60S SE
TODAY.
AREA REMAINS IN DEEP SW FLOW ALOFT AHEAD OF THE 5H TROF TO THE NW
TONIGHT AND IN WEAK LOW LEVEL WESTERLY TRAJECTORY WITH THE SURFACE
HIGH NOSING IN FROM THE MIDWEST. LOOKS LIKE THIS WILL KEEP MOISTURE
BANKED UP ACROSS THE UPSLOPE REGIONS WITH SOME SPOTTY LIGHT
SNOW/RAIN SHOWERS POSSIBLE. HOWEVER DEPTH OF MOISTURE LIKELY ONLY
ENOUGH TO SUPPORT MORE DRIZZLE THAN ANYTHING SO NO MORE THAN 20ISH
POPS SIMILAR TO THE LATEST WRF/NAM. CLOUDS SHOULD BE LIMITED COMING
EAST OF THE BLUE RIDGE WITH PC TO CLEAR SKIES OUT EAST OVERNIGHT
WITH SOME INCREASE IN HIGH CLOUDS BY MORNING. LOW TEMPS 29-33 WEST
UNDER OOZING 85H COLD ADVECTION WHILE MOSTLY 30S EAST WHERE BETTER
RAD CONDITIONS MAY ALLOW VALUES TO FALL BELOW MOS IN SPOTS.
&&
.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
ON FRIDAY INTO FRIDAY EVENING...SURFACE HIGH PRESSURE WILL BE
BUILDING INTO THE REGION. WILL HAVE A DRY FORECAST...HOWEVER...WILL
HAVE INCREASING CLOUD COVER AS A CIRRUS SHIELD ADVANCES IN
ASSOCIATION WITH A SYSTEM HEADING NORTH ALONG THE ATLANTIC COAST.
LATE FRIDAY NIGHT INTO SATURDAY NIGHT OUR FOCUS SHIFTS TO THE
WESTERN ATLANTIC LOW AND AN ASSOCIATED WESTERN FLANK DEFORMATION
ZONE THAT WILL BE TRACKING NORTH ALONG THE EAST COAST IN ASSOCIATION
WITH IT. GUIDANCE STILL HAS VARIABILITY REGARDING THE MAGNITUDE AND
PATH OF THIS FEATURE. THE 00Z GFS AND ECWMF BRING THE CORE OF THIS
MOISTURE OVER THE AREA ON SATURDAY. THE 00Z NAM AND GEM SOLUTIONS
SUGGEST THE CORE OF THE BEST MOISTURE WILL BE EAST OF THE
REGION...WITH THE SOUTHEAST PART OF THE FORECAST AREA BEING IMPACTED
BY THE WESTERN EDGE OF CORE OF BEST MOISTURE. HAVE TRENDED UPWARD
WITH POPS DURING THIS PERIOD...WITH THE FOCUS FOR THE BEST CHANCES
OF PRECIPITATION ACROSS THE SOUTHEAST PART OF THE REGION. THIS
PLACES LOW END LIKELY POPS IN THIS AREA...WITH HIGH END CHANCE POPS
ELSEWHERE.
LOW LEVEL TEMPERATURE AND DEW POINT PROFILES SUGGEST EITHER A RAIN
OR SNOW FORECAST DEPENDING UPON SURFACE AND BOUNDARY LAYER
TEMPERATURES DURING THE PERIOD. MOST OF THE REGION WEST OF THE BLUE
RIDGE WILL HAVE A SNOW FORECAST...WITH A MIX OF RAIN AND SNOW A
COUPLE TIERS OF COUNTIES EAST OF THE BLUE RIDGE...WITH A NEARLY ALL
RAIN FORECAST FOR SOUTHSIDE VIRGINIA AND NEIGHBORING PARTS OF
CENTRAL NORTH CAROLINA. QPF AMOUNTS RANGE FROM AROUND FOUR TO FIFTH
TENTHS OF AN INCH IN THE EAST...TO LESS THAN ONE TENTH IN THE WEST.
SOME OF THIS VARIABILITY INVOLVES POPS FOR A PORTION OF THE PERIOD
LESS THAN 45 PERCENT WITH STRATIFORM PRECIPITATION IN THE
WEST...THUS YIELDING A ZERO QPF AND ZERO SNOW AMOUNTS SUMMED INTO
THE TOTALS.
SUNDAY INTO SUNDAY NIGHT...HIGH PRESSURE RETURNS TO THE REGION ALONG
WITH A DRY FORECAST.
TEMPERATURES THROUGH THE PERIOD HAVE BUILT UPON THE PREVIOUS
FORECAST TEMPERATURES BLENDED WITH PERCENTAGE OF THE LATEST MOSGUIDE
AND ADJMET NUMBERS. THE RESULT IN MOST LOCATIONS AND TIME PERIODS IS
FOR A COLDER FORECAST.
&&
.LONG TERM /MONDAY THROUGH WEDNESDAY/...
LEANED MEDIUM RANGE TOWARDS HPCGUIDE WHICH WAS A BLEND OF ECMWF AND
GFS ENSEMBLES. QUASI ZONAL FLOW EXPECTED WITH SOME AMPLIFICATION OF
THE PATTERN ON TUESDAY INTO WEDNESDAY. ON SUNDAY AND MONDAY...THE
UPPER LEVEL TROUGH WILL PUSH EAST INTO THE ATLANTIC OCEAN AS HIGH
PRESSURE/RIDGE ALOFT BUILDS EAST ACROSS OUR AREA. FRONTAL BOUNDARY
APPROACHES FROM THE WEST MONDAY NIGHT INTO TUESDAY. AS THE LOW
PRESSURE CENTER AND FRONT SPREAD EAST THE CHANCES OF PCPN INCREASE
BY MIDWEEK.
&&
.AVIATION /11Z THURSDAY THROUGH MONDAY/...
TRUE COLD FRONT IS JUST WEST OF THE REGION...BUT SHOULD BE
SWINGING THROUGH THE WEST JUST AFTER 12Z WITH AN ADDITIONAL WIND
MAXIMA. BY THE LATE MORNING...THE FLOW ACROSS THE MOUNTAINS...AND
MUCH OF THE REGION WILL BE FROM THE WEST TO NORTHWEST. THIS WILL
HELP ERODE CLOUD COVER EAST OF THE MOUNTAINS...WHILE HELPING TO
MAINTAIN A MVFR OR LOW END VFR CIG ACROSS MAINLY THE MOUNTAINS OF
SE WVA AND NEIGHBORING PORTIONS OF SW VA. WILL ALSO SEE SCATTERED
RAIN SHOWERS OVER THE WEST DURING THE DAY WITH SOME SNOW SHOWERS
MIXING IN AFTER SUNSET. WINDS WILL GRADUALLY TREND LOWER THROUGH
THE DAY. LOW LEVEL WEST TO NW FLOW WILL CONTINUE OVERNIGHT WITH
CIGS LIKELY LOWERING BACK INTO MVFR OR EVEN IFR AT KBLF/KLWB THIS
EVENING. OUT EAST SOME INCREASE IN HIGH LEVEL CLOUDS LIKELY
TONIGHT OTRW VFR.
UPSLOPE LOW CLOUDS TO KEEP MVFR CONDITIONS ACROSS SE WVA INTO
AT LEAST FRIDAY MORNING WITH VFR ELSEWHERE. ANOTHER STORM SYSTEM
COULD BRING LOWER CIGS AND POSSIBLY A LITTLE MORE WINTRY PRECIP
FOR FRIDAY NIGHT AND SATURDAY FOLLOWED BY VFR UNDER HIGH PRESSURE
FOR SUNDAY INTO MONDAY.
&&
.HYDROLOGY...
WIDESPREAD WETTING RAINS OF 1-2 INCHES WILL RESULT IN RISES ON
AREA RIVERS. NO FLOODING IS FORECAST ATTM. PRELIMINARY FORECASTS
SUGGEST THE DAN RIVER AT SOUTH BOSTON MAY RISE TO NEAR BANKFULL
THURSDAY NIGHT. AN UPDATED FORECAST FOR ALL THE RIVERS WILL BE
ISSUED BETWEEN 10-11AM TODAY. PLEASE SEE THE LATEST SPECIAL RIVER
STATEMENT (WBCRVSRNK) THAT WILL BE ISSUED EARLY THIS MORNING FOR
THE LASTEST INFORMATION.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WIND ADVISORY UNTIL NOON EST TODAY FOR VAZ009-012>020-022.
NC...WIND ADVISORY UNTIL NOON EST TODAY FOR NCZ001-002-018.
WV...NONE.
&&
$$
SYNOPSIS...AMS/JH
NEAR TERM...JH
SHORT TERM...DS
LONG TERM...KK
AVIATION...DS/JH/KK
HYDROLOGY...
