Area Forecast Discussion
Issued by NWS Blacksburg, VA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KRNK 011124
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
724 AM EDT FRI AUG 1 2014

.SYNOPSIS...
AN UPPER TROUGH OF LOW PRESSURE WILL CONTINUE TO RETROGRADE WEST
TO THE MISSISSIPPI RIVER VALLEY...AND THE CENTER OF SURFACE HIGH
PRESSURE WILL SHIFT TO OUR EAST TODAY. AN UPPER DISTURBANCE
TRACKING JUST SOUTHEAST OF THE AREA WILL BRING MORE IN THE WAY OF
WIDESPREAD RAINFALL INTO THIS AFTERNOON. LINGERING MOISTURE IN
THE WAKE OF THIS FEATURE WILL COMBINE WITH HEATING TO RESULT IN
MORE SHOWERS AND STORMS OVER THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 240 AM EDT FRIDAY...

UNUSUAL WIDESPREAD RAIN EVENT FOR MID SUMMER LOOKS IN STORE FOR
MUCH OF TODAY AS SHORTWAVE ENERGY CURRENTLY OVER SOUTHERN S
CAROLINA TRACKS NE CROSSING THE EASTERN PORTIONS OF THE CWA BY
THIS EVENING. THIS WILL CONTINUE TO ENHANCE THE OVERRUNNING OF
WARM/MOIST AIR ON SE FLOW OVERTOP A DEVELOPING COOL WEDGE EARLY
THIS MORNING...WITH SOME DEGREE OF PRECIP SPREADING NORTH AND WEST
ACROSS MUCH OF THE REGION BY 12Z. STILL APPEARS THAT THE HEAVIEST
RAINFALL WILL BE ACROSS SOUTHERN SECTIONS AND ENHANCED ALONG THE
SOUTHERN BLUE RIDGE BY UPSLOPE FLOW OF NEAR 2 INCH PWATS INTO THIS
AFTERNOON. HOWEVER APPEARS CONVECTION ALONG THE COASTAL CAROLINAS
CONTINUES TO DISRUPT THE DEEPER SE TRAJECTORY WITH MORE CONVECTIVE
NATURE COVERAGE FARTHER TO THE SOUTH IN CONJUNCTION WITH THE
HIGHER THETA-E AIR BEING ADVECTED ACROSS THE FRONT INTO THE
N CAROLINA COASTAL PLAINS. THIS MAY HAVE ALSO CAUSED THE MODEL
INIT TO BE TOO FAR WEST WITH THE CORE OF HEAVIER RAINFALL BUT
EXPECT THE CURRENT AXIS TO PIVOT MORE NORTH- SOUTH ORIENTED
SIMILAR TO THE LATEST HRRR AS THE WAVE HELPS SHARPEN THE TROF
WHILE BACKING THE FLOW ALOFT THIS MORNING. QUESTION IS WHETHER OR
NOT WILL GET ENOUGH HEAVIER RAINFALL OVER A PROLONGED PERIOD TO
PRODUCE FLOOD ISSUES GIVEN DRY CONDITIONS PER LATEST FFG SHOWING 6
HOUR AMOUNTS OF 3.5-4.5 INCHES TO CAUSE FLOODING. SINCE EXPECTING
MOST OF THE RAINFALL TO REMAIN MORE STRATIFORM WITH EMBEDDED
HEAVIER DOWNPOURS WONT POST A WATCH OVER THE SW FOR NOW BUT EXPECT
UPSLOPE MAY CAUSE A GOOD 2-3+ INCHES ALONG THE EASTERN SLOPES.

BEST LIFT SPREADS NE WITH THE WAVE THIS AFTERNOON CAUSING THE SOLID
AXIS OF PRECIP TO SHIFT ACROSS EASTERN/NE SECTIONS DURING THE
AFTERNOON WITH SOME TAPERING TO LIGHTER SHRA WEST/SW. COULD EVEN
SEE A FEW BREAKS DEVELOP FAR WEST ON THE PERIMETER OF THE COOL AIR
OTRW CLOUDY AND VERY COOL TO START AUGUST. HIGHS QUITE TRICKY AS
SOME SPOTS MAY SEE MORE OF A WINTER CAD EVENT WITH TEMPS ONLY
RISING A FEW DEGREES AT MOST ALONG THE BLUE RIDGE WHERE KEEPING IT
IN THE 60S FOR THE MOST PART. THINK SPOTS OVER THE PIEDMONT
INCLUDING SW VA INTO SE WVA MAY BE ABLE TO BUMP VALUES INTO THE
LOW/MID 70S ESPCLY IF THE RAINFALL DIMINISHES A BIT FASTER AND
THINGS BRIGHTEN SLIGHTLY.

IMPULSE EXITS THIS EVENING LEAVING THE REGION WITHIN THE RESIDUAL
WEDGE BUT UNDERNEATH A CONTINUED DIFFLUENT PATTERN ALOFT ON THE
FRONT OF THE 5H TROF. LITTLE UPPER SUPPORT REMAINING OVERNIGHT FOR
MUCH ADDED RAINFALL ESPCLY AFTER MIDNIGHT BUT LIKELY ENOUGH WEAK
UPSLOPE TO KEEP LIKELY OR HIGHER POPS GOING BLUE RIDGE INTO LATE
THIS EVENING. FLOW BEHIND THE DEPARTING WAVE MAY ACTUALLY TURN
WESTERLY ENOUGH TO SHUT OFF SHRA WESTERN HALF LATE SO CUT POPS
BACK TO MAINLY CHANCE AFTER MIDNIGHT WHEN MAY BE MORE DRIZZLE/FOG
OUT EAST. CONTINUED COOL WITH LOWS LIKELY ONLY FALLING A FEW
DEGREES BUT AFTER A CHILLY DAY WONT TAKE MUCH TO GET INTO THE 50S
WEST AND LOW 60S EAST.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
AS OF 314 AM EDT FRIDAY...

A BERMUDA HIGH REMAINS OVER THE WESTERN ATLANTIC WHILE AN UPPER
LEVEL TROUGH IS DRAPED OVER THE MISSISSIPPI VALLEY THIS WEEKEND.
WITH THE FORECAST AREA IN BETWEEN THESE TWO SYNOPTIC
FEATURES...IMPULSES WITH TROPICAL MOISTURE WILL KEEP A GOOD CHANCE
FOR SHOWERS AND SCATTERED THUNDERSTORMS IN THE AREA OVER THE
WEEKEND. COMPARED TO YESTERDAY...MODELS HAVE SHIFTED THE AXIS OF
HEAVY STEADY RAIN EAST ALONG THE COAST. THE FORECAST AREA WILL STILL
SEE A FAIR AMOUNT OF RAIN OVER THE WEEKEND...BUT WILL BE MORE
CONFIDED TO THE AFTERNOON AND EVENING HOURS. DESPITE THE MODELS
TRENDING DRIER...KEEP POPS THROUGH THE ENTIRE PERIOD WITH LOW CHANCE
DURING NON-DIURNAL HEATING HOURS AND HIGH CHANCE-LIKELY DURING THE
AFTERNOON AND EVENING. ALSO WITH THE DRIER MODEL SOLUTIONS...EDGE
TEMPERATURES UP A FEW DEGREES EACH AFTERNOON. DESPITE WARMING THE
FORECAST TEMPERATURES...THEY WILL REMAIN COOLER THAN NORMAL BY AT
LEAST 10F FOR THE FIRST WEEKEND IN AUGUST.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
AS OF 330 PM EDT THURSDAY...

MONDAY THROUGH WEDNESDAY THE TROFFING IN THE EAST FLATTENS. A
SURFACE COLD FRONT COMES SOUTH THROUGH NEW ENGLAND MONDAY
TUESDAY...BUT WILL ONLY MOVE SO FAR SOUTH WITH THE BOUNDARY PARALLEL
TO THE UPPER FLOW.

THIS WILL KEEP THE FORECAST AREA ON THE WARM UNSTABLE AIR MASS ON
THE SOUTH SIDE OF THE FRONT THROUGH THURSDAY. DEEPEST MOISTURE AND
BEST LIFT WILL BE FOCUSED ALONG THE COAST FRONT ACROSS THE CAROLINAS
AND GEORGIA. NOT SEEING ANY ORGANIZED FORCING FOR THE COUNTY WARNING
AREA.

TEMPERATURES WILL BE NEAR NORMAL THROUGH THE PERIOD.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
AS OF 650 AM EDT FRIDAY...

FLYING CONDITIONS WILL CONTINUE TO DETERIORATE THIS MORNING AS AN
AXIS OF SHOWERS WITH EMBEDDED HEAVY RAIN SLIDES SLOWLY
NORTH...LIKELY COVERING MOST OF THE REGION BY MID MORNING. MODELS
CONTINUE TO SHOW THIS SCENARIO WITH WIDESPREAD RAINFALL ESPCLY
BLUE RIDGE EAST INTO THIS AFTERNOON BUT DIFFER ON EXACTLY WHERE
THE HEAVIEST MAY TAKE SHAPE. STILL APPEARS SOUTHERN SECTIONS
RUNNING UP ALONG THE EASTERN SLOPES OF THE SOUTHERN BLUE RIDGE
WILL SEE THE HEAVIEST RAINFALL INCLUDING WIDESPREAD MVFR TO IFR
FOR MUCH OF TODAY...AND PERHAPS INTO THE OVERNIGHT. WESTERN
LOCATIONS SUCH AS KBLF/KLWB MAY BREAK BACK OUT INTO VFR AFTER
EARLY RAINFALL GIVEN DOWNSLOPE AND PASSAGE OF DEEPER MOISTURE TO
THE EAST SO WENT CLOSER TO THE LESS PESSIMISTIC GFS THERE. ELSW
STAYING CLOSER TO THE LOWER CIGS SUGGESTED BY THE NAM BY THIS
AFTERNOON GIVEN EASTERLY FLOW ONCE THINGS BECOME SATURATED THIS
MORNING. ALSO PERIODS OF MVFR VSBYS LIKELY ESPCLY FROM THE
MOUNTAINS EAST INTO THE AFTERNOON...WITH POSSIBLE IFR AT TIMES IN
HEAVIER RAIN/FOG NEAR THE BLUE RIDGE...INCLUDING LOCATIONS SUCH
AS KBCB/KROA.

DESPITE THE EXODUS OF THE WAVE THIS EVENING...LINGERING WEDGE AND
DIFFLUENCE ALOFT LIKELY TO KEEP AT LEAST SOME SPOTTY RAIN/DRIZZLE
AROUND WHICH MAY HOLD MVFR TO IFR CIGS ALONG WITH FOG IN PLACE
UNTIL EARLY SATURDAY MORNING. OTRW WILL HAVE WIDESPREAD IFR CONDITIONS
FROM THE BLUE RIDGE EAST OVERNIGHT WITH MVFR AT KBLF AND LIFR LATE
AT KLWB DUE TO DENSE FOG.

EXTENDED AVIATION DISCUSSION...
THE BROAD UPPER TROUGH OF LOW PRESSURE WILL LINGER ACROSS THE
EASTERN UNITED STATES THROUGH SUNDAY CONTINUING TO RETROGRADE
FROM THE EASTERN/CENTRAL GREAT LAKES TO THE WESTERN GREAT LAKES BY
THE WEEKEND.

FOR SATURDAY AND SUNDAY...THE AIR MASS WILL SLOWLY BECOME WARMER
AND MORE UNSTABLE. SCT SHRA/TSRA EXPECTED AGAIN SATURDAY WITH
ONLY LIMITED INSTABILITY EVIDENT. FOR SUNDAY...BETTER CHANCE OF
TSRA WITH BETTER INSTABILITY ACROSS MUCH OF THE CWA...SW FLOW
ALOFT...AND INCREASING MOISTURE LEVELS. THUS...BRIEF PERIODS OF
MVFR-IFR CIGS/VSBYS EXPECTED IN SHRA/TSRA SATURDAY AND MORE
LIKELY SUNDAY AFTERNOON. SOME DRYING WITH A RETURN TO OVERALL VFR
POSSIBLE MONDAY INTO TUESDAY AS ANOTHER WEAK COOL FRONT SWEEPS IN
FROM THE NW AND TAKES MOST MOISTURE TO THE SE OF THE REGION.

&&

.HYDROLOGY...
AS OF 330 AM EDT FRIDAY...

STEADY LIGHT TO MODERATE RAINFALL WILL SPREAD SLOWLY NORTH THROUGH
THE MORNING WITH PERIODS OF HEAVY RAIN POSSIBLE FROM THE SOUTHERN
BLUE RIDGE...FOOTHILLS EAST ACROSS THE PIEDMONT. RAINFALL TOTALS OF
1-3 INCHES IS EXPECTED ALONG THE ENHANCED UPSLOPE REGIONS OF THE
BLUE RIDGE AND FOOTHILLS MAINLY SOUTH OF ROANOKE WITH A GOOD 1-2
INCHES ELSW OVER THE PIEDMONT SECTIONS OF NORTHWEST NORTH CAROLINA
INTO SOUTHSIDE VIRGINIA BY THIS AFTERNOON. GIVEN THE VERY DRY
ANTECEDENT CONDITIONS OF LATE AND THE OVERALL LACK OF HEAVIER
RAINFALL RATES...WIDESPREAD FLOODING OR FLASH FLOODING IS NOT
EXPECTED BUT LOCALIZED SMALL STREAM AND POOR DRAINAGE FLOODING
COULD OCCUR ESPCLY WHERE HEAVIER DOWNPOURS ARE REALIZED. RAINFALL
TOTALS SHOULD QUICKLY TAPER OFF HEADING INTO FAR WESTERN VIRGINA
AND SE WEST VIRGINIA WHERE ONLY UP TO A HALF INCH LOOKS POSSIBLE
WITH AN INCH OR MORE LIKELY IN AREAS AROUND LYNCHBURG.
&&

.EQUIPMENT...
THE NOAA WEATHER RADIO AT WYTHEVILLE VA...WZ2500...BROADCASTING
ON A FREQUENCY OF 162.450 MHZ...IS OFF THE AIR. TECHNICIANS ARE
WAITING ON DELIVERY OF PARTS TO MAKE REPAIRS. THE EARLIEST THE
RADIO WILL BE WORKING AGAIN IS LATER TODAY.

&&

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

&&

$$
SYNOPSIS...JH/NF
NEAR TERM...JH
SHORT TERM...RCS
LONG TERM...AMS
AVIATION...JH/NF/WP
HYDROLOGY...JH
EQUIPMENT...DS



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.