Flash Flooding and Debris Flow in West Virginia, April 15, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
215 AM EDT SUN APR 15 2007

.UPDATE...
FOR AVIATION.

&&

.AVIATION /06Z-06Z/...

A LOW PRESSURE SYSTEM AND ITS ASSOCIATED COLD FRONT WERE
PROGRESSING EAST THROUGH EASTERN KENTUCKY TOWARDS THE REGION. IN
ADVANCE OF THE FRONT...A SHIELD OF RAIN WITH EMBEDDED HEAVIER RAIN
SHOWERS...WAS ADVANCING NORTHEAST OUT OF THE CAROLINAS INTO THE
FAR SOUTHEASTERN PARTS OF THE REGION. LOOKING FOR COVERAGE TO
EXPAND ACROSS A MORE GENEROUS PORTION OF THE EASTERN PART OF THE
AREA PRIOR TO DAYBREAK. IN THIS REGION...CIGS AND VSBYS WILL MAINLY
BE IN THE IFR CATEGORY WITH OCCASIONAL JUMPS UP TO MVFR OR DOWN
TO LIFR. A STRONG SOUTHERLY JET JUST OFF THE SURFACE WILL
MAINTAIN LOW LEVEL WIND SHEAR AS WELL. WEST THE CREST OF THE
BLUERIDGE WILL BE MAINLY RAIN-FREE UNTIL THE LOW AND FRONT MOVE
INTO THIS AREA AROUND DAYBREAK...BUT IFR OR LOWER VSBYS FOR
MIST/FOG AND THE LOW LEVEL WIND SHEAR WILL A ISSUE HERE.

AFTER THE FRONT MOVES THROUGH...AREAS CAN EXPECT AN ABRUPT SHIFT
IN THE WINDS TO THE NORTHWEST WITH VSBYS/CIGS IMPROVING A SOMEWHAT
SLOWER RATE LAGGING INTO THE LATE MORNING WITH RAIN SHOWERS WILL A
POSSIBILITY WITH THE MAIN UPPER TROUGH YET TO PASS THROUGH THE
REGION. SURFACE WINDS IN MOST AREAS BY THE AFTERNOON WILL BE
ACCOMPANIED BY GUSTS IN THE 20 TO 30 KTS RANGE.

THIS EVENING THAT UPPER TROUGH DOES SLIDE THROUGH THE AREA WITH
STRONG SUBSIDENCE BEHIND IT AND 850 MB WINDS PROGGED TO INCREASE
TO 50 TO 60 KTS IN SOME PARTS OF THE AREA. RESIDUAL MOISTURE AND
FALLING TEMPERATURES WILL PUT A GENEROUS COVERAGE OF IFR SNOW
SHOWERS IN THE MOUNTAINS OF SE WV WITH THE POTENTIAL FOR MORE
SCATTERED MVFR/VFR SNOW SHOWERS AS FAR EAST AS THE FOOTHILLS OF THE
BLUE RIDGE. SURFACE GUSTS IN THE MOUNTAINS 06Z APPROACHES MAY BE
AS HIGH AS 40 TO 60 KTS IN THE MOUNTAINS...WITH 30 TO 40 KTS IN
THE FOOTHILLS AND POINTS EAST.

&&

.PREV DISCUSSION...
/ISSUED 844 PM EDT SAT APR 14 2007/

SHORT TERM /REST OF TONIGHT/...

OVERALL RAINFALL CONTINUES TO BE DISORGANIZED ATTM WITH INIT
PREFRONTAL BAND OF SHRA MOVING ACROSS THE WEST WHILE DEEPER
CONVECTION STILL LIMITED TO NC AND POINTS SOUTH PER BETTER
INSTABILITY. ELONGATED AREA OF LOW PRESSURE REMAINS ACROSS THE TN
VALLEY BUT SHOULD GRADUALLY CONSOLIDATE OVER NW NC OVERNIGHT AS
UPPER TROF STARTS TO CATCH UP WITH THE SYSTEM. THIS SHOULD ALSO
START TO ENHANCE UVV UNDER APPROACHING JET MAX FROM THE LOWER MISS
VALLEY. HOWEVER STILL CONCERN OVER ROBBERY OF RH INFLOW VIA SE
CONVECTION SINCE APPEARS THE MAJORITY OF ANY SURFACE BASED
INSTABILITY WILL REMAIN JUST SOUTH/SE OVERNIGHT. LATEST MODEL
GUIDANCE INCLUDING THE WRF REMAIN CONSISTENT IN SHOWING A DEEPER
AXIS OF HEAVIER SHRA BLUE RIDGE EAST AFTER MIDNIGHT SO KEEPING
FORECAST ABOUT STATUS QUO LATER ON BUT IFFY IN REGARDS TO HEAVIER
QPF. HOWEVER WILL TWEAK DOWN QPF OVER THE NEXT FEW HOURS GIVEN
LIGHT RAINFALL RATES AND SHIFT HEAVIER TO SOUTHERN TIER WHERE
BETTER SHOT AT ELEVATED CONVECTION. OTRW WILL CONTINUE ABOUT MAXED
OUT ON POPS OVERNIGHT WITH GOING FLOOD WATCH REMAINING IN PLACE
FOR NOW. DESPITE EXPECTED SLOW TEMP RISES...WILL LOWER TEMPS A CAT
OR SO CENTRAL/NORTHERN SPOTS GIVEN BETTER INSITU WEDGE PER NE
FLOW...AND ELSEWHERE ALONG THE BLUE RIDGE WHERE ALREADY AT OR
BELOW FORECAST LOWS.

PREV DISCUSSION...
/ISSUED 750 PM EDT SAT APR 14 2007/

AVIATION /00Z-24Z/...

BAND OF RAIN MOVING ACROSS WRN PORTION OF FORECAST AREA THIS
EVENING WILL SHIFT EAST OVERNIGHT. LOOK FOR CIGS/VSBYS TO DROP
INTO LOW MVFR TO LIFR RANGE OVERNIGHT...WITH LOWEST CIGS ACROSS
THE MOUNTAINS. RAIN WILL BE MODERATE TO HEAVY AT TIMES AS WELL.
RULING OUT THUNDER AT THIS STAGE...AS BEST INSTABILITY WILL STAY
SOUTH OF THE FORECAST AREA. WIND DIRECTIONS WILL VARY AT
TIMES...AS THE SFC LOW MOVES ACROSS NRN NC LATE TONIGHT. DURING
THE DAY SUNDAY...RAIN SHOULD TAPER OFF TO LIGHT SHOWERS...WHILE AT
LEAST MVFR CIGS REMAIN. BY THE AFTERNOON...WINDS INCREASE FROM THE
NORTHWEST AND GUST TO 25 KNOTS CAN BE EXPECTED. BEYOND THIS
PERIOD...WINDS WILL INCREASE EVEN MORE...WITH GUSTS TO 50-60 KNOTS
POSSIBLE OVER THE HIGH TERRAIN...AND JUST LEE OF THE MOUNTAINS.

PREV DISCUSSION...
/ISSUED 346 PM EDT SAT APR 14 2007/

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...

TONIGHT THROUGH SUNDAY...
MODELS ARE IN GOOD AGREEMENT ON THE TRACK OF THE SFC LOW
OVERNIGHT...AND HAVE BEEN FAIRLY CONSISTENT THE PAST FEW RUNS. THE
TRACK IS GENERALLY EASTWARD ACROSS THE SOUTHERN APPALACHIANS THROUGH
06Z...AND THEN A NORTHEASTWARD TURN ACROSS CENTRAL VA. THE GFS IS A
LITTLE SLOWER THAN THE NAM...BUT THE TRACKS ARE SIMILAR. MAIN
DIFFERENCE IN THE MODELS IS THE PLACEMENT OF THE HEAVIER PRECIP
ASSOCIATED WITH THE CONVECTION MOVING NORTHWARD AHEAD OF THE SFC
LOW. THE GFS KEEPS MOST OF IT SOUTH OF THE CWA IN CEN NC...WHILE THE
NAM BRINGS IT RIGHT ACROSS THE MTNS. WE ARE THINKING THAT THE GFS
SOLUTION IS PROBABLY CLOSER TO WHAT WILL HAPPEN...BUT THAT THE
CONVECTION AND HEAVIER RAIN HAS A GOOD CHANCE OF SPREADING FURTHER
NORTHWARD INTO THE FOOTHILLS AND PIEDMONT OF NW NC AND SW VA. THIS
LOOKS MORE LIKE THE CSTAR COOL SEASON CASE WHERE A SLOWLY
PROPAGATING BAND OF CONVECTION IS MOVING EAST WITH A STRONG LLJ
AHEAD OF IT...AND THAT GENERALLY BRINGS HEAVIER PRECIP NORTHWARD
INTO OUR AREA THAN MODELS FORECAST. THE WARM FRONT MAKES IT AS FAR
NORTH AS SOUTHSIDE VA...WITH STRONG LOW LEVEL MOISTURE FLUX AND
CONVERGENCE...AND MODELS SHOW PLENTY OF DYNAMICS AROUND 06Z. IN
ADDITIONALLY...PWATS ARE AROUND 1.5 INCHES AT 06Z...WHICH IS WELL OVER
200 PCT OF NORMAL. THERE ARE ENOUGH CONDITIONS THAT HEAVY RAIN IS A
REAL GOOD BET...SO WE WILL ISSUE A FLOOD WATCH FOR ALL OF OUR CWA
EAST OF THE BLUE RIDGE OVERNIGHT.

RAIN SHOULD END SHORTLY AFTER DAYBREAK AS THE SFC LOW TRACKS OFF
SHORE AROUND NOON SUNDAY. MOST THE THE HEAVY RAIN SHOULD BE IN THE
OVERNIGHT PERIOD...SO THE FLOOD WATCH WILL JUST BE THROUGH 600 AM.
WRAPAROUND MOISTURE MOVES INTO THE MTNS IN THE AFTERNOON...AND BY
NIGHTFALL THERE IS ENOUGH COLD AIR THAT WE WILL BE SEEING SNOW IN
THE MTNS- ESPECIALLY HIGHER ELEVATIONS. THE PRECIP OVERNIGHT SHOULD
QUICKLY BECOME MAINLY WESTERN SLOPE SNOW SHOWERS...BUT WITH ENOUGH
LOW LEVEL MOISTURE FOR ACCUMULATING SNOWS IN THE FAVORED WESTERN
SLOPE AREAS. CURRENT THINKING IS THAT THE AIR IS NOT COLD ENOUGH TO
PICK UP MOISTURE FROM THE GREAT LAKES THOUGH...SO IT DOES NOT LOOK
LIKE WE WILL BE SEEING A PROLONGED PERIOD OF HEAVY UPSLOPE SNOW
SHOWERS. IN ADDITION...IT IS LIKELY TO WARM ENOUGH DURING THE DAY
MONDAY SO THAT FURTHER ACCUMULATION WILL BE TOUGH...SO WE ARE
THINKING THAT MOST OF THE ACCUMULATION WILL OCCUR SUNDAY NIGHT. WE
HAVE 4 TO 6 INCHES IN WESTERN GREENBRIER COUNTY...3 TO 4 INCHES IN
THE HIGHEST ELEVATIONS OF THE NC MTNS...AND GENERALLY 1 TO 2 INCHES
IN THE REST OF THE WESTERN SLOPES AREAS. THIS WOULD BE ENOUGH FOR AN
ADVISORY...ESPECIALLY CONSIDERING THE TIME OF YEAR...BUT SINCE IT IS
THE THIRD PERIOD AND WE ARE MORE CONCERNED WITH THE HEAVY RAIN
THREAT TONIGHT AND THE STRONG WINDS BEGINNING SUNDAY NIGHT WE WILL
WAIT ON ISSUING ANY WINTER WEATHER PRODUCTS.

OCCLUDED NOREASTER STILL HOVERING OFF THE NORTHEAST COAST. AS LONG
AS THIS SYSTEM REMAINS IN THIS AREA...WE WILL HAVE WINDY CONDITIONS
PERSISTING ACROSS THE AREA...ESPECIALLY ALONG AND WEST OF THE BLUE
RIDGE. NORTHWEST NORTH CAROLINA MOUNTAINS COULD HAVE SUSTAINED WINDS
OF 25 TO 40 MPH WITH GUSTS UP TO 70 MPH. THE NEW RIVER AND SOUTH
SHENANDOAH VALLEYS AND ALLEGHANY HIGHLANDS WILL ALSO BE WINDY WITH
SUSTAIN WINDS OF 20 TO 35 MPH WITH GUSTS UP TO 60 MPH. FOR THESE
AREAS...WE HAVE ISSUED A HIGH WIND WATCH SUNDAY NIGHT AND MONDAY. WE
HAVE ALSO ISSUED A HIGH WIND WATCH FOR THE FOOTHILLS OF SOUTHWEST
VIRGINIA AND NORTHWEST NORTH CAROLINA MOUNTAINS. THIS AREA WILL
LIKELY SEE WIND ADVISORY CRITERIA BUT WITH THE GROUND BEING
SATURATED...DOWN TREES AND POWER OUTAGES ARE POSSIBLE. OTHER AREAS
OUTSIDE THE WATCH COULD ALSO SEE DOWN TREES AND POWER OUTAGES BUT
WILL WAIT TO SEE IF LATER MODELS INCREASE WINDS OVER THE AREA AND
HOW MUCH RAIN THEY GET TONIGHT.

LONG TERM /MONDAY THROUGH SATURDAY/...

HOPEFULLY THIS NOREASTER WILL MOVE OUT TO SEA ON TUESDAY. THIS WILL
GIVE THE AREA A BRIEF BREAK FROM THE PRECIPITATION AND THE WIND. THE
NEXT SYSTEM TO BRING RAIN BACK INTO THE REGION WILL BE WEDNESDAY
THROUGH THURSDAY. SINCE WE HAVE CONCERNS IN THE SHORT TERM...RELIED
HEAVILY ON HPCS FORECAST. THEIR DISCUSSION IS PROVIDED BELOW...

ALL GUIDANCE INDICATES FORMATION OF BRIEF OMEGA BLOCKING OVER THE US
DURING THE MEDIUM RANGE PD. THIS BLOCKING APPEARS TO GRADUALLY BREAK
DOWN BY 10 DAYS. HPC PROGS BASED ON 00Z ECMWF MASS FIELDS FOR
PRELIMS SINCE MODEL HAS SHOW BEST CONTINUITY AND TRACK RECORD SINCE
FLOW BECAME BLOCKY ACROSS THE NATION OVER A WEEK AGO. VORTEX
COMPRISING RIGHT ARM OF OMEGA WILL KEEP PERSISTENT NLY GRADIENT
ALONG ATL SEABOARD...WITH IMPLICATIONS FOR TIDES ON
OCEAN...RIVERS...AND BAYS.  MEAN RIDGE CENTERED OVER ERN PLAINS WILL
KEEP THAT REGION DRY FOR SOME TIME TO COME...WITH SEVERAL PAC
SYSTEMS PILING INTO LEFT ARM OF BLOCK OVER THE WRN HALF OF THE US
BRINGING UNSETTLED WEATHER THERE.  FRONTAL SYSTEM FORMING TO THE LEE
OF THE ROCKIES MID PD WILL BE SLOW TO DISLODGE...KEEPING FOCUS OVER
THE HIGH PLAINS FOR PCPN.

HYDROLOGY...

RAINFALL OF 2 INCHES OR MORE IS LIKELY OVERNIGHT IN THE
FOOTHILLS AND PIEDMONT OF NORTHWEST NORTH CAROLINA AND SOUTHWEST
VIRGINIA. RAINFALL OF THIS AMOUNT WOULD CAUSE SOME SMALL STREAM
FLOODING...AND WOULD ALSO CAUSE AT LEAST MINOR FLOODING ALONG THE
DAN RIVER...WITH SIGNIFICANT WITHIN BANK RISES ON THE ROANOKE
RIVER AND THE JAMES RIVER. THERE IS A POTENTIAL FOR THUNDERSTORMS
WITH VERY HEAVY RAINFALL TO MOVE INTO THE NORTHWEST PIEDMONT OF
NORTH CAROLINA AND SOUTH SIDE VA.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...HIGH WIND WATCH FROM THIS EVENING THROUGH MONDAY AFTERNOON FOR
     VAZ009>020-022>024-032>035.

     FLOOD WATCH UNTIL 6 AM EDT EARLY THIS MORNING FOR VAZ032>035-
     043>047-058-059.

NC...HIGH WIND WATCH FROM THIS EVENING THROUGH MONDAY AFTERNOON FOR
     NCZ001>003-018-019.

     FLOOD WATCH UNTIL 6 AM EDT EARLY THIS MORNING FOR NCZ003>006-
     019-020.

WV...NONE.
&&

UPDATE...
AVIATION...DS

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE BLACKSBURG VA
355 PM EDT SAT APR 14 2007

NCZ004>006-020-VAZ043>047-058-059-152000-
STOKES-ROCKINGHAM-CASWELL-YADKIN-HENRY-PITTSYLVANIA-CAMPBELL-
APPOMATTOX-BUCKINGHAM-HALIFAX-CHARLOTTE-
355 PM EDT SAT APR 14 2007

...FLOOD WATCH IN EFFECT FROM 9 PM EDT THIS EVENING THROUGH LATE
TONIGHT...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL NORTH
CAROLINA...NORTHWEST NORTH CAROLINA...CENTRAL VIRGINIA AND SOUTH
CENTRAL VIRGINIA.

.DAY ONE...TONIGHT

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   FLOOD WATCH

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

STRONG NORTHWEST WINDS WILL OCCUR IN THE WAKE OF THE EXITING STORM
SYSTEM SUNDAY NIGHT AND MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED.

NCZ001-002-018-VAZ009>020-022>024-152000-
ASHE-ALLEGHANY NC-WATAUGA-SMYTH-BLAND-GILES-WYTHE-PULASKI-MONTGOMERY-
GRAYSON-CARROLL-FLOYD-CRAIG-ALLEGHANY VA-BATH-ROANOKE-BOTETOURT-
ROCKBRIDGE-
355 PM EDT SAT APR 14 2007

...HIGH WIND WATCH IN EFFECT FROM SUNDAY EVENING THROUGH MONDAY
AFTERNOON...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHWEST NORTH
CAROLINA...SOUTHWEST VIRGINIA AND WEST CENTRAL VIRGINIA.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   HIGH WIND WATCH

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE SUNDAY INTO MONDAY.

VAZ007-WVZ042>045-152000-
TAZEWELL-MERCER-SUMMERS-MONROE-GREENBRIER-
355 PM EDT SAT APR 14 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHWEST VIRGINIA AND
SOUTHEAST WEST VIRGINIA.

.DAY ONE...TONIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

SNOW SHOWERS WILL FOLLOW IN THE WAKE OF THE STORM SYSTEM SUNDAY
NIGHT INTO MONDAY NIGHT LIKELY RESULTING IN SEVERAL INCHES OF
SNOWFALL ACROSS THE HIGHER TERRAIN. IN ADDITION STRONG NORTHWEST
WINDS WILL FOLLOW THE SYSTEM SUNDAY NIGHT INTO MONDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

NCZ003-019-VAZ032>035-152000-
SURRY-WILKES-PATRICK-FRANKLIN-BEDFORD-AMHERST-
355 PM EDT SAT APR 14 2007

...FLOOD WATCH IN EFFECT FROM 9 PM EDT THIS EVENING THROUGH LATE
TONIGHT...
...HIGH WIND WATCH IN EFFECT FROM SUNDAY EVENING THROUGH MONDAY
AFTERNOON...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL NORTH
CAROLINA...NORTHWEST NORTH CAROLINA...CENTRAL VIRGINIA...SOUTH
CENTRAL VIRGINIA...SOUTHWEST VIRGINIA AND WEST CENTRAL VIRGINIA.

.DAY ONE...TONIGHT

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   FLOOD WATCH

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   HIGH WIND WATCH

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED.