Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 262220
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
620 PM EDT TUE MAY 26 2015

.SYNOPSIS...
HIGH PRESSURE OFF THE SOUTHEAST COAST WILL MAINTAIN A BROAD
SOUTHERLY FLOW OF DEEP MOISTURE INTO THE REGION THROUGH MUCH OF
THIS WEEK. AN UPPER LEVEL TROUGH OF LOW PRESSURE TO THE NORTHWEST
WILL GRADUALLY SLIDE EAST AND INTERACT WITH THIS MOISTURE ACROSS
THE AREA. THIS WILL RESULT IN PERIODIC ROUNDS OF SHOWERS AND
STORMS OVER THE NEXT FEW DAYS.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 600 PM EDT TUESDAY...

MADE SOME ADJUSTMENTS...MAINLY TO POP/WX GRIDS AT THIS TIME IN
CONCERT WITH LATEST HRRR AND NSSL WRF SIMULATED RADAR
FORECASTS...WHICH SEEM TO BE IN LINE WITH LATEST SYNOPTIC SCALE
MODEL TRENDS AS WELL REGARDING PRECIPITATION. INITIAL AREA...NOW
EXITING THE SOUTHERN SHENANDOAH VALLEY INTO LWX CWA...WILL
CONTINUE TO MOVE NORTHEAST AWAY FROM THE AREA. THE NEXT AREA TO
WATCH IS NOW DOWN IN GEORGIA PACKING QUITE A PUNCH THERE. FEEL
THAT THE REMNANTS OF THIS WILL WORK ITS WAY NORTHEAST INTO OUR CWA
TOWARD MIDNIGHT AND SEVERAL HOURS THEREAFTER...ALBEIT IN A
DIMINISHING STATE. THUS...HAVE DECREASED POPS FOR THE NEXT FEW
HOURS...THEN INCREASED FROM THE SOUTHWEST FROM 06Z ONWARD TOWARD
DAYBREAK WESTERN HALF. USED A BLEND OF SYNOPTIC AND MESOSCALE
MODEL POPS THROUGH 12Z...LEANING HEAVILY TOWARD THE HRRR.

TEMPS WERE A LITTLE TOO WARM IN RAIN COOLED AREAS AND A LITTLE TOO
COOL ACROSS THE PIEDMONT. MADE SOME MINOR ADJUSTMENTS TO BRING
BETTER IN LINE WITH CURRENT OBSERVATIONS. OTHERWISE...REMAINING
GRIDS LOOK GOOD AT THIS TIME AND DID NOT NEED ADJUSTMENT.

AS OF 215 PM EDT TUESDAY...

BANDS OF CONVECTION CONTINUE TO DEVELOP AND PUSH SLOWLY NE MAINLY JUST
WEST OF THE BLUE RIDGE WHERE 1000 J/KG ML CAPE EXISTS AND MOISTURE IS
DEEPER NEAR A FAINT SHORTWAVE LIFTING NE. MOST SHORT TERM GUIDANCE
CONTINUES TO FOLLOW SUIT WITH THE LATEST HRRR AND HIRES MODELS SLIDING
CLUSTERS OF DEEPER CONVECTION NE...PASSING ACROSS THE HIGHLANDS AND SRN
SHENANDOAH VALLEY BY EARLY THIS EVENING. EITHER SIDE OF THIS
AXIS...EXPECTING ONLY ISOLATED COVERAGE MAINLY ALONG THE BLUE RIDGE
WITH LITTLE OVER THE FAR EAST PER RIDGING...AND FAR WEST WHERE IN
BETWEEN LIFT SOURCES. THUS WILL HAVE CONTINUED LIKELY POPS FOR A WHILE
LONGER OVER PARTS OF THE WEST INTO THIS EVENING AND LOW TO SLIGHT
ELSEWHERE BEFORE TRIMMING BACK TOWARD SUNSET.

MAIN CONCERN OVERNIGHT SHIFTS TO ENERGY NOW WELL TO THE SW ALONG THE
LEADING EDGE OF THE NEXT UPSTREAM 5H TROUGH THAT WILL HELP EJECT A
SHORTWAVE NE INTO THE WESTERN PORTIONS AFTER MIDNIGHT. MODELS DISAGREE
ON THE DEGREE OF RESIDUAL DEEP CONVECTION WITH THIS FEATURE WITH SOME
HOLDING IT TOGETHER OVER THE FAR WEST LATE AND OTHERS FIZZLING
COVERAGE INTO LIGHTER SHOWERS BY DAYBREAK. GIVEN SPEED OF MOVEMENT WITH
THIS FEATURE AND PROGGED STRONG 85H THETA-E ALONG WITH GOOD MOISTURE
TRANSPORT OFF MOST GUIDANCE WILL REINTRODUCE LIKELY POPS WEST
AFTER THIS EVENING...AND SLIDE BETTER COVERAGE TOWARD THE BLUE
RIDGE EARLY IN THE MORNING AS CONVECTION WEAKENS. LEFT TEMPS CLOSE
TO THE LATEST MAV MOS WITH LOWS MOSTLY IN THE 60S PER DEEP
MOISTURE AROUND.

WEAK DAMPENING WAVE SLIDES EAST ACROSS THE REGION WEDNESDAY FOLLOWED BY
ANOTHER WEAK SHORTWAVE OVER THE SW LATE IN THE DAY. DESPITE DEEP
MOISTURE AND HIGH PWATS ESPCLY EAST...TIMING OF THIS FEATURE AND DEGREE
OF HEATING/INSTABILITY REMAINS IN QUESTION. LATEST SREF CONSENSUS WOULD
SUGGEST INITIAL BATCH OF SHRA WILL FADE NEAR THE BLUE RIDGE WED
MORNING FOLLOWED BY REDEVELOPMENT ACROSS EASTERN SECTIONS IN THE
AFTERNOON WHERE HEATING AND FORECAST CAPES APPEAR BEST. POTENTIAL
MORE OF A WEST WIND AND DRYING ALOFT PER LATEST SOUNDINGS COULD
LIMIT THINGS IN THE MOUNTAINS WHERE CLOUDS MAY LINGER LONGER.
THEREFORE TRIMMED BACK POPS A BIT BUT UPPED ALONG/JUST EAST OF THE
BLUE RIDGE WHERE CONVERGENCE LOOKS BETTER. HOWEVER OVERALL LIKELY
TO CHANCE POPS WITH SOME HEAVY RAIN POTENTIAL GIVEN EVEN LIGHTER
STEERING THAT TODAY. FOLLOWED CLOSER TO THE COOLER MAV TEMPS GIVEN
MORE CLOUDS AND MOISTURE/SHRA AROUND EARLY.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 225 PM EDT TUESDAY...

THE AREA RESETS IN THE SENSE THAT THE EXTRA INFLUENCE OF AN UPPER
TROUGH HEADING THROUGH THE NORTHERN END OF THE UPPER RIDGE ENDS.
WHAT IS LEFT OF THE TROUGH IS ALMOST WASHED OUT AND HEADS THROUGH
SOUTHEAST CANADA WEDNESDAY NIGHT INTO THURSDAY. WHAT REMAINS IS THE
PERSISTENT SOUTHEAST U.S. UPPER RIDGE...AND THERE WILL BE A NEW
UPPER TROUGH DEEPENING IN NORTHERN PLAINS STATES. THIS WILL PLACE
OUR AREA IN A SCENARIO COMPARABLE TO THE CONDITIONS OF TODAY. THERE
WILL BE PLENTY OF MOISTURE IN THE LOW LEVELS WITH GOOD DAYTIME
HEATING. UPPER LEVEL SUPPORT WILL BE AT A MINIMUM...SO SHOWER AND
THUNDERSTORM ACTIVITY DURING THIS PORTION OF THE FORECAST WILL BE
PRIMARILY DIURNAL IN NATURE. A ROUGE BIT OF ENERGY COULD GET EJECTED
EASTWARD OFF THE MAIN UPPER TROUGH TO HELP ENHANCE OR PROLONG
COVERAGE...BUT AT THIS TIME...PROJECTING ACCURATELY WHEN OR IF THAT
HAPPENS WOULD BE CHALLENGING.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 PM EDT TUESDAY...

SATURDAY INTO SUNDAY THE NEXT UPPER TROUGH MAKES HEADWAY INTO THE
RIDGE...JUST LIKE ITS PREDECESSOR A FEW DAYS PRIOR. ANTICIPATE THIS
FEATURE TO GENERATE A GREATER COVERAGE OF SHOWERS AND
STORMS...ESPECIALLY ACROSS THE WESTERN HALF OF THE AREA. THIS
ASSOCIATED SURFACE COLD FRONT IS EXPECTED TO THE AREA SUNDAY
NIGHT....AND STALL OVER OR JUST TO OUR SOUTH ON MONDAY. THE FRONT
WILL BUCKLE BACK NORTH EARLY NEXT WEEK AS SOUTHERLY FLOW AROUND THE
WEST SIDE OF THE HIGH RE-ESTABLISHES ITSELF. THIS WILL KEEP THE
CHANCE OF SHOWERS AND STORMS IN THE FORECAST...AGAIN WITH THE FOCUS
WITH THE GREATEST CONCENTRATION IN THE WEST.

&&

.AVIATION /22Z TUESDAY THROUGH SUNDAY/...
AS OF 1245 PM EDT TUESDAY...

STARTING TO SEE ISOLATED CONVECTION POP UP ACROSS THE FAR WEST
EARLY THIS AFTERNOON WHERE MOISTURE REMAINS DEEPER AND AIDED BY
DIFFERENTIAL HEATING. EXPECT THIS AREA TO GRADUALLY FILL IN AND
BECOME A BIT MORE ORGANIZED WHICH WILL AFFECT THE KBLF-KLWB
CORRIDOR AND POSSIBLY AROUND KBCB IF SHRA/TSRA SPILL FARTHER EAST.
THUS WILL CARRY A PREVAILING VCTS/VCSH AND TEMPO IN MORE IN THE
WAY OF MVFR TO IFR CONDITIONS PENDING IF A SHOWER OR STORM
DIRECTLY IMPACT ONE OF THESE LOCATIONS. OTRW EXPECTING MAINLY 4-6K
FT VFR CIGS THIS AFTERNOON WITH LITTLE SHOWER COVERAGE AT
KLYH/KDAN WITH ISOLATED POTENTIAL AT KROA. WINDS THIS AFTERNOON
WILL REMAIN OUT OF THE SOUTH 5-10KTS...WITH GUSTS 14-18KTS.

EXPECTING CONVECTION TO FADE WITH LOSS OF HEATING THIS EVENING AND
IN THE WAKE OF A WEAK IMPULSE SLIDING BY TO THE NE. THIS MAY LEAVE
MOST OF THE REGION IN VFR UNDER MID DECK WITH PERHAPS SOME MVFR IN
FOG THIS EVENING WHERE EARLIER RAIN OCCURRED. NEXT SHORTWAVE
TROUGH NOW TO THE SW WILL SLIDE INTO THE AREA LATER TONIGHT WITH
AN ASSOCIATED BAND OF SHRA/ISOLATED TSRA SPREADING IN FROM THE SW
AFTER MIDNIGHT. GUIDANCE HAS MOST OF THIS AFFECTING THE MOUNTAINS
MAINLY KBLF/KLWB LATE AND EAST TO KBCB/KROA AROUND DAYBREAK IF NOT
A BIT SOONER. THUS INCLUDING A PERIOD OF PREVAILING MVFR IN SHRA
EARLY WEDNESDAY MORNING WITH SOME OF THIS PERHAPS SLIDING INTO
KROA/KLYH WEDNESDAY MORNING WITH POSSIBLE MVFR. LOW CLOUDS AHEAD
OF THIS FEATURE MAY ALSO BRING MVFR TO IFR CIGS ALONG AND EAST OF
THE BLUE RIDGE OVERNIGHT BUT IFFY GIVEN MODEL TENDENCY TO BRING IN
STRATUS SO HELD OFF GOING THAT PESSIMISTIC FOR NOW.

EXTENDED AVIATION DISCUSSION...

WEDNESDAY...THE UPPER DISTURBANCE WILL CONTINUE TO SHIFT EAST
ACROSS THE REGION WITH DECREASING ACTIVITY OVER THE WEST BY MIDDAY
LIKELY REDEVELOPING ALONG AND EAST OF THE BLUE RIDGE WEDNESDAY
AFTERNOON. TIMING OF THIS WEAK TROUGH TRICKY AS COULD SEE MORE
DRYING ALOFT OVER THE WEST BY AFTERNOON PER LATEST BUFKIT
SOUNDINGS WITH CONVERGENCE OVER THE EAST. LATEST GUIDANCE EVEN
SUGGESTS A RETURN TO VFR WEST OF THE BLUE RIDGE WEDNESDAY
AFTERNOON WITH PERIODS OF MVFR/IFR OUT EAST PENDING CONVECTIVE
COVERAGE. THIS BOUNDARY DRIFTS INTO EASTERN VA THU BEFORE WASHING
OUT...SO ACTIVITY COULD BE SOMEWHAT MORE FOCUSED ALONG- EAST OF
THE BLUE RIDGE THURSDAY.

FOR THE REMAINDER OF THE PERIOD...A MOIST UNSTABLE AIR MASS
REMAINS ACROSS THE REGION WITH WEAK TRIGGERING MECHANISMS AND
DYNAMICS. A FRONTAL SYSTEM WILL APPROACH FROM THE NORTH BY THE
WEEKEND...BUT WILL LIKELY REMAIN WELL NORTH OF THE CWA. THUS...NO
CHANGE IN AIR MASS OR THE OVERALL SYNOPTIC PATTERN IS EXPECTED
THROUGH THE PERIOD.

EARLY MORNING LOW CLOUDS/FOG AND ASSOCIATED IFR-LIFR CIGS/VSBYS BECOME
INCREASINGLY MORE LIKELY THROUGH THE PERIOD...ESPECIALLY FOLLOWING
ANY LATE DAY RAINFALL. OTHERWISE...EXPECT MOSTLY VFR-MVFR CIGS
OUTSIDE HEAVIER SHOWERS/THUNDERSTORMS. WINDS REMAINING SW 5-10KTS
THROUGH MUCH OF THE PERIOD...EXCEPT VARIABLE AND GUSTY IN/NEAR
THUNDERSTORMS.

&&

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

&&

$$
SYNOPSIS...JH
NEAR TERM...JH/RAB
SHORT TERM...DS
LONG TERM...DS
AVIATION...JH/PM



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