Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 040023
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
823 PM EDT SUN MAY 3 2015

.SYNOPSIS...
WITH HIGH PRESSURE SHIFTING OFF THE COAST TONIGHT...EXPECT A
SUMMER LIKE WEATHER PATTERN WITH SPOTTY SHOWERS AND A FEW
THUNDERSTORMS DEVELOPING ACROSS THE MOUNTAINS ON MONDAY AND
TUESDAY. A TROPICAL LOW PRESSURE SYSTEM WILL PUSH NORTH FROM THE
CARIBBEAN TOWARD THE CAROLINA COAST ON WEDNESDAY...WHICH WILL
HELP DRAW A BACKDOOR COLD FRONT ACROSS THE MID ATLANTIC WEDNESDAY
NIGHT AND THURSDAY.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 823 PM EDT SUNDAY...

UPDATED POPS TO REMOVE THE ISOLATED SHOWERS ALONG THE SOUTHERN
BLUE RIDGE MOUNTAINS. THIS IS SUPPORTED BY THE HIRESW-ARW
AND RNK WRFARW. MID AND HIGH CLOUDS AS SEEN ON SATELLITE IMAGES
PUT A LID ON THE INSTABILITY ACROSS THE HIGH TERRAIN AND
CONVECTION ASSOCIATED WITH WEAK UPPER LEVEL SHORTWAVE HAS
DISSIPATED. LIKE YESTERDAY EXPECT THE LOW CLOUDS TO ERODE OR
DIMINISH THIS EVENING INTO TONIGHT WITH THE LOSS OF SOLAR
HEATING...LEAVING ONLY OCCASIONAL PASSING HIGH CLOUDS OVERNIGHT.
HIGH PRESSURE WILL CONTINUE TO MOVE EAST ALONG THE CAROLINA COAST
TONIGHT. A SOUTHWESTERLY FLOW WILL PRODUCE A WARMER OVERNIGHT
WITH LOW TEMPERATURES READINGS FROM THE LOWER 40S IN THE COLDER
NORTHWEST VALLEYS TO THE LOWER 50S IN THE PIEDMONT.

A WARMER SOUTHWEST FLOW CONTINUES MONDAY AS THE UPPER LEVEL
RIDGING OVER THE CENTER OF THE COUNTRY DRIFTS EASTWARD. SCATTERED
LOW CLOUDS WILL DEVELOP LATE MORNING AND EXPECT A FEW SHOWERS AND
ISOLATED THUNDERSTORM DURING THE AFTERNOON. THE BEST CHANCE OF
CONVECTION WILL OCCUR SOUTHERN PORTIONS OF FORECAST AREA...WITH
THE DEEPER MOISTURE AND BETTER INSTABILITY ASSOCIATED WITH A WEAK
UPPER LEVEL DISTURBANCE. THE NAM...RAP...HIRESW-ARW SHOWED
CONVECTION DEVELOPING AFTER 18Z ESPECIALLY ALONG THE SOUTHERN
BLUE RIDGE. THE GFS IS THE MOST ROBUST WITH CONVECTION AND FURTHER
NORTH COMPARED TO MOST OF THE REST OF SOLUTIONS. BELIEVE THE GFS
IS OVERDONE BECAUSE OF THE DRY AIRMASS IN PLACE. HIGH TEMPERATURES
MONDAY WILL RANGE FROM AROUND 70 DEGREES IN THE MOUNTAINS TO THE
LOWER 80S IN THE PIEDMONT.


AS OF 330 PM EDT SUNDAY...

SATELLITE IMAGERY INDICATES SCATTERED CLOUDS ACROSS THE REGION
THIS AFTERNOON...A MIXTURE OF HIGH AND LOW CLOUDS. RAPID UPDATE
MODELS HAVE BEEN HINTING AT THE POSSIBILITY OF A FEW SHOWERS
DEVELOP ACROSS THE NORTH CAROLINA HIGHLANDS INTO EXTREME SOUTHERN
VIRGINIA THIS AFTERNOON THROUGH EARLY EVENING...HOWEVER RADAR
REMAINS CLEAR AS OF THIS WRITING...AND HIGH CLOUDS PASSING OVER
THE AREA SEEM TO BE KEEPING A LID ON INSTABILITY. WILL SIMPLY
CONTINUE TO MONITOR AS THE EVENING PROGRESSES.

EXPECT LOW CLOUDS TO DIMINISH TOWARD SUNSET...LEAVING ONLY
OCCASIONAL PASSING HIGH CLOUDS IN OTHERWISE CLEAR SKIES OVERNIGHT.
WITH HIGH PRESSURE NOW CENTERED NEAR THE CAROLINA COAST...MILDER
SOUTHWESTERLY WIND FLOW HAS BECOME ESTABLISHED...AND EXPECT
WARMER OVERNIGHT LOWS FOR MOST LOCATIONS...GENERALLY RANGING FROM
THE MID 40S TO THE LOW 50S.

MONDAY`S WEATHER PATTERN WILL BE SIMILAR TO THAT OF TODAY...ALBEIT
SLIGHTLY WARMER AS UPPER LEVEL RIDGING OVER THE CENTER OF THE
COUNTRY DRIFTS EASTWARD. WHILE STARTING THE DAY MOSTLY CLEAR...WE
CAN EXPECT ANOTHER ROUND OF SCATTERED LOW CLOUDS TO DEVELOP DURING
LATE MORNING...WITH A SPOTTY SHOWERS AND A FEW THUNDERSTORMS
DEVELOPING DURING THE AFTERNOON. HIGHEST RAIN CHANCES WILL BE FOUND
ACROSS THE MOUNTAINS SOUTH OF HIGHWAY 460...WHERE DEEPER MOISTURE
AND BETTER INSTABILITY ASSOCIATED WITH A WEAK UPPER LEVEL
DISTURBANCE WILL BE LOCATED. HOWEVER...WOULD NOT BE SURPRISED TO
SEE A FEW SHOWERS DEVELOP FURTHER TO THE NORTH AS WELL. AFTERNOON
HIGHS WILL BE SLIGHTLY WARMER COMPARED TO SUNDAY...RANGING FROM
THE MID AND UPPER 70S ACROSS THE MOUNTAINS...TO THE LOW 80S
FURTHER EAST.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 315 PM EDT SUNDAY...

GIVEN THE LIMITED ISOLATED CONVECTION MAY FORM OVER THE HIGHER
TERRAIN DURING THE DAY MONDAY WILL QUICKLY WEAKEN BUT MAY SLIDE INTO
THE FOOTHILLS BEFORE IT COMPLETELY DIES WITH THE MEAN FLOW EASTERLY
BUT WEAK. DOES NOT APPEAR THAT WEAK UPPER WAVE OVER SOUTHEASTERN NC
WILL HAVE ANY INFLUENCE ON KEEPING ANYTHING GOING OVERNIGHT AND
THERE IS STILL PRETTY DRY AIR ALOFT. WHILE LOW LEVEL MOISTURE EVER
SO SLOWLY INCREASES AGAIN FOR TUESDAY...INSTABILITY REMAINS VERY
LIMITED.  SOUTHERLY LOW LEVEL FLOW...WITH WEAK NORTHERLY FLOW AT MID
LEVELS...WILL HELP WITH CONVERGENCE ALONG BLUE RIDGE AND ANY WEAK
STORMS WILL HARDLY MOVE. THUS WHILE COVERAGE OF CONVECTIVE ACTIVITY
WILL BE LIMITED...STORMS COULD PRODUCE SOME LOCALLY HEAVY RAINFALL
AMOUNTS DUE TO LITTLE MOVEMENT...AND EVEN WITH PRECIP WATER VALUES
GENERALLY BELOW ONE INCH...WILL HAVE TO WATCH FOR ISOLATED GULLY
WASHERS ALONG BLUE RIDGE...ESPECIALLY NW NC AND FAR SW VA.

ANY CONVECTION WILL BE STRONGLY TIED TO DIURNAL HEATING SO SHOULD
DISSIPATE AGAIN FAIRLY QUICKLY BY EARLY EVENING. WITH SLIGHT
INCREASING TREND IN LOW LEVEL MOISTURE THROUGH THIS PERIOD MIN TEMPS
SHOULD BE A COUPLE DEGREES MILDER COMPARED TO MONDAY NIGHT.

UPPER RIDGE REMAINS DOMINANT WEDNESDAY WITH MAX TEMPS PERHAPS THEIR
WARMEST OF THE WEEK...MID 80S PIEDMONT TO MID AND UPPER 70S MANY MTN
LOCATIONS.  WITH WEAK EASTERLY FLOW AT LOW LEVELS AND STILL SOME
CONVERGENCE OVER HIGHER TERRAIN...WILL ONCE AGAIN SEE SCATTERED WEAK
CONVECTION OVER HIGHER TERRAIN MAINLY...AND AGAIN SLOW MOVING. BY
LATE IN THE DAY A BACK DOOR COLD FRONT MAY APPROACH THE NORTHEAST
PORTION OF THE FCST AREA AS RIDGE AMPLIFIES OVER OHIO VALLEY BUT SO
DOES TROUGH OVER NEW ENGLAND AND DOWN INTO NEW JERSEY. THERE COULD
BE A SLIGHT ENHANCEMENT TO COVERAGE OF ANY WEAK CONVECTION ACROSS
THE NORTHERN EDGES BECAUSE OF THIS BOUNDARY...SO INCREASED POPS A
BIT TO THE NORTH OF A ROA TO LYH LINE. STILL ONLY LOW CHC CATEGORY
THOUGH. FARTHER SOUTH IN PIEDMONT OF SOUTHSIDE VA AND NORTH-CENTRAL
VA MAY NOT SEE ANYTHING BUT WITH OVERALL MOISTURE STILL INCREASING A
TAD FROM TUES AND POTENTIAL FOR THIS BACK DOOR COOL FRONT TO SNEAK
FARTHER SOUTH BY LATE IN THE DAY...THREW IN A SLIGHT CHC POP. THEN
ONCE AGAIN DAYTIME CONVECTION SHOULD DIE FAIRLY QUICKLY MOST
LOCATIONS...WITH POSSIBLE EXCEPTION OF NEAR BLUE RIDGE WHERE BETTER
UPSLOPE FLOW ALONG AND BEHIND BACK DOOR FRONT COULD KEEP ISOLATED
SHOWERS GOING A LITTLE LATER INTO OVERNIGHT. DONT SEE ENOUGH
MOISTURE AND COOL AIR ADVECTION FROM A STRONG ATLANTIC FETCH TO BE
TOO CONCERNED ABOUT LOW STRATUS AND FOG.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 335 PM EDT SUNDAY...

MAIN ISSUE THIS PERIOD WILL BE INTERPLAY BETWEEN SUB-TROPICAL LOW
DEVELOPING OFF OF THE FLORIDA ATLANTIC COAST AND THEN INITIALLY
DRIFTING NORTH...AND THE POSITION OF THE BACK DOOR FRONTAL BOUNDARY.
BECOMING MORE CONFIDENT THAT ON THURSDAY THE FRONT WILL CONTINUE TO
MOVE SOUTHWESTWARD...POSSIBLY AIDED BY THE STRENGTHENING LOW OFF THE
SOUTHEAST U.S. COAST. THIS WILL PLACE A FOCUS ON ANY CONVECTIVE
DEVELOPMENT MAINLY ACROSS THE WESTERN PORTION OF THE FCST
AREA...MAINLY WEST OF I-77...AND POSSIBLY EVEN FARTHER SOUTHWEST IF
TRENDS CONTINUE. A LITTLE TRICKIER IN SOUTHEAST WV AS FRONTAL
BOUNDARY COULD GET HUNG UP THERE OR COULD AT LEAST STILL BE IN THAT
AREA EARLIER IN THE DAY...SO KEPT A CHANCE POP FROM ALLEGHANY
HIGHLANDS SOUTH TOWARD NW NC FOOTHILLS. THIS ALL MAY NEED TO BE
PULLED FARTHER TOWARD SOUTHWEST AS WE GET CLOSER TO THURSDAY.

BY FRIDAY MOST LONGER RANGE MODELS ARE THEN SHIFTING THE LOW BACK
TOWARD THE WEST OR STALLING IT...WELL SOUTH OF US AND STILL PROBABLY
OFF THE COAST...AS PATTERN BECOMES BLOCKED.  IN THIS POSITION THERE
COULD ACTUALLY BE INCREASING SUBSIDENCE OVER OUR REGION INTO THE
WEEKEND...PERHAPS WITH STILL WEAK CONVERGENCE OVER MTNS AND AT LEAST
ISOLATED SHOWER ACTIVITY. THINK THUNDER CHANCES WOULD BE LIMITED
GIVEN THIS SUBSIDENCE ALOFT...SO KEPT THUNDER MENTION OUT BY
SATURDAY AND SUNDAY. THIS OF COURSE IS ALL VERY DEPENDENT ON WHERE
THIS SUB-TROPICAL LOW...POTENTIALLY WITH SOME TROPICAL
CHARACTERISTICS...ENDS UP DRIFTING. SO OVERALL A FAIRLY LOW
CONFIDENCE FORECAST. WHILE APPEARING LESS LIKELY WITH ALL 12Z MODEL
CYCLES THAT THIS WILL DRIFT NORTHWESTWARD ALL THE WAY INTO THE
SOUTHERN APPALACHIANS...THIS SYSTEM NEEDS TO BE WATCHED CLOSELY
SINCE A TRACK THIS FAR NORTH COULD MEAN SIGNIFICANT RAINFALL IF IT
DID. SUCH A PATH WOULD ALSO HAVE A MAJOR INFLUENCE ON HIGH TEMPS BY
LATE WEEK INTO THE WEEKEND...BUT FOR NOW THE RATHER WARM CONDITIONS
WITH RIDGE BEING THE DOMINANT FACTOR LOOK THE MOST LIKELY.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 745 PM EDT SUNDAY

VFR CIGS EXPECTED THROUGH THE TAF VALID PERIOD. HOWEVER...THERE IS
A PERSISTENT LAYER OF TRAPPED MID-LEVEL MOISTURE IN THE 050-080
RANGE UNDERNEATH AN PRONOUNCED INVERSION. THIS WILL PERSIST INTO
MONDAY WITH HIGH PRESSURE ALOFT OVER THE REGION. THUS...THERE WILL
BE PERIOD OF SCT-BKN050-080 CIGS...MOST PRONOUNCED DURING THE
MID-AFTERNOON/EARLY EVENING HOURS. A FRONTAL SYSTEM WILL ENCROACH
ON THE FAR NORTHERN FRINGES OF THE CWA LATE MON/MON NIGHT...BUT
WILL NOT ENTER THE CWA UNTIL TAKING ON A BACKDOOR CONFIGURATION
TUE- WED. SOME CIRRUS WILL AGAIN SPILL INTO THE REGION FROM THE
NORTHWEST IN ASSOCIATION WITH UPSTREAM CONVECTION ACROSS THE MID-
WEST/OHIO VALLEY. ADDED A BRIEF PERIOD OF EARLY MORNING GROUND FOG
FOR LYH/DAN...NOTING THAT MOISTURE LEVELS ARE SLOWLY
INCREASING...EARLY MORNING WINDS CALM...AND SEEING THAT DANVILLE
OBSERVED SUCH THIS MORNING. IF ANYTHING...MOISTURE LEVELS WILL
CONTINUE TO INCREASE WITH SOUTH FLOW...SO SEEMS EVEN MORE LIKELY
THAT A BRIEF PERIOD OF BR COULD OCCUR AT THESE LOCATIONS MON
MORNING. DID NOT INCLUDE AT LWB YET AS THE SFC AIR MASS THERE IS
MUCH DRIER. WILL NEED TO WATCH BCB...AS IT IS POSSIBLE THERE...BUT
NOT LIKELY. NO NEED FOR ANY FOG AT BLF/ROA AT THIS POINT. WINDS
PREVAILING SSE-SSW THROUGH MUCH OF THE TAF VALID PERIOD...VEERING
A LITTLE MORE TOWARD SW BY MON AFTERNOON. SPEEDS 5KTS OR LESS
OVERNIGHT...BECOMING 5-10KTS WITH SOME LOW END GUSTS AT
ROA/DAN/BCB/BLF AFT 17Z MON.

WHILE THE THREAT FOR SCT -SHRA INCREASES MON AFTERNOON NEAR THE
BLUE RIDGE AND INTO SW VA...PROBABILITIES REMAIN TOO LOW TO
INCLUDE AT SPECIFIC POINTS/TAF SITES AT THIS TIME.

MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD.
HIGH CONFIDENCE IN VFR VSBYS THROUGH 08Z...THEN MEDIUM CONFIDENCE
IN VSBYS...THEN HIGH CONFIDENCE AFT 14Z.
MEDIUM CONFIDENCE IN WIND DIR THROUGH THE TAF VALID
PERIOD...MEDIUM TO HIGH CONFIDENCE IN WIND SPD THROUGH THE TAF
VALID PERIOD.

NOTE...THE VISIBILITY SENSOR AT THE ASOS AT KBLF CONTINUES TO BE
SPORADICALLY OUT OF SERVICE. REPAIRS MAY NOT BE POSSIBLE UNTIL THE
END OF MAY. WILL CONTINUE WITH AMD NOT SKED APPENDED TO BLF TAF.

EXTENDED AVIATION DISCUSSION...

SCATTERED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS ARE
EXPECTED ALONG THE SOUTHERN BLUE RIDGE ON TUESDAY...WHICH WOULD
YIELD PERIODS OF MVFR CONDITIONS.

SHOWERS AND THUNDERSTORMS WILL BE MORE WIDESPREAD ON WEDNESDAY
AND THURSDAY AS A BACK DOOR FRONT ENTERS THE REGION. HIGH
PRESSURE ALOFT WILL LIMIT MUCH IN THE WAY OF ANY SYNOPTIC-SCALE
FORCING THROUGH THE PERIOD.

EXTENDED PERIODS OF SUB-VFR CIGS/VSBYS APPEAR UNLIKELY THIS WEEK...BUT
MORNING FOG WILL BECOME AN INCREASING ISSUE THROUGHOUT THE WEEK AT
THE USUAL SPOTS...LYH/DAN/BCB/LWB. WINDS OVERALL WILL BE ON THE
LIGHT SIDE THROUGH THE WEEK.

&&

.EQUIPMENT...
AS OF 200 PM EDT SUNDAY...

THE VISIBILITY SENSOR AT THE BLUEFIELD...KBLF...ASOS WILL ALTERNATE
BETWEEN AVAILABLE AND UNAVAILABLE UNTIL FURTHER NOTICE.

&&

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

&&

$$
SYNOPSIS...AMS/NF
NEAR TERM...KK/NF
SHORT TERM...SK
LONG TERM...SK
AVIATION...JR/NF/RAB
EQUIPMENT...AMS



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