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 282355
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
755 PM EDT THU MAY 28 2015

.SYNOPSIS...
A WEAK FRONTAL BOUNDARY WILL APPROACH THE AREA FROM THE NORTHWEST...
BUT IT WILL BE UNABLE TO DISLODGE THE WARM AND HUMID AIR
ENTRENCHED ACROSS THE REGION. THIS WILL KEEP SHOWERS AND
THUNDERSTORMS IN OUR FORECAST THROUGH THE END OF THE WEEK. HIGH
PRESSURE WILL BRIEFLY BUILD IN AND GIVE THE AREA A MOSTLY DRY
SATURDAY...BEFORE ANOTHER FRONTAL SYSTEM BRINGS SHOWERS AND
THUNDERSTORMS BACK TO OUR FORECAST FOR SUNDAY. COOLER AND SOMEWHAT
DRIER CONDITIONS WILL THEN BUILD IN FROM THE NORTH THROUGH THE
FIRST PART OF NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
AS OF 755 PM EDT THURSDAY...

PREVIOUS FORECAST FOR OVERNIGHT PERIOD STILL ON TRACK AND
VERIFYING WELL...ALTHOUGH HAVE MADE A FEW ADJUSTMENTS TO GRIDS
OVER THE PAST SEVERAL HOURS TO KEEP UP WITH SIGNIFICANT CHANGES TO
HOURLY TEMPERATURES IN TIME AND SPACE ASSOCIATED WITH
SHOWER/THUNDERSTORM OUTFLOW BOUNDARIES. ALSO BUMPED UP THREAT OF
PRECIPITATION ACROSS PIEDMONT FROM CAMPBELL COUNTY VA EAST...WHERE
LARGE AREA OF SLOW MOVING CONVECTIVE ACTIVITY HAS SET UP.

TRENDS DURING THE PAST HOUR HAVE BEEN TOWARD SLOW STRATIFICATION
OF AIRMASS AND DECREASING INTENSITY/COVERAGE AS LOSS OF DAYTIME
HEATING AND BOUNDARY LAYER INCREASINGLY BECOMING OVERWHELMED BY
COOL OUTFLOW BOUNDARIES. WILL UPDATE GRIDS AGAIN SHORTLY TO
REFLECT AREA THAT WILL HAVE THE GREATEST THREAT FOR SOME LATE
NIGHT FOG...SPECIFICALLY WHERE RAIN HAS FALLEN AND SKIES CLEAR.

OTHERWISE...FORECAST FOR LATER TONIGHT AS FAR AS TEMPS/DEW POINTS
AND DIMINISHING THREAT OF ANY ADDITIONAL RAIN STILL LOOKS GOOD.

AS OF 330 PM EDT THURSDAY...
AMORPHOUS WEATHER PATTERN WITH AMPLE INSTABILITY BUT WEAK
DYNAMICS CONTINUES TO AFFECT THE REGION THROUGH THE SHORT TERM. A
DIFFUSE FRONT TO OUR NORTHWEST WILL SAG IN OUR DIRECTION AND ADD A
LITTLE SUPPORT TO OROGRAPHIC FORCING OF DIURNAL CONVECTION TO
GENERATE THE BETTER CHANCES OF PRECIPITATION FROM THE BLUE RIDGE
WEST. HOWEVER...SCATTERED ACTIVITY IS EXPECTED TO SPILL INTO THE
UNSTABLE AIR OVER THE PIEDMONT AS. WITH LACK OF DYNAMIC SUPPORT
THE OVERALL SEVERE THREAT IS LOW BUT OUTFLOW BOUNDARY INTERACTION
MAY GENERATE A PULSE STORM OR TWO THAT WARRANT ATTENTION. MAINLY
EXPECTING RELATIVELY SLOW MOVING HEAVY RAINERS BUT QUITE DRY
ANTECEDENT CONDITIONS WILL PROHIBIT ANY HYDRO ISSUES. ACTIVITY
WILL QUIET DOWN WITH LOSS OF HEATING AFTER SUNSET SO EXPECTING
MAINLY DRY CONDITIONS FOR THE OVERNIGHT. BY TOMORROW...HIGH
PRESSURE CENTERED OFF THE COAST WILL BRING SOUTHEASTERLY WINDS TO
THE REGION AND PUSH THE WASHED OUT FRONTAL BOUNDARY BACK
NORTHWARD. THIS WILL AGAIN BRING THE GREATEST CHANCES FOR SHOWERS
AND THUNDERSTORMS TO AREAS FROM THE BLUE RIDGE WEST WITH THE
PIEDMONT/SOUTHSIDE LOOKING MOSTLY DRY. NO AIRMASS CHANGE SO
CONDITIONS WILL REMAIN WARM AND A BIT HUMID WITH MINS TONIGHT
AROUND 60 WEST OF THE RIDGE TO LOW/MID 60S EAST...AND HIGHS FRIDAY
GENERALLY UPPERS 70S/LOWER 80S WEST TO MIDDLE 80S EAST.

&&

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

CONVECTION SHOULD CONTINUE TO HAVE A STRONG DIURNAL TENDENCY WITH
ANY WEAK FORCING LIFTING WELL TO NORTH FRIDAY NIGHT AND ONLY WEAK
SOUTHERLY FLOW TO KEEP A FEW SHWRS GOING INTO THE EVENING NEAR THE
BLUE RIDGE. OTHERWISE REDUCING POPS BELOW SLIGHT CHANCE BY MIDNIGHT
OR SOON THEREAFTER.

MODELS IN AGREEMENT THAT SOME DRIER AIR WRAPS CLOCKWISE AROUND THE
SURFACE HIGH OFF THE MID ATLANTIC COAST FRIDAY NIGHT INTO SATURDAY
AND THIS CAN BE SEEN READILY IN THE PRECIPITABLE WATER FORECASTS
AND MODEL SOUNDINGS. THUS INSTABILITY LOOKS MUCH MORE LIMITED FOR
SATURDAY AFTERNOON AND OTHER THAN THE HIGHEST RIDGES PERHAPS
GETTING ENOUGH LIFT FOR SOME SHOWER OR ISOLD THUNDER...MAINLY IN
WEST VIRGINIA...THINK MOST AREAS WILL ACTUALLY BE DRY AND ALSO
FAIRLY WARM FOR SATURDAY. LOWERED POPS TO SLIGHT CHC FROM BLUE
RIDGE AND NORTHWESTWARD...WITH LOW CHC CONFINED TO WEST VIRGINIA
COUNTIES AND ALONG STATE BORDER WITH VIRGINIA...INCLUDING
ALLEGHANY HIGHLANDS. MAY HAVE TO WATCH PIEDMONT AREAS OVERNIGHT
SAT NIGHT FOR A STRAY SHOWERS AS MOISTURE BEGINS TO RETURN
AGAIN...BUT FOR NOW LEAVING POPS BELOW MENTIONABLE THRESHOLD THERE
FROM SAT THROUGH SAT NIGHT.

BY SUNDAY MOISTURE CONTINUES TO INCREASE SLIGHTLY FROM THE SOUTH BUT
THEN ALSO FROM THE NORTHWEST AS INCREASED CONVERGENCE ALONG A SLOWLY
APPROACHING WEAK FRONTAL BOUNDARY BEGINS TO SQUEEZE DEEPER MOISTURE
BACK INTO AREA.  THUS LOOKING LIKE A RETURN TO MORE ACTIVE DAY FOR
CONVECTION...BUT GIVEN THE GENERALLY WEAK FORCING AM STILL NOT
CONVINCED THAT COVERAGE WILL BE ALL THAT WIDESPREAD...AND THUS THINK
CHANCE POPS MAY STILL BE ADEQUATE TO DESCRIBE EXPECTED COVERAGE IN
MOST AREAS.  LOWERED POPS SOMEWHAT...BUT STILL LEAVING SOME LOW
LIKELY VALUES IN MOUNTAINS...BUT HOLDING OFF ON ANY MENTION IN
PIEDMONT UNTIL AFTERNOON AND KEEPING LOW CHANCE THERE.  NAM DEPICTS
SLIGHTLY MORE SOUTHERLY FLOW WITH GFS A BIT MORE SW...THUS SOME QSTN
HOW FAR EAST OF BLUE RIDGE STORMS MAY DRIFT BY LATE AFT/EVE...BUT
WITH THE CONVERGENCE FROM WEAK BOUNDARY THIS COULD BE AN OVERNIGHT
WHERE SOME SHOWERS OR EVEN A THUNDERSTORM OR TWO LINGER MUCH OF THE
NIGHT...SO KEPT POPS UP IN THE CHC CATEGORY SUNDAY NIGHT.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 330 PM EDT THURSDAY...

MODELS HAVE CLUSTERED AROUND A BASIC SOLUTION OF BUILDING A DECENT
SUMMER WEDGE BUILDS ON OVER THE FORECAST AREA MONDAY NIGHT INTO
WEDNESDAY. WILL TRIM BACK MAXIMUM TEMPERATURES A CATEGORY OR TWO BUT
AMOUNT OF HEATING WILL DEPEND ON AMOUNT OF CLOUDS. PLUS THE WEDGE
WILL BE SHALLOW. THE BOUNDARY AT 850 NEVER MAKES IT SOUTH THROUGH
THE REGION AND WITHOUT A BIG CHANGE IN AIRMASS...MOIST DEW POINTS
WILL LIMIT HOW COOL IT GETS AT NIGHT AND SO EACH DAY WILL BE
STARTING WITH MILD TEMPERATURES. THE EAST TO SOUTHEAST SURFACE WINDS
WILL PROVIDE SOME UPSLOPE COMPONENT FOR INCREASED PROBABILITY OF
PRECIPITATION ALONG THE BLUE RIDGE THROUGH TUESDAY NIGHT.

BY WEDNESDAY AND THURSDAY AREA WILL BE UNDER RIDGING ALOFT WITH LOW
LEVEL FLOW GENERALLY OUT OF THE SOUTHEAST. SURFACE BOUNDARY AND
WEDGE TRICKY TO DISTINGUISH BY DAY 7. WILL HAVE DRY WX ON
THURSDAY.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
AS OF 755 PM EDT THURSDAY...

LATEST RADAR TRENDS SHOWING DIMINISHING AREA OF SHOWERS/STORMS
WITH LOSS OF DAYTIME HEATING AND INCREASING CONTAMINATION OF
BOUNDARY LAYER DUE TO COOL OUTFLOW BOUNDARIES. NO TERMINAL
FORECAST POINT EXPECTED TO SEE ANY ADDITIONAL RAIN TONIGHT...
ALTHOUGH WILL CONTINUE TO MENTION VCTS AT KBLF AND KDAN UNTIL 02Z-
03Z/10PM-11PM UNTIL WEATHER IN THAT AREA DISSIPATES.

HOWEVER...WITH CLEARING SKIES AND A MOIST GROUND NOW IN MANY
AREAS...EXPECT TO SEE DEVELOPMENT OF LATE NIGHT FOG...AND THIS
HINTED WELL IN LAMP GUIDANCE. SHOULD SEE LATE NIGHT PERIOD OF IFR
TO LIFR RESTRICTIONS...AT LEAST TO VISIBILITY...AT
KLYH...KDAN...KBCB...KLWB WHERE RAIN FELL EARLIER THIS
EVENING...WITH MVFR RESTRICTIONS POSSIBLE AT KBLF. FOR NOW...HEAT
ISLAND EFFECT AROUND KROA SHOULD KEEP VISIBILITY OUT OF MVFR
RANGE...BUT BRIEF INTRUSION TO 4-5SM POSSIBLE RIGHT AROUND
SUNRISE CAN NOT ENTIRELY BE RULED OUT.

ANY LATE NIGHT FOG/STRATUS WILL BURN OFF RAPIDLY AFTER DAYBREAK
ON FRIDAY...TO BE FOLLOWED BY ANOTHER ROUND OF DIURNALLY-DRIVEN
CONVECTION BY OR SHORTLY AFTER NOON IN THE MOUNTAINS AND
FOOTHILLS...PERHAPS A COUPLE-FEW HOURS LATER OUT ACROSS THE
PIEDMONT TERMINAL FORECAST SITES. HOWEVER...CONFIDENCE FOR EXACT
PLACEMENT OF CONVECTIVE CELLS STILL TOO FAR OUT/LOW TO PLACE
ANYTHING OTHER THAN A VCTS IN THE TERMINAL FORECAST TEXT.

EXTENDED AVIATION DISCUSSION...

THROUGH THE UPCOMING WEEKEND...A MOIST UNSTABLE AIR MASS WILL
REMAIN IN PLACE ACROSS THE REGION WITH ONLY WEAK FORCING. THIS
WILL RESULT IN MAINLY SLOW MOVING DIURNALLY DRIVE DEEP CONVECTION
DURING THE AFTERNOON AND EVENING HOURS FOLLOWED BY STABLE
CONDITIONS AT NIGHT.

A FRONTAL SYSTEM WILL APPROACH FROM THE NORTH DURING THE
WEEKEND...BUT WILL LIKELY REMAIN WELL NORTH OF THE FORECAST AREA
THROUGH SUNDAY. THUS...NO CHANGE IN AIR MASS IS EXPECTED THROUGH
THE PERIOD.

WITH MOIST/STABLE CONDITIONS AT NIGHT...PATCHY LATE NIGHT/EARLY
MORNING LOW CLOUDS/FOG AND ASSOCIATED IFR-LIFR CIGS/VSBYS WILL BE
POSSIBLE EACH MORNING...BUT LIMITED TO A FEW HOURS BEFORE DAYBREAK
AND QUICKLY BURNING OFF AFTER SUNRISE.

&&

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

&&

$$
SYNOPSIS...MBS
NEAR TERM...MBS/WERT
SHORT TERM...SK
LONG TERM...AMS
AVIATION...MBS/PM/WERT



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