Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 242353
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
753 PM EDT SUN MAY 24 2015

.SYNOPSIS...
HIGH PRESSURE BOTH SURFACE AND ALOFT WILL REMAIN OVER THE EASTERN
UNITED STATES THROUGH MONDAY. THIS WILL ENSURE DRY WEATHER FOR THE
REMAINDER OF THE HOLIDAY WEEKEND WITH TEMPERATURE AND HUMIDITY
TRENDING HIGHER. MOISTURE WILL RETURN TO THE AREA BY MONDAY AND
TUESDAY...WITH SHOWERS AND THUNDERSTORMS DEVELOPING
TUESDAY...BECOMING MORE WIDESPREAD ACROSS THE REGION WEDNESDAY
THROUGH THURSDAY.

&&

.NEAR TERM /THROUGH MONDAY/...
AS OF 230 PM EDT SUNDAY...

18Z SFC MAP SHOWS AXIS OF HIGH PRESSURE OFF THE ATLANTIC COAST
NOSING INTO THE REGION. MORE CUMULUS HAS FORMED TODAY UNDER NOSE OF
55+ DEGREE DEWPOINTS THAT HAVE ADVECTED INTO CENTRAL/EASTERN VA
AND NC.

SOUTHERLY WINDS ON WESTERN PERIPHERY OF DEPARTING HIGH WILL HELP
ADVECT A SHALLOW LEVEL OF LOW LEVEL MOISTURE INTO THE FAR SOUTHWEST
PORTION OF THE FORECAST AREA...AND THIS MAY BRING A BLANKET OF
STRATUS CLOUDS IN THIS REGION EARLY MONDAY MORNING. 850MB WINDS AT
15-20KTS TONIGHT WILL LIKELY HELP CREATE ANOTHER LARGE RIDGE/VALLEY
SPLIT IN TEMPS. SIMILAR TO SATURDAY MORNING...WENT A FEW DEGREES
ABOVE GUIDANCE FOR LOWS AT BLF AND OTHER HIGHER ELEVATION
SITES...WITH LOWS BELOW GUIDANCE IN THE VALLEYS SUCH AS BURKES
GARDEN.

HUMIDITY BEGINS TO RETURN MONDAY AS THE EASTERN EDGE OF PWAT PLUME
MOVES INTO FAR SW VA AND NW NC ON MONDAY. AS THE UPPER RIDGE AXIS
MOVES EAST...AND WE COME UNDER THE INFLUENCE OF A DEEP
SOUTH/SOUTHWESTERLY FLOW...WEAK DISTURBANCES WELL IN ADVANCE OF
NEGATIVELY TILTED UPPER LEVEL TROUGH IN THE CENTRAL U.S. BEGINS TO
ENCROACH OUR FAR SOUTHWEST AREA. THIS...COMBINED WITH SOME MODEST
INSTABILITY...MAY GENERATE WIDELY SCATTERED SHOWERS/STORMS MONDAY
AFTERNOON AND KEPT SMALL POPS IN THIS AREA.

TEMPS SHOULD AGAIN BE A COUPLE OF DEGREES WARMER MONDAY...SO LEANED
TOWARD THE WARMER GUIDANCE FOR HIGHS.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
AS OF 230 PM EDT SUNDAY...

UPPER LEVEL RIDGING WILL GRADUALLY SHIFT FARTHER EAST MONDAY NIGHT
ALLOWING PWATS TO QUICKLY INCREASE FROM THE SW AS MOISTURE TRANSPORT ON
DEEPENING SOUTHERLY FLOW TAKES SHAPE. THIS MAY ALLOW SHOWERS/ISOLATED
STORMS TO LINGER WELL WEST OF THE BLUE RIDGE INTO EARLY TUESDAY AS
MODELS SHOW A LOBE OF DEEPER MOISTURE REMAINING ALONG THE WESTERN
SLOPES.

REMAINING RIDGING ALOFT FINALLY DEPARTS BY TUESDAY NIGHT IN RESPONSE TO
LOWERING HEIGHTS PER 5H TROFFINESS SWINGING BY TO THE NW. HOWEVER THE
PERSISTENT MOISTURE AXIS TO THE WEST MAY STILL BE SLOW TO PUSH EAST
GIVEN NEGATIVE TILT TO THE UPPER TROUGH AND PARALLEL SOUTHERLY FLOW
ALONG THE BACK OF THE DEPARTING RIDGE. THIS MAY TEND TO HOLD THE BEST
CONVECTION TO THE FAR WESTERN MOUNTAINS TUESDAY WITH COVERAGE SLOWLY
SHIFTING EAST TUESDAY NIGHT AS A WEAK MID LEVEL WAVE RIDES UP FROM THE
SW. THUS WILL EDGE CHANCE POPS ONLY EAST TO THE FOOTHILLS TUESDAY
AFTERNOON GIVEN WEAK CAPES DESPITE INCREASING MOISTURE. APPEARS BEST
COVERAGE TUESDAY NIGHT WESTERN RIDGES WHERE WILL BUMP POPS TO LOW
LIKELYS FAR WEST OVERNIGHT...BUT STILL ONLY LOW CHANCE BLUE RIDGE AND
POINTS EAST AS THE TROUGH TO THE WEST SHARPENS.

WEAK SURFACE TROUGH ASSOCIATED WITH THE WEAKNESS ALOFT SLIDES ACROSS
THE REGION WEDNESDAY...STALLING ACROSS THE EAST WEDNESDAY NIGHT.
FORECAST PWATS OF 1.5-2.0 INCHES ALONG WITH CAPES OF 500-1K J/KG SHOULD
COMBINE WITH COOLING ALOFT/LESS CAP TO PRODUCE MORE IN THE WAY OF
WIDESPREAD SHRA/TSRA ESPCLY MOUNTAINS...AND ACROSS THE EAST WEDNESDAY
AFTERNOON/EVENING WITH A WEAK LEE TROUGH. THEREFORE WILL KEEP HIGHER
LIKELY POPS GOING MOUNTAINS WITH AT LEAST CHANCE COVERAGE EAST LATER IN
THE DAY/EVENING. WINDS ALOFT NOT VERY IMPRESSIVE WHILE STEERING QUITE
WEAK AND GIVEN HIGH MOISTURE CONTENT COULD BE MORE OF A HEAVY RAIN VS
SEVERE THREAT INTO WEDNESDAY NIGHT.

TEMPS TO BECOME WARM/MUGGY THROUGH THE PERIOD AS DEWPOINTS RISE INTO
THE 60S AND CLOUDS INCREASE ESPCLY WEST. APPEARS OVERALL HIGHS MOSTLY
75-80 WEST AND LOW/MID 80S EAST WITH LOWS 60-65.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
AS OF 145 PM EDT SUNDAY...

A VERY WARM AND MUGGY PERIOD MORE REMINISCENT OF SUMMER LOOKS TO
PREVAIL FOR LATE WEEK INTO NEXT WEEKEND AS A MOIST SOUTH/SW FLOW
PERSISTS BETWEEN HIGH PRESSURE OFFSHORE AND UPPER TROFFINESS TO THE NW.
THIS PROVIDED STRONG HEATING SHOULD RESULT IN AT LEAST DIURNAL SHOWERS
AND STORMS ESPCLY OVER THE MOUNTAINS WHERE AIDED BY OROGRAPHICS AND
DIFFERENTIAL HEATING. HOWEVER COVERAGE MAY BE A BIT LESS...AND PERHAPS
MORE IN THE EAST THURSDAY...IN THE WAKE OF AN EARLIER PASSING SURFACE
TROUGH THAT WILL PRODUCE A WEAK WEST/NW TRAJECTORY THURSDAY AFTERNOON.
THIS SEEN VIA A SLIGHT DROP IN MODEL PWATS BEFORE RETURN SW FLOW TAKES
SHAPE FRIDAY WHEN OVERALL FOCUS WILL BE LESS...BUT WITHOUT MUCH CAP
APPEARS SOME SCATTERED CONVECTION LIKELY.

UPPER HEIGHTS WILL SLOWLY FLATTEN NEXT WEEKEND AS ANOTHER 5H TROUGH
STARTS TO SINK SOUTH FROM THE UPPER MIDWEST WITH ITS ASSOCIATED COLD
FRONT LIKELY OOZING TOWARD THE AREA BY SUNDAY. MODELS DIFFER ON HOW
FAST THIS BOUNDARY PUSHES SE WITH THE EARLIER EC MORE HUNG UP TO THE NW
PER WAVES ALONG THE FRONT...WHILE THE GFS MORE BACKDOOR FASHION AND
FASTER. HOWEVER APPEARS THAT THE BOUNDARY WILL BE CLOSE ENOUGH TO
PRODUCE MORE WIDESPREAD SHOWERS/STORMS SUNDAY AFTERNOON ESPCLY
NORTHERN/WESTERN SECTIONS...WITH MORE SCATTERING SATURDAY OUTSIDE OF
THE NW WHERE MORE ORGANIZED PRE-FRONTAL BANDS COULD DROP IN LATE.

OTHERWISE OVERALL TREND OF EARLY FOG TO BECOMING PC DURING THE DAY WITH
MORE CLOUDS BY SUNDAY...AND DIURNAL CHANCE POPS...EXCEPT SOME LIKELY
POPS WEST LATER IN THE WEEKEND. EXPECT TEMPS TO SLOWLY CLIMB EACH DAY
WITH HIGHS POSSIBLY TOUCHING 90 OUT EAST OVER THE WEEKEND WITH MAINLY
80S ELSEWHERE. LOWS LOOK QUITE WARM AND MUGGY..ONLY IN THE 60S AT BEST
GIVEN MOISTURE AROUND.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
AS OF 740 PM EDT SUNDAY...

VFR CIGS EXPECTED TO CONTINUE THROUGH THE TAF VALID
PERIOD...ALTHOUGH SOME SUBTLE SIGNS OF BIGGER CHANGES TO TAKE
PLACE THROUGH THE WEEK...WILL BECOME EVIDENT THIS TAF VALID
PERIOD. THE UPPER RIDGE CENTERED OVER THE REGION WILL CONTINUE TO
DRIFT SLOWLY EAST THROUGH MONDAY...MOVING TOWARD THE COAST BY
TUESDAY. A BROAD DIFFLUENT UPPER TROUGH ENCOMPASSES MUCH OF THE
U.S. WEST OF THE MISSISSIPPI RIVER...AND THIS WILL BE EXPANDING
FURTHER EAST THROUGH THE MID PART OF THE WEEK. A SERIES OF UPPER
SHORT WAVES WILL TRACK FROM THE MID-SOUTH TO THE NORTHEAST MON-
WED...EACH BREAKING DOWN THE UPPER RIDGE AND FORCING IT TO SHIFT
FURTHER EAST. LOW-LEVEL MOISTURE WILL BE ON THE INCREASE WITH
SOUTHWEST FLOW AROUND A BERMUDA HIGH. THIS WILL RESULT IN
INCREASING CU DEVELOPMENT IN THE 040-060 RANGE MON
AFTERNOON WITH PERIODS OF BKN CIGS IN THIS VFR RANGE POSSIBLE MON
AFTERNOON...ESPECIALLY WEST OF THE BLUE RIDGE...BUT FEEL THAT THE
POTENTIAL FOR SHRA/TSRA WILL REMAIN WEST OF THE CWA FOR MON.
SLIGHT CONCERN FOR LOWER CIGS IN STRATUS WEST OF THE BLUE RIDGE IN
THE 10Z-14Z TIME FRAME AS ADVERTISED BY NAM/GFS LOW-LEVEL MOISTURE
FIELDS...BUT HAVE LEFT OUT FOR NOW WITH LIMITED SUPPORT VIA BUFKIT
SOUNDINGS OR MODEL GENERATED TAFS. THE INCREASED MOISTURE IN THE
BOUNDARY LAYER MAY LEAD TO SOME BRIEF MVFR BR AT THE USUAL SPOTS
MON MORNING...BUT OVERALL FEELING IS THAT THE POTENTIAL FOR SUCH
IS LOW AT THIS POINT. EARLY LOW END GUSTY WINDS WILL DECREASE TO
5KTS OR LESS BY 02Z...BACKING SLIGHTLY TO SSE AT MANY LOCATIONS
WHERE NOT CALM. WINDS WILL BECOME SSW-SW AFT 13Z MON WITH SPEEDS
7-10KTS AND LOW END GUSTS LIKELY AT BLF/ROA/BCB BY LATE MORNING
THROUGH THE AFTERNOON.

MEDIUM TO HIGH CONFIDENCE IN CEILINGS THROUGH THE TAF VALID
PERIOD. MEDIUM TO HIGH CONFIDENCE IN VISIBILITIES THROUGH THE TAF
VALID PERIOD. MEDIUM TO HIGH CONFIDENCE WIND SPEED/DIRECTION
THROUGH THE TAF VALID PERIOD.

EXTENDED AVIATION DISCUSSION...

SOUTH-SOUTHWEST WINDS WILL CONTINUE TO BRING INCREASING MOISTURE
LEVELS INTO THE REGION...ESPECIALLY WEST OF THE BLUE RIDGE TUESDAY.
MEANWHILE...THE UPPER-LEVEL WILL BECOME INCREASINGLY FAVORABLE FOR
SHOWERS/THUNDERSTORMS AS DISTURBANCES EMANATE FROM A BROAD UPPER
TROUGH ACROSS THE CENTRAL/WESTERN U.S. EXPECT SCATTERED
SHOWERS/THUNDERSTORMS MAINLY THROUGH THE I-77 CORRIDOR TUESDAY
AFTERNOON...SPREADING FURTHER EAST ACROSS MUCH OF THE CWA
WEDNESDAY THROUGH THE END OF THE WEEK. WED-THU AT THIS POINT
APPEAR TO BE THE MOST ACTIVE DAYS FOR THUNDERSTORMS...WITH SOME
STRONG THUNDERSTORMS AND HEAVY RAIN POSSIBLE DURING THIS TIME
FRAME. THE THREAT FOR SHOWERS/THUNDERSTORMS MAY WELL LINGER FOR
SEVERAL SUBSEQUENT DAYS AS A WEAK FRONTAL BOUNDARY/BAROCLINIC ZONE
STALL ACROSS THE REGION WITH ADDITIONAL UPSTREAM ENERGY REMAINING
IN PLACE.

OUTSIDE SHOWERS/THUNDERSTORMS...CONDITIONS SHOULD GENERALLY BE VFR
OR MVFR AT WORST...BUT INCREASING LIKELIHOOD OF EARLY MORNING
IFR- LIFR CONDITIONS IN BR/FG AND LOW CLOUDS AS MOISTURE LEVELS
INCREASE AND LATE DAY SHOWERS LEAVE WET GROUND IN PLACE.

&&

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

&&

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


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