Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 281825
AFDRNK

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

.SYNOPSIS...
HIGH PRESSURE IS CENTERED OFF THE SOUTHEAST ATLANTIC COAST AND WILL
MAINTAIN A BROAD SOUTHERLY FLOW OF MOISTURE INTO THE REGION
THROUGH THE REMAINDER OF THIS WEEK...A PATTERN THAT WILL FEATURE
WARM/HUMID SUMMERLIKE CONDITIONS. IN ADDITION TO THE HEAT/HUMIDITY...
THERE WILL BE A DAILY THREAT OF SCATTERED SHOWERS/STORMS. FOR
TODAY THE STORM POTENTIAL WILL BE MOST PRONOUNCED ALONG A WEAK
COLD FRONT THAT WILL BE APPROACHING THE AREA FROM THE NORTHWEST.
ADDITIONAL SHOWERS/STORMS WILL ACCOMPANY AN UPPER LEVEL
DISTURBANCE THAT WILL BE MOVING NORTHEAST THROUGH THE TENNESSEE
VALLEY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 955 AM EDT THURSDAY...

NO CHANGES NEEDED TO THE CURRENT FORECAST GRID SET. VISIBLE
SATELLITE IMAGES SHOW MOSTLY CLEAR SKIES OVER THE AREA AS ANY EARLY
MORNING FOG/STRATUS HAS BURNED OFF. APPROACHING BROAD/DIFFUSE
FRONTAL ZONE COMBINED WITH TROFINESS OVER THE REGION SHOULD BE
MORE THAN ENOUGH TO GENERATE SOME CONVECTIVE ACTIVITY THIS
AFTERNOON WITH OROGRAPHIC AFFECTS ADDING ENHANCEMENT FROM THE
BLUE RIDGE WESTWARD. WATER VAPOR IMAGERY SHOWED A BIT OF DRY AIR
ALOFT AND THIS WAS EVIDENT IN THE MORNING RNK SOUNDING AS WELL.
HOWEVER...THE COLUMN WILL MOISTEN TODAY AND EXPECT THE PROSPECT OF
SLOW MOVING THUNDERSTORMS WITH HEAVY RAIN IS STILL A GOOD BET.

PREVIOUS AFD...

A WEAK COLD FRONT EXTENDS FROM WESTERN NEW YORK INTO THE OHIO
VALLEY. THIS FRONT WILL MOVE SOUTHEAST INTO THE VA/WV HIGHLANDS
TODAY BEFORE DISSIPATING OVER THE REGION TONIGHT. IN ADDITION TO
THE FRONT...AN UPPER LEVEL DISTURBANCE WILL BE MOVING NORTHEAST
THROUGH THE TENNESSEE VALLEY...AND WILL INTERACT WITH THE
APPROACHING SURFACE FRONT TO PROVIDE LIFT FOR SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND EVENING. BEST COVERAGE OF
SHOWERS/STORMS TODAY WILL BE ACROSS THE MOUNTAINS WEST OF THE BLUE
RIDGE. STEERING WINDS ARE WEAK...SFC-20KFT MEAN FLOW OF 10KTS OR
LESS. THIS SUGGESTS ANY ACTIVITY THAT DEVELOPS TODAY WILL BE SLOW
MOVING AND WILL PROLONG THE HEAVIER SHOWERS ONCE THEY DEVELOP.
BOTH THE HIGH RES-WRF AND HRRR INDICATE THAT SHOWERS WILL BEGIN TO
DEVELOP OVER OUR MTNS AROUND MID-DAY...BECOMING MOST PRONOUNCED
BETWEEN 20Z/3PM AND SUNSET 01Z/9PM.

THE OVERALL THREAT FOR WIDESPREAD HAZARDOUS WEATHER IS
LOW...HOWEVER WITH PRESENCE OF THE UPPER LEVEL DISTURBANCE...CAN`T
RULE OUT SOME PULSE SEVERE STORMS THIS AFTERNOON. MODEL FORECAST
CAPE OF 2500 J/KG COUPLED WITH FORECAST DCAPE OF 1000 MAY BE
ENOUGH FOR SOME ISOLATED MICROBURSTS.

TEMPERATURES TODAY WILL BE SUMMER-LIKE WITH HIGHS IN THE
80S...COMPLIMENTED BY DEWPOINTS IN THE U50S-LOWER 60S.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
AS OF 500 AM EDT THURSDAY...

UPPER LEVEL RIDGING WILL REMAIN IN PLACE ALONG THE EAST COAST ON
FRIDAY...BUT WILL SLOWLY BREAK DOWN DURING THE WEEKEND...GIVING WAY
TO A FLATTENING...MORE ZONAL PATTERN AS AN UPPER LEVEL TROUGH SHIFTS
ACROSS EASTERN CANADA. THE PASSAGE OF THIS TROUGH WILL PUSH A COLD
FRONT SOUTHWARD...WHERE IT WILL ENTER OUR AREA SUNDAY AFTERNOON
BEFORE STALLING.

FOR FRIDAY AND SATURDAY...SPOTTY SHOWERS AND THUNDERSTORMS WILL
DEVELOP ACROSS THE MOUNTAINS EARLY BOTH AFTERNOONS...WITH COVERAGE
PEAKING DURING EARLY EVENING. CONVECTION WILL WEAKEN AND FADE AROUND
SUNSET WITH LOSS OF HEATING...BUT STILL EXPECT LIGHT SHOWER TO TWO
TO FLOAT ACROSS THE AREA OVERNIGHT. MAY SEE ONE OR TWO STORMS BECOME
STRONG...BUT THE BIGGER CONCERN IS LIGHT UPPER LEVEL WINDS/SLOW CELL
MOVEMENT...WHICH MAY RESULT IN LOCALLY HEAVY RAIN IF CELLS STALL OR
TRAIN. AFTERNOON HIGHS WILL RANGE FROM THE UPPER 70S AND LOW 80S
ACROSS THE MOUNTAINS...TO THE MID 80S ACROSS THE PIEDMONT. OVERNIGHT
LOWS WILL FALL INTO THE LOW/MID 60S.

EXPECT GREATER COVERAGE OF SHOWERS AND THUNDERSTORMS ON SUNDAY AS
THE COLD FRONT APPROACHES. WHILE THE UPPER LEVEL DYNAMICS STILL
APPEAR TO BE MARGINAL...INCREASED CONVERGENCE IN THE LOW LEVELS
SHOULD BE ENOUGH TO SUPPORT A SLIGHTLY BETTER CHANCE OF STRONG
STORMS DURING THE AFTERNOON AND EVENING...PERHAPS WITH A FEW STORMS
BECOMING SEVERE. THE COLD FRONT WILL ENTER THE INTERSTATE 64
CORRIDOR BY EARLY EVENING...AND EVENTUALLY STALL SOMEWHERE ACROSS
OUR AREA FOR THE REMAINDER OF THE NIGHT...PROVIDING THE FOCUS FOR
SPOTTY SHOWERS INTO MONDAY MORNING. INCREASED CLOUDS WILL MAKE FOR
SLIGHTLY COOLER TEMPERATURES ACROSS THE MOUNTAINS...WITH HIGHS IN
THE MID/UPPER 70S...WHILE THE PIEDMONT WILL REACH THE UPPER 80S.
LOWS WILL BE IN THE UPPER 50S NEAR INTERSTATE 64...AND HOLD IN THE
MID 60S FURTHER SOUTH.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 500 AM EDT THURSDAY...

BY MONDAY...THE UPPER PATTERN WILL HAVE ESTABLISHED A SPLIT FLOW
REGIME ACROSS THE NORTHERN TIER OF STATES AS A CLOSED LOW DEVELOPS
OVER THE LOWER MISSISSIPPI VALLEY AND SLOWLY SINKS SOUTHWARD THROUGH
THE MIDDLE OF NEXT WEEK. SOME RIDGING WILL ALSO BE TAKING PLACE OVER
THE MID ATLANTIC REGION AND SET UP A SLUGGISH BLOCKY PATTERN.

AT THE SURFACE...HIGH PRESSURE PASSING EAST ACROSS THE GREAT LAKES
WILL SPREAD ACROSS THE NORTHEAST AND WEDGE DOWN THE EASTERN
SEABOARD...GIVE THE COLD FRONT A RENEWED PUSH THROUGH OUR AREA. THE
HIGH WILL BRING COOLER/NEAR NORMAL TEMPERATURES TO THE REGION.
HOWEVER...THE PATTERN WILL KEEP US MOIST WITH DEEP SOUTHEASTERLY
FLOW AND EXPECT ENOUGH FORCING BETWEEN OROGRAPHIC UPSLOPE AND
DIURNAL EFFECTS TO KEEP SOME SHOWER ACTIVITY...AND POSSIBLY A
THUNDERSTORM...IN THE FORECAST THROUGH THE PERIOD.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
AS OF 215 PM EDT THURSDAY...

VISIBLE SATELLITE IMAGES SHOW CU/CB DEVELOPMENT THIS AFTERNOON
ESPECIALLY PREVALENT FROM THE BLUE RIDGE WEST...AND RADAR SHOWS
SCATTERED SHOWERS/THUNDERSTORMS MATCHING IN A SIMILAR PATTERN.
WHILE THERE IS AMPLE INSTABILITY ACROSS THE REGION TO SUPPORT
CONVECTION WE CONTINUE TO LACK ANYTHING RESEMBLING SIGNIFICANT
DYNAMICS SO STORMS WILL LACK ORGANIZATION SAVE FOR WHAT THEY
CAN MUSTER THROUGH OUTFLOW BOUNDARY INTERACTION. THIS WILL MAKE
IT DIFFICULT TO PIN ACTIVITY TO A SINGLE LOCATION/TIME SO EXPECT
VFR CONDITIONS OUTSIDE OF SHOWERS/STORMS. WILL USE VCTS AT ALL
LOCATIONS EARLY IN THE TAF PERIOD AND AMEND AS CONDITIONS DICTATE.

SHOWERS AND STORMS SHOULD TAPER OFF RAPIDLY WITH LOSS OF HEATING
AFTER SUNSET. MEDIUM TO LOW CONFIDENCE IN FOG POTENTIAL AS IT WILL
BE CONTINGENT ON HOW MUCH MID/UPPER CLOUD DEBRIS LINGERS OVER THE
AREA TO HINDER RADIATIONAL COOLING. WILL GO ALONG WITH GUIDANCE
AND PERSISTENCE FROM LAST NIGHT AND INTRODUCE SOME FOG/STRATUS
MOST LOCATIONS TOWARD DAYBREAK. ANY LOCATIONS THAT GET
PRECIPITATION TODAY WILL LIKELY FOG IN BUT WILL HAVE TO WAIT AND
SEE HOW THINGS UNFOLD THROUGH THIS EVENING. ANY FOG/STRATUS WILL
BURN OFF AFTER DAYBREAK TOMORROW AND ANOTHER ROUND OF DIURNAL
CONVECTION WILL BEGIN TOWARD THE END OF THE TAF PERIOD...BUT
CONFIDENCE IS FAR TO LOW TO INDICATE CONVECTIVE INITIATION
SPECIFIC TO TAF SITES THAT FAR OUT.

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...PM
NEAR TERM...MBS/PM
SHORT TERM...NF
LONG TERM...NF/MBS
AVIATION...MBS/PM



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