Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 051720
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
120 PM EDT SUN JUL 5 2015

.SYNOPSIS...
AN UPPER LOW WILL DRIFT SLOWLY FROM EAST TENNESSEE TODAY TOWARD
WESTERN PENNSYLVANIA BY LATE MONDAY BRINGING WIDESPREAD RAIN AND
A FEW THUNDERSTORMS TO THE AREA TODAY THROUGH MONDAY. A COLD FRONT
WILL MOVE INTO THE REGION FROM THE OHIO VALLEY BY WEDNESDAY...THEN
STALL AND LIFT BACK NORTH AS A WARM FRONT LATE IN THE WEEK AS HIGH
PRESSURE ALOFT BUILDS ACROSS THE SOUTHEAST STATES. SCATTERED
SHOWERS AND THUNDERSTORMS WILL ACCOMPANY THE FRONT. BELOW NORMAL
TEMPERATURES EARLY IN THE WEEK WILL TREND TO ABOVE NORMAL
TEMPERATURES BY THE END OF THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 952 AM EDT SUNDAY...

FLASH FLOOD WATCH REMAINS IN EFFECT FOR FAR WEST THROUGH TONIGHT.
THIS MORNING 12Z RNK SOUNDING SUPPORTS THE POTENTIAL FOR HEAVY
RAIN WITH S-SW FLOW AND INCREASED PWATS AT 1.5 INCH. FFG IS
RELATIVELY LOWER IN THE FAR WEST.

MODIFIED POPS AND PRECIPITATION TOWARDS RADAR TRENDS THIS
MORNING...THEN LEANED TOWARDS HRRR SOLUTION FOR LATE MORNING INTO
THIS AFTERNOON. IN GENERAL...TRIMMED BACK POPS IN THE EAST THIS
MORNING. ADJUSTED TEMPERATURES WITH LATEST SURFACE OBS AND
BLENDED TOWARDS ADJMAV...WHICH SEEMED TO CAPTURE COOLER
TEMPERATURES IN THE MOUNTAINS. MORE CHANGES LATER TODAY...

AS OF 515 AM EDT SUNDAY...

A CLOSED LOW WILL BE SPLITTING OFF FROM THE MEAN TROF AND SLOWLY
MOVING OVER THE REGION TODAY AND TONIGHT. THIS WILL SET THE AREA UP
FOR SOME WIDESPREAD RAINFALL WITH UPPER DIFFLUENCE AND DEEP E/SE
FLOW WITH GOOD MOISTURE TRANSPORT GENERATING PRECIPITABLE WATER
VALUES APPROACHING TWO INCHES. THANKFULLY ANTECEDENT CONDITIONS ARE
NOT AS WET AS THEY COULD HAVE BEEN AND THE MOST VULNERABLE AREAS TO
HYDRO CONCERNS ARE FROM THE MOUNTAIN EMPIRE REGION UP THROUGH
SOUTHEAST WEST VIRGINIA...SO A FLASH FLOOD WATCH HAS BEEN POSTED FOR
THOSE COUNTIES FROM LATE THIS MORNING THROUGH TONIGHT.

AS THE LOW SPINS SLOWLY TO OUR WEST...WE WILL SEE A BIT OF A DRY SOT
WORK IN FROM THE SOUTHWEST. SEVERAL MODELS ARE QUITE AGGRESSIVE WITH
SHUTTING DOWN THE PRECIPITATION QUICKLY BUT WITH A CLOSED LOW AND
DECENT SYNOPTIC SUPPORT IN PLACE WILL SHADE THINGS TOWARD THE
SLOWER/WETTER SOLUTIONS.

WITH A GOOD AMOUNT OF CLOUD COVER EXPECTED WE SHOULD SEE
TEMPERATURES TODAY JUST A FEW DEGREES COOLER THAN YESTERDAY WITH
LOW/MID 80S EAST TO LOW/MID 70S WEST. LOWS TONIGHT WILL GENERALLY
BE 65 TO 70 EAST...WITH 60 TO 65 WEST.

&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
AS OF 430 AM EDT SUNDAY...

CLOSED UPPER LOW WILL BE NEAR THE VA/WV/KY BORDER INTERSECTION AT
12Z MON...DRIFTING NORTH-NORTHEAST INTO WESTERN PA BY EVENING. THE
WARM ADVECTION AND HEAVIEST PART OF THE RAINFALL SHOULD BE LIFTING
TOWARD THE I-64 CORRIDOR AT THE START OF THIS PERIOD...THEN INTO
NORTHERN VA/WV BY AFTERNOON/EVENING. AS IT DOES SO...A BAROCLINIC
ZONE WILL DEVELOP ON THE WEST SIDE OF THE UPPER LOW. SOMEWHAT OF A
DRY SLOT IS EVIDENT WORKING ITS WAY INTO THE PIEDMONT AND AREAS
EAST OF THE BLUE RIDGE BY AFTERNOON. WIDESPREAD RAIN SHOWERS
DURING THE MORNING SHOULD FOCUS MORE TOWARD THE NORTHERN AND
WESTERN PART OF THE CWA BY AFTERNOON INTO THE EARLY
EVENING...BEFORE TAPERING OFF IN THESE AREAS AFTER SUNSET. THE
HEAVIEST RAIN DURING THE DAY SHOULD FALL ROUGHLY NEAR THE I-77 AND
I-64 CORRIDORS WITH THE COMBINED EFFECT OF WARM ADVECTION RAINFALL
EARLY IN THE EVENT...TRANSITIONING TO DEFORMATION RAINFALL WEST DURING
THE AFTERNOON. AFTERNOON PRECIPITATION SHOULD BE LIMITED TO A FEW
SPOTTY SHOWERS ACROSS AREAS EAST OF THE BLUE RIDGE WITH AN
ANTICIPATED DRY SLOT IN THAT REGION. WILL HOLD ONTO LIKELY POPS
ACROSS WEST MUCH OF THE DAY...WITH POPS DECREASING INTO THE SLIGHT
CHANCE CATEGORY NC COUNTIES BY EVENING. QPF AFT 12Z SHOULD RANGE
FROM 3/4 INCH IN THE WEST AND NORTHWEST TO 1/4 INCH IN THE
SOUTHEAST PART OF THE CWA. THIS RAINFALL SHOULD NOT BE ENOUGH TO
EXACERBATE ANY FLOODING PROBLEMS...BUT LATER SHIFTS WILL NEED TO
EVALUATE IF THE FLASH FLOOD WATCH WILL NEED TO CONTINUE BEYOND THE
CURRENT 10Z MON EXPIRATION.

BY MONDAY NIGHT...THE UPPER LOW WILL HAVE MOVED FAR ENOUGH NORTH
AWAY FROM THE AREA...AS WELL AS SHEARING OUT...THAT ANY ASSOCIATED
RAINFALL ACROSS OUR REGION SHOULD HAVE ENDED. LOW CLOUDS AND
PATCHY DRIZZLE MAY LINGER ACROSS THE MOUNTAINS...BUT NO
APPRECIABLE RAINFALL IS EXPECTED.

FOR TUESDAY...PROGRESSIVE FLOW ACROSS THE NORTHERN STATES WILL
QUICKLY PUSH A NEW FRONTAL ZONE AND ASSOCIATED WEAK UPPER TROUGH
INTO THE REGION FROM THE WEST. LINEAR ORIENTED...POTENTIALLY
STRONG CONVECTION...APPEARS LIKELY WITH THIS SYSTEM. THIS ACTIVITY
WILL LIKELY REACH WESTERN WV/FAR SOUTHWEST VA AND THEN DIMINISH AS
IT ATTEMPTS TO CROSS THE MOUNTAINS DURING THE LESS FAVORABLE
EVENING HOURS. THIS AGREES WELL WITH THE MARGINAL RISK SPC HAS
ADVERTISED ON DAY 3 ENDING JUST SHY OF OUR WESTERN BORDER.
OTHERWISE...MUCH OF THE DAY TUESDAY SHOULD OFFER A MINIMUM OF
PRECIPITATION ACTIVITY ACROSS THE CWA...ESPECIALLY EAST OF THE
BLUE RIDGE. HAVE GENERALLY ADVERTISED ONLY SLIGHT CHANCE POPS FOR
AREAS EAST OF THE BLUE RIDGE WITH A WARM...MOIST ATMOSPHERE IN
PLACE...BUT DYNAMICS WILL BE LIMITED AT BEST.

WEDNESDAY HAS BECOME MORE PROBLEMATIC TODAY AMONG THE MODELS THAN
INDICATED YESTERDAY AS A RESULT OF INCREASED SUBTROPICAL RIDGING
ACROSS THE SOUTHEAST STATES. THIS ALLOWS THE TUESDAY FRONT TO
DRIFT INTO THE CWA AND THEN LIFT BACK NORTH. IT SHOULD LINGER LONG
ENOUGH IN THE REGION WEDNESDAY TO SERVE AS A FOCUS FOR SCATTERED
IF NOT NUMEROUS CONVECTION DURING AFTERNOON HEATING.

TEMPERATURES SHOULD REMAIN BELOW NORMAL WEST OF THE BLUE RIDGE
MONDAY WITH WIDESPREAD CLOUDS AND RAIN. HOWEVER...EAST OF THE
BLUE RIDGE SOME INSOLATION IS EXPECTED DURING THE AFTERNOON AND WE
SHOULD SEE MAXIMUM TEMPERATURES CLOSER TO NORMAL IN THOSE AREAS.

MAXIMUM TEMPERATURES FINALLY REACH ABOVE NORMAL LEVELS IN MUCH OF
THE CWA TUESDAY WITH INCREASED AMOUNTS OF SUNSHINE AND SOUTHWEST
SURFACE FLOW. WESTERN AREAS WILL SEE MAXIMUM TEMPERATURES CLOSER
TO NORMAL AGAIN WEDNESDAY WITH CLOUDS AND PRECIPITATION. MINIMUM
TEMPERATURES WILL AVERAGE WELL ABOVE NORMAL THROUGH MUCH OF THE
PERIOD...THANKS TO CONTINUED HIGH MOISTURE CONTENT AND DEWPOINTS.

&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
AS OF 500 AM EDT SUNDAY...

EXTENDED PERIOD TRENDING WARMER...BUT STILL SOMEWHAT UNSETTLED.
MODELS...TO VARYING DEGREES...ADVERTISING AN INTENSIFYING UPPER
RIDGE ACROSS THE SOUTHEAST STATES INTO THE MID-ATLANTIC. THE
GFS/CANADIAN ARE STRONGEST WITH THE UPPER RIDGE...THE ECMWF IS THE
WEAKEST...KEEPING A MORE ACTIVE WESTERLY FLOW ACROSS THE REGION.
AT ANY RATE...INSTABILITY WILL BE GREATER THAN IN RECENT DAYS.
AT THIS POINT...IT APPEARS THAT THURSDAY SHOULD OFFER THE BEST
CHANCE FOR WIDESPREAD CONVECTION...BUT CONDITIONS SHOULD BECOME
MORE UNFAVORABLE FOR WIDESPREAD ORGANIZED CONVECTION THROUGH THE
END OF THE WEEK INTO THE WEEKEND WITH UPPER RIDGING TAKING HOLD OF
THE REGION FROM THE SOUTH. THIS SHOULD PUSH THE MORE ACTIVE
BAROCLINIC ZONE INTO OH/PA/MD/NJ. WILL NEED TO WATCH LATER TRENDS
OF THE MODELS TO MAKE SURE THIS TREND CONTINUES...AS OPPOSED TO
SHIFTING THE BAROCLINIC ZONE FURTHER SOUTH AND WITH NORTHWEST
FLOW ALOFT...SHOULD THE UPPER RIDGE DRIFT FURTHER WEST AND REMAIN
LESS AMPLIFIED THAN CURRENTLY INDICATED.

WITH THE UPPER RIDGING...WE WILL HAVE TO START TALKING ABOUT HIGHS
IN THE 90S AGAIN ACROSS THE PIEDMONT. HUMIDITY LEVELS WILL BE HIGH
WITH DEWPOINTS NEAR 70...SO WILL NEED TO WATCH APPARENT TEMPERATURES
IN THOSE AREAS TOWARD MID-WEEK. NEEDLESS TO SAY...TEMPERATURES APPEAR
DESTINED TO ABOVE NORMAL LEVELS THROUGH MUCH OF THE PERIOD.

&&

.AVIATION /18Z SUNDAY THROUGH THURSDAY/...
AS OF 120 PM EDT SUNDAY...

POOR AVIATION CONDITIONS EXPECTED THROUGH THE TAF VALID PERIOD. A
CLOSED UPPER LOW OVER EASTERN TENNESSEE THIS AFTERNOON WILL DRIFT
SLOWLY NORTHEAST TONIGHT AND REACH WESTERN PENNSYLVANIA BY LATE
MONDAY. MVFR CONDITIONS WILL PREVAIL WITH POCKETS OF IFR/LIFR IN
CONVECTION AND LOW CLOUDS.

SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP THIS AFTERNOON INTO
TONIGHT...WITH THE BEST COVERAGE AND DURATION ACROSS THE WESTERN
SITES...ESPECIALLY KLWB AND KBLF. LOCATIONS WITH A GOOD CHANCE FOR
THUNDERSTORMS ARE WHERE SOLAR HEATING WILL COMBINE WITH ENOUGH
INSTABILITY TO SUPPORT THUNDERSTORMS. DAN IS THE TAF SITE WITH BEST
CHANCE FOR A THUNDERSTORM THIS AFTERNOON INTO THIS EVENING.

MOST OF THE STORMS WILL DIMINISH WITH LOSS OF HEATING BUT SOME
SHOWERS MAY LINGER IN THE WEST TONIGHT. AREAS OF LOW
CLOUDS...FOG...AND DRIZZLE WILL LIKELY PERSIST OVERNIGHT AFTER THE
HEAVIER RAIN DRIFTS NORTH OF THE AREA.

UNSETTLED WEATHER WILL CONTINUE MONDAY WITH MVFR/IFR SHOWERS AND
EMBEDDED THUNDERSTORMS. THE BEST CHANCE FOR CONVECTION WILL OCCUR
ACROSS THE NORTH.

OUTSIDE OF THUNDERSTORMS...EAST TO SOUTHEAST WINDS WILL PREVAIL
AT 4-7KTS TONIGHT. THEN WINDS BECOMING LIGHT AND VARIABLE
OVERNIGHT INTO MONDAY. WINDS WILL BECOME SOUTH TO SOUTHWEST AT
5-10 KTS MONDAY AFTERNOON.

MEDIUM CONFIDENCE IN CEILINGS...VISIBILITIES AND WINDS DURING THE
TAF PERIOD.

EXTENDED AVIATION DISCUSSION...

POOR AVIATION CONDITIONS TO CONTINUE INTO NEXT WEEK...BUT WINDOWS
OF OPPORTUNITY FOR VFR CONDITIONS INCREASE TUE. UPPER LOW/TROUGH
WILL MOVE INTO WESTERN PA BY MONDAY EVENING. MEANWHILE...A COLD
FRONT WILL APPROACH FROM THE OH VALLEY BY WED. THIS LEAVES A VERY
UNSETTLED/WET PATTERN ACROSS THE REGION THROUGH MOST OF THE
PERIOD. TUE THROUGH THE DAY OFFERS THE BEST CHANCE FOR SEVERAL
HOURS OF VFR...ESPECIALLY EAST OF THE BLUE RIDGE.

EXPECT WIDESPREAD LATE NIGHT/EARLY MORNING LOW CLOUDS/FOG WITH
IFR-LIFR CIGS/VSBYS. OVERALL...CONDITIONS SHOULD IMPROVE TO MVFR-
VFR OUTSIDE SHRA/TSRA ACTIVITY DURING THE AFTERNOONS.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR VAZ007-009-010-012.
NC...NONE.
WV...FLASH FLOOD WATCH THROUGH LATE TONIGHT FOR WVZ042-043-507-508.

&&

$$
SYNOPSIS...MBS
NEAR TERM...AMS/KK/MBS
SHORT TERM...RAB
LONG TERM...PM/RAB
AVIATION...KK/RAB


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