National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 231143
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
743 AM EDT THU MAY 23 2013

.SYNOPSIS...
A STRONG COLD FRONT WILL MOVE THROUGH THE REGION FROM WEST TO EAST
THIS AFTERNOON AND TONIGHT. MEANWHILE...A DEEP UPPER LOW WILL
SWING THROUGH THE OHIO VALLEY AND MID-ATLANTIC REGION THROUGH
SATURDAY...THEN SHIFT OFF THE MID-ATLANTIC COAST SUNDAY. HIGH
PRESSURE AT THE SURFACE AND ALOFT WILL BUILD ACROSS THE REGION
SUNDAY THROUGH THE FIRST PART OF NEXT WEEK. SHOWERS AND
THUNDERSTORMS TODAY WILL GIVE WAY TO MUCH COOLER...DRIER WEATHER
FOR THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 430 AM EDT THURSDAY...

MAIN CONCERN THROUGH THE NEAR TERM WILL BE THE PASSAGE OF THE COLD
FRONT AND ASSOCIATED CONVECTION. RADAR AND SFC OBS SUGGEST THAT
THAT THE ACTUAL FRONT IS NEAR A DAY-CVG LINE. MODELS IN GENERAL
AGREEMENT THAT THE FRONT WILL MOVE INTO THE WESTERN PART OF THE
CWA DURING THE AFTERNOON...REACHING THE EASTERN PART OF THE CWA
BEFORE MIDNIGHT. ECMWF/GFS BOTH SUGGEST CONVECTIVE ACTIVITY WILL
INCREASE THROUGH THE MORNING WITH POTENTIAL LINEAR DEVELOPMENT
EARLY IN THE DAY...PERHAPS AS EARLY AS DAYBREAK. RADAR SUGGESTING
AT LEAST WEAK POTENTIAL FOR THIS AT THE CURRENT TIME. GFS/ECMWF
SUGGEST THAT THE BEST POTENTIAL FOR SHRA/TSRA ACTIVITY WILL BE
ACROSS THE PIEDMONT AS THE DAY PROGRESSES NAM SUGGESTS MORE
SCATTERED...UNORGANIZED ACTIVITY THROUGH MUCH OF THE DAY...WITH
MORE ORGANIZED LINEAR ACTIVITY LATE IN THE DAY. THIS THEORY IS NOT
TOTALLY DISCREDITED AS THE GFS...ESPECIALLY...ATTEMPTS TO MOVE
FRONTAL ACTIVITY EAST TOO QUICKLY. CONSIDERABLE INSTABILITY AND
MOISTURE REMAIN IN PLACE...SO HAVE ADVERTISED CATEGORICAL
POPS...FOCUSING ON THE HIGHEST POPS IN THE WEST DURING THE FIRST
HALF OF THE DAY...AND THE EAST DURING THE LATER HALF. HAVE ALSO
TRENDED THE BETTER THREAT FOR THUNDER FROM THE WEST THROUGH 18Z TO
THE EAST AFTER 18Z. THERE REMAINS SOME THREAT FOR SEVERE GIVEN
THE DEGREE OF INSTABILITY...CAPES > 1000 ACROSS THE PIEDMONT AND
LIS DURING THE AFTERNOON TO -4 EASTERN AREAS AS WELL.
HOWEVER...OVERALL COVERAGE OF SEVERE SHOULD BE LESS THAN OBSERVED
WED. AS OF NOW...SPC HAS THE AREA IN A SEE TEXT...MAINLY FOR WIND
THREAT...BUT WITH COLDER TEMPS ALOFT SPREADING INTO THE AREA WITH
AN UPPER LOW APPROACHING...THERE SHOULD BE SOME HAIL THREAT AS
WELL.

FOR TONIGHT INTO FRI MORNING...OUR ATTENTION WILL TURN TO AN
ANOMALOUSLY DEEP UPPER LOW...A RECURRING PATTERN SINCE MID-
WINTER...PROGGED TO SETTLE ACROSS THE MID-ATLANTIC INTO THE
WEEKEND. A SECONDARY VORT LOBE WILL SWEEP THROUGH LATE
TONIGHT/EARLY THU...AND BRING WINTERLIKE UPSLOPE CLOUDS/-SHRA TO
THE WESTERN SLOPES OF THE ALLEGHANYS...MAINLY IN EASTERN WV.
INCREASING DOWNSLOPE SHOULD END PCPN ACROSS THE PIEDMONT...WITH
ONLY SMALL CHANCES FOR THE REMAINDER OF THE CWA OUTSIDE THE FAR
WESTERN SLOPES OF SW VA/NW NC...AND SE WV AS MENTIONED ABOVE.
TEMPERATURES WILL BE NOTICEABLY COOLER BY EARLY FRI AS WE ENTER A
PERIOD OF WELL BELOW NORMAL TEMPERATURES THAT WILL LAST INTO THE
WEEKEND. 850MB TEMPS WILL DROP TO NEAR ZERO C ACROSS THE NORTHERN
PORTIONS OF THE CWA BY THE WEEKEND.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/...
AS OF 400 AM EDT THURSDAY...

FOR FRIDAY MORNING...WILL BE UNDER A WEATHER PATTERN FOUND MORE
OFTEN DURING THE WINTER MONTHS...ALBEIT WARMER...WITH AN 8MB
PRESSURE GRADIENT SITUATED ACROSS OUR AREA AS CANADIAN HIGH PRESSURE
BUILDS IN FROM THE UPPER MIDWEST. WILL START THE DAY WITH RESIDUAL
SHOWER ACTIVITY ACROSS THE MOUNTAINS THAT WILL LINGER INTO EARLY
AFTERNOON...BUT THE MAIN CONCERN WILL BE STRONG NORTHWEST WINDS THAT
WILL REMAIN ACROSS THE REGION THROUGH THE DAY. WITH CLOUD COVER
CLEARING OUT EARLY...THE STRONGER WINDS ALOFT WILL MIX DOWN TO THE
SURFACE DURING THE MORNING...AND WILL NOT BE SURPRISED TO SEE 30+
MPH GUSTS COMMON ACROSS THE MOUNTAINS AND 25 MPH GUSTS ACROSS THE
PIEDMONTS. GUSTS WILL BE STRONGER ABOVE 3000 FEET...AND BELIEVE WE
WILL SEE ADVISORY LEVEL GUSTS ACROSS THE NORTH CAROLINA MOUNTAINS
INTO SOUTHWEST VIRGINIA. THE CANADIAN HIGH PRESSURE WILL BRING
SIGNIFICANTLY COOLER TEMPERATURES...WITH FRIDAY AFTERNOON HIGHS
RANGING FROM THE UPPER 50S TO THE LOW 60S ACROSS THE MOUNTAINS...TO
THE LOW 70S ACROSS THE PIEDMONTS. KEEP IN MIND THAT THE GUSTY WINDS
MAY ADD AN ADDITIONAL CHILL TO THE AIR...SO KEEPING A LIGHT JACKET
HANDY MAY BE A GOOD IDEA.

WINDS WILL REMAIN SOMEWHAT GUSTY SATURDAY...ALTHOUGH NOT AS STRONG
AS THOSE ON FRIDAY...AS A LOW PRESSURE SYSTEM DEEPENS OFF THE NEW
ENGLAND COAST. WILL START THE MORNING OFF WITH RATHER COOL
TEMPERATURES...RANGING FROM THE MID/UPPER 30S ACROSS THE MOUNTAINS
TO THE MID 40S FURTHER EAST. BELIEVE WINDS WILL REMAIN STRONG ENOUGH
TO PREVENT FROST FROM DEVELOPING IN THE COOLER SPOTS IN THE
MOUNTAINS...HOWEVER THOSE WITH TENDER VEGETATION SHOULD KEEP AN EYE
ON THE FORECAST JUST THE SAME...AND BE PREPARED TO PROTECT THESE
PLANTS IF NECESSARY. AT ANY RATE...TEMPERATURES WILL REBOUND INTO
THE LOW/MID 60S WEST...TO THE LOW 70S EAST BY AFTERNOON.

HIGH PRESSURE REMAINS IN CONTROL OF THE WEATHER PATTERN ON SUNDAY...
ALTHOUGH TEMPERATURES WILL BEGIN TO MODERATE AS LOW PRESSURE OVER
NEW ENGLAND BEGINS TO PUSH NORTHEAST INTO CANADA. WEATHER IS
EXPECTED TO REMAIN DRY ONCE AGAIN...BUT WILL BE KEEPING AN EYE ON A
WARM FRONT STRETCHING FROM THE LOWER GREAT LAKES TO THE CENTRAL
APPALACHIANS THAT WILL LIFT NORTHWARD DURING THE DAY. THIS WARM
FRONT WILL PLAY A ROLE IN OUR WEATHER AS WE GET INTO THE NEXT
WORKWEEK.

&&

.LONG TERM /MONDAY THROUGH WEDNESDAY/...
AS OF 1245 PM EDT WEDNESDAY

EXPECT COOL TROUGH TO LINGER INTO SUNDAY BEFORE LIFTING EAST.
MEANWHILE A STRONG TROUGH DIGS INTO THE PACIFIC NORTHWEST BY MONDAY
WITH INCREASING HEIGHTS ARRIVING OVER OUR AREA NEXT WEEK. THE
WEATHER PATTERN WILL BE MAINLY DRY SAT NIGHT-MONDAY...BUT AS WE CAN
SEE WITH A WESTERLY FLOW ALOFT THE CHANCE THAT CONVECTION THAT FIRES
ALONG A WARM FRONT OVER THE OHIO/MID MISSISSIPPI VALLEY COULD SHIFT
EAST AND AFFECT OUR MOUNTAINS.

WILL LEAN TOWARD AN ECMWF/WPC BLEND SOLUTION. THIS WILL KEEP THE
CHANCE POPS IN THE AREA BY MONDAY AFTERNOON THROUGH TUESDAY. THE
WARM FRONT LIFTS NORTH TOWARD THE GREAT LAKES BY MIDWEEK WITH
HEIGHTS CONTINUING TO BUILD. AT THE SFC...HIGH PRESSURE WILL BE
SITUATED ACROSS THE MID ATLANTIC COAST THEN SHIFT OFF THE COAST
MIDWEEK. DEWPOINTS WILL BE INCREASING AGAIN BY NEXT WEEK WITH TEMPS
WARMING BACK TO NORMAL OR JUST ABOVE.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
AS OF 740 AM EDT THURSDAY...

FRONTAL SYSTEM RESPONSIBLE FOR CONVECTION LAST TWO DAYS WILL
FINALLY MOVE THROUGH THE FORECAST AREA LATE IN THE TAF VALID
PERIOD...GENERALLY FROM 20Z WEST TO 04Z EAST. THE AIR MASS REMAINS
QUITE MOIST AND UNSTABLE FOR MORNING HOURS...THUS SCATTERED POPUP
SHRA NOTED THROUGH MUCH OF THE CWA AT 12Z. THIS SHOULD
CONTINUE...THEN INCREASE IN AERIAL COVERAGE AND INTENSITY AS THE
DAY PROGRESSES AND THE FRONTAL SYSTEM APPROACHES. EXPECT THE BULK
OF SHRA/TSRA ACTIVITY TO OCCUR WITHIN THE 14Z-00Z TIME FRAME FROM
WEST TO EAST. LINGERING IFR CIGS DAN/LYH/ROA SHOULD LIFT TO MVFR
OR BETTER BY MID-MORNING. MOSTLY MVFR CIGS WILL ACCOMPANY
SHRA/TSRA ACTIVITY TODAY. OTHERWISE...IT SHOULD BE VFR AFTER MID-
MORNING AT MOST SITES. SCT -SHRA SHOULD PERSIST BEHIND THE
STRONGER CONVECTION UNTIL THE FRONT ACTUALLY ARRIVES DURING THE
AFTERNOON WEST TO EVENING EAST. PATTERN SHIFTS TO MORE OF A
WINTER PATTERN AFTER THIS EVENING...WITH TYPICAL UPSLOPE
CLOUDS/-SHRA LWB- BLF WITH MVFR CIGS...AS A DEEP UPPER LOW SINKS
DOWN ACROSS THE MID-ATLANTIC REGION FOR THE WEEKEND. FURTHER EAST...
TOWARD ROA/LYH/DAN...CIGS SHOULD IMPROVE TO VFR WITH PCPN ENDING
BY LATE AFTERNOON/EVENING. VSBYS MOSTLY VFR...EXCEPT MVFR IN AREAS
OF BR/-SHRA AND/OR TSRA. WINDS SSW-SW 5-8KTS UNTIL FRONTAL PASSAGE
THIS AFTERNOON...THEN WSW-W 7-10KTS...WITH LOW END GUSTS BLF AND
ROA ESPECIALLY.

MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH TAF VALID PERIOD.
MEDIUM CONFIDENCE IN TSRA TIMING AND COVERAGE.
HIGH CONFIDENCE IN WIND SPD/DIR THROUGH TAF VALID PERIOD.

EXTENDED AVIATION CONDITIONS...STRONG HIGH PRESSURE WILL BRING
MUCH DRIER AIR BY FRIDAY WITH VFR LIKELY TO PREVAIL THROUGH THE
WEEKEND INTO EARLY NEXT WEEK. SOME UPSLOPE CLOUDS LINGER INTO FRI
ACROSS SE WV. INCREASING POTENTIAL FOR NW FLOW DRIVEN THUNDERSTORM
ACTIVITY EARLY NEXT WEEK...MOST CONDITIONS OVERALL VFR FOR THE
MOST PART.
-- End Changed Discussion --

&&

.EQUIPMENT...
THE NOAA WEATHER RADIO AT ROANOKE VIRGINIA IS OFF THE AIR THIS
EVENING DUE TO A PROBLEM AT THE TRANSMITTER SITE. RESTORATION TIME
IS UNKNOWN AT THIS POINT.

&&

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

&&

$$
SYNOPSIS...RAB
NEAR TERM...RAB
SHORT TERM...NF
LONG TERM...WP
AVIATION...RAB
EQUIPMENT...JH