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 010805 CCA
AFDRNK

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE BLACKSBURG VA
405 AM EDT TUE SEP 1 2015

.SYNOPSIS...
AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL STRENGTHEN OVER THE
APPALACHIANS AND CENTRAL MID ATLANTIC REGION TODAY...KEEPING US
IN A RATHER STAGNANT PATTERN WITH ISOLATED AFTERNOON AND EVENING
SHOWERS AND THUNDERSTORMS THROUGH LATE IN THE WEEK. A WEAK
BACKDOOR COLD FRONT WILL DROP SOUTH THROUGH THE AREA BY THE
WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 223 AM EDT TUESDAY...

RIDGING BOTH SURFACE/ALOFT TO STRENGTHEN ACROSS THE REGION TODAY IN THE
WAKE OF A WEAK PASSING SHORTWAVE EARLY THIS MORNING AND AHEAD OF THE
WEAK UPPER DISTURBANCE NOW IN THE WESTERN OHIO VALLEY. THIS SHOULD
RESULT IN LIMITED FORCING WITH ANY CONVECTIVE COVERAGE MAINLY TIED TO
OROGRAPHICS AND LOW LEVEL CONVERGENCE BETWEEN WEAK ONSHORE FLOW OUT
EAST AND WEAK NW TRAJECTORIES OVER THE WEST. MODELS ALSO INDICATED
POCKETS OF HIGHER SURFACE-85H THETA-E OVER THE WEST/SW AND IN THE FAR
NW LATER ON. HOWEVER MOST SOLUTIONS REMAIN WITH AN OVERALL DISORGANIZED
SHOTGUN PATTERN TO SHOWERS DESPITE DECENT INSTABILITY PER STRONG
HEATING AND LACK OF MUCH CAP ALOFT. THEREFORE RUNNING WITH OVERALL
SLIGHT POPS MAINLY MOUNTAINS WITH RIBBONS OF MORE CHANCE NATURE
COVERAGE ALONG THE HIGHER RIDGES IN A FEW SPOTS. WILL BE ON THE HOT
SIDE TO START SEPTEMBER GIVEN A BIT MORE SUN THAN THE LAST FEW DAYS AND
LIGHT FLOW. THIS COULD PUSH HIGHS ABOVE 90 SE AND WELL INTO THE 80S
ELSEWHERE OUTSIDE THE HIGHER ELEVATIONS.

WEAK NW FLOW MAY TAKE A FEW SHRA/ISOLATED TSRA JUST EAST OF THE
MOUNTAINS INTO EARLY THIS EVENING BEFORE FADING BUT GIVEN LACK OF
SUPPORT THINK MOST ABOUT GONE AROUND SUNSET. OTHERWISE OPENING UPPER
WAVE SLIPS SOUTHEAST TOWARD THE REGION LATER TONIGHT AND HELPS LOWER 5H
HEIGHTS UNDER STRONG SURFACE RIDGING. THIS SYSTEM COULD SPARK A BAND OR
TWO OF SHOWERS MAINLY NW LATE BUT GIVEN LACK OF MUCH LIFT AFTER LOSS OF
HEATING CUT BACK TO MOSTLY SLIGHT CHANCE POPS OVERNIGHT MAINLY NW.
HOWEVER THIS FEATURE MAY BRING ENOUGH CLOUDS TO KEEP LOW TEMPS UP A BIT
MORE SO APPEARS MOSTLY UNIFORM MID TO UPPER 60S OVERNIGHT.

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/...
AS OF 345 AM EDT TUESDAY...

VERY DIFFUSE UPPER-LEVEL PATTERN IN PLACE AT THE BEGINNING OF THIS
PERIOD...WITH WEAK...SMALL CHANGES THROUGH THE PERIOD THAT WILL
DICTATE THE WEATHER. WE BEGIN WITH A BUILDING UPPER RIDGE
ENCOMPASSING MUCH OF THE EASTERN 2/3RD OF THE NATION SOUTH OF THE
CANADIAN BORDER. UNDERLYING THIS BROAD UPPER RIDGE ARE SEVERAL
WEAK SYSTEMS...A WEAK UPPER TROUGH TRAVERSING THE NORTHERN
PERIPHERY OF THE UPPER RIDGE THROUGH THE OH VALLEY AND THE
REMNANTS OF ERIKA OFF THE NC COAST. THE AFOREMENTIONED UPPER
TROUGH WILL SLIDE SOUTHEAST THROUGH THE DAY ALLOWING FOR A BRIEF
LOWERING OF UPPER HEIGHTS. THIS FEATURE WILL ALSO TRACK INTO THE
REGION DURING PEAK HEATING...WHICH SHOULD BE SUFFICIENT TO SPARK
ISOLATED TO SCATTERED AFTERNOON CONVECTION...ESPECIALLY ACROSS THE
MOUNTAINS. WARM TEMPS ALOFT WILL INHIBIT ANY SIGNIFICANT COVERAGE
WITH THIS FEATURE. CONVECTION WILL BE LARGELY DIURNAL AND SHOULD
DISSIPATE QUICKLY AFTER SUNSET. MOST FAVORED AREAS FOR
SHOWERS/THUNDERSTORMS WED AFTERNOON/EVENING SHOULD BE NEAR THE
I-64 CORRIDOR. HOWEVER...WITH LIMITED DYNAMICS...20-30 POPS
SHOULD BE SUFFICIENT.

FOR THURSDAY...THE WEAK UPPER TROUGH CONTINUES TO SLIDE SOUTHWARD
INTO THE CAROLINAS OR EASTERN TN VALLEY. MEANWHILE...THE UPPER
RIDGE BECOMES VERY HIGH AMPLITUDE INTO EASTERN CANADA WITH 588DM
HEIGHTS EVEN NORTH OF THE GREAT LAKES...ALL IN RESPONSE TO
DEEPENING LOW PRESSURE ALONG THE WEST COAST. WITH THE UPPER
TROUGH WEAKENING AND RIDGING ALOFT...CONVECTION WILL BE ISOLATED
TO SCATTERED AT BEST AND ALMOST ENTIRELY DRIVEN BY
DIURNAL/DIFFERENTIAL HEATING. BEST FOCUS SHOULD BE ACROSS THE
WESTERN MOUNTAINS. LITTLE SUPPORT FOR MORE THAN 30 POPS
ANYWHERE...MOSTLY 20 POPS.

BY FRIDAY...A STRONG 1030MB HIGH BEGINS TO TAKE SHAPE ACROSS
SOUTHEAST CANADA AND NEW ENGLAND UNDERNEATH THE STRONG/HIGH
AMPLITUDE UPPER RIDGE. 590DM HEIGHTS ARE NOTED EVEN NORTH OF THE
CANADIAN BORDER. AS THE RIDGE BUILDS INTO NEW ENGLAND...THE MID-
WEEK WEAK UPPER TROUGH SINKS SOUTH INTO THE SOUTHEAST U.S...WHICH
COULD BECOME A FOCUS FOR PRECIPITATION IN THE EXTENDED DEPENDING
ON ITS NORTHWARD EXTENT. MORE IMPORTANTLY FOR OUR REGION AT THIS
POINT IS A HEALTHY BACKDOOR FRONT BEGINNING TO TAKE SHAPE ACROSS
THE MID-ATLANTIC THAT WILL ADVECT SOUTHEAST INTO THE CWA BY
SATURDAY. A MARKED INCREASE IN INSTABILITY IS NOTED IN ADVANCE OF
THIS FEATURE...WHICH WILL REPRESENT SLIGHT COOLING AND MODEST
DRYING. WE SHOULD SEE AN INCREASE IN CONVECTION ALONG AND IN
ADVANCE OF THE BOUNDARY FROM THE NORTH AND NORTHEAST BY FRIDAY
AFTERNOON...AND THIS HAS BEEN REFLECTED IN THE POPS.

TEMPERATURES WILL REMAIN ABOVE NORMAL THROUGH THIS
PERIOD...GENERALLY ON THE ORDER OF 5 DEGREES FOR DAYTIME MAX TEMPS
AND NEARLY 10 DEGREES ABOVE NORMAL FOR MIN TEMPS. MOST MODELS WERE
IN GENERAL AGREEMENT ON MAX/MIN TEMPS THROUGH THE PERIOD.

&&

.LONG TERM /SATURDAY THROUGH MONDAY/...
AS OF 400 AM EDT TUESDAY...

THE BACKDOOR COLD FRONT WILL MOVE SOUTHWARD THROUGH THE REGION
SATURDAY...FOLLOWED BY DRIER/SLIGHTLY COOLER AIR...ESPECIALLY
SUN-MON AS SFC HIGH PRESSURE SLIDES SOUTHWARD ALONG THE MID-
ATLANTIC COAST. THE MID-WEEK WEAK UPPER LOW WILL BECOME CUT OFF
IN THE AL/GA/SC REGION. MEANWHILE...A STRONG UPPER RIDGE WILL
REMAIN FIRMLY ENTRENCHED ACROSS THE REGION WITH 500MB HEIGHTS IN
THE 593DM RANGE THROUGH THE WEEKEND. SHOWERS/THUNDERSTORM CHANCES
SATURDAY WILL BE BEST IN THE WEST/SOUTHWEST PART OF THE CWA NEAR
THE SOUTHWESTWARD MOVING BACKDOOR FRONT. CONVECTION CHANCES SUN-
MON WILL BE CONFINED TO THE FAR SOUTH CENTRAL/SOUTHWEST PARTS OF
THE CWA NEAR THE CUTOFF UPPER LOW AND STALLED BACKDOOR FRONT.

TEMPERATURES WILL BE SLIGHTLY COOLER THROUGH MUCH OF THE CWA THIS
PERIOD THANKS TO THE BACKDOOR FRONT AND INCREASING NORTHEAST-EAST
MARITIME FLOW. DEWPOINTS/RH VALUES WILL ALSO BE LESS...ESPECIALLY
ACROSS THE NORTHEAST PART OF THE CWA. THE EXCEPTION MAY BE THE
SOUTHWEST PART OF THE CWA...WHICH WILL LIKELY REMAIN WARMER AND
MORE HUMID GIVEN THE SYNOPTIC PATTERN IN PLACE. THE COOLING WILL
BE MOST NOTABLE IN MAX TEMPS...WHICH WILL BE NEAR NORMAL...WHILE
MIN TEMPS ARE LIKELY TO REMAIN WELL ABOVE NORMAL.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
AS OF 100 AM EDT TUESDAY...

SKIES MAINLY CLEAR ACROSS THE REGION TONIGHT WITH PATCHY FOG
STARTING TO DEVELOP IN THE LOW SPOTS/VALLEYS WITH STRATUS JUST
EAST OF THE REGION IN SPOTS CLOSER TO THE COAST. LATEST MODELS
SUGGEST MUCH OF THE STRATUS TO STAY TO THE EAST WHILE STILL
EXPECTING SOME DEVELOPMENT OF FOG IN THE VALLEYS ALONG WITH AREAS
OF STRATUS. THUS KEEPING THE GOING SCENARIO OF SEEING LIFR/IFR AT
KBCB/KLWB BY DAYBREAK AND SPOTTY MVFR TO IFR AT TIMES ACROSS THE
EAST.

FOG/STRATUS WILL LIFT AFTER SUNRISE TUESDAY SO EXPECT VFR CONDITIONS
TO TAKE SHAPE BY MID/LATE MORNING WITH THE NEXT ROUND OF DIURNAL
CONVECTION HOLDING OFF UNTIL TUESDAY AFTERNOON. THUS KEPT VCSH AT
KBLF/KLWB WITH BKN VFR CIGS AT 4-6KFT. MAY SEE SOME BROKEN VFR
CIGS ELSEWHERE ALONG THE BLUE RIDGE BUT KEEPING LOCATIONS AROUND
KBCB/KROA DRY FOR NOW.

EXTENDED AVIATION DISCUSSION...

THE FORECAST AREA WILL REMAIN IN A WEAKLY FORCED SYNOPTIC
ENVIRONMENT THROUGH MIDWEEK...WITH CHANCES FOR DIURNAL CONVECTION
MAINLY FROM THE BLUE RIDGE WEST...AND SOME MVFR/IFR FOG/STRATUS
DEVELOPMENT AT NIGHT...ESPECIALLY AT KBCB AND KLWB.

FOR FRIDAY INTO SATURDAY WILL SEE HIGH PRESSURE IN CONTROL THOUGH
THE POSITION OF THE HIGH OVER THE MID ATLANTIC MAY SLIDE MORE MVFR
CIGS OFF THE ATLANTIC INTO OUR EASTERN TAF LOCATIONS.

&&

.EQUIPMENT...
AS OF 400 AM EDT MONDAY...

THE DEW POINT READING AT KJFZ...RICHLANDS VA AWOS...IS INCORRECT.
AT THIS TIME WE DO NOT KNOW WHEN THIS SENSOR WILL BE REPAIRED.

&&

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

&&

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


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