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[Printable]
515
FXUS61 KRNK 190733
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
333 AM EDT FRI SEP 19 2014

.SYNOPSIS...
A WEAK TROUGH OF LOW PRESSURE WILL SHIFT WEST ACROSS THE MOUNTAINS
TODAY AHEAD OF STRONG HIGH PRESSURE BUILDING IN FROM THE NORTH BY
THIS AFTERNOON. THE HIGH WILL WEDGE SOUTH ALONG THE EASTERN
SLOPES OF THE APPALACHIANS TONIGHT INTO SUNDAY KEEPING DRY
WEATHER IN PLACE. A COLD FRONT SHOULD CROSS THE AREA FROM THE
NORTHWEST LATER SUNDAY NIGHT INTO MONDAY FOLLOWED BY COOLER AND
DRIER WEATHER INTO NEXT WEEK.
&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 230 AM EDT FRIDAY...

COMBINATION OF A WEAK SURFACE TROUGH ACROSS THE PIEDMONT AND LOW LEVEL
THETA-E RIDGING EAST OF THE BLUE RIDGE CONTINUES TO LEAD TO ISOLATED
SLOW MOVING SHOWERS IN SPOTS EARLY THIS MORNING. EXPECT THIS TO PERSIST
A WHILE LONGER PER LATEST HRRR BEFORE THE DEVELOPING WEDGE STARTS TO
ENHANCE FROM NE TO SW BUT A BIT SLOWER THAN EARLIER THOUGHT. THIS
SHOULD START TO PRODUCE SOME SPOTTY -DZ ALONG THE EASTERN SLOPES AS
SHOWERS WANE PER INCREASING STABILITY BUT LOOKS LESS THAN PREVIOUS
GIVEN DRY AIR SAGGING IN FROM THE NORTH OFF MSAS. HOW FAST/DEEP ANY OF
THE LOW CLOUDS CAN BANK IN ALONG THE EASTERN SLOPES KEY TO CLOUDS/TEMPS
THIS AFTERNOON WITH MODELS NOW SLOWER IN INITIALLY PUSHING THE CAD
SOUTH AND WEST. THIS MAY LEAD TO AN AXIS OF MODEST INSTABILITY ESPCLY
ALONG THE I-77 CORRIDOR EARLY THIS AFTERNOON WHERE GUIDANCE REDEVELOPS
SHRA ALONG THE WESTWARD MOVING SURFACE TROUGH. SINCE THIS IN LINE WITH
CONSENSUS...BUMPED UP CHANCE POPS ACROSS NW NC...AND SW VA LATER WHILE
TRIMMING ANY -DZ/-RA TO ISOLATED -SHRA BLUE RIDGE...AND LITTLE MORE
THAN CLOUDS EAST-NE AS BUILDING HIGH PRESSURE START TO ENHANCE INLAND
FROM THE MID ATLANTIC COAST. ALSO INCLUDED AN ISOLATED -TSRA MENTION NW
NC RIDGES/FOOTHILLS WHERE BEST LOW LEVEL CONVERGENCE LINES UP WITH THE
PASSING TROUGH UNDER DECENT 85H THETA-E RIDGING.

OTRW CLOUD COVER AND TEMPS THE MAIN ISSUES ESPCLY BLUE RIDGE WHERE
LIKELY TO BE STUCK MOSTLY IN THE 60S UNDER LOW DECK AND EASTERLY FLOW.
HOWEVER COULD ACTUALLY SEE READINGS PUSH INTO THE 70S FAR WEST GIVEN
THE SLOWER WEDGING...AS WELL AS OVER THE SOUTH/EAST IF CAN GET MORE
SUNNY BREAKS AS MOISTURE STARTS TO DECREASE FROM THE EAST LATE.

SURFACE RIDGING STRENGTHENS FROM THE NE OVERNIGHT HELPING PUSH THE
RESIDUAL AXIS OF MOISTURE FARTHER WEST WHICH SHOULD BRING AN END TO
POPS DURING THE EVENING. BANKED UP LOW LEVEL MOISTURE THOUGH LIKELY TO
REDEVELOP OR PERSIST BLUE RIDGE WHERE LOTS OF LOW CLOUDS/FOG POSSIBLE.
APPEARS AREAS OVER THE EAST/SE FROM HIGHWAY 29 EAST COULD SEE SOME
CLEARING AS MOISTURE GETS PINCHED FARTHER WEST AHEAD OF THE DRIER
EASTERLY FLOW. OTRW VARYING DEGREE OF CLOUDS FROM THE BLUE RIDGE WEST
WITH LOWS MAINLY IN THE 50S PER LATEST SIMILAR MAV/MET MOS.
&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 300 AM EDT FRIDAY...

THE HIGH PRESSURE CENTER THAT WAS OVER NEW ENGLAND WILL MOVE OUT
INTO THE ATLANTIC OVER THE WEEKEND. HOWEVER...THIS RIDGE WILL REMAIN
WEDGE BACK OVER THE MID ATLANTIC AND SOUTHEASTERN STATES INTO
SATURDAY NIGHT. A GULF STREAM DISTURBANCE WILL HELP KEEP THIS WEDGE
IN THE AREA AND ALSO PROVIDE SUBSIDENCE TO KEEP THE FORECAST AREA
DRY SATURDAY. THESE DISTURBANCE WILL HAVE MOST OF ITS RAIN FALLING
ON ITS EASTERN FLANK AS DRY AIR IS ENTRAINED INTO THE WESTERN SIDE.
THIS DISTURBANCE WILL TRACK TO THE NORTHEAST AND WILL REMAIN
OFFSHORE THROUGH THE WEEKEND.

MODELS HAVE SPED UP THE TIMING OF THE NEXT FRONTAL PASSAGE FROM
MONDAY TO SUNDAY. THIS FRONT STILL LOOKS LIKE A TYPICAL FALL FRONTAL
PASSAGE WITH RAIN FALLING ALONG WESTERN SLOPES...LOSING THEIR
INTENSITY MOVING TO THE BLUE RIDGE. THIS PRECIPITATION MAY THEN JUMP
THE FOOTHILLS AS A WEAK LINE OF CONVECTION DEVELOPS OVER THE
PIEDMONT WHERE A LEE TROUGH WILL RESIDE SUNDAY AFTERNOON. THE NAM
AND ECM LOOK SIMILAR WITH KEEPING BULK OF THE RAIN OVER THE
MOUNTAINS. THE GFS PROGRESSIVELY MOVES THE FRONT AND RAINFALL ACROSS
THE ENTIRE FORECAST AREA...DISREGARDING DOWNSLOPE. THE FORECAST DID
NOT DISCREDIT THE GFS...BUT MORE WEIGHT WAS PLACED WITH THE NAM/ECM
FOR SUNDAY.

SATURDAY TEMPERATURES WILL RUN WARMER THAN NORMAL WITH UPPER 70S TO
LOWER 80S. AREAS NOT SEEING RAIN UNTIL LATER IN THE DAY SUNDAY
SHOULD HAVE TEMPERATURES IN THE LOWER TO MID 80S. WESTERN SLOPES
SHOULD HAVE RAIN FALLING BY THE AFTERNOON AND MAY SEE HIGHS IN THE
MID 70S SUNDAY.
&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 200 PM EDT THURSDAY...

THIS PERIOD IS SHAPING UP TO BE DRY AND SEASONAL. ANOTHER SHORTWAVE
DROPS SOUTHEAST ACROSS THE TN VALLEY MONDAY AND COULD BRING ISOLATED
SHOWERS TO THE ENTIRE AREAS AS FLOW BACKS ALOFT SOME. THEN HIGH
PRESSURE ACROSS THE MIDWEST PUSHES EAST OVER THE MID ATLANTIC
TUE- WED. TEMPS BEHIND THIS SYSTEM EARLY NEXT WEEK WILL COOL DOWN
SOME...BUT NOT LOOKING AS CHILLY AS EARLIER THOUGHT...WITH 8H
TEMPS +10-12C.

HIGHS WILL RUN FROM THE 60S WEST TO 70S EAST...WITH LOWS MAINLY IN
THE 40S...WITH SOME 50S ACROSS THE PIEDMONT.
&&

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

HIGH END STRATO-CU ALONG WITH WIDESPREAD MID DECK PREVAIL ACROSS
MUCH OF THE REGION ATTM WITH WEAK MOISTURE CONVERGENCE BEING FED
VIA RESIDUAL LOW LEVEL THETA-E RIDGING JUST EAST OF THE BLUE
RIDGE. ACTUAL COOL FRONT THAT WILL SET A MORE EASTERLY REGIME INTO
MOTION OVERNIGHT STILL LAGGING TO THE NORTH SO IFFY AS TO HOW MUCH
CIGS WILL FALL BY DAYBREAK GIVEN CURRENT CANOPY. THIS SIMILAR TO
EARLIER IN THE WEEK WITH LOW LEVEL MOISTURE STUCK TO THE SOUTH
AND BOUNDARY LAYER DRY ADVECTION WINNING OUT ACROSS THE REGION.
THIS SHOWN IN DIFFERING MODEL SOLUTIONS FROM IFR IN STRATUS/DZ/FOG
TO VFR OUTSIDE OF PATCHY FOG LATE. FOR NOW WILL CONTINUE GOING
TRENDS OF LOWERING CIGS THROUGH MVFR TO IFR IN SPOTS BY DAWN
ESPCLY BLUE RIDGE WHILE SLOWING DOWN THE ONSET A BIT. MAY END UP
WITH A RIBBON OF ONLY IFR/LIFR AT KBCB/KROA AND MAINLY MVFR TO
BRIEF IFR ELSW BUT LOW CONFIDENCE. SPOTTY SHOWERS REMAIN ACROSS
THE FAR NE NEAR KLYH AND JUST SW OF KDAN SO WILL INCLUDE A VCSH
MENTION IN THESE SPOTS EARLY ON AND KEEP SOME -DZ MENTION ALONG
THE BLUE RIDGE.

ONCE CIGS DO LOWER EARLY FRIDAY...EXPECT LITTLE CHANGE DURING THE
MORNING WITH SOME IMPROVEMENT IN THE AFTERNOON AS CIGS TEND TO
LIFT SOME ESPCLY AWAY FROM THE BLUE RIDGE. OTRW OVERALL LITTLE
IMPROVEMENT IS EXPECTED WITH CIGS REMAINING MVFR MOST SITES ALL
DAY...BUT VSBYS SHOULD BE MOSTLY VFR AFT 15Z/11AM. WINDS BECOMING
ENE- ESE OVERNIGHT AT SPEEDS OF 5-7KTS...INCREASING TO 7-10KTS AFT
14Z/10AM FRI. SOME POTENTIAL FOR LOW END GUSTS IN USUALLY FAVORED
SOUTHEAST WIND AREAS...SUCH AS BLF...AFT 15Z FRI.

CIGS MAY LOWER AGAIN FRIDAY EVENING PENDING DEGREE OF
EROSION/COVERAGE HEADING INTO LATE FRIDAY AFTERNOON SO TRENDING
BACK TOWARD MVFR FROM THE BLUE RIDGE EAST EARLY FRIDAY NIGHT.
ANOTHER ROUND OF LOW CIGS IN FOG AND STRATUS LIKELY LATER FRIDAY
NIGHT INTO EARLY SATURDAY WITH SOME ADDED PATCHY -DZ POSSIBLE.

EXTENDED AVIATION DISCUSSION...

WEDGE SHOULD ERODE FAIRLY QUICKLY SATURDAY IN RESPONSE TO AN
UPSTREAM TROUGH. SOME LOW CLOUDS MAY LINGER THROUGH THE MORNING
ALONG WITH PATCHY FOG...BUT OVERALL VFR CONDITIONS EXPECTED SAT. A
FRONTAL SYSTEM WILL APPROACH SUN WITH -SHRA AND PERHAPS AN ISOLD
TSRA WEST OF THE ALLEGHANY FRONT. INSTABILITY IS QUITE LIMITED AND
SO IS DEEP MOISTURE. WITH A POSSIBLE TROPICAL SYSTEM DEVELOPING
OFF THE COAST AT THE SAME TIME...WE MAY BE IN A STRONG SUBSIDENCE
AREA AND SEE LITTLE MORE THAN -SHRA OR SPRINKLES EAST OF THE
ALLEGHANY FRONT. EXPECT MOSTLY VFR-PERIODS OF MVFR CIGS SUN-EARLY MON
AS THE TROUGH MOVES THROUGH. HIGH PRESSURE BUILDS IN FOR THE FIRST
HALF OF NEXT WEEK WITH DRY NW FLOW. THUS...EXPECT MOSTLY VFR
CONDITIONS THROUGH THE PERIOD WITH LOCAL EARLY MORNING MVFR-IFR
FOG CONDITIONS.

&&

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

&&

$$
SYNOPSIS...JH/KK
NEAR TERM...JH
SHORT TERM...RCS
LONG TERM...WP
AVIATION...JH/KK/RAB




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