Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 230528
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
128 AM EDT TUE SEP 23 2014

.SYNOPSIS...
HIGH PRESSURE SYSTEM WILL MOVE EAST TONIGHT COVERING MUCH OF THE
EASTERN UNITED STATES THROUGH WEDNESDAY. LOW PRESSURE WILL DEVELOP
ALONG THE SOUTHEAST COAST THURSDAY AND FRIDAY.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 830 PM EDT MONDAY...

NOT A LOT OF CHANGE OVERNIGHT WITH LOW CLOUDS ACROSS THE FAR WEST
SLOWLY FADING WHILE PERSISTENT AXIS OF HIGH LEVEL MOISTURE
CONTINUES TO SHEAR NORTH ACROSS THE REMAINDER OF THE REGION ATTM.
MOST GUIDANCE HUMIDITY FIELDS KEEP THIS CANOPY OF HIGH CLOUDS AT
LEAST OVER THE EAST THROUGH MORNING WITH THE GFS EVEN BENDING BACK
WESTWARD IN RESPONSE TO THE DEVELOPING CUTOFF 5H SYSTEM TO THE
SOUTH. HOWEVER APPEARS GIVEN VERY DRY AIR OFF EVENING SOUNDINGS
THAT MOST CIRRUS OUTSIDE OF THE PIEDMONT SHOULD STAY THIN ENOUGH
TO ALLOW GOOD RADIATIONAL COOLING AS THE SURFACE HIGH SINKS IN
FROM THE NORTH OVERNIGHT. LATEST LAV MOS SIMILAR TO EARLIER
FORECAST LOWS SO ONLY MAKING SMALL ADJUSTS...MAINLY TO LOWER A BIT IN
A FEW MORE OF THE WESTERN VALLEYS WHERE EARLIER COOP MOS WAS THE
COLDEST. ALSO ADDED A BIT MORE DEEP VALLEY FROST BUT GIVEN WARM GROUND
TEMPS/VEGETATION AND FOG POTENTIAL APPEARS ANY FROST VERY BRIEF
AND NOT ENOUGH FOR ANY HEADLINES AT THIS POINT. ALSO GIVEN CURRENT
WIDE TEMP/DEWPT SPREAD IN SPOTS...SLOWING DOWN FOG FORMATION A
WHILE LONGER TO MOSTLY THE EARLY MORNING HOURS FOR NOW. OTRW
CALLING IT CLEAR TO PC THROUGH HIGH CLOUDS WITH LOWS 37-44 FAR
WEST...LOW/MID 40S BLUE RIDGE...AND LOW 50S SE WHERE MORE CLOUDS
AND HIGHER DEWPOINTS SHOULD NEGATE COOLING TO SOME DEGREE.

PREVIOUS VALID DISCUSSION AS OF 230 PM EDT MONDAY...

HIGH PRESSURE TO MOVE OVER THE MID ATLANTIC LATE TONIGHT. CLOUDS
THIS AFTERNOON WILL ERODE IN THE MOUNTAINS TONIGHT BUT AT THE SAME
TIME AS UPPER LEVEL SYSTEM MOVES ACROSS THE WESTERN CAROLINAS AND
CLOSES OFF...EXPECT THE UPPER LEVELS TO MOISTEN UP AND SEND SOME
CIRRUS NORTH ACROSS THE EASTERN HALF OF THE FORECAST AREA...THOUGH
NOT TOO CONFIDENT ON DENSITY OF THE CIRRUS...BUT THINK THE SKY WILL
BE PARTLY CLOUDY. BIG ISSUE TONIGHT WILL BE TEMPS...AS WINDS
DECOUPLE...AND SKY IN THE WEST TO BE CLEAR. THINK TEMPS WILL BE
DROPPING INTO THE MID TO UPPER 30S ACROSS THE VALLEYS OF BATH AND
GREENBRIER WITH MOST STAYING ABOVE 37F. PATCHY FROST IN THE VALLEYS
APPEARS POSSIBLE SO HIGHLIGHT BATH AND GREENBRIER IN THE HWO FOR
PATCHY FROST. NOT ENOUGH COVERAGE TO WARRANT A FROST ADVISORY BUT
EVENING SHIFT CAN TAKE ANOTHER LOOK AT TRENDS IN
TEMP/DEWPOINT/WIND/SKY IN CASE THREAT OF MORE FROST INCREASES.

NONETHELESS THE COOLEST NIGHT WE HAVE HAD SINCE LATE MAY...WITH
UPPER 30S/LOWER 40S MOUNTAINS...TO MID 40S-50 EAST.

DURING THE DAY TUESDAY...UPPER LOW/TROUGH STAYS OVER THE CENTRAL
PORTIONS OF THE CAROLINAS...AND MAINLY KEEPING A STREAM OF HIGH
CLOUDS SITUATED OVER THE PIEDMONT. HIGH WILL BE MILD WITH UPPER 60S
TO LOWER 70S ACROSS MUCH OF THE CWA.

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY/...
AS OF 240 PM EDT MONDAY...

STILL LOOKING DRY TUESDAY NIGHT BUT MODEL DIFFERENCES SHOW UP IN
TERMS OF THIS UPPER TROUGH INTO WEDNESDAY...AND HOW MUCH MOISTURE
SPREADS WEST FROM THE EAST FLOW AROUND THE WEDGE. THE ECMWF HAS BEEN
PERSISTENT IN SHOWING THIS AND THE 12Z NAM IS COMING INTO THIS
TREND AS WELL...WITH THE GFS STILL DRIER. THINK THE DRY LOW LVLS
WILL TAKE A WHILE TO MOISTEN UP BUT LATE WED NIGHT-THU SHOULD SEE
ENOUGH BETWEEN THE HIGH OVER THE NE/MID ATLANTIC AND A COASTAL
TROUGH/FRONT/LOW TO BRING A SLIGHT CHANCE TO LOW CHANCE OF RAIN TO
THE EASTERN HALF OF THE CWA...WITH CLOUDS INCREASING. THE WEDGE IN
PLACE WILL MAKE FOR A COOLER DAY THURSDAY...THAN WEDNESDAY. HIGHS
WEDNESDAY WITH MORE SUN WILL WARM INTO THE UPPER 60S TO MID
70S...THEN WITH CLOUDS AND LIGHT RAIN THURSDAY EXPECT MID TO
UPPER 60S WHERE ITS CLOUDY WITH RAIN CHANCES...WITH LOWER TO MID
70S ACROSS THE FAR SW VA CORRIDOR HEADING WEST OF MARION AND
TAZEWELL.

LOWS WILL ALSO MODIFY DURING THIS PERIOD...BUT STILL COOL WED
MORNING WITH LOWER 40S MOUNTAIN VALLEYS...TO MID TO UPPER 40S MOST
LOCATIONS...EXCEPT LOWER 50S SOUTHEAST.

LOWS THURSDAY MORNING WILL BE IN THE 50 TO 55 DEGREE RANGE.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
AS OF 300 PM EDT MONDAY...

CONSIDERABLE UNCERTAINTY EXISTS IN THE EXTENDED PERIOD AS A
FAIRLY COMPLEX UPPER LEVEL PATTERN DEVELOPS BY THE WEEKEND WITH
HIGHLY AMPLIFIED UPPER RIDGE OVER THE NORTH CENTRAL U.S. EXTENDING
INTO CANADA WITH TROUGHING OVER THE WESTERN ATLANTIC AND ACROSS
THE WESTERN STATES.

THE 12Z EURO IS MUCH FURTHER WEST WITH ATLANTIC TROUGH WITH
RESULTANT SURFACE LOW MEANDERING ALONG THE MID- ATLANTIC COAST
FRI-SAT BUT NOT FAR ENOUGH WEST FOR PRECIP THIS FAR INLAND. BUT
WOULD LIKELY SEE SUBSTANTIAL CLOUDINESS FROM THIS ALONG WITH THE
CAD-LIKE EFFECTS FROM A VERY SLOW-MOVING SURFACE HIGH OVER THE
NORTHEAST. IN FACT THE UPPER RIDGE TO THE NORTH RETARDS THE
NORTHWARD MOVEMENT OF THIS COASTAL SYSTEM WELL INTO SUNDAY.
GFS IS MUCH LESS DEVELOPED WITH ANY COASTAL SYSTEM WITH DRY HIGH
PRESSURE IN CONTROL THROUGH WEEKEND. ELECTED TO REFLECT MORE
OPTIMISTIC GFS SOLUTION AT THIS POINT WITH MORE SUN.

TEMPS NEAR TO ABOVE NORMAL WITH MAINLY 70S AND 50S FOR
HIGHS/LOWS. BOTH GFS/EURO SHOW SURFACE LOW OR INVERTED TROUGH
DEVELOPING OVER THE LOWER MISSISSIPPI VALLEY BY EARLY NEXT WEEK
WITH GRIDS SHOWING CLOUDS SPREADING IN FROM SW TO NE AS EARLY AS
SUNDAY NIGHT.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
AS OF 125 AM EDT TUESDAY...

EXPECTING VFR CONDITIONS TO PREVAIL OVERNIGHT AT KROA/KLYH/KBLF
AND KDAN. SCATTERED TO BROKEN HIGH CLOUDS WILL MUCH OF CENTRAL AND
EASTERN VIRGINIA AND NORTH CAROLINA TODAY AND TONIGHT.

GOOD RADIATIONAL COOLING WILL LEAD TO PATCHY RIVER BOTTOM FOG.
THIS WILL RESULT IN A FEW HOURS OF LIFR CONDITIONS AT KLWB.
MVFR/IFR CONDITIONS POSSIBLE AT KBCB FOR AN HOUR OR TWO RIGHT
AROUND DAWN. BY 14Z/10AM TUESDAY ALL TAF LOCATIONS WILL BE VFR AND
HIGH CONFIDENCE THAT CONDITIONS WILL STAY VFR THROUGH THE
REMAINDER OF THE TAF PERIOD.

EXTENDED AVIATION DISCUSSION...

HIGH PRESSURE AND DRIER AIR IN THE REGION THROUGH WEDNESDAY WILL RESULT
IN MAINLY VFR CONDITIONS. RIVER VALLEY FOG WILL STILL BE POSSIBLE AT
NIGHT AS WINDS DIMINISH AND COOL AIR MASS DECOUPLES. THERE IS STILL
SOME MODEL DIFFERENCES REGARDING A LOW PRESSURE SYSTEM FORMING FROM THE
GULF COAST LATER THIS WEEK. SEVERAL MODELS SHOW MOISTURE INCREASING
OVERNIGHT WEDNESDAY THROUGH THURSDAY EVENING WHICH MAY RESULT IN
PERIODS OF IFR/MVFR CEILINGS AND VSBYS. APPEARS HIGH PRESSURE WILL
AGAIN RE-ESTABLISH OVER THE REGION LATE IN THE WEEK RESULTING IN
RETURN TO WIDESPREAD VFR BY THE WEEKEND.

&&

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

&&

$$
SYNOPSIS...WP
NEAR TERM...JH/WP
SHORT TERM...WP
LONG TERM...PC
AVIATION...AMS/JH



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