369
FXUS61 KRNK 152347
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
747 PM EDT MON JUL 15 2019
SYNOPSIS
A RIDGE OF HIGH PRESSURE WILL START SHIFTING EAST TO THE COAST
TONIGHT INTO TUESDAY, AS A LOW PRESSURE TROUGH OVER THE OHIO VALLEY
BEGINS HEADING EASTWARD. THIS SYSTEM WILL BRING INCREASED TROPICAL
MOISTURE ACROSS OUR AREA WEDNESDAY INTO THURSDAY. A RIDGE OF HIGH
PRESSURE WILL AGAIN TRY TO GAIN A FOOTHOLD OVER OUR REGION FOR THE
WEEKEND.
NEAR TERM /THROUGH TUESDAY/
AS OF 747 PM EDT MONDAY...SEVERAL STRONG, WITH A FEW SEVERE
STORMS CONTINUE TO MAINLY AFFECT THE BLUE RIDGE AS WELL AS
ACROSS THE NORTHERN THIRD OF THE FORECAST AREA. WHILE CONVECTION
WHICH FIRED ACROSS BATH THROUGH BUCKINGHAM COUNTIES WAS IN
ASSOCIATION WITH A STALLED FRONTAL ZONE OVER CENTRAL VA, APPEARS
ACTIVITY IN THE BLUE RIDGE IS BEING SPAWNED FROM REMNANT
OUTFLOWS. WHILE AIR MASS CONTINUES TO BE MODERATELY UNSTABLE,
ELEVATED DCAPE VALUES DRIVEN BY STRONG DAYTIME HEATING ARE
ESPECIALLY PREVALENT ACROSS THE BLUE RIDGE AND EASTWARD INTO THE
PIEDMONT. UNTIL THE BOUNDARY LAYER STABILIZES AFTER SUNSET, ANY
STORMS WHICH CAN MOVE INTO THIS DCAPE-RICH ENVIRONMENT SHOULD
PROVE CAPABLE OF GUSTY WINDS; THOSE STORMS WHICH REFORM AND MOVE
OVER THE SAME AREAS COULD ALSO POSE A LOCALIZED HYDRO RISK AS
WELL. RELATIVE MIN IN STORM COVERAGE IS EXPECTED INTO THE
FOOTHILLS AND PIEDMONT/SOUTHSIDE AREAS OF VA/NC - AND MOST OF
THESE AREAS SHOULD STAY LARGELY DRY.
THERE'S SOME QUESTION HOW LONG ONGOING SHOWERS/STORMS MAY
LINGER, ESPECIALLY IN THE WEST. WHILE STORMS SHOULD BE GENERALLY
FIZZLING SHORTLY AFTER SUNSET, GUIDANCE IS OFFERING MIXED
SIGNALS ON WHEN WE GO FULLY CLEAR. BOTH THE 18Z NAM AND GFS
SUGGEST SLIGHT/LOW CHANCE POPS MAY BE WARRANTED IN THE WEST
UNTIL MIDNIGHT, WITH THE SUBTROPICAL RIDGE AXIS SHIFTING ENOUGH
EAST OFF THE MOUNTAINS TO FOSTER CONTINUED SPOTTY SHOWERS. DID
SHOW POPS A LITTLE LONGER, BUT THESE MAY STILL BE UNDERDONE.
WILL LET TRENDS AND INCOMING 00Z DATA DICTATE ANY FURTHER
CHANGES, THOUGH DID STRETCH SOME ISOLATED SHOWERS THROUGH 03Z IN
THE WESTERN MOUNTAINS. SHOULD SEE FOG IN THE TYPICAL RIVER
VALLEYS OVERNIGHT, AS WELL AS NEAR AREAS WHICH RECEIVED WETTING
RAINS.
NO CHANGES MADE ATTM TO LOWS WHICH STILL LOOK ON PACE.
PREVIOUS DISCUSSION FROM 245 PM MONDAY...
ISOLATED TO SCATTERED SHOWERS AND STORMS WILL CONTINUE ACROSS PARTS
OF THE AREA THROUGH THE REMAINDER OF THE AFTERNOON, AND LINGER INTO
THE EVENING HOURS. A FEW MAY REMAIN UNTIL MIDNIGHT. THE ACTIVITY
CONTINUES TO BE FOCUSED NEAR AN OLD FRONTAL BOUNDARY THAT HAS BEEN
FLUCTUATING ACROSS THE REGION THE PAST COUPLE OF DAYS. IT HAS BEEN
STUCK UNDER A SHORTWAVE RIDGE, AND HAS HAD VERY LITTLE IN THE WAY OF
A STEERING FLOW TO MOVE IT ALONG.
OVERNIGHT, WE ARE EXPECTING ANOTHER SITUATION WHERE EASTERN SECTIONS
OF THE REGION EXPERIENCE MORE CLEAR SKIES THAN CLOUDS, BUT WITH THE
OPPOSITE OVER THE MOUNTAINS. A RETURN OF AREAS OF LOW LEVEL CLOUD
COVER AND SOME PATCHY RIVER/MOUNTAIN VALLEY FOG IS EXPECTED. THE
GREATEST CONCENTRATION WILL BE IN PARTS OF THE GREENBRIER AND NEW
RIVER BASINS. ALSO, A CHANGE FROM LAST NIGHT, SOME EASTERN SECTIONS
THAT RECEIVE SOME RAINFALL THIS EVENING, WILL HAVE AN INCREASED
CHANCE OF PATCHY FOG BY MORNING. AREAS ALONG AND NORTH OF THE JAMES
RIVER BASIN LOOK THE MOST PROMISING BASED UPON THE LATEST RADAR AND
MESO-SCALE FORECAST TRENDS.
FOR TUESDAY, WE EXPECT THE TREND OF INCREASING COVERAGE OF AFTERNOON
SHOWERS AND STORMS TO CONTINUE. THE AXIS OF THE UPPER LEVEL
SHORTWAVE RIDGE IS EXPECTED TO SHIFT CLOSER TO THE COAST, AND AN
UPPER LEVEL TROUGH ACROSS THE LOWER OHIO VALLEY WILL START MAKING
HEADWAY EASTWARD. THIS TRANSITION WILL HELP WEAKEN THE CAP ALOFT,
INCREASE DYNAMICS, AND THUS MAKE SHOWER AND STORM DEVELOPMENT A BIT
EASIER. PLUS, THE OLD FRONTAL BOUNDARY WILL STILL BE WASHED OUT
ACROSS THE REGION, AND THERE WILL BE LINGERING BOUNDARIES STILL
AROUND FROM THIS EVENING'S CONVECTION FOR DAYTIME HEATING TO USE AS
A FOCAL POINT OF INITIATION.
TEMPERATURES WILL CONTINUE TO BE ON THE MILD SIDE FOR THIS TIME OF
YEAR. LOWS TONIGHT ARE EXPECTED TO RANGE FROM THE MID TO UPPER 60S
ACROSS THE MOUNTAINS WITH LOWER 70S ACROSS THE PIEDMONT. HIGHS ON
TUESDAY ARE FORECAST IN THE MID TO UPPER 80S ACROSS THE MOUNTAINS
WITH 90 TO 95 ACROSS THE PIEDMONT.
SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/
AS OF 330 PM EDT MONDAY...
WEATHER FOR MID-WEEK WILL FEATURE REMNANTS FROM BARRY, THE CRUX
OF THE UPPER SUPPORT PASSING TO OUR NORTH, BUT WITH AN AXIS OF
VORTICITY TRAILING TO THE SOUTH AS THE CLOSED FEATURE BEGINS TO
SHEAR INTO AN OPEN WAVE. INSTABILITY FROM WEDNESDAY INTO
THURSDAY IS EXPECTED TO BE PLENTIFUL, SO ANTICIPATE SCATTERED TO
NUMEROUS SHOWERS WITH EMBEDDED THUNDERSTORMS.
MODELS SUGGEST THE MOST FAVORABLE TIME FRAME FOR MEASURABLE
RAINFALL DIRECTLY ASSOCIATED WITH THE TROPICAL REMNANTS WILL BE
FROM WEDNESDAY AFTERNOON THROUGH THURSDAY MORNING... THE VORT
AXIS PASSING OVERHEAD AT THAT TIME. QPF IS FORECAST TO BE THE
HEAVIEST FROM THE OHIO VALLEY INTO THE WESTERN SLOPES WHERE
WESTERLY FLOW ALOFT WILL ACT TO ENHANCE THE RAINFALL, BUT AS THE
SYSTEM CROSSES THE APPALACHIANS, PRECIP PRODUCTION IS EXPECTED
TO GO DOWN PER WESTERLY DOWNSLOPE FLOW. ATTM OUR 1-3 DAY
FORECAST RAIN TOTALS AVERAGE FROM ABOUT AN INCH OF QPF ON THE
WESTERN SLOPES TO A GENERAL QUARTER OF AN INCH ACROSS THE
PIEDMONT. TEMPERATURES ARE EXPECTED TO BE SEASONALLY WARM,
TEMPERED TO SOME DEGREE BY THE SHOWERS AND ANTICIPATED CLOUD
COVER. THE HIGH DEWPOINTS HOWEVER, WITH READINGS FORECAST IN THE
70S, WILL MAINTAIN THE MUGGINESS.
LONG TERM /FRIDAY THROUGH MONDAY/
AS OF 345 PM EDT MONDAY...
FOR FRIDAY AND INTO THE UPCOMING WEEKEND... THE UPPER RIDGE
STRENGTHENS WITH POTENTIAL FOR 500 MB HEIGHTS TO TEST 595 DM.
AS SUCH, PATTERN FAVORS SOME VERY WARM TEMPERATURES FOR THE
WEEKEND, 85H TEMPS OF +23 TO +24 DEG C, YEILDING SURFACE
READINGS WELL INTO THE 90S EAST OF THE BLUE RIDGE. DEWPOINTS
ARE ALSO EXPECTED TO REMAIN ELEVATED, SO HEAT INDICES MAY
ECLIPSE 100 FOR SEVERAL DAYS IN A ROW...POTENTIALLY TESTING 105
DEGREES BY SATURDAY. SOME RELIEF MAY COME FROM POP-UP
AFTERNOON/EVENING SHOWERS AND THUNDERSHOWERS, BUT COVERAGE IS
EXPECTED TO BE LIMITED PER LACK OF ANY SIGNIFICANT FORCING
MECHANISM AND OVERALL SUBSIDENCE FROM THE UPPER LEVEL RIDGING.
AVIATION /23Z MONDAY THROUGH SATURDAY/
AS OF 747 PM EDT MONDAY...
SCATTERED STRONG THUNDERSTORMS WITH BRIEF SUB-HOURLY RESTRICTIONS
AS LOW AS IFR AND GUSTY OUTFLOW WINDS WILL REMAIN POSSIBLE
THROUGH 02Z, AT MOST TAFS EXCEPT DANVILLE. HAVE INDICATED VCTS
AND WILL TREAT ANY THUNDERSTORM THREAT SPECIFIC TO AN AIRFIELD
WITH TEMPOS. STORM COVERAGE SHOULD GENERALLY DIMINISH THROUGH
MIDNIGHT, BUT A FEW SHOWERS MAY LINGER IN THE WESTERN MOUNTAINS
THROUGH AT LEAST THAT TIMEFRAME. SHOULD ALSO SEE PATCHY IFR OR
LOWER FOG ACROSS THE NON-ROANOKE WESTERN TERMINALS, AS WELL AS
IN LYNCHBURG OVERNIGHT.
AFTER FOG BURNS OFF, WE SHOULD AGAIN SEE CUMULUS DEEPEN INTO
THUNDERSTORMS IN THE MOUNTAINS BY EARLY TO MID AFTERNOON, THEN
PROGRESS EASTWARD OFF THE BLUE RIDGE INTO THE PIEDMONT TOWARD
THE END OF THE TAF PERIOD. SOME QUESTION ON STORM COVERAGE
TOMORROW - IF IT WILL BE MORE THAN TODAY OR LESS SO; HAVE
MAINTAINED VCSH AT MOST TERMINALS FOR TUESDAY AFTERNOON.
CONFIDENCE IN AVIATION FORECAST ELEMENTS IS MODERATE; LOWER
CONFIDENCE ON COVERAGE OF FOG AND WHEN PRECIPITATION ENDS
TONIGHT, AND ON STORM COVERAGE TUESDAY.
EXTENDED AVIATION DISCUSSION
THE OCCURRENCE OF SUB-VFR CONDITIONS WILL INCREASE WEDNESDAY
INTO THURSDAY AS A SHORTWAVE TROUGH APPROACHES AND THE CROSSES
THE AREA, BRINGING ALONG WITH IT THE TROPICAL MOISTURE
ASSOCIATED WITH THE REMNANTS OF BARRY. EXPECT AN INCREASE IN
SHOWER AND THUNDERSTORM COVERAGE, AND SUBSEQUENT LATE
NIGHT/EARLY MORNING STRATUS/FOG.
BY FRIDAY INTO SATURDAY, A SHORTWAVE RIDGE RETURNS OVERHEAD, AND
THIS WILL CURTAIL, BUT NOT REMOVE THE POTENTIAL FOR DIURNALLY
BASED SHOWERS AND STORMS, WITH THE FOCUS FOR MOST ACTIVITY
ACROSS THE MOUNTAINS. DEPENDING UPON GROUND MOISTURE FOR THE
DAYS HEADING INTO THE WEEKEND, LATE NIGHT/EARLY MORNING FOG
COULD AGAIN BE A POSSIBILITY.
CONFIDENCE IN THE ABOVE AVIATION SCENARIO IS MODERATE.
EQUIPMENT
AS OF 400 PM EDT MONDAY...
THE CEILOMETER AT LWB IS HAVING PERIODIC PROBLEMS WHICH MAY
CAUSE INTERMITTENT LOSS OF DATA.
RNK WATCHES/WARNINGS/ADVISORIES
VA...NONE.
NC...NONE.
WV...NONE.
SYNOPSIS...DS
NEAR TERM...AL/DS
SHORT TERM...PM
LONG TERM...PM
AVIATION...AL/DS
EQUIPMENT...DS
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