707
FXUS61 KRNK 161426
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1026 AM EDT TUE JUL 16 2019
SYNOPSIS
WEAK HIGH PRESSURE OVER THE SOUTHERN APPALACHIANS WILL SLOWLY
MOVE EAST TODAY WHILE A FRONT ACROSS NORTHERN VIRGINIA MOVES TO
THE NORTHERN MID-ATLANTIC. LOW PRESSURE THAT WAS ONCE TROPICAL
STORM BARRY WILL PUSH ACROSS THE OHIO VALLEY WEDNESDAY. A
FRONTAL BOUNDARY MOVES THROUGH THE REGION THURSDAY MORNING.
NEAR TERM /THROUGH TONIGHT/
AS OF 1015 AM EDT TUESDAY...
ONLY MINOR TWEAKS TO EXISTING GRIDS THIS MORNING AS SCATTERED
SHOWERS AND THUNDERSTORMS STILL POSSIBLE TODAY BUT POPS REMAIN
ONLY IN THE 20-30 PERCENT CHANCE RANGE. AIR MASS REMAINS
SEASONABLY MOIST WITH PWAT OF 1.41 INCHES ON 12Z KRNK SOUNDING
WHICH IS DOWN SLIGHTLY FROM YESTERDAY EVENING BUT STILL ABOVE
MID-JULY CLIMO AT ABOUT 75TH PERCENTILE. ANY SLOW-MOVING STORMS
WOULD STILL BE CAPABLE OF PRODUCING DECENT RAIN TOTALS. SEEING
MORE CLOUDS FROM THE REMAINS OF BARRY THIS MORNING WHICH MAY
HOLD DOWN INSTABILITY SOME BUT UNLIKELY TO SUPPRESS ALL
CONVECTION.
AS OF 250 AM EDT TUESDAY...
UPPER RIDGE CONTINUES TO STAY OVER THE SOUTHEAST TODAY, WHILE
THE FRONT THAT WAS OVER NORTHERN VIRGINIA LIFTS NORTHEAST TODAY
AHEAD OF THE REMNANTS OF BARRY. FOR OUR AREA, WILL SEE ISOLATED
TO SCATTERED CONVECTION ONCE AGAIN FIRING UP AROUND MIDDAY, THEN
SHIFTING SLOWLY MAINLY IN AN EAST TO NORTHEAST FASHION. HOWEVER
WIND FLOW WILL BE WEAK, SO NOT OF THE QUESTION TO SEE HEAVY
RAINERS AND LOCALIZED FLOODING. AS FAR AS THE SEVERE THREAT,
CANNOT RULE OUT ISOLATED STRONG TO SEVERE STORMS WITH DOWNBURSTS
THE MAIN THREAT. THE STORM PREDICTION CENTER HAS JUST A GENERAL
THUNDERSTORM OUTLOOK FOR US, AND GIVEN SUCH AN ISOLATED THREAT,
THIS MAKES SENSE.
HIGHEST POPS TODAY WILL BE ALONG THE SOUTHERN BLUE RIDGE AS NUMEROUS
MODELS AGREE ON CONVECTION FIRING HERE WITH OROGRAPHIC EFFECTS, SO
WENT 40-50 HERE...AND THIS COULD BE ANOTHER AREA TO WATCH FOR
LOCALIZED FLOODING IF THUNDERSTORMS ARE SLOW AND STAY ANCHORED ON
THE MOUNTAINS.
BY THIS EVENING, THE SHOWERS AND STORMS FADE AGAIN TOWARD MIDNIGHT.
THE UPPER RIDGE BEGINS TO BREAK DOWN AS UPPER TROUGH/LOW ASSOCIATED
WITH BARRY MOVES CLOSER TOWARD THE OHIO VALLEY. SHOULD SEE CLEARING
SKIES AND FOG POTENTIAL AGAIN WHERE IT RAINED AND IN TYPICAL
MOUNTAIN VALLEYS.
EXPECT HIGH TEMPS CLOSE TO WHAT WE HAD MONDAY WITH LOWER 80S NC
MOUNTAINS AND PORTIONS OF THE ALLEGHANYS ALONG THE WV/VA BORDER,
FIGURING THUNDERSTORMS ARE GOING TO FIRE UP HERE EARLIER, WITH MID
TO UPPER 80S ELSEWHERE IN THE MOUNTAINS. ROANOKE AND POINTS EAST
WILL REACH THE LOWER TO MID 90S. DEWPOINTS SHOULD DROP INTO THE
UPPER 60S THIS AFTERNOON, RESULTING IN HEAT INDICES OF 95 TO 99,
WITH THE HIGHER HEAT INDICES ABOVE 100 EXPECTED EAST OF A FARMVILLE
VA TO DURHAM NC LINE.
LOWS TONIGHT AGAIN NOT CHANGING MUCH AS PERSISTENT PATTERN/AIRMASS
SHOULD KEEP TEMPS IN THE MID TO UPPER 60S IN THE MOUNTAINS, TO
AROUND 70 TO LOWER 70S EAST.
FORECAST CONFIDENCE IN TEMPS/WIND AND SKY IS ABOVE NORMAL, WITH
AVERAGE CONFIDENCE ON STORM COVERAGE.
SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/
AS OF 210 AM EDT TUESDAY...
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 VORTICITY 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. AT THE MOMENT, OUR DAY 2-3 FORECAST RAIN
TOTALS AVERAGE FROM ABOUT AN INCH OF QPF ON THE WESTERN SLOPES TO A
GENERAL QUARTER OF AN INCH ACROSS THE PIEDMONT. KEEP IN MIND PWATS
ARE RUNNING AROUND 2 INCHES, THEREFORE LOCALIZED TORRENTIAL
DOWNPOURS ARE POSSIBLE. 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.
A FRONTAL BOUNDARY WILL SLOWLY MOVE ACROSS THE REGION THURSDAY
MORNING, STALLING OVER THE PIEDMONT IN THE AFTERNOON. BEHIND THIS
BOUNDARY, PWATS FALL TO AROUND 1.50 INCHES WHILE AHEAD THEY REMAIN
NEAR 2.00 INCHES. RIDGING ALOFT BEGINS TO BUILD EASTWARD THROUGH THE
DAY, WHICH SHOULD LIMIT CONVECTIVE ACTIVITY. HOWEVER, DIURNAL
HEATING AND A STALLED BOUNDARY/LEE TROUGH COULD PRODUCE SOME STORMS
ALONG AND EAST OF ROUTE 29 WHICH MAY CONTAIN HEAVY DOWNPOURS DURING
THE AFTERNOON AND EVENING HOURS.
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 /14Z TUESDAY THROUGH SATURDAY/
AS OF 720 AM EDT TUESDAY...
EXPECT THE LITTLE BIT OF FOG AT LWB/BCB TO BE GONE BY 13Z. VFR
CONDITIONS THROUGH THE DAY STILL EXPECTED AND INTO TONIGHT.
SCATTERED DEVELOPMENT FOR SHOWERS/STORMS ACROSS THE MOUNTAINS
EARLY THIS AFTERNOON WILL SHIFT EAST TOWARD THE PIEDMONT THROUGH
LATE AFTERNOON. ABOUT 30 PERCENT COVERAGE SO ADDED VCTS AT ALL
SITES EXCEPT DAN.
STORMS SHOULD BE GONE BY LATE EVENING WITH MAINLY VFR MID AND
HIGH CLOUDS. POTENTIAL FOR FOG EXISTS AGAIN WHERE IT RAINS, BUT
CONFIDENCE ONLY HIGH ENOUGH TO HAVE MVFR VSBYS AT LWB/BCB, BUT
POTENTIAL IS THERE FOR LOWER VSBYS IF WE CLEAR OUT ENOUGH.
FORECAST CONFIDENCE OUTSIDE THE STORMS IS GOOD THROUGH THE
PERIOD.
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.
RNK WATCHES/WARNINGS/ADVISORIES
VA...NONE.
NC...NONE.
WV...NONE.
SYNOPSIS...DS/WP
NEAR TERM...PC/WP
SHORT TERM...RCS
LONG TERM...PM
AVIATION...AL/WP
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