540
FXUS61 KRNK 022317
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
717 PM EDT SUN AUG 2 2026
WHAT HAS CHANGED
00Z AVIATION UPDATE...
A FLOOD WATCH REMAINS IN EFFECT THROUGH EARLY MONDAY MORNING
FOR INSTANCES OF FLASH FLOODING.
KEY MESSAGES
1) FLASH FLOOD POTENTIAL REMAINS ELEVATED THROUGH LATE TONIGHT
ALONG WITH MARGINAL RISK FOR STRONG TO SEVERE STORMS.
2) UNSETTLED WEATHER CONTINUES THROUGH MUCH OF THE WEEK.
DISCUSSION
KEY MESSAGE 1...FLASH FLOOD POTENTIAL REMAINS ELEVATED THROUGH
LATE TONIGHT ALONG WITH MARGINAL RISK FOR STRONG TO SEVERE
STORMS.
AN ANOMALOUS SLOW MOVING UPPER LEVEL LOW CENTERED OVER THE LOWER
OHIO VALLEY WILL CONTINUE TO PLAGUE THE FORECAST AREA WITH BROAD
AND IMPRESSIVE SYNOPTIC ASCENT IMPINGING INTO AN ABUNDANCE OF
MOISTURE LADEN AIR OVER THE EASTERN CONUS. MORNING 12Z U/A
REGIONAL SOUNDINGS MEASURED PWATS FROM 1.8 TO 2.2 INCHES, WELL
ABOVE THE 90TH PERCENTILE, AND RECORD SETTING FOR THE DATE HERE
AT RNK. THIS ENVIRONMENT IS RIPE FOR FOR HEAVY RAINFALL WITHIN
ANY CONVECTION WHICH DEVELOPS YIELDING OFF THE CHART KIND OF
RAINFALL RATES. FORECASTERS WORKING THE MOUNT AIRY EMERGENCY
FROM LAST NIGHT SAID RADAR WAS ESTIMATING RAINFALL RATES IN
EXCESS OF 5-7 INCHES AN HOUR. WITHIN 3 HOURS TIME BETWEEN 4-8
INCHES OF RAIN FELL WITHIN THE HEADWATERS OF THE ARARAT RIVER
BASIN RESULTING IN MAJOR FLOODING IN MT. AIRY NC. EXTENSIVE
PROPERTY AND ROAD DAMAGE WAS OBSERVED IN ADDITION TO SWIFT WATER
RESCUES.
CONCERN THROUGH THIS EVENING AND INTO THE OVERNIGHT TONIGHT IS
REDEVELOPMENT OF THESE RAIN EFFICIENT SHOWERS AND
THUNDERSTORMS. THUNDERSTORM CLUSTERS ARE EXPECTED TO DEVELOP
WITHIN AN ENVIRONMENT SUPPORTED BY MODERATE INSTABILITY, SURFACE
DEWPOINTS IN THE 70S, AND PWATS NEAR 2 INCHES, SUGGESTING MAIN
THREAT FROM ANY STORM ACTIVITY THAT DEVELOPS WILL BE FROM THE
POTENTIAL FOR EXCESSIVE RAINFALL. ALTHOUGH LAPSE RATES WILL
REMAIN POOR AND VERTICAL SHEAR WEAK, WATER LOADING MAY LEAD TO
ISOLATED STRONG WIND GUSTS. INCREASING DIRECTIONAL SHEAR AROUND
THE UPPER LOW MAY ALSO LEAD TO WEAK ROTATION...SO AN ISOLATED
TORNADO CAN'T TOTALLY BE RULED OUT EITHER, ESP FOR OUR
NEIGHBORING WV COUNTIES CLOSER TO THE UPPER LOW.
FOR NOW WILL CONTINUE TO HIGHLIGHT A VERY BROAD AREA FOR THE
FLOOD WATCH. UNLIKE YESTERDAY WHEN CAMS WERE HIGHLIGHTING THE
SOUTHERN BLUE RIDGE. THIS EVENING THE CONVERGENCE SEEMS TO BE
ALIGNING WITH BACK EDGE OF CLOUD FIELD OVER THE WESTERN CWA
WHERE DRY SLOT AROUND THE UPPER LOW HAS ALLOWED FOR SOME
CLEARING AND RESULTANT SURFACE HEATING AND INCREASING CAPE.
KEY MESSAGE 2...UNSETTLED WEATHER CONTINUES THROUGH MUCH OF THE
WEEK.
THE CLOSED LOW IS FORECAST TO GRADUALLY SETTLE SOUTHEAST OVER
THE SOUTHERN APPALACHIANS MONDAY INTO TUESDAY BEFORE WEAKENING
AND FILLING MID WEEK. MODELS MAINTAIN CONTINUED OPPORTUNITY
FOR SHOWERS AND THUNDERSTORMS WITH MARGINAL RISK OF EXCESSIVE
RAINFALL. AFTER MID-WEEK, WE STILL HAVE DAILY AFTERNOON AND
EVENING THUNDERSHOWER CHANCES, BUT NO REAL CHANGE IN AIRMASS. IN
GENERAL WEATHER WILL STAY MOIST WITH SURFACE DEWPOINTS FLIRTING
WITH 70.
AVIATION /00Z MONDAY THROUGH FRIDAY/
CEILINGS WILL LIFT FROM MVFR TO VFR AS SOUTHERLY FLOW
STRENGTHENS AHEAD OF AN APPROACHING WEAK COLD FRONT. HOWEVER, A
LINE OF THUNDERSTORMS MOVING IN WITH THE FRONT WILL BRING HEAVY
RAINFALL THAT TEMPORARILY LOWERS VISIBILITIES. BEHIND THE
FRONTAL PASSAGE, DENSE FOG WILL BE POSSIBLE DURING THE MORNING
IF SKIES CLEAR SUFFICIENTLY, THOUGH A DECK OF LOW CLOUDS WITH
PATCHY FOG APPEARS MORE LIKELY, ESPECIALLY ACROSS MOUNTAIN
AIRPORT TERMINALS.
EXTENDED AVIATION OUTLOOK...
SCATTERED SHOWER/STORM ARE EXPECTED FOR MUCH OF THE UPCOMING
WEEK, BUT FAVORING THE PEAK HEATING HOURS OF THE DAY,
DIMINISHING AFTER SUNSET. THE MOISTURE LADEN AIRMASS WILL FAVOR
SUB-VFR FLIGHT CONDITIONS FOR MUCH OF THE WEEK. FOG WILL ALSO BE
POSSIBLE EACH MORNING.
HYDROLOGY
FLOOD WATCH THROUGH 06Z TONIGHT. CONCERN EXISTS FOR EXCESSIVE
RAINFALL. MORNING 12Z U/A REGIONAL SOUNDINGS MEASURED PWATS FROM
1.8 TO 2.2 INCHES, WELL ABOVE THE 90TH PERCENTILE, AND RECORD
SETTING FOR THE DATE HERE AT RNK. THIS ENVIRONMENT IS RIPE FOR
FOR HEAVY RAINFALL WITHIN ANY CONVECTION WHICH DEVELOPS YIELDING
OFF THE CHART KIND OF RAINFALL RATES. FORECASTERS WORKING THE
MOUNT AIRY EMERGENCY FROM LAST NIGHT SAID RADAR WAS ESTIMATING
RAINFALL RATES IN EXCESS OF 5-7 INCHES AN HOUR. WITHIN 3 HOURS
TIME BETWEEN 4-8 INCHES OF RAIN FELL WITHIN THE HEADWATERS OF
THE ARARAT RIVER BASIN RESULTING IN MAJOR FLOODING IN MT. AIRY
NC. EXTENSIVE PROPERTY AND ROAD DAMAGE WAS OBSERVED IN ADDITION
TO SWIFT WATER RESCUES. AN OBSERVER NEAR PILOT MOUNTAIN MEASURED
8.87 INCHES OF RAIN.
WE CONTINUE TO SEE A SIGNAL FOR FLASH FLOODING THIS EVENING DUE
TO A COMBINATION OF STRONG MID AND UPPER LEVEL FORCING AND THE
MOISTURE LADEN AIRMASS. TRAINING CELLS AND HIGH RAIN RATES MAY
RESULT IN LOCALIZED TOTALS OF 2 TO 4 INCHES, WITH HIGHER
AMOUNTS POSSIBLE IF THE STORMS BECOME ANCHORED ON THE TERRAIN.
RNK WATCHES/WARNINGS/ADVISORIES
VA...FLOOD WATCH UNTIL 2 AM EDT MONDAY FOR VAZ007-009>020-022>024-
032>035-043.
NC...FLOOD WATCH UNTIL 2 AM EDT MONDAY FOR NCZ001>004-018>020.
WV...FLOOD WATCH UNTIL 2 AM EDT MONDAY FOR WVZ042>044-507-508.
DISCUSSION...PM
AVIATION...PM/RCS
HYDROLOGY...PM
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