878
FXUS61 KRNK 181147
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
747 AM EDT THU APR 18 2019
SYNOPSIS
A WARM FRONT LIFTS NORTH TODAY. A STRONG COLD FRONT MOVES INTO
THE MID- ATLANTIC AND SOUTHEAST STATES FRIDAY. HIGH PRESSURE
BUILDS BACK IN LATE IN THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
AS OF 730 AM EDT THURSDAY...
SCATTERED THUNDERSTORMS HAVE DEVELOPED RATHER UNEXPECTEDLY EARLY
THIS MORNING ACROSS PARTS OF THE NEW RIVER VALLEY POSSIBLY
ALONG THE WEAK FRONTAL BOUNDARY ANALYZED ACROSS THE AREA.
STORMS ALREADY SHOWING SOME SIGNS OF WEAKENING AS THEY LIFT OFF
TOWARD THE NORTHEAST. STILL EXPECTING AT LEAST PARTIAL CLEARING
BY LATE MORNING ACROSS MOST OF THE AREA AS THE BOUNDARY DEPARTS
AND SOUTHERLY FLOW INCREASES AHEAD OF THE DEEPENING TROUGH OVER
THE LOWER MS VALLEY.
PREVIOUS VALID DISCUSSION..
AS OF 315 AM EDT THURSDAY...
WARM FRONT LIFTS WELL NORTH OF THE AREA TODAY WITH SOME GUSTY
SOUTHERLY WINDS DEVELOPING BY LATE AFTERNOON/EVENING. WINDS
COULD NEAR ADVISORY CRITERIA IN THE FAR SOUTHWEST MAINLY AT
HIGHER ELEVATIONS. THIS IS AHEAD OF A COMPLEX AND FAIRLY POTENT
UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT APPROACHING FROM
THE WEST. THIS SYSTEM HAS ALREADY PRODUCED SOME SEVERE WEATHER
AND HEAVY RAINFALL OVER PARTS OF THE ARKLATEX AND LOWER MIDWEST
THIS MORNING AND THE GENERAL THREAT FOR BOTH SEVERE AND HEAVY
RAIN WILL BE SHIFTING EAST OVER THE NEXT 24 HOURS. CLOUDS WILL
INCREASE LATE TODAY AND TOWARD EVENING WITH PRECIPITATION
CHANCES INCREASING, FIRST IN THE SW MOUNTAINS OF NC AND FAR SW
VA WITH CATEGORICAL POPS BY 8-12Z FRIDAY IN THAT AREA AND CHANCE
POPS ELSEWHERE BUT THE BULK OF THE RAIN AND POSSIBLE STRONG TO
SEVERE STORMS WILL BE AFTER 12Z FRIDAY. HIGHS MID 70S TO NEAR 80
FAR SE TODAY AND REMAINING QUITE MILD OVERNIGHT WITH CLOUDS AND
SOUTHERLY FLOW.
SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/
AS OF 255 AM EDT THURSDAY...
GENEROUS AMOUNT OF RAINFALL ANTICIPATED FRIDAY INTO FRIDAY EVENING
PER SYNOPTIC MODELS AND WPC WITH TOTALS OF 1-2 INCHES LIKELY. THERE
ARE 3 POSSIBLE IMPACTS TO THE AREA FRIDAY.
1ST IS THE SEVERE THREAT: MODELS ALL SHOWING STRONG SHEAR
ENVIRONMENT BUT LOW CAPE. EXPECT A LINE OF SHOWERS AND STORMS FRIDAY
MORNING TO EXTEND FROM THE MID TN VALLEY TO NORTHERN GA. AHEAD OF
THIS LINE, STRONG SOUTHEAST WINDS WILL PROVIDE ENOUGH ENHANCEMENT
WITH GOOD MOISTURE TRANSPORT TO PRODUCE SHOWERS ACROSS THE SOUTHERN
BLUE RIDGE INTO THE REST OF THE MOUNTAINS. THE LINE CONTINUES EAST
INTO THE PIEDMONT THROUGH THE DAY. SEVERE PARAMETERS FAVOR BETTER
CHANCES OF DAMAGING WINDS/ISOLATED TORNADOES EAST OF THE BLUE RIDGE.
THE STORM PREDICTION CENTER HAS AN ENHANCED RISK ROUGHLY EAST OF
LINE FROM FARMVILLE, VA TO REIDSVILLE, NC, WITH A SLIGHT RISK AS FAR
WEST AS THE WV/VA BORDER. EVEN WITH PLENTY OF CLOUD COVER, A 50-60KT
LOW LEVEL JET MAY MIX DOWN WITH ENHANCED SHOWERS/ISOLATED STORMS IN
THE WEST, BUT OVERALL, NOT SEEING AS MUCH THUNDERSTORM THREAT IN THE
MOUNTAINS GIVEN THE EARLY START OF THE RAIN.
THE SECOND THREAT WILL BE HEAVY RAIN/FLOODING. PWATS WILL RUN 1.5 TO
1.75 INCHES WITH DEEP SOUTHERLY FLOW, AND POTENTIAL SLOWING OF THE
EASTWARD PROGRESSION OF THE LINE AS UPPER FLOW PARALLELS THE SURFACE
FRONT. WPC HAS THE SLIGHT RISK FOR EXCESSIVE RAINFALL RUNNING ACROSS
MOST OF THE FORECAST AREA. STILL A LITTLE EARLY FOR A FLOOD/FLASH
FLOOD WATCH, BUT MAY NEED ONE IF PROGRESSION OF FRONT IS SLOWER.
HOWEVER, SOME CONVECTIVE ALLOWING MODELS ARE NOT SHOWING AS MUCH
COVERAGE OVERALL COMPARED TO THE SYNOPTIC MODELS. ENSEMBLE FOR THE
RIVERS CONTINUE TO HIGHLIGHT THREAT OF MINOR TO MODERATE FLOODING
ALONG THE DAN AND PORTIONS OF THE ROANOKE AND JAMES, BUT STILL 30
PERCENT CHANCE OF IT HAPPENING, WITH THE DAN THE BETTER CHANCE.
THE THIRD THREAT WILL BE GRADIENT WINDS AHEAD OF THE FRONT. A 50-60
KT 8H JET MOVES FROM THE TN VALLEY EARLY FRIDAY INTO THE MOUNTAINS
BY 12Z FRIDAY. APPEARS HIGHER RIDGES FROM THE NC MOUNTAINS TO
SOUTHERN WV AND THE SOUTHERN BLUE RIDGE OF VA WILL SSE GUSTS
EXCEEDING 45 MPH AS SHOWERS MOVE IN OR JUST AHEAD OF THEM. WILL LOOK
AT ONE MORE RUN OF THE MODELS TODAY TOO SEE IF WIND HEADLINES WILL
BE WARRANTED, OR IF WE FIND THAT CONVECTIVE WARNINGS WITH A LINE OF
SHOWERS WILL BE NEEDED. THE STRONGEST GRADIENT WINDS WILL BE IN THE
09Z FRIDAY TO 18Z FRIDAY TIME FRAME.
CONFIDENCE IS HIGH ON SOME THREAT OF STRONG/DAMAGING WINDS AT
SOME POINT FRIDAY WITH AVERAGE CONFIDENCE ON FLOODING.
AS WE HEAD INTO FRIDAY NIGHT AND SATURDAY THE UPPER LOW PUSHES FROM
SOUTHERN KY NORTH INTO OHIO. WILL SEE A DRY SLOT WORK ACROSS THE
AREA, BUT WITH SUCH A STRONG SYSTEM, ALLOWING FOR SHOWER CHANCES AT
LEAST INTO SATURDAY. COLDER AIR ALOFT WILL BE ENOUGH TO BRING A FEW
SNOW SHOWERS TO THE HIGHER RIDGES SATURDAY MORNING, WHERE AN INCH OR
LESS IS POSSIBLE ON GRASSY SURFACE. ENOUGH INSTABILITY WITH THE COLD
POOL SATURDAY AFTERNOON ALLOWS FOR ISOLATED THUNDER INTO THE
PIEDMONT AND ESPECIALLY NORTH OF A ROANOKE TO LYNCHBURG LINE.
UNTIL THE UPPER LOW HEADS EAST SUNDAY WILL NEED TO KEEP SHOWER
CHANCES IN THE AREA THROUGH SUNDAY MORNING THEN SHOULD BE DRY MOST
AREAS SUNDAY INTO SUNDAY NIGHT, AS HIGH PRESSURE WORKS IN FROM THE
SOUTH.
TEMPS WILL BE CLOSE TO NORMAL FOR HIGHS FRIDAY WITH LOWER TO MID 60S
WEST, TO LOWER 70S, EAST, THEN 10 DEGREES BELOW NORMAL SATURDAY WITH
HIGHS IN THE UPPER 40S TO LOWER 50S MOUNTAINS, TO UPPER 50S TO LOWER
60S EAST, THEN BACK TO NORMAL SUNDAY, WITH LOWER TO MID 60S WEST TO
AROUND 70 EAST.
CONFIDENCE IS AVERAGE FOR THE FORECAST SATURDAY-SUNDAY.
LONG TERM /MONDAY THROUGH WEDNESDAY/
AS OF 1230 PM EDT WEDNESDAY...
MODELS IN POOR AGREEMENT WITH 500MB PATTERN MONDAY THROUGH
WEDNESDAY. OVERALL ZONAL FLOW WITH NO SIGNIFICANT SYNOPTIC SCALE
SYSTEMS EXPECTED DURING THIS TIME FRAME. WILL BE LEANING TOWARD
CONTINUITY AND THE WPC SOLUTION WHICH TAKES A BLEND OF
ENSEMBLES. COLDER AIR WITH THE UPPER LOW RETREATS NORTHEAST AND
850MB TEMPERATURES RECOVER TO ABOVE +10 FOR MONDAY THROUGH
WEDNESDAY. SO AFTER SUNDAY TEMPERATURES RETURN TO ABOVE NORMAL.
AVIATION /12Z THURSDAY THROUGH MONDAY/
AS OF 725 AM EDT THURSDAY...
AS NOTED IN THE NEAR TERM DISCUSSION, A FEW THUNDERSTORMS HAVE
DEVELOPED ACROSS THE MOUNTAINS EARLY THIS MORNING. THE UPDATED
12Z TAFS NOW CARRYING VCTS OR TEMPO GROUPS FOR A FEW HOURS OF
THIS ACTIVITY AT THE WESTERN TAF SITES (ALL EXCEPT LYH AND DAN).
STILL EXPECT IFR CONDITIONS LATER AS A WARM FRONT LIFTS NORTH
OF THE AREA ALLOWS INCREASING SOUTHERLY FLOW OUT AHEAD OF THE
NEXT SYSTEM APPROACHING FROM THE WEST. WINDS WILLS BE GUSTING
OVER 20 TO 30 MPH AND POSSIBLY HIGHER OVER THE ELEVATED RIDGES.
IN ADDITION, CLOUDS ASSOCIATED WITH THIS STRONG UPPER LOW WILL
BE ON THE INCREASE THIS EVENING, LOWERING TO MVFR TOWARD THE END
OF THE VALID TAF PERIOD.
EXTENDED AVIATION DISCUSSION...
A STRONG COLD FRONT FRIDAY TRIGGERS NUMEROUS SHOWERS AND
THUNDERSTORMS AND SUB-VFR CONDITIONS THROUGH FRIDAY NIGHT.
SCATTERED SHOWERS WILL CONTINUE ON SATURDAY ESPECIALLY IN THE
MOUNTAINS. WINDS WILL BE GUSTY FROM THE WEST AND NORTHWEST
BEHIND THIS FRONT ON SATURDAY AND SATURDAY NIGHT. VFR
ANTICIPATED FOR SUNDAY AND MONDAY.
RNK WATCHES/WARNINGS/ADVISORIES
VA...NONE.
NC...NONE.
WV...NONE.
SYNOPSIS...WP
NEAR TERM...PC
SHORT TERM...WP
LONG TERM...AMS
AVIATION...KK/PC
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