784  
FXUS61 KRNK 261110  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
710 AM EDT WED SEP 26 2018  
   
SYNOPSIS
 
 
A COLD FRONT WILL APPROACH FROM THE WEST TODAY BEFORE SLIDING  
ACROSS THE AREA THIS EVENING. THE FRONT WILL STALL OVER THE  
CAROLINAS TONIGHT ALLOWING AREAS OF WEAK LOW PRESSURE TO RIDE  
ALONG THE BOUNDARY THURSDAY INTO THURSDAY NIGHT. A WEAK  
SECONDARY COLD FRONT WILL APPROACH ON FRIDAY AND SWING THROUGH  
THE REGION SATURDAY RESULTING IN DRIER WEATHER FOR THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 315 AM EDT WEDNESDAY...  
 
BRIEF RIDGING ACROSS THE AREA WILL TRANSITION TO DEEPENING SOUTHWEST  
FLOW ALOFT AS AN UPPER TROUGH AXIS SWINGS BY TO THE NORTH LATER  
TODAY AND TONIGHT. THIS SHOULD PROPEL AN UPSTREAM COLD FRONT TOWARD  
THE WESTERN MOUNTAINS THIS AFTERNOON WITH THE BOUNDARY CROSSING THE  
REGION THIS EVENING, BEFORE SPILLING TO THE SOUTH AND STALLING  
OVERNIGHT. MULTIPLE BANDS OF CONVECTION PRECEDING THE FRONT THE MAIN  
CONCERN THIS AFTERNOON AND EVENING ESPCLY EAST OF THE MOUNTAINS  
WHERE INSTABILITY LOOKS STRONGER WITHIN MORE OF A BACKED LOW LEVEL  
SOUTHWEST TRAJECTORY.  
 
OTHERWISE MODELS BASICALLY REMAIN CONSISTENT IN PUSHING SOME SHOWERS/CLOUDS  
INTO THE WEST THIS MORNING AHEAD OF THE MAIN PRE- FRONTAL CONVERGENCE  
AXIS THAT WILL WEAKEN OVER THE FAR WEST BY EARLY AFTERNOON. THEN  
APPEARS SOME JUMP TO ALONG/EAST OF THE BLUE RIDGE BY MID/LATE AFTERNOON  
AS DEEPER MOISTURE WORKS AROUND THE LOW LEVEL WESTERLY DOWNSLOPE  
OVER THE WEST. HOWEVER BEST SUPPORT LOOKS TO REMAIN JUST NORTH  
WITH SEVERE PARAMETERS RATHER UNCERTAIN TO THE STRENGTH/ORGANIZATION  
OF LINEAR BANDS OUT EAST ALONG THE TAIL OF THE PASSING VORT  
AXIS AND WITHIN UNIDIRECTIONAL FLOW ALOFT. THINK BEST POTENTIAL  
FOR ISOLATED SEVERE SOUTHEAST SECTIONS IF CAN GET UNSTABLE  
ENOUGH AFTER EARLY FOG, WHILE ALSO SEEING ENOUGH LIFT ALONG  
LIMITED THETA-E RIDGING AS LOW LEVEL LAPSES REMAIN RATHER WEAK.  
THIS MAY ALSO LEAVE A VOID IN SHOWERS ACROSS THE WEST EXCEPT  
WITH THE ACTUAL FRONT ARRIVING NORTHWEST SECTIONS LATE IN THE  
DAY WHERE WILL HAVE A COUPLE ROUNDS OF HIGHER POPS. OTHERWISE  
SLOWED DOWN TIMING SOME THROUGH EARLY AFTERNOON WITH LIKELY POPS  
TAKING SHAPE SOUTHWEST- EAST, BUT ONLY CHANCE COVERAGE NEW  
RIVER VALLEY AND POINTS NORTH WHERE SHOWERS MORE APT TO BE CLIPPED  
BY THE WESTERLY FLOW ACROSS THE RIDGES. HIGHS TO REBOUND UNDER  
WARM ADVECTION VIA WEST/SOUTHWEST FLOW AHEAD OF THE FRONT WITH  
MID 80S LIKELY EAST, AND 75-80 WEST OUTSIDE OF WHERE EARLY  
CLOUDS MAY HINDER RISES EARLY ON.  
 
FRONT FOLDS TO THE SOUTH OVERNIGHT IN ADVANCE OF ANOTHER SHORTWAVE  
TROUGH APPROACHING FROM THE SOUTHERN PLAINS LATE. THIS FEATURE LOOKS  
TO BRING THE ONSET OF RETURN FLOW OVERTOP A DEVELOPING LOW LEVEL  
WEDGE OVERNIGHT PER COOL HIGH PRESSURE BUILDING IN FROM THE NORTH.  
GUIDANCE TIMING ISSUES LINGER IN JUST HOW FAST BETTER ISENTROPIC  
LIFT WILL DEVELOP OVERNIGHT WITH DIFFERENCES IN JUST HOW MUCH  
CONVECTION FROM EARLIER MAY TEND TO PUSH SOUTH AND DELAY BETTER  
OVERRUNNING. FOR NOW WILL FOLLOW CLOSER TO THE LATEST HREF IN  
HAVING SOME DECREASE IN SHOWERS THIS EVENING BEFORE RAMPING BACK  
UP FROM SOUTHWEST TO NORTHEAST INTO THE EARLY MORNING HOURS.  
HOWEVER THIS TO BE MORE STRATIFORM NATURE RAINFALL WITH LOWER  
RATES, BUT STILL PERHAPS RESULTING IN UPWARDS OF ANOTHER INCH  
SOUTHERN BLUE RIDGE BY LATE TONIGHT. THUS WILL OPT TO NOT HOIST  
A FLOOD WATCH AT THIS TIME PENDING COVERAGE/AMOUNTS FROM THIS  
AFTERNOON. LOWS A BIT COOLER AS THE WEDGE DEVELOPS FROM THE  
NORTH ALLOWING FOR SOME TEMPS IN THE 50S, WITH OVERALL 60S  
ELSEWHERE UNDER AN INCREASING NORTHEAST BREEZE.  

 
   
SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/
 
 
AS OF 330 AM EDT WEDNESDAY...  
 
BEHIND THE COLD FRONT, HIGH PRESSURE WILL WEDGE DOWN THE EAST SIDE OF  
THE MOUNTAINS AND DRIVE A BACKDOOR FRONT THROUGH THE REGION. 850MB  
WINDS WILL ENHANCE A BIT FROM THE SOUTHWEST AND RUN OVER THE TOP OF  
NORTHEASTERLY WINDS IN THE WEDGE. THIS WILL ESTABLISH A GOOD AMOUNT OF  
ISENTROPIC LIFT AND COMBINE WITH SOME SHORT WAVE ENERGY TO BRING  
WIDESPREAD RAINFALL TO THE APPALACHIANS AND CENTRAL MID ATLANTIC REGION  
THURSDAY AND THURSDAY NIGHT. LOCATIONS ALONG THE PERIPHERY OF THE WEDGE  
IN THE NC PIEDMONT AND INTO THE MOUNTAINS OF NC/GRAYSON HIGHLANDS OF  
VIRGINIA WILL ALSO HAVE A BIT OF INSTABILITY PRESENT AND ALLOW FOR SOME  
EMBEDDED THUNDER. WHILE THE OVERALL DYNAMIC ENVIRONMENT IS NOT  
IMPRESSIVE, SHEAR ALONG THE WEDGE FRONT WILL BE SUBSTANTIAL SO ANY  
EMBEDDED THUNDER WILL HAVE TO BE WATCHED CLOSELY FOR SIGNS OF LOW  
TOPPED SEVERE.  
 
RAINFALL TOTALS ALONG THE SOUTHERN BLUE RIDGE OF AROUND ANOTHER 1.5  
INCHES THURSDAY AND THURSDAY NIGHT, WITH LOCALLY HIGHER AMOUNTS  
POSSIBLE, WILL BRING THE POSSIBILITY OF FLOODING. WILL HAVE TO SEE  
EXACTLY HOW THE ELEMENTS COME TOGETHER BEFORE CONTEMPLATING ANY FLOOD  
OR FLASH FLOOD WATCHES.  
 
A RIBBON OF SHORT WAVE ENERGY WILL PUSH THROUGH ON FRIDAY AS THE UPPER  
PATTERN BECOMES MORE ZONAL, ALLOWING FOR A GRADUAL DECREASE IN  
PRECIPITATION CHANCES AND GRADUAL IMPROVEMENT INTO THE WEEKEND, THOUGH  
SOME LINGERING INSTABILITY WILL KEEP A CHANCE OF SHOWERS AND  
THUNDERSTORMS AROUND THROUGH FRIDAY.  
 
TEMPERATURES ON THURSDAY WILL PEAK IN THE 60S EARLY, THEN LIKELY FALL  
THROUGH THE DAY AS THE WEDGE BUILDS IN WITH A GOOD DOSE OF MID/UPPER  
50S ACROSS THE REGION BY THURSDAY EVENING. AS THE WEDGE GIVES WAY INTO  
THE WEEKEND, TEMPERATURES WILL REBOUND TO SEASONAL NORMS WITH MID  
70S/NEAR 80 EAST OF THE BLUE RIDGE AND LOW/MID 70S TO THE WEST.  
 

 
   
LONG TERM /SUNDAY THROUGH TUESDAY/
 
 
AS OF 1240 PM EDT TUESDAY...  
 
ZONAL 500 MB PATTERN OVER THE MID ATLANTIC REGION SATURDAY  
THROUGH MONDAY. SOME DIFFERENCES IN THE MODELS WITH THE AMOUNT  
OF RIDGING IN THE SOUTHEAST BY TUESDAY. SHORT WAVE COMING OUT OF  
THE SOUTHERN PLAINS AND WEAKENING AS IT MOVES EAST MAY REACH  
THE AREA ON SUNDAY. OTHERWISE LITTLE ORGANIZED FORCING THIS TIME  
FRAME.  
 
NEXT COLD FRONT CROSSES THE REGION SATURDAY THEN STALLS AND  
WEAKENS FATHER SOUTH, ACROSS SOUTH CAROLINA AND GEORGIA. HIGH  
PRESSURE WILL COVER THE OHIO VALLEY AND GREAT LAKES, AND  
EVENTUALLY THE MID ATLANTIC STATES BEHIND THE FRONT SUNDAY AND  
MONDAY. MID AND LOW LEVEL MOISTURE MAY NOT PROGRESS OUT OF THE  
AREA UNTIL SUNDAY.  
 
THE HIGH MOVES OFFSHORE ON TUESDAY WITH RETURN FLOW ON THE  
WESTERN SIDE PUSHING WARMER AIR BACK INTO THE TENNESSEE AND OHIO  
VALLEYS. ECMWF SUGGESTING A NEXT WAVE ALONG THE BOUNDARY WILL  
CROSS THE REGION TUESDAY. PLAN ON KEEPING SATURDAY NIGHT THROUGH  
MONDAY DRY OR VERY LOW PROBABILITY OF PRECIPITATION, THEN  
CHANCE OF RAIN RETURNS TUESDAY. SATURDAY THERE WILL BE A BRIEF  
COOLING OF 850MB TEMPERATURES THEN TEMPERATURES WILL BE ABOVE  
NORMAL, ESPECIALLY MINIMUM TEMPERATURES BY 10 TO 15 DEGREES.  
 
CONFIDENCE AVERAGE FOR ALL ELEMENTS.  
 

 
   
AVIATION /11Z WEDNESDAY THROUGH SUNDAY/
 
 
AS OF 705 AM EDT WEDNESDAY...  
 
CLEARING HAS ALLOWED AREAS OF FOG TO DEVELOP IN SPOTS ACROSS  
THE REGION ESPCLY ALONG AND EAST OF THE BLUE RIDGE WHERE WINDS  
ARE NEAR CALM. THUS HAVE BEEFED UP IFR CONDITIONS ACROSS THE  
EASTERN SITES EARLY THIS MORNING WITH VFR TO MVFR OVER THE WEST.  
 
COLD FRONT THEN BEGINS TO MOVE SLOWLY EASTWARD TOWARD THE AREA  
THIS AFTERNOON ALLOWING FOR A PERIOD OF MVFR SHOWERS AND  
THUNDERSTORMS ESPECIALLY BETWEEN MID AFTERNOON AND THIS EVENING.  
NOT CERTAIN ON HOW MUCH WE CAN DESTABILIZE BUT POTENTIAL EXISTS  
FOR ISOLATED STORMS TO BECOME STRONG MAINLY ACROSS EASTERN  
SECTIONS THIS AFTERNOON. RAIN CHANCES WILL LIKELY BE MORE  
FOCUSED IN THE LATE MORNING/EARLY AFTERNOON FOR WESTERN TAFS,  
AND THEN TEND MORE IN THE LATE AFTERNOON TO EARLY EVENING ACROSS  
THE PIEDMONT AND SOUTHERN BLUE RIDGE WHERE HAVE INCLUDED A LATE  
DAY VICINITY THUNDER MENTION. LOOK FOR INITIAL LIGHT/VARIABLE  
WINDS TO BECOME SOUTHWEST AND INCREASE TO 10-15 KTS THROUGH THE  
DAY.  
 
FRONT STALLS TO THE SOUTH OVERNIGHT INTO THURSDAY NIGHT WITH  
RIPPLES OF LOW PRESSURE RIDING ALONG THE BOUNDARY AS COOL HIGH  
PRESSURE WEDGES IN FROM THE NORTH. THIS TO RESULT IN WIDESPREAD  
SUB-VFR LATER TONIGHT INTO THURSDAY NIGHT INCLUDING PERIODS OF  
LIFR CEILINGS AND IFR VSBYS IN RAIN/FOG.  
 
CONFIDENCE IS MODERATE ON MOST TAF ELEMENTS, EXCEPT LOW ON  
TIMING AND COVERAGE OF SHRA/TSRA THIS AFTERNOON.  
 
EXTENDED DISCUSSION...  
 
SOME SLOW IMPROVEMENT APPEARS LIKELY ON FRIDAY AS DEEPER  
MOISTURE EXITS AND WEAK HIGH PRESSURE BUILDS IN WITH PERHAPS A  
RETURN TO VFR FRIDAY AFTERNOON. DRIER AIR BEHIND A PASSING  
SECONDARY COLD FRONT SHOULD RESULT IN VFR SATURDAY INTO SUNDAY  
WITH HIGH PRESSURE BUILDING JUST NORTH OF THE REGION.  

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

 
 

 
SYNOPSIS...JH  
NEAR TERM...JH  
SHORT TERM...MBS  
LONG TERM...AMS  
AVIATION...AL/JH/RCS  
 
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