849  
FXUS61 KRNK 130900  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
500 AM EDT TUE APR 13 2021  
   
SYNOPSIS
 
 
LOW PRESSURE ALOFT WILL SLOWLY SHIFT EASTWARD FROM THE EASTERN  
GREAT LAKES INTO PENNSYLVANIA AND NEW YORK TODAY. MEANWHILE,  
ANOTHER SIMILAR AREA OF LOW PRESSURE ALOFT WILL DRIFT FROM THE  
UPPER MIDWEST INTO THE WESTERN GREAT LAKES THROUGH WEDNESDAY.  
THE PROXIMITY OF THESE LOW PRESSURE AREAS AND ASSOCIATED  
DISTURBANCES WILL KEEP PERIODS OF CLOUDS AND SOMEWHAT UNSETTLED  
WEATHER ACROSS THE REGION DURING THE NEXT SEVERAL DAYS.  
A FEW SHOWERS POSSIBLE IN THE WEST TODAY WITH BETTER COVERAGE  
AND INTENSITY OF SHOWERS AND A FEW THUNDERSTORMS WEDNESDAY.  
SHOWER CHANCES WILL LINGER THROUGHOUT THE WEEK AND INTO THE  
WEEKEND. TEMPERATURES WILL CONTINUE TO TREND TO BELOW NORMAL  
LEVELS WITH LOWS IN THE 30S AND 40S AND HIGHS IN THE 50S  
AND 60S INTO THE WEEKEND.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
AS OF 445 AM EDT MONDAY...  
 
...VARIABLE CLOUDINESS AND SEASONABLE TEMPERATURES TODAY &  
TONIGHT...  
 
A SERIES OF LOW PRESSURE SYSTEMS ALOFT WILL CONTINUE TO DOMINATE  
THE NORTHERN STREAM, ONE EXITING TO THE EAST ACROSS PA/NY WHILE  
ANOTHER MOVES INTO THE WESTERN GREAT LAKES BY WEDNESDAY. THIS  
WILL KEEP A SOMEWHAT UNSETTLED PATTERN IN PLACE ACROSS THE  
REGION, ESPECIALLY IN TERMS OF VARIABLE CLOUDINESS. CONSIDERABLE  
MID/HIGH CLOUD COVER IS EXPECTED TO TRAVERSE THE REGION AGAIN  
TODAY. RAIN CHANCES WILL REMAIN LOW AGAIN TODAY AND BE CONFINED  
MAINLY TO UPSLOPE AREAS DURING THE AFTERNOON AS A WEAK  
DISTURBANCE MOVES INTO THE AREA FROM THE TN VALLEY. OVERALL, THE  
REGION WILL BE DOMINATED BY A WEAK SHORT WAVE RIDGE BETWEEN THE  
TWO UPPER LOW PRESSURE AREAS MENTIONED ABOVE. THIS WILL MINIMIZE  
PRECIPITATION FOR TODAY AND POPS ARE KEPT AT OR BELOW 20% FOR  
TODAY/TONIGHT.  
 
TEMPERATURES TODAY WILL BE VERY SIMILAR TO THOSE OBSERVED  
MONDAY AS 850MB TEMPERATURES HOVER IN THE LOWER TO MIDDLE SINGLE  
DIGITS, ROUGHLY 4C-6C ACROSS THE AREA. LOOK FOR HIGHS IN THE 50S  
AND 60S WITH A FEW LOWER 70S IN SUNNIER AREAS OF THE PIEDMONT.  
LOW TEMPERATURES TONIGHT/EARLY WEDNESDAY SHOULD BE MOSTLY IN THE  
40S.  
 
/CONFIDENCE IN FORECAST PARAMETERS/  
MODERATE TO HIGH CONFIDENCE IN TEMPERATURES,  
MODERATE CONFIDENCE IN PRECIPITATION PROBABILITIES,  
MODERATE CONFIDENCE IN WIND SPEED AND DIRECTION,  
LOW CONFIDENCE IN THUNDERSTORM PROBABILITIES.  
 

 
   
SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/
 
   
..MARGINAL RISK OF SEVERE WEATHER WEDNESDAY AFTERNOON
 
 
ON WEDNESDAY MORNING, AND UPPER LOW WILL BE SITUATED ACROSS THE  
GREAT LAKES REGION AND ITS ASSOCIATED COLD FRONT WILL BE EXTENDING  
SOUTH THROUGH CENTRAL PENNSYLVANIA AND FARTHER SOUTH TO ALONG THE  
WEST VIRGINIA/VIRGINIA AND TENNESSEE/NORTH CAROLINA BORDERS. IN  
ADVANCE OF THIS FRONT, DEW POINTS WILL BE INCREASING AS THE DAY  
PROGRESSES ACROSS OUR REGION WITH THE LOWER 50S EXPECTED OVER  
SOUTHSIDE VIRGINIA BY THE LATE AFTERNOON. HOWEVER, DESPITE THIS  
INCREASE, LOW LEVEL THERMAL PROFILES ARE SUGGESTING AN INVERTED-V  
SIGNATURE WITH DCAPE INCREASING TO NEAR 500 J/KG. ALSO ACROSS THIS  
REGION, AND NEIGHBORING SECTIONS OF CENTRAL NORTH CAROLINA, MUCAPE  
VALUE ARE EXPECTED TO INCREASE TO A LITTLE OVER 500 J/KG. SURFACE TO  
500MB MEAN SHEAR IS EXPECTED TO INCREASE TO AROUND 45KTS, AND 0-3KM  
SRH IS EXPECTED TO BE AROUND 100-200 M2/S2. WHILE WE WILL STILL BE  
FORECASTING ISOLATED TO SCATTERED SHOWERS ACROSS CENTRAL, EASTERN,  
AND SOUTHERN PARTS OF THE REGION, THE LATEST DAY-2 CONVECTIVE  
OUTLOOK FROM SPC FOR THIS TIME PERIOD IS OFFERING A MARGINAL RISK  
FOR SEVERE WEATHER WITH DAMAGING THUNDERSTORM WINDS THE MAIN THREAT.  
ANY THAT OCCUR WOULD MOSTLY LIKELY WOULD BE ACROSS THE FAR  
SOUTHEASTERN SECTIONS OF THE FORECAST AREA.  
 
HEADING INTO WEDNESDAY EVENING, THE POTENTIAL FOR SCATTERED  
THUNDERSTORMS WILL CONTINUE OVER THIS FAR SOUTHEASTERN SECTION WITH  
SCATTERED SHOWERS POSSIBLE ELSEWHERE. AFTER MIDNIGHT, ONLY ISOLATED  
SHOWERS ARE EXPECTED ACROSS THE FAR EASTERN SECTIONS OF THE AREA,  
NEAREST THE DEPARTING COLD FRONT.  
 
THURSDAY THROUGH FRIDAY, THE PARENT UPPER LOW WILL MAKE SLOW  
PROGRESS EASTWARD FROM THE GREAT LAKES TO OFF THE NEW ENGLAND COAST.  
DURING ITS JOURNEY, AN INCREASED PRESSURE GRADIENT IS EXPECTED  
ACROSS THE AREA WHICH WILL ALLOW FOR GUSTY WINDS ACROSS THE  
MOUNTAINS. AT THIS TIME WE ARE NOT EXPECTING ADVISORY LEVEL GUSTS,  
BUT ONES MORE IN THE 20 TO 30 MPH RANGE AT THE HIGHEST PEAKS, WITH  
LESSER VALUES IN THE VALLEYS AND ACROSS THE PIEDMONT.  
 
BY FRIDAY NIGHT, THE PRESSURE GRADIENT SLACKENS AS AN UPPER LEVEL  
SHORTWAVE RIDGE BUILDS OVER THE REGION. LITTLE IF ANY PRECIPITATION  
IS EXPECTED THURSDAY INTO FRIDAY. THE BEST CHANCES WOULD BE FOR SOME  
ISOLATED UPSLOPE PRECIPITATION ACROSS WESTERN GREENBRIER COUNTY, WV.  
AT THIS TIME, THE POTENTIAL IS TOO LOW TO INCLUDE IN THE FORECAST,  
BUT WE WILL NEED TO MONITOR THE TRENDS AS GET CLOSER TO THE DAYS IN  
QUESTION.  
 
TEMPERATURES WILL TREND COOLER DURING THIS PORTION OF THE FORECAST  
WITH READINGS AVERAGING FIVE DEGREES BELOW NORMAL BY FRIDAY INTO  
FRIDAY NIGHT.  
 
CONFIDENCE IN THIS PORTION OF THE FORECAST IS MODERATE.  
 

 
   
LONG TERM /SATURDAY THROUGH MONDAY/
 
 
AS OF 1215 AM EDT TUESDAY...  
   
..UNSETTLED WEATHER PATTERN
 
 
LOW CONFIDENCE ABOUNDS DURING THIS PORTION OF THE FORECAST IN REGARD  
TO SPECIFIC TIMING OF POTENTIAL ROUNDS OF SHOWERS. ALL GUIDANCE  
KEEPS A PROGRESSIVE PATTERN ACROSS OUR REGION WITH MULTIPLE  
OPPORTUNITIES FOR UPPER LEVEL SHORTWAVE TROUGHS TO SWING THROUGH THE  
AREA WITH THEIR ASSOCIATION ROUNDS OF SHOWERS. UNFORTUNATELY, ALL  
GUIDANCE IS EQUALLY UNIQUE ON THE TIMING OF THESE FEATURES. A COUPLE  
COME CLOSE ON SIMILAR TIMING FOR ONE OR TWO OF THESE FEATURES, BUT  
NOT WITH A UNIFORM CONSENSUS.  
 
OUR FORECAST FOR THIS TIME PERIOD WILL WEIGH HEAVILY ON THE NATIONAL  
BLEND OF MODELS. THIS SOLUTION PLACES LITTLE IF ANY CONFIDENCE ON  
SHOWERS FOR SATURDAY, WITH PERHAPS ISOLATED COVERAGE SUNDAY INTO  
MONDAY.  
 
TEMPERATURES DURING THIS PORTION OF THE FORECAST ARE EXPECTED TO  
AVERAGE A FEW DEGREES ABOVE NORMAL FOR HIGH TEMPERATURES, AND AROUND  
NORMAL FOR LOW TEMPERATURES.  
   
AVIATION /09Z TUESDAY THROUGH SATURDAY/
 
 
AS OF 200 AM EDT TUESDAY...  
 
VFR CONDITIONS ARE EXPECTED TO CONTINUE THROUGH MOST OF THE TAF  
VALID PERIOD. A WEAK SHORT WAVE RIDGE ALOFT WILL MOVE ACROSS  
THE REGION TODAY. UPSTREAM CLOUD COVER WILL CONTINUE TO STREAM  
INTO THE AREA CREATING BKN-OVC MOSTLY MID/HIGH CLOUDS BUT  
CEILINGS FOR THE MOST PART, EXCEPT POSSIBLY IN THE 10Z-14Z TIME  
FRAME THIS MORNING, ARE EXPECTED TO REMAIN AOA 030. FOG  
DEVELOPMENT IS EXPECTED TO BE LIMITED AT BEST DUE TO A RELATIVELY  
DRY SURFACE AIR MASS, NORTHWEST TO NORTH WINDS 5-8 MPH, AND  
CLOUD COVER. LIMITED POTENTIAL FOR BRIEF PERIOD OF FOG AT KLWB,  
BUT NOT LIKELY DUE TO CLOUD COVER. WINDS WILL REMAIN MOSTLY  
NORTHWEST THROUGH THE PERIOD, ALTHOUGH SOME PERIODS OF NORTH TO  
NORTH-NORTHEAST WINDS ARE POSSIBLE AT KLYH AND KLWB. SPEEDS WILL  
RANGE FROM 5-8 MPH FOR THE MOST PART, OCCASIONALLY 10-12 MPH  
DURING THE DAYLIGHT HOURS.  
 
/CONFIDENCE LEVELS IN FORECAST PARAMETERS/  
MODERATE CONFIDENCE IN CEILINGS,  
MODERATE TO HIGH CONFIDENCE IN VISIBILITIES,  
MODERATE TO HIGH CONFIDENCE IN WIND SPEED/DIRECTION.  
 
EXTENDED AVIATION DISCUSSION...  
 
ANOTHER UPPER-LEVEL DISTURBANCE WILL TRACK INTO THE GREAT  
LAKES WEDNESDAY WITH PERIODS OF SUB-VFR CONDITIONS AND SHOWERS  
AND/OR THUNDERSTORM CHANCES ON THE INCREASE. THE MOST LIKELY  
PROBABILITY OF PRECIPITATION WILL BE WEDNESDAY AFTERNOON AND  
WEDNESDAY NIGHT ACROSS SOUTHERN VIRGINIA AND NORTHERN NORTH  
CAROLINA.  
 
UPSLOPE SHOWERS AND GUSTY WINDS ARE EXPECTED BEHIND THIS SYSTEM  
FOR THURSDAY. SOME MVFR CEILINGS ARE POSSIBLE IN THE MOUNTAINS.  
CONDITIONS WILL BECOME VFR EAST OF THE BLUE RIDGE.  
 
FRIDAY AND SATURDAY WILL BE DRY. VFR CEILINGS AND VISIBILITIES  
ARE FORECAST THROUGHOUT THE MID ATLANTIC REGION.  
 

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

 
 

 
SYNOPSIS...RAB  
NEAR TERM...RAB  
SHORT TERM...DS  
LONG TERM...DS  
AVIATION...RAB/WP  
 
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