490  
FXUS61 KRNK 172331  
AFDRNK  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BLACKSBURG VA  
731 PM EDT SUN OCT 17 2021  
   
SYNOPSIS
 
 
CANADIAN HIGH PRESSURE WILL DRIFT SLOWLY FROM THE MIDWEST INTO  
THE MID-ATLANTIC REGION THROUGH TUESDAY. THIS WILL BRING MOSTLY  
SUNNY CONDITIONS TO THE REGION ALONG WITH SEASONABLY COOL  
TEMPERATURES. PATCHY FROST CAN BE EXPECTED IN THE WESTERN  
MOUNTAIN VALLEYS TONIGHT AND TUESDAY MORNING. THE NEXT FRONTAL  
SYSTEM WILL ARRIVE BY THE END OF THE WEEK BRINGING THE NEXT  
CHANCE FOR ANY PRECIPITATION TO THE REGION.  
 

 
   
NEAR TERM /THROUGH MONDAY/
 
 
AS OF 645 PM EDT SUNDAY...  
 
SEASONABLY COOL TONIGHT WITH SOME FROST POSSIBLE IN THE MOUNTAINS.  
 
HIGH PRESSURE TO OUR WEST WILL BUILD INTO OUR REGION TONIGHT INTO  
MONDAY BEHIND THE DEPARTING TROUGH. THE PROXIMITY OF THE HIGH  
PRESSURE AS WELL AS VERY DRY AIR ALOFT AND DIMINISHING WINDS SHOULD  
LEAD TO GOOD RADIATIONAL COOLING CONDITIONS OVERNIGHT AND THE  
DEVELOPMENT OF FROST IN SOME AREAS. FROST ADVISORY HAS BEEN POSTED  
FOR LOCATIONS WHERE FROST COULD BE MORE WIDESPREAD IN THE WEST.  
PATCHY FROST MAY ALSO DEVELOP IN THE MOUNTAINS VALLEYS  
ESPECIALLY THE GREENBRIER VALLEY. MODIFIED TEMPERATURES FOR THIS  
EVENING INTO TONIGHT UTILIZING THE LATEST SURFACE OBS,THEIR  
TRENDS AND BLENDED IN NBM. OVERNIGHT LOW TEMPERATURES WILL  
VARIED FROM AROUND 30 DEGREES IN MOUNTAINS TO THE LOWER 40S  
IN THE EAST. AFTER A CHILLY START, HIGH TEMPERATURES MONDAY  
WILL RANGE FROM MID 50S IN THE MOUNTAINS TO THE LOWER 70S IN THE  
PIEDMONT.  
 
MODERATE CONFIDENCE IN NEAR TERM FORECAST PERIOD.  
 
PREVIOUS DISCUSSION:  
AS OF 145 PM EDT SUNDAY...  
 
CHILLY TONIGHT WITH SOME FROST POSSIBLE IN THE MOUNTAINS.  
 
UPPER TROUGH WITH A CUTOFF LOW CENTERED NEAR JAMES BAY WILL RETREAT  
EAST-NORTHEAST OVER THE NEXT 24 HOURS. OVERALL THE OMEGA BLOCK  
PATTERN THAT IS IN PLACE WILL TRANSLATE EAST, PUTTING THE SOUTHERN  
APPALACHIANS MORE SQUARELY INTO THE NE FLOW ON THE WEST SIDE OF THE  
TROUGH. HIGH PRESSURE AT THE SURFACE STRENGTHENS AND MOVES TOWARDS  
THE TN VALLEY.  
 
TODAY HAS BEEN QUITE COOL WITH READINGS IN THE 40S AND 50S IN THE  
MOUNTAINS, AND IN THE MID 50S TO LOWER 60S IN THE PIEDMONT. PWATS ON  
THIS MORNING'S SOUNDINGS WERE AROUND A QUARTER INCH, AND THIS WILL  
NOT IMPROVE APPRECIABLY OVERNIGHT. THE PROXIMITY OF THE HIGH  
PRESSURE AS WELL AS VERY DRY AIR ALOFT AND DIMINISHING WINDS SHOULD  
LEAD TO AGREEABLE RADIATIONAL COOLING CONDITIONS AND THE DEVELOPMENT  
OF FROST IN SOME AREAS. MOST LIKELY SPOTS TO HAVE WIDESPREAD FROST  
ARE THE GRAYSON AND ALLEGHANY HIGHLANDS WHERE A FROST ADVISORY HAS  
BEEN ISSUED. PATCHY FROST MAY APPEAR ELSEWHERE, INCLUDING THE  
GREENBRIER VALLEY, FOR A COUPLE OF HOURS, BUT IT SHOULD NOT BE  
WIDESPREAD ENOUGH FOR AN ADVISORY. CURRENTLY THE ONLY LOCATIONS THAT  
MAY SEE FREEZING TEMPERATURES IS THE BURKE'S GARDEN AREA.  
 
OTHERWISE, SITES WEST OF THE BLUE RIDGE WILL SEE A CLEAR AND VERY  
CHILLY NIGHT WITH LOWS A FEW DEGREES ABOVE FREEZING. TO THE EAST,  
TEMPERATURES WILL BE IN THE UPPER 30S TO LOWER 40S. WINDS  
DECREASE OVERNIGHT BUT TO GENERALLY 5-10 MPH OUTSIDE OF THE  
ADVISORY AREA. AFTER A COLD START HIGHS REBOUND DURING THE DAY  
TUESDAY, AND SHOULD BE A FEW DEGREES WARMER THAN TODAY, REACHING  
THE UPPER 50S TO LOWER 70S WEST TO EAST. DAYTIME MIXING WILL  
AGAIN CREATE GUSTY WINDS AROUND 10-20 MPH.  
 
FORECAST CONFIDENCE IS HIGH FOR POPS AND QPF, MODERATE FOR WINDS  
AND TEMPERATURES.  
 

 
   
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/
 
 
AS OF 145 PM EDT SUNDAY...  
 
TRANQUIL WEATHER CONTINUES...  
 
500MB PATTERN IS PROGRESSIVE AND MOVES LONG WAVE TROUGH OFF THE EAST  
COAST MONDAY NIGHT AND TUESDAY. BY WEDNESDAY MUCH OF THE EAST WILL  
HAVE HIGHER 500 MB HEIGHTS AND UPPER RIDGING. AT THE SURFACE, HIGH  
PRESSURE MOVES OFFSHORE ON WEDNESDAY. AIR MASS SHOULD BE WARMING TO  
AROUND +12 AT 850MB BY WEDNESDAY. STILL SOME 45 KNOT 850 MB WINDS  
OVER THE HIGHER ELEVATIONS OF THE ALLEGHANY HIGHLANDS AND SOUTHEAST  
WEST VIRGINIA ON MONDAY EVENING. LITTLE CLOUD COVER IS EXPECTED  
THROUGH WEDNESDAY NIGHT AS AIR MASS REMAINS DRY.  
 

 
   
LONG TERM /THURSDAY THROUGH SUNDAY/
 
 
AS OF 140 PM EDT SUNDAY..  
 
KEEPING FORECAST DRY UNTIL FRONT ARRIVES THURSDAY..  
 
TROUGH OFF THE WEST COAST MOVES ACROSS THE CONUS, REACHING THE OHIO  
VALLEY ON THURSDAY. HEIGHTS CONTINUE TO FALL AS THE LONG WAVE TROUGH  
OVER THE EAST AMPLIFIES BY SATURDAY. BY THURSDAY, REGION IS BETWEEN  
THE SURFACE HIGH OFFSHORE AND LOW PRESSURE OVER THE GREAT LAKES AND  
OHIO VALLEY. THIS LOW PRESSURE SYSTEM BRINGS A FRONT THROUGH THE MID  
ATLANTIC REGION LATE THURSDAY. CANADIAN, ECMWF AND GFS ARE IN DECENT  
AGREEMENT FOR THE TIMING OF THE FRONT. SURFACE HIGH PRESSURE WILL  
BUILD IN BEHIND THE FRONT ON SATURDAY AND SUNDAY. HIGHEST  
PROBABILITY OF PRECIPITATION WILL BE ON THURSDAY AND THURSDAY NIGHT  
IN THE MOUNTAINS. WILL BE REMOVING PROBABILITY OF PRECIPITATION FOR  
SATURDAY. EVEN THE UPSLOPE CLOUDS IN THE MOUNTAINS WILL ERODE BY  
SATURDAY AFTERNOON.  
 

 
   
AVIATION /00Z MONDAY THROUGH FRIDAY/
 
 
AS OF 731 PM EDT SUNDAY...  
 
VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD.  
 
HIGH PRESSURE FROM THE MIDWEST WILL BUILD ACROSS THE REGION  
THROUGH MONDAY. CONDITIONS ARE EXPECTED TO BE VFR THROUGH THE  
TAF CYCLE. WESTERLY WINDS WILL DIMINISH THIS EVENING INTO  
TONIGHT, AND THEN RETURN AFTER SUNRISE TUESDAY. GUSTS SHOULD  
STAY IN THE 10-20 MPH RANGE FOR TAF SITES.  
 
/CONFIDENCE LEVELS IN FORECAST PARAMETERS/  
- HIGH CONFIDENCE IN CEILINGS,  
- HIGH CONFIDENCE IN VISIBILITIES,  
- MODERATE TO HIGH CONFIDENCE IN WIND DIRECTION AND SPEED.  
 
EXTENDED AVIATION DISCUSSION...  
 
MOSTLY VFR CONDITIONS EXPECTED THROUGH THE PERIOD. HIGH  
PRESSURE REMAINS OVERHEAD THROUGH AT LEAST WEDNESDAY BOTH AT THE  
SURFACE AND ALOFT. THE NEXT COLD FRONT WILL ARRIVE LATE IN THE  
WEEK. MOISTURE WILL BE LIMITED BUT A FEW MVFR SHOWERS ARE  
EXPECTED WITH THAT FRONT LATE THURSDAY OR FRIDAY. SOME LATE  
NIGHT/EARLY MORNING FOG WILL BE POSSIBLE IN VERY ISOLATED  
LOCATIONS MONDAY MORNING (E.G., LWB) AND IN OTHER AREAS NEAR  
RIVERS/MOUNTAIN VALLEYS TOWARD MIDWEEK.  
 

 
   
RNK WATCHES/WARNINGS/ADVISORIES
 
 
VA...FROST ADVISORY FROM 4 AM TO 9 AM EDT MONDAY FOR VAZ007-009-010-  
012-015.  
NC...FROST ADVISORY FROM 4 AM TO 9 AM EDT MONDAY FOR NCZ001-002-018.  
WV...NONE.  
 

 
 

 
SYNOPSIS...SH  
NEAR TERM...KK/SH  
SHORT TERM...AMS  
LONG TERM...AMS  
AVIATION...KK/SH  
 
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