234  
FXUS63 KBIS 171932  
AFDBIS  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BISMARCK ND  
232 PM CDT TUE SEP 17 2019  
   
SHORT TERM
 
(THIS EVENING THROUGH WEDNESDAY)  
ISSUED AT 153 PM CDT TUE SEP 17 2019  
 
A SURFACE LOW PRESSURE WITH AN ASSOCIATED COLD FRONT ALONG THE  
NORTH DAKOTA/MONTANA BORDER THIS AFTERNOON IS FORECAST TO MOVE  
EAST THROUGH TONIGHT. THE FRONT WILL BE THE FOCUS FOR SCATTERED  
THUNDERSTORMS, SEVERAL MAY BE STRONG TO SEVERE.  
 
WE SEE THE POTENTIAL FOR STRONG CONVECTION VERY LATE THIS  
AFTERNOON, BUT THIS COULD SLIP TILL THIS EVENING, THROUGH  
MIDNIGHT. THE 12Z GFS SHOWS THE 0-6 KM SHEAR ALIGNED WITH THE  
FORECAST FRONTAL POSITIONS, WHICH SUGGEST THE STORM MODE WILL BE A  
BIT MESSY AND COMPLEX, MAINLY MULTICELL WITH LINES WITH AN  
ISOLATED SUPERCELL.  
 
CORFIDI VECTORS ALSO SUGGEST SOME TRAINING, SO CAN'T RULE OUT  
SOME HEAVY RAIN POTENTIAL WEST THIS EVENING AND OVERNIGHT.  
THE PRECIPITABLE WATER IS RELATIVELY HIGH, BUT WITH CAPPING IN  
PLACE, AND A RELATIVELY NARROW PERIOD FOR FREE CONVECTION ALONG  
THE FRONT, FEEL THE HEAVY RAIN POTENTIAL IS REALISTICALLY LOW.  
 
CONVECTION WILL BE EXITING THE REGION WEDNESDAY MORNING AS TEH  
SHORTWAVE TROUGH MOVES THROUGH.  
 
THE MUCH ABOVE TEMPERATURES THAT WERE ASSOCIATED WITH A STRONG  
H500 RIDGE OVER THE CENTRAL AND NORTHERN PLAINS WILL BE COMING TO  
AN END. HIGHS WEDNESDAY WILL BE IN THE LOWER TO MID 70S.  
 
   
LONG TERM
 
(WEDNESDAY NIGHT THROUGH TUESDAY)  
ISSUED AT 153 PM CDT TUE SEP 17 2019  
 
AS THE H500 RIDGE DRIFTS EAST EARLY IN THE EXTENDED PERIOD  
THURSDAY, A LARGE H500 TROUGH, CURRENTLY MOVING INTO THE PACIFIC  
NORTHWEST WILL MIGRATE EAST BY WEEKEND. THIS WILL INITIALLY BRING  
A LONG FETCH OF SOUTHWEST FLOW ALOFT FROM SOUTHERN CALIFORNIA  
INTO THE NORTHERN PLAINS. LOW LEVEL MOISTURE WILL RETURN INTO THE  
REGION AHEAD OF THIS SYSTEM, SETTING UP A SLOW MOVING COLD  
FRONT/BAROCLINIC ZONE ACROSS THE NORTHERN PLAINS. WHAT CAN BE  
EXPECTED IS A RATHER EXTENDED PERIOD OF SHOWERS AND THUNDERSTORMS  
THURSDAY NIGHT, FRIDAY, AND FRIDAY NIGHT.  
 
AGAIN, PRECIPITABLE WATER WILL BE WELL ABOVE NORMAL, AND  
WIDESPREAD RAINFALL BETWEEN ONE AND 2 INCHES WILL BE POSSIBLE  
THURSDAY NIGHT THROUGH FRIDAY NIGHT, WITH THE HIGHEST AMOUNTS  
GENERALLY ACROSS THE NORTH.  
 
COOLER, BUT MORE NORMAL TEMPERATURES IN TEH 60S TO AROUND 70 ARE  
EXPECTED AT THIS TIME. SUNDAY THROUGH TUESDAY WILL SEE SOME  
TRANSIENT SCATTERED SHOWERS, WITH HIGHS IN THE 60S.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)  
ISSUED AT 1221 PM CDT TUE SEP 17 2019  
 
A SURFACE LOW PRESSURE AND AN ASSOCIATED COLD FRONT IN EASTERN  
MONTANA THIS AFTERNOON IS FORECAST TO MOVE SLOWLY EAST THIS  
FORECAST PERIOD. THE FRONT WILL BE THE FOCUS FOR THUNDERSTORMS  
LATE THIS AFTERNOON SOUTHWEST AND ACROSS THE WESTERN HALF OF THE  
STATE TONIGHT. VFR CONDITIONS ARE EXPECTED.  
 

 
   
BIS WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM...WAA  
LONG TERM...WAA  
AVIATION...WAA  
 
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