806  
FXUS65 KBOU 190929  
AFDBOU  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DENVER/BOULDER CO  
329 AM MDT TUE SEP 19 2017  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 209 AM MDT TUE SEP 19 2017  
 
AN UPPER LEVEL TROUGH WILL MOVE ACROSS THE NRN ROCKIES THIS AFTN AND  
EVENING WITH BRISK WSW FLOW ALOFT OVER NRN CO. THERE WILL BE SOME  
MID LVL ASCENT, WHICH WILL COMBINE WITH JUST ENOUGH MOISTURE TO  
PRODUCE A CHC OF SHOWERS IN THE MTNS MAINLY NR THE WY BORDER LATE  
THIS AFTN AND EVENING. OTHERWISE THE REST OF THE AREA WILL BE DRY  
WITH GUSTY WINDS THRU THE AFTN HOURS. AS FOR TEMPS, WITH DOWNSLOPE  
WSW LOW LVL FLOW, THIS SHOULD ALLOW FOR AFTN HIGHS TO REACH THE  
MID 80S TO LOWER 90S OVER NERN CO.  
 
FOR TONIGHT THE SHOWER THREAT IN THE NRN MTNS SHOULD END BY  
MIDNIGHT. MEANWHILE A PACIFIC FNT WILL MOVE ACROSS THE PLAINS  
DURING THE EARLY EVENING HOURS WITH A BRIEF PERIOD OF GUSTY NWLY  
WINDS BEHIND IT WHICH WILL BRING COOLER TEMPERATURES.  
 
   
LONG TERM
 
(WEDNESDAY THROUGH MONDAY)  
ISSUED AT 335 AM MDT TUE SEP 19 2017  
 
WEST-SOUTHWESTERLY FLOW ALOFT IS PROGGED ON WEDNESDAY. THE FLOW  
ALOFT BECOMES SOUTHWESTERLY WEDNESDAY NIGHT TROUGH THURSDAY NIGHT.  
AS AN UPPER TROUGH/CLOSED LOW GETS INTO THE GREAT BASIN BY 12Z  
FRIDAY MORNING, THE SOUTHWESTERLY FLOW ALOFT OVER COLORADO  
INCREASES IN SPEED. THE SYNOPTIC SCALE ENERGY IS BENIGN WEDNESDAY  
TROUGH THURSDAY, BUT WEAK UPWARD MOTION GETS OVER THE CWA THURSDAY  
NIGHT ON THE QG OMEGA FIELDS. FOR THE BOUNDARY LAYER WINDS, THERE  
IS SOUTHEASTERLIES PROGGED ON WEDNESDAY, NORMAL DRAINAGE PATTERNS  
WEDNESDAY NIGHT, DOWNSLOPING SOUTHWESTERLIES ON THURSDAY AND MORE  
DRAINAGE THURSDAY NIGHT. THERE IS LITTLE MOISTURE AROUND THROUGH  
THE PERIODS. PRECIPITABLE WATER VALUES ARE IN THE 0.25 TO 0.50  
INCH RANGE FOR THE CWA WEDNESDAY THROUGH THURSDAY NIGHT. THERE IS  
NO MEASURABLE RAINFALL ON THE QPF FIELDS WEDNESDAY THROUGH  
THURSDAY NIGHT. NO POPS. FOR TEMPERATURES, WEDNESDAY'S HIGHS ARE  
1-4 C COOLER THAN TUESDAY. THURSDAY'S READINGS ARE 1-5 C WARMER  
THAN WEDNESDAY'S. CONCERNING THE DAYS FRIDAY THROUGH MONDAY,  
INCREASING SOUTHWESTERLY ALOFT IS PROGGED ON FRIDAY. A FAIRLY  
STRONG COLD FRONT MOVES IN FRIDAY NIGHT. THERE IS A JET MAXIMUM  
OVER THE CWA ON SATURDAY WITH SOUTHWESTERLY FLOW ALOFT. SOUTH-  
SOUTHWESTERLY FLOW ALOFT IS PROGGED SUNDAY. ON MONDAY THE ECMWF  
STARTS GETTING THE TROUGH INTO THE FORECAST AREA. THE GFS STILL  
HAS SOUTHWESTERLY FLOW ALOFT WITH THE TROUGH AXIS STILL TO OUR  
WEST. MOISTURE INCREASES SIGNIFICANTLY LATER FRIDAY THROUGH NEXT  
MONDAY. THERE IS SOME QPF AS WELL. TEMPERATURES COOL OFF TO BELOW  
SEASONAL NORMALS SATURDAY THROUGH MONDAY.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)  
ISSUED AT 209 AM MDT TUE SEP 19 2017  
 
VFR CONDITIONS TODAY THRU TONIGHT. WINDS WILL BE SSW EARLY THIS  
MORNING HOWEVER AM NOT VERY CONFIDENT ABOUT DIRECTIONS LATS THIS  
MORNING INTO THE EARLY AFTN HOURS. BOTH THE HRRR AND RAP INDICATE  
A WEAK SFC LOW WILL DEVELOP NEAR OR SW OF DIA BY LATE MORNING  
WHICH WOULD KEEP WINDS MORE S OR SE THRU 20Z. BY 21Z BOTH SHOW  
WINDS BECOMING WSW AS MIXING OCCURS WITH SOME GUSTS UP TO 25 MPH  
THRU 01Z. BY 04Z OR 05Z A COOL FNT WILL MOVE ACROSS WITH WINDS  
BECOMING NLY FOR A FEW HOURS. OVERNIGHT EXPECT WINDS WILL  
GRADUALLY SHIFT TO DRAINAGE BY 09Z.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 335 AM MDT TUE SEP 19 2017  
 
CRITICAL TO EXTREME FIRE DANGER WILL EXIST THIS AFTN INTO THE  
EARLY EVENING HOURS ACROSS MOST OF THE AREA DUE TO LOW HUMIDITY  
AND GUSTY WINDS. FIRE DANGER WILL DECREASE AFTER 8 PM AS WINDS  
GRADUALLY DECREASE AND HUMIDITY LEVELS RECOVER BEHIND A COOL  
FRONT. WEDNESDAY IS EXPECTED TO BE A COOLER AND A LITTLE LESS  
WINDY BUT THERE WILL STILL BE ELEVATED FIRE DANGER. TEMPERATURES  
INCREASE AGAIN THURSDAY, BUT THE WINDS ARE NOT VERY STRONG. THERE  
WILL STILL BE ELEVATED FIRE DANGER.  
 

 
   
BOU WATCHES/WARNINGS/ADVISORIES
 
 
RED FLAG WARNING FROM 11 AM THIS MORNING TO 8 PM MDT THIS  
EVENING FOR COZ212>216-238>251.  
 

 
 

 
 
SHORT TERM...RPK  
LONG TERM...RJK  
AVIATION...RPK  
FIRE WEATHER...RPK/RJK  
 
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