910  
FXUS65 KBOU 210918  
AFDBOU  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE DENVER/BOULDER CO  
318 AM MDT MON OCT 21 2019  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 302 AM MDT MON OCT 21 2019  
 
COLORADO WILL BE UNDER A STRONG NORTHWEST FLOW PATTERN THROUGH  
TONIGHT AS A STRONG NORTHWEST TO SOUTHEAST ORIENTED 140KT JET CORE  
SHIFTS ACROSS THE STATE THROUGH TONIGHT. SATELLITE IMAGERY STILL  
SHOWING PLENTY OF LOW LEVEL MOISTURE UPSTREAM OF COLORADO, SO  
EXPECT CONTINUED OROGRAPHIC SNOW SHOWERS TO CONTINUE OVER THE  
MOUNTAINS TODAY. LAPSE RATES WILL REMAIN RELATIVELY STEEP AT  
7-8C/KM WITH A STEADY NORTHWEST WIND AT 20-30KT AT 700MB. THESE  
CONDITIONS WILL SUPPORT TO CONTINUE THE WINTER WEATHER ADVISORY  
FOR THE MOUNTAINS THROUGH THIS EVENING. BASED ON ABOVE, ADDITIONAL  
SNOWFALL OF 2-7 INCHES LOOKS RESONABLE WITH HIGHER AMOUNTS ON  
HIGHER WEST FACING SLOPES. MOISTURE DEPTH BECOMES MORE SHALLOW  
THIS EVENING AS THE JET CORE SHIFTS EAST OF THE MOUNTAINS. CROSS  
SECTIONS SHOWING CROSS BARRIER FLOW REMAINING AROUND 30-40KT SO  
THIS WILL SUPPORT CONTINUED GUSTS IN THE 40-60 MPH OVER MOUNTAIN  
PASSES THROUGH TONIGHT.  
 
ACROSS LOWER ELEVATIONS TODAY, TEMPERATURES WILL BE SIMILAR AS  
700MB TEMPERATURES REMAIN UNCHANGED FROM YESTERDAY. MORE SUNSHINE  
ACROSS THE FAR NORTHEAST PLAINS WILL RESULT READINGS BACK INTO THE  
LOWER 50S. NOT AS WINDY TODAY, BUT STILL WELL MIXED AIRMASS WILL  
STILL RESULT IN WIND GUSTS IN THE 20-30KT RANGE. COULD STILL SEE  
SOME HIGHER GUSTS OVER THE FAR NORTHEAST PLAINS OF 30-40KT IN  
CLOSER PROXIMITY TO THE STRONG DEPARTING CYCLONE THIS MORNING.  
THE WINDS WILL DIMINISH THIS EVENING ON THE PLAINS AS THE AIRMASS  
DECOUPLES.  
   
LONG TERM
 
(TUESDAY THROUGH SUNDAY)  
ISSUED AT 302 AM MDT MON OCT 21 2019  
 
NW FLOW ALOFT WILL CONTINUE, OVER THE AREA, TUE THRU TUE NIGHT  
AS A SFC LEE TROUGH BECOMES ESTABLISHED ALONG THE FRONT RANGE.  
CROSS-SECTIONS SHOW SHALLOW MOISTURE EMBEDDED IN THE FLOW THRU TUE  
AFTN, BUT WILL INCREASE BY TUE NIGHT. LAPSE RATES WILL GENERALLY  
BE IN THE 4-5 C/KM RANGE. OVERALL WILL SEE SOME SNOW SHOWERS,  
ESPECIALLY IN THE NRN MTNS, BUT ACCUMULATIONS WILL BE ON THE LIGHT  
SIDE. MEANWHILE THERE WILL BE SOME POTENTIAL FOR HIGH WINDS TUE  
NIGHT, IN THE NRN FOOTHILLS, AS A MTN WAVE DEVELOPS AND COMPONENT  
ALONG WINDS INCREASE TO 50-55 KTS. AT THIS POINT, NOT SURE HOW  
WIDESPREAD WINDS WILL BE, SO WILL HOLD OFF ON A WATCH FOR NOW.  
ACROSS NERN CO, IT WILL BE DRY WITH WARMER TEMPERATURES ON TUE.  
 
ON WED, AN UPPER LEVEL TROUGH, IN NORTHWEST FLOW ALOFT, WILL MOVE  
SOUTH SOUTHEAST FROM THE NRN ROCKIES. THIS FEATURE WILL AFFECT  
THE AREA MAINLY WED NIGHT INTO EARLY THU. MEANWHILE A COLD FRONT  
WILL MOVE INTO NERN CO BY MIDDAY WED.  
 
OVERALL, WILL SEE INCREASING MOISTURE BY AFTN INTO WED NIGHT,  
WITH UPSLOPE FLOW DEVELOPING. CROSS-SECTIONS SHOW FAVORABLE QG  
ASCENT WITH DECENT LAPSE RATES AS WELL. ALSO, NRN CO WILL BE IN  
THE FAVORABLE LEFT FRONT QUADRANT OF AN UPPER LEVEL JET. THUS,  
SNOW SHOULD BECOME LIKELY IN THE MTNS DURING THE AFTN, AND  
GRADUALLY SPREAD ACROSS THE FOOTHILLS AND FRONT RANGE BY WED  
EVENING AND CONTINUE OVERNIGHT. THE SNOW WILL THEN GRADUALLY END  
THU MORNING, FROM NORTH TO SOUTH, AS THE UPPER LEVEL TROUGH MOVES  
SOUTH OF THE AREA. CURRENTLY BOTH THE ECMWF AND GFS SHOW DECENT  
SNOW ACCUMULATIONS OVER THE HIGHER TERRAIN AND ACROSS PORTIONS  
OF THE FRONT RANGE URBAN CORRIDOR. AS FOR TEMPERATURES, WILL KEEP  
HIGHS FROM 55 TO 60 OVER NERN CO ON WED AND THEN DROP THEM INTO  
40S FOR THU.  
 
FOR FRI AND SAT AN UPPER LEVEL RIDGE WILL SLOWLY BUILD INTO THE  
AREA. CROSS-SECTIONS SHOW VERY LITTLE MOISTURE EITHER DAY SO WILL  
NOT MENTION ANY PRECIP. MEANWHILE WILL ALSO SEE A GRADUAL WARMING  
TREND AS WELL.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)  
ISSUED AT 302 AM MDT MON OCT 21 2019  
 
GENERALLY LIGHT WEST TO NORTHWEST WINDS WILL INCREASE BY  
AFTERNOON WITH GUSTS IN THE 15-30KT RANGE BEFORE DIMINISHING BY  
EVENING. VFR CONDITIONS WILL REMAIN THROUGH TONIGHT.  
 

 
   
BOU WATCHES/WARNINGS/ADVISORIES
 
 
WINTER WEATHER ADVISORY UNTIL 9 PM MDT THIS EVENING FOR COZ031-  
033-034.  
 

 
 

 
 
SHORT TERM...ENTREKIN  
LONG TERM...RPK  
AVIATION...ENTREKIN  
 
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