981  
FXUS65 KGJT 211135  
AFDGJT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND JUNCTION CO  
535 AM MDT THU OCT 21 2021  
   
SHORT TERM
 
(TODAY THROUGH FRIDAY)  
ISSUED AT 305 AM MDT THU OCT 21 2021  
 
HIGH CLOUDS ARE BEGINNING TO ENCROACH UPON THE NORTHERN AND  
CENTRAL CWA AS A WEAK SHORTWAVE TROUGH IS EJECTED ACROSS THE  
SOUTHERN CANADIAN PRAIRIES AHEAD OF A PERSISTENT TROUGH SITTING  
OFF THE PACIFIC NORTHWEST COAST. SKIES ARE EXPECTED TO CLEAR AND  
BECOME MOSTLY SUNNY BY MID AFTERNOON AS THE RIDGE OF HIGH PRESSURE  
RE-ESTABLISHES ITSELF ACROSS THE GREAT BASIN. HIGHS TODAY WILL BE  
WARMER THAN YESTERDAY BUT STILL A FEW DEGREES BELOW NORMAL.  
 
HIGH CLOUDS WILL MOVE ACROSS THE CWA FROM THE SOUTHWEST AS THE  
PACIFIC TROUGH PUSHES ONSHORE BY FRIDAY AFTERNOON, ALLOWING THE  
RIDGE AXIS TO ALSO SHIFT DIRECTLY OVERHEAD. A LEADING SHORTWAVE  
WILL EJECT OUT AHEAD OF THIS PARENT TROUGH ACROSS THE  
INTERMOUNTAIN WEST BY FRIDAY EVENING. OUR CWA WILL BARELY GET  
CLIPPED BY THIS TROUGH, RESULTING IN PERHAPS SOME BREEZY  
WINDS ACROSS NORTHEAST UTAH AND NORTHWEST COLORADO. TEMPERATURES  
WILL BUMP UP ON THE NORTH SIDE OF NORMAL DUE TO BETTER MIXING AS A  
RESULT OF INCREASED SOUTHWEST FLOW ON FRIDAY.  
   
LONG TERM
 
(FRIDAY NIGHT THROUGH WEDNESDAY)  
ISSUED AT 305 AM MDT THU OCT 21 2021  
 
THE FIRST IN A SERIES OF PACIFIC TROUGHS WILL MOVE ONSHORE AND  
LIFT NORTHEAST ACROSS THE INTERMOUNTAIN WEST LATE FRIDAY AND INTO  
SATURDAY. A SUBTLE SPLIT WILL SEE A WEAK VORT MAX QUICKLY TREK  
ACROSS NORTHEAST UTAH AND NORTHWEST COLORADO SATURDAY NIGHT AND  
INTO SUNDAY. SOME GUIDANCE FEATURES A SHALLOWER TROUGH THAN  
OTHERS WHICH WILL ULTIMATELY DETERMINE WHICH AREAS RECEIVE  
PRECIPITATION. FOR NOW, FAVORING AREAS ALONG AND NORTH OF I-70 FOR  
THE BEST CHANCE OF SHOWERS, THOUGH THE SOUTHERN MOUNTAINS LOOK TO  
SEE AT LEAST ISOLATED SNOWFALL SATURDAY NIGHT. THIS FEATURE WILL  
QUICKLY LIFT NORTHEAST TOWARDS THE FRONT RANGE SUNDAY MORNING WITH  
LIGHT SNOW SHOWERS LINGERING OVER THE NORTHERN MOUNTAINS IN THE  
FAVORED NORTHWESTERLY FLOW THROUGHOUT THE DAY. WHEN ALL IS SAID  
AND DONE, A COUPLE UP TO A FEW INCHES OF SNOW WILL FALL IN THE  
NORTHERN AND CENTRAL MOUNTAINS WITH A FEW TENTHS IN THE SAN JUANS  
(UNLESS THIS SYSTEM DRIFTS FURTHER SOUTH, RESULTING IN SLIGHTLY  
BETTER SHOWER COVERAGE AND SUBSEQUENT ACCUMULATION). REGARDLESS,  
AFTER THIS SUBADVISORY EVENT A RIDGE OF HIGH PRESSURE WILL BUILD  
OVER THE REGION FOR MONDAY. TEMPERATURES LOOK TO RECOVER QUICKLY  
AFTER BEING KNOCKED DOWN A COUPLE OF DEGREES IN RESPONSE TO  
SUNDAY'S SYSTEM WITH HIGHS ON MONDAY TRENDING 5 TO 10 DEGREES  
ABOVE NORMAL.  
 
THE POWERHOUSE OF AN UPPER LEVEL TROUGH RESPONSIBLE FOR THE  
PROLONGED ATMOSPHERIC RIVER EVENT ACROSS THE NORTHWESTERN CONUS  
WILL FINALLY BEGIN TO SLOWLY PUSH INLAND ON MONDAY. ITS BASE WILL  
ELONGATE AND EXTEND AS FAR SOUTH AS BAJA. THIS WILL RESULT IN A  
PROMINENT SHIFT TO SOUTHWEST FLOW ACROSS EASTERN UTAH AND WESTERN  
COLORADO (ACCOUNTING FOR THAT NOTABLE JUMP IN TEMPERATURES MONDAY  
AFTERNOON). IN ADDITION TO THE WARMER TEMPERATURES, IT'LL BE A  
BREEZY DAY AS THE UPPER LEVEL JET DIGS INTO THE GREAT BASIN  
RESULTING IN A TIGHTENING GRADIENT OVERHEAD. UNFORTUNATELY, IT'S  
FROM TUESDAY ONWARDS THAT CONFIDENCE BEGINS TO DEGRADE AS  
DISCREPANCIES CONTINUE TO PLAGUE THE EXTENDED MODELS IN TERMS OF  
HOW THE TROUGH WILL EVOLVE AS WELL AS HOW QUICKLY IT WILL PROGRESS  
EAST. WHILE WE COULD SEE SHOWERS DEVELOP OVER THE WESTERN ZONES  
AS EARLY AS MONDAY AFTERNOON, IT LOOKS LIKE THE BETTER PUSH WILL  
COME LATE MONDAY NIGHT AND INTO TUESDAY. REGARDLESS, A WIDESPREAD  
PRECIPITATION EVENT LOOKS LIKELY WITH THE PREVIOUS ESTIMATE OF A  
QUARTER OF AN INCH AND UP TO OR EXCEEDING AN INCH OF QPF STILL ON  
TRACK FOR MUCH OF THE REGION.  
 
700MB TEMPERATURES WILL DROP FROM A MILD 6 TO 12 DEGREES C MONDAY  
AFTERNOON TO -3 TO -6 DEGREES C AT THE MIDWEEK POINT. WITH THE  
WARM ANTECEDENT CONDITIONS CONFIDENCE IS NOT HIGH ON SNOW REACHING  
MANY VALLEYS AT THIS TIME OR IN NARROWING DOWN IMPACTS IN THE  
HIGHER ELEVATIONS. STILL PLENTY OF TIME FOR THINGS TO CHANGE AND  
FOR THE MODELS TO REACH A BETTER CONSENSUS (ESPECIALLY IN REGARDS  
TO THE POTENTIAL CUTOFF LOW OVER THE FOUR CORNERS BEFORE THIS  
SYSTEM DEPARTS). OVERALL THOUGH, THE END OF THE LONG TERM PERIOD  
LOOKS TO REMAIN COOL AND UNSETTLED.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)  
ISSUED AT 534 AM MDT THU OCT 21 2021  
 
HIGH CLOUDS WILL TRAVERSE THE CWA FROM WEST TO EAST THROUGH THE  
MORNING HOURS WITH CLEARING BY MID TO LATE AFTERNOON. WINDS WILL  
REMAIN LIGHT AND TERRAIN DRIVEN WITH OCCASIONAL BREEZY CONDITIONS  
AT THE HIGHER ELEVATION TAF SITES. VFR CONDITIONS WILL PREVAIL.  
 

 
   
GJT WATCHES/WARNINGS/ADVISORIES
 
 
CO...NONE.  
UT...NONE.  

 
 

 
 
SHORT TERM...MDA  
LONG TERM...MMS/MDA  
AVIATION...MDA  
 
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