527  
FXUS65 KGJT 221001  
AFDGJT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND JUNCTION CO  
401 AM MDT SAT SEP 22 2018  
   
SHORT TERM
 
(TODAY THROUGH SUNDAY)  
ISSUED AT 401 AM MDT SAT SEP 22 2018  
 
SKIES WERE AGAIN CLEAR OVER MOST OF THE FORECAST AREA OVERNIGHT AS  
A LOW-AMPLITUDE RIDGE LINGERED OVER THE REGION. HOWEVER, AREAS OF  
ALTOCUMULUS WERE EVIDENT IN IR IMAGERY OVER THE SOUTHWEST SAN  
JUAN MOUNTAINS. MODELS INDICATED A WEAK DISTURBANCE MOVING OVER  
THE SOUTH EARLY THIS MORNING WAS RESPONSIBLE FOR SUSTAINING THESE  
CLOUDS. GFS SOLUTION NOT WITHSTANDING, THERE IS EXCEEDINGLY LITTLE  
CHANCE THAT THESE CLOUDS WILL GENERATE PRECIPITATION DURING THE  
REMAINDER OF THE NIGHT OR AFTER SUNRISE THIS MORNING. IN FACT,  
IT'S UNCLEAR HOW THERE WILL BE SUFFICIENT MOISTURE TO FUEL ANY  
MOIST CONVECTIVE ACTIVITY DURING THE AFTERNOON EITHER GIVEN THE  
DRY WEST-SOUTHWEST FLOW ALOFT. THEREFORE, IGNORED GFS INPUT AND  
LEFT OUT ANY MENTION OF PRECIPITATION TODAY, THOUGH THERE WILL BE  
PARTLY CLOUDY SKIES OVER THE SAN JUAN MOUNTAINS DURING THE  
AFTERNOON. ELSEWHERE, LOOK FOR ANOTHER SUNNY AND MILD/WARM DAY.  
 
UNEVENTFUL WEATHER CONTINUES OVERNIGHT AND INTO SUNDAY MORNING AS  
FLOW ALOFT SHIFTS TO THE SOUTHWEST IN RESPONSE TO A MID-LEVEL  
TROUGH MOVING ASHORE OVER THE PACIFIC NORTHWEST. OVERNIGHT LOWS  
WILL BE LESS CHILLY IN RESPONSE TO A MODEST INCREASE IN MID-LEVEL  
MOISTURE.  
 
THE TROUGH MENTIONED PREVIOUSLY WILL CONTINUE TO PUSH EASTWARD  
ACROSS THE NORTHWEST AND THE WESTERN GREAT BASIN ON SUNDAY. THE  
COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL SHIFT TO NORTHERN  
WYOMING AND EXTREME NORTHWEST UTAH SUNDAY AFTERNOON. THE PRE-  
FRONTAL PRESSURE GRADIENT INCREASE ASSOCIATED WITH THIS MOVEMENT  
WILL BRING BREEZY SOUTHWEST WINDS TO THE AREA FROM LATE MORNING  
THROUGH THE AFTERNOON WITH THE FOCUS ALONG AND NORTH OF THE I-70  
CORRIDOR. MODELS MIXED ON PRECIPITATION CHANCES SUNDAY AFTERNOON,  
BUT CAN'T ENTIRELY RULE OUT ISOLATED HIGH BASED THUNDERSTORMS OVER  
THE PEAKS. MEANWHILE, TEMPERATURES WILL CONTINUE TO RUN WARMER  
THAN NORMAL FOR THIS TIME OF YEAR, AND HEWED AFTERNOON HIGHS  
PRETTY CLOSE TO PERSISTENCE.  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 401 AM MDT SAT SEP 22 2018  
 
FOLLOWING THE NICE WEATHER THIS WEEKEND, A FAST MOVING UPPER  
LEVEL TROUGH AND SURFACE COLD FRONT WILL BRING CLOUDS AND LIGHT  
PRECIPITATION. MODELS HAVE BEEN IN FAIRLY GOOD AGREEMENT DEPICTING  
THE JET STREAM DROPPING DOWN FROM THE NORTH SUNDAY NIGHT THROUGH  
MONDAY PROVIDING THE UPPER LEVEL SUPPORT FOR THIS SYSTEM. HOWEVER,  
THE UPPER LEVEL SUPPORT IS RATHER WEAK WITH A JET CORE OF AROUND  
75 KTS. THIS IS BORNE OUT BY MODELS SHOWING GENERALLY LIGHT  
PRECIPITATION AMOUNTS. THE GFS IS A BIT MORE AGGRESSIVE WHILE THE  
NAM HAS SCALED BACK SOME. AS THE UPPER LEVEL SUPPORT REMAINS ON  
THE WEAK SIDE, THE NAM IS A BIT MORE BELIEVABLE AT THE MOMENT. THE  
FRONT WILL JUST BE ENTERING THE CWA EARLY MONDAY MORNING AND WILL  
REACH THE I-70 CORRIDOR AROUND NOON BEFORE MOVING THROUGH THE SAN  
JUANS IN THE EVENING. A FEW SHOWERS AND AN ISOLATED THUNDERSTORM  
WILL CERTAINLY BE POSSIBLE. SNOW LEVELS LOOK TO BE AROUND 11 TO  
12 KFT SO SOME MINOR ACCUMULATION IS NOT OUT OF THE QUESTION FOR  
THE HIGHER PEAKS. FALL IS HERE. AFTER THAT, NORTHWESTERLY FLOW  
SETS UP BRINGING IN MORE SEASONABLE TEMPERATURES AS PIECES OF  
ENERGY DROP DOWN FROM THE NORTH. WE'LL BE FAR ENOUGH WEST TO NOT  
SEE ANY OF THESE DISTURBANCES AFFECT OUR WEATHER OUTSIDE OF SOME  
INCREASED CLOUDS FROM TIME TO TIME.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)  
ISSUED AT 1143 PM MDT FRI SEP 21 2018  
 
VFR CONDITIONS WILL CONTINUE FOR THE NEXT 24 HOURS. SOME GUSTY  
WINDS UP TO 20 TO 25 KTS ARE EXPECTED TOMORROW AFTERNOON BUT  
SHOULDN'T POSE ANY THREATS TO AVIATION.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 401 AM MDT SAT SEP 22 2018  
 
EXPECT SOUTHWEST WINDS TO INCREASE OVER NORTHWEST COLORADO AND  
PORTIONS OF NORTHEAST UTAH THIS WEEKEND AHEAD OF AN APPROACHING  
PACIFIC TROUGH. VEGETATION REMAINS VERY DRY ACROSS THE REGION SO  
GUSTY SOUTHWEST WINDS COMBINED WITH ABOVE NORMAL TEMPERATURES AND  
LOW RELATIVE HUMIDITY COULD RESULT IN CRITICAL FIRE WEATHER  
CONDITIONS.  
 
THE FIRE WEATHER WATCH FOR NORTHWEST COLORADO FOR THIS AFTERNOON  
AND EVENING FOR FIRE WEATHER ZONE 200 HAS BEEN UPGRADED TO A RED  
FLAG WARNING. MODELS INDICATED JUST A BIT MORE WIND ACROSS THE  
AREA TODAY AS COMPARED TO FRIDAY WHILE RH REMAINS QUITE LOW.  
HOWEVER, HELD OFF UPGRADING THE FIRE WEATHER WATCH ON SUNDAY FOR  
COLORADO FIRE WEATHER ZONE 200, THOUGH DID EXPAND THE WATCH TO  
INCLUDE UTAH FIRE WEATHER ZONE 487. BOTH AREAS APPEARED BORDERLINE  
IN LATEST MODEL RUNS, THOUGH THIS TIME WIND GUSTS SEEM MORE  
CERTAIN TO EXCEED 25 MPH WHILE RH WILL BE HOVERING NEAR OR ABOVE  
15 PERCENT.  
 

 
   
GJT WATCHES/WARNINGS/ADVISORIES
 
 
CO...FIRE WEATHER WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING  
FOR COZ200.  
 
RED FLAG WARNING FROM NOON TODAY TO 8 PM MDT THIS EVENING FOR  
COZ200.  
 
UT...FIRE WEATHER WATCH FROM SUNDAY AFTERNOON THROUGH SUNDAY EVENING  
FOR UTZ487.  
 

 
 

 
 
SHORT TERM...NL  
LONG TERM...TGR  
AVIATION...TGR  
FIRE WEATHER...TGJT  
 
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