408  
FXUS65 KGJT 190532  
AFDGJT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND JUNCTION CO  
1132 PM MDT WED SEP 18 2019  
   
SHORT TERM
 
(TONIGHT THROUGH THURSDAY NIGHT)  
ISSUED AT 400 PM MDT WED SEP 18 2019  
 
THE MID-LEVEL PACNW LOW HAS MOVED INLAND THIS AFTERNOON,  
TIGHTENING THE PRESSURE GRADIENT OVER EASTERN UTAH AND WESTERN  
COLORADO. SOUTHWEST WINDS WILL CONTINUE TO INTENSIFY AS THE UPPER  
LEVEL JET ROUNDING THE BASE OF THE TROUGH APPROACHES THE CWA.  
STRONG MIXING WILL PREVENT TEMPERATURES FROM PLUNGING TONIGHT AND  
CONTINUE TO MIX GUSTY WINDS DOWN TO THE SURFACE. EXPECT MOSTLY  
CLEAR SKIES TONIGHT ACROSS NORTHEAST UTAH AND NORTHWEST COLORADO,  
HOWEVER, MOISTURE WILL CREEP INTO THE REGION FROM THE SOUTH.  
 
ISOLATED TO SCATTERED SHOWERS ARE POSSIBLE ACROSS WESTERN COLORADO  
BY THURSDAY AFTERNOON/EVENING FAVORING HIGHER TERRAIN IN SOUTHWEST  
COLORADO AND ALONG THE DIVIDE. PW VALUES INCREASING TO AS HIGH AS  
0.5 TO 0.75 INCHES ALONG THE UT/CO BORDER MAY KEEP RH LEVELS  
ABOVE CRITICAL CONDITIONS. HOWEVER, DRY PERIODS AND STRONG WINDS  
LEAVE BORDERLINE FIRE WEATHER CONDITIONS ACROSS SOUTHEAST UTAH.  
CRITICAL CONDITIONS APPEAR SPOTTY IN TIMING AND LOCATION DUE TO  
MOISTURE CONTENT, SO NO HIGHLIGHTS HAVE BEEN ISSUED, ALTHOUGH,  
KEEP IN MIND, WINDY CONDITIONS WILL PERSIST. EXPECT TEMPERATURES  
TO CLIMB A FEW DEGREES WARMER THURSDAY AS WE MIX THROUGH A DEEPER  
LAYER IN THE ATMOSPHERE WHILE INCREASED CLOUD COVER THURSDAY NIGHT  
WILL KEEP TEMPERATURES MILD OVERNIGHT AS WELL.  
   
LONG TERM
 
(FRIDAY THROUGH WEDNESDAY)  
ISSUED AT 400 PM MDT WED SEP 18 2019  
 
ON FRIDAY THE MID LEVEL CLOSE LOW PRESSURE WILL BE LOCATED OVER THE  
NORTHERN GREAT BASIN, AND LIFTING NORTHEASTWARD THROUGH THE DAY. AS  
IT DOES IT WILL WEAKEN INTO AN OPEN WAVE THEREFORE THE FORCING WILL  
BE ON A DOWN TREND. THE CHALLENGE DURING THIS PERIOD IS THE COVERAGE  
OF AFTERNOON SHOWERS AND THUNDERSTORMS. A JET STREAK MOVING THROUGH  
THE AREA WILL PROVIDE MODEST OROGRAPHIC LIFT, BUT MODELS ARE ALSO  
INDICATING A SYNOPTIC DRY SLOT. WITH DAYTIME HEATING THIS AIR WILL  
MIXING TO THE SURFACE, WHICH MAY LIMIT STORM COVERAGE TO ISOLATED  
AND PERHAPS SCATTERED. THE MORE MODEST LIFT SHOULD OCCUR IN  
NORTHEAST UTAH AND NORTHERN COLORADO CLOSER TO THE MID LEVEL  
DYNAMICS. A COLD FRONT APPEARS TO CLIP PORTIONS OF NORTHWEST  
COLORADO FRIDAY AFTERNOON AND EVENING, WHICH COULD BE THE FOCUS  
FOR STORMS. CRITICAL FIRE WEATHER CONDITIONS WILL BE POSSIBLE  
MAINLY ACROSS SOUTHEAST UTAH ON FRIDAY AFTERNOON.  
 
ON SATURDAY THE TROUGH AXIS FINALLY DRAGS THROUGH THE AREA AND DRY  
AIR FILTERS IN FROM THE NORTHWEST. THE LINGERING PRESSURE GRADIENT  
MAY KEEP CONDITIONS WINDY WITH AN OVERALL DECREASE LATER IN THE  
WEEKEND. ON SUNDAY A WEAK MIDLEVEL RIDGE QUICKLY RACES OVER THE  
REGION IN BETWEEN THE NEXT SYSTEM THAT MOVES ON SHORE OF THE PACIFIC  
NORTHWEST. EARLY NEXT WEEK THE MODELS CONTINUE TO STRUGGLE WITH THE  
EVOLUTION OF THE PACIFIC NORTHWEST SYSTEM. THE GFS IS RATHER  
AGGRESSIVE WITH A CLOSED LOW DIVING SOUTHEASTWARD RIGHT INTO THE  
FORECAST AREA, AND TO SOME DEGREE THE CANADIAN AGREES. THE ECMWF IS  
CUTTING THE LOW OFF OVER THE GREAT BASIN AND DROPPING IT SOUTHWARD  
TOWARDS SOUTHERN CALIFORNIA.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)  
ISSUED AT 1128 PM MDT WED SEP 18 2019  
 
BIGGEST CONCERN OVER THE NEXT 24 HOURS WILL BE GUSTY SURFACE WINDS  
THANKS TO AN APPROACHING TROUGH AND SOME MIXING FROM THE JET  
STREAM ALOFT. GUIDANCE SUGGESTING ALL TAF SITES WILL SEE SOME  
GUSTS RANGING FROM 20 TO 30KTS FROM THE SOUTH FOR MUCH OF THE  
DAY. WINDS SHOULD PICKUP FROM ABOUT 16 TO 17Z ONWARDS AND CONTINUE  
THROUGH 00Z BEFORE LIGHTENING SOME. SOME MIDLEVEL BROKEN CEILINGS  
WILL MOVE IN TOWARDS THE LATE AFTERNOON AND EARLY EVENING BUT  
SHOULDN'T POSE ANY AVIATION THREATS. WITH WINDS LIKE THIS, SOME  
WIND SHEAR IS POSSIBLE ALONG WITH SOME MOUNTAIN WAVE TURBULENCE.  
 

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

 
 

 
 
SHORT TERM...ERW  
LONG TERM...KJS  
AVIATION...TGR  
 
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