301  
FXUS65 KGJT 182328  
AFDGJT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND JUNCTION CO  
528 PM MDT FRI SEP 18 2020  
   
SHORT TERM
 
(TONIGHT THROUGH SATURDAY NIGHT)  
ISSUED AT 253 PM MDT FRI SEP 18 2020  
 
SATELLITE IMAGERY SHOWS HIGH CLOUDS DRIFTING INTO THE CWA AS A  
DEEPENING PACIFIC NW LOW DRAWS MOISTURE INTO THE GREAT BASIN.  
FLOW TRANSITIONING TO THE SOUTHWEST AHEAD OF THE TROUGH'S AXIS  
WILL ALLOW FOR SOME UPPER LEVEL MOISTURE TO FILTER IN, AND THUS,  
RESULT IN AN INCREASE IN HIGH CIRRUS CLOUDS SPREADING ACROSS  
EASTERN UTAH AND WESTERN COLORADO THIS EVENING. TEMPERATURES WILL  
RUN SLIGHTLY WARMER TONIGHT IN RESPONSE TO CLOUD COVER AND  
LIMITED RADIATIONAL COOLING.  
 
THE TROUGH AXIS WILL SWOOP ACROSS THE NORTHERN ROCKIES OVERNIGHT  
AND INTO TOMORROW, PRODUCING STRONG SOUTHWESTERLY WINDS ALOFT AS  
THE PRESSURE GRADIENT TIGHTENS OVERHEAD. WINDS WILL INTENSIFY ON  
SATURDAY AS A SURFACE BOUNDARY APPROACHES FROM THE NORTHWEST. DRY  
SOUTHWESTERLY FLOW AHEAD OF THIS SYSTEM WILL PRODUCE CRITICAL FIRE  
WEATHER CONDITIONS FOR PORTIONS OF EAST- CENTRAL UTAH. A RED FLAG  
WARNING IS NOW IN EFFECT FOR FIRE WEATHER ZONE 490. ELEVATED  
MOISTURE NEAR THE BOUNDARY WILL MAINTAIN DECENT CLOUD COVER AS THE  
SYSTEM APPROACHES, WHICH WILL ALSO LIMIT THE SPREAD OF FIRE  
WEATHER CONCERNS ACROSS NORTHEAST UTAH AND NORTHWEST COLORADO.  
HOWEVER, LOCALIZED CRITICAL CONDITIONS ARE POSSIBLE, AS WINDS WILL  
BE WHIPPING. ISOLATED SHOWERS WILL FIRE OVER HIGHER TERRAIN ACROSS  
NORTHEAST UTAH AND WESTERN COLORADO SATURDAY AFTERNOON, AS THE  
SURFACE BOUNDARY DIPS INTO THE CWA. LACK OF LOW LEVEL MOISTURE  
TIED TO THIS SYSTEM WILL LIMIT PRECIPITATION FROM REACHING THE  
SURFACE ACROSS VALLEY FLOORS, WHILE MOUNTAINOUS TERRAIN WILL  
LIKELY ONLY SEE A FEW HUNDREDTHS TO A TENTH OF AN INCH.  
 
THE SYSTEM'S HARD TRACK NORTHWARD ON SATURDAY WILL LIMIT THE  
EFFECTS OF THE FRONTAL BOUNDARY TO THE NORTHERN HALF OF THE CWA.  
HIGH TEMPERATURES WILL DIP 3 TO 8 DEGREES COOLER ACROSS THE  
NORTHERN TIER OF THE CWA, WHILE OUR SOUTHERN REGION WILL REMAIN  
FAIRLY CONSISTENT WITH TEMPERATURES OBSERVED TODAY. UNFORTUNATELY,  
THESE STRONG WINDS MAY ALSO CARRY A THICKER PLUME OF SMOKE FROM  
CALIFORNIA FIRES INTO THE AREA, SO ANTICIPATE ANOTHER HAZY  
AFTERNOON. ONCE THE SYSTEM EXITS TO OUR NORTHEAST, WE'LL BE  
LEFT UNDER ZONAL FLOW BY SATURDAY NIGHT. DRY WESTERLY WINDS WILL  
ALLOW FOR CLEARING SKIES OVERNIGHT...OTHER THAN SMOKE...  
   
LONG TERM
 
(SUNDAY THROUGH FRIDAY)  
ISSUED AT 253 PM MDT FRI SEP 18 2020  
 
HEIGHTS WILL INCREASE SUNDAY IN THE WAKE OF SATURDAY'S TROUGH  
PASSAGE AND REMAIN IN A ZONAL OR RIDGING PATTERN THROUGH THE WEEK  
IN OUR NECK OF THE WOODS. EXPECT ENOUGH LINGERING MOISTURE FOR  
BUILDUPS OVER THE TERRAIN IN THE AFTERNOON INSTABILITY AND  
OROGRAPHIC CIRCULATIONS. THE SOUTHERN MOUNTAINS STILL THE MOST  
PROBABLE LOCATION TO GET SOME MOISTURE TO THE GROUND AND LIMITED  
POPS REMAIN THERE. SPLIT FLOW PATTERN DEVELOPS OVER THE PACIFIC  
COASTLINE WITH THE SUBTROPICAL JET LIFTING TOWARD THE 4 CORNERS  
LATE MONDAY. VERY DIFFUSE QG PATTERN OVER OUR CWA MONDAY NIGHT  
INTO TUESDAY AS THIS JET CORE LINGERS NEAR OUR SOUTHERN BORDER.  
THE GFS REMAINS QUITE AGGRESSIVE WITH THE PRECIPITATION DURING  
THIS TIMEFRAME AND HAVING DIFFICULT TIME FIGURING OUT WHY. THETA  
SURFACES DO SHOW SOME MOISTURE WEAK MOISTURE RETURN IN A SHALLOW  
UPGLIDE REGIME. NOT HARD TO MAKE CONVECTION IN THIS SCENARIO AS  
MODERATE INSTABILITY WILL BE IN PLACE. CONFIDENCE NOT HIGH MUCH  
WILL REACH THE GROUND WITH MODELS NOT TOO AWARE OF THE DROUGHT  
CONDITIONS AND THE EVAPORATIVE DEMAND IN THE LOWER LAYERS. THERE  
ARE SOME BROAD POPS GOING INTO MONDAY NIGHT THEN AGAIN TUESDAY  
WHEN THE NOSE OF THE NORTHERN STREAM JET TRANSLATES ACROSS THE  
ROCKIES. CAN SEE SOME PRECIPITATION IMPACTING THE TERRAIN BUT NOT  
MUCH OF CHANCE IN THE LOWER ELEVATIONS SO WILL BE INTERESTING TO  
SEE HOW THIS PLAYS OUT. CONFIDENCE IS HIGH THE DROUGHT WILL  
CONTINUE UNABATED. HIGH PRESSURE BUILDS BACK IN WEDNESDAY AND  
THURSDAY AHEAD OF A MUCH STRONGER TROUGH HEADING TOWARD THE PACNW.  
FAMILIAR FIRE WEATHER PATTERN SETTING UP TO END OUT THE WEEK AS  
THIS TROUGH BEGINS TO LEAN THE RIDGE EASTWARD. HIGH TEMPERATURES  
WILL OSCILLATE THROUGH THE FORECAST BUT ULTIMATELY STAY AT OR  
ABOVE NORMAL. AS FOR THE PERSISTENT HAZY SKIES...UNTIL A LOT OF  
THE BIG FIRES OUT WEST GET PUT OUT IT SEEMS WE HAVE SOME TAP TO  
THE SMOKE STREAM.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 528 PM MDT FRI SEP 18 2020  
 
HAZY CONDITIONS WITH HIGH CLOUDINESS WILL PERSIST THIS EVENING AND  
INTO SATURDAY MORNING. WINDS WILL BE GRADUALLY INCREASING FROM  
THE SOUTHWEST OVERNIGHT WHICH COULD LEAD TO SOME LIGHT MOUNTAIN  
WAVE TURBULENCE...WHILE ALSO HELPING TO PUSH SOME OF THE SMOKE OUT  
OF THE AREA. MIDLEVEL CLOUDS WILL FILTER INTO THE REGION ON  
SATURDAY AFTERNOON WITH GUSTY WINDS OF 20 TO 25 KNOTS DEVELOPING  
ACROSS THE AREA AFTER 18Z. WIDESPREAD VFR CONDITIONS WILL PREVAIL  
THROUGH THE END OF THE TAF PERIOD.  
 

 
   
FIRE WEATHER
 
 
ISSUED AT 253 PM MDT FRI SEP 18 2020  
 
WINDS WILL INCREASE OVERNIGHT AND INTO SATURDAY AS A LOW PRESSURE  
SYSTEM AND ITS ASSOCIATED FRONTAL BOUNDARY APPROACH THE REGION.  
DRY SOUTHWEST FLOW AHEAD OF THE BOUNDARY WILL RESULT IN CRITICAL  
FIRE WEATHER CONDITIONS TOMORROW AFTERNOON ACROSS EAST-CENTRAL  
UTAH. STRONG WINDS WILL DRAPE ACROSS NORTHEAST UTAH AND NORTHWEST  
COLORADO, HOWEVER, INCREASED CLOUD COVER MAY LIMIT RH FROM  
DROPPING TO CRITICAL LEVELS FOR THESE REGIONS. EXPECT LOCALIZED  
CRITICAL CONDITIONS FOR NORTHERN FIRE WEATHER ZONES, AS WELL AS  
ISOLATED SHOWERS AND STORMS DEVELOPING OVER HIGHER TERRAIN DURING  
THE AFTERNOON.  
 

 
   
GJT WATCHES/WARNINGS/ADVISORIES
 
 
CO...NONE.  
UT...RED FLAG WARNING FROM NOON TO 8 PM MDT SATURDAY FOR UTZ490.  
 

 
 

 
 
SHORT TERM...ERW  
LONG TERM...15  
AVIATION...TGJT  
FIRE WEATHER...TGJT  
 
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