792  
FXUS65 KGJT 200950  
AFDGJT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND JUNCTION CO  
350 AM MDT SUN AUG 20 2017  
   
SHORT TERM
 
(TODAY THROUGH MONDAY)  
ISSUED AT 350 AM MDT SUN AUG 20 2017  
 
AS MODELS HAD PREDICTED, LOW PRESSURE ALONG THE WEST COAST  
ENCROACHING ON HIGH PRESSURE TO THE SOUTH HAS BROUGHT A  
SOUTHERLY FLOW TO AREAS SOUTH OF THE I-70 CORRIDOR. THIS PATTERN  
SHIFT IS EXPECTED TO BRING A MODEST INCREASE IN MOISTURE ACROSS  
THE SOUTHERN HALF OF THE FORECAST AREA. THIS, IN TURN, SHOULD LEAD  
TO AN UPTICK IN DIURNALLY DRIVEN SHOWER/THUNDERSTORM ACTIVITY  
OVER THE SOUTHERN AND CENTRAL MOUNTAINS THIS AFTERNOON AND  
EVENING. MOISTURE REMAINS RELATIVELY HIGH BASED SO MAIN THREAT  
WILL BE FROM OUTFLOW WINDS AND LIGHTNING. POCKETS OF MODERATE TO  
HEAVY RAIN BECOME POSSIBLE AS SUBCLOUD MOISTURE INCREASES LATER IN  
THE AFTERNOON AND INTO THE EVENING.  
 
DIURNAL COOLING IS EXPECTED TO BRING AN END TO MOIST CONVECTION BY  
MIDNIGHT, THOUGH ITS LIKELY AREAS OF VIRGA WILL PERSIST AS HAS  
BEEN THE CASE LAST NIGHT AND AGAIN EARLY THIS MORNING. THE PATTERN  
APPEARS LARGELY UNCHANGED OVER THE AREA ON MONDAY, SO EXPECT MORE  
OF THE SAME WITH A MODEST INCREASE IN SHOWER/THUNDERSTORM COVERAGE,  
MAINLY OVER THE HIGHER TERRAIN SOUTH OF THE I-70 CORRIDOR.  
 
FORECAST HIGHS ARE EXPECTED TO RESPOND INVERSELY TO THE INCREASED  
CLOUDS/SHOWERS, MOST NOTICEABLY ACROSS SOUTHEAST UTAH AND  
SOUTHWEST COLORADO TODAY AND MONDAY. IN CONTRAST, OVERNIGHT LOWS  
ARE EXPECTED TO BE FAIRLY PERSISTENT.  
   
LONG TERM
 
(MONDAY NIGHT THROUGH SATURDAY)  
ISSUED AT 350 AM MDT SUN AUG 20 2017  
 
ENSEMBLE AND OPERATIONAL MODELS SUGGEST THE UPPER RIDGE WILL  
REMAIN A DOMINANT FEATURE OVER THE SOUTHERN/CENTRAL ROCKIES  
THROUGH MID WEEK. THE RIDGE AXIS IS GENERALLY OVER OUR CWA AND  
THIS DOESN'T SEEM TO BE THE BEST LOCATION TO FULLY TAP THE MONSOON  
REGION. IN FACT PWAT ANOMALIES EARLY THIS WEEK SUGGEST DRIER AIR  
BEING FORCED INTO THE GULF OF CALI REGION WITH THE SUBTROPICAL TAP  
BEING ENTRAINED INTO THE LOW OFF THE LEFT COAST AND POOLING WELL  
TO OUR WEST. BY LATE WED THERE IS STRONGER NORTHERN STREAM LOW  
DROPPING OUT OF THE GULF OF AK WITH THE ATTENDANT TROF BEGINNING  
TO FORCE THE CALI LOW INLAND BY THURSDAY MORNING. THIS PATTERN  
SHIFT IN THE WEST WILL BE ENOUGH TO FORCE THE RIDGE AXIS EAST AND  
WE SHOULD GET A BETTER PUSH OF MOISTURE IN THE REGION. FORCING  
FROM A PIECE OF THE WEAKENING SOUTHERN LOW TO OUR WEST WILL  
COMBINE WITH THE MOISTURE FOR PROBABLY THE BEST PRECIPITATION  
CHANCES THURSDAY INTO EARLY FRIDAY. OTHERWISE THE TYPICAL  
DIURNALLY DRIVEN STORMS FAVORING THE TERRAIN CAN BE EXPECTED  
TUESDAY INTO WEDNESDAY AND AGAIN FRIDAY. NORTHWEST FLOW SETTING UP  
OVER THE ROCKIES BY NEXT WEEKEND DUE TO THE RIDGE REBOUNDING BACK  
TO THE WEST SUGGEST A DRIER FORECAST. TEMPERATURES WILL FOLLOW A  
SIMILAR PATTERN WITH NEAR TO ABOVE NORMAL GOING INTO THURSDAY THEN  
COOLER LATE WEEK BEFORE POPPING BACK UP FOR THE WEEKEND.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 350 AM MDT SUN AUG 20 2017  
 
VFR CONDITIONS ARE EXPECTED TO PERSIST ACROSS EASTERN UTAH AND  
WESTERN COLORADO DURING THE NEXT 24 HOURS, HOWEVER THERE WILL BE  
SOME WEATHER ACROSS THE AREA. SPECIFICALLY DAYTIME WARMING WILL  
BRING ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS TO THE HIGHER  
TERRAIN THIS AFTERNOON AND EVENING. THIS ACTIVITY WILL BE A BIT  
MORE WIDESPREAD THAN YESTERDAY ENHANCING THE POTENTIAL FOR BRIEF  
SHOWER/THUNDERSTORM ACTIVITY OVER TAF SITES SITUATED CLOSEST TO  
THE MOUNTAINS. THESE SITES INCLUDE KASE, KGUC, KTEX AND KDRO. KASE  
MAY EXPERIENCE A BRIEF PERIOD WHERE CIGS FALL BELOW ILS  
BREAKPOINTS, BUT IT'S UNLIKELY THAT CONDITIONS WILL DETERIORATE  
BELOW VFR LEVELS.  
 

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

 
 

 
 
SHORT TERM...NL  
LONG TERM...15  
AVIATION...NL  
 
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