567  
FXUS65 KGJT 191030  
AFDGJT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE GRAND JUNCTION CO  
430 AM MDT SAT AUG 19 2017  
   
SHORT TERM
 
(TODAY THROUGH SUNDAY)  
ISSUED AT 430 AM MDT SAT AUG 19 2017  
 
THE WEATHER PATTERN FEATURED LOW PRESSURE OVER SOUTHERN CALIFORNIA  
AND A BROAD AREA OF HIGH PRESSURE EXTENDING FROM THE SOUTHERN  
PLAINS WEST-NORTHWESTWARD ACROSS NEW MEXICO TO THE WESTERN GREAT  
BASIN. A DISORGANIZED MASS OF CLOUDS WERE CAUGHT UP IN THE WEAK  
DEFORMATION BETWEEN THESE SYSTEMS, LOOSELY ALIGNED EAST-WEST  
ACROSS CENTRAL NEVADA AND UTAH.  
 
MODEST MOISTURE LEVELS COMBINED WITH DAYTIME HEATING ARE EXPECTED  
TO FUEL ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS OVER THE  
MOUNTAINS FROM LATE MORNING INTO THE EVENING. THIS ACTIVITY WILL  
BE HIGH BASED JUDGING FROM EVENING SOUNDINGS AND BUFR FORECAST  
SOUNDINGS. CONSEQUENTLY, LOOK FOR MORE WIND THAN RAIN FROM TODAY'S  
ACTIVITY.  
 
THE LOW OVER SOUTHERN CALIFORNIA ERODES THE HIGH OVER THE REGION  
TO SOME DEGREE ON SUNDAY. THIS CAUSES THE DEFORMATION TO BECOME  
REPOSITIONED OVER SOUTHWEST COLORADO. ACCORDING TO GFS AND NAM  
THIS SUBSTANTIALLY INCREASES SHOWER AND THUNDERSTORM ACTIVITY OVER  
THE SAN JUAN MOUNTAINS. EC WAS LESS INSISTENT, BUT NOT ENTIRELY  
INCONSISTENT. IN ANY EVENT, APPEARS THE REGION IS IN STORE FOR AN  
UPTICK IN MOIST CONVECTION SUNDAY AFTERNOON WITH STORMS  
TRANSITIONING FROM HIGH BASED TO MORE EFFICIENT RAIN PRODUCERS.  
 
TEMPERATURES WILL RUN A LITTLE BIT ABOVE NORMAL TODAY WITH SLIGHT  
COOLING IN STORE SUNDAY WITH THE ANTICIPATED INCREASE IN SHOWERS  
AND THUNDERSTORM ACTIVITY.  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 430 AM MDT SAT AUG 19 2017  
 
THE GFS REMAINS CONSISTENT WITH INITIATING A CHANGE IN CONDITIONS  
BY SUNDAY NIGHT AS MONSOON MOISTURE INCREASES FROM THE SOUTH. A  
SLOW MOVING OLD CLOSED LOW WILL SETTLE OVER SOUTHERN CALIFORNIA  
AND HIGH PRESSURE WILL CONSOLIDATE OVER TEXAS. THE FLOW BETWEEN  
THESE TWO SYSTEMS WILL FUNNEL MOISTURE NORTH INTO SOUTHERN AZ AND  
NM. THIS FLOW WILL REMAIN IN PLACE THROUGH MUCH OF THE WEEK. THE  
ONLY CHANGE IN THE GFS TO CONSIDER IS THAT INITIALLY, SUNDAY  
EVENING THROUGH TUESDAY, MOST OF THE MOISTURE BARELY CLIPS THE SW  
PORTION OF THE CWA BEFORE BENDING TO THE EAST OVER SE CO, MUCH AS  
THE EC HAD BEEN DOING THE LAST FEW DAYS. UNFORTUNATELY, THE  
POSSIBILITY IS HIGH FOR CLOUD COVER TO INTERFERE WITH VIEWING THE  
SOLAR ECLIPSE MONDAY OVER MUCH OF WESTERN CO AND EASTERN UT.  
 
MOISTURE WILL CONTINUE SLOWLY INCREASING THROUGH TUESDAY WITH  
INCREMENTALLY HIGHER PRECIP CHANCE EACH DAY, ESPECIALLY BETWEEN  
00Z AND 06Z EACH EVENING. WEDNESDAY, ESPECIALLY WED. EVENING,  
APPEARS TO BRING THE FIRST BIG SURGE OF MONSOON MOISTURE AS THE  
SOUTHERN CA LOW MOVES EAST AND OVER THE FORECAST AREA, DRAWING  
SUBSTANTIAL MOISTURE WITH IT. THE LOW IS PROJECTED TO PASS OVER  
THE AREA THURSDAY WHICH SHOULD BRING THE GREATEST AREAL COVERAGE  
OF PRECIP. SLIGHTLY DRIER NW FLOW ALOFT IS EXPECTED FRIDAY.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)  
ISSUED AT 430 AM MDT SAT AUG 19 2017  
 
MODERATE MOISTURE IN A WESTERLY FLOW ALOFT IS EXPECTED TO GENERATE  
ISOLATED TO LOW END SCATTERED THUNDERSTORMS OVER THE HIGHER  
TERRAIN AGAIN THIS AFTERNOON AND EVENING. THERE IS A SLIGHT CHANCE  
THAT THUNDERSTORMS COULD BRIEFLY IMPACT KASE, KTEX AND KGUC  
BRINGING STRONG OUTFLOW WINDS TO 45 MPH AND LIGHT RAIN. HOWEVER,  
IT'S UNLIKELY THIS WILL CAUSE CIGS TO FALL BELOW ILS BREAKPOINTS  
AND VFR CONDITIONS SHOULD CONTINUE. THE REMAINING TAF SITES WILL  
CONTINUE TO EXPERIENCE VFR CONDITIONS OVER THE NEXT 24 HOURS.  
OUTFLOW GUSTS ASIDE, WINDS ARE EXPECTED TO BE RELATIVELY LIGHT AND  
TERRAIN DRIVEN.  
 

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

 
 

 
 
SHORT TERM...NL  
LONG TERM...CC  
AVIATION...NL  
 
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