Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 192108
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
308 PM MDT SAT JUL 19 2014

.SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT)
ISSUED AT 308 PM MDT SAT JUL 19 2014

MODERATE MID-LEVEL MOISTURE COMBINED WITH DAYTIME HEATING
GENERATED SCATTERED SHOWERS AND THUNDERSTORMS OVER THE EASTERN
UINTA MOUNTAINS AND THE CENTRAL AND SOUTHERN COLORADO MOUNTAINS
BEGINNING A LITTLE AFTER 17Z. SUBCLOUD LAYER NOT PARTICULARLY
MOIST AS EVIDENCED BY DEWPOINT VALUES WHICH WERE IN THE LOW 30S
NORTH...WITH MID-30S ACROSS THE CENTRAL PORTION OF EASTERN UTAH
AND WESTERN COLORADO...AND IN THE MID TO UPPER 30S ACROSS THE
SOUTH. LITTLE SHEAR TO WORK WITH AND CAPE MARGINAL SO LITTLE
CHANCE FOR ORGANIZED STORMS AND EXPECT STORMS WILL CONTINUE TO BE
WEAK SINGLE/MULTI CELL VARIETY. THEREFORE...EXPECT THE MAIN THREAT
DURING THE REMAINDER OF THE AFTERNOON AND INTO THE EVENING WILL BE
GUSTY OUTFLOW WINDS TO 35-40 MPH AND LIGHTNING. DIURNAL COOLING
IN THE ABSENCE OF LIFTING MECHANISM SHOULD BRING AN END TO
SHOWERS/THUNDERSTORMS THIS EVENING WITH PARTIAL CLEARING
OVERNIGHT.

PATTERN SHIFTS A BIT SUNDAY AS A WEAK LOW OVER SOUTHERN CALIFORNIA
LIFTS TO THE NORTH IN PHASE WITH A TROUGH MOVING INTO THE PACIFIC
NORTHWEST. MEANWHILE...HIGH PRESSURE IS DRIVEN EASTWARD TO NORTH-
CENTRAL NEW MEXICO. RESULTANT SOUTHWESTERLY FLOW ALOFT CARRIES
MOISTURE FROM ARIZONA/SOUTHERN UTAH OVER THE NORTHERN HALF OF THE
FORECAST AREA INCREASING PRECIPITABLE WATER BY 0.1 TO 0.2 INCHES
WITH A LESS NOTICEABLE INCREASE SOUTH. AS A RESULT...EXPECT AN
UPTICK IN THUNDERSTORM ACTIVITY SUNDAY AFTERNOON AND EVENING WITH
WEAK JET LEVEL DIVERGENCE ALSO PLAYING A ROLE. EXPECT THE NORMAL
DOWNTURN IN ACTIVITY SUNDAY EVENING...HOWEVER EXIT REGION OF 50 KT
JET STREAK MAY BE SUFFICIENT TO SUSTAIN MOIST CONVECTION
OVERNIGHT.

INCREASED MOISTURE WILL BRING TEMPERATURES DOWN A FEW DEGREES ON
SUNDAY TO NEAR NORMAL LEVELS. DISCOUNTED THE MAV GUIDANCE WHICH
APPEARED MUCH TOO WARM AND SHADED IT CLOSER TO...BUT A LITTLE
ABOVE MET GUIDANCE.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 308 PM MDT SAT JUL 19 2014

DRIER AIR WILL BE STREAMING IN FROM THE SOUTHWEST ON MONDAY AS A LOW
PRESSURE SYSTEM MOVES OFF THE SOUTHERN CALIFORNIA COAST AND THE
UPPER HIGH SHIFTS TO SOUTHERN NEW MEXICO. THIS IS USUALLY A GOOD
POSITION TO BE PULLING MONSOON MOISTURE TO THE 4 CORNERS BUT THE
AMPLIFICATION OF THE RIDGE TO THE NORTH WILL BE SUPPRESSED BY A
DIP IN THE POLAR JET STREAM ACROSS THE NORTHERN US BORDER. THIS
JET RETREATS ON TUESDAY AND PULLS MONSOONAL MOISTURE WORKS BACK TO
THE NORTH OUT OF THE SIERRA MADRE. HOWEVER THE BULK OF THIS WILL
BE TO THE WEST OF OUR CWA...WHICH THEN GETS SWEPT INTO THE
COLORADO ROCKIES ON WEDNESDAY BY THE ARRIVAL OF AN UPSTREAM SYSTEM
TO THE NORTHWEST STATES. ATTM PWATS NOT OVERLY IMPRESSIVE AND
REALLY MOVING BACK TOWARD NORMAL AND WELL UNDER AN INCH. THIS PUSH
OF MOISTURE HAS SOMETIMES BEEN UNDERESTIMATED BY MODELS AND WILL
CONTINUE TO MONITOR...BUT FOR NOW WILL JUST HAVE TO CARRY
SCATTERED POPS OVER THE DIVIDE MOUNTAINS. DRIER AIR IS FORCED BACK
INTO THE CWA BY THE PACIFIC NW WAVE DIGGING INTO THE PLAINS
THROUGH THE LATE WEEK PERIOD. SO IN GENERAL A FAIRLY DRY AND HOT
FORECAST FOR THE UPCOMING WEEK LOOKS ON TAP. GUIDANCE NUMBERS FOR
THE LOWER DESERT VALLEYS STILL SUGGEST UPPER 90S TO LOW 100S
THROUGH THE MID WEEK PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1041 AM MDT SAT JUL 19 2014

MODERATE LEVELS OF MOISTURE WILL FUEL SHOWERS AND THUNDERSTORMS
THROUGH 03Z/SUN...MAINLY OVER THE SOUTHERN MOUNTAINS. THESE STORMS
WILL RESULT IN AREAS OF MOUNTAIN OBSCURATION...OTHERWISE VFR
CONDITIONS WILL BE THE RULE. THERE IS A SLIGHT CHANCE (LESS THAN
20 PERCENT) THAT STORMS WILL AFFECT TAF SITES WITH KTEX AND KDRO
MOST FAVORED. OUTFLOW WINDS TO 40 MPH FROM THESE STORMS OF PRIMARY
CONCERN THOUGH HEAVY RAIN COULD YIELD BRIEF MVFR VSBY. CONDITIONS
IMPROVE LATE IN THE EVENING WITH VFR CONDITIONS PERSISTING THROUGH
18Z/SUN.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...NONE.
UT...NONE.

&&

$$

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



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