Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 200915
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
315 AM MDT SUN JUL 20 2014

CORRECTED TO INCLUDE FIRE WEATHER WATCH IN GJT WATCHES/WARNINGS
SECTION

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 308 AM MDT SUN JUL 20 2014

NO MAJOR CHANGES IN FORECAST THINKING AS THE NOSE OF A 60+KT JET
STREAK MOVES INTO THE 4 CORNERS REGION TODAY. THIS UPPER LEVEL
SUPPORT WILL ALLOW MORE WIDESPREAD CONVECTION TO FIRE WHILE ALSO
INCREASING MOISTURE CONTENT. GRAND JUNCTION RAOB SHOWED .46 INCHES
OF PWAT YESTERDAY EVENING WHICH THE NAM12 FORECAST FAIRLY WELL.
TODAY...THE NAM12 IS SHOWING AN INCREASE TO ABOUT .8 INCHES BY
THIS AFTERNOON SO 2 INGREDIENTS...LIFT FROM THE JET AND INCREASING
MOISTURE...ARE IN PLACE. LAPSE RATES DO BECOME STEEPER THIS
AFTERNOON WITH FORECAST SKEW-TS SHOWING CONDITIONAL INSTABILITY
ACROSS THE CWA SO WITH ALL 3 INGREDIENTS IN PLACE...STORMS AND
SHOWERS ARE A SOLID BET.  SOME SHEAR ALSO EXISTS WHICH WILL ALLOW
STORMS TO PERSIST A LITTLE LONGER THAN THE POP AND DROP WE`VE SEEN
OVER THE LAST FEW DAYS SO DO EXPECT SOME RAINSHOWERS AND
THUNDERSTORMS TO DRIFT INTO VALLEYS LATER IN THE DAY. HRRR REALLY
LIGHTING UP THE SAN JUANS WHICH IS ALSO FAVORED BY BOTH THE GFS
AND NAM SO HIGH POPS IN PLACE LOOK GOOD.

SHOWERS AND THUNDERSTORMS ARE NOT EXPECTED TO INITIATE AFTER
SUNSET...BUT WILL MAINTAIN ORGANIZATION THROUGH ABOUT MIDNIGHT
WITH THE 60KT JET STREAK AT H3 PLAYING A ROLE.

A WEDGE OF DRY AIR WILL MOVE INTO THE REGION ON MONDAY AS THE LOW
OFF OF THE COAST OF CALIFORNIA RETREATS WEST AND THE UPPER LEVEL
HIGH CAN SHIFT BACK OVER SOUTHERN COLORADO AND NORTHERN NEW MEXICO.
AS MENTIONED BY THE PREVIOUS FORECASTER...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.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 235 AM MDT SUN JUL 20 2014

THIS JET RETREATS NORTHWEST ON TUESDAY AFTERNOON. SOUTHWEST FLOW
WILL PULL SUBTROPICAL MOISTURE BACK INTO SOUTHERN COLORADO
BEGINNING LATE TUESDAY.

THE CENTER OF HIGH PRESSURE WILL WOBBLE OVER OUR FORECAST AREA
FROM WEDNESDAY THROUGH SATURDAY WITH MOISTURE UNDER THE RIDGE RECYCLING
EACH DAY ALLOWING CONVECTION TO FIRE WEDNESDAY INTO THURSDAY.
AFTER THAT...A CLOSED LOW WILL MOVE ACROSS THE US/CANADIAN BORDER
FLATTENING THE HIGH PRESSURE OVER US. THIS FLATTENING WILL CAUSE
WINDS TO BECOME W TO NWLY AND LIMITING THE MEAGER AMTS OF MOISTURE
THAT WERE STREAMING UP FROM THE SOUTH. DUE TO THIS...FRIDAY AND
SATURDAY LOOK TO BE HOT AND DRY WITH LITTLE...IF ANY...PRECIP
EXPECTED.

TEMPERATURES WILL CONTINUE TO RUN HOT...ABOUT 5 DEGREES ABOVE
NORMAL.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 308 AM MDT SUN JUL 20 2014

TRANQUIL CONDITIONS OVERNIGHT WILL CHANGE FROM ABOUT 17Z WHEN
CONVECTION WILL FIRE IN RESPONSE TO AN UPPER LEVEL DISTURBANCE
MOVING OVERHEAD. COVERAGE WILL BE GREATER THAN SEEN THE LAST FEW
DAYS WITH PLENTY OF CU BUILD UP EXPECTED ALONG WITH THUNDERSTORMS
AND RAINSHOWERS. HIGHER TERRAIN WILL BE FAVORED BUT SOME SHEAR
WILL ALLOW SOME CONVECTION TO DRIFT INTO VALLEYS. SOME HEAVY RAIN
IS ALSO POSSIBLE ALONG WITH GUSTY WINDS REACHING 40 MPH UNDER AND
NEAR THE STRONGEST CELLS. PER THE NORM...INCLUDED VCTS FOR
KASE...KEGE...AND KTEX LATER IN THE AFTERNOON. SOME CONVECTION MAY
LINGER THROUGH 06Z THOUGH NO AERODROMES SHOULD BE AFFECTED AFTER
03Z.


&&

.FIRE WEATHER...
ISSUED AT 308 AM MDT SUN JUL 20 2014

AN APPROACHING UPPER LEVEL DISTURBANCE WILL MOVE OVER UT/CO TODAY
AND MONDAY WITH THE STRONGEST WINDS MOVING OVER MONDAY...ESPECIALLY
FOR NORTHERN PORTIONS OF COLORADO. DEEP MIXING IS FORECAST TO REACH
500MB OR SO ALLOWING SFC WINDS TO REACH 20 KTS WITH OCCASIONAL
GUSTS TO 30 KTS. ALONG WITH THE WINDS...SFC RH`S WILL BE BETWEEN
10 TO 15 PERCENT AS DRY AIR REMAINS ACROSS THE AREA. THIS
COMBINATION WILL CAUSE CRITICAL FIRE WEATHER CONDITIONS FOR CO
FIRE ZONE 200. TO THAT END...WILL ISSUE A FIRE WEATHER WATCH FOR
THAT ZONE ON MONDAY FROM NOON TO 8PM.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...FIRE WEATHER WATCH FROM NOON MONDAY THROUGH MONDAY EVENING
     FOR COZ200.

UT...NONE.
&&

$$

SHORT TERM...TGR/JAM
LONG TERM...JAM/TGR
AVIATION...TGR
FIRE WEATHER...TGR



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