Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 312239
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
439 PM MDT FRI OCT 31 2014

.SHORT TERM...(TONIGHT THROUGH SATURDAY NIGHT)
ISSUED AT 337 PM MDT FRI OCT 31 2014

A COLD PACIFIC TROUGH APPROACHING THE WEST COAST THIS AFTERNOON WILL
MOVE INLAND LATE TONIGHT. A POOL OF HIGHER PRECIPITABLE WATER OVER
AZ/NM GETS DRAWN NORTHWARD TONIGHT IN WARM ADVECTIVE SOUTHWEST FLOW.
COMBINATION OF ISENTROPIC UPGLIDE AND UPSLOPE FLOW INTO THE SRN MTNS
WILL BRING A CHANCE OF LIGHT SHOWERS TO MAINLY SE UT/SW CO LATE THIS
EVENING AND OVERNIGHT. BELIEVE MODELS WERE TOO AGGRESSIVE ON RAISING
POPS WITH DRIER AIR STILL AT THE SURFACE INITIALLY...AND CUT BACK
VALUES FOR THE GRIDDED FORECAST.

SATURDAY LOOKS WINDY. GUSTS OF 30-40 MPH ARE LIKELY ACROSS THE
TYPICALLY WINDIER VALLEYS OF SE UT AND NW CO...WITH GUSTS 20-30 MPH
ELSEWHERE. THIS THE RESULT OF A TIGHTENING GRADIENT AS A FAIRLY WELL-
DEFINED SHORTWAVE CURRENTLY IN THE BASE OF THE PACIFIC TROUGH EJECTS
NORTHEAST ACROSS NV...AS THE MAIN TROUGH SPLITS INTO TWO PIECES.
THIS EJECTING SHORTWAVE SHOULD CONCENTRATE DYNAMIC LIFT AND MOISTURE
TO OUR WEST SAT AFTERNOON WHILE SOME DRYING WORKS ACROSS THE FOUR
CORNERS. WILL SHIFT THE BEST CHANCE OF SHOWERS MORE TOWARD NE UT SAT
AFTERNOON AND TAPER POPS DOWN ACROSS MUCH OF WRN CO. ISOLATED
THUNDERSTORMS POSSIBLE. WITH A BIT MORE SUN ANTICIPATED IN STILL
MILD SW FLOW...BUMPED HIGH TEMPS UP A TAD ON SAT.

THE SPLITTING TROUGH MOVES INTO THE WRN GREAT BASIN SAT NIGHT.
TRAILING COLD FRONT FROM THE EJECTING SHORTWAVE PUSHES IN FROM
THE W-NW. 700 MB TEMPS NOT AS COLD AS EARLIER MODEL RUNS AS THE
OVERALL SYSTEM IS NOW SLOWER...BUT THIS 700 MB FRONT/BAROCLINIC
ZONE SHOULD BE THE FOCUS FOR A BETTER CHANCE OF VALLEY RAIN AND
MOUNTAIN RAIN/SNOW...AIDED BY 300 MB JET THAT REFORMS NEAR THE
FOUR CORNERS BY 12Z SUNDAY. BOOSTED POPS LATE SAT NIGHT AS A
RESULT.

WILL CONTINUE WITH THE SPECIAL WEATHER STATEMENT HIGHLIGHTING THE
CHANGING WEATHER EXPECTED THIS WEEKEND.

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 337 PM MDT FRI OCT 31 2014

THIS COMPLEX SYSTEM CONTINUES TO SPLIT WITH THE NORTHERN PORTION
OVER THE NORTHERN ROCKIES BY SUNDAY MORNING. THE SOUTHERN PART
CONTINUES TO DIG WITH THE SOUTHERN EDGE OF THE TROUGH OVER THE
SOUTHWESTERN UNITED STATES. WINDS INCREASE ALOFT IN FRONT OF THE
TROUGH SUNDAY MORNING. THE TROUGH WILL MOVE EAST OVER EASTERN UTAH
AND WESTERN COLORADO SUNDAY. PRECIPITATION WILL INCREASE SUNDAY
AND INTO SUNDAY NIGHT. MOISTURE WILL INCREASE SUNDAY MORNING AND
AGAIN SUNDAY NIGHT. INCREASED PRECIPITATION CHANCES AS MODELS ARE
SLIGHT MORE CONSISTENT. THE TROUGH AXIS IS POSITIVELY SLANTED
FROM NORTHEAST TO SOUTHWEST OVER WESTERN COLORADO AND EASTERN
UTAH BY MONDAY MORNING. THE NORTHERN PORTION OF THIS TROUGH IS
PROGRESSIVE AND MOVES EAST OF THE DIVIDE BY MONDAY EVENING.
SHOWERS WILL PERSIST MONDAY OVER THE HIGHER TERRAIN OF COLORADO.
PRECIPITATION SHOULD END FROM WEST TO EAST MONDAY EVENING. THE
SOUTHERN PART OF THE TROUGH DIGS FARTHER SOUTH AND CUTS OFF OVER
NORTHERN MEXICO. ONE MODEL TAKES THIS EAST INTO TEXAS WHILE THE
OTHER HINTS AT THE NORTHERN PART OF THIS LOW SKIRTING THE
SOUTHERN EDGE OF THE CWA THURSDAY.

AFTER THE TROUGH EXITS THE REGION LATE MONDAY PRECIPITATION
CHANCES DECREASE TO NEAR NOTHING AND TEMPERATURES SLOWLY START TO
INCREASE AGAIN.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 438 PM MDT FRI OCT 31 2014

MID AND HIGH LEVEL MOISTURE CONTINUES TO WORK INTO THE 4 CORNERS
REGION LATE THIS AFTERNOON. THROUGH 01/06Z THIS SHOULD STAY MAINLY
IN THE FORM OF MID TO HIGH LEVEL CLOUDINESS. PERSISTENT SOUTHERLY
FLOW INTO THE SOUTHERN AND CENTRAL COLORADO MOUNTAINS WILL
GRADUALLY ALLOW CIGS TO LOWER AND ISOLATED TO SCATTERED SHOWERS
DEVELOP. OBSCURATION OF THE HIGH TERRAIN IS MOST LIKELY AS
CONFIDENCE OF LOWERED FLIGHT CRITERIA AT TAF SITES REMAINS VERY
LOW. SO FOR NOW VFR CONDITIONS PREVAIL AT THE AREA FORECAST
TERMINALS.

&&

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

$$

SHORT TERM...JAD
LONG TERM...AS
AVIATION...TGJT



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