Area Forecast Discussion
Issued by NWS Grand Junction, CO

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586
FXUS65 KGJT 051731
AFDGJT

AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO
535 AM MDT THU MAY 5 2016

UPDATE TO SHORT TERM SECTION ABOUT FRIDAY STORM POTENTIAL

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 535 AM MDT THU MAY 5 2016

CURRENT SATELLITE INDICATES A PLUME OF MID LEVEL MOISTURE ON ITS
WAY FROM THE SOUTHWEST TODAY. FORECAST MODELS HAVE BEEN SHOWING AN
UPTICK IN PRECIPITATION ACTIVITY THIS AFTERNOON AND FRIDAY FOR
AWHILE NOW...SO THIS IS RIGHT ON TRACK. THE HIGH PRESSURE WHICH
HAD CLEARED OUT ALL OF THE RECENT MOISTURE ACROSS THE REGION WILL
BE BREAKING DOWN TODAY AS A LARGE -20C CORE LOW PRESSURE SYSTEM
MOVES ONSHORE CALIFORNIA TODAY. WINDS WILL INCREASE SUBSTANTIALLY
LATE THIS AFTERNOON ACROSS THE REGION AS THE GRADIENT TIGHTENS AND
SHOWERS AND THUNDERSTORMS DEVELOP OVER MAINLY THE HIGHER TERRAIN
THIS AFTERNOON. THE VAD WIND PROFILE VIA GJX RADAR IS ALREADY
PICKING UP 30+ MPH WINDS ABOVE 10KFT. A WEATHER STATION AT 11700
FEET IN THE LA SAL MOUNTAINS IS GUSTING TO 30 MPH ALREADY THIS
MORNING...AND THESE WIND MEASUREMENTS WILL ONLY INCREASE BY THIS
EVENING.

THE SIZE OF THIS INCOMING WEATHER SYSTEM ALONE INDICATES QUITE A
FEW DAYS OF UNSTABLE WEATHER. ON FRIDAY...MOST PRECIPITATION IS
EXPECTED OVER NE UTAH AND NW COLORADO ALONG A COLD FRONT
ASSOCIATED WITH THIS SYSTEM...BUT HIGH LAPSE RATES WILL BRING
SCATTERED SHOWERS AND THUNDERSTORMS TO MUCH OF THE AREA BY THE
LATE AFTERNOON. A STEADY HOURS-LONG RAIN EVENT IS NOT EXPECTED AT
THIS TIME IN ANY AREA IN PARTICULAR...BUT RATHER STRONG STORM
CELLS VERY CONVECTIVE IN NATURE WILL BE THE MAIN THREAT. THE STORM
PREDICTION CENTER HAS PUT NORTHWEST COLORADO AND NORTHEAST UTAH IN
A MARGINAL RISK AREA FOR SEVERE WEATHER ON FRIDAY...WITH THE
BIGGEST THREAT BEING HAIL EQUAL TO OR GREATER THAN ONE INCH AND
POTENTIALLY WIND GUSTS GREATER THAN 58 MPH ASSOCIATED WITH
THUNDERSTORMS. WILL NEED TO MONITOR THE VERNAL AND DINOSAUR AREAS
FOR THIS THREAT THROUGHOUT THE NEXT FEW FORECAST CYCLES.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 345 AM MDT THU MAY 5 2016

BY SATURDAY MORNING...THE CORE OF THE CLOSED LOW WILL BE OVER UTAH
AND STALLING AS IT REACHES EASTERN UT AND WESTERN CO. WITH THE
COLD FRONT HAVING PASSED BY SATURDAY...CONDITIONS WILL BE ON THE
COOL SIDE. FORECAST MODELS ARE INDICATING FAIRLY WIDESPREAD CLOUD
COVER...BUT EMBEDDED CONVECTION WILL LIKELY FIRE ON SATURDAY
WITHIN THE CLOUD SHIELD. FORECAST LAPSE RATES ACROSS THE FOUR
CORNERS ARE ON THE HIGH SIDE SATURDAY AFTERNOON...WHICH MAY BE
INDICATING A BREAK IN THE CLOUDS ACROSS THIS AREA. PRECIPITATION
INCREASES ON SUNDAY AS THE CLOSED LOW CENTER MOVES INTO
WYOMING...BUT MOISTURE WRAPS BACK INTO UTAH AND COLORADO FROM THE
NORTH. SPECIFIC HUMIDITY IS PROGGED TO INCREASE LATE SUNDAY AND
MONDAY TO NEAR 5 G/KG...ABOVE AVERAGE FOR THIS TIME OF YEAR. GOOD
AGREEMENT ON THE GFS AND EURO OF A WET SUNDAY NIGHT INTO MONDAY
ACROSS NORTHWESTERN COLORADO. WILL FEEL MORE CONFIDENT ON THIS
TOMORROW NIGHT IF WE ARE SEEING THE SAME FEATURE. WITH A CLOSED
LOW IT IS GOOD TO BE WEARY OF THESE SMALL DETAILS 4 DAYS IN
ADVANCE. SNOW LEVEL THROUGHOUT THIS STORM IS EXPECTED TO BE HIGH
AS MENTIONED IN THE PREVIOUS DISCUSSION...NEAR 10KFT TO 11KFT.

LONG RANGE MODELS ARE CONSISTENT ON FEATURING A SECOND CLOSED LOW
DROPPING INTO THE ROCKIES ON TUESDAY. AT THIS TIME...THIS SYSTEM
IS NOT FORECAST TO DROP INTO COLORADO BUT RATHER TO BRUSH NE UTAH
AND NW COLORADO AS IT EXITS TO THE EAST ACROSS WYOMING. NEXT WEEK
LOOKS TO REMAIN ACTIVE WITH TEMPERATURES REMAINING A FEW DEGREES
NORMAL WITH SHADOWING CLOUD COVER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1131 AM MDT THU MAY 5 2016

SOUTHERLY FLOW WILL BE INCREASING ALOFT AHEAD OF THE NEXT
APPROACHING STORM SYSTEM TO OUR WEST. MID AND HIGH LEVEL MOISTURE
WILL BRING CIGS AOA 120KFT AGL WITH LITTLE CHANCE OF PRECIPITATION
AT AREA TAF SITES THE NEXT 24 HOURS. THEREFORE VFR CONDITIONS ARE
EXPECTED TO PREVAIL. RIDGETOP WINDS MAY SEE GUSTS OVER 45 MPH
OVERNIGHT WITH AREAS OF MECHANICAL TURBULENCE POSSIBLE. LOW
PROBABLILITIES OF LLWS IN THE SOME OF THE VALLEY TERMINALS CAN BE
EXPECTED AND WILL CONTINUE TO BE EVALUATED.

&&

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

$$

SHORT TERM...JAM
LONG TERM...JAM
AVIATION...JAM



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