Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 211137
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
537 AM MDT THU MAY 21 2015

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 355 AM MDT THU MAY 21 2015

ANOTHER SURGE OF MOISTURE DRIVES NORTHWARD ACROSS THE FORECAST
AREA TODAY...WITH PRECIPITABLE WATER VALUES CLIMBING BACK ABOVE A
HALF INCH. NOSE OF DEEPER SURGE ARRIVES OVER THE SAN JUANS BY
MIDDAY AND LIFTS INTO THE NORTHERN ZONES BY MID AFTERNOON. SFC
HEATING AND LIFTING ALONG OUR MOUNTAINOUS BARRIERS WILL FIRE
SHOWERS AND THUNDERSTORMS OVER THE HIGHER TERRAIN BY EARLY
AFTERNOON WITH STORMS EXPECTED TO MOVE OVER THE VALLEYS AFTER 3
PM. GUSTY OUTFLOW WINDS TO 40 MPH AND HEAVY RAIN WILL BE THE MAIN
FOCUS WITH THIS ACTIVITY WITH MARGINAL DIRECTIONAL SHEAR
ANTICIPATED IN DEEP SOUTHERLY FLOW. IN THE HIGH COUNTRY FOR THE
SAN JUANS AND CENTRAL HIGH MOUNTAINS...ANOTHER ROUND OF SNOW IS
EXPECTED. SNOW ACCUMULATIONS ABOVE 9000 FEET APPEAR SUFFICIENT FOR
A WINTER WEATHER ADVISORY.

DRIER AIR STARTS TO NUDGE INTO THE WESTERN ZONES LATE IN THE DAY
THEN SHOVES THE DEEPER MOISTURE PLUME BACK TO THE EAST AS ANOTHER
PACIFIC STORM MOVES ONSHORE. THIS WILL SHUT THINGS DOWN AFTER
MIDNIGHT TONIGHT WITH A BREAK EXPECTED THROUGH AT LEAST MIDDAY
FRIDAY BEFORE WE START TO SEE THE INFLUENCES OF THE NEXT UPPER
LOW. THIS SYSTEM IS EXPECTED TO BE IN THE VICINITY OF LAS VEGAS BY
LATE FRIDAY AFTERNOON. NAM TAPPING SOME DRIER AIR TO THE SOUTH AND
KEEPS CONVECTION IN CHECK FOR MUCH OF THE DAY...WHILE THE GFS
REMAINS WETTER AND IS THE PREFERRED SOLUTION BASED ON RECENT
PERFORMANCE. WILL KEEP AT LEAST SCT MOUNTAIN CONVECTION ROLLING AS
FORCING ALONG PEAKS AND INFLUENCE OF DIFLUENCE ALOFT HELP TRIGGER
CONVECTIVE SHOWERS BY LATE IN THE DAY. TEMPERATURES WILL BE
RUNNING NEAR SEASONAL NORMS TODAY AND AGAIN ON FRIDAY.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 355 AM MDT THU MAY 21 2015

CLOSED LOW MOVES TOWARD UTAH ON FRIDAY NIGHT AND WILL BE
POSITIONED DIRECTLY OVER THE FORECAST AREA ON SATURDAY. THIS WILL
RESULT IN SOMEWHAT UNSEASONABLE COOL CONDITIONS FOR MEMORIAL DAY
WEEKEND WITH SHOWERS/THUNDER WITH MORE NUMEROUS SHOWERS OVER THE
HIGH TERRAIN. THE UPPER LOW EJECTS NORTHEAST ON SUNDAY...BUT THE
AIR MASS WILL STAY CONDITIONALLY UNSTABLE INTO MEMORIAL DAY AS
WEAK CIRCULATION CONTINUE TO ROTATE THROUGH THE BROAD DISORGANIZED
CENTRAL CONUS TROUGH. WITH 700 MB TEMPS AT OR BELOW 0C...MORE HIGH
COUNTRY SNOW IS EXPECTED BOTH FRIDAY AND SATURDAY NIGHTS.

TUESDAY AND WEDNESDAY...ANOTHER TROUGH FORMS ALONG THE WEST COAST
AND THIS BRINGS DRIER SOUTHWEST FLOW INTO THE FOUR CORNERS REGION.
DIURNALLY DRIVEN SHOWERS/STORM WILL EXIST EACH DAY OVER THE WRN
COLORADO HIGH COUNTRY...ALTHOUGH DESERT VALLEYS ACROSS ERN UTAH
INTO EXTREME WRN COLORADO MAY STAY DRY WITH REBOUNDING TEMPS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 537 AM MDT THU MAY 21 2015

SHOWERS WITH EMBEDDED STORMS WILL BE DEVELOPING OVER THE SRN
MOUNTAINS AFTER 17Z AND SPREADING NORTH...REACHING THE I70
CORRIDOR BETWEEN 21Z-24Z THIS AFTERNOON. CIGS WILL LOWER TO BELOW
ILS BREAKPOINTS FROM PASSING SHOWERS/STORMS AT MOUNTAIN TAF SITES.
SHOWERS WILL BE PERSISENT OVERNIGHT...ESPECIALLY SW COLORADO AND
THE WEST CENTRAL MOUNTAINS WITH THE SNOW LEVEL LOWERING TO 9K
FEET. MOUNTAINS WILL BE PARTIALLY OBSCURED AT TIMES.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM MDT
     FRIDAY FOR COZ010-012-018-019.

UT...NONE.
&&

$$

SHORT TERM...JDC
LONG TERM...PF
AVIATION...PF


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