Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 141000
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
400 AM MDT SUN SEP 14 2014

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 400 AM MDT SUN SEP 14 2014

LOW PRESSURE OFF THE WEST COAST COMBINED WITH A TRANSIENT LOW
PRESSURE TROUGH SWEEPING ACROSS THE NORTHERN PLAINS HAS SHIFTED
HIGH PRESSURE OVER THE SOUTHWEST SLIGHTLY TO THE EAST. IN
RESPONSE...MID-LEVEL MOISTURE HAS ADVECTED OVER THE AREA. A WEAK
DISTURBANCE COMBINED WITH DAYTIME HEATING WILL BRING ABOUT
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS OVER THE HIGHER
TERRAIN THIS AFTERNOON WITH THE SAN JUAN MOUNTAINS FAVORED.
MOISTURE IS HIGH-BASED SO EXPECT THE GREATEST THREAT FROM THESE
STORMS WILL BE LIGHTNING AND GUSTY OUTFLOW WINDS. WARM AIR
ADVECTION NOT ADEQUATELY CAPTURED IN BIAS-CORRECTED MODEL OUTPUT
SO BOOSTED TEMPERATURES TOWARD GUIDANCE VALUES.

DISORGANIZED MID LEVEL DISTURBANCE PASSING THROUGH THE WESTERN
STATES UPPER RIDGE WITH SCATTERED MID AND HI LEVEL CLOUDS TONIGHT
LIKELY TO BE OF LITTLE CONSEQUENCE FOR OUR CWA. AS UPPER RIDGE
BUILDS AND AIRMASS CONTINUES TO WARM...SHOULD EXPERIENCE MAX
TEMPERATURES ON MONDAY A FEW DEGREES HIGHER THAN TODAY. AND EXPECT
CONVECTION FROM DAYTIME HEATING TO PRODUCE A FEW HIGH-BASED SHOWERS
AND ISOLATED THUNDERSTORMS OVER MOUNTAINS.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 400 AM MDT SUN SEP 14 2014

MONDAY NIGHT THROUGH TUESDAY NIGHT...
LITTLE CHANGE IN RELATIVELY DRY PATTERN AS THE HIGH AMPLITUDE
UPPER RIDGE AXIS MOVES SLOWLY EASTWARD AND OVER OUR CWA TUESDAY
NIGHT. EXPECT WARMING TREND TO CONTINUE TUESDAY AS H7 TEMPERATURES
SHOULD BE ABOUT ANOTHER 2C HIGHER THAN MONDAY...AND MAX TEMPS
TUESDAY SHOULD BE ANOTHER FEW DEGREES WARMER THAN MONDAY. AGAIN
EXPECT A FEW LATE DAY HIGH-BASED SHOWERS AND ISOLATED
THUNDERSTORMS OVER THE MOUNTAINS ON TUESDAY DUE TO DAYTIME
HEATING.

WEDNESDAY THROUGH SATURDAY...
RIDGE HOLDS OVER THE REGION WEDNESDAY AS HURRICANE ODILE MOVES
SLOWLY NORTHWESTWARD OFF THE BAJA COAST. AS A RESULT...EXPECT
ANOTHER ROUND OF DIURNAL SHOWERS AND THUNDERSTORMS. TEMPERATURES
SHOULD REMAIN WARMER THAN NORMAL BELOW THE RIDGE AND BOOSTED HIGHS
ACCORDINGLY.

ECMWF AND GFS CONTINUED TO STRUGGLE WITH THE LATTER PART OF THE
WEEK. LATEST ECMWF CARVES OUT A CLOSED LOW OFF OF KSFO ON THURSDAY
WITH ODILE STALLED JUST OFF THE NORTHERN BAJA PENINSULA.
CONSEQUENTLY...MOISTURE IS A BIT LATE TO ARRIVE OVER THE FORECAST
AREA. HOWEVER...ENERGY IN THE NORTHERN BRANCH SENDS A SHORTWAVE
TROUGH ACROSS THE GREAT BASIN WHILE MOISTURE DEEPENS AHEAD OF
IT...THOUGH WHETHER REMNANTS OF ODILE BECOME ENTRAINED IS UNCLEAR.
AS A RESULT...BEST CHANCES FOR PRECIPITATION AND HEAVY RAIN COMES
THURSDAY NIGHT AND FRIDAY FOLLOWED BY DRYING ON SATURDAY.

IN CONTRAST...THE GFS40 EJECTS A MORE COHERENT SHORTWAVE AHEAD OF
THE MAIN TROUGH IN CONJUNCTION WITH A SURGE OF SUBTROPICAL
MOISTURE. THIS SOLUTION GENERATES SIGNIFICANTLY MORE WIDESPREAD
AND SIZABLE QPF THURSDAY AFTERNOON. THE MAIN TROUGH PUSHES ACROSS
THE GREAT BASIN THURSDAY NIGHT AND FRIDAY FOR MORE WIDESPREAD
SHOWER AND THUNDERSTORM ACTIVITY AHEAD OF DRYING SATURDAY. LIKE
THE ECMWF...A BIT UNCLEAR AS TO HOW MUCH OF ODILE/S MOISTURE
REACHES THE AREA. GFS PW VALUES PEAK RIGHT AROUND 1 INCH...SO DOES
NOT APPEAR THAT THE REGION WILL SEE MUCH OF THE HURRICANE/S
MOISTURE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 400 AM MDT SUN SEP 14 2014

VFR CONDITIONS THROUGH THE PERIOD. WINDS WILL FOLLOW NORMAL THE
DIURNAL CYCLE. ISOLATED SHRA OR TSRA ARE POSSIBLE OVER THE
MOUNTAINS THIS AFTERNOON...ESPECIALLY SOUTH. THE ONLY IMPACT MAY
BE GUSTY ERRATIC OUTFLOW WINDS AT KDRO...KTEX...KMTJ...KEGE...AND
KASE AFTER 21Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...NL/JRP
LONG TERM...JRP/NL
AVIATION...TGJT



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