Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 221109
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
509 AM MDT MON SEP 22 2014

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 506 AM MDT MON SEP 22 2014

TODAY...SHOWERS AND THUNDERSTORMS WILL CONTINUE MOVING ACROSS
MUCH OF THE AREA THIS MORNING. A BRIEF CLEARING BAND WILL MOVE
OVER WESTERN CO EARLY THIS MORNING FOLLOWED BY ANOTHER BAND OF
SHOWERS AND THUNDERSTORMS IN THE LATE MORNING. THIS SECOND BAND IS
ASSOCIATED WITH 2 SHORTWAVE TROUGHS AHEAD OF THE MAIN UPPER
TROUGH...AND A JET STREAK PASSING OVER NE UT AND NW CO. THESE
FEATURES WILL MOVE OVER NW CO BEFORE 10 AM...THEN THE MAIN 500 MB
TROUGH WILL MOVE THROUGH BETWEEN 18Z AND ABOUT 22Z. WITH GRADUALLY
CLEARING SKIES THIS AFTERNOON OVER THE NW PART OF THE CWA...AND
THE UPPER FEATURES MOVING THROUGH...BELIEVE CLEAR AREAS WILL
FORM...BUT RESULTANT SURFACE HEATING WILL ALLOW SHOWERS AND
THUNDERSTORMS TO CONTINUE DEVELOPING THROUGH MID TO LATE
AFTERNOON. THUS HAVE KEPT THE CHC OF RAIN AND CLOUD COVER ON THE
HIGH SIDE FOR MOST OF NORTHWEST AND CENTRAL CO.

OVER SW CO THIS MORNING THE LAST OF MONSOON RELATED MOISTURE WILL
AFFECT THE SAN JUAN MTS AND THE LOWER ELEVATIONS OF THE FOUR
CORNERS UNTIL ABOUT 9 AM MDT...THEN AS WINDS ALOFT SHIFT TO THE
WEST...CLEARER CONDITIONS CURRENTLY OVER SE UTAH WILL MOVE INTO
THE AREA. HAVE CONTINUED THE FLASH FLOOD WATCH...ALONG WITH 2
AREAL FLOOD ADVYS...THROUGH MID MORNING.

TONIGHT AND TUESDAY...THE UPPER LOW WILL BE ARCING FROM THE NORTHERN
ROCKIES TO THE HIGH PLAINS OVERNIGHT. ENERGY ROTATING THROUGH THE
BACKSIDE OF THE LOW WILL BRUSH NORTHERN COLORADO DURING THE LATE
EVENING HOURS. ISOLATED TO SCATTERED SHOWERS WILL PERSIST ACROSS
THIS PORTION OF OUR CWA BEFORE DRIER AND MORE STABLE AIR WORKS IN
THE FLOW VEERING MORE TO THE NORTHWEST. THE NAM WANTS TO KEEP SOME
SHOWERS IN THE SOUTHEAST MOUNTAINS DUE TO MOIST UPGLIDE BUT SEEMS TO
BE THE ODD MAN OUT SO HAVE LOW POPS AND MOSTLY CLEAR SKIES BY
SUNRISE TUESDAY. SUBSIDENT FLOW BEHIND THE WAVE PROMISES DRY AND
MOSTLY SUNNY CONDITIONS FOR TUESDAY WITH A WARMING TREND AS RIDGING
BEGINS TO AMPLIFY NORTHWARD OUT OF THE SOUTHWEST DESERTS. HIGHS
SHOULD PUSH BACK TO OR EXCEED NORMALS.

&&

TUESDAY NIGHT INTO WEDNESDAY...LOW PRESSURE DEEPENS ALONG THE
OFFSHORE WATERS OF THE NORTHWEST CONUS. THE HIGH PRESSURE RIDGE AXIS
EXTENDS ACROSS OUR CWA AND AGAIN EXPECT A QUIET PERIOD WITH MAINLY
CLEAR SKIES. THIS SHOULD BRING A LARGER DIURNAL SWING IN TEMPERATURE
WITH LOWS DROPPING A FEW DEGREES FROM DAYS PAST AND HIGHS ON
WEDNESDAY PUSHING UP A FEW DEGREES OVER TUESDAY.

WEDNESDAY NIGHT...THURSDAY AND FRIDAY SHOULD CONTINUE DRY BUT THE
UPPER RIDGE WILL WEAKEN CONSIDERABLY AS THE PACIFIC TROUGH MOVES
INLAND OVER WA...OR...AND NORTHERN CA. THE MIDRANGE MODELS SHOW
DISAGREEMENT ON HOW QUICKLY THIS STRONG PACIFIC STORM MOVES ACROSS
THE WESTERN U.S. THE GFS CONTINUES TO BE CONSIDERABLY FASTER...AS
IT KEEPS THIS STORM AS AN OPEN WAVE AT 500 MB UNTIL IT REACHES
KBOI ON SAT AT 18Z. THE GFS PUSHES THE SURFACE COLD FRONT THROUGH
THE FORECAST AREA LATE SAT MORNING THROUGH SAT AFTERNOON...WITH A
GOOD LINE OF PRECIP ACCOMPANYING IT. THE ECMWF IS MUCH SLOWER AS
IT DEVELOPS A DEEPER CLOSED LOW ALONG THE NRN CA COAST SAT
MORNING...AND STALLS THE SYSTEM OVER NRN CA THROUGH SAT NIGHT. THE
EC`S COLD FRONT DOESN`T PUSH THROUGH THE FORECAST AREA UNTIL
SUNDAY AFTERNOON... 24 HOURS BEHIND THE GFS PROJECTION.

THIS ALL LEADS TO GREAT UNCERTAINTY IN TIMING THE SYSTEM THROUGH
THE AREA LATE THIS WEEK...THOUGH THROUGH THE DIVERSITY OF
SOLUTIONS THERE IS CONSENSUS THE A SIGNIFICANT PACIFIC STORM WILL
AFFECT THE WESTERN U.S. IN THE SAT THROUGH MONDAY TIME FRAME.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 502 AM MDT MON SEP 22 2014

WIDESPREAD PRECIP ACROSS THE FORECAST AREA WILL BRING RAIN SHOWERS
AND OCCASIONAL THUNDERSTORMS TO ALL THE TAF SITES THIS MORNING.
MVFR CIGS AND VSBY...AND IN SOME CASES...BRIEF IFR CONDITIONS ARE
POSSIBLE IN HEAVY RAIN. MOUNTAINS WILL BE OBSCURED AT TIMES AND
GUSTY AND UNPREDICTABLE OUTFLOW WINDS TO 45 MPH WILL EMANATE FROM
THE STRONGER CELLS.

SKIES WILL GRADUALLY CLEAR AND CONDITIONS IMPROVE THIS AFTERNOON
AND OVERNIGHT.

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FLASH FLOOD WATCH UNTIL 9 AM MDT THIS MORNING FOR COZ019-022-023.

UT...NONE.
&&

$$

SHORT TERM...CC/15
LONG TERM...CC/15
AVIATION...CC



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