Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 091850
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1250 PM MDT WED JUL 9 2014

.UPDATE...
ISSUED AT 1245 PM MDT WED JUL 9 2014

AT NOON CONVECTION HAD BEGUN TO FIRE ON THE MOUNTAINS WITH CELLS
SHOWING VERY LITTLE MOTION. FIRST THUNDERSTORM WAS OVER THE
TAVAPUTS PLATEAU AND LA SALS WITH THE SAN JUANS NOT FAR BEHIND.
THE POTENTIAL FOR LOCALIZED HEAVY RAIN AND FLASH FLOODING CONTINUE
TO DAY DUE TO VERY LIGHT WINDS ALOFT AND DEEP MOISTURE. 0-6KM
WINDS WILL BE 5MPH OR LESS TODAY THROUGH THURSDAY. MOISTURE HAS
INCREASED TO OVER 1 INCH PWAT VALUES IN THE FOUR CORNERS ZONES.
THE LOWER PWAT VALUES IN THE EASTERN PORTION OF THE FORECAST AREA
ARE MORE INDICATIVE OF THE HIGHER TERRAIN THAN AN ABSOLUTE LOWER
MOISTURE VALUE. WHAT SEEMS LACKING TODAY IS GOOD INSTABILITY WITH
CONVECTIVE TEMPERATURE NEAR THE FORECASTED MAX.

NO GOOD DYNAMICAL FOCUS IS SEEN IN SATELLITE OR THE LATEST
MODELS. THERE IS A WEAK H3 POT VORT LOBE LAYING OVER NE UT- NW CO
TONIGHT THAT MAY PROVIDE SOME LIFT ENHANCEMENT OVER THE CENTRAL
CWA. MODEL QPF FIELDS ARE NOT FOCUSED THERE BUT SHOW ISOLATED
CONVECTION MAINLY SOUTH OVERNIGHT. MESOSCALE BOUNDARIES WILL
LIKELY BE THE DRIVERS FOR NOCTURNAL STORMS.

GOOD MOISTURE AND SLOW STORM MOTION REMAIN IN PLACE ON THURSDAY.
THE NAM ESPECIALLY IS INCREASING THE AFTERNOON INSTABILITY
APPARENTLY DUE TO INCREASED LOW-LEVEL MOISTURE. STORMS WILL AGAIN
FIRE OVER THE MOUNTAINS FIRST WITH SECOND OR THIRD GENERATION
STORMS FORMING OVER NEARBY VALLEYS LATER INTO THE AFTERNOON-
EVENING HOURS.

&&

.SHORT TERM...(TODAY THROUGH THURSDAY)
ISSUED AT 406 AM MDT WED JUL 9 2014

FEW LIGHT SHOWERS LINGERING THIS MORNING ALONG LINGERING OUTFLOW
BOUNDARIES FROM CONVECTION LAST EVENING. ACTIVITY HAS BEEN LIGHT
AND GENERALLY CONFINED TO AREAS ALONG THE BOOKCLIFFS AND TAVAPUTS
PLATEAU NORTH OF INTERSTATE 70. EXPECT THESE SHOWERS TO DISSIPATE
AFTER SUNRISE WITH BRIEF SUBSIDENCE SETTLING IN BEFORE WE RE-
CHARGE LATER THIS MORNING AS TEMPS START CLIMBING.

DEEPER MOISTURE WILL BE SHIFTING EAST INTO THE FOUR CORNERS REGION
TODAY AS GREAT BASIN RIDGING GETS NUDGED INTO THE ROCKY MOUNTAINS
SENDING PRECIPITABLE WATER VALUES OVER ONE INCH BY THIS AFTERNOON.
THIS WILL LEAD TO MORE WIDESPREAD CONVECTION ACROSS THE REGION
THIS AFTERNOON...WITH HEAVY RAIN BECOMING MORE AND MORE LIKELY.
HAVE TWEAKED POPS UP A BIT FROM EARLIER FORECAST AND CURRENT FLASH
FLOOD WATCH LOOKS REASONABLE CONSIDERING LITTLE TO NOW STEERING
FLOW...SO STORMS WILL BE SLOW MOVING TO STATIONARY. TEMPS WILL
DOWN A FEW DEGREES WITH INCREASED LOW LEVEL MOISTURE AND CLOUD
COVER IN PLACE.

MADE LITTLE CHANGE TO THE GOING FORECAST FOR TONIGHT AND THURSDAY.
WITH THE UPPER HIGH CENTER SETTLING OVER NM...CLOCKWISE CIRCULATION
AROUND IT WILL KEEP SUBTROPICAL MOISTURE ACROSS THE FORECAST AREA.
NAM/GFS MODELS KEEP PRECIPITABLE WATER VALUES ROUGHLY IN THE 0.75 TO
1.00 INCH RANGE WITH THE HIGHEST VALUES ACROSS SOUTHEAST UT AND
SOUTHWEST CO WHERE THE FLASH FLOOD WATCH CONTINUES. PRECIPITATION
SHOULD SHOW THE TYPICAL DIURNAL DECREASE TONIGHT BEFORE PICKING UP
AGAIN THU WITH DAYTIME HEATING. THE 0-6KM VERTICAL WIND SHEAR
REMAINS WEAK THOUGH...SO THUNDERSTORMS NOT LIKELY TO BE LONG-LIVED.
MAY SEE STORMS EARLY IN THE AFTERNOON TURN TO MORE RAIN SHOWERS
LATER ON AS CLOUD COVER INCREASES.

.LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 406 AM MDT WED JUL 9 2014

MODELS KEEP THE UPPER HIGH CENTER OVER THURSDAY NIGHT AND FRIDAY. AN
EMBEDDED SHORTWAVE TROUGH IS SHOWN CROSSING NORTHEAST UT AND
NORTHWEST CO ON FRIDAY WHICH INCREASES VERTICAL SHEAR A BIT ACROSS
THE NORTH FOR THE POSSIBILITY OF A FEW STRONGER STORMS THERE. GFS
HINTS AT SOME DRIER AIR INTRUDING INTO THE 4 CORNERS FRIDAY...SO
SOMETHING TO WATCH. BUT FOR NOW...WILL KEEP WITH THE FLASH FLOOD
WATCH FOR THE SOUTH ON FRIDAY.

DEEPER MOISTURE PLUME SHIFTS EAST OF THE DIVIDE OVER THE WEEKEND
WITH ONLY ISOLATED CONVECTION EXPECTED OVER OUR HIGHER MOUNTAINS
SATURDAY AND SUNDAY. RIDGE SLIPS BACK TO THE WEST LATE
SUNDAY...WITH ANOTHER SURGE LIFTING NORTH INTO THE FOUR CORNERS
SUNDAY NIGHT AND MONDAY. THIS WILL SIGNAL ANOTHER ROUND OF
AFTERNOON AND EVENING CONVECTION MONDAY AND TUESDAY...EVEN WITH
THE RIDGE BREAKING DOWN TUESDAY AFTERNOON AS ANOTHER WAVE SLIDES
SOUTHEAST ACROSS WYOMING. NO MAJOR SWINGS IN TEMPS EXPECTED
THROUGH THIS PERIOD WITH READINGS RUNNING NEAR SEASONAL NORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY NOON)
ISSUED AT 1245 PM MDT WED JUL 9 2014

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS WILL OCCUR THROUGH
THE PERIOD. THUNDERSTORMS WILL BE LIMITED TO THE HIGHER TERRAIN
UNTIL 21Z TODAY THEN THE THREAT FOR REGIONAL AIRPORTS INCREASE
BETWEEN 00Z AND 06Z THIS EVENING. LOCALLY HEAVY RAIN AND MORE
WIDESPREAD WIND GUSTS OF 30 TO 40 MPH ARE POSSIBLE. TERMINAL
SITES ARE EXPECTED TO REMAIN VFR...ALTHOUGH THEY WILL STAND A 30
PERCENT CHANCE OF BEING IMPACTED BY THUNDERSTORMS THIS AFTERNOON
AND EVENING. ISOLATED CIRCUMNAVIGABLE STORMS ARE EXPECTED TO
CONTINUE OVERNIGHT FAVORING THE SOUTH AND CENTRAL ZONES.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FLASH FLOOD WATCH THROUGH FRIDAY EVENING FOR COZ006-007-009-011-
     017>023.

UT...FLASH FLOOD WATCH THROUGH FRIDAY EVENING FOR UTZ022-027>029.

&&

$$

UPDATE...JOE
SHORT TERM...JDC/JAD
LONG TERM...JAD/JDC
AVIATION...JOE



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