Damaging Winds in Colorado, July 2, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
333 AM MDT FRI JUL 2 2010

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT...
MONSOON MOISTURE WILL CONTINUE ROLLING THROUGH THE AREA TODAY THROUGH
SATURDAY.  THE SOUTHWEST FLOW BETWEEN HIGH PRESSURE TO THE EAST THE
LOW PRESSURE TO THE WEST WILL KEEP THE MONSOONAL PLUME OVER EASTERN
AZ...EASTERN UT...AND MUCH OF CO. A SIGNIFICANT CHANNELED VORT MAX
WILL ALONG THE EAST SIDE OF THE GREAT BASIN TROUGH WILL CONTINUE TO
FOCUS THUNDERSTORM DEVELOPMENT OVER NORTHEAST UTAH AND WESTERN MOFFAT
COUNTY CO THIS MORNING INTO THIS AFTERNOON. MUCH DRIER AIR RESIDES
OVER WESTERN UT AND NEVADA...BUT IT DOES NOT LOOK LIKE IT WILL MAKE
IT INTO OUR AREA UNTIL SAT NIGHT AND SUNDAY.

SHORT-RANGE MODELS DO NOT MOVE THE MOISTURE TONIGHT...SO BELIEVE
SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THE EVENING AND
SLOWLY TAPER OFF OVERNIGHT.

SATURDAY SHOULD NOT SEE MUCH CHANGE. THE NAM12 SHOWS A BRIEF DRY
PERIOD SAT MORNING...BUT THE MONSOON IS PROJECTED TO SHOW ITSELF
AGAIN BY EARLY AFTERNOON AND CONVECTION SPROUTS OVER WESTERN CO.
ABOUT THE ONLY DIFFERENCE IS A SHIFT OF THE PLUME OUT OF EASTERN
UTAH...WITH THE MAIN FOCUS FOR CONVECTION OVER WEST-CENTRAL AND
SOUTHWEST CO.  RIGHT NOW IT LOOKS LIKE THE DRY SLOT WILL FINALLY
SPREAD ACROSS THE AREA AFTER MIDNIGHT SAT NIGHT. THEN ANOTHER TROUGH
APPROACHES FROM THE NORTHWEST WHICH WILL COMPLICATE SUNDAYS
FORECAST.

.LONG TERM...SUNDAY THROUGH THURSDAY...

...MOSTLY DRY 4TH OF JULY WITH ISOLATED MTN THUNDERSTORMS POSSIBLE...

FORECAST CHALLENGE THROUGH THE LONG TERM IS THE TIMING OF THE
WESTERN TROUGH PASSAGE AS WELL AS HOW LONG MOISTURE WILL HANG
AROUND. OVER THE PAST FEW DAYS THE MODELS HAVE BEEN TRENDING TOWARD
A SLOWER TROUGH PASSAGE AND TONIGHT'S RUNS ARE NO EXCEPTION. MODELS
ARE NOW INDICATING TROUGH PASSAGE LATE SUN AND EVEN AS LATE AS EARLY
MON IN THE ECMWF. IN ADDITION...MOISTURE DOES NOT CLEAR OUT QUITE AS
QUICKLY AS THE PREVIOUS THINKING. THE GFS STILL BRINGS THE DRY AIR
IN ON SUN KEEPING THE CWA MOSTLY DRY...WHEREAS THE NAM AND ECMWF
KEEP MOISTURE AND LIGHT QPF AMOUNTS LINGERING AROUND THROUGH SUN
EVENING. PW VALUES IN THE NAM/SREF SUN AFTERNOON ARE STILL UP AROUND
0.40 TO 0.60 INCHES...ESPECIALLY ACROSS THE N. ALSO...THE TROUGH
PUSHES A FRONTAL BOUNDARY ACROSS THE N BY SUN EVENING THAT WILL WORK
WITH ANY AVAILABLE MOISTURE TO SQUEEZE OUT AN ISOLATED THUNDERSTORM.
WITH THE RECENT TREND OF THE MODELS SLOWING DOWN...FEEL THAT IT MAY
CONTINUE AND THE GFS IS TO QUICK TO DRY THINGS OUT. SO HAVE ADDED
ISOLATED THUNDERSTORMS MAINLY OVER THE MTNS TO THE 4TH OF JULY
FORECAST AND THIS WILL HAVE TO BE WATCHED FOR ANY FURTHER SLOWING.

BELIEVE THE DRY AIRMASS WILL FINALLY OVERSPREADS THE AREA BY LATE
SUN NIGHT WITH DRY WEATHER PREVAILING THROUGH THE BEGINNING OF NEXT
WEEK. FORECAST AREA REMAINS ON THE WESTERN EDGE OF BROAD HIGH
PRESSURE ENCOMPASSING MUCH OF THE SRN U.S. THROUGH MUCH OF NEXT WEEK
WITH AN INDICATION THAT SOME MOISTURE WILL RETURN SOMETIME IN THE
WED/THURS TIME FRAME.

DAYTIME TEMPS FOR THE 4TH OF JULY HOLIDAY WILL BE A FEW DEGREES
COOLER WITH TROUGH PASSAGE BUT EXPECT A WARMING TREND EARLY NEXT
WEEK AS HIGH PRESSURE BUILDS.

&&

.AVIATION...
SCATTERED AFTERNOON AND EVENING SHOWERS/THUNDERSTORMS WILL RESULT IN
SOME MOUNTAIN OBSCURATION AND LOCAL MVFR CONDITIONS THROUGH THE
REMAINDER OF THE WEEK.  OCCASIONAL HEAVY SHOWERS AND GUSTY WINDS
ARE POSSIBLE WITH ANY OF THESE STORMS.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

SHORT TERM.....CJC
LONG TERM......MCS
AVIATION.......TGJT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
335 AM MDT FRI JUL 2 2010

COZ001>014-017>023-UTZ022>025-027>029-031030-
ANIMAS RIVER BASIN-ARCHES/GRAND FLAT-CANYONLANDS/NATURAL BRIDGES-
CENTRAL COLORADO RIVER BASIN-
CENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASIN-
CENTRAL YAMPA RIVER BASIN-DEBEQUE TO SILT CORRIDOR-
EASTERN UINTA BASIN-EASTERN UINTA MOUNTAINS-
ELKHEAD AND PARK MOUNTAINS-FLAT TOPS-
FOUR CORNERS/UPPER DOLORES RIVER-
GORE AND ELK MOUNTAINS/CENTRAL MOUNTAINS-GRAND AND BATTLEMENT MESAS-
GRAND VALLEY-LA SAL AND ABAJO MOUNTAINS-LOWER YAMPA RIVER BASIN-
NORTHWEST SAN JUAN MOUNTAINS-PARADOX VALLEY/LOWER DOLORES RIVER-
ROAN AND TAVAPUTS PLATEAUS-SAN JUAN RIVER BASIN-SOUTHEAST UTAH-
SOUTHWEST SAN JUAN MOUNTAINS-TAVAPUTS PLATEAU-
UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE-UPPER GUNNISON RIVER VALLEY-
UPPER YAMPA RIVER BASIN-WEST ELK AND SAWATCH MOUNTAINS-
335 AM MDT FRI JUL 2 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN UTAH AND WESTERN
COLORADO.

.DAY ONE...TODAY AND TONIGHT

MORE SHOWERS AND THUNDERSTORMS ARE EXPECTED TODAY AND TONIGHT AS A
PLUME OF MONSOON MOISTURE CONTINUES TO AFFECT THE AREA. THESE STORMS
WILL LAST WELL INTO THE EVENING. A FEW STORMS WILL PRODUCE WIND GUSTS
TO ABOUT 45 MPH AND LOCALLY HEAVY RAIN.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

ISOLATED TO SCATTERED LATE DAY SHOWERS AND THUNDERSTORMS ARE
POSSIBLE...FAVORING THE MOUNTAINS OF SOUTHWEST COLORADO. LATE-
DAY STORMS ON SATURDAY THREATEN TO PRODUCE LOCALLY HEAVY SHOWERS AND
STRONG ERRATIC OUTFLOW WINDS. CHANCES FOR THUNDERSTORMS AND SHOWERS
WILL DIMINISH LATE SUNDAY.

.SPOTTER INFORMATION STATEMENT

SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY OR TONIGHT.

CJC