Flood in Colorado, May 23 to 27, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
937 PM MDT MON MAY 22 2006

...UPDATED AFTER RED FLAG WARNING AND WIND ADVISORIES EXPIRED...

.SHORT TERM (TONIGHT THROUGH WEDNESDAY)...
THUNDERSTORMS TRANSITIONED TO RAIN SHOWERS EARLIER THIS EVENING.
WINDS HAVE DECREASED AS WELL...ALLOWING BOTH THE RED FLAG
WARNING AND WIND ADVISORY TO EXPIRE. NO OTHER CHANGES TO
THIS DISCUSSION.

TONIGHT...MAIN CONCERN THIS EVENING WILL BE THE EFFECTS FROM THE
NEGATIVELY TILTED SHORTWAVE AND ITS ASSOCIATED COLD FRONT.
THUNDERSTORMS DEVELOPED EARLY TODAY AND THEY HAVE BEEN ENHANCING
THE ALREADY STRONG GRADIENT WINDS. WHILE MOST STORMS HAVE NOT
PRODUCED SVR TSTM WINDS...WIND GUSTS HAVE REACHED WIND ADVISORY
CRITERIA AT MANY LOCATIONS. THEREFORE HAVE EXPANDED THE WIND
ADVISORY AREA ACROSS THE ENTIRE FORECAST AREA. HAVE ONLY RECEIVED A
FEW REPORTS OF SMALL HAIL SO FAR...BUT THIS MAY BECOME MORE OF AN
ISSUE EARLY THIS EVENING AS THE FRONT GETS CLOSER. HOWEVER...THE
FRONTAL TIMING WILL BE AFTER MAX HEATING. ALSO THE EXTENSIVE CLOUD
COVER HAS ACTED TO SUPPRESS THINGS A LITTLE. WIND ADVISORY WILL
CONTINUE UNTIL 9 PM. ONCE THE FRONT MOVES EAST...WINDS AND
THUNDERSTORMS WILL DIMINISH. HOWEVER SOME STORMS MAY CONTINUE THROUGH
THE NIGHT...MAINLY OVER THE NORTH AND EAST. TEMPS WILL REMAIN WARM
TONIGHT IN SPITE OF THE COOLER TEMPS ALOFT DUE TO THE PCPN
AND WIDESPREAD CLOUDS.

FIRE WEATHER...WILL KEEP UP THE RED FLAG WARNING FOR WESTERN COLORADO
UNTIL IT IS SCHEDULED TO EXPIRE AT 8 PM...OR UNTIL WE GET MORE
REPORTS OF WETTING RAINS. STORMS ARE MOVING SO FAST THAT LOCATIONS
HAVE HAD A HARD TIME RECEIVING A TENTH OF AN INCH OF RAIN IN SPITE OF
SOME GOOD RAINFALL RATES. SO LOTS OF LIGHTNING WITH LITTLE RAINFALL
WILL CONTINUE FOR AWHILE.

TUESDAY-WEDNESDAY...NAM AND GFS40 IN GOOD LARGE SCALE AGREEMENT.  BY
TUESDAY...THE TROUGH QUICKLY EJECTS OUT OF THE AREA TO THE
NORTHEAST...WITH LINGER MID LEVEL MOISTURE AND LOW THETA-E AIR ALOFT
KEEPING POSTFRONTAL THUNDERSTORMS A POSSIBILITY OVER THE NORTHERN
MOUNTAINS THROUGH EARLY TUESDAY AFTERNOON.  BY TUESDAY EVENING...
SUBSIDENCE ALOFT WILL SQUASH FURTHER CUMULUS DEVELOPMENT AND THE
LOWER LEVELS WILL DRY QUICKLY. TEMPERATURES WILL DROP QUITE A BIT
OVERNIGHT ON TUESDAY AS SKIES WILL BECOME MOSTLY CLEAR AND WINDS
SLACKEN OFF QUITE A BIT.  HIGH PRESSURE ALOFT WILL BE IN FULL EFFECT
BY WEDNESDAY DURING THE DAY...WITH A WARMING TREND TO LAST INTO THE
EXTENDED FORECAST PERIOD.

.LONG TERM (WEDNESDAY NIGHT THROUGH MONDAY NIGHT)...
BOTH GFS40 AND DGEX PRODUCE A LOW AMPLITUDE RIDGE IS EXPECTED
TO STRETCH ACROSS THE WESTERN CONUS...WITH ITS LOW AMPLITUDE NATURE
UNABLE TO TAP INTO ANY BAJA MOISTURE...BUT RATHER THE FLOW ORIGINATES
FROM OVER THE COLD WATERS OF SOUTHWEST COASTAL CALIFORNIA.  LIMITED
MOISTURE AND STRONG SUBSIDENCE WILL RESULT IN A WARMING TREND FROM
BEGINNING PERIOD THROUGH SATURDAY AFTERNOON.  BY SATURDAY
AFTERNOON...A COLD PACIFIC TROUGH IS ANTICIPATED TO IMPINGE ON THE
RIDGE...WITH A TIGHTENING HEIGHT GRADIENT ALOFT AND A TIGHTENING
ZONAL PRESSURE GRADIENT NEAR THE SURFACE.  IN THIS SCENARIO...
SOUTHWESTERLY WINDS WILL BECOME STRONG NEAR THE SURFACE AND WILL
ACCELERATE DRYING OF THE SURFACE ACROSS THE AREA.  THESE GUSTY WINDS
AND THE DRYING POTENTIAL MAY BE CAUSE FOR FIRE WEATHER CONCERNS
DURING THE LATTER HALF OF THE WEEKEND.  DGEX SHOWS THIS NORTHWESTERLY
TROUGH MOVING THROUGH THE NORTHERN HALF OF THE FORECAST AREA
BEGINNING EARLY SUNDAY...WHEREAS THE GFS40 SHOWS THE TROUGH LIFTING
INTO THE NORTHERN ROCKIES INSTEAD.  THERE SEEMS TO BE NO EVIDENCE OF
WHY THE GFS DOES NOT KEEP THIS SYSTEM PROGRESSIVE...AS NO BLOCKING
FROM DOWNSTREAM RIDGE IS APPARENT AT AS OF 12Z MODEL RUN...EVEN
THOUGH LAST DGEX RUN IS FROM 06Z.  PRECIPITATION WITH THE SUNDAY AND
MONDAY TROUGH APPEAR TO BE MOSTLY AT HIGH ELEVATIONS...AS THE COOL
PACIFIC NORTHWEST MOISTURE TAP MAY BE LACK IN DEEP MOISTURE...
HOWEVER THE BAROCLINIC ZONE DEVELOPS NICELY OVER EASTERN UTAH ON
SUNDAY AFTERNOON...AND DECREASES IN INTENSITY BY LATE MONDAY.
53 ZUMPFE

&&

.HYDROLOGY...MANY RIVERS...SMALL CREEKS AND STREAMS WILL CONTINUE
TO SEE RISES...WITH PEAKS OCCURRING THE FIRST HALF OF NEXT WEEK.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
.CO...NONE.
.UT...NONE.

&&

ELH/DEZ/HLO/MM/CJC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
942 PM MDT MON MAY 22 2006

COZ001>014-017>023-UTZ022>025-027>029-231100-
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-
942 PM MDT MON MAY 22 2006

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

.DAY ONE...TONIGHT

LINGER SHOWERS AND A FEW THUNDERSTORMS WILL LAST UNTIL AROUND
MIDNIGHT...THEN DECREASE.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

NO SIGNIFICANT WEATHER IS EXPECTED THROUGH THE THIS PERIOD.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND THIS
EVENING.