Flash Flood in Utah, September 9, 2005

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
359 AM MDT FRI SEP 9 2005

.SHORT TERM (TODAY THROUGH SATURDAY NIGHT)...
A VIGOROUS UPPER LOW CURRENTLY OVER CENTRAL CALIFORNIA IS SET TO
MOVE ACROSS THE GREAT BASIN AS AN OPEN WAVE TODAY. THE SYSTEM WILL
THEN LIFT NORTHEAST ACROSS EASTERN UTAH AND WESTERN COLORADO TONIGHT
AS ANOTHER UPPER LOW OVER BRITISH COLUMBIA MOVES SOUTH OVER THE
PACIFIC NORTHWEST. SOUTHWEST FLOW WILL STRENGTHEN OVER THE AREA
TODAY WITH A STRONG JET SEGMENT SLIDING OVERHEAD LATE TODAY
AND TONIGHT. WITH THE MOISTURE ALREADY IN PLACE, OROGRAPHIC AND
DYNAMIC FORCING WILL BE ON THE INCREASE TODAY AND WILL RESULT IN
WIDESPREAD SHOWERS AND THUNDERSTORMS. CLOUDS WILL LIKELY HOLD
DOWN THE INSTABILITY BUT INCREASED SHEAR AND DYNAMIC FORCING
LOOK SUFFICIENT ENOUGH TO SUPPORT A FEW SEVERE STORMS THIS
AFTERNOON AND EVENING. STORMS WILL MOVE ALONG AT A PRETTY GOOD PACE
TODAY BUT STILL EXPECT SOME AREAS OF HEAVY RAIN DUE TO TRAINING
CELLS AND PERSISTENT PRECIPITATION IN TERRAIN FAVORING SOUTHWEST
FLOW. ALTHOUGH WINDS WILL BE PICKING UP TODAY HUMIDITIES SHOULD
REMAIN ABOVE CRITICAL LEVELS WITH RESPECT TO FIRE WEATHER.

DRIER AIR WILL ADVECT OVER THE AREA SATURDAY BUT THERE WILL BE ENOUGH
LOW LEVEL MOISTURE FOR A CONTINUED CHANCE OF ISOLATED TO SCATTERED
SHOWERS OR THUNDERSTORMS. A COLD FRONT WILL APPROACH THE AREA AND
STALL ACROSS NORTHEAST UTAH. SOUTHWEST FLOW AHEAD OF THE FRONT WILL
YIELD SOME BREEZY CONDITIONS SATURDAY. HUMIDITIES SHOULD TREND DOWN
A LITTLE SATURDAY BUT STILL REMAIN ABOVE CRITICAL THRESHOLDS.
LINDQUIST

.LONG TERM (SUNDAY THROUGH FRIDAY)...COMMUNICATION PROBLEM BETWEEN
NWSTG AND NCF HAS RESULTED IN NO 00Z MODEL DATA GETTING INTO AWIPS.
AS A RESULT...WILL BASE LATEST FORECAST OFF 18Z/08 GFS AND DGEX...
AND 12Z/08 ECMWF.

SUNDAY AND MONDAY...TROUGH OVER THE PACIFIC NORTHWEST WILL GRADUALLY
SLIDE EAST ACROSS THE NORTHERN ROCKIES BUT SHOULD REMAIN NORTH OF
THE FORECAST AREA. A MODERATE SOUTHWEST FLOW WILL PLACE THE AREA
WITHIN THE DRY SLOT REGION. BREEZY TO LOCALLY WINDY CONDITIONS WILL
DEVELOP SUNDAY AS H7 FLOW INCREASES 20-30KTS BY 00Z/MON. COLD FRONT
WILL ENTER NORTHWEST UTAH SUNDAY AFTERNOON...THEN SLIDE EAST
AFFECTING NORTHEAST UTAH/NORTHWEST COLORADO SUNDAY NIGHT INTO MONDAY.
COOLER TEMPS CAN BE EXPECTED MONDAY...MAINLY NORTH OF I-70. WITH
THE EXCEPTION OF THE MOUNTAINS OF NORTHEAST UTAH AND NORTHWEST
COLORADO...DRY CONDITIONS WILL EXIST WITH NO CHANCE OF PRECIP.

TUESDAY THROUGH FRIDAY...A WEAK RIDGE OF HIGH PRESSURE WILL AFFECT
THE AREA AS AN UPPER LEVEL LOW APPROACHES THE CALIFORNIA COAST BY
WEDNESDAY. THIS LOW IS EXPECTED TO EVENTUALLY MOVE EAST AND OPEN UP
ACROSS THE GREAT BASIN THURSDAY. DRY CONDITIONS WILL PREVAIL UNTIL
THURSDAY. MOISTURE APPEARS LIMITED AT THIS TIME...SO WILL MAINTAIN
SLIGHT CHANCE PRECIP. TEMPS WILL BE SEASONAL WITH NO SIGNIFICANT
WARMING OR COOLING SEEN THROUGH THE PERIOD. NADLER.83

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

&&

TAL/DJN

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
214 PM MDT FRI SEP 9 2005

COZ001>014-017>023-UTZ022>025-027>029-101300-
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-
214 PM MDT FRI SEP 9 2005

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

.DAY ONE...THIS AFTERNOON AND TONIGHT...

THUNDERSTORMS WILL INCREASE THROUGHOUT WESTERN COLORADO AND EASTERN
AFTERNOON OVER THE REMAINDER OF THE AFTERNOON. AS THESE STORMS MOVE
QUICKLY NORTHEASTWARD ACROSS THE AREA...HEAVY RAIN...HAIL...
DANGEROUS LIGHTNING...AND WIND GUSTS UP TO 45 MPH CAN BE EXPECTED.
HOWEVER...THERE IS A POSSIBILITY THAT SOME OF THESE STORMS COULD
BECOME SEVERE. KEEP AN EYE ON THE SKY...ESPECIALLY IF YOU ARE
OUTDOORS...AND BE ALERT TO ANY WARNINGS THAT MAY BE ISSUED.

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

ISOLATED THUNDERSTORMS ARE EXPECTED SATURDAY AND SUNDAY...AND AGAIN
ON WEDNESDAY AND THURSDAY...MAINLY OVER THE MOUNTAINS. LOCALLY HEAVY
RAIN...SMALL HAIL...GUSTY WINDS AND CLOUD TO GROUND LIGHTNING MAY
OCCUR WITH THE STORMS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.