Flash Flood Warning 9, NWS Grand Junction, CO

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
336 PM MDT THU OCT 5 2006

DELETED OUTDATED TEXT FROM EARLIER DISCUSSION

.SHORT-TERM (TONIGHT THROUGH SATURDAY)...
A WIDESPREAD SIGNIFICANT PRECIPITATION EVENT EXPECTED FOR EASTERN
UTAH AND WESTERN COLORADO THROUGH SATURDAY. DEEP SUBTROPICAL
MOISTURE CONTINUES TO STREAM ACROSS THE AREA AHEAD OF A STRONG UPPER
LEVEL LOW SITUATED ALONG THE CALIFORNIA COAST. A STRONG UPPER JET
AND DIFLUENCE ALOFT OVER RELATIVELY WARM AND MOIST SOUTHERLY FLOW IS
RESULTING IN NUMEROUS SHOWERS AND THUNDERSTORMS OVER UTAH AND MUCH
OF WESTERN COLORADO THIS AFTERNOON. THE CALIFORNIA LOW WILL MOVE
SOUTHEAST ALONG THE COAST TONIGHT AND THEN MOVE INLAND AND LIFT
NORTHEAST ACROSS THE GREAT BASIN FRIDAY AND FRIDAY NIGHT WHILE
ANOTHER UPPER LOW FORMS OVER CENTRAL CALIFORNIA.

SYNOPTIC SCALE FORCING WILL INCREASE OVER THE FORECAST AREA TONIGHT
AND FRIDAY AS THE LOW SHIFTS INLAND. HEAVY RAINFALL AND POTENTIAL FOR
FLOODING IS THE MAIN CONCERN WITH THIS SYSTEM. FLOW ALOFT WILL MOVE
STORMS ALONG FAIRLY QUICKLY BUT ABUNDANT MOISTURE ALONG WITH SOME
TRAINING STORMS AND BANDS OF PERSISTENT MODERATE TO HEAVY RAIN WILL
LIKELY YIELD AT LEAST SOME LOCALIZED FLOODING BEFORE THIS SYSTEM
MOVES OUT. EAST CENTRAL AND SOUTHEAST UTAH INITIALLY IN THE GREATEST
THREAT AREA FOR FLASH FLOODING RAINS THROUGH TONIGHT. THE FLASH FLOOD
THREAT WILL INCREASE ACROSS WESTERN COLORADO FRIDAY AND HAVE ISSUED
FLASH FLOOD HIGHLITES FOR MUCH OF WEST CENTRAL AND SOUTHWEST
COLORADO. OTHER CONCERN IS FOR SEVERE THUNDERSTORM POTENTIAL FRIDAY.
WIND SHEAR AND DEEP MOISTURE HAS POTENTIAL TO SUPPORT SOME ORGANIZED
SEVERE CONVECTION PRIMARILY FOR EASTERN UTAH FRIDAY. BOTTOM LINE...
FRIDAY COULD BE A VERY BUSY DAY ACROSS THE FORECAST AREA WITH
FLOODING AND SOME SEVERE STORMS.

PRECIPITATION SHOULD BE ON THE WANE LATE FRIDAY NIGHT THROUGH
SATURDAY AS THE UPPER LOW OPENS UP AND ACCELERATES ACROSS EASTERN
IDAHO AND NORTHWEST WYOMING. A COLD FRONT WILL PUSH INTO THE AREA
FRIDAY NIGHT AND BECOME NEARLY STATIONARY AND WEAKEN OVER THE
FORECAST AREA ON SATURDAY WHICH WILL HELP FOCUS LINGERING
PRECIPITATION ACROSS THE CENTRAL AND SOUTHERN MOUNTAINS. WIDESPREAD
CLOUDS AND PRECIPITATION AHEAD OF THE FRONT WILL MAKE ANY COOL DOWN
BEHIND THE FRONT FAIRLY MINOR.

SNOW LEVELS TO REMAIN HIGH IN SOUTHERLY FLOW AHEAD OF THE SYSTEM.
EXPECT SOME 2-4 ACCUMULATIONS ABOVE THE 11-12K FOOT LEVELS TONIGHT
AND AGAIN FRIDAY. POTENTIAL FOR SOME SOME 3-5 INCH AMOUNTS ABOVE
9500 FEET FRIDAY NIGHT INTO EARLY SATURDAY MORNING. LINDQUIST

.LONG-TERM (SATURDAY NIGHT THROUGH THURSDAY)...
FOR SATURDAY NIGHT...WILL SEE A BRIEF BREAK BETWEEN THE AREA OF
PRECIPITATION WE ARE NOW JUST STARTING TO EXPERIENCE AND THE NEXT
INFLUX OF MOISTURE WE ARE EXPECTING FOR SUNDAY. MODELS REMAIN IN GOOD
AGREEMENT WITH STREAMING DEEP LAYER MOISTURE INTO THE FORECAST AREA
SUNDAY AS THE UPPER LOW REMAINS PARKED JUST OFF THE CALIFORNIA COAST.
ALTHOUGH IT IS LOOKING FAIRLY WET SUNDAY AND SUNDAY NIGHT...WE WILL
NOT SEE PRECIP TOTALS EVEN NEAR THOSE WE ARE EXPECTING OVER THE
NEXT FEW DAYS. SOME MOISTURE WILL THEN REMAIN OVER THE AREA MONDAY
THROUGH WEDNESDAY AS WE ARE POSITIONED BETWEEN THE UPPER LOW TO OUR
WEST AND NORTHERN STREAM TROUGHING TO OUR EAST. SHOWER AND
THUNDERSTORM ACTIVITY WILL CONTINUE THROUGH THIS PERIOD...WITH
DIURNAL TRENDS BECOMING MORE DOMINANT THAN SYNOPTIC FORCING.

NORTHERN STREAM TO REMAIN QUITE ACTIVE OVER CANADA SUNDAY THROUGH
TUESDAY WITH EACH SUCCESSIVE SHORTWAVE DIGGING FURTHER SOUTH AND WEST
INTO THE NORTHERN PLAINS. GFS/EURO/UKMET ALL DROP A PIECE OF ENERGY
FROM A POLAR VORTEX NORTH OF 70N LATITUDE INTO THE NORTHERN STREAM
AND CARVE A MASSIVE UPPER LOW THAT COVERS MUCH OF CENTRAL CANADA AND
THE NORTHERN PLAINS BY WEDNESDAY NIGHT. PAST FEW GFS RUNS HAVE THEN
DROPPED A STRONG SHORTWAVE DOWN THE BACKSIDE OF THIS SYSTEM AND INTO
COLORADO. THIS WOULD PUSH A VERY POTENT COLD FRONT THROUGH AT LEAST
THE NORTHERN PORTION OF THE FORECAST AREA IF IT DOES OCCUR. EURO
MODEL DOES NOT SHOW THIS SHORTWAVE...AND SINCE IT IS STILL FAIRLY FAR
OUT IN THE FORECAST...WILL NOT JUMP ON THIS SOLUTION FOR NOW.
ALTHOUGH...GIVEN SUCH A HIGHLY AMPLIFIED PATTERN...THIS SCENARIO
WOULD NOT BE UNLIKELY. THIS SHORTWAVE DROPPING DOWN THE BACKSIDE OF
THE MAIN LOW WOULD ALSO SERVE TO SHEAR OUT THE MUCH SMALLER CUT-OFF
LOW THAT WILL CONTINUE TO MEANDER NEAR SOUTHERN CALIFORNIA. WENT
ABOVE MEX GUIDANCE FOR THE DAY 6 AND 7 FORECAST GIVEN SUCH AN
ANOMALOUS PATTERN. HOWEVER...IF CONFIDENCE WITH THE SHORTWAVE
INCREASES...WE WILL HAVE TO DROP TEMPS CONSIDERABLY.
&&

.GJT WATCHES/WARNINGS/ADVISORIES...
.CO...FLASH FLOOD WATCH FRIDAY AND FRIDAY EVENING FOR MUCH OF WEST
      CENTRAL AND SOUTHWEST COLORADO...ZONES 03...06...07...09...
      11...17...18...19...20...21 AND 22.
.UT...FLASH FLOOD WATCH TODAY THROUGH FRIDAY AFTERNOON FOR EAST
      CENTRAL AND SOUTHEAST UTAH...ZONES 22...25...27...28 AND 29.

TAL/HLO

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
407 PM MDT THU OCT 5 2006

UPDATED TO EXTEND AND EXPAND FLASH FLOOD WATCH

COZ001>014-017>023-UTZ022>025-027>029-061200-
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-
407 PM MDT THU OCT 5 2006

...FLASH FLOOD WATCH FOR EASTERN CENTRAL AND SOUTHEAST UTAH TODAY
THROUGH FRIDAY AFTERNOON...

.DAY ONE...TONIGHT

SHOWERS AND THUNDERSTORMS WILL INCREASE AND BECOME MORE NUMEROUS
THIS EVENING. STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE OVER
EASTERN UTAH. A FLASH FLOOD WATCH IS IN EFFECT FOR EASTERN UTAH
UNTIL MIDNIGHT FRIDAY. THUNDERSTORMS OVER EASTERN UTAH THIS EVENING
WILL BE CAPABLE OF PRODUCING RAINFALL OF ONE HALF TO ONE INCH
OVER A SHORT PERIOD OF TIME. THESE STORMS WILL ALSO HAVE THE
POTENTIAL TO GENERATE STRONG WIND GUSTS TO 40 MPH AND SMALL HAIL.
ISOLATED SEVERE THUNDERSTORMS COULD ALSO DEVELOP OVER UTAH THIS
EVENING. SEVERE THUNDERSTORMS HAVE THE POTENTIAL TO PRODUCE
WIND GUSTS IN EXCESS OF 55 MPH AND LARGE HAIL. SHOWERS AND
THUNDERSTORMS...SOME CONTAINING HEAVY RAINFALL...WILL OCCUR
OVERNIGHT.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A FLASH FLOOD WATCH IS IN EFFECT FOR EASTERN UTAH UNTIL MIDNIGHT ON
FRIDAY. A FLASH FLOOD WATCH HAS ALSO BEEN ISSUED FOR WESTERN
COLORADO...EFFECTIVE FROM 600 AM FRIDAY MORNING UNTIL MIDNIGHT FRIDAY
NIGHT. WIDESPREAD SHOWERS AND THUNDERSTORMS...SOME PRODUCING HEAVY
RAINFALL...WILL OCCUR ACROSS MUCH OF EASTERN UTAH AND WESTERN
COLORADO ON FRIDAY. THE GREATEST THREAT FOR FLASH FLOODING EXISTS
FROM EASTERN UTAH WESTWARD INTO COLORADO...EXTENDING ROUGHLY TO A
LINE FROM DURANGO TO MONTROSE TO MEEKER. RAINFALL AMOUNTS OF BETWEEN
ONE AND TWO INCHES ARE EXPECTED TO OCCUR OVER A WIDESPREAD AREA.
LOCALLY HIGHER AMOUNTS UP TO THREE INCHES ARE ANTICIPATED.

THUNDERSTORMS ARE LIKELY TO OCCUR ON FRIDAY. THESE STORMS WILL
PRODUCE VERY HEAVY RAINFALL...HAIL AND WIND GUSTS UP TO 40 MPH.
ISOLATED SEVERE THUNDERSTORMS WILL PRODUCE LARGE HAIL...DAMAGING
DOWNBURST WINDS AND EVEN THE POSSIBILITY OF A TORNADO. SNOW LEVELS
WILL BE ABOVE 10000 FEET WITH SNOW ACCUMULATIONS LIMITED TO THE
MOUNTAIN PASSES.

PRECIPITATION WILL TAPER OFF OVER EASTERN UTAH FRIDAY EVENING...THEN
OVER WESTERN COLORADO BY SATURDAY MORNING. RIVERS AND STREAMS OVER
EASTERN UTAH AND WESTERN COLORADO ARE LIKELY TO SEE RISES OF ONE TO
TWO FEET BY SATURDAY.

BY SUNDAY...SLIGHTLY DRIER CONDITIONS WILL RESIDE OVER THE REGION...
WITH SCATTERED SHOWERS AND THUNDERSTORMS OCCURRING...MAINLY OVER THE
MOUNTAINS. THIS ACTIVITY WILL CONTINUE DURING THE AFTERNOON AND
EVENING HOURS ON MONDAY AND TUESDAY AS WELL. GUSTY WINDS TO 40 MPH...
LOCALLY HEAVY RAIN AND SMALL HAIL WILL ACCOMPANY THE STRONGER
THUNDERSTORMS. SNOW LEVELS WILL GENERALLY BE AT OR ABOVE 10000 FEET
DURING THE DAY THEN LOWER TO NEAR 9000 FEET OVERNIGHT.

.SPOTTER INFORMATION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED FRIDAY. SPOTTERS ARE ENCOURAGED TO
REPORT SEVERE WEATHER...FLOODING...AND SIGNIFICANT RAINFALL AMOUNTS
TONIGHT AND FRIDAY.