Severe Thunderstorm Warning 20, NWS Grand Junction, CO

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
838 AM MDT FRI SEP 3 2004

...UPDATED TO ADD WIND ADVISORY FOR ALL OF WRN CO AND ERN UT TODAY...

COMBINATION OF STRONG SFC PRES GRAD...JET ALOFT AND DEEP MIXING...AND
ADDED CONVECTIVE OUTFLOW GUSTS FROM ANY TSTMS PROMPTED THE ISSUANCE OF
WIND ADVISORY FROM 1000-2200 MDT TODAY FOR ENTIRE FORECAST AREA. THE
WINDS WILL LIKELY BE STRONGEST DURING THE MID TO LATE AFTERNOON
PERIOD.

.SHORT TERM (TODAY THROUGH SATURDAY)...
A LONGWAVE TROUGH CONTINUES TO SHARPEN OVER THE WESTERN STATES AS JET
ENERGY ALONG THE PAC NW COAST DIGS DOWN THE BACK SIDE OF THE TROUGH.
STRONG SOUTHWEST FLOW IS OVER EASTERN UTAH AND WESTERN COLORADO
AHEAD OF THE SYSTEM WITH KGJX RADAR SHOWING 35KTS JUST OFF THE
SURFACE. A COLD FRONT HAS BECOME STATIONARY ACROSS NORTHEAST UTAH
AND NORTHWEST COLORADO. AN UPPER JET STREAK EXTENDING FROM
SOUTHERN NEVADA INTO WESTERN COLORADO APPEARS TO BE AIDING IN
THE DEVELOPMENT OF ISOLATED SHOWERS AND THUNDERSTORMS ACROSS
THE FORECAST AREA. PROBABLY ONLY SPRINKLES REACHING THE GROUND
THOUGH WITH CLOUD BASES 10K FEET OR BETTER OFF THE DECK.

SOME NOTABLE CHANGES MADE TO THE FORECAST WITH THE MODELS IN
AGREEMENT THAT THE SYSTEM WILL BE SLOWER TO MOVE THROUGH THE AREA.
THE COLD FRONT WILL RETREAT NORTH TODAY WITH STRONG SOUTHWEST FLOW
BLANKETING THE ENTIRE FORECAST AREA THIS AFTERNOON. MAIN CONCERN
AGAIN TODAY IS FIRE WEATHER. STRONG AND WARM SOUTHWEST PRE-
FRONTAL FLOW WILL KEEP RELATIVE HUMIDITY LEVELS CRITICALLY LOW ACROSS
THE CENTRAL AND SOUTHERN PORTIONS OF THE AREA. STRONG GRADIENT FLOW
AND THUNDERSTORMS POTENTIAL ALSO RAISES FIRE WEATHER CONCERNS.
GRADIENT FLOW AND DEEP MIXING THIS AFTERNOON WILL PRODUCE STRONG WIND
GUSTS ACROSS THE AREA. RAOBS AND MODEL CROSS SECTIONS ALSO INDICATE
THAT MOISTURE WILL BE CONFINED TO THE MID LEVELS THIS AFTERNOON WHILE
DEEP FORCING DEVELOPS. THIS WILL RESULT IN HIGH BASED OR DRY
THUNDERSTORMS ACROSS THE AREA WHICH WILL ADD TO THE STRONG WIND
GUST POTENTIAL. A NUMBER PARAMETERS COMING TOGETHER FOR A CRITICAL
FIRE WEATHER DAY AND WILL HOIST A RED FLAG WARNING FOR THE ENTIRE
FORECAST AREA.

THE COLD FRONT WILL SLOWLY MOVE SOUTH ACROSS THE FORECAST AREA
TONIGHT. MODELS CUT OFF A LOW IN THE BASE OF THE TROUGH WHICH WILL
ONLY SLOW THE PROGRESS OF THE FRONT AND IT NOW LOOKS LIKE SATURDAY
MORNING BEFORE THE FRONT MOVES COMPLETELY THROUGH WESTERN COLORADO.
SCATTERED TO LIKELY POPS TONIGHT WITH STRONG DYNAMICS OVER THE AREA
AND MOISTENING LOW LEVELS. MUCH COOLER SATURDAY WITH SHOWERS AND
THUNDERSTORMS A GOOD BET IN UNSTABLE POST FRONTAL AIRMASS AND THE MID
LEVEL COLD POOL TO MOVE OVER THE AREA. LINDQUIST

.LONG TERM (SATURDAY NIGHT THROUGH THURSDAY)...
H5 TROUGH AXIS WILL SLIDE ACROSS WESTERN COLORADO SATURDAY EVENING
ENDING PRECIP FROM WEST TO EAST. LOOK FOR VERY COOL TEMPERATURES
OVERNIGHT AS SKIES CLEAR AND WINDS DIMINISH. RAPID SURFACE COOLING
AND DRYING ALOFT COULD CREATE THE POTENTIAL FOR AREAS OF DENSE FOG
EARLY SUNDAY MORNING IN THE HIGH VALLEYS OF NORTHERN/CENTRAL
COLORADO...DEPENDING ON THE AMOUNT OF LINGERING BOUNDARY LAYER
MOISTURE.

SUNDAY WILL BE DRY AND WARMER AS A WEST-NORTHWEST FLOW DEVELOPS.
STABLE CONDITIONS AND LIMITED MOISTURE SHOULD SQUASH CONVECTION
DURING THE AFTERNOON SO HAVE KEPT DRY FORECAST. TEMPERATURES WILL
REBOUND A BIT ACROSS EASTERN UTAH/SW COLORADO BUT STILL REMAIN BELOW
NORMAL FOR ONE MORE DAY.

MONDAY THROUGH THURSDAY...UPPER LEVEL RIDGE WILL STRETCH FROM OLD
MEXICO INTO CENTRAL TEXAS BY TUESDAY WITH A SOUTHERLY FLOW DEVELOPING
AROUND THE FOUR CORNERS. MONDAY WILL BE ANOTHER DRY DAY WITH TEMPS
WARMING ABOUT 5-10F DEGREES.  TUESDAY...THE 02/18Z DGEX SHOWS AN
INCREASE IN MOISTURE ACROSS SE UTAH/SW COLORADO WITH A WEAK SHORTWAVE
LIFTING FROM ARIZONA. WILL MENTION SLT CHANCE PRECIP ACROSS SOUTHERN
ZONES LATE TUESDAY...AND EXPAND THIS AREA NORTH WEDNESDAY. UPPER HIGH
CENTER REMAINS OVER THE SOUTHERN PLAINS WED/THU WITH TRAPPED MID LVL
MOISTURE GENERATING AFTERNOON/EVENING THUNDERSTORMS ACROSS MAINLY THE
HIGHER TERRAIN. TEMPS WILL HOVER AROUND NORMAL WED/THU.  DJN.83

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
.CO...RED FLAG WARNING FROM 1200 MDT TO 2000 MDT TODAY FOR
      FIRE WEATHER ZONES 201...203...205 AND 207.
      WIND ADVISORY FROM 1000 MDT TO 2200 MDT TODAY FOR ALL WRN CO
      ZONES.
.UT...RED FLAG WARNING FROM 1200 MDT TO 2000 MDT TODAY FOR FIRE
      WEATHER ZONES 442...443...444...445...446...447...448 AND
      449.
      WIND ADVISORY FROM 1000 MDT TO 2200 MDT TODAY FOR ALL ERN UT
      ZONES.

TAL/DJN/JAD

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
829 AM MDT FRI SEP 3 2004

UPDATED TO INCLUDE WIND ADVISORY

COZ001>005-013-UTZ023>025-041200-
LOWER YAMPA RIVER BASIN-CENTRAL YAMPA RIVER BASIN-
ROAN AND TAVAPUTS PLATEAUS-ELKHEAD AND PARK MOUNTAINS-
UPPER YAMPA RIVER BASIN-FLAT TOPS-EASTERN UINTA MOUNTAINS-
EASTERN UINTA BASIN-TAVAPUTS PLATEAU-
829 AM MDT FRI SEP 3 2004

...RED FLAG WARNING THIS AFTERNOON AND EARLY EVENING...
...WIND ADVISORY TODAY AND TONIGHT...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST UTAH AND
NORTHWEST COLORADO.

.DAY ONE...TODAY AND TONIGHT...

THE COMBINATION OF SCATTERED DRY THUNDERSTORMS...GUSTY SOUTHWEST
WINDS...AND DRY FUELS WILL PRODUCE CRITICAL FIRE WEATHER CONDITIONS
THIS AFTERNOON AND EARLY EVENING. HIGH RATES OF SPREAD MAY OCCUR WITH
ANY ONGOING FIRES...AND NEW FIRE STARTS ARE LIKELY DUE TO LIGHTNING.
STRONG AND ERRATIC OUTFLOW WINDS AND CLOUD TO GROUND LIGHTNING WILL
BE THE MAIN THREAT WITH THE THUNDERSTORMS. WARM SOUTHWEST WINDS OF
20 TO 35 MPH CAN ALSO BE EXPECTED...WITH OCCASIONAL GUSTS UP TO 50
MPH IN VALLEY LOCATIONS. GUSTS OF 60 TO 70 MPH ARE POSSIBLE IN
ELEVATIONS ABOVE 7500 FEET.

SCATTERED THUNDERSTORMS WILL OCCUR TONIGHT...MAINLY BEFORE MIDNIGHT.
CLOUD TO GROUND LIGHTNING...STRONG GUSTY WINDS...AND BRIEF MODERATE
RAIN ARE POSSIBLE WITH THE STORMS. LIGHT SNOW ACCUMULATIONS ARE
POSSIBLE TONIGHT ACROSS THE HIGH ELEVATIONS...MAINLY ABOVE 10000
FEET.

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

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY AND THURSDAY.
GUSTY WINDS...SMALL HAIL...AND CLOUD TO GROUND LIGHTNING WILL BE
POSSIBLE WITH THE STORMS. LIGHT SNOW ACCUMULATIONS MAY OCCUR
SATURDAY AND SATURDAY NIGHT ABOVE 9000 FEET.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.

COZ006>012-014-017>023-UTZ022-027>029-041200-
GRAND VALLEY-DEBEQUE TO SILT CORRIDOR-CENTRAL COLORADO RIVER BASIN-
GRAND AND BATTLEMENT MESAS-GORE AND ELK MOUNTAINS/CENTRAL MOUNTAINS-
CENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASIN-
WEST ELK AND SAWATCH MOUNTAINS-UPPER GUNNISON RIVER VALLEY-
UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE-NORTHWEST SAN JUAN MOUNTAINS-
SOUTHWEST SAN JUAN MOUNTAINS-PARADOX VALLEY/LOWER DOLORES RIVER-
FOUR CORNERS/UPPER DOLORES RIVER-ANIMAS RIVER BASIN-
SAN JUAN RIVER BASIN-ARCHES/GRAND FLAT-LA SAL AND ABAJO MOUNTAINS-
CANYONLANDS/NATURAL BRIDGES-SOUTHEAST UTAH-
829 AM MDT FRI SEP 3 2004

...RED FLAG WARNING THIS AFTERNOON AND EARLY EVENING...
...WIND ADVISORY TODAY AND TONIGHT...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHEAST UTAH AND
WEST-CENTRAL AND SOUTHWEST COLORADO...OR AREAS ALONG AND SOUTH OF
INTERSTATE 70.

.DAY ONE...TODAY AND TONIGHT...

THE COMBINATION OF GUSTY SOUTHWEST WINDS...LOW HUMIDITY...DRY
FUELS...AND ISOLATED DRY THUNDERSTORMS WILL PRODUCE CRITICAL
FIRE WEATHER CONDITIONS THIS AFTERNOON AND EARLY EVENING. A FEW NEW
FIRE STARTS ARE LIKELY DUE TO LIGHTNING. EXTREME FIRE BEHAVIOR...AND
HIGH RATES OF SPREAD MAY OCCUR WITH ANY ONGOING FIRES OR NEW FIRE
STARTS. GUSTY AND ERRATIC OUTFLOW WINDS...AND CLOUD TO GROUND
LIGHTNING WILL BE THE MAIN THREAT FROM THE STORMS. WARM SOUTHWEST
WINDS OF 20 TO 35 MPH CAN ALSO BE EXPECTED...WITH OCCASIONAL GUSTS UP
TO 50 MPH IN VALLEY LOCATIONS. GUSTS OF 60 TO 70 MPH ARE POSSIBLE IN
ELEVATIONS ABOVE 7500 FEET.

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

THERE IS A CHANCE OF THUNDERSTORMS SATURDAY AND THURSDAY.
GUSTY WINDS...SMALL HAIL...AND CLOUD TO GROUND LIGHTNING WILL BE
POSSIBLE WITH THE STORMS. LIGHT SNOW ACCUMULATIONS MAY OCCUR
SATURDAY AND SATURDAY NIGHT ABOVE 9500 FEET.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.

BA