Hail in Colorado, August 18, 2003

WESTERN COLORADO & EASTERN UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
428 AM MDT MON AUG 18 2003

SHORT TERM DISCUSSION (TODAY THROUGH TUESDAY)...
AS MODELS HAVE DEPICTED OVER THE PAST SEVERAL RUNS...LOW PRESSURE
SYSTEM WAS DIVING SOUTH ACROSS WESTERN WY DURING THE NIGHT. 60 KT
JET ROUNDING THE BASE OF THE UPPER LEVEL TROF WITH SFC TROF EXTENDING
ACROSS CENTRAL CO PROVIDED FOCUS FOR LATE NIGHT SHOWERS AND TSTMS
WHICH WERE CONTINUING ACROSS THE CENTRAL MOUNTAINS EARLY THIS
MORNING. ANOTHER AREA OF ACTIVITY ACROSS WAS LOCATED ACROSS THE
SOUTHERN MOUNTAINS WHERE DIFFLUENT FLOW ALOFT COMBINED WITH VORT LOBE
ROTATING AROUND THE BASE OF THE LOW APPARENTLY THE TRIGGER FOR STORMS
ACROSS THE SOUTH. MEANWHILE...APPEARS FROM PRESSURE RISES AND WIND
SHIFT ACROSS THE NORTH THAT COLD FRONT HAS MOVED INTO THE EASTERN
UINTAH BASING AND THE WESTERN PART OF THE NORTHERN PLATEAU OF
COLORADO.

00Z MONDAY ETA MODEL APPEARED TO HAVE EXCELLENT POSITIONING AND
STRENGTH OF THE STORM SYSTEM DIVING SOUTH OVERNIGHT AND WILL BASE
FORECAST ON THIS MODEL. AS THE LOW MOVES TO THE WY/CO/UT TRIPLE
POINT DURING THE DAY DYNAMICS WILL FAVOR THE NORTHERN AND CENTRAL
MOUNTAINS. HOWEVER...FAVORABLE WESTERLY FLOW WORKING ON A MOIST
AIRMASS ACROSS THE SAN JUAN MOUNTAINS AND OTHER FAVORED HIGHER
TERRAIN WILL GENERATE SCATTERED SHOWERS AND THUNDERSTORMS ACROSS
THOSE AREAS AS WELL. IN CONTRAST...SOME DRYING ALREADY ONGOING IN
EASTERN UT SO WILL CUT BACKS ON POPS ACROSS THAT REGION. TEMPS
ACROSS THE NORTH WILL COOL WHILE REMAINING FAIRLY CLOSE TO
YESTERDAYS VALUES ELSEWHERE. STORM DYNAMICS WORKING ON A MOIST AND
UNSTABLE AIRMASS COMBINED WITH THE SURFACE FRONT WILL LIKELY RESULT
IN SOME ISOLATED SEVERE WEATHER DURING THE DAY. HEAVY RAIN IS ALSO A
THREAT...THOUGH SHEAR PROFILE INDICATES STORMS WILL MOVE AT A DECENT
CLIP MINIMIZING THE FLOOD THREAT.

LOW CENTER MOVES EAST OF THE DIVIDE LATE TONIGHT...HOWEVER EXPECT
DIURNAL HEATING COMBINED WITH DYNAMICS TO KEEP SHOWERS AND TSTMS
GOING INTO THE EVENING HOURS. PCPN WILL TAPER OFF IN THE OVERNIGHT AS
AIRMASS COOLS AND DRIER AIR CONTINUES TO WORK ITS WAY INTO THE AREA.
PARTIAL CLEARING ACROSS MUCH OF THE REGION WILL BRING COOLER
TEMPERATURES BEHIND THE COLD FRONT WORKING SOUTHWARD ACROSS THE CWFA.

ETA INDICATES A DRIER/MORE STABLE AIRMASS ON TUESDAY. HOWEVER...
SUSPECT THERE WILL BE ENOUGH RESIDUAL LOW LEVEL MOISTURE TO WARRANT
LOW CHANCE POPS...MAINLY DURING THE AFTERNOON. HIGHS WILL REBOUND
SLIGHTLY AS SHORTWAVE RIDGE BEGINS TO BUILD.   NL

WEDNESDAY THROUGH FRIDAY...
A WEST TO NORTHWEST FLOW WILL DEVELOP BEHIND THE DEPARTING SYSTEM
WITH MID LEVEL DRYING AND SUBSIDENCE. HOWEVER...EXPECT RESIDUAL
MOISTURE AND FAVORABLE FLOW ALONG THE DIVIDE...TO CREATE THE CHANCE
OF SHOWERS AND THUNDERSTORMS.

UPPER LEVEL HIGH PRESSURE WILL REDEVELOP OVER THE DESERT SOUTHWEST
AND FOUR CORNERS AREA BY WEDNESDAY...WITH THE RIDGE AXIS SHIFTING
OVER SOUTHERN COLORADO THURSDAY AND FRIDAY. THE FORECAST AREA WILL
BE BACK TO ABOVE NORMAL TEMPERATURES AND DIURNALLY-DRIVEN SHOWERS
AND THUNDERSTORMS IN THE MOUNTAINS AND HIGH VALLEYS THROUGH FRIDAY
AS MOISTURE RE-CIRCULATES AROUND THE UPPER HIGH.  IN RESPONSE TO THE
POSITION OF THE UPPER HIGH RIDGE AXIS...A WEAK SOUTHWEST FLOW WILL
AFFECT MUCH OF THE AREA THURSDAY AND FRIDAY.  DJN.83

.SUNDAY-MONDAY...HIGH PRESSURE CENTER PUSHES A BIT EAST ON SUNDAY
AND RETURNS OVER COLORADO MONDAY. APPARENT WEATHER REFLECTED
REASONABLY WELL IN EXTENDED WITH TREND FOR SLIGHT REDUCTION IN
DIURNAL PRECIPITATION. WITH RIDGE PROGGED EAST ON SUNDAY DROPPED
TEMPERATURE SLIGHTLY WITH MONDAY MORE IN LINE WITH SATURDAY. DJC

.GJT...NONE.

COZ001>014-017>023-UTZ022>025-027>029-191100-

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1136 AM MDT MON AUG 18 2003

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

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

SCATTERED THUNDERSTORMS WILL OCCUR OVER MUCH OF WESTERN COLORADO
AND EASTERN UTAH THIS AFTERNOON AND EVENING. ISOLATED STORMS COULD
BECOME SEVERE...WITH HAIL UP TO 1 INCH IN DIAMETER...AND STRONG
DAMAGING WINDS. AREAS OF MOST CONCERN WILL BE SOUTHEAST ROUTT...
EAGLE AND PITKIN COUNTY IN NORTH CENTRAL COLORADO. IN ADDITION...
LOCALLY HEAVY RAIN CAN BE EXPECTED...CAUSING SUDDEN WATER RISES IN
NORMALLY DRY CREEKS...SMALL STREAMS AND ARROYOS. STREET FLOODING...
ALONG WITH MUD FLOWS AND ROCK SLIDES WILL BE POSSIBLE...ESPECIALLY
IN STEEP TERRAIN...AND IN AREAS THAT HAVE BEEN BURNED BY RECENT
WILDFIRES.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SATURDAY...

SCATTERED TO ISOLATED THUNDERSTORMS WILL BE POSSIBLE EACH AFTERNOON
AND EVENING...ESPECIALLY OVER THE MOUNTAINS. THE MAIN THREATS FROM
THESE STORMS WILL BE HEAVY RAIN...CLOUD TO GROUND LIGHTNING...WIND
GUSTS TO 40 MPH...AND SMALL HAIL.

.SPOTTER INFORMATION STATEMENT...
WEATHER SPOTTERS SHOULD BE PREPARED FOR POTENTIALLY SEVERE
THUNDERSTORMS THIS AFTERNOON AND EVENING. SPOTTERS ARE ENCOURAGED
TO PHONE IN REPORTS OF STRONG WINDS...HAIL AND HEAVY RAINFALL.

DJN/NL