Severe Thunderstorm Warning 30, NWS Grand Junction, CO

WESTERN COLORADO & EASTERN UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1256 PM MDT FRI AUG 18 2000

AS WEAK VORT MAX EXISTS CWA TO NORTHEAST ALONG WITH CLDS AND SHWRS
FROM OLD FRONTAL ZONE...MID AND UPPER LEVEL DRYING AND CLEARER SKIES
ACROSS UT TO SPREAD OVER NWRN CO. FIRST TSTMS OF THE DAY OVER UTS
AND COS TAVAPUTS PLATEAY MAY BE DUE TO AFFECTS OF EITHER R/R QUAD OF
SMALL JET MAX PUSHING IN BEHIND THE VORT CENTER NE OF EEO OR
BEGINNING OF 500 MB COOLING AND RESULTING DESTABILIZATION...OR BOTH.
THIS LINEAR CU DVLPMT SHOULD CONTINUE TRACKING EAST AND BE OUT OF THE
CWA BEFORE MAX HEATING. MODELS PROJECTED NVA OVER THE AREA IN THE
SHORT TERM AND THIS SEEMS TO BE TRUE WITH CONVECTION SUPPRESSED AND
CLDS DSPTG OVER REST OF UTAH. BUT...CLEARING SKIES WITH MORE SUN AND
AN L.I. REMAINING BETTER THAN -2...PLUS ABUNDANT LOW LEVEL MOISTURE
AVAILABLE...POINTS TO CONVECTION OVERPOWERING THE SUBSIDENCE THIS
AFTERNOON AND CONTINUING THIS EVENING.

SATURDAY DOES LOOK DRIER IN THE MODELS ABOVE 500 MB...BUT BLV
MOISTURE BLO THIS AND UNSTABLE AFTERNOON CONDITIONS WILL ALLOW TSTM
AREAL COVERAGE TO ONLY DROP ONE KNOTCH CENTRAL AND SOUTHERN AREAS...
WITH ACTIVITY DECREASING MORE OVER EXTREME NE UT AND NW CO. THE
CLEARER SKIES AND SLIGHTLY DRIER CONDITIONS SHOULD ALLOW MAX TEMPS TO
BUMP UP A BIT. FCST SOUNDINGS SHOW GOOD INSTABILITY SAT AND SUN
AFTERNOON WITH A STABLE LAYER ABOVE 500 MB...AND A LITTLE MORE THAN
HALF THE CURRENT PW.  MODELS DISSAGREE ON HOW STRONGLY AND HOW SOON
THE BETTER MONSOON WILL RETURN...SO WILL KEEP A CHC IN THE EXTENDED.
CUOCO

.GJT...NONE.

COZ001>014-017>023-UTZ022>025-027>029-190200-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1205 PM MDT FRI AUG 18 2000

...SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING...SOME WITH
   SMALL HAIL AND LOCALLY HEAVY RAIN...

SHOWERS AND THUNDERSTORMS WILL DEVELOP THIS AFTERNOON AND INCREASE IN
COVERAGE THROUGH THE EVENING ACROSS EASTERN UTAH AND WESTERN
COLORADO. THESE THUNDERSTORMS WILL PRODUCE HEAVY RAIN SHOWERS...SMALL
HAIL...FREQUENT LIGHTNING...AND WIND GUSTS TO 35 MPH. AT NOON MDT...
SATELLITE IMAGERY AND DOPPLER RADAR SHOWED THUNDERSTORMS DEVELOPING
OVER THE SAN JUAN MOUNTAINS AND BOOK CLIFFS OF WESTERN COLORADO...AS
WELL AS THE TAVAPUTS PLATEAU OF EASTERN UTAH. THE CURRENT WEATHER
PATTERN SUGGESTS THAT THE HEAVIEST RAINFALL WILL BE SOUTH OF THE I-70
CORRIDOR...INCLUDING THE GRAND MESA. RAINFALL RATES WILL WILL BE
GREATER THAN AN INCH PER HOUR AT TIMES. LOCALIZED FLOODING OF SMALL
STREAMS AND CREEKS...AS WELL AS MINOR FLOODING AND DEBRIS SPILLS
ACROSS ROADWAYS IS POSSIBLE.

THE SHOWERS AND THUNDERSTORMS WILL DIMINISH LATE TONIGHT.

IF A THUNDERSTORM APPROACHES YOUR LOCATION...PLEASE SEEK SHELTER.
AVOID LOW LYING AREAS AND WATERWAYS IF HEAVY RAINS DEVELOP. DO NOT
ATTEMPT TO CROSS FLOODED ROADS IN A VEHICLE OR ON FOOT. AS LITTLE AS
6 INCHES OF RUNNING WATER CAN WASH YOUR VEHICLE OFF THE ROADWAY.

TGJT