Damaging Wind in Colorado, May 20, 2001

WESTERN COLORADO & EASTERN UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
205 PM MDT SUN MAY 20 2001

STRONG COLD FRONT WILL DROP SOUTH OUT OF WYOMING AND ACROSS EASTERN
UTAH AND WESTERN COLORADO EARLY THIS EVENING.  FRONT WENT THROUGH
RIVERTON WYOMING EARLIER THIS AFTERNOON WITH TEMPERATURES DROPPING
FROM 55F TO 34F IN JUST 2 HOURS...WITH LIGHT SNOW AND WIND GUSTS
TO 44KTS ALSO ACCOMPANYING THE FRONT.  THIS WILL BE THE TREND THIS
EVENING FOR OUR FORECAST AREA AS THE FRONT MOVES THROUGH BETWEEN 22Z
AND 06Z TONIGHT. STRONG DYNAMICS ASSOCIATED WITH VIGOROUS SHORTWAVE
AND LEFT EXIT REGION OF UPPER JET WILL ENHANCE PRECIP THREAT OVER THE
NRN MTNS THIS EVENING. EXPECTING SCATTERED SNOW SHOWERS TO DEVELOP
OVER THE NRN AND CENTRAL MTNS SHORTLY AFTER FRONTAL PASSAGE WITH
SOME LIGHT ACCUMULATIONS OVER THE HIGHER PASSES. HOWEVER...FAST
MOVEMENT OF SYSTEM...LACK OF DEEP MOISTURE AND LOW LEVEL FLOW
BECOMING MORE NORTHERLY WILL PREVENT SIGNIFICANT ACCUMULATIONS. A
SLIGHT CHANCE OF SHOWERS ALSO IN STORE OVER THE EASTERN UINTA
MOUNTAINS IN NORTHEAST UTAH WHERE NORTHERLY LOW LEVEL FLOW MORE
FAVORABLE FOR LOCAL OROGRAPHICS.

REMAINDER OF THE FORECAST AREA WILL SEE AN INCREASE IN CLOUD COVER
ALONG WITH GUSTY WIND AND COLDER TEMPS TONIGHT. INCREASE IN CLOUD
COVER WILL BE SHORT-LIVED OUTSIDE OF OROGRAPHIC REGIONS...AND WINDS
WILL DECOUPLE OVER THE NORTHERN HALF OF THE AREA THIS EVENING...
SETTING UP GOOD RADIATIONAL COOLING LATER TONIGHT. FREEZING TEMPS
WILL BE LIKELY OVER MUCH OF THE NW PLATEAU...ALONG WITH THE HIGHER
MOUNTAIN VALLEYS OF WEST CENTRAL COLORADO. WITH AVERAGE LAST FREEZE
DATES STILL IN EARLY JUNE FOR THESE AREAS...WILL NOT ISSUE A FREEZE
ADVISORY TONIGHT. HOWEVER...WILL SEND OUT ANOTHER SPS ADVISING OF THE
COLDER TEMPERATURES OVERNIGHT TONIGHT.

BY MONDAY...ATMOSPHERE DRIES SIGNIFICANTLY...WITH A COOL STABLE
AIRMASS IN PLACE.  WESTERN U.S. RIDGE THEN STRENGTHENS OVER THE
FORECAST AREA TUE WITH DRY AND WARMER CONDITIONS EXPECTED. COLTON

EXTENDED...A STRONG UPPER LEVEL RIDGE OF HIGH PRESSURE WILL RESULT
IN DRY AND WARM CONDITIONS ACROSS THE CWFA WED THROUGH FRI. A RETURN
FLOW WILL GRADUALLY INCREASE MOISTURE...MAINLY OVER THE SOUTHERN
ZONES THU/FRI...POSING THE THREAT OF ISOLD MTN CONVECTION AS EARLY AS
THU AFTN. SOME CHANGES IN STORE BY NEXT WEEKEND AS A PACIFIC TROUGH
APPROACHES CALIFORNIA ON SAT. THIS WILL DEVELOP A SOUTHERLY FLOW...
ALLOWING ADDITIONAL MOISTURE TO SPREAD OVERTOP THE REGION SAT/SUN AND
INCREASING THE THREAT OF MAINLY MTN CONVECTION. SLIGHTLY COOLER
CONDITIONS ARE EXPECTED SAT/SUN FROM THE RAPID MIDWEEK WARM-UP.
DJN.83

.GJT...NONE.

COZ001>014-017>023-UTZ022>025-027>029-210500-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
305 PM MDT SUN MAY 20 2001

...COOLER WEATHER FOR THE REGION TONIGHT AND MONDAY...

A STRONG COLD FRONT WILL MOVE ACROSS WESTERN COLORADO AND EASTERN
UTAH TONIGHT. CLOUDS AND SCATTERED SHOWERS WILL RESULT ALONG AND
AHEAD OF THE FRONT...MAINLY CONFINED TO THE MOUNTAINS ALONG THE
CONTINENTAL DIVIDE. THE AIRMASS WILL BE COLD ENOUGH TO SUPPORT A
BRIEF SHOT OF SNOW IN THE NORTH CENTRAL MOUNTAINS OF COLORADO THIS
EVENING...WITH 1 TO 3 INCHES POSSIBLE OVER THE PASSES. IN ADDITION...
A HARD FREEZE WILL OCCUR FOR PORTIONS OF THE NORTHWEST PLATEAU AND
OTHER HIGHER VALLEYS IN WESTERN COLORADO...AS MONDAY MORNING LOW
TEMPERATURES DROP INTO THE 20S.

WINDY CONDITIONS WILL EXIST THROUGHOUT THIS EVENING. EXPECT AN
ABRUPT WIND SHIFT TO THE NORTH AND VERY GUSTY WIND TO OCCUR WITH THE
FRONTAL PASSAGE. THERE IS THE POTENTIAL FOR WIND GUSTS TO 40 MPH
OVER RIDGETOPS AND EXPOSED HIGHER TERRAIN THIS EVENING.

PEOPLE TRAVELING THROUGH THE MOUNTAINS TONIGHT...ESPECIALLY IN HIGH
PROFILE VEHICLES...SHOULD BE AWARE OF RAPIDLY CHANGING WEATHER
CONDITIONS. CURRENT F?ORECASTS AND STATEMENTS ARE ALSO AVAILABLE ON
THE GRAND JUNCTION NATIONAL WEATHER SERVICE WEBSITE AT:
http://www.crh.noaa.gov/gjt