Heavy Snow in Colorado, December 15, 2001

SOUTH CENTRAL AND SOUTHEAST COLORADO AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PUEBLO COLORADO
137 PM MST FRI DEC 14 2001

...STORM SYSTEM FOR FRIDAY NIGHT THROUGH SATURDAY NIGHT MAIN
CONCERN...

CURRENTLY...PARTLY TO MOSTLY SUNNY WEATHER ACROSS THE REGION WITH
SOME WINDY CONDITIONS OVER THE HIGHER MOUNTAINS AS SEEN BY MONARCH
PASS AND LA VETA PASS AWOSES.  SNOW COVER OVER LOWER ARKANSAS RIVER
VALLEY DOING A GOOD JOB OF KEEPING TEMPERATURES COOLER AT KLHX AND
KLAA.  WHERE THE ATMOSPHERE IS MIXED TEMPERATURES ON THE PLAINS ARE
IN THE 40S AND 50S.

THE ETA AND AVN ARE FINALLY AGREEING ON A GENERAL SOLUTION FOR
THE SYSTEM.  LOOKING AT THE INITIAL CONDITIONS...THE MAIN JET STREAK
RESPONSIBLE FOR THE EVOLUTION OF THE SYSTEM IS STILL OFFSHORE SO
THERE STILL IS SOME QUESTION AS TO THE EXACT EVOLUTION.  COMPARISON
OF INITIAL CONDITIONS WITH OBSERVATIONS ON AWIPS SUGGESTS THE JET
STREAK MAY BE SOMEWHAT WEAKER THAN INITIALIZED...BUT DATA WE CAN SEE
ARE LIMITED.  I WILL STILL FOLLOW THE EVOLUTION AS SEEN IN THE
MODELS.

FOR TONIGHT...SOUTH TO SOUTHWEST FLOW WILL DEVELOP OVER THE SAN
JUANS TONIGHT.  LOOKING AT THE MODEL SPECIFICS...THE MOISTURE WILL
NOT MAKE IT INTO THE REGION UNTIL AROUND 06Z.  COMPARISON OF
SATELLITE WITH VARIOUS ETA FIELDS SUGGEST SO FAR ETA HAS A DECENT
HANDLE ON THE EVOLUTION.  THE SNOW MODEL ONLY GAVE ABOUT 4-6 INCHES
TONIGHT FOR WOLF CREEK PASS...USING VALUES WHICH MAXIMIZE THE
OROGRAPHICS.  IT LOOKS AS IF THERE WILL BE A QUICK SHOT SO SNOW
TONIGHT BEFORE THE WINDS BECOME MORE WESTERLY BY 15Z.  A PERIOD OF
SYNOPTIC ENHANCEMENT WILL OCCUR AS THE COLD FRONT MOVES ACROSS LATER
IN THE NIGHT.  AS A RESULT...I WILL ISSUE A SNOW AND BLOWING
ADVISORY FOR ZONE 61 AS 4 TO 8 INCHES ARE A REASONABLY GOOD BET.  IN
ADDITIONS...WINDS MAY BECOME GUSTY ALONG WITH THE FRONTAL PASSAGE.

ON SATURDAY...THE MAIN FOCUS SHIFTS TO THE EAST.  SOUTHWEST FLOW
ALOFT WILL BRING A PERIOD OF SNOW TO THE SANGRES IN THE MORNING WITH
A COUPLE OF INCHES POSSIBLE.  DURING THE AFTERNOON...A CYCLONE
DEVELOPS OVER THE EASTERN PLAINS AND DRIFTS SOUTH.  A WEAK SURGE
APPEARS WITH THE FLOW EVENING BECOMING NORTH NORTHEAST AT 700MB FOR
A PERIOD IN THE EVENING.  ONE MAIN CONCERN WILL BE THE CREST OF
MONUMENT HILL DURING THE AFTERNOON.  PERIOD OF SIGNIFICANT SNOW WILL
BE FAIRLY SHORT...BUT IT WILL BE COMBINED WITH GUSTY WINDS.  THERE
COULD BE A PERIOD OF A FEW HOURS WITH SNOW AND BLOWING SNOW OVER
MONUMENT HILL.  CURRENTLY I BELIEVE THE AMOUNTS WILL STAY BELOW
ADVISORY CRITERIA.  SINCE THIS IS THE SECOND PERIOD...MIDNIGHT SHIFT
CAN DECIDE IF CONDITIONS WILL BE NASTY ENOUGH FOR AN ADVISORY.   FOR
NOW...I WILL TRY TO HIT THE ZONE HARD SATURDAY AFTERNOON.  IN THE
EVENING...THE WET MOUNTAINS AND EASTERN SLOPES OF THE SANGRES SET UP
FOR A QUICK SHOT OF SNOW.  I WILL UP POPS TO LIKELY FOR THESE ZONES
ON SATURDAY NIGHT.  IT IS TOO EARLY TO TELL HOW MUCH SNOW WILL
OCCUR...BUT ADVISORY AMOUNTS ARE NOT OUT OF THE QUESTION.

BY SUNDAY...THE TROUGH MOVES EAST WITH NORTHWEST FLOW OVER THE
AREA.  WITH COLD NW FLOW...I WILL LEAVE SOME SNOW SHOWERS IN ZONES
58 AND 59.

IN THE EXTENDED...LATEST EXTENDED DISCUSSION OUT OF HPC INDICATES
THAT MRF MAY BE HAVING SIGNIFICANT PROBLEMS WITH DEVELOPMENT OF
BLOCKING HIGH OVER CANADA...AND AS A RESULT THE PATTERN IN THE
LOWER 48  LATEST MRF PUTS A SIGNIFICANT TROUGH OVER ARIZONA ON
FRIDAY.  MY CONFIDENCE IN SPECIFICS ON DAY 7 IS TYPICALLY NOT
HIGH...BUT IT IS EVEN LOWER WHEN THERE IS A TRANSITION IN THE
FLOW.  FOR NOW...I WILL BUY INTO THE MRF AND PUT IN SLIGHT CHANCE
SNOW PLAINS AND MOUNTAINS.

THANKS GJT AND BOU FOR COORD.

WOLYN

.PUB...SNOW AND BLOWING SNOW ADVISORY MIDNIGHT TO NOON SAT ZONE 61
       (EASTERN SAN JUANS).