Avalanche in Colorado, February 24, 2002

WESTERN COLORADO & EASTERN UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
230 PM MST SUN FEB 24 2002

S/W TROUGH MOVED ACROSS NRN CO THIS MORNING WITH GENERAL SWATH OF 2
TO 4 INCHES SNOW. MOISTURE WAS LIMITED AS SUB-TROPICAL JET SHEARED
THE DEEPER MOISTURE AHEAD OF THE TROUGH. LITTLE BIT OF SUN THIS
MORNING ENOUGH TO DESTABILIZE AIRMASS AS CU FIELD HAS FORMED. PIECE
OF ENERGY ROLLING ACROSS WRN COLORADO THIS AFTN IN WRLY FLOW. KGJX
RADAR SHOWING AREA OF PRECIP DEVELOPING TO NW.

FORECAST...WILL BE WATCHING STRONG S/W ENERGY DIVING FROM ID/MT
TONIGHT ACCOMPANIED BY MUCH COLDER TEMPERATURES FROM CANADA. S/W
WILL BE MOVING INTO NW COLORADO AFTER 06Z/TONIGHT WITH GOOD UPR JET
SUPPORT. ACROSS THE NRN MTNS (COZN 4)...DEEP INSTABILITY (H7-5 LAPSE
RATES..8.0C/KM) COUPLED WITH OROGRAPHIC FLOW (28030KT)...WILL CREATE
POTENTIAL FOR SIGNIFICANT SNOW EVENT. UPR JET DYNAMICS WEAKEN AND
SLIDE SOUTH MONDAY...DECREASING THE HEAVY SNOW THREAT. WILL ISSUE
WINTER STORM WARNING FOR COZN 4 TONIGHT THROUGH MIDDAY MONDAY FOR
HEAVY SNOW AND STRONG WINDS. FOR FLATTOPS AND CENTRAL MTNS...WILL
ISSUE SNOW AND BLO SNOW ADV TONIGHT AND MONDAY...WITH PERIOD OF
HEAVIEST SNOW OCCURRING BETWEEN 09Z-18Z/MON WITH STRONG NW FLOW AND
BEST MID LVL DYNAMICS. HOWEVER...BELIEVE ATTM SNOW AMOUNTS WILL
REMAIN BELOW WARNING (12 INCHES) LEVEL. NW SAN JUAN MTNS WILL SEE
ANOTHER PERIOD OF SHSN LATE TONIGHT THOUGH MONDAY WITHIN NW FLOW
THOUGH GENERAL AMOUNTS WILL BE LESS THAN 5 INCHES.

ELSEWHERE...GUSTY WEST SFC WINDS WILL PREVAIL AHEAD OF CANADIAN
FRONT (OVER NRN WYOMING AT 22Z). FRONT AND COLDER AIR INVADES FROM
NRN ZONES BY 12Z/MON. COLD AIRMASS APPEARS DEEP ENOUGH TO SPILL
OVERTOP HIGHER TERRAIN AND MAKE IT INTO CENTRAL AND SOUTHERN VALLEYS
BY MONDAY EVENING. STRONG CANADIAN HIGH PRESSURE BUILDS IN MONDAY
NIGHT WITH CLEARING AND COLD CONDITIONS. A FEW SHSN MAY LINGER ALONG
THE DIVIDE MON NIGHT WITH COLD AND SHALLOW MOIST LAYER IN PLACE AND
PERSISTENT NW FLOW. H7 TEMPS DROP TO -19C TO -24C ACROSS THE CENTRAL
AND NORTHERN ZONES BY 12Z/TUE. THIS SUGGESTS VERY COLD SFC TEMPS
ACROSS THE CWFA BENEATH M.CLEAR SKIES. ONLY CAVEAT WILL BE IF
NORTHERLY WINDS STAY UP AHEAD OF SFC HIGH...KEEPING LOWER ATMOSPHERE
WELL-MIXED. WILL GO CLOSE TO GUIDANCE TEMPS FOR TUES MORNING.

TUESDAY WILL BE TRANQUIL DAY WITH NRLY FLOW HOLDING BACK ANY WAA
RESULTING IN A COOL/BELOW NORMAL TEMP DAY. TUESDAY NIGHT...AHEAD OF
PAC NW S/W DIVING TOWARD NRN CWFA...MID/HIGH CLOUDS WILL INCREASE.
PRECIP THREAT WILL HOLD OFF UNTIL WEDNESDAY...CONFINED TO MAINLY
THE NRN/CENTRAL MTNS AND NW ZONES ONCE AGAIN.
NADLER.83

EXTENDED (THU-SUN)...MRF DIFFERS FROM EURO SOLUTION ON FRIDAY WITH A
PROGRESSIVE OPEN WAVE IN NORTHWESTERLY FLOW.. AND WEAKER SHORT WAVE
COMPARED WITH THE PREVIOUS MRF RUN.  EURO MODEL SHOWS A CLOSED LOW
OVER THE FOUR CORNERS AREA.  WILL LEAN TOWARDS TO THE EURO MODEL
WITH A CHANCE OF SNOW SHOWERS FOR THURSDAY AND FRIDAY.  FOR NEXT
WEEKEND.. THE MRF THEN DEVELOPS A STRONG WESTERLY FLOW WITH BROAD
CYCLONIC FLOW OVER THE NORTHEAST PACIFIC OCEAN TO THE CENTRAL
PLAINS.  THIS SOLUTION MAY NOT BE OUT OF LINE.. BUT THE MRF PROBABLY
DEVELOPS THIS PATTERN TOO FAST.  MORE INCLINED TO BELIEVE A WARM
RIDGE WILL BE ACROSS THE AREA FIRST BEFORE THE WESTERLIES SAG
SOUTHWARD.  ANY PRECIPITATION THREAT WOULD BE CONFINED ACROSS THE
NORTHERN ZONES. PF

.GJT...WINTER STORM WARNING TONIGHT AND EARLY MONDAY COZN 4.
    ...SNOW AND BLOWING SNOW ADVISORY TONIGHT THROUGH MIDDAY
       MONDAY COZN 10/13.
    ...SNOW ADVISORY TONIGHT THROUGH MIDDAY MONDAY COZN 5.