Heavy Snow in Utah, February 18, 2002

UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
330 AM MST MON FEB 18 2002

.SYNOPSIS...A BROAD COOL LOW WILL MOVE INTO THE CENTRAL ROCKIES
TODAY.  A SERIES OF FAST MOVING STORMS WILL AFFECT THE AREA TUESDAY
AND WEDNESDAY.

.DISCUSSION...UPPER LEVEL LOW OVER SOUTHERN NEVADA WILL CONTINUE TO
MOVE EAST TONIGHT AND TOMORROW THROUGH SOUTHERN UTAH.  THE AIR MASS
WILL BECOME LESS STABLE THROUGH TODAY AS THE COLD AIR ASSOCIATED
WITH THE BROAD TROF MOVES OVER THE FORECAST AREA.  THE COLDER POCKET
WITH THE LOW WILL REMAIN ACROSS THE SOUTH.  CURRENTLY...MAIN PRECIP
IS ASSOCIATED WITH THIS COLD POCKET NEAR THE LOW.  CONVECTIVE BANDS
AROUND THE LOW COULD PRODUCE SOME BRIEF HEAVY PRECIP THROUGH TODAY.
BUT...THIS SHOULD REMAIN OVER SOUTHERN UTAH CLOSER TO THE LOW AND
COLDER AIR.  OTHER FACTORS HELPING PRECIP IN THE SOUTH IS THE LOW
LEVEL CONVERGENCE AND VORT ADVECTION WITH THE UPPER LOW. MAY ADD
ZONE 20 TO ADVISORY DUE TO UPSLOPE IN THAT AREA.  PRECIP UP NORTH IS
A BIG QUESTION. AIR MASS IS CONDITIONALLY UNSTABLE...BUT NOT MUCH
OTHER FORCING AVAILABLE. TROF AXIS AT 700MB DOES NOT PASS THROUGH THE
FORECAST AREA UNTIL AROUND MIDDAY.  THIS IS WHEN MOST AREAS UP NORTH
WILL SEE MORE WIDESPREAD PRECIP.  OROGRAPHIC COMPONENT NOT THAT
STRONG...SO PRECIP WILL BE MAINLY LIGHT IN NATURE.  IT IS POSSIBLE
WITH THE LOW TRAVELING THROUGH SOUTHERN UTAH AND TROF PUSHING
THROUGH COULD CREATE SOME BANDING NORTHWEST OF THE LOW. FOR THE
SOUTHERN MOUNTAINS...PRECIP SHOULD TAPER CONSIDERABLY THIS AFTERNOON
AS THE TROUGH PASSES.  IN ADDITION...AREAS PREVIOUSLY FAVORED BY
SOUTHERLY FLOW WILL SHUT OFF AND TURN TO AREAS FAVORED BY NORTHWEST
FLOW.

WARMING TO START OVERNIGHT WITH SOME STABILIZATION TO OCCUR AS THE
LOW MOVES INTO NEW MEXICO BY TUESDAY MORNING.  HOWEVER...AIR MASS TO
REMAIN UNSTABLE IN THE LOW LEVELS UP NORTH.  THIS COULD MEAN AREAS
FAVORED BY NORTHWEST FLOW WILL CONTINUE TO SNOW THROUGH MUCH OF THE
NIGHT.  THIS WILL REMAIN A VERY SHALLOW PRECIP FIELD FOR THE
MOUNTAINS.  MAY NEED SNOW ADVISORY FOR NORTHERN MOUNTAINS FOR THE
TWO PERIODS TODAY AND TONIGHT.

WARMING STARTED OVERNIGHT WITH THE AIR MASS BECOMING QUITE STABLE
THROUGH THE DAY TUESDAY.  THIS IS AHEAD OF THE NEXT SYSTEM MOVING OUT
OF NORTHWEST FLOW IN AN AMPLIFYING RIDGE IN THE EASTERN PACIFIC.
THERE IS A STRONG JET ASSOCIATED WITH THIS SHORT WAVE TROF.  EXPECT
THAT THE THREAT OF PRECIP FOR NORTHERN UTAH WILL BE OVERNIGHT TUESDAY
INTO WEDNESDAY AT THIS TIME.  BIG QUESTION IS HOW FAR SOUTH COLD
POCKET WITH THIS FEATURE EXTENDS INTO UTAH.  ETA COOLER WITH THE
SYSTEM...BUT BELIEVE AVN BETTER SOLUTION.  RIDGE BUILDS INTO THE
WESTERN U.S. OVERNIGHT WEDNESDAY WITH WARMING AT ALL LEVELS.   STRONG
WARMING TO TAKE PLACE THURSDAY AS RIDGE MOVES OVER THE GREAT BASIN.

ALL MEDIUM RANGE MODELS BUILD RIDGE BY THURSDAY OVER THE WEST.  THE
DIFFERENCE COMES IN HANDLING THE NEXT TROUGH WHICH IS NEAR 145W BY
THURSDAY MORNING.  EC AND UK SLOWER WITH THE PROGRESSION THAN THE
MRF.  THEREFORE...PRECIP CHANCES WOULD HOLD OFF UNTIL SATURDAY
NIGHT/SUNDAY RATHER THAN FRIDAY NIGHT/SATURDAY.  ENSEMBLES FROM THE
MRF DEPICT NOT MUCH SPREAD FOR THIS TIME FRAME.  FOR NOW...WILL
SPLIT THE DIFFERENCE AND KEEP CHANCE FOR SATURDAY AND LEAVE SUNDAY
MOSTLY CLOUDY.

SLC 4644 CDC 6621  NELSON

.SLC...SNOW ADVISORY TONIGHT THROUGH TOMORROW FOR SOUTHERN UTAH
       MOUNTAINS.

UTZ002-UTZ003-UTZ004-UTZ006-UTZ007-UTZ008-190100-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE FORECAST OFFICE
SALT LAKE CITY UTAH

HAZARDOUS WINTER WEATHER POTENTIAL FOR NORTHERN UTAH
525 AM MST MON FEB 18 2002

OVERVIEW:
A SURFACE LOW PRESSURE SYSTEM MOVES THROUGH UTAH TODAY, BRINGING
CLOUDY SKIES AND LIGHT SNOW SHOWERS, ESPECIALLY OVER THE
MOUNTAINS.  ACCUMULATIONS WILL BE UP TO AN INCH IN THE VALLEYS,
IF ANY, AND 1-2 INCHES AT THE MOUNTAIN VENUES. SNOW SHOWERS WILL
END TONIGHT UNDER MOSTLY CLOUDY SKIES.

...OGDEN CANYON/WEBER CANYON/TRAPPERS LOOP...

TODAY (6AM-6PM)

WEATHER:
MOSTLY CLOUDY WITH LIGHT SNOW SHOWERS LIKELY, ESPECIALLY IN THE
MOUNTAINS.

TEMPERATURES (F):              8AM         NOON        4PM
WEBER CANYON PARK AND RIDE      34           36         40
MOUNTAIN GREEN PARK AND RIDE    29           30         29

WIND:
LIGHT SOUTH WINDS LESS THAN 10 MPH, BECOMING LIGHT NORTHWEST
WIND LESS THAN 10 MPH THIS AFTERNOON.

COMMENTS:
NONE

TONIGHT (6PM-6AM)

WEATHER:
MOSTLY CLOUDY.

TEMPERATURES (F):                OVERNIGHT MINIMUM
WEBER CANYON PARK AND RIDE               25
MOUNTAIN GREEN PARK AND RIDE             19

WIND:
LIGHT WEST WINDS LESS THAN 10 MPH.

COMMENTS:
NONE

...I-80/MOUTH OF PARLEYS CANYON/PARLEYS SUMMIT/KIMBALL JUNCTION...

TODAY (6AM-6PM)

WEATHER:
MOSTLY CLOUDY WITH LIGHT SNOW SHOWERS LIKELY, ESPECIALLY IN THE
MOUNTAINS.

TEMPERATURES (F):              8AM         NOON        4PM
MOUTH OF PARLEYS CANYON         41           42         39
PARLEYS SUMMIT                  28           29         30
KIMBALL JUNCTION                27           28         28

WIND:
NORTHEAST 5 TO 15 MPH, EXCEPT AT PARLEYS SUMMIT WITH SOUTHWEST
WINDS 10 MPH.

COMMENTS:
NONE

TONIGHT (6PM-6AM)

WEATHER:
MOSTLY CLOUDY.

TEMPERATURES (F):                OVERNIGHT MINIMUM
MOUTH OF PARLEYS CANYON                  25
PARLEYS SUMMIT                           19
KIMBALL JUNCTION                        20

WIND:
NORTHEAST 5 TO 15 MPH, EXCEPT AT PARLEYS SUMMIT WITH SOUTHWEST
WINDS 10 MPH.

COMMENTS:
NONE

...PROVO CANYON TO HEBER...

TODAY (6AM-6PM)

WEATHER:
MOSTLY CLOUDY WITH LIGHT SNOW SHOWERS LIKELY, ESPECIALLY IN THE
MOUNTAINS.

TEMPERATURES (F):              8AM         NOON        4PM
MOUTH OF PROVO CANYON           35           38         39
HEBER                           28           30         31

WIND:
LIGHT SOUTH WINDS LESS THAN 10 MPH, BECOMING LIGHT NORTHWEST
WIND LESS THAN 10 MPH THIS AFTERNOON.

COMMENTS:
NONE

TONIGHT (6PM-6AM)

WEATHER:
MOSTLY CLOUDY.

TEMPERATURES (F):               OVERNIGHT MINIMUM
MOUTH OF PROVO CANYON                    25
HEBER                                    19

WIND:
LIGHT NORTH WINDS LESS THAN 10 MPH.

COMMENTS:
NONE

...SALT LAKE VALLEY...

TODAY (6AM-6PM)

WEATHER:
MOSTLY CLOUDY WITH LIGHT SNOW SHOWERS POSSIBLE.

TEMPERATURES (F):              8AM         NOON        4PM
DOWNTOWN SALT LAKE CITY         32           36         39
UNIVERSITY OF UTAH              36           37         38

WIND:
LIGHT SOUTH WINDS LESS THAN 10 MPH, BECOMING LIGHT NORTHWEST
WIND LESS THAN 10 MPH THIS AFTERNOON.

COMMENTS:
NONE

TONIGHT (6PM-6AM)

WEATHER:
MOSTLY CLOUDY.

TEMPERATURES (F):                OVERNIGHT MINIMUM
DOWNTOWN SALT LAKE CITY                  25
UNIVERSITY OF UTAH                       24

WIND:
LIGHT NORTH WINDS LESS THAN 10 MPH.

COMMENTS:
NONE

...OGDEN/I-15 IN DAVIS-WEBER COUNTIES...

TODAY (6AM-6PM)

WEATHER:
MOSTLY CLOUDY WITH LIGHT SNOW SHOWERS POSSIBLE.

TEMPERATURES (F):              8AM         NOON        4PM
DOWNTOWN OGDEN                  29           33         35

WIND:
LIGHT SOUTH WINDS LESS THAN 10 MPH, BECOMING LIGHT NORTHWEST
WIND LESS THAN 10 MPH THIS AFTERNOON.

COMMENTS:
NONE

TONIGHT (6PM-6AM)

WEATHER:
MOSTLY CLOUDY.

TEMPERATURES (F):                OVERNIGHT MINIMUM
DOWNTOWN OGDEN                           24

WIND:
LIGHT NORTH WINDS LESS THAN 10 MPH.

COMMENTS:
NONE

...UTAH COUNTY...

TODAY (6AM-6PM)

WEATHER:
MOSTLY CLOUDY WITH LIGHT SNOW SHOWERS POSSIBLE.

TEMPERATURES (F):              8AM         NOON        4PM
DOWNTOWN PROVO                  35           37         39

WIND:
LIGHT SOUTH WINDS LESS THAN 10 MPH, BECOMING LIGHT NORTHWEST
WIND LESS THAN 10 MPH THIS AFTERNOON.

COMMENTS:
NONE

TONIGHT (6PM-6AM)

WEATHER:
MOSTLY CLOUDY.

TEMPERATURES (F):                OVERNIGHT MINIMUM
DOWNTOWN PROVO                           24

WIND:
LIGHT NORTH WINDS LESS THAN 10 MPH.

COMMENTS:
NONE