Heavy Snow in Utah, January 3, 2002

UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
341 AM MST THU JAN 3 2002

.SYNOPSIS...A SPLITTING PACIFIC STORM SYSTEM WILL MOVE ACROSS THE
AREA TODAY AND TONIGHT.  A COLD NORTHWEST FLOW WILL DEVELOP FRIDAY.

.DISCUSSION...RIDGE PASSING FORECAST AREA TONIGHT WITH THE FLOW
ALOFT TURNING SOUTHWEST.  CLOUDS STARTING TO INCREASE ALONG THE
WESTERN PORTIONS THIS MORNING AS TROUGH JUST MAKING ITS WAY INTO THE
GREAT BASIN.

TROUGH IN TWO PARTS WITH VORT MAX PROGRESSING THROUGH
SOUTHERN/CENTRAL CALIFORNIA. COLD POCKET ASSOCIATED WITH THIS NOT
THAT GOOD.  HOWEVER...PRECIP WILL SPREAD INTO SOUTHWEST UTAH AS A
RESULT OF THIS WAVE LATER TODAY.  SECOND VORT MAX WITH A GOOD COLD
POCKET IS MOVING THROUGH OREGON CURRENTLY.  THIS WAVE WILL TRACK
THROUGH IDAHO AND CLIP THROUGH NORTHERN UTAH.  NORTHERN PORTION OF
THE STORM LAGGING SOUTHERN PORTION A LITTLE...BUT OVERALL TROUGH AXIS
STILL EXPECTED TO CROSS INTO UTAH AROUND 00Z.  THE TROUGH AXIS WILL
BE ACCOMPANIED BY A SURFACE COLD FRONT.  DO NOT EXPECT MUCH
PRE-FRONTAL PRECIP EXCEPT SOUTHWEST UTAH AND AREAS ALONG THE IDAHO
BORDER.  JET SUPPORT REALLY LACKING WITH EITHER PORTION OF THE STORM.
THERE IS A LITTLE EARLY WITH THE FRONT THIS AFTERNOON IN THE NORTH
AHEAD OF THE COLD POCKET.  NOT MUCH THERMAL PACKING AT 700MB TO
WARRANT A MODERATE...MUCH LESS STRONG COLD FRONT.  WINDS ARE NOT THAT
STRONG ALOFT EITHER.  BUT GRADIENT BECOMES QUITE FAVORABLE TONIGHT
FOR A CONSTANT NORTHWEST WINDS BEHIND THE FRONT.  THIS WILL KEEP LOW
CLOUDS AND FOG AT BAY.

FLOW ALOFT TURNS NORTHWEST THROUGH THE EVENING OVER THE ENTIRE
FORECAST AREA WITH THE COLD FRONT MAKING ITS WAY THROUGH BY FRIDAY
MORNING.  WITH THE LACK OF JET SUPPORT AND STRONG COLD FRONT...SNOW
AMOUNTS WILL BE BELOW ADVISORY LEVEL IN THE VALLEYS.  HOWEVER...LOW
LEVEL INSTABILITY AROUND OVERNIGHT THURSDAY AND THROUGH MUCH OF THE
DAY FRIDAY. COMBINED WITH A FAVORABLE OROGRAPHIC COMPONENT...THE
NORTHERN MOUNTAINS SHOULD DO WELL OVERNIGHT INTO FRIDAY MORNING.
WILL DECIDE LATER WHETHER TO ISSUE SNOW ADVISORY THIS MORNING OR WAIT
FOR THE DAY CREW TO ISSUE.

JET AND VORT MAX ON BACKSIDE OF THE TROUGH TO MOVE THROUGH THE STATE
FRIDAY KEEPING PRECIP GOING THROUGH THE MORNING HOURS.  THIS WILL
ALSO INCREASE THE FLOW ALOFT OVER THE FORECAST AREA. NORTHERLY FLOW
ALOFT AND FAVORABLE SURFACE PRESSURE GRADIENT THROUGH FRIDAY FOR
BREEZY NORTH WINDS.

SOME WARMING ALOFT TO TAKE PLACE LATER IN THE AFTERNOON...EFFECTIVELY
STABILIZING THE AIRMASS.  SKIES SHOULD CLEAR OVERNIGHT FRIDAY WITH
AREAS OF FOG AND LOW CLOUDS STARTING TO DEVELOP BY SATURDAY MORNING.
PRESSURE GRADIENT STRONG ENOUGH FOR GAP WINDS TO DEVELOP IN
WASHINGTON COUNTY.  COMBINED WITH A STRONG TEMPERATURE GRADIENT AND
700MB WINDS...A HIGH WIND WARNING MAY BE ISSUED.  FOR NOW...STRONG
WINDS IN THE FORECAST UNTIL CLOSER TO EVENT.

RIDGE STRONGLY IN PLACE BY SATURDAY. DO NOT EXPECT THAT TO CHANGE
THROUGH THE REMAINDER OF THE FORECAST PERIOD. THIS WILL BRING BACK
THE STAGNATION FOR THE VALLEYS. A COUPLE DISTURBANCES ARE ANTICIPATED
TO PUSH OVER THE RIDGE...BUT WILL NOT AFFECT THE FORECAST AREA EXCEPT
POSSIBLE FLURRIES IN THE NORTHERN MOUNTAINS. WILL TAKE OUT CHANCES IN
EXTENDED FOR NOW.

SLC 674 CDC 562  NELSON

.SLC...SNOW ADVISORY NORTHERN MOUNTAINS...SEE SLCWSWSLC FOR DETAILS.