FXUS65 KSLC 261130
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
430 AM MST SAT DEC 26 2009

.SYNOPSIS...WEAK HIGH PRESSURE WILL REMAIN OVER THE REGION TODAY
THROUGH SUNDAY THEN SHIFT EAST MONDAY. A WEAK DISTURBANCE FROM
THE PACIFIC WILL MOVE THROUGH THE HIGH SUNDAY WITH AN INCREASINGLY
MOIST SOUTHWEST FLOW EXPECTED FOR MONDAY.

&&

.DISCUSSION...UTAH REMAINS AT THE WESTERN PERIPHERY OF THE LARGE
UPPER LOW OVER THE CENTRAL US THIS MORNING WITH A LIGHT NELY FLOW
ALOFT OVER THE CWA AND SOME MOISTURE FROM THIS LOW OVER ABOUT THE
NERN 1/3 OF THE AREA. STRATUS AND FOG HAS BEEN EXPANDING ALONG THE
WASATCH FRONT AND THE NORTHWEST DESERT. OTHER AREAS OF FOG ARE
NOTED IN THE SEVIER VALLEY AND AROUND EVANSTON. EXPECT THESE TO
PERSIST TODAY WITH SOME DISSIPATION AROUND THE EDGES THEN REFORM
AGAIN TONIGHT AS THERE IS ONLY LITTLE CHANGE FORECAST FOR THE
AIRMASS. 

UT WILL COME UNDER THE COL AREA TONIGHT BETWEEN THE PINCHED OFF
CLOSED HIGH OVER WRN CANADA AND THE WEAK RIDGE TO THE SOUTH AND
THE CENTRAL US LOW AND THE LOW IN THE ERN PAC. MOISTURE IS
FORECAST TO GRADUALLY INCREASE OVER THE CWA OVERNIGHT THEN THE
WESTERLIES START TO BREAK THROUGH THE RIDGE SUN AND BRING
ADDITIONAL MOISTURE TO THE AREA. 

THIS PROCESS CONTINUES INTO TUE AS THE RIDGE AXIS SHIFTS EAST AND
A DIFFUSE UPPER TROF STARTS TO MOVE THROUGH THE WESTERN STATES.

MODELS HAVE BEEN STRUGGLING WITH THIS BREAK THRU ON HOW FAR NORTH
MOISTURE WILL GET AND HOW FAR SOUTH THE MAIN ENERGY WITH THE TROF
WILL END UP. LATEST GFS IS MORE MOIST FOR THE ENTIRE CWA AS THE
TROF IS MORE DIFFUSE AND LESS CONCENTRATED AT THE SRN END. THIS
MOISTURE WILL INITIALLY BE MAINLY CLOUDS BUT SCATTERED LIGHT
PRECIP IS POSSIBLE OVER THE WEST AND NORTH AS EARLY AS SUN AS THE
FIRST WEAK WAVE BREAKS THRU. THE CLOUD COVER SHOULD START TO
WEAKEN THE INVERSIONS AND EXPECT A REDUCED THREAT OF FOG BY SUN
MORNING. 

THE MAIN TROF AXIS NOW MOVES THRU ON TUE WITH A TRAILING SHORT
WAVE IN NWLY FLOW FOR WED. THE 00Z EC AND THE 06Z GFS ARE NOW IN
BETTER AGREEMENT ON THIS SCENARIO. STILL...HAVE KEPT POPS ON THE
LOW SIDE AS CONFIDENCE IS STILL NOT THAT HIGH IN THE GUIDANCE
BEYOND SUN.  

&&

.AVIATION...MVFR CEILINGS IN STRATUS AT THE SLC TERMINAL ARE 
EXPECTED TO IMPROVE TO VFR BETWEEN 15Z AND 17Z. HOWEVER...THERE IS A 
30 PERCENT CHANCE THAT THE LOWER CEILINGS WILL PERSIST UNTIL BETWEEN 
18Z AND 20Z. LIGHT SOUTHEASTERLY WINDS SHOULD SHIFT TO THE NORTHWEST 
BETWEEN 17Z AND 19Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.

&&

$$

WILENSKY/TRAPHAGAN

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)