FXUS65 KSLC 241611
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
911 AM MST THU DEC 24 2009
.SYNOPSIS...STRONG HIGH PRESSURE ALOFT ALONG THE WEST COAST WILL
SLIDE EAST INTO THE INTERIOR WEST THIS WEEKEND.
&&
.DISCUSSION...WATER VAPOR LOOP SHOWS A RIDGE BUILDING IN TO THE WEST
COAST. A DISTURBANCE WAS ROTATING ATOP THE RIDGE OVER BRITISH
COLUMBIA...WHILE A SECOND DISTURBANCE WAS WEAKENING AS IT NEARS
OREGON. 400-250MB ACARS WIND OBSERVATIONS PLACES A 80-110KT
NORTHERLY JET FROM BRITISH COLUMBIA INTO THE FOUR CORNERS. 12Z 700MB
ANALYSIS PLACES A RIDGE ALONG THE WEST COAST. WARM ADVECTION IS
OCCURRING WITH -14C REPORTED AT KSLC AND -9C UPSTREAM AT KBOI. 12Z
KSLC RAOB SHOWS 3 TO 7C OF COOLING BELOW 650MB WITH LITTLE THERMAL
CHANGE ALOFT DURING THE PAST 24 HOURS. A 2C INVERSION IS LOCATED
NEAR 730MB.
GOES/RUC PRECIPITABLE WATER INDICATE VALUES RANGE FROM LESS THAN A
TENTH OF AN INCH ACROSS THE NORTH AND EAST...TO NEAR A QUARTER INCH
ACROSS FAR SOUTHERN UTAH.
PATCHY FOG IS IMPROVING THIS MORNING...THOUGH STATUS REMAINS ALONG
THE GREAT SALT LAKE AND TRAPPED IN THE CENTRAL VALLEYS. HAVE TWEAKED
SKY GRIDS TO INDICATE THAT THIS MOISTURE WILL LIKELY HANG AROUND
INTO THE AFTERNOON...WHILE LOWERING SKY COVERAGE ELSEWHERE. ALSO
TWEAKED TEMPERATURES AND WINDS BASED ON LATEST OBSERVATIONS AND
GUIDANCE.
PREVIOUS DISCUSSION BELOW...
THE HIGH AMPLITUDE UPPER RIDGE ALONG THE WEST COAST PRODUCING A LONG
NORTHERLY CYCLONIC FLOW INTO THE GREAT BASIN. SHEAR VORTICITY LOBES
MOVING THROUGH THE FLOW WILL OFFER LITTLE THREAT FOR SNOW AS THERMAL
ADVECTION WEAK AT BEST AND THE LOW-LEVELS REMAIN RATHER COLD AND
STABLE. THE ONLY REAL WEATHER ISSUES THE NEXT SEVERAL DAYS WILL BE
THE COLD VALLEYS TEMPS AND THE DEVELOPMENT OF SOME FOG AND URBAN
HAZE HEADING INTO AND THROUGH THE COMING WEEKEND.
LONG RANGE GUIDANCE MATCHING UP REASONABLY WELL DURING THE EARLY
AND MIDDLE PORTIONS OF NEXT WEEK. THE HIGH AMPLITUDE RIDGE IS
SCHEDULED TO PINCH OFF THE NRN PORTION OVER SRN CANADA/NRN ROCKIES
WITH THE WESTERLIES UNDERCUTTING ACROSS THE SRN GREAT BASIN. A
COUPLE OF DECAYING SHORTWAVES EMBEDDED WITHIN THE WESTERLIES WILL
MOVE THROUGH THE BASIN LATE IN THE WEEKEND. WEAK DYNAMIC LIFT AND
MINIMAL THERMAL ADVECTION SUGGEST THAT ANY PRECIP THAT DEVELOPS
WILL BE ON THE LIGHT SIDE WITH LIMITED COVERAGE. A MORE ENERGETIC
SYSTEM WILL REACH THE COAST AND SPLIT EARLY NEXT WEEK. THE BULK
OF THE ENERGY WILL DIVE SOUTHEAST INTO NRN MEXICO...AND WILL BE
FAR REMOVED FROM EVEN SRN UTAH. HAVE KEPT A MENTION OF PRECIP FOR
MONDAY/TUESDAY...BUT SUSPECT THAT NRN UTAH WILL END UP DRY AND SRN
UTAH WILL SEE SPOTTY PRECIP AT BEST AS THIS FEATURE PASSES WELL TO
THE SOUTH.
&&
.AVIATION...VFR CONDITIONS EXPECTED TO PERSIST AT KSLC THROUGH
TONIGHT. OTHERWISE CURRENT STRATUS DECK IN THE 4-5KFT RANGE SHOULD
SCATTER OUT BY 17-18Z. SURFACE WINDS WILL REMAIN LIGHT THROUGH THE
PERIOD.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...ROGOWSKI/CONGER
AVIATION...CHENG
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
