FXUS65 KSLC 260343
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
843 PM MST FRI DEC 25 2009
.SYNOPSIS...A COLD NORTHERLY FLOW WILL CONTINUE ACROSS UTAH THROUGH
EARLY SATURDAY. A SERIES OF WEAK DISTURBANCES WILL MOVE ACROSS THE
GREAT BASIN THROUGH MUCH OF NEXT WEEK.
&&
.DISCUSSION...WATER VAPOR LOOP SHOWS AN EXPANSIVE CENTRAL CONUS
UPPER LOW IS EXPANDING WEST INTO THE GREAT BASIN...AS THE WESTERN
CONUS RIDGE PINCHES OFF OVER THE PACIFIC NORTHWEST. 400-250MB ACARS
WIND OBSERVATIONS PLACES A NORTHERN 75-105KT JET FROM WESTERN
MONTANA THROUGH WESTERN UTAH ON THE WESTERN PERIPHERY OF THE CENTRAL
CONUS STORM SYSTEM. 00Z 700MB ANALYSIS PLACES A RIDGE OVER THE
PACIFIC NORTHWEST AND INTO BRITISH COLUMBIA. COLD ADVECTION IS
OCCURRING WITH -14C REPORTED AT KSLC AND -17C UPSTREAM AT KRIW. 00Z
KSLC RAOB SHOWS 3C OF WARMING NEAR 750MB...WITH 5 TO 10C OF COOLING
ALOFT DURING THE PAST 24 HOURS. SEVERAL WEAK INVERSIONS ARE LOWERING
TO THE SURFACE FROM RIDGETOP LEVEL.
GOES/RUC PRECIPITABLE WATER INDICATE VALUES RANGE FROM A TENTH TO
QUARTER INCH ACROSS THE REGION.
LIGHT SNOW HAS BEEN OBSERVED NEAR EVANSTON AND IN THE SOUTHERN
WASATCH MOUNTAINS THIS EVENING AS A WEAK VORT LOBE PROGRESSES WEST
INTO NORTHERN UTAH FROM WYOMING. CURRENT FORECAST HANDLES THIS WELL
THUS NO NEED TO UPDATE POPS/QPF AT THIS TIME.
FOG IS THE OTHER CONCERN DURING THE OVERNIGHT HOURS. VISIBILITIES
HAVE BEEN REDUCED SLIGHTLY ACROSS THE SALT LAKE VALLEY AND NORTHERN
WASATCH FRONT...WITH VISIBILITIES BRIEFLY DROPPING TO A HALF MILE AT
BRIGHAM CITY. HAVE RETAINED CURRENT FOG WORDING OVERNIGHT.
UPDATING TO TWEAK TEMPERATURES/DEWPOINTS...WINDS AND SKY BASED ON
RECENT OBSERVATIONS AND MODEL DATA. REST UNCHANGED.
PREVIOUS DISCUSSION FOLLOWS...
THE RIDGE WILL GET PINCHED OFF THIS WEEKEND WITH A CLOSED UPPER HIGH
OVER ALBERTA AND NEAR ZONAL FLOW DEVELOPING OVER SOUTHERN UTAH AND
ARIZONA. VERY WEAK DISTURBANCES WILL CROSS THE AREA IN THIS FLOW
SUNDAY AND MONDAY. HOWEVER...MOISTURE AND DYNAMICS WILL BE RATHER
LIMITED WITH THESE WAVES...SO ANY PRECIPITATION THAT DOES MANAGE TO
FALL WILL BE LIGHT. HAVE KEPT POPS LOW FOR THIS PERIOD AS A RESULT.
MODEL DIFFERENCES STILL EXIST FOR THE MIDWEEK PERIOD. THE GFS
CONTINUES TO SUGGEST A SHORTWAVE TROUGH WILL MOVE ACROSS
UTAH...SPREADING PRECIPITATION TO MUCH OF THE AREA ON WEDNESDAY. THE
EC IS WEAKER AND A BIT FARTHER NORTH WITH THIS DISTURBANCE...SO IN
THIS SCENARIO MUCH OF THE AREA WILL BE DRIER. CONFIDENCE IS STILL
TOO LOW AT THIS TIME TO BRING POPS MUCH ABOVE CLIMO. A BROADER AREA
OF HIGH PRESSURE WILL SETTLE ACROSS THE REGION FOR THE LATTER PART
OF NEXT WEEK.
&&
.AVIATION...MID AND HIGH LEVEL MOISTURE WILL CONTINUE TO SPREAD
WESTWARD AND MOVE ACROSS THE SLC TERMINAL AROUND 06Z. CLOUDS SHOULD
BASICALLY KEEP ANY SIGNIFICANT FOG FROM DEVELOPING. ASOS SUGGESTS
VISIBILITIES 4-5 MILES IN HAZE...ALTHOUGH OBSERVERS PREFER A HIGHER
VALUE. AS A RESULT...EXPECT VFR CONDITIONS TO PREVAIL WITH A 20
PERCENT CHANCE OF HIGH END MVFR CONDITIONS IN HAZE DUE TO LOWERED
VISIBILITY. WINDS LIGHT NORTHERLY TURNING SOUTHEAST AFTER 08Z.
&&
.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&
$$
PUBLIC...ROGOWSKI/CHENG
AVIATION...YOUNG
FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)
