822  
FXUS65 KSLC 232315  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
415 PM MST TUE JAN 23 2018  
   
SYNOPSIS
 
HIGH PRESSURE WILL RETURN MIDWEEK BEFORE A FAST  
MOVING STORM SYSTEM IMPACTS THE AREA THURSDAY INTO FRIDAY MORNING.  
HIGH PRESSURE IS EXPECTED TO RETURN FOR THE UPCOMING WEEKEND.  
 

 
   
SHORT TERM (THROUGH 00Z SATURDAY)
 
RISING HEIGHTS AND MID-LEVEL  
WARM AIR ADVECTION SIGNAL THE ARRIVAL OF HIGH PRESSURE ACROSS THE  
INTERIOR WEST. SATELLITE IMAGERY INDICATES SNOW COVER REMAINS IN  
PLACE ACROSS NEARLY ALL OF SOUTHWESTERN AND WEST CENTRAL UTAH THIS  
AFTERNOON OUTSIDE OF THE LOWEST ELEVATIONS NEAR ST. GEORGE. THIS  
SNOW COVER HAS KEPT MANY LOCATIONS FROM REALIZING EXPECTED HIGH  
TEMPERATURES THIS AFTERNOON. ANTICIPATE THESE AREAS WILL COOL WELL  
BELOW MOST AVAILABLE MODEL GUIDANCE THIS EVENING INTO TONIGHT  
UNDER MAINLY CLEAR SKIES. MANY AREAS FROM MILFORD TO DELTA TO  
CEDAR CITY ARE IN FOR QUITE A COLD JANUARY NIGHT. PATCHY DENSE FOG  
WILL BE POSSIBLE ACROSS THE CACHE VALLEY AND THE WASATCH BACK  
TONIGHT.  
 
EXPECT SOUTHWESTERLY FLOW TO INCREASE THROUGH WEDNESDAY AFTERNOON  
AND EVENING, THOUGH MANY OF THE VALLEY LOCATIONS WILL REMAIN  
INVERTED THROUGH THIS TIME. ANY REMAINING INVERSIONS SHOULD MIX  
OUT WEDNESDAY NIGHT INTO THURSDAY MORNING AHEAD OF THE COLD FRONT  
AS WINDS INCREASE FURTHER.  
 
THE PREVIOUSLY MENTIONED COLD FRONT HAS TRENDED INTO A RATHER  
BLASE EVENT OVER THE LAST FEW MODEL RUNS. MUCH OF THE GLOBAL MODEL  
GUIDANCE FEATURE A WEAKENING TROUGH ENTERING THE STATE THURSDAY.  
WHILE THE AIRMASS IN THE WAKE OF THE COLD FRONT IS QUITE COLD,  
DYNAMIC FORCING IS LIMITED. AT THIS TIME, IT APPEARS THE COLD  
FRONT WILL MOVE THROUGH THE STATE THURSDAY MORNING INTO THURSDAY  
AFTERNOON WITH A LIMITED FRONTAL BAND OF SNOW TO VALLEY FLOORS.  
WITH MARGINAL WEST TO NORTHWEST FLOW, EXPECT A PERIOD OF  
OROGRAPHIC ENHANCEMENT IN FAVORED MOUNTAIN AREAS, BUT THE LATEST  
RUNS OF BOTH THE GFS AND THE EC INDICATE A BRIEF WINDOW OF  
POTENTIAL.  
 
AS THE BACKSIDE OF THE TROUGH CROSSES THE STATE FRIDAY, EXPECT  
ANOTHER ROUND OF SNOW SHOWERS ACROSS MAINLY THE HIGHER TERRAIN OF  
UTAH. SNOW TOTALS FROM THIS PORTION OF THE TROUGH ARE EXPECTED TO  
BE LOW AS WELL.  
   
LONG TERM (AFTER 00Z SATURDAY)
 
MODELS ARE IN BETTER AGREEMENT  
TODAY FOR THE START OF THE LONG TERM PERIOD. BOTH NOW INDICATE A  
WARM ADVECTION NORTHWEST FLOW WILL BE IN PLACE ACROSS THE NRN CWA  
WITH THE WAA BECOMING STRONGER ON SAT LASTING INTO SUN. THE GFS  
CONTINUES TO SHOW MORE MOISTURE IN THIS FLOW EXTENDING FARTHER  
SOUTH, WITH A LITTLE BETTER CHANCE OF SNOW THAN THE EC, BUT THE EC  
HAS COME TOWARDS THE GFS SOLUTION IN THIS NEW 12Z RUN.  
 
EVEN WITH THIS MORE ROBUST WAA PATTERN, MODEL QPF REMAINS LOW AND  
SPOTTY. THESE CAN END UP BEING HIGH POP LOW QPF EVENTS BUT FOR  
NOW SEEING AS THIS IS DAY 4, HAVE KEPT POPS ON THE LOW SIDE BUT  
DID EXPAND THEM TO COVER MORE OF THE NRN CWA FRI NIGHT THRU SUN.  
 
MODELS ARE NOW ALSO IN AGREEMENT ON SHORT WAVE RIDGING BRINGING  
DRY CONDITIONS SUN NIGHT THRU MON. THE NEXT DEEPER PAC TROF IS  
FORECAST TO START MOVING INTO THE NORTHWESTERN STATES MON NIGHT  
WITH A WEAK LEADING SHORT WAVE CROSSING THE CWA EARLY TUE. THE  
MAIN TROF ARRIVES TUE NIGHT AND WOULD BRING A BAND OF SNOW ALONG  
THE COLD FRONT TO ABOUT THE NRN 2/3 OF THE CWA, AS CURRENTLY  
DEPICTED IN THE GFS. THE EC IS SIMILAR BUT SOMEWHAT SLOWER ALTHO  
BOTH ARE QUITE COLD PAST DAY 7. CONFIDENCE IS STILL NOT THAT HIGH  
IN THE GUIDANCE FOR THIS TIME FRAME SO JUST RAISED POPS ABOUT 10  
PERCENT ABOVE CLIMO FOR TUE NIGHT.  
 

 
   
AVIATION
 
THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGHOUT THE  
NIGHT. THE CLOUDS AROUND 6000 FT ARE DISSIPATING AND ANY CIGS THAT  
FORM WILL BE WELL ABOVE THAT LEVEL. NORTHERLY WINDS ARE EXPECTED TO  
RETURN TO THE SOUTHEAST BETWEEN 03Z AND 05Z.  
 

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

 
 

 
 
KRUSE/WILENSKY  
 
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...  
HTTP://WEATHER.GOV/SALTLAKECITY  
 
FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION  
VISIT...  
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP  
 
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