003  
FXUS65 KSLC 192218  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
318 PM MST WED FEB 19 2020  
   
SYNOPSIS
 
 
THE DRY UPPER LEVEL TROUGH MOVING SOUTH THROUGH THE NORTHERN  
ROCKIES WILL BRING COLDER AIR AND LIMITED CLOUD COVER TO THE AREA  
TODAY. DRY AND STABLE CONDITIONS WILL PERSIST THROUGH THE END OF  
THE WEEK AS HIGH PRESSURE ALOFT EXPANDS EAST ACROSS THE GREAT  
BASIN. A STORM SYSTEM MOVING INTO ARIZONA WILL BRING RAIN AND SNOW  
TO SOUTHERN UTAH THIS WEEKEND.  
 

 
   
SHORT TERM (THROUGH 12Z SATURDAY)
 
 
A VERY STRONG SURFACE ANTICYCLONE WILL SET UP ACROSS SOUTH CENTRAL  
WYOMING TONIGHT TIGHTENING UP THE PRESSURE GRADIENT. THIS ALONG  
WITH COLD ADVECTION BEHIND THE PASSING DRY TROUGH WILL SUPPORT  
GUSTY CANYON WINDS ALONG THE WASATCH FRONT AND OUTLYING DIXIE  
TONIGHT INTO TOMORROW MORNING. WINDS MAY NEAR ADVISORY CRITERIA  
FOR OUTLYING DIXIE, BUT WILL VERY LIKELY BARELY REACH IT FOR A FEW  
HOURS, SO WILL NOT BE ISSUING A WIND ADVISORY WITH THIS FORECAST  
PACKAGE.  
 
INVERTED CONDITIONS WILL BE THE RULE THROUGH FRIDAY NIGHT, WITH A  
RIDGE BUILDING INTO THE REGION. FOG IS THE PRIMARY CONCERN,  
ESPECIALLY ACROSS THE CACHE VALLEY, WASATCH BACK EAST INTO  
SOUTHWEST WYOMING BASED ON A MODIFIED UPS TECHNIQUE METHODOLOGY.  
THIS THREAT WILL CONTINUE THROUGH FRIDAY NIGHT. HAVE UNDERCUT  
GUIDANCE TEMPERATURES ACROSS THESE AREAS AS WELL GIVEN THE  
SNOWPACK AND FANTASTIC RADIATIONAL COOLING CONDITIONS.  
 
ANTICIPATE AIR QUALITY WILL CONTINUE TO DETERIORATE, AND HAVE  
MENTIONED URBAN HAZE BEGINNING TOMORROW.  
   
LONG TERM (AFTER 12Z SATURDAY)
 
 
MODEL ENSEMBLES ARE IN GOOD AGREEMENT IN BRINGING A PACIFIC  
CLOSED LOW ACROSS SOUTHERN NEVADA AND NORTHWESTERN ARIZONA AND  
SKIRTING SOUTHERN UTAH THROUGH THE WEEKEND. A SLIGHT CHANGE NOTED  
OVER THE PAST 24 HOURS FROM PREVIOUS FORECASTS IS HOW BOTH MODELS  
HAVE SHOW A DEEPER LOW AND HAVE ADJUSTED THE ONSET OF THE HEAVIEST  
PRECIPITATION ARRIVING IN SOUTHERN UTAH BACK 12 HOURS TO NOW  
SHOWING THE BULK OF THE PRECIPITATION ARRIVING SUNDAY. THE  
TEMPERATURE PROFILE WITH THIS SYSTEM SHOWS H7 TEMPERATURES IN THE  
-6C TO -5C IN THE CORE OF THE STORM. WARM SOUTHERLY FLOW AHEAD OF  
THE STORM WILL PUSH SNOW LEVELS WELL ABOVE THE VALLEY FLOORS AND  
SNOW WILL BE PRIMARILY FOUND IN THE HIGHER ELEVATIONS ABOVE 5500FT  
IN THE PINE VALLEY MOUNTAINS. STORM TOTAL ACCUMULATION ANALYSIS  
SEEMS TO BE RUNNING HOT BASED ON THE GEFS OUTPUTS OVER VARIOUS  
PERCENTILES. AFTER LOOKING A VARIOUS QPF FIELDS, OVERALL FORECAST  
IS CONFIDENT IN A GOOD RAIN EVENT ACROSS SOUTHERN UTAH. LOOKING AT  
A STORM TOTAL ANYWHERE BETWEEN 1/2 TO 3/4" IN THE VALLEYS WITH  
ACCUMULATIONS OVER AN INCH IN THE HIGHER TERRAIN.  
 
AS THIS LOW TRANSVERSES ACROSS SOUTHERN UTAH A WEAKENING TREND  
SEEMS TO BE THE CONSENSUS AND THE PRECIPITATION AND THE LOW ITSELF  
WILL QUICKLY MOVE EAST OUT OF UTAH AS A WEAK UPPER LEVEL DISTURBANCE  
BRINGS SOME MOUNTAIN SNOW SHOWERS TO NORTHERN UTAH.  
 
GOING INTO DAY 5 AND BEYOND IN THE LONG RANGE FORECAST, THE MEAN  
OUTPUT FROM THE H5 GRAPH CLUSTER ANALYSIS HINTS AT A WEAK TROUGH  
ACROSS SOUTHER IDAHO AND A SOMEWHAT ZONAL NORTHWESTERLY FLOW  
PERSISTING THROUGH THE LONG TERM. VARIATIONS IN THE IN THE AMPLITUDE  
OF THE UPSTREAM RIDGE AXIS AND STRENGTH OF THE TROUGH CONTINUE TO  
SHOW UP IN BOTH THE GEFS AND EPS SOLUTIONS THAT WOULD INFLUENCE THE  
POP CHANCES THROUGH THIS TIME PERIOD AS WELL AS TEMPERATURES. THE  
FORECAST GOING FORWARD WILL CONTINUE TO ADVERTISE HIGHER POPS TO THE  
NORTHERN HALF OF THE FORECAST AREA, ESPECIALLY IN THE MOUNTAINOUS  
TERRAIN, WITH SOME LINGERING POPS ACROSS THE HIGH TERRAIN OF THE  
SOUTH.  
 

 
   
AVIATION
 
 
THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGH THE TAF PERIOD.  
NORTHWEST WINDS ARE EXPECTED TO PREVAIL THROUGH 04-05Z THIS  
EVENING THEN BECOME SOUTHEAST.  
 

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

 
 

 
 
SHORT TERM/AVIATION...10  
LONG TERM...WOODWARD  
 
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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