139  
FXUS65 KSLC 191042  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
342 AM MST SUN JAN 19 2020  
   
SYNOPSIS
 
 
HIGH PRESSURE ALOFT WILL STRENGTHEN OVER UTAH THROUGH SUNDAY  
BEFORE SHIFTING EAST OF THE STATE MONDAY. A RATHER WEAK WEATHER  
DISTURBANCE WILL BRING MOSTLY CLOUDS TO THE AREA FOR MONDAY NIGHT  
AND TUESDAY. THE NEXT BEST CHANCE FOR PRECIPITATION WILL ARRIVE  
MIDWEEK.  
 

 
   
SHORT TERM (THROUGH 00Z THURSDAY)
 
 
A RIDGE AMPLIFIES OVERHEAD TODAY BRINGING BENIGN WEATHER. PATCHY  
FOG WILL REMAIN POSSIBLE ACROSS OUTLYING INVERTED VALLEYS THROUGH  
MID MORNING.  
 
THE SENSIBLE WEATHER WILL BE DRIVEN IN THE SHORT TERM BY THE  
EVOLUTION OF VALLEY INVERSIONS, WITH A STRONG SUBSIDENCE  
INVERSION NOTED ON THE KSLC RAOB NEAR 710MB LAST EVENING. AFTER A  
COLD START DUE TO THE RECENT SNOWPACK AND MOSTLY CLEAR CONDITIONS,  
TEMPERATURES ACROSS MANY OUTLYING VALLEYS WILL STRUGGLE TO WARM  
ABOVE FREEZING TODAY.  
 
MID AND HIGH CLOUDS ARE EXPECTED TO INCREASE TONIGHT, THOUGH THERE  
WILL BE ANOTHER OPPORTUNITY FOR FOG DEVELOPMENT ACROSS OUTLYING  
INVERTED VALLEYS BEFORE THE CLOUDS THICKEN LATER IN THE NIGHT.  
 
A WEAK PACIFIC SYSTEM DRAWS IN MOISTURE MONDAY, WITH PRECIPITABLE  
WATER VALUES INCREASING BEYOND 200% OF NORMAL DUE TO THE  
SUBTROPICAL JET RACING ACROSS THE SOUTHWEST CONUS. THE PASSING  
TROUGH MONDAY NIGHT AND TUESDAY HAS TRENDED TO SHOW AN INCREASE  
IN COLD ADVECTION COMPARED TO GUIDANCE LAST NIGHT. THEREFORE GIVEN  
THE MOISTURE CONTENT IN THE COLUMN, THE CHANCE FOR PRECIPITATION  
DURING THIS PERIOD APPEARS TO BE A BIT GREATER THAN SEEN LAST  
NIGHT, DESPITE THE LACK OF A NOTABLE JET IN THE REGION.  
 
THERE IS QUITE A SPREAD IN GUIDANCE WHEN IT COMES TO THE DEPTH OF  
THE NEXT TROUGH TUESDAY NIGHT AND WEDNESDAY. THE GFS IS COLDEST  
AMONG OPERATIONAL MODELS. THE GEFS SHOW SUBSTANTIAL SPREAD, WITH  
SOME MEMBERS JUST AS WARM AS THE OTHER GUIDANCE. GIVEN THIS, HAVE  
KEPT THE FORECAST CLOSER TO THE IDEA OF THE EUROPEAN, WHICH SLIDES  
THE BULK OF THE DYNAMICS TO OUR NORTHEAST DUE TO A MORE AMPLIFIED  
WEST COAST RIDGE.  
 
NEVERTHELESS, GIVEN THE MOISTURE CONTENT OF THE COLUMN, AND  
PROXIMITY TO BETTER DYNAMICS ALONG WITH ANOTHER SHOT OF MODEST  
COLD ADVECTION, THE LATE TUESDAY NIGHT AND WEDNESDAY MORNING  
PERIOD APPEARS TO BE THE BEST OPPORTUNITY FOR PRECIPITATION. A  
RAIN/SNOW MIX IS EXPECTED FOR VALLEYS, TRENDING TO ALL SNOW WITH  
SNOW LEVELS FALLING TO THE VALLEY FLOOR WEDNESDAY. LIGHT VALLEY  
ACCUMULATIONS ARE POSSIBLE, WITH THE POTENTIAL OF SEVERAL INCHES  
OF FRESH SNOW IN THE NORTHERN MOUNTAINS.  
   
LONG TERM (AFTER 00Z THURSDAY)
 
 
AS THE MIDWEEK'S TROUGH SLIDES EASTWARD DURING THE BEGINNING OF  
THE LONG TERM FORECAST, A PERIOD OF RIDGING IS EXPECTED TO DEVELOP  
OVER THE GREAT BASIN REGION THROUGH A MAJORITY OF THE WEEKEND.  
WHILE BOTH THE EPS AND GEFS POINT TOWARD THIS PERIOD OF RIDGING,  
THERE ARE SOME SUBTLE DIFFERENCES THAT MAY MAKE OR BREAK THE  
CHANCE OF SEEING ANY PRECIPITATION OVER THE WEEKEND. THE GEFS  
SOLUTION SUPPORTS A MUCH MORE AMPLIFIED RIDGE TO THE WEST OF OUR  
CWA, WHICH WOULD FAVOR A DRY NORTHWEST FLOW ALOFT THROUGH THE  
WEEKEND. ON THE OTHER HAND, THE EPS SUPPORTS A LESS AMPLIFIED  
RIDGE WITH ITS AXIS SHIFTED FURTHER EASTWARD. EMBEDDED SHORTWAVE  
DISTURBANCES ROLLING OVER THIS RIDGE FROM A RELATIVELY ACTIVE  
NORTHEAST PACIFIC PATTERN MAY PACK ENOUGH ENERGY TO STIR UP SOME  
SHOWERS OVER THE FAR NORTHERN PORTIONS OF UTAH ON FRIDAY AND  
SATURDAY. HAVE STUCK WITH POPS FROM THE NBM OVER THE WEEKEND TO  
ILLUSTRATE THIS CHANCE FOR SOME SHOWERS ACROSS NORTHERN UTAH.  
 
MODEL GUIDANCE SUGGESTS A TROUGH TO QUICKLY DEVELOP OFF THE NORTH  
COAST OF CALIFORNIA BY THE END OF THE LONG TERM PERIOD, POTENTIALLY  
WORKING ITS WAY INLAND BY SUNDAY NIGHT. IT SEEMS AS THOUGH MORE  
RECENT MODEL RUNS ARE SLOWING THE PROGRESSION OF THIS TROUGH,  
HOWEVER, COULD STILL SEE SOME SHOWERS BY LATE SUNDAY. AGAIN, THE  
GEFS AND EPS DEPICT DIFFERENT PHASES AND AMPLITUDES OF THIS FEATURE  
THAT WILL LIKELY BE KEYED IN ON IN THE COMING DAYS.  
 

 
   
AVIATION
 
 
VFR CONDITIONS WILL BE MAINTAINED AT THE SLC TERMINAL THROUGH THE  
VALID TAF PERIOD UNDER PARTLY CLOUDY SKIES. LIGHT SOUTHERLY  
DRAINAGE WINDS ARE EXPECTED TO REVERT BACK TO NORTHERLY AROUND  
18Z.  
 

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

 
 

 
 
SHORT TERM...10  
LONG TERM/AVIATION...WEBBER  
 
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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