238  
FXUS65 KSLC 242139  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
339 PM MDT WED MAY 24 2017  
   
SYNOPSIS
 
A COLD FRONT WILL SAG SOUTH THROUGH NORTHERN UTAH  
TONIGHT PRIOR TO STALLING OVER CENTRAL UTAH THURSDAY AS AN  
UPPER TROUGH NOSES INTO THE AREA. A SECONDARY TROUGH WILL  
MOVE ACROSS THE AREA FRIDAY MAINTAINING UNSETTLED CONDITIONS  
INTO THE FIRST HALF OF THE HOLIDAY WEEKEND.  
 

 
   
SHORT TERM (THROUGH 12Z SATURDAY)
 
MSAS MSLP ANALYSIS PLACES A  
COLD FRONT STRETCHING FROM EXTREME NW WYOMING SE ACROSS CENTRAL  
IDAHO. AFTERNOON WATER VAPOR AND H5 ANALYSIS INDICATES THE CORE OF  
THE UPPER TROUGH ITS TIED TO CONTINUES TO DEEPEN OVER SOUTHERN  
ALBERTA. A SHORT WAVE LOBE DEVELOPING ALONG THE WESTERN PERIPHERY  
OF THIS TROUGH WILL DROP SOUTHEAST INTO NORTHERN UTAH DRIVING THIS  
FRONT SOUTH OVERNIGHT PRIOR TO STALLING ACROSS CENTRAL PORTIONS  
OF THE AREA DURING THE DAY TOMORROW.  
 
PRIMARY CONCERN MOVING FORWARD RELATES TO PRE-FRONTAL CONVECTION  
ATTEMPTING TO TAKE FORM ATTM. MID LEVEL MOISTURE CONTINUES TO  
INCREASE WHILE ADVECTING IN FROM THE SW COINCIDENT WITH THE  
SOUTHERN BRANCH JET. DEEP MIXING COMBINED WITH A VERY DRY BOUNDARY  
LAYER CONTINUES TO ENHANCE AN INVERTED-V SIGNATURE IN VERTICAL  
PROFILES, AND COUPLED WITH WEAK INSTABILITY AND MODEST SHEAR (BOTH  
GREATEST OVER THE FAR NORTH), DO EXPECT A CONTINUED UPTICK IN  
CELLULAR DEVELOPMENT INTO THIS EVENING. HRRR-3KM CONTINUES TO  
DEVELOP CONVECTION OVER EASTERN NV OVER THE NEXT FEW HOURS, THEN  
TRANSLATES IT ENE ACROSS THE WASATCH FRONT PERIODICALLY BETWEEN  
00-06Z. GUSTY MICROBURST WINDS WILL BE THE PRIMARY THREAT, WITH  
SOME ISOLATED SEVERE SPEEDS POSSIBLE (ESPECIALLY WEST DESERT).  
 
AREAL COVERAGE OF SHOWERS/CONVECTION IS EXPECTED TO INCREASE  
THROUGH THE MIDDLE OF THE NIGHT TIED CLOSELY TO THE AREA OF BEST  
BAROCLINICITY SHIFTING NW-SE ACROSS NORTHERN UTAH/SW WY, PRIOR TO  
SLOWLY PHASING AWAY TOWARDS DAWN OVER CENTRAL PORTIONS AS THE  
FRONT STALLS AND TRENDS MORE DIFFUSE. WITH LOSS OF UPPER SUPPORT  
FOR THE TIME BEING, ANY CONVECTION THURSDAY WILL LIKELY REMAIN  
ISOLATED AND ONCE AGAIN TIED TO THE REMNANT BOUNDARY, OR SPARKED  
BY DIURNAL INFLUENCES OVER THE MOUNTAINS DURING THE PEAK HEATING  
HOURS.  
 
TEMPS THIS AFTERNOON HAVE BEEN THE WARMEST YET THUS FAR THIS WARM  
SEASON (KSLC JUST HIT 89 F), BUT CAA IN WAKE OF FRONTAL PASSAGE  
WILL COOL THE NORTHERN HALF OF THE AREA DOWN TO NEAR NORMAL  
LEVELS OVER THE NEXT 24 HOURS. GUSTY SW WINDS WILL REMAIN SOUTH  
OF THE FRONTAL BOUNDARY AS WELL ACROSS THE SOUTH TOMORROW, BUT ARE  
EXPECTED TO REMAIN SUB-ADVISORY.  
 
THE AFOREMENTIONED NORTHERN ROCKIES TROUGH WILL CONTINUE TO SPIN  
UP THROUGH FRIDAY, WITH ANOTHER SHORT WAVE LOBE DROPPING INTO THE  
AREA FROM THE NORTHWEST DURING THE DAY. BAROCLINICITY WILL ONCE  
AGAIN TIGHTEN OVER THE AREA, AND COUPLED WITH MODEST UPPER FORCING  
AND DIURNAL TRENDS DO EXPECT SCATTERED CONVECTION TO DEVELOP  
ACROSS THE NORTHERN HALF OF THE AREA ONCE AGAIN. MADE MINIMAL  
CHANGES TO POPS AS FORECAST TRENDS REMAIN ON TRACK.  
   
LONG TERM (AFTER 12Z SATURDAY)
 
A MID LEVEL RIDGE IS FORECAST TO  
BE THE DOMINANT WEATHER FEATURE THROUGH THE MAJORITY OF THE FORECAST  
PERIOD. INITIALLY THIS RIDGE WILL REMAIN CENTERED WEST OF THE  
FORECAST AREA ALONG THE WEST COAST, AS THE LAST IN A SERIES OF  
SHORTWAVE TROUGHS EXITS THE FORECAST AREA DURING THE DAY SATURDAY.  
AFTER THIS TIME, AS THE RIDGE AXIS SLOWLY BUILDS EASTWARD, EXPECT A  
WARMING TREND THROUGH THE LATTER HALF OF THE WEEKEND INTO THE MIDDLE  
PART OF NEXT WEEK. LINGERING MOISTURE WILL PROVIDE A SMALL CHANCE OF  
AFTERNOON AND EVENING CONVECTION PRIMARILY ALONG THE TERRAIN EAST OF  
I-15. THE LONG RANGE MODELS DIVERGE A BIT DURING THE  
WEDNESDAY/THURSDAY TIMEFRAME, WITH THE GFS BREAKING DOWN THE  
RIDGE, WHILE THE EC HOLDS ONTO A STRONGER RIDGING SOLUTION OVER  
THE GREAT BASIN. AS SUCH HAVE HELD OFF ON MAKING ANY SIGNIFICANT  
CHANGES TO THE LATTER PORTION OF THE FORECAST PERIOD.  
 

 
   
AVIATION
 
MAIN CONCERNS AT KSLC THIS AFTERNOON/EVENING WILL BE THE  
POTENTIAL FOR STRONG (>30 KTS.) ERRATIC MICROBURST WINDS...WITH  
THESE WINDS MOST LIKELY BETWEEN 23-03Z. SOME LIGHTNING IS ALSO  
POSSIBLE WITH THESE AFTERNOON/EVENING STORMS BUT PRECIPITATION  
SHOULD BE MINIMAL. AWAY FROM STORMS VFR CONDITIONS AND NORTHWEST  
WINDS SHOULD PREVAIL THROUGH THE PERIOD.  
 

 
   
FIRE WEATHER
 
UPPER LEVEL STORM SYSTEM WITH ATTENDANT COLD FRONT  
CONTINUES TO ENCROACH ON NORTHERN UTAH THIS AFTERNOON, WITH  
FRONTAL ZONE PASSAGE ANTICIPATED TO ENTER THE FAR NORTH LATER THIS  
EVENING. ISOLATED SHOWERS AND STORMS ARE BEGINNING TO FIRE AHEAD  
OF THIS FRONT ATTM, AND EXPECT AREAL COVERAGE TO INCREASE AND PEAK  
BY MID EVENING. HIGH BASED NATURE OF STORMS AND VERY DRY LOW  
LEVELS WILL PROMOTE A GUSTY MICROBURST THREAT ACROSS THE NORTHERN  
THIRD OF THE DISTRICT THIS EVENING, AND THE MIDDLE THIRD OVERNIGHT  
COINCIDENT WITH THE FRONT.  
 
THE FRONTAL BOUNDARY WILL STALL ACROSS CENTRAL UTAH THURSDAY  
MAINTAINING IN GENERAL AN ISOLATED SHOWER/STORM THREAT, BUT WILL  
THEN PUSH SOUTH FRIDAY ACROSS THE REMAINDER OF THE DISTRICT WITH  
WIDELY SCATTERED SHOWERS/STORMS EXPECTED. TRENDS IN RH WILL CLIMB  
BEGINNING TONIGHT.  
 
GUSTY SOUTHWESTERLY WINDS ARE EXPECTED TO CONTINUE SOUTH OF THE  
FRONT TOMORROW, WITH SOME SITES ALONG THE UT/AZ BORDER REGION  
GUSTING AT TIMES AROUND 30 MPH IN THE AFTERNOON.  
 

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

 
 

 
 
MERRILL/SEAMAN/CARR  
 
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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