294  
FXUS65 KSLC 180948  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
348 AM MDT THU SEP 18 2025  
   
SYNOPSIS  
DRY AND WARM CONDITIONS CAN BE EXPECTED OVER THE AREA  
TODAY. MOISTURE RETURNS TO THE AREA TONIGHT INTO THE WEEKEND,  
WITH INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS.  
 
 
   
SHORT TERM (THROUGH 12Z SATURDAY)  
THE MEAN UPPER LOW CENTERED  
OVER THE NORTHERN PLAINS WILL CONTINUE TO SHIFT EAST TODAY, ALLOWING  
FOR A SHORTWAVE RIDGE TO BUILD INTO UTAH. THIS RIDGE WILL RESULT IN  
WARMER AND DRY CONDITIONS ACROSS THE AREA TODAY WITH GENERALLY LIGHT  
WINDS. AFTERNOON MAX TEMPERATURES ARE EXPECTED TO TREND NEAR TO JUST  
SLIGHTLY ABOVE CLIMATOLOGICAL NORMALS. MEANWHILE, UPSTREAM, A STORM  
SYSTEM THAT HAS INGESTED TROPICAL SYSTEM REMNANTS IS CHURNING OFF  
THE SOCAL COAST.  
 
AS THE SHORTWAVE RIDGE SHIFTS EASTWARD TONIGHT, SOUTH TO  
SOUTHWESTERLY FLOW DEVELOPING OVER UTAH WILL DRAW MOISTURE FROM THE  
UPSTREAM SYSTEM INTO THE AREA. MODELS SHOW PWATS INCREASING FAIRLY  
RAPIDLY THIS EVENING. FOR EXAMPLE, ACROSS THE SOUTHWEST CORNER OF  
UTAH, ENSEMBLE MEAN PWATS FROM THE HREF IS FORECAST TO RISE FROM  
BETWEEN 0.4-0.5 INCHES AROUND 18Z TO 0.9-1.0+ INCHES BY 06Z. THIS  
MOISTURE, COUPLED WITH INCREASED FORCING FROM THE APPROACHING STORM  
SHOULD BRING SHOWERS TO THE AREA BEGINNING WITH SOUTHWEST UTAH  
TONIGHT BEFORE SPREADING INTO AT LEAST CENTRAL UTAH AND POTENTIALLY  
FARTHER NORTH THROUGH THE DAY FRIDAY. THE INITIAL ROUND OF SHOWERS  
ARE LIKELY TO REMAIN HIGH-BASED AND PRODUCE GUSTY MICROBURST WINDS.  
THEN, AS THE LOWER LEVELS CONTINUE TO MOISTEN, HEAVIER RAIN MAY  
BECOME MORE LIKELY WITH THE STRONGER STORMS.  
 
MODEL SPREAD IS MAKING THE TIMING OF THE ONSET OF SHOWERS AS WELL AS  
THE LOCATION OF ANY STRONGER STORMS DIFFICULT AT THIS POINT.  
FURTHERMORE, SOME HREF MEMBERS INSIST THAT OVERNIGHT AND EARLY  
MORNING SHOWERS ACROSS SOUTHWEST UTAH WILL LEAVE THAT AREA LARGELY  
SUPPRESSED BY PEAK DAYTIME HEATING FRIDAY AFTERNOON, DESPITE MEAN  
HREF SBCAPE VALUES OF 250-750J/KG. WPC HAS AN EXCESSIVE RAINFALL  
OUTLOOK OF MARGINAL ACROSS SOUTHWEST UTAH FOR FRIDAY, WHICH IS NOT  
UNREASONABLE, BUT IS CONDITIONAL ON HAVING SHOWERS IN THE FIRST  
PLACE.  
   
LONG TERM (AFTER 12Z/6AM SATURDAY)  
ABOVE-NORMAL MOISTURE WILL BE  
IN PLACE AT THE START OF THE LONG-TERM PERIOD, REACHING UP TO 200%  
OF NORMAL ACROSS WESTERN UTAH (150% ACROSS EASTERN UTAH/SOUTHWEST  
WYOMING). MID-LEVEL FLOW WILL BE LARGELY ZONAL ON SATURDAY, THOUGH  
WEAK SYNOPTIC DYNAMICS FROM A 80-90KT JET STREAK AND SUBTLE  
SHORTWAVE TROUGH WILL HELP SCATTERED SHOWERS AND THUNDERSTORMS TO  
DEVELOP ACROSS THE FORECAST AREA BY SATURDAY AFTERNOON. DESPITE  
APPRECIABLE COLUMN MOISTURE, MODEL SOUNDINGS ACTUALLY SUGGEST THAT  
DRIER AIR WILL MOVE INTO THE MID LEVELS ACROSS THE STATE,  
POTENTIALLY LIMITING CONVECTIVE DEVELOPMENT AND FLASH FLOOD  
POTENTIAL. BY SUNDAY, THIS TREND WILL CONTINUE, WITH MOST CONVECTION  
EXPECTED ACROSS NORTHERN UTAH AND PRIMARILY OVER HIGHER TERRAIN  
GIVEN AN OVERALL LACK OF SYNOPTIC LIFT.  
 
BY LATE SUNDAY, A GRAZING TROUGH WILL ADVECT MUCH DRIER AIR INTO THE  
REGION, WITH PWATS DIPPING DOWN TO 50% OF NORMAL BY LATE MONDAY.  
INTERESTINGLY, THERE ARE STILL ROUGHLY 20% OF ENSEMBLE MEMBERS THAT  
ACTUALLY FAVOR A STRONGER TROUGH OVERHEAD INSTEAD OF JUST GRAZING  
OUR AREA; THIS COULD PRODUCE COOLER AND WETTER CONDITIONS TO START  
THE WORK WEEK, IF THIS SCENARIO WERE TO PAN OUT. HIGH PRESSURE WILL  
THEN BUILD OVER UTAH BEHIND THIS TROUGH, THOUGH FORECAST CONFIDENCE  
DECREASES SIGNIFICANTLY AFTER TUESDAY. MODELS CAN AGREE ON THE  
DEVELOPMENT OF A CUTOFF LOW OVER SOCAL, BUT THEY DIVERGE GREATLY  
WITH REGARDS TO WHERE/WHEN THIS LOW MOVES BY MID-WEEK. ULTIMATELY,  
THIS WILL IMPACT HOW LONG HIGH PRESSURE RESIDES OVER OUR AREA. BY  
DAY 7/THURSDAY, NOW 61% OF ENSEMBLE MEMBERS FAVOR HIGH PRESSURE  
STILL OVERHEAD, WITH OR WITHOUT AN STRONG UPSTREAM TROUGH. ANOTHER  
23% FAVOR A WEAK TROUGH, WHILE THE REMAINING 16% ARE STILL HANGING  
ONTO A POTENT TROUGH OVER THE WESTERN US...LOWER THAN WHERE CHANCES  
WERE YESTERDAY.  
 
 
   
AVIATION...KSLC  
LIGHT, SOUTHEASTERLY WINDS WILL CONTINUE THROUGH  
THE MORNING, LIKELY TRANSITIONING TO NORTHWESTERLY AROUND ~20-21Z,  
WITH A LOW CHANCE OF OCCURRING AS EARLY AS 19Z. VFR CONDITIONS WILL  
PREVAIL WITH CLEAR SKIES. HIGH CLOUDS WILL BEGIN TO MOVE INTO THE  
AREA BY THURSDAY EVENING.  
   
REST OF UTAH AND SOUTHWEST WYOMING  
WINDS WILL REMAIN LARGELY  
LIGHT AND TERRAIN-DRIVEN THROUGH THE VALID TAF PERIOD, THE EXCEPTION  
BEING AN INCREASE IN WESTERLY WINDS NEAR KSGU THURSDAY EVENING AHEAD  
OF SOME RAIN SHOWERS. WHILE MOST LOCATIONS WILL BE DRY WITH CLEAR  
SKIES, HIGH-BASED SHOWERS COULD MOVE INTO KSGU AS EARLY AS 23Z AND  
KCDC AS EARLY AS 02Z, WITH GUSTY OUTFLOW WINDS BEING THE MAIN THREAT.  
 
 
   
FIRE WEATHER  
HIGH PRESSURE OVER THE AREA TODAY WILL RESULT IN  
WARMER AND DRY CONDITIONS ACROSS THE AREA. AS THIS HIGH PRESSURE  
MOVES EAST OF THE AREA, SOUTH TO SOUTHWEST FLOW WILL DRAW MOISTURE  
INTO THE AREA BEGINNING TONIGHT AND INTO THE WEEKEND. EXPECT SHOWERS  
AND THUNDERSTORMS TO BE POSSIBLE ACROSS SOUTHWEST UTAH TONIGHT,  
SPREADING INTO CENTRAL AND POTENTIALLY PORTIONS OF NORTHERN UTAH  
DURING THE DAY FRIDAY. SHOWERS NEAR THE LEADING EDGE OF THE MOISTURE  
SURGE WILL MORE LIKELY RESULT IN ISOLATED DRY LIGHTNING AND GUSTY  
MICROBURST WINDS. WITH SURFACE HUMIDITIES INCREASING, WETTING RAIN  
CHANCES WILL GRADUALLY INCREASE THROUGH THE DAY. BY SATURDAY AND  
SUNDAY, PRECIPITATION CHANCES WILL BECOME INCREASINGLY FOCUSED OVER  
NORTHERN UTAH. DRIER AIR WILL THEN SPREAD BACK INTO UTAH EARLY NEXT  
WEEK. ANOTHER ROUND OF MOISTURE WILL BE POSSIBLE BY THE MIDDLE OF  
NEXT WEEK, BUT WITH SIGNIFICANT MODEL SPREAD, CONFIDENCE REMAINS ON  
THE LOW SIDE FOR NOW.  
 
 
   
SLC WATCHES/WARNINGS/ADVISORIES  
 
UT...NONE.  
WY...NONE.  
 
 
 
 
CHENG/CUNNINGHAM  
 
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