963  
FXUS65 KSLC 171019  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
419 AM MDT THU JUL 17 2025  
   
SYNOPSIS
 
MONSOONAL MOISTURE WILL SPREAD NORTHWARD INTO THE AREA  
THROUGH FRIDAY. THIS WILL BRING AN INCREASING THREAT OF HEAVY  
RAINFALL ACROSS THE AREA, PARTICULARLY FOR SOUTHERN UTAH. A DRYING  
TREND WILL DEVELOP BY EARLY NEXT WEEK.  
 

 
   
SHORT TERM (THROUGH 12Z/6AM SATURDAY)
 
HIGH PRESSURE IS STARTING  
TO RE-AMPLIFY OVER THE GREAT BASIN THIS MORNING AS A CLOSED LOW  
MOVES NORTHWARD ALONG THE BAJA CALIFORNIA COAST. THE BUILDING  
RIDGE IS SHIFTING THE FLOW ALOFT OVER UTAH AND SOUTHWEST WYOMING  
TO A SOUTHERLY DIRECTION, ALLOWING MONSOONAL MOISTURE TO BE DRAWN  
NORTHWARD. THIS INCREASE IN MOISTURE IS ALREADY EVIDENT, WITH  
SATELLITE DERIVED PW VALUES IN THE 0.9 TO 1.1 INCH RANGE OVER  
SOUTHERN UTAH, HIGHEST NEAR THE UTAH/ARIZONA BORDER, WITH VALUES  
IN THE 0.6 TO 0.8 INCH RANGE ELSEWHERE. IN THIS RATHER MOIST  
AIRMASS, WILL SEE A RATHER NOTICEABLE INCREASE IN COVERAGE OF  
SHOWERS AND THUNDERSTORMS, PRIMARILY FOR SOUTHERN UTAH, WITH SOME  
MORE FAVORABLE DYNAMICS EXPECTED TO BE PROVIDED THIS AFTERNOON BY  
A COUPLE OF WEAK SHORTWAVES RIPPLING THROUGH. THUS, SEEING A  
HEIGHTENED THREAT OF STORMS WITH HEAVY RAIN CAPABLE OF FLASH  
FLOODING, AND HAVE INCREASED THE FLASH FLOOD POTENTIAL TO PROBABLY  
FOR A GOOD PORTION OF SOUTHERN UTAH.  
 
THE MOISTURE WILL CONTINUE TO SPREAD NORTHWARD THROUGH FRIDAY.  
HOWEVER, THE NORTHWARD SPREAD OF THE MOISTURE WILL ACT TO BRING  
PWS DOWN A BIT ACROSS SOUTHERN UTAH. GUIDANCE IS INDICATING PWS  
PRIMARILY IN THE 0.8 TO 1.0 INCH RANGE ACROSS ALL OF UTAH AND  
SOUTHWEST WYOMING BY FRIDAY AFTERNOON. BY THIS POINT, THE BAJA LOW  
IS EXPECTED TO BE AROUND SOUTHERN CALIFORNIA AS ANOTHER SYSTEM  
MOVES ONSHORE ALONG THE PACIFIC NORTHWEST COAST. A BOUNDARY IS  
EXPECTED TO DEVELOP BETWEEN THESE TWO FEATURES OVER NORTHERN UTAH  
THAT COULD ACT AS THE FOCUS FOR CONVECTION FRIDAY AFTERNOON,  
THOUGH COVERAGE OF CONVECTION SHOULD BE HIGH OVER SOUTHERN UTAH AS  
WELL.  
   
LONG TERM (AFTER 12Z/6AM SATURDAY)
 
BY SATURDAY, A LONGWAVE TROUGH  
WILL DIG INTO WESTERN CANADA, WHILE AN EXPANSIVE RIDGE OF HIGH  
PRESSURE FROM THE SOUTHERN PLAINS INTO THE SOUTHEAST U.S. AMPLIFIES.  
FLOW FOR THE REGION WILL BECOME MORE SOUTHWEST, WHICH WILL ADVECT  
DRIER AIR INTO SOUTHWEST WYOMING AND UTAH. EXPECT SLIGHTLY LESS  
COVERAGE OF SHOWERS AND THUNDERSTORMS THAN PRIOR IN THE WEEK, BUT  
ENOUGH MOISTURE AND FORCING WILL BE IN PLACE FOR GUSTY, ERRATIC  
OUTFLOW WINDS AND LOCALIZED FLASH FLOODING IF A THUNDERSTORM  
PRODUCING HEAVY RAIN TRACKS INTO A VULNERABLE LOCATION.  
 
THE LONGWAVE TROUGH WILL DIG INTO THE PACNW SUNDAY, WHILE RIDGING TO  
THE SOUTHEAST AMPLIFIES. THIS SET UP WILL BRING A DOWNTREND IN  
PRECIPITATION, WITH MOST SHOWERS AND THUNDERSTORMS ISOLATED AND  
AROUND MOUNTAINOUS TERRAIN. THE APPROACHING LONGWAVE TROUGH WILL  
ENHANCE SOUTHWEST FLOW. SOUTHWEST WINDS WILL LIKELY BE BELOW RED  
FLAG WARNING CRITERIA, BUT GUSTS WILL LIKELY TOP OUT AROUND 25 MPH  
FOR SOUTHWEST UTAH. RELATIVE HUMIDITY WILL RANGE FROM AROUND 10-20%.  
 
CRITICAL FIRE WEATHER CONDITIONS BECOME MORE LIKELY MONDAY AS THE  
LONGWAVE TROUGH WILL DIG SLIGHTLY FURTHER SOUTH AND THE RIDGE TO THE  
SOUTHEAST WILL BE LARGELY UNCHANGED. FLOW WILL BE WEST TO SOUTHWEST,  
GUSTING IN EXCESS OF 25 MPH THROUGHOUT SOUTHWEST WYOMING AND MOST OF  
WESTERN UTAH. RELATIVE HUMIDITY VALUES WILL LIKELY RANGE FROM THE  
SINGLE DIGITS TO TEENS.  
 
ENSEMBLES VARY ON THE TRACK OF THE LONGWAVE TROUGH INTO THE WEEK,  
WITH SOME MEMBERS BREAKING OFF A CLOSED LOW THAT WOULD TRACK  
SOUTHWEST TO OFF THE WEST COAST. OTHER MEMBERS SLIDE THE TROUGH  
EASTWARD, WITH IT REMAINING NORTH OF UTAH. THE RIDGE TO THE  
SOUTHEAST WILL LIKELY RETROGRADE INTO THE WEEK, WHICH WILL ALLOW FOR  
LIGHTER WINDS. IT WOULD ALSO BRING BETTER MOISTURE ADVECTION, WITH  
MORE OF A SOUTHERLY FLOW. MODELS AND ENSEMBLES ARE IN GOOD AGREEMENT  
ON THAT, WITH A GENERAL UPTREND IN PRECIPITABLE WATER VALUES TUESDAY  
THROUGH MUCH OF THE WEEK.  
 
VALLEY HIGH TEMPERATURES FROM THE WEEKEND THROUGH MUCH OF THE WEEK  
WILL BE NEAR NORMAL IN THE LOW OR MID 90S.  
 

 
   
AVIATION...KSLC
 
MOSTLY CLEAR CONDITIONS WILL LAST INTO THE  
AFTERNOON. LIGHT SOUTHEAST WINDS WILL INCREASE AROUND 15Z, WITH  
GUSTS AROUND 20 KNOTS THROUGH 19Z. WINDS WILL TRANSITION TO  
NORTHWEST AROUND 19Z. CLOUDS WILL INCREASE AFTER 21Z, WITH ISOLATED  
SHOWERS OR THUNDERSTORMS CAPABLE OF GUSTY, ERRATIC OUTFLOW WINDS.  
   
REST OF UTAH AND SOUTHWEST WYOMING
 
SCATTERED AFTERNOON SHOWERS  
AND THUNDERSTORMS, PRIMARILY IN SOUTHERN UTAH, WILL BE CAPABLE OF  
GUSTY, ERRATIC OUTFLOW WINDS AND LOCALLY HEAVY RAIN FROM 18-00Z. VFR  
CONDITIONS WILL PREVAIL FOR SOUTHERN UTAH, BUT EXPECT BROKEN OR  
OVERCAST CLOUDS. CLOUDS WILL INCREASE INTO NORTHERN UTAH AFTER 21Z,  
WITH ISOLATED SHOWERS OR THUNDERSTORMS CAPABLE OF GUSTY, ERRATIC  
OUTFLOW WINDS THROUGH 00Z.  
 

 
   
FIRE WEATHER
 
WITH SOUTHERLY FLOW ACROSS THE AREA, MONSOONAL  
MOISTURE WILL BE DRAWN UPWARD INTO THE AREA FROM SOUTH TO NORTH  
THROUGH FRIDAY. THE PRESENCE OF THIS MOISTURE WILL BRING  
INCREASING COVERAGE OF AFTERNOON AND EVENING SHOWERS AND  
THUNDERSTORMS WITH A HIGHER POTENTIAL FOR WETTING RAINS,  
PARTICULARLY ON FRIDAY. MOISTURE COULD BEGIN TO DECREASE AS EARLY  
AS SATURDAY, WITH A MORE PRONOUNCED DRYING TREND EXPECTED TO  
COMMENCE ON SUNDAY.  
 

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

 
 

 
 
SHORT TERM/FIRE WEATHER...TRAPHAGAN  
LONG TERM/AVIATION...WILSON  
 
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...  
HTTP://WEATHER.GOV/SALTLAKECITY  
 
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