429  
FXUS65 KSLC 081032  
AFDSLC  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SALT LAKE CITY UT  
432 AM MDT WED APR 8 2020  
   
SYNOPSIS
 
THE LOW PRESSURE SYSTEM OFF THE SOUTHERN CALIFORNIA  
COAST WILL TURN EAST AND ADVANCE INTO EXTREME SOUTHERN NEVADA BY  
LATE THURSDAY. SOMEWHAT COOLER AND WET CONDITIONS WILL IMPACT  
MUCH OF UTAH THROUGH MIDWEEK, WITH DRIER CONDITIONS RETURNING LATE  
IN THE WEEK.  
 

 
   
SHORT TERM (THROUGH 12Z SATURDAY)
 
THE UPPER LOW CURRENTLY  
POSITIONED JUST OFF THE SOUTHERN CALIFORNIA COAST WILL MOVE INLAND  
LATER THIS AFTERNOON. FROM THERE THIS LOW WILL TRACK SLOWLY EAST-  
NORTHEAST, REACHING EXTREME SOUTHERN NEVADA BY LATE THURSDAY.  
 
THE INITIAL PRECIPITATION ASSOCIATED WITH THE ADVANCING UPPER LOW  
COULD REACH INTO EXTREME SOUTHWEST UTAH BY LATE THIS AFTERNOON.  
SHORTWAVE ENERGY ROTATING NORTH AHEAD OF THE LOW THROUGH WESTERN  
ARIZONA WILL CLIP THE SOUTHWEST CORNER BY LATE AFTERNOON. SOMEWHAT  
COOLER AIR AT THE MID-LEVELS ASSOCIATED WITH SHORTWAVE ALONG WITH  
DECENT SURFACE HEATING WILL LIKELY BRING A MODEST INCREASE TO  
INSTABILITY ACROSS THE SOUTHWEST WHEN THE SHORTWAVES PASSES  
THROUGH THE AREA.  
 
ANTICIPATING A RAPID INCREASE IN SYNOPTIC-SCALE LIFT ACROSS SOUTHERN  
THROUGH WEST-CENTRAL UTAH TONIGHT. STRONG, DEEP LAYER THERMAL  
ADVECTION AND INCREASING DYNAMIC LIFT FROM THE APPROACHING LOW  
WILL LEAD TO AN EXPANDING AREA OF LIGHT TO MODERATE PRECIP  
OVERNIGHT. LOCALLY HEAVIER CONVECTIVE PRECIP WILL BE POSSIBLE THIS  
EVENING AS THE NOSE OF THE JET REACHES INTO NORTHWEST ARIZONA AND  
EXTREME SOUTHWEST UTAH.  
 
THE LOW-LEVEL BAROCLINIC ZONE THAT MOVED NORTH THROUGH SOUTHERN  
UTAH OVERNIGHT WILL LIKELY HOLD TOGETHER AS ROTATES INTO NORTHERN  
UTAH THURSDAY. SOLID CONVERGENCE INTO THIS LOW-LEVEL BOUNDARY  
WITH DYNAMIC SUPPORT FROM VORTICITY LOBES ROTATING AROUND UPPER  
LOW POSITION SHOULD GENERATE A BAND OF LIGHT/MODERATE PRECIP  
ALONG AND JUST NORTH OF THE BAROCLINIC ZONE THURSDAY AFTERNOON AND  
EVENING. SOUTH OF THIS BOUNDARY COLD AIR INSTABILITY ALONG WITH  
DYNAMIC SUPPORT FOR LIFT IN PROXIMITY TO THE UPPER LOW SHOULD  
MAINTAIN SHOWERY PRECIP ACROSS PORTIONS OF SOUTHERN AND CENTRAL  
UTAH THROUGH EARLY THURSDAY EVENING.  
 
THE DETERMINISTIC MODEL GUIDANCE CONTINUES TO SHOW A GRADUAL  
SOUTHWEST DRIFT TO THE LOW CENTER THURSDAY NIGHT THROUGH FRIDAY  
MORNING BEFORE THIS FEATURES EJECTS EAST ACROSS SOUTHERN ARIZONA  
FRIDAY AFTERNOON. THE DEFORMATION AXIS ALONG THE NORTHERN FLANK OF  
THE LOW WILL REACH NORTH TO AROUND THE UTAH/ARIZONA REGION FRIDAY  
AFTERNOON/EVENING. SHOWERY PRECIP ALONG AND SOUTH OF THE  
DEFORMATION WILL LIKELY REMAIN ACROSS NORTHERN ARIZONA, THOUGH  
SUSPECT A FEW SHOWERS WILL DRIFT IN AND OUT OF EXTREME SOUTHERN  
UTAH DURING THE AFTERNOON/EARLY EVENING HOURS. DRIER AND MORE  
STABLE CONDITIONS WILL MOVE INTO UTAH FROM THE NORTH LATER FRIDAY  
NIGHT.  
 
   
LONG TERM (AFTER 12Z SATURDAY)
 
HIGH PRESSURE WILL BE CENTERED OFF  
THE PACIFIC COAST TO START THE FORECAST PERIOD, BUT A FEW DIFFERENT  
STORM SYSTEMS ARE EXPECTED TO MOVE OVER THE TOP OF THIS RIDGE TO  
IMPACT THE WEATHER OVER UTAH AND SOUTHWEST WYOMING. THE FIRST ONE  
LOOKS LIKE IT WILL IMPACT THE AREA SOMETIME BETWEEN LATE SATURDAY  
INTO EARLY MONDAY. OVERALL SPREAD IN THE GUIDANCE HAS DECREASED  
NOTICEABLY COMPARED TO THIS TIME YESTERDAY, SO CONFIDENCE IS  
INCREASING IN A SIGNIFICANT COOLDOWN FOR MUCH OF THE AREA BEGINNING  
SUNDAY. MAXES ON SUNDAY ARE EXPECTED TO RUN AT LEAST 5F BELOW  
SEASONAL NORMALS, AFTER RUNNING UP TO 10F ABOVE THOSE VALUES ON  
SATURDAY. SOME PRECIP IS ALSO ANTICIPATED, PARTICULARLY FOR  
NORTHEASTERN PORTIONS OF THE FORECAST AREA, BUT MOISTURE WITH THIS  
SYSTEM LOOKS A BIT LIMITED, WHICH IS OFTEN THE CASE WITH BACK DOOR  
SYSTEMS.  
 
AFTER A BRIEF BREAK IN THE ACTION ON MONDAY, ANOTHER TROUGH IS  
EXPECTED TO SLIDE OVER THE TOP OF THE RIDGE INTO THE AREA TUESDAY  
INTO WEDNESDAY. SPREAD IN THE GUIDANCE IS HIGHER WITH THIS SYSTEM  
THAN THE PREVIOUS, ESPECIALLY WITH REGARD TO ITS PRECISE TRACK,  
HOWEVER IT SEEMS THIS SYSTEM WILL BE MUCH WEAKER THAN THE FIRST ONE.  
 

 
   
AVIATION
 
THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGHOUT THE  
DAY WITH MOSTLY CLEAR SKIES. SOUTHEAST WINDS ARE EXPECTED TO SHIFT  
TO THE NORTHWEST BETWEEN 17Z AND 19Z.  
 

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

 
 

 
 
CONGER/TRAPHAGAN  
 
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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