670
FXUS65 KSLC 172217
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
417 PM MDT SAT MAY 17 2025
SYNOPSIS
A COLD, WINTER-LIKE SYSTEM WILL IMPACT THE REGION
THROUGH MONDAY. HIGH PRESSURE WILL BUILD INTO THE AREA MIDWEEK,
BRINGING MUCH WARMER TEMPERATURES AND A RETURN TO SUMMER.
DISCUSSION
AN UPPER TROUGH WILL CONTINUE TO DEEPEN ACROSS THE
GREAT BASIN THIS EVENING BEFORE SWINGING ACROSS UTAH LATE TONIGHT
INTO TOMORROW. AHEAD OF THIS TROUGH, A MILD SOUTHWESTERLY FLOW ALOFT
IS CURRENTLY IN PLACE OVER UTAH. SOME STRONGER GUSTS TO AROUND 40+
MPH ARE NOTED ACROSS WEST-CENTRAL AND SOUTHWEST UTAH, BUT WINDS HAVE
REMAINED BELOW ADVISORY CRITERIA, ESPECIALLY AS ABUNDANT CLOUD COVER
HAS LIMITED THE EXTENT OF MIXING.
ACROSS NORTHERN UTAH, DIFFLUENT FLOW ALOFT HAS AIDED ASCENT TO
PRODUCE SCATTERED SHOWERS. INSTABILITY HAS BEEN FAIRLY MODEST,
HOWEVER, DUE IN PART TO THE CLOUD COVER IN PLACE. AS SUCH,
THUNDERSTORM ACTIVITY HAS BEEN RELATIVELY LIMITED, WITH THE
STRONGEST STORMS THUS FAR HAVING BEEN LOCATED ACROSS FAR NORTHEAST
UTAH AND SOUTHWEST WYOMING EARLIER ALONG THE LEADING EDGE OF THE
CLOUD COVER. THERE IS EXPECTED TO BE A BIT OF AN UPTICK IN
THUNDERSTORMS LATE THIS AFTERNOON INTO THIS EVENING NEAR THE FRONTAL
BAND, WITH GUSTY AND ERRATIC WINDS THE MAIN THREAT. ALTHOUGH THERE
IS A THREAT FOR SEVERE THUNDERSTORMS, THIS THREAT WILL BE A BIT
LIMITED GIVEN THE AFOREMENTIONED MODEST INSTABILITY ALONG WITH
RELATIVELY WEAK (FOR THIS AREA) DCAPE.
THE SURFACE FRONT HAS ALREADY MOVED INTO NORTHWEST UTAH AND SHOULD
REACH SLC BEFORE 00Z. HOWEVER, H7 BAROCLINIC ZONE WILL TRAIL THE
SURFACE FEATURE AND WILL NOT REALLY BECOME SUBSTANTIAL UNTIL LATER
TONIGHT, GENERALLY AFTER MIDNIGHT. HEAVIER PRECIPITATION IS EXPECTED
NEAR THIS BAROCLINIC ZONE. WITH THE COLDER AIR SPREADING INTO THE
AREA, SNOW LEVELS WILL FALL AND REACH AS LOW AS 7000-7500 FT
TOMORROW. BY TOMORROW LATE MORNING OR AFTERNOON, THE FRONTAL BAND
WILL SHIFT EAST OF THE AREA BUT OROGRAPHIC PRECIPITATION WILL THEN
CONTINUE FOR NORTHWEST-FACING ASPECTS AS A MOIST NORTHWEST FLOW
REMAINS IN PLACE. LOCALLY SIGNIFICANT VALLEY RAIN AND MOUNTAIN SNOW
IS EXPECTED FOR THE MOUNTAINS (MAINLY SOUTH OF I-80) AND ALONG THE
WASATCH FRONT AND I-15 CORRIDOR. PRECIPITATION TOTALS COULD EXCEED 1
INCH OF WATER IN SOME AREAS, WITH 6-12 INCHES IN MANY MOUNTAIN
AREAS (LOCALLY UP TO 15 INCHES).
PRECIPITATION WILL WIND DOWN TOMORROW EVENING. HOWEVER, A TRAILING
DISTURBANCE IS FORECAST TO ROTATE INTO UTAH LATE TOMORROW NIGHT INTO
MONDAY MORNING. THERE IS STILL SOME MODEL SPREAD REGARDING THE
LOCATION AND EXTENT OF PRECIPITATION ASSOCIATED WITH THIS FEATURE,
BUT FOR THE MOST PART, IT LOOKS TO BE A QUICK-HITTER FOR WEST-
CENTRAL AND SOUTHWEST UTAH WITH JUST MINOR ADDITIONAL SNOWFALL IN
THE MOUNTAINS. OTHERWISE, COLDER AIR WILL SETTLE INTO THE AREA
TOMORROW NIGHT AND AGAIN ON MONDAY NIGHT. SOME OUTLYING AREAS COULD
SEE FREEZING TEMPERATURES, WHICH COULD AFFECT EARLY-SEASON
AGRICULTURE.
HIGH PRESSURE WILL GRADUALLY BUILD INTO THE AREA BY MIDWEEK,
REMAINING IN PLACE THROUGH LATE WEEK. THIS IS NOT A HIGHLY AMPLIFIED
RIDGE, AS A SERIES OF WEAK DISTURBANCES RIPPLE BY NORTH OF UTAH.
HOWEVER, THESE DISTURBANCES WILL REMAIN FAR ENOUGH NORTH TO HAVE
VERY LITTLE TO NO IMPACTS ON UTAH. RATHER, WARMER AND DRIER
CONDITIONS CAN BE EXPECTED DURING THIS TIMEFRAME.
EXISTING HEADLINES REMAIN IN PLACE. HOWEVER, OPTED TO SHIFT TO AN
EARLIER ONSET FOR THE WINTER WEATHER ADVISORY IN THE CENTRAL AND
SOUTHERN MOUNTAINS GIVEN LATEST MODEL TRENDS. ALSO, ADDED THE
WESTERN UINTA BASIN TO THE FREEZE WATCH.
AVIATION....KSLC
BUILDING CUMULUS AND ASSOCIATED SHOWERS WILL
CONTINUE TO DEVELOP THIS AFTERNOON AHEAD OF A COLD FRONT APPROACHING
THE REGION. THERE REMAINS AN APPROXIMATELY 30% CHANCE OF LIGHTNING
WITHIN VICINITY OF THE TERMINAL LATE THIS AFTERNOON THROUGH MID
EVENING, OTHERWISE PREDOMINANTLY VFR CONDITIONS ARE EXPECTED INTO
THE EVENING THOUGH WITH LOWERING CIGS AND INCREASING RAIN CHANCES.
SOUTHERLY WINDS WILL SWITCH TO NORTHWESTERLY BETWEEN 23Z AND 01Z,
WITH A BETTER CHANCE OF THE SWITCH OCCURRING EARLIER IN THAT WINDOW.
SHOWERS WILL BECOME HEAVIER AND MORE FREQUENT OVERNIGHT, WITH A
PERIOD OF MODERATE TO HEAVY RAIN EXPECTED BETWEEN AROUND 12Z AND 18Z
(WITH A 30% CHANCE OF LINGERING FOR SEVERAL HOURS BEYOND 18Z). THIS
HEAVIER PRECIPITATION IS LIKELY TO BE ACCOMPANIED BY MVFR CIGS/VSBYS
AND TERRAIN OBSCURATIONS, WITH ABOUT A 20% OF CONDITIONS FURTHER
DETERIORATING TO IFR IF THE HEAVIER PRECIPITATION SHOWN IN SOME
MODELS MATERIALIZES.
REST OF UTAH AND SOUTHWEST WYOMING
INCREASING SHOWER/THUNDERSTORM
COVERAGE TODAY FROM WEST TO EAST ASSOCIATED WITH AN APPROACHING COLD
FRONT. AHEAD OF THE FRONT, EXPECT GUSTY SOUTH WINDS AREA WIDE THIS
AFTERNOON/EVENING. IN ADDITION, NORTHERN UTAH AND SOUTHWEST WYOMING
WILL HAVE A HIGHER THREAT OF GUSTY/ERRATIC WINDS DUE TO HIGH-BASED
SHOWER AND THUNDERSTORM OUTFLOWS THIS AFTERNOON AND EVENING.
ALONG/BEHIND THE FRONT, THERE IS HIGH CONFIDENCE IN INCREASING RAIN
SHOWERS AND MOUNTAIN OBSCURATION WITH MEDIUM (50%) CHANCES FOR MVFR
CIGS. THERE IS A 20-30% CHANCE FOR IFR CIGS SATURDAY NIGHT-SUNDAY
MORNING, ESPECIALLY OVER NORTHERN UTAH ALONG THE I-15 CORRIDOR. THE
ONLY EXCEPTION TO THE CHANCES LISTED ABOVE IS KSGU TO KKNB AND
EASTWARD TO LAKE POWELL WHEREIN THE PROBABILITIES ARE MUCH LOWER.
FIRE WEATHER
A MILD SOUTHWESTERLY FLOW WILL TRANSITION TO MORE
NORTHWESTERLY TONIGHT INTO TOMORROW AS A STRONG COLD FRONT MOVES
INTO THE AREA. AHEAD OF IT, EXPECT INCREASING SHOWERS WITH ISOLATED
TO WIDELY SCATTERED EMBEDDED THUNDERSTORMS TO INCREASE THIS EVENING.
GUSTY AND ERRATIC WINDS WILL BE LIKELY WITH SHOWERS AND
THUNDERSTORMS, WITH A SMALL (10%) CHANCE OF LOCALIZED GUSTS GREATER
THAN 55 MPH THROUGH ACROSS NORTHERN UTAH EARLY THIS EVENING. WITH
THE COOLER AIR MOVING IN, SNOW LEVELS WILL FALL TO AROUND 7000-7500
FEET BY TOMORROW. EXPECT WIDESPREAD LOCALLY MODERATE TO HEAVY VALLEY
RAIN AND MOUNTAIN SNOW AS A RESULT TONIGHT THROUGH TOMORROW.
PRECIPITATION WILL DECREASE BY TOMORROW EVENING, BUT A TRAILING
WEATHER DISTURBANCE MAY BRING ANOTHER QUICK ROUND OF VALLEY RAIN AND
MOUNTAIN SNOW TO MAINLY CENTRAL AND SOUTHERN UTAH EARLY MONDAY.
THEREAFTER, HIGH PRESSURE WILL GRADUALLY BUILD BACK INTO THE AREA,
WITH TEMPERATURES TRENDING WARMER AND THE AIRMASS DRIER FOR THE
MIDDLE THROUGH LATTER PART OF NEXT WEEK.
SLC WATCHES/WARNINGS/ADVISORIES
UT...FREEZE WATCH FROM SUNDAY EVENING THROUGH MONDAY MORNING FOR
UTZ103-107-114>116-118-122.
WINTER WEATHER ADVISORY FROM 3 AM TO 6 PM MDT SUNDAY FOR
UTZ110>113-117-125.
WY...NONE.
CHENG/VAN CLEAVE
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