817
FXUS65 KSLC 102308
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
408 PM MST FRI JAN 10 2025
SYNOPSIS
A WINTER STORM WILL IMPACT NORTHERN AND CENTRAL UTAH
THIS WEEKEND, WITH COLD, DRY AIRMASS BUILDING INTO THE REGION FOR
EARLY NEXT WEEK.
SHORT TERM (THROUGH 00Z MONDAY)
A QUICK BUT POTENT SYSTEM WILL
BRING ACCUMULATING SNOW TO PORTIONS OF NORTHERN AND CENTRAL UTAH
THROUGH SATURDAY AFTERNOON, WITH A PERIOD OF HEAVY MOUNTAIN SNOW
EXPECTED NEAR AND ALONG THE COLD FRONT LATER THIS EVENING INTO
EARLY SATURDAY MORNING. MIX IN LAKE EFFECT/LAKE ENHANCED SNOW
POTENTIAL AND IT LOOKS LIKE A TRADITIONAL UTAH SNOWSTORM.
EARLY AFTERNOON UPPER AIR AND SATELLITE ANALYSIS INDICATES A SHARP
SHORTWAVE TROUGH PROGRESSING INTO THE GREAT BASIN, WITH A BROAD
UPPER LEVEL RIDGE ACROSS THE EASTERN PACIFIC. THIS SHORTWAVE
TROUGH WILL BEGIN TO SPLIT ACROSS UTAH. THE MAJORITY OF ENSEMBLE
MEMBERS SUPPORT A COHESIVE TROUGH CROSSING NORTHERN AND CENTRAL
UTAH, HOWEVER A SUBSET DO SHOW THIS SPLIT OCCURRING EARLIER, WITH
A DRIER, LESS IMPACTFUL FRONTAL BAND MOVING THROUGH UTAH. FOR NOW,
OUR FORECAST LEANS ON THE MAJORITY OF THE ENSEMBLE MEMBERS, NOT
THE OUTLIER SOLUTION...BUT IT REMAINS A POSSIBILITY, EVEN IF A LOW
CHANCE OUTCOME.
AS THE FRONT CROSSES THROUGH THE NORTHERN MOUNTAINS, A PERIOD OF
MODERATE TO HEAVY MOUNTAIN SNOW IS EXPECTED...ALONG WITH A 1-2
HOUR OR SO PERIOD OF SNOW FOR THE ADJACENT VALLEYS. UNLIKE MANY
PREVIOUS STORMS, THIS ONE WILL NOT STRUGGLE WITH SNOW
LEVEL/PRECIPITATION TYPE ISSUES...WITH TEMPERATURES COLD ENOUGH TO
SHIFT TO SNOW AT ONSET. NOTABLY, MOST NORTHERN VALLEYS ARE SEEING
DEWPOINTS IN THE LOW 20S TO UPPER TEENS, WHICH MAY RESULT IN
LOWER PRECIPITATION AMOUNTS DUE TO INITIAL NEED TO MOISTEN THE
LOWER ATMOSPHERE.
WITH VERY COLD 700MB TEMPERATURES, SOMEWHERE AROUND -12 TO -14C,
A SUFFICIENT TEMPERATURE DIFFERENCE WILL EXIST BETWEEN THE GSL AND
THE COLDER AIRMASS TO SUPPORT AT LEAST LAKE ENHANCED
PRECIPITATION. LOOKING AT 700MB FLOW, EXPECT INITIAL LAKE
EFFECT/LAKE ENHANCED PRECIPITATION TO IMPACT AREAS SOUTHEAST OF
THE GSL EARLY SATURDAY MORNING, INCLUDING THE COTTONWOOD CANYONS
AND PORTIONS OF THE EAST BENCH. MAJORITY OF THE GUIDANCE SUGGESTS
A SHIFT TO MORE NORTH TO NORTH-NORTHWEST FLOW WITHIN A FEW HOURS
OF GENESIS, BRINGING THE BAND SLOWLY THROUGH SALT LAKE COUNTY AND
INTO EASTERN TOOELE COUNTY.
THIS WOULD LIKELY ENHANCE SNOW TOTALS FOR THE COTTONWOODS,
DEPENDING ON RESIDENCE TIME. CURRENT GUIDANCE WOULD SUPPORT AT
LEAST SEVERAL ADDITIONAL INCHES IN HEAVIER SNOW...FOLLOWED BY A
GENERAL SHIFT TOWARD THE EASTERN TOOELE VALLEY. CURRENT FORECAST
IS A BLEND OF GUIDANCE, BUT INDICATES EAST BENCH, SOUTHERN AND
SOUTHWESTERN SALT LAKE, EASTERN TOOELE COUNTY AND FAR NORTHERN
UTAH COUNTY (TOWNS SUCH AS SARATOGA SPRINGS, HIGHLAND, ALPINE AND
LEHI) MAY APPROACH OR EXCEED WINTER WEATHER ADVISORY CRITERIA.
FOR NOW, HELD OFF DUE TO LOW CONFIDENCE (RESIDENCE
TIME/ORIENTATION OF LAKE EFFECT/LAKE ENHANCEMENT IS NOTORIOUSLY
DIFFICULT TO FORECAST), BUT EVENING SHIFT WILL MONITOR 00Z OUTPUT
AND CONSIDER WHETHER TO ADD WINTER WEATHER ADVISORIES TO THESE
LOCATIONS AS WELL AS THE GREATER PARK CITY AREA. ISSUED WINTER
WEATHER ADVISORIES FOR THE NORTHERN AND CENTRAL MOUNTAINS.
GUSTY WINDS ARE LIKELY ACROSS THE GREAT SALT LAKE DESERT AND
MOUNTAINS, ESPECIALLY DOWNWIND OF THE RAFT RIVERS, THE PILOT RANGE
AND NEAR WENDOVER. THERE IS SOME POTENTIAL WINDS MAY APPROACH
50-55 MPH. HELD OFF ON ANY WIND ADVISORIES POST-FRONTAL EARLY
SATURDAY MORNING DUE TO CONFIDENCE AND RELATIVELY SMALL AREA OF
IMPACT. SIMILARLY, EXPECT STRONG WINDS ALONG RIDGELINES TO REMAIN
ANCHORED TO THE TERRAIN ACROSS CENTRAL AND SOUTHERN UTAH.
PATCHY BLOWING SNOW WILL BE A THREAT NEAR THE I-84 CORRIDOR
BETWEEN TREMONTON TO SNOWVILLE, ACROSS LOGAN SUMMIT, ACROSS THE
CACHE VALLEY AND NEAR STRAWBERRY RESERVOIR. IN COORDINATION WITH
UDOT, ADDED PATCHY BLOWING SNOW TO THE FORECAST IN THESE AREAS.
SNOW SHOWERS ARE LIKELY TO CONTINUE IN NORTHWEST FLOW INTO SUNDAY,
ESPECIALLY ACROSS THE NORTHERN MOUNTAINS.
LONG TERM (AFTER 00Z MONDAY)
BESIDES A FEW MOUNTAIN SNOW
SHOWERS ACROSS NORTHERN UTAH ON MONDAY MORNING FROM A TRAILING
SHORTWAVE, THE LONG TERM PERIOD WILL LIKELY BE DRY AND COLD. A REX
BLOCK PATTERN WILL SET UP OFF THE WEST COAST AS A LOW CUTS OFF
THE CALIFORNIA COAST AND A RIDGE BUILDS INTO THE PNW. THIS WILL
BLOCK ANY TROUGHS FROM MOVING INTO OUR AREA THROUGH LATE NEXT
WEEK.
WITH THE COLDEST AIR OF THE SEASON ARRIVING WITH THIS UPCOMING
TROUGH (H7 TEMPS ~-14C) EXPECT VERY COLD CONDITIONS FOR THE FIRST
HALF OF THE WEEK WITH HIGHS STRUGGLING TO GET ABOVE FREEZING FOR
MOST LOCATIONS OUTSIDE OF FAR SOUTHERN UTAH. TEMPERATURES MONDAY,
TUESDAY, AND WEDNESDAY MORNING WILL BE VERY COLD IN THE SINGLE
DIGITS AND TEENS ACROSS MOST AREAS. EVEN TEMPERATURES ACROSS FAR
SOUTHERN UTAH WILL BE IN THE MID TO LOW 20S. THIS WILL POSE A
THREAT FOR UNSHELTERED POPULATIONS.
TEMPERATURES WILL GRADUALLY BEGIN TO WARM TOWARDS THE SECOND HALF
OF THE WEEK AS A RIDGE BUILDS INTO THE PNW. THIS WARMING ALOFT
COULD LEAD TO SOME TEMPERATURE INVERSIONS ACROSS MOST VALLEYS
WEDNESDAY AND THURSDAY. THESE INVERSIONS SHOULD BE SHORT LIVED AS
A TROUGH TO THE NORTH APPROACHES LATE FRIDAY INTO SATURDAY AND THE
CUTOFF LOW STARTS TO MIGRATE INLAND AND INCREASE FLOW ALOFT. THE
AFOREMENTIONED TROUGH WILL BE THE NEXT CHANCE FOR PRECIPITATION
ACROSS THE REGION, BUT THE CONTINENTAL NATURE OF THE TROUGH LIKELY
WON'T HAVE TOO MUCH MOISTURE WITH IT.
AVIATION...KSLC
SOUTHERLY WINDS WILL CONTINUE UNTIL A COLD
FRONT ARRIVES AROUND 07-08Z, TRANSITIONING WINDS TO NORTHWESTERLY.
A FEW LIGHT SNOW SHOWERS ARE POSSIBLE AFTER 03Z, THOUGH THE MOST
IMPACTFUL SNOW IS EXPECTED TO OCCUR BETWEEN 07-12Z, WITH MVFR
CIGS/VIS AND INTERMITTENT IFR CIGS/VIS. THERE IS A CHANCE THAT
THESE CONDITIONS LAST BEYOND 12Z IF LAKE-EFFECT SNOW DEVELOPS OVER
THE SALT LAKE VALLEY (40% CHANCE); THIS POTENTIAL BAND WILL TREND
FURTHER WEST DURING THE MORNING HOURS IF IT DOES DEVELOP.
REST OF UTAH AND SOUTHWEST WYOMING
LIGHT SNOW WILL ENTER
NORTHWESTERN UT AROUND 00-01Z, WITH A COLD FRONT FOLLOWING BY
AROUND 05-06Z. THIS FRONT WILL PUSH ACROSS MUCH OF THE AREA DURING
THE OVERNIGHT HOURS, BRINGING MVFR-IFR SNOWFALL AND A TRANSITION
TO NORTHWESTERLY WINDS. MUCH OF THE SNOWFALL WILL WEAKEN BY THE
TIME IT REACHES THE SOUTHERN SITES, THOUGH VERY GUSTY NORTHERLY
WINDS ARE EXPECTED AT THESE SITES BY THE MORNING. LAKE-EFFECT SNOW
MAY DEVELOP ACROSS THE SALT LAKE VALLEY BY MORNING, MOVING
WESTWARD INTO THE TOOELE VALLEY BY MID DAY (40% CHANCE).
SLC WATCHES/WARNINGS/ADVISORIES
UT...WINTER WEATHER ADVISORY FROM 11 PM THIS EVENING TO 8 PM MST
SATURDAY FOR UTZ110>113.
WINTER WEATHER ADVISORY FROM 2 AM TO 5 PM MST SATURDAY FOR
UTZ117.
WY...NONE.
KRUSE/MAHAN/CUNNINGHAM
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
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