250
FXUS65 KSLC 091123
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
423 AM MST THU JAN 9 2025
SYNOPSIS
A COOL NORTHERLY FLOW WILL PREVAIL ACROSS THE REGION
TODAY. THE NEXT STORM SYSTEM WILL CROSS THE AREA OVER THE WEEKEND,
BRINGING A POTENTIAL FOR ACCUMULATING SNOWFALL TO PORTIONS OF
NORTHERN AND CENTRAL UTAH.
SHORT TERM (THROUGH 00Z SATURDAY/5PM FRIDAY)
A LONGWAVE RIDGE
SITUATED JUST OFF THE PACIFIC COAST CONTINUES TO MAINTAIN A COOL
NORTHERLY FLOW ALOFT ACROSS THE GREAT BASIN. A SHORTWAVE EMBEDDED
WITHIN THIS FLOW IS DIGGING THROUGH THE FOUR CORNERS REGION EARLY
THIS MORNING, ENHANCING LOW LEVEL COLD AIR ADVECTION ACROSS
SOUTHWEST UTAH, AND RESULTING IN A FAVORABLE SETUP FOR GUSTY GAP
WINDS ACROSS PORTIONS OF WASHINGTON COUNTY. THIS SETUP WILL
PERSIST THROUGH THE DAY TODAY, AND GOING WIND ADVISORY HANDLES
THIS WELL. IN THE WAKE OF THIS WAVE, MAX TEMPS TODAY WILL RUN
NEAR TO SLIGHTLY BELOW SEASONAL NORMS ACROSS THE NORTH, AND
ROUGHLY 5F BELOW ACROSS SOUTHERN UTAH.
MID LEVEL RIDGING WILL BUILD INLAND AND INTO THE GREAT BASIN
TONIGHT THROUGH FRIDAY, AS A PROGRESSIVE SHORTWAVE TROUGH
APPROACHES THE PACIFIC COAST. AS THIS RIDGE TEMPORARILY BUILDS
INLAND WARMING TEMPERATURES ALOFT WILL BE REALIZED ACROSS THE
HIGHER ELEVATIONS, AS WELL AS WELL MIXED AREAS OF SOUTHWEST UTAH
SUCH AS CEDAR CITY. HOWEVER MOST VALLEYS WILL LIKELY BECOME
TEMPORARILY INVERTED, WITH LITTLE IN THE WAY OF WARMING REALIZED
ALONG THE WASATCH FRONT AND MOST NORTHERN, CENTRAL AND EASTERN
VALLEYS.
LONG TERM (AFTER 00Z SATURDAY/5PM FRIDAY)
FORECAST FOR THE
UPCOMING WEEKEND STORM REMAINS ON TRACK THIS MORNING AS MODELS
CONTINUE TO SHOW SOLID AGREEMENT ON A TROUGH DIVING THROUGH THE
REGION FROM THE PACNW. RECENT MODEL TRENDS HAVE NOTED A SLIGHTLY
EARLIER INTRODUCTION OF A SURFACE COLD FRONT INTO NORTHERN UTAH ON
FRIDAY EVENING, HOWEVER, ONSET OF PRECIPITATION STILL LOOKS TO
ARRIVE AFTER THE COMMUTING HOURS (MOST WIDESPREAD ARRIVING AFTER 7PM
ON FRIDAY). WITH A BULK OF THE MOISTURE ARRIVING AFTER SUNDOWN AND A
COLDER ANTECEDENT AIRMASS, SNOWFALL FOR THE LOWER ELEVATION VALLEYS
IN NORTHERN UTAH (I.E. THE WASATCH FRONT) WILL SEE A VERY HIGH
PROBABILITY (>90%) OF SEEING SNOW THROUGH THE DURATION OF THE EVENT.
WITH A GENERAL LACK OF MOISTURE AVAILABILITY AND A QUICKLY
PROGRESSING FRONTAL BOUNDARY, THINKING THAT THE VALLEY AREAS WILL
SEE MINIMAL IMPACTS FROM ACCUMULATION SNOW. THAT SAID, MOST LIKELY
ACCUMULATION RANGES (25TH TO 75TH PERCENTILE) RANGE FROM ABOUT 0.1
TO 2 INCHES FOR THE WASATCH FRONT AND CACHE VALLEY AREAS, AND 1 TO 4
INCHES ON THE WASATCH BACK WITH LOCALLY UP TO 6 INCHES IN THE PARK
CITY AREA. FOR THE MOUNTAINS OF NORTHERN UTAH, WIDESPREAD 3 TO 6
INCHES WITH LOCALLY UP TO 12 INCHES IN THE UPPER COTTONWOODS WILL BE
THE MOST LIKELY SCENARIO, WITH AMOUNTS DECREASING SIGNIFICANTLY
SOUTH OF THE MT. NEBO AREA. THINKING THAT THE WASATCH MOUNTAINS FROM
SALT LAKE COUNTY NORTHWARD WILL SEE THE HIGHEST IMPACT THROUGH THIS
STORM AS THESE AREAS WILL BE THE MOST LIKELY TO SEE SNOW TOTALS
TOWARD THE 75TH PERCENTILE RANGE. WILL NEED TO CONSIDER HEADLINES
FOR THIS AREA AFTER COORDINATION WITH CORE PARTNERS.
A MAJORITY OF THE SNOWFALL IS EXPECTED BETWEEN FRIDAY EVENING AND
SATURDAY EVENING, HOWEVER, SHORTWAVE ENERGY TRANSLATING THROUGH THE
LONGWAVE TROUGH PAIRED WITH LOW LEVEL MOISTURE COULD KEEP
PRECIPITATION GOING IN THE MOUNTAINS OF NORTHERN UTAH THROUGH AT
LEAST SUNDAY. FOR THE VALLEY AREAS, SHOULD SEE THINGS TAPER OFF BY
SATURDAY EVENING. THE EXCEPTION HERE WILL BE THE VALLEY AREAS
ADJACENT TO LARGE TERRAIN (WASATCH MOUNTAINS) AND THE SALT LAKE AREA
(WHICH SHOWS POTENTIAL TO SEE LAKE EFFECT SHOWERS).
FOR SALT LAKE COUNTY SPECIFICALLY, INCLUDING THE MOUNTAINS, THE 75TH
AND 90TH PERCENTILE ACCUMULATIONS COULD BE A VERY REAL POSSIBILITY
DUE TO POST-FRONTAL GREAT SALT LAKE INDUCED SNOWFALL. WILL NEED TO
SEE HOW THE HIGH RESOLUTION MODELS HANDLE THE CONVECTIVE POTENTIAL,
HOWEVER, 700MB TEMPERATURES WILL BE PLENTY COLD TO SUPPORT SURFACE
BASED CONVECTION OVER THE LAKE. WILL WE GET THE CORRECT WIND
ALIGNMENT? WILL THERE BE ENOUGH LOW LEVEL MOISTURE TO SUPPORT
CONVECTION? THESE ARE ALL QUESTIONS THAT WILL BECOME MORE CLEAR IN
THE NEXT 24-36 HOURS. TO GIVE AN IDEA OF THE REASONABLE WORST CASE
SCENARIO, NBM 90TH PERCENTILE SNOWFALL IN THE SALT LAKE VALLEY
RANGES FROM AROUND 2-4 INCHES ON THE VALLEY FLOOR TO UPWARDS OF 6
INCHES ON THE EAST BENCH. FOR THE MOUNTAINS, THESE NUMBERS ARE
UPWARDS OF 18 INCHES. AGAIN, THIS WILL BE DEPENDENT ON HOW
PRODUCTIVE THE POST-FRONTAL ENVIRONMENT BECOMES.
OUTSIDE OF THE SNOWFALL POTENTIAL, THE PROGRESSION OF THE COLD FRONT
IS LIKELY TO BRING INCREASING NORTHWEST WINDS WITH GUSTS INTO THE 20-
30 MPH RANGE ACROSS THE WESTERN HALF OF UTAH ON SATURDAY, AND
POTENTIALLY HIGHER IN THE CASTLE COUNTY REGION AND THE I-15 CORRIDOR
BETWEEN CEDAR CITY AND ST. GEORGE. NOT EXPECTING A NEED FOR WIND
HEADLINES IN THESE AREAS AT THIS TIME, BUT WILL CONTINUE TO MONITOR
TRENDS IN THE MODELED WINDS GOING FORWARD.
A CUTOFF LOW LOOKS TO FORM OVER THE SOUTHWESTERN U.S. AS THE
NORTHERN BRANCH TROUGH DEPARTS TO THE EAST, WHICH CREATES A BIT OF
UNCERTAINTY IN THE FORECAST PAST TUESDAY. NOT EXPECTED ANY
SIGNIFICANT WEATHER IMPACTS FROM THIS SETUP, JUST SOME UNCERTAINTY
WITH LIGHT SHOWERS. IF THE LOW PINCHES OFF CLOSER TO UTAH, WE'LL SEE
PRECIPITATION STICK AROUND FOR LONGER, WHILE A CUTOFF FARTHER TO THE
SOUTH WILL ALLOW FOR A BREAK. IN ADDITION TO UNCERTAINTY IN THE
PRECIPITATION FORECAST, THE TEMPERATURE FORECAST IS ALSO GOING TO
TAKE A HIT. CURRENT NBM 10TH TO 90TH PERCENTILE TEMPERATURE OUTPUT
FOR KSLC SHOWS ABOUT 10 DEGREES OF SPREAD, WITH THE HIGH END PUSHING
INTO THE LOW 50S. WILL BE CURIOUS TO SEE WHERE MODELS TREND OVER THE
NEXT 24-48 HOURS.
AVIATION...KSLC
VFR CONDITIONS WILL BE MAINTAINED OVER THE KSLC
TERMINAL THROUGH THE VALID TAF PERIOD. NORTHERLY WINDS ARE EXPECTED
TO PREVAIL THROUGH THE DAY, WITH A RETURN TO SOUTHERLY FLOW FORECAST
THIS EVENING AROUND 04Z. THERE IS ABOUT A 20-30% CHANCE THAT FULL
SOUTHERLY FLOW DOES NOT DEVELOP, AND WE END UP WITH VARIABLE FLOW
THROUGH THE OVERNIGHT.
REST OF UTAH AND SOUTHWEST WYOMING
VFR CONDITIONS ARE EXPECTED
ACROSS UTAH AND SOUTHWEST WYOMING THROUGH THE NEXT 24 HOURS. STRONG
NORTH TO NORTHEAST WINDS ARE EXPECTED ACROSS SOUTHERN AND EASTERN
UTAH THIS AFTERNOON, WITH GUSTS OF UPWARDS OF 40 MPH (MAINLY IN
EASTERN UTAH).
SLC WATCHES/WARNINGS/ADVISORIES
UT...WIND ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR UTZ123.
WY...NONE.
SEAMAN/WEBBER
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
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