907
FXUS65 KSLC 180950
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
250 AM MST TUE FEB 18 2025
SYNOPSIS
A TROUGH WILL EXIT THE AREA THIS MORNING, ALLOWING
HIGH PRESSURE TO BRIEFLY RETURN LATER TUESDAY INTO EARLY
WEDNESDAY. ANOTHER STORM SYSTEM IS EXPECTED TO MOVE THROUGH THE
AREA WEDNESDAY AFTERNOON INTO THURSDAY, WITH A DRIER PATTERN
DEVELOPING THEREAFTER.
SHORT TERM (THROUGH 00Z THURSDAY)
AS THE BACK EDGE OF A PACIFIC
NORTHWEST TROUGH MOVES ACROSS NORTHERN UTAH AND SOUTHWEST WYOMING,
JUST A FEW SNOW SHOWERS CONTINUE, FOCUSED OVER THE HIGHER TERRAIN
OF NORTHERN UTAH. THE TROUGH WILL EXIT THE AREA BY AROUND MIDDAY,
WITH HIGH PRESSURE BUILDING IN BEHIND IT. ENOUGH MOISTURE WILL
PERSIST TO ALLOW SHOWERS TO LINGER OVER THE MOUNTAINS OF NORTHERN
UTAH INTO THE AFTERNOON BEFORE DISSIPATING. IN THE WAKE OF THE
SYSTEM, HIGH TEMPERATURES BOTH TODAY AND WEDNESDAY WILL BE RIGHT
AROUND SEASONAL NORMALS ACROSS THE FORECAST AREA. THE DRY
CONDITIONS WILL PERSIST INTO WEDNESDAY MORNING, BEFORE
PRECIPITATION STARTS TO DEVELOP AGAIN WITH THE NEXT APPROACHING
STORM SYSTEM, DISCUSSED FURTHER IN THE LONG TERM DISCUSSION.
LONG TERM (AFTER 00Z THURSDAY)
* LOW CONFIDENCE, BUT INCREASING POTENTIAL, FOR LIGHT SNOW
ACCUMULATIONS (20-30% CHANCE GREATER THAN AN INCH) FOR NORTHERN
AND CENTRAL UTAH VALLEYS LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING, WITH POTENTIAL IMPACTS TO THE THURSDAY MORNING COMMUTE.
* HIGH CONFIDENCE IN ACCUMULATING MOUNTAIN SNOW WEDNESDAY NIGHT INTO
THURSDAY MORNING, WITH ABOUT A 20-50% CHANCE OF EXCEEDING WINTER
WEATHER ADVISORY CRITERIA FOR THE WASATCH, BEAR RIVER, AND WESTERN
UINTA MOUNTAINS (HIGHEST POTENTIAL IN THE UPPER COTTONWOODS)
* HIGH CONFIDENCE IN A PERIOD OF ABOVE AVERAGE TEMPERATURES AND
BELOW AVERAGE PRECIPITATION FROM THIS WEEKEND INTO EARLY NEXT WEEK
THE MAIN TREND IN THE FORECAST OVER THE LAST DAY HAS BEEN A SLOWLY
INCREASING POTENTIAL FOR ACCUMULATING SNOW EARLY THURSDAY MORNING
FOR THE NORTHERN UTAH VALLEYS, AND THE CENTRAL UTAH VALLEYS TO A
LESSER EXTENT. STILL, FORECAST CONFIDENCE REMAINS LOW FOR VALLEY
IMPACTS. BREAKING THIS DOWN FURTHER, A SHORTWAVE TROUGH WILL BECOME
DISLODGED FROM THE MAIN JET STREAM AS IT TRACKS FROM THE PACIFIC
NORTHWEST TO THE FOUR CORNERS REGION WEDNESDAY THROUGH EARLY FRIDAY.
AS A RESULT, A MODESTLY COOL AIRMASS WILL ACCOMPANY THIS STORM
SYSTEM, AND THUS WILL RESULT IN A MARGINAL THERMODYNAMIC PROFILE FOR
THE NORTHERN UTAH VALLEYS. HOWEVER, TIME OF DAY IS LOOKING
INCREASINGLY FAVORABLE, WITH THE POTENTIAL PEAK IN PRECIPITATION
RATES OCCURRING DURING THE PRE-DAWN HOURS THURSDAY MORNING. COMBINE
THIS WITH A *SLIGHT* TREND TOWARD COOLER H7 TEMPERATURES MORE
QUICKLY THURSDAY MORNING (-7 TO -9C) IN THE RECENT ENSEMBLE SUITE,
AND THERE IS CERTAINLY AN INCREASING POTENTIAL FOR ACCUMULATING SNOW
IN THE VALLEYS. THE SECOND PIECE TO THE PUZZLE WILL BE DETERMINING
WHERE PRECIPITATION RATES WILL BE HIGHEST, AS DYNAMICAL COOLING AND
HIGHER RATES MAY BE NEEDED TO HELP OVERCOME THE OTHERWISE MARGINAL
TEMPERATURES. WHILE ENSEMBLES ARE LOCKED IN ON THIS TROUGH PASSAGE
AND GENERAL TIMING, THERE REMAINS AN NUMBER OF FINE SCALE DETAILS TO
IRON OUT WHICH WILL HELP DICTATE WHERE THOSE HIGHER RATES MAY BE
ABLE TO MATERIALIZE. TO BOIL THIS ALL DOWN, THE RANGE IN
PRECIPITATION TOTALS RANGES FROM JUST A FEW HUNDREDTHS OF WATER, TO
AROUND 0.3" INCHES OF WATER, OR A REASONABLE RANGE OF SNOW TOTALS
FROM AROUND A TRACE TO 3 INCHES OR SO OF SNOW.
FOR THE NORTHERN UTAH MOUNTAINS, THERE IS NO MYSTERY THAT THE
PRECIPITATION WILL COME AS ACCUMULATING SNOW, BUT THE AFOREMENTIONED
FINE SCALE DETAILS IN HOW THE WAVE PASSAGE OCCURS WILL DICTATE WHICH
LOCATIONS FAIR THE BEST/WORST WITH SNOW TOTALS. CURRENTLY THERE IS
ABOUT A 20-50% CHANCE OF EXCEEDING ADVISORY LEVEL SNOW (9 INCHES IN
THE WASATCH / BEAR RIVERS, AND 6 INCHES IN THE WESTERN UINTAS), WITH
THE HIGHEST LOCALIZED POTENTIAL IN THE UPPER COTTONWOODS (>60%),
WHERE FAVORABLE COLD ADVECTION, MOIST, NORTHWEST FLOW WILL LINGER
THROUGH THE DAY ON THURSDAY, BEFORE DRIER AIR FINALLY WORKS IN FROM
THE WEST LATE THURSDAY. THIS WOULD TRANSLATE TO A 25TH - 75TH
PERCENTILE RANGE OF ABOUT 3-10 INCHES FOR THE MOUNTAINS, AND LOCALLY
6-14 INCHES FOR THE UPPER COTTONWOODS.
AFTER THIS STORM SYSTEM DEPARTS, THERE IS HIGH CONFIDENCE IN A RIDGE
BUILDING ACROSS THE WESTERN US THIS WEEKEND THROUGH AT LEAST MID
NEXT WEEK. THIS WILL BRING ABOVE AVERAGE TEMPERATURES AND BELOW
AVERAGE PRECIPITATION. THE ONLY SCENARIO THAT COULD BRING SOME
LIMITED MOISTURE TO FAR NORTHERN UTAH BY MONDAY AND TUESDAY NEXT
WEEK IS A FLATTER RIDGE WITH MOISTURE SNEAKING AROUND THE NORTH SIDE
OF THE RIDGE. HOWEVER THIS IS ONLY REPRESENTED IN ABOUT 15% OF
ENSEMBLE SOLUTIONS, AND THUS THIS CORRELATES TO THE ~15% POPS IN THE
FAR NORTHERN UTAH MOUNTAINS. OUTSIDE OF THIS LOW-END POTENTIAL IN
THE NORTHERN MOUNTAINS, THERE IS VIRTUALLY NO CHANCE OF
PRECIPITATION FOR THE REST OF THE STATE FROM THE WEEKEND INTO AT
LEAST MID NEXT WEEK. LOOKING EVEN LONGER RANGE TOWARD VERY END OF
FEBRUARY AND INTO EARLY MARCH, THERE IS SOME HINT THAT THE RIDGE
OVER THE WEST WILL START TO BREAK DOWN. THE TAIL END OF THE CPC 8-14
DAY OUTLOOK, INTO THE 3-4 WEEK OUTLOOK (FIRST TWO WEEKS OF MARCH),
BRINGS BACK A SLIGHT LEANING TOWARD ABOVE AVERAGE PRECIPITATION IN
FAR NORTHERN UTAH.
AVIATION...KSLC
LIGHT AND VARIABLE WINDS EXPECTED THROUGH MID-
MORNING, WITH SCATTERED LIGHT RAIN SHOWERS (OCCASIONALLY MIXING WITH
SNOW OR GRAUPEL) PERSISTING THROUGH AROUND 12-14Z THIS MORNING.
DESPITE THE SHOWERS, LARGELY VFR CONDITIONS EXPECTED, WITH ABOUT A
30% CHANCE OF BRIEF MVFR RESTRICTIONS. SHOWERS DIMINISH BY MIDDAY
WITH A RETURN TO TYPICAL DIURNAL WINDS THIS AFTERNOON / TONIGHT.
REST OF UTAH AND SOUTHWEST WYOMING
SCATTERED SHOWERS WILL PERSIST
THROUGH ROUGHLY 12-14Z ACROSS CENTRAL/NORTHERN UT/SOUTHWEST WY,
ROUGHLY NORTH OF I-70, PRODUCING OCCASIONAL MVFR CONDITIONS,
PARTICULARLY FOR HIGHER ELEVATION SITES (KEVW, KHCR). MOST LOWER
ELEVATION SITES WILL SEE A RAIN-SNOW MIX, WITH OTHER SITES (KEVW,
KHCR, EVEN KLGU) WILL REMAIN ALL SNOW. SHOWERS ARE EXPECTED TO
DIMINISH BY MIDDAY GIVING WAY TO CLEARING/DRYING AND VFR CONDITIONS
INTO TONIGHT.
SLC WATCHES/WARNINGS/ADVISORIES
UT...WINTER WEATHER ADVISORY UNTIL NOON MST TODAY FOR UTZ110>112.
WY...NONE.
SHORT TERM...TRAPHAGAN
LONG TERM/AVIATION...CHURCH
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
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