797
FXUS65 KSLC 082237
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
337 PM MST WED JAN 8 2025
SYNOPSIS
A COLD BUT DRY STORM SYSTEM WILL CROSS UTAH THIS EVENING
INTO THURSDAY. ANOTHER SYSTEM WILL THEN IMPACT THE AREA OVER THE
WEEKEND, BRINGING A POTENTIAL FOR ACCUMULATING SNOWFALL TO
PORTIONS OF NORTHERN AND CENTRAL UTAH.
SHORT TERM (THROUGH 12Z/5AM FRIDAY)
CURRENT SYNOPTIC PATTERN
INCLUDES A BROAD POSITIVE TILT TROUGH EXTENDING FROM THE NORTHERN
ROCKIES DOWN INTO THE FOUR CORNERS REGION, WITH AN ASSOCIATED
MID/UPPER LOW ATTEMPTING TO CUT OFF OFF NEAR THE LOWER CA/AZ
BORDER. STRONGER EASTERLY CANYON WINDS ALONG THE NORTHERN WASATCH
FRONT HAVE CEASED GIVEN A MUCH RELAXED GRADIENT BY THIS AFTERNOON,
THOUGH SOME MODEST GAP WIND GUSTS (GENERALLY IN THE 30-40 MPH
RANGE) HAVE STILL BEEN OBSERVED IN A FEW SPOTS ACROSS LOWER
WASHINGTON COUNTY. OTHERWISE, FAIRLY BENIGN CONDITIONS ACROSS THE
FORECAST REGION THIS AFTERNOON WITH SOME HIGH CLOUDS CONTINUING TO
FILTER THROUGH OVERHEAD AND TEMPERATURES RUNNING NEAR SEASONAL
NORMAL LEVELS.
DESPITE A BRIEF PERIOD OF SHORTWAVE RIDGING AND INCREASING H7
TEMPS, NEXT SYSTEM QUICKLY LOOKS POISED TO MOVE THROUGH LATE THIS
EVENING INTO EARLY THURSDAY. MODELS CONTINUE TO MAINTAIN GOOD
AGREEMENT IN LIMITED MOISTURE WITH THIS SHORTWAVE, AND THUS
MINIMAL QPF OR SNOW ACCUMULATIONS. WHILE A FEW MOUNTAIN FLURRIES
WILL LIKELY BE EXPERIENCED ELSEWHERE, ONLY THE UINTAS CURRENTLY
CARRY ACCUMULATING SNOW, AND EVEN THEN CURRENT FORECAST ONLY HOLDS
A GENERAL 1-3". MODEL GUIDANCE DOES HOWEVER ALSO RETAIN CONSENSUS
ON A FAIRLY STRONG BAROCLINIC ZONE WITH THIS SYSTEM, WITH H7
TEMPS QUICKLY FALLING BACK INTO THE -9C TO -12C RANGE ACROSS THE
FORECAST REGION. THIS WILL HELP REINFORCE SEASONABLY COOL
TEMPERATURES FOR THURSDAY.
AS THE BAROCLINIC ZONE RACES SOUTHWARD OVERNIGHT, THE PRESSURE
GRADIENT ACROSS SOUTHERN UTAH WILL BEGIN TO TIGHTEN. THE
TIGHTENING GRADIENT ALONG WITH A MORE FAVORABLE ORIENTATION WILL
ALLOW FOR STRONG LOWER WASHINGTON COUNTY GAP WINDS TO ONCE AGAIN
BECOME REINVIGORATED, LIKELY BY THURSDAY MORNING. THESE STRONG
WINDS THEN LOOK FAVORED TO PERSIST THROUGH THE DAY, WITH SOME
AREAL EXPANSION OF GUSTS EVEN OUTSIDE OF NORMAL GAP/CANYON AREAS.
BY LATE THURSDAY EVENING TO THE OVERNIGHT HOURS, THE GRADIENT
BEGINS TO RELAX AND BECOME LESS FAVORABLY ORIENTED, AND WINDS
SHOULD TREND DOWNWARDS ACCORDINGLY. CURRENT GUIDANCE FAVORS GUSTS
IN GAP/CANYON AREAS TO GENERALLY FALL IN THE 45-55 MPH RANGE,
THOUGH 12Z HREF DID INCLUDE A ROUGHLY 20% PROBABILITY OF GUSTS IN
EXCESS OF 60 MPH. HIGHER PROBS ARE NOTED FOR SOME OF THE HIGHER
TERRAIN AND FAVORABLY ORIENTED CANYONS FROM THE PINE VALLEY, BULL
VALLEY, AND BEAVER DAM MOUNTAINS. GIVEN THE GOOD MODEL CONSENSUS,
OPTED TO ISSUE A WIND ADVISORY FOR LOWER WASHINGTON COUNTY FOR
THESE CANYON WINDS FROM 5AM THURSDAY THROUGH MIDNIGHT. ONE
INTERESTING TREND SOME GUIDANCE DEPICTS IS A QUICK INITIAL UPTICK
IN GUSTS BETWEEN AROUND 8AM TO NOON, A SLIGHTLY WEAKER PERIOD
DURING THE DAY, AND ANOTHER STRONGER PERIOD BETWEEN 5PM AND 10PM.
IN ANY CASE, THOSE DRIVING HIGH PROFILE VEHICLES IN PARTICULAR
WILL WANT TO REMAIN AWARE OF THE POTENTIAL FOR ENCOUNTERING THESE
WINDS IF DRIVING IN THE AREA.
LONG TERM (AFTER 12Z/5AM FRIDAY)
SHORTWAVE RIDGING WILL TRACK
INTO SOUTHWEST WYOMING AND UTAH AS A POSITIVELY-TILTED TROUGH TO
THE SOUTH LIFTS NORTHEAST. DRY CONDITIONS WILL LAST THROUGH MUCH
OF FRIDAY FOR SOUTHWEST WYOMING AND NORTHERN UTAH, WITH DRY
CONDITIONS THROUGH THE DAY ELSEWHERE. ENSEMBLES ARE IN GOOD
AGREEMENT ON A SHORTWAVE TROUGH DIGGING INTO SOUTHWEST WYOMING AND
UTAH FRIDAY INTO SATURDAY. THE SHORTWAVE TROUGH WILL BRING ENOUGH
FORCING, MOISTURE, AND COLD AIR FOR BOTH VALLEY AND MOUNTAIN SNOW
THROUGH THE EVENT.
NATIONAL BLEND OF MODELS 25-75TH PERCENTILE FOR QPF FOR NORTHERN
VALLEYS IS FROM ROUGHLY A TRACE-0.15". AS COLD AIR BUILDS IN WITH
THE SYSTEM, SNOW RATIOS WILL INCREASE FROM AROUND 10:1 TO AROUND
15:1. WITH THAT RANGE OF QPF AND SNOW RATIO, NORTHERN VALLEY SNOW
ACCUMULATION OF A TRACE-2 INCHES IS MOST LIKELY. THERE IS
POTENTIAL FOR LAKE-EFFECT SNOW FOLLOWING THE SYNOPTIC SNOW
SATURDAY INTO SUNDAY, WITH STRONG LAPSE RATES AND SUFFICIENT LOW
LEVEL MOISTURE, BUT CONFIDENCE ON DETAILS IS LOW.
FOR THE NORTHERN MOUNTAINS, THE 25-75TH PERCENTILE QPF IS FROM
ROUGHLY 0.20-0.50". SNOW RATIOS THROUGH THE EVENT WILL INCREASE
FROM ROUGHLY 10:1 TO 15:1, WITH CORRESPONDING SNOWFALL
ACCUMULATION OF 2- 6 INCHES. LOCALLY HIGHER SNOWFALL IS LIKELY FOR
NORTHERN MOUNTAIN LOCATIONS WITH UPSLOPE OROGRAPHIC ENHANCEMENT
FROM THE NORTHWEST.
GUSTY POST-FRONTAL WINDS ARE LIKELY IN DOWNSLOPE LOCATIONS OF
WESTERN CASTLE COUNTRY SATURDAY. SIMILARLY, GUSTY GAP WINDS IN
LOWER WASHINGTON COUNTY ARE LIKELY INTO SUNDAY.
SHORTWAVE ENERGY IS LIKELY TO BRING SNOW SHOWERS, AT LEAST FOR
THE NORTHERN MOUNTAINS FOR THE END OF THE WEEKEND AND INTO MONDAY,
BUT ACCUMULATIONS AFTER SATURDAY WILL BE RELATIVELY LIGHT.
FURTHER INTO THE WEEK, ENSEMBLES ARE IN GOOD AGREEMENT OF A
CLOSED LOW TO THE SOUTHWEST AS RIDGING BUILDS IN FROM THE WEST.
THIS REX BLOCK SET UP COULD LAST MUCH OF THE WEEK. WITH LIMITED
MIXING, VALLEY INVERSION CONDITIONS WITH HAZE WOULD BE LIKELY.
AVIATION...KSLC
VFR CONDITIONS WILL PERSIST FOR THE KSLC TERMINAL
THROUGH THE PERIOD. A DRY COLD FRONT WILL PUSH THROUGH THE
TERMINAL WITH THE ONLY NOTICEABLE CHANGE BEING A FEW HIGH CLOUDS
AND A SHIFT TO LIGHT NORTHERLY WINDS AROUND 00Z. OTHERWISE,
CONDITIONS WILL REMAIN DRY WITH CLEARING SKIES AND LIGHT NORTHERLY
WINDS PREVAILING.
REST OF UTAH AND SOUTHWEST WYOMING
VFR CONDITIONS WILL PERSIST
FOR THE ENTIRE AIRSPACE THROUGH THE PERIOD. A DRY COLD FRONT WILL
PUSH THROUGH THE AIRSPACE THIS EVENING BRINGING ONLY A FEW HIGH
CLOUDS. WINDS WILL REMAIN LIGHT AND VARIABLE ACROSS THE NORTH WITH
STRONGER NORTHERLY WINDS DEVELOPING ACROSS THE SOUTH CLOSER TO
SUNRISE.
SLC WATCHES/WARNINGS/ADVISORIES
UT...WIND ADVISORY FROM 5 AM THURSDAY TO MIDNIGHT MST THURSDAY NIGHT
FOR UTZ123.
WY...NONE.
SHORT TERM...WARTHEN
LONG TERM...WILSON
AVIATION...MAHAN
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
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