119
FXUS65 KSLC 181127
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
427 AM MST THU DEC 18 2025
KEY MESSAGES
- COOLER CONDITIONS EXIST ON THURSDAY ALONGSIDE LIGHT SNOWFALL IN
THE NORTHERN UTAH MOUNTAINS.
- A WARM STORM SYSTEM WILL BRING VALLEY RAIN AND HIGH ELEVATION
MOUNTAIN SNOW FROM FRIDAY THROUGH SATURDAY, AS WELL AS ANOTHER
ROUND OF STRONG WINDS ACROSS SOUTHWEST WYOMING AND THE NORTH
SLOPE OF THE UINTA MOUNTAINS.
- AFTER A RELATIVE LULL IN ACTIVE WEATHER EARLY NEXT WEEK, A LATE
WEEK STORM WILL BRING ANOTHER POTENTIAL ROUND OF VALLEY RAIN AND
MOUNTAIN SNOW.
SHORT TERM (THROUGH 00Z MONDAY/ 5PM SUNDAY)
A POST FRONTAL
ENVIRONMENT WILL KEEP TEMPERATURES MUCH COOLER ACROSS A VAST
MAJORITY OF UTAH AND SOUTHWEST WYOMING THROUGH THE DAY TODAY,
THOUGH HIGH TEMPERATURES WILL REMAIN WELL ABOVE NORMAL FOR THIS
TIME OF YEAR. ALONGSIDE THE COOLER, YET STILL ABOVE NORMAL
TEMPERATURES, A TRAILING SHORTWAVE WILL PASS THROUGH THE REGION
THROUGH THE SECOND HALF OF THE DAY. A BRIEF ADVECTION OF MOISTURE
WILL PAIR WITH THIS WAVE, HELPING TO KICK OFF A ROUND OF LIGHT
PRECIPITATION ACROSS THE NORTHERN UTAH MOUNTAINS (MAINLY FOR AREAS
NORTH OF I-80). INITIALLY, TEMPERATURES WILL BE COLD ENOUGH TO
SUPPORT SNOWFALL IN THE LOWER ELEVATION VALLEYS OF NORTHERN UTAH
(E.G. CACHE AND OGDEN VALLEY), HOWEVER, THE INTRODUCTION OF
MOISTURE IN THE REGION WILL ALSO BE PAIRED WITH STEADY WARM
ADVECTION WHICH WILL ACT TO RAPIDLY INCREASE SNOW LEVELS. AS SUCH,
LITTLE TO NO ACCUMULATION IS EXPECTED FOR THESE LOWER ELEVATION
VALLEYS. EVEN FOR THE HIGHER ELEVATIONS, ANY ACCUMULATION OF SNOW
WILL BE SHORT-LIVED AS THE LOWER LEVEL MOISTURE QUICKLY DEPARTS
THE REGION BY THURSDAY EVENING. BY AROUND 6-7PM, HIGH ELEVATION
SNOW AND VALLEY RAIN WILL QUICKLY DIMINISH AS THE WAVE PASSES.
JUST AS QUICK AS THIS SHOT OF MOISTURE DEPARTS THE REGION, ANOTHER
ARRIVES AT THE DOORSTEP BY LATE FRIDAY MORNING AS A DECAYING
ATMOSPHERIC RIVER PENETRATES INLAND. WITH STEADY WARM ADVECTION
SPREADING ACROSS THE ENTIRETY OF THE FORECAST AREA FOLLOWING THE
THURSDAY WAVE, SNOW LEVELS WILL BE QUITE HIGH AT THE ONSET OF
PRECIPITATION ON FRIDAY, WITH LEVELS RANGING FROM 6,500-7,000FT IN
FAR NORTHERN UTAH TO UPWARDS OF 8,000FT IN THE SOUTHERN WASATCH
AND WESTERN UINTAS. INITIALLY, LIGHT SNOWFALL CAN BE EXPECTED IN
THE BEAR RIVER MOUNTAINS AS UPSLOPE FLOW PAIRS WITH INCREASING
MOISTURE. A POORLY DEFINED AREA OF BAROCLINICITY WILL GRADUALLY
DIP INTO NORTHERN UTAH THROUGH THE EVENING ON FRIDAY, HELPING TO
FOCUS FORCING FOR ASCENT WHEN PAIRED WITH TRANSIENT MID-LEVEL
SHORTWAVE ENERGY. AS SUCH, ANTICIPATE HIGHER INTENSITY
PRECIPITATION LATE FRIDAY EVENING THROUGH EARLY SATURDAY MORNING.
A BULK OF THE MID-LEVEL FORCING WILL DEPART THE REGION THROUGH THE
REMAINDER OF SATURDAY MORNING, ALLOWING FOR PRECIPITATION TO TAPER
OFF. ANOTHER WAVE OF ENERGY AND ATMOSPHERIC RIVER MOISTURE WILL
PUSH INTO NORTHERN UTAH ON SUNDAY AFTERNOON, HOWEVER, WE WILL FIND
OURSELVES ON THE SOUTHERN PERIPHERY OF THE MOISTURE WHICH WILL
LIMIT THE OVERALL IMPACT TO THE NORTHERN BEAR RIVERS. WITH WARM
TEMPERATURES SPREADING OVER THE AREA, ANTICIPATE YET ANOTHER HIGH
DENSITY HIGH ELEVATION SNOWFALL WITH RAIN FOR AREAS BELOW ABOUT
8,000-8,500FT.
LONG TERM (AFTER 00Z MONDAY/5PM SUNDAY)
ATMOSPHERIC RIVER (AR)
MOISTURE WILL BE DECREASING SUNDAY INTO MONDAY AS A TROUGH NEAR
BRITISH COLUMBIA DIGS SOUTH AND TRANSITIONS SYNOPTIC FLOW TO THE
SOUTHWEST. THAT WILL RESULT IN THE MOISTURE SOURCE LIFTING NORTH.
PRECIPITATION THROUGH MONDAY WILL LARGELY BE NEAR THE IDAHO BORDER,
WITH MORE SHOWERY PRECIPITATION SOUTH TO THE WESTERN UINTAS AND
COTTONWOODS. SNOW LEVELS WILL BE AROUND 8000 FEET AT THIS POINT OF
THE EVENT, WITH LIGHT ADDITIONAL MOUNTAIN SNOW ACCUMULATION.
MOST GEFS, EPS, AND GEPS MEMBERS BRING A TROUGH FROM NEAR THE GULF
OF ALASKA INTO THE EASTERN PACIFIC FROM MONDAY THROUGH WEDNESDAY.
THAT WOULD BRING DRY CONDITIONS THROUGHOUT SOUTHWEST WYOMING AND
UTAH FROM AFTER PRECIPITATION TAPERS OFF MONDAY THROUGH TUESDAY.
THERE WOULD BE ENHANCEMENT OF SOUTHWEST FLOW FROM THE LONGWAVE
TROUGH WITH WARM AIR ADVECTION PUSHING VALLEY TEMPERATURES INTO THE
50S FOR MOST OF UTAH MONDAY THROUGH MUCH OF THE WEEK.
THE LONGWAVE TROUGH WILL LIKELY BECOME THE NEXT AR EVENT FOR THE
WESTERN U.S. THE MAIN DIFFERENCE FROM PREVIOUS ONES WILL BE THE MORE
SOUTHWARD TRACK THROUGH CALIFORNIA OF THE MOISTURE PLUME AND FORCING
THAT ENSEMBLES ARE IN GOOD AGREEMENT ON. FOR SOUTHWEST WYOMING AND
UTAH, THAT WOULD RESULT IN SOME DOWNSLOPE EFFECTS FROM THE SIERRA
NEVADA MOUNTAINS. HOW MUCH WILL DEPEND ON THE SEVERAL FACTORS,
INCLUDING THE TRACK OF THE STORM SYSTEM, MOISTURE ADVECTION, AND
FLOW WITH THE TROUGH. EVEN WITH DOWNSLOPE EFFECTS, THE MORE SOUTH
TRACK WOULD BE MUCH BETTER FOR PRECIPITATION FOR SOUTHERN UTAH THAN
SIMILAR STORM SYSTEMS FURTHER NORTH. LIKE OTHER AR EVENTS, SNOW
LEVELS WOULD BE HIGH. THERE IS UNCERTAINTY WITH SOME DETAILS LIKE
TIMING, WITH A RANGE FROM EARLY WEDNESDAY TO THURSDAY FOR A VALLEY
RAIN AND MOUNTAIN SNOW TO BUILD INTO UTAH.
AVIATION...KSLC
SOUTHEAST WINDS WILL LAST THROUGH THE DAY. SPEEDS
WILL GENERALLY BE LIGHT, BUT THERE WILL BE GUSTS AROUND 20 KNOTS
AFTER 18Z. SCATTERED TO BROKEN CLOUDS IN VFR RANGE WILL LAST THROUGH
THE TAF PERIOD. THERE IS AROUND A 20% CHANCE FOR LIGHT RAIN SHOWERS
FROM 20-00Z.
REST OF UTAH AND SOUTHWEST WYOMING...SCATTERED TO BROKEN CLOUDS IN
VFR RANGE WILL PREVAIL THROUGHOUT SOUTHWEST WYOMING AND NORTHERN
UTAH. THERE WILL BE SCATTERED RAIN AND SNOW SHOWERS FOR SOUTHWEST
WYOMING AND NORTHERN UTAH, MAINLY NORTH OF KSLC, FROM 18-03Z. RAIN
SHOWERS WILL BE CAPABLE OF LOWERING CONDITIONS INTO MVFR RANGE, WITH
SNOW SHOWERS AT KLGU AND KEVW LOWERING CONDITIONS INTO IFR RANGE.
WINDS WILL BE FROM SOUTHEAST TO SOUTHWEST, WITH GUSTS AROUND 25
KNOTS AFTER 18Z FOR SOUTHWEST WYOMING AND 20 KNOTS FOR MOST OF UTAH.
SLC WATCHES/WARNINGS/ADVISORIES
UT...NONE.
WY...NONE.
SHORT TERM...WEBBER
LONG TERM...WILSON
AVIATION...WILSON
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
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