117
FXUS65 KSLC 092252
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
352 PM MST THU JAN 9 2025
SYNOPSIS
GUSTY WINDS ACROSS SOUTHERN UTAH DECREASE THROUGH
THURSDAY NIGHT. THE NEXT STORM SYSTEM IS THEN EXPECTED TO PASS
THROUGH THE REGION FRIDAY NIGHT INTO THE WEEKEND, BRINGING POTENTIAL
FOR ACCUMULATING SNOW FROM CENTRAL UTAH NORTHWARD. DRIER AND COLDER
CONDITIONS THEN SETTLE IN FOR EARLY NEXT WEEK.
SHORT TERM (THROUGH 00Z SUNDAY)
IN THE WAKE OF THE PASSING AND
MOSTLY DRY SYSTEM, GUSTY CONDITIONS CONTINUE ACROSS MUCH OF
SOUTHERN UTAH. THIS SEEMS TO BE OCCURRING AS A MIX OF THE
ANTICIPATED STRONG GAP/CANYON WINDS AT AREAS DOWNWIND OF FAVORED N
TO NE ORIENTED CANYONS (GIVEN THE STRONG SURFACE PRESSURE
GRADIENT), AS WELL AS JUST GENERAL SYNOPTIC MIXING OF HIGHER
MOMENTUM AIR DOWN ACROSS A BROADER AREA. THE LATTER HAS RESULTED
IN AN EXPANSION OF THE WIND ADVISORY'S AREAL EXTENT GIVEN THE
OBSERVED MAGNITUDES. ANTICIPATE THE GAP WINDS WILL PERSIST A BIT
LONGER INTO THE EVENING ACROSS LOWER WASHINGTON COUNTY THAN THE
GENERAL SYNOPTIC GUSTS ELSEWHERE, SO HAVE THE WIND ADVISORY
EXPIRATION TIMES SET ACCORDINGLY. WHILE SOME STRONGER GUSTS MAY
ACCELERATE THROUGH A FEW LOCALIZED N TO NE ORIENTED CANYONS
OVERNIGHT, ANTICIPATE A GENERAL TREND DOWNWARD AS THE PRESSURE
GRADIENT RELAXES.
MOVING INTO FRIDAY, THE TROUGH ASSOCIATED WITH THE PRIOR SYSTEM
WILL SHIFT SOUTH AND EASTWARD AWAY FROM THE REGION, WITH MID LEVEL
RIDGING FLEXING IN FROM THE WEST IN ITS PLACE. FOR MUCH OF THE
DAY, DRY AIR ASSOCIATED WITH THE RIDGE WILL HELP KEEP CONDITIONS
DRY. ADDITIONALLY, WILL SEE H7 TEMPS WARM SEVERAL DEGREES THROUGH
THE DAY. MODEL FORECAST SOUNDINGS CONTINUE TO SUGGEST SHELTERED
LOWER ELEVATION VALLEY AREAS MAY SEE VERY LITTLE MIXING, IF NOT
STAY INVERTED, LIMITING HOW MUCH DAYTIME HIGHS ACTUALLY INCREASE.
HIGHER TERRAIN WILL REALIZE SOME WARMER TEMPS THOUGH, AS WILL ANY
VALLEY THAT SUCCESSFULLY MIXES OUT A BIT MORE. WITH THE TRANSIENT
NATURE OF THE RIDGE, NOT REALLY ANTICIPATING ENOUGH TIME TO SEE
MUCH IN THE WAY OF HAZE BUILDUP OR ASSOCIATED AIR QUALITY
CONCERNS.
THE NEXT SYSTEM THEN PUSHES IN FRIDAY EVENING ONWARD INTO THE
WEEKEND. BY FRIDAY EVENING, INCREASING PRECIPITATION CHANCES WILL
COINCIDE WITH INCREASING SYNOPTIC FORCING AHEAD OF A MORE ROBUST
SHORTWAVE AND ASSOCIATED COLD FRONT. PRECIPITATION CHANCES THEN
LOOK TO BE MAXIMIZED FOR A PERIOD COINCIDING WITH (AND IN THE
PERIOD AFTER) FRONTAL PASSAGE, LIKELY SOMETIME FRIDAY NIGHT INTO
SATURDAY MORNING, THOUGH SOME TIMING DIFFERENCES REMAIN AMONG
VARIOUS MODELS/ENSEMBLES. THIS WILL ALSO MARK THE PERIOD OF
HIGHEST PRECIPITATION RATES FOR MOST LOCATIONS. LOWER ELEVATION
PRECIPITATION WILL GENERALLY TAPER OFF OR DECREASE IN COVERAGE
THROUGHOUT THE DAY, WITH MOUNTAINS SEEING MORE PERSISTENT SNOW,
ESPECIALLY THOSE THAT DO WELL OROGRAPHICALLY IN STRONGER WEST TO
NORTHWEST FLOW REGIMES.
THE BIGGEST QUESTION WITH THE SYSTEM CONTINUES TO APPEAR TO BE
HOW MUCH MOISTURE WILL IT CARRY AND WHAT WILL THE EXACT TRAJECTORY
BE. PRECIPITATION TYPE ON THE OTHER HAND LOOKS MORE CERTAIN, WITH
QUICK INTRUSION OF COLD H7 TEMPS ENSURING SNOW LEVELS SUPPORT
SNOW AREAWIDE (WHERE PRECIPITATION OCCURS, OF COURSE). WITH THAT,
CURRENT FORECAST DOES CARRY ROUGHLY 0.5-1.0" SNOW FOR LOWER
ELEVATIONS, INCLUDING THE CACHE VALLEY AND WASATCH FRONT SOUTHWARD
TO AROUND THE I-70 CORRIDOR OR SO. EVEN THE 25TH PERCENTILE
AMOUNTS CARRY SOME MINOR LOW ELEVATION ACCUMULATIONS, WITH 75TH
PERCENTILE BRINGING SOME PLACES UP CLOSER TO 2" OR SO (AND OF
COURSE MORE AT BENCH AREAS). WHILE ARGUABLY SOMEWHAT MEAGER
AMOUNTS, GIVEN A RELATIVE LACK OF LOW ELEVATION SNOW THIS SEASON,
THOSE PLANNING ON TRAVEL SHOULD KEEP AN EYE ON ROAD CONDITIONS.
THE HIGH TERRAIN FROM CENTRAL UTAH NORTHWARD SHOULD SEE A BIT MORE
APPRECIABLE TOTALS. 25TH PERCENTILE AMOUNTS GENERALLY SIT IN THE
2-6" RANGE FOR MOST MOUNTAINS, WITH THE 75TH PERCENTILE MORE
AGGRESSIVE IN THE 4-12" RANGE. BETTER ODDS FAVOR TERRAIN FURTHER
NORTH, AS WELL AS TERRAIN OROGRAPHICALLY FAVORED IN THAT STRONGER
WEST TO NORTHWESTERLY FLOW REGIME (SUCH AS THE UPPER COTTONWOODS).
ANOTHER LOW CONFIDENCE FACTOR TO MONITOR WILL BE POTENTIAL FOR
LAKE EFFECT/LAKE ENHANCED SNOW SHOWERS SATURDAY, GIVEN THE
COLDNESS OF THE AIRMASS SETTLING IN.
FOR THIS FORECAST, OPTED TO HOLD OFF ON ISSUING ANY ADVISORIES
GIVEN THE CURRENT GRIDDED/DETERMINISTIC AMOUNTS ONLY HAVE A VERY
SMALL HANDFUL OF AREAS WHICH HIT LOCAL CRITERIA. FURTHER
UNCERTAINTY IS NOTED ON WHETHER WE TREND MORE TOWARDS THE 25TH
PERCENTILE (EVEN LESS AREAS LIKELY TO HIT) OR THE 75TH PERCENTILE
(EASIER HEADLINE DECISION). ADDITIONALLY, THE FIRST LOOK AT
AVAILABLE HIGH RES GUIDANCE RAISES SOME QUESTIONS. 18Z HRRR FOR
EXAMPLE ONLY SHOWS ADVISORY LEVEL ACCUMULATION IN A SMALL HANDFUL
OF LOCALIZED MOUNTAIN AREAS, WHILE THE 18Z HIGH RESOLUTION NAM
CARRIES MORE APPRECIABLE AMOUNTS. A NUMBER OF COARSER GLOBAL
ENSEMBLE MEMBERS ALSO SHOW POTENTIAL FOR MORE LIMITED SNOW
ACCUMULATIONS. DESPITE THIS UNCERTAINTY AND ASSOCIATED LACK OF
CURRENT WINTER HEADLINES, ANYONE PLANNING TRAVEL TO HIGHER
ELEVATIONS (ESPECIALLY IF IT COINCIDES WITH THE PERIOD OF HIGHEST
PRECIP RATES) SHOULD BE AWARE OF POTENTIAL ADVERSE DRIVING
CONDITIONS AND PLAN ACCORDINGLY.
LONG TERM (AFTER 00Z SUNDAY/5PM SATURDAY)
A COLD POST-FRONTAL
AIRMASS WITH NORTHERLY FLOW ALOFT WILL BE IN PLACE SATURDAY
EVENING WITH A FEW LINGERING SHOWERS REMAINING ACROSS THE CENTRAL
AND NORTHERN MOUNTAINS. THESE SHOWERS WILL DWINDLE AS FLOW ALOFT
WEAKENS AND SHORTWAVE RIDGING BUILDS INTO THE AREA. WITH A COLD
NORTHERLY FLOW REMAINING IN PLACE, TEMPERATURES OVERNIGHT SATURDAY
WILL BE QUITE COLD. ADDITIONALLY, GUSTY NORTHERLY WINDS WILL
PERSIST ACROSS SOUTHERN UTAH, BUT LIKELY REMAIN BELOW ADVISORY
CRITERIA.
A SECONDARY SHORTWAVE WAVE WILL MOVE INTO NORTHERN UTAH OVERNIGHT
SUNDAY INTO MONDAY MORNING. WITH SOME LINGERING LOW LEVEL
MOISTURE AND SUBFREEZING TEMPERATURES AREAWIDE, ANY SNOW THAT IS
ABLE TO FALL WITH THIS SHORTWAVE WILL QUICKLY STICK TO ALL
SURFACES. THIS COULD MAKE FOR A HAZARDOUS MORNING COMMUTE ON
MONDAY MORNING. NOT ALL GUIDANCE IS ON BOARD WITH THIS, HOWEVER,
WITH SOME MEMBERS BRINGING MORE OF A NORTHEASTERLY FLOW AHEAD OF
CUTOFF LOW EVOLVING. THIS WOULD LEAD TO DRY CONDITIONS ACROSS THE
WASATCH FRONT. THIS SHORTWAVE IS STILL OUTSIDE OF THE HIGH-RES
WINDOW SO THERE WILL BE A BETTER PICTURE OF WHAT THIS MIGHT ENTAIL
ONCE WE GET INTO RANGE OF THE HIGH-RES GUIDANCE.
BEYOND THIS SHORTWAVE, DRIER CONDITIONS WILL SETTLE INTO THE AREA
ALONG WITH COLDER THAN NORMAL AIR FOR MUCH OF NEXT WEEK. A VERY
SIMILAR PATTERN LOOKS TO EVOLVE NEXT WEEK THAT WE SAW WITH THIS
PAST WEEK'S TROUGH THAT LED TO A LOW DEVELOPING AND SHIFTING
SOUTHWEST WHICH LEAD TO SOME GUSTY DOWNSLOPING WINDS ACROSS THE
WASATCH FRONT. MOST GUIDANCE IS IN AGREEMENT WITH A CUTOFF LOW
DEVELOPING OFF THE COAST OF CALIFORNIA THAT COULD BRING EASTERLY
DOWNSLOPING WINDS TO NORTHERN UTAH BY TUESDAY/WEDNESDAY. THE
LOCATION OF THIS LOW PRESSURE WILL DETERMINE HOW MUCH EASTERLY
FLOW, IF ANY, DEVELOPS. EVENTUALLY, THIS LOW MOVES BACK ON SHORE
WHICH COULD BRING MORE PRECIPITATION TO THE REGION BY THE END OF
NEXT WEEK.
AVIATION...KSLC
WINDS OUT OF THE NORTHWEST WILL PERSIST THROUGH
THE REST OF THE AFTERNOON AND EARLY EVENING, BECOMING LIGHTER
AFTER 02Z. WINDS MAY BECOME LIGHT AND VARIABLE AFTER 04Z, WITH
PROMINENT SOUTH FLOW AROUND 5-6KTS NOT PREVAILING UNTIL AS LATE AS
12Z. VFR CONDITIONS WILL CONTINUE.
REST OF UTAH AND SOUTHWEST WYOMING
GUSTY NORTHERLY WINDS ARE
EXPECTED TO CONTINUE THROUGH THE AFTERNOON AND EARLY EVENING
ACROSS MANY AREAS. ACROSS THE NORTH, GUSTS HAVE LARGELY BEEN
20-30KTS AT MOST. SOUTHERN SITES HAVE SEEN EVEN HIGHER GUSTS, WITH
LOCALLY HIGH GUSTS UP TO 40-50KTS DOWNWIND OF HIGHER TERRAIN,
SUCH AS AT KSGU, KBCE, AND KHVE. THESE WINDS WILL LARGELY DECREASE
THROUGH THE EVENING, THOUGH KSGU COULD SEE THESE WINDS PERSIST AS
LATE AS 06- 07Z. VFR CONDITIONS WILL PREVAIL, ASIDE FROM A SMALL
(25%) CHANCE OF FOG DEVELOPING NEAR KLGU IN THE EARLY MORNING.
SLC WATCHES/WARNINGS/ADVISORIES
UT...WIND ADVISORY UNTIL MIDNIGHT MST TONIGHT FOR UTZ123.
WIND ADVISORY UNTIL 9 PM MST THIS EVENING FOR UTZ127-128-130-131.
WY...NONE.
SHORT TERM...WARTHEN
LONG TERM...MAHAN
AVIATION...CUNNINGHAM
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
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