836
FXUS65 KSLC 141103
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
403 AM MST TUE JAN 14 2025
SYNOPSIS
A COLD AIRMASS WILL REMAIN IN PLACE ACROSS THE REGION
THROUGH AT LEAST MIDWEEK WHEN HIGH PRESSURE WILL MOVE IN, BRINGING
DRY, STABLE CONDITIONS. THE NEXT WEATHER SYSTEM AND ASSOCIATED
COLD FRONT IS POISED TO MOVE INTO THE REGION IN THE LATE FRIDAY TO
SATURDAY TIMEFRAME, POTENTIALLY BRINGING THE COLDEST AIR SO FAR
THIS SEASON TO THE REGION BY NEXT WEEKEND AND EXTENDING INTO EARLY
NEXT WEEK.
SHORT TERM (AFTER 12Z/5AM FRIDAY)
AS OF 3AM MST TUESDAY
MORNING, SEASONABLY COLD, DEEP-LAYER NORTHERLY FLOW WAS IN PLACE
ACROSS UTAH AND SW WYOMING BEHIND A DEPARTING TROUGH THAT HAD
PROGRESSED INTO ARIZONA. A REX BLOCK HAD DEVELOPED ACROSS THE
EASTERN PACIFIC, WITH A HIGH PRESSURE RIDGE CENTERED OFF OF THE
SOUTHWEST OREGON COASTLINE AND A CLOSED LOW BETWEEN 120W AND 130W
LONGITUDE. LOCALLY, WIDESPREAD STRATUS DEVELOPED IN THE WAKE OF
THE ABOVE-MENTIONED TROUGH, WITH STRATUS MOST EVIDENT ALONG/EAST
OF THE GREAT SALT LAKE AS WELL AS OVER PORTIONS OF CENTRAL UTAH.
THIS STRATUS WAS PREVENTING FAVORABLE RADIATING CONDITIONS, WITH
TEMPERATURES IN THE PRESENCE OF STRATUS HAVING LEVELED OFF SINCE
LATE MONDAY EVENING. THE STRATUS WAS ALSO PREVENTING THE
DEVELOPMENT OF FOG ACROSS FOG-PRONE AREAS OF THE FORECAST AREA,
NAMELY THOSE VALLEYS IN CLOSE PROXIMITY TO WATER BODIES. MODEL
SUITE SUGGESTS MOST OF THE STRATUS WILL LARGELY MIX OUT BY MID TO
LATE THIS AFTERNOON. HOWEVER, WITH THE RIDGE FORECAST TO
GRADUALLY BUILD ACROSS THE PACNW, ASSOCIATED MID-LEVEL WARM
ADVECTION AND ASSOCIATED DEVELOPING SUBSIDENCE WILL RESULT IN THE
DEVELOPMENT AND EVENTUAL STRENGTHENING OF VALLEY INVERSIONS.
THESE INVERSIONS COULD BRING AN ALTERNATE FORECAST SCENARIO TO THE
TABLE BY ACTING TO LOCK IN STRATUS, RESULTING IN GREATER SPATIAL
AND TEMPORAL COVERAGE THAN CURRENTLY FORECAST. SUCH A SCENARIO WOULD
BOTH SUPPRESS HIGH TEMPERATURES AND ELEVATE FORECAST LOW
TEMPERATURES. THESE TRENDS WILL BE MONITORED OVER THE NEXT 24
HOURS OR SO FOR POTENTIAL FORECAST ADJUSTMENTS. FOR THOSE
LOCATIONS THAT DO EXPERIENCE A LOSS OF STRATUS, TEMPERATURES WILL
BE SUCH THAT UNSHELTERED POPULATION WILL BE AT AN INCREASED RISK
OF ADVERSE EFFECTS OF THE COLD, SUCH AS HYPOTHERMIA.
BY WEDNESDAY, THE RIDGE AXIS IS FORECAST TO TAKE ON
A EAST-WEST ORIENTATION AS IT BUILDS INTO THE GREAT BASIN. AS THE
RIDGE BUILDS OVERHEAD, VALLEY INVERSIONS WILL STRENGTHEN. THESE
CONDITIONS ARE FORECAST TO REMAIN IN PLACE THROUGH THE REMAINDER
OF THE SHORT TERM PORTION OF THE FORECAST. GIVEN THE LIMITED
DURATION OF INVERSION CONDITIONS (2-3 DAYS), IMPACTS ARE NOT
EXPECTED TO RIVAL THOSE OF EARLY DECEMBER. MOST LIKELY, A THIN
LAYER OF HAZE DEVELOPS ACROSS NORTHERN VALLEYS. CHECK UTAH DEQ FOR
THE LATEST AIR QUALITY FORECASTS AND OBSERVATIONS. WITH THE
ARRIVAL OF A COLD FRONT ON FRIDAY, INVERSIONS WILL DIMINISH.
LONG TERM (AFTER 12Z/5AM FRIDAY)
AS THE REX BLOCK PATTERN THROUGH
MUCH OF THE WEEK BREAKS DOWN, MODELS AND ENSEMBLES ARE IN GOOD
AGREEMENT THAT A LONGWAVE TROUGH WILL BRING COLDER CONDITIONS AND
SNOW. THERE IS UNCERTAINTY ON DETAILS WITH THE STORM SYSTEM, AS THE
STORM TRACK COULD RANGE FROM A GRAZING TROUGH TO ONE THAT BRINGS
MUCH COLDER CONDITIONS AND MORE SNOW INTO SOUTHWEST WYOMING AND
UTAH.
THE MAIN SCENARIO REPRESENTED BY GEFS MEMBERS IS WITH A GLANCING
TROUGH THAT DIGS MORE SO ALONG THE EASTERN EDGE OF THE ROCKIES. MOST
CANADIAN ENSEMBLE MEMBERS HAVE THE TROUGH TRACKING FURTHER WEST,
WITH A STRONGER BAROCLINIC ZONE, MORE COLD AIR ADVECTION, AND MORE
SNOW. EPS MEMBERS HAVE CONSISTENTLY RANGED BETWEEN MOST GEFS AND
CANADIAN ENSEMBLE MEMBERS. THE VARIOUS TRACKS WILL HAVE A BIG ROLE
IN TEMPERATURES THROUGH THE WEEKEND INTO NEXT WEEK. ANY OUTCOME WILL
BE COLD, AS THE WARMER SCENARIO REPRESENTED BY MOST GEFS MEMBERS
BRINGS LOW TEMPERATURES FROM AROUND 0F FOR THE COLDEST VALLEYS TO
THE TEENS IN THE URBAN CORRIDOR OF NORTHERN UTAH FOR SEVERAL NIGHTS
STARTING SUNDAY. THE COLDEST SCENARIO WOULD ALLOW FOR LOW
TEMPERATURES AS COLD AS AROUND -20F FOR THE BEAR RIVER VALLEY, BELOW
ZERO IN THE CACHE VALLEY AND SOUTHWEST WYOMING, AND INTO THE SINGLE
DIGITS FOR THE URBAN CORRIDOR OF NORTHERN UTAH.
WITH HOW COLD OF A SYSTEM IT WILL BE, IT WILL BE RATHER DRY. SNOW
TOTALS WILL BE INFLUENCED BY THE STORM TRACK, BUT NOT AS MUCH AS HOW
COLD CONDITIONS ARE. VALLEY AND MOUNTAIN SNOW ARE LIKELY FROM FRIDAY
EVENING THROUGH SATURDAY. ACCUMULATIONS WILL LIKELY BE BELOW
ADVISORY CRITERIA THROUGHOUT SOUTHWEST WYOMING AND UTAH.
AVIATION...KSLC
LOW STRATUS IN VFR RANGE WILL DIMINISH THROUGH
THE DAY. MOSTLY CLEAR CONDITIONS ARE LIKELY BY AROUND 00Z. LIGHT
SOUTHEAST WINDS WILL PREVAIL THROUGH AROUND 19Z. WINDS WILL
TRANSITION TO NORTHWEST FROM AROUND 19-04Z.
REST OF UTAH AND SOUTHWEST WYOMING
LOW STRATUS MAY LOWER INTO
MVFR RANGE IN SOUTHWEST WYOMING, THE CACHE VALLEY, AND HEBER VALLEY
THROUGH AROUND 19Z. LOW STRATUS GENERALLY IN VFR RANGE WILL DIMINISH
THROUGH THE DAY. WINDS WILL BE RELATIVELY LIGHT THROUGHOUT.
SLC WATCHES/WARNINGS/ADVISORIES
UT...NONE.
WY...NONE.
ADESMET/WILSON
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
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