003
FXUS65 KSLC 192218
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
318 PM MST WED FEB 19 2020
SYNOPSIS
THE DRY UPPER LEVEL TROUGH MOVING SOUTH THROUGH THE NORTHERN
ROCKIES WILL BRING COLDER AIR AND LIMITED CLOUD COVER TO THE AREA
TODAY. DRY AND STABLE CONDITIONS WILL PERSIST THROUGH THE END OF
THE WEEK AS HIGH PRESSURE ALOFT EXPANDS EAST ACROSS THE GREAT
BASIN. A STORM SYSTEM MOVING INTO ARIZONA WILL BRING RAIN AND SNOW
TO SOUTHERN UTAH THIS WEEKEND.
SHORT TERM (THROUGH 12Z SATURDAY)
A VERY STRONG SURFACE ANTICYCLONE WILL SET UP ACROSS SOUTH CENTRAL
WYOMING TONIGHT TIGHTENING UP THE PRESSURE GRADIENT. THIS ALONG
WITH COLD ADVECTION BEHIND THE PASSING DRY TROUGH WILL SUPPORT
GUSTY CANYON WINDS ALONG THE WASATCH FRONT AND OUTLYING DIXIE
TONIGHT INTO TOMORROW MORNING. WINDS MAY NEAR ADVISORY CRITERIA
FOR OUTLYING DIXIE, BUT WILL VERY LIKELY BARELY REACH IT FOR A FEW
HOURS, SO WILL NOT BE ISSUING A WIND ADVISORY WITH THIS FORECAST
PACKAGE.
INVERTED CONDITIONS WILL BE THE RULE THROUGH FRIDAY NIGHT, WITH A
RIDGE BUILDING INTO THE REGION. FOG IS THE PRIMARY CONCERN,
ESPECIALLY ACROSS THE CACHE VALLEY, WASATCH BACK EAST INTO
SOUTHWEST WYOMING BASED ON A MODIFIED UPS TECHNIQUE METHODOLOGY.
THIS THREAT WILL CONTINUE THROUGH FRIDAY NIGHT. HAVE UNDERCUT
GUIDANCE TEMPERATURES ACROSS THESE AREAS AS WELL GIVEN THE
SNOWPACK AND FANTASTIC RADIATIONAL COOLING CONDITIONS.
ANTICIPATE AIR QUALITY WILL CONTINUE TO DETERIORATE, AND HAVE
MENTIONED URBAN HAZE BEGINNING TOMORROW.
LONG TERM (AFTER 12Z SATURDAY)
MODEL ENSEMBLES ARE IN GOOD AGREEMENT IN BRINGING A PACIFIC
CLOSED LOW ACROSS SOUTHERN NEVADA AND NORTHWESTERN ARIZONA AND
SKIRTING SOUTHERN UTAH THROUGH THE WEEKEND. A SLIGHT CHANGE NOTED
OVER THE PAST 24 HOURS FROM PREVIOUS FORECASTS IS HOW BOTH MODELS
HAVE SHOW A DEEPER LOW AND HAVE ADJUSTED THE ONSET OF THE HEAVIEST
PRECIPITATION ARRIVING IN SOUTHERN UTAH BACK 12 HOURS TO NOW
SHOWING THE BULK OF THE PRECIPITATION ARRIVING SUNDAY. THE
TEMPERATURE PROFILE WITH THIS SYSTEM SHOWS H7 TEMPERATURES IN THE
-6C TO -5C IN THE CORE OF THE STORM. WARM SOUTHERLY FLOW AHEAD OF
THE STORM WILL PUSH SNOW LEVELS WELL ABOVE THE VALLEY FLOORS AND
SNOW WILL BE PRIMARILY FOUND IN THE HIGHER ELEVATIONS ABOVE 5500FT
IN THE PINE VALLEY MOUNTAINS. STORM TOTAL ACCUMULATION ANALYSIS
SEEMS TO BE RUNNING HOT BASED ON THE GEFS OUTPUTS OVER VARIOUS
PERCENTILES. AFTER LOOKING A VARIOUS QPF FIELDS, OVERALL FORECAST
IS CONFIDENT IN A GOOD RAIN EVENT ACROSS SOUTHERN UTAH. LOOKING AT
A STORM TOTAL ANYWHERE BETWEEN 1/2 TO 3/4" IN THE VALLEYS WITH
ACCUMULATIONS OVER AN INCH IN THE HIGHER TERRAIN.
AS THIS LOW TRANSVERSES ACROSS SOUTHERN UTAH A WEAKENING TREND
SEEMS TO BE THE CONSENSUS AND THE PRECIPITATION AND THE LOW ITSELF
WILL QUICKLY MOVE EAST OUT OF UTAH AS A WEAK UPPER LEVEL DISTURBANCE
BRINGS SOME MOUNTAIN SNOW SHOWERS TO NORTHERN UTAH.
GOING INTO DAY 5 AND BEYOND IN THE LONG RANGE FORECAST, THE MEAN
OUTPUT FROM THE H5 GRAPH CLUSTER ANALYSIS HINTS AT A WEAK TROUGH
ACROSS SOUTHER IDAHO AND A SOMEWHAT ZONAL NORTHWESTERLY FLOW
PERSISTING THROUGH THE LONG TERM. VARIATIONS IN THE IN THE AMPLITUDE
OF THE UPSTREAM RIDGE AXIS AND STRENGTH OF THE TROUGH CONTINUE TO
SHOW UP IN BOTH THE GEFS AND EPS SOLUTIONS THAT WOULD INFLUENCE THE
POP CHANCES THROUGH THIS TIME PERIOD AS WELL AS TEMPERATURES. THE
FORECAST GOING FORWARD WILL CONTINUE TO ADVERTISE HIGHER POPS TO THE
NORTHERN HALF OF THE FORECAST AREA, ESPECIALLY IN THE MOUNTAINOUS
TERRAIN, WITH SOME LINGERING POPS ACROSS THE HIGH TERRAIN OF THE
SOUTH.
AVIATION
THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGH THE TAF PERIOD.
NORTHWEST WINDS ARE EXPECTED TO PREVAIL THROUGH 04-05Z THIS
EVENING THEN BECOME SOUTHEAST.
SLC WATCHES/WARNINGS/ADVISORIES
UT...NONE.
WY...NONE.
SHORT TERM/AVIATION...10
LONG TERM...WOODWARD
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY
FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP
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