139
FXUS65 KSLC 191042
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
342 AM MST SUN JAN 19 2020
SYNOPSIS
HIGH PRESSURE ALOFT WILL STRENGTHEN OVER UTAH THROUGH SUNDAY
BEFORE SHIFTING EAST OF THE STATE MONDAY. A RATHER WEAK WEATHER
DISTURBANCE WILL BRING MOSTLY CLOUDS TO THE AREA FOR MONDAY NIGHT
AND TUESDAY. THE NEXT BEST CHANCE FOR PRECIPITATION WILL ARRIVE
MIDWEEK.
SHORT TERM (THROUGH 00Z THURSDAY)
A RIDGE AMPLIFIES OVERHEAD TODAY BRINGING BENIGN WEATHER. PATCHY
FOG WILL REMAIN POSSIBLE ACROSS OUTLYING INVERTED VALLEYS THROUGH
MID MORNING.
THE SENSIBLE WEATHER WILL BE DRIVEN IN THE SHORT TERM BY THE
EVOLUTION OF VALLEY INVERSIONS, WITH A STRONG SUBSIDENCE
INVERSION NOTED ON THE KSLC RAOB NEAR 710MB LAST EVENING. AFTER A
COLD START DUE TO THE RECENT SNOWPACK AND MOSTLY CLEAR CONDITIONS,
TEMPERATURES ACROSS MANY OUTLYING VALLEYS WILL STRUGGLE TO WARM
ABOVE FREEZING TODAY.
MID AND HIGH CLOUDS ARE EXPECTED TO INCREASE TONIGHT, THOUGH THERE
WILL BE ANOTHER OPPORTUNITY FOR FOG DEVELOPMENT ACROSS OUTLYING
INVERTED VALLEYS BEFORE THE CLOUDS THICKEN LATER IN THE NIGHT.
A WEAK PACIFIC SYSTEM DRAWS IN MOISTURE MONDAY, WITH PRECIPITABLE
WATER VALUES INCREASING BEYOND 200% OF NORMAL DUE TO THE
SUBTROPICAL JET RACING ACROSS THE SOUTHWEST CONUS. THE PASSING
TROUGH MONDAY NIGHT AND TUESDAY HAS TRENDED TO SHOW AN INCREASE
IN COLD ADVECTION COMPARED TO GUIDANCE LAST NIGHT. THEREFORE GIVEN
THE MOISTURE CONTENT IN THE COLUMN, THE CHANCE FOR PRECIPITATION
DURING THIS PERIOD APPEARS TO BE A BIT GREATER THAN SEEN LAST
NIGHT, DESPITE THE LACK OF A NOTABLE JET IN THE REGION.
THERE IS QUITE A SPREAD IN GUIDANCE WHEN IT COMES TO THE DEPTH OF
THE NEXT TROUGH TUESDAY NIGHT AND WEDNESDAY. THE GFS IS COLDEST
AMONG OPERATIONAL MODELS. THE GEFS SHOW SUBSTANTIAL SPREAD, WITH
SOME MEMBERS JUST AS WARM AS THE OTHER GUIDANCE. GIVEN THIS, HAVE
KEPT THE FORECAST CLOSER TO THE IDEA OF THE EUROPEAN, WHICH SLIDES
THE BULK OF THE DYNAMICS TO OUR NORTHEAST DUE TO A MORE AMPLIFIED
WEST COAST RIDGE.
NEVERTHELESS, GIVEN THE MOISTURE CONTENT OF THE COLUMN, AND
PROXIMITY TO BETTER DYNAMICS ALONG WITH ANOTHER SHOT OF MODEST
COLD ADVECTION, THE LATE TUESDAY NIGHT AND WEDNESDAY MORNING
PERIOD APPEARS TO BE THE BEST OPPORTUNITY FOR PRECIPITATION. A
RAIN/SNOW MIX IS EXPECTED FOR VALLEYS, TRENDING TO ALL SNOW WITH
SNOW LEVELS FALLING TO THE VALLEY FLOOR WEDNESDAY. LIGHT VALLEY
ACCUMULATIONS ARE POSSIBLE, WITH THE POTENTIAL OF SEVERAL INCHES
OF FRESH SNOW IN THE NORTHERN MOUNTAINS.
LONG TERM (AFTER 00Z THURSDAY)
AS THE MIDWEEK'S TROUGH SLIDES EASTWARD DURING THE BEGINNING OF
THE LONG TERM FORECAST, A PERIOD OF RIDGING IS EXPECTED TO DEVELOP
OVER THE GREAT BASIN REGION THROUGH A MAJORITY OF THE WEEKEND.
WHILE BOTH THE EPS AND GEFS POINT TOWARD THIS PERIOD OF RIDGING,
THERE ARE SOME SUBTLE DIFFERENCES THAT MAY MAKE OR BREAK THE
CHANCE OF SEEING ANY PRECIPITATION OVER THE WEEKEND. THE GEFS
SOLUTION SUPPORTS A MUCH MORE AMPLIFIED RIDGE TO THE WEST OF OUR
CWA, WHICH WOULD FAVOR A DRY NORTHWEST FLOW ALOFT THROUGH THE
WEEKEND. ON THE OTHER HAND, THE EPS SUPPORTS A LESS AMPLIFIED
RIDGE WITH ITS AXIS SHIFTED FURTHER EASTWARD. EMBEDDED SHORTWAVE
DISTURBANCES ROLLING OVER THIS RIDGE FROM A RELATIVELY ACTIVE
NORTHEAST PACIFIC PATTERN MAY PACK ENOUGH ENERGY TO STIR UP SOME
SHOWERS OVER THE FAR NORTHERN PORTIONS OF UTAH ON FRIDAY AND
SATURDAY. HAVE STUCK WITH POPS FROM THE NBM OVER THE WEEKEND TO
ILLUSTRATE THIS CHANCE FOR SOME SHOWERS ACROSS NORTHERN UTAH.
MODEL GUIDANCE SUGGESTS A TROUGH TO QUICKLY DEVELOP OFF THE NORTH
COAST OF CALIFORNIA BY THE END OF THE LONG TERM PERIOD, POTENTIALLY
WORKING ITS WAY INLAND BY SUNDAY NIGHT. IT SEEMS AS THOUGH MORE
RECENT MODEL RUNS ARE SLOWING THE PROGRESSION OF THIS TROUGH,
HOWEVER, COULD STILL SEE SOME SHOWERS BY LATE SUNDAY. AGAIN, THE
GEFS AND EPS DEPICT DIFFERENT PHASES AND AMPLITUDES OF THIS FEATURE
THAT WILL LIKELY BE KEYED IN ON IN THE COMING DAYS.
AVIATION
VFR CONDITIONS WILL BE MAINTAINED AT THE SLC TERMINAL THROUGH THE
VALID TAF PERIOD UNDER PARTLY CLOUDY SKIES. LIGHT SOUTHERLY
DRAINAGE WINDS ARE EXPECTED TO REVERT BACK TO NORTHERLY AROUND
18Z.
SLC WATCHES/WARNINGS/ADVISORIES
UT...NONE.
WY...NONE.
SHORT TERM...10
LONG TERM/AVIATION...WEBBER
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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