Area Forecast Discussion
Issued by NWS Salt Lake City, UT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KSLC 282303
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
403 PM MST SUN DEC 28 2014

.SYNOPSIS...A COLD STORM SYSTEM WILL SETTLE INTO THE AREA THROUGH
MONDAY. VERY COLD AIR WILL SPILL SOUTHWARD ACROSS UTAH MONDAY NIGHT
THROUGH TUESDAY. THE COLD STORM SYSTEM WILL INTENSIFY AGAIN OVER
SOUTHERN UTAH MIDWEEK.

&&

.SHORT TERM (THRU 12Z WED)...A BROAD COLD TROF CONTINUES TO DEEPEN
OVER THE PACNW AND NRN ROCKIES THIS AFTN AND HAS PUSHED A COLD FRONT
INTO NRN UT THAT IS SITTING BETWEEN ABOUT PROVO AND NEPHI AT THIS
TIME.

PRECIP ALONG THIS FRONT HAS BEEN SPOTTY IN THE VALLEYS SO FAR AND
HAS TAPERED OFF NORTH OF DAVIS CO BUT THE SRN WASATCH MTNS HAVE BEEN
PICKING UP DECENT ACCUMULATION. EXPECT PERIODIC SURGES OF SNOW ALONG
THE FRONTAL BOUNDARY AS IS MOVES SLOWLY SWD OVERNIGHT INTO MON BUT
THE MAIN IMPACT SHOULD REMAIN ON THE BENCHES FROM ABOUT OGDEN SWD
THRU UT CO AND IN THE SRN WASATCH MTNS. WINTER STORM WARNINGS WERE
DOWNGRADED EARLIER DUE TO THE PATCHY NATURE OF THE SNOWFALL AND WILL
KEEP THESE UNCHANGED AT THIS TIME.

THE THREAT OF LAKE EFFECT SNOW SHOWERS IS NOW LOWER THAN IT WAS
EARLIER MAINLY DUE TO THE LACK OF SATURATION IN THE LOW LEVELS BUT
THERE IS STILL THE POTENTIAL OF LAKE ENHANCEMENT OF SNOW SHOWERS
DOWNWIND ACROSS SRN DAVIS AND ERN SALT LAKE COUNTIES IN TIME TO
IMPACT THE MON MORNING COMMUTE OVER PARLEYS AND INTO THE CENTRAL
WASATCH FRONT VALLEYS.

THE ARCTIC AIRMASS THAT IS CURRENTLY SPILLING SWWD INTO THE
DEVELOPING BROAD UPPER TROF CROSSES WY DURING THE DAY MON AND
STARTS TO SPILL INTO NRN UT BY LATE IN THE DAY. THIS TIGHTENS THE
SURFACE PRESSURE AND THERMAL GRADIENT AND THIS PLUS EASTERLY FLOW
ALOFT SHOULD GENERATE STRONG GUSTY CANYON WINDS ALONG THE WASATCH
FRONT MON NIGHT THRU MIDDAY TUE. THIS APPEARS THAT IT WILL BE A
WARNING LEVEL EVENT BUT WIND GUSTS ARE NOT EXPECTED TO EXCEED
ABOUT 60-65 MPH. WE HAVE ISSUED A HIGH WIND WATCH FOR THIS EVENT.

THE OLD FRONTAL BOUNDARY GETS OVERTAKEN BY THE ARCTIC SURGE AND
SOME SNOW COULD ACCOMPANY THIS THRU CENTRAL UT MON NIGHT INTO
TUE.

&&

.LONG TERM (AFTER 12Z WEDNESDAY)...12Z GLOBAL MODELS CONTINUED TO
REMAIN IN NEAR LOCKSTEP REGARDING THE EVOLUTION OF THE DESERT
SOUTHWEST CLOSED LOW. CHANGED LITTLE TO FORECAST IN THIS PACKAGE
OTHER THAN CONTINUING TO NOSE POPS UP ACROSS THE FAR SOUTH WED
THROUGH THU...ESPECIALLY TERRAIN ACROSS THE GIANT STAIRCASE AND
AREAS FAVORED BY SOUTHEASTERLY FLOW/UPSLOPE SUCH AS THE
BOULDER/ESCALANTE AREAS. THIS SAID...18Z GFS JUST NOW VIEWED AND HAS
BECOME A BIT MORE PROGRESSIVE AND LESS EXPANSIVE W/QPF ACROSS THE
SOUTH AS THE LOW SKIRTS ACROSS NORTHERN AZ/NM. FORECAST IS NOT BASED
ON THAT SOLUTION BUT WILL HAVE TO MONITOR RUN TO RUN CONSISTENCY
OVER THE NEXT FEW.

BOTTOM LINE...WIDESPREAD SNOW REMAINS LIKELY FOR AREAS GENERALLY
SOUTH OF I-70 WED/THU...WITH SNOW LEVELS FALLING TO ALL AREAS
INCLUDING UTAHS DIXIE AND THE LAKE POWELL AREA. MSLP GRADIENT
ORIENTED N-S ACROSS DIXIE WILL LIKELY LIMIT ACCUMULATION POTENTIAL
THERE AS DOWNSLOPING WINDS WILL TREND TO DRY THE LOWER LEVELS AND
MINIMIZE LOW LEVEL LIFT POTENTIAL...BUT SOME SNOW REMAINS FORECAST.

THE UPPER LOW DEPARTS TO THE SOUTHEAST THURSDAY NIGHT BRINGING AN
END TO ACCUMULATING SNOWFALL ACROSS THE SOUTH...BUT VERY COLD TEMPS
WILL REMAIN ACROSS THE AREA.

LARGE SCALE PATTERN THEREAFTER REMAINS A LOW CONFIDENCE FORECAST AS
GLOBAL MODELS GO OUT OF PHASE LATE WEEK ON. 12Z ECMWF HINTING AT A
FAIRLY HIGH AMPLITUDE RIDGE BUILDING IN FROM THE SOUTHWEST WHILE GFS
RETAINS CYCLONIC FLOW ALOFT ACROSS THE NORTH DUE TO A BROAD LONG
WAVE TROUGH FROM THE GREAT LAKES WEST THROUGH THE NORTHERN ROCKIES.
NO CHANGES MADE TO FORECAST DUE TO LACK OF MODEL TO MODEL
AGREEMENT/LOW CONFIDENCE ATTM.

&&

.AVIATION...LIGHT SNOW SHOWERS WILL CONTINUE INTERMITTENTLY AT THE
KSLC TERMINAL THROUGH TONIGHT. AS SUCH...CIGS AOB 6000 FT AGL REMAIN
FORECAST WITH A 50 PERCENT CHANCE OF VISIBILITIES LOWERING TO IFR
FOR BRIEF PERIODS. SOUTHEASTERLY SURFACE WINDS ARE EXPECTED TO
SWITCH TO A WEST OR NORTHWEST BETWEEN 23-00Z THIS EVENING AND REMAIN
IN PLACE THROUGH 09-10Z AT LEAST.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER WEATHER ADVISORY UNTIL 4 PM MST MONDAY FOR UTZ001>004-
     006>010.

     HIGH WIND WATCH FROM MONDAY EVENING THROUGH TUESDAY AFTERNOON
     FOR UTZ002.

WY...WINTER WEATHER ADVISORY UNTIL 10 PM MST MONDAY FOR WYZ021.

&&

$$

SHORT TERM...WILENSKY
LONG TERM/AVIATION...MERRILL

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)

FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP (ALL LOWER CASE)



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.