Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 222326
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
426 PM MST SUN FEB 22 2015

.SYNOPSIS...A COLD UPPER LOW WILL STALL OVER THE WESTERN GREAT
BASIN THROUGH MONDAY THEN TRACK EAST MONDAY NIGHT THROUGH TUESDAY.
HIGH PRESSURE WILL BRIEFLY RETURN TO THE REGION LATER TUESDAY. A
SERIES OF DISTURBANCES WILL CROSS THE REGION WEDNESDAY THROUGH
NEXT WEEKEND.

&&

.SHORT TERM (THRU 00Z WED)...A COLD UPPER TROF EXTENDS FROM WRN
WY SWWD TO CENTRAL CA THIS AFTERNOON AND CONTINUES TO GENERATE
WIDESPREAD SNOW ACROSS ABOUT THE SRN HALF OF UT WITH RAIN BELOW
ABOUT 5000 FT.

THE UPPER TROF CLOSES OFF INTO A LOW NEAR RENO NV BY MON MORNING
THEN SLOWLY ELONGATES EWD ACROSS SRN NV DURING THE DAY. THE LOW
THEN TRACKS SLOWLY EAST ACROSS NRN AZ MON NIGHT THRU TUE MORNING
THEN OFF TO THE EAST TUE AFTN.

THIS KEEPS PRECIP GOING ACROSS THE SRN CWA WITH GENEROUS AMOUNTS
EXPECTED. SNOW SHOULD LOWER TO LAKE LEVEL AT LAKE POWELL THIS EVE
AND REMAIN THAT LOW THRU EARLY TUE. THIS SHOULD GENERATE
SUFFICIENT ACCUMULATION TO WARRANT EXPANDING THE WARNING TO
INCLUDE THIS ZONE AND HAVE DONE SO. CURRENT WARNING ON TRACK
ELSEWHERE AND RAISED FORECAST TOTALS SOMEWHAT ESPECIALLY IN THE
CEDAR CITY AREA. SNOW LEVELS COULD DIP TO JUST BELOW 4000 FT IN
THE DIXIE AREA BUT DONT ANTICIPATE ANY SIGNIFICANT ACCUMULATION
BELOW ABOUT 4500 FT IN THIS AREA AND HAVE LEFT THEM OUT OF THE
WARNING.

PRECIP SHOULD WIND DOWN FAIRLY QUICKLY FROM THE WEST LATE MON
NIGHT THRU TUE MORNING AS THE LOW SPINS OFF TO THE EAST.

THE TIGHT EASTERLY PRESSURE GRADIENT REMAINS IN PLACE ACROSS SRN
WY AND NRN UT AND IS FORECAST TO TIGHTEN A BIT TONIGHT BEFORE
RELAXING MON. THIS WILL KEEP GUSTY EAST WINDS GOING ALONG THE
WASATCH FRONT FROM NERN SALT LAKE CO NWD THRU THE CACHE VALLEY.
STRONGEST WINDS HAVE AS USUAL BEEN IN DAVIS CO WHERE CURRENT
WARNING IS ON TRACK. EXPECT THE WINDS TO PICK UP TONIGHT MAINLY
WEBER DAVIS AND SALT LAKE COUNTIES AS THE GRADIENT TIGHTENS AND
WINDS AT AND BELOW 700 MB INCREASE AS WELL. HAVE EXPANDED THE HIGH
WIND WARNING SWD INTO NERN SALT LAKE CO AS EXPECT VERY STRONG
GUSTS OUT OF THE CANYONS IN THIS AREA BUT KEPT THE HIGHLIGHTS OUT
OF THE CACHE VALLEY AS SPEEDS THERE ARE NOT EXPECTED TO GET MUCH
ABOVE MARGINAL ADVISORY LEVELS.

THE WINDS SHOULD DROP OFF DURING THE DAY MONDAY AS THE SURFACE
GRADIENT REVERSES TO NWLY BY LATE IN THE DAY.

EXPECT SMALL DIURNAL TEMPERATURE RANGES SRN UT TONIGHT THRU MON
UNDER OVERCAST SKIES WILL WIDESPREAD PRECIP THEN LOWS SHOULD FALL
ACROSS THE SW MON NIGHT AS PRECIP STARTS TO TAPER OFF. SKIES
SHOULD REMAIN MOSTLY CLEAR ACROSS THE NRN CWA THRU TUE BUT THE
COLD EASTERLIES WILL KEEP TEMPS SOMEWHAT BELOW NORMAL FOR A
CHANGE.

&&

.LONG TERM (AFTER 00Z WEDNESDAY)...A SHORTWAVE RIDGE WILL MOVE
OVER THE CWA TUESDAY NIGHT INTO WEDNESDAY. HOWEVER...THE EC SHOWS A
WEAK DISTURBANCE BRUSHING BY SOUTHWEST WYOMING AND THE WESTERN
UINTAS WEDNESDAY. THERE WAS ONE GFS ENSEMBLE MEMBER ALSO INDICATING
SAID DISTURBANCE SO LEFT SOME TOKEN POPS IN FOR THE HIGHER TERRAIN
OF THE NORTHERN WASATCH AND UINTAS BUT DO NOT HAVE MUCH CONFIDENCE
THAT ANYTHING WILL HAPPEN.

TIMING DIFFERENCES OCCURS AFTER THIS FOR THURSDAY NIGHT INTO THE
WEEKEND BETWEEN THE GFS AND THE EC WHICH KEEPS THE CONFIDENCE IN
PINPOINTING TIME FRAME FOR GREATEST THREAT OF PRECIP DOWN DURING
THIS PERIOD. THE OVERALL GENERAL SOLUTION IS FOR A COUPLE OF
DISTURBANCES TO MOVE SOUTHEAST ACROSS THE CWA IN A SOMEWHAT ACTIVE
NORTHWEST FLOW THURSDAY INTO FRIDAY BEFORE BOTH THE GFS AND EC CARVE
A LONG WAVE TROUGH OVER THE GREAT BASIN AND CALIFORNIA LATE FRIDAY
INTO SUNDAY. THE EC IS A LITTLE MORE PROGRESSIVE AND KEEPS MORE
ENERGY MOVING THROUGH NORTHERN UTAH WHILE THE GFS OPERATIONAL RUN
CLOSES OFF A CIRCULATION TEMPORARILY OVER CALIFORNIA SATURDAY NIGHT.
THIS HAS HUGE IMPLICATIONS AS FAR AS WHERE AND HOW MUCH PRECIP
OCCURS ACROSS THE CWA. THE GENERAL IDEA OF HIGHER THAN CLIMO POPS
LOOKS GOOD AND HAVE EVEN BOOSTED SOME POPS SATURDAY AND SATURDAY
NIGHT OVER THE HIGHER TERRAIN OF MAINLY NORTHERN AND CENTRAL UTAH.
HOWEVER FOR THE LOWER ELEVATIONS IT WAS HARD TO JUSTIFY PUSHING POPS
HIGHER THAN CHANCE AT THIS POINT. TEMPERATURES WILL REMAIN NEAR
NORMAL ACROSS THE REGION THROUGH THE PERIOD BUT COULD HAVE SOME
PLACES BE SEVERAL DEGREES ABOVE NORMAL WEDNESDAY UNDER THE RIDGE BUT
AREAS OVER SOUTHERN UTAH MAY NOT EXPERIENCE THE WARMING AS MUCH DUE
TO AN EXTENSIVE AND POSSIBLY DEEP SNOW COVER.

DUE TO THE TIMING AND CONFIGURATION DIFFERENCES BETWEEN THE GLOBAL
MODEL SOLUTIONS HAVE BACKED OFF ON THE MAGNITUDE OF THE SOUTHERLY
WIND FOR SATURDAY THAT THE GFS WAS FORECASTING. THE REASON IS IF THE
EC IS CORRECT THE WINDS WOULD BE NORTHWESTERLY. A COUPLE OF THE GFS
ENSEMBLE MEMBERS SUPPORTED THE EC SOLUTION SO THE VERDICT IS OUT AS
WHAT WILL HAPPEN. THERE IS NEARLY 100 METERS VARIANCE IN THE GFS
ENSEMBLE MEMBERS 500 MB HEIGHTS WEST OF CALIFORNIA 06Z SATURDAY.

&&

.AVIATION...NORTH NORTHEAST WINDS ARE EXPECTED TO BE THE PREDOMINANT
WIND DIRECTION THROUGH THIS EVENING AT THE SLC TERMINAL.
HOWEVER...DUE TO LOCAL EDDY EFFECTS FROM EASTERLY WINDS OFF THE
NEARBY WASATCH MOUNTAINS...OCCASIONAL TEMPORARY WIND SHIFTS TO ANY
DIRECTION ARE POSSIBLE. NO VSBY OR CIG ISSUES.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING UNTIL 8 AM MST TUESDAY FOR UTZ013-014-016-
     020-021-517-518.

     HIGH WIND WARNING UNTIL 11 AM MST MONDAY FOR UTZ002-003.

WY...NONE.
&&

$$

SHORT TERM...WILENSKY
LONG TERM/AVIATION...STRUTHWOLF

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)



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