Area Forecast Discussion
Issued by NWS Salt Lake City, UT

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 222201
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
401 PM MDT SUN MAR 22 2015

.SYNOPSIS...A FAST MOVING UPPER LEVEL DISTURBANCE WILL MOVE
THROUGH NORTHERN PORTIONS OF THE AREA TOMORROW. A SECONDARY
DISTURBANCE WILL MOVE THROUGH PRIMARILY FAR NORTHERN UTAH AND
SOUTHWEST WYOMING TUESDAY. STRONG HIGH PRESSURE ALOFT WILL RETURN
FOR THE LATTER HALF OF THE WEEK.

&&

.SHORT TERM (THROUGH 00Z THURSDAY)...AFTERNOON WATER VAPOR AND H5
ANALYSIS SHOWS AN EJECTING SHORT WAVE TROUGH BECOMING NEGATIVELY
TILTED ALONG THE NORCAL COASTLINE...WITH LONG WAVE EXTENDING
NORTHWEST INTO THE GULF OF AK. MEAN RIDGE POSITION HAS SHIFTED
EAST WITH AXIS WELL DOWNSTREAM OF THE AREA ATTM. AFOREMENTIONED
SHORT WAVE AND EVOLUTION/TRACK OF THE REMNANT LONG WAVE ARE THE
PRIMARY FORECAST ISSUES IN THE SHORT TERM THROUGH MIDWEEK.

THE INITIAL SHORT WAVE REMAINS ON TRACK TO PASS THROUGH NORTHERN
UTAH TOMORROW...WITH THE LEADING EDGE COLD FRONT PASSING THROUGH
THE WASATCH FRONT AROUND DAYBREAK. A PERIOD OF SOLID CAA FOR
SEVERAL HOURS BOTH AT THE LOW LEVELS AND ALOFT REMAINS ON TAP AS
SOLID TILT EXISTS THROUGH ABOUT H5 AND THE MID LEVEL COLD POOL
WILL TRACK OVERHEAD LATE AFTERNOON/EVENING. INCREASINGLY UNSTABLE
CONDITIONS ARE EXPECTED BY THE AFTERNOON HOURS AS SUCH...COINCIDENT
WITH INCREASING DYNAMIC LIFT DUE TO MODEST PVA AND FAVORABLE UPPER
ASCENT ASSOCIATED WITH THE LEFT EXIT REGION OF THE UPPER JET
NOSING IN. BOTTOM LINE...SHOWERY PRECIP ASSOCIATED WITH COLD
FRONTAL PASSAGE IN THE MORNING SHOULD TREND MORE STRATIFORM
MIDDAY/AFTERNOON FROM ROUGHLY KPVU NORTH. PERIODS OF MODEST PI
RATES CAN BE EXPECTED DUE TO DEEP LAYER FORCING AND INCREASING
INSTABILITY. WITH H7 TEMPS FALLING FROM 0 C TO -6 C BY 00Z
TUE...EXPECTING SNOW LEVELS TO LOWER TO MOUNTAIN VALLEY AREAS
TOMORROW AFTERNOON AND POSSIBLY THE HIGHEST BENCHES DURING THE
PERIODS OF MORE NOTABLE PI RATES.

PROGRESSIVE NATURE OF THE SHORT WAVE WILL TRACK THE BULK OF UPPER
SUPPORT EAST OF THE AREA TOMORROW EVENING AND THE UPPER JET WILL
LIFT NORTH AND EAST INTO SO. IDAHO. EXPECTING A NOTED LULL IN
PRECIP FOR THE LATTER HALF OF TUE NIGHT AS THIS OCCURS. THE SURFACE
FRONT WILL CONTINUE SOUTH HOWEVER WITH PASSAGE ACROSS THE SOUTHERN
TIER DRY. LOWERED POPS IN THE 06Z-12Z TUE WINDOW TO ACCOUNT FOR
THIS BREAK.

NOT OVERLY ENTHUSED WITH THE SECONDARY SHORT WAVE TUESDAY. UNLESS
THINGS CHANGE IN THE GUIDANCE...THE ONLY REAL MECHANISM FOR LIFT
OCCURS ALONG A MID LEVEL FRONT TRACKING SOUTH ACROSS THE NORTHERN
QUARTER OF THE AREA. UPPER JET SUPPORT REMAINS NORTH AND EAST OF
THE AREA...THERMAL PACKING IS MODEST AT BEST AND LITTLE TO NO
SURFACE REFLECTION EXISTS. THIS SAID...PRECIP REMAINS LIKELY
LARGELY KSLC NORTH WITH THE FOCUSED AREA STRETCHING FROM THE UT/ID
BORDER SOUTHEAST ACROSS SOUTHWEST WYOMING. TRENDED FORECAST
TOWARDS THE EC/CANADIAN/NAM VS. THE WETTER/MORE AREAL EXPANSIVE
GFS DUE TO UPPER SUPPORT REMAINING LARGELY NORTH/EAST OF THE
AREA.

OPTED NOT TO ISSUE A WINTER WEATHER HIGHLIGHT FOR THE NORTHERN
MOUNTAINS AS IMPACTS TO ROADS WILL REMAIN LARGELY ABOVE 7000FT
/UPPER COTTONWOODS AND UPPER LOGAN CANYON/ AND SNOW TOTALS ARE
MARGINAL AT BEST...WITH 4 TO 8 INCHES POSSIBLE ACROSS THE NORTHERN
MTNS/UINTAS BY WEDNESDAY.

&&

.LONG TERM (AFTER 00Z THURSDAY)...ALTHOUGH NEITHER THE EC NOR THE
GFS SHOW ANY QPF BETWEEN 00Z THURSDAY AND 06Z THURSDAY THERE APPEARS
TO BE ENOUGH DYNAMICS WITH THE JET ALOFT AND 700 MB MOISTURE NOT TO
BE ABLE TO COMPLETELY WRITE IT OFF...HENCE HAVE SOME SLIGHT CHANCE
OVER THE NORTHERN MOUNTAINS AND UINTAS. WINDS MAY BE GUSTY THROUGH
THE CANYONS OF SOUTHWEST UTAH WEDNESDAY EVENING WITH THE STRONG
SURFACE HIGH AND 700MB FLOW ALIGNING.

THE JET MOVES EAST OF UTAH BY THURSDAY AS THE RIDGE BUILDS INTO THE
REGION. DESPITE BEING UNDER A NORTHERLY FLOW THE H7 TEMPS WARM BY
ABOUT 5C SO DECENT WARMING IS EXPECTED IN BOTH THE VALLEYS AND THE
MOUNTAINS BETWEEN WEDNESDAY AND THURSDAY. A DRY AND WARMING TREND IS
EXPECTED TO CONTINUE FRIDAY THROUGH SATURDAY.

THE GLOBAL MODELS DIVERGE SIGNIFICANTLY FROM EACH OTHER BY SUNDAY
WITH THE EC BEING THE LONE MODEL SHOWING A CLOSED LOW PINCHING OFF
FROM AN UPSTREAM TROUGH AND PROGRESSING INTO SOUTHERN CALIFORNIA.
THIS WOULD PLACE SOUTHWEST UTAH UNDER A DEFORMATION ZONE SUNDAY WITH
CLOUDS AND A CHANCE OF PRECIPITATION. HOWEVER...SINCE THE EC IS THE
ONLY MODEL WITH THIS SOLUTION DID NOT BUY OFF ON IT. HAVE LEANED
HEAVILY TOWARDS THE GFS SOLUTION WHICH KEEPS THE RIDGE FIRMLY IN
PLACE OVER THE CWA. THEREFORE REMOVED THE LOW CHANCE POPS FROM
EARLIER FORECAST FOR SATURDAY NIGHT AND SUNDAY.

&&

.AVIATION...LIGHT NORTHWEST WINDS AT THE SLC TERMINAL THE REST OF
TODAY AND THIS EVENING THEN BACK TO SOUTHEAST BETWEEN 03 AND 04Z.
CIGS WILL LOWER BELOW 7K FT AGL BETWEEN 12 AND 14Z MONDAY ALONE WITH
A WIND SHIFT TO NORTHWEST BEHIND A PASSAGE OF A COLD FRONT. CIGS OF
3-5K FT AGL LIKELY TO PREVAIL MONDAY WITH A 40 PERCENT CHANCE THAT
CIGS WILL GO BELOW MVFR CONDITIONS AFTER 13-14Z TOMORROW.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...NONE.
WY...NONE.
&&

$$

MERRILL/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)



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