Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 240302
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
902 PM MDT TUE SEP 23 2014

.SYNOPSIS...HIGH PRESSURE WILL BUILD INTO THE AREA THROUGH LATE
WEEK. ANOTHER STORM SYSTEM WILL MOVE INTO THE REGION FOR THE
WEEKEND.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS A RIDGE OVER THE SOUTHWEST
CONUS WITH A LARGE CLOSED LOW OFF THE PACIFIC NORTHWEST. AMDAR
400-250MB WIND OBSERVATIONS REVEAL A CYCLONIC 75-115KT JET OVER
THE PACIFIC NORTHWEST...AND A WESTERLY 50-75KT JET OVER THE
SOUTHWEST CONUS. GOES/GPS/RAP/00Z RAOB INDICATE THE PRECIPITABLE
WATER VALUE RANGES BETWEEN 0.40" SOUTHWEST UTAH TO 1.00" ACROSS
NORTHWEST UTAH.

IR SATELLITE SHOWS MID AND HIGH LEVEL CLOUDS SPILLING INTO NORTHERN
UTAH ATOP THE AFOREMENTIONED RIDGE. HAVE INCRESED CLOUD COVER ACROSS
THE NORTHWEST AS A RESULT.

MOST AREAS ARE SEEING A 3-8F DROP IN DEWPOINTS DURING THE PAST 24
HOURS...EXCEPT NORTH OF BOUNTIFUL WHERE DEWPOINTS HAVE RISEN 2-5F.
00Z KSLC RAOB SHOWS LOW LEVEL WINDS VEERING INDICATING WARM
ADVECTION...WHILE BOTH RAP AND NAM INDICATE THE 850-700MB THICKNESS
INCREASES ACROSS NORTHERN UTAH OVERNIGHT. GIVEN ALL THIS AND SOME
APPROACHING CLOUDS...WARMED OVERNIGHT LOWS A BY A FEW DEGRESS NORTH
OF INTERSTATE 80.

&&

.PREVIOUS DISCUSSION...HIGH PRESSURE CONTINUES TO BUILD INTO THE
AREA THIS AFTERNOON WITH MOSTLY SUNNY SKIES THE RULE ACROSS MUCH OF
THE CWA. TEMPERATURES ARE AVERAGING 5 TO 10 DEGREES ABOVE AVERAGE OR
SO FOR MANY LOCATIONS. THIS TREND WILL CONTINUE AS THE RIDGE ACROSS
THE WEST AMPLIFIES IN RESPONSE TO A LARGE...STRONG AND COLD PACIFIC
TROUGH APPROACHING THE WEST COAST. TEMPERATURES WILL CONTINUE TO
INCREASE ABOVE NORMAL LEVELS...REACHING ABOUT 10 TO 15 DEGREES ABOVE
NORMAL WEDNESDAY THROUGH FRIDAY ACROSS MANY LOCATIONS.

ATTENTION THEN TURNS TO THE PREVIOUSLY MENTIONED TROUGH AS IT
APPROACHES THE PACIFIC COAST. TWO MAIN SCENARIOS HAVE BEEN DEPICTED
BY THE GLOBAL MODELS AND BOTH HINGE ON THE STRENGTH OF A SHORTWAVE
UPSTREAM OF THE MAIN TROUGH. AS THE TROUGH CONTINUES TO MOVE
ONSHORE...THE 12Z GFS BEGINS TO ATTEMPT TO CUT THE LOW FROM THE MAIN
FLOW. EARLIER RUNS OF THIS MODEL CUT THE LOW COMPLETELY OFF WHILE
THE 12Z RUN IS LESS AMBITIOUS DUE TO A WEAKER UPSTREAM SHORTWAVE.

THE 12Z EC FEATURES A MUCH STRONGER UPSTREAM SHORTWAVE THAT KEEPS
THE TROUGH FROM CUTTING OFF OVER THE WESTERN GREAT BASIN AND PUSHES
A STRONG BUT PROGRESSIVE TROUGH THROUGH THE CWA. THE MAIN MESSAGE
FROM BOTH MODELS IS THAT PERIOD OF WIDESPREAD PRECIPITATION IS
LIKELY FOR MUCH OF THE STATE SATURDAY INTO SUNDAY. BOTH 12Z MODELS
ARE A BIT WARMER ALOFT THAN PREVIOUS RUNS...KEEPING SNOW LEVELS
AROUND 10000 FEET SUNDAY.

WITH THE STRONGER UPSTREAM WAVE...THE EC BRINGS A VERY FALL-LIKE
COLD FRONT THROUGH AREA MID-WEEK NEXT WEEK...WITH 700MB TEMPERATURES
FALLING TO NEAR -6C ACROSS NORTHERN UTAH. THE 06Z GFS WAS SOMEWHAT
SIMILAR IN THIS REGARD. THE 12Z GFS HAS MORE OF A WEAK
FEATURE...PASSING THROUGH THE NORTHERN INTERMOUNTAIN REGION MIDWEEK.

THE MAIN POINTS TO TAKE AWAY FROM THE FORECAST ARE TO EXPECT A
PERIOD OF ABOVE NORMAL TEMPERATURES THROUGH FRIDAY. A PATTERN SHIFT
TO A WETTER...COOLER AND MORE PROGRESSIVE PATTERN LOOKS LIKELY THIS
WEEKEND AND PERHAPS THROUGH MIDWEEK NEXT WEEK AT LEAST. THOSE WHO
MAY BE TRAVELING TO THE HIGHER ELEVATIONS OF NORTHERN AND CENTRAL
UTAH THIS WEEKEND SHOULD CONTINUE TO MONITOR
FORECASTS...PARTICULARLY IF TRAVELING ABOVE 9000 FEET.

&&

.AVIATION...WINDS AT THE SLC TERMINAL HAVE SWITCHED TO SOUTHEAST
FOR THE NIGHT. VFR CONDITIONS WILL PREVAIL UNDER MOSTLY CLEAR
SKIES.

&&

.FIRE WEATHER...HIGH PRESSURE WILL REMAIN OVER THE AREA THROUGH
TOMORROW BEFORE SHIFTING EAST THURSDAY AS A PACIFIC STORM SYSTEM
MOVES TOWARD THE CALIFORNIA COAST. TEMPERATURES WILL CONTINUE TO
WARM AND WILL REMAIN EXTREMELY MILD INTO THE UPCOMING WEEKEND. AS
THE STORM SYSTEM APPROACHES...SOUTHERLY WINDS WILL INCREASE FOR THE
LATTER HALF OF THE WORK WEEK...BECOMING GUSTY IN SOME LOCATIONS. THE
STORM SYSTEM IS EXPECTED TO MOVE INTO THE AREA SATURDAY NIGHT AND
WILL REMAIN IN PLACE INTO THE EARLY PART OF THE UPCOMING WEEK.

&&

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

$$

PUBLIC...ROGOWSKI/KRUSE
FIRE WEATHER...TRAPHAGAN
AVIATION...ROGOWSKI

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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