Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 222228
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
428 PM MDT TUE JUL 22 2014

.SYNOPSIS...SOUTHWEST FLOW WILL CAUSE MOISTURE TO INCREASE FROM
THE SOUTH TONIGHT AND WEDNESDAY. THIS MOISTURE WILL LINGER OVER
SOUTHERN UTAH THURSDAY AND FRIDAY BEFORE HIGH PRESSURE BUILDS OVER
THE WEEKEND...BRINGING DRYING AND WARMING CONDITIONS.


&&

.DISCUSSION...A DRY AIRMASS REMAINS OVER THE FORECAST AREA THIS
AFTERNOON WITH SOUTHWEST FLOW ALOFT. SKIES ARE MOSTLY CLEAR WITH
THE EXCEPTION OF A BIT OF CUMULUS DEVELOPING OVER THE UINTAS AND
THE CENTRAL AND SOUTHERN MOUNTAINS. DO NOT EXPECT ANY OF THIS TO
DEVELOP INTO SHOWERS THROUGH THE EVENING HOURS. TEMPERATURES
REMAIN QUITE MILD THIS AFTERNOON WITH MAXES RUNNING SLIGHTLY ABOVE
CLIMO. GUSTY SOUTHERLY WINDS ARE PRODUCING SOME CRITICAL FIRE
WEATHER CONDITIONS WHERE FUELS ARE DRY.

THE SLUG OF DRY AIR OVER THE STATE WILL SHIFT NORTH OVERNIGHT AS A
MORE MOIST AIRMASS MAKES ITS WAY INTO SOUTHERN UTAH IN ITS PLACE.
BY TOMORROW AFTERNOON...MOISTURE AXIS SHOULD RUN NORTHEAST TO
SOUTHWEST ACROSS UTAH AND SOUTHWEST WYOMING. PWS ARE PROGGED TO
RUN IN EXCESS OF ONE INCH OVER THE SOUTHEAST HALF OF THE
STATE...WITH THE GFS INDICTING PWS APPROACHING 1.4 INCHES IN SOME
LOCATIONS...IN EXCESS OF TWO STANDARD DEVIATIONS ABOVE NORMAL FOR
THIS TIME OF YEAR. ADDITIONALLY...A SHORTWAVE IS EXPECTED TO MOVE
ACROSS THIS AREA TOMORROW AFTERNOON. HOWEVER...THERE IS CONCERN IN
SITUATIONS LIKE THIS THAT EXTENSIVE CLOUD COVER WILL LIMIT
CONVECTIVE DEVELOPMENT AND THUS WILL LIMIT THREAT OF FLASH
FLOODING. THERE IS ALSO CONCERN ALONG THE DEVELOPING MOISTURE
GRADIENT TOMORROW THAT DRY LIGHTNING AND/OR DRY MICROBURST TYPE
WINDS WILL DEVELOP. HOWEVER...THE PREVIOUSLY MENTIONED CONCERNS
ABOUT CLOUD COVER APPLY HERE AS WELL.

BY THURSDAY...MODELS CONTINUE TO INDICATE A PACIFIC NORTHWEST
TROUGH MOVING NORTH OF THE AREA THAT WILL FLATTEN THE
RIDGE...TURNING THE FLOW MORE WESTERLY. THIS WILL MAKE THE
MOISTURE AXIS MORE WEST/EAST ORIENTED AND WILL CAUSE AN OVERALL
DECREASE IN MOISTURE. THE TROUGH WILL ALSO PUSH A DRY BOUNDARY
INTO NORTHERN UTAH...BRINGING TEMPERATURES BACK TO AROUND CLIMO
FOR THURSDAY AND INTO FRIDAY. MODELS AGREE THAT THE RIDGE AXIS
STRENGTHENS OVER UTAH AND SOUTHWEST WYOMING OVER THE
WEEKEND...RESULTING IN DRYING AND WARMING CONDITIONS. THERE IS
SOME INDICATION THAT MOISTURE WILL MOVE BACK IN FOR THE EARLY TO
MIDDLE PART OF NEXT WEEK.

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL AT KSLC THROUGH THE
EVENING...WITH NORTH WINDS SWITCHING TO THE SOUTH AROUND 03Z.

&&

.FIRE WEATHER...THERE ARE TWO MAIN FIRE WEATHER CONCERNS OVER
THE NEXT FEW DAYS. THE FIRST IS GUSTY WINDS AND LOW RELATIVE
HUMIDITY...AND THE SECOND IS THE POTENTIAL FOR DRY THUNDERSTORMS
ACROSS PORTIONS OF SOUTHWEST AND CENTRAL UTAH TOMORROW AFTERNOON.

AS FAR AS WINDS...CRITICAL WINDS ARE STILL EXPECTED TO DEVELOP
ACROSS WESTERN UTAH THIS AFTERNOON...THOUGH THEY WILL NOT BE AS
WIDESPREAD AS YESTERDAY. GUSTY SOUTHWESTERLY WINDS WILL DEVELOP
AGAIN TOMORROW AFTERNOON ACROSS NORTHWESTERN UTAH. THESE
WINDS...COMBINED WITH LOW HUMIDITY...WILL COMBINE TO CREATE
HAZARDOUS FIRE WEATHER CONDITIONS...AND SO THE RED FLAG WARNING
FOR WINDS AND LOW RH HAS BEEN EXTENDED THROUGH TOMORROW EVENING
FOR ZONE 478...THE NORTHWEST CORNER OF UTAH.

AS FAR AS LIGHTNING GOES...MOISTURE WILL SPREAD INTO SOUTHERN
UTAH OVERNIGHT TONIGHT...AND CONTINUE NORTHWARD INTO CENTRAL UTAH
THROUGH LATE TOMORROW MORNING. THIS MOISTURE WILL RESULT IN
SHOWERS AND THUNDERSTORMS ACROSS THE HIGHER TERRAIN TOMORROW
AFTERNOON. ACROSS SOUTHEASTERN UTAH WHERE THE MOISTURE IS
DEEPEST...MOST STORMS WILL BE ACCOMPANIED BY WETTING RAIN.
HOWEVER...ACROSS PORTIONS OF SOUTHWEST AND CENTRAL UTAH...MOISTURE
WILL BE LARGELY CONFINED TO THE MID AND UPPER LEVELS...INCREASING
THE THREAT FOR DRY LIGHTNING. DRY LIGHTNING IS CHALLENGING TO
FORECAST...AND SO THERE IS THE POSSIBILITY THAT MOST OF THE STORMS
ACROSS SOUTHWEST AND CENTRAL UTAH WILL ALSO BE ACCOMPANIED BY
WETTING RAIN. HOWEVER...FEEL THAT THE THREAT FOR DRY LIGHTNING IS
HIGH ENOUGH TO WARRANT A RED FLAG WARNING FOR PORTIONS OF
SOUTHWEST AND CENTRAL UTAH.

A SHALLOW FRONT WILL MOVE INTO NORTHWEST UTAH THURSDAY
MORNING...ADVANCING INTO CENTRAL UTAH BY LATE AFTERNOON. THIS IS A
WEAK FRONT...AND THE MAIN IMPACT WILL BE A SHIFT OF SURFACE WINDS
TO THE NORTH WITH THE FRONT. WINDS WILL REMAIN ELEVATED ACROSS
NORTHERN UTAH THURSDAY AND FRIDAY...BUT AT THIS TIME IT APPEARS
THAT SPEEDS WILL REMAIN JUST BELOW CRITICAL LEVELS.

HIGH PRESSURE WILL BUILD OVER THE FORECAST AREA THIS WEEKEND
BRINGING A WARMING...DRYING TREND AND A DECREASE IN WINDS.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...RED FLAG WARNING FROM NOON TO 10 PM MDT WEDNESDAY FOR UTZ488-489-
     492-493-495-496.

     RED FLAG WARNING UNTIL 10 PM MDT WEDNESDAY FOR UTZ478.

     RED FLAG WARNING UNTIL 10 PM MDT THIS EVENING FOR UTZ492-495.

WY...NONE.
&&

$$

PUBLIC...TRAPHAGAN
FIRE WEATHER...HOSENFELD
AVIATION...SEAMAN

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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