Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 131055
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
455 AM MDT MON APR 13 2015

.SYNOPSIS...HIGH PRESSURE ALOFT ACROSS UTAH TODAY WILL BE
FOLLOWED BY A COLD AND STRONG PACIFIC STORM SYSTEM AFFECTING THE
REGION TUESDAY THROUGH WEDNESDAY NIGHT. HIGH PRESSURE ALOFT WILL
RETURN LATE IN THE WEEK.

&&

.SHORT TERM (THROUGH 00Z FRIDAY)...THE LOW-AMPLITUDE UPPER RIDGE
OVER UTAH WILL SHIFT OFF TO THE EAST THIS MORNING AHEAD OF A VERY
COLD AND ENERGETIC PACIFIC TROUGH SCHEDULED TO ARRIVE OVER UTAH
TUESDAY NIGHT. TEMPERATURES WILL INCREASE SUBSTANTIALLY TODAY AS A
WARM SOUTHWEST FLOW ALOFT DEVELOPS OVER THE STATE THIS AFTERNOON.
A BREEZY AND MILD NIGHT WILL FOLLOW AS THE TROUGH CONTINUES TO
ADVANCE THROUGH THE GREAT BASIN.

VERY WINDY CONDITIONS WILL DEVELOP ACROSS THE FORECAST AREA ON
TUESDAY. A STRONG COLD FRONT SUPPORTED BY SOLID LOW-LEVEL COLD
ADVECTION WILL PRESS EAST ACROSS NEVADA TONIGHT...SETTLING INTO
NORTHEAST NEVADA BY EARLY TUESDAY. AHEAD OF THE FRONT THE NEAR
700MB WINDS WILL RANGE BETWEEN 35 AND 45 KNOTS ACROSS WESTERN UTAH
DURING THE MORNING...LEADING TO AN START TO STRONG SOUTH WINDS
DURING THE MORNING. GOOD LATE MORNING AND AFTERNOON MIXING AHEAD
OF THE ADVANCING FRONT WILL LEAD TO VERY STRONG AND GUSTY SURFACE
WINDS ACROSS MUCH OF THE STATE. AT THIS POINT IN APPEARS TO BE A
SOLID WIND ADVISORY OR MARGINAL HIGH WIND EVENT FOR THE WESTERN
VALLEYS PRE-FRONTAL. SOUTHERN AND EASTERN UTAH APPEAR TO BE MORE
IN LINE FOR A HIGH-END WIND ADVISORY EVENT TUESDAY AFTERNOON AND
EARLY EVENING. IN THE POST-FRONTAL ENVIRONMENT STRONG LOW-LEVEL
COLD ADVECTION AND A TIGHT SURFACE GRADIENT WOULD SUPPORT A BRIEF
PERIOD OF HIGH WINDS ACROSS NORTHWEST UTAH DURING THE LATE
AFTERNOON AND EVENING HOURS. THIS POST-FRONTAL AREA WILL BE THE
MOST LIKELY AREA TO REACH HIGH WIND CRITERIA ASSOCIATED WITH THE
COLD FRONT. WILL LEAVE THE HIGH WIND WATCH UP FOR NOW...THOUGH
SUSPECT THAT ONLY THE NORTHWEST DESERTS AND A FEW OTHER WIND PRONE
AREAS OF NORTHWEST AND WEST-CENTRAL UTAH WILL MEET CRITERIA. OTHER
AREAS OF THE WATCH WILL LIKELY END SOLID ADVISORY-LEVEL CRITERIA.

SOLID FRONTAL LIFT SUPPORTED BY A RAPIDLY DESTABILIZING AIRMASS
WITH ARRIVAL OF THE MID-LEVEL COLD AIR IN THE TROUGH SHOULD
PRODUCE DEEP CONVECTION ALONG AND BEHIND THE SURFACE FRONT LATE
TUESDAY AFTERNOON AND EVENING. A BRIEF BUT INTENSE CONVECTIVE
PRECIP EVENT ASSOCIATED WITH THE FRONT WILL PUT DOWN A COUPLE OF
QUICK INCHES OF SNOW IN THE MOUNTAINS...WITH RAIN AND/OR SNOW
SHOWERS IN THE VALLEYS/FOOTHILLS. PRECIP COULD DECREASE IN
INTENSITY/AREAL COVERAGE BEHIND THE FRONT FOR A TIME LATE TUESDAY
NIGHT...THEN RETURN AGAIN AS WIDESPREAD SNOW SHOWERS ACROSS
NORTHERN/CENTRAL UTAH AS THE TROUGH EVOLVES INTO A CLOSED LOW
SQUARELY OVER THE REGION LATE TUESDAY NIGHT/WEDNESDAY. THE LATEST
RUNS OF THE GFS ARE CLEARLY MORE FAVORABLE FOR PRECIP ACROSS
NORTHERN UTAH AS THE CENTER OF THE NOW DEVELOPED UPPER LOW
POSITIONS ACROSS SOUTHWEST WYOMING OR NORTHEAST UTAH. THE
RESULTANT UNSTABLE NORTH-NORTHWEST FLOW WOULD BE IDEAL FOR
MODERATE TO HEAVY PRECIP ACROSS PORTIONS OF NORTHERN UTAH THAT
FAVOR THIS PATTERN. SIGNIFICANT SNOW ACCUMULATIONS ARE LIKELY FOR
THE NORTHERN MOUNTAINS THROUGH WEDNESDAY EVENING. CENTRAL UTAH
WILL BE ON THE SOUTHERN FRINGE OF THE HEAVIER PRECIP...AND AS SUCH
WILL SEE SIGNIFICANTLY LESS ACCUMULATIONS OUTSIDE OF THE MOST
FAVORED NORTH AND NORTHWEST SLOPES.

PRECIP WILL BEGIN TO WIND DOWN LATE WEDNESDAY NIGHT AS THE UPPER
LOW SETTLES INTO A POSITION OVER OR A BIT TO THE SOUTH OF THE FOUR
CORNERS REGION. EASTERN AND SOUTHERN UTAH COULD STILL SEE
ORGANIZED PRECIP RESULTING FROM THE SYNOPTIC SCALE LIFT ASSOCIATED
WITH THE UPPER LOW. INSTABILITY SHOWERS WILL LINGER OVER THE
NORTH THROUGH EARLY THURSDAY. AN ANTICYCLONIC NORTHERLY FLOW
DEVELOPING BEHIND THE FOUR CORNERS UPPER LOW WILL BRING AN END TO
PRECIP ACROSS THE NORTH LATE THURSDAY.

.LONG TERM (AFTER 00Z FRIDAY)...CLOSED LOW OVER THE GENERAL
WESTERN NEW MEXICO REGION WILL BE CLOSE ENOUGH TO SOUTHEASTERN
PORTION OF CWA TO HAVE INSTABILITY SHOWERS CONTINUING INTO THE
EVENING. THE EC IS A LITTLE MORE EXCITED ABOUT THIS AS FAR AS
PRODUCING QPF BUT THE GFS IS ACTUALLY COLDER ALOFT OVER SOUTHEAST
UTAH WHICH MAKES ME BELIEVE THAT AT LEAST ISOLATED SHOWERS WILL
OCCUR.

WHAT SHAPE THE CLOSED LOW WILL TAKE ON FRIDAY THROUGH SATURDAY
CIRCULAR OR AMOEBA WILL HAVE A BEARING ON WHETHER LOBES OF ENERGY
WILL ROTATE OR NOT ACROSS THE EASTERN PORTION OF THE CWA. FIGURED
THAT IT WILL BE CLOSE ENOUGH TO SPREAD CLOUDS ACROSS THE REGION BUT
THE AIR MASS WILL BE BECOMING MORE STABLE SO HAVE LEFT POPS OUT FOR
NOW. TEMPERATURES WILL WARM GRADUALLY FROM DAY TO DAY AS H7 TEMPS
ONLY CHANGING 2 TO 3 DEGREES CELSIUS EACH DAY.

BY SUNDAY THERE IS QUITE A LARGE DISPARITY BETWEEN MODELS. HAVE
LEANED TOWARDS THE GFS AS THE EC APPEARS TO BE HAVING THE BIGGEST
RUN TO RUN VARIATIONS IN ITS SOLUTIONS. ALTHOUGH THE GFS SHOWS SOME
BLOTCHY QPF SUNDAY AND MONDAY HAVE NOT BEEN ABLE TO IDENTIFY WHAT IS
CAUSING THE LIFT. THEREFORE HAVE LEFT THE POPS BELOW 15 PERCENT.

&&

.AVIATION...WINDS AT THE SLC TERMINAL ARE EXPECTED TO REMAIN
SOUTHEAST THROUGH EARLY AFTERNOON BEFORE SHIFTING TO THE NORTHWEST
AROUND 20-21Z. THERE IS A 40 PERCENT CHANCE THAT WINDS WILL SHIFT
BACK TO SOUTHEAST EARLIER THAN 02Z. WINDS WILL INCREASE FROM THE
SOUTH THROUGHOUT MONDAY NIGHT.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...HIGH WIND WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING
     FOR UTZ011>013-019>021.

     WINTER STORM WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY
     AFTERNOON FOR UTZ007>010-517.

     HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING FOR
     UTZ001>006-014>016.

     HARD FREEZE WARNING UNTIL 9 AM MDT THIS MORNING FOR UTZ001-004.

     HIGH WIND WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY MORNING
     FOR UTZ518.

WY...HIGH WIND WATCH FROM TUESDAY MORNING THROUGH TUESDAY EVENING FOR
     WYZ021.

&&

$$

SHORT TERM...CONGER
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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