Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 311143
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
543 AM MDT TUE MAR 31 2015

.SYNOPSIS...A WARM SOUTHWEST FLOW ALOFT WILL DEVELOP ACROSS UTAH
TODAY...FOLLOWED BY A COUPLE OF COLD PACIFIC WEATHER DISTURBANCES
FOR THE MIDDLE PORTION OF THE WEEK. HIGH PRESSURE ALOFT WILL RETURN
FOR LATE FRIDAY AND INTO THE FIRST HALF OF THE UPCOMING WEEKEND.

&&

.SHORT TERM (THROUGH 12Z FRIDAY)...THE RIDGE AXIS HAS SHIFTED EAST
OF UTAH THIS MORNING AS AN UPSTREAM TROUGH PUSHES INTO THE PACIFIC
NORTHWEST STATES. A COLD FRONT ASSOCIATED WITH THE STORM SYSTEM IS
CURRENTLY DRAPED ACROSS EASTERN OREGON AND INTO WESTERN NEVADA PER
LATEST RAP AND SURFACE ANALYSIS. AHEAD OF THE FRONT...SOUTHWEST FLOW
ALOFT WILL INCREASE OVER UTAH TODAY AND COMBINED WITH A TIGHTENING
SURFACE PRESSURE GRADIENT AHEAD OF THE FRONT WILL YIELD ENHANCED
SOUTH TO SOUTHWEST WINDS ACROSS MUCH OF THE AREA...INCLUDING BREEZY
TO WINDY CONDITIONS ACROSS WESTERN UTAH. THE AIRMASS ACROSS UTAH
WILL REMAIN VERY WARM...AS MODELS INDICATE H7 TEMPERATURE OF +7C AT
SLC THIS AFTERNOON. THIS AIRMASS COMBINED WITH GOOD MIXING DUE TO
THE WINDS WILL LIKELY RESULT IN THE WARMEST DAY OF THE YEAR SO FAR
WITH RECORD HIGH TEMPERATURES EXPECTED IN SEVERAL AREAS.

THE COLD FRONT WILL COME KNOCKING THIS AFTERNOON AND PUSH THROUGH
NORTHWEST UTAH EARLY THIS EVENING. CURRENT ESTIMATED ARRIVAL TIME AT
SLC IS AROUND 03Z. THE FRONT WILL THEN CONTINUE THROUGH CENTRAL UTAH
OVERNIGHT AND INTO SOUTHERN UTAH TOMORROW MORNING. A VERY
SIGNIFICANT DROP IN TEMPERATURES IS STILL EXPECTED BEHIND THE
FRONT...BUT THE BULK OF THE COLD AIR WILL BE CONFINED TO NEAR 700MB
AND BELOW...AS THE UPPER SUPPORT WILL REMAIN NORTH OF UTAH. AS A
RESULT...THE FRONT WILL LOSE SOME OF ITS PUSH THE FARTHER SOUTH IT
GOES. THAT BEING SAID...NEAR-FRONTAL AND POSTFRONTAL WINDS ACROSS
NORTHWEST UTAH WILL HAVE THE POTENTIAL TO BECOME QUITE STRONG SO A
WIND ADVISORY HAS BEEN ISSUED.

A NARROW AND RELATIVELY SHALLOW BAND OF MOISTURE IS PROGGED TO
SPREAD INTO THE AREA IN ADVANCE OF THE COLD FRONT. HAVE KEPT A
MENTION OF ISOLATED CONVECTION ACROSS THE NORTHERN MOUNTAINS FOR
THIS AFTERNOON. THEN...WITH THE LOW-LEVEL FORCING ACCOMPANYING THE
COLD FRONT ACROSS NORTHERN UTAH...WOULD THINK A FEW ADDITIONAL
SHOWERS MAY DEVELOP AS WELL. HAVE ALSO KEPT SOME MENTION OF ISOLATED
SHOWERS IN A FEW VALLEY AREAS GIVEN THE ENTHUSIASM OF THE GFS AND 00Z
NAM QPF FIELDS...BUT MORE THAN LIKELY THE DRY BOUNDARY LAYER WILL
PRECLUDE MEASURABLE PRECIPITATION AT LOWER ELEVATION SITES.

TEMPERATURES WILL BE NOTICEABLY COOLER TOMORROW. CURRENT FORECAST
HAS A 20-25 DEGREE CHANGE ACROSS NORTHERN UTAH AND 10-15 DEGREE
CHANGE ACROSS SOUTHERN UTAH BETWEEN TODAYS AND TOMORROWS MAXES.
ISOLATED SHOWERS REMAIN POSSIBLE ACROSS THE HIGH TERRAIN OF CENTRAL
AND SOUTHERN UTAH TOMORROW ALTHOUGH MOISTURE REMAINS LIMITED...WHILE
NORTHERN UTAH WILL HAVE BECOME TOO STABLE.

THE NEXT TROUGH WILL START CARVING INTO THE WEST COAST TOMORROW AND
CROSS THE GREAT BASIN TOMORROW NIGHT INTO THURSDAY. THIS APPROACHING
TROUGH WILL INCREASE CONVERGENCE INTO THE EXISTING BOUNDARY AND
MODELS INDICATE PRECIPITATION DEVELOPING ACROSS WEST-CENTRAL THROUGH
NORTHEAST UTAH ON THURSDAY MORNING. COLDER AIR ALOFT WILL ALSO WORK
ITS WAY INTO THE AREA...WITH INSTABILITY SHOWERS GRADUALLY TAKING
OVER AS THE FRONTOGENIC FORCING WEAKENS AND EXITS THE AREA DURING
THE AFTERNOON. WITH THE COLD AIRMASS IN PLACE...EXPECT PRECIPITATION
THAT REACHES THE VALLEY FLOORS TO TAKE THE FORM OF SNOW OR A
RAIN/SNOW MIX.

THE STORM WILL EXIT THE AREA THURSDAY NIGHT. WITH SKIES EXPECTED TO
CLEAR OUT QUITE A BIT BY EARLY MORNING...TEMPERATURES WILL LIKELY
TAKE A NOSEDIVE. AS A RESULT...OVERNIGHT MINS ARE FORECAST TO BE
BELOW FREEZING ACROSS ALL BUT FAR SOUTHERN UTAH...AND A HARD FREEZE
WILL BE POSSIBLE.

&&

.LONG TERM (AFTER 12Z FRIDAY)...WEAK SHORTWAVE RIDGING WILL BUILD
OVER THE REGION ON FRIDAY...AS THE TROUGH FULLY EXITS TO THE EAST.
MAX TEMPERATURES SHOULD REMAIN SLIGHTLY BELOW NORMAL VALUES AS
COOLER LOW LEVEL AIR LINGERS ACROSS THE AREA. WARMING SHOULD BE MORE
SUBSTANTIAL ON SATURDAY...WITH INCREASING SOUTHERLY FLOW AND WARM
ADVECTION. DESPITE AN APPROACHING PACIFIC TROUGH...THE CWA WILL
LIKELY REMAIN IN THE WARM SECTOR FOR SUNDAY AS WELL...WITH BOTH THE
GFS AND ECMWF PUTTING THE ASSOCIATED COLD FRONT NEAR UTAHS NORTHWEST
CORNER AROUND 00Z MONDAY.

HEADING INTO THE BEGINNING OF NEXT WORK WEEK...SOME DIFFERENCES
REMAIN BETWEEN THE GLOBAL MODELS...BUT SOLUTIONS HAVE GENERALLY
CONVERGED A BIT WITH THE 00Z RUNS. THE CANADIAN AND GFS REMAIN MORE
PROGRESSIVE THAN THE ECMWF...BRINGING THE TROUGH THROUGH THE CWA ON
MONDAY. THE EC STILL HANGS THE TROUGH BACK A BIT ON MONDAY...BUT HAS
MOVED TOWARD THE OTHER TWO...PUSHING THE TROUGH THROUGH IN EARNEST
LATE MONDAY THROUGH TUESDAY.

THIS TROUGH LOOKS FAIRLY SIMILAR TO THE ONE IN THE SHORT TERM
FORECAST...WITH COLD AIR BUT RELATIVELY LITTLE MOISTURE. AS
SUCH...HAVE KEPT POPS ON THE LOW END THROUGH THE EXTENDED...THOUGH
THEY WILL LIKELY HAVE TO BE RAISED A BIT ONCE MODELS FURTHER
CONVERGE ON TIMING...AS AT LEAST SOME SHOWERS APPEAR ON EACH MODEL
AS THE TROUGH PASSES. HAVE KEPT THE COOLING TREND IN PLACE FOR
MONDAY...AND PUSHED TEMPERATURES EVEN COLDER FOR TUESDAY...WITH
MODELS IN GOOD AGREEMENT ABOUT COOLER LOW LEVEL AIR PUSHING IN
THROUGH THE DAY...WITH 700MB TEMPS OVER SLC OF ABOUT -6C BY 00Z
WEDNESDAY. BEYOND DAY 7...THE CURRENT CONSENSUS FORECAST IS FOR
RIDGING TO RE-BUILD BEHIND THIS WAVE FOR THE MIDDLE OF NEXT
WEEK...BUT WITH SIGNS THAT THE PATTERN MAY REMAIN SOMEWHAT
PROGRESSIVE HEADING INTO THE SECOND WEEK OF APRIL.

&&

.AVIATION...SOUTHERLY WINDS WILL INCREASE AT THE SLC TERMINAL
THROUGH THE MORNING...LIKELY BECOMING GUSTY BETWEEN 12Z AND 16Z. THE
BIG QUESTION IS WHETHER A LAKE BREEZE WILL OCCUR THIS AFTERNOON.
THIS FORECAST IS RELATIVELY LOW CONFIDENCE...BUT THE MOST LIKELY
SCENARIO IS FOR A SWITCH TO WEST-NORTHWEST WINDS BETWEEN 21Z AND
00Z. HOWEVER...THERE IS A 40 PERCENT CHANCE THAT WINDS WILL REMAIN
STRONG OUT OF THE SOUTH UNTIL A COLD FRONT MOVES THROUGH THE AREA
BETWEEN 01Z AND 04Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 4 AM MDT WEDNESDAY FOR
     UTZ005.
WY...NONE.
&&

$$

CHENG/SCHOENING

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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