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 222215
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
415 PM MDT WED APR 22 2015

.SYNOPSIS...THE UPPER LEVEL LOW PRESSURE SYSTEM TO THE SOUTHWEST
OF UTAH WILL RETURN SOUTH AND WEAKEN ON THURSDAY. AN UPPER LEVEL
WEATHER DISTURBANCE CROSSING THE NORTHERN ROCKIES WILL BRING A
COLD FRONT THROUGH THE AREA THURSDAY. A COLD AND ENERGETIC
PACIFIC STORM SYSTEM WILL IMPACT THE REGION THIS WEEKEND.

&&

.SHORT TERM (THROUGH 00Z SUNDAY)...THE UPPER LOW POSITIONED TO
THE WEST OF LAS VEGAS APPEARS TO STOP ITS NORTHWARD DRIFT THIS
AFTERNOON. THE ASSOCIATED DEFORMATION AXIS APPEARS WELL-DEFINED IN
THE WATER VAPOR IMAGERY ACROSS CENTRAL UTAH THIS AFTERNOON.
ORGANIZED CONVECTION ALONG THIS BOUNDARY CONTINUES TO INCREASE IN
AREAL COVERAGE...WITH THE STRONGEST SHOWERS/STORMS AHEAD OF AN
APPARENT VORTICITY MAXIMUM MOVING TO THE NORTHWEST THROUGH
SOUTHWEST UTAH COUNTY AT THIS TIME. ELSEWHERE SUFFICIENT MOISTURE
EXISTS TO SUPPORT THE SCATTERED TERRAIN-BASED CONVECTION
STATEWIDE.

FOR THIS EVENING THE DEFORMATION AXIS WILL BEGIN TO BREAK UP AS
THE UPPER LOW TO THE SOUTHWEST BEGINS TO DRIFT BACK TO THE SOUTH.
CONVECTION WILL CONTINUE OVER/NEAR THE HIGHER TERRAIN. THIS
ACTIVITY WILL SHOW A DECREASING TREND DURING THE MID TO LATE
EVENING...WITH LINGERING LIGHT SHOWERS LATE TONIGHT.

FOR THURSDAY THE WEAK UPPER TROUGH LEFT BY THE EXITING UPPER LOW
WILL HOLD ENOUGH MOISTURE TO BRING TERRAIN-BASED CONVECTION BACK
TO LIFE FOR THE LATE MORNING AND AFTERNOON HOURS. A SHORTWAVE
MOVING EAST ACROSS THE NORTHERN ROCKIES WILL DRAG A WEAK COLD
FRONT INTO NORTHERN UTAH/SOUTHWEST WYOMING. THE FRONTAL BOUNDARY
COULD BECOME THE FOCUS FOR STRONGER CONVECTION BY AFTERNOON. WILL
CONCENTRATE THE HIGHEST POPS ALONG AND A LITTLE NORTH OF THIS
BOUNDARY THROUGH THURSDAY EVENING.

CONVECTION WILL REAPPEAR FRIDAY...WITH THE EARLY CONVECTION LIKELY
TIED TO THE HIGHER TERRAIN. A SHORTWAVE EJECTING OUT AHEAD OF THE
COLD UPPER TROUGH ENTERING THE PACIFIC NORTHWEST WILL PUSH A
FRONTAL BOUNDARY INTO NORTHWEST UTAH LATE IN THE DAY. SUSPECT THAT
CONVECTION WILL LINE UP ALONG THIS BOUNDARY...THOUGH THE STRONGEST
CONVECTION WILL LIKELY REMAIN CONFINED TO THE NORTHWEST CORNER OF
UTAH AND POINT NORTH LATE AFTERNOON THROUGH EARLY EVENING.

A MAJOR PRECIP EVENT APPEARS TO BE SHAPING UP FOR THE LATER HALF
OF THE UPCOMING WEEKEND. THE ABOVE MENTION TROUGH IS PROGGED BY
BOTH THE GFS AND ECMWF TO TAKE ON A NEGATIVE-TILT ORIENTATION AND
STRENGTHEN AS IT SETTLES SOUTHEAST INTO THE GREAT SATURDAY. A
DECENT SURFACE COLD FRONT WILL LEAD THIS SYSTEM INTO UTAH WITH
GOOD DYNAMIC AND COLD AIR SUPPORT TO GENERATE STRONG SYNOPTIC-
SCALE LIFT. HAVE TREND POPS UPWARD SATURDAY...THOUGH MOST OF THE
EVENT WILL CONTINUE AFTER THE END OF THE SHORT-TERM FORECAST
PERIOD.

.LONG TERM (AFTER 00Z SUNDAY)...FRONTAL BOUNDARY SWEEPS THROUGH THE
STATE SATURDAY NIGHT/SUNDAY MORNING. THE CENTER OF THE TROUGH IS
EXPECTED TO REACH WESTERN UTAH BEFORE DIGGING SOUTH LATE MORNING
THROUGH THE AFTERNOON. INSTABILITY SHOWERS WILL STICK AROUND OVER
MOST OF THE AREA SUNDAY AFTERNOON BUT THE BEST FORCING WILL BE OUT
OF THE AREA. THE SYSTEM IS PROGGED TO MOVE EAST ACROSS ARIZONA AND
NEW MEXICO SUNDAY NIGHT/MONDAY MORNING AND ASSOCIATED PRECIP SHOULD
TAPER OFF OVER THE FORECAST AREA DURING THAT TIME. EC SHOWING 700 MB
TEMPS DIPPING AS LOW AS -6C SUNDAY AFTERNOON WHILE THE GFS GETS AS
LOW AS -8C. HOWEVER...THINK PRECIP WILL LIKELY BE MOSTLY IF NOT ALL
RAIN FOR MUCH VALLEY LOCATIONS AS THE COOLEST TEMPERATURES ARE NOT
EXPECTED TO ARRIVE UNTIL MOST OF THE PRECIP IS OVER. BEHIND THE
TROUGH...HIGH PRESSURE IS EXPECTED TO MOVE BACK IN...RESULTING IN A
WARMING AND DRYING TREND FOR THE UPCOMING WEEK.

&&

.AVIATION...THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGH THE
EVENING. THE OUTFLOW FROM SHOWERS IN THE VICINITY OF THE TERMINAL
IS EXPECTED TO CREATED ERRATIC AND SHIFTING WINDS THROUGH EARLY
THIS EVENING. WINDS ARE EXPECTED TO STAY SOUTHERLY AFTER THE
CONVECTIVE SHOWERS EXIT THE TERMINAL AREA BY LATE THIS EVENING.

&&

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

$$

SHORT TERM...CONGER
LONG TERM/AVIATION...TRAPHAGAN

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.