Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 201208
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
507 AM MST TUE JAN 20 2015

.SYNOPSIS...A WEAK WEATHER DISTURBANCE WILL IMPACT EXTREME SOUTHERN
UTAH TONIGHT INTO WEDNESDAY...FOLLOWED BY HIGH PRESSURE ALOFT
EXPANDING ACROSS THE WESTERN STATES DURING THE LATTER HALF OF THE
WEEK.

&&

.SHORT TERM (THROUGH 12Z FRIDAY)...A COOLER NORTHWEST FLOW REMAINS
IN PLACE ACROSS THE FORECAST AREA THIS MORNING AFTER A WEAK
DISTURBANCE YESTERDAY SWEPT A COLD FRONT THROUGH THE AREA. A PATCH
OF STRATUS STILL LINGERS ACROSS MAINLY WEST-CENTRAL PORTIONS OF UTAH
THIS MORNING. HOWEVER...WITH VALLEY INVERSIONS HAVING LIFTED A BIT
DUE TO THE FRONT...THIS STRATUS LAYER CURRENTLY EXISTS BETWEEN 5-
6.5KFT. IT MAY LOWER A BIT BEFORE SCATTERING OUT BY THIS AFTERNOON.
OTHERWISE...EASTERN VALLEYS DID NOT MIX AS WELL AND LOWER PORTIONS
OF THE UINTA BASIN REMAINS IN FOG THIS MORNING.

A WEAK SPLITTING STORM SYSTEM IS STILL ON TRACK TO ENTER SOUTHERN
CALIFORNIA THIS EVENING AND TRACK ACROSS ARIZONA TOMORROW. WARMER
SOUTHWEST FLOW DEVELOPING AHEAD OF THIS FEATURE IS STILL PROGGED TO
COLLIDE WITH THE EXISTING COLD FRONT NEAR THE UTAH/ARIZONA BORDER.
MODELS STILL GENERATE A BAND OF PRECIPITATION ALONG THIS CONVERGENCE
ZONE TONIGHT INTO TOMORROW BUT LATEST GUIDANCE PRODUCTS STILL
MAINTAIN THAT THIS WILL MOSTLY REMAIN SOUTH OF THE BORDER.

THIS TROUGH IS EXPECTED TO PHASE WITH A NORTHERN BRANCH WAVE AND
DRAG IT SOUTH ACROSS FAR EASTERN UTAH AND WESTERN COLORADO. THIS
WILL TURN THE FLOW MORE NORTHERLY OVER UTAH AND KEEP THE COOLER
AIRMASS IN PLACE TOMORROW INTO THURSDAY MORNING. THIS NORTHERLY FLOW
COULD BRING ENHANCED CANYON WINDS TO WASHINGTON COUNTY TOMORROW
AFTERNOON THROUGH TOMORROW NIGHT. OTHERWISE...THE BEST UPPER SUPPORT
WITH THIS NORTHERN STREAM WAVE WILL REMAIN WELL EAST OF THE AREA SO
PRECIPITATION IS NOT EXPECTED WITH THIS FEATURE.

AN UPPER RIDGE WILL BUILD BACK INTO THE AREA BY THURSDAY MORNING
ALLOWING VALLEY INVERSIONS TO STRENGTHEN ONCE AGAIN.

&&

.LONG TERM (AFTER 12Z FRIDAY)...RIDGE AXIS WILL REMAIN ALONG THE
WEST COAST THROUGH SUNDAY BEFORE MOVING INLAND INTO THE GREAT BASIN
FOR MONDAY AND TUESDAY. WITH THE RIDGE AXIS NEAR THE COAST FRIDAY
THROUGH SUNDAY THIS WILL ALLOW PASSING WEAK DISTURBANCES TO RIPPLE
OVER THE TOP AND THEN SOUTHEAST ACROSS UTAH. THE CANADIAN AND GFS
ARE STRONGER THAN THE EC WITH ONE SUCH DISTURBANCE ON FRIDAY WITH
MINUS 6C 700MB TEMP BUT AT 500 MB THIS DISTURBANCE IS BARELY
IDENTIFIABLE WITH MINUS 20C COOL POCKET. THIS RESULTS IN A LAPSE
RATE OF 14C WHICH IS STILL RATHER STABLE. THEREFORE DESPITE SOME H7
MOISTURE HAVE HELD OFF ON INTRODUCING ANY POPS.

THE DISTURBANCE ON SUNDAY IS EVEN WEAKER THERMODYNAMICALLY AND
SHOULD BE JUST A CLOUD PRODUCER DUE TO WARM ADVECTION AHEAD OF THE
APPROACHING RIDGE ACROSS NORTHERN HALF OF THE CWA.

TEMPERATURES DURING THIS LONG TERM PERIOD ARE SOMEWHAT OF A
CHALLENGE AS VALLEY INVERSIONS THIS TIME OF YEAR USUALLY KEEPS TEMPS
FROM WARMING UP BUT WITH NO SNOW COVER THE TEMPERATURES HAVE BEEN
RESPONDING WELL OF LATE. THEREFORE HAVE PUSHED TEMPS UP A COUPLE
DEGREES. IN THE MOUNTAINS...TEMPERATURES SHOULD EASILY REACH INTO
THE MID TO UPPER 40S WITH ISOLATED 50 PLUS COME MONDAY AND TUESDAY
AS THE H7 TEMPS ARE FORECAST TO REACH ABOVE 5C. THE EC AND CANADIAN
ARE SIMILAR WITH PLUS 6-8C TEMPS TUESDAY WHILE THE GFS IS THE COOLER
OF THE GLOBAL MODELS AT ONLY 0-2C. HAVE LEANED STRONGLY TOWARDS THE
EC AND CANADIAN. SOUTHERN UTAH MAY HAVE ITS FIRST 70S OF THE YEAR.

&&

.AVIATION...LIGHT NORTHERLY SURFACE WINDS ARE EXPECTED AT THE SLC
TERMINAL THROUGHOUT THE TAF PERIOD. CIGS BETWEEN 6 AND 7K FT AGL ARE
EXPECTED TO DISSIPATE AROUND 13Z BUT THERE IS A 30 PERCENT CHANCE OF
LINGERING THROUGH 15Z. VFR CONDITIONS ARE EXPECTED TO BE MAINTAINED.

&&

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

$$

CHENG/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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