Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 232206
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
306 PM MST MON FEB 23 2015

.SYNOPSIS...AN UPPER LEVEL LOW PRESSURE SYSTEM WILL TRACK EAST
SOUTHEAST ACROSS NORTHERN ARIZONA ON TUESDAY. HIGH PRESSURE ALOFT
WILL BRIEFLY RETURN TO THE REGION TUESDAY NIGHT...FOLLOWED BY A
COUPLE OF WEAK WEATHER DISTURBANCES CROSSING THE REGION MIDWEEK.

&&

.SHORT TERM (THROUGH 12Z THURSDAY)...
WATER VAPOR LOOP SHOWS A CLOSED LOW OVER CENTRAL CALIFORNIA.
AMDAR 400-250MB WIND OBSERVATIONS INDICATE A CYCLONIC JET OF
100-130KT JET AROUND THE CLOSED LOW...WITH THE LEFT EXIT REGION
NEAR THE FOUR CORNERS. GOES/GPS/RAP/12Z RAOB INDICATE THE
PRECIPITABLE WATER VALUE RANGES BETWEEN 0.05-0.10" FAR NORTH...TO
0.45-0.50" FAR SOUTH. BLENDED TOTAL PRECIPITABLE WATER PRODUCT
INDICATES A MOISTURE TAP INTO THE SOUTHWEST CONUS. THERE IS A
STRONG DELINEATION BETWEEN ABNORMALLY DRY AND MOIST AIRMASSES NEAR
INTERSTATE 70.

SURFACE PRESSURE GRADIENT CONTINUES TO LOOSEN AND PIVOT TO MORE OF A
NORTHERLY GRADIENT PER RAP. THUS...EXPECT DOWNTREND IN EASTERLY
GUSTS ACROSS NORTHERN WASATCH TO CONTINUE. THERE COULD BE A SEVERAL
HOUR PERIOD THIS EVENING WHERE WINDS INCREASE A BIT WITH SUNSET DUE
TO DIURNAL AFFECTS...BUT THE DOWNTREND WILL CONTINUE OVERNIGHT.

WINTER STORM WILL CONTINUE TO MIGRATE EASTWARD TONIGHT. THE NOSE OF
THE UPPER LEVEL JET CONTINUES TO PROPAGATE OUT OF THE REGION...WITH
WEAKENING 700MB FRONTOGENESIS THE RESULT. EXPECTING SNOW TO DECREASE
IN COVERAGE AND SNOW RATES TO DECREASE THIS EVENING AND OVERNIGHT.
HAVE ELECTED TO TRIM BACK THE EXPIRATION TIME FOR THE WARNING TO
BEFORE SUNRISE. TRIMMED BACK POPS TUESDAY MORNING WITH THE CLOSED
LOW SINKING SOUTH ACROSS ARIZONA.

ATTENTION THEN TURNS TO TEMPERATURES AND POTENTIAL FOR FOG IN THE
WAKE OF THE STORM. SINCE WE ARE IN A NEW REGIME...HAVE TAKEN A
FEW DEGREES OFF OF BIAS CORRECTED GUIDANCE ACROSS THE REGION. THE
EXCEPTION IS TONIGHT ACROSS THE SOUTH WHERE THERE IS COPIOUS CLOUD
COVER. BEYOND TONIGHT...CLEARING SKIES AND A DEEP SNOWPACK SHOULD
SUPPORT TEMPERATURES WELL BELOW GUIDANCE FOR THE NEXT SEVERAL
DAYS. TUESDAY NIGHT AND WEDNESDAY COULD SUPPORT FOG GIVEN
DROPPING TEMPERATURES AIDED BY CLEAR SKIES AND A FRESH SNOWPACK
WITH SOME DAYTIME MELTING.

SEVERAL DISTURBANCES PASS OVER THE ROCKIES WEDNESDAY AND WEDNESDAY
NIGHT. WITH A DRY STABLE AIRMASS IN PLACE NOT CONCERNED ABOUT
PRECIPITATION. BIGGEST CONTRIBUTION FROM THESE SYSTEMS WILL LIKELY
BE TO KICK UP DOWNSLOPE WINDS ACROSS FAVORED AREAS OF FAR NORTHWEST
UTAH...AND EAST CENTRAL/SOUTHERN UTAH...ALONG WITH SOME PASSING
MID AND HIGH CLOUDS.

&&

.LONG TERM (AFTER 12Z THURSDAY)...
THE SERIES OF WEAK DISTURBANCES MOVING ACROSS THE REGION IN
NORTHWEST FLOW WILL CONTINUE INTO THURSDAY WITH NORTHERN UTAH
BEING THE MOST LIKELY AREA TO SEE ANY PRECIPITATION. HOWEVER THIS
NORTHWEST FLOW WILL END BY FRIDAY AS THE GLOBAL MODEL SOLUTIONS
INDICATE THE LONGWAVE TROUGH DEVELOPING OVER THE GREAT BASIN AND
WEST COAST. BY 06Z SATURDAY THE EC INDICATES THIS BROAD TROUGH TO
HAVE TWO MAIN SPOKES OF ENERGY...ONE OVER SOUTHERN NEVADA AND ONE
ALONG THE NORTHERN CALIFORNIA/SOUTHERN OREGON COAST. MEANWHILE THE
OPERATIONAL GFS AND THE MEAN OF THE GFS ENSEMBLE HAS MOST OF ITS
ENERGY ASSOCIATED WITH THE OREGON/CALIFORNIA FEATURE. THERE ARE
SOME ENSEMBLE MEMBERS WHICH ARE LIKE THE EC WITH TWO
FEATURES...WHICH MAKES THIS FORECAST EXTRA DIFFICULT DUE TO TIMING
AND STRENGTH VARIABILITY`S. THE GENERAL FORECAST IS FOR
TEMPERATURES TO RUN NEAR OR SLIGHTLY BELOW NORMAL FROM FRIDAY
THROUGH MONDAY WITH UNSETTLED WEATHER. NORTHERN UTAH APPEARS TO
HAVE THE GREATEST THREAT OF PRECIPITATION FRIDAY BUT THEN AS THIS
LONGWAVE TROUGH DEVELOPS THE EMPHASIS OF PRECIPITATION IS EXPECTED
TO SHIFT ACROSS CENTRAL AND SOUTHERN UTAH SATURDAY THROUGH SUNDAY
NIGHT. HAVE LEFT SOME TOKEN POPS IN THE NORTH...MAINLY
MOUNTAINS...INTO SUNDAY AND MONDAY DUE TO THE EC AND CANADIAN
MODELS SHOWING ANOTHER SHORTWAVE WITHIN THIS BROAD LONGWAVE TROUGH
EFFECTING THE REGION.

&&

.AVIATION...MINIMAL WEATHER CONCERNS AT THE SLC TERMINAL THROUGH THE
TAF PERIOD UNDER CLEAR SKIES. NORTHWESTERLY WINDS WILL BE THE
PREDOMINANT WIND DIRECTION THROUGH THIS EVENING THEN SHOULD SHIFT TO
THE SOUTHEAST BETWEEN 07 AND 09Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER STORM WARNING UNTIL 4 AM MST TUESDAY FOR UTZ013-016-020-
     021-517-518.

WY...NONE.
&&

$$

SHORT TERM...ROGOWSKI
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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