Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 302247
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
347 PM MST FRI JAN 30 2015

.SYNOPSIS...A DEVELOPING UPPER LOW OVER THE SOUTHERN GREAT BASIN
WILL SPREAD MOISTURE INTO UTAH THROUGH SATURDAY. THE DEEPEST
MOISTURE WILL REMAIN PRIMARILY OVER CENTRAL AND SOUTHERN UTAH.


&&

.DISCUSSION...
.SHORT TERM (UNTIL 00Z TUE)...SATELLITE IMAGERY SHOWING THE MOIST
SUB TROPICAL CONNECTION FROM SOUTHERN BAJA STREAMING NORTHWARD
INTO THE CWA. THE BEST DYNAMICS ARE ASSOCIATED WITH THE JET
LOCATED OVER SOUTH CENTRAL AND EASTERN UTAH AT THIS TIME WHICH
WILL SLIDE EAST NORTHEAST THIS EVENING. DECENT RAINFALL AMOUNTS
HAVE BEEN OBSERVED UNDER THIS JET WITH 2/3 OF AN INCH AT BULLFROG
ON LAKE POWELL AND OVER 0.50 OF AN INCH AT TELEGRAPH FLAT RAWS.
THE SNOW WATER EQUIVALENT HAS BEEN ALSO SIGNIFICANT OVER THE SOUTH
CENTRAL MOUNTAINS WHERE OVER 1.00 INCH HAS BEEN OBSERVED. AN
ADDITIONAL 0.50 TO 0.75 OF AN INCH OF WATER IS STILL EXPECTED
TONIGHT INTO MIDDAY SATURDAY SO THE CURRENT WINTER WEATHER
ADVISORY IS WARRANTED AND REMAINS IN EFFECT.

FARTHER WEST THERE HAVE BEEN DECENT RAIN AMOUNTS AS WELL UNDER
MORE OF THE DEFORMATION ZONE OF THE LOW ACROSS SOUTHWEST UTAH.
THIS AREA HAS BEEN EXPANDING NORTH NORTHEAST AND VERY LIGHT RAIN
IS NOW OCCURRING AS FAR NORTH AS SLC. THIS DEFORMATION ZONE WILL
WEAKEN BY 06-08Z TONIGHT AND THE THREAT OF PRECIP MAKING IT ANY
FARTHER NORTH THAN OGDEN IS MINIMAL. HAVE THROWN SLIGHT CHANCE
POPS INTO THE NORTHERN WASATCH ZONE FOR THIS EVENING BUT ONCE THE
FLOW BECOMES NORTHERLY AROUND MIDNIGHT THE PRECIP WILL END.

MOS GUIDANCE APPEARED TO BE ON THE COLD SIDE FOR MANY AREAS
TONIGHT ACROSS THE CWA SO HAVE BOOSTED TEMPS BY A FEW DEGREES
EXPECTING THE EXTENSIVE CLOUD COVER AND HIGH DEW POINTS TO KEEP
TEMPS FROM FALLING MUCH.

THE STORM MOVES AWAY RAPIDLY WITH A MUCH DRIER NORTHWEST FLOW
MOVING ACROSS THE REGION FROM NORTH TO SOUTH DURING THE DAY
SATURDAY. THE NAM FORECAST SOUNDING FOR SLC SHOWS LOW LEVEL
MOISTURE TRAPPED UNDER A SHALLOW INVERSION FOR SATURDAY SUPPORTING
A STRATUS DECK WHILE THE GFS DOES NOT. THE NAM HAS BEEN NOTORIOUS
FOR TRAPPING LOW LEVEL MOISTURE SO IT WAS DISCARDED. TEMPERATURES
WILL REMAIN MILD.

CLEAR SKIES ARE EXPECTED SATURDAY NIGHT BUT WITH LOW LEVEL
REMAINING RATHER MOIST THERE SHOULD BE PATCHY FOG IN THE
FAVORABLE MOUNTAIN VALLEYS IN THE NORTH AND A LITTLE MORE
WIDESPREAD ACROSS WEST CENTRAL AND SOUTHWEST VALLEYS AS WELL AS
SOUTH CENTRAL VALLEYS INCLUDING THE LAKE POWELL REGION.

THE RIDGE GETS FLATTEN BY MONDAY AS A WESTERLY FLOW SETTLES INTO
NORTHERN UTAH BRINGING CLOUDS AND A THREAT OF PRECIP TO THE
NORTHERN MOUNTAINS AND ADJACENT VALLEYS.


.LONG TERM (AFTER 00Z TUE)...THE WEAK SHORT WAVE RIDGE OVER THE
REGION AT 00Z TUE FLATTENS MON NIGHT AS A LEADING WEAK SHORT WAVE
TROF IN WEST-NORTHWEST FLOW APPROACHES THEN PASSES TO OUR NORTH ON
TUE. THIS PUSHES A WEAK FRONTAL BOUNDARY INTO THE NRN CWA WITH THE
THREAT OF A LITTLE LIGHT PRECIP NORTH OF ABOUT SLC MON NIGHT THRU
TUE.

THIS SHORT WAVE WILL BE EAST OF THE AREA BY LATE TUESDAY BUT LEAVES
THE TRAILING FRONTAL BOUNDARY IN PLACE ACROSS THE NRN CWA. THIS
STARTS TO SAG SWD AGAIN TUE NIGHT AS THE NEXT LOW AMPLITUDE WAVE
DROPS OUT OF THE PACNW AND INTO ID BY 12Z WED. THIS WAVE ENHANCES
THE LIFT ALONG THIS BOUNDARY INCREASING THE THREAT OF LIGHT PRECIP
AGAIN OVER THE CWA FROM ABOUT PROVO NORTH LATE TUE NIGHT THRU WED
MORNING. THE BOUNDARY CONTINUES TO SAG SWD WED AFTN AS THE UPPER
WAVE PASSES LOSING INTEGRITY AS IT GOES WITH THE THREAT OF PRECIP
DROPPING OFF RAPIDLY.

THE BOUNDARY THEN LIFTS BACK NORTH WED NIGHT INTO THU AS A WEAKENING
WARM FRONT AT THE NOSE OF THE UPSTREAM RIDGE WITH A SMALL THREAT OF
ADDITIONAL LIGHT PRECIP BEFORE THE RIDGE MOVES IN AND SHUTS THINGS
DOWN. THE AIR MASS COULD BE COLD ENOUGH FOR SNOW TO THE VALLEY
FLOORS ALONG THE ID BORDER WITH THIS EVENT BUT EXPECT ONLY LIGHT
ACCUMULATION. THE MOUNTAINS WILL PICK UP SEVERAL INCHES BUT
AMOUNTS SHOULD REMAIN SUB ADVISORY.

THIS RIDGE THEN DOMINATES THE WEATHER PATTERN THU AFTN THRU THE
WEEKEND WITH A LITTLE MOISTURE MOVING OVER THE TOP BRINGING SOME
CLOUDINESS BACK INTO NRN UT. THE AIR MASS GETS QUITE MILD AGAIN
AND DO NOT EXPECT INVERSIONS TO BE TIGHT ENOUGH TO PREVENT VALLEYS
FROM REALIZING AT LEAST SOME OF THIS WARMING.

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL AT THE SLC TERMINAL THROUGH
TONIGHT. CIGS WILL BE NEAR OR BELOW 6000 FT THROUGH ABOUT 09-10Z
THEN RISE ABV THAT LEVEL AFTER THAT. WINDS WILL REMAIN OUT OF THE
NORTH THROUGH THE NIGHT AND ALL DAY SATURDAY. WINDS COULD BECOME
LIGHT AND VARIABLE FOR A TIME AFTER ABOUT 09Z UNTIL ABOUT 15Z.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...WINTER WEATHER ADVISORY UNTIL 4 PM MST SATURDAY FOR UTZ010-013-
     517-518.

WY...NONE.
&&

$$

PUBLIC...STRUTHWOLF/WILENSKY
AVIATION...WILENSKY

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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