Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 122303
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
403 PM MST FRI FEB 12 2016

.SYNOPSIS...HIGH PRESSURE OVER UTAH TODAY WILL WEAKEN AS A COUPLE
OF WEAK WEATHER DISTURBANCES CROSS NORTHERN UTAH THIS WEEKEND.
HIGH PRESSURE ALOFT WILL REBOUND ACROSS THE REGION EARLY NEXT WEEK.

&&

.SHORT TERM (THROUGH 00Z TUESDAY)...THE PERSISTENT RIDGE OF THE LAST
FEW DAYS WILL CONTINUE TO FLATTEN THROUGH TONIGHT...FINALLY GIVING
WAY TO A VERY WEAK SHORTWAVE TROUGH BRUSHING NORTHERN UTAH AROUND
MID-DAY SATURDAY. THIS TROUGH WILL BE QUICKLY FOLLOWED BY ANOTHER
SLIGHTLY STRONGER IMPULSE EARLY SUNDAY. EACH IMPULSE WILL SERVE TO
GRADUALLY WEAKEN THE STUBBORN INVERSION FOR CENTRAL AND NORTHERN
UTAH. WE ARE CURRENTLY EXPECTING MUCH OF THE LOW CLOUDS AND FOG TO
DISSIPATE BY SATURDAY AFTERNOON...THOUGH HAZE AND SMOG WILL LIKELY
LINGER FOR THE WASATCH FRONT URBAN CORRIDOR AS COMPLETE MIXING IS
NOT LIKELY.

A FEW SHOWERS WILL MOVE INTO THE NORTHERN MOUNTAINS AND PERHAPS THE
VALLEYS AS WELL BY SUNDAY MORNING. WITH H7 TEMPERATURES FALLING TO
AROUND -6C AT SLC AND GIVEN THE PERSISTENT COLDER AIR AT THE LOWER
LEVELS...ANY PRECIPITATION IN THE VALLEYS IS EXPECTED TO BEGIN AS
MOSTLY SNOW. HOWEVER...MODIFICATION OF THE TEMPERATURE PROFILE AND
GRADUAL WARMING AS THE INVERSION WEAKENS SHOULD ALLOW RAIN TO
GRADUALLY MIX IN BY SUNDAY AFTERNOON. PRECIPITATION IS EXPECTED TO
LINGER THROUGH MONDAY MAINLY ACROSS THE NORTHERN MOUNTAINS AND
ADJACENT UPSLOPE REGIONS IN A MOIST NORTHWEST FLOW ALOFT.

.LONG TERM (AFTER 00Z TUESDAY)...TWO PRIMARY CONCERNS DURING THE
LONG TERM ARE THE STRENGTH OF LINGERING INVERSIONS ACROSS THE
NORTHERN/WESTERN BASINS AND THE RESULTANT EFFECT ON
TEMPERATURES...AS WELL AS TIMING OF A PROGRESSIVE SHORTWAVE TROUGH
DURING THE LATTER PORTION OF THE WEEK.

REGARDING TEMPERATURES DURING THE MIDWEEK PERIOD...WITH THE
ASSUMPTION VALLEY INVERSIONS ARE WEAKENED BUT NOT COMPLETELY
DISLODGED BY THE SUNDAY TROUGH ASSUME COLD AIR WILL REMAIN IN PLACE
TO SOME DEGREE ACROSS THE WESTERN VALLEYS. AS MID LEVEL RIDGING
EXPANDS TUESDAY THROUGH WEDNESDAY WARMING ALOFT WILL ACT TO FURTHER
STRENGTHEN/REDEVELOP THESE INVERSIONS AND AS SUCH HAVE GENERALLY
GONE BELOW GUIDANCE TUESDAY ACROSS THESE AREAS WHILE TRENDING CLOSER
TO GUIDANCE ACROSS THE HIGHER ELEVATIONS AS WELL AS THE
SOUTHERN/EASTERN VALLEYS. THE ONE CAVEAT WOULD BE IF INVERSIONS DO
INDEED DISSOLVE OVER THE WEEKEND WESTERN VALLEYS MAY WARM
CONSIDERABLY MORE THAN CURRENTLY FORECAST.

THIS MID LEVEL RIDGE AXIS SHIFTS EAST WEDNESDAY ALLOWING FOR A
STRENGTHENING SOUTHWESTERLY FLOW AND DEVELOPING SOUTHERLY GRADIENT.
IT WOULD SEEM MOST VALLEYS SHOULD MIX OUT WITH THIS SCENARIO AND
HAVE TRENDED TEMPERATURES CLOSER TO A GUIDANCE CONSENSUS...ALTHOUGH
NOT OUT OF THE QUESTION WE COULD SEE A FEW STUBBORN COLD POOLS
LINGER.

BOTH THE GFS AND EC BRING A PROGRESSIVE MID LEVEL TROUGH THROUGH THE
REGION DURING THE LATTER PORTION OF THE WEEK. THE GFS IS MORE
PROGRESSIVE WITH THIS WAVE THAN THE 12Z EC...WHICH ITSELF HAD
TRENDED FASTER FROM ITS 00Z PREDECESSOR. GIVEN UNCERTAINTY IN TIMING
HAVE MAINTAINED POPS IN THE CHANCE RANGE FOR THURSDAY INTO THURSDAY
NIGHT...ALTHOUGH DID LOWER POPS JUST A BIT THURSDAY GIVING DEFERENCE
TO THE EC SOLUTION. THIS SYSTEM WILL BE MILD WITH VALLEY
RAIN/MOUNTAIN SNOW AS THE P-TYPE.

&&

.AVIATION...PREVAILING IFR CONDITIONS IN HAZE/FOG AND LOW STRATUS
ARE EXPECTED TO REMAIN IN PLACE AT THE KSLC TERMINAL THROUGH THE
VALID TAF PERIOD...WITH A 30 PERCENT CHANCE OF TEMPORARY LOW END
MVFR CONDITIONS THROUGH 02Z. LIFR IN DENSE FOG AND/OR CIGS NEAR 200
FEET ARE ONCE AGAIN EXPECTED TO DEVELOP BETWEEN 04-06Z THIS EVENING
AND PERSIST THROUGH THE OVERNIGHT HOURS...WITH A 30 PERCENT CHANCE
OVERNIGHT CONDITIONS REMAIN IN THE IFR CATEGORY.

&&

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

$$

VAN CLEAVE/CHENG/SEAMAN

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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