Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 102233
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
333 PM MST WED FEB 10 2016

.SYNOPSIS...HIGH PRESSURE ALOFT WILL REMAIN THE DOMINANT WEATHER
FEATURE OVER THE INTERMOUNTAIN WEST THROUGH THE END OF THE WEEK.
A COUPLE OF WEAK WEATHER DISTURBANCES WILL CROSS NORTHERN UTAH
THIS WEEKEND.

&&

.SHORT TERM (THROUGH 12Z SATURDAY)...
WATER VAPOR LOOP SHOWS A RIDGE DOMINATING THE WEST. AMDAR
400-250MB WIND OBSERVATIONS PLACE A 125-160KT ANTICYCLONIC JET
FROM CENTRAL CANADA INTO THE EASTERN GULF COAST. GOES/HRRR/GPS/12Z
SLC RAOB INDICATE THE PRECIPITABLE WATER VALUE RANGES BETWEEN
0.05"-0.10" MOUNTAINS...TO 0.20"-0.30" NORTHERN/WEST CENTRAL
VALLEYS.

WITH AN INVERSION IN PLACE...MAIN CONCERN IS HAZE/FOG/STRATUS AND
TEMPERATURES.

HAVE CONCERNS THAT IF WE CONTINUE TO IMPROVE THIS AFTERNOON...THAT A
DENSE FOG BANK WILL SLOSH BACK INTO THE ADJACENT VALLEYS WITH
SUNSET.

THE INVERSION HAS LOWERED TO 846MB WITH A STRENGTH OF 11.5C. HAVE
BECOME MORE AGGRESSIVE WITH FOG/STRATUS DEPICTION. WENT WITH AREAS
OF DENSE FOG FOR MANY VALLEYS...BACKING OFF TO PATCHY FOG DURING
THE AFTERNOON. STRATUS MAY ERODE AT EDGES SUCH AS ALONG WASATCH
FRONT AND CEDAR CITY DURING THE DAYTIME...BUT WENT WITH MORE
PESSIMISTIC CLOUD CONDITIONS DUE TO UNCERTAINTY.

TEMPERATURES ARE NEARLY PERSISTENT IN STRONGLY INVERTED
VALLEYS...WITH A BLEND OF GUIDANCE IN THE MOUNTAINS AND FAR
SOUTHERN/SOUTHEASTERN VALLEYS.

&&

.LONG TERM (AFTER 12Z SATURDAY)...
A WEAK SHORTWAVE TROUGH BEGINS TO DIVE SOUTH THROUGH THE
INTERMOUNTAIN WEST ON SATURDAY...THOUGH MODELS HAVE GENERALLY
TRENDED TOWARD THIS BEING MORE OF A BRUSH-BY FOR UTAH AND
SOUTHWEST WYOMING. HAVE MAINTAINED SOME 20-30 PERCENT POPS IN THE
FAR NORTH AND ALSO INCREASED THE CLOUD COVER...BUT THE BIGGER
QUESTION IS WHAT IMPACT THIS TROUGH WILL HAVE ON LOW LEVEL
TEMPERATURE INVERSIONS. CURRENT THINKING IS THAT WHILE COOL
ADVECTION ALOFT MAY HELP WEAKEN THESE INVERSIONS...THE STORM DOES
NOT LOOK STRONG ENOUGH TO TRULY SCOOP OUT THE VALLEYS.

TRENDED THE TEMPERATURE FORECAST TOWARD THE IDEA OF WEAKER BUT STILL
CONTINUING INVERSIONS FOR SATURDAY. HOWEVER...THE BIGGER IMPACT FOR
TEMPERATURES MAY BE THE ADDITIONAL CLOUD COVER THAT MOVES INTO THE
AREA SUNDAY AND MONDAY IN A COOL NORTHWEST FLOW. THESE MOSTLY CLOUDY
CONDITIONS DURING A COUPLE OF OVERNIGHT PERIODS...COMBINED WITH A
COUPLE OF WEAK WAVES THAT MOVE THROUGH THE AREA...MAY BE ENOUGH TO
MODIFY THE TEMPERATURES AND ALLOW A SLOW WARMING TREND. HAVE BUILT
THIS WARMING TREND INTO THE FORECAST FOR SUNDAY THROUGH TUESDAY.

THE RIDGE RE-CENTERS OVER THE AREA ON TUESDAY...WHICH WILL LIKELY
ALLOW SOME WEAK INVERSIONS TO RE-FORM...BUT THE WARMER PRE-RIDGE
AIRMASS AND HIGHER MID-FEBRUARY SUN ANGLE SHOULD PREVENT
TEMPERATURES FROM BEING AS COLD AS THE CURRENT ONGOING INVERSION.
INCREASED MIXING COULD ALSO BE IN THE CARDS FOR WEDNESDAY...AS
GLOBAL MODELS ARE IN FAIR AGREEMENT ABOUT INCREASING SOUTHWESTERLY
FLOW AHEAD OF A PACIFIC TROUGH. THERE IS STILL SOME UNCERTAINTY
ABOUT THE STRUCTURE OF THIS TROUGH...BUT IF INCREASING SOUTHWESTERLY
WINDS REMAIN IN THE FORECAST THEN THE WARMING ON WEDNESDAY COULD BE
SIGNIFICANT...POTENTIALLY THE WARMEST TEMPERATURES OF THE CALENDAR
YEAR THUS FAR.

&&

.AVIATION...FOG AND STRATUS WILL BE THE MAJOR WEATHER IMPACTS AT THE
SLC TERMINAL THROUGH THE TAF PERIOD. CEILINGS MAY BRIEFLY BECOME
SCATTERED AT TIMES BETWEEN 22Z AND 03Z...BUT IN GENERAL IFR OR WORSE
CEILINGS WILL PREVAIL. DENSE FOG IS LIKELY TO RETURN TONIGHT...BUT
TIMING IS LOW CONFIDENCE. THE MOST LIKELY TIME FOR DENSE FOG TO
BEGIN IS BETWEEN 05Z AND 09Z...BUT THERE IS A CHANCE IFR FOG
COULD RETURN AS EARLY AS 00-03Z.

&&

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

$$

SHORT TERM...ROGOWSKI
LONG TERM/AVIATION...SCHOENING

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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