Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 112056
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
256 PM MDT THU SEP 11 2014

.SYNOPSIS...A TROUGH AND ASSOCIATED COLD AIR SLIDING DOWN THE
EAST SIDE OF THE CONTINENTAL DIVIDE WILL RESULT IN COLD
TEMPERATURES AND LOCALIZED GAP WINDS FRIDAY MORNING OVER THE
NORTHERN PORTION OF THE FORECAST AREA. A WARM DRY RIDGE WILL
DEVELOP OVER THE GREAT BASIN THROUGH THE WEEKEND AND EARLY NEXT
WEEK.

&&

.DISCUSSION...SHALLOW COLD AIR ASSOCIATED WITH UNSEASONABLY COLD
TROUGH SLIDING SOUTH JUST EAST OF THE CONTINENTAL DIVIDE. THIS
COLD AIR HAS MADE MORE PROGRESS MOVING SOUTH THROUGH SOUTHEAST
IDAHO TODAY THAN IT DID IN WYOMING. HRRR AND NAM WERE VERY GOOD ON
PREDICTING THIS.

TONIGHT THE WYOMING COLD AIR WILL MAKE ANOTHER RUN AT OUR AREA AND
THE RESULT WILL BE A 10-11 MB PRESSURE GRADIENT ACROSS THE WASATCH
MOUNTAINS TO CENTRAL WY. NOT MUCH SUPPORT FOR DOWNSLOPE WINDS
ALOFT...SO EXPECT A GAP WIND TYPE EVENT WITH GUSTS TO NEAR 40 MPH
NEAR THE MOUTHS OF CANYONS ALONG THE WASATCH FRONT AND PERHAPS THE
CACHE VALLEY.

THE COLD AIR WILL ALSO BRING SOME AREAS OF FROST TO THE CACHE
VALLEY AND WASATCH BACK. NOT COLD ENOUGH FOR A HARD FREEZE
WARNING.

HAVE CREATED SOME GRAPHICS FOR WEB PAGE AND SOCIAL MEDIA TO
DESCRIBE THE WIND AND FROST THREAT.

A COOL DAY FRIDAY OVER THE NORTH AND NEAR AVERAGE OVER THE SOUTH.
THEN A SIGNIFICANT WARMING TREND BEGINS SATURDAY WITH ABOVE
AVERAGE TEMPS EXPECTED TO CONTINUE THROUGH MID WEEK. SOME DIURNAL
TERRAIN BASED CONVECTION BECOMES POSSIBLE FROM MONDAY ONWARD...BUT
LIMITED IN AREAL EXTENT.

VERY DIFFERENT SOLUTIONS IN THE EC AND GFS FOR WED/THUR. 06Z AND
12Z GFS BRING THE NEXT BAJA HURRICANE AND MOISTURE NORTHWARD NEXT
WEEK IN A PATTERN THAT IS QUITE SIMILAR TO THE DELUGE WE JUST HAD
EARLIER THIS WEEK. PRECIPITABLE WATER VALUES GET VERY CLOSE TO
WHAT WE JUST HAD. LATEST 12Z EC HAS SOME SUBTLE BUT SIGNIFICANT
DIFFERENCES IN THE WAY IT HANDLES A TROUGH IN THE EAST PACIFIC MID
WEEK AND THE RESULT IS THE HURRICANE DRIFTS WESTWARD RATHER THAN
NORTH ALONG THE BAJA COAST. JUST MILD AND DRY UFN IN THE EC.
CURRENT FORECAST POPS FOR WED/THU ARE NEAR CLIMO GIVEN THE VERY
UNCERTAIN FORECAST.

&&

.AVIATION...GUSTY NORTHWESTERLY WINDS AROUND 20 KNOTS ARE EXPECTED
TO CONTINUE THROUGH THE AFTERNOON AT THE KSLC TERMINAL. NORTHERLY
WINDS WILL DIMINISH OVERNIGHT BUT ARE NOT EXPECTED TO SWITCH BACK TO
SOUTHEASTERLY UNTIL 09-10Z. THIS SAID...A 30 PERCENT CHANCE EXISTS
THAT WINDS WILL PRIMARILY BE LIGHT AND VARIABLE AT THAT TIME.
OUTSIDE OF THE WINDS OPERATIONAL WEATHER CONCERNS WILL REMAIN
MINIMAL THROUGH THE VALID TAF PERIOD.

&&

.FIRE WEATHER...A DRY NORTHWEST FLOW WILL REMAIN OVER THE DISTRICT
THROUGH SATURDAY. A DRY COLD FRONT WORKING INTO NORTHERN UTAH THIS
AFTERNOON HAS BROUGHT GUSTY WEST WINDS TO PORTIONS OF THE NORTH.
THESE WINDS WILL SHIFT TO MORE NORTHERLY THIS EVENING THEN DIMINISH.
LOCAL GUSTY CANYON WINDS ARE POSSIBLE ALONG THE WASATCH FRONT AND IN
THE CACHE VALLEY LATE TONIGHT INTO FRIDAY MORNING. A COOL STABLE
AIRMASS WITH LIGHT WINDS WILL COVER THE DISTRICT FRIDAY. THIS WILL
LOWER THE CLEARING INDICES BELOW 500 IN MOST AREAS. AIRMASS WARMING
AND INCREASING TRANSPORT WINDS WILL IMPROVE CLEARING INDICES
SATURDAY AND SUNDAY.

&&

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

$$

PUBLIC...DUNN
FIRE WEATHER...WILENSKY
AVIATION...MERRILL

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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