Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 172116
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
316 PM MDT FRI OCT 17 2014

.SYNOPSIS...A WEAK STORM SYSTEM WILL BRING SOME MOISTURE INTO
SOUTHERN UTAH THROUGH THIS WEEKEND. A COLD FRONT IS EXPECTED MID
WEEK.

&&

.SHORT TERM (THROUGH 00Z TUESDAY)...
WATER VAPOR LOOP SHOWS A RIDGE OVER THE GREAT BASIN...A
DISTURBANCE OVER FAR SOUTHERN ARIZONA...AND A TROUGH APPROACHING
THE WEST COAST. AMDAR 400-250MB WIND OBSERVATIONS REVEAL A
CYCLONIC 75-105KT JET OVER THE NORTHERN ROCKIES AND INTO THE
PLAINS. GOES/GPS/RAP/12Z RAOB INDICATE THE PRECIPITABLE WATER
VALUE RANGES BETWEEN 0.25" MOUNTAINS...TO 0.60" WESTERN VALLEYS.

NOT A LOT OF CHANGE TO THE SHORT TERM FORECAST THINKING. THE
APPROACHING DISTURBANCE WEAKENS SOUTHEAST OF THE AREA...WITH A PIECE
PIVOTING OVER UTAH DURING THE WEEKEND. THIS SUPPORTS AN INCREASE IN
CLOUD COVER AND A SLIGHT CHANCE TO CHANCE OF SHOWERS ACROSS SOUTHERN
AND CENTRAL UTAH. REMOVED ANY MENTION OF THUNDER UNTIL SUNDAY
AFTERNOON...WHEN SHORT RANGE ENSEMBLES BEST SUPPORT IT. IN
FACT...BEST INSTABILITY IS SUNDAY GIVEN COOLING ALOFT SO HAVE
GREATER POPS THAN MOST MODEL QPF WOULD SUPPORT DUE TO PROXIMITY OF
WEAKENING WAVE.

PROFILES SHOW ELEVATED CLOUD BASES SO ANY CONVECTION THAT DOES FORM
POSES A SMALL CHANCE OF LOCALLY GUSTY WINDS WITH THE STRONGEST DRY
MICROBURSTS THIS WEEKEND ACROSS CENTRAL AND SOUTHERN UTAH.

TOOK MAX TEMPERATURES DOWN A FEW NOTCHES ACROSS NORTHERN UTAH
VALLEYS THIS WEEKEND AS HIGH RESOLUTION WRF BUFKIT SOUNDINGS
CONTINUE TO SUPPORT INVERTED CONDITIONS.

MONDAY APPEARS TO BE A TRANSITION DAY. WHILE DO HAVE SOME
INSTABILITY IN PLACE STILL...KEPT FORECAST DRY AS A DRYING
SOUTHWESTERLY FLOW DEVELOPS AHEAD OF THE NEXT TROUGH. GIVEN THIS
INCREASE IN FLOW AND THERMAL PROFILES SHOWN IN FORECAST
SOUNDINGS...DID NOT COMPENSATE FOR INVERTED CONDITIONS IN FORECAST
TEMPERATURE FIELDS. TEMPERATURES ACROSS A FEW STUBBORN NORTHERN
VALLEYS MAY LOCALLY NEED TO BE REDUCED A COUPLE OF DEGREES IF THEY
DONT LOOK LIKE THEY WILL MIX OUT COMPLETELY.

&&

.LONG TERM (AFTER 00Z TUESDAY)...
HEIGHTS BEGIN DROPPING MONDAY NIGHT WITH INCREASING SOUTHWESTERLY
FLOW AHEAD OF TWO WEAKENING SHORT WAVES REMNANT FROM THE EASTERN
PACIFIC LONG WAVE TROUGH. INCREASING HIGH CLOUDS AND SAID FLOW
WILL LIKELY LEAD TO A FAIRLY MILD NIGHT AS SUCH. MAY NEED TO BUMP
UP OVERNIGHT LOWS AS EXTENT OF HIGH CLOUDS BECOMES MORE DEFINED.

REGARDING THE SHORT WAVES...MODELS IN QUITE FAIR AGREEMENT REGARDING
TIMING AND PLACEMENT IN 12Z OUTPUT. THE INITIAL WAVE WILL LIFT
NORTHEAST INTO IDAHO SURGING A MODERATELY SHALLOW COLD FRONT INTO
NORTHERN UTAH TUESDAY MORNING DAYLIGHT HOURS. FORCING FROM THIS
SHOULD PRODUCE SCATTERED SHALLOW CONVECTION IN THE NORTH. DOWNSTREAM
AREAS POTENTIALLY SEEING ISOLATED TO WIDELY SCATTERED AND MORE
AIRMASS TYPE SHOWERS WITH MOISTURE IN PLACE FROM THE WASATCH PLATEAU
AND POINTS EAST. SHOWERS THE KEY WORD.

THE SECONDARY SHORT WAVE TRAILS RAPIDLY BEHIND THE FIRST DIGGING
SLIGHTLY FURTHER EAST THROUGH THE AREA TUESDAY NIGHT INTO
WEDNESDAY...THIS DRIVING THE PREVIOUS FRONT THROUGH MUCH OF THE
AREA. DETAILS REGARDING BREADTH OF CAA REMAIN A LITTLE OFF WITH THE
ECMWF ABOUT 2 C COOLER AT H7...-1 C KSLC...THAN THE GFS. HOWEVER DID
LOWER SNOW LEVELS TO 8500 FT AS REMNANT FRONTAL MOISTURE AND
MODERATE FORCING SHOULD PRODUCE ANOTHER ROUND OF RAIN AND HIGH
ELEVATION SNOW SHOWERS IN THE NORTH AND EAST LATE NIGHT INTO
WEDNESDAY MORNING. DID TRIM POPS FROM THE SOUTHWEST DUE TO BETTER
MODEL TO MODEL CONSISTENCY AND LACK OF MUCH IF ANY FORCING.

BUILDING HEIGHTS WEDNESDAY NIGHT THROUGH THE END OF THE WEEK REMAIN
ON TRACK WITH RIDGING BEING THE DOMINANT FEATURE ACROSS THE WESTERN
CONUS...POTENTIALLY A BLOCKING PATTERN SETTING UP. MAINTAINED A DRY
AND WARMING FORECAST AS SUCH.

&&

.AVIATION...NORTHWESTERLY WINDS WILL CONTINUE AT THE SLC TERMINAL
THROUGH 02-03Z. OTHERWISE...PERIODS OF HIGH CLOUDS WILL REMAIN
ACROSS NORTHERN UTAH.

&&

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

$$

SHORT TERM...ROGOWSKI
LONG TERM...MERRILL
AVIATION...KRUSE

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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