Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 180327
AFDSLC

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

.SYNOPSIS...A WEAK STORM SYSTEM TRACKING EATS THROUGH ARIZONA WILL
BRING A FEW SHOWERS TO EXTREME SOUTHERN UTAH TONIGHT. A SECOND
SYSTEM WILL BRING ADDITIONAL PRECIPITATION TO MAINLY SOUTHERN UTAH
THROUGH THE WEEKEND.

&&

.SHORT TERM (UNTIL 00Z TUESDAY)...DEFINABLE VORTICITY MAX MOVING
INTO EASTERN ARIZONA THIS EVENING HAS SPREAD LIGHT SHOWERS AND
VIRGA INTO SOUTH-CENTRAL THROUGH SOUTHEAST UTAH THIS EVENING.
THIS ACTIVITY MAY INCREASE A BIT IN AREAL COVERAGE LATER TONIGHT
AS THE VORTICITY MAX MOVES JUST SOUTH OF THE FOUR CORNERS REGION.

THE UPPER TROUGH CURRENTLY OVER THE WEST COAST STATES IS IN THE
EARLY STAGES OF A PRONOUNCED SPLIT OVER THE WESTERN CONUS. THE
NORTHERN PORTION OF THE SPLIT WILL HAVE LITTLE IMPACT ON THE AREA
AS THIS FEATURE RIDES UP AND OVER THE UPPER RIDGE ACROSS THE
NORTHERN/CENTRAL ROCKIES.

THE SOUTHERN PORTION OF THE SPLIT WILL OFFER UP AT LEAST A
REASONABLE CHANCE FOR LIGHT PRECIP OVER THE WEEKEND. THE VARIOUS
GLOBAL MODEL GUIDANCE HAVE SHOWN RUN-TO-RUN CONSISTENCY IN
DEVELOPING A CLOSE LOW ALONG THE ARIZONA/NORTHWEST MEXICO BORDER
BY SATURDAY NIGHT. THE BEST CHANCE FOR ANY LIGHT PRECIP WILL
LIKELY COME IN THE WEAK AND SOMEWHAT MOIST SOUTHERLY FLOW PRIOR TO
THE LOW CLOSING OFF. AFTER THAT THE LOW MAY BE SUFFICIENTLY FAR
REMOVE TO THE SOUTH WITH A SOUTHEASTERLY FLOW ALOFT CUTTING OFF
MUCH OF THE DEEP LAYER MOISTURE FOR THE LATTER HALF OF THE
WEEKEND.

HIGH PRESSURE ALOFT WILL BECOME THE DOMINANT FEATURE ONCE AGAIN
FOR EARLY IN THE UPCOMING WEEK. TEMPS WILL CLIMB A BIT WITH THE
RETURN OF THE UPPER HIGH...THOUGH WITH LIGHT FLOW...A GENERALLY
STABLE LOW-LEVEL AIRMASS AND A SEASONALLY LIMITED AMOUNT OF
EFFECTIVE SUNLIGHT THE INCREASE IN TEMPS PROBABLY WONT STRAY FAR
FROM SEASONAL NORMS ON MONDAY.

&&

.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...LIGHT SOUTHEAST DRAINAGE WINDS WILL RETURN TO THE
KSLC TERMINAL BETWEEN 03Z AND 05Z THIS EVENING. HIGH-BASED
CEILINGS WILL REMAIN AT OR ABOVE 12 KFT THROUGHOUT THE TAF PERIOD.

&&

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

$$

PUBLIC...CONGER
AVIATION...

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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