Area Forecast Discussion
Issued by NWS Salt Lake City, UT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KSLC 202231
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
431 PM MDT WED AUG 20 2014

.SYNOPSIS...THE AIRMASS OVER THE FORECAST AREA WILL SLOWLY DRY
THROUGH FRIDAY...ALTHOUGH CONDITIONS WILL REMAIN UNSETTLED. A
COLD TROUGH WILL MOVE ACROSS NORTHERN UTAH OVER THE WEEKEND
BRINGING COOLER CONDITIONS AND A WET START TO THE WEEKEND.

&&

.DISCUSSION...UPPER LEVEL TROUGH OVER THE NRN INTERMOUNTAIN REGION
THIS AFTERNOON WITH CUTOFF LOW ALONG THE SRN CALIFORNIA COAST.
MOIST AIRMASS REMAINS IN PLACE OVER UTAH THIS AFTERNOON WITH GOES
SOUNDER PRECIPITABLE WATER VALUES STILL HOVERING BETWEEN .75" AND
1" OVER MOST OF THE STATE. SBCAPE VALUES IN EXCESS OF 1000 J/KG
THIS AND SCATTERED CONVECTION HAS DEVELOPED ACROSS THE STATE.
DEEP LAYER SHEAR MAXED OUT IN EAST CENTRAL UTAH EARLY THIS
AFTERNOON AND IS NOW DECREASING. MEANWHILE SHEAR HAS INCREASED
ACROSS FAR NORTHWEST UTAH TO 25-30 KTS AHEAD OF APPROACHING
SHORTWAVE. GIVEN INSTABILITY THAT IS PRESENT AND INCREASING
SHEAR...POTENTIAL FOR STRONG STORMS WILL CONTINUE INTO THE
EVENING HOURS....ESPECIALLY ACROSS THE NORTHWEST PORTION OF THE
STATE. ANTICIPATE THAT CONVECTION WILL DIMINISH QUICKLY ACROSS THE
SOUTH THIS EVENING. HOWEVER...IN THE NORTH CONVECTION WILL LIKELY
CONTINUE WELL INTO THE NIGHT. NAM INDICATES THAT MID LEVEL
SHORTWAVE IN NE NV AND SRN ID THIS AFTERNOON WILL MOVE ACROSS
NORTHERN UTAH TONIGHT. THIS WILL PROVIDE SUFFICIENT FORCING TO
KEEP NOCTURNAL SHOWERS AND STORMS GOING AND HRRR MODEL HAS BEEN
CONSISTENT IN SHOWING THIS ACROSS MULTIPLE MODELS RUNS.
ACCORDINGLY...HAVE INCREASED POPS AND CLOUD COVER ACROSS NRN UTAH
OVERNIGHT.

THURSDAY AND THURSDAY NIGHT...TROUGH OVER THE PACIFIC NORTHWEST
BEGINS TO DEEPEN AND CUTOFF LOW BECOMES AN OPEN WAVE AND MOVES
EAST THROUGH ARIZONA. IN BETWEEN THESE TWO FEATURES...MODEL
GUIDANCE CONTINUES TO SHOW DRYING TREND OVER UTAH.
HOWEVER...MODELS HAVE BEEN CONSISTENTLY OVERZEALOUS WITH THE
DRYING TREND OVER UTAH. BELIEVE SUFFICIENT MOISTURE WILL REMAIN IN PLACE
ON THURSDAY TO ONCE AGAIN SEE SCATTERED MTN CONVECTION WITH
ISOLATED STORMS OVER VALLEY LOCATIONS. COVERAGE OF VALLEY STORMS
MAY BE A LITTLE GREATER NEAR THE IDAHO BORDER AS MID LEVEL
BAROCLINIC ZONE PROVIDES CONVERGENCE ALONG AN AXIS FROM NE NV
INTO SRN ID.

ATTENTION THEN TURNS TOWARD DEEPENING TROUGH IN THE PACIFIC NW.
ON FRIDAY...STRONG JET CORE ON UPSTREAM SIDE OF TROUGH INDICATING
THAT TROUGH IS STILL DIGGING A BIT. 90 KT CORE THEN ROUNDS THE
BASE OF THE TROUGH FRI NIGHT. AS A RESULT OF THE STRONG AND
COMPACT CYCLONIC CURVATURE ASSOCIATED WITH THE TROUGH THE FLOW AT
THE BASE OF THE TROUGH HIGHLY SUB-GEOSTROPHIC. THIS LEADS TO A
AREA OF UPPER LEVEL DIVERGENCE OVER NRN UT FRI NIGHT INTO SAT.
BENEATH THIS AREA OF UPPER LEVEL DIVERGENCE MODELS DEPICT
CONVERGENCE ALG 700 MB BAROCLINIC ZONE AS IT MOVES INTO NRN UT FRI
NIGHT. THUS ANTICIPATE THAT BAROCLINIC ZONE WILL BE QUITE ACTIVE
FRI NIGHT INTO SATURDAY AND HAVE INCREASED POPS QUITE A BIT
ACROSS NRN UT DURING THIS PERIOD.

700 MB TEMPERATURES DROP TO 4-6C ACROSS NRN UT AND 7-10C ACROSS
SRN UT FOR SAT AND AND SUN. THIS WILL BRING MUCH COOLER
TEMPERATURES TO THE STATE AND MAX TEMPS ON SAT AND SUN WILL BE
AROUND 10 DEGREES F BELOW NORMAL IN MANY AREAS.

BAROCLINIC ZONE STALLS OUT IN CENTRAL UT SAT NIGHT AND SUN BEFORE
LIFTING BACK NORTH ON MONDAY. THIS ALLOWS TEMPERATURES TO REBOUND
A BIT FOR THE START OF THE WEEK. ANOTHER SHORTWAVE WILL THEN DROP
DOWN THE BACKSIDE OF THE NRN INTERMOUNTAIN REGION TROUGH AND DRIVE
THE BAROCLINIC ZONE BACK TROUGH UT MON NIGHT AND TUESDAY. SOME
UNCERTAINTY ON HOW ACTIVE THE BOUNDARY WILL BE...BUT WITH THE
POTENTIAL FOR RESIDUAL MOISTURE TO STILL BE IN PLACE...AND THE
STRENGTH OF THE WAVE...HAVE INCREASED POPS ACROSS THE STATE
DURING THIS PERIOD.

&&

.AVIATION....ELEVATED SOUTH WINDS WILL PREVAIL AT THE SLC
TERMINAL INTO THE EARLY EVENING...ALTHOUGH THERE IS A 10 PERCENT
CHANCE OF WINDS BRIEFLY SHIFTING TO THE NORTHWEST BETWEEN
2300-0100 UTC. GUSTY AND ERRATIC OUTFLOW WINDS ARE POSSIBLE WITH
VICINITY SHOWERS THROUGH THE EVENING HOURS. TYPICAL SOUTHEAST
DRAINAGE FLOW SHOULD RESUME BETWEEN 0300-0500 UTC.

&&

.FIRE WEATHER...ACTIVE WEATHER WILL CONTINUE INTO THIS WEEKEND BEFORE
BRIEFLY DRYING ON SATURDAY NIGHT/SUNDAY. RESIDUAL MOISTURE IN PLACE
WILL RETAIN ELEVATED RH FOR THE NEXT FEW DAYS ALLOWING ISOLATED
VALLEY AND SCATTERED MOUNTAIN SHOWERS AND STORMS THROUGH FRIDAY. AN
APPROACHING COLD FRONT DRIVEN BY A STRONG PACIFIC TROUGH WILL RAMP
SOUTHERLY WINDS ACROSS THE WEST DESERTS FRIDAY AFTERNOON BUT FORECAST
RH REMAINS AT OR ABOVE 20 PERCENT AND BULK OF FUELS REMAIN NON CRITICAL.
THE COLD FRONT WILL MOVE NORTH TO SOUTH THROUGH THE AREA LATE FRIDAY
NIGHT THROUGH SATURDAY SPREADING FAIRLY WIDESPREAD WETTING RAINS
ACROSS THE NORTHERN HALF OF THE DISTRICT AT THAT TIME. BRIEF DRYING
IS EXPECTED FOR SUNDAY BUT ANOTHER PACIFIC TROUGH/COLD FRONT IS
EXPECTED MONDAY INTO TUESDAY.

&&

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

$$

PUBLIC...GRAHAM
FIRE WEATHER...MERRILL
AVIATION...GRAHAM

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)


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.