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 251040
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
440 AM MDT TUE AUG 25 2015

.SYNOPSIS...MOISTURE WILL SPREAD NORTHWARD ACROSS THE AREA LATE
TODAY THROUGH TONIGHT...AS AN UPPER LEVEL DISTURBANCE MOVES
NORTHWARD ACROSS THE REGION TONIGHT THROUGH WEDNESDAY. HIGH
PRESSURE WILL RETURN FOR THE LATTER HALF OF THE WEEK INTO THE
UPCOMING WEEKEND.

&&

.SHORT TERM (THROUGH 06Z SATURDAY)...MID LEVEL RIDGING CENTERED
ACROSS SOUTHWEST CO EARLY THIS MORNING WILL DRIFT EAST THROUGH THE
DAY...AND ALLOW A DEEP LAYER SOUTHERLY FLOW TO DEVELOP ACROSS THE
FORECAST AREA BY THIS AFTERNOON. THIS FLOW WILL ADVECT MOISTURE
CURRENTLY IN PLACE ACROSS THE DESERT SOUTHWEST NORTHWARD ACROSS
THE FORECAST AREA OVER THE NEXT 24-36 HOURS.

IN ADVANCE OF THE ARRIVAL OF THIS MOISTURE SURGE A DRY BOUNDARY
LAYER REMAINS IN PLACE ACROSS THE EASTERN GREAT BASIN. IN ADDITION
TO SCATTERED TERRAIN BASED CONVECTION THIS AFTERNOON FROM THE
UINTAS SOUTHWARD...MAY SEE HIGH BASED CONVECTION WITH GUSTY WINDS
DEVELOP ALONG THE LEADING EDGE OF THIS MOISTURE SURGE ACROSS
SOUTHERN UT THIS AFTERNOON...THEN INTO CENTRAL AND NORTHERN UT
LATE THIS AFTERNOON INTO THIS EVENING.

A WAVE ASSOCIATED WITH ONGOING CONVECTION ACROSS NORTHERN MX IS
FORECAST TO LIFT NORTHWARD THROUGH THE EASTERN GREAT BASIN TONIGHT
THROUGH WEDNESDAY. THIS WAVE WILL BE ACCOMPANIED BY A SUBSTANTIAL
INCREASE IN PRECIPITABLE WATER...WITH VALUES IN THE 1.00 TO 1.25
INCH RANGE ACROSS THE FORECAST AREA BY MIDDAY WEDNESDAY. AS IS
OFTEN THE CASE WITH THESE WAVES...EXTENSIVE CLOUD COVER AND
MARGINAL MID LEVEL LAPSE RATES WILL LIKELY LIMIT THE DEGREE OF
INSTABILITY WEDNESDAY...HOWEVER LARGE SCALE ASCENT SHOULD PROVIDE
FOR A GOOD CHANCE FOR SHOWERS AND SCATTERED THUNDERSTORMS
TONIGHT INTO WEDNESDAY MORNING. SOME DISCREPANCIES EXIST WITH
RESPECT TO HOW QUICKLY THIS WAVE EXITS TO THE NORTH...AND AS SUCH
HAVE KEPT POPS ELEVATED INTO THE AFTERNOON HOURS PARTICULARLY
ACROSS THE NORTH. IN THE WAKE OF THIS WAVE WOULD ANTICIPATE LARGE
SCALE SUBSIDENCE WILL LIMIT ADDITIONAL CONVECTION. WITH EXPECTED
CLOUD COVER AND PRECIPITATION A BLEND OF GUIDANCE KEEPS
TEMPERATURES WELL BELOW CLIMO AND HAVE MAINTAINED THIS TREND.

BY THURSDAY MID LEVEL RIDGING IS FORECAST TO AMPLIFY ACROSS THE
AREA...WITH LARGE SCALE SUBSIDENCE AND MID LEVEL DRYING
SUPPRESSING CONVECTION ACROSS MOST AREAS. WITH THE REBOUNDING
RIDGE TEMPERATURES SHOULD QUICKLY REBOUND TO NEAR NORMAL VALUES.
THIS RIDGE AXIS SHIFTS SLIGHTLY EAST FRIDAY WITH LIGHT
SOUTHWESTERLY FLOW RESULTING IN A CONTINUED WARMING TREND WITH
CONVECTION REMAINING FAIRLY SPARSE...AND LARGE LIMITED TO THE
HIGHER TERRAIN.

.LONG TERM (AFTER 06Z SATURDAY)...

&&

.LONG TERM (AFTER 06Z SATURDAY)...THE GFS AND EC HAVE CONVERGED ON
THEIR SOLUTIONS THROUGH FRIDAY MORNING BUT THEY BEGIN TO DIVERGE BY
THE TIME SATURDAY ROLLS AROUND. THEY BOTH WEAKEN THE SHORTWAVE
TROUGH WHICH CONTAINED THE CIRCULATIONS 24 HOURS EARLIER NEAR 140W
AND 40N...ALTHOUGH THE EC KEEPS A LITTLE MORE AMPLITUDE AS IT SWINGS
INTO THE PACIFIC NORTHWEST. PROBABLY NOT MUCH OF A DIFFERENCE
WEATHER WISE FOR UTAH. HOWEVER THE ENERGY FLOWING INTO THE LONGWAVE
TROUGH OFF THE COAST IS HANDLED DIFFERENTLY BY THE EC AND GFS. THE
EC TAKES THIS ENERGY AND MAKES THE ENTIRE TROUGH PROGRESSIVE MOVING
IT INTO PACIFIC NORTHWEST SUNDAY NIGHT AND ACROSS THE NORTHERN
ROCKIES EARLY MONDAY WITH THE ASSOCIATED COLD FRONT MOVING ACROSS
NORTHERN UTAH MONDAY. ANOTHER LOBE OF ENERGY ROTATES ACROSS THE
PACIFIC NORTHWEST/NORTHERN ROCKIES MONDAY NIGHT WITH ANOTHER TUESDAY
AFTERNOON. MEANWHILE THE GFS KEEPS THE TROUGH OFF THE COAST UNTIL
MONDAY NIGHT NIGHT WHICH KEEPS UTAH UNDER A DRY SOUTHWEST FLOW
THROUGH THE PERIOD. THIS GFS SOLUTION APPEARS TO BE THE MOST
CONSISTENT AND HAVE LEANED IN THAT DIRECTION BUT CONFIDENCE IS STILL
LOW TO MODERATE WITH THE TYPHOONS IN THE PACIFIC HAVING A NEGATIVE
IMPACT ON THE OVERALL CONSISTENCY OF THE MODELS. GUSTY SOUTHWEST
WINDS ARE EXPECTED OVER THE WESTERN VALLEYS AND HIGHER TERRAIN
SATURDAY AND SUNDAY AND POSSIBLY INTO EARLY NEXT WEEK.

&&

.FIRE WEATHER...THE LEADING EDGE OF THE MONSOONAL MOISTURE WILL MOVE
NORTHWARD INTO SOUTHERN UTAH BY MIDDAY AND INTO NORTHERN UTAH
TONIGHT. THERE IS A THREAT OF ISOLATED DRY LIGHTNING TODAY
ESPECIALLY OVER SOUTHERN AREAS AND HIGHER TERRAIN OF CENTRAL AND
NORTHERN UTAH LATER TODAY AND TONIGHT. HOWEVER...WETTING RAINS ARE
LIKELY TO ACCOMPANY A DISTURBANCE THAT IS EMBEDDED WITHIN THIS
MONSOONAL SURGE AS IT MOVES INTO SOUTHERN UTAH THIS EVENING AND
ACROSS NORTHERN UTAH WEDNESDAY. A DRYING TREND COMMENCES FOR THE
LATTER PORTION OF THE WEEK. GUSTY SOUTHERLY WINDS ARE EXPECTED THIS
WEEKEND AS A STRONG TROUGH SETS UP OFF THE PACIFIC NORTHWEST COAST.

&&

.AVIATION...WINDS AT THE SLC TERMINAL ARE EXPECTED TO BE SOUTHERLY
THROUGH AT LEAST 21Z BEFORE SHIFTING TO THE NORTHWEST. THERE IS A 30
PERCENT CHANCE THAT WINDS COULD REMAIN SOUTHERLY THROUGH THE TAF
PERIOD. SHOWERS AND THUNDERSTORMS ARE POSSIBLE AFTER 05Z WITH THE
POTENTIAL OF PRODUCING GUSTY WINDS OVER 30 MPH.

&&

&&

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

$$

SEAMAN/STRUTHWOLF

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.