Area Forecast Discussion
Issued by NWS Salt Lake City, UT

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 311016
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
416 AM MDT FRI JUL 31 2015

.SYNOPSIS...A RIDGE OF HIGH PRESSURE WILL REMAIN OVER THE REGION
THROUGH SATURDAY...THEN SHIFT EASTWARD SUNDAY. AN UPPER LEVEL
DISTURBANCE WILL CROSS THE REGION SUNDAY AND SUNDAY NIGHT.
MOISTURE WILL REMAIN LIMITED TO SOUTHERN UTAH THROUGH
SATURDAY...THEN SPREAD NORTHWARD ON SUNDAY.

&&

.SHORT TERM (THROUGH 00Z MONDAY)...THE UPPER-LEVEL RIDGE AXIS AT 500MB
THAT EXTENDED FROM THE SOUTHERN PLAINS WESTWARD THROUGH UTAH AND
NEVADA INTO NORTHERN CALIFORNIA HAS SPLIT WITH A HIGH FORMING OVER
NORTHWEST NEVADA. THIS HIGH WILL SHIFT EASTWARD ALONG THE NEVADA
IDAHO BORDER THROUGH SATURDAY MORNING. THIS HIGH WILL KEEP A
NORTHERLY FLOW COMPONENT ACROSS MOST OF THE CWA NOT ONLY AT 700MB
WHICH HAS BEEN ADVERTISED FOR A FEW RUNS BUT ALSO AT 500MB. THE LOW
LEVELS BELOW 500MB ARE DRY ACROSS NORTHERN AND MOST OF CENTRAL UTAH
AND THIS WILL REMAIN THE CASE THROUGH SATURDAY. THE HIGH PWS WHICH
ARE SKIRTING SOUTHERN UTAH TODAY ARE STILL A REFLECTION OF HIGH
LEVEL MOISTURE AND NOT SO MUCH AT LOW LEVELS. THEREFORE THE THREAT
OF PRECIPITATION WILL BE MINIMAL WITH HIGH BASED THUNDERSTORMS
PRODUCING MORE WIND THEN RAIN. HAVE BACKED OFF THE POPS FROM CHANCE
TO SLIGHT CHANCE ACROSS THE MOUNTAINS AND CHANGED THE FORECAST TO
DRY THUNDERSTORMS FOR BOTH TODAY AND SATURDAY. THE LIFTED INDEX AT
BRYCE IS SHOWN BY THE NAM TO ACTUALLY BE LESS UNSTABLE ON SATURDAY
THAN TODAY. NOT CONFIDENT IN THIS SCENARIO SO LEFT POPS NEARLY THE
SAME AT THIS TIME.

BY SUNDAY...BOTH THE EC AND GFS HAVE THE TROUGH OFF THE CALIFORNIA
COAST PICK UP THE CIRCULATION THAT IS LOCATED OFF THE BAJA COAST AND
BRING IT NORTHWARD ACROSS THE CWA. THE GFS IS A LITTLE FASTER WITH
THE 300MB VORT MAX REACHING WESTERN UTAH BY SUNDAY MORNING WHILE THE
EC MOVES IT INTO SOUTHWEST UTAH SUNDAY AFTERNOON. BECAUSE OF THIS
TIMING DISCREPANCY HAVE SPREAD POPS ACROSS THE ENTIRE CWA FOR SUNDAY
AFTERNOON. DUE THE ADDITIONAL DYNAMICAL LIFT HAVE INCREASED THE POPS
SOME ACROSS MOST OF THE CWA BUT DUE TO FORECAST SOUNDINGS SHOWING
SOMEWHAT OF DRY SUB CLOUD LAYER HAVE NOT GONE OVERBOARD WITH THE
POPS.

.LONG TERM (AFTER 00Z MONDAY)...UPPER LEVEL DISTURBANCE WILL LIFT
THROUGH NORTHERN AND EASTERN PORTIONS OF FORECAST AREA SUNDAY
NIGHT.  WITH AMPLE MOISTURE IN PLACE...PRECIPITABLE WATER VALUES
NEAR AN INCH...CURRENT SLIGHT CHANCE TO CHANCE WORDING STATEWIDE
SUPPORTED.

FLOW WILL BECOME MORE WESTERLY ON MONDAY...USHERING IN DRIER AIR.
THIS SAID...LINGERING MOISTURE DOES SUPPORT SLIGHT CHANCE TO
CHANCE WORDING FOR SHOWERS AND THUNDERSTORMS...PRIMARILY ACROSS
SOUTHERN AND EASTERN PORTIONS OF FORECAST AREA.

AS MODELS CONTINUE DRY SOUTHWEST FLOW ON TUESDAY AND
WEDNESDAY...WILL ONLY GO WITH SLIGHT CHANCE WORDING FOR HIGHER
TERRAIN OF SOUTHERN AND EASTERN UTAH AND FOR NORTHWEST
UTAH...WHERE WEAK UPPER LEVEL DISTURBANCES WILL CLIP REGION.

GFS AND ECMWF MODELS SOLUTIONS DIVERGE A BIT FOR THURSDAY. BOTH
GFS AND ECMWF SHIFT RIDGE OF HIGH PRESSURE EASTWARD...BUT GFS
SUGGESTS BETTER MOISTURE TRANSPORT THROUGH FORECAST AREA...WHILE
ECMWF SOLUTION INDICATED DEEPER MOISTURE WILL REMAIN CONFINED TO
FAR EASTERN UTAH. GFS IS ALSO STRONGER WITH UPPER LEVEL
DISTURBANCE MOVING ACROSS FORECAST AREA. WITH SUPPORT FROM SEVERAL
GFS ENSEMBLE MEMBERS...WILL LEAN TOWARD GFS SOLUTION. THUS...WILL
GO WITH SLIGHT CHANCE TO CHANCE WORDING ACROSS BULK OF FORECAST
AREA.

&&

.AVIATION...LIGHT SOUTHEAST WINDS WILL PREVAIL AT THE SLC TERMINAL
THROUGH ABOUT 17Z BEFORE SHIFTING TO THE NORTHWEST. THERE IS A 40
PERCENT CHANCE THAT THESE WINDS SHIFT TO NORTHWEST BY 16Z. NO OTHER
WEATHER CONCERNS THROUGH TODAY.

&&

.FIRE WEATHER...MOISTURE HAS MADE LITTLE PROGRESS NORTHWARD INTO
SOUTHERN UTAH DURING THE PAST 12-18 HRS AS IT CONTINUES TO SKIRT
WESTWARD ALONG THE ARIZONA-UTAH BORDER. THIS MOISTURE WHICH IS MAINLY
AT HIGH LEVELS IS EXPECTED TO REMAIN OVER THE SOUTHERN PORTIONS OF
UTAH TODAY AND ONLY CREEP A LITTLE FARTHER NORTHWARD SATURDAY. THERE
IS NO ORGANIZED FEATURE TO HELP GENERATE CONVECTION SO EXPECT
ISOLATED DRY THUNDERSTORMS WITH GUSTY ERRATIC WINDS TO BE THE
MAIN THREAT FROM ABOUT ZONE 496 SOUTHWARD TODAY AND POSSIBLY
SPREAD NORTHWARD INTO FIRE ZONES 495 AND 493 SATURDAY.

A DISTURBANCES IS EXPECTED TO MOVE NORTHWARD ACROSS THE FIRE
DISTRICT SUNDAY BRINGING THE BEST CHANCE FOR CONVECTION BUT BECAUSE
FORECAST MODELS CONTINUE TO SHOW SOMEWHAT OF A DRY SUB CLOUD LAYER
THE CHANCE FOR WETTING RAINS WILL BE MINIMAL AT BEST. THEREFORE BE
ALERT FOR THE POSSIBILITY OF DRY THUNDERSTORMS CONTINUING THROUGH
SUNDAY. IN THE WAKE OF THIS SUNDAY DISTURBANCE...A DRIER SOUTHWEST
FLOW IS EXPECTED TO DEVELOP MONDAY THROUGH WEDNESDAY WITH BREEZY
SOUTHWEST WINDS POSSIBLE TUESDAY AND WEDNESDAY.

&&

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

&&

$$

PUBLIC...STRUTHWOLF/BARJENBRUCH
AVIATION...STRUTHWOLF
FIRE WEATHER...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.