Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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431
FXUS65 KSLC 242146
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
346 PM MDT SUN APR 24 2016

.SYNOPSIS...A STORM SYSTEM ALONG THE WEST COAST WILL MOVE INTO
THE GREAT BASIN TONIGHT...THEN SLOWLY EAST ACROSS UTAH ON MONDAY.
YET ANOTHER STORM SYSTEM WILL IMPACT THE AREA TOWARDS THE END OF
THE WEEK.

&&

.SHORT TERM (THROUGH 12Z WEDNESDAY)...AN UPPER TROUGH CURRENTLY
MOVING ONSHORE ALONG THE PACIFIC COAST IS FORECAST TO CONTINUE
EASTWARD INTO THE GREAT BASIN TONIGHT...BEFORE EVENTUALLY CLOSING
OFF AND SLOWLY TREKKING EASTWARD ACROSS THE FORECAST AREA MONDAY
THROUGH MONDAY NIGHT. THIS FEATURE WILL TAKE A MORE SOUTHERN PATH
THAN THE LOW WHICH CROSSED THE AREA SATURDAY...AND THUS
PRECIPITATION WILL EXTEND MUCH FURTHER SOUTH INTO SOUTHERN UTAH
WITH THIS SYSTEM.

INITIALLY ANTICIPATE PRECIPITATION MONDAY WILL REMAIN MORE
CONVECTIVE IN NATURE WITH PERHAPS THE EXCEPTION OF THE FAR NORTH
IN THE VICINITY OF AN INVERTED TROUGH AXIS WHICH WILL PROVIDE
BETTER FORCING. AS THE LOW CONTINUES EAST ANTICIPATE PRECIPITATION
WILL BECOME MORE STRATIFORM AND ORGANIZED WITHIN A REGION OF
WRAP AROUND MOISTURE ON THE BACK SIDE OF THE LOW MONDAY NIGHT INTO
TUESDAY MORNING ALONG THE I-15 CORRIDOR AS WELL AS THE ADJACENT
TERRAIN.

SNOW LEVELS INITIALLY WILL REMAIN AROUND 7 KFT THROUGH MUCH OF
MONDAY...BUT FALL TO NEAR 6 KFT BY TUESDAY MORNING WITH SEVERAL
INCHES OF DENSE SNOW EXPECTED ACROSS THE HIGHER TERRAIN. AT THIS
POINT IMPACTS WOULD SEEM FAIRLY MINIMAL AND DO NOT ANTICIPATE
NEEDING WINTER WX HEADLINES WITH THIS SYSTEM.

.LONG TERM (AFTER 12Z WEDNESDAY)...ACTIVE WEATHER PATTERN CONTINUES
THROUGH THIS EXTENDED PERIOD. THE GLOBAL MODELS ARE IN PRETTY GOOD
AGREEMENT SO THE FORECAST COMES DOWN TO HOW WELL THE MODELS ARE
DEPICTING THE DYNAMICS AND HOW MUCH OF THE QPF FORECAST IS BEING
DRIVEN BY DAYTIME CONVECTION.

BY WEDNESDAY AFTERNOON THE GFS AND EC DRIVE A 500MB TROUGH DOWN INTO
SOUTHERN CALIFORNIA WITH A 700MB CIRCULATION DEVELOPING OVER
SOUTHERN NEVADA. MOISTURE IS SHOWN TO SPREAD ACROSS MUCH OF THE CWA
BUT THE BEST DYNAMICAL LIFT APPEARS TO BE ASSOCIATED WITH SOME 500MB
VORTICITY MOVING INTO SOUTHWEST WEST CENTRAL UTAH BY 00Z THURSDAY.
HOWEVER...THIS LIFT IS RATHER WEAK SO HAVE TRIMMED THE POPS TO
SLIGHT CHANCE IN THE VALLEYS AND LEFT LOW END CHANCE IN THE CENTRAL
AND SOUTHERN MOUNTAINS AND REMOVED POPS OVER THE EASTERN VALLEYS AS
WELL AS ALONG THE CENTRAL AND NORTHERN WASATCH FRONT AND MUCH OF THE
GREAT SALT LAKE DESERT FOR WEDNESDAY. LEFT LOW POPS IN ACROSS
SOUTHWEST WYOMING AND NORTHERN MOUNTAINS AS BOTH GFS AND EC SHOW QPF
BUT HARD PRESSED TO DISCERN WHAT IS CAUSING IT OTHER THEN POSSIBLY
SOLAR HEATING.

A LOBE OF ENERGY SWINGS NORTHEAST THEN NORTH ACROSS CENTRAL AND
NORTHERN MOUNTAINS SOUTH OF I-80 WEDNESDAY NIGHT INTO THURSDAY.
SINCE BOTH THE EC AND GFS IDENTIFY THIS FEATURE HAVE BOOSTED POPS
SOME FOR THIS OVERNIGHT PERIOD AND THURSDAY. THE FOCUSING MECHANISM
ON THURSDAY SHOULD BE THE TROUGH AXIS ITSELF MIGRATING ACROSS THE
SOUTHERN AND CENTRAL PORTIONS OF THE CWA.

BY THURSDAY NIGHT A MOIST NORTH NORTHWEST FLOW IS EXPECTED OVER THE
WESTERN VALLEYS SO KEPT CHANCE POPS THERE AS WELL AS OVER THE
MOUNTAINS...BUT LOWERED POPS ACROSS THE EASTERN VALLEYS AS DOWN
SLOPING SHOULD HINDER MUCH SHOWER ACTIVITY FROM MAKING IT THERE.

A WEAK SHORT WAVE RIDGE AT 700 MB IS FORECAST TO MOVE OVER THE
REGION FRIDAY NIGHT WHICH WILL RESULT IN MUCH LESS SHOWER ACTIVITY.
HOWEVER ANOTHER SHORT WAVE WILL MOVE SOUTHEAST ACROSS THE REGION
SATURDAY AFTERNOON AND NIGHT AND THIS SHOULD BRING SHOWERS TO MAINLY
NORTHERN PORTIONS OF THE CWA AND MOUNTAINS OF CENTRAL AND SOUTHERN
UTAH. FINALLY DRIER AIR WORKS ITS WAY INTO THE REGION
SUNDAY...ALTHOUGH SHOWERS ARE STILL POSSIBLE ACROSS THE MOUNTAINS.

TEMPERATURES ARE EXPECTED TO RUN WITHIN A FEW DEGREES OF NORMAL
THROUGHOUT THIS EXTENDED PERIOD.

&&

.AVIATION...WINDS AT THE SLC TERMINAL ARE EXPECTED TO BE NORTHWEST
THROUGH EARLY THIS EVENING THEN SWITCH TO THE SOUTHEAST. CIGS WILL
REMAIN ABOVE 7K FT AGL THROUGH AT LEAST 09Z WITH A 40 PERCENT CHANCE
OF REMAINING ABOVE 7K FT AGL THROUGH 18Z.

&&

.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)



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