Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 182124
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
324 PM MDT MON MAY 18 2015

.SYNOPSIS...A BROAD STORM SYSTEM OVER CALIFORNIA AND SOUTHERN
NEVADA THIS AFTERNOON WILL MOVE NORTHEAST INTO NORTHERN PORTIONS
OF NEVADA AND UTAH TONIGHT THROUGH TUESDAY. THE NEXT STORM SYSTEM
WILL ARRIVE LATE IN THE WEEK AND IMPACT MUCH OF UTAH THROUGH AT
LEAST THE FIRST HALF OF THE WEEKEND.


&&

.SHORT TERM (UNTIL 06Z FRIDAY)...ELONGATED AMOEBA SHAPED
CIRCULATION OVER CALIFORNIA INTO NEVADA HAS A LOBE OF ENERGY OVER
SOUTHERN NEVADA THAT WILL ROTATE NORTHWARD INTO SOUTHWEST AND
WESTERN UTAH LATE THIS AFTERNOON INTO THIS EVENING. ANOTHER AREA
OF CONVECTION ASSOCIATED WITH A WEAK CIRCULATION AT LOW LEVELS AND
GOOD DIFFLUENCE ALOFT IS OCCURRING OVER NORTHWEST UTAH THIS
AFTERNOON. WHILE THE LOW LEVEL CIRCULATION IS EXPECTED TO
DISSIPATE AS IT MOVES NORTHWEST OVER THE GREAT SALT LAKE
DESERT...THE DIFFLUENCE ALOFT IS EXPECTED TO REMAIN OVER NORTHERN
UTAH THROUGH THIS EVENING. THEREFORE HAVE GONE WITH NUMEROUS
SHOWERS AND SCATTERED THUNDERSTORMS ACROSS ALL OF WESTERN UTAH AND
ALSO ACROSS NORTHERN UTAH FOR THIS EVENING. THE HRRR SUPPORTS THIS
IDEA BUT THE NAM12 DOES NOT...SO I GUESS TIME WILL TELL WHICH ONE
IS CORRECT.

THE ELONGATED LOW WILL STRETCH FROM CENTRAL NEVADA ACROSS NORTHERN
UTAH TUESDAY FOR CONTINUED THREAT OF SHOWERS AND ISOLATED
THUNDERSTORMS WHILE THE EXTREME SOUTH WILL BE UNDER A SOMEWHAT
DRIER SOUTHWEST FLOW. HAVE SCATTERED THUNDERSTORMS MENTIONED OVER
EASTERN PORTIONS OF THE CWA AS THERE IS STILL ABOUT A 20C SPREAD
BETWEEN H7 AND H5 ENOUGH FOR SOME INSTABILITY.

THE REMNANTS OF THE LOW WILL BE NORTH OF THE CWA WEDNESDAY BUT THE
AIR MASS WILL STILL REMAIN RATHER MOIST ACROSS NORTHERN UTAH FOR
ISOLATED TO SCATTERED SHOWERS. THE SOUTHERN VALLEY SHOULD BE RAIN
FREE WEDNESDAY AS A WEAK RIDGE BUILDS IN. TEMPERATURES OVERALL
WILL WARM 5-8 DEGREES WEDNESDAY DUE TO H7 TEMPERATURES WARMING BY
2-4 DEGREES C.

BY THURSDAY THE NEXT STORM SYSTEM IS ROLLING INTO THE WESTERN GREAT
BASIN PLACING THE CWA UNDER UPPER LEVEL DIFFLUENCE ONCE AGAIN FOR
AN INCREASE CHANCE OF SHOWERS AND THUNDERSTORMS.


.LONG TERM (AFTER 06Z FRIDAY)...THE CLOSED LOW OFF THE SOUTHERN
CALIFORNIA COAST ON THURSDAY IS FORECAST TO MOVE THROUGH CALIFORNIA
ON THURSDAY NIGHT...THEN OVER NORTHERN ARIZONA THROUGH THE DAY
FRIDAY. UTAH AND SOUTHWEST WYOMING LOOK TO BE ONCE AGAIN IN THE
CROSSHAIRS OF SOME OF THE BEST PRECIPITATION...ESPECIALLY HEADING
INTO SATURDAY AS THE TROUGH MIGRATES NORTHEASTWARD...FIRST OVERHEAD
AND THEN EXITING THROUGH COLORADO AND WYOMING.

THE NORTHERN PORTIONS OF THE CWA COULD EVEN GET INTO SOME WRAP-
AROUND PRECIPITATION AGAIN LATE SATURDAY INTO SUNDAY...THOUGH SOME
OF THAT DEVELOPMENT MAY BE INFLUENCED BY YET ANOTHER CLOSED LOW
MOVING IN FROM THE PACIFIC NORTHWEST SATURDAY INTO SUNDAY. THERE IS
SOME DISCREPANCY ABOUT WHETHER THIS LOW WILL CONTINUE TO LINGER
ACROSS THE PACIFIC NORTHWEST INTO THE BEGINNING OF NEXT WORK WEEK OR
DIVE SOUTHWARD INTO THE GREAT BASIN. CURRENT POPS FOR DAY 7 ARE
FOCUSED ACROSS THE NORTH...BUT THESE WOULD HAVE TO BE EXPANDED
SOUTHWARD AND INCREASED SIGNIFICANTLY IF THE LOW SPINS FOR A COUPLE
DAYS OVER THE GREAT BASIN AS THE ECMWF HAS BEEN PROMOTING.

BOTTOM LINE FOR THE EXTENDED...YET ANOTHER PERIOD OF WET AND ACTIVE
WEATHER FOR THE AREA. HAVE GENERALLY CONTINUED THE UPWARD TREND OF
POPS...AND ALSO LOWERED MAX TEMPS TO ACCOUNT FOR INCREASED CLOUD
COVER THROUGH MUCH OF THE HOLIDAY WEEKEND.

&&

.FIRE WEATHER...A MOIST SPRING WEATHER PATTERN WILL REMAIN IN PLACE
THROUGH MUCH OF THE UPCOMING WEEK. SHOWERS AND THUNDERSTORMS WILL
CONTINUE TO DEVELOP ACROSS MUCH OF UTAH THROUGH TUESDAY...WITH SNOW
LEVELS GENERALLY AROUND 8-9KFT. THESE SHOWERS WILL BECOME LESS
WIDESPREAD WEDNESDAY AND THURSDAY...AND CONDITIONS WILL WARM AND DRY
A BIT AS THE STATE IS BETWEEN STORM SYSTEMS. HOWEVER...THE NEXT
STORM WILL MOVE THROUGH THE AREA LATE THURSDAY AND INTO THE
WEEKEND...WITH WETTING RAINS ONCE AGAIN POSSIBLE IN MANY LOCATIONS.
&&

.AVIATION...PERIODIC SHOWERS WITH POSSIBLY A THUNDERSTORM OR TWO CAN
BE EXPECTED IN AND AROUND THE KSLC TERMINAL THROUGH THE EVENING.
CONDITIONS WILL PRIMARILY REMAIN IN THE VFR RANGE...ALTHOUGH BRIEF
PERIODS WITH MVFR CIGS/VIS. THE WIND FORECAST IS A LOW CONFIDENCE
ONE...AS OUTFLOW WILL LIKELY DICTATE THE OVERALL WIND PATTERN
THROUGH THE EVENING. THE MOST LIKELY DIRECTION THROUGH 03Z SEEMS TO
BE WEST-NORTHWEST BASED ON MESONET OBSERVATIONS AND SURFACE PRESSURE
ANALYSIS...HOWEVER PERIODS OF SOUTHERLY OR EVEN EASTERLY WINDS WILL
BE POSSIBLE.

&&

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

$$

PUBLIC...STRUTHWOLF
AVIATION...SEAMAN

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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