Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 220908
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
308 AM MDT FRI MAY 22 2015

.SYNOPSIS...THE LOW PRESSURE SYSTEM OVER SOUTHERN CALIFORNIA
WILL TURN NORTHEAST AND SLOWLY TRACK NORTHEAST THROUGH THE GREAT
BASIN THIS WEEKEND.

&&

.SHORT TERM (THROUGH 12Z MONDAY)...
WATER VAPOR LOOP SHOWS A CLOSED OVER SOUTHERN CALIFORNIA. AMDAR
400- 250MB WIND OBSERVATIONS SHOW A 75-110KT CYCLONIC JET FROM THE
EASTERN PACIFIC INTO THE SOUTHERN ROCKIES. GOES/GPS/RAP/00Z SLC
RAOB INDICATE THE PRECIPITABLE WATER VALUE RANGES BETWEEN
0.25"-0.50" MOUNTAINS...TO 0.50"-0.75" ACROSS THE VALLEYS.

MAIN FEATURE THIS MORNING IS A SHORTWAVE PIVOTING FROM EAST CENTRAL
UTAH LATE OVERNIGHT...INTO SOUTHWEST WYOMING AND NORTHEAST UTAH THIS
AFTERNOON. DEFORMATION ZONE WILL BUILD INTO WESTERN UTAH THIS
AFTERNOON...WITH BETTER DEEP LAYER SHEAR CONFINED DOWNWIND OF THE
TROUGH OVER THE FOUR CORNERS. THESE FEATURES WILL COMBINE WITH
MODEST INSTABILITY TO ONCE AGAIN SUPPORT SCATTERED TO NUMEROUS
SHOWERS AND THUNDERSTORMS THROUGH THE EVENING HOURS.

GREATEST DCAPE SHOULD BE SOUTH OF INTERSTATE 80 DUE TO DRIER LOW
LEVELS...SUPPORTING A HIGHER CHANCE FOR DRY MICROBURSTS. OTHERWISE
STORMS WILL ALSO CONTAIN CLOUD TO GROUND LIGHTNING...SMALL
HAIL...AND A BRIEF HEAVY RAIN.

EXPECTING DEFORMATION ZONE TO SUPPORT GREATER STORM COVERAGE
OVERNIGHT.

THE BEST COVERAGE OF RAIN IS LIKELY SATURDAY INTO SATURDAY NIGHT
WHEN WRAP-AROUND PRECIPITATION DUE TO MID LEVEL WARM ADVECTION
ARRIVES FROM THE NORTHEAST. GLOBAL MODELS ARE BEGINNING TO FOCUS IN
ON NW UTAH SATURDAY MORNING...THEN DOWN THE NEVADA BORDER REGION
TOWARD DELTA AND CEDAR CITY SATURDAY AFTERNOON...AND SOUTHWEST/SOUTH
CENTRAL UTAH SATURDAY EVENING. RE-FOCUSED POPS TO THESE AREAS WITH
THIS IN MIND.

CONVECTIVE COVERAGE SHOULD DECAY SATURDAY NIGHT INTO SUNDAY MORNING
AS THE CLOSED LOW LIFTS INTO THE CENTRAL ROCKIES DUE TO AN UPSTREAM
WAVE SINKING SOUTH OVER CALIFORNIA. WHILE THIS FEATURE DOES NOT PASS
OVERHEAD SUNDAY...COMBINATION OF MODEST INSTABILITY AND A NEW AREA
OF DEFORMATION BETWEEN THESE SYSTEMS WILL LIKELY LEAD TO ANOTHER
ROUND OF SHOWERS AND THUNDERSTORMS SUNDAY AFTERNOON AND EVENING.
DECAY THE ACTIVITY FROM NW TO SE OVERNIGHT SUNDAY WITH INFUSION OF
DRIER AIR ALOFT ON DRYING NORTHWEST FLOW AS RIDGING BUILDS IN OVER
NEVADA.

.LONG TERM (AFTER 12Z MONDAY)...
UNSETTLED PATTERN LOOKS TO CONTINUE TO REMAIN IN PLACE DURING THE
UPCOMING WEEK. A PACIFIC TROUGH WILL DIG INTO ARIZONA MONDAY
MORNING BEFORE CROSSING INTO NEW MEXICO MONDAY EVENING...PROVIDING
INSTABILITY OVER THE FORECAST AREA. A MORE ZONAL FLOW IS PROGGED
TO DEVELOP FOR TUESDAY...BUT LINGERING MOISTURE AND INSTABILITY
WILL PROVIDE FUEL FOR AFTERNOON SHOWERS AND
THUNDERSTORMS...PARTICULARLY OVER THE HIGHER TERRAIN OF NORTHERN
UTAH.

SOME DIFFERENCES REMAIN IN THE GLOBAL MODELS WITH THE HANDLING OF
THE PACIFIC NORTHWEST STORM SYSTEM THAT APPROACHES AFTER THIS.
GFS/EC BOTH MOVE THE SYSTEM ONSHORE OVER WASHINGTON MONDAY NIGHT BUT
IN THE LATEST EC THIS TRACKS EAST NEAR THE UNITED STATES/CANADA
BORDER AS IT WEAKENS THROUGH THE MIDDLE OF THE WEEK...BRINGING A
PUSH OF MOISTURE INTO NORTHERN AND CENTRAL UTAH FOR WEDNESDAY AND
THURSDAY BEFORE DRIER AIR MOVES IN FOR DAY 7. THE PROGRESSION OF THE
SYSTEM IS A BIT SLOWER IN THE GFS...AS THE SYSTEM REMAINS STALLED
OVER WASHINGTON AND OREGON THROUGH THURSDAY BEFORE FINALLY MOVING
EAST AND WEAKENING ON FRIDAY. THIS WOULD KEEP MOISTURE OVER NORTHERN
UTAH...BUT WOULD RESULT IN A SOMEWHAT DRIER SOLUTION FOR CENTRAL AND
SOUTHERN UTAH. FOR NOW...HAVE OPTED TO KEEP POPS AROUND TO A BIT
ABOVE CLIMO GIVEN THAT ALL GUIDANCE IS CONTINUING TO INDICATE AT
LEAST A SOMEWHAT MOIST AND UNSTABLE PATTERN.

&&

.AVIATION...VFR CONDITIONS ARE EXPECTED AT THE SLC TERMINAL
THROUGHOUT THE DAY. CIGS WILL GENERALLY REMAIN ABOVE 6000 FT
AGL...BUT SHOWERS DEVELOPING THIS AFTERNOON WILL LIKELY BRING CIGS
TO OR BELOW THAT VALUE FOR PERIODS. SOUTHERLY WINDS ARE EXPECTED TO
PREVAIL...BUT THE SHOWERS WILL PRODUCE PERIODS OF GUSTY AND/OR
ERRATIC WINDS.

&&

.FIRE WEATHER...THE NEXT STORM SYSTEM ARRIVES TODAY AND PERSISTS
THROUGH THE HOLIDAY WEEKEND. SHOWERS AND THUNDERSTORMS WILL GROW
MORE NUMEROUS ACROSS THE REGION...WITH THE GREATEST COVERAGE IN
ACTIVITY EXPECTED SATURDAY...ESPECIALLY ACROSS WESTERN AND SOUTHERN
UTAH. TEMPERATURES WILL TREND COOLER AND HUMIDITY WILL TREND HIGHER.
SNOW LEVELS WILL BE BETWEEN 8-9KFT...FALLING TO 7KFT UNDER THE
HEAVIEST ACTIVITY. CLOUD TO GROUND LIGHTNING...GUSTY/ERRATIC
WINDS...A BRIEF HEAVY DOWNPOUR...AND SMALL HAIL ARE ALL POSSIBLE
WITH THE STRONGER ACTIVITY.

&&

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

$$

SHORT TERM/FIRE WEATHER...ROGOWSKI
LONG TERM/AVIATION...TRAPHAGAN

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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