429
FXUS65 KSLC 081032
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
432 AM MDT WED APR 8 2020
SYNOPSIS
THE LOW PRESSURE SYSTEM OFF THE SOUTHERN CALIFORNIA
COAST WILL TURN EAST AND ADVANCE INTO EXTREME SOUTHERN NEVADA BY
LATE THURSDAY. SOMEWHAT COOLER AND WET CONDITIONS WILL IMPACT
MUCH OF UTAH THROUGH MIDWEEK, WITH DRIER CONDITIONS RETURNING LATE
IN THE WEEK.
SHORT TERM (THROUGH 12Z SATURDAY)
THE UPPER LOW CURRENTLY
POSITIONED JUST OFF THE SOUTHERN CALIFORNIA COAST WILL MOVE INLAND
LATER THIS AFTERNOON. FROM THERE THIS LOW WILL TRACK SLOWLY EAST-
NORTHEAST, REACHING EXTREME SOUTHERN NEVADA BY LATE THURSDAY.
THE INITIAL PRECIPITATION ASSOCIATED WITH THE ADVANCING UPPER LOW
COULD REACH INTO EXTREME SOUTHWEST UTAH BY LATE THIS AFTERNOON.
SHORTWAVE ENERGY ROTATING NORTH AHEAD OF THE LOW THROUGH WESTERN
ARIZONA WILL CLIP THE SOUTHWEST CORNER BY LATE AFTERNOON. SOMEWHAT
COOLER AIR AT THE MID-LEVELS ASSOCIATED WITH SHORTWAVE ALONG WITH
DECENT SURFACE HEATING WILL LIKELY BRING A MODEST INCREASE TO
INSTABILITY ACROSS THE SOUTHWEST WHEN THE SHORTWAVES PASSES
THROUGH THE AREA.
ANTICIPATING A RAPID INCREASE IN SYNOPTIC-SCALE LIFT ACROSS SOUTHERN
THROUGH WEST-CENTRAL UTAH TONIGHT. STRONG, DEEP LAYER THERMAL
ADVECTION AND INCREASING DYNAMIC LIFT FROM THE APPROACHING LOW
WILL LEAD TO AN EXPANDING AREA OF LIGHT TO MODERATE PRECIP
OVERNIGHT. LOCALLY HEAVIER CONVECTIVE PRECIP WILL BE POSSIBLE THIS
EVENING AS THE NOSE OF THE JET REACHES INTO NORTHWEST ARIZONA AND
EXTREME SOUTHWEST UTAH.
THE LOW-LEVEL BAROCLINIC ZONE THAT MOVED NORTH THROUGH SOUTHERN
UTAH OVERNIGHT WILL LIKELY HOLD TOGETHER AS ROTATES INTO NORTHERN
UTAH THURSDAY. SOLID CONVERGENCE INTO THIS LOW-LEVEL BOUNDARY
WITH DYNAMIC SUPPORT FROM VORTICITY LOBES ROTATING AROUND UPPER
LOW POSITION SHOULD GENERATE A BAND OF LIGHT/MODERATE PRECIP
ALONG AND JUST NORTH OF THE BAROCLINIC ZONE THURSDAY AFTERNOON AND
EVENING. SOUTH OF THIS BOUNDARY COLD AIR INSTABILITY ALONG WITH
DYNAMIC SUPPORT FOR LIFT IN PROXIMITY TO THE UPPER LOW SHOULD
MAINTAIN SHOWERY PRECIP ACROSS PORTIONS OF SOUTHERN AND CENTRAL
UTAH THROUGH EARLY THURSDAY EVENING.
THE DETERMINISTIC MODEL GUIDANCE CONTINUES TO SHOW A GRADUAL
SOUTHWEST DRIFT TO THE LOW CENTER THURSDAY NIGHT THROUGH FRIDAY
MORNING BEFORE THIS FEATURES EJECTS EAST ACROSS SOUTHERN ARIZONA
FRIDAY AFTERNOON. THE DEFORMATION AXIS ALONG THE NORTHERN FLANK OF
THE LOW WILL REACH NORTH TO AROUND THE UTAH/ARIZONA REGION FRIDAY
AFTERNOON/EVENING. SHOWERY PRECIP ALONG AND SOUTH OF THE
DEFORMATION WILL LIKELY REMAIN ACROSS NORTHERN ARIZONA, THOUGH
SUSPECT A FEW SHOWERS WILL DRIFT IN AND OUT OF EXTREME SOUTHERN
UTAH DURING THE AFTERNOON/EARLY EVENING HOURS. DRIER AND MORE
STABLE CONDITIONS WILL MOVE INTO UTAH FROM THE NORTH LATER FRIDAY
NIGHT.
LONG TERM (AFTER 12Z SATURDAY)
HIGH PRESSURE WILL BE CENTERED OFF
THE PACIFIC COAST TO START THE FORECAST PERIOD, BUT A FEW DIFFERENT
STORM SYSTEMS ARE EXPECTED TO MOVE OVER THE TOP OF THIS RIDGE TO
IMPACT THE WEATHER OVER UTAH AND SOUTHWEST WYOMING. THE FIRST ONE
LOOKS LIKE IT WILL IMPACT THE AREA SOMETIME BETWEEN LATE SATURDAY
INTO EARLY MONDAY. OVERALL SPREAD IN THE GUIDANCE HAS DECREASED
NOTICEABLY COMPARED TO THIS TIME YESTERDAY, SO CONFIDENCE IS
INCREASING IN A SIGNIFICANT COOLDOWN FOR MUCH OF THE AREA BEGINNING
SUNDAY. MAXES ON SUNDAY ARE EXPECTED TO RUN AT LEAST 5F BELOW
SEASONAL NORMALS, AFTER RUNNING UP TO 10F ABOVE THOSE VALUES ON
SATURDAY. SOME PRECIP IS ALSO ANTICIPATED, PARTICULARLY FOR
NORTHEASTERN PORTIONS OF THE FORECAST AREA, BUT MOISTURE WITH THIS
SYSTEM LOOKS A BIT LIMITED, WHICH IS OFTEN THE CASE WITH BACK DOOR
SYSTEMS.
AFTER A BRIEF BREAK IN THE ACTION ON MONDAY, ANOTHER TROUGH IS
EXPECTED TO SLIDE OVER THE TOP OF THE RIDGE INTO THE AREA TUESDAY
INTO WEDNESDAY. SPREAD IN THE GUIDANCE IS HIGHER WITH THIS SYSTEM
THAN THE PREVIOUS, ESPECIALLY WITH REGARD TO ITS PRECISE TRACK,
HOWEVER IT SEEMS THIS SYSTEM WILL BE MUCH WEAKER THAN THE FIRST ONE.
AVIATION
THE SLC TERMINAL WILL SEE VFR CONDITIONS THROUGHOUT THE
DAY WITH MOSTLY CLEAR SKIES. SOUTHEAST WINDS ARE EXPECTED TO SHIFT
TO THE NORTHWEST BETWEEN 17Z AND 19Z.
SLC WATCHES/WARNINGS/ADVISORIES
UT...NONE.
WY...NONE.
CONGER/TRAPHAGAN
FOR MORE INFORMATION FROM NOAA'S NATIONAL WEATHER SERVICE
VISIT... HTTP://WEATHER.GOV/SALTLAKECITY
FOR FREQUENTLY ASKED QUESTIONS ABOUT THE AREA FORECAST DISCUSSION
VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY/GENERAL/AFD_FAQS.PHP
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