224
FXUS65 KSLC 202232
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
432 PM MDT WED OCT 20 2021
SYNOPSIS
HIGH PRESSURE WILL BUILD INTO THE REGION THROUGH
FRIDAY. A WEAK DISTURBANCE WILL CLIP NORTHERN UTAH SATURDAY WITH A
MORE SIGNIFICANT STORM TO IMPACT THE ENTIRE AREA LATE SUNDAY INTO
EARLY NEXT WEEK.
SHORT TERM (THROUGH 12Z/6AM MDT SATURDAY)
SCATTERED TO BROKEN MID / HIGH CLOUDS CONTINUE TO STREAM IN FROM THE
WEST THIS AFTERNOON. EXPECT THESE CLOUDS TO CONTINUE INCREASING
OVERNIGHT, LEADING TO SLIGHTLY WARMER OVERNIGHT TEMPERATURES. SKIES
LOOK TO CLEAR AGAIN THROUGH THE LATE MORNING HOURS AS HIGH PRESSURE
CONTINUES TO BUILD ACROSS THE AREA AND WILL DOMINATE AGAIN ON
THURSDAY. ON FRIDAY, FLOW TURNS TOWARD THE SOUTHWEST AHEAD OF AN
APPROACHING TROUGH OVER THE WEST CONUS COAST. MODELS SHOW THIS
TROUGH AXIS PASSING THROUGH THE FORECAST AREA ON FRIDAY EVENING.
THANKS TO THIS DISTURBANCE, PRECIPITATION CHANCES INCREASE SLIGHTLY
STARTING ON FRIDAY UP NORTH. AS THE LARGE PARENT MID LEVEL LOW GETS
CLOSER TO THE PACIFIC NW, PRECIPITATION CHANCES CONTINUE TO
GRADUALLY INCREASE ACROSS NORTHWEST UTAH AS MOISTURE BECOMES MORE
PRONOUNCED OVER THE FORECAST AREA THROUGH FRIDAY NIGHT.
LONG TERM (AFTER 12Z/6AM MDT SATURDAY)
LOW PRESSURE SPINNING OFF THE GULF OF ALASKA WILL BE DRIVING AN
UNSETTLED WEATHER PATTERN THROUGH THE LONG TERM. THE FIRST TROUGH
EJECTED FROM SAID LOW WILL CLIP THE NORTHWEST CORNER OF UTAH BY
SATURDAY MORNING, SHIFTING THE RIDGE OF HIGH PRESSURE EAST AND
TRANSITIONING MID-LEVEL FLOW FROM THE SOUTHWEST TO MORE ZONAL.
STRONG WESTERLY WINDS ACROSS NORTHERN UTAH WILL TRANSPORT LEFT OVER
MOISTURE FROM AN ATMOSPHERIC RIVER (AR) EVENT ACROSS THE NORTHERN
WASATCH SATURDAY INTO SUNDAY. VARIABILITY WITH THIS FIRST PULL OF
MOISTURE IS EVEN APPARENT IN CLUSTER ANALYSES ON DAY 3, WHICH WOULD
ATTRIBUTE TO NOTABLE DIFFERENCES DETECTED IN DETERMINISTIC GUIDANCE.
THE 00Z/ECMWF, FOR INSTANCE, PULLS MORE MOISTURE ACROSS THE REGION
SATURDAY AFTERNOON, AND DRAGS PRECIPITATION AND COOLER AIR FURTHER
SOUTH THAN WHAT’S DEPICTED BY THE 12Z/GFS. THUS, SOME UNCERTAINTY
STILL LIES WITH THE EVOLUTION OF THIS FIRST SYSTEM WITH REGARD TO
TIMING AND TOTAL QPF THROUGH SUNDAY MORNING.
HOWEVER, BY THIS TIME, A DEEPER AND ANOMALOUSLY LOWER TROUGH WILL BE
PRIMING THE PUMP FOR ANOTHER SURGE OF MOISTURE, AS THE NEXT LOW DIPS
SOUTH ALONG THE PACIFIC NORTHWEST. EVEN THOUGH DISCREPANCIES PERSIST
WITH THE DEPTH AND TIMING OF THE APPROACHING SYSTEM, THERE IS HIGHER
CONFIDENCE IN A STRONG AR IMPACTING THE REGION EARLY NEXT WEEK.
PRECIPITABLE WATER VALUES ARE ESTIMATED TO INCREASE BY 200 TO 300
PERCENT OF NORMAL BY MONDAY NIGHT, RESULTING IN WIDESPREAD
PRECIPITATION CONTINUING INTO TUESDAY NIGHT. TOTAL QPF VALUES RANGE
FROM 1.5 TO 2.0 INCHES OVER THE CENTRAL NORTHERN WASATCH AND WESTERN
UINTAS BY THE TIME THIS SYSTEM EXITS ON WEDNESDAY. IN ADDITION,
EXPECT COLDER AIR ASSOCIATED WITH THE SECOND SYSTEM, DROPPING DAILY
HIGHS 5 TO 10 DEGREES BY MID-WEEK. DESPITE TIMING DIFFERENCES EARLY
ON IN THE LONG TERM PERIOD, FORECAST GUIDANCE AND ENSEMBLE MEANS
CONTINUE TO FAVOR A WET PERIOD FROM DAY 5 THROUGH DAY 7.
AVIATION...KSLC
CONTINUED VFR CONDITIONS ARE EXPECTED FOR THE
DURATION OF THE VALID TAF PERIOD. MID AND HIGH CLOUD COVER WILL
REMAIN FOR THE MAJORITY OF THE DAY AND OVERNIGHT. GENERALLY LIGHT
WINDS ARE EXPECTED WITH A BRIEF PERIOD OF NORTHWEST FLOW THIS
EVENING BEFORE RETURNING TO A SOUTHEAST DRAINAGE FLOW OVERNIGHT.
REST OF UTAH AND SOUTHWEST WYOMING...LINGERING FOG AND LOW STRATUS
SHOULD CLEAR FROM VALLEY LOCATIONS STATEWIDE. MID LEVEL CLOUD DECKS
WILL REMAIN ACROSS MUCH OF THE FORECAST AREA, WITH PATCHY MOUNTAIN
OBSCURATION POSSIBLE, ESPECIALLY EARLY IN THE AFTERNOON BUT THINNING
INTO THE EVENING. GENERALLY LIGHT WINDS ARE EXPECTED AT ALL
TERMINALS THROUGHOUT THE DAY AND OVERNIGHT.
SLC WATCHES/WARNINGS/ADVISORIES
UT...NONE.
WY...NONE.
STEARNS/WALTER/WESSLER
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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page