Area Forecast Discussion
Issued by NWS Salt Lake City, UT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KSLC 070343
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
943 PM MDT WED MAY 6 2015

.SYNOPSIS... A COLD UPPER LOW WILL MOVE SOUTH FROM THE PACIFIC
NORTHWEST AND SETTLE INTO THE GREAT BASIN FOR THE WEEKEND
MAINTAINING ACTIVE WEATHER ACROSS THE REGION.


&&

.DISCUSSION...AN UPPER LOW CONTINUES TO DIVE INTO CALIFORNIA THIS
EVENING. ON THE EAST SIDE OF THIS LOW...LINGERING MOISTURE AND
UPPER DIVERGENCE HAS CONTINUED HEAVY RAIN SHOWERS OVER NORTHERN
UTAH. LIGHTNING WAS QUITE ACTIVE EARLIER IN THE NIGHT...BUT HAS
DECREASED SIGNIFICANTLY AS OF 0330Z. COMBINED WITH DIMINISHING
INSTABILITY PARAMETERS AND DECREASING CHANCE OF THUNDERSTORM IN
SPC CALIBRATED PRODUCTS...FORECAST OF LITTLE TO NO LIGHTNING AFTER
06Z LOOKS TO BE IN GOOD SHAPE. MODERATE-TO-HEAVY RAINFALL SHOULD
CONTINUE ITS NORTHWARD MIGRATION BETWEEN 03Z AND 06Z...AND
SCATTERED SHOWERS WILL REMAIN POSSIBLE IN THE NORTHWEST PORTION OF
THE CWA THROUGH THE NIGHT.

AS FAR AS THE SOUTHERN HALF OF UTAH GOES...LOW LEVEL DRIER AIR
BEGAN WORKING IN THERE EARLIER TODAY...AND WILL CONTINUE TO DO SO
AS THE AREA GETS DRY SLOTTED AHEAD OF THE LOW TONIGHT INTO
THURSDAY MORNING. THAT SAID...THERE IS STILL ENOUGH LINGERING MID
LEVEL MOISTURE TO HELP INITIATE SOME ISOLATED THUNDERSTORMS OVER
THE SOUTHEASTERN QUADRANT OF THE CWA THIS EVENING...SO HAVE
UPDATED THE FORECAST EARLIER THIS MORNING TO ADD MENTIONABLE POPS
TO THE SOUTHEAST THROUGH THE NIGHT.

OTHER THAN THE MINOR POP AND SKY UPDATES IN THE SOUTHEAST...THE
REST OF THE FORECAST FOR TONIGHT LOOKS GOOD...AND NO OTHER UPDATES
ARE ANTICIPATED FOR THE EVENING. THE PREVIOUS DISCUSSION
FOLLOWS...INCLUDING MORE DETAIL IN DAYS 2 THROUGH 7.

&&

.PREV DISCUSSION...A DEEP UPPER LOW CURRENTLY CENTERED OVER
OREGON CONTINUES TO CHURN SOUTH THIS AFTERNOON. WEAK UPPER
DIVERGENCE ON THE DOWNSTREAM SIDE OF THIS TROUGH EXISTS OVER
NORTHWESTERN UTAH...WHILE A MID LEVEL SHORT WAVE CONTINUES TO
SLOWLY TRACK NORTH THROUGH CENTRAL AND NORTHERN UTAH. A DRYING
SOUTHWESTERLY FLOW CONTINUES TO ADVECT INTO SOUTHERN UTAH BEHIND
THE WAVE AND HAS REACHED ROUGHLY THE I-70 CORRIDOR. NORTH OF THAT
LINE WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS HAVE DEVELOPED
AND CONTINUE TO TRACK GENERALLY NORTHEAST COINCIDENT W/THE TRACK
OF THE WAVE. ENHANCEMENT HAS BEEN NOTED BENEATH THE DIVERGENCE
ZONE ALSO COINCIDENT WITH INCREASING SW SHEAR THROUGH THE CLOUD
LAYER. EXPECT BULK OF THE THUNDERSTORM ACTIVITY TO REMAIN OVER THE
NORTHWEST THIS EVENING WHERE UPPER LEVEL EVACUATION EXISTS...BUT
TRENDS POINT MORE TOWARDS WIDESPREAD RAIN ELSEWHERE ACROSS THE
NORTH. LOCALLY HEAVY AND PERIODS OF STEADY MODERATE RAIN REMAIN A
POTENTIAL...BUT AS A WHOLE THE AIRMASS IS BECOMING A BIT
OVERDEVELOPED HAMPERING FURTHER CONVECTIVE POTENTIAL OUTSIDE OF
THOSE AREAS NOTED.

CONTINUED SOUTHERLY TRACK OF THE UPPER LOW INTO NORCAL TONIGHT
WILL FURTHER TIGHTEN UPSTREAM BAROCLINICITY ACROSS NE NEVADA AND
SO. IDAHO...SHEAR AXIS DEVELOPMENT NOTED IN GUIDANCE ACROSS FAR
NORTHERN/WESTERN UT ASSOCIATED WITH THIS WILL LIKELY MAINTAIN
PRECIP WELL INTO OR THROUGH THE NIGHT TONIGHT. DRIER AIR
INTRUSION WILL LIMIT PRECIP POTENTIAL ACROSS MUCH OF THE WESTERN
2/3RDS.

DIVERGENT FLOW ALOFT WILL INCREASE TOMORROW ACROSS MUCH OF THE
AREA AS THE LOW CONTINUES TO PROGRESS INTO CENTRAL CAL. THOUGH
WORKING ON A SOMEWHAT DRIER AIRMASS...BOTH EFFECTIVE SHEAR AND
UPPER SUPPORT WILL INCREASE ALLOWING FOR ANOTHER ROUND OF
SHOWERS/STORMS TO DEVELOP BY MIDDAY. POTENTIAL FOR SOME STRONG
CELLS EXIST WITH FOCUS MTN SPINE FROM THE SOUTHERN MTNS TO UINTAS
AND POINTS WEST. SHOULD SEE A BRIEF REPRIEVE THE FIRST HALF OF
THURSDAY NIGHT WITHIN THE PEAK OF THE DRY SLOT...BUT BY DAWN
FRIDAY SHOWERS WILL BE WORKING BACK INTO THE SOUTHWEST AS THE LOW
BEGINS TURNING EAST TOWARDS THE STATE.

GOOD AGREEMENT IN MODEL SUITE REGARDING TRACK AND EVOLUTION OF
THIS LOW FRIDAY THROUGH THE WEEKEND...THIS ACROSS FAR SOUTHERN
UTAH FRIDAY BEFORE LIFTING NORTHEAST INTO THE NORTHERN PLAINS
STATES THROUGH SUNDAY. EXPECTING A LONG DURATION PRECIP EVENT TO
IMPACT THE CWA PERIODICALLY THROUGH THAT TIME...FOCUS ACROSS THE
SOUTH W/PASSAGE OF THE COLD CORE FRIDAY INTO THE NIGHT AND MOST
PREVALENT ACROSS THE NORTH FRIDAY NIGHT INTO SUNDAY WITHIN THE
WRAP AROUND ENVIRONMENT. HAVE LOWERED SNOW LEVELS SIGNIFICANTLY
FOR SEVERAL PERIODS DUE TO COLD CORE TRACK FRIDAY...AND STRONG
CAA FROM THE NORTHEAST WITHIN THE WRAP AROUND. SNOW LEVELS LIKELY
DOWN TO 6000FT AT TIMES FRI/SAT NIGHT. SIGNIFICANT PRECIP
POTENTIAL EXISTS MOST ALL AREAS...BUT DO WANT TO NOTE ANY IMPACTS
RELATED TO MTN OR MTN VALLEY SNOW SHOULD REMAIN MINIMAL.

MID LEVEL RIDGING WILL GRADUALLY BUILD FROM THE SOUTH EARLY NEXT
WEEK AS THE NEXT UPPER LOW IS PROGGED TO DIG SOUTH ALONG THE
PACIFIC COAST...AND THE WEEKEND TROUGH CONTINUES A NET DOWNSTREAM
PROGRESSION. CONVECTIVE POTENTIAL REMAINS MODEST ACROSS THE FAR
NORTH THROUGH THE PERIOD THOUGH A GENERAL DECREASE IN PRECIP
POTENTIAL IS EXPECTED. CONTINUE TO MAINTAIN POPS CLOSER TO CLIMO
FOR NOW.

&&

.AVIATION...THE AREA OF MODERATE TO HEAVY RAINFALL IS EXPECTED TO
CLEAR THE SLC TERMINAL BETWEEN 0400-0430Z. MVFR
VISIBILITIES/CEILINGS WILL RAPIDLY IMPROVE ONCE THE PRECIPITATION
DECREASES IN INTENSITY. WEST TO NORTHWEST WINDS ARE EXPECTED TO
SHIFT TO SOUTH TO SOUTHEAST BETWEEN 05-07Z. CEILINGS ARE EXPECTED
TO REMAIN BELOW 7000 FEET AGL FOR MOST OF THE NIGHT.

&&

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

$$

PUBLIC...SCHOENING
AVIATION...KRUSE

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)


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.