Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 052156
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
356 PM MDT TUE MAY 5 2015

.SYNOPSIS...A LOW PRESSURE SYSTEM OVER NORTHERN ARIZONA WILL MOVE
EAST INTO THE SOUTHERN AND CENTRAL ROCKIES THIS EVENING. A COLD
PACIFIC WEATHER DISTURBANCE WILL MOVE SOUTH OUT OF THE PACIFIC
NORTHWEST AND IMPACT MUCH OF THE GREAT BASIN FRIDAY AND THROUGH
THE WEEKEND.

&&

.DISCUSSION...4-CORNERS LOW HAS RAPIDLY TRANSITIONED OVER CENTRAL
COLORADO OVER THE LAST FEW HOURS PER WATER VAPOR AND H5 ANALYSIS.
PRE-EXISTING DEFORMATION AXIS OVER NORTHERN/CENTRAL UT SHOWING
SIGNS OF DISSIPATING AS MID LEVEL FLOW IS NOW BECOMING A LIGHT
NORTHWESTERLY ACROSS MUCH OF WESTERN/NORTHERN UTAH. NUMEROUS
SHOWERS AND ISOLATED THUNDERSTORMS EXIST WITH AREAL COVERAGE
GREATEST SOUTH AND EAST OF KSLC...AND BENEATH THE ENTRANCE REGION
OF THE UPPER JET ACROSS THE EXTREME NORTHWEST. HAVE NOTED ISOLATED
HEAVY RAINERS NEAR THIS JET ENTRANCE REGION DUE TO THE MOIST LOW
LEVEL AIRMASS IN PLACE AND WEAK FLOW AT THE SURFACE ON UP THROUGH
THE MID LEVELS...GOOD EVACUATION POTENTIAL EXISTING ALOFT.

AFOREMENTIONED MID LEVEL NORTHWESTERLY PUSH WILL CONTINUE TO DRIVE
SOUTH AND EAST THIS EVENING AND OVERNIGHT. GUIDANCE INDICATING
FOCUSED MOISTURE CONVERGENCE ALONG AND SOUTH OF THIS AXIS ACROSS
WEST CENTRAL/CENTRAL UTAH TONIGHT PROVIDING LIFT FOR NOCTURNAL
SHOWERS/STORMS THOSE AREAS. LEFT HIGH CHANCE AND LIKELY POPS THOSE
AREAS WHILST AREAS TO NORTH WILL BE WITHIN A DRYING/STABILIZING
REGIME...ESPECIALLY ACROSS THE WASATCH FRONT AND POINTS
NORTHWEST.

THE DEEP PACNW CLOSED LOW CURRENTLY SPINNING OVER SOUTHERN
BRITCOL/WASHINGTON WILL TRANSLATE DUE SOUTH REACHING NORCAL BY
THIS TIME TOMORROW. GLOBAL MODELS INDICATE A STRENGTHENING UPPER
JET OVER THE WEST DESERTS/NW THROUGHOUT THE DAY...WHILE THE ZONE
OF MID LEVEL CONVERGENCE RETREATS BACK NORTH AS A DRYING MID LEVEL
SOUTHWESTERLY FLOW PUNCHES INTO FAR SOUTHERN UTAH TOMORROW
AFTERNOON. SPC SREF SHOWING A NET INCREASE OF EFFECTIVE SHEAR /ON
THE ORDER OF 30-40 KTS/ LATE AFTERNOON THROUGH THE EVENING BENEATH
THIS JET. STRONG OR ISOLATED SEVERE STORMS CAN NOT BE RULED OUT
ACROSS GENERALLY WESTERN TOOELE/BOX ELDER COUNTIES FOR A WINDOW AS
SUCH.

GLOBALS CONTINUE TO PAINT A SIMILAR PICTURE REGARDING TRACK AND
EVOLUTION OF THIS LOW THU THROUGH THE WEEKEND. GENERAL IDEA TURNS
THE LOW EAST THURSDAY EVENING THEN TRACKS THE CORE OF THE UPPER
CIRCULATION AND ASSOCIATED COLD POOL THROUGH NORTHERN
ARIZONA/SOUTHERN UTAH FRIDAY THROUGH SATURDAY. SUBTLE DIFFERENCES
IN TRACK /EITHER NORTHERN AZ OR CENTRAL AZ/ SEEM TO HAVE IRONED
OUT IN 12Z GUIDANCE. WIDESPREAD AND POTENTIALLY MODERATE TO HEAVY
AT TIMES PRECIP IS EXPECTED AT TIMES THROUGH THIS PERIOD...WITH
FOCUSED PRECIP LIKELY ALONG THE NORTHERN AND WESTERN PERIPHERIES
OF THE CIRCULATION CENTER. H7 TEMPS WILL BE FALLING ENOUGH FOR
SNOW LEVELS TO RUN BETWEEN 8-9 KFT NORTH...65-75 KFT SOUTH WHERE
ACCUMULATIONS ARE LIKELY BUT WITH MINIMAL IMPACT.

GLOBALS CONTINUE TO MAINTAIN INCREASED SPREAD SUNDAY INTO EARLY
NEXT WEEK...SPECIFICALLY REGARDING DOWNSTREAM TRANSLATION OF THE
UPPER LOW AND ANY MID LEVEL RIDGING THAT MAY OR MAY NOT BUILD IN
FROM THE WEST. GFS REMAINS MUCH LESS PROGRESSIVE AND POTENTIALLY
MORE UNSETTLED. TRENDING POPS TOWARDS CLIMO FROM THEIR PREVIOUSLY
ELEVATED LEVELS REMAINS THE BEST BET FOR THE TIME BEING FOR THE
LATTER PERIODS.

&&

.AVIATION...SHOWERS WILL CONTINUE NEAR THE SALT LAKE CITY TERMINAL
THROUGH AT LEAST 01Z WEDNESDAY...WITH A SLIGHT CHANCE THAT SHOWERS
CONTINUE PAST 06Z. THESE SHOWERS WILL CONTINUE TO MAKE THE WINDS A
LOW CONFIDENCE FORECAST...BUT A GENERAL WESTERLY COMPONENT IS LIKELY
TO CONTINUE BETWEEN 21Z AND 01Z. THERE IS A 10 PERCENT CHANCE THAT A
STRONGER THUNDERSTORM PASSES OVERHEAD...WHICH COULD RESULT IN BRIEF
MVFR CONDITIONS OR CLOUD-TO-GROUND LIGHTNING.

&&

.FIRE WEATHER...THIS WEEK WILL GENERALLY BE WET...WITH MOIST RH AND
SEASONAL TO COOL TEMPERATURES.

THROUGH TONIGHT...THE WEATHER WILL BE DOMINATED BY A SLOW MOVING
DISTURBANCE PROPAGATING FROM THE FOUR CORNERS INTO COLORADO. EXPECT
SCATTERED SHOWERS AND THUNDERSTORMS. DEWPOINTS HAVE RISEN INTO THE
40S AND 50S INCREASING THE CHANCE OF WETTING RAIN. PRIMARY THREATS
INCLUDE CLOUD TO GROUND LIGHTNING ALONG WITH GUSTY/ERRATIC WINDS
NEAR SHOWERS. SNOW LEVELS SHOULD BE 9-10KFT.

DRIER AIR DEVELOPS TOMORROW ACROSS SOUTHERN UTAH AS SOUTHWEST WINDS
BEGIN TO GUST. THIS SHOULD LEAD TO LESS STORM COVERAGE VS FURTHER
NORTH. THURSDAY LOOKS TO BE THE DRIEST DAY WITH AN INCREASING GUSTY
SOUTHWESTERLY FLOW AHEAD OF A LARGE STORM SYSTEM DROPPING SOUTH
ALONG THE WEST COAST. THIS STORM WILL MOVE THROUGH THE GREAT BASIN
INTO THE WEEKEND...BRINGING COOLER AND WETTER CONDITIONS ONCE AGAIN.
SNOW LEVELS LOOK TO LOWER BELOW 8KFT BY THE END OF THE WEEK.

&&

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

$$

MERRILL/SCHOENING/ROGOWSKI


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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