Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 202218
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
418 PM MDT MON OCT 20 2014

.SYNOPSIS...A DRY AND MILD SOUTHWESTERLY FLOW WILL GIVE WAY TO A
PACIFIC COLD FRONT ON TUESDAY. DRY AND MILD SOUTHWEST FLOW WILL
RETURN FOR THURSDAY AND FRIDAY.

&&

.SHORT TERM (THRU 00Z FRI)...SOUTHERLY FLOW IS OVER THE CWA THIS
AFTN TO THE EAST OF AN ELONGATED UPPER TROF MOVING ON TO THE WEST
COAST. A LITTLE TROPICAL MOISTURE IS IN PLACE AND SOME AFTN
CONVECTION HAS DEVELOPED OVER MAINLY THE HIGHER TERRAIN. THIS
SHOULD LAST INTO THE EVENING AND COULD PERSIST LATER TONIGHT
ACROSS THE NORTH AND EAST AS DYNAMICS INCREASE AHEAD OF THE WEST
COAST TROF. ONLY EXPECT LIGHT PRECIP FROM THIS AND NO THUNDER.

THE PAC TROF LIFTS NEWD TONIGHT THRU TUE AS AN UPSTREAM TROF
FORCES IT TO WEAKEN AND EJECT INTO THE NRN ROCKIES. THE TRAILING
COLD FRONT MAINTAINS ENOUGH INTEGRITY THAT COMBINED WITH THE
MOISTURE IN PLACE TO PRODUCE AN ORGANIZED BAND OF PRECIP FOR THE
NRN CWA TUE MORNING EXTENDING SWD INTO W CENTRAL UT. THIS BAND
SHIFTS TO NERN TO CENTRAL UT ALONG THE STALLING FRONT IN THE
AFTN AND STARTS TO WEAKEN.

THE EJECTING NATURE OF THIS TROF PREVENTS MUCH COLD AIR FROM
REACHING THE CWA AND IT APPEARS THE BULK OF THE PRECIP FOR NRN UT
OCCURS BEFORE IT GETS COD ENOUGH FOR ANY REAL HIGH ELEVATION SNOW
ACCUMULATION. SO IMPACTS LOOK NEGLIGIBLE FROM SNOWFALL.

AS THE FRONT DOES NOT MAKE IT THROUGH THE CWA...LINGERING MOISTURE
ACROSS THE SOUTH LIFTS NWD WED AS THE STALLED BOUNDARY LIFTS NWD
AS A WEAK WARM FRONT. MODELS DO NOT GENERATE ANY QPF FROM THIS
HOWEVER. INCREASING SWLY FLOW THU RETURNS DRY AND MILD WX TO THE
CWA.

&&

.LONG TERM (AFTER 00Z FRIDAY)...CONFIDENCE IN A LATE WEEKEND TROUGH
IMPACTING THE EASTERN GREAT BASIN CONTINUES TO INCREASE. THOUGH
DETAILS DIFFER ON A VARIETY OF LEVELS REGARDING TIMING...
AMPLIFICATION...AND NOW PER 12Z ECMWF BREADTH OF COLD AIR...SUNDAY
IS EXPECTED TO BE A MUCH COOLER AND WETTER DAY ACROSS MUCH OF THE
FORECAST AREA.

DETAILS...12Z ECMWF A LITTLE SHARPER WITH THE SPLITTING NATURE OF
THE TROUGH AS IT COMES ON SHORE SATURDAY/SATURDAY NIGHT. THOUGH THE
SOUTHERN SPLIT CONTINUES TO TAKE AIM ON THE AREA SUNDAY...SAID RUN
CLOSES THE UPPER LOW OFF OVER SOUTHERN NEVADA BEFORE ENTERING THE
STATE... MODERATING AS IT LOSES CONNECTION TO COLDEST AIR. H7 TEMPS
ONLY DROP TO AROUND ZERO AT KSLC DURING PEAK OF CAA WHICH IS A
MODEST 5 TO 6 DEGREE INCREASE FROM PREVIOUS RUNS AND THAT OF THE THE
LAST SEVERAL GFS SOLUTIONS. CAN SEE THIS AS A POTENTIAL DUE TO A
DECENT WAVELENGTH TO YET ANOTHER TRAILING TROUGH NEAR 150W ATTM WITH
RIDGING BETWEEN...BUT CHANCES OF IT CLOSING OFF MORE SHARPLY TO OUR
WEST SLOWING PROGRESSION DOWN FURTHER APPEAR MINIMAL DUE TO SAID
UPSTREAM TROUGH. MINIMAL CHANGES RUN TO RUN IN GFS THOUGH
PROGRESSIVE NATURE APPEARS TO BE ABOUT AS FAST AS IT CAN GET. THUS
INCREASED POPS SIGNIFICANTLY FOR THE PERIOD THAT FALLS
BETWEEN...SUNDAY...AND TOOK A BLENDED APPROACH TO OTHER DETAILS IN
LATEST FORECAST EXPECTING THESE TO CHANGE OVER TIME AS MODEL TO
MODEL CONSISTENCY TRENDS MORE POSITIVE. INCREASED POPS ON BOTH SIDES
OF THAT PERIOD AS WELL...BUT AGAIN...QUITE BLENDED DUE TO
DIFFERENCES IN SPEED OF TRACK. REGARDLESS OF THESE DIFFERENCES AN
ALL DRY BUT COOL FORECAST REMAINS FOR MONDAY BENEATH BUILDING
HEIGHTS.

&&

.AVIATION...THE LAKE BREEZE IS CURRENTLY STALLED ON THE FAR NORTHERN
END OF THE KSLC TERMINAL AFTER MAKING AN EARLIER SURGE. SEEING AN
ADDITIONAL SURGE NORTH OF THE TERMINAL SO WILL MAINTAIN LATEST TAF
TIMING OF 2230-23Z FOR A SWITCH TO NORTHWEST WINDS. THIS SAID...A 40
PERCENT CHANCE EXISTS THAT WINDS WILL REMAIN SOUTHERLY THROUGH
TONIGHT.

A COLD FRONT WILL MOVE THROUGH THE TERMINAL BETWEEN 14-16Z TUESDAY
BRINGING GUSTY NORTHWEST WINDS...LIGHT RAIN AND CIGS AT OR BELOW
6000FT AGL THROUGH MIDDAY.

&&

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

$$

SHORT TERM...WILENSKY
LONG TERM/AVIATION...MERRILL

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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