Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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000
FXUS65 KSLC 021022
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
422 AM MDT SUN AUG 2 2015

.SYNOPSIS...A WEAK WEATHER SYSTEM WILL SLOWLY CROSS THE REGION
FROM SOUTH TO NORTH TODAY THROUGH TONIGHT. A DRIER SOUTHWESTERLY
FLOW WILL FOLLOW THROUGH MIDWEEK...WITH MOISTURE POTENTIALLY
RETURNING BY THE END OF THE WEEK.

&&

.SHORT TERM (UNTIL 00Z WEDNESDAY)...A NEGATIVELY TILTED TROUGH
AXIS OVER THE SOUTHERN HALF OF CALIFORNIA STRETCHING INTO WESTERN
ARIZONA WILL SWING NORTHEAST ACROSS THE CWA TODAY INTO MONDAY. THE
AIR MASS AHEAD OF THIS TROUGH AXIS IS INCREASINGLY MOIST ACROSS
SOUTHERN UTAH...BUT ACROSS NORTHERN UTAH AND SOUTHWEST WYOMING THE
AIR MASS REMAINS DRY TODAY DUE TO AN EASTERLY MID LEVEL FLOW. THIS
TROUGH AXIS WILL HELP DESTABILIZE THE AIR MASS ACROSS SOUTHERN AND
CENTRAL UTAH TODAY AS MOISTURE INCREASES ACROSS THE NORTH TONIGHT
IT WILL ALSO DESTABILIZE. THE CLOUD SHIELD IS EXPECTED TO INHIBIT
THE OVERALL CONVECTION TODAY ALTHOUGH ALONG THE LEADING EDGE OF
CLOUD SHIELD/MOISTURE SURGE THERE COULD BE SOME SCATTERED
THUNDERSTORMS. OTHERWISE EXPECT ONLY ISOLATED THUNDERSTORMS.

TEMPERATURES OVER NORTHERN UTAH WILL BE RATHER WARM ONCE AGAIN
TODAY AS IT WILL BE UNDER THE H7 THERMAL RIDGE. FARTHER SOUTH
THOUGH HAVE LOWERED TEMPS A LITTLE MORE FROM WHERE THEY WERE
YESTERDAY AS CLOUD SHIELD AND SHOWERS WILL BE A BIG INHIBITOR TO
THE HEATING.

HAVE EXPANDED THE ISOLATED SHOWERS ACROSS NORTHERN AND INTO
CENTRAL UTAH MONDAY AFTERNOON BASED ON THE NAM SHOWING THE SHEAR
AXIS OF THE UPPER LEVEL TROUGH STILL AS FAR SOUTH AS UTAH COUNTY
AT MIDDAY...DESPITE NOT SHOWING MUCH IN THE WAY OF THE QPF. ON THE
OTHER HAND THE GFS SHOWS THE SHEAR AXIS ALREADY INTO IDAHO BY
MIDDAY MONDAY BUT IT LINGERS QPF OVER CENTRAL UTAH INTO THE
AFTERNOON. PLAYED IT CAUTIOUSLY FOR NOW AS THE SREF HOLDS ONTO
THE MOISTURE INTO THE AFTERNOON AS WELL.

A DRIER SOUTHWEST FLOW SETS IN ACROSS CENTRAL AND SOUTHERN UTAH
TUESDAY BUT A DISTURBANCE SHOWS UP IN THE GFS AND EC FOR TUESDAY
AFTERNOON SO HAVE KEPT LOW POPS ACROSS NORTH FOR THAT REASON
ALTHOUGH CONFIDENCE IS LOW FOR THIS FEATURE.

.LONG TERM (AFTER 00Z WEDNESDAY)...THE SUBTROPICAL RIDGE AXIS IS
FORECAST TO REMAIN CENTERED ACROSS AZ/NM DURING THE MIDWEEK
PERIOD...RESULTING IN RELATIVELY DRY SOUTHWESTERLY TO WESTERLY
FLOW ALOFT. A WEAK SHORTWAVE EMBEDDED WITHIN THIS FLOW IS FORECAST
TO CROSS THE NORTHERN GREAT BASIN WEDNESDAY...AND WILL BRING A
SMALL THREAT FOR CONVECTION TO NORTHERN UT DURING THE AFTERNOON
AND EVENING HOURS. HEIGHT RISES IN THE WAKE OF THIS FEATURE WILL
LIKELY SUPPRESS ANY CONVECTIVE THREAT ACROSS THE FORECAST AREA
DURING THE DAY THURSDAY.

BY FRIDAY THE MEDIUM RANGE MODELS ARE IN GENERAL AGREEMENT WITH
THE IDEA OF AN UPPER LOW APPROACHING THE NORTHERN CA COAST...BUT
DIFFER BEYOND THIS POINT IN BOTH THE TIMING AND TRACK OF THIS WAVE
AS IT MOVES INLAND...AS WELL AS MOISTURE RETURNING NORTHWARD INTO
THE AREA. THE GFS REMAINS THE FASTER AND MORE AGGRESSIVE
MODEL...WHILE THE EC IS SLOWER WITH THE EASTWARD PROGRESS OF THIS
LOW AND MUCH LESS AMBITIOUS WITH RESPECT TO THE RETURN OF
MOISTURE. FOR NOW HAVE MAINTAINED POPS ACROSS THE SOUTHERN THIRD
OF THE AREA FRIDAY...WITH A TREND TOWARD CLIMO POPS DURING THE
UPCOMING WEEKEND.

TEMPERATURE-WISE...WITH THE RIDGE AXIS REMAINING SUPPRESSED SOUTH
GUIDANCE KEEPS TEMPERATURES A FEW DEGREES BELOW CLIMO THROUGH THE
MIDDLE TO LATTER PORTION PORTION OF THE WEEK...AND HAVE MAINTAINED
THIS IDEA IN THE GOING FORECAST.

&&

.AVIATION...LIGHT SOUTHERLY WINDS AT THE SLC TERMINAL THROUGH ABOUT
18Z ALTHOUGH THERE IS A 20 PERCENT CHANCE THAT THEY SHIFT AT 17Z.
ANY THREAT OF SHOWERS WILL HOLD OFF UNTIL AT LEAST 06Z.

&&

.FIRE WEATHER...DISTURBANCE OVER EXTREME SOUTHERN NEVADA WILL WORK
ITS WAY NORTHWARD INTO CENTRAL UTAH TODAY AND ACROSS NORTHERN UTAH
MONDAY. A SIGNIFICANT CLOUD SHIELD ASSOCIATED WITH THIS DISTURBANCE
IS LIKELY GOING TO INHIBIT THUNDERSTORM DEVELOPMENT TO SOME DEGREE
AS WELL AS THE INTENSITY OF THE THUNDERSTORMS AND SHOWERS. THEREFORE
THE THREAT OF WETTING RAINS HAS BEEN LOWERED FOR MOST AREAS TODAY
AND TONIGHT. BEST CHANCE FOR ANY SCATTERED THUNDERSTORMS WILL BE
ALONG THE LEADING EDGE OF THE MOISTURE/CLOUD SHIELD AS IT MOVES
NORTHWARD TODAY. DRYING WILL BEGIN TO WORK ITS WAY INTO ZONE 497 BY
THIS AFTERNOON AND THEN ACROSS THE REST OF THE SOUTHWEST AND SOUTH
MONDAY. SOUTHWEST WINDS WILL INCREASE SOME OVER WESTERN VALLEYS
TUESDAY BUT BE THE STRONGEST ON WEDNESDAY WITH GUSTS OVER 30 MPH
POSSIBLE. ANOTHER MONSOON TAP IS EXPECTED FRIDAY.

&&

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

$$

STRUTHWOLF/SEAMAN

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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