Red Flag Warning 20, NWS Salt Lake City, UT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
325 PM MDT SUN AUG 8 2010

.SYNOPSIS...ABUNDANT MOISTURE WILL REMAIN ACROSS UTAH AND EXTREME
NORTHWEST WYOMING TONIGHT AS AN UPPER LEVEL DISTURBANCE LIFTS
NORTHEAST ACROSS THE REGION.  THE MAIN UPPER TROUGH WILL SLIDE
ACROSS THE NORTHERN REACHES OF THE FORECAST AREA ON MONDAY.  A RIDGE
OF HIGH PRESSURE WILL BUILD OVER THE REGION THROUGH THE MIDDLE OF
THE WEEK.

&&

.DISCUSSION...WATER VAPOR IMAGERY INDICATES TROUGH OF LOW PRESSURE
FROM OREGON TO SOUTHERN CALIFORNIA...WITH A SERIES OF UPPER LEVEL
DISTURBANCES LIFTING NORTHEAST OUT OF THIS TROUGH.  VISIBLE IMAGERY
INDICATES BUILDING CUMULUS FIELD AMD LATEST RADAR IMAGERY INDICATES
STRENGTHENING OF CELLS PUSHING NORTHEAST INTO UTAH.  AIRMASS HAS
DESTABILIZED THIS AFTERNOON...WITH CAPES NOW AROUND 1000 J/KG.
ANALYSIS ALSO INDICATES INCREASING SHEAR...NEAR 40 KTS...OVER
SOUTHWEST UTAH.

WITH UPPER DISTURBANCE WORKING ACROSS SOUTHWEST UTAH...AS WELL AS 75
KT UPPER JET...EXPECT THUNDERSTORM COVERAGE AND INTENSITY TO
INCREASE DURING LATE AFTERNOON HOURS...WITH A FEW SEVERE STORMS
POSSIBLE. HEAVY RAINFALL REMAINS A POSSIBILITY AS AIRMASS STILL
RATHER MOIST...WITH PRECIPITABLE WATER VALUES NEAR AN INCH.  WILL
MAINTAIN EXISTING FLASH FLOOD WATCH...THOUGH HAVE ADDED A MENTION OF
HEAVY RAIN FOR AREAS ADJACENT TO WATCH.

WITH UPPER LEVEL TROUGH SLIDING ACROSS FORECAST AREA ON
MONDAY...CHANCE FOR SHOWERS AND THUNDERSTORMS WILL
CONTINUE...ESPECIALLY NORTH AND EAST SECTIONS.  DRIER AIR WILL
ADVECT INTO SOUTHWEST PORTIONS.

WITH A MUCH DRIER AIRMASS IN PLACE...PRIMARILY DRY WEATHER EXPECTED
ON TUESDAY.

FORECAST CHALLENGE FOR REMAINDER OF WEEK IS FOR DIURNAL THUNDERSTORM
ACTIVITY AS MODELS SUGGEST UPPER LEVEL RIDGE REMAINS JUST FAR ENOUGH
EAST FOR MOISTURE TO PUSH BACK INTO REGION WITH SOUTHERLY FLOW.
THUS...HAVE BOOSTED CHANCES FOR PRECIPITATION TO CLIMO LEVELS FOR
WEDNESDAY THROUGH SUNDAY PERIOD.

&&

.AVIATION...VFR CONDITIONS AND GUSTY SOUTH WINDS ARE EXPECTED TO
CONTINUE AT KSLC INTO THE EVENING.  THERE IS A 30 PERCENT CHANCE
THAT THUNDERSTORMS WILL IMPACT THE TERMINAL...PRIMARILY AFTER 23Z...
WITH THE PRIMARY CONCERN BEING STRONG GUSTY AND ERRATIC WINDS.

&&

.FIRE WEATHER...MOIST AIRMASS IS STILL OVER MUCH OF THE DISTRICT
THIS AFTERNOON...AND WILL REMAIN IN PLACE THROUGH MONDAY ALONG AND
AHEAD OF A PACIFIC TROUGH THAT WILL MOVE THROUGH THE AREA. AHEAD OF
THE TROUGH...PRESSURE GRADIENT HAS INCREASED...ALLOWING FOR BREEZY
WINDS...PARTICULARLY OVER NORTHWESTERN UTAH. RED FLAG WARNING ISSUED
EARLIER FOR NORTHWESTERN UTAH HAS BEEN CANCELED BECAUSE RELATIVE
HUMIDITY VALUES ARE TOO HIGH FOR CRITICAL CONDITIONS. AS THE TROUGH
EXITS THE STATE BY EARLY TUESDAY...A DRIER AIRMASS WILL MOVE INTO
THE DISTRICT.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...FLASH FLOOD WATCH THROUGH THIS EVENING FOR
     UTZ016-019-020-518.
     SEVERE THUNDERSTORM WATCH IN EFFECT UNTIL 9 PM MDT
     UTC001-017-021-023-025-027-031-039-041-
     053-055.
     WY...NONE.

&&

AVIATION/PUBLIC...BARJENBRUCH
FIRE WEATHER...TRAPHAGAN

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)