FXUS65 KSLC 270945
AFDSLC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
245 AM MST FRI NOV 27 2009

.SYNOPSIS...A SPLITTING PACIFIC STORM SYSTEM WILL SLIDE ACROSS
THE REGION TONIGHT AND SATURDAY. A RIDGE OF HIGH PRESSURE WILL
BUILD OVER THE AREA EARLY NEXT WEEK.

&&

.DISCUSSION...WATER VAPOR LOOP SHOWS A SHEARING TROUGH ALONG THE 
PACIFIC NORTHWEST COAST...AS AN UPPER LOW ENTERS THE GULF OF ALASKA. 
400-250MB ACARS WIND OBSERVATIONS SHOWS LIGHT ANTICYCLONIC FLOW 
ALOFT...WITH A 100-125KT ANTICYCLONICALLY CURVED JET FROM THE 
PACIFIC NORTHWEST TOWARD LAKE WINNIPEG. 00Z 700MB ANALYSIS PLACED 
THE RIDGE ACROSS ARIZONA WITH A COLD FRONT CUTTING ACROSS THE 
PACIFIC NORTHWEST. ADVECTION HAS TURNED NEUTRAL LOCALLY...WITH +4C 
AT BOTH KSLC AND UPSTREAM AT KNKX. 00Z KSLC RAOB INDICATES 3-5C OF 
WARMING BELOW 650MB WITH LITTLE THERMAL CHANGE ALOFT DURING THE PAST 
24 HOURS. AN INVERSION REMAINS JUST ABOVE 850MB.

GOES/RUC PRECIPITABLE WATER INDICATE VALUES HAVE FALLEN TO BETWEEN A 
TENTH AND A QUARTER INCH ACROSS THE STATE.

AIR QUALITY HAS BEEN ON THE DECLINE DURING THE PAST SEVERAL DAYS 
ACROSS THE NORTHERN VALLEYS AS THE INVERSION SET IN. WHILE HAZE HAS 
BEEN VISIBLE...VISIBILITIES HAVE BEEN BEHAVING SO WILL LEAVE OUT 
MENTION IN THE FORECAST.

SAME INVERSION HAS BEEN LIMITING AFTERNOON WARMING ACROSS THE 
NORTHERN VALLEYS. AS THE NEXT FRONT APPROACHES FROM THE NORTHWEST 
TODAY...PRESSURE GRADIENT SHOULD START TO INCREASE AND PROMOTE 
BETTER MIXING OF THE STRENGTHENING SOUTHERLY FLOW AT 700MB. HAVE 
THEREFORE GONE A LITTLE WARMER FOR TODAY. EXPECT THE MOUNTAINS TO BE 
A BIT COOLER TODAY AS THE RUC ANALYSIS ALREADY SHOWS 700MB 
TEMPERATURES COOLING FROM +4C TO +2C OVERNIGHT.

MODEL SUITE CONSISTING OF NAM/GFS/CANADIAN/EUROPEAN ALL SHOW THE 
NEXT SYSTEM ARRIVING TOMORROW...WITH THE MID LEVEL REFLECTION 
SPLITTING SOUTHWEST TOWARD SOUTHERN CALIFORNIA. THIS LEAVES THE 
GREAT BASIN WITH WANING DYNAMICS MEETING UP WITH MEAGER AMBIENT 
MOISTURE. THEREFORE LOWERED POPS ACROSS THE NORTHERN AND CENTRAL 
VALLEYS SATURDAY...LEAVING SALT LAKE VALLEY...UTAH COUNTY AND 
RICHFIELD LOCALES WITHOUT MENTION.

INCREASING FRONTOGENESIS SATURDAY AFTERNOON AND NIGHT ACROSS 
SOUTHERN UTAH AHEAD OF THE SPLIT FEATURE WILL BE THE BEST FOCUS OF 
POPS FROM THIS SYSTEM. 21Z SHORT RANGE ENSEMBLES INDICATE A CHANCE 
OF NEGATIVE LIFTED INDICES AND MUCAPE GREATER THAN 50 J/KG 
SATURDAY AFTERNOON. HAVE MENTION OF CONVECTIVE WEATHER SATURDAY 
AFTERNOON AND NIGHT...BUT HAVE NOT SEEN ENOUGH INSTABILITY THIS FAR 
NORTH TO MENTION THUNDER AT THIS POINT.

INCREASING NORTHERLY FLOW AND COOLING TO ABOUT -7C AT 700MB SUNDAY 
WILL ATTEMPT TO SCOUR OUT NORTHERN VALLEYS...THOUGH CONFIDENCE IS 
NOT HIGH AT THAT AT THIS TIME THAT IT WILL BE ENOUGH TO DO SO. 00Z 
KSLC NAM BUFKIT FORECAST SOUNDING SHOWS MIXING UP TO 825MB SUNDAY 
AFTERNOON WITH ENOUGH RELATIVELY WARM AIR AT 750MB TO PREVENT 
COMPLETELY MIXING OUT THE INVERSION.

GUIDANCE SUITE SHOWS AN AMPLIFIED RIDGE BUILDING IN FROM THE WEST 
COAST SUNDAY AND MONDAY...BRINGING TRANQUIL WEATHER BACK TO THE 
REGION.

GUIDANCE BEGINS TO DIVERGE HEADING INTO MID WEEK. 
GFS/CANADIAN/EUROPEAN ALL SHOW NEXT COLD FRONT CROSSING SOUTH INTO 
THE PACIFIC NORTHWEST MONDAY EVENING FROM WESTERN CANADA...THOUGH 
THE CANADIAN MODEL IS FASTER. THE CANADIAN SHOWS A COLD FRONTAL 
PASSAGE FOR THE AREA TUESDAY...THE EUROPEAN ON WEDNESDAY. THE GFS 
MODEL CONTINUES TO BE AN OUTLIER TAKING THE COLD AIRMASS INTO THE 
MIDWEST. OPTED TO CONTINUE TO SUPPORT A CANADIAN/EUROPEAN TRACK 
LEANING CLOSER TO THE EUROPEAN FOR TIMING. 

PATTERN IS DIFFICULT TO RESOLVE BEYOND MIDWEEK...SO CONFIDENCE IS 
LOWER THAN TYPICAL IN THE LONG RANGE.

&&

.AVIATION...LIGHT SOUTHEAST WINDS WILL CONTINUE AT THE KSLC TERMINAL 
THROUGH THE NIGHT. WINDS WILL INCREASE SOMEWHAT TODAY AHEAD OF NEXT 
UPSTREAM SYSTEM BUT ARE NOT EXPECTED TO KEEP NORTHWEST LAKE BREEZE 
OUT. EXPECT NORTHWEST WINDS AROUND 19Z TO 20Z. VFR CONDITIONS ARE 
EXPECTED UNDER MOSTLY CLEAR SKIES. THERE IS A 20 PERCENT CHANCE
OF MVFR VISIBILITIES ASSOCIATED WITH HAZE OR FOG THROUGH 15Z.

&&

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

&&

$$

PUBLIC...ROGOWSKI
AVIATION...YOUNG

FOR MORE INFORMATION FROM NOAA/S NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/SALTLAKECITY (ALL LOWER CASE)