FXUS65 KSLC 290945
AFDSLC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SALT LAKE CITY UT
245 AM MST SUN NOV 29 2009
.SYNOPSIS...AN UPPER LOW OVER SOUTHERN CALIFORNIA WILL CONTINUE TO
MOVE SOUTHEAST TODAY. HIGH PRESSURE WILL BUILD INTO THE AREA FROM
THE NORTHWEST TODAY AND PERSIST THROUGH EARLY NEXT WEEK.
&&
.DISCUSSION...WATER VAPOR LOOP SHOWS AN UPPER LOW CROSSING ARIZONA
WITH RIDGING ACROSS THE EASTERN PACIFIC. ANOTHER UPPER LOW IS
CROSSING THE GULF OF ALASKA FROM THE SOUTH...AS A COMPACT
DISTURBANCE NEAR 48N/160W CONTINUES ITS TREK EASTWARD. 400-250MB
ACARS WIND OBSERVATIONS CONFIRMS THE PLACEMENT OF THE UPPER LOW OVER
WESTERN ARIZONA...WHILE SHOWING A 100-115KT NORTHEASTERLY JET FROM
WEST CENTRAL UTAH INTO CENTRAL CALIFORNIA. 00Z 700MB ANALYSIS SHOWS
A CYCLONE ACROSS SOUTHERN CALIFORNIA WITH RIDGING ACROSS THE PACIFIC
NORTHWEST. COLD ADVECTION IS OCCURRING LOCALLY...WITH -4C AT KSLC
AND -8C UPSTREAM AT KRIW. 00Z KSLC RAOB INDICATES ABOUT 3C OF
WARMING BELOW 850MB WITH 5C OF COOLING ALOFT DURING THE PAST 24
HOURS. AN INVERSION REMAINS IN PLACE NEAR 830MB...BUT HAS WEAKENED
FROM 6C FRIDAY EVENING TO ABOUT 1C SATURDAY EVENING.
GOES/RUC PRECIPITABLE WATER INDICATE VALUES HAVE FALLEN TOWARD A
TENTH OF AN INCH ACROSS NORTHERN UTAH...RISING TO BETWEEN A THIRD OF
AN INCH TO HALF INCH ACROSS CENTRAL AND SOUTHERN UTAH.
DEFORMATION AXIS HAS SHIFTED SOUTH INTO FAR SOUTHERN UTAH AS THE MID
LEVEL CIRCULATION MOVES EAST INTO ARIZONA. GOES SOUNDER REMAINS MORE
UNSTABLE THAN THE RUC MODEL...INDICATING LIFTED INDEX VALUES OF -2
TO -4C VS. +2C. EXPECT REDEVELOPMENT OF CONVECTIVE SHOWERS ACROSS
FAR SOUTHERN UTAH THIS MORNING AS INSTABILITY IS REALIZED. WILL KEEP
MENTION OF THUNDER OUT OF THE FORECAST AS CURRENT TRENDS AND 21Z
SHORT RANGE ENSEMBLES INDICATE THAT THE INSTABILITY AXIS WILL BE
SHIFTING SOUTHEAST THIS MORNING...SO THE TIME WINDOW FOR THUNDER
WILL REMAIN SMALL EARLY THIS MORNING.
IR SATELLITE SHOWS CLOUD TOPS ACROSS SOUTHERN UTAH ARE WARMING AS
CURRENT BAND OF CONVECTION DIMINISHES. THIS PRESENTS AN OPPORTUNITY
FOR FOG FORMATION GIVEN SATURATED LOWER LEVELS AND SEVERAL MORE
HOURS OF NOCTURNAL COOLING. WILL MONITOR OBSERVATIONS AND UPDATE THE
GRIDS AND FORECAST AS NEEDED THIS MORNING.
CONDITIONS ACROSS NORTHERN UTAH ARE MUCH MORE BENIGN AS CLEARING HAS
TAKEN PLACE. THE CHANGE OF AIRMASS HAS CLEARED THE HAZE OUT OF THE
NORTHERN VALLEYS...THOUGH THE 00Z KSLC RAOB SHOWED A WEAK INVERSION
REMAINS IN PLACE. IN FACT...AFTER MIXING OUT FRIDAY...UTAH COUNTY IS
NOW BUILDING SOME HAZE.
ITS AS COLD AS ITS GOING TO GET ALOFT THIS MORNING. AS THE STORM
SYSTEM BEGINS TO PULL AWAY TODAY...TEMPERATURES ALOFT WILL BEGIN TO
WARM AGAIN. THE TREND WILL CONTINUE MORE SIGNIFICANTLY MONDAY AND
TUESDAY WITH RIDGING BUILDING IN. RIDGETOP TEMPERATURES SHOULD WARM
ANOTHER 4C BETWEEN THIS EVENING AND TOMORROW EVENING. THIS WILL
SUPPORT A STRENGTHENING INVERSION...WITH A TREND FOR DEGRADING AIR
QUALITY INTO AT LEAST MID WEEK.
CONFIDENCE CONTINUES TO BE LOWER THAN TYPICAL IN THE LONG
RANGE...MID TO LATE WEEK.
GFS/CANADIAN/EUROPEAN ALL SHOW NEXT COLD FRONT CROSSING SOUTH INTO
THE NORTHERN ROCKIES MONDAY NIGHT FROM WESTERN CANADA. GUIDANCE
CONTINUES TO SUGGEST THAT THE COLD FRONT WILL SURGE SOUTHEAST ACROSS
THE NORTHERN ROCKIES AND UPPER MIDWEST THROUGH MID WEEK. THIS
SUPPORTS CONTINUED DRY WEATHER AND ALSO SUGGESTS THAT THE INVERSION
REMAINS IN TACT FOR MUCH OF NEXT WEEK. THE EUROPEAN SHOWS A SHEARED
WAVE AND ASSOCIATED COOLING PASSES THROUGH THURSDAY...THOUGH THE
GFS AND CANADIAN ARE MUCH FURTHER SOUTHWEST AND DISMISSIVE OF THIS
FEATURE.
HAVE GONE WITH A GFS/CANADIAN BLEND FRIDAY AND BEYOND AS THE
EUROPEAN STILL HAS NO SUPPORT NEXT WEEKEND. THE GFS/CANADIAN
CONTINUE TO SHOW A STRONG COLD FRONT ARRIVING FROM THE PACIFIC
NORTHWEST FRIDAY. BOTH MODELS INDICATE SIGNIFICANT COOLING ALOFT AS
THE SYSTEMS SPLITS AND DEEPENS IN THE AREA NEXT WEEKEND. THERE ARE
DIFFERENCES BETWEEN THE TWO MODELS IN HOW THIS OCCURS...THOUGH BOTH
WOULD SUGGEST A POSSIBILITY OF A WINTER STORM AT THE TAIL END OF THE
FORECAST CYCLE. WITHOUT THE SUPPORT OF THE EUROPEAN AND AT THIS
LENGTH OF TIME FROM THE POSSIBLE EVENT...HAVE GONE WITH LOW END
SLIGHT CHANCE TO CHANCE POPS ACROSS THE STATE HEADING INTO NEXT
SUNDAY. SHOULD CONFIDENCE INCREASE...MENTION WILL BE NEEDED IN THE
HAZARDOUS WEATHER OUTLOOK.
&&
.AVIATION...VFR CONDITIONS ARE EXPECTED TO CONTINUE AT THE KSLC
TERMINAL THROUGH THE TAF PERIOD. NORTHWEST WINDS ARE EXPECTED TO
BECOME SOUTHEAST BETWEEN 0900 AND 1100 UTC. A 30 PERCENT CHANCE THAT
THE WINDS WILL REMAIN NORTHWEST THROUGH THE NIGHT REMAINS.
&&
.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)
