Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 301652
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
952 AM MST FRI JAN 30 2015

UPDATED AVIATION SECTION

.UPDATE...
ISSUED AT 905 AM MST FRI JAN 30 2015

ADJUSTED POP AND WX GRIDS FOR THE NEXT 12 HOURS TO ACCOUNT FOR
CURRENT PRECIPITATION COVERAGE. SNOW LEVELS LOOK GOOD...AS PTYPE
AT CORTEZ IS RAIN AND DURANGO/PAGOSA SPRINGS ARE EXPECTED TO
SWITCH OVER TO RAIN SOON. ADVISORIES LOOK ON TRACK WITH SOME
SNOWFALL IN THE DURANGO/PAGOSA SPRINGS VALLEYS BUT WEBCAMS SHOWING
MOST OF THE SNOW MELTING ON SURFACE CONTACT AND LITTLE
ACCUMULATION ON THE NON-ROADWAY SURFACES. IN ANALYZING H5 VORT
MAX FIELDS AND CURRENT SATELLITE...AN UPTICK IN PRECIPITATION
INTENSITY CAN BE EXPECTED THIS AFTERNOON AS A PIECE OF ENERGY
SWINGS INTO SW COLORADO.

&&

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 430 AM MST FRI JAN 30 2015

SURFACE OBSERVATIONS...WEB CAMS AND THE CHAIN LAW ON HIGHWAY 550
OVER THE SAN JUANS INDICATE THAT SNOW HAS BEEN ACCUMULATING OVER
THE SOUTHERN MOUNTAINS SINCE LAST EVENING AND THROUGH EARLY THIS
MORNING. DEEP MOISTURE HAS BEEN INVADING FROM THE SOUTH AND
SATELLITE IMAGES SHOW ITS SOURCE ORIGINATING IN THE TROPICAL
PACIFIC NEAR 10-15 DEGREES NORTH AND ROUGHLY AROUND 110 DEGREES
WEST. A LOW PRESSURE SYSTEM OFF THE COAST OF SOUTHERN CA/BAJA HAS
BEEN RESPONSIBLE FOR PUMPING THIS MOISTURE INTO THE REGION. AND AS
THE LOW SHIFTS INTO SOUTHERN CALIFORNIA TODAY...AND THEN OVER THE
NORTHERN SEA OF CORTEZ ON SATURDAY ABUNDANT MOISTURE WILL CONTINUE
OVER THE AREA. ISENTROPIC UPGLIDE OVER THE REGION HAS PROVIDED
SYNOPTIC SCALE LIFT WHICH WILL CONTINUE THROUGH TODAY...THEN
WEAKEN OVERNIGHT. THEN DURING THE DAY ON SATURDAY THE FLOW
GRADUALLY SWITCHES AROUND AS THE NORTHERN STREAM BECOMES MORE OF
A PLAYER FOR OUR AREA. A WAVE IS PROGGED TO DROP INTO MONTANA...
AND THE SOUTHERN LOW SLOWLY SHIFTS TO THE SOUTH-SOUTHEAST.
THROUGH THIS EVENT THE SOUTHERN PORTION OF THE FORECAST AREA WILL
BE FAVORED...BUT REALLY THE BEST ACTIVITY WILL STAY TO OUR SOUTH
OVER ARIZONA AND NEW MEXICO.

FOR TODAY...PRECIPITATION WILL CONTINUE TO INCREASE AND SPREAD
NORTH AS THE DEEPER MOISTURE PROGRESSES FROM SOUTH TO NORTH.
HOWEVER DUE TO THE TROPICAL ORIGIN OF THE AIR MASS...SNOW LEVELS
WILL STAY ON THE HIGH SIDE. IT APPEARS THAT THE SNOW LEVEL IS
AROUND 7000-7500 FEET EARLY THIS MORNING WITH SNOW REPORTED IN
PAGOSA SPRINGS...BUT RAIN IN DURANGO. EXPECT THE SNOW LEVELS WILL
RISE TODAY...BEFORE FALLING AGAIN TONIGHT. HOWEVER THERE JUST IS
NOT MUCH COOLING INDICATED THROUGH SATURDAY...SO SNOW LEVELS WILL
AGAIN RISE ON SATURDAY. GOOD PRECIPITATION WILL CONTINUE INTO
SATURDAY...GRADUALLY WINDING DOWN SOMEWHAT DURING THE AFTERNOON
AS A DRIER NORTHWEST FLOW MOVES DEVELOPS.

WENT AHEAD AND STARTED THE SNOW ADVISORIES FOR THE SOUTHERN
MOUNTAINS EARLIER SINCE SNOW HAD ALREADY STARTED ACCUMULATING.
OTHERWISE NO CHANGES IN THE COVERAGE. HOWEVER OTHER MOUNTAIN
AREAS THAT BEAR WATCHING INCLUDE THE GRAND MESA AND POSSIBLE THE
WEST ELKS.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 430 AM MST FRI JAN 30 2015

PRECIPITATION DIMINISHES SATURDAY NIGHT AS THE CLOSED LOW DRIFTS
SOUTHWARD IN RESPONSE TO A SHORTWAVE TROUGH SWEEPING SOUTHEASTWARD
ACROSS THE NORTHERN ROCKIES. QUIET...DRY WEATHER RETURNS SUNDAY
WITH TEMPERATURES RUNNING A BIT ABOVE NORMAL.

HOWEVER...BY LATE SUNDAY NIGHT...THE FIRST OF A SERIES OF SHORT
WAVE TROUGHS IN NORTHWEST FLOW WILL BEGIN TO GENERATE SNOW OVER
THE NORTHERN MOUNTAINS. MODELS WERE CONSISTENT IN DEPICTING SNOW
CONTINUING OFF AND ON OVER THE NORTHERN...AND PORTIONS OF THE
CENTRAL COLORADO MOUNTAINS...THROUGH MIDWEEK BEFORE THE RIDGE
OVER THE WEST FINALLY AMPLIFIES FORCING THE POLAR JET TO THE EAST.
ACCUMULATIONS NOT VERY IMPRESSIVE ACCORDING TO MODEL DATA...BUT
WILL HAVE TO MONITOR FOR POSSIBLE HIGHLIGHTS EARLY NEXT WEEK.

TEMPERATURES WILL CONTINUE TO MODERATE WITH READINGS RISING TO
LEVELS OF AROUND 10 DEGREES ABOVE NORMAL BY EARLY NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 951 AM MST FRI JAN 30 2015

UPPER LOW OVER EXTREME SRN CA WILL SLOWLY MOVE INTO WESTERN AZ AND
WILL CONTINUE TO PUMP TROPICAL MOISTURE ACROSS THE FOUR CORNERS
THROUGH SAT MORNING. PRECIPITATION BECOMING WIDESPREAD SOUTH OF A
KPUC-KSBS LINE WILL RESULT FREQUENT MOUNTAIN OBSCURATION IN CLOUDS
AND SNOW. SNOW LEVELS WILL VARY BETWEEN 6000 FT MSL AND 8000 FT MSL.
PRECIPITATION RESULTING IN VERY MOIST SURFACE AIR WILL ALSO RESULT
IN AREAS OF FOG AT THE LOWER ELEVATIONS AND OFTEN MVFR CIGS.  EXPECT
VSBY AND CIGS TO IMPROVE SOMEWHAT AT KDRO THIS AFTERNOON AS -SN
CHANGES TO -SNRA OR -RA UNTIL 03Z. CONDITIONS BEGIN IMPROVING FROM
THE NW SAT AFTERNOON.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 8 PM MST SATURDAY FOR COZ017>019.

UT...WINTER WEATHER ADVISORY UNTIL 8 PM MST SATURDAY FOR UTZ028.

&&

$$

UPDATE...JAM
SHORT TERM...EH
LONG TERM...NL
AVIATION...JAD


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