Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 290608
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1108 PM MST WED JAN 28 2015

.SHORT TERM...(TONIGHT THROUGH THURSDAY NIGHT)
ISSUED AT 320 PM MST WED JAN 28 2015

CLOUDS AND SOME LIGHT SNOW PERSISTED ACROSS THE NORTHERN CO MTNS
THIS AFTERNOON...PRETTY MUCH NORTH OF AN ASPEN-VAIL LINE...IN
SLIGHTLY UNSTABLE NW FLOW BEHIND AN UPPER DISTURBANCE. THESE WILL
TAPER OFF THIS EVENING AS A TRANSIENT UPPER RIDGE SLIDES IN LATER
TONIGHT.

HIGH CLOUDS WILL STREAM IN FROM THE SOUTHWEST TONIGHT OVERSPREADING
THE FORECAST AREA THURSDAY. A FEW LIGHT SHOWERS ARE POSSIBLE ACROSS
THE MOUNTAINS THURSDAY AFTERNOON BUT...BY AND LARGE...TOMORROW WILL
BE DRY WITH CONTINUED UNSEASONABLY WARM TEMPERATURES.

THE CLOUDS ARE AHEAD OF AN ELONGATED PACIFIC TROUGH THAT REACHES THE
WEST COAST THURSDAY NIGHT. AN UPPER LOW DEVELOPS IN THE SOUTHERN
PORTION OF THIS TROUGH AND CIRCULATES A GOODLY AMOUNT OF PACIFIC
MOISTURE INTO THE DESERT SOUTHWEST. CLOUDY SKIES WILL RULE THURSDAY
NIGHT WITH VALLEY RAIN AND MOUNTAIN SNOW EXPECTED TO REACH SE UT AND
SW CO BY FRI MORNING.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 320 PM MST WED JAN 28 2015

THE CLOSED UPPER LEVEL LOW IS EXPECTED TO BE SITUATED OVER BAJA
CALIFORNIA ON FRIDAY MORNING AND FEEDING MOISTURE INTO THE FOUR
CORNERS. SHOWERS WILL INCREASE OVER THE HIGHER TERRAIN FIRST AND
THEN SPREAD FROM SOUTHWEST TO NORTHEAST IN THE VALLEYS THROUGHOUT
THE DAY ON FRIDAY AS THE CLOSED LOW GRADUALLY MOVES TO THE NORTH
AND THEN EAST ON SATURDAY. THE CENTER OF THE LOW PRESSURE IS
EXPECTED TO REMAIN ACROSS SOUTHERN ARIZONA FRIDAY THROUGH SUNDAY
AND NEVER PROGRESS FURTHER TOWARD THE FOUR CORNERS. A PIECE OF
ENERGY AND PLENTY OF MOISTURE IS EXPECTED TO BRING WIDESPREAD
PRECIPITATION TO SOUTHEASTERN UTAH AND SOUTHWESTERN COLORADO ON
FRIDAY THROUGH SATURDAY NIGHT. THE RAIN/SNOW LINE WILL BE THE
BIGGEST CHALLENGE...WITH H7 TEMPS LINGERING AROUND THE -2C TO -4C
RANGE DURING THIS TIME FRAME. THIS SHOULD KEEP THE SNOW LEVEL
AROUND 7500 FT OR 8000 FT DEPENDING ON THE TIME OF DAY...WITH
HEAVIER ACCUMULATIONS AT ELEVATIONS ABOVE 9000 FT. ASSUMED A 9:1
OR 10:1 SLR FOR THIS SYSTEM...BUT THERE IS THE POSSIBILITY FOR
SOME HIGHER RATIOS AT HIGHER ELEVATIONS. DECIDED TO ISSUE A WINTER
STORM WATCH FOR THE SOUTHERN SAN JUANS FOR LOCATIONS ABOVE 9000 FT
CONSIDERING SEASONABLY-HIGH PRECIPITABLE WATER VALUES AND GOOD
CONSISTENCY ON PRECIPITATION COVERAGE IN THE SOUTHERN SAN JUANS.
AT THIS POINT AM ANTICIPATING A RAIN/SNOW MIX IN THE SOUTHWEST
COLORADO VALLEYS AND HIGHER SOUTHEAST UTAH VALLEYS
(MONTICELLO...ETC). THE LOWER VALLEYS WILL SEE ONLY RAIN
THROUGHOUT THE SYSTEM.

DRIER AIR WILL MOVE INTO THE AREA ON SATURDAY NIGHT...THOUGH THE
REGION WILL REMAIN ON THE ACTIVE LEEWARD SIDE OF THE WEAKENED
RIDGE OVER THE WEST COAST. THIS MEANS THAT WEAK SHORTWAVES IN
NORTHWEST FLOW ARE PROBABLE THROUGHOUT THE WEEK MAINLY IMPACTING
THE NORTHCENTRAL MOUNTAINS OF COLORADO. NO MAJOR IMPACTS ARE
EXPECTED NEXT WEEK AS HIGH PRESSURE GRADUALLY BUILDS TO THE EAST
THROUGHOUT THE WEEK.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1108 PM MST WED JAN 28 2015

OVER THE NORTHERN PORTION OF THE AREA...SOME MID CLOUDS WILL
PERSIST THROUGH THE NEXT FEW HOURS...THINNING BY SUNRISE. ACROSS
THE SOUTH...HIGH CLOUDS HAVE INVADED THE REGION...AND WILL
CONTINUE TO SPREAD NORTHWARD THROUGH TONIGHT. DEEPER MOISTURE WILL
BEGIN TO SPREAD IN FROM THE SOUTH THURSDAY AFTERNOON AND EVENING
AS THE NEXT STORM SYSTEM MOVES OVER THE DESERT SOUTHWEST. A FEW
SHOWERS WILL BE POSSIBLE THURSDAY AFTERNOON OVER THE SOUTHERN
MOUNTAINS AND WILL INCREASE DURING THE EVENING. HOWEVER THROUGH
THE NEXT 24 HOURS...VFR IS EXPECTED TO PERSIST AT ALL TAF SITES.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER STORM WATCH FROM FRIDAY MORNING THROUGH SATURDAY
     AFTERNOON FOR COZ019.

UT...NONE.
&&

$$

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



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