Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 170553
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1153 PM MDT THU APR 16 2015

UPDATED AVIATION SECTION

.UPDATE...
ISSUED AT 916 PM MDT THU APR 16 2015

ALLOWED THE WIND ADVISORY FOR THE ERN UINTA BASIN/NW COLORADO
EXPIRE AS SURFACE WINDS HAVE TAPERED OFF. GUSTY WINDS MAY DEVELOP
AGAIN ON FRIDAY AFTERNOON...BUT THE HOURLY AVIATION GUIDANCE AND
00Z NAM INDICATE WINDS MAY NOT BE AS STRONG AS EARLIER THIS
AFTERNOON. NO PLANS TO HOIST ANOTHER WIND ADVISORY AT THIS
TIME...BUT THE 00Z NAM DOES SHOW 25KTS AT 850MB FRIDAY AFTERNOON.
CANNOT DISCOUNT THE POSSIBILITY THAT STRONG WINDS OCCUR FOR ONE
MORE DAY...BUT NOT LIKELY.

&&

.SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)
ISSUED AT 426 PM MDT THU APR 16 2015

A COLD AND DYNAMIC UPPER LOW WAS OVER SE UT/NE AZ THIS AFTERNOON AND
IS EXPECTED TO SLOWLY TRAVEL EAST ACROSS THE FOUR CORNERS TONIGHT
AND FRIDAY. DISTURBANCES ROTATING COUNTERCLOCKWISE AROUND THIS LOW
AND UP INTO CO WILL PRODUCE PERIODS OF HEAVIER SHOWERS AT TIMES
THROUGH FRI NIGHT. PRECIPITATION WILL LIKELY COME IN WAVES WITH SOME
LULLS IN BETWEEN DISTURBANCES. THIS WILL ALSO MAINTAIN A POTENTIAL
FOR GUSTY NE WINDS ACROSS NE UT AND NW CO...WHERE A WIND ADVISORY
REMAINS IN EFFECT THROUGH THIS EVENING.

CLOUD TOPS WERE COOLING AND EXPANDING ACROSS SW CO AHEAD OF THE NEXT
WAVE ROTATING THROUGH THE BASE OF THE UPPER LOW. CONVECTIVE
INSTABILITY LED TO A FEW ISOLATED THUNDERSTORMS OBSERVED EARLIER...
AND WILL KEEP A MENTION OF SUCH INTO THIS EVENING. EXPECT SNOW TO
EXPAND AGAIN ACROSS THE CENTRAL AND SRN MTNS TONIGHT AS THIS UPPER
DISTURBANCE ARRIVES. 700 MB LOW SHOWN LIFTING ACROSS THE SAN JUAN
MTNS UP THE DIVIDE LATE TONIGHT AND SATURDAY MORNING. UPGRADED THE
WATCH TO WINTER STORM WARNING FOR THE NW SAN JUANS MTNS BEGINNING
TONIGHT AND COUNTING ON OROGRAPHICALLY FAVORABLE NW FLOW LATER FRI
NIGHT INTO SAT TO MAINTAIN SNOWFALL AND POSSIBLY TARGET THE
UNCOMPAHGRE GORGE. ALSO ADDED WINTER WEATHER ADVISORIES FOR THE
GUNNISON/CERRO SUMMIT AREAS AND THE SWRN SAN JUAN MTNS WITH THE 700
MB LOW MOVING ACROSS.

EASTERLY FLOW DEVELOPS ACROSS THE NORTH TONIGHT AND FRI WITH
MOISTENING WARM ADVECTIVE UPGLIDE ON THE 295K/300K INSENTROPIC
SURFACES INCREASING PRECIP CHANCES THERE. THIS ALSO CREATES A
TIGHTENING 700 TEMP GRADIENT ACROSS THE CENTRAL MOUNTAINS LATE
TONIGHT AND FRIDAY THAT SHOULD ENHANCE PRECIP AS DISTURBANCES ROTATE
THROUGH.  BEST ACCUMULATIONS SHOULD BE ABOVE ABOUT 9000 FEET THOUGH
STRONGER CONVECTION AND NIGHTTIME COOLING WILL DRIVE SNOW TO SOME
VALLEY FLOORS. THOUGH LOCATION AND STRENGTH OF THIS 700 MB
BAROCLINIC ZONE DIFFER BETWEEN MODELS...WENT AHEAD AND UPGRADED
GRAND MESA TO WINTER STORM WARNING.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 426 PM MDT THU APR 16 2015

THE REGION`S RESIDENT LOW PRESSURE SYSTEM WILL MEANDER AROUND
EAST/NORTHEAST COLORADO ON SATURDAY BEFORE FINALLY BEING KICKED
EASTWARD INTO THE PLAINS. WRAP AROUND MOISTURE AND ENERGY WILL
CONTINUE TO KEEP WESTERN COLORADO ACTIVE THROUGH SATURDAY. THE
FLOW WILL BECOME MORE NORTH OR EVEN NORTHWEST FOR A TIME WHICH
WILL FAVOR THE NORTH-NORTHWEST FACING SLOPES.

THEN LATE SATURDAY NIGHT AND SUNDAY...THE KICKER DISTURBANCE IN
THE FORM OF A PACIFIC TROUGH...WILL MOVE ACROSS THE NORTHWEST
STATES. AS THE FIRST LOW MOVES AWAY AND THE SECOND TROUGH BRUSHES
NORTHEST UT AND NORTHWEST CO...THE NORTH TO NORTHWEST WILL BECOME
MORE DOMINANT. ADDITIONAL MOISTURE...WEAK DYNAMICS FROM THIS
SECOND DISTURBANCE...AND FAVORABLE OROGRAPHICS WILL RESULT IN
CONTINUED SHOWERS...ESPECIALLY OVER THE NORTHWEST COLORADO...AND
OVER ALL THE NORTH-FACING SLOPES OF THE COLORADO MOUNTAINS.

IT APPEARS THAT THE PATTERN WILL REMAIN SOMEWHAT UNSETTLED OVER
THE FORECAST AREA THROUGH THE PERIOD AS A COMPICATED SERIES OF
WEAKER DISTURBANCES MOVE ACROSS THE WESTERN CONUS. AT THIS TIME
NONE OF THESE SEEM OVERLY STRONG. THE TIMING AND TRACK OF THESE
DISTURBANCES ARE STILL NOT RESOLVED...SO WILL KEEP A BROAD-BRUSHED
FORECAST FOR THE WORK WEEK.

TEMPERATURES DO SLOWLY INCREASE. BY TUESDAY MORE NORMAL READINGS
ARE EXPECTED.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1141 PM MDT THU APR 16 2015

IMPACTS TO AIRPORTS WILL CONTINUE OVER THE NEXT 24 HOURS AS LOW
CIGS AND VIS WILL BE COMMON DURING PERIODS OF RAIN OR SNOW WITH
THE SNOW LEVEL RANGING FROM 5K TO 6K FEET. IFR/MVFR CIGS WILL BE
COMMON THROUGH THE FORECAST PERIOD. BURSTS OF HEAVY SNOW OR RAIN WILL
BRING TAF SITES SUCH AS KRIL...KASE...KEGE...CIGS BELOW ILS
BREAKPOINTS FREQUENTLY IF NOT PERSISTENTLY. SOME IMPROVEMENT LOOKS
POSSIBLE FOR THE I-70 AIRPORTS BETWEEN 16 AND 22Z...BUT THEN
ACTIVITY WILL PICK UP AGAIN AROUND 00Z FOR A FEW HOURS. AFTER 00Z
FRIDAY EVENING SHOWERS WILL BEGIN TO WIND DOWN FROM WEST TO EAST AS
THIS LARGE WEATHER SYSTEM STARTS TO MOVE EAST.

KVEL WILL EXPERIENCE GUSTY NORTHEAST WINDS TO 25 MPH THROUGH THE
NIGHT...BUT EXPECT EVEN STRONGER GUSTS TO 35 MPH AFTER 15Z FRI.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 6 PM MDT FRIDAY FOR COZ014.

     WINTER STORM WARNING UNTIL NOON MDT SATURDAY FOR COZ009-010-012-
     018.

     WINTER WEATHER ADVISORY UNTIL 6 AM MDT SATURDAY FOR COZ017-019.

     FREEZE WATCH FROM LATE FRIDAY NIGHT THROUGH SATURDAY MORNING FOR
     COZ021.

     FREEZE WARNING UNTIL 9 AM MDT FRIDAY FOR COZ021.

     WINTER WEATHER ADVISORY UNTIL NOON MDT SATURDAY FOR COZ004-013.

UT...WINTER STORM WARNING UNTIL 6 AM MDT SATURDAY FOR UTZ023.

&&

$$

UPDATE...PF
SHORT TERM...JAD
LONG TERM...EH
AVIATION...TGJT


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