Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 231800
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1100 AM MST SUN NOV 23 2014

.UPDATE...
ISSUED AT 1050 AM MST SUN NOV 23 2014

THE COLD FRONT HAS SAGGED INTO CENTRAL AZ-NM. A FEW LIGHTNING
STRIKES WERE OBSERVED NEAR PAGOSA-WOLF CREEK PASS EARLY THIS
MORNING NEAR THE EXITING FRONT. THE INITIAL DISTURBANCE HAD PASSED
INTO SE CO AND THE SECOND WAS WORKING OVER NW CO THIS AFTERNOON.
DYNAMICAL SUPPORT IS DISORGANIZED WITH THIS AFTERNOONS SYSTEM BUT
STRONG COLD ADVECTION/INSTABILITY AND NW OROGRAPHICS WILL CONTINUE
TO PRODUCE SNOW ACCUMULATIONS. EASTERN UTAH AND FAR WESTERN
COLORADO WILL SEE ONLY ISOLATED TO SCATTERED SHOWERS. SNOW LEVEL
REMAINS AROUND 5000FT THROUGH THE AFTERNOON.

A DOWNTURN IN SNOWFALL EXPECTED TONIGHT. AIR MASS STABILIZES WITH
WARM ADVECTION AT 500MB. OROGRAPHIC SNOWFALL EXPECTED TO CONTINUE
IN THE NW CO MTNS BUT THE CENTRAL MTNS WILL SEE LITTLE ADDITIONAL
ACCUMULATIONS. THE ADVISORIES IN AND AROUND THE NW SAN JUAN MTNS
WILL END THIS AFTERNOON THOUGH LIGHT ACCUMULATIONS WILL PROBABLY
CONTINUE ALONG AND NORTH OF CERRO SUMMIT AND RED MTN PASS UNTIL
SUNSET. THE GRAND MESA AND WEST ELK MTNS TOO ARE NOT FAVORED TO
RECEIVE MUCH SNOWFALL OVERNIGHT AND INTO MONDAY MORNING...SO MAY
PULL DOWN THE WARNINGS THERE SOMETIME THIS EVENING. FOG MAY FORM
IN THE I-70 CORRIDOR...ROARING FORK VALLEY...AND ALONG N-FACING
SLOPES IN COLORADO AFTER MIDNIGHT.

A STRONGER AND COLDER DISTURBANCE IN NW FLOW WORKS THROUGH
WESTERN CO MONDAY AFTERNOON AND EVENING. THIS WILL AGAIN FAVOR THE
NW CO MTNS WITH SNOW ACCUMULATIONS. SNOWFALL WILL INCREASE AGAIN
OVER THE GRAND MESA...WEST ELKS...NW SAN JUANS...BUT AMOUNTS ARE
PERSISTENTLY FORECAST TO BE ON SUB-ADVISORY...2-5 INCHES...THERE.

UPDATE ISSUED AT 602 AM MST SUN NOV 23 2014

ALLOWED THE WINTER WEATHER ADVISORIES FOR THE CENTRAL YAMPA RIVER
VALLEY AND THE EASTERN UINTA MOUNTAINS TO EXPIRE.

&&

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 358 AM MST SUN NOV 23 2014

PRECIPITATION IS ONGOING ACROSS MUCH OF THE FORECAST AREA EARLY
THIS MORNING. RAIN HAS BEEN A LITTLE SLOW TO CHANGE OVER TO SNOW
IN SOME OF THE MIDDLE VALLEYS...WITH RIFLE STILL REPORTING RAIN
AT 3AM MST. BUT RIFLE FINALLY SWITCHED OVER AT AT 320 AM. FEEL
OTHER VALLEYS WILL FOLLOW SUIT IN THE NEXT HOUR OR SO. ITS BEEN
HARD TO PICK OUR A DISTINCT FRONTAL BAND AS THE FOCUS FOR THE
PRECIPITATION. HOWEVER THE WESTERN VALLEYS SEEM TO HAVE ALREADY
SEEN THEIR BEST PRECIPITATION. RADAR IMAGES INDICATE THAT
OROGRAPHICS HAVE BEEN A BIG PLAYER SO FAR...AND EXPECT THAT WILL
CONTINUE TO BE THE CASE.

THE FORECAST REMAINS ON TRACK WITH THE UPPER TROUGH AXIS MOVING
OVER THE FORECAST AREA BEFORE DAYBREAK...AND THE 500MB COLD CORE
OF -32C DROPPING OUT OF THE NORTH-NORTHWEST AND OVER THE NORTHWEST
TO NORTH CENTRAL COLORADO THIS AFTERNOON. THE IR SATELLITE LOOP
SHOWS AN AREA OF ENHANCEMENT HEADING OUR WAY...THAT SHOULD BE OVER
THE NORTHWEST CORNER AS THIS FORECAST GOES TO PRESS. SNOW WILL
PICK UP OVER NORTHWEST CO AS THIS ENHANCED AREA MOVES INTO THE
CWA. THIS ALONG WITH THE FAVORABLE OROGRAPHICS...AND THE COLD CORE
ALOFT THIS AFTERNOON WILL RESULT IN CONTINUED GOOD ACCUMULATIONS
OVER THE HIGHER MOUNTAINS...ESPECIALLY ALONG THE FAVORED NORTHWEST
SLOPES. WILL GO AHEAD AND EXTEND THE ADVISORY FOR ZONE 3...THE
COLORADO TAVAPUTS AND ROAN PLATEAU...UNTIL NOON. MOISTURE
DIMINISHES THIS AFTERNOON...EXCEPT FOR AREAS NEARER THE DIVIDE.

SNOW WILL DIMINISH FIRST OVER THE SAN JUANS EARLY THIS EVENING AS
MOISTURE DECREASES...AND STABILITY INCREASES AS A QUICK MOVING
SHORTWAVE RIDGE MOVES ACROSS THE AREA. AS A RESULT...THE FLOW WILL
RELAX A BIT. WHILE SNOW WILL LIGHTEN UP ALSO OVER THE CENTRAL AND
NORTHERN COLORADO MOUNTAINS...I DO NOT EXPECT MUCH OF A BREAK FOR
THESE AREAS.

THEN ON MONDAY THE NEXT DISTURBANCE EMBEDDED IN THE NORTHWEST
FLOW WILL SWEEP OVER THE AREA BRINGING ANOTHER COLD SHOT WITH
500MB TEMPS AGAIN DROPPING TO AROUND -32C. THEREFORE THE
HIGHLIGHTS FOR THE CENTRAL AND NORTHERN MOUNTAINS REMAIN JUSTIFIED
TO ACCOUNT FOR THIS NEXT WAVE. THERE IS ALSO THE POTENTIAL FOR
GOOD SNOWFALL AMOUNTS IN THE NORTHERN SAN JUANS ON MONDAY...WHICH
ARE ALSO FAVORABLE IN THIS FLOW REGIME. HIGHLIGHTS MAY BE NEEDED
FOR ZONE 18...BUT TO AVOID CONFUSION...I CHOSE NOT TO HOIST ANY AT
THIS TIME.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 358 AM MST SUN NOV 23 2014

THE REGION WILL FINALLY SEE A BREAK IN THE ACTION LATE MONDAY
NIGHT AS THE DEEP TROUGH OVER THE SOUTHERN PLAINS BEGINS TO SLIDE
TO THE EAST. THIS WILL BRING THE JET OVERHEAD WITH THE RIGHT EXIT
REGION OF THE 140 KT POLAR JET SETTLING OVER NORTHWEST COLORADO.
WAA AT MID-LEVELS WILL CAUSE LAPSE RATES TO STABILIZE AND...WHEN
COMBINED WITH SUBSIDENCE ALOFT...SHOULD BRING SNOW TO AN END IN
THE NORTHERN AND CENTRAL MOUNTAINS.

HOWEVER...FOR THE NORTHERN COLORADO MOUNTAINS THIS BREAK WILL BE
SHORT-LIVED AS MOISTURE AND A SERIES OF WEAK DISTURBANCES MOVES
OVER THE AREA MONDAY AND MONDAY NIGHT. LAPSE RATES WILL HINDER
SIGNIFICANT ACCUMULATIONS WITH LIFT SUPPLIED PRIMARILY BY
OROGRAPHICS DURING THIS PERIOD. THAT SAID...ELKHEAD...PARK...AND
GORE RANGES AND THE FLAT TOPS COULD SEE ADVISORY LEVEL SNOW ALONG
WITH BLOWING SNOW AS RIDGE-LEVEL FLOW REMAINS BRISK. WILL HOLD OFF
ON ADDITIONAL HILITES FOR NOW AS CONFIDENCE NOT THERE YET AND
DON/T WANT TO CAUSE ANY CONFUSION AS THERE ARE A NUMBER OF WINTER
WEATHER PRODUCTS ALREADY IN PLACE WITH THE CURRENT STORM.

EXCEPT FOR A FEW LINGERING SHOWERS OVER THE NORTHERN COLORADO
MOUNTAINS IN THE MORNING...EXPECT DRY WEATHER ACROSS THE FORECAST
AREA ON WEDNESDAY AS FLOW VEERS A BIT TO THE WEST DRIVING THE
MOISTURE STREAM NORTH OF THE FORECAST AREA. A FLAT RIDGE OVER THE
WEST WILL HOLD MOISTURE AT BAY THROUGH THANKSGIVING. HOWEVER...
MODELS CONTINUE TO STRUGGLE WITH THE OUTLOOK FOR FRIDAY INTO
SATURDAY. ECMWF NOW BACK TO A SOLUTION FEATURING A LOW AMPLITUDE
POSITIVELY TILTED TROUGH BRINGING LIGHT SNOW TO THE NORTHERN
MOUNTAINS FRIDAY AND FRIDAY NIGHT. IN CONTRAST...GFS40 HANGS ONTO
THE FLAT RIDGE AND MAINTAINS DRY CONDITIONS ACROSS THE ENTIRE
FORECAST AREA FRIDAY AND SATURDAY. GIVEN MODEL DIFFERENCES AND
LACK OF RUN-TO-RUN CONSISTENCY WILL DEFER TO THE BLENDED MODEL
SOLUTION FOR NOW.

TEMPERATURES WILL REMAIN WELL BELOW NORMAL ON TUESDAY BEFORE
TRENDING WARMER FOR THE LATTER PART OF THE WEEK. LATEST GUIDANCE
INDICATED NEAR NORMAL TEMPERATURES BY THANKSGIVING.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY NOON)
ISSUED AT 1050 AM MST SUN NOV 23 2014

A WINTER STORM WILL CONTINUE TO BRING WIDESPREAD SNOW AND BLOWING
SNOW TO THE MOUNTAINS THROUGH MONDAY. MOUNTAINS WILL BE OBSCURED
AND THERE WILL BE MODERATE TO STRONG TURBULENCE ACROSS THE HIGHER
TERRAIN. EAST OF A LINE FROM KVEL TO KPSO...INCLUDING KRIL KEGE
KASE KMTJ KTEX...EXPECT PERIODS OF VIS BLO 1SM CIGS BLO 010
THROUGH 00Z...THEN VIS BLO 3SM CIGS BLO 025 THROUGH NOON MONDAY.
THE REMAINING TAF SITES WILL HAVE SCATTERED SHOWERS IN THE
VICINITY BUT LOWERED CIGS AND VSBY WILL BE BRIEF. EXPECT FOG TO
FORM IN THE VALLEYS AND MOUNTAIN TOPS AND NORTH- FACING SLOPES TO
REMAIN OBSCURED AT TIMES TONIGHT AND INTO MONDAY MORNING.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY UNTIL 3 PM MST THIS AFTERNOON FOR COZ007-
     008-011-014-018-019.

     WINTER STORM WARNING UNTIL 6 PM MST MONDAY FOR COZ004-005-009-
     010-012-013.

     WINTER WEATHER ADVISORY UNTIL NOON MST TODAY FOR COZ003.

UT...NONE.
&&

$$

UPDATE...JOE
SHORT TERM...EH
LONG TERM...NL
AVIATION...NL


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