Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 122141
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
341 PM MDT SAT APR 12 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY NIGHT)
ISSUED AT 341 PM MDT SAT APR 12 2014

SRN STREAM SHORT WAVE WILL SKIRT ACROSS THE SRN PORTION OF THE
FORECAST AREA THIS EVENING BEFORE SLIDING EAST. ENOUGH
MOISTURE FOR THUNDERSTORMS BUT MOSTLY OF THE GUSTY WIND VARIETY AS
SURFACE DEW POINTS ARE BARELY IN THE 30S. GIVEN ITS EARLY SEASON
AND THE UPPER LEVEL SHORT WAVE MOVES EAST...ISOLATED EVENING
STORMS SHOULD END BY MID EVENING.

ATTENTION FOCUSES ON THE UPSTREAM POTENT WAVE OVER THE NRN
ROCKIES. LOOKS LIKE A CLASSIC SPRINGTIME SNOWSTORM FOR THE
COLORADO ROCKIES. LINGERING MOISTURE AND INSTABILITY FROM TODAYS
CONVECTION GETS LIFTED AHEAD OF THE MAIN TROUGH...KEEPING A FEW
NOCTURNAL SHOWERS ONGOING THROUGH THE NIGHT. BUT THESE SHOWERS
WILL BE EXPANDING TOWARD DAYBREAK AS LARGE SCALE ASCENT INCREASES.

TIGHT CIRCULATION FORMS OVER UTAH SUNDAY MORNING BEFORE
STRENGTHENING OVER THE WRN SLOPE IN THE AFTERNOON...THEN MOVES
DOWNSTREAM LATE IN THE SHORT TERM PERIOD.  INTENSE THERMAL
GRADIENT OVER WYOMING DROPS INTO NW COLORADO AS THE MID LEVEL
CIRCULATION TIGHTENS. NICE COUPLET ON THE QG DIAGNOSTICS THAT
INDICATE A WELL STRUCTURED. DEEP LAYERED ASCENT COINCIDES WITH
POTENTIAL INSTABILITY DUE TO STRONG MID LEVEL COLD ADVECTION.
WHILE SNOW LEVELS WILL BE HIGH IN THE EARLY STAGES OF THIS
EVENT...700 MB TEMPS BECOME COLDER THAN -10C ALONG THE DIVIDE.
THIS IS COLD ENOUGH FOR SIGNIFICANT ACCUMULATIONS IN THE HIGH
COUNTRY...AND IT WILL FALL FAST AND FURIOUS AND POSSIBLE HIGH
IMPACTS TO TRAVEL OVER MOUNTAIN PASSES DUE TO WET HEAVY SLUSH.
ELECTED TO UPGRADE THE WINTER WEATHER ADVISORY TO WARNINGS (EXCEPT
FOR THE SWRN SAN JUANS THAT HAVE AN UNFAVORABLE OROGRAPHIC
COMPONENT.)

QPF FORECAST IS CHALLENGING GIVEN THE STRONG CONVECTIVE COMPONENT.
USED THE WPC QPF GUIDANCE AS MY BASE FORECAST...BUT BLENDED WITH
THE HIGHER RESOLUTION WRF MODELS TO PICK UP THE FINER DETAILS.
THIS WILL NOT BE CLOSE TO PERFECT AS CONVECTIVE SPRING SNOWSTORMS
PICK THEIR OWN BULLSEYE. WITH THE MID LEVEL CIRCULATION TRACKING
DIRECTLY OVERHEAD...SNOWFALL AMOUNTS WILL BE GENEROUS WITH
LOCALIZED HEAVY AMOUNTS.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 341 PM MDT SAT APR 12 2014

THE WEATHER PATTERN DURING THE UPCOMING WEEK LOOKS TO BE A BIT MORE
PROGRESSIVE AS THE AMPLIFIED WESTERN RIDGE WILL NOT HAVE A CHANCE TO
RE-ESTABLISH ITSELF. THIS WILL BRING A MORE SEASONABLE REGIME BACK
TO THE REGION AND TEMPERATURES WILL GENERALLY HOVER NEAR NORMAL.
THERE WILL BE SOME FLUCTUATIONS IN TEMPERATURES EITHER WAY AS A MORE
DEFINED SYSTEM WORKS THROUGH MID-WEEK...BUT OTHERWISE DRY
CONDITIONS LOOK ON TAP.

FOR MONDAY THIS SPRING STORM WILL BE MOVING QUICKLY OUT BY SUNRISE
WITH CLEARING EXPECTED THROUGH THE DAY. COOL AIR LEFT BEHIND THE
PASSAGE OF THE COLD FRONT WILL BE DROPPING TEMPERATURES 20 TO 25
LOWER THAN TODAY/S ABOVE NORMAL READINGS. A FLATTENING...TRANSITORY
RIDGE WORKS ACROSS THE ROCKIES MONDAY NIGHT AND TUESDAY BEING PUSHED
EAST BY THE NEXT PACIFIC NORTHWEST TROUGH. MODEL DIVERGENCE STILL IN
PLACE IN THE HANDLING OF THIS TROUGH AS IT DROPS ACROSS THE CENTRAL
ROCKIES ON WEDNESDAY. THE GFS A BIT MORE BULLISH AND VERY SIMILAR TO
THIS SYSTEM BY TAKING A CLOSED CIRCULATION ACROSS OUR NORTHERN
MOUNTAINS. THE EURO IS MORE OPEN AND THEREFORE PROGRESSIVE WITH THIS
WAVE...FOCUSING MORE OF THE PRECIPITATION EAST OF THE ROCKIES WHERE
ANOTHER SHOT OF COLD AIR WILL BE HEADING. SOME OF THE ENSEMBLES ARE
LEANING TOWARD THE GFS SOLUTION...BUT POPS WILL REMAIN ON THE LOW
SIDE FOR NOW UNTIL SOME BETTER CONSENSUS DEVELOPS WITH THE
OPERATIONAL MODELS. BEHIND THIS WAVE A RATHER FLAT PATTERN SETS UP
WITH LOW PRESSURE TRACKING ALONG THE SOUTHWEST CONUS BORDER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY EVENING)
ISSUED AT 1151 AM MDT SAT APR 12 2014

MOSTLY BROKEN CLOUD LAYER ACROSS THE REGION BUT WELL ABOVE
MOUNTAIN TOPS. SCATTERED -SHRA WITH LOCALIZED THUNDERSTORMS WILL
OCCUR THROUGH 03Z WITH THE BEST CHANCE OF OCCURRENCE OVER SW
COLORADO AND NEAR THE UINTA MOUNTAINS OF NE UTAH. SOME
TURBULENCE WILL OCCUR WITH THE SCATTERED CONVECTION.

APPROACHING FRONT FROM THE NORTHWEST WILL REACH NW COLORADO
BETWEEN 12Z-15Z AND THE I70 CORRIDOR BETWEEN 15Z-18Z. WEATHER
CONDITIONS WILL DETERIORATE WITH LOWER CIGS WITH INCREASING AREAS
OF SNOW IN THE NRN HIGH COUNTRY AND A MIXTURE OF RAIN/SNOW SHOWERS
FOR THE SRN HIGH COUNTRY. AREAS OF TURBULENCE WILL CONTINUE.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM 6 AM SUNDAY TO 3 AM MDT MONDAY FOR
     COZ019.

     WINTER STORM WARNING FROM 6 AM SUNDAY TO 6 AM MDT MONDAY FOR
     COZ012-018.

     WINTER STORM WARNING FROM 3 AM SUNDAY TO 3 AM MDT MONDAY FOR
     COZ004-009-010-013.

UT...WINTER WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO 6 PM MDT SUNDAY
     FOR UTZ023.

&&

$$

SHORT TERM...PF
LONG TERM...15
AVIATION...PF



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