Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 242302
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
402 PM MST WED DEC 24 2014

.SHORT TERM...(TONIGHT THROUGH THURSDAY NIGHT)
ISSUED AT 359 PM MST WED DEC 24 2014

TRICKY FORECAST COMING UP FOR CHRISTMAS AND FRIDAY WITH GENERAL
GIST REMAINING THE SAME...MORE SNOW. IT`S THE AMOUNTS THAT MAKE
IT DIFFICULT. TO START...UPPER LEVEL SUPPORT IS REALLY WEAK AND
DIFFUSE WITH A 70KT STREAK MOVING OVERHEAD WHICH WILL PRODUCE SOME
LIFT BUT NOTHING LIKE WE SAW WITH THE PREVIOUS STORM. MOISTURE IS
ALSO STREAMING DOWN FROM THE PACNW AND WILL GET WRUNG OUT AS IT
MAKES THE TREK SOUTHWEST INDICATED BY SPECIFIC HUMDITIES OF 3 G/KG
OR SO. BIG PICTURE WISE...AN APPROACHING TROUGH WILL BRING PRECIP
TO THE AREA EARLY CHRISTMAS MORNING BEFORE CLOSING OFF A LOW OVER
CENTRAL UT AND SLOWING DOWN SOMEWHAT. AS THIS OCCURS...SNOW WILL
BE FALLING IN THE MTNS AND SOME RAIN/SNOW IN THE VALLEYS. THIS
WILL BE THE WARM PART OF THE STORM DUE TO SW FLOW. AT THIS
POINT...H7 STREAMLINES THEN SHOW SOME CONVERGENCE OVER THE GRAND
VALLEY SLOWLY SHIFTING TO THE SAN JUANS FOLLOWING THE AREA OF LOW
PRESSURE. FLOW WILL THEN SHIFT AND START COMING FROM THE NORTH
WHICH `SHOULD` ALLOW TEMPS TO DROP BELOW FREEZING SO SOME
ACCUMULATIONS POSSIBLE FOR THE GRAND VALLEY...1 TO 2 INCHES LOOK
GOOD FOR NOW...AND SOME HEAVIER SNOW SOUTH.

MODEL SNOW AMOUNTS ALL OVER THE PLACE WITH THE EC SHOWING ONLY 2
TO 4 INCHES FOR ENTIRE FORECAST AREA...WAY UNDERDONE...GFS GOING 5
TO 12 INCHES AND NAM A LITTLE HIGHER THAN THAT. MODEL
UNCERTAINTY...UNFORTUNATELY...REMAINS HIGH WITH ANY CHANGES TO LOW
TRACK...STRENGTH...AND SFC TEMPS CAUSING NOTICEABLE CHANGES TO
FORECAST ESPECIALLY IN THE VALLEYS. ALL THAT BEING SAID...ALL
WATCHES ARE NOW ADVISORIES WITH GENERALLY 8 TO 10 INCHES FOR MTNS
WITH SOME LOCALES SEEING A FOOT OR MORE AND 3 TO 6 FOR THE
VALLEYS. IF YOU ARE TRAVELLING THIS HOLIDAY SEASON...EXPECT
HAZARDOUS DRIVING CONDITIONS ESPECIALLY OVER MOUNTAIN PASSES. GIVE
YOURSELF EXTRA TIME TO GET TO YOUR DESTINATION AND MAKE SURE YOU
HAVE A JOYOUS HOLIDAY SEASON!

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 359 PM MST WED DEC 24 2014

THE 12Z MODELS HAVE REACHED CONSENSUS ON THE LOCATION OF THE H7
LOW PRESSURE SYSTEM FOR FRIDAY...WHICH IS PROGGED TO BE OVER THE
FOUR CORNERS EARLY FRIDAY MORNING AND THEN TRACK EAST ACROSS
SOUTHERN COLORADO THROUGHOUT THE DAY. THAT BEING SAID...THE
VORTICITY MAXIMA IS EXPECTED TO REMAIN SOUTH OF THE FORECAST AREA
IN AZ AND NM SO NO AREA OF EASTERN UTAH OR WESTERN COLORADO WILL
BE PARTICULARLY PRONE TO HEAVY SNOW...YET THE POSSIBILITY OF
SCATTERED SNOW SHOWERS WILL EXIST NEARLY EVERYWHERE. THE CHANCE OF
SNOW WILL DECREASE FROM WEST TO EAST THROUGHOUT THE DAY FRIDAY
WITH ONLY A FEW LINGERING SHOWERS IN NORTHWEST FLOW BY SATURDAY
MORNING. SNOW RATIOS ARE EXPECTED TO BE SOMEWHERE BETWEEN 15 TO 1
AND 18 TO 1 WITH GOOD COLD AIR ADVECTION MOVING IN.

THE WEATHER WON/T STAY DRY FOR LONG AS ANOTHER TROUGH WILL SWING
DOWN INTO THE GREAT BASIN FROM THE PAC NW AND REACH NORTHERN
COLORADO BY SUNDAY MORNING. THE GFS AND EC DIVERGE SOMEWHAT WITH
THIS SYSTEM...BUT THERE IS REASONABLE CONFIDENCE THAT THE BULK OF
THE PRECIPITATION ON SUNDAY WILL STAY NORTH OF THE I-70 CORRIDOR.
HOWEVER...ON MONDAY WHEN THE UPPER LEVEL LOW ASSOCIATED WITH THIS
TROUGH SWINGS THROUGH...THE AREA OF PRECIPITATION IS FORECAST TO
SWING SOUTHWARD INTO SE UTAH AND SW COLORADO. WILL HAVE TO FIGURE
OUT DETAILS ON THIS NEXT SYSTEM OVER THE NEXT FEW DAYS...AS SOLNS
AGREE TO AN ACTIVE PATTERN BUT A CHANGE IN THE LOW CENTER/S
POSITIONING WILL MAKE ALL THE DIFFERENCE IN SNOWFALL AMOUNTS. THE
GOOD NEWS IS...AT THIS POINT WE CAN FAIRLY CONFIDENTLY SAY THAT
ALL PRECIPITATION WILL FALL AS SNOW.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1106 AM MST WED DEC 24 2014

VFR CONDITIONS WILL REMAIN PROMINENT TODAY THOUGH SOME HIGH CLOUDS
WILL START STREAMING IN FROM THE NW AHEAD OF THE NEXT STORM SYSTEM.
EXPECT BKN TO OVC SKIES TO BE ON THE INCREASE THROUGH THE
AFTERNOON AND EVENING. THEY WILL START DROPPING OVERNIGHT REACHING
BETWEEN 5 TO 10K FEET BY MORNING. PRECIP CHANCES INCREASE AFTER
09Z WITH SOME -RA AND -SN POSSIBLE ACROSS MUCH OF THE AREA. TAF
SITES SHOULD NOT BE AFFECTED WITH ANY PRECIP UNTIL AFTER 12Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER WEATHER ADVISORY FROM 3 AM THURSDAY TO 6 PM MST FRIDAY
     FOR COZ001-002.

     WINTER WEATHER ADVISORY FROM 6 AM THURSDAY TO MIDNIGHT MST
     FRIDAY NIGHT FOR COZ003-004-008>010-012-013-017>019.

UT...WINTER WEATHER ADVISORY FROM 3 AM THURSDAY TO 6 PM MST FRIDAY
     FOR UTZ023-025.

&&

$$

SHORT TERM...TGR
LONG TERM...JAM
AVIATION...TGR


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