Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 300013
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
613 PM MDT MON SEP 29 2014

.UPDATE...
ISSUED AT 600 PM MDT MON SEP 29 2014

THE SIGNIFICANT WEATHER ASSOCIATED WITH THE STRONG TROUGH THAT
MOVED OVER THE AREA THIS MORNING AND AFTERNOON HAS MOVED TO THE
EASTERN PORTION OF THE FORECAST AREA. SCATTERED RAINSHOWERS WITH
SNOW OVER THE HIGHER ELEVATIONS WERE GENERALLY OVER AND AREA
NORTHEAST OF A LINE FROM KGUC TO KRIL TO KCAG. ALL THIS ACTIVITY
WILL MOVE GRADUALLY NORTHEAST AND OUT OF THE FORECAST AREA BY
ABOUT MIDNIGHT.

&&

.SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 337 PM MDT MON SEP 29 2014

ENERGETIC UPPER SHORTWAVE DISTURBANCE WAS NEAR THE 4 CORNERS THIS
AFTERNOON AS THE LARGER UPPER TROUGH OVER THE GREAT BASIN WAS
FINALLY BEGINNING TO LIFT TO THE NORTHEAST. SHOWERS AND
THUNDERSTORMS FROM EAST-CENTRAL UT ACROSS SW CO IN THE FAVORED LEFT
ENTRANCE OF AN UPPER JET CUTTING ACROSS NW NM. SOME STORMS HAVE
PRODUCED STRONG GUSTY WINDS AND SMALL HAIL ALONG WITH LOCALLY HEAVY
RAINFALL. SNOW DOWN AS LOW AS 9000-9500 FT ELEVATION PER WEBCAMS AND
SPOTTER REPORTS OF SNOW IN TELLURIDE...SILVERTON...WOLF CREEK PASS
AND CAUSE SOME TEMPORARY SLOWDOWNS AND SUB-PAR ROAD CONDITIONS FOR
TRAVELERS ALONG HWY 550 SOUTH OF RIDGWAY AND HWY 50 APPROACH TO
MONARCH PASS.

THIS DISTURBANCE CROSSES SW CO LATE THIS AFTERNOON/EARLY EVENING
AFTER WHICH SHOWERS AND THE STRONGER STORMS SHOULD DECREASE.
HOWEVER...TRAILING SHORTWAVE EVIDENT OVER THE NE CORNER OF NV WILL
ROTATE THROUGH TONIGHT KEEPING SOME PRECIPITATION AROUND ACROSS THE
NORTH HALF OF THE FORECAST AREA.

THE NEXT PACIFIC JET WILL ALREADY BE NOSING INTO THE GREAT BASIN ON
TUESDAY AND WILL KEEP SOME PRECIPITATION ACROSS THE NORTH TUESDAY
AFTERNOON AND TUESDAY NIGHT. IN CONTRAST....SE UT AND SW CO SHOULD
SEE SOME DRIER CONDITIONS. TEMPERATURES WILL REMAIN COOL.

SOME AREAS OF FREEZING TEMPERATURES IN THE MID AND HIGH VALLEYS
TONIGHT. WENT AHEAD AND ISSUED FREEZE WARNINGS FOR THE GUNNISON AND
PAGOSA SPRINGS AREAS WHERE GUIDANCE GAVE LOW TEMPS BETWEEN 28-32F
TONIGHT.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 337 PM MDT MON SEP 29 2014

MODELS STILL HAVE SOME DIFFERENCES IN TIMING OF THE NEXT COLD
FRONT AND UPPER LEVEL TROUGH PASSAGE SCHEDULED FOR WED-WED NIGHT.
THE UPPER LEVEL SHORTWAVE WILL MOSTLY BRUSH THE NORTHERN HALF OF
THE AREA...HOWEVER THE COLD FRONT IS EXPECTED TO PROGRESS SOUTH-
SOUTHEASTWARD ACROSS THE ENTIRE FORECAST AREA. THE NAM AND ECMWF
HAVE CONSISTENTLY BEEN THE FASTER MODELS WITH THE GFS LAGGING
BEHIND ABOUT 6 HOURS OR SO. WILL GENERALLY GO WITH THE FASTER
TIMING FOR THIS FORECAST...BUT WILL NOT END ACTIVITY TOO SOON TO
ACCOUNT FOR THE SLOWER GFS. ALSO...THE NORTHWEST FLOW BEHIND THIS
TYPE OF SYSTEM PROVIDES FAVORABLE OROGRAPHICS FOR THE NORTHERN
MOUNTAINS...WITH SHOWERS OFTEN LINGERING LONGER THAN MODELS
SUGGEST.

THE COLD FRONT SHOULD ALREADY BE OVER THE NORTHWEST CORNER OF THE
FORECAST AREA BY DAYBREAK WED...AND WILL QUICKLY SWEEP TO THE
SOUTH-SOUTHEAST THROUGH THE DAY. THE NAM SHOWS THE FRONT SOUTH OF
THE CO/NM BORDER BY EARLY EVENING. THIS IS A VIGOROUS FRONT WITH
700MB TEMPERATURES DROPPING TO AROUND -4C NORTH...TO 1-2C
SOUTH...WITH ZERO C OR BELOW OVER ALL BUT THE SOUTHERN EDGE BY THU
MORNING. THE BEST SHOWERS/THUNDERSTORMS WILL MOSTLY BE ALONG THE
FRONT...WITH A DRIER NORTHWEST FLOW IN ITS WAKE. ALSO GUSTY WINDS
WILL BE WIDESPREAD ALONG THE FRONT AND AFTERNOON AND EVENING
THUNDERSTORMS AGAIN THREATEN STRONG OUTFLOW GUSTS. THEREFORE WED
IS LOOKING LIKE THE NEXT ACTIVE WEATHER DAY FOR EASTERN UT/WESTERN
CO. THERE IS ALSO THE POTENTIAL FOR ACCUMULATING SNOW IN THE
MOUNTAINS...ESPECIALLY NORTH...AND POSSIBLY LIGHTER AMOUNTS INTO
THE HIGHER NORTHERN VALLEYS. ALSO TEMPERATURES MAY DROP BELOW THE
FREEZING POINT AT MANY OF THE HIGHER AND NORTHERN VALLEYS WED
NIGHT.

AFTER THIS SYSTEM PASSES...HIGH PRESSURE WILL BUILD OVER THE
SOUTHWEST. THURSDAY WILL CONTINUE TO BE COOL...IN THE WAKE OF THE
COLD FRONT. BUT THE RIDGE TO OUR SOUTHWEST WILL RESULT IN A
WARMING AND DRYING TREND THAT WILL THEN PERSIST THROUGH EARLY NEXT
WEEK OR BEYOND.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 600 PM MDT MON SEP 29 2014

SIGNIFICANT WEATHER CLEARED OUT OF EASTERN UTAH AND SOUTHWEST
CO...SO VFR CONDITIONS ARE EXPECTED OVER KCNY...KVEL...KGJT...
KDRO AND KTEX OVERNIGHT. AREAS OF RAIN SHOWERS...WITH SNOW
SHOWERS ABOVE ABOUT 8000 FEET WILL CONTINUE TO PRODUCE OBSCURED
MOUNTAINS AND MVFR CIGS AND VSBYS OVER THE CO CENTRAL AND NW MTS
THROUGH ABOUT 06Z. ISOLATED REMNANT CLOUDS AND SHOWERS WILL HUG
THE NORTHERN AND CENTRAL CO MTNS OVERNIGHT CAUSING LOCAL MT
OBSCURATIONS. VFR CONDITIONS WILL PREVAIL TUESDAY MORNING. AFTER
18Z ISOLATED TO SCATTERED SHOWERS AND A FEW THUNDERSTORMS WILL
CAUSE LOCAL MOUNTAIN OBSCURATIONS ACROSS THE AREA...WITH ONLY A
SLIGHT CHANCE OF SHOWERS AFFECTING FLIGHT CONDITIONS AT
KEGE...KRIL...KASE...AND KTEX.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...FREEZE WARNING FROM MIDNIGHT TONIGHT TO 8 AM MDT TUESDAY FOR
     COZ014-023.

UT...NONE.
&&

$$

UPDATE...CC
SHORT TERM...JAD
LONG TERM...EH
AVIATION...CC



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