Area Forecast Discussion
Issued by NWS Grand Junction, CO

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017
FXUS65 KGJT 170930
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
330 AM MDT SUN MAY 17 2015

.SHORT TERM...(TODAY THROUGH MONDAY)
ISSUED AT 328 AM MDT SUN MAY 17 2015

AN UPPER LEVEL SHORTWAVE WILL ROTATE AROUND THE BASE OF THE UPPER
LEVEL LOW CENTERED OVER SOUTHWEST WYOMING.  THIS UPPER LEVEL LOW AND
SHORTWAVE WILL MOVE ACROSS THE AREA EARLY THIS MORNING WITH THE
NORTHERN COLORADO MOUNTAINS FAVORED FOR THE BEST SNOWFALL
ACCUMULATIONS IN A WESTERLY FLOW. DECENT ASCENT INDICATED BY
ISENTROPIC LIFT FAVORS THE NORTHERN MOUNTAINS WITH FAVORED
OROGRAPHICS. IT LOOKS LIKE THE SOUTHERN EXTENT OF THIS SHORTWAVE
WILL BE THE GRAND MESA AND WEST ELKS AND ELK MOUNTAINS THAT WILL
ALSO PICK UP SOME DECENT ACCUMULATIONS.  THE BEST PERIOD OF
PRECIPITATION WILL LAST THROUGH 15Z/9 AM.  THE NORTHERN COLORADO
VALLEYS ALSO LOOK TO BENEFIT FROM THIS SHORTWAVE...HOWEVER IN THE
FORM OF RAIN AS SNOW LEVELS LOOK TO BE AOA 8KFT.  REMAINING WINTER
ADVISORIES LOOK ON TRACK IN TERMS OF AMOUNTS OF ADDITIONAL 2 TO 4
INCHES AND THE TIMING WITH THEM ENDING BY 9 AM.  INCREASED POPS
HOWEVER DUE TO THIS SHORTWAVE WHICH INDICATES DECENT LIFT/OMEGA AND
AN AREA OF 1.5 PVU POTENTIAL VORTICITY LOBE MOVING THROUGH AT THE
SAME TIME.

THE UPPER LEVEL JET ON THE SOUTHERN END OF THE EXITING LOW LIFTS TO
THE NORTH THROUGH THE AFTERNOON AS A TRANSITORY SHORTWAVE RIDGE
MOVES IN PLACE FROM THE SOUTH. SOME RESIDUAL MOISTURE AND
INSTABILITY EXISTS FOR CONVECTION TO FIRE OVER THE HIGHER TERRAIN
THIS AFTERNOON AND SHOWERS TO LINGER NORTH OF I-70...BUT OVERALL
MUCH DRIER THAN PREVIOUS FEW DAYS WITH MANY VALLEYS REMAINING FAIRLY
DRY WITH PLENTY OF SUNSHINE.

THE FLOW WILL SHIFT AROUND TO THE SOUTH AS ANOTHER UPPER LEVEL LOW
PRESSURE SYSTEM MOVES ONTO THE CALIFORNIA COAST BY EARLY MONDAY.  A
110 KT JET WILL ROUND THE BASE OF THE TROUGH AND NOSE INTO THE FOUR
CORNERS REGION BY LATE MONDAY AFTERNOON.  MOISTURE WILL BE
INCREASING AS SOME GULF MOISTURE WORKS ITS WAY UP THE DIVIDE
MOUNTAINS AS INDICATED IN MOISTURE TRANSPORT VECTORS WITH SPECIFIC
HUMIDITY VALUES INCREASING TO 3 TO 4 G/KG.  STRONG WARM AIR
ADVECTION WILL ALSO OCCUR WITH 7H TEMPS OF 8-9 DEGREES C FOR A
FAIRLY WARM AFTERNOON ON MONDAY WITH TEMPS BACK ABOVE NORMAL.
INVERTED V FORECAST SOUNDINGS INDICATE THAT MOISTURE WILL INITIALLY
BE HIGH BASED WITH GUSTY OUTFLOW WINDS BEING THE PRIMARY THREAT WITH
STORMS THAT FORM INITIALLY OVER THE HIGHER TERRAIN AND DRIFT OVER
THE VALLEYS LATER IN THE AFTERNOON.

.LONG TERM...(MONDAY NIGHT THROUGH SATURDAY)
ISSUED AT 328 AM MDT SUN MAY 17 2015

THE NEXT STORM SYSTEM WILL BE ON OUR DOORSTEP MONDAY AS PRECIP
OVERSPREADS THE AREA WITH SHOWERS AND STORMS EXPECTED. UPPER LEVEL
FLOW WILL BE FROM DUE SOUTH SO PLENTY OF WARM AIR WILL BE
ADVECTED AHEAD OF THIS SYSTEM AS WELL AS MOISTURE. PWATS WILL
INCREASE TO NEAR .7 INCHES BY MIDNIGHT SO PLENTY OF MOISTURE FOR
THIS SYSTEM TO WORK WITH. THE SOUTHERLY FLOW WILL ALSO CAUSE SNOW
LEVELS TO RISE TO NEAR 11K FEET SO SOME ACCUMULATIONS POSSIBLE
ABOVE TIMBERLINE AT THE START OF THIS EVENT. PRECIP COVERAGE AND
INTENSITY WILL INCREASE OVERNIGHT REACHING A MAXIMUM FROM DAYBREAK
TUESDAY AND PERSISTING THROUGH MUCH OF THE DAY. LAPSE RATES WILL
INCREASE AS THE DAY PROGRESSES INDICATING INCREASING INSTABILITY
SO SOME CONVECTION WILL LIKELY COME INTO PLAY. GUSTY WINDS AND
HEAVY RAINS WILL LIKELY BE THE MAIN PLAYERS FOR ANY STORMS THAT
FORM.

BY WEDNESDAY MORNING...MOST OF THE PRECIP WILL HAVE MOVED
NORTH AND EAST ALLOWING SOME DRYING TO OCCUR FOR THE CWA. THIS
WILL LIKELY BE SHORT-LIVED THOUGH AS A SIMILAR SET-UP OCCURS
WEDNESDAY EVENING AS A TRANSITORY RIDGE MOVES OVER THE REGION WITH
SOME LGT PRECIP AFFECTING THE MTNS THRU THUR MORNING. THE NEXT
AREA OF LOW PRESSURE WILL BE OVER CALIFORNIA AND WRN NV THOUGH GFS
KEEPS HEAVIER PRECIP TO OUR N WHILE EC DIGS LOW A BIT FURTHER
SOUTH BRINGING MORE PRECIP TO THE REGION. WITH SUCH SIMILARITIES
FROM PREVIOUS SYSTEM TO THIS...WOULD NOT BE SURPRISED TO SEE
ANOTHER SHOT OF PRECIP AFFECTING THE CWA. STAY TUNED AS WE WORK
OUT THE FINER DETAILS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 258 AM MDT SUN MAY 17 2015

PLENTY OF SHOWERS CONTINUE THIS MORNING WITH SOME CIGS NEAR OR
JUST BELOW MVFR THOUGH MOST CIGS/VIS REMAIN VFR. THESE CONDITIONS
WILL CONTINUE THROUGH THE DAY AS CONVECTION BRINGS MORE
CLOUDS...SHOWERS AND SOME STORMS. VCSH WILL BE COMMON AT TAF SITES
THOUGH EXPECT VFR TO BE THE RULE TODAY...MAYBE SOME QUICK MVFR/IFR
IF A STRONG SHOWER MOVES OVER ANY TAF SITES. CONDITIONS WILL
IMPROVE AFTER 03Z THOUGH SOME LINGERING SHOWERS WILL PERSIST
THROUGH DAWN.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...WINTER WEATHER ADVISORY UNTIL 9 AM MDT THIS MORNING FOR COZ004-
     009-010-012-013.

UT...NONE.
&&

$$

SHORT TERM...MDA
LONG TERM...TGR
AVIATION...TGR



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