Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 182017
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
217 PM MDT SAT OCT 18 2014

.SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT)
ISSUED AT 216 PM MDT SAT OCT 18 2014

SATELLITE LOOP SHOWED AN UPPER LOW OVER NERN NM HEADED INTO THE
OK/TX PANHANDLES WHILE A PACIFIC TROUGH MOVING INTO THE WESTERN
GREAT BASIN WAS IN THE PROCESS OF SPLITTING. MID-LEVEL CLOUD ACROSS
MUCH OF ERN UT/WRN CO THIS AFTERNOON ASSOCIATED WITH AN AREA OF
UPPER DIVERGENCE AND A SHORTWAVE DISTURBANCE MOVING INTO SERN UT.
INSTABILITY SUFFICIENT FOR SOME CONVECTIVE DEVELOPMENT PER KGJX
RADAR RETURNS AND VISIBLE SATELLITE IMAGES...BUT NO LIGHTNING
DETECTED IN OUR AREA AS OF 20Z. HIGH RESOLUTION MODELS STILL FOCUS
SOME PRECIP MAINLY OVER THE SAN JUAN MTNS THIS AFTERNOON...SO WILL
KEEP ISOLATED TO SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS IN THE
FORECAST INTO EARLY EVENING FOR THE SWRN CO MTNS.

THE SOUTHERN END OF THE SPLITTING TROUGH FORMS A CLOSED UPPER LOW
NEAR THE CA/AZ BORDER TONIGHT...THEN DRIFTS ALONG THE ARIZONA/MEXICO
BORDER ON SUNDAY/SUNDAY NIGHT. WEAK FLOW ALOFT WILL PROVIDE LITTLE
JET SUPPORT IN THE SPLIT FLOW PATTERN OVERHEAD ON SUNDAY. HOWEVER...
SOUTHERLY DIVERGENT FLOW ON THE FRONT SIDE OF THE UPPER LOW DEVELOPS
OVER SWRN CO SUNDAY AFTERNOON. THIS AND WEAK INSTABILITY SUPPORT A
CHANCE OF SHOWERS OVER THE CENTRAL AND ESPECIALLY SOUTHERN MTNS
SUNDAY AFTERNOON. ISOLATED AND SHORT-LIVED THUNDERSTORM WILL ALSO BE
POSSIBLE. SOME LIGHT SNOW MAY OCCUR ABOVE 11K FEET.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 216 PM MDT SAT OCT 18 2014

SOMEWHAT UNSETTLED WEATHER WILL CONTINUE OVER THE REGION THROUGH
MIDWEEK AS A PSEUDO REX BLOCK PATTERN SLOWLY DRIFTS EAST OVER THE
WESTERN US THROUGH EARLY NEXT WEEK. THE LOW PRESSURE CROSSING OVER
NORTHERN MEXICO WILL WEAKEN BY TUESDAY AS A TROUGH MOVES ONSHORE
THE WEST COAST AND PROGRESSES THE PATTERN EASTWARD. THIS TROUGH
PUSHES THE HIGH PRESSURE CURRENTLY IN PLACE TO THE EAST...OPENING
A WEAK MONSOONAL TAP FOR PRECIPITATION DEVELOPMENT. A WEAK 45KT
JET NOSES INTO NORTHEAST UT AND NORTHWEST CO ON TUESDAY...BUT
WEDNESDAY IS DYNAMICALLY MORE INTERESTING WITH A 70 KT JET
OVERHEAD COMBINED WITH AN ELONGATED VORTICITY MAXIMA MOVING
THROUGH. THIS VORT MAX IS ASSOCIATED WITH AN UPPER LEVEL TROUGH
MOVING EAST THROUGH THE FORECAST AREA ON TUESDAY EVENING AND
WEDNESDAY. EXPECTING PRECIPITATION TO START FROM WEST TO EAST
TUESDAY MORNING THROUGH WEDNESDAY AFTERNOON. TEMPERATURES WILL
REMAIN NEAR NORMAL FOR THIS TIME OF YEAR DURING THE PRECIPITATION
EVENTS...SO SNOW LEVEL WILL REMAIN RELATIVELY HIGH...ABOUT 10500+
FEET

BY WEDNESDAY NIGHT...HIGH PRESSURE WILL BEGIN TO BUILD BACK INTO
THE REGION AND KEEP CONDITIONS DRY AND UNSEASONABLY WARM DURING
THE END OF THE WEEK THROUGH THE WEEKEND.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1050 AM MDT SAT OCT 18 2014

AN UPPER LOW MOVING ACROSS NRN NM AND A PACIFIC TROUGH MOVING INTO
THE WESTERN GREAT BASIN WILL RESULT IN A FAIRLY EXTENSIVE MID-LEVEL
CLOUD DECK ACROSS ERN UT AND THE SRN TWO-THIRDS OF WRN CO THROUGH
THIS EVENING. WEAK INSTABILITY SHOULD LEAD TO ISOLD-SCT SHOWERS
MAINLY OVER THE SAN JUAN MTNS BUT A FEW COULD REACH AS FAR NORTH AS
GRAND MESA AND THE ELK MTNS. ISOLD TS POSSIBLE OVER THE SAN JUANS
THIS AFTERNOON. ACTIVITY SHOULD DIMINISH BY 06Z TONIGHT.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.
&&

$$

SHORT TERM...JAD
LONG TERM...JAM
AVIATION...JAD



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