Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 212039
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
239 PM MDT THU MAY 21 2015

.SHORT TERM...(TONIGHT THROUGH FRIDAY NIGHT)
ISSUED AT 239 PM MDT THU MAY 21 2015

AREAS OF SCATTERED SHOWER AND THUNDERSTORM ACTIVITY FIRED OVER
PORTIONS OF NORTHWEST AND WEST-CENTRAL COLORADO EARLY THIS
AFTERNOON. THIS ACTIVITY WILL INCREASE IN AREAL COVERAGE AND
INTENSITY LATE THIS AFTERNOON AS TEMPERATURES WARM AND DYNAMIC
LIFT INCREASES. LIFT IS PROVIDED BY A VORT LOBE EJECTED FROM A
LOW PRESSURE SYSTEM OFF THE COAST OF SOUTHERN CALIFORNIA.

THE LOBE OF ENERGY IS PROGGED TO TRACK SOUTHWEST TO NORTHEAST
ACROSS THE AREA TONIGHT WHICH WILL SUSTAIN SHOWERS BEYOND THE
NORMAL DIURNAL RANGE AND WELL INTO THE NIGHT. FALLING TEMPERATURES
WILL RESULT IN SNOW LEVELS LOWERING TO NEAR 9000 TO 9500 FEET BY
FRIDAY MORNING. AS A RESULT...EXPECT ACCUMULATING SNOW ON THE HIGH
PASSES OF SOUTHWEST AND CENTRAL COLORADO OVERNIGHT. THIS
UNSEASONABLE SNOW WILL LIKELY RESULT IN ICE AND SLUSH ON ROADWAYS
OVER MOUNTAIN PASSES SO...GIVEN HEIGHTENED TRAVEL ANTICIPATED
AHEAD OF THE MEMORIAL DAY WEEKEND...WILL CONTINUE THE WINTER
WEATHER ADVISORY ABOVE 9000 FEET TONIGHT.

CLOUDS AND PRECIPITATION WILL OFFSET RADIATIONAL LOSSES AND EXPECT
OVERNIGHT LOWS WILL BE RIGHT AROUND NORMAL.

ON FRIDAY...THE NEXT LOW PRESSURE SYSTEM WILL HEAD NORTHEAST FROM
SOUTHERN CALIFORNIA AT THE BREAK OF DAY...TO THE SOUTHERN TIP OF
NEVADA BY LATE AFTERNOON. THE LOW WILL CONTINUE NORTHEAST
OVERNIGHT...REACHING SOUTH/CENTRAL UT BY DAYBREAK SAT. WHILE
SOMEWHAT DRIER AIR WILL WRAP INTO OUR FORECAST AREA AHEAD OF THE
LOW...ENOUGH MOISTURE WILL LINGER FOR ANOTHER RELATIVELY WET DAY
FOR WESTERN CO AND EASTERN UT. DIFFLUENCE ALOFT AHEAD OF THE
LOW...AND THE DIFFERENTIAL AND DIURNAL HEATING WILL HELP PRODUCE
AND SUSTAIN THE SHOWERS AND AFTERNOON THUNDERSTORMS. THIS
CONVECTIVE ACTIVITY WILL DIMINISH LATE IN THE EVENING. HOWEVER
SOME NOCTURNAL SHOWERS WILL PERSIST AS THE LOW CONTINUES TO
APPROACH.

HIGH TEMPERATURES ON FRIDAY WILL BE SIMILAR TO SLIGHTLY HIGHER
THAN TODAY`S DUE TO A LITTLE MORE SUNSHINE. OVERNIGHT LOWS WILL
ALSO BE SIMILAR...BUT POSSIBLY JUST A TAD COOLER.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 239 PM MDT THU MAY 21 2015

ON SATURDAY THE SLOW-MOVING LOW WILL MOVE OVER THE FORECAST
AREA...REACHING THE FOUR CORNERS LATE AFTERNOON/EVENING.
THEREFORE EXPECT AN UPTURN IN SHOWERS AND THUNDERSTORMS AS THIS
DISTURBANCE MOVES OVERHEAD AND INSTABILITY/DYNAMICS INCREASE. THE
LOW WILL CONTINUE TO SIT OVER THE AREA OVERNIGHT AND POSSIBLY INTO
SUNDAY. THESE PERIODS PROMISE TO BE QUITE WET...WITH SNOW OVER THE
HIGHER TERRAIN THAT MAY AFFECT TRAVEL DURING THE NIGHTTIME HOURS.
BY THE SECOND HALF OF THE WEEKEND...MODELS SOLUTIONS SHOW LESS
AGREEMENT. THE GFS HAS A SECONDARY SHORTWAVE DROPPING INTO THE
GREAT BASIN ON SUNDAY...WHILE THE ECMWF KEEPS THE PARENT LOW OVER
THE AREA. IN ANY CASE...PLENTY OF MOISTURE AND INSTABILITY WILL
PERSIST THROUGH SUNDAY...FOR CONTINUED SHOWERS AND THUNDERSTORMS.
HOWEVER COVERAGE IS NOT EXPECTED TO BE QUITE AS EXTENSIVE...AND
SHOULD BE MORE TIED TO THE TERRAIN. UNSETTLED CONDITIONS WILL
CONTINUE THROUGH THE END OF THE PERIOD AS ADDITIONAL DISTURBANCES
PASS OVER THE REGION. BUT THE DETAILS REMAIN ELUSIVE.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1103 AM MDT THU MAY 21 2015

SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER
THE HIGHER TERRAIN AFTER 18Z RESULTING IN AREAS OF MOUNTAIN
OBSCURATION. THIS ACTIVITY WILL ALSO BE CAPABLE OF GENERATING
STRONG OUTFLOW WINDS TO 35 MPH. SOME STORMS WILL MOVE OVER
ADJACENT VALLEYS FROM 21Z ONWARD POSSIBLY BRINGING MVFR VSBY AT
SOME AIRPORTS THROUGH 06Z. CONDITIONS IMPROVE LATER TONIGHT THOUGH
ISOLATED LIGHT SHOWERS WILL CONTINUE.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM MDT
     FRIDAY FOR COZ010-012-018-019.

UT...NONE.
&&

$$

SHORT TERM...NL/EH
LONG TERM...EH
AVIATION...NL



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