Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 070627
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1227 AM MDT THU MAY 7 2015

.UPDATE...
ISSUED AT 1223 AM MDT THU MAY 7 2015

QUICK UPDATE TO GRIDDED POP FIELDS TO INCREASE THE CHANCE OF
PRECIPITATION FOR THE REMAINDER OF THE NIGHT. LATEST HRRR KEEPS
ACTIVITY IN THE REGION THROUGH 5 AM THIS MORNING WITH YET ANOTHER
WAVE LIFTING NORTHEAST ACROSS THE REGION. PRECIP AMOUNTS NOT
EXPECTED TO BE AS HEAVY AS EARLIER TODAY...BUT SOILS ARE SATURATED
IN MANY AREAS...SO WILL KEEP A CLOSE EYE ON CELLS...ESPECIALLY AS
THEY APPROACH POPULATED AREAS.

UPDATE ISSUED AT 940 PM MDT WED MAY 6 2015

HAVE INCREASED THE PRECIPITATION COVERAGE THROUGH TONIGHT AS
THERE CONTINUES TO BE SHOWERS WITH A FEW EMBEDDED THUNDERSTORMS
UPSTREAM. IT APPEARS THAT THERE WILL CONTINUE TO BE WEAK EMBEDDED
DISTURBANCES IN THE SOUTHWEST FLOW OVER THE FORECAST AREA. THIS
WILL BE ENOUGH TO KEEP ISOLATED TO SCATTERED SHOWERS AT TIMES
THROUGHOUT THE NIGHT...GRADUALLY WINDING DOWN TOWARDS MORNING. THE
SOUTHERN PORTION HAS CONTINUED TO BE MORE ACTIVE THAN EXPECTED
WITH ENERGY STREAMING OVER THE FOUR CORNERS AT THIS TIME. THIS
SHOULD PERSIST FOR THE NEXT FEW HOURS. THEREFORE THE FORECAST WILL
SEE THE BIGGEST CHANGES THERE.

&&

.SHORT TERM...(TONIGHT THROUGH THURSDAY NIGHT)
ISSUED AT 309 PM MDT WED MAY 6 2015

THE STRONG LOW THAT MOVED OVER THE AREA LAST NIGHT AND THIS
MORNING WILL CONTINUE MOVING INTO THE HIGH PLAINS TONIGHT.
NW AND CENTRAL CO AND NE UT WILL BE BENEATH THE NW FLOW ALOFT
ON THE WEST SIDE OF THE STORM...WHERE UNSTABLE AND MOIST
CONDITIONS WILL CONTINUE TO PRODUCE RAIN SHOWERS AND THUNDERSTORMS
OVER MUCH OF THE AREA. A FEW STORMS HAVE BEEN STRONG ENOUGH TO
PRODUCE SMALL HAIL AND HEAVY RAIN. A WEAK SHORTWAVE TROUGH MOVING
OVER NORTHWEST CO AND NE UT WILL ALSO AS SOME SUPPORT FOR
CONVECTION UNTIL ABOUT 03Z THIS EVENING. SUBSIDENCE AND GRADUALLY
DRIER AIR WILL FILTER INTO EASTER UT...AND NORTHWEST AND CENTRAL
CO AFTER MIDNIGHT. OVER SW CO...THE HRRR AND NAM12 SHOW ANOTHER
WEAK SHORTWAVE WILL BRING INCREASING CLOUDS AND ISOLATED
PRECIPITATION LATE TONIGHT.

THURSDAY MORNING...IN SOUTH FLOW A WEAK WAVE WORKS THROUGH THE
FOUR CORNERS REGION. AVAILABLE MOISTURE WILL BE DIMINISHING THERE
SO ONLY ISOLATED SHOWERS ARE FORECASTED ACROSS THE SOUTH FAVORING
THE SAN JUANS. DEEPER MOISTURE REMAINS ACROSS THE NORTH THURSDAY
ALONG WITH SOME WEAK FRONTAL FORCING. MARGINAL AFTERNOON
INSTABILITY WILL LIMIT THUNDERSTORM COVERAGE MAINLY OVER MTNS
NORTH OF I-70.

THURSDAY NIGHT DRIER SW FLOW INVADES LIMITING NIGHTTIME SHOWERS
TO NEAR THE CONTINENTAL DIVIDE. TEMPERATURES REMAIN NEAR NORMAL.

THE NEXT STRONGER PACIFIC LOW SINKS THROUGH CALIFORNIA ON THURSDAY
THEN BEGINS TO AMBLE INLAND THURSDAY NIGHT.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 309 PM MDT WED MAY 6 2015

A HIGHLY AMPLIFIED PROGRESSIVE PATTERN CONTINUES THROUGH THESE
PERIODS. ONE STRONG UPPER LOW WILL PASS ON SATURDAY BRINGING A
BLAST OF NORTHERN AND MOUNTAIN SNOW. TWO OTHER TROUGHS CURRENTLY
ARE TIMED TO PASS MID TO LATE NEXT WEEK.

FRIDAY THE UPPER LOW WITH A MODIFYING BUT IMPRESSIVE -26C COLD
CORE WORKS NORTH OF LAS VEGAS TO SOUTHCENTRAL UTAH FRIDAY NIGHT
AND THROUGH THE FORECAST AREA ON SATURDAY. THE THERMAL RIDGE
BLOSSOMS OVER THE FORECAST AREA FRIDAY AND HAVE RAISED
TEMPERATURES CLOSER TO THE WARMER NAM GUIDANCE. A 70KT JET NOSE
POKES INTO SE UTAH IN THE AFTERNOON AND RAKES THE SOUTH OVERNIGHT.
COOL ADVECTION ALOFT BEGINS TO DESTABILIZE BUT AVAILABLE MOISTURE
IS LIMITED AND MAINLY ACROSS THE NORTH.

SATURDAY THE POTENTIAL VORTICITY CENTER RAKES THE NORTH AS THE
JET WRAPS UP THE FRONT RANGE. FRONTAL FORCING SEEN IN THE PARK
RANGE BY THE AFTERNOON. THE BEST SHOWER COVERAGE WILL BE OVER THE
NORTHERN MOUNTAINS BUT WILL EXTEND INTO THE CENTRAL CO MTNS. SNOW
LEVELS DROP TO AROUND 8KFT...AND WILL BRIEFLY BE LOWER IN
STRONGER CONVECTION. THE LOW LIFTS THROUGH THE NORTHERN PLAINS
SATURDAY NIGHT THROUGH SUNDAY. WRAP- AROUND MOISTURE WILL CONTINUE
TO PRODUCE SHOWERS FAVORING THE NORTH. SUNDAY...SNOW LEVELS LOWER
INTO THE NORTHERN VALLEYS WITH 700MB TEMPS AT -4C THERE.

SIGNIFICANT SNOWFALL IS EXPECTED FOR THIS WEEKEND FOR THE EASTERN
UINTAS AND THE COLORADO MOUNTAINS FROM WYOMING DOWN INTO THE NW
SAN JUANS. TRAVEL THROUGH THESE MOUNTAINS COULD BE HAZARDOUS THIS
WEEKEND. COLDER THAN NORMAL TEMPERATURES EXPECTED ACROSS THE
REGION THROUGH SUNDAY NIGHT. HIGH VALLEY FREEZES ARE POSSIBLE.

MONDAY WARM ADVECTION BEGINS AS A RIDGE BUILDS IN FROM THE WEST.
FLOW ALOFT QUICKLY SWITCHES BACK TO SW AND INCREASES INTO THE NEW
WEEK AS THE NEXT TROUGH WORKS INTO THE PACIFIC NW ON TUESDAY AND
THE GREAT BASIN ON WEDNESDAY. AN ASSOCIATED ZONAL JET FROM CENTRAL
CALIFORNIA INTRUDES INTO THE NORTHERN-CENTRAL FORECAST AREA ON
WEDNESDAY BEGINNING THE CHANCE OF MAINLY RAIN SHOWERS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1145 PM MDT WED MAY 6 2015

SCATTERED -SHRA WITH A FEW -TSRA WILL OCCUR DURING THE OVERNIGHT
HOURS...ESPECIALLY SW AND WEST CENTRAL COLORADO AS A SHORT WAVE
LIFTS ACROSS THIS PORTION TONIGHT. AFTER A MORNING LULL WITH
ISOLATED -SHRA...SCATTERED TSRA WILL DEVELOP ONCE AGAIN WITH THE
PRIMARY FOCUS OVER NW COLORADO AND THE UINTA MOUNTAINS. DIURNAL
STORMS WILL BE LESS NUMEROUS OVER SW COLORADO. SMALL HAIL AND
GUSTY WINDS TO 30KTS WILL BE POSSIBLE WITH THE STRONGEST STORMS.


&&

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

$$

UPDATE...JDC
SHORT TERM...CC/JOE
LONG TERM...JOE
AVIATION...PF


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