Area Forecast Discussion
Issued by NWS Grand Junction, CO

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

000
FXUS65 KGJT 311130
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
530 AM MDT FRI OCT 31 2014

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 413 AM MDT FRI OCT 31 2014

HIGH PRESSURE AXIS ALONG THE SPINE OF COLORADO WILL BE SHIFTING TO
THE WESTERN PLAINS TODAY. A WEAK UPPER LEVEL WAVE OVER NEVADA...MORE
DISCERNIBLE AT THE 300 MB LEVEL...REACHES WRN COLORADO THIS
AFTERNOON. THIS WILL PUSH HIGH LEVEL MOISTURE AS THE DAY PROGRESSES.
RADAR OBSERVATION SHOW WEAK DBZ RETURNS INDICATING THERE IS SOME
MID LEVEL MOISTURE. MODELS DO PAINT SOME LIGHT QPF OVER SW
COLORADO LATE IN THE DAY. SOMETIMES THIS IS OVERDONE AFTER A
PROLONG DRY PERIOD...BUT REASONABLE THAT SOME VIRGA SHAFTS WILL
EXIST WITH A FEW SPRINKLES REACHING THE GROUND. ANOTHER MILD DAY
EXPECTED...PERHAPS 1-3 DEGREES WARMING (EVEN WITH SOME CLOUDS
SPREADING FROM THE WEST.)

STILL A DIFFICULT FORECAST COMING UP THIS WEEKEND ESPECIALLY WHEN
THIS PLEASANT FALL WEATHER WILL BE TAKING A SHORT HIATUS. 00Z H5
ANALYSIS SHOWS THE AMPLIFIED PATTERN ACROSS THE LOWER 48 THAT THE
MODELS HAD BEEN PREDICTING. THIS AMPLIFICATION WILL AID IN
FORMING A RATHER DEEP TROUGH IN THE GREAT BASIN OVERNIGHT...WHERE
IT PERSISTS INTO SUNDAY. TONIGHT INTO SATURDAY/S FORECAST LOOKS
SIMILAR TO 24 HOURS AGO AND GIVES SOME CONFIDENCE...HOWEVER SOME
DETAILS ARE STILL A BIT FUZZY. 305K THETA SURFACES CONTINUE TO
SHOW MOISTURE HEADING NORTHWARD OUT OF THE SONORAN REGION
TODAY...WITH MOISTURE SOURCES FROM THE GULF AND PACIFIC CONVERGING
THERE THIS MORNING. WEAK UPGLIDE AND OROGRAPHICS LOOKS TO SPREAD
MOISTURE INTO THE 4 CORNERS REGION AFTER MIDNIGHT BUT OVERALL
LARGE SCALE ASCENT IS LACKING AND FOCUSED WELL TO THE WEST.
SHOWERS APPEAR BEST ON THE NOSE OF THE MID LEVEL JET THAT FORMS
OVERNIGHT IN OUR SOUTHERN ZONES. POPS LOOK GOOD HERE. CROSS
SECTIONS THEN SHOW DRIER AIR FILTERING IN THROUGH THE
AFTERNOON...WHICH WILL ADD SOME DEGREE OF INSTABILITY TO HELP
PRODUCE ISOLATED THUNDERSTORMS...BUT ALSO THINK IT WILL LIMIT
COVERAGE AS THE DENDRITIC LAYER WILL NOT BE SATURATED.
TEMPERATURES A BIT TRICKY WITH CLOUD COVER IN PLACE...BUT AIDED BY
STRONG MIXING AND REALIZED WIND GUSTS AT THE SURFACE. THERE IS
STILL A 10 DEGREE SPLIT IN GUIDANCE AND GUT FEELING IS TO LEAN
TOWARD THE WARMER SIDE...BUT STAYED WITH GOING FORECAST FOR NOW.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 413 AM MDT FRI OCT 31 2014

BY LATE SATURDAY THE SPLIT IN THE WESTERN TROUGH WILL BE MORE
APPARENT...WITH THE MAIN FOCUS LIFTING INTO THE NORTHERN ROCKIES AND
HIGH PLAINS BY MIDNIGHT. EARLY SUNDAY ANOTHER JET MAX BEGINS TO
REFORM ON THE UPSTREAM SIDE OF THE TROUGH AND IT WILL REINFORCE WHAT
IS LEFT OF THE SOUTHERN SPLIT WITH UPSTREAM ENERGY. STILL NOT VERY
ACTIVE OUR CWA WITH LIFT TO THE WEST. HOWEVER MODELS SUGGEST A WEAK
FRONT PUSHING THOUGH AS THE TROUGH SPLITS AND BRINGS SOME CAA.
OROGRAPHICS SEEM THE PRIMARY SOURCE OF LIFT AND SHOULD KEEP SOME
LIGHT PRECIP AROUND THE HIGH COUNTRY BUT THE DENDRITIC LAYER REMAIN
DRY. THE BIGGER PUSH BEGINS ON SUNDAY AS THE JET AND UPPER LEVEL
ASCENT SHIFTS OVER THE 4 CORNERS REGION.  STRONG PV FROM THE JET
MOVING IN ALOFT REDUCES STATIC INSTABILITY...MOISTURE UNDER THIS
LAYER PUSHING IN FROM THE SOUTH SHOULD INCREASE SHOWERS ACROSS THE
SOUTHERN MOUNTAINS AND POPS LOOK GOOD THERE FOR NOW. THE MAIN FRONT
SHOULD BE HUNG UP TO THE NORTHWEST EARLY DUE TO STRONG SOUTHERLY
FLOW...BUT BEGIN TO SHIFT INTO NORTHEAST UTAH LATE IN THE DAY AND
EXPECT SHOWERS TO PICK UP IN THAT DIRECTION. IN THE MIDDLE ISOLATED
TO LOW CHANCE POPS SUFFICE FOR NOW UNTIL PICTURE CLEARS JUST A BIT
ON TIMING. TEMPERATURES DROP SOME 10 DEGREES WITH PUSH OF COLDER AIR
ALOFT AND INCREASED CLOUD COVER.

MONDAY...COLD TROUGH WITH A CLOSED LOW CENTERED OVER COLORADO
WILL BE MOVING ACROSS THE STATE. POTENTIAL FOR WRAPAROUND MOISTURE
AND THEREFORE THE ENTIRE FORECAST AREA HAS THE POTENTIAL FOR SOME
RAIN OR SNOW SHOWERS (RELATIVELY LOW SNOW LEVEL BETWEEN 5500 TO 6000
FEET). SHADED POPS TOWARD WPC GUIDANCE TO CORRECT FOR MODEL SPREAD
INHERENT IN THE INITIAL CONSENSUS POP FIELD. THE SYSTEM DEPARTS
THE REGION MONDAY NIGHT.

TRAILING ENERGY FROM THE COLD TROUGH DEVELOPS INTO A CLOSED LOW
CIRCULATION OVER OLD MEXICO AND TEXAS. WITH THE PACIFIC JET
REDEVELOPING OVER THE NORTHERN ROCKIES...A WEST TO EAST RIDGE
AXIS WILL LAY ACROSS UTAH AND COLORADO. THIS RESULTS IN DRY
WEATHER WITH ANOTHER WARMING TREND AND A FEW MORE DAYS OF MILD
TEMPERATURES.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 530 AM MDT FRI OCT 31 2014

VFR CONDITIONS IS EXPECTED AT ALL TAF SITES THROUGH THE PERIOD.
MID TO HIGH LEVEL CLOUDS WILL SPREAD ACROSS THE REGION TODAY AND
THIS EVENING.

FOR SW COLORADO...ISOLATED VIRGA SHAFTS OR -SHRA WILL FORM AFTER
20Z THIS AFTERNOON...BECOMING SCATTERED -SHRA AFTER 03Z THIS
EVENING.

&&

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

$$

SHORT TERM...PF/15
LONG TERM...15/PF
AVIATION...PF



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.