Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 011116
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
516 AM MDT FRI MAY 1 2015

.SHORT TERM...(TODAY THROUGH SATURDAY)
ISSUED AT 348 AM MDT FRI MAY 1 2015

00Z KGJT RAOB SHOWS WE HAVE BOOSTED OUR PRECIPITABLE WATER TO NEAR
HALF OF AN INCH THIS EVENING. THE BULK OF THIS HOWEVER IS LOCATED AT
500MB OR ABOVE. THE H5 HAND ANALYSIS PLOT SHOWS THE NORTHERN STREAM
TROUGH MOVING OFF THE NORTHERN ROCKIES. THIS ENERGY HAS SEPARATED THE
AMPLIFIED RIDGE THAT HAD BEEN IN PLACE THE PAST FEW DAYS BY
PUSHING THE NORTHERN EXTENT TOWARD THE WESTERN GREAT LAKES...AND
LEAVING THE BASE OVER THE DESERT SOUTHWEST AND SOUTHERN ROCKIES.
THE SPLIT FLOW PATTERN WILL BECOME A BIT MORE EVIDENT BY SATURDAY
AS AN EAST PACIFIC LOW NUDGES THE SOUTHERN RIDGE EASTWARD. THIS IN
TURN BACKS UPPER LEVEL WINDS TO THE SOUTHWEST AND BRINGS A FETCH
OF MOISTURE FROM THE SUBTROPICS. THIS MOIST SOUTHWEST FLOW MERGES
WITH THE STRONGER WESTERLIES OF THE NORTHERN STREAM OVER NORTHERN
COLORADO BY LATE SATURDAY AND THIS SHOULD LEAD TO A BIT MORE OF AN
ACTIVE PERIOD GOING INTO THE NEW WEEK. HOWEVER UNTIL THEN THERE IS
NOT MUCH TO HANG YOUR HAT ON. MID LEVEL LAPSE RATES STAY
MODERATELY STEEP UNDER THE RIDGE AND IN THE TRANSITION TO
SOUTHWEST FLOW. HOWEVER THE DYNAMIC TROP FIELD IS FAIRLY DIFFUSE
AND VOID A DEFINITE WAVE MOVING THROUGH THE FLOW TOWARD OUR CWA.
THIS LEAVES THE TERRAIN CIRCULATIONS AS THE MAIN FORCING AND WILL
CONTINUE TO RUN POPS HIGHEST ON THE RIDGES THE NEXT FEW AFTERNOONS
WITH ONLY VERY SMALL CHANCES OF A DECENT SHOWER REACHING THE LOWER
VALLEY FLOORS. THE INSTABILITY DOES STAY STRONG OVERNIGHT AS WELL
BUT WITH LACK OF A DEFINITE SIGNAL WILL ALLOW POPS TO RAPIDLY
DWINDLE AFTER SUNSET. THE LARGEST H5 TO H7 DELTA T IS OVER THE 4
CORNER REGION THROUGH THE NIGHT AND MODELS DO HINT AT A BATCH OF
MID LEVEL MOISTURE MOVING INTO THAT REGION. ACCAS SEEM THE MORE
LIKELY OUTCOME SITTING ON TOP THE EML. AS FOR TEMPERATURES...THEY
CONTINUE TO RUN WELL ABOVE NORMAL WITH FAIRLY A FAIRLY MILD NIGHT
EXPECTED AGAIN TONIGHT.

.LONG TERM...(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 348 AM MDT FRI MAY 1 2015

A WEAK SHORT WAVE THAT IS CURRENTLY ALONG THE SRN CALIF AND BAJA
COAST WILL CROSS THE FOUR CORNERS REGION SUNDAY MORNING. THIS
KEEPS THE AIR MASS UNSETTLED FOR SUNDAY AFTERNOON...ALTHOUGH
MOISTURE WILL BE SOMEWHAT LIMITED AND CONFINED TO THE MID/HIGH
LEVELS. SHOWERS OR SOME THUNDERSTORMS WILL BE RELATIVELY HIGH
BASED WITH A PREFERENCE FOR THE HIGH COUNTRY.

A BETTER STRUCTURED SHORT WAVE LIFTS NORTHEAST FROM THE SRN
CALIF/BAJA COAST REGION EARLY NEXT WEEK...REACHING THE FOUR
CORNERS REGION BY TUESDAY MORNING. MONDAY WILL BE A SIMILAR DAY
WITH SCATTERED SHOWERS WITH SOME THUNDER OVER THE HIGH TERRAIN.
BUT THE CHANCE FOR SHOWERS BECOMES MORE WIDESPREAD ON TUESDAY
WITH HIGHER RAINFALL AMOUNTS. INCREASED CLOUD COVER WILL LOWER
DAYTIME TEMPS.

SIGNIFICANT MODEL SPREAD EXISTS FOR DAYS 6 AND 7 THAT LEADS TO
GREATER UNCERTAINTY. THE UPPER LOW CIRCULATION THAT AFFECTS THE
FORECAST AREA ON TUESDAY LIFTS NORTHWARD ON WEDNESDAY. THE GFS
MODEL DEPICTS A DEEPER CLOSED LOW SYSTEM FROM THE PACIFIC DROPS
TOWARD THE CALIF/NEVADA BORDER. THE ECMWF DIFFERS SIGNIFICANT AS
IT SHOWS THE PACIFIC CIRCULATION TRACKING EASTWARD INTO CANADA AND
THE PACIFIC NORTHWEST. CONSENSUS BLENDED POPS APPEARS TO SPLIT
THE DIFFERENCE AND THAT MAY BE THE BEST CHOICE FOR NOW. SPRINGTIME
CLOSED LOW CIRCULATIONS HAVE A STRONG TENDENCY TO DISPLAY
"ERRATIC" BEHAVIOR...NO EXCEPTION THIS TIME AROUND.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 515 AM MDT FRI MAY 1 2015

NO AVIATION WEATHER HAZARDS EXPECTED UNTIL 19Z THIS AFTERNOON WHEN
A FEW CONVECTIVE TOWERS BEGIN TO FORM. SCATTERED -SHRA/-TSRA WILL
BE DEVELOPING ALONG THE HIGH TERRAIN. BY LATE IN THE DAY...ISOLATED
CONVECTIVE MAY DRIFT OVER THE ADJACENT LOWER VALLEYS. ELEVATED TAF
SITES SUCH AS KASE...KEGE...KTEX COULD OBSERVE A BRIEF SHOWER OR
THUNDERSTORM WITH GUSTY WINDS TO 30-35KTS (ABOUT A 20 PERCENT
CHANCE). -TSRA COULD BE IN THE VICINITY OF KGJT...KRIL...AND KMTJ
BETWEEN 21Z- 02Z. AFTER 02Z...CONVECTION DISSIPATES FOR THE DAY.

&&

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

$$

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


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