Area Forecast Discussion
Issued by NWS Grand Junction, CO

Home | 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 44 45 46 47 48 49 50

000
FXUS65 KGJT 161109
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
509 AM MDT SAT AUG 16 2014

.SHORT TERM...(TODAY THROUGH SUNDAY)
ISSUED AT 340 AM MDT SAT AUG 16 2014

WATER VAPOR SHOWS DRIER AIR ALOFT ADVECTING ACROSS UTAH AND WRN
COLORADO...BUT ALSO EVIDENT IS AN EMBEDDED DISTURBANCE THAT
MANAGED TO KEEP PERSISTENT NOCTURNAL THUNDERSTORMS IN THE
VICINITY OF KCNY...ARCHES NP...AND MOAB FOR A FEW HOURS. HIGH
PRESSURE OVER UTAH AND WRN COLORADO AND ITS DRIER AIR MASS WILL
BE THE DOMINANT FEATURE TODAY. HOWEVER LOWER LEVEL MOISTURE
(SURFACE DEW POINTS REMAIN AROUND 50F) AND STEEP AFTERNOON LAPSE
RATES WILL TRIGGER SOME AFTERNOON CONVECTION. THE AIR MASS IS
DRIER TODAY AS PRECIPITABLE WATER VALUES HAVE DROPPED TO THREE
QUARTERS OF AN INCH (PER KGJT SOUNDING). AREAL COVERAGE OF STORMS
WILL BE LESS NUMEROUS THAN FRIDAY AFTERNOON. NO DISTURBANCE IS
EVIDENT IN THE MODEL DATA...SO STRONG SURFACE HEATING WILL BE THE
PRIMARY TRIGGER MECHANISM.

A DISTURBANCE PASSES THROUGH THE CANADIAN ROCKIES TONIGHT
FLATTENING THE RIDGE. A VERY WEAK ASSOCIATED WAVE PASSES ALONG THE
CO-WY BORDER...BUT MOISTURE LOOKS VERY LIMITED. SO NOCTURNAL
STORMS ARE NOT EXPECTED.

SUNDAY...PRECIPITABLE WATER VALUES ARE AROUND 0.6 INCH WHICH IS
LOW FOR MID AUGUST. ISOLATED AFTERNOON STORMS ARE POSSIBLE OVER
ALL MOUNTAINS WITH LITTLE RAINFALL CHANCE IN THE VALLEYS. STORM
MOTION WILL BE TO THE EAST AT AROUND 15 KTS. AFTERNOON
TEMPERATURES WILL BE A FEW DEGREES ABOVE NORMAL.

.LONG TERM...(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 340 AM MDT SAT AUG 16 2014

LITTLE CHANGE IS EXPECTED SUNDAY NIGHT THROUGH MONDAY. THE BROAD
RIDGE IS CENTERED NEAR THE FOUR CORNERS WITH ONLY MARGINAL
RESIDUAL MOISTURE AVAILABLE FOR LATE-DAY STORMS. A TROUGH IS
DEVELOPING ALONG THE WEST COAST. MOISTURE BEGINS TO SURGE INTO SE
UTAH AS EARLY AS MONDAY AFTERNOON OR EVENING. THERE IS STILL SOME
UNCERTAINTY ON THE TIMING AND DEPTH OF THIS MOISTURE SURGE. BUT
THE GFS AND SREF PRODUCE PRECIPITABLE WATER VALUES OVER AN INCH IN
SE UTAH TOWARDS TUESDAY MORNING. HAVE ADDED ISOLATED LATE NIGHT
THUNDERSTORMS SPREADING NORTHWARD ALONG THE UT-CO STATELINE.

INCREASING CONFIDENCE THAT THE MONSOONAL MOISTURE TAP DEEPENS BY
TUESDAY AND WILL LAST INTO NEXT FRIDAY. THE GFS REMAINS THE MOST
AGGRESSIVE MODEL WITH A SIGNIFICANT LONG WAVE TROUGH ALONG THE
WEST COAST THAT STRENGTHENS THE SOUTHERLY COMPONENT. WITH
TIME...ENERGY EMBEDDED IN THE WESTERLIES ABSORBS THE CLOSED LOW
WITH SHORT WAVE ENERGY MOVING ACROSS THE GREAT BASIN TOWARD THE
CENTRAL ROCKIES. THE ECMWF MODEL SHOWS THE MID LEVEL CLOSED LOW
CIRCULATION ALONG THE CENTRAL CALIFORNIA COAST...ALLOWING FOR A
MONSOONAL MOISTURE INTO UTAH AND COLORADO. BUT THE ECMWF ALLOWS
THE CLOSED LOW TO RETROGRADE WESTWARD. SOME UNCERTAINTY ON HOW
THIS EVOLVES NEXT WEEK AND THIS WILL DICTATE THE STRENGTH OF THIS
MONSOONAL SURGE AND AREAL COVERAGE OF THUNDERSTORMS AND NOCTURNAL
STORM ACTIVITY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 509 AM MDT SAT AUG 16 2014

ISOLATED -SHRA/-TSRA WILL DEVELOP AFTER 18Z AND LAST THROUGH 01Z
THIS EVENING...WITH A FEW MORE STORMS NEAR THE DIVIDE.  AFTERNOON
STORMS WILL BE IN THE VICINITY OF MOUNTAIN TAF SITES. SKIES WILL
BECOME CLEAR AFTER -TSRA/-SHRA DISSIPATE.

&&

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

$$

SHORT TERM...PF/JOE
LONG TERM...JOE/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.