Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 210901
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
301 AM MDT MON JUL 21 2014

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 255 AM MDT MON JUL 21 2014

SOME CLOUDS REMAIN OVER SOUTHERN AREAS...AND MAY PERSIST THROUGH
DAYBREAK...WHILE THE REST OF THE CWA REMAINS FAIRLY CLOUD-FREE.
MODELS HAVE BEEN HIGHLIGHTING DRIER AIR MOVING INTO THE AREA FOR
THE LAST FEW DAYS AND THIS IS PANNING OUT WITH WATER VAPOR SHOWING
PLENTY OF DRY AIR ALOFT MOVING INTO UT AND CO. PWATS REMAIN
FORECAST TO DROP TO .4 INCHES OR SO AND WHILE A WEAK JET STREAK
CONTINUES TO MOVE OVERHEAD...JUST NOT ENOUGH LIFT OR MOISTURE FOR
ANY WIDESPREAD CONVECTION TODAY. THIS STREAK WILL ALLOW FOR SOME
GUSTY WINDS HOWEVER...ESPECIALLY UP NORTH WHERE GUSTS OF 20 TO 30
MPH WILL BE COMMON. MORE ON THAT IN THE FIRE DISCUSSION BELOW.

EVEN WITH MOISTURE DECREASING TODAY...MODELS STILL LIKE THE SAN
JUANS FOR CONVECTION TODAY DUE TO FAVORABLE OROGRAPHIC LIFT.
EXPECT SOME WEAK STORMS/SHOWERS TO FORM AGAIN THIS AFTERNOON AND
EVENING. NAM12 HINTING AT SOME STORMS OVER NRN AND CENTRAL MTNS SO
A SLIM CHANCE EXISTS THERE BUT DID NOT PUT IN FORECAST AS COVERAGE
IS MINIMAL AT BEST AND CONFIDENCE REMAINS LOW.

THROUGH EARLY THIS EVENING...MODEL SOUNDINGS AND LAV GUIDANCE
CONTINUE TO SHOW STRONG WINDS ALOFT OVER NORTHWEST COLORADO AND
PORTIONS OF NORTHEAST UTAH AS THE JET ALOFT COMBINES WITH A DEEP
MIXING LAYER TO TRANSLATE TO THE SFC. EXPECTING RADAR ECHOES
TONIGHT...IF ANY...TO BE OVER THE EASTERN SAN JUANS AND EXTREME
CENTRAL COLORADO MOUNTAINS IN OUR FORECAST AREA.

THE 60KT JET STEAK BACKS NORTHWEST OUT OF THE REGION DURING THE
DAY ON TUESDAY AND THE UPPER LEVEL HIGH PRESSURE BUILDS WEST OVER
THE AREA. EXPECTING SOME ISOLATED WIND GUSTS OF 25 MPH OVER
EXTREME NW COLORADO AND NE UTAH TUESDAY AFTERNOON...BUT OVERALL
WINDS WILL BE NOTICEABLY LIGHTER.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 255 AM MDT MON JUL 21 2014

A LOW PRESSURE SYSTEM AND ASSOCIATED TROUGH OFF OF THE COAST OF
WASHINGTON PUSHES INLAND OVER THE PAC NW ON WEDNESDAY WHICH WILL
TIGHTEN THE PRESSURE GRADIENT SLIGHTLY OVER THE REGION. THIS WILL
CAUSE SOUTH WINDS TO INCREASE SLIGHTLY AND PULL MOISTURE NORTH
INTO THE FORECAST AREA. H5 VORT FIELD SHOWS A WEAK DEFORMATION
ZONE ACROSS SW UTAH AND NW COLORADO AS WELL WHICH WILL HELP TO
INITIATE SCATTERED SHOWERS AND THUNDERSTORMS ALONG THE DEFORMATION.
CAPE VALUES ARE ENHANCED SLIGHTLY ON WEDNESDAY...ESPECIALLY OVER
TERRAIN...SO CAN BET ON STORMS DEVELOPING OVER THE MOUNTAINS
WEDNESDAY AFTERNOON...BUT EXPECTING ISOLATED COVERAGE IN THE
VALLEYS. DIVERGENCE ALOFT DOES NOT SHOW MUCH OF A SIGNAL...BUT
MODERATE SHEAR WOULD KEEP SHOWERS AND THUNDERSTORMS SOMEWHAT ORGANIZED.

DIURNAL CONVECTION WILL BE THE RULE FROM WEDNESDAY THROUGH FRIDAY WITH
STORMS AND SHOWERS FIRING EACH AFTERNOON UNDER HIGH PRESSURE. SOME
SUBTROPICAL MOISTURE WILL AID CONVECTIVE DEVELOPMENT BUT A
PERSISTENT STREAM OF MOISTURE NORMALLY SEEN WITH THE MONSOON
DOESN`T APPEAR TO BE DEVELOPING AT THIS TIME. THE RIDGE WILL
FLATTEN SOMEWHAT INTO THE WEEKEND DUE TO A DISTURBANCE WELL TO OUR
NORTH. THIS WILL CAUSE A DOWNTICK IN PRECIP FOR AREAS GENERALLY N
OF I-70 WHILE AREAS SOUTH WILL CONTINUE TO SEE AFTN/EVENING
PRECIP.

TEMPERATURES WILL BE HOT DURING THE PERIOD AS THE CWA IS SITTING
ALMOST DIRECTLY UNDER THE CENTER OF HIGH PRESSURE.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 255 AM MDT MON JUL 21 2014

MOSTLY VFR CONDITIONS EXPECTED FOR THE NEXT 24 HOURS WITH ONLY THE
SAN JUANS LOOKING FAVORED FOR CONVECTION. WILL NOT MENTION VCTS IN
ANY TAF SITES AS CONVECTION LOOKS TO FORM EAST OF KTEX WITH KEGE
AND KASE NOT FAVORED. LATER SHIFTS CAN UPDATE IF CONVECTION DOES
START FIRING NEARER TO AERODROMES. SOME GUSTY SFC WINDS OF 20 TO
30 MPH ALSO ANTICIPATED TODAY...GENERALLY N OF THE I-70 CORRIDOR.

&&

.FIRE WEATHER...
ISSUED AT 255 AM MDT MON JUL 21 2014

CURRENT WATER VAPOR SATELLITE SHOWS DRIER AIR MOVING INTO UTAH AND
NORTHWESTERN COLORADO. THIS TREND WILL CONTINUE THROUGHOUT THE
DAY. THE PRESSURE GRADIENT ALOFT WILL INCREASE TODAY ACROSS THE
NORTHERN PORTION OF THE FORECAST AREA...ALLOWING DEEP MIXING TO DRIVE
SURFACE WINDS TO 15 TO 20 KTS SUSTAINED WITH OCCASIONAL GUSTS TO
30 KTS. DAYTIME WARMING COMBINED WITH AN INFLUX OF DRYING WILL
CAUSE RELATIVE HUMIDITIES TO FALL TO BETWEEN 10 TO 15 PERCENT
THIS AFTERNOON AND EARLY IN THE EVENING. THE COMBINATION OF LOW
RH...STRONG SOUTHWEST WINDS...AND DRY FUELS WILL LEAD TO CRITICAL
FIRE WEATHER CONDITIONS FOR PORTIONS OF NORTHWEST COLORADO AND
NORTHEAST UTAH. RED FLAG WARNINGS FOR CO FIRE WEATHER ZONES 200
AND 202...AS WELL AS UT FIRE WEATHER ZONES 483...484...AND 487
EXIST FROM NOON TO 8 PM TODAY.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...RED FLAG WARNING FROM NOON TODAY TO 8 PM MDT THIS EVENING FOR
     COZ200-202.

UT...RED FLAG WARNING FROM NOON TODAY TO 8 PM MDT THIS EVENING FOR
     UTZ483-484-487.

&&

$$

SHORT TERM...TGR/JAM
LONG TERM...JAM/TGR
AVIATION...TGR
FIRE WEATHER...TGJT



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