Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 181708
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1108 AM MDT MON AUG 18 2014

.UPDATE...
ISSUED AT 1108 AM MDT MON AUG 18 2014

A JET STREAK OVER NORTHERN COLORADO CONTINUES TO SUSTAIN SHOWERS
OVER THE UINTA BASIN OF EASTERN UTAH AND FROM ABOUT RANGELY TO
VAIL PASS IN NORTHERN COLORADO. LITTLE PRECIPITATION IS EXPECTED
WITH THESE SHOWERS. ANTICIPATING A FEW SHOWERS DEVELOPING OVER
SOUTHEASTERN UTAH WITHIN THE NEXT FEW HOURS AHEAD OF THE DEEPER
PLUME OF MOISTURE WHICH WILL REACH THE FOUR CORNERS TONIGHT.

&&

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 241 AM MDT MON AUG 18 2014

TODAY...STARTING OUT OVERNIGHT INTO THE EARLY MORNING WITH A FEW
SHOWERS AND THUNDERSTORMS MAINLY THE NORTHERN PORTION OF THE NW
SAN JUAN MOUNTAINS AND ALSO IN AREAS OF NW CO AND NE UT. THEN
DAYTIME HEATING WILL RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS
THIS AFTERNOON MAINLY MOUNTAINS. WITH PWATS DOWN TO LESS THAN 0.75
INCH TODAY...ONLY EXPECT BRIEF MODERATE RAINFALL FROM STORMS...
THOUGH GUSTY OUTFLOW WINDS COULD BE IN EXCESS OF 45 MPH FROM SOME
STORMS. EXPECT MAX TEMPERATURES ABOUT THE SAME OR SLIGHTLY LOWER
THAN YESTERDAY.

THEN CONFIDENCE IS HIGH FOR THE NEXT MONSOONAL SURGE TONIGHT
THROUGH TUESDAY ESPECIALLY IN EASTERN UTAH AND FAR WESTERN
COLORADO. SEVERAL FACTORS SUPPORT THIS. FIRST AN UNSEASONABLY
VIGOROUS UPPER LOW WORKS DOWN THE CALIFORNIA COAST PUSHING THE
SUBTROPICAL HIGH CENTER OUT INTO TEXAS. 0-6KM SW FLOW ADVECTS DEEP
MOISTURE FROM THE BAJA REGION. SE UTAH PRECIP WATER VALUES CLIMB
OVER AN INCH THIS EVENING REACHING NEAR 1.2 INCHES BY NOON
TUESDAY. A SIGNIFICANT CHUNK OF JET-SUPPORTED ENERGY LIFTS THROUGH
EASTERN UTAH ON TUESDAY WITH THE BEST FORCING IN THE RIGHT
ENTRANCE QUAD OF THE 70KT JET OVER NE UTAH. THE BEST MIXTURE OF
FORCING AND DEEP MOISTURE LOOKS TO BE IN SE-EASTCENTRAL UTAH AND
FAR WESTERN COLORADO. INSTABILITY LOOKS LIMITED DUE TO LESS
SURFACE HEATING. STILL THE STRONGEST CELLS WILL PRODUCE SMALL
HAIL. STORM MOTION WILL BE TO THE NNE AT 20-25KTS SO OUTFLOW WIND
GUSTS OF 30-40 MPH SHOULD BE COMMON IN THE WESTERN CWA. THE
EASTERN CWA IS EXPECTED TO HAVE A LOWER THREAT OF HEAVY RAINS THAN
THE WESTERN PORTION.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 241 AM MDT MON AUG 18 2014

TUESDAY NIGHT THROUGH WEDNESDAY NIGHT...
FORCING LIFTS NE OF THIS FORECAST AREA TUESDAY EVENING BUT DEEP
MOISTURE AND BOUNDARY INTERACTION SHOULD KEEP STORMS FIRING BEYOND
MIDNIGHT. WEDNESDAY THE WEST COAST TROUGH SETTLES NEAR SAN DIEGO.
SLIGHTLY DRIER AIR WORKS OVER UTAH. NO ORGANIZED DISTURBANCES SEEN
EJECTING OFF THE SOUTHERN CALIFORNIA LOW BUT MINOR WAVES WILL
LIKELY PROVIDE ADDITIONAL LIFT. STORM MOTION WILL BE TO THE ENE AT
20KTS AGAIN THREATENING GUSTY OUTFLOW WINDS. HEAVY RAIN POTENTIAL
DECREASES SOMEWHAT ON WEDNESDAY. THE MODELS END SHOWERS WEDNESDAY
EVENING. BUT PRECIP WATER VALUES REMAIN OVER 0.75 INCH OVER THE
SOUTHERN 2/3 OF THE CWA SO ISOLATED NOCTURNAL STORMS ARE
ANTICIPATED TO PERSIST THERE.

THURSDAY AND FRIDAY...
MODELS START OUT EARLY THURSDAY WITH CLOSED LOW CENTERED NEAR
SOUTHERN CA COAST...THEN THEY DIVERGE THEREAFTER. THE GFS MOVES
THE UPPER LOW INLAND THURSDAY AND INTO OUR CWA ON FRIDAY AS IT
COMES INTO PHASE WITH THE TROUGH TO THE NORTH. EC AND CANADIAN
MODELS WAIT TO MOVE THE UPPER LOW INLAND UNTIL FRIDAY AND SLOWLY
BRING IT UP TO THE FOUR CORNERS AREA BY SUNDAY. THE GFS SOLUTION
HAS ANOTHER SURGE OF MONSOONAL MOISTURE FOR OUR CWA ON THURSDAY
AND FRIDAY...WITH DRIER WESTERLY FLOW OVER THE WEEKEND. IN
CONTRAST...EC IS DRIER ON THURSDAY AND FRIDAY WITH THE MONSOONAL
MOISTURE FOR OUR CWA FRIDAY NIGHT INTO SUNDAY. NO SINGLE MODEL
SOLUTION PREFERRED AT THIS TIME...AND BELIEVE THE BROAD BRUSH
TREATMENT WITH SCATTERED SHOWERS AND THUNDERSTORMS IS THE BEST
FORECAST DURING THIS TIME PERIOD. MAX TEMPERATURES SHOULD
GENERALLY BE A LITTLE LOWER THAN NORMAL THROUGH THIS PERIOD DUE TO
CLOUDS AND SHOWERS...WHILE MIN TEMPERATURES LIKELY TO BE NEAR OR
A LITTLE ABOVE NORMAL DUE TO CLOUD COVER AND ELEVATED DEW POINT
TEMPERATURES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1108 AM MDT MON AUG 18 2014

A LINE OF -SHRA SOUTH OF KCAG BUT NORTH OF THE BOOKCLIFFS
CONTINUES TO MOVE EAST THROUGH THE AREA THANKS TO A WEAK WEATHER
DISTURBANCE ACROSS NORTHERN COLORADO. ISOLATED -RA/-TSRA WILL
INCREASE IN COVERAGE OVER THE MOUNTAINS AROUND 18Z. KEGE AND KASE
HAVE A SLIGHT CHANCE OF RECEIVING A SHOWER OR THUNDERSTORM TODAY.
MOISTURE WILL INCREASE AFTER 12Z TUESDAY MORNING FROM THE
SOUTHWEST AND INCREASE THE COVERAGE OF RAIN SHOWERS AND
THUNDERSTORMS BY 18Z TUESDAY.

&&

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

$$

UPDATE...JAM
SHORT TERM...JRP/JOE
LONG TERM...JOE/JRP
AVIATION...JAM


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