Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 020552
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1152 PM MDT SAT AUG 1 2015

.SHORT TERM...(TONIGHT THROUGH SUNDAY NIGHT)
ISSUED AT 300 PM MDT SAT AUG 1 2015

MOISTURE CONTINUES TO STREAM NORTHWARD ACROSS OUR SOUTHERN BORDER
WITH AZ AND NM AS HIGH PRESSURE REMAINS ANCHORED OVER THE
INTERMOUNTAIN REGION. THIS MORNING`S KGJT 12Z SOUNDING REPORTED
0.9 INCH PRECIPITABLE WATER (PW). THIS WAS UP SHARPLY COMPARED TO
YESTERDAY. SO BETTER MOISTURE HAS MADE IT INTO THE CENTRAL PORTION
OF THE FORECAST AREA AS ADVERTISED BY MODELS. SHOWERS AND
THUNDERSTORMS STILL FAVOR THE SOUTHERN THIRD AS EXPECTED...BUT BY
2 PM CONVECTION HAD DEVELOPED AS FAR NORTH AS THE
TAVAPUTS/FLATTOPS. EXPECT THIS WILL GENERALLY BE THE NORTHERN
LIMIT FOR THIS DIURNAL CYCLE. BUT MORE EXCITEMENT IS IN STORE FOR
SUNDAY.

CONVECTION WILL CONTINUE TO INCREASE AND SPREAD ACROSS THE
SOUTHERN 2/3RDS OF THE FORECAST AREA LATE THIS AFTERNOON AND EARLY
THIS EVENING BEFORE GRADUALLY WINDING DOWN ONCE DAYTIME HEATING
FADES. EVEN SO...EXPECT SHOWERS AND A FEW THUNDERSTORMS WILL
CONTINUE OVERNIGHT AS STRIP OF HIGHER VORTICITY STAYS STRETCHED
ALONG OUR SOUTHERN EDGE. THEREFORE THE REMAINING ACTIVITY WILL
AGAIN FOCUS MORE OVER THE SOUTHERN THIRD TOWARDS MORNING.

SUNDAY STILL ON TRACK TO BE A FAIRLY ACTIVE DAY WITH THE DEEPEST
MOISTURE SEEN THIS WEEK MOVING OVER THE REGION. PRECIPITATION WILL
BE AIDED BY A SLOW MOVING SHORTWAVE DISTURBANCE THAT WILL
STRENGTHEN NEAR THE FOUR CORNERS SUNDAY MORNING AND LIFT NORTHWARD
THROUGH THE SOUTHERN AND CENTRAL CWA BEFORE REACHING THE I-70
CORRIDOR SUNDAY NIGHT. WARM CLOUD DEPTH IS MODEST WITH VALUES OF
2000-3000 METERS SUNDAY MORNING SO PRECIPITATION WILL BE DOMINATED
BY WARM CLOUD PROCESSES. PRECIPITABLE WATER VALUES OF AN INCH
EXTEND TOWARDS THE CO-WY BORDER WITH UP TO 1.3 INCHES NEAR THE
FOUR CORNERS. STORM MOTION WILL BE SLOW WITH LIGHT STEERING FLOW
AND WEAK SHEAR OF 5 TO 10 KTS. SO EXPECTING BRIEF PERIODS OF
MODERATE TO HEAVY RAIN WITH STORMS THAT FORM AND LIGHT TO MODERATE
RAIN UNDER THE STEADY SHOWERS AS THEY SLOWLY TRACK ACROSS THE
AREA.

THE MAIN CONCERN IS THAT THERE MAY BE TOO MUCH CLOUD COVER SUNDAY
MORNING GIVEN THE AMOUNT OF MOISTURE AND SLOW MOVING NATURE AND
TIMING OF THE SHORTWAVE...WHICH MAY LIMIT SURFACE HEATING AND
CONVECTIVE POTENTIAL WITH STRATIFORM-LIKE PRECIPITATION
CONTINUING THROUGH THE MORNING HOURS ACROSS THE SOUTHERN CWA.
AS THE SHORTWAVE SLOWLY LIFTS NORTHWARD...SHOWERS WILL LIKELY
PROGRESS NORTHWARD INTO THE SOUTHERN AND CENTRAL PORTIONS OF THE
CWA SUNDAY AFTERNOON AND EVENING WITH SOME CONVECTIVE DEVELOPMENT
AND EMBEDDED THUNDERSTORMS. THE SHORTWAVE AND 45KT JET STREAK
MOVING INTO SW COLORADO WILL HELP AID IN LIFT. IF THERE ARE ANY
BREAKS IN THE CLOUD COVER...SURFACE HEATING MAY ENHANCE CONVECTION
BUT AM THINKING THAT THIS WILL BE LIMITED AND TEMPERATURES WILL BE
COOLER AS A RESULT. SOME LOCALIZED FLOODING IS POSSIBLE IN SOME
AREAS GIVEN THE AMT OF MOISTURE AND SLOW STORM MOTION BUT DUE TO
LIMITED CONVECTIVE POTENTIAL AND EXTENSIVE CLOUD
COVER...WIDESPREAD FLOODING IS NOT EXPECTED SO DECIDED NOT TO
ISSUE A WATCH AT THIS TIME. WILL LET THE EVENING SHIFT REASSESS
WITH THE LATEST MODEL RUNS.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 300 PM MDT SAT AUG 1 2015

MONDAY...THE SHORTWAVE DISTURBANCE WILL CONTINUE TO LIFT NORTHWARD
WITH THE FOCUS FOR PRECIPITATION BEING CENTRAL AND NORTHERN PORTIONS
OF NORTHWEST COLORADO. SHOWERS WILL CONTINUE THROUGH THE MORNING
BEFORE ACTIVITY PICKS UP DURING THE AFTERNOON FOR NW COLORADO. NW
COLORADO WILL BE IN THE FAVORED LEFT EXIT REGION OF A 45 KT UPPER
LEVEL JET WITH DRIER AIR PUNCHING IN BEHIND IT INTO NE UTAH. THE
STEERING FLOW IS BETTER THAN SUNDAY WITH 7H WINDS OF 20 TO 25 KTS
FROM THE SOUTHWEST AND 5H WINDS OF 30 TO 40 KTS FROM THE WEST. PW
VALUES BETWEEN 0.75 INCHES AND 1 INCH WILL REMAIN NORTH OF I-70.
STORMS WILL HAVE BETTER MOTION AND BETTER CHANCE OF SUSTAINING
UPDRAFTS WITH THE STRONGEST STORMS ANTICIPATED ON THE BOUNDARY
BETWEEN THE DRY AND MOIST AIR. SOME BRIEF HEAVY RAINERS WITH SOME
GUSTY OUTFLOW WINDS ARE EXPECTED WITH STORMS ON MONDAY. ACTIVITY IS
EXPECTED TO WIND DOWN AFTER SUNSET AS THE SHORTWAVE AND JET LIFT OUT
OF THE REGION TAKING THE MOISTURE WITH IT AND DRIER AIR MOVES IN
FROM THE WEST FOR A FAIRLY CLEAR MONDAY NIGHT.

TUESDAY THROUGH SATURDAY...THE RIDGE OF HIGH PRESSURE BUILDS BACK
OVER ARIZONA AND NEW MEXICO SHUTTING OFF THE MOISTURE TAP INTO THE
FOUR CORNERS REGION. A DRIER PERIOD IS IN STORE FOR MUCH OF NEXT WEEK
WITH SOME AFTERNOON CONVECTION POSSIBLE OVER THE HIGHER TERRAIN
GIVEN LINGERING MOISTURE. A SHORTWAVE SKIRTS ACROSS THE NORTHERN
BORDER OF OUR CWA ON THURSDAY BUT APPEARS TOO WEAK AND DRY TO
PRODUCE ANY SHOWERS. MONSOONAL MOISTURE LOOKS TO RETURN TO THE
AREA NEXT SATURDAY BUT LOW CONFIDENCE ON THE TIMING OF THIS RETURN
AS EACH MODEL RUN APPEARS TO PUSH THE TIMING AHEAD BY 12 TO 24
HOURS. SO WILL TAKE THE WAIT AND SEE APPROACH.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1152 PM MDT SAT AUG 1 2015

SCATTERED -SHRA WITH EMBEDDED TSRA WILL CONTINUE OVERNIGHT OVER SW
COLORADO. SOME NOCTURNAL STORMS WILL SPILL INTO SE UTAH. SHOWERS
AND STORMS WILL EXPAND ACROSS THE ENTIRE REGION ON SUNDAY
AFTERNOON...SHOWERS BECOMING NUMEROUS SOUTH OF I-70. THE STRONGEST
CELLS WILL PRODUCE 4SM +TSRA CIGS BKN030. ILS CIGS AND OBSCURATIONS
WILL BE COMMON AT MOUNTAIN TAF SITES AS SHOWERS/STORMS MOVE OVERHEAD.
SHOWERS WILL CONTINUE INTO SUNDAY EVENING. WITH SHORT WAVE PASSING
THROUGH UTAH AND COLORADO ON SUNDAY...CONVECTIVE CELLS WILL BE
LONGER LIVED AND MERGERS MAY OCCUR TO ENHANCE +SHRA WITH FREQUENT
LIGHTNING.

&&

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

$$

SHORT TERM...EH/MDA
LONG TERM...MDA
AVIATION...PF



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