Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 042243
AFDGJT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
443 PM MDT MON MAY 4 2015

.SHORT TERM...(TONIGHT THROUGH TUESDAY NIGHT)
ISSUED AT 250 PM MDT MON MAY 4 2015

SHOWERS AND THUNDERSTORMS WILL DECREASE IN COVERAGE AFTER SUNSET
THIS EVENING IN NE UTAH AND NW COLORADO...BUT WILL CONTINUE
THROUGH THE OVERNIGHT HOURS ACROSS THE SOUTH TONIGHT WITH
UNSTABLE AND MOIST SOUTHERLY FLOW IN PLACE. SHORT TERM MODELS
INDICATE A SLIGHT BREAK JUST BEFORE MIDNIGHT ACROSS THE REGION BUT
PRECIPITATION INCREASING IN THE VALLEYS OF SE UTAH AND SW COLORADO
JUST AFTER MIDNIGHT ASSOCIATED WITH AN APPROACHING UPPER LEVEL
LOW. THIS LOW PRESSURE SYSTEM IS EXPECTED TO REACH THE FOUR
CORNERS AROUND DAYBREAK ON TUESDAY.

A SIGNIFICANT WET PERIOD IS IN STORE FOR TUESDAY THROUGH
WEDNESDAY. THERE IS GOOD MODEL AGREEMENT FOR NEAR RECORD MOISTURE
AVAILABLE...WITH PRECIPITABLE WATER VALUES UP IN THE LATEST RUNS
TO NEAR 0.90 INCHES ON TUESDAY. A MILD PACIFIC LOW LIFTS FROM THE
FOUR CORNERS TUESDAY MORNING ALONG THE COLORADO SPINE THROUGH THE
EVENING. THERE IS ALSO GOOD AGREEMENT WITH ONLY MARGINAL
INSTABILITY. 700-500MB LAPSE RATES RANGE FROM 6 TO 7 C/KM W-E
ACROSS THE SOUTH TUESDAY AFTERNOON WITH CAPE VALUES REACHING 800
J/KG OVER THE CENTRAL MTNS IN THE AFTERNOON.

THE MODELS DIFFER WITH LOCATION AND STRENGTH OF THE FORCING WITH
THE PASSING LOW. THE NAM PRODUCES STRONGER FORCING. IT HAS 70KT
JET SUPPORT IN THE PAGOSA SPRINGS AREA TUESDAY MORNING THEN UPPER
DIVERGENCE LIFTING ALONG THE CO SPINE THROUGH THE AFTERNOON AND
OVERNIGHT. WIDESPREAD SHOWERS WILL DEVELOP THROUGH THE MORNING
ACROSS THE SOUTH SPREADING INTO THE CENTRAL-NORTHERN MOUNTAINS
THROUGH THE AFTERNOON AND CONTINUING OVERNIGHT. THOUGH NEARLY ALL
AREAS WILL SEE RAINFALL...THE COLORADO ZONES FROM MONARCH PASS
NORTHWARD COULD SEE PERIODS OF HEAVY RAIN SHOWERS TUESDAY
AFTERNOON THROUGH WEDNESDAY AFTERNOON AND NEED TO BE WATCHED FOR
POTENTIAL RUNOFF PROBLEMS. THE LIGHTEST RAINFALL IS EXPECTED IN
THE UINTA BASIN.

SNOW LEVELS WILL BE WELL ABOVE TIMBERLINE ON TUESDAY THEN LOWER
TO AROUND 9000FT ALONG THE CONTINENTAL DIVIDE OVERNIGHT. DAYTIME
TEMPERATURES WILL BE BELOW NORMAL WITH THE OVERNIGHT LOWS MILD.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 250 PM MDT MON MAY 4 2015

WEDNESDAY THE LOW TRACKS TO THE ENE OF THE FORECAST AREA. SOME
WEAK SHEARED VORTICITY AND A DIVERGENCE/CONVERGENCE COUPLET
REMAINS STRETCHED ACROSS THE CENTRAL FORECAST AREA THROUGH THE DAY
CONCENTRATING SHOWERS THERE. MOISTURE DIMINISHES SHARPLY WEDNESDAY
NIGHT THOUGH HIGHER TERRAIN SHOWERS MAY LINGER OVERNIGHT AND
THROUGH THURSDAY IN SW FLOW. BREEZY CONDITIONS EXPECTED THROUGH
THE AFTERNOON. TEMPERATURES REBOUND TO NEAR NORMAL.

BY FRIDAY THE NEXT COLDER PACIFIC LOW IS PROGRESSING INTO THE
GREAT BASIN PRODUCING DIVERGENT FLOW ALOFT. MOISTURE REMAINS
LIMITED THOUGH. THERE IS CONTINUED GOOD MODEL AGREEMENT TRACKING
THE UPPER LOW AND ITS COLD FRONT THROUGH THE FORECAST AREA ON
SATURDAY. WRAP-AROUND SHOWERS CONTINUE ON SUNDAY OVER NE UTAH AND
THE CO MTNS. TEMPERATURES WILL BE WELL BELOW NORMAL WITH NEAR
FREEZING LOW TEMPERATURES POSSIBLE ACROSS THE NORTHERN VALLEYS
SATURDAY NIGHT AND SUNDAY NIGHT.

A RIDGE BUILDS IN FROM THE WEST ON MONDAY GIVING US A SHORT
REPRIEVE FROM SHOWERS. ANOTHER PACIFIC TROUGH THREATENS SHOWERS
BY MID WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 443 PM MDT MON MAY 4 2015

AN ACTIVE WEATHER DAY HAS DEVELOPED ACROSS THE AREA WITH SHOWERS
AND THUNDERSTORMS MOVING FROM SOUTH TO NORTH. OUTFLOW WINDS TO 40
MPH ARE POSSIBLE NEAR SHOWERS AND THUNDERSTORMS UNTIL ABOUT 05Z
THIS EVENING. TAF SITES WILL MOSTLY REMAIN AT VFR. HOWEVER MVFR
CONDITIONS ARE POSSIBLE IN A PASSING SHOWER THROUGH LATE THIS
EVENING...ESPECIALLY AT THE MOUNTAIN TAF SITES. THOUGH SHOWERS
WILL TAPER OFF AFTER 02Z...THE BREAK WILL BE SHORT-LIVED BEFORE
ADDITIONAL MOISTURE MOVES INTO SOUTHWEST COLORADO IN THE LATE
TONIGHT/EARLY TUESDAY MORNING. SHOWERS AND THUNDERSTORMS WILL THEN
INCREASE AND SPREAD NORTH THROUGHOUT THE DAY. MOUNTAINS AT TIMES
WILL BE OBSCURED IN SHOWERS AND LOW CLOUDS.

&&

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

$$

SHORT TERM...JAM/JOE
LONG TERM...JOE
AVIATION...EH



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