Flash Flooding and Heavy Rain in Colorado, July 15, 2013

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1032 AM MDT MON JUL 15 2013

.SHORT TERM...(TODAY THROUGH TUESDAY)
ISSUED AT 425 AM MDT MON JUL 15 2013

ANOMALOUS CLOSED UPPER LOW OVER OKLAHOMA WILL BE TRACKING WESTWARD
TODAY AND WILL BRING SIGNIFICANT RAINS TO SOUTHWEST COLORADO.
DEFORMATION AXIS WITH DEEP MOISTURE THAT MOVES ACROSS WRN COLORADO
THIS AFTERNOON AND EVENING. THIS IS A SLOW MOVING SYSTEM AND
BRINGS THE THREAT OF LOCAL FLOODING TO SW COLORADO. MOISTURE
TRANSPORT VECTORS STRENGTHENS AS THE DAY PROGRESSES AND EXTENDS
FARTHER NORTH...SUGGESTING THAT THERE COULD BE BACK BUILDING
CELLS. GIVEN THE DEEP MOISTURE WITH THE GFS 700 MB SPECIFIC
HUMIDITY SHOWING 12 G/KG OVER THE SAN JUAN MOUNTAINS...CLOUD TOP
TEMPS WILL BE AROUND -65C OR COLDER. THE BULLSEYE PRECIPITATION
MAXIMA (GREATER THAN 1.00") APPEARS TO BE CENTERED OVER LA PLATA
COUNTY...BUT COVERS MESA VERDE NATIONAL PARK AND ARCHULETA COUNTY.
WILL EXPAND AND EXTEND THE FLASH FLOOD WATCH TO COVER THE ENTIRE
SOUTHWEST COLORADO CORNER THROUGH MIDNIGHT. THE DEFORMATION ZONE
WEAKENS LATE TONIGHT AND PUSHES FARTHER WESTWARD...WITH THE DRY
SLOT WORKING INTO SW COLORADO.

THE NRN EXTENT OF THE DEEP MOISTURE PLUME COULD AFFECT THE ELK AND
WEST ELK MOUNTAINS...BUT THE WIDTH OF THE PLUME IS SMALLER WHICH
WILL YIELD LOWER RAINFALL AMOUNTS. ON THE WRN EDGE OF THE
DEFORMATION AXIS SHOULD BE PLENTY OF LIGHTNING THAT AFFECTS THE
NORTHWEST COLORADO CORNER. THE ONLY SPOT THAT MIGHT ESCAPE ANY
CONVECTIVE ACTIVITY THIS AFTERNOON IS THE UINTA BASIN.

COLLIDING OUTFLOW BOUNDARIES AND SOME DYNAMIC SUPPORT/UPPER
DIVERGENCE OVER A TIGHT 700 MB THETA-E GRADIENT SHOULD SUSTAIN
SCATTERED SHOWERS AND THUNDERSTORMS ACROSS MUCH OF THE SOUTH
BEYOND MIDNIGHT.

MOISTURE WILL REMAIN PLENTIFUL AT THE SURFACE AND LOWER LEVELS ON
TUESDAY. AS THE UPPER LOW TRACKS SOUTHWEST ACROSS NM...SOME MID-
LEVEL DRYING AT 500 MB INDICATED AS A DRY SLOT WRAPS IN FROM THE
NORTHEAST IN THE COUNTERCLOCKWISE FLOW AROUND THE LOW. MAY NOT
HAVE AS GREAT OF COVERAGE ON TUE BUT STORMS MIGHT BE A LITTLE
STRONGER INITIALLY BECAUSE OF THIS. WEAK VERTICAL SHEAR OVER MOST
OF THE AREA NOT THAT FAVORABLE FOR LONG-LIVED STORMS...HOWEVER.

.LONG TERM...(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 425 AM MDT MON JUL 15 2013

WEDNESDAY...THE UPPER LOW IS EXPECTED TO TRACK FROM NEW MEXICO
INTO NW OLD MEXICO. MOISTURE PERSISTS AND DAYTIME
HEATING/INSTABILITY COMBINED WITH ANY WEAK DISTURBANCE SHOULD
BRING ANOTHER ROUND OF AFTERNOON SHOWERS AND THUNDERSTORMS.
COVERAGE WILL FAVOR THE MOUNTAINS AND THE CENTRAL AND SOUTHERN
VALLEYS.

THURSDAY THROUGH SUNDAY...THE ANOMALOUS CLOSED LOW COULD INDIRECTLY
AFFECT THE ENTIRE THE LONG TERM PERIOD AS THE MODELS HINT THAT
SMALLER SCALE FEATURES AND THE POSITIONING OF THE DEFORMATION AXIS
WITH THE MAIN WESTERLIES WILL KEEP THE AIR MASS MOIST AND
CONDITIONALLY UNSTABLE...MOST NOTABLY ACROSS THE SOUTH. THE MEDIUM
RANGE MODELS TRY TO ADVECT DRIER AIR INTO NE UTAH/NW COLORADO NEXT
WEEKEND...BUT THIS DEVELOPMENT DEPENDS ON THE POSITIONING OF THE
CLOSED UPPER LOW. SO WHILE THE TYPICAL MONSOONAL PATTERN IS
DISRUPTED...THERE STILL EXISTS A SOURCE OF MOISTURE TO FEED
CONVECTIVE STORMS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1032 AM MDT MON JUL 15 2013

WIDESPREAD MVFR/IFR CONDITIONS WILL DEVELOP ACROSS SOUTHWEST
COLORADO STARTING EARLY THIS AFTERNOON AND LASTING THROUGH 06Z
TONIGHT FROM +SHRA/+TSRA...POSSIBLY EXTENDING AS FAR NORTH AS
KASE. CONDITIONS WILL IMPROVE BEYOND 06Z...BUT ISOLATED MVFR/IFR
CIGS/VSBY WILL BE POSSIBLE IN RAIN SHOWERS AND LOCALIZED FOG.

WEST OF A LINE FROM KHDN-KCEZ...EXPECT SCATTERED -TSRA WITH GUSTY
WINDS THIS AFTERNOON AND EARLY EVENING BUT VFR WILL PREVAIL. BRIEF
MVFR CONDITIONS MAY ACCOMPANY THUNDERSTORMS.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...FLASH FLOOD WATCH THROUGH THIS EVENING FOR COZ018-019-021>023.

UT...NONE.

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
633 AM MDT MON JUL 15 2013

COZ001>014-017>023-UTZ022>025-027>029-161300-
LOWER YAMPA RIVER BASIN-CENTRAL YAMPA RIVER BASIN-
ROAN AND TAVAPUTS PLATEAUS-ELKHEAD AND PARK MOUNTAINS-
UPPER YAMPA RIVER BASIN-GRAND VALLEY-DEBEQUE TO SILT CORRIDOR-
CENTRAL COLORADO RIVER BASIN-GRAND AND BATTLEMENT MESAS-
GORE AND ELK MOUNTAINS/CENTRAL MOUNTAIN VALLEYS-
CENTRAL GUNNISON AND UNCOMPAHGRE RIVER BASIN-
WEST ELK AND SAWATCH MOUNTAINS-FLATTOPS-
UPPER GUNNISON RIVER VALLEY-UNCOMPAHGRE PLATEAU AND DALLAS DIVIDE-
NORTHWEST SAN JUAN MOUNTAINS-SOUTHWEST SAN JUAN MOUNTAINS-
PARADOX VALLEY/LOWER DOLORES RIVER-
FOUR CORNERS/UPPER DOLORES RIVER-ANIMAS RIVER BASIN-
SAN JUAN RIVER BASIN-SOUTHEAST UTAH-EASTERN UINTA MOUNTAINS-
EASTERN UINTA BASIN-TAVAPUTS PLATEAU-ARCHES/GRAND FLAT-
LA SAL AND ABAJO MOUNTAINS-CANYONLANDS/NATURAL BRIDGES-
633 AM MDT MON JUL 15 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EASTERN UTAH AND WESTERN
COLORADO.

.DAY ONE...TODAY AND TONIGHT

AREAS OF HEAVY RAIN SHOWERS WILL BE POSSIBLE OVER SOUTHWEST
COLORADO...WHERE A FLASH FLOOD WATCH IS IN EFFECT FROM NOON
THROUGH MIDNIGHT. SOME AREAS IN THE WATCH AREA MAY EXCEED 1.00
INCH OF RAIN BY LATE TONIGHT. RECENT BURN SCARS WILL BE VULNERABLE
TO FLASH FLOODING.

OUTSIDE OF THE FLASH FLOOD WATCH AREA...SCATTERED SHOWERS AND
THUNDERSTORMS CONTINUES TO BE THE PRIMARY WEATHER HAZARD. BRIEF
MODERATE TO HEAVY RAIN SHOWERS AND GUSTY WINDS WILL ACCOMPANY
STORMS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

SCATTERED SHOWERS AND THUNDERSTORMS...MORE NUMEROUS IN THE
MOUNTAINS...ARE EXPECTED EACH AFTERNOON AND EVENING. LOCAL HEAVY
SHOWERS ARE POSSIBLE WITH PASSING STORMS. DRIER AIR MAY FILTER
INTO THE REGION ON SATURDAY FOR A LESSER THREAT OF SHOWERS AND
THUNDERSTORMS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED...HOWEVER SPOTTERS ARE
ENCOURAGED TO RELAY RAINFALL AMOUNTS OR ANY OBSERVED FLOODING TO
THE GRAND JUNCTION FORECAST OFFICE.