Winter Storm Watch 12, NWS Denver/Boulder, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
240 PM MST THU NOV 10 2011

SHORT TERM...MODERATE NORTHWEST FLOW ALOFT ACROSS COLORADO WITH
UPPER LEVEL RIDGE OVER GREAT BASIN. CURRENTLY SOME WIND GUSTS TO
40 MPH OVER THE HIGHER MOUNTAIN PASSES. MODELS SHOW RIDGE MOVING
EAST ACROSS WESTERN COLORADO OVERNIGHT...WITH FLOW ALOFT BECOMING A
BIT MORE WESTERLY. BOTH NAM AND RUC CROSS SECTIONS INDICATE A WEAK
MOUNTAIN WAVE DEVELOPING OVERNIGHT...WITH CROSS MOUNTAIN FLOW
INCREASING TO AROUND 35 KTS. MAY SEE SOME GUSTS REACHING 50 MPH OVER
THE HIGHER RIDGES OVERNIGHT WITH GUSTS TO 40 MPH ALONG THE
FOOTHILLS. WILL BOOST THE WIND GRIDS A BIT OVERNIGHT. AS FOR
PLAINS...SHOULD SEE SOME ENHANCED DRAINAGE FLOW NEAR FOOTHILLS
TONIGHT WITH LIGHT WINDS ELSEWHERE AS AIRMASS DECOUPLES. WRF
SYNTHETIC SATELLITE IMAGERY SUGGESTS AN INCREASE IN WAVE CLOUD ALONG
FOOTHILLS OVERNIGHT. MAY BE A BIT OVERDONE...BUT WILL ADD A BIT MORE
CLOUD TO THE GRIDS. ON FRIDAY...MODERATE WESTERLY FLOW ALOFT TO
PREVAIL ACROSS REGION AS RIDGE SHIFTS INTO EASTERN COLORADO. NAM
CROSS SECTIONS SHOW CROSS MOUNTAIN FLOW INCREASES TO AROUND 40 KTS
AT MOUNTAIN TOP BY THE AFTERNOON. WILL NEED TO INCREASE THE WINDS A
BIT FOR THE MOUNTAINS AND FOOTHILLS. CROSS SECTIONS SHOW GRADUAL
SOME INCREASE IN MID AND HIGH LEVEL MOISTURE THROUGH THE DAY. NO
PRECIPITATION THROUGH FRIDAY. MODELS HINT AT A SURFACE DENVER
CYCLONE DEVELOPING BY THE AFTERNOON...WITH WEAK EASTERLY WINDS
ACROSS THE DENVER AREA. WILL ADJUST WINDS ACCORDINGLY. FORECAST
SOUNDS AS WELL AS GUIDANCE INDICATING HIGHS IN THE MID 50S TO MID
60S ACROSS THE PLAINS. CURRENT TEMPERATURE GRIDS IN LINE WITH
GUIDANCE AND LOOK REASONABLE. LITTLE CHANGES NEEDED AT THIS POINT.
HUMIDITY WILL BE LOW ACROSS THE PLAINS FRIDAY AFTERNOON...BUT WINDS
SHOULD PRECLUDE ANY RED FLAG HILITE.

LONG TERM...MAIN CONCERN WILL BE THE HIGH WIND POTENTIAL OVER EAST
SLOPES AND FRONT RANGE FOOTHILLS THIS WEEKEND ALONG WITH SNOW
POTENTIAL FOR THE MOUNTAINS FOR BOTH SATURDAY AND SUNDAY. THE RIDGE
ALOFT WILL FLATTEN ON FRIDAY AS THE FLOW ALOFT BACKS AROUND MORE
WESTERLY. A VIGOROUS UPPER LEVEL TROF WHICH IS NOW OVER ALASKA WILL
SWEEP ACROSS THE NORTHERN ROCKY MOUNTAIN STATES ON SATURDAY.
WESTERLY WINDS WILL INCREASE SUBSTANTIALLY LATE FRIDAY NIGHT AND
SATURDAY ACROSS COLORADO. THIS APPEARS LIKE A GOOD SETUP FOR A HIGH
WIND EVENT OVER OUR EAST SLOPES AS CROSS BARRIER FLOW OFF THE LATEST
NAM INCREASES TO 60 TO 80KT ON THE HIGHER EAST SLOPES. THE 12Z NAM
EVEN SHOWED 100KT OF WEST FLOW AROUND 700MB. I DON'T BELIEVE I HAVE
EVER SEEN A NUMBER THAT HIGH. GIVEN THE IMPACT OF THIS EVENT OVER
ALASKA THIS MIGHT BE SOMETHING TO MONITOR CLOSELY. THE SHEAR AND
STABILITY PROFILE ALSO LOOK GOOD FROM MOUNTAIN WAVE AMPLIFICATION.
LOCAL SANGSTER WINDS ALSO SHOW AREA FLIRTING IN THE WATCH/WARNING
WINDOW FOR LATE FRIDAY NIGHT AND SATURDAY. WILL GO WITH A HIGH WIND
WATCH FOR THE FRONT RANGE FOOTHILLS AND ADJ PLAINS FOR LATE FRI NITE
AND SATURDAY. THE WINDS SHOULD DECREASE LATE SATURDAY AS COLD FRONT
SWEEPS ACROSS AS MTN TOP INVERSION LAYER GOES AWAY AND PRECIP
INCREASES ALONG AND WEST OF THE DIVIDE. THERE MAY BE A SECONDARY
WINDY PERIOD LATE SATURDAY NIGHT AND SUNDAY WITH STRONG MID LEVEL
WARMING OCCURRING BEHIND THE TROF. TO KEEP THINGS SIMPLE WILL JUST
WORRY ABOUT ONE EVENT AT A TIME.

AS FOR THE SNOW POTENTIAL...MOISTURE WILL INCREASE OVER THE
MOUNTAINS LATE FRIDAY NIGHT AND SATURDAY. THIS SHOULD MAKE FOR A
GOOD OROGRAPHIC SNOW EVENT WITH 700MB WINDS IN THE 35-45KT RANGE.
WINDS WILL INITIALLY FAVOR ZONES 31..33 AND THEN EFFECT ZONE 34 MORE
AS WINDS SHIFT MORE WESTERLY BY SAT AFTERNOON. MOISTURE CONTINUES
WELL INTO SUNDAY AFTERNOON. WILL THEN GO WITH A WINTER STORM WATCH
FOR ALL OUR MOUNTAIN ZONES OF 31..33..34 FOR THE WEEKEND. THERE WILL
BE BREAKS AT TIMES BUT WILL BE HARD TO PINPOINT EXACT TIMING.

FOR MUCH OF NEXT WEEK COLORADO WILL BE UNDER A STRONG NORTHWEST FLOW
PATTERN WITH WINDY PERIODS IN THE MOUNTAINS WITH A SLIGHT CHANCE OF
SNOW SHOWERS EACH DAY. ACROSS LOWER ELEVATIONS...IT WILL BE
GENERALLY DRY AND MILD WITH BREEZY CONDITIONS.

AVIATION...LIGHT SOUTH TO SOUTHWEST WINDS ACROSS AREA AIRPORTS...
WITH SOME GUSTS TO AROUND 15 KTS AT KAPA. SOUTHWEST WINDS TO
CONTINUE OVERNIGHT. SHOULD SEE SOME ENHANCED DRAINAGE WINDS BY 04Z
WITH SPEEDS AROUND 15 KTS. SOME INCREASE IN MAINLY HIGH LEVEL CLOUD
OVERNIGHT WITH VFR CONDITIONS CONTINUING. WEAK DENVER CYCLONE TO
DEVELOP BY 15Z...EXPECTED TO PERSIST THROUGH THE DAY. AS A
RESULT...WINDS TO HAVE AN EASTERLY DIRECTION WITH SPEEDS LESS THAT
10 KTS. EXCEPTION WILL BE AT KBJC WITH A WESTERLY COMPONENT
PREVAILING. VFR CONDITIONS TO PERSIST...WITH SOME MID AND HIGH LEVEL
CLOUDS.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...HIGH WIND WATCH FOR FRONT RANGE
FOOTHILLS AND ADJACENT WESTERN PLAINS FOR LATE FRI NIGHT
SATURDAY...ZONES 35..36..38..39.
.WINTER STORM WATCH...NORTHERN MOUNTAINS FOR SATURDAY THROUGH
SUNDAY...ZONES 31..33..34.
&&

SHORT TERM...D-L
LONG TERM....SWE
AVIATION...D-L

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1102 AM MST THU NOV 10 2011

COZ030>051-111300-
JACKSON COUNTY BELOW 9000 FEET-WEST JACKSON AND WEST GRAND
COUNTIES ABOVE 9000 FEET-GRAND AND SUMMIT COUNTIES BELOW 9000
FEET-SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/
NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET-SOUTH AND SOUTHEAST
GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/GILPIN/CLEAR CREEK/
SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET-LARIMER AND
BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET-JEFFERSON AND WEST
DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK
COUNTIES BELOW 9000 FEET-CENTRAL AND SOUTHEAST PARK COUNTY-LARIMER
COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY-BOULDER AND JEFFERSON
COUNTIES BELOW 6000 FEET/WEST BROOMFIELD COUNTY-NORTH DOUGLAS
COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE COUNTIES/
EAST BROOMFIELD COUNTY-ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES
ABOVE 6000 FEET-NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD
COUNTY-MORGAN COUNTY-CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES-
NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN
COUNTY-SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN
COUNTY-LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS
COUNTY-
1102 AM MST THU NOV 10 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL
COLORADO.

.DAY ONE...TODAY AND TONIGHT

HIGH PRESSURE WILL REMAIN ACROSS THE REGION WITH MODERATE WEST TO
NORTHWEST FLOW ALOFT. WEST WINDS OF 15 TO 25 MPH WITH SOME GUSTS TO
35 MPH WILL CONTINUE ACROSS THE MOUNTAINS AND FOOTHILLS THROUGH
TONIGHT...WITH SOME GUSTS TO 50 MPH POSSIBLE AFTER MIDNIGHT.
TEMPERATURES WILL BE SLIGHTLY ABOVE NORMAL.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A PACIFIC STORM SYSTEM WILL BRING ANOTHER ROUND OF SNOW TO THE
MOUNTAINS AND HIGH VALLEYS SATURDAY AND SUNDAY. FOR THE FRONT RANGE
FOOTHILLS AND ADJACENT PLAINS...STRONG WINDS ARE POSSIBLE LATE
FRIDAY NIGHT AND SATURDAY. A NORTHWEST FLOW OVER THE REGION MAY
PRODUCE SNOW SHOWERS IN THE MOUNTAINS INTO EARLY NEXT WEEK. GUSTY
WINDS WILL CONTINUE ALONG THE FOOTHILLS THROUGH WEDNESDAY WITH
STRONG WINDS POSSIBLE AGAIN EARLY NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.

D-L/SWE