000
FXUS65 KBOU 221037
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
336 AM MST FRI JAN 22 2010
.SHORT TERM...STG SSW FLOW ALOFT WILL BE OVER THE AREA AS AN UPPER
LEVEL TROUGH MOVES ACROSS THE AREA. DESPITE FAVORABLE UPPER LEVEL
DIVERGENCE...MID LVL QG ASCENT AND DECENT LAPSE RATES UNFAVORABLE
OROGRAPHIC COMPONENT IS KEEPING ANY SNOW IN THE MTNS ON THE LIGHT
SIDE WHICH WILL BE THE CASE THRU THE AFTN HOURS. OVER LOWER
ELEVATIONS MAY SEE A FEW LIGHT -SHRA/-SHSN OVER THE PLAINS THIS
MORNING WITH A SLIGHT CHC OF -SHRA THIS AFTN. MEANWHILE AREAS OF
LOW CLOUDS AND FOG ARE DEVELOPING ALONG THE CO-WY-NE BORDER AS A SFC
LOW FORMS NEAR DENVER. ITS POSSIBLE LOW CLOUDS MAY EVENTUALLY WRAP
AROUND MAIN SFC LOW AND INTO NRN AND WRN AREAS OF THE URBAN CORRIDOR
BY SUNRISE. HIGHS TODAY WILL DEPEND ON HOW FAST MID AND HIGH LVL
CLOUD SHIELD MOVE OUT OF THE AREA. IF CLOUD COVER BREAKS UP BY AFTN
WITH SWLY DOWNSLOPE FLOW IN PLACE ALONG THE FRONT RANGE TEMPS COULD
REACH THE LOWER 50S FROM DENVER SE TOWARDS LIMON WITH MAINLY 40S
ESLEWHERE.
FOR TONIGHT THE FLOW ALOFT WILL BECOME MORE WLY IN THE MTNS WHICH
WILL IMPROVE OROGRAPHICS SO MAY SEE A BETTER CHC OF SNOW OVERNIGHT.
OVER NERN CO IT SHOULD BE DRY WITH ONLY A SLIGHT CHC OF -SHRA/-SHSN
OVER THE FAR NERN CORNER EARLY IN THE EVENING.
.LONG TERM...MODELS HAVE A BROAD UPPER TROUGH AXIS PUSHING ACROSS
THE FORECAST AREA ON SATURDAY WITH WEAK WEST-SOUTHWESTERLY FLOW
ALOFT. THE TROUGH AXIS MOVES ACROSS BY EARLY SATURDAY EVENING AND
THERE IS SLIGHTLY STRONGER NORTHWESTERLY FLOW ALOFT PROGGED FOR
SATURDAY NIGHT AND SUNDAY. ON SUNDAY NIGHT...STRONGER NORTH-
NORTHWESTERLY FLOW ALOFT IS PROGGED OVER THE FORECAST AREA...WITH
THE GFS SHOWING A 130 KNOT JET MAXIMUM. THE NAM DOES NOT HAVE THIS
JET MAXIMUM. DOWNWARD SYNOPTIC SCALE MOTION IS PROGGED FOR THE
FORECAST AREA SATURDAY THROUGH SUNDAY NIGHT. THE BOUNDARY LAYER
FLOW IS ALL DOWNSLOPING SATURDAY THROUGH SUNDAY NIGHT...MAINLY
NORTHWESTERLY IN DIRECTION. ON SUNDAY ...THE NORTHWESTERLY WINDS
LOOK PRETTY STRONG...ESPECIALLY OVER THE EASTERN HALF OF THE
PLAINS. ON SATURDAY...THE PLAINS ARE PRETTY DRY...JUST SOME MID AND
UPPER LEVEL MOISTURE HERE AND THERE...THE MOUNTAINS HAVE DEEP
MOISTURE. IN FACT...DEEP MOISTURE IS PROGGED OVER THE MOUNTAINS
SATURDAY NIGHT AND MUCH OF SUNDAY...BEFORE GRADUALLY DRYING OUT LATE
IN THE DAY THROUGH SUNDAY NIGHT. THE GFS DRIES THE MOUNTAINS OUT
QUICKER THAN THE NAM. OVER THE PLAINS SATURDAY NIGHT THROUGH SUNDAY
NIGHT...THERE IS PLENTY OF MID AND UPPER LEVEL MOISTURE OVER THE
EASTERN HALF...WITH STRONG DOWNSLOPING-DRYING OVER THE WESTERN
PLAINS. THE MOISTURE GETS INTO THE LOWER LEVELS OVER THE EASTERN
PLAINS SUNDAY AFTERNOON AND EVENING ON THE NAM ONLY. THE QPF FIELDS
HAVE SOME MEASURABLE SNOW FOR THE MOUNTAINS SATURDAY THROUGH SUNDAY
NIGHT. THERE IS A TAD OVER THE EASTERN PLAINS SATURDAY NIGHT
ONLY. FOR MOUNTAIN POPS...OROGRAPHIC ENHANCEMENT LOOKS OK WITH THE
PROGGED MOUNTAIN TOP WINDS...LAPSE RATES ARE FAIRLY STEP...AND THERE
IS DECENT MOISTURE. NO UPWARD MOTION HOWEVER. WILL GO "LIKELY"S
SATURDAY THROUGH SUNDAY...THEN DECREASE THE POPS SUNDAY NIGHT. THE
SNOW MODEL YIELDS UP TO 12 INCHES OVER ZONES 31 AND 34...WITH
SOMEWHAT LESS FOR ZONE 33. THIS IS OVER THE 36 HOUR PERIOD
HOWEVER...SO NO HIGHLIGHTS. FOR THE PLAINS...WILL GO MINIMAL POPS
FOR THE NORTHEAST ONLY SATURDAY NIGHT AND SUNDAY...NO POPS FOR THE
REST OF THE PLAINS. CONCERNING TEMPERATURES...SATURDAY'S HIGHS ARE
2-4 C COLDER THAN TODAY'S. SUNDAY'S HIGHS ARE 2-4 C COLDER THAN
SATURDAY'S. FOR THE LATER DAYS...MONDAY THROUGH THURSDAY...MODELS
HAVE AN UPPER RIDGE MOVING IN AND ACROSS THE FORECAST AREA MONDAY
INTO EARLY WEDNESDAY. A WEAK UPPER TROUGH IS PROGGED TO MOVE INTO
THE FORECAST AREA WEDNESDAY EVENING THROUGH THURSDAY. AGAIN...THE
GFS INDICATES VERY DEEP MOISTURE OVER ALL THE FORECAST AREA FROM
TUESDAY NIGHT THROUGH THURSDAY. THE ECMWF HAS SIGNIFICANTLY LESS
MOISTURE WITH THIS WEAK UPPER TROUGH. WE'LL SEE...WILL CHANGE
LITTLE THIS UPDATE.
&&
.AVIATION...MAIN CONCERN THIS MORNING WILL BE IF LOW CLOUDS AND
PATHCY FOG WILL WRAP AROUND MAIN SFC LOW AND AFFECT THE AIRPORT IN
THE 12Z-15Z TIMEFRAME. NAM SHOWS THIS COULD HAPPEN WHILE LATEST RUN
OF THE RUC SAYS IT WILL NOT. OVERALL CONFIDENCE IS NOT HIGH WITH
EITHER SCENARIO SO MAY MENTION A TEMPO GROUP FOR LOW CLOUDS IN THE
12Z-15Z PERIOD JUST IN CASE. WINDS THIS MORNING WILL BE SSE AT
10-15 MPH AND THEN BECOME MORE SSW BY 18Z WITH SPEEDS IN THE 10-20
MPH RANGE AND THEN MORE WLY BY 21Z OR 22Z. AFTER 01Z WINDS WILL
BECOME MORE SSW.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...NONE.
$$
RPK/RJK
