FXUS65 KBOU 040919
AFDBOU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
220 AM MST FRI DEC 04 2009
.SHORT TERM...GENERALLY DRY NW FLOW ALOFT WILL BE OVER THE AREA THRU
TONIGHT. MEANWHILE SFC HIGH PRESSURE WILL WEAKEN AS LEE TROUGH
BEGINS TO DVLP ALONG THE FOOTHILLS. THIS WILL ALLOW FOR DOWNSLOPE
LOW LVL FLOW TO DVLP TODAY SO SHOULD SEE SOME MODERATION OF
TEMPERATURES OVER NERN CO. 700 MB TEMPS ARE FCST TO WRM AROUND 10
DEGREES C SO SO SHOULD SEE AFTN HIGHS REACH INTO THE LOWER 30S WITH
MID TO UPPER 30S POSSIBLE CLOSER TO THE FOOTHILLS. FOR LATER THIS
AFTN AND TONIGHT WILL BEGIN TO SEE A WEAK MTN WAVE DVLP AS COMPONENT
ALONG FLOW INCREASES TO AROUND 30KTS. THUS WILL SEE AN INCREASE IN
WND IN THE MTNS AND FOOTHILLS HOWEVER SPEEDS WILL STAY BLO HIGH WIND
CRITERIA. IN ADDITION THIS SHOULD ALLOW FOR WARMER OVERNIGHT LOWS
ESPECIALLY IN AND NR THE FOOTHILLS.
.LONG TERM...SATURDAY WILL BE A DAY OF TRANSITION AS THE START OF
THE DAY WILL FEATURE THE FLOW ALOFT INCREASING FROM THE
WEST/SOUTHWEST IN THE MORNING...RESULTING IN SOME STRONG DOWNSLOPE
WEST WINDS OVER THE MOUNTAINS AND FOOTHILLS. EXPECT SOME GUSTS IN
THE 50-60KT RANGE OVER THE MOUNTAINS...BUT THIS DOES NOT LOOK LIKE A
HIGH WIND EVENT WITH A LACK OF STRONG MOUNTAIN TOP STABILITY. THIS
WESTERLY FLOW IS IN RESPONSE TO AN UPPER LEVEL TROF WHICH IS DIGGING
ACROSS THE NRN ROCKY MOUNTAIN REGION. THIS TROF WILL SEND AN
ASSOCIATED COLD FRONT ACROSS EASTERN CO BY SATURDAY
AFTERNOON...ENDING THE DOWNSLOPE FLOW AS COOLING BEGINS ACROSS THE
NORTHEAST PLAINS. THE AIRMASS WILL BEGIN TO SATURATE SAT NIGHT UNDER
DEEPENING UPSLOPE FLOW AND MODEST UPWARD...QG VERTICAL VELOCITIES.
BACK TO WINTER TIME ACROSS ALL OF THE CWA DURING THE DAY ON SUNDAY
WITH CONTINUED SHALLOW UPSLOPE FLOW AND AS THE WEAKENING UPPER TROF
MOVES ACROSS COLORADO. MODELS FAIRLY CONSISTENT WITH THIS
EVOLUTION...THOUGH THERE ARE SOME MINOR TIMING DIFFERENCES...AS THE
GFS IS A BIT QUICKER WITH THE MOISTURE DEEPENING ON SAT EVENING.
THIS STILL LOOKS LIKE A LIGHT SNOW EVENT ACROSS MUCH OF THE PLAINS
AND WILL CONTINUE THE UPWARD TREND OF POPS AND EXPAND FURTHER EAST
WHILE TAKING TEMPS DOWN A FEW MORE DEGREES ON SUNDAY. TEMPERATURES
WILL STRUGGLE TO REACH 20 DEGREES ON SUNDAY AS 700MB TEMPS PLUNGE TO
-20C AGAIN.
BEYOND SUNDAY...THE MODELS BEGIN TO DIVERGE ON THE NEXT MAJOR TROF
WHICH DIVES SOUTHWARD ALONG THE WEST COAST DUE TO HIGHLY AMPLIFIED
EASTERN PAC RIDGE. THE BEST CONSENSUS SEEMS TO SHOW THIS WAVE COME
ACROSS COLORADO AS AN OPEN WAVE ON TUESDAY WITH ANOTHER SHOT OF SNOW
FOR THE ENTIRE AREA FOR MONDAY AND TUESDAY. THE 00Z GFS OPERATIONAL
RUN KEEPS THE TROF MORE CLOSED OFF AS IT INTENSIFIES THE SFC LOW
ACROSS SOUTHEAST COLORADO ON TUESDAY. HOWEVER...MAJORITY OF THE GFS
ENSEMBLE MEMBERS AND 00Z EUROPEAN KEEP THE TROF MORE OPEN. THE 00Z
EUROPEAN HAS SHIFTED ITS SOLUTIONS FURTHER SOUTH FROM THE PREVIOUS
FURTHER NORTH AND DRIER TRACK FROM ITS 12Z SOLUTIONS. WILL NOT
CHANGE MUCH IN CURRENT GRIDS IN THE MON-TUE TIMEFRAME UNTIL SOME
BETTER CONSENSUS IS REACHED. REGARDLESS...LOOKS LIKE THE COLD
TEMPERATURES ARE HERE TO STICK AROUND FOR AWHILE WITH MAYBE SOME
WARMUP BY LATER NEXT WEEK.
&&
.AVIATION...VFR THU TONIGHT. WINDS TODAY SHOULD BE SSW WIND AROUND
10 MPH AND CONTINUE THAT WAY THROUGH TONIGHT.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...NONE.
$$
RPK/SWE
