FXUS65 KPUB 272203
AFDPUB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PUEBLO CO
303 PM MST FRI NOV 27 2009

.SHORT TERM...
(TONIGHT AND SATURDAY)

CURRENTLY...WEAK LEE TROUGH AT THE SURFACE OVER THE EASTERN PLAINS 
HAS ALLOWED DRY AND WARM DOWNSLOPE FLOW TO SPREAD EAST TO NEARLY THE 
KANSAS BORDER TODAY...WITH MAX TEMPS IN THE 60S AND 70S AT MOST 
PLAINS LOCATIONS. WITH MID AND UPPER LEVEL FLOW TURNING SOUTHWEST 
AHEAD OF THE WESTERN U.S. UPPER TROUGH...MOUNTAINS HAVE WARMED 
NICELY AS WELL...WITH 30S AND 40S WIDESPREAD OVER THE HIGHER 
TERRAIN. DEWPOINTS OVER THE AREA HAVE REALLY TANKED...WITH READINGS 
IN THE SINGLE DIGITS ABOVE AND BELOW ZERO PRODUCING RATHER 
WIDESPREAD SINGLE DIGIT RELATIVE HUMIDITY MANY LOCATIONS.  

TONIGHT...UPPER TROUGH CONTINUES TO DIG SOUTH ALONG THE WEST 
COAST...WITH WARM AND DRY SOUTHWEST FLOW CONTINUING OVER COLORADO. 
WINDS ALOFT ARE FAIRLY WEAK...BUT SHOULD BE STRONG ENOUGH TO KEEP 
USUAL EASTERN MOUNTAIN DOWNSLOPE LOCATIONS MIXED AND FAIRLY WARM 
THROUGH THE NIGHT...WITH AREAS ALONG AND WEST OF I-25 ONLY BRIEFLY 
DROPPING BELOW FREEZING. FARTHER WEST...THE USUAL COLD VALLEYS
WILL DECOUPLE AND DRAIN...WITH SEASONABLY COLD READINGS AT KALS
AND KLXV.

SATURDAY...COLD FRONT REACHES NORTHERN COLORADO EARLY IN THE 
MORNING...THEN SWEEPS ACROSS MOST OF THE STATE BY LATE AFTERNOON. 
MAX TEMPS WILL THUS BE 15-20F COLDER MOST LOCATIONS OVER THE 
FORECAST AREA...THOUGH THESE READINGS WILL STILL BE SOME 5-10F ABOVE 
SEASONAL AVERAGES. GUIDANCE TEMPS AND CURRENT FORECAST TEMP GRIDS IN 
GOOD AGREEMENT...SO FEW CHANGES MADE. 18Z NAM CONTINUES TO SLOW THE 
ONSET OF PRECIP SAT AFTERNOON...WITH ONLY SOME VERY ISOLATED -SHSN 
OVER THE CONTINENTAL DIVIDE AND HIGHER PEAKS OF THE EASTERN 
MOUNTAINS BY 21Z. NOT ENOUGH UPSLOPE OVER THE PLAINS/I-25 CORRIDOR 
DURING THE DAY TO PRODUCE PRECIP...THOUGH HIGH AND MID LEVEL CLOUDS 
WILL THICKEN AND LOWER BY LATE AFTERNOON. 

.LONG TERM...
(SATURDAY NIGHT THROUGH FRIDAY)

...SNOW FOR THE SOUTHERN MOUNTAINS TOMORROW NIGHT AND SUNDAY...

TWO FORECAST HEADACHES PERSIST IN THE EXTENDED...FIRST THE IMPACT
OF A STORM SYSTEM MOVING THROUGH ON SUNDAY...AND THEN THE POSSIBILITY
OF A COLD AIR INTRUSION LATE NEXT WEEK.

MODELS HAVE COME INTO REASONABLY GOOD AGREEMENT WITH THE SYSTEM THIS
WEEKEND. TRACK OF THE CLOSED LOW IS STILL WELL TO THE SOUTH...THROUGH
MEXICO. OTHER MODELS HAVE FOLLOWED THE TREND OF THE NAM TO KEEP
THE BULK OF THE HEAVIER PRECIP OVR NEW MEXICO FOR THIS STORM. ON
THE NEGATIVE SIDE...LLVL WINDS LOOK ERLY AND RELATIVELY LIGHT OVR
THE SAN JUANS...WHICH DOES NOT BODE WELL FOR OROGRAPHIC SNOW.
TEMPS ALOFT ARE MODERATE...RESULTING IN POOR LAPSE RATES AND NOT
MUCH HELP FOR DENDRITIC GROWTH. ON THE PLUS SIDE...THE SUBTROPICAL
JET IS VERY STRONG...AND THERE IS GOOD MOISTURE AND UPPER DIVERGENCE
ASSOCIATED WITH THE STORM. LOOKS LIKE AN ADVISORY LEVEL EVENT FOR THE
SRN MTS...WITH MAYBE 4-8 INCHES OF SNOW. GIVEN THE HIGH TRAVEL VOLUME
ON SUN...WILL HAVE TO CONTINUE TO MONITOR CLOSELY.

FOR THE PLAINS AND I-25 CORRIDOR...DOES NOT LOOK LIKE A
SIGNIFICANT EVENT AT ALL...THOUGH TEMPS WILL FALL CONSIDERABLY ON
SUN AND IT WILL CERTAINLY FEEL MORE LIKE WINTER. THERE COULD BE A
BRIEF PERIOD OF LIGHT TO MODERATE SHSN MOVING THROUGH LATE SAT
NIGHT OR SUN MORNING AS THE FRONT PUSHES THROUGH. BEST CHANCE OF
ACCUMULATING SNOW WILL BE OVR THE HYR TRRN SOUTH OF HIGHWAY 50.
COULD PICK UP A COUPLE INCHES OF SNOW IN PLACES LIKE WALSENBURG
FOR EXAMPLE. ENOUGH TO KEEP TRAVELERS ON THEIR TOES SUN.

BIGGER HEADACHE IS THE EXTENT OF A POSSIBLE ARCTIC OUTBREAK IN THE
LATTER PART OF THE WEEK. THE ECMWF HAS CONSIDERABLY BACKED OFF THE
EARLIER PROGS OF A MAJOR COLD SURGE...NOW BRINGING MODIFIED ARCTIC
AIR INTO NRN CO TOWARDS THE END OF THE WEEK. THE 12Z CANADIAN IS
HOLDING FAST TO A STRONG ARCTIC FRONT MIDWEEK. THE GFS OVR THE PAST
COUPLE OF DAYS MAINTAINS THAT LITTLE IF ANY COLD AIR WILL MAKE IT THIS
FAR SOUTH THROUGH NEXT WEEKEND. WHILE THE EC HAS NOT PERFORMING
TOO WELL LATELY IN THE LONG TERM...IT HAS HAD BETTER CONTINUITY
THAN THE GFS FOR THE H5 PATTERN IN THE EXTENDED...SO HAVE STUCK
CLOSER TO THE ECMWF SOLUTION. THIS WOULD MEAN COLD BUT NOT FRIGID
WEATHER FOR THE LATTER PART OF THE WEEK...WITH TEMPS IN THE 30S
OVR THE PLAINS. ROSE

&&

.AVIATION...

LIGHT WINDS AND VFR CONDITIONS EXPECTED AT TAF SITES TONIGHT THROUGH 
MIDDAY SATURDAY. COULD SEE SOME ISOLATED SNOW SHOWERS AND MOUNTAIN 
OBSCURATION ALONG THE CONTINENTAL DIVIDE SATURDAY AFTERNOON...WITH 
MVFR CIGS AND VIS SPREADING EASTWARD TO MOST MOUNTAIN AREAS SATURDAY 
EVENING.    

&&

.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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