NORTHEAST AND NORTH CENTRAL COLORADO AREA FORECAST DISCUSSION
NWS DENVER COLORADO
AFDDEN 420 AM MST TUE JAN 29 2002
SHORT TERM DISCUSSION: ACARS SOUNDINGS FROM KDEN SHOW THE SHALLOW
COLD AIRMASS THAT HAS SPREAD ACRS NE CO. THE COLD AIR IS ABT 2000
FT IN DEPTH WITH A VERY STRONG INVERSION ON TOP OF THAT. FLURRY
ACTIVITY OUT OF THIS SHALLOW COLD AIR HAS BEEN PERSISTENT OVR THE
PAST FEW HOURS. A LITTLE HEAVIER BAND OF SNOW HAS BEEN EVIDENT OVR
LARIMER COUNTY MUCH OF THE MRNG. THIS SNOW IS BEING PRODUCED BY THE
UPR LVL MSTR EMBEDDED IN THE STRONG SWLY FLOW ALOFT. THE WX FOR
TODAY SHUD BE A CONTINUATION OF VRY LIGHT PCPN ON THE PLAINS AND
DVLPG SNOW SHOWERS OVR THE MTNS. THE SITUATION FOR NE CO IS
PRIMARILY ONE OF NOT ENOUGH INGREDIENTS COMING TOGETHER TO PRODUCE
SIGNIFICANT PCPN. LOW LVL MSTR IS THE PRIMARY MISSING INGREDIENT.
THE COLD LOW LVL TEMPS ARE NOT CAPABLE OF HOLDING MUCH MSTR AND THE
WARMER AIR ABV THE INVERSION IS PRESENTLY VRY DRY. THESE CONDITIONS
WL BEGIN CHANGING LATER TONIGHT WHICH WL ALLOW FOR SNOW ALG THE
FTHLS AND PALMER DVD TO INCREASE. MM5 PCPN FIELDS SHOW ONLY LIGHT
PCPN AMNTS IN THE MTNS THRU TONIGHT AND ALMOST NO PCPN ON THE
PLAINS. FOR THESE REASONS HAVE NOT GONE HOG WILD ON FCSTG
SIGNIFICANT SNOWFALL. MTNS MAY SEE A FEW INCHES OF SNOW
TONIGHT...BUT IT APPRS MOST OF THE DYNAMICS WITH THE APPCHG TROF ARE
GOING TO BE SOUTH OF OUR AREA.
COLD TEMPS ARE THE OTHER THING THAT A LOT OF PEOPLE ARE GOING TO
NOTICE OVER THE NEXT 24 HOURS. THIS HAS BEEN A PART OF THE FCST FOR
A FEW DAYS NOW...SO WON'T MAKE ANY BIG CHANGES TO THAT. KDRBY
LONG TERM DISCUSSION: SFC AND UPPER AIR MODEL FEATURES IN REASONABLY
GOOD AGREEMENT OUT THROUGH 60 HOURS...THOUGH LATEST AVN HAD LOWER
700 AND 500 MB HTS WITH THE TROUGH OVER THE DESERT SW OUT THROUGH 48
HRS. AFTER WHICH TIME AVN HEIGHTS COME AROUND TO THOSE OF THE ETA
WITH THE UPR TROUGH MOVING OVER THE RCKY MTN RGN. ARCTIC AIR EAST
OF THE MTNS NEVER REALLY THAT DEEP WITH MODEL DERIVED SOUNDINGS AND
LAPSE RATE CROSS SECTIONS SHOWING A STRONG STABLE LAYER (700-600
MBS) TOPPING COLD AIRMASS OUT THROUGH WEDNESDAY AFTERNOON. STABLE
LAYER WEAKENS WEDNESDAY NIGHT WITH COOLING AT MID-LVLS AS WINDS
ALOFT SLOWLY SWING AROUND TO NWLY DIRECTION WITH PASSAGE OF UPR
TROUGH. MEANWHILE...MOISTURE BELOW 700 MB LEVEL AND EAST OF MTNS
APPEARS TO INCREASE SOME DURING THE DAY WEDNESDAY WITH THE UPSLOPE
PRESSURE GRADIENT TIGHTENING IN RESPONSE TO PRESSURE FALLS ON THE
WEST SLOPE. SNOW ACCUMULATION AND QPF GRIDS SHOW LIGHT SNOW
ACCUMULATION OVER THE NRN FRONT RANGE AND LARIMER CTY AREA WEDNESDAY
MORNING SHIFTING TO THE SOUTHERN HALF OF FRONT RANGE FOOTHILLS...THE
SOUTHERN URBAN CORRIDOR AND THE MONUMENT RIDGE BY LATE WEDNESDAY
AFTERNOON AND EVENING. I WOULDN'T PUT TOO MUCH FAITH IN THIS TIME
TABLE...BUT IT DOES SEEM REASONABLE THAT WITH TROUGH PASSAGE ANY
PCPN BEING PRODUCED BY THE JET WILL SHIFT SOUTH AND EAST WITH THE
TROUGH WEDNESDAY NIGHT. SNOWFALL AMOUNTS OFF THE GRIDS RANGE FROM A
TRACE IN THE NERN CORNER OF THE STATE TO AROUND 3 INCHES ON THE
HIGHER TERRAIN SOUTH AND WEST OF DENVER FOR THE 18-HOUR PERIOD
ENDING 06Z/THU. THESE AMTS LOOK REASONABLE. SEE VERY LITTLE
WARMING THURSDAY BOTH IN THE MTNS AND ON THE PLAINS.
IN THE MTNS...OROGRAPHIC SNOW MODEL PRODUCED SIMILAR AMOUNTS...BUT
WITH MODERATE 700-300MB QG ASCENT OVER AREA DURING THE PERIOD SHOULD
ADD A COUPLE INCHES TO THESE NUMBERS. DO NOT SEE MUCH WIND IN THE
MTNS WEDNESDAY WITH THE TROUGH PRETTY MUCH OVERHEAD. NOT UNTIL
THURSDAY WILL NWLY RIDGETOP WINDS INCREASE ON THE BACK SIDE OF THE
TROUGH. BY THEN MODELS SHOW A MUCH DRIER ATMOSPHERE TOGETHER WITH
SLIGHTLY WARMER 700-500MB TEMPS. ON THE PLAINS...SEE LITTLE WARMING
THURSDAY WITH LOW CLOUDS HANGING AROUND FOR PART OF THE DAY. ANY
PCPN SHOULD BE SOUTH AND EAST OF OUR CWFA BY THEN...NOT COUNTING THE
SCATTERING OROGRAPHIC SNOW SHOWERS LINGERING IN THE MTNS.
FOR LATER IN THE PERIOD...DRY AND WARMER CONDITIONS RETURN TO THE
FORECAST AREA FRIDAY AND SATURDAY. SUNDAY THRU TUESDAY COULD SEE
PERIODS OF LIGHT SNOW IN THE MTNS WITH PASSAGE OF A SERIES OF WEAK
UPR-LVL SYSTEMS. WHILE ON THE PLAINS ONLY LOOKING FOR PERIODS OF
CLOUD COVER WITH LITTLE TEMPERATURE CHANGE DURING THE SAME PERIOD.
BAKER
.DEN...NONE.