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Fri 11/21/08 1:42:38am MST
000 FXUS65 KBOU 202228 AFDBOU AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DENVER CO 328 PM MST THU NOV 20 2008 .SHORT TERM...UPSLOPE FLOW WEAKENING AS NOTED BY LATEST SURFACE OBS AND PLATTEVILLE PROFILER. SATELLITE STILL SHOWING STATUS ACROSS MUCH OF PLAINS AND ALONG FOOTHILLS...THOUGH CEILINGS MAINLY MVFR. WEB CAMS...OBSERVATIONS AND RADAR INDICATING PRECIPITATION HAS ENDED. ADVISORIES FOR FREEZING DRIZZLE HAVE SINCE BEEN CANCELLED. DRIER AIR CONTINUES TO MOVE ACROSS PLAINS FROM THE NORTHEAST. BOUNDARY LAYER WIND AND HUMIDITY PROGS KEEP CONSIDERABLE MOISTURE ACROSS FOOTHILLS AND PLAINS THIS EVENING...SLIDING THE MOISTURE FURTHER EAST AFTER MIDNIGHT AS WINDS SHIFT TO THE SOUTHWEST. WITH THE DRIER AIR WORKING INTO AREA...PRECIP CHANCES NIL AND WILL DROP FROM THE GRIDS. WILL KEEP SOME FOG ALONG FOOTHILLS AND ADJACENT PLAINS THIS EVENING. ON FRIDAY...MODELS CONTINUE TO SHOW SHORTWAVE MOVING ACROSS WYOMING. CROSS SECTIONS SHOW MINIMAL MOISTURE THROUGH THE DAY. DESPITE SOME WEAK QG ASCENT DURING THE AFTERNOON...AIRMASS LOOKS TOO STABLE FOR ANY SNOW TO GENERATE AS LAPSE RATES OF AROUND 4 C/KM ARE PROGGED THROUGH THE DAY. SO...HAVE TAKEN OUT ANY MENTION OF SNOW FOR THE MOUNTAINS DURING THE DAY. WESTERLY GRADIENT INCREASES BY 18Z WITH CROSS MOUNTAIN FLOW NEARING 50 KTS. A BIT OF A MOUNTAIN TOP INVERSION SHOWS UP ON CROSS SECTIONS AND FORECAST SOUNDINGS. SANGESTER WIND FORECAST PROGRAM SHOWS VERY LOW CHANCE FOR WINDS REACHING HIGH WIND CRITERIA. GRIDS ALREADY HAVE GUSTY WINDS. WILL INCLUDE SOME GUSTS TO 50 MPH OVER THE HIGHER TERRAIN. TEMPERATURE AND THICKNESS PROGS ANS WELL AS GUIDANCE SUGGEST HIGHS IN THE 40S ACROSS THE PLAINS. THIS LOOKING REASONABLE. CURRENT TEMPERATURE GRIDS IN LINE WITH GUIDANCE...LITTLE CHANGES NEEDED. .LONG TERM...PRETTY GOOD MODEL AGREEMENT NOW THROUGH EARLY NEXT WEEK. A WEAK UPPER TROUGH WILL MOVE ACROSS THE NORTHERN PLAINS FRIDAY NIGHT WITH THE ONLY EFFECT A BIT MORE WIND IN THE MOUNTAINS AND SOME HIGH CLOUD COVER. THE NEXT TROUGH IS STRONGER BUT FOLLOWS THE SAME PATH ON SUNDAY. THIS SHOULD BRING MORE COOLING BUT AGAIN LOOKS TO BE TOO DRY FOR PRECIPITATION. MODELS BEGIN TO DIVERGE WITH THE AMOUNT AND LOCATION OF RIDGING ON MONDAY AND TUESDAY BUT EVERYTHING LOOKS DRY WITH THE CONSENSUS A BIT WARMER THAN WHAT WE HAD SO I RAISED TEMPERATURES A LITTLE...IF THE WARMER SOLUTIONS ARE RIGHT WE WILL BE BACK IN THE 60S AS THE RIDGE AXIS PASSES. THERE IS ALSO MODEL AGREEMENT ON THE WEST COAST TROUGH DEVELOPING AND A TENDENCY TOWARD SPLIT FLOW. LATEST GFS AND ECMWF SOLUTIONS SHOWING MORE OF A SHORTWAVE IN THE NORTHERN STREAM DROPPING INTO THE MIDWEST BY THANKSGIVING DAY. 12Z GFS WAS AN OUTLIER WITH THIS BRINGING SHARP COOLING TO DENVER...BUT ECMWF SOLUTION WITH A LITTLE COOLING SEEMS PLAUSIBLE. STILL MANY RUNS WITH THE SOUTHERN STREAM TROUGHING OVER THE SOUTHWEST OR OFF CALIFORNIA DOMINATING WITH MILDER SOUTHWEST FLOW OVER COLORADO. THESE SOLUTIONS WOULD HAVE LESSER COOLING...OR NONE DEPENDING ON CLOUD COVER. CHANCE OF PRECIPITATION REMAINS LOW THROUGH THANKSGIVING WITH SOME POSSIBILITY OF LIGHT MOUNTAIN SNOW. SOME POSSIBILITY OF SOMETHING COMING OUT OF THE WESTERN TROUGH LATER IN THE WEEKEND...BUT NOT LOOKING LIKE TOO FAVORABLE OF AN ENVIRONMENT TO START WITH. && .AVIATION...DRIER AIR WORKING INTO AREA FROM THE NORTHEAST...NO PRECIP EXPECTED. MVFR CEILINGS TO PERSIST THROUGH 06Z...THEN IMPROVE AS SURFACE WINDS SHIFT TO THE SOUTHWEST. PATCHY FOG COULD DEVELOP ACROSS AREA THIS EVENING...VISIBILITIES SHOULD REMAIN VFR. VFR CONDITIONS FRIDAY WITH SURFACE WINDS BECOMING WESTERLY BY 18Z. && .BOU WATCHES/WARNINGS/ADVISORIES...NONE. $$ D-L/CMG
