Issued by NWS Pueblo, CO
000 FXUS65 KPUB 202158 AFDPUB AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PUEBLO CO 258 PM MST FRI NOV 20 2009 .SHORT TERM... (TONIGHT AND SATURDAY) ...INCREASING CLOUDINESS SATURDAY... THE RIDGE OF HIGH PRESSURE ALOFT WILL CONTINUE MOVING EAST...AS A WEAK STORM MOVES THROUGH WYOMING AND INTO THE PLAINS BY LATE SATURDAY. USED THE WRF AS A BASIS OF THE FORECAST...AS WINDS APPEARED CONSISTENT...AND THE SYSTEM KEPT ANY PRECIPITATION NORTH OF OUR CWA THROUGH SATURDAY AFTERNOON. WINDS ALSO APPEARED TO BE REASONABLE...WITH SOME DOWNSLOPE WINDS ALONG THE MOUNTAINS WEST OF THE I-25 CORRIDOR OVERNIGHT...WHICH WILL KEEP TEMPERATURES WARMER THAN THOSE EXPECTED IN THE LOWER AREAS OF THE ARKANSAS RIVER VALLEY. WITH MAINLY CLEAR SKIES EXPECTED OVERNIGHT...THE HIGH MOUNTAIN VALLEYS WILL AGAIN COOL INTO THE SINGLE DIGITS TO LOW TEENS. CLOUDS WILL INCREASE SATURDAY AS THE SYSTEM MOVES A WEAK COLD FRONT ACROSS MAINLY THE CENTRAL MOUNTAINS...BUT...SINCE THE LOWER LEVELS ARE DRY...NO PRECIPITATION IS EXPECTED THROUGH THE DAY. THE MAIN PROBLEM WILL BE INCREASING WINDS ACROSS THE HIGHER MOUNTAINS AND ALONG THE EASTERN SLOPES AHEAD OF AND WITH THE COLD FRONT. --JKH-- .LONG TERM... (SATURDAY NIGHT THROUGH FRIDAY) FIRST SHORTWAVE WILL CROSS THE CO ROCKIES SAT NIGHT. THIS SYSTEM LOOKS RELATIVELY DRY...BRINGING A BRIEF SHOT OF SNOW TO THE CENTRAL MOUNTAINS AND DRAGGING A DRY COLD FRONT THROUGH THE REMAINDER OF THE AREA BY EARLY SUNDAY MORNING. THIS SYSTEM IS FAIRLY PROGRESSIVE...WHICH SHOULD KEEP SNOWFALL AMOUNTS ON THE LIGHT SIDE ACROSS THE SAWATCH AND MOSQUITO RANGES. MOISTURE SHALLOWS OUT QUICKLY ALONG THE CONTDVD ON SUNDAY BEHIND THE SYSTEM...THOUGH THERE WILL BE ENOUGH MOISTURE FOR SOME ISOLATED OROGRAPHIC SNOW SHOWERS ACROSS THE HIGHER PEAKS. TEMPS SHOULD BE AROUND 5 TO 10 DEGREES COOLER THAN THE DAY BEFORE...ESPECIALLY ACROSS THE PLAINS. THE NEXT UPPER TROF WHICH DROPS IN SUNDAY NIGHT/MONDAY HAS THE POTENTIAL TO BE THE STRONGEST OF THE WEEK. THERE IS STILL SOME VARIABILITY BETWEEN THE MODELS WITH 12Z NAM AND GFS DROPPING THE OPEN TROF THROUGH WY/NRN CO INTO THE CENTRAL PLAINS...GIVING SOUTHERN CO MORE OF A GLANCING BLOW BEFORE IT CLOSES OFF AND HEADS TOWARDS THE UPPER MID WEST. THE 00Z AND 12Z ECMWF AND NOW THE 18Z NAM ARE STRONGER AND FARTHER WEST WITH THE SOUTHEASTWARD TRACK OF THIS SYSTEM...WITH ECMWF THE STRONGEST AND SLOWEST OF THE BUNCH... CLOSING OFF THE UPPER LOW ACROSS WRN KS/ERN CO BY MON AFTN. EVEN WITH THE STRONGER SOLN...MOST OF THE FORECAST AREA WILL BE UNDER THE DRY DOWNSLOPE PORTION OF THE STORM...HOWEVER NRN PORTIONS OF THE PLAINS...PALMER DIVIDE AND ALONG WITH THE CENTRAL MOUNTAINS COULD SEE SOME ACCUMULATING SNOWS UNDER THE DEVELOPING TROWAL ON MONDAY. GIVEN THE UNCERTAINTIES...WILL LEAVE THE LOW GRADE ISOLATED POPS IN FOR THE SOUTHEAST PLAINS SUNDAY NIGHT/MONDAY. THE CENTRAL MOUNTAINS COULD SEE A FEW INCHES OF ACCUMULATION WITH THIS SYSTEM AS WELL. REGARDLESS OF THE MODEL...THE SYSTEM SHOULD WELL EAST OF THE AREA BY TUES WITH A RETURN OF DRY WEATHER AND REBOUNDING TEMPERATURES. GFS HAS TRENDED WESTWARD WITH THE NEXT ROUND OF ENERGY DROPPING DOWN THE EAST SIDE OF THE UPPER RIDGE THROUGH THE CENTRAL PLAINS TUES NIGHT/EARLY WED. THIS SYSTEM WILL SEND ANOTHER FRONT THROUGH THE SE PLAINS...AND WHICH IF LATEST GFS IS CORRECT COULD BE ACCOMPANIED BY SOME ISOLATED LIGHT SNOW SHOWERS. FOR NOW WILL KEEP FORECAST DRY FOR THE PLAINS AS PREVIOUS RUNS AND ECMWF KEEPS THE TRACK OF THIS SYSTEM FARTHER OFF TO THE EAST. THIS SHOULD AT LEAST BRING SOME DEGREE OF A COOL DOWN FOR WEDNESDAY. UPPER RIDGE WILL TRANSLATE IN ALOFT FOR THURS BEFORE GETTING CUT DOWN AND TRANSITIONING TO ZONAL FLOW FOR FRI AS NEXT SYSTEM ENTERS THE PACIFIC NORTHWEST. THIS SHOULD BRING WARMER TEMPERATURES AND A TREND TOWARDS BREEZY/WINDY CONDITIONS TO THE AREA THROUGH LATE NEXT WEEK. -KT && .AVIATION... VFR CONDITIONS ARE EXPECTED AT ALL THREE TAF SITES THROUGH THE PERIOD. GUSTY WINDS MAY DEVELOP ALONG THE EASTERN MOUNTAIN SLOPES LATE TONIGHT AND EARLY SATURDAY AS A DRY COLD FRONT MOVES THROUGH THE AREA FROM WEST TO EAST. THE GUSTY WINDS ARE NOT EXPECTED TO AFFECT THE TAF SITES...BUT COULD CAUSE PROBLEMS FOR GENERAL AVIATION TRYING TO FLY FROM THE PLAINS INTO THE MOUNTAINS. --JKH-- && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ 51/31
