000 FXUS63 KTOP 272149 CCA AFDTOP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TOPEKA KS 345 PM CST MON DEC 27 2004 .DISCUSSION... A RETURN TO WINTER WEATHER CONDITIONS STARTING NEXT WEEK THE 12Z UPPER AIR MAPS ALONG WITH THE LATEST WATER VAPOR SATELLITE IMAGERY SHOWED AN UPPER LEVEL LOW OFF THE NORTHERN CA COAST WITH A DOWN STREAM UPPER LEVEL RIDGE ACROSS THE WESTERN HIGH PLAINS. AN UPPER LEVEL TROUGH WAS LOCATED OVER EASTERN CANADA AND NEW ENGLAND. THE 20Z SURFACE MAP SHOWED A LEE SFC TROUGH ACROSS THE WESTERN HIGH PLAINS WITH A SFC RIDGE ACROSS MIDWEST AND MS RIVER VALLEY. SOUTHERLY WINDS HAVE HELPED TO WARM TEMPERATURES INTO THE LOWER TO MID 50S ACROSS THE FA THIS AFTERNOON. EXPECT SCATTERED TO BROKEN HIGH CLOUDINESS TO MOVE EAST ACROSS THE AREA TONIGHT. LOW TEMPERATURES TONIGHT WILL ONLY DROP INTO THE LOWER TO MID 30S. RESIDUAL GULF MOISTURE OVER CENTRAL TX MAY GET ADVECTED NORTHWARD LATE TONIGHT. WEAK ISENTROPIC LIFT OF THE RETURN FLOW MAY CAUSE LOW CLOUDS TO DEVELOP AROUND SUNRISE OVER THE EASTERN COUNTIES OF THE FA. THE LOW-CLOUDS SHOULD MIX OUT BY 18Z. TEMPERATURES TOMORROW WILL BE WARMEST ACROSS THE SOUTHWEST COUNTIES...DUE TO GREATER SOLAR INSOLATION...WHERE HIGHS WILL WARM INTO THE MID TO UPPER 50S. WHILE TUESDAY AFTERNOON HIGHS WILL ONLY REACH THE LOWER MID 50S. IF THE LOW CLOUDS DEVELOP AND HANG ON THROUGH THE DAY TUESDAY...HIGH TEMPERATURES ACROSS THE EASTERN COUNTIES MAY BE A FEW DEGREES COOLER THAN FORECASTED. THE ETA AND GFS MODEL SOLUTIONS ARE IN FAIRLY GOOD AGREEMENT THROUGH 00Z FRI. TEMPERATURES WILL CONTINUE TO WARM AS THE DOWN STREAM 5H RIDGE AMPLIFIES AND MOVES EAST ACROSS THE PLAINS STATES LATE TUESDAY AND EARLY WEDNESDAY. TEMPERATURES WILL WARM WELL INTO THE 50S WEDNESDAY AFTERNOON. BOTH MODEL SOLUTIONS SHEAR OUT THE 5H TROUGH AS IT MOVES NORTHEAST ACROSS THE CENTRAL PLAINS EARLY THURSDAY. MOST OF THE QG FORCING AND WAA AHEAD OF THE 5H TROUGH WILL OCCUR NORTH OF THE FA. RESIDUAL MOISTURE RETURN MAY BE SUFFICIENT FOR SCATTERED RAIN SHOWERS TO DEVELOP WEDNESDAY NIGHT. AS THE 5H TROUGH LIFTS NORTHEAST INTO IA THU MORNING THE LOW-LEVELS WINDS WILL VEER TO THE SOUTHWEST BRINGING IN DRIER AIR. ANY LEFT OVER SHOWERS SHOULD MOVE NORTHEAST OF THE FA BY NOON ON THU. HIGH TEMPERATURES ON THU WILL WARM INTO THE UPPER 50S TO LOWER 60S. THE EXTENDED FORECAST MODELS DIVERGE IN THEIR SOLUTIONS BY LATE WEEK AND EARLY NEXT WEEK. THE ECMWF DIGS A TROUGH OFF THE WA COAST LATE THU SOUTHEAST INTO NV BY SUNDAY EVENING. THE SOUTHERN PLAINS WILL BE UNDER STRONG SOUTHWEST FLOW AHEAD OF THE 5H TROF. THIS SOLUTION WOULD PREVENT A COLD ARCTIC AIR MASS FROM MOVING SOUTH ACROSS THE PLAINS EARLY NEXT WEEK. THOUGH IF THE ARCTIC AIR MOVES INTO THE NORTHERN HIGH PLAINS ON SATURDAY IT WILL BE DIFFICULT TO KEEP IT NORTH OF THE FA NEXT SUNDAY AND MONDAY. IF THE ECMWF VERIFIES WARM AIR ALOFT WILL ADVECT ABOVE THE SHALLOW ARCTIC AIR AND WE MAY SEE FREEZING RAIN WITH ANY MINOR 5H SHORTWAVE THAT EJECTS NORTHEAST ACROSS THE REGION SUNDAY NIGHT AND MONDAY. THE GFS SOLUTION KEEPS THE 5H TROUGH OPEN AND MOVES IT EAST INTO THE CENTRAL PLAINS LATE SUNDAY AND MONDAY. THE GFS MODEL SHOWS THE DEEPER ARCTIC AIR MOVING SOUTHWARD INTO THE NORTHERN COUNTIES OF THE FA DURING THE DAY ON SUNDAY. THE GFS HAS PRECIPITATION IN THE FORM OF SNOW ACROSS THE NORTHERN COUNTIES SUNDAY NIGHT AND MONDAY...AND RAIN OR FREEZING RAIN ACROSS THE SOUTHERN COUNTIES. ATTM I WILL PLACE SLIGHT CHANCES OF SNOW OR FREEZING RAIN SUNDAY NIGHT. ON MONDAY I WILL GO WITH A SLIGHT CHANCE OF SNOW MONDAY ACROSS THE NORTHERN COUNTIES AND SNOW OR RAIN ACROSS THE SOUTHERN COUNTIES. HIGH TEMPERATURES WILL BE BACK NEAR SEASONAL NORMS SUNDAY AND NEXT MONDAY. && .TOP WATCHES/WARNINGS/ADVISORIES...NONE. && $$