000 FXUS63 KEAX 280425 CCA AFDEAX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO 940 PM CST MON DEC 27 2004 CORRECTED TO REMOVE PREVIOUS AVIATION TEXT .DISCUSSION... RAISED TEMPERATURES A LITTLE FOR TONIGHT AS TEMPERATURES FALLING VERY LITTLE WITH BREEZY SOUTH TO SOUTHWEST WINDS. PRESSURE GRADIENT WILL REMAIN TIGHT THROUGH THE NIGHT...WITH ONLY A VERY SLOW FALL THE REMAINDER OF THE NIGHT. .AVIATION DISCUSSION... CONCERN IS MAINLY DURING THE MORNING HOURS AS THE MESOETA SUGGEST THAT A LOW STRATUS DECK MAY DEVELOP A COUPLE OF HOURS AFTER SUNRISE. STILL NO SIGN OF ANY STRATUS DECK WELL TO OUR SOUTH. HOWEVER...EVENING UPPER AIR INDICATED 925MB MOISTURE ACROSS SRN TEXAS THIS EVENING. STG 925MB WINDS OF 50-60 KNOTS TO TRANSPORT THIS MOISTURE NWD INTO THE TERMINAL SITES. QUESTION IS WHETHER MOISTURE ENOUGH TO PRODUCE SCATTERED OR BROKEN DECK. AT THIS TIME...BELIEVE THE LOW CLOUD DECK WILL BE BROKEN IN NATURE WITH THE CEILING INCREASING IN HEIGHT AND BECOMING THINNER THROUGHOUT THE DAY DUE TO MIXING. PROFILERS NOW INDICATING 35 KNOTS AT ABOUT 2000 FEET ABOVE THE SURFACE. AS MENTIONED ABOVE...WINDS TO INCREASE IN THIS LAYER TONIGHT...THUS CREATING THE POTENTIAL FOR LOW LEVEL WIND SHEAR THROUGH MID-MORNING. DB && .PREV DISCUSSION... 335 PM THE UPPER LOW OFF THE CALIFORNIA COAST LOOKS IMPRESSIVE THIS AFTERNOON. FORECASTING THE TRACK AND INTENSITY OF THIS SYSTEM WILL BE THE MAIN FORECAST CONCERN FOR THE NEXT FEW DAYS. LOTS OF COLD CUMULUS CLOUDS ARE WRAPPING AROUND THE BACK OF THIS FEATURE. GFS INITIALIZED 500MB TEMPERATURES -30C TO -33C. ANALYSTS FROM THE HPC SUGGESTED THAT THE GFS AND ESPECIALLY THE ETA DID NOT INITIALIZE THIS UPPER LOW STRONG ENOUGH. THE KICKER THAT WILL EJECT A PORTION OF THE UPPER LOW INTO THE MIDWEST LATER IN THE WEEK IS TRACKING THROUGH THE GULF OF ALASKA THIS AFTERNOON. THIS OPEN WAVE JUST EAST OF THE ALEUTIAN ISLANDS IS PROGRESSING FASTER THAN YESTERDAYS MODELS SUGGESTED, AND IT NOW APPEARS THAT THE FORCING WITH THE CYCLONE AS IT TRACKS THROUGH THE PLAINS WILL ARRIVE LATE WEDNESDAY NIGHT INTO THURSDAY MORNING. SINCE THE GFS INITIALIZED THE UPPER LOW DEEPER THAN THE ETA, I FEEL THAT ITS SLIGHTLY SLOWER SOLUTION IS BETTER. I ALSO FIND THE SCANT QPF FROM THE ETA SUSPICIOUS GIVEN THE STRONG WARM ADVECTION AND Q-VECTOR CONVERGENCE FORECAST WEDNESDAY NIGHT AND THURSDAY MORNING. MOISTURE WILL BE A LIMITING FACTOR WITH THIS SYSTEM SINCE COLD SURFACE HIGH PRESSURE HAS BEEN PUSHED FAR SOUTH OVER THE GULF. LOW LEVEL MOISTURE WILL BE SLOW TO RETURN, SO I HESITATE TO POST PRECIPITATION CHANCES HIGHER THAN 40 OR 50 PERCENT AT THIS TIME. IT WILL BE IMPORTANT TO MONITOR DEWPOINTS OVER TEXAS DURING THE NEXT FEW UPPER AIR LAUNCHES TO SEE IF THE 1000MB TO 850MB LAYER WILL MOISTEN UP. KOCH PRECIPITATION CHANCES ARE EXPECTED TO SHUT OFF THURSDAY NIGHT AS THE UPPER SHORTWAVE TROUGH AXIS MOVES EAST OF THE FORECAST AREA. ZONAL FLOW WILL SET UP FOR FRIDAY BETWEEN THE TROUGH EXITING TOWARD THE EAST COAST AND ANOTHER MOVING ON SHORE OVER THE NORTHWEST U.S. COAST...WITH ABOVE NORMAL TEMPERATURES CONTINUING INTO THE FIRST DAY OF THE NEW YEAR. MEDIUM RANGE MODEL SOLUTIONS THEN DIVERGE BY SUNDAY AS TO THE EXTENT OF ARCTIC HIGH PRESSURE SHIFTING SOUTH. THE ECMWF PROGS A NORTH-SOUTH ORIENTED TROUGH OVER THE WEST WITH STRONGER RIDGING ACROSS THE CENTRAL STATES...KEEPING THE BRUNT OF THE COLD AIR NORTH OF THE FORECAST AREA. THE GFS HAS A MUCH COLDER SOLUTION FOR THIS REGION WITH SHALLOW ARCTIC AIR SPREADING AS FAR SOUTH AS CENTRAL PORTIONS OF KANSAS AND MISSOURI. FOR NOW HAVE LOWERED TEMPERATURES 3 TO 5 DEGREES ACROSS THE BOARD FOR SUNDAY INTO MONDAY...MORE IN LINE WITH HPC GUIDANCE BUT STILL SEVERAL DEGREES ABOVE THE COLDER GFS GUIDANCE NUMBERS. WEAK SHORTWAVES IN THE SOUTHWEST FLOW WILL RESULT IN THE POSSIBILITY OF PRECIPITATION FROM EARLY SUNDAY THROUGH MONDAY. HAVE KEPT THE HIGHEST CHANCES OF PRECIPITATION ON SUNDAY...WITH SLIGHT CHANCES FOR MONDAY. PRECIPITATION TYPE IS QUITE UNCERTAIN AT THIS POINT...WITH FREEZING/FROZEN PRECIPITATION DEPENDENT UPON THE PLACEMENT OF THE SHALLOW ARCTIC COLD AIR. STOFLET .PREV DISCUSSION... 345 AM... MAIN FORECAST CONCERN IS WITH PRECIPITATION CHANCES WEDNESDAY NIGHT AND THURSDAY. ALSO STARTING TO TAKE A LOOK AT POSSIBILITY OF COLDER AIR COMING IN NEXT SUNDAY. SHORT WAVE OFF OF WEST COAST EXPECTED TO GET KICKED INTO NORTH CENTRAL PLAINS BY THURSDAY MORNING. TIMING STILL A BIT OF A QUESTION MARK. PREFER SLOWER GFS SOLUTION AS CUT OFF LOWS SUCH AS THESE ARE USUALLY A LITTLE SLOWER TO MOVE OUT THAN WHAT MODELS EXPECT. HOWEVER...ONCE THIS SYSTEM DOES GET MOVING...SHOULD MAKE PRETTY RAPID PROGRESS ACROSS REGION. WILL KEEP A FAIRLY WIDE TIME FRAME FOR RAIN CHANCES...FROM WEDNESDAY NIGHT THROUGH THURSDAY EVENING IN THE FORECAST AREA...BUT EXPECT WE WILL BE ABLE TO NARROW THIS GAP DOWN IN SUBSEQUENT FORECASTS AS UPPER AIR ANALYSIS AND MODELS GET BETTER HANDLE ON THE TIMING. EVEN AFTER THIS SHORT WAVES PASSAGE...NOT TAPPING INTO ANY COLD AIR AS PATTERN BECOMES MORE ZONAL. THE BIG QUESTION OF TAPPING THE COLD AIR WILL COME AFTER THE FIRST OF THE YEAR. GFS IS SUGGESTING A STRONG ARCTIC PUSH SOUTHWARD BEGINNING SUNDAY MORNING. EUROPEAN MODEL IS SHOWING THIS PUSH NOT UNTIL SUNDAY NIGHT. WILL TREND TEMPS DOWN JUST A BIT ON SUNDAY...WITH POSSIBILITY OF CLOUDS AND PRECIPITATION...BUT NOT GO EXCESSIVELY COLD AT THIS POINT. PC && .EAX WATCHES/WARNINGS/ADVISORIES... KS...NONE. MO...NONE. $$ WFO EAX