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000 FXUS63 KGID 210514 AFDGID AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE HASTINGS NE 1114 PM CST FRI NOV 20 2009 .AVIATION...06Z TAF. MAIN CONCERN FOR THE TAF PERIOD IS THE POTENTIAL FOR THE ARRIVAL OF STRATUS JUST AFTER DAYBREAK ON SATURDAY. THE LEADING EDGE OF THE STRATUS CLOUDS IS LOCATED ACROSS SOUTH CENTRAL KANSAS ATTM AND WITH INCREASING SOUTHERLY FLOW OVERNIGHT AND SATURDAY...THE LOW CLOUDS WILL ADVECT NORTHWARD. FOR NOW HAVE KEPT CEILINGS IN THE MVFR RANGE FOR A FEW HOURS AND THEN SCATTERED THE CLOUDS IN THE AFTERNOON. IN A TIGHTENING SURFACE GRADIENT...SOUTHERLY WINDS WILL INCREASE ON SATURDAY WITH GUSTS AROUND 25KTS POSSIBLE. && .PREV DISCUSSION... /ISSUED 1004 PM CST FRI NOV 20 2009/ UPDATE...MAIN UPDATE THIS EVENING WAS TO INSERT MENTION OF PATCHY FOG INTO PORTIONS OF NORTH CENTRAL KS MAINLY EAST OF HIGHWAY 281. MOST FAVORABLE CONDITIONS FOR FOG DEVELOPMENT SHOULD REMAIN JUST TO THE SOUTH/EAST OF THE CWA WHERE WEAK MOISTURE ADVECTION IS ENHANCED...BUT FELT THAT PATCHY MENTION WAS STILL WARRANTED AS LIGHT SOUTHERLY RETURN FLOW AROUND THE RIDGE AXIS SHOULD REMAIN WEAKEST HERE AS WELL. OTHERWISE MADE ONLY SOME MINOR TWEAKS TO TEMPS/DEWPOINTS/SKY COVER. PREV DISCUSSION... /ISSUED 338 PM CST FRI NOV 20 2009/ SHORT TERM...TONIGHT THROUGH 12Z SUNDAY. NOT MUCH IN THE WAY OF WEATHER IN THIS PERIOD. SURFACE RIDGE IS MOVING ACROSS THE AREA THIS AFTERNOON WITH SOUTHERLY FLOW RETURNING. SURFACE TROUGH WILL DEVELOP AND STRENGTHEN ACROSS THE WESTERN HIGH PLAINS TONIGHT AND SATURDAY. THIS WILL INCREASE THE PRESSURE GRADIENT AND SO WILL THE WINDS. EXPECT A BREEZY DAY ON SATURDAY WITH SOUTH WINDS OF 15 TO 25 MPH. LITTLE IN THE WAY OF MOISTURE IN PLACE NOW SO CLEAR SKIES WILL PREVAIL INTO SATURDAY. AS SOUTHERLY FLOW CONTINUES INTO SATURDAY NIGHT...LOW LEVEL MOISTURE WILL INCREASE AND WILL BRING LOW CLOUDS AND SOME PATCHY FOG/DRIZZLE TO THE AREA BY SUNRISE SUNDAY. LONG TERM...12Z SUNDAY THROUGH FRIDAY. THE MAIN FOCUS OF THIS FORECAST IS ON EARLY NEXT WEEK SYSTEM...WHICH LOOKS TO BE A PRETTY SIGNIFICANT WEATHER MAKER FOR THE AREA DURING THE MONDAY/TUESDAY TIMEFRAME. STARTING OUT SUNDAY MORNING...WILL BE DEALING WITH LOW CLOUDS...FOG AND DRIZZLE ACROSS THE CWA. A WEAK SURFACE FRONT WILL BE BISECTING THE CWA FROM NORTH TO SOUTH...WITH SOUTHERLY LOW-LEVEL FLOW AHEAD OF THE BOUNDARY KEEPING RICH LOW-LEVEL MOISTURE IN PLACE. SOUNDINGS CONTINUE TO SUPPORT FOG AND DRIZZLE...WITH SATURATED LOW LEVELS BENEATH A DRY PROFILE ALOFT...AND HENCE PREFER THE INHERITED DRIZZLE MENTION VERSUS SHOWERS. FORCING AHEAD OF AN OPEN UPPER WAVE ACTING ON THE MOIST LOW LEVELS SHOULD BE SUFFICIENT TO SQUEEZE OUT SOME DRIZZLE ACROSS THE EASTERN HALF OR SO OF THE CWA SUNDAY MORNING...POSSIBLY LINGERING INTO THE AFTERNOON HOURS IN THE FAR SOUTHEAST. TEMPERATURES ARE TRICKY ON SUNDAY. THE SURFACE BOUNDARY WASHES OUT AND A FAIRLY WARM AIRMASS IS IN PLACE /H85 TEMPS GENERALLY +3-5C/...BUT LOW CLOUDS WILL BE SLOW TO CLEAR ESPECIALLY IN THE EAST. WILL AIM HIGHS IN THE MID 40S TO LOWER 50S...BUT THIS COULD EASILY TILT EITHER WAY BASED ON CLEARING TRENDS. SHOULD CATCH A BREAK BETWEEN SYSTEMS SUNDAY NIGHT...BEFORE A MUCH STRONGER UPPER LOW BEGINS TO IMPACT THE AREA ON MONDAY. MODELS /EXCLUDING THE GFS/ HAVE BEGUN TO COME INTO MUCH BETTER AGREEMENT ON THIS EARLY WEEK SYSTEM...WITH THE TREND TOWARD A MUCH DEEPER/STRONGER/SLOWER AND MORE IMPACTFUL SYSTEM FOR THE AREA. THE LAST COUPLE RUNS OF BOTH THE ECMWF AND CMC GEM HAVE SHOWN THIS SOLUTION...AND THE NAM THROUGH 84 HOURS IS ALSO CARVING OUT A DEEPER LOW. THE GFS REMAINS THE OUTLIER IN KEEPING A MUCH MORE NORTHERN AND PROGRESSIVE TRACK THROUGH THE PLAINS. HAVE TRENDED THE FORECAST TOWARD THE ECMWF/GEM SOLUTION WHICH HAS MUCH MORE SUPPORT THAN THE GFS AT THIS POINT...SEEMS MORE REALISTIC GIVEN THE UPPER JET ENERGY DIGGING DOWN THE BACKSIDE OF THE SYSTEM...AND IS THE PREFERRED HPC SOLUTION. FOLLOWING THIS SOLUTION...AN UPPER LOW WILL DIG THROUGH THE CENTRAL ROCKIES...CLOSING OFF OVER NORTHWEST KS BY MONDAY EVENING...THEN TRACKING EITHER EAST OR NORTHEAST OVER NORTHERN KS OR SOUTHERN NE MONDAY NIGHT THROUGH TUESDAY NIGHT BEFORE PUSHING INTO IA/MO BY WEDNESDAY. HOWEVER...THE EXACT TRACK IT TAKES ACROSS KS/NE AND THE TIMING OF THE LOW/S MOVEMENT IS STILL HIGHLY UNCERTAIN AND WILL HAVE A HUGE IMPACT ON THE AREA/S WEATHER DURING THE MONDAY NIGHT THROUGH TUESDAY NIGHT TIMEFRAME. FOR EXAMPLE...THE 20/12Z ECMWF SLOWED THE PROGRESSION OF THE SYSTEM DOWN BY NEARLY 12 HOURS COMPARED TO THE PREVIOUS 20/00Z RUN...WHICH OBVIOUSLY SLOWS DOWN THE INTRUSION OF COLDER AIR INTO THE CWA ON THE BACKSIDE AND RESULTANT CHANGEOVER TO SNOW. IT WAS LOOKING LIKE THIS CHANGEOVER WOULD OCCUR MONDAY NIGHT OVER MOST OF THE CWA...BUT THE SLOWER 12Z ECMWF WOULD LIKELY DELAY IT UNTIL TUESDAY FOR MOST IF NOT ALL AREAS. BY THAT TIME HOW MUCH COLD AIR WILL BE AVAILABLE FOR THE SYSTEM TO WORK WITH COMES INTO QUESTION SINCE THE SYSTEM IS NO LONGER DEEPENING...THEREBY SQUELCHING THE DYNAMIC COOLING...AND THE TAP OF COLDER AIR FROM THE NORTH BEGINS TO GET CUT OFF DUE TO THE CLOSED NATURE OF THE LOW. ON THE OTHER HAND...THE GEM IS STILL QUITE AGGRESSIVE WITH THE COLD AIR SURGE MONDAY NIGHT INTO TUESDAY...WHICH WOULD MEAN A SIGNIFICANT SNOW STORM FOR THE AREA. NEEDLESS TO SAY...A LOT OF UNCERTAINTY LOOMS WITH THIS SYSTEM. IT DOES LOOK ACTIVE/WET LATE MONDAY INTO TUESDAY...MAYBE TUESDAY NIGHT...BUT THE DETAILS INCLUDING PRECIP TYPE AND AMOUNT ARE STILL QUITE UNCERTAIN. MAIN CHANGES TO THE FORECAST WERE TO INSERT/INCREASE POPS MONDAY THROUGH TUESDAY NIGHT...COOL DAYTIME TEMPERATURES DURING THIS TIME...AND INTRODUCE A RAIN/SNOW MIX. WINDS WILL BE PRETTY STRONG ON THE BACKSIDE OF THE SYSTEM MONDAY NIGHT/TUESDAY...SO DEPENDING ON THE PRECIP PHASE THIS COULD CAUSE MORE PROBLEMS. WILL HAVE TO KEEP A CLOSE EYE ON THIS SYSTEM THROUGH THE WEEKEND...WITH MANY ADJUSTMENTS TO THE FORECAST LIKELY YET TO COME. FORTUNATELY...THIS SYSTEM PUSHES EAST PRIOR TO THE THANKSGIVING DAY HOLIDAY AND THE BIG TRAVEL DAY ON WEDNESDAY. A NORTH/NORTHWEST FLOW WILL RETURN ON WEDNESDAY IN BETWEEN THE DEPARTING SYSTEM AND UPPER RIDGING OVER THE WESTERN CONUS. DRY CONDITIONS THEN PREVAIL WEDNESDAY THROUGH FRIDAY AS THE WESTERN UPPER RIDGE GRADUALLY PROPAGATES EAST. MODELS HAVE BEEN BACK AND FORTH WITH A POSSIBLE TRAILING WAVE WEDNESDAY...WHICH COULD BRING IN A REINFORCING SHOT OF COLDER AIR...DELAYING THE WARM-UP...BUT DOESN/T LOOK TO BRING ANY PRECIP WITH IT. WILL SEE MODERATING TEMPERATURES WEDNESDAY THROUGH FRIDAY AS HIGHS CLIMB BACK INTO THE 50S BY WEEK/S END...MAKING FOR A NICE HOLIDAY. && .GID WATCHES/WARNINGS/ADVISORIES... NE...NONE. KS...NONE. && $$
