FXUS63 KTOP 252038
AFDTOP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
238 PM CST WED NOV 25 2009
.DISCUSSION...
SHORT TERM (THROUGH THURSDAY)...
SHORTWAVE TROUGH/CLOSED UPPER LOW THAT SPREAD MIDLEVEL CLOUDINESS
ACROSS NORTHEAST KANSAS THIS MORNING HAS SHIFTED EAST OF THE
AREA...WITH A BROAD REGION OF DRYING AND SUBSIDENCE IN ITS WAKE.
THIS HAS ALLOWED AFTERNOON SKIES TO CLEAR...SAVE FOR STRATOCU NOSING
THROUGH THE NORTH CENTRAL PART OF THE STATE...AND SFC WINDS TO PICK
UP TO 15-20MPH WITH HIGHER GUSTS. OTHERWISE...20Z WATER VAPOR
IMAGERY DEPICTED A LONG WAVE TROUGH WITH SEVERAL EMBEDDED IMPULSES
IMPACTING THE EASTERN CONUS...RIDGING EXTENDING FROM THE WEST COAST
TO THE ROCKIES...AND AN UPSTREAM TROUGH OFF THE WESTERN CANADIAN
COASTLINE.
TONIGHT...925:700MB RH FIELD ON THE NAM/GFS/RUC INDICATED THAT
MOISTURE AND CLOUD COVER ROTATING AROUND THE UPPER LOW WILL REMAIN
NORTH AND EAST OF THE FORECAST AREA. THEREFORE...REDUCED CLOUD COVER
ALL AREAS...AND LOWERED LOWS A TOUCH IN THE NORTH CENTRAL PART OF
THE STATE...WITH GOOD RADIATIONAL COOLING EXPECTED...AND SLACKENING
WIND FIELD. KEPT LOWS A BIT WARMER SOUTH AND EAST WHERE LL WIND
FIELD REMAINS A BIT MORE MIXY. NEVERTHELESS...PORTIONS OF EAST
CENTRAL KANSAS YET TO OBSERVE A HARD FREEZE THIS SEASON MAY DO SO
EARLY THURSDAY MORNING.
FOR THANKSGIVING...A PLEASANT DAY TAKING SHAPE ACROSS THE REGION.
MID AND LOW LEVEL COLD ADVECTION PERSISTS FOR MUCH OF THE DAY...TILL
AFOREMENTIONED UPPER RIDGE BEGINS TO SHIFT EAST...AND WIND FIELD
BACKS DURING THE EVENING. MIXED DOWN TEMPS FROM NEAR 900MB FOR
AFTERNOON HIGHS...WHICH YIELDED VALUES NEAR GOING FORECAST HIGHS IN
THE MID TO UPPER 40S.
LUNDE
LONG TERM (FRIDAY THROUGH TUESDAY)...
FRIDAY LOOKS TO BE THE NICEST DAY OUT OF THE NEXT SEVEN AS AN
UPPER LEVEL RIDGE BUILDS OVER THE TOP OF 24 HOURS WORTH OF WARM
AIR ADVECTION. TEMPERATURES IN THE 60S APPEAR TO BE A SAFE BET
OVER MUCH OF THE REGION. SOUTH WINDS WILL HELP THE BOUNDARY LAYER
MIX UP A BIT...BUT ANY DEEPER MIXING WOULD ALLOW FOR EVEN WARMER
TEMPERATURES AS THERE WILL BE A NICE LAYER OF WARM AIR AROUND 850
HPA. THE WARM AIR WILL HANG AROUND THROUGH FRIDAY NIGHT AND IN TO
THE FIRST PART OF SATURDAY.
THE FORECAST GETS QUITE INTERESTING AT THIS POINT WITH SMALL
DIFFERENCES IN THE FORECAST MODEL FIELDS LEADING TO SIGNIFICANT
DIFFERENCES IN SENSIBLE WEATHER FOR TOP CWA. GFS SOLUTIONS HAVE
BEEN ALL OVER THE MAP OVER THE LAST 3 TO 4 MODEL RUNS WHILE THE
NAM APPEARS TOO DEEP WITH THE SOUTHWESTERN ENERGY AND THE ECMWF
HAS REMAINED FAIRLY CONSISTENT BUT STILL WITH ITS WOBBLES IN
SYSTEM STRENGTH AND LOCATION. MUCH OF THIS VARIABILITY IS DUE TO
JUST HOW EACH MODEL RUN HANDLES THE SPLIT ENERGY AS IT COMES
ONSHORE. THE CURRENT PREFERENCE FOR THIS FORECAST...AS WELL AS THE
PREFERENCE OF HPC TODAY...IS THE 12Z ECMWF SOLUTION IN TERMS OF
THE OVERALL PATTERN...WITH MANY DETAILS YET TO BE SORTED OUT.
ON TO THE SENSIBLE WEATHER...BY LATER ON SATURDAY A COLD FRONT
WILL BEGIN TO WORK ITS WAY INTO NORTHERN KANSAS AS THE NORTHERN
STREAM SHORT WAVE EJECTS OUT INTO THE NORTHERN PLAINS. A COLD
AIRMASS WILL BE PULLED OUT OF SOUTHERN CANADA DROPPING HIGHS INTO
THE LOWER TO MID 40S BY SUNDAY. AT THE SAME TIME...A STRONGER
PIECE OF UPPER LEVEL ENERGY WILL BE MAKING ITS WAY OUT OF SOUTHERN
CALIFORNIA. MOISTURE RETURN WILL RAPIDLY ENSUE AHEAD OF THIS
SYSTEM WITH A BROAD AREA OF PRECIPITATION DEVELOPING ACROSS THE
SOUTHERN HALF OF THE PLAINS ON SUNDAY OUT AHEAD OF THE MAIN UPPER
LOW. MEANWHILE...WITH THE COLD FRONT ALREADY THROUGH THE CWA...
TEMPERATURES WILL BE PLENTY COLD FOR A CHANGEOVER TO WINTRY
PRECIPITATION.
UNFORTUNATELY...THERE ARE SIMPLY TOO MANY UNKNOWN DETAILS AT THIS
POINT TO TRY AND FORECAST THE EXACT PRECIPITATION TYPE. WILL SAY
THAT RAIN DOES APPEAR TO BE THE LIKELY TYPE EARLY ON...WITH SNOW
THE LIKELY PRECIP TYPE BY THE END OF THE EVENT ON THE NORTH SIDE
OF THE LOW. THE IN BETWEEN TIME IS WHERE IT GETS QUITE TRICKY. IN
ADDITION...AND JUST TO ILLUSTRATE THE AMOUNT OF UNCERTAINTY IN THIS
FORECAST...PURE MODEL OUTPUT SUGGESTS ANYWHERE FROM 0.00 TO 1.50
INCHES OF LIQUID PRECIPITATION IN PORTIONS OF EAST CENTRAL KANSAS.
NEEDLESS TO SAY...SOME FORECAST CHANGES AND ADDED DETAIL WILL BE
LIKELY OVER THE NEXT SEVERAL PERIODS AS THE STORM SYSTEM COMES ON
SHORE AND IS SAMPLED BETTER BY THE UPPER AIR OBSERVATION NETWORK.
BARJENBRUCH
&&
.AVIATION...
FOR THE 18Z TAFS...VFR CONDITIONS EXPECTED THROUGH THE TAF PERIOD.
PRIMARY CONCERN LIES WITH WINDS...WITH GOOD MIXING POST-FROPA THIS
AFTERNOON. TOP/FOE/MHK ALREADY GUSTING TO NEAR 30MPH...BUT WINDS
ALOFT GRADUALLY SLOW THROUGH THE DAY. THEREFORE...WILL MONITOR
WIND GUST OBS THROUGH THE AFTERNOON...BUT DO NOT EXPECT THEM TO
GET MUCH STRONGER THAN ALREADY OBSERVED AS THE DAY PROGRESSES.
LUNDE
&&
.TOP WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
