FXUS63 KDDC 050956
AFDDDC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DODGE CITY KS
356 AM CST SAT DEC 5 2009
.DISCUSSION...
DAYS 1-2...
PRECIP CHANCES AND TYPE SUNDAY AND SUNDAY NIGHT WILL BE THE MAIN
FORECAST CONCERN FOR THE PERIOD.
A LARGE UPPER TROUGH CONTINUES OVER THE CENTRAL CONUS AS OF 00Z,
WITH THE AXIS MAINLY OVER THE MS VALLEY AND EASTERN PLAINS. THE
NEXT UPPER TROUGH WAS SEEN DIGGING INTO NORTHERN ID AND MT, WITH
210 M HEIGHT FALLS. THE TRULY FRIGID AIR HAD SHIFTING EASTWARD
ALONG WITH THE TROUGH AXIS, AND THE MID LEVEL TEMPS HAD WARMED
ABOUT 5 C FROM THIS TIME YESTERDAY. AT THE SFC, A LEE TROUGH
EXTENDED ACROSS THE WESTERN PLAINS, WITH SOUTH TO SOUTHWESTERLY
WINDS. WITH CLEAR SKIES AND LOW DEWPOINTS, SFC TEMPS ARE STILL
DOWN IN THE TEENS WITH A FEW SINGLE DIGITS HERE AND THERE. THE
UPPER TROUGH WILL CONTINUE TO DIG INTO THE ID/UT REGION TODAY, AND
THE NORTHERN END OF THE SFC TROUGH AXIS STARTS TO MOVE EAST. NAM
AND GFS BOTH START CLOSING OFF A SFC LOW WEST OF EHA BY THIS
AFTERNOON, WHICH WILL SWITCH WINDS TO A MORE NORTHEASTERLY
DIRECTION ACROSS OUR NORTHERN CWA. HOWEVER, THE TRUE COLD AIR
ADVECTION HOLDS OFF, SO THINK THAT TEMPS WILL STILL GET FAIRLY
MILD. WITH PLENTY OF SUN, KEPT HIGHS IN THE MID 40S. STRONG COLD
AIR ADVECTION KICKS IN SATURDAY NIGHT AS THE SFC LOW MOVES
SOUTHEASTWARD. THERE WILL ALSO BE INCREASING CLOUDS HOWEVER, AND
THE NORTHERLY WINDS WILL KEEP US FAIRLY MIXED. LOWS SHOULD BOTTOM
OUT MAINLY IN THE TEENS.
BY SUNDAY, A WEAK LEAD SHORTWAVE MOVES OUT INTO THE PLAINS, WHILE
THE MAIN UPPER TROUGH REMAINS OVER THE WESTERN CONUS. THE
SHORTWAVE WILL BE FAST MOVING AND PROBABLY WON'T PRODUCE AN
EXTENDED PERIOD OF SYNOPTIC SCALE LIFT. HOWEVER, THE NAM AND GFS
BOTH SET UP A DECENT 700MB BAROCLINIC ZONE OVER OUR NORTHERN
COUNTIES. THE DEFORMATION IS NOT HUGELY IMPRESSIVE, AND WE ARE
JUST ON THE EDGE OF THE BEST RH VALUES, WITH THE BETTER MOISTURE
TO OUR NORTH. WE ALSO SHOULD BE IN THE FAVORABLE LEFT EXIT REGION
OF A 110-120 KT JET MOVING IN BY SUNDAY AFTERNOON. DO NOT THINK
WE WILL GET A WHOLE LOT OF ACCUMULATION WITH THE FAST MOVING
SYSTEM, BUT CAN'T RULE OUT SOME SNOW UP AROUND THE I-70 CORRIDOR.
BUMPED UP POPS IN OUR FAR NORTHERN COUNTIES. BEST ACCUMULATIONS
WILL BE TO THE NORTH AND EAST, BUT UP TO AN INCH COULD BE
POSSIBLE.
MODEL SOUNDINGS SHOW THAT MOST LOCATIONS WILL BE DEEPLY ENTRENCHED
BY COLD AIR BY THE TIME THE PRECIP ARRIVES, SO SNOW WILL BE THE
MOST LIKELY TYPE. THE EXCEPTION TO THIS WILL BE IN OUR
SOUTHEASTERN COUNTIES. THERE, NAM AND GFS SOUNDINGS AND TIME/HEIGHT
PLOTS SHOW A VERY SHALLOW LAYER OF MOISTURE AND LIFT. THERE IS A
GOOD AMOUNT OF DRY AIR ABOVE THIS, AND THEN ANOTHER MOIST LAYER WELL
ABOVE AROUND 400MB, PROBABLY TOO FAR FOR FEEDER-SEEDER MECHANISM.
THE LOW LEVEL MOIST LAYER LOOKS TO BE MOSTLY -4 C OR ABOVE, WHICH
WOULD NOT BE FAVORABLE FOR ICE CRYSTAL GROWTH. THUS, INCLUDED FZDL
MENTION AROUND P28. MODELS ARE ALL IN PRETTY GOOD AGREEMENT WITH
TAKING THE GOOD OMEGA OFF TO THE NORTHEAST AROUND 21-00Z, SO
TAPERED POPS OFF PRETTY QUICKLY SUNDAY EVENING.
AS FOR TEMPERATURES SUNDAY AND SUNDAY NIGHT, THE ARCTIC AIR WILL
BUILD IN THROUGHOUT THE PERIOD. WITH PLENTY OF CLOUDS AND 850MB
TEMPS BACK DOWN CLOSE TO -10 C, HIGHS ON SUNDAY WILL STAY MAINLY
IN THE 20S. THE EXCEPTION TO THIS COULD BE THE FAR SOUTHEAST. THE
NAM 2 M TEMPS HAVE READINGS CLOSE TO 40 SUNDAY AFTERNOON. HOWEVER,
IT IS PROBABLY NOT CATCHING ON THE THE COLD AIR VERY WELL, SO WILL
KEEP HIGHS AROUND P28 IN THE LOW 30S. THE SFC HIGH WILL BUILD DOWN
EVEN FURTHER BY SUNDAY NIGHT, ALTHOUGH NORTHERLY WINDS WILL STAY
UP AND ALONG WITH LINGERING CLOUDS, KEEP US FROM COMPLETELY
BOTTOMING OUT. WILL KEEP LOWS MAINLY IN THE LOW TEENS.
DAYS 3-7...
THERE WILL BE A WINTER STORM SYSTEM TO AFFECT THE CENTRAL PLAINS
REGION ON TUESDAY. THE ONLY QUESTION WILL BE WHERE EXACTLY THIS LATE
FALL WINTER SYSTEM WILL TRACK AND HOW MUCH RAIN AND SNOW MIGHT BE
POSSIBLE.
OVER THE LAST COUPLE OF RUNS, THE OPERATIONAL MODELS HAVE TRENDED
TOWARD LESS OF A DEFINED CLOSED LOW SYSTEM EJECTING FROM THE
POSITIVELY TILTED TROUGH OVER CANADA INTO THE WESTERN UNTIED STATES,
TO FAVOR AN OPEN 500 MB TROUGH INSTEAD. COLD SURFACE AIR WILL BECOME
INVIGORATED ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST, EXTENDING
INTO THE CENTRAL HIGH PLAINS BY TUESDAY MORNING WHILE CYCLOGENESIS
BEGINS DEVELOPING IN RESPONSE TO UPPER LEVEL HEIGHT FALLS OVER
SOUTHEAST COLORADO AND SOUTHWEST KANSAS.
THE TROUGHING NOW OCCURRING ACROSS THE WESTERN PLAINS IS INDICATING
THAT THE LEAD ANTICYCLONE IS SHIFTING INTO THE SOUTHERN MISSISSIPPI
VALLEY - A SETUP FOR RETURN BOUNDARY LAYER MOISTURE INTO OKLAHOMA
AND MISSOURI IS DEVELOPING, WHICH WILL BE IMPORTANT FOR A DEVELOPING
MOIST CONVEYOR BELT ON TUESDAY. THE GFS WHICH AT THE MOMENT HAS THE
FARTHER NORTHWARD SOLUTION FOR HEAVY PRECIPITATION DEVELOPS 30 TO 40
DEGREE DEWPOINTS NORTHWARD INTO SOUTH CENTRAL KANSAS ON TUESDAY. THE
ECMWF SEEMS DEEPER AND COLDER AS WELL AS A LITTLE SLOWER EJECTING
THE SURFACE LOW OUT OF THE PANHANDLES, AND STILL DEVELOPS THE RICHER
SURFACE DEW POINTS IN SOUTH CENTRAL KANSAS TUESDAY. FOR THIS
REASON, WE PLACED A CHANCE FOR RAIN OR SNOW IN OUR SOUTHEAST
COUNTIES TUESDAY GIVEN THE EXPECTED WARM ADVECTION, WHILST OVERALL
INCREASING POPS SIGNIFICANTLY ACROSS MOST AREAS OF THE FORECAST
AREAS.
SNOW AMOUNTS OF COURSE WILL BE HIGHLY DEPENDENT ON A MID LEVEL
WARM FRONT POSITION AND AVAILABLE MOISTURE; THERE ARE SIGNIFICANT
DIFFERENCES OF ABOUT A CATEGORY BETWEEN THE MODELS, BUT A RANGE OF
2-4 INCHES IS REASONABLE ACROSS CENTRAL KANSAS, WITH HIGHER TOTALS
MOST LIKELY NEAR THE I-70 CORRIDOR. PROBABLY JUST AS OR MORE
IMPORTANT OR LIKELY TO CAUSE SIGNIFICANT IMPACT MAY BE THE GRADIENT
WINDS BEHIND THE LOW TUESDAY EVENING, AS MODELS AND MOS ALL PRETTY
WELL AGREE ON 25 KNOT SUSTAINED WINDS WHICH MAY CAUSE CONSIDERABLE
BLOWING SNOW IN OUR EASTERN SECTIONS.
ANOTHER ROUND OF COLD TEMPERATURES WILL AGAIN AFFECT THE AREA, MOST
NOTABLY ON WEDNESDAY, AND THIS TIME PERHAPS WILL BE MUCH COLDER WITH
HIGHS ONLY INTO THE TEENS OVER ANY SNOW COVERED AREAS, BUT WARMER TO
NEAR THE FREEZING MARK IN WESTERN AND SOUTHERN COUNTIES ALONG THE
COLORADO AND OKLAHOMA LINES.
&&
AVIATION...
WEAK LEE SIDE SURFACE TROUGHING WILL CONTINUE TO INTENSIFY THIS
MORNING, ALLOWING SURFACE WINDS TO INCREASE VEERING SOUTHEAST TO
AROUND 15 KTS LATE THIS MORNING, AND WEAKEN TO LIGHT AND VARIABLE
AHEAD OF THE NEXT FRONTAL BOUNDARY EXPECTED SUNDAY. CLOUD COVER WILL
INCREASE ACROSS THE AREA, MOST SIGNIFICANTLY AFTER 00Z SUN WHEN
BOUNDARY LAYER COOLING , PRESSURE FALLS AND MOISTURE ADVECTION AND
CONVERGENCE BEGINNING TO HELP DEVELOP LOWERED IFR CEILINGS WHICH MAY
POSSIBLY AFFECT THE KHYS TERMINAL BY AS EARLY AS 06Z SUNDAY, BUT
MORE LIKELY AROUND 12Z.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 45 18 27 13 / 0 10 30 10
GCK 45 17 25 11 / 0 10 30 10
EHA 47 16 29 10 / 0 10 20 10
LBL 48 18 29 12 / 0 10 20 10
HYS 44 17 24 12 / 0 10 60 30
P28 45 24 35 17 / 0 10 30 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
FN26/33/33
