FXUS63 KEAX 152329
AFDEAX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
528 PM CST TUE DEC 15 2009
...UPDATED AVIATION DISCUSSION...
.DISCUSSION...
/353 PM CST TUE DEC 15 2009/
MAIN CHALLENGE IN THE SHORT TERM DEALS WITH TEMPERATURES WITH WINDS
BECOMING SOUTHERLY AND SNOW PACK STILL PRESENT ACROSS THE NORTH OF
THE FORECAST.
TONIGHT:
SURFACE HIGH PRESSURE WILL SLIDE THROUGH THE REGION WHICH FOR A
PERIOD OF TIME WILL LEAD TO GOOD RADIATIONAL COOLING. WITH DRY AIR
ALREADY IN PLACE AND CLEAR SKIES EXPECTED THE PRIMARY ITEM LACKING
TO PLUMMET TEMPERATURES APPEARS TO BE THE TIMING OF THE HIGH THROUGH
THE REGION. BY EARLY TOMORROW MORNING THE HIGH SHOULD BE TO OUR EAST
SO WINDS SHOULD RETURN TO A SOUTHERLY/SOUTHEASTERLY DIRECTION AND
THUS LIMIT JUST HOW COLD WE GET. REGARDLESS OVERNIGHT LOWS WILL STILL
FALL AT LEAST INTO THE LOW TEENS ACROSS OUR SOUTH AND INTO THE SINGLE
DIGITS ACROSS THE NORTH OVER THE SNOW PACK.
WEDNESDAY - WEDNESDAY NIGHT:
A DECENT WARM UP IS EXPECTED FOR MOST LOCATIONS WITH SOUTHERLY
SURFACE FLOW AND SOUTHWESTERLY FLOW ALOFT ADVECTING WARMER AIR INTO
THE REGION. THIS WARM UP WILL BE MOST NOTICEABLE ACROSS THE SOUTHERN
HALF OF THE FORECAST AREA. WITH SNOW COVER STILL LIKELY IN THE NORTH
THERE WILL BE A LIMITATION TO JUST HOW WARM THAT AREA GETS. JUST HOW
MUCH IS A BIG QUESTION BUT THE AREAS OF DEEPEST SNOW COVER WILL
LIKELY REMAIN BELOW FREEZING.
THURSDAY:
WITH MOISTURE ADVECTING INTO THE AREA OVER ANY REMAINING SNOW COVER
IT IS LOOKING MORE LIKELY THAT FOG MAY FORM ACROSS THE NORTHERN
PORTIONS OF THE FORECAST AREA EARLY THURSDAY MORNING. AT THIS TIME
CONFIDENCE REMAINS FAIRLY LOW DUE TO UNCERTAINTIES WITH LOW LEVEL
MOISTURE BUT WILL NEED TO WATCH THIS PERIOD FOR THE POTENTIAL FOR
FOG. REGARDING TEMPERATURES...IT LOOKS SIMILAR TO WEDNESDAY FOR
HIGHS BUT MAY BE A BIT WARMER ACROSS THE SOUTH AND 3 TO 5 DEGREES
WARMER ACROSS THE NORTH.
CDB
MEDIUM RANGE (FRIDAY THROUGH TUESDAY)...
LATEST RUN OF MID RANGE MODELS STILL ADVERTISE THAT A QUASI-ZONAL
FLOW...ACROSS THE PLAINS MOST OF THE WORK WEEK...WILL QUICKLY
TRANSITION INTO A MORE AMPLIFIED PATTERN AS A DOWN STREAM BLOCKING
PATTERN /ACROSS GREENLAND/ RETROGRADES TOWARDS CENTRAL CANADA. THE
RESULTING MERIDIONAL COMPONENT OF THE FLOW LOOKS POISED TO SPREAD
STILL MORE COLD AIR SOUTH INTO THE CENTRAL PLAINS STARTING
FRIDAY...AND NOT LET UP THROUGH THE LAST HALF OF THE FORECAST. HAVE
HEDGED TEMPERATURES A LITTLE COOLER THAN GOING FORECAST NUMBERS AS A
RESULT...ESPECIALLY FOR THE OVERNIGHT PERIODS ALONG THE IOWA
BORDER...BUT HAVE AVOIDED GOING TOO MUCH COOLER AS DETAILS IN THE
CLOUD COVER AND SURFACE WINDS COULD PREVENT TEMPERATURES FROM
FALLING TOO FAR.
OTHERWISE...MAIN FOCUS FOR THE LAST HALF OF THE FORECAST IS ON THE
POTENTIAL FOR PRECIPITATION AS SOME SHORTWAVES MOVE THROUGH THE
PLAINS. FIRST OF THE EXPECTED SHORTWAVES WILL ARRIVE FRIDAY AS IT
MOVES OVER THE TOP OF THE WEAK RIDGE POSITIONED OVER THE WESTERN
CONUS. GFS/ECMWF/AND GEM ALL ADVERTISE AT A MINIMUM SOME SNOW
OCCURRING WITH THIS SYSTEM AS IT MOVES THROUGH...BUT THE NAM80 IS AN
OUTLIER BEING A BIT WARMER AND LESS INCLINED TO SQUEEZE ANY MOISTURE
OUT ACROSS THE REGION. HAVE CONTINUED TO LEAN THE FORECAST TOWARDS
THE CONSENSUS SOLUTION OFFERED BY THE MAJORITY OF THE MODELS...
BRINGING THE WAVE IN ACROSS KANSAS AND THROUGH SOUTHERN MISSOURI.
WITH THIS IN MIND...FRONTOGENIC FORCING IS LOOKING MODEST AT BEST AT
THIS TIME ACROSS THE CWA. LOOKING AT SOUNDINGS...PREVIOUS
FORECASTERS NOTED THAT SATURATION WILL NEED TO OCCUR IN A TOP-DOWN
FASHION...AND THAT STILL LOOKS TRUE. PUTTING THIS ALL TOGETHER...AND
HAVE OPTED TO KEEP POPS IN THE SLIGHT CHANCE CATEGORY FOR FRIDAY AND
FRIDAY NIGHT AS THE SHORTWAVE MOVES THROUGH DUE TO CONCERNS ON LIFT
AND MOISTURE. FOR SATURDAY...HAVE KEPT SLIGHT CHANCE POPS GOING FOR
CONTINUING COLD AIR ADVECTION IN THE CLOUD BEARING LAYERS ALOFT.
LATER IN THE WEEKEND...INTO THE FOLLOWING WORK WEEK...ANOTHER
SHORTWAVE IS EXPECTED TO ENTER THE NORTHERN/CENTRAL PLAINS. AT THIS
POINT CONSENSUS IS A LITTLE HARD TO FIND AMONG THE VARYING
MODELS...THOUGH THE GEM AND ECMWF ARE OFFERING THE BEST COMBINATION
OF CONSISTENCY AND AGREEMENT. GFS IS A BIT OF AN OUTLIER AS IT
REALLY WANTS TO BRING A STRONG SHORTWAVE IN WITH LOTS OF
PRECIPITATION. ULTIMATELY...THE RESULTING SOLUTION FOR THE FAR SIDE
OF THE WEEKEND WILL DEPEND ON IF AND WHEN A POLAR VORTEX MOVES IN
ACROSS THE GREAT LAKES...WHICH HAS A LOT TO DO WITH THE GREENLAND
BLOCKING PATTERN THAT WILL BE BACKING INTO CENTRAL CANADA.
POTENTIALLY A LOT OF IF'S THERE. WITH THE GENERAL IDEA THAT WE WILL
STILL BE IN A PREVAILING NORTHWEST FLOW...HAVE OPTED TO KEEP THE
FORECAST DRY OF ANYTHING OTHER THAN SILENT SLIGHT CHANCE
POPS...ALONG THE IOWA BORDER SUNDAY...DUE TO LOW CONFIDENCE IN
CURRENT SOLUTIONS. AS FRIDAYS EVENT GET PINNED DOWN...ANTICIPATE THE
LATE WEEKEND EARLY NEXT WORK WEEK PERIODS TO BECOME A BIT MORE
CLEAR.
CUTTER
&&
.AVIATION...
FOR THE 00Z TAFS...VFR CONDITIONS WILL PREVAIL THROUGHOUT THE VALID
PERIOD. WINDS WILL BE LIGHT AND VARIABLE THROUGH EARLY MORNING AS A
SURFACE HIGH PRESSURE MOVES ACROSS THE AREA. AS THE HIGH MOVES EAST
WINDS SHOULD SWING TO A SOUTHEAST THEN SOUTH DIRECTION ON WEDNESDAY.
PC
&&
.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
