FXUS63 KDDC 070942
AFDDDC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DODGE CITY KS
342 AM CST MON DEC 7 2009
.DISCUSSION...
DAYS 1-2...
UNCERTAINTY ABOUT THE EXTENT OF MODIFICATION OF THE ENTRENCHED
ARCTIC AIR IN THE CENTRAL PLAINS AS THE DEEP SURFACE CYCLONE
DEVELOPS IN SOUTHEAST COLORADO TUESDAY MORNING MAKES TEMPERATURE
FORECASTING A REAL CHALLENGE...ESPECIALLY ALONG THE OKLAHOMA
BORDER...ON TUESDAY. SOME UNCERTAINTY IN THE TEMPERATURE PROFILE AND
THE EVOLUTION OF A WARM LAYER ALOFT MAKES PRECIPITATION TYPE
PROBLEMATIC, AS WELL.
STRONG UPPER LEVEL RIDGING CONTINUES FROM THE EASTERN PACIFIC ACROSS
ALASKA TO THE FRIGID ARCTIC, AND A DEEP LOBE OF THE POLAR VORTEX IS
BEGINNING TO DROP SOUTHWARD INTO NORTHERN CANADA. SLOW RETROGRESSION
OF THE HIGH LATITUDE UPPER LEVEL ANTICYCLONE AND MAINTENANCE OF LONG
WAVE TROUGH IN THE WESTERN UNITED STATES IS CONSISTENT WITH EASTWARD
PROGRESSION OF THE MADDEN JULIAN OSCILLATION INTO THE WESTERN
HEMISPHERE. THE GFS, CANADIAN AND 12Z ECMWF ARE IN GOOD AGREEMENT
WITH EVOLUTION OF THE ATMOSPHERE THROUGH MID WEEK, ALTHOUGH THE 00Z
CANADIAN AND GFS ARE SLIGHTLY FASTER WITH THE POWERFUL UPPER LEVEL
TROUGH THAT WILL MOVE ACROSS THE CENTRAL PLAINS TUESDAY. THE GFS HAS
DEMONSTRATED GOOD RUN TO RUN CONSISTENCY AND LARGELY WAS USED FOR
MINOR GRID MODIFICATIONS TODAY.
DEEP, COLD AIR WILL REMAIN IN PLACE ACROSS WESTERN KANSAS FOR THE
NEXT WEEK. CONSIDERABLE HIGH LEVEL TROPICAL MOISTURE HAS SPREAD FROM
THE EASTERN PACIFIC INTO THE WESTERN UNITED STATES AND WILL CONTINUE
TO INVADE THE CENTRAL PART OF THE COUNTRY THIS MORNING. THE DEEP
UPPER LEVEL TROUGH NEAR THE NORTHERN CALIFORNIA COAST WILL MOVE INTO
THE GREAT BASIN TONIGHT AND WILL APPROACH WESTERN KANSAS TUESDAY.
LOWERING PRESSURES IN THE LEE OF THE ROCKIES THIS AFTERNOON WILL
INCREASE ISENTROPIC LIFTING OVER THE ENTRENCHED ARCTIC AIR, AND
LIGHT SNOW CAN BE EXPECTED TO REDEVELOP THIS AFTERNOON. A MINOR
UPPER LEVEL TROUGH EVIDENT IN SATELLITE IMAGERY NEAR 30N/125W WILL
MOVE RAPIDLY EASTWARD IN THE STRONG FLOW AND SHOULD REACH THE
CENTRAL PLAINS BY LATE AFTERNOON AND MAY ENHANCE DEVELOPMENT OF
LIGHT PRECIPITATION. SUBSIDENCE WITH THE SURFACE RIDGE IN WESTERN
KANSAS HAS RESULTED IN EROSION OF THE STRATUS DECK THIS MORNING, BUT
INCREASING MID AND HIGH LEVEL CLOUDINESS WILL RESULT IN ONLY LIMITED
INSOLATION TODAY. TEMPERATURES WILL BE SLOW TO RISE, AND HIGHS FROM
THE UPPER TEENS TO THE MID 20S CAN BE EXPECTED.
ISENTROPIC LIFTING WILL INCREASE TONIGHT AS CYCLOGENESIS OCCURS IN
SOUTHERN COLORADO AND SOUTHEAST FLOW INCREASES ABOVE THE ARCTIC AIR.
ALTHOUGH LOW LEVEL MOISTURE IS LIMITED ALONG THE TEXAS GULF COAST,
THE COOL AIR THAT INVADED THE GULF HAS MODIFIED SIGNIFICANTLY OVER
THE WARM WATER. DEWPOINTS JUST OFF THE TEXAS COAST HAD RECOVERED TO
THE UPPER 60S BY MIDNIGHT. LOW LEVEL MOISTURE WILL RETURN QUICKLY
TODAY AND TONIGHT, AND SHOULD REACH THE CENTRAL PART OF THE COUNTRY
ON TUESDAY. WIDESPREAD LIGHT SNOW SHOULD DEVELOP WITH CONTINUED
ISENTROPIC LIFTING TONIGHT. WITH DEEP MOISTURE, THERE SHOULD BE
SUFFICIENT ICE CRYSTALS TO KEEP THE PRECIPITATION SNOW UNTIL AT
LEAST LATE TONIGHT. MODEL SOUNDINGS INDICATE SUFFICIENT WARM AIR
ADVECTION TO DEVELOP A WARM LAYER BETWEEN H8 AND H7 BY 12Z TUESDAY,
AND THE PRECIPITATION MAY CHANGE TO LIGHT FREEZING DRIZZLE OR LIGHT
FREEZING RAIN NEAR THE OKLAHOMA BORDER. WITH THE COLD GROUND, ANY
FREEZING PRECIPITATION THAT DEVELOPS WILL CAUSE TRAVEL PROBLEMS, AND
A WINTER WEATHER ADVISORY SEEMS APPROPRIATE TO COVER THE SNOWFALL
AND POTENTIAL MIXED PHASE. STRONGER MID LEVEL FRONTOGENESIS ALONG
THE SHARP MID LEVEL BAROCLINIC ZONE JUST NORTH OF THE MID LEVEL
CYCLONE WILL SUPPORT HEAVIER SNOWFALL MONDAY NIGHT AND TUESDAY, AND
A WINTER STORM WARNING WAS ISSUED FOR THE THE NORTHERN COUNTIES. THE
NUMERICAL MODELS LIKELY ARE TOO QUICK TO ERODE THE ARCTIC AIR, AND
COLD TEMPERATURES WERE MAINTAINED ON TUESDAY WITH HIGHS NEAR THE
FREEZING MARK ONLY NEAR THE OKLAHOMA BORDER.
MODEL SOUNDINGS BECOME INCREASINGLY UNSTABLE DURING THE DAY TUESDAY,
AND HIGH SNOWFALL RATES ARE LIKELY IN NORTHERN KANSAS WITH TOTAL
SNOW ACCUMULATIONS APPROACHING A FOOT LOCALLY. THERE MAY BE
SUFFICIENT INSTABILITY ABOVE THE COLD AIR TO SUPPORT A THUNDERSTORM
IN SOUTH CENTRAL KANSAS WHEN THE UPPER LEVEL COLD POOL APPROACHES
TUESDAY AFTERNOON.
FRIGID ARCTIC AIR WILL PLUNGE SOUTHWARD BEHIND THE DEEP SURFACE
CYCLONE TUESDAY AFTERNOON AND TUESDAY NIGHT, AND STRONG NORTH WINDS
WILL PRODUCE NEAR BLIZZARD CONDITIONS IN AREAS WITH SIGNIFICANT
SNOWFALL. WIND SPEEDS APPEAR TO BE MARGINAL FOR A BLIZZARD, BUT THE
WINTER STORM WARNING MAY HAVE TO BE UPGRADED AS THE EVENT EVOLVES.
TEMPERATURES LIKELY WILL DROP BELOW ZERO IN WEST CENTRAL KANSAS
TUESDAY NIGHT AS ARCTIC HIGH PRESSURE BUILDS SOUTHWARD AND WINDS
DIMINISH.
DAYS 3-7...
A BROAD UPPER TROUGH EXTENDING FROM NORTHERN CANADA INTO THE CENTRAL
CONUS WILL HELP BRING VERY COLD TEMPS BEHIND TUESDAY'S STORM. COLD
SFC HIGH PRESSURE WILL BE IN PLACE WITH 850MB TEMPS DOWN INTO THE
LOW TEENS C. GOING FORECAST HAD WEDNESDAY'S HIGHS IN THE TEENS AND
20S, WITH WEDNESDAY NIGHT LOWS DIPPING BELOW ZERO F IN OUR NORTH.
SEE LITTLE REASON TO MAKE BIG CHANGES TO THIS. HEIGHTS WILL START
TO RISE ON THURSDAY, WITH THE SFC HIGH MOVING EAST AND SOUTHEASTERLY
WINDS RETURNING. WHILE SOME OF THIS WILL BE THE RECIRCULATION OF
COLDER AIR, THINK THAT THERE SHOULD BE SOME RECOVERY OF TEMPS.
TOWARDS THE END OF THE WEEK AND INTO THE WEEKEND. THE MODELS ALL
START TO TRANSITION TO NEAR ZONAL FLOW, ALTHOUGH THERE ARE
SIGNIFICANT DIFFERENCES IN MINOR SHORTWAVES MOVING THROUGH. THE
ECMWF HAS A FAIRLY VIGOROUS SHORTWAVE MOVING INTO THE PLAINS ON
FRIDAY, WHILE THE CANADIAN AND GFS ARE NOT NEARLY AS STRONG. THE
GFS ON THE OTHER HAND, BREAKS OUT A DECENT AMOUNT OF PRECIP THURSDAY
NIGHT OVER NORTHERN OK AND SOUTHERN KS DUE TO PRETTY GOOD ISENTROPIC
LIFT. NCEP ENSEMBLES PRECIP PROBABILITIES ARE FAVORABLE, BUT THE
CANADIAN ENSEMBLE MEMBERS ARE NOT. DUE TO THE UNCERTAINTY, WILL
HOLD OFF ON ADDING ANY PRECIP FOR THE THURSDAY/FRIDAY TIME FRAME,
BUT DID INCREASE CLOUD COVER SOMEWHAT. THE NEAR ZONAL FLOW WILL
CONTINUE INTO THE WEEKEND, WITH DETERMINISTIC MODELS SHOWING ANOTHER
SHORTWAVE TROUGH MOVING BY TO THE NORTH. THE ECMWF SOLUTION TAPS
THE COLD AIR AND BRINGS ANOTHER ARCTIC FRONT DOWN LATE ON SUNDAY,
WHILE THE GFS CONTINUES TO KEEP THINGS FAIRLY MILD. GOING FORECAST
HAD TEMPS COOLING BY MONDAY, AND LOOKING AT THE LARGE SPREAD ON THE
NAEFS PLOTS, WILL KEEP THIS TREND FOR NOW.
&&
AVIATION...
MVFR CONDITIONS HAVE CONTINUED TO HANG ON OVER SOUTHERN AND EASTERN
PORTIONS OF THE FORECAST AREA. HOWEVER, SAT TRENDS SHOW CLEARING IN
OUR NORTH AND WEST, WITH KGCK AND KHYS ALREADY GOING VFR. THINK
THIS TREND WILL CONTINUE AND KDDC WILL GO VFR BEFORE 12Z. MID AND
HIGH CLOUDS WILL CONTINUE, AND NORTH WINDS AROUND 10-15 KTS WILL
SHIFT AROUND TO THE EAST BY LATE AFTERNOON. VFR CONDITIONS WILL
CONTINUE THROUGH 03-06Z OR SO, THEN CEILINGS WILL GO DOWN TO IFR OR
LOWER AS THE NEXT UPPER TROUGH MOVES OUT. THERE WILL ALSO BE A
DECENT AMOUNT OF -SN TOWARDS 12Z, WHICH COULD HELP REDUCE VIS DOWN
TO IFR CATEGORIES.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 21 19 28 5 / 30 80 90 20
GCK 20 19 27 1 / 50 80 90 20
EHA 24 23 33 6 / 20 40 40 10
LBL 25 22 33 7 / 30 50 50 10
HYS 19 16 23 2 / 60 100 100 40
P28 26 22 36 12 / 20 70 70 30
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 6 PM THIS EVENING UNTIL MIDNIGHT CST
TUESDAY NIGHT FOR KSZ030-031-044>046-064>066.
WINTER WEATHER ADVISORY FROM 6 PM CST /5 PM MST/ UNTIL MIDNIGHT CST
/11 PM MST/ TUESDAY NIGHT FOR KSZ043-061>063-074>081-084>090.
&&
$$
FN01/26
