FXUS63 KDDC 102155
AFDDDC
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DODGE CITY KS
355 PM CST THU DEC 10 2009
.DISCUSSION...
DAYS 1-2...
A BROAD SYNOPTIC MID LEVEL CYCLONIC FLOW IS WELL ESTABLISHED ACROSS
THE CONUS TODAY, MARKED BY TREMENDOUSLY DEEP COLD AIR ACROSS THE
NORTHERN AND CENTRAL PLAINS AND UPPER MIDWEST INTO THE OHIO VALLEY.
A DEEP TROPOSPHERIC JET ALSO EXTENDED FROM THE SOUTHERN PLAINS AND
MISSISSIPPI VALLEY, THROUGH THE EAST COAST. AN 850 MB LEVEL
TEMPERATURE ISOTHERM OF AROUND -10 DEGREES COINCIDED ROUGHLY WITH
THE SOUTHERN EXTENT OF THE SNOW PACK NEAR THE KANSAS OKLAHOMA LINE
THIS MORNING.
FORECAST CHALLENGES ACROSS THE NEXT 60 OR SO HOURS WILL REVOLVE
AROUND TEMPERATURES, HOW MUCH SNOW MIGHT MELT AND THEN RESULTING
TEMPERATURES DUE TO WARM AIR ADVECTION AND CLOUD COVER FROM AN
APPROACHING MID TROPOSPHERIC WAVE AROUND THE SATURDAY TIMEFRAME.
THE CYCLONIC FLOW PATTERN IS CURRENTLY UNDERGOING A TRANSITION TO
ZONAL FLOW AS SIGNIFICANT MID LEVEL HEIGHT RISES ARE ONGOING FROM
THE NORTHERN ROCKIES THROUGH THE CENTRAL PLAINS, AND MOSTLY
RESPONSIBLE FOR A SIGNIFICANT JUMP IN TEMPERATURES TO THE 20S EVEN
ACROSS THE DEEP SNOW AREA ALONG THE INTERSTATE 70 CORRIDOR THIS
AFTERNOON. TEMPERATURES TONIGHT WILL BE NOT AS COLD AS THIS
MORNING, SINCE HIGHER SURFACE PRESSURE IS SHIFTING EASTWARD AND
INCREASED WINDS FROM THE SOUTH-SOUTHEAST SHOULD BE DEVELOPING. A
LITTLE HIGH THIN CIRRUS MAY ALSO BE PART OF THE EQUATION LIMITING
RADIATIONAL COOLING A BIT DURING THE OVERNIGHT HOURS, BUT CLEARING
WOULD PROBABLY FOLLOW TOWARD 9-12Z TIMEFRAME. AS WINDS TURN SOUTHERLY
TONIGHT, SOME WARMER/HIGHER THETA-E AIR WILL BE PULLED NORTH ACROSS
THE SURFACE COLD AIR ESPECIALLY IN THE WESTERN COUNTIES, AND
DEWPOINT DEPRESSIONS WILL BE QUITE LOW. GIVEN THIS, THE POTENTIAL
EXISTS FOR PATCHY OR AREAS OF LIGHT FOG TO DEVELOP IN OUR WESTERN
SECTIONS AND ALTHOUGH THE CONFIDENCE IS NOT GREAT, IT MAY BE
MENTIONED IN THE ZONE FORECASTS TONIGHT.
SNOW MELTING SHOULD ACCELERATE ON FRIDAY AS TEMPERATURES WARM CLOSER
TO THE 30 DEGREE MARK ACROSS FARTHER NORTH PORTIONS OF THE FORECAST
AREA, BUT MUCH OF THE INCREASED NEAR SURFACE ENERGY WILL BE GOING
INTO SNOW MELT ESPECIALLY ACROSS OUR NORTHEAST HALF FORECAST AREA. A
PREFRONTAL TROUGH WILL DEVELOP ACROSS THE HIGH PLAINS ON SATURDAY,
AND BY SATURDAY NIGHT, A SITUATION COULD DEVELOP WHERE INCREASING
WARM ADVECTION BEGINS IN OUR SOUTHEAST SECTIONS WHILE MELTED SNOW
BEGINS REFREEZING IN THE NORTH, AND SOME FOG OR EVEN FREEZING FOG
DEVELOPS.
MORE SIGNIFICANT MELTING SHOULD OCCUR SATURDAY OF REMAINING SNOW IN
THE HODGEMAN-EDWARDS COUNTIES NORTH TO INTERSTATE 70 REGION, IN
ADVANCE OF A MID LEVEL SHORTWAVE THAT IS AGREED UPON BY ALL THE
MODELS, WHICH GENERALLY COINCIDES WITH A PREFRONTAL SURFACE TROUGH
FOR THE WEEKEND. HAVE LEFT THE POTENTIAL FOR A LITTLE LIGHT DRIZZLE
IN THE FAR EAST EARLY SATURDAY AS IMPRESSIVE LIFT SHOULD BE
SOMEWHERE ACROSS CENTRAL OR EASTERN KANSAS.
RUSSELL
DAYS 3-7...
THE MAIN FORECAST PROBLEM IS THE EXTENT OF THE WARMUP SUNDAY AND THE
TIMING AND STRENGTH OF THE SHALLOW COLD SURGE SUNDAY NIGHT AND
MONDAY.
THE ECMWF HAS BEEN CONSISTENTLY SHOWING A STRONG DOWNSLOPE
SURGE SUNDAY FROM DDC SOUTH TO THE BORDER. WITH SNOW COVER GONE IN
OUR SOUTHERN COUNTIES, TEMPS SHOULD EASILY RISE INTO THE 50S AND EVEN
60S GIVEN THAT THE WINDS WILL BE BLOWING FROM A REGION THAT WILL
HAVE NO SNOW COVER. THIS IS ESPECIALLY TRUE IF WE GET DEEP VERTICAL
MIXING LIKE I EXPECT. THE BEST CHANCE OF GETTING WARM WILL BE ON THE
LOWER TERRAIN OF CLARK AND COMANCHE COUNTIES, BUT EVEN DDC SHOULD
REACH WELL INTO THE 50S AND MAYBE WARMER. SOMETIMES A WEAK TROUGH CAN
DEVELOP NEAR THE OKLAHOMA BORDER THAT CAN KEEP THE WARMEST AIR TO OUR
SOUTH.
SHALLOW COLD SURGES TYPICALLY ARRIVE FASTER THAN INDICATED IN THE
MODELS. THE 12Z ECMWF IS INDEED FASTER THAN THE 00Z RUN WITH THE
COLD SURGE BY SUNDAY NIGHT AND MONDAY. THE SOURCE REGION OF THIS SURGE IS
NORTHERN CANADA WHERE TEMPS ARE -25F CURRENTLY. THE GLOBAL MODELS
USUALLY CANNOT RESOLVE THE STRENGTH OF THE LOW LEVEL COLD SURGE WITH
THESE AIRMASSES. THIS LAST ARCTIC SURGE WAS DEEP(AT LEAST IN WESTERN
KANSAS) AND THE MODELS DID A DECENT JOB AT MAXES AND MINS. BUT THIS
COLD SURGE WILL INITIALLY BE VERY SHALLOW, SO I SUSPECT THE MODELS
WILL BE TOO WARM WITH THIS ONE. ANY REMAINING SNOW COVER FROM
CENTRAL KS NORTHWARD COULD PREVENT THE ARCTIC AIR FROM MODIFYING AS
FAST AS IT NORMALLY DOES. I LOWERED MAXES FOR MONDAY INTO THE 20S
FROM DDC NORTHEAST. I HAVE A FEELING THAT MONDAY WILL BE COLDER THAN
THIS. TEMPS MAY GET DOWN TO ZERO MONDAY MORNING WITH HIGHS IN THE
TEENS FROM DDC TO HAYS. SURFACE PRESSURES ARE STILL PROGGED TO BE
FAIRLY HIGH ON TUESDAY AS A REINFORCING ARCTIC HIGH SURGES
SOUTHWARD. HIGHS WERE ADJUSTED DOWN FOR TUESDAY SEVERAL DEGREES
ESPECIALLY FROM GCK EASTWARD. VERTICAL MIXING SHOULD BE AT A MINIMUM
(SHALLOW BOUNDARY LAYER) WHICH WILL ALSO KEEP TEMPS FROM RISING A
LOT.
TEMPERATURES WILL MODERATE AFTER TUESDAY AS A FAIRLY ZONAL PATTERN
DEVELOPS. HIGHS COULD REACH THE 50S BY THURSDAY. NO SIGNIFICANT
PRECIP IS EXPECTED THROUGH DAY 10.
&&
AVIATION...
VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD.
FINCH
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 10 32 22 39 / 0 0 0 0
GCK 5 29 19 37 / 0 0 0 0
EHA 15 37 17 49 / 0 0 0 0
LBL 13 37 21 47 / 0 0 0 0
HYS 0 28 16 31 / 0 0 0 10
P28 15 41 22 44 / 0 0 0 20
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
FN33/26
