FXUS63 KFSD 120301
AFDFSD

AREA FORECAST DISCUSSION FOR SOUTHEAST SD/SOUTHWEST MN/NORTHWEST IA 
NATIONAL WEATHER SERVICE SIOUX FALLS SD
900 PM CST FRI DEC 11 2009

.DISCUSSION...
INCRG SLY GRADIENT HOLDING UP TEMPS THIS EVE EVEN WITH THE FRESH 
SNOW COVER AND CLEAR SKIES...AND EARLIER UPDATED GRIDS FOR THIS. 
BEST CHC OF TEMP DROPOFF WILL BE IN LWR ELEVATIONS...IN SERN CWA
WITH LESS GRADIENT THIS EVE...AND IN NWRN CWA WITH LESSENING 
GRADIENT TOWARDS MORN. SO OVERALL RAISED LOWS SOME...MAINLY IN 
HIGHER ELEVATIONS OF SWRN MN AND IN THE WRN CWA WHERE TEMPS ARE
STILL ARND 20. ANOTHER EARLIER UPDATE WAS TO OUR HWO...MAINLY FOR 
THE POTENTIAL SNOW NORTH OF I90 SUN NGT...FLWD BY MORE VERY COLD
AIR FOR MON THRU TUES IN THE CWA. MUCH COLDER LOW LVL AIR SHOULD 
SEEP SWD FM CANADA INTO THE AREA THIS WEEKEND...PROBABLY MORE THAN 
MODELS. AS A STRONG UPR WAVE MOVES EWD OUT OF THE RELATIVELY DATA 
POOR PACIFIC OVER CALIFORNIA SAT NGT TO THE CNTRL PLAINS SUN NGT...
IT WILL TAP INTO A DECENT E/W BAROCLINIC ZONE IN THE CWA...WITH
THE MAIN SATURATION NORTH OF I90. SPCTRL MODELS LOOK A LOT BTR
THAN THE WEAK NAM RUNS WITH THIS SYSTEM. /RYRHOLM

&&

.AVIATION...
NEW NAM CONTS THE TREND TO BRING LO LVL MOISTUREUP INTO SERN CRNR OF 
FCST AREA STARTING JUST BEFORE 13/00Z...MOST NOTABLE AT H925. WHILE 
NAM HAS SOME HISTORY OF BEING TO FAST WITH THESE LO LVL MOISTURE 
INCREASES...THE ADDED MOISTURE INTO AIT THIS COLD AT LO LVLS SHUD 
SATURATE THE AIR AND PRODUCE ST IN THE ABV AREA. LOW CIGS MAY HOLD 
OFF TILL ARND 00Z AT KSUX AND A BIT LATER AT KFSD WITH EVE COOLING 
AIDING ST FORMATION. FSD A CLOSE CALL BUT LO LVL FLOW LOOKS FAVRBL 
TO GET IT UP THIS FAR. HAVE BEEN KEEPING INIT DECK TO ARND 2K FT 
WITH LWRNG PSBL BY END OF PD AT 13/06Z. VFR OVER ALL OF FCST AREA 
THRU 12/22Z AND NWRN HALF INCLUDG KHON THRU 13/06Z. / WILLIAMS

&&

.PREV DISCUSSION...

TEMPERATURES CONTINUED TO BE A CHALLENGE TODAY AS SURFACE RIDGING 
PUSHED SLOWLY TO THE EAST...WITH TEMPERATURES WARMING MORE THAN 
ANTICIPATED UNDER THE INCREASING LOW LEVEL SOUTHERLY FLOW ON THE 
BACKSIDE OF THE HIGH.  THIS CHALLENGE WILL CONTINUE TONIGHT...AS 
ELEVATION WILL PLAY SOMEWHAT OF A ROLE IN TEMPERATURES AS WINDS WILL 
INCREASE PRETTY DRAMATICALLY WITH HEIGHT AS A LOW LEVEL JET SWINGS 
ACROSS THE AREA. WITH THAT...HOURLY TEMPERATURES WILL BE RATHER 
SQUIRRELLY OVERNIGHT...FALLING AND RISING DEPENDENT ON THE WINDS. 
OVERALL HOWEVER...LOWS SHOULD DROP BACK TO NEAR ZERO TO THE SINGLE 
DIGITS ABOVE ZERO.  LOOKS LIKE MOST OF THE NIGHT WILL BE RELATIVELY 
CLOUD FREE...WITH JUST A FEW HIGH/MID CLOUDS MAINLY OVER THE NORTH.  
/JM

LOOKS LIKE SATURDAY WILL BE THE NICEST DAY THIS WEEKEND FOLLOWED BY 
COLD TEMPS AGAIN SUN THRU WED. SHUD WARM UP INTO 20S MOST PLACES 
AHEAD OF NEXT CDFNT THAT WL SAG SWD ACRS CWA DURING AFTN AND EVE. IF 
SNOW COVER WAS NOT SO WDSPRD AND FRESH...WUD PBLY WARM INTO 30S ACRS 
CWA ON SAT.

SOME LLM WL RETURN N SAT NIGHT AND OVERRUN COLDER ARCTIC SFC AIR. 
THIS CUD BE ENUF TO PRODUCE SOME PATCHY FOG OR FREEZING DRIZZLE OVR 
FAR SERN CWA. SO WL KEEP THIS MENTIONED ACRS NW IA SAT NIGHT.

COLDER AIR WL CONT TO SPILL INTO CWA FM THE N SAT NITE...AND SUN WL 
AGAIN BE COLD WITH HIGHS GENLY IN THE TEENS WITH LOWER 20S FAR SE. 
IF COLD SURGE IS A LTL STRONGER THAN PROGGED THEN MAY HAVE A HARD 
TIME HITTING 10 ABOVE ACRS THE N WITH TEENS S.

DECENT S/W WL PUSH EWD ACRS THE NRN PLAINS SUN NITE WITH SOME DECENT 
MID LEVEL WAA AND ISEN LIFT ACRS NRN CWA. WUD EXPECT AT LEAST SOME 
LIGHT SNOW ACRS CWA SUN NITE WITH BEST CHC N. WUD NOT BE SUPRISED TO 
SEE 1 OR 2 INCHES OF FLUFF ACRS THE FAR N AS SYS WL BE EFFICIENT AT 
SQUEEZING OUT SNOW. DID UP POPS ACRS NRN CWA SUN NITE TO LIKELY WITH 
CHC ACRS THE S. 

ANOTHER SURGE OF COLDER AIR WL FOLLOW THIS S/W ALONG WITH GUSTY N 
WINDS. SO CUD SEE SOME BLOWING SNOW ACRS CWA ON MON ALONG WITH COLD 
WIND CHILLS. 

SHUD CLEAR OUT MON NITE AND WITH ARCTIC HIGH SETTLING OVR THE WRN 
DAKOTAS BY TUES MORN...WL PBLY ONCE AGAIN SEE LOWS NEAR 10 BELOW IN 
MANY LOCATIONS. 

TUES WL REMAIN COLD WITH SOME WEAK WAA WARMING TEMPS UP A BIT ON WED 
AND WARMER FOR THU AND FRI AS FLOW ALOFT BECOMES A LTL MORE ZONAL. 
FOR NOW WL LEAVE TUES THRU FRI DRY ALTHOUGH WEAK S/W WED NITE OR THU 
CUD PRODUCE A FEW FLURRIES. 

&&

.FSD WATCHES/WARNINGS/ADVISORIES...

SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.

&&

$$