FXUS63 KDMX 041137
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
540 AM CST FRI DEC 4 2009

.SHORT TERM [TODAY]...
COLD AIR TO REMAIN IN PLACE ACROSS THE CWA 
TODAY...WITH H85 TEMPERATURES HOVERING AROUND -15C. SOME WEAK WAA 
WILL PUSH INTO THE WESTERN CWA BY LATE THIS AFTERNOON WITH SOME 
SCATTERED FLURRIES POSSIBLE AND INCREASING CLOUD COVER. SOME CLEAR 
SPOTS ACROSS THE CENTRAL CWA EARLY THIS MORNING...BUT EXPECT THESE 
TO BE FILLED IN THROUGHOUT THE MORNING HOURS INTO THE EARLY 
AFTERNOON WITH THE WEAK WAA AHEAD OF THE NEXT WEAK WAVE PUSHING INTO 
THE CWA THIS AFTERNOON. EVEN WITH THE WAA...TEMPERATURES STARTING 
OFF PRETTY COOL THIS MORNING...AND WITH THE INCREASING CLOUDS EXPECT 
TEMPS TO HAVE A TOUGH TIME WARMING TOO MUCH. THEREFORE HAVE TRENDED 
TEMPS COOLER THAN THE PREVIOUS FORECAST...BUT WILL HAVE TO MONITOR 
AS THE OPTIMISTIC 10 TO 15 DEGREE RISES MAY BE TOO MUCH ESPECIALLY 
ACROSS AREAS UP NORTH WHERE THERE MAY STILL BE SNOWCOVER. WINDS WILL 
REMAIN BLUSTERY OUT OF THE WEST...BUT GRADIENT NOT QUITE AS 
TIGHT ACROSS THE CWA SO SHOULD NOT BE QUITE AS WINDY AS IN PREVIOUS 
DAYS. 

.LONG TERM [TONIGHT THROUGH THURSDAY]...
A MUCH MORE INTERESTING AND WINTER LIKE FORECAST THROUGH THE NEXT 
SEVEN DAYS THAT INCLUDES ROUND OF SNOW MAINLY SUNDAY NIGHT...A 
POTENTIAL SIGNIFICANT WINTER STORM MID NEXT WEEK FOLLOWED BY AN 
ARCTIC INTRUSION. FOR TONIGHT...SKY CONDITIONS WILL CLEAR FROM 
SOUTHWEST TO NORTHEAST. A MODEST WARM UP IS STILL ANTICIPATED ON 
SATURDAY THOUGH HIGHS WILL ONLY BE IN THE 30S. 

AS DISCUSSED PREVIOUS NIGHTS...A SIGNIFICANT AMOUNT OF ENERGY IS 
DIVING DOWN INTO THE PACIFIC NORTHWEST. A PIECE OF THIS ENERGY WILL 
EJECT OUT TOWARDS THE MIDWEST SATURDAY NIGHT INTO SUNDAY WITH SNOW 
DEVELOPING OVER WESTERN IOWA LATE SUNDAY AND SPREADING EAST ACROSS 
THE REMAINDER OF THE STATE SUNDAY NIGHT. STILL SOME UNCERTAINTY 
REMAINS WITH THE TRACK OF THE SYSTEM WITH THE DETERMINISTIC GFS AND 
THE SREF SUGGESTING A LITTLE FARTHER SOUTH TRACK WITH THE COLDER AIR 
DIGGING A LITTLE FARTHER SOUTH. MOISTURE WILL BE LIFTING NORTH FROM 
THE GULF AS THIS SYSTEM APPROACHES IOWA. INITIAL INDICATIONS ARE 
THAT THE WARM CONVEYOR BELT WILL NOT WRAP AROUND THE WEAK SFC LOW 
THUS SHUNTING MUCH OF THE GULF MOISTURE OFF TO THE EAST. ADVISORY 
CRITERIA SNOWFALLS COULD OCCUR SHOULD SOME OF THIS MOISTURE GET 
INGESTED. 

MONDAY WILL BE A REPRIEVE FOR IOWA THOUGH WITH A POTENTIAL NEW SNOW 
FALL...IT WILL BE QUITE COOL. BY MONDAY NIGHT...THE LEADING EDGE OF 
THE POLAR VORTEX DIVING SOUTH INTO ALBERTA...WILL EJECT THE MAJOR 
SHORT WAVE OVER THE PACIFIC NW TO THE EAST AND TOWARDS THE MIDWEST. 
STRONG CYCLONE GENESIS IS EXPECTED MONDAY NIGHT AND TUESDAY AS THE 
UPPER LEVEL SYSTEM BEGINS TO CROSS THE ROCKIES. AN INITIAL SURGE OF 
WARM ADVECTION SNOWFALL IS LIKELY OVER IOWA AHEAD OF THE SYSTEM 
MONDAY NIGHT AND TUESDAY. INITIAL DETERMINISTIC TRACKS OF THE SFC 
LOW BY THE ECMWF/GEM/GFS ARE ACROSS CNTRL TO NORTHERN MO WITH THE 
DEFORMATION ZONE MOVING ACRS IA. HINTS THAT THE SYSTEM WOULD BOMB 
OUT AS IT MOVED EAST OF IA TOWARDS THE GREAT LAKES 
REGION...RESULTING IN A NEARLY 30 MB PRESSURE GRADIENT ACROSS IA 
ALONG WITH 50 TO 55 KTS IN THE MIXED LAYER NEAR 925 MB BY WED 
MORNING. AN ABUNDANT AMOUNT OF MOISTURE WOULD BE AVAILABLE WITH THIS 
SYSTEM WITH THE GULF WIDE OPEN BUT POSSIBLY MORE IMPORTANTLY THAT 
HAS BEEN A FACTOR WITH MANY PAST EVENTS IS A TROPICAL FEED FROM THE 
PACIFIC MAY BE IN PLACE. NOW THAT ALL OF THE DOOM AND GLOOM HAS BEEN 
MENTIONED...THE TRACK RECORD FOR MODELS TO NAIL A SYSTEM 5 DAYS OUT 
IS NOT GOOD AND AM SURE THERE WILL BE ADJUSTMENTS TO STORM TRACK AND 
OVERALL INTENSITY BEFORE THEN. CERTAINLY INTENSITY TENDS TO BE 
OVERESTIMATED BUT EVERY NOW AND THEN IT DOES OCCUR SUCH AS MARCH 
2007. WILL GENERALLY MENTION POTENTIAL SIGNIFICANT STORM IN THE HWO 
WITHOUT MANY DETAILS AT THIS TIME. ADDITIONAL DETAILS CAN BE ADDED 
AS CONFIDENCE INCREASES.

&&

.AVIATION...
04/06Z...SOME CLEAR SPOTS ACROSS THE CWA MAINLY ACROSS THE 
NORTHEASTERN CWA...WITH VFR/MVFR CIGS PUSHING INTO KFOD...KDSM...AND 
KOTM ALONG WITH SOME FLURRIES. CLOUDS EXPECTED TO SPREAD ACROSS 
ENTIRE CWA THROUGH THE MORNING/AFTERNOON HOURS WITH MAINLY VFR 
CIGS...COULD SEE A FEW MVFR CIGS AS WELL. VSBYS ALSO SUPPOSED TO 
REMAIN VFR WITH THE FLURRIES. WESTERLY WINDS TO PICK UP TO AROUND 15 
MPH WITH SOME HIGHER GUSTS THROUGHOUT THE DAY...WITH THE WINDS 
SHIFTING AROUND TO THE SOUTHWEST TO SOUTH BY TONIGHT. 

&&

.DMX WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...BEERENDS
AVIATION...BEERENDS
LONG TERM...DONAVON