FXUS63 KDMX 020935
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
335 AM CST WED DEC 2 2009
.SHORT TERM [TODAY]...
MAIN FORECAST CONCERN IS WITH STRONG NORTH
WINDS THROUGHOUT THE DAY TODAY...AS WELL AS CLOUD COVER AND TEMPS.
STRONG CAA HAS DEVELOPED OVER THE CWA OVERNIGHT AND WILL CONTINUE
FOR MUCH OF THE DAY AS THE STATE IS SANDWICHED BETWEEN STRONG
SURFACE LOW OVER THE OHIO VALLEY AND DEEP TROUGH DIGGING IN FROM
CANADA. WINDS LOOK TO BECOME FAIRLY CLOSE TO ADVISORY CRITERIA
DURING THE AFTERNOON HOURS WITH SOME DECENT MIXING DOWN FROM 850MB.
HOWEVER...CONFIDENCE WAS LOW WITH THE TIMING AND HOW WIDESPREAD THE
ADVISORY WINDS THAT MAY AFFECT THE CWA. TEMPERATURES NOT EXPECTED TO
REBOUND MUCH AT ALL TODAY WITH THE STRONG CAA AND CLOUD COVER. HAVE
HIGHS ABOUT 4 TO 5 DEGREES HIGHER THAN THE CURRENT TEMPS...09Z WED.
LOW STRATUS DECK ALREADY HAS PUSHED IN NORTHERN IOWA AND SHOULD BE
INTERMITTENT THROUGH THE REMAINDER OF THE MORNING. KEPT WITH MID
LEVEL STRATUS DECK THROUGH THE AFTERNOON...BUT EXPECTING TO SEE A
FEW BREAKS IN THE CLOUDS TO SEE SOME SUN WITH THE STRONG MIXING.
.LONG TERM [TONIGHT THROUGH TUESDAY]...
COLDER AIR WILL CONTINUE TO ADVECT INTO CNTRL IA THE NEXT FEW DAYS
WITH A COUPLE MORE ROUNDS OF COLD ADVECTION ARRIVING TONIGHT AND
AGAIN ON THURSDAY. DESPITE THE COLD ADVECTION OVERNIGHT...LOWS WILL
BE NEAR TO A FEW DEGREES ABOVE NORMAL LOWS WITH SOME MIXING
CONTINUING OVERNIGHT AND THE PRIMARY COLD ADVECTION TAKING PLACE
ALOFT. FOR EXAMPLE...500 MB TEMPERATURES OVER DSM WILL BE DROPPING
FROM AROUND -21C AT 12Z THIS MORNING TO NEAR -34C BY 12Z THU AND AS
LOW AS -40C OVER NORTHERN IOWA THURSDAY EVENING. AS MENTIONED IN TUE
MORNINGS DISCUSSION...THIS WILL RESULT IN WARMER TEMPERATURES AT
NIGHT DUE TO MIXING BUT RESULT IN LITTLE ROOM TO WARM DURING THE DAY
THU AND FRI.
THE UPPER LEVEL LOW PRESSURE WILL DROP INTO NORTHERN IOWA DURING THE
DAY ON THU. LOW LEVEL PROFILES WILL SATURATE ENOUGH UP TO 700-600 MB
TO PROVIDE A SUFFICIENT DENDRITIC GROWTH ZONE ACROSS THE NORTH AS QG
FORCING ARRIVES AHEAD OF THE SYSTEM LATE TONIGHT AND THU. EXPECT
SNOW SHOWERS TO DEVELOP WITH THE POTENTIAL FOR MINOR ACCUMULATIONS
GENERALLY LESS THAN ONE INCH. FLURRY POTENTIAL WILL CONTINUE THU
NIGHT.
LOW LEVEL FLOW BECOMES MORE WESTERLY ON FRIDAY AS THE UPPER LOW
BEGINS TO LIFT NORTHEAST. THE STATE WILL REMAIN IN CYCLONIC FLOW
ALOFT HOWEVER AND EXPECT ANOTHER VERY COOL DAY WITH HIGHS MAINLY
ONLY IN THE 20S. THE CYCLONIC FLOW BREAKS ON SATURDAY WITH A
TRANSITION TO MORE ZONAL CONDITIONS. SOME UNCERTAINTY REMAINS FOR
SUN THRU TUE. THE LATEST DETERMINISTIC ECMWF AND GFS RIPPLE A PIECE
OF ENERGY THROUGH THE FLOW SUNDAY NIGHT INTO MONDAY THEN ANOTHER
POTENTIAL SYSTEM FOR TUESDAY. CONTINUITY DURING THIS PERIOD REMAINS
LOW AND HAVE OPTED TO LEAVE THIS PERIOD UNCHANGED UNTIL BETTER
RESOLUTION CAN BE DETERMINED. OF OTHER INTEREST...THE POLAR VORTEX
WILL CROSS OVER INTO NORTH AMERICA THIS WEEK AND GET AS FAR SOUTH AS
MANITOBA AND SASKATCHEWAN MID NEXT WEEK. A PORTION OF THIS MAY BREAK
OFF AND MAY PROVIDE A GLANCING BLOW INTO IOWA DURING DURING THE 8 TO
10 DAY TIMEFRAME.
&&
.AVIATION...
02/06Z...COLD FRONT NEARLY OUT OF THE FORECAST AREA TONIGHT. . CIGS
CONTINUE TO DROP NORTH OF US OVERNIGHT AND INTO WED HERE. NW FLOW
WILL INCREASE ON WED AND IS NOW BEING MODELED BETTER. SOUNDINGS
SUGGEST WINDS WILL GUSTING TO 25-28KTS OVER THE AREA WED AFTERNOON.
CLOUDS WILL REMAIN VFR...BUT SHOW SOME LOWERING TO MVFR BY 15Z.
COLDEST AIR AND LOWER CIGS WILL HIT THE NORTHERN TWO TAF SITES...
KALO AND KMCW MORE THAN KDSM...KOTM...AND KFOD. SOME SNOW SHOWERS TO
APPROACH DEVELOP IN THE EVENING HOURS WED WHEN DEEP UPPER LOW DROPS
SOUTH INTO THE REGION./REV
&&
.DMX WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...PODRAZIK
AVIATION...REV
LONG TERM...DONAVON
