FXUS63 KDMX 091149 AAA
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
545 AM CST WED DEC 9 2009
...DANGEROUS BLIZZARD CONDITIONS TO CONTINUE TODAY....
.SHORT TERM /TODAY/...
SFC LOW BOMBING JUST EAST OF IA THIS MORNING WITH CENTRAL PRESSURE
CLOSING IN ON 980MB. BROAD AREA OF DEFORMATION AND LIFT WILL
PERSIST ACRS THE CWA THIS MORNING WITH LIGHT TO OCCASIONALLY
MODERATE SNOW...WITH MOST ACCUMULATING SNOW IN THE NORTHEAST HALF OF
THE CWA. AN ADDITIONAL 1 TO 3 INCHES WILL BE POSSIBLE DURING THE
MORNING ADDING TO ALREADY IMPRESSIVE TOTALS FROM THIS STORM.
HOWEVER...WIND IS NOW BECOMING THE PRIMARY ISSUE WITH A RECENT GUST
TO 53KTS AT KEST. GRADIENT WL CONTINUE TO TIGHTEN THROUGH MID
MORNING AND PULL EAST AND WL SEE THE SHIFT OF STRONGEST WINDS FROM
THE NORTHWEST PORTION OF THE FORECAST AREA TO EAST OF I35 BY MID
MORNING. ALREADY HAVE NUMEROUS REPORTS OF NEAR ZERO VISIBILITY IN
OPEN AREAS WEST OF I35 AND MOST AUTOMATED SITES IN THE NORTHWEST ARE
NOW UNDER ONE QUARTER OF A MILE. BLIZZARD HEADLINES WILL REMAIN
INTACT THROUGH 00Z TODAY ALTHOUGH SHOULD SEE SOME IMPROVEMENT BY
THIS AFTERNOON AS GRADIENT BEGINS TO WEAKEN WITH SFC LOW SHIFTING
INTO THE UPPER GREAT LAKES.
.LONG TERM /TONIGHT THROUGH MONDAY/...
MAJORITY OF BLOWING SNOW TO DIMINISH IN THE EARLY EVENING HOURS
AS WINDS GRADUALLY QUIET DOWN OVERNIGHT. HOWEVER...WITH VERY COLD
AIR NOW IN PLACE AND WEST NORTHWEST OF 10 TO 18 MPH IN PLACE...WIND
CHILLS WILL DROP TO 20 BELOW OR COLDER OVER THE NORTHERN THIRD OF
THE STATE TNT. WILL BE NEEDING AN ADVISORY FOR WIND CHILL THERE
THROUGH ABOUT MID MORNING ON THURSDAY. WILL LATE DAY SHIFT POST THAT
AFTER THE BLIZZARD WARNING EXPIRES. DESPITE THE INTENSE LOW NOW
PULLING AWAY...SOME CLOUDS WILL BE PASSING INTO THE AREA THROUGH THE
NEXT FEW DAYS AS NORTHWEST WINDS ALOFT TRANSPORT SOME CLOUDS OUR
WAY. THOUGH VERY COLD H850 TEMPS TO FOLLOW THE SYSTEM FOR THE NEXT 2
DAYS...SOME SURPRISING CHANGES ARE SHOWING UP IN THE MODELS FOR LATE
FRIDAY AND INTO THE WEEKEND. WARM AIR ADVECTION COMMENCES TO OUR
WEST AND H850 TEMPS MODERATE QUITE A BIT. THIS SHOULD HAVE TWO
EFFECTS. ONE...THE TEMPERATURE WILL INCREASE BUT SO WILL THE CHANCES
FOR SOME FOG OR CLOUD COVER. MODELS ARE ALSO ATTEMPTING TO CREATE
SOME DRIZZLE FOR SATURDAY NIGHT...BUT STILL SOME LOW CONFIDENCE FOR
NOW AND WILL HOLD OFF. OTHER THAN THAT GUIDANCE APPEARS TOO HIGH ON
TEMPS...ESPECIALLY THE MEX GUIDANCE WHICH HAS THE REGION WARMING TO
NEAR 40 BY SUNDAY. IT LIKELY DOESNT HAVE A HANDLE ON THE SNOW DEPTH
ATTM AND WILL IGNORE THE LARGE WARM UP FOR NOW. THE SOUTH SHOULD
WARM INTO THE MID TO UPPER 20S...BUT WITH THE BITTER COLD
TEMPERATURES EXPECTED FOR THE NEXT 24 TO 36 HOURS...IT IS NOT LIKELY
FOR SUCH A RAPID RECOVERY LOOKING OUT ONLY 3 DAYS...ESPECIALLY WHEN
ANY WARM AIR IS MORE LIKELY TO RISE ABOVE THE COLD SFC AND NOT WARM
THE REGION UP SIGNIFICANTLY. THE MODERATION LOOKS TO CONTINUE INTO
THE WEEKEND THOUGH CONFIDENCE LOWERS AS THE 12Z EURO MODEL SUGGESTS
A LOW TRACKING OVER THE REGION SUNDAY NIGHT AND MONDAY WHILE THE GFS
REMAINS DRY. QUIETER WNW FLOW WILL BE REMAIN INTO EARLY NEXT WEEK.
&&
.AVIATION...
09/12Z...WORST OF THE WINDS ARE CURRENTLY OCCURRING WITH WIDESPREAD
IFR AND LIFR CONDITIONS IN CENTRAL IOWA. LITTLE IMPROVEMENT THROUGH
18Z IS EXPECTED AS STRONG NORTHWEST WINDS PERSIST WITH VSBYS BELOW
ONE MILE AT ALL TAF SITES AND CIGS GENERALLY UNDER 1KFT. HOWEVER...
PRESSURE GRADIENT WILL BEGIN TO RELAX BY THIS AFTERNOON WITH VSBYS
AND CIGS INCREASING. BY TONIGHT...VFR CONDITIONS WILL SPREAD FROM
WEST TO EAST ACRS THE STATE AS LOW CLDS MOVE TO THE EAST.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
BLIZZARD WARNING THROUGH WEDNESDAY AFTERNOON FOR
ADAIR-ADAMS-APPANOOSE-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-
CALHOUN-CARROLL-CASS-CERRO GORDO-CLARKE-CRAWFORD-DALLAS-
DAVIS-DECATUR-EMMET-FRANKLIN-GREENE-GRUNDY-GUTHRIE-
HAMILTON-HANCOCK-HARDIN-HUMBOLDT-JASPER-KOSSUTH-LUCAS-MADISON
-MAHASKA-MARION-MARSHALL-MONROE-PALO ALTO-POCAHONTAS-POLK-
POWESHIEK-RINGGOLD-SAC-STORY-TAMA-TAYLOR-UNION-WAPELLO
-WARREN-WAYNE-WEBSTER-WINNEBAGO-WORTH-WRIGHT.
&&
$$
SHORT TERM...COGIL
AVIATION...COGIL
LONG TERM...REV
