FXUS63 KDMX 060947
AFDDMX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
347 AM CST SUN DEC 6 2009
...MAJOR WINTER STORM SET TO AFFECT IOWA ON TUESDAY AND WEDNESDAY...
.SHORT TERM /TODAY AND TONIGHT/...
MAIN ITEM OF INTEREST DURING THIS PART OF THE FCST PD IS THE
APPROACHING WINTER WX SYSTEM LATER TODAY. -SN IS EXPECTED TO BEGIN
IN THE WESTERN CWA BETWEEN 18Z-00Z...AND SPREAD EASTWARD TO AFFECT
THE ENTIRE CWA BY 00Z. ALTHOUGH SNOW AMOUNTS WILL BE RELATIVELY LOW
/1 TO 4 INCHES/...HAVE DECIDED TO ERR ON THE SIDE OF CAUTION AND
ISSUE A WINTER WEATHER ADVISORY IN CONJUNCTION WITH THIS SYSTEM.
MAIN REASONING IS THAT FOR MUCH OF THE CWA...THIS WILL BE THE FIRST
WINTER WX SYSTEM WITH MEASURABLE SNOWFALL...ESPECIALLY FROM HWY 20
SOUTHWARD INCLUDING THE DES MOINES METRO AREA. THE SNOW IS EXPECTED
TO BE ENOUGH TO CAUSE SOME TRAVEL ISSUES...DUE MAINLY TO SLICK
ROADS. SYSTEM WILL WEAKEN AS IT MOVES EASTWARD ACROSS THE CWA.
BLOWING AND DRIFTING SNOW IS NOT EXPECTED TO BE MUCH OF AN ISSUE.
.LONG TERM /MONDAY THROUGH SATURDAY/...
MONDAY MAY SEE SOME LINGERING FLURRIES IN FAR EASTERN AREAS EARLY IN
THE DAY...HOWEVER FORCING WL DIE OFF QUICKLY AS SFC RIDGING BUILDS
INTO THE MISSOURI RIVER VALLEY. HOWEVER...ATTENTION WILL BE TURNING
TO A MAJOR SYSTEM THAT WILL AFFECT THE CENTRAL US ON TUESDAY AND
WEDNESDAY. ALL MODELS SEEM TO BE LINING UP ON A FINAL SOLUTION
WHICH TAKES A SFC LOW FROM EASTERN COLORADO THROUGH MISSOURI AND
INTO INDIANA DURING THAT TIME. 00Z EURO IS PARTICULARLY OMINOUS
WITH SFC LOW DEEPENING TO 976MB BY 12Z WEDNESDAY AND TO A LESSER
EXTENT ON THE GEM AND GFS. AT THIS POINT...IT APPEARS TO BE A LONG
DURATION SNOWFALL EVENT OF 24 TO 30 HOURS OVER PORTIONS OF THE CWA
WITH NAM/GFS AND EURO ALL SPITTING OUT OVER 1 INCH OF QPF ACRS
SOUTHERN IA. COBB OUTPUT ON SNOWFALL RANGED FROM OVER 15 INCHES IN
THE SOUTH TO AROUND 8 INCHES IN THE NORTH. IN ANY CASE...IT APPEARS
THAT MUCH OF THE STATE WILL SEE WARNING CRITERIA SNOWFALL. THE MORE
WORRISOME ASPECT OF THIS STORM IS THE AFOREMENTIONED DEPTH OF THE
LOW. SHOULD THE EURO BE CORRECT...WE WOULD SEE BLIZZARD CONDITIONS
ACRS THE CWA LATE TUESDAY NIGHT THROUGH WEDNESDAY AFTERNOON. EURO
925MB WINDS AT 12Z ON WEDNESDAY WERE 50+KTS WITH SFC WINDS
APPROACHING 35KTS. GIVEN THE AMOUNT OF SNOWFALL...THESE WINDS WOULD
PRODUCE WHITEOUT CONDITIONS WITHOUT MUCH OF A PROBLEM.
HOWEVER...EURO REMAINS THE STRONG OUTLIER WITH OTHER MODELS SOMEWHAT
WEAKER...YET STILL QUITE STRONG IN OVERALL DEPTH. WILL HIT HWO VERY
HARD AND ANTICIPATE THAT WATCHES WILL BE ISSUED LATER TODAY. THE
EURO SOLUTION WOULD PRODUCE THE WORST CONDITIONS IN THE STATE SINCE
THE MARCH 1ST BLIZZARD OF 2007 THAT AFFECTED MUCH OF WESTERN AND
NORTHERN IOWA. AFTER SYSTEM PASSES...WL SEE COLD AIR ENTRENCHED
ACRS THE STATE FOR MUCH OF THE REST OF THE WORK WEEK ALONG WITH
RELATIVELY DRY CONDITIONS.
&&
.AVIATION...
06/06Z...MID AND HIGH LEVEL CLOUD COVER WILL PERSIST OVER THE CWA
THROUGH 15Z BUT VFR CONDITIONS SHOULD PREVAIL. ONE EXCEPTION...SOME
BORDERLINE MVFR CLOUD COVER OVER SRN MN MAY SAG INTO KMCW.
CONDITIONS DETERIORATE AFT 06/21Z AS THE AFOREMENTIONED SYSTEM MOVES
OUT OF THE CENTRAL/SRN PLAINS NORTHEASTWARD ACROSS MO AND PRODUCES A
BAND OF SNOW WITH HIGHER SNOWFALL AMOUNTS BETWEEN I-80 AND HWY 30
CORRIDORS AND SOME HIGHER AMOUNTS OVER KOTM/KALO TOWARDS THE END OF
THE FCST PD AS WRAP AROUND/DEF ZONE PRECIP AFFECTS THOSE AREAS.
MVFR/IFR COND EXPECTED AFTER 0623Z THROUGH THE END OF THE FCST PD.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST MONDAY
FOR BLACK HAWK-BOONE-BREMER-BUTLER-DALLAS-FRANKLIN-GRUNDY-HAMILTON-
HARDIN-HUMBOLDT-JASPER-MADISON-MARION-MARSHALL-POLK-POWESHIEK-STORY-
TAMA-WARREN-WEBSTER-WRIGHT.
WINTER WEATHER ADVISORY FROM NOON TODAY TO 3 AM CST MONDAY FOR
ADAIR-AUDUBON-CALHOUN-CARROLL-CASS-CRAWFORD-GREENE-GUTHRIE-POCAHONTAS
-SAC.
&&
$$
SHORT TERM...ZOGG
AVIATION...FAB
LONG TERM...COGIL
