FXUS63 KDMX 061152 AAA
AFDDMX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
551 AM CST SUN DEC 6 2009
...UPDATED AVIATION DISCUSSION...
...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...
06/12Z...SFC COLD FRONT HAS MADE IT THROUGH ALL TERMINALS EXCEPT
KOTM...AND WILL PASS THROUGH THAT LOCATION BY AROUND 15Z. CONDITIONS
WILL DETERIORATE BEGINNING THIS EVENING AT ALL TERMINALS AS ANOTHER
WX SYSTEM APPROACHES OUR REGION. ACCUMULATING SNOW IS EXPECTED AT
ALL TERMINALS. THE HEAVIEST SNOW WILL FALL OVERNIGHT...WITH THE
HEAVIEST SNOW AFFECTING THE KFOD AND KALO TERMINALS. CONDITIONS
AFTER 06Z MAY AT TIMES BE LIFR...BUT I WAS NOT CONFIDENT ENOUGH TO
INCLUDE IT EVEN AS A TEMPO IN THE FORECAST.
&&
.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/AVIATION...ZOGG
LONG TERM...COGIL
