Blizzard Watch 3, NWS Des Moines, IA

Adair County, IA, Adams County, IA, Appanoose County, IA, Audubon County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cass County, IA, Cerro Gordo County, IA, Clarke County, IA, Crawford County, IA, Dallas County, IA, Davis County, IA, Decatur County, IA, Emmet County, IA, Franklin County, IA, Greene County, IA, Grundy County, IA, Guthrie County, IA, Hamilton County, IA, Hancock County, IA, Hardin County, IA, Humboldt County, IA, Jasper County, IA, Kossuth County, IA, Lucas County, IA, Madison County, IA, Mahaska County, IA, Marion County, IA, Marshall County, IA, Monroe County, IA, Palo Alto County, IA, Pocahontas County, IA, Polk County, IA, Poweshiek County, IA, Ringgold County, IA, Sac County, IA, Story County, IA, Tama County, IA, Taylor County, IA, Union County, IA, Wapello County, IA, Warren County, IA, Wayne County, IA, Webster County, IA, Winnebago County, IA, Worth County, IA, Wright County, IA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
1145 AM CST MON DEC 7 2009

...UPDATED AVIATION DISCUSSION...

...DANGEROUS WINTER STORM STILL ON TRACK FOR TUESDAY AND WEDNESDAY...

.SHORT TERM /TONIGHT THROUGH MONDAY/...
FIRST ROUND OF WINTER WX IS ON THE WANE ACROSS OUR CWA. WSR-88D
REFLECTIVITY AND SURFACE OBS INDICATE THE -SN HAS DECREASING IN
INTENSITY AND COVERAGE...WITH SURFACE VSBYS ACROSS THE NORTHWEST
3/4THS OF THE CWA AOB 6SM. WENT AHEAD AND CANCELED THE WINTER WX
ADVISORY EARLY DUE TO THIS FACT. ALTHOUGH THE -SN IS WINDING
DOWN...PAVEMENT AND WALKING SURFACES WILL REMAIN SLICK FOR AT LEAST
THE NEXT FEW HOURS...THOUGH...SO THE MORNING COMMUTE WILL BE SLOWER
THAN NORMAL IN SOME AREAS.

NORTHERLY TO NORTHWESTERLY WINDS WILL PREVAIL TODAY AS THE SURFACE
WX SYSTEM DEPARTS OUR REGION...AND A SURFACE PRESSURE RIDGE BUILDS
IN. DECREASE IN CLOUDS WILL BE MINIMAL THOUGH...AS CLOUDINESS FROM
THE NEXT WX SYSTEM SPREADS IN THIS AFTERNOON.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ALL EYES WILL BE ON INTENSE WINTER STORM SET TO AFFECT MUCH OF THE
REGION LATE TONIGHT INTO WEDNESDAY.  WILL SEE WAA BEGIN TONIGHT IN
RESPONSE TO THE DEEPENING WESTERN SYSTEM.  ISENTROPIC LIFT INCREASES
DURING THE OVERNIGHT ALONG WITH SOME WEAK QG FORCING.  MAY BEGIN TO
SEE A FEW FLAKES BEFORE MIDNIGHT IN OUR SOUTHWEST WHERE EARLIEST
SATURATION OCCURS.  AS FORCING CONTINUES THROUGH THE NIGHT...WL SEE
SNOW SPREAD ACROSS THE SOUTHERN HALF TO TWO-THIRDS OF THE STATE BY
DAYBREAK TUESDAY.  HAVE INCREASED POPS TO CATEGORICAL IN THE SOUTH
WITH UP TO AN INCH OF NEW SNOWFALL SOUTH OF I80 BY TUESDAY MORNING.
THE LIGHTER SNOW PERSIST INTO TUESDAY MORNING AND SPREADS NORTHWARD
ACRS THE ENTIRE CWA AS ISENTROPIC LIFT PERSISTS.  HOWEVER...MUCH
STRONG Q-G FORCING ARRIVES ON TUESDAY AFTERNOON AS SFC LOW RACES
ACRS SOUTHERN KS.  SNOWFALL RATES ARE FORECAST TO INTENSIFY THROUGH
THE AFTERNOON WITH MODERATE TO HEAVY SNOW...ESPECIALLY SOUTH OF
HIGHWAY 20 WITH GOOD DENDRITIC GROWTH.  THE STRONG FORCING AND
HEAVIER PCPN WILL CONTINUE INTO TUESDAY EVENING BEFORE THE BULK OF
FORCING SHIFTS TO THE EAST BY WEDNESDAY MORNING.
THEREFORE...CONDITIONS ARE EXPECTED TO DETERIORATE RAPIDLY BY
TUESDAY AFTERNOON AND EVENING DUE TO HEAVY SNOWFALL AND FAST
ACCUMULATIONS.  TOTAL ACCUMULATIONS BY WEDNESDAY MORNING ARE
GENERALLY 9 TO 12 INCHES ACROSS ALMOST THE ENTIRE FORECAST AREA AND
THERE WILL LIKELY BE AREAS WHICH RECEIVE MORE THAN A FOOT.
HOWEVER...THIS SNOW IS JUST THE FIRST PART OF THE SYSTEM.  AS THE
STORMS PULLS TO THE EAST THE DEEPENING UPPER SYSTEM BECOMES
NEGATIVELY TILTED.  SFC LOW PRES OF 980MB IS REACHED BY 12Z ON
WEDNESDAY NEAR THE SOUTHERN END OF LAKE MICHIGAN.  THE PRESSURE
GRADIENT TIGHTENS QUICKLY AFTER 06Z WEDNESDAY WITH EURO STILL
INDICATING 50KTS+ AT 925MB WITH NAM/GFS SLIGHTLY WEAKER.  MIXED
LAYER WINDS ON THE GFS ARE AROUND 40-45KTS BY 12Z WEDNESDAY AND IT
APPEARS SFC WIND GUSTS TO 45 MPH WILL BE POSSIBLE.  CERTAINLY WITH
THE AMOUNT OF SNOW ON THE GROUND AVAILABLE FOR TRANSPORT...BLOWING
AND DRIFTING SNOW WILL BECOME PROBLEMATIC.  NEAR WHITEOUT CONDITIONS
ARE LIKELY BY DAYBREAK WEDNESDAY WITH TRAVEL DIFFICULT IF NOT NEAR
IMPOSSIBLE BY THEN.  THE WINDS WILL BE STRONGEST THROUGH WEDNESDAY
MORNING BUT SHOULD SLOWLY SUBSIDE DURING THE AFTERNOON AS THE SYSTEM
PULLS RAPIDLY INTO THE UPPER GREAT LAKES REGION. AS FOR
HEADLINES...WL LEAVE THE WINTER STORM WATCH IN PLACE AS IT CURRENTLY
STANDS.  WL LIKELY SEE A WARNING BY THIS AFTERNOON AND POSSIBLY A
BLIZZARD WATCH ISSUED FOR LATE TUESDAY NIGHT INTO WEDNESDAY FOR THE
WINDY PORTION OF THE STORM. HAVE DONE LITTLE IF ANY MODIFICATION TO
THE FORECAST BEYOND WEDNESDAY NIGHT.

&&

.AVIATION...
07/18Z...MVFR STRATOCU HANGING AROUND AT KDSM...KOTM AND KALO FOR
PORTIONS OF THIS AFTN...BUT SHOULD SCATTER OUT. MEANWHILE...HIGH
CLOUDS SPREADING NORTHEAST AHEAD OF MAJOR SYSTEM TO AFFECT US
TUESDAY WILL GRADUALLY LOWER AFT 00Z. ANTICIPATE LIGHT SNOW BREAKING
OUT AS EARLY AS 06Z AT KDSM AND KFOD...AND SPREADING EAST
THEREAFTER. SNOW INTENSITY SHOULD REMAIN ON THE LIGHTER SIDE THROUGH
12Z...THEN PICK UP SOME AFT 12Z...ESPECIALLY AT KDSM AND KOTM WHERE
LIFR CONDITIONS ARE FORECAST. MAY END UP WITH MORE WIDESPREAD LIFR
CONDITIONS...BUT CONFIDENCE NOT HIGH ENOUGH TO REVEAL IN THE TAF AT
THIS POINT.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WATCH FROM LATE MONDAY NIGHT 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...ZOGG
LONG TERM...COGIL
AVIATION...MOYER

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DES MOINES IA
1049 AM CST MON DEC 7 2009

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097-081700-
EMMET-KOSSUTH-WINNEBAGO-WORTH-PALO ALTO-HANCOCK-CERRO GORDO-
POCAHONTAS-HUMBOLDT-WRIGHT-FRANKLIN-BUTLER-BREMER-SAC-CALHOUN-
WEBSTER-HAMILTON-HARDIN-GRUNDY-BLACK HAWK-CRAWFORD-CARROLL-GREENE-
BOONE-STORY-MARSHALL-TAMA-AUDUBON-GUTHRIE-DALLAS-POLK-JASPER-
POWESHIEK-CASS-ADAIR-MADISON-WARREN-MARION-MAHASKA-ADAMS-UNION-
CLARKE-LUCAS-MONROE-WAPELLO-TAYLOR-RINGGOLD-DECATUR-WAYNE-APPANOOSE-
DAVIS-
1049 AM CST MON DEC 7 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...TODAY AND TONIGHT

SNOW IS EXPECTED TO SPREAD INTO SOUTHERN AND CENTRAL IOWA TONIGHT. A
WINTER STORM WATCH IS IN EFFECT FOR THE ENTIRE AREA. PLEASE REFER
TO THE NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES
FOR FURTHER DETAILS.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

AN INTENSE SYSTEM WILL AFFECT ALL OF CENTRAL IOWA ON TUESDAY INTO
WEDNESDAY. POTENTIALLY DANGEROUS CONDITIONS ARE FORECAST FROM
HEAVY SNOW AND VERY STRONG WINDS. A WINTER STORM WATCH IS IN
EFFECT FOR THE AREA. PLEASE REFER TO THE NATIONAL WEATHER SERVICE
WEBSITE AT WEATHER.GOV/DESMOINES FOR FURTHER DETAILS.

.SPOTTER INFORMATION STATEMENT...

A CONFERENCE CALL FOR EMERGENCY MANAGEMENT COORDINATORS WILL BE
CONDUCTED AT 2 PM CST TODAY.

SPOTTER REPORTS OF SNOWFALL AND OTHER WINTER WEATHER IMPACTS WOULD
BE GREATLY APPRECIATED FROM TONIGHT INTO WEDNESDAY.

MOYER