Wind Chill Advisory 1, NWS Des Moines, IA

Appanoose County, IA, Black Hawk County, IA, Boone County, IA, Bremer County, IA, Butler County, IA, Calhoun County, IA, Carroll County, IA, Cerro Gordo County, IA, Clarke 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, Sac County, IA, Story County, IA, Tama 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
1142 PM CST SUN JAN 11 2009

UPDATED AVIATION DISCUSSION

.DISCUSSION...
IT IS A TALE OF TWO SYSTEMS FOR THIS FORECAST...THE FIRST COMING
LATE TONIGHT AND MONDAY AND THE SECOND ON TUESDAY NIGHT INTO
WEDNESDAY. BOTH OF THESE PERIODS ARE FRAUGHT WITH THE POTENTIAL FOR
SIGNIFICANT WEATHER IMPACTS.

AS TO THE FIRST SYSTEM...AND AMPLIFYING MID-LEVEL SHORTWAVE AND
SURFACE LOW WILL MOVE QUICKLY DOWN THE NORTHERN PLAINS TONIGHT AND
ACROSS IOWA ON MONDAY. THIS SCENARIO HAS BEEN WELL ADVERTISED FOR
SEVERAL DAYS WITH THE DETAILS GRADUALLY COMING INTO BETTER
ALIGNMENT. THERE WILL BE A DOUBLE SHOT OF SNOW WITH THIS
SYSTEM...THE FIRST COMING IN THE FORM OF A BAND OF MODERATE TO HEAVY
SNOW TRAVERSING WEST TO EAST ACROSS THE STATE DURING THE MORNING
HOURS. FORECAST MODELS INDICATE VERY GOOD LIFT ASSOCIATED WITH THE
SHORTWAVE FEATURE AND WELL COLLOCATED WITH A SATURATED DENDRITIC
LAYER. IT APPEARS LIKELY THAT THIS BAND WILL PRODUCE SIGNIFICANT
SNOWFALL RATES...HOWEVER ITS TRANSITORY SPEED WILL LIMIT
ACCUMULATIONS SOMEWHAT. DURING THE AFTERNOON THE LIFTING WILL FADE
IN THE WEST AND GRADUALLY DIMINISH IN THE EAST AS THE SHORTWAVE
PULLS AWAY...BUT ENOUGH WILL REMAIN WITH GOOD MOISTURE IN THE COLUMN
FOR LIGHT TO MODERATE SNOW TO PERSIST...PRODUCING ADDITIONAL
ACCUMULATIONS ESPECIALLY IN THE EAST WHERE THE LIFT WILL REMAIN
LONGER.

A STRONG COLD FRONT TRAILING FROM THE LOW WILL CROSS THE STATE
BETWEEN THESE TWO SNOW AREAS...WITH A VERY TIGHT PRESSURE GRADIENT
ON THE BACK SIDE OF THE LOW PRODUCING VERY STRONG WINDS IN THE
AFTERNOON AND EVENING. BUFKIT SOUNDINGS ARE CONSISTENTLY SHOWING
GUSTS EXCEEDING 40 KT AT TIMES. COMBINED WITH THE NEW
SNOW...PRE-EXISTING SNOW PACK...AND STRONG COLD AIR ADVECTION BEHIND
THE FRONT...WE WILL SEE A THREE-PRONGED HAZARD OF SNOW...BLOWING
SNOW...AND DANGEROUS WIND CHILLS FROM MONDAY THROUGH MONDAY NIGHT.
THE BLIZZARD WATCH ISSUED EARLY THIS MORNING HAS BEEN EXPANDED TO
INCLUDE OUR SOUTHEASTERN COUNTIES AS IT APPEARS THAT THE SNOWFALL
AND WINDS WILL BE AS HIGH THERE AS IN OTHER PARTS OF THE WATCH. A
WINTER WEATHER ADVISORY HAS ALSO BEEN ISSUED COINCIDENT WITH THE
BLIZZARD WATCH FOR THE MORNING HOURS BECAUSE OF THE BAND OF MODERATE
TO BRIEFLY HEAVY SNOW MOVING THROUGH...WITH SIX HOUR ACCUMULATIONS
OF 2 TO 3 INCHES ACROSS THE ADVISORY AREA.

AS TO THE SECOND SYSTEM...AFTER A BRIEF RESPITE PROVIDED BY QUICKLY
MOVING HIGH PRESSURE ON TUESDAY...ANOTHER SHORTWAVE/SURFACE LOW
COMBO WILL SHOOT DOWN THE NORTHERN PLAINS...FOLLOWING A TRACK ALMOST
IDENTICAL TO THAT OF THE FIRST SYSTEM AND CROSSING IOWA ON WEDNESDAY
MORNING. AS WITH THE FIRST SYSTEM WE WILL FACE A TRIPLE THREAT OF
SNOW...BBLOWING SNOW...AND DANGEROUS WIND CHILLS. HOWEVER...IN THIS
CASE THE LIFT AND MOISTURE DO NOT APPEAR TO BE AS IMPRESSIVE AND
MOST OF THE SNOW ACCUMULATIONS WILL BE LIMITED TO THE NORTHEAST ON
THE EAST AND NORTH SIDES OF THE SURFACE LOW. IT IS TOO FAR OUT TO
PREDICT WHETHER A SNOW/BLOWING SNOW ADVISORY OR WORSE WILL BE
WARRANTED BUT IT IS POSSIBLE. IF NOTHING ELSE A WIND CHILL HAZARD
PRODUCT IS A VIRTUAL LOCK FOR WEDNESDAY NIGHT AND THURSDAY NIGHT
WITH BITTERLY COLD ARCTIC AIR STREAMING IN BEHIND THIS SYSTEM.

OTHER THAN THE VERY COLD TEMPERATURES AND WIND CHILLS THE FORECAST
FOR THE REMAINDER OF THE WEEK INTO NEXT WEEKEND IS RELATIVELY
BENIGN. THE GFS IS PERSISTENT IN ATTEMPTING TO BRING
ANOTHER...WEAKER SYSTEM THROUGH ON THURSDAY NIGHT OR FRIDAY.
HOWEVER...THIS IS OCCURRING BECAUSE OF A PATTERN SHIFT RESULTING
FROM THE GFS MOVING THE LARGE MID/UPPER GYRE NEAR HUDSON BAY
EASTWARD IN THE MIDDLE OF THE WEEK. THE GEM AND ECMWF ARE KEEPING
THIS CYCLONE MORE STATIONARY DURING THAT TIME...AND AS A RESULT
HOLDING HIGH PRESSURE NEAR THE AREA. THIS WILL BE MONITORED BY
SUBSEQUENT SHIFTS AS IT IS STILL AT LONG RANGE AND WE HAVE TWO MORE
POTENT SYSTEMS TO GET THROUGH FIRST.

&&

.AVIATION...12/06Z
APPEARS THAT A SOLID MVFR CEILING WILL BE OVER CENTRAL IOWA
OVERNIGHT...GENERALLY 500 FT EITHER SIDE OF 1800 FT...THOUGH AT
TIMES IT COULD DIP BELOW 010...ESPECIALLY AT KFOD AND KMCW. WARM
FRONT OR FORCING ON NORTHEAST SIDE OF ADVANCING SFC LOW WILL PASS
THROUGH AFT 12Z...WITH A 1-3 HR WINDOW OF HEAVIER SNOWFALL RATES AND
LIFR TO POTENTIALLY VLIFR CONDITIONS. EXACT TRACK OF PARENT SFC LOW
THROUGH CENTRAL IOWA WILL BE A LARGE FACTOR IN DETERMINING EXACT
DIRECTION AND SPEED OF WIND AT ANY GIVEN LOCATION BETWEEN 15-21Z.
HAVE GIVEN IT MY BEST ATTEMPT AT THIS POINT. I HAVE DELAYED THE
ONSET OF STRONG WINDS BY AN HOUR OR TWO DUE TO SLOWER MOVEMENT IN
00Z MODELS. HOWEVER...AFT 20Z NW AND 23Z FARTHER SOUTHEAST...NW
WINDS WILL BE INCREASING SUBSTANTIALLY AND THERE WILL LIKELY BE
ANOTHER SURGE OF SNOWFALL...THOUGH LIGHTER IN INTENSITY. BLOWING
SNOW WILL BECOME A SIGNIFICANT CONCERN IN THE LAST 9 HOURS OF THE
TAF PERIOD.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY FROM 6 AM TO 12 PM CST MONDAY FOR
APPANOOSE-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-
CERRO GORDO-CLARKE-CRAWFORD-DALLAS-DAVIS-EMMET-FRANKLIN-GREENE-
GRUNDY-GUTHRIE-HAMILTON-HANCOCK-HARDIN-HUMBOLDT-JASPER-KOSSUTH-
LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-PALO ALTO-
POCAHONTAS-POLK-POWESHIEK-SAC-STORY-TAMA-WAPELLO-WARREN-WAYNE-
WEBSTER-WINNEBAGO-WORTH-WRIGHT.

BLIZZARD WATCH FROM MONDAY AFTERNOON THROUGH LATE MONDAY NIGHT
FOR APPANOOSE-AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-
CARROLL-CERRO GORDO-CLARKE-CRAWFORD-DALLAS-DAVIS-EMMET-FRANKLIN-
GREENE-GRUNDY-GUTHRIE-HAMILTON-HANCOCK-HARDIN-HUMBOLDT-JASPER-
KOSSUTH-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-PALO ALTO-
POCAHONTAS-POLK-POWESHIEK-SAC-STORY-TAMA-WAPELLO-WARREN-WAYNE-
WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

SHORT TERM...SMALL
LONG TERM...LEE
AVIATION...MOYER

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
400 PM CST SUN JAN 11 2009

IAZ004>007-015>017-023>028-033>039-044>050-057>062-072>075-
083>086-095>097-121200-
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-MADISON-WARREN-MARION-MAHASKA-CLARKE-LUCAS-MONROE-
WAPELLO-WAYNE-APPANOOSE-DAVIS-
400 PM CST SUN JAN 11 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

LIGHT TO LOCALLY MODERATE SNOW IS EXPECTED TO SPREAD ACROSS
AREAS WEST OF INTERSTATE 35 AFTER MIDNIGHT TONIGHT. HALF AN INCH
TO AN INCH OF SNOW IS POSSIBLE THROUGH 6 AM MONDAY ALONG AND WEST
OF A LINE FROM ESTHERVILLE TO AUDUBON.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A WINTER WEATHER ADVISORY IS IN EFFECT FOR THE AREA FROM 6 AM
UNTIL NOON MONDAY. A BLIZZARD WATCH IS IN EFFECT FOR THE AREA
FROM NOON MONDAY THROUGH LATE MONDAY NIGHT. PLEASE REFER TO THE
NATIONAL WEATHER SERVICE WEBSITE AT WEATHER.GOV/DESMOINES.

A BAND OF MODERATE TO LOCALLY HEAVY SNOW WILL CROSS THE AREA FROM
WEST TO EAST ON MONDAY MORNING...PRODUCING 1 TO 3 INCHES OF SNOW
BY NOON. LIGHT TO MODERATE SNOW WILL PERSIST IN THE AFTERNOON
BEFORE TAPERING OFF IN THE EVENING...WITH ADDITIONAL ACCUMULATIONS
RANGING FROM AROUND HALF AN INCH IN THE WEST TOWARD DENISON TO 2
INCHES IN THE NORTHEAST AROUND MASON CITY AND WATERLOO. THAT WILL
BRING STORM TOTAL ACCUMULATIONS TO 3 TO 5 INCHES IN MOST LOCATIONS.

VERY STRONG NORTH TO NORTHWEST WINDS OF 25 TO 35 MPH WITH GUSTS TO
NEAR 50 MPH WILL SPREAD WEST TO EAST ACROSS THE AREA IN THE
AFTERNOON...PERSISTING THROUGH THE EVENING BEFORE GRADUALLY
DIMINISHING MONDAY NIGHT. WITH THE NEW SNOWFALL ANTICIPATED ON
MONDAY ON TOP OF THE FRESH SNOW PACK FROM FRIDAY NIGHT AND
SATURDAY MORNING...THE STRONG WINDS ARE LIKELY TO CAUSE
SIGNIFICANT BLOWING AND DRIFTING OF SNOW AS WELL AS NEAR WHITE
OUT CONDITIONS. IN ADDITION TO THE BLIZZARD CONDITIONS...EXTREMELY
DANGEROUS WIND CHILLS OF 10 TO 30 BELOW ZERO ARE EXPECTED MONDAY
NIGHT...WITH THE COLDEST VALUES IN THE NORTH.

ANOTHER STORM SYSTEM IS FORECAST TO PRODUCE LIGHT TO MODERATE SNOW
OVER THE AREA ON TUESDAY NIGHT AND WEDNESDAY. LIGHT SNOW
ACCUMULATIONS ARE EXPECTED. EXTREMELY COLD TEMPERATURES WILL
FOLLOW THIS SYSTEM WEDNESDAY NIGHT THROUGH FRIDAY. TEMPERATURES
WILL PLUMMET INTO THE SINGLE DIGITS AND TEENS BELOW ZERO WEDNESDAY
NIGHT AND THURSDAY NIGHT. WIND CHILL READINGS AS LOW AS 35 BELOW
ZERO ARE EXPECTED IN NORTHERN IOWA.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED BUT SNOWFALL REPORTS ARE
ALWAYS APPRECIATED.

IAZ070-071-081-082-092>094-121200-
CASS-ADAIR-ADAMS-UNION-TAYLOR-RINGGOLD-DECATUR-
400 PM CST SUN JAN 11 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL IOWA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

LIGHT TO LOCALLY MODERATE SNOW IS EXPECTED TO SPREAD ACROSS AREAS
WEST OF INTERSTATE 35 AFTER MIDNIGHT TONIGHT. HALF AN INCH TO AN
INCH OF SNOW IS POSSIBLE THROUGH 6 AM MONDAY ALONG AND WEST OF A
LINE FROM AUDUBON TO BEDFORD.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A BAND OF MODERATE SNOW WILL CROSS THE AREA ON MONDAY
MORNING...PRODUCING 1 TO 2 INCHES OF SNOW BY NOON. LIGHT SNOW
WILL PERSIST IN THE AFTERNOON BEFORE TAPERING OFF BY
EVENING...WITH ADDITIONAL ACCUMULATIONS RANGING FROM HALF AN INCH
TO AN INCH. THAT WILL BRING STORM TOTAL ACCUMULATIONS TO 2 TO 3
INCHES ACROSS THE AREA.

VERY STRONG NORTH TO NORTHWEST WINDS OF AROUND 30 MPH WITH GUSTS
IN EXCESS OF 40 MPH WILL SPREAD ACROSS THE AREA IN THE
AFTERNOON...PERSISTING THROUGH THE EVENING BEFORE DIMINISHING
MONDAY NIGHT. WITH THE NEW SNOWFALL ANTICIPATED ON MONDAY ON TOP
OF REMAINING SNOW FROM FRIDAY NIGHT AND SATURDAY MORNING...THE
STRONG WINDS ARE LIKELY TO CAUSE BLOWING AND DRIFTING OF SNOW
REDUCING VISIBILITY SIGNIFICANTLY AT TIMES AND MAKING TRAVEL
DIFFICULT. IN ADDITION...DANGEROUS WIND CHILLS OF 5 TO 15 BELOW
ZERO ARE EXPECTED MONDAY NIGHT.

ANOTHER STORM SYSTEM IS FORECAST TO PRODUCE LIGHT SNOW OVER THE
AREA ON TUESDAY NIGHT AND WEDNESDAY. VERY COLD TEMPERATURES WILL
FOLLOW THIS SYSTEM WEDNESDAY NIGHT THROUGH FRIDAY. TEMPERATURES
WILL PLUMMET INTO THE SINGLE DIGITS BELOW ZERO WEDNESDAY NIGHT
AND THURSDAY NIGHT. WIND CHILL READINGS OF 15 TO 20 BELOW ZERO
ARE EXPECTED DURING THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED BUT SNOWFALL REPORTS ARE
ALWAYS APPRECIATED.

LEE