Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 250546
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1146 PM CST TUE FEB 24 2015

.UPDATE...
ISSUED AT 958 PM CST TUE FEB 24 2015

MODELS CONTINUE TO COME IN FARTHER NORTHEAST WITH EACH RUN AND THE
00Z NAM AND GFS KEEPS THE TREND GOING. HAVE INCLUDED A FEW MORE
COUNTIES INTO THE WARNING AREA AND THIS MAY NEED TO BE MODIFIED
EVEN MORE WITH THE OVERNIGHT PACKAGE. FORCING STILL VERY
IMPRESSIVE WITH THE SYSTEM AND RAW OUTPUT FROM BOTH NAM AND GFS
SUGGEST AMOUNTS OF 6 TO 8 INCHES WITH SOME AMOUNTS APPROACHING 10
FROM NEAR KFOD TO KTNU AND KOTM BY MIDNIGHT WEDNESDAY NIGHT. THIS
WILL NEED TO BE TO BE EVALUATED DEEPER BY OVERNIGHT SHIFT WITH
ADDITIONAL AMOUNT ADJUSTMENTS LIKELY AS WELL.

&&

.SHORT TERM /TONIGHT/...
ISSUED AT 319 PM CST TUE FEB 24 2015

MAIN FORECAST CONCERN WAS FOCUSED ON SNOW DEVELOPING
OVERNIGHT ACROSS WESTERN IOWA. THE ECMWF/SREF/CANADIAN HAVE BEEN THE
MOST CONSISTENT WITH THE SNOW BAND ORIENTATION FROM NORTHWEST TO
SOUTHEAST SECTIONS OF THE FORECAST AREA. THE NAM/GFS HAVE COME IN
LINE WITH THE AFOREMENTIONED BLEND AND THUS LEANED TOWARD THE
SREF/ECMWF.

AREA OF STRONG AND DEEP FORCING PUSHES INTO WEST-CENTRAL TO
NORTHWEST IOWA PAST 09Z WEDNESDAY AND QUICKLY TRANSITIONS SOUTH AND
EAST BY 12Z TOWARDS THE FOD AREA. FORECAST SOUNDINGS QUICKLY BECOME
DEEPLY SATURATED AT SLB TO FOD TO FRM B/T 09-12Z WEDNESDAY. THE
BETTER FORCING WITHIN THE DENDRITIC LAYER LOOKS TO BE AFTER 12Z
WEDNESDAY BUT SHOULD SNOWING HARD ENOUGH TO OVER THE DRY LAYER B/T
900-800MB. INCREASED POPS OVER THE WEST NORTHWEST AFTER 09Z TO
CATEGORICAL AND BUMPED UP QPF/SNOW AMOUNTS ALONG THE WESTERN
EDGES OF POCAHONTAS TO EMMET COUNTIES.

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
ISSUED AT 319 PM CST TUE FEB 24 2015

STRONG LIFT THROUGH THE DGZ WILL MAKE FOR AN EFFICIENT SYSTEM
WITH WIDESPREAD LIGHT TO MODERATE SNOW FOR SEVERAL HOURS.
UPGRADED MUCH OF THE WATCH OT A WARNING AND WENT WITH AN ADVISORY
FOR THE REST OF THE CWA. A LOW END WARNING WITH NO REAL BLOWING TO
SPEAK OF. SNOW AMOUNTS IN THE 4 TO 7 INCH RANGE AREA
LIKELY...CONCERN REMAINS WITH THE COBB RATIOS INCREASING TO NEAR
20 TO 1 AVERAGE. USED ABOUT A 17 TO 1 WITH THE FORECAST AND WILL
WAIT FOR ADJUSTMENTS...THOUGH FEEL CONFIDENT WITH THE WARNING.

COLD WILL SETTLE BACK IN WITH WIND CHILLS AT OR BELOW ADVISORY
CRITERIA ONCE AGAIN TOWARD FRI AND SAT MORNING. PERIODIC WEATHER
SYSTEMS WILL BRING SNOW TO THE ARE...BUT THINKING AT THIS TIME IS
THAT THESE WILL BE ON THE LIGHT SIDE AND NOT REQUIRE HEADLINES.

&&

.AVIATION...25/06Z
ISSUED AT 1140 PM CST TUE FEB 24 2015

VERY SIMILAR TO PREVIOUS DISCUSSION WITH STORM STILL ON TRACK TO
PASS THROUGH THE STATE ON WEDNESDAY INTO WEDNESDAY NIGHT. VFR
CEILINGS WILL CONTINUE TO OVERSPREAD THE STATE TONIGHT WITH
UNRESTRICTED VISIBILITIES. SURFACE WINDS WILL SWING AROUND TO THE
EAST OVERNIGHT AS SURFACE LOW DEEPENS ACROSS THE PLAINS.
CONDITIONS WILL QUICKLY BECOME IFR TO LIFR ACROSS ALL OF CENTRAL
IOWA TERMINALS ON WEDNESDAY AS SNOW OVERSPREAD THE STATE. BOTH
VISIBILITIES AND CEILINGS WILL BE SEVERELY RESTRICTED IN THE
FALLING SNOW WITH LITTLE IMPROVEMENT UNTIL LATE IN THE DAY AS THE
SNOW BEGINS TO END FROM NORTHWEST TO SOUTHEAST. SURFACE WINDS WILL
GRADUALLY SHIFT FROM EAST IN THE MORNING TO NORTHWEST BY WEDNESDAY
EVENING AS SURFACE LOW MOVES INTO MISSOURI.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING FROM 9 AM TO 9 PM CST WEDNESDAY FOR
APPANOOSE-DAVIS-GRUNDY-HARDIN-JASPER-LUCAS-MADISON-MAHASKA-
MARION-MARSHALL-MONROE-POLK-POWESHIEK-STORY-TAMA-WAPELLO-WARREN-
WAYNE.

WINTER WEATHER ADVISORY FROM 6 AM TO 9 PM CST WEDNESDAY FOR
AUDUBON-CASS-CRAWFORD-EMMET-HANCOCK-KOSSUTH-WINNEBAGO.

WINTER STORM WARNING FROM 6 AM TO 9 PM CST WEDNESDAY FOR BOONE-
CALHOUN-CARROLL-DALLAS-GREENE-GUTHRIE-HAMILTON-HUMBOLDT-PALO
ALTO-POCAHONTAS-SAC-WEBSTER-WRIGHT.

WINTER WEATHER ADVISORY FROM 9 AM TO 9 PM CST WEDNESDAY FOR
ADAIR-ADAMS-BLACK HAWK-BREMER-BUTLER-CERRO GORDO-CLARKE-DECATUR-
FRANKLIN-RINGGOLD-TAYLOR-UNION-WORTH.

&&

$$

UPDATE...COGIL
SHORT TERM...PODRAZIK
LONG TERM...MS
AVIATION...COGIL



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