Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 251738
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1238 PM CDT SAT OCT 25 2014

.UPDATE...
ISSUED AT 536 AM CDT SAT OCT 25 2014

THE FOG CONTINUES TO DISSIPATE AND MOVE OUT OF THE REGION. HAVE
CANCELLED THE ADVISORY...NO FOG DENSE FOG EXPECTED FOR THE
REMAINDER OF THE MORNING.

&&

.SHORT TERM /TODAY/...
ISSUED AT 345 AM CDT SAT OCT 25 2014

MAIN CONCERN WILL BE DEPARTURE OF FOG...WHICH IS ALREADY
OCCURRING VERY SLOWLY OVER THE REGION. SFC TROUGH HEADING
SOUTHEAST WILL TAKE RIBBON OF HIGHER MOISTURE EAST OF THE AREA BY
13Z. THIS SHOULD HELP TO SLOWLY LESSEN THE FOG THREAT BY THIS
MORNING. WILL NEED TO EXTEND THE FOG ADVISORY A FEW MORE HOURS TO
12Z AND TRIM AS NEEDED...A WEAK COOL FRONT OVER NORTHERN MN AND
NORTH SOUTH DAKOTA AT 04Z WILL DROP SOUTH AND THEN PROGRESS NEARLY
DUE EAST...TAKING BAND OF MID LEVEL CLOUDS ALONG IA/MN BORDER WITH
CLOUDS DISSIPATING TOWARD MIDDAY. OTHERWISE LOOKING FOR A PLEASANT
AND DRY AFTERNOON AS HIGH PRESSURE BUILDS ACROSS THE REGION TODAY.
WITH H850 TEMPS STILL HOLDING IN THE 10 TO 14C RANGE AND FAVORABLE
WNW MIXING TO 10 TO 15 MPH DURING THE AFTERNOON... SHOULD SEE
HIGHS IN THE 60S AND 70S OVER THE AREA WITH FEW IF ANY CLOUDS THE
REMAINDER OF THE AFTERNOON HOURS.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 345 AM CDT SAT OCT 25 2014

RELATIVELY QUIET FORECAST FOR THE LATTER PART OF THE WEEKEND AND
NEXT WEEK. SURFACE HIGH PRESSURE SLIDES SOUTHEASTWARD FROM SW
MINNESOTA TO NORTHERN ILLINOIS TONIGHT THROUGH SUNDAY
MORNING....PASSING OVER NORTHEAST IOWA DURING THE OVERNIGHT.
EXPECT TEMPERATURES UNDER THE HIGH TO DROP OFF THE CLIFF OVER THE
NORTHEASTERN CWA WITH MODEL SOUNDINGS DENOTING A LARGE WEDGE OF
DRY AIR BELOW 800 MB IN CONJUNCTION WITH THIS HIGH. LOWERED MIN
TEMPS 4-5 DEGREES FROM THE PREVIOUS FORECAST ACROSS THIS REGION
BUT EVEN THIS MIGHT BE TOO WARM WITH DEWPOINTS IN THE LOW 30S.

CLOUDS INCREASE FROM THE WEST ON SUNDAY AS A LARGE SLAB OF THETA-E
ADVECTION/ISENTROPIC LIFT PUSHES THROUGH THE CWA...HOWEVER SHOWERS
ARE NOT ANTICIPATED WITH THE VERTICAL COLUMN STILL MOSTLY DRY.
850 MB TEMPS BEHIND THIS WAA RISE TO +19C OVER SOUTHWEST IOWA
SUNDAY AFTERNOON WITH SURFACE TEMPS PUSHING 80 DEGREES IN THE
SOUTHWEST. AN UPPER LEVEL WAVE ATTENDANT WITH A WEST COAST
CYCLONE WILL SHIFT ACROSS THE ROCKIES LATE ON SUNDAY. THIS WILL
DRAG A SURFACE COLD FRONT ACROSS THE STATE ON MONDAY. MOISTURE
REMAINS FAIRLY LIMITED WITH THIS SYSTEM AND ONLY SCATTERED SHOWERS
ANTICIPATED...WITH A FEW THUNDERSTORMS NOT OUT OF THE QUESTION IN
THE SOUTHEAST WHERE MUCAPES RANGE FROM 400-700 J/KG. FOG IS ALSO
POSSIBLE AHEAD OF THIS SYSTEM ON MONDAY MORNING BUT CONFIDENCE
WAS NOT HIGH ENOUGH TO MENTION IN THE GRIDS. HIGHS ON MONDAY MAY
BE AN ISSUE...WITH THE NAM IN PARTICULAR HOLDING THE FOG AND/OR
LOW STRATUS THROUGH MUCH OF THE MORNING AND EARLY AFTERNOON IN
CENTRAL AND NORTHERN IOWA...WHICH MAKES SENSE GIVEN A STRONG
INVERSION ABOVE 900 MB AND LIGHT WINDS AROUND THE BROAD SURFACE
TROUGH THAT WOULD INHIBIT MIXING. THIS COULD RESULT IN COOLER
HIGHS THAN CURRENTLY FORECAST.

THIS SYSTEM PUSHES OUT EARLY TUESDAY WITH A LARGE SYNOPTIC RIDGE
BUILDING IN THE WEST. A SECOND LOW...SIMILAR IN CHARACTER TO AN
ALBERTA-CLIPPER...RACES THROUGH ON THURSDAY. MOISTURE ALSO
REMAINS LIMITED WITH THIS LOW AND FOLLOWED THE CONSENSUS GUIDANCE
IN WITHHOLDING PRECIP FROM THE FORECAST. A STRONG CANADIAN HIGH
QUICKLY BUILDS BEHIND THIS LOW AND DRAGS COLDER AIR DOWN WITH IT
WITH 850 MB TEMPS MIDDAY FRIDAY AROUND -1C.

&&

.AVIATION...25/18Z
ISSUED AT 1234 PM CDT SAT OCT 25 2014

HIGH PRESSURE OVER THE DAKOTAS WILL MOVE OVER IA TONIGHT AND TO
THE EAST BY MORNING. WARM FRONT WILL DEVELOP SOUTH OF IA AND LIFT
NORTH INTO THE STATE SUNDAY. VFR CONDITIONS FOR THE TAFS...BUT
WILL PUT IN A SCATTERED MFR DECK IN THE SWRN SITES AS CIGS WILL
LIFTING NWD WILL LIKELY BE APPROACHING BY 18Z.

OUTLOOK...MVFR CIGS AS WARM FRONT LIFTS NORTH SUNDAY AFTERNOON AND
EVENING. COLD FRONT WILL PASS MONDAY...WITH A STRONGER PUSH OF
COLDER AND DRIER AIR TUE.

SIDENOTE...IT APPEARS HARVEST DUST IS AFFECTING SOME OF THE
SENSORS, KFOD RECENTLY.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...REV
SHORT TERM...REV
LONG TERM...SKOW
AVIATION...MS OCT 14



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