Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 130233
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
933 PM CDT FRI SEP 12 2014

.UPDATE...
ISSUED AT 931 PM CDT FRI SEP 12 2014

UPDATE COMING OUT IN A FEW MINUTES IS ONLY FOR COSMETIC CHANGES
AND SOME HOURLY ADJUSTMENTS. PRECIP IS OVER AND TEMPS FALLING A
BIT FASTER.

&&

.SHORT TERM /TONIGHT/...
ISSUED AT 304 PM CDT FRI SEP 12 2014

HIGH PRESSURE PROPAGATING EASTWARD WILL PUSH CLOUDS TO EAST OF CWA
BY AROUND SUNSET. SIGNIFICANT DRY AIR ENTRAINMENT AND SUBSIDENCE
ASSOC WITH THIS HIGH WILL CLEAR SKIES VERY RAPIDLY AFTER SUNSET.
WINDS ALSO TO BECOME LIGHT WITH THIS APPROACHING HIGH. ALL OF THE
ABOVE FACTORS WILL LEAD TO STRONG RADIATIONAL COOLING TONIGHT. KEPT
TEMPERATURES IN LOW TO MID 30S ACROSS CWA. RECORD LOWS FOR DES
MOINES AND WATERLOO IS 33 AND 31...RESPECTIVELY. WENT A FEW DEGREES
ABOVE THESE VALUES AS MOISTURE FROM TODAYS RAIN MAY HELP KEEP TEMPS
UP A FEW DEGREES VERSUS WHERE THEY WOULD OTHERWISE FALL TO WITH A
DRY SFC. ADDED FROST ADVISORY IN LOCATIONS NORTH AND WEST OF DES
MOINES. URBAN HEAT ISLAND EFFECT TO KEEP DES MOINES WARM ENOUGH TO
WHERE FROST NOT LIKELY. HOWEVER...TENDER VEGETATION MAY BE
AFFECTED BY THE COOL TEMPS.

.LONG TERM /SATURDAY THROUGH FRIDAY/...
ISSUED AT 304 PM CDT FRI SEP 12 2014

EXPANSIVE SURFACE RIDGE WILL SLIDE ACROSS AND EAST OF THE FORECAST
AREA ON SATURDAY. SUBSIDENCE AND DRY AIRMASS WILL LEAD TO PLENTY
OF SUNSHINE DURING THE DAY WITH COOL CANADIAN AIRMASS KEEPING HIGHS
WELL BELOW NORMAL. SOME MODERATION WILL TAKE PLACE BY SUNDAY AS
WARM ADVECTION INCREASES ALTHOUGH THIS WILL BE TEMPERED SOME BY
INCREASING CLOUDINESS BY AFTERNOON. CLOUDINESS IS IN RESPONSE TO
SHORTWAVE DROPPING INTO THE NORTHERN PLAINS AND INCREASED QG LIFT
AND THERMAL ADVECTION. HOWEVER...DEEPER SATURATION WILL TAKE SOME
TIME AS AIRMASS WILL INITIALLY BE QUITE DRY AND BULK OF
PRECIPITATION IS FORECAST TO HOLD OFF UNTIL SUNDAY NIGHT.

GOOD FORCING WILL PERSIST INTO SUNDAY NIGHT AS WEAK INSTABILITY
AXIS EDGES INTO THE STATE IN ADVANCE OF FRONT DROPPING SOUTH
THROUGH IOWA. HAVE INCLUDED SOME THUNDER IN THE FORECAST ACROSS
THE SOUTH FOR THE WEAK ELEVATED INSTABILITY AS IT PASSES THROUGH
THE STATE. FORCING WILL DIMINISH INTO MONDAY MORNING WITH
PRECIPITATION ENDING FROM NORTHWEST TO SOUTHEAST DURING THE DAY.
SOME LINGERING SHOWERS MAY AFFECT THE FAR SOUTHEAST IN THE
AFTERNOON BUT INCREASING SUBSIDENCE ON BACKSIDE OF SYSTEM SHOULD
EFFECTIVELY END PRECIPIATION ELSEWHERE. THEREAFTER....RELATIVELY
QUIET WEATHER INTO MIDWEEK WITH READINGS REMAINING BELOW NORMAL.

&&

.AVIATION...13/00Z
ISSUED AT 636 PM CDT FRI SEP 12 2014

HIGH PRESSURE WILL BUILD INTO THE AREA TONIGHT AND SATURDAY. VFR
CLOUDS AND SHOWERS WILL END BY AROUND SUNSET WITH SKIES CLEARING
AND WINDS BECOMING LIGHT AND VARIABLE. ONLY HIGH CLOUDS EXPECTED
SAT WITH WINDS BECOMING SLY.

OUTLOOK...HIGH WILL MOVE OFF THE EAST SATURDAY NIGHT WITH THE NEXT
FRONTAL SYSTEM EXPECTED TO ARRIVE SUNDAY NIGHT AND MON WITH AN
AREAS OF SHOWERS AND ISOLATED THUNDERSTORMS.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
FROST ADVISORY FROM 3 AM TO 8 AM CDT SATURDAY FOR ADAIR-ADAMS-
AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CALHOUN-CARROLL-CASS-
CERRO GORDO-CRAWFORD-DALLAS-EMMET-FRANKLIN-GREENE-GRUNDY-GUTHRIE-
HAMILTON-HANCOCK-HARDIN-HUMBOLDT-KOSSUTH-MADISON-MARSHALL-PALO
ALTO-POCAHONTAS-RINGGOLD-SAC-STORY-TAYLOR-UNION-WEBSTER-
WINNEBAGO-WORTH-WRIGHT.

&&

$$

UPDATE...MS SEP 14
SHORT TERM...KOTENBERG
LONG TERM...COGIL
AVIATION...MS SEP 14


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