Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 261755
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1255 PM CDT SUN OCT 26 2014

.SHORT TERM /TODAY/...
ISSUED AT 400 AM CDT SUN OCT 26 2014

RIDGE OF HIGH PRESSURE WILL MOVE EAST BY AFTERNOON WITH WARM AIR
ADVECTION AND SOME LIFT ALONG A WARM FRONT CURRENTLY SOUTH OF THE
STATE...BEGINNING TO INCREASE CLOUDS AND SFC MOISTURE ACROSS THE
AREA TODAY. H850 MOISTURE SHOWING UP ACROSS FAR SOUTHERN IOWA...
KANSAS...AND NEBRASKA EXPECTED TO BE PULLED NORTH TODAY. BUFR
SOUNDINGS SHOW INTRUSION OF MOIST LAYER AT 2800 TO 3000 FT THROUGH
DAY TODAY AND BEGINNING OVER THE WEST AND SOUTH THIS MORNING. WE
WILL LIKELY TO SEE SCT TO BKN LAYER OF LOW TO MID LEVEL CLOUDS
DEVELOP OVER MISSOURI AND MOVE NORTH INTO SOUTHERN SECTIONS PRIOR TO
SUNRISE...THEN MOVE NORTH WITH TIME AS ISENTROPIC LIFT BECOMES MORE
FOCUSED OVER NORTHERN IOWA AND SOUTHEAST MN/WESTERN WI BY 00Z
MONDAY. MODELS HINT AT PASSING SHOWER FROM 18Z TO 00Z NORTH OF
US20...BUT WITH NEAR SFC LAYERS STILL VERY DRY...WILL MAINTAIN DRY
FORECAST TODAY. STRONG WARM AIR ADVECTION WILL BE PRESENT MOST OF
THE DAY AS AN AREA OF LOW PRESSURE DEVELOPS OVER THE CENTRAL PLAINS
DURING THE AFTERNOON HOURS. MOST OF OUR AREA WILL REMAIN NORTH OF
THE WARM FRONT...HOWEVER. WITH SOUTHEAST FLOW NEAR THE SFC...TEMPS
WILL NOT WARM QUITE AS MUCH AS POSSIBLE...IF THE BOUNDARY WERE
LIFTING FARTHER NORTH AND SW WINDS AND A DEEPER MIXED LAYER WERE TO
DEVELOP.  MIXING WILL BEGIN AROUND 15Z AND INCREASE FROM 18Z TO 21Z
THIS AFTERNOON. SOUTHEAST WIND GUSTS LIKELY NEAR 18 TO 23 MPH SOUTH
HALF AND FROM 22 TO 30 NORTH HALF DURING THE AFTERNOON HOURS. THOUGH
MUCH OF THE WARM AIR WILL INITIALLY REMAIN ALOFT...MIXING SHOULD
HELP PUSH HIGHS INTO THE MID 70S OVER THE WEST AND LOWER TO MID 70S
SOUTH WHILE NORTH REMAINS UNDER THICKER CLOUDS AND HIGHS REACHING
MAINLY THE MID 60S DUE TO CLOUD COVER AND SLIGHTLY COOLER AIR ALOFT.
OVERALL A PRETTY NICE DAY FOR LATE OCTOBER.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 400 AM CDT SUN OCT 26 2014

WARM FRONT WILL BE LIFTING NORTHEAST ACROSS THE NORTHEASTERN CWA
AT THE BEGINNING OF THE PERIOD. ELEVATED SHOWERS AND STORMS LOOK
TO REMAIN JUST NORTHEAST OF THE CWA...THOUGH THERE IS A WINDOW OF
OPPORTUNITY BETWEEN 03 AND 06Z WHERE MUCAPES ON THE MASON CITY
AND WATERLOO BUFR SOUNDINGS EXCEED 1000 J/KG AND INHIBITION
WEAKENS. A STRAY STORM IS POSSIBLE DURING THIS TIMEFRAME BUT
SHOULD QUICKLY EXIT THE AREA IF IT DOES FORM. AT THIS POINT...DID
NOT ADD PRECIP TO THE GRIDS BUT THIS MAY NEED TO BE REASSESSED
LATER TODAY.

AS THE MAIN UPPER LEVEL TROUGH APPROACHES FROM THE WEST IT WILL
DRAG A BROAD AND WEAK SURFACE COLD FRONT EAST OVER THE CWA AFTER
06Z MONDAY. INTRODUCED FOG WORDING TO THE SOUTHERN TWO THIRDS OF
THE CWA AFTER 06Z WITH LIGHT WINDS AND AMPLE MOISTURE POOLING
AHEAD OF THE BOUNDARY. THE TIMING AND LOCATION OF PRECIP ON MONDAY
REMAINS SOMEWHAT UNCERTAIN WITH BROAD SYNOPTIC FORCING APPEARING
TO BE THE MAIN DRIVER FOR THIS EVENT. TWO AREAS OF PRECIP ARE
POSSIBLE...ONE OVER THE NORTH IN JUNCTION WITH THE POLAR JET AND
ANOTHER OVER THE SOUTHEAST TIED IN WITH THE SUBTROPICAL JET.
MODELS ARE IN GOOD AGREEMENT WITH THESE TWO STREAMS PHASING OVER
EASTERN IOWA AFTER 06Z TUE...WITH THE MAIN BAND OF PRECIP ALSO
FORMING EAST OF THE CWA. HOWEVER...MAINTAINED SLIGHT TO CHANCE
WORDING OVER ALL OF CENTRAL IOWA DURING THE DAY MONDAY GIVEN THE
PROXIMITY OF THE SURFACE BOUNDARY AND THE POSSIBILITY OF THE FOG
LIFTING INTO A LOW...DRIZZLE PRODUCING STRATUS DECK. SOUNDINGS
ACROSS CENTRAL AND SOUTHERN IOWA ARE SUPPORTIVE OF THIS LATTER
SCENARIO WITH A STOUT INVERSION AT 850 MB AND SATURATED PROFILES
BELOW 900 MB. ALSO LOWERED HIGHS ON MONDAY BASED ON THIS SAME
REASONING.

ELEVATED THUNDERSTORMS ARE ONCE AGAIN POSSIBLE OVER THE EASTERN
CWA LATE IN THE DAY ON MONDAY AS THE UPPER LEVEL TROUGH DIGS AND
PUSHES THE SURFACE BOUNDARY TO THE EAST. SPED UP THE DEPARTURE OF
THE SYSTEM AS A WHOLE EARLY ON TUESDAY PER A CONSENSUS OF THE
FASTER GFS AND SLOWER EC. AFTERWARDS A MEAN LONGWAVE RIDGE BUILDS
INTO THE WEST WITH ONE WEAK WAVE AND SURFACE LOW DIVING SOUTHEAST
OVER IOWA ON THURSDAY. PROFILES REMAIN RATHER DRY BUT THERE IS
ENOUGH FORCING TO WARRANT THE CONTINUANCE OF SLIGHT CHANCE WORDING
OVER THE NORTHEAST. SUCCESSIVE SHOTS OF COLDER AIR ARRIVE FOR BOTH
TUESDAY AND FRIDAY WITH TEMPERATURES RETURNING TO AT OR EVEN
BELOW SEASONABLE NORMS...ESPECIALLY ON FRIDAY AND SATURDAY.

&&

.AVIATION...26/18Z
ISSUED AT 1249 PM CDT SUN OCT 26 2014

A WARM FRONT FROM NERN KS INTO SERN MO WILL LIFT NORTH ACROSS THE
STATE TONIGHT AS LOW PRESSURE IN NORTH CENTRAL KS MOVES INTO IA BY
12Z MONDAY SELY FLOW WITH INCREASING MOISTURE. SOME MVFR FOG
DEVELOPING OVER THE NORTH HALF OF IOWA LATE TONIGHT. COLD FRONT
WILL MOVE INTO NWRN IA MONDAY MORNING. MVFR CIGS LIKELY TO DEVELOP
IN ITS WAKE.

OUTLOOK...HIGH PRESSURE WILL BRING CLEARING CONDITIONS FOR TUE AND
WED WITH A NEW FRONTAL SYSTEM MOVING IN WED NIGHT.

&&

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

$$

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



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