Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 302053
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
353 PM CDT THU OCT 30 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 328 PM CDT THU OCT 30 2014

SECOND IN A SERIES OF UPPER LEVEL WAVES QUICKLY DROPPING SOUTH INTO
IOWA THIS EVENING. MOISTURE REMAINS LIMITED BUT SHOWERS STILL
EXPECTED TO MOVE SOUTHEAST OUT OF SOUTHERN MN LATE AFTERNOON AND
EARLY EVENING...POSSIBLY BRINGING A FEW SPRINKLES TO NORTHEAST AND
NORTH CENTRAL SECTIONS IN IN THE EVENING HOURS. MAIN CONCERNS THIS
PERIOD WILL BE THE WINDS AND MINS OVERNIGHT TONIGHT AS THE DEEPENING
UPPER LEVEL WAVE DROPS SOUTH TONIGHT WITH A SECONDARY COLD FRONT.
RAPIDLY STRENGTHENING H850 WINDS AND STRONG COLD AIR ADVECTION/
SUBSIDENCE WILL ACCOMPANY THE BOUNDARY AND PROMOTE SIGNIFICANT
MIXING AFTER 02Z ACROSS THE NORTH AND SPREAD SOUTHEAST THROUGH THE
OVERNIGHT HOURS. SOUNDINGS SUPPORT WINDS TO NEAR 40 MPH AT TIMES
NORTHEAST FROM 9 PM THROUGH ABOUT 4 AM WITH SLIGHTLY LESSER GUSTS
ACROSS THE CENTRAL AND SOUTHEAST. WITH THE PASSAGE OF STRONG COLD
FRONT...SKIES WILL LIKELY CLEAR MOST AREAS AFTER MIDNIGHT WITH CLEAR
SKIES LEFT BY SUNRISE. THOUGH WINDS WILL RELAX A BIT BY SUNRISE IN
THE SOUTH AND WEST...GUSTS TO NEAR 25 MPH MAY STILL OCCUR OVER THE
NORTHEAST. TEMPERATURE GUIDANCE IS ALL OVER THE BOARD FOR OVERNIGHT
MINS TONIGHT WITH THE MAV THE COLDEST...ECE A BIT WARMER...AND THE
MET GUIDANCE THE WARMEST. LOOKING UPSTREAM INTO SOUTHERN CANADA...
CURRENT DAYTIME READINGS ARE ONLY IN THE MID TO UPPER 20S. THE
STRENGTH AND ACCELERATION OF THE SYSTEM TONIGHT WILL BE KEY IN HOW
MUCH COLD AIR ARRIVES BY MORNING. THE MIXING OVERNIGHT SHOULD
MODERATE THE AIRMASS AS IT HEADS SOUTH BUT THE COLD AIR SHOULD STILL
ARRIVE QUICKLY. HAVE LOWERED THE TEMPS OVER THE SOUTH ABOUT 2-3
DEGREES AND NORTH ABOUT A DEGREE GIVEN THE UPSTREAM CONDITIONS AND
LIKELIHOOD THAT THE ACCELERATING UPPER LEVEL WAVE WILL BE ABLE TO
FORCE THE COLD AIR INTO IOWA QUICKLY BY MORNING. WITH THE LOW TEMPS
DROPPING INTO THE 20S NORTH AND PERSISTENT WINDS THROUGH SUNRISE...
WIND CHILLS WILL DROP INTO THE TEENS ACROSS THE NORTH HALF OF THE
AREA AND IN THE 20S SOUTH FOR THE MORNING COMMUTE TO WORK AND
SCHOOL.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 328 PM CDT THU OCT 30 2014

NOT MUCH CHANGE IN THE EXTENDED FORECAST. HIGH PRESSURE WILL BE
FIRMLY ENTRENCHED OVER THE UPPER MIDWEST ON FRIDAY AND IT WILL
LIKELY BE THE COLDEST DAY OF THE WEEK.

ON SATURDAY WE WILL STILL HAVE THE UPPER RIDGE IN PLACE BUT THE
AXIS OF THE SURFACE HIGH WILL SHIFT TO THE EAST DURING THE
AFTERNOON. THIS WILL RESULT IN A WEAK RETURN FLOW ACROSS IOWA SO
TEMPS ON SATURDAY WILL NOT BE AS COLD AS FRIDAY BUT STILL BELOW
AVERAGE.

THE NEXT SYSTEM TO AFFECT IOWA WILL BE A LARGE TROUGH DEVELOPING
OVER THE ROCKIES AND SHIFTING INTO THE PLAINS MONDAY THROUGH
TUESDAY. FLOW ACROSS THE REGION WILL BECOME SOUTHWESTERLY AND
MOISTURE WILL INCREASE ACROSS IOWA BEGINNING MONDAY AFTERNOON
THROUGH TUESDAY. RAINFALL WILL|OVERSPREAD THE STATE MONDAY BUT THE
SYSTEM IS FAIRLY PROGRESSIVE AND SHOULD EXIT THE STATE BY TUESDAY
AFTERNOON. DURING THIS TIME WILL BE PERIODS OF BETTER FORCING AND
SOME INSTABILITY. WHILE I CANNOT RULE OUT AN ISOLATED
THUNDERSTORM...CONFIDENCE IS NOT HIGH ENOUGH AT THIS POINT TO PUT
ISOLATED THUNDERSTORMS IN THE FORECAST FOR DAY 4/5. THERE ISN`T
ANY REAL COLD AIR BEHIND THIS SYSTEM SO TEMPS BEHIND THIS SHOULD
REMAIN SEASONAL.

THERE WILL BE ANOTHER SHORTWAVE PUSHING ACROSS THE NORTHERN PLAINS
WED/THU BUT MOST OF THE FORCING AND PRECIP SHOULD REMAIN NORTH OF
IOWA.

&&

.AVIATION...30/18Z
ISSUED AT 1247 PM CDT THU OCT 30 2014

MAIN CONCERNS THIS PERIOD WILL BE A BAND OF MVFR CIGS WITH
APPROACHING COLD FRONT AND WINDS FOLLOWING FRONT. CURRENT SYNOPTIC
FEATURES INCLUDE SYSTEM DROPPING SOUTH OUT OF MN THIS AFTERNOON.
THIS WILL BRING A BAND OF LIGHT SHOWERS OR SPRINKLES AND BRIEF
PERIOD OF MVFR CIGS TO THE NORTHEAST BY 22Z AND END BY 02Z WITH
STRONG NORTH WINDS INCREASING AFT 02Z NORTH THROUGH THE ENTIRE
AREA THROUGH 12Z. SUSTAINED WINDS INCREASING TO 16 TO 22KTS WITH
GUSTS 20 TO 35KTS. THE STRONGER WINDS WILL BE OVER THE EAST AT
KMCW...KALO...AND KOTM. STEEP LAPSE RATES DEVELOP IN WITH COLD AIR
POOL AND STRONG SUBSIDENCE WILL AID IN PERIOD OF STRONGER WINDS
OVERNIGHT. /REV


&&

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

$$

SHORT TERM...REV
LONG TERM...FAB
AVIATION...REV



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