Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 241141
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
641 AM CDT MON AUG 24 2015

...UPDATED AVIATION DISCUSSION...

.SHORT TERM /TODAY/...
ISSUED AT 308 AM CDT MON AUG 24 2015

ANOTHER BREEZY AND BELOW NORMAL DAY IN STORE FOR CENTRAL IOWA
WITH GOOD MIXING TO AROUND 875-900MB THIS AFTERNOON. WINDS ATOP
THE MIXED LAYER IN THE 24-28 KNOT RANGE AND THE HIGHEST WINDS LOOK
TO BE OVER NORTHERN TO NORTHEAST PORTIONS OF THE FORECAST AREA.
TWEAKED UP MAX TEMPS 1-2 DEGREES WITH THE GOOD MIXING AND PLENTY
OF SUNSHINE. LEANED CLOSER TO A BLEND OF THE MET/ECE GUIDANCE FOR
HIGHS TODAY AS THINKING THE MAV WAS TOO WARM.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 308 AM CDT MON AUG 24 2015

FEW CONCERNS FOR THE NEXT COUPLE OF DAYS...OTHER THAN ADJUSTING TO
MORE FALL LIKE TEMPERATURES. NO CONCERNS FOR ANY RECORD LOWS AS
THOSE CONTINUE TO RUN ABOUT 10 DEGREES COOLER THAN MINS PROJECTED
THE NEXT FEW DAYS. TONIGHTS 03Z SUBJECTIVE SFC ANALYSIS SHOWS DEEP
LOW JUST NORTHWEST OF LAKE SUPERIOR WITH LARGE CLOUD SHIELD AND
WRAP AROUND SHOWERS ACROSS SOUTHERN MANITOBA THIS EVENING. A WEAK
TROUGH OR MINOR FRONT EXTENDS SOUTHWEST THROUGH IOWA...INDICATED
ONLY BY A RIPPLE IN THE PRESSURE FIELD. A PERSISTENT RIDGE AT
H500 OVER NOVA SCOTIA WILL KEEP THE LOW FROM MOVING MUCH THROUGH
MONDAY AFTERNOON. THE LOW WILL THEN SLOWLY SLIDE EAST NORTHEAST
INTO QUEBEC BY 00Z WED... KEEPING THE NORTHERN PLAINS AND MOST OF
THE GREAT LAKES UNDER NORTH NORTHWEST FLOW. ANOTHER WEAK BACK DOOR
COOL FRONT WILL PUSH WEST TUESDAY AND REINFORCE THE COOLER
CONDITIONS OVER THE EASTERN PORTION OF THE FORECAST AREA INTO
WEDNESDAY MORNING. AT THE SAME TIME...A RIDGE OF HIGH PRESSURE
CURRENTLY RESIDING TO OUR WEST WILL DRIFT EAST INTO THE STATE BY
TUESDAY AFTERNOON. THE COMBINATION OF THESE TWO SYSTEMS WILL KEEP
US IN A COMFORTABLE AND DRY AIRMASS WITH HIGHS IN THE 60S/70S AND
LOWS IN THE 40S/50S FOR THE NEXT TWO TO THREE DAYS. WITH THE
GREAT LAKES HIGH ANCHORED TO OUR EAST THROUGH THURSDAY MORNING...
WE CAN EXPECT TO SEE MORE OF THE SAME UNTIL THEN.

BY MIDDAY THURSDAY A TROUGH OF LOW PRESSURE WILL DEVELOP ACROSS THE
ROCKIES. THIS WILL BEGIN A TREND TOWARD MORE ACTIVE WEATHER FROM
THURSDAY THROUGH SUNDAY. CONFIDENCE WITH THE LATE WEEK SYSTEM IS
MEDIUM AT THIS TIME DUE TO FORECAST MODEL DIVERGENCE. TONIGHT...THE
SYSTEM THAT WILL AFFECT US APPEARS TO BE PARTLY FROM A WAVE IN THE
PACIFIC AT 30N - 125W AND A PIECE OF MONSOONAL ENERGY ROUNDING THE
RIDGE OVER THE SOUTHWEST US/NORTHERN OLD MEXICO. THE WAVE EVENTUALLY
MOVES UNDER THE UPPER LEVEL H500 RIDGE...THEN AMPLIFIES AS IT GETS
CLOSER TO THE MEAN UPPER LEVEL TROUGH OVER THE CENTRAL PLAINS BY
THURSDAY. THIS WILL EVENTUALLY DEEPEN NEAR IOWA ON FRIDAY...
INDUCING A SFC FEATURE THAT WILL WEAKEN AS IT CROSSES THE
MID/UPPER MISSISSIPPI VALLEY. CHALLENGES REMAIN WITH THE
PROGRESSION/EVOLUTION OF THIS FEATURE. OVERALL...THE SIGNAL IS
PERSISTENT BUT THE PLACEMENT BY THE MODELS IS NOT. THE GFS MORE
NORTHERLY BIAS IS PLAYING OUT WITH THE GEM/EURO PREFERRING A MORE
SOUTHERLY TRACK. THE LATTER SCENARIO WOULD BRING THE FORECAST AREA
A RATHER WET PERIOD FROM THURSDAY NIGHT THROUGH FRIDAY NIGHT
BEFORE THIS SLOW MOVING FEATURE LEAVES THE REGION TO THE EAST
SOUTHEAST. THE GFS IS A BIT FARTHER NORTH WITH THE BEST LIFT...BUT
TIMING IS SIMILAR. FOR NOW WILL STICK WITH THE EURO/GEM PLACEMENT
SINCE THESE TWO MODELS HAVE BEEN TRENDING THE SAME OVER THE PAST 3
NIGHTS. WITH THE LOW OVER OUR AREA ON FRIDAY...HIGHS MAY BE MUCH
COOLER THAN CURRENTLY PROGGED...POSSIBLY BY AS MUCH AS 5 DEGREES.
WILL NEED TO SEE HOW THIS DEVELOPS OVER THE NEXT 2 TO 3 DAYS. ONCE
THIS SYSTEM EXITS A STRONG LOW EXPECTED TO DEVELOP OVER ALASKA AND
THE NORTH PACIFIC BY WEDNESDAY WILL AMPLIFY A TROUGH/RIDGE COUPLET
FROM THE PACIFIC NORTHWEST INTO THE PLAINS BY NEXT WEEKEND. THE
RIDGING HERE SHOULD ALLOW FOR TEMPS TO WARM INTO THE 80S WITH LOWS
IN THE MID 60S.

&&

.AVIATION...24/12Z
ISSUED AT 637 AM CDT MON AUG 24 2015

VFR CONDITIONS ARE EXPECTED TODAY INTO TONIGHT WITH MAIN CONCERN
OF WINDS INCREASING LATE THIS MORNING AND INTO THE AFTERNOON.

&&

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

&&

$$

SHORT TERM...PODRAZIK
LONG TERM...REV
AVIATION...PODRAZIK


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