Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 231135
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
635 AM CDT THU APR 23 2015

.SHORT TERM /TODAY/...
ISSUED AT 347 AM CDT THU APR 23 2015

HIGH PRESSURE RIDGE OVER IOWA WILL DRIFT EAST TODAY AND BE OVER
WESTERN ONTARIO INTO THE TENNESSEE VALLEY BY THIS EVENING.  LIGHT
WINDS TODAY WILL BECOME LIGHT SOUTHEAST OVER THE WEST HALF OF THE
THE STATE BY EVENING.  AN AREA OF MID LEVEL CLOUDS HAS FORMED OVER
WESTERN IA IN RESPONSE TO WEAK WAA.  EXPECT THEM TO PERSIST FOR A
FEW HOURS YET...BUT GRADUALLY BREAK UP AFTER SUNRISE.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 347 AM CDT THU APR 23 2015

WARM ADVECTION WILL BE STRONGER AND FASTER TONIGHT THAN PREVIOUSLY
FORECAST. IN ADDITION...FORCING IS PROGGED TO MOVE INTO MUCH OF
CENTRAL IOWA BETWEEN 06Z AND 12Z FRIDAY THIS I DID BRING POPS INTO
WESTERN IOWA OVERNIGHT. IN ADDITION...THE FORCING WILL PROBABLY BE
ENOUGH FOR SOME ISOLATED STORMS. BY LATE FRIDAY AND FRIDAY NIGHT A
SHORTWAVE WILL BE PASSING ACROSS IOWA AND INTO THE SOUTHERN
PLAINS. THE LOCATION AND TRACK OF THE SURFACE LOW IS STILL IN
QUESTION WITH THE NAM AND GFS TRACKING IT ACROSS SOUTHERN IOWA
WHILE THE EURO TRACKS IT FURTHER SOUTH. INSTABILITY...WHICH WAS
MINIMAL TO NON-EXISTENT WITH PREVIOUS MODEL RUNS IS NOW INTO
SOUTHERN IOWA TO SOME EXTENT...STILL VARYING WITH MODELS TIED TO
THE LOCATION OF THE LOW. DURING THE EVENING HOURS OF FRIDAY WE
WILL ALSO HAVE SOME WEAK TO MODERATE SHEAR PRESENT ACROSS SOUTHERN
IOWAWHICH WOULD BE SUPPORTIVE OF AT LEAST A FEW STRONGER
STORMS...PERHAPS ENOUGH FOR SOME STORMS TO PRODUCE MARGINALLY
SEVERE HAIL. AS A RESULT...POPS WERE INCREASED ACROSS THE FAR
SOUTH AND WORDING IN THE ZONES AND HWO PRODUCTS WERE ENHANCED SOME
TO COVER THIS POSSIBILITY.

BY SATURDAY MORNING THE SURFACE LOW WILL BE FAR ENOUGH EAST THAT
THE THREAT FOR STORMS WILL BE DIMINISHING BUT LINGERING PRECIP
CHANCES WILL REMAIN...ESPECIALLY IN THE MORNING. RIDGING THEN
MOVES IN FOR SUNDAY/MONDAY FOR A DRIER AND WARMER PERIOD.

BEYOND MONDAY MODELS ARE STILL IN DISAGREEMENT WITH THE EURO STILL
HOLDING ON TO RIDGING DEVELOPING OVER THE WESTERN U.S. AND A
SHORTWAVE OVER THE NORTHERN PLAINS THAT SWEEPS ACROSS THE UPPER
MIDWEST WITH LITTLE FANFARE. THE GFS AND NOW THE CANADIAN HOLD ON
SOMEWHAT TO THE GFS`S SOLUTIONS OF A STRONG SOUTHERN STREAM LOW
MOVING ACROSS THE SOUTHERN PLAINS WITH A STRONG NORTHERN PLAINS
LOW DROPPING TO THE SOUTH JUST WEST OF IOWA AND GETTING INGESTED
INTO THE SOUTHERN STREAM LOW. THE DIFFERENCE IS THAT NOW INSTEAD
OF THE FUJIWARA EFFECT THAT THE GFS HAD YESTERDAY THE INGESTING OF
THE NORTHERN STREAM LOW KICKS THE SOUTHERN STREAM LOW MORE TO THE
EAST NOW. BOTH THE EURO AND GFS HAVE AT LEAST FEASIBLE SOLUTIONS
BUT THE EURO WOULD BE DRIER AND AT LEAST AT THIS POINT IS MORE
CONSISTENT. FOR NOW...DUE TO SMALLER CHANCES FOR PRECIP OVER IOWA
AND THE UNCERTAINTY OF THE MODELS I DID LEAVE POPS VIRTUALLY OUT
OF THE EXTENDED BUT THE REALITY WILL BE ONCE THE MODELS CONVERGE
ON A MORE SIMILAR SOLUTION...SOME POPS WILL NEED TO BE ADDED BACK
AT SOME POINT. JUST TOO DIFFICULT TO DETERMINE JUST WHERE AT THIS
POINT AND KEEPING ENDLESS 20 POPS IN THE FORECAST THAT FAR OUT
DOES NOT DO THE FORECAST JUSTICE.

&&

.AVIATION...23/12Z
ISSUED AT 632 AM CDT THU APR 23 2015

HIGH PRESSURE FROM MANITOBA AND WESTERN ONTARIO INTO THE LOWER
TENNESSEE VALLEY WILL MOVE EAST WITH LIGHT FLOW BECOMING
SOUTHEASTERLY TONIGHT LOW PRESSURE WILL DEVELOP IN THE ROCKIES AND
SPREAD DETERIORATING CONDITIONS INTO WESTERN IOWA AFTER 06Z.

OUTLOOK...LARGE AREA OF RAIN AND STRATUS WILL OVERSPREAD THE SITES
WITH MVFR AND IFR CONDITIONS EXPECTED TO DEVELOP BY FRIDAY NIGHT
AND CONTINUE THROUGH SATURDAY. HIGH PRESSURE WILL BRING
IMPROVEMENT SUNDAY.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING UNTIL 8 AM CDT THIS MORNING FOR ADAIR-ADAMS-
APPANOOSE-BLACK HAWK-BREMER-BUTLER-CASS-CERRO GORDO-CLARKE-DAVIS-
DECATUR-EMMET-FRANKLIN-GRUNDY-HAMILTON-HANCOCK-HARDIN-HUMBOLDT-
JASPER-KOSSUTH-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-PALO
ALTO-POLK-POWESHIEK-RINGGOLD-STORY-TAMA-TAYLOR-UNION-WAPELLO-
WARREN-WAYNE-WEBSTER-WINNEBAGO-WORTH-WRIGHT.

&&

$$

SHORT TERM...MS APR 15
LONG TERM...FAB
AVIATION...MS APR 15



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