Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 220841
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
341 AM CDT WED APR 22 2015

.SHORT TERM /TODAY/...
ISSUED AT 330 AM CDT WED APR 22 2015

LARGE UPPER LOW OVER ONTARIO WILL CONTINUE TO SLOWLY PULL AWAY TODAY
WITH SURFACE RIDGING APPROACHING FROM THE WEST.  RELATIVELY DRY
AIRMASS WILL BE IN PLACE TODAY WITH SUNNY SKIES AND FAIRLY DEEP
MIXING. FORECAST SOUNDINGS INDICATE A MIXING DEPTH OF 6-8KFT ACROSS
MUCH OF THE STATE WITH WINDS OF 30-40KTS AT TOP OF MIXED LAYER.
THEREFORE...STILL ANTICIPATE A WINDY DAY...ESPECIALLY IN THE
NORTHEAST WHERE WINDS WILL APPROACH ADVISORY CRITERIA ONCE AGAIN.
IT APPEARS PRESSURE GRADIENT IS NOT QUITE AS TIGHT AND WINDS ARE NOT
AS STRONG THROUGH THE MIXED LAYER AS WAS THE CASE OVER THE PAST TWO
DAYS AND THEREFORE WILL FORGO ANY HEADLINES. TEMPERATURES WILL
CONTINUE TO HOLD BELOW NORMAL WITH THERMAL TROF STARTING OUT ACROSS
THE STATE THIS MORNING THEN SHIFTING EASTWARD DURING THE DAY.

.LONG TERM /TONIGHT THROUGH TUESDAY/...
ISSUED AT 330 AM CDT WED APR 22 2015

TONIGHT THROUGH THURSDAY NIGHT WE WILL HAVE LITTLE CONCERN AS IOWA
WILL BE IN BETWEEN RIDGING TO THE WEST AND THE DEPARTING LARGE LOW
OVER THE EASTERN GREAT LAKES.  WE WILL HAVE CONCERNS FOR FROST AGAIN
TONIGHT WITH CLEAR SKIES OVERHEAD AND NORTHWEST WINDS DROPPING OFF
TO AT OR BELOW 5 KTS. HOWEVER THE COLDEST TEMPS WILL HIT AN HOUR
OR SO BEFORE SUNRISE AND WILL NOT LAST LONG AND BEING STILL FAIRLY
EARLY IN THE SEASON I HAVE OPTED NOT TO HEADLINE PATCHY TO AREAS
OF FROST ALTHOUGH IT IS IN THE GRIDS.

I WAS LESS IMPRESSED WITH PRECIP CHANCES ON FRIDAY/SATURDAY BEFORE
BUT TONIGHT`S MODEL RUNS REALLY COME TOGETHER AND BRING A LARGE AREA
OF FORCING ACROSS CENTRAL IOWA DURING THE DAY FRIDAY INTO FRIDAY
NIGHT FOLLOWED ON SATURDAY BY A LOW AND SHORTWAVE TRAVERSING THE
SOUTHERN PLAINS.  SOUNDINGS ACROSS CENTRAL IOWA SATURATE DURING THE
MORNING HOURS FRIDAY BUT THE STRONGEST FORCING IS NOT UNTIL THE
AFTERNOON AND EVENING SO THERE WILL BE TIMING OF THE START OF PRECIP
TO FORECAST BUT ITS A LITTLE TO FAR OUT FOR SPECIFICS ON THAT JUST
YET. HIGHEST POPS WILL LIKELY BE LATE FRIDAY AFTERNOON/FRIDAY
NIGHT.

WE ARE NOT PARTICULARLY UNSTABLE EITHER SO I AM NOT COMPLETELY SOLD
ON THUNDERSTORMS YET BUT AS THE WAVE SHIFTS EAST ACROSS THE SOUTHERN
PLAINS SOME INSTABILITY IS POSSIBLE ACROSS SOUTHERN IOWA.  ALSO WITH
AS STRONG AS THE FORCING IS PROGGED TO BE IT WILL NOT BE TOO
DIFFICULT TO GET A RUMBLE OR TWO OF THUNDER.  AT THIS POINT THE
ISOLATED WORDING WE HAVE GOING IS PROBABLY THE BEST WAY TO HANDLE
THINGS.

UPPER LEVEL RIDGING REBUILDS INTO THE STATE SUNDAY FOR A BREAK IN
THE PRECIP AND SOME MODERATION IN TEMPS AS A SURFACE HIGH MOVES EAST
OF THE STATE PUTTING IOWA IN RETURN FLOW.  THEN FOR EARLY NEXT WEEK
A TROUGH WILL MOVE IN FROM THE WEST BUT SOUNDINGS DO NOT SATURATE
UNTIL MONDAY NIGHT/TUESDAY TIME FRAME BUT BY THEN...DEPENDING ON
WHICH MODEL YOU BELIEVE...RIDGING STARTS TO WORK ITS WAY INTO THE
WEST.  THE GFS IS VERY UGLY LOOKING AND THIS FAR OUT...PROBABLY THE
LEAST BELIEVABLE.  THE GFS HAS A STRONG LOW ACROSS THE SOUTHERN
PLAINS WITH ANOTHER STRONG LOW ACROSS CANADA AND THE NORTHERN
PLAINS.  THE NORTHERN LOW DROPS SOUTH AND BECOMES INGESTED IN THE
SOUTHERN STREAM LOW WHICH FUJIWARA`S ACROSS ILLINOIS THEN RETROGRADES
SLIGHTLY BACK WEST INTO EASTERN IOWA.  IF THIS WERE TO HAPPEN WE
WOULD BE VERY WET FOR AN EXTENDED PERIOD.  FOR NOW THE EURO MODEL`S
SOLUTION LOOKS MUCH MORE FEASIBLE BUT THIS WILL BE WATCHED AND
IF THE GFS LOOKS LIKE IT MAY VERIFY THEN POPS WILL DEFINITELY NEED
TO BE INCREASED.

&&

.AVIATION...22/06Z
ISSUED AT 1147 PM CDT TUE APR 21 2015

WIND GUSTS CONTINUE OVER NORTHERN SITES...BUT SHOULD DIMINISH AFT
08 TO 09Z. CLOUD DECK OF BKN040 WILL SHIFT EAST SOUTHEAST BY 10Z
WITH FEW-SCT REDEVELOPING AFT 15Z AS NORTHWEST WINDS INCREASE
AGAIN. EXPECTING NORTHWEST WINDS 20 GUST 30 KTS FOR NORTHERN SITES
AT KMCW AND KALO...BUT THEN DIMINISHING BY 23Z. LIGHT WINDS
EXPECTED REMAINDER OF PERIOD AS HIGH PRESSURE RIDGE BUILDS INTO
AREA. /REV

&&

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

$$

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



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