Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 281750
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1250 PM CDT SAT MAR 28 2015

.SHORT TERM /TODAY/...
ISSUED AT 353 AM CDT SAT MAR 28 2015

UPPER JET MAX AND SHORTWAVE WILL BE DEPARTING THIS MORNING WITH ONLY
A FEW SCATTERED FLURRIES EXPECTED WEST OF I35...PRIMARILY BEFORE
SUNRISE.  WILL SEE DECENT HEIGHT RISES TODAY BEHIND THE SHORTWAVE AS
UPPER RIDGING BUILDS INTO THE STATE.  INITIALLY...LOW LEVEL THERMAL
ADVECTION WILL BE RELATIVELY NEUTRAL...HOWEVER AS THE DAY
PROGRESSES...WARM ADVECTION WILL INCREASE AHEAD OF THE NEXT
APPROACHING SHORTWAVE EXPECTED TO ARRIVE LATER TONIGHT.  IN
ADDITION...CLOUDS ACROSS THE WEST ARE EXPECTED TO WANE THROUGH THE
DAY WITH SUBSIDENCE BEHIND THE SHORTWAVE AND DRIER AIR ADVECTING
INTO THE LOW LEVELS FROM THE SOUTHEAST. WITH THE SUNSHINE
REAPPEARING BY THE AFTERNOON AND INCREASING WARM
ADVECTION...ANTICIPATE TEMPERATURES TO BE AROUND 5 DEGREES WARMER IN
MOST LOCATIONS WITH THE WEST SEEING THE BEST REBOUND AS THE THERMAL
RIDGE WILL BE CLOSER.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 353 AM CDT SAT MAR 28 2015

OVERALL TRENDS OF THE FORECAST IN THE LONG TERM REMAIN UNCHANGED.
THERE REMAINS SOME QUESTION ABOUT INSTABILITY AND THUNDER POTENTIAL
AND ALSO SOME TIMING ISSUES.

A POTENT SHORTWAVE WILL BREAKDOWN THE UPPER RIDGE ACROSS THE
INTERMOUNTAIN WEST TONIGHT INTO SUNDAY AS IN PUSHES ACROSS THE
NORTHERN PLAINS AND UPPER MIDWEST.  THERE IS SOME WEAK INSTABILITY
ASSOCIATED WITH THIS AND THE NAM IS A LITTLE MORE ORGANIZED WITH THE
INSTABILITY THAN THE GFS BUT THEY ARE BOTH WEAK IN THE 0-6KM LAYER
WITH NO INSTABILITY TO SPEAK OF IN THE LOWER LEVELS.  AS WARM
ADVECTION INCREASES TONIGHT I CANNOT RULE OUT AN ISOLATED RUMBLE OF
THUNDER BUT IT WOULD BE BRIEF AND ISOLATED AND MY CONFIDENCE IN IT
OCCURRING OVER A GIVEN AREA WAS NOT HIGH ENOUGH TO INCLUDE AT THIS
POINT BUT IF IT WERE TO OCCUR IT WOULD PROBABLY HAPPEN ACROSS THE
NORTHWEST INTO WEST CENTRAL LATE TONIGHT.  SOUNDINGS ARE HAVING A
HARD TIME WITH DEEPER SATURATION WITH THIS SYSTEM EXCEPT FOR A BRIEF
PERIOD FROM ABOUT 09Z UNTIL 12-15Z SO I AM NOT LOOKING FOR MUCH OUT
OF THIS SYSTEM IN TERMS OF QPF EITHER.  WINDS ALOFT ARE PRETTY
STRONG AND WITH MIXING WE WILL SEE WIND GUSTS SUNDAY AFTERNOON
AROUND 35 MPH SO SUNDAY WILL BE WINDY AND WARMER WITH ANY PRECIP
CHANCES MAINLY IN THE MORNING HOURS.  THERE WILL BE SOME CONCERN FOR
FIRE WEATHER ON SUNDAY WITH THE WARMING TEMPS AND WINDY CONDITIONS.
HOWEVER... AT THIS POINT WE ARE EXPECTING SOME PRECIP AND RH VALUES
DIP INTO THE MID 30S FOR A FEW HOURS IN THE AFTERNOON WHICH WILL NOT
LIKELY BE ENOUGH TO HOIST HEADLINES...AT LEAST AT THIS POINT.

THE UPPER RIDGE REBUILDS OVER THE ROCKIES MONDAY INTO TUESDAY AND
MODELS DIFFER ON THE HANDLING OF A SHORTWAVE ON MONDAY WITH THE EURO
A LITTLE MORE AGGRESSIVE WITH IT AND THE GFS AND SREF KEEPING ANY
PRECIP TO THE NORTH AND EAST.  I KEPT THE CWA DRY ON MONDAY THROUGH
TUESDAY WITH WARMING TEMPS EACH DAY.

WE ARE STILL LOOKING AT A POTENT SHORTWAVE TO MOVE ACROSS THE REGION
ON WEDNESDAY.  MOISTURE WILL GET ADVECTED INTO IOWA AHEAD OF THIS
FEATURE AND THE GFS IS SHOWING SOME DECENT INSTABILITY.  LOW LEVEL
FORCING LOOKS DECENT THOUGH THE MID LEVEL FORCING IS WEAKER AND
ARRIVES LATER.  HOWEVER THE SHORTWAVE DOES ARRIVE DURING THE
AFTERNOON HOURS SO I DID LEAVE SCATTERED THUNDERSTORMS MENTIONED FOR
WEDNESDAY AFTERNOON INTO THE EVENING HOURS.

A MORE BROAD SHORTWAVE MOVES ACROSS THE AREA THURSDAY ON THE HEELS
OF THE FIRST WAVE BUT THIS WAVE LACKS THE FORCING AND INSTABILITY OF
THE WEDNESDAY SYSTEM SO I ONLY HAVE SHOWERS MENTIONED WITH THAT.
COOLER AIR WILL ALSO MOVE IN DURING THE THURSDAY/FRIDAY TIME FRAME
SO HIGHS ARE BACK INTO THE 50S BY FRIDAY AND I DID NUDGE HIGHS A
COUPLE DEGREES COOLER THAN WE HAD.

THE RIDGE OVER THE WEST TRIES TO REBUILD NEXT WEEKEND BUT THE EURO
AND GFS VARY AS TO THE DEGREE THAT OCCURS AND THE HANDLING OF ANY
SHORTWAVES.  THAT FAR OUT I KEPT THE PERIOD DRY THOUGH THERE WILL
LIKELY BE A NEED TO ADD POPS AT SOME POINT AS THE PATTERN REMAINS
FAIRLY ACTIVE.  HIGHS WARM A BIT FOR SATURDAY WITH READINGS BACK IN
THE 50S TO LOWER/MID 60S SOUTHWEST.

&&

.AVIATION...28/18Z
ISSUED AT 1245 PM CDT SAT MAR 28 2015

VFR CONDITIONS ARE EXPECTED FOR THE REST OF THE DAY WITH SOUTH TO
SOUTHEASTERLY WINDS OF AROUND 10 TO 15 KTS WITH A FEW HIGHER
GUSTS. SCATTERED SHOWERS AND POSSIBLY A THUNDERSTORM ARE EXPECTED
BETWEEN 09Z AND 15Z AS A FRONTAL BOUNDARY PASSES THROUGH THE STATE.
CEILINGS MAY DROP BELOW VFR AT TIMES DURING THESE STORMS. WINDS
WILL ALSO INCREASE OUT OF THE NORTHWEST AT 15 TO 25 KTS WITH
HIGHER GUSTS BEHIND THE FRONT ON SUNDAY.

&&

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

$$

SHORT TERM...COGIL
LONG TERM...FAB
AVIATION...SKOW



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