Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 302332
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
632 PM CDT TUE JUN 30 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 345 PM CDT TUE JUN 30 2015

STORY REMAINS THE SAME WITH REGARDS TO THE OVERALL FLOW ACROSS IOWA
WITH NORTHWEST FLOW DOMINATING FOR THE NEXT FEW DAYS.  FOR THE SHORT
TERM...THE STORY WILL BE THE SHOWERS/WEAK CONVECTION OFF TO THE WEST
THAT WILL SLOWLY WORK ITS WAY INTO AND ACROSS THE CWA. IN GENERAL A
FEW LIFTING METHODS EXIST...BUT ARE GENERALLY ON THE WEAK SIDE IN
THEIR OWN RIGHT...INCLUDING WAA MOVING DOWN THE MISSOURI VALLEY...A
SHORT WAVE VORT MAX...AND ISENTROPIC LIFT WITH THE BAROCLINIC ZONE.
THE ISENTROPIC LIFT IS THE STRONGEST...KEEPING THE BEST CHANCES FOR
SHOWERS/STORM IN WESTERN HALF OF IOWA THIS EVENING/OVERNIGHT.
HAVE BOOSTED POPS IN PARTS OF WESTERN IOWA TO LIKELY THIS EVENING
AS THE HRRR HAS HANDLED THIS THE BEST SO FAR...WITH OTHER HI-RES
GUIDANCE GENERALLY AGREEING AGREEING. WITH PRIMARILY AN
EVENING/OVERNIGHT TIMING INSTABILITY WILL BE WANING AND SHOULD BE
GENERAL THUNDERSTORMS AT BEST. REGARDING SMOKE...HIGHS DID HAVE
TROUBLE REACHING GUIDANCE IN A FEW LOCATIONS...BUT OVERALL WERE
NOT TOO FAR OFF. DID NOT DO MUCH ADJUSTMENT TO OVERNIGHT LOWS AS A
RESULT...ESPECIALLY WITH CLOUD COVER MOVING IN ACROSS THE STATE
OVERNIGHT.

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
ISSUED AT 345 PM CDT TUE JUN 30 2015

PRIMARY WEATHER CONCERNS WILL BE PRECIP INTO WED...AND THEN AGAIN
EARLY NEXT WEEK. PATTERN WILL UNDER GO A GRADUAL CHANGE THROUGH THE
PERIOD...EVOLVING FROM WRN CONUS RIDGE/ERN TROUGH TO A BROADER MEAN
TROUGH CENTERED THROUGH CENTRAL CANADA. AT ONSET THE FOCUS WILL
BE ON LIFT ASSOCIATED WITH RIGHT ENTRANCE REGION OF ERN GREAT
LAKES JET AND FORCING WITH CURRENT MT/ND/SASKATCHEWAN SHORT WAVE.
WEAK/MODERATE AND FAIRLY DEEP THERMODYNAMIC AND KINEMATIC FORCING
WILL PASS THROUGH IA WITH THIS FEATURE. INSTABILITY WILL BE BELOW
SEASONAL LIMITS HOWEVER SO STRONG TO SEVERE STORMS ARE NOT
ANTICIPATED. SOME WEAK PRECIP MAY LINGER SOUTH INTO THE
EVENING...BUT MUCH OF THE FORCING IS EXPECTED TO EXIT INTO MO/IL
BY 06Z. CHANCE POPS WILL RETURN SOUTH AND WEST INTO THU AND THU
NIGHT WITH JUST TOKEN FORCING IN PERSISTENT NW FLOW...BUT
CONTINUED AIRMASS STABILITY WILL KEEP ANY CONVECTION RELATIVELY
INACTIVE.

PATTERN WILL THEN BEGIN CHANGING OVER THE WEEKEND WITH GULF OF AK
LOW PASSING THROUGH WRN CANADIAN PROVINCES AND EVENTUALLY EVOLVING
INTO FAIRLY BROAD CANADIAN TROUGH. RETURN FLOW WILL INCREASE AHEAD
OF THIS FEATURE WITH A PERIOD OF WARMING AND INSTABILITY. THERE ARE
TIMING QUESTIONS ON HOW THIS WILL BE REALIZED HOWEVER WITH
DETERMINISTIC ECMWF FASTER THAN RESPECTIVE GFS 12Z SOLUTION. ECMWF
ENSEMBLES WOULD TEND TO FAVOR SLOWER GFS SOLUTION. THUS WILL HIT
POPS THE HARDEST SUN NIGHT INTO MON WITH HIGH PLAINS SURFACE BASED
CONVECTION EVENTUALLY REACHING IA INTO THE NIGHT WITH SUFFICIENT
LARGE SCALE FORCING TO KEEP IT GOING IN SOME FORM INTO MON. GFS
MLCAPES SUGGEST VALUES MAY REACH 2-3K DURING PEAK HEATING. DEEP
SHEAR WILL BE SUFFICIENT FOR ORGANIZATION SO SEVERE THREAT WILL
CERTAINLY BE THERE...BUT SOMEWHAT CONDITIONAL DEPENDING ON TIMING
OF FROPA.

OUTSIDE OF WARMING SURGE JUST AHEAD OF SYSTEM EARLY NEXT WEEK THIS
PATTERN WITH BELOW NORMAL HEIGHTS WILL KEEP OUR TEMPS BELOW
NORMAL TO VARIED DEGREES THROUGH MUCH OF THE PERIOD. HEAVY RAINS
MAY ACCOMPANY THE CONVECTION EARLY NEXT WEEK...BUT THE PATTERN
SEEMS PROGRESSIVE ENOUGH TO PRECLUDE MUCH ADDITIONAL FLOODING
CONCERNS.

&&

.AVIATION...01/00Z
ISSUED AT 632 PM CDT TUE JUN 30 2015

MAIN CHALLENGE THIS PERIOD WILL BE EVOLUTION OF SYSTEM TRACKING
THROUGH THE AREA. MODELS SPLIT ON TRACK OF SYSTEM THROUGH 00Z WITH
MESO MODELS/EURO BUILDING SHOWERS FARTHER NORTH COMPARED TO
GFS/NAM. HAVE INCREASED AND EXTENDED -SHRA CHANCES THROUGH 00Z FOR
SOUTHERN/CENTRAL SITES AS WELL AS INCLUDED VCSH FOR KFOD AFT 17Z.
AFT 18Z POTENTIAL FOR LIMITED THUNDER INCREASES ACROSS SOUTH WITH
VCTS AT KOTM. CIGS MAINLY VFR WITH EXCEPTION OF SOUTHERN SITES AFT
18Z. CURRENT -SHRA OVER WESTERN IOWA HAVING DIFFICULT TIME
SATURATING AIRMASS...BUT -SHRA ACTIVITY WILL EVENTUALLY WIN OUT.
WINDS NOT MUCH OF AN IMPACT BUT SOME VSBY ISSUES WITH -SHRA AND
ALOFT WITH SMOKE. EARLIER...SMOKE LAYER ESTIMATED BETWEEN 5 AND
17KFT WITH SOME RESTRICTIONS TO VSBY...DOWN TO LESS THAN SEVERAL
MILES IN THICKER SMOKE AT THOSE LEVELS. -SHRA SHOULD HELP REMOVE
SMOKE OVER NEXT 24 HOURS. /REV

&&

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

$$

SHORT TERM...CURTIS
LONG TERM...SMALL
AVIATION...REV


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