Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 222329
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
629 PM CDT TUE APR 22 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 338 PM CDT TUE APR 22 2014

SURFACE HIGH WILL BE PUSHING TO THE EAST OVERNIGHT WHILE THE UPPER
RIDGE REMAINS LARGELY TO THE WEST.  WITH MOST OF THE NIGHT UNDER THE
INFLUENCE OF THE HIGH NOT EXPECTING MUCH IN THE WAY OF SENSIBLE
WEATHER.  TEMPS WILL COOL QUICKLY IN THE EVENING UNDER A CLEAR SKY
AND LIGHT WIND.  AS THE SURFACE HIGH RETREATS TO THE EAST OVERNIGHT
MID AND HIGH LEVEL CLOUDS WILL INCREASE AFT 08Z OR SO AHEAD OF A LOW
DEVELOPING OVER THE HIGH PLAINS WITH AN ATTENDANT WARM FRONT
STRETCHING INTO NW IA. WARM ADVECTION WILL BE INCREASING ACROSS
CENTRAL IOWA THROUGH THE OVERNIGHT INTO WEDNESDAY AND MODELS HAVE
BEEN CONSISTENT IN NOSING A BROAD AREA OF THETA-E ADVECTION INTO FAR
WESTERN IOWA ALONG WITH DECENT QG FORCING BY 12Z.  THE PROBLEM FOR
ANY PRECIP HOWEVER DISTINCT LACK OF MOISTURE SHOWN BY THE SOUNDINGS.
AS A RESULT I HAVE PULLED POPS FROM MOST OF THE TONIGHT PERIOD AND
BLENDED IN WITH NEIGHBORS THE LAST COUPLE OF HOURS.

BY 11Z MOISTURE TRANSPORT INCREASES ACROSS THE STATE MAINLY POINTING
TOWARDS THE EASTERN DAKOTAS/EASTERN NEBRASKA.  SHOWERS AND ISOLATED
STORMS COULD EEK INTO THE FAR WESTERN PORTION OF THE CWA BETWEEN 11
AND 12Z BY THIS TIME.  FROM 12Z AND BEYOND THE THETA-E ADVECTION
SHIFTS INTO ABOUT THE WESTERN HALF OF THE FORECAST AREA AND DEEPER
MOISTURE DOES WORK INTO THE FAR WESTERN PORTION OF THE FORECAST AREA
SO PRECIP CHANCES WILL INCREASE A FAIR AMOUNT THROUGH THE MORNING
HOURS.  INSTABILITY REMAINS MEAGER THOUGH SO WE ARE LIKELY LOOKING
AT SHOWERS WITH AN ISOLATED THUNDERSTORM POSSIBLE TOWARDS DAYBREAK.

.LONG TERM /WEDNESDAY THROUGH TUESDAY/...
ISSUED AT 338 PM CDT TUE APR 22 2014

STRONG WARM ADVECTION WILL BE ONGOING AT THE START OF THE PERIOD
TOMORROW AHEAD OF SURFACE LOW MOVING INTO THE HIGH PLAINS. WILL
ALSO SEE INCREASING THETA-E ADVECTION AND EXPECT SOME SCATTERED
SHOWERS ACROSS THE FORECAST AREA IN THE MORNING. ELEVATED
INSTABILITY WILL BE VERY LIMITED BUT MAY STILL CRANK OUT A FEW
ISOLATED STORMS GIVEN THE GOOD LIFT ASSOCIATED WITH THE WARM
ADVECTION. THIS ACTIVITY WILL MOVE TO THE NORTH AND EAST DURING
THE AFTERNOON WITH A GOOD PORTION OF THE FORECAST AREA SEEING
LITTLE ACTIVITY IN THE AFTERNOON. WINDS WILL BE QUITE STRONG FROM
THE SOUTH TOMORROW WITH TIGHT PRESSURE GRADIENT AND RAPIDLY
INCREASING WINDS ABOVE THE SURFACE. WINDS WILL BE MARGINALLY CLOSE
TO ADVISORY CRITERIA FOR BOTH SUSTAINED AND GUSTS BUT REMAIN
QUESTIONABLE GIVEN CLOUDS AND LIFT. HAVE FOREGONE HEADLINES AT
THIS POINT AND WILL LET MID SHIFT EVALUATE FURTHER.

UPPER TROF PROGRESSES ACROSS THE PLAINS ON WEDNESDAY NIGHT WITH
THE BULK OF STRONGER CONVECTION WEST OF IOWA DURING THE EVENING.
HOWEVER...THIS WILL BEGIN TO BLEED ACROSS THE MISSOURI RIVER
DURING THE EVENING AND INTO MUCH OF THE CWA BY DAYBREAK ON
THURSDAY. AT THIS POINT...ANY SEVERE CONVECTION APPEARS LIMITED
WITH LIMITED INSTABILITY. THE PRECIPITATION WILL PASS THROUGH
CENTRAL IOWA ON THURSDAY MORNING WITH SOME LINGERING SHOWER IN THE
AFTERNOON AS INSTABILITY DEVELOPS UNDERNEATH THE TROF...ESPECIALLY
NORTH AND EAST. WINDS WILL ALSO REMAIN STRONG BUT FROM THE WEST
BEHIND THE FRONT.

QUIET WEATHER IS ANTICIPATED THURSDAY NIGHT THROUGH MUCH OF
SATURDAY AS A DRY AIRMASS REMAINS IN PLACE ACROSS IOWA. NEXT
SYSTEM WILL BEGIN TO AFFECT IOWA BY LATE SATURDAY AS POTENT
SHORTWAVE CROSSES THE WEST AND INDUCES CYCLOGENESIS ACROSS THE
PLAINS ON SATURDAY. GFS AND EURO HAD INITIALLY KEPT IOWA IN THE
COOL SECTOR WITH THIS STORM AND GENERALLY ELEVATED CONVECTION OR
RAIN. HOWEVER...LATEST 12Z RUNS OF BOTH MODELS ARE NOW BRINGING
THE SYSTEM FARTHER NORTH WITH EURO SETTING UP WARM FRONT ACROSS
NORTHERN IOWA BY SUNDAY AND COULD PRODUCE SOME STRONG OR POSSIBLY
SEVERE CONVECTION LATE SUNDAY. GFS IS NOT AS BULLISH BUT STILL
MORE ACTIVE THAN PREVIOUS RUNS AND THEREFORE THE EVOLUTION OF THIS
SYSTEM REMAINS IN FLUX. IN EITHER CASE...IT APPEARS WET FROM
SUNDAY INTO EARLY NEXT WEEK AS UPPER SYSTEM PROGRESSES INTO THE
REGION AND THEN SLOWLY MEANDERS. TEMPERATURES WILL BE WELL BELOW
NORMAL INTO THE EARLY PART OF NEXT WEEK WITH THE LINGERING THREAT
OF PRECIPITATION.

&&

.AVIATION...23/00Z
ISSUED AT 625 PM CDT TUE APR 22 2014

HIGH PRESSURE RIDGE OVER IA WILL MOVE TO THE EAST WITH WINDS
BECOMING SELY OVER NIGHT. WINDS WILL INCREASE AND BECOME GUSTY ON
WED. A WARM FRONT WILL LIFT NORTH IN TO THE STATE AND BRING
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS...MAINLY TO THE NRN
TAFS. CONDITIONS WILL REMAIN VFR THROUGHOUT THE TAF PERIOD.

OUTLOOK...COLD FRONT AND LOW PRESSURE AREA WILL MOVE INTO IA FROM
THE WEST WED NIGHT AND THU. CONDITIONS WILL DETERIORATE WED NIGHT
AND THU WITH SHOWERS AND THUNDERSTORMS BECOMING WIDESPREAD.

&&

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

&&

$$

SHORT TERM...FAB
LONG TERM...COGIL
AVIATION...MS APR 14



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