Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 282016
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
316 PM CDT THU AUG 28 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 315 PM CDT THU AUG 28 2014

PRIMARY FORECAST QUESTION FOR TONIGHT IS COVERAGE AND TIMING OF
PRECIPITATION. RECENT RADAR TRENDS AND HIGH RESOLUTION MODELS SUCH
AS THE WRF AND HRRR HAVE INDICATED A SIGNIFICANT DECREASING TREND IN
PRECIP COVERAGE LATE THIS AFTERNOON AND EVENING...HOWEVER MOST SHORT
RANGE MODELS CONTINUE TO FORECAST AN INCREASE ONCE AGAIN AFTER DARK
TONIGHT. THIS IS CONSISTENT WITH THE SYNOPTIC SCENARIO CHARACTERIZED
BY BROAD UPPER LEVEL DIFFLUENCE OVER A SATURATED ATMOSPHERE. HAVE
CARRIED GENERALLY CHANCE POPS/SCATTERED WORDING THROUGH THE NIGHT
GIVEN THE SUPPORT FOR REDEVELOPMENT...BUT HAVE LITTLE CONFIDENCE IN
DETAILS OF TIMING AND LOCATION THUS THE POP FORECAST IS BROADBRUSHED
FOR NOW. OTHERWISE LITTLE CHANGE WAS MADE TO THE ONGOING FORECAST.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 315 PM CDT THU AUG 28 2014

WITH UPPER LEVEL TROUGH STILL WEST OF THE AREA THROUGH EARLY
SATURDAY MORNING...LIKELY TO SEE SOME ADDITIONAL ROUNDS OF
THUNDERSTORMS ACROSS THE REGION THROUGH THAT TIME. OVER THE NEXT 24
TO 36 HOURS...THE HIGHEST PRECIPITABLE WATER VALUES WILL GRADUALLY
SHIFT EAST OF THE REGION AS H850 MOISTURE TRANSPORT BEGINS TO SHIFT
EAST AS WELL.  BY 12Z FRIDAY...ONE ADDITIONAL WAVE...THE KICKER
WAVE...WILL BE LOCATED OVER SOUTHEAST KS/WESTERN MO. THIS SHOULD
LIFT NORTHEAST DURING THE NEXT 24 HOURS RESULTING IN INCREASING LIFT
OVER THE REGION FRIDAY AFTERNOON AND EVENING. IN COMBINATION WITH
THAT A COLD FRONT AND UPPER LEVEL LOW OVER SOUTHERN CANADA WILL
DRIFT SOUTHEAST AND ALSO AID IN DISPLACING THE TROUGH ACROSS THE
GREAT PLAINS. THROUGH THE PERIOD FRIDAY INTO EARLY SATURDAY...
ANOTHER HALF INCH TO INCH OF RAINFALL IS LIKELY TO FALL WITH THE
HEAVIER TOTALS OVER THE NORTH AND NORTHEAST PORTION OF THE FORECAST
AREA. WITH RAINFALL RATES SLOWING DOWN...FLASH FLOODING IS PROBABLY
NO LONGER A THREAT...BUT SATURATED GROUND MAY LEAD TO SOME MINOR
RUNOFF PROBLEMS AT TIMES INCLUDING SOME PONDING OF WATER AND MINOR
STREET FLOODING IN AREAS OF POOR DRAINAGE. TEMPERATURES TOMORROW
WILL LIKELY WARM A BIT IN THE SOUTHEAST IN THE LOWER 80S...AHEAD OF
THE WAVE WITH WARM AIR ADVECTION AND SOME POTENTIAL BREAKS IN THE
CLOUD COVER IN THE SOUTHEAST. AS THE COOL FRONT MOVES EAST PRECIP
CHANCES SHOULD END ACROSS THE REGION SATURDAY MORNING WITH SOME
SUNSHINE RETURNING TO THE AREA BY MORNING. HIGHS WILL BE SLIGHTLY
WARMER...BUT STILL WITHIN THE A FEW DEGREES OF HIGHS OF FRIDAY WITH
MORE SUNSHINE...BUT SOME SLIGHT COOL AIR ADVECTION. MODELS IN
GENERAL AGREEMENT WITH THE NEXT STRONG WAVE EXPECTED TO ARRIVE BY
SUNDAY AFTERNOON....WITH A RATHER WARM DAY AHEAD AS H850 RISE TO
NEAR 20C BY AFTERNOON. THE GFS SHOWS THAT PWATS WILL ONCE AGAIN RISE
TO NEAR OR SLIGHTLY ABOVE 2 INCHES ALONG THE BOUNDARY AS IT MOVES
INTO WESTERN IOWA BY 00Z. UPPER LEVEL WIND FIELDS AGAIN SHOW A
MODEST INCREASE AS A MODESTLY STRONG WAVE APPROACHES FROM THE
SOUTHWEST WITH 0-6KM BULK SHEAR OVER 40 KTS ACROSS THE AREA. THIS
SHOULD BE ENOUGH TO PROMOTE SEVERE STORMS DURING THE LATE AFTERNOON
AND EVENING HOURS. ANOTHER ROUND OF STORMS WITH OVER AN INCH OF RAIN
IN SOME OF THE HEAVIER STORMS IS EXPECTED. FINALLY...THE REMAINDER
OF THE FORECAST SUGGESTS THAT A BREAK FROM THE ACTIVE WEATHER WILL
RETURN FROM LATER ON MONDAY THROUGH WEDNESDAY...WITH SOME POTENTIAL
FOR A QUICK MOVING STORM AGAIN BY THURSDAY.

&&

.AVIATION...28/18Z
ISSUED AT 1220 PM CDT THU AUG 28 2014

MORNING SHOWERS AND THUNDERSTORMS ARE CLEARING THE AREA TO THE
NORTHEAST...BUT WILL LINGER ESPECIALLY AT MCW/OTM INTO THIS
AFTERNOON. BR AND IFR/LIFR CIGS ARE SIMILARLY TRYING TO CLEAR OUT
AND SHOULD EXIT FOD/DSM WITHIN THE NEXT HOUR OR TWO...BUT AGAIN AT
MCW/OTM MAY PERSIST LONGER AND IT IS DIFFICULT TO TELL WHETHER
THEY WILL LIFT AT ALL AT MCW TODAY. TONIGHT EXPECT MORE SHRA/TSRA
DEVELOPMENT ESPECIALLY AT FOD/MCW...ALONG WITH MORE LOWER CIGS AND
BR IN MOST AREAS AFTER MIDNIGHT. HAVE TAKEN A SHOT AT TRENDING
THIS WAY IN THE 18Z TAFS...BUT DETAILS WILL NEED TO BE REFINED
THIS EVENING/TONIGHT.

&&

.HYDROLOGY...
ISSUED AT 315 PM CDT THU AUG 28 2014

SEVERAL ADDITIONAL EPISODES OF RAIN ARE EXPECTED THROUGH SATURDAY
MORNING AND AGAIN ANOTHER SUNDAY AFTERNOON THROUGH MONDAY MORNING.
AT THIS TIME EXPECTED RAINFALL AMOUNTS THROUGH SATURDAY MORNING WITH
EACH EVENT SHOULD BE LIGHT TO MODERATE. THIS WILL LIMIT THE LIKELIHOOD
OF FLASH FLOODING BUT STILL HAVE SOME EFFECT ON RISES ON SMALL STREAM
AND AREA RIVERS. THERE IS A GREATER RISK OF MORE SUBSTANTIAL RAINFALL
OVER PORTIONS OF THE FORECAST AREA SUNDAY EVENING. THIS TIME PERIOD
WILL BE MONITORED FOR BOTH SHORT TERM FLOODING AND RIVER FLOODING
OVER THE UPCOMING HOLIDAY WEEKEND.

&&

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

$$

SHORT TERM...LEE
LONG TERM...REV
AVIATION...LEE
HYDROLOGY...REV



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