Area Forecast Discussion
Issued by NWS Des Moines, IA

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081
FXUS63 KDMX 290503
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1203 AM CDT FRI APR 29 2016

...UPDATED AVIATION DISCUSSION...

.SHORT TERM.../TONIGHT/
ISSUED AT 305 PM CDT THU APR 28 2016

CLOUDY TO MOSTLY CLOUDY SKIES WILL CONTINUE THROUGH THE SHORT TERM
AS SURFACE AND UPPER-LEVEL LOWS SHIFT EASTWARD AWAY FROM THE
CWA. BOUNDARY LAYER RH VALUES REMAIN HIGH...SO LOW CLOUDS WILL
REMAIN IN PLACE. SLIGHTLY LESS MOISTURE IN THE SOUTH BUT STILL
HIGH ENOUGH VALUES FOR AMPLE CLOUD COVER. INSTABILITY
SHOWERS/SPRINKLES THAT HAVE CROPPED UP THIS AFTERNOON WILL
DIMINISH BY SUNSET AS DIABATIC HEATING WANES AND LOWER LEVELS
STABILIZE.

PATCHY FOG IS A POSSIBILITY TONIGHT...ESPECIALLY ACROSS THE WEST
WHERE RECENT RAINFALL AMOUNTS HAVE BEEN HIGHER. AT THIS TIME WILL
NOT INCLUDE MENTION OF FOG IN THE FORECAST AS THE FOG LOOKS TO BE
MORE AVIATION FOG THAN PUBLIC IMPACT FOG.

.LONG TERM.../FRIDAY THROUGH THURSDAY/
ISSUED AT 305 PM CDT THU APR 28 2016

LONGWAVE TROUGH WILL LINGER ACROSS THE CONUS THROUGH EARLY NEXT
WEEK BEFORE SHARP RIDGING BUILDS IN FOR MUCH OF NEXT WEEK. THIS
WILL RESULT IN CONTINUED COOL AND DAMP WEATHER THROUGH THE WEEKEND
WITH DRY WEATHER AND GRADUAL WARMING NEXT WEEK. SHORTWAVE H500
RIDGE AXIS WILL TRANSIT THE MID MISSISSIPPI RIVER VALLEY ON FRIDAY
AND BRING A PERIOD OF DRY WEATHER...BUT EASTERLY FLOW OFF A HUDSON
BAY SURFACE HIGH WILL KEEP SKIES MOSTLY CLOUDY AND HIGHS ONLY IN
THE 50S. SHORT RANGE GUIDANCE HAS SLOWED THE NORTHEASTWARD
PROGRESSION OF A SOUTHERN PLAINS SURFACE LOW ON FRIDAY EVENING AND
HAVE LIKEWISE TRIMMED BACK POPS IN THE SOUTHWEST THROUGH 00Z.

BROAD ISENTROPIC ASCENT AHEAD OF THE LOW WITH GOOD GULF MOISTURE
TRANSPORT WILL RESULT IN WIDESPREAD MODERATE TO HEAVY RAIN WORKING
INTO SOUTHERN IOWA FRIDAY NIGHT INTO SATURDAY MORNING.
SOME SPREAD EXISTS IN THE PLACEMENT OF THE SURFACE CYCLONE STARTING
ON SATURDAY AMONGST THE MID RANGE GUIDANCE WITH THE GFS IN
PARTICULAR TAKING THE LOW MUCH FARTHER SOUTH. DID NOT ADJUST
SATURDAY POP FIELDS BY MUCH GIVEN THE CURRENT UNCERTAINTY. WAVE OF
H850 THETA-E ADVECTION UNDER A WEAK CONVECTIVELY UNSTABLE PROFILE
MAY SPARK SOME THUNDERSTORMS SATURDAY MORNING SOUTH OF I-80.

SURFACE LOW WILL DEPART LATE IN THE WEEKEND AS CANADIAN HIGH
PRESSURE BUILDS SOUTHWARD. ZONAL FLOW WILL SET IN FOR THE BULK OF
NEXT WEEK...LEADING TO A SLOW WARMING TREND THROUGH MIDWEEK AS
H850 TEMPS RISE FROM +3 TO +12 C BETWEEN 00Z MONDAY AND 12Z
WEDNESDAY.

&&

.AVIATION.../FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT/
ISSUED AT 1157 PM CDT THU APR 28 2016

IFR TO MVFR CIGS WILL PERSIST THROUGH THE MORNING HOURS BEFORE
LIFTING TO MVFR CIGS INTO THE AFTERNOON. MCW AND POSSIBLY ALO MAY
SEE LIFR CIGS OVERNIGHT AND FOG LOOKS TO DEVELOP AND MENTIONED
MVFR VIS AT ALO/MCW.

&&

.HYDROLOGY...
ISSUED AT 305 PM CDT THU APR 28 2016

72-HR QPF CONTINGENCY FORECASTS SUGGEST MODERATE TO SIGNIFICANT
WITHIN-BANK RISES ALONG SEVERAL AREA RIVES IN RESPONSE TO RAINFALL
FROM THE NEXT SYSTEM THIS COMING WEEKEND. ONE OR TWO LOCATIONS MAY
REACH FLOOD STAGE IN THE LOWER RACCOON RIVER BASIN AND THE DES
MOINES RIVER DOWNSTREAM OF DES MOINES...HOWEVER REMAIN IN THE LOWER
END OF THE MINOR FLOODING CATEGORIES. THESE CONTINGENCY FORECASTS
ARE BASED ON TOTAL QPF FROM THE NEXT SYSTEM OF 0.75-1.25 IN.

&&

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

$$

SHORT TERM...ZOGG
LONG TERM...SKOW
AVIATION...PODRAZIK
HYDROLOGY...ZOGG



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