Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 282005
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
305 PM CDT THU APR 28 2016

.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 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON/
ISSUED AT 1220 PM CDT THU APR 28 2016

MVFR CIGS EXPECTED THROUGH THE TAF PERIOD...WITH SOME IFR CIGS
POSSIBLE OVERNIGHT TONIGHT. ALTHOUGH SURFACE LOW WILL CONTINUE
TRACKING EASTWARD AND DEPART IOWA LATER TODAY...MOISTURE WILL REMAIN
HIGH IN THE BOUNDARY LAYER AND CLOUDS WILL REMAIN. AFTER A BRIEF
IMPROVEMENT IN CIGS THIS AFTN...CIGS WILL AGAIN LOWER THIS EVENING.
FOG IS POSSIBLE OVERNIGHT ESPECIALLY AT THE WESTERN AND NORTHERN
TERMINALS. SOME INSTABILITY SHRA IS POSSIBLE THIS AFTN BUT WILL
DISSIPATE TOWARD SUNSET.

&&

.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...ZOGG
HYDROLOGY...ZOGG



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