Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 020441
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1141 PM CDT SUN MAY 1 2016

.SHORT TERM.../TONIGHT/
ISSUED AT 315 PM CDT SUN MAY 1 2016

UPPER LOW SPINNING OVER SOUTH CENTRAL IOWA...WITH THE ENTIRE SYSTEM
SLOWLY MOVING EAST. RAIN SHIELD HAS BEEN DECREASING OVER THE PAST
HOUR WITH SOME DRYING NOTED AND CIGS BEGINNING TO LIFT SOME. AS THE
SYSTEM CONTINUES TO PUSH EAST...RAIN WILL PUSH EAST AND CONTINUE TO
DIMINISH IN COVERAGE WHILE IT MOVES OUT. THEREFORE HAVE MAINLY DRY
CONDITIONS FOR THE CWA THIS EVENING INTO THE OVERNIGHT HOURS.
CONCERN SHIFTS TO FOG POTENTIAL LATE TONIGHT...AS COULD SEE THE
CLOUDS CLEAR OUT OF THE NORTHERN CWA BY EARLY MONDAY MORNING.
NORTHERLY WINDS TO BECOME LIGHTER...HOWEVER DEWPOINTS TO DROP OFF AS
WELL. THEREFORE UNCERTAINTY IN THE POTENTIAL FOR FOG...AND HAVE JUST
MENTIONED PATCHY FOG FOR NOW.

.LONG TERM.../MONDAY THROUGH SUNDAY/
ISSUED AT 315 PM CDT SUN MAY 1 2016

PATTERN WILL BE UNDERGOING A SIGNIFICANT CHANGE TO A MORE
AMPLIFIED FLOW WITH IA SEEING LESS PRECIPITATION AND MORE SEASONAL
TEMPERATURES. SOME MINOR PRECIP CHANCES WILL LINGER INTO
MONDAY...AND POSSIBLY WITH A SEPARATE SYSTEM NORTHEAST TUE
NIGHT...BUT OTHERWISE THE FORECAST SHOULD REMAIN DRY UNTIL NEXT
WEEKEND. AT ONSET LINGERING LOW LEVEL MOISTURE AND WEAK FORCING
MOVING OUT OF THE SWRN CONUS TROUGH MAY PRODUCE SOME WEAK SHOWERS
INTO PEAK HEATING MONDAY. AS THE DEEPER MOISTURE EXITS SOUNDINGS
DO SUGGEST MIXING TO 1KM PLUS WITH WEAK CONVECTION SO HAVE
CONTINUED LOW END POPS. THERE IS LITTLE IN THE WAY OF FORCING OR
MOISTURE MON NIGHT AND INTO EARLY TUE WITH THE CURRENT MANITOBA
SHORT WAVE TAKING A FAR ENOUGH WEST TRACK TO NOT AFFECT IA.
HOWEVER A STRONGER WAVE AND ASSOCIATED FORCING WILL PASS THROUGH
THE GREAT LAKES LATE TUE REINFORCING THE APPALACHIAN LONG WAVE
TROUGH AND MAY JUST BRUSH NERN SECTIONS WITH SHOWERS TUE NIGHT.
MOISTURE WILL BE QUITE LIMITED HOWEVER SO IT IS NOT EXPECTED TO
AMOUNT TO MUCH.

THE MIDDLE OF THE WORK WEEK LOOKS UNEVENTFUL WITH A LONG WAVE RIDGE
APPROACHING THE MO VALLEY AND IA IN WEAK SURFACE FLOW. RETURN FLOW
WILL BEGIN BY FRI HOWEVER FINALLY TRYING TO BOOST TEMPERATURES BACK
ABOVE NORMAL AND INCREASING MOISTURE LEVELS. THIS MAY INTERACT WITH
THE TRAILING END OF A FRONTAL BOUNDARY DRIVEN BY A CANADIAN SHORT
WAVE WHICH SHOULD INTERSECT WITH THE SURFACE REFLECTION OF A LARGE
MEANDERING ERN CONUS CLOSED LOW. THIS WILL ALLOW INSTABILITY TO
INCREASE AND TIE INTO DECENT H85/H7 FORCING ALONG THE BAROCLINIC
ZONE SO EXPECT A MORE ACTIVE CONVECTIVE REGIME TO RETURN INTO
NEXT WEEKEND...AT LEAST TO SOME DEGREE.

&&

.AVIATION.../FOR THE 06Z TAFS THROUGH 06Z MONDAY NIGHT/
ISSUED AT 1141 PM CDT SUN MAY 1 2016

FORECAST IS COMPLEX OVERNIGHT WITH MULTIPLE LAYERS OF
CLOUDS...HOLES OF CLEARING...AND SOME FOG DEVELOPMENT LEADING TO
POCKETS OF MVFR OR LOWER CONDITIONS THAT WILL PERSIST ERRATICALLY
UNTIL SUNRISE. THE MOST LIKELY AREAS TO SEE IFR OR LOWER WILL BE
DSM AND ESPECIALLY OTM...WHERE CIGS HAVE REFUSED TO BREAK UP AND
ACTUALLY LOWERED SINCE 00Z AND ARE THUS MAINTAINED THROUGH THE
NIGHT. DURING THE DAY MONDAY VFR CONDITIONS SHOULD BECOME
PREVALENT...WITH SCATTERED -SHRA POSSIBLE IN THE AFTERNOON BUT OF
TOO LITTLE COVERAGE/IMPACT TO INCLUDE IN THE TAFS AT THIS TIME.

&&

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

&&

$$

SHORT TERM...BEERENDS
LONG TERM...SMALL
AVIATION...LEE



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