Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 160510
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1210 AM CDT TUE SEP 16 2014

.UPDATE...
ISSUED AT 909 PM CDT MON SEP 15 2014

QUICK UPDATE OUT SHORTLY WITH A DROP IN TEMPS OF A COUPLE
DEGREES...TAKING CLOUDS OUT AS WELL.

&&

.SHORT TERM /TONIGHT/...
ISSUED AT 327 PM CDT MON SEP 15 2014

A 1025 MB SURFACE HIGH WILL SLIDE SOUTHEASTWARD FROM THE DAKOTAS
INTO SOUTH CENTRAL IOWA TONIGHT. THE DIURNALLY DRIVEN STRATOCUMULUS
DECK THAT FORMED IN THE CAA BEHIND THE FRONT WILL DISSIPATE DURING
THE LATE AFTERNOON/EVENING HOURS AND CLEAR SKIES WILL CONTINUE
THROUGH THE NIGHT. WITH THE HIGH PASSING OVER SOUTHWEST
IOWA...DROPPED LOW TEMPS SEVERAL DEGREES BELOW GUIDANCE IN LOW LYING
AREAS SUCH AS THE NISH VALLEY. LOWS WILL STILL BE SEVERAL DEGREES
WARMER THAN OUR LAST COLD SNAP AND FROST IS NOT MUCH OF A CONCERN.
FOG WILL LIKELY FORM ACROSS SOUTHERN IOWA BETWEEN 06-12Z WHERE THE
CENTER OF THE HIGH WILL PASS THROUGH AND MORE WIDESPREAD RAIN FELL
THIS MORNING. AS WITH LOWS...BEEFED UP THE FOG WORDING IN THE NISH
VALLEY.

.LONG TERM /TUESDAY THROUGH MONDAY/...
ISSUED AT 327 PM CDT MON SEP 15 2014

THERE ARE NO MAJOR CHANGES TO THE EXTENDED AS YET SINCE MODELS ARE
MAINTAINING THEIR BIASES EXCEPT THAT MOISTURE TRANSPORT LATER THIS
WEEK IS A LITTLE SLOWER THAN THE MODELS PREVIOUSLY HAD. TUESDAY
THROUGH MOST OF THURSDAY SHOULD BE BEAUTIFUL DAYS...MOSTLY SUNNY
WITH TEMPERATURES MODERATING EACH DAY BACK INTO THE MID 70S. UPPER
LEVEL RIDGING WILL BUILD INTO THE PLAINS AND MOVE INTO THE MIDWEST
DURING THIS PERIOD WHILE AT THE SURFACE...HIGH PRESSURE SHIFTS TO
THE NORTHEAST PROVIDING FOR A SOUTHERLY FLOW TO RETURN TO THE
AREA. THE ONE EXCEPTION IS TUESDAY NIGHT INTO WEDNESDAY MORNING
WHEN A WEAK SHORTWAVE DROPS THROUGH THE NORTHWEST FLOW. THE
SHORTWAVE AND ANY WEAK FORCING ASSOCIATED WITH IT JUST BRUSHES FAR
SW IA AND A SMALL PORTION OF OUR CWA. WEAK THETA-E ADVECTION DOES
HOWEVER CREEP INTO OUR FAR SW. ANY AFFECTS WOULD BE GONE BY EARLY
WEDNESDAY MORNING AND IT WOULD AMOUNT TO MUCH BUT I DID THINK IT
WAS WORTHY OF A SLIGHT CHANCE WORDING IN THAT AREA.

THURSDAY IS A LITTLE UP IN THE AIR AS YET ANOTHER WEAK SHORTWAVE
DROPS DOWN IN THE NORTHWEST FLOW. THE FORCING IS VERY WEAK AND THE
THETA- E ADVECTION WITH THIS WAVE KIND OF LAGS BEHIND SO I KEPT
THURSDAY DRY...ALTHOUGH YOU COULD MAKE AN ARGUMENT FOR AT LEAST
SLIGHT CHANCE POPS IN THE FAR WEST LATE IN THE DAY.

THURSDAY NIGHT THINGS BECOME A LITTLE MORE MUDDLED AS MODELS DIFFER
ON THEIR SOLUTIONS OF HANDLING THE REMNANTS OF ODILE AS WELL AS THE
STRENGTH AND TIMING OF A DEVELOPING SURFACE TROUGH EXPECTED TO MOVE
THROUGH THE UPPER MIDWEST.  WE ARE STILL UNDER THE INFLUENCE OF AN
UPPER LEVEL RIDGE ACROSS THE REGION BUT A SURFACE TROUGH DEVELOPS
OUT WEST AND WARM ADVECTION STRENGTHENS AS THETA-E ADVECTION LIFTS
ACROSS THE AREA.  THERE IS ALSO SOME WEAK FORCING THAT LIFTS ACROSS
THE AREA BUT IT IS MAINLY CONFINED TO NORTHERN IOWA AND LOCATIONS
NORTH. WE SHOULD SEE AT LEAST SOME SHOWERS AND THUNDERSTORMS WITH
THIS.

ON FRIDAY THE MODELS REMAIN SLIGHTLY DIFFERENT AS THE GFS BRINGS
THE REMNANTS OF ODILE AS A CLOSED LOW ACROSS THE DESERT S.W. AND
THEN BECOMES INGESTED IN THE FLOW AS A STRONG SHORTWAVE THAT LIFTS
ACROSS IOWA FRIDAY NIGHT AND SATURDAY. THE EURO ON THE OTHER HAND
WEAKENS ODILE ACROSS THE DESERT S.W. AND SUGGESTS THAT IT WILL GET
INGESTED IN THE FLOW IN PIECES VERSUS A CLOSED LOW THAT OPENS UP
INTO A SHORTWAVE. THE LATEST EURO IS CLOSER TO THE GFS IN THAT IT
NOW DEVELOPS A DECENT SHORTWAVE ACROSS IOWA AS WELL BUT IT IS
SLOWER AND APPEARS TO TIE THE WAVE TO A NORTHERN SYSTEM RATHER
THAN DEEPEN IT BY INGESTING WHAT IS LEFT OF ODILE. IT WILL BE
INTERESTING TO SEE WHICH SOLUTION PLAYS OUT.

IF YOU LOOK AT MOISTURE...THE GFS INITIALLY BRINGS THE MOISTURE OF
ODILE UP INTO THE REGION QUICKER WHILE AT THE SURFACE...A COLD FRONT
BEGINS TO PUSH ACROSS THE REGION FRIDAY THROUGH SATURDAY.  THE EURO
IS SLOWER AND THE MOISTURE IS OVER A MORE NARROW CHANNEL.  AT THIS
POINT THE GFS WOULD BE A SET UP FOR MORE ROBUST THUNDERSTORM
DEVELOPMENT ALONG THE FRONT AND A POTENTIAL FOR HEAVY RAINFALL
SOMEWHERE BUT THE 12Z EURO IS CATCHING ON AND SIMILAR WITH THE 12Z
GFS.

FOR SUNDAY INTO NEXT WEEK...HIGH PRESSURE BUILDS IN AT THE SURFACE
AND ALOFT WITH A DRIER NW FLOW OVER IOWA.  BOTH THE GFS AND EURO
INDICATE A DRY PERIOD WITH SEASONAL HIGHS IN THE MID 70S.

&&

.AVIATION...16/06Z
ISSUED AT 1200 AM CDT TUE SEP 16 2014

HIGH PRESSURE NWRN KS INTO LAKE SUPERIOR WILL MOVE SOUTHEAST AND
EAST SOUTHEAST OF IOWA BY TUE EVENING. AREAS OF MVFR FOG AROUND
SUNRISE...WITH PATCHY IFR CONDITIONS. THIS WILL IMPROVE RAPIDLY
AFTER SUNRISE WITH VFR THE REST OF THE TAF PERIOD.

OUTLOOK...A SERIES OF UPPER LEVEL DISTURBANCES WILL BRING A CHANCE
OF SHOWERS MAINLY TO THE WEST OF THE TAF SITES WED-FRI WITH A MORE
WIDESPREAD RAIN EVENT FOR THE WEEKEND.


&&

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

$$

UPDATE...MS SEP 14
SHORT TERM...SKOW
LONG TERM...FAB
AVIATION...MS SEP 14



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