Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 232335
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
635 PM CDT MON MAR 23 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 339 PM CDT MON MAR 23 2015

OVERNIGHT FORECAST BECOMING COMPLICATED BY STRATUS DEVELOPMENT
TODAY AND MUCH COOLER HIGHS THAN ANTICIPATED. WITH NORTHEAST FLOW
AT THE SURFACE...DEW POINTS WILL REMAIN IN THE MID TO UPPER 20S FOR
THE OVERNIGHT HOURS UNTIL WINDS BECOME MORE SOUTHEAST AFTER 06Z. THIS
SHOULD ACT TO CAP ANY COOLING OVER THE SOUTH AND ACTUALLY RESULT IN
A EITHER STEADY OR A SLOW RISE IN TEMPERATURE AND DEW POINTS OVER
THE REGION BY 12Z. SOUNDINGS CONTINUE TO SHOW DRY AIR IN THE
FORECAST AREA WILL NEED TO BE OVERCOME PRIOR TO ANY PRECIPITATION
REACHING THE GROUND. THE GFS/NAM ARE MOST AGGRESSIVE WITH
SATURATION...THOUGH THE GFS HAS BACKED OFF A BIT ON THE ONSET OF
PRECIPITATION. THE EURO HAS BEEN SIMILAR IN THE PAST 2 MODEL
SOLUTIONS IN DELAYING MOST OF THE PRECIPITATION WITH THE EXCEPTION
OF THE FAR SOUTH UNTIL 09-12Z. AFTER LOOKING AT THE HRRR AND SEEING
THAT THE MESO SCALE MODELS ARE CONTINUING WITH AN EARLIER
ONSET...HAVE TAKEN A BLEND OF THE EURO/GFS SOLUTIONS. BACKED OFF A
BIT ON THE ONSET FROM THE PREVIOUS PACKAGE AND ALSO HAVE TRIMMED
BACK THUNDER CHANCES OVER THE SOUTH WITH ONLY THE FAR SOUTH LIKELY
TO SEE ANY ISO THUNDER THROUGH 12Z. THOUGH MOST OF ANY PRECIPITATION
THAT FALLS SHOULD REMAIN LIQUID...THERE IS STILL A RISK FOR SOME
LIGHT FREEZING RAIN ON THE NORTHERN EDGE OF THE PRECIPITATION SHIELD
AND OVER SOUTHEAST SECTIONS AS THE PRECIPITATION COMMENCES. THIS IS
MAINLY DUE TO TODAYS LACK OF DAYTIME HEATING...THE RELATIVELY DRY
AIR AND THE EXPECTATION THAT OVERNIGHT LOWS OVER THOSE AREAS WILL
LIKELY BE AT OR JUST BELOW THE FREEZING MARK BY SUNRISE. WITH
LIMITED MOISTURE EXPECTED OVERNIGHT...WILL NOT HAVE ANY HEADLINES AT
THIS TIME DUE TO THE POTENTIAL OF MAINLY VERY LIGHT ACCUMULATIONS OF
A HUNDREDTH OR TWO. LOWS WILL RANGE FROM THE 20S NORTHEAST TO THE
LOWER TO MID 30S OVER THE SOUTHWEST.

.LONG TERM /TUESDAY THROUGH MONDAY/...
ISSUED AT 339 PM CDT MON MAR 23 2015

PRECIPITATION EXPECTED TO BE ONGOING ACROSS THE SOUTHERN HALF OF
THE CWA AND WILL CONTINUE TO SPREAD NORTH ACROSS THE REMAINDER OF
THE CWA TUESDAY AS A DOUBLE-BARRELED UPPER LEVEL SYSTEM IMPACTS
THE REGION. INITIAL WAVE ROTATING THROUGH THE BASE OF THE OTHER
LOW TO SWING THROUGH IOWA LATE TUESDAY INTO TUESDAY NIGHT BRINGING
THE MAJORITY OF THE CHANGES OF PRECIPITATION THROUGH WEDNESDAY
NIGHT. WARM FRONT ALOFT TO LIFT NORTHWARD THROUGH THE CWA...WAA
AND MOISTURE ADVECTION IN PLACE ACROSS MUCH OF THE AREA TUESDAY.
STILL EXPECTING A MAIN AREA OF WAA PRECIP TO LIFT THROUGH THE CWA
TUESDAY MORNING...WITH A DRY PERIOD ACROSS PORTIONS OF
CENTRAL/SOUTHERN IOWA MOST LIKELY LATER TUESDAY MORNING INTO EARLY
AFTERNOON. SHOWER AND POTENTIAL ISOLATED THUNDERSTORM
REDEVELOPMENT EXPECTED IN THE AFTERNOON HOURS...AS THE MAIN UPPER
LOW MOVES OVERHEAD. WIDESPREAD PRECIPITATION EXPECTED ACROSS THE
ENTIRE CWA WITH THE MAIN LOW MOVING THROUGH...WITH PRECIPITATION
EXPECTED TO TAPER OFF FROM WEST TO EAST TUESDAY EVENING AS THE
UPPER LOW PUSHES EAST NORTHEAST INTO THE GREAT LAKES REGION.

CONTINUE TO SEE CHANCES FOR ELEVATED THUNDER ACROSS THE SOUTHERN
HALF OF THE CWA TUESDAY INTO TUESDAY EVENING. DYNAMIC COOLING OF
THE COLUMN WITH MORE INTENSE PRECIPITATION AREAS SHOULD ALLOW FOR
A MIXING OF RAIN/SNOW OR COMPLETE CHANGEOVER TO ALL SNOW ACROSS
THE FAR NORTHERN AREAS LATE TUESDAY AFTERNOON INTO TUESDAY
EVENING. A QUICK INCH OR TWO OF SNOW IS POSSIBLE BEFORE
PRECIPITATION CHANCES TAPER OFF TUESDAY EVENING. WIDESPREAD HALF
INCH QPF AMOUNTS CAN BE EXPECTED FROM THIS SYSTEM.

SECOND LOBE OF THE UPPER LEVEL SYSTEM TO DROP SOUTHWARD TOWARD THE
AREA WEDNESDAY...WITH A COLD FRONT DROPPING THROUGH THE CWA. MAY
HAVE SOME PRECIPITATION FORM ALONG AND AHEAD OF THE COLD FRONT BY
LATE AFTERNOON ACROSS FAR SOUTHERN IOWA. ARCTIC HIGH PRESSURE TO
THEN BUILD INTO THE REGION FOR THURSDAY INTO FRIDAY...WITH H85
TEMPS DROPPING INTO THE TEENS BELOW CELSIUS. THIS SHOULD ALLOW
TEMPS ACROSS THE AREA TO REMAIN WELL BELOW AVERAGE TO CLOSE OUT
THE WEEK. THE HIGH QUICKLY SHOVES SOUTHEAST THROUGH AS THE THERMAL
RIDGE BUILDS IN ALOFT OVER THE UPCOMING WEEKEND WITH UPPER LEVEL
RIDGING BUILDING INTO THE CENTRAL US. THEREFORE TEMPS SHOULD WARM
BACK TO NEAR THE SEASONAL AVERAGES OR ABOVE BY SUNDAY AND INTO
EARLY NEXT WEEK.

&&

.AVIATION...24/00Z
ISSUED AT 635 PM CDT MON MAR 23 2015

SURFACE LOW AND WARM FRONTAL BOUNDARY WILL REMAIN SOUTH OF THE
STATE FOR DURATION OF FORECAST. THEREFORE...ANTICIPATE
STRENGTHENING EASTERLY FLOW...ESPECIALLY INTO TUESDAY AS THE LOW
PASSES ACROSS KANSAS THEN MISSOURI. ALONG WITH THE EASTERLY
FLOW...LOW MVFR TO IFR CEILINGS ARE EXPECTED FOR THE DURATION OF
THE FORECAST AS WELL AS LOW LEVELS REMAIN MOIST. WITH THE INCREASE
IN FORCING BY DAYBREAK WITH WARM ADVECTION...PRECIPITATION WILL
SPREAD INTO SOUTHERN IOWA AND CONTINUE TO EXPAND NORTHEAST THROUGH
THE DAY. MOSTLY RAIN IS EXPECTED ALTHOUGH A BRIEF PERIOD OF MIXED
PRECIPITATION WILL BE POSSIBLE AT THE ONSET BEFORE DAYTIME HEATING
HELPS TO TRANSITION PRECIPITATION TO ALL RAIN.

&&

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

&&

$$

SHORT TERM...REV
LONG TERM...BEERENDS
AVIATION...COGIL



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