Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 112018
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
ISSUED BY NATIONAL WEATHER SERVICE OMAHA/VALLEY NE
318 PM CDT THU SEP 11 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 230 PM CDT THU SEP 11 2014

MAIN FORECAST CONCERN WILL BE WITH  CHANCE THROUGH THE
OVERNIGHT. NARROW BAND OF SHOWERS STRETCHING ACROSS CENTRAL NE WILL
CONTINUE TO PUSH EASTWARD INTO WEST THROUGH THE EVENING
HOURS...THOUGH WILL GENERALLY BE LIGHT. MAIN SYSTEM WILL BRING A
MUCH MORE WIDESPREAD CHANCE FOR RAIN TO THE AREA OVERNIGHT AS UPPER
LEVEL TROUGH...CURRENTLY IN MT/WY REGION...PUSHES EAST. THIS IS A
BIT FURTHER WEST ATTM THAN PREVIOUS MODEL RUNS ANTICIPATED...AND
HAVE THEREFORE SLOWED ONSET OF PRECIPITATION...CLOSER TO 06Z.
HOWEVER...ISENTROPIC ANALYSIS SHOWS MOISTURE QUICKLY INCREASING AND
PUSHING EAST THROUGH THE OVERNIGHT. THEREFORE...ONCE PRECIPITATION
BEGINS EXPECT IT TO QUICKLY SPREAD EASTWARD BEFORE PUSHING SOUTH AS
SYSTEM DIGS.  PERSISTENT LOW CLOUDS ACROSS CENTRAL IOWA THROUGHOUT
THE DAY HAVE KEPT MAX T A BIT UNDER FORECAST IN SOME LOCATIONS.
THEREFORE HAVE DROPPED OVERNIGHT LOWS A FEW DEGREES...THOUGH WILL
REMAIN FAIRLY STEADY AS CLOUDS LINGER THROUGH THE NIGHT.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 230 PM CDT THU SEP 11 2014

PRECIPITATION WILL BE ONGOING AND WIDESPREAD AT THE BEGINNING OF
FRIDAY WITH DECENT MID LEVEL QG FORCING AND ISENTROPIC LIFT OVER
CENTRAL IOWA. THE LIFT WILL SHIFT EAST DURING THE DAY AS UPPER
TROF CROSSES THE STATE DURING THE AFTERNOON. WHILE THE BULK OF
PRECIPITATION IS EXPECTED IN THE MORNING...SOME LINGERING SHOWERS
WILL BE POSSIBLE INTO THE AFTERNOON UNDERNEATH THE UPPER
SYSTEM...ALTHOUGH ANY OF THIS ACTIVITY WILL QUICKLY END WITH
PASSAGE OF TROF AND DIMINISHMENT OF DAYTIME HEATING.

VERY COOL AIRMASS WILL EASE INTO THE STATE FRIDAY NIGHT AS
CANADIAN HIGH PRESSURE MOVES INTO IOWA. LIGHT WINDS...CLEAR SKIES
WILL ALLOW FOR GOOD RADIATIONAL COOLING ALTHOUGH RECENT
RAINFALL/MOIST CONDITIONS SHOULD KEEP READINGS A DEGREE OR TWO
WARMER THAN OTHERWISE WOULD BE EXPECTED IN SUCH INSTANCES. STILL
COLD ENOUGH FROM SOME PATCHY FROST TO DEVELOP IN PORTIONS OF
IOWA...GENERALLY NORTH OF INTERSTATE 80 ALTHOUGH FURTHER SOUTH IN
THE NISHNABOTNA VALLEYS OF THE WEST. MUCH OF THE REST OF THE
WEEKEND WILL BE QUIET WITH SLOW MODERATION BUT READINGS STILL WELL
BELOW NORMAL.

ANOTHER SYSTEM DROPS SOUTHEAST INTO THE UPPER MIDWEST BY LATE IN
THE WEEKEND AS WARM ADVECTION INCREASES ACROSS IOWA. THE
ASSOCIATED LIFT AND THETA-E ADVECTION WILL BEGIN TO PRODUCE SOME
LIGHT PRECIPITATION ACROSS THE MISSOURI VALLEY BY LATE AFTERNOON.
ISENTROPIC LIFT WILL OVERSPREAD THE STATE SUNDAY NIGHT WITH A FEW
SHOWERS AND EVEN A THUNDERSTORMS POSSIBLE OVERNIGHT INTO EARLY
MONDAY BEFORE SUBSIDENCE INCREASES ON MONDAY. CONDITIONS REMAIN
RELATIVELY DRY INTO THE MIDDLE PART OF NEXT WEEK WITH SLOW
MODERATION IN TEMPERATURES.

&&

.AVIATION...11/18Z
ISSUED AT 1215 PM CDT THU SEP 11 2014

LARGE AREA OF MVFR STRATUS WILL CONTINUE TO AFFECT SITES THROUGH
THE AFTERNOON...THOUGH WILL LIFT THROUGH THE LATE AFTERNOON
RETURNING TO VFR BY 00Z. WINDS WILL BE PRIMARILY FROM THE NORTH
THROUGH THE PERIOD...THOUGH MAY BE GUSTY AT SITES THROUGH 00Z.
SHRA/RA WILL BEGIN TO IMPACT SITES AROUND 06...REACHING ALL SITES
NEAR 12Z. WITH SHRA...ANTICIPATE LOW MVFR OR LOWER CEILINGS AND
POSSIBLY VISIBILITY RESTRICTIONS AS WELL. HOWEVER...HAVE ONLY
TRENDED THAT WAY ATTM...GIVEN UNCERTAINTIES IN TIMING.

&&

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

&&

$$

SHORT TERM...AWB
LONG TERM...COGIL
AVIATION...AWB



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