Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 021737
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1237 PM CDT TUE JUN 2 2015

.SHORT TERM /TODAY/...
ISSUED AT 322 AM CDT TUE JUN 2 2015

THE PRIMARY FORECAST CHALLENGE TODAY WILL BE CLOUD TRENDS WITH
STRATUS LIFTING NORTH/NORTHWEST FROM MISSOURI AND ILLINOIS AND HIGH
CIRRUS BLOW OFF FROM STORMS ACROSS THE DAKOTAS AND NEBRASKA. THE
AREA OF STRATUS IS ASSOCIATED WITH A RIBBON OF MOISTURE ADVECTION
LIFTING OUT OF THE OHIO VALLEY. THIS MOISTURE ADVECTION WILL BE
FOCUSED OVER CENTRAL IOWA THOUGH MUCH OF THE DAY. SOUNDINGS SHOW
THAT THIS MOIST LAYER IS QUITE SHALLOW THEREFORE AFTER CLOUDS EXPAND
INTO CENTRAL AND SOUTHERN IOWA THIS MORNING...THE STRATUS SHOULD BE
SCATTERING BY THIS AFTERNOON. THE HIGH LEVEL CLOUDS FROM THE WEST
SHOULD EVENTUALLY DIMINISH AS WELL AS OVERNIGHT CONVECTION TO THE
WEST WEAKENS.

THE LARGE AREA OF HIGH PRESSURE THAT IS RIDGED THROUGH THE CENTRAL
GREAT LAKES WILL CONTINUE A SLOW SHIFT TO THE EAST TODAY. THIS IS
ALLOWING FOR THE SHALLOW MOISTURE RETURN DURING THE DAY.
PRECIPITATION CHANCES WILL BE NIL WITH A CAP IN PLACE AROUND 850 MB.
HIGH TEMPERATURES ARE IN ANTICIPATION OF SOME SUN BY THIS AFTERNOON
WITH HIGHS IN THE LOW TO MID 70S.

.LONG TERM /TONIGHT THROUGH MONDAY/...
ISSUED AT 322 AM CDT TUE JUN 2 2015

ACTIVE WEATHER PATTERN SETTING UP FOR EXTENDED WITH MULTIPLE
CHANCES FOR THUNDERSTORMS EXPECTED THROUGH THE END OF THE
WEEK...WITH HEAVY RAIN POSSIBLE AT TIMES. UPPER LEVEL LOW ACROSS
CANADA WITH ASSOCIATED BOUNDARY AND SURFACE LOW CURRENTLY LOCATED
IN WESTERN DAKOTAS WILL PUSH EAST FOR THE BEGINNING OF
PERIOD...BEGINNING TO INFLUENCE IOWA BY LATE TONIGHT. TRACK OF
SURFACE LOW IS SLIGHTLY MORE EASTERLY...HELPING TO DELAY ONSET OF
PRECIPITATION IN THE NORTHWEST...AND HAVE TRENDED SLOWER FOR ONSET
OF PRECIPITATION. PRECIPITATION CHANCES WILL PERSIST THROUGH THE
DAY WEDNESDAY...THOUGH MODELS INDICATING HEAVIEST RAINFALL MAY BE
FURTHER NORTH INTO SOUTHERN MN WITH ONGOING MCS PUSHING EAST INTO
MN...THOUGH ENOUGH FORCING AND MOISTURE FURTHER NORTH TO WARRANT
PRECIPITATION CHANCES ACROSS IOWA ALONG BOUNDARY. WITH AFTERNOON
CONVECTION WILL SEE A CHANCE FOR SEVERE THUNDERSTORMS
WEDNESDAY...WITH CAPE VALUES GENERALLY 1000-2000 J/KG THROUGH THE
LATE AFTERNOON. MODELS INDICATE SLIGHT CAP WHICH ERODES BY LATE
AFTERNOON. SHEAR WILL BE SUFFICIENT TO ALLOW FOR ANY STORMS WHICH
DO FORM TO PERSIST...THOUGH BULK SHEAR VALUES OF 20-30 KTS WILL
HELP TO KEEP SEVERE THREAT LIMITED...WITH HAIL AND HIGH WINDS THE
MAIN THREATS. IN ADDITION...PWAT VALUES WILL BE NEAR OR ABOVE 1.5
INCHES...HIGH FOR JUNE...AND WILL ALLOW FOR HEAVY RAIN POTENTIAL
WITHIN THUNDERSTORMS...ESPECIALLY IN THE NORTH.

SYSTEM WILL PUSH SLOWLY EAST WEDNESDAY NIGHT...THOUGH STALLED
SURFACE LOW IN CENTRAL KS WILL KEEP PERSISTENT CHANCES FOR
PRECIPITATION ACROSS IOWA AS RIDGE BUILDS INTO UPPER MIDWEST.
MAY SEE ANOTHER MCS DEVELOP WHICH PUSHES EAST INTO IOWA LATE IN
THE OVERNIGHT WEDNESDAY AND THROUGH THE DAY THURSDAY.
HOWEVER...MODELS ARE NOT IN GOOD AGREEMENT WITH PLACEMENT OF
SYSTEM...WITH GFS FURTHER NORTH THAN ECMWF. TIMING AND LOCATION OF
PRECIPITATION WILL BE HEAVILY DEPENDENT ON TRACK OF OVERNIGHT MCS
ACTIVITY THROUGHOUT THE WEEK. THEREFORE...DO NOT HAVE HIGH
CONFIDENCE IN LOCATION OF BEST RAINFALL POTENTIAL ATTM...THOUGH
HAVE TRENDED TOWARDS THE GENERAL MODEL CONSENSUS OF FURTHER
SOUTHWEST FOR THURSDAY AS LLJ PUSHES INTO SOUTHERN NE WEDNESDAY
NIGHT. ONCE AGAIN...AFTERNOON THUNDERSTORMS WILL BE POSSIBLE
THURSDAY WITH BOUNDARY EXPECTED TO REMAIN ACROSS CENTRAL IOWA.
SMILIER TO WEDNESDAY...CAPE VALUES WILL BE BETWEEN 1000-2000 J/KG
OR HIGHER...THOUGH SHEAR WILL BE STRONGER WITH BULK SHEAR VALUES
NEAR OR ABOVE 30KTS...WITH BETTER LOW LEVEL SHEAR....ESPECIALLY IN
THE SOUTHWEST...THOUGH BETTER SET UP TO THE WEST OF IOWA IN
NE...WHICH WILL PUSH EASTWARD OVERNIGHT. THURSDAY NIGHT WILL SEE
THE BEST CHANCES FOR HEAVY RAINFALL WITH STRONG MOISTURE
TRANSPORT AND DEEP WARM CLOUD DEPTHS. IN ADDITION...PWAT VALUES
WILL BE HIGH...NEAR 1.6 INCHES. SYSTEM WILL PERSIST INTO FRIDAY
BEFORE FINALLY PUSHING SOUTH...HOWEVER GFS LINGERS SYSTEM LONGER
THAN ECMWF...AND HAVE KEPT PRECIPITATION CHANCES INTO FRIDAY NIGHT
THOUGH MAY BE TOO LONG. WILL SEE A BRIEF BREAK IN PRECIPITATION
CHANCES FOR SATURDAY WITH HIGH PRESSURE BUILDING INTO TEXAS
BEFORE ANOTHER TROUGH DIGS ACROSS UPPER PLAINS FOR LATE SATURDAY
AND SUNDAY.

TEMPERATURES WILL REMAIN FAIRLY STEADY THROUGH PERIOD WITH HIGHS
IN THE 70S AND 80S AND LOWS IN THE 50S AND 60S...THOUGH MAY BE
LOWER WITH OVERNIGHT PRECIPITATION. IN ADDITION...IF CLOUDS CLEAR
DURING THE DAY...MAY BE TOO COOL ON HIGHS.

&&

.AVIATION...02/18Z
ISSUED AT 1233 PM CDT TUE JUN 2 2015

MVFR STRATUS OVER SOUTHERN IOWA WILL CONTINUE TO LIFT AND ERODE
THROUGH THE COURSE OF THE AFTERNOON. SOUTH TO SOUTHEASTERLY WINDS
OF 10 TO 15 KTS WILL PERSIST THROUGH THE AFTERNOON WITH A FEW
HIGHER GUSTS POSSIBLE. SHOWERS AND THUNDERSTORMS MOVE INTO WESTERN
IOWA TOWARDS SUNRISE ON WEDNESDAY AND SPREAD EAST THROUGH THE
MORNING...WEAKENING AS THEY MOVE INTO CENTRAL AND EASTERN IOWA.

&&

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

$$

SHORT TERM...DONAVON
LONG TERM...AWB
AVIATION...SKOW



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