000
FXUS63 KDMX 171723
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1223 PM CDT FRI MAY 17 2013

.UPDATE...
ISSUED AT 1217 PM CDT FRI MAY 17 2013

AREAS OF ISOLATED THUNDERSTORMS HAVE DEVELOPED ALONG A WEAK
BOUNDARY...LIKELY REMNANT FROM OVERNIGHT/EARLY MORNING CONVECTION
ACROSS WESTERN PORTIONS OF THE CWA. HAVE UPDATED FORECAST TO
ACCOUNT FOR THESE THUNDERSTORMS...AS THEY ARE LIKELY TO CONTINUE
THROUGHOUT THE DAY...WITH LITTLE INHIBITION TO SUPPRESS
DEVELOPMENT. IN ADDITION...ANTICIPATE AN EASTWARD PUSH OF
DEVELOPMENT AND HAVE INCLUDED ISOLATED MENTION FURTHER EAST.

&&

.SHORT TERM.../TODAY /...
ISSUED AT 400 AM CDT FRI MAY 17 2013

CONVECTION ONGOING ACROSS THE NORTH ON THE NOSE OF 850MB THETA-E
ADVECTION IN ADVANCE OF A WEAKENING SHORTWAVE TROUGH LIFTING THROUGH
THE WEAK UPPER LEVEL RIDGE. OVERALL WEAK SHEAR AND OK
INSTABILITY...SO SEVERE THREAT IS LIMITED. HOWEVER DUAL-POL ANALYSIS
CONTINUES TO INDICATE SOME SMALL HAIL WITHIN THE STRONGER STORMS AND
MAIN THREAT OF STORMS TO BE HEAVY RAIN ESPECIALLY WITH CELLS NOW
TRAINING SOME WITH EASTERLY MOVEMENT. EXPECT CHANCE FOR PRECIP TO
CONTINUE LINGER INTO THE MORNING ACROSS THE NORTHERN CWA...WITH
FORCING WEAKENING TOWARD LATE MORNING INTO THE AFTERNOON HOURS.
ENERGY ROTATING AROUND A WEAK UPPER LEVEL SYSTEM MOVING THROUGH
MISSOURI. MAY SEE SOME SHOWER/THUNDERSTORM DEVELOPMENT WITH THIS
SYSTEM TOWARD THIS AFTERNOON...WITH STORMS LIFTING NORTHWARD INTO
THE FAR SOUTHEASTERN CWA. OVERALL THOUGH BEST CHANCES FOR PRECIP
TODAY...WILL BE WITH THE LINGERING CONVECTION THIS MORNING. AIR MASS
ALOFT AGAIN SIMILAR TO PREVIOUS DAYS...SO STICK NEAR PERSISTENCE
WITH MAX TEMPS EXCEPT KEPT THE NORTH A BIT COOLER WITH CLOUDS/PRECIP
CHANCES.

.LONG TERM.../TONIGHT THROUGH THURSDAY/...
ISSUED AT 400 AM CDT FRI MAY 17 2013

UPPER LEVEL RIDGE BUILDING INTO THE CENTRAL PLAINS WILL BRING AN
END TO PRECIPITATION CHANCES TONIGHT INTO SATURDAY AS THE WARM
SECTOR SPREADS ACROSS THE STATE. THE RIDGE WILL SHIFT EAST
SATURDAY NIGHT AS A VIGOROUS UPPER LEVEL SYSTEM DIVES INTO THE
NORTHERN HIGH PLAINS. THIS WILL CREATE AN ACTIVE SOUTHWEST FLOW
ACROSS THE STATE. STRONG MOISTURE TRANSPORT WILL LIFT INTO
SOUTHWEST IOWA AS THE LOW LEVEL JET INCREASES ACROSS EASTERN
KANSAS AND POINTS INTO THE STATE. A GOOD ELEVATED MIXED LAYER WILL
BE IN PLACE WITH A FAIR AMOUNT OF DRY AIR TO OVERCOME AND THIS
MAY LIMIT OVERALL COVERAGE BUT STILL SOME STORMS SHOULD DEVELOP
AND WILL BRING THE THREAT FOR LARGE HAIL AND HEAVY RAIN GIVEN
INCREASING PWATS TO 1.5 INCHES AND STORM MOVEMENT AT 25 TO 30 KTS
TO THE NORTHEAST.

THE BEST SEVERE WEATHER THREAT THROUGH THE PERIOD WILL BE ON
SUNDAY AS A STRONG UPPER WAVE ROTATES AROUND THE DEVELOPING CLOSED
LOW TO THE WEST. THE GREATEST THREAT WILL BE DURING THE AFTERNOON
AND EVENING. THE SURFACE LOW IS EXPECTED TO BE OVER EASTERN
NEBRASKA TO FAR WEST CENTRAL IOWA WITH THE WARM FRONT EXTENDING
INTO SOUTHERN OR CENTRAL IOWA. CONDITIONS CONTINUE TO LOOK
FAVORABLE FOR SUPERCELLULAR DEVELOPMENT WITH VERY LARGE HAIL
EXPECTED. TORNADO THREAT STILL LOOKS FAVORABLE ACROSS THE
SOUTHWEST HALF WITH INCREASING CONFIDENCE THAT THE SFC WINDS WILL
BACK LEADING TO INCREASED LOW LEVEL SHEAR. THE MID LEVEL FLOW IS
NOT REAL STRONG AND COULD BE A LIMITING FACTOR HOWEVER LATEST
FORECAST MODELS SOUNDINGS SUGGEST LCLS WILL BE LOWER THAN
PREVIOUSLY EXPECTED. HEAVY RAIN WILL REMAIN A THREAT WITH PWATS UP
TO 1.75 INCHES AND RIGHT MOVER SUPERCELL MOTIONS OF 20 TO 30 KTS.
COULD CERTAINLY DEVELOP INTO A VOLATILE SITUATION.

THE DRY SLOT WILL THEN LIFT SOUTHWEST TO NORTHEAST SUNDAY NIGHT
AND INTO A PORTION OF MONDAY. A FEW SEVERE STORMS ARE POSSIBLE
YET MONDAY BY THE PRIMARY SHOW WILL BE SUNDAY. THE UPPER LOW WILL
SLOWLY FILL AND ROTATE THROUGH THE AREA THROUGH MID WEEK AND WILL
KEEP PRECIPITATION CHANCES IN THE FORECAST. UPPER RIDGE FINALLY
SHIFTS INTO THE REGION TOWARD THE END OF THE PERIOD AND BRING
DRIER WEATHER AND WARMER TEMPERATURES.

&&

.AVIATION...17/18Z
 ISSUED AT 1217 PM CDT FRI MAY 17 2013

CEILINGS WILL REMAIN PRIMARILY VFR...WITH ISOLATED THUNDERSTORMS
BETWEEN18-00Z WHICH MAY BRING LOWER MVFR CEILINGS TO
SITES...ESPECIALLY NORTHERN SITES KFOD/KMCW/KDSM. HOWEVER...IMPACT
WILL BE BRIEF. HAVE INCLUDED MENTION OF VCTS...WITH ISOLATED
NATURE OF STORMS. CEILINGS WILL BE LIFTING AS SYSTEM PUSHES
FURTHER EAST WITH WINDS BECOMING MORE SOUTHERLY AND LIGHT
OVERNIGHT.

&&

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

&&

$$

UPDATE...AWB
SHORT TERM...BEERENDS
LONG TERM...DONAVON
AVIATION...AWB