Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 260500
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1200 AM CDT TUE APR 26 2016

...UPDATED AVIATION DISCUSSION...

.SHORT TERM.../TONIGHT/
ISSUED AT 337 PM CDT MON APR 25 2016

STRATOCU DECK IN PLACE ACROSS THE NORTH WITH THE UPPER LOW SLOWLY
LIFTING NORTHEAST OF THE STATE. EXPECT SOME CLEARING INTO THE
EVENING HOURS...ACROSS THE NORTH WITH THE DECK TO BUILD BACK IN AS
STRATUS OVERNIGHT ACROSS THE NORTH/NORTHEAST. SOME WEAK LIFT WITH
HIGHER LOW LEVEL MOISTURE MAY LEAD TO SOME DRIZZLE JUST OFF TO THE
NORTH AND EAST OF THE CWA LATE TONIGHT. OTHERWISE WINDS TO
DIMINISH AND SHIFT AROUND TO THE EAST TOWARD EARLY TUESDAY. EXPECT
TEMPS TO FALL INTO THE UPPER 40S NORTH TO MID 50S SOUTH. SOMEWHAT
CONCERNED THAT TEMPS MIGHT STAY UP A BIT IN THE NORTH WITH THE
CLOUDS...SO MAY BE A BIT COOL IN THAT AREA.

.LONG TERM.../TUESDAY THROUGH MONDAY/
ISSUED AT 337 PM CDT MON APR 25 2016

ATTENTION FOR THE LONG TERM REMAINS FIXED ON SEVERE WX POTENTIAL
TUESDAY LATE AFTERNOON INTO WEDNESDAY. SEASONABLY STRONG UPPER
LEVEL TROUGH OVER THE INTER-MOUNTAIN WEST WILL CLOSE OFF AND
MIGRATE EASTWARD TONIGHT...ACQUIRING A NEGATIVE TILT AS IT LIFTS
NORTHEASTWARD OVER THE CENTRAL HIGH PLAINS TUESDAY AND WEDNESDAY.
THE 995 MB SURFACE CYCLONE REFLECTION WILL MOVE INTO KANSAS BY 00Z
WEDNESDAY WITH THE WARM FRONT DRAPED ALONG I-70 IN MISSOURI AND A
DRY LINE PUSHING ACROSS EASTERN KANSAS. THE 12Z GUIDANCE PACKAGE
HAS SLOWED THE SYSTEM SLIGHTLY COMPARED TO EARLIER RUNS AND
SHIFTED THE WARM FRONT FURTHER TO THE SOUTH...STRENGTHENING THE
H800-H700 WARM NOSE OVER IOWA THROUGH THE AFTERNOON AND OVERNIGHT
HOURS. HAVE TRENDED THE FORECAST IN THIS DIRECTION AND DELAYED
POPS BY SEVERAL HOURS.

THE THREAT FOR ANY NEAR-SURFACE BASED CONVECTION SHOULD BE LIMITED
TO THE FAR SOUTHWEST CORNER OF THE STATE. CONVECTION OVER NEBRASKA
IS EXPECTED TO GROW UPSCALE OVER THE COURSE OF THE EVENING INTO A
QLCS WITH THE POSSIBILITY OF A FEW ELEVATED SUPERCELLS DEVELOPING
JUST AHEAD OF THE LINE AS FALLING HEIGHTS HELP ERODE THE CAP.
SHOULD ANY ISOLATED CONVECTION DEVELOP...MUCAPE VALUES OF OVER
2000 J/KG AND EFFECTIVE BULK SHEAR VALUES OF 30 TO 40 KTS WILL
SUPPORT A LARGE HAIL THREAT SOUTH OF HWY 34 AND WEST OF HWY 169
BETWEEN 01 AND 04Z. WITH STRONG AND DEEP MOISTURE TRANSPORT INTO
THE AREA...THE BIGGEST SENSIBLE WEATHER THREAT IS LIKELY TO BE
HEAVY RAINFALL WITH AMOUNTS OF ONE TO TWO INCHES POSSIBLE IN
SOUTHWEST IOWA.

THE LINEAR COMPLEX WILL LIFT NORTHEASTWARD ACROSS THE CWA THROUGH
WEDNESDAY MORNING...WEAKENING THROUGH THE NIGHT AS THE ELEVATED
INSTABILITY AND THETA-E FORCING WANES. ATTENTION THEN TURNS BACK
TO SOUTHERN IOWA FOR WEDNESDAY AFTERNOON AS THE SURFACE LOW
PIVOTS ACROSS SE NEBRASKA AND BEGINS TO SLIDE EASTWARD. THIS WILL
BRING THE SURFACE WARM FRONT AROUND THE IA/MO BORDER DURING PEAK
HEATING...WITH THE EC FURTHER NORTH THAN THE GFS. THE
JUXTAPOSITION OF THE UPPER LEVEL CYCLONE...STEEP LOW AND MID LEVEL
LAPSE RATES... AND SBCAPE VALUES 1500-2000 J/KG MAY YIELD A MULTI-
FACETED SEVERE WEATHER EVENT WITH THE POSSIBILITY OF LANDSPOUT
TORNADOES NEAR ANY RESIDUAL OUTFLOW BOUNDARIES OR THE MAIN
SYNOPTIC FRONT.

THE UPPER LOW WILL ELONGATE ON THURSDAY AND DEPARTS LATE IN THE
DAY AS SHORTWAVE RIDGING BUILDS NORTHWARD FROM THE SOUTHERN
PLAINS. REMOVED THE TOKEN SLIGHT CHANCE POPS FOR THIS TIMEFRAME
GIVEN GOOD CONSENSUS ON THE POSITION OF THE RIDGE. THE PARADE OF
SPRING CYCLONES CONTINUES ON FRIDAY WITH ANOTHER LOW EJECTING
ACROSS THE SOUTHERN PLAINS. IOWA LOOKS TO REMAIN ON THE COLD SIDE
OF THIS WEEKEND SYSTEM WITH HIGHS ONLY IN THE 50S TO LOW 60S.

&&

.AVIATION.../FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT/
ISSUED AT 1159 PM CDT MON APR 25 2016

MVFR CIGS WILL AFFECT MCW THROUGH 08-09Z...OTHERWISE...EXPECT VFR
CONDITIONS TO PREVAIL UNTIL LATE IN THE PERIOD. EASTERLY WINDS
INCREASE DURING THE AFTERNOON AND EVENING TUESDAY. HAVE MENTION OF
VCSH ACROSS THE SOUTH AT DSM.

&&

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

&&

$$

SHORT TERM...BEERENDS
LONG TERM...SKOW
AVIATION...PODRAZIK



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