Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 190815
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
315 AM CDT FRI SEP 19 2014

.SHORT TERM /TODAY/...
ISSUED AT 315 AM CDT FRI SEP 19 2014

SOUTHERLY FLOW OVER THE STATE TODAY WILL DRAW WARMER AND MORE MOIST
AIR.  FIRST ISSUE IS WITH THE STRONG THETA-E ADVECTION INTO THE
THE STATE THIS MORNING.  THIS IS A CONDITIONAL
SITUATION...HOWEVER SOUNDINGS INDICATE A CASE FOR ISOLATED
CONVECTION IF THE SATURATION CAN OCCUR CLOSE TO THE H8 LEVEL.
SAT PIX INDICATE SOME POSSIBILITY AS AC STREAMS DOWN FROM
THE NORTH AND LOW LEVEL MOISTURE SPREADING INTO ERN NEBRASKA AND
FAR WESTERN IA IS IN PLACE.  WILL KEEP THE NARROW BAND OF
ISOLATED CONVECTION FOR A FEW HOURS UNTIL THE H8 JET BREAKS
DOWN.  HIGHS TODAY WILL BE WARMER THAN YESTERDAY.  CLOUDS WILL
BE AN ISSUE...BUT WILL GO FOR MID 70S EAST AND LOW 80S WEST.
WINDS WILL BECOME GUSTY DURING THE AFTERNOON WITH TIGHTER
GRADIENT IN PLACE.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 315 AM CDT FRI SEP 19 2014

SFC BOUNDARY WILL SLOWLY SINK INTO NORTHERN IOWA OVERNIGHT AS AN
APPROACHING UPPER SHORT WAVE SUPPRESSES THE UPPER RIDGE LEADING TO
A TRANSITION TO NORTHWEST FLOW. KINEMATIC FORCING WILL INCREASE
OVER NW IA WITH THE APPROACH OF THE UPPER SHORT WAVE IN ADDITION
TO UPPER LEVEL DIVERGENCE WITH THE AID OF A SLIGHTLY COUPLED JET.
MUCAPES IN EXCESS OF 1500 J/KG CONCURRENT WITH THE AFOREMENTIONED
FORCING AND SUFFICIENT DEEP LAYER SHEAR GREATER THAN 35 KTS WILL
BE SUPPORTIVE OF ORGANIZED UPDRAFTS WITH GOOD VERTICAL
ACCELERATION AT TIMES. THIS COULD RESULT IN AN ISOLATED SEVERE
STORM OR TWO. ANY ACTIVITY SHOULD DIMINISH TOWARD 12Z THEN NOT
EXPECTING MUCH PRECIPITATION BETWEEN 12-20Z WITH A LACK OF SFC
CONVERGENCE...SOME LOW LEVEL CAPPING AND A LACK OF UPPER LEVEL
SUPPORT. DIURNAL HEATING MAY BE ENOUGH TO ACTIVATE THE BOUNDARY
OVER FAR SOUTHERN IOWA BY MID TO LATE SATURDAY AFTERNOON BEFORE
THE ACTIVITY SHIFTS SOUTH INTO MISSOURI. HIGH TEMPERATURES
SATURDAY WILL BE WARM AND RANGE FROM THE UPPER 70S NORTH TO THE
LOW TO MID 80S CENTRAL AND SOUTH. ANOTHER VIGOROUS SHORT WAVE WILL
DROP QUICKLY INTO THE NORTHERN PLAINS SATURDAY AFTERNOON AND
EVENING. WITH ITS CURRENT TRAJECTORY...ANY PRECIPITATION
ASSOCIATED WITH THE SYSTEM SHOULD REMAIN NORTH AND EAST OF THE
AREA.

SURFACE HIGH PRESSURE ORIGINATING FROM THE PACIFIC WILL ARRIVE
SATURDAY NIGHT INTO SUNDAY AND WILL BE THE DOMINANT FEATURE
THROUGH TUESDAY AND WILL RESULT IN PLEASANT CONDITIONS. THE UPPER
FLOW WILL BECOME PROGRESSIVE DURING THIS PERIOD THOUGH AS THE
UPPER RIDGE BEGINS TO SHIFT BACK EAST WHILE THE WESTERN CUTOFF LOW
BEGINS TO SHIFT EAST/NORTHEAST AS WELL. THIS SYSTEM WILL BRING A
RETURN FOR PRECIPITATION CHANCES BY LATE TUESDAY OVER THE WEST AND
TO THE ENTIRE AREA WEDNESDAY AND WEDNESDAY NIGHT.

&&

.AVIATION...19/06Z
ISSUED AT 1145 PM CDT THU SEP 18 2014

MAINLY VFR CONDITIONS EXPECTED THROUGH 20/00Z.  SFC WIND WILL
INCREASE AFT 15Z TO 15G25KTS ACROSS TAF SITES AS WARMER AIR SURGES
IN...PEAKING BETWEEN 20-22Z AROUND 20KTS SUSTAINED.  WINDS STAY UP
HIGHER THAN THEY DID LAST NIGHT SO DESPITE THE EXISTENCE OF LOW
LEVEL MOISTURE...WE SHOULD NOT SEE THE LOW VSBYS WE DID LAST NIGHT
HOWEVER WINDS DO DIMINISH A BIT BETWEEN 10Z AND 13Z SO I DID PUT A
BRIEF PERIOD OF MVFR CIG/VSBY DURING THIS TIME.


&&

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

&&

$$

SHORT TERM...MS SEP 14
LONG TERM...DONAVON
AVIATION...FAB



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