Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 281730
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1230 PM CDT SUN JUN 28 2015

.SHORT TERM /TODAY/...
ISSUED AT 206 AM CDT SUN JUN 28 2015

MAIN FORECAST CONCERN DURING THE SHORT TERM PERIOD WILL BE SHRA/TSRA
TRENDS THROUGH MIDDAY...THEN SVR POTENTIAL THIS AFTERNOON.

STRONGLY FORCED SHORTWAVE WAS MAKING ITS WAY SE THRU SOUTHERN
MINNESOTA EARLY THIS AM...AND WILL CONTINUE ITS SOUTHEAST TRAJECTORY
INTO THIS AFTERNOON. SURFACE LOW REFLECTION WAS ALSO TRACKING
SOUTHEAST...AND WILL CONTINUE MOVING SOUTHEAST TODAY AS WELL. AREA
OF SHRA/TSRA HAS HELD TOGETHER AS EXPECTED AS IT TRACKS SOUTHWARD
FROM MINNESOTA INTO IOWA. EXPECT THIS CONVECTION TO PERSIST AS MOVES
SOUTHEAST ACROSS THE CWA THIS MORNING.

SPENT MOST OF THE TIME FOR THIS FORECAST CONCENTRATING ON SVR
POTENTIAL THIS AFTERNOON. FCST PARAMETERS ARE COMING TOGETHER TO
SUGGEST A RATHER DECENT RISK OF SVR WX ACROSS THE EASTERN INTO
SOUTHEASTERN AND SOUTH CENTRAL CWA. INSTABILITY...OWING TO DIABATIC
HEATING...INCREASES THIS AFTERNOON IN ADVANCE OF THE SURFACE FRONT
AS IT MOVES SOUTHEAST. THE NAM IS BULLISH...AS TYPICAL...WITH
MUCAPES AS HIGH AS 4000 J/KG ACROSS THE E AND SE. HOWEVER EVEN THE
GFS IS ADVERTISING ROBUST INSTABILITY...THOUGH...WITH MUCAPES AS
HIGH AS 2000 J/KG OR MORE. COINCIDENT 0-6 KM BULK SHEAR VALUES ARE
PROGGED AS HIGH AS 40 TO 50 KT ACROSS THE E AND SE CWA. FCST
SOUNDINGS SHOW FAVORABLE LOW- AND MID-LEVEL LAPSE RATES IN THAT AREA
AS WELL...IN ADDITION TO A VEERED WIND PROFILE AND RELATIVELY
IMPRESSIVE CURVED HODOGRAPHS ESPECIALLY IN THE SOUTHEAST CWA. LCLS
ARE PROGGED TO BE AROUND 1000 M DURING THE TIME FRAME IN THAT AREA.
PRESENT THINKING IS THAT SUPERCELLS ARE POSSIBLE ESPECIALLY EARLY IN
THE EVENT. IF INITIAL UPDRAFTS ARE STRONG ENOUGH THEN SOME TORS MAY
RESULT...ESPECIALLY IN THE SE CWA /INCLUDING THE OTTUMWA AREA AND
POSSIBLY AS FAR NW AS THE OSKALOOSA AREA/ WHERE THE PARAMETERS COME
TOGETHER THE BEST. LARGE HAIL WILL BE A THREAT AS WELL IN
CONJUNCTION WITH THE STRONGER UPDRAFTS. EXPECT THE CONVECTION TO
EVENTUALLY CONGEAL INTO MORE OF A LINEAR MODE AS TIME GOES ON.
LOCALLY HEAVY RAINFALL WILL ALSO BE POSSIBLE...HOWEVER AM NOT OVERLY
CONCERNED ABOUT WIDESPREAD HEAVY RAINFALL OR FLASH FLOOD POTENTIAL
DUE TO THE RELATIVELY PROGRESSIVE NATURE OF THE CONVECTION. THE
CONVECTION WILL SCOOT E/SE AND EXIT THE CWA SOON THEREAFTER.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 206 AM CDT SUN JUN 28 2015

OVERALL LITTLE CHANGE IN THE LONG TERM OVER THE LAST COUPLE OF
FORECAST CYCLES. THE OVERARCHING STORY THROUGH THE LONG TERM IS
THE CONTINUED NORTHWEST FLOW THROUGH FRIDAY WITH PERIODIC
SHORTWAVES AND PRECIP CHANCES...AND A BREAKDOWN IN AMPLIFIED FLOW
OVER THE WEEKEND GIVING WAY TO A MORE MUDDLED/WEAKLY ZONAL FLOW.
TEMPERATURES AS A RESULT WILL CONTINUE TO BE SEASONABLY COOL IN
THE UPPER 70S TO LOW 80S THROUGH THE PERIOD.

BLEEDING INTO THE BEGINNING OF THE LONG TERM IS THE BACK END OF
A RIGOROUS SHORTWAVE. PRIOR TO EXITING...A SHORT WINDOW OF
OPPORTUNITY EXISTS FOR SEVERE WEATHER IN THE EASTERN AND SOUTHEAST
PORTIONS OF THE CWA AND STATE. THE INGREDIENTS CERTAINLY APPEAR TO
BE PRESENT WITH MODELS PRODUCING FAIR AMOUNTS OF CAPE OUT AHEAD OF
THE SURFACE BOUNDARY...WHILE MODELS VARY WITH THE NAM BULLISH AND
GFS MORE RESERVED...EVEN A MODEST BLEND RESULTS IN AROUND 2000
J/KG OF CAPE IN THE AFTERNOON/EVENING. SUPPORTIVE 0-6KM SHEAR
AROUND 35KTS...AND STRONGLY VEERING WIND PROFILES BOOST CHANCES
FOR ORGANIZATION...AND FALL IN LINE WITH THE SPC SLIGHT AND
MARGINAL PLACEMENTS. THE THREAT IN THE CWA SHOULD BE FLEETING AS
IT IS MORE PRIMED FOR DAVENPORTS AREA AND DOWN INTO
MISSOURI/ILLINOIS. REGARDLESS...THE OPPORTUNITY FOR A FEW SEVERE
STORMS IS THERE.

MONDAY AND ON THROUGH FRIDAY WILL SEE MULTIPLE WEAK SHORTWAVES
PROGRESS THROUGH THE NORTHWEST FLOW...RESULTING IN WHAT SEEMS LIKE
NEVER ENDING LOW END POPS AND COOL TEMPERATURES. WITH THE COOL
WEATHER AND LIMITED OPPORTUNITY FOR RETURN FLOW/BUILDING
INSTABILITY...SEVERE WEATHER APPEARS UNLIKELY FOR THE AREA. FRIDAY
INTO SATURDAY THE EURO...AND TO A LESSER EXTENT CANADIAN...BRINGS
IN A SHORTWAVE TROUGH WHICH MAY BE WORTH KEEPING AN EYE ON...BUT
THE GFS FAILS TO DEVELOP THIS FEATURE...NOT TO MENTION ITS LATE DAY
6 INTO DAY 7. WHILE NORTHWEST FLOW SHOULD BREAK DOWN OVER THE
WEEKEND...MODELS HINT AT ANOTHER HIGH BUILDING IN THE SOUTHWEST
EARLY INTO THE NEXT WEEK.

&&

.AVIATION...28/18Z
ISSUED AT 1230 PM CDT SUN JUN 28 2015

COMPLEX SHORT TERM FORECAST WITH WEAK LOW NEAR KDSM AT 17Z AND
UPPER LEVEL VORT MAX NEAR KFRM IN SOUTHERN MINNESOTA TRACKING
NEARLY DUE SOUTH SOUTHEAST. MVFR CIGS ASSOCIATED WITH THE UPPER
LEVEL FEATURE FILLING IN ACROSS NORTHERN AREAS...THOUGH BOUNDARY
LAYER MAY LIFT TO VFR THIS AFTERNOON. ACROSS THE SOUTH QUITE
UNSTABLE WITH SFC TROUGH ALIGNED ALONG I35 CORRIDOR WHERE MOISTURE
CONVERGENCE AND INSTABILITY IS INCREASING. SCT THUNDER SHOULD
DEVELOP FROM I35 EAST...NEAR TRACK OF UPPER LEVEL VORT AND SFC
BOUNDARY. COVERAGE IN QUESTION SO HAVE GENERALLY INCLUDED VCTS FOR
NOW...BY 15Z MONDAY MAY SEE SOME ADDITIONAL -SHRA OVER THE EAST
AS UPPER LEVEL CYCLONIC CURVATURE HOLDS. LOW SPOTS NEAR 11Z MAY
EXPERIENCE PATCHY 3-5SM BR AS WELL WITH MOISTURE BOUNDARY LAYER.
/REV

&&

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

$$

SHORT TERM...ZOGG
LONG TERM...CURTIS
AVIATION...REV


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