Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 061155
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
655 AM CDT WED MAY 6 2015

.SYNOPSIS...
ISSUED AT 322 AM CDT WED MAY 6 2015

DIFFUSE WARM FRONTAL BOUNDARY ACROSS THE CWA WILL LIFT NORTH
TODAY AND TONIGHT. A COLD FRONT WILL MOVE OUT OF THE ROCKIES AND
REACH SOUTHEAST IOWA BEFORE STALLING OUT IN RESPONSE TO THE THE
NEXT S/WV. LOW PRESSURE WILL DEVELOP OVER THE SOUTHERN ROCKIES SAT
AND LIFT NORTHEAST ACROSS THE AREA SUNDAY NIGHT.

&&

.SHORT TERM /TODAY/...
ISSUED AT 322 AM CDT WED MAY 6 2015

ALL ELEMENTS WILL REMAIN A CONCERN TODAY WITH CHANGING WEATHER
CONDITIONS ANTICIPATED. UPPER LOW CONTINUES TO ADVANCE OUT OF THE
CENTRAL/SRN PLAINS TOWARD THE MO RIVER VALLEY. CONVECTION IS MAINLY
DRIVEN BY KINEMATICS WITH LITTLE BAROCLINICITY.  THERE ARE TWO BANDS
OF THETA-E ADVECTION NOTED FROM THE DAKOTAS INTO MN...AND KS INTO
MO...BUT THESE APPEAR TO BE BASED MORE ON MOISTURE THAN THERMAL
GRADIENTS.  OUTSIDE OF SMALL CONVECTIVE CLUSTERS NOW MOVING NORTH TO
SOUTH THROUGH THE FORECAST AREA...THE MAIN CONCERN WILL BE THE
PROGRESSION OF THE LOBE OF KS/OK PRECIP AS IT LIFTS NORTH AND EAST.
MUCAPES STAY BELOW 1000 J/KG AND MLCAPE/CINHS ARE ONLY SLIGHTLY
LOWER SUGGESTING A SURFACE BASED POTENTIAL. 0-6KM SHEAR PUSHES
NORTHEAST WITH THE PRECIP SO WHILE THE SEVERE THREAT IS CERTAINLY
NOT HIGH DUE TO LIMITED INSTABILITY...WOULD NOT BE SURPRISED TO SEE A
STRONG/SEVERE STORM.  MODELS SUGGEST RAINFALL INTENSITY SHOULD
DECREASE INTO THE AFTERNOON AS WELL...AND QPF GENERALLY REFLECTS
THIS. HOWEVER PROJECTED 1.5 PWS WOULD BE WELL ABOVE 90TH PERCENTILE
FOR EARLY MAY WITH STRONGER LOW LEVEL MOISTURE TRANSPORT AND SO
WOULD NOT BE SURPRISED TO SEE A FEW POCKETS OF HEAVIER RAIN EITHER.

SURFACE WARM FRONT APPEARS TO BE FROM SERN IA INTO ERN SD AT 08Z AND
SHOULD SLOWLY MOVE NORTHWARD TODAY FINALLY ALLOWING FOR BETTER
MIXING.  RAIN WILL LIKELY KEEP TEMPS DOWN SOMEWHAT HOWEVER SO HAVE
DEPICTED A COOLER/WEST WARMER/EAST GRADIENT.  EXPECT SOME MIXING SO
CANNOT SEE A REASON TO DEVIATE MUCH FROM MOS SUGGESTIONS. THIS
MIXING MAY ALSO PROMOTE A BRIEF PERIOD OF GUSTY WINDS WITH BUFKIT
PROJECTED MIXING SHOWING GUSTS OVER 30KTS POSSIBLE NW BY AFTERNOON.
NO CHANGES TO CURRENT DENSE FOG ADVISORY.  VISIBILITIES MAY NOT BE
DOWN TO CRITERIA IN ALL AREAS...BUT ENOUGH TO JUSTIFY STATUS QUO FOR
THE NEXT FEW HOURS.  MAY HAVE TO TRIM SOME AREAS OR CANCEL BEFORE
9AM HOWEVER.

.LONG TERM /TONIGHT THROUGH TUESDAY/...
ISSUED AT 322 AM CDT WED MAY 6 2015

MUCH OF THE ACTION WILL REMAIN WEST OF THE CWA TONIGHT WITH
THUNDERSTORMS ENCROACHING FROM THE WEST AFTER MIDNIGHT AS THE COLD
FRONT BEGINS TO INFLUENCE THE AREA. THE STRONG STORMS ARE LIKELY
TO REMAIN WEST OF THE CWA. AS THE COLD FRONT ADVANCES...RAIN WILL
CONTINUE THURSDAY NIGHT INTO FRIDAY.

THE FRONT WILL STALL WITH RELATIVELY QUIET WEATHER FOR SATURDAY.
NORTHERN IA WILL LIKELY REMAIN DRY...WITH THE SOUTH BEING AFFECTED
BY THE STALLED FRONT. THE TRICKY PART OF THE FORECAST IS SUNDAY.
VARIOUS SOLUTIONS WITH THE S/WV LIFTING OUT AND JUST WHERE THE
SURFACE LOW WILL GO. THE ECMWF HAS BEEN THE MOST CONSISTENT WITH
THE TIMING AND POSITIONING...IS ALSO THE FARTHEST NORTH. CANADIAN
REG MAKES FOR A REASONABLE COMPROMISE BETWEEN THE EC...WHICH
DOESN`T LOOK TOO BAD...AND THE GFS THAT APPEARS TOO FAR SOUTH. EC
IS CLASSIC WITH THE DRY LINE...WITH THE OTHER MODELS SUGGESTING A
SIMILAR SITUATION...JUST NOT AS PROMINENT. THE SEVERE WEATHER
THREAT FOR SUNDAY AND SUNDAY NIGHT LOOKS SIGNIFICANT AND WILL NEED
TO BE MONITORED.

FOLLOWING THE PASSAGE OF THE SYSTEM SUNDAY...MUCH COLDER AIR WILL
SWEEP INTO THE UPPER MIDWEST. WRAP AROUND SHOWERS I THE 0 TO -3 C
H8 AIR WILL MAKE FOR SOME RAW WEATHER BY MONDAY NIGHT WITH TEMPS
IN THE 40S AND SHOWERS. THE COOL WEATHER WILL BE SHORT LIVED WITH
WARMING BY WED.

&&

.AVIATION...06/12Z
ISSUED AT 654 AM CDT WED MAY 6 2015

SHARP SW-NE GRADIENT ACROSS TAF SITES THIS MORNING DUE TO WARM
FRONT BISECTING THE STATE...VFR SW TO LIFR NE INCLUDING KMCW/KALO.
DEGRADED CONDITIONS NE SHOULD IMPROVE FAIRLY QUICKLY THIS
MORNING...HOWEVER JUST BRIEFLY BECOMING AT LEAST MVFR UNTIL
SCATTERED SHOWERS SPREAD SW-NE DURING THE DAY. ADDITIONAL PRECIP
AND POTENTIALLY MVFR CIGS MAY IMPACT NWRN SITES /KFOD/KMCW/
OVERNIGHT AS WELL.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR BLACK HAWK-
BREMER-BUTLER-CERRO GORDO-EMMET-FRANKLIN-GRUNDY-HAMILTON-HANCOCK-
HARDIN-HUMBOLDT-KOSSUTH-TAMA-WINNEBAGO-WORTH-WRIGHT.

&&

$$

SYNOPSIS...MS MAY 15
SHORT TERM...SMALL
LONG TERM...MS MAY 15
AVIATION...SMALL


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