Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 011150
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
650 AM CDT SAT AUG 1 2015

.SHORT TERM /TODAY/...
ISSUED AT 334 AM CDT SAT AUG 1 2015

WEAK WAVE ASSOCIATED WITH EARLIER EVENING SOUTHWEST STORMS AND THE
LINGERING THUNDERSTORMS OVER LUCAS/APPANOOSE/DAVIS COUNTIES IN THE
SOUTHEAST BETWEEN 06-08Z NOW HEADING OUT OF THE AREA. THE MAIN
SYSTEM TODAY IS UPSTREAM AND ASSOCIATED WITH A WEAK SFC LOW NEAR
WESTERN SD/ND AND EASTERN WYOMING WITH A WARM FRONT/STATIONARY FRONT
DRAPED EAST ACROSS SOUTH DAKOTA TO SOUTHERN MN AT 07Z. FEATURES AND
SFC WIND FIELDS RATHER WEAK WHICH WILL HAVE AN IMPACT ON FORECAST
LATER TODAY. THIS ESPECIALLY TRUE REGARDING INITIATION OF EXPECTED
THUNDERSTORMS THEN INTO THE OVERNIGHT PERIOD. MEANWHILE WARM AIRMASS
IN PLACE WITH EXPECTED RETURN OF MOISTURE BY MID TO LATE AFTERNOON.
WITH H850 TEMPS 20 TO 22C OVER THE AREA AND SSW H850 WINDS OF 15 TO
25 KTS...TEMPS WILL EASILY MIX INTO THE UPPER 80S TO LOWER 90S BY
LATE AFTERNOON...PRIMING AN AREA OF MUCAPE OF 1500-2500 J/KG ACROSS
THE WEST AT THE SAME TIME. PWATS INCREASE AS WELL...WITH GFS VALUES
NEARING 2 INCHES OVER NORTHWEST SECTIONS AT 00Z. VARIOUS SOLUTIONS
OF MESO MODELS...HRRR/NMM SHOW AN MCS DEVELOPING FROM THE CURRENT
CLUSTER OF STORMS OVER SOUTH DAKOTA...THEN MOVING INTO EASTERN
NEBRASKA/SOUTHWEST SECTIONS BY 21Z. THE SYNOPTIC SCALE MODELS FAVOR
A MORE NORTHERLY TRACK OF DEVELOPMENT FROM THE SFC LOW LATER THIS
AFTERNOON NEAR SIOUX FALLS EAST/SOUTHEAST WITH TIME THROUGH THE
EVENING. THE NMM DOES SUGGEST SECONDARY DEVELOPMENT OVER IA LATER IN
THE EVENING. NEEDLESS TO SAY...LOW CONFIDENCE WITH POTENTIAL FOR
SEVERAL MCS THROUGH THE NEXT 24 HOURS AND MIXTURE OF SOLUTIONS. FOR
NOW AM FAVORING THE HRRR/NMM SOLUTION OF STORMS TRACKING ESE
TODAY...ENTERING FAR WESTERN SECTIONS BETWEEN 21-00Z WITH SOME
ADDITIONAL DEVELOPMENT OVER FAR NORTHWEST SECTIONS IN THE SAME TIME
PERIOD. WE REMAIN OUTLOOKED FOR SVR DAY1...WITH POSSIBILITY THAT
VERY LATE IN THE PERIOD TODAY THE FIRST BATCH MAY OCCUR...BETTER
CHANCES AFT 00Z.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 334 AM CDT SAT AUG 1 2015

A MORE ACTIVE PATTERN SETTING UP ACROSS THE AREA FOR THE MID/LONG
RANGE BEGINNING TONIGHT. A SHORTWAVE TROUGH WILL CONTINUE TO PUSH
EAST/SOUTHEAST THROUGH THE REGION TODAY/TONIGHT...WITH A FRONTAL
BOUNDARY EXPECTED TO DROP THROUGH THE CWA LATE TONIGHT AND BE ACROSS
SOUTHERN IOWA SUNDAY BEFORE DROPPING SOUTH OF THE STATE SUNDAY
NIGHT. A WARM FRONT IS EXPECTED TO LIFT NORTH THROUGH THE STATE
TODAY...WITH THE CWA IN THE WARM SECTOR BY EARLY EVENING. AS THE
SHORTWAVE TROUGH APPROACHES THE REGION...CONVECTIVE ACTIVITY
EXPECTED TO DEVELOP ACROSS SE SD WITH AN MCS TO PUSH ESE ACROSS THE
CWA TONIGHT. NAM/GFS/EC ALL SHOW MORE OF A NORTHERN ROUTE...WITH THE
HI-RES MODELS A BIT FURTHER SOUTH. HAVE GONE WITH A BLEND OF THE TWO
AS EXACT PLACEMENT STILL UNCERTAIN. EITHER WAY...DECENT SHEAR AND
INSTABILITY IN PLACE SO SEVERE WEATHER IS EXPECTED. PWATS AROUND 1.6
TO 1.8 INCHES SO DECENT MOISTURE IN PLACE AND FZ LVL AROUND 12.4
KFT. THEREFORE COULD AGAIN SEE SOME HEAVY RAIN...BUT OVERALL RAIN
RATES NOT EXPECTED TO BE AS HIGH AS IN RECENT EVENTS EARLIER IN THE
WEEK. SOME LINGERING ACTIVITY EXPECT IN VICINITY OF THE FRONT SUNDAY
MORNING...WITH THE FRONT DROPPING SOUTH OF THE AREA LATE
SUNDAY/SUNDAY NIGHT.

ANOTHER WEAK WAVE MAY SLIDE BY AND KICK OF SOME PRECIP JUST TO THE
NORTH/EAST OF THE CWA SUNDAY NIGHT...WITH INCREASING CHANCES FOR
ADDITIONAL PRECIP LATE MONDAY INTO MONDAY NIGHT AS MODELS SHOW
ANOTHER MCS MOVING ACROSS THE AREA. ACTIVE PATTERN WILL CONTINUE
INTO THE END OF THE WEEK/NEXT WEEKEND WITH A NORTHWEST FLOW PATTERN
IN PLACE AND WEAK IMPULSES TOPPING THE WESTERN US RIDGE. WARM
TEMPERATURES EXPECTED WITH HUMIDITY CREEPING UP THIS WEEKEND AND
HEAT INDICES PUSHING INTO THE MID TO UPPER 90S. TEMPS TO DROP BACK
INTO THE 80S BEHIND THE FRONT FOR MONDAY INTO TUESDAY...WITH ANOTHER
SHOT OF COOL AIR SENDING TEMPS DOWN INTO THE 70S ACROSS THE STATE
FOR HIGHS LATE NEXT WEEK.

&&

.AVIATION...01/12Z
ISSUED AT 650 AM CDT SAT AUG 1 2015

QUIET CONDITIONS CONTINUE FOR NOW...WITH LINE OF THUNDERSTORMS TO
THE WEST IN NEBRASKA. CURRENT TRENDS AND MODEL SOLNS KEEP THIS
AREA GENERALLY WEST OF REGION THROUGH EARLY AFTERNOON...THOUGH A
FEW DECAYING SHOWERS MAY ADVECT EAST TOWARD KDSM BY 17Z. STILL
LOW CONFIDENCE AFT 20Z WITH INITIATION OF STORMS EXPECTED OVER
WESTERN/NORTHWEST IOWA AFT 02Z WITH STORMS DEVELOPING SOUTH AND
EAST. CONFIDENCE IN COVERAGE AND TIMING STILL IN QUESTION...SO
HAVE CONTINUED WITH VCTS TRENDS THROUGH FORECAST. EXPECT COVERAGE
TO DIMINISH TOWARD 12Z WITH DIURNAL INSTABILITY WANING AND
STRONGER FORCING MOVES EAST/NORTHEAST OF REGION AT THAT TIME. /REV

&&

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

$$

SHORT TERM...REV
LONG TERM...BEERENDS
AVIATION...REV



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