Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 292345
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
645 PM CDT WED JUL 29 2015

.SHORT TERM /TONIGHT/...
ISSUED AT 350 PM CDT WED JUL 29 2015

AFTER SEVERAL DAYS OF STRONG TO SEVERE THUNDERSTORMS THAT BROUGHT
STRONG WINDS...VERY HEAVY RAINFALL...AND FREQUENT LIGHTNING TO THE
DMX CWA...SENSIBLE WEATHER HAS QUIETED DOWN FOR TODAY. HIGH PRESSURE
HAS BEEN PROPAGATING EASTWARD ACROSS NEBRASKA ALL DAY. AHEAD OF THIS
HIGH...850MB WINDS +2 TO +3 STD DEV FROM THE NW HAVE BEEN ADVECTING
SIGNIFICANTLY DRIER AND COOLER AIR INTO IOWA. SFC DWPTS DROPPED FROM
THE MID TO UPPER 70S OF YESTERDAY TO MID TO UPPER 50S TODAY. WITH
THE HIGH NEARING IOWA OVERNIGHT...WINDS WILL DIMINISH TO THE 5KT
RANGE. SFC DWPT DEPRESSIONS SHOULD BE HIGH ENOUGH AND WINDS EVER SO
STRONG ENOUGH TO KEEP RADIATIONAL FOG FROM BECOMING AN ISSUE
THURSDAY MORNING.

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
ISSUED AT 350 PM CDT WED JUL 29 2015

FOR THURSDAY...850MB TEMPS WILL INCREASE ABOUT 2 TO 3C FROM
WEDNESDAY AND START OFF AT 16C IN OUR NE TO 19C IN OUR SW. WITH SKC
EXPECTED...SHOULD BE EASY TO MIX DOWN VALUES TO THE MID TO UPPER 80S
FOR MUCH OF CWA.

FRIDAY MORNING...A WEAK BOUNDARY/COLD FRONT WILL SLIDE FROM OUR
NW DOWN BETWEEN HIGH PRESSURE TO OUR SOUTH AND HIGH PRESSURE TO
OUR NORTH. FCST SOUNDINGS SHOW A LOT OF DRY AIR. FCST PWATS AROUND
1 TO 1.1 INCHES WHICH IS AT 0 STD DEV. NOT MUCH UPPER LEVEL
SUPPORT. IN ALL...SHOULD BE ENOUGH THERE TO GET LIGHT CONVECTION
DURING PEAK DAYTIME HEATING. ISSUE WILL BE LOCATION OF BOUNDARY
DURING THESE HOURS. AS OF NOW...IT APPEARS BOUNDARY WILL BE SOUTH
OF OUR CWA AT THIS TIME. IF BOUNDARY SHIFTS NORTH IN FUTURE
RUNS...WILL PROBABLY NEED TO ADD LIGHT POPS IN OUR SOUTHERN
COUNTIES.

HIGH PRESSURE COMES IN QUICKLY BEHIND THIS BOUNDARY AND WILL CLEAR
US OUT FOR SATURDAY MORNING. HAVE LOWERED MIN TEMPS VS GUIDANCE TO
ACCOUNT FOR ADDED SINKING AIR/COOLING. THIS HIGH MOVES OVER EASTERN
IOWA BY THE AFTERNOON...PUTTING THE WESTERN PART OF OUR CWA IN
RETURN FLOW. THE NAM IS A SLOW OUTLIER WITH MOVING THIS HIGH THROUGH
IOWA SO LEANED AWAY FROM IT TIMING-WISE. PWATS INCREASE SLIGHTLY TO
AROUND 1 TO 1.25 INCHES IN WESTERN IOWA AS A SHORTWAVE WILL HELP
TRANSPORT SOME MOISTURE INTO WESTERN IOWA. THESE PWAT VALUES STILL
AT 0 STD DEV. ALL MODELS PICKING UP ON A WEAK BOUNDARY TO SERVE AS A
FOCUSING MECHANISM FOR PRECIP. WITH AIR RELATIVELY DRY...SOUNDINGS
DO NOT SUGGEST EFFICIENT RAIN PRODUCERS AS WE HAVE SEEN RECENTLY.
AS SATURDAY PM/SUNDAY NEARS...COULD BE A HIGH POP/LOW QPF SETUP.
LINGERED THIS PRECIP INTO SUNDAY AFTERNOON TO GIVE TIMING BUFFER.

BEYOND SUNDAY...LONG TERM MODELS HINTING AT A BAROCLINIC ZONE
TRYING TO ESTABLISH ITSELF OVER OUR SOUTHERN CWA THROUGH MID WEEK.
WITH THE REGION IN WESTERLY TO NORTHWESTERLY FLOW ALOFT...HAVE
LEFT IN BROAD- BRUSHED POPS DAYS 5 THROUGH 7 UNTIL CONFIDENCE CAN
BE INCREASED TO NARROW DOWN TIMING AND LOCATION OF POPS. MODELS
PLACE 850MB TEMPS ROUGHLY IN THE 16C TO 20C RANGE. THIS REMAINS 0
STD DEV ABOVE NORMAL AND SUGGESTS TEMPS ROUGHLY TO REMAIN IN THE
MID TO UPPER 80S INTO AT LEAST THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...30/00Z
ISSUED AT 645 PM CDT WED JUL 29 2015

HIGH CONFIDENCE IN VFR CONDITIONS THROUGH THE PERIOD. SKIES SHOULD
GENERALLY BE CLEAR...BUT SCT/BKN MID CLOUDS MAY BRUSH SRN SITES
/KDSM/KOTM/ TONIGHT. WINDS SHOULD BE FAIRLY LIGHT TONIGHT...EITHER
WLY OR NWLY...WITH VERY MINOR GUSTS DEVELOPING THROUGH THE DAY THU
WITH MIXING.

&&

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

&&

$$

SHORT TERM...KOTENBERG
LONG TERM...KOTENBERG
AVIATION...SMALL


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