Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 031736
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1236 PM CDT THU SEP 3 2015

...18Z AVIATION UPDATE...

.SHORT TERM /TODAY/...
ISSUED AT 335 AM CDT THU SEP 3 2015

PRECIPITATION CHANCES TODAY WILL BE MAIN FORECAST CONCERN. HAVE SEEN
DEVELOPMENT OF ONGOING LIGHT AND SCATTERED SHOWERS ACROSS SW
PORTIONS OF STATE...GENERALLY ALONG THE NOSE OF LLJ...AND EXPECT
THIS PRECIPITATION TO CONTINUE INTO THE EARLY MORNING
HOURS...DISSIPATING QUICKLY AFTER 12Z AS FORCING DIMINISHES. HAVE
TRENDED TOWARDS HIGH RES SOLUTIONS...THOUGH MAY BE TOO AGGRESSIVE
WITH EXTENT OF NORTHERN EDGE OF PRECIPITATION AND PERSISTENCE.
CHANCES FOR PRECIPITATION WILL THEN SHIFT TO THE NORTHEASTERN
PORTIONS OF THE CWA LATE IN THE PERIOD. MODELS INDICATE DECENT
INSTABILITY ACROSS THE AREA...THOUGH SOUNDINGS SHOWING A WEAK CAP
WHICH SHOULD BE SUFFICIENT TO KEEP PRECIPITATION CHANCES OUT OF CWA.
HAVE THEREFORE KEPT FORECAST DRY...WITH BEST FORCING FURTHER EAST OF
THE AREA. HOWEVER...DO NOT HAVE HIGH CONFIDENCE AND MAY SEE
THUNDERSTORMS DEVELOP IN THE AFTERNOON IN THIS AREA.

HAVE KEPT TEMPERATURES NEAR GOING...TOWARDS THE HIGHER GUIDANCE.
WITH GOOD SOUTHERLY SURFACE FLOW AND WARMER TEMPERATURES ALOFT
SHOULD SEE TEMPERATURES WARM TODAY. HUMID CONDITIONS WILL PERSIST
WITH HEAT INDEX VALUES GENERALLY 95-100 DEGREES IN THE AFTERNOON.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 335 AM CDT THU SEP 3 2015

A FEW MORE DAYS OF SUMMER WHILE THE UPPER RIDGE REMAINS OVER THE
STATE. HIGH TEMPERATURES IN THE MID 80S TO LOWER 90S ARE EXPECTED TO
LAST THROUGH SUNDAY HOWEVER CHANGE IS ON THE WAY. SEVERAL FEATURES
TO MONITOR THROUGH THE PERIOD. THE FIRST WILL BE THE INCREASING
MONSOONAL FLOW AS AN UPPER LOW DIGS INTO THE PACIFIC NORTHWEST
FRIDAY INTO SATURDAY. THIS FLOW ENHANCE THE MOISTURE TRANSPORT INTO
THE REGION AND ALSO WILL INGEST TROPICAL VORTICITY FRAGMENTS FROM
THE SYSTEM CURRENTLY TROPICAL STORM KEVIN. THIS WILL BRING
INCREASING CHANCES FOR THUNDERSTORMS SATURDAY NIGHT INTO SUNDAY
AND WILL BE FOLLOWED BY ADDITIONAL CHANCES SUNDAY NIGHT AS A COLD
FRONT PASSES THROUGH THE STATE.

THIS WILL BE THE BEGINNING OF AN EVOLUTION TO A MORE FALL LIKE
PATTERN THAT OCCUR THROUGH THE PERIOD AS THE UPPER RIDGE IS
SUPPRESSES TO SOUTH AND EAST WHILE THE PACIFIC UPPER LOW LIFTS INTO
SOUTH CENTRAL CANADA AND WILL HELP DRIVE THE BOUNDARY INTO THE
STATE. THIS WILL PLACE THE MIDWEST IN A MORE PROGRESSIVE ZONAL FLOW
NEXT WEEK. THE BOUNDARY SUNDAY NIGHT WILL NOT BE ABLE TO DROP TOO
FAR SOUTH DUE TO THE ZONAL FLOW AND WILL LIFT BACK NORTH AS A WARM
FRONT TUESDAY. A STRONGER BOUNDARY WILL PUSH THROUGH TUESDAY NIGHT
INTO WEDNESDAY. EVEN COOLER AIR IS LIKELY TO ARRIVE JUST BEYOND THE
EXTENDED AND LIKELY SIGNALS THE END TO THE HOT AND HUMID WEATHER FOR
THE YEAR BEYOND THIS WEEKEND. WITH SUCH AN ACTIVE PATTERN AND STRONG
SYSTEMS...CAN NOT DISCOUNT A FEW SEVERE STORMS NEXT WEEK.

&&

.AVIATION...03/18Z
ISSUED AT 1229 PM CDT THU SEP 3 2015

WITH THE UPPER LEVEL RIDGE FIRMLY PLANTED ABOVE...ANYTHING OF
CONSEQUENCE WILL STAY TO THE WEST AND NORTHWEST OF THE TAF SITES.
MODEL SOUNDINGS HINT AT SOME LOCALIZED FOG TOMORROW MORNING...BUT
WITH HRRR DEPICTING OTHERWISE AND LITTLE CHANGE OVERNIGHT
OTHERWISE...HAVE KEPT FOG MENTIONS OUT FOR THIS ITERATION.

&&

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

$$

SHORT TERM...AWB
LONG TERM...DONAVON
AVIATION...CURTIS


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