Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 271138
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
638 AM CDT SUN JUL 27 2014

.SHORT TERM /TODAY/...
ISSUED AT 345 AM CDT SUN JUL 27 2014

FIRST IN A SERIES OF COOL FRONTS DRIVING SOUTHEAST THROUGH THE AREA
THIS MORNING. WEAK WINDS SO FAR ALONG THE BOUNDARY BUT ALREADY SOME
MIXING IS TAKING PLACE ACROSS THE NORTHERN COUNTIES AS COOLER AIR
ALOFT BEGINS TO MOVE SOUTHEAST. SECOND BOUNDARY IS ABOUT HALFWAY
THROUGH MN AND WILL THE DRIVING FORCE BEHIND THE WEATHER TODAY. SOME
PATCHY FOG EARLY SOUTHEAST WILL DISSIPATE AS WINDS PICK UP THIS
MORNING. OTHERWISE COOLER TEMPS ALOFT ASSOCIATED WITH THE UPPER
LEVEL SYSTEM CROSSING WISCONSIN/MINNESOTA TODAY PROVIDED ENOUGH
FORCING AND ENHANCE INSTABILITY OVER THE NORTHEAST TO GEN UP SOME
SHOWERS AND ISO THUNDER AFTER THE NOON HOUR TODAY...DIMINISHING
TOWARD EVENING. WITH THE INCREASED FLOW ALOFT AND STEEPENING LAPSE
RATES...WINDS WILL MIX CONSIDERABLY TODAY OVER ALL OF THE AREA.
EXPECTING SFC GRADIENT WINDS OF 20KTS WITH GUSTS TO 35KTS BY LATE
MORNING AND AFTERNOON. THE SYSTEM WILL QUICKLY EXIT THE AREA BY THIS
EVENING AND WINDS SHOULD RELAX QUICKLY TOWARD SUNSET. MOST OF
SOUTHERN SECTIONS THAT DONT EXPERIENCE FULL BLOWN CLOUD DECK AND
SHOWERS WILL SEE SCT-BKN FAIR WX CLOUDS ABOUT 4-5KFT DURING THE
AFTERNOON. HIGHS WILL RANGE FROM THE LOWER TO MID 70S NORTH AND IN
THE UPPER 70S TO LOWER 80S ACROSS THE SOUTH.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 345 AM CDT SUN JUL 27 2014

THE WEATHER WILL BE QUITE UNEVENTFUL THROUGH THE PERIOD WITH LITTLE
PATTERN CHANGE AS BLOCKY WRN RIDGE/ERN TROUGH REMAINS IN PLACE AS
PNA INDEX CONTINUES TO RISE. ONLY A FEW POTENTIAL WINDOWS OF PRECIP
EXIST AND ANY OF THOSE WOULD BE INSIGNIFICANT.  THE FIRST SUCH
WINDOW OCCURS MON WHEN SOME UNORGANIZED BUT UNCAPPED WEAK MLCAPES
DEVELOP DURING PEAK HEATING AND POTENTIALLY AIDED BY PASSAGE OF JET
SEGMENT AND ASSOCIATED WEAK SHEAR VORTICITY FORCING. HI RES MODELS
DO DEPICT ISOLATED SHOWERS AND THIS SCENARIO WOULD MAKE SENSE WITH
LITTLE CONVERGENCE.  ANYTHING THAT WOULD FORM SHOULD QUICKLY
DISSIPATE TOWARD SUNSET.

THE OVERALL FLOW WEAKENS INTO EARLY NEXT WEEK BUT THE PATTERN
ESSENTIALLY REMAINS UNCHANGED WITH PERSISTENT MO VALLEY SURFACE HIGH
PRESSURE THROUGH THE COMING WORK WEEK.  EXAMINATION OF SYNOPTIC
SCALE MOISTURE AND FORCING SUGGESTS LITTLE TO NO PHASING OF THE TWO
FOR MUCH IN THE WAY OF PRECIP.  HOWEVER THERE APPEARS TO BE SOME
THERMODYNAMIC RECOVERY AHEAD OF A WEAK SHORT WAVE PASSAGE IN THE NW
FLOW AROUND FRIDAY...SO HAVE KEPT LOW POPS THEN AND AGAIN SAT
ALTHOUGH CONFIDENCE IN SAT IS NOT GREAT.

THIS PATTERN WILL OBVIOUSLY KEEP TEMPS BELOW NORMAL AS WELL WITH NO
SIGN OF RETURN FLOW THROUGH AT LEAST NEXT WEEKEND. HIGHS MAY TOP 80
AT TIMES...BUT OFTEN REMAIN IN THE 70S WITH LOWS IN THE 50S OR LOWER
60S.

&&

.AVIATION...27/12Z
ISSUED AT 638 AM CDT SUN JUL 27 2014

UPPER LEVEL TROUGH HEADING SOUTHEAST TODAY WILL INCREASE MIXING
OVER THE AREA. LIMITED FG/BR SOUTHEAST LIFTING IN THE NEXT HOUR AT
KOTM...OTHERWISE CIGS WILL DEVELOP ACROSS NORTHEAST WITH MVFR
CONDITIONS EXPECTED...FOR THE SOUTH VFR CONDITIONS AFT 15-17Z AS
COLD POOL ALOFT BEGINS TO DESTABILIZE THE REGION. OVER THE
NORTHEAST SCT -SHRA AND ISO T FOR KALO AND KMCW AFT 17Z AS MID
LEVEL LAPSE RATES STEEPEN WITH COLDER AIR FILTERING IN ALOFT. BY
23Z SHOULD SEE WINDS BEGIN TO RELAX AND CLOUDS BREAK UP WITH LOSS
OF DAYTIME HEATING. LIGHT NW FLOW TO RETURN AFT 02Z WITH
DECOUPLING AND VFR CONDITIONS REGION WIDE. /REV


&&

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

$$

SHORT TERM...REV
LONG TERM...SMALL
AVIATION...REV


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