Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 081117
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
617 AM CDT TUE JUL 8 2014

.SHORT TERM /TODAY/...
ISSUED AT 303 AM CDT TUE JUL 8 2014

TODAY WILL BE COOLER...BREEZY AND DRY AS HIGH PRESSURE BUILDS
DOWN THE HIGH PLAINS IN WAKE OF LAST NIGHTS COLD FRONT. NORTHWEST
WINDS WILL PUMP IN LOWER DEWPOINTS FROM THE NORTHWEST AND KEEP
TEMPERATURES DOWN DESPITE PRETTY AMPLE SUNSHINE. FORECAST
SOUNDINGS INDICATE A SHALLOW MOISTURE LAYER THIS AFTERNOON
CONSISTENT WITH FAIR WEATHER CUMULUS OR STRATOCUMULUS AS WOULD BE
EXPECTED WITH A COLD AIR ADVECTION REGIME THIS TIME OF YEAR. LARGE
SCALE MODELS CONTINUE TO SPIT OUT LIGHT SPOTTY QPF ACROSS OUR
NORTH AND INTO MINNESOTA...AN APPARENT SIGNAL FOR DIURNALLY DRIVEN
ISOLATED LIGHT SHOWERS. HOWEVER...GIVEN THE LACK OF MOISTURE AND
INSTABILITY AND VERY LOW COVERAGE AND INTENSITY OF ANY SHOWERS
THAT DO MANAGE TO FORM...HAVE MAINTAINED A DRY FORECAST FOR THE
AFTERNOON.

.LONG TERM /TONIGHT THROUGH SUNDAY/...
ISSUED AT 303 AM CDT TUE JUL 8 2014

ANOMALOUSLY DEEP TROF FOR THIS TIME OF YEAR WILL CONTINUE TO
IMPACT THE WX OVER THE CWA FOR THE NEXT SEVERAL DAYS. THE LONG
TERM PERIOD BEGINS WITH SEASONABLY COOL TEMPERATURES WITH
SEASONABLY LOW HUMIDITY LEVELS IN THE WAKE OF A COOL FRONT WHICH
WAS SLIDING THROUGH THE CWA OVERNIGHT.

RELATIVELY QUIET WX WILL DOMINATE THE CWA UNTIL LATE
THURSDAY...WITH H5 TROFFING PERSISTING ACROSS THE EASTERN CONUS
AND RIDGING ACROSS THE INTERMOUNTAIN WEST. BY LATE
THURSDAY...HOWEVER...THE INTERMOUNTAIN H5 RIDGE IS PROGGED TO
FLATTEN DUE TO A STRONG H5 SHORTWAVE...AND A WEAKER LEAD H5
SHORTWAVE IS EXPECTED TO DIVE FROM THE DAKOTAS INTO THE MN-IA
AREA. AT THE SFC. RETURN FLOW WILL BEGIN ON THE BACK SIDE OF THE
DEPARTING SFC HIGH PRESSURE. STRONG H85-H7 THETA-E ADVECTION ON
THE NOSE OF THE UPPER-LEVEL JET WILL BRING INCREASING TSRA CHANCES
TO THE CWA THURSDAY EVENING...BEGINNING ACROSS THE WEST. PRESENT
THINKING IS THAT AN MCS WILL DEVELOP IN THE SD/NE/MN AREA AND
SLIDE SE ACROSS IA DURING THE NIGHT...BRINGING CHANCES FOR HVY
RAIN AS WELL AS POSSIBLY ISOLD/MARGINAL SVR HAIL. DO NOT EXPECT
SIGNIFICANTLY HIGH RAINFALL AMOUNTS THOUGH DUE TO THE RATHER
PROGRESSIVE NATURE OF THE H5 SHORTWAVE.

THE STRONGER SHORTWAVE IS THEN EXPECTED TO BRING A FRONTAL
BOUNDARY TO THE SD/NE/MN/IA REGION BY SATURDAY NIGHT...BUT SLOW
ITS SOUTHWARD PROGRESS. STRONG H85-H7 THETA-E ADVECTION IS
EXPECTED TO AGAIN BE FACILITATED BY THE UPPER-LEVEL JET...HOWEVER
THIS TIME FOCUSED SLIGHTLY FARTHER NORTH. GFS KEEPS BEST
THERMODYNAMIC AND KINEMATIC FORCING IN THE NORTHERN IA AND
SOUTHERN MN AREA...WHERE IT DEVELOPS ANOTHER MCS AND TRACKS IT
EASTWARD. THERE IS SOME DISAGREEMENT IN THE GUIDANCE REGARDING HOW
FAR SOUTH THE SFC BOUNDARY AND FORCING WILL GO...THUS HAVE KEPT
CHANCE POPS ACROSS MUCH OF THE CWA DURING THIS TIME.

H5 SHORTWAVE IS PROGGED TO PUSH THE SFC FRONT SOUTH TO AT LEAST
THE SOUTHERN CWA BY SUNDAY...SO HAVE TENDED TO KEEP THE HIGHEST
POPS THERE.

&&

.AVIATION...08/12Z
ISSUED AT 617 AM CDT TUE JUL 8 2014

VFR CONDITIONS WILL PREVAIL THROUGH THE FORECAST PERIOD. SCT
CLOUDS ARE EXPECTED TO DEVELOP BY THIS AFTN...POSSIBLY BKN AT
TIMES ESP AT MCW/ALO...BUT FORECAST SOUNDINGS AND DEWPOINT SPREADS
INDICATE ANY CIG HEIGHTS SHOULD BE VFR AROUND FL035-040.
OTHERWISE...TAFS ARE ONLY BROKEN UP FOR WINDS WITH INCREASING
SPEEDS AND GUSTS BY MIDDAY TODAY AND DIMINISHING AGAIN AROUND
SUNSET THIS EVE.

&&

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

&&

$$

SHORT TERM...LEE
LONG TERM...ZOGG
AVIATION...LEE


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