Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 180859
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
359 AM CDT THU SEP 18 2014

.SHORT TERM /TODAY/...
ISSUED AT 359 AM CDT THU SEP 18 2014

COOL HIGH PRESSURE WAS LOCATED OVER WESTERN ONTARIO THIS MORNING
WITH A RIDGE EXTENDING SOUTH INTO THE TENNESSEE VALLEY.  HIGH WILL
MOVE EAST TODAY WITH RIDGING EXTENDING BACK INTO THE CENTRAL U.S.
SOME FOG HAS FORMED IN LOW LYING AREAS AND ALONG RIVERS.  DO NOT
EXPECT TO SEE WIDESPREAD FOG...BUT SOME LOCAL VISIBILITY DOWN TO 1/4
MILE AT TIMES.  COOL SOUTHEAST SURFACE FLOW OUT OF THE HIGH WILL
HOLD TEMPERATURES BACK BACK TO A FEW DEGREES COOLER THAN YESTERDAY
IN MANY LOCATIONS.  DRIER FLOW FROM THE SOUTHEAST WILL ALSO KEEP WAA
PRECIPITATION TO THE WEST OF THE CWA.

.LONG TERM /TONIGHT THROUGH WEDNESDAY/...
ISSUED AT 359 AM CDT THU SEP 18 2014

GREAT LAKES HIGH PRESSURE WILL SHIFT EAST INTO THE NORTHEAST CONUS
LATE TONIGHT INTO FRIDAY. STRONG THETA-E ADVECTION WILL COMMENCE
OVER WESTERN IA AFT 06Z. EXPECT A FEW THUNDERSTORMS TO DEVELOP
WITH THE BAND OF MOISTURE ADVECTION. THE CHANCE FOR STORMS WILL
TRANSLATE EAST FRIDAY MORNING THEN SHOULD BE OUT OF THE AREA BY
THE AFTERNOON AS THE ELEVATED MIXED LAYER BUILDS INTO THE STATE
AND EFFECTIVELY CAPS THE AREA. THE PRIMARY FRONTAL BOUNDARY AND
SHORT WAVE ARRIVE FRIDAY NIGHT INTO SATURDAY. FORCING WITH THE
SYSTEM STILL LOOKS TO BE MODEST WITH NO STRONG CONVERGENCE NEAR
THE FRONT AND A LACK OF KINEMATIC FORCING ACROSS THE STATE. THE
MAIN FOCUS FOR A STATICALLY UNSTABLE ENVIRONMENT IS FROM SOUTHERN
MINNESOTA THROUGH NORTHEAST IOWA AND INTO NORTHERN ILLINOIS ON
SATURDAY AND SHOULD BE A MORE PRIMED REGION FOR MORE WIDESPREAD
ACTIVITY. THERE WILL LIKELY BE SOME DECAYING CONVECTION OVER
NORTHERN IOWA SATURDAY MORNING FOLLOWED BY PEAK HEATING
REDEVELOPMENT OVER SOUTHERN IA BY MID AFTERNOON. NOT EXPECTING THE
BOUNDARY TO BE VERY ACTIVE BETWEEN THE TWO PERIODS. THE MOISTURE
AXIS IS RELATIVELY NARROW WITH THE TROPICAL ELEMENTS BLOCKED TO
THE SOUTH...THUS ANY ACTIVITY WILL BE NARROWLY FOCUSED WITH MOST
OF THE DAY DRY. GOOD MIXING IS EXPECTED SATURDAY AS WELL WITH MOST
LOCATIONS REACHING THE 80S.

ANOTHER LARGE AREA OF HIGH PRESSURE WILL FOLLOW SUNDAY AND WILL BE
THE DOMINANT FEATURE THROUGH MID WEEK. THIS HIGH IS OF PACIFIC
ORIGIN THUS WILL NOT BE AS COOL AS THE PAST FEW SYSTEMS AND VERY
WELL MAY HAVE HIGHS IN THE LOW TO MID 70S EARLY NEXT
WEEK...THEREFORE EXPECT AN OUTSTANDING START TO THE WEEK.
PRECIPITATION CHANCES WILL CREEP BACK INTO THE STATE LATE IN THE
PERIOD AS THE HIGH SHIFTS EAST AND RETURN FLOW BEGINS TO LIFT GULF
MOISTURE BACK TOWARD THE STATE.

&&

.AVIATION...18/06Z
ISSUED AT 1143 PM CDT WED SEP 17 2014

A WEAK DISTURBANCE WILL PASS ACROSS WRN IA TONIGHT.  MID CLOUDS ARE
SPREADING IN FROM THE WEST BUT VFR CONDITIONS ARE STILL EXPECTED
THROUGHOUT THE TAF PERIOD WITH A LIGHT AND VARIABLE WIND.  THERE MAY
BE SOME LIGHT SHOWERS OR SPRINKLES AROUND BUT WAY TOO ISOLATED TO
PUT IN TAFS...WHICH WOULD MAINLY ONLY AFFECT KFOD BRIEFLY FROM 06Z-
08Z.  PATCHY FOG IS POSSIBLE OVER THE NORTHEAST/EAST WITH SKIES
HAVING A BIT LESS CLOUDS AND WINDS BEING LIGHT.  THE FOG SHOULD
MOSTLY BE SHALLOW AND IN LOW LYING AREAS.  THE WIND WILL INCREASE
AFT 16-18Z TO AROUND 10 KTS.


&&

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

$$

SHORT TERM...MS SEP 14
LONG TERM...DONAVON
AVIATION...FAB



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