Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 171141
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
641 AM CDT SUN AUG 17 2014

.UPDATE...
ISSUED AT 435 AM CDT SUN AUG 17 2014

FOG CONTINUES TO BECOME MORE WIDESPREAD. WILL ISSUE FG.Y THROUGH
9 AM THIS MORNING FOR A LARGE PART OF CENTRAL IOWA...OUT SOON.

&&

.SHORT TERM /TODAY/...
ISSUED AT 325 AM CDT SUN AUG 17 2014

RATHER QUIET MESO SCALE/SYNOPTIC PATTERN OVERNIGHT AND TODAY WITH
LIGHT WINDS ASSOCIATED WITH WEAK LOW PRESSURE EXITING THE REGION
OVER MISSOURI AND ANOTHER WEAK DISTURBANCE ACROSS EASTERN SOUTH
DAKOTA. MESO HIGH OVER THE REGION TONIGHT...THIS FORMED BEHIND THE
STRONG MCV THAT MOVED INTO SOUTHERN IOWA FRIDAY NIGHT AND BROUGHT
HEAVY RAINFALL TO THE AREA. ALL THAT COMBINED...WITH RATHER HIGH
LEVELS OF BOUNDARY LAYER MOISTURE HAS RESULTED IN PATCHY FOG WITH
DENSE FOG AS WELL EARLY TODAY. CURRENTLY VSBY BOUNCING UP AND DOWN
THOUGH RIVER VALLEY AREAS APPEARING TO DROP AND STAY DOWN. WILL
CONTINUE TO MONITOR AND IF CONDITIONS WORSEN OR BECOME MORE
WIDESPREAD...MAY ISSUE A FG.Y PRIOR TO 6 AM THIS MORNING.
OTHERWISE EXPECT FOG TO SLOWLY LIFT THIS MORNING BY 8-9 AM. SHORT
WAVE AND ISENTROPIC LIFT MOVING OVER NORTHWEST AND NORTHERN
SECTIONS TODAY MAY SPARK SOME THUNDERSTORMS THIS MORNING AND
AFTERNOON WHILE THE REMAINDER OF THE AREA SEES SOME SUN AND TEMPS
IN THE UPPER 70S TO LOWER 80S. NOT EXPECTING TO SEE MUCH IN TERMS
OF THUNDER ACROSS THE SOUTH TODAY...THOUGH BUFR SOUNDINGS SHOW
MODEST INSTABILITY DURING THE AFTERNOON HOURS THERE AND BETTER
INSTABILITY ACROSS THE NORTH TO ABOUT WATERLOO BY 21-00Z. WINDS
WILL BE LIGHT ONCE AGAIN WITH ANOTHER IDEAL AFTERNOON OF LIGHT
WINDS AND MILD TEMPERATURES.

.LONG TERM /TONIGHT THROUGH SATURDAY/...
ISSUED AT 325 AM CDT SUN AUG 17 2014

RAIN CHANCES CONTINUE TO BE THE MAIN FOCUS OF THE EXTENDED WITH
SEVERAL SHORTWAVES PROGGED TO PUSH THROUGH THE REGION TOWARD THE
END OF THE WORK WEEK. DECENT MODEL CONTINUITY TONIGHT THROUGH
TUESDAY BEFORE DISCREPANCIES DEVELOP WITH THE EXTENDED MODELS.
LEANED TOWARD A GFS/ECMWF/SREF BLEND TONIGHT INTO TUESDAY AS NAM
IS TOO FAR SOUTH AND FAST WITH VORT MAX TONIGHT INTO MONDAY.

TONIGHT INTO TUESDAY...TWO SEPARATE SHORTWAVES LOOK TO MAINLY
AFFECT NORTHERN IOWA WITH THE FIRST ONE QUICKLY MOVING THROUGH THIS
EVENING BEFORE THE SECOND ENTERS WESTERN IOWA MONDAY MORNING AND
INTO THE AFTERNOON. THE BETTER FORCING AND GOOD THETA-E ADVECTION
MOVE INTO NORTHWEST IOWA PAST 06Z MONDAY AND TRANSITIONS EAST
THROUGHOUT THE DAY MONDAY. LOW CONFIDENCE WITH MUCH QPF OUT OF THE
FIRST WAVE TONIGHT WITH LIMITED DEEP MOISTURE AVAILABLE. MORE
SIGNIFICANT MOISTURE WITH THE STRONGER SHORTWAVE TROUGH AND
ASSOCIATED COLD FRONT TO MOVE THROUGH ON MONDAY AND INCREASED POPS
ACROSS THE NORTH ON MONDAY AFTERNOON. SURFACE HIGH QUICKLY BUILDS
IN BEHIND THE COLD FRONT MONDAY NIGHT INTO TUESDAY AND TRENDED
TOWARD QUICKER EXIT OF PRECIP DURING THIS TIME. DRY AND WARMER
TUESDAY AND TWEAKED UP MAX TEMPS A DEGREE OR TWO ACROSS THE
FORECAST AREA WITH MORE SUNSHINE ANTICIPATED AND SOME MIXING
DEVELOPING BY THE AFTERNOON.

WEDNESDAY THROUGH FRIDAY...WITH THE SURFACE HIGH OVERHEAD EARLY
WEDNESDAY MORNING...MENTIONED PATCHY FOG ACROSS THE NORTHEAST PER
RADIATIONAL COOLING AND WITH THE EXPECTED PRECIP ON MONDAY TO
PROVIDE SOME ADDITIONAL LOW LEVEL MOISTURE. CUT BACK ON POPS
DURING THE DAY WEDNESDAY TO THE SOUTHWEST AS HIGH SLOW TO MOVE
EAST BEFORE NEXT SHORTWAVE ENTERS THE STATE BY THE
AFTERNOON/EVENING HOURS. UPPER LEVEL RIDGE STRENGTHENS THURSDAY
INTO FRIDAY AND PLACES NORTHERN IOWA IN THE RING OF FIRE TOWARDS
THE END OF THE WEEK. TWO TO THREE ADDITIONAL
SHORTWAVES...DEPENDING ON THE MODEL...MOVE ACROSS NORTHERN IOWA
AND PROVIDE CHANCE POPS THURSDAY THROUGH FRIDAY NIGHT.

&&

.AVIATION...17/12Z
ISSUED AT 640 AM CDT SUN AUG 17 2014

MAIN CONCERN IS FOG THIS MORNING. VLIFR CONDITIONS WILL GRADUALLY
GIVE WAY TO MVFR/VFR BY 14-15Z THIS AM AS INSOLATION INCREASES
ACROSS THE REGION. REMAINDER OF THE DAY A WEAK SHORT WAVE WILL
PASS OVER MN AND BRING SOME CHANCES FOR THUNDER NORTH MAINLY AFT
16-17Z TODAY THROUGH 01Z. ANOTHER SYSTEM APPROACHES LATE TONIGHT
WITH ADDITIONAL CHANCES FOR THUNDER AS THETAE ADVECTION AND
INCREASING SOUTHWEST FLOW ALOFT INCREASES MOISTURE TRANSPORT AND
LIFT OVER THE REGION. /REV

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR ADAIR-ADAMS-
AUDUBON-BLACK HAWK-BOONE-BREMER-BUTLER-CASS-CERRO GORDO-CLARKE-
DALLAS-DECATUR-FRANKLIN-GREENE-GRUNDY-GUTHRIE-HAMILTON-HANCOCK-
HARDIN-JASPER-LUCAS-MADISON-MAHASKA-MARION-MARSHALL-MONROE-POLK-
POWESHIEK-RINGGOLD-STORY-TAMA-TAYLOR-UNION-WAPELLO-WARREN-WAYNE-
WEBSTER-WRIGHT.

&&

$$

UPDATE...REV
SHORT TERM...REV
LONG TERM...PODRAZIK
AVIATION...REV


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