Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 252006
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
306 PM CDT SAT OCT 25 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 305 PM CDT SAT OCT 25 2014

A TRANQUIL NIGHT IS IN STORE WITH HIGH PRESSURE SETTLING INTO THE
STATE. WITH DEW POINTS FALLING OFF THIS AFTERNOON QUITE
NICELY...EXPECT TO SEE TEMPS FALL FAST THIS EVENING UNDER CLEAR
SKIES AND LIGHT AND VARIABLE WINDS. WENT BELOW MOS FOR LOWS
TONIGHT WITH THAT IN MIND.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 305 PM CDT SAT OCT 25 2014

NO SIGNIFICANT CHANGES WERE MADE TO THE LONG-TERM PERIOD OF THE
FORECAST. RELATIVELY QUIET WX IS STILL EXPECTED. MAIN
OPPORTUNITIES FOR PRECIP WILL BE MONDAY INTO MONDAY NIGHT...AND
WEDNESDAY NIGHT INTO THURSDAY MORNING.

FCST PERIOD BEGINS WITH DEPARTING SFC PRESSURE RIDGE. RETURN FLOW
ON ITS BACK SIDE AND THETA-E ADVECTION FOLLOW IT CLOSELY WILL
AFFECT THE CWA DURING THE DAY ON SUNDAY...AS A WARM FRONT
APPROACHES THE REGION. RH VALUES WITHIN THE COLUMN ARE NOT
EXPECTED TO BE HIGH ENOUGH TO FACILITATE PCPN...SO HAVE CONTINUED
THE TREND OF PARTLY TO MOSTLY CLOUDY ONLY. GFS AND NAM BRING IN
LOW-LEVEL MOISTURE FROM SUN AFTN THROUGH MON MORNING. IF LOW
CLOUDS END UP BEING MORE PLENTIFUL THAN EXPECTED SUN AFTN THEN
FCST MAXES MAY BE TOO HIGH. SUBSEQUENT SHIFTS WILL HAVE TO MONITOR
FOR POTENTIAL TWEAKS TO SUNDAY MAX TEMPS IN THAT REGARD.

ELEVATED TSTMS ARE POSSIBLE SUNDAY NIGHT FROM NORTHEAST IA INTO
WI AS ELEVATED INSTABILITY COMBINES WITH AMPLE FORCING WITHIN THE
WAA REGIME THERE. ATTM BELIEVE THE BEST COMBINATION OF
INSTABILITYAND FORCING WILL REMAIN NORTHEAST OF THE CWA SO HAVE
LEFT THE FCST DRY DURING THE TIME.

COLD FRONT IS PROGGED TO PUSH THRU THE CWA ON MONDAY. ALTHOUGH
MOISTURE WILL BE MINIMAL...SUFFICIENT FORCING WILL MOISTURE AND
INSTABILITY WILL BE SUFFICIENT FOR AT LEAST ISOLD-SCT PCPN INVOF
THE BOUNDARY. INSTABILITY WILL BE HIGH ENUF FOR AT LEAST SOME
ISOLD TSRA ESPECIALLY ACROSS THE SOUTHEAST HALF OF THE CWA...WHERE
MUCAPES OF 400+ J/KG ARE PROGGED TO EXIST. ALTHOUGH FOG REMAINS A
POSSIBILITY MONDAY MORNING BEFORE THE BOUNDARY
ARRIVES...CONFIDENCE WAS NOT HIGH ENUF FOR IT TO BE IMPACTFUL ENUF
TO MENTION. SUBSEQUENT SHIFTS WILL HAVE TO MONITOR FOR POTENTIAL
IMPACTS TO FORECAST MAXES AND CLOUD COVER.

AFTER THE SYSTEM DEPARTS THE CWA MONDAY NIGHT...NEXT CHANCE OF
PCPN WILL ARRIVE WEDNESDAY NIGHT INTO THURSDAY MORNING. BRIEF
RIDGING BUILDS IN BEHIND THE DEPARTING SYSTEM WEDNESDAY...BUT THEN
HEIGHTS FALL AGAIN AS THE NEXT SYSTEM APPROACHES. ALTHOUGH
MOISTURE WILL BE LIMITED...FORCING WILL BE AMPLE ENOUGH FOR SOME
SCATTERED SHRA MAINLY ACROSS THE EASTERN CWA.

MODELS BEGIN DIVERGING NOTICEABLY IN THEIR SOLUTIONS OF THIS
PARTICULAR SYSTEM...WITH THE ECMWF BEING THE STRONGEST/COLDEST.
REGARDLESS OF PARTICULAR MODEL...THOUGH...THEY ARE IN AGREEMENT
WITH A SEASONABLY COOL CANADIAN AIR MASS FILLING IN BEHIND IT.
FCST MINS ON FRIDAY MORNING ARE IN THE 20S AND 30S.

&&

.AVIATION...25/18Z
ISSUED AT 1234 PM CDT SAT OCT 25 2014

HIGH PRESSURE OVER THE DAKOTAS WILL MOVE OVER IA TONIGHT AND TO
THE EAST BY MORNING. WARM FRONT WILL DEVELOP SOUTH OF IA AND LIFT
NORTH INTO THE STATE SUNDAY. VFR CONDITIONS FOR THE TAFS...BUT
WILL PUT IN A SCATTERED MFR DECK IN THE SWRN SITES AS CIGS WILL
LIFTING NWD WILL LIKELY BE APPROACHING BY 18Z.

OUTLOOK...MVFR CIGS AS WARM FRONT LIFTS NORTH SUNDAY AFTERNOON
AND EVENING. COLD FRONT WILL PASS MONDAY...WITH A STRONGER PUSH OF
COLDER AND DRIER AIR TUE.

SIDENOTE...IT APPEARS HARVEST DUST IS AFFECTING SOME OF THE
SENSORS, KFOD RECENTLY.

&&

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

&&

$$

SHORT TERM...MS OCT 14
LONG TERM...ZOGG
AVIATION...MS OCT 14



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