Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 220928
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
328 AM CST SAT NOV 22 2014

.SHORT TERM /TODAY/...
ISSUED AT 327 AM CST SAT NOV 22 2014

MUCH OF THE DRIZZLE HAS MOVED OUT OF THE CWA. PATCHY ECHOES KEEP
DEVELOPING WITH THE MOISTURE ADVECTION HOWEVER. FEEL BEST CHANCES
ARE OVER THE SOUTHEAST AND WILL HOLD LOW POPS IN THOSE AREAS. HAVE
TRIMMED BACK THE FREEZING RAIN ADVISORY WITH TEMPS AND DEW POINTS
WELL ABOVE FREEZING TO THE U.S. 30 CORRIDOR NOW. REPORTS INDICATE
THAT EVEN WITH THE COLD GROUND. THE MID 30S DEW POINTS ARE ENOUGH
TO KEEP ICING FROM OCCURRING. PAVEMENT TEMPS PAVEMENT TEMPS ARE
RIGHT AT FREEZING IN THE ADVISORY AREA...SO HESITANT TO DROP
ADVISORY WITH PATCHY PRECIP STILL THERE. THE CONCERN IS MAINLY IN
PROTECTED AREAS. AT THE OFFICE, THOUGH OUR PAVEMENT TEMPS ON THE
IEM SITE ARE IN THE UPPER 30S...SOIL TEMPS AT 2 1/2 INCHES REMAIN
AT 29.5 YET.

THE OTHER PROBLEM WITH THE DAY IS WITH CLOUDS. THE MOISTURE AREA
IS NOT ALL THAT DEEP. AREAS OF FOG WILL CONTINUE INTO MID
MORNING...BUT SHOULD LIFT. WITH THE LOW SUN ANGLE IT WILL LIKELY
BE DIFFICULT TO BREAK THE STRATUS LAYER. WENT CAUTIONS ON TEMPS
FOR THAT REASON. WILL MAKE THE LOW 50S SOUTH EVEN WITH THE
CLOUDS...WITH 40S OVER THE REST OF THE STATE.

.LONG TERM /TONIGHT THROUGH FRIDAY/...
ISSUED AT 327 AM CST SAT NOV 22 2014

A BROAD 500 MB TROUGH COMING ASHORE OVER THE PACIFIC NORTHWEST
THIS MORNING WILL CROSS THE NORTHERN ROCKIES TODAY AND
TONIGHT...THEN DIG SOUTHEAST AND DEEPEN SIGNIFICANTLY AS THE
WEEKEND PROGRESSES. AT THE SURFACE...THIS WILL RESULT IN MODEST
SOUTHERLY FLOW ACROSS IOWA WITH INCREASING MOISTURE ADVECTION
PROMOTING STRATUS...FOG AND DRIZZLE AFTER SUNSET AND INTO SUNDAY
MORNING. MEANWHILE A SURFACE LOW PRESSURE SYSTEM WILL LIFT QUICKLY
INTO THE OZARKS TONIGHT AND UP ACROSS MISSOURI AND ILLINOIS LATE
SUNDAY AND SUNDAY NIGHT...SPREADING SOME RAIN ACROSS SOUTHEAST
IOWA...WHILE A SYNOPTIC TROUGH DEVELOPS ACROSS THE EASTERN DAKOTAS
AND NEBRASKA TONIGHT. THE SURFACE FRONT WILL PUSH THROUGH ON
SUNDAY AND SUNDAY NIGHT...DEFLECTING THE RAIN FROM THE
SOUTHEASTERN LOW OFF INTO EASTERN IOWA AND BEYOND BY LATE SUNDAY.
HAVE MADE NO SIGNIFICANT CHANGES TO THE FORECAST FOR THE LATTER
HALF OF THE WEEKEND WITH RELATIVELY WARM TEMPERATURES OFFSET BY
THE GREY AND DAMP CONDITIONS.

BY SUNDAY NIGHT AS THE 500 MB TROUGH DEEPENS ACROSS THE CENTRAL
U.S. IT WILL SWING A LOBE OF VORTICITY DOWN OVER
IOWA...COMMENSURATE WITH A RAPID DEEPENING OF THE SURFACE LOW NOW
MOVING OFF TO OUR EAST INTO THE GREAT LAKES. THIS WILL INCREASE
THE SURFACE PRESSURE GRADIENT ACROSS OUR FORECAST AREA RESULTING
IN STRONG WINDS AROUND MONDAY...ALONG WITH SOME BROAD BUT MODEST
FORCING WITHIN A RELATIVELY SHALLOW SATURATED LAYER AS CONFIRMED
BY FORECAST SOUNDINGS. THIS WILL GENERATE LIGHT SNOW SHOWERS
ACROSS MUCH OF THE AREA FROM MONDAY INTO MONDAY NIGHT. ALTHOUGH
AMOUNTS WILL BE LIGHT AND SPOTTY...THE STRONG WINDS MAY CAUSE SOME
BLOWING SNOW ISSUES ESPECIALLY ACROSS OUR NORTHERN COUNTIES...AND
HAVE MAINTAINED WORDING TO ACCOUNT FOR THIS IN THE OUTGOING
FORECAST.

THE SNOW SHOWERS WILL COME TO AN END ON MONDAY NIGHT EVEN AS THE
500 MB TROUGH BECOMES CARVED OUT ACROSS NEARLY THE ENTIRE
CONTINENTAL U.S. THIS WILL BRING PERSISTENTLY COLD WEATHER AGAIN
FOR THE BULK OF NEXT WEEK...WITH GENERALLY DRY CONDITIONS POSSIBLY
INTERRUPTED BY MORE LIGHT SNOW FROM A WEAK CLIPPER SYSTEM MOVING
OVERHEAD AROUND WEDNESDAY OR SO.

&&

.AVIATION...22/06Z
ISSUED AT 1159 PM CST FRI NOV 21 2014

LOW MVFR AND IFR CEILINGS AND VISIBILITIES WILL IMPACT SITES
THROUGH MUCH OF PERIOD AS BAND OF DZ CONTINUES TO PUSH EASTWARD.
LOWEST CEILINGS AND VISIBILITIES WILL COME NEAR 12Z BEFORE
SUNRISE...AND MAY SEE LIFR CONDITIONS AT TIMES...ESPECIALLY AT
NORTHERN SITES KMCW/KALO. MAY SEE CEILINGS RISE TO LOW VFR
BRIEFLY BEYOND 18Z...THOUGH ANTICIPATE MVFR CONDITIONS TO RETURN
ONCE AGAIN NEAR 00Z. WINDS WILL BE FROM THE SOUTH AROUND 12KTS
WITH HIGHER GUSTS POSSIBLE THROUGH PERIOD.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
FREEZING RAIN ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR
BLACK HAWK-BREMER-BUTLER-CERRO GORDO-FRANKLIN-GRUNDY-HAMILTON-
HARDIN-WORTH-WRIGHT.

&&

$$

SHORT TERM...MS
LONG TERM...LEE
AVIATION...AWB


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