Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 200539
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
1139 PM CST WED NOV 19 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 234 PM CST WED NOV 19 2014

FRONTAL BOUNDARY WHICH PUSHED ACROSS CWA IN THE EARLY MORNING....HAS
PUSHED WELL SOUTH OF THE REGION BY LATE AFTERNOON. BEHIND BOUNDARY
LARGE UPPER LEVEL LOW PRESSURE SYSTEM...CURRENTLY LOCATED NEAR GREAT
LAKES REGION WILL KEEP PERSISTENT FORCING ACROSS CWA. MOISTURE IS
CONFINED TO LOW LEVELS...BUT GIVEN COLD TEMPERATURES PUSHING
SOUTH...LOW LEVEL MOISTURE IS WITHIN DENDRITIC GROWTH ZONE AND WILL
BE SUFFICIENT FOR FLURRIES AND LIGHT SNOW THROUGH THE BEGINNING OF
THE PERIOD. LOW PRESSURE SYSTEM WILL PUSH EASTWARD WITH HIGH
PRESSURE PUSHING INTO THE WEST OVERNIGHT. FEEL MODELS ARE TOO
AGGRESSIVE WITH TIMING OF HIGH PRESSURE PUSHING IN...AND THEREFORE
WILL KEEP CLOUD COVER AND FLURRIES THROUGH 06Z. GIVEN INCREASED
CLOUD COVER...HAVE BUMPED TEMPERATURES UP A FEW DEGREES...ESPECIALLY
IN THE EAST AND CENTRAL. WINDS WILL BEGIN TO DIMINISH AFTER
00Z...HELPING TO LIMIT BLOWING SNOW POTENTIAL IN THE NORTH...AND
HAVE ONLY KEPT BLOWING SNOW MENTION IN BEGINNING OF PERIOD.

.LONG TERM /THURSDAY THROUGH WEDNESDAY/...
ISSUED AT 234 PM CST WED NOV 19 2014

SURFACE RIDGE WILL SLIDE ACROSS THE FORECAST AREA ON THURSDAY WITH
LIKELY THE CALMEST DAY OF THE LONGER TERM. WILL SEE WARM ADVECTION
BEGIN IMMEDIATELY ON THE BACKSIDE OF THE RIDGE ON THURSDAY NIGHT
INTO FRIDAY. LOW LEVEL MOISTURE IS ALSO EXPECTED TO MOVE NORTHWARD
RAPIDLY IN INCREASING STRONG LOW LEVEL SOUTH FLOW WITH STRATUS
OVERSPREADING CENTRAL IOWA ON FRIDAY. WITH SATURATION OCCURRING IN
THE LOW LEVELS...THE MID AND UPPER LEVELS REMAIN RELATIVELY DRY
AND DONT ANTICIPATE MUCH IN THE WAY OF ICE INTRODUCTION.
THEREFORE...AS PRECIPITATION THREAT INCREASES ON FRIDAY
EVENING...WILL INITIALLY SEE FREEZING DRIZZLE SPREADING NORTHWARD
INTO THE STATE. HOWEVER...WARM ADVECTION WILL BE SUFFICIENT FOR
TEMPERATURES TO CLIMB ABOVE FREEZING FROM SOUTH TO NORTH ACROSS
CENTRAL IOWA DURING THE NIGHT. THIS WILL PRODUCE A TRANSITION TO
DRIZZLE/VERY LIGHT RAIN FOR ALL AREA BUT THE FAR NORTHEAST BY
DAYBREAK. THE DEEPEST LOW LEVEL MOISTURE WILL CONTINUE TO STREAM
ACROSS THE SOUTHEAST HALF OF THE FORECAST AREA INTO SATURDAY WITH
THE CONTINUED THREAT OF DRIZZLE/LIGHT RAIN.

THE MORE SIGNIFICANT WAVE ARRIVES SUNDAY WITH THE EURO REMAINING
THE FARTHEST WEST AS THE NORTHERN WAVE COMBINES WITH THE SOUTHERN
SYSTEM. IT HAS REMAINED QUITE CONSISTENT AND CANNOT ARGUE WITH THE
HIGHER POPS ACROSS THE FORECAST AREA DURING THIS TIME.
FORTUNATELY...WARM AIR WILL STILL BE IN PLACE FOR THE MAJORITY OF
THIS SYSTEM WITH RAIN EXPECTED...WITH HEAVIEST ACROSS THE EAST
NEAR THE TRACK OF UPPER LOW. ALSO ANTICIPATE FOG DEVELOPMENT AS
HIGHER DEWPOINTS OVERSPREAD THE RELATIVELY COOL GROUND FROM THE
RECENT COLD AND SNOW. STRONG COLD ADVECTION ARRIVES LATE SUNDAY
INTO SUNDAY NIGHT AS SYSTEM PASSES. BOTH MODELS INDICATED
ADDITIONAL LIGHT SNOW INTO EARLY NEXT WEEK AS ANOTHER WAVE DROPS
DOWN THE BACKSIDE OF THE LARGE EASTERN TROF WITH TEMPERATURES
REMAINING WELL BELOW NORMAL.

&&

.AVIATION...20/06Z
ISSUED AT 1139 PM CST WED NOV 19 2014

STRATUS CONTINUES TO THIN ACROSS CENTRAL IOWA. KDSM MAY HAVE A
BRIEF PERIOD OF MVFR CIGS BEFORE THE STRATUS DEPARTS. OTHERWISE
WIDESPREAD VFR IS FORECAST. WEST TO NORTHWEST WINDS WILL PREVAIL
THROUGH THURSDAY THEN GRADUALLY BECOMING SOUTH TO SOUTHEAST
THURSDAY EVENING.

&&

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

$$

SHORT TERM...AWB
LONG TERM...COGIL
AVIATION...DONAVON


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