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000
FXUS63 KDMX 302103
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
303 PM CST SAT NOV 30 2013

.SHORT TERM /TONIGHT/...
ISSUED AT 303 PM CST SAT NOV 30 2013

TROUGH OF LOW PRESSURE WILL CONTINUE TO PROGRESS THROUGH CENTRAL
IOWA THIS EVENING. WEAK COLD ADVECTION IS ASSOCIATED WITH THE
BOUNDARY. DEWPOINTS UPSTREAM ARE IN THE LOW TO MID 20S WHICH IS A
GOOD INDICATOR OF LOW TEMPERATURE POTENTIAL OVERNIGHT. A BAND OF
MID LEVEL CLOUDS WILL DROP THROUGH THE STATE TONIGHT ALSO.
POSSIBLE THE CLOUDS WILL HELP HOLD TEMPERATURES UP A FEW DEGREES
OTHERWISE NO SIGNIFICANT WEATHER DURING THE PERIOD.

.LONG TERM /SUNDAY THROUGH SATURDAY/...
ISSUED AT 303 PM CST SAT NOV 30 2013

THE FIRST HALF OF THE COMING WEEK WILL BE CHARACTERIZED BY WEST
NORTHWEST FLOW ALOFT WITH A COUPLE OF SHORTWAVE TROUGHS MOVING
OVERHEAD...RESULTING IN FAIRLY QUIET BUT CLOUDIER WEATHER WITH A
RETURN OF LIGHT PRECIPITATION CHANCES. THE FIRST WAVE WILL MOVE
OVER SUNDAY NIGHT WHILE AT THE SURFACE A RIDGE MOVES OFF TO THE
EAST. THIS WILL PRODUCE THICK MID LEVEL MOISTURE BUT WITH A LOW
LEVEL DRY AIR IN PLACE WHICH IS ALSO EVIDENCED IN FORECAST
SOUNDINGS. IT IS EXPECTED THAT LIGHT SNOW WILL EVENTUALLY FALL
OVER ABOUT THE NORTH/NORTHEAST HALF OF THE FORECAST AREA...BUT IT
WILL TAKE SOME TIME AND THE SNOW WILL HAVE TROUBLE PENETRATING THE
NEAR SURFACE DRY LAYER AT LEAST INITIALLY. THUS HAVE SLOWED POPS
AND TRENDED THEM A BIT FURTHER TOWARD THE NORTH/NORTHEAST FOR
SUNDAY NIGHT/MONDAY.

AS ADDITIONAL 500 MB RIPPLES MOVE OVERHEAD AND WARM AIR/MOISTURE
ADVECTION SLOWLY INCREASE WITH SOUTHEASTERLY LOW LEVEL
FLOW...EXPECT THAT LIGHT PRECIPITATION WILL REMAIN POSSIBLE
ESPECIALLY ACROSS THE NORTHEASTERN HALF OF THE AREA FROM LATE
MONDAY THROUGH TUESDAY NIGHT. THE PRECIPITATION MAY SWITCH BETWEEN
RAIN AND SNOW AT TIMES...BUT ANY ACCUMULATION WILL BE VERY LIGHT
AND IS NOT EXPECTED TO HAVE MUCH IF ANY IMPACT. MEANWHILE...ON
MONDAY A COMPACT BUT POWERFUL 500 MB LOW WILL COME ASHORE OVER THE
PACIFIC NORTHWEST AND BRITISH COLUMBIA. MOST PROGNOSTIC MODELS ARE
DIGGING AND STRETCHING THIS LOW DOWN THE WEST COAST AND
ROCKIES...PRODUCING A LONGWAVE TROUGH BY THE MIDDLE OF THE WEEK.
HOWEVER...THE GFS IS TAKING A RADICALLY DIFFERENT APPROACH IN
EJECTING MUCH OF THE ENERGY OF THE LANDFALLING SYSTEM RAPIDLY
EASTWARD IN A BOWLING BALL 500 MB LOW ACROSS THE UPPER MIDWEST.
THIS SOLUTION IS AN OUTLIER AND SEEMS UNREALISTIC GIVEN THE
SYNOPTIC PATTERN AND HAVE LARGELY DISREGARDED IT.

IT APPEARS LIKELY THAT THE WARMING TREND AND LOW POPS WILL
PERSIST INTO WEDNESDAY BEFORE THE SLOWER/DEEPER TROUGH DEPICTED IN
THE OTHER MODELS AFFECTS IOWA AROUND WEDNESDAY/WEDNESDAY NIGHT.
DEPENDING ON THE EVOLUTION OF THIS TROUGH PASSAGE ANOTHER ROUND OF
PRECIPITATION IS A DISTINCT POSSIBILITY...BUT PROBABLY MORE
SIGNIFICANTLY IT WILL BRING IN MUCH COLDER TEMPERATURES TO END THE
WEEK WITH HIGHS IN THE UPPER 30S AND 40S ON TUESDAY AND
WEDNESDAY...BUT ONLY IN THE TEENS AND 20S ON THURSDAY. THE COLD
WEATHER WILL PROBABLY PERSIST...AND POSSIBLY EVEN DROP
FURTHER...THROUGH NEXT WEEKEND.

&&

.AVIATION...30/18Z
ISSUED AT 1140 AM CST SAT NOV 30 2013

VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE PERIOD.
WESTERLY WINDS WILL GRADUALLY BECOME MORE NORTH/NORTHEAST THROUGH
TONIGHT THOUGH WILL REMAIN LIGHT. MID LEVEL CLOUDS WILL INCREASE
OVERNIGHT THROUGH CIGS WILL BE AOA 5 KFT.

&&

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

&&

$$

SHORT TERM...DONAVON
LONG TERM...LEE
AVIATION...DONAVON