Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 202142
AFDDMX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
342 PM CST THU NOV 20 2014

.SHORT TERM /TONIGHT/...
ISSUED AT 342 PM CST THU NOV 20 2014

CENTER OF THE SURFACE HIGH PRESSURE LOCATED OVER SOUTHERN
IOWA AND NORTHERN MISSOURI WILL CONTINUE TO PRESS EAST THIS EVENING
INTO THE OVERNIGHT HOURS. WINDS LOOK TO SHIFT SOUTH TO SOUTHEAST
PAST 06Z AND INCREASE TOWARDS SUNRISE FRIDAY MORNING...MAINLY ACROSS
THE WESTERN PORTIONS OF THE FORECAST AREA. HAVE A NON-DIURNAL
TEMPERATURE TREND GOING ACROSS THE WEST TO HANDLE THE WEAK WAA
DEVELOPING. OTHERWISE...LEANED TOWARD GOING SLIGHTLY ABOVE GUIDANCE
OVER THE CENTRAL TO SOUTHWEST SECTIONS OF THE FORECAST AREA WHILE
NEAR OR SLIGHTLY BELOW NAM ACROSS THE NORTHEAST WHERE THE WAA DOES
NOT DEVELOP AFTER 12Z FRIDAY.

.LONG TERM /FRIDAY THROUGH THURSDAY/...
ISSUED AT 342 PM CST THU NOV 20 2014

WARM ADVECTION WILL BE UNDERWAY ON FRIDAY AS SURFACE RIDGE
CONTINUES SLIDING EAST. LOW LEVEL MOISTURE RETURNING NORTHWARD
WILL LEAD TO DEVELOPMENT OF STATUS FROM SOUTH TO NORTH DURING THE
DAY. SOUNDINGS CONTINUE TO INDICATE SATURATION OCCURRING IN ONLY
THE LOW LEVELS WITH MID AND HIGH LEVELS RELATIVELY DRY. WILL BEGIN
TO SEE SOME PRECIPITATION INTO THE FAR SOUTH BY LATE AFTERNOON
THEN SPREADING NORTHEAST FRIDAY NIGHT. TEMPERATURES WILL BE NEAR
FREEZING IN THE SOUTH AT THE ONSET WITH EITHER FREEZING DRIZZLE OR
DRIZZLE EXPECTED. HOWEVER...THE LIGHT PRECIPITATION WILL OUTRUN
THE WARMING OVERNIGHT WITH PATCHY FREEZING DRIZZLE EXPANDING ACROSS
MUCH OF CENTRAL IOWA EXCEPT THE NORTHWEST AREAS. THE STRONG WARM
ADVECTION WILL PERSIST WITH THE FREEZING LINE MOVING NORTHWARD
ALONG WITH THE TRANSITION LINE. BY MORNING SATURDAY...ALL
LOCATIONS BUT THE FAR NORTHEAST ARE EXPECTED TO BE ABOVE FREEZING
WITH LIQUID PRECIPITATION ONLY. THIS FIRST WAVE OF PRECIPITATION
WILL PASS BY SATURDAY MORNING WITH ONLY THE FAR SOUTHEAST SEEING
PCPN POTENTIAL BY MIDDAY SATURDAY.

THE MORE POTENT SHORTWAVE BEGINS TO MOVE NORTHEAST SATURDAY NIGHT
INTO SUNDAY. ALL MODELS NOW INDICATE A FARTHER SOUTHEAST SOLUTION
WITH THIS NEGATIVELY TILTED SYSTEM. THIS WILL SHIFT FORCING AND
LIFT FARTHER EAST ALONG WITH AXIS OF HEAVIER PRECIPITATION. IT
STILL APPEARS SOME LIGHT PRECIPITATION WILL OVERSPREAD THE
FORECAST AREA ON SATURDAY NIGHT BUT FOCUS EAST OF INTERSTATE 35 ON
SUNDAY WITH HEAVIEST RAINFALL AMOUNTS IN NORTHERN ILLINOIS.
ADVECTION FOG STILL APPEARS LIKELY AS HIGHER DEWPOINTS OVERSPREAD
THE RELATIVELY COOLER GROUND WITH SATURDAY NIGHT APPEARING TO THE
BE BEST CHANCE OF SEEING LOW VISIBILITIES. FRONT WILL MOVE THROUGH
SUNDAY AFTERNOON WITH STRONG COLD ADVECTION INTO SUNDAY NIGHT AND
MONDAY. ONCE AGAIN...THE MODELS HAVE BACKED OFF ON THE POTENTIAL
OF SNOW ON THE BACKSIDE OF THE SYSTEM INTO EARLY NEXT WEEK
ALTHOUGH SOME SNOW SHOWER ACTIVITY STILL SEEMS LIKELY GIVEN THE
SOUNDINGS PROXIMITY TO THE DENDRITIC LAYER. SOME SLOW MODERATION
IS ANTICIPATED INTO THE MIDDLE OF THE WEEK ALTHOUGH SOME
SIGNIFICANT DIVERGENCE IS NOTED BETWEEN THE GFS AND EURO BY
MIDWEEK.

&&

.AVIATION...20/18Z
ISSUED AT 1148 AM CST THU NOV 20 2014

SURFACE HIGH PRESSURE WILL CONTINUE TO TRANSITION ACROSS THE STATE
TODAY AND ALLOW FOR VFR CONDITIONS THROUGH THE TAF PERIOD. WINDS
SHIFT AND INCREASE FRIDAY MORNING OUT OF THE SOUTH AHEAD OF NEXT
SYSTEM. CLOUD DECK REMAINS VFR THROUGH 18Z FRIDAY.

&&

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

&&

$$

SHORT TERM...PODRAZIK
LONG TERM...COGIL
AVIATION...PODRAZIK



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