FXUS63 KDMX 011138 AAA
AFDDMX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DES MOINES IA
538 AM CST TUE DEC 1 2009

...UPDATED 01/12Z AVIATION DISCUSSION...

.SHORT TERM [TODAY]...
MAIN FORECAST CONCERN IS WITH TIMING OF COLD 
FRONT LATE THIS AFTERNOON INTO THE NORTHERN PORTIONS OF THE CWA.  IN 
ADDITION...CLOUD COVER AND WINDS OUT AHEAD OF THE FRONT ACROSS THE 
NORTH WHICH WILL PLAY A ROLE IN THE HIGH TEMPS.  NAM/GFS IN GOOD 
AGREEMENT WITH TIMING THIS AFTERNOON WITH THE NAM ONLY SLIGHTLY 
SLOWER. SURFACE COLD FRONT LOOKS TO ENTER THE NORTHWEST CWA B/T 
18-21Z BRINGING THE HIGH CLOUD COVER AS WELL. VERY GOOD WAA AHEAD OF 
FRONT AS PRESSURE GRADIENT TIGHTENS THROUGH THE MORNING. WITH TEMPS 
REMAINING IN THE MID-30S AND MODERATE SOUTHWEST FLOW ACROSS THE 
NORTH OVERNIGHT...TWEAKED HIGH TEMPS UP A DEGREE OR TWO. OVER THE 
SOUTH HALF OF THE CWA...SUNSHINE AND SOUTHWEST FLOW WILL DOMINATE 
TODAY.  THIS SHOULD PROVIDE WELL ABOVE NORMAL TEMPS FOR THE FIRST OF 
THE DECEMBER...SO WENT AT OR SLIGHTLY ABOVE PREVIOUS FORECAST WHICH 
REMAINS 2 TO 4 DEGREES ABOVE GUIDANCE.

.LONG TERM [TONIGHT THROUGH MONDAY]...
PRIMARY IMPACT DURING THE PERIOD WILL BE THE COLD FRONT MOVING 
THROUGH IOWA OVERNIGHT...THEN SUBSEQUENT ROUNDS OF COLD ADVECTION 
ROTATING ACROSS IOWA THROUGH FRIDAY. THE COLD AND DRY AIR ASSOCIATED 
WITH THE COLD FRONT WILL HELP HOLD SYSTEM...WHICH WILL MOVE THROUGH 
THE SOUTHERN PLAINS AND INTO THE OHIO VALLEY TODAY AND 
WEDNESDAY...TO THE SOUTH AND SOUTHEAST OF THE FORECAST AREA. 

MUCH OF THE COLD AIR MOVING IN TONIGHT AND WEDNESDAY WILL BE BASED 
NEAR 900 MB WITH DEEPER COLD AIR ARRIVING WED NIGHT. NO 
PRECIPITATION IS EXPECTED WITH THE FRONTAL PASSAGE WITH THE AIRMASS 
LACKING SUFFICIENT MOISTURE. LITTLE REBOUND TO HIGH TEMPERATURES ON 
WEDNESDAY FROM 12Z READINGS AS LOW LEVEL COLD ADVECTION REMAINS IN 
PLACE DURING THE DAY. THE DIURNAL RANGE WILL REMAIN SMALL THU AND 
FRI WITH THE DEEP COLD AIR MASS OVERHEAD. THIS IS TYPICAL WITH DEEP 
COLD AIR MASSES AS THEY TEND TO REMAIN MIXED OVERNIGHT RESULTING IN 
RELATIVELY WARM LOWS COMPARED TO SIMILAR LOW LEVEL AIR MASSES WITH A 
LARGE INVERSION OVERHEAD. THAT SAID...THE OVERNIGHT LOWS WILL BE THE 
COLDEST THUS FAR THIS FALL...JUST NOT AS COLD AS THEY POTENTIALLY 
COULD BE.  HIGH TEMPERATURES IN THE DEEP COLD AIR MASS THEN HAVE 
LITTLE ROOM TO INCREASE BECAUSE THE PROFILE WAS ALREADY MIXED AT THE 
BEGINNING OF THE DAY RESULTING IN COOLER HIGHS.  HAVE INCREASED LOWS 
AND LOWERED HIGHS...THOUGH THERE ARE INDICATIONS THAT THE DIURNAL 
RANGE MAY BE EVEN LOWER THAN FORECAST. HIGHS ON FRIDAY COULD VERY 
WELL BE IN THE LOW TO MID 20S.

FLURRIES OR LIGHT SNOW SHOWERS ARE POSSIBLE WED NIGHT THRU THU NIGHT 
AS A LOW BASED AND DEEP DENDRITIC LAYER DEVELOPS BELOW 750 MB. 
DESPITE MINIMAL FORCING...THESE AIR MASSES TEND TO AT LEAST PRODUCE 
AN EXTENDED PERIOD OF FLURRIES AND THIS EVENT APPEARS NO DIFFERENT. 
BRIEF WARM ADVECTION BEGINS FRI NIGHT INTO SAT BEFORE COLD ADVECTION 
CIRCULATES BACK THRU BY SUNDAY.

&&

.AVIATION...01/12Z...VFR CONDITIONS CONTINUE THROUGHOUT THE ENTIRE 
TAF PERIOD.  MAIN FORECAST CONCERN IS WITH WIND SPEED AND SHIFT BY 
THIS AFTERNOON AND TONIGHT WITH COLD FRONT PUSHING ACROSS THE 
STATE.  HAVE WINDS INCREASING THIS MORNING FROM THE SOUTHWEST...THEN 
SLOWLY SHIFTING WEST TO NORTHWEST BEGINNING WITH FOD/MCW FIRST BY 
THE LATE AFTERNOON.  THE REMAINDER OF THE TAF SITES LOOK TO SHIFT 
PAST 03Z WEDNESDAY. STRONGEST WINDS LOOK TO BE BEHIND THE 
FRONT...WITH SOME GUST TO 20KT TOWARDS THE END OF THE TAF PERIOD. 
INCREASING CLOUDS TONIGHT INTO TOMORROW MORNING...BUT CIGS REMAIN 
AOA 4KFT. 

&&

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

&&

$$

SHORT TERM...PODRAZIK
LONG TERM...DONAVON
AVIATION...PODRAZIK