324 
fxus63 kdmx 212338 
afddmx 


Area forecast discussion 
National Weather Service Des Moines Iowa 
540 PM CST Sat Nov 21 2009 


Short term /tonight/... 
the fog and stratus was slow to dissipate today...which is typical 
for November. Low level moisture advection will commence this 
evening with the moisture depth increasing. Considering the residual 
low level moisture in place and additional moving up tonight... 
another round of dense fog is a concern. The difference 
tonight is expect lows to occur early this evening then rising 
readings thereafter. Not absolutely confident that dense fog will be 
able to maintain with rising temperatures. Despite increasing 
moisture depth...it still likely will not be sufficient for rain 
production. Drizzle rather would be the precipitation type if 
anything occurs. 


Long term /Sunday through Saturday/... 
weak wave over the Southern Plains today will drift north by early 
sun and with weak lift may see some light sprinkles or drizzle into 
the morning hours. Though temperatures should not fall as much as Sat am 
hours when fog lasted until approx 11 am...airmass will continue to 
experience some modification with increasing dew points overnight. 
With that in mind...will keep some fog and drizzle going into the 
middle morning hours with a slight chance of showers late morning 
northwest nearer a weakening cold front. Low clouds will begin the 
day though soundings show some drying through the column during the 
afternoon hours. Temperatures to be warmer on Sunday...though some 
concern that guidance may be a bit optimistic given the 
possibility of morning fog and some clouds through the afternoon 
hours. Models continue to have some issues with the early week 
system. GFS tracking low farther north and then wings it southeast 
while Gem/Euro continue with more southerly track and then focus 
energy northeast over time. GFS is trending toward a line of showers 
over the east Monday evening while the Gem/Euro have better chances 
for any showers farther south. Though instability is increasing 
late day Monday...have opted to not include any thunder chances for 
now primarily due to lack of any strong signal in the models and 
some consistency issues with storm evolution. Low occludes early on 
Tuesday...with colder air wrapping around low and some light snow 
mixing in with light rain west sections Tuesday night and continuing 
Wednesday. Area of best snow chances will remain northwest of 
low...and far northwest areas may need some attention late Tuesday 
afternoon for possibility of minor snow accumulations. Presently 
not expecting any major travel problems over the forecast area. By 
Thursday secondary upper level system and much colder air is 
expected to drop quickly south into the upper Midwest and Great 
Plains. Thursday looks rather cold...with highs only in the 30s to 
lower 40s. Scattered flurries look possible with brisk northwest flow. A 
cold night is in store for Thursday night and Friday morning before 
a fast moving ridge heads east of the area...and southerly flow 
returns with a quick warm up for the start of the weekend. Highs 
conservatively placed in the 40s to lower 50s for now. 


&& 


Aviation... 
trickier aviation forecast tonight...with middle level stratus 
spreading northward across the area could preclude some of the fog 
development. Therefore hit the fog hardest across the 
east/northeastern sites where should see clearer skies initially 
allowing for better cooling. Otherwise with the southerly flow and 
moisture increasing across the area...could see the middle level 
stratus deck lower through the night into IFR/LIFR ceilings with drizzle 
as well. Clouds/any fog that does develop will linger through much 
of Sunday. 


&& 


Dmx watches/warnings/advisories...none. 


&& 


$$ 


Short term...donavon 
long term...rev 
aviation...beerends