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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 77 °
• Low: 52 °
• Clear

• Tuesday
• 
• High: 81 °
• Low: 61 °
• Clear

• Wednesday
• 
• High: 86 °
• Low: 66 °
• Partly Cloudy

• Thursday
• 
• High: 90 °
• Low: 64 °
• Partly Cloudy

• Friday
• 
• High: 84 °
• Low: 66 °
• Chance of Rain

Area forecast discussion 
National Weather Service Des Moines Iowa 
636 am CDT Monday may 21 2012 


..updated aviation discussion... 


Short term /today/... 
high pressure settled over the region will remain throughout the day 
Monday. Conditions will be calm with light winds. Temperatures will 
warm throughout the day with good afternoon mixing. 


Long term /tonight through Sunday/... 
main concerns remain the middle to end of period forecast. Tonight will 
remain quiet with ridge passing east of the region by 00z and south 
winds beginning to increase during the night. Some clouds will 
return in response to exiting ridge with warm air advection 
increasing over the eastern Dakotas and Nebraska by late tonight. 
Models continue to break out a small area of convection across 
stronger gradient over northwest Iowa through SW Minnesota with very 
weak apparent cape. Activity will quickly die by 13-14z as low level 
jet mixes out. Not all that impressed with precipitation chances as airmass 
remains dry over the region prior to arrival...so have only included 
slight chances at kest for now. Rest of area will remain dry. Main 
weather event on Tuesday will be increasing southerly flow with 
gradient winds increasing to 20 to 25 miles per hour and gusts to about 30 to 
35 miles per hour by 20z over northwest sections. Meanwhile h850 temperatures will 
return to lower to middle teens resulting in highs in the upper 70s 
east to the lower 80s west. As large scale trough enters the Pacific 
northwest and Central Plains of Canada...surface low over the eastern 
Dakotas should deepen and lift northeast increasing the warm flow 
into the region through Wednesday. Overnight Tuesday night gradient 
winds will remain keeping overnight lows in the upper 50s to lower 
60s across the region. Wednesday promises to be a warm day as 
thickness and h850 temperatures continue to warm and winds increase to 
south at 15 to 25 miles per hour with gusts to near 35 miles per hour once again. 
Differences again arise as we hit the Thursday through Saturday 
period with the GFS being the bigger outlier in terms of consensus 
between the three medium range models. Though some adjustments have 
taken place with the Euro/Gem over the past several runs...the GFS 
is still most Adamant about strengthening the northern stream low 
far more than the other two models and concurrently dragging rather 
cool air into the Great Plains...displacing the cold front well 
south into Missouri by 00z Saturday and only lifting it back north 
by midday Sunday. The Euro/Gem still differ drastically from the GFS 
by holding the front over the area longer on Thursday and dropping 
it into the state for Friday but then quickly pulling it back north 
by 00z Sunday. Thus...only a brief cool down is anticipated with the 
Euro/Gem vs a 2 day cool off by the GFS. The GFS is the current 
outlier with its overamplification of the northern stream trough at 
h500 which seems suspect for its strength this time of year. The 
h500 low deepens to 537dm over Ontario by 12z Friday compared to the 
Euro h500 550dm low and the Gem having nothing other than an 
elongated trough across the region. For now...continue to doubt the 
GFS solution based on its more extreme development. Front looks to 
stall over Iowa on Thursday and drift north later Friday afternoon 
and night keeping northern sections cooler on Friday with showers 
and thunderstorms while south will recover into the lower to middle 80s 
on Friday. A rather warm night is in store for Friday night as front 
retreats and south winds along with increasing dew points advect 
back north across the region. Depending on the frontal position... 
dew points may be in the middle to upper 60s by late Friday night. By 
Saturday the Euro/Gem have the warm front lifting back toward the 
iamn border with h850 temperatures rising to 22 to 24c over central and 
southern Iowa. This would easily place the region into the upper 80s 
to lower 90s by late afternoon. 


&& 


Aviation 21/12z... 
high pressure will keep conditions VFR through period. Winds will be 
light and variable under the high at kfod and kdsm through the day. 
As the high pushes south winds will shift to the south through the 
period. Will see gusts in the afternoon at kotm with good mixing. 


&& 


Dmx watches/warnings/advisories...none. 


&& 


$$ 


Short term...awb 
long term...rev 
aviation...awb