National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDMX Received: 2017-09-14 09:00 UTC

FXUS63 KDMX 140900

Area Forecast Discussion
National Weather Service Des Moines IA
400 AM CDT Thu Sep 14 2017

.SHORT TERM.../Today through Tonight/
Issued at 400 AM CDT Thu Sep 14 2017

Primary focus in the short term is the very warm to hot conditions 
today then low grade precip chances tonight.

Today...Forecast Confidence:  Medium/High

00Z upper air analysis and water vapor imagery indicated a remnant 
trough from Irma over the Ohio River Valley...upper ridging over the 
central Plains...and another stronger shortwave trough over the 4-
corners region of the desert Southwest.  At the sfc...a ~1000mb sfc 
low was centered over srn SD yielding a broad sly wind flow over IA. 
A nocturnal LLJ developed overnight over NE/KS...which has yielded 
isolated/wdly scattered showers and thunderstorms. As of 09z...radar 
mosaic showed this activity drifting e/sely near the Missouri River. 
Current trends should keep most/all of this activity just southwest 
of the forecast area.  

Primary challenge today is the temperature forecast.  WAA regime in 
the low levels will allow 850mb temps to climb a few more degrees C 
today into the +20C to +22C range. This combined with a breezy south 
to southwest wind and bone dry soil moisture conditions will lead to 
very efficient mixing /likely near 750mb/.  Inched high temperatures 
up another degree or two into the upper 80s north to the lower 90s 
in the central.  It should be noted that some of the raw 2-meter 
temp guidance is even warmer into the mid-90s...which would be near 
record territory. Due to the potential for mid-level clouds did not 
go quite that warm at this point. These hot and dry conditions /with 
low RH/ will also yield an elevated fire risk today.  Luckily most 
vegetation has yet to this should temper an otherwise 
higher risk. Finally...a few of the hi-res CAM solutions do indicate 
the potential for a very isolated shower or storm this afternoon. 
Any coverage should be 10% or less...thus no explicit mention in the 

Tonight...Forecast Confidence:  Medium

LLJ is expected to re-strengthen overnight resulting in a period of 
isentropic ascent and a modest influx of moisture/thetaE between H8 
and H7. While model soundings and cross sections show the potential 
for mid-level saturation and weak instability...the PBL will remain 
quite dry.  At this point will keep PoPs confined to the slight 
chance /20 percent/ category...mainly across the north and west. Its 
quite possible that much of this will be virga or sprinkles...but at 
least a few areas could pick up measurable rain. With the thicker 
cloud cover and persistent southerly breeze expecting very mild lows 
in the low-mid 60s.

.LONG TERM.../Friday through Wednesday/
Issued at 400 AM CDT Thu Sep 14 2017

Still expecting some rain chances and a fairly active extended 
forecast, with a developing western US upper level trough to end the 
week. Southerly flow expected to increase ahead of a developing 
surface trough across the mid-section of the country with a 
continued push of Gulf moisture and WAA. Best chances for 
precipitation appear to be Friday night into early Saturday and 
again Saturday night. Friday night the sfc trough is expected to be 
situated from central MN southwestward into ern NE and central KS, 
with a strong LLJ streaming moisture into the western portion of IA. 
Storms are expected to form in the afternoon closer to the sfc 
trough axis and then will spread eastward into the northwestern 
portion of the forecast area late Friday night. Additionally could 
see some storms develop across the west/central toward Saturday 
morning in the warm sector along a push of theta-e advection with 
the line dissipating some through mid-day. Additional storm 
development then expected into Saturday night with the sfc trough 
axis and subsequent cold front pushing through the state. Any storms 
moving through late Friday night should remain elevated with 
marginal shear and decent instability, so an isolated severe storm 
still possible. Better setup for sfc-based storms into Saturday 
afternoon/night, however deep layer shear still somewhat marginal 
suggesting again possibility of maybe only an isolated strong to 
severe storm. 

Cold front to stall south of the state into Sunday, and will wobble 
northward into early next week as a warm front with an isolated 
shower/storm possible in vicinity of the boundary early next week. 
Extended range model then diverge through mid-week, with the GFS the 
most bullish with the forecast. GFS tries to bring some tropical 
remnants from off the west coast of Mexico northward into the 
southwest upper level flow pattern and tap into Gulf moisture 
bringing the upper wave through Tuesday into Wednesday. This would 
suggest an increasingly wet scenario. However the EC keeps a central 
US upper ridge in place and tries to bring that tropical moisture 
into the western US trough later in the week and lifting the upper 
trough into central Canada. This would essentially make for a drier 
forecast across IA. At this time stuck close to the blend pops which 
have put some low chance pops across much of the forecast area for 
the middle of next week at this time. 

As for temperatures, warm air to remain in place into Saturday with 
mainly 80s to around 90 expected, with Friday the warmest day as H85 
temps climb into the mid 20s Celsius. Cold front to drop H85 temps 
back into the mid teens by Sunday, which should send temperatures 
back into the 70s to around 80 Sunday into Monday. Slight warm-up 
then into the middle of next week with temps climbing back into the 
upper 70s to mid 80s.


.AVIATION.../For the 06Z TAFS through 06Z Thursday night/
Issued at 1120 PM CDT Wed Sep 13 2017

Few changes to going forecast. Slow return of warmer air across
the region ovn will reduce any chances for fog across the region.
Light/var to south winds will continue through 15z when winds mix
significantly west...closer to KDSM/KFOD/KMCW until 23z. Otherwise
mid level clouds expected through 18z and again aft 00z over the
region as another impulse moves northeast. Airmass dry enough to
keep mention of any thunder out of fcst./rev





LONG TERM...Beerends