National Weather Service Raw Text Product

080 
FXUS63 KDMX 141745
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1245 PM CDT Thu Jun 14 2018

...Updated for 18z Aviation Discussion...

.SHORT TERM.../Today through Tonight/
Issued at 409 AM CDT Thu Jun 14 2018

Strong theta-e advection ongoing into central Iowa this morning 
as strong low level jet directing moisture into the state. 
Convection has recently developed where this strong moisture 
advection is occurring on the nose of strong MUCape. Have had a 
few reports of hail with a two inch report near Moorland early 
this morning with one of the stronger storms. Will continue to see
a few storms approach or exceed severe criteria into this morning
as the instability builds into the state with main concern 
continuing from large hail. The CAMs slowly progress this 
convection east this morning with an apparent MCV developing as 
the storms become more widespread. Also anticipate heavy rainfall 
with these storms with PWATs climbing to over 1.5". 

Most of the storms will pass east of the forecast area by midday 
with building thickness/heat into the state thereafter. 
Temperatures should climb nicely, especially in the west where 
clouds from the morning convection should give way to some 
sunshine. This warmth will continue into tonight with lows around 
70s in most locations as the warm/humid airmass spreads over the 
state. Convection tonight will mainly be north and east of the 
forecast area where the strongest moisture advection will occur 
although the far northeast portions of the forecast area may see 
a stray storm.

.LONG TERM.../Friday through Wednesday/
Issued at 409 AM CDT Thu Jun 14 2018

From Friday through Sunday our weather will be dominated by a
mid-level ridge centered over the southeast U.S. and building over
Iowa. This will bring persistent hot weather to our forecast area,
with high temperatures well into the 90s and heat index values
approaching or topping 100 degrees each day. In addition southerly
breezes will hold overnight temperatures in the 70s, with lows in
the mid to upper 70s in many areas. This scenario will likely
justify a long-duration heat advisory, which could be issued as
soon as this afternoon. All outdoor interests this weekend should
plan to take appropriate precautions for potentially hazardous
heat. The aforementioned mid-level ridge will also set up a
proverbial "ring of fire" scenario in which multiple rounds of
convection will fire on the northwestern periphery of the ridge.
Initially these storms may sneak into our far northern counties,
on Friday night and/or Saturday night, but generally the bulk of
the activity will remain to our north and northwest across South
Dakota and Minnesota.

On Sunday night or Monday the ridge will begin to break down, at
least across our region, as a broad 500 mb trough slowly
approaches from the west. This will bring a surface trough through
Iowa, accompanied by showers and thunderstorms. However, various
prognostic model runs continue to show a high degree of 
variability in both the timing of this trough passage and also in 
the extent to which it will progress south of the area as opposed 
to stalling out nearer to the Iowa/Missouri border. Either way, by
Tuesday and possibly by Monday we will see relief from the heat 
as the trough moves through, and it will then remain to be seen 
whether we get a few days of sunny and dry weather or whether the 
decayed frontal zone comes back northward much quicker, bringing a
return of clouds and rain. This makes the forecast quite 
uncertain toward the middle of next week, though the one thing 
that can be said with some confidence is that the upcoming heat 
wave will not last past Monday at the latest.

&&

.AVIATION.../For the 18Z TAFS through 18Z Friday afternoon/
Issued at 1239 PM CDT Thu Jun 14 2018

Morning convection exiting TAF sites by 19z Thu. No thunder/precip
expected remainder of TAF period. Post-thunderstorm, localized
wind direction/speed impacts should also depart the area this
afternoon. Once winds "normalize", expecting widespread 10 to 20
kt winds throughout tonight. 

LLWS along and east of I-35 does seem prudent for tonight as low-
level jet to move over the central to western portion of Iowa.


&&

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

$$

SHORT TERM...Cogil
LONG TERM...Lee
AVIATION...Kotenberg