National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDMX Received: 2018-06-14 05:06 UTC


239 
FXUS63 KDMX 140506
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1206 AM CDT Thu Jun 14 2018

.DISCUSSION.../Tonight through Wednesday/
Issued at 345 PM CDT Wed Jun 13 2018

Storm chances tonight into Thursday along with the heatwave Friday 
into the weekend were the main focus of the forecast. Leaned 
closer the latest couple of runs of the HRRR, but most of the 
hires models are in good agreement with timing and location of 
storms/showers this evening into Thursday. Friday through Monday, 
leaned slightly closer to the GFS/NAM as thinking the ECMWF is too
warm with the temps and too dry with the dew points. 

Tonight into Thursday...weak convection over South Dakota looks to 
trickle into northern Iowa this evening. The latest
HRRR/ARW/NMM/RAP continue this thundershower activity through 
around 02-04z tonight along the Highway 20 corridor before
dissipating. Confident to insert low pops through the evening 
across portions of northern Iowa to coincide with the HRRR as it 
has performed fairly well recently. However, low confidence with 
anything measurable as there remains a deep dry layer for 
precipitation to contend with before reaching the ground. Thus, 
QPF remains NIL through 06z. 

Better forcing moves into the state past 06z tonight with a decent 
slug of 925-700mb theta-E advection. Little concern with the 
severe potential overnight into Thursday morning due to the lack 
of instability and weak shear. Some pockets of brief moderate to 
heavy rain are possible b/t 06-15z Thursday as precipitable water 
values range around 1.5 inches and warm layer cloud depths near 
13kft. The slight delay in the system to depart on Thursday will 
keep max temperatures a bit cooler than previously anticipated as 
cloud cover hangs around into the afternoon. 

Friday through Monday...Hot and humid conditions along with winds 
remain on track during this period. The most notable changes were
to the winds/gusts Friday afternoon and Saturday afternoon as 
deep mixing develops both days providing some gusts to 30 mph. 
Increased winds roughly 3-5 knots, especially over the western 
half of the CWA where the mixing looks to be slightly deeper. The 
other issue is with the stronger winds, the dew points are likely 
to mix and thus be slightly drier than previous forecast. Not a 
significant change to the ongoing dew point forecast over the 
central to eastern sections of the CWA, but lowered dew points 
across the west slightly with the stronger winds anticipated. With
the large upper level ridge in place through weekend over the 
state, a few weak shortwaves may ride the ridge and bring cloud 
cover and storm chances to far northern Iowa into southern 
Minnesota. One more notable shortwave looks to bring storms b/t 
06-12z Saturday but will quickly move east and allow the breezy 
and hot conditions to return. The WAA persists Friday night and 
again Saturday night into Sunday and likely to keep minimum 
temperatures from dropping off too drastically. Kept with the mid- 
70s for much of the forecast area through the weekend and not 
allowing any relief to the daytime heat. Another concern to the 
heatwave is Monday where the ECMWF and GFS are coming into better 
agreement with the slower progression of the trough. Confidence is
increasing for another hot and humid day on Monday with highs 
remaining in the lower to middle 90s over the central to southern 
parts of the forecast area. Certainly a headline is likely to be 
needed over the weekend. 

Tuesday and Wednesday...Finally some relief to the heat with a
cold front to move through the region late Monday night into 
Tuesday morning. The ECMWF stalls the front across southern Iowa 
into the middle of the week, while the GFS brings in a surface 
high pressure system during the same time frame. 

&&

.AVIATION.../For the 06Z TAFS through 06Z Thursday night/
Issued at 1206 AM CDT Wed Jun 13 2018

Confidence is fairly high that a thunderstorm complex will blossom
from near KSUX into central IA overnight. Confidence in whether
that will result in MVFR or less conditions at any particular site
is lower however so have kept VFR VCTS wording for a start. The
convection should end later Thu morning however with higher
confidence in a return to VFR later in the day. LLWS will be
possible near KFOD in the last few hours of the valid period as 
well.

&&

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

&&

$$

DISCUSSION...Podrazik
AVIATION...Small