Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 182342
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
641 PM CDT Thu Aug 18 2016

...Updated for 19/00Z Aviation Discussion...

.SHORT TERM.../Tonight/
Issued at 402 PM CDT Thu Aug 18 2016

Main concern tonight is storms, and even severe, potential over
far northern Iowa. The latest radar trajectory brings the current
severe storm in south-central Minnesota into southeast Minnesota
to northeast Iowa. This is coincident with the instability
gradient oriented in this fashion as well as the 0-3km bulk shear
vector. The latest HopWRF and operational HRRR are handling the
convective trends fairly well and keep storms northeast of the
CWA. Still a potential for something to develop further south if
off the outflow boundary, but if anything does, it`ll remain
confined to far northern Iowa this afternoon into the early
evening. Kept a sliver of pops going tonight in this location. The
shortwave looks to move east of the state past 06z leaving a dry
period overnight into tomorrow morning.


.LONG TERM.../Friday through Thursday/
Issued at 402 PM CDT Thu Aug 18 2016

Friday into Friday night...Cut back on pops during the morning
hours per the slower progression of the cold front tomorrow
afternoon into the evening. Mainly went completely dry across the
south to southeast until the late afternoon hours. Potential for
some WAA convection to develop ahead of the main trough/cold front
during the afternoon hours Friday. This looks to be over west to
northwest Iowa. Storms will transition and spread southeast past
21z Friday and continue to spread over much of the forecast area
b/t 00-06z Saturday. Some lingering storms anticipated b/t 12-18z
Saturday, before pushing into eastern Iowa Saturday afternoon.

Severe potential looks to mainly be limited to damaging wind
threat and possibly some brief hail with a decent amount of
instability building into the state ahead of the trough. Deep
layer shear ranges from 25 to 30 knots with low level shear very
weak. Moderately unstable mid-level lapse rates and DCAPE in the
800-1200 J/kg range across the area. Low confidence with anything
other than the damaging wind threat attm. However, heavy rain
threat is the other concern with warm layer cloud depths ranging
from 13kft to 14kft, PWATs around 1.5 inches, and strong moisture
transport into the area. The isolated flash flood threat exist
and now confident to hoist a watch attm.

Saturday through Thursday...Much cooler air mass settles into the
state on Saturday and last through early next week. 850mb
temperatures drop as low as +10C Saturday afternoon with decent
CAA for late August. Increased winds throughout the day Saturday.
Otherwise, high pressure dominates over the region until another
cold front sweeps across the state late Tuesday into Wednesday.
Models are in decent agreement with timing and placement of QPF,
and trended toward a drier forecast by Wednesday night.

&&

.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 641 PM CDT Thu Aug 18 2016

VFR conditions will prevail through the TAF period. Mainly expecting
a wind shift tonight and tomorrow morning. A cold front will bring
chances of SHRA/TSRA Friday afternoon and evening...which has been
reflected in the TAFs.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

SHORT TERM...Podrazik
LONG TERM...Podrazik
AVIATION...Zogg



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