National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDMX Received: 2018-02-09 11:53 UTC


720 
FXUS63 KDMX 091153
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
553 AM CST Fri Feb 9 2018

.SHORT TERM.../Today through Tonight/
Issued at 410 AM CST Fri Feb 9 2018

Obvious primary concern will be precip trends and associated 
headline decisions this morning. The band of snow from Thursday 
evening was phased with decent H5/H6 frontogenetic Fn response and
low static stability above per +/- zero H5/H4 EPV. The 
banding/frontogenesis has fallen apart recently however, but 
spotty patches of stronger echoes upstream suggest low stability 
remains in place and is likely creeping eastward crossing the MO 
river per H7/H5 EPV <=0. Recent RAP and HRRR runs seem to have a 
good handle on reality with a few weaker bands pushing south and 
east through the morning in the broader, departing warm advection.
Visibilities are now generally several miles with just a few 
lingering 1-2sm reports so additional accumulations should be 
minimal at this point, <=1 inch. Thus have scaled headlines back 
quite a bit in time and space per the following.

* All headlines along and NE of a Denison-Pocahontas-Forest City 
  line where snow has ended and amounts relatively low have been 
  canceled
* Kept the Winter Storm Warning going along Highway 20 from
  Webster City toward Waterloo where light snow is still in
  progress but shallow blowing snow may be a concern in the
  heaviest snow accums
* Downgraded western edge and Highway 30 warning sections to 
  advisory where either no additional snow is anticipated or 
  amounts were lighter than expected but blowing snow may be an 
  issue.
* Cancel portions of advisory I80 and south
* All remaining headlines will end at 12z per RAP/HRRR simulated 
  reflectivities and be replaced by an SPS

Later today the aforementioned lower stability may still produce 
some isolated snow showers, which appear more convective in nature
per the radar mosaic. Any accumulations should be less than an 
inch and sporadic. Looking ahead into the early evening hours 
the next surge of forcing in the Pacific NW short wave train along
the jet should cross the MO river into IA. Much of this forcing 
will be mid level, and while there will be fairly deep moisture, 
QG subsidence and cold advection is in place 1-3km. This mid level
UVM will be coincident with a somewhat deeper dendritic growth 
zone however so 1-3 inch accums will be possible south half by 
12z due to a prolonged light snow.

.LONG TERM.../Saturday through Thursday/
Issued at 410 AM CST Fri Feb 9 2018

The overall pattern and precip mechanism from tonight will linger
into the start of this period with additional lingering light 
snow possible southeast into Saturday Night with more minor accums
possible. Farther north cold temperatures will be the main theme 
through the weekend with lows in the single digits above and below
zero and far northern sections flirting with headline criteria 
/-20F/ wind chills once again.

The outlook into the next work week looks predominately dry and 
cool with Iowa still influenced by the broad mean central CONUS 
trough. There are some subtle precip chances late in the period, 
but these look minor and confidence is low. Models are uncertain 
on the evolution of the midweek Baja cutoff and its interaction 
with Pacific NW short waves of varied strength.

&&

.AVIATION.../For the 12Z TAFS through 12Z Saturday morning/
Issued at 552 AM CST Fri Feb 9 2018

Conditions are quite variable across Iowa at 12z due to snow south
and patchy lower ceilings elsewhere resulting in anywhere from VFR
to IFR conditions. Conditions are expected to gradually transition
to mainly VFR later today, but additional snow is expected over
the south half of the state into tonight. This will likely bring
IFR conditions to KDSM and KOTM, driven more by visibilities than
ceilings. 

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST early this morning for 
IAZ007-016-017-024>027-034-035-045>050.

Winter Storm Warning until 6 AM CST early this morning for 
IAZ028-036>039.

&&

$$

SHORT TERM...Small
LONG TERM...Small
AVIATION...Small