000
FXUS63 KDVN 212301
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
501 PM CST Fri Feb 21 2020

...00Z AVIATION UPDATE...

.SYNOPSIS...
Issued at 244 PM CST Fri Feb 21 2020

High pressure moved south of the area today as southwest winds
brought warmer, more moist air to the area. This trend is
expected to continue through the period with warming temps. This
afternoon, the entire area was above freezing, leading to melting
snow.

&&

.SHORT TERM...(This Evening through Saturday)
ISSUED AT 244 PM CST Fri Feb 21 2020

Key Messages:

1. Above average temperatures with clear skies expected Saturday.

Discussion:

Quiet weather again from a sensible weather perspective with
temperatures being the main story in the period. Tomorrow could
have a wide variety of temperatures based on if there is snow on
the ground or not. Most models have areas that don`t have snow
reaching well in to the 50s. If there is snow, temperatures try to
push 40.

.LONG TERM...(Saturday Night through Friday)
ISSUED AT 244 PM CST Fri Feb 21 2020

As mentioned yesterday the flow aloft across the northern hemisphere
will be re-amplifying next week and going from three to four waves.
This amplification will allow continental polar air to drop into the
Midwest for the end of February and into early March producing below
normal temperatures. Run-to-run continuity of the models may briefly
drop as a result of the pattern change.

Saturday night and Sunday
Assessment...high confidence

Dry and warmer than normal temperatures will be seen across the
area. Attention then turns to the next storm system.

Sunday night through Wednesday night
Assessment...high confidence on one or more storm systems in the
Midwest. Low confidence on timing and precipitation type/amounts.

The ECMWF/CMC global/UKMET continue to slow down the arrival of the
next system but the WRF/GFS not as much. Additionally there
continues to be a slow southward trend in the track of the system.
This southward trend makes sense given the low amplitude longwave
trof around 90W.

Like yesterday most of the models suggest that there will be a sharp
gradient with precipitation on the north and west side of the system.

Thus for Sunday night into Monday there seems to be some agreement
that precipitation will be mainly rain with a a rain/snow mix
developing Monday.

The model consensus has slight chance to chance pops Sunday evening
south of an Ottumwa, IA to Macomb, IL line and then south of highway
30 after midnight. The possibility does exist that most of the area
will remain dry until sunrise Monday.

For Monday the model consensus has slight chance to likely pops for
the entire area. If the sharp gradient in precipitation occurs on
the north and west side of the system as suggested, then areas west
of a Dubuque to Belle Plaine, IA line may remain dry.

For the Sunday night into Monday time frame any snow accumulations
would be less than an inch and be mainly on grassy and elevated
surfaces.

Monday night through Wednesday night the global models diverge
considerably with their solutions.

The CMC global and GFS maintain precipitation in the form of
accumulating snow across the area.

The UKMET quickly moves the system east of the area with late
Tuesday night through Wednesday night being mainly dry.

The ECMWF maintains precipitation in the form of snow across the
area Monday night but then brings in a strong upper low behind the
system which produces accumulating snow Tuesday into Wednesday with
snow ending Wednesday evening. The ECMWF has done a significant
change compared to 24 hours ago (in terms of the upper low) so its
solution much be cautiously questioned.

Regardless of which solution is right there will be some snow
accumulation with the upper level disturbance or low. How much is
dependent upon how the upper level system develops and evolves as
the first storm system exits the area.

Thursday into Friday
Assessment...low to medium confidence

Once the storm system departs the area a cold Canadian high will
build into the Midwest.

The model consensus has mainly dry conditions during this time
period but there will be several upper level disturbances moving
through in the flow aloft. If sufficient moisture is available for
the disturbances then there is a real possibility of snow showers
and/or flurries occurring Thursday into Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday Evening)
ISSUED AT 500 PM CST Fri Feb 21 2020

VFR conditions expected to persist through the TAF cycle. Winds will
remain from the south-southwest and gusty at times, though with less
frequency tonight, which will lead to the potential for low level
wind shear late evening and overnight as a low level jet strengthens
over E Iowa and N Illinois.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...08
AVIATION...McClure