Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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303
FXUS64 KOUN 221018
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
418 AM CST Thu Feb 22 2018

.DISCUSSION...
The big challenge for this forecast is how quickly will shallow
arctic airmass retreat/mix out, and implications for precipitation
type. Early this morning areas of freezing drizzle continue across
the area. Temperatures are in the mid to upper 20s at most
locations, except far southeast sections of the forecast area
where temperatures were right around freezing. Google maps traffic
data continued to indicate travel impacts from yesterday`s sleet
and freezing rain, and the ongoing freezing drizzle. Outside our
office, a light glaze has formed on sidewalks over top of sleet
that feel yesterday.

The shortwave trough now clearly seen in the Four Corners region
will move northeast quickly and in response, another isentropic
ascent precipitation event is expected today. Models agree on
saturation/ascent on 290-300k surfaces moving through from mid
morning in the southwest to late afternoon in the east. This will
be sufficient for light precipitation amounts averaging around
0.10". This will occur over residual arctic air mass which hasn`t
been modeled particularly well. Current observations and recent
model performance would suggest temperatures will stay below
freezing across much of the area this morning, warming above
freezing first in our southeast counties, and then eventually
elsewhere by evening. Model forecast soundings do show weak
elevated instability and this could result in locally higher
QPF/icing amounts. If more widespread/heavier precipitation were
to occur, this could help mix down warmer temperatures aloft and
result in a rise in temperatures above freezing more quickly.

It`s worth noting that some areas already have around a tenth of
an inch or slightly more of ice accumulation on elevated surfaces
and additional accumulation could push a quarter inch total in
some areas which could be enough weight for some tree/powerline
issues. Widespread impacts from ice accumulation are not expected,
however. Travel difficulties will continue to be the main concern
through the morning and for some areas into the afternoon.

Winds will finally become southeasterly first in the west late
this afternoon and then across the whole area tonight.
Temperatures should be steady or slowly rise overnight and by
Friday afternoon several locations will reach 50 degrees. By this
time, yet another precipitation event (all rain this time) is
expected as broad area of ascent increases within entrance region
of strengthening upper level jet to our north. As another
shortwave trough approaches from the west during that time, low
level southeasterly flow and moisture advection could bring
drizzle to much of the area overnight. Once large scale ascent
reaches us later in the night through the first part of Saturday,
showers and a few storms are expected. This will be our final
round of rain until a low probability event happens Tuesday into
Wednesday as another southwestern trough moves our way.
Differences in medium range deterministic guidance and not much
help from the ensembles caused us to keep probabilities low for
now.

BRB

&&

.FIRE WEATHER...
Strengthening downslope flow, breezing, warmer, and dry conditions
are expected to increase fire spread potential this weekend.
Elevated to near critical conditions may develop across western
Oklahoma and western north Texas. ERC-G values are expected to be
on the high end up normal up to around the 75th percentile.

BRB

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  34  33  50  43 /  70  10  60  40
Hobart OK         34  31  51  43 /  70   0  30  30
Wichita Falls TX  35  33  47  46 /  80   0  70  50
Gage OK           35  28  54  40 /  20   0  10  20
Ponca City OK     34  31  50  43 /  60  10  10  40
Durant OK         40  40  52  50 /  80  30  90  80

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Winter Weather Advisory until 3 PM CST this afternoon for
     OKZ004>031-033>040-044-045.

     Winter Weather Advisory until noon CST today for OKZ032-041>043-
     046>048-050>052.

TX...Winter Weather Advisory until 3 PM CST this afternoon for
     TXZ083>090.

&&

$$

09/12



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