Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 190449
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
1049 PM CST Mon Feb 18 2019

.AVIATION...
TAFs 1906/2006...


VFR ceilings will prevail through at least 12-14Z with a breezy
northeast wind. As precipitation overspreads Oklahoma and western
north Texas, ceilings will become MVFR at most sites (by 18Z).
With the exception of SPS, most of the precipitation will be snow
and sleet during the late morning and early/mid afternoon. As mid-
level drying occurs, freezing rain and or drizzle is expected.
Ceilings should lower to IFR by mid afternoon and may last through
6Z Wednesday. Snow may reduce visibility to below 1 mile during
the early to mid afternoon.

&&

.PREV DISCUSSION... /issued 538 PM CST Mon Feb 18 2019/

AVIATION...
Light returns associated with an area of mid-level clouds,
will continue northeast through the evening. Mid clouds will
again increase overnight through early Tuesday as forcing
increases ahead of a trough to the west. By mid to late morning,
precipitation will begin, mainly in the form of snow, sleet and
some freezing rain. As mid-level drying occurs and or warming at
lower levels, some light freezing rain/drizzle may become the
predominant precipitation type by late Tuesday afternoon. It`s
possible that mainly freezing rain will occur at SPS through the
event.

MVFR ceilings Tuesday morning should lower to IFR Tuesday
afternoon. Snow will certainly lower visibility to at least 1 to
2 miles at times perhaps lower.

PREV DISCUSSION... /issued 347 PM CST Mon Feb 18 2019/

DISCUSSION...
Main forecast challenge this period focuses on winter weather
expected tomorrow into tomorrow night. Overall, models have been
fairly consistent in showing a quick shot of strong warm air
advection in mid levels that will move northward across the area
late tomorrow morning into tomorrow afternoon. This will likely be
when most areas receive the bulk of their precipitation totals,
but exactly what form precipitation falls in is, as usual,
somewhat uncertain at this point. Forecast soundings show the
strongest warm nose up around 750 mb, with temperatures in this
layer above freezing most areas except across northwest OK. A
deep subfreezing layer is then shown below this layer for most
areas outside of southeast OK. Altogether this would suggest
mostly snow across northwest Oklahoma with this initial wave, a
mix of sleet and freezing rain for areas near and southeast of the
I-44 corridor, with mainly rain for southeast OK and portions of
our northwest Texas counties. After this initial wave of
precipitation, models then show drying within the dendritic
growth zone later tomorrow afternoon as a dry slot works into the
area. This would suggest most locations would transition to either
drizzle or freezing drizzle tomorrow afternoon into the evening,
depending on surface temperatures.

As far as forecast totals, model QPF is generally light, with
widespread 0.10-0.25" amounts across western and central OK and 0.25-
0.50" across southeastern OK. As of now it appears the subfreezing
temperatures will avoid the area of heaviest precipitation across
southeast OK, keeping wintry precip totals light but still enough to
cause significant travel disruption, especially for areas that see
ice. We are forecasting snow totals of 1-3" for northwest Oklahoma
down to a trace of snow along the I-44 corridor. Ice amounts could
reach near a tenth of an inch along the I-44 corridor, with a trace
to close to 0.05" of ice accretion to the southeast of this zone.
Uncertainty still remains regarding exact totals as a few degrees
difference in temperatures aloft or at the surface could have
significant impacts on snow/ice amounts. Greatest uncertainty is
across the I-44 corridor where a slightly less pronounced warm
nose could result in more snow and less ice than currently
forecast. Likewise, areas across southeast Oklahoma will be right
around the freezing mark and slightly cooler surface temperatures
than forecast would mean higher ice totals. Either way, travel
impacts should be expected beginning late tomorrow morning, and
the evening commute will likely be very messy. All of the
precipitation should be clear of the region around or slightly
after midnight, with temperatures remaining in the 20s and 30s for
lows.

After this system moves out, western troughing looks to reload
bringing another system towards the area Friday into Saturday. This
system looks warmer and expect all liquid precipitation this time
around. Forecast soundings show some CAPE as well, so included a
mention of thunder during the day on Saturday. A few strong storms
may be possible but for now it looks like the greater threat for
this will be east of our area. Expect temperatures to exhibit a
warming trend as the system approaches, with many areas seeing 60s
for highs by Saturday. Temperatures don`t look to cool much
behind this system, with highs remaining in the 50s and 60s.

Ware

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  25  30  25  43 /   0  80  60   0
Hobart OK         23  30  22  47 /   0  60  40   0
Wichita Falls TX  30  34  29  54 /  10  90  20   0
Gage OK           15  26  17  40 /   0  50  60   0
Ponca City OK     22  31  25  37 /   0  80  80  10
Durant OK         32  36  31  52 /   0  90  40   0

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Winter Weather Advisory from 6 AM Tuesday to midnight CST
     Tuesday night for OKZ004>042-044>046.

TX...Winter Weather Advisory from 6 AM Tuesday to midnight CST
     Tuesday night for TXZ083>090.

&&

$$


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