Scientific Forecaster Discussion
fxus64 koun 171828 aaa
Area forecast discussion...updated
National Weather Service Norman OK
1228 PM CST sun Dec 17 2017
added patchy drizzle to parts of central and north central Oklahoma
this afternoon. Remove fog mention in southern Oklahoma this
afternoon. Adjusted afternoon sky cover, mainly to increase it
north of the Red River.
cloudy and cool weather will continue across much of Oklahoma this
afternoon. Some sunshine will occur this afternoon in western
North Texas and far western Oklahoma.
Added drizzle mention based on the latest ktlx radar imagery
depicting light echoes near the radar site in the Oklahoma City
area. This drizzle may continue and slowly push northward this
Fog potential this afternoon has decreased across southern
Oklahoma as visibilities have climbed above 5 miles near Durant,
Ardmore, Ada, and Atoka.
Sky cover this afternoon remains tricky. So far, clouds have been
slow to erode across Oklahoma. Latest models have not handle the
low level cloud cover well. The latest nam12/rap13 may be having
the best handle on these clouds which depicted a slower clearing
trend this afternoon and evening.
Dense fog potential tonight into Monday morning remains a concern
and will continue to look into this possibility, especially east
of an Altus to Enid line.
Previous discussion... /issued 1153 am CST sun Dec 17 2017/
aviation discussion for 18 UTC tafs is below.
have very low confidence with the tafs in the next 24 hours.
Vlifr conditions are possible at many sites after 00 UTC.
Before 00 UTC, believe MVFR/IFR ceilings (700-2500 ft agl) will
occur at most taf sites. Kokc and koun have the highest chance for
IFR ceilings. Improvement to VFR conditions can be expected
across parts of western Oklahoma and western North Texas, though
timing remains uncertain.
After 00 UTC, MVFR/IFR ceilings will likely continue to erode
west to east across Oklahoma and North Texas, though the timing
remains uncertain. Once ceilings move out of a given location,
much worse conditions with br/fog will likely form, mainly east of
kend-klts. Went with vlifr conditions forming at kokc, koun,
kpnc, ksps, and klaw 08-11 UTC where confidence of occurrence
is moderate. These sites may go below Airport minimums. Not sure
on how quickly the vlifr conditions form, which may be as early as
01 UTC. A slow improving trend may occur after 16 UTC. Br/fog is
possible across western Oklahoma taf sites (kcsm, kwwr, khbr, and
kgag), but did not mention due to low confidence.
Previous discussion... /issued 953 am CST sun Dec 17 2017/
added fog mention today for locations southeast of a Waurika to
Pauls Valley to Holdenville line. Added patchy fog mention tonight
into Monday morning east of a Medford to Enid to Lawton to
Henrietta, Texas line. Lowered afternoon highs today east of a
Medford to Enid to Lawton to Henrietta, Texas line. Removed
drizzle mention today. Adjusted sky cover today, generally to
cloud cover will be stubborn to erode today, especially east of a
Medford to Enid to Lawton to Henrietta, Texas line where low
levels are quite moist from rainfall that occurred last night and
early this morning. Fog, possibly dense, is another concern east
of this line, especially tonight into Monday morning.
Latest observations at of 945 am depicted visibilities 1 to 3
miles from Ardmore to Durant to Ada to Atoka. With weak low level
southerly winds and increasing low level moisture advection
combined with a very low sun angle, think this fog will be slow
to erode during the day today and may actually expand northward.
Thus, added mention of fog in these areas today.
Dense fog (visibilities 1/4 mile or less) may become a big
concern tonight into Monday morning east of a Medford to Enid to
Lawton to Henrietta, Texas line, including the Oklahoma City,
Ponca City, Stillwater, Pauls Valley, Ardmore, Durant, and Atoka
areas due to abundant low level moisture with surface dewpoints in
the 40s and light generally southerly winds. The 09 UTC hrrrx
indicated this potential. Not sure how widespread or dense the fog
will become, especially as cloud cover 300-2000 ft above ground level may not
erode and limit radiational cooling. However, if clouds clear
tonight, dense fog would be possible in these areas. There could
be a small chance of freezing fog as well with temperatures
approaching 32f tonight in these areas, assuming skies clear and
allow for sufficient radiational cooling. Will closely monitor.
Cloud cover and fog will keep temperatures from rising much
east of a Medford to Enid to Lawton to Henrietta, Texas line today,
thus lowered them thinking temperatures will not get out of the
40s. West of this line, some clearing should occur this afternoon
and allow temperatures to rise into 50s and lower 60s in western
Do not think any more light rain/drizzle will occur today due to
the lack of deep moisture and due to large scale mid and upper
level subsidence over Oklahoma and North Texas.
Products will be updated shortly.
Previous discussion... /issued 642 am CST sun Dec 17 2017/
added mention of patchy drizzle to central Oklahoma this morning.
small area of drizzle visible at the lowest returns nearest ktlx
this morning. Additionally, a few reports of drizzle have come in
this morning. Observations at okc and Norman are for light fog,
but mist/drizzle are the more likely culprit. Will leave the
drizzle mention in through sunrise.
Previous discussion... /issued 551 am CST sun Dec 17 2017/
17/12z tafs. IFR/LIFR conditions expected to continue at most
terminals through at least 16z, with slowest improvement across
central into north-central Oklahoma thereafter. VFR evolution
expected across western Oklahoma down to ksps 15-18z with MVFR
likely to linger across kokc/koun up to kpnc through the
afternoon. In these areas, will keep the MVFR conditions late
today through end of forecast with potential for MVFR to IFR
conditions near and east of weakening surface trough.
Previous discussion... /issued 426 am CST sun Dec 17 2017/
clouds will be slow to clear today across the eastern half of
Oklahoma, east of weakening boundary that will try to bring somewhat
drier air into western parts of Oklahoma and western North Texas.
Southern and central/eastern Oklahoma will remain dominated in
mainly south and southeast flow next few days which will keep a
marginal threat for fog and stratus each morning Monday through
Thursday, until a strong cold front passes over the region during
the day Thursday. Ahead of this cold front, there will be chances
for rain late Monday through Tuesday night. The ecm, which has
been the most aggressive model with precip, is trending toward the
more progressive and drier GFS and NAM. Greatest chances for rain
will be over southeast Oklahoma Tuesday afternoon/evening as
height falls spread quickly over northern Texas.
Still looks like at least elevated fire weather on Thursday,
primarily across southwest Oklahoma and western North Texas where
drier and warmer conditions will be seen ahead of the front.
Although it will be breezy ahead of the cold front, northerly
winds behind the front will be much stronger.
The highest impacts through the forecast period will be potential
for Post frontal precipitation. All models have trended less
aggressive with wintry precipitation and this makes sense given
the drier meridional flow regime. We can still see respectable
snow accumulations with this pattern, but given the more
progressive S/wvs and developing large northeast cyclone, looks
mainly dry and quite cold to end 2017.
Preliminary point temps/pops...
Oklahoma City OK 49 40 62 45 / 10 0 0 10
Hobart OK 53 31 60 41 / 0 0 10 10
Wichita Falls Texas 59 39 63 47 / 0 0 10 10
gage OK 51 27 62 36 / 0 0 0 0
Ponca City OK 50 35 61 41 / 10 0 0 0
Durant OK 49 43 62 51 / 10 0 20 30