Scientific Forecaster Discussion
fxus64 koun 200315
Area forecast discussion
National Weather Service Norman OK
915 PM CST Sat Jan 19 2019
a thin band of high clouds over western Oklahoma will gradually
erode and/or move eastward tonight. By early Sunday morning, high
clouds will again increase from the west. A lower cloud deck over
eastern Oklahoma will also erode and move east overnight.
Meanwhile, surface high pressure will bring a period of relatively
light to calm winds tonight with a south wind returning over
northwestern Oklahoma by sunrise Sunday. Therefore, rather decent
radiation cooling will result in rather cold overnight low
temperatures. Other than adjusting overnight lows down a few
degrees over southwest Oklahoma and North Texas the forecast is
in good shape.
Previous discussion... /issued 621 PM CST Sat Jan 19 2019/
north wind will diminish this evening and become light late
tonight. South wind will become gusty Sunday afternoon in western
Oklahoma. VFR conditions are expected.
Previous discussion... /issued 248 PM CST Sat Jan 19 2019/
a progressive amplified upper flow pattern is expected the next
several days. Robust moisture return preceding the next few waves
is not expected so precipitation chances are minimal for at least
the next week. Periodic windy conditions will occur, the first of
which will start Monday as high-level flow strengthens across The
Rockies forcing Lee pressure falls. South winds 20-30 mph will be
common by Monday afternoon. Veering winds will support a
substantial warming, and western portions of the area could reach
or exceed 70 degrees.
Increasing flow aloft signals the approach of the next trough.
Despite response of surface winds, upstream moisture is limited.
Thus, widespread/organized precipitation will not occur. The best
chance will be with 1) initial low level moistening/saturation and
low level confluence yielding some drizzle late Monday
night/early Tuesday, and 2) mid-level forcing as trough axis
passes possibly coupled with possibly just enough moistening for
brief light precipitation band Tuesday afternoon. This trough
will force a cold front through northwest Oklahoma Tuesday
morning, and through the rest of the area by the end of the day.
Diurnal heating will probably not be enough to offset cold
advection so temperatures may fall throughout the day.
For the rest of the forecast, our temperatures generally reflect a
consensus of guidance and are not very far from climatology.
Confidence in our temperature forecast is below average given the
highly amplified flow pattern that develops with significant
negative 500-mb anomalies to our east and significantly positive
anomalies to our west. Periodic cold surges with embedded
shortwave troughs should primarily be east of our area, but a
trend toward a broader longwave and/or more amplified embedded
shortwaves could bring colder temperatures to our area. Likewise,
a trend toward weaker or more eastward placement of eastern trough
could yield more veered flow and warmer conditions for US.
Deterministic and ensemble spread is significant enough to not
have confidence in either scenario at this time.
Any shortwave within northwesterly flow late week into the weekend
is unlikely to produce precipitation given the lack of opportunity
for deep moisture return and pwats remaining below climo.