Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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172
FXUS64 KOUN 241038
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
538 AM CDT Mon Apr 24 2017

.DISCUSSION...
Aviation discussion for the 12 UTC TAFs is below.

&&

.AVIATION...
VFR conditions are expected to continue.

Will add non-convective low level wind shear before 15 UTC at a
few locations as confidence of occurrence is rather high.
Non-convective low level wind shear will again be possible after
01 UTC at many sites, but will not mention due to lower confidence
of occurrence.

MBS

&&

.PREV DISCUSSION... /issued 355 AM CDT Mon Apr 24 2017/

DISCUSSION...
Severe potential Tuesday night into early Wednesday mainly east
of I-35 then severe thunderstorm and heavy rainfall/flooding
potential Friday through Sunday are the forecast challenges of
the day.

Today, sunny, breezy, and warmer conditions are expected. Some
gusts may approach 40 mph in western Oklahoma, but think most
gusts will stay just below 40 mph so no Wind Advisory is expected
to be issued. MOS guidance highs in upper 70s to mid 80s seemed
reasonable and were accepted.

Tuesday, even warmer conditions are expected compared to today.
MOS highs appeared to be too cool based on raw model 925/850 mb
temperatures, so went several degrees above them. Model 925 mb
temperatures +30 to +33C across western north Texas would yield
highs in the mid to upper 90s if mixed dry adiabatically to the
surface which would not be too far from records for this time of
year. Think that the cap will remain too strong for storm
formation before 7 pm, though mid and high level cloud cover may
increase by late afternoon. The hot and dry conditions may elevate
fire weather concerns across western north Texas and southwestern
Oklahoma during the afternoon and early evening hours.

Tuesday night, will monitor for the potential of strong to severe
thunderstorms. Still appears locations near and east of I-35 have
the highest potential for severe storms capable of mainly large
hail to due strong shear (0-6 km bulk shear 40-70 kt), plenty of
potential instability (MUCAPE 1500-3000 J/kg), and where surface
dewpoints are forecast to rise into the 60s. First storms would
likely form near the front somewhere near the Kansas Oklahoma
border close to or just after 7 pm. The greater chance for severe
storms will likely stay across northeastern Oklahoma where
capping will be weakest. If storms occur near and east of I-35,
locally heavy rainfall and damaging wind gusts could be also
possible. Another area of weaker storms may form near or just
behind the cold front in northwestern Oklahoma due to sufficient
nearby moisture and increasing lift from an approaching mid/upper
disturbance. Cooler conditions will move into the area behind
the front.

Wednesday, much cooler conditions can be expected. There are some
indications morning storms could linger across the southeastern
half of Oklahoma, while weak light rain showers may linger mainly
across northwestern Oklahoma. The 00 UTC NAM12 even suggested
that a few snowflakes could mix in with any light rain across
northwestern Oklahoma, though this model appeared to be a cold
outlier. A slow clearing trend is expected by the afternoon hours.
Highs will be well below average and should not get of the 50s
across parts of central and northern Oklahoma.

Wednesday night through Thursday night, most latest models have
been suggesting a drier weather pattern during this time frame.
Moisture and elevated instability are expected to slowly return
by Thursday night which could allow for some elevated
thunderstorms with hail and heavy rainfall to form across southern
Oklahoma if the latest 00 UTC ECMWF model verifies. Confidence of
storms/rain occurring during this time frame remains quite low.
Highs on Thursday remain uncertain as well, though should be
higher compared to Wednesday.

Friday through Sunday, chances for showers and thunderstorms are
expected to increase during this time frame, though exact details
remain very uncertain. A warm front may lift northward and could
serve as a focus for shower and thunderstorm development late on
Friday. Forecast model instability (MUCAPE 2000-5000 J/kg),
moisture (surface dewpoints in the 60s to lower 70s), and shear
(0-6 km shear 40-70 kt) will be near climatological maximums for
this time of year which could support significant severe storms
and very heavy/excessive rainfall that could result in flooding.
Strong capping south of the warm front Friday and Friday night
could limit storm development in the warm sector. The stronger
lift and forcing appears to occur north of the warm front Friday
night as the low level jet increases then across much of Oklahoma
and north Texas Saturday into Saturday night as the mid/upper low
approaches. Most models have been hinting that a slow moving line
of storms with very heavy rainfall could form and slowly move
eastward Saturday and Saturday night. Rain chances may decrease
late Saturday into Sunday as the system moves northeast of the
area. Will continue to monitor to see how this system evolves over
the next few days.

MBS

CLIMATE...
Highs on Tuesday, April 25, 2017 may be near record levels. Here
are the records.

Oklahoma City...91 degrees...set in 1939
Wichita Falls...98 degrees...set in 2012

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  77  59  87  50 /   0   0  10  30
Hobart OK         80  59  89  50 /   0   0  10  20
Wichita Falls TX  81  62  94  57 /   0   0   0  10
Gage OK           84  57  81  43 /   0   0  10  50
Ponca City OK     77  57  83  48 /   0   0  10  50
Durant OK         77  58  85  64 /   0   0   0  20

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&

$$

10/99/17



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