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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS64 KOUN 202318
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
618 PM CDT Tue Apr 20 2021

...New AVIATION...

.SHORT TERM...
(This evening through Wednesday)
Issued at 206 PM CDT Tue Apr 20 2021

Sky should continue to clear across the region from northwest to
southeast late this afternoon and early evening, and gusty north
wind will also subside. With dry air in place, dewpoints primarily
in the bottom half of the 20s, good radiational cooling conditions
will exist at least through the evening hours. Thereafter, mid-high
level cloud cover will increase which will be make low temperature
forecasts difficult. Majority of the model guidance has the thickest
cloud cover over west/southwest portions of Oklahoma and western
north Texas after midnight, and farther north and east into central
Oklahoma toward daybreak Wednesday. This will leave far north
central and southeast parts of Oklahoma with the longest duration of
decent radiational cooling conditions. These are the areas where
widespread frost is expected, with the cloud cover expected to
temper that development. Still think a majority of the forecast area
will see a freeze tonight/Wednesday morning, but the increase in
cloud cover will likely keep a majority of the forecast area from
experiencing a hard freeze (temps 28 deg or colder for at least a
few hours). Some of the normally colder locations (low lying areas)
may still see temperatures briefly dip into the middle 20s. With
this and previous forecast cycles, we are forecasting many areas
across the southern half of Oklahoma and western north Texas to
break record low temperatures, including OKC, LAW, and SPS which
somewhat surprisingly all have the same record for tomorrow, 34 deg.

After a cold start tomorrow, still looks like temperatures will
recover into the 50s and 60s despite sporadic mid-high level cloud
cover. The southerly flow, which will allow moisture to increase
ahead of our next weather system, will commence late in the day.

&&

.LONG TERM...
(Wednesday night through next Monday)
Issued at 206 PM CDT Tue Apr 20 2021

As the surface ridge continues eastward, return flow will strengthen
Thursday night into Friday ahead of our next system. Significant
moisture advection is forecast to occur ahead of a surface low and
dryline that will sharpen over the TX panhandle during the day
Friday. Moisture advection and degree of surface heating will be
key to surface-based warm sector thunderstorm development ahead
of the dryline, as a significant cap is evident on forecast model
soundings. The best chance for this to occur will be across
southern OK closer to the deeper moisture. Elevated convection may
also be possible as a cold front moves southward across northern
and central OK Friday evening and forcing from the upper wave
arrives. We are still several days out, but given the forecast
environment storms across southern OK would be capable of damaging
hail and strong wind gusts, with a low tornado risk as well if
surface-based storms can develop. The severe risk across
northern/central OK would be most likely confined to a hail threat
due to the elevated nature of the convection.

This cold front will clear the area by Saturday morning, but the
airmass behind the front will not be particularly cold. Highs
Saturday will still reach into the upper 60s to low 70s. Upper
ridging will build over the area Sunday into Monday, with warming
temperatures and breezy south winds. Another trough is then
forecast by most models to affect the area by next Tuesday, with
uncertainty surrounding timing and the degree of moisture return
across our area. At this point, the greatest risk for
thunderstorms and any associated severe weather looks to be
focused across the eastern half of OK.

Ware

&&

.AVIATION...
(00Z TAFS)
Issued at 613 PM CDT Tue Apr 20 2021

VFR conditions are expected through the TAF period. Gusty
northerly winds will slowly decrease this evening, becoming
variable tomorrow throughout the day. An increase in mid-level
clouds are expected early tomorrow morning.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  31  59  42  56 /   0   0   0  20
Hobart OK         30  59  41  55 /   0   0   0  20
Wichita Falls TX  32  61  44  59 /   0   0  10  20
Gage OK           27  57  37  55 /   0   0  10  10
Ponca City OK     29  58  37  54 /   0   0   0  30
Durant OK         32  62  45  63 /   0   0  10  10

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Freeze Warning from 1 AM to 9 AM CDT Wednesday for OKZ004>048-
     050>052.

TX...Freeze Warning from 1 AM to 9 AM CDT Wednesday for TXZ083>090.

&&

$$

SHORT TERM...11
LONG TERM....08
AVIATION...13