Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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129
FXUS64 KOUN 250012
AFDOUN

Area Forecast Discussion
National Weather Service Norman OK
712 PM CDT Fri Mar 24 2017

.DISCUSSION...


&&

.AVIATION...
Light showers will move east across central Oklahoma this evening
underneath an upper low pressure system. Gusty southwest winds
will become north in central Oklahoma late this evening when a
front passes northwest-to-southeast. Gusty winds will slowly
diminish Saturday morning. A period of MVFR ceilings will sweep
across the northern two-thirds of Oklahoma overnight with the
upper storm.

&&

.PREV DISCUSSION... /issued 244 PM CDT Fri Mar 24 2017/

DISCUSSION...
Closed vertically stacked low is evident in radar and satellite
observations over the eastern Texas Panhandle. The presentation in
water vapor channel is particularly impressive and a well-defined
mid-level intrusion of dry air is seen moving across central
Oklahoma at this time. As deep mixing into this dry area
continues, surface dew points continue to fall and many locations
are already experiencing relative humidity values in the teens
already early this afternoon. The combination of dry air (dries
across central Oklahoma beneath the dry slot) and strong
southwesterly winds leads to continuation of fire weather
concerns. Near critical to critical fire weather conditions will
persist into the evening and so the Red Flag Warning continues.

Further west, with the main low circulation, visible satellite
and surface observations show fairly high based cumulus and
strato- cumulus. Radar shows bands of showers as well. Instability
to the east is meager owing to deep mixing/drying and so as the
low progresses east, much of western Oklahoma should not
experience more than passing light showers. Although, some
momentum transfer from showers could lead to brief bursts of
stronger winds and evaporative cooling process will probably cause
a sudden drop in temperatures.

Further east, where deep mixing is occurring, veering of surface
winds have been observed. Meanwhile to the east, winds remained
slightly backed with low level moisture still flowing north-
northwest into the far east and especially northeast portion of
the area. There may be an opportunity for deeper convection across
this area, particularly as fairly dramatic mid-level cooling with
the deep low approaches. Forecast soundings from RAP suggest
around 700 j/kg MLCAPE and veering low level winds and deep layer
shear supportive of storm organization/persistence. Thermal
profiles and distribution of CAPE, as well as character of the
CAPE within the hail growth zone would be supportive of marginally
severe hail, although some storms may be capable of fairly
sizeable quantities of smaller hail. North-central Oklahoma is
where the greatest threat of strong/severe thunderstorms exists.

Further south, significant mid-level moistening in close proximity
to the deep low could result in a period of high based showers,
and at least a low probability of measurable amounts as far south
as around I-40.

Fairly short wavelength between departing upper low and the next
shortwave/closed low raises some question on magnitude of moisture
return. Nevertheless, moisture seems sufficient to support at
least modest instability and thunderstorm formation east of a
dryline Sunday afternoon, with upscale growth likely into the
evening as deeper moisture advects in. The severe threat will
exist including the possibility of supercells. The details with
regard to low level moisture, low level shear, etc., will need to
be better refined before we have confidence on convective hazards.

Another concern Sunday is dry windy conditions behind the dryline
Sunday. Fuels visually are becoming green especially along roads
in ditches, but open fields still have plenty of dormant fuels
and ERC-G values are on the very high end of normal. Given this,
at least elevated to near critical conditions seem likely across a
good portion of the area. Mainly southwest Oklahoma and western
north Texas.

The active pattern continues into next week. Confidence is growing
on a much needed rain event from late Tuesday into early Thursday.
Timing of the highest precipitation probabilities and amounts will
need to be refined as ensemble spread lessens and determinist
guidance comes into better agreement.

BRB

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK  49  67  47  80 /  30   0   0  30
Hobart OK         45  70  47  80 /  20   0   0  10
Wichita Falls TX  49  72  50  85 /  10   0   0  10
Gage OK           41  69  44  76 /  20   0   0  20
Ponca City OK     48  62  43  75 /  40  10   0  40
Durant OK         52  71  49  81 /  10   0   0  40

&&

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

$$

04/09/09



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