Area Forecast Discussion
Issued by NWS Tulsa, OK

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FXUS64 KTSA 212315
AFDTSA

Area Forecast Discussion
National Weather Service Tulsa OK
615 PM CDT Sun May 21 2017

...UPDATE...

.AVIATION...
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.

VFR conditions should prevail through the period. There is a
chance of tempo MVFR visibilities in light fog toward daybreak at
BVO/FYV. The greatest TSRA potential should be after the valid TAF
period, but there is a small enough potential after 21Z at the E
OK terminals to include PROB30 groups.

&&

.PREV DISCUSSION... /Issued 325 PM CDT Sun May 21 2017/

DISCUSSION...

A very nice late May afternoon is ongoing, with surface high
pressure sitting over the region. Looking aloft, westerly flow
prevails to the south of deep troughing over central NOAM. A small
PV anomaly currently rounding the base of the larger scale upper
trough over UT, and another larger PV max diving south out of
Canada will bring changes to our sensible weather over the next 48
hours.

Low level warm advection begins tonight as 925-850 flow turns
around to the south above a cool surface layer. The latest runs of
the HRRR show some shower activity approaching the Red River
toward 12Z and can`t completely rule out a shower near Hugo so a
20 percent PoP was added to the forecast. Will expand that north
some going into Monday morning and insert slight chance thunder
with a small increase in elevated instability. Focus then turns to
the west and north for the afternoon and nighttime PoPs. Lift from
the UT PV max will aid storm development in a couple different
areas, over the central High Plains and along the surface front
over Kansas, with the activity expected to move E/SE with time.
Some of this activity could clip portions of eastern OK and/or
western AR during the late afternoon and evening hours. As was
stated yesterday, the best moisture/instability will be confined
well to the south along the stalled front over central/southern
TX, so this should keep severe weather potential pretty low.
Thunderstorm potential will be focused over in far eastern OK and
western AR on Tuesday ahead of the front as it sweeps thru.

The Canadian PV max will dive down into the mid-Mississippi valley
by the middle of the week. With the cold air aloft, there could be
a few showers over NW AR Wednesday afternoon. Below average temps
can be expected Wednesday and Wednesday night behind the front.

A fairly quick transition from NW to W to SW flow aloft will occur
by the end of the work week as mid-CONUS upper trough lifts out
and another trough digs down into the Pac NW. As a result, a quick
transition from cool and dry to warm and humid is expected. The
best chance for elevated convection with the returning front will
be north of us, as warm mid-level temps overspread our area and
will act to keep things capped. Eventually, convection organizing
along a boundary over Kansas will work its way down into our area
by the holiday weekend.

Lacy

&&

.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&

$$

AVIATION...22



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