Area Forecast Discussion
Issued by NWS Tulsa, OK

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278
FXUS64 KTSA 211140
AFDTSA

Area Forecast Discussion
National Weather Service Tulsa OK
540 AM CST Tue Feb 21 2017

.AVIATION...
CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG.
Dense fog at the eastern Oklahoma sites will improve rapidly by
around 9 am, with VFR conditions then expected for the rest of the
forecast period at the Oklahoma TAF sites. The Arkansas sites
will see occasional MVFR conditions this morning with scattered
areas of light rain. VFR conditions will then prevail this
afternoon and evening at the Arkansas sites, but conditions will
deteriorate overnight as fog develops at the Arkansas sites.

&&

.PREV DISCUSSION... /Issued 243 AM CST Tue Feb 21 2017/

DISCUSSION...

The main items of interest in this morning`s forecast are: 1) Fog
and precip chances today, 2) Temps, namely the near record warmth
this week followed by much cooler start to the weekend, 3) Winds
and fire weather concerns Wed/Thurs, and 4) Precip/thunder chances
early next week.

Dense fog has become more widespread as of the 2 am obs across
eastern Oklahoma. The mid and high cloud cleared out, which
combined with the light winds ahead of a boundary and moist
boundary layer, has allowed the fog to develop and become more
widespread. Headlines have already been issued to cover this
hazard. Mid level cyclogenesis is occurring this morning at the
tail end of what was a full latitude upper trough. Wrap-around
moisture will bring some showers to western Arkansas thru the
day, per the latest HRRRX runs, and current obs. Thus, slight
chance pops were added to cover.

With mild low level thermal fields in place behind this system, we
should see another well above average day today, especially where
there is insolation after the fog burn off. The low level thermal
ridge gradually intensifies and eventually expands east across
Oklahoma by Thursday. This should result in some record or at
least near record warmth Thursday ahead of a cold front. This cold
front will push thru the region Thursday night in response to a
vigorous and progressive shortwave trough aloft over the central
Plains. This front will be a dry one for a few reasons. Today`s
system is forecast to drop south into the Gulf by midweek, and
this should disrupt the flow of moisture back into the country
ahead of this system. The flow ahead of the front will tend to
veer out and thus there will not be strong convergence and lift
with the boundary either. Much cooler temps behind the front will
knock highs back by almost 30 degrees by Friday, though only to
near average for this time of year. Some sub-freezing lows are
expected over the weekend.

Strong south winds and the warm temps ahead of the strong late
week shortwave trough will raise fire weather concerns. The
strongest winds on Wednesday will be north and west of I-44, and
over all of eastern Oklahoma and northwest Arkansas by Thursday.
Stronger winds on Thursday will yield elevated fire spread
conditions.

The pattern will remain fairly active over the CONUS as we head
into next week as well. The upper jet will be situated either
overhead or fairly close, with mean upper troughing to our west.
Warm and moist advection will ensue over the Plains by late in the
weekend and into early next week. Chances for rain and storms will
increase ahead of the next progressive shortwave trough, somewhere
in the Mon or Tues timeframe next week.

Lacy

&&

.TSA WATCHES/WARNINGS/ADVISORIES...
OK...Dense Fog Advisory until 10 AM CST this morning for OKZ049-053-
     056-057-060>062-064>068-070>076.

AR...None.

&&

$$

AVIATION...05



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