Area Forecast Discussion
Issued by NWS Tulsa, OK

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FXUS64 KTSA 181724
AFDTSA

Area Forecast Discussion
National Weather Service Tulsa OK
1224 PM CDT Wed Apr 18 2018

...UPDATE...

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

VFR conditions will persist through the period, with FEW to SCT
afternoon cu possible at the NW AR terminals. Gusty west to
northwest winds will continue through the afternoon before
diminishing this evening.

&&

.PREV DISCUSSION... /Issued 942 AM CDT Wed Apr 18 2018/

..UPDATE...

DISCUSSION...
Short term forecast concern revolves around continued fire weather
danger across mainly parts of northeast Oklahoma. Winds have
picked up again this morning from the northwest, behind last
night`s cold frontal passage. Short term models and upstream
observations indicate that the drop off in the wind speeds from
mid to late afternoon may not end up being as substantial as
earlier thought, but afternoon relative humidities and
temperatures both appear fairly marginal as far as Red Flag
considerations go. Main area of concern continues to be across
Osage and Pawnee counties, where fuels remain prime for potential
fire. Confidence remains low enough that warning conditions will
be met to preclude an upgrade of the existing watch in Osage and
Pawnee so the watch will be maintained for the next few hours
anyway in these counties. The watch has been dropped for the
remaining counties, as confidence is fairly high that conditions
will remain above critical thresholds. Expect further updates into
early afternoon as the fire weather situation becomes clearer.

PREV DISCUSSION... /Issued 336 AM CDT Wed Apr 18 2018/

DISCUSSION...

The main forecast concerns in the short term remain winds and fire
weather conditions. Focus then turns to increasing rain chances
this weekend with the next upper level storm system.

Strong cold front is pushing southeast across the region
currently, lying from near Vinita to Tulsa to Okemah. Some
impressive wind gusts were observed in western and central
Oklahoma earlier with the front, but the gradient is weakening as
the surface cyclone lifts northeast into MO. An optimal deep
mixing/momentum transfer regime will prevail behind the cold front
today, so another windy day is ahead. 925mb winds do drop off some
from the morning into the afternoon as the cyclone moves farther
away from the region, so there may be a slight downward trend in
winds during the afternoon when RHs should be at their lowest.
Since forecast fire weather conditions stay just below critical
levels, I have elected to just let the going fire weather watch
ride for now, leaving some room for uncertainty in the forecast
since RH is a sensitive forecast parameter.

Rain chances ramp up quickly on Saturday with the approach of the
next upper level storm system. The models have been consistent
for several days so feel comfortable going categorical PoPs in
some areas Saturday into Saturday night. Some higher PoPs were
maintained into Sunday as the upper low moves across the region.
Models still keep the warm sector well to our south, thus only
isolated storms were kept in the forecast across the south
initially. The ECMWF offers potential for at least isolated storm
activity beneath the upper low and along an inverted surface trof
axis on Sunday. Bottom line though...severe potential still looks
low at this point. The rain areas should stay progressive enough
to avoid any major flooding issues.

Below average temps will be the rule thru the weekend, with a
slight warming trend back to near average early next week.

Lacy

&&

.TSA WATCHES/WARNINGS/ADVISORIES...
OK...Fire Weather Watch until 8 PM CDT this evening for OKZ054-059.

AR...None.
&&

$$


AVIATION.....22



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