Area Forecast Discussion
Issued by NWS Oklahoma City, OK

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FXUS64 KOUN 212353

Area Forecast Discussion
National Weather Service Norman OK
653 PM CDT Wed Mar 21 2018

TAFS 2200/2224...
High clouds should thin some this evening and overnight;
otherwise, a southeast to south wind will prevail. The wind will
become gusty by late Thursday morning and gusty conditions will
continue through the afternoon.


.PREV DISCUSSION... /issued 346 PM CDT Wed Mar 21 2018/

A significant warming trend will start today and above normal
temperatures will persist until they return to around normal for mid-
late March by Tuesday. Warm, breezy, and dry conditions will lead to
increased wildfire potential on Friday. Shower and thunderstorm
chances will increase on Sunday and persist periodically through
much of next week. Severe thunderstorms and heavy rainfall will be
possible during this period, but the pattern doesn`t fit a
significant and/or widespread severe episode. See details below.

An amplifying western ridge is clearly seen in water vapor loop
early this afternoon. Positive mid-level height anomalies
associated with this building ridge will drift slowly eastward
tomorrow, centered on the southern High Plains and
lessening/deamplifying some by Friday as a shortwave trough moves
into the central Plains. Although Thursday will be quite warm in
response to this, veering/strengthening flow and transport of
deeply mixed plume into our region on Friday will result in very
warm conditions. Statistical guidance can often capture these
scenarios best and so we have nudged significantly to the warmer
MOS guidance. Many locations across far western Oklahoma and
western north Texas will reach 90 degrees. Further east, most
locations (except the far southeast) will reach or at least
approach 80 degrees.

A couple of days of southerly flow with trajectories off the western
gulf will bring low-level moisture back into the area east of a
dryline which should be positioned somewhere near our western
border. But, strong capping EML is expected to prevent convection
from development. Ascent from central Plains shortwave will be
strongest to our north and won`t be enough to overcome this cap
over our area. Details on the dryline placement will have
implications for fire weather potential (more on this in the Fire
Weather section below).

Medium range guidance is in agreement in large deep closed low
across the west and meridional flow across our area. This system
will move slowly east and we could have several periods of showers
and thunderstorms as it does so. Mean meridional flow patterns
like this generally support anomalous moisture/PWATs and heavy
rainfall potential, but generally modest severe weather chances at
best since instability tends to be limited. We increased
probabilities further west following the trend seen in
deterministic guidance and ensemble mean of a slightly more west
position, and thus a more westward placement of the dryline
(typical trend with these type systems). We`ll further refine when
periods of greatest chances will be later this week.


Southerly winds will pick up tomorrow, but with gradually
increasing moisture, any pockets of elevated fire weather
conditions should be brief around peak heating.

For Friday, we`ve had a little trouble at this time range pinning
down the position of the dryline with the last couple of systems
(a westward trend with time). This scenario is a little different
in that a fairly low amplitude wave to our north and associated
mid-level speed max being orthogonal to the dryline should help
it mix eastward Friday afternoon at least through our northwest
counties. Given the warm temperatures, low RH values, and momentum
transfer resulting in strong winds, we have issued a Fire Weather
Watch for this area. This may need to be adjusted slightly as we
get a better handle on timing of shortwave/mid-level speed max
and resultant dryline position.



Oklahoma City OK  44  76  59  83 /   0   0   0  10
Hobart OK         44  79  60  87 /   0   0   0   0
Wichita Falls TX  44  79  61  84 /   0   0   0   0
Gage OK           40  82  54  90 /   0   0   0   0
Ponca City OK     39  76  55  83 /   0   0   0  10
Durant OK         43  74  58  73 /   0   0   0  10


OK...Fire Weather Watch from Friday afternoon through Friday evening
     for OKZ004-005-009-010-014-021.


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