Severe Thunderstorm Warning 255, NWS Fort Worth, TX

Area Forecast Discussion
National Weather Service Fort Worth TX
335 PM CDT Sun May 28 2017

.DISCUSSION...
Within the next hour we expect storms to begin developing along a
surface frontal boundary that lies somewhere along a line from
Killeen to Waco to Canton as of 3 pm. Ongoing convection along and
north of Interstate 20 is within a 925-850 mb frontal zone north
of the surface boundary, and is also on the southern edge of the
strongest 500 mb winds associated with an upper level trough
currently sliding across northern Oklahoma. A few of these storms
have become robust and may be capable of strong winds and small
hail. In addition, a Severe Thunderstorm Watch has now been issued
along and ahead of the surface front through 10 pm CDT.

Along the surface frontal boundary, increasing cloud cover may
affect initiation, but storms that form will be in a highly
unstable environment characterized by 3000-5000 J/kg but with
weak to moderate wind shear around 30 kts. However, storms may
quickly become severe due to the high instability with a threat
for large hail and damaging winds. Low level wind flow is weak,
but an isolated tornado cannot be completely ruled out as the
surface winds ahead of the front are backed and vortex lines may
be quickly stretched as a result of the high CAPE values.

We expect the severe weather threat will wane during the mid to
late evening hours and most of the activity may push south of the
region by 8-9 pm. Decent rain chances however will remain
overnight, mainly across Central Texas as lift continues and the
925-850 mb front remains north of the surface boundary. A few
strong storms will be possible and may also produce brief heavy
rainfall.

Not much has changed for the Memorial Day forecast with a chance
for rain across mainly the southern half of the region. Any
storms should be elevated as the surface front will have pushed
south of the region before stalling. I expanded PoPs farther
north than the previous forecast due to uncertainty about where
the elevated fronts may be, and this area may have to be adjusted
again after additional analysis of where the fronts are following
tonight's convection. A few strong storms are possible with a
threat for strong winds, small hail and brief heavy rainfall. An
isolated severe storm or two is possible but widespread severe
weather is not expected at this time.

On Monday night and Tuesday, the front will retreat north in
response to another upper level disturbance and trough approaching
from the west. Rain chances will continue each day as we remain
humid and unstable in a southwest flow pattern with a series of
troughs to our west. Upper level disturbances will move into the
Southern Plains starting Thursday and rain chances will increase
by the end of the week. It is likely a severe weather threat will
exist at some time(s) Thursday afternoon through the weekend.

JLDunn

&&

.AVIATION...
/ISSUED 106 PM CDT Sun May 28 2017/
18 UTC TAF Cycle

Concerns---IFR cessation at select Metroplex TAF sites, otherwise
MVFR through the afternoon and early evening with a potential for
-SHRA/TS at all TAF sites. VFR this evening, with a low chance for
additional convection after 00 UTC.

For the Metroplex TAF sites---Intermittent IFR cigs have persisted
at a few sites across the Metroplex early this afternoon in the
presence of modest low level ascent. Some of these IFR cigs may be
perpetrated by the very shallow ascent, but this is expected to
end shortly. Most cigs should lift into the MVFR category (around
FL015) this afternoon as more robust convection likely helps in
overturning the boundary layer. The next challenge will be the
timing of this convection. At this time current lightning data
indicates the convection to the west is not overly impressive in
terms of its lightning production, so I'll simply prevail -SHRA
at all Metroplex TAF sites. If activity to the west starts showing
more signs of generating additional lightning, then a quick
amendment to include VCTS/TS may be necessary. VFR is expected to
return late this afternoon and into the early evening hours. There
is a potential for additional VCSH and perhaps VCTS around the
00-03 UTC time period, but confidence is too low to include in the
TAFs at this time. Should convection occur, the main impacts
would be potentially small hail and perhaps gusty winds/turbulence
below the cloud base.

For the Waco TAF site---MVFR will continue through the early
afternoon before the late May sun helps to erode cigs from the
south and east. With the front still located to the north of the
Waco terminal and increasing instability ahead of this feature,
there appears a reasonably high enough chance for TS at the
terminal. I have moved up the timing of VCTS by several hours
(closer to 22 UTC) to account for this and it's possible that a
prevailing group for TS may be warranted in future amendments. The
chances for convection should dwindle this evening, but the
trends will need to be monitored. Main hazards with thunderstorms
will be hail and strong winds. Reductions to visibility and
ceilings will also be possible.

24-Bain

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    66  85  67  86  70 /  10  20  20  20  20
Waco                66  80  65  84  67 /  50  50  20  30  20
Paris               63  83  64  84  65 /  10  10  10  20  20
Denton              62  86  63  86  66 /  10  10  10  20  20
McKinney            63  84  64  85  66 /  10  10  10  20  20
Dallas              67  86  68  87  70 /  20  20  20  20  20
Terrell             65  81  66  84  67 /  20  20  20  20  20
Corsicana           66  79  67  84  68 /  40  50  20  20  20
Temple              66  80  65  84  67 /  60  60  20  30  20
Mineral Wells       63  85  62  86  66 /  10  10  20  20  20

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&

24/82

Hazardous Weather Outlook
National Weather Service Fort Worth TX
345 PM CDT Sun May 28 2017

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-291200-
Montague-Cooke-Grayson-Fannin-Lamar-Young-Jack-Wise-Denton-Collin-
Hunt-Delta-Hopkins-Stephens-Palo Pinto-Parker-Tarrant-Dallas-
Rockwall-Kaufman-Van Zandt-Rains-Eastland-Erath-Hood-Somervell-
Johnson-Ellis-Henderson-Comanche-Mills-Hamilton-Bosque-Hill-Navarro-
Freestone-Anderson-Lampasas-Coryell-Bell-McLennan-Falls-Limestone-
Leon-Milam-Robertson-
345 PM CDT Sun May 28 2017

This Hazardous Weather Outlook is for North and Central Texas.

.DAY ONE...This Afternoon and Tonight.

Isolated to scattered thunderstorms are possible this afternoon for a
good portion of North and Central TX. The better risk for strong to
severe thunderstorms, however, will be along and south of a Lampasas
to Emory line. The primary hazards with any strong to severe storms
will be large hail and strong downburst winds, but an isolated
tornado cannot be ruled out.

Any storms north of this area this afternoon and evening may produce
small hail and gusty winds.

Overnight, additional thunderstorms are possible mainly along and
south of a Sulphur Springs to DFW to Cisco line. Some storms could be
strong producing small hail, gusty winds and brief heavy rainfall.

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

Thunderstorm chances will continue Memorial Day and Monday night
along and south of a line from Cooper to DFW to Breckenridge. A few
strong storms are possible producing gusty winds, hail and brief
heavy rainfall.

Storm chances continue through the rest of the week, as an unsettled
weather pattern continues across the region. Widespread severe
weather is not anticipated Tuesday through Wednesday. However, a few
strong storms containing strong winds, small hail, and brief heavy
rainfall are possible. An upper level trough may bring better chances
for severe storms later in the week.

.SPOTTER INFORMATION STATEMENT...
Spotter activation may be requested, mainly for areas along and south
of a Lampasas to Emory line this afternoon and tonight.

JLDunn

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