397 
FXUS64 KFWD 151044 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
544 AM CDT Fri May 15 2020


.SHORT TERM... /NEW/
Update:
No significant changes to the earlier short term discussion below
outside of raising highs a degree or two across the areas 
along/west of I-35/35W. 

Think there could be a little more insolation than previously 
expected across those areas. Linear MCS across the Ozarks well 
north-northeast of the area is already becoming outflow dominated,
so have my doubts if it doesn't mix and wash out as it approaches
the Red River Valley around midday or early afternoon. Hard to 
say, but an elevated cap across North Texas, not sure how much
coverage of convection develops before late afternoon or early  
evening. 

05/

Previous Discussion:
/Overnight Through Friday Night/

We will continue with our unsettled, mid-May pattern as we move 
through the weekend. The pre-dawn hours through this afternoon 
should be relatively quiet with breezy, warm, and humid conditions
continuing. A strong 30-40 knot LLJ early this morning will help 
draw up widespread stratus and maintain the muggy conditions we 
saw yesterday morning as well. As we warm and begin mixing late 
this morning, ceilings should rise and become broken by midday, 
before scattering late today with additional mid-high clouds aloft
as a relatively strong capping inversion keeps the area dry. 
Despite breezy conditions, highs will warm to between 85 to 90 
degrees across much of the area. In addition, an MCS is forecast 
to drop south-southwest out of Southeast KS and The Ozarks right 
around sunrise as it follows the better instability. However, this
activity will weaken through the day as it runs into said capping
farther south and the loss of good low level inflow after prime 
mixing late this morning. I can't rule out isolated to scattered 
strong to severe storms along the immediate Red River Valley along
a possible outflow boundary later this afternoon with instability
being the main driver for localized downburst winds and large 
hail. 

The dryline across the Texas Panhandle and Western Oklahoma then 
becomes active late in the afternoon and continue into the evening
hours, as a mid-level impulse lifts out across far West Texas 
during peak heating. As these storms propagate along the eastern 
edge of the extreme instability into our northwest counties just 
before sunset, we can expect the potential for damaging downburst 
winds and large hail to be a threat. By sunset and after, another
strong southerly 35-45 knot low level jet will feed into these 
storms across Northwest and West-Central Texas. This feature will 
help to congeal convective activity likely into a broken line of 
severe storms, or possibly a couple of severe line segments as it
moves into western North and Central Texas after dark. As this 
occurs, damaging winds to 70 mph will become the primary hazard 
along with locally heavy rainfall (totals between 1-2 inches) and
minor flooding. Any embedded supercells within the line will 
still be able to produce some good size hail as well considering 
the steep mid level lapse rates between 7-8 Deg C within the hail 
growth zone. 

As this activity pushes east or southeast into the I-35 and I-20 
corridors by midnight and after, it will eventually weaken as it 
moves into a more stable and capped airmass during the pre-dawn 
hours Saturday. Another factor will be the relatively weak deep 
layer northwest shear 25 knots or less. Another factor that will 
likely cause some demise in storm intensity and strength will be a
linear storm complex exploding across South-Central and the Texas
Coastal bend in response to a secondary shortwave lifting out 
from Mexico and across the Upper Rio Grand Valley and Hill 
Country. This more southern complex of strong to severe storms 
will likely intercept/interrupt the better moisture flux and 
southeasterly inflow within the 925mb-800mb layer. Despite the 
expected weakening trend of thunderstorms across much of our CWA, 
my feeling is strong to severe convection may continue along and 
south of the I-14 corridor all the way into daybreak Saturday due 
to this area and it's environment still be unstable and available 
for convection to feed off of.

05/

&&

.LONG TERM... /Issued 323 AM CDT Fri May 15 2020/
/The Weekend through Next Thursday/

The main weather headline in the long term forecast period will 
be the potential for widespread rain and thunderstorms...particularly
on Saturday. Showers and a few storms may linger some into Sunday.
Thereafter, generally rain/storm-free weather is anticipated.

Ongoing showers and thunderstorms are expected at the start of the
long term period as a slowly decaying Mesoscale Convective System
(MCS) overspreads the region. A severe weather threat may persist
as CAPE values may still be in the 1000-1500 J/kg range. The
primary hazard would be damaging winds. Accompanying the damaging
wind threat will be the potential for heavy rain. I'll discuss
this a bit more later. Current thinking is that the complex will 
take on an increasingly north-south orientation and move toward 
the east and southeast. While weakening, this line should be 
expansive enough to induce a Mesoscale Convective Vortex or 
MCV...somewhere across Central TX. 

The MCV will be the impetus for heavy rain and a possible flood 
event somewhere between I-35 and the U.S. HWY 75/I-45 corridors. 
PWATs on Saturday will likely climb into the 1.4-1.6" range which 
is roughly 150-175% of normal. 30-60 day percent of normal 
rainfall for locations south of I-20 and east of I-35 reveal that 
above normal rainfall has been received across this region---though
some short term drying has been noted over the last two weeks. 
The QPF remains tricky, but model guidance is starting to converge
on a solution that places the axis of greatest rainfall likely 
near and east/southeast of a Cameron to Dallas to Sulphur Springs
line. GEFS mean QPF shakeout to a 3" to 5" swath of rainfall 
Saturday into Sunday across the Brazos Valley and parts of East 
Texas with the deterministic ECMWF not being too far behind with
its QPF. The NAM remains the excessively wet outlier with 
rainfall total (in the 4" to 6" range). While the NAM was largely
disregarded, if the MCV evolves as suggested by this model, the 
deep easterly fetch through the 500mb layer, PWATs close to 175% 
above normal and skinny CAPE profile would foster convective cells
supportive of rainfall amounts offered by the NAM in some 
capacity. 

HREF probability match mean QPF appears to offer a decent 
solution for PoPs/QPF and I've tailored the official forecast to 
mimic these trends. While it has been dry recently for parts of 
East Texas and the Brazos valley, the longer term rainfall 
analysis suggests that rainfall rates needed for efficient runoff
processes may not need to be overly high. Given that the official
QPF is closer to 2" to 3" across this area, we'll forgo any Flash
Flood/Flood Watches, but we'll need to closely monitor this 
potential over the next couple of shifts---especially if the NAM
solution appears more correct. That being said, I expect at least
some minor to possibly moderate flooding along parts of the 
Trinity and Brazos River basins across parts of East and Central 
Texas. 

Rain and storm chances may linger into the day on Sunday near and
ahead of a front. The best rain chances will reside across East
Texas and Central Texas where an additional 1/4" to 1/2" of rain
will be possible. After the weekend, it appears that the weather 
pattern across the Southern Plains will become less active, 
outside of perhaps diurnal showers/storms across the 
Caprock/Panhandles as an omega pattern should set up. With ridging
overhead, high temperatures will climb closer to seasonal 
normals. At this time, it appears that the ridge will be strong 
enough to ward off any nocturnal MCSs that can sometimes sneak in 
underneath the upper ridge during this time of year. 

Bain

&&

.AVIATION... /NEW/
/12z TAFs/

Concerns and challenges: MVFR cigs this morning becoming VFR
before 18z. Exact timing of VCTS later this evening and best 
window for TEMPO TSRA. 

MVFR cigs BLO FL015 already has been at Waco Regional Airport a
few hours and has surged north toward the Red River just E of
DAL/GKY. I expect these cigs to expand west across most, if not
all of DFW D10 airports through 15z-16z. All airports should rise
into low VFR AOB FL050 by 18z, then eventually scatter in the 
lower levels with SCT-BKN150-300. 

I have maintained VCTS arriving between 03z-05z at all airports.
Across DFW Metro airports, decided there was too much uncertainty
to take a stab at a window for likely TSRA with so many scenarios
possible. 18z TAFs and beyond will be able to better assess the
more categorical TS impacts at all terminals. 

S/SE surface winds 10-15 knots with occasional gusts in excess of
20 knots will prevail through 02z- 03z, but a few models showing 
potential outflow boundary with a shift to E/NE at 10 knots 
possible. With uncertainty on evolution of any TS outflow this 
evening, will keep south flow prevailing at DFW. 

05/

&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    89  68  80  66  83 /  20  80  90  30  10 
Waco                89  68  79  65  82 /  20  80  90  30  20 
Paris               83  67  77  64  78 /  40  60  70  70  30 
Denton              88  68  80  65  83 /  30  80  80  30  10 
McKinney            87  68  79  65  82 /  30  80  90  40  10 
Dallas              88  70  80  67  83 /  20  80  90  30  10 
Terrell             86  67  78  66  81 /  20  70  90  50  20 
Corsicana           87  69  77  66  80 /  20  70  90  40  30 
Temple              90  68  79  65  82 /  20  80  90  20  20 
Mineral Wells       90  66  79  65  83 /  20  70  60  20   5 

&&

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

$$

05/24