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Area Forecast Discussion (AFD)

Issued by Fort Worth/Dallas, TX (FWD)

FXUS64 KFWD 210004

Area Forecast Discussion
National Weather Service Fort Worth TX
704 PM CDT Sat Apr 20 2019

/00Z TAFS/

VFR will continue to prevail through the period with southerly
winds around 10 kt overnight increasing to 20+kt during the day
Sunday. Low level moisture will increase during the overnight
hours but should remain mostly over the Hill Country. We'll keep
skies VFR through the period at Waco, but there could be some
pockets of MVFR cigs to the south and west. Otherwise, moisture
will really begin to surge northward late Sunday night into early
Monday morning and will be addressed in the next issuance.



.SHORT TERM... /Issued 322 PM CDT Sat Apr 20 2019/
/Tonight through Monday Evening/

The main concern through Monday evening will be the breezy 
conditions on Easter. Rain and storm chances late Monday appear to
reside just outside of the valid short term forecast period.

A beautiful day continues across North and Central Texas as mid- 
level ridging has remained in place. Southerly breezes have 
continued to increase this afternoon and shouldn't drop off too 
much tonight. In fact, winds may actually increase after midnight.
The southerly breezes may usher in some patchy stratus mainly 
across Central Texas, but mostly clear skies are anticipated for 
most areas with no threat for rain during the pre-dawn hours on 
Easter Sunday. It'll remain mild with low temperatures in the mid
50s to near 60 degrees around sunrise. 

For the afternoon hours on Easter, low level flow will remain
strong with 925mb flow in the 35 to 40 knot range. This will be
particularly true near and north of the I-20 corridor. I
contemplated a Wind Advisory as we will likely be close to our
criteria. For now, I'll let the evening and overnight crews have 
a closer look at the higher resolution guidance to make the 
ultimate call. Regardless, it'll be windy---sustained winds near 
25 MPH and gusts to near 35 MPH---and those with outdoor 
festivities will need to secure loose outdoor articles. It'll also
be quite blustery out on area lakes, so boaters should use 
caution. Once morning stratus dissipates, it should be a a very 
nice day with mostly sunny skies and temperatures in the 80s. A 
few locales out west may climb close to the 90 degree mark as low 
level flow may veer a bit more. 

Sunday night into Monday should feature even milder conditions as
surface to 925mb flow remains strong. Additional low level
moisture will also help to keep temperatures a little greater than
the previous night and most areas will only fall into the low 60s
for lows. Monday should not be as breezy as Sunday as a front
surges southward from the north. This will loosen the surface
pressure gradient and will yield winds closer to 15 to 20 MPH. 
With slightly less veered flow and more moisture (thus cloud 
cover), highs will be a few degrees lower on Monday compared to 
Sunday. At this time, all indications are that any threat for 
rain/storms associated with the aformentioned front will remain 
north/northwest of North Texas. 



.LONG TERM... /Issued 322 PM CDT Sat Apr 20 2019/
/Monday Night Through Friday/

Our organizing mid level trough will continue to approach the area
Monday night into Tuesday morning. A lead shortwave will lift
across the area late in the night and Tuesday morning -- right
over the top of weak cold front entering our far northwest
counties. The NAM/Euro are a little faster with the surface cold
front entering the northwest counties. I leaned toward the
slightly faster cold frontal push and slightly cooler temperatures
in the northwest on Tuesday due to a few factors. 

1. These models resolve sub-boundary layer conditions and shallow
density pushes below the boundary layer better than the GFS. 

2. Overnight Monday through sunrise Tuesday...mainly elevated 
convection will become widespread across the Southern High Plains 
into western Oklahoma along the slow-moving cold front, aided by 
steepening mid level lapse rates, a 30-40 knot nocturnal low 
level jet, and the left-exit region of a cyclonically curved 
100-120 knot upper level jet arriving over West Texas. 

3. The expected cold pool from this complex of showers and storms
should help in aiding a slightly faster and further southward 
push of the surface cold front.

Showers and a few thunderstorms will become more numerous along 
and west of I-35 Tuesday as the weak surface front acts an 
additional for convective development, while our capping inversion
further east maintains much lower coverage of convection. Either
way, if there was a window to pinpoint for a few strong to
marginally severe storms with hail and gusty winds, this period
would be it before the environment can get too corrupted by
widespread activity. Though surface-based instability will be 
somewhat uncertain, mid level lapse rates on the order of 7-8 deg 
C/km and effective/deep-layer shear 35-40 knots could lend for a 
brief severe weather threat across the western CWA. 

Wednesday through Thursday morning, we begin to focus more on a
hydrologic, localized flooding threat, as the aformentioned strong
upper jet rounds the base of the main longwave trough, helping to
move this feature slowly eastward -- all the while interacting
with precipitable water values(PWAT) near 1.5 inches (right 
around the max PWAT values for our region in mid-late April). 
Where the shallow surface front lays up will likely be where an 
axis of 2-3 inch rainfall amounts, with isolated higher values 
sets up. At this time, I'm projecting this boundary to be south of
I-20 and across Central Texas due to reasons I already noted 
earlier in the discussion. The GFS stripes the highest QPF further
north, likely due to it's stalling of the surface front, but feel
it's not taking into account cooling of the low level airmass 
from widespread rainfall ongoing initially beginning to the 
northwest of our region late Monday through early Tuesday. 

For the end of the week (later on Thursday into Friday), the 
forward momentum of this system should continue to increase, as 
the jet maximum aloft over Southeast Texas and the Upper Texas 
Coast shifts eastward across the Central Gulf Coast. In addition,
an amplifying, northern stream shortwave trough across the Great 
Lakes will surge into the Ohio Valley and should help to pick up 
our system somewhat and assist in lifting it away from the area in
quicker fashion. I'm expecting a fairly rapid west to east ending
of rainfall Thursday night and early Friday. Medium range models 
do have some discrepancies and differences on the evolution and 
speed of the system and it's associated inverted surface trough/low
moving northeast across Central Texas in the late week period. 
For now, I'm buying off on a more open and progressive- moving mid
level trough and a more southern trajectory of the inverted 
surface trough/low moving out of northern Mexico and across South 
Texas. We will continue to fine tune the mid-late week forecast, 
as our upper-air network better samples this system moving through
Easter and into the early part of the week.

Temperatures will remain above normal on the more, mostly rain- 
free days and in the lower-mid 80s, while remaining closer to 
normal values in the 70s during the main window of rain and 
thunderstorms during the middle of the weekend. 



Dallas-Ft. Worth    60  83  63  81  66 /   0   0   0   0   5 
Waco                59  82  63  80  65 /   0   0   0   0   0 
Paris               54  79  58  79  62 /   0   0   0   0   5 
Denton              59  82  62  81  64 /   0   0   0   0  10 
McKinney            58  81  62  80  64 /   0   0   0   0   5 
Dallas              61  84  64  81  66 /   0   0   0   0   5 
Terrell             58  82  62  81  64 /   0   0   0   0   5 
Corsicana           57  82  62  79  64 /   0   0   0   0   0 
Temple              58  82  62  80  65 /   0   0   0   0   0 
Mineral Wells       58  85  62  82  63 /   0   0   0   0  10