Some concerning wording from FWD regarding the metroplex. Emphasis mine
000
FXUS64 KFWD 221917
AFDFWD
Area Forecast Discussion
National Weather Service Fort Worth TX
217 PM CDT Wed Apr 22 2020
.SHORT TERM... /Issued 1251 PM CDT Wed Apr 22 2020/
/Through Thursday/
/Overview/
Confidence continues to increase in the likelihood of severe
weather this afternoon and evening. All modes of severe weather
including tornadoes (some strong), large hail, and damaging winds
will all be possible. The greatest threat for severe weather will
exist near and east of a line from Gainesville to Arlington to
Cameron. The greatest tornado threat will exist from Sherman to
Terrell to Palestine, and points eastward. The highest
thunderstorm chances can be expected at...
- Dallas/Fort Worth Area: 3 pm thru 9 pm.
- Sherman/Denison: 3 pm thru 9 pm.
- Waco/Killeen/Temple: 6 pm thru 9 pm.
- East Texas: 6 pm thru midnight.
- West of I-35: now thru 3 pm.
Morning surface analysis shows a 1001 mb surface low over
southwestern Oklahoma, with a dryline extending to the south
across the Big Country and Edwards Plateau. A cold front lies to
the west of this dryline across the Permian Basin and Trans-Pecos
region. A warm front extends from the surface low across southern
Oklahoma. The warm sector east of the dryline and south of the
warm front is characterized by dewpoints in the upper 60s to near
70. Aloft, a potent upper-level shortwave trough can be seen on
water vapor satellite over the High Plains of Oklahoma and the
Texas Panhandle.
/Central Texas this afternoon/
Strong ascent ahead of the aforementioned shortwave trough
combined with increasing warm air advection has led to the
development of showers and thunderstorms across parts of Central
Texas. Steep lapse rates in excess of 7 C/km above rich boundary
layer dewpoints have led to large CAPE values of over 2,000 J/kg
across Central Texas. Mesoanalysis also suggests some CINH still
exists in this region, and thunderstorms are likely rooted above
the boundary layer. For this reason, the primary severe weather
threat in Central Texas over the next few hours is expected to be
large hail. Still, thunderstorms may become more surface-based
later this afternoon as they track southeast. Because of
exceptional low-level wind shear, if any thunderstorms do manage
to become surface-based, a tornado threat will certainly exist. A
Tornado Watch was issued for this portion of our CWA about an hour
ago to cover this potential threat. It is possible however that
these storms do not become tornadic until they have exited our CWA
to the east and southeast.
/North and East Texas late afternoon and evening/
Later this afternoon, our attention will turn to the dryline.
Successive runs of the HRRR have continued to slow the dryline,
with it now forecast to reach the west side of the Metroplex
around 21Z (4 p.m.), and not clearing the east side until after
00Z (7 p.m.). For this reason, the severe threat has increased for
eastern portions of the Metroplex. It is still believed that the
greatest threat will be just east of the Metroplex and into East
Texas, but we absolutely cannot rule out areas as far west as a
Gainesville to Hillsboro line.
While cloud cover remains thick across North and East Texas, very
rich boundary layer dewpoints approaching 70 F along with
steepening mid-level lapse rates will produce very large
instability. Forecast soundings just ahead of the dryline indicate
SBCAPE approaching 5,000 J/kg. Additionally, a strengthening low-
level jet will lead to increasingly large and curved hodographs,
allowing effective SRH to increase to more than 150 m2/s2. This
parameter space, combined with wind shear vectors oriented
perpendicular to the surging dryline will favor supercell
thunderstorms. Initially, the primary threat will be large hail,
with some instances of hail larger than two inches in diameter
likely. As we head later into the evening, a strengthening
nocturnal low-level jet will further enhance low-level shear,
leading to a more substantial tornado threat. The ultimate threat
area for tornadoes will depend on how far east the dryline is by
the time this nocturnal low-level jet begins to develop. Right
now, it is believed the dryline will likely be roughly along a
line from Bonham to Dallas to Waco. This would likely place the
greatest tornado threat from the eastern suburbs of the Metroplex
and into East Texas. Note however that there is obviously a margin
of error here, and recent runs of the HRRR have slowed the
dryline.
/Late Evening through Thursday/
Thunderstorms should finally exit our CWA by 10 pm this evening.
The cold front should overtake the dryline. As this cold front
passes, winds will veer out of the northwest, ushering in drier
air. Thursday looks to be a rather nice day with highs forecast to
climb into the lower 80s under mostly sunny skies. Humidity
should also be substantially lower with dewpoints only in the 40s
to lower 50s.
Godwin
