Areal Flood Advisory 21, NWS Fort Worth, TX

Area Forecast Discussion
National Weather Service Fort Worth TX
603 AM CDT Tue May 18 2021

...New Short Term, Aviation...

.SHORT TERM... /NEW/
Update:

PoPs were adjusted through the morning based on latest radar
trends. New vigorous convection has developed across West Texas
over the last few hours and will spread into our western counties
this morning. A few additional showers/storms have developed just
northwest of the Metroplex and these will continue to drift
northeast with time. The environment was pretty worked over from
overnight rainfall, but winds have recovered and instability is
creeping back northward. This trend should continue through the
morning with an uptick in convection expected across the region
through midday into the afternoon. RAP objective analysis
indicates steep mid level lapse rates have once again overspread
North Texas and low level moisture advection is becoming focused
along and west of the I-35 corridor. With persistent lift from the
slow moving upper low to the west, we should see continued
convective development into the afternoon. Some of these storms
could be severe with a large hail or damaging wind threat.

The bigger concern over the next 24 to 36 hours will be the
potential for flash flooding as grounds are already saturated in
many areas and efficient rain production will result in rain rates
of 1-2"/hr through tonight. There remains some uncertainty with
respect to tonight's forecast after today's activity, but the main
ingredients for additional convective development should be in
place. We'll keep PoPs pretty high through the next 24 hours.
Additional rainfall amounts of 2 to 5 inches will be possible
through Thursday.

Dunn

&&

Previous Discussion:
/Rest of Tonight through Wednesday/

An MCS is currently making its way across North Texas tonight
although it has primarily been sub-severe with heavy rainfall and
gusty winds being the main threat. At this hour, it is bearing
down on the Metroplex, extending from near the Red River to Fort
Worth to Comanche. It will continue through the region over the
next several hours with only isolated severe wind gusts expected.
The southern end of the line moving into Central Texas has a
little better instability to work with and we'll continue to
monitor for further intensification.

With our main upper trough still to the west over New Mexico,
airmass recovery should be quick in the wake of this mornings
activity. Dewpoints are already back in the lower 60s off to the
northwest, so after a few hours of a lull in the convection later
this morning, we should see additional development again off to
our west. This activity should spread across North and Central
Texas through the midday and early afternoon hours with an
additional threat for severe weather and flash flooding. Modest
instability and a little stronger shear associated with the upper
trough will support a few instances of large hail and damaging
winds. Backed low level flow in the vicinity of any boundaries
could also enhance the low level shear profile, so a tornado or
two cannot be ruled out through this evening.

Unfortunately, high res model guidance diverges significantly with
respect to additional development Tuesday night into Wednesday and
it will likely be highly dependent upon what happens today. If
today's convection takes longer to materialize or is generally
weaker, then another round or two of showers and thunderstorms
will be possible late Tuesday night into Wednesday. We'll keep
PoPs relatively high to account for this uncertainty, but it still
looks like there will be a significant amount of additional
rainfall over the next 48 hours which will likely lead to
continued flooding problems across the region. This threat
increases east of I-35 through Wednesday.

Dunn

&&

.LONG TERM... /Issued 310 AM CDT Tue May 18 2021/
/Wednesday Night Onward/

Wet and active weather will continue through the long-term period,
along with additional chances for heavy rainfall and flooding
through the end of the work week. Confidence in when and where
storms will occur each day isn't particularly high as models
remain in disagreement. Nonetheless, the best chances of rain will
likely be Wednesday night through Friday evening, with drier
weather possible over the weekend.

There is some indication a mid-level ridge will attempt to build
in from the east this weekend, shunting much of the precipitation
and Gulf moisture to our west. This would result in a drier
forecast late this weekend and early next week, with pleasant,
spring-time weather potentially making its return. However, the
upper-level ridge may remain just far enough east to allow for
the development of a few showers and thunderstorms. Therefore, low
PoPs have been maintained early next week across our west and
along the Red River.

A slight warm up is possible next week as more sunshine is
expected across the area. However, temperatures will likely remain
below average by late May standards. Low temperatures will be in
the 60s, with high temperatures peaking in the low to mid 80s.

Barnes

&&

.AVIATION... /NEW/
/12Z TAFs/

Scattered showers have developed just northwest of the Metroplex
this morning, but more robust convection is still out over West
Texas. We'll see a gradual uptick in showers/thunderstorms later
this morning through early afternoon. VFR cigs have generally
prevailed overnight, and we'll continue this trend today with
TEMPO MVFR cigs in heavier convection. Activity should decrease
later this afternoon with additional showers/storms expected
tonight. Exact timing of TS will be difficult over the next 24
hours but for now we'll keep the 17-21Z TEMPO this afternoon and
keep VCTS overnight from 6Z onward.

Dunn

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    79  66  78  66  76 / 100  80  70  60  70
Waco                81  68  78  66  76 / 100  80  80  70  70
Paris               78  65  75  65  76 /  90  80  90  70  80
Denton              76  64  77  66  76 / 100  80  70  60  60
McKinney            77  65  76  65  77 / 100  90  80  70  70
Dallas              81  68  78  66  76 / 100  80  80  70  70
Terrell             80  65  77  65  77 / 100  80  80  70  80
Corsicana           81  67  78  65  76 / 100  80  90  70  80
Temple              81  66  77  65  75 / 100  80  80  60  60
Mineral Wells       77  64  78  64  75 /  90  60  60  40  50

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through Wednesday morning for TXZ091>095-
100>107-115>123-129>135-141>148-156>162-174-175.

&&

Hazardous Weather Outlook
National Weather Service Fort Worth TX
310 AM CDT Tue May 18 2021

TXZ091>095-100>107-115>123-129>135-141>148-156>162-174-175-190815-
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-
310 AM CDT Tue May 18 2021

This Hazardous Weather Outlook is for North and Central Texas.

.DAY ONE...Today and Tonight.
Widespread thunderstorms are expected today, some of which could be
severe. Additionally, heavy rainfall will likely result in flash
flooding.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.
Thunderstorm chances will continue through the weekend. Additional
rounds of heavy rainfall may cause further flooding issues and
significant rises on area rivers through late this week. Additionally,
a few strong to severe thunderstorms may be possible.

.SPOTTER INFORMATION STATEMENT...
Spotter activation is not expected at this time.