Area Forecast Discussion
Issued by NWS Dallas/Fort Worth, TX

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FXUS64 KFWD 190237

Area Forecast Discussion
National Weather Service Fort Worth TX
837 PM CST Sun Feb 18 2018

Have decided to tweak convective chances overnight (best just west
through north of the D/FW Metroplex), as we monitor a strong mid
level shortwave over far West Texas. The shortwave out west has
some clear definition on various GOES-16(R) water vapor imagery
and will be fairly progressive, as it moves northeast through the
area from the pre-dawn hours through mid-morning Monday. A surface
warm front was just now progressing north through Waco with much
of Central Texas already in the modified warm sector to the south
of this feature.

Current mesoanalysis locally and from SPC, as well as high-
resolution models and their soundings indicate steepening
700-500mb lapse rates to between 7-8 deg C/km, as well as some
MUCAPE near 500 J/KG just in advance of this shortwave. This will
be more than ample to provide some embedded, at least isolated
coverage of elevated thunderstorms to go along with increasing
shower activity toward sunrise Monday. Combined with west-
northwest effective bulk shear values 35-40 knots, an elevated
strong storm or two with increasing lightning strikes and the
possibility of small hail cannot be ruled out in the pre-dawn
hours. This is especially true across the northwest half of the
CWA where MUCAPE values may briefly even approach 1000 J/KG.

Otherwise, I have left some patchy fog and drizzle north of I-20
in advance of the surface warm front. Otherwise, low temperatures
north of the warm front are likely occurring now with the
possibility of steady or even slowly rising temperatures toward
daybreak Monday.



.AVIATION... /Issued 626 PM CST Sun Feb 18 2018/
/00z TAFs/

North and Central Texas airports will remain within a very moist
and challenging regime with regards to cigs and -RA/-SHRA chances
through Monday evening, as low level warm advection amplifies
quite a bit tonight. As we sit in a lull between mid level
shortwaves and precipitation, we await the intensifying low level
warm advection to crank up and surge a surface warm frontal
boundary rapidly northward later this evening.

DFW Metro airports will continue to see increasing SSE winds go
from 10-15 knots to 15-20 knots and occasionally gusty by late
evening and beyond as a southerly LLJ just above the surface
increases to between 40-50 knots. Mostly IFR cigs will prevail
through 03-04z, before briefly going MVFR (or even possibly low
VFR BLO 040 after warm FROPA if the HRRR/RAP projections are to be
believed) late this evening and just past 06z. As increasing light
showers or rain arrives with the next shortwave during the pre-
dawn hours, the boundary layer should cool enough to see cigs fall
once again through MVFR into IFR fairly quickly and linger through
midday Monday. Cigs are expected to improve into MVFR with warming
surface temperatures and gusty S winds 15-20 knots afterward.

Waco should see warm FROPA occur by 03z with their improvement
window with regard to cigs and vsbys into MVFR or even low VFR
happening afterward. SSE winds less than 10 knots will increase
to near 15 knots and become occasionally gusty like DFW terminals
through 06z. However, they will also see cigs fall back into MVFR
and eventually into IFR sooner and no later than 09z Monday, as
Gulf moisture surges northward. Cigs will improve into MVFR after
midday Monday as surface temps warm and low level mixing ensues.



.SHORT TERM... /Issued 252 PM CST Sun Feb 18 2018/

Moisture return will be in full swing tonight ahead of a deepening
upper trough along the West Coast. Shortly after one shortwave
moves east of the forecast area this evening, larger scale lift
will begin to arrive overnight as the main upper trough axis
drops south through the Great Basin. Strong warm/moist
advection and weak large-scale ascent should be enough to
generate occasional showers through the overnight hours. Once
this initial shortwave moves to our east, however, overall
coverage should be fairly low, and POPs will remain predominantly
in the slight chance category. Patchy fog and drizzle will
continue to be a possibility tonight, though winds are expected to
remain strong enough to preclude the potential for dense fog.
Otherwise, after a chilly day, increasing dewpoints means that
temperatures will either hold steady or actually increase



.LONG TERM... /Issued 252 PM CST Sun Feb 18 2018/
/Monday through Sunday/

A persistent large scale trough in the west and the passage of
several shortwaves will bring multiple opportunities for rain and
thunderstorms through next weekend.

Scattered showers and isolated thunderstorms are expected on
Monday as increasing low level moisture joins forces with broad
large scale lift associated with the upper trough to the west. We
were concerned over the past couple of days that the dryline
would enter the western zones during the afternoon, but this seems
unlikely now. We will also have a strong cap in place through the
day which will keep any convection on Monday elevated, therefore,
only isolated storms are expected.

Mid level lapse rates will increase Monday night into Tuesday and
moisture will deepen ahead of the approaching upper trough and
associated cold front. This will result in numerous showers and
thunderstorms. The primary hazard associated with these storms
will be from heavy rainfall since precipitable water values will
be at or above 1.5 inches across much of the region. There will be
a potential for a few surface based/marginally severe storms
Tuesday afternoon as a dryline makes a run at the western
counties but widespread severe weather is not expected.

A cold front will cross the Red River Tuesday night and become a
focus for additional showers and thunderstorms with the best
chances for storms with heavy rainfall shifting to the east and
southeast zones overnight through Wednesday. Rainfall totals
across the eastern counties of North Texas through Wednesday will
likely exceed 2 inches with some areas receiving well above 3
inches. Rainfall of this magnitude will likely result in localized
flooding and possibly even some river flooding. It still appears
that the flooding threat will be localized so we will not issue a
a watch at this point in time.

Temperatures Wednesday night will fall into the 30s across the
northwest zones and some locations will even see some freezing
temperatures. Since the rainfall will have ended in the areas that
cool into the lower 30s, we don`t anticipate any freezing

Although precipitation chances will temporarily end from northwest
to southeast Wednesday night, they will return on Thursday and
continue through Saturday as the cold front lifts back to the
north in response to another approaching upper trough and
associated surface lee trough. Precipitation chances will decrease
from west to east Saturday night through Sunday with the passage
of another cold front.

Temperatures through the week will be a roller coaster ride with
highs Monday and Tuesday mainly in the 70s, falling into mainly
the 40s and 50s Wednesday and Thursday, then warming back into the
60s Friday through Sunday. The coldest morning will be Thursday
with lows ranging from near 30 in the northwest to the middle 40s
in the southeast. Most other mornings this week will see
temperatures near or above seasonal normals.



Dallas-Ft. Worth    60  73  65  72  42 /  30  40  60  80  60
Waco                56  74  66  72  51 /  20  30  40  80  80
Paris               54  71  63  70  43 /  20  40  50  90  70
Denton              58  73  63  71  38 /  40  40  60  80  60
McKinney            58  71  64  69  40 /  20  40  50  90  70
Dallas              61  73  65  71  43 /  20  40  50  80  70
Terrell             61  72  65  71  46 /  20  40  50  80  70
Corsicana           59  74  66  72  53 /  20  30  40  80  80
Temple              63  74  65  71  54 /  20  30  40  80  80
Mineral Wells       59  77  61  72  37 /  50  40  70  80  50




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