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

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FXUS64 KFWD 171810 AAB
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
1210 PM CST Fri Feb 17 2017

.AVIATION...
VFR this afternoon/evening. IFR ceilings likely Saturday morning.
South flow throughout.

An upper low over North Texas will move over the Ouachitas early
Saturday morning. Its lift has produced some showers across East
Texas, but the column remains too dry along the I-35 corridor
where any precipitation should remain as virga. Passing mid clouds
will clutter the skies this afternoon, but as mid-level dry air
begins to filter in on the backside of the departing low, sunshine
will become more abundant. Breezy south winds will steadily return
Gulf moisture to the region, and some cumulus clouds may appear
before nightfall.

As a low-level jet ensues tonight, stratus will surge into East
Texas. The I-35 corridor may be near the western periphery of this
deck as an approaching surface low veers the winds and initiates
dry advection to our west. For now, will maintain MVFR-becoming-
IFR ceilings, but there may be a sharp western edge near FTW/AFW.
As the dry advection spreads east, the thin layer of stratus will
be shunted to the northeast. Central Texas will likely become VFR
before Metroplex TAF sites. VFR conditions will prevail until the
next stratus intrusion Sunday morning.

25

&&

.PREV DISCUSSION... /ISSUED 341 AM CST Fri Feb 17 2017/
A split flow pattern persists across the Central CONUS today with
a southern stream upper low over West-Central TX and a ridge over
the Upper Mississippi Valley. Light RADAR echoes are occasionally
popping up just west of the forecast area in the vicinity of the
upper low center. Most of this precipitation will be in the form
of virga as the system moves east-northeast towards the Red River
region of North Texas later today, but a few sprinkles cannot be
ruled out. Better chances for precipitation will occur this
afternoon and evening over the eastern half of the forecast area,
where moisture levels will be slightly higher. Slight chance POPs
will be kept generally along and east of I-35, though any
measurable precipitation would likely remain minimal based on the
0.80-0.90 PWAT forecast for the area.

As the upper low heads east Saturday, a larger and deeper upper
level trough will be digging southeast across Northern Mexico. A
plume of Gulf moisture will surge north Saturday night and Sunday
morning as the system starts to enter far West Texas. Widespread
forcing for ascent will enter the western counties by late
Sunday morning, where chance POPs will be introduced. Scattered
showers and thunderstorms should increase in coverage Sunday
afternoon as the best lift shifts slowly east, due to increasing
instability associated with surface heating and continued warm-
moist advection. There will be a sharp increase in moisture along
I-35 during the afternoon hours, with PWATs increasing into the
1.4-1.5 inch range. This may create a localized heavy rain and
flooding threat late Sunday through early Monday, for areas
generally along and east of I-35 where the deepest moisture will
exist.

As far as the intensity of the convection is concerned, the first
thought was that unidirectional meridional flow will keep the
severe threat fairly limited. However, during the late Sunday
afternoon and Sunday night time, the NAM solution indicates an
impressive wind profile with backed low level flow and bulk shear
values at or above 50KT. This is in combination with CAPE
approaching 1000 J/KG. The GFS is less impressive with regard to
shear and instability. This solution shows more southerly winds
at the surface, lower SRH values and about half the CAPE
advertised by the NAM. Either way, there appears to be slightly
higher chance of at least a few severe storms with damaging winds
being the main threat.

Convection will likely organize into a line as it spreads east
across the eastern half of the region, with the low-end damaging
wind and flood threat continuing overnight into early Monday. The
southern half of the upper trough is progged to evolve into a
cut-off low late Monday and Tuesday as it moves east to the TX-LA
border and adjacent coastal waters. It looks like there will be
lingering lift on the back edge on the system Monday night with
enough wrap-around moisture to keep a chance of showers across
the eastern half of the area through Tuesday morning.

Precipitation will end from west to east during the day Tuesday,
with generally dry weather and above-normal temperatures mid to
late next week.

30

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    72  55  76  58  76 /  20  10  10   0  40
Waco                72  54  80  59  76 /  20  10   0   5  50
Paris               68  52  68  54  76 /  20  20  20   0  10
Denton              71  53  74  56  74 /  10  10  10   0  40
McKinney            71  54  72  56  76 /  20  10  10   0  30
Dallas              71  56  75  59  76 /  20  10  10   0  30
Terrell             70  55  74  58  77 /  20  20  10   0  30
Corsicana           72  56  76  59  79 /  20  10  10   5  30
Temple              72  54  80  60  75 /  20  10   0  10  50
Mineral Wells       74  49  77  55  74 /  10   5   0   5  50

&&

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

$$

25/91



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