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

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FXUS64 KFWD 251105

Area Forecast Discussion
National Weather Service Fort Worth TX
605 AM CDT Sun Oct 25 2020

...New Short Term, Aviation...

The main focus of this morning`s forecast was to accentuate the
expected temperature contrast across the forecast area today now
that there is more confidence in the sky cover forecast. All signs
point towards more substantial clearing across our southwest this
afternoon with the exception of some cirrus spilling in from the
west. Our east/northeast on the other hand will likely remain
socked into overcast skies for the majority of the day, and afternoon
highs have been adjusted accordingly.

The rest of the previous forecast (included below) is on track
regarding the approaching arctic front set to arrive this
evening/tonight, and minimal changes were made.


Previous Discussion:
/Through Monday/

The first ~36 hours of the forecast will feature some big changes
to sensible weather, beginning with a slightly warmer day today
followed by the arrival of an arctic cold front to begin the

Significant model discrepancy exists through the short term
portion of the forecast, and have relied heavily on NAM and
SREF/HREF guidance for the majority of this forecast issuance.
That means a cooler and cloudier day is now forecast today as
opposed to previous issuances, with the majority of recent high-
res guidance keeping much of the forecast area socked in with
cloud cover as an ill-defined surface warm front lifts northward
into North Texas throughout the day. Ample theta-e advection south
of this boundary should allow for fairly widespread cloud cover
to persist, with perhaps the exception of our western zones where
the day may begin with some sunshine. Temperature spreads of ~15
degrees exist for this afternoon`s highs among guidance, but have
hedged heavily towards the cooler side given the above sky cover
forecast. No precipitation is expected through the afternoon, but
that`ll change by the evening.

By 6 or 7 pm, an arctic cold front will be pushing into North
Texas from the northwest, making relatively slow progress
southeastward into Monday morning. This front is not being driven
by a strong upper shortwave, but rather is seeping southward down
the Plains heavily influenced by terrain and cold air damming
along the High Plains east of the Rockies. That means ascent
locally will primarily consist of upglide along the frontal
surface as the coldest air seeps into North Texas tonight. With
ample warm/moist advection preceding the front within the
southerly flow regime, rapid saturation of the boundary layer will
occur, leading to widespread low stratus along with some
drizzle/mist. This may eventually transition to a broad shield of
light rain later tonight, particularly near and north of the
frontal boundary.

By daybreak Monday, our front should roughly bisect the CWA from
southwest to northeast as it continues to make slow southeastward
progress. This will complicate the high temperature forecast for
tomorrow, with temperatures falling throughout the day behind the
front, while areas to the southeast still manage to warm into the
70s in the afternoon prior to the front`s arrival. By mid
afternoon, temperatures should range from the mid 70s in our
southeast to the mid 30s in the northwest with cold advection
continuing within a brisk northerly surface wind. Wind chill
values in North Texas will be in the 20s and 30s during this time
period, so it`s finally time to dig out the warmer clothing from
the back of the closet.

Meanwhile, fairly widespread rain/drizzle/mist will continue,
especially through the morning hours. Energy from the strong
upper-level low responsible for this system will impinge on our
area during the morning, leading to steeper lapse rates and
stronger mid-level ascent above the frontal inversion in parts of
Northwest Texas. When combined with significant isentropic ascent
along the 850mb front, a band of moderate to heavy rainfall
should materialize across our northwestern zones in the morning
which may pivot eastward with time. Due to the steeper lapse
rates, this precipitation would likely be more convective in
nature, and perhaps feature embedded thunderstorms well behind the
surface cold front where temperatures will have already fallen
into the 30s and low 40s. In fact, given the cold nature of the
column, a few instances of small hail could even occur (not to be
mistaken for sleet). By late Monday afternoon or early evening,
the front will finally have pushed through our remaining
southeastern zones with cloudy, cold, and drizzly conditions
resuming heading into the night.



.LONG TERM... /Issued 357 AM CDT Sun Oct 25 2020/
/Monday night through the Next Weekend/

The big weather story in the extended period continues to be the
multiple rounds of precipitation, the anomalous cold temperatures
across much of the region, and the potential for freezing rain
across the northwest Monday night into Tuesday morning. While our
forecast continues to convey the most likely scenario, there`s
still plenty of uncertainty especially with the position of the
freezing line during this time period. Model guidance continue to
show decent spread in temperatures which will impact the locations
where freezing rain might develop. We know that these back and
forth changes in the models will continue, but hopefully will be
reduced as we get close to the date. As a result, we opted to not
deviate much from the previous forecast and continue to message
the best potential for light freezing rain generally to the west
of a line that extends from south Eastland Co. to the far north
Young Co. At this time, the best time period for freezing rain
appears to be from late Monday night through Tuesday morning. We
can`t rule out some light accumulations on trees, but we expect
that the highest accumulations and impacts will stay to the
west/northwest of our area.

Beyond this complex part of the forecast, things are expected to be
more straightforward as we won`t have to deal with freezing temps.
Most of North and Central TX will remain on a wet pattern through
Wednesday night as the closed upper-low exits to the east.
Rainfall totals will vary from over 2.5" along the Red River
counties to near half an inch across the far southeastern zones.

A warming trend is expected late week and into the weekend with
subsidence and clearing skies. The high temps will still remain
below normal with values in the 50s to 60s on Thursday and 60s to
low 70s Friday and Saturday. For those interested in the
temperatures for Halloween, the forecast shows temps in the 50s
and 60s during the evening hours at this time.



/12z TAFs/

Low stratus will continue to periodically invade Metroplex TAF
sites from the east this morning. While predominantly MVFR
conditions are expected, some cigs below 1 kft are a possibility
through ~15z or so. Some improvement is eventually expected by
midday with VFR cigs likely continuing through the afternoon.
Waco, on the other hand, will likely remain removed from low
stratus for the next several hours.

By this evening, an arctic cold front will approach, causing cigs
to lower once again while also increasing the potential for light
rain and drizzle. Increasing saturation of the boundary layer
will result in a steady lowering of cigs to MVFR around 00z, IFR a
few hours later, and perhaps eventually LIFR late tonight. In
addition, areas of mist/drizzle or light rain are expected to
develop in the 03-06z time period and persist through the night.

Otherwise, a wind shift to the east and northeast will occur over
a period of several hours late this afternoon and evening, but
speeds will generally remain around 10 kts or less through
midnight. A stronger north wind will materialize behind the front
heading into Monday.



Dallas-Ft. Worth    72  57  57  40  48 /   5  60  90  60  50
Waco                77  64  65  44  51 /   5  40  80  50  40
Paris               62  55  55  45  54 /   5  50  80  70  30
Denton              72  52  52  37  46 /  10  70  90  60  60
McKinney            69  57  57  40  49 /   5  60  90  60  50
Dallas              73  60  60  43  50 /   5  60  90  60  50
Terrell             71  60  60  44  53 /   5  40  80  60  30
Corsicana           76  65  66  47  56 /   5  30  70  50  30
Temple              78  65  69  44  51 /   5  30  60  50  30
Mineral Wells       77  49  49  35  41 /   5  70  90  60  60



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