314
FXUS64 KFWD 081920
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
120 PM CST Wed Jan 8 2025

...New Aviation...

.KEY MESSAGES...

- Portions of North Texas are likely to experience impactful
  snowfall accumulations including isolated snowfall amounts in
  excess of 8 inches. A Winter Storm Warning has been issued for
  parts of North Texas. A Winter Weather Advisory is now in effect
  for most other areas in North and Central Texas not covered by
  the warning.

- Most likely snowfall/sleet totals still range between 2 and 4
  inches mainly along and north of I-20. Snowfall amounts in
  Central Texas are expected to be minimal.

- There is an increasing likelihood of ice accumulations. Ice
  accumulations up to 1/10" are expected on average, but there is
  about a 10% chance of accumulations near 1/4".

- Main travel impacts are expected on Thursday and Thursday night
  with conditions improving some Friday afternoon.

&&

.SHORT TERM... /Issued 536 AM CST Wed Jan 8 2025/
Update:

No major changes in the short term through tonight. We`ve made
some minor adjustments to cloud cover to keep skies mostly cloudy
today. This will likely impact high temperatures and have nudged
those down a degree or so across the board. Otherwise, the next 18
hours will be quiet before precipitation starts to spread in from
the west early tomorrow.

Dunn

Previous Discussion:
/Overnight through Wednesday Night/

High clouds continue to stream in across North Texas tonight ahead
of a powerful upper low that spins over the northern Baja
peninsula. This system will eventually eject eastward and bring a
bout of wintry precipitation to North Texas on Thursday. Until
then, a steady influx of mid and high level moisture will continue
through today and tonight. Weak cold advection will continue
across North Texas overnight and Wednesday with north winds around
10 mph. Sporadic thick cloud cover should help limit high
temperatures to some degree and we`ll maintain forecast highs near
the consensus of the MOS guidance in the upper 30s and lower 40s.

By tonight, the first significant wave of mid level isentropic
ascent will spread eastward from the Baja upper low and into West
Texas as an upstream trough digs into the Four Corners region.
Given an ample supply of mid level moisture streaming in from the
Eastern Pacific, we`ll likely see an increase in mid-level radar
echoes late Wednesday night across the Big Country and into
western North Texas. This will mark the beginning of the winter
event for our region with an appreciable uptick in precipitation
intensity expected by Thursday morning as the Baja upper low
begins to eject eastward spreading strong forcing for ascent
across North Texas.

Initial precipitation type will likely be in the form of sleet
late Wednesday night across the southwestern parts of the CWA
given a dry sub cloud layer that will promote significant wet bulb
cooling potential. Some light snow may also occur with time toward
early Thursday morning as saturation takes place. Forecast thermal
profiles are a little warm initially, but given the strong forcing
for ascent, we`ll keep p-type all sleet/snow across the southwest
through 12Z Thursday. Additional details concerning the brunt of
the winter storm from 12Z Thursday on will be discussed further in
the updated long term discussion out a little later tonight.

Dunn

&&

.LONG TERM... /Issued 424 AM CST Wed Jan 8 2025/
/Thursday through Tuesday/

Light wintry precipitation will likely be ongoing across parts of
western North Texas early Thursday morning, but a rapid expansion
eastward and an increase in intensity is expected through the late
morning hours. This will be in response to increasing deep layer
isentropic ascent as strong height falls spread into North Texas
through midday. As the lower half of the atmosphere quickly cools
and saturates, precipitation rates will increase.
Temperatures are expected to be below freezing during the morning
hours and precipitation type will likely initially be a mix of snow
and sleet with some light freezing rain across our Central TX
counties. As we head into midday Thursday, surface temperatures will
climb into the mid 30s and would support primarily rain south of I-
20 where low level thermal profile warm above freezing in the strong
southerly flow regime. A mix of rain and snow is likely farther
north from the Metroplex north toward the Red River.
Snowfall accumulations are generally expected to be light through
the early afternoon given the combination of a rain/snow mix and
surface temperatures above freezing, so impacts may initially be
minimal.

Things will get more interesting during the late afternoon and
particularly Thursday evening when the main upper trough begins to
eject eastward. Strong forcing for ascent will begin to overspread
the region and mid level isentropic ascent within the 700-500 mb
layer will be aided by 70 kt of flow within a completely saturated
layer. Most, if not all of the guidance shows a reinvigoration of
precipitation production initially across our northwest counties,
then extending along and north of the I-20 corridor into the Red
River and Arklatex during the late evening. This appears to be
tied to an intense band of mid level frontogenesis between 700-400
mb. An examination of the frontal circulation within both the GFS
and ECMWF guidance indicates the presence of weak stability which
develops around 21Z Thursday and continues through around 3Z
Friday. The orientation of this strong frontogentic forcing in
line with very strong deep layer shear and weak stability suggests
the potential for one or more intense bands of snowfall to occur
during this time. While these mesoscale features are extremely
difficult to pin down with much advance notice, the conditions
appear to be setting up for at least some potential for a few
areas to pick up much more snow than the current broader based
amounts being forecast. This is also supported by the ECMWF
extreme forecast index which highlights an area just north of the
Metroplex toward the Paris area as a potential area for
significant snowfall. We`ll still maintain a general forecast of 2
to 4 inches in this area, however a reasonable higher end total
within any banded precipitation could top 6 to 9 inches. With the
later onset of frozen precipitation Thursday evening into the
nighttime hours, more of this is likely to impact roads and travel
during the overnight hours into early Friday morning when
temperatures will be in the upper 20s. Precipitation will taper
off very quickly late Thursday night into early Friday morning
with Friday being a cold and cloudy day. Skies will clear by
Friday evening with temperatures dropping back into the low 20s
Friday night areawide. A slow warmup is expected through the
weekend with quiet weather expected into early next week.

Given the potential impactful snowfall accumulations across the
Metroplex and increasing potential for isolated banded heavy snow
north and northeast of the Metroplex, we`ve opted to upgrade a
portion of the Winter Storm Watch to a Winter Storm Warning. The
remaining areas will be assessed further today for potential
inclusion or upgrade to a winter weather advisory for lighter
amounts.

Dunn

&&

.AVIATION... /NEW/
/18Z TAFs/

VFR conditions will continue today with north winds near 10 knots.
Poor flying conditions will begin overnight with the onset of
winter precipitation. A wintry mix is likely throughout the day
Thursday. A full transition to rain may occur at KACT around
midday, but winter precipitation will likely resume beyond the
current TAF period Thursday evening. The primary precipitation
type across the Metroplex is currently expected to be a snow/sleet
mix, transitioning to primarily a rain/sleet mix during the day.
A full transition to snow is likely across the Metroplex late
Thursday evening, with precipitation likely not ending until early
Friday morning.

Confidence in expected precipitation types and timing is still up
in the air, as it is heavily dependent on the existence and
magnitude of a warm layer just above the surface. It`s possible we
end up with more of a freezing rain scenario Thursday morning, but
we will continue to assess trends today and overnight and update
the TAFs as anything changes. Otherwise, southerly winds return
tonight but will remain light through the end of the period at
around 5 knots or less.

Barnes

&&


.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    29  33  30  41  24 /  10 100 100  10   0
Waco                30  35  31  41  24 /  10 100 100  10   0
Paris               25  32  29  38  18 /   5 100 100  30   0
Denton              25  33  29  39  21 /  10 100 100  10   0
McKinney            26  32  29  39  21 /   5 100 100  10   0
Dallas              29  33  31  40  23 /   5 100 100  10   0
Terrell             26  33  30  39  22 /   5 100 100  20   0
Corsicana           30  35  31  41  27 /   5 100 100  20   0
Temple              29  35  31  43  24 /  10 100 100  10   0
Mineral Wells       26  32  29  41  21 /  20 100  80   5   0

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from midnight CST tonight through late
tonight for TXZ091-100-101-115-116-121>123-129>134-141.

Winter Storm Watch Friday afternoon for TXZ091-100-101-115-116-
121>123-129>134-141.

Winter Weather Advisory from 6 AM Thursday to noon CST Friday
for TXZ091-100-101-115-116-129>135-141>148-156-157-159-161.

Winter Storm Warning from 6 AM Thursday to noon CST Friday for
TXZ092>095-102>107-117>123.

&&

$$