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

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FXUS64 KFWD 080526
AFDFWD

Area Forecast Discussion
National Weather Service Fort Worth TX
1126 PM CST Wed Dec 7 2016

.AVIATION...
North winds of 15-20 KT and MVFR conditions will be the norm
overnight in wake of the strong cold front, which was pushing
into the Waco area during the past hour. Recent hi-resolution model
data was indicating the potential for some light precipitation
across Central Texas Thursday morning so we will keep -DZ at KACT
during the 9-15Z timeframe. At this time it appears that
temperatures will remain above freezing if and when any
precipitation falls. Conditions are expected to improve to VFR
during the morning hours Thursday. Winds will eventually fall
below 10KT after sunset Thursday.

30

&&

.UPDATE...
The Arctic cold front extended southeast of a Paris to DFW to
Cisco line at of 9 PM. Northerly winds start to gust to 25 mph or
so and temperatures drop 3 or 4 degrees with frontal passage. This
is not one of those fronts where there is a dramatic drop in
temperatures but with cold advection overnight, we should see
temperatures steadily fall with Thursday morning lows expected to
range from the mid 20s northwest to the upper 30s southeast. Have
adjusted the morning lows up a degree or two across all but the
northwestern zones. Any precipitation that falls overnight is
expected to be light but will leave a mention of the possibility
of some light freezing drizzle in the southwestern zones toward
daybreak. Thursday looks to be cold with highs in the 30s to
lower 40s. Have left the mention of a chance of light wintry mix
of rain/freezing rain and/or sleet across areas from Cisco to West
of Waco and Temple for Thursday morning. Updates have been sent.

58

&&


.SYNOPSIS...
Cool conditions will continue through the afternoon and evening
hours with generally cloudy conditions. Very light rain/drizzle is
expected over parts of the area tonight along and behind the
front. Some light wintry precipitation will be possible mainly
across southwestern zones late tonight and in through the early
portion of the day on Thursday. Cold conditions are expected on
Thursday and the coldest air of the year is still expected on
Friday morning. Thereafter, temperatures will moderate through the
weekend with low rain chances on Sunday morning and afternoon.

&&

.SHORT TERM (Tonight through Friday)...
Cloud cover has filled in across much of the area this afternoon
as low level moisture has lifted northward atop the cooler
airmass. A subtle pre-frontal trough continues to slip to the
south of the Red River at this time and has resulted in north
winds which has induced some weak cold air advection down at the
surface. The weak ascent associated with the moisture advection
appears to be instigating some light rain/drizzle across northeast
zones and given trends, I`ve included a mention of this for the
rest of the afternoon and into the evening hours across this area.
There also appears to be a chance for some patchy drizzle across
southern zones associated with convergence along the pre-frontal
trough and weak ascent over the cooler airmass. The sharp cold
front that we`ve been advertising over the past week continues to
progress southward, albeit a little slower than I thought
yesterday. Currently it appears to be located across the TX
panhandle and back towards western and Central OK. A bulk of the
colder air lags behind this boundary by about 50 miles or so.

For tonight---The cold front is still expected to dive southward
towards the Red River over the next couple of hours and should
accelerate through the CWA as the parent upper low across the
Great Lakes slides eastward. Good pressure rises in the wake of
the front should aid in strong breezes with sustained winds of 15
to 20 MPH with gusts up towards 30 to 35 MPH. The most noticeable
forced ascent will likely occur along and just behind the front
itself and precipitation (at least initially) should be in the
form of light rain or light drizzle. Some weak synoptic scale
ascent in the form of the RRQ of an upper jet may provide
additional lift for a higher concentration of light rain across
eastern and southeastern zones. I`ve kept a mention of light rain
from the previous forecast back further to the west, but it`s
possible that only patchy drizzle occurs.

After midnight, temperatures should begin to plummet as the
colder air plunges southward into North TX. The true surface front
should have swept through the remainder of our Central TX counties
at this time. As this cold air arrives, it appears that a majority
of the strong lift will be a bit displaced further to the south.
Model (GFS and ECMWF) PoP and QPF still suggest likely PoPs along
and south of the I-20 corridor and appears to be lobe of mid-level
vorticity. This lobe, however, appears pretty diffuse and given
that I don`t buy the deep moisture advertised by the models, I`ve
undercut their PoP/QPF quite a bit in agreement with the previous
forecast and hi-res model output. With that in mind, it does
appear that there will be a juxtaposition of some pockets of
drizzle and sub-freezing temperatures and the most likely area
will be out across western zones across the Big Country. Thus,
brief periods of very light freezing drizzle are expected. If the
column is as saturated as GFS and NAM model forecast soundings
indicate, it`s conceivable that sleet would be possible with
around 2 C of warm air aloft. What I believe to be more likely,
however, is that the layer of moisture will be quite shallow
(meaning a high probability of mainly supercooled water drops)
and thus a p-type of freezing drizzle/light freezing rain.

Thursday---Through the morning hours on Thursday, colder and
deeper air will move southward. The colder air will slide further
south out across western zones before spilling over the remainder
of the forecast area through sunrise. As mentioned above, ascent
appears weak, but some hi-res model guidance is a bit more
aggressive with developing some precip along and south of a Cisco
to Meridian to Athens line. With some agreement with hi-res
models, there`s a low chance for a mix of freezing rain and/or
sleet across western zones.

Impacts of any wintry precipitation are expected to be VERY
limited given the light amounts expected. In addition, ground
temperatures remain quite warm with readings in the 50s. Breezy
north winds in the wake of the front will also make it difficult
for precipitation to accumulate on any road surfaces. That being
said, I won`t rule out a few slick spots on elevated
surfaces/structures across western and southwestern zones.
With regards to the north winds---they will be strong in the wake
of the front and I contemplated a wind advisory for a few counties
down south. After looking at the strength of the 925mb winds,
there does appear to be a signal of speeds of around 30 to 35
knots. While pressures do rise quickly, post-FROPA, the amount of
mixing should be somewhat limited given the time of day. With that
in mind, I`ll hold off on any wind advisories for now and defer to
the evening and early morning shifts. Feel-like conditions,
however, will be QUITE frigid with wind chill values in the single
digit along the Red River with teens and twenties elsewhere.
Individuals across North and Central TX will definitely want to
dress in layers when headed out early Thursday morning.
Precipitation chances should diminish through the day, though I
wouldn`t completely discount some lingering drizzle across the
area if dry air doesn`t completely scour out the low level
moisture. Thursday should be a raw and cool day with breezy north
winds continuing.

Thursday Night into Friday---Thursday night into Friday proves to
be tricky with regards to temperatures. Raw model output indicates
that it should be a very good radiational cooling night.
Inspection of forecast soundings, however, suggest that a
scattered to perhaps even broken deck of clouds will exist across
North and Central TX. With there being a good consensus among
model output and based on some MOS output, I`ve elected to nudge
temperatures upward by several degrees. That being said, it still
looks to be cold with temperatures in the 20s across a good
portion of North and Central TX. Friday should remain cold, but
dry with temperatures in the upper 30s and 40s across the area.
High pressure should settle in resulting in a slow return to south
flow through the day on Friday.

&&

.LONG TERM (Saturday through Tuesday)...
On Saturday and Sunday---Temperatures will rebound with afternoon
highs climbing into the 50s and 60s each day. Zonal flow atop the
Rockies should help to induce decent lee-side cyclogenesis. While
modification of the cold airmass will occur on Saturday, it`ll be
a tad slow given the dense low level air in place. With the strong
upper jet to the north, some model guidance does paint some light
QPF along and west of I-35 on Saturday. For now, I`ve gone with a
dry forecast given that a good majority of moisture will be
scoured out and it`s unlikely a ton will return northward.

Sunday appears to be the more likely day for some light rain and
the chances will be limited to areas along and east of the I-35
corridor. Forecast soundings indicate that the depth of low level
moisture will remain confined to the lowest 1-2 km of the
atmosphere and given that a majority of this is below the 0
degrees C isotherm, I`ve decided to remove the mention of thunder
during this part of the forecast. In fact, it`s possible that
drizzle will be the main precipitation type as opposed to even
light rain, but given the timing, it`s too far to get that
specific. The weak trough axis/front will sweep eastward through
North and Central TX through Sunday afternoon confining the best
precipitation chances to far East TX.

For Monday and Tuesday---Dry conditions along with seasonal
temperatures appear to be in store for much of Monday and into a
good portion of the day on Tuesday. Weak return flow across the
Big Country may result in some low rain chances out west, but
given the scarcity of moisture, I`ve kept a mostly dry forecast.

24-Bain

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    31  38  25  42  32 /  10  10   0   0   0
Waco                34  40  24  44  31 /  20  20   5   0   0
Paris               29  38  18  41  29 /  10  10   0   0   0
Denton              29  38  19  41  30 /  10  10   0   0   0
McKinney            30  38  20  40  30 /  10  10   0   0   0
Dallas              32  38  27  42  32 /  10  10   0   0   0
Terrell             32  38  25  42  30 /  20  10   5   0   0
Corsicana           34  39  25  43  31 /  20  10   5   0   0
Temple              35  40  24  44  32 /  20  20   5   0   0
Mineral Wells       29  38  19  42  29 /  10  10   0   0   0

&&

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

$$

30/58


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