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Area forecast discussion 
National Weather Service Fort Worth Texas
1153 am CST Tue Dec 6 2016

Aviation...
north and central Texas will remain in Post-frontal north flow
through the evening. The wind will become light east/southeast
overnight/Wednesday morning as a surface low develops over the
northern Texas Panhandle. The wind will remain light southeast
after sunrise Wednesday ahead of an approaching Arctic cold front.
The front should approach the metroplex taf sites late Wednesday
afternoon so will include a wind shift in the extended portion of
the dfw taf around 23z.

VFR to high end MVFR ceilings will prevail at the metroplex taf
sites through mid afternoon with ceilings lifting and scattering
above 3500 ft by late afternoon. IFR ceilings will prevail in Waco
through mid afternoon with ceilings lifting above 2000 ft by late
afternoon and above 3000 ft after sunset. MVFR ceilings should
develop again overnight at all terminals as some shallow moisture
is transported northward into the developing surface low. MVFR
ceilings should remain in place at all taf sites through late
morning Wednesday.

79

&&

Update...
main update this morning was to remove mention of dense fog for
all of north and central Texas as well as to cancel the advisory
that was in effect. Added a mention of patchy fog/drizzle during
the overnight hours into Wednesday morning for areas south of
I-20. We also will monitor the potential for some light wintry
precipitation mainly south of I-20 and west of I-35 on Thursday
morning. More details on that will come with the full afternoon
forecast package.

Surface analysis at this hour showed a precipitation-free cold
front slicing southward through much of the Southern Plains this
morning. The strong mixing in the wake of the front coupled with
some dry air advection limited fog production this morning and
conditions improved drastically. As a result, I went ahead and
cleared all of our counties from the dense fog advisory a little
earlier. Low level clouds will remain this afternoon across a bulk
of the region with good cold air advection continuing. There may be some partial
clearing along northern zones this afternoon as a deeper batch of
drier air slides southward. While partial clearing may occur, a
bulk of the strongest cold air advection should occur here where the deepest cold
air is present. I won't make any adjustments to temperatures right
now as they look to be fairly reasonable. Zonal flow across The
Rockies should help north winds become easterly and perhaps even
southeasterly. With the gradual upglide and weak moisture
advection, we could see another round of patchy fog/low
clouds/drizzle, mainly across southern zones tonight. With this
potential, i've included a mention of patchy fog down across this
area.

The strong cold front that we've been advertising still appears
to be on track with some challenges still revolving around frontal passage
timing. The front will be very shallow in nature, bringing the
coldest air of the year southward into north and central Texas. As
mentioned previously, models typically struggle with the timing of
these shallow and cold air masses. As a result, this introduces the
concern for light wintry precipitation, mainly south of I-20 and
west of I-35 early Thursday morning and we examine this potential
very closely with the afternoon package.

24-Bain

&&

Previous discussion... /issued 252 am CST Tue Dec 6 2016/
a challenging forecast expected today, especially this morning as
areas of fog, some dense have formed well out ahead of a cold
front that is now moving into northwest Texas and southwest OK
currently. A dense fog advisory currently exists until 8 a.M. CST
for all but some of our far western and northeast counties. Per
BUFKIT and high-resolution model guidance, along with trends on
fog infrared imagery of moisture building southwestward ahead of
the cold front, I have included all but Mills and Lampasas
counties in the southwest, and Lamar, Delta, and Hopkins County in
the northeast. Tracking the front, I have extended the dense fog
advisory across our central Texas counties through late morning.

One caveat here with the fog is the strong westerly 925mb winds
via WSR-88D vwps just to the west and south of the County Warning Area. The strong
westerly 925mb component could likely result in any dense fog
lasting only an hour or two across my far west/southwest counties.
We will have to continuously monitor the fog through the morning
hours and adjust as needed. Once the cold front passes through
much of the area by midday with help from a shortwave transversing
east across the Central Plains, expect some patchy lingering
drizzle through the afternoon hours. BUFKIT rap/NAM forecast
sounding analysis indicates some buoyancy and low level laspe
rates continuing through much of the afternoon within the stratus
layer. Any drizzle will be light and patchy and not expected to affect
visibility behind the cold front. The cold front will stall across
south-central and southeast TX, before lifting slowly north as a
weak warm front into our County Warning Area late tonight into Wednesday. As such,
moisture will not get scoured completely out and the airmass will
not cool down too much. A shortwave will transition eastward
across the state late Wednesday into Wednesday evening and have
continued low rain chances across mostly the eastern half of the
County Warning Area. Moisture isn't overly rich, so do not expect rainfall to
total more than a tenth of an inch, if even that.

The larger scale central Continental U.S. Upper trough deepens over the
plains for the latter half of the week, which support our first
Arctic cold front and airmass intrusion of the season Thursday and
Friday. As has been noted recently, this will be the coldest
airmass our area has seen in two years. It is highly recommended
you cover outdoor faucets and pipes, as well as make sure you
check on people who may not have adequate heating. Outdoor pets
should also be prepped for the frigid weather expected the latter
half of the week. We will not reach our official hard freeze
criteria of 10 degrees or less for any highlights. That said, with
the warm growing season having lingered longer than expected this
year, it's a good idea to take necessary precautions now. Highs on
Thursday will be hard pressed to get out of the 30s, with lows
Friday morning ranging from the mid teens northwest to the mid 20s
across parts of central Texas. Some gradual modification of the
airmass will occur Friday, as the broad surface high and colder
air shift gradually east. However, I still undercut guidance
temperatures by several degrees and may still be too warm on
Friday. Models do have a tendency to scour out dense Arctic
air masses too quickly and the better low level warm advection
looks to hold off until late in the day Friday and Friday night.

We will see a rapid modification to the Arctic airmass this
weekend, as the main central U.S. Longwave trough lifts northeast
into eastern Canada and heights rise over the Southern Plains with
a strong zonal flow in place. This pattern usually leads to strong
Lee surface cyclogenesis to our northwest with a return breezy
southerly winds. After a chilly start, highs Saturday should
rebound into the 50s most places. A shortwave will move east
across the plains with best moisture flux occurring from East Texas into
The Ark-la-TX and lower Mississippi Valley moving into the latter
half of the weekend. I see enough instability aloft and low level
warm advection above the shallow frontal inversion to maintain a
low chance of showers and thunderstorms across areas east of I-35,
with a few lingering showers across the east moving into early
next week. Highs will briefly modify into the 60s Sunday, before
another cold front, not of Arctic nature, drops high temperatures
slightly to between 55 and 65 degrees.

05/




&&



Preliminary point temps/pops...
Dallas-ft. Worth 53 41 55 29 37 / 10 5 5 20 5
Waco 54 41 59 32 39 / 10 5 5 20 10
Paris 51 39 50 27 36 / 10 5 20 20 5
Denton 51 37 53 26 36 / 10 5 5 10 0
McKinney 51 39 53 28 36 / 10 5 10 20 0
Dallas 52 42 55 30 37 / 10 5 5 20 5
Terrell 54 41 55 30 37 / 10 5 10 20 5
Corsicana 57 44 57 33 38 / 10 5 5 20 10
Temple 56 43 59 33 39 / 10 5 10 20 10
Mineral Wells 49 35 54 27 36 / 10 5 5 10 5

&&

Forward watches/warnings/advisories...
none.
&&

$$

79/24

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