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Area forecast discussion
National Weather Service Fort Worth Texas
546 am CST Wed Nov 13 2019



Aviation...
/12z tafs/

Concerns -- lowering cigs and increasing rain chances late this
evening and into Thursday. Frontal passage on Thursday morning.

All taf sites are VFR with weak south winds this morning as high
pressure continues to move off to the east. An upper-level low
will approach from the southwest later today. Moisture will
increase...leading to increasing cloud cover from southwest to
northeast through the day. Cigs will likely lower to MVFR during
the evening...and become IFR by late tonight. Greatest coverage of
rain expected to remain in central Texas...thus went with -ra br at
kact...and vcsh at metroplex terminals. A weak cold front will
approach from the northwest by daybreak Thursday...with cigs
improving and rain chances ending following frontal passage.

37

&&



Short term... /issued 329 am CST Wed Nov 13 2019/
/through Thursday/

A rather cold morning across north and central Texas this morning,
with temperatures in the 20s across the entirety of the forecast
area. A few temperatures in the teens are noted in our far western
counties. Surface analysis reveals a 1033 mb high centered over
Evansville, in, with the axis of the ridge extending to the
southwest along a line from Little Rock, Arkansas to Dallas, Texas to San
Antonio, Texas. To the West, Lee cyclogenesis is underway, with a
1010 mb surface low noted near Scottsbluff, NE. A trough axis
extends south of this low along the Front Range of the Rocky
Mountains. In the upper levels, 500 mb analysis reveals a closed
low over Chihuahua.

Over the next 24 hours, the upper-level low will slide east across
central and south Texas, before being picked up by a shortwave
trough ejecting out of the Great Plains. Positive differential
vorticity advection associated with the eastward translation of
this low will result in increasing synoptic-scale ascent across
the Lone Star state. Ascent will be further enhanced by low-level
warm air advection from continued pressure falls along the Lee of
The Rockies. Widespread, but light precipitation is expected to
develop, mainly over central Texas. The highest rain chances will
be along an Athens to Gatesville line. In terms of precipitation
type, temperatures should be warm enough to keep most/all
precipitation in the form of liquid rain. That being said, there
is an outside chance of seeing a few sleet pellets in central
Texas Wednesday evening. Forecast soundings from the hrrr and NAM
within the expected precipitation shield show a saturated profile
in the dendritic growth zone (the layer in which temperatures
range from -10 c to -20 c), which would support ice Crystal
formation. A deep warm layer exists beneath this zone, which would
cause hydrometeors to melt. Surface temperatures are expected to
be above freezing during the evening hours, but near-surface wet
bulb temperatures may be just cold enough that a few sleet reports
are not out of the question, especially anywhere we can get some
convective elements, leading to enhanced near-surface evaporative
cooing. Sleet was kept out of the grids for now however, as
accumulations are not expected, and impacts should be minimal.

There looks to be a brief respite in precipitation Thursday
morning as the upper-level low moves to the east and synoptic-
scale ascent wanes. A renewed round of precipitation is expected
on Thursday afternoon however as the shortwave trough dives south.
This shortwave trough will also drive a weak cold front across
north and central Texas. Temperatures ahead of the warm front
should be well above freezing, keeping any precipitation as all
liquid.

37

&&

Long term... /issued 329 am CST Wed Nov 13 2019/
/Thursday night Onward/

Precipitation from thursday's disturbance and front is expected to
have exited the area by the evening, with skies clearing
overnight. This should allow much of the forecast area to fall to
near or below freezing within the cooler and drier Post-frontal
air, with some 20s likely across the northwest. However, with
ample insolation and a return to south winds during the day on
Friday, temperatures should be able to rebound in the 50s to end
the week. Pleasant weather is expected to continue into Saturday
with a gradual warming trend as we remain between systems with
upper ridging occurring.

Another vigorous shortwave will approach the Southern Plains
Saturday night into Sunday, overspreading the region with strong
ascent while driving another cold front into the area. With
intensifying southerly flow ahead of this disturbance, moisture
will increase sufficiently to support some rainfall across parts
of the forecast area on Sunday, although its fast-moving nature
will limit amounts. Instability will be practically nonexistent,
so even thunder appears unlikely with this activity. An increase
in clouds and modestly cooler Post-frontal air will mean an
interruption to our warming trend, and highs may only reach the
upper 40s or low 50s on Sunday across parts of North Texas. All
precip is expected to taper off to the east Sunday evening.

It appears upper ridging will prevail across much of the central
US during the first half of next week. This will mean a return to
near or above normal temperatures Monday through at least
Wednesday with gradually increasing dewpoints. The absence of lift
or deep moisture will keep the forecast area mostly dry during
this time period. However, deep troughing is expected to develop
to our west during the second half of the week, likely allowing
for another frontal intrusion and increasing thunderstorm chances
in the day 7-9 time frame.

-Stalley

&&

Preliminary point temps/pops...
Dallas-ft. Worth 51 36 55 33 58 / 0 30 10 0 0
Waco 48 36 54 33 58 / 20 50 40 5 0
Paris 48 33 53 29 55 / 0 10 5 0 0
Denton 50 32 54 31 57 / 0 10 5 0 0
McKinney 49 34 54 32 56 / 0 20 5 0 0
Dallas 51 37 55 34 58 / 0 30 10 0 0
Terrell 51 35 55 32 57 / 0 40 20 0 0
Corsicana 51 37 52 33 56 / 0 70 40 5 0
Temple 48 37 51 32 58 / 20 40 50 10 0
Mineral Wells 52 34 53 28 57 / 0 10 5 0 0

&&

Forward watches/warnings/advisories...
none.

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