Scientific Forecaster Discussion
fxus64 kfwd 191251
Area forecast discussion
National Weather Service Fort Worth Texas
751 am CDT Sat Oct 19 2019
The vigorous shortwave that gave parts of the area some widely
scattered, brief, elevated showers and storms this morning is
quickly exiting the area. Meanwhile, a cold front continues to
enter the far western County Warning Area as of sunrise.
I am removing the slight chances for storms in the far eastern
counties and adding some patchy-areas of fog across our far
southeast counties. South winds 5-10 mph winds in advance of the
cold front has helped to advect rich low level surface dew points
temperatures in the upper 50s to lower 60s across this area with
stratus and some fog. Though isolated areas of dense fog are
possible, I don't believe it will be widespread enough for any
advisories this morning. This fog should be short-lived and begin
dissipating readily after mid-morning, as strong insolation heats
up surface temperatures rapidly.
Aviation... /issued 655 am CDT Sat Oct 19 2019/
Concerns and challenges: frontal passage 15z-18z will shift south winds
around 10 mph to the west, then northwest 10-15 knots by 18z.
Otherwise, VFR with no precipitation expected.
A vigorous mid level impulse continues moving east of the airports
this morning with just scattered mid-high level clouds in it's
wake. Eventually, sky clear conditions will prevail as a cold front
arrives later this morning...putting dfw and Dal into north flow.
Waco will likely see the wind shift a few hours later; or between
Northwest winds 10-15 mph behind the cold front later today are expected
to become light north or calm after sunset tonight, as the dry boundary
layer decouples rapidly and high pressure at the surface slides
into the area.
Short term... /issued 350 am CDT Sat Oct 19 2019/
/today through tonight/
A vigorous mid level impulse is moving east across the County Warning Area early
this pre-dawn, Saturday morning. Low level southerly flow on area
vwps from local radars was impressive and currently southerly at
40-45 knots, which shows the influence this strong shortwave is
having even on the dry, lower levels. GOES satellite imagery was
even indicating a Gravity wave shooting out well in advance of the
elevated convection across central Texas. Widely scattered, high-
based and elevated showers and tstorms continue racing east across
mostly the area from I-35 and to the east, where strong vertical
motions are saturating and destabilizing the mid levels quite
impressively considering the initial dry environment this system
arrived into. Central Texas areas are a bit more displaced south,
but isolated storms were occurring as far south as Cleburne and
Italy in Johnson/Ellis counties per latest regional radar. I can't
rule out isolated, short-lived elevated convection through mid-
morning across the far eastern counties per the real-time data. In
addition, pooling of relatively higher dew points > 60 degrees
across parts of Milam, Robertson, and Leon counties may result in
brief fog development from the Highway 6 corridor east toward I-45
around sunrise. I do not expect any impacts from any fog
development with fog dissipating quickly by mid morning in
response to rapidly warming temperatures and increasing surface
Beyond mid-morning and in wake of this morning's shortwave
disturbance exiting the area, we should see the cold front sweep
readily southeast through the area through this afternoon. This
front will mainly drawn in slightly drier air into the region
with any thermal advection being negligible. Plentiful sunshine
will prevail with highs warming into the upper 70s northwest to
near 90 degrees across parts of central Texas. It will be breezy
from the I-35 corridor and points west where northwest winds 10
to 15 mph will contain occasional gusts to around 20 mph as
momentum Transfer with the boundary layer is easily achieved. A
mostly clear and seasonably cool night is expected for your
Saturday night as surface high pressure settles across the area.
A good radiational cooling set up will occur as wind speeds come
down quickly after sunset with decoupling of the dry boundary
layer. Lows by Sunday morning are expected to be mostly in the 50s
with near calm winds to start a day that will become much more
active later on.
Long term... /issued 350 am CDT Sat Oct 19 2019/
/Sunday through Friday/
the cold front will stall out across south central and southeast
Texas Sunday morning but as a longwave trough deepens over the
central part of the country, southerly flow will intensify over
the region. The southerly flow and sunshine will certainly result
in very warm temperatures as highs will reach the low 90s in the
west to the mid 80s in the east. Elevated grass fire danger will
occur across the western zones as relative humidity drops to near 25% and surface
winds increase to 10 to 20 mph.
Moisture pooled on the south side of the front will return
northward during the day but the primary forecast uncertainty is
how much, how fast, and how deep will the moisture layer be by the
early evening hours when synoptic forcing for ascent begins to
impinge upon the region. The moisture quality will control
whether the atmosphere can convect while temperatures are still
warm enough from daytime heating to support surface based
convection and a more substantial severe weather risk. This
moisture layer looks to be very shallow west of I-35, but have
more depth east of I-35. At this time most of the guidance does
not show the moisture arriving fast enough for storms anywhere in
the County Warning Area Sunday evening, but a couple of the cams and the European model (ecmwf) do
show it making it into the northeast zones where it juxtaposes
with forcing for a risk of supercells and severe weather. Should
this occur, all modes of severe weather would be possible with
this activity between 6 PM and 10 PM Sunday evening mainly across
the northeast zones. Storm Prediction Center has outlooked a part of the County Warning Area in
slight risk, but given the uncertain and highly conditional nature
of this threat, that forecast may be a bit aggressive.
With the loss of daytime heating temperatures will cool after
sunset and cinh will increase over the entire area. However
increasing forcing for ascent will attempt to remove the capping
inversion and it is likely that once a cold front begins to plow
into the County Warning Area around midnight that we will see a line of storms
develop along it. The line may initially be broken across the northwest
zones, but should fill in as it reaches the dfw metroplex around 2
am. Have increased pops into the likely and categorical range for
the entire County Warning Area except for the northwest zones. While deep layer shear
and instability values are both squarely in the severe weather
parameter space, the Mode of the convection (a line parallel to
the shear vector) should mitigate the severe weather threat.
Still, some marginally severe hail or wind may occur with this
line as it progresses through the County Warning Area. Rainfall will average 1/10
of an inch in the northwest to over 1 inch in the east.
Drier northwesterly winds on Monday will bring some cooler air
into the region with highs topping out in the 70s in what should
be a pretty nice day after any lingering morning rain/clouds exit
to the southeast. Excellent radiational cooling is expected Monday
night and temps will drop into the 40s for most locations.
Gradually warming temperatures will occur Tuesday and Wednesday
with pleasant weather prevailing in dry northwesterly flow aloft.
The next system will noticeably impact our sensible weather on
Thursday as a longwave trough amplifies and deepens over the
central US. There is a bit of uncertainty on whether this system
will be progressive (ecmwf) or slower with a closed low at the
base of it (gfs/gefs). Either way it looks like a front will
arrive on Thursday afternoon with a chance of showers and storms.
Either the trough will be progressive and send colder air in here
faster, or be slower and result in overrunning clouds/rain
continuing into Friday. Both scenarios warrant lowering high
temperatures Friday with temps possibly struggling to reach 60.
Fear not, another pleasant autumn weekend should follow.
Preliminary point temps/pops...
Dallas-ft. Worth 83 55 88 56 74 / 0 0 10 80 10
Waco 88 56 90 58 76 / 0 0 10 80 20
Paris 80 55 80 57 71 / 5 0 10 90 20
Denton 81 53 87 53 74 / 0 0 10 60 10
McKinney 82 54 86 56 73 / 0 0 10 80 10
Dallas 84 58 88 57 74 / 0 0 10 80 10
Terrell 84 55 88 59 74 / 0 0 10 90 20
Corsicana 86 57 86 59 73 / 5 0 20 90 30
Temple 88 58 89 59 76 / 0 0 20 70 30
Mineral Wells 81 52 89 53 74 / 0 0 10 50 5