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

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FXUS64 KFWD 210837

Area Forecast Discussion
National Weather Service Fort Worth TX
337 AM CDT Wed Mar 21 2018

/Today and tonight/

Pacific moisture arcing around the top of an upper ridge over the
Desert Southwest is resulting in occasional cirrus across North
and Central Texas. At the surface, a ridge axis has begun to shift
east of the region, which will is resulting in a switch-over to
southeast winds. Wind speeds will be fairly light today, but may
increase to 10-15 MPH across the western third of the region this
afternoon as the gradient begins to tighten.

Otherwise, a pleasant day is in store with high temperatures in
the upper 60s to lower and mid 70s. Increasing dewpoints and
southeast winds should keep tonight`s low temperatures a tad
warmer than the past few nights.



/Thursday through Tuesday/

The warmup will continue Thursday into Friday as the Plains are
dominated by mid and upper level ridging. With the center of surface
high pressure shifting farther to the east, southerly winds will
begin to increase during the day Thursday and this trend will
continue into Friday. Highs on Thursday should top out in the mid
to upper 70s with further warming into the 80s on Friday. We`ll be
centered just to the east of the ridge axis during this time which
will keep northwest flow aloft overhead and little to no chance
for precipitation.  As we head into late Friday and Saturday the
upper ridge will begin to slide east of the region as a large
upper trough digs into the western U.S. As it does, surface
pressures will fall in the Plains, tightening the pressure
gradient across North Texas and allowing southerly winds to really
increase. This will also help pull some better Gulf moisture

By Saturday, a large surface cyclone will be moving into the
Midwest states dragging a cold front southward into the Plains.
We`ll have ample moisture across North Texas, but we should remain
strongly capped for much of the day as the front approaches the
Red River. Thanks to westerly winds above the surface, 850 mb
temps will warm considerably during this time and we should see
highs climb into the mid and upper 80s despite an increase in
cloud cover.

Saturday night looks like it will mark the beginning of an active
period of weather across North Texas with a couple of shots of
severe storms followed by a more significant threat of heavy
rainfall through next week. As the aforementioned front lifts
northward Saturday night, the nose of a 110 kt upper jet will
spread into southwest Oklahoma resulting in a broad area of
diffluence aloft over the region. Stronger height falls spread
into west Texas during this time and low level warm advection
begins to ramp up. We could see some elevated showers and
thunderstorms develop mainly north of I-20 into Oklahoma during
this time.

This initial impulse will move northeast of the region early
Sunday although flow aloft will continue to strengthen as the
upper trough continues to dig over the southwestern U.S. We should
see a good dryline surge eastward by Sunday afternoon into our
western counties. With an upper pattern favorable for weak
embedded perturbations to provide sufficient forcing for ascent
to overcome weakened capping along and east of the dryline,
scattered thunderstorms are expected into the evening hours,
mainly west of I-35. Steep mid level lapse rates and modest deep
layer bulk shear will support severe thunderstorms with a
hail/wind threat. Convection should diminish in coverage later in
the night.

We should see a similar setup again on Monday afternoon, with
another eastward dryline push and the potential for scattered
severe storms mainly across the west and northwest counties. We
will begin to transition from a severe threat to more of a heavy
rainfall threat beginning late Monday night into Tuesday. This is
when the large upper trough begins to close off over the southwest
U.S. Meanwhile, a cold front will slide southward into the
Southern Plains Monday night, likely reinvigorating earlier
convection across parts of North Texas. This trend continues into
Tuesday and Wednesday. While forecast confidence typically
diminishes beyond 5-7 days, the model signal for heavy rainfall is
quite strong and is reflected as well in numerous GFS/ECMWF
ensemble perturbations. The upper pattern definitely has the
classic features of a heavy rainfall event with a slow moving
upper low, strong persistent upper diffluence over North Texas,
surging precipitable water values, and surface frontal features
to concentrate low level convergence. We`ll continue to monitor
this over the next several days.



.AVIATION... /Issued 1128 PM CDT Tue Mar 20 2018/

A surface high will slide east and settle across the area
tonight, before shifting east toward the Lower Mississippi Valley
on Wednesday. Northwest winds less than 10 knots early this
evening will become light west or near calm overnight, before
southeast winds 7-10 knots return by early Wednesday afternoon.

Northwest flow aloft will result in streaks of cirrostratus at
times, but low levels will remain very dry and continue to be
cloud-free. VFR will persist through Wednesday evening.



Dallas-Ft. Worth    73  51  77  60  80 /   0   0   0   0   5
Waco                73  48  78  58  81 /   0   0   0   0   5
Paris               67  45  73  55  73 /   0   0   0   0  10
Denton              71  48  77  58  79 /   0   0   0   0   5
McKinney            69  47  75  57  77 /   0   0   0   0   5
Dallas              72  51  78  60  80 /   0   0   0   0   5
Terrell             70  47  76  57  78 /   0   0   0   0   5
Corsicana           71  48  76  58  78 /   0   0   0   0   5
Temple              74  49  77  58  81 /   0   0   0   0   5
Mineral Wells       73  49  78  58  85 /   0   0   0   0   0



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