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Area Forecast Discussion (AFD)

Issued by Fort Worth/Dallas, TX (FWD)

                            
000
FXUS64 KFWD 191234 AAA
AFDFWD

Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
634 AM CST Tue Feb 19 2019

.AVIATION...
/12Z TAFs/

Steadily deteriorating conditions today with widespread rain.

The rapid return of Gulf moisture over the top of a shallow
postfrontal layer has steadily lowered ceilings overnight. These
ceilings are falling below FL030 and will quickly become IFR this
morning as the ongoing precipitation increases in intensity and 
areal coverage. Heavier downpours may occur, particularly from mid
morning through early afternoon, with the potential for temporary
LIFR ceilings/visibility. With little rise in temperatures and 
northeast/east flow, the surface layer will only become soupier
this afternoon with drizzle and LIFR ceilings likely. Surface 
winds will back tonight, and drier air will invade from the 
west/northwest. Although this will rapidly improve the visibility,
wrap-around moisture may maintain MVFR ceilings, particularly 
within the Metroplex. VFR should return during the daylight hours
of Wednesday morning.

25

&&

.SHORT TERM... /Issued 450 AM CST Tue Feb 19 2019/
/Today and Tonight/

The wide breadth of arctic air from the Northern Rockies to the 
Canadian Maritimes helped intensify an extraordinarily strong
polar jet across the CONUS. Above 30kft, speeds exceed 200kts 
through the Mid-Atlantic states. Well upstream of this jet max, 
the FWD RAOB from 00Z Monday evening sampled a 5-mile thick layer 
of 100+kt winds above 22kft. Although the core of the jet will 
steadily move poleward, North and Central Texas will remain within
its right entrance region as an upper trough in the Desert
Southwest approaches from the west.

Gulf moisture has begun to ride over the top of the shallow cold
surface layer, resulting in showers (and even a few thunderstorms)
from South Texas into Louisiana. This low-level moisture will
spread across all of North and Central Texas this morning, rain
expanding in areal coverage and steadily increasing in intensity.
Many of the radar echoes currently on the scope are still aloft,
the genesis of the precipitation developing aloft that will take 
some time to saturate the dry surface layer. This will be 
hastened by the moist advection within the frontal inversion 
(2500-5000ft AGL). PoP trends this morning follow these processes,
increasing from southeast to northwest.

As the initial bouts of light rain reach the surface, wet bulbing
will diminish temperatures, which may not reach their daily
minimums until mid to late morning. Temperatures will likely fall
below freezing in areas north and west of the Dallas/Fort Worth
Metroplex. Freezing rain may result in icing on trees and 
elevated surfaces, bridges and overpasses within the advisory area
the first roadways to develop icy patches. As the morning 
progresses, the precipitation will increase in intensity; and as 
the T/Td spread narrows, the downward transport of warm air will 
begin to dominate. While this may not raise surface temperatures 
right away, it will reduce the icing potential as the warner water
maintains the residual heat in the ground. However, icing on 
trees and other elevated objects may continue.

Thunderstorms will be more likely within the deeper moisture 
across Central and East Texas. However, thunder may also occur 
within the advisory area where steepening mid-level lapse rates 
will enhance the elevated instability, allowing for embedded 
convective elements. Although the erosion of the lingering warm 
nose may be offset by the burgeoning warm advection within the
same layer, creating a sounding generally unfavorable for frozen 
precipitation, the updrafts may be sufficient to produce a GS/PL 
hybrid. With temperatures near or below freezing, sudden bursts of
sleet or graupel could result in accumulations on roadways. By
midday, the warm advection will overwhelm the winter weather
potential, and rain with embedded thunderstorms will prevail
during the afternoon hours. Steady temperatures will slowly
recover this afternoon, but the combination of rain and 
northeasterly/easterly surface flow will keep high temperatures 
well below normal. The northwestern half of the CWA will peak in
the 30s.

Some drizzle or light rain will linger this evening, but rain
chances will end from west to east tonight as drier air invades 
from the west. Skies will be slow to clear, but with the cold
start to the night, temperatures will easily bottom out in the
upper 20s northwest to upper 30s southeast.

25

&&

.LONG TERM... /Issued 450 AM CST Tue Feb 19 2019/
/Wednesday Through Monday/

Our first system continues to exit east away from the area on
Wednesday. Lingering morning cloudiness is expected to hang on 
north of I-20 and east of I-45 during the morning hours within 
wrap-around moisture on the back side of the exiting system. 
Otherwise, westerly winds 10-15 mph and more abundant sunshine 
arrive in the afternoon. Temperatures will recover in the 
afternoon hours into the 50s, with a few readings in the lower 60s
across western Central Texas with some downslope component and 
drier air entraining. Normally, I'd be concerned with some 
elevated fire weather concerns across areas along and west of U.S.
281. However, with the relatively cool temperatures and expected 
moist 1-10 hour fuels from today's rainfall, I believe the grass 
fire threat will remain low areawide. If today's rainfall amounts 
west of I-35/35W corridors are considerably less than currently 
advertised, then it's a good bet high temperatures could be
several degrees warmer than the current forecast for highs on 
Wednesday. 

Surface high pressure settles in quickly Wednesday evening, 
before transiting slowly east across the Ark-La-Tex and Far East 
Texas. Light southeast winds return by sunrise Thursday, along 
with the prospects for some patchy light fog. However, I have 
decided against introducing any prospect for fog with low level 
warm advection and isentropic ascent increasing over our eastern 
Central Texas counties for some light shower activity along with 
potentially the prospect for some patchy drizzle by daybreak 
Thursday. Similar to the prospects for any patchy fog, confidence 
is too low on the transitory low level environment for me to 
introduce into late Wednesday night/early Thursday morning 
forecast, but bears watching. 

Thursday looks to be a cloudy and cool day as well, as shortwave
energy streaming northeastward within the progressive southwest
flow aloft maintains plenty of mid-high level cloudiness around.
The more impressive warm advection and ascent, as well as prospects
for any substantial convection delaying until later Thursday night
and on Friday. A few rogue light showers will be possible within 
a slightly richer moisture axis by Thursday afternoon south of 
I-30 and east of I-35 in Central Texas, but nothing worth noting 
with only very light amounts anticipated with low level moisture 
fairly limited. Highs will prevail mostly in the 50s with a few 
readings in the lower 60s certainly possible in the far western 
counties. Southerly winds in the 925mb-850mb layer and associated 
warm advection increases substantially later Thursday night, as a
more substantial shortwave lifts east across northern Mexico and 
West-Central and North Texas by 12z Friday morning. More 
widespread rainfall and low level cloud cover will result in 
holding low temperatures up into the upper 30s and 40s with east 
winds near 10 mph. Weak elevated instability may provide a rumble 
or two of thunder overnight, but do not expect significant 
convection to develop. This activity will be just a precursor to 
more widespread rainfall and more substantial convection arriving 
later on Friday and through the beginning of the weekend. 

The continuous stream of shortwave energy within the strong
southwesterly mid level flow overhead will provide the prospect
for more widespread shower activity through the day on Friday.
Another another cool, but not overly cold afternoon is expected
with best rainfall chances expected across the eastern half of the
area where stronger ascent will correlate with richer moisture
streaming north from the Gulf of Mexico. Again, enough instability
contained well aloft across our Central Texas and eastern counties
may be enough to produce the occasional rumble of thunder. No
severe weather is anticipated Friday. 

A brief reprieve in rain chances will arrives in time for Friday 
evening, as the lead shortwave energy shunts east and we remain in
a weak, subsident lull awaiting the main storm system moving east
across Arizona, New Mexico, and northern Mexico. An even more mild
night is expected as shower activity begins increasing within the
new found and increasing warm advection within the 925mb-700mb
layer during the pre-dawn hours west of I-35/35W. Lows will be
hard pressed to fall below 50 degrees with readings by daybreak
Saturday in the mid 50s to around around 60 degrees across Central
Texas. Our main Southwest U.S./northern Mexico system lifts 
across the Southern High Plains and across northern Oklahoma and 
Kansas on Saturday. A surface dryline will begin progressively 
moving east through our western counties Saturday morning, before 
exiting the area to the east by late afternoon or early evening. 
Kinematics, as one would expect, will be impressive. However, warm
sector cloudiness, widespread shower and scattered morning storm 
activity will play a big role on how much instability will be 
available for any strong to possibly severe storms across areas 
east of I-35 into East Texas. Due to the potential impact of 
morning clouds and rainfall, we believe the severe threat should 
be limited, though gusty winds, small hail, and frequent lightning
will all certainly be attainable with the strongest storms across
the eastern CWA on Saturday. 

A surface low will transit eastward across Oklahoma/Kansas moving 
rapidly from northwestern Oklahoma and into Kansas/western 
Missouri Saturday afternoon into early evening. Though showers and
storm chances linger across the far eastern counties early-mid 
afternoon, much of this activity exits east with the better 
moisture and ascent late in the day. With a cold front holding off
until Saturday night, the clearing skies, gusty west winds, and 
warm temperatures ranging from the mid 60s northwest to the lower-
mid 70s elsewhere are expected. Drier air will entrain into 
especially our far western counties fairly quickly and depending 
on previous, antecedent rainfall, at minimum elevated fire weather
conditions will be possible along/west of U.S. 281 due to the 
warm and windy conditions. 

Brisk west winds will continue into Saturday evening, as a strong
westerly pressure gradient continues to reside across the area in
advance a cold front arriving into our western and Red River 
counties just before sunrise Sunday. Low temperatures will not be
overly cold, as stronger low level cold advection shunts more 
east than south in the wake of our system. Lows Sunday will range
between 35-45 degrees, with sunny skies and light winds providing
a nice afternoon, as surface high pressure settles in and highs 
warm into the upper 50s and 60s. As has been the case the past 
several weeks, the nice conditions don't last long as shortwave 
energy approaches within the resultant strong, low-amplitude flow
overhead Sunday night into Monday. Low rain chances return Monday
across eastern Central Texas where increasing mid-high level 
moisture returns. Highs will still warm into the 60s areawide, 
after a cool start in the 30s and 40s. 

05/

&&

.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth    38  34  56  38  56 /  90  30   0   0   5 
Waco                41  32  59  38  56 /  90  30   0   5  10 
Paris               38  34  50  36  54 / 100  60   0   0  10 
Denton              37  31  56  37  56 /  90  30   0   0   5 
McKinney            37  32  52  37  55 / 100  30   0   0   5 
Dallas              38  34  55  39  56 /  90  30   0   0   5 
Terrell             39  33  53  37  55 / 100  40   0   0  20 
Corsicana           43  35  54  38  55 / 100  30   0   5  20 
Temple              41  35  61  40  56 /  80  30   0  10  20 
Mineral Wells       36  30  58  37  57 /  80  20   0   0   5 

&&

.FWD WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 2 PM CST this afternoon for TXZ091-
100>102-115-116-129.

&&

$$

25/05