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

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FXUS64 KFWD 262045

Area Forecast Discussion
National Weather Service Fort Worth TX
345 PM CDT Tue Sep 26 2017

/Through Tonight.../

The 3 PM surface analysis indicated that a cold front extended
from southwestern Missouri southwestward through McAlester
Oklahoma to Wichita Falls and Abilene to south of Midland. This
front will move southeast to near a Sulphur Springs to Killeen by
midnight and through the rest of the forecast area before daybreak
Wednesday. Expect scattered to numerous showers and isolated
thunderstorms along and west of the I-35 corridor with the PoPs
tapering off pretty quickly to the east. Some locally heavy rain
is possible with some 1+ inch an hour rainfall rates.

Winds will shift to the northeast at 10 to 15 mph with frontal
passage before decreasing to 5 to 10 mph. Lows will range lower
60s northwest to the lower 70s southeast.



/Wednesday and Beyond.../

Our much advertised cold front will have nearly pushed through the
forecast area as we begin the long term period on Wednesday
morning. A dearth of low-level convergence and upper-level
dynamics should greatly limit precipitation coverage along and
east of the front, but isentropic upglide--maximized near the
310-320 K theta surfaces--will be ongoing above the shallow
frontal inversion to the west. This will facilitate the
maintenance of a broad sheath of mainly light to moderate
stratiform precipitation through the morning and afternoon hours,
primarily across the Concho Valley and up through the Rolling
Plains, but the eastern fringes of ascent will be close enough to
warrant likely PoPs across our far western counties. PoPs will
decrease the farther east you go and head farther away from the
focused ascent. Lapse rates above the frontal surface tending
towards moist adiabatic will result in meager amounts of
instability, and this tune will remain true through the remainder
of the week, resulting in only sporadic chances for embedded
thunderstorms. Freezing levels up near 14-15 kft will continue to
result in fairly deep warm cloud layers, with PWATs continuing to
push 1.6-2 inches. As a result, a risk for locally heavy rainfall
will persist, but with the brunt of forcing for ascent displaced
well to our west, the threat for widespread flood-producing rains
appears quite low at this juncture.

Based on upstream observations indicating temperatures, which are
having a hard time breaking out of the 60s across Central Oklahoma
this afternoon, we`ve reduced high temperatures by a few degrees
west of I-35 where the effects of the frontal passage will be most
strongly felt. As was the case today (Tuesday), a stark west-east
temperature gradient will exist, with highs near 70 west, to near
90 across the east.

A rather similar scenario looks to play out on Thursday as
perturbations embedded within the high-level flow zip across the
region. On Thursday night and into Friday, the combination of an
intruding drier low-level airmass, and large scale height rises
should result in gradually decreasing precipitation chances.
However, a bit of a conundrum exists during this portion of the
forecast as several pieces of guidance suggest another sprocket
of energy may impinge upon the region during this time period, and
deliver one final chance at precipitation across the region. While
the deterministic GFS paints a decidedly drier picture, the EPS
(ECMWF Ensemble), and GEFS agree to an extent that this drying
trend may take a little longer to occur. As a result, opted to
nudge PoPs up a bit across the forecast area Thursday night and
into Friday from the previous forecast.

As drying below below 700 mb continues, precipitation chances will
finally come to an end area-wide Friday night and into Saturday,
although plentiful mid and high cloud cover should persist. This
will have the added benefit of keeping temperatures down a bit
with highs over the weekend pegged only in the upper 70s to
middle 80s. Temperatures will then gradually moderate towards the
upper 80s/90 next week, but a dry forecast will prevail.



.AVIATION... /Issued 1259 PM CDT Tue Sep 26 2017/
Scattered to numerous showers and isolated thunderstorms are
expected this afternoon mainly west of Interstate 35/I-35W but
some showers may work their way into the TAF sites late afternoon
into this evening. Thus, have included VCSH for for the 21z-03z
period in the Metroplex TAF sites. Mostly VFR conditions are
expected through this evening outside of showers. Ceilings should
lower to around 5000 feet by 21z and MVFR ceilings are expected by
12z Wednesday. Some IFR conditions are possible Wednesday morning
and have highlighted that possibility with a TEMPO BKN009 between
12z and 16z. VFR conditions are expected to improve Wednesday
afternoon so have placed a SCT015 BKN040 starting at 19z for the
extended portion of the DFW TAF.

At Waco, mostly VFR conditions are expected through tonight.
Isolated showers are possible this afternoon and scattered showers
are possible this evening. Have placed VCSH starting at 18z and
placed a TEMPO 6SM SHRA during the 00z through 06z periods.
Ceilings are expected to lower to MVFR by 15z Wednesday.



Dallas-Ft. Worth    71  85  70  81  65 /  40  30  30  30  30
Waco                71  87  71  85  66 /  40  40  30  40  40
Paris               68  87  68  81  63 /  10  30  20  30  10
Denton              67  83  66  78  62 /  50  40  30  30  30
McKinney            69  86  67  80  62 /  30  30  30  30  30
Dallas              71  87  70  82  66 /  30  30  30  30  30
Terrell             70  89  69  84  64 /  20  30  30  30  20
Corsicana           71  90  71  86  66 /  20  30  20  30  20
Temple              71  86  70  82  66 /  40  40  30  40  50
Mineral Wells       66  78  64  75  61 /  70  50  40  50  50




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