Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Fort Worth Texas
1222 PM CDT Tuesday Sep 30 2014
cumulus will continue to bubble across the region this
afternoon... affecting all taf sites. Ceilings should remain above
3k feet this afternoon at all sites. Southerly winds will pick up
a bit this afternoon as well... easing some after sunset. Stratus will
build from the south early Wednesday morning... with IFR ceilings
affecting kact by about 10z. Currently thinking stratus deck will
remain scattered further north.
current forecast is on track per area soundings as another warm
early fall day can be expected throughout the forecast area.
Another few days of warm weather before rain chances increase from
the north late Wednesday and Thursday. A cold front will move
through late Thursday and early Friday...and will effectively end
rain chances as drier...and slightly cooler air settles in for the
Zone forecast product/pfm/afm out shortly.
Previous discussion... /issued 343 am CDT Tuesday Sep 30 2014/
water vapor shows a potent upper level low ejecting northeast out
of Colorado and into the northern plains this morning. This system
will result in the erosion of the persistent low level ridge over
the lower Mississippi Valley that brought US several days of light
easterly winds. Our winds will increase and become southerly
today and tap into some higher Gulf moisture. There is actually
good agreement among the models that a small amount of uncapped
instability will be available over the eastern zones this
afternoon for isolated convection. This instability resides below
15000 feet and is not enough for thunder...but saturating low to
middle level moisture profiles do look favorable for a few showers.
This activity is unlikely to produce any significant rainfall but
warrants a mention in the forecast. Otherwise...high temperatures will
increase a degree or two over yesterdays values and generally top
out near 90...but the increase in humidity will make it feel
warmer. A dry line will set up in West Texas by this
afternoon...but any convection that fires along it will remain
well northwest of our County Warning Area.
South winds and muggy conditions are expected tonight...and the
continuation of moisture advection into the area should result in
some low stratus and possibly brief advection fog over central
Texas by Wednesday morning. The unseasonably warm and humid
weather will continue into Wednesday and Thursday with temperatures
about 10 degrees above normal.
Model guidance is in good agreement regarding the track and
timing of an upper level shortwave trough that will swing through
the Red River valley Thursday. However...model guidance has become
more spread with the timing and strength of the cold front that
pushes through the area Thursday afternoon and night. The 0z NAM
was significantly slower than the other guidance with the GFS the
fastest...but all guidance has slowed the timing by about 6 hours.
The slower timing is probably better news for rainfall prospects
over the region...as this means the front will have a little more
daytime heating to work with to remove the cap over the region.
Therefore have increased probability of precipitation a little over the eastern zones
where confidence in a line of storms along the front is growing.
Will bring low probability of precipitation into the northern zones Thursday morning. Any
rainfall Thursday morning would be associated with elevated
convection being forced ahead of the shortwave trough. This
activity will likely produce only light quantitative precipitation forecast. The more significant
convection will occur along the frontal boundary when it moves
into the area during the afternoon. But since the shortwave trough
will be exiting before the front arrives...surface winds will veer
to the southwest by the afternoon. This veering will result in hot
temperatures...with low 90s or even middle 90s likely over all but
the northern zones. These southwesterly winds however will tend to
deplete moisture and will limit convergence along the front. For
that reason...convection will have a harder time developing along
the front west of I-35 where moisture is rather limited...but will
probably fill into a more solid line as the front moves east by
late afternoon. Will continue with just a 20 percent chance west
of I-35 and increase probability of precipitation to the 30-40 percent east of I-35. The
highest probability of precipitation of 50 percent will be reserved for the northeast
zones where upper level forcing and moisture/instability all look
most favorable. Deep layer shear and instability look adequate for
a low risk of severe hail or wind gusts...especially over the
northeast zones. Locations that do see thunderstorms may record
over a half inch of rain.
Have slowed the progression of cooler air into the region Thursday
night and Friday due to weaker northerly winds and cold advection
prognosticated in the wake of the front. Still temperatures should fall into
the 60s for lows by Friday morning...with highs in the low 80s
north to middle 80s south Friday afternoon. While thermal advection
is limited...rapid drying at the surface and aloft will occur as
northwesterly flow through the depth of the troposphere sets ups.
The surface highs should settle into the area Friday night and
radiational cooling looks excellent. Lows will bottom out in the
upper 40s in a few of the traditionally cooler spots...with 50s
elsewhere. The pleasant and seasonable weather continues into
Saturday afternoon but southerly winds return by Sunday morning
resulting in a moderation of temperatures. Temperatures will be
back above normal by early next week...and likely approaching 90
again in 7 to 8 days.
Preliminary point temps/pops...
Dallas-ft. Worth, Texas 91 73 92 75 90 / 5 5 5 10 30
Waco, Texas 91 70 92 74 93 / 5 5 5 5 30
Paris, Texas 87 69 88 73 86 / 10 5 5 10 50
Denton, Texas 89 70 91 73 88 / 5 5 5 20 30
McKinney, Texas 90 69 90 74 88 / 5 5 5 10 50
Dallas, Texas 90 73 91 75 90 / 5 5 5 10 40
Terrell, Texas 90 72 91 75 91 / 10 5 5 10 40
Corsicana, Texas 90 72 91 75 92 / 10 5 5 5 30
Temple, Texas 90 70 92 74 92 / 5 5 5 5 20
Mineral Wells, Texas 90 69 93 72 88 / 0 5 5 20 20