Area forecast discussion...updated
National Weather Service Amarillo Texas
1138 PM CDT Friday may 17 2013
Aviation...
IFR ceilings will continue to push west across the Ama and Guy taf sites
by early Saturday morning. Will start this forecast out with IFR ceilings
at the Guy and Ama taf sites and will add a tempo group at dht for
later on as confidence is not as high there. Low clouds are expected
to clear out quickly just after sunrise as winds turn more to the
south and southwest. The winds will get up close to 20 knots with
higher gusts by middle to late morning on Saturday at all taf sites. A
surface trough may move through dht Friday evening turning the winds
more westerly...but winds will likely stay out of the south at Guy
and Ama through the end of this forecast.
&&
Previous discussion... /issued 614 PM CDT Friday may 17 2013/
Aviation...
a dryline was moving back to the west early this evening. Ama and Guy
already have southeast winds to the east of the dryline. The dryline
will push west across the dht taf site by late this evening. Expect
southeast winds around 15 knots with higher gusts this evening. Low
clouds are expected to move back over Ama and Guy overnight. For now
have not mentioned any fog as confidence is fairly low right now. The
ceilings should get down into the MVFR range at Ama and Guy. Dht is
expected to stay out of the low clouds. Clouds will break up by middle
morning on Saturday and a southwest wind will pick up to around 20
knots with higher gusts.
Previous discussion... /issued 358 PM CDT Friday may 17 2013/
Discussion...
through tonight: the dry line has advanced slightly farther eastward
than models suggested yesterday, and as a result, temperatures are
near record levels at Amarillo, Borger, and Dalhart. Although visible
satellite imagery shows some cumulus clouds developing across the
southern Texas Panhandle, visual observations indicate these clouds
have a flat appearance -- an indication of the warm temperatures
aloft (the cap). Due to the strength of the cap, we're not expecting
any showers or storms to develop in our area. For the third night in
a row, it looks like another round of low clouds and/or fog will
develop after 3 am for locations east of an Elkhart to canyon line.
There could be a few isolated spots across the northeast panhandles
that see visibilities dip to 1/2 mile at times. Lows will be quite
mild overnight, ranging from the upper 50s to near 70.
Saturday-Saturday night: low clouds and fog should scatter out by the
late morning hours as the dry line begins to sharpen and mix eastward
quickly. As south southwesterly winds increase, temperatures will
warm into the lower 90s to lower 100s during the afternoon. A deep
western trough will begin to approach the forecast area by the
afternoon hours with large scale forcing for ascent impinging on the
dry line. The million dollar question is where will the dry line be
located tomorrow afternoon. Research over the last few years suggests
the NAM is typically the Superior model with respect to the dry line
position during modest flow aloft. The 12z NAM was shifting the dry
line into western Oklahoma by late tomorrow afternoon, but the 18z
run has now shifted the dry line slightly farther westward. The
ECMWF, GFS, UKMET, and high-resolution models hang up the dry line
over the eastern panhandles. Based on the uncertainty, we kept a
mention of thunderstorms east of a Beaver to Clarendon line. If the
farther west solution with respect to the dry line verifies, we'll
likely be dealing with severe storms if the cap breaks. Speaking of
the cap, 700 mb temperatures are expected to be 13-14 c, but
strong insolation, confluence along the dry line, and forcing from
the approaching trough may provide sufficient lift to trigger
isolated thunderstorms after 4 PM. With mixed layer cape values up
to 2000 j/kg and deep layer shear values up to 35 kt, some storms
could take on supercellular characteristics. The main hazards with
any storms appear to be large hail up to the size of Golf balls and
damaging winds in excess of 60 miles per hour. Despite decent wind shear in the
lowest 1 km, high cloud bases will greatly limit the tornado
potential for our area. Storms will likely move east of our area by
9 PM with the severe weather threat quickly ending.
Sunday-Monday night: a weak cold front will move through the area on
Sunday. As a result, temperatures will be slightly cooler with highs
ranging from the lower 80s to middle 90s. We've added a slight chance
of thunderstorms across the northeast Sunday afternoon where some
Post-frontal moisture will be lingering as an upper disturbance moves
across the area. A reinforcing cold front will move through on
Monday afternoon. With some lingering moisture behind the front,
some showers and storms will also be possible across the northern and
northwestern sections. Highs on Monday will range from the middle 70s to
lower 90s.
Tuesday-friday: temperatures will be much cooler on Tuesday behind
the cold front with highs ranging from the middle 70s to middle 80s.
Temperatures will warm slightly on Wednesday as upper heights begin
to rise. Moisture will return after Wednesday night as southwest flow
aloft re-develops in response to a western US trough. The end of
this forecast period is still looks more stormy, especially Thursday
and Friday afternoons. It's possible there could be some severe
weather on Thursday afternoon given a favorable combination of
buoyancy and shear. Temperatures will also warm up considerably as we
head into Thursday and Friday with highs back into the 90s.
Jackson
Fire weather...
critical fire weather conditions are expected to develop Saturday
afternoon and evening across the western two thirds of the panhandles
where relative humidity values will drop between 6 and 15 percent
along with south southwesterly 20 foot winds between 20 and 25 miles per hour
with higher gusts. Relative humidity recoveries tonight will
generally be good across the eastern half of the Fire Weather Watch
area, but only fair across the western half of the Fire Weather
Watch. The potential for slightly increased fire potential is
compounded by the fact that 60-day percent of normal rainfall across
the Fire Weather Watch area is between 5 percent and 50 percent and
erc values will range between the 75th and 96th percentile. However,
with the recent green up and lack of fuel loading, significant wild
fire potential will be low.
Elevated to near critical fire weather conditions will be possible
across the southern and southwestern Texas Panhandle on Sunday.
Elevated fire weather conditions may also occur across the western
Texas Panhandle on Monday, but the timing of a cold front leads to
low confidence at this time. After a break from fire weather
conditions Tuesday and Wednesday, it looks like elevated fire weather
conditions may return on Thursday across the western panhandles.
&&
Ama watches/warnings/advisories...
Texas...Fire Weather Watch from Saturday afternoon through Saturday
evening for the following zones: Armstrong...Carson...
Dallam...Deaf Smith...Donley...gray...Hansford...Hartley...
Hutchinson...Moore...Ochiltree...Oldham...Potter...
Randall...Roberts...Sherman.
OK...Fire Weather Watch from Saturday afternoon through Saturday
evening for the following zones: Beaver...Cimarron...Texas.
&&
$$
15/09
