Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/21/17
Area Forecast Discussion
National Weather Service Amarillo TX
637 PM CDT Fri Oct 20 2017
.AVIATION...
For the 00z TAFs...
South-southwest surface winds may continue to gust above 30 kt for
the first 2 hours of the forecast. Otherwise, moderately strong
surface winds sustained in the 20 to 25 kt range are expected this
evening. There is some suggestion by the NAM and HRRR of a
stratus layer below 1000 feet advancing northward toward AMA
between 07z and 15z Saturday. Will include a scattered layer
during these hours for the AMA TAF and watch for a better signal
for development before including an IFR or MVFR ceiling.
Otherwise, a clear sky is expected overnight. VFR conditions
expected for the next 24 hours with no visibility restrictions
foreseen.
Surface winds expected to gust into the 25 to 35 kt range after
15z Saturday. Cold front will shift surface winds from southwest
to northwest around 16z at DHT and GUY, and around 19z at AMA,
with continued veering, trending to north by late afternoon.
Mid-level cloud layer with bases above 10,000 feet expected
during the afternoon.
Cockrell
&&
.PREV DISCUSSION... /Issued 259 PM CDT Fri Oct 20 2017/
DISCUSSION...
Weak upper level disturbance over the eastern Panhandles will
continue to move away tonight. A few showers will still be possible
in its wake this evening, so have kept some slight chances in the
far eastern Panhandles.
Vigorous upper level short wave trough over the northwest U.S. will
continue to plow southeastward and its leading edge will be into
western Oklahoma by late Saturday afternoon. At this point, it looks
like all of the dynamics and moisture associated with this upper
level disturbance will be to our east by the time showers and
thunderstorms develop in the late afternoon. But, will continue to
mention a low chance of showers and thunderstorms in the far
southeast CWA just in case the system is a little slower. A cold
front will push through the region Saturday afternoon and early
evening bringing north winds in the 20 to 30 mph range with higher
gusts. Temperatures may fall into the lower to mid 30s by early
Sunday morning causing another round of frost in the western and
central Panhandles.
A large upper trough will get carved out across the eastern U.S.
through mid week next week. Meanwhile, an upper level ridge will
build across the western U.S. This will put the Panhandles in a
northwest flow aloft which will tend to bring an occasional cold
front through.
A strong upper level short wave is expected to dive southward out of
Canada and into the central U.S. by late in the week. This should
open the door for much colder air to spill southward into our area.
Some models want to try to squeeze out some rain and snow across our
northern areas Thursday night, but this is the fist time that some
of the models have agreed on this colder scenario, so things could
change over the next several days.
&&
.PRELIMINARY POINT TEMPS/POPS...
Amarillo TX 55 72 39 67 44 / 5 5 0 0 0
Beaver OK 57 73 37 72 43 / 20 5 0 0 0
Boise City OK 49 63 33 68 41 / 0 0 0 0 0
Borger TX 59 74 41 71 45 / 5 0 0 0 0
Boys Ranch TX 55 73 37 71 42 / 0 0 0 0 0
Canyon TX 54 73 39 68 43 / 5 0 0 0 0
Clarendon TX 57 78 44 70 46 / 5 5 5 0 0
Dalhart TX 51 69 34 70 40 / 0 0 0 0 0
Guymon OK 55 68 36 71 43 / 5 0 0 0 0
Hereford TX 54 75 37 69 42 / 0 5 0 0 0
Lipscomb TX 61 76 41 71 45 / 20 10 5 0 0
Pampa TX 58 74 41 69 45 / 5 5 0 0 0
Shamrock TX 58 79 44 71 45 / 10 20 10 0 0
Wellington TX 59 83 44 72 45 / 5 20 10 0 0
&&
.AMA Watches/Warnings/Advisories...
TX...None.
OK...None.
&&
$$
03/21
Area Forecast Discussion
National Weather Service Des Moines IA
635 PM CDT Fri Oct 20 2017
.SHORT TERM.../Tonight through Sunday/
Issued at 333 PM CDT Fri Oct 20 2017
Upper ridging that has been in place the past few days will continue
to push east through the OH Valley tonight with a broad trough in
place across the western/central US. This has set up southwest flow
aloft with moisture return in the lower levels from the Gulf. The
upper trough will elongate and push eastward through the central US
into Saturday/Saturday night, with an associated area of surface low
pressure centered across Manitoba by late Saturday night. An
associated strong cold front is expected to sweep through the state
by late Saturday into Saturday night. An initial shortwave
trough/impulse of energy will approach the state tonight with the
associated moisture advection and lift. This will allow for showers
and some thunderstorms to develop across the region and spread
across portions of western and central IA. CAMS not too robust with
this activity as overall theta-e advection somewhat weak and deep
moisture more limited. Into Saturday morning, weak lift and moisture
likely to keep more of the isolated to scattered shower/storm
development possible and allow for increased cloud cover. As the
main upper trough moves out into the central and northern plains, a
line of thunderstorms is expected to develop in vicinity of the
frontal boundary and spread across central IA as the front pushes
east. Frontal passage timing slowing a bit, but overall expected to
be situated across far western IA by the late afternoon hours at the
time of convective initiation. Strong CAP evident on soundings ahead
of the front, so have lowered pops some across the central/eastern
forecast area through the day Saturday with more of a focus on the
passage of the front. Steep mid level lapse rates will allow the CAP
to erode as the front approaches with sfc-based storms becoming
possible. Expect storms to merge into a line, with MUCAPE values
expected in the 1000-1500 J/kg range. Deep layer shear around 30kts
or slightly higher, with decent SRH values around 100-200. Therefore
this will suggest there is the potential for a damaging winds
threat, especially with fast storm motions. Additionally with a
squall line/line segments and the shear profile/SRH, brief
tornadoes/QLCS tornado activity cannot be ruled out. The front will
quickly progress through the forecast area with some lingering
showers expected behind the front, otherwise as this system moves
east, cooler and dry conditions are expected for Sunday with a west
to northwest upper level flow pattern taking shape.
.LONG TERM.../Monday through Friday/
Issued at 333 PM CDT Fri Oct 20 2017
Another broad upper trough will drop into the north central US into
Monday/Tuesday. This will bring another push of cold air into the
state with a chance for some weak showers Monday afternoon with the
frontal passage. This front will send temperatures closer to the
seasonal averages for the middle of next week. Another stronger
broad upper level trough will drop through the area Thursday into
Friday with another very strong cold front. Could see some showers
with this front and maybe even a little snow mixing in the backside
as showers taper off. H85 temps will drop into the -8C to -10C
range across the state by late Thursday which should send lows into
the 30s and possibly even upper 20s in spots. This night is when the
greatest frost/freeze potential exists. The cold will continue into
Friday as highs top out in the mid 40s to around 50.
&&
.AVIATION.../For the 00Z TAFS through 00Z Saturday evening/
Issued at 631 PM CDT Fri Oct 20 2017
VFR conditions overnight. Southerly winds should stay somewhat
mixed allowing for gusty winds to continue through the night
which should limit degree of LLWS so did not put into TAFS. HRRR
and other short-range models continue to generate fast moving
convection across part of Iowa late due to warm advection and
moisture advection. Expect line of storms with cold front Saturday
evening. Introduced showers and VCTS for TAFS Saturday afternoon
as front approaches. Model soundings suggest plentiful low-level
moisture and saturation so SC deck looks likely on Saturday.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Beerends
LONG TERM...Beerends
AVIATION...Johnson
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1015 PM CDT Fri Oct 20 2017
.UPDATE...
A quiet evening on the radar with just a few light showers off of
Galveston Island/Bolivar Peninsula moving onshore this hour.
Forecast has scattered showers with isolated storms forming
across the nearshore waters and moving inland through the mid to
late Saturday morning hours. Water vapor channel possibly shows a
weak disturbance crossing southern Texas and this may be the
impetus to early morning near coastal precipitation. As a upper
trough moves out of the Rockies and into the western Plains
tomorrow...there may be just enough mid-level convergence across
eastern Texas (within a 1.6 to 1.8 inch PWAT air mass) to increase
shower and storm coverage to chance probs once lower 80F convective
temperatures are met. Highest precipitation chances will occur
during the first half of Sunday...or just ahead of a passing cold
front. 31
&&
.PREV DISCUSSION... /ISSUED 658 PM CDT Fri Oct 20 2017/
AVIATION...
There are a few lingering very light showers around, but majority
of precip has mostly pushed off to the east for the time being.
Though there may be a few breaks early, but MVFR cigs generally
along and east of I-45 will likely stick around all night. It`s
not out of the question they`ll dip into IFR territory late
tonight and toward morning. We`ll probably see some patchy 3-6nm
fog develop as winds die off later as well. Speed convergence
along the coast should allow for some sct shra & iso tsra to
redevelop overnight. Exact location and timing isn`t clear, but
expect some amendments once we see some development. Ceilings
should slowly lift in the morning hours, probably back to VFR by
lunch or slightly before. Highest coverage of sct precip looks to
be generally north of Highway 59 during the day Saturday. 47
&&
PREV DISCUSSION... /ISSUED 401 PM CDT Fri Oct 20 2017/
DISCUSSION...
Latest radar imagery shows widespread showers and thunderstorms in
the Gulf off the coast of High Island. Other scattered showers and
isolated thunderstorms stretched north of High Island towards
Cleveland and Crockett. None of this activity has been producing
heavy rainfall except for the activity in the Gulf where it does
not matter. A brief band of storms formed over SW Fort Bend County
and W Brazoria County where radar estimated 1 to 4 inches of
rainfall. With no rain gages in the band to get ground truth we
can only speculate that actual rainfall may have been higher since
the radar had been underestimating rainfall amounts.
Water vapor imagery shows the first short wave trough pushing out
of W Texas into W Oklahoma this afternoon. Trough axis is just
about to push into SE Texas so there may only be a few more hours
of potential shower and thunderstorm activity. Latest HRRR model
runs line up with this thinking with shower and thunderstorm
activity quickly dropping off between now and 8PM. Even the
activity embedded within the plume of higher precipitable water
should be decreasing over east Texas. There may be a few showers
overnight but otherwise expect quite conditions with low
temperatures in the 70s.
Saturday moisture may increase again with precipitable water
values back to around 1.7 to 1.9 inches. Water vapor imagery shows
a weak vorticity max approaching El Paso but the models seem to
lose this feature tonight into tomorrow. There is some weak signal
in the vorticity fields Saturday afternoon which results in a band
of showers and storms from Sugar Land to Huntsville. Still overall
activity looks isolated to widely scattered despite having CAPE
over 2000 J/kg. Lift from any kind of disturbance just does not
look strong enough to trigger widespread convection or support
severe weather. SPC does have a marginal risk for Saturday night
as a pre-frontal trough/cold front approach the area but expect
the line of storms to be weakening as it pushes south due to more
stable airmass overnight.
Sunday morning synoptic and mesoscale models are pretty good
agreement with the squall line of storms entering the forecast
area by 12Z Sunday. WRF-ARW/NMM 12z runs both show the squall line
reaching College Station to Crockett. The Texas Tech WRF shows a
similar timing but unlike the GFS/ECMWF/NAM, it basically has the
squall line decaying as it reaches the coast by 17-18Z Sunday.
There is high confidence that the area will see rain Sunday
morning with the line of storms, but rainfall amounts could be
less than forecast if trends with the mesoscale models continue.
As for severe weather, GFS/NAM/ECMWF support the possibility of it
but again the squall line could out run any of the stronger upper
level dynamics with large scale ascent occurring mainly over the
Arklatex into Arkansas. SPC has general thunderstorms for the day
3 outlook and see no reason to disagree with this assessment. The
Texas Tech WRF evolution of the line of storms certainly supports
this. We still do not want to let our guard down as for pattern
recognition supports the possibility. There will still be high
moisture over the area, strong large scale ascent although maybe
slightly north of the area, and favorable jet configuration with
the trough. The problems may come in the boundary layer as 850mb
winds become SW ahead of the line and could advect higher moisture
east faster than expected. This could be the reason why the Texas
Tech WRF shows a decaying system.
Cold front still pushes through all of the area by the end of the
day Sunday with northerly boundary layer flow continuing Monday
and Tuesday. By Tuesday the upper level pattern becomes quite
amplified which supports another frontal passage and re-enforcing
colder air. By the end of next week models suggest another deep
trough over the Rockies and Plains. This front looks much stronger
and both the GFS/ECMWF have the 850mb freezing line between
Palestine and Crockett by 12Z Saturday October 28. Again this is
the day 7-8 forecast but there is some decent model agreement with
the strength of the front. 39
&&
MARINE...
Winds/seas are remaining elevated in/near the strong storms over
the coastal waters this afternoon. With the activity persisting
into the evening, will go ahead and keep the SCEC in place for
both the near/ offshore waters through tonight. The onshore flow
is expected to become a bit more established overnight/early tomorrow
with the surface high scoots further E/NE. The increased long
fetch and strengthening SE flow could keep SCEC flags in place
tomorrow. The next cold front remain on track for passage into the
Gulf waters Sun afternoon. SCEC and SCA flags are likely in the
wake of the front.
The persistent easterly wind component today has helped with the
elevated tides this afternoon. So far...projections are on track
as we are currently nearing high tide. Minor coastal flooding is
possible along the Bolivar Peninsula and near Surfside through
early this evening. 41
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 70 87 67 77 51 / 20 40 60 60 10
Houston (IAH) 72 86 72 82 56 / 20 30 40 80 10
Galveston (GLS) 76 84 77 83 63 / 30 30 30 80 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...SMALL CRAFT SHOULD EXERCISE CAUTION until 4 AM CDT Saturday for
the following zones: Galveston...Matagorda.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 4 AM CDT Saturday for
the following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Coastal waters from High
Island to Freeport out 20 NM...Waters from Freeport to the
Matagorda Ship Channel from 20 to 60 NM...Waters from High
Island to Freeport from 20 to 60 NM.
&&
$$
Discussion...31
Area Forecast Discussion
National Weather Service Jacksonville FL
813 PM EDT Fri Oct 20 2017
.UPDATE...High pressure aloft will remain centered over
forecast area. At the surface...high pressure will remain
centered north of forecast area...maintaining easterly to
northeasterly surface flow over the area. Only isolated
small showers detected early this evening over our southeastern
counties...could see more showers over coastal waters late
tonight. Otherwise clear to partly cloudy skies expected...with
high clouds spreading in from the west. Low temp forecast looks
good...with upr 50s to lwr 60s interior se GA...mid 60s interior
ne FL...65-70 I-95 corridor...and around 70 coast. Maintained
mention of patchy fog late tonight interior se GA as hinted by
latest HRRR model.
&&
.AVIATION...Generally VFR conditions are expected next 24hrs...
with just some high cloudiness spreading in from the west late
Tonight. Could be some patchy light fog...included this in
KGNV/KVQQ TAFs.
&&
.MARINE...No changes are planned for next CWF issuance.
High pressure will be north of area waters into Saturday
then to the Northeast Saturday night into Monday. Onshore
winds will decrease some but will still have an exercise
caution for the waters. A strong cold front will sweep across
the region from the West Monday night into Tuesday. A strong
line of storms will be possible as this front moves through.
Small Craft Advisory conditions appear likely with the front.
Rip Currents: The High Risk is continued through late Saturday
due to lingering east swells and onshore flow.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 58 83 66 84 / 10 10 10 30
SSI 68 79 73 81 / 10 10 30 30
JAX 66 82 70 84 / 10 20 20 30
SGJ 72 81 72 83 / 10 20 30 30
GNV 65 86 67 86 / 10 10 10 30
OCF 65 86 68 87 / 10 10 10 50
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Saturday evening for Coastal Duval-
Coastal Nassau-Flagler-St. Johns.
Coastal Flood Warning until 8 AM EDT Saturday for Clay-Coastal
Duval-Flagler-Inland Duval-Putnam-St. Johns.
GA...High Rip Current Risk through Saturday evening for Coastal
Camden-Coastal Glynn.
AM...None.
&&
$$
Wolf/Zibura/McGinnis