Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 01/26/20
Area Forecast Discussion
National Weather Service Houston/Galveston TX
547 PM CST Sat Jan 25 2020
.AVIATION [00Z TAF Issuance]...
Radar is picking up a few returns this evening with mainly a few
showers caught in the isentropic lift through the 850mb to 700mb
layers. This is fairly evident on one of the HOU AMDAR soundings
and there is some drier air below this layer which precipitation
may be evaporating through leading to wet-bulbing. Boundary layer
should saturate up and cool slightly due to this so showers/rain
will become more widespread tonight. TAFs reflect this trend along
with lowering ceilings. Look for MVFR to IFR after 06Z tonight
and perhaps a couple hours around 12Z to 15Z for some LIFR. May
need a TEMPO for any LIFR conditions. We would not be surprised to
see an isolated TS pop up in the morning around 09Z to 13Z as
large scale lift increases. Rain should end 12Z to 16Z. Ceilings
improve in the afternoon as the upper trough axis moves across the
area.
Overpeck
&&
.PREV DISCUSSION /Issued 353 PM CST Sat Jan 25 2020/...
.SHORT TERM [Tonight Through Tomorrow]...
Persistent moderate southeast flow in the wake of a departing
surface high has allowed for an influx of Gulf moisture across SE
Texas today ahead of an advancing upper trough and associated weak
coastal low. This system looks to bring widespread rain showers
with the potential for isolated thunderstorms beginning after
sunset tonight and lasting into the afternoon hours tomorrow.
Synoptic scale guidance (i.e. GFS, ECMWF, NAM) remains in good
agreement that the highest rainfall amounts associated with this
system will remain offshore. As a result, have remained fairly
confident that most inland areas will receive around 0.5 to 1" of
total rainfall.
Some mesoscale guidance sources such as the TTU-WRF and HRRR
continue to suggest the potential for the development of a band of
heavier rainfall reaching inland areas overnight tonight. Should
this scenario materialize, some localized rainfall totals up to 3"
in and around Galveston Bay are possible. Showers and isolated
thunderstorms diminish by Sunday afternoon as the coastal low
pushes further eastward across the Gulf. This should be
accompanied by clearer skies heading into tomorrow afternoon and
evening, as well as a shift to lighter northwest winds.
Cady
.LONG TERM [Monday Night Through Saturday]...
The next in a series of storm systems still looks to bring our area
the next batch of showers and isolated thunderstorms Monday night
through Tuesday evening. After this system moves off to the east,
expect a quiet/dry Wednesday. Another system brings increasing
rain chances back to our area during a Thursday-Friday time period.
Next weekend is still looking to be dry.
For temperatures, no lows near of below freezing are expected (most
areas will be in the 40s and 50s) while highs will be in the 60s and
70s. 42
.MARINE...
Moderate southeast winds continue this evening as a storm system
approaches from the west. With winds reaching 15 to 20 knots in
the nearshore waters and 20 to 25 knots in the offshore waters,
have posted caution flags and a Small Craft advisory respectively
for these areas through 3AM. As the system approaches our area
this evening, look for widespread rain with isolated thunderstorms
to develop across the coastal waters. As this system departs late
on Sunday, a lighter offshore wind will develop and seas will
diminish. Surface high pressure behind the departing system
pushes eastward on Monday. Winds will become east to southeast by
Tuesday as the next storm system and associated rains moves
across the area.
Cady
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 56 70 45 71 50 / 60 20 0 0 20
Houston (IAH) 57 71 50 70 52 / 70 60 0 0 10
Galveston (GLS) 62 68 56 65 59 / 80 70 0 0 0
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 3 AM CST Sunday for
the following zones: Coastal waters from Freeport to
Matagorda Ship Channel TX out 20 NM...Coastal waters from
High Island to Freeport TX out 20 NM.
Small Craft Advisory until 3 AM CST Sunday for the following
zones: Waters from Freeport to Matagorda Ship Channel TX
from 20 to 60 NM...Waters from High Island to Freeport TX
from 20 to 60 NM.
SMALL CRAFT SHOULD EXERCISE CAUTION until 6 PM CST this evening
for the following zones: Waters from Freeport to Matagorda
Ship Channel TX from 20 to 60 NM...Waters from High Island
to Freeport TX from 20 to 60 NM.
&&
$$
AVIATION...Overpeck
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
826 PM CST Sat Jan 25 2020
.UPDATE...
826 PM CST
Lingering light snow from today`s departing system has just about
ended early this evening, with a few diminishing returns on radar
over the southern CWA. Meanwhile, an area of light precip has
developed over southern WI in response to weak isentropic ascent
around the 280K surface, roughly in the 900-850 hPa layer. This
forcing is acting on cloud depths of at least 3kft to produce the
precip. However, cloud bases around 1kft have been high enough to
limit the amount of precip reaching the ground. There have been
sporadic obs of light snow or light drizzle with this precip in
southern WI. This mixed precip type is not surprising given recent
AMDAR soundings out of MKE showing temps as low as -8 to -9C at the
top of the cloud layer. Little should change in the overall pattern
of the forcing and precip as it shifts SSE into the CWA this
evening. Though, the focus for better chances of precip will be
across the northeast half of the CWA. With temps expected to remain
hovering around freezing, some freezing drizzle is possible. This
would potentially create some slippery spots on untreated surfaces.
Precip should exit to the southeast by 3-4am as the forcing shifts
out of the area.
Given the very light and patchy nature of the precip combined with
most areas having already received frozen precip of some sort over
the past 24 hours, there are no plans for a Winter Weather Advisory
or SPS for this activity at this time.
Kluber
&&
.SHORT TERM...
130 PM CST
Through Sunday night...
The center of the deep upper low has shifted to the vicinity of
Lake Huron early this afternoon. There is still an elongated
band of snow out of ahead one well demarcated deformation zone on
the eastern flanks of the low. There is fairly sharp edge to the
slightly deeper moisture with this band of snow. Surface
temperatures are largely at freezing or higher and therefore the
impacts from this band have largely been limited to some
visibility reductions. Behind this band the moisture is subtly
more shallow, but likely enough to result in some loss of ice
nucleation aloft, thus we do still anticipate a transition to
drizzle this evening. With temperatures expected to remain above
freezing this should largely not be a problem, but locations that
drop just a degree or two could see some light icing.
There is another sheared out wave on the far northern extent of
the upper low across the upper Great Lakes, and some weak radar
returns upstream of this can be seen across northern/central WI.
Therefore the drizzle/freezing drizzle concern this evening. With
coverage patchy and with marginal surface temperatures tonight,
we will likely let the winter weather advisory to expire a bit
early given the minimal impacts from the snow today (just a few
tenths of accums) and signs of improved road conditions. But if
any targeted areas (such as north central Illinois where slightly
lower dewpoints may be) dip a bit colder or drizzle coverage is
greater, we could envision a short fused special statement could
handle this potential hazard this evening. This will bear
monitoring and remains the near term forecast concern.
As the low pulls away tonight the light precip chances will end ,
but low level flow will remain cyclonic should allow skies to
remain mostly cloudy on Sunday. Expect temperatures to remain
fairly consistent only reaching the low to mid 30s. There is a
subtle wave that will pass through or to our west Sunday night.
Most guidance is dry with this across our area.
KMD
&&
.LONG TERM...
221 PM CST
Monday through Saturday...
A quiet and relatively mild stretch of weather appears to be in
store for the coming week, at least in terms of avoiding wide
temperature swings. Discounting the GFS which is a cold outlier,
daytime highs should start in the mid 30s on Monday then very
gradually increase to the upper 30s north and lower 40s south by the
weekend. Residual snow cover could keep some locations a bit
cooler, though even the cold outlier GFS generally has highs a
degree or two above normal through the period. Lows too will be a
few degrees above seasonal norms, in the mid-upper 20s. So while
it will not exactly be considered a warm stretch, the last week of
January a year ago saw daytime highs below -10 and overnight lows
colder than 20 to 30 below zero.
Regarding rain and snow chances, a decent shortwave passing through
Monday appears to be too moisture starved to support precipitation.
A deeper wave toward midweek may support a better chance, but even
this is seeing trends heading downward from what they first
appeared. Models give it a third try toward next weekend with
milder southerly flow and better moisture, but considerable
disagreement in the deterministic runs warrants only a chance
mention at this range. Ensembles generally support this idea with
an open longwave dropping into the Great Lakes by next weekend.
Lenning
&&
.AVIATION...
For the 00Z TAFs...
The primary aviation weather concerns this period are:
-Timing out the back edge of lingering -SN
-Potential for -DZSN or -FZDZ developing later this evening and
possibly into the overnight
-Prevailing IFR cigs transitioning to low-MVFR through Sunday
The back edge of the main area of light snow continues to shift
southeastward early this evening and should exit the region over
the next few hours. The main concern is the potential for an
additional area of light precipitation to develop later this
evening and possibly into the overnight hours as another axis of
subtle lift in the low-levels begins to develop. Forecast
soundings (and recent PIREPs) indicate that we are losing cloud
ice as the mid-levels are drying out. As a result, there is some
concern for the development of -DZ (as opposed to -SNDZ) later
this evening. Temperatures aren`t all that cool upstream
indicating a lack of cold advection, so temperatures won`t be
plunging tonight but instead likely to hold steady or creep slowly
downwards a degree or two from where they are currently.
Confidence in the development of -FZDZ was not quite high enough
(given the marginal temperatures at or just above freezing) and
questions about the subtle nature of ascent tonight to warrant an
explicit mention in the TAFs, but this is something we will be
monitoring closely. Main window looks to be somewhere in the
03-10z window.
MVFR cigs look to prevail through the day on Sunday, if not well
into Sunday evening.
Carlaw
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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