Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/03/17
Area Forecast Discussion
National Weather Service Denver/Boulder CO
854 PM MDT Mon Oct 2 2017
.UPDATE...
Issued at 842 PM MDT Mon Oct 2 2017
Shower band is progressing eastward and weakening, perhaps an hour
or two slower than expected. Still lots of light snow showers in
the mountains but not much accumulation anymore. Snow level got
down to between 5500-6000 feet, and closer to 5000 feet near the
Wyoming border. Still a fair amount of uncertainty about the
timing of clearing tonight. Higher level clouds should be gone by
early morning, but the low clouds may last longer. Not clear which
will win between low clouds, clearing then fog, and frost. With
temperatures already ranging from 33 at the border to the upper
30s in the Denver area, I went ahead and issued a frost advisory
figuring there will be some areas with either a frost or light
freeze. Around Denver it would probably be limited to the colder
locations such as lower areas away from the city center. Further
north it will be more widespread if there is some clearing. We
will also need to monitor the potential for dense fog. Again, this
would likely not be too widespread unless there low clouds break
up first.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 400 PM MDT Mon Oct 2 2017
Latest GOES-16 water vapor imagery, local radars, and webcams
continue to indicate bands of convective precipitation forming
across the Central and Northern mountains, and moving over the
adjacent Plains as well. The convection is associated with a well
defined deformation zone extending from the Four Corners
northeast into Wyoming. As this feature propagates east, bands of
moderate precipitation will be possible from now through late
evening. With snow levels around 7000 feet MSL across the
I-70/U.S. 40 corridor, and as low as 6000 feet near the Wyoming
border across Larimer and Jackson Counties, bursts of moderate
snow capable of dropping 1-3 inches in 60-90 minutes are possible
in the mountains. Several rounds of short bursts of precipitation
are possible as well, adding to the storm total snow across the
mountains. After dark these bands could make for slick travel from
Georgetown to Vail Pass and at elevations above 8000 feet.
Further east across the lower elevations rain showers with
isolated thunderstorms are likely this evening, generally from
metro Denver north to Wyoming, and along and north of I-76. High
res models like the HRRR and ESRL HRRR have a good handle on the
evolution of the convective bands of showers, lifting them
northeast with the strong southwest flow. The best instability and
forcing pulls away from the northeast corner of the state after
midnight tonight, shutting down precipitation chances most areas
outside the Central and Northern Mountains. Enough moisture and
cold air should allow for light snow showers across the central
and northern mountains through early morning Tuesday but little to
no snow accumulation expected after about 10 PM.
Tonight will be cool but generally too warm for frost across the
Plains. The exception is across the northern border counties with
Wyoming. If it clears tonight patchy frost is likely and have
including this in the forecast there. Will not issue a Frost
Advisory for those areas due to low confidence in full clearing
overnight. Tuesday will see the beginning of a warming trend and
most areas should remain dry throughout the day under subsidence
aloft with near normal temperatures expected.
.LONG TERM...(Tuesday night through Monday)
Issued at 400 PM MDT Mon Oct 2 2017
Tuesday night into Wednesday southwest flow aloft continues
across Colorado with one partially cut off trough across the
Sierra Nevadas of central California, and the other trough across
North Dakota. South of these two troughs a subtropical jet will
advect moisture into eastern Colorado. Models are in agreement
that a moderate amount of synoptic scale lift across the northeast
part of Colorado will occur throughout the day Wednesday as the
upstream trough moves into eastern Nevada, generating
thundershowers across the eastern Plains Wednesday afternoon and
evening, mainly east of a Akron to Limon line. CAPE/shear
combinations point to non-severe thunderstorms with small hail
and gusty winds. Elsewhere, the location of the jet and SSW flow
at 700mb advecting warm/dry air means precip chances will remain
low for the mountains and I-25 urban corridor.
Wednesday night into Thursday southwest flow continues aloft with
the trough over Idaho. At the surface a lee trough develops
across much of Eastern colorado Thursday morning. Significant
drying occurs in the mid levels such that precipitation chances
are very low through midday area-wide. By Thursday afternoon
another shortwave trough passes just north of Colorado and with it
an increase in moisture will lead to afternoon and evening
showers in the mountains. Snow levels should remain pretty high,
limiting accumulations to areas above 11,000 feet. Rich low-level
moisture is advected into northeast Colorado, with near 60 deg
dewpoints. Thunderstorms are possible across the eastern Plains,
with the best chances across
Lincoln/Washington/Logan/Phillips/Sedgwick counties nearest the
rich low-level moisture. Temperatures will be near seasonal
normals for highs on Thursday.
Friday through Monday the global models differ on the evolution
of the persistent western U.S. trough. The GFS builds a strong
ridge across the Eastern Pacific Ocean, and generates a strong Jet
across the PacNW, putting Colorado in dry northwest flow and
ejecting the trough into the Northern Plains on Friday. The ECMWF
has a much weaker ridge of the West Coast which allows the open
wave positively tilted trough to dig south into Colorado. The EC
solution would lead to a continuation of rain on the Plains and
mountains (snow level still around 11,000 feet or so) Thursday
night into Friday, while the GFS would keep us Friday during the
day and through the weekend. Sided more with the ECMWF as it`s
outperformed the GFS the past week relative to trough evolution,
and bumped up PoPs for Friday vs. the blended model solution
starting point. Good agreement and higher confidence in this
weekends weather, namely that the weekend will be dry since we`ll
be downstream of a strong ridge with WNW flow aloft and the storm
track well north of Colorado across the northern Rockies. The 700
mb ridge moves across Colorado on Saturday, and with the aid of
downslope flow, above average temps should occur most areas with
highs in the mid 70s across the Plains, and +8C 700 mb temps in
the high country resulting in highs in the 50s to mid 60s. The WNW
flow should pull a cold front across the state on Sunday,
dropping temps to seasonal norms Sunday and Monday. Left the
blended forecast alone for the weekend and Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 842 PM MDT Mon Oct 2 2017
There is uncertainty about when the low clouds along the Front
Range will dissipate, and if any dense fog will form. Areas of
MVFR or IFR conditions are likely through 15z, though earlier
clearing is possible in the Denver area. There is a slight chance
of LIFR conditions between 10z and 15z. VFR conditions are
expected after 17z.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Frost Advisory from midnight tonight to 9 AM MDT Tuesday for
COZ038>045-048.
Winter Weather Advisory until midnight MDT tonight for COZ030-
034-035.
Winter Storm Warning until midnight MDT tonight for COZ031-033.
&&
$$
UPDATE...Gimmestad
SHORT TERM...Schlatter
LONG TERM...Schlatter
AVIATION...Gimmestad/Cooper
Area Forecast Discussion
National Weather Service Dodge City KS
945 PM CDT Mon Oct 2 2017
.UPDATE...
Issued at 945 PM CDT Mon Oct 2 2017
Cancelled the tornado watch for Finney, Kearny, Hamilton and Ness
counties. The last supercell has exited Scott county, and barring
anymore development, they will be cleared from the tornado watch
shortly. Last supercell may clip NW Trego county, so will keep the
watch going there through 11 PM. Initial supercell/tornado across
Scott County was the strongest, and has produced at least some
tornado damage across the northern portions of the county. Strong
cold front will enter the northern zones overnight, and HRRR
solutions suggest some further convective development is possible
along that boundary overnight.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 105 PM CDT Mon Oct 2 2017
Thunderstorm development is likely across portions of the Western
High Plains tonight as an increasingly difluent southwest flow aloft
prevails across the region. A frontal boundary, now bisecting
southwest Kansas into north central Kansas, is projected to lift
slightly back to the north this evening giving way to a south to
southeast upslope flow across southwest and central Kansas.
Meanwhile, an attendant dryline stretching southward across extreme
southwest Kansas into the Oklahoma Panhandle is not expected to move
much. Moisture will lift back into the area ahead of the dryline
with surface dewpoints climbing up into the lower to mid 60s(F).
Steepening low/mid level lapse rates, increasing instability with
MLCAPE values upward of 2000 J/kg, and favorable shear will
contribute to isolated to widely scattered thunderstorm development.
The best chance for storms will be in an axis of increased
convergence associated with the frontal boundary/dryline late this
afternoon. Timing and placement of initial development will be
dependent on how soon the prevailing cloud deck erodes and how
far the boundary moves in that time frame. A +70kt upper level jet
and favorable 0-6km shear will increase the potential for
rotating supercells, and subsequent severe storms. Large damaging
hail and damaging winds will be the primary threat while a few
isolated tornadoes cannot be ruled out.
A cold front will push through western Kansas tonight allowing for
cooler air to filter southward into far western portions of the
state. Look for lows well down into the 50s(F) across west central
and portions of southwest Kansas with the 60s(F) likely further east
toward south central Kansas. A much cooler air mass spreading across
western Kansas will limit highs climbing above the 60s(F) across
west central and much of southwest Kansas Tuesday with the 70s(F)
still possible further east.
.LONG TERM...(Tuesday night through Monday)
Issued at 220 PM CDT Mon Oct 2 2017
Precip chances will continue virtually each day through the end of
the week as a difluent southwest flow aloft prevails across the
Western High Plains downstream of a stationary trough axis. A
frontal boundary pushing through western Kansas later tonight, is
expected to move into the Texas Panhandle and northern Oklahoma
before stalling out late Tuesday/early Wednesday, providing a focal
point for shower and thunderstorm development early in the period.
Periods of precip can be expected Thursday as the stalled frontal
boundary lifts back to the north through western Kansas, returning a
southeast upslope flow to the high plains. Steep low/mid level lapse
rates and increased instability may be enough to support storm
development as H5 vort maxima eject out of the Southern Rockies into
the high plains of eastern Colorado and western Kansas. Another
frontal passage is projected toward week`s end bringing more precip
chances to western Kansas.
A cooler air mass settled across the high plains and reinforced by
surface high pressure moving eastward across the Upper Midwest, will
keep highs capped in the 60s(F) and 70s(F) Wednesday afternoon.
Warmer temperatures are likely Thursday as the boundary, initially
stalled to our south, lifts northward across the region. Should
see more seasonal highs Thursday afternoon, if not a little above.
Another frontal passage late in the week will end the small warming
trend Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 600 PM CDT Mon Oct 2 2017
Any convection is expected to avoid the terminals this evening, so
opted to keep out of the 00z TAFs. Strong S/SE winds will persist
through the evening hours, diminishing somewhat again after
sunset. Expect low level wind shear to return by around 06z with
another low level jet. South winds will decrease toward daybreak,
as a cold frontal boundary sinks south to a Hays-Syracuse line by
12z Tue. Cold front will pass the terminals 12-15z with a shift to
north winds of 10-20 kts. High confidence that MVFR (and possibly
IFR) stratus cigs will develop along/behind the frontal boundary
Tuesday morning, with reduced vis in BR/FG also expected.
Consensus of short term models suggests that MVFR stratus (1-2k
ft AGL) will persist much of daylight Tuesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 63 65 56 69 / 20 50 70 70
GCK 58 64 54 65 / 30 50 80 70
EHA 56 66 54 68 / 20 50 70 60
LBL 65 69 58 70 / 10 50 70 60
HYS 61 63 54 64 / 40 40 80 70
P28 69 80 63 74 / 10 30 60 70
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Turner
SHORT TERM...JJohnson
LONG TERM...JJohnson
AVIATION...Turner
Area Forecast Discussion
National Weather Service Houston/Galveston TX
959 PM CDT Mon Oct 2 2017
.UPDATE...
Evening surface analysis placed a small surface low near the
lower Galveston Bay, with an associated enhanced pressure gradient
resulting in 20-25 knot southeasterly wind gusts along Bolivar
Peninsula. These elevated onshore winds are not only resulting in
a high rip current risk per the Galveston Beach Patrol but have
also pushed tide levels to around 2.5 feet MLLW at the Galveston
Bay Entrance. These winds are expected to result in tides rising
above 3 feet early Tuesday morning around high tide. As a result,
a Beach Hazards Statement has been issued to cover rip current and
minor coastal flooding issues that may result from these
conditions.
The majority of the shower activity over the Houston metro this
evening has mostly dissipated, but light rain bands associated
with this low are developing near the Sabine Pass and lifting
towards the northwest. Have lowered rain chances for this evening
based on radar trends as well as both the THOU and KHGX wind
profiles showing veering 925 and 850 MB winds (reflecting the
presence of the low and some very weak dry air advection). As this
surface low moves farther inland/ loses definition, RAP vertical
wind profiles show low level winds backing more to the southeast
and this would provide a few windows for additional showers during
the overnight hours. Expect greatest coverage across the
southeastern forecast area and eastern waters where directional
and speed wind convergence is maximized.
Huffman
&&
.PREV DISCUSSION... /ISSUED 621 PM CDT Mon Oct 2 2017/
AVIATION...
The disturbance over the Gulf will move inland this evening and
should provide area TAF sites with some showers especially coastal
TAF sites. Will carry VCSH generally south of KIAH tonight.
Moisture levels deepen further early Tuesday and fcst soundings
look supportive of thunder and potentially heavy rain. Models
differ with regard to placement of the heaviest rain and timing so
confidence on when to TEMPO thunder is low. Showers will begin to
diminish late Tuesday or early Tuesday evening. 43
PREV DISCUSSION... /ISSUED 343 PM CDT Mon Oct 2 2017/
DISCUSSION...
Precipitation coverage across SE TX is expected to continue increasing
through the rest of this afternoon as moisture continues to move
in from the Gulf. This activity should wind down shortly after
sunset with development likely over the coastal waters overnight/toward
sunrise. Showers/thunderstorms will be more widespread tomorrow
as a slug of slightly deeper moisture (PWs up to 2.5 inches) moves
in from the Gulf. Locally heavy rain to remain the main
threat...but storms will be moving and still not seeing any
indications of low level boundaries/upper level disturbances to
enhance development at this time.
As the upper ridge builds in from the E/NE on Wed, this moisture
will be shifting off to the W/SW portions of the CWA. The ridging
aloft should make for quieter/warmer weather for the rest of the
week. Temperatures progged to climb back up to near 90F during
this time frame, with only a slight chance of rain generally
during the day with the seabreeze. 41
MARINE...
A non-tropical area of low pressure can be see in GOES 16 visible
satellite imagery about 40 miles SE of Galveston and is moving NW
around 15 knots. The system should push inland around 00-01Z or 7-
8PM CDT this evening. The system does have some convection around it
but it is mainly enhancing E to NE winds along the Upper Texas Coast
and Galveston Bay. Tides are about 1.5 to 2 feet above normal
with overall water levels around 3-3.5ft above MLLW. Tides along
the coast are headed towards low tide so impacts may be limited to
the next few hours along Bolivar Peninsula and Galveston Island.
Overall the forecast looks to be on track with moderate to strong
east winds developing Tuesday through the end of the week. These
winds have a pretty long fetch which should support rough seas
developing along with some low swells. Look for small craft advisory
conditions developing late Tuesday and persisting into Thursday.
Moderate seas will continue into the weekend with decreasing winds.
Overpeck
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 75 87 73 88 70 / 20 60 50 30 20
Houston (IAH) 75 87 74 87 71 / 30 60 50 40 20
Galveston (GLS) 80 86 79 88 78 / 40 60 50 40 20
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 5 AM CDT Tuesday for
the following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Galveston Bay...Waters
from Freeport to the Matagorda Ship Channel from 20 to 60
NM.
Small Craft Advisory until 5 AM CDT Tuesday for the following
zones: Coastal waters from High Island to Freeport out 20
NM...Waters from High Island to Freeport from 20 to 60 NM.
&&
$$
Discussion...14
Area Forecast Discussion
National Weather Service Omaha/Valley NE
1033 PM CDT Mon Oct 2 2017
.UPDATE...
Issued at 1026 PM CDT Mon Oct 2 2017
Have canceled Severe Thunderstorm Watch 493 for our CWA.
Storms have markedly lost intensity and structure over the last
hour over watch area, with more concentrated band of scattered
storms now setting up northwest of severe watch and in Flash Flood
Watch area. Training of showers/storms still looking likely there.
UPDATE Issued at 933 PM CDT Mon Oct 2 2017
Will maintain current Severe Thunderstorm Watch 493 configuration
for the next couple of hours. And Flash Flood Watch will also
remain intact.
Radar intensity trends have been on the decrease over the last
hour or so across current watch area in our CWA. However latest
RAP analysis indicates lingering elevated instability over 1000
J/kg and increasing low level jet of 45-55kt impinging on cold
frontal zone running from Columbus to Sioux City, yielding
effective shear near 50kt. While not as robust as earlier,
supercellular structures were still evident in radar data in south
central Nebraska and tracking toward our watch area. Can not rule
out some intensification of this activity as of yet, thus will
maintain Severe Watch.
A more likely heavy rain scenario is setting up where current
Flash Flood Watch is situated, given robust moisture transport
over frontal zone aided by mid level forcing ahead of shortwave
ejecting through the Plains. Precipitable water values near 1.5"
and training of storms will maintain threat of flooding rains for
several more hours at least.
&&
.SHORT TERM...(Tonight through Thursday)
Issued at 254 PM CDT Mon Oct 2 2017
Moderate risk for excessive rainfall tonight over the northern CWA.
WV imagery this afternoon showing a large upper level low pretty
much encompassing the western half of the CONUS with the circulation
centered over the northern Plains. Noted was a speed max rounding
the base with a 140kt jet on the backside. At the surface...a
distinct quasi-stationary boundary extending from the western Great
Lakes region to about SW KS.
Given influx of moisture the last couple days...the environment
remains moisture rich as seen from morning HPC PWS graphics of
195%/181%/200% of normal at KOMA/KTOP/KDDC...respectively. SPC Meso
Analysis indicating strong low level theta-E advection underway with
PWS 1.4"-1.5" on the south side of the boundary.
Stout theta-E advection will continue through tonight, allowing an
increase of PWS to roughly 1.75 with continuous moisture
convergence/deep ageostrophic forcing along the quasi-stationary
boundary parallel to mean 850-300MB wind. Both NAM/GFS show max
omega phasing well with best moisture with 20-30 microbars of lift
focused over the northern CWA. And with stagnant layer differential
divergence contributing to large scale forcing...conditions will be
quite favorable for a prolong period of moderate to heavy rainfall
overnight.
Given antecedent conditions...300%-400% of normal pcpn this past
week/moist soil/FFG...flash flooding over the northwestern CWA seems
quite probable. Thus will go with a headline highlighting this.
The western trof splits into 2 distinct circulations on Tuesday, one
centered over the Dakotas and the other centered over the Great
Basin. Surface high building in from the northern Plains will slowly
nudge the stagnant surface boundary south of the I-80 corridor
before it stalls again Tuesday evening in the vicinity of the
southern CWA. Thus shift best pcpn chances through Wednesday
morning.
Wednesday afternoon through Thursday...models are in poor agreement
wrt boundary position. Therefore, due to uncertainties, prefer to
just blanket area with high end CHC PoPs.
.LONG TERM...(Thursday night through Monday)
Issued at 254 PM CDT Mon Oct 2 2017
Models continue to advertise a wet and relatively cool pattern
heading into this weekend in part to another potent shortwave
trof/attendant cold front crossing the region. As of
now...GFS/CMC/ECM show the potential for significant convective pcpn
Thursday night and Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 633 PM CDT Mon Oct 2 2017
Cold front just southeast of KOFK will remain nearly stationary
during the evening, then push southeast overnight. Scattered
showers and thunderstorms will be common near and behind the cold
front. Also, IFR cigs behind front should remain at KOFK through
18Z. Thunderstorms may affect KLNK and KOMA during the evening,
but better chance comes with cold front after 09Z. Associated
MVFR/IFR conditions in storms will occur at that time. Also, MVFR
to IFR cigs will settle into KLNK and KOMA by 12Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flash Flood Watch until 3 AM CDT Tuesday for NEZ011-012-016>018-
030-031.
IA...None.
&&
$$
UPDATE...Dergan
SHORT TERM...DEE
LONG TERM...DEE
AVIATION...Dergan