Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/05/17
Area Forecast Discussion
National Weather Service Denver/Boulder CO
846 PM MST Wed Jan 4 2017
.UPDATE...
Issued at 845 PM MST Wed Jan 4 2017
Drier air noted on satellite recently passed overhead to weaken
snowfall over the area. Some areas have completely stopped
snowing. Do not be fooled and let your weather preparedness guard
down. Additional moisture is seen upstream, especially on radar
over the Salt Lake City area and pushing into western Colorado.
Colder air expected to push in overnight will combine with the
incoming moisture to ramp up snowfall, likely around or after
midnight. Due to this, will not be adjusting snowfall totals.
UPDATE Issued at 450 PM MST Wed Jan 4 2017
Have added winter weather advisories for the rest of the Northeast
plains of Colorado with the exception of Lincoln county. Already
reports of 2-3 inches of snow in Sterling and radar indicates some
banding precip as well and potential developing further south as
the night goes along. Overall 3-6 inches possible over the far
plains. Elsewhere, heavier snow is developing over the adjacent
plains and everything else appears is on track. Will watch the
development of the heavier banded snowfall this evening and adjust
forecasts as needed.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 224 PM MST Wed Jan 4 2017
Overview: A significant snowstorm looks on track for much of
Colorado today through Thursday morning. The primary mid and upper
level vorticity maximum is located across central Oregon this
afternoon. It is pulling an impressive stream of moisture from the
Central Pacific into CA and Nevada. Downstream of the vorticity
maximum the nose of a West-Northwest 130 kt jet stream will
push across Colorado this overnight. By Thursday morning the
northern half of Colorado is located under the left entrance
region of the jet, and by Thursday afternoon the jet stream
dynamics shift to the south of Colorado and winds turn west at the
jet stream level. The 500 mb low moves very slowly tonight
through Thursday setting the stage for a prolonged period of snow
across Colorado but especially in the mountains. By Thursday
evening the 500 mb low moves to western Utah, keeping very strong
west-northwest flow at 500 mb of 70 kt over Colorado. At 700 mb
flow remains out of the west through Thursday given the fact that
the mid level vorticity max is moving into a long wave trough
over C. and E. Canada. Arguably the most impressive aspect of this
system is the availability of moisture. Upstream Precipitable
water values via raobs and via satellite derived products are
twice the normal amount and above the 90 percentile relative to
normal for January 4. This set up favors sustained, moist, strong
WNW flow through Thursday midday and significant snowfall.
Mountains: Warning criteria snow amounts over the mountains and
west slope will be met easily over the next 24 hours. Snow is
ongoing this afternoon and will continue tonight and tomorrow
morning. With the strongest jet dynamics shifting south by
Thursday afternoon and some drying at and above 700 mb, expect
snow will taper off most of the mountains by Thursday evening,
other than the favored westerly upslope areas of Summit and Park
Counties. Steep lapse rates between 700 and 500 mb overnight and
the presence of the jet streak favor convective bands across the
mountains this evening and overnight, most likely occurring after
8 PM. HRRR and ESRL HRRR both indicate banded precipitation over
the mountains through about 3 AM. While pinpointing where these
mesoscale convective bands set up is not possible, it is important
to note that where they set up will lead to hazardous travel
given intense snow rates of 1-2 inches per hour, lasting for
several hours at a time on top of the orographic snow that had
already been piling up. The bands should translate slowly
southward overnight and do not appear likely after sunrise in the
mountains. All mountain areas should do quite well in terms of
storm total snow amounts with the moist upslope flow and potential
for heavy bands to set up for several hours. Amounts will be
highest across the west slope of the Continental Divide from Rocky
Mountain NP southward to Gilpin and Clear Creek Counties and for
the Medicine bow range....2 feet or more is possible in those
areas. Elsewhere in the mountains 8-16 inches are expected with
locally higher amounts occurring along westerly upslope areas and
anywhere the mesoscale bands develop.
Plains: Snowfall amounts across the Plains are trickier for this
storm. With a lack of deep easterly upslope flow the forecast snow
amounts are somewhat challenging. First, lee troughing under WNW
flow begin in earnest this afternoon and is strongest south of
the Palmer Divide. This area of surface low pressure doesn`t move
much, extending from southern Colorado into northern New Mexico
overnight through Thursday. The response is a reinforcing surge of
cold air from the north this afternoon across the northern third
of the Plains of Colorado. Trajectories our of the ENE at the
surface favor upslope flow along and west of the I-25 corridor and
along the north side of the Palmer Divide. Additional lift will
be provided by low level frontogenesis later this evening in the
vicinity of the frontal boundary. Latest high res model guidance
does not show significant banding east of the mountains, other
than the 3km NAM. HRRR, HRRRX, RUC do not seem to think banding
will occur east of the mountains. There is evidence to suggest
banding is possible...the Northern Front Range will be in the
right exit region of a strong jet tonight and decent frontogenesis
will occur associated with the front. Anywhere a band develops
would result in snow total on the high end of the current snowfall
totals shown on our probabilistic snowfall graphics, e.g. what is
shown in the 90% graphic. Even without snowbands, light to
moderate rates along and west of I-25 overnight into tomorrow
morning with result in significant travel impacts across the urban
corridor, with the best chance of getting over 12 inches in and
very close to the foothills, 6-12 inches for the I-25 corridor,
and far less amounts across the far eastern forecast zones.
Finally, we went a bit above the GEFS and SREF ensemble mean
totals. Snow should end all areas of the Plains by late Thursday.
Snow will likely be falling in the Winter Storm Warning area at 11
AM when the warning expires, but latest thinking is that any
additional accumulation will be on the light side.
.LONG TERM...(Thursday night through Wednesday)
Issued at 224 PM MST Wed Jan 4 2017
The jet will continue to sink south Thursday night taking the
snow with it. Light snow will remain possible over the mountains,
mainly south of Interstate 70 and along the Palmer Divide.
Additional snow is expected to be light with up to 2 additional
inches in the mountains. It is expected to clear out Thursday
night over the northern Colorado. The clear skies, fresh snow, and
light winds will allow temperatures to plummet Thursday night.
Low will fall below zero, well below zero in the northern mountain
valleys.
Warming trend begins Friday as an upper level ridge begins to
build over the western CONUS. Highs Friday will be cool with
readings mainly in the 20s. Low lying areas, like the South Platte
River valley, and mountain valleys will be cooler.
The upper level ridge will shift east over the Central Rockies
this weekend. Dry conditions and mostly clear skies are expected
to prevail under his ridge. Temperatures will continue to warm
through the weekend. For Sunday, highs may reach the lower 50s
along the base of the foothills. However, the low lying areas
could be as much as 20 degrees cooler for highs. Latest models
show Pacific moisture moving back into the mountains Sunday and
will add pops to the forecast for this.
A strong Pacific system will move onto the west coast early next
week. This will push the upper level ridge over the Central Rockies
east of the region and replace it with a strong zonal flow. Models
showing two systems embedded in the westerly flow that is expected
to bring snow to the mountains. The timing among the models is off
though. Will go with a good chance for snow in the mountains, Monday
through Wednesday. Downslope flow will keep the Front Range and
eastern plains mild, dry and windy at times.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 845 PM MST Wed Jan 4 2017
Snow is very banded in nature this evening, allowing for drastic
changes in ceilings and visibility. Drier air evident on satellite
overhead will push east with greater moisture to move in just
before midnight. This coupled with colder air pushing down should
reintensify overall snowfall, with banding still possible.
Snowfall rates will then be one-half to one-inch per hour through
the rest of the night. Will continue to try and time some of the
heavier snowbands tonight, still expecting a period of heavier
snow from 08z- 11z. Total snowfall at KDEN and KAPA is expected
to be 6 to 8 inches. If a heavy snow band sets up, snowfall
amounts will be higher. KBJC should see a couple more inches of
snow than KDEN, 9 to 12 inches.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 11 AM MST Thursday for COZ042-
044>046-048>051.
Winter Storm Warning until 11 AM MST Thursday for COZ030>036-
038>041-043.
&&
$$
UPDATE...Kriederman
SHORT TERM...Schlatter
LONG TERM...Meier
AVIATION...Kriederman
Area Forecast Discussion
National Weather Service Cheyenne WY
537 PM MST Wed Jan 4 2017
.UPDATE...
Issued at 535 PM MST Wed Jan 4 2017
Went ahead and upgraded advisories for Laramie and Saratoga this
evening as we are still looking at an additional 2-4 inches of
snow overnight. Talking with the Albany County EM, there are
developing impacts in Laramie as crews are having a hard time
keeping up with the roads. Updates have been sent.
&&
.SHORT TERM...(This evening through Friday)
Issued at 230 PM MST Wed Jan 4 2017
Main difficulty will be additional snowfall amounts overnight
before the snow comes to an end late tonight/early Thursday
morning.
Light snow continues to fall across the CWA this afternoon with
some bands of moderate to heavy snow close to the Colorado border.
Determining where these bands will be will be the critical factor
in where heavier snow falls. Boundary has pushed south across far
se Wy this afternoon...a little faster than anticipated...and
current radar depicting a heavier snow bands along the Wy/Co
border just south of Cheyenne and Laramie. Believe this is where
the heavier snow will fall the rest of this afternoon into this
evening with lighter snow to the north...over much of the CWA. As
a result total snowfall looks to be a little less across far se Wy
but totals still decent...generally in the 5-7 inch range outside
of the mtns...with snow cover higher from earlier snow. Will keep
current winter hilites as is.
The snow will taper off from north to south overnight as an upper
trough moves south across the region with snow expected to clear
the CWA by late Thursday morning. Colder arctic air will build in
over the CWA overnight with mins below zero over most of the CWA.
The coldest will be over northern parts and with even light winds
the wind chills will drop to very cold levels so will continue the
wind chill advy for that area into Thursday morning. Clearing and
cold Thursday with highs in the single digits to teens. Coldest
night will be Thursday night as light winds...mainly clear skies
and snow cover will allow temps to fall well below zero across the
CWA. Will likely need additional wind chill hilites for that.
Warmer temperatures ensue Friday as the cold arctic high slides
southeast of the area and downslope flow returns.
.LONG TERM...(Friday night through Wednesday)
Issued at 230 PM MST Wed Jan 4 2017
A quiet weather pattern should prevail early in the forecast period
with upper-level ridging in place over the central Rockies. We will
likely see a gradual warming trend through Sunday as H7 temps climb
to +2 to +4 deg C along/east of the Laramie Range. The medium range
models are in good agreement w/ moist southwest flow aloft from Sun
onward, leading to an increase in precipitation chances to the west
of the Laramie Range. Westerly downslope flow will likely keep much
of the high plains dry through early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 429 PM MST Wed Jan 4 2017
Slowly improving conditions this evening as an arctic front begins
to move south into Colorado this evening. KRWL and KCDR will see
these improvements intially with southern airports improving by
late evening. Last airport to improve will likely be KLAR which
will be the last location for snow to end. Followed latest HRRR
guidance on timing. VFR all locations Thursday, but very cold.
&&
.FIRE WEATHER...
Issued at 230 PM MST Wed Jan 4 2017
See no concerns for the rest of the week with snow cover and cold
temperatures over the area.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Wind Chill Advisory from 11 PM this evening to 11 AM MST
Thursday for WYZ101-102.
Winter Weather Advisory until 6 AM MST Thursday for WYZ103>105-
107>109.
Winter Storm Warning until 6 AM MST Thursday for WYZ106-110>119.
NE...Wind Chill Advisory from 11 PM this evening to 11 AM MST
Thursday for NEZ002-003-095.
Winter Weather Advisory until 6 AM MST Thursday for NEZ019-020-
054-096.
&&
$$
UPDATE...GCC
SHORT TERM...RE
LONG TERM...CLH
AVIATION...GCC
FIRE WEATHER...RE
Area Forecast Discussion
National Weather Service Quad Cities IA IL
504 PM CST Wed Jan 4 2017
...AVIATION UPDATE...
.SYNOPSIS...
Issued at 320 PM CST Wed Jan 4 2017
Arctic airmass was in place across much of the Midwest and there
has been plenty of sunshine for much of the day in the dvn cwa. 3
pm temperatures ranged from 7 above at Dubuque to 21 at Keokuk.
Elsewhere, a short wave trough was spreading an area of light snow
into western Nebraska with high level clouds pushing eastward into
the dvn cwa.
&&
.SHORT TERM...(This Evening through Thursday)
ISSUED AT 320 PM CST Wed Jan 4 2017
Forecast focus on snow tonight in our southern cwa.
Tonight: Operational models similar in tracking a short wave
trough across the area. Overlaying the dendritic growth zone (-12
to -18C) with the 100 percent RH and omega (vertical motion)the
best location for the highest snow accumulations will be south of
the dvn cwa. Across southeast IA, northeast MO and western IL the
mean RH is about 85 percent, and farther north the saturation and
lift decreases rapidly. The highest pops will be in our far south
with only chance pops along Interstate 80. Farther north no
precipitation is expected. The HRRR suggests the snow spreading
into our southern counties during the mid to late evening then
ending rather quickly by sunrise. Snowfall amounts should range
from 1 to 2 inches in our far southern cwa, to up to 1/2 inch at
Burlington. Farther north not expecting any accumulation. Lows
will range from around zero along Highway 20 to around 12 in far
northeast MO. During the snowfall the winds will be rather light
so impacts appear minimal. Therefore, winter weather headlines
will not be issued at this time.
Thursday: In the wake of the trough even colder air builds
southward with 850 mb temperatures dropping to -23C in our far
north. 500 mb temperatures will be as cold as -36C which will set
up steep lapse rates during the afternoon. Time height sections
indicate limited low level moisture but there may be enough to
support scattered flurries. Highs will be mainly in the teens,
except around 10 along Highway 20.
.LONG TERM...(Thursday Night through Wednesday)
ISSUED AT 320 PM CST Wed Jan 4 2017
The main forecast concerns will be chances of precipitation through
the period as well as wind chills. The models are in good overall
agreement through the period.
Below normal temperatures are expected through Sunday with a a
deep trough across the eastern third of the US. Warm advection ahead
of next weeks systems will raise temperatures back above normal on
Monday and Tuesday with temperatures near normal by the middle of
next week. In addition to the cold temperatures, wind chills may be
an issue north of US Highway 30 on Friday morning and again on
Sunday morning with wind chills of -15 to -20 below possible on
both days.
The active pattern continues through the long term with transitions
from northwesterly flow to start to more of a zonal flow by early
next week. Disturbances will pass to our north Friday night into
Saturday as well as Sunday night into Tuesday. Currently, it looks
like both systems will be moisture starved with the better
chances of precipitation near the best support.
An open/neutral 500 hpa wave will move across the region toward the
end of the long term period on Tuesday and Wednesday with strong
warm advection ahead of the wave. This will bring a warming trend as
well as a chance precip changing from snow over to rain through the
day on Tuesday and then back again overnight as slightly cooler air
overspreads the region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday Evening)
ISSUED AT 459 PM CST Wed Jan 4 2017
Light snow expected to impact KBRL overnight, with mainly MVFR
ceilings and visibilities after 05Z. The snow should end near 10z,
followed by continued MVFR ceilings. Little or no snow expected to
the north, with mainly low VFR ceilings developing overnight and
continuing through the day Thursday.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
SYNOPSIS...Haase
SHORT TERM...Haase
LONG TERM...Cousins
AVIATION...RP Kinney
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
930 PM CST Wed Jan 4 2017
.UPDATE... /INCREASED LOW CLOUDS TO ALTER MINS...ADD DRIZZLE SE
THURS/
Surface winds over the Rio Grande Plains can be seen turning
southerly, and the BL winds on the recent RUC runs and VAD wind
profiles confirm that the low cloud deck will mix out a bit more
this evening, then surge north again. By daybreak, enough
isentropic lift looks present to generate some light rain or
drizzle over the Coastal Prairies on Thursday. Min Temperatures
were modified slightly upward over the SE counties and downward
slightly near Burnet. Given a longer period of cloud cover for
tomorrow, Thursday Max T was lowered slightly over the eastern
counties.
&&
.PREV DISCUSSION... /ISSUED 548 PM CST Wed Jan 4 2017/
UPDATE...
00Z Aviation Update Below.
AVIATION...
A BKN stratus deck around 4K feet SAT-AUS may lower slightly
through the evening. There is a chance it could lower into high
end MVFR. The cloud deck should move east early Thu morning.
Otherwise VFR conditions until Thu evening, at which time a MVFR
stratus deck may develop behind another cold front. Weak SE-NE
winds around 5 kts or less this evening. The winds should become
light from the SW overnight and Thu morning at SAT/AUS. Pre-frontal
SW-W 5-9 kts winds will develop Thu afternoon at SAT/AUS. The
aforementioned cold front will arrive at AUS around 22Z Thu,
SAT around 00Z Fri, and DRT 03Z Fri. N to NE winds 12-18 kts will
initially develop behind the front, then strengthen and become
gusty Thu night at SAT/AUS, with gusts 25-30 kts possible.
PREV DISCUSSION... /ISSUED 209 PM CST Wed Jan 4 2017/
SHORT TERM (Tonight through Thursday Night)...
Upper air analysis this morning showed zonal flow across the
southern part of the country. At the surface, winds were from the
north to northeast behind a cold front. Temperatures and dew
points were five to ten degrees lower than 24 hours ago. The
frontal boundary will come back through as a warm front tonight.
Another cold front will drop through our CWA Thursday. This will
all mean shifting winds and a warm day Thursday ahead of the
front. Temperatures will drop Friday morning behind the cold
front with freezing along and northwest of I-35.
LONG TERM (Friday through Wednesday)...
Friday the front will continue moving slowly away from our area
and there will be a slight chance for precipitation across our
south and east. Any precipitation should be in areas that stay
above freezing and be rain. Friday night there could be some
lingering rain in the extreme southeast. Saturday upper level
ridging will build in from the west and move slowly across the
Southern Plains over the weekend and into the beginning of next
week. This will mean a dry period through the end of the forecast
period. Cold air will settle in for the weekend and then
temperatures will warm Monday through Wednesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 39 61 30 38 26 / 0 10 - 10 10
Austin Bergstrom Intl Airport 38 64 31 38 26 / 0 10 - 10 10
New Braunfels Muni Airport 41 67 32 39 26 / 0 20 - 10 10
Burnet Muni Airport 34 54 25 34 22 / 0 - - 10 -
Del Rio Intl Airport 43 70 37 45 29 / 0 0 - 10 0
Georgetown Muni Airport 35 56 27 35 23 / 0 10 - 10 10
Hondo Muni Airport 43 71 35 41 26 / 0 0 - 10 -
San Marcos Muni Airport 40 64 31 39 26 / 0 20 - 20 10
La Grange - Fayette Regional 42 63 34 40 28 / 0 20 - 20 10
San Antonio Intl Airport 43 69 33 39 28 / 0 10 - 10 10
Stinson Muni Airport 44 70 35 40 29 / 0 20 - 20 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...Runyen
Synoptic/Grids...Oaks
Public Service/Data Collection...Williams
Area Forecast Discussion
National Weather Service Hastings NE
542 PM CST Wed Jan 4 2017
.SHORT TERM...(This evening through Thursday)
Issued at 355 PM CST Wed Jan 4 2017
The biggest issue will be determining snow amounts and this could be
a bit tricky.
Temperatures are cold enough for 20 to 30:1 snow ratios, and even
though there is not a whole lot of moisture, the light and fluffy
snow could add up to a good couple of inches this evening for some
spots. After all is said and done, our total amounts should be in
the 1 to 3 inch range with a localized 4 inch here or there. I like
the HRRR the best for timing, and the snowfall could vary quite a
bit with just a difference of a couple hundredths qpf. For now, I
tamped down snow amounts a bit on the Nebraska side this evening,
while later on tonight I increased amounts for north central Kansas
to the 1 to 2 inch range as the band shifts south. Models
indicate a potential of some lingering snow in the early morning
on Thursday, but qpf amounts generally look fairly light. We`ll
have to keep a close eye on north central Kansas in case they wind
up with a bit more qpf, but I`ve already gone a few hundredths
greater than Superblend as it stands now. Nonetheless, there could
be a narrow band that develops that gives us more.
.LONG TERM...(Thursday night through Wednesday)
Issued at 355 PM CST Wed Jan 4 2017
For the rest of the forecast, the arctic blast persists for the work
week and into Saturday, with a ridge ensuring a modest warmup into
the 40s for Sunday into next week. Not much at all change has
occurred from the previous forecast here.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday evening)
Issued at 542 PM CST Wed Jan 4 2017
The main aviation forecast concern is the continuation of snow and
how that will impact visibilities and ceiling height. Currently
ceilings are hovering around 3000ft...but upstream, ceilings are
in the MVFR range and expect that is possible at both KEAR/KGRI as
well through the majority of the snowfall. Visibilities will drop
with more moderate snow, but MVFR visibilities are also expected.
Brief periods of lower visibilities are possible if a heavier band
moves through, but this is not expected to be long lived. Will
monitor this and amend if necessary. Winds are generally light and
north to northeasterly. They will become more northwesterly
through the period and gusty by afternoon Thursday.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory until 6 AM CST Thursday for NEZ039>041-
046>049-060>064-072>077-083>087.
KS...None.
&&
$$
SHORT TERM...Heinlein
LONG TERM...Heinlein
AVIATION...Billings Wright
Area Forecast Discussion
National Weather Service Houston/Galveston TX
900 PM CST Wed Jan 4 2017
.DISCUSSION...
Latest IR/11-3.9 micron satellite imagery shows low stratus clouds
moving into SE Texas from the SW over S Texas. Obs show ceilings
anywhere from 1500 to 5000 feet coming into the area. Latest HRRR
seems to have initialized well enough with this scenario and
analysis of 295K/290K shows some isentropic lift coming from the
SW in line with cloud development in the satellite. This also
corresponds well with warm advection in the 925-850mb layer. This
means that temps overnight may actually warm a bit from current
readings. Temps may drop another degree or two over the next
couple of hours, but should rebound with increased cloud cover and
warm advection. Based on hi-res mesoscale models, 20 PoPs were
added to the forecast for tomorrow morning along the coast and
ahead of the front tomorrow afternoon.
Cold front pushes through SE Texas Thursday afternoon and
evening. Look for temperatures to slowly fall with strong cold
advection. Temperatures may only remain steady for slowly fall
through the day Friday. That brings us to Friday night when a
embedded short wave trough moves along the Red River. The NAM is a
good 3-6 hrs faster with this shortwave than the GFS and the ECMWF
is about 3-6 hrs slow. Canadian and GFS are fairly close. All the
models show a weak vorticity max that appears to be getting
stretched. Front at 850mb will be pushing through 00-06Z Saturday
so there will be some low level lift along with Q-G large scale
ascent. But looking at model soundings, moisture will be really
limited. Doubt there will be any precip at all except along the
coast after 06Z Saturday. Model soundings do moist below 700mb
from 21Z Friday to 03Z Saturday but there is practically no
moisture above -10C height. Temperature profiles do slide below
freezing by 03Z Saturday in areas from Madisonville to Lufkin but
due to the lack of moisture, precipitation type will likely be
drizzle or freezing drizzle should surfaces be cold enough.
Decided to modify the forecast for rain/drizzle/freezing drizzle
precip type based on this as it will be hard to get any other
precip type. Should there be much stronger lift than what is being
shown by the models, then sleet will be possible. Overall this
winter precip event for the northern most counties of the forecast
area is very borderline, and there is a much higher chance of it
not occurring than occurring.
Overpeck
&&
.PREV DISCUSSION... /ISSUED 543 PM CST Wed Jan 4 2017/
AVIATION...
With clouds at MVFR levels beginning to crop up at several sites,
have sped up the onset of MVFR ceilings a little bit this evening.
Still unsure on low level moisture return, so hitting visibility
reductions late tonight/tomorrow morning a little softer than the
guidance still, and keeping them restricted from DWH/IAH
coastward. With a cold front beginning to enter from the
northwest at the end of the period, a wind shift will be in the
offing, but at the end of this forecast period, only the
northernmost sites should see that impact, and CXO to a limited
extent.
Luchs
PREV DISCUSSION... /ISSUED 348 PM CST Wed Jan 4 2017/
DISCUSSION...
Visible satellite imagery currently shows a high cloud deck
scattered over much of SE Texas this afternoon. Expecting saturation
to rise as winds shift from the north to out of the southwest,
enhancing moisture due to weak onshore flow beginning Thursday
morning. Forecast soundings have precipitable waters on the rise
Thursday after the wind shift, and PoPs will rise slightly over the
offshore waters. Therefore, a slight chance of showers can be
expected over the offshore waters and along the eastern coastal
zones Thursday afternoon.
Early Thursday evening, a strong cold front begins to slide into the
forecast area and will eventually clear the coast by Friday morning.
Chances for precip will be on the rise ahead of the cold front
Thursday evening. Overnight, in the northeastern zone of our
forecast area will see some mix of light drizzle and wintery
precip. Model guidance, especially indicative in the forecast
soundings show dry air aloft in the mid to upper layers with a
small layer of saturation closer to the surface. Temperature will
be warmer than freezing at the surface while the precip is
falling, and conditions will be drier than previous forecasted.
Therefore, it appears as though the models are lacking confidence
towards the precip being more ice pellets or sleet, but instead
will more likely be drizzle or light rain. Eventually a large
part of forecast area will fall below freezing temperatures, once
the precip has pushed southward.
Cold air will usher in behind the front, leaving temperatures below
normal climatology for this time of year. High pressure will build
in following the front. Expect the impact from this front to
linger through the weekend, keeping things cold and breezy. A
Coastal Wind Advisory may be needed along the immediate coast
beginning sunrise Friday and through the afternoon. Friday and
Saturday night we will see low temperatures slightly below normal
climatology, remaining quite chilly. The warm up will begin
Sunday, as the winds begin to veer Sunday afternoon. By next week
temperatures will be back above normal for this time of the year.
Hathaway
MARINE...
Maritime northeasterly winds will weaken through the overnight
hours...becoming light onshore early Thursday as surface high
pressure transitions from eastern Texas into the eastern United
States. A light south to southwesterly wind over low seas with
periods of light precipitation Thursday. A cold frontal passage
Thursday evening will back winds around to the northwest to
northeast while strengthening to advisory criteria during the day
Friday. Post frontal cold air moving into the area tightening the
offhsore pressure gradient will produce cautions for the bays and
Gulf advisories through Saturday morning. As of now...there will be
occasional gusts to near gale across the far offshore waters Friday
that may prompt a Gale Watch. East winds will weaken going into and
through Sunday. Friday wave heights will reach near 9 feet
offshore...around 6 to 7 feet 20 nm from the coast...in response to
those advisory level northerlies. Increasing moisture over cooler
nearshore and bay waters early next work week heightens the late
period sea fog threat. 31
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 42 62 34 41 26 / 0 10 10 20 10
Houston (IAH) 47 63 41 45 31 / 0 20 10 30 20
Galveston (GLS) 54 64 47 49 38 / 10 20 20 40 30
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&
$$
Discussion...39
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
937 PM EST Wed Jan 4 2017
.UPDATE...
Issued at 937 PM EST WED JAN 4 2017
Clouds are starting to make their way into north central KY ahead
of the incoming disturbance. Updated sky grids to push clouds in
an hour or two earlier than originally forecast, but overall the
change is subtle. Pops and weather still seem reasonable with
latest hi-res guidance, so did not adjust at this time. Loaded in
the latest observations for temps, dew points, and winds to make
sure the near term forecast was on track with the current
conditions. Despite some slightly quicker temp drop offs so far
this evening, expect incoming cloud cover to prevent continued
steep falls throughout the overnight once it moves in. Otherwise,
will continue to monitor temps in case the diurnal curve and/or
low`s need to be adjusted. All changes have been published and
sent to NDFD/web. A new forecast package will be sent out next
hour to change to overnight wording. An updated WSW will also be
issued before 11 pm, though overall information is expected to
change little.
UPDATE Issued at 653 PM EST WED JAN 4 2017
Clear conditions this evening across eastern Kentucky, with the
loss of daytime heating allowing winds to calm over the last hour
or so. Main update was to make sure the near term forecast
reflected the ongoing conditions, so loaded in the latest
observations from the last hour into the forecast. All changes
have been published and sent to NDFD/web. No updates to the
forecast packages will be needed at this time.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 425 PM EST WED JAN 4 2017
20z sfc analysis shows high pressure quickly building into the
area with west to northwest winds bringing in colder air. Thanks
to the sunshine this afternoon, and despite the CAA, temperatures
did manage to tick up a notch this afternoon from morning lows.
They still are running in the mid to upper 30s most places with
low 30s found in the northwest. Dewpoints have come down through
the area and are now in the 15 to 20 degree range most places.
The models are in good agreement aloft through the short term
portion of the forecast. They all depict a series of moderately
strong short waves scooting through Kentucky in advance of a
larger northern stream trough pivoting south into the Ohio Valley
on Thursday and Thursday night. A 300 mb jet streak passing
through Kentucky will help to generate lift through the area,
particularly Thursday evening. Given the model agreement and
trends have favored the model blend with a strong lean toward the
HRRR in the near term and the NAM12 thereafter - through 12z
Friday.
Sensible weather will feature a chilly night under mostly clear
skies through midnight. Clouds will increase, though. as a
clipper system rapidly approaches. This moves into the area
shortly after dawn with quick saturation of the lower levels and
good lift into the dendritic zone from midday Thursday into the
evening across the area starting in the northwest early and then
spreading into the southeast toward sunset. The snow will
continue into the night for most locations before tapering to
light amounts and flurries Friday morning. The models have come
into a consensus for a high range advisory snowfall for most
places - the exception will be western parts of the Cumberland
Valley where amounts will average from 1 to 2 inches. A WSW has
been issued for the entire area starting Thursday morning and
going into Friday morning.
The CONSShort and ShortBlend provided a good starting point for
most of the wx elements with only minor adjustments made to QPF
to better hit the terrain effects and some spot temperature tweaks
tonight/Thursday night. Also, beefed up the blended PoPs Thursday
and Thursday night to hit 100 percent for a good portion of the
time.
.LONG TERM...(Friday through Wednesday)
Issued at 508 PM EST WED JAN 4 2017
Models are in general agreement with mid/upper level synoptic
scale features. And despite a very progressive pattern our
weather will remain fairly quiet through the bulk of the extended.
A deepening trough does sweep across the southeastern CONUS late
Friday through Saturday, following on the heels of a first
disturbance which will be exiting to our east early in the
period. But the effects of this second storm system remain for the
most part south of our area. Another trough then marches across
the CONUS and into the Ohio Valley by the end of the extended.
For sensible weather snow showers will be tapering off through the
day Friday as our initial disturbance moves off to the east.
However, precipitation associated with the second storm system
tracking through the deep south may reach far enough north to
affect our southernmost zones late Friday into Friday evening,
effectively keeping some light snow going along the Kentucky-
Tennessee-Virginia state line Friday evening. The ECMWF favors
this solution but is a bit more of an outlier when compared with
the GFS and Canadian. For now leaned towards the drier GFS and
Canadian solutions for late Friday and Friday night. Another
storm system will approach the Ohio Valley by Tuesday with
precipitation possible over our Bluegrass counties early as
Tuesday morning.
Much colder air will be invading the area during the upcoming
weekend. We will drop below freezing Thursday night and remain
there through Monday morning. With H850 temps dropping to near
-20 C, high temperatures will only climb into the 20s both
Saturday and Sunday. Lows are expected to drop into the single
digits Sunday and Monday mornings for a good portion of eastern
Kentucky, especially our colder valley spots as a center of
surface high pressure transits our area. Overnight lows could be
even colder depending on how much snow cover we get with the
exiting system Friday. Temperatures will dip back down into the
mid 20s Tuesday morning after reaching the mid 30s on Monday. Thus
any precipitation that overspreads the area Tuesday may begin as a
wintry mix at the onset. But temperatures appear to increase
quickly enough that precipitation should switch to just rain
through the morning Tuesday and remain so through Wednesday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 707 PM EST WED JAN 4 2017
Clear conditions this evening across eastern Kentucky, with the
loss of daytime heating allowing winds to calm over the last hour
or so. VFR conditions will remain in place through much of the
night. A disturbance will move across the region tomorrow,
bringing chances for precip in the form of snow throughout much of
the day and into the overnight Thursday night. CIGs will lower
throughout the day Thursday, reaching low end MVFR by the end of
the TAF period. Wouldn`t be surprised if CIGs deteriorated into
IFR after this point. Snow will arrive in the afternoon at most
TAF sites, though as early as 14Z at KSYM. Tried to time out
scattered snow in the forecast with VCSH in the TAFS, and then
numerous snow showers with predominate -SN. Llvl winds should
remain light during this time with a surface high pressure center
sitting across KY, however winds will increase substantially as
you go aloft, with 50 knots expected through much of the day
tomorrow above 7k feet as a mid level jet sets in across the
region. Will not rule out some possible wind shear concerns during
this time.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 8 AM Thursday to 8 AM EST Friday
for KYZ044-050>052.
Winter Weather Advisory from 10 AM Thursday to 8 AM EST Friday
for KYZ058>060-068-069-104-106>109-111-112-114.
Winter Weather Advisory from noon Thursday to 8 AM EST Friday
for KYZ079-080-083>088-110-113-115>120.
&&
$$
UPDATE...JMW
SHORT TERM...GREIF
LONG TERM...RAY
AVIATION...JMW
Area Forecast Discussion
National Weather Service Omaha/Valley NE
627 PM CST Wed Jan 4 2017
.SHORT TERM...(tonight through Saturday)
Issued at 245 PM CST Wed Jan 4 2017
Snow event tonight and temperatures during the period will remain
primary concern in this forecast.
A narrow band of light snow has persisted for much of the day
across far southeast nebraska with more significant snow reported
in western parts of the state. Surface reports and DOR cameras
show little if any accumulation up to this point in southeast
Nebraska with primary period of snow still indicated after 00Z.
Recent RAP model however is trying to show a gap developing in
the snow band across southeast Nebraska with primary axis focusing
across northern Missouri. At this time will continue with current
headlines across southern parts of the area for tonight along with
1-3 inch potential.
Temperatures remain quite cold this afternoon ranging from near 10
north to the mid teens south at 20Z. Not much change expected in
temperatures tonight into Thursday with readings similar to this
morning and this afternoon as clouds hang on acrossd the area.
As skies clear Thursday night and winds diminish should our
coldest temperatures on Friday morning with most of the area
seeing subzero lows. Depending on actual snowfall tonight the lows
Friday morning may be even colder than current forecast.
Slight moderation on Friday as winds become southwesterly but
still rather cold into Saturday before a warming trend begins on
Sunday.
.LONG TERM...(Saturday night through Wednesday)
Issued at 245 PM CST Wed Jan 4 2017
Upper ridge begins to build over the western CONUS Saturday night
then works slowly east by Monday before flattening as next strong
trough heads into the west coast. As the trough pushes eastward
Monday night into Tuesday potential exists for another round of
mixed precipitation but current models keep better chance to the
north and east of the area. Not much change indicated to the
overall pattern with strong zonal flow remaining through the
upcoming week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 621 PM CST Wed Jan 4 2017
Forcing related to an upper level trough/mid level frontogenetic
band/lift through the frontogenetic layer will yield MVFR/IFR
conditions (FL015-035 and vsbys 1 to 5) with snow for the TAF
sites through the evening hours. Patchy MVFR conditions will
persist, however there will be general improvement to VFR 06Z to
09Z.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory until 6 AM CST Thursday for NEZ065>068-
078-088>093.
IA...Winter Weather Advisory until 6 AM CST Thursday for IAZ090-091.
&&
$$
SHORT TERM...Fobert
LONG TERM...Fobert
AVIATION...Zapotocny
For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php
Area Forecast Discussion
National Weather Service Topeka KS
937 PM CST Wed Jan 4 2017
.UPDATE...
Issued at 919 PM CST Wed Jan 4 2017
Snowfall reports suggest that the forecast of very high
snow:liquid ratios in the 17-22:1 range is coming to fruition as
very light returns on radar are resulting in dendrite flakes and
accumulating snow. Visibility has dropped to 1 mile or less at
times. Current focus is over northeast KS mainly north of a
Belleville to Holton line where the heavier snow should fall
through 11 PM. Then a second focus is in the next wave producing
areas of moderate snow in NW KS. This will move into the forecast
area but may focus along and just south of I-70 with support from
several updated model runs on that solution. Have thus increased
snow amounts over southern parts of the area and now have a
forecast of 1-3" for the entire forecast area and expanded the
winter weather advisory accordingly. Still see potential for parts
of Brown Marshall and Nemaha counties in particular to approach 4
inches.
&&
.SHORT TERM...(This evening through Thursday)
Issued at 309 PM CST Wed Jan 4 2017
Westerly to slightly northwesterly flow aloft this afternoon as
water vapor imagery shows a shortwave trough deepening southward
across the Dakotas. Meanwhile an elongated trough axis was stretched
just off the Oregon coastline through Oregon into Idaho. In response
at the sfc, a few areas of low pressure have developed across the
northern CO and UT areas. Narrow area of frontogenesis ahead of the
sfc low in northern CO stretched across southern NE has developed
areas of light snow this afternoon. Despite the dry airmass below
850 mb, persistent evaporative cooling has allowed a few locations
near the Kansas and Nebraska border to observe light snow falling
for a brief time, therefore have kept the chances for light snow
near the border through 00Z.
Forecast for the evening has remained mostly unchanged with the
exception of slight changes in snowfall amounts being increased west
of the previous Winter Weather Advisory. Current analysis was mostly
driven by short term guidance from the 4 km WRF solutions along with
the several runs of the HRRR and Rap models. These models have been
fairly persistent in developing snowfall across the northern
portions of the cwa in the 00-03Z time frame, with snow chances
becoming likely for much of the CWA by 06Z. Cross sections reveal a
brief time aft 06Z of mid level frontogenesis being aligned with
slightly negative epv values to enhance snowfall rates across areas
along and just north of Interstate 70. Short term guidance would
also suggest the heavier qpf amounts and associated snowfall to push
east towards far east central Kansas from 09Z to 12Z on Thursday.
This would differ slightly with the ECMWF, GFS, and SREF which
produce a few hundredths more of qpf, commence snowfall earlier this
evening and end precip later on Thursday, resulting in snowfall
amounts up to 4 inches in Brown county. Overall consensus lead me to
adjust snowfall totals to add higher amounts further west towards
the Concordia and Manhattan areas from 1.5 to 2 inches. Another tier
of counties was added to the Winter Weather Advisory still expected
to go into effect at 00Z tonight. Total snowfall accumulations still
reside in the dusting to 3 inch range, with locally higher amounts
up to 4 inches possible.
Snowfall tapers off Thursday late morning from west to east as
residual lift from the upper wave exits the area. Skies remain
mostly cloudy through the day with lows starting out in the teens.
Highs are mostly in the upper teens to near 20 degrees. Winds
tonight are not too much of an issue from the north at 5 to 10 mph,
however they increase Thursday afternoon from 10-15 mph sustained,
causing some blowing or drifting snow.
.LONG TERM...(Thursday night through Wednesday)
Issued at 309 PM CST Wed Jan 4 2017
Once the quick storm system passes east of the area on Thursday,
models show dry conditions prevailing for the region through early
next week. With the mid-level trough shifting to the east and
surface high pressure advancing into the Northern and Central Plains
Thursday night, the northwesterly flow over some snow pack will
support caa into Friday. As a result, frigid conditions are expected
Thursday night with lows near the 0 degree mark and wind chill
values plunging into the -3 to -12 range. High temperatures on
Friday will be well below the seasonal normals with readings only in
the upper teens to low/mid 20s.
This weekend the mid-level trough will be stretched across the
eastern U.S. with a ridge in place over the western U.S. With
surface high pressure slowly shifting east of the area, temperatures
will gradually moderate over the weekend into early next week with
the return of southerly flow. Surface low pressure will move into
the High Plains region Sunday night into Monday with the decent
southwesterly flow supporting waa over the CWA. As a result, high
temperatures should rise into the 40s on Monday and into the 50s for
Tuesday before a weak cold front tracks eastward Tuesday/Tuesday
night. There is still model uncertainty with whether or not any
precipitation will develop along the front, but have dry forecast
going at this time. The frontal passage will likely drop high
temperatures back into the 40s for Wednesday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 919 PM CST Wed Jan 4 2017
Snow will impact all TAF sites this evening through approximately
08Z-10Z before coming to an end. Within the snow, expect
visibility to periodically fall to 1SM but should otherwise be
mainly in the 3-5SM range. Cigs will generally be in the 1000-2000
ft range during snow, increasing to VFR as snow ends. While a few
snow showers may continue after 10Z, VFR conditions are likely.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM CST Thursday for KSZ008>012-
020>024-026-034>040-054>056-058-059.
&&
$$
UPDATE...Barjenbruch
SHORT TERM...Prieto
LONG TERM...Hennecke
AVIATION...Barjenbruch