Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/07/17
Area Forecast Discussion
National Weather Service Caribou ME
909 PM EST Wed Dec 6 2017
High pressure will build south of the region tonight into
Thursday and remain to our south Thursday night into Friday. Low
pressure will develop off the East Coast Friday night and track
to our east on Saturday.
.NEAR TERM /THROUGH THURSDAY/...
9:09 pm update...Low pressure is seen on satellite pictures
pulling just east of James Bay. The 00Z KCAR sounding showed
strong southwest flow aloft around a mid to upper level low in
Canada. Clouds have been increasing over the past couple of
hours across the western Saint John Valley and North Woods, and
another patch of clouds more or less just developed in place
across the Bangor Region. Other clouds are along the immediate
coast. The clouds are having an impact on temperatures, and have
caused them to hold steady or rise a couple of degrees where
they have either formed or moved into an area. Regional and MRMS
radar data and observations indicating snow showers in parts of
northern NY (lake effect) and an isolated snow shower or some
flurries could move into mainly far western portions of the CWA
overnight. Made some tweaks based on the latest conditions, but
at this time nothing too significant.
Previous discussion... Colder but still above normal for the
first week of December.
The cold front has pushed its way into the coastal waters
w/clouds pulling away w/it. Things are setting up to be much
colder tonight than last night w/skies starting out mostly
clear. An upper disturbance is forecast to move across the
region tonight into early Thursday. This feature was picked up
well on the satl wv imagery moving across Ontario. The NAM and
RAP pick up this feature well and show increasing clouds
overnight especially north and west. 12Z UA showed a 50 kt jet
streak residing across Ontario. Then NAM and RAP push this
feature across our CWA overnight into early Thursday. The 12z
run of the GFS was picking up on this feature as well. The
sounding data showed moisture available from 850mbs to about
700mbs. Weak forcing could be enough to set off some flurries or
perhaps a snow shower. Interesting enough, the BTV SNSQ
parameter showed some potential for activity for northern and
western areas. Other parameters such as CAPE and 850-700 mb
lapse rates are lacking. Therefore, decided to go w/slight
chance(20%) for snow showers across the far western areas by
early Thursday morning. Temps will be held up some w/the clouds
especially across the north and west where the cloud cover will
be most prominent.
For Thursday, that trof is shown to move across the CWA w/the
potential for some snow showers/flurries again north and west.
The downslope component to the winds will aid in keeping skies
partly sunny. Winds will pick up later in the morning at speeds
of 10 to 15 mph adding a chill to the early December air.
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
A large trough of low pressure will be anchored over the northeast
Thursday night. We will be in a corridor or dry air that runs
between a long band of moisture along a southern branch jet stream
to our south and some moisture pooled in the center of the trough to
our west. Some of the moisture from the center of the trough may
bring a few flurries to the higher elevations to the west later
Thursday night or Friday. Low pressure will be forming along the
southern branch jet stream to our south Friday night into Saturday
as a strong upper level shortwave dives south through the Great
Lakes. The wave of low pressure offshore appears very flat with the
flow open and positively tilted. Therefore, it will likely slide out
to sea well to our east but may brush the eastern Downeast coast
with a bit of light snow late Friday night into early Saturday. It
is noted that the Canadian model and the ECMWF bring the system
close enough for some light to moderate snow over our region. The
GFS and its ensembles, however, favor the system sliding away to
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
A large, deep cold trough will remain over the northeast through the
weekend and into early next week. Some moisture from within the
trough may bring some light snow or flurries across the area
Saturday night into Sunday and again on Monday. However, currently
there are no well organized storms to bring more than some light
snow. A more substantial storm is still expected to form off the
southeast coast and intensify as it lifts north on Wednesday. Latest
GFS guidance is showing the eastern trough to be too large and
too far east to allow this system to impact us, possibly taking
it well to our east and out to sea during the mid-week period.
The ECMWF, however, brings the storm much closer with possibly
a significant impact on our region. Will just introduce chances
for precipitation this far out.
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
NEAR TERM: VFR for this term for all terminals.
SHORT TERM: VFR conditions are likely Downeast Thursday night
through Friday with some occasional MVFR conditions possible in
patchy stratus over the far north. VFR conditions are likely
Friday night through Saturday. Coastal areas may briefly drop
to MVFR late Friday night through Saturday morning as low
pressure slides to our east. MVFR conditions are likely across
the north Sunday in low to mid level clouds and flurries with
VFR to MVFR conditions Downeast.
NEAR TERM: The wind has diminished on the coastal waters this
evening below SCA levels and the seas have subsided to 7 to 8
feet on the coastal waters. The wind will likely pick up again
as the colder air spills out over the waters, so at this time
will not transition to a small craft advisory for seas only as
there likely will be a pick up in the wind later tonight into
Thursday is tricky as the GFS and NAM both show a 25 kt wind at
925 mbs over the waters w/the passage of the trof. Conditions
for a full SCA(Winds/Seas) appears marginal attm. The later
crews can assess this further w/the later model guidance.
SHORT TERM: A SCA may be needed Thursday night for winds
gusting up to 30 kt over the offshore waters. Winds may remain
close to SCA Friday into Friday night over the offshore waters.
Winds should then be below SCA Saturday into Sunday unless the
offshore storm system ends up stronger or closer in to the
MARINE...Small Craft Advisory until 4 AM EST Thursday for ANZ050-051.
Please see the 00Z aviation forecast discussion below.
Light rain is ongoing across all TAF sites and is expected to
continue through the overnight hours into Thursday morning. Models
show a little more dry air in place at AUS when compared to SAT, SSF
and DRT. For AUS, we will keep -RA in the forecast overnight, along
with VFR cigs. Shortly after sunrise Thursday, the rain shield should
shift south of the terminal and we will remover the mention of -RA
and keep skies VFR. At SAT and SSF, the low-levels will be a little
more saturated and will go with MVFR cigs and light rain through
mid-morning Thursday. Rain should begin to taper after 16Z and will
show conditions improving to VFR. At DRT, we will also keep MVFR cigs
and -RA in the forecast overnight. There is a concern that some of
the rain could mix with light snow early Thursday morning during the
08Z-12Z time frame. At this time, am not quite confident enough to
mention any frozen precipitation in the forecast. In addition,
surface temperatures are expected to remain above freezing overnight.
PREV DISCUSSION... /ISSUED 341 PM CST Wed Dec 6 2017/
SHORT TERM (Tonight through Thursday Night)...
A very complicated short term period in regards to winter weather
prospects overnight and through Thursday. The rain shield currently
observed across South Central Texas will evolve to include snow mixed
in this evening and overnight for locations mainly on the Plateau and
Hill Country but could reach as far east as the I-35 corridor.
Exhaustive interrogation of forecast soundings have not made things
much easier either. While surface temperatures will struggle to fall
due to an extensive cloud shield over the region, they will come very
close to the freezing threshold across western Val Verde, much of
Edwards and Real counties, and into Gillespie and Kerr counties.
However, low level temperature profiles have been trending colder
lending more credence to the possibility for snow/rain mix, and
perhaps even all snow for periods of time after midnight until
daybreak for these same areas. Farther to the southeast, reaching the
I-35 corridor, rain should be the most dominant precip type, but
still cannot rule out some snowflakes mixed in as well.
Regardless, with surface temperatures likely to hover at or just
above freezing for these areas, and still quite a bit above freezing
elsewhere, little to no accumulations are expected. If accumulations
do occur, they will likely be dustings at best, likely in far western
Val Verde and across our northern CWA border to Gillespie county.
Perhaps more of a concern is any standing water due to today`s
rainfall activity freezing on bridges and overpasses where
temperatures will be the coldest, again in the Hill Country and
Tomorrow morning, some folks may wake to find a few snowflakes still
before transitioning back to all rain late in the morning and into
the afternoon hours. The rain shield is expected to push slowly
southward over the course of the day and likely south of San Antonio
shortly after the noontime hour. Have trended PoPs down over the
course of the day tomorrow closely following the trends of the TTU-
WRF and HREF.
Even colder temperatures are expected Thursday night and overnight
into Friday morning and if lingering rain activity continues in the
southern zones when temperatures begin to fall to near freezing, some
wintry mix could be seen in our southwestern zones, but again, no
accumulation is expected at this time.
LONG TERM (Friday through Wednesday)...
As the shortwave responsible for this cold front passes over Friday,
it will begin a trend of warming through the weekend, reaching highs
in the 60s over the weekend and through the first half of next week.
By mid week, a broad and weak low over the Gulf of California is
expected to slowly traverse over the US/Mexico border. While a dry
forecast is expected through the week during this transition, our
next best shot at PoPs could be Friday as this low further weakens
into a shortwave as it passes over Texas.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 43 38 51 31 55 / 90 70 30 10 0
Austin Bergstrom Intl Airport 43 36 51 30 56 / 90 80 40 20 0
New Braunfels Muni Airport 43 37 50 32 55 / 90 90 60 20 0
Burnet Muni Airport 41 36 48 27 55 / 90 70 20 10 0
Del Rio Intl Airport 46 37 46 31 55 / 80 90 60 20 0
Georgetown Muni Airport 42 38 50 28 54 / 90 70 20 10 0
Hondo Muni Airport 46 38 49 29 57 / 90 100 80 20 0
San Marcos Muni Airport 43 37 49 31 55 / 90 90 60 20 0
La Grange - Fayette Regional 42 37 49 31 52 / 90 90 60 30 0
San Antonio Intl Airport 44 37 49 34 56 / 90 90 70 20 0
Stinson Muni Airport 45 38 48 34 55 / 90 100 80 30 0
Public Service/Data Collection...Williams
Area Forecast Discussion
National Weather Service Jackson MS
933 PM CST Wed Dec 6 2017
...WINTER WEATHER POTENTIAL THURSDAY INTO FRIDAY...
Updated for evening discussion.
Previous forecast remains on track, with a precipitation shield
draped across the southern half of the CWA as moisture aloft
interacts with a frontal boundary parked to our south over the
north-central Gulf of Mexico. It consists primarily of light
rainfall, although some sleet could continue to mix in
occasionally throughout the overnight period. No sleet
accumulation is expected. Light northwesterly surface flow will
continue overnight and low temps will be in the upper 30s for most
Prior discussion below:
Getting some reports of some light sleet in Northeast Louisiana as
well as our Southern Mississippi counties. So have included light
sleet in the forecast through the night. Latest HRRR model
soundings shows some low level wet bulbing in the low level dry
layer going on through the night for some patchy sleet to
continue. With warm ground temps expecting no impacts on
Prior discussion below:
Been getting reports of some patchy light sleet across the
southern counties late this afternoon due to wet bulbing. So have
included it in the grids through this evening until midnight.
Expect no impacts on road conditions./17/
Prior discussion below:
Through the day Thursday:
Expect cold and generally cloudy conditions to continue across the
region through tomorrow afternoon with light precipitation
intermittently spreading east/northeast-ward across mainly the
southern half of zones. All this is occurring as the big surface
frontal boundary that came through our region yesterday remains
stalled in the northern Gulf of Mexico and moisture aloft overruns
the sloped frontal surface in advance of another upper wave digging
into the backside of the big trough overhead.
Some sleet has been observed this morning in central zones where the
sub-cloud layer was dry enough to create ice pellets through a wet-
bulbing process a few thousand feet above the ground. No impacts
were seen as surface temperatures were at least several degrees
above freezing. The same process could occur, primarily on the
northern edge of the precipitation shield, tonight into tomorrow,
with the potential for impacts through this time remaining very low
because temperatures will be above freezing. At this time we will
keep mention of anything of this sort (at least through tomorrow
afternoon) out of the official forecast because rain will be
predominate and any sleet non-impactful. Of course the forecast
could be modified if sleet becomes prevalent at times. Once again
tomorrow the presence of thicker clouds and continuing light
precipitation will keep the chilliest high temperatures oriented
in southern zones (contrary to what is usually the case). /BB/
Thursday night through next week:
Thursday night into Friday will be the most impactful part of the
long term forecast as well as the most challenging part. The
lingering axis of stratiform rain over the southeast parts of our
CWA will continue to slowly push out of the area, but not until much
colder air advects into the area overnight Thursday and early
Friday morning. Temps will fall into the upper 20s in the north
and near to slightly above freezing in the south. Beginning after
midnight Friday morning, a slow transition from rain to snow is
likely in areas south of the Natchez Trace Parkway. The question
continues to be how much dry air will filter in on the backside of
the precip axis and at what rate will the precip fall. This
precip rate could be a factor of how much snow accumulates, how
much rain is able to transition to snow, or even more importantly
how cold the temperature even falls. The science behind rain to
snow transition and latent heat release is very intricate and
holds the way for a lot different possibilities. Overall, the Euro
and Canadian models still show more precip and precip farther
north with this system. For this forecast, we went with a blend of
the Euro and the main guidance. Confidence continues to increase
in snow chances. Flurries in the metro area cannot be ruled out
now. Any snow is not expected to impact roadways at this point and
is only expected to accumulate on grassy areas or rooftops. As
the temperature rises Friday morning after sunrise, there will be
another transition back to all rainfall with the rain finally
pushing out of the area in the afternoon.
The trough axis will cross the CWA Friday night and bring the
coldest temps of the season so far. A hard freeze is certainly
expected Saturday morning. One thing to watch for that morning
will be black ice. If any roads have not dried by then, then black
ice will certainly be a threat. Once on the back side of the
trough though and with rising heights, temps will warm into the
50s for the rest of the weekend. Skies will clear with subsident
air around a surface high pressure over the northern Gulf Coast.
Temps will continue warming on Monday to about normal for this
time of year. Going into early Tuesday next week, another upper
trough will swing through the eastern U.S. and slide an associated
dry cold front into the CWA and once again cool temps off just a
00Z TAF discussion:
Expecting mainly VFR conditions through the next 24 hours although
there will be plenty of clouds around and a fair amount of light
rain spreading across along and south of the I-20 corridor through
this time. A few sleet pellets mixing in with the rain at times
cannot be ruled out over this period but surface temperatures
where this is occurring will be above freezing and no impact is
expected, at least through tomorrow afternoon. Ceilings will be
lowest intermittently through this time at MEI/HBG, although even
here they will almost entirely be above 3 kft. Winds will be light
from the north/northeast through 24 hours. /17/BB/
.PRELIMINARY POINT TEMPS/POPS...
Jackson 39 50 31 43 / 28 24 21 20
Meridian 38 47 32 42 / 33 47 34 38
Vicksburg 38 49 31 44 / 22 16 17 13
Hattiesburg 39 45 34 41 / 79 86 61 66
Natchez 38 48 31 43 / 53 43 27 23
Greenville 37 48 29 42 / 5 2 3 3
Greenwood 36 49 28 43 / 7 5 4 4
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
949 PM EST Wed Dec 6 2017
A cold front will be stalled offshore through the end of the week
with areas of low pressure developing along it. An arctic air mass
will move in over the weekend behind a stronger cold front. Another
arctic cold front will move through by mid week next week.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 940 PM Wednesday...Bands of light rain continues to move
northeast across the region through the overnight hours. Latest
HRRR shows continuing light rain with light QPF overnight before
thinning out inland late tonight. Will continue with near 100
percent PoPs overnight as most areas will at least receive
measurable rain. No other big changes to the forcast as lows
should be in the upper 30s to lower 40s in most locations with
mid 40s along the Outer Banks.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
As 3 PM Wed...A break in the widespread rain occurs on Thursday
as weak ridging briefly builds in from the north. Have just chc
pops northern half while likely pops reside across the southern
half, with best chances of rain along the Crystal Coast.
Otherwise, cloudy and chilly conditions will be the rule. Highs
expected to reach the upper 40s.
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
As of 330 AM Wednesday...Models continue to indicate cold and
wet period through Friday night, followed by Arctic air mass
spreading in over weekend. Some model differences persist on
timing of precip ending Saturday, otherwise in good agreement
most of period. Main adjustments with this issuance were to have
likely to categorical POPs across most of area through Friday
night, and did add mention of possible mix with light snow over
western-most sections late Friday night and Sat morning.
Thursday Night through Friday night...Models remain in good
agreement of wet pattern this period as slow moving upper trough
from eastern Canada to SW U.S. will tap atmospheric river from
Pacific Ocean for favorable overrunning precip development with
frontal boundary stalled offshore. This will result in periods
of light to occasionally moderate rain through Friday night with
storm total rainfall of 1 to 3 inches, heaviest along and east
of Hwy 17. Have adjusted POPs accordingly with main threat of
moderate rain mentioned Thu night and Friday as main trough axis
begins to approach from west, resulting in stronger low
pressure wave development south and east of area along stalled
Main core of colder air mass will remain west and north of area
until late Friday night into Saturday. Still looks mainly likely
cold air moving in as moisture exits but enough support to
mention rain possibly mixed with some light snow over
west/northwest portions of Duplin-Martin counties late Friday
night into Saturday morning. No accumulation expected due to
relatively warm ground temps.
Temps mainly between 35-45 degrees most of period except some
highs near 50 along coast.
Saturday...Model timing differences continue with GFS faster on
upper trough while ECMWF slower and lingering precip through the
day. Used model blend with chance POPs lingering over eastern
sections during the day, then tapering off by evening. Highs
from lower 40s inland to near 50 coast.
Saturday night through Monday...Arctic air mass will spread
over area producing temps 10-15 degrees below normal. Lows
mainly mid 20s to mid 30s and a few degrees colder Sun night
with possibly frost or light freeze for Outer Banks where
growing season has not ended. Highs Sunday mainly in 40s,
moderating to around 50 Monday.
Monday night and Tuesday...Approach of next upper trough will
lead to moderating air mass Monday night and low chance POP for
showers on Tuesday. 00Z ECMWF is faster with this trough and is
indicating potential for light mixed or frozen precip, while GFS
slower and warmer. Given uncertainty for day 7, will keep precip
as just rain showers at this time.
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
Short Term /Through 00Z Friday/...
As of 630 PM Wednesday...MVFR conditions currently observed at
KEWN, KPGV and KOAJ. With precipitation remaining light, think
this will continue for a few hours before becoming VFR as rain
area starts to diminish later tonight. A break in the rain
expected on Thursday , especially for KISO and KPGV where some
drier air works in from the north. Winds will be light northerly
through the period.
Long Term /Thursday Night through Sunday/...
As of 400 AM Tuesday...Sub-VFR conditions likely with widespread
overrunning precip Thu night through Friday night. Conditions
improving to VFR for weekend with drier and colder air mass
Short Term /Through Tonight/...
As of 950 PM Wednesday...Based on current observations showing
generally 10-15 knot winds and 3-5 foot seas, have allowed the
SCA for the waters north of Oregon Inlet to expire. Will
continue the SCA into noon Thursday from Oregon Inlet south to
Ocracoke where winds are more gusty with seas hovering around 6
feet. Expect northerly winds of 10-20 knots overnight and
Thursday. Seas should subside in all areas by midday Thursday.
Long Term /Thursday night through Sunday/...
As of 400 AM Wednesday...Elevated seas will linger into Thu
morning. Persistent gradient between high pressure to west and
low pressure development along stalled front offshore will keep
NW-N winds 10-15 KT through Thu night. Models have trended
stronger with winds Friday and Friday night with stronger low
development and adjusted forecast to indicate period of 15-25 KT
winds mainly outer waters. Winds will become NW and diminish to
10-15 KT Saturday, then increase to 20-25 KT Sat night and
Sunday as Arctic air mass moves in.
Seas will subside to 3-5 ft Thu night, then some 6 foot heights
expected outer waters Friday into Saturday and 5-7 ft there Sat
night into Sunday.
MARINE...Small Craft Advisory until noon EST Thursday for AMZ152-154.
Area Forecast Discussion
National Weather Service Blacksburg VA
943 PM EST Wed Dec 6 2017
A cold front will stall off the coast tonight. Colder and drier
weather continues into Thursday. Friday, low pressure will shift
along the front bringing some snow the piedmont/foothills. This
system pulls east by Saturday morning.
.NEAR TERM /THROUGH THURSDAY/...
As of 930 PM EST Wednesday...
The late evening update will continue to reflect little change
in the overall forecast. Have made some minor adjustments to the
exiting scattered sprinkles across the the far southeastern
sections of the region as that activity continues to edge
eastward. Sky cover has remained on the cloud side across the
entire area. A decrease in coverage across the northwestern
sections looks more probable later tonight. Temperatures are
within a couple of degrees of the forecast values, so not
notable adjustments there.
As of 610 PM EST Wednesday...
The forecast update for early this evening will reflect little
change from the afternoon issuance. However, one adjustment
will be the inclusion of some patchy sprinkles across parts of
Southside Virginia and neighboring sections of north central
North Carolina. Radar returns are indicating dBZ values in the
20s to lower 30s values over parts of this area. Given cloud
heights are still around 10,000 ft AGL, suspect that at best
some sprinkles are reaching the ground in a few spots.
Currently, there is an enhanced band of these 20-30s dBZs along
a line from near Reidsville, NC to Danville, VA to Phenix, VA.
Have also adjusted hourly temperature, dew point, wind, gusts,
and sky cover to better reflect the latest observations and
expected trends through the late evening hours.
As of 145 PM EST Wednesday...
Upper flow remains southwest this evening with jet induced
cirrus/cirrostratus overhead, so sky cover will stay mainly cloudy
this evening. Stronger shortwave dives into the Lower Great Lakes
late tonight with several embedded vorts ahead of it moving across
the southern Appalachians into Virginia. 8h flow will be northwest
with models favoring some upslope lower clouds overnight in the west
but precip threat will be very low with deeper moisture along
baroclinic zone along the coast. Some low/mid level cloudiness early
on this evening in southside VA and may see a sprinkle.
Lows tonight will be actually closer to normal, with mid to upper
20s in the mountains, to lower to mid 30s east.
Thursday, more of the same with mid/high clouds keeping the area
cloudier, with main moisture axis of precip well to our southeast,
as main shortwave shifts toward the eastern Ohio Valley to mid
Mississippi Valley. Highs should range from the mid 30s higher
ridges, with upper 30s to around 40 rest of the mountains/west of
Blue Ridge, with mid to upper 40s east.
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM EST Wednesday...
The region will remain in the RR quad of energetic upper jet with broad
synoptic ascent through Friday night, while waves of low pressure
ripple along a baroclinic zone along the coast. As the baroclinic zone
buckles a bit, additional forcing associated with deformation on the
northwest side of a wave will push precipitation into the piedmont
Friday/Friday night. As the precipitation nudges into the region
Friday, precipitation type will favor all snow up to the Blue Ridge
where QPF will be lightest and result in just some flurries. In the
piedmont where a bit more QPF is expected it is looking like a mix of
rain/snow and with the ground still warm any accumulations will be
limited to a slushy coating. Latest model runs are trending the back
edge of the precipitation a bit further to the northwest. If this
continues QPF may increase with a corresponding change to any snow
accumulations, so this will be watched closely. Any lingering
precipitation will be pulling off to the east late Friday
After a brief lull Saturday afternoon, a vigorous short wave will drive
a low through the Great Lakes and into New England with a trailing cold
front moving through the Appalachians. This will bring a good chance
of upslope snow showers to locations west of the Blue Ridge Saturday
night/early Sunday morning, along with very blustery winds ushering
another shot of cold air.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 300 PM EST Wednesday...
CONUS remains locked in an amplified pattern featuring a western ridge
and an eastern trof, keeping the Appalachians and central mid Atlantic
region in temperatures well below normal through the middle of next
week. Short wave energy moving through the upper trof will fuel
blustery northwest winds as they drive periodic reinforcing surges of
cold air into the region. There will also be a chance for upslope snow
showers west of the Blue Ridge mainly through the first part of next
week, possibly mixed with rain. There are also hints of some synoptic
forcing developing along a baroclinic zone just off to our southeast
which may brush close enough to bring some rain and/or snow showers to
Southside and portions of the piedmont Tuesday, though the bulk of
precipitation will remain closer to the coast.
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
As of 605 PM EST Wednesday...
VFR conditions are expected during the extent of the TAF
forecast period concluding at 00Z Friday/7PM Thursday.
Winds will generally be light and variable or light from the
west overnight. During the course of the daylight hours
Thursday, most areas will see a slightly stronger west or
Should see continued VFR Thursday night into early Friday with
light north to northwest winds, as a disturbance rides along a
frontal zone well south of our region.
The front to our southeast will have a low pressure wave along
it while the upstream trough digs a little. Could see some snow
and sub-VFR cigs/vsbys toward DAN/LYH in the Friday afternoon
through Saturday time frame.
An arctic cold front this weekend, could also bring snow showers
to the mountains with potential sub- VFR ceilings and intervals
of sub- VFR vsby mainly at BLF/LWB, with post- frontal strong
northwest winds Saturday night into early Sunday.
VFR conditions then return Sunday evening.
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Thursday)
Issued at 231 PM CST Wed Dec 6 2017
An elongated region of H925-H850 Fg forcing was wrapping
southward along the upstream flank of an H500 trough axis early
this afternoon. Light to moderate snow has been reported across
central Nebraska and western Iowa with this forcing band with
visibilities of a mile or less in a few locations. CAA behind this
line coupled with large T/Td spreads and wet bulb temps near
freezing has allowed SN to be reported despite surface temps near
40 degrees. The HRRR has done a decent job depicting this region
of forcing and continues to weaken it through the afternoon.
RAP/NAM model along with the 12Z TOP RAOB depict a wedge of dry
air over SE Nebraska and NE Kansas under the precip generating
layer with surface Td depressions of 10 to 15 C. Thus, leveraged a
compromise in the precip forecast for the rest of the afternoon,
trending upwards in coverage and intensity in the far northern
counties while at the same time decaying the band rapidly from 22
to 01Z. Likewise increased cloud cover through the evening hours
for the passage of the band--which clears out quickly before 06Z.
Surface ridging builds for the day on Thursday with and -12 C
H850 thermal trough overhead and keeping surface temps around the
.LONG TERM...(Thursday night through Wednesday)
Issued at 231 PM CST Wed Dec 6 2017
The extended pattern will be characterized by continued NW flow due
to a strong synoptic block anchored over the west coast. Multiple
weak perturbations will drop southward during this time, but with
minimal forcing and moisture to realize, the sensible weather
effects will be minimal. A downslope airmass will translate
southeastward into the region starting on Friday, with increasing
H850 temps through the weekend. By late Sunday, H850 temps will be
above +10 C with corresponding surface temps in the upper 50s to
near 60. A second push of cold air will arrive for early next week
and drop temps back to near average. The next decent chance of
precip may not be until next Monday has the H500 wave/vort max
drops through, along with some very low chances of
flurries/sprinkles attendant to synoptic jet dynamics on Friday
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 514 PM CST Wed Dec 6 2017
VFR conditions are expected throughout the period. There is a
slight chance for some flurries at sites for the next couple
hours, but with such scattered coverage of precipitation have left
this mention out of the TAF.