Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/09/17
Area Forecast Discussion
National Weather Service Denver/Boulder CO
843 PM MST Sun Jan 8 2017
Issued at 842 PM MST Sun Jan 8 2017
Another burst of heavier mountain snowfall is ongoing this
evening, but latest radars to the west are showing a rapid
decrease. That was due to some mid level ridging and drying as
noted on the Salt Lake City 00Z sounding. GJT sounding showed very
strong warm advection with 700 mb temps near 0C. Snow levels will
probably rise a little overnight with further warm advection, but
intensity was expected to decrease overnight with the drying so
overall little impact on the going forecast. The brunt of the
mountain snowstorm will hit the high country Monday and Monday
night with the heaviest snowfall and significant blowing snow.
Snowfall rates up to 2" per hour are expected as maximum
precipitable water plume (3rd standardized anomaly) hits the
mountains in the afternoon. Cold advection will begin as well and
lapse rates improve.
With regard to the wind threat, there may be some opportunity for
wave amplification late tonight as mountain snowfall decreases.
We still aren`t very confident in the highest winds spreading all
the way down the Front Range, but given the watch for the adjacent
zones from Fort Collins to Boulder and the western Denver suburbs
started late tonight we opted to go with the warning. Could
be a marginal event with lack of significant mountain wave
amplification, but decent gradient as seen in the forecast
Sangster data could help. The other point of concern was the
Palmer Divide. Very rarely does this area blow very strong but
with the west/southwest flow over the Rampart Range we should get
some amplification there. Latest HRRR and RAP also supporting wind
gusts in excess of 60 mph there so lined that up with Pueblo`s
new high wind warning in El Paso county.
Finally, there were some echoes noted over the northeast plains
but almost all virga with cloud decks at or above 7000 feet.
.SHORT TERM...(This evening through Monday)
Issued at 320 PM MST Sun Jan 8 2017
Very moist Pacific air will be transported into the Central
Rockies tonight and Monday. IR Satellite and radar showing an area
of increased precipitation over Utah at this time. Expect snow to
increase over the Colorado mountains early evening as this batch
of moisture moves across Colorado. Relatively drier air behind it
will bring a decrease to the mountain snow late tonight.
Snow will increase and become heavy at times Monday as very moist
air spreads across the Rockies. Snowfall amounts are expected to be
significant with 1 to 2 feet of snow for the mountains. Up to 3 feet
will be possible near Rabbit Ears Pass and in the mountains of
Western Jackson County. Will not issue any highlights for the
mountain valleys. Uncertain if it will be cold enough for all snow
in the valleys. Also, with the main forcing being orographic, the
valleys may miss out on a good part of the moisture.
Strong winds are also expected with this system along the east
slopes east to about Interstate 25. Models showing a stable layer a
little below 500 mb early Monday morning, which should help produce
a mountain wave. The 18z NAM shows winds at 700 mb up to 100 knots
in the foothills. GFS not quite as strong with peak 700 mb winds
around 70 knots. Expect this to produce wind gusts to at least 75
mph in the foothills. With the stable layer being somewhat high,
there some uncertainty if the strong winds will spread out from the
foothills. Will keep the High Wind Watch in place for this area.
It will be windy even if the strong winds don`t surface. This will
keep overnight lows mild and above freezing in many locations.
Highs will also be mild Monday with the western part of Denver
Metro area reaching 60 degrees.
.LONG TERM...(Monday night through Sunday)
Issued at 320 PM MST Sun Jan 8 2017
A swift zonal flow aloft will continue to drive waves of
moisture rich maritime air into the mountains and high western
valleys of Colorado through Tuesday night. There will be
interruptions in this plume of moisture...but not long enough to
allow any notable clearing or significant reduction in
precipitation during the period. Mid-level cooling with passing
shortwave trough monday night should enhance high country snowfall
rates...as before mainly along and west of the Continental
Divide. Could see 1-2 inch per hour rates in the park...Gore and
Rabbit Ears ranges as well as over the higher west slopes in
Summit County. Wind gusts in the 30-50 mph also possible resulting
in areas of blowing and drifting snow. Elsewhere...gusty
downslope winds will continue in the Front Range foothills and
nearby plains Monday night into Tuesday but winds not expected to
be as strong or as warm with shift to a Bora wind. However areas
up along the Wyoming and Nebraska borders may actually see more
wind with a shift to west- northwest flow aloft and cold
advection. Furthermore could see a few snow showers drift off the
foothills and over portions of the I-25 corridor Monday night.
Chance of accumulation quite small.
Looking ahead to the period Wednesday through Sunday...Models
indicate a modest drop of in high country snowfall early on
Wednesday only to ramp up again with another blast of very moist
Pacific air. Snow amounts and rates not expected to be as great
with southwest flow and mid-level warming. Through the day deep
layer qg ascent and lapse rates increase in advance of a shortwave
trough moving out of the great Basin. Could see a period of
moderate to heavy snow on west slopes Wednesday night which may
require issuing some sort of winter weather highlight at some
point. Whereas areas east of the mtns look to remain dry for
another 24 hours. This will change on Thursday with a cold front
dropping in from Wyoming and a swath of moisture passing over the
CWA. Will go with likely pops in the high country and a chance of
snow at lower elevations. By Friday and into Saturday much drier
air sweeps east across the region once the upper trough swings
across the region. Although the ECMWF shows a closed upper low
over southern Arizona slinging moisture back up into eastern
Colorado on Saturday which require at least a slight chance of
precip and more cloud cover. Will hold off on introducing this
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 842 PM MST Sun Jan 8 2017
Winds will be the main issue tonight and Monday at the Denver
airports. Southerly winds are expected through 14z Monday at KDEN
and KAPA. However, any mountain wave amplification could push
westerly winds off the foothills. Eventually (toward 16Z-19Z
Monday), westerly winds to around 40 knots are expected at KDEN
and KAPA. At KBJC, strong west winds are expected to develop 09Z-
12Z with gusts to 50-60 knots possible til 00z Tuesday.
VFR conditions will prevail through Monday with only mid/high
clouds in strong downslope flow.
High Wind Warning from 2 AM to 5 PM MST Monday for COZ038-039-
High Wind Warning until 5 PM MST Monday for COZ035-036.
Winter Storm Warning until 11 AM MST Tuesday for COZ031-033-034.
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
954 PM CST Sun Jan 8 2017
Southerly lower level flow is rapidly bringing back moisture and
warmer temperatures to South Central Texas. The leading edge of
the stratus is along a Carrizo Springs to San Antonio to Bastrop
to Brenham line and moving north at 20 MPH. It will spread across
the remainder of our area in the next few hours. Temperatures will
generally stop or slow their fall after the stratus moves over an
area and have followed the HRRR temperatures/dewpoints overnight
into Monday morning. Radar VAD winds show a low level jet of 25
KTs and this may impact fog development. Remainder of South
Central Texas forecast is on track. 18Z models continue trend of
uncertainty with lack of consensus and consistency for Friday
through next weekend.
.PREV DISCUSSION... /ISSUED 526 PM CST Sun Jan 8 2017/
VFR conditions will prevail for the first several hours of this
forecast period. Winds will be S/SE 4-8 knots at the I-35 sites
and 10-15 knots at KDRT before becoming easterly and decreasing to
5-10 knots after 02z. Do expect MVFR cigs to develop around 07z-
08z at the I-35 terminals with an increasing low level jet.
Conditions will lower to IFR cigs 11z-12z and likely remain there
until late morning then returning to high end MVFR by 20Z. KDRT
has the potential to see a brief period of MVFR cigs after
sunrise. have covered this with a tempo group. Winds after 17z
will be S/SE at 10-15 knots. KDRT will likely once again see wind
gusts to near 20 knots during the afternoon.
PREV DISCUSSION... /ISSUED 231 PM CST Sun Jan 8 2017/
SHORT TERM (Tonight through Monday Night)...
Upper air analysis this morning showed northwesterly flow over
Texas between a trough to the east and a ridge to the west. At the
surface, high pressure was centered to the east and winds have
shifted to the south to southeast. Low level moisture has begun to
return with dewpoint temperatures in the 30s over the Coastal
Plains. This moisture return and warm advection will continue
during this period. Low temperatures tonight will be around 20
degrees warmer than this morning and we will gain another 15
degrees or so Monday night. High temperatures Monday will be about
10 to 15 degrees warmer than today.
LONG TERM (Tuesday through Sunday)...
The upper level ridge will continue to dominate into the middle of
the week. The low level southerly to southeasterly will continue.
There will be dry weather with warming temperatures. Highs will
reach the middle to upper 70s most places with a few spots
reaching 80 by mid-week. The upper ridge will begin to break down
Wednesday with the flow becoming more zonal and then
southwesterly. This may allow for some isentropically driven lift
and a slight chance for rain Thursday and Friday. Another frontal
boundary will move through the region sometime during the end of
the week. Models are not in good agreement at this point with the
timing on the front, but do show an extended wet period Friday
night through Sunday. They also show some agreement on a
significant rain event with an inch or more over the couple of
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 41 64 56 75 60 / 0 - 0 - 0
Austin Bergstrom Intl Airport 37 66 56 76 58 / 0 - - - 0
New Braunfels Muni Airport 40 65 55 75 58 / 0 - - - 0
Burnet Muni Airport 36 62 53 75 55 / 0 - 0 0 0
Del Rio Intl Airport 36 64 46 73 51 / 0 0 0 0 0
Georgetown Muni Airport 37 63 56 75 58 / 0 - 0 0 0
Hondo Muni Airport 39 64 52 76 54 / 0 0 - - 0
San Marcos Muni Airport 37 66 55 75 58 / 0 - 0 - 0
La Grange - Fayette Regional 41 67 58 77 63 / 0 10 0 - 0
San Antonio Intl Airport 43 64 56 76 58 / 0 - 10 - 0
Stinson Muni Airport 45 65 56 76 57 / 0 - - - 0
Public Service/Data Collection...Williams
Area Forecast Discussion
National Weather Service Flagstaff AZ
332 PM MST Sun Jan 8 2017
.SYNOPSIS...A strong subtropical jet will supply plenty of
moisture on Monday to deliver a rainy and windy day across most
of northern Arizona. The snow level will be between 8000 and 9000
feet on Monday. Unsettled weather is then in store for the
remainder of this week.
.DISCUSSION...Focus this shift has been on the wind and
precipitation event forecast to affect northern Arizona from late
tonight through Monday. First, the wind. Forecast models,
including hi-res models such as the HRRR and Hi-Res windows, show
that southwest wind gusts to the lee of high terrain features
will likely not become too strong until after midnight tonight or
so. Forecast soundings indicate that high terrain features such as
the San Francisco Peaks will be above the stable layer tonight,
so it`s questionable exactly how strong wind gusts will be once
they make it to the surface. The NAM and GFS both develop 55-65
kt or higher winds at 700 mb during the day on Monday, especially
near the Utah state line. During the day on Monday, expect breezy
to windy conditions but again, due to clouds and extensive rain
maintaining a stable layer, it`s uncertain how strong near-
surface wind gusts will be.
Next, the precipitation. We expect strong moisture advection
associated with a subtropical jet to begin over northwest
Arizona late tonight, with the peak of moisture transport
occurring during the afternoon on Monday. NAEFS mean moisture
transport values over far northern Arizona are near maximum
values for this time of year, but the period during which values
remain this high will likely not be more than a few hours. That
being said, expect precipitation to begin over the Kaibab and
Coconino Plateaus early tomorrow morning, moving farther south and
east through the day. Snow levels are forecast to be largely
between 8000 and 9000 feet, so most roadways and populated areas
of northern Arizona may expect rain.
Largely zonal flow is expected to impact northern Arizona through
much of the remainder of the week. Though it`s difficult to pin
much confidence on any individual feature/short wave trough moving
through the flow during the mid-week period, enough moisture will
remain that chances of precipitation are included through this
time frame. By Friday into Saturday, several model solutions are
indicating a closed low moving near the area with lower snow
levels. The NAEFS mean hints that this low center will travel
south of our area, but with several days of zonal flow this is a
particularly low-confidence pattern so keep checking.
.AVIATION...For the 00Z forecast...VFR conditions will continue
through tonight. SW winds will increase during the overnight hours
with gusts of 30+ kts likely northeast(downwind) of mountainous
terrain aft 06Z. Winds gusting 30-40 kts will become more widespread
during the daytime hours Monday lasting through the evening. Expect
showers to cross west to east through the area Monday, most numerous
during the afternoon hours with areas of MVFR to IFR developing.
Snow levels to remain above 8000 feet MSL. Aviation discussion not
updated for TAF amendments.
For Northern Arizona weather information visit
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
940 PM EST Sun Jan 8 2017
Cold high pressure will linger atop the region through Monday before
giving way to a southerly flow and rising temperatures by Wednesday.
Low pressure is forecast to approach our region from the west next
.NEAR TERM /THROUGH MONDAY/...
930 PM Update...Based on IR imagery and RAP progs of continued ulvl
moisture traversing the backside of the h5 trof...have bumped min temps
up a couple degrees mainly across the wrn zones. Hr/ly temps have
been persiting warmer than the fcst curve so a new diurnal has been
625 PM Update...Made some upward adjs to hr/ly temps due to stream
of Ci rounding base of ulvl trof. May have to tweak min temps up
most locales as well with next update.
430 PM Update...No major changes needed to the going fcst. Increased
sky cover across the wrn half as ulvl jet streak has enhanced
incoming Ci shield. Temps and Tds are right on track.
As of 235 PM EST...Arctic high pressure settling over the area
tonight will remain in place Monday. This leads to a tricky low temp
forecast for tonight. Normally, one would expect lows to be colder
than the operational guidance with light winds and good radiational
conditions. The lingering snow pack across the area would just add
to the confidence of this scenario. However, the cirrus moving into
the western CWFA will just become thicker and more widespread
through the night as a jet streak moves overhead bringing in high
level moisture. With the jet moving through, this will help
orographic mountain wave cirrus to develop. Could even see some mid
cloud as well. Therefore, expect temps to cool quickly early but
slow down as the clouds build. Would normally expect a negative
lapse rate across the mountains with good radiational conditions
and deep low level inversion setting up. Still show this trend
across most of the mountains, but not as strongly as normal given
the clouds and snow pack. Still, that gives us single digits across
most of NC, with teens across most of SC and NE GA. With winds
dropping off through the night, wind chill values should remain
above advisory levels for all but the highest elevations of the NC
mountains. Will reissue the black ice advisory for most of NC, the
northern tier of the Upstate, and the NE GA mountains. Kept Union NC
and York out since they had much less wintry precip and sat pix show
little to no snow there.
The cirrus moves east quickly after daybreak Monday as the jet
streak moves out of the area. Expect more areas to rise above
freezing with sunshine returning and rising thickness. Of course,
with the cold air mass and continued snow pack, highs will be well
below normal across the board.
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 230 PM EST Sunday: The short term fcst period kicks off on
Monday night amidst dry/cold surface high pressure, reinforced
by H5 ridging aloft. Pattern evolution through the period will
be highlighted by falling heights across the East/Central CONUS
as a consequence of a progressive upstream trof, while a sfc wave
deepens across the Great Lakes. With that, a cold front will push
through the OH/TN valleys on Tuesday as the persistent east coast
surface ridge retreats out to sea. Moisture/lift associated with
the front will move into the western tier of the fcst area Tuesday
night as waa increases regionwide thanks to veered southerly flow.
As such, favored a nearly flat temperature profile on Tuesday
night, while pops were allowed to increase from the west to feature
likely levels along the TN line, tapering down to slight chances
southeast into the NC/SC Piedmont. Said surface front does look to
stall out along/north of I40 corridor into late morning to early
afternoon Wednesday warranting continuation of the previously stated
pop trend, eventually tapering down near periods end as the front
finally looks to lift back to the north. Temperatures through the
short term period will start out below normal on Tuesday, however
warming back to around normal for Wednesday amidst southerly flow,
despite partly/mostly cloudy skies.
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 215 PM Sunday, A quasi-zonal flow regime at the start of the
period will evolve into a high-amplitude/non-progressive patter by
the end of the week, as upper level low pressure closes off across
the southwest Conus, and a ridge builds along the East Coast. As a
result of the evolving non-progressive pattern, a frontal zone will
remain more or less stationary from the Arklatx through the TN and
Ohio Valleys through the first half of the period, leaving our area
within a warm sector marked by relatively moist low levels. Lift
will be minimal within this warm sector, but southerly flow could
result in some mechanical left near the southern mountains, so token
low chance pops will be carried across western area through Fri
night. Temps will also be well above normal through this time,
albeit somewhat tempered by the potential for low clouds.
Over next weekend, the global models are in decent agreement in
building high pressure into the northeast Conus (although they
disagree widely on the strength of the high), allowing cold air
damming to evolve down the Eastern Seaboard. This is expected to
knock temps down closer to climo, while pops increase slightly owing
to increasing upglide over the developing wedge.
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
At KCLT and Elsewhere: No restrictions through the TAF period.
Strong high pressure centers over the area Mon and slowly shifts
east. This will keep winds light...veering through the afternoon.
KAVL will shift from down-valley to up-valley arnd 18z. Mainly
sct/bkn Ci fist half becoming few by afternoon. The mountain sites
will likely see some mlvl clouds btw 06z-13z as well.
Outlook: VFR conditions expected into Tuesday as high pressure
slowly moves off the Atl coast. A frontal system moves toward the
area Wednesday and into the area Thursday bringing the chance of
precipitation and associated restrictions.
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% High 100% High 100% High 100%
KHKY High 100% High 100% High 100% High 98%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% High 100% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
GA...Winter Weather Advisory until noon EST Monday for GAZ010-017.
NC...Winter Weather Advisory until noon EST Monday for NCZ033-
SC...Winter Weather Advisory until noon EST Monday for SCZ001>008.