Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/27/17
Area Forecast Discussion
National Weather Service State College PA
1012 PM EST Thu Jan 26 2017
Windy and seasonably cold weather with occasional lake effect
and orographically enhanced snow is in store right through the
end of what has been a very mild month.
.NEAR TERM /THROUGH FRIDAY/...
Colder NW flow is establishing behind a secondary cold front
that passed late this afternoon. This will set the stage for a
prolonged period of breezy NW flow and plentiful cloudiness for
much of western and central PA, along with a light to moderate
snow event for the western high terrain.
The current radar shows numerous snow showers moving into my
western higher elevation counties, then dissipating as they
down- slope into central areas. The HRRR shows these multiband
snow showers continuing non-stop throughout the night into
As a result, the long duration Winter weather Advisory for the
Laurels and Warren Co continues through 06Z Sat.
.SHORT TERM /FRIDAY NIGHT/...
Nearly constant stream of lake moisture and steady state cyclonic
flow will lead to occasional, but generally only light to
moderate snow for the Alleghenies/Laurels and Lake Effect Snow
The stronger orographic component orthogonal to and up the
steep slopes of the Laurels will generate a more-constant snow
than what might occur directly off LE. But most of the moisture
flowing into the Laurels will be off distant Lake Michigan.
The best dual lake effect (Huron and Erie) will occur across the
NW snowbelt, but even there the air/water temp difference is
not all that great. However, the combination of these two
components will be sufficient to generate numerous LES bands -
mainly short in length due to a good amount of speed shear in
the vertical. This fetch and overall synoptic set-up are
usually only problematic for NW Warren Co. As with storm totals
over the Laurels (that could reach 8-10" on the highest ridges
west of RT 219 by early Saturday, the 5-8" of expected snow
accumulation will fall over a long...36-hour period, but many of
those 12 hour periods inside the length of the advy have the
potential to get 2-3".
Even under such a persistent west-northwest flow pattern with
LES conditions, daytime temps will be near to a few deg F above
.LONG TERM /SATURDAY THROUGH THURSDAY/...
A long wave pattern of deep troughing in eastern Canada and good
flow into the Great Lakes and Mid-Atlantic from the Northwest
Territories will result in a mainly dry but lake-effect filled
time of seasonable (read: cold) temperatures.
A clipper system embedded in the cyclonic flow may expand snow
accumulation to the east of the Allegheny Mountains Sun-Mon. A
second clipper is forecast to take a similar path
midweek. Global model and ensemble consensus keeps a mean
trough in the Eastern U.S. next week which should favor
continuation of typical late January/early February cold. Within
this flow regime...no major synoptic scale winter storms are on
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
The strong westerly flow will keep gusty winds at most TAF sites
through the first half of the overnight period. The westerly
flow will keep upslope/orographic flow to enhance any low cloud
development, which will result in IFR cigs with light snow
showers through the NE for reduced vsbys as well. Further east
across the Susq Valley, a downsloping/strong westerly flow will
yield better flying conditions, with primarily VFR conditions
Itermittent IFR at BFD will continue overnight before
lifting/dissipating early Friday morning. IFR and JST will
continue as the westerly flow will keep moist low level flow
entrenched over the region through most of the day. There should
be some improvment of conditiosn to MVFR tomorrow afternoon and
Outlook... Fri-Mon...IFR to MVFR in snow showers BFD/JST. VFR-
ocnl MVFR east.
KCCX radar is back up...for now. Technicians will return Friday
to affect a more permanent repair.
KFIG surface observation will be offline for an extended period
of time due to failed power feed to the DCP.
Lake Effect Snow Advisory until 1 AM EST Saturday for PAZ004.
Winter Weather Advisory until 1 AM EST Saturday for PAZ024-033.
NEAR TERM...La Corte/Lambert
Area Forecast Discussion
National Weather Service Jacksonville FL
844 PM EST Thu Jan 26 2017
...Much Colder Tonight through Sat...
.UPDATE...Surface cold front continued to press south across
north-central Florida this evening trailed by a fading thin line
of post-frontal light showers/drizzle that was across the Ocala
National Forest and southern Flagler county this hour. Much cooler
and drier low level air air was funneling across the local forecast
area under NW flow up to about 900 mb with surface temperatures
falling into the 50s across much of the area. HRRR and NMM
guidance suggested another band of spotty showers developing
across the forecast area tonight under passing mid level energy
tracking over the area form the Gulf. At this time continued to
only indicate 10% chances of rainfall as low level airmass was
drying very quickly in the wake of the surface front with a low
level NW flow...but giving passing energy and mid level moisture
over the area tonight...there could be very light non-measurable
sprinkles at times overnight through sunrise. Passing mid and
high clouds will continue to stream over the area through the
night which in concert with dry low level air will prevent fog
formation. Low temperatures will fall into the low/mid 40s inland
to low/mid 50s coast.
.AVIATION...Prevailing VFR conditions. Breezy WNW winds will
develop Friday with gusts up to 15-20 kts at times.
.MARINE...WNW winds 15-20 kts expected over the outer waters
tonight where exercise caution headlines will continue.
Rip Currents: An extended period of offshore flow is expected
through early next week. A low risk of rip currents is expected.
.PRELIMINARY POINT TEMPS/POPS...
AMG 43 62 36 56 / 10 0 0 0
SSI 46 63 40 54 / 10 0 0 0
JAX 48 64 39 57 / 10 0 0 0
SGJ 50 64 39 59 / 10 0 0 0
GNV 49 63 37 59 / 10 0 0 0
OCF 51 63 39 60 / 20 0 0 0
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
932 PM CST Thu Jan 26 2017
Issued at 932 PM CST Thu Jan 26 2017
Going forecast still looks on track with low clouds staying in
over the region much of the night. Have gotten fewer reports of
flurries in the last hour. Did some minor tweaking to
temperatures based on trends.
.SHORT TERM... (Through Late Friday Afternoon)
Issued at 349 PM CST Thu Jan 26 2017
Scattered flurries will continue through the early evening, and some
locations could see a light dusting of snow.
An elongated trough axis stretched from Ontario to the SoCal coast
early this afternoon per water vapor imagery and RAP output. Several
embedded vorticity maxima were noted within the trough axis, which
will continue pivoting across the country tonight and tomorrow.
Clouds and occasional flurries will continue through tomorrow
afternoon until the trough axis has moved through the area, leaving
northwest flow aloft in its wake. West to northwest surface winds
will occasionally gust to around 20 kts on Friday due to diurnal
.LONG TERM... (Friday Night through Next Thursday)
Issued at 349 PM CST Thu Jan 26 2017
The synoptic pattern at the start of the long term period will
feature an amplifying trough across the east coast, which will place
the Midwest within active north/northwesterly flow through the
weekend. Some deamplification of the pattern will occur by the
beginning and middle of next week as a western ridge attempts to
nudge eastward into the Central Plains.
Friday night into Saturday will feature the first of two rather
potent PV anomalies diving southeast across the region. However,
despite the impressive cold pocket of air aloft and associated
height falls, this system will have very limited moisture to work
with. Forecast soundings depict a shallow near-surface moist layer,
but saturation only reaches up to around -6 or -7C. At these
temperatures, ice nuclei activation is unlikely, thus will continue
to leave flurries out of the forecast for now and just stick with a
mostly cloudy forecast an temperatures in the mid to upper 30s.
By Saturday night and especially into Sunday, moisture depth will
increase ahead of yet another strong PV anomaly diving southeast
through the northwesterly flow. The increasing moisture depth
coupled with the ascent from the strong shortwave will lead to a
better chance of flurries, and even a chance of some light snow
showers. By the afternoon, low-level lapse rates will steepen
significantly (especially across far eastern MO and western IL) to
perhaps produce some convective snow showers, which may be able to
spit out some brief/light accumulations. Have upped pops during
this timeframe given the latest trends in guidance.
By Monday through the middle of next week the flow should begin to
deamplify as the eastern trough lifts out and the persistent ridge
out west attempts to shift to the east/southeast into the southern
and central Plains. This should allow the main storm track to be
displaced generally to the north of the region, thus dry weather is
expected from Monday onward. Temperatures will moderate into the
40s Monday and Tuesday, but another surface cold front associated
with low pressure passing to our north will knock temperatures back
into the 30s/low 40s by Wednesday.
.AVIATION... (For the 00z TAFs through 00z Friday Evening)
Issued at 540 PM CST Thu Jan 26 2017
Light flurries will be possible this evening, and may reduce
visibilities within the VFR range temporarily. Otherwise...expect
mainly MVFR or low VFR ceilings through at least midday Friday
before ceilings improve and eventually scatter out by late in the
SPECIFICS FOR KSTL: Some light flurries will be possible this
evening, but expect VFR visibilities. Otherwise expect MVFR
ceiling through mid afternoon on Friday before they rise to VFR
and skies eventually scatter out by tomorrow evening.
Area Forecast Discussion
National Weather Service Pueblo CO
751 PM MST Thu Jan 26 2017
Issued at 749 PM MST Thu Jan 26 2017
SNOW SHOWERS HOLDING TOGETHER AND ACTUALLY INTENSIFYING OVER
PUEBLO COUNTY AT THIS HOUR. LOCAL ACCUMULATIONS UP TO AN INCH
POSSIBLE...MAKING ROADS SLICK. ACTIVITY SHOULD CONTINUE SOUTH
ALONG THE I-25 CORRIDOR...WITH TROUGH...NEXT FEW HOURS. POPS
HAVE BEEN INCREASED ACROSS THE PUEBLO COUNTY AREA TO LIKELY.
UPDATE Issued at 528 PM MST Thu Jan 26 2017
IN LIGHT OF ONGOING AND DEVELOPING SNOW SHOWERS DROPPING SOUTH
WITH UPPER DISTURBANCE...UPDATED GRIDS AND FORECAST WITH HRRR
VERSION OF THINGS FOR THIS EVENING. THE HRRR HAS SNOW SHOWERS
DROPPING SOUTH ALONG AND WEST OF THE I-25 CORRIDOR THROUGH THE
EVENING AS INSTABILITY ROLLS THROUGH WITH UPPER TROUGH PASSAGE.
ACCUMULATIONS SHOULD BE GENERALLY LIGHT...AN INCH OR LESS FOR THE
LOWER ELEVATIONS ALONG AND WEST OF I-25...AND GENERALLY 2 INCHES
OR LESS FOR THE HIGHER TERRAIN. COULD BE SOME LOCAL ACCUMULATIONS
UP TO 3 INCHES ALONG AND SOUTH OF THE WET MOUNTAINS THIS EVENING
AS A LITTLE BIT MORE INTENSE CONVECTION DEVELOPS DOWN THAT WAY.
.SHORT TERM...(This evening through Saturday Night) Issued at 321
PM MST Thu Jan 26 2017
Western portion of the deep Great Lakes/Ern Canada upper trough still
in place across Colorado today, with another round of flurries and
snow showers over mainly the mountains this afternoon. Have also seen
just enough weak s/se upslope to generate some flurries near the
Palmer Divide and east slopes of the Rampart Range/Pikes Peak,
with clouds slow to clear over El Paso county. For tonight, a few
mesoscale models suggest mountain flurries/light snow showers will
develop from Teller county southward into the Wets and Sangres this
evening, though any accumulations will be minor. Remaining
mountains will see some flurries as well, with perhaps a brief
flurry across nrn El Paso county until shortly after sunset.
Expect enough clearing overnight for min temps to fall to fairly
cold levels, with San Luis and upper Rio Grande Valleys well below
zero once again.
On Friday, upper trough drops south of the state, and with warming
temps aloft, snow showers should come to an end by early morning and
will keep the bulk of the day precip free across the entire area.
Max temps will begin a slow climb back toward seasonal values Fri
afternoon, though again most interior valleys will struggle to break
strong morning inversions and only reach the teens/20s at best.
On Saturday, nly flow aloft will actually bring in some warmer
air in the mid levels, with max temps back to well above freezing
across the plains and I-25 corridor, while mountains and valleys see
less dramatic warming with readings creeping up into the 20s at most
.LONG TERM...(Sunday through Thursday) Issued at 321 PM MST Thu
Jan 26 2017
Not much change the forecast thinking with better agreement
between the Ensembles, GFS and ECMWF. This leads to higher
forecast confidence through Wednesday before minor differences
arise on Thursday.
A highly amplified pattern, with a trough over the Ohio Valley,
and high pressure along the west coast, will shift east through
the extended period and become more zonal with time. Broad
northwest flow across the region Sunday into Monday will shift
east as the upper ridge moves over head Tuesday into Wednesday.
Dry and warm conditions are expected to prevail through Tuesday
with highs in the 50s, to perhaps a few low 60s Monday. A cold
front is forecast to back west across the Plains Tuesday night.
The GFS wants to develop light drizzle across the Plains behind
the front late Tuesday night into Wednesday morning, but there is
low confidence in this happening at this time. Temperatures on
Wednesday will be slightly cooler with lower 50s for highs. By
Thursday the upper level flow pattern becomes more zonal. The GFS
brings a decent shortwave trough across Colorado with a round of
mountain snow. The ECMWF has a much weaker disturbance that moves
across the area in the zonal flow, but no precipitation associated
with it. At this time based on the ensemble support, kept the
forecast dry on Thursday like the ECMWF. Mozley
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 321 PM MST Thu Jan 26 2017
At KALS...main concern is the potential for a brief period of
stratus and ground fog near the terminal 09z-16z. Given most model
guidance suggest drier air filtering into the valley overnight and
lack of any snow melt today, will hold off on any IFR conditions in
the TAF and just mention some sct lower clouds. VFR conditions then
likely from mid morning through the day Fri.
At KCOS...very weak s/se upslope has kept patchy MVFR cigs and
flurries going through much of the day near/just north of the
terminal, though most cigs have risen to VFR levels as of 22z. Will
keep a VCSH mention and VFR cigs in the TAF through about 04z,
though very brief MVFR conditions may be possible under any heavier
-shsn. Nly flow from late this evening and overnight should end the
threat of -shsn and help dissipate any residual cloud cover, with
VFR conditions from after 06z through the day on Fri.
At KPUB...VFR tonight and Fri with winds becoming light nly.
Over the mountains...areas of -shsn will occasionally obscure the
higher peaks into the evening, with some partial clearing overnight
as showers end. Expect mainly VFR on Fri as threat of -shsn
Area Forecast Discussion
National Weather Service Blacksburg VA
930 PM EST Thu Jan 26 2017
Our area will progressively trend cooler beginning tonight and
lasting into Monday. While dry conditions are expected for most
of the forecast area, periods of light accumulating snow
showers will develop at times in parts of southeast West
Virginia, far southwestern Virginia and into the North Carolina
high country through Monday. Temperatures look to be near to
below normal into early next week before moderating by mid next
.NEAR TERM /THROUGH FRIDAY/...
As of 920 PM EST Thursday...
Not much in the way of snow showers this evening with main vort
lobe tracking north of our CWA, but will see a better vort lobe
pass across from southern KY overnight, mainly between 10pm and
2am which should increase the coverage, mainly over the west.
Did not change much to accumulations but a half inch to an inch
is not out of the question by dawn in western Greenbrier county,
with a dusting south to the NC high country.
Previous discussion from early afternoon...
The central and southern Appalachians into the VA/NC Piedmont
continues in a post-frontal west- northwest flow this afternoon
in broad cyclonic mid-level flow aloft. Aided by low-level cold
advection, winds this afternoon have been breezy to gusty with
area Doppler radar wind profilers indicating west-northwest
winds of 40 kts through 5000 ft. Visible satellite reveals
expansive stratocumulus field to our northwest associated with
the cold pool of air aloft. While the forecast area is presently
dry, composite radar imagery indicates some light radar returns
northwest of Charleston, WV into the Ohio Valley.
For the rest of the afternoon: Best WNWly low-level jet should
be occurring within the next couple of hours per the 12z 4-km
NAM output. To this point, peak winds have only topped out in
the lower 40 mph range at sites such as Boone, Roanoke and Hot
Springs. Will let the Wind Advisory continue as scheduled
through 7 PM. By nightfall, diminishing low-level wind fields
and stabilizing low-level lapse rates with cooler temps should
reduce magnitude and frequency of gusts.
Advancing into tonight...focus then shifts to cooling
temperatures and the start of what projects to a long duration
light accumulating upslope snowfall for the favored upslope
areas in southeast West Virginia, the Mountain Empire/Grayson
Highlands and into the NC High Country (continuing at least
periodically into the weekend). Cooling thermal profiles aloft
and 2-m AGL temps should allow for a transition of light rain
over to snow showers. Focus for PoPs being across western
Greenbrier County southwestward into Mercer and Summers Counties
in West Virginia into narrow bands oriented parallel to the
low-level flow (per HRRR and 4-km NAM depictions in simulated
reflectivity progs). I kept PoPs in the slight to lower Chance
range in far southern Virginia, the Alleghany Highlands and into
the mountains of North Carolina. In these areas, there`s some
question how far south and east these precip bands actually make
it. The best chance for light accumulations is in the
southeastern West Virginia county, which through 12z Friday are
about a coating to an inch, ramping up to 1-2" in western
Greenbrier County. Snowfall amounts are lower than Winter Wx
Advisory thresholds, and the accumulation forecast is
complicated initially by likely mild pavement temperatures
(given several preceding days of above-normal temperatures) that
may keep accumulations limited to grassy surfaces until well
after dark. Elsewhere, clear skies and cooling temperatures
should allow for temps to fall to near freezing along/east of
the Blue Ridge, with mid/upper 20s west.
For Friday: Continued variable amounts of cloud cover, greatest
west in periods of light upslope flow snow. While light upslope
snows should continue in southeast West Virginia, the 12z GFS
and NAM show a vort max rippling through the broad cyclonic flow
in the morning hours that may help lead to a greater coverage of
snow showers in southwest Virginia and the NC mountains. So
while PoPs are high chance to low likely in most of southeast
West Virginia, I upped them in the morning hours in southwest
Virginia and northwestern North Carolina. There`s some question
if morning snows end in these areas by the afternoon as there`s
uncertainty if any additional vorts in the flow may lead to any
additional accumulations in Smyth, Grayson, Ashe and Watauga
Counties. Those vort energy details probably will be a common
question mark in this broad longwave troughiness that we look to
be stuck in. Additional light accumulations of a coating to 2
inches for the first half of Friday, greatest in western
Greenbrier County. Otherwise, it should feel the coolest it has
been in some time for our area as highs only top out near or a
few degrees above freezing west of the Blue Ridge into the North
Carolina high country, but greater moderation in the 40s along
and east of the Blue Ridge where less cloud cover is expected.
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
As of 317 PM EST Thursday...
During this portion of the forecast, the region will continue to be
under the influence of a broad upper level trough with periodic
embedded shortwave troughs rounding the base of the main trough. The
result will be a prevailing west to northwest flow across the
region. For southeast West Virginia south into the Northern
Mountains of North Carolina, this will mean a prolonged period of
upslope snow showers and abundant cloud cover. The snow will be
nearly continuous, but come in heavier spurts, coincident to the
passing of the shortwave troughs. The farther east one gets toward
the crest of the Blue Ridge, the less snow is expected, as well as
somewhat less cloud cover. East of the crest of the Blue Ridge, the
prevailing west to northwest flow will yield subsidence with limited
cloud cover, and milder conditions. The best opportunity for light
snow to progress east of the crest of the Blue Ridge will be late
Sunday afternoon into Sunday night when the most vigorous of the
shortwave troughs is projected to cross the region.
During the time period from tonight through Sunday night the region
between southeast West Virginia, south to near Marion and Richlands,
VA, and into the Northern Mountains of North Carolina an average of
two to four inches of snow is expected. Western sections of
Greenbrier County, WV will more likely receive an average of four to
seven inches of snow with some isolated eight inch amounts at the
highest elevations. At this point, no advisories are being issued
given the long duration it will take for this amount of snow to
accumulate, and most of the snow will come in distinct bursts. The
most likely time period where an advisory may be warranted would be
Sunday into perhaps Monday when the strongest of the shortwave
troughs passes across the area. At the current time, any
accumulating bursts of snow will be addressed within Special Weather
Temperatures during this portion of the forecast will be near, to
slightly below normal across the mountains and near, to slightly
above normal across the Piedmont.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 317 PM EST Thursday...
Monday morning, the influence of the passing vigorous shortwave
trough will still be felt across the region with additional light
measurable snow still probable across the preferred upslope regions
in the west.
Monday night through Wednesday, the area may see a small break in
the prevailing northwest flow during the Monday night into early
Tuesday time period. However, the overall general pattern of a broad
trough across the northeast U.S. will continue. Fewer embedded
shortwave troughs are progged to swing through the primary trough
and impact the western sections of the area. However, the overall
general northwest flow pattern will continue to allow for scattered
light snow showers across primarily parts of southeast West
Virginia. The best chance currently looks like Tuesday night into
Wednesday when the added energy of a shortwave trough is expected to
cross the region.
Wednesday night into Thursday may be the start of a pattern change.
Guidance suggests the broad trough in the northeast will be replace
by more of a zonal flow. The forecast for this time period offers no
Temperatures during this portion of the forecast are expected to be
near normal Monday and Tuesday, but then trend to about five to ten
degrees above normal Wednesday and Thursday.
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
As of 730 PM EST Thursday...
Higher confidence in conditions east of the Blue Ridge, lower
confidence to the west.
The Appalachians and central mid Atlantic region will remain
between large high pressure over the Rockies and large low
pressure north of the Canadian maritimes. This will keep TAF
sites in a brisk west/northwest flow of cold air over the
region, with upslope conditions west of the Blue Ridge and
downslope conditions to the east. As a result, KLYH, KDAN, and
KROA can generally expect VFR conditions with gusty winds
through Friday, while KBCB, KBLF, and KLWB will have bouts of
snow showers/flurries and MVFR/IFR visibilities and ceilings
with the gusty winds through the period. The mostly likely
timing for sub-VFR conditions in the west will be tonight
through Friday morning with some improvement expected heading
into Friday afternoon. Winds will also slacken a bit toward the
end of the TAF period.
Extended Aviation Discussion...
Cold west to northwest wind flow will persist into Sunday with
mountain snow showers likely for the weekend including sub- VFR
cigs/vsbys espcly across the southeast West VA locations. A
final weak disturbance could bring more in the way of widespread
mountain MVFR/IFR in low clouds and light snow Sunday night into
Monday morning. Should finally see improving conditions later
Monday with a gradual end of the upslope snow showers in the
west, as the persistent northwest flow weakens and turns more