Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/14/18
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
721 PM CST Sat Jan 13 2018
Issued at 719 PM CST SAT JAN 13 2018
Surface ridge in place over the forecast area keeping things
chilly this Saturday afternoon. This ridge will shift east with
time, which will get some southerly winds moving into the area
through the overnight period. This warm air advection should start
a moistening process that will get the atmosphere primed for some
light snow to form once a shortwave trough moves into the area
from the northern High Plains. In the mid levels northwest flow
continues to dominate the area, as it has most of this winter.
Radar echoes and IR imagery indicates an area of light snow over
western South Dakota and NW Nebraska. The mid level ascent
associated with this area of light snow will make its way into
northeast Kansas and west Central Missouri later tonight. Timing
of this wave is a bit in question still, with the NAM/GFS
indicating snow starting in the area after midnight, lasting
through mid morning Sunday. The HRRR has been fairly consistent
with bringing the wave and precipitation into the area a couple
hours earlier than the NAM. Will need to watch this carefully, but
the early indication of the HRRR might have some difficulties
considering the dry low levels that any snow will have to compete
with before saturation. Moisture will be limited and the duration
of lift will be rather short, relegated to around 3-5 hours,
therefore QPF for this Sunday morning system will be very light,
on the order of around .05" across the advisory area. Snow ratios
around 15 to 20:1 will yield amounts around an inch, with some
areas perhaps seeing 1-2 inches before the quick hitting system
moves out of the area by Sunday afternoon.
A second round of snow will move into the area Sunday night into
Monday morning. While this system isn`t expected to bring much in
the way of new snow, it may be a bit more widespread with
accumulations. In the mid levels another weak shortwave trough
will glide through the area from the north/northwest. A surface
and low level ridge will plow through the area, bringing stiff
northerly winds. Mid level frontogenesis will bring a second quick
hitting period of snow Sunday night into Monday morning. Once
again, considering the moisture limitations and short duration of
snow, only expecting around an inch to 2 inches with this round of
Monday morning snow. All told with these two systems we can
expect roughly 1 to 3 inches of snow across most of the area, with
the western half of the CWA seeing slightly more snow than the
eastern half. Winds remaining in the 10 to 20 mph range with very
cold air moving in behind the low level cold front will bring wind
chills down to around 15 to 25 below across far northern Missouri
and down to around 15 below along the I-70/MO River corridor
Monday night into Tuesday morning.
The middle part of next week looks to be dry as high pressure
settles into the low levels. This ridge will keep temperatures
cool for Tuesday and Wednesday. By Thursday mid level ridging
moves into the area, with some western low level troughing, which
will bring a warm up into the Thursday/Friday time period. Expect
Thursday to finally reach above freezing, with Friday being
perhaps 5 to 10 degrees above normal. A closed low in the mid
levels should veer south of the forecast area on Friday, but there
is a potential for some clouds and maybe a low chance for some
light rain across the far southern CWA as this system passes to
the south. A more significant system is possible toward next
weekend, as models continue to show a trough coming on shore and
eventually ejecting into the plains. Timing/location/intensity of
this trough is very much in the air, so will forego details this
far out, but it`s a system that bears some watching as we go
through next week.
.Aviation...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 513 PM CST SAT JAN 13 2018
The main impact through the forecast period will be in the form of
light snow during the overnight hours through early Sunday
morning. Initial overhead precip prior to 06Z should evaporate
given existing dry lower levels. This will eventually be overcome
with precip making its way to the surface shortly after 06Z,
while increasing in coverage near 09Z - 10Z. Ceiling heights will
degrade to MVFR during this time, with IFR visibilities also
possible Sunday morning. Conditions will gradually improve by the
late morning. A secondary round of snowfall is then possible
KS...Winter Weather Advisory from midnight tonight to noon CST Sunday
MO...Winter Weather Advisory from midnight tonight to noon CST Sunday
Area Forecast Discussion
National Weather Service Hastings NE
702 PM CST Sat Jan 13 2018
Issued at 654 PM CST Sat Jan 13 2018
Adjusted the snow totals ever so slightly mainly just sliding the
1-2" and 2" snow band about 10-15 miles southwest based on
current radar trends and the HRRR being slightly further
southwest. The most likely location for the slightly higher 2" or
just a little bit over 2" band by late tonight should run from
around Hastings and Grand Island to around Hebron.
UPDATE Issued at 537 PM CST Sat Jan 13 2018
Forecast seems reasonably on track for the snow this evening. Am
considering sliding the snowband slightly further southwest based
on the trends in the HRRR model and actual snow band location as
it`s beginning to form now over the sandhills. Any shifting of the
snow band further southwest would probably be rather minor at
only a 10 to 15 mile shift. Will continue to watch radar trends
and make possible adjustments to our snow forecast as we head
through the evening. Overall the 1-2 inches in the primary band
through the heart of our forecast area from northwest to southeast
looks good with some isolated 3 inch amounts possible. A south
wind at 5 to 15 mph averaging around 10 mph is light enough to not
have much of an impact.
.SHORT TERM...(This evening through Sunday)
Issued at 246 PM CST Sat Jan 13 2018
Forecast is still mainly on track with a few nudges made. I
increased POPS and snow amounts a bit as there seems to be
increasing agreement in short term models. We could even see a few
three inch reports, but this depends on where the mid-level jet
streak axis winds up being with the associated low-amplitude wave.
The bulk of any snow should be late evening and early overnight.
Lows tonight will be in the 11-14 range early and will rise
overnight as anticipated as a warm front approaches. Our quick
break from the cold still on track for Sunday with highs in the
mid 30s to lower 40s, but I went a bit more pessimistic for highs
and with with CONSshort.
.LONG TERM...(Sunday night through Saturday)
Issued at 246 PM CST Sat Jan 13 2018
Arctic air make another return with more snow possible with the
cold push, with possibly some brief sleet in transition from rain
to snow. Snow amounts do not look like a whole lot, but wind
chills could be pushing -30 Monday morning. Wind chills look like
they will be in the -15 to -20 range Tuesday morning. Another
modest warmup is on the way toward the end of the long term.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 537 PM CST Sat Jan 13 2018
The main concern will be the accumulating snow with most of it
falling this evening/tonight between 7pm and 2am. Visibility will
likely bounce around as the snow intensity varies but should
range from around 1/2 mile up to around 3SM through most of the
event. Ceilings will also fall with the snow into at least low end
MVFR and possibly into IFR range at times. Everything improves
as the snow ends and we near dawn.
Area Forecast Discussion
National Weather Service Paducah KY
730 PM CST Sat Jan 13 2018
Issued at 730 PM CST Sat Jan 13 2018
For now, am not planning on changing our low temperature forecast.
Some guidance, especially the RAP and CMC suggest below zero
numbers over snow cover. Tough call with dew points still 9 to 14
degrees many areas, coupled with 800mb moisture and associated
mid clouds moving ESE across the area. Best course of action is no
action at this point. We did have to raise hourly temps through
08z as we are not falling as fast as forecast. However should we
have a late night period of mostly clear, then we could achieve
our going lows.
UPDATE Issued at 521 PM CST Sat Jan 13 2018
.SHORT TERM...(Tonight through Monday night)
Issued at 253 PM CST Sat Jan 13 2018
First question is just how cold will we get tonight? Some
guidance has us mostly clear to partly cloudy, with others
bringing in more clouds, but with all showing light to calm winds.
Any areas with snow cover along with clear skies for any time
will see a big drop in temperatures. This makes tonight`s low
challenging. In areas with less snow cover and the better chance
of more clouds, basically west of the Mississippi River, went with
lows from 5 to 14 degrees. For the rest of our area, went with
lows from around zero to near 5 above zero.
On Sunday, a weak upper level trof may allow some light
snow/flurries to skirt the Ozark foothills of Missouri Sunday
morning, but the main effect will be increasing clouds from the
west. Approaching low pressure will shift our winds to the south
through the day Sunday. Temperatures will still only reach the
middle to upper 20s for highs, but the south winds Sunday night
will keep temperatures up, with lows in the lower 20s.
The approaching low will give our northern counties a chance of
light snow Sunday night, but the main show will be Monday into
Monday night. As the low slides to our north, the associated cold
front will spread light snow across our region from the northwest
through the day Monday. The best chances will be across southern
Illinois, southwest Indiana and northwest Kentucky Monday
afternoon, and across west Kentucky Monday evening. Any lingering
chances will be confined to our southeast counties late Monday
Overall, models show the front moving through fairly quickly,
which should help keep snow amounts less than yesterday`s event.
At this time, expected snowfall amounts are in the 1 to 2 inch
range across our northern half of counties, to a half an inch to
an inch in west Kentucky. Southern portions of southeast Missouri
may see only a few tenths. High temperatures Monday will be in the
30s, and our southern counties may see a rain/snow mix for a few
hours in the afternoon with temperatures above freezing, thus
lowering snow amounts.
Colder air will be quickly filtering in behind the front. Lows
Monday night will drop back into the single digits for most of
the region. Wind chills will be potentially dropping into the zero
to fifteen below zero range.
.LONG TERM...(Tuesday through Saturday)
Issued at 253 PM CST Sat Jan 13 2018
In the wake of a clipper system, skies are expected to clear
temporarily, but a scattered to broken stratocumulus deck will
probably reform by Tue afternoon mainly over the Evansville Tri-
State region. These clouds should linger through at least Wed
morning as a mid level trof axis moves into TN.
Another frigid airmass will sweep into the PAH forecast area behind
the front on northwesterly winds. By Wed afternoon, the center of
Arctic high pressure will be in our vicinity. As a result, with snow
on the ground, highs Tue and Wed will be in the teens and lower 20s,
with lows in the single digits to mid teens. The coldest morning
will be Wed, with negative single digit lows east of the MS River.
These numbers, which we are fairly confident about, are before wind
chill calculations are applied. An wind chill advisory should
eventually be issued for wind chills Tue and Wed morning ranging
from -15 northeast to -5 southwest.
Some moderation in temps/dewpoints should be seen by Thu afternoon,
as temps may rise above freezing over southeastern MO and parts of
western KY/southern IL under brief ridging or quasi-zonal flow
aloft. By then, southerly low level winds are forecast to start up
on the backside of the surface high.
The medium range models have understandably had a bit of difficulty
with the position/evolution/timing of a tight low pressure system
that may develop in the Gulf Coast region by late in the week.
However, this system may not affect us at all. Increased moisture
transport from the Gulf does look pretty likely by Sat ahead of a
large trof developing across the Rockies and central Plains. While
the warmup continues, there will be increased cloudiness and perhaps
some light rain showers on Day 7 (Sat, with a chance of a wintry mix
Issued at 521 PM CST Sat Jan 13 2018
VFR conditions tonight through Sunday. Occasional mid clouds are
forecast. Light north winds will gradually become south,
southeast tonight through Sunday.
Area Forecast Discussion
National Weather Service Raleigh NC
740 PM EST Sat Jan 13 2018
Chilly high pressure will build into the Carolinas through the rest
of the weekend. This high will retreat to our northeast Monday,
bringing more seasonable temperatures on Tuesday. A strong upper
level trough and associated cold front will cross the region Tuesday
night through Wednesday night.
.NEAR TERM /THROUGH TONIGHT/...
As of 740 PM Saturday...
Stratocumulus layer is thinning as it tries to spread south and west
concurrent with the dry surface ridge oozing down the Atlantic
seaboard. Have made some tweaks to current coverage and trend
towards clear by sunrise per forecast soundings off the HRRR and
RAP. Dew points are running a couple of degrees below forecast, so
some minor tweaks there. Otherwise...steady as she goes.
Previous Discussion: A complication has popped up for this evening`s
forecast. The surface trough is currently moving SE of the forecast
area, with periodically gusty NW winds and falling dewpoints in its
wake. Meanwhile, another low level boundary, evident on high-res
visible satellite imagery, extends from south central VA along the
Roanoke River basin southeastward to the central Outer Banks,
pushing toward the S and SW. Stratocu lingers both ahead of and
behind this feature, within a diffuse front and zone of weak low
level convergence evident at 900-850 mb, and we`re even seeing some
spotty light rain and drizzle at Ahoskie in the last hour. This
moisture is trapped beneath a growing subsidence inversion aloft and
near the top of a well-mixed surface-based layer, and with weak flow
through that layer, it`s lacking any opportunity to disperse
horizontally, too. The GFS has been consistently showing this deck
of clouds pushing SSW into central NC through this evening, and now
the recent HRRR runs depict it as well, even showing deep enough
moisture for a little precip at the ground over the NE Piedmont
around mid evening. And based on the HRRR forecast soundings, with
little to no ice in the cloud and with falling surface wet bulbs as
colder air rushes in, whatever falls may transition from patchy
drizzle to patchy freezing drizzle in some areas. In any case,
anything that might make it to the ground would be extremely light
and short-lived. Have added a brief period of patchy drizzle along
this feature from now through mid evening from the NE CWA
southwestward through the central Piedmont. Otherwise, expect partly
to mostly cloudy skies over the N and E CWA through evening,
trending toward gradual clearing overnight as drier air is entrained
in the low levels. Lows 20-26, with some teens likely in the
normally colder areas. -GIH
.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 240 PM Saturday...
The weakening mid level shear axis will be heading to our east Sun
morning, as the cold surface high noses in from the N. The column is
projected to be stable and quite dry, and expect plenty of sunshine
Sun. Taking the 925 mb parcel down to the surface dry adiabatically
yields highs of 33-41, very close to the earlier forecast and
statistical guidance. A slug of moisture aloft and weak mid level
DPVA arrives late Sun night from the SW, so expect a few high clouds
to streak into the area from the SW overnight. Lows 14-20. -GIH
.LONG TERM /MONDAY THROUGH SATURDAY/...
As of 230 PM Saturday...
A initially strongly positively-tilted, and similarly strongly
meridional trough aloft, will pivot across the MS Valley Mon-Tue,
then to the East Coast while assuming a neutral tilt, by Wed-Thu.
Forecast details in the Tuesday night to Wednesday period continue
to evolve with latest model guidance.
At the surface, increasingly modified Arctic high pressure will be
in the place from Atlantic Canada to the sern US early next week,
while an occluding clipper low will have migrated to the Great Lakes
through Tue. Along the trailing Arctic front, an initially flat,
triple point wave will meanwhile develop from the mid MS Valley to
the cntl Appalachians through Tue. A warm front preceding the triple
point is expected to cross cntl NC Mon night, but not manifest as a
noticeable increase in surface temperatures until diurnal heating on
Tue. The Arctic boundary is then forecast to collapse east of the
Appalachians and across cntl NC Tue night, with following Arctic
high pressure that will build into, and modify over, the sern US
through the end of the week.
Strong jet dynamics and deep layer frontogenesis accompanying the
upper jet/front and related low level frontal zone should be
sufficient to support at least a light precipitation event over cntl
NC Tue night-Wed. That precipitation would likely fall in the form
of light rain or rain mixed with snow early Tue night, since
temperatures will have warmed considerably, into the upr 40s to lwr
50s for most Tue afternoon; and the models are typically too quick
in surging cold air masses east of the cntl Appalachians of VA/NC.
However, partial thickness values and boundary layer temperatures
are both forecast to become supportive of a west to east changeover
to snow late Tue night into Wednesday. If the trough aloft is weaker
and more positively-tilted as it approaches NC, then a light rain,
to inconsequential snow event would result.
Temperatures are expected to otherwise turn colder by Wed, before
moderating to around or slightly above seasonal normals by the end
of the week.
.AVIATION /00z SUNDAY THROUGH FRIDAY/...
As of 620 PM Saturday...
24-Hour TAF Period: High confidence VFR conditions will persist
through the TAF period as high pressure builds into the area. Some
mid clouds around 5 KFT will pass over KRWI and possibly KFAY and
KRDU, otherwise some lingering high clouds are expected into
tonight. Some drizzle may occur with the mid-clouds, but conditions
should remain VFR. Northwesterly winds will remain in the 5-10 kt
range overnight, but will vary from northwesterly to north-
Looking ahead: Chilly high pressure will extend into the region
through Mon, with VFR conditions. Next chance for sub-VFR conditions
will arrive Tue into Wed as a potent upper level trough slowly
crosses the region. -GIH