Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/14/20
Area Forecast Discussion
National Weather Service La Crosse WI
556 PM CST Sun Dec 13 2020
.SHORT TERM...(This evening through Monday)
Issued at 251 PM CST Sun Dec 13 2020
Early afternoon analysis showed plenty of low clouds across the
region and upstream into northwest Minnesota with some shortwave
energy inching into western Minnesota. At the surface, a cold
front was seen stretching from southwest Ontario, through
northwest Minnesota and into the Dakotas. Radar/surface obs show
light snow falling along said front. In addition, good isentropic
ascent has led to another band of snow developing well ahead of
the front (over the eastern MN/northwest WI) and will continue
eastward into the forecast area. However, still a fair amount of
dry air to overcome over our forecast area, isentropic ascent is
is progged to weaken a bit, and frontogenesis looks to remain weak
as the snow enters the forecast area (mainly along and north of
Interstate 94). Still, RAP soundings at Medford, WI, do show a
fairly deep dendritic growth zone, along with a few hour period
this evening (roughly 00Z to 03Z) of deep enough saturation for
some light snow. At this point, accumulation of 1/2 inch or less
seems reasonable and HREF guidance supports that. With better
forcing and/or moisture, this could be a sneaky 1 to 2" event, but
given current model data, looking like it`ll remain lower than
that. Even so, looks like there could be enough snow to lead to
some slick spots.
Behind the front tonight, expect a period of gustier winds
(around 20 kts or so) out of the northwest, with drier air working
in and clouds scattering out. This should set the stage for a
mostly sunny, but cooler day on Monday, with high temperatures
generally in the 20s.
.LONG TERM...(Monday night through Sunday)
Issued at 251 PM CST Sun Dec 13 2020
Quiet weather and dry conditions are expected through the week.
Monday night into Tuesday, the upper-level flow begins to split as
a surface high-pressure system moves eastward towards the Great
Lakes Region. An upper-level low and associated mid-level short-
wave trough dips into the southern Great Plains. Cloud cover
increases throughout the day on Tuesday as the trough continues
progressing eastward through the region by mid-week. No
precipitation expected with its passing as plenty of dry air
remains above the surface to around the 850 mb layer in wake of
the departing surface high- pressure system.
Upper-level flow becomes southwesterly ahead of the next
approaching shortwave with chances for precipitation returning
Friday night into Saturday. NBM guidance was mostly dry with this
system. Decided to use a blended 50th percentile model guidance
for precipitation chances as confidence has been increasing that
there will be some precipitation this weekend. Ensemble model
guidance have continued to show precipitation this weekend across
the region. Although, chances are still relatively low as there
are some differences between deterministic models and ensemble
members with the exact placement and progression of this system.
Temperatures will be impacted by cloud cover and recent snowfall
accumulations in the southern portions of the region. Currently
anticipating Tuesday morning low temperatures to dip into the
single digits and teens then increasing into the 20s for the
afternoon. Otherwise through the rest of the week and into the
weekend, temperatures will be slightly above the seasonal average
with afternoon highs in the 30s with overnight lows in the teens
and 20s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 556 PM CST Sun Dec 13 2020
MVFR ceilings are expected tonight, with improvement to VFR possible
by Monday morning. A brief period of light snow might also impact
KLSE early this evening, with brief visibility reductions.
Radar shows a very narrow band of light snow/flurries moving
toward KLSE at the beginning of the TAF period. This may very
briefly impact visibility, but should not last very long. While
some guidance would suggest MVFR ceilings improve to VFR later
this evening, models have been tending to improve ceilings too
quickly lately and will go with the more pessimistic guidance for
the overnight, keeping MVFR in the TAFs. There is a gap in the
MVFR several counties to the west of KRST which may briefly bring
things back up to VFR, but more MVFR clouds are sinking southward
behind a cold front moving toward the area. Winds will become more
northwesterly tonight behind the front, with gusts near 20 kts
possible. Skies should clear out Monday morning as high pressure
works into the area, with northwest winds gradually decreasing.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...CA
LONG TERM...Peters
AVIATION...Lee
Area Forecast Discussion
National Weather Service Fort Worth TX
545 PM CST Sun Dec 13 2020
...New Short Term, Aviation...
.SHORT TERM... /NEW/
/Tonight through Monday Night/
Water vapor imagery and the latest RAP analysis indicates the core
of the mid level shortwave trough is tracking eastward just north
of I-20 this evening. Strong mid level forcing for ascent
associated with this feature and sufficient moisture where this
forcing is occurring is resulting in continued areas of rain along
with some rain/snow mix mainly north of I-20 from the Metroplex
northeastward. This will continue for another few hours before
pushing off to the east with the upper trough. No significant
accumulations are expected this evening.
Behind the front, gusty winds prevail across much of the region
and this will also continue at least through late evening before
higher pressure settles in and the gradient relaxes a bit. The
current wind advisory will remain unchanged and allowed to expire
at 9 pm.
Low clouds will clear out later tonight, and temperatures will
fall rapidly as clearing fills in from northwest to southeast.
Overnight lows are expected to fall into the low/mid 20s west and
northwest of the Metroplex by early Monday morning with temps near
freezing elsewhere. Strong north winds will diminish through the
overnight to less than 5 mph. High pressure will traverse the
region on Monday with winds becoming more southeasterly late in
the day ahead of the next system on Tuesday. It`ll be a chilly day
with highs in the upper 40s and lower 50s under abundant sunshine.
Dunn
&&
.LONG TERM... /Issued 314 PM CST Sun Dec 13 2020/
/Monday Night Onward/
Another chilly night is expected Monday night with lows dipping
into the upper 20s to mid 30s. Another cold front is expected to
cross our western border midday Tuesday. The front will slowly
sweep eastward across the area with the center of the surface low
passing directly over North Texas. As the low exits to the east
Tuesday night, wrap around moisture may be sufficient for a
rain/snow mix to occur near and along the Red River. Confidence in
wintry precipitation is considerably low at this time as moisture
will be quite shallow and temperature profiles may be slightly
too warm. However, the potential will continue to be monitored in
future updates.
Another cold night is expected Wednesday night with lows dropping
into the mid 20s to low 30s. Chilly conditions will continue into
Wednesday with highs only in the 40s to mid 50s. As southerly
flow is re-established early Thursday, temperatures will quickly
rebound into the 50s and low 60s late this week. Rain chances will
be on the rise for areas near and east of Highway 281 beginning
Friday evening as isentropic ascent increases ahead of our next
cold front. The front is expected to enter the area overnight
Friday night. Showers will continue throughout the day Saturday
for areas east of I-35 until dry air behind the front brings an
end to the rain from west to east. The only noticeable change
behind this front will be a couple of cooler mornings in the 30s
both Sunday and Monday. Otherwise, rain-free weather and above-
normal temperatures are expected as we head into next week.
Barnes
&&
.AVIATION... /NEW/
/00Z TAFs/
MVFR conditions prevail this evening at all sites with lingering
precipitation. This light rain will continue to move east over the
next few hours and we`ll hang on to a TEMPO for 5SM -RA through
2Z. Otherwise, low clouds will remain in place for much of the
overnight with clearing expected before sunrise. Gusty north winds
will diminish overnight and become southeasterly by late Tuesday.
VFR will prevail on Tuesday at all sites.
Dunn
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 30 50 35 52 34 / 20 0 0 10 5
Waco 32 51 35 56 32 / 0 0 0 5 0
Paris 29 48 31 44 32 / 70 0 0 10 20
Denton 24 50 31 51 33 / 20 0 0 10 5
McKinney 28 49 32 50 34 / 40 0 0 10 5
Dallas 31 51 37 52 33 / 20 0 0 10 5
Terrell 29 50 32 51 33 / 30 0 0 5 5
Corsicana 33 51 37 53 34 / 5 0 0 5 5
Temple 31 51 34 60 33 / 0 0 0 5 0
Mineral Wells 25 50 32 53 29 / 5 0 0 5 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 9 PM CST this evening for TXZ115>118-129>133-
141>145-156>160-174.
&&
$$
Area Forecast Discussion
National Weather Service Lincoln IL
829 PM CST Sun Dec 13 2020
.SYNOPSIS...
Issued at 220 PM CST Sun Dec 13 2020
While a storm system spreads rain and snow across the Ohio Valley
tonight, much of our area will remain mostly cloudy but dry. Skies
are expected to clear on Monday, as high pressure drifts into the
Great Lakes region. The next storm system will spread some light
snow across areas near and south of I-70 Tuesday night.
&&
.UPDATE...
Issued at 829 PM CST Sun Dec 13 2020
Overcast conditions will prevail for the next several hours before
clearing currently over central/western Iowa tries to work into
central Illinois late tonight. HRRR cloud forecast has been
varying run to run, so confidence in any one solution is low.
Based on latest satellite loops, it appears partial clearing could
arrive across the Illinois River Valley between 09z and 12z.
However as a storm system passes well south of Illinois, the
boundary layer flow will likely lead to a slowing trend. As a
result, think skies will remain mostly cloudy across the KILX CWA
through the night, followed by a gradual west to east clearing on
Monday. Low temperatures tonight will be in the middle to upper
20s.
&&
.SHORT TERM...(This evening through Monday)
ISSUED AT 220 PM CST Sun Dec 13 2020
Early afternoon water vapor imagery shows a well defined upper low
sliding along the Texas/Oklahoma border, with a separate shortwave
moving across Minnesota and western Ontario. While radar mosaics
show widespread echoes across southern Missouri and up the Ohio
River, surface observations indicate that much of the
precipitation is from south central Missouri and areas to the
south/southwest. Nearly all the model guidance is in agreement
that this should largely slide to our south, though a few
sprinkles or flurries can`t be ruled out in areas from Flora to
Lawrenceville.
Main challenge in this period will be with cloud cover. Plenty of
stratocumulus continues across the region, with earlier holes
filling in. There is also an expansion of the cloud shield across
Iowa, nearly to the Mississippi River now. 925 mb relative
humidity plot off the RAP, close to the level which would
correspond to the cloud heights, indicates these clouds should be
slower to clear out than earlier projections. Will go more
pessimistic with the sky cover tonight, keeping it mostly cloudy
in most areas. A little more uncertainty northwest of the Illinois
River, but will go partly cloudy there and monitor for updates
over the next few hours.
.LONG TERM...(Monday night through Sunday)
ISSUED AT 220 PM CST Sun Dec 13 2020
Upper level pattern will remain in a split flow through midweek,
with the trough currently off the Pacific Northwest coast our next
weather maker. Morning model guidance in decent agreement with the
trough deepening as it advances across Missouri Tuesday night.
Main surface low expected to track just southeast of Illinois,
with our area more on the fringes of the precipitation.
Initialized guidance from the NBM seemed too low with PoP`s
Tuesday night and Wednesday morning, so a forecast closer to a
blend of the GFS and the previous grids will be used. That
continues to concentrate light snow chances near and south of
I-70, with potential for some flurries as far northwest as a
Taylorville-Danville line. Some 20% PoP`s will linger into early
Wednesday morning east of I-57.
Upcoming weekend storm system continues to have some continuity
difficulties. GFS remains on the wetter side of the guidance, and
while last night`s European run was close to that, the morning run
significantly backs away from the PoP`s until the front has passed
east of Illinois. Consequently, no changes were made to the NBM
guidance, which has widespread slight chance PoP`s.
No significant cold surges are expected this week, with
temperatures moderating late week ahead of the developing storm
system.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 529 PM CST Sun Dec 13 2020
Low clouds blanket all of Illinois and much of Iowa/Missouri late
this afternoon. With light boundary layer from the northwest, it
appears clearing will be delayed until Monday morning at the
earliest. Based on satellite trends and latest HRRR forecast, have
carried MVFR ceilings at all terminals through the entire night.
Have scattered the overcast at KPIA by 15z...then further east to
KCMI by around 18z. Winds will initially be NW at 5-10kt tonight,
then will increase to 10-15kt on Monday.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Barnes
SYNOPSIS...Geelhart
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Barnes
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
937 PM EST Sun Dec 13 2020
.UPDATE...
Issued at 936 PM EST SUN DEC 13 2020
At 230z, an ~1008mb surface low was located near Jackson,
Mississippi with a broad area of rain across much of the Lower
Mississippi Valley and spreading across the Lower Ohio and
Tennessee valleys. Some snow is also noted over the Ozarks along
the NW periphery of the system. Across eastern Kentucky,
reflectivity echoes continue to spread ENE in across the forecast
area from central Kentucky. However, most of this precipitation is
evaporating as it falls into a very dry layer of air between 850
and 700mb, as per RAP, HRRR, and 00z BNA soundings.
As the better mid-level frontogenesis and ascent, evidenced by a
stronger band of reflectivity from south central Kentucky to
northeast Arkansas, pushes eastward, the dry layer should rapidly
saturate and cool to its wet-bulb temperature. For areas closer
to central KY light showers and sprinkles will develop over the
next couple of hours, but should hold off until 6 to 7z across the
far east.
Recent T, Td trends suggest that the dry layer is located just
above Black Mountain. Therefore, expect a rapid temperature drop
to near freezing via wet-bulb cooling aloft and a shallow layer of
dynamic cooling near the mountain top there soon after the onset
of precipitation. This will lead to a quick transition from rain
over to snow atop Black Mountain. Thereafter, soundings indicate
that the dynamic cooling will initially cause a fairly quick
lowering of the snow level to between 2,000 and 3,000 feet.
Current expectations are for up to 1-4 inches of snow between
2,000 and 4,000 feet. Given this potential, a Winter Weather
Advisory has been issued for elevations above 2,000 feet in Bell,
Harlan, Letcher, and Pike counties. Some minor accumulations are
also possible across the highest elevations in adjacent counties.
At elevations below 2,000 feet, the 2-3k foot layer of above
freezing dew points will take longer to overcome by latent heat
and melting. However, with that being said, the HRRR and other
CAMS do suggest the potential for banding and localized QPF rates
of 0.3+ inches. If precipitation rates of this intensity
materialize, it is possible for the dynamic cooling processes to
prevail, causing the rain to change over to moderate snow,
especially toward sunrise as the above freezing near-surface
air layer becomes shallower. Any heavier banding that occurs
early Monday morning could lay down a quick slushy coating to
inch, especially over the ridges.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 424 PM EST SUN DEC 13 2020
A mid/upper level low currently over the OK/TX border will weaken
and get absorbed by the prevailing flow as it moves east across
the TN valley tonight and early Monday. It is prompting surface
low development near the east TX coast this afternoon. As the
upper level support tracks east, so will the surface low, reaching
the Carolinas Monday morning. The model consensus is for a cold
stratiform rain to overspread the JKL forecast area on the north
side of the system tonight. As temperatures cool, it will mix snow
late tonight and Monday morning, first at higher elevations.
Temperatures are expected to bottom out near or just below
freezing at the highest elevations near the VA border on Monday
morning. With temperatures marginally cold enough for
accumulations at the highest elevations toward the end of the
event, a small change up or down could make a substantial
difference for amounts. Based on blended models, the best estimate
is for an inch or two above about 2500 feet.
The system pulls out to the east during the day Monday. Much drier
air tries to advect in behind the system, but will be battling
cold air advection and upslope flow. The best shot at seeing sun
will be in our western counties, with clouds remaining more
prominent near the VA border, but confidence in the sky forecast
is not high. As the frontal inversion behind the system lowers on
Monday night, the coverage of low clouds will continue to shrink,
but high clouds may offset this somewhat overnight.
.LONG TERM...(Tuesday through Sunday)
Issued at 405 PM EST SUN DEC 13 2020
Quite a complicated forecast, if only for a short period of time.
Tuesday will start off dry with strong high pressure located to our
north taking hold of the region as it progresses eastward.
Meanwhile, a strong upper level shortwave will be deepening across
the Southern Plains, proving strong SW flow aloft. The result will
be cool northerly flow at the surface vs. stronger and warmer SWrly
flow in the mid and upper levels...keeping temperatures in the upper
30s to low 40 degree range.
As we head into the overnight, this is where things start to get
very tricky very fast. The shortwave and a surface low pressure
system are expected to push eastward quickly. Precip will accompany,
but will have a lot of dry air to overcome. However, as the center
of the low pressure system passes just to our SE, this should be
enough to saturate, and allow precip to begin falling in the JKL by
around 6Z, quickly increasing in coverage and strength as we head
into the morning hours. Between 6 and 12Z, JKL will be located on
the NW of the surface low as it passes by, according to all the
models, which is generally the coldest sector. Meanwhile, the upper
level shortwave will be to our west, across the Mississippi River
Valley during this time, with strengthening S to SW flow across the
region, result in WAA. The fact that the system is moving in during
the colder overnight also complicates things.
It seems as though there has been a trend in the models to increase
a degree or few based on previous runs, likely given the strong
southerly flow in the mid and upper levels. However, the NBM samples
from some of the older models, and is also incorporating some lower
values such as the Canadian and previous ECMWF. With that in mind,
my personal opinion is that the NBM lows are perhaps a degree or two
too low...however after chatting with neighboring offices, there was
no desire to increase the temps at this point, and so the NBM will
stand for now. This will put lows in the upper 20s across much of
eastern Kentucky. So as the precip moves in, and temperatures drop
to the upper 20s at the surface, but warmer air above freezing
exists aloft, this creates a set up that could lead to some mixed
precip and more so...freezing rain. As was noted before, the NBM
temps do seem a bit too low, so if this is true, the amount of
freezing rain could be overdone a bit. However, if the temps do hold
true...which granted we are still period 5 for this event...freezing
rain is a definite possibility. Will continue to monitor this next
system closely as things continue to evolve.
Precip will change back to rain on Wednesday as temperatures warm
back to just above freezing. The only exception will be the high
terrain, which may struggle to increase throughout the day as the
upper level shortwave passes over, and we start to cool aloft. The
question, however, is will the highest mountains remain in freezing
rain, or transition to rain/snow or snow. This much is still up in
the air.
The system should exit almost as quickly as it arrived, with all
precip out of the region by Wednesday evening. Strong high pressure
will then take hold from the SW this time, centering across the
state by Thursday evening. Meanwhile, there will be an upper level
shortwave moving across the state as well. The GFS and, to some
degree, the ECMWF, show some isolated to scattered light pops across
the far eastern CWA...but these did not translate to the NBM, and
given the amount of dry air in place, did not change the NBM to
account for any pops at this time. By Thursday night, with the high
pressure system directly overhead, and the backside of the shortwave
passing through (NW flow), expect temperatures to drop quite
substantially overnight. Lows are forecast in the low 20s.
Temperatures are then expected to start a warming trend heading into
the weekend as upper level ridging takes hold, followed by SW flow
ahead of the next shortwave that will approach and pass over
Saturday.
There remains considerably good agreement in the models with this
shortwave, even this far in the extended, as it passes across the
Ohio Valley and points to our south Saturday and the first part of
the day Sunday. Both the GFS and ECMWF show widespread precip moving
through during this time, which is starting to be reflected in the
NBM with chance to likely pops. Expect these will continue to
increase over the coming runs. High temperatures for Saturday will
be in the upper 40s to around 50 head of this next system, dropping
a few degrees for Sunday as it passes over.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 700 PM EST SUN DEC 13 2020
Conditions at TAF issuance were mainly VFR, except near and north
of I-64 where some high-end MVFR was noted at SYM and IOB. Some
virga will be possible north of the Hal Rogers Parkway this
evening before a steady rain develops between 3-6z. After the rain
begins, visibilities and ceilings will quickly drop to IFR or
potentially lower through the rest of the night. The rain is
expected to mix with or change to snow toward sunrise over
southeastern Kentucky and the higher elevations before tapering
off Monday morning. Gradual improvement to MVFR is expected during
Monday afternoon.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 AM to 10 AM EST Monday for KYZ087-
088-118-120.
&&
$$
UPDATE...GEERTSON
SHORT TERM...HAL
LONG TERM...JMW
AVIATION...GEERTSON/HAL
Area Forecast Discussion
National Weather Service Memphis TN
908 PM CST Sun Dec 13 2020
.UPDATE...
Rain associated with a deepening low pressure system continues to
fall over the Mid-South at this time. This will begin to change
shortly. Snow should begin to mix in with the rain over Northeast
Arkansas as Walnut Ridge just reported snow. Also, just saw a
report of rain changing to snow in Piggott, AR. The latest HRRR
shows all snow at Jonesboro by 11 PM CST and possibly at Memphis
by 1 AM CST. Still expecting little to no accumulations as ground
temperatures remain warm. Current forecast is on track. Will only
update to remove evening wording.
KRM
&&
.DISCUSSION... /issued 355 PM CST Sun Dec 13 2020/
Radar shows rain increasing across the area. Surface analysis
charts show a low pressure center located over souther TX/souther
LA with the warm front stretching into central AL. Temperatures
are in the low 40s to low 50s across the Mid-South. Clouds are
increasing across the region with mostly cloudy skies over the
Mid-South.
Rain coverage will continue to increase across the County Warning
Area this evening and into the overnight hours as the upper-level
trough moves through southern AR and central TN overnight.
Temperatures will drop overnight which means snow mixed with rain
will be possible after midnight - mainly over areas north of I-40.
The best chance for snow will be over northeast AR, the MO
Bootheel, and northwest TN. At this time, the only accumulations
expected would be on grassy surfaces as well as bridges/overpasses
as ground temps are still well above freezing. If we can get heavy
enough snow and enough evaporational cooling, we could see light
accumulations over the northwestern counties of the CWA.
Temperatures will drop down into the 30s overnight.
High pressure will move in to start off the workweek. We`ll stay
dry and cold through Tuesday. Temperatures will remain below
normal with highs reaching the 40s and lows dipping down into the
20s.
Another trough will dig down from the northwest and bring another
shot of cold air Tuesday night. This system is a tricky forecast
due to model inconsistencies and uncertainties of where the dry
air will set up. This system certainly has a bust potential. At
this time, the trough is expected to track through KY with most of
the moisture developing south of I-40 and north of I-22. Once
again, rain mixed with rain will be possible but over a larger
portion of the Mid-South as the 540 line reaches northern MS.
Temperatures will remain in the 40s and 50s for highs with lows in
the 20s and 30s. Dry weather will move in behind the system.
KRF
&&
.AVIATION...
Conds are lowering across the Mid-South as rain moves into the
region. Expect cigs to lower to IFR across the Mid-South with
MVFR ocnl IFR vsbys in moderate to heavy rain. Winds will be
increasing out of the NNE and becoming gusty at times. Expect some
mixing with snow across the northern part of the area overnight and
perhaps a brief change to all snow at KJBR before ending. Warm
ground and surface temps remaining above freezing = little to no
impacts. There is some uncertainty with regard to clouds clearing
out Monday morning. The majority of the guidance is quick to clear
but will hold on to a MVFR deck for a few extra hours given the
NAM soundings and HRRR.
SJM
&&
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
619 PM CST Sun Dec 13 2020
.SHORT TERM...(This evening through Monday night)
Issued at 257 PM CST Sun Dec 13 2020
A few respectable bands of snow showers are continuing eastward across
the Upper Mississippi Valley this afternoon ahead of a cold front
pushing through western Minnesota. Accumulations have been minor
overall, but a few reports of over an inch have been received near
Milaca and Mora where the snow has been most persistent. The cold
front will progress across the remainder of the area by early this
evening with gusty northwest winds and strong CAA developing behind
it. Much drier air will scour out the cloud cover late this evening,
setting up a clear overnight and Monday morning. Lows tonight will
reach the single digits across central and western Minnesota, with
low teens across southern Minnesota and western WI. Thermal troughing
overhead Monday will make it difficult to reach 20 for a high.
Increasing clouds and light return flow will keep temps steady or
allow them to rise slowly Monday night in most areas. The exception
may be across central Minnesota and western WI where calm winds and
clear skies will persist well into Monday evening. Here, temperatures
may drop lower than currently forecast, but it will depend on the
timing of the high and mid level clouds.
.LONG TERM...(Tuesday through Sunday)
Issued at 257 PM CST Sun Dec 13 2020
Thicknesses and heights will increase into late week with pesky,
weak disturbances remaining confined to Canada or the far northern
CONUS. A trough over the west midweek should eject into the Plains
and Midwest Friday and Friday night. This feature appears to shear
out as it does so, but it could bring a little light rain or snow
(less than a tenth of QPF), much like the system currently impacting
the area. Not really impressive at all. Highs ahead of the front
could reach 40 Friday.
A brief cool down would then follow Saturday before thicknesses rise
again into early next week. Could see low 40s again Sunday. ECMWF
even has 50s by Monday. Too early to say what could transpire closer
to Christmas, but deterministic models are adverting some sort of
system in the center of the CONUS on the 23rd and 24th. Ensemble QPF
spread increases during this time with some members showing a more
active period finally developing. Ensembles have been showing that
for the past several weeks now, only to see the spread shrink back
down to zero by day 7 or 8 though. It does look rather likely,
however, that no arctic airmasses are in store through at least the
rest of the month. It`s very hard to get a prolonged period of below
normal temperatures in winter without a stout snowpack. Snowpack is
so common this time of year that its influence is significant in
climatological temperature normals.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 619 PM CST Sun Dec 13 2020
Snow band that moved through earlier will clear EAU by 2z. That won`t
be the end for snow though. Right behind the front we`ve seen sites
get about an hour of light snow, while in central MN, the cloud deck
is completely within the dendritic snow growth zone, so we continue
to see snow easily get generated across central into northern MN.
Biggest change with this TAF package was to delay the clearing by
several hours at all terminals based on moisture we see through the
night pretty much at all terminals in forecast soundings. In central
MN, these clouds will likely be MVFR, but expect this stratus to move
up to around 4k feet through the night everywhere else before
clearing out. High pressure moves in on Monday, resulting in mainly
clear skies and wind speeds that will be diminishing during the day.
KMSP...Cold front is just now moving through MSP. Radar and upstream
obs show we`ll have a brief period of flurries/light snow right
behind the front, but no significant vis restrictions are expected.
NAM shows clouds clearing MSP around 7z and the RAP not until around
12z. With some back filling of clouds noted along the MN/SD border,
pushed out the clearing to 10z, though do expect heights to be VFR
much of the night.
/OUTLOOK FOR KMSP/
Tue...VFR. Winds SSE 5-10kts.
Wed...VFR. Winds S 5-10 kts.
Thu...VFR. Winds S 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
SHORT TERM...Borghoff
LONG TERM...Borghoff
AVIATION...MPG
Area Forecast Discussion
National Weather Service Paducah KY
711 PM CST Sun Dec 13 2020
.UPDATE...
Issued at 711 PM CST Sun Dec 13 2020
Updated aviation discussion.
&&
.SHORT TERM...(Tonight through Tuesday)
Issued at 216 PM CST Sun Dec 13 2020
Precip has been expanding rapidly northeast across the Ozarks
today, mostly in the form of snow in Missouri and the higher
elevations of north Arkansas. In the near term, hrrr and other
high res guidance blossoms precip across se Missouri and the lower
Ohio Valley by 00z. This precip correlates well with strong mid
level frontogenetic forcing on the northeast side of an
approaching mid level low.
The high res models indicate a band of moderate precip will focus
from the Ozark foothills east-northeast into the lower Ohio Valley
by 00z. This band will sink southeastward across western Kentucky
tonight. The freezing level is forecast to remain just a little
too high for appreciable snow, ranging from 1500 to 2000 ft at
kpah this evening. The exception is in the Ozark foothills, where
the higher elevations will likely have some minor impacts from
snow this evening.
Brief periods of wet snow or a snow/rain mix are possible anywhere
in the forecast area tonight. The highest chances of snow will be
associated with bands of heavier precip and associated dragging
down of colder air. However, any impacts are likely to be
restricted to the Ozark foothills region, where an advisory
remains in effect. Ground temps are still quite warm, and surface
temps will also be above freezing until after the precip ends.
Where and when snow occurs, model soundings indicate large wet
snowflakes. A rather deep and saturated dendritic growth zone,
combined with a near-freezing isothermal layer in the low levels,
should result in ideal conditions for large flakes. The high
reflectivity values on radar to our west are indications of these
large wet targets.
Clearing skies will occur late tonight and Monday morning as the
system pulls away to our northeast and weakens. North winds around
10 knots will keep temps from climbing out of the lower 40s in
most areas Monday. Overnight lows will be in the 20s Monday night
as winds slacken and skies become partly cloudy. Clouds will
increase Tuesday ahead of the next system.
.LONG TERM...(Tuesday night through Sunday)
Issued at 216 PM CST Sun Dec 13 2020
Forecast confidence is moderate through the period, as the medium
range guidance is in good agreement in the larger-scale details.
However, there is some spread in the finer details of precipitation
amounts and type especially Tuesday night into Wednesday and again
Saturday.
The 12Z guidance in general has trended farther north with the
surface trough/low early Wednesday, and that has pushed the surface
freezing line farther north and west. As for QPF the models have
trended almost completely dry for Tuesday evening. The focus for 06Z-
15Z Wednesday is over the eastern half of the region with the
greatest QPF over the Tri State and Pennyrile.
Although the model soundings are warming in the low-levels, there
still is no significant warm layer off the surface, so a good bit of
the precipitation will fall as snow, with the exception of the
southern Pennyrile where it may be all rain. The impact, if any,
will be determined by the surface temperatures. The GFS and ECMWF
ensembles continue to lower the probability of sub-freezing surface
air over the Tri State with the 50% threshold being near I-64.
Figure that any potential for travel impacts early Wednesday will be
along and north of I-64 in southwest Indiana and then on the back
edge of the precipitation shield over southeast Illinois. We still
have up to near an inch of snowfall in the grids, but the current
expectation is that the surface will be warm enough in most places
to limit any accumulations to grassy areas.
We will remain dry and cool Wednesday afternoon through Thursday,
but then short wave ridging aloft will push the surface high east of
the area and allow south winds to develop Thursday night into
Friday. Forecast confidence dwindles as we head into next weekend,
as there is considerable variation in the timing of our next storm
system. There will be southerly low-level flow ahead of it, and no
fresh cold air coming into the back side of the system, so wintry
impacts are not expected. There is no instability in the GFS, so
thunder is not a concern either. We will have PoPs spread out from
late Saturday through Sunday due to the spread in the model timing,
but in reality it will likely be a 12 to 18 hour event.
&&
.AVIATION...
Issued at 711 PM Sun Dec 13 2020
A low pressure system will pass well to our south tonight. Its
associated widespread precipitation will be spread across mainly
western KY and parts of se Missouri until not long after midnight.
IFR conditions are expected in the precip, mainly from 00z to 08z.
Farther north around KMVN, little if any precip is expected, so
there is no mention of IFR conditions there.
In the wake of the system, clearing skies are expected between 09z
and 12z at most locations. Light north winds will increase to around
10 knots late tonight.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...Winter Weather Advisory until midnight CST tonight for MOZ100-
107-108.
IN...None.
KY...None.
&&
$$
SHORT TERM...MY
LONG TERM...DRS
AVIATION...MY/DB
Area Forecast Discussion
National Weather Service Pendleton OR
230 PM PST Sun Dec 13 2020
.Updated Aviation Discussion.
.SHORT TERM...The main sensible weather concerns begin with the
current winter weather event with advisories in the eastern
Cascades, southern Blues, and the Grande Ronde Valley with a
winter storm warning in effect for the Northwest Blues and
Northern Blues of OR. Otherwise, next round of winter weather is
expected Tuesday-Tuesday night with generally light snowfall in
the mountains. Wintry mix to light snow possible Tuesday morning
elsewhere with rain then more so possible in the afternoon. Light
breezes will also be possible in the foothills and northeast OR
Tuesday afternoon-Tuesday night as well. Latest water vapor
imagery shows a upper trough extending across the eastern North
Pacific southeast into the Pacific Northwest and offshore with the
main shortwave trough approaching the northern CA coast. Recent
radar display shows precip mainly confined to the foothills of the
Blues and the Blues with a few spotty showers in parts of the
Basin. Snowfall rates generally look to be light though there has
been some instances with visibilities down to a half mile to a
mile suggesting 1 to 0.25 per hr rates at times, though not
for a longer duration or frequent in nature.
The aforementioned upper trough will weaken as the primary
shortwave moves onto northern CA and dives southward over the
Central Great Basin overnight. Current thinking is we will
continue to see snow at times in the eastern Cascades and parts of
the Blues tonight with upslope enhancement favoring the northern
Blues. While we may see some spotty precip (mix or snow) at times in
the OR Basin and foothills tonight, precip chances there and
south central WA will be low. Most recent HREF and recent runs of
the HRRR continue to depict occasional to periods of snow in the
Blues put coverage looks limited elsewhere by and large. Shortwave
ridge builds upstream Monday and moves into the region late. This
should provide fair conditions by and large tomorrow through
tomorrow night ahead of the next system. Of which, ensembles and
deterministic guidance in good agreement with a upper closed low
developing late Monday-Monday night offshore British Columbia and
its warm front moving onto the OR coast Tuesday morning. Decent
moisture with this system with precipitable waters increasing
125-150% of normal Tuesday and modest transport seen via IVT
directed eastward into the region. Moderate-high confidence in the
placement and location of IVT given closeness of the GEFS and
GFS thus moisture should be sufficient for some wintry conditions
in the higher terrain. Greatest snowfall amounts look to be seen
4,000 ft and higher with amounts peaking 2-4 in the northern
Blues of OR into WA. Elsewhere, 2-6 are forecast in parts of
the WA/OR Cascades generally above 3,000 ft with increasing snow
levels then late Tuesday.
.LONG TERM...WEDNESDAY THROUGH SUNDAY...The extended period will
be rather active, as several systems are expected to drive
through the PacNW. A transient upper level ridge will be departing
our area through Wednesday morning, opening the door to an
incoming system that will be increasing rain and snow chances
through the afternoon and evening hours on Wednesday. Expect light
valley rain and mountain snow to occur with the passing of this
system, producing the majority of the associated precip Wednesday
evening through Thursday morning. Areas of higher elevations will
continue to see light snow through much of the day on Thursday,
while lower elevation rain should taper off by Thursday morning.
Models are still in disagreement with timing and intensity, but
they are slowly coming to a compromise. The ECMWF is still the
wetter and slightly earlier product by about 3 hours, which is
down from 6 hours from yesterday`s model comparison. The GFS is
much drier because it holds onto a relatively strong high pressure
center over western Colorado which helps to break up the incoming
system, where the ECMWF slides the high more east and south,
delaying its influence until the system begins to reach Idaho.
Forecast is leaning toward the ECMWF with snow levels between
3000-4500 feet, snow amounts of 1-5 inches, and valley rain
amounts hovering around 0.1-0.2 inches.
Another transient upper level ridge and associated surface high will
move onshore Thursday night. This ridge will continue to move
quickly east through our area overnight before driving into southern
Idaho and northern Utah by Friday evening, which should coincide
with another approaching system from the NW. The initial wave of
this system will be rather weak, and should bring rain and snow
showers to the Cascades and west of the Cascade crest Saturday
morning. Models are also having a tough time with this system as
well, as the GFS pushes moisture over and into the Basin, but the
ECMWF keeps it confined along the Cascades. The initial wave will be
reinforced by the main trough late Saturday into Sunday, which looks
rather robust. At this time, snow levels should be high enough to
warrant rain showers across the area, with the exception of mountain
snow above 4000 feet. This system will be a slow mover, keeping
mountain snow and low elevation rain in the forecast into the
beginning of the workweek. Snow levels will initially be between
3000-4500 feet, but are expected to increase along with the frontal
passage to 5000-6500 feet. Guidance on rain/snow amounts are
currently quite erratic, but the hypothesized results could be
double what we experienced earlier in the week due to this
lingering, slow moving system. 75
&&
.AVIATION...00Z TAFS...Variable conditions currently across all
sites, with LIFR for PDT/ALW, MVFR at DLS/YKM, and VFR for
RDM/BDN/PSC. Conditions will continue to degrade to LIFR/IFR for all
sites except for RDM/BDN, which should bottom out in MVFR after 03Z.
LIFR expected to continue for PDT/ALW until 18Z due to the low cigs
and vsby associated with the frontal passage and developing fog
overnight into tomorrow morning. PSC also will be wondering into
LIFR land near 10Z as cigs drop and haze develops into the morning
hours. 75
&&
.PRELIMINARY POINT TEMPS/POPS...
PDT 29 41 28 43 / 40 10 0 50
ALW 30 40 31 43 / 50 10 0 60
PSC 30 38 31 43 / 20 10 0 20
YKM 25 39 26 39 / 10 0 0 30
HRI 30 42 29 43 / 20 10 0 30
ELN 25 38 26 37 / 10 0 0 50
RDM 26 44 26 46 / 30 0 0 30
LGD 28 40 24 36 / 60 20 0 70
GCD 29 40 25 39 / 60 20 0 60
DLS 34 45 33 43 / 30 10 0 50
&&
.PDT WATCHES/WARNINGS/ADVISORIES...
OR...Winter Weather Advisory until 4 AM PST Monday for ORZ049-503-509.
Winter Storm Warning until 4 AM PST Monday for ORZ502.
WA...Winter Weather Advisory until 4 AM PST Monday for WAZ520.
Winter Storm Warning until 4 AM PST Monday for WAZ030.
&&
$$
SHORT TERM...80
LONG TERM....75
AVIATION...75
UPDATE...
FIRE WEATHER...
Area Forecast Discussion
National Weather Service Springfield MO
455 PM CST Sun Dec 13 2020
.SHORT TERM...(This evening through Monday)
Issued at 221 PM CST Sun Dec 13 2020
Near term forecast: Snow over far se KS and southern MO will end
later this afternoon and this evening. We have had some reports
of road impacts right along the nw AR/southwest MO border region
where a few inches have fallen so far. No plans to make big
changes to the advisory, but may knock out a few counties over the
northern and western part where warm temperatures have limited
accumulation. KSGF airport area has seen snow for a couple of
hours with no accumulation. Will have to watch trends in our
eastern counties going into the evening hours with temperatures
dropping a degree or two.
Overnight into Monday: HRRR and some other guidance is slower to
clear shallow stratus out tonight, and hedged a little bit that
way with the forecast, a bit warmer and cloudy/mostly cloudy. Moist
layer looks too shallow for much drizzle, but will need to watch.
We should clear out any stratus very early Monday leaving a sunny
sky and light winds with a sfc ridge moving through.
.LONG TERM...(Tuesday through Sunday)
Issued at 221 PM CST Sun Dec 13 2020
Tuesday: Another shortwave moving onshore along the northern CA
coast will shift quickly into the southern Plains Tuesday
supporting a chance for some light snow/flurries late
Tuesday/Tuesday evening. Moisture will be lacking for this system,
and progged accumulation looks limited.
Wednesday-Sunday: A progressive pattern will continue, but a lack
of low level moisture will limit precip chances for the rest of
the work week. Should see a nice warmup by Friday with gusty
south-southwest winds and a sharp upper level ridge. There is
good general agreement for another frontal passage early next
weekend with a brief window of opportunity for some showers, but
again, only limited/modified Gulf moisture looks to be available
for us with better chances for rain expected to be to our east.
Sunday looks dry.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 453 PM CST Sun Dec 13 2020
For the 00z TAFS, light to moderate snow will gradually diminish
over the next few hours at the TAF sites and then come to an end
from northwest to southeast by mid to late evening. A clearing sky
is expected overnight from west to east. Until then, we are
expecting IFR conditions to continue.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...Winter Weather Advisory until midnight CST tonight for MOZ082-
083-091-092-096>098-104>106.
Winter Weather Advisory until 9 PM CST this evening for MOZ090-
093>095-101>103.
KS...NONE.
&&
$$
SHORT TERM...DSA
LONG TERM...DSA
AVIATION...Lindenberg