Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/28/21
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
831 PM CST Sat Feb 27 2021
.UPDATE...
Issued at 820 PM CST Sat Feb 27 2021
00Z models are just beginning to roll in. The latest NAM suggests
upping QPF/SnowAmts along the I90 corridor. Will await more CAMS
before making any significant changes to those elements, but did
trend up pcpn amounts overnight a bit. The HRRR has been less
aggressive along I90, but has been consistent last few runs in
pushing out a bit more snow over western Stanley county, so placed
them in the advisory. Rest of the forecast appears fine for now.
&&
.SHORT TERM...(This Evening through Sunday Night)
Issued at 337 PM CST Sat Feb 27 2021
Two impressive short waves will affect SD through tonight. One
impressive spinner on satellite was in eastern WY moving east while
the other one was in southwest NE lifting northeast. Both short
waves had impressive cloud shields on satellite. The WY short wave
will affect central SD tonight while the NE short wave will affect
northeast SD/WC MN tonight. The current regional radar shows returns
increasing in coverage across southwest and into central SD this
afternoon with echoes starting to develop into southeast SD. With
warm temperatures and low dewpoints in C SD this afternoon, expect
the precipitation to begin as light rain and then with evaporative
cooling change over to snow this evening. The NE short wave lifting
northeast across SE SD will spread snow into our eastern cwa
tonight. The lift from both short waves will move away Sunday
morning. Lowered qpf and snowfall amounts a little for tonight
across the region. Kept the winter weather advisory going for Jones,
Lyman, and Deuel for 1 to 3 inches. Otherwise, skies will clear
quickly on Sunday morning as winds turn from north to west and
southwest through the day. Any snow cover will affect highs for
Sunday despite the sunshine and warmer west winds. At this time, 30s
and lower 40s for highs look good. The winds Sunday night will again
turn from west southwest to north through the night as a cold front
pushes in. Although, expect it to be dry with clear to partly cloudy
skies for Sunday night.
.LONG TERM...(Monday through Saturday)
Issued at 337 PM CST Sat Feb 27 2021
The challenge in the extended is determining just how warm to go
with high temperatures. NBM still likely being affected by the cool
bias and am a bit suspect to inherited temps. Went in and raised
several periods of high temps more towards the 75th percentile,
especially over the typical "over-achieving" sites. Otherwise,
conditions look mostly dry though the period, and will likely be
dealing with elevated fire danger during any windy periods, mainly
over central SD where forecast RH readings are on the dry side.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday Evening)
Issued at 518 PM CST Sat Feb 27 2021
Terminals KABR,KATY,KPIR,KMBG
MVFR cigs/vsbys are expected across much of the region through
tonight, as a system moves mostly south of the area. KMBG,
however, will likely remain VFR overnight.
&&
.ABR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 6 AM CST /5 AM MST/ Sunday for
SDZ023-033-045-048.
MN...None.
&&
$$
UPDATE...TDK
SHORT TERM...Mohr
LONG TERM...TMT
AVIATION...TDK
Area Forecast Discussion
National Weather Service La Crosse WI
559 PM CST Sat Feb 27 2021
.SHORT TERM...(This evening through Sunday)
Issued at 206 PM CST Sat Feb 27 2021
Main focus is on snow/wintry mix tonight into Sunday.
Currently watching a shortwave trough over WY which will translate
eastward tonight into Sunday, interacting with northern stream
energy dropping out of the Dakotas. Surface low pressure will track
from the southern high plains towards La Crosse by Sunday morning
and deepen as it passes to the northeast into the Great Lakes.
The forecast remains quite challenging with respect to precip types
and amounts across the area. Strong warm advection/moisture
transport will develop ahead of the wave later this evening with
0.50 inch pwats surging into the area. The strong warm advection
will also help intensify the low to mid level baroclinic zone.
Guidance is in reasonable agreement that an initial areas of precip
will lift northeast across the area late in the evening and into the
overnight associated with the moisture transport/warm advection,
highest chances over the northwest 2/3 of the area. There are even
hints of a bit of elevated instability trying to work north with
steep mid-level lapse rates. Expect loss of cloud ice behind the
deeper lift with the initial warm advective band as the warm nose
aloft spreads north. Similarly, guidance varies with respect to
surface temps, which would impact freezing potential. The RAP and
consensus among short range models has trended towards temp just
above freezing with the strong warm advection and would favor more
rain south/east of the low track. However, given the potential
convective nature of the precip, some sleet/snow couldn`t be ruled
out and if the colder solutions verify, may see some freezing rain.
Ridgetops and elevated surfaces stand a higher chance for light
icing. Behind this band, a drizzle/fog environment could persist
into Sunday morning near/south of the low track with low-level
saturation beneath drier mid-level air.
To the north, there remains good agreement that a potentially heavy
frontogenetic snow band will set up overnight into Sunday morning.
While individual models vary on the placement, overall consensus
from south-central MN through northern WI has been fairly steady
over model cycles. GEFS plumes show lower overall precip over
northeast IA with increasing mean values and spread into the I-90
corridor (likely due to band placement), with somewhat better
clustering in amounts closer to Eau Claire. Given the strong
moisture transport feeding the band and band orientation parallel to
the motion, this certainly has the ingredients for a very narrow
heavy 6 to 8+ inch snowfall. HREF ensemble max amounts, which likely
would handle the accumulation potential in the band best in this
scenario, supports 6+ inch amounts, with the mean band placement
just north of the area.
Collaborated with neighboring offices to add a Winter Weather
Advisory for Clark/Taylor Counties in WI. Confidence in snowfall
amounts is lower than usual, given uncertainty in band placement,
with northern portions of these counties more likely to see several
inches of snow. However, the wintry mix overnight could pose travel
impacts as well. That said, any southward shift, as suggested by a
few of the high res models, could push higher snow amounts into
southeast MN and north-central WI. Farther south, confidence isn`t
high enough with the freezing rain potential overnight for an
advisory. Will have to monitor trends this evening for any changes
for both the wintry mix potential and snow band placement. Some
short-fused headline changes could be necessary.
The snow will wind down across north central WI by late
morning/early afternoon with clearing spreading in from the west
through the day. Winds will become gusty from the northwest through
the day as the low deepens northeastward.
.LONG TERM...(Sunday night through Saturday)
Issued at 206 PM CST Sat Feb 27 2021
Main forecast concerns in the long term are on snow chances Sunday
night then focus turns to temperature trends the rest of the week.
A shortwave trough dives through the area Sunday night into Monday
morning bringing light snow chances to areas mainly near and north
of Interstate 94. Monday night will be the coldest night of the
week with lows falling into the single digits to teens. Then a
warmup is expected across the region as flow aloft turns more zonal
and 850 mb temperatures warm to around 3 C. The rest of the week
looks quiet as far as precipitation chances go. Plan on highs in
the 40s and possibly 50s at times. By late next week, much of our
remaining snowpack could be melted. Will have to keep a close eye
on temperature in the forecast. It`s possible highs are too cool,
depending on how much snow we melt off.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 559 PM CST Sat Feb 27 2021
VFR conditions are expected this evening, but IFR to LIFR conditions
are expected late tonight into Sunday morning as a winter system
moves through.
Mainly mid/high clouds and light southeast winds are expected this
evening, but lowering ceilings and precipitation chances will spread
in from southwest to northeast after 06Z as low pressure approaches.
Tricky precipitation type forecast, with surface temperatures
expected to be hovering near freezing. Given warm air aloft, it`s
looking like a rain/snow mix moving in overnight, but where
surface temperatures are at or below freezing, some light
freezing rain is also possible. Confidence is still lower on
whether this will occur, so have opted to keep this going in the
TAF at KRST for now. At KLSE, slightly warmer surface temperatures
could keep things more of a rain/snow mix. Temperature trends
will have to be carefully monitored as precipitation comes in
tonight, however. As low-level moisture increases, ceilings should
lower into IFR and possibly LIFR by Sunday morning. Ceilings look
to improve by afternoon as low pressure pushes east and
precipitation ends. Gusty northwest winds are expected in the
tight pressure gradient behind the low, with gusts of 25 to 30
kts.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from midnight tonight to noon CST Sunday
for WIZ017-029.
MN...None.
IA...None.
&&
$$
SHORT TERM...JM
LONG TERM...Wetenkamp
AVIATION...Lee
AREA FORECAST DISCUSSION
National Weather Service Sioux Falls SD
935 PM CST Sat Feb 27 2021
.UPDATE...
Issued at 930 PM CST Sat Feb 27 2021
Precipitation has been slow to develop this evening with dry low
level air hard to overcome, but current obs, radar, and web cams
are indicating light rain and snow finally beginning to develop.
Current mesoanalysis indicates a midlevel level thermal boundary
lifting northward across the area - generally oriented along and
north of the Interstate 90 corridor, with increasing instability
above the front. With that we should see precipitation increase
across portions of the area as a mid/upper level shortwave
presently pushing into southwestern SD/the NE panhandle continues
to slide eastward. One trend that has been noticed with the most
recant CAM runs, and supported by the 00Z NAM run and HREF
ensembles, is a northward shift of the heaviest band snow
overnight. Because of this, did shift the higher QPF amounts
slightly northward. There are are also indications that the dry
slot will work northward toward 09Z tonight and may diminish
precipitation over much of northwest IA for a time later tonight.
Because of the late onset of precipitation this evening, did cut
back on rain/snow amounts through 06Z over the previous forecast.
What all this means in terms of snowfall amounts is that the
overall amounts have been reduced a bit and shifted slightly to
the north. Even so, we are still looking for 4 to 6 inches of snow
in the heaviest band, and will keep current headlines as is until
there are better indications of how things are going to evolve.
&&
.SHORT TERM...(This Evening through Sunday)
Issued at 312 PM CST Sat Feb 27 2021
The primary concern in the short-term is a quick band of heavy
snow that is expected to move across the area tonight. GOES-16
satellite shows a compact wave over central Wyoming with larger
wave in Colorado. Already a strand of potential vorticity extends
northeast of this wave toward south central South Dakota. The
result has been the development of snow in southwestern South
Dakota and the Nebraska panhandle with virga and perhaps light
precipitation extending east toward south central South Dakota.
This is indicative of a strengthening frontal circulation centered
at 700 mb. South of this front, WV imagery shows dry and
potentially unstable air over southern Nebraska that is slowly
moving north. This will provide a source of instability as this
system develops overnight.
The expected evolution has been handled fairly well by the HRRR. A
broader area of light snow is expected to develop above the
600-700 mb frontal surface later this afternoon and this evening
as the PV anomaly continues to move northeast. This area of snow
is expected to extend from around Chamberlain toward Marshall. Then
as the stronger PV anomaly moves into Nebraska, more unstable air
will move into far southern South Dakota and gradually into far
southwestern Minnesota. Model soundings shows CAPE of 50-150 J/kg
moving above the frontal boundary after 03Z. The expected result
is that the strengthening frontal circulation combined with
unstable air moving toward I-90 will result in an intense band of
snow on the south side of the band. This band will result in
snowfall rates of 1-2" per hour between 03Z and 10Z. To the north
of this intense band of snow - the original area of snow will
slowly weaken through the night. At this time, it appears any one
location will see heavy snow for 1-3 h. While a few locations
could see over 6 inches of snow, our expectation is that the
limited duration will keep snowfall less than 6 inches for most
areas. Should the band of snow become stationary, then a larger
area could see more than 6 inches.
While confidence is high that a band of heavy snow will develop
overnight, there is a lot of uncertainty over location which leads
to a lower confidence forecast on snowfall amounts. An
examination of multiple RAP and HRRR runs shows the band could be
as far north as Chamberlain to Marshall or as far south as
Vermillion to Jackson. The most likely area for heavy snow (3-6
inches) is from Windom to Sioux Falls to Parkston. To the south of
this area, there may be a period of rain as temperature remain
above freezing and precipitation rates are also lighter. As a
result south of the heavy band of snow we are expecting a sharp
gradient in snowfall. So any shift in the band of heavy snow of
even 10-20 miles could result in snowfall changes of 2 or more
inches. With snow expected to pick up rapidly between 03Z and 06Z,
road conditions could rapidly deteriorate where the heaviest snow
is falling. Given the uncertainty in the location of this
snowband, persons planning travel overnight should monitor the
latest forecasts before starting travel.
Outside of the snow, there is the possibility of drizzle of
freezing drizzle over portions of northwestern Iowa. At this
point, we are expecting temperatures to stay above freezing around
SUX, SPW and SLB such that precipitation will primarily be liquid.
However, as temperatures cool toward dawn with the low moving to
the east, precipitation could end as freezing drizzle if it does
not change to snow. Any precipitation is expected to end shortly
after sunrise.
Winds of 10 to 20 mph with gusts over 25 mph are expected
overnight. This may cause some blowing and drifting snow when the
snow is falling. With this being a wetter snow, any blowing snow
should end once the snow ends later tonight.
Lingering snow over southwestern Minnesota will end by mid to
late morning on Sunday. Skies will then become sunny and in the
James and Missouri River Valleys where less snow is expected
highers will reach the mid to upper 30s. Elsewhere upper 20s to
lower 30s are expected.
.LONG TERM...(Sunday Night through Saturday)
Issued at 312 PM CST Sat Feb 27 2021
With the expected weather tonight into Sunday, did not make many
changes to the forecast. Overall, quiet weather with a gradual
warming trend is expected across the area.
On Sunday night, an Alberta clipper will move from ND into
southern Wisconsin. No precipitation is expected but westerly
winds will bring warmer air briefly into the area overnight. Then
a strong cold front will drop south through the area late Sunday
night into Monday. The result will be steady to even slowly rising
temperatures overnight. Then temperatures will fall rapidly behind
the cold front with lows falling into the teens and lower 20s
around sunrise. The combination of strong cold advection and new
snow cover will keep many areas below freezing on Monday. Once
again the warmest temperatures will in the James and Missouri
Valleys where less snow will allow temperatures to rise into the
upper 30s to lower 40s.
Temperatures will continue to warm through midweek. Snow cover may
keep temperatures on Tuesday in much of southwestern Minnesota
into portions of southeastern South Dakota in the 40s. Other
areas will warm into the 50s with 60 degrees possible in the James
and Missouri Valleys of South Dakota. Tuesday could also be windy
with gusts of 20 to 30 mph possible. The remainder of the week
should see temperatures in the 40s and 50s with a few 60s
possible. No precipitation is expected after Sunday morning.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 520 PM CST Sat Feb 27 2021
Light rain showers early this evening will quickly transition to
snow by mid evening from west to east, though remain light rain
over parts of northwestern IA until later tonight, when a brief
period of freezing drizzle will be possible. The heavier snow will
reside from south central SD, southeastern SD, into southwestern
MN, where visibility will be reduced to 1/2 a mile at times. Snow
will quickly come to an end by 12Z on Sunday,with MVFR/IFR
ceilings slowly clearing though late morning. Northerly winds will
pick up overnight, gusting 20 to 25 kts into Sunday morning.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 6 AM CST Sunday for SDZ040-050-
054>070.
MN...Winter Weather Advisory until 6 AM CST Sunday for MNZ071-072-080-
081-089-090-097-098.
IA...Winter Weather Advisory until 6 AM CST Sunday for IAZ001>003.
NE...NONE.
&&
$$
UPDATE...JM
SHORT TERM...Schumacher
LONG TERM...Schumacher
AVIATION...JM
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
603 PM CST Sat Feb 27 2021
.UPDATE...
Issued at 601 PM CST Sat Feb 27 2021
The Red Flag Warning was allowed to expire at 6 pm. While winds
will be steady behind a cold front, relative humidity values have
increased.
&&
.DISCUSSION...(This evening through Saturday)
Issued at 218 PM CST Sat Feb 27 2021
Interesting day across the local area today as widespread fog this
morning across Kansas transitioned into widespread stratus across
much of the area this afternoon...helping to keep temperatures
down to start the day. That said...continue to see rapid clearing
on the southern edge of this stratus and could still see a late
day spike in temps. As a result...did not adjust high temps
significantly...just the diurnal curve some...and kept the RFW in
tack for Rooks county this afternoon...despite conditions still
not quite reaching near critical thresholds as of this time. This
should change over the next hour or two...however...especially
across Rooks county...where the RAP continues to indicate RH
values dropping to near 15 percent for a couple of hours late this
afternoon.
For tonight...expect the focus to shift north as an approaching
cold front pushes across the local area. Initially inherited a
small chance for thunderstorms across our far eastern fringes this
evening...but models have backed off on this some...with the RAP
still indicating a weak line of showers developing just to our
east around sunset. Given the instability axis positioned just to
our east...think if any storms are able to develop, they should
remain primarily in OAXs area. Otherwise...could see some light
precip across our north and east overnight with the passing cold
front...but any accumulation (liquid or otherwise) should be
minimal...with only a hundredth or two in the forecast...and even
that is questionable.
For Sunday...expect a cooler day across the area with sunshine
returning by afternoon. This will likely be the coolest day of the
forecast...as upper level ridging beings to work its way across
the local area by Monday and a pair of systems next week
(Tuesday/Thursday) are both expected to slide primarily south of
the local area. Despite some subtle differences in overall timing
of these next two upper lows...the overall pattern from the GFS/EC
is in fair agreement...and anticipate a dry week across the local
area...with only the smallest chance for some light rain across
north central Kansas with the second low Thursday/Thursday night.
As a result...the mild temperatures through the middle to latter
half of the extended periods will likely be main story...with
temperatures Tuesday through Saturday running 10-20 degrees above
seasonal norms.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Monday)
Issued at 501 PM CST Sat Feb 27 2021
Satellite imagery shows persistent stratus over KEAR which looks
to hold for a couple of hours...then scatter briefly...then low
cloud cover is expected to fill back in behind a cold front
tonight and linger thru at least mid morning Sunday before
scattering. Look for winds to increase form the northwest behind
the front around 05Z- 06Z with gusts of 20-25kts.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
UPDATE...Fay
DISCUSSION...Rossi
AVIATION...Fay
Area Forecast Discussion
National Weather Service Wichita KS
538 PM CST Sat Feb 27 2021
.SHORT TERM...(This evening through Tuesday night)
Issued at 301 PM CST Sat Feb 27 2021
Tonight:
Combination of sharp moisture gradients and lingering low clouds
make forecast challenging at the onset, with front moving through
during the night. Low level moist axis has worked north across
western half of forecast area, while relatively drier air
recirculated into southeast KS. Very dry air over western KS has
remained just west of the forecast area so far. With front pushing
into central KS this evening, it is becoming less certain that
significantly drier air will arrive before frontal passage. RAP
has been better than most models on the moisture so far today and
gave it more weight with precipitation chances tonight - which are
are generally slim until front reaches far southeast KS late
tonight. Forecast soundings do show some elevated instability that
could result in isolated convection and will keep it mentioned
in the forecast.
Sunday-Monday:
Temperatures will drop closer to normals this period, with brisk
north to northwest winds in wake of the front on Sunday. With
surface ridging on Monday, winds will be light.
Monday Night-Tuesday:
Fairly decent agreement that weakening cut off upper low will
track across OK. Little incentive to deviate from initialization
grids, but have doubts about precipitation chances north of
highway 400. With weak flow at or below 850MB, deeper moisture and
good baroclinic zone are lacking. Temperatures appear to be cold
enough for flurries or light snow. However given warm temperatures
on Monday and quick rebound of temperatures on Tuesday, if snow
does occur, would not expect any significant impacts. -Howerton
.LONG TERM...(Wednesday through Saturday)
Issued at 301 PM CST Sat Feb 27 2021
Medium range models have come into basic agreement with upper
pattern, with another upper low tracking across the southern
plains Thursday-Saturday. Biggest difference, which is
substantial, is GFS is much quicker to develop the corresponding
surface low and much deeper with it. This leads to more moisture
rotating around low into the forecast area despite its more
southern track. ECMWF is weaker with a more north track, so it
also generates light precipitation across the forecast area. Main
point of agreement is precipitation chances will be much higher
in the south than the north. Temperatures during this period
should be well above normal on Wednesday in advance of system
given dry air and some downslope flow off the deck. For Thursday-
Saturday, temperatures will be more dependent on clouds and
precipitation so confidence is low at this point and didn`t
stray far from initialization. -Howerton
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 535 PM CST Sat Feb 27 2021
Widespread MVFR ceilings continue to impact south central and
southeast Kansas with abundant low level moisture and breezy south
to southeasterly winds. A cold front will arrive this evening
across central Kansas shifting winds to the northwest and scouring
out the low level moisture. This will allow flight categories to
improve in it`s wake. Meanwhile, narrow T/Td depressions will
likely result in some fog ahead of the front and maintained a
shower mention in the KCNU TAF. Breezy north winds will prevail
across the region on Sunday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 35 54 27 55 / 20 0 0 0
Hutchinson 32 52 25 54 / 10 0 0 0
Newton 33 52 25 54 / 20 0 0 0
ElDorado 35 54 27 54 / 30 0 0 0
Winfield-KWLD 38 55 28 55 / 20 0 0 0
Russell 28 50 22 54 / 0 0 0 0
Great Bend 28 51 22 54 / 0 0 0 0
Salina 30 52 24 55 / 20 0 0 0
McPherson 31 51 23 54 / 20 0 0 0
Coffeyville 43 55 28 55 / 50 10 0 0
Chanute 41 54 27 54 / 50 0 0 0
Iola 40 53 26 54 / 40 0 0 0
Parsons-KPPF 41 54 28 54 / 50 0 0 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...PJH
LONG TERM...PJH
AVIATION...MWM
Area Forecast Discussion
National Weather Service Lincoln IL
918 PM CST Sat Feb 27 2021
.SYNOPSIS...
Issued at 226 PM CST Sat Feb 27 2021
Showers will spread into central and southeast Illinois later this
evening through the overnight hours. While most of the area will
see light rainfall amounts of one quarter of an inch or
less...heavier totals in excess of one inch will be likely south
of the I-70 corridor.
&&
.UPDATE...
Issued at 915 PM CST Sat Feb 27 2021
Rain showers are advancing northward into our forecast area pretty
much on track with the forecast database. Thunderstorms have
developed along the leading edge farther west than originally
expected. Instability params in the HRRR and RAP still limit
thunder potential to mainly south of I-70, but lightning
observations suggest potential will extend north and west of
there. Have added isolated thunder as far north as Sangamon
County. There could be some enhanced rainfall rates in during any
thunderstorms, due to precipitable water values climbing over 1"
in the southern half of our CWA. The primary coverage of
persistent rains still look to remain east of I-55, where PoPs are
in the Likely to Categorical range. The latest high res models are
trying to slow down the exit of rainfall to the east on Sunday,
but we did not make noticeable adjustments with that possibility
just yet. Persistent cloud cover and steady southeast winds overnight
will help keep low temps on the mild side, in the 40s. Basically,
temps will remain nearly steady the rest of the night.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 226 PM CST Sat Feb 27 2021
Low pressure currently organizing in the lee of the Rockies across
western Kansas will track northeastward...reaching northeast Iowa
by Sunday morning and southern Ontario by Sunday evening. 12z Feb
27 models are in excellent agreement that the most widespread
precipitation with the approaching system will be focused within
the deep-layer southwesterly flow noted on latest water vapor
imagery from Texas to the Ohio River Valley...and further
northwest in closer proximity to the low track across Iowa into
Wisconsin. In between...much of central Illinois will only see
scattered showers with total rainfall of less than one quarter of
an inch. The exception will be along and south of the I-70
corridor where the rain will be more persistent/heavier. With
NAM precipitable water values increasing to 1.25-1.50 across the
SE KILX CWA later tonight, expected rainfall amounts have
increased to over one inch south of I-70. In addition, NAM MuCAPE
values of 400-500J/kg warrants thunder mention across the SE as
well. Based on latest radar mosaic showing showers still well to
the south across the Ozarks, have delayed onset of precip by a few
hours. HRRR has been trending slower as well, with much of the
evening remaining dry. As a result, have kept locations north of a
Macomb...to Lincoln...to Paris line dry through midnight. Showers
will overspread the entire area overnight, with likely to
categorical PoPs focused across the SE half of the CWA.
As low pressure tracks into the northern Great Lakes, a cold front
will get pulled through central Illinois on Sunday. Until the
front passes, there will still be a chance for showers...have
therefore lingered PoPs slightly longer than previously forecast.
Will maintain PoPs along/east of I-55 through Sunday morning and
along/south of I-70 through the afternoon. Once the front departs,
winds will veer to the west and increase markedly with gusts of
30-35mph from late morning through afternoon. Highs will again be
on the warm side...ranging from the upper 40s northwest of the
Illinois River to the lower 60s along/south of I-70.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 226 PM CST Sat Feb 27 2021
An upper trough currently over the Rockies will track eastward and
allow a cooler airmass to settle into the region early next week.
As a result, temperatures will drop back into the 40s for Monday
and Tuesday. Once the trough pushes further east and a zonal
west-to-east flow develops across the CONUS, temperatures will
moderate into the 50s for the remainder of the week. Will need to
keep an eye on a short-wave trough tracking across the southern
Plains into the Tennessee River Valley late Monday into Tuesday.
Previous runs of the GFS had shown the wave coming far enough
north to potentially bring light precip into central Illinois:
however, the latest run has shifted further south in line with the
GEM. Meanwhile, the ECMWF has shifted its track further north.
Given poor model agreement, have maintained just slight chance
PoPs across the S/SE CWA Tuesday into Tuesday evening. Other than
that, the remainder of the extended is dry.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 600 PM CST Sat Feb 27 2021
VFR conditions will prevail through this evening before ceilings
lower and showers develop overnight. Forecast soundings suggest
ceilings becoming MVFR at all terminals between 06z and
08z...with a further lowering to IFR between 08z and 10z. The
bulk of the rain appears to be focusing along/south of the I-70
corridor, so have only mentioned VCSH at the W/NW TAF sites
overnight into early Sunday morning. Have included predominant
light rain between 10z and 15z at KDEC and between 09z and 15z at
KCMI. Once the showers depart, IFR ceilings are expected to
persist through at least midday, with some improvement to MVFR by
mid-afternoon. Winds will initially be SE this evening. Winds
will then veer to W/SW and gust into the 20-25kt range by mid to
late Sunday morning.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SYNOPSIS...Barnes
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Shimon
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
503 PM CST Sat Feb 27 2021
.UPDATE...For 00Z Aviation discussion below
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 306 PM CST Sat Feb 27 2021
So long as you aren`t under the stratus of western MN, it`s quite
the nice late winter day, with temperatures in the low to mid 40s,
but tonight, we take a quick run back into winter that will last
through Monday night. As for that snow tonight, we went with an
advisory everywhere and narrowed in a heavy snow axis of 4-6" from
Redwood/Brown counties northeast through the Twin Cities and on to
Ladysmith in WI. With this increase in snow, did bring Pepin and Eau
Claire counties in WI into the advisory.
For the snow tonight, there`s still a good deal of spread in both
the CAMs and deterministic models, though we look to really be
narrowing in on the axis mentioned in the previous paragraph, which
is where GEFS/EPS probs for snowfall greater than 3" are greatest.
There are some models, like the RAP and NMM with this snow axis
angled more from Fairmont to Eau Claire, but with the 18z HRRR
lifting it`s heaviest QPF axis toward where the EPS/GEFS have the
highest snow probabilities, feeling a bit more confident in the
forecast we now have.
As for what`s forcing this snow, it`s the positively tilted shortwave
coming out of CO into Nebraska. This wave will maintain its positive
tilt as it drives a surface low from near Omaha at 6z tonight, to
near Escanaba, MI by 18z Sunday. Mean h7 low from the HREF tracks
from near Sioux Falls, to Mankato, Hastings, and eventually
Rhinelander in WI. Just northwest of the h7 low track is where you
would expect the heaviest snow and this is what we have forecast
now. What could lead this forecast astray is just exactly where/how
we initiate fgen forced precip. We`ll see light precip push in late
this afternoon in west central MN on fgen up more in the h7-h6
layer, but between 3z and 6z, we`ll see frontal forcing down more in
the 925-850mb layer take over, with the energy of this snow shifting
that direction. If we end up establishing this 925-850mb band
earlier than forecast, then that would result in this snow band
setting up farther south than currently forecast (the Fairmont to
Eau Claire solutions). At this point though, guidance from the
HREF/GEFS/EPS heavily favor a solution with the snow coming up into
the Twin Cities metro, so that`s what we went with. Not expecting
much in the way of 6+" amounts from this system though, mainly given
the positively tilted nature of the trough and the speed with which
it will move through.
We`ll see skies clear out on Sunday behind this system, but models
are definitely trending stronger with a northwest flow shortwave
swinging down across northern MN into central WI Sunday night. Did
boost PoPs up to likely between 6z and 12z Sunday night. There`s
some uncertainty with the north/south placement of the heaviest
precip, but with most models showing a max QPF of 0.1"-0.15", it
does look like we could see a fast 1-2" of snow out of that.
Greatest threat for seeing that much snow Sunday night right now is
along and northeast of a line from Eau Claire to Mora.
.LONG TERM...(Monday through Saturday)
Issued at 306 PM CST Sat Feb 27 2021
For the extended period, the forecast looks very quiet regarding
precipitation. Split, zonal upper-level flow will spread over the
CONUS after Monday, with the northern and southern streams located
to the north and south of our region, respectively. This will leave
us in no mans land for any strong dynamical synoptic lifting
mechanisms through at least late next week. A chilly Monday is
forecast as a brief shot of cold, arctic air shifts through the
region following a cold frontal passage Sunday night. Model guidance
spread with respect to Mondays high temperatures has improved a bit
since yesterday, with a cooling trend noticed in most of the
guidance. Though, the GFS still remains the cold outlier. Highs in
the upper-teens to lower 20s are a good possibility for the MPX CWA,
with some slightly warmer temperatures possible along the Buffalo
Ridge. Temperatures Monday night will also be cool, especially east,
before the cold air mass departs. Lows are forecast to be near 10 in
west-central WI, warming to the mid to upper teens in western MN.
Once the aforementioned split, zonal upper-level flow takes over
post Monday, leeside warming will occur east of the Rocky Mountains.
With the development of southwesterly 850 mb flow over the Central
to Northern Plains working to advect this warmer air eastward,
slight ridging will build over the central CONUS by mid-week.
Tuesdays highs rebound into the upper 30s in west-central WI to mid
40s in western MN. Winds could also be breezier Tuesday with the
enhanced southwesterly low-level flow and thus have slightly bumped
up sustained winds to 10-20 mph and gusts to 25-30 mph. Temperatures
will continue to slowly warm, remaining at least 5-10 degrees above
normal the remainder of the period. Thursdays highs are currently
forecast in the mid 40s to near 50. Temperatures become more
uncertain by next weekend as spread within the guidance increases.
However, the EPS and GEFS mean show MSP reaching the mid-50s for
highs next Saturday and Sunday. Thus, a very nice early Spring
weekend for the MPX CWA looks hopeful but, time will tell if this
indeed comes to fruition.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 503 PM CST Sat Feb 27 2021
IFR conditions are expected to become common tonight as snow
overspreads the area. KAXN looks to be the one site situated to the
northwest of the accumulating snow, but still expect BR to cause
visibility 3SM reductions there, along with the IFR-level stratus.
Variable winds become north-northwesterly overnight, and increase to
15G25 knots for Sunday. VFR conditions look to develop from west to
east across the sites on Sunday afternoon.
KMSP...Still expecting around a 3 hour window where vsby in snow
will be 3/4sm or less...most likely centered around 10Z-13Z. Snowfall
amounts of 3-4 inches have the highest probability of occurrence
based on the latest forecast.
/OUTLOOK FOR KMSP/
Mon...VFR. Wind NW 5-10 kts becoming SW late.
Tue...VFR. Wind SW 15G25 kts.
Wed...VFR. Wind WSW 5 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...Winter Weather Advisory from midnight tonight to 10 AM CST Sunday
for Anoka-Carver-Dakota-Goodhue-Hennepin-Ramsey-Scott-
Washington-Wright.
Winter Weather Advisory from 9 PM this evening to 8 AM CST Sunday
for Blue Earth-Brown-Faribault-Le Sueur-Martin-McLeod-Nicollet-
Redwood-Renville-Rice-Sibley-Steele-Waseca-Watonwan-Yellow
Medicine.
Winter Weather Advisory from midnight tonight to noon CST Sunday
for Chisago.
WI...Winter Weather Advisory from midnight tonight to noon CST Sunday
for Barron-Chippewa-Dunn-Eau Claire-Pepin-Pierce-Polk-Rusk-St.
Croix.
&&
$$
SHORT TERM...MPG
LONG TERM...CTG
AVIATION...LS
...Updated Aviation Forecast Discussion...
.DISCUSSION...
Issued at 247 PM CST Sat Feb 27 2021
We will see a chance of rain developing, especially in northeast
NE this evening, and that rain will likely change to snow along
the NE/SD border. And it`s that area that could be in slight
deformation zone overnight with light snow diminishing to flurries
by daybreak Sunday. Model consensus indicates 1-2" possible for a
couple of counties, Knox and Cedar, and even a couple models hint
at possible slightly more in the 3-4" range along the SD border.
Thus will issue a winter weather advisory for Knox and Cedar
counties through 6 am Sunday morning.
Farther south, as the inverted trough moves through the are this
evening, could see a isolated showers develop. There is just a
hint of some very limited mid level instability, with computed
850mb LI slightly negative during the evening. SPC keeps the
general thunder outlook south of the area, as does the calibrates
SPC HREF model. The SREF hints at a narrow corridor of thunder
probabilities, but overall, have removed the mention of any
thunder this evening. Where it rains, amounts will be light at
less than one tenth of an inch.
After slightly cooler days Sunday and Monday with highs mostly in
the lower to mid 40s, (albeit still near normal), the remainder
of the forecast Tuesday through Saturday looks warm and dry and
very mild with highs mostly in the 50s, but a few low 60s here and
there as well.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 525 PM CST Sat Feb 27 2021
A vigorous shortwave trough and associated surface low are
forecast to move through the area overnight with southeast or east
winds switching to the northwest with the passage of the weather
system to the east. Strengthening forcing for ascent amidst a
moistening boundary layer and a plume of steep mid-level lapse
rates has fostered some vertical convective cloud growth over
Saline County as of 5 PM. And, isolated showers appear possible
in the KLNK and KOMA vicinities this evening. RAP objective fields
suggest a pocket of weak instability in that area with EL
temperatures supportive of some in-cloud charge separation. As
such, a rumble of thunder appears possible.
Isolated showers appear possible at KOFK later this evening.
Best potential for a change over to snow will be closer to the SD
border.
Ceilings will continue to lower with MVFR conditions expected at
KOFK within the next hour or so, and closer to midnight at KOMA
and KLNK.
&&
.HYDROLOGY...
Issued at 247 PM CST Sat Feb 27 2021
The flood watch remains for the Platte and Elkhorn River basins
through Monday. We do have two ongoing ice jams and associated
flooding along the Platte River, the first near Schuyler, and the
second near Fremont. Flood warnings continue for those two
locations with no substantial changes or improvement noted.
River observers have reported that lower portions of both rivers
were perhaps seeing some clearing out with more free flowing water
noticed. And that`s good news to allow any additional ice breakup
coming downstream to hopefully continue to move through the
system. We are continuing to seeing higher flows on the Platte
from North Bend downstream, so we know there is likely some ice
moving through the channels. We are also seeing stages drop at
Waterloo on the Elkhorn River, which confirms the visual
observations that ice was clearing out there, and likely making it
into the Platte River.
Given the high uncertainty of if, or when any additional ice jams
could develop, we will continue the flood watch at this time. We
did trim a couple of counties in the upper reaches of the Elkhorn
River out of the flood watch since river observations there
indicate the water seems to be flowing mostly OK, with plenty of
room in the banks if something were to happen. And we`ll continue
to monitor closely, in cooperation with river observers, NRDs, and
local Emergency Management to alert of any additional ice jams if
they develop.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Flood Watch through Monday morning for NEZ032-033-042>045-
050>053-067.
Winter Weather Advisory until 6 AM CST Sunday for NEZ011-012.
IA...None.
&&
$$
DISCUSSION...DeWald
AVIATION...Mead
HYDROLOGY...DeWald
Area Forecast Discussion
National Weather Service Reno NV
238 PM PST Sat Feb 27 2021
.SYNOPSIS...
Blustery and chilly conditions will continue for the remainder of
today as light snow showers taper along and east of Highway 95.
Temperatures remain cool on Sunday with lighter, easterly winds.
Dry conditions will prevail for much of the upcoming week with
above average temperatures. The next chance for rain or snow may
arrive by next weekend.
&&
.SHORT TERM...
Not too much change to the short term forecast this cycle besides
for decreasing low temperatures a few degrees in some of the
colder valley spots for tonight into Sunday morning.
Northwest to north winds have increased across the region early
this afternoon with most locations in western-central Nevada
gusting around 30 mph. Blowing dust is possible for these
locations during this time with rough conditions expected on
Pyramid Lake. The Lake Wind Advisory for Pyramid Lake is in effect
through 7 pm this evening. Conditions on Lake Tahoe are not quite
as rough with surface winds currently gusting around 20-25 mph.
However, it doesn`t take too much wind to generate hazardous
conditions on Lake Tahoe. Expect these breezy to gusty winds to
continue throughout the remainder of the day, decreasing in
intensity after sunset.
Very light, isolated to scattered snow showers currently remain on
radar for areas along and east of US-95. Had a report from the
Lovelock Airport earlier this afternoon of light snow with
visibility down to 3 miles, but it only lasted about 20 minutes.
Short range model guidance (including the HRRR & NAM 3km) show the
snow shower activity lessening throughout this afternoon and
finally moving out of the region by this evening as the core of
the low pressure trough shifts southeastward. As this happens,
winds are forecast to shift to a more easterly direction,
decreasing in intensity across western Nevada, but increase along
the Sierra ridges and the western slopes of the Sierra overnight.
Cold, overnight low temperatures are expected tonight into Sunday
morning for the Sierra and western Nevada as clouds clear and
winds diminish behind a cold front. Lows are forecast to be 5-10
degrees below average for the end of February. By Sunday
afternoon, temperatures will still be on the cool side (a few
degrees below average) with light easterly flow, but bump back up
to average for Monday as a warming trend begins into midweek.
-LaGuardia
.LONG TERM...Tuesday through next weekend...
There were no significant changes made to the forecast. All medium
range model guidance continue to show the formation and digging of a
weak upper low off the West Coast Monday. The biggest question
remains what the inland trajectory of this low will be. Nearly all
model solutions depict the low swinging into southern California
early Tuesday. However, model solutions begin to differ once the low
departs southern California. The GFS/ICON/GEFS lift this low off to
the northeast Tuesday, while the ECMWF/EC-ENS push the low off to
the east. If the more northeasterly path solutions hold, very light
snow showers could occur across the Sierra with around 0.10" of
liquid accumulation. If the other solutions hold, the Sierra will
remain dry.
Meteorological spring looks to start rather ordinarily with a short-
wave ridge building overhead. This ridge will allow afternoon highs
to rebound to near 60 degrees for western Nevada valleys and low 50s
for Sierra valleys Wednesday into Friday.
Shifting our attention to next weekend, short-wave troughs look to
reinvigorate over the eastern Pacific. A deep subtropical moisture
tap does not look to occur with these waves, which could hinder the
chances for heavier precipitation. Depending on how progressive
these waves are, we could see gusty winds and winter travel impacts
across the Sierra and into western Nevada Friday or Saturday next
week. However, the timing and strength of these waves remain
uncertain. -Johnston
&&
.AVIATION...
Northerly winds will continue to bring areas of turbulence and gusty
winds/areas of blowing dust to KLOL-KNFL-KHTH this afternoon. This
dust could lower slantwise visibility near the aforementioned
terminals. Winds become east-northeasterly tonight with speeds
decreasing across the lower elevations with stronger ridgetop winds
and turbulence expected west of the Sierra crest.
As the easterly pressure gradient weakens, lighter winds and VFR
conditions are expected through the early part of the coming week.
-Johnston
&&
.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory until 7 PM PST this evening for Pyramid Lake
in NVZ004.
CA...None.
&&
$$
For more information from the National Weather Service visit...
http://weather.gov/reno
Area Forecast Discussion
National Weather Service Blacksburg VA
914 PM EST Sat Feb 27 2021
.SYNOPSIS...
Abundant moisture will combine with a frontal boundary to bring
periods of rainfall to the Appalachians and central mid Atlantic
region through the weekend. After a brief break of dry weather
on Tuesday, unsettled conditions return by the middle of next
week as an area of low pressure moves through the deep south.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of 914 PM EST Saturday...
Flood Watch in effect Sunday morning through Monday morning for
VAZ019-020-024 and WVZ042>044-507-508.
Flood Watch in effect from Sunday afternoon through Monday
morning for VAZ007-009>014-018-022-023.
KFCX 88D images showed showers moving into western portions of
the forecast area tonight. The latest rnk 00z sounding indicated
that pwats have climbed to 1.27 inch with a 50 knot west jet
around 700 mb. Placement of flood watch look reasonable at this
time. Model solution this evening place the best chance for rain
in the northwest portions of the forecast area tonight into
Sunday morning. Made a few minor adjustments in temperatures for
tonight. In general, temperatures lowered a few degrees mainly
in the west tonight. Also added more fog especially in the south
overnight. More changes later tonight.
As of 630 PM EST Saturday...
Made some minor adjustments to temperatures this evening into
tonight utilizing the latest surface obs, their trends and
blended in the NBM heading into Sunday morning. Modified pops
and weather initially with radar trends, then with mix of
Highres-ARW-East, HRRR and NAM. In general, slow down the
advance of rain this evening and kept highest pops in the
northwest portions of the forecast area. More changes later
tonight.
As of 215 PM EST Saturday...
Multiple waves rippling along the a frontal boundary will bring
periods of rainfall tot he region through Sunday. The most
likely locations to see rain will be west of the Blue Ridge and
from route 460 northward. However, waves moving along the front
will cause it to waver around a good bit. Believe a good portion
of the area south of 460 will see some lengthy gaps in
significant precipitation tonight and for most of Sunday, with
little in the way of precipitation outside from Southside into
the piedmont. Rain will be most persistent along the I-64
corridor from the Alleghany Highlands into southeast West
Virginia.
Ingredients favoring heavy rainfall remain in place with a
precipitable water values exceeding 3 standard deviations above
normal by late Sunday and deep layer lift aided by a frontal
boundary along with some convective instability. Rainfall this
morning has already primed the saturated ground in the mountains
so any additional rainfall will generate substantial runoff.
Flood watches have been issued for locations most likely to see
excessive rainfall and flooding. Believe the most problematic
time will be Sunday evening through Sunday night as the frontal
boundary moves through and convective elements enhance rainfall
rates. Flooding of mainstem in the New and James basins is
becoming more likely as well with moderate flooding at some
locations falling within the ensemble envelope of possible
solutions.
Winds may also become gusty tomorrow with guidance indicating
potential for better mixing as the low level flow amplifies.
This may allow stronger winds to reach the surface so expect
winds to increase notably during the afternoon.
Temperatures will be running well above normal through tomorrow.
Expect readings into the lower 70s east of the Blue Ridge
Sunday afternoon with mid/upper 60s to the west.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 215 PM EST Saturday...
Looking at widepspread rain along and behind a cold front through
Monday morning then turning windy, dry and colder into Tuesday
night.
Northern stream amplifies on Monday and Tuesday and pushes the long
wave trough axis across the eastern United States Monday night. This
leaves the Mid Atlantic region and Carolinas in deep northwest flow
through Tuesday.
Very strong upper diffluence in the right entrance region of a 160
knot upper jet Sunday night and Monday. Good continuity in the
models too for widespread precipitation Sunday night and Monday
morning. The surface cold front comes through Sunday night with some
precipitation post-frontal. Temperatures drop enough just before
the precipitation ends Monday morning in the higher elevations of
southeast West Virginia to change the rain to snow. Will be adding a
small area of snow in for western Greenbrier County early Monday
morning, but with little to no accumulation.
Winds gusty behind the front Monday and Monday night, supported by
cold air advection, a 45 to 55 knot low level jet and good pressure
rises, then diminish on Tuesday. Given the amount of upslope flow
expected, it may take until Tuesday morning for the low clouds along
the western slopes of the central Appalachians to dissipate. Will be
increasing wind speeds and gusts for Monday afternoon and Monday
night.
Behind the intense cold front 850MB temperatures drop to its lowest
values,in the 0 to -8 range on Monday night. Temperatures moderate
Tuesday and Tuesday night. Air mass significantly dries out above
850mb behind the front Monday night and Tuesday.
Synoptic scale models continue to differ in the timing of the next
closed low in the central United States. Will lean toward the slower
ECMWF solution that has the low over the Mid Mississippi Valley
Tuesday. Expecting return flow of moisture between high pressure off
the Virginia coast and low pressure over the southeast United States
on Tuesday night. This will will lead to increasing cloud cover.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 215 PM EST Saturday...
Multiple areas of low pressure brush close by to our south
leaving chances for rain for the middle and end of next week...
Model guidance continues to diverge on two separate areas of low
pressure that look to affect the region Wednesday and Friday. The
first system looks to affect the region on Wednesday. The GFS and
Euro depict this as a relatively qucik and weak wave of low pressure
pushing into from the Mid-South. The GFS remains further south into
North Carolina with the over track of the low and resultant
shortwave energy. The Euro is further north along the VA/NC line and
colder with a wedge similar to that of the Canadian and central
guidance. All 3 models are in good agreement though when it comes to
timing pushing the low toward the VA/NC coast fairly quickly late
Wednesday morning into Wednesday afternoon. FOr now kept a chance
Pops in play for region based upon model discrepancies in overall
location of the low.
High pressure returns overhead Thursday before retreating north into
the Ohio River Valley and Great Lakes region late. This opens the
door for another wave of low pressure that looks to eject out of the
southern Plains and Gulf Coast region Friday into Saturday. Once
again there remains subtle differences in the models based upon
timing and the placement of the low. Today`s 12z model suite
suggest a system that is further south of the region shunted away by
the northern stream and large 1034 mb high pressure acting as a
block from the eastern Ohio River Valley.
With that said precip would mainly be confined to North Carolina
during the Friday into Saturday timeframe as the low heads toward
the coast. The 12z Euro and Canadian solutions both depict this
while the GFS remains the aggressor keeping things wet at least for
the first half of the weekend. For now I have trended on the drier
side of things keeping Pops confined to the mountains where
northwest upslope flow will take over as the low kicks toward the
coast and cold air advection drains in.
High pressure sinks south into Sunday allowing for riding to build
for early next week. Temperatures will be at or slightly above
normal through the period with the exception of a cooldown come the
weekend ahead.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
As of 641 PM EST Saturday...
Poor flying conditions with a good degree of variability in
flight categories during the TAF period due to rain,low clouds
and fog.
MVFR and VFR conditions this evening will lower to MVFR/IFR
tonight with isolated LIFR, then some improvements expected
Sunday morning into Sunday afternoon. Periods of LIFR are
possible especially in the west with rain and fog.
Expect multiple waves of precipitation through the valid
period. The most likely sites to see best coverage/duration of
rain will be west of the Blue Ridge at KLWB and KBLF.
Precipitation will be more scattered in nature in the east.
Winds will remain light through tonight. By Sunday, guidance is
indicating potential for better mixing as the low level flow
amplifies. This may allow stronger winds to reach the surface so
will indicate some gusts Sunday afternoon.
Extended Aviation Discussion...
Prolonged periods of sub-VFR flight conditions will persist
into early next week. A frontal boundary/baroclinic zone will
persist from southwest to northeast across the area with a moist
Pacific-based southwest flow aloft. Numerous waves of low
pressure moving along the front, bringing periods of
precipitation, mostly in the form of rain. The rain will be
heavy at times.Some improvement in conditions is possible by
Tuesday. Drier weather is expected on Wednesday into Wednesday
night. Thursday will remain dry with warmer temperatures.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Flood Watch from Sunday afternoon through Monday morning for
VAZ007-009>014-018-022-023.
Flood Watch from 6 AM EST Sunday through Monday morning for
VAZ019-020-024.
NC...None.
WV...Flood Watch from 6 AM EST Sunday through Monday morning for
WVZ042>044-507-508.
&&
$$
SYNOPSIS...MBS
NEAR TERM...KK/MBS
SHORT TERM...AMS
LONG TERM...ET
AVIATION...KK/MBS
Area Forecast Discussion
National Weather Service Shreveport LA
944 PM CST Sat Feb 27 2021
.UPDATE...
Added Dense Fog Advisory to the overnight and lowered temps North.
&&
.SHORT TERM...
It has been solid with dense fog of 1/4 to 1/2 mile since sunset
from Idabel to El Dorado, but it appears we are on the fringe with
ground fog perhaps now lifting a bit. We will continue monitor
for improvement, but last to go will be the valleys as this warm
front edges northward. So another update to remove some of this
advisory has a little more optimism now, but the frontal boundary
did lose some ground last night so potential good news only if
the warmer air continues to arrive. Otherwise HRRR showing some
development of rain showers mainly along and north of I-30
overnight, spreading down into the I-20 corridor early tomorrow.
/24/
&&
.PREV DISCUSSION... /issued 629 PM CST Sat Feb 27 2021/
AVIATION...
For the ArkLaTex terminals the warm front is through all but
KTXK/KELD with a 5 degree jump last hr or 2 and looking for S
winds soon. Aloft we are S/SE 20-30KT at 1-2kft up. So this LIFR
may break for a short while this evening. However, more will dvlp
overnight. Lowering cigs and not so much vsby issues on this side
of the warm front with little in the way rain until Sunday late
ahead of our next cold front arriving late on Sunday aftn/eve. Sfc
winds shift to N, but SW aloft keeps with rain into Mon/Tues. /24/
PREV DISCUSSION... /issued 328 PM CST Sat Feb 27 2021/
SHORT TERM.../Tonight through Sunday Night/
The aforementioned warm front, currently located just north of
the Interstate 20 corridor, will continue to push northward
through the evening hours out of the region. Earlier convection
that developed north of the front has rapidly move northward
today, and is almost out of the region. Can`t rule out some
additional convection getting into our extreme NW zones, as
developing isolated showers/t-storms shift northeastward out of
North Texas. Elsewhere across the region, temperatures have warmed
into the 70s in wake of the frontal boundary. There has even been
a few breaks in cloud cover. A few warm air advection showers
have developed across our central and northeast Louisiana
parishes, but this activity should diminish by sunset. Expect low
clouds to return overnight with warmer temperatures areawide, as
overnight lows will range from the upper 50s north, to mid 60s
across our southern zones.
By Sunday, a longwave trough will dive SE through the Rockies and
into the Four Corners region on Sunday, before eventually closing
off Sunday night over southern New Mexico. The will allow for deep
SW Flow aloft to remain over the region through early next week. At
the same time, a cold front will drift SE into the region by midday
Sunday/Sunday afternoon and slowly push through the region by early
Monday morning bringing widespread convection to the region.
Although sfc instability is marginal with this system, effective
bulk shear is over 50 kts and there could be just enough elevated
instability and decent mid-level lapse rates for some hail and
high winds with elevated convection. There is also the potential
for additional heavy rains to fall across the region. With already
saturated areas of NE TX/SW AR from previous rainfall this past
week, minor flooding of low lying and poor drainage areas will be
possible. As of now, models suggest QPF will be just below flash
flood guidance, so will hold off on any flood watches at this
time. Warm and humid conditions are expected on Sunday ahead of
the front, with temps in the 70s areawide. Cooler conditions
expected by Monday morning in wake of the front, with post
frontal precip expected across the region. /20/
LONG TERM.../Monday through Saturday/
By Monday morning, the cold front should be exiting the region into
SE TX/Cntrl LA, although deep SW flow atop the shallow post-frontal
air mass will continue, ahead of a closed low that will enter NW TX.
Elevated isentropic forcing is expected to continue ahead of this
low Monday, thus continuing the post-frontal rains over much of the
region even as the low begins to open up into a more progressive
wave upon entering OK. Have maintained likely and categorical pops
over much of the area Monday and Monday night, with large scale
ascent increasing just ahead of the trough Monday night. Did taper
back max temps Monday afternoon from the milder NBM mainly along/S
of the I-20 corridor given the persistent rains and weak cold
advection, while also trending max temps Tuesday a bit cooler as
well to depict the slower movement of the low from the
ECMWF/Canadian than the more progressive GFS, which seems more
likely given the initial closed solution as it drifts E across OK/N
TX.
Drier air aloft will quickly entrain E beneath the departing trough
Tuesday afternoon, with sfc ridging over the Ozarks into ECntrl TX
building S into the region. This should set the stage for good
radiational cooling Wednesday night (assuming any lingering stratus
near and E of the MS River doesn`t advect back WSW into the area),
resulting in what should be the coolest temps expected through the
forecast period as min temps fall into the 30s to near 40 degrees.
This ridging will weaken as it drifts off to the E Thursday, as we
await the approach of another closed low that will shift E into the
Srn Plains late Thursday. A SW flow aloft will again develop ahead
of this approaching low, with a gradual increase in large scale
forcing resulting in the development of elevated SHRA, which would
have to saturate the air mass from the top down, given the weak low
level moisture advection expected to be in place. Have gradually
stepped up the pops for the Thursday timeframe, with chance pops
returning Thursday afternoon and especially Thursday night. Again
prefer the slower ECMWF/Canadian consensus than the more progressive
GFS, which clears the rains out about 12hrs faster. Thus, have
maintained chance pops into much of Friday, before drier air and
increasing subsidence taper the rains in wake of the attendant cold
front that enters the region late in the day. This front looks to
have little sensible effect on temps for late week into next
weekend, with readings near the seasonable norms. /15/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 66 77 51 54 / 10 60 90 80
MLU 68 78 52 55 / 10 40 90 80
DEQ 54 72 44 56 / 40 90 70 30
TXK 59 74 47 53 / 30 90 90 50
ELD 60 76 45 53 / 20 80 90 70
TYR 66 74 49 53 / 10 80 90 80
GGG 65 76 49 54 / 10 80 90 80
LFK 66 78 56 60 / 10 40 90 90
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Dense Fog Advisory until 9 AM CST Sunday for ARZ050-051-059>061-
070>073.
LA...None.
OK...Dense Fog Advisory until 9 AM CST Sunday for OKZ077.
TX...Dense Fog Advisory until 9 AM CST Sunday for TXZ096-097.
&&
$$
24/20/15
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
830 PM MST Sat Feb 27 2021
.UPDATE...
Issued at 830 PM MST Sat Feb 27 2021
Current surface analysis shows low pressure over southeastern NE,
with a frontal boundary across northeast WY and southern SD and weak
low pressure along it east-southeast of the Black Hills. Upper
level analysis shows broad trough covering the Rockies and high
Plains, with embedded low pressure now noted over far southwest
SD. A fairly compact area of snowfall associated with the upper
low is now located from far northeast WY to the Black Hills,
southern SD and far northern NE. Some bands of moderate to heavy
snowfall, likely producing an inch or more an hour, are noted over
parts of the area, especially over the northeastern Black Hills
and foothills, as well as east of the Black Hills, just north of
the main circulation. Temps are mostly in the 20s with northerly
winds picking up some across western SD.
Changes to the forecast, including snowfall amounts, are
mostly minor, but enough to make some adjustments to headlines.
The radar trends with the heavier snowfall have been a bit further
north across the area. Much of the northern Black Hills may be on
the lower end of potential snowfall, but at least a few areas
should see 6 inches or more, especially the northeastern slopes.
Some areas to the east of the Black Hills where heavier snowfall
has persisted early this evening will likely reach 6 inches,
especially in southern Meade, far eastern Pennington, and portions
of Jackson County. Have upgraded these areas to a winter storm
warning with new forecast totals of 4 to 7 inches. Snowfall still
looks like it will taper off fairly quickly from west to east
overnight as the upper low weakens and the system speeds up a bit.
&&
.DISCUSSION...(This Evening Through Saturday)
Issued at 134 PM MST Sat Feb 27 2021
Upper-level trough axis is over the Rockies, with a baroclinic
leaf evident on water vapor imagery. This feature is pushing into
the northern plains, while low clouds/fog cover ND and the
northern portion of our CWA. Radar shows bands of precip from SW
to south central SD, lifting northward, and some echoes are
appearing near the northern Hills. Surface map shows low pressure
over eastern WY and also southeastern CO; winds across the CWA are
northeasterly, around 10-15 kts. Temperatures range from the 20s
across northwestern SD to the mid 40s across south central SD.
Upper wave will cross the region today/tonight, with best PVA
sliding along the SD/NE border. As the 700 mb low briefly closes off
across SD/NE this afternoon/evening, precipitation will expand
across the southern 2/3 of our CWA. Expecting most precip to fall as
snow (except for some rain mixed in across south central SD early)
as cooler air moves in today, along with effects of easterly flow
and evaporative cooling. Still expecting some upslope enhancement
over the northern Black Hills: NAM Froude is greater than 1
briefly this afternoon before falling below 1, while HRRR Froude
indicates supercritical flow this afternoon, but then is 1-2
overnight. Froude for RAP looks similar to that of yesterday, with
some upslope enhancement possible this afternoon/evening as winds
become northeasterly and breezy. Snow amounts across the
northeastern foothills will depend greatly on the extent to which
upslope enhancement develops. Additional snow maxima will be
possible in any banding that develops, anywhere from the Black
Hills region to south central SD, coincident with the areas of
best lift within the dendritic growth zone. A favored area agreed
upon by several models is around the Oglala Lakota/Bennett/Jackson
counties, where current band of snow is this afternoon, and also
where the swath of snow to the northwest of the low will wrap
around and slide southeastward overnight. NAM/GFS are now placing
the best frontogenesis farther eastward, across southeastern SD.
Snow will end early Sunday morning as best forcing and moisture
exit the area.
QPF varies across deterministic solutions, with maxima ranging from
around a quarter inch in the 12Z ECMWF to over an inch from the 12Z
GFS. Both the Canadian and NAM have a half to three-quarters of an
inch QPF total across the favored northern Black Hills to Oglala
Lakota/Jackson areas. Some also bring heavier amounts into south
central SD. WPC QPF looks like a reasonable forecast based on these
solutions. As would be expected, snow amounts also vary greatly for
the aforementioned deterministic models. Hi-res solutions depict
over a foot of snow in varying locations across the CWA. With the
potential for banding to greatly increase snow in one area versus
another nearby area, not surprising that ensemble spread is high for
this near-term event. For example, 12Z GEFS plumes show 1 to 10
inches possible for KRAP, with the mean around 6 (increased from 5
in the 06Z run); however, the 12Z SREF snow amount plumes indicate
up to 7 inches possible, mean less than 2. Wouldn`t be surprised
if the 12Z ECMWF ensemble keeps its low snowfall forecast - the
00Z run gives KRAP about one inch of snow.
Latest snowfall forecast has slightly increased amounts, shifted
slightly southward. Still looks like the northern Black Hills could
receive 6-9 inches of snow. Places that could see up to 6 inches of
accumulation include the northern/eastern foothills and the Oglala
Lakota/Jackson/Bennett areas. Considered adding the Spearfish
foothills zone to the warning, but confidence is not high that
upslope enhancement will result in warning criteria snow over much,
if any, of that zone. Also considered adding Fall River to the
advisory to match neighbors, but forecast snowfall amounts in that
downsloped area are marginal, and even lower across the southern
foothills. Northeastern WY is also marginal. Timing, area, and type
of headlines look good for now.
Upper trough will continue moving out of the region Sunday, as upper
ridging builds over the west coast. A couple of upper lows will
slide across the southern states this week, but upper ridging will
dominate our weather pattern. Dry weather and a warming trend are
expected for the next week. Due to forecast snowcover, lowered highs
across the southern 2/3 of the CWA Sunday to the 30s; some lower 40s
will be possible across the north. Temperatures will warm into the
40s on Monday, and most places will see 50s on Tuesday. A Canadian
shortwave will flatten the upper ridge Tues/Wed, but besides some
breezy winds, should have little effect on our mild/dry weather.
Upper ridge restrengthens towards the end of the week. As the upper
ridge axis slides over the northern plains Fri/Sat and low-level
flow becomes southwesterly, expecting temperatures to warm further.
NBM box/whisker plots show the possibility of 70+ degree
temperatures next weekend. Warmed temperatures slightly to account
for NBM cold bias, but kept temps in the 50s/60s for now.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening)
Issued At 446 PM MST Sat Feb 27 2021
Snow and MVFR/IFR conditions can be expected across a good
portion of northeast WY, southwest SD, and into south central SD
this evening. Some LIFR conditions in bands of moderate to heavy
snow can be expected across these areas well, especially southwest
into south central SD. MVFR conditions and areas of light snow
can be expected across northwest SD, with little or no snow across
far northwest SD. Conditions will gradually improve from west-
northwest to east-southeast after 06z, with snow ending by 12z or
so over south central SD. VFR conditions can be expected on
Sunday.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 11 PM MST this evening for SDZ025-
028-029-072.
Winter Weather Advisory until 5 AM MST /6 AM CST/ Sunday for
SDZ026-030>032-042>044-046-047-049-073-074.
Winter Storm Warning until 11 PM MST this evening for SDZ024.
WY...Winter Weather Advisory until 11 PM MST this evening for WYZ057.
&&
$$
Update...26
DISCUSSION...Pojorlie
AVIATION...26