Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/30/19
Area Forecast Discussion
National Weather Service Grand Rapids MI
643 PM EST Sun Dec 29 2019
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 341 PM EST Sun Dec 29 2019
- Areas of dense fog into tonight
- Heavy rain with some localized nuisance flooding possible
tonight and Monday morning
- Strong winds with snow Monday afternoon into Tuesday
- Rain and snow possible by the end of the week
&&
.DISCUSSION...(This evening through next Sunday)
Issued at 341 PM EST Sun Dec 29 2019
-- Areas of dense fog into tonight --
With abnormally high sfc dew points and abundant low level
moisture/light winds this afternoon and evening, dense fog has
started to form especially east of I-69. This threat may linger
into tonight prior to precipitation onset and could form just
about anywhere north of the sfc warm front (located across
southern Lower MI at this time).
-- Heavy rain with some localized nuisance flooding possible
tonight and Monday morning --
Multi-radar, multi-sensor (MRMS) rainfall estimates from earlier
today show round 1 of this storm`s precipitation produced
generally 0.50"-0.75" across the region with a swath of
0.75"-1.25" across west central Lower Michigan. Unfortunately,
much more rain is on the way tonight as has been well advertised.
Probabilities are high that most areas will get another inch or
more of rain by 18z Monday as a new low rapidly deepens across
IN/OH and moves into Michigan Monday morning.
This low is now forecast to be a bit further east than
yesterday`s model guidance indicated and that will bring the
heaviest swath of rain right over western and central Lower
Michigan. Some of the high resolution CAMs are running pretty hot
with this second round, with some solutions (eg. HRRR and 2.5km
Canadian) showing an additional 2" of rain in swaths especially
near and east of a line from Big Rapids to Grand Rapids and toward
the US 127 corridor. Regardless of exact amounts, minor flood
impacts across roadways and other nuisance flooding problems are
likely given the current extreme soil moisture and antecedent
conditions. One of the tipping points for a Flood Advisory is how
much rain we are expecting to fall in a 6-8 hour period. We are
looking at potentially an inch or more of rain in a very short
period for this time of year. The ground has no more room to take
in water at this point, hence travel impacts (hydroplaning risk,
flooded intersections, etc.) may materialize overnight and into
Monday morning. The area we are most concerned with is near/north
of a Holland to Lansing line.
-- Strong winds with snow Monday afternoon into Tuesday --
12z model guidance has caught our attention with regard to
potentially higher impact wind gusts than originally thought. Of
first interest will be the immediate cold advection on the back
side of the deepening low across south central Lower Michigan
early Monday morning. While several HRRR runs have been off the
charts with some surface wind gusts across the US 127 corridor
(occasionally over 80 mph from Jackson to Lansing from 09z-12z
Mon) we do not believe this is realistic and may be a byproduct of
the model over-deepening the low and simulating winds that are too
high 1k-2k ft off the ground. However, with the Euro ensemble
members jumping on board with a high wind threat across the same
region (especially east of US 131 from 09z-12z Mon) we are
more concerned now.
The ensemble mean wind gust at JXN for 12z Monday is 55 mph and
for LAN it is 58 mph. Thus we are anticipating a swath of 55-60
mph wind gusts to surge into south central Lower Michigan as the
sfc low deepens overhead, bringing with it a threat for power
outages on the morning of New Year`s Eve. Wind gusts of 40-50 mph
may also stretch all the way west toward Lake Michigan early
Monday morning. Once we are entrenched in cold air advection
Monday afternoon/evening, wind gusts hold up in the 35-45 mph
range with gusts to 50 mph along the lakeshore. Scattered power
outages may continue to be a problem throughout the day.
For the winter aspect, things look on track and if anything we
have bumped up snow totals a bit. The hardest hit areas look to be
east of the immediate lakeshore given the wind speeds smearing
lake enhanced bands of snow inland, but coastal locations will
still accumulate. Totals will likely reach 3"-7" near and west of
US 131, with some local amounts over 7" possible. East of this
region, a general 1"-3" is expected even as far east as US 127.
Model snow water equivalent has consistently been in the
0.30"-0.50" range for the snow portion of the system. Using our
Bufkit snow tool with various models yields the 3"-7" forecast we
are currently running with for the hardest hit areas. Heavy snow
rates can be expected prior to and right during the Tuesday
morning commute when an inch or more per hour is possible. Surface
temperatures at or below freezing combined with steady snow will
cause slick travel and delays.
We have decided to combine the snow and wind impacts into one
Winter Weather Advisory product as opposed to two. We will
already be lighting up the map with a Lakeshore Flood Advisory and
areal Flood Advisory, so condensing the Winter and Wind headlines
into one is favored to avoid over complicating our WWA system.
-- Rain and snow possible by the end of the week --
Models continue to indicate a threat for both rain and snow by the
end of the week. If anything our confidence is increasing a bit
but significant impacts are not expected at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 643 PM EST Sun Dec 29 2019
Areas of LIFR in dense fog and low stratus should transition to
IFR in moderate rain later this evening. The rain will slowly
transition to snow on Monday as colder air moves in. Southwest
winds will increase to over 20 knots on Monday morning with gusts
to 40 knots possible.
&&
.MARINE...
Issued at 341 PM EST Sun Dec 29 2019
High wave action of 9 to 11 feet Monday into Tuesday will lead to
minor lakeshore flooding and erosion given the long duration
expected. Some of the more vulnerable coastal sections across
Muskegon, Ottawa, and Allegan Counties are most at risk for
erosion given the wind direction and longevity of 9 to 11 foot
waves hitting the shoreline. Conditions improve Tuesday night.
&&
.HYDROLOGY...
Issued at 341 PM EST Sat Dec 28 2019
Basin average rainfall amounts were 0.50"-0.75" for the Grand
River and 0.50"-1.00" for the Muskegon River basins earlier this
morning. An additional basin average of 1.00" or more for both
basins is expected overnight. Rivers will surge higher and could
come close to flood stage. Small rivers and streams, especially
near/north of Holland to Lansing, may flood. This could cause
nuisance flood impacts to adjacent properties. Overall, the
Muskegon River is the most likely main stem river to get near
flood stage. At this time we are not forecasting crests above
flood stage, however. As a result, significant flood impacts to
properties are not anticipated along the Muskegon River.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory from 4 AM Monday to 7 PM EST Tuesday for
MIZ037>040-043>046-050>052-056>059-064>067-071>074.
Lakeshore Flood Advisory from 7 AM Monday to 7 AM EST Tuesday
for MIZ037-043-050-056-064-071.
Dense Fog Advisory until midnight EST tonight for MIZ059-066-067-
074.
LM...Gale Warning from 7 AM Monday to 7 AM EST Tuesday for LMZ844>849.
&&
$$
SYNOPSIS...Hoving
DISCUSSION...Hoving
AVIATION...Ostuno
HYDROLOGY...Hoving
MARINE...Hoving
Area Forecast Discussion
National Weather Service Jacksonville FL
701 PM EST Sun Dec 29 2019
...SEA FOG OVER THE SOUTHEAST GEORGIA WATERS...
.NEAR TERM [Through Tonight]...Shower activity has decreased over
ne Fl/se Ga and will likely increase after midnight as showers
develop and approach from the west ahead of a cold front. Dense
fog was reported at SSI and have issued Dense Fog Advisory for
coastal Camden/Glynn counties and adjacent marine zones. HRRR and
SREF models have been showing coastal fog with dewpoints above
water temperatures producing conditions for sea fog development.
Expect conditions to improve around 13z-15z Monday as SSE winds
become SSW. Weak elevated instability shown by models may result
in isolated thunder late tonight as upper trough approaches from
the west. Cold front will move across the area on Monday bringing
showers and isolated thunderstorms. Vertical wind shear will be
strong but lift and instability will be weak for severe weather.
&&
.AVIATION...[Through 00Z Tuesday]
Conditions have improved to VFR this evening as showers have
decreased over the area. Expect lowering to IFR/MVFR cigs/vsbys
again tonight after 04z with shower activity increasing. Dense
sea fog in vicinity of SSI will likely produce LIFR/IFR
conditions til around 14z. South-southeast winds tonight will
become southwest tomorrow morning ahead of cold front.
&&
.PREV DISCUSSION [231 PM EST]...
.SHORT TERM [Monday Through Tuesday Night]...
Showers and isolated thunderstorms will move across the forecast
area on Monday and, while the chances for severe weather
developing on Monday are low, the potential for deep layer shear
can persist through into Monday morning resulting in a potential
for wind gusts upwards of 40-55mph in association with stronger
storms. Following the passage of the cold front late Monday
night, cool air and dry conditions will settle in over the area
leading to clear skies on Tuesday, with high pressure becoming
the dominant feature for New Year`s Eve. Temperatures will
noticeably cool next week after the front has completed its
passage across the region, with max temps dropping from out of
the 70s and 80s on Monday down into the 60s on Tuesday. Overnight
low temperatures will reach into the 40s and 30s as the cold air
mass settles in, with the coolest temperatures occuring on
Tuesday night heading into early Wednesday morning.
.LONG TERM [Wednesday Through Sunday]...
High pressure conditions continue on into New Year`s Day with
cool temperatures and clear skies. Starting Thursday, high
pressure over the region will begin to weaken and move off
towards the east. This will lead to a shift in the prevailing
flow to becoming more out of the southwest, resulting in an
influx of warm moist air over southeast Georgia and northeast
Florida. This will lead to rainy conditions by the end of the
week, ahead of the next cold front that is expected to push
through from out of the west on Friday and Saturday. Temperatures
will increase towards the end of the week prior to the next
frontal passage, with max temps rising from out of the 60s on
Wednesday up into the 70s by Friday. Overnight low temperatures
will similarly rise from out of the 40s into the upper 50s and
low 60s, with temps dropping after the next frontal passage.
.MARINE...
High pressure will build to the east this afternoon and then
southeast tonight. A cold front will move southeast across area
Monday. High pressure will build from the west Tuesday, then
overhead Wednesday. The high will move to the east Thursday into
Friday, as a cold front crosses from the northwest Friday night
into Saturday.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 65 72 42 59 38 / 40 30 0 0 0
SSI 64 72 46 61 42 / 30 40 10 0 0
JAX 67 77 46 64 41 / 30 30 10 0 0
SGJ 68 76 49 64 44 / 50 30 10 0 0
GNV 67 77 48 64 41 / 30 40 10 0 0
OCF 68 78 50 66 43 / 40 40 10 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...Dense Fog Advisory until 9 AM EST Monday for Coastal Camden-
Coastal Glynn.
AM...Dense Fog Advisory until 10 AM EST Monday for Coastal waters
from Altamaha Sound to Fernandina Beach FL out 20 NM.
&&
Area Forecast Discussion
National Weather Service North Platte NE
609 PM CST Sun Dec 29 2019
.UPDATE...
Issued at 606 PM CST Sun Dec 29 2019
The Winter Storm Warning continues through 6am CST Monday for
eastern Cherry, Keya Paha, Brown, Rock, Boyd, and Holt Counties.
Elsewhere, have allowed the Winter Storm Warning to expire given
the threat for accumulating snow has ended and improving
visibility across the area.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 320 PM CST Sun Dec 29 2019
There are two main concerns this period. The first is additional
snowfall pops and amounts. Have lowered the pops for the remainder
of the afternoon into evening across southwest Nebraska, as
isentropic lift is a lot weaker in this area and there has not
been really much development across southwest Nebraska. Did
increase snow amounts slightly across portions of north central
Nebraska, mainly eastern Cherry County down towards Lincoln
County. Still a concern for light to moderate snowfall in this
area the rest of the afternoon into the evening.
The next area of concern is with the winds. Wind gust this
afternoon were above 50 mph across several locations including
Valentine, Imperial and North Platte. Forecast continues to trend
with NAM and HRRR forecast soundings with wind speeds 45 to 50 kts
near the 850mb layer mixing down to the surface. The highest wind
gust will occur this afternoon into this evening mainly before
midnight. Winds will remain high through the overnight into
Monday. Winds will gradually decrease late Monday afternoon and
evening. Blowing snow will remain a concern especially across
north central and portions of central Nebraska where heaviest snow
has fallen. Also to note, wind chills tonight will dip into the
single digits.
.LONG TERM...(Tuesday through Sunday)
Issued at 320 PM CST Sun Dec 29 2019
Temperatures remain mostly in the 30s and 40s through the rest of
the forecast period. The next chance for precipitation arrives New
Year`s evening and overnight into Thursday. At this time,
precipitation chances look minimal.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 552 PM CST Sun Dec 29 2019
For tonight, the strong storms system will continue to bring
strong northwest winds and areas of light snow tonight. At KVTN,
NW winds will gust as high as 45KT through mid evening with
1 1/2SM -SN BLSN, then up to 40kt overnight and 3sm BLSN overnight.
VFR ceilings expected. At KLBF, NW winds will gust around 35KT
tonight into Monday. VFR ceilings expected.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 AM CST /5 AM MST/ Monday for
NEZ005>010.
&&
$$
UPDATE...Jurgensen
SHORT TERM...Gomez
LONG TERM...Gomez
AVIATION...Roberg
Area Forecast Discussion
National Weather Service Marquette MI
651 PM EST Sun Dec 29 2019
.NEAR TERM...(This evening and tonight)
Issued at 422 PM EST SUN DEC 29 2019
The heavier rain from earlier today has exited the area with mainly
fog and drizzle remaining over the area as dry mid level air has
overspread Upper Michigan. Little change in the weather conditions
is expected through the evening with dry air and subsidence in the
mid levels remaining over the area.
The big story will be the next round of precipitation associated with
a rapidly developing area of low pressure. Water vapor imagery this
afternoon indicated a baroclinic leaf starting to form over Arkansas
as the shortwave has begun to lift north. Fairly rapid cyclogenesis
will take place though the evening hours with the surface low
centered over Ohio by late tonight.
&&
.SHORT TERM...(Monday through Tuesday night)
Issued at 422 PM EST SUN DEC 29 2019
Water vapor satellite shows depicts well the high amplitude upper
level trough over the central U.S., the river of deep moisture
streaming northwards through the Midwest into the Upper Great Lakes.
In addition, it shows the next short wave moving through the trough,
currently digging into south Texas. The overall synoptic picture for
tonight and tomorrow hasn`t changed; this wave is still expected to
round the base of the trough and then lift northeastward across the
Mississippi Valley, spinning up a surface cyclone over lower
Michigan early Monday morning and then driving it quickly north into
the eastern U.P. by Monday afternoon. The whole region will see
precip from the initial surge of theta-e advection in the morning.
This looks like it will start as some freezing rain over the
interior east. Kept temps right around 32 so ice accums are limited
to around 0.1" for now but it`s possible that they end up with 0.25"
or even more. ZR seems believable since an ENE wind out of Ontario
often helps reinforce low-level cold over the east. Temps will be
critical tonight so this forecast may need an evening update.
After this initial slug of WAA precip, focus turns to the developing
fgen band/commahead. It is still expected to cover most of the U.P.,
but there has been a slight trend east with the strongest fgen late
morning into the afternoon (identified well by the 700 mb fgen) with
the morning model runs. It`s now possible that it sets up just east
of Marquette. The 12z NAM still parked it right over Marquette and
the extended range HRRR still has it over the western U.P., but the
hot-off-the-presses 18z NAM did shift east as well.
Not only is this forecast an issue of where the fgen band sets up
and pivots, but it also matters how much precip ends up getting
wrung out of it in the heavy band. The NAM is an outlier on QPF, but
the convective signal is there so this is one of those cases where
it may be prudent to not write it off immediately. A NAM xsec from
NW to SE is classic for very heavy snow with strong fgen tilted
towards the cold air. There is -EPV in the 700-500 mb layer, and
even some folding over the saturation isentropes indicating pockets
of elevated CAPE (and plenty of CSI where they`re not folded over
but vertical enough for geostrophic momentum surfaces to show a
temporary negative change with height in theta-e*). So we have
strong forcing, instability, and anomalously high moisture amounts
(PWATs of about 0.75" would be near-record for the combined
APX/Sault Ste Marie sounding climo) so it`s definitely believable
that the NAM`s QPF could end up verifying.
And then there`s the contributions from lake enhancement and upslope
flow. The NE low-level flow becoming N and then NW as cold air wraps
into the developing cyclone means that the favored upslope/LES belts
should do well regardless of the exact placement of the fgen
band/commahead.
By Monday night, the now filling low will be spinning overhead with
a combination of lake-effect and synoptic snow showers persisting
across most of the area through the night. Contrary to earlier in
the storm, by this point the DGZ will be thicker and much closer to
the surface, so expecting SLRs in the 15:1 to 20:1 range - closer to
typical LES values. Because of the cyclonic flow centered overhead,
it looks like an unusual case Monday night where there will be LES
ongoing in both the NW wind belts of the west, and off of Lake
Michigan into southeast Schoolcraft County and Luce County. Dry air
works in from west to east late Tuesday, bringing an end to the lake-
effect snow.
As for storm impacts... have to say I`m a little concerned that the
very heavy/wet snow on top of the trees and power lines that already
have ice on them from today may lead to more widespread power
outages than previously thought. Regardless, this will be heavy wet
"heart attack" snow that will be very difficult to shovel. It will
also make a mess of the roads as it accumulates perhaps 1-3" per
hour for a period from morning through afternoon. Travel is strongly
discouraged across the area tomorrow.
.LONG TERM...(Wednesday through Sunday)
Issued at 422 PM EST SUN DEC 29 2019
The main focus of the forecast has been on the near term with the
complex weather system moving though the area tonight into
Tuesday. Mainly went with the blended model solution for the long
term. There are varying solution for late week with some models
bringing another storm system though the area. While models don`t
agree well on the details it does look like colder air could
arrive late next weekend bringing temperatures back towards
average or possibly below average.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 651 PM EST SUN DEC 29 2019
LIFR conditions will mostly prevail thru this fcst period at
KIWD/KCMX/KSAW. Only exception should be at KIWD this evening as
downslope component to the wind may work to hold conditions at IFR.
Conditions may be blo landing mins at times at KCMX/KSAW. There will
be some -dz or perhaps a -shra thru the evening. Later tonight and
Mon, a vigorous disturbance and deepening low pres will lift thru
Lower MI and toward eastern Lake Superior. Rain will develop
overnight, then quickly change to +SN Mon morning at all terminals.
Expect conditions blo landing mins at all terminals for a number of
hrs during the period of heaviest snowfall. Some slight improvement
will occur during the aftn hrs at KSAW/KCMX.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance) Issued
at 422 PM EST SUN DEC 29 2019
Winds over the western arm of Lake Superior have been
decreasing this afternoon as the surface low over central MN is now
weakening. Have replaced the Storm Warning with a Gale Warning to
cover the period of gales through this evening, thereafter winds
will fall below gale. Meanwhile the next surface low pressure has
been taking shape over Arkansas and will track rapidly north tonight
bringing increasing east to northeast winds to much of Lake Superior
with gales over the eastern two thirds of the lake by Monday mid
morning. Have extended the Gale Warnings through Monday but it
should be noted that there will be a period tonight where winds will
be less than gale. Winds get complicated on Monday night as a tight
surface low drifts over eastern Lake Superior. This will bring
strong northeast gales and possibly a few gusts to storm force over
the central areas. Over the east, close to the low pressure center,
winds will fall to around 25 knots or less but vary significantly in
direction and speed as the low drifts southeast Monday afternoon
through Tuesday morning.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Storm Warning from 7 AM EST /6 AM CST/ Monday to 1 AM EST
/midnight CST/ Tuesday for MIZ001>006-009>014-084-085.
Lakeshore Flood Advisory until 10 PM EST this evening for MIZ001-
003.
Winter Storm Warning from 1 AM Monday to 1 AM EST Tuesday for
MIZ007.
Lake Superior...
Gale Warning until 7 PM EST Monday for LSZ265>267.
Gale Warning until 10 AM EST /9 AM CST/ Tuesday for LSZ241>244-
263-264.
Gale Warning until 7 PM EST this evening for LSZ245>251.
Gale Warning until 11 PM EST /10 PM CST/ this evening for LSZ162.
Lake Michigan...
None.
&&
$$
SHORT TERM...RJC
LONG TERM...NL
AVIATION...Rolfson
MARINE...NL
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
816 PM EST Sun Dec 29 2019
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
Big picture, not much change from the thinking in the previous
discussion. Latest HRRR and RAP trends still consistent with
previous runs. Not a whole lot of excitement with this first wave
of showers but don`t let your guard down as our window of main
concern will be from roughly 02z through 06z. This is when the
best dynamics will be in place as the trough axis swings through
and the LLJ is at its peak. Also, this is the window in which the
RAPP is still showing SBCAPE values increasing over the central
and southern Cumberland Plateau as well as across the southern TN
Valley. We have the shear and dynamics moving into place: We are
just waiting on the CAPE. In these HSLC, high shear low cape,
environments it doesn`t take much CAPE. Main threats that we are
still focused on is an isolated, weak, tornado or two and isolated
flash flooding. Again, our main window of concern is still to
come but will end around or shortly after 06z. Isolated damaging
wind gusts still possible area-wide as any heavier showers could
potentially transfer stronger winds aloft down to the surface. It
would`t surprise me to see a few trees come down with showers of
higher DBZs and no associated lightning.
Main update to the forecast was to further refine the hourly POPs
through the rest of the night. Also had to adjust hourly temps
quite a bit as previous forecast had them falling too quickly.
Will send out new zones.
SR
&&
.AVIATION...
00Z TAF DISCUSSION.
First wave of showers entering the southern TN Valley now and
will soon affect CHA. CHA will go back to MVFR once the showers
move in. TYS will stay VFR but could go MVFR as showers move
through, not confident enough to include in TAFS though because
of downsloping winds. TRI will stay VFR until the downsloping
winds subside with the 850 MB wind shift from southerly to west-
southwest then go MVFR. Winds will be gusty at all sites with
gusts from 20 kts to 30kts at times. All sites will be near LLWS
criteria now through 09Z but not confident enough to include in
TAFS. Moisture quickly clears behind the front with skies going
SCT at all sites but gusty winds remain through the period.
&&
.PREV DISCUSSION...
/ISSUED 327 PM EST Sun Dec 29 2019/
SHORT TERM...(This Evening through Monday)...
Active weather pattern the next 18 hours due to a strong upper
jet moving northeast from the lower Mississippi valley into the
Tennessee/Ohio valleys this evening and tonight. This jet streak
is inducing surface cyclogenesis over Mississippi. This low will
move across northern Alabama, middle Tennessee into Kentucky.
The associated pre-frontal trough and cold front (enhanced by the
upper jet dynamics) will sweep across this evening through early
Monday morning. The associated strong southerly low-level jet has
already pulled dewpoints into the middle 60s across southeast
Tennessee. Temperatures across the northern and central valley
have increased in the middle 70s due to downslope winds into the
valley.
Model soundings and HREF show MLCAPEs of 100-400 J/Kg with the
greatest instability over the Plateau and southeast Tennessee
between 01-06Z. Low-level (0-3km) CAPES increase to around 25-40
J/Kg which is marginal enough for updraft strength. Very strong
low-level jet will produce a high shear environment with 0-1km of
45-50kts and effective shear of 55-65kts. Given this environment,
can not rule out an isolated tornado with the main threat being
the Plateau and southeast Tennessee where STP values of 1 to 1.5
is noted.
Besides the isolated tornado threat, the strong low-level 850mb
jet combined with marginal instability may be pull damaging winds
to the surface as a line of convective moves across the area.
Given the expected speed of the system, the brief heavy rain will
not be located at one location very long limiting amounts. The
threat for flooding has diminished.
Due to the strength of the low level jet, will continue with the high
wind warning through early Monday morning. For the rest of the
area (including the valley), due expect periods of windy
conditions with southerly winds of 15 to 25 mph with gusts to 40
mph possible, especially ridge tops.
For late tonight/Monday, dry air quickly advects into the region
clear sky. Still fairly tight pressure gradients will produce
breezy conditions tomorrow with cooler temperatures but still
pleasant for late December.
Long Term...(Monday night through Sunday)...Models in decent
agreement to start, with some weak short wave energy rotating around
the Great Lakes Region upper low bringing some clouds at least to
northern parts of our area. However, Monday night through Wednesday
should be dry across our area with seasonable temperatures.
By Thursday another mid/upper level trough will be shifting east out
of the Plains with a surface low tracking northeast toward the Great
Lakes Region. A cold front will push through our area most likely
around the Friday/Friday night time frame. We will see rain
spreading back across the area, and the most concentrated period of
rain looks to be late Thursday into early Friday. While it is still
early, there appears to be at least some potential for heavy
rainfall/localized flooding with this system so will keep the
mention in the HWO for now.
Models are in poor agreement for the end of the period, with the GFS
wanting to keep more energy hanging back and keeping the possibility
of some rain or snow showers for the weekend, while the ECMWF has a
drier solution with the main energy shifting quickly eastward. For
now will carry some low PoPs Saturday and Saturday night with a dry
Sunday, but forecast confidence is low at this point for the
weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 47 57 35 51 32 / 80 0 0 10 0
Knoxville McGhee Tyson Airport, TN 50 57 35 49 31 / 70 0 10 10 10
Oak Ridge, TN 47 55 35 48 31 / 80 0 10 10 10
Tri Cities Airport, TN 50 57 31 45 29 / 60 10 10 10 10
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...High Wind Warning until 4 AM EST Monday for Blount Smoky
Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
Mountains-Southeast Carter-Southeast Greene-Southeast
Monroe-Unicoi.
VA...NONE.
&&
$$
Area Forecast Discussion
National Weather Service Nashville TN
741 PM CST Sun Dec 29 2019
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Latest model guidance and the last several runs of the HRRR
suggest nearly all of the precipitation will have moved east of
Middle Tennessee, including the Cumberland Plateau, by 06Z, with
only a few light stragglers hanging around afterwards. Have
massaged the hourly grids to move the rain out a little earlier
than previously forecast. Otherwise, ongoing flooding is occurring
across several locations. The strongest cells are currently
affecting the Upper Plateau and also areas south of Murfreesboro.
The line of mainly light showers just now crossing the Tennessee
River appears to be the last gasp for this weather system. The
cold front is now east of Nashville, but has not yet reached
Crossville.
&&
.AVIATION...
00Z TAF DISCUSSION.
BNA/MQY/CKV/CSV...An area of heavy showers is barreling through
Middle Tennessee as we head into the evening, with the heaviest
cells forming a line just ahead of the surface front. The HRRR
shows the rain ending from west to east rather quickly during the
evening, with ceilings improving to VFR by 12Z. Winds will remain
gusty throughout the night and tomorrow morning, then diminishing
during the afternoon. Low-level jet remains quite strong, so we`ll
leave some LLWS remarks in the 00Z TAF`s where applicable.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......08
AVIATION........08
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
905 PM EST Sun Dec 29 2019
.SYNOPSIS...
A cold front will move across the Appalachians tonight and cross the
state on Monday, bringing scattered showers and isolated
thunderstorms. Behind the front, colder air will move into the
region before the chance of rain returns Thursday afternoon.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 905 PM Sunday...
Evening update: Just minor tweaks to POPs this evening as the
primary batch of warm sector rain is moving through the eastern
Piedmont and coastal plain. Radar trends and HRRR sim ref suggest a
lull in measurable precip for most of the overnight period, though
patchy drizzle will likely continue, especially over the NW
Piedmont. The convective line over central TN/AL will continue to
weaken as it moves into the southern Appalachians, with the
effective front not forecast to reach the western Piedmont until
after 12Z. Prefrontal temps will remain very mild in the mid and
upper 60s. -Smith
Previous discussion: A stacked vertical low currently sits over
southern Minnesota, with multiple fronts extending out from the
center. Another surface low is expected to develop down near
Louisiana along a cold front and move north overnight. This second
surface low over Michigan will become the dominant surface low by
Monday morning, with the energy from the upper low also transferring
east.
The cold front, currently across Tennessee, will slowly push east
overnight, reaching the Appalachian Mountains by morning. While rain
coverage has not been as widespread as expected, rain will move
northeast into the region during the afternoon and evening hours.
The eastern edge of likely pops extends to the Triangle and
Fayetteville, with locations farther east only having a chance of
rain overnight. Rainfall amounts will be light, with less than a
quarter inch expected overnight. Temperatures will not follow a
diurnal curve tonight; in fact, they should remain nearly steady
overnight with all locations remaining in the 60s.
&&
.SHORT TERM /MONDAY THROUGH MONDAY NIGHT/...
As of 310 PM Sunday...
The cold front will move even more slowly tomorrow, only moving
offshore tomorrow evening. In the meantime, rainfall coverage is
expected to drop overall with the best dynamics continuing to
transition well north of the area. However, a narrow line of showers
and thunderstorms is still expected with the cold front itself. Have
stuck with likely pops in the morning across the western half of the
forecast area, but switched to scattered coverage during the
afternoon. In addition, over the last 24 hours have noticed that
model soundings continue to show increased values of instability
along with favorable wind shear profiles. Have added isolated
wording for thunder across all areas, and while it`s not explicitly
represented in the forecast, think that the best chance for
thunderstorms will be across the east due to increased heating
through the day. While locations in the Triad will remain nearly
steady for another 12 hours with temperatures in the 60s, locations
from the Triangle south and east should rise into the low to mid 70s.
With the front passing by Monday evening, skies will clear and
colder air will spill into the region, with low temperatures 20 to
25 degrees colder than tonight, ranging from the mid 30s to the mid
40s.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
As of 232 PM Sunday...
Looks like 2019 will end and 2020 will begin with pleasant dry and
warm weather thanks to westerly flow and a sfc high set to slide
across the Carolinas during the midweek period. Temps will average
about 5-10 deg above normal (both highs and lows) Tuesday and
Wednesday.
On Thursday both the sfc high and ridge axis aloft will slide east
as a longwave trough moves east across the middle of the country.
Ahead of the trough, moisture will advect from the GOM toward our
area thanks to deepening/increasing S/SW flow. As such, look for
increasing cloudiness during the day Thursday, with the said SW flow
aloft resulting in overrunning/WAA light precip developing from SW
to NE across our area as the afternoon and evening progresses. A
subsequent cold front, and it`s assoc precip will arrive either
Thursday night or Friday as the longwave trough moves across the
Great Lakes and pushes the front eastward (GFS is still faster with
fropa compared to ECWMF). Temps during the late-week period will
continue to run above normal thanks to the prefrontal southerly
flow.
For next weekends weather...Friday`s cold front will be exiting our
area early Saturday, with improving weather as the day progresses.
But clouds may move back in with perhaps a few sprinkles across our
northern zones Saturday night into Sunday morning as the upper
trough axis moves across.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 638 PM Sunday...
Through 00Z Tuesday: Regional radar, satellite, and obs show
widespread IFR and MVFR flt conditions across much of central NC,
with the lowest cigs west, including INT/GSO. Until all of the pre-
frontal rain exits by 18Z Monday, look for reduced flt conditions
across most of central NC overnight and Monday morning. In fact,
the lower conditions attm across the western half of the state are
expected to spread eastward, so cigs/vis at RDU, RWI, and FAY should
be decreasing over the next few hours, along with occasional patches
of rain moving through. As mentioned, once the front moves through,
look for drying and improving flt conditions beginning Monday
afternoon. It`s also worth noting that prefrontal SW winds are
expected to increase to 10-20 kts with some higher gusts across all
of central NC overnight and lingering through the daytime hours
Monday, then gradually diminishing after sunset Monday.
After 00Z Tuesday: VFR conditions will return by Monday night and
remain through Wednesday night. Clouds and rain chances will
increase on Thursday, along with the potential for reduced flight
conditions, Thursday through Friday assoc with the next frontal
system.
&&
.CLIMATE...
Records:
DATE RDU GSO FAY
High Hi Min High Hi Min High Hi Min
12/29 76 1984 61 1954 74 1984 60 1954 79 2015 64 2007
12/30 76 1996 63 2015 76 1984 52 1974 76 1984 66 2015
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Green
NEAR TERM...Green/Smith
SHORT TERM...Green
LONG TERM...np
AVIATION...np
CLIMATE...RAH
Area Forecast Discussion
National Weather Service Springfield MO
517 PM CST Sun Dec 29 2019
.SHORT TERM...(This evening through Monday)
Issued at 300 PM CST Sun Dec 29 2019
An Intense upper low was located over southern Minnesota this
afternoon. A shortwave trough was rotating around the low lifting
across southern Missouri. Lift associated with this feature had
pushed showers back into the eastern Ozarks, and these will
continue into the early evening hours before finally pushing
eastward. RAP and to a lesser extent the 12Z NAM is showing a very
light area of precipitation across the northern counties this
evening. This could be some sprinkles/snow flurries, but not
expecting it to have any impacts. Evening shift will have to
monitor this as it moves it manifests itself later this evening.
By late tonight, a cloudy, cooler but dry period from late tonight
through Monday. Lows tonight will drip to around or just below
the freezing mark, with highs Monday only in the low to mid 40s,
which is close to normals for late December. In addition, the
pressure gradient remains rather tight across the area tonight
into Tuesday, with blustery westerly winds.
.LONG TERM...(Monday Night through Sunday)
Issued at 300 PM CST Sun Dec 29 2019
For Monday night and Tuesday, area remains sandwiched between a
closed low over the Great Lakes and a closed low near Baja
California. In between a surface high pressure area will drift
across the region with a continuation of the quiet but cool weather
for southeast Kansas and the Missouri Ozarks, with lows in the 20s
and highs in the 40s.
As the high slides east Wednesday, southerly winds will return to
the area marking the beginning of a warming trend. As the southern
closed low dives southward into Mexico, the flow over the central
Conus becomes more zonal. A weak shortwave trough tracks across the
area late Wednesday night into Thursday bringing with it a chance
for some scattered showers. Afternoon highs will return to the 50s,
with overnight lows in the 30s.
A more significant trough then digs across the central Conus on
Friday continuing the rain chances. This will exit east Friday
night, with mild and quiet weather then expected for Saturday.
A slightly cooler day, but dry is expected to end the weekend as
highs return back closer to seasonal normals.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 514 PM CST Sun Dec 29 2019
A very intense low pressure system was located over southern
Minnesota early this evening. Shortwave energy and gusty west
winds in association with this low were affecting the forecast
area, along with some lower MVFR cloud cover. The winds are
actually expected to strengthen tonight and Monday with some gusts
of 30 to 35 mph expected. An area of light snow in Kansas may
quickly push across central MO this evening, but we are currently
not expecting any impacts at the terminal locations.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
SHORT TERM...Raberding
LONG TERM...Raberding
AVIATION...Lindenberg