Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/28/19
Area Forecast Discussion
National Weather Service Bismarck ND
920 PM CST Fri Dec 27 2019
.UPDATE...
Issued at 920 PM CST Fri Dec 27 2019
Latest fog/stratus loop shows fog development from Linton to
Oakes and have utilized a blend of the RAP/HRRR along with manual
editing to tailor the area correctly through this evening. This
is the leading edge of the low level moisture increasing as
advertised by the RAP 925mb south-southwesterly winds. Latest 00Z
NAM as well as the suite of the high resolution models bring the
precipitation/snow into the southern James River Valley between
09z-12z Saturday, which is in line with the current forecast. A
couple of the high resolution models suggest an hour or two of
possible light freezing rain over Dickey and LaMoure counties, but
the overall consensus is snow from the rest of the model suite.
The 00Z NAM really keeps a tight snow gradient centered over the
James River Valley - especially Sunday, in concert with gusty
northerly winds. NAM heavy banded snow cross sections show the
potential for an intense banding of snow in far southeastern North
Dakota and western Minnesota Sunday, and perhaps will see that
extend into the southern James River Valley, but not as intense.
It would appear that snow for south central North Dakota may
result more from a persistent TROWAL shifting from east to west
Sunday afternoon and Sunday night before dissipating. Will see.
Current headlines with the highest snowfall and greatest impacts
in the James River Valley looks on track.
UPDATE Issued at 500 PM CST Fri Dec 27 2019
Current winter weather headlines look good concerning the winter
storm Saturday through Sunday night. In the near term, current
satellite imagery and surface observations show a clear sky across
western/central North Dakota. The leading edge of high clouds
were just beginning to stream into northern South Dakota. Will be
monitoring for fog development across far southwest and also in
the southern James River Valley this evening, as low level moisture
increases and advects in ahead of the snow that will develop just
after midnight.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 319 PM CST Fri Dec 27 2019
Will be issuing a Winter Storm Warning beginning Saturday morning
for some counties in far south central through the James Valley. See
the long term portion of this discussion for other counties in south
central North Dakota beginning Saturday night.
The models are in better agreement today regarding the development
of the anticipated winter storm system.
For Sioux, Emmons, Kidder, Logan, McIntosh counties as well as the
James Valley counties of Dickey, LaMoure, Stutsman and Foster:
Winter Storm warning for the entire event:
Late tonight (after midnight) the chances for light snow developing
reaches far south central into far southeastern North Dakota...then
continues expanding north and east during the daytime. There is also
some warm air aloft entraining into the system, bringing a good
possibility of some freezing rain developing in Dickey, LaMoure, and
perhaps into McIntosh County. By Saturday evening, we expect that we
could have 3 to 5 inches of snow on the ground as well in the
aforementioned counties in the Winter Storm Warning.
For the surrounding counties of Grant, Morton, Burleigh, Sheridan
and Wells Counties: only light snow amounts of an inch or less and
no threat of freezing rain for Saturday.
All other counties in western and north central North Dakota - not
expecting much in the way of precipitation on Saturday.
Lows tonight should range from the single digits north to 5 to 15
above south. Highs Saturday from the upper teens north to the mid
20s south.
.LONG TERM...(Saturday night through Friday)
Issued at 319 PM CST Fri Dec 27 2019
Possible blizzard conditions for mainly the James Valley, along with
continued moderate to heavy snowfall for south central North Dakota
highlights the long term period Saturday night through Sunday night.
The models depict the storm track moving from Colorado Saturday to
eastern SD/NE and MN/IA by Sunday morning, then dumbelling around
that area through Sunday night before moving northeastward towards
the western Great Lakes on Monday.
As the storm track center approaches North Dakota, northerly winds
will begin increasing Saturday night, with the strongest northerly
winds on Sunday, especially in the James Valley areas, where
northerly sustained winds of 30 to 40 mph with gusts over 45 mph are
expected. The combination of strong winds and continued snow will
make for a large area of blowing snow...with possible blizzard
conditions - especially in the James Valley and east.
The Winter Storm Warning continues for these counties (Sioux,
Emmons, Kidder, Logan, McIntosh, Foster, Stutsman, LaMoure, Dickey)
through Sunday night. The counties in the Winter Storm Warning can
expect storm total snowfall of 8 to 12 inches for Sioux, Emmons,
Kidder and Foster counties...and 10 to 16 inches for Logan,
McIntosh, Stutsman, LaMoure and Dickey counties over the 48-hour
period (Saturday through Sunday night).
In addition to the Winter Storm Warning counties, a Winter Weather
Advisory has been issued for the peripheral counties beginning
Saturday night and continuing until daybreak Monday morning. These
peripheral counties are Grant, Morton, Burleigh, Sheridan, and
Wells. We are expecting storm total snow in these counties from 3 to
6 inches over a 36 hour period (Saturday night through Sunday
night). Blowing snow will also be possible in these areas, though
blizzard conditions are not expected here at this time.
After this winter storm system exits the Northern Plains, the upper
level flow becomes more zonal, with fast-moving systems traversing
the region. Only quick shots of some light snow possible with these
systems. Relatively mild fro late December and early January, with
highs in the 20s and 30s and lows from the single digits, teens or
lower 20s above zero.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 503 PM CST Fri Dec 27 2019
VFR cigs/vsbys will dominate most terminals this taf period,
including KXWA/KMOT/KDIK. However, a significant winter storm
will impact KJMS beginning as early as 13z Saturday. Snow is
favored during the day Saturday at KJMS with CIGS/VSBYS deteriorating
to MVFR/IFR. KBIS will be on the fringes MVFR/IFR cigs especially
Saturday afternoon, but for now will keep them in low VFR status
with light snow and unrestricted visibilities.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 PM CST /5 PM MST/ Saturday to 6
AM CST /5 AM MST/ Monday for NDZ022-023-034-035-042.
Winter Storm Warning from 6 AM CST /5 AM MST/ Saturday to 6 AM
CST /5 AM MST/ Monday for NDZ025-036-037-045>048-050-051.
&&
$$
UPDATE...KS
SHORT TERM...JV
LONG TERM...JV
AVIATION...KS
Area Forecast Discussion
National Weather Service Columbia SC
1004 PM EST Fri Dec 27 2019
.SYNOPSIS...
Moisture will increase over the weekend into early next week as
a cold front moves through the Southeast. Scattered to numerous
showers are expected Saturday evening through early Monday. Dry
and cooler weather is expected midweek before another storm
system takes shape to our west and arrives late in the week
bringing another chance of rain.
&&
.NEAR TERM /UNTIL 7 AM SATURDAY MORNING/...
The high cirrus that has plagued us the last couple of days is
finally moving away as the jet that supported the related
divergence moves along with it to the northeast. This will allow
for a little better radiational night, especially as the winds
have already dropped to near calm most places.
The forecast problem of the evening is the battle between fog
and low clouds. 18Z EC and HREF are still on board with dense
fog pretty much everywhere south of I-20, while most recent HRRR
has backed off a bit and instead puts the emphasis on low
clouds, maintaining just enough weak isentropic lift. Given that
we are already seeing some ground fog being reported at AGS and
AIK, I am still leaning toward the fog solution for the I-20
corridor and points southeast, with more of a mix of fog and
low clouds to the north and west. I think the subsidence behind
the departing weak shortwave aloft will overcome any attempt at
low level lift and mixing.
&&
.SHORT TERM /7 AM SATURDAY MORNING THROUGH MONDAY/...
The upper ridge will still be over the region on Saturday even
as surface high pressure moves east. Mostly dry conditions can
therefore be expected, despite the storm system approaching from
the west. There could be a few showers in the CSRA late in the
day, but model consensus continues to slow down the arrival of
this next storm. Chances for rain increase on Sunday as a warm
front brings deepening southwesterly flow and moisture off the
Gulf of Mexico. Sunday night the upper trough to the west will
become negatively tilted as it lifts into the Ohio Valley which
will push a cold front into the forecast area on Monday morning.
The best moisture transport over the area will occur during
this period with PWAT values increasing to around 1.5-1.6 inches
(250-300 percent of normal) and rain is very likely across the
area. The best upper forcing and heaviest rainfall totals are
expected to remain to our north and west but expect rainfall
amounts around 0.25-0.50 inches. There is also a slight chance
of thunderstorms Sunday night into Monday morning, with the GFS
showing surface based LI around -3, and an elevated Showalter
Index.
Temperatures are expected to be warm and well above normal with
highs Saturday and Sunday in the upper 60s to lower 70s.
Overnight lows will be quite mild as well in the 50s to lower
60s. It will take a little while for cooler air to filter in
behind the front, so Monday should be mild as well, at least
during the day. Southerly winds will become breezy on Sunday
night, then shift westerly with the frontal passage on Monday,
but remain gusty.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Cooler and drier conditions will follow Monday`s cold front,
with lows on Monday night in the upper 30s to low 40s. On
Tuesday and Wednesday highs will then be in the 50s to near 60
with upper troughing still over the region, but these are
normal temperatures for this time of year. It will start to
warm some towards the end of the week as weak ridging builds in
from the south. Models now remain in agreement that the next
chance for rain probably won`t be until Thursday night or Friday
in association with a moisture laden deep upper trough.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Isolated light rain showers to linger in the CAE/CUB vcnty
through around 05Z. Otherwise expect deteriorating conditions
through the early morning hours. Already seeing MVFR/IFR fog
development.
Stratus/fog expected to become widespread late tonight given
shallow low level moisture...some mid level drying and near calm
surface winds. All guidance showing a period of MVFR or lower
developing. Have continued predominant IFR/LIFR 08z-15z. Should
see slow improvement beginning around mid-morning with VFR
developing during the afternoon.
EXTENDED AVIATION OUTLOOK...Cig/vsby restrictions expected
Saturday night. Rain and associated restrictions are expected
Sunday into Monday morning associated with a frontal system.
Breezy conditions may occur behind the front Monday.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Cheyenne WY
815 PM MST Fri Dec 27 2019
.UPDATE...
Issued at 802 PM MST Fri Dec 27 2019
Increased the value of PoPs on our western and northern borders
of Carbon County for the 6Z-18Z time periods with a blend of the
forecast and Euro model to match our neighboring office for the
purpose of consistency. This shouldn`t impact snow totals much
because the higher snow totals are still expected to be in the
Nebraska Panhandle overnight and into Saturday.
UPDATE Issued at 636 PM MST Fri Dec 27 2019
Overnight low temperatures were reduced by a few degrees in most
locations from Laramie to the west into Carbon county with the
evening forecast update. Observed temperatures at 5pm and 6pm
have dropped quickly due to a clearing in skies in that region.
Without the clouds present, temperatures will continue to drop a
few more degrees until the clouds to the south propagate
northward into our area. When this occurs the observed
temperatures should recover to higher levels in a short amount of
time. Little to no changes were made with the type of weather and
snow totals overnight due to confidence in the weather system
still being at a medium threshold. The overnight period will need
to be monitored closely as localized snow bands are being
advertised by the HRRR to set up in portions of northeast Laramie
County. This would easily boost snow totals by an inch or two in
only a couple of hours if that solution comes to fruition.
Southeast winds have been observed east of the Laramie Range the
last couple of hours, so the mention of fog has been continued in
the forecast for certain locations due to this upslope flow regime
continuing for the short term period.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 255 PM MST Fri Dec 27 2019
Afternoon WV/IR imagery revealed a potent upper low situated just
west of the Four Corners. Abundant moisture in the mid and upper
levels was spreading northward over the Rockies and Plains. Stronger
diffluent flow aloft and steep lapse rates were producing scattered
convection with some lightning across southern CO. Rain and freezing
rain was occurring over eastern CO. All this precipitation will
continue to spread north into southeast WY and western NE later this
afternoon into the evening. Initial onset of precipitation across
the high plains will be in the form of light freezing rain and/or
snow pellets, then transition to snow later tonight. Areas along
and west of the Laramie Range can expect light snow.
Despite some model differences, confidence is improving for widespread
accumulating snowfall during the next 24 to 36 hours as the winter
storm tracks northeast into the Central Plains this weekend. There
are outliers like the GFS, high-resolution models (HRRR), and NAM
that are predicting significantly higher snowfall totals, compared
to the Euro, Canadian and other international models. The storm
total snowfall forecast was collaborated with surrounding WFOs and
WPC.
Overall, the trend has been changing with lesser amounts across the
I-80 corridor from Laramie to Sidney. Much of the NE Panhandle into
portions of southeast WY can expect higher totals on the order of
4 to 8 inches. Areas along and surrounding the Pine Ridge may measure
7 to 11 inches. Gusty north to northwest winds of 30 to 40 mph will
develop Saturday and continue through Sunday night as the winter
storm intensifies as it tracks into the Central Plains. The combination
of blowing snow, very low visibilities and snow-covered roads will
create difficult post-Christmas travel this weekend.
In regards to winter weather headlines, Goshen County was upgraded
from a Winter Weather Advisory to a Winter Storm Warning for the
potential of 4 to 8 inches. Winter Storm Warnings for the NE Panhandle
and remainder of eastern WY remain unchanged. Winter Weather Advisories
for 2 to 6 inches of snow and blowing snow remain in effect for the
I-25 corridor from the CO border to west of Douglas, as well as the
North Snowy Range Foothills (Arlington/Elk Mountain).
Snow will taper off Sunday, however gusty northwest winds of 30 to
40 mph will continue to produce slick, snow-covered roadways and
poor visibilities. Below normal temperatures are forecast this
weekend with highs from the upper teens to the upper 20s. Lows in
the mid teens to mid 20s Saturday will fall into the single digits
to middle teens Sunday. Wind chill temperatures by Sunday morning
will range from 5 above to 15 below zero.
.LONG TERM...(Monday through Thursday)
Issued at 426 AM MST Fri Dec 27 2019
Ridging pattern sets in the wake of the departing low on Monday
giving a reprieve of accumulating snow though patchy areas of
blowing snow linger in the fresh snowpacked areas. High temps
across the High Plains will linger from the low 30s to low 40s
into the New Year. A bit chilly for New Year`s Eve festivities
with lowest minimum apparent temps east of the Laramie Range in
the upper single to low double digits with sub-zero temps west of
the Laramie Range with winds gusting into the low teens. High wind
potential looks promising to start off New Year`s day and again
next week Friday. 850mb height gradients between Craig and Bordeaux
on the latest GFS around 80 to 109 meters at 12z Wednesday. Similar
height gradients return starting 12z on Friday as well though heights
are better this time around also for Arlington. Near-normal low
temperatures to persist as an approaching Pacific way moves onshore
in CA Monday evening with upper level shortwave passing through late
Wednesday into Thursday for another chance of snow though still early
western portion of CWA trending with latest solutions to see higher
snowfall amounts than this weekend`s event.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 412 PM MST Fri Dec 27 2019
Expecting rapidly deteriorating conditions this evening as a low
pressure system continues to track into northeast Colorado.
Already seeing IFR conditions at KCYS and KSNY and expect the
lower ceilings to fill in over the Panhandle from south to north.
Once down...ceilings expected to remain low through Saturday in
snow and blowing snow.
&&
.FIRE WEATHER...
Issued at 215 PM MST Fri Dec 27 2019
No fire weather concerns expected through the weekend as a winter
storm impacts the districts. Areas west of the Laramie Range can
expect snowfall accumulations of 2 to 5 inches. Areas east of the
Laramie Range can expect moderate to heavy snowfall accumulations
as well as a wintry mix tonight through Saturday. Strong north to
northwest winds of 30 to 40 mph will produce blowing snow and poor
visibility. Periods of light precipitation and strong winds are
expected from New Years Day through the end of next week.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning until 6 AM MST Sunday for WYZ102-108-119.
Winter Weather Advisory until 6 AM MST Sunday for WYZ101-103-106-
107-110-116>118.
NE...Winter Storm Warning until 6 AM MST Sunday for NEZ002-003-
019>021-054-055-095-096.
&&
$$
UPDATE...BW
SHORT TERM...MAJ
LONG TERM...WM
AVIATION...GCC
FIRE WEATHER...MAJ
Area Forecast Discussion
National Weather Service Dodge City KS
529 PM CST Fri Dec 27 2019
...Updated Aviation Discussion...
.SHORT TERM...(This evening through Saturday)
Issued at 342 PM CST Fri Dec 27 2019
The initial phase of our precipitation event began earlier today as
a cold rain and even freezing rain event across mainly far southwest
Kansas bordering Oklahoma. We did receive some reports of light
icing, but temperatures gradually warmed up to slightly above 32 as
of late morning or midday, with the exception of Colorado border
areas. As of early afternoon, we had reports of minimal problems
around Hamilton County, but a new larger area of precipitation had
moved into Stanton and Hamilton County which could lead to some at
least light icing. As of 330 PM CST, we do not have a winter weather
advisory for these counties, as we expect temperature to slowly warm
above 32 even in Hamilton County, but it will be very close.
Rain showers will continue to expand in coverage as the main upper
level low draws near through the night. We will be watching upstream
across the Texas panhandle and far eastern New Mexico through the
night, as this will be the initial development region of
thunderstorm activity tonight. These storms will advance north-
northeastward, with much of southwest Kansas remaining in the warm,
moist sector through the night. All this warm, moist advection, even
at the surface will only increase through the night, and this will
manifest as dense fog outside of the rain shower regions. All the
short term high resolution models show quarter mile visibility on
both sides of the model-depicted rain areas all the way through mid
to late morning Saturday. Hence, we have decided at the last hour of
this shift to hoist a Dense Fog Advisory for the entire forecast
area through Noon Saturday.
.LONG TERM...(Saturday night through Friday)
Issued at 342 PM CST Fri Dec 27 2019
With all the attention on the short term weather today, there was
not much focus on the Long Term part of the forecast going into next
week. The latest NationalBlend guidance keeps southwest Kansas dry
through next Friday. There will likely not be any major arctic
airmass intrusion through this period as well. Of note in the latest
ECMWF is a low amplitude trough that will be moving across western
Kansas some time Thursday or Thursday Night, bringing a cold front
and increased northerly winds behind it. The EC also shows some
light QPF behind the front as well, but as mentioned, the official
forecast will remain dry for this time frame.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 516 PM CST Fri Dec 27 2019
Based on moist upslope easterly flow in the surface to 2000ft AGL
level from the latest RAP and NAM BUFR soundings these LIFR
conditions will continue overnight through early Saturday morning.
Ceilings and visibilities may briefly improve as an area of
steadier rainshowers cross each TAF site between 00z and 06z but
once this rain tapers off between 03z and 06z Saturday the LIFR
conditions are then expected to return. In addition to the period
of steadier rainfall overnight a few isloated thunderstorms will
also be possible. The Hays area can expected a few hours of MVFR
conditions between 00z and 03z before low IFR/LIFR conditions
spread across south central Kansas.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 33 47 23 38 / 100 60 20 0
GCK 33 42 20 38 / 100 30 20 0
EHA 32 41 23 40 / 90 10 10 0
LBL 33 43 22 40 / 100 30 10 0
HYS 33 44 23 36 / 100 70 30 0
P28 35 56 27 40 / 80 90 20 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until noon CST /11 AM MST/ Saturday for
KSZ030-031-043>046-061>066-074>081-084>090.
&&
$$
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...Burgert
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
920 PM EST Fri Dec 27 2019
.SYNOPSIS...
Warm high pressure will remain over the region through Saturday, but
with steadily increasing clouds. Moisture will return Saturday night
and Sunday ahead of our next storm system. A cold front is expected
to move across the region Sunday night and Monday morning, bringing
widespread rain. Dry and cooler weather returns early next week.
&&
.NEAR TERM /THROUGH SATURDAY/...
As of 930 PM EST Friday: Evening update included increasing pops
across the Smokies as upglide ahead of the shortwave is allowing
some showery activity to form. HRRR and other CAMs picking up on
this as well, but all show this activity diminishing in the next few
hours. Temperature trends look good for now, and guidance continues
to back off on the idea of fog formation across the
Upstate/Lakelands, so no other changes at this time.
Otherwise, satellite imagery shows a closed, southern-stream, low
pressure system rotating over Arizona and a downstream ridge axis
over the southeast coastline. Fairly abundant moisture continues to
stream northeast across Texas from Pacific sources ahead of the
trough axis, with a secondary feed across the Deep South from the
Gulf of Mexico into the ridge axis. The wavelength of the upper
pattern will shorten as the closed system deepens over the Plains by
the end of the period late Saturday. This will backbuild the eastern
ridge axis over our area, meaning that all features of interest will
be at lower levels through the near term.
850 mb moisture increased somewhat today and coupled with weak
isentropic lift to produce better cloudiness in the southern tier of
the forecast area. However, any additional increase in 950-850 mb
moisture will be modest through Saturday as it doesn`t appear that
the Atlantic and Gulf moisture fetches get going in earnest until
closer to 00Z Sunday. Anticipate the fairly dry surface high pressure
nose to dominate the pattern, with just low-end slight chances of
light rain around the far southern fringe at times through the
period. Low clouds and fog could end up being a bigger near-term
issue around daybreak Saturday, but this is quite uncertain and
highly dependent on the thickness and height of the clouds. There
should be just enough cloudiness to keep the forecast area from
seeing widespread dense fog, but if it happens anywhere it will be
the southeast piedmont fringe. Mins tonight, and maxes on Saturday,
should run a degree or two higher than today`s values.
&&
.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 130 PM EST Friday: Overall confidence has increased with the
frontal system progged to cross the FA Sun night. The GFS and the
ECMWF have slowed the progression of the front and are now more NAM-
like with the FROPA and trailing sfc trof. Mass fields are still a
little different when the system crosses the ern zones as the GFS
dries up quickly after 12z. The NAM on the other hand has a line of
possible linear or QLCS convection moving east arnd and south of the
CLT area thru mid morning. This is sigfnt because the NAM also bumps
sbCAPE into the 500 J/kg range at that time. This timeframe could be
the best window of CAPE/shear overlap...yet the NAM also has the
strongest llvl shear outrunning the better thermal forcing while
SHERB values currently only reach 0.7 or so. So...things arent quite
clear cut for this Day 3 convective threat which isnt unusual.
In the meantime...there is good agreement with the upslope enhanced
precip event over the srn BL beginning Sat night continuing into Mon
morning. The rain amts wont be much for the first 24 hrs...likely
near an inch...but the last 12 hrs shud add another 1.5 inches as
frontal forcing increases and combines with continued mech lift. A
look at QPF/FFG ratios indicate the best time for possible flooding
issues to begin would be btw 00Z-06Z Mon. Will continue the HWO
mention of isol minor hydro issues for the same mtn zones. Winds
dont look that strong behind the system with little CAA...yet a llvl
jet arnd 50+ kts will align along the front and could affect higher
elevations within WAA flow. Temps will remain abv normal thru the
period by 10 degrees or so and a non/diurnal temp trend or
steady-state environ will setup Sun night.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 210 PM EST Friday: Dry Canadian hipres will slowly build
across the region Mon night and become broadly centered over the FA
early Thu. This will maintain and general w/ly to sw/ly flow thru
most of the period with low-end CAA occurring on Tue. Soundings show
deep dry air and good insol...so expect max temps a little abv
normal and mins near normal. The models continue to go back and
forth with the advancement of precip associated with a srn stream
system Thu. The ECMWF continues to be wetter and quicker but it has
slowed somewhat. PoPs have been cut back from guidance to allow for
a dry period Thu morning with slt chance isent showers across the SW
NC mtns by the afternoon and increasing in coverage into the day 8
period. There may be a -ra/sn mix across the higher elevations of
the NC mtns Thu afternoon...but warming temps wont allow for any
sigfnt duration nor snow accum by the evening. The system looks to
affect the area beyond the fcst period and it may produce a good amt
of rainfall over the NC srn mtns thru Fri.
&&
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: High clouds across the area will generally
keep VFR conditions in overnight, even restricting mountain valley
fog potential, but moisture lifting north from the Midlands could
lead to the formation/advection of restrictions into portions of the
Upstate and KCLT vicinity. New guidance is backing off on the
northward extent of this, so have converted lower conditions for
KCLT to a TEMPO for MVFR, though some IFR can`t be totally ruled
out. Otherwise kept restrictions only at KAND. Surface high pressure
building in from the north will swing winds around to the NE and E
by tomorrow afternoon (except SE down-valley at KAVL), but speeds
remaining light (<5kt). Additional moisture moving in will affect
outperiods at KCLT, where MVFR and PROB30 -SHRA has been introduced.
Outlook: Moisture will return from the southwest through the latter
half of the weekend ahead of a cold front arriving Sunday night.
Restrictions are likely with the deeper moisture, and isolated
thunderstorms cannot be rule out early Monday. Mainly VFR conditions
will prevail from later Monday through mid-week as dry high pressure
returns behind the front.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL High 100% High 100% High 100% High 100%
KHKY High 100% High 100% High 100% High 100%
KGMU High 100% High 100% High 100% High 100%
KAND High 100% Low 35% Med 72% High 96%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...HG/SBK
NEAR TERM...HG/TDP
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...TDP
Area Forecast Discussion
National Weather Service Jackson MS
926 PM CST Fri Dec 27 2019
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Updated to be more widespread with slight chances for some showers
this evening. Broad ascent across the region continues with weak
diffluence aloft and plenty of moisture advecting into the region
from the southeast. Swath of showers on radar this evening likely
to continue to progress slowly northward. HRRR and RAP both
suggesting the showery activity to continue. Have broadbrushed
the overnight with very low pops to handle the activity.
Prior discussion below:
Tonight and Saturday: A continuation of warmer than normal
temperatures, cloudy skies, and low chances of light rain are
expected through Saturday afternoon. Mid afternoon water vapor
imagery/RAP analysis showed the circulation around a closed low
spinning over Arizona. This closed low will track northeast across
the Four Corners region tonight and over the Central Plains Saturday
while helping develop a surface low over the Plains as well. This
will maintain southwest flow aloft across our region atop of
southeast to southerly low level flow thanks to a surface ridge
nosing west across the Gulf coast states. Together these features
will increase deep moisture back over our CWA with PWATs back
around an inch and a half and surface dew points in the low to mid
60s by Saturday afternoon and continue to fuel rain chances.
Currently local radars show the most significant area of rain
lifting north over our northeast zones with only a few very light
returns elsewhere. Hi-res models suggest additional development of
light rain will occur from the southeast as this evening progresses.
Patchy fog can be expected in the southeast toward morning but
gradient winds should lead to more elevated stratus than fog to the
northwest. Temperatures will remain above normal through the period.
Low temperatures Saturday morning will be in the upper 50s to lower
60s. Afternoon highs Saturday will top out a couple degrees warmer
than today and range from the upper 60s northeast to the mid 70s
southwest. /22/
Saturday night through Friday. The forecast for Saturday night
was still on track with a marginal risk for severe across the
west/northwest zones. The models may be a little slower with the
timing, so the marginal risk through Sunday was good. Also, held
on to thunder in the northwest and maintained everywhere through
the day Sunday with the system was a little slower clearing the
area. Overall, no big changes to the long term forecast.
Models show the main low pressure system deepening as it tracks
northeast well away from the area. However, a pre-frontal trough
along with a 50 kt low level jet move into the west/northwest zones
around midnight with the latest NAM. There was also a narrow band of
decent mid level lapse rates over the same area (model soundings
showed some mid level instability over the MS Delta and northeast
LA) but generally weak instability. Dewpoints will likely be in the
lower to mid 60s everywhere by Sunday and it will be unseasonably
warm.
The boundary should be in the area mid morning into early Sunday
afternoon bringing another round of thunderstorms and the risk for
strong to severe storms as it passes. Although weak, looking at
model soundings, instability, vertical totals and a few other
indicators improve Sunday between 18-00z but quickly fall off. With
the system again appearing to be a little slower, it is looking more
like the storms will be limited to the northwest zones, but of
course that will depend on the timing.
Monday through Wednesday should be dry with near normal temps. Euro
guidance was more in line with raw output, where the GFS was a bit
warmer behind the front. Either way, it will be cooler (50-60) than
the next few days, with lows back into the 30s Monday and Tuesday
nights. Tuesday night looks good for fireworks and outdoor
activities to bring in the new year. Guidance values for pops/temps
were good.
Mid to Late next week, models suggest a warm front and low pressure
system will move into the area maybe late Wednesday into Thursday
which is slightly slower than the current forecast. There will be
more unseasonably warm air and rain returning for a day or two.
Models show an upper trough drop into the northern Mexico, putting
the area into the warm sector. For now guidance temps were in the
60s, with the area not really cooling much before the next system
and values across the south Texas and northern Mexico in the mid 70s
to 80s in a few spots, could see values being a little warmer. There
will be plenty of warm air and moisture advection ahead of the
system, with flow likely from the Pacific and the Gulf as the system
moves through region. The trough seems to weaken as it moves east
and the surface feature seemed weak also as it moved through the
ARKLAMS. However, there was a good amount of moisture so this may be
an efficient rain. Guidance brought pops in a little earlier than
the raw models on Wednesday. Right now, it looks like that system
will also be a little slower and rain may hold off until late
Wednesday/early Thursday morning. Tried to go with the slower trend.
&&
.AVIATION...
00Z TAF discussion:
VFR for now in most locations, though the east is still mostly
MVFR with some light returns on radar working in some light shra
this evening. Given ample moisture continuing to stream into the
region, expect cigs to drop in the overnight, with some patchy fog
possible in the southeast. Other than that, winds expected to stay
up a bit and counter any potential for more widespread fog through
central TAF sites. Southeasterly flow continues through the
forecast.
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 59 73 63 71 / 29 31 85 99
Meridian 56 69 63 73 / 28 37 70 97
Vicksburg 59 74 61 70 / 19 42 92 98
Hattiesburg 60 73 62 73 / 39 47 69 93
Natchez 60 75 63 70 / 19 47 72 98
Greenville 56 71 58 65 / 18 52 96 96
Greenwood 57 72 62 68 / 20 36 96 99
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
HJS
Area Forecast Discussion
National Weather Service North Platte NE
549 PM CST Fri Dec 27 2019
.SHORT TERM...(This evening through Saturday night)
Issued at 311 PM CST Fri Dec 27 2019
Most of the models have come into very good agreement lifting a
h700mb warm front through Nebraska tonight and then deepening an
h700mb low across ern Colorado Saturday. This low will then track
northeast through central and northeast Nebraska Saturday night. As
this happens, a band of moderate to heavy snow should develop across
swrn or ncntl Nebraska. How far south this band will develop remains
uncertain but the blended forecast appears to form it near highway 2
A check on the 15z SREF shows this band developing across swrn
Nebraska reaching south to near North Platte.
The models came in a bit warmer for highs Saturday with mid 30s and
rain across parts of scntl, ncntl and Nebraska- subfreezing
temperatures across nwrn Nebraska. The resulting rain/drizzle-
freezing rain-snow line will move slowly east Saturday and Saturday
night. There was a slight drop in the snowfall amounts across nrn
Nebraska where around 12 inches is predicted. Amounts across swrn
Nebraska dropped to less than 4 inches in spots. This is the result
the expected location of a secondary snow band the models show
developing Saturday afternoon across ncntl Nebraska.
The forecast leans on the short term model blend plus bias
correction, where appropriate. This produced a temperature forecast
featuring warmer lows tonight and Saturday night, and warmer highs
Saturday across swrn and ncntl Nebraska. The wind forecast uses the
guidance blend plus bias correction plus 1 to 3 kts at times to line
up with the 500m AGL wind speeds. North winds should increase
Saturday afternoon to 20-25 mph across the Panhandle. This wind
field will progress slowly east toward ncntl Nebraska overnight.
The ice forecast is problematic as some models like the 15z RAP show
very little ice and more snow tonight. The blended model approach
suggests both with up to 3 inches of snow and up to two tenths of
ice accumulation. Furthermore, the HRRR echo tops product suggests a
few storm tops reaching 25kft which would support isolated lightning
strikes.
.LONG TERM...(Sunday through Friday)
Issued at 311 PM CST Fri Dec 27 2019
Wrap around snow should continue Sunday across nrn Nebraska
and wind speeds should increase throughout wrn and ncntl Nebraska to
25 to 30 mph. The h700mb low and attendant sfc low will stall for a
time across ern SD/wrn MN Sunday and this should cause the wind
field to expand. The storm system is expected to pull away toward
the Great Lakes Sunday night. All models indicate 25-30 mph winds
continue Monday.
The snow forecast uses the model blend and the total snowfall for
the event came in a few inches lower, The forecast still predicts 8
to 12 inches across nrn Nebraska but just 3 to 6 inches across swrn
Nebraska. This is close to WPC but less than the ECM and GFS
ensemble which suggested around 15 inches near the SD border. The
lower amounts in the official forecast are the result of the
secondary snow band developing a bit farther north Saturday.
Nonetheless, a storm system of this caliber...record moisture,
strong dynamics and a slow motion of less than 15 mph could
present a few surprises. Locally higher amounts of snowfall are
possible and the southern extent of the heavy snow remains
uncertain.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 549 PM CST Fri Dec 27 2019
A wintry mix of freezing rain, sleet, and snow is expected tonight
at both sites. A wintry mix is already falling at KLBF and slowly
moving northward. The wintry mix will arrive at KVTN later this
evening. Visibility reductions down to a mile are possible as well
as slippery runways. Gusty northwest winds are also a concern
heading into Saturday night. These winds could cause blowing and
drifting snow.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 6 PM CST /5 PM MST/ Sunday for
NEZ004>010-022>029-035>038-056>059-069>071-094.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Kulik
Area Forecast Discussion
National Weather Service Phoenix AZ
501 PM MST Fri Dec 27 2019
.UPDATE...
Updated 00Z aviation discussion.
&&
.SYNOPSIS...
The strong storm system that brought valley rain and mountain snow
to the Desert Southwest will move eastward into the Rockies tonight
and Saturday. Rain will taper off across the lower deserts, however
lingering moisture across the higher terrain east of Phoenix will
result in accumulating snow through Saturday. In the wake of this
system, temperatures will remain below normal, though a warming trend
is likely through next week. The next chance of precipitation will
be early next week as another Pacific low pressure system affects
the region.
&&
.DISCUSSION...
Latest RAP streamline analysis places the center of the
weakening upper low across north-central Arizona.
Presentation on satellite indicates the low pressure system is
post-occlusion and in the cyclolysis phase. Although the main
circulation is no longer as tight and organized as it once was, this
has beget several smaller vort maxes. One vort, in particular has
produced occasional rainfall and drizzle across south-central Arizona
today, along with very low clouds and unseasonably cool conditions.
Main focus for the remainder of today is the potential for
convection across south-central Arizona as partial clearing
gives way to limited diabatic heating in the wake of the
aforementioned vort max. Latest HREF maximum indicates only minimal
MUCAPE, though anomalously low 500 mb temperatures point to the
potential for isolated/scattered storms capable of producing heavy
rain and perhaps small hail. The models remain in good agreement
that the activity will finally taper off this evening as the trough
axis migrates east of the area.
The low pressure system will slide eastward into the southern Rockies
Saturday. However, the eastward progression has trended a bit slower,
owing to to an elongated vort lobe draped meridionally across the
Rockies that will reinforce the trough. Model consensus indicates a
period of PVA-induced ascent, which will support light to moderate
snowfall across the higher terrain of Gila County, particularly
during the morning. A few inches of additional accumulation are
possible, generally above 5000 ft and a Winter Weather Advisory
continues for these areas. A drier, subsident flow will develop
across the lower deserts, while temperatures will remain well below
normal with highs only reaching the lower 50s.
Latest guidance continues to suggest Sunday morning will be quite
cold. A ridge will build across the Great Basin, which will promote
areas of clear skies, light winds and radiational cooling. Forecast
low temperatures have been weighted heavily towards the National
Blend, which continues to trend a bit colder. Although a freeze
event is not anticipated in the Phoenix area, some of the outlying
areas will likely fall below freezing and a Freeze Watch has been
issued for the areas including Wickenburg, Tonto Basin and portions
of Pinal County and Queen Creek.
Early next week the focus will shift to the west coast again, where
another Pacific low pressure system will impact southern California.
ECMWF-E is still exhibiting a large normalized spread, which
reflects the uncertainty in its evolution. The ECMWF-E mean
depicts the strongest negative height anomalies and highest QPF far
to our south across Mexico. Given the general ECMWF
trajectory, another significant snowfall in JTNP would be
possible, though this bears watching as the GEFS is a bit further
north. Nevertheless, temperatures will remain well below normal
through Thursday, followed by a warming trend as an anticyclone
builds across the eastern Pacific.
&&
.AVIATION...Updated at 0000Z.
South-Central Arizona including KPHX, KIWA, KSDL, and KDVT:
Isolated to scattered showers will continue through 01-02Z for
most of the Phoenix terminals as the cold core low aloft
associated with the upper level disturbance passes overhead. Brief
SCT-BKN low MVFR ceilings are possible with any of this shower
activity, but BKN-OVC ceilings should generally remain between 3-5
kft. This shower activity will likely persist a bit longer over
the far East Valley including KIWA, so we have VCSH there until
04Z. Another shortwave digging south around the ejecting low may
trigger another round of isolated showers overnight for the East
Valley including KIWA, but confidence was too low to include them
in their TAF at this time. Regardless, SCT-BKN high MVFR ceilings
with BKN-0VC ceilings around 5 kft should persist overnight before
gradually lifting on Saturday morning and remaining above 7-8 kft
by the afternoon hours. Winds will generally retain SE to S-SW
headings through about 15Z before becoming westerly as one final
shortwave digs south. Strong 15-20 knot wind gusts are expected
tomorrow afternoon with this feature, with westerly gusts up to
25-30 knots indicated by some models.
Southeast California/Southwest Arizona including KIPL and KBLH:
Ceilings will continue to improve across the region tonight before
generally becoming clear except over far eastern portions of Yuma
and La Paz Counties. KIPL will feature light northwest or variable
winds, whereas KBLH will generally retain northwesterly headings
with 15-20 knot gusts expected on Saturday afternoon.
&&
.FIRE WEATHER...
Sunday through Thursday:
Temperatures will remain well below normal throughout the period.
Another storm system will approach the Southwest Monday into
Wednesday, bringing a slight chance of showers to the region.
However, rainfall totals are expected to be light. Humidity values
will only bottom out in the 30s and 40s with very good overnight
recoveries. Winds should mostly be on the light side through the
bulk of the period.
&&
.SPOTTER INFORMATION STATEMENT...
Spotters should follow standard reporting procedures.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...Freeze Watch from late Saturday night through Sunday morning for
AZZ534-538-547-551>554-556-561.
Winter Weather Advisory until 11 AM MST Saturday for AZZ557-558-
563.
CA...None.
&&
$$
DISCUSSION...Hirsch
AVIATION...Hopper
FIRE WEATHER...Rogers