Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/09/20
AREA FORECAST DISCUSSION
National Weather Service Albany NY
948 PM EST Tue Dec 8 2020
Brisk and chilly conditions will persist into Thursday, before
turning warmer with above normal temperatures by the end of the
week. A passing disturbance will bring a period of some light
accumulating snow showers across the forecast area Wednesday
into Wednesday night. Accumulations should generally range from
a dusting to 3 inches with locally higher amounts possible in
the western Adirondacks and southern Green Mountains. Tranquil
weather returns Thursday through Friday.
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 948 PM EST...Clouds continue to erode, although there are
still patches of mostly cloudy skies over mainly higher terrain
areas west/east of the Capital District. Made some minor
adjustments to reflect current observations and trends. Partial
clearing will persist into the overnight before additional
clouds increase from the west late. Latest trends in the
guidance (including CAMs) indicate snow showers will develop for
areas north/west of the Capital District between 4-6 AM.
The rest of this evening will be rather quiet. Clouds will
thicken and lower in elevation tonight ahead of a shortwave that
will dive southeastward out of Canada tonight.
Winds will be out of the west-northwest 5-15 mph through this
afternoon before becoming light and variable this evening/tonight.
Another cold night is on tab with low temperatures expected to fall
into the 20s (teens across the higher elevations).
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
The main weather focus during the short term period will be on
the potential for some light accumulating snow across the
forecast area Wednesday through Wednesday night. Precipitation
type will by and large (spatially and temporally) be snow. The
only exception will be in the Hudson Valley where p-types will
be a rain/snow mix during the afternoon hours as sfc
temperatures are expected to warm into the upper 30s amid
Light snow will develop from west to east courtesy of a
shortwave that will move over the forecast area tonight through
Wednesday. Light snow is expected to begin across our northwest
zones (i.e. Herkimer county) between 3-4 am EST and across the
Capital District, southern VT and the Berkshires between 5-7am
EST Wednesday morning. Delta T values between Lake Ontario and
850 mb will be on the order of 12-13C. This will be sufficient
enough for some lake enhancement under a west-northwest flow
aloft regime. Lake effect snow will mostly affect our
northwestern zones. Some hi-res models such as the HREF HRRR
member are indicating that a band of lake effect rain/snow
showers could shift southward into western Mohawk Valley,
Schoharie Valley into the Capital District Wednesday afternoon
into Wednesday evening. Should this materialize, this has the
potential to produce at times brief burst of snow potentially
worthy of SPS/Special Weather Statements. Will have to monitor
these trends. Upslope snow is expected over southern VT into the
Berkshires. With snow ratios ranging between 7:1 (valleys) to
13:1 (higher elevations), snow amounts will generally range from
a dusting to 3 inches with the higher amounts across the SW
Adirondacks of Herkimer County and possibly over the higher
terrain of southern VT. Areas across northwestern Herkimer
county (adjacent to KBUF`s winter weather advised counties)
could see locally higher amounts greater than 3 inches (up to 5
inches). Have opted to not issue a Winter Weather Advisory at
this time due to the fact that much of Herkimer county will
average around 3 inches of snow (sub-advisory levels).
Snow will come to an end by Thursday morning as high pressure
builds in from the southwest. Tranquil weather will persist
High temperatures will moderate across the valleys from the
upper 30s Wednesday to the mid 40s on Friday (cooler higher
elevations). Low temperatures will mainly be in the 20s
Wednesday morning through Friday morning with some teens across
the higher elevations Wednesday morning.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
The period starts out on Friday with ridging aloft and a
southerly low level flow in place, with high pressure positioned
off the east coast. This will result in dry conditions with
mild temperatures. High temps expected to be around 10 degrees
above normal. Dry conditions should prevail through at least
Friday night and possible through Saturday morning, as upper
ridging remain in place, although it will likely be flattening
out somewhat by Saturday.
Chances for showers will start to increase later on Saturday
and especially Saturday night, as a cyclone tracks northeastward
into the south/central Great Lakes region. Moisture flux
associated with increasing southerly flow and increasing
isentropic lift will result in some showers developing.
Forecast confidence decreases Saturday night through Sunday, as
the GFS is indicating a stronger primary cyclone, with high
pressure positioned well north/east while the ECMWF is depicting
a weaker cyclone, with the high positioned closer (south/east
of the GFS). The CMC is most similar to the GFS at this time, so
not yet ready to completely lean towards any camp just yet and
will go with a blend for temperatures, but will lower from the
mean NBM values. Low level thermal profiles will have
significant implications regarding precip type, as ECMWF would
indicate a potential wintry mix across northern and eastern
zones, while the GFS/CMC would result in more plain rain. Will
mention some rain/snow mix for now, with time to refine the
forecast as the guidance comes into better agreement.
In wake of the weekend system, seasonable cool and breezy
conditions expected for Monday, with a few snow showers possible
mainly over the higher terrain. Very low forecast confidence
for Monday night thhrough Tuesday, as the ECMWF is showing a
strong southern stream storm approaching from the south/west,
while the GFS is depicting an innocuous zonal flow pattern with
dry conditions. Overall there is a lot of volatility in the
weather pattern through early next week.
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Low level clouds stuck in place at KALB/KGFL/KPSF, with cigs
borderline VFR/MVFR at KALB/KGFL and MVFR at KPSF. However,
clouds are slowly scouring out from SW to NE across the area as
there are no low level clouds at KPOU. Expecting at least some
partial clearing for the rest of the TAF sites later this
evening, before additional clouds increase from west to east
overnight into early Wednesday morning, ahead of an approaching
upper level disturbance.
Snow showers will develop from NW to SE and become prevalent
between 12Z-15Z at KGFL, KALB, then KPSF. Scattered snow
showers may affect KPOU for a short time, but not expected to be
widespread there, so will mention PROB30. Will mention MVFR
conditions for KGFL/KALB/KPSF at this time, although there is a
chance of IFR developing especially at KPSF. Will monitor trends
for subsequent TAF issuances.
Winds will become light and variable overnight, then shifting to
the southwest around 5-10 kt on Wednesday.
Wednesday Night: No Operational Impact. NO SIG WX.
Thursday: No Operational Impact. NO SIG WX.
Thursday Night: No Operational Impact. NO SIG WX.
Friday: No Operational Impact. NO SIG WX.
Friday Night: No Operational Impact. NO SIG WX.
Saturday: Low Operational Impact. Slight Chance of RA.
Saturday Night: Moderate Operational Impact. Chance of RA.
Sunday: Moderate Operational Impact. Chance of RA.
Mainly cool and dry conditions are expected through tonight,
with only some light precipitation possible Wednesday into early
Thursday, mainly in the form of snow. This will allow river
levels to slowly recede.
For details on specific area rivers and lakes, including
observed and forecast river stages and lake elevations, please
visit the Advanced Hydrologic Prediction Service /AHPS/ graphs
on our website.
AREA FORECAST DISCUSSION
National Weather Service Kansas City/Pleasant Hill MO
352 PM CST Tue Dec 8 2020
Issued at 351 PM CST TUE DEC 8 2020
Low sun angle and weak flow has made it a struggle to shake low
clouds and stratus today. Have seen an improvement through the
afternoon hours across central and eastern Missouri, but am a bit
concerned that atmosphere was unable to adequately mix out the low
level moisture. HRRR has hinted at the potential for fog re-
development along and east of highway 63, though there remains some
question in terms of density and areal coverage. For now, have
added patchy fog mention across eastern Missouri through the
overnight, but think fog development would favor low lying areas.
Low level jet increases overnight ahead of a subtle cold front that
moves through the area tomorrow morning. Behind the front, 925 hpa
temperatures cool through the day, and thus have dropped forecast
highs on Wednesday a few degrees. With that said, still looks like
a very pleasant day for December with 925 hpa temperatures of 11-13
C leading to highs in the lower 60s F.
Mild conditions continue into Thursday, but will start trending
towards cooler conditions as a boundary approaches from the
northwest and becomes oriented more in an east/west fashion Thursday
night into Friday. As leading wave in upper trough approaches on
Friday, isentropic lift increases to the point where light rain is
expected to develop across central Missouri, but will have to keep
an eye on far northwestern Missouri. Models are differing on the
depth of stratus and lift embedded within, but GFS soundings would
suggest the potential for soundings wet bulbing to freezing drizzle.
As the cooler air settles southward, could see precipitation mix
with and change over to snow Friday night into Saturday as short
wave train continues aloft.
Once the upper trough works through the area on Sunday, quieter
weather is expected early next week with seasonal temperatures.
.Aviation...(For the 18Z TAFS through 18Z Wednesday Afternoon)
Issued at 1109 AM CST TUE DEC 8 2020
VFR conditions will slowly spread from west to east through the
afternoon hours. Potential for fog to linger through the early
afternoon hours across central Missouri. West to southwest winds
will prevail through the period. Subtle cold front will work
through the area Wednesday morning with flow becoming northwest.
Area Forecast Discussion
National Weather Service Grand Rapids MI
657 PM EST Tue Dec 8 2020
Issued at 330 PM EST Tue Dec 8 2020
- Small chances for very light precipitation tonight
- Weekend system has many questions yet
- Potential for another weak system early next week
.DISCUSSION...(This evening through next Tuesday)
Issued at 330 PM EST Tue Dec 8 2020
-- Small chances for very light precipitation tonight --
A warm front will move into the area tonight with the potential
for some very light precipitation. The 18Z HRRR is for the most
part dry, but we feel there could be a little light drizzle. This
appears to be a non event however as ground temperatures are in
the upper 30s and air temperatures will be near to slightly above
freezing. The temperatures may end up being slightly warmer than
some of the models indicate (a few spots may dip slightly below
freezing) due to the fact that winds will be strong and a bit mixy
tonight, along with a direction off of Lake Michigan with water
temperatures that are in the 40s. Bottom line...we may see a
little drizzle tonight, but we are not expecting any of the
freezing variety due to the above factors.
-- Weekend system has many questions yet --
The main story in the 7 day forecast is the potential for an
impactful system over the weekend. The upper systems do not phase
well and at best the phasing could be described as disjointed
right now. The evolution of multiple upper waves is complex and
is 5 days out yet in the forecast. The main players in our weather
for the weekend are a cutoff low off the Baja of Mexico, a
shortwave trough west of Washington and Oregon over the Pacific
and another trough further west south of the Aleutian Island
chain of Alaska. So, we have some ground to traverse yet before we
start nailing down any details.
What we know...1) Models have converged on a low moving through
the Great Lakes over the weekend, 2) the exact track of that low
is up for considerable debate, 3) as is the depth of the low
depending on how the upper waves phase (or not) and 4) there is
the potential for some impacts.
The operational GFS and ECMWF bring a low up through Indiana and
Ohio to near Lake Erie and then off into Ontario. Many of the lows
in the ensembles of both models though are tracking over the
Lower Peninsula, or a bit further north and west than their
deterministic runs. That would be a warmer solution and more in
the way of rain. The operational runs would favor a swath of snow
through portions of the Southwest Quarter of Lower Michigan.
At this point it is probably safe to say that we are looking at
the potential of rain and possibly some snow in the Friday
through Sunday time frame, but there is just way too much play in
the evolution to nail much more down than that. Especially given
the range in the forecast and we are talking about the interplay
of 2 shortwaves and a cut off low that are all still over the
Pacific (one of which is half way across the Pacific).
Bottom line...stay tuned as we watch the evolution of this system
over the coming days. Accumulating snow is certainly possible, but
temperatures both aloft and at the surface are a bit marginal and
as stated above there is quite a bit of uncertainty.
-- Potential for another weak system early next week --
A weak upper shortwave and associated surface low move through the
area next Monday night and Tuesday. At this point it looks like
some very small chances for some light rain or snow. We could
remain dry as well given what the operational runs of the ECMWF
and GFS are showing.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 657 PM EST Tue Dec 8 2020
Widespread MVFR cigs of 1500-2500 ft this evening are expected to
trend down to IFR or LIFR late tonight into Wednesday morning,
accompanied by some areas of fog as well. Conditions improving
Wednesday afternoon, with cigs gradually lifting into MVFR
Confidence is low however as to whether or not we eventually
clear out this persistent stratus deck and go VFR by mid to late
afternoon. The best chance of that occurring would be west of LAN
and JXN. Southwest sfc winds of 10 to 20 kts this evneing will
diminish to around 10 kts and become west later tonight into
Issued at 330 PM EST Tue Dec 8 2020
Small Craft Advisory remains in affect through midday on
Wednesday. We are just entering into the period of stronger winds
(southwest 20-30 knots) from about 300pm through 300am. Webcams
along the lakeshore are already showing rolling whitecaps so we
fully expect to see 5-7 footers at the peak later this evening and
tonight. Waves and water levels are expected to remain below
criteria for the issuance of a Lakeshore Flood headline. Winds and
waves will steadily diminish on Wednesday as the winds subside a
bit. The next period of potentially higher winds and waves will
come into next weekend, most likely on the backside of a low
pressure system (Saturday into Sunday).
LM...Small Craft Advisory until 1 PM EST Wednesday for LMZ844>849.
Area Forecast Discussion
National Weather Service Jackson MS
842 PM CST Tue Dec 8 2020
Updated for evening discussion.
Have made some minor updates to the forecast this evening to add
in some patchy fog after midnight. Dewpoints are slow to drop, and
winds have already gone calm. Though NAMNest is by far the most
aggressive, the GFSlamp, HRRR and RAP13 are all trending to more
of a patchy fog overnight.
Prior discussion below:
Tranquil and near seasonal wx conditions continue to prevail over
the lower MS Valley this Tue afternoon, under predom sunny skies.
A sharp upper trough pattern across much of the ern CONUS is also
helping to usher sig drier above H85 into the region, with current
temps ranging from the mid 50s NE to the mid 60s SW. Little change
in this overall pattern is xpcted thru tonight and into mid week,
with lows early Wed from the upper 30s/around 30F, before temps
rebound well into the mid 60s later in the day. A gradual warming
trend may then develop Wed night into Fri, as the sfc high exits
the mid/srn Atlantic Coasts to the east.
The latest model suites are then hinting at rain chances coming
back to the forecast starting late Fri and continuing into Sat, as
an upper low/trough axis quickly lifts NE out of the SW states,
while a sfc reflection out of the mid Plains traverses NE thru the
Midwest/NE states. This sfc low will quickly pull a cold front ewd
thru the Mid South/lower MS Valley areas late Fri thru Sat, with
showers developing along/just ahead of the approaching boundary.
In fact, some weak instability may develop late Fri night as the
front initially moves into the wrn half of the area. This may
translate into a few embedded tstms possible within increasing
showers. As mentioned, the front will then quickly exit to the
east Sat evening, with rainfall tapering off.
Overall temps look to trend near/slightly above normal during the
first half of the weekend, before cooler air once again spreads
into the lower MS Valley from the NW Sun into Mon following the
passage of the cold front.
00Z TAF discussion:
Generally VFR conditions with light and variable winds throughout
the TAF pd. Chance for some MVFR/IFR vis, particularly in the
southeast before dawn. Have some concerns that there may be more
patchy fog elsewhere...but guidance so far is less pervasive.
.PRELIMINARY POINT TEMPS/POPS...
Jackson 36 66 39 70 / 0 0 0 0
Meridian 34 66 38 69 / 0 0 0 0
Vicksburg 35 67 41 71 / 0 0 0 0
Hattiesburg 37 68 39 71 / 0 0 0 0
Natchez 38 66 41 70 / 0 0 0 0
Greenville 36 66 40 69 / 0 0 0 0
Greenwood 36 65 40 68 / 0 0 0 0
Area Forecast Discussion
National Weather Service Memphis TN
906 PM CST Tue Dec 8 2020
We continue to see strong northwest flow aloft across the Mid-
South this evening. A strong polar jet is diving southeast
across the Great Lakes, spilling abundant mid/high clouds into the
OH Valley, but subsidence associated with the subtropical jet
along the Gulf coast has been eroding this cloud cover as it
approaches. We do anticipate an increase in sky cover overnight,
mainly in the northeast half of the CWA and this should help
temperatures level out a bit. Otherwise, some areas have already
reached forecast minimum temperatures, necessitating a quick
update. Min temperatures were lowered mainly across interior west
TN where subtle terrain chances allow the colder air to pool.
Otherwise, the main forecast issue tonight will be the potential
for fog after 06z. We`re already seeing a few sites reporting
minor visibility obstructions and that trend should continue. The
HREF and HRRRE probabilities are rather high for visibility less
than 1 mile across north MS and southwest TN tonight. Patchy fog
was continued, but wording may need to be enhanced if trends hold
.PREV DISCUSSION... /issued 343 PM CST Tue Dec 8 2020/
Currently...An upper trough is pushing off the eastern seaboard
while upper ridging is building into the southern Plains. Surface
high pressure covers the southern U.S. with light and variable
winds across the Mid-South. After a chilly start temps have
recovered into the 50s with Clarksdale breaking the 60F barrier.
Tonight...Main concern is whether fog will develop. Dewpoints have
rebounded into the mid and upper 30s and with mostly clear skies
and light winds temps will fall to the crossover temp. The HRRR
indicates some dense fog developing over parts of the Delta and
north MS while the HREF shows higher chances over NE MS and SE
west TN. High clouds moving south into the region also add another
aspect into the equation. For now will go with patchy fog over
most of the area after midnight. Low temps will generally range
from 33 to 37 degrees though would not be surprised to see some
lows below the freezing mark in the typically colder spots in
north MS and west TN. If some dense fog does form in those areas
there could be some slick spots.
Wednesday and Thursday...Some really nice late fall weather is on
tap. Upper ridging will move across the area as light southwest
surface flow brings in some mild air. Expect plenty of sunshine
with highs well into the 60s and maybe even a 70 possible on
Friday and Saturday...A large trough will develop over the western
U.S. and approach the Mid-South Friday. Most of the Mid-South
will squeak out another really nice day on Friday with well above
normal temps and some sun before rain chances increase west of the
river in the afternoon. Expect numerous to widespread showers and
a few thunderstorms Friday night Saturday morning. Instability
continues to look meager so severe threat remains low but will be
keeping an eye on it. Rain chances will taper off during the day
on Saturday from west to east with cooler temps.
Saturday night through Sunday night...Models are all over the
place Sunday and Monday as they handle the evolution of the upper
trough in much different ways. The operational ECMWF cuts off an
upper low over the Lower MS Valley while the operational GFS
pushes the upper trough through the region and transitions to fast
zonal flow with some dry weather for a couple of days. Their
respective ensemble systems echo their operational counterparts
with the ECMWF ensembles much wetter than the GEFS. The Canadian
system is also trending wetter. Pops have been added Saturday
night through Sunday night.
Monday and Tuesday...Looks like a dry and cool period as either
the GFS pans out or the system picked up by the ECMWF and Canadian
has moved east.
VFR conds through much of the period. The exception may be light
MVFR fog overnight at JBR...MKL..and TUP.
Light and variable winds over the next several hours becoming
southwest around 4 kts or less around midnight. High clouds will
continue to stream in from the north overnight. These clouds
should keep fog from becoming too dense overnight. Southwest
winds will strengthen to 7-9 kts by late tomorrow morning.