Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/18/19
Area Forecast Discussion
National Weather Service Burlington VT
1005 PM EST Tue Dec 17 2019
.SYNOPSIS...
Snow will taper off across the North Country as the night wears
on tonight. Most areas will see an additional dusting to an
inch before the snow ends. An active weather day is expected on
Wednesday. First there will be lake effect snow showers moving
across parts of northern New York in the morning with 1 to 3
inches possible. Then during the late morning hours snow squalls
will form over northeast New York and move across Vermont
during the afternoon hours. Expect difficult travel conditions
as the snow squalls move across the area as impacts include a
burst of heavy snow, wind gusts in the 30 to 40 mph range, and
whiteout conditions. Very cold air will follow in behind the
squalls with bitterly cold wind chills Wednesday night into
Thursday.
&&
.NEAR TERM /THROUGH WEDNESDAY NIGHT/...
As of 831 PM EST Tuesday...Have updated the forecast to add
patchy freezing drizzle to central and southern VT through
midnight. Note that the latest RAP moisture profiles show
abundant low-level moisture lying below the favored snow growth
zone, especially in southern sections. This looks to persist
through about midnight, when the moisture will increase in the
snow growth zone, allowing precip to change back over to plain
snow. We have had reports of light freezing drizzle across
portions of central and southern VT, along with a slight glaze
of ice. Have therefore issued an SPS as well as adding to the
forecast for the remainder of the evening. Otherwise the
forecast is in good shape and no other changes were needed.
Previous discussion...We have received 1 to 3 inches of
snowfall today based on reports and snow is expected to continue
through the evening hours before tapering off later tonight.
Additional snow amounts will be a dusting to an inch. Favorable
850 and 700 millibar frontogenesis, which helped produce today`s
snowfall, is weakening and moving east late this afternoon
which will help limit the amount of additional snowfall. The
overnight hours should be relatively quiet with plenty of clouds
around and lows in the upper 20s to mid 30s.
Everything remains on track for a fairly widespread snow squall
event across the North Country. There will be travel impacts as we
are expecting bursts of heavy snow...1 to 3 inches in a short period
of time...wind gusts in the 30 to 40 mph range...and whiteout
conditions. At this time it appears we should start to see snow
squalls over northeast New York during the late morning
hours...across the Champlain Valley during the early afternoon
hours...and during the mid to late afternoon hours across the
remainder of Vermont.
We continue to see stronger signals than some of the recent snow
squall events to suggest snow squalls on Wednesday could be more
intense. The amount of instability is noticeably greater given the
depth of steeper lapse rates. Strong frontogenetic forcing will
exist in the afternoon and the northern half of Vermont will be in
the favorable northeast quadrant of the strong upper low moving in.
This will help to maximize lift across the area and enhance the snow
squalls. Given the instability and forcing feel there will be some
locations that could see heavier snow amounts and at this time it
appears the northern half of Vermont has the best potential to see
the heavier snow. This of course will cause whiteout conditions,
especially with gusty west to northwest winds of 30 to 40 mph with
the snow squalls. Local study related to snow squalls continue to
highlight strong signals for snow squalls on Wednesday as well. Thus
we will continue to message the idea that these snow squalls will
occur and be impactful.
The coldest air of the season moves in Wednesday night with low
falling into the single digits above and below zero. At the same
time we will have gusty northwest winds and thus create bitterly
cold wind chills. These conditions should continue into Thursday
morning and we will be monitoring for a potential wind chill
advisory.
&&
.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 341 PM EST Tuesday...Thursday and Thursday night will be
cold but quieter on the weather front. Surface high pressure
will ridge into the area, and strong northwesterly upper level
flow will remain in place. Early Thu morning 850 temps near -20
C will warm to around -16 C by 00z, eventually -10 C by early
Friday morning. Despite the slow warming trend, temperatures
will still be well below seasonal normals for Thursday and
Thursday night. Early Thu morning with temperatures still in the
single digits above and below zero and winds out of the
northwest around 10 to 15 kts with higher gusts will result in
wind chill values near 20 below zero in some locations, and even
colder in the higher elevations of the Dacks and Greens where
the winds will be stronger. Temperatures will struggle to get
out of the single digits on Thursday, some lower teens in the
Champlain valley. Winds will slowly decrease through the day and
into Thursday night.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 341 PM EST Tuesday...Quiet weather continues from Friday
onward, as well as a gradual warming trend beginning. Friday and
Friday night will continue to feature surface high overhead,
and also some upper level ridging over the north country. From
Saturday onwards the GFS and ECMWF not in very much agreement. A
weak surface low pressure system passes north of the Great
Lakes, and GFS brings this feature down and across our area
while ECMWF keeps the low well to our north with a much less
amplified pattern represented. If the GFS solution holds true,
would have to mention chance for snow showers both Saturday
night and Sunday.
&&
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Through 00Z Thursday...Widespread ceilings in the 1000 to 3000
foot range will continue through about 06z before lifting into
the 2000 to 4000 foot range for the remainder of the period.
Visibilities will be in the 1 to 3 mile range through 06z with
brief periods of visibilities around a mile as snow continues
over the area. The snow will taper off from west to east after
03z and visibilities will be improving into the VFR category
after 06z and persist there through 12z. Thereafter, expect
MVFR/IFR conditions at KSLK and KMSS in lake enhanced snow. An
area of snow squalls is expected to move from west to east from
mid-morning onward as an arctic front crosses the region.
IFR/LIFR conditions possible in any squalls. Winds will be light
and variable overnight, becoming southwest 5-10 kt on Wednesday,
then turning to the west and becoming gusty 20-25 kt behind the
cold front.
Outlook...
Wednesday Night: VFR. Slight chance SHSN.
Thursday: VFR. NO SIG WX.
Thursday Night: VFR. NO SIG WX.
Friday: VFR. NO SIG WX.
Friday Night: VFR. NO SIG WX.
Saturday: VFR. NO SIG WX.
Saturday Night: Mainly VFR, with local MVFR possible. NO SIG WX.
Sunday: Mainly VFR, with local MVFR possible. NO SIG WX.
&&
.BTV WATCHES/WARNINGS/ADVISORIES...
VT...None.
NY...None.
&&
$$
SYNOPSIS...Evenson
NEAR TERM...Evenson/Hastings
SHORT TERM...Neiles
LONG TERM...Neiles
AVIATION...Evenson/Hastings
Area Forecast Discussion
National Weather Service Goodland KS
429 PM MST Tue Dec 17 2019
.SHORT TERM...(This evening through Thursday night)
Issued at 123 PM MST Tue Dec 17 2019
Water vapor imagery and RAP 500mb analysis showed northerly flow
over the region today with a few clouds passing through to the
south. A closed low continued to track across Canada north of the
Great Lakes, with its trough extending south through the Upper
Midwest to the Texas panhandle. West of the High Plains, upper
ridging built onto the Rockies. At 1 PM MST, temperatures ranged in
the upper 30s to low 40s with northwest winds at 15 to 20 mph,
gusting up to 30 mph in spots.
Flow aloft turns to the northwest tonight as the upper ridge noses
into the Plains. Temperatures fall into the teens and low 20s, with
west winds around 10 mph or less under clear to mostly clear skies.
The ridge progresses over the area on Wednesday, with sunny skies
expected through the day and highs in the 50s. The main concern
during this timeframe will be the potential for elevated fire
weather conditions, particularly during the afternoon hours. Relative
humidity values are forecast to fall into the 15 to 20 percent range
for locations roughly along and south of I-70, with southwest winds
gusting up to 25 mph in this area as well. Will continue to monitor.
For Wednesday night, temperatures fall into the upper teens and low
20s. Clouds increase from the west overnight as an upper trough
makes its way to the Rockies. Limited moisture is in place as this
disturbance pushes to the Plains through Thursday night, and dry
weather prevails. We will see a slight drop in temperatures on
Thursday (mid 40s to low 50s) as the trough passes through and
clouds linger. Low temperatures should be in the upper teens and low
20s once again for Thursday night with clearing skies.
.LONG TERM...(Friday through Tuesday)
Issued at 1214 PM MST Tue Dec 17 2019
Once the upper trough moves east of the region on Friday, skies
will clear again and temperatures will continue to warm each day
through the weekend as another large upper ridge of higher
pressure moves over the Rockies and High Plains. Conditions will
remain dry through Sunday with highs around 50 on Friday warming
to the lower 60s by Sunday. Overnight lows will remain mainly in
the 20s.
Just beyond the long term period, it looks like Christmas Day and
the couple of days that follow could be active as southwest flow
aloft lifts several disturbances out of the desert southwest and
across the central High Plains region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 429 PM MST Tue Dec 17 2019
High pressure cresting over the region will allow for VFR
conditions to prevail thru the forecast period.
Winds will be NW around 10kts at both sites with a transition to
WSW between 03z-05z Wednesday. KGLD will have SW around 10kts by
19z.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...JBH
LONG TERM...LOCKHART
AVIATION...JN
Area Forecast Discussion
National Weather Service Green Bay WI
856 PM CST Tue Dec 17 2019
Updated aviation portion for 06Z TAF issuance
and new information added to update section
.UPDATE...
Issued at 850 PM CST Tue Dec 17 2019
No changes to the Wind Chill Advisory planned this evening. Hourly
temperatures have been tracking reasonably well, so anticipate the
wind chills in the forecast for late tonight will work out pretty
well. This will be a marginal event, but wind chills across much
of the northwest 1/3 of the area should drop to around 20 below
zero at times late tonight. Will issue an SPS to highlight the
cold across the rest of the area. Updated WSW will be out ASAP.
&&
.SHORT TERM...Tonight and Wednesday
Issued at 230 PM CST Tue Dec 17 2019
The latest RAP analysis and satellite/radar imagery show an arctic
cold front moving southeast across far northern Wisconsin early
this afternoon. A broken low overcast deck with scattered flurries
and light snow showers continue ahead of the front. Snow showers
have been more widespread over central WI than further east.
Additional light snow showers are occurring right along the front
which should move southeast across the area during through the
late afternoon or early evening hours. Behind the front, clearing
skies are moving across northern Minnesota, while lake effect snow
showers are occurring over the Upper Peninsula. Forecast concerns
include snow shower trends, and potential for wind chill advisory
late tonight.
Tonight...The arctic cold front will be exiting northeast and
east-central WI by 8 pm to 9 pm. A few light snow showers may
therefore linger over the Fox Valley and Lakeshore areas through
this time. Meanwhile, other areas should be seeing clearing skies
as northwest winds drive in dry, arctic air into the area. The
exception will be over far northern WI where trajectories are
favorable for lake effect snow showers. However, the incoming
airmass is very cold and dry, with 850mb temps falling to -25C
over western Lake Superior. This will limit potential
accumulations, since temps will be too cold for dendritic snow
growth. Will show up to an inch of accumulations. Though winds
will be diminishing late, temps falling well below zero combined
with winds of 10 to 15 mph will result in wind chills falling to
20 to 25 below over north- central WI. Will issue a wind chill
advisory with coordination from surrounding offices. Lows ranging
from 10 below over the northwoods to 5 above near Lake Michigan.
Wednesday...Arctic high pressure will become centered across the
state. Backing winds will end the lake effect snow showers over
north-central WI by midday or early afternoon. Otherwise, it will
be a quiet and mostly sunny day with mid and high clouds pushing
overhead. It will also be much colder with temps ranging from 7
above to the mid teens.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 230 PM CST Tue Dec 17 2019
Quiet weather is expected through much of the extended forecast. The
trend will be toward well above normal temperatures into the
upcoming weekend.
Wednesday night through Thursday night: A weak surface trough is
expected to be in place across Lake Superior/Upper Michigan
Wednesday night into Thursday morning. Weak forcing along the front
along with a minimal amount of moisture, may lead to a few light
snow showers or flurries through Thursday morning. Farther south,
away from the UP/WI border, increased cloud cover will likely be the
only impact. Temperatures will continue to remain below normal for
this time period as the area remains on the western fringes of the
upper-level trough axis. Daytime highs are expected to be in the 20s
to around 30. Overnight lows will warm from the single digits above
zero Wednesday night to the teens and low 20s for Thursday night.
The rest of the extended continues to look fairly quiet with only a
few subtle/moisture starved features passing through the area. The
largest of these features will likely brush through the area Friday
into Friday night, allowing for increased clouds and perhaps a few
flurries or sprinkles, but conditions generally looks dry for that
time period. Upper-level zonal flow to more of a ridging pattern
will build across much of the area into the upcoming weekend. This
will result in steadily warming temperatures, with many places
warming above normal by the end of the work week into the weekend.
In fact, some places could see upper 30s to around 40 from Friday
through much of the weekend. One concern from the warmer daytime
temperatures will be the potential for fog formation overnight into
the morning hours with warmer air moving in over the snowpack.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 850 PM CST Tue Dec 17 2019
A colder and drier air mass will continue settle into the area
overnight. Skies were clearing in all but the areas immediately
downwind of Lake Superior. Anticipate MVFR conditions in the
snowbelt, and VFR conditions elsewhere.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
Wind Chill Advisory from midnight tonight to 8 AM CST Wednesday
for WIZ005-010-011-018-019-030.
&&
$$
UPDATE.........Skowronski
SHORT TERM.....MPC
LONG TERM......Cooley
AVIATION.......Skowronski
Area Forecast Discussion
National Weather Service Grand Rapids MI
1050 PM EST Tue Dec 17 2019
LATEST UPDATE...
Synopsis/Update
.SYNOPSIS...
Issued at 1049 PM EST Tue Dec 17 2019
- Heaviest snow showers occurring now through 200am
- Snow continues overnight into Wednesday morning at a lighter
intensity
- Cold on Wednesday with snow showers tapering off through the day
- Quiet weather Friday through Christmas with above normal
temperatures expected most of Christmas week
&&
.UPDATE...
Issued at 1049 PM EST Tue Dec 17 2019
Bottom line: No changes to the ongoing headlines with this update.
That said, we feel the most significant snow is occurring now and
will taper off significantly after 200am. A key component to look
at to determine the strength and intensity of lake effect snow is
the moisture and lift in the 850mb-700mb layer. Essentially, this
is the upper half of what would be deeper lake effect snow, as
most of the time it occurs at and below 10,000ft. When moisture
and lift ends in this layer (5,000 to 10,000ft) lake effect tapers
off in coverage and intensity typically. Tonight, moisture and
lift rapidly peel away to the south and east at or around 100am.
Overnight, we should see more typical wind parallel lake effect
snow bands with a lighter intensity as opposed to the stronger
bands we are seeing now. The overnight shift will look into
whether or not counties will be able to be cancelled early. Given
ongoing snow in all of the counties in the advisory feel compelled
to keep the advisory going for travel conditions which are
certainly being impacted according to the MIdrive website. The
highest totals so far have come in from the band that has set up
from Ottawa County into Southern Kent. 4 inches near Jenison and
Byron Center. These totals will be more the outlier vs the rule.
Most locations will see totals in the trace to 2 inch range.
&&
.DISCUSSION...(This evening through next Tuesday)
Issued at 321 PM EST Tue Dec 17 2019
No significant changes in our forecast thinking for tonight and
Wednesday. The passage of an arctic front will bring a short
period of snow showers with gusty winds and some blowing snow to
locations near and west of US-131 tonight into early Wednesday.
All areas likely will have snow showers from late afternoon over
the northern sections early to mid evening over the southern
sections of our forecast area.
We have a digging northern stream shortwave and associated upper
level closed upper low that makes it almost as far south as Lake
Superior tonight. That puts our area in the cyclonic side of the
upper jet for a few hours. It is during this time we get deeper
moisture with cyclonic (to over 700 mb) and there is strong lift
in the DGZ. Also with the 30 knot northwest winds, the snow bands
will make it well inland and the max snowfall band will be inland
of the lake shore, nearly one entire county inland in fact. So
the heaviest snowfall amounts will be closer to US-131 than US-31.
At any one location the stronger snow showers will be only around
3 hours, so nearly all the expected accumulations will have to
happen in that time frame. During that time the latest HRRR shows
the best lift is centered in the DGZ so this will make for fluffy
snowflakes and that will allow higher snowfall amounts. The HREF
and HRRRv4 are suggesting 1 to 2 inches over our advisory area but
with some localized bands of 2 to even 4 inches. Given the gusty
winds associated with this there will be blowing and drifting
snow with these snow squalls.
As it turns out and as I had suggested last week when I wrote
about this event, there is another strong Pacific system upstream
so that will kick this system out rather quickly. By mid morning
the polar jet core will be lifting our of this area and that will
end the significant snow showers. However the shallow cold air
does not get pushed out until the surface warm front comes through
Thursday during the day. The lift on that warm front will have
enough moisture to create more snow Thursday but that will be
north of our forecast area. Here the air should be to dry so in
fact we may see some sunshine once again (like mid morning today).
That same upstream Pacific system will build a deep trough just
off shore of our CONUS west coast by Friday. That in turn results
in upstream ridging so until that upstream trough gets to Michigan
(after Christmas) we will have split flow with polar jet in
northern Canada and the southern stream south of Michigan. That
will lead to an extended period of dry weather. The last such
event was in 2010 when between the 13th and the 28th we had only 3
days with measurable precipitation. Most recent Decembers it`s
hard to get 3 days in a row with no precipitation. Likely we will
see some days with highs into the 50s next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 717 PM EST Tue Dec 17 2019
We are expecting a burst of snow to move through the TAF sites
between 00z and 06z. During this time, conditions will dip at
least to MVFR, if not IFR for shorter periods of time. Overnight,
after 06z, the lake effect snow will be a lighter, so any MVFR
conditions should migrate back to the lakeshore, towards MKG.
On Wednesday the snow showers will taper considerably, essentially
to flurries. VFR weather is expected inland, with MVFR ceilings
likely through midday at MKG. Even at MKG we are expecting VFR
weather to develop in the afternoon.
Northwest winds of 10-20 knots with higher gusts are expected
through 06z. Winds will gradually taper a bit late tonight and
more so into Wednesday afternoon and evening.
&&
.MARINE...
Issued at 321 PM EST Tue Dec 17 2019
We now have a coastal flood advisory and small craft advisory
through Wednesday afternoon. The small craft advisory goes until
midnight tomorrow night. This is more than typical for a strong
cold advection event at this time of year (really any time of
year).
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until noon EST Wednesday for MIZ050-
056>058-064>066-071>073.
Lakeshore Flood Advisory until 4 PM EST Wednesday for MIZ037-043-
050-056-064-071.
Winter Weather Advisory until 4 PM EST Wednesday for MIZ037>039-
043-044.
LM...Small Craft Advisory until 11 PM EST Wednesday for LMZ844>849.
&&
$$
UPDATE...Duke
SYNOPSIS...WDM
DISCUSSION...WDM
AVIATION...Duke
MARINE...WDM
Area Forecast Discussion
National Weather Service Lincoln IL
812 PM CST Tue Dec 17 2019
.SYNOPSIS...
Issued at 210 PM CST Tue Dec 17 2019
Clouds will linger this evening across much of central and
southeast Illinois. Some clearing is expected toward Wednesday
morning, so expect more sunshine tomorrow. Colder than normal
conditions will continue through Wednesday night, before a warming
trend develops. Drier weather is expected over the next week,
possibly all the way through Christmas Day.
&&
.UPDATE...
Issued at 812 PM CST Tue Dec 17 2019
Low stratus deck continues to ooze toward the I-70 corridor this
evening. Been getting a few reports of very light snow or freezing
sprinkles, though this does not seem to be causing any impacts at
the moment. High-res model guidance has been persistent in showing
some dense fog developing in many areas east of the Illinois
River, before settling into southeast Illinois. While this seems
to be overly ambitious, some fog seems more plausible along the
leading edge of the stratus deck, and visibilities have recently
been lowering some at Paris and Mattoon. Have added a mention of
some patchy fog in these areas.
On the back edge, HRRR guidance appears to be clearing it out too
quickly. Made some adjustments to the timing of the clearing,
focusing more on the post-midnight period across the northern CWA,
and leaving the central and southeast mostly cloudy through the
night.
Updated zones/grids have been sent.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 210 PM CST Tue Dec 17 2019
A blanket of low clouds continues to slowly drift eastward this
afternoon, but still has yet to reach Champaign to Mattoon. The
cloud layer appears thin, based on visible satellite images,
allowing for some erosion of the clouds on the southern and
eastern peripheries. High resolution guidance continue to point
toward the cloud mass advancing all the way to the Indiana border,
especially for areas north of I-70 initially, then eventually
drifting into our southeast counties. Confidence not too high on
that scenario based on the rate of erosion of the clouds. However,
nocturnal inversions can halt clearing of clouds, and actually
facilitate expansion again. So will continue with a cloudy
forecast for most of the area through the evening and even after
midnight for much of the forecast area. Cloud cover will help to
keep low temps warmer that under clear conditions, with lows in
mid to upper teens.
Wednesday will feature high pressure becoming more established,
with drying conditions and more sunshine. Despite the sun, Wed is
slated to be our coldest day of the next 7 days. Highs will be a
few degrees colder than today, with readings in the lower 20s in
our NE counties, and mid to upper 20s farther southwest, from
Rushville to Springfield to Lawrenceville.
&&
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 210 PM CST Tue Dec 17 2019
An prolonged period of quiet weather is on tap for the entire
extended forecast, as above normal temperatures develop. Upper
level ridging and rising heights will initiate the warming trend
on Thursday, before a weak upper level trough on Friday into
Saturday temporarily stalls the warming trend for Saturday. More
pronounced ridging is indicated in the GFS/ECMWF/Canadian NH for
Sunday and Monday, triggering a steady southerly surface flow.
Surface high temperatures will climb well above normal by early
next week, with readings in the upper 40s to around 50 by Monday
and Tuesday next week. Those conditions will likely melt all snow
that has accumulated from this past event.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 527 PM CST Tue Dec 17 2019
IFR conditions widespread over the TAF sites at 23Z, with ceilings
between 300-800 feet. Significant improvement will be slow, with
the worst conditions through 06Z. Back edge of the low clouds
near KMLI now with ceilings closer to 1200 feet. This may reach
KPIA around mid evening, but most sites should be after 06Z. VFR
conditions likely to hold off until about 09-12Z.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SYNOPSIS...Shimon
SHORT TERM...Shimon
LONG TERM...Shimon
AVIATION...Geelhart
Area Forecast Discussion
National Weather Service Memphis TN
949 PM CST Tue Dec 17 2019
.UPDATE...
Satellite imagery shows clear skies across the Mid-South. An
upper-level trough is situated over the area and is helping bring
in much cooler temperatures with west-northwest flow. Temperatures
are already in the mid 20s to mid 30s and are expected to drop
down into the low to upper 20s overnight. High pressure is located
upstream and will build in to the region over the next couple of
days. With that, temperatures will start to rebound starting
tomorrow afternoon but we`ll still remain about 5-10 degrees
below normal.
KRF
&&
.PREV DISCUSSION... /issued 551 PM CST Tue Dec 17 2019/
.DISCUSSION...
A cloudy, cold post-frontal air mass remains in
place across the Mid-South this afternoon. The clearing line has
been slow to cross the CWA, but we`ll see improvement throughout
the remainder of the afternoon and evening. Temperatures have
warmed into the upper 30s and lower 40s where the sun has peeked
through, but most of the area remains in the mid 30s as of 3 PM.
A broad trough remains in place across central CONUS with
shortwave ridging over the Southwest. The mid-level trough axis
has moved east of the CWA, but the lagging 500 mb axis will swing
through tonight. North winds continue to advect drier air into
the Mid-South with dewpoints generally at or below 30F.
Diminishing winds after sunset, along with dry air and clearing
sky conditions, will promote strong radiational cooling
overnight. Temperatures are forecast to drop into the 23-28F
range.
We`ll see a a few nice days to round out the remainder of the
work-week as the Southwest shortwave ridge translates across the
lower MS Valley. Expect mostly sunny conditions midweek with
temperatures warming into the upper 40s and lower 50s by Thursday
afternoon. Cloud cover will begin to increase Thursday night as a
digging trough moves across the Southern Rockies.
The 12z global model consensus is for this trough to close off it
it ejects into the Southern Plains, moving ESE toward the central
Gulf Coast. This keeps much of the lift associated with this wave
south of the CWA, but it will be close enough to maintain low rain
chances Friday night into early Sunday, mainly across north MS.
Confidence is rather low at this time as slight deviations in the
storm track could result in higher PoPs (or removal of PoPs) with
this system. Either way, the Pacific air mass behind this system
doesn`t look to have a significant impact on temperatures.
Mid-range global ensembles are in good agreement on the
development of a ridge over the central CONUS early next week,
with a deep trough over the West Coast. This will give us a few
dry days to start the week with temperatures warming into the 60s
across most of the area by Tuesday. Christmas looks to arrive with
above normal temperatures across the region, so the potential for
a White Christmas across the Mid-South is quickly melting away.
MJ
&&
.AVIATION...
00Z TAFs
MVFR strato-cu cleared MEM and MKL at 2330Z. TUP a few hours left
to go, but should clear as well.
NAM soundings depicted dense fog developing at most of the TAF
sites toward 06Z, but this was not corroborated by RAP soundings.
925mb (FL020) winds of 34020KT are not climatologically favorable
for dense fog, but will continue to monitor surface VSBY trends,
as well as the upstream IFR deck over the snow in southern MO.
PWB
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Marquette MI
647 PM EST Tue Dec 17 2019
.SHORT TERM...(This evening through Wednesday)
Issued at 424 PM EST TUE DEC 17 2019
WV imagery and RAP analysis indicated a mid/upper level low over
northern Ontario resulting in cyclonic westerly flow through the
northern Great Lakes. A shortwave trough into western Upper Michigan
and nw WI had boosted the w to nw flow LES early this afternoon as
850 mb temps dropping to around -21C.
Tonight, expect the LES to continue for nw flow favored locations as
850 mb temps drop to around -25C, providing plenty of instability.
The shorter fetch into the west with inversion heights to around 5k
ft and DGZ shrinking to near the surface will limit snowfall amounts
to the 1 to 3 inch range. Over the east, with a longer fetch,
inversion heights into the 6k-7k ft range and a greater portion of
the DGZ in the convective layer will support snowfall amounts of 2
to 5 inches with some locally higher amounts where any stronger
bands persist.
The arctic air moving into the area will drop temps into the zero to
5 below range inland. The cold air combined with winds to around 10
mph will result in wind chills in the -10 to -25 range. Northwest
winds will provide enough modification from Lake Superior to keep
temp temps from dropping off as far as locations farther to the west
and south.
Wednesday, the LES will gradually diminish as surface high pressure
builds into the region. Inversion heights dropping to around 3k ft
over the west should limit additional amounts to around an inch.
Over the east, 1 to 3 inch amounts are expected. High temps will
struggle to around 10.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 440 PM EST TUE DEC 17 2019
The long-term period will be generally quiet after snow showers move
east of the area early on Thursday. On Thursday morning, a quick
passive shortwave will move across Lake Superior bringing a period
of snow showers across the Keweenaw and eastern UP. Not expecting
much snow accumulations, with 1 to 2 inches possible Wednesday
night, wrapping up shortly after daybreak. Heights will rise through
the beginning of the day on Thursday, before stalling out as
troughing continues across New England. Then into Friday, a
shortwave will approach the Northern Plains from Canada and looks to
cross Lake Superior Friday night. This shortwave may bring a period
of -SHRASN overnight, but not biting too much on this. If anything,
precipitation will look to remain off the the north as the shortwave
wraps up and passes to the north through Canada.
After this wave passes, precipitation chances look minimal. Global
ensembles suggest a ridge building across the central CONUS which
will bring 850 temperatures above 0C Saturday through Monday. This
will bring an increase to the high temperatures across Upper
Michigan between 5F to 10F above normal through Monday. Skies will
remain mostly cloudy through the weekend, but the upcoming
freeze/thaw cycle may bring the threat of icy spots on untreated
surfaces.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 640 PM EST TUE DEC 17 2019
Northwest flow lake effect snow and clouds will prevail through the
forecast period with mainly MVFR cig expected. Expect IFR vsby at
KCMX tonight when the most frequent and heavier LES will occur
while KIWD will see vsby fluctuate between MVFR and IFR. Look for
VFR vsby at KSAW with only ocnl MVFR vsby possible. In addition
the northwest winds will be strong enough at KCMX, gusting to
around 25 knots, to which will also reduce vsby at times in BLSN.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 424 PM EST TUE DEC 17 2019
Gale warnings and heavy freezing spray warnings will dominate Lake
Superior through early Wednesday with the heavy freezing spray
potential lasting well into Wednesday. Winds later Wed are
expected to drop off fairly quickly as high pressure builds in
from the west. Sustained winds of less than 20 knots to prevail
late Wednesday through early Friday. By mid-morning Friday, winds
will pick back up out of the SE with near gale-force gusts
possible Friday afternoon. By Saturday morning, winds are
anticipated to drop back below 20 knots sustained, generally
prevailing through the weekend as high pressure looks to build
back in by Sunday. Some SW sustained winds could locally approach
25 knots late Saturday. The fairly settled winds are looking to
then continue into early next week.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Winter Weather Advisory until 1 PM EST Wednesday for MIZ006-007-
085.
Lake Superior...
Heavy Freezing Spray Warning until 3 PM EST Wednesday for LSZ251-
267.
Gale Warning until 9 AM EST Wednesday for LSZ243>245-248>251-
264>267.
Heavy Freezing Spray Warning until 1 PM EST /noon CST/ Wednesday
for LSZ240>245-249-250-263-264-266.
Heavy Freezing Spray Warning until 9 AM EST /8 AM CST/ Wednesday
for LSZ162.
Heavy Freezing Spray Warning until 11 AM EST Wednesday for
LSZ246>248-265.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...JAW
AVIATION...Voss
MARINE...JLB
Area Forecast Discussion
National Weather Service San Francisco Bay Area
512 PM PST Tue Dec 17 2019
.SYNOPSIS...Unsettled weather returns later today and tomorrow,
bringing the next chance for rain along with a slight chance of
thunderstorms along the coast tonight. Although there may be some
light rain possible across North Bay Thursday into Friday, more
widespread rain will develop for this weekend, as a cold front
moves through the region.
&&
.DISCUSSION...as of 01:48 PM PST Tuesday...Satellite imagery
still showing mid to high level clouds moving over the region
ahead of an approaching surface low and weak cold front. KMUX
radar has begun to pick up some echos well out over the waters.
Lightning detection continues to show some pulses and strikes out
over the ocean closer to the surface low. Temperatures remain
mainly in the 50s this afternoon with a few spots right around 60
deg F. Overnight lows tonight will be chilly once again, although
likely a few degrees warmer than this morning given the persistent
cloud clover. Expect lows in the 40s for most locations with
isolated cooler spots in the mid to upper 30s. Some cooling is
forecast for tomorrow`s afternoon high temperatures in the wake of
the exiting cold front. Highs will remain mainly in the 50s once
again, but probably a few degrees cooler than today.
As mentioned this morning, a slight chance of thunderstorms has
been added into the forecast beginning late this afternoon over
the waters and for coastal areas tonight and into early tomorrow
morning. High res models show precipitation arriving along the
coast by late this evening along with increased instability. Very
little change with rainfall amounts from this next system forecast
generally at 0.10"-0.25" for most locations, 0.25"-0.5" for
coastal areas, and possibly 1"-1.5" for coastal mountains. Snow
levels still look to be about 3500 ft or so this afternoon and
early evening, but the precip may not arrive in time for those
peaks to see any snowfall. As showers begin to move through, snow
levels will rise to around 4500 to about 5000 ft limiting
accumulating snow to the higher portions of Monterey/San Benito
counties. Only minor accumulations are expected at this point with
no significant impacts. Showers may linger into the early afternoon
tomorrow before tapering off for most locations.
Once those showers move out, most of the forecast area will see a
break in precipitation into Thursday. The exception will be
possible light shower activity across the North Bay ahead of the
next system. A weak warm front over northern California on
Thursday will keep light showers north of San Francisco Thursday
and into Friday. Rainfall amounts expected to be light at less
than 0.25" between Thursday and Friday.
The main event will arrive over the coming weekend as a cold front
moves through the area. Timing still brings the front through
sometime on Saturday and into Sunday with lingering showers
persisting into early next week. Will have more details on exact
timing, rainfall amounts, and forecasted wind speeds/gusts as we
get closer to the weekend and within the scope of the higher res
models. Looking out further into next week, the GFS and ECMWF
still keep us in a wet pattern through Christmas. Additionally,
the CPC 6-10 and 8-14 day outlooks both show below normal
temperatures and above average precipitation for most of
California. This is still fairly far out in time and details will
likely change between now and then, but active weather looks to
continue.
&&
.AVIATION...as of 5:12 PM PST Tuesday...It`s VFR at the terminals
per latest metar observations. Incoming weather is a difficult
pattern to analyze and forecast in the 00z tafs. The primary
surface low is approx 300 miles west of Eureka CA, the latest
WRF/NAM show a secondary surface low developing to the south along
the cold front tonight, the low is forecast to reach the
Mendocino Coast early Wednesday morning moving a cold front
eastward over much of the forecast area Wednesday morning. Due to
smaller scale forecast developments upstream in the nearest term
and large disagreements in the details between meso-scale model
output and global models and 12z statistical guidance, confidence
is low; more time is needed to further analyze current weather and
adjust tafs to latest meso-scale model output timing.
Surface wind decoupling is likely tonight as lower level south winds
ramp up, low level wind shear (llws) likely per WRF model output.
May need to include llws in 00z tafs. Slight chance of thunderstorms
is advertised for the overnight as a negatively tilting 500 mb trough
accompanied by a vorticity lobe rotates through to the east late
tonight and Wednesday morning. Bottom line: expect lowering ceilings
and visibilities with pre-cold frontal rain as advertised becoming
post frontal showers Wednesday, including low level wind shear late
tonight into Wednesday morning.
VFR-MVFR in unstable atmosphere with scattered showers Wednesday.
Vicinity of KSFO...VFR with E-SE wind continuing into the evening,
cloud ceilings steadily lowering with wet runways developing by late
evening or midnight. MVFR ceiling Wednesday morning. Will look into
adjusting to earlier timing of cold frontal passage Wednesday morning.
A period of low level wind shear also likely tonight per WRF and RAP
model output.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...VFR with E-SE winds increasing in the
Salinas Valley, ceilings steadily lowering in wet weather by late
evening or midnight. MVFR ceilings Wednesday morning. May be a
period of low level wind shear tonight, need more time to analyze
the weather and meso-scale model output.
&&
.MARINE...as of 3:49 PM PST Tuesday...A line of rain showers over
the western outer waters is moving east toward the California
coast. Southerly winds will be moderately strong and gusty out a
head of the cold front driving the rain. Expect these southerly
winds to persist through mid-week. Some lightning was spotted via
satellite earlier today while monitoring this system. As the cold
front tracks eastward, the coastal waters are forecast to see
rain this afternoon and into the evening. As the northwest swell
has subsided slightly today, it is forecast to rebuild once again
tonight. The strong winds associated with the front with a longer
period swell will create hazardous seas conditions over the
waters, particularly for smaller vessels. Expect these hazardous
conditions to persist in some form, due to either winds or swell,
through much of the week.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...SCA...Pigeon Pt to Pt Pinos 0-10 nm until 3 AM
SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm until 3 AM
SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm until 3 AM
SCA...Pt Arena to Pt Reyes 0-10 nm
SCA...Pt Reyes to Pigeon Pt 0-10 nm
SCA...Pt Arena to Pigeon Pt 10-60 nm
SCA...SF Bay from 9 PM until 3 AM
&&
$$
PUBLIC FORECAST: AS
AVIATION: Canepa
MARINE: DK
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Area Forecast Discussion
National Weather Service Paducah KY
235 PM CST Tue Dec 17 2019
.SHORT TERM...(Tonight through Thursday night)
Issued at 235 PM CST Tue Dec 17 2019
Dry and cold conditions are expected through Wednesday night,
followed by slight moderation on Thursday. The main issue tonight
and Wednesday is the potential for low stratus clouds to develop
or move into our region. The clouds would of course impact
temperatures. Visible satellite imagery indicates the southern
edge of the snowpack is just north of a Mt. Carmel IL to Mt.
Vernon IL to Perryville MO line. The snowpack will indirectly
affect temps until the northwest low-level flow backs more
westerly or southwesterly.
As of 20z, a large area of low stratus clouds blanketed much of
northern and western Missouri, as well as central Illinois. The
leading edge of the stratus was creeping east toward the kstl
metro area. The low levels are already moist over the lower Ohio
Valley, as evidenced by the broken stratocumulus deck. Nocturnal
cooling will favor persistence and/or development of low clouds
through the early morning hours. Forecast model soundings for kevv
from the rap model indicate low stratus will occur there after
midnight and linger through at least mid-morning Wed. The models
are the most bullish on low clouds along and north of a kmdh to
Madisonville line late tonight into Wed. Will follow that trend in
the forecast, though low stratus is possible anywhere by late
tonight. Along with that, some flurries or freezing drizzle cannot
be ruled out, but any impacts are a very low probability.
On Wednesday, the idea is that any low clouds will mix out in the
afternoon. Climatologically, this would be hard to accomplish with
the sun near its lowest angle of the year. Highs will range from
near freezing along the Interstate 64 corridor to near 40 along
the Tennessee border.
On Thursday, southwest winds on the back side of the surface
high will dry out the low levels. Mainly sunny skies are expected
Thursday. High temperatures will be in the mid to upper 40s.
Despite the south flow aloft, lows should be down in the 20s
Thursday night. Decoupling of the boundary layer is hard to avoid
on these long December nights.
.LONG TERM...(Friday through Tuesday)
Issued at 155 PM CST Tue Dec 17 2019
By Fri, the mid/upper flow across the CONUS is forecast to split
into northern and southern streams across the country`s midsection.
By the middle of the weekend, the northern stream will be in a broad
trof pattern. Meanwhile, the southern stream will develop a vigorous
low pressure system which is progged to steadily move across the
Deep South, missing the PAH forecast area, according to most of the
deterministic models, ensemble means, and most GEFS members. The CMC
was the odd model out with a solution more reluctant to split the
trof energy. Cloudiness is expected to increase somewhat across our
region early, dissipating by the end of the weekend. Measurable pcpn
associated with the Dixie system is unlikely to occur in our region,
with an axis of high surface pressure that should be more-or-less in
place over our region through Day 7. The presence of this feature
will be more conducive to a dry forecast than not. Another effect
will be relatively light winds.
Post-weekend, a strong ridge aloft is progged to build across the
country`s midsection. This will result in a ramp-up of the slow
warming trend already occurring in the extended period. Highs of 60
degrees appear possible near the TN state line by Day 6 and Day 7
under plentiful sunshine. Lows should be mostly above freezing
by Day 7. Nice, but not very much like Christmas Eve.
&&
.AVIATION...
Issued at 1158 AM CST Tue Dec 17 2019
Skies cleared out across most of se Missouri and srn Illinois by
18z. The back edge of the mvfr cigs has slowed down near the Ohio
River. As a result, kevv/kowb/kpah may continue with mvfr cigs
through part of the afternoon. The tafs will be amended as needed to
account for any delays in the clearing trend.
Another area of low clouds over western and northern Missouri is
making slow eastward progress. These clouds bear watching. Some
potential exists for widespread mvfr cigs again tonight and
Wednesday. At this time, it appears to be a low probability.
Northwest winds around 10 kt will become light this evening.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
SHORT TERM...MY
LONG TERM...DB
AVIATION...MY
Area Forecast Discussion
National Weather Service Pittsburgh PA
903 PM EST Tue Dec 17 2019
.SYNOPSIS...
A reinforcing cold front will return snow showers and squalls
Wednesday. Dry weather and a warming trend takes hold thereafter into
Christmas.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Adjusted sky cover for the mid-evening update as subsidence in
shortwave ridging is supporting clearing sky trends across eastern
Ohio. This trend should be short lived as cloud cover should increase
once again in advance of the next, approaching shortwave. The
remainder of the forecast remains on track.
Previous discussion...
Low temperature will return to seasonal averages tonight in cold
nwly flow.
850mb RAP temperature analysis suggests a rather potent arctic front
upstream across the Great Lakes. This front and its associated,
upper low will pivot across the region by pre-dawn Wednesday.
Steepening low level lapse rates and deep moisture within the
dendritic snow growth zone will support a window of efficient
snowfall, with reduced visibilities in gusty wind in conjunction
with the crossing cold front and in nwly flow thereafter. High
resolution model scenarios maintain the placement of any snow bands
in different locations, though the potential is there for a quick 1-3
inches where they persist. This would most likely be for the the
I-80 corridor due to lake enhancement. As such, verbiage was
maintained within the HWO to indicate this threat.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
Snow showers will diminish with building high pressure Wednesday
night. Cold temperature will persist before rebounding in warm
advection late Thursday/Friday.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A weak Central CONUS trough should result in increasing clouds
Saturday, though a lack of deep layer moisture and lift should limit
precip chances. Another building ridge should result in dry weather
and a gradual warming trend through the rest of the period.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
MVFR cigs and -shsn will be alleviated by building high pres this
eve. VFR may then be expected until a shortwave trough and
associated sfc cdfnt cross the region Wednesday with MVFR cigs and
snow showers.
.Outlook...
High pres is expected to support genl VFR through the weekend.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.
&&
$$