Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/12/16
Area Forecast Discussion
National Weather Service Wakefield VA
831 PM EST Sun Dec 11 2016
.SYNOPSIS...
A warm front lifts through the Mid Atlantic overnight as low
pressure moves into the Great Lakes. The trailing cold front
crosses the region late Monday and stalls across the Southeast
through Wednesday as high pressure builds north of the region. A
strong cold front crosses the area Wednesday and ushers in
Canadian high pressure for Thursday and Friday.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
The current surface analysis places 1032+mb sfc high pressure
now offshore of the Mid-Atlantic coast. To the south, coastal
front/warm front noted moving inland along the Carolina coast, to
near KHSE at 01z. Early evening GOES IR/WV sat imagery showing a
vigorous trough digging across the Upper Midwest. Have noted
increasing/lowering clouds over the past few hours, which has
halted the lowering temp trend over most of the area.
The trough pushes into the Great Lakes tonight with the mid-
level ridge axis sliding offshore. This will allow for the
coastal/warm front to lift NNW through the Mid-Atlantic overnight.
Rain chances are low through early this morning, and given dry air
still aloft, would be nothing more than some patchy drizzle or
very light rain. After 09z/4am, Rain chances increase over the
piedmont as better moisture/forcing arrives from the west. Again
expect any pcpn to be light across the SE coast, patchy dz or
light rain. Farther inland, rather narrow/shallow layer of
overrunning moisture will result in more areas of light rainfall
to move across the NW half of the area...with these showers
gradually weakening into later Monday morning.
Becoming damp and chilly from the interior coastal plain to the
Piedmont. Temps will rise late tonight, but will be slower to rise
inland as the cool air will be stubborn to erode in the cool air
wedge inland. Temperatures currently in the mid 30s to low 40s reach
the low to mid 40s inland late...low/mid 50s along the immediate
coast by 12z Monday.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
A potent nrn stream shortwave trough tracks from the Ern Great
Lakes Monday morning to the Saint Lawrence Valley, which will
push the associated cold front into the area Monday aftn. Srn
stream moisture will pass across the region Monday morning.
Forecast PoPs are highest across the north in closer proximity to
the best forcing for ascent. PoPs diminish during the late morning
and aftn from west-east as drier air pushing into the region
erodes any lingering showers. Deep-layered w-sw flow will limit
QPF, which at this time is forecast to be aob 0.3" for most of the
area, with slightly higher amounts possible over the MD Ern Shore.
Milder with highs ranging from the mid 50s n/nw, to the low/mid
60s se.
The cold front pushes south of the region Monday night and stalls
across the Southeast into Tuesday as it becomes aligned parallel to
strong zonal flow aloft. A slight chc PoP continues for se portions
during the evening. Otherwise, cooler drier air will filter in from
the nw. Clouds initially decrease from nw-se Monday night, before
mid/high clouds likely increase from west-east ahead of a shortwave
trough tracking across the Deep South. Lows range from the low/mid
30s n/nw to the mid 40s se. This shortwave tracks across the
Southeast Tuesday. 11/12z data has suppressed this system, so only a
20% PoP will be maintained for extreme se VA and much of ne NC, with
~30% PoP adjacent to the Albemarle Sound. Partly sunny north to
mostly cloudy south with highs ranging from the upper 40s north to
low/mid 50s south.
An active srn stream continues Tuesday night into Wednesday as the
front remains stalled to the south of the area, and high pressure
remains to the north. The high should be the dominant feature, with
cool/dry air keeping much of the rain potential to the south. PoPs
will generally be 20-30% for far srn VA into ne NC, with PoPs < 15%
across the nrn 2/3rds of the area. Generally partly cloudy north to
mostly cloudy south. Lows Tuesday night range from the low/mid 30s
north to the upper 30s south, followed by highs Wednesday in the
upper 40s north, to low/mid 50s south.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A broad upper level trough crossing nrn Ontario into the Great
Lakes Region finally digs through the Mid Atlantic Region Wed
night...pushing a weak coastal trough (and its associated precip)
out to sea. Precipitation on the back edge may transition over to
snow before coming to an end, however little to no accumulations
are anticipated at this time. As the upper trough drops into the
region Wed night, another arctic airmass is expected to blast into
the area late Wed night...especially as the winds shift to the nw
and increase. Wind speeds along the immediate coast should reach
20-25 mph on Thu with gusts of 30-35 mph...likely resulting in
wind chills of 15-25F during Thu morning. Breezy conditions along
the coast will persist through Fri morning before improving.
Canadian high pressure settles over the Mid Atlantic Region
Fri/Fri night and then slides out to sea on Sat. As the sfc ridge
moves away from the coast, warm air advection processes will very
slowly erode the remaining cold air wedge. Meanwhile, sfc low
pressure pushes out of the Central Plains Fri night and tracks
into the Great Lakes/srn Ontario on Sat. The combination of a warm
front lifting through the Mid Atlantic Region and progressive sw
flow ahead of the approaching cold front could easily pull Gulf
moisture along the Appalachians and cause overrunning precip to
develop in west and northwest counties of the forecast area. Mixed
precip-type likely an issue at the onset Sat morning within the
aforementioned counties before precip changes to all rain by late
morning. However, there is too much uncertainty regarding timing
and placement of moisture this far out in the forecast to define
anything beyond a basic rain or snow precip- type. Will keep a
close eye on this feature and enhance wording/concern as
warranted.
Temperatures typically slower to fall in strong arctic scenarios
versus dewpoints, which tend to plummet first. Lows Wed night in
the mid-upper 20s nw to low-mid 30s se. Arctic airmass arrives in
full force for Thu and highs will struggle to reach the mid-upper
30s most areas (lower 40s far se coastal areas) with wind chills
in the 20s more areas (lower 30s far se coastal areas). Coldest
night of the season is anticipated for Thu night with lows in the
mid teens nw to lower 20s (mid 20s beaches), which is about 1 std
dev below normal. High temps even colder on Fri (low-mid 30s most
areas /mid-upper 30s far se) as high pressure settles directly
overhead. This is roughly 1.5-1.75 std dev below normal. Sfc ridge
axis shifts ewd off the coast Fri night. Overnight temps rebound
by a few degrees with increasing clouds from the southwest,
however the area will stay well wedged within the arctic airmass.
Lows Fri night in the mid-upper 20s (lower 30s far se coastal
areas). Temps slow to warm Sat morning but should warm quickly in
the aftn as a cold front approaches the region and winds become
more south and breezy. Highs Sat 45-50F nw to mid- upper 50s se).
Warmer Sat night with lows in the upper 30s to lower 40s nw to mid
40s to lower 50s se.
&&
.AVIATION /01Z MONDAY THROUGH FRIDAY/...
VFR conditions prevailed at the TAF sites early Sunday evening but
moisture will spread northeast as a warm front lifts through the
area. This will result in lowering conditions and periods of light
rain and drizzle Monday morning. A cold front will cross the region
late in the day Monday.
Ceilings of 4 to 7 Kft were developing over southern Virginia as of
00Z. These ceilings will spread northeast this evening and then
lower to MVFR/IFR in the morning. Rain and drizzle will develop
Monday morning. Conditions slowly improve from the west Monday
afternoon.
A south to southwest low level jet will produce 40 to 45 knots
winds at 2k feet Monday morning and periods of LLWS is indicated
in the forecast.
Outlook: The cold front stalls over the Carolinas and dry weather is
expected Monday night and Tuesday. There will be the possibility of
MVFR or IFR conditions Tuesday morning. Otherwise mainly VFR is
expected into WEdnesday. There will be a chance for precipitation
late Wednesday and Wednesday night associated with a strong cold
front. Drier conditions return Thursday through Friday.
&&
.MARINE...
7 PM update...Winds are increasing a little sooner than expected
especially along the western side of the Bay. Blended the forecast
with HRRR for the first the first six hours of the forecast and
started the SCA 3 hours earlier...at 10 PM.
Previous discussion...
SCA flags added for mouth of James River and Currituck Sound after
midnight tonight into Mon morning. Sfc pressure gradient tightens
in response to a weak coastal trough developing ahead of a low
pressure system tracking across the Great Lakes tonight and across
New England on Mon. Low-end s-sw SCA winds of 15-20kt (gusts
25-30kt Bay/Ocean) are expected to develop after midnight tonight
and persist into Mon morning before diminishing. Seas build to
3-5ft after midnight and will be slower to subside below 5ft for
coastal waters north of Cape Charles Light until late Mon aftn.
Waves building to 2-3ft. The cold front crosses the waters Mon
evening with scattered showers tapering off quickly from west to
east. The airmass behind the front is not much cooler than
pre-frontal antecedent conditions and n winds are expected to
remain aob 15kt all waters late Mon night.
Weak sfc high pressure moves quickly into the region on Tue with
more coastal troughing developing off the Southeast Coast Tue
night/Wed. Meanwhile, broad upper level troughing across nrn
Ontario into the Great Lakes Region should keep the latest coastal
system/trough generally suppressed along/south of the VA/NC border
during this time. The combination of these features will result in
light n-ne winds aob 10kt in this timeframe. Seas 2-3ft/waves
1-2ft. The upper trough finally digs through the Mid Atlantic
Region Wed night...pushing the weak coastal trough out to sea and
bringing another arctic blast to the area. Winds shift to the nw
late Wed night and increase to solid SCA conditions (15-25kt),
which will persist over the waters through Fri morning before
conditions improve. Seas build to 3-5ft by Thu morning/waves build
to 3ft with periods of 4ft waves possible Thu/Thu night. Canadian
high pressure settles over the waters on Fri and SCA conditions
should fully abate by Fri aftn/early evening.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 1 PM EST Monday for ANZ630>634.
Small Craft Advisory until 8 AM EST Monday for ANZ638.
Small Craft Advisory until 4 PM EST Monday for ANZ650-652-654.
Small Craft Advisory until 10 AM EST Monday for ANZ656-658.
&&
$$
SYNOPSIS...AJZ/MPR
NEAR TERM...AJZ/MAM
SHORT TERM...AJZ/MPR
LONG TERM...BMD
AVIATION...AJB/LSA
MARINE...BMD/LSA
Area Forecast Discussion
National Weather Service Gaylord MI
909 PM EST Sun Dec 11 2016
.UPDATE...
Issued at 909 PM EST Sun Dec 11 2016
Mid level short wave trough axis is advancing into the midwest
this evening with the main short wave center pushing into
Wisconsin, and a secondary circulation punching across Iowa.
Attending deepening surface low analyzed over eastern Wisconsin
lifting northeastward into lower Michigan and trailing cold front
stretching down through Missouri. Nice moisture feed up into the
lower lakes region, combined with decent mid level frontogenesis
and upper level jet divergence has lead to a prolonged period of
heavier snowfall through the day, stretching from the midwest
into lower Michigan. Heaviest of the snow has fallen (and
continues to fall) from Chicago across southern lower Michigan
with totals up near 10 inches in a few spots. Lesser amounts up
across northern Michigan with >4 inches south of M-72, trailing
off to under an inch in the tip of the mitt and eastern upper
Michigan.
Axis of widespread snowfall will continue to peel off to the east
as the mid level short wave trough presses into the western Great
Lakes by morning, and surface low pressure pivots up into northern
Michigan. Snowfall has already largely ended for the N/W part of
the CWA. But E/SE parts of the CWA will continue to see widespread
snowfall through around midnight or so before ending, and perhaps
an inch or two of additional snow accumulations.
Only exception, one can just make out sneaky SE flow enhanced
lake bands on radar streaming into the far eastern parts of
eastern upper MI around Drummond Island and De Tour. That will
continue for several more hours until low level SE flow finally
breaks down. Thus have beefed up localized snow accumulations for
that area into the 3 to 5 inch range.
Overnight, upstream mid level short wave and associated "wrap
around" deformation enhancement will be sliding through northern
Michigan late tonight through Monday morning. This will bring
another period of lake enhanced snow showers back into parts of
eastern upper and northwest lower Michigan as winds swing back
around to the W/NW. May pick up another inch or two through
Monday from that.
Headlines: I may be able to trim out some of the counties in
northern lower Michigan as snow has already ended. Will keep
eastern upper Michigan in the advisory for now given the lake
enhanced bands, as well as the E/SE counties.
&&
.NEAR TERM...(Tonight)
Issued at 344 PM EST Sun Dec 11 2016
...Widespread snow winds down tonight...
High Impact Weather Potential...Accumulating snow will continue into
this evening.
Pattern Synopsis/Forecast...Surface low will travel from near the
WI/IL border to eastern Lake Huron by Monday morning. Meanwhile a
strong shortwave/vort max will cut across northern Wisconsin and
Michigan, supporting a cyclonic circulation over northern Lake
Michigan that will lead to lake enhanced snow bands late tonight.
Primary Forecast Concerns...Widespread light snow will be ongoing
into early evening across northern Michigan as weakening isentropic
and frontogenetic lift continue but become more diffuse. DGZ depth
will be shrinking as we head into the late afternoon and evening
with the best omega found further aloft. So, expect snowfall rates
to continue diminishing over the next several hours with just a few
lingering pockets of more moderate snowfall. As the surface low
lifts towards northern MI this evening, models show the snow
tapering off first across northern Lower. Moisture currently over
southern WI and northern IL will continue to stream generally
northeastward, placing our southeastern counties under the remaining
snowfall from this event for the longest duration. This will lead to
perhaps another 2-3 inches near Saginaw Bay before the snow finally
winds down there. Elsewhere expect generally another inch or two
through this evening, though locally higher amounts from lake
enhancement are likely across eastern Chippewa County.
The snow will clear out of our eastern counties early Monday morning
as the cold front sweeps eastward. However, a potent shortwave
clipping the Upper Great Lakes will support the development of a
compact surface low over northern Lake Michigan after midnight. Both
synoptic and hi-res models show this, though the hi-res models
obviously capture potential lake enhanced snow bands in better
detail. The NMM, ARW, and HRRR all show the bands coming ashore
between Leelanau and Manistee counties between 06-12Z Monday, but
they should be fairly narrow and orient themselves parallel to the
coast as they wrap around the low. Thus, not expecting them to
produce prolonged snowfall for any particular location.
Will be trimming back the Winter Weather Advisory to 09Z Monday as
the bulk of the accumulating snow will be winding down and moving
out of the area early Monday.
&&
.SHORT TERM...(Monday through Wednesday)
Issued at 344 PM EST Sun Dec 11 2016
...Arctic Air Arrives Midweek...
High Impact Weather Potential: Burst of snow and gusty winds
possible with arctic boundary Monday night into Tuesday morning.
More lake snows in the traditional snow belts Wednesday.
Pattern Synopsis/Forecast: Current snow-producing system will exit
quickly stage right Monday morning, with all attention then directed
toward deep troughing/attendant very cold core temperature anomolies
dropping south across northern Canada (-20F surface temperatures!).
This troughing will continue to dig southeast over the coming days,
the core of which passes across northern Ontario during the day
Wednesday. Attendant arctic front crosses the northern Lakes early
Tuesday, with bitter cold air quickly to follow it for the midweek
period.
Primary forecast concerns: Plenty! Addressing lingering lake
enhanced snow concerns Monday, lake enhanced snow potential Monday
night into Tuesday morning, and downward temperature trends and
additional lake snows into Wednesday.
Details: Lingering lake effect Monday in those traditional snow belt
locations as vort max and brief surge of cooler air follow departing
system. Attention then turns to rapidly approaching arctic front
Monday night. Multiple forecast issues with this front, with initial
focus on brief window of southwest flow lake enhancement impacting
areas of far northwest lower and up into the Straits region. Time of
favorable wind direction is a short one, but strong forcing tied to
frontal passage and good moisture profiles support at least a window
of some very impressive snowfall rates. Front passes quickly Tuesday
morning, with gusty west winds in its wake. These winds will usher
in a progressively colder airmass, with temperatures likely falling
through the teens during the afternoon (wind chill values several
degrees colder!). Simple magnitude of caa will likely result in some
lake snows in favored areas, although aggressive drying and limited
inversion heights should keep snow intensity in check. However, even
with limited new snow, those gusty winds will likely result in
plenty of blowing and drifting and some treacherous driving
conditions. West flow lake effect continues Tuesday night and
Wednesday, likely steadily increasing in organization and intensity
as synoptic moisture contribution increases. While upstream
temperatures look cold enough to keep fluff producing DGZ near the
surface, would expect lake modification to be extreme, likely
"warming" the profiles enough to place the DGZ within the convective
cloud layer. This, combined with simple persistence of the wind
direction, will likely result in several inches of snow across
northwest lower and for areas near Whitefish Point/Paradise up in
eastern upper Michigan. Add in those gusty west winds, and may see
some whiteout conditions in open exposed areas. Perhaps bigger story
will be the temperatures, with highs struggling into the lower teens
away from the big waters and wind chill values several degrees below
zero. Can definitely see the need for some winter type headlines as
this period draws near. Will continue to use our latest hazardous
weather products as avenues to express this potential high impact
period of weather.
.LONG TERM...(Wednesday night through Sunday)
Issued at 344 PM EST Sun Dec 11 2016
A very active and wintry pattern to continue across the Great
Lakes through the period. At upper levels, a sharp 500mb trough
over the region Thursday will exit east Friday, before a second
500mb trough digs into the the northern Plains and Great Lakes for
the weekend. 850mb temps in this pattern will be between -20c and
-24c...warming only briefing to around -10c Friday in advance of
approaching second 500mb trough. This will keep afternoon highs
well below normal, in the teens, through hte period. Periods of
snow will continue across northern Michigan through the
period...as a storm system exits east Thursday while a second
system pushes across the Great Lakes during the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 742 PM EST Sun Dec 11 2016
Widespread snowfall will diminish/end from W-E as we go through
the evening hours bringing a return to VFR vsbys. CIGS will
continue to bounce from high MVFR to low VFR overnight. But
another smaller batch of snow showers will rotate through the
region late overnight through Monday morning, particularly
impacting NW lower Michigan.
&&
.MARINE...
Issued at 344 PM EST Sun Dec 11 2016
Gusty southeast winds become west and increase in speed later
tonight into Monday as low pressure crosses the region. SCA
conditions will be experienced on some nearshore waters.
Conditions only worsen Tuesday night through Thursday as very
gusty west to northwest winds spread across all the big waters.
Gale conditions are looking increasingly likely during this
period.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY until 4 AM EST Monday for MIZ008-015>036-
041-042.
LH...NONE.
LM...SMALL CRAFT ADVISORY from midnight tonight to noon EST Monday
for LMZ346.
LS...NONE.
&&
$$
UPDATE...TBA
NEAR TERM...MEK
SHORT TERM...MSB
LONG TERM...SWR
AVIATION...TBA
MARINE...MEK
Area Forecast Discussion
National Weather Service Charleston SC
1027 PM EST Sun Dec 11 2016
.SYNOPSIS...
High pressure will prevail until the passage of a coastal trough
tonight. A cold front will move into the area Monday night before
stalling and then likely lingering through mid week. The front will
push offshore Wednesday night, followed by colder high pressure for
late week. Another coastal trough and cold front may affect the
region by next weekend, which would bring more unsettled
weather.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Late this evening: Well, the showers that developed and pushed
onshore across portions of the Tri-County earlier were
surprisingly heavy. That activity has now diminished and moved
off to the northeast while other showers are developing within
the trough offshore. Have updated PoP`s to increase values over
water and land through the early morning hours as this is
supported well by the HRRR and RAP. No change in thinking with
regard to the fog threat overnight. It is still complicated and
an increase in coverage of precipitation would only add to the
complexity. Previous discussion follows below.
Early this evening: The main forecast issue for the overnight
revolves around fog potential. Once the coastal trough gets
north of the area, a mild and moist southerly flow will prevail
into Monday morning. Moisture is nicely concentrated in the
lower levels of the atmosphere and the overall flow will be
relatively light. It is certainly not a traditional radiation
fog setup with plenty of stratocumulus already in the vicinity
and elevated winds just above the surface. In fact, a perusal of
model soundings shows 15-20 knots of flow in the 500-1000 foot
layer and this is supported by the winds from the 00z RAOB. So,
the low level wind setup is certainly not ideal for widespread
fog or even dense fog. However, model soundings show a nice
stratus build down signature, which may allow fog to persist
despite the low level flow. Another complication is the fact
that the suite of models show varying degrees of shower activity
increasing across the area late tonight. The forecast continues
to feature patchy fog everywhere and areas of fog mainly along
and west of I-95, similar to the previous forecast. Certainly
not enough confidence to increase fog wording or entertain the
idea of a dense fog advisory at this time. No other significant
changes to the forecast at this time.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
Overview...A much more unsettled pattern through mid week. Higher
chances for rainfall with temperatures starting off above normal
Monday, then near to slightly below normal Tuesday and Wednesday.
Monday and Monday night...A weak cold front will be approaching the
area from the west. Moisture and forcing is limited with this front,
and have continued with low end chance to slight chance pops,
highest over the west. Expect mostly cloudy skies, but with
southwest low level flow, temperatures will rebound into the lower
70s north to mid 70s south. Monday night...models show the front
stalling over the forecast area, but exact location differs between
the models, which will impact temperatures. For now, have gone with
the front stalling over the central forecast area with lows in the
mid 50s north to the upper 50s around 60 south. Another weak surface
wave begins to approach from the southwest and sets up an
overrunning situation for later at night. Again, models differ on
timing on when precip would begin. Have gradually increased pops
from west/southwest to east/northeast through the night ending in
the high end chance level late. Guidance also showing the potential
for low ceilings and fog, especially SC zones. Have added patchy
fog entire area for now. Have also kept patchy sea fog near the
coast.
Tuesday and Tuesday night...Looks like a weak surface low will ride
across the stalled front from the southwest, which should result in
widespread light rain across the area. Have increased pops to low
end likely to high end chance for now. Hung on to some patchy sea
fog near the coast through early afternoon given southwest winds
advecting relatively warm/moist air over the cooler shelf waters.
Temperatures will be tricky and dependent on where front sets up.
Currently have a large range with low 60s extreme north to lower 70s
extreme south. Tuesday night...Chances for light rain will continue,
but models do show the potential for lower pops during this period
with one surface low lifting northeast of the area and the next one
forming over the northern Gulf of Mexico. Lows in the lower 50s
north to the upper 50s south, but will be very dependent on where
the stalled front is located.
Wednesday...Another weak surface wave is shown by all models to move
back over the stalled front from southwest to northeast. Again,
expect this to bring widespread light rain if it verifies. Given
uncertainty this far out, have kept low end likely to high end
chance pops. Temperatures will continue to be difficult, with the
potential for a big range from north to south. Have highs in the
lower 60s north to around 70 south.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
An approaching upper trough should push the stationary front
offshore Wednesday night with colder high pressure to build in from
the north through Friday. Highs Friday may struggle to 50 degrees
for at least the interior portions of the forecast area toward the
Pee Dee/Midlands/CSRA. Another coastal trough will likely develop
later Friday and could bring some showers especially Friday
night/Saturday across SC. Rain chances should then increase either
late Saturday night or Sunday as a cold front begins to affect the
area. After near normal temperatures Thursday and below normal
temperatures Friday, temperatures should be above normal for the
weekend.
&&
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
A very tricky next 12 hours. There is broad agreement that some
combination of ceilings/visibilities will support MVFR and
eventually IFR flight categories. However, confidence is still
low regarding the timing and exact impacts at KCHS and KSAV.
This looks like a potential stratus build down event which could
overcome some of the ingredients missing for a dense fog event.
Model guidance is quite consistent that MVFR conditions will
begin around or just after 06z at both sites, with IFR a couple
of hours later. Overall confidence is higher at KSAV which has a
lesser chance of showers late tonight and in an area with weaker
flow. The forecast now features IFR conditions at both sites,
starting earlier and lasting longer at KSAV. Improvement to MVFR
and then VFR is expected by late morning and early afternoon.
Extended Aviation Outlook: Through Wednesday...Expect at least
periods of flight restrictions, mainly in the form of lower
ceilings, with a stalled front likely between KCHS and KSAV as
weak surface lows move along the front from southwest to
northeast. By Friday, another weak coastal trough may develop,
which depending on moisture return, could bring the return of
some flight restrictions, but confidence low out that far into
the forecast.
&&
.MARINE...
Tonight: The persistent coastal through will gradually push
north tonight with south winds eventually prevailing across the
local marine area. Winds will pick up east of the cooler shelf
waters with speeds reaching as high as 15-20 kt across the
Georgia offshore waters and the far eastern portions of the
Charleston County waters. Lower speeds will occur across the
remaining nearshore waters and Charleston Harbor. The current
thinking is that sea/marine fog development could wait until
land based fog and stratus develops and then bleeds into the
coastal waters early Monday morning. Do not anticipate
widespread dense fog development at this time, but this will
have to be watched. Seas will average 2-3 ft nearshore waters
with 3-4 ft Charleston County waters and 4-5 ft Georgia offshore
waters.
Monday through Wednesday...No highlights expected at this time. A
weak cold front is expected to stall over the waters later Monday
through Wednesday. Southwest winds are expected to increase to 15-20
kts, especially 20 nm or more offshore ahead of the front Monday
afternoon. Monday night through Wednesday, this front is expected to
stall in a west-east orientation across the central portion of the
waters. Periods of weak surface low systems are shown by the models
to move across this front brining scattered shower/light rain
periodically through the period. At least patchy sea fog is possible
Monday through Monday afternoon with near shore southwest winds
advecting warmer/more moist air over the cooler shelf waters.
Wednesday night through Friday...A stronger cold front moves through
the waters Wednesday night. Behind the front, strong cold advection
will bring the potential for Small Craft Advisory conditions, which
could persist into Friday.
&&
.TIDES/COASTAL FLOODING...
Astronomical influences (lunar perigee and full moon) along with
periods of onshore winds could push tides to Coastal Flood Advisory
levels near the times of the morning high tides along the South
Carolina coast at least through the mid week. Right now, the best
chance for minor coastal flooding looks to be Tuesday morning with
the most pronounced northeast low level flow. However, given a front
is expected to stall over the region through mid week, it will be
difficult to predict the probability for any coastal flooding, since
the wind direction will directly impact whether it will occur or not.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...BSH
SHORT TERM...RFM
LONG TERM...RJB
AVIATION...BSH/RFM
MARINE...BSH/ST/RFM
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service State College PA
1050 PM EST Sun Dec 11 2016
.SYNOPSIS...
Low pressure will track north of Pennsylvania through the Great
Lakes tonight. The trailing cold front will sweep through Monday,
followed a period of more tranquil weather that will last through
mid week.
A true arctic air airmass and frigid temperatures will push
southeast Into the area Thursday and Friday, accompanied by
frequent snow showers and squalls.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
03Z radar loop showing precip redeveloping across Central Pa as
low level jet and associated WAA overspreads the region from the
west. At 0330Z, a wintry mix was falling over the Laurel Highlands
with snow falling across the NW Mtns. KCCX CC returns also suggest
mixed precip has spread into much of Cambria/Somerset/Bedford
counties as of 0330Z, with snow further north. Radar trends and
HRRR suggest precip will spread into the Susq Valley between
04Z-06Z.
Model soundings support a ptype of snow to rain across the
northern half of the state late tonight, while a freezing
rain/rain mix turns to all rain in the south. Worst conditions in
terms of travel should be late tonight, with improving conditions
by the AM commute, as temps rise above the freezing mark over
nearly the entire area by dawn. Additional snowfall based on
latest model QPF and earlier superblend, is likely to range from
2-4 inches across the NW Mtns, to 1-2 along the I-80 corridor and nothing
over roughly the southern third of the state.
High pressure east of Pa, rather than over Northern New Eng, is
in a less than ideal location to hold in the cold low level air,
so expect only a brief period of freezing rain during the ptype
transition late tonight. Stuck close to WPC ice accums of less
than 0.1 inch across the Central Mtns, with perhaps a bit more on
the ridgetops and less in the valleys.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
The low level jet and bulk of WAA will be shifting east of Pa by
12Z, so expect little additional precip during the daylight hours
of Monday. Will maintain the chance for a bit of light rain
during the AM hours associated with passage of trailing cold
front. Lack of deep moisture in model soundings suggest any precip
Monday morning will more likely fall as areas of drizzle,
especially over the Alleghenies, where orographic forcing will
play a role.
As colder air flows over the lakes, a bit of lake effect snow is
likely during the afternoon across the NW Mtns, where a fresh
dusting appears possible by Mon evening. Elsewhere, expect patchy
drizzle to last into the afternoon across the high ground of the
Alleghenies, while downsloping flow yields brightening skies
late in the day across the Susq Valley. Partial sunshine and later
arrival of cold front should result in max temps Monday of close
to 50F across the Lower Susq Valley, while cloud cover hold temps
to the 30s across the Alleghenies.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
Cold front will bring a shot of greatly modified polar air into
the region Mon night. High pressure slides through on Tue as flow
aloft turns westerly.
Digging trough dropping into NC U.S. and across Great Lakes
midweek will be preceeded by a weak cold front and poss for light
snow showers on Wed. Arctic front arrives Wed night, bringing the
coldest airmass of this young winter into the region for Thursday
and Friday. Temps Thursday could conceivably stay in the single
digits across the higher terrain of the NW mtns and Laurel
Highlands. The GEFS shows a large area of -2 to -3 sigma temps at
850 mb with min values around -20 F.
Gusty West-Northwest wind accompanying the cold air will create
below zero wind chills for much of the region Thu morning and
only in the single digits during the daylight hours. Skies will
become mainly clear with the wind dying off Thursday night as a
1025 mb sfc high build east from the nation`s heartland. Min
temps early Friday could dip to zero to 5 below across the fresh
snow covered ground of the Laurel Highlands and NW mtns, and will
be in the single digits to teens across the Central and SE zones.
Fair and dry (but very cold) weather is expected to persist Friday
and Friday night. However, a moisture-laden storm will likely
impact a large chunk of the region (beginning Friday night or
Saturday) with snow changing to mixed precip or rain from the SW
as a strong and rapidly warming southerly jet overruns the colder
surface air (850mb temps may rise as much as 20-25C over a 36hr
period from 12z Fri through 00z Sun). Although it`s still too
early to give specifics on that storm w/resp to snowfall, both the
EC and GEFS do show the parent storm heading NE from the mid
Mississippi to the Upper Great Lakes. Since this storm track is so
far to the NW, the deep valleys in Central PA could easily trap
the cold, sub- freezing air into Saturday afternoon, bringing a
slower or only partial changeover further north and east.
As trough on back side of this system lifts across the Great
Lakes, could see a period of light snow Sat night before high
pressure builds in again on Sunday.
&&
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
21Z TAFS sent.
Not a lot of change for the 00Z TAF package.
Details below.
Where it is snowing, it is IFR. Where it is not it is generally
VFR.
A general area of steady light snow is falling along and north of
a line from about JST-UNV-SEG and will continue into the evening.
Expect visibilities in the 1-3 mile range with ceilings generally
under 3000` right through Monday morning.
South of that line conditions will remain mainly VFR into early
evening when a larger area of precipitation will overspread from
the SW bringing widespread IFR/MVFR. South of I-80 a mix of
freezing rain/snow and sleet will develop and continue overnight
with the precipitation tapering off the mainly rain showers Monday
morning. North of I-80 it will remain mainly snow with some sleet
or freezing rain mixing in later tonight.
Precipitation will taper off to scattered showers Monday with
slowly improving conditions into Monday afternoon. Central and
eastern terminals will likely improve to VFR by mid to late
afternoon, while the higher elevation airports of the west and
north will remain sub VFR probably into Tuesday.
Outlook...
Tue-Wed...MVFR/IFR snow showers NW. VFR elsewhere.
Thu...MVFR/IFR snow showers NW. Windy. Snow Squalls possible with
arctic fropa.
Fri...No sig wx.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 AM EST Monday for PAZ004>006-
010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063.
Winter Weather Advisory until 4 AM EST Monday for PAZ064>066.
&&
$$
SYNOPSIS...Fitzgerald/La Corte
NEAR TERM...Fitzgerald
SHORT TERM...Fitzgerald/La Corte
LONG TERM...Lambert/RXR
AVIATION...La Corte/Martin
Area Forecast Discussion
National Weather Service Duluth MN
918 PM CST Sun Dec 11 2016
.UPDATE...
Issued at 918 PM CST Sun Dec 11 2016
The upper level shortwave was moving over far western Lake
Superior as of 03Z per latest radar/satellite/model data. This
wave will continue east clearing northwest Wisconsin and the
Arrowhead after 06Z. The wave was enhancing the lake effect snow
over western Lake Superior and causing light snow inland. KDLH
low level velocity data supports the model low level wind forecast
which showed the low level flow backing through the evening. As
this has occurred, the snow showers have diminished along the
North Shore into Duluth. As the wind continues to back, we expect
lake effect snow to move through northern Douglas and Bayfield
counties and possibly into portions of Ashland and Iron overnight.
We do think as the wave departs, the lake snow showers will not be
as intense as they are now. A shorter fetch will also keep the
snow showers intensity lower than what has been occurring.
We will likely be able to cancel the advisories and warnings for
the Arrowhead to Duluth over the next hour but will keep them
going for Douglas and Bayfield counties.
UPDATE Issued at 746 PM CST Sun Dec 11 2016
Moderate to heavy Lake effect snow continued along portions of the
North Shore into the Twin Ports area with light snow occurring
further inland. Most of the snow has ended over western areas and
clouds have diminished. The surface wind continued to back this
evening and KDLH has gone north. It will take longer for the
925/850mb flow to back, but it will as the evening progresses.
Lake effect snow will impact northern portions of Douglas and
Bayfield counties through the evening but should diminish after
midnight. We added those two counties to an advisory through
midnight. An upper level shortwave was enhancing the lake effect
snow and that is expected to move through the Northland late this
evening or shortly after midnight.
We left the snowbelt region of Ashland and Iron counties out of
the advisory for now as confidence is not as high lake effect snow
will impact those areas. The RAP sounding near Hurley shows a low
level inversion present as winds veer then it lifts late tonight
before winds go westerly. There may be a window of heavier lake
effect that impacts those areas, but it should be brief.
&&
.SHORT TERM...(This evening through Monday)
Issued at 404 PM CST Sun Dec 11 2016
Snow continued across much of the Northland as of 330 PM. The
heaviest snow stretched from the Duluth area, northeastward along
the North Shore of Lake Superior. Snowfall amounts have been quite
varied in this corridor, and the heaviest amounts correlated well
with the location of the snow bands on Duluth radar this
afternoon. The bands have been fairly stationary at times.
The big focus will remain the snow accumulation tonight. The
upper level vort max in association with the upper level wave will
continue to bring waves of snow across the area this evening. High
resolution models continue to indicate high QPF across the North
Shore late this afternoon, shifting to the south shore of Lake
Superior overnight. Decided to upgrade the advisory that was in
effect for the coastal lake zones of the North Shore to a Winter
Storm Warning. The interior portion of the Arrowhead will remain
in an advisory, and the Duluth area has been added to the advisory
as well.
The focus for snow will shift to the South Shore of Lake Superior
tonight, as winds become northeast, and eventually more north.
This setup typically causes a band of locally heavy snow to
develop in northern Douglas and Bayfield counties of northwest
Wisconsin, and some of the high resolution models have hinted at
that feature developing and then eventually breaking up later in
the night as winds shift more to the west. Could see some decent
accumulation along the south shore overnight, before winds switch
to the west.
The big focus for Monday will be the powerful cold front that is
expected to push southeastward across the region. Much colder
Arctic air will push in behind the cold front, and a band of
persistent snow is expected to move through in association with
the front during the day. This front will usher in some of the
coldest air of the season thus far.
.LONG TERM...(Monday night through Sunday)
Issued at 502 PM CST Sun Dec 11 2016
Main concerns for the long term period involve much colder
temperatures and the potential for accumulating snow later this
week into the first half of the weekend.
Strong cold air advection will continue Monday night behind the
Arctic front expected to arrive during the afternoon. Northwest
winds should remain somewhat strong Monday night, between 5 and 15
mph. Low temperatures will drop into the low single digits to
teens below zero. The combination of winds and much colder
temperatures will result in wind chills between 25 and 30 below
zero by Tuesday morning. Wind speeds will increase to 15 to 25
knots over western Lake Superior behind the front Monday night.
Gusts to 30 knots are likely. Occasional gale force gusts to 35
knots are possible over portions of the nearshore waters by
Tuesday morning.
Another Arctic cold front will advance southeastward through the
Northland by Tuesday afternoon and evening. Winds will be strong
once again during the overnight period with cold wind chills of 25
to 35 below zero expected. Winds will increase as the pressure
gradient between strengthening surface high pressure over the
Northern Plains and low pressure over northwest Ontario. Frequent
gale-force gusts to 40 knots are possible over portions of the
nearshore waters Tuesday through Thursday. Temperatures will
fight to reach zero Fahrenheit with cold air advection continuing
and partly to mainly cloudy skies expected. Wind chill values may
remain in the 20s below zero through the day Wednesday before
plummeting again Wednesday night.
Low pressure over Ontario will eventually drift eastward toward
New England Thursday night and Friday as ridging builds into the
western Great Lakes. Winds will diminish and back southwesterly by
Thursday. Temperatures may moderate slightly while remaining below
normal for mid-December. Attention then shifts to another
potential winter storm moving through the region during the
Thursday night through Sunday morning timeframe. I won`t spend
much time on details with this update. Suffice to say
deterministic and ensemble guidance continues to feature a strong
cyclone moving through the region, which could bring widespread
accumulating snow to the Northland. Focusing on amounts at this
time would toe the line of hubris. However, anyone with travel
plans late this week into the weekend are encouraged to keep up
with the forecast through the remainder of the week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 546 PM CST Sun Dec 11 2016
The Northland continued to be impacted by a shortwave and surface
low pressure system as well as lake processes. These features were
combining to produce light snow over much of the Northland with
moderate to heavy snow in spots around Lake Superior, mainly from
the North Shore down into the Twin Ports. Surface winds were
backing and KDLH has gone to north-northeast and KTWM/KBFW have
also had backing winds. As this continues and the 925mb/850mb flow
backs later this evening, the heavier lake effect snow will
diminish and shift to the South Shore. The visibility has been as
been as low as a half mile but most areas were 1 to 4 miles. The
visibility will continue to increase for most areas but remain
lower longer around Lake Superior. Ceilings will be a mix of MVFR
and VFR and some clearing will impact at least the western half of
Minnesota and possibly spots further east.
Another quick moving shortwave will bring a chance for more snow
on Monday and conditions will drop to MVFR/IFR.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 7 12 -8 4 / 100 70 10 10
INL -9 6 -12 1 / 60 60 20 20
BRD -2 10 -9 5 / 20 60 10 10
HYR 10 16 -7 5 / 100 30 40 10
ASX 14 18 -1 8 / 100 30 30 20
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory until midnight CST tonight for WIZ001-
002.
MN...Winter Weather Advisory until midnight CST tonight for MNZ012-
037.
Winter Storm Warning until midnight CST tonight for MNZ020-021.
LS...Small Craft Advisory until 4 AM CST Monday for LSZ121-140>148.
&&
$$
UPDATE...Melde
SHORT TERM...DAP
LONG TERM...Huyck
AVIATION...Melde
Area Forecast Discussion
National Weather Service Peachtree City GA
751 PM EST Sun Dec 11 2016
...updated for 00z aviation discussion...
.AVIATION...
00Z Update...
expect cigs to begin/continue to lower toward IFR throughout the
evening as warm air advection continues ahead of an approaching
front. Not much change from the previous thinking of a chance of
LIFR cigs just before or after sunrise ahead of the rain showers
that will be moving into the TAF sites by late morning. cigs are
not expected to improve much during the day with the rain and
should remain around 1kft. biggest challenges are in the 10z to
14z timeframe and when cigs may drop to around 003 and winds shift
to the SSW. expect shra most of the day and tapering off near
sunset with continued low cigs behind the rain. winds will be
tricky as ssw direction is expected in the early AM and a gradual
westerly direction takes hold the remainder of the day. A shift to
the north is expected late in the taf period.
//ATL
Confidence...00Z Update...
Med confidence all elements.
low confidence on timing of low cigs and wind shift in the AM.
30
&&
.PREV DISCUSSION... /Issued 245 PM EST Sun Dec 11 2016/
SHORT TERM /Tonight through Monday Night/...
Tricky forecast on tap for overnight and Monday...and most of it
revolves around the clouds. Persistent NE flow has kept much of
northeast GA in the clouds this afternoon...while erosion of the
deck has occurred on the south and west sides. Do expect most areas
to fill back in after dark...but as the winds shift to the SW
overnight ahead of a frontal boundary...the clouds should begin to
erode again on the south and west sides.
None of the models have a great handle on the winds overnight. The
RAP at least keeps winds out of the east a bit longer across the NE
and have chosen to populate the wind grids with the latest version.
However, the models...even the hi-res ones...don`t handle these
types of situations very well. So, low to med confidence in the
cloud forecast overnight.
Pops will increase from the NW late tonight as a cold front nears
the CWFA. The best chances for measurable rainfall will be in the NW
overnight. Areas that get socked in with low clouds could have
patchy drizzle/sprinkles overnight.
There is also some question on exactly how far south the frontal
boundary will make it on Monday. With the 500mb flow begin zonal,
the front may end up stalling a little further north than the models
are currently progging. So, have lingered the highest pops in the
vicinity of the I-20 corridor through Monday afternoon.
NListemaa
LONG TERM /Tuesday through Sunday/...
Overall forecast looks to be on track through the extended period.
Have mainly made adjustments to Day 7 temperatures and pops to
better align with the (little) model consensus. Have also made
some slight adjustments to dew points on Friday, which seemed a
tad warm given the latest solutions. Otherwise, previous
discussion still seems appropriate, and is included below.
31
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 38 61 45 58 / 30 60 60 60
Atlanta 41 61 49 61 / 40 60 60 60
Blairsville 37 55 38 55 / 70 80 40 40
Cartersville 40 59 45 58 / 60 70 50 30
Columbus 47 69 56 67 / 30 50 60 60
Gainesville 38 57 44 55 / 50 60 60 50
Macon 44 70 55 66 / 20 40 50 60
Rome 41 60 44 58 / 70 80 40 30
Peachtree City 41 63 49 62 / 30 60 60 70
Vidalia 50 73 59 70 / 20 30 40 40
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...30
LONG TERM....17
AVIATION...30
Area Forecast Discussion
National Weather Service Wilmington NC
930 PM EST Sun Dec 11 2016
.SYNOPSIS...
A coastal trough will push inland tonight. A cold front will
drop into the area Monday night and possibly stall in the
vicinity through Tuesday, before a stronger cold front moves
through Wednesday night. As a result, a chance of rain can be
expected through Wednesday with colder temperatures returning
Thursday and Friday. Another coastal front and cold front may
possibly affect the area next weekend.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 930 PM Sunday...The coastal trough is at least 12 or 15
miles inland in Southeastern North Carolina. Between 8 and 9 PM
the air temperature at the ILM airport rose from 49 to 59
degrees along with an increase in wind speed from calm to about
8 mph from the SE. The Sunset Beach nearshore buoy has just
recently gone to a southeast wind and 61 degree air temp, so
Myrtle Beach and the remainder of the Brunswick and Horry County
coastline should see the trough push onshore very shortly.
This forecast update makes tweaks to tighten the temperature
gradient in the vicinity of this coastal trough over the next
several hours as it begins to move inland from the coast. The
other concern is the current anemic coverage of rain on the
radar. PoPs have again been delayed, with hopes riding on an
expansion in the intensity of isentropic lift along the 295K
surface after midnight. The latest HRRR model not enthused about
precip chances overnight, but if it`s going to happen it will be
within this ribbon of relatively stronger lift expected to
develop along the coast between 1-4 AM.
Discussion from 630 PM follows...
A touchy/tricky temperature forecast as moderate warm advection
develops tonight and erodes away the increasingly shallow
residual arctic air from the past couple of days. The coastal
trough just offshore is moving westward and should bring rising
temperatures overnight. The key question is do temperatures fall
any over the next 2-3 hours due to modest radiational cooling
through breaks in the clouds before warmer gulf stream air
overspreads the area? The answer is probably a weak `yes` near
the coast, but `no` inland where a more solid overcast appears
to be settling in.
I`ve put my best shot at it in this latest forecast update...
lowering forecast lows by about 6 degrees at ILM, 2 degrees at
LBT, but raising lows by 1 degree at FLO and 3 degrees at CRE.
This gives low temperatures in the low to mid 40s inland with a
narrow strip of upper 40s to lower 50s along the NC coast, and
lower to mid 50s along the immediate SC coast.
Rain chances probably won`t become significant until better
isentropic lift develops after midnight, so I`ve trimmed back
PoPs through the evening hours to slight chance across the SC
Pee Dee region and dry elsewhere. In terms of the current
position of the coastal trough it appears the 18z NAM and 12z
WRF-ARW have the best handle on this, and both models support
that idea for precipitation timing overnight.
&&
.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
As of 300 PM Sunday...Fast but broad cyclonic flow in the mid-
levels will allow features to move quickly this period, but
maintain unsettled weather into mid-week.
A coastal trough/warm front will be north of the area Monday
morning, and Monday will feature temperatures well above normal. The
MET/MAV numbers are in good agreement with highs around 70 at the
coast, but only around 60 well inland. This is due to the current
wedge, which will be difficult to break down despite the lifting
front as mid-level thicknesses stay relatively constant. The
guidance tends to break these wedges down too quickly, so will hedge
towards the coolest guidance for Monday but note large bust
potential if WAA does overcome more strongly. While much of Monday
will likely be dry, continued isentropic lift as well as forced lift
along the boundary will create light showers through late morning,
focused primarily near the NC coastal counties. NAM is very
aggressive with rainfall Monday, and is ruled out due to lack of
forcing, and continued dry mid-level air. Showers will end by early
aftn from SW to NE, before a cold front trailing from a New England
low pressure moves into the Carolinas Monday night. Moisture return
ahead of this feature is limited, but showers may redevelop Monday
night ahead of the boundary.
This front will stall either across, or just south, of the CWA on
Tuesday, leading to cooler temperatures and continued cloudiness.
Strengthening isentropic lift atop this front and the high pressure
behind it will again lead to increasing rain chances, and forecast
profiles suggest the deepest saturation of the short term will be
late Tuesday. Once again, do not expect a high QPF event, but many
places will receive a second round of light rain late on Tuesday,
but temps will remain above seasonable levels.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
AS OF 300 PM Sunday...1200 UTC GFS and 0000 UTC ECMWF are
generally similar in the extended pattern. Low pressure is
expected to be located off the NC coast Wednesday with a strong
cold front approaching from the northwest. A better moisture
profile is evident during Wednesday into Thursday evening before
significant drying and subsidence occurs with the passage of
the aforementioned front. Isentropic glide is mostly neutral by
Wednesday morning and low- level theta-e advection is nominal as
well. However UVVs are present with support from strong H3 jet
north of the region and the low- level front lingering across
the area. The resulting categorical GFS POPs may be overdone as
a result, but in the end the chance of rain will persist until
Wednesday night. Low-level wind fields increase Wednesday night
and persist into Thursday. If the current scenario pans out then
expect gusty northwest winds Thursday as mixing occurs. Gusty
northerly winds would also be a good bet Friday morning given
the strength of the wind field prior to weakening later in the
day.
The surface high will ridge into the area from the Midwest Thursday
then translate to the Mid-Atlantic coast Friday evening and another
spate of below normal temperatures will occur through at least
Friday night. Trends this weekend are for another coastal trough to
move inland with return flow developing ahead of another cold front
very late in the period. Chance POPs will be needed by this weekend
to account for the coastal trough and late in the weekend for the
next cold front. At this time it appears that temperatures will warm
in time before any precip arrives late Friday night into Saturday
morning. However given the level of uncertainty this far out in
time, a slight concern exists that the earlier arrival of
precipitation Friday night would be more closely aligned with the
colder temperatures and a very slight potential for P-type issues.
&&
.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 00Z...VFR conditions prevail at all terminals attm though MVFR
conditions are expected to develop tonight. LIFR/IFR CIGS are also
possible toward 12z along with potential for -DZ/-RA. A coastal
trough has begun to push inland allowing the winds to veer to an E
direction at the coastal terminals. Additional veering of the winds
is expected as this feature is drawn inland.
Extended Outlook...CIGs improving Mon afternoon or evening. Periods
of MVFR/-RA Mon night through Wednesday with IFR most likely during
the morning hours. VFR Thursday in the wake of a cold front
Wednesday night.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 930 PM Sunday...According to buoy and coastal weather
observations, the coastal trough is now west of the coastal
waters with south to southeast winds now increasing across the
area. Air temperatures have risen into the lower to middle 60s,
and could rise even further overnight near Cape Fear as
southerly winds strengthen. Models still support minimal small
craft advisory conditions developing near and north of Cape Fear
after midnight with 20-25 kt winds and seas reaching 5-6 feet
in open waters away from shore.
Discussion from 630 PM follows...
A coastal trough is located about 15-30 miles off the coast as
indicated by latest observed wind directions showing east to
northeast wind on the beaches but southeast winds out at the
Frying Pan Shoals buoy. This trough is best defined in the 18z
NAM and 12z WRF-ARW models, and these have been used for this
forecast update tonight. The main change in the forecast was to
show a much more backed wind direction this evening before the
coastal trough moves onshore and turns winds solidly southerly.
No changes have been made to the Small Craft Advisory as
increasing southerly winds overnight should make conditions more
hazardous late, especially across the North Carolina waters.
SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 300 PM Sunday...The period begins with an SCA in place
across the NC zones due to gusty southerly winds of 15-25 kts
and 4-6 ft seas. Across SC waters, morning conditions will be
slightly better, with 10-20 kts and 3-4 ft seas. As the coastal
trough currently across the waters lifts north on Monday, wind
speeds will ease to 10- 15 kts, and then shift abruptly to the
NW Monday night behind a cold front. This front will then waver
across the waters much of Tuesday creating highly variable winds
around 10 kts, becoming north late. After the initial SCA
threshold seas, wave heights will fall to 3-4 ft by Monday
night, and then remain at these amplitudes through the end of
the period.
LONG TERM /WEDNESDAY THROUGH FRIDAY/...
As of 300 PM Sunday...Low pressure off the NC coast Wednesday
with a cold front south of the waters will maintain light N-NE
flow which is expected to become variable later in the day and
evening. Offshore flow will quickly ramp-up Wednesday night as
low pressure exits and a stronger cold front sweeps across the
waters. Small Craft Advisory conditions will likely concern as
the NWly winds peak Thursday. High pressure originally northwest
of the waters during Thursday will build eastward toward the
Mid-Atlantic region allowing the winds to gradually subside and
veer to a NEly direction Friday. Seas around 3 ft will build to
Small Craft thresholds Thursday morning with 6-7 footers
possible off Cape Fear. Seas will only slowly improve through
Friday as the Nly fetch becomes NE.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory until 10 AM EST Monday for AMZ250-252.
&&
$$
SYNOPSIS...SRP
NEAR TERM...TRA
SHORT TERM...SRP
LONG TERM...SRP
AVIATION...RAN
Area Forecast Discussion
National Weather Service Indianapolis IN
958 PM EST Sun Dec 11 2016
.UPDATE...
The NEAR TERM Section has been updated below.
&&
.SYNOPSIS...
Issued at 246 PM EST Sun Dec 11 2016
The winter storm system currently moving through the Midwest will
keep chances for rain south and a wintry mix north going until
late tonight. After that high pressure builds in to dry things out
across the area through the week. Temperatures will drop off
starting Tuesday night and drop sharply for Wednesday night and
Thursday, with wind chills possibly getting well below zero early
Thursday morning. The next storm system to impact the area will
arrive Friday to bring in precip chances for next weekend.
&&
.NEAR TERM /Overnight/...
Issued at 959 PM EST Sun Dec 11 2016
More widespread precipitation spreading back into the northwestern
half of the forecast area ahead of the cold front currently
tracking across Illinois. With southwest flow now across the
area...the low levels continue to warm with 02Z temps ranging from
just above the freezing mark over far northern counties to near 40
degrees in the far south.
Primary focus is on precipitation for the next 6 hours or so as
this band of light precipitation slowly rotates east through the
forecast area. Low level thermal profiles remain suggestive that
snow is mixing in with the rain over far northern portions of the
forecast area. HRRR analysis over the next several hours keeps
the potential for snow and/or sleet to briefly mix in with the
rain generally north of a Crawfordsville to Anderson to Muncie
line with rain over the rest of the area. May see an additional
light snow accum less than an inch within the advisory area over
the next few hours and will miaintain headlines as is.
Steady precip should be east of the forecast area by 08-09Z with
low clouds lingering. Will need to monitor potential for some
pockets of drizzle or...as surface temps fall once the front
passes...freezing drizzle towards daybreak as model soundings
favoring development of a sharp inversion around 2-2.5kft as drier
air aloft advects into the region. This will also serve to keep a
thick low stratus in place through daybreak as well.
Temps will rise a few more degrees ahead of the cold front...then
expect temps to fall predawn with much of the forecast area north
of I-70 below freezing by daybreak. Zone and grid updates out.
&&
.SHORT TERM /Monday through Wednesday/...
Issued at 246 PM EST Sun Dec 11 2016
The short term will be relatively quiet weather-wise as high
pressure builds over the area from the northern plains. Weak cold
advection will be in place Monday through Tuesday but may also see
the sun in places to offset that, so looking for highs in the 30s
both days. By Tuesday night though the cold advection gets a
little stronger and should see colder air moving in, with low
temperatures dropping into the single digits in the north Tuesday
night. Wind chills Tuesday night into Wednesday morning could drop
below zero in the northern counties as a result.
&&
.LONG TERM (Wednesday night through Sunday)...
Issued at 211 PM EST Sun Dec 11 2016
Although the deterministic models have differences, they lend good
confidence in an arctic airmass overspreading the area at the
beginning of the short term and a strong weekend weather maker.
Wednesday night looks to be the coldest night in 11 months and
possibly or more as arctic high pressure builds in from the Missouri
Valley and results in mostly clear skies. With strong potential for
strong radiational cooling, went along with adjacent offices on
lowering overnight lows a couple degrees to 0 degrees or slightly
lower for our northern boundary and near 10 degrees across our
southern boundary. Highs Thursday should only reach the upper single
digits northern sections.
After that, the high will shift to Appalachia on Friday. Return flow
around the high and ahead of a deepening Rockies system will allow
for a nice warm up with highs back up in the 20s and lower 30s on
Friday per the blend. It will also result in overrunning
accumulating snow that will continue through at least Friday night.
Model soundings, critical thicknesses and blend temperatures suggest
the snow could mix with or change to freezing rain Friday night or
Saturday and rain later in the day on Saturday. The 00z ECWMF was
slightly quicker and stronger with the system, moving the associated
cold front through the state by 18z Saturday. The GFS continued
showing QPF through Sunday associated with fast moving upper
impulses, while the ECMWF was dry. Small regional blend pops into
Saturday night and dry Sunday look like a reasonable blend.
&&
.AVIATION /Discussion for 120300Z TAF Update/...
Issued at 959 PM EST Sun Dec 11 2016
Ceilings continue to tumble as more widespread precipitation
spreads back into central Indiana. Made some minor tweaks based on
current obs...otherwise no changes needed.
00Z discussion follows.
Poor flying conditions will continue through tonight with only
gradual improvements in low ceilings on Monday.
A combination of reports received...LAPS sounding analysis and
hydrometeor classification via the 88D all suggesting that the
only terminal still experiencing mixed precip is at KLAF. The
other three sites are warm enough for a cold rain. The near
surface layer will continue to warm over the next several hours as
low level flow veers to the southwest as low pressure tracks into
the western Great Lakes. Will continue with a ra/sn mix at KLAF
into the evening.
Deeper moisture will depart after 06Z with the cold front
following shortly thereafter during the predawn hours. This will
effectively shut off the precipitation with the possible exception
of DZ or perhaps FZDZ as surface temps slip back below freezing
prior to daybreak Monday.
The primary issue for aviators going forward into Monday will be
if and how quickly the stratus deck and lift and scatter as model
soundings show a sharp inversion developing at 2-2.5kft and
holding for the better part of the day. With much drier air aloft
building into the region along with high pressure...can certainly
see a scenario play out where the moisture remains deep enough
trapped beneath the inversion to keep the cloud deck in place most
of if not the entire day. The strength of the inversion also
opens the possibility for a continuation of pockets of DZ/FZDZ or
even a few flurries. Will try to be somewhat optimistic and allow
for scattering of the deck at both KBMG and KHUF where the
inversion is likely to be weaker. Have held onto the stratus at
both KIND and KLAF for most of the day. Will hold off on any
mention of DZ/FZDZ/Flurries...but will monitor closely into the
overnight. Winds will shift to W/NW behind the front Monday at
10-15kts.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 1 AM EST Monday for INZ021-031.
&&
$$
SYNOPSIS...CP
NEAR TERM...RYAN
SHORT TERM...CP
LONG TERM....MK
AVIATION...RYAN
Area Forecast Discussion
National Weather Service Northern Indiana
633 PM EST Sun Dec 11 2016
.SYNOPSIS...
Issued at 628 PM EST Sun Dec 11 2016
Periods of snow will continue through the evening and may mix with
drizzle or freezing drizzle at times. This will keep roads
slippery and hazardous overnight. The snow will gradually end
overnight. Dry weather is expected on Monday and Tuesday with
much colder temperatures arriving for Wednesday through Friday.
Highs on Thursday may only be in the single digits with lows below
zero. There could also be some light lake effect snow when the
colder air arrives.
&&
.SHORT TERM...(This Evening through Monday)
Issued at 332 PM EST Sun Dec 11 2016
Strong LLJ ahead of approaching wave and in right rear quadrant of
intensifying 300mb jet continuing to support broad swath of 290K
isentropic ascent and mod snow. This activity will continue across
our north through the early evening with a brief lull in our
southern counties before main convergent boundary swings through the
area 00-06Z. Loss of midlevel moisture/ice nucleation currently
generating light freezing drizzle in our southern counties but RAP
and HRRR suggest deeper moisture will return around 00Z. As
previously mentioned, earlier snowfall associated with strong
isentropic ascent and slightly colder profiles seen in 12Z guidance
prompted an increase in snow forecast and expansion of headlines
along the US-24 corridor. However, no other expansion is planned
given latest reports in northern tier of advisory only 5-6 inches
with freezing drizzle/compaction and only another inch or two this
evening. Still expect a brief mix of just rain/drizzle in our far SE
counties and this will prevent much additional accumulation. Models
indicate there will be a brief uptick in elevated fgen across our NW
counties around 00-03Z this evening as main wave approaches. With
some decent instability above 600mb, this could lead to some heavier
bands developing. This would primarily be in our NW third...well NW
of US-24. Inherited forecast reflects this reasonably well and only
minor changes made for this package. End time of 06-09Z still
appears in very good shape and no changes planned to end time of
headlines. Slight concern for very brief freezing drizzle on
backside of exiting front but abrupt/deep dry air advection and
isentropic descent should be enough to cut off all precip by the
time DGZ is unsaturated. Dry conditions expected during the day
Monday with temps holding around 30F.
&&
.LONG TERM...(Monday Night through Sunday)
Issued at 332 PM EST Sun Dec 11 2016
Main story for the rest of the period is very cold temps. 850mb
temps drop (in stairstep fashion) to near -25C by early Thursday
with 925mb temps around -20C. This yields high temps in the single
digits with lows below zero. Cut consensus blends which appear too
heavily weighted toward climo and may need further cuts, especially
to overnight lows Thursday night. Wind chill headlines may be
necessary on Thursday with a modest gradient in place.
A few periodic chances for lake effect snow in NW CWA, particularly
on Thursday with coldest thermal profiles. Extreme dry air
entrainment expected given arctic airmass with limited convective
depths and instability despite high delta-T`s. This will limit
snowfall amounts and only light accumulation expected.
Attention then turns to next longwave trough slated to arrive late
Friday into Saturday. GFS and ECMWF in reasonable agreement on the
big picture but differ with regard to important details that will
determine precip types and amounts. Mixed precip is certainly
possible during this time but still much too early to discuss any
specifics. Will leave precip type as just snow for now with plenty
of time for adjustment.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
Issued at 628 PM EST Sun Dec 11 2016
Loss of ice nucleation with mid level dry slot has led to drizzle
and freezing drizzle. KSBN should see pcpn back to snow shortly as
deeper moisture along frontal zone works back east. Period of
moderate snow expected at KSBN as indicated by upstream
observations and mid level forcing this evening. KFWA likely to
see a few more hours of the DZ/FZDZ until deeper moisture arrives
and light snow develops again. Expect all pcpn to diminish late
tonight with a very small chance for another brief period of FZDZ
as pcpn diminishes. Monday should be dry with improving
conditions.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...Winter Weather Advisory until 4 AM EST Monday for INZ020-022>027-
032>034.
Winter Storm Warning until 4 AM EST /3 AM CST/ Monday for
INZ003>009-012>018.
MI...Winter Storm Warning until 4 AM EST Monday for MIZ077>081.
OH...Winter Weather Advisory until 4 AM EST Monday for OHZ016-024-025.
Winter Storm Warning until 4 AM EST Monday for OHZ001-002-004-
005-015.
LM...Small Craft Advisory until 4 PM EST Monday for LMZ043-046.
&&
$$
SYNOPSIS...AGD
SHORT TERM...AGD
LONG TERM...AGD
AVIATION...Lashley
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AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1034 PM EST Sun Dec 11 2016
.UPDATE...
Issued at 1034 PM EST SUN DEC 11 2016
Widespread rain is solidly in place near and north of the I-64
corridor. The rain will continue to spread across the rest of the
area through the overnight hours. Forecast has this covered well.
Temperatures have stayed quite a bit higher prior to the onset of
rain, so have adjusted temperatures up prior to the rainfall
overnight. In fact, many areas are still in the low 50s at this
late hour.
UPDATE Issued at 548 PM EST SUN DEC 11 2016
Updated to toss in some sprinkles through the early evening hours
before we saturate enough to allow for better rainfall potential
later this evening. Some light radar returns continue to work into
the area. The heavier rainfall looks to hold off until late
evening into the overnight hours.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 355 PM EST SUN DEC 11 2016
20z sfc analysis shows a fairly deep area of low pressure moving
into the mid Mississippi Valley and helping to tighten up the
gradient in pressure through Kentucky thanks to a high off to the
east. The winds picked up in conjunction with this so that they
are gusting to the 20 to 25 mph range from the south to southwest
for many sites in the higher terrain of the east and the more
open locations to the west. Just thin and patchy high clouds in
the east also helped to mix down higher winds from aloft and
contribute to pleasant temperatures rising into the upper 40s to
lower 50s for most locations. Dewpoints, meanwhile, remained in
the lower 20s and upper teens yielding relative humidity levels
down near 25 percent.
The models are in good agreement aloft through the short term
portion of the forecast. In fact, they are nearly identical with
the way they handle the trough crossing north of the Great Lakes.
South of this, energy will zip through the Ohio Valley in the
fast flow - sweeping through tonight as the heights fall with the
trough passing. However, the core of this rather low amplitude
wave will stay well to the north of Kentucky. Heights will hold
fairly steady into Tuesday morning as fast and mostly zonal flow
continues through the area at mid levels. Given the agreement in
the models have favored a general blend for the forecast with a
lean toward the latest HRRR and NAM12 for specifics through
tonight.
Sensible weather will feature temperatures dropping off a few
degrees for most places this evening before the thicker and lower
clouds push in with an extended period of rain showers ahead of
the front. Continued southwest flow will support temperatures
holding fairly steady in the mid 40s most places overnight during
the rain. The front passes through eastern Kentucky by mid morning
Monday - drying out the CWA from northwest to southeast - with
just some limited CAA on its heels. Do still expect a bump up in
temperatures for an afternoon high on Monday. High pressure then
moves quickly overhead by evening and ending the CAA before
midnight along with only marginal radiation cooling anticipated
that night due to lingering low clouds. The net result will be
temperatures pretty much near normal for this time of year and
only liquid pcpn seen for us from this system.
Again started with the CONSShort and ShortBlend for the grids
through the short term with only minor temperature adjustments
tonight given the non-diurnal curve anticipated. Did also adjust
the PoPs to better define the fropa tonight into midday Monday.
.LONG TERM...(Tuesday through Sunday)
Issued at 355 PM EST SUN DEC 11 2016
The period begins with surface high pressure attempting to build
south as it cruises across the Ohio Valley. Meanwhile a surface
low develops across portions of MS and AL and will remain south of
eastern KY. Therefore not buying into the ECMWF bringing precip
this far north Tue and in Tue evening and therefore backed off the
superblend for that period. The weather remains quiet after this
as the clipper system seen in previous model iterations has
shifted north across the northern Ohio Valley region. However, the
NW flow pattern could lead to some upslope flurries Thursday
morning with soundings suggesting just enough moisture residing in
the dendritic growth zone. Otherwise cold air mass and high
pressure will build across the region. Thursday night will be the
colder night with temperatures dropping into the teens area wide
and even a few single digits possible in the eastern valley sites.
Opted not to go too crazy given the crest of the surface high
remains in question, but certainly could see this trending colder.
The forecast becomes convoluted moving into the late week time
frame as models struggle to become consistent. The onset of the
next system could be some kind of wintery precip, however what
kind of ptype remains the question. Given we are talking day 6 and
the inconsistency opted to keep this simple mix/snow/rain type
setup. That said, the concern right now is the onset Saturday
morning, with model soundings and ascendant conditions suggesting
a short window of freezing rain potential before WAA takes over.
The precip will then switch to and remain rain through much of the
day on Saturday into Saturday evening. Finally we will see another
switch from rain, mix to snow by Saturday night into Sunday
morning. Given the overall timing issues will continue to lean
heavily toward the superblend for the overall forecast evolution.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 800 PM EST SUN DEC 11 2016
A cold front advancing across eastern Kentucky tonight into Monday
will bring lowering ceilings through tonight, eventually getting
into the IFR range late. Widespread rain will also spread across
the area overnight and lead to some patchy fog at times. All the
rain should depart early Monday, but IFR clouds will be slow to
lift to MVFR on Monday and we may not get out of MVFR skies on
Monday. Gusty south winds will be seen ahead of the front this
evening before we see them transition to southwest and turn
lighter.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...KAS
SHORT TERM...GREIF
LONG TERM...DJ
AVIATION...KAS
Area Forecast Discussion
National Weather Service Melbourne FL
922 PM EST Sun Dec 11 2016
.UPDATE...
...Fog/Low Stratus Expected Early Mon Morning...
Tonight...The center of a large high pressure area will move
steadily away from the mid Atlantic coast. This will cause low
level winds to veer to a southerly direction late while weakening.
Canaveral profilers still show east/southeast winds around 20 knots
in the low levels, and this was generating scattered showers over
the Atlantic, with a few bands moving into the coast. The steady
veering of low/mid level winds will keep most of this shower
activity over the Atlantic by late tonight.
There is going to be considerable low/mid level cloudiness lingering
most of the night, but as low level winds diminish in saturated
environment, expect low stratus and areas of fog to develop late.
The GFS MOS has been consistent in the past 24 hours showing this.
Not sure with the boundary layer flow staying near 10 knots how low
surface visibilities will go, but these "sloppy" warm front type
situations can often produce dense fog. The HRRR and local WRF have
been showing low visibilities primarily inland and near the north
coast. Have broadened mention of areas of fog to include much of the
area and would expect some patches of dense fog towards sunrise.
&&
.AVIATION...Isolated to scattered showers were moving northwest over
the Atlantic and along portions of the coast. This has been
producing mainly MVFR conditions. After midnight, most of this
activity will stay over the Atlantic as low-mid level winds veer to
southerly and gradually diminish. Then, the very moist low levels
will promote low stratus and fog. MOS guidance has been hitting
areas along and west of the I-4 corridor hard with LIFR conditions.
Trended the ceilings/visibilities down considerably from the
previous forecast. With the widespread low cloudiness it should
take until at least 15z to get back to MVFR-VFR conditions.
&&
.MARINE...
Tonight-Mon...The latest surface analysis shows the pressure
gradient starting to slacken, even though the GFS has a solid 20 knot
east/southeast flow in the low levels. The models have been showing
a decrease in the gradient as winds veer around to the south. Gusty
conditions will likely continue overnight, especially in the Gulf
Stream, so won`t change small craft advisory that is in place until
4 am. Exercise caution conditions will likely continue Mon morning,
especially offshore, then by afternoon southwest winds will diminish
to 10 knots or less.
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...Small Craft Advisory until 4 AM EST Monday for Sebastian Inlet
to Jupiter Inlet 0-20 nm-Sebastian Inlet to Jupiter Inlet
20-60 nm-Volusia-Brevard County Line to Sebastian Inlet 0-
20 nm-Volusia-Brevard County Line to Sebastian Inlet 20-60
nm.
&&
$$
Lascody/Blottman
Area Forecast Discussion
National Weather Service Omaha/Valley NE
941 PM CST Sun Dec 11 2016
.UPDATE...
Issued at 920 PM CST Sun Dec 11 2016
The main changes for the evening updates were to exit some
flurries/clouds out of the area and significantly lower low
temperatures. By 03z...temperatures already close to zero near the
SD border and approaching with around 10 deg. at FET. Still 1 to
3 inches of snowcover in northeast Nebraska, so conditions
favorable to bottom out. The RAP seemed to have the best trend for
temps as the other models were too warm. Surface winds will
continue to diminshing with mostly clear skies and cold high
pressure over the area. Low level winds do come around to the
southwest and increase to 30kts by 12Z and in turn could result
in some increasing clouds and possibly flurries later in the am.
The saturated layer is only 40mb thick with a lot of dry air
below...so something to pass on to the next shift.
&&
.SHORT TERM...(tonight through Wednesday night)
Issued at 257 PM CST Sun Dec 11 2016
Flurries/snow pellets are on their way out, with quieter weather to
follow for the next few days. Subjective 12Z upper-air analysis
indicates fast and mainly zonal flow, with a few shortwave troughs
rippling through the flow. Also zonal upper-level jet extended from
OR/northern CA through WY-CO/SD-NE toward the Great Lakes and
southern New England. An 850mb low was centered in ND, with a
fairly tight temperature gradient/baroclinic zone from BC through
MT/SD before loosening over the upper MS River valley/western Great
Lakes. Surface trough at 20Z extended from southern WI through
eastern IA to an elongated low from northeast MO to northeast OK.
Surface high was noted across the Dakotas into western NE.
Main forecast concern in the short term is potential for on and off
flurries, along with a few temperature swings. As long as fast
zonal flow with weak ripples and some mid=level moisture all
continue across the central US, some flurries could occur as any
wave passes. Tonight into Monday looks safe as surface to mid-level
ridging passes through. Mins tonight should reach early lows in
the western CWA before return flow allows some improvement behind
the surface ridge. Despite cold lows tonight, warm air advection
and mainly partly cloudy skies on Monday should allow temperatures
to recover into the 30s and 40s across the area.
Plunging cold front on Monday evening should bring much colder
readings on Monday night and Tuesday. Maybe the front brings a
flurry or two, but do not currently have a mention in the forecast
given the low confidence. Otherwise, lows in the single digits to
teens and highs in the upper teens to 20s are expected. Another one
of those upper-level shortwave ripples may slide through around
Tuesday night, but with little moisture, again think that the best
it might muster are flurries, which again are not mentioned given
low confidence. Temperatures remain generally neutral through
Wednesday night, with lows in the upper single digits to lower teens
and highs in the upper teens to mid-20s.
.LONG TERM...(Thursday through Sunday)
Issued at 257 PM CST Sun Dec 11 2016
Upper-level trough is progged to dig into the western US from
Thursday into the early weekend before ejecting across the central
US through the weekend. GFS/ECMWF solutions are actually in fairly
good agreement on the feature, with some minor differences on
timing. Ahead of the system, warm air advection on Thursday into
Friday may boost temps particularly on Thursday night and Friday,
when highs might reach back into the upper 20s to upper 30s,
depending on solution. Do have a small area of light snow mentioned
later Thursday, but confidence is rather low. Thursday night, a band
of snow in the warm air advection seems likely across the Dakotas
into MN/IA, which may just clip the northeasternmost CWA. Despite
slight chance POPs on Friday morning, actually think most of Friday
could be dry until front passes through later on Friday and into
Saturday. Even then, dry slotting could keep part of the CWA dry or
with lower chances of precipitation (especially the southern CWA),
while confidence is higher in precipitation in the northern CWA.
Current thermal profiles would suggest all-snow north, and perhaps a
rain-snow mix on Friday afternoon in the southern CWA if it does in
fact rain. That said, thermal profiles on the edge of freezing are
tricky to forecast reliably at day 6, and mixed-phase precipitation
in general is possible. Precipitation should end as snow as cold-
air advection continues in earnest Friday evening through Saturday.
Any lingering snow on Saturday will move eastward and out of the
area, with cold air plunging into the central US. Coldest temps
will be expected where any snowpack remains from the late week
event. That said, with high pressure near on Saturday night, along
with clearing skies behind the exiting system, imagine it will be a
very cold night in some areas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 520 PM CST Sun Dec 11 2016
Patchy MVFR conditions will end early this evening with decreasing
clouds and VFR conditions overnight. Northwest winds will diminish
and become southerly on Monday as high pressure builds through the
region. The next cold front will push through the area Monday
afternoon but did not include another group for that wind shift at
this time.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&
$$
UPDATE...Zapotocny
SHORT TERM...Mayes
LONG TERM...Mayes
AVIATION...Miller
Area Forecast Discussion
National Weather Service Norman OK
749 PM CST Sun Dec 11 2016
.UPDATE...
Updated cloud cover and min temperatures.
&&
.DISCUSSION...
Cold air advection and diurnal cooling continue this evening and
temperatures were already falling below current hourly grids.
Although we will have some cirrus to contend with (and have
updated sky grids to account for this cirrus), light winds and
partly cloudy skies will still allow for some good radiational
cooling as surface ridge moves into the northwest. The RAP and
HRRR seemed to have a good handle on current temperature trends
and both forecast cooler temperatures by sunrise in northern and
western Oklahoma than were in the grids, so have lowered mins in
the north and west closer to the mins forecast by the high-
resolution models.
&&
.PREV DISCUSSION... /issued 612 PM CST Sun Dec 11 2016/
DISCUSSION...
AVIATION...
MVFR ceilings will move southeast of central Oklahoma this evening
in the wake of a weak cold front. Gusty north winds will subside
by midnight. VFR conditions and light winds are expected until
mid-day tomorrow when south winds will arrive to western Oklahoma.
Speeds are expected under 12 kts generally.
PREV DISCUSSION... /issued 302 PM CST Sun Dec 11 2016/
DISCUSSION...
An active pattern is expected through this week with a series of
cold fronts expected to pass by Oklahoma and north Texas.
The first cold front is progressing southeastward today with
temperatures falling into the 40Fs and gusty northerly winds
behind the front. Ahead of the front, temperatures have warmed
into the upper 60Fs and low 70Fs. Expect the passage of this
front to result in high temperatures to be near average (low to
mid 50Fs) for tomorrow afternoon.
On Tuesday, the next cold front is expected to gradually pass by
the area. Temperatures will only be slightly cooler behind this
front. An even stronger, reinforcing push of cold air is expected
on Wednesday. This will drop high temperatures 10-15F below
average for Wednesday and Thursday.
Significant warm air advection--aided by an intense 50-55 knot
low-level jet--is expected to commence late Thursday into Friday.
Rain and/or drizzle may develop due to isentropic ascent in
response to the warm air advection. Currently, anticipate any
areas of precipitation to be coincident with temperatures above
freezing as temperatures will likely warm through the night.
Therefore, expect any precipitation to stay liquid for now.
Increased wind speeds on Friday beyond blended guidance based on
925-850 mb wind speeds and the tight surface pressure gradient.
Also opted to raise temperatures above blended guidance for
Friday afternoon as low-level thermal fields are progged to be
quite warm (850 mb temps >=15C across the west) with west-
southwest flow. Many locations may reach the 60Fs with some
temperatures near 70F possible across western north Texas. Some
remnant warm air advection rain/drizzle will be possible on
Friday.
On Saturday, another seasonably strong cold front is expected to
pass by Oklahoma and north Texas. In the front`s wake, falling
temperatures into the 30Fs and gusty northerly winds are expected.
The 11/12Z GFS and ECMWF are in better agreement that
precipitation chances look very low behind the cold front.
Therefore, opted to keep post-frontal weather dry on Saturday for
now. Seasonably cold temperatures are expected to persist into
Sunday.
Mahale
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 29 51 31 47 / 0 0 0 0
Hobart OK 29 49 32 47 / 0 0 0 0
Wichita Falls TX 28 53 36 54 / 0 0 0 0
Gage OK 23 50 24 43 / 0 0 0 0
Ponca City OK 24 48 25 41 / 0 0 0 0
Durant OK 36 55 42 55 / 10 0 0 0
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$