Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/12/17
Area Forecast Discussion
National Weather Service Taunton MA
951 PM EST Mon Dec 11 2017
.SYNOPSIS...
Low pressure in the Ohio Valley will move across New England
Tuesday and northeast of the region Wednesday. It will bring
a mixed bag of weather with snow northwest, a mix to rain
central, and rain southeast late tonight and Tuesday. A shot of
arctic air follows Wednesday and Thursday with a period of
strong winds and bitterly cold wind chills. Another low pressure
system may bring more snow to the region sometime in the
Thursday night to Friday night timeframe, if it tracks close
enough to the coast. Somewhat milder weather will arrive by the
end of the upcoming weekend.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
10 PM update...
Not much change from previous forecast. New 00z
NAM/RGEM/ARW/NMM/RAP and HRRR continue to have onset of precip
across western and central MA 4 am - 7 am, although low level
dry air may linger long enough to delay precip until 9 am - noon
across RI and southeast MA. Thus may have to push back onset
times across this area. Also given the lack of cloud cover this
evening along the south coast has allowed good radiational
cooling 930 pm temps in the mid to upper 20s across Cape Cod and
Nantucket. Therefore will adjust hourly temps to reflect this
current trend however temps will level off and then rise
overnight in the coastal plain with increasing cloud cover and
onshore winds developing. Otherwise previous forecast is on
track.
Previous discussion...
A strong short wave trough seen on water vapor over IL will be
rapidly moving east tonight and to eastern NY late tonight.
Low pressure at the surface over Ohio will move into New York
state overnight. Warm air advection cloudiness will increase
across our region overnight and snow is likely to break out in
northwest MA before daybreak. There is a chance that
precipitation could reach as far as northern CT and central MA
by daybreak. Although 850 mb temperatures are cold enough for
snow, the 925 mb temperatures warm enough such that a few hours
of freezing rain are possible in northern CT, northwest RI, and
into southern Worcester and Middlesex Counties in MA within a
few hours of daybreak. This could be a problem for the morning
commute.
We have expanded the Winter Weather Advisory southward and
eastward a bit, to include Hartford, Tolland, Windham (in CT),
northwest Providence County (in RI), and central and northwest
Middlesex Counties (in MA). In these areas, a thin
coating...less than one tenth of an inch...of ice is possible
before daybreak. The Advisory remains in effect for the
remainder of western and central MA.
Lows tonight will be in the 20s except low to mid 30s Cape Cod
and the islands. Light winds becoming southeast. Temperatures
may begin to rise late in southern areas as southeast winds
become established.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Tuesday...
Any freezing rain should be short-lived but it could be a factor
during the morning commute in the Hartford, Springfield, and
Worcester areas, as well as the northwest suburbs of Providence.
925 mb temps warm very rapidly on strong southerly low level
winds, so it should change to plain rain across most of southern
New England during the morning. In fact, high temperatures will
reach 50 degrees in RI and southeast MA!
In the higher terrain of northern Worcester County and in the
slopes of the Berkshires, snow will be moderate to heavy for a
few hours in the morning, with total accumulations ranging from
2 to 4 inches, with local amounts of 5 or 6 inches in the
extreme northwest corner of Franklin County, MA. Even there,
some sleet and freezing rain may mix in during the afternoon.
Southeast winds will become gusty...with up to 25-35 mph gusts
possible along the coast. We have discounted the NAM, which has
what appears to be way too strong of a LLJ of 80 kt at 850 mb
and 50-60 kt gusts at the surface. All other models are more
like 40-50 kt at 850 mb.
Tuesday night...
Winds shift to the west behind the departing storm system.
However, as a vigorous upper level low approaches, scattered
snow showers or squalls are possible, which could add some
light accumulations, especially in western sections toward
Wednesday morning.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Wednesday...
There is a chance of snow squalls continuing into Wednesday
morning as an arctic front progresses across Southern New
England. Very little snow accumulation is expected with these
passing showers, likely up to an inch at most west of the
Worcester Hills.
Winds will pick up in the afternoon as there is an impressive upper
level jet overhead. Models are in agreement with 40kts at 925mb
mixing down to the surface Wednesday afternoon. The GFS suggests
the strongest winds will be over the northern tip of the Cape
and extend into Mass Bay. Wind gusts between 40 to 50 mph are
not out of the question. Winds will likely peak by 00Z Thursday
as the upper level jet sits directly over the region.
Wednesday night temperatures will range in the teens due to the
arctic airmass now over the region. With the combination of the
arctic airmass and strong surface winds, wind chills are likely
to hover near zero degrees overnight. With minimal cloud cover
as well, radiational cooling will add to the low apparent
temperatures.
Thursday and Friday...
Strong winds will continue into Thursday morning but begin to
dissipate throughout the afternoon and evening.
Both the ECMWF and NAM point towards a weak system that brings
light snow to the islands and southern coast of New England
Thursday afternoon. The system will likely not linger off the
coast for very long, resulting in minimal snow accumulations, if
any at all.
The arctic airmass remains over the region through Thursday and
Friday resulting in much below normal afternoon temperatures. With
the winds diminishing by Thursday evening, wind chills should not be
an issue, however overnight temperatures will continue to range in
the teens across much of the region.
Friday night and Saturday...
A coastal low is expected to clip the region Friday/Saturday
resulting in periods of heavy snow along the 95 corridor.
Unfortunately, the models are not in agreement with timing or
position for when it does make its way up to Southern New
England.
Going with guidance from the ECMWF and NAM, precipitation will push
north across the region starting at 18z. As the low moves further
northeast, east of the 95 corridor will likely see the most
accumulation. The coastal low is expected to push offshore by
Saturday afternoon.
Sunday...
A ridge builds in Sunday morning behind the coastal low. Winds will
turn to the southwest, advecting warmer temperatures into the region
by midday. Dry and seasonable temperatures will continue through
early next week.
&&
.AVIATION /03Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Tuesday Night/...
03z update...
No major changes to 00z TAFs. Precip begins approximately 09z-
12z across western and central MA, 14z-17z remainder of the
area. Previous discussion below.
==================================================================
Tonight...Moderate confidence.
VFR to start, will give way to MVFR early AM Tue as CIGS lower
and light SN/FZRA moves in mainly after 06Z along and north of
route 2. SN accums would be light. Light winds shift around to
the E, except SE along the coast.
Tuesday...Moderate confidence. Mixed MVFR and occasional IFR
conditions in a mix of SN/FZRA giving way to all RA through
sunrise into midday Tue. Risk for NW MA to remain SN long
enough for accums to reach 3-6 inches with little or no snow
accumulation southeast of a Hartford to Boston line. Period of
FZRA before the change to RA. Conditions improve after 20Z.
Winds gusting to 20-30 kt along the coast.
Tuesday night...Moderate confidence. MVFR ceilings and scattered
snow showers moving from west to east across the region. Local
IFR in any heavier snow showers, especially in western sections.
West winds gusting to 20-25 kt at times.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF. Potential for wintry mix
between 12Z-14Z.
Outlook /Wednesday through Saturday/...
Wednesday: Mainly VFR, with local IFR possible. Windy with
gusts to 35 kt. Slight chance SHSN.
Wednesday Night: VFR. Strong winds with local gusts to 40 kt.
Thursday through Thursday Night: VFR. Breezy.
Friday: Mainly VFR, with local IFR possible. Chance SN.
Friday Night: Mainly VFR, with areas IFR possible. Breezy.
Chance SN.
Saturday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Tuesday Night/...
Tonight...High confidence. Winds are slowly diminishing. Seas
will slowly subside...to below SCA criteria over the southern
waters by this evening. Quiet boating weather tonight, but that
will be very temporary.
Tuesday...Moderate confidence. Winds gradually shift around to
the SE. Gusts 25-30 kt expected on the S waters with 35-40 kt
possible on the E waters. Gale Warnings are in effect for the
eastern waters with Small Craft Advisories posted for all other
waters. Rough seas of up to 5 to 10 ft on the outer waters.
Tuesday night...Winds shift to the southwest to west. Winds
still gusting to 25-30 kt and seas still quite rough, especially
over the southern outer waters.
Outlook /Wednesday through Saturday/...
Wednesday: Moderate risk for gale force winds with gusts up to
40 kt. Rough seas up to 14 ft. Slight chance of snow showers.
Visibility 1 to 3 nm.
Wednesday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Rough seas up to 14 ft.
Thursday: Moderate risk for Small Craft Advisory winds with
local gusts up to 30 kt. Local rough seas. Local visibility
1 to 3 nm.
Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of snow. Areas of visibility 1 to 3 nm.
Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Chance of snow. Visibility
1 to 3 nm.
Saturday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Rough seas up to 10 ft. Local visibility
1 to 3 nm.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory from 4 AM to 10 AM EST Tuesday for
CTZ002>004.
MA...Winter Weather Advisory from 4 AM to 1 PM EST Tuesday for
MAZ005-010>012.
Winter Weather Advisory from 4 AM to 4 PM EST Tuesday for
MAZ002>004-008-009-026.
RI...Winter Weather Advisory from 4 AM to 10 AM EST Tuesday for
RIZ001.
MARINE...Small Craft Advisory from 9 AM Tuesday to 6 AM EST Wednesday
for ANZ231>234.
Small Craft Advisory from 1 PM to 7 PM EST Tuesday for ANZ230-
236.
Small Craft Advisory until 6 AM EST Wednesday for ANZ235-237-
255-256.
Gale Warning from 10 AM to 7 PM EST Tuesday for ANZ250-251-254.
&&
$$
SYNOPSIS...Correia/GAF
NEAR TERM...Nocera/Correia/GAF
SHORT TERM...GAF
LONG TERM...Correia
AVIATION...Nocera/Correia/GAF
MARINE...Correia/GAF
Area Forecast Discussion
National Weather Service Dodge City KS
500 PM CST Mon Dec 11 2017
...Updated Aviation...
.SHORT TERM...(This evening through Tuesday)
Issued at 318 PM CST Mon Dec 11 2017
Mid-afternoon water vapor and RAP analysis showed a rather vigorous
shortwave trough moving quickly southeast around the larger scale
trough, which remained a stronghold across the eastern CONUS and
Canada. The mentioned shortwave trough led to strong surface winds
behind the downslope-modified cold front. Surface winds over a large
area of the central and northern Great Plains were in the 25 to 35
mph range with higher gusts. Even with the north winds, temperatures
still warmed up into the lower and even mid 60s across much of west
central and southwest Kansas thanks to downslope trajectories off
the higher terrain of Wyoming. The strongest surface cold advection
was well off to the northeast in eastern Nebraska and Iowa.
Tonight we will see a marked drop off in wind speed after sunset as
surface high center behind the shortwave trough shifts rapidly to
the southeast into western KS. The light winds, mostly clear sky,
and very low dewpoints will support lows down into the lower to mid
20s most locations (coldest out west). On Tuesday, upper level
heights rise once again along with mid level temperatures as the
influence of the shortwave trough pulls away from the Great Plains.
850mb temperatures will warm upstream, back into the +10 to +13C
range across the High Plains by 00z Wednesday. Shallower mixing
is expected tomorrow due to light winds and directional shear in
the low levels, thus surface temperatures will not get as warm as
850mb temperatures would seem to otherwise suggest. Actually, our
afternoon highs tomorrow are expected to be a touch cooler than
today with most areas seeing upper 50s for highs.
.LONG TERM...(Tuesday night through Monday)
Issued at 318 PM CST Mon Dec 11 2017
The next in a series of northwest flow shortwave troughs will dive
southeast towards Kansas Wednesday. Again, we will see an
enhancement in northwest surface winds, and looks a lot like today`s
setup with temperatures warming up into the lower 60s with fairly
strong north-northwest winds and cold air advection not really
getting going until late afternoon -- allowing temperatures to warm
quite midday to early afternoon. Yet another wave, a bit stronger,
will be quick on its heels Thursday. This northwest flow jet streak
will be a bit farther west, so we will see colder lower tropospheric
temperatures than the past several waves. Wednesday and Thursday
diurnal winds will be fairly strong, and collaborated with
neighboring WFOs on increasing these winds over the SuperBlend
starting point...closer to the CONSMOS guidance which has shown a
bit better skill in these windy regimes.
Flat ridging will build in behind Thursday`s system, so we will
return right back to a westerly downslope pattern, warming us back
up to the upper 50s or lower 60s Friday and Saturday. Late weekend,
the three global spectral models ECMWF, GFS, Canadian all show a
decent synoptic trough across the Central Plains, but the trough
will be embedded in a larger scale zonal flow regime, so it is hard
to imagine much in the way of any precipitation chances with this
wave across western Kansas.
&&
.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 500 PM CST Mon Dec 11 2017
Again VFR/SKC through Tuesday. Better flying weather expected this
TAF period with less wind. Strong NW winds will weaken rapidly at
sunset, and back from NW to westerly overnight at 10 kts or less.
West winds will tick upward after 15z Tuesday, but very modestly,
averaging 10-15 kts. A few gusts near 20-22 kts in the afternoon.
&&
.FIRE WEATHER...
Issued at 325 PM CST Mon Dec 11 2017
Near critical to perhaps critical fire weather conditions will
develop again Wednesday with very dry low levels and stronger
northwest winds. Strong winds will again occur Thursday during the
day, but stronger cold advection with lower temperatures should
yield higher diurnal relative humidity to keep western Kansas out of
the near-critical levels, but it will still be very dry. There is no
sign of any wetting precipitation in the next 7 to perhaps even 10
days, and as long as we maintain downslope trajectories with the
progressive pattern, daytime dewpoints and RH will be very low.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 24 60 33 61 / 0 0 0 0
GCK 23 61 30 59 / 0 0 0 0
EHA 25 63 32 61 / 0 0 0 0
LBL 22 61 29 61 / 0 0 0 0
HYS 25 55 32 58 / 0 0 0 0
P28 28 55 31 63 / 0 0 0 0
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 6 PM CST /5 PM MST/ this evening for
KSZ030-031-043>046-061>066-074>081-084>090.
&&
$$
SHORT TERM...Umscheid
LONG TERM...Umscheid
AVIATION...Turner
FIRE WEATHER...Umscheid
Area Forecast Discussion
National Weather Service Hastings NE
739 PM CST Mon Dec 11 2017
.UPDATE...
Issued at 737 PM CST Mon Dec 11 2017
Updated the forecast to include sprinkles/flurries in the forecast
for much of the evening. Radar picking up on some light returns as
well as observations from Ord doing the same. The HRRR does a good
job on picking up on this and advertises that this should end by
midnight.
UPDATE Issued at 540 PM CST Mon Dec 11 2017
Updated the forecast earlier as we allowed the Red Flag Warning to
expire. Wind speeds should continue to gradually decrease this
evening.
&&
.SHORT TERM...(This evening through Tuesday)
Issued at 335 PM CST Mon Dec 11 2017
Clouds have moved into much of the forecast area this afternoon,
with just a band of mostly clear skies between a couple of bands of
clouds. The north to northwest winds have started to subside a
little bit, but are still gusty across the area.
The winds should continue to subside this afternoon, but the
gustiness should continue into the evening hours before slowly
decreasing. The clouds should continue through sunset, but decrease
some during the evening before moving out of the area early Tuesday
morning. Tuesday will be mostly sunny and the west winds will be
around 10 mph.
.LONG TERM...(Tuesday night through Monday)
Issued at 335 PM CST Mon Dec 11 2017
Another cold front moves through the forecast area Tuesday night.
There will be little more than the wind shift during the night
Tuesday night, but on Wednesday the colder air filters into the area
and the winds start to pick up again. Winds will be breezy again and
have raised wind speeds a little. There is also some moisture that
gets pushed into the area and there could be a few more clouds
during the later afternoon and evening. The cooler air starts to
filter in Wednesday night and temperatures are a little cooler on
Thursday. There will be an upper level wave that moves through the
area Thursday. There will be a push of moisture into the area as the
wave moves in and temperatures aloft are cooling. Models have some
light precipitation in the northeast part of the forecast area
during the day on Thursday. Temperatures at 850mb are cold enough,
but the temperatures at the surface warm a little. It could start as
snow in the morning, mix with and change to rain during the day,
then maybe have a little mix in the afternoon before the
precipitation comes to an end.
Thursday night the wave moves out, the low level moisture moves east
and the clouds move out. It will be cool that night before the warm
advection mixes down to the surface. The next cold front will be
moving through the area late Friday night into Saturday morning.
There will be a few more clouds and breezy north winds again but it
should remain dry. Northwest flow will continue Sunday and Monday
with mild temperatures.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Tuesday)
Issued at 540 PM CST Mon Dec 11 2017
Trickiest part of the forecast will be ceilings flirting with MVFR
this evening, especially for GRI. Currently VFR, but we could
temporarily go MVFR for short periods of time before VFR
conditions completely take a foothold.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
UPDATE...Heinlein
SHORT TERM...JCB
LONG TERM...JCB
AVIATION...Heinlein
Area Forecast Discussion
National Weather Service Wilmington NC
923 PM EST Mon Dec 11 2017
.SYNOPSIS...
The week looks dry although there is some risk for rainfall on
Friday. Sunshine will bring a modest temperature rise and we
will be close to normal by Tuesday. A strong cold front will
move across the area late Tuesday with Arctic air returning
Tuesday night through Wednesday night. Temperatures will
moderate late week. A cold front may bring a brief cool down to
start the weekend followed by a return to seasonable temperatures
early next week.
&&
.NEAR TERM /THROUGH TUESDAY/...
As of 900 PM Monday...With the sfc based inversion having
developed after sunset, winds have decoupled. This has resulted
in temps nose-diving rather quickly even where winds have not
decoupled entirely. The best rad cooling conditions and the
stronger sfc based inversion will occur across the Northeast
portions of the ILM CWA. With the sfc pg progged to tighten-some
tonight and a low level southwesterly 35+ MPH jet at 950mb,
SW winds will become active across the entire FA, wiping out
much of the sfc based inversion. As a result, temps will bottom
out this evening, close to their respective dewpoints, but then
hold steady initially, then look for a slow increasing trend
for temps. Lows tonight will likely occur late this evening or
just after the midnight hour.
Previous.........................................................
As of 300 PM Monday...A cool but beautiful afternoon ongoing
across the Carolinas as broad high pressure centered across the
Gulf Coast expands into the region. This is accompanied by very
dry air noted on WV imagery, and cloudless sky conditions are
present across the entirety of the Southeast. Well upstream into
the western Great Lakes, a surface low pressure beneath a
strong shortwave is producing clouds in that region, with the
accompanying cold front draping into the MO VLY.
This front will cross the area on Tuesday, but before this occurs
increasing WAA around the southern high pressure will create
relatively warm temperatures for the next 24 hours. This is due to
warm advection on increasing SW flow within the warm sector ahead of
the aforementioned front. Moisture will slowly increase within the
column, but latest RAP soundings show PWATs only to around 0.5
inches tonight, so the area will remain mostly cloud free. The
exception may be well NW where a few mid/high clouds may advect in
from the NW. Temperatures will drop quickly in the dry column after
dark, but then will begin to level off as S/SW LLJ increases to 25-
35 kts. This will keep mins from bottoming out as radiational
cooling gets inhibited, and mins are forecast to be 40-42 at the
coast, 36-39 inland.
SW winds increase Tuesday ahead of the front, and may gust above
25mph during the aftn/eve. THe strong cold front will cross the
region precip-free thanks to the dry column, but mid-level
cloudiness will increase during the aftn with FROPA occurring from
NW to SE during the evening. Strong CAA follows this front and 850mb
temps plummet from +1C to +3C early Tuesday, to -4C to -7C by the
end of the period. This will be accompanied by gusty NW winds, and a
very chilly night is forecast just beyond this period as temps begin
to crash Tuesday evening from aftn highs very near 60 degrees.
&&
.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...An arctic blast will bring the coldest day
of this season so far. Temps will drop into the mid 20s most
places Tues night in a rush of cold and dry air with Wed afternoon
highs only making it into the 40s under bright sunshine. The
brisk NW winds will make it feel even colder with apparent temps
down in the teens right around daybreak Wed and feeling like
the 30s most of the day. A very dry air mass will remain in
place through Wed with dewpoint temps down in the teens and pcp
water values a quarter of an inch or less.
By Wed night, another shortwave will ride through the base of
the long wave trough in place over the eastern CONUS. The
associated sfc low will move by to our north, but may see some
passing clouds overnight Wed into Thurs morning. The winds will
back slightly but not expecting much of moisture return. Pcp
water values will not even reach a half inch with moisture
profiles showing potential for some mid level clouds as
shortwave passes through overnight Wed into early Thurs morning.
Temps overnight Wed may be a bit tricky as warmer air just above
the surface may mix down if winds spike up at all overnight.
Basically expect atmosphere to decouple allowing temps to drop
out down to the upper 20s to around 30 most places, a few
degrees warmer than previous night. Overall, a very cold and dry
period from Tues night through Wed night.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 300 PM Monday...The East Coast longwave trough will reload
late this week as another strong shortwave moves through the
Carolinas on Friday. This upper system should induce low pressure to
develop at the surface over North Carolina during the day Friday.
Moisture is going to be tough to find given deep layer winds have so
much offshore component, virtually eliminating Gulf of Atlantic
inflow. In fact the only moisture I can find arrives in the 850-700
mb layer from the northwest -- most likely Pacific moisture that
came onshore in British Columbia several days earlier. Dynamics are
going to be so strong that I still think there will be some light
measurable rainfall around, and I`m including a 30 percent chance of
showers in the forecast for Friday.
Dry weather will develop for Saturday and Sunday as a weak upper
level ridge pokes north from the Caribbean and surface high pressure
moves eastward along the Gulf Coast. Model depictions of another
shortwave trough arriving on the East Coast Monday vary quite a bit
from model to model, reducing confidence about what impacts we may
see. PoPs of 30 percent have been introduced into the forecast for
Monday along with some increased cloud cover.
Temperatures will be on a roller coaster ride through the weekend,
likely coolest on Saturday as the upper trough moves overhead and
offshore.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
As of 00Z...High confidence for VFR conditions through the forecast
period. Winds will go calm this evening, however they are expected
to pick up overnight with winds over 30 kts just above the surface.
Tuesday, a dry front will move through the region at the end of the
forecast period. Gusty west southwest winds are forecast ahead of
the front.
Extended Outlook...VFR.
&&
.MARINE...
NEAR TERM /THROUGH TUESDAY/...
As of 915 PM Monday...Light and variable winds early this
evening, will become southwest thruout at 10 to 15 kt by
midnight as the sfc pg begins to tighten. In addition, a low
level SW 30+ knot jet, will eventually partially mix down to the
ocean sfc late tonight into daylight Tue. Latest SSTS are not
quite cold enough yet for a deep sfc based marine layer to
prevent that mixing to the ocean sfc. With that said, winds will
reach SCA thresholds late in the pre-dawn Tue hours and
continuing thru daylight Tue. With the CFP slated for Tue aftn,
SCA threshold westerly winds will veer to the NW and become
gusty at times. The increasing NW winds will be the result of
a continued tightened sfc pg and CAA occurring across relatively
mild SSTs.
Previous......................................................
As of 300 PM Monday...Light S/SW winds across the waters are
occurring in response to broad high pressure ridging eastward
from the Gulf Coast. These winds will generally become all SW
and increase steadily tonight and on Tuesday in the warm sector
ahead of a strong cold front. The current wind speeds of 5-10
kts will become 20-25 kts this evening and on Tuesday, becoming
NW at these same speeds behind the FROPA Tuesday evening. These
winds will push seas quickly up from their current amplitudes of
2-3 ft to 4-6 ft by Tuesday morning, and the ongoing SCA
remains in place. Have started the hazard a bit earlier than
inherited to capture the 20-25 kt winds just before seas climb
towards 6 ft, and the SCA goes into effect at 6am Tuesday.
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM Monday...A rush of cold arctic air will keep
marine layer well mixed in gusty NW winds up to 20 to 25 kts
Tues night. A Small Craft Advisory will remain in effect through
early Wed in this surge, but winds will back and diminish
through the day on Wed allowing seas to subside. Overall expect
seas up to 4 to 6 ft Tues night dropping down to 2 to 3 ft by
Wed night. The off shore flow will keep highest seas in the
outer waters.
LONG TERM /THURSDAY THROUGH SATURDAY/...
As of 300 PM Monday...An active and windy weather pattern will
continue into Thursday and Friday. Another Canadian cold front will
slide across the area on Friday. Low pressure is expected to develop
along the front, helping produce a surge of offshore winds Friday
night. The latest GFS model is actually showing gale-force winds
Friday afternoon and night, but other model guidance is not that
strong, instead keeping winds strong but below 30 knots. Our
forecast will go with this weaker wind forecast for now, implying a
period of Small Craft Advisory conditions (W winds 20-25 kt) Friday
into Friday night. Winds and seas should improve on Saturday as
Canadian high pressure builds in from the west.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory from 6 AM Tuesday to 7 AM EST Wednesday
for AMZ250-252-254-256.
&&
$$
SYNOPSIS...JDW
NEAR TERM...DCH/JDW
SHORT TERM...RGZ
LONG TERM...TRA
AVIATION...DL
Area Forecast Discussion
National Weather Service Nashville TN
828 PM CST Mon Dec 11 2017
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Latest surface observations show cold front now entering the
northwest part of Middle Tennessee although bulk of cold air lags
well behind the initial wind shift. Satellite imagery also
depicts increasing clouds ahead of clipper system expected to
bring our next round of snow showers to the forecast area. Latest
18Z/00Z model runs including the HRRR show a relatively brief
window from roughly 11Z to 16Z tomorrow morning of snow showers
spreading across the Mid State, with the heaviest activity and
most QPF along the favored upslope areas of the northern
Cumberland Plateau from Monterey to Jamestown. Vertical moisture
plots show moisture will be quite limited with this system and
mainly below 850mb, and total QPF amounts on most guidance average
only around 0.03 inches. Even with snow ratios forecast to be
around 13:1 or 14:1, this would only give around a half inch of
snow accumulation so it may be difficult to reach our advisory
criteria of 1 inch or more. Nevertheless, with favorable northwest
flow and orographic lift, an inch of snow is certainly not of the
question in some spots as we have seen in the past, and will
leave the advisory as is. It should be noted that some light snow
accumulations will also be possible along the rest of the
Cumberland Plateau southward to Grundy County. The rest of the
area will see some flurries at times but no accumulation is
expected outside the Upper Cumberland due to even less moisture
and warmer temperatures. Forecast remains on track and only minor
tweaks were made.
&&
.AVIATION...
00Z TAF DISCUSSION.
Clipper system to move across the area late tonight and Tuesday
morning. Light snow shower activity is possible across the
Cumberland Plateau area. WIll include vcsh for the CSV taf.
Otw...higher clouds to move in this evening with low clouds
after midnight. Otw, look for winds to shift to west-northwest
between 02z and 08z. It will be on the breezy side by Tue
afternoon as the pressure gradient tightens.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 5 AM to 10 AM CST Tuesday for
Cumberland-Fentress-Overton-Pickett-Putnam.
&&
$$
DISCUSSION......Shamburger
AVIATION........21