Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/02/18
Area Forecast Discussion
National Weather Service Taunton MA
1034 PM EST Thu Feb 1 2018
.SYNOPSIS...
An arctic cold front tonight into Friday morning should lead to
another period or wintry precipitation, before wind chills fall
to zero to 10 below Friday night. A storm system should bring
rain to the coast and snow inland Sunday into Monday morning,
but there is uncertainty as to how far inland the milder air
will get. Another storm system may bring more rain and/or snow
Wednesday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
1030 PM Update...
No major changes to the forecast this evening. Winter Weather
Advisories continue as previously posted. This headline is
more about the impact late tonight and Friday morning, and not
for achieving numerical goals such as snow accumulation.
Last few runs of the HRRR appear to have a good handle on
timing and orientation of the precipitation overnight per
observed radar trends. Leaned heavily upon the latest HRRR and
HRRR ensemble runs to tweak the timing of precipitation
overnight. This timing will be critical, as will the
temperatures. We need both to be in sync to get accumulating
snow. Currently thinking, rain changing to a mix, then to all
snow from NW to SE after midnight.
Previous discussion...
Tonight into Friday morning...
*Accumulating snowfall and flash freeze during the morning commute*
Broad upper level trough across the region as potent shortwave
begins to approach from the Great Lakes. Southwesterly flow ahead of
this system will continue to saturate the column with an approaching
Arctic front from the north. Expect rain showers to become more
widespread during the evening and into the overnight hours.
Upper level shortwave pushing through the flow will drive an Arctic
front quickly through the region. This will result in temperatures
quickly falling and rain showers transitioning to snow prior to the
morning commute. While this is just a nuisance event, the
timing however will be quite impactful.
BUFKIT soundings show saturation through the column and thus when
cooler temperatures begin to advect into the region, expect a quick
transitions from rain to snow. The changeover will occur around
10 pm and 2 am for western/central MA and northern CT. For RI
and eastern MA around 2-5 am. If the front slows down by an hour
than snowfall amounts may be less and vice versa if it speeds
up. Trended temps towards the cooler guidance as this approaching
airmass is near 2-3 STD below normal.
Aside from the p-types, both the NAM and GFS continue to show decent
omega within the snowgrowth region. This will result in a brief
burst of snowfall that will quickly coat area surfaces ahead of the
morning commute. This is also in conjunction with strong F-gen and
secondary shortwave pushing through the flow. Snowfall amounts near
an inch an hour could occur which will limit vsbys below 0.5 a mile.
Fortunately this system is quite progressive and thus will be out of
the region by 10 am Friday morning.
In terms of snowfall, overall expect 0.5-2 inches of snowfall.
Valley locations may see less as BL temps may be a bit slow to flip,
but if the intensity of the snowfall is strong, then more snow is
possible. Went ahead and upgraded the high terrain of the Worcester
and Connecticut hills to a winter weather advisory for 2-4 inches of
snowfall. This is the region where confidence is the highest as
thermal will allow for precip to switch quicker and thus accumulate
more snow. Most hi-res guidance including the HRRR and HREF are
really pointing at this region. One area to watch is across
southeast MA. BL temps may still be a bit warm, but guidance is
pinning strong snowfall rates in this region. A winter weather adv
may be needed in this area mainly for the impact as this area will
be seeing accumulating snowfall right during the rush hours.
Temperatures will also be crashing towards the morning resulting
in a quick drop of surface temps. Thus cannot rule out the
potential for a flash freeze across the region.
Overall, complex system approaching from the west. Rain to start but
will flip to snow by the overnight hours. Motorist should be aware
of the accumulating snowfall potential and flash freeze during
the commute and plan for extra travel time.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Friday afternoon...
The rest of Friday appears blustery and frigid behind the front as
850 mb temps fall below -20C. Temps at the surface may remain steady
or fall during the day, as heating will be limited. Westerly winds
will increase to 25-30 MPH resulting in wind chill values in the
single digits. Cannot rule out a few lake effect streamers moving
through the region if they can make it over the Berks.
Friday night...
Generally dry weather as high pressure across the Mid-Atlantic
builds. CAA will continue across the area. Winds will still be a bit
gusty so do not expect a true radiational cooling night, but it will
be chilly. Overnight temps will fall into the single digits to low
teens resulting in wind chill values around -10 to -15C for the
higher terrain.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Big Picture...
Longwave scale shows a persistent ridge west/trough east
pattern through the end of next week. Shortwave scale is
similar, but both mass and thermal fields show a couple of
troughs moving through the flow drawing bursts of milder than
normal air north ahead and colder than normal air south behind.
Expect changeable temperatures through the period.
One upper shortwave moves off through the Maritimes Saturday, while
others move through our area around Monday and midweek. Mass fields
show agreement through Monday. Mass fields agree on development on
the mid-week shortwave, but differ on timing with the GGEM 12 hours
faster than the GFS and ECMWF. Thermal fields are similar through
Monday with differences by midweek. Confidence is moderate.
Details...
Saturday...
High pressure in place over the region with diminishing winds
turning west-southwest. Thermal and mass fields are below
normal, so cold air will be firmly in place during the day. As
the high shifts offshore, expect winds to shift from the west
and southwest. Mixing to 900 mb and winds in that layer support
gusts of 15-20 knots. Temperatures of -10C to -13C at the top
of the mixed layer support max temps in the 20s.
Increasing and deepening moisture aloft late Saturday/Saturday night
suggest increasing clouds. The clouds and southwest flow should keep
low temps closer to seasonal normals...roughly mid teens to mid
20s...with early night min temps followed by rising temps overnight
as the clouds thicken.
Sunday-Monday...
Two shortwaves during this period. The first, more subtle, is
associated with a strong upper jet and generates surface low over
the Plains that moves east to the vicinity of New England.
Positioning of the low varies among the models, ranging from the
Canadian border to just south of the Islands. Either way, this means
increasing chance of precipitation on Sunday which lingers until
this upper trough and surface system move past on Monday morning.
Diminishing chance of precip west to east on Monday morning.
We remain under the influence of high pressure offshore with south
to southwest flow at the surface. This would mean warming temps
through the day. While an initial period of snow is possible, rising
temps should change this to rain in at least the coastal plain and
possibly the interior as well. Model data for this storm will need
to be monitored over the next couple of days.
The second shortwave sweeps down from northern Canada across the
Great Lakes and New England, crossing our area on Monday. This is
associated with the cold air...it brings 18C temperature drops at
850 mb and 12C drops closer to the surface at 950 mb during Monday.
Surface temperatures may climb a few degrees Monday morning, but
early afternoon temps aloft support max temps in the 30s and this
trends lower through the afternoon. So expect steady or falling
temps in the afternoon.
Tuesday through Thursday...
High pressure brings dry and cold weather Tuesday. The next
shortwave generates surface low pressure that moves up the Ohio
Valley midweek and spreads precip into New England by Wednesday.
There are differences among the models in timing as well as storm
track, with resulting differences in precip type. For now we will
mention chance pops for snow changing to rain. High pressure then
brings drier weather for Thursday.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Friday Night/...High confidence.
Conditions lower to MVFR tonight in rain showers, especially
after midnight when rain transitions to snow from NW to SE. IFR
conditions likely toward daybreak Fri from a burst of snow.
Most locations could see a dusting to an inch or two of
snowfall, but cannot rule an isolated 3 inch amounts across the
higher terrain.
Friday afternoon into the evening...Conditions improve to VFR.
Blustery westerly winds towards the evening with gusts near
25-35 kts.
KBOS Terminal...High confidence in TAF. Morning push could be
impact with IFR conditions from burst of snowfall as well as
effects of temperatures near freezing.
KBDL Terminal...High confidence in TAF. After midnight, IFR
conditions from burst of snowfall is possible.
Outlook /Saturday through Tuesday/...
Saturday: VFR. Breezy.
Saturday Night: VFR. Breezy. Slight chance SN extreme west
Massachusetts late.
Sunday: MVFR/IFR conditions possible. Breezy. RA likely, chance
SN.
Sunday Night: MVFR/IFR conditions possible. Breezy. RA, SN
likely.
Monday: Mainly VFR, with local IFR possible early. Windy with
local gusts to 30 kt. Slight chance SN.
Monday Night: VFR. Windy with local gusts to 30 kt.
Tuesday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Short Term /through Friday Night/...High confidence.
Persistent southerly swells will keep seas up across the
southern waters. Arctic front will swing through during Friday
morning resulting in strong CAA across the waters. Gale Warnings
have been issued for all waters from Friday afternoon into
Saturday morning. Heavy freezing spray will also be occurring at
that time.
Outlook /Saturday through Tuesday/...
Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.
Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft.
Sunday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Rain. Local visibility 1 to 3 nm.
Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Rain.
Monday: Moderate risk for Small Craft Advisory winds with areas
of gusts up to 30 kt. Areas of rough seas. Chance of rain.
Monday Night: Low risk for Small Craft Advisory winds with
local gusts up to 30 kt. Areas of rough seas.
Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until 9 AM EST Friday for CTZ003-004.
MA...Winter Weather Advisory from 3 AM to 9 AM EST Friday for
MAZ005-006-013-014.
Winter Weather Advisory until 9 AM EST Friday for MAZ004-012-
026.
RI...Winter Weather Advisory from 3 AM to 9 AM EST Friday for
RIZ001.
MARINE...Heavy Freezing Spray Warning from 4 PM Friday to 7 AM EST
Saturday for ANZ231>235-237.
Gale Warning from 1 PM to 7 PM EST Friday for ANZ230-232>234-
236.
Gale Warning from 1 PM to 10 PM EST Friday for ANZ231-251.
Heavy Freezing Spray Warning from 4 PM Friday to 1 AM EST
Saturday for ANZ236.
Gale Warning from 1 PM Friday to 1 AM EST Saturday for ANZ235-
237-250-254>256.
Heavy Freezing Spray Watch from Friday afternoon through
Saturday morning for ANZ250-254>256.
Heavy Freezing Spray Warning from 1 PM Friday to 7 AM EST
Saturday for ANZ251.
&&
$$
SYNOPSIS...WTB/Dunten
NEAR TERM...WTB/Belk/Dunten
SHORT TERM...Dunten
LONG TERM...WTB
AVIATION...Belk/WTB/Dunten
MARINE...WTB/Dunten
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1009 PM EST Thu Feb 1 2018
.SYNOPSIS...
An arctic front will cross the region early Friday with cold and
gusty air moving in behind it after another round of rain and snow
late tonight and early Friday morning. High pressure will build
in for the weekend. Sunday temperatures will begin to warm up.
Low pressure will develop Sunday with precipitation moving into
the area Sunday night into Monday. This will be all snow in the
mountains with mixing snow and rain along the coast. Brief high
pressure again moves in for Tuesday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
1010 PM Update...
Adjusted precipitation timing slightly as well as PoPs to
account for current trends and latest CAM models. Echoes are
just entering the CWA at this time. HRRR has been trending less
QPF so will not issue any headlines but will continue to
highlight the possible impact the weather may have on the
morning commute.
730 PM Update...
Only minor changes to the forecast at this time...temperatures
are in the mid 20s north to lower to upper 30s across the
south.
Precipitation is making its way through NY state and PA and is
on track to reach NH later tonight . Latest run of the HRRR has
backed off on QPF a bit for this event...with the heaviest (but
still light) amounts brushing the coast. The majority of the
precipitation will remain offshore but a few locations will see
1-3" with isolated 4" amounts. Will be issuing a statement
shortly to mention hazardous driving conditions for the morning
commute which may include rain, snow, and some mixed precip.
Previous discussion...
Precipitation has ended across the forecast area as of 3 pm as
forcing for ascent has moved off to the north. However, a wave
of low pressure will develop to our southwest overnight along an
advancing strong cold front. This will allow for more stratiform
precipitation to develop across the region from sw to ne late
this evening.
Boundary layer temperatures will be marginal for snow in some
areas (mainly southern NH and the coastal plain), but 950-925mb
temperatures will be even warmer over a wider area due to an
strengthening southwesterly low level jet. Therefore, the next
batch of precipitation is expected to start as rain or a
rain/snow mix for most locations on the coastal plain,
foothills, and southern NH. Areas west and north of there should
see mainly light snow but a little rain may even mix in there
at the start.
As the wee hours of the morning progress, the low levels will
get colder and the rain or mix will change to snow from west to
east. The low pressure wave is stronger in the models today and
this will result in more precipitation. There may even be a very
brief period of freezing rain and sleet in the transition zone
between snow and rain as the 950mb air stays warmer a little
longer than the SFC does.
Most areas should see another 1-2 inches of snow out of
this after changeover but a few locations that cool quicker may
see a bit more (higher elevations as well as the I-95 corridor
northeast of Lewiston ME). Will have to continue to watch for
further amplification overnight as this could mean a bit more
snow than forecast in some areas.
Winds will kick up pretty stoutly toward dawn as well as strong
CAA kicks in. Gusts around 30 MPH likely toward sunrise.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Snow will taper off and end early Friday morning but not before
the morning commute ends. This will make for a slippery morning
commute with snow falling, falling temperatures, and any roadway
slush freezing up. Blowing snow may be an issue as well as winds
gust to around 30 MPH. Friday morning is going to be a bit of a
different world in terms of sensible weather as compared when
people go to bed tonight. Temperatures will fall all day Friday
with cold wind chill values. We may need a wind chill advisory
for the mountains for later Friday afternoon and especially
night.
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
A series of shortwaves will rotate around the base of a larger
500mb trough dominating much of eastern North America.
Saturday will begin cold in the wake of the Arctic front that
moved through on Friday however high pressure will steadily
build into the region through the weekend. As it does we`ll see
south to southwesterly flow set up with climbing heights and warming
temperatures. By Sunday highs should be above freezing along
the south coast.
The focus of the extended forecast is from Sunday night into
Monday when low pressure begins to form near the Great Lakes and
moves eastwards across the forecast area. There is high
confidence of widespread precipitation occuring across the entire
region from Sunday night into Monday, however the precipitation
type is still fairly low confidence.
Rather than one well defined system, this scenario presents a
face off between a Great Lakes low which will move northeast up
the St Lawrence valley and ultimately pass north of the area,
and a coastal low will will try to initiate off the delmarva
peninsula and track much closer to the coastline. The former
would push the warm air further northward with the corresponding
rain/snow line further inland. Meanwhile a coastal solution
would leave all but the immediate coastline in snow. This tug of
war is likely to continue for at least the next 24 to 36 hours
and the two low centers battle it out in the guidance. Overnight
we saw a shift to favor the more inland Great lakes low and
warmer solution. I am however, hesitant to call this a trend at
this point as the ultimate source of both of these lows would be
initial disturbances moving out of a blocking pattern in the
Gulf of Alaska. Ensemble sensitivity would also point to the
source of our uncertainty in this region. Overall have opted to
pick a fairly middle ground solution which allows mixing to come
into southern New Hampshire and Maine.
The storm will exit the region on Monday afternoon allowing high
pressure to build in for Tuesday. The break will be short lived
as the next wave rounds the base of the trough setting off
another round of precipitation for Wednesday. This track looks a
bit further inland with the rain/snow line.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Short Term...MVFR to IFR conditions in rain and snow will once
again arrive late this evening and overnight...and these will
likely last through the 15z time frame Friday. Thereafter,
mainly VFR conditions are expected with NW winds gusting to
around 30 kt well into Friday evening.
Long Term...VFR conditions will prevail for the weekend
throughout the area as high pressure dominates. The next system
approaches on Sunday night with increasing clouds in the
afternoon. Expect a drop to IFR in Snow with sleet and rain
mixing in along the coast. The storm will depart Monday morning
with all but the northern mountains quickly improving to VFR.
&&
.MARINE...
Short Term...Gale warnings have been posted for all waters
except for Casco Bay...for Fri afternoon into Saturday morning.
Freezing spray advisories for all waters.
Long Term...Gales will subside on Saturday morning as high
pressure builds into the region. Sunday southwesterly flow will
increase ahead of a developing low. This will result in
widespread small craft criteria with gales again possible for
the outer waters.
&&
.HYDROLOGY...
The latest Winter/Spring flood potential outlook was issued this
afternoon. The flood potential is near to somewhat below normal
in western Maine and northern New Hampshire. The flood potential
is below normal in southern New Hampshire. The potential for ice
jam flooding is above normal. See ESFGYX for more detailed
analysis.
&&
.TIDES/COASTAL FLOODING...
Will continue to watch the midday tide Friday afternoon for any
sort of minor coastal flooding, but developing strong offshore
winds orthogonal to the coastline should mitigate the threat.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...Small Craft Advisory from 5 AM Friday to midnight EST Friday
night for ANZ153.
Freezing Spray Advisory from 2 PM Friday to noon EST Saturday
for ANZ150>154.
Gale Warning from noon Friday to midnight EST Friday night for
ANZ150>152-154.
&&
$$
NEAR TERM...Hanes
SHORT TERM...Ekster
LONG TERM...Curtis
Area Forecast Discussion
National Weather Service Wilmington NC
1023 PM EST Thu Feb 1 2018
.SYNOPSIS...
A cold front will bring showers late tonight and Friday
morning, before clearing out Friday afternoon. A cold and sunny
Saturday, will be followed by increasing rain chances, and
milder temperatures Sunday. Drier air will move in early next
week, before a cold front arrives at the coast next Wednesday.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 800 PM Thursday...High pressure offshore is slowly
retreating to the east in advance of a cold front which will
cross offshore early on Friday. Clouds will steadily increase
overnight ahead of this feature, which combined with return flow
around the offshore high will keep mins elevated tonight.
Forecast lows are only in the mid 40s most places, a full 15
degrees warmer than last night.
The front will approach late tonight, and along it is expected
to be a line of showers. Forecast profiles from both the NAM
BUFR and RAP do become saturated sufficiently for precip, but
remain dry above 700mb, and the temporal duration of even low-
level saturation is minimal. This suggests that QPF will be
light, especially as the best dynamics stay north and PWATs
hover around 1 inch, and thunder is not expected. However, low-
level wind fields to climb ahead of the boundary, and 12z NSSL
4km WRF depicts a solid line of showers along the front,
weakening as it heads east. This seems reasonable and with 850mb
winds climbing to near 50 kts and 925mb winds up to 30 kts,
there is potential for some moderate to strong wind gusts
within any heavier showers. Latest HRRR however suggests the
showers may dissipate entirely as the boundary shifts east,
which seems reasonable based off shifting dynamics to the NE, so
best chance for any wind will be inland NC zones, as will be the
best rain chances.
Front shifts quickly offshore Friday morning with rapid drying
occurring thereafter. Dry and cold advection occurs all day, so
highs will climb only to a degree or two either side of 50 on
Friday, and wind gusts of 25-30 mph are possible through the
aftn.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM Thursday...Strong cold advection will take place
as surface high pressure builds in later in the day behind
Friday mornings cold front. Lows Friday night will be well
below normal, mainly in the mid 20s.
On Saturday, the surface high will shift overhead and eventually
into the Atlantic through the day, while a weak coastal trough
develops offshore. The flow aloft will remain fairly zonal. Lack of
any significant forcing mechanisms and pronounced dry layer up to
around 700mb will preclude any mentionable PoPs, however cloud cover
will begin to increase. Much cooler with highs topping out in the in
the mid 40s across most locations. Lows Saturday night will be
closer to normal.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 300 PM Thursday...Sunday will be the most active day of
the period as an area of low pressure over the Gulf coast states
lifts northeast across GA & SC before pushing off the coast.
Details in location of the surface low and timing is a bit
uncertain, however signals are pretty clear that it will be a
wet day. Deep moisture in combination with ample large scale
forcing (isentropic ascent, vort energy, and upper divergence)
will support likely to categorical rain chances. Rain should
spread from south to north throughout the day. Thunder potential
looks limited given minimal instability. Highs will be near
normal.
Surface low pressure and an associated cold front will quickly
exit the area early Monday, taking rain chances with it. High
pressure, moderate cold advection and drying will follow. The
early week airmass will be fairly seasonable through Tuesday.
Another cold front will bring rain chances to the region on
Wednesday.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
As of 00Z Friday...VFR conditions are expected at all terminals
through late evening hours. Gusty southwest winds will diminish to 5
to 10 kts this evening. MVFR cigs/vsbys with low clouds and showers
will reach the inland terminals between 06Z and 10z, then spreading
east to remaining terminals within an hour or two later. Conditions
should improve to VFR once a cold front passes the terminals,
starting around 14z at KFLO/KLBT, then around 16z for coastal
terminals. Winds will veer around to the W and then NW early Fri as
a cold front moves becoming gusty up to 15 to 20 kts by
afternoon with SKC between 15-17z most terminals.
Extended Outlook: VFR Sat. IFR Sun-Mon morning as low pressure
approaches from the west.
&&
.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 800 PM Thursday...High pressure offshore will gradually
give way to a cold front approaching from the west. SW winds
around this high will slowly increase through the night,
becoming 15-20 kts, before shifting rapidly to the NW early on
Friday with a short increase to 20-25 kts across NC waters,
slightly lower across the SC waters. This has prompted an SCA
which is in effect for AMZ250 and AMZ252 beginning at 1am and
persisting into Friday morning for the gusty winds. Despite
these increasing winds, seas will struggle to amplify thanks to
primarily an offshore wind direction, so seas of 3-5 ft are
expected, 2-4 ft SC waters. Winds will gradually ease through
Friday while shifting to the north, and a SCEC may be needed
once the SCA expires.
SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 300 PM Thursday...Conditions will remain fairly elevated
through Friday evening before improving Saturday morning as the
pressure gradient relaxes. Winds will gradually veer from the
north to eventually east Saturday as high pressure shifts
overhead and then into the Atlantic. Seas on average will be 2-4
feet.
LONG TERM /SUNDAY THROUGH MONDAY/...
As of 300 PM Thursday...An area of low pressure will lift northeast
into the area late Sunday, although discrepancies in models on track
and timing of the low are leading to higher uncertainty in the
forecast, especially wind directions. At this time, no additional
small craft advisories are expected. The aforementioned low and an
associated cold front will push away from the area Monday, with high
pressure to build in its wake. Rather benign marine conditions are
expected, with winds and seas below Small Craft Advisory criteria.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...Small Craft Advisory from 5 AM to 1 PM EST Friday for AMZ250-
252.
&&
$$
SYNOPSIS...99
NEAR TERM...JDW
SHORT TERM...99
LONG TERM...99/MBB
AVIATION...RGZ
MARINE...
Area Forecast Discussion
National Weather Service Raleigh NC
1011 PM EST Thu Feb 01 2018
.SYNOPSIS...
A pair of cold fronts will cross central NC through Fri morning.
Following, Arctic high pressure will build from the mid MS Valley
Friday to the the southern middle Atlantic states Friday night, then
offshore on Saturday.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 1005 PM Thursday...
A nrn stream trough evident in evening observational data from
Quebec swwd into the mid-South and lwr MS Valley will migrate
generally ewd, with the core of associated 120-180 meter mid level
height falls forecast to spread across the nrn middle Atlantic
states by 12Z Fri. Meanwhile, an active srn stream emanating from a
large closed low over the sern N. Pacific, ewd across nrn Mexico and
the U.S. Gulf coast, will remain generally stationary, well south
of cntl NC.
In the lower levels, between the surface and 850 mb, a pair of
closely-spaced and sharp frontal zones (within several hundred miles
of the other) were analyzed from the nrn middle Atlantic states swwd
into the lwr MS Valley and srn Plains. These include, at the
surface, a lead cold front analyzed at 03Z from a 1011 mb frontal
wave over nrn VA, swwd along a line closest to home from RNK to TNB,
then swwd through nrn GA, cntl AL, and srn MS. A cold-frontal rain
band and gusty (~35 kt) winds accompany this lead cold front over
GA, AL, and MS; and this feature is forecast to become increasingly
defined with time and newd extent into cntl NC as the associated
frontal zone and strong frontogenesis fully crests the NC Blue Ridge
and subsequently collapses sewd across the NW NC Piedmont by 05-
06Z, the cntl and srn Piedmont (including the Triangle) between 06-
08Z, and the Coastal Plain between 07-11Z. A band of light
stratiform rain will trail the lead front and weak/shallow
convective band, with an associated 3-4 hr period of precipitation
at any given location. A trailing surface front that marked the
leading edge of truly Arctic air was analyzed from cntl NY and PA
swwd through sern OH and e-cntl KY; and this boundary will cross
cntl NC during the first half of Fri.
Despite only very weak and brief elevated instability (MUCAPE) of
less than 50 J/kg, the aforementioned cold-frontal rainband is
forecast to strengthen as it moves into and crosses cntl NC
overnight, likely owing to the presence and release of conditional
symmetric instability (CSI); and as such, precipitation amounts have
been increased slightly over the ern half of the forecast area, with
some around quarter inch amounts probable there.
CAA-driven lows will likely be met 2-3 hrs after sunrise - around
freezing nw to around 40 degrees in the Coastal Plain. A few slick
spots cannot completely be ruled out over the NW Piedmont given
these around freezing temperatures, but both a strong nwly wind and
relative minimum of precipitation there (generally less than a tenth
of an inch) suggests most moisture will evaporate prior to
potentially freezing.
&&
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 340 PM Thursday...
Rain chances are expected to be moving out of our SE counties by
around 12z Fri morning. Otherwise, rapid clearing will continue
through the SE CWA, resulting in plentiful sunshine as cold high
pressure builds in from the west with a dry column. With steady cold
air advection, the daytime temp recovery will be minimal, with
readings potentially holding steady or rising just a few degrees.
Expect daytime highs to end up in the 36-48 range NW to SE. A steady
NW wind should occasionally gust to around 20-25 kts, based on
downward momentum transfer noted on RAP soundings. Fri evening and
night will feature diminishing winds and frigid temps as the surface
high settles overhead late. Lows 15-21, a shade under statistical
guidance. -GIH
&&
.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 305 PM Thursday...
Surface high pressure will begin the day Saturday overhead but will
move quickly off of the east coast and continue northeastward by
Saturday night. This will lead to a dry first half of the weekend
with increasing clouds and temperatures in the low to mid 40s.
Things get very interesting on Sunday morning as a weak wedge
remains over the area and a Miller B type system begins to approach
from the southwest consisting of two low pressure systems, one to
the south and one to the northwest of central NC. These systems
usually are a challenge for P-type forecasting and this system is no
different. As such there will be a brief period between 6-9z where
rain or snow or even sleet will be possible, but there is also a
chance that precipitation holds off until a little later, in which
case all rain or freezing rain is the most likely scenario given the
large warm nose in the forecast soundings and provided surface
temperatures fall low enough overnight. We will call it a mixed bag
for now and the greatest threat of this will be in the Triad and the
VA border counties between 6-13z sunday. At this time no
accumulation of snow or ice is expected. After 13z, temperatures
will warm and precipitation will change to all rain. Significant
rain is expected Sunday and Sunday night with totals between a half
of an inch and an inch possible. As the system moves out early
Monday morning there will be a chance for some snow flurries but it
will be a case of cold air chasing the moisture and at this time
looks like it may not catch up in time to see any snow. This will
continue to be a very difficult forecast over the next couple of
days so stay tuned for updates as the system evolves.
After precipitation exits on Monday, dry weather will ensue through
Tuesday night with highs near 50 degrees and lows Monday night in
near freezing but moderating into the upper 30s to low 40s with
southerly flow by early Wednesday morning. The next frontal system
is progged to move in on Wednesday through Wednesday night with all
liquid precipitation expected as highs soar into the mid 50s to mid
60s. Thursday will represent a return to dry weather with cooler
temps in the upper 40s to lower 50s.
&&
AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 640 PM Thursday...
A cold front that will move SE across the area between 04z
and 10z. A band of showers will accompany the front, with a few
hours of MVFR CIGS and VSBYS with light rain showers, 03z-07z at
INT/GSO, 05z-09z at RDU, and 06z-10z at RWI/FAY. Gusty SW winds
ahead of the front of 10-20kt expected. Winds will shift to the NW
behind the front at 15kt. Winds will increase after sunrise and
continue much of the day at 15-25kt. Otherwise, a return to VFR
conditions is expected after 12z at all terminals.
Outlook for Friday night into Saturday night... VFR conditions
expected. Another low pressure and cold front will bring MVFR to IFR
CIGS and VSBYS with rain and fog Sunday into Sunday night.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...Hartfield
LONG TERM...Ellis
AVIATION...Badgett/Hartfield
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
755 PM EST Thu Feb 1 2018
.UPDATE (Overnight and Friday)...
01Z water vapor and H4 RAP analysis showing an amplified
mid/upper level trough digging over the eastern half of the
nation...with the trough base reaching down to about the
I-10 corridor. The Florida peninsula will remain in a benign
weather regime overnight to the south of the trough`s
influence...and still under the control of Atlantic high
pressure ridging westward across the state.
The light pressure gradient in place along the trough axis
may allow for some shallow field fog in places late
tonight...however should not be a significant impact to the
early morning commute...and will burn off quickly with
sunrise. The dry atmosphere, and light winds will allow for
another cool night...but not as chilly as previous nights.
Low temperatures by sunrise will range form the upper 40s
over the far north...to the lower and middle 50s elsewhere.
Friday...A secondary piece of shortwave energy migrating
across the TN valley within the eastern CONUS trough will
help propel a weak cold front down into the state/eastern
Gulf of Mexico...and then off to our south Friday evening.
This front will bring a slightly cooler and drier airmass in
its wake for the first half of the weekend...but will have
a fairly uneventful passage. All of the large scale/synoptic
support for ascent associated with the eastern trough will
remain well to our north...and a very limited moisture
profile will not be able to support shower activity by the
time the low level focus along the front gets this far
south. All the available moisture for clouds will be under
10KFT...where environmental temperatures are well above 0C.
Would need to get cloud tops up to at least 15-17KFT before
ice would be present in the cloud and heterogeneous
nucleation could commence. With this in mind...feel
confident in the forecast of a dry frontal passage. Just a
band of clouds around 5KFT and a wind shift to the north.
With most areas (other than the far northern zones) being
ahead of the front for the majority of the diurnal heating
cycle...and being within the thermal ridge ahead of the
front...this will support a rather warm final day of the
work week. Will start out cool, but should see afternoon
highs in the mid/upper 60s around Chiefland...ranging to
the lower/mid 70s through the I-4 corridor...and solidly
into the middle 70s away from the immediate coast to the
south of I-4. Locations along the immediate coast will end
up a few degrees cooler as the strong terrestrial heating
and still weak gradient promotes another weak sea-breeze
circulation to form in the afternoon and advect some cooler
air off the shelf waters after 18-19Z.
&&
.AVIATION (02/00Z through 03/00Z)...
VFR conditions prevail across west-central and southwest
Florida for the rest of the evening. Late tonight the
potential for areas of shallow field fog will exist for
KLAL/KPGD/KRSW...however...the aggressive statistical
guidance has been too aggressive as of late, and have not
gone with anything under MVFR vis for a few hours around
sunrise at these locations. After any early morning fog
lifts, VFR conditions prevail through Friday. A period of
4-6KFT BKN cigs is expected around the Tampa Bay terminals
in the afternoon with the passage of a cold front...however
not significant aviation concerns are expected. Expect winds
to shift to the NW and north in the wake of this front
Friday afternoon/evening.
&&
.Prev Discussion... /issued 219 PM EST Thu Feb 1 2018/
SHORT TERM (Tonight - Friday)...
The weather pattern over the short term period will be rather
tranquil. Upper ridging still holds over southern Florida while
troughing moves through the central U.S. This troughing will remain
well to the north of the area with no effect on the local weather
through the short term. On the surface, high pressure near Bermuda
ridges west-southwest over Florida and into the eastern Gulf of
Mexico keeping pleasant weather over the area tonight into early
Friday. Farther north and northwest, an area of low pressure over
New England extends a cold front southwest through Tennessee and
further south off the Louisiana coast. The front will move north of
the area on Friday, not really playing a role in the weather here in
Florida except for some increasing cloudiness and a slight chance of
showers over the northern counties. Strong high pressure builds back
into the region behind the front producing pleasant weather late
Friday and into the weekend. Temperatures will run right around
seasonal average or a couple of degrees warmer.
LONG TERM (Friday Night through Thursday)...
At the start of the long range period, persistent broad cyclonic
flow will remain anchored over the Great Lakes and eastern Canada.
Within this quasi-zonal flow pattern, several shortwave troughs and
associated cold fronts will move through the region. This will bring
periods of increasing rain chances, and shots of cooler air,
maintaining pleasant winter conditions across the region.
As we head into the weekend, a remnant front will stall across
southern Florida with high pressure extending across the peninsula.
This will maintain easterly flow and mild temperatures. A developing
low pressure system will move across the Florida panhandle/northern
Florida Sunday into Sunday night. This will bring a very good chance
of rain to areas along and north of I-4 with more spotty activity
south of the I-4 corridor. Rain should end from north to south as a
trailing cold front moves through the region. At this time, it does
not appear adequate moisture and instability will have returned for
much in the way of thunderstorms due to a dry frontal passage late
tomorrow into Saturday. However, a stray storm or two would not be
out of the question, primarily over the warmer Gulf waters.
Drier cooler air will move in for the first of next week, but
temperatures will quickly modify by mid week as another approaching
shortwave and associated cold front result in returning moisture and
rising upper level heights. Rain chances look to increase once more
toward the end of the period, though confidence in overall
timing/amounts remains very low at this time.
Temperatures will generally remain just a couple of ticks above
normal, falling to near or just below normal in the wake of the two
cold fronts.
MARINE...
High pressure in the western Atlantic will keep light winds over the
coastal waters today, turning onshore this afternoon with a sea
breeze. A dry cold front will move southeast into the coastal waters
late Friday. A tighter pressure gradient along and behind the front
will cause an increase in northerly winds Friday afternoon through
Saturday, with exercise caution level conditions expected offshore.
Another front will arrive on Sunday, bringing an increase in rain
chances and a shift in winds to the south-southeast, although winds
are forecast to remain around 15 knots or less. No other marine
impacts expected.
FIRE WEATHER...
Surface high pressure in the western Atlantic will keep light winds
in place across the area today with a weak sea breeze circulation. A
dry cold front will push into the area Friday afternoon, with winds
increasing and turning to the northwest and north. Relative humidly
will remain well above critical thresholds. No widespread
significant fog is expected through the next few days, but some
patchy ground fog will be possible late tonight into early Friday
morning.
&&
.Preliminary Point Temps/PoPs...
TPA 56 72 52 70 / 0 10 0 10
FMY 57 76 57 73 / 0 0 10 10
GIF 54 75 51 70 / 0 10 0 10
SRQ 56 71 54 70 / 0 10 0 10
BKV 51 72 47 70 / 0 10 0 0
SPG 56 72 53 70 / 0 10 0 10
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...None.
Gulf waters...None.
&&
$$
UPDATE/AVIATION...Mroczka
Previous Discussion...Wynn/Austin