Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/01/21
Area Forecast Discussion
National Weather Service Gaylord MI
1014 PM EST Sun Feb 28 2021
.UPDATE...
Issued at 1014 PM EST Sun Feb 28 2021
993mb low is north of Georgian Bay, with a cold front extending to
the south toward western Lk Erie. Cold advection is very much
underway, though surface temps remain near or above freezing at
this hour. That will be changing, with mid-20s temps in central
upper MI, and teens and colder on the other side of Superior.
Readings will fall well into the teens in eastern upper and far
northern lower MI by dawn, with upper teens to mid 20s elsewhere.
Winds have been a little uppity this evening. A number of gusts
circa 40mph occurred with and just after fropa, with GLR the
exception on the high side at 47mph. That was fine. Just in the
past hour though, several gusts in the 45-50mph range have come
out of eastern upper MI. Nam Bufr soundings suggest circa-45mph
gusts or a touch higher are possible thru about midnight, as
momentum is transfered downward in a mixed layer some 3k ft deep.
Toward and after midnight, the pressure gradient and associated
wind gusts should relax. Given the short duration of continued
gusty winds, have issued an SPS to highlight winds late this
evening, instead of issuing a very short wind advisory (though
that was considered).
Lake effect banding just barely starting on APX radar into nw
lower MI. More prominent banding has organized east of MQT. 00Z
Nam Nest output, and latest HRRR runs, continue to have the
strongest band developing into Whitefish Pt/Paradise, and on se
across the bay into Brimley/Kinross. Think the idea of the
previous forecast is sound: fairly lousy conditions are likely
tomorrow morning in the above area due to falling/blowing snow,
gusty winds, and cold temps. Did fine tune the location of best
snow accums a bit tomorrow, pushing a little further east away
from Luce Co. Regardless, 2-6" snow accums are likely overnight
into Monday in the area noted above. So posted an advisory for
western Chippewa, and ultimately decided to include central Chip
as well. Do not think this will be a huge event for the Sault, but
places w and s of there (again, Brimley to Kinross) should get
enough snow and have enough impact (including to I-75) to warrant
including the central Chip zone.
No need for winter wx headlines elsewhere, as least yet. Nam Nest
and other near-term guidance are not bullish on snow amounts in
other parts of northern MI.
&&
.NEAR TERM...(Through Monday)
Issued at 328 PM EST Sun Feb 28 2021
...Much colder air and lake snow showers returning...
High Impact Weather Potential: Colder air spills into the region
tonight leading to single digit wind chills for Monday.
Accumulating lake effect snow showers for the snowbelts.
Pattern Synopsis/Forecast: 20Z satellite/composite analysis
reveals our open short-wave circulation rolling through northern
Wisconsin. Associated slowly deepening surface low pressure is
passing through the Iron Mountain area heading toward the eastern
U.P. with 3 hour pressure falls centered across that area. Axis
of deformation/f-gen forced snowfall continues to pivot through
western/central Upper Michigan along the N/NW side of the
wave/surface low. Expansive warm conveyor belt/axis of rainfall
stretches from Oklahoma ENE across the Mid Atlantic.
Much of lower Michigan still sitting in "no-mans" land of sorts
between axis of snow to the north and rain to the south. Lower
cloud cover has expanding up through our area and there is some
showery/drizzly looking returns on radar sliding up through
northern Lower Michigan with a little better coverage in eastern
Upper. But in all, precip across this CWA has been paltry thus
far.
Through this evening: Short-wave and surface low will track
across eastern Upper Michigan over the next several hours, back-
side deformation axis just skirting through eastern Upper Michigan
through early- mid evening. Given the further north track of the
low, precip across E.UP. will likely remain mainly liquid through
early evening anyway until colder air begins to fold back into the
region resulting in a few hours of light accumulating snow.
South of the bridge, spotty rain showers will continue to move
through northern Lower Michigan through early-mid evening with
maybe a brief transition over to snow before ending.
System continues quickly into eastern Canada tonight. Higher
impacts follow with substantially colder air spilling into the
state on gusty northwest winds...later tonight through Monday.
This will drive temperatures down into the teens by Monday morning
with only modest rebounding anticipated during the day Monday. But
gusty winds will result in single digit above and below zero wind
chill readings Monday morning, quite the change from where have
been over the last few days.
Lake snows are another matter. Strong cold advection tonight
drives H8 temps down to -18C to -22C through Monday resulting in
lake induced CAPE values of near 500 J/Kg on Michigan and a little
better still on Superior (BufKit suggests a period of moderate to
extreme lake effect conditions on Monday). Incoming airmass will
be on the drier side however, with single digit dewpoints and PWAT
values under 0.10", which might throttle lake effect to some
degree. But think we will be able to muster some moderate snow
accumulations in the snowbelts. Along with gusty winds and blowing
snow, we may need to hoist an advisory for Monday.
&&
.SHORT TERM...(Monday night through Wednesday)
Issued at 328 PM EST Sun Feb 28 2021
High Impact Weather Potential: Minimal
Pattern Synopsis/Forecast:
Ridging makes a return to the Great Lakes for the start of the short
term...as strong, anomalous troughing departs (some would say, good
riddance). As we get into high pressure on the back side of this
troughing...lake effect should be winding down as temps aloft
rise...and potential for diminishing cloud cover with still quite
cold air aloft should lead to one more very cold night before things
warm up again Tuesday. A weak northern stream shortwave will be the
next thing to watch going into late Tuesday and early
Wednesday...with a more potent shortwave staying well to our
south...and that troughing from Monday, still anomalous as it spins
off the coast of Nova Scotia (hold that thought till the long term).
By Wednesday...upstream flow over the Pacific becomes more
amplified...with troughing digging south of Alaska as ridging behind
it strengthens...setting the scene for a cutoff low to get kicked
eastward into Southern California. As troughing digs toward the
western North American coast...will see ridging across the west-
central US begin to amplify Wednesday...lending a slight troughy
look to eastern portions of the US.
Primary Forecast Concerns: Lingering LES, cold temps/cloud cover
Monday night...gusty winds and precip chances Tuesday into Wednesday.
As shortwave departs eastward Monday night...will see pressure
gradient begin to slacken as surface high pressure builds in. This
should act to decrease winds for a time. Will see mid-level
subsidence move in during the night...which should lead to a
decrease in cloud cover. Recent guidance seems to be trending things
a tad warmer for Monday night...though there is still a pretty
reasonable chance for some locations to bottom out below normal
Monday night. Aforementioned mid-level subsidence should also help
bring LES chances to a close through the night as inversion heights
fall. Can`t rule out it lingering longer into the night
north/northwest flow lake effect across eastern Upper and perhaps
near or right off the sunrise coast of northern Lower...where 850 Ts
look to stay cold enough through at least 6z.
As northern stream shortwave (aka, clipper system) approaches from
the northwest Tuesday...will see moisture increase from top down.
However...at the same time...southwesterly flow will be ramping up
as well...between departing surface high to our southeast and low
moving through southern Manitoba/Ontario...with a lot of dry air
still in the midlevels...and gulf moisture kept busy to our south by
potent shortwave moving through the southern stream of the flow
across the Gulf coast states. Precipitation may have a hard time
reaching the ground...though may have a slightly better chance
further north across Eastern Upper, and maybe the tip of the mitt,
where synoptic moisture from the clipper will be stronger, and where
better dynamics will be located. Will at least see some increased
cloud cover...but bigger news will be warmer temperatures as system
drags a warm front through the region through the day.
Additionally...with strengthening pressure gradient between surface
high and incoming low...will likely see winds pick up again during
the day Tuesday...leading to another gusty day...though warm
advection will be in play this time around.
Latest model runs may be trending perhaps a little cooler for
Wednesday than they have the last few days...with that northern
stream system dragging a west-to-east-oriented cold front into the
Great Lakes. Will have to keep half an eye on this for temperature
trends...though at least for now, it looks to stay dry.
.LONG TERM...(Wednesday night through Sunday)
Issued at 328 PM EST Sun Feb 28 2021
High Impact Weather Potential: Minimal...?
Remember when I said to hold that thought about Monday`s troughing
lingering off Nova Scotia? Well, that pesky bugger may end up
helping to bookend our week with colder weather...as it looks to
linger near the St. Lawrence River/Nova Scotia through the
week...and actually attm appears to retrograde for a time, swinging
some lobes of colder air into the Great Lakes perhaps even as early
as Wednesday night. Perhaps cold enough air aloft to bring LES
chances back into the picture...especially if it pans out that the
downstream trough will send little lobes of energy knocking on our
northern door through the end of the week into next weekend. As
such, will have to watch for another incursion of cold air for
Friday into Saturday as northerly flow could be continually
reinforced across the Great Lakes region for the last half of the
week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 640 PM EST Sun Feb 28 2021
Cigs improving to MVFR this evening. Drizzle/rain ending, -SHSN
later tonight into Monday.
Low pressure just ne of ANJ. Cold front moving across ne lower MI.
Cigs will improve behind the front, with current IFR cigs/vsbys in
spots improving to MVFR this evening. But eventually, the incoming
air will be cold enough to spawn lake effect snow. Brief vsby
restrictions will be possible late tonight into Monday at MBL/PLN
and especially TVC. Otherwise a mix of MVFR to VFR cigs.
Gusty w winds will veer nw tonight, remaining gusty thru the TAF
period.
&&
.MARINE...
Issued at 328 PM EST Sun Feb 28 2021
...Back into a gusty period of time on the lakes...
Winds will veer around to the northwest this evening and increase.
Might be a short period of gale force gusts on Lake Michigan this
evening. But a longer period of gale gusts will be found on
northern Lake Huron tonight through Monday. Gale warnings will
remain intact as is.
Winds will diminish Monday night. But another round of gusty winds
is possible Tuesday with gale force gusts possible on Lake
Michigan.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY from 3 AM to 4 PM EST Monday for MIZ086-
087.
LH...SMALL CRAFT ADVISORY until 9 PM EST Monday for LHZ345-349.
GALE WARNING until 9 PM EST Monday for LHZ347-348.
SMALL CRAFT ADVISORY until 3 AM EST Tuesday for LHZ346.
LM...SMALL CRAFT ADVISORY until 9 PM EST Monday for LMZ323-341-342-
344>346.
LS...NONE.
&&
$$
UPDATE...JZ
NEAR TERM...ADAM
SHORT TERM...FEF
LONG TERM...FEF
AVIATION...JZ
MARINE...ADAM
Area Forecast Discussion
National Weather Service Bismarck ND
916 PM CST Sun Feb 28 2021
.UPDATE...
Issued at 916 PM CST Sun Feb 28 2021
Snow continues this evening north and east of a surface low
centered in far south central North Dakota. The clipper has been
pushing south a bit quicker than expected, with snow expanding
through the southern James River Valley earlier than forecast, but
is also lingering on the back end longer than expected, with snow
still ongoing at Minot as of 3 UTC. Made some adjustments to POPs
to account for the current radar trends. Snow has become more
organized since the last update, maybe not quite to a legitimate
banding scenario, but enough to show a moderate area of stronger
radar reflectivities where visibilities have been reduced to
three- quarters of a mile.
UPDATE Issued at 609 PM CST Sun Feb 28 2021
The surface low bringing light snow to the area is currently
centered in far west central North Dakota. Snow is ongoing from
Crosby, through most of the north central, and into the
Harvey/Carrington area, with visibilities dropping as low as one
mile at Minot. Some isolated higher radar returns are seen in the
south central, but ceilings are still around 5-7K feet, and we
haven`t seen any evidence of snow making it to the ground in these
areas just yet. Regardless, did go ahead and expand POPs through
much of the south central to account for this. Not much change in
our thinking regarding snow totals and location, but will keep an
eye on things in case we start seeing significantly reduced
visibilities and higher snowfall rates, especially since it looks
like we`re still an hour or two from the strongest forcing seen in
high-res guidance.
&&
.SHORT TERM...(This evening through Monday)
Issued at 159 PM CST Sun Feb 28 2021
Main forecast issue in the short term period will be snow amounts
and placement with the clipper system tonight.
Currently, low pressure is developing near Glasgow in northeast
Montana. Clouds continue to thicken over western and central ND.
Highs should top out in the upper 30s and lower 40s today west of
the Lake and Missouri River, with only teens along the Canadian
border.
For tonight, the surface low that is situated over northeast
Montana will track southeast through west central and south
central ND and is expected to be around Aberdeen by around
Midnight. This will bring a swath of light snow northwest into
central and eastern North Dakota.
The trend today has been for this band to shift farther west. The
band of heaviest snow, squarely over eastern ND on the midnight
shift, is now situated from around Bantry and Towner, to Harvey
and Carrington, and southeast to Valley City. The latest few runs
of the RAP/HRRR shift it even a little farther west. We are still
talking amounts below advisory criteria, but we`re aiming at a
moving target. There are a few additional factors complicating
things as well. First, there are some indications of some possible
banding precipitation along the northern edge of the snow band.
The latest RAP shows a band of negative EPV, strong 2D forcing and
steep lapse rates from Harvey and Carrington to just North of
Jamestown in the 01-04Z timeframe. This is also congruent with
strong deformation zone and at tight baroclinic zone within this
same area. Second, the latest forecast RAP sounding are quite
impressive with the depth of the Dendritic growth zone. Especially
from Jamestown and Carrington, where the DGZ extends from the
surface to around 700 MB. The DGZ is a bit deeper at Carrington,
but the Omega is stronger at Jamestown. Both depict the omega
throughout the depth of the DGZ. This resulted in us bumping up
the snow ratio`s and finally, the QPF has been increasing with
each run. This has resulted in a band of 1 to 2 inches of snow
from roughly the Towner area in McHenry county south and east
through Harvey and Carrington to northeast Stutsman, with
Jamestown right around 1 inch and higher amounts east and north
toward Valley City and Cooperstown in eastern ND. if we do get the
banding, maybe we see some locally higher amounts to around 3
inches. But the limiting factor is the overall quick movement of
the system, as any one area would likely see only 3-5 hours of
snowfall, with the heaviest snowfall probably only lasting a
couple of hours. The entire area of snow exits the southern James
River Valley shortly after midnight. Evening shift will have to
monitor any trends in placement and possible banding setting up.
It will be cold behind the exiting clipper with lows around 10
below zero near the Turtle mountains, and single digits above or
below zero for areas north and east of the big Lake and the
Missouri River. The far southwest will be mild spot with lows only
dropping into the teens. Monday warms nicely behind the exiting
clipper with highs climbing into the 40s and maybe lower 50s west
central and southwest. the Turtle Mountains into the James River
Valley will be the cool spot with highs around 30.
.LONG TERM...(Monday night through Sunday)
Issued at 159 PM CST Sun Feb 28 2021
Mild Pacific air builds into the Northern Plains Tuesday through
Wednesday with with widespread highs in the 40s northeast to 50s
south and west.
Upper level ridge amplifies across the Rockies and eventually
moves into the Great Plains Fri-Sat. Opted to again go above NBM
for daytime highs, going with 60/40 blend of NBM 75th percentile
and straight NBM. This results in forecast highs into the 60s
Fri-Sun for the west and south central, with 50s reaching the
Turtle Mountains area over the weekend. These forecast highs are
25-30 degrees above normal for early March, and we could see a
few Max temperature records reached. Also, with these warm
temperatures, minimum relative humidity will drop into the upper
teens and 20s late in the Work week and through the weekend,
elevating fire weather concerns. At this time, the best potential
for the combination of strong winds and low RH will be on
Saturday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 609 PM CST Sun Feb 28 2021
A clipper moving through is bringing snow to the area this evening
and tonight, with KMOT/KJMS likely the only two terminals
affected through 06Z. MVFR ceilings and visibilities are possible
in any areas of snow. KBIS/KDIK/KXWA are expected to stay VFR
through the TAF period. Winds will be variable southwest to
southeast ahead of the clipper, then shift northerly behind the
system.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...MJ
SHORT TERM...TWH
LONG TERM...TWH
AVIATION...MJ
Area Forecast Discussion
National Weather Service Boston/Norton MA
1026 PM EST Sun Feb 28 2021
.SYNOPSIS...
A frontal system moving northeast from the mid-Atlantic region will
spread steady light rains across Southern New England tonight into
Monday, clearing by Monday afternoon. A strong Arctic cold front
will usher in scattered snow showers and possible snow squalls
Monday night. It will also produce unseasonably cold temperatures,
low wind chills and gusty winds Monday night into Tuesday.
Temperatures return to above average levels for midweek, before
turning cooler and unsettled late in the week into the weekend.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
10 PM Update...
No major changes in the latest update other than adjusting
precipitation chances toward high res guidance. This generally
keeps chances before midnight north of the MA Pike. Better
opportunities of precip south of the MA Pike before 06Z. Best
chances of precip are after 06Z, but precip moving in beforehand
will generally act to moisten up the lower levels as we are
still working on eroding the dry air. Still have the possibility
of light spotty freezing rain where the previous SPS was issued
and think that this is not out of the question with dewpoints
in the lower 30s. After 06Z should see the temps and dewpoints
climbing above 32 in the higher terrain.
635 PM Update:
Regional radar shows initial slug of isentropically-forced light
rains mainly across our southern coastal waters and into
adjacent southern CT/Long Island. Drier air seen on morning
RAOBs appears to be holding the northward advance of this rain
at bay, and while some radar returns are showing up across
Hartford County and western MA, looks to be diminishing on
approach. Though the HRRR and the 18z NAM-3km still show the
best chance of rains across central/southern RI into adjacent
southeast MA/Cape thru 02z, I`ve started to decrease PoPs toward
lower Chance in that same timeframe for the remainder of
Southern New England. Any precipitation that falls will be on
the light side, especially further north one goes. It still is
possible that some very light frozen precip/freezing rain could
result across the higher terrain, though it`s looking more
questionable than earlier as dewpoints are rising into the low
30s and lighter precip rates that should temper stronger wet-
bulb cooling.
The second round of rains then arrives starting after midnight
on northeast into the overnight hours, associated with a weak
wave low on a frontal zone. Second round of rains should be more
steadier than this initial round. It still looks like eastern
and southeastern New England stands the best chance of rains
from this second slug of precip closer to the track of the weak
surface low. Less rains further inland (western/central MA,
northern/western CT). This looks on track and didn`t make any
significant change for the second half of the night.
Previous discussion:
Initial surge of light rain approaching southern CT/RI assocd
with isentropic lift. Soundings show pronounced dry layer below
850 mb which will slow onset of rainfall but the low levels
eventually moisten up this evening from SW to NE. Rain will be
overspreading CT/RI and SE MA this evening then pushing
northward across rest of SNE. This initial shot of rainfall will
be light as best isentropic lift is forecast to pass south of
New Eng.
There is some concern with shallow cold air across the
Berkshires and northern Worcester hills for a time tonight.
Dewpoints here in the mid/upper 20s so wet bulb cooling may
allow temps to fall to near 32 degrees. This could result in
pockets of freezing rain later this evening but coverage is
expected to be limited. No advisories planned but will issue an
SPS to increase awareness.
Another period of rain expected overnight as next shortwave and
attendant surface wave approaches New Eng. Focus for this
rainfall will be across the coastal plain and SE New Eng coast
with moderate rain at times with lighter rain further in the
interior.
Low temps will be in the 30s, but rising into the 40s SE New Eng
toward daybreak. Areas of fog will also develop overnight.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday...
Lingering rain in the morning assocd with the shortwave passage
and low track across SE New Eng. Then we expect rapid
improvement in the afternoon as cold front sweeps through
followed by rapid drying in the column with PWATs decreasing
from around 1" to less than 0.2" by 00z. Expect partial sunshine
developing from west to east in the afternoon, although strong
shortwave approaching from the west may lead to a few snow
showers in far western MA late in the day.
Strong cold advection will result in gusty W/NW winds
developing with gusts 25-35 mph. Mild temps in the pre-frontal
airmass with highs 40s and even some lower 50s in the coastal
plain before temps fall sharply mid/late afternoon in the cold
advection.
Monday night...
A piece of the polar vortex will drop south across northern New
Eng with shortwave energy rotating through SNE. Secondary
arctic front will move south across the region 03-06z and may be
accompanied by a few snow showers and locally heavy squalls.
There is a good signal with the snow squall parameter and steep
low level lapse rates with a shortwave passage and arctic fropa.
However, 0-2km moisture is somewhat limited and the snow growth
region never truly saturates. This may limit areal coverage
with more widely sct activity. Potential for brief heavier snow
showers but timing will be after the evening commute.
Strong winds will be an issue for Mon night in strong cold
advection and deep boundary layer promoting excellent mixing.
Soundings show potential for wind gusts to 50+ mph after the
arctic front passage. As a result a wind advisory was issued
for all SNE.
Arctic chill will be ushered in on these strong NW winds as 850
mb temps drop to -20 to -24C by 12z Tue which is down to the
lowest 1st percentile of 850 mb temps for this time of year
compared to climatology. Expect lows dropping into single
numbers over the higher terrain and low to mid teens elsewhere,
except upper teens outer Cape/Islands. Combined with the gusty
winds, wind chills will drop to zero to -10F by Tue morning and
as cold as -15F in the Berkshires and northern Worcester hills
where wind chill advisories may eventually be needed.
&&
.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights...
* Unseasonably cold and gusty Tuesday. Daytime single-digit to teens
wind chills.
* Temperatures rebound back into the 40s on Wed.
* Mainly dry, but turning unsettled and cooler than normal late in
the week into the weekend.
Details:
Tuesday:
Sunny, but unseasonably cold temperatures and gusty conditions will
be the main story as strong Arctic shortwave/lobe of the polar
vortex translates into the Canadian Maritimes by Tues night.
Model soundings continue to show at least very good mixing given the
shot of cold air aloft (850 mb temps around -20 to -24C/-15 to -19C
at 925 mb). While these temperatures do warm a bit as the day wears
on and the 925/850 mb thermal trough shifts eastward/offshore, we
still expect mixing to at least to 900 mb (not as deep as Monday
night). BUFKIT momentum transfer still supports gusts at Advisory
levels (45 to 50 mph) for at least the Tues morning hrs. By
afternoon, the inversion height continues to lower, sustained winds
decrease with a weakening p-gradient and mixed layer wind speeds
also diminish. This should allow for decreasing winds/speeds as we
move into the afternoon, a trend which will continue into the
evening.
Though we are looking at full sun, only looking at high temperatures
in the 20s, with temps around freezing across southeast MA, eastern
RI and Cape Cod/Islands. Will see single-digit wind chills thru noon
(still a chance for sub-zero wind chills in the Berkshires) given
the 25-35 mph sustained winds, these values "warming" to the teens
by afternoon with the slackening winds. Regardless, Tues will be
quite cold and more reminiscent of mid-winter than the 2nd day of
climatological spring.
Tuesday Night:
Winds continue to slacken as a ridge of high pressure builds into
SNE. This ridge axis shifts eastward for the second half of the
overnight enough for a SW return flow to commence. Kept lows in the
upper teens to mid 20s, but could see values in the low teens in the
sheltered areas in NW MA if winds can stay light enough.
Wednesday into Wednesday Night:
Temperature roller-coaster continues into Wed with milder SW flow
between the offshore ridge and a weak Clipper low that passes to our
north. Still looking for dry conditions with 925/850 mb temps on Wed
around -1 to -4C, supporting highs back into the 40s, with upper 40s
towards SE MA and the metro areas. Lows mainly in the mid-20s to
near freezing.
Thursday into the Weekend:
Deterministic and ensemble solutions point to a pattern change
toward cooler than normal temperatures and generally unsettled
weather for this period. The Arctic shortwave on Tuesday retrogrades
into northern Quebec, establishing a broad longwave trough across
the Northeastern CONUS. This longwave is reinforced by periodic
shortwave disturbances aloft into the weekend, these individual
shortwave features digging southward into the mid-Atlantic.
We are not looking for temperatures to be as cold as Tuesday, but
below average temperatures are expected each day in this period. 850
mb temps range around -13 to -17C and -9 to -13C @ 925mb support
highs mainly in the upper 20s to upper 30s. Lows in the upper teens
to mid 20s.
Though cyclonic flow will maintain generally unsettled conditions,
really isn`t much in the way of significant precipitation to speak
of. That which does transpire may only be spotty/showery with the
cold pool aloft and variable amounts of cloudiness. All in all, it`s
a generally dry period. Models do continue to simulate a coastal low
late in the weekend coming out of the Carolinas; not ready to write
off this progged low as yet but the majority of ensemble low tracks
are far enough SE of the 40N/70W benchmark that presently favor more
of a miss at this point. Will offer a dry forecast following NBM,
but will also continue to monitor subsequent guidance/trends for the
late-weekend coastal system.
&&
.AVIATION /03Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00Z TAF Update:
Tonight: High confidence in trends, moderate on timing.
Ceilings/visbys should remain at VFR levels at least through
04z. Initial precip looks quite light and shouldn`t result in
restrictions either from cigs or visbys. Deterioration to IFR-
LIFR then looks on track for after midnight and overnight with
the next round of rains. Though the exact start time is still
less clear, deteriorating flight categories should be the case
starting 05-07z. SE gusts to 20 kt possible over Cape/Islands
overnight.
Monday...High confidence in trends.
IFR/LIFR improving to VFR in the afternoon as winds shift to
W/NW behind cold front. Gusts to 25-30 kt developing in the
afternoon.
Monday night...High confidence.
VFR, but brief and localized MVFR/IFR possible in any heavier
snow showers/squalls passing through. NW gusts to 35-45 kt.
KBOS TAF...High confidence in trends. Expect a period of
IFR/LIFR late tonight and Mon morning, improving to VFR in the
afternoon.
KBDL TAF...High confidence in trends. Expect a period of
IFR/LIFR late tonight and Mon morning, improving to VFR in the
afternoon.
Outlook /Tuesday through Friday/...
Tuesday: VFR. Strong winds with gusts up to 45 kt.
Tuesday Night: VFR. Windy with local gusts up to 30 kt.
Wednesday: VFR. Breezy.
Wednesday Night: VFR.
Thursday: VFR. Breezy.
&&
.MARINE...
A period of SE gusts to 25+ kt expected on the eastern waters
late tonight and early Mon, but the main concern is the strong
NW winds late Mon and especially Mon night.
We have upgraded to a gale warning for all waters for late Mon
into Tuesday behind the cold front. Strong NW gales expected
with even an outside chance of marginal storm force gusts.
Currently we have gusts to 45 kt with a few G50 kt possible. In
addition, expect widespread moderate freezing spray Mon night
into Tue morning and so a freezing spray advisory was issued.
Outlook /Tuesday through Friday/...
Tuesday: Moderate risk for gale force winds with gusts up to 45
kt. Rough seas up to 14 ft. Freezing spray.
Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Areas of rough seas.
Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft.
Wednesday Night: Winds less than 25 kt. Seas locally
approaching 5 ft.
Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft.
&&
.TIDES/COASTAL FLOODING...
Tides are astronomically high Monday, with Boston at 11.0 FT
MLLW (12:36 PM), Nantucket 3.6 FT MLLW (12:02 PM), and
Providence at 5.0 FT MLLW (9:23 AM). Current expectation is for
a surge of less than one foot along the south coast, and perhaps
around 1 foot along eastern MA coast, which would keep the
total water level below the minor flood category for both
coasts.
In addition, winds are expected to shift to the W/NW in the
morning as a cold front moves offshore, lessening the potential
along E MA coast. If front ends up slowing down, it is possible
we could see minor splashover (sub-Coastal Flood Advisory level)
along both coasts, but that seems to be a worst case scenario
right now.
Does not appear to be a prolonged period of strong enough S/SE
winds to build up seas offshore more than 4-5 FT, so beach
erosion is not expected to be an issue right now either.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Wind Advisory from 4 PM Monday to 10 AM EST Tuesday for
CTZ002>004.
MA...Wind Advisory from 4 PM Monday to 10 AM EST Tuesday for
MAZ002>006-008>021-026.
Wind Advisory from 4 PM Monday to 1 PM EST Tuesday for MAZ007-
022>024.
RI...Wind Advisory from 4 PM Monday to 10 AM EST Tuesday for
RIZ001>008.
MARINE...Freezing Spray Advisory from midnight Monday night to 1 PM EST
Tuesday for ANZ231>237-250-251-254>256.
Gale Warning from 4 PM Monday to 7 PM EST Tuesday for
ANZ230>232-251-255-256.
Gale Warning from 4 PM Monday to 4 PM EST Tuesday for
ANZ233>237.
Gale Warning from 4 PM Monday to 10 PM EST Tuesday for ANZ250-
254.
&&
$$
SYNOPSIS...KJC/BL/Loconto
NEAR TERM...KJC/BL/Loconto
SHORT TERM...KJC
LONG TERM...Loconto
AVIATION...KJC/Loconto
MARINE...KJC/Loconto
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
745 PM CST Sun Feb 28 2021
.UPDATE...
Very minor updates to the ongoing forecast package. Did retrend
hourly temperatures/winds to reflect the current position of the
front and make some slight chances to the PoP forecast given the
quiet radar at this hour, the expected showers along the front later
this evening, and the anticipated thunderstorms forming across the
Rio Grande and moving eastward later tonight.
Looking at the brand new 00z Sounding out of KDRT there is a 2-3
Degree C inversion just above 950 mb with southwesterly wind bringing
in some weak air advection at that lay. It is important to note that
the front was north of KDRT at the time of the sounding. Decent shear
of over 70 knots and Surface CAPE values near 100 J/kg were reported.
A 700mb-500mb low crawling across Southern Arizona and New Mexico
(evident on GOES-EAST/WEST Water Vapor) will come into play later
this evening.
The cold front is currently extending from a Rocksprings to Kerrville
to Lago Vista to Taylor line as it continues to move to the south and
east. Earlier in the evening a few elevated showers developed across
Llano county, but these quickly died out behind the front. Additional
light showers have formed to the northeast of the area near Cameron
and Caldwell, and a thin line of isolated showers is show in many of
the mesoscale and high resolution models forming along the front
later this evening. Some aircraft soundings out of AUS and SAT still
show a weak capping inversion which may work against these showers.
The main show will be with the approach of the low pressure to the
west. Ahead of it, as it moves into southeastern New Mexico and the
Texas Panhandle later tonight the low and mid-level winds will
strengthen ahead of it. This will move more air in the mid and upper
atmosphere out of the way, causing air at the low levels to fill that
void there-by creating lift. With the front already through the area
and based on the notes about the 00z DRT sounding, any convection
that does form will be elevated. With enough instability, shear, and
moisture in the area a few elevated supercells remain possible. The
HRRR remains consistent in showing a few developing between 10pm and
midnight across Val Verde County. The 12z ARW and NMM high resolution
models also supported this solution while the NSSL WRF was the least
bullish, and the NAM Nest somewhere in the middle with isolated
storms across the Hill Country. Even if the CAP wins out and the
severe risk is conditional, the lift from the upper low should
produce scattered showers and thunderstorms across the Rio Grande
Plains into the Hill Country through the early morning hours,
spreading eastward towards the I-35 corridor. SPC maintained their
marginal risk of severe weather in their 01z update to the Convective
outlook, noting that if strong to severe storms do form that hail
remains the primary threat. We will monitor the trends of the 00z
High Resolution models and provide further updates this evening in
NWSChat and on Social Media. Rain chances continue with cool
temperatures on Monday. What a change in just a few weeks...from
snow/sleet/thunder sleet to the chance of strong to severe storms!
&&
.PREV DISCUSSION... /ISSUED 523 PM CST Sun Feb 28 2021/
AVIATION...
The cold front that will be the main driver of the TAF through the
period is already pushing into the Hill Country producing a few
showers between KAQO (Llano) and KBMQ (Burnet). Ahead of the front,
the prefrontal trough have already turned winds out of the north
along the I-35 corridor. Winds will pick up out of the north and be
gusty once the front arrives at all terminals between 03z and 05z.
Showers will be possible with ceilings dropping to MVFR as the front
arrives and moves through with thunderstorm chances, at least in the
vicinity, increasing between 09z at AUS and DRT and 11z at SAT/SSF.
Chances for thunderstorms will linger into the mid-morning Monday
with gusty north winds continuing. Rain showers, MVFR cigs, and gusty
north winds will continue through much of tomorrow, before finally
beginning to clear late in the day. Timing of the clearing will be
the focus of future TAFs, while this set focuses on the precipitation
chances.
PREV DISCUSSION... /ISSUED 236 PM CST Sun Feb 28 2021/
SHORT TERM (Tonight through Monday Night)...
Afternoon surface observations show a warm and moist air mass in
place with current temperatures in the upper 60s to lower 80s.
Dewpoint temperatures are impressive for this time of year and range
from the upper 50s in the Hill Country to the upper 60s in the
coastal plains. For the remainder of this afternoon, we could see a
few light showers develop across portions of the Hill Country and
along and east of the I-35/I-37 corridors. In addition, a cold front
will move in from the north and could help generate isolated
thunderstorms across portions of Burnet and Llano counties.
As the above mentioned front continues to move southward this
evening, a line of showers and thunderstorms is expected to develop
along and especially behind the cold front. These storms will be
elevated in nature, that is they will not be rooted in the flow near
the surface. Favorable MUCAPE and shear should result if some strong
to possibly severe thunderstorm development during the mid-evening
into the overnight hours across a good portion of south central
Texas. The current SPC Day 1 outlook has most of our counties in a
Marginal risk (Level 1 out of 5) for severe weather. Given most
storms should occur behind the boundary, the main concern with these
thunderstorms will be the potential for hail up to around 1" in
diameter. Mesoscale models generally agree the best chance for storm
development will be from the Hill Country into the I-35 corridor. We
have noted the fairly consistent trend from the HRRR model in
showing some activity developing over the Serranias del Burro
mountains of Mexico. Should this occur, this activity would likely
remain intact as it moves into the Rio Grande plains and southern
Edwards Plateau. With this in mind, we did raise precipitation
chances slightly across the above mentioned areas this evening.
For tomorrow morning, we should see decent coverage of post-frontal
showers and thunderstorms across a good portion of south central
Texas. Temperatures will also be much cooler and we have opted to
trend toward the cooler guidance numbers with the expected
precipitation, cloud cover and cold air advection behind the front.
Highs are expected to range from the mid 40s in the Hill Country to
the upper 50s in the Rio Grande and coastal plains. It will be
blustery behind the front on Monday with northerly winds of 15
gusting to near 25 mph across a good portion of the region. Wind
speeds will not be in any rush to decrease Monday evening, but
should begin a slow, downward trend through the overnight hours.
Rain chances will also be on the decrease from west to east Monday
night.
LONG TERM (Tuesday through Sunday)...
The long term periods are looking less eventful as the deterministic
models have been trending with a slower and weaker storm system to
pass through the Southern Plains late in the week. The result of this
trend leaves a lower amount of cloud cover for Tuesday into Wednesday
and a more gradual mid-week return of southerly flow. This means
wider diurnal ranges and less available moisture in advance of the
late week storm system. MOS guidance trends have arrived much drier
over the past 24 hours in regards to the rain chances for Friday and
have all but removed any thoughts of potential rain for late
Thursday. The weaker trends of the late week disturbance also signals
a weaker cold air advection pattern and milder temperature trends
for next weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 80 48 50 42 62 / 30 70 70 30 10
Austin Bergstrom Intl Airport 81 48 51 42 63 / 30 70 70 30 10
New Braunfels Muni Airport 81 51 52 44 65 / 20 70 60 30 10
Burnet Muni Airport 78 44 48 40 60 / 30 60 70 20 10
Del Rio Intl Airport 83 52 59 41 66 / 0 40 20 - -
Georgetown Muni Airport 79 46 49 42 60 / 40 70 80 30 10
Hondo Muni Airport 81 49 55 41 67 / - 60 50 20 10
San Marcos Muni Airport 80 49 51 42 63 / 20 70 60 30 10
La Grange - Fayette Regional 82 51 53 45 61 / 20 70 70 40 20
San Antonio Intl Airport 80 51 53 43 64 / 20 60 60 20 10
Stinson Muni Airport 80 51 54 43 64 / 10 60 50 20 10
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term/Aviation...Treadway
Long-Term...YB
Area Forecast Discussion
National Weather Service Grand Forks ND
932 PM CST Sun Feb 28 2021
.UPDATE...
Issued at 930 PM CST Sun Feb 28 2021
CLipper system moving through is bringing snowfall rates up to an
inch an hour per radar estimate in portions of Barnes County this
past hour. Given the shallow frontogensis and the speed of the
clipper tracking to the southeast snowfall amounts will generally
be an inch or less with a few locations in the southern valley
expected to see a possible 2 to maybe 3 if higher intensity
snowfall persists. RAP runs consistently paint the highest totals
from the Valley City area southeast overnight. This would place
Fargo just to the north of the risk area for the 2 to 3 inch
band.
UPDATE Issued at 654 PM CST Sun Feb 28 2021
Small clipper system beginning to show its hand with a more
intense band snowfall setting up near Minot within a broader area
of light snow. CAMs continue to paint the higher intensity snow to
move to the southeast to from Minot through the Carrington and
New Rockford areas towards Valley City. Some guidance then has the
band move into the Fargo area and some to the southwest of Fargo.
Will monitor the eastward extent this evening on radar trends and
surface obs. Within the stronger echoes of the band visibility
will be reduced under a mile at times and a quick 1 to 3 inches of
snow will be possible depending on the residence time of any
location under the band.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 254 PM CST Sun Feb 28 2021
Snow amounts and placement with the clipper system tonight will be
the primary challenge for the period.
Main upper low has been digging down into southern Canada, with
some decent snow currently going over southeastern Saskatchewan.
The shortwave/clipper system will dig further into the region
tonight, with a strong cold front coming with it. Several of the
models indicate some pretty strong frontogenesis co-located with
synoptic lift from the upper shortwave trough. The SPC meso page
seems to verify the mid-level frontogenetical forcing, so banding
potential looks pretty good. The main fly in the ointment will be
the very fast movement of the system, as higher snowfall rates
will not stay very long at one spot. Both CAMs and the larger
scale models have been trending further south with the track of
the snow, coming down over Fargo when previous forecasts have more
along the Highway 2 corridor. At this point, think amounts that
the previous shift messaged seem reasonable, generally in the
trace to 1 inch range with localized 2 to 3. Some gusty winds as
cold air advection kicks in behind the system, but think that they
will not be high enough for substantial blowing snow impacts.
Snow will be exiting the area by morning.
The quick shot of cold air behind the clipper along with clearing
skies will drop temps below zero overnight, but think readings
should recover during the day on Monday. The surface high
building down behind the front overnight will be short-lived,
with winds quickly shifting back to the south by Monday afternoon.
Could see some drifting in the Devils Lake Basin, but at our
current wind speeds would need falling snow for any restrictions
to visibility, which will not be happening. The winds will shift
more southwesterly by Monday night as upper flow becomes more
zonal. There will be some very strong warm air advection, and this
should help keep temps in the teens to 20s above zero.
.LONG TERM...(Tuesday through Sunday)
Issued at 254 PM CST Sun Feb 28 2021
The Tuesday through Saturday period is expected to see quiet
weather with seasonably warm temperatures. Ensemble guidance is in
good agreement on a solution of zonal flow aloft on Tuesday
shifting to northwesterly flow as an upper level ridge builds in
to our west. The main forecast questions will ultimately revolve
around the strength and location of the upper level ridging.
Tuesday will see zonal flow aloft, 850 hPa temperatures above zero,
and a breezy west-southwesterly wind at the surface that will help
temperatures begin their rapid ascent to above normal. Resultant
high temperatures should range from the 40s across the northern
forecast area, to the 50s south of I-94. A shift toward more
northwesterly flow aloft is expected to occur by Wednesday as an
upper level ridge begins to build in to our west. The upper level
ridging will be a mainstay through the rest of the extended period,
but the location of this feature will have an impact on the
magnitude of the impending warming trend. The CMC and ECMWF
ensembles are less progressive, and place the ridge axis over MT/WY
for much of the week before pushing it eastward by the weekend. The
GEFS ensemble solution is more progressive in pushing the ridge
aloft further eastward sooner. A more progressive solution would see
our temperatures warm up more toward the 90th percentile (upper 40s
to mid 50s) high temperatures, while a less progressive ridge would
keep our highs closer to the 50th to 75th (40s to low 50s)
percentile range. Regardless of the exact evolution, the ridge
should shift east into our forecast area by the weekend at the
latest. The presence of the upper level ridging over the forecast
area should push our temperatures to well above normal values in the
50s to low 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 544 PM CST Sun Feb 28 2021
Clipper system to bring a quick round of snow to eastern ND
impacting the DVL, GFK and FAR TAFs this evening into the
overnight. Will see CIGs and VSBY lower quickly as snow saturates
and MVFR conditions develop. Within the strongest snow bands IFR
conditions are possible for brief periods. In the wake of the snow
the winds will turn to the north and some gusts will develop for a
few hours overnight. Skies become VFR by morning with sfc high
pressure and light winds expected for much of Monday.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...JK
SHORT TERM...JR
LONG TERM...Rick
AVIATION...JK
Area Forecast Discussion
National Weather Service Jacksonville FL
904 PM EST Sun Feb 28 2021
.UPDATE...
Winds are dropping with sunset. Mesoscale models continue to
indicate shower activity developing over north-central Florida
and moving north through dawn. At this time, just not seeing any
indications that that is going to happen nor is there an obvious
lifting mech to get them going. So right now not going to amend
the Zones to account for this possibility but will keep VCSH in
the TAFs.
&&
.PREV DISCUSSION [618 PM EST]...
.NEAR TERM [Through Tonight]...
...DENSE FOG POTENTIAL FOR INTERIOR SE GA & SUWANNEE VALLEY
TONIGHT...
Low stratus decks from this morning have broken up leaving a layer
of flat cumulus amid south to southwesterly flow induced by the
persistent surface high pressure to the east over the Atlantic.
Despite extensive cumulus and cirrus drifting overhead on WSW flow
aloft, filtered sunshine and deep-layer ridging will lead to another
afternoon of near-record highs. Strong temperature contrast with
record-level heat and cool coastal Atlantic waters will be able push
inland this afternoon, combating the background southwesterly flow.
Another sea breeze will sweep eastward from the Gulf, colliding with
the Atlantic sea breeze along the I-95 corridor. Converging fronts
may provide enough lift to overcome the weak capping inversion
resulting in a few light showers late this afternoon and early
evening, mainly along and east of the I-95 corridor from St
Augustine southward.
Low level flow will veer further southwesterly tonight ahead of a
cold front approaching from the northwest and high pressure ridge
axis to the south. Weak isentropic ascent in southwesterly flow will
generate another batch of showers after midnight for areas south of
I-10 with chances around 20-30%. In addition to shower chances,
there will be potential for low stratus and fog across SE GA and the
Suwannee Valley as sea fog advects inland from the northwestern Gulf
of Mexico. Patchy fog may develop across the rest of NE FL but
shower activity may disrupt development. Warm, moist airmass and
intrusion of low stratus will limit cooling again tonight with lows
only reaching the mid 60s.
.SHORT TERM [Monday Through Tuesday Night]...
...HEAVY RAINFALL POSSIBLE TUESDAY NIGHT ACROSS PORTIONS OF SE
GA...
A cold front will continue to move southeastward, reaching the
Altamaha River basin during the mid afternoon Monday before it
slowly continues southward and eventually stalls across north-central
FL early Tuesday morning. Ahead of the front, southwesterly flow
will increase, breaking up morning low stratus by noon Monday.
Showers chances will increase from northwest to southeast along
the front Monday. HiRes guidance indicates a potential for
embedded storms across SE GA as the front pushes southward, but
due to the loss of heating and appreciable instability, t-storm
potential will be very low once the front enters NE FL Monday
evening. Overrunning southwesterly flow and associated isentropic
lift will continue rain chances through Monday night, primarily
across SE GA.
A surface low will develop across the northwestern Gulf Tuesday
morning as an upper low pivots over the lower Mississippi River
valley. The surface low will drift into the northeast Gulf coast
by Tuesday evening with an associated stationary front draped
across SE GA. Elevated showers are expected in the vicinity of the
front through Tuesday afternoon, with rain chances favoring
locations north of I-10. As the surface low tracks inland Tuesday
evening, it will shift across SE GA as it develops northeastward
toward the Carolina coast. Strong forcing for ascent amid PWATs of
1-1.5" will bring a chance for heavy rainfall across northern
zones of SE GA through Tuesday night, where rainfall totals of
1-2" are possible with localized higher amounts (WPC has outlined
this area with a marginal risk for excessive rain). The cold front
will trail behind the low as it shifts from the Gulf to the
Atlantic through the predawn hours on Wednesday, bringing a
chance of showers and slight chances of elevated t-storms across
Suwannee Valley and SE GA.
Another unseasonably warm day is expected on Monday ahead of the
first cold front. Cloudy conditions in tandem with a cooler
airmass settling into the area on Tuesday will bring a much cooler
afternoon with highs ranging in the mid/upper 50s across SE GA
and mid/upper 60s across NE FL. There could be some variability in
the temperatures with the stationary boundary stretched somewhere
across north-central FL. Southerly flow will quickly shunt that
boundary back to the north as warm front Tuesday evening,
restricting low to the upper 50s and low 60s across NE FL whereas
the cold side of the boundary will let temps drop to the upper 40s
and low 50s across SE GA.
.LONG TERM [Wednesday Through Sunday]...
Aforementioned trailing cold front will exit into the Atlantic by
Wednesday afternoon. As it does so, skies will clear from northwest
to southeast as cooler and slightly drier filters into the area on
the periphery of an expanding surface high pressure northwest of the
area. Surface high pressure will develop southward toward the
Tennessee Valley on Friday with broad longwave troughing aloft. This
will promote increasing onshore flow and potential coastal trough
development. Still significant uncertainity this weekend, with a
stark contrast in the medium range guidance compared to 24 hours
ago. Sparing the details, another cold front is still progged to
cross the region this weekend as an upper shortwave pivots into the
northern Gulf and into the Florida Peninsula. This system will bring
the next chance of rain to the area after a quiet, sligtly cooler
than average end to the week.
.AVIATION...
[Through 00Z Tuesday]
The sea breeze is pinned over KJAX at this time will make little
further headway inland. HRRR is insistent upon developing some
showers along the sea breeze convergence zone and moving then
north toward the KSGJ/KJAX metro area. If showers move over any
of the fields it is most likely to be KSGJ and have added a brief
tempo overnight there. Otherwise included VCSH for the JAX Metro
fields.
Might see some fog in the Gainesville area and given that field`s
propensity for briefly dropping down below guidance toward
sunrise did go to 1sm in a tempo. Visibility restrictions should
be very brief if it does happen.
As the frontal system approaches tomorrow evening have a brief
tempo for showers after 1800 utc but timing looks closer to 21-24
utc for most fields. Ceilings should be in the 2.5-5.0 kft range
tomorrow afternoon.
.MARINE...
Southerly breezes will become more southwesterly overnight
and through Monday afternoon ahead of a cold front, which will reach
the southern Georgia waters by late Monday afternoon and continue
southward across north Florida coastal waters Monday evening.
Scattered showers are likely along the leading edge of the front
with winds quickly shifting northerly then northeasterly behind it.
Winds and combined seas will elevate in the northeasterly flow on
Tuesday with winds between 15-20 kts across near shore waters and 20-
25 knots offshore. A Small Craft Advisory headline may need to be
considered for this period. Another cold front will pass over the
waters Wednesday with winds shifting to the south ahead of it and
northerly behind it.
Rip Currents: Moderate Risk at area beaches through Monday, with an
increase to High Risk Tuesday with increasing onshore flow.
.FIRE WEATHER...
Southerly surface and transport winds will increase as the become
more southwesterly through Monday ahead of an approaching cold
front. This will allow peak daytime dispersion between 40-60 units
on Monday. Showers and embedded storms are possible across SE GA
along the cold front through Monday afternoon; showers will continue
into NE FL Monday evening with limited potential for storms.
Overrunning will favor rain chances continuing Monday evening and
into Tuesday across SE GA. Despite limited mixing on Tuesday with
overcast conditions, easterly transport flow will lead to marginal
dispersion on Tuesday, except across north-central FL where
weaker transport wind will lead to low dispersions.
.HYDROLOGY...
Potential for heavy rainfall across portions of southeast Georgia
between Monday and Tuesday night may prolong or exacerbate ongoing
flooding in area river systems.
MODERATE RIVER FLOODING: Mod flooding that is ongoing along the
upper Alapaha is expected to lower into minor flooding this week.
Moderate flooding is expected on Santa Fe River near Three Rivers
Estates this evening and is forecast to persist into early next week.
MINOR RIVER FLOODING: Ongoing along most of the Satilla, Altamaha,
Santa Fe, and lower portions of the Suwannee Rivers. Minor flooding
is expected to continue through this week and potentially into next
weekend along the lower portions of the Suwannee River.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 62 80 51 56 48 / 0 60 40 70 80
SSI 62 79 54 60 54 / 0 40 40 70 80
JAX 64 83 57 64 57 / 10 20 30 50 60
SGJ 64 82 60 67 60 / 30 30 20 40 40
GNV 63 83 60 69 60 / 20 20 20 40 40
OCF 64 84 62 76 63 / 30 10 20 30 30
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EST Sun Feb 28 2021
.SHORT TERM...(This evening through Monday)
Issued at 403 PM EST SUN FEB 28 2021
Quick-moving winter storm is now beginning to exit the area. Surface
obs show cyclonic flow over the south-central pointing to the
surface low being centered over south-central Marquette County.
Correspondingly, radar shows the dryslot doing its dirty work
causing the precip shield to erode quickly across the central U.P.
Totals will end up being more impressive across the west half where
the better fgen banding set up this morning. The synoptic precip
shield will be out of the central U.P. by 00z and out of the CWA
entirely by around 02z. Because snow is still ongoing even in the
southern tier counties, left the Winter Weather Advisories as they
were. However, evening shift can probably cancel the southern tier
counties in about an hour.
Tonight, as the system continues to pull away to the northeast, a
strong northern stream short wave will dig into Northern Ontario.
This wave and the associated surface cold front will usher in
unseasonably cold air. Any wet or slushy surfaces will flash-freeze
tonight which could lead to additional icy spots and slippery travel
for the Monday morning commute. In addition, tightening pressure
gradient and 3-hour pressure rises of 5-7 mb on the western flank of
the deepening/departing low will lead to gusty winds. These gusty
winds will be short-lived in most areas, except over the eastern
U.P. where they will persist through the night where model soundings
show the PBL remaining mixed to around 2-3 kft. Went with the HRRR
over there which is near the highest in gusts, showing 30-35 mph
gusts through the night. This wind will lead to waves building to as
high as 14 feet on the east half of Lake Superior, so have issued a
Lakeshore Flood Advisory for Alger & Luce counties. Winds, and thus
waves, will decrease slightly early Monday morning before ramping
back up during the day Monday with the strong CAA push. Waves should
fall below criteria by mid afternoon Monday.
Once this cold air settles in, lake effect snow showers will develop
in the NW wind LES belts, mainly east half. The question for the
west half will be how much over western Lake Superior is covered in
ice and how well the CAMs are resolving it. Right now based on the
GLERL ice cover analysis it looks like there is enough ice cover to
inhibit most LES. However, it could shift around, and the analysis
could be off. Model soundings across the west half snow belts are
mostly dry except for just a thin saturated layer/cloud deck.
Nonetheless, manually increased POPs to get at least chance snow
showers in the forecast. However, between the lack of open water and
heights rising/the column drying out, do not think there will be
enough moisture to see anything more than scattered light snow
showers west. East half, where there is more open water and a longer
fetch, should see persistent LES through Monday afternoon, amounting
to generally 1-3". Some CAMs hint at a more dominant band clipping
northern and eastern Luce County which could produce up to 5" but
most of the heavy snow with this band, if it develops, will fall
just east of the CWA. With 850 mb temps around -22 to -24 C midday,
even mixing out to 1 km AGL only gives highs around 12-14 F most
areas. So March will indeed come in like a lion this year.
.LONG TERM...(Monday night through Sunday)
Issued at 222 PM EST SUN FEB 28 2021
Long term period continues to suggest a busy beginning of the week
followed by a slower and dry middle to end of week. Initially, with
the outgoing Monday shortwave and ridge axis shifting east over the
region, clear skies, recent snowfall and dry conditions will help
send Monday night temps near or just below zero for the interior
regions and single digits above by the lakeshores.
The culprits for the busier Tuesday look to be the aforementioned
ridge axis tied to a weakening 1031mb high shifting into the Ohio
Valley and a surface low and shortwave moving through Ontario. Being
caught in the middle of these systems, a tight pressure gradient
with a stout LLJ will move over the forecast area during the day.
Winds at 850mb within this jet look to be near 60kts. Model
soundings suggest we could mix up to around 900-875mb, which could
bring widespread 25-30 mph winds to the surface. Some areas,
particularly the higher terrain and near Lake Michigan could see
gusts approaching 35 mph during the day. These winds will also
raises concerns for lakeshore flooding and beach erosion along the
Lake Michigan lakeshores. This regime will also bring strong WAA
into the area which should quickly bounce temps into the mid-
upper 30s by afternoon. Some places in the west and south could
even climb into the low 40s. By the evening, winds should begin
settling down as the low over Ontario skates southeast just north
of Lake Superior and we lose the dinural mixing. Expect lows
Tuesday night to bottom out in the 20s with some isolated high
teens possible in the interior portions of central Upper Michigan.
An amplifying pattern over the CONUS begins to develop as ridging
sets up over the western Plains and slowly shifts eastward into the
weekend, and deep troughing associated with an upper level low over
western Greenland shifts westward. This will initially put Upper
Michigan in near zonal flow on Wednesday, but will develop into NW
flow mid-upper level flow beginning Wednesday night. At the surface,
various highs are progged to dip south and keep the region mostly
dry with the exception of potential light drizzly or flurries
developing downwind of Lake Superior. Despite light surface flow
generally off Lake Superior in some form with a few cold punches at
850mb being possible, slightly normal to slightly above normal
highs are largely expected. Daytime highs look to largely be in
the 30s with some high 20s possible on Friday. Overnight lows in
the teens to single digits in the interior west are generally
expected, with low 20s by the lakeshores.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 735 PM EST SUN FEB 28 2021
The fast moving snow storm has ended at all terminals with just
flurries being reported at SAW. Expect MVFR cigs to prevail at all
TAF sites tonight into Monday morning with brief periods of VFR cigs
possible, especially at IWD around 00z. Gusty northwest winds are
expected to continue tonight resulting in a steady stream of lake
effect clouds and a few light snow showers at IWD and CMX. A drier
air mass is expected to move in Monday afternoon with cigs improving
to VFR at all terminals.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 222 PM EST SUN FEB 28 2021
As today`s low pressure system moves through the lake, expect
increasing northwesterly winds to develop. In the east gales to 40kt
look possible this evening and into tomorrow. Additionally as this
low lifts, increasing CAA will surge cold air back into the area,
prompting heavy freezing spray concerns lake-wide tonight into
tomorrow. Both gale and heavy freezing spray warnings are in affect
tonight and tomorrow.
Tuesday southeasterly winds are expected as a low moves into Ontario
and high shifts into the Ohio Valley. Winds should increase again
with widespread 30kts to low end gales during the day as a stout LLJ
moves over the Upper Great Lakes. As high pressure builds in after
the low to the north skates away, expect calm winds below 20kts to
settle in late Tuesday night and linger through at least Friday.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Lakeshore Flood Advisory from midnight tonight to 3 PM EST
Monday for MIZ006-007.
Lake Superior...
Heavy Freezing Spray Warning until 1 AM EST Tuesday for
LSZ243>251-264>267.
Gale Warning until 7 PM EST Monday for LSZ249>251-266-267.
Heavy Freezing Spray Warning until 7 PM EST /6 PM CST/ Monday
for LSZ162-240>242-263.
Gale Warning from 1 AM to 1 PM EST Monday for LSZ243>248-264-265.
Gale Warning from 4 AM EST /3 AM CST/ to 10 AM EST /9 AM CST/
Monday for LSZ240>242-263.
Lake Michigan...
None.
&&
$$
SHORT TERM...RJC
LONG TERM...JP
AVIATION...EK
MARINE...JP
Area Forecast Discussion
National Weather Service Pittsburgh PA
943 PM EST Sun Feb 28 2021
.SYNOPSIS...
Crossing low pressure will promote periods of rain through early
Monday morning. Building high pressure should then support mainly
dry and cool conditions through the week.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Recent RAP analysis at 700mb suggests boundary layer saturation
(RH >70%) has commenced across the forecast area, with precipitation
gradually increasing as moisture advection in srly flow ensues ahead
of an approaching cold front. Strong warm advection is evident in
recent sfc temperature observations in the upper 50s / low 60s
across srn portions of the region, with the 00Z sounding out of KPIT
suggesting steepening mid-level lapse rates above a strong sfc
temperature inversion. As the cold front nears, categorical PoPs
should overspread the forecast area after midnight. With elevated
instability evident; enhanced rainfall rates may occur at times,
especially across sern portions of the forecast area where
convergence associated with frontogenesis remains. In this area, an
additional 0.50 to 1.00 inches may be realized, contributing to
ongoing hydro concerns. Both areal and river flood hazards should
persist with anticipated rainfall and continued snowmelt runoff.
Please see the Hydrology section below for more information related
to river rises.
Precipitation will quickly end with the passage of the cold front
Monday morning, potentially mixing with snow in the higher elevations
as cold nwly flow ensues.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY NIGHT/...
Remaining vorticity advection associated with a mature upper level
trough will rotate southward and contribute to the chance for snow
showers for a brief period of time on Monday north of Pittsburgh.
Pressure rises, with isallobaric acceleration will create breezy
conditions, with wind gusts of 25 to 30 mph at times on Monday
afternoon. Given environmental conditions and a shortwave temperature
trough, the possibility for convective snowbands does exist but lack
of moisture is likely to limit any long term organization.
Accumulation will be minimal and confined to locations north of I-80.
High pressure should then support minimal precipitation chances
through Wednesday, with flattening flow aloft supporting below
average temperature through Tuesday before moderating under gradual rising
heights by Wednesday.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
Long term pattern suggests high pressure will maintain quiet weather
for the majority of the period. Troughing near Hudson Bay, Canada may
contribute to lower than normal temperature into the weekend.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
IFR/MVFR restrictions continue this evening with a brief lull in
rainfall. Cigs will all lower into IFR within the next several hours
as a second wave of rainfall moves into the area ahead of a cold
front. SE`ly wind should veer to the SW/W with frontal passage.
A return to VFR is expected by late Monday morning with dry post-
frontal advection.
.Outlook...
Restriction potential returns Wed S of PIT with low pres.
&&
.HYDROLOGY...
An additional 0.50 to 1.00 inches of rain is forecast through
early Monday in the Flood Watch area. Combined with snowmelt, this
is likely to promote ongoing flooding on some area small creeks and
streams.
River Flood Warnings have also been posted at several points along
the Monongahela and Cheat Rivers. The Cheat in particular will have
to be watched closely, as snowmelt and rainfall will be highest in
that basin. Flooding in the major category is currently forecast
at Rowlesburg and Point Marion. Minor flooding is also expected
at Parsons on the same river, and minor to moderate flooding is
foreseen at Point Marion, Charleroi, and Elizabeth on the
Monongahela.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch until 4 AM EST Monday for PAZ075-076.
OH...None.
WV...Flood Watch until 4 AM EST Monday for WVZ021-509>514.
&&
$$
Area Forecast Discussion...UPDATED
National Weather Service Blacksburg VA
933 PM EST Sun Feb 28 2021
.SYNOPSIS...
Low pressure moving northeast through the Great Lakes tonight
will push a cold front through the Mid Atlantic region along
with moderate to heavy showers and isolated thunderstorms. The
weather turns windy and colder behind the front on Monday and
Monday night. High pressure and dry weather build in for
Tuesday and Tuesday night.
&&
.NEAR TERM /THROUGH MONDAY/...
As of 915 PM Sunday...
Line of showers and embedded convective elements is now moving
into the Blue Ridge and gradually shifting ESE. A large area of
stratiform rain had spread across WV, with some stronger cells
to our southeast in KY and TN. Have expanded isolated thunder
across western and west central VA as the front continues to
push through tonight. We have issued a flash flood warning for
portions of Greenbrier County WV and Bath County VA. In these
areas rainfall totals of up to 2" have fallen in the last 24
hrs, and we are expecting localized higher amounts before the
rain ends.
Ahead of the front, there was a sharp gradient in PoPs, with
nothing falling yet across much of central VA and northern NC.
The rain will eventually push through during the overnight and
morning hours Monday as a short wave kicker deepening in
Ontario Province shoves the surface system and associated front
into the Atlantic and Gulf of Mexico.
Have added some dense fog and also put up a dense fog advisory
for the central Piedmont of VA- south of the convective line
and still in a shallow in-situ wedge. This will eventually be
scored out by the FROPA, with temperatures and dew points
gradually falling during the day tomorrow.
As of 310 PM EST Sunday...
Flood Watch in effect through Monday morning for areas along
and west of a Marion to Pearisburg to Lexington line.
Low clouds and fog remained in the foothills and piedmont of
Virginia late this afternoon. The wedge had eroded over the rest
of southwest Virginia into southeast West Virginia and the
mountains and foothills of North Carolina. Outside of the wedge
winds were gusting from the southwest at 15 to 30 mph.
HREF and HRRR guidance have the main axis of showers from
central West Virginia through western Tennessee through
midnight. Between midnight and noon the band of showers and
associated cold front cross the Appalachians and will move in
eastern sections of Virginia and North Carolina.
Temperatures will be mild overnight as dew points rise across
the area. However, temperatures will drop during the day behind
the front in the mountains.
There will be a sharp gradient in rainfall amounts on the
western slopes of the central Appalachians. The heaviest
rainfall through Monday morning will be west of a western Bath
County, VA to western Watauga County, NC line. No changes have
been made to the Flood Watches that are in effect or will go
into effect at 7PM this evening.
&&
.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/...
As of 300 PM EST Sunday...
A brief touch of wintry weather in the mid-week...
A transient surface high will enter the area from the upper midwest
late Monday and begin to clear out sky cover from north to south.
Behind Monday`s front, winds will pick up for the overnight hours
into Tuesday. Higher elevation areas will experience gusts 25-35 kt,
and lower valley areas and east into the Piedmont will gust more int
the 15-25 kt range. Most of Tuesday will remain clear with zonal
flow dominating the eastern half of the CONUS. An eye will be kept
on a small cut off low set to come out of the southern states
Wednesday morning.
This little system will approach the region Wednesday morning and
restore cloud cover, but ought to get swept east and off the coast
by Wednesday night/early Thursday morning. Most of the action from
this smaller system will remain south of the NC/VA border and will
be shortlived. The NC Highlands may see a quick inch or so of snow,
up to 2 in the very upper elevations. Elsewhere in the mountains, a
dusting is the most to be expected. Snow will become rain as
temperatures warm on Wednesday. East of the Blue Ridge this will be
an entirely rain event. By Thursday morning the cut off low will be
out to sea, and calmer weather will prevail.
Temperatures will be above normal for this forecast period, with
even a slight warming trend. Daytime highs will be in the 40s and
50s. The temperature profile will cool just enough Tuesday
night/Wednesday morning to allow that bit of snow in the mountains,
but most will stay above freezing in the mid 30s for overnight lows.
&&
.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 215 PM EST Sunday...
A much calmer second half of the week and weekend...
A broad ridge will move into place over much of the CONUS. This will
provide us with dry mild weather through the end of the forecast
period. The only disruption could be another low forming in the
southern states late on Sunday and moving north to bring more rain
to the area. However, this currently seems a less likely scenario
than the broad ridge extending its influence almost as far south as
the Gulf. This will serve to fend off any encroaching low pressure
systems from approaching us from that direction.
High temperatures will be slightly above normal for this entire
portion of the forecast, while lows look to be right around normal.
&&
.AVIATION /02Z MONDAY THROUGH FRIDAY/...
As of 645 PM EST Sunday...
Wedge conditions are holding fast east of the Blue Ridge to
include KROA and KLYH with LIFR conditions. However, the wedge
retreated just a bit this afternoon so all other locations are
outside of the wedge with VFR conditions. Believe KROA and KLYH
will remain with very poor flight conditions until the
approaching cold front finally dislodges the wedge late tonight.
Expect conditions at other sites will be trending down as the
front approaches and lower CIGs and showers move in.
The front will clear the region early Monday morning with
steadily improving conditions to VFR all sites. However, expect
winds will increase significantly across the entire region by
the afternoon with gusts at or above 30kt for KROA possible.
Extended Aviation Discussion...
Drier weather and VFR conditions are expected to across the
region Tuesday and Tuesday night. A quick moving low pressure
system moving across the southeastern U.S. Wednesday and
Wednesday night may bring VFR clouds to the Carolinas. Some MVFR
upslope clouds are possible in southeast West Virginia
Wednesday.
Tranquil VFR weather is expected for Thursday and Friday.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...Flood Watch through Monday morning for VAZ007-009>011-018-023.
Flood Watch until 7 AM EST Monday for VAZ019-020-024.
Dense Fog Advisory until 4 AM EST Monday for VAZ022>024-034-
035-045>047-059.
NC...None.
WV...Flood Watch until 7 AM EST Monday for WVZ042>044-507-508.
&&
$$
SYNOPSIS...AMS
NEAR TERM...AMS/SH/MBS
SHORT TERM...VFJ
LONG TERM...VFJ
AVIATION...AMS/MBS