Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/26/21
Area Forecast Discussion
National Weather Service La Crosse WI
1015 PM CDT Thu Mar 25 2021
.SHORT TERM...(This evening through Friday)
Issued at 218 PM CDT Thu Mar 25 2021
At 130 PM, skies were partly to mostly cloudy, with spotty light
rain showers noted over parts of northeast Iowa into southwest
Wisconsin. Winds were beginning to turn more northeasterly ahead
of surface low pressure located in Missouri.
The aforementioned surface low will continue to eject
northeastward through Illinois and into southeast Michigan this
afternoon/tonight, with good consensus that the heavier wrap
around precipitation stays to our southeast where the better
forcing will be. However, high resolution guidance continues to
show light rain from northeast Iowa into southwest and even
central Wisconsin through this afternoon and evening on the fringe
of the shortwave forcing and in the vicinity of some mid-level
frontogenesis. Given this, will maintain PoPs in this area. As
temperatures cool into the 30s by late evening, a few snowflakes
could mix in east, but not expecting accumulations given light
precipitation and a relatively warm ground. The RAP does suggest
saturation is slow to decrease tonight, so there could be a period
of drizzle following the rain, but forcing looks to wane as the
night wears on.
Friday looks like a dry day, as ridging builds into the area.
Models disagree on how quickly cloud cover diminishes, however,
with the RAP suggesting low-level moisture gets trapped and clouds
linger all day long, whereas other guidance would have skies
scatter out tonight or early Friday morning and bring a sunnier
day for Friday. For now, will lean toward the sunnier forecast
with clouds being more scattered/diurnal in nature thus far this
afternoon.
.LONG TERM...(Friday night through Thursday)
Issued at 218 PM CDT Thu Mar 25 2021
The next chance for precipitation still looks to be on track for
Friday night into Saturday night. A long wave trough is currently
taking shape over the western conus as several short wave troughs
move onshore from the northern Pacific. One of the lead short wave
troughs will advance northeast across the region Friday night and
Saturday followed by another short wave trough coming in from the
northwest Saturday night in the mean long wave trough. These
waves look to produce a couple rounds of weak to moderate pv
advection in the 500-300 mb layer as they move across. A weak area
of low pressure should develop over southwest Kansas Friday and
then advance northeast across Iowa into eastern Wisconsin Friday
night and Saturday. Decent warm air advection ahead of the low
will produce 2 to 4 ubar/s of up glide on the 290K isentropic
surface. With some weak moisture transport occurring in
conjunction with this warm air advection/isentropic up glide, the
column is expected to quickly saturate with precipitation
spreading over much of the area late Friday night. A band of weak
mid-level frontogenesis should form on the northwest side of the
surface low Saturday afternoon and combine with the forcing from
the second short wave trough to maintain some precipitation into
Saturday evening. Temperatures look to be warm enough for most of
this to fall as rain. The possible exception to this will be along
the leading edge of the precipitation Friday night as it moves
into the Interstate 94 corridor. Temperatures there look to be
cold enough for some light snow to initially occur. Also not
completely out of the question is a short period of some light
freezing rain if dew points are slow to rise before the
precipitation moves in. This should not last very long if it does
occur, but a light glaze is not out of the realm of possibilities.
As for whether there is still a chance for some light
precipitation early next week remains rather murky. The 25.00Z
ECMWF and 25.12Z GEM still suggest a piece of energy will drop out
of the southern end of the long wave trough over the weekend and
then move northeast early next week. These models have shifted
this short wave trough farther southeast and more into the Ohio
River Valley than yesterday`s solutions. The 25.12Z GFS has gone
away from this idea and does not drop any energy out of the long
wave trough over the weekend and thus does not have any system
advancing northeast early next week.
After that, a cold front should advance through the area Tuesday
ahead of a positive tilt long wave trough in association with an
upper level low advancing east across central Canada. Some light
precipitation could occur along and behind the front Tuesday and
Tuesday night.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1015 PM CDT Thu Mar 25 2021
Cigs: low cloud potential a lot more unclear at late evening, with
northward advancement having slowed and meso models not as bullish.
RAP/HRRR/NAM12 all show different things and don`t capture current
conditions very well. Latest trends do lean toward KRST staying just
north of MVFR while KLSE might still get into it for a time
overnight. Confidence not very high and anticipate adjustments as
the night wears on.
Meanwhile, ribbon of low level saturation for the afternoon should
result in sct-bkn cu deck...and a few hours of MVFR possible. Will
hold scattered for now. High/mid clouds on the return Fri night
ahead of shortwave trough lifting northeast out of the southern
plains, and then back into MVFR for much of Sat.
WX/vsby: no impacts anticipated.
Winds: light and northerly tonight, staying light with a shift to
more south/southwest Friday afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Lee
LONG TERM...04
AVIATION...Rieck
Area Forecast Discussion
National Weather Service Birmingham AL
652 PM CDT Thu Mar 25 2021
.UPDATE...
Evening Update and 00Z Aviation.
&&
.SHORT TERM...
/Updated at 0624 PM CDT Thu Mar 25 2021/
Long track damaging tornadoes have moved across Central Alabama
this afternoon. Significant damage has taken place. At this
writing, no tornado warnings are in effect. A Tornado Watch
remains in effect until 8 pm and may be extended.
So what now, a warm front was located just north of the area while
a cold front/trough was still back to the west. The latest RAP
analysis has SBCAPE values still over 2000 and will become even
more suppressed to the southern reaches the next few hours. A
rain induced boundary or axis of a mixed up atmosphere was west to
east across Central Alabama from TCL to ANB. SRH values will
slowly go down as the low level jet exits northward. So at this
time, it appears the greatest threat will reside south of a line
from Sumter County to Randolph County. The threat north of this
area is certainly not zero, and will keep a mention of severe
storms including tornadoes, but the threat is lower than earlier
this afternoon. So will make some changes to the graphics suite
but the overall trend in the forecast looks ok.
75
Previous short-term discussion:
/Updated at 450 AM CDT Thu Mar 25 2021/
Today through Friday.
So far this AM we have had widespread showers with embedded
thunderstorms as it spread NE across C AL. The activity has been
elevated and while we are watching for any rogue storms, severe
activity during the early morning hours should be marginal at
best until the warm front makes its way northward later today. We
have increased the severe threat in the NW half of C AL for this
afternoon and evening. This probably doesn`t come as much of a
surprise as this system is ramping up to be significant there with
strong tornadoes a possibility. The SE half of C AL is a
different story. While we have a marginal threat this AM for
portions of C AL, for the rest of the afternoon and evening,
parameters are much lower in the SE counties with convection not
as likely there until later this evening. After the current
convection currently on the radar pushes N, we should have a
somewhat lull in activity in the SE.
In contrast, by around 11am, our warm front should be to the N of
the area. Models suggest some cellular activity will likely pop
up in the NW first. MUCAPE will not be lacking, but will be
highest in the west for this afternoon. 0-6km bulk shear will be
in ample supply across C AL. However, 0-1km shear will be
decidedly higher in the NW. Although amounts vary, guidance is in
agreement decreasing this low level shear significantly after 6z
as the bulk of the instability skirts to the NE. This will be not
only with the front moving across, but our negatively tilted upper
shortwave that is expected to be over the Arklatex ~18z today
expected to race off toward IL/IN by midnight tonight. With the
bulk of the activity in the SE counties expected for later this
evening, this greatly decreases the chance for severe weather for
them S of the I85 corridor. This is the reason for the sharp risk
gradient in our severe graphics. Timing is pretty similar to what
we had yesterday except possibly starting in the NW at 11am
instead of noon. The front is expected to make progress after
midnight with the risk for TS in the SE counties much lower for
the day on Friday with lower dew points moving in behind the
front.
08
.LONG TERM...
/Updated at 450 AM CDT Thu Mar 25 2021/
Friday night through Wednesday.
Rain chances should be minimal for Friday evening but increase
after midnight into the pre-dawn hours on Saturday with some
thunderstorms possible in the NW with shortwave activity. Rain
chances increase once again for Saturday into Sunday with the
approach of another frontal system number 2. However, the upper
dynamics still need to be worked out. The upper setup does not
show a negatively tilted system like front 1. However, we will
have warm and moist air waiting for this springtime front. While
some strong storms cannot be ruled out, will hold off adding
severe just yet with the weekend system. Extended guidance
diverges on timing and strength of the upper low/shortwave behind
the front for Mon/Tue time frame, so only going with low pops for
now. A third front approaches by end of the extended by Wednesday
with elevated shower and thunderstorm chances returning.
08
&&
.AVIATION...
00Z TAF Discussion.
Showers and thunderstorms will still affect the terminals the next
several hours until a cold front/trough moves through. Until then,
showers and thunderstorms with gradually lowering ceilings. It
appears the general trend will be for the ceilings to hold in the
MVFR range at 015-030. Winds will also be gusty at times even
outside convection. Low level winds will eventually lift north of
the area, reducing any LLWs and wind gusts. The northern terminals
will eventually become VFR by 15-18z while some clouds may hold on
near TOI and MGM. As the surface boundary moves through, winds
will go from south to west northwest.
75
&&
.FIRE WEATHER...
A moist air mass with high relative humidity values will develop
and continue through the weekend with multiple episodes of showers
and thunderstorms. A warm front will lift northward today and
produce numerous showers and a few thunderstorms. Southerly winds
will increase to 10 to 15 mph with higher gusts today as a strong
storm system approaches from the west. There is risk of severe
thunderstorms with tornadoes this afternoon and evening. Rain
chances are lower on Friday, but more showers and thunderstorms
are expected for over the weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 52 75 54 79 61 / 100 10 40 70 80
Anniston 57 78 59 82 63 / 100 10 40 60 60
Birmingham 55 76 60 81 64 / 100 10 50 70 80
Tuscaloosa 54 78 62 82 64 / 80 10 40 60 80
Calera 57 76 62 82 64 / 100 10 40 60 70
Auburn 63 76 64 82 64 / 80 30 20 30 20
Montgomery 64 78 65 85 67 / 90 20 20 30 30
Troy 65 80 66 85 67 / 80 40 20 20 20
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
Wind Advisory until 10 PM CDT this evening for the following
counties: Autauga...Barbour...Bibb...Blount...Bullock...
Calhoun...Chambers...Cherokee...Chilton...Clay...Cleburne...
Coosa...Dallas...Elmore...Etowah...Fayette...Greene...Hale...
Jefferson...Lamar...Lee...Lowndes...Macon...Marengo...Marion...
Montgomery...Perry...Pickens...Pike...Randolph...Russell...
Shelby...St. Clair...Sumter...Talladega...Tallapoosa...
Tuscaloosa...Walker...Winston.
&&
$$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
949 PM MDT Thu Mar 25 2021
.UPDATE...
Issued at 945 PM MDT Thu Mar 25 2021
Showers moving off the higher terrain over the plains are
producing more wind than precipitation. QG lift will be
increasing, so expect these gusty showers to continue through
midnight before decreasing. New 00z models are coming in to show
less moisture available tonight, as the 18z NAM was showing
widespread low stratus and fog overnight into the early morning.
This seemed like the outlier solution, and the 00z models are
following this thinking. Will keep out the widespread low clouds
and fog for tomorrow morning`s forecast.
For tomorrow, PoPs seemed to be a bit too heavy handed in the late
morning to early afternoon, so dialed them back just a little.
Still expect isolated to scattered rain mixed with snow showers
across the plains and numerous to widespread snow showers over
the mountains. Can`t totally rule out a roll of thunder, as CAPE
is 200-300 J/kg. Though cooler, relatively warm temperatures on
the plains will allow for little to no accumulation. Over the
mountains, should see 1 to 3 inches through tomorrow evening,
though there will be pockets of higher amounts, possibly 4 to 6
inches, due to the convection expected.
&&
.SHORT TERM...(This evening through Friday)
Issued at 230 PM MDT Thu Mar 25 2021
A broad long wave trough will slowly approach eastern Colorado
tonight and Friday. It`s currently located across the Pacific
northwest and will dig south into the Four Corners by mid morning
Friday. Ahead of the trough, west flow will bring in cold
advection aloft across all of Colorado. However, because the
trough is so broad, the flow between 700 - 500 mb is not
particularly strong, thus the west upslope flow will also be not
particularly strong. What this system has going for it is decent
moisture and instability. PW values increase to 0.2" in the
mountains and nearly 0.4" across the plains. Expect convective
showers this evening across the mountains, and spreading east
across portions of the plains through about 2-4 AM. No snow
accumulation is expected, and it may remain in the form of rain
below 6,000 ft this evening. Above 6,000 ft, all snow expected
this evening into early Friday with 1-4" for the northern
mountains, less along and south of I-70 with T-2" possible
overnight.
On Friday with the trough approaching and cold advection aloft,
and mostly cloud skies across most of the area other than the far
eastern plains, temperatures during the afternoon will be a few
degrees cooler than today. Expect highs mostly in the 40s other
than the sunnier spots across Lincoln County with low to mid 50s.
The mountain valleys and foothills should be in the mid to upper
30s. QG lift from the trough is strongest across the northern half
of Colorado from late morning into the late afternoon hours. This
lift, combined with steep lapse rates aloft, will result in
convective showers developing over the high country from the late
morning through the early evening hours as the trough axis
approaches. HRRR CAPE values across the mountains, foothills, and
much of the plains range from 100-500 J/kg during the afternoon.
Can`t rule out a rumble or two of thunder in the strongest
convection later in the afternoon. The most likely scenario for
convective evolution is one or two rounds of convection forming
over the high county and moving east during the afternoon/evening
hours. With wet bulb temps in the mid to upper 30s during the
afternoon hours, expect it to fall as rain below 6500 ft. Above
6500 ft, it should fall as snow. Snow accumulations could be
significant in the heavier showers with a few inches falling in
60-90 minutes with the stronger convection. Travel above 9,000 ft
across the mountain passes could be impacted Friday afternoon and
evening with a convective shower overhead. Total snow
accumulations for the mountains and foothills will be discussed
in the longer term discussion below.
.LONG TERM...(Friday night through Thursday)
Issued at 230 PM MDT Thu Mar 25 2021
Rain and snow showers will be winding down Friday as the system
exits the region. A few snow showers could linger into Saturday
morning over the mountains. Temperatures rebound Saturday with
highs in the 50s over northeast Colorado. The warming trend will
continue into Sunday as a ridge slides across the Central Rockies.
Highs will be in the 60s across northeast Colorado.
Westerly flow aloft increases Monday as an upper level trough
tracks across the Great Basin and Northern Rockies. Gusty west to
southwest winds will prevail. This will usher in warmer air. Highs
for Monday are expected to be in the upper 60s to lower 70s
across northeast Colorado. The trough progresses eastward across
the Central and Northern Rockies Tuesday. The main circulation and
lift will stay well north of Colorado, tracking across the
U.S./Canada border. A cold front pushes through Monday evening and
will bring much cooler conditions for Tuesday. A secondary
circulation and upslope flow behind the cold front should bring a
period of snow to the mountains, foothills, and plains on Tuesday.
Temperatures look cold enough that precipitation will fall mainly
as snow.
Temperatures warm Wednesday after the system exits the region.
However, northwest flow aloft will keep temperatures below normal.
Will have low PoPs over the mountains where light orographic snow
will be possible. The 12Z GFS shows a weak wave dropping southeast
across the state, while other models don`t. Will have PoPs for
Wednesday confined to the mountains until more models show this
second wave. Ridging and warmer air should move over Colorado
Thursday bringing warmer and dry conditions to the region.
&&
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 230 PM MDT Thu Mar 25 2021
Isolated to scattered showers, mostly snow, are pushing out over
the airports, though these have more wind than precipitation with
them. With temperatures in the low to mid 30s and already warm
runways, we do not expect any accumulation this evening or
overnight. Winds could be gusty under or near any of the showers,
the most likely direction is WNW to NNW. All showers should end
after 2-4 AM. ILS conditions are expected later this evening and
should continue through most of Friday. During and after showers
CIGs should be 030-050.
On Friday winds should shift to NE by midday but 10 kts or less.
Lower clouds will increase by mid afternoon and another round or
two of showers are expected to move across the terminals late
afternoon and evening. With CIG around 050, expect ILS
conditions. Gusty winds up to 20-25 kts are possible in and around
the showers through the evening hours. Once again, it`s most
likely to be rain until after 10 PM or so, when it could mix with
or change over to snow. No accumulation is expected on the runways
and CIGs may drop below 030 during the showers.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Kriederman
SHORT TERM...Schlatter
LONG TERM...Meier
AVIATION...Schlatter/Kriederman
Area Forecast Discussion
National Weather Service Buffalo NY
1019 PM EDT Thu Mar 25 2021
.SYNOPSIS...
A warm front moving in tonight will generate widespread rain and
possibly a few thunderstorms. A strong storm system passing
close to the region will then produce strong to damaging winds
Friday, along with some more showers and additional thunderstorms.
Much cooler weather is expected in the wake of the system into
early next week.
&&
.NEAR TERM /THROUGH FRIDAY/...
A deepening storm tracking across the Mid Western states
overnight will push a warm front into our region. Radar showers
an initial line of showers with a segment of this front moving
into western New York Lake this evening. This area of showers
will continue to expand, as widespread rain develops across the
area overnight. There should be enough elevated instability to
maintain the mention of a few thunderstorms. Rainfall generally
up to a half inch although locally higher amounts will be
possible in any convection.
A high wind event still looks to be on track for Friday with STRONG
TO DAMAGING winds likely. 12z model guidance still supporting a
storm track just off to our west with a favorable 925 mb jet
positioning of 50-60 knots focused right across western New
York. Elected to limit High Wind Warning to western areas where
best low level jet is focused and best 3-hour pressure couplet
is forecast. Latest HRRR guidance supports this warning, but
suggests a fairly narrow time window with the strongest winds
lasting 2-3 hours. The burst of strongest winds (about 60 mph)
will reach Buffalo around 11 a.m. and Rochester around 1 p.m.
Along with the strong winds, showers will continue and possibly
thunderstorms. This will especially be the case across the
Eastern Lake Ontario region where there will be a chance for
more robust convection. SPC has placed this region in a marginal
risk for severe weather on Friday.
Temperatures Friday will peak early in the day then fall back
from west to east during the afternoon as the strong winds
usher in notably cooler air.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/...
High pressure will move into the eastern Great Lakes Friday night
through Saturday. The pressure gradient between exiting low pressure
off the coast of Newfoundland and approaching high pressure from the
west will keep winds on the gustier side for the first half of
Friday night, before quickly diminishing from west to east.
Northwest flow and lingering wraparound moisture Friday night will
allow a changeover to snow across the North Country. This leaves
some chances for a quick dusting of snow on the Tug Hill late Friday
night. Mid levels quickly dry out in the second half of the night as
high pressure builds into the area by Saturday morning. Overnight
lows will be in the mid 30s, with some upper 20s possible for the
Tug Hill.
Cold air advection will result in 850mb temperatures falling to -2C.
While a bit cooler than the recent warm stretch, temperatures will
remain mild on Saturday with highs in the mid to upper 50s across
western NY and the mid to upper 40s east of Lake Ontario. Dry
conditions expected on Saturday as high pressure remains in control.
Weak warm air advection Saturday night into Sunday ahead of the next
system will help keep temperatures steady through Saturday night,
with overnight lows only dipping into the mid 40s, mid to upper 30s
east of Lake Ontario.
More active weather returns as a deepening upper level trough moves
across the Great Lakes region late Saturday night into Sunday. A
rapidly intensifying 250MB jet on the east side of the trough will
enhance cyclogenesis as low pressure moves to the northwest of the
region. A strong cold front will track across the region during the
day Sunday, with deep moisture and large scale ascent resulting in
widespread rain across the eastern Great Lakes. Strong cold air
advection behind the front will drive Canadian air into the region,
allowing rain to change over to light snow showers late Sunday night
into Monday. 850mb temperatures will likely drop low enough to
generate some lake enhancement late Sunday night and into Monday as
well. Highs on Sunday will peak early in the day with upper 40s and
low 50s before quickly falling behind the front. Lows Sunday night
will drop into the mid 20s to low 30s.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
Drier air will quickly build in to start the period as high pressure
located just to the west moves eastward over the lower Great Lakes.
Other than a leftover stray light rain or wet snow shower,
expect a mainly dry, but cool and breezy start to the new work
week. High pressure will remain in control of our weather
through at least late Tuesday keeping dry conditions intact, all
while a milder airmass quickly moves back across the region
owed to a southerly return flow as aforementioned surface high
pressure moves off the southern New England coast and upper
ridge crests over the Northeast on Tuesday. As far as how this
impacts temperatures, daytime highs ranging from mainly in the
mid 30s to mid 40s on Monday will climb substantially for
Tuesday with highs ranging mainly from the lower 50s to lower
60s.
Next chance for any precip returns Tuesday night as the upper ridge
axis moves east over New England, while an embedded shortwave rides
northeast up the back side of the ridge. Meanwhile its` surface
reflection in the form of a warm front will move toward our area
from the Ohio Valley. The combination of these two features may
bring a few scattered light showers Tuesday night. Decent forcing
but a lack of overall moisture will limit overall shower coverage.
Warm front moves north of the area later Tuesday night, with a brief
period of mainly dry conditions possible Wednesday morning. This
will place our region firmly in the warm sector for Wednesday, with
most areas climbing at least into the 60s.
A strong cold front is then poised to plow across the region
sometime late Wednesday and Wednesday night bringing the next best
chance for some widespread beneficial rainfall. Mother Nature may be
playing the April Fool`s joke this year as a much colder airmass
pours across the eastern third of the CONUS in the wake of the cold
frontal passage, making for a chilly and raw start to the month of
April with the possibility of a mix of rain and snow showers. Highs
Thursday may not get out of the 30s across the higher terrain, with
mainly lower 40s elsewhere.
&&
.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
A warm front lifting north across the region will lead to
lowering cigs tonight. Cigs will lower to MVFR and possibly IFR
across the lake plains due to a northeasterly flow just before
the front moves through. After this, expect brief improvement as
winds shift to the SSW with downsloping helping to raise cigs a
bit. During this time showers will spread from south to north
this evening, followed by steadier rain late tonight.
Low pressure will pass just to the north on Friday, with winds
increasing significantly with its passage. Strongest winds will
be 15Z to 21Z with peak gusts around 50 kts at KBUF/KIAG/KROC.
Otherwise, some showers and possibly a thunderstorm with mainly
MVFR cigs and patchy IFR possible northeast of the lakes and
across higher terrain.
Outlook...
Friday night and Saturday...Mainly VFR.
Sunday...VFR/MVFR. Showers likely.
Monday and Tuesday...Mainly VFR.
&&
.MARINE...
A deepening storm system will track across the mid western states
tonight. This will encourage winds to freshen from the east-
southeast during the course of the night.
The strong storm system will then pass through the Lower Great Lakes
region on Friday with winds intensifying to gale force by mid morning
to early afternoon. West to southwest gales during the afternoon
will then drop off late in the day and Friday night. Gale warnings
are in effect for all of the Lower Great Lakes as well as for the
entire length of the Niagara River.
Small Craft headlines were issued for the St. Lawrence River
to Ogdensburg, with weaker winds north of Ogdensburg since the
surface low is expected to track near that area.
Winds will continue to weaken on Saturday, as high pressure will
pass over the region.
&&
.HYDROLOGY...
The combination of about an inch of rain along with snow melt from
warm weather will cause rises on Black River and its tributaries in
the Friday night through Sunday night timeframe. Rainfall
amounts is the main forecast challenge with high confidence in
warm weather and a steady run-off from the snow pack which is
still in place across higher terrain.
Latest modeling places around an inch of rain in the basin from
the Friday system, producing action level rises. Latest GEFS and
NAEFS ensembles suggest that there`s at least some risk for
Watertown to reach flood stage but this probably would be
following a second system on Sunday. Probabilities of flooding
at Boonville and McKeever are non-zero but very low. The HEFS
which accounts for some model QPF bias shows a lower risk for
flooding, and this seems the most likely scenario and the one
the NERFC is forecasting. There is still a small risk of
flooding if basin average rainfall amounts from the two systems
reaches around 2 inches. For now, will maintain a mention in the
HWO for the Black River basin with confidence well below 50
percent, the threshold for issuing a Flood Watch.
&&
.TIDES/COASTAL FLOODING...
Higher than normal water levels on Lake Erie combined with a period
of gale force southwest winds Friday will result in the sharply
rising lake levels on the east end of the lake and some
lakeshore flooding. At this time, levels are expected to peak
between 8 and 9 ft at the Buffalo NOS gauge.
&&
.BUF WATCHES/WARNINGS/ADVISORIES...
NY...High Wind Warning from 8 AM to 4 PM EDT Friday for NYZ001>003-
010>012-019-020-085.
Lakeshore Flood Warning from 8 AM to 4 PM EDT Friday for
NYZ010-019-085.
Wind Advisory from 10 AM to 8 PM EDT Friday for NYZ004>007-013-
014-021.
MARINE...Gale Warning from 11 AM to 6 PM EDT Friday for LEZ020.
Gale Warning from 8 AM to 6 PM EDT Friday for LEZ040-041.
Gale Warning from 11 AM to 6 PM EDT Friday for LOZ030-
042-062.
Gale Warning from 2 PM to 8 PM EDT Friday for LOZ043>045-
063>065.
Small Craft Advisory from 2 PM to 8 PM EDT Friday for
SLZ022.
&&
$$
SYNOPSIS...TMA
NEAR TERM...Apffel/TMA
SHORT TERM...PP
LONG TERM...JM
AVIATION...Apffel/RSH/TMA
MARINE...Apffel/RSH/TMA
HYDROLOGY...Apffel/RSH
TIDES/COASTAL FLOODING...RSH/TMA/Apffel
Area Forecast Discussion
National Weather Service Peachtree City GA
1033 PM EDT Thu Mar 25 2021
.UPDATE...
Expanded Tornado Watch into far NW counties given some cell
redevelopment trends in eastern AL and collab with SPC.
Baker
&&
.PREV DISCUSSION... /Issued 1013 PM EDT Thu Mar 25 2021/
PREV DISCUSSION... /Issued 846 PM EDT Thu Mar 25 2021/
UPDATE...
Training cells and heavy rain across far north GA has resulted in
1-3 inches and locally higher near 5 inches this evening. Keeping
Flash Flood Watch going through overnight with additional 1-3
inches possible along with ongoing warnings in effect. Still
monitoring for severe/tor potential given ample high shear and
decent instability axis advecting in from west and south ahead of
main front. Tornado Watch in effect through 2 AM across northwest
half of CWA. Made slight pop adjustments and added severe mention
in weather grids, otherwise previous fcst and expected storm
threats continue with little change made.
Baker
PREV DISCUSSION... /Issued 810 PM EDT Thu Mar 25 2021/
UPDATE...
00z Aviation update below.
Baker
PREV DISCUSSION... /Issued 348 PM EDT Thu Mar 25 2021/
SHORT TERM /Tonight through Friday Night/...
Widespread showers and a few thunderstorms are underway across
north Georgia this afternoon, mainly along and north of a line
from Cedartown to Roswell to Flowery Branch, where a warm front is
situated. This warm front is extending out from a surface low
located over the ArkLaMiss, placing the CWA within a warm, moist,
unstable environment this afternoon. A Tornado Watch is in effect
for northwestern GA until 9 PM EDT, where 0-1 km SRH values are an
impressive 350-450 m^2/s^2. In addition to the tornado threat,
this area will be ripe for supercells capable of large hail and
damaging wind gusts through the afternoon and evening.
The threat for severe storms will continue overnight into early
Friday morning as the surface low (at that point located over the
Great Lakes region) drives a cold front across the CWA from west
to east. CAMs generally show a broken line of storms entering
northwestern GA around 02z-04z, pushing through metro Atlanta
between 05z-10z. The threat for severe storms will continue to be
maximized across northern and western GA, where several severe
weather parameters are forecast to come together. At the upper
levels, a strong shortwave trough will lift northeast across the
Great Lakes region overnight, maintaining broad ascent across the
CWA (though the strongest upper dynamics will remain well to our
northwest). Still, some 65-75 kts of bulk shear will be in place
over northern and western GA overnight. In addition, 0-3 km SRH
values of 350-450+ m^2/s^2 and 0-1 km SRH values of 250-350+
m^2/s^2 will maintain a threat for organized, rotating storms with
tornadic potential. RAP and NAM significant tornado parameter
values across this portion of the CWA are 3 to 6, so the concern
for isolated tornadoes (some strong and/or long-tracked possible)
is certainly there. Even with the nighttime arrival of the storms,
MUCAPE will be 1000-1500 J/kg and forecast soundings suggest mid-
level lapse rates around 7.5-8.0 C/km, so large hail will also be
a threat with the storms overnight.
The line of storms will continue progressing eastward tomorrow
morning into the afternoon across central and eastern GA, but
severe storm parameters look to be much more marginal. That said,
decent shear and instability could make for a few strong to severe
storms.
Martin
&&
.LONG TERM /Saturday through Thursday/...
At the start the forecast period on Saturday, the lingering
frontal boundary will begin to quickly lift back north across
north Georgia as a warm front. The best chance for rainfall will
thus be across the northern third or so of the area on Saturday.
Some embedded thunderstorm activity will be possible Saturday
initially associated with elevated instability north of the warm
front. Rainfall coverage will diminish farther south of the cold
front where temperatures will soar well into the 80s in central
Georgia.
On Sunday, shower and thunderstorm coverage will increase
appreciably as the cold front pushes southeastward into the CWA.
The threat for strong/severe thunderstorms appears considerably
lower with this system at this time as dynamics will be much more
limited, though a few stronger storms can`t be ruled out. The
primary risk from Saturday into Sunday will be additional heavy
rainfall and flooding concerns across far north Georgia. These
areas will have already seen several inches of rain prior to the
weekend event, which could add another 1-2 inches of rainfall.
Guidance diverges by next week with respect to the evolution of
the upper low over the Southwest. The GFS maintains a southern
track shortwave along the Gulf Coast while the ECMWF lifts the low
northeastward into the Plains. At this point, kept slight chance
to low end chance PoPs on Tuesday given uncertainty. By midweek,
the next surface front approaches bringing increasing rain chances
areawide.
RW
&&
.AVIATION...
00Z Update...
TSRA could be in several rounds with initial pushing in from east
AL (tempo TS with VRB gusts near KATL for 01-05z period), then
could have redevelopment closer to front for the early morning
hours so will monitor for any tempo extension. Looks like MVFR
cigs overnight as well then improving from the north after 12/15z.
Southern sites could have more lingering showers or again some
storms Friday afternoon with stalling front. Winds initially
10-12 kts with some low end gusts possible out of SSE to SSW
(favoring SSW for KATL), then more west to NW shift 6-7 kts
behind front after 12z.
//ATL Confidence...00Z Update...
Medium on all elements.
Baker
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 63 78 57 80 / 70 40 20 50
Atlanta 61 75 60 81 / 70 30 30 40
Blairsville 55 73 49 71 / 100 20 30 80
Cartersville 58 75 55 80 / 100 20 40 60
Columbus 66 77 64 85 / 60 50 20 10
Gainesville 60 75 55 75 / 90 30 30 70
Macon 68 77 63 86 / 50 50 20 20
Rome 57 76 53 79 / 100 10 40 70
Peachtree City 62 75 59 83 / 70 40 20 30
Vidalia 68 84 66 88 / 10 30 5 10
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
Tornado Watch until 2 AM EDT Friday for the following zones:
Banks...Barrow...Bartow...Carroll...Catoosa...Chattooga...
Cherokee...Clarke...Clayton...Cobb...Coweta...Dade...Dawson...
DeKalb...Douglas...Fannin...Fayette...Floyd...Forsyth...Gilmer...
Gordon...Gwinnett...Hall...Haralson...Harris...Heard...Henry...
Jackson...Lumpkin...Madison...Meriwether...Murray...Newton...
North Fulton...Oconee...Paulding...Pickens...Pike...Polk...
Rockdale...South Fulton...Spalding...Troup...Union...Walker...
Walton...White...Whitfield.
Flash Flood Watch until 8 AM EDT Friday for the following zones:
Bartow...Catoosa...Chattooga...Cherokee...Dade...Dawson...
Fannin...Floyd...Gilmer...Gordon...Lumpkin...Murray...Pickens...
Polk...Towns...Union...Walker...White...Whitfield.
&&
$$
SHORT TERM...Martin/Baker
LONG TERM....RW
AVIATION...Baker
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
630 PM CDT Thu Mar 25 2021
.DISCUSSION...(This evening through Thursday)
Issued at 319 PM CDT Thu Mar 25 2021
Lingering stratus and redeveloping cumulus has kept skies partly
to mostly cloudy this afternoon. As a result, highs may struggle
to reach 50 degrees in some spots, especially in eastern portions
of the area. This will clear out this evening and overnight,
allowing temperatures to dip into the low to mid 30s. The HRRR
shows some fog over eastern portions of the area early Friday
morning as moisture returns ahead of the next system. Confidence
in this remains low, so this was kept out of the forecast for now.
Southeast winds increase on Friday as an upper shortwave and
associated surface low move out into western Kansas. A few rain
showers are possible through the morning, but rain amounts will
remain pretty light. By afternoon, a warm front should set up just
south of the Kansas/Nebraska state line, with moisture and
instability increasing near and south of it. By late afternoon,
the HREF mean shows MUCAPE between 500-1000J/kg for areas south of
I-80. This is coincident with effective shear of 35-40kts. With
the relatively limited CAPE, updrafts will not be overly intense,
but the abundant shear may allow the strongest updrafts to
organize into isolated low-topped supercells with the primary
threat being marginally severe hail/wind.
Models are in general agreement that the highest coverage of
storms will be in southeastern portions of the area, but an
isolated storm or two cannot be ruled out across the entire area.
Activity will shift east of the area after midnight as the upper
trough axis moves through.
Behind this system, a deeper upper trough will push through,
ushering in gusty northwest winds on Saturday. Then a warming
trend will will take hold Sunday into early next week as upper
level ridging builds overhead. High temperatures in the 70s appear
likely on Monday. This warmth and increasing south winds may also
lead to some near-critical fire danger Monday.
A cold front then moves through Monday night into Tuesday,
leading to a strong northwest winds and noticeable cooldown on
Tuesday. Some light rain is also possible as a deep upper trough
passes through Tuesday night into Wednesday morning. This will
keep temperatures near to below normal as we start the month of
April. Beyond that, there is good agreement in medium range
ensembles for a return to above-normal temperatures for Easter
weekend.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 619 PM CDT Thu Mar 25 2021
Quiet weather with VFR conditions are expected this evening into
the overnight hours...though confidence suffers a bit for KGRI
with the potential for it to be on the western edge of some fog
development. Not all models/guidance agree with it occurring, so
kept visibility at 6SM at this point. As we get into Friday, an
upper level wave moving into the region will bring the potential
for some shower mid-morning into part of the afternoon, but
uncertainty remains with just how much activity there actually is,
so have a VCSH mention at both terminals. There will be increasing
chances for more activity (and thunderstorms) in the latter few
hours of this period, but at this point the main focus looks to be
to the south of the terminals. Winds through the period are
expected to remain generally southeasterly, can`t rule out a few
gusts near 20 MPH tomorrow.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...NONE.
KS...NONE.
&&
$$
DISCUSSION...Mangels
AVIATION...ADP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1036 PM EDT Thu Mar 25 2021
.SYNOPSIS...
A vigorous cold front is expected to move through the area later
tonight and into Friday and could produce isolated strong to severe
convection along with significant rainfall. The active pattern
continues this weekend as another cold front slides through the
area on Sunday bringing another round of showers and thunderstorms.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1025 PM Thursday: The cold front was pushing through central
TN and AL with more discrete convection continuing to fire ahead of
it. A couple of these cells tried and failed to hold together as
they pressed into far northeast GA largely due to them running
into the more stable environment. The latest SPC HRRR shows that
later discrete cell should hold together into the western
Carolina`s and especially northeast GA as a tongue of 500-1000
CAPE noses into the area from the south thanks to increasing
southerly flow ahead of the front. Feel this could be a bit
overdone but with impressive shear and helicity values should be
enough for at least a few super cell thunderstorms capable of
damaging winds, an isolated tornado, and perhaps large hail.
This threat should be mainly west of I-26 and between roughly
midnight and 4 am. Flood concerns will continue especially for
the southwest mountains. Rainfall totals have already exceeded
5-6 inches at some higher elevations with an additional 1-2
inches possible before all is said and done. The Flash Flood
Watch has been updated accordingly.
As of 830 PM Thursday: The latest surface analysis shows what
appears to be a weak insitu-wedging roughly along and north of I-85
this evening that developed from the steady rainfall from earlier
today. This is indicated by weak high pressure nosing southwest from
the NC Piedmont towards northern GA. This will limit surface based
CAPE and instability overall for this area. This combined with
gradually diminishing upper support as the parent low moves
northeast into the Great Lakes and loss of daytime heating should
limit the coverage of severe thunderstorms compared to neighbors to
our west. That being said SPC recently issued a Tornado Watch for
much of northern GA good through 2 am, just to our west, so we will
be watching the developing situation closely. On that note, high
values of shear/helicity will continue along and ahead of the cold
front, so it probably won`t take much instability to maintain strong
to severe thunderstorms (a high shear/low cape environment). Steady
rain with embedded heavy rain will likely continue especially near
the southwest mountains overnight. So we will likely see additional
flooding during this time with the current Flash Flood Watch
seemingly well placed for the time being.
Otherwise, we remain under a weak WAA regime and influence of a
subtropical ridge off the SE Coast. This ridge is downstream of an
expansive trough, within which a potent shortwave will move today,
driving development of a low pressure system over the lower MS
Valley. A significant severe outbreak is expected over portions of
the TN, MS, and AL. Fairly brisk southerly flow has already
initiated convection over the high terrain. The depth and strength
of moisture advection will be impressive, leading to PWATs peaking
near +3 SD, and IVT parameter values that are also anomalously
large. Deep layer hodographs will already be long and curving, but
midlevel lapse rates are not the greatest; the limited instability
will keep our severe threat comparatively small during the day, with
convective layers too shallow to realize all the shear. This does
somewhat limit our heavy rain threat as well, though there will be
widespread coverage and potential for multiple rounds thru tonight.
WPC Day 1 ERO includes most of our SW mtns in a Moderate Risk,
partly because of the aforementioned anomalies and high
probabilities for significant rain rates from the HREF. We are
hoisting a Flash Flood Watch from 18z today to 12z Fri. The same
southerly flow will lead to rather gusty winds, and higher
elevations of the mtns will be exposed to near Wind Advisory-level
conditions.
LLJ is expected to precede the cold front into our area in the
early evening, again enhancing precip generation along the srn
end of the Appalachians; a narrow tongue of sfc based instability
will linger until the front itself enters in the late evening. A
convective line, likely with some embedded rotation will support
vague supercell structure. The dynamic lift provided by the
shortwave will mostly miss our area to the NW as the wave tracks
north of the OH River; this coupled with the unfavorable timing,
and diminishing instability, should begin to impact the convection
particularly as it crosses the mountains. Nevertheless, a narrow
line of strong showers with a few embedded tstms could progress
across the area overnight. Prog soundings reveal that the line will
encounter poor low to midlevel lapse rates, and this would limit sfc
based updrafts and thus tornado risk. The SPC slight risk extending
only into the mtns looks well-placed and even extended slightly
further east. Recent short-term consensus PoPs as well as hourly
NBM seem to be keying better on the shadowing effect of the mtns,
and timing/chances have been revised thru tonight in new fcst grids.
The frontal boundary should push out of the region by 18z Friday
as sfc high builds in to the NW and we enter a post-frontal
environment by the very end of the forecast period. Drier weather
will prevail, with highs in the low 80s in most locations outside
the mountains and 70s in the higher elevations. One factor that
can play a role is how fast the cold front exits the region and
allows for the clouds to scour out.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
As of 145 PM EDT Thursday: the short term picks up at 00Z Saturday,
with a shortwave trough rounding the broader ridge sitting over the
east coast. By this time, forcing from the trough will largely
be tapering off to the north of our CWA, and a brief bout of
dry weather is in store for Friday night. Renewed southwesterly
flow over the Tennessee Valley will pump Gulf moisture into the
lower troposphere through the day Saturday, working with weak
mid-level forcing to produce scattered afternoon showers across TN,
spreading into the Blue Ridge Mountains and western SC Upstate
by late Saturday afternoon. The developing surface low skirts
its way northeast along the Appalachians and drags a cold front
across our area early Sunday afternoon.
Ample WAA ahead of this front paired with decent solar insolation
should prime the environment for convection, with the Piedmont
and Upstate seeing SBCAPE values in the 500-1000 J/kg range and a
40-50kt LLJ riding out ahead of the frontal boundary. Given the
timing of the frontal passage in the early afternoon, this is a
pattern to keep an eye on over the next day or two. Some precip
may still be falling for at least the eastern part of our CWA by
the end of the short term at 00Z Monday, as the front tapers off
to the east.
Temps are on track to stay several degrees above normal on Saturday
and Sunday, before dropping back to near-normal Sunday night in
the wake of the cold front.
&&
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 200 PM EDT Thursday: by Sunday night, good mid-level forcing
associated with the latest trough is exiting the region to the east,
and precip drops off overnight behind the departing cold front.
We then enter a weak upper ridging regime as high pressure builds
in at the surface. So, Monday should be dominated by clear,
dry weather as the frontal boundary stalls well south of us.
Meanwhile, the GFS and ECMWF depict a closed upper low meandering
out of the Southern Plains and causing coastal cyclogenesis along
the stagnant frontal boundary. The resulting surface low tracks
from the Gulf Coast out to the NC/SC coastline. It looks to only
graze our CWA at this point, yielding chance PoPs on Tuesday
afternoon and overnight. On Thursday, yet another surface low
pushes into the region from the west, bringing another bout of
rainfall to the region to cap out the week.
Temperatures on Monday and Tuesday look to be a couple degrees
below normal, before southerly WAA brings them back to near-normal
later in the week.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: Below normal confidence in 00Z TAFs due to
uncertainty in timing and strength of convective line to move
through the area from west to east between roughly 05Z and 15Z.
Steady rain with isolated TSRA is expected ahead of this feature
with IFR and lower cigs/vsbys likely in heavier shra/tsra. Front may
stall south of TAF sites into Friday with little if any impact to
terminals.
Outlook: Another system may bring showers Saturday with
thunderstorms possible by Sunday.
Confidence Table...
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 86% High 97% High 81% High 100%
KGSP Med 77% Med 61% High 100% High 100%
KAVL Med 73% Med 60% High 100% High 100%
KHKY Med 67% Med 72% High 100% High 100%
KGMU Med 79% Med 72% High 100% High 100%
KAND High 87% High 86% High 100% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:
www.weather.gov/gsp/aviation
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Flash Flood Watch until 8 AM EDT Friday for GAZ010.
NC...Flash Flood Watch until 8 AM EDT Friday for NCZ051-052-058-059-
062>064.
SC...None.
&&
$$
SYNOPSIS...MPR
NEAR TERM...CAC/Munroe
SHORT TERM...MPR
LONG TERM...MPR
AVIATION...Munroe
Area Forecast Discussion
National Weather Service Indianapolis IN
1144 PM EDT Thu Mar 25 2021
...Updated Aviation Discussion...
.Forecast Update...
Issued at 950 PM EDT Thu Mar 25 2021
Sent update to the High Wind Warning and Wind Advisory. Some
concerns per latest HRRR model, wind gusts away from convection may
not be quite as high as anticipated. That said, center of low
pressure will deepen tonight and lift northeast across west central
and northern Indiana. This will result in low level wind
acceleration and jetlet lifting northeast across the forecast area.
So, will keep the headlines going.
With dry slot lifting northeast across southwestern parts of the
forecasts area, lowering PoPs look on track. Will be dropping Knox
and Daviess from the Tornado Watch as well with support from SPC.
&&
.Short Term...(This Afternoon through Friday night)
Issued at 233 PM EDT Thu Mar 25 2021
...SEVERE STORMS POSSIBLE THIS EVENING...
...HIGH WIND EVENT EXPECTED TONIGHT...
This Afternoon and Tonight...
Initial area of warm advection precipitation currently moving
through the area is expected to lift off to the northeast by the
late afternoon hours. Little to no surface or elevated instability
exists over the area at this time, although short term model data
suggest decent elevated instability for this time of year may
begin advecting in from the south towards evening, courtesy of
steeper mid level lapse rates in the wake of this afternoon`s
rainfall.
Short term models suggest another area of significant lift,
associated with the upper low/vorticity lobe and surface cold
front/occlusion moving out of the Missouri and Arkansas area, will
approach the southwest zones around 260000Z-260100Z. As a result,
expecting more widespread showers and thunderstorms to begin
developing by that time. Deep layer shear and helicity values
continue to look very high ahead of the front this evening,
especially over about the southeast two thirds of the forecast area.
This coupled with the elevated instability should support rotating
storms, both along and ahead of the front, but limited surface based
instability may help to keep any circulations elevated. Will have to
closely monitor instability trends this evening.
The front is expected to pass off to the northeast by 260500Z or so,
which should end any convective severe threat. Some wrap around
rainfall, associated with the upper low, may move through mainly the
northern zones during the early morning hours of Friday, so will
keep PoPs a little higher in those areas late tonight.
Models continue to suggest near dry adiabatic lapse rates up to
about 900mb in the immediate wake of the frontal passage, along
with a 50-60 kt low level jet wrapping around the back side of the
low. This scenario supports the potential for winds in excess of 50
kts to mix down for a period in the post frontal zone late tonight.
Based on above, decided to expand the warning a bit farther west,
and especially southeast, where it appears the best momentum
transfer may occur, given the expected surface low track.
Friday and Friday night...
Expecting winds to diminish fairly rapidly Friday morning, as the
surface and upper systems move away quickly.
Otherwise, this period looks rather quiet, with surface high pressure
moving into the local area by Friday afternoon and evening.
&&
.Long Term...(Saturday through Thursday)
Issued at 233 PM EDT Thu Mar 25 2021
On Saturday and Saturday Night...
The GFS and ECMWF shows a deep trough aloft moving through the
Plains states with SW flow in place across Indiana. Good forcing is
seen across Indiana ahead of the approaching upper trough axis.
Meanwhile at the surface a quick moving area of low pressure is
expected to push from Iowa to the Great Lakes...dragging a cold
front across Indiana on Saturday night. These features will have
ample moisture and forcing to work with...thus will include higher
pops at that time.
Sunday through Tuesday...
Dry weather will be expected as the GFS and ECMWF show broad
ridging in place aloft across the plains with some lee side
subsidence over the Ohio Valley. This results in a broad high
pressure system slowly pushing across our region through the early
part of the work week. Thus will trend toward partly cloudy days and
night and not veer far from the NBM on temps.
Tuesday Night Through Wednesday Night...
Another round of precip looks possible for the middle of the next
work week. The GFS and ECMWF once again show the development of a
broad upper trough settling across the plains states. This once
again results in southwest flow in place across Indiana and the Ohio
valley...allowing ample moisture and embedded short waves within the
flow to provide forcing. Lower levels depict a cold front
approaching Indiana and pushing across the state on Wednesday
Night. Thus have included higher pops in this window. With expected
rain will trend lows warmer and high cooler than NBM.
Thursday...
Dry weather should return at this time as high pressure is expected
to build across the area from the plains in the wake of the front.
Once again strong Ridging builds across the northern
plains...allowing subsidence to build across the Great Lakes and
Ohio Valley.
&&
.Aviation...(06Z TAF Issuance)
Issued at 1144 PM EDT Thu Mar 25 2021
IMPACTS:
- Gusts over 35 knots and up to 50 knots through 10z-13z.
- Wind direction SW and W.
- MVFR and occasional IFR ceilings through 21z or so and then VFR.
- Showers ending 08z-10z.
DISCUSSION: Strong low pressure system will move lift out northeast
from northern Indiana to the eastern Great Lakes ovenight. Windy
conditons overnight and dropping off sharply after 12z as the system
moves away. The showers will be ending overnight as well from
southwest to northeast.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until 9 AM EDT Friday for INZ021-029>031-
036>042-045>049-053>057-062>065-070>072.
Wind Advisory until 9 AM EDT Friday for INZ028-035-043-044-051-
052-060-061-067>069.
&&
$$
Update...MK
Short Term...JAS
Long Term...Puma
Aviation...MK
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1135 PM EDT Thu Mar 25 2021
.UPDATE...
Issued at 1135 PM EDT THU MAR 25 2021
The forecast package was updated to include the tornado watch for
the southwest parts of the CWA through 2 am. The wind shear aloft
remains sky high some instability has been advected into that
area where the individual cells are now capable of being organized.
A broken lines of strong to severe storms is preceding the cold
front now pushing through central Kentucky. QLCS conditions and
the environment support the tornado threat for the watch area
until the synoptic boundary races east into the more stable and
worked over air over further east in the JKL CWA. Added and
adjusted the severe threat in the grids as well as including the
latest obs and trends for the T/Td grids. These updates have been
sent to the NDFD and web servers along with the issuance of the
WCN, HWO, ZFP, and SAF.
UPDATE Issued at 820 PM EDT THU MAR 25 2021
23z sfc analysis shows a fairly deep area of low pressure moving
through western Kentucky with its warm front now north of most of
the JKL CWA putting the area in the warm sector. The latest batch
of pcpn associated with the warm front is lifting out but not
before stabilizing the air mass, if only briefly. The strong wind
shear remains in place aloft and will be available to help
sustain any stronger storms that manage to redevelop, but
instability will need to mostly advect in ahead of the system`s
cold front to give us a good shot at seeing some severe weather.
We will be under the gun until the front moves through after
midnight, though, so near term model and radar trends will be key
for any potential warnings or statements this evening and early
overnight. The updraft helicity swaths from the HRRR does suggest
a window from 10 pm to just past midnight with that front when
the storms could be strongest moving through the CWA. Otherwise,
gradient synoptic winds will be strong enough to break off tree
limbs or blow some poorly anchored ones down through the overnight
- with the Wind Advisory addressing this threat even outside of
stronger storms. Otherwise, temperatures are generally in the low
to mid 60s while dewpoints range from the mid 50s northeast to the
low 60s west under cloudy skies. Winds are still south to
southeast at 10 to 20 mph with gusts pushing 30 mph for most. Have
updated the forecast to time the best storm chances through the
next 6 hours or so and also to add in the latest obs and trends.
These updates have been sent to the NDFD and web servers with an
update to the ZFP to be issued shortly.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 510 PM EDT THU MAR 25 2021
Late this afternoon, a shortwave trough was approaching the mid MS
and Lower OH valley region with a gradually deepening sfc low
approaching the confluence of the OH and MS Rivers at this time.
The shortwave trough will track across the OH Valley this evening
and into the overnight reaching the Great Lakes late tonight
before moving across the northeast and into the Canadian maritimes
Friday to Friday night. The sfc low will continue to deepen and
take this same path, sending a cold front east across the
Commonwealth through this evening into the early portions of the
overnight hours. Height rises and a mid and upper level ridge will
shift across East KY and the Appalachian region for Friday into
Friday night. Meanwhile, sfc high pressure will shift across the
area, settling across the central Appalachians on Friday night.
Locally winds have been southeast to south southeast behind the
initial area of showers that affected East KY this morning into
the afternoon. The early day showers and clouds have limited
heating. Dewpoints are currently in the upper 50s to low 60s
across the region, although some low to mid 50s are occurring
nearer to the VA border where the downslope affects area bit
stronger at present. Dewpoints are higher in the low to mid 60s
across portions of east TN into middle TN and western and central
KY. Convection has been developing over middle TN and portions of
East TN over the past couple of hours with the strongest storms at
present in the Nashville TN vicinity and nearing the Cookeville
TN area.
As the sfc low tracks northwest of the area and a warm front lifts
toward the southwestern portions of the area this evening, the
convection now south of the area will move into the Lake
Cumberland/Cumberland Valley area, likely before sunset. A
discrete cell or two is is possible with this activity, but
instability is limited with north and northeastward extent. Some
increase in instability is expected in advance of the approaching
cold front and some filtered sunshine has been occurring across
the far south and southwest. The severe threat across the region
still appears to be somewhat conditional on instability as shear
will not be an issue. After any initial activity before sunset, a
line or broken line along or in advance of the cold front should
affect the area late this evening and reach the WV border an hour
or two after midnight. With such strong wind fields aloft, 850 mb
winds likely in the 60 to 70KT range if not briefly higher, this
activity could translate higher momentum to the surface. Wind
fields likely diminish toward dawn on Friday.
The primary threat with any pre sunset activity or activity near
or along the cold front still appears to be strong wind gusts.
Shear is substantial so in the area where instability is expected
to be greatest west and south of eastern KY, chances for
tornados will be highest. The threat does appear to extend into
locations from near Mount Vernon to Middlesboro and west where
limited instability is expected to extend north. Thus, a couple of
isolated tornados cannot be ruled out.
Also, outside of any thunderstorm activity, some of the higher
momentum should be mixed to the sfc at times with gusts of 35 to
45 mph possible. These gusts could be locally higher across the
west and north as well as the highest elevations along the VA
border. Thus a Wind Advisory has been issued through 8 AM on
Friday as well.
The Friday into Friday night period will be dry with high pressure
dominating. Eastern valleys should drop off well into the 40s on
Friday night.
.LONG TERM...(Saturday through Thursday)
Issued at 350 PM EDT THU MAR 25 2021
The extended period continues to look active, with multiple
weather systems forecast to move through the region this weekend
and parts of next week. The first batch of active weather is
slated to occur Saturday through Sunday, as a large trough of low
pressure aloft makes its way across the northern CONUS. A southern
stream system will combine its energy with a northern stream low,
both of which are forecast to move across the Great Lakes and
lower Tennessee valley regions Saturday through Sunday. The latest
model data is suggesting that there will be enough lift, moisture,
and instability to not only produce thunderstorms Saturday and
Saturday evening, but that enough ingredients may be in place to
create a few strong to marginally severe storms. That being said,
a couple of storms Saturday afternoon and early Saturday evening
could produce strong gusty winds. As the surface cold front with
the northern stream system moves through the area Saturday night
and Sunday, we will likely see widespread rain showers continue
around eastern Kentucky. Any storms should come to an end by late
Saturday evening. The last bit of rain should move out of the area
early Sunday evening. Clear skies and light winds, along with
ample surface moisture, will set the stage for frost formation
late Sunday night into early Monday morning, especially in our
deeper and normally colder valley locations. High pressure will
keep the weather nice otherwise through the end of the day on
Monday.
Another area of low pressure may bring a few rain showers to
eastern Kentucky late Monday night and Tuesday. Another weather
system on the heels of the Tuesday system is progged to move
through the region Wednesday evening through Thursday. The front
associated with the third system may spark a few thunderstorms
late Wednesday afternoon and early Wednesday evening. This third
batch of rain will likely persist through Thursday.
Temperatures in the extended should generally be above normal,
with daily highs most days topping out in the upper 60s to low
70s. Nightly lows, with the exception of Sunday night, should be
above normal as well. Lows by Monday morning may fall into the low
to mid 30s, coldest in the valleys, which will set the stage for
frost formation.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
ISSUED AT 745 PM EDT THU MAR 25 2021
Lead area of pcpn associated with the approaching system is
lifting through eastern Kentucky ATTM with mainly just some
showers and weak thunderstorms. Winds are roaring aloft and some
these have been able to come to the sfc with these showers as
evident by the 35kt gust at JKL this past hour. Later, look for a
line or broken line of convection moving into the aviation
forecast area along or just ahead of a cold front generally during
the 02 to 05z timeframe. Some ongoing MVFR restrictions in
departing showers should improve to VFR for a couple of hours.
However, additional restrictions back into the MVFR or even IFR
range are possible, at least briefly within convection that occurs
after 02z. Some of the storms could be strong to severe with wind
gusts in excess of 50 kts possible locally. Chances for severe
thunderstorms are greatest along and west of I-75 including the
KSME and KLOZ sites.
Otherwise, winds will increase through 03z out of the south to
southwest into the 10 to 20 kts range with gusts as high as 40
kts possible. These strong winds will gradually diminish from 10
to 15z as the front departs. Likewise, look for MVFR CIGS to
start to lift back to VFR in the afternoon on Friday - generally
from west to east.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 8 AM EDT Friday for KYZ044-050>052-058>060-
068-069-079-080-083>088-104-106>120.
&&
$$
UPDATE...GREIF
SHORT TERM...JP
LONG TERM...AR
AVIATION...JP/GREIF
Area Forecast Discussion
National Weather Service Melbourne FL
927 PM EDT Thu Mar 25 2021
.DISCUSSION...
Mild and humid conditions will continue, with temps only falling
as low as the mid to upper 60s late tonight (potentially not
falling below the 70 degree mark for coastal locations south of
the Cape) as a light southerly flow persists across the region.
Despite the persistence of hi-res model guidance wanting to
generate a few showers from the sea breeze collision over the
interior this evening, subsidence from ridge aloft and overall dry
airmass will keep rain chances out of the forecast. Some fog
development may be possible late tonight toward daybreak Friday,
but HRRR and MOS guidance not showing much in the way of lower
visibilities overnight. This may be due to an increase in low
level southerly flow off the surface. Stratus development may be
more likely, however, increasing cloud cover for portions of the
area late.
&&
.AVIATION...Mostly VFR. Can`t completely rule out some stratus and
patchy fog development late tonight through early Friday morning,
producing tempo IFR/MVFR conditions roughly between 09-13Z.
However, confidence wasn`t high enough to include in the TAFs at
this time. Should any fog/stratus develop, it will quickly lift
and burn off after sunrise.
&&
.MARINE...South to southeast winds around 10-15 knots will
continue across the waters into tonight, with seas around 3-4
feet.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 65 88 66 84 / 0 0 10 0
MCO 68 92 67 90 / 10 0 10 0
MLB 69 87 68 83 / 10 0 10 0
VRB 66 87 66 82 / 10 0 10 0
LEE 67 91 68 91 / 0 0 10 0
SFB 68 91 67 90 / 10 0 10 0
ORL 68 92 69 90 / 10 0 10 0
FPR 66 88 66 83 / 10 0 10 0
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Weitlich/Sedlock
Area Forecast Discussion
National Weather Service Marquette MI
735 PM EDT Thu Mar 25 2021
.SHORT TERM...(This evening through Friday)
Issued at 405 PM EDT THU MAR 25 2021
WV Imagery and RAP analysis indicated a broad mid/upper level trough
over the west into the central CONUS and a ridge off the east coast
resulting in sw flow through the Great Lakes. A vigorous shrtwv into
sw Missouri was lifting to the northeast with mainly just high
clouds spreading into Upper Michigan. At the surface, high pressure
extended from Hudson Bay into the northern Great Lakes bringing
colder air into the area on northerly winds. The shallow cold air
moving in across Lake Superior also supported extensive low clouds
across Upper Michigan into northern WI along with an occasional light
flurry or two.
Tonight, expect any pcpn from the southern stream shrtwv and sfc low
to remain well to the south. However, with a slightly tighter
pressure gradient and winds veering to the northeast will also
strengthen. 3k ft temps around -10C will provide just enough
instability for flurries or light snow showers for north central
Upper Michigan, favored by upslope flow. Even though the temp
profile will also be marginal for ice nuclei, expect even limited
convective clouds and drier sub cloud layer will continue to
favor mainly snow rather than any freezing drizzle.
Friday, surface and mid level ridging building into the area with
drier air and diminishing winds moving in from the west will bring an
end to any light -shsn chances. Otherwise, even with some clearing
in the afternoon from the west, temps will remain below average with
readings in the low to mid 30s north to the low 40s south.
.LONG TERM...(Friday night through Thursday)
Issued at 423 PM EDT THU MAR 25 2021
A deepening surface low is expected to produce widespread light rain
changing to light snow this weekend. The next feature of note is a
seasonably strong cold front expected to move through late
Tuesday/early Wednesday.
Clouds increase early Saturday morning as a shortwave trough
transports moisture into the area. A northern-stream shortwave
approaches the area late on Saturday bringing a noticeably colder
air mass with it. Precipitation spreads over the area from southwest
to northeast during the day on Saturday associated with warm air
advection forcing broad isentropic lift across the area. Differences
in modeled surface low track/intensity results in uncertainty in
precipitation types, but the big picture favors rain transitioning
to snow as the temperature profile cools. It appears most QPF falls
in the warm air advection regime of this system with only light lake
enhanced precipitation within the systems decaying deformation zone.
Deterministic guidance shows potential for mesoscale banding
associated with substantial 850-700 mb frontogenesis. However, I
feel it`s too early to get cute with placement of banding features
and decided to lower storm total QPF amounts to around 1/3" across
the CWA. P-type issues, relatively warm surface temperatures, and
daytime precipitation onset are all working against snow
accumulations with less than 2 inches expected across the CWA.
Snow ends from west-to-east on Sunday as the system pulls away from
our CWA resulting in a temperature roller coaster next week. Cooler
temperatures and blusterly northwest winds within a broad area of
cold air advection will make Sunday feel chilly. However, the cooler
weather will be short-lived as a <50 knot southwesterly LLJ
overspreads the area on Monday and intensifies to >55 knots Monday
night. As a result, temperatures are expected to rise into the 50s
on Monday and could breach 60F across the interior west on Tuesday.
A cold front is expected to moves across the CWA Tuesday night
bringing a much cooler air mass into the area for mid to late next
week. Precipitation chances ramp up near the cold front, but amounts
appear light and p-type should be predominantly rain. 12Z
operational and ensemble guidance favors 850 mb temperatures falling
to near or below -15C by Wednesday morning, which should be cold
enough for light lake effect snow accumulations in NW wind snow
belts. Once again, cooler temperatures will be short-lived as long-
range CIPS analogs indicate a return to warmer and drier than
normal conditions for the first week of April.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 734 PM EDT THU MAR 25 2021
N to NE flow of cold air across Lake Superior will upslope into
Upper MI, supporting persistent MVFR cigs at KIWD/KCMX/KSAW for most
of this fcst period. Late Fri aftn/early evening, expect these lower
clouds to scatter out as drier air makes inroads with approaching
high pres.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 405 PM EDT THU MAR 25 2021
Northeast winds below 20 knots will increase again to 25-30 kts
across much of the lake tonight as a strong low passes by well to
the south. Winds will subside below 20 kts again Friday morning. The
next period of strong winds will be on Sunday over the east half
when gales will be possible with a shot of cold air. Freezing spray
may also develop. The active weather period will continue from
Monday into Tuesday as wind gusts of 25-30 kts persist through that
timeframe.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...EK
AVIATION...Rolfson
MARINE...JLB
Area Forecast Discussion
National Weather Service Nashville TN
833 PM CDT Thu Mar 25 2021
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Updated suite of forecast products to reflect issuance of Tornado
Watch 54 through 1 AM CDT Friday. Blended latest NAMNest,
CONSShort, and HRRR models per best initialization and evolution
of main line of showers and thunderstorms moving across mid state
region during these early to mid evening hours. Tweaked hourly
temperature, dewpoint, and wind speed/direction grids. Remainder
of forecast continues to be on track.
&&
.AVIATION...
00Z TAF DISCUSSION.
CKV/BNA/MQY/CSV...Several admendments probable for rounds of
shwrs/tstms across mid state region thru 26/04Z. Generally VFR
ceilings and vsbys expected thru 26/24Z. With continuing
uncertainty of tstms moving across terminals, continue to mention
vcnty tstm at terminals thru 26/04Z. With strong low level jet
dynamics in place, wind shear at top of 2 Kft layer 45-55kts.
During relatively same time frame, surface wind gusts to around
30kts possible. Initial sustained southerly winds 7-12kts will
veer to west thru 26/24Z. Convection should end across mid state
region by no later than 26/06Z. Surface pressure gradient
influences should weaken by around 26/10Z.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 1 AM CDT Friday for Bedford-Cannon-
Cheatham-Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson-
Fentress-Giles-Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence-
Lewis-Macon-Marshall-Maury-Montgomery-Overton-Perry-Pickett-
Putnam-Robertson-Rutherford-Smith-Stewart-Sumner-Trousdale-Van
Buren-Warren-Wayne-White-Williamson-Wilson.
Wind Advisory until 4 AM CDT Friday for Bedford-Cannon-Cheatham-
Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson-Fentress-Giles-
Grundy-Hickman-Houston-Humphreys-Jackson-Lawrence-Lewis-Macon-
Marshall-Maury-Montgomery-Overton-Perry-Pickett-Putnam-Robertson-
Rutherford-Smith-Stewart-Sumner-Trousdale-Van Buren-Warren-Wayne-
White-Williamson-Wilson.
&&
$$
DISCUSSION......JB Wright
AVIATION........JB Wright
Area Forecast Discussion
National Weather Service Pocatello ID
822 PM MDT Thu Mar 25 2021
.SHORT TERM...THIS AFTERNOON THROUGH SATURDAY NIGHT. A quick update
this evening to decrease the chance of precipitation across the
Island Park region to reduce forecast issues with Great Falls. Other
than that, the upper low remains overhead and supportive of ongoing
showers tonight. See the previous discussion below. Huston
Widespread areas of light rain and snow continue early this
afternoon across the CWA. High-res model reflectivity guidance
suggests the activity will become a bit more convective/showery as
the low pressure center embedded in this latest shortwave moves
overhead tracking SE. We discussed whether thunder would be needed
in the forecast this afternoon/eve...however, NAMNest LIs struggle
to reach -1 and HREF mean MUCAPE remains below 100 J/kg with
widespread cloud cover favored to continue (almost no instability),
so even if we squeak out a brief heavier snowfall/rainfall rate
under a core and/or a few lightning strikes, potential looks quite
marginal/isolated at best and will leave thunder out. Highway grip
levels are really doing well as temps have creeped up today (and
snow has changed to rain as expected in the ern Magic Valley/lower
Snake Plain), so plan is to let the ongoing SPS expire as scheduled
at 3 PM. Some slick spots could certainly redevelop this eve as
temps cool and snow showers continue, especially across mntn zones
and over passes, but overall impacts shouldn`t be significant. As
always, we will monitor everything closely.
This evening (7 PM to 4 AM window from north to south), wind
evolution across the srn central mntns into the Snake Plain does
look favorable for some potential convergence-zone snowfall
development, and there`s MAYBE a hint of this on the HRRR, but
otherwise guidance isn`t excited about it at all. We broadbrushed
some additional PoPs/light QPF into the forecast over this region to
cover this just in case, with snowfall amounts generally 1/2 inch or
less if development occurs, but confidence is low. We also allowed
some patchy fog in the grids tonight for some valleys...the HRRR cig
product/MOS guidance aren`t terribly excited about fog, but given
plenty of sfc moisture and recent precip, could easily see isolated
pockets. Otherwise, generally ran with NBM guidance for all
parameters with few edits. A few light snow showers may linger Fri
in the Bear Lake region and WY border corridor, but otherwise expect
a clearing trend over the course of the day. GORGEOUS weather
follows for Sat with plenty of sunshine and highs rising into the
mid 40s to upper 50s (and it only gets better for Sun with highs
approaching 70 for Burley and Shoshone!). - KSmith
.LONG TERM...SUNDAY THROUGH NEXT THURSDAY...
Gorgeous weather will be short-lived. A vigorous, fast-moving
cold front is headed our way on Monday. Deterministic models
remain in good agreement with the progression of the system with
onset of precipitation in the 06Z- 12Z timeframe in the Central
Mountains. Passing through southeast Idaho at about 35 mph, the
front exits the state around 18Z Monday. Thus there should be
little snow accumulation and valley rain. Best snowfall amounts
are in the Central Mountains with about 3 to 6 inches accumulation
on Monday. The main impact will be winds starting Sunday night.
Have boosted forecast winds to a blend of MEX and the NBM 90th
percentile. Winds at 700mb still in the 50 to 60 kt range ahead of
the front, dropping off to 40 to 45 kts behind it. Temperatures
Monday will be noticeably cooler by 15 to 20 degrees across the
region thanks to the front-- also thanks to Sunday highs being
well above normal! Broad ridging will build back into the region
through Thursday as temps warm throughout the week. - Hinsberger
&&
.AVIATION...
Snow remains the predominant precip type at TAF issuance, but
temperatures rising herald the changeover to rain or at least a
mix soon. Widespread cloud cover is varying between VFR and MVFR
with visibility mainly VFR, though IFR visibility is observed at
KIDA at 18Z. What`s concerning is the 1/4SM visibility observed at
KJER, just outside our border. Convective trends seen in the
high-res models support the potential for heavier showers and
possibly an isolated thunderstorm. SPC guidance extends the
thunderstorm threat into the vicinity of KBYI this afternoon.
Some high-res models also show the possibility of a snow band
developing late afternoon/early evening between KIDA and KPIH.
- Hinsberger
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
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visit...
http://weather.gov/saltlakecity/general/afd_faqs.php