Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/28/21
Area Forecast Discussion
National Weather Service La Crosse WI
1037 PM CDT Sat Mar 27 2021
.SHORT TERM...(This evening through Sunday)
Issued at 235 PM CDT Sat Mar 27 2021
Incoming trough from the west will bring continued shower chances
into the evening, with the highest chances near and north of I-90
where mid-level frontogenesis will be strongest. As the trough
pushes through, northwest winds will become quite gusty in cold air
advection, with some gusts of 20 to 30 mph possible this evening
given around 25 kts to mix down and steep lapse rates per model
soundings. Falling temperatures may cause rain to change over to
snow showers in Clark/Taylor counties late this evening.
Accumulations look light, but WPC 90th percentile is up to a little
over an inch at Medford, so a few slick roads are possible.
Lingering precipitation should push east of the area by shortly
after midnight, with clearing skies and lows in the 20s and low 30s.
The RAP does suggest low-level saturation and clouds could linger
until morning, however, so will have to keep an eye on clearing
Surface and upper level ridging build in for Sunday, bringing a
drier and sunnier day to the area. While the pressure gradient
relaxes as the day goes on, steep low-level lapse rates should allow
a fair amount of mixing and could keep some gusts in the 20-25 mph
range into the afternoon, especially east of the Mississippi River.
This could lead to elevated fire weather conditions, as discussed in
the fire weather section of the AFD. Although the day looks sunny,
cold air aloft will likely hold highs down into the 40s.
.LONG TERM...(Sunday night through Saturday)
Issued at 235 PM CDT Sat Mar 27 2021
Sunday Night into Monday...Warm advection returns later in the
day Sunday and really maximizes in the morning hours Monday as
southwest winds increase in a strong pressure gradient ahead of an
approaching cold front from the northwest. 850 mb temperatures
increase 15-17C from Sunday to Monday afternoon for a big warm up.
This strong warm advection aloft will cap the mixing extent on
Monday somewhat, but consensus in a well-agreed upon synoptic
regime, still mixes to about 850 mb. This is troublesome with
model consensus 50-55kt speeds at 850mb by later Monday
afternoon. It looks like a Wind Advisory will be needed for most
of the area ahead of the cold front into early evening. These
winds have implications for fire spread, which is handled below
in the fire weather discussion section.
Monday night through Wednesday...The polar cold front then
blasts through on Monday night with cold advection in earnest
Tuesday, with a reinforcing arctic front shifting through
Wednesday. Some precipitation/showers may be on the cold front and
have chances of rain Monday night. Have lowered temperatures for
these days with 40s and 30s expected on Tuesday and Wednesday,
respectively. Afternoon gusts in the 20 to 30 mph range will make
these days, especially Wednesday, feel quite cool.
Thursday through Saturday...offer large scale ridge building and a
slow warming with 70F possible for Saturday!
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1033 PM CDT Sat Mar 27 2021
A band of light precipitation precipitation will continue to push
out of the area early in the TAF period. KRST and KLSE have MVFR
ceilings, however these should improve to VFR fairly quickly early
this morning. Northwest winds 10 to 20kts with gusts 20 to 30kts
this morning. The winds will remain brisk Sunday, decreasing
to under 12Kts by late in the afternoon.
Issued at 235 PM CDT Sat Mar 27 2021
Sunday: Steep lapse rates will allow for afternoon deep mixing
which will likely allow dry air and gusty winds from aloft to mix
down. Have trended below the NBM for dewpoints during the
afternoon, especially in the favored areas of central Wisconsin,
where minimum relative humidities could approach 25-30 percent. In
fact, with mixing to around 850 mb possible, dewpoints could be
even lower than forecast area-wide which would lead to RHs
approaching 25-30 percent over a wider area. Combined with wind
gusts of around 20 to 25 mph, this will lead to elevated fire
weather conditions, although recent rain should help with slightly
less dry vegetation.
Monday certainly called for additional analysis as winds are
expected to be in the 20 to 30 mph sustained range with gusts
40-50 mph possible. Deeper mixing in the afternoon, in
combination with increasing winds, presents some favorable
conditions for fire spread. Consensus in the model guidance
suggests this southerly flow will bring some moisture return with
it Monday, lifting relative humidities into the 30s percent. With
warm air increasing aloft, mixing depths should be somewhat
capped providing a bit of a floor to lower dewpoints and RH
dropping due to mixing. Even though high temperatures will reach
the 60s, a min RH of 25% or less for critical fire spread
conditions/and a Fire Weather Watch/ seems to be a low probability
event for Monday at this time. However, this forecast did take a
baby step toward critical conditions. Thus, elevated /but not
critical/ fire spread weather is still expected.
Tuesday and Wednesday will be much cooler with high temperatures in
the 40s and 30s respectively. Afternoon winds will be gusty again
(25 to 30 mph), and RH values will need to be monitored and are
currently forecast in the 25-35 percent range.
Area Forecast Discussion
National Weather Service Columbia SC
810 PM EDT Sat Mar 27 2021
A weak stationary front will remain over the northern Midlands
tonight. A strong cold front brings a chance for thunderstorms
Sunday. Following cooler temperatures and ridging Monday,
another chance of rain moves in Tuesday and later in the week.
.NEAR TERM /THROUGH SUNDAY/...
A surface boundary from convection has sagged into the northern
Midlands this evening. This will stall out overnight, then move
back north as a weak front towards morning. There remains some
showers and isolated storms, both across portions of NC, the
upstate of SC, and eastern Ga. This should slowly diminish with
the loss of heating, and the severe threat is minimal with this
activity. Later tonight, a weak shortwave will push into the
area which may generate some additional showers or possibly
elevated thunderstorms, especially in the western forecast area
around or shortly after midnight. Any lingering convection
should dissipate by sunrise. Lows remain mild, in the mid 60s.
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Sunday and Sunday night...Active weather is expected as a deep
upper trough moves eastward through the Ohio Valley as a surface
low lifts northeastward into southeast Canada. This will push a
cold front across the Appalachians during the afternoon hours,
eventually crossing the forecast area Sunday evening. Ahead of
the front, the forecast area will be well within the warm sector
starting off the day very mild in the mid to upper 60s. Strong
southwesterly flow is expected to result in deep mixing through
the early afternoon prior to the arrival of the cold front and
associated convection which should support high temperatures
well into the 80s across most of the forecast area with upper
80s in the southeastern Midlands and lower CSRA. Depending on
how fast clouds and precipitation arrive into the western
Midlands it could impact the highs there which may be closer to
the lower to mid 80s.
Wind field will be increasing with the approach of the upper
trough and cold front and the deep mixing should also result in
windy conditions at the surface with winds 15 to 25 mph common
with gusts over 30 mph. Will issue a lake wind advisory for
winds of 15 to 25 knots with gusts to 30-35 knots.
There continues to be a threat of severe weather with SPC
outlooking the area in a slight risk for severe storms with
damaging winds as the primary threat, and to a lesser extent
large hail. The pre-storm environment will feature strong shear
in excess of 50 knots which will support organized storms along
the cold front. While temperatures will be quite warm the deep
mixing will actually limit the instability a bit with forecast
MLCAPE values less than 500 J/kg and SBCAPE values around
500-750 J/kg. Despite the limited instability the strong shear
and expected cold pool dominated convection along the front
should be enough to bring the threat into our area. The bulk of
the upper forcing will be off to the north so the northern and
western Midlands are the areas most likely to experience severe
winds with a lower threat to the south and east, but not ruling
it out there. Latest hi-res guidance shows general agreement on
timing with the NSSL WRF, ARW, NMM all bringing a line of
convection into the western Midlands around 20z while the HRRR
is faster by a couple of hours bringing it into the western
Midlands by 18z. Expect the line of storms to continue to push
eastward through the region and exiting the forecast area during
the 00z-03z time frame. Increased pops to likely across the
region with the passage as measurable rainfall seems likely.
The front will shift east of the region overnight with cold
advection supporting overnight lows about 20 degrees colder than
tonight ranging from the lower to mid 40s west to upper 40s
Monday and Monday night...High pressure will continue to build
over the area with generally zonal westerly 500mb flow aloft.
This should provide a relief from some of the 80 degree days of
late as 850mb temps will be around +4C to +6C yielding high
temperatures ranging through the mid and upper 60s, despite
plenty of sunshine. A weak upper disturbance along the western
Gulf Coast region will lift northeastward into the southeastern
states Monday night with some increasing clouds overnight. Think
there may be too much dry air to overcome to result in any
measurable precipitation through 12z Tuesday but ensemble
guidance suggesting it is not out of the question so will carry
some low pops to account for that. Overnight lows will be
limited by increasing clouds and expect lows in the mid 40s
north to around 50 south.
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Extended forecast features active weather early in the period
followed by a significant cool down late in the week into the
weekend. A weak upper disturbance will cross the area on Tuesday
in advance of a digging upper trough over the middle of the
country. Deep southwesterly mid level flow will persist over the
region through Wednesday night until the upper trough swings
through the region. In the lower level southeasterly to
southerly flow will provide continued moisture transport into
the region which will keep chances of rain in the forecast.
While thunderstorms are possible the chances of severe weather
look limited at this time given marginal instability, despite
strong wind fields Wednesday afternoon and Wednesday night.
There is some uncertainty about possible wedge conditions
developing on Tuesday as the surface high shifts east into the
Atlantic but temperatures will be dependent on how strong it may
be. Temperatures should warm well back into the 70s on Wednesday
ahead of an approaching cold front that will push through late
Wednesday night. Much cooler, below normal temperatures
expected Thursday and Friday with possible frost/freeze
concerns both nights. Some air mass modification should result
in warmer temperatures on Saturday.
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
VFR expected overnight, MVFR possible with afternoon
thunderstorms tomorrow towards the end of the TAF period.
Warm southwest flow is established across the forecast area
beneath a stationary front draped across the Piedmont and ahead
of an approaching cold front dropping out of the Appalachians
towards the end of the forecast period. Upper level trough will
cross from west to east between 03-10Z with enough instability
to spark isolated showers...VCSH reflected in TAFs. Tempo MVFR
is possible, but confidence not high enough to include. Other
then that, instability and a decent pressure gradient will keep
winds between 5-8 knots, so we do not expect any MVFR-IFR
visibility restrictions in mist/fog. Pressure gradient on Sunday
ahead of the approaching front will strengthen, with
southwesterly gusts 20-25 kts expected after 14-15Z. Convective
tools indicate high potential for thunder, and VCTS indicated in
TAFs as a strong cold front approaches 20-21Z, passing through
between 29/00-02Z. Timing and severity will be refined in the
next few TAF cycles.
EXTENDED AVIATION OUTLOOK...Cooler high pressure building in
will result in no restrictions Monday through Tuesday. Onshore
flow and another approaching frontal system will result in
aviation weather restrictions Wednesday into Thursday.
Heavy rainfall in the Upper Savannah, Broad, Catawba and Pee
Dee Basins over the past 24 hours is moving southward into area
rivers. Flooding is occurring on Midland and Pee Dee rivers.
For the latest river flood warnings, see our web page at
GA...Lake Wind Advisory from 11 AM Sunday to 5 AM EDT Monday for
SC...Lake Wind Advisory from 11 AM Sunday to 5 AM EDT Monday for
Area Forecast Discussion
National Weather Service Glasgow MT
929 PM MDT Sat Mar 27 2021
Minimal changes to the forecast. With fire weather concerns due to
low relative humidity and gusty winds, the relative humidity was
nudged slightly down by blending with the HRRR for Sunday. Winds
begin to ramp up Sunday and stay up through Monday. Wind gusts
during this timeframe were also nudged up. The Red Flag Warning
and the High Wind Watch are still expected. Roxy
After the dense freezing fog from this morning lifted and burned
off, temperatures warmed back up into the mid 40s to lower 50s.
The stage seems to be set for some differently impactful weather
conditions over the next 2 to 3 days.
Sunday, a ridge of high pressure from the west and southwest will
bring some suddenly warm temperatures and dry humidity to the
area. The pressure gradient is tightly packed and some pretty
gusty winds are expect to accompany that ridge. Current Red Flag
Warning seems well in hand. More discussion below.
On Monday, a strong cold front, packed with unusually gusty winds
is expected to move through the region, beginning early Monday
morning. The expected snow shower activity accompanying this cold
front could easily enhance the wind gusts. A little uncertainty
remains with extensive cloud cover, so we felt it was best to lead
out with a High Wind Watch for now, which could be upgraded or
cancelled based on the latest model information coming up tonight
and tomorrow. The cold front looks to be quite pronounced. Some
snow showers with accumulations up to half and inch are possible.
Lingering cold and breezy conditions are expected through Tuesday.
From Wednesday afternoon onward, a more stead ridge of warm, high
pressure settles into the region.
FLIGHT CONDITIONS: VFR
LLWS: Possible this morning before winds begin ramping up after
DISCUSSION: High clouds and generally dry weather expected. Windy
conditions are expected over the next couple days. Cloud cover
begins to increase Sunday night.
WINDS: Light and variable tonight, then from the south and
southwest on Sunday morning up to 15 kts. Expect west winds by
mid day up to 30 kts at times lasting through the afternoon.
Warm and dry conditions are expected on Sunday along with
increasing west winds. The combination of low relative humidity,
as low as 12 percent, and gusty winds up to 45 mph, will lead to
high fire danger from early Sunday morning through at least the
early Monday evening. Any fire starts will spread rapidly toward
the east in these conditions.
Strong winds are expected at times Sunday night into Monday as
well, but the fire danger should begin to subside as cooler
temperatures, increased cloud cover, and rain and snow showers
enter into the region.
Red Flag Warning from 9 AM to 8 PM MDT Sunday for
High Wind Watch from late Sunday night through Monday evening
for Central and Southeast Phillips...Central and Southern
McCone...Northern Phillips...Northern Valley...Petroleum...
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1046 PM EDT Sat Mar 27 2021
A strong cold front will cross Tennessee tonight then cross
our area around midday to early afternoon Sunday. This front will
be preceded by another round of thunderstorms. Behind the front,
temperatures will return to normal as high pressure builds in for
Monday. More unsettled weather looks to be in store for the region
by the middle of the week as another strong cold front reaches our
region from the northwest.
.NEAR TERM /THROUGH SUNDAY/...
As of 1030 pm: Isolated to widely scattered convection continues to
fire in the vicinity of an outflow boundary across the Lakelands and
upper Savannah River Valley region. However, the combination of
relatively stable outflow air and nocturnal cooling has shoved much
of the appreciable surface-based instability southwest of the
forecast area, and convection has therefore become increasingly
benign, with even lightning becoming increasingly difficult to come
by. Meanwhile, scattered to numerous convective coverage continues
across middle and east Tennessee, but with the exception of a
right-move that fell apart across the TN mtns, this activity has
been consistently streaming northwest west of the Appalachians. As
such, while isolated to widely scattered convection may initiate off
and on throughout the night across out forecast area, coverage
should remain relatively muted and intensity quite benign until the
cold front sweeps in from the west after sunrise. Considering the
continued poor antecedent hydro conditions across esp the NC mtns,
can`t completely rule out a localized hydro problem overnight if
cells are able to train over the same area, but even those concerns
should largely hold off until ~late Sunday morning.
In term of the cold front and anticipated accompanying convective
band, some timing discrepancies are noted in the hires models with
the HRRR abt 3 hrs ahead of the 4km NAM. This would make a big
difference as to available sbCAPE, but for now, believe the
pre-storm environment will feature sbCAPE values on the order of
800-1200 J/kg. Shear levels will also begin to increase and the
timing of the strongest shear still looks to be a little quicker
than the best destabilization, but enuf overlap is anticipated for a
line of stg/svr organized storms beginning before noon and
traversing east thru the afternoon. The main threats will be
damaging winds and large hail, however, a few tornadoes are not out
of the question as well with right turning hodos noted in the model
soundings while a llvl jet increases. There could be another
convective watch issued by the SPC for tomorrow afternoon.
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 230 PM EDT Saturday: High pressure will begin to build into
the area Sunday leading to more tranquil conditions through Monday
night. Moisture will begin to return to the area by Tuesday as the
high moves of the east coast and return flow sets up. Highs both
Monday and Tuesday will be in the 60s in the Piedmont and mountain
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 230 pm EDT Saturday: A broad trof will dig into the middle of
the country for the middle of the week, shifting into the
northeastern states by late week. Expect showers and some
thunderstorms for our area Wednesday and Wednesday night. A cold
front will move through bringing much cooler conditions into the
area on Thursday and Friday.
Temperatures at or below freezing appear possible Friday morning
across the forecast area. Since the frost/freeze program will begin
again on April 1 for northeast Georgia, the SC foothills and
Piedmont and the southern NC foothills and Piedmont, headlines may
be needed Friday morning.
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Convective coverage has diminished this
evening to just a couple of isolated cells near KGMU/KGSP. Once this
activity clears those two terminals, additional development
overnight doesn`t appear likely, especially in light of the cooler/
relatively stable air that has overspread the Terminal Forecast Area
in the wake of this afternoon`s convection. Nevertheless, chances
are sufficient to include a VCSH for much of the overnight at all
terminals. Confidence is low regarding cig/visby trends overnight,
as cool/relatively stable air mass gradually becomes displaced by
one with higher surface dewpoints. Confidence is relatively high in
low cigs...IFR or worse developing near KHKY, but confidence
decreases farther south, and will generally feature MVFR conditions
developing at the other sites. Shower/tstorm chances increase again
from late Sunday morning into the afternoon, warranting at least
Prob30s for TSRA at the terminals.
Winds will generally remain light NE at most locales this evening,
but gradually return to the SW late tonight. Winds will increase to
10 to 15 kts by late Sunday morning, with gusts as high as 30 kts
possible during the afternoon.
Outlook: VFR conds return Mon with a couple more moist systems and
flight restrictions possibly affecting the region as early as Tue.
02-08Z 08-14Z 14-20Z 20-00Z
KCLT High 100% Med 79% High 100% High 100%
KGSP High 100% High 84% Med 79% High 98%
KAVL High 92% High 100% High 98% High 97%
KHKY High 100% High 82% Med 70% High 82%
KGMU High 100% High 87% Med 75% High 98%
KAND High 100% High 100% Med 69% High 90%
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:
NC...Flash Flood Watch through Sunday evening for NCZ033-048>053-
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1115 PM EDT Sat Mar 27 2021
Issued at 1115 PM EDT SAT MAR 27 2021
The heavy rain has been slow to lift out of Tennessee all evening,
but now appears to be making a more believable push north into
eastern Kentucky. Given the increasing moisture convergence ahead
of the approaching cold front and jet dynamics there is concern
for flash flooding in the watch area and especially for locations
nearer the Tennessee border. The IR sat loop shows a continuing
mass of cooling cloud tops in north central Tennessee that seems
to now be edging north. The window for this excessive rain threat
is primarily from midnight through 8 am before the front will
progressively send the heavier rains east of the area. Have
updated the QPF and PoPs for the rest of the night with another 2+
inches anticipated along the Tennessee border and in places that
saw soaking rains earlier in the day. Advisories and warnings
will become increasingly likely over the next few hours for these
location. These updated grids have been sent to the NDFD and web
UPDATE Issued at 745 PM EDT SAT MAR 27 2021
23z sfc analysis shows low pressure approaching from the west
with a boundary lifting into eastern Kentucky. So far the stronger
storms have been having trouble crossing the Kentucky border and
sustaining themselves. Expect that to be the case for the next
hour or so, but see better prospects later this evening as the low
moves in. The latest HRRR run, among other CAMs, support this
idea, as well. Have drawn the updated PoPs with that in mind. The
southern parts of the area remain under the gun for heavy rain
with the northern areas likely seeing more progressive bouts of
convection after midnight. Will keep a close eye out for our
southern counties in the watch for flood issues through the
evening as the training potential is highest there. Otherwise,
temperatures are generally in the upper 50s to lower 60s with
dewpoints well into the mid and upper 50s across the area.
Meanwhile, winds are generally from the south at 5 to 10 mph.
Also, applied the latest obs and trends into the T/Td grids with
this update. These grids have been sent to the NDFD and web
servers along with a freshening of the ZFP and SAFs.
.SHORT TERM...(This evening through Sunday night)
Issued at 435 PM EDT SAT MAR 27 2021
Late this afternoon, an upper level ridge was centered in the
vicinity of Cuba and extends northeast into the Atlantic and
southwest toward the Yucatan while another ridge was centered over
the eastern Pacific. In between an upper level ridge axis extended
from the Hudson Bay region into the northern Plains/upper midwest
to the southern Rockies/Plains. At the surface, a nearly stationary
frontal zone was south of the region extending from the mid south
region across the TN Valley to the Carolinas. Meanwhile, a sfc low
was moving into the MS Valley in the eastern IA vicinity with a
cold front trailing south and southwest to the southern Plains. A
secondary cold front extended into the upper midwest to northern
Plains. Cloud cover from earlier convection has limited solar
insolation across the area, especially central to southern
sections with convection largely occurring south of the area
closer to the nearly stalled boundary. Some showers are still
moving across the southern counties, however.
Tonight, the upper level shortwave trough will approach the area
tonight, while the sfc low track across the Great Lakes and the
trailing cold front nears eastern KY. The cold front should move
east of the area on Sunday morning while the secondary front
should work across the area Sunday afternoon along with the
shortwave trough axis. Height rises will follow to end the period
on Monday night.
PW will increase this evening into tonight into the 1.25 to 1.5
inch range in advance of the cold front. Warm advection/isentropic
lift should bring an increase in shower activity from southwest to
northeast as the evening progresses with the convection lingering
overnight ahead of the cold front. MUCAPE is progged to increase
to 500 J/kg to perhaps as much as 750 J/kg during the evening
while bulk shear is expected to be on the order of 50KT or so. At
the same time, mid level lapse rates may near or exceed 7C/km as
well for a time during the evening. This scenario should lead to
generally elevated storms, especially across the southwest portion
of the area, with heavy rain rates and the risk for hail,
possibly near the quarter size mark. Strong wind gusts cannot be
ruled out. Wind gusts appear more probable with prefrontal
convection late tonight to perhaps early on Sunday in the far
southeast. Locally heavy rain appears to be a higher threat for
this during the overnight or predawn hours. With heavy rain having
fallen across the flood watch area from Pulaski to Letcher county
earlier today, soils there are saturated or nearing saturation.
Tonight into Sunday, an additional 1 to 2 inches is expected on
average generally south of the Mountain Parkway with the higher
amounts in the watch area. Most of it should fall tonight. Locally
higher amounts near 3 inches cannot be ruled out in the watch
area. The most recent trends and guidance continue to support the
current areal extent of the Flood Watch.
The coverage of showers should diminish on Sunday morning as the
front departs, but a couple of additional showers cannot be ruled
out in the afternoon until the shortwave trough and secondary
boundary move across the area. Depending on how much rain falls
tonight into early Sunday, rises on creeks and area rivers to
bankfull or into flood in some instances may occur on Sunday.
Portions of the Cumberland or Kentucky Rivers may run high
through Sunday night.
Otherwise, high pressure will usher a drier and colder airmass
into the region behind the front. Temperatures should fall well
into the 30s if not upper 20s in some cases with frost likely
developing in many areas.
.LONG TERM...(Monday through Saturday)
Issued at 310 PM EDT SAT MAR 27 2021
The primary forecast issue in the extended will much colder
temperatures and the potential for frost. In fact, we will likely
see several nights and early mornings when widespread frost occurs
around eastern Kentucky. The nights with best frost potential will
be Sunday night, Thursday night, and Friday night. On each of
those night, colder air will be filtering into the area behind
departed, strong areas of low pressure, and those systems surface
cold fronts. The coldest spots will be our normally colder
valleys. A few of our eastern valleys may even see some frost
We will see a chance of rain and thunderstorms from Tuesday night
through Thursday evening. Enough cold air will make its way into
the area late Wednesday night. Little or no snow accumulation is
expected with this. Once the precip comes to an end early Thursday
morning, we should see an extended period of dry weather across
The coldest nights will see lows plummeting into the 20s and lower
30s. The other nights should see closer to normal values in the
mid 30s to upper 40s. Daily highs will range from the lower 40s to
the lower 50s Thursday and Friday. The warmest day will be
Tuesday, when highs may reach the upper 60s and lower 70s. The
other days of the week will have max temperatures ranging from the
mid 50s to the lower 60s.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 820 PM EDT SAT MAR 27 2021
Additional showers/thunderstorms will develop more northeastward
across the region later this evening, bringing times of MVFR and
IFR conditions, particularly after 06z. Mainly MVFR conditions
should then prevail after 09z near and after the boundary passes.
Winds are expected to be south to southwest mainly in the 5 to
10 kt range through 06z, with some higher gusts possible in
thunderstorms. Winds become more southwesterly between 06 and 12z
- increasing to near 10 kts, before becoming west to northwest
Sunday morning. Gusts up to 20 kts are possible Sunday afternoon.
Additionally, winds aloft will increase ahead of the front this
evening and a threat of LLWS will exist from now into mid morning
Flood Watch through Sunday evening for KYZ079-080-083>088-113-
Area Forecast Discussion
National Weather Service Louisville KY
1038 PM EDT Sat Mar 27 2021
...Updated Mesoscale Discussion...
Issued at 1035 PM EDT Sat Mar 27 2021
The convection along the cold front in MO/IL/IN has had some surges
and fluctuations in strength, but over the last 30 minutes or so,
regional radars have shown signs of cores weakening aloft across
most of the line in IL/MO. High-res guidance implies that this line
should steadily weaken as it approaches from the west, but we may
see additional cellular convection fire off ahead of it. Overall
environment is quite strong with shear though very limited with
instability, but there may be enough CAPE to support some strong to
isolated severe storms as it pushes through. Think the strong/severe
storm threat with that line will be mainly confined to southern IN
and northern KY as convective debris with storms across TN/AR will
likely negatively impact mid-level lapse rates for ongoing
showers/storms in southern IL and eastern MO.
Meanwhile, the convection to our south will begin moving into
southern KY here shortly. The 00z sounding from OHX revealed quite a
bit of stable air in the lowest ~5kft, and recent high-res CAMs
suggest that we won`t see much air mass recovery across northern TN
and southern KY for much of the overnight hours. As a result, think
our wind/tornado severe chances across southern KY have diminished
quite a bit, and unless we see a big surge of warmer air and
dewpoints ahead of developing convection it seems unlikely it would
become surface based. The bigger concern with convection overnight
across southern KY will be flash flooding. Still appears that areas
within the flash flood watch will see one to three inches of rain
with locally higher amounts. The KY mesonet shows our southern tier
of KY counties within the flash flood watch have already seen a half
inch to nearly an inch of rain so far today. 1/3hr FFG across
portions of Lake Cumberland are in the 1.5-2" range, so if the
forecast amounts verify, we are likely to have some flooding issues
early tomorrow morning.
Issued at 655 PM EDT Sat Mar 27 2021
Monitoring two areas of convection at this hour that will have
impacts for the overnight period. The first is along an old
stationary front/outflow boundary that stretches from northeastern TX
into northern TN. The second is along a cold front currently
stretching from central IL into southeastern OK.
Showers and storms along the stationary front/outflow boundary have
already drifted into southern KY at this hour. A quick look at the
environment/mesoanalysis reveals that instability is at a relative
minimum along and east of I-65, while it increases steadily as you
head west. This is largely due in part to weaker mid level lapse
rates from clouds/convective debris earlier in the day that drifted
into central/eastern Kentucky. Storms that have also pushed east of
the I-65 corridor in southern Kentucky have also tended to weaken
and fall apart, which makes sense given the lack of `fuel` storms
have to work with to the east.
Over the next several hours, we will see showers and storms increase
in coverage as they fire off along the stationary front/outflow
boundary to our south. Latest high-res model runs have shown a
slight northern trend with the heaviest QPF axis, and now have it
crossing into portions of south-central and eastern Kentucky. The
flash flood watch was expanded earlier in the day to account for
this potential, and so far looks good. Will monitor for any westward
expansion if trends continue, though think it`s current placement
will handle the bulk of things.
The severe weather threat remains complicated overnight. As the cold
front approaches from the west, we could see instability slightly
increase across the region as a +50kt LLJ noses into western and
central Kentucky and increases low level moisture/Td`s. But, it`s
possible that convection to our south in TN/AR/AL could disrupt some
of that moisture transport northward and hamper storms currently
along the cold front. Some of the latest HRRR runs show this
scenario playing out with the convection along the cold front
weakening as it pushes into southern IN and central KY due to very
weak instability. Perhaps a more concerning signal to watch will be
near the Lake Cumberland region, where an organized cluster or line
of storms coming out of TN with access to limited instability but a
lot of shear could result in a low-end wind and tornado threat.
In summary, think the best chances for flooding and severe weather
will be across southern KY tonight into early tomorrow morning,
though portions of central KY and southern IN could see some
isolated strong to severe storms as well. Most activity looks to
push east of the region by sunrise.
.Short Term...(This evening through Sunday)
Issued at 250 PM EDT Sat Mar 27 2021
...Slight Risk for Severe Storms Tonight...
Low pressure is analyzed over eastern Iowa this afternoon, and a
warm front remains draped across the Tennessee Valley. Persistent,
moderate isentropic lift and moisture transport across this boundary
has fueled numerous showers and storms across TN today. The
persistent convection has produced 0.50-1.00 inches of rain across
southern KY, including some areas with relatively low FFG (<2" in 3
hours). Given the arrival of record PW values tonight and the
likelihood of additional convection, will expand the Flash Flood
The sprawling convection across TN certainly seems to be impeding
destabilization to the north over central KY. Occasional
precipitation, plenty of clouds, and rain-cooled outflow pushing
north will likely continue to affect the northward extent of
appreciable CAPE this afternoon and evening. HRRR and other hi-res
models keep convection to a minimum over central KY through sunset.
Tonight, a positively-tiled upper level trough swings over the Upper
Midwest and mid-Mississippi Valley. This finally helps induce a
stronger low-level response by 06-12z Sunday with sfc cyclogenesis
over Michigan. The southwesterly LLJ steadily increases in intensity
this evening and overnight ahead of the approaching trough.
Currently have 30 kts at 850 mb over Mississippi and southwest TN,
but values of 40-50 kts will develop over the area by 03-06z
Between 00-03z this evening, the best chance for scattered storms is
in southern KY within the warm conveyor belt. Around and after
midnight, convection will increase in coverage as the cold front
begins to approach from the west. A narrow plume of MLCAPE >= 500
J/kg seems probable ahead of the cold front, but the degree of
destabilization remains the biggest limiting factor in the overall
severe threat. A high shear, low CAPE environment will likely emerge
ahead of a quasi-linear convective system with damaging winds as the
primary threat. There is also a risk for QLCS tornadoes, which are
typically very quick to develop and as quick to dissipate. The main
time frame of concern is roughly 11 pm - 6 am EDT, but instability
may already be nil by 6 pm (depending on prior development and
evolution upstream). Still like the Slight Risk from SPC, and it`s
more of a Marginal threat from Lexington northward in the Bluegrass
region where moisture return and destabilization are both weaker.
Showers continue over the eastern forecast area Sunday morning, with
dry conditions expected area-wide in the afternoon. Sunday looks
windy and cool with temperatures generally in the 50s.
.Long Term...(Sunday night through Saturday)
Issued at 235 PM EDT Sat Mar 27 2021
To start the extended period, expect to find upper level trough
exiting off to the east as upper level ridging moves across the
central CONUS. At the surface, area of high pressure will drift
across the OH Valley Monday and move just off the East Coast by
Tuesday morning. Mostly dry weather will prevail Monday and most of
Tuesday. High temperatures on Monday will remain in the upper 50s to
lower 60s and then warm into the upper 60s and lower 70s for Tuesday
as we move into deeper southerly flow on the backside of the high.
By Tuesday evening, a large upper trough will be progressing across
the central CONUS with an associated surface low rotating northward
into the Hudson Bay. Expect trailing N-S oriented cold front to push
through the OH Valley Tuesday night into Wednesday, bringing
increasing chances for precipitation. Compared to tonight`s system,
the influx of moisture ahead of the front Tuesday night is expected
to be weaker, with PWATs currently progged to top out in the 1.0 -
1.2 inch range. GEFS and EPS members suggest QPF values ranging from
T - 1.0 inch across the area with mean values in the 0.2 - 0.4 inch
range which corresponds well with WPC QPF.
In the wake of the cold front, surface high pressure will build in
from the northwest and dominate our weather through the end of the
work week. WPC Cluster Analysis shows good agreement between models
on this with all four clusters suggesting dry conditions for
Thursday and Friday. Temperatures will remain cooler on Thursday
under steady northerly flow and CAA, with highs topping out in the
40s. Additionally, low temperatures Thursday and Friday morning are
forecast to drop into the 20s and may see some frost. Temperatures
will then gradually moderate into the weekend with highs reaching
into the 60s again by Saturday.
.Aviation...(00Z TAF Issuance)
Issued at 658 PM EDT Sat Mar 27 2021
A cold front will move through the region overnight, and
showers/storms are expected to form ahead of it. Cigs/Vis will
likely drop into the MVFR range with isolated instances of LIFR/IFR
in heavier showers/storms. Gusty, variable winds are also possible
within the vicinity of thunderstorms. The precipitation should push
east of the region after sunrise, but MVFR cigs will persist into
the early afternoon hours before finally beginning to lift and break
KY...Flash Flood Watch through Sunday morning for KYZ073>078-081-082.
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
856 PM CDT Sat Mar 27 2021
855 PM CDT
Any strong thunderstorm potential in the southern forecast area
has now ended. A cold front is moving eastward through the CWA,
with the front positioned not far east of I-39 as of 830 PM. Ahead
of this front remains showers in the southeast CWA within broad
upper-mid level forcing for ascent (95 kt 500 mb jet), an 850-700
mb zone of moisture transport, and low-level confluence. Isolated
lightning remains possible until 10 or 11 PM south of the
Kankakee River Valley but dwindling fast as the steeper lapse
rates disappear with the moistening. There also have been
scattered showers immediately ahead of the front, but these cores
have been small and are diminishing in coverage.
The true cold advection push lags the cold front some and is just
arriving over the Mississippi River. As this expands eastward,
winds will become more northwesterly and increase in speed. Still
forecasting gusts of 30 to 35 mph late tonight through early to
mid afternoon Sunday.
232 PM CDT
Through Sunday night...
No substantial changes to the short term thinking here, with a
limited risk for a few strong-severe storms developing into the
late afternoon and early-evening hours mainly for our locales both
south of I-80 and generally east of I-55.
Temperatures have managed to claw their way into the mid and upper
60s across much of the forecast area, sans areas near the lake
across northeast Illinois where persistent onshore winds have held
temperatures in the upper 40s/near 50--typically conditions for
this time of year with a sharpening warm front. Somewhat increased
low-level moisture continues to steadily advance north and
eastward, although the localized 60 degree dewpoints advertised by
the recent RAP seem a bit overcooked given upstream observations.
Either way, the highest theta-e values look to be contained to the
aforementioned areas, and this is where we`ll continue to monitor
trends as convection is expected to slowly intensify through the
rest of the afternoon. The special 18z ILX sounding remains pretty
unimpressive from a thermodynamic perspective, indicating a large
degree of lingering inhibition to surface-based parcels, although
this will continue to change with the poleward transport of
marginally increased near-surface moisture. Latest 1-minute GOES
visible satellite imagery shows clumping/congested cumulus
developing into Ford County along and subtle axis of enhanced
surface convergence, with an additional corridor stretching back
along a Farmington to Quincy line. These are the two corridors
we`ll be monitoring for gradual shower/storm intensification
through 4-5 pm.
Impressive kinematics in place, with effective deep layer shear
values approaching 55-60 kts may promote the development of some
beefier updrafts with time later this afternoon, and given the
fast flow in place (and deep shear vectors more-or-less aligned
with the convergence axes), some fast-moving bowing
segments/clusters capable of producing some sporadic wind damage
are possible. Latest guidance suggests things remaining too
disorganized for much of a QLCS tornado threat, although one can`t
ever be totally discounted in scenarios with non-zero low-level
instability given the impressive low-level shear in place.
Convective chances will quickly diminish later this evening with
the arrival of a cold front.
Main story for later tonight and Sunday will be the strong and
gusty northwesterly winds. Deep mixing in the cold advective
regime will promote momentum transfer up to possibly 5-6 kft
tomorrow, which looks good to transport some 35-40 mph gusts to
the surface. Main question with the wind magnitudes for tomorrow
is how pervasive stratus remains, but did nudge our wind gusts up
a bit with this forecast. Look for cooler conditions on Sunday,
with high temperatures generally in the upper 40s and lower 50s.
156 PM CDT
Monday through Saturday...
As an upper-level ridge builds into the Great Lakes on Monday, a
quintessential spring-like southwest to northeast-oriented pressure
gradient will develop across the central United States. Such will
allow for decidedly breezy southwest winds to develop and gust 30-35
mph Monday afternoon. Northwest of a line from Mendota to McHenry,
gusts in the 35 to 45 mph range appear likely which may down
twigs/small tree limbs and blow around trash cans. High temperatures
Monday are also poised to jump back into the 60s. Considering the
breezy winds, warm temperatures, and cured fine fuels (though
admittedly the grass outside our window is just starting to green
up), outdoor burning is discouraged on Monday.
Tuesday, a cold front will swing through the Great Lakes dropping
temperatures and flopping winds toward the northwest. Precipitation
chances (in the form of scattered showers) along the front look best
generally along and southeast of I-55 based on the timing of the
front and potential for a short-wavelength trough to sneak in
from the southwest. With 850 mb temperatures poised to fall below
-10 C, the effects of the front will be felt Wednesday and
especially Thursday when highs struggle to climb into the 40s. In
fact, the ECMWF ensemble depicts a 70% chance highs on Thursday
don`t get above 40 across northeastern Illinois! Thursday night
also looks chilly with overnight lows in the low to mid 20s. While
somewhat unwelcome, the cool down will not be unprecedented with
daily records at both Chicago and Rockford looking quite safe.
Warming temperatures are then expected from Friday onward as a
ridge builds into the Great Lakes. In fact, highs in the upper 60s
to lower 70s are not out of question by the weekend!
For the 00Z TAFs...
632 PM...Forecast concerns include...
Chance of showers this evening.
Mvfr cigs later this evening through late Sunday morning.
Strong/gusty northwest winds overnight and Sunday.
There is still a chance of showers across the Chicago area
terminals this evening but the bulk of the rain is expected to
stay south of the terminals with thunderstorms staying well south
of the terminals. There is a small chance of rain showers early
Sunday morning through daybreak. Confidence is rather low both for
coverage and location, though northeast IL and northwest IN would
be the favored areas.
Mvfr cigs are expected to develop/spread back across the area
later this evening and continue overnight into Sunday morning.
There is some potential for cigs to drop into low mvfr, especially
across northwest IL. Thus only medium confidence for specific
cigs. Mvfr cigs will slowly lift Sunday morning and scatter out
from west to east in the afternoon.
Generally southwest winds are expected early this evening, turning
more westerly by mid evening. There is a lake breeze boundary that
has become generally stationary just north of ord. Its possible
that this boundary may sag south toward ord if any showers were to
develop north of it, helping push it south. Confidence is very low
and opted to carry prevailing southwest winds at ord for now. A
cold front will move across the area late this evening/early
Sunday morning, shifting winds to the northwest. Speeds/gusts will
increase behind this cold front with gusts into the 30kt range
through late Sunday morning. Speeds/gusts will diminish slowly
Sunday afternoon then rapidly with sunset Sunday evening. cms
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742...4 AM Sunday to 7
Small Craft Advisory...LMZ743-LMZ744-LMZ745...4 AM Sunday to 10
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Area Forecast Discussion
National Weather Service Marquette MI
745 PM EDT Sat Mar 27 2021
.SHORT TERM...(This evening through Sunday)
Issued at 428 PM EDT SAT MAR 27 2021
WV imagery and RAP analysis indicated a mid/upper level trough from
Manitoba through the Northern Plains resulting in sw flow through
the western Great Lakes. A shortwave trough was moving through
southeast SD. At the surface, an inverted trough extended to the
west end of Lake Superior from low pressure over eastern IA. An area
of rain over northern WI was supported by WAA and isentropic ascent
ahead of the low while another area of snow/rain from northeast MN
through nw WI into southern MN was associated with 850-700 mb
deformation/fgen ahead of the mid level trough. Temps ranged from
the mid 40 west to the mid 30s central where lower clouds supported
by moist southerly flow have been more persistent.
Models suggest that the bulk of the northern WI rain will move off
to the east northeast. However, the fgen band and area of pcpn to
the west will slide through Upper Michigan tonight. Leftover warm
air will cool quickly with the onset of the pcpn with a changeover
to snow during the evening. Models consensus of overall pcpn
amounts in the 0.25-0.50 inch range seemed reasonable. 850 mb
temps to around -7C during the period of strongest lift will be
marginal for lake enhancement but with increasing upslope
northerly flow developing snowfall amount in some higher terrain
locations to around 4 inches may be possible. Since there is some
uncertainty with how quickly the change to snow will occur and how
efficiently snow will accumulate will temps are in the low to mid
30s, an SPS was issued highlighting potential for mainly 1 to 3
inch amounts over most of the north.
Strong drying will spead quickly across the area from west to east
Sunday bringing an end to the snow early over the west and by late
morning or early afternoon from the central into the east. Forecast
momentum transer with the CAA suggest that nnw winds will gust into
the 30-35 mph range central with some higher gusts to 40 mph also
possible, especially near Lake Superior. Highs temps will also only
in the low 30s north and upper 30s south.
.LONG TERM...(Sunday night through Saturday)
Issued at 339 PM EDT SAT MAR 27 2021
The area will be under a progressive pattern with up and down
temperatures though mid week. Ridging on Monday giving way to a cold
front and trough before we start to transition to a blocking pattern
with weak ridging developing over the central U.S. Get out and enjoy
the unseasonably warm temperatures on Monday as Tuesday and Wednesday
look much colder. Once we get past the mid-week cool down we`ll
start a warming trend into next weekend.
As our Sunday system departs to the east another trough will begin
to deepen along the lee side of the Rockies in northern Alberta and
eject into the Canadian prairies. While this low is expected to track
well to the north of the area strong southerly flow will develop on
Monday ahead of the approaching surface trough and cold front. This
will lead to an unseasonable warm day with high temperatures 20
degrees above average in the west, not quite as warm out east with
southerly flow cooling as it travels up the length of Lake Michigan.
A strong southerly 50-60kt low level jet will develop Monday into
Monday night. The strongest winds will be out east and the NBM seems
to be doing a good job picking up on these, a few knots stronger
than the raw model blends. Went with a blend of the NBM and NBM 90th
percentile for winds. Wind gusts should get to around 30 knots by
Monday evening and possibly higher. The cold front will move though
Tuesday cooling the low and mid levels with good mixing behind the
front. This could lead to a windy day, particularly in the west,
with the potential for 40+ knot gusts. Didn`t go that high with the
forecast yet but something that should be watched.
As far as precipitation it looks like light precipitation should
accompany the front as it passes though the area on Tuesday,
starting as rain and mixing with or briefly changing to snow before
ending as the band traverses the area. Most of the precipitation
should exit the area by Tuesday night. Strong CAA will result in
850mb temps falling down to near -20C by Wednesday afternoon,
however, drier air looks like it will inhibit LES with inverted-v
Temps will warm back into the 30s for Thursday, however westerly
winds continuing to bring dry air into the area could bring humidity
down to around 20% in the west in the afternoon.
Looking further out into late next week we could be headed into a
warmer stretch up here in the U.P though it could be a slow
transition with the area on the downstream side of a building ridge
initially. NCEP Ensemble clusters all represent a blocking pattern
strengthening over the Atlantic with strong positive height
anomalies over the mid-Atlantic, extending north into Greenland. A
bit of a slower response with ridging over the central U.S but
positive height anomalies begin to build over several days starting
late in the week. Looking at the dprog/dt the CMC members were
clustered in more of a zonal pattern a few days ago but have trended
towards the blocking solution suggested by the EC and GEFS on the
most recent run.
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 745 PM EDT SAT MAR 27 2021
Low pres moving across the western Great Lakes will bring -sn and
mostly IFR conditions to KIWD/KCMX/KSAW tonight. However, at KCMX,
pcpn will begin as -ra along with VFR conditions, but pcpn will
switch to -sn over the next few hrs with conditions falling to IFR.
Some periods of LIFR are possible at all of the terminals tonight.
On the backside of the system, gusty nw winds will develop. At KIWD,
gusts to around 20kt are expected overnight thru Sun morning. At
KSAW/KCMX nnw winds should gust to 30-35kt, perhaps up to 40kt at
times, late tonight/Sun morning. As the system departs, -sn will end
late tonight at KIWD, Sun morning at KCMX and late morning/early
aftn at KSAW. Conditions will improve to MVFR as the snow ends, and
some periods of VFR will be possible during the day Sun.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 428 PM EDT SAT MAR 27 2021
Stronger winds arrive late tonight into Sunday over central and
eastern Lake Superior when gale force gusts to 35-40 knots are
expected with colder air moving in. The active weather period will
continue from Monday into Wednesday night as wind gusts of around 30
knots persist through that timeframe over the lake. There could be a
few gale force gusts to 35 knots over north central Lake Superior on
Gale Warning from 9 AM to 8 PM EDT Sunday for LSZ251-267.
Gale Warning from 5 AM to 6 PM EDT Sunday for LSZ266.
Gale Warning from 4 AM to 2 PM EDT Sunday for LSZ264-265.
Gale Warning from 5 AM to 5 PM EDT Sunday for LSZ249-250.
Gale Warning from 5 AM to 2 PM EDT Sunday for LSZ248.
Gale Warning from 5 AM to 1 PM EDT Sunday for LSZ243>245.
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
927 PM EDT Sat Mar 27 2021
The late afternoon and evening has been steady and busy. Flooding
remains the biggest threat, however, a few storms have produced
some large hail in some areas. The latest HRRR and RAP are in good
agreement on timing with the next round of strong storms. That
appears to be between 5 AM ET to 11 AM...moving from west to east
fairly rapidly. We expect strong winds, potentially damaging winds
along the edge of the stronger storms. On top of that will be the
additional heavy rainfall contributing to additional flooding.
No major changes to the ongoing forecast were needed.
A lull in convection for TAF sites will persist for the next few
hours. There may be a few showers pass over an airfield but
believe the biggest threat will be early in the morning when a
line of strong thunderstorms moves through the region. Some wind
gusts may exceed current TAF forecast. Timing confidence is medium
to high when strongest storms move through. After 12z tomorrow
confidence lowers on prevailing conditions but should be MVFR/VFR
especially after 18Z.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 60 68 40 65 46 / 80 90 10 0 10
Knoxville McGhee Tyson Airport, TN 57 67 37 62 41 / 80 90 10 0 10
Oak Ridge, TN 56 67 36 62 41 / 80 90 10 0 10
Tri Cities Airport, TN 56 66 34 61 38 / 80 90 20 0 10
NC...Flash Flood Watch through Sunday evening for Cherokee-Clay.
TN...Flash Flood Watch through Sunday evening for Anderson-Bledsoe-
Blount Smoky Mountains-Bradley-Campbell-Claiborne-Cocke
Smoky Mountains-East Polk-Grainger-Hamblen-Hamilton-Hancock-
Morgan-North Sevier-Northwest Blount-Northwest Carter-
Northwest Cocke-Northwest Greene-Northwest Monroe-Rhea-
Roane-Scott-Sequatchie-Sevier Smoky Mountains-Southeast
Carter-Southeast Greene-Southeast Monroe-Sullivan-Unicoi-
Wind Advisory from 2 AM to 2 PM EDT Sunday for Blount Smoky
Mountains-Cocke Smoky Mountains-Johnson-Sevier Smoky
Mountains-Southeast Carter-Southeast Greene-Southeast
VA...Flash Flood Watch through Sunday evening for Lee-Russell-Scott-