Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/10/21
Area Forecast Discussion
National Weather Service Boston/Norton MA
1008 PM EDT Fri Apr 9 2021
High pressure centered just east and south of New England,
continues to move slowly southeastward and offshore tonight
into Saturday. This will allow for mainly dry weather and result
in quite mild temperatures away from the coasts.Weakening low
pressure passing to our south will result in a turn to much
cooler temperatures on Sunday along with a period of rain at
least across interior Southern New England. Cooler afternoons
are on tap for much of next week with onshore flow and
considerable cloudiness at times.
.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
1000 PM Update:
Regional radar mosaic shows a narrow NNW to SSE oriented line of
really light showers across eastern NY into western/southwestern
CT. These showers continue to fizzle with eastward approach
given drier air in place over Southern New England. Will
continue to see mainly mid-level clouds overspread as the night
The exception is along the South Coast, Cape Cod and the
Islands. Stratus has advanced from Block Island, Rhode Island
Sound and Buzzards Bay landward per nighttime microphysics RGB
imagery. In addition, temperatures in the low 40s near dewpoints
has permitted areas of fog along these same areas. Have
increased sky cover a little sooner than prior indications,
using a blend of the 01z HRRR time- lagged ensemble and the 12z
HREF which best captures cloud cover trends the best. RAP-based
fcst soundings at EWB, HYA and OQU indicate shallow RH remains
locked in, which reinforces the idea that low clouds and fog
stand to persist for the balance of the overnight across these
areas. Stratus may advance as far north as HFD, IJD, PVD, TAN
and PYM. Temps project the coolest in these areas in the low to
mid 40s. Milder lows in the upper 40s to low/mid 50s should be
more common away from the South Coast and Cape Cod, with mid
clouds allowing for tempered cooling.
Previous forecast is on track. High pressure offshore coupled
with cooling boundary layer, light southerly flow and dewpoints
in the 40s will result in another round of low clouds and fog
developing on the south coast, Cape and Islands. Latest
satellite imagery and observations already showing this
occurring in Newport. So while low clouds and fog, some of which
may be dense will overspread the south coast, Cape and Island
over the next several hours it should not get much further north
than that. South to southwest low level flow should be enough to
keep it confined to mainly that region overnight.
Otherwise, mid and high level cloudiness will impact the rest of
the region. While dry weather will be the main story overnight,
we can not rule out a few brief spot shower or two across
western MA and CT. While upper level ridging is in control,
there will be a shortwave shearing out will approach from the
west. Subsidence should keep us mainly dry, but enough
elevated instability may result in a spot shower or two in this
As for temperatures, they currently ranged from the 40s on the
south coast to the 60s across much of western and northern MA.
We should see most locations bottom out in the 40s by daybreak
with the current large temperature spread diminishing.
.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Expect to start off the morning with considerable cloudiness, due to
moisture associated with the short waves and flattening of the mid
level ridge, and surface high center moving further SE from our
area, placing us in return flow allowing for south coastal stratus.
However mid level ridging builds back into our area to some degree,
and as short wave moves out expect to see decreasing clouds and
skies becoming partly to mostly sunny. Exception should be along the
immediate south coasts of RI/MA, where marine stratus could linger
through the day due to that continued prevailing SW flow.
SW winds will also keep the south coasts of MA and RI (including
Cape/Islands) cooler. Shallower mixing and onshore SW winds (which
may gust into the 20-25 mph range) should keep highs in the mid-
upper 50s to mid 60s in that area. However, away from the south
coast, this drier/warmer trajectory will allow for warming into the
upper 60s to mid 70s. Winds at H925 may be strong enough to preclude
a sea breeze at Boston, and pending no sea breeze we would have
highs in the low 70s there.
Occluded low pressure tracks into the Great Lakes Region, while high
pressure slides further offshore. Warm front associated with the low
moves towards our area, and S/SW flow allows for increasing moisture
and hence increasing cloud cover. We could see some patchy light
rain during the overnight, but bulk of rain is expected to hold off
until Saturday. Mild overnight lows in the mid 40s to low 50s.
.LONG TERM /SUNDAY THROUGH FRIDAY/...
* Turning much cooler Sun into Sun night with some rain across
the interior, but uncertain on eastward extent
* Cool afternoons much of next week especially across eastern MA
* Need to watch offshore low pressure late next week, but
whether it can bring any appreciable rain is uncertain
Tricky forecast in regards to rainfall amounts across interior
southern New England and how much/if any appreciable rainfall
survives into eastern New England. Deep closed low over the
Great Lakes will send a piece of shortwave energy into southern
New England. However, this shortwave will shear out/weaken some
as it enters upper level ridging in place. A band of mid level
forcing and some elevated instability will survive and be
competing with some dry air/subsidence especially across eastern
Give the reasoning above we do expect a band of rain to arrive
across southwest MA and CT by late Sunday morning or afternoon.
Low level dry air coming in from the northeast will be fighting
this band of rain as it attempts to move northeast. While a bit
of rain may survive into eastern MA; any amounts will probably
be rather light. This forecast will certainly need to be fine
tuned with later guidance, but highest confidence in some
appreciable rain Sunday into Sunday night will be across
southwest MA and northern CT. The threat for appreciable
rainfall diminishes the further north and east one gets from
As for temperatures, high pressure across Canada and weakening
low pressure passing to our south will allow the passage of a
backdoor cold front by early to mid morning on Sunday. It is
possible temps get into the 60s towards the CT River Valley if
the backdoor cold front is delayed. Otherwise, temperatures will
mainly be in the 50s perhaps even the middle to upper 40s in
spots during the day Sunday.
Monday through Friday...
The main story for much of next week will feature a closed upper
level low spinning just southeast of the Canadian Maritimes with
upper level ridging to the north. The result will be an onshore
flow much of the time along with a fair amount of cloudiness,
but still expect periods of partial sunshine. Overall though
afternoon temperatures quite a bit cooler than what we have
experienced this week. High temperatures will be held mainly in
the 50s although some spots may break 60 at times particularly
towards the CT River Valley.
Much of the week will feature little if any organized rainfall
other than a few showers and perhaps some drizzle/fog at times.
However, by late next week will have to watch an offshore low
pressure system. If it can track close enough to the coast,
there could be a more of a threat for a period of widespread
rain but that remains uncertain at this time.
.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels.
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight: Moderate confidence.
VFR conditions expected for most airports away from RI and the South
Coast. Areas near the south coast as well as the Cape Cod and
ACK airports will see another round of IFR-LIFR in status and
fog developing over the next several hours. Winds becoming light from
Saturday: High confidence, except Moderate confidence south coast.
VFR most terminals. Exception is across south coastal
MA/RI/Cape/Islands, starting out at IFR/LIFR in stratus and fog,
should trend MVFR/VFR for most airports by midday. SW winds increase
to around 10 kt. Strongest sustained winds across Cape Cod with
gusts up to 20 kt.
Saturday Night: Moderate confidence.
Mainly VFR during the evening, with MVFR/IFR CIGs developing
overnight. Slight chance SHRA.
KBOS TAF...High confidence in TAF. During Sat expecting SW wind to
prevail during the day, but there is a low probability for a
brief sea breeze developing for a couple of hours during the
KBDL TAF...High confidence in TAF.
Outlook /Sunday through Wednesday/...
Sunday: MVFR/IFR conditions possible. Breezy. Chance SHRA,
Sunday Night: Mainly VFR, with local IFR possible. Breezy.
Monday through Tuesday: Mainly MVFR, with areas VFR possible.
Breezy. Slight chance SHRA.
Tuesday Night: Mainly MVFR, with areas VFR possible. Chance
Wednesday: Mainly MVFR, with areas VFR possible. Breezy. Chance
Tonight and Saturday...
Winds and seas are expected to remain below
small craft advisory levels during tonight and Saturday.
SE winds around 10 kt today will come around to S then SW late
tonight and Saturday. Some increase in SW winds is expected Saturday
with gusts to 20 kt. Seas in the 3-4 ft range on the offshore
waters, 1 to 2 ft near shore. Areas of fog re-develop tonight with
visibility locally below 1 mile, mainly along the southern
waters. Fog lingers into Saturday along the southern waters.
Saturday Night...SW winds 10-15 kts with gusts around 20 kts. Seas
mainly 2 to 4 feet, except may build to 3 to 5 feet along the outer
waters. SCA headlines may be needed. Areas of fog are possible.
Outlook /Sunday through Wednesday/...
Sunday: Low risk for Small Craft Advisory winds with gusts up
to 20 kt. Seas up to 5 ft. Chance of rain showers, patchy fog.
Local visibility 1 nm or less.
Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas. Chance of rain showers,
Monday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Local rough seas. Slight chance of rain showers.
Monday Night through Tuesday: Winds less than 25 kt. Seas up to
5 ft. Slight chance of rain showers.
Tuesday Night through Wednesday: Winds less than 25 kt. Local
rough seas. Chance of rain showers.
Area Forecast Discussion
National Weather Service State College PA
1126 PM EDT Fri Apr 9 2021
An unsettled weather pattern will plague central Pennsylvania
through the upcoming weekend, bringing more clouds than sun and
periods of showers. Temperatures will remain mild/above average
into early next week.
.NEAR TERM /THROUGH SATURDAY/...
Radar loop at 03Z shows scattered showers lifting across
Lancaster County in region of minimal elevated CAPE ahead of mid
level shortwave. Radar trends and latest HRRR suggest the
showers should clear the forecast area by 06Z.
Large scale subsidence behind the departing shortwave should
ensure an uneventful and largely precipitation-free conditions
late tonight. However, will maintain the chance of spotty
drizzle, mainly on the windward slopes, through late tonight
along and southeast of I-81, where model soundings continue to
indicate a nearly saturated 0-1km layer. Southeast flow off of
of the Atlantic should keep the entire region blanketed under
stratus overnight. The overcast skies and plenty of low level
moisture should result in only very slowly falling temperatures
tonight, with lows mostly in the lower 50s.
.SHORT TERM /SATURDAY NIGHT/...
Most places start off cloudy and damp early Saturday. The
question will be how much sunshine can break through the low
clouds. Model guidance remains most optimistic on the northern
and western fringes of the CWA, where mostly sunny skies appear
likely by midday. Across the southeast half of the forecast
area, stratus will be more persistent. However, model soundings
and latest HREF suggest partly sunny skies are likely by
mid afternoon. Based southeast flow/cold air damming signature,
will continue to undercut NBM temps in favor of the cooler
Superblend east of the mountains. Strong April sunshine should
push readings to near 70F east of the mountains and well into
the 70s across the northwest mountains.
The CAD will remain in place with only weak E/S wind picking up
a little through the day on Sat. But, the system advancing from
the west will likely not bring rain in until after sunset in the
west. Held just a low PoP for the SW before 00Z Sun. Clouds
invade/lower/thicken through the evening with 100 PoPs o/o.
Excellent moisture feed, but only for 3-6 hrs at any one
location. Some convective elements should be able to develop
since we will destabilize before the forcing arrives. But,
nighttime could turn them elevated or squash any thunder before
it gets more than 40-50mi into the CWA. QPF of 0.50-0.75" still
looks good. This should continue to help reduce the
wildfire/spread threat. RHs are expected to remain above 30pct
for the weekend and into next week.
.LONG TERM /SUNDAY THROUGH FRIDAY/...
Latest model guidance shows potential for some convection to
develop Sunday afternoon (in the wake of morning rain) over the
eastern part of the area. Sunday should be the warmest day of
the long-range period south and east of the Allegheny Front,
where highs should reach the low to mid 70s.
Expect cooler temperatures for next work-week, as upper-level
low pressure continues to slowly progress from the Great Lakes
across the northeastern United States. This will also maintain a
daily chance of showers, with the highest POPs during peak
heating of the afternoon as GEFS plumes show.
.AVIATION /03Z SATURDAY THROUGH WEDNESDAY/...
Expect the MVFR cigs to lower to IFR overnight across the region
overnight with moist SE llvl flow. Some DZ and FG is expected
late tonight, especially along the windward slopes. Some
improvement is expected during the day Saturday. Dry air from
the west will mix down thanks to mid April sun angle/heating and
most areas will see VFR conditions in the afternoon. The
exception may be KMDT and KLNS where low clouds could hang on
longer into the late afternoon.
Sun...AM IFR/SHRA east, then improvement to VFR in most
locations from west to east thru the rest of the day.
Mon-Wed...Lingering -SHRA and MVFR conds poss N; otherwise VFR.
The high temperature of 77F at Bradford on Thursday 4/8 broke
the previous record high of 76F set in 2001.
Area Forecast Discussion
National Weather Service Cheyenne WY
523 PM MDT Fri Apr 9 2021
.SHORT TERM...(This evening through Sunday night)
Issued at 320 PM MDT Fri Apr 9 2021
Current KCYS radar loop shows rain/snow showers and flurries
across the mountains and along the I-25 corridor this afternoon
which was advertised well on this morning`s HRRR 15z run. With
temperatures in the mid 30s to low 40s or higher, any snowfall is
not expected to amount to anything with brief reduction in
visibility possible into this evening.
Models show a shortwave ridge axis quickly pushing into the region
from the west on Saturday. Temperatures will rebound quickly
Saturday afternoon with highs in the 60s along/west of the I-25
corridor and upper 60s to low 70s across western Nebraska. This
warming trend will be very brief as another Pacific cold front
will be quick to follow the fast moving ridge axis. All models
show this front moving across the area midnight late Saturday
night through early Sunday morning. Morning high temperatures may
briefly nudge into the mid 50s to around 60 southeast of a
Cheyenne to Alliance line before the front moves across the
eastern plains by noon Sunday. Temperatures on Sunday will be much
colder with highs generally in the 40s northwest of a Cheyenne to
Alliance line. Expect temperatures to lower slightly in the
afternoon as the colder air moves into the region under partly to
mostly cloudy skies. Precipitation and snowfall should be minimal
since the system will be moving rapidly; plus dynamics and
moisture will be limited across the area. Best chance for snowfall
will be north of I-80 across Carbon and Albany counties, and west
of I-25 across Platte and Converse counties early Sunday. Any
precipitation should push east and diminish in intensity Sunday
afternoon. Clearing skies will result in temperatures 10 to 15
degrees below freezing Sunday night across the whole area, which
is around 10 degrees below normal for this time of the year.
.LONG TERM...(Monday through Thursday Night)
Issued at 145 PM MDT Fri Apr 9 2021
Ridging out in the Pacific will funnel shortwave energy down the
Olympic Mtns. and into OR before taping into an evolving zonal jet
stream moving east into our region behind exiting shortwave that
will pass through during the weekend. Model solutions maintain trend
from 00z group overall with development of closed upper low. Both
latest GFS and EURO maintain a slow eastward progression that as
stated in previous discussion will need to be monitored as solution
differences hopefully are reconciled between models. Overall though,
a slow eastward progression with decent moisture tap from the Gulf
of Mexico would aid in drought reduction for the region. Initial
thoughts at this time are for periods of heavy snowfall banding
particularly in the overnight with cold enough temperatures. Main
concern with the delay in movement is the increased chance and
likelihood of more WAA and warm temperature overrunning limiting
daytime snowfall amounts and restricting precipitation type to rain.
Either way, any precipitation to add to the region is welcomed.
Temperatures will remain more early springlike with daytime highs
into the middle 40s for places east of the Laramie Range and about
10-15 degrees cooler to the west. Overnight lows will be below
freezing so for avid gardeners enjoying their spring blooms, some
action will need to be taken to ensure their flowers can survive the
temps and freezing precipitation.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 521 PM MDT Fri Apr 9 2021
Wyoming TAFS...VFR. Wind gusts to 32 knots until 02Z, then to
35 knots after 15Z Saturday.
Nebraska TAFS...VFR. Wind gusts to 40 knots until 02Z.
Issued at 159 PM MDT Fri Apr 9 2021
Although fire weather concerns are pretty low overall, elevated
conditions are possible along and west of I-25 Saturday afternoon
due to low relative humidities and windy conditions. Fuels are not
critical in these areas, but there is some concern due to a
combination of the winds and low RH. Further east, the fuels are
ready across western Nebraska, but winds will be relatively light.
Minimal fire weather concerns expected through next week as more
high elevation snow and low elevation rain is possible for several
Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
853 PM CDT Fri Apr 9 2021
The dry line has stalled just west of Austin to San Antonio, with the
sea-breeze meeting up with it. The cap held and what little
convection developed earlier quickly dissipated. The cold front is
moving quickly south through west-central Texas, and will arrive into
the northern Hill Country just before midnight and into the I-35
corridor around 1-2AM. Breezy and gusty conditions will develop
behind it. There was some dust along the front in west Texas and
can`t rule out some of that reaching the northwest CWA.
.PREV DISCUSSION... /ISSUED 651 PM CDT Fri Apr 9 2021/
AVIATION (00Z TAFs)...
VFR conditions outside of any stray or isolated SHRA or TSRA that
has a low chance of developing through 02Z near and north of AUS. So
far the cap has resulted in only short-lived convection just to the
north. Due to the low probability, and radar trends, we have elected
to keep TSRA mention out of AUS TAF. Main issue are the winds. There
should be a reduction in wind speeds temporarily after sunset. Then
the cold front will move through the area between 04Z-08Z, with north
winds over the Hill Country and along and east of the I-35 corridor,
including SAT/AUS, increasing to around 15KT with gusts around 25KT.
PREV DISCUSSION... /ISSUED 544 PM CDT Fri Apr 9 2021/
The dry line is now moving into the I-35 corridor counties. Recent
aircraft soundings out of AUS show the cap has weakened, although
still there. Earlier convection that try to go up along the dry-
line just north of the CWA quickly weakened. Recent visible imagery
indicates the Cu looking better across Burnet County. There remains
a small window over the next couple of hours for isolated convective
development across the far northeast CWA, as additional low level
moisture convergence is encountered between the dry line and slightly
backed winds east of it. Should any deeper convection develop, it
has the potential to quickly go strong to severe given the CAPE and
shear parameters in place. But this is all highly conditional on the
We have expanded to Red Flag Warning another row of counties
eastward and extended through 8PM. Critical fire weather conditions
are ongoing across the Hill Country and southern Edwards Plateau,
with localized extreme fire weather conditions along the Rio Grande,
where RH values around 5% and wind gusts between 30 and 40 mph are
Wind speeds will begin to decrease temporarily after sunset.
However, a north wind shift will occur late in the evening and
overnight behind a cold front with gusty winds re-developing. A
brief period of critical fire weather conditions may re-develop
west of I-35 to the Rio Grande as this happens, before cooler
temperatures allow RH values to recover.
PREV DISCUSSION... /ISSUED 249 PM CDT Fri Apr 9 2021/
SHORT TERM (Today through Saturday Night)...
After an overcast start to the day, clouds are finally beginning to
lift for areas along and east of I-35 as a clearing line makes it`s
way over the area. Dryline that has now made it into the western
Hill Country will continue to progress eastward this afternoon. The
timing and extent of this eastward progression will have impacts for
how far east the fire weather threat will be and how high
temperatures can climb behind it. Critical fire weather will be in
place for the Hill Country, Edwards Plateau, and Rio Grande Plains
through this evening and has prompted a Red Flag Warning for these
areas through 700 PM. Potentially record setting temperatures will
occur this afternoon for western areas with Del Rio`s record of 102
for April 9th likely being matched or broken. Depending on how far
the dryline can make it, could near record high temperature for SAT
Looking at the big picture, upper level longwave troughing is in
place across much of the CONUS with a pair of upper level lows
embedded, one over the Great Lakes and the other moving across the
Central Plains today. This has led to a surface low developing in
the northern portion of the state that is currently being analyzed
to be centered over Wichita Falls. This feature will bring a front
across the region during the overnight period with a strong
northerly windshift and cooler temperatures for Saturday.
There is a substantial amount of instability in place across
northeastern zones this afternoon with SFC CAPE nearing 4500 J/kg.
Forecast soundings show a decent cap in place though across the
entire area with high resolution models suggesting this cap will
hold. The HRRR was showing a few isolated supercells initiating over
Williamson and Travis County on some early model runs this morning
but has backed off now. Current thinking is that we will remain
capped and will see little to no convective activity this afternoon.
However, if an isolated cell is able to initiate, it will likely
turn severe very quickly with large hail and damaging winds being
the main hazards. Will have to keep a close eye on high res model
and radar trends this afternoon.
Overnight, best estimate for FROPA is reaching the northern CWA by
05Z, reaching San Antonio by 07Z and exiting the CWA by 09Z. Near
seasonal temperatures for much of the area on Saturday but still
remaining above normal for southwestern zones. Upper 70s to mid 80s
for Hill Country and I-35 corridor and upper 80s to low 90s for
southwestern zones. Mostly clear skies with winds gradually becoming
northeasterly then easterly and returning to southeasterly by the
end of the short-term period.
Critical fire weather conditions are in store this afternoon and
evening across the Rio Grande plains, southern Edwards Plateau and
western Hill Country. A dryline that is currently progressing
eastward out of the Rio Grande Plains and into the Western Hill
Country has led to well above normal heat and much drier air. Breezy
west to northwest winds and very low humidities to the above
mentioned areas will continue through the afternoon. A Red Flag
Warning is in effect for the Rio Grande plains, southern Edwards
Plateau and western Hill Country until 7 PM today.
Temperatures will begin to decrease after sunset, but dry air
remains intact for areas generally west of the Interstate 35
corridor. A brief period of near critical fire weather conditions
may occur west of I-35 as a cold front brings an abrupt northerly
LONG TERM (Sunday through Thursday)...
As noted at the end of the short term southerly flow returns by
Sunday morning. Sunday will be another hot day with afternoon highs
well above normal under sunny skies. Monday will follow suite but a
surface low moving across North Texas will help drive a cold front
through the state late in the day on Monday. Forecast soundings show
decently dry air at the surface as well as a capping inversion across
the I-35 corridor. These factors may limit the overall coverage of
showers and thunderstorms, but with the front providing extra lift at
least isolated showers and storms are possible. If a storm is able to
get going, especially across the Rio Grande Plains, there could be a
wind threat associated with it.
The front stalls out somewhere between the I-10 corridor and the
coast. Upper level flow becomes generally west-south westerly thanks
to a large trough of low pressure sitting across the Mountain West
for much of next week. With the washed out front and a series of weak
disturbances, moving through the WSW flow rain chances look to stick
around through much of next week. While moisture stays pooled across
the area, surface flow will be light and northerly or easterly
through much of the week.
While rain chances are present for basically Monday through Thursday
the big question will be rainfall amounts. The 12z ECMWF came in much
drier and closer in line with the GFS that generally only shows 1/10
to 1/4 inch across the I-35 with as much as 1/2 to 3/4 of an inch
across the Rio Grande Plains. The Canadian is still the wettest of
the models with more widespread 1/2 to 1.5 inch totals by the end of
next week. With no real defined sources of good lift most areas may
only see generally light or more isolated precipitation. Will have to
monitor the trends over the weekend, but for now it does seem like a
slightly wetter pattern.
Along with the rainfall temperatures behind Monday`s front will be on
a slow decline with near normal afternoon highs by Wednesday, while
lows remain mild and above normal.
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 58 81 53 90 62 / 10 0 0 0 0
Austin Bergstrom Intl Airport 58 81 51 91 61 / 10 0 0 0 0
New Braunfels Muni Airport 60 84 53 92 61 / 10 0 0 0 0
Burnet Muni Airport 54 79 52 89 61 / 10 0 0 0 0
Del Rio Intl Airport 61 88 61 96 66 / 0 0 0 0 0
Georgetown Muni Airport 56 80 51 90 61 / 10 0 0 0 0
Hondo Muni Airport 61 87 54 94 63 / 0 0 0 0 0
San Marcos Muni Airport 58 82 51 91 60 / 10 0 0 0 0
La Grange - Fayette Regional 61 80 52 90 61 / 10 0 0 0 0
San Antonio Intl Airport 61 84 56 92 64 / - 0 0 0 0
Stinson Muni Airport 62 85 55 92 64 / - 0 0 0 0
Area Forecast Discussion
National Weather Service New Orleans LA
958 PM CDT Fri Apr 9 2021
.UPDATE...Main concern is the severe threat for tonight. So far
not much has changed in the thinking however did make some
adjustments to the current forecast. Pretty much brought all
sites up to 100% chance of rain from the I-10 corridor north.
That is the least of the issues. Severe potential is still looking
pretty strong but there are a lot of question marks still and
that is mainly to how many rounds of storms we see.
Over the last 6 hours many of the CAMs were hinting at a line of
storms trying to pop over SELA and southern MS during the late
evening hours. This apparently looked to be associated with an
old outflow boundary and increasing LL convergence. Already it
looks like a band of showers is trying to develop in this area
along I-55. Looking at WV there appears to be a very subtle
increase in lift approaching from the southwest. Whether that gets
into SELA or not is still in question but it could be the kick
needed to get that area to really pop and if it does then the
potential for severe storms capable of producing large hail and
tornadoes will increase. Why large hail well the mid level lapse
rates are expected to remain in the 7-8 C/km range through the
night while the cape is pretty high in the 0 to -20C column (thick
fat cape). The LL shear is also expected to increase over the
next few hours in response to the developing LL jet. 0-1 km
helicity in the region is already around 100-150 s2/m2 and is
expected to increase to 200 or greater, 0-3km could approach
300-350. Already have 50-60kt of 0-6km bulk shear in place and
that should remain like that until just before the main line gets
So if any storms can become rooted between 3-8z along and east of
I-55 and north of I-10 they will have the potential to produce
all modes of severe weather. This includes heavy rain,
thunderstorms are already efficient rain producers but given PWs
of 1.5" which is expected to increase and increasing divergence
aloft the efficiency will increase. They may not quite lead to
flash flooding but could obviously prime a few rivers with more
rainfall than initially expected.
Now the issue has been can storms develop in that area ahead and
so far in our region the answer has been no but that subtle
increase in lift over the northwestern Gulf may be the catalyst.
As for the line, still have some questions about it and whether it
is one or two lines. What is suppose to be the main line is already
developing in eastern OK and should continue to build down into
eastern TX over the next few hours. This line will race to the
southeast through the overnight hours. However, what about the
convection ahead of of it in northern and west-central LA. overall
that convection was suppose to continue to slide east-southeast
and eventually be overtaken by the line as it approached southwest
MS and SELA but it is already ahead of where the latest HRRR said
it would be and if this line solidifies it could cold pool and
race out ahead moving into the area between 6 and 12z with the
second now weaker line between 10-15z. Not quite ready to bite off
on that scenario yet as the southwestern portions of the line are
still struggling to solidify so still feel like we are looking at
the second line being the main squall line. Everything still
suggest a really good rear inflow jet behind the squall line which
should lead to scattered if not widespread strong to damaging
All grids and zones have been udpated and sent. /CAB/
.PREV DISCUSSION... /issued 643 PM CDT Fri Apr 9 2021/
AVIATION...00Z TAF Package...Main issues for the next few hours
will be low cigs as convection likely holds off till closer to
5/6z. Convection is the main concern this and likely the next 2
TAF packages. We should begin to see a few storms impact a few
terminals like MCB/HDC/ASD around 5/6z but the main line of storms
will move through the area from 8z-13z. Very strong winds out of
the northwest are expected with this squall line and am carrying a
2 hr tempo window in all TAFs for this line. Will refine the
timing as the line finally develops and solidifies. Winds could
easily gust over 40kts with the line and am showing 45 to even 50
kts at most terminals. Conditions should quickly improve late
tomorrow morning. /CAB/
PREV DISCUSSION... /issued 351 PM CDT Fri Apr 9 2021/
Main low near the west end of Lake Superior this afternoon, with a
cold front southwest to a second low over north central Texas.
Aloft, an upper low over Wisconsin with a shortwave moving
southward along the east slopes of the Rockies around the low, and
another moving eastward along the Red River.
Locally, onshore flow well established, but there is an area of
low level convergence near the Pearl River where outflow from
convection to the southeast is merging with the synoptic scale
flow. There have been a few cells of convection developing along
this convergence band, but nothing has gotten out of hand at this
point. as temperatures between 850 and 700 mb have warmed since
Temperatures have over-achieved a bit with many areas in the
mid 80s, and won`t be surprised to see one or two stations report
upper 80s for a max today. Dew points running from the upper 60s
to mid 70s in most areas.
SHORT TERM (through Sunday night)...
Main forecast concerns will be in the first 18-24 hours of the
Multiple opportunities for severe weather in this period, as Red
River shortwave shift eastward, scattered convection could develop
across the area this evening in a very unstable airmass. The main
concern, however, is convection only now beginning to develop over
Oklahoma ahead of the cold front. How the two areas of convection
interact is still in some question, but certainly, instability and
shear don`t appear to be issues. While there is potential for
scattered severe storms with the lead shortwave, all signs point
to an MCS moving southeastward into the area late tonight,
probably entering the CWA around 08-09z and moving rapidly
southeast. Potential for significant damaging winds appears to be
greatest across the extreme northern portion of the area, per
The other thing of concern is that some model solutions slow down
the west end of the boundary and lay it east-west across some
portion of our area Saturday morning. At this time, our forecast
doesn`t reflect this solution, but if this occurs, there will be
the potential for excessive very heavy rainfall to develop across
some portion of the CWA, but the majority of solutions right now
carry the convection out into the Gulf of Mexico. Even so, a quick
2-3 inch rain dump is not out of the question.
Once the rain exits the area, remainder of the weekend should be
dry. Will accept the blended temperatures for now. 35
LONG TERM (Monday and beyond)...
Northern stream shortwaves try to lay out a boundary near the
coast early next week. As weak shortwaves move overtop of a
southern Gulf of Mexico upper ridge, there will be several
potential rounds of convection that would produce heavy rainfall.
Confidence in specific timing of these shortwaves is obviously
fairly low, but there will be mention of the chance of
thunderstorms as early as Monday afternoon, continuing each day
through the end of the workweek. Blended temperatures will suffice
until wet/dry periods become more defined. 35
Will keep current headlines, although a few elevated observations
near convection may already be near Small Craft Advisory criteria
in excess of 20 knots. Main concern will be convection overnight,
then conditions should subside later in the day with no major
issues through most of the remainder of forecast period. 35
.PRELIMINARY POINT TEMPS/POPS...
MCB 65 80 53 80 / 100 40 0 0
BTR 67 81 54 81 / 100 40 0 0
ASD 67 82 57 81 / 100 80 10 10
MSY 70 82 63 81 / 100 90 10 10
GPT 67 79 59 80 / 90 100 10 10
PQL 64 78 59 80 / 90 100 10 10
GM...Small Craft Advisory until 4 PM CDT Saturday for GMZ532-536-538-
GM...Small Craft Advisory until 4 PM CDT Saturday for GMZ536-538-550-
Updated for 00Z aviation forecast discussion.
.SHORT TERM...(Tonight through Sunday night)
Issued at 310 PM CDT Fri Apr 9 2021
A few showers have developed from an area of agitated cumulus from
the Ozark Foothills northeast along a confluence zone across
southern Illinois and into Gibson county Indiana. Instability is
fairly limited east of the Mississippi, so would expect some
bubbling to continue with possibly a stray lightning strike, but
the stronger showers and any storms should have a hard time
sustaining themselves for long.
SPC`s mesoanalysis indicates that there is around 1000J/kg of
mixed-layer CAPE over much of southeast Missouri, but it may still
be struggling with a cap. Therefore the cu field is locked to the
better terrain for now. A broken band of thunderstorms is lifting
northeast into southwest/south central Missouri along a
progressive outflow. The 0-3KM bulk shear and SRH is not great, so
not thinking that there will be much organization of the
convection through the early evening.
The HRRR lifts a few cells into southeast Missouri through 00Z,
and then tries to push them eastward into west Kentucky this
evening. Meanwhile, storms are expected to fire along the cold
front over eastern Kansas and Oklahoma around 00Z. This convection
is likely to become organized as it primarily dives east southeast
into Arkansas through the evening. The northward extent of this
development is in doubt, but cannot rule out a few stronger cells
with wind or hail in our southwest counties after 06Z tonight.
The overall signal is for the frontal convection to do a split
with a mean-looking MCS diving to our south and more disorganized
convection lifting north with the surface low. Not sure if there
will be much convection left by 12Z as it attempts to push east of
the Mississippi. The cold front will reach the Mississippi by 15Z
Saturday and then clear the entire area by 21Z. At least scattered
showers will continue along and ahead of it. A few storms will
also be possible until the front passes.
A few wraparound showers may skirt the northwest and northern
edges of the forecast area late Saturday and Saturday night, but
most of this activity will stay northwest/north of the region.
.LONG TERM...(Monday through Friday)
Issued at 310 PM CDT Fri Apr 9 2021
The next work week still looks rather uneventful. Generally dry
conditions are forecast through the period. Temperatures compared to
this week will be cooler, with highs mainly in the 60s.
The longer term global models have been strongly hinting at a major
cooldown, but they have delayed the timing of the cooldown. As a
result, forecast temps will remain constant through the week. Highs
will be warmest on Monday ahead of a cold front, ranging from the
mid 60s to mid 70s. Otherwise, expect highs in the 60s with lows in
the 40s through Friday.
As far as precip chances, very little if any precip is expected.
There is a slight chance of showers with the cold front passage
Monday and Monday night. Tuesday appears dry behind the front.
Beyond Tuesday, the ensembles continue to depict a broad area of
negative 500 mb height anomalies over the northern states. These
negative height anomalies are forecast to slowly sink south and
increase late in the week. However, there is really not much of a
signal for precip despite the falling 500 mb heights and lack of a
strong surface high. The national model blend has littered the
forecast with 20 percent pops starting Wednesday. Given the model
differences in the large area of upper-level troughing approaching
our region, it is tough to rule out a few showers.
Issued at 645 PM CDT Fri Apr 9 2021
00Z tafs reflect ongoing convection, which should be weakening
over the next hour or two. Our attention then turns to a band of
showers, possibly some storms, that is expected to move eastward
across the region overnight into Saturday morning. Not sure if
there will be much impact on visibilities, but certainly cannot
rule out MVFR conditions in the showers, possibly IFR at times.
Winds will be light out of the south or southeast tonight, and
then pick up and become gusty from the southwest behind the cold
front Saturday morning and especially into the afternoon, when
gusts of 30 to 35 mph will be possible.