Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/03/17
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
643 PM CDT Sun Apr 2 2017
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...A dry front is through MFE with moderate and gusty
north winds in its wake. The HRRR shows only a couple more hours
of any type of convection possibility based on diurnal heating,
sea breeze and frontal boundary interaction. Winds will shift at
HRL and BRO over the next several hours as the front pushes toward
the coast, with much drier air in its wake. North winds will
settle down overnight as the new air mass takes over. Overall,
looking for VFR conditions tonight.
&&
.PREV DISCUSSION... /issued 309 PM CDT Sun Apr 2 2017/
SHORT TERM (Tonight through Monday Night):The few forecast challenges
are in the near term (through late evening) and only for the Lower
Valley mainly along/east of the US 77/IH 69E corridor. This in
response to the tail of energy associated with the primary 500 mb
trough that is assisting the necessary lift to hammer Louisiana with
severe weather/tornadoes this afternoon. Thereafter, the entire
trough lifts quickly northeast through the mid Mississippi Valley
later tonight and early Monday and on toward Lake Michigan later
monday, leaving a "micro-ridge" in its wake through Monday evening
before the next in a parade of waves dives into the Great Basin
by early Tuesday morning.
Near Term (through midnight): Skies cleared behind the tail of
morning convection, but over the past few hours along the axis of
transition (dewpoints in the upper 50s to lower 60s) fair weather
cumulus with still lingering haze has formed from eastern Starr
County through Brooks County. Expect fair weather in all areas for
the balance of the afternoon. By sunset, the shear axis moves into
the Valley and attempts to link up with the remaining southeast/east
flow near the coast with a quick opportunity to work off of the
remaining instability to form a thin, broken line of
showers/thunderstorms from Brownsville to Harlingen and points east.
HRRR hourly runs have been very consistent all day for this
development, mainly between 00Z and 04Z, before cruising into the
Gulf thereafter. This solution, however, may only be a "reasonable
worse case". Latest water vapor and GFS time-height cross sections
remain bone dry with just a hint of moisture near 700 mb near the
height of the mixing inversion, which argues for nothing more than
convergent clouds before the dry line clears things out.
For now, that adds up to status quo with the current forecast, which
has a 7 pm to 1 AM (buffer) for just slight chances of
showers/thunderstorms with "gusty winds" as it wouldn`t take much to
push 40+ mph gusts to the surface.
Remainder of short term (midnight through 7 AM Tuesday): Lowering
humidity overnight and north/northwest winds in the low levels will
clear out the haze and moderately yucky air quality leaving a
noticeably pleasant start to Monday with upper 50s to lower 60s area-
wide as fresh winds lay down by sunrise. Monday itself will be pure
blue skies with light winds to start, though an east/southeast sea
breeze will return by afternoon near the coast. Low levels of the
atmosphere are plenty warm so 90 to 95 is a lock for most areas but
low humidity and clean air will make it much nicer than today...a
good hair day to start the work week.
The rapid movement of upper level features will not keep the quiet
winds for long, and southerlies appear to pick up a bit Monday night
but low level moisture remains in check so the entire night should
be comfortable despite air temperatures only falling into the 60s
with some mixing continuing.
LONG TERM (Tuesday through Sunday):Fairly zonal pattern as trough
exits to the northeast and another s/w trough ejects out of the
Rockies. Leeside cyclogenesis occurs over the southern Plains as
the s/w trough digs in, pushing a cold front south across Texas on
Wednesday. S/W trough continues to dig in as it traverses across
the midwest and the eastern US, while a mid level ridge builds
across the western US.
Looking at hot temperatures on Tuesday, especially across the
western brush county and upper and mid Valley, with temperatures
approaching the century mark. Winds veer to the southwest and
west, for areas west of Highway 281, as a dryline moves east
across the area, stopping just shy of the coastal counties. Dry
air filters into the region, dropping RH values into the teens
across Zapata, Jim Hogg, and Starr counties. Although there is dry
air, 20 ft wind values look to below fire weather criteria at
this time, though this is something that should be monitored by
upcoming shifts. Cold front pushing across Texas expected to
slide across the CWA Wednesday morning, bringing breezy and gusty
northerly winds and cooler temperatures. Limited moisture with the
front will likely preclude any precipitation. Any precipitation
that does develop would likely be over the coastal waters, where
the moisture is better. Marginal fire weather conditions possible
once again Wednesday afternoon for the western counties as
dewpoints drop. Surface high pressure builds in, in the wake of
the front and shifts east through the remainder of the week.
Plenty of sunshine will be on tap, with mostly clear skies
prevailing through Thursday. Moving into Friday southeasterly flow
resumes and low level moisture increases, resulting in warming
temperatures, a few more clouds and possibly some streamer
activity.
MARINE (Now through Monday): In the big picture, elevated seas
will continue through the period courtesy of moderate values (4 to
6 feet) generated from the recent southeast/south flow and swell
followed by the quick burst of 15 to 20 knot northerly winds and
perhaps a veering of the swell direction to the east or northeast
for much of Monday. The quick movement of the weak surface high
through the western Gulf Monday and on into the central/eastern
Gulf Monday night will turn winds back to the south overnight and
likely...and briefly...reduce seas a couple of feet before the
bigger rise comes behind the more notable front by mid week.
For now, best period for exercise caution looks to be late tonight
into midday Monday especially offshore. Laguna Madre should be best
of all especially for Monday and Tuesday morning fishing trips.
Otherwise, will need to keep eye on convective development as the
nearshore line could pick up intensity while over the Gulf.
Potential for Gale force gusts and rough seas the main threats
if/when any line moves through, and all should be done a few hours
after midnight.
Tuesday through Friday: Surface high pressure quickly moves into
the eastern Gulf of Mexico Tuesday and off the southeast US
Tuesday night. The next cold front is poised to surge across the
lower Texas coastal waters on Wednesday, bringing strong northerly
winds and building seas, with Small Craft Advisories likely needed
for all waters Wednesday. High pressure quickly moves in behind
the front and winds relax and wave heights begin to subside
Thursday and favorable marine conditions expected Friday.
FIRE WEATHER...Have issued a fire danger statement for Zapata Jim
Hogg and Starr (mainly northern half) for expected increase in mid
to late afternoon wind gusts combined with temperatures surging
above 90 while humidity plummets to between 15 and 20 percent.
Unencumbered mixing heights nearing 10 thousand feet also promotes
the potential for erratic fire behavior. Will keep close eye on
just how low humidity and how high winds, including gusts, get
before pulling any triggers on a short (4 hour duration) Red Flag
for the 15/15 (15+ mph and <15 percent humidity) rule. For now,
things are leaning on the no issue side.
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
54/65
Area Forecast Discussion
National Weather Service Dodge City KS
627 PM CDT Sun Apr 2 2017
...Updated aviation discussion...
.SHORT TERM...(This evening through Monday)
Issued at 141 PM CDT Sun Apr 2 2017
Stratus has been slow to clear, but it clearing from west to east this
afternoon. The clouds have kept temps down a bit. A sfc trough axis
will move across the region through the overnight. There will be a
bit of downslope wind associated with this as it moves though. This
goes into the concern for patchy fog. Normally, a northwest wind is
unfavorable for fog formation. However, both HRRR and NMMB show some
fog potential. Given the very wet ground from the recent rains, have
patchy fog in the weather grids for tomorrow morning. Confidence is
not particularly high, however, T/Td depressions are not that large
this afternoon and remain close in a forecast for the overnight period.
Overnight lows will range from the 30s northwest to 40s southeast,
where dewpoints are running higher. For tomorrow, a warm up is expected
with highs running in the upper 60s to lower 70s. Any precipitation
will hold off until early Tuesday.
.LONG TERM...(Monday night through Sunday)
Issued at 141 PM CDT Sun Apr 2 2017
For Tuesday, a compact UL trof will move through. Rapid cyclogenesis
is expected across the Southern Plains. SW Kansas will be on the deformation/
isentropic lift side. EC and even the GFS are still being generous with
QPF in association with this baroclinic band. Amounts of 1/2" to 1"
look fairly likely, with the higher amounts depending on where the
band is actually located. The winds will also increase Tuesday and
Wednesday with the deepening of the low. A wet snow is possible on
the backside of the system, however, the overall synoptic system is
fairly warm without much cold air in dendritic layer. The main impact
from this system will be another round of much needed rain across the
forecast district. There is a little MUCAPE forecast, so there could
be isolated thunder as well. Beyond this system, the forecast will
dry out. The overall UL pattern is a ridge over the Central Plains
and troffing out west. Temps in the long term period look fairly pleasant
after this system passes Wednesday. The FB temp grid might be running
a little high on Tuesday with all the clouds and precip around.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 626 PM CDT Sun Apr 2 2017
Scattered to broken low level cloudiness around Hays and Dodge City
will persist for an hour or two at the beginning of this period but
should dissipate this evening, leaving only some scattered high cloudiness.
Patchy fog is expected to develop, resulting in some IFR visibilities.
LIFR visibilities could develop at Hays later tonight where low
level moisture will be more established. VFR conditions will
return to all the terminals Monday morning as a surface trough
moves through and winds become northwest.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 39 68 40 42 / 0 0 60 80
GCK 37 67 38 38 / 0 0 60 80
EHA 38 67 36 36 / 0 10 70 70
LBL 38 70 39 39 / 0 0 60 70
HYS 42 66 41 44 / 0 0 30 80
P28 47 72 44 51 / 20 0 30 60
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Sugden
LONG TERM...Sugden
AVIATION...Gerard
Area Forecast Discussion
National Weather Service Peachtree City GA
1113 PM EDT Sun Apr 2 2017
.UPDATE...
Have gone ahead and adjusted POPs for the next 24 hours based on
latest data/trends.
GOES-R water vapor loop this evening reveals a very potent
southern stream shortwave trough across the Southern Plains...with
this system progged to become negatively tilted as it ejects
northeast into the Midwest/western TN Valley on Monday. Associated
surface low /currently in Red River Valley vicinity/ will also
eject into the same region as parent upper low. As this occurs...a
warm front will push north across Georgia tonight through first
part of Monday...while a cold front approaches from the west.
Warm frontal passage overnight into early Monday will usher in a
more unstable airmass. Showers and a few thunderstorms will be
possible within warm frontal vicinity beginning around mid
morning Monday into the afternoon. This activity will be more
discrete and will carry the potential to become
supercellular...mainly across eastern Georgia and eventually into
SC.
Main concern will be the squall line expected to roll through with
the cold front. Latest satellite and radar data show leading edge
of MCS/precip moving into western Alabama as of 03z. The 3km HRRR
has a decent handle on this right now...and has this leading edge
pushing into northwest Georgia right before daybreak Monday. Have
sped up POPs accordingly...while keeping trend of other hi-res
solutions and overall meteorology in mind. Main squall line timing
looks ok for now. However...
Having slight concern right now that leading edge of MCS over Gulf
states will tamper with destabilization tomorrow. If a large area
of widespread rain and thunder affects the area early
tomorrow...there may not be enough "energy" left in the afternoon
to support a widespread severe event as the line moves in. Too
early to determine this now...just something to watch for. Morning
cloud cover could also tamper with an earlier arrival of the
system. Nonetheless...It still remains imperative to plan for a
significant squall line to move through majority of Georgia Monday
afternoon...with the potential for damaging
wind...tornadoes...hail and a few discrete cells ahead of it. If
this system encounters an unstable airmass across Georgia when it
arrives...all severe ingredients will be in place.
Could see some scattered storms behind the main squall line before
entire system pulls north overnight Monday into Tuesday.
Kovacik
&&
PREV DISCUSSION... /Issued 347 PM EDT Sun Apr 2 2017/
SHORT TERM /Tonight through Monday Night/...
Current satellite loop shows complex of storms developing oping
across the ArkLaTex region this afternoon. This system will be
moving our way tonight pushing showers and thunderstorms with
isolated severe storms into GA Monday/Monday night. Currently we
still have a high pressure ridge over the area but it is eroding
fast and moist East to Southeasterly flow will set up over night
ahead of the approaching system. Looking at the Hi-res models they
are all showing a line of thunderstorms moving into NW GA right
around 13z-14z...and moving SE through the CWA. This main line
looks like it will move into the ATL area between 18z-22z which is
also when the best Cape, Shear, LIs, and PWs are over the state.
In addition, very good mid level support will also be present in
the form of a negatively tilted trough and steep lapse rates.
Looking for damaging winds, large hail, frequent lighting, periods
of heavy rain, and Isolated tornadoes to accompany the expected
severe storms. With the very moist airmass in place, there is also
very good potential for locally heavy rainfall. Not confident
enough to issue a flood watch at this time, since the heaviest QPF
is just outside of our area.
01
LONG TERM /Tuesday through Sunday/...
No changes have been made to the extended. The next storm system
is still expected to affect us mid week. Have only tweaked the
pops for Tuesday night to include a slight chance of thunderstorms
over central GA ahead of the warm front. The previous discussion
is included below.
41
PREV DISCUSSION... /Issued 403 AM EDT Sun Apr 2 2017/
LONG TERM /Monday Night through Saturday/...
Potential for ongoing severe weather across the area
Monday night. This severe storm potential as well as the
wet weather is expected to end overnight as the dynamics
pass by. Forecast low temperatures are running 12-15 degrees
above normal.
Another round of storm potential and wet weather looks to be
in the cards Wednesday into Thursday as a more pronounced
cold front and associated upper trough/short wave move to and
across the area. GFS is faster with the cold front than the European
along with a deeper upper trough. The parent surface low moves across
the mid MS valley toward the OH valley Wednesday into Thursday.
Capes significantly increase on Wednesday ahead of the cold front
along with Low Level Shear of 30-35 kts. This could lead to another
round of severe storm potential. Shower and storm potential look
to end early Thursday. Wrap around moisture of the upper low will
potentially affect the far northern counties into Friday. You can
not completely rule out some snow showers late Thursday night/early
Friday in the much cooler air over the far NE.
Saturday and Sunday are looking dry at this time.
Temperatures are expected to be above normal until the cold front
moves through on Thursday with temperatures cooling into the 30s
and 40s Friday and Saturday mornings.
BDL
AVIATION...
00Z Update...
Tonight will be quiet before a storm system moves through on
Monday. Cirrus will increase from the west overnight before low
level moisture /lower end MVFR to high-end IFR cigs/ move in
towards sunrise Monday. These conditions should improve to VFR
towards noon with some showers and perhaps isolated thunderstorms
developing around this time. A line of strong/severe thunderstorms
will move across the TAF sites early-mid afternoon through mid
evening. These storms will likely produce dangerous aviation
conditions during this timeframe. Should see a clearing trend
going towards midnight Monday night. Winds will remain on the east
side until late afternoon Monday before shifting southwest.
Sustained winds this period likely to be 10-20kts with gusts
20-25kts. Winds will be stronger in vicinity of storms.
//ATL Confidence...00Z Update...
Medium on all elements
Kovacik
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 81 59 76 60 / 0 20 100 50
Atlanta 82 62 75 60 / 0 20 100 50
Blairsville 75 55 67 54 / 0 30 100 40
Cartersville 81 61 74 58 / 0 30 100 50
Columbus 88 64 80 62 / 0 20 100 80
Gainesville 76 58 71 58 / 0 20 100 50
Macon 86 62 81 62 / 0 20 90 80
Rome 83 60 74 57 / 0 30 100 50
Peachtree City 84 60 76 59 / 0 20 100 50
Vidalia 86 63 83 66 / 0 20 80 80
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Kovacik
LONG TERM....Deese
AVIATION...Kovacik
Area Forecast Discussion
National Weather Service Grand Rapids MI
1124 PM EDT Sun Apr 2 2017
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 330 PM EDT Sun Apr 2 2017
A low pressure system over Texas this afternoon will move northeast
and continue to strengthen and bring rain and potential for a few
thunderstorms Monday afternoon through Monday night. Locally heavy
rainfall is possible. Another strong low pressure system will
bring rain and a chance of thunderstorms Wednesday through
Wednesday night. Showers will linger Thursday and a much cooler
airmass will move in late in the week into next weekend.
&&
.UPDATE...
Issued at 1124 PM EDT Sun Apr 2 2017
Sent an update to raise POPs for the overnight based on radar
and hi-res model trends. HRRR showing showers filling in a bit
more overnight as mid level warm advection and moisture transport
continues into Lower Michigan.
&&
.SHORT TERM...(This evening through Tuesday night)
Issued at 330 PM EDT Sun Apr 2 2017
A strengthening low pressure system will move ne into the lower
Great Lakes region Monday and bring rain and potential for a
few thunderstorms Monday afternoon through Monday night. Overall
short range model guidance trends the past 24 hours suggest that
this system will move further north with a strong sfc low on the
order of 987-989 mb up into lower Michigan Monday night.
Given this guidance trend we expect elevated instability will
increase a bit late Monday afternoon through Monday evening and
potentially become sufficient enough for scattered convective
development to occur into our southern fcst area. Some locally
heavy rainfall is possible as well as this system will pull ample
gulf moisture northward.
Severe weather tomorrow through tomorrow evening will stay well
south of our fcst area from the Ohio Valley region further south
where much stronger instability will develop out ahead of the cold
front. It will be breezy and cooler on the back side of this
system on Tuesday with some lingering showers. Fair wx will very
briefly return Tuesday evening as a weak high pressure ridge
briefly builds in.
.LONG TERM...(Wednesday through Sunday)
Issued at 330 PM EDT Sun Apr 2 2017
Cool and wet will be the norm through the long term.
Another in a series of southern stream systems will track from
roughly Kansas City to Toledo in the Wed thru Thu period. This
system looks to be equally wet with the potential of over an inch of
rain. Some elevated instability will be the wild card for localized
thunder and the potential for localized heavier rains. Seems like
the SE half of the CWA would be under the gun for the heaviest
rains, leading to an increased hydro threat. And the models have
trended colder on the backside of the system, where some snow may
mix in over the NW CWA by late Wednesday night into Thursday. This
will be an intensifying system leading to brisk winds Wednesday
night and Thursday.
Some very light snow accums will be possible into Thursday night,
before the pcpn finally ends late Thursday night or Friday morning.
Surface ridging gives the area a break from the pcpn through the
rest of Friday and into Friday night.
A big swing toward warmer temps appears set for the weekend,
especially into Sunday. By then the Great Lakes will be on the back
side of the surface ridge, with upper ridging also building in.
After much of the period in the 40s and 50s, we should reach the 60s
Sunday. A few thunderstorms could be possible by late Sunday as a
cold front approaches.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 752 PM EDT Sun Apr 2 2017
Although a few showers will be moving through this evening, VFR
conditions should continue overnight. Steady rain moves in MOnday
morning with ceilings lowering to IFR by the afternoon. LIFR can
be expected by late afternoon. There will also be the chance for
thunderstorms in the afternoon across the southeast half of Lower
Michigan.
&&
.MARINE...
Issued at 330 PM EDT Sun Apr 2 2017
Minimal wind speeds and wave heights below 2 feet are forecast
through Sunday afternoon. However wave heights and wind speeds
will increase late Monday night through Tuesday on the back side
of a strong low pressure system which will be over the eastern
Great Lakes region.
&&
.HYDROLOGY...
Issued at 330 PM EDT Sun Apr 2 2017
River levels are above normal in Southern Lower Michigan with minor
river flooding ongoing. The crests from recent heavy rains are
moving down the river systems. Around an inch of rain is expected
Monday into Tuesday with another three quarters of an inch possible
later in the week. This could not only keep river levels from
falling, but could lead to increased flooding. Minor river flooding
will continue in the Grand River and Kalamazoo River basins.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
UPDATE...Ostuno
SYNOPSIS...Laurens
SHORT TERM...Laurens
LONG TERM...JK
AVIATION...Ostuno
HYDROLOGY...63
MARINE...Laurens
Area Forecast Discussion
National Weather Service Lincoln IL
935 PM CDT Sun Apr 2 2017
.UPDATE...
Issued at 931 PM CDT Sun Apr 2 2017
Updated forecast to lower PoPs for the rest of the night into
early Monday. The lead band of rainfall to the northeast of the
approaching surface low continues to diminish, likely a result of
the significant storm complex over the Gulf coast states
intercepting much of the available moisture. This trend has been
picked up on the high-resolution guidance to varying degrees, but
the trend is definitely for a drier overnight period. The
remainder of the going forecast was in pretty good shape with only
minor hourly tweaks needed overnight.
&&
.SHORT TERM...(This evening through Monday)
ISSUED AT 255 PM CDT Sun Apr 2 2017
A storm system currently over Texas will pivot northeastward over
the next 24 hours...spreading showers and thunderstorms into central
Illinois late tonight into Monday morning. The airmass is initially
quite dry below 850mb, so think it will take awhile for sufficient
top-down moistening to occur before measurable precipitation can
reach the ground. Models differ on the exact timing of the precip,
but general consensus suggests light showers will develop across the
S/SE KILX CWA by late evening, with showers becoming more widespread
across the board overnight. MUCAPE values remain negligible, so
will only mention isolated thunder across the south close to dawn.
As low pressure tracks from northeast Oklahoma early Monday morning
to west-central Illinois by evening, strengthening upper dynamics in
association with deep-layer moisture will produce widespread showers
and thunderstorms throughout the day Monday. There is some evidence
from high-res models such as the HRRR that a brief lull in the
precip will be possible during the morning, followed by a return to
rainy weather by afternoon. Overall scenario will be a wet and
stormy day across central and southeast Illinois, with rainfall
totals ranging from 0.75-1.25. Thunder chances will increase
markedly across the southern half of the CWA during the afternoon as
MUCAPES climb into the 1000-1500J/kg range: however, severe weather
risk will remain low due to weak wind shear parameters. High
temperatures will range from the upper 50s far northwest around
Galesburg to the upper 60s south of I-70.
.LONG TERM...(Monday night through Sunday)
ISSUED AT 255 PM CDT Sun Apr 2 2017
Surface low pressure will be pushing off to our northeast Monday
evening as the next strong shortwave tracks into the southern
Rockies early Tuesday. Looks like one quiet day on Tuesday in
between the storm systems before our shower and thunderstorm
chances start to ramp up again Tuesday night through Wednesday as
the strong upper wave translates east into the Midwest. Models
have trended a bit quicker and further south with the track of the
surface system late Tuesday night into Wednesday which seems a
bit surprising for an amplified upper wave, which most models are
now tracking east-northeast across south-central Illinois late
Wednesday morning, with the main threat for severe storms along
and south of the I-70 corridor Wednesday afternoon. Confidence at
this point not that great with respect to the track of the surface
low so the threat for severe storms still not out of the question
Wednesday afternoon but the faster trend and further south track
to the upper and surface waves lends credence to a further south
and east severe threat with the last couple of model runs.
The deepening surface low on Wednesday night into Thursday will
bring an abrupt end to the mild weather we will enjoy for the
first few days of the new work week. Strong winds and colder
temperatures plow into our area Wednesday night and Thursday
coupled with scattered showers, and possibly a rain-snow mix late
Wednesday night into early Thursday morning across our north,
which will make outdoor conditions rather miserable Thursday.
Northwest winds are forecast to range from 25 to 30 mph with a few
gusts up to 40 mph at times late Wednesday afternoon through
Thursday with highs during the day Thursday struggling to reach
the 50 degree mark across our north. Winds should gradually
subside Thursday night as the deep low pressure pulls away from
the Midwest and high pressure settles in from the west. The
coldest night looks to be late Thursday night into early Friday
when early morning lows will approach the freezing mark across the
north. A nice recovery in temperatures expected on Saturday with
highs back into the 60s most areas and with an increasing south to
southwest wind on Sunday, the mercury will rise into the upper
60s to lower 70s ahead of the next weather system that will bring
rain chances back to central Illinois, but not until Sunday night
into next Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 641 PM CDT Sun Apr 2 2017
VFR conditions will degrade to MVFR/IFR during the day Monday as
low pressure tracks across the area. The low is currently over the
southern Plains, and it is forecast to lift northeast into the
Great Lakes by Monday night. Showers, lower CIGS, & VSBYS will
accompany the passage of the system. Thunderstorms are also
possible during the day Monday.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Bak
SHORT TERM...Barnes
LONG TERM...Smith
AVIATION...Bak
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
924 PM CDT Sun Apr 2 2017
.UPDATE...
Issued at 916 PM CDT Sun Apr 2 2017
Have updated PoPs overnight into Mon morning to generally lower
thru this time period. Precip shield continues to dissipate
somewhat as it moves nwd. However, believe a somewhat narrow band
will hold together. This precip shud be along a KCOU/KSTL/KSLO
line around 0300z, then KMYJ to K3LF by 0430z before moving out of
the CWA. There shud be some redevelopment along the wrn flank of
this precip, tho it shud remain light.
More questions after this band move thru. Expect more SHRA
development near sunrise Mon as a s/w approaches the region with
some elevated instability. This also coincides with a more sly LLJ
and increased moisture convergence. Timing this, as well as
pinning down location for higher coverage, will be difficult. Have
focused higher PoPs further west, but kept mid to high range
chance PoPs across much of the CWA as some sct develop is possible
elsewhere.
The prev forecast for late Mon morning thru the afternoon hours
still appears to be on track.
&&
.SHORT TERM... (Through Late Monday Afternoon)
Issued at 345 PM CDT Sun Apr 2 2017
Low pressure developing over eastern Texas will move northeast over
the next 24 hours through Missouri and into Illinois by 00Z Monday.
The first wave of precipitation associated with this system is
currently over Arkansas and will be moving up into the CWFA this
evening. Convection allowing models (CAMs) are all weakening this
precip as well as shrinking its areal coverage by the time it gets
up here. However, most models show some decent moisture convergence
during the mid to late evening on a 30-40kt low level jet. Only
reason I`m not going with PoPs higher than 60-70 tonight is the
drier CAMs. After 06Z, the warm advection and moisture convergence
weakens over much of the area as the low level jet veers and becomes
more parallel to the 850mb baroclinic zone. Instability will be
somewhat limited for most of the night according to the RAP and
GFS...less than 500 J/Kg of MUCAPE except over southern Missouri
late tonight so have kept mention of thunder to isolated/slight
chance.
More widespread thunderstorm activity is expected on Monday as the
storm system moves across the area. Severe threat is not zero as
guidance is showing some decent instability of around 1500
J/Kg...but deep layer shear isn`t all that impressive when the
instability is greatest in the afternoon with only about 20-25kts
across the area. Might be enough for some hail or high wind gusts
if storms can get organized. Temperatures tonight and Monday will
be highly dependent on precipitation and the track of the low/speed
of the cold front behind it. Stuck pretty close to the consensus
blend for hourly temperatures through the period which yields lows
in the 50s tonight and highs ranging from around 60 in northeast MO
to near 70 in southeast MO on Monday.
Carney
.LONG TERM... (Monday Night through Next Sunday)
Issued at 345 PM CDT Sun Apr 2 2017
An active period is on tap for the first half of the upcoming week
due to a progressive and amplified flow regime, with rather potent
systems forecast to impact the region on Monday and again late
Tuesday night/Wednesday.
A negatively-tilted upper trof/closed low will eject northeast and
weaken as it moves through the lower-mid MS Valley Monday and into
the OH Valley Monday night. The models have come into better
agreement with this system, with the attendant surface low tracking
from northeast OK across southwest MO and just north of St. Louis
into central IL in the 12Z-00Z time frame. Large scale ascent is
impressive with this system and in tandem with a stout southerly
LLJ, will contribute to widespread precipitation including elevated
thunderstorms across the entire CWA. The aforementioned surface low
track will result in an expanding warm sector as the low tracks
northeastward, which will be supportive of surface-based
thunderstorms along and in advance of the trailing dryline/cold
front. While the instability is not forecast to be particularly
robust, there is sufficient CAPE given the 35-45 kts of deep layer
shear to support at least isolated severe thunderstorms across
the southeast third of the CWA in the afternoon. Lingering showers
and an isolated thunderstorm will possible across the eastern
half of the CWA early on Monday evening, as the system quickly
exits to the east and CAA insues in the wake of the cold front.
Tuesday looks to be a down day with tranquil conditions as ridging
dominates both at the surface and aloft. Temperatures should remain
above normal in spite to the Monday cold fropa.
The next in the series of potent systems will impact the area late
Tuesday night into Wednesday. This system looks bit different
compared to the model forecasts from 24h ago. There remain some
differences in speed and positions with the GFS the fastest
solution. However the big similarity and difference from earlier
solutions is the system is further south and faster, and more wound-
up with nearly vertically stacked lows. These factors would diminish
the severe threat on Wednesday, however there will be a threat of
elevated thunderstorms late Tuesday night and general thunderstorms
on Wednesday ahead of the advancing surface low/cold front. The
northwest quadrant of the system will also bear close watching.
There are signs of potentially some late season wet snow, however
boundary layer temps are forecast to be a bit warm at this point.
The upper trof will continue to deepen and evolve as it moves to the
east Thursday into early Friday dominating the eastern half of the
Nation and resulting in cooler, below average temps along with some
showers. The cooler weather is short-lived however as heights aloft
rise heading thru the weekend and a strong low level WAA regime gets
underway.
TES
&&
.AVIATION... (For the 00z TAFs through 00z Monday Evening)
Issued at 621 PM CDT Sun Apr 2 2017
Ongoing SHRA over srn MO into nrn AR shud weaken somewhat as they
move nwd while SHRA continue to develop along a sfc trof. These
more nly SHRA shud continue to move nwd out of the region. After
the srn SHRA move thru the terminals, a lull in precip is
expected, tho lower cigs are expected to arrive around this time.
A second round of SHRA, with isod TS, is expected to arrive Mon
morning and persist thru much of the day. IFR cigs are also
expected to arrive around this time as the sfc low approaches and
moves thru the region. Precip shud be ending near or just after
the current TAF period. Cigs may improve briefly as precip ends,
tho wud expect this to be short lived.
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX