Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/24/21
Area Forecast Discussion
National Weather Service Lincoln IL
706 PM CDT Tue Mar 23 2021
Issued at 314 PM CDT Tue Mar 23 2021
A cold front will move through the area this evening, bringing
rain and thunderstorms, a few of which may be strong. Lows
tonight will be in the upper 40s to mid 50s. Wednesday will be
dry, with high temperatures ranging from the mid 50s to upper 60s,
and wind gusts approaching 35 miles per hour. Additional rain is
possible on Thursday.
Issued at 656 PM CDT Tue Mar 23 2021
Line of low topped convection is moving across the Mississippi
River this hour and will move across central Illinois through the
mid to late evening hours. 00Z KILX raob shows just under 300
J/kg MLCAPE with effective shear near 30 kt and effective SRH over
200 m2/s2. Near term guidance does suggest instability will be
very slow to wane so expect the thunderstorm threat associated
with the approaching line to continue well into the forecast area
this evening with a low but non-zero severe threat, including a
tornado threat given the favorable shear and veering wind profile.
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 314 PM CDT Tue Mar 23 2021
An expansive low pressure system lifting northeast across Kansas
is bringing weather impacts to the central third of the CONUS
today. This afternoon, a band of light rain continues to lift
north across central IL, with most of the activity north of I-74
as of 3pm.
Instability remains the limiting factor for severe weather this
evening. Partial clearing has occurred in the warm sector across
Missouri, and afternoon RAP analysis suggests a few hundred J/kg
of SBCAPE has materialized there. No clearing has occurred across
west central IL as of 3pm, but the corridor of instability that
developed across Missouri this afternoon should pivot into the
area later this evening. High-res guidance continues to suggest
the cold front won`t move into the ILX CWA until around 00z, by
which time the surface- based instability will begin to diminish.
Forecast wind profiles remain supportive of a conditional threat
for severe weather, with 0- 1 km storm-relative helicity in excess
of 300 m2/s2 and effective bulk shear of 30-40 knots. Given the
diminishing, but likely non- zero, instability, it appears a brief
window for strong to severe thunderstorms will exist as the front
moves in this evening. The threat will quickly diminish as the
instability wanes after sundown. By 06z Wednesday, any precip
associated with the front should be east of the I-55 corridor, and
by 09z precip should be out of the area.
As the low lifts north towards the Great Lakes on Wednesday, a
baroclinic zone will remain situated across IL. North of I-72, skies
will be partly to mostly cloudy with highs in the mid 50s to low
60s, while south of I-72 mostly sunny skies will warm temps into the
upper 60s. It will once again be breezy during the day on Wednesday,
with gusts to 30 knots possible.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 314 PM CDT Tue Mar 23 2021
An active pattern will continue into next week as multiple waves
of energy move through both the northern and southern branches of
the jet stream. There is still substantial model disagreement
regarding the evolution of a shortwave that is set to move through
the Ohio Valley on Thursday. The GFS is still more progressive
than the ECMWF, but has trended west and with a deeper surface low
(closer to the ECMWF evolution). While the finer details are
still uncertain, strong synoptically-driven wind gusts, heavy
rain, and some thunderstorms are possible Thursday into Thursday
night. Rainfall totals of 1 to 1.5 inches are possible on
Thursday. As this shortwave exits, much of Friday should be dry
before yet another system brings rain chances on Saturday. High
temps will slowly trend cooler after Wednesday, ranging from the
mid 50s to mid 60s on Thursday, then the upper 50s on Friday.
Southerly flow returns on Saturday, warming highs back into the
mid to upper 60s. Given the continued model disagreement and
inconsistencies regarding the Thursday system, did not make many
changes to the blended guidance.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 606 PM CDT Tue Mar 23 2021
Scattered showers will continue to lift north across central
Illinois this evening contributing to primarily MVFR conditions
and patchy IFR. A better organized line of showers and perhaps an
isolated storm or two will move across the region later this
evening marking the back edge of precip chances. Ceilings should
improve back to VFR behind the line for several hours before MVFR
returns Wednesday. Breezy SE winds will veer to the SSW behind the
line of showers and become gusty again during the day Wednesday.
Area Forecast Discussion
National Weather Service Jacksonville FL
918 PM EDT Tue Mar 23 2021
Weak pressure gradient in place tonight with a weak coastal trough
and partly cloudy skies. A few radar returns well offshore but
should stay well to the east and so no mention of showers in the
forecast tonight. Additional showers to our west may push in to
southeast GA late tonight but may be just virga and no showers
expected tonight at this time. East to northeast flow has continued
to bring in additional moisture with dewpoints in the mid 50s to
around 60 to the area. Weak low level decoupling in conjunction with
light to calm winds will support patchy to areas of fog tonight.
High clouds and slow temp fall may only gradually lower
visibilities, except along the coast where combo of radiational and
sea fog may contribute to faster fog development. Have expanded
areas of fog a bit in the forecast and pushed it into the coastal
waters based on latest guidance and the possibly the fact that weak
trough along the coast also allow some of the low stratus/fog to
slowly push into the nearshore waters near and after sunrise. No
significant changes in low temps in the mid and upper 50s.
No changes except for addition in the patchy fog for the nearshore
coastal waters early Wednesday based on SREF and HRRR guidance.
.PREV DISCUSSION [808 PM EDT]...
.NEAR TERM [Through Tonight]...
Latest visible imagery, as of 3 pm, reveals extensive cumulus
field across NE FL and portions of SE GA along with broken bands
of high cirrus drifting overhead on a near zonal flow aloft. A
weak Atlantic sea breeze has pushed inland this afternoon amid the
weakening background northeasterly flow. Winds will continue to
decrease tonight as an expansive surface high pressure becomes
established near Bermuda. With some moisture pooling due to the
sea breeze, patchy dense fog development is possible late tonight
through early Wednesday morning. Guidance has been trending toward
more pessimistic in terms of Areas of dense fog, especially
between the Highway 301 and I-95 corridors. A frontal zone is
progged to stall well west of the region Tonight as it loses upper
support from a poleward ejecting upper low. A few light showers
associated with the stalling front may graze across portions of SE
GA near the Altamaha River basin, with areas elsewhere remaining
dry. Under a blanket of low stratus lows will remain on the mild
side with readings in the mid to upper 50s.
.SHORT TERM [Wednesday Through Thursday Night]...
A stalled and weakening frontal zone will stay just to our west
Wednesday. A few isolated light rain showers may extend into the
Suwannee valley northward into the Altamaha Basin through the
afternoon as a vort ribbon drifts over the area. With confidence
being low in any measurable QPF with shower activity, PoPs have been
kept "silent" (10-14%). Winds will veer southerly through
Thursday as surface ridge axis extends from a high centered near
Bermuda. Meanwhile aloft, a strong ridge will build near Cuba. As
the ridge builds through Thursday upper flow will back to the
south-southwest which should help steer upstream disturbances away
from the area, keeping them to our north. Gradients will tighten
as a cold front marches west across the Deep South on Thursday,
resulting in a gusty southerly winds between 20-25 mph during the
afternoon hours. Despite increasing moisture through Wednesday,
winds will be strong enough to limit fog potential Thursday
morning. Temperatures will continue to trend upward with afternoon
highs in the upper 80s to near 90 and lows in the mid 60s by
.LONG TERM [Friday Through Tuesday]...
Uncertainity in the extended forecast continues to increase as
with diverging solutions from medium-range guidance. The two
factors that will have the most influence on the extended will be
the persistence of the strong ridge aloft and the progressiveness
of the northerly stream and whether it reintegrates a cutoff low
over the Desert Southwest. The main trend has been to keep the
ridge aloft stronger and more persistent. If that comes to
fruition, temperatures will remain above normal into early next
and winds will remain southerly as fronts approach and stall to
our west. Because of general low confidence, rain chances remain
fairly low despite the potential of a fropa early next week. Will
iron out the details as confidence increases.
[Through 00Z Thursday]
Moist onshore flow and diminishing winds will continue to support
a round of fog and low stratus tonight. Thus, will continue to
show low stratus and fog later tonight, with cigs and vsby coming
down eventfully to LIFR cigs and IFR vsby. May begin to see some
reduced cigs and/or vsby first at SSI by late evening. In general,
have trended cigs and vsby down a bit around the 09Z-13Z time
frame based on latest guidance and model soundings. Some
indications there could be a slower improvement in cigs and vsby
in the 13Z-15Z time frame so will likely need some refinement in
subsequent forecasts. Anticipate VFR returning around 15Z-16Z but
could be lingering low clouds around SSI until early afternoon as
southerly winds slowly increase.
Improving conditions will continue over area waters as winds and
combined seas continue to decrease through the rest of the
afternoon and through the evening.
Lighter onshore winds and more favorable conditions are expected
Wednesday, as a front stalls well west of the region and an
expansive high pressure becomes centered near Bermuda. Winds will
veer southerly and strengthen to 15-20 knots ahead of another
frontal system on Thursday and Friday, which will stall west of the
area through the weekend. Though confidence is low, the influx of
warm and moist air over the cool shelf waters may support patchy fog
development overnight on Thursday and Friday - but strengthening
winds may limit potential.
RIP CURRENTS: Though winds have decrease, they will remain directed
onshore which keep a MODERATE RISK of rips Wednesday. Increasing
southerly winds will enhance longshore currents and elevate rip
current risk further on Thursday.
Surface and transport winds will veer southerly over the next
couple of days as cold front approaches from the west, eventually
stalling northwest of the region on Friday. Winds will increase
with the southerly flow resulting in day-over-day increases in
daytime dispersion through the end of the week. High dispersion is
likely across region on Thursday and Friday. Low stratus clouds
will surface as fog in areas of light to calm winds Wednesday
morning, which should roughly in be between the 301 and I-95
corridors. Despite moisture increase, fog potential will be
limited on Thursday due to winds.
.PRELIMINARY POINT TEMPS/POPS...
AMG 57 81 58 87 64 / 10 10 10 0 10
SSI 56 74 61 79 64 / 0 10 10 0 0
JAX 56 81 61 86 64 / 0 0 0 0 0
SGJ 59 78 61 82 64 / 0 0 0 0 0
GNV 56 84 58 89 62 / 0 0 0 0 0
OCF 57 85 59 90 63 / 0 0 0 0 0
FL...High Rip Current Risk until 5 AM EDT Wednesday for Coastal Duval-
Coastal Flagler-Coastal Nassau-Coastal St. Johns.
GA...High Rip Current Risk until 5 AM EDT Wednesday for Coastal
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
915 PM CDT Tue Mar 23 2021
Issued at 915 PM CDT Tue Mar 23 2021
Given the increase in upper level forcing across ern SD and the decrease
in radar returns across ncntl Nebraska, a forecast update is in
place which lowers snow accumulations to little or no accumulation
across the ncntl Nebraska area. The rest of the forecast is on
.SHORT TERM...(This evening through Wednesday night)
Issued at 321 PM CDT Tue Mar 23 2021
Precipitation continues to be the main concern in the short term. As
the sfc low continues to track northeast rain will continue to
slowly rotate around the low from the northeast. The sfc low will be
across northeastern Iowa Wednesday morning, taking all rain chances
eastward by Monday morning. Did make adjustments to the snow amounts
as it appears less likely we will see much of an all snow chance
overnight with temperatures hovering near to above freezing. The
most likely precip mode will be rain and a rain/snow mix with very
little accumulation expect, generally just around a trace.
One other forecast concern has been the strong sfc winds. 850mb
winds around 40 to 60 mph have been able to mix down to the sfc late
morning and early afternoon with wind gust approaching 45 mph at
times. The RAP model had the best handle on the winds so trended the
forecast towards the RAP increasing wind speeds around 5 mph or more
in some locations. Winds should stay up the remainder of the
afternoon into the early evening and should start to diminish as the
low continues to move northeast.
Wednesday will be drier and temperatures will reach the upper 40s to
around 50 degrees across southwest Nebraska.
.LONG TERM...(Thursday through Tuesday)
Issued at 321 PM CDT Tue Mar 23 2021
Temperature will remain mild the rest of the week with highs in
the 50s. Another system will move into the High Plains on Friday
with precipitation chances increasing on Friday and the best
chance of precipitation Friday afternoon into the evening. At this
time the temperatures will be warm enough during the day that
precip will fall as rain and although temperatures cool overnight,
they should hover near freezing where only a mix of rain/snow
will briefly be possible.
High pressure moves in Sunday and Monday with mostly mild and dry
conditions expected through the remainder of the forecast period.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 747 PM CDT Tue Mar 23 2021
Conditions will gradually improve the next 24 hrs, but still
expect at least a few areas of MVFR ceilings to linger into
Wednesday morning. By afternoon Wednesday all areas should be VFR.
Winds will be gusty from the north to northwest through the day
Area Forecast Discussion
National Weather Service Lake Charles LA
956 PM CDT Tue Mar 23 2021
Radar this evening showing persistent band of rain and embedded
thunderstorms stretching from the northern Gulf waters onshore
into the Lower Atchafalaya Basin and SE LA. Localized rainfall
maximums a bit in excess of 6" were noted near Cypremort Point,
with amounts tapering off somewhat moving into interior St. Mary,
Iberia, and Lower St. Martin Parishes. The heaviest of this band
has flexed east so far this evening, but guidance suggests some
light to moderate rain will remain a possibility for the next
several hours before diminishing more significantly and/or moving
northward on Wednesday.
Otherwise, stalled cold frontal boundary draped from SE TX into
Central LA is beginning to retreat back to the west this evening.
In turn, the brief shot of dry air some locations experienced
behind this front will be short lived, as moisture will push back
in readily as the front slides away. Combined with light winds and
saturated soil, fog is expected to set in tonight... Not enough
confidence at this time to issue any advisories, though there will
be the potential for some areas of dense fog, and will be
something to monitor going forward.
In regards to the grids, only made minimal changes to the
inherited forecast based on short term trends and guidance.
.PREV DISCUSSION... /issued 634 PM CDT Tue Mar 23 2021/
For the 24/00Z TAF Issuance.
Surface boundary/dry line feature is located across the region
just west of a KAEX-KLCH line. Terminals near this and to the west
are experiencing VFR conditions with mainly clear skies.
Meanwhile, off to the east deeper moisture resides and low clouds
with IFR ceilings remain for KLFT/KARA.
Shower activity has pushed off to the east and should not affect
terminals for the remainder of the night. IFR ceilings look to
hang around for KLFT/KARA through the night into Wednesday
morning. Meanwhile, with clear skies, light winds, and residual
wet grounds, patchy fog and stratus should begin to develop at
KAEX/KBPT/KLCH by 24/06Z with MVFR/IFR conditions that will
continue to lower to possibly LIFR before sunrise.
PREV DISCUSSION... /issued 404 PM CDT Tue Mar 23 2021/
The line of convection that dumped 5 to 7 inches of rain across
parts of southwest Louisiana this morning has been steadily
dropping moderate to heavy rainfall across the atchafalaya basin
and surrounding parishes this afternoon. HRRR and other short
range guidance indicate that this convection will very slowly
continue to drift east into southeast Louisiana by late this
evening. Until then, nuisance flooding will be a possibility
across this region and flash flood warnings may be needed shortly.
The sharp clearing line immediately behind the line of storms has
allowed southeast Texas and southwest Louisiana to spend much of
the day in unanticipated sunshine...A welcome relief after this
morning`s deluge. Short range guidance is pinging on fog
development overnight and although clouds will fill in overnight,
the saturated soils and light winds expected certainly point in
that direction so added patchy fog wording from 06Z through 14Z.
The stalled frontal boundary will lift back across the region
Wednesday spawning another round of scattered to widespread
showers and thunderstorms. Gave some thought to issuing a flash
flood watch across the areas that saw high rainfall totals today,
but don`t think precip tomorrow will be nearly as heavy as what
was seen today so opted to hold off. The convection will begin
near the coast before working inland along with the warm front
through the afternoon.
There will likely be a bit of a lull in precipitation late
Wednesday night between the warm front lifting to the north and a
stronger cold front that will approach and push quickly through
the region Thursday morning. SPC has hatched the area in a slight
risk for severe weather with the passage of this front which will
likely take the shape of a broken squall line.
Some moderate CAA will develop in the wake of the front Thursday
night into Friday allowing overnight lows Friday morning to drop
into the mid 50s. High pressure quickly traverses the region
through the day Friday with return flow quickly developing
Saturday ahead of another frontal boundary expected early next
week. However, there are significant differences in model
solutions with regards to the orientation, intensity and timing of
this boundary. Thus, the official forecast hedges with low end
PoPs on days six and seven.
Scattered to widespread showers and thunderstorms will continue
across the coastal waters of southwest and south central Louisiana
this afternoon and early evening before shifting east by late
evening. Moderate onshore flow will continue through the night
with stronger winds and higher seas beyond 20 NM. Isolated showers
and thunderstorms will redevelop Wednesday morning before lifting
inland through the day.
A cold front will push through the area Thursday morning
accompanied by a line of showers and thunderstorms. Winds behind
the front will turn offshore late Thursday and Friday before
turning back onshore this weekend.
.PRELIMINARY POINT TEMPS/POPS...
AEX 57 77 66 77 / 0 60 70 90
LCH 61 79 68 80 / 0 40 40 60
LFT 62 78 69 79 / 20 60 50 70
BPT 61 79 66 79 / 0 40 30 50
GM...Small Craft Advisory until 4 AM CDT Wednesday for GMZ475.
Small Craft Exercise Caution until 4 AM CDT Wednesday for GMZ455.
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
828 PM CDT Tue Mar 23 2021
828 PM CDT
Only minor tweaks to going forecast this evening, mainly to refine
hourly pops and thunder chances based on observed trends and high-
res model forecasts. Main isolated thunder timing looks to be late
evening into the early overnight hours, prior to passage of surface
occluded front across the eastern cwa in the 3-5 AM timeframe.
Evening GOES water vapor imagery shows the mid-level circulation
associated with an upper level low lifting northeast across the Iowa-
Missouri border at 01Z/8 PM. One smaller-scale sheared short wave
had wrapped north-northwest across the area this afternoon and early
this evening, with a pocket of better mid-level moisture producing
an area of rain with decent coverage which has largely lifted into
southern/southeast Wisconsin. Additional scattered/areas of showers
were noted developing across parts of central and northern Illinois
this evening however, in association with a southerly 40-50 kt low
level jet east of the main circulation. These showers and a few
isolated thunderstorms will likely increase in coverage as forcing
increases late this evening, and particularly with the approach of a
surface occluded front currently moving into western Illinois.
Thunder potential should increase across the cwa during this period,
with mid-level lapse rates approaching 7 C/km and RAP forecast
soundings indicating 200-400 J/kg of elevated CAPE spreading across
the area, for parcels based around 835 mb. High-res guidance
indicates a marked decrease in coverage and intensity of showers and
thunderstorms in the wake of the surface front (and arrival of the
mid-level dry slot) prior to sunrise. Made some relatively minor
adjustments to hourly gridded pop/thunder potential grids to add a
little detail to the next 8-12 hours based on these trends.
Temperatures have been holding steady in the mid-50s in most spots
this evening, except along the IL lake shore where the onshore winds
have held readings in the mid-upper 40s. Temps may rise into the
lower 50s toward sunrise in these locations as the wind shifts south-
southwest behind the front.
Updated digital and text forecast products available.
155 PM CDT
Through Wednesday night...
The center of deep low pressure is back across northeast KS. The
system has become a bit more vertically stacked but still
undergoing some strengthening with the slight negative tilt to
the upper low and strong upper jet on its leading edge.
Closer to home, a bit better moisture transport along the nose of
jet has allowed arc of showers to shift into central Illinois and
this will expand across northeast IL and northwest IN this
afternoon/early evening. As this occurs, a bit stronger pressure
gradient ahead of the low will also bring some wind gusts to 30 mph
or so for a time. After this leading band of rain showers, there
could be a brief lull or tapering to more scattered showers. This
should be short lived as height falls with approaching upper low and
more robust moisture transport on an expanding low level jet will
lead to a re-expansion of showers to continue at times through the
evening. Some weak instability will be present and will continue an
isolated thunderstorm mention. Forecast soundings show narrow
instability and plentiful low level moisture to suggest coverage of
storms should be somewhat low. We will have lower clouds this
evening, but any stronger showers may bring down a bit stronger
winds as the mean 925-850 mb wind field increases to 40-45 kt this
evening, with the higher concern area still remaining just to our
It appears the last hurrah with this system will come with the
occluding frontal boundary late this evening into the early
overnight hours. This band of showers will be in a weakening phase
as the system begins occluding and this activity outruns the
forcing. Showers will decrease as the dry slot spreads in
This system will fill to our north on Wednesday. There will be a
decent pressure gradient on its south side, but not a huge pressure
rise given the gradient orientation. Lower clouds will limit mixing
at least for a decent portion of the day, but some clearing should
occur east of I-57 and with time farther northwest. Gusts to 30 mph
are likely, maybe a bit higher in the clearing axis. With the upper
low close by and some lingering energy aloft and with the
approaching cold from, a few showers will be found mainly
northwest of Chicago through the day. Wednesday evening will
provide a brief break in the action ahead of a quickly developing
low for the later half of the week.
314 PM CDT
Thursday through Tuesday...
Active weather will continue through the upcoming weekend as the
overall pattern remains characterized by a western CONUS longwave
trough and strong western Atlantic ridging. Two storm systems
will be in focus for our area, the first with the potential for
heavy rain and gusty winds mainly Thursday night, and the second
with a quick-hitting period of rain on Saturday. Temps will remain
seasonable through the period.
Thursday through Friday: An upper-level low currently centered
near Las Vegas will drift across the Four Corners region through
tonight before ejecting into the mid-Mississippi River Valley by
Thursday. An impressive coupled upper jet structure over the
region combined with an increasingly negatively tilted mid-level
trough will result in rapid strengthening of a surface low by as
much as 15mb in 18 hours Thursday into Thursday night as the low
achieves lowest pressure somewhere across central IL into Indiana
Thursday night. With a strong moisture flux of >1" PWATs into the
area on Thursday, the potential exists for heavy rain with
embedded thunderstorms and strong gusty winds. While ensemble and
deterministic guidance varies in both the track and timing of
strengthening, there is increasing agreement that a anomalously
strong spring storm will shift across the region Thursday into
Thursday night. Of increasing likelihood is for at least the
southeast half of the CWA to reside in the northwest deformation
axis of the low, resulting in a swath of 1"+ of precip. Meanwhile,
N/NE winds have the potential to gust in excess of 40 mph for a
window Thursday night. While the strongest winds should occur over
a relatively short window, the potential for minor lakeshore
flooding exists for the southern tip of Lake Michigan late
Thursday night into Friday morning. Of final note, this system
should remain warm enough for all rain, but there is the potential
for some minor wet snow accumulations on the northwest edge of
the precip shield as colder air filters in from the northwest as
the precip is ending. Conditions will quickly improve Friday
morning as ridging rapidly builds across the region.
Friday night through Tuesday: A compact mid-level wave will
rapidly track from Colorado to the Upper Great Lakes on Saturday.
This will bring a round of light to possibly briefly moderate rain
across the area late Friday night through the day Saturday. The
coldest conditions of the week will follow on Sunday amid gusty
northwest winds, with highs possibly struggling to rise much above
50F for most of the area. Moderating conditions are expected
early next week as a progressive meridional pattern establishes
another trough west of the area.
For the 00Z TAFs...
Aviation forecast concerns for this TAF period include:
-Periodic showers continuing into this evening
-Periods of MVFR ceilings and visibilities possible through much
of the TAF period with potential for brief IFR ceilings or
-Gusty southeast winds continuing tonight with gusty southwest
winds expected Wednesday
Periods of mainly light showers have been ongoing at the terminals
for a few hours now, and the expectation is that this will
continue through tonight as a low pressure system to our west
continues to track northeastward. Some of the more convectively-
driven showers currently popping up across central Illinois will
move in later this evening and could be briefly heavier at times.
The showers will end sometime between 06Z and 10Z tonight from
west to east as a cold/occluded front associated with the surface
low passes through the area. With weak instability present, the
more robust showers could feature some isolated thunder, but given
that the thunderstorm coverage tonight will likely be minimal,
have omitted any TSRA mentions in the TAFs for now.
Ceilings look to remain MVFR for the most part this evening,
though they could at least briefly drop to IFR at times,
especially at RFD. Visibilities will also generally fall into MVFR
range within most showers, but will at least get close to IFR
within any heavier downpours. Some reprieve from the MVFR ceilings
and visibilities will come after a dry slot slides in behind the
aforementioned front, but ceilings could fall back down to MVFR
soon after daybreak Wednesday with the low-level moisture wrapping
around the low as it tracks into Wisconsin. Scattered light
showers may also sprout across the area Wednesday afternoon with
this, but uncertainty about overall shower coverage precluded any
formal -SHRA or VCSH mention in the TAFs at this time.
Southeast winds will continue to gust into the 20-30 kt range this
evening, possibly even locally higher underneath any more robust
showers/thunderstorms. Winds will then turn southerly overnight
and then southwesterly Wednesday morning. Gusts to 30-35 kts
appear likely during the afternoon hours on Wednesday.
LM...Small Craft Advisory...nearshore waters
until 10 PM Wednesday.
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Area Forecast Discussion
National Weather Service Lubbock TX
621 PM CDT Tue Mar 23 2021
A cold front will make its way through the region this evening and
overnight shifting winds to the east-northeast with increasing
speeds. An upper level system approaching the area on Thursday may
bring chances for light rain at all TAF sites from mid morning
through the afternoon. Lower CIGS will be possible with any rain
shower activity but confidence in sub-VFR is low at the moment.
.PREV DISCUSSION... /issued Issued by National Weather Service Amarillo TX/
SHORT TERM...Today through Tomorrow Night...
Pleasant conditions across West Texas today with light winds and
mostly clear skies. Areas with a southwest wind are more likely to
warm up today into the 60s and even lower 70s. Some mid to high
level clouds will move in during the late evening and overnight
hours ahead of the next system. Mid-level satellite water vapor and
500mb RAP analysis shows some weak ridging over West Texas alluding
to the nice weather today. Meanwhile, the next system is positioned
over the southern tip of Nevada and will bring the chance for
rain/snow to the area tomorrow. The best chance for snow remains in
the far northwest forecast area with on and off light rain showers
elsewhere due to warmer surface temperatures limiting the snow
potential. However, with the left entrance region of the upper level
jet over the area tomorrow morning, this additional lift may provide
enough dynamic forcing to see additional transitioning to snowfall
further east and south for a short period of time during the early
to mid-morning hours. Due to warmer surface temperatures,
accumulation amounts will be little to none, except for areas across
Parmer County and the northwest half of Castro County that may see
upwards of 0.5" to 1.5" of snowfall due to slightly cooler surface
temperatures and potentially heavier snowfall rates.
A surface low is expected to form during the overnight hours tonight
in southeastern New Mexico and bring gusty winds of 15 to 25 mph
with gusts up to 30 to 35 mph across West Texas into the morning
hours. These winds could cause a decrease in visibility, especially
in areas with more moderate rain showers or snow. With the surface
low positioned in southeast New Mexico, the surface cold front will
sit across Lubbock with temperatures potentially able to warm into
the 50s and 60s south of this boundary. However, by the evening
hours the surface low will push southeast and bring the front
completely through with temperatures to drop into the 20s and 30s
tomorrow night. Much of the Caprock will be below freezing
temperatures going into Thursday morning. Lingering moisture will
continue during the late evening and overnight hours tomorrow night
as the upper level trough swings over western Texas. With the
temperatures dipping below freezing, some of these rain showers may
transition to snow across areas more in the west along and on the
Caprock. Little accumulation is expected with this later moisture.
LONG TERM...Thursday through Tuesday...
By Thursday, the region will be on the backside of the mid-upr
trough that will cross the area on Wed. A 150 kt jet max and
adjacent S/WV in NW flow along the Pacific NW will combine to
reinforce a trough across the Rockies through Fri. This will
induce SFC cyclogenesis near SW CO through Friday with breezy SW
winds and very dry conditions developing as a result. The
combination of the wind and RH values close to 10 percent will
lead to RFTI values of 2-4 across the western half of the area.
While conditions are expected to be near legacy Red Flag criteria,
the ERCs are generally forecast to remain less than the 50th
percentiles except in the far south where pockets of 60-75th
percentile are forecast by WFAS. So for now, the combination of
ERC and RFTI are not flagging Friday Red Flags conditions but the
SW corner is showing elevated fire weather conditions. This will
have to be monitored through the week.
Models are in good agreement the highly amplified upper level
pattern will help push a cold front across the area on Saturday,
however timing difference are noted between the quicker GEM and
slower ECMWF/GFS solutions. For now am holding off on cooling temps
until Sat night and into Sunday, but even then forecast temps are
really just near climo post fropa. Med range models are not in good
agreement regarding the evolution of the aforementioned trough beyond
Friday. The disagreement centers around how much energy (if any)
from the base of the trough will be left behind as the northern
portion of the trough progresses east towards the east coast over
the weekend. The 00z/12Z ECMWF and 12Z GEM were most aggressive in
holding significant energy back and develop a closed low across
different parts of the WRN US. The 00Z ECMWF showed the low centered
just west of the Four Corners and generates precipitation across the
area Monday as the system lifts NE from there and a southern stream
jet streak pushes across West Texas. The 12Z run develops the low
further SW but still generates good QPF as it rapidly ejects across
CO on Monday. GEM develops the low much further SW near CA initially
and is weaker with less precip potential as it lifts from there
through Monday (slightly weaker than ECMWF). The GFS, as is many
times the case, is most progressive and generates just a tiny bit of
QPF near the area late Saturday as a rather moisture starved,
positively tilted trough, traverses the area. Given the uncertainly,
it is hard to argue against the NBM slt chc POPs which are focused
on Sunday night into Monday during this period. It is also difficult
to speculate on details beyond the basic POP forecast based on the
high degree of uncertainty given model/ensemble output for now.
...Update to aviation forecast discussion...
Issued at 313 PM CDT Tue Mar 23 2021
A closed upper low was located over the forecast area per the
1930Z water vapor and profiler imagery. A surface low was also
located just north of MHK. We have been monitoring conditions for
brief tornadoes as model progs of 0-3km CAPE suggest the potential
for some stretching of pre-existing surface vorticity near the
surface low. The main limiting factor is the amount of
destabilization as updrafts have not necessarily been that
intense. But there are some breaks in the clouds with better
insolation helping temps to warm into the upper 50s from Clay
Center to Marysville. This threat should wane fairly quickly
through the late afternoon as the sun lowers and the boundary
layer begins to cool. Meanwhile models show some scattered precip
lingering near the NEB state line through the evening. So have
some POPs going through the evening. Moisture rotating around the
back side of the closed low is expected to keep cloud cover over
the area through tonight and into Wednesday. This is expected to
help keep lows in the 40s for most areas.
A break in the precip is expected for the bulk of Wednesday before
another shortwave lifts across the area Wednesday night bringing
another chance for showers. Models show some decent mid level lapse
rates but elevated instability from forecast soundings is to weak to
mention thunder in the forecast. With much of the guidance showing a
compact wave with a good PV anomaly affecting the forecast area,
have increased POPs into the likely range. But overall precip
amounts look to remain around a quarter of an inch or less. The
forecast holds onto some chance POPs for Thursday across east
central KS, but confidence in these POPs is below average. They are
in the forecast because the ECMWF develops a deeper low across
central MO on Thursday with some wrap around precip possibly
impacting eastern KS in the afternoon. However other guidance is
weaker and further east with the low pressure system. So will need
to see how the pattern evolves in the coming days. Weak cold air
advection and limited insolation on Wed and Thursday is expected to
keep highs in the 50s. Although the cloud cover should also keep
lows around 40 for Thursday morning.
Another shortwave potentially moves across the forecast area Friday
and Friday night with a chance for some showers and possibly a
thunderstorm or two. Then a cold front moves through on Saturday
with some drier air advecting in from the northwest. An active
weather pattern is progged to persist into next week with the
possibility for another system to move through Monday or Tuesday.
However there are differences in the timing and track of this wave,
so confidence in the forecast is marginal towards next week. Have
some slight chance POPs in for Monday from the national blend of
models. But will need to see the models come together before
increasing POPs for early next week.
Temps are forecast to trend warmer through the weekend and into next
week. The front on Saturday does not appear to have a lot of cold
air with it so only a modest cool down is anticipated from Friday.
Then a southerly return flow is progged to set up by Monday with
highs potentially warming to around 70.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 625 PM CDT Tue Mar 23 2021
Surface low center passes just north of the terminals this evening
as southerly winds weaken below 10 kts while veering to the west
through 05Z. Light showers approaching KTOP/KFOE should linger
through 02Z before dissipating. Still some uncertainty on IFR
stratus dropping southward aft 06Z as predominant MVFR stratus is
observed upstream while forecast short term RAP and HRRR models
are not initializing correctly and over saturate the boundary
layer too quickly. Decided to maintain low MVFR with introduction
of IFR at KFOE. Period of IFR should be brief as drier air and
gusty northwest winds lift cigs back to MVFR in the early