Forecast Discussions mentioning any of
"ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/02/20
Area Forecast Discussion
National Weather Service Louisville KY
1057 PM EST Sun Mar 1 2020
.Forecast Update...
Issued at 1055 PM EST Sun Mar 1 2020
...A few wind gusts above 30 MPH this evening...
We`ve seen a few pretty strong gusts in the 30-39 mph range over the
past hour. After a closer look, this appears to be occurring as high
based showers precipitate through an impressively dry lowest 7000
feet. Forecast and recent AMDAR soundings show a T/Td spread around
20-25 degrees through a pretty deep layer, and think that this is
allowing the higher momentum air (40-45 kt low level jet) to be
brought down to the surface as it begins to precipitate.
The good news is that we don`t expect it to last too long as the
column should steadily saturate as more widespread precipitation
arrives. Nevertheless, will monitor over the next little bit to see
if a short fuse Special Weather Statement may be needed.
Issued at 735 PM EST Sun Mar 1 2020
The forecast is on track so far this evening as light rain showers
have started to move into our NW CWA. Expect chances to steadily
increase from W to E across our CWA through the overnight hours.
Did want to mention that there will be some potential for some small
hail with any 40+ dbz radar returns. Given some meager elevated
instability combined with freezing levels around 7 K feet the
ingredients are there. It will be most likely to happen around the
time of precipitation onset as a notable dry layer still exists in
the lowest several thousand feet, which will slow the melt of any
ice below 7 K feet (freezing level). Did get a report of this
occurring upstream over Warrick county a bit earlier, and wouldn`t
be surprised to see a few reports in our area as the evening
progresses.
&&
.Short Term...(This evening through Monday)
Issued at 247 PM EST Sun Mar 1 2020
A cold front reaching from the Great Lakes to Texas will approach
the Ohio Valley tonight. Ahead of it, warm air and moisture will
surge northward behind high pressure off the Carolina coast. Clouds
will lower and thicken, and showers will become widespread by
midnight. A moderate low level jet from the lower Mississippi Valley
to the eastern Lakes will aid in moisture transport and a few
elevated rumbles of thunder may be heard in western Kentucky after
midnight. Although dew points are in the 30s this afternoon, with
strong warm advection and thickening cloud cover tonight will still
go on the warm side of guidance for lows as we get deeper into the
warm sector, from the mid/upper 40s in the Blue Grass to the low 50s
west.
On Monday the cold front will continue its advancement and will
arrive in central Kentucky by mid to late afternoon. Widespread
showers and scattered thunder will continue in association with this
feature. High temperatures will mostly be in the 55-60 degree range.
Gusts of 25-30 mph will be possible, especially east of I-65 in the
afternoon in the area of tightest isobar packing ahead of the
surface boundary.
.Long Term...(Monday night through Sunday)
Issued at 301 PM EST Sun Mar 1 2020
...Drying trend continues...
First, though, a wave moving up a slow-moving cold front will bring
widespread showers and scattered thunder to the region Monday night,
gradually tapering off over the course of the day Tuesday as the
wave and front exit the region. A southern stream system will scoot
from the Desert Southwest eastward along the Gulf Coast states
Monday night - Thursday. The trend of pushing this feature south
remains true and there is good model agreement keeping its rain
south of Indiana and Kentucky. After collaborating with
neighbors, will continue to trend PoPs downward, below guidance.
Thursday-Friday a potent upper vort max will charge from the
Northern Plains through the Great Lakes to the Northeast. Surface
ridging from the mid-Atlantic to the Ozarks will force this system
to rely on Pacific moisture for its precipitation, and right now it
looks like precipitation associated with this feature will remain
just off to our northeast. However, any southward shift in the track
would bring inclement weather into the forecast so will hold on to
some small PoPs in the east.
Next weekend looks nice as a strong ridge of high pressure cruises
through.
Meteorological spring has sprung, at least for now, and afternoon
highs this week will mostly be in the 50 to lower 60s. Friday may be
a bit cooler as that northern stream system brushes by to our
northeast...highs in the 40s.
&&
.Aviation...(00Z TAF Issuance)
Issued at 647 PM EST Sun Mar 1 2020
The TAF sites will start out VFR this evening, with steady S or SSW
winds, occasionally gusting up around 20-25 mph. Rain chances will
steadily increase from W to E ahead of the next weather system
tonight, with ceilings falling to MVFR after Midnight. IFR ceilings
appear to be a good bet from around sunrise through the early to mid
afternoon at HNB/SDF/LEX, while BWG should hold onto low MVFR for
much of the time. Rain persists for much of the day on Monday,
although may see some drying by late afternoon/early evening from W
to E. Winds should be pretty stout throughout this forecast cycle,
with potential for some 20-25 mph gusts at least through tomorrow
afternoon. Did also want to mention some marginal LLWS overnight
tonight.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...BJS
Short Term...13
Long Term...13
Aviation...BJS
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
848 PM CST Sun Mar 1 2020
.UPDATE...
846 PM CST
Main update this evening was to tighten up the PoP gradient on
the northwestern flanks and to generally reduce thunder chances to
a narrower corridor across our far southeastern counties
overnight.
Mid-evening moisture channel imagery reveals our initiating
shortwave in question translating fairly swiftly across central
Missouri. Based on its current more easterly translation
component, it appears most of the large-scale DCVA-induced forcing
for ascent will remain confined mainly to our far south and
eastern counties overnight. Noting developing elevated showers off
to our southwest at the edge of the main mid-level moisture
plume, and this spotty activity should continue to develop
northeastward through the evening hours, although this may
initially struggle as it moves into a drier airmass. At the surface,
a cold front is just about to move through the Rockford area and
will continue to push through the forecast area overnight. This
intrusion of cooler/drier air will set a northwestern terminus to
any potential shower or embedded thunderstorm activity that will
be continually marching southeastward with time.
Surface observations show the 50 degree isodrosotherm is still
well off to our south, closer to the I-64 corridor across southern
Illinois, which is notably farther south than midday model
guidance (RAP/HRRR) would have suggested. Recent VAPOR AMDAR
soundings out of Midway reveal that things are pretty parched
through the low and mid-levels, and even ILX`s evening RAOB
sampled plentiful lingering dry air below 600 mb. So, while mid-
level lapse rates are more than supportive of thunderstorm
development, pretty marginal moisture and thermodynamic profiles
look to chew into this potential a good deal tonight.
With this in mind, have confined the thunder mention for the rest
of the overnight to areas south of a Pontiac to Valparaiso line
and also trimmed PoPs in the vicinity of I-55 as the incoming
front looks to scour moisture out before the main slug of mid-
level moisture arrives. Should still see some pretty good shower
coverage east of I-57 tonight before everything shifts east of our
area by daybreak on Monday. Updated products have been sent.
Carlaw
&&
.SHORT TERM...
135 PM CST
Through Monday night...
A significant but somewhat short lived air mass change continues
this afternoon as dewpoints climb into upper 30s and the 40s are
knocking on the door. Several features of note on water vapor
pictures, a strong jet core across the southern tier of states,
with a few smaller scale disturbances in mostly westerly flow
aloft to our south, maybe a slightly more distinguishable wave
moving into MO early this afternoon.
Morning soundings out of Little Rock, AR and Springfield, MO depict
the airmass that will advect toward the area ahead of an approaching
cold front this evening. A noted but modest increase in PWATs up to
0.55" but with impressive lapse rates in excess of 8 deg/km around
the 700-500 mb layer, and quite the elevated mixed layer a bit
further upstream at Fort Worth, TX and PWATs in excess of 0.75". RAP
modeled soundings are a tad moist at this point.
The driver for the cold is a more significant upper low across the
northern international border region. This will drive through the
upper Great Lakes tonight and push the cold front into the area this
evening and through the area by Monday morning. This aforementioned
features will lead to an expansion of showers and thunderstorm
across the mid Mississippi valley late this afternoon. The cold
front will provide for a sharp cut off in the precip axis which
still roughly aligns with the I-55 corridor. The better moisture
will certainly shift into the Ohio Valley thus some mixed signals
on the strength of the precip and instability this far north, but
enough moisture will advect to our area to support a period of
some decent showers. Cannot argue against the chance of a few
thunderstorms given the impressive lapse rates upstream, and
narrow ribbon of moisture ahead of the front, with a little
better signal south of I-80 across east central IL and into
central IN. Main time window is 9PM CST until about 2-3AM CST.
The cold front will quickly move through overnight ending precip
chances. Northwest flow will maintain a cold advection regime on
Monday, with highs back more in the department of normal or slightly
above under mixed sun and clouds. Noted the previous AFD mention of
lake breeze potential which should form. Current 12z runs depict
925-950 mb flow would be strong enough to keep it at bay for most
of the day before the flow weakens at a diurnally unfavored time
for a lake breeze to move inland too much, but this will be more
of a mesoscale feature to see how the hi-res models resolve
tomorrow.
High pressure will shift through the lower Great Lakes region Monday
night supporting cool temperatures and fog would be possible in some
areas, with some hints that this may be favored across the recently
rained areas of EC IL and NW IN, though there is enough low level
flow to suggest it would shallow.
KMD
&&
.LONG TERM...
125 PM CST
Tuesday through Sunday...
A split flow regime will remain in place mid week with a strong jet
across the Ohio Valley ahead of a southwest trough and the northern
stream pushing out of the Canadian northwest/Rockies. The southern
jet should keep the better moisture south of the Great Lakes with
our weather potentially more influenced by the northern stream.
The surface low associated with the shortwave trough in the
northern stream will pass well north of our area, which should
keep precip limited with the first wave Tuesday morning, but a
weak cold front will nevertheless slide through Tuesday night
accompanied by a sharper upper trough. After a day of mixing and
the cut-off low preventing any northward transport of meaningful
moisture, The front will likely come through dry.
Wednesday will be breezy with northwest winds in the wake of the
cold front and with the front of Pacific origin we will likely only
see a smaller dip in temperatures, though it may feel cooler with
the northwest breezes. Winds will quickly become southwesterly again
by Thursday in advance of the next shortwave trough, which will help
boost temperatures toward the upper 50s.
The second cold more potent front of the week will sweep through
Thursday evening. Model guidance does paint some light QPF with this
stronger front, though moisture is still limited and this front
may yet still some through dry in with the cut-off low still
meandering along the Gulf hogging moisture. A pocket of colder air
will be found behind the front this time around, Friday will end
up the coolest day this week with highs in the 40s, still near or
maybe a tad above normal, though it will be breezy again to make
it feel cooler, especially lakeside. There are some lakeshore
flooding concerns in Northwest and portions of Cook County given
the gusty winds behind this stronger front.
The weekend will begin dry and mild as upstream ridging and deep
south-southwest flow returns (some cooling IL lakeside due to some
SE component possible), but there are some inconsistencies in model
guidance as to if the ridge will hold precip off through the whole
weekend, but conditions will remain on the mild side.
KMD
&&
.AVIATION...
For the 00Z TAFs...
A cold front will shift southeast across the area late this evening
into the early overnight hours. Observational data and model
guidance has suggested a southward trend with associated SHRA and
embedded TS that is expected to develop along the front late this
evening. While ORD/DPA/RFD were already expected to remain dry, the
southward shift will likely keep MDW dry as well and push the TS
chance south of GYY. However, an isolated light shower cannot be
ruled out for MDW around midnight, while scattered showers are
expected around the same time for GYY.
The southward trend in precip has also resulted in a trend to higher
ceilings for all Chicago metro sites, with VFR ceilings now expected
at all sites but GYY through the period.
SW winds around 10 knots ahead of the front will become NW 10-15
knots, with some gusts nearing 20 knots possible at times on
Monday.
Kluber
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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