Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/01/21
Area Forecast Discussion
National Weather Service Lincoln IL
910 PM CDT Wed Mar 31 2021
.SYNOPSIS...
Issued at 315 PM CDT Wed Mar 31 2021
Below average temperatures are expected tonight and Thursday,
with lows in the 20s and highs in the 40s. Breezy northwest winds
will continue tonight and tomorrow. A warming trend will begin
Friday and continue into the weekend, and no rain is expected
through at least Sunday.
&&
.UPDATE...
Issued at 910 PM CDT Wed Mar 31 2021
Some winter-like air will settle into Illinois tonight. The axis
of coldest 850mb air temps (-10C to -13C) will be centered from NE
to SW across Illinois at 12z/7am Thursday. Steady NW winds at
10-15 mph will continue through the night, but that will not be
enough to slow the cooling process like usual. Skies will be clear
though the night, helping radiational cooling. Low temps tonight
will be firmly down in the mid 20s, with low 20s toward Galesburg
to Lacon. No changes are needed to that part of the forecast. Same
with the freeze warning in our far SE counties, where some growing
has started.
&&
.SHORT TERM...(Tonight through Thursday night)
ISSUED AT 315 PM CDT Wed Mar 31 2021
500-mb RAP analysis for this afternoon showed a trough axis
over the Great Plains, with a ridge over the West Coast. These
features will translate east over the next several days, driving
the weather pattern in the process. Below average temperatures are
on the way through Thursday night as breezy northwest flow behind
yesterday`s cold front ushers in cooler air. Lows tonight and Thur
night will be in the 20s. Highs Thursday will be in the mid 40s,
which is about 10-15 degrees below normal for late March. A
modest pressure gradient over the area tonight will keep winds
from becoming calm, resulting in wind chills in the teens.
The 500-mb trough axis will sweep through overnight tonight into
Thursday. Behind the trough, a broad area of surface high pressure
shifts east, moving directly over Illinois by Thursday evening.
This will result in clear skies and light winds, allowing for
efficient radiational cooling. Low temperatures will again fall
into the mid 20s Thursday night. MRCC guidance and discussions
with core partners indicate that there is at least some vegetation
susceptible to freezing temperatures in the southernmost counties
of the ILX CWA, where a freeze warning has been issued for
Wednesday night and a freeze watch has been issued for Thursday
night. The threat for damaging cold in the southeast appears
greatest Thursday night, when several hours of mid 20s
temperatures are expected. The entire CWA will experience below
freezing temperatures both Wednesday and Thursday night, so
regardless of whether or not freeze headlines are in effect, if
you do have at-risk vegetation take action to protect it from the
cold.
.LONG TERM...(Friday through Tuesday)
ISSUED AT 315 PM CDT Wed Mar 31 2021
Ridging will persist over the central CONUS from Friday into next
week. On Friday, southerly flow returns and initiates the
beginning of a warming trend that will continue through the
weekend. The return flow will be more robust over the western half
of the ILX CWA on Friday, resulting in highs in the mid-50s west
of I-55 and near 50 degrees further to the east. Highs will rise
into the 60s on Saturday, then the 70s for Sunday and into early
next week. Over this period, breezy south to southwesterly winds
are expected everyday.
Precipitation chances appear few and far between at this time, with
dry conditions expected through at least Sunday. There is some
chance for precipitation on Monday, however, models have trended
further north with this disturbance and it may miss central IL
entirely. Additional precip chances exist by the middle of next
week, but little detail can be added to the forecast at that
range.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 644 PM CDT Wed Mar 31 2021
The strong NW wind gusts to 25-30KT from this afternoon will
linger a few hours into the evening, but will generally subside by
03z. It will still remain breezy overnight, as sustained winds
continue in the 10-15kt range. Winds will veer to a more northerly
direction tomorrow morning, with sustained speeds in the 13-16kt
range through the day. VFR conditions are expected to prevail
through the period.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 1 AM to 9 AM CDT Thursday for ILZ071>073.
Freeze Warning from midnight Thursday night to 9 AM CDT Friday
for ILZ071>073.
&&
$$
UPDATE...Shimon
SYNOPSIS...Erwin
SHORT TERM...Erwin
LONG TERM...Erwin
AVIATION...Shimon
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1155 PM EDT Wed Mar 31 2021
.UPDATE...
Issued at 1155 PM EDT WED MAR 31 2021
At 330z, a few leftover showers, perhaps mixed with a few flakes
over at the highest elevations, were exiting far eastern Kentucky.
Much drier air, evident in the low-level WV imagery and surface
obs, continues to move in from the west. The latest mesoanalysis
shows a relative lull in the CAA late this evening before another
CAA surge arrives along with a robust vorticity lobe. Dew points
south of the Mountain Parkway and east of I-75 remain relatively
high, in the mid 30s to around 40. While the incoming airmass is
very dry, this lingering low-level moisture combined with some
lifting ahead of the vort lobe will probably generate some
increased low to mid-level cloud cover. In fact, this already
appears to be happening over the Bluegrass, as per the latest
satellite trends. The CAMS seem to be underplaying the lingering
moisture over eastern Kentucky and thus could be missing the
potential for a few flurries late tonight. Have kept mention of
flurries and slight chance snow showers through the night over
Southeast Kentucky even though the NAMNEST is the only hi-res
model showing this potential.
UPDATE Issued at 815 PM EDT WED MAR 31 2021
Another round of showers is crossing our area, courtesy the right
entrance region of a 120+ knot 300mb jet residing over eastern
Kentucky this evening. This jet is leading to strong isentropic
ascent over a sloping anafront surface, as evident by the
strongly backed flow in the JKL radar base velocity imagery. Some
ice pellets have mixed with the rain in some of the more intense
precipitation areas, but well above freezing surface temperatures
will ensure that this remains a novelty. The HRRR and RAP seem to
be handling this activity the best; therefore, the overnight
forecast has been adjusted toward those models. The intensity and
coverage of the precipitation is expected to increase over the
next couple of hours across southeast Kentucky before the best jet
dynamics exit to the east. As the anafront advances eastward,
expect snow to mix in at elevations above 2,500 feet. While there
should be no travel impacts due to the very warm ground
temperatures, a quick dusting to an inch of snow cannot be ruled
out on grassy and elevated surfaces above about 3,000 to 3,500
feet. Once the steady precipitation exits to the east, some
shallow convection will likely continue under the strong CAA
regime. Some of the most robust convection could produce a few
more snow showers, flurries, and lower elevation sprinkles through
the late night hours, mainly for areas south of the Mountain
Parkway and east of Jackson where lingering low-level moisture
will be greater.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 621 PM EDT WED MAR 31 2021
An amplifying pattern is underway across the CONUS, as a seasonably
deep upper level trough is sharpening up from the Great Lakes down
through the southern Plains. At the surface, a cold front has
made it east of the Appalachians, with high pressure centered near
the central Great Basin through the central Plains region.
Temperatures across eastern Kentucky have retreated to the 40s,
with light precipitation starting to fill back in across the area.
The models have maintained good agreement through the short term.
The upper level trough will continue to deepen as it swings from
the Mississippi Valley to the Eastern Seaboard through early
Friday morning. At the surface, high pressure will gradually build
in across the Ohio Valley through the period, with northwesterly
flow allowing for well below normal temperatures across our area.
A passing upper level jet streak will allow for another round of
light to occasionally moderate precipitation early this evening
across eastern Kentucky. As temperatures fall off, this will
change over to snow across the highest elevations of eastern
Kentucky, with perhaps 1 to 2 inches seen atop Black Mountain.
Warm ground temperatures should prevent much in the way of
impacts. Precipitation will diminish to a few flurries/light snow
showers overnight. Ongoing cold air advection will allow for lows
in and around the 30 degree mark by dawn, so will let the Freeze
Warning ride.
Short wave energy will swing through on the backside of the
departing trough axis Thursday into Thursday night, with colder
temperatures continuing to advect in aloft. This will allow for
some fairly steep lapse rates of 7 to 7.5C/km across the area
during the afternoon, as surface temperatures struggle to reach
the 40 degree mark. Expect mostly cloudy skies and some isolated
snow shower activity to break out across the area during the day,
before diminishing by dusk. Clouds will gradually clear out
Thursday night, setting the stage for a hard freeze area-wide, as
temperatures dip into the upper teens and lower 20s, likely
breaking record lows at Jackson and London. Given the model
consistency regarding the expected air mass, have upgraded the
Freeze Watch to a Freeze Warning for Thursday night.
.LONG TERM...(Friday through Wednesday)
Issued at 506 PM EDT WED MAR 31 2021
The majority of the extended remains fairly uneventful. The main
element of more significance is the colder temperatures near the
beginning of the period.
There is pretty good agreement over most of the period up through
Sunday. Models depict our area starting out Friday just to the west
of a departing trough and sitting under an area of stronger
northwesterly flow, helping with the continued advection of a much
colder airmass. Broad ridging lies across most of the CONUS going
forward through the weekend and into Monday. At the surface, high
pressure dominates across our region, providing calm and clear
conditions. Temperatures starting off Friday morning will be frigid,
getting down in the mid 20s to right around 20 and a Freeze Warning
will be in effect to 11 AM. Temperatures moderate going forward but
are still chilly Friday night with temperatures getting down into
the mid/upper 20s, and even lower in the valleys. However, a
headline for this time period specifically has not been done, given
the distance into the future and that there are already two
headlines out for early Thursday morning and late Thursday night
into Friday morning. It will be mentioned in the HWO for now.
Temperatures continue to moderate going through the weekend, but
Saturday night still looks a bit chilly, especially down in the
valleys, and some frost is possible. However, a hard freeze looks
unlikely at this point.
Moving into early next week, some uncertainty arises as models are
not in the best agreement. They are struggling with the evolution of
a trough moving towards the Pacific Northwest on Monday. Generally,
a northern stream wave splits from this initial trough while a
southern stream trough stays behind for a bit over the western U.S.
coast. Beyond this general idea, there are some decent
discrepancies, particularly with timing. This leads to a lack of
confidence in the evolution of any surface features and the sensible
weather experienced here. Overall, stayed relatively close to the
blended guidance, and kept PoPs out for most of the forecast period.
Some PoPs were introduced near the very end of the forecast period
as a frontal boundary attempts to move towards the area, but these
were limited to a very low slight chance at most. Again, confidence
in that part of the forecast is not very high at this point and
there exists a decent chance for change.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 839 PM EDT WED MAR 31 2021
At 0030z, VFR ceilings were observed across the area except for
far eastern Kentucky (ie. KPBX and KSJS) where MVFR conditions
were noted due to a passing band of heavier rain showers along a
mid-level cold front. While that band should quickly exit to the
east by around 1z, allowing for a brief improvement in ceilings
over far eastern Kentucky, another band of showers and lower
ceilings will likely move through far eastern Kentucky during the
130-330z timeframe. Outside of far eastern Kentucky, showers and
virga will diminish from west-to-east through 3z while ceilings
remain solidly VFR.
As colder air continues to advect in on northwest winds, some
flurry or light snow shower activity will be possible later
tonight and again on Thursday. Ceilings will generally remain
VFR, although some temporary MVFR visibilities will be possible in
the more sustained snow showers. Northwest winds of 5 to 8 kts,
will turn more gusty by late Thursday morning, as deeper mixing
takes place.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Freeze Warning from 3 AM to 10 AM EDT Thursday for KYZ044-
050>052-058>060-068-069-079-080-083>088-104-106>120.
Freeze Warning from 11 PM Thursday to 11 AM EDT Friday for
KYZ044-050>052-058>060-068-069-079-080-083>088-104-106>120.
&&
$$
UPDATE...GEERTSON
SHORT TERM...GEOGERIAN
LONG TERM...HAS
AVIATION...GEERTSON/GEOGERIAN