Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/28/20
Area Forecast Discussion
National Weather Service Gaylord MI
1148 PM EDT Fri Mar 27 2020
.UPDATE...
Issued at 939 PM EDT Fri Mar 27 2020
All sorts of unsettled wx to our s and sw, but in our neck of the
woods things are quiet...for now. Earlier stratus/fog that
bedeviled the Straits and some other coastal locales into late
afternoon has been shoved westward by developing east winds.
(Though OSC now has a scattered deck at 500ft, so hello Lake
Huron. But sat imagery is showing very little low clouds there.)
Thin cirrus is presently overhead, thanks to the active wx to our
s. Some mid clouds have pushed into central lower MI. Actual
precip is found in far southern lower MI, and the south half of
WI.
Surface low is continuing to spin up in the high plains, and
warm/moist advection ahead of it is increasing. Models are in
good agreement that we will /not/ see a solid wall of precip push
into northern MI overnight. But, it is interesting to see some
banded fgen-like radar echoes starting to form over central WI.
And it is also interesting to see the Rap and HRRR models push
scattered precip as far north as PLN by 12Z. The going forecast is
slow to push pops north, in deference to dry low-level air
sampled by the 00Z APX sounding (dew pt depressions 10-20C below
850mb). But, stepping back, this is dry but not /very/ dry (and
note that surface dew points did not crater particularly hard
during our sunny afternoon).
So am thinking we need to push chancy pops north to the tip of
northern lower MI by morning. Can probably hold back from pushing
into parts of ne lower MI (Rogers-APN-Harrisville), as well as
eastern upper.
Some heavier convective showers (though probably not thunderstorms)
could develop as far north by central lower MI by morning. Gladwin
Co is the most likely to perhaps see heavier precip rates by
morning.
&&
.NEAR TERM...(Through Saturday)
Issued at 344 PM EDT Fri Mar 27 2020
...Showers spread into the region overnight and Saturday...
High Impact Weather Potential: Minimal for now.
Pattern Synopsis/Forecast: Low amplitude short-wave ridging
spans much of the eastern CONUS while surface high pressure
extends from eastern Canada down into the Great Lakes. Surface
low pressure is across the central-southern Plains with a stalled
boundary stretching eastward through the Ohio Valley. Across
northern Michigan, quiet/nice conditions now across the region
after our stubborn low stratus finally mixed out. That said, there
is still a good amount of marine stratus across Lake Michigan and
far northern Lake Huron that is skirting some of the coastal
locations of the CWA.
Surface low pressure will continue to organize/deepen in the
central Plains tonight before lifting up through the Midwest on
Saturday/Saturday night. This spreads showers up into the region
starting overnight.
Primary Forecast Concerns: Minimal.
Details: First wave of strong warm advection forcing is expected
to develop across the lower lakes region tonight along with the
first wave of showers just edging up into the southern part of the
forecast area overnight into Saturday morning. Initially, there
will be quite a wedge of lower level dry air to overcome across
northern Michigan through the overnight period. So confidence in
getting any substantial precip up into the region is somewhat low
through Saturday morning. But, will maintain change to low likely
PoPs for the southern parts of the CWA at this juncture.
Second stronger surge of moisture/forcing spreads into the region
as we go through the day Saturday bringing steady increasing rain
chances, particularly during the afternoon hours. Thunderstorm
chances eventually enter the picture, but probably not until very
late afternoon/evening.
&&
.SHORT TERM...(Saturday night through Monday)
Issued at 344 PM EDT Fri Mar 27 2020
High impact weather potential: Chance for thunderstorms Saturday
evening/night.
Pattern synopsis/forecast: By Saturday evening, vertically stacked
low pressure system is expected to be centered across northwest
Iowa. Larger scale parent upper-level wave will continue to become
negatively titled as it deepens through Saturday night while
progressing northeastward across the Great Lakes region. Strong
divergence aloft should fairly readily aid in supporting a sub-990
mb sfc cyclone through this time frame before the system`s
cold/occluded front is expected to press west to east across the
forecast area early Sunday morning. However, wrap around moisture is
expected to encompass much of the region on the backside of the
departing system through Sunday evening.
High pressure returns to the area as early as Sunday night into
Monday, ultimately bringing a return to more tranquil conditions.
Primary forecast concerns/challenges: Thunderstorm chances Saturday
evening/night. Low chance for some gusty winds/hail across southern
parts of the forecast area?
The primary focus through the forecast period revolves around the
Saturday evening/night time frame as a swath of deeper moisture is
expected to yield some heavier rain rates and even a few
thunderstorms. Despite surface temperatures in the upper 30s and
lower 40s, model soundings suggest elevated instability on the order
of several hundred J/kg that may support a few rumbles of thunder,
primarily across northern lower. Rather impressive veering wind
profiles depicted, along with upwards of 50-60 kts of bulk shear may
pose a low chance for some hail/gusty winds with any stronger cells
able to sustain themselves. This represented well in SPCs Day 2
outlook that paints areas along/south of M-55 in a Marginal Risk for
severe storms.
By the second half of Saturday night into early Sunday morning,
precip chances are expected to diminish from southwest to northeast
with the associated frontal passage and deep layer dry air moving in
aloft. However, this trend isn`t expected to last long as wrap
around moisture arrives from the northwest as early as late morning
through much of the afternoon, ultimately renewing shower chances
across much of northern Michigan. Some guidance even suggests a bit
of lake induced precip continuing into Sunday night; however, very
marginal delta Ts and declining deep layer moisture yields little
confidence in this solution, and gut feeling is that we`ll have more
dry time Sunday night into Monday across the vast majority of the
forecast area.
High pressure anchored to our north early next week makes its
effects felt locally as early as Monday with the expectation of dry
weather across the forecast area, despite somewhat cooler
temperatures than seen this weekend. Sunday`s highs in the upper 40s
to low 50s, falling into the low 40s for most on Monday.
.LONG TERM...(Monday night through Friday)
Issued at 344 PM EDT Fri Mar 27 2020
High impact weather potential: Minimal for now.
Initially tranquil conditions expected across the northern Great
Lakes at the start of the period as Saturday-Sunday`s area of low
pressure continues to trek eastward. Focus transitions to another
well-defined shortwave across the Four Corners region Monday
afternoon, which latest trends suggest should safely pass by to our
south as it ejects eastward across the southeastern US. Confidence
diminishes thereafter in any given solution; however, perhaps the
most likely revolves around another system arriving into the Pacific
Northwest during the day Tuesday before moving eastward midweek...
perhaps increasing precipitation chances locally at times Wednesday-
Thursday. Highs through the period are expected to be close to
seasonal averages in the mid 40s for many across northern Michigan.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1148 PM EDT Fri Mar 27 2020
Gradually worsening conditions as rain moves in Saturday.
Low pressure is advancing out of the high plains, moving ne.
This low will move ne-ward, reaching La Crosse WI by late Saturday
evening. High and mid clouds will continue to thicken and lower
overnight. Some showers could approach the nw lower MI TAF sites
late in the overnight. Precip is expected to be somewhat spotty
and light until very late on Saturday, when a stronger push of
moisture arrives. Still, cigs will lower, and all sites will see
MVFR cigs at some point Saturday, though it will wait until very
late in the day at APN and PLN. Saturday night, IFR cigs/vsbys
arrive, with some potential for LIFR cigs closer to midnight.
East to se winds will increase tonight and into Saturday, gusty
during the day on Saturday.
&&
.MARINE...
Issued at 344 PM EDT Fri Mar 27 2020
Quiet weather anticipated tonight. Low pressure in the Plains will
further organize/deepen and lift up through the Midwest Saturday,
and the western Great Lakes Saturday night into Sunday. Increasing
E/SE flow with this system will likely result in small craft
advisories for most nearshore areas Saturday and Saturday night.
Winds veer into the southwest then west on Sunday as the system
passes through the region. Some gale force gusts are possible on
Lake Michigan Sunday and plan to hoist a gale watch accordingly.
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...GALE WATCH from late Saturday night through Sunday evening for
LMZ345-346.
LS...NONE.
&&
$$
UPDATE...JZ
NEAR TERM...BA
SHORT TERM...MG
LONG TERM...MG
AVIATION...JZ
MARINE...BA
Area Forecast Discussion
National Weather Service La Crosse WI
1052 PM CDT Fri Mar 27 2020
.SHORT TERM...(This evening through Saturday)
Issued at 251 PM CDT Fri Mar 27 2020
At 2 PM, skies were partly to mostly cloudy across the Upper
Mississippi River Valley. Temperatures were in the 40s in Clark and
Taylor counties in north-central Wisconsin, and in the mid and upper
50s across the remainder of the region.
As the 850 mb moisture increases ahead of a shortwave trough
ejecting out of the Central Plains late this afternoon and evening,
showers will rapidly develop across the Upper Mississippi River
Valley. This will occur south of Interstate 90 between 4 PM and 8 PM
and across the remainder of the area between 8 PM and 1 AM. Rainfall
totals will be up to a quarter of an inch.
On Saturday morning, showers and even a few thunderstorms will
continue ahead of yet another shortwave trough ejecting out of the
Central Plains. There continues to be questions on how much elevated
instability will move into the region. Most have very little, but
the HRRR and RAP have elevated CAPES in the 500 to 1500 J/kg range.
With ample shear aloft, there is a potential of elevated supercells
with hail being the primary threat.
On Saturday afternoon, the models continue to struggle on whether
the thunderstorms will be able to become surface-based or not across
northeast Iowa and southwest Wisconsin. Both the HRRR and RAP say
that this is a possibility, but many of the other models say no. If
we do get into the warm sector, the 0-1 km shear could be in the
excess of 40 knots and 0-1 km helicity of 300 to 400. This would
provide the potential of supercell tornadoes between 4 PM and 7 PM.
Even if they do not become surface based, there will be the threat
of hail.
Like the past couple of days, there continues to be a marginal risk
of excessive rain. Precipitable water values will be in the 1 to
1.25 inch range south of Interstate 90. This is 2 to 3 standard
deviations above-normal.
.LONG TERM...(Saturday night through Friday)
Issued at 251 PM CDT Fri Mar 27 2020
Deep sub-990 mb low pressure will move from north-central Iowa to
central Wisconsin Saturday night, with the earlier wave of showers
and storms moving off to the northeast in the evening. There could
be a few strong storms continuing to move across central Wisconsin
early in the evening before moving quickly northeast. We may then
get a brief break in the rain for part of Saturday night as the
dry slot moves overhead, but wrap-around showers will increase in
coverage late overnight and continue throughout Sunday. There may
even be a few snow flakes mixing in Sunday morning, but surface
temperatures in the mid to upper 30s will make accumulations
unlikely. As the low moves away Sunday morning, a tight pressure
gradient and large pressure rises (+8 to +10 mb in 6 hours) on the
back side of the low will lead to gusty west-northwest winds into
the early afternoon. Soundings suggest speeds at the top of the
mixed layer of 35-40 knots, and while we may not mix quite that
much downward to the surface, gusts of 30 to 40 mph will still be
possible during the day, slowly tapering off in the late afternoon
and evening as the pressure gradient relaxes. Showers should also
diminish by evening as the low moves farther away from the area.
Ridging takes over for Monday into Tuesday morning, before a
shortwave ejects eastward out of the southern plains Tuesday into
Wednesday. This system looks to stay south of our area, and thus the
bulk of the precipitation associated with this looks to stay south
as well. Deterministic models would suggest Tuesday stays dry, but
several GEFS members have light precipitation approaching from the
west and this has been carried over into the blend. Details are
murky toward the end of the week as several models show
differences in temperatures and precip. during this period. Beyond
this, there does seem to be a signal for cooler conditions
working southward at some point during the weekend.
&&
.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1052 PM CDT Fri Mar 27 2020
MVFR/IFR conditions expected through the period as a potentarea
of low pressure lifts from the Central Plain into the region. Plan
on periods of rain overnight through Saturday with even some
thunderstorms in the vicinity mainly in the 20-02z time frame.
Gusty west-northwest winds will set in after midnight Saturday
night, lasting into Sunday along with scattered showers. More
detail will be given with the 12z TAF issuance.
&&
.HYDROLOGY...
Issued at 251 PM CDT Fri Mar 27 2020
Widespread 0.75" to 1" of rainfall is expected through this weekend,
much of it falling Saturday. With already elevated river levels and
fairly saturated soils from recent rainfall over the past week, this
will lead to additional rises on area rivers and possibly flooding
in some spots this weekend into early next week. In addition,
heavier rain is expected to fall to the northwest of the forecast
area which will lead to continued rises along the Mississippi River
through next week.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Boyne
LONG TERM...Lee
AVIATION...DAS
HYDROLOGY...Lee
Area Forecast Discussion
National Weather Service Denver/Boulder CO
918 PM MDT Fri Mar 27 2020
.UPDATE...
Issued at 850 PM MDT Fri Mar 27 2020
No significant changes to the forecast package this evening. It
appears the heavier showers over Denver area are starting to shift
to the east. Although the snow appears to be done in the foothills
of Larimer County, light to moderate snow showers continue in
Boulder County. Will let the winter weather advisory ride there for
now, but it could be cancelled by midnight. No changes regarding
the highlights over the northeast plains. Light rain showers or
drizzle along and east of a Sterling to Akron line should switch
over by midnight once the colder air moves in from the west.
Light to moderate snow developing over eastern Weld to just east
of Denver. Latest HRRR shows a band of snow through midnight then
a short break until 3 am, then the snow cranks up again. Strongest
winds should get going around 3 am. No changes to the timing to
the blizzard, but the best combination of snow and wind will be
after midnight.
UPDATE Issued at 526 PM MDT Fri Mar 27 2020
Some thunderstorms developing over eastern Elbert and northern
Lincoln counties late this afternoon, so updated to include
thunderstorms there until 8 pm.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 300 PM MDT Fri Mar 27 2020
Water vapor imagery shows a strong trough moving across the Four
Corners region with convective showers developing over the
mountains. This trough will strengthen tonight as it moves onto
the Central Plains and becomes a closed low. At the surface, a
lee cyclone is developing over the Arkansas River Valley in
southeastern Colorado. On the north side of the cyclone, upslope
flow has kept cool and relatively moist air in place today.
Instability over the mountains along with convergent flow is
beginning to produce showers across our CWA. These showers will
increase in coverage and intensity throughout the rest of the
afternoon and evening. Initially, rain will be falling across the
plains but a cold front will push southeastward out of Wyoming
this evening changing the precipitation over to snow from west to
east. The urban corridor will be the first to see snow this
evening but it should end rather quickly as northwest, downslope
flow dissipates precipitation by the late evening. This is why the
urban corridor was left without any advisories since snow amounts
and impacts will be much lower than other areas. As the surface
cyclone deepens tonight, it will greatly strengthen northwest
winds across the eastern plains as moderate to heavy snowfall
develops. Models have come into better agreement that areas from
the Palmer Divide to northern Washington County will be the focus
for heavy snowfall as 4 to 10 inches are possible there. The heavy
snow combined with wind gusts up to 55 mph will create blizzard
conditions and extremely hazardous travel conditions. A Blizzard
Warning was issued from 9pm through noon tomorrow for Washington,
Lincoln, and NE Elbert Counties. One of the bigger forecast
changes was to increase PoPs and QPF tomorrow morning since the
system will be much slower to move out of the region than
originally expected. In the mountains, there will be generally
light snowfall with the highest amounts north of I-70 were a
Winter Weather Advisory is in effect.
Strong northwest winds will persist throughout the day tomorrow
with clouds decreasing from west to east. A few light snow showers
will be possible in the mountains but other areas will remain dry
besides the morning snow on the far eastern plains.
.LONG TERM...(Saturday night through Friday)
Issued at 300 PM MDT Fri Mar 27 2020
Short and medium range models each have the upper level
low well east of Colorado by tomorrow evening with weak west to
northwest flow aloft over the state. Mountain areas will have a
little moisture trapped west of the Continental Divide which will
produce some weak snow showers overnight. By Sunday morning, flow
aloft will be switching to west and southwesterly, ahead of the next
developing upper trough over the southwestern United States. This
will bring warmer temperatures back to the area.
The next upper trough is expected to be moving over the region
Monday with another round of mountain snow showers and plains rain
showers Monday afternoon and evening. Warm air will move up over
eastern Colorado ahead of the trough, which will keep the showers on
the plains in the liquid form.
After Monday`s system moves through, moderate to strong westerly
flow aloft will dominate through the first half of the week. Some
Pacific moisture will be embedded in the flow, causing some
orographic snow showers over the mountains. Snowfall amounts in the
mountains will be light through the next several days as the trough
moves through quickly, and the subsequent westerly flow aloft will
not have that much moisture. The plains will be dry for the majority
of the week.
At the end of next week, the medium range models show the next upper
trough arriving. Models have different ideas concerning the
magnitude and timing of the arrival of this trough. For the time
being, Monday`s trough will be the last significant weather for the
week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 850 PM MDT Fri Mar 27 2020
Heavy, wet snow may decrease visibilities below a mile mainly
between 03-06Z. Snowfall at the Denver airports is expected to be
between 2 to 4 inches. Strong gusty winds will also affect the
airports with gusts up to 35 knots possible late tonight.
Saturday, skies clear out as strong northwest winds persist.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from midnight tonight to noon MDT
Saturday for COZ048-050-051.
Winter Weather Advisory until 3 AM MDT Saturday for COZ033-035.
Winter Weather Advisory until 6 AM MDT Saturday for COZ041-042-
044-045.
Blizzard Warning until noon MDT Saturday for COZ046-049.
&&
$$
UPDATE...Cooper
SHORT TERM...Danielson
LONG TERM...Dankers
AVIATION...Cooper
Area Forecast Discussion
National Weather Service Cheyenne WY
723 PM MDT Fri Mar 27 2020
.UPDATE...
Issued at 705 PM MDT Fri Mar 27 2020
Most precipitation has shifted south and east, along and east of a
Cheyenne-Torrington-Harrison line, though generally light snow
showers will continue to the west of this line through tomorrow.
This line will not move quickly out of the region however, as the
deep surface low moves slowly from the southeast corner of
Colorado and shifts northeast through Kansas and finally gets
kicked further northeast tomorrow afternoon. In the meantime,
still expected quite a bit of snow accumulation overnight along
and east of the aforementioned line. At the moment, temperatures
are still above freezing across the Panhandle with precipitation
falling as rain. Will see a gradual transition to snow in the
next few hours. This will lead to several overnight and morning
travel hazards as snow accumulates on roads (temperatures and the
sun angle were preventing snow accumulations along the roadways
earlier today, but that will soon come to an end across the area),
becoming slick and snowpacked. We`ll also see reduced visibility
across much of the region as patchy fog develops overnight.
Additionally, as the surface low deepens and gains strength,
winds will increase over the far southeast portion of Wyoming and
the southern portion of the Nebraska Panhandle creating areas of
blowing snow, that may continue through the day tomorrow, even
after the showers taper off. Looking towards warming daytime
temperatures to limit driftability as the fresh snowpack crusts
over.
In this latest update, dropped the Winter Storm Warnings that had
been in place over the Snowy and Sierra Mountain Ranges, as only
light linger snow showers remain. Also, downgraded the -i80 Summit
and South Laramie Foothills to an advisory as the heavier bands
shifted east and only 1 to 3 inches of snow accumulation is
expected. All other hazards remain in place.
&&
.SHORT TERM...(This evening through Saturday)
Issued at 249 PM MDT Fri Mar 27 2020
Lee cyclogenesis has been ongoing this afternoon across southern
Colorado slightly farther south than earlier models had been
indicating. The low will continue to deepen and push through SE
CO into late this afternoon and evening. So far this afternoon,
the majority of snowfall has been confined to along the Laramie
Range as depicted by current radar imagery and webcams. More
widespread lift will move into the region over the next few hours
as ongoing cyclogenesis continues increasing coverage of
precipitation along the CO/WY border and the Cheyenne Ridge.
Recent low-level water vapor imagery trends support this. Recent
runs of the HRRR and NAMNEST have had much better agreement with
each other than earlier with a bullseye over northeast Laramie
County and lower snowfall amounts to the north. Much of the NE
Panhandle has started off as rain, but will transition over to
snow this evening with the North Platte River Valley staying the
warmest and taking the longest to transition to snow limiting
accumulation amounts.
Changes to headlines include expanding the Winter Weather Advisory
to the rest of the NE Panhandle. Widespread 1-2 inches of snowfall
is expected tonight with localized spots up to 5 inches along the
Pine Ridge and Wildcat Hills. Additionally, models have slowed
down the system over the past 24 hours. Therefore, the Winter
Weather Advisories for the southern NE Panhandle were extended
through 9 AM MDT Saturday. Snow will completely move out of SE
portions of the CWA by late Saturday morning.
On the backside of the deepening surface low, strong northerly
winds will develop over the southern NE Panhandle Saturday
morning lasting through the afternoon. Gusts to 40 MPH are likely
with a fresh snowpack which could prolong slick road conditions
and reduced visibility with blowing snow. However, afternoon
temperatures will climb into the low 40s so expecting the fresh
snowpack to crust over by midday limiting the driftability of
snow. Otherwise, clearing skies expected across the region through
the day Saturday.
.LONG TERM...(Saturday night through Friday)
Issued at 249 PM MDT Fri Mar 27 2020
The GFS & ECMWF both show a rather fast-moving short wave
tracking across the Four Corners on Monday/ Tuesday. Widespread
precipitation will be possible with this storm system, but gusty
westerly winds should keep things fairly dry for the most part.
Trending colder mid to late week with a strong cold fropa over the
northern and central plains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 520 PM MDT Fri Mar 27 2020
Wyoming TAFS...VFR at Rawlins. Wind gusts to 30 knots after 15Z
Saturday.
IFR at Laramie until 06Z, then MVFR until 12Z, then VFR. Wind
gusts to 35 knots after 16Z Saturday.
IFR at Cheyenne until 13Z, then VFR. Wind gusts to 30 knots after
06Z.
Nebraska TAFS...IFR at Chadron and Alliance until 12Z, then MVFR
until 16Z, then VFR. Wind gusts to 30 knots after 16Z Saturday.
VFR at Scottsbluff until 02Z, with occasional MVFR, then MVFR from
02Z to 04Z, with occasional IFR, then IFR until 13Z, then MVFR
until 16Z, then VFR. Wind gusts to 35 knots after 16Z Saturday.
VFR at Sidney until 03Z, with occasional MVFR, then IFR until 13Z,
then VFR. Wind gusts to 43 knots after 13Z Saturday.
&&
.FIRE WEATHER...
Issued at 410 AM MDT Fri Mar 27 2020
No fire weather concerns w/ widespread measurable precipitation &
cooler temperatures.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory until 5 AM MDT Saturday for WYZ103-
105>108-110-115>118.
Winter Weather Advisory until 9 AM MDT Saturday for WYZ119.
NE...Winter Weather Advisory until 5 AM MDT Saturday for NEZ002-003-
095-096.
Winter Weather Advisory until 9 AM MDT Saturday for NEZ019>021-
054-055.
&&
$$
UPDATE...AB
SHORT TERM...MB
LONG TERM...CLH
AVIATION...RUBIN
FIRE WEATHER...CLH
Area Forecast Discussion
National Weather Service Lincoln IL
901 PM CDT Fri Mar 27 2020
.SYNOPSIS...
Issued at 353 PM CDT Fri Mar 27 2020
Periods of showers and thunderstorms will affect central and
southeast IL through Saturday evening. There is a risk of severe
storms through Saturday along with locally heavy rains, with the
greatest potential for severe weather Saturday afternoon and
evening. Expect mild temperatures and an increasing temperature
trend, reaching the 70s by Saturday afternoon. Dry and seasonably
cool weather will return to the area overnight Saturday night and
Sunday along with windy conditions.
&&
.UPDATE...
Issued at 900 PM CDT Fri Mar 27 2020
Surface analysis shows the warm front is lingering roughly near
the I-70 corridor as of mid-evening. High resolution guidance
still point toward a scenario where the warm front lifts north and
storms develop north of the boundary as it progresses. NAMnest and
HRRR are indicating an axis of storm development from SW to NE
roughly along I-72 to start, between 04z-06z. Additional
development north of a line from Rushville to Bloomington is
expected shortly after midnight through late tonight.
A corridor of instability (MLCAPE around 1500-2000 J/kg) will
support a few vigorous updrafts the rest of the night. That
instability is expected to shift north ahead of the warm front
overnight, along with surface dewpoints increasing toward the low
60s. The addition of 0-6km bulk shear values of 60-70 kts across
the entire area will help a few supercells produce hail, possibly
an inch or larger at times. Can`t rule out the possibility of a
severe thunderstorm watch for a portion of our CWA toward the 05z
time frame.
Current forecast database has a decent handle on the forecast, so
minor PoP/weather updates were done to match short term convection
trends.
&&
.SHORT TERM...(This evening through Saturday)
ISSUED AT 353 PM CDT Fri Mar 27 2020
The surface cold front that pushed southward into southern IL
overnight has returned northward to around I-70 with very little
shower activity in the region early this afternoon, although
activity should increase late this afternoon and evening as an
additional disturbance approaches, increases warm advection aloft.
Hail and locally damaging wind will be the primary severe weather
threats in today and tonight`s highly sheared and increasingly
unstable environment, however the threat for hail should be higher
to the north of the warm front.
Batches of showers and thunderstorms, possibly severe, will continue
through tonight near the warm front as it lifts toward I-74 by
dawn, and into northern IL for the afternoon. At this point, central
IL will be well within the warm sector with high temperatures in the
mid 70s and dewpoints in the mid 60s. Instability and shear
resulting from a potent low pressure system centered over Iowa and
tracking toward Wisconsin has prompted the issuance of a moderate
risk severe thunderstorm outlook over a large portion of northwest
and central IL, with enhanced to slight risk over areas farther
southeast. All severe weather hazards including large hail, damaging
downburst winds, and tornados will be possible with discrete
supercell thunderstorms that form during the daytime, especially
afternoon and evening. Favorable areas for these storms to form will
be near the warm front, as well as ahead of the approaching cold
front in western IL or Eastern IA/northeast MO. Thunderstorm
activity should shift eastward across the central IL forecast area
during the late afternoon and evening, likely ending as far east as
the IN state line by midnight.
.SHORT TERM...(This evening through Saturday)
ISSUED AT 353 PM CDT Fri Mar 27 2020
The surface cold front that pushed southward into southern IL
overnight has returned northward to around I-70 with very little
shower activity in the region early this afternoon, although
activity should increase late this afternoon and evening as an
additional disturbance approaches, increases warm advection aloft.
Hail and locally damaging wind will be the primary severe weather
threats in today and tonight`s highly sheared and increasingly
unstable environment, however the threat for hail should be higher
to the north of the warm front.
Batches of showers and thunderstorms, possibly severe, will continue
through tonight near the warm front as it lifts toward I-74 by
dawn, and into northern IL for the afternoon. At this point, central
IL will be well within the warm sector with high temperatures in the
mid 70s and dewpoints in the mid 60s. Instability and shear
resulting from a potent low pressure system centered over Iowa and
tracking toward Wisconsin has prompted the issuance of a moderate
risk severe thunderstorm outlook over a large portion of northwest
and central IL, with enhanced to slight risk over areas farther
southeast. All severe weather hazards including large hail, damaging
downburst winds, and tornados will be possible with discrete
supercell thunderstorms that form during the daytime, especially
afternoon and evening. Favorable areas for these storms to form will
be near the warm front, as well as ahead of the approaching cold
front in western IL or Eastern IA/northeast MO. Thunderstorm
activity should shift eastward across the central IL forecast area
during the late afternoon and evening, likely ending as far east as
the IN state line by midnight.
.LONG TERM...(Saturday night through Friday)
ISSUED AT 353 PM CDT Fri Mar 27 2020
Following Saturday night`s cold front, strong west winds 20-25 mph
with gusts 30-40 mph should develop for Sunday, along with highs
reaching only the mid 50s to low 60s. Seasonably cool temperatures
with highs in the 50s should continue the remainder of the work
week. A southern stream system should pass by largely to the south
Tuesday, but bringing a chance for rain, mainly the southern half of
Illinois.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 714 PM CDT Fri Mar 27 2020
IFR clouds are lingering ahead of our next period of showers and
storms this evening. Isolated VFR ceilings have occurred, but they
should be short lived as lower clouds develop in the vicinity of
the warm front that will lift north into our CWA tonight.
Scattered showers and thunderstorms will be possible through
tonight across central IL, along that warm front. The front is
expected to reach toward I-74 by 12Z/7 am Sat. Low ceilings below
1k ft along with reduced vsbys with rain showers and some fog will
occur at times through tonight, north of the warm front. NE to ENE
winds of 8-14 kts to veer SE to SSE tonight as warm front lifts
over across central IL. Very strong storms tomorrow later
afternoon could produce significant wind damage with large hail
possible. Some tornadoes could develop near the terminal sites,
mainly after 22z tomorrow toward PIA/SPI, then advancing eastward
Saturday evening.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SYNOPSIS...37
SHORT TERM...37
LONG TERM...37
AVIATION...Shimon
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1105 PM EDT Fri Mar 27 2020
.UPDATE...
Issued at 1105 PM EDT FRI MAR 27 2020
The radar trends in the downstream convection keep the better
chances of seeing an isolated storm generally in the Bluegrass
region. Overall the threat looks low at this point with isolated
to widely scattered coverage at best. Otherwise just some
adjustments to the deeper valleys were needed as they have
decoupled despite the clouds.
UPDATE Issued at 831 PM EDT FRI MAR 27 2020
We are seeing broken to overcast skies this evening in the warm
sector. We are seeing a upper level wave in Missouri that is
expected to push through tonight. This could spark an isolated
storm under ample elevated instability, strong mid level lapse
rates and strong shear. The HRRR has started to indicate an
isolated storm could develop in the recent runs in far northern
Kentucky, but this still remains more conditional at this point.
Given this will lean toward slowing the PoPs down, but keeping the
same general idea of isolated convection. The trends will
continued to be watched through the evening. Otherwise this is
more of a minor update in terms of the other weather elements.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 312 PM EDT FRI MAR 27 2020
Current conditions across the region features scattered cloud
cover with a warm front draped across northern Kentucky and into
West Virginia. The scattered cloud cover over eastern Kentucky has
lead to some surface heating over the area. Thus some surface
temps are creeping into the upper 70s and possibly near 80 in some
parts. This has also lead to some impressive dew point
depressions across the area with 10 to 15 degree spreads in
place. Model soundings have indicated some increasing cap heading
into tonight. Thus will keep pops out of the forecast until about
22Z but with a weak wave approaching the area may spark off a few
showers or a storm or two but the chances are low here. After
this, the chance for pops will be nil through the rest of tonight
and into the day on Saturday. In fact a bit of clearing tonight
into southeastern KY may lead to a few instances of ridge to
valley temperature differences. Still, in this very above normal
pattern, lows will only be in the 60s with strong southerly flow.
Into the day on Saturday, cloud cover will be on the increase with
the approach of the cold front to the west. Thus will see another
period of dry conditions as the cap in place will become too
strong with the daytime heating and WAA in place. Will expect
highs to top 80 in many place tomorrow. By the Saturday night the
front will approach the region. With the amount of heating and the
lift associated with the approaching front, there will be a
concern for winds mainly with any thunderstorm development. Hail
will be a possibility as well but wind will be the main threat
with a LL jet nearing 40 knots. Moisture will be a concern with
the front approach and thus leading to minimal instability but
the threat associated with the front will be the main concern.
Will time the approach into the area by 03Z to 06Z. Once again
wind remains the main threat and prompting SPC to go with a Slight
to Marginal Risk of severe weather Saturday night. Conditions
right now are looking on the Marginal side with concern to winds
and will mention this in the HWO.
.LONG TERM...(Sunday through Friday)
Issued at 430 PM EDT FRI MAR 27 2020
The period is expected to begin with ridging in portions of the
western Atlantic, and upper level low nearing the western Great
Lakes, shortwave ridging extending through the high Plains and an
trough near the west coast of the Conus. At the surface, a sfc low
is expected to be centered over WI to begin the period with a
triple point in the Great Lakes and a cold front trailing south
into the OH Valley and Appalachians. Current trends point toward
the cold front working across East KY at the very start of the
period.
The upper level and sfc low are expected to move into MI by Sunday
evening with the trailing cold front crossing eastern KY early i
the period. Showers are expected to accompany the boundary early
on Sunday with chances for rain diminishing quickly during the
morning. Drier air should move into and across the Commonwealth
rather quickly on Sunday in the post frontal dry conveyor belt.
This should allow ample solar insolation and mixing down of higher
momentum from aloft. This should result in sustained winds in the
10 to 20 mph range with gusts as high as 30 to 35 mph from later
in the morning into the afternoon. Opted for more pessimistic
dewpoints compared to NBM data due to the expected mixing,
hedging toward the lower MAV and MET MOS numbers.
Sfc and upper level ridging will gradually build into the region
Sunday night and Monday. However, the axis of the upper level
ridge will move east of the area by dawn on Tuesday as the next
shortwave moving across the Plains near the MS Valley. After dry
weather from late Sunday morning into Monday evening, moisture
and clouds will increase on isentropic lift ahead of the
approaching system on Monday night and showers could occur late.
A shortwave trough should move from the Plains/mid south into the
OH Valley on Tuesday afternoon and Tuesday night in quasizonal
flow. This shortwave trough will depart to the northeast late
Tuesday night and Wednesday. Sfc low pressure should track across
the OH and TN Valley regions on Tuesday with redevelopment
occurring along the eastern seaboard Tuesday evening and Tuesday
night. This system will lead to a good chance for showers across
the area and a few thunderstorms are possible late Tuesday into
Tuesday evening. Another soaking rain should fall from this
system.
Height rises should follow Wednesday into the day on Thursday as
an upper level ridge moves across the southeast and OH Valley. Sfc
high pressure will also build into the area during this time. This
pattern should result in a drier second half of the week as the
next system should not reach the area until next weekend.
The airmass should be sufficiently dry that some valley frost
could occur on Thursday night with high pressure dominating. If
drying occurs quickly enough on Wednesday, patchy valley frost
might occur in the west on Wednesday night though confidence in
this was not high enough to include that at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
ISSUED AT 720 PM EDT FRI MAR 27 2020
The cumulus will dissipate through the evening and mostly mid and
high level clouds will be left in place. These VFR CIGs will
continue through the TAF period. We will see an inversion setup
across the region tonight and this will combine with increased low
level jet leading to LLWS late tonight into early Saturday
morning. The winds will generally remain out of the southwest
through the night before we mix out in the late morning and we
will see 5 to 10 knots sustained and gusts of 15-20 knots through
the afternoon on Saturday.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...DJ
SHORT TERM...SHALLENBERGER
LONG TERM...JP
AVIATION...DJ
Area Forecast Discussion
National Weather Service North Platte NE
631 PM CDT Fri Mar 27 2020
.SHORT TERM...(This evening through Saturday night)
Issued at 307 PM CDT Fri Mar 27 2020
The models continue to show a powerful cyclone developing across
western Kansas and northeast Colorado late tonight. The storm will
lift rapidly northeast through ern Nebraska Saturday and deepen
in the process. It appears the storm will pull dry air through ern
Wyoming, wrn SD and the Nebraska Panhandle supporting evaporative
and near sfc cooling. The NAM even suggests the potential for
dynamic and near sfc cooling across ncntl Nebraska. A period of
wet snow is in the forecast in that region Saturday afternoon as
well as most of western Nebraska. The snow forecast leans on the
cooler NAM solution for several inches of wet snow across the
higher terrain of western Nebraska. A Winter Weather advisory is
in place late tonight and Saturday morning covering parts of
western Nebraska.
There is little change in the model predicted dynamical forcing for
the storm. Strong frontogenesis and the approach of a PV anomaly
will fuel a convectively enhanced rain-snow line stretching from
southwest to north central Nebraska Saturday. The western Sandhills
will be affected tonight and early Saturday morning. Sporadic 1 inch
per hour snowfall rates are suggested by the NAM, ARW, NMM models.
The GFS, RAP and HRRR are keeping the pcpn mostly rain but these
models are known to mix deeply. Our forecast is for a more shallow
mixed layer. Ample cold air aloft for snow growth will present
itself on the west side of the h700mb low.
The wind forecast leans on the guidance blend which is in the middle
of the road for wind speeds of 30 to 40 mph. This forecast is close
to the 500m AGL winds speeds adjusted downward for friction. The
wind gust forecast uses a regression for gusts of 45 to 55 mph. This
might be too light considering the 12z HRRR indicated 4 or 5 hours
of gusts to around 60 mph and the HRRR was quite correct predicting
our last high wind event. The NAMnest also shows a few hours of
gusts to near 60 mph affecting parts of wrn and ncntl Nebraska. It
is quite possible the region will experience sporadic gusts to 60
mph Saturday. The precipitation and wind will end or subside
Saturday evening.
.LONG TERM...(Sunday through Friday)
Issued at 307 PM CDT Fri Mar 27 2020
Another storm system will move through the central Plains Monday.
The h700mb low track suggests the bulk of the rain will fall
across nrn KS and srn Nebraska. Likely rain chances are in place
across srn Nebraska Monday. This system will exit Monday night.
The latest development in the extended forecast is for a closed
upper level low to form across srn Canada Tuesday and Wednesday. WPC
is holding this low over southwest Canada while the morning runs of
the models would suggest the low will drift slowly east through srn
Canada throughout next week. The position of the upper low will have
a big impact on temperatures as cold air will be colocated beneath
the low. Cold fronts will draw this air south, possibly affecting
Nebraska.
The model consensus is in very good agreement pursuing a warming
trend through Tuesday followed by a cold front Wednesday. The warmer
GFS ensemble is holding the cold front north of Nebraska while the
ECM and GFS are cooling highs into the 40s Wednesday and beyond. The
forecast uses a blended approach for highs in the 50s. The rain
forecast Wednesday and beyond is basically dry except for isolated
chances with the front Tuesday night and Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 631 PM CDT Fri Mar 27 2020
A strong springtime storm will present multiple aviation weather
hazards to western and north central Nebraska through Saturday,
including low cigs, reduced visby, and strong winds. Moisture
overspreads the region tonight, mainly in the form of rain, as
cigs drop into IFR (for terminals not already in it). Rain mixes
with and switches to snow overnight, then transitions back during
the day. Meanwhile, northerly winds strengthen through the
forecast period with peak gusts near 40 kts early afternoon.
&&
.HYDROLOGY...
Issued at 303 PM CDT Fri Mar 27 2020
North Central Nebraska is under a Flood Watch late tonight through
Saturday afternoon.
There is little change in the model solution which suggest 1 to 1
and 1/2 inches of rainfall. Most of this rain will fall during the
day Saturday potentially causing overland flooding across the
Sandhills, flooding of small creeks and mainstem flooding on the
Elkhorn river. The Elkhorn river near Atkinson is near action stage
from a previous storm.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 1 AM CDT /midnight MDT/ to 1 PM CDT
/noon MDT/ Saturday for NEZ004-022>024-035-036-056>058-069-094.
Flood Watch from 1 AM CDT Saturday through Saturday evening for
NEZ006>010-026>029-038.
&&
$$
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Snively
HYDROLOGY...CDC
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
940 PM CDT Fri Mar 27 2020
.UPDATE...
940 PM CDT
No big changes to forecast tonight. Broad zone of warm air
advection continues over a large portion of the Midwest this
evening. Already seeing areas of showers and some isolated
thunderstorms developing across portions of IA, MO, and IL. The
more robust convective development at this time is underway over
central Missouri. This is closer to the greater instability
observed on the 00z KSGF sounding where some fairly impressive
lapse rates were sampled along with better moisture. Already
seeing a broad low level nocturnal wind maximum developing over
the MS Valley which will help advect the deeper moisture and
instability northward tonight. The strengthening theta-e advection
should also promote increasing coverage of convection overnight.
Short range CAMS agree and current forecast of ramping up POPs
overnight looks good. Given the moderate instability and strong
effective shear with steepening lapse rates, potential for
elevated supercells overnight with attendant large hail threat
look reasonable.
The 00z model guidance suite is in the process of rolling in,
oncoming shift will take a look at the full suite of data to
access the severe threat for Saturday.
- Izzi
&&
.SHORT TERM...
238 PM CDT
Through tonight...
A period of active weather will commence this evening and a powerful
upper level jet takes aim at the region.
Warm advection continues to ramp up in the southwest flow ascending
the warm front, which at the surface is still through central
Missouri to St Louis then on east through the Ohio Valley. Plentiful
impulses exist in the flow which will lead to continued/increased
shower coverage in waves tonight. There is some limited, though
elevated instability well north of the warm front such that some
thunder is expected south of I-80 but severe weather is not
anticipated in the afternoon hours.
The instability axis will shift northward tonight, though the
surface warm front really should not make it into the area for most
of the overnight hours. Still, RAP indicates some 500-1000 J/Kg of
elevated instability will nose farther into the area tonight. As the
low level jet gets cranking a bit more late this evening and
overnight, expect a further expansion of showers and
thunderstorms. These pose mainly a risk for severe hail given the
strength of the shear in the hail growth region. These would be
favored south of I- 80, as GFS/EC are much more limited in the
degree of instability farther north. Still a few rumbles of
thunder are possible area wide.
PWAT values will also increase significantly tonight. Training
storms to not appear all that favorable, and storms will be moving
somewhat quickly. So in spite of some favorable regeneration of
storms near the front in the Kankakee and Iroquois River basins, the
flash flood risk does not appear high enough to warrant a flash
flood watch. Still, some periods of locally heavy rain in this
corridor is possible with localized ponding of water favored as the
soils are a little more damp than usual this time of the year.
Meanwhile, the cool marine airmass and the warm moist air to the
southwest continue to clash close to the lake. Clouds and fog
continue near Lake Michigan, especially on the Illinois side. Fog
will continue to be a concern right along the shoreline. Anticipate
fog may become more of a concern overnight in between waves of
precipitation as onshore flow continues while dewpoints continue to
creep up.
Some showers and storms will linger in the morning, but we could
be in between waves for a time as the morning progresses.
KMD
Saturday afternoon and evening...
Concerns are increasing that a significant severe weather event will
occur for portions of northern Illinois late Saturday afternoon into
mid-evening, with the potential for tornadic supercells.
A slightly negatively tilted trough axis rounding a strong mid-level
over the central Great Plains Saturday morning will shift northeast
across northern IL late Saturday afternoon into the evening. A
surface low associated with the mid-level low will drift northeast
from northwest/far north-central Kansas Saturday morning to near
Omaha by early evening.
Surface theta-e progs indicate a warm front will extend eastward
from the low across far northern Missouri to along roughly the I-72
corridor in Illinois at daybreak Saturday. The front will drift
north through early afternoon as the low begins to occlude over
southeast Nebraska. The occluded triple point will shift ENE from
roughly near Des Moines mid-afternoon to near Clinton by 00z, then
tracking to around or just north of Chicago by 03Z.
Dynamics are rather impressive with this system, highlighted by the
nose of a 150kt upper jet and 100kt mid-level jet shifting into
northern Illinois during the afternoon. The impressive wind profile
extends down to the surface, producing deep layer shear values on
the order of 80-90kts, 0-3km shear of 40-50kts, and 0-1km shear of
30-40kts. A narrow ribbon of MLCAPE in excess of 1000 j/kg just
ahead of the cold front is expected where rapid erosion of CIN will
be underway in response to the incoming jets and trough. This sets
the stage for a potentially significant severe weather event for at
least a portion of the area.
Deep layer shear vectors nearly perpendicular to the cold front
support discrete supercell structures. With the surface low only
slowly moving ENE across Iowa, surface winds will remain backed in
the vicinity of the triple point, especially west of the I-39
corridor. Resultant 0-1km SRH values in this area will be 200-300
m2/s2, with rather curved low-level hodographs present in forecast
soundings. Combined with LCL heights around 500m or potentially
lower, there is an increased risk of tornadic supercells. Fixed
layer STP values in excess of 5 and previously mentioned parameters
support the potential for significant tornadoes with any well-
established supercells. The greatest risk for this potential is
roughly south of I-88, particularly in the western CWA from Lee to
La Salle to Livingston counties.
North of I-88, any sustained elevated supercell will be capable of
large hail given favorable mid-level lapse rates of 7-8C/km.
A couple caveats exist, as is usually the case with any severe
weather set-up. First, the longevity of elevated convection north of
the warm front and its impacts on the northward movement of the warm
front remain somewhat unclear. However, with the strong dynamics in
place, a late afternoon northward surge in the warm front is
expected. Second, substantial MLCIN will be present in the warm
sector and as a decent amount of cloud cover reduces diurnal
warming. But again, the potent jets combined with the cold front
should rapidly remove inhibition, resulting in convection remaining
confined to the cold front. Lastly, if enough low-level
destabilization/warming does not occur, shear may be too high to
maintain/develop significant updrafts.
The window of greatest concern is 5-10pm, earliest west and latest
east. Timing for the Chicago metro is roughly 7-9pm for the west
suburbs and 8-10pm for the remainder of the metro and Chicago.
Kluber
&&
.LONG TERM...
238 PM CDT
Sunday through Friday...
As the center of the strong synoptic system pushes off to the
east, winds will continue to be strong on the back side of the low
on Sunday. Combined with a strong isallobaric response and strong
low level jet winds mixing down to the surface, could see wind
gusts to 45+ mph, possibly higher at times based on the past few
ECMWF runs. Depending on the exact track of the surface low, winds
turn westerly by Sunday morning. Winds gradually diminish though
the day on Sunday, although gusts could still be as high as 30-40
mph late Sunday afternoon. Rain showers may also linger though the
day on Sunday as precip wraps around the low. High temperatures
for the day will likely occur in the morning hours for most areas
with temperatures expected to decrease through the remainder of
the day, lows Monday morning will drop into the upper 30s.
Beyond Sunday, as the lead trough shifts east, a secondary trough
and an associated developing surface low is expected to translate
east across the central plains and southern Ohio Valley early
next week. It is still several days out, but current trends keep
much of this activity primarily to our south, but it isnt out
of the question that our far southern counties could see some
precipitation on Tuesday. Onshore flow is expected through
Wednesday which will keep temps cooler for areas along Lake
Michigan.
Considerable model variability exists beyond Tuesday. Models are
struggling to handle what happens behind the secondary trough
moving through with respect to the split upper jet pattern and an
interesting retrograding low over Canada. It is worth noting that
the 12Z GFS has come more into alignment with the 00Z Euro
suggesting ridging will build in over across the eastern CONUS
into the latter part of next week.
Petr
&&
.AVIATION...
For the 00Z TAFs...
630 PM CDT
The primary aviation concerns through the next 24 to 36 hours
are:
* Development of low-level stratus deck and fog overnight lasting
through much of Saturday
* Potential for several rounds of thunderstorms with hail and
gusty winds
* Strong southwesterly winds and eventually westerly winds at the
end of the TAF period.
A busy aviation period is expected with multiple potential.
impacts.
Ceilings and visibilities: While the low-level stratus deck that
has plagued ORD/MDW/GYY/DPA has shown signs of eroding over the
past hour, persistent easterly flow off Lake Michgian and an
influx of low- level moisture from the south will lead to a
redevelopment within a few hours of the start of the TAF period,
spreading to all terminals by midnight. Dense fog development is
also possible with visibility drops below 1 mile. The soupy
conditions will last overnight through much of Saturday as the
terminals remain on the north side of a northward-surging warm
front. As easterly winds increase modestly after noon Saturday in
response to an increasing surface pressure gradient, modest
improvement to conditions is possible but confidence is low.
Ceiling and visibility conditions will finally improve toward the
very end if not just after the TAF period as the warm front lifts
northward, and in the wake of an eastward- surging cold front.
Several rounds of thunderstorms: Showers are increasing in
coverage at press time in response to increasing low-level warm
air advection. Thunder chances appear low for the first portion of
the TAF period as the instability axis is well south of the
terminals, though lightning has been noted recently near RFD. A
more substantial push of showery activity is expected after
midnight within which thunderstorms are possible. At this point,
it seems the best chance for thunderstorms will be south of the
terminals but opted to maintain the inherited PROB30 group at all
TAF sites for now. Any thunderstorm overnight will have the
potential to produce small hail. A lull in activity is possible
from roughly daybreak through mid-afternoon Saturday, but with
continued low-level warm air advection, would not be surprised to
see activity fester with a continued small hail threat. Confidence
is high that a band of thunderstorms will sweep through the
terminals Saturday evening, though confidence is low on exact
timing. At this point, it seems they will pass through toward the
very end if not just after the 24 hour TAF period and in the last
6 hours of the TAF period at MDW/ORD. Note that any thunderstorm
Saturday evening may produce damaging hail and strong winds.
Gusty winds at end of the TAF period: In the wake of the cold
front, strong southwesterly to westerly gradient winds are
expected at all TAF sites, with the strongest winds after daybreak
Sunday (and indeed after the TAF period). Wind gusts may exceed
40 kts. While the strongest winds will occur after the 24-30 hr
TAF period, felt it would be prudent to mention continued aviation
impacts beyond the explicit forecast.
Borchardt
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Dense Fog Advisory...Wilmette Harbor to Michigan City IN until 10
AM Saturday.
Small Craft Advisory...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...1 PM
Saturday to 4 AM Sunday.
Gale Watch...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...4 AM
Sunday to 10 PM Sunday.
Small Craft Advisory...LMZ740...7 AM Saturday to 4 AM Sunday.
&&
$$
Visit us at weather.gov/chicago
Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/NWSChicago
www.twitter.com/NWSChicago
www.youtube.com/NWSChicago
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
918 PM CDT Fri Mar 27 2020
.UPDATE...
Issued at 915 PM CDT Fri Mar 27 2020
Strong to severe storms have developed over central Missouri
along the quasi-stationary front. Latest objective analysis is
showing that the MUCAPES have increased into the 1000-2000+ J/kg
range with deep layer shear of 70-80KTS. This latest development
is occurring as a 35kt low level jet has intersected the front.
Expect these storms to continue to develop and move quickly
northeast across central and east central Missouri into southwest
Illinois. RAP mass fields and CAMS still support thunderstorms
becoming more numerous late this evening into the overnight across
northeast Missouri into west central Illinois as the front begins
to lift north. Still expect the rain to decrease in areal extent
late tonight as the low level jet veers.
Britt
&&
.SHORT TERM... (Through Late Saturday Night)
Issued at 455 PM CDT Fri Mar 27 2020
Quasi-stationary has moved very little today and was located
roughly along I-70 late this afternoon. Latest objective analysis
was showing MLCAPES of 1000-2000 J/kg with deep layer shear values of
70kts. Forecast from the RAP are depicting that these values will
develop across central and east central Missouri as well as
southwest Illinois by early evening. Severe thunderstorms have
developed over southwest Missouri in this unstable airmass. The
CAMS have been fairly consistent today in developing thunderstorms
along the front by early-mid evening. This will occur as the RAP
is showing a 35 kt low level jet intersecting the front. Given the
amount of shear/instability available in addition to the
700-500mb lapse rates in the 7-8C/km range, expect the primary
threat to be large hail, with damaging winds and a tornado or two
also possible in the vicinity of the front. These storms will
spread across northeast Missouri and west central Illinois
overnight before chances decrease by 12Z as the low level jet
veers. A few storms tonight may also produce locally heavy
rainfall, particularly where any storms can train.
Focus then switches to tomorrow when an upper low moves across the
Plains which will bring large scale ascent to Missouri and
Illinois during the afternoon and early evening. It will also
cause an attendant front to move east across the CWA during the
late afternoon and evening. Forecast MLCAPES ahead of the front
will be around 2000 J/kg with deep layer shear around 80kts which
be favorable for supercells. Greatest threat will be over
northeast Missouri and west central Illinois which will be closest
to the retreating warm front and CAMS is showing the most
discrete cells, particularly given the orientation of the deep shear
vector to the front. Will continue to message all severe hazards
tomorrow afternoon and early evening.
Will continue to mention that straight line wind gusts outside of
thunderstorms will be in the 35-45 mph range given the tight
pressure gradient associated with the deep surface low that will
move from the Plains into the Upper Midwest. Winds will continue
to be breezy Saturday night into Sunday.
Temperatures will remain above normal through Saturday night.
Expect the warm front to move north of the area on Saturday, so
with sun during the afternoon, still expect highs in the mid 70s-
low 80s.
Britt
.LONG TERM... (Sunday through Next Friday)
Issued at 455 PM CDT Fri Mar 27 2020
Sunday into Monday continues to look mainly dry as both the GEFS
and EPS show a upper ridge/surface high moving across the area.
The next chance for showers will be on Monday into Tuesday as a
upper trough moves out of the western CONUS and across Missouri
and Illinois.
Britt
&&
.AVIATION... (For the 00z TAFs through 00z Saturday Evening)
Issued at 641 PM CDT Fri Mar 27 2020
Showers and thunderstorms are expected to continue to develop
across the area this evening into the overnight hours. This
activity is expected to affect all of the terminals mid-late
evening, with showers persisting into the overnight hours. These
showers and storms will bring MVFR/possible IFR conditions with
possible hail and wind gusts over 35KTS. Storms will move out of the
area after 12Z with low chances for showers and possible MVFR
conditions through 18Z. There will be another chance of
thunderstorms ahead of a cold front on Saturday afternoon. Winds
will gust to 30KTS ahead of this front on Saturday afternoon.
SPECIFICS FOR KSTL:
Thunderstorms are expected to develop at or near the terminal by
01Z and persist through 06Z with lesser chances between 06-12Z.
The strongest storms may produce hail and wind gusts in excess of
35KTS. Mainly dry and VFR conditions are expected tomorrow
morning, though there is another chance of thunderstorms after 21Z
on Saturday. Wind gusts will be near 30KTS on Saturday afternoon.
Dry and VFR conditions are expected after 00Z.
Britt
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Marquette MI
740 PM EDT Fri Mar 27 2020
.SHORT TERM...(This evening through Saturday)
Issued at 342 PM EDT FRI MAR 27 2020
Light southerly winds under high pressure have given us a warm and
mostly clear day across the UP. The exception has been this
morning`s fog in the central UP, caused by moist lower levels capped
by an inversion. As temps warmed up in the late morning/early
afternoon, the inversion broke, allowing for more dry and warm air
to mix down. This broke the fog and cleared the skies. On Lake
Michigan and on the Bay of Green Bay, advisory level fog has
advected in from the southeast, slowly enveloping the nearshore
zones.
For the remainder of the afternoon into the evening, high pressure
will continue to dominate the region. Positive tilted trough exiting
the Rockies will transition into a slightly negative closed low
moving across the central Plains toward the Upper Midwest. As the
accompanying surface low approaches, light southerly flow will back
easterly tonight, advecting more fog into the Bay of Green Bay and
Lake Michigan nearshore zones. The light winds and high dewpoints
relative to surface temps, capped by an inversion will once again
create some patchy fog across the central CWA.
In terms of timing of precip arriving in the CWA Saturday, the NAM
has been notably earlier then other deterministic models today, but
the extended RAP started picking up on it this as well. For the
moment, have chance PoPs beginning during the mid-late morning,
becoming likely in the afternoon. Upper-level dynamics with
isentropic lift should be enough to pop out about an inch of liquid
for this event but mainly after this forecast period.
.LONG TERM...(Saturday night through Friday)
Issued at 430 PM EDT FRI MAR 27 2020
Models suggest that pattern amplification taking place this weekend
will continue through much of next week. The trough over the western
CONUS will shift through the Rockies into the Plains as a ridge
builds over the southeast. As a result, a vigorous shortwave/closed
low and associated sfc low is expected to lift from the central
Plains into the western Great Lakes bringing a period of widespread
moderate to possibly heavy pcpn into Upper Michigan late Sat into
Sat night with some lingering wraparound pcpn into Sun for west and
north central sections of the U.P. By next week, a split flow
pattern is expected bringing mild and mainly dry weather into the
region as the heavier pcpn remains to the south with the stronger
southern stream shortwave and sfc low.
Beginning Sat night, strong 700-300 mb q-vector convergence, upper
diffluence and 290k-300k isentropic ascent ahead of the Plains storm
system lifting northeast into the region will support widespread
moderate to possibly heavy pcpn spreading across Upper Michigan Sat
evening. Still some differences noted with the 12Z deterministic
model runs...with the ECMWF/NAM/Canadian farther nw than the GFS
although the GFS appears to be trending farther west on this latest
run. Based on the SREF ensemble mean and a blend of the 12z
ECMWF/NAM/CMC would expect the sfc low to track along or just west
of a Menominee-Escanaba-Newberry line. This likely scenario will
push enough warm air into the area for mainly rain through most of
Saturday night across much of the U.P. Forecast soundings suggest
that the rain may change to snow late Sat night over the west.
Sun, even though the heaviest pcpn will have moved off to the north
and east with the exiting system, cold conveyor moisture wrapping
around in a moist northerly cyclonic low level flow could support
the potential for several inches of wet snow into the west,
especially from IWD to the Porcupine Mtns where orographic
enhancement would be strongest. Eventually enough cold air will
filter into the rest of the Upper Michigan for a rain/snow mix that
could bring additional light accumulations of wet snow over the
higher terrain of northwest and north central Upper Mi.
Rainfall and overall pcpn QPF amounts to around an inch along with
melting snow will result in some ponding of water in low lying areas
and rises on streams and rivers into Sun and perhaps even Mon.
Mon-Fri, mid level and sfc ridging is expected to build into the
area Mon bringing a general drying/warming trend into the middle of
next week. The CMC and ECMWF do hint at some pieces of shortwave
energy lingering across the area Mon-Tue from the weakened storm
system to the east, although it remains to be seen if these features
will be able to initiate any isolated showers. Although model spread
increases significantly by Thu-Fri, trends suggest that a mid-level
trough and associated inverted sfc trough will approach the area
with increasing chances for pcpn (especially by Fri), mainly in the
form of rain.
&&
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 740 PM EDT FRI MAR 27 2020
VFR ceilings and visibilities continue this evening, there is the
potential for fog development beyond that which is occurring along
the Lake Michigan shores this evening. Southerly winds at KSAW will
advect that low level moisture toward that TAF site this evening
before winds slacken later on and and a NE flow slowly develops. The
NE upslope flow also is good for fog development, and with plenty of
antecedent moisture around from today`s snowmelt, fog is a given at
KSAW. The timing and reduction to visibilities and ceilings is
resulting an a very tricky forecast for KSAW in the short term.
Expecting IFR conditions there for a time overnight, mainly for
visibilities.
Elsewhere, the cloud cover thickens overnight, with ceilings
gradually lowering through the day. MVFR ceilings expected at all
three sites by late in the forecast, but can not discount IFR cigs
at KSAW as rain approaches and weak NE flow increases slightly.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 342 PM EDT FRI MAR 27 2020
Light winds today under high pressure will give way tomorrow to a
vigorous low pressure moving into the Upper Great Lakes. Winds will
shift easterly this evening, increasing during the afternoon and
becoming predominately NE. The low is progged to transit through the
Upper Peninsula Sunday, shifting the axis of higher winds from the
eastern half into the central lake by afternoon, and then into the
east half by Sunday evening. NE gales are anticipated in the western
half beginning Saturday evening and then northern gale force gusts
will be possible Sunday night in the eastern half. Sustained
northerly winds above 20kts in the eastern half of the Lake will
linger into mid-afternoon Monday. Beyond Monday afternoon, winds
should be light.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
Gale Warning from 7 PM EDT /6 PM CDT/ Saturday to 11 AM EDT /10
AM CDT/ Sunday for LSZ162.
Gale Warning from 2 AM to 2 PM EDT Sunday for LSZ263-264.
Lake Michigan...
Dense Fog Advisory until 11 AM EDT Saturday for LMZ221-248-250.
&&
$$
SHORT TERM...JP
LONG TERM...Voss
AVIATION...RJT
MARINE...JP
Area Forecast Discussion
National Weather Service Shreveport LA
1050 PM CDT Fri Mar 27 2020
.AVIATION...
For the ArkLaTex S/SSE winds 5-10KT with ocnl gust will persist
in advance of a deep upper trough and eventual fropa this wknd.
VFR will go MVFR 09-15Z. S10-20KT with KTYR 1st up seeing the
ra/-tsra by 12Z for a few hrs as S shifts to SW and W by 18Z.
Other sites will have similar 3-6 hr window with push to the E
mid/late a.m. as system progresses. KGGG/KTXK will shift 15Z and
KSHV/KLFK at 18Z. Thunder ongoing for our KELD/KMLU sites 21Z/00Z
respectively. SFC winds shifting w/ dry line and the fropa will be
dry and pass overnight. /24/
&&
.PREV DISCUSSION... /issued 1013 PM CDT Fri Mar 27 2020/
UPDATE...
To add a slight chance for showers in our NW corner before 06Z.
SHORT TERM...
Hearty range of 70s this evening with few gusts with still good
South winds 5-10 mph. The evening will remain quiet areawide, but
a few more showers may brush into Red River and McCurtain counties
before midnight. We have seen on good cell NW of our area earlier
and that has become an area of light showers draping into SE OK
at this time. Amounts will be light if at all. Now after midnight
little change on timing anticipated. The new NAM is still the
slowest solution at 00Z. The HRRR for its time frame shows a few
showers in central LA by around 09Z and we have a slight pop here
too. /24/
PREV DISCUSSION... /issued 331 PM CDT Fri Mar 27 2020/
SHORT TERM.../Tonight through Saturday night/
Another day of dry conditions and above normal temperatures as
upper ridging continues to expand into our region, with the
center of the ridge still parked over the Gulf of Mexico.
By tonight, the upper ridge will start to shift eastward as
the center of the high in the gulf moves east. However, another
near record warm night is expected. Low-level southerly flow will
push low clouds into the region after midnight, limiting
radiational cooling, as temps will only fall into the mid to upper
60s. At the same time, an upper trough in the Great Basin Region
will push eastward into Colorado and will start to strengthen and
close off as it moves into the Central Plains by Saturday morning,
dragging a cold front with it towards our region.
The front will move into our northwestern zones by
Saturday morning. Scattered convection should develop ahead of
the front, likely just east of Interstate 35 in Oklahoma and Texas
Saturday morning, then increase in intensity and coverage as they
move into our forecast area on Saturday. Deep layer shear well
over 50 kts and CAPE values of 1000-1500 J/kg will support a
threat for a few severe thunderstorms, particularly Saturday
afternoon over Southern Arkansas and Northern Louisiana. Wind
shear will be largely unidirectional, which suggests primarily a
damaging wind threat. Given the recent rainfall and wet soils, any
training or heavy rainfall could result in an isolated flash
flood threat. Most of the convection should be out of the area
late Saturday evening/Sunday morning, as the cold front pushes
east of the region. Noticeably cooler and drier conditions will
move into the region as temperatures by Sunday morning will be in
the upper 40s and lower 50s. /20/
LONG TERM....LONG TERM.../Sunday through Friday/
By Sunday morning near sunrise, expect a strong short wave trough
centered over WI to continue moving E into the New England area
through late Sunday. The line of decaying TSTMS on the backside of
the trough exits NE LA into MS through Sunday morning.
The next short wave trough then moves into the Central Plains states
by Monday afternoon with strong warm air advection developing across
OK, AR, E TX, and LA. This trough then proceeds to deepen and
become negatively tilted through Tuesday. Expect a line of TSTMS,
some likely severe, to develop by late Monday afternoon and then
exit NE LA and SE AR by late Tuesday morning. Fortunately, the
system does not tarry and moves quickly enough to avoid excessive
rainfall issues.
With these two shortwave trough passages, expect the early season
subtropical ridge that recently and currently provided our balmy
March temperatures to retrograde W into Mexico and weaken. Expect
temperatures to accordingly to return to near normal for late March
and early April, that is highs in the lower 70s and overnight lows
in the lower to mid 50s. /VIII/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 69 78 51 75 / 10 80 10 0
MLU 69 85 55 77 / 10 60 70 10
DEQ 66 75 47 73 / 20 60 0 0
TXK 68 76 49 72 / 20 70 0 0
ELD 68 79 50 74 / 10 80 30 0
TYR 68 75 49 74 / 20 70 0 0
GGG 68 76 49 74 / 20 70 0 0
LFK 70 79 52 78 / 20 80 10 10
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
24/20/08
Area Forecast Discussion
National Weather Service Tulsa OK
855 PM CDT Fri Mar 27 2020
...UPDATE...
.DISCUSSION...
The biggest short term forecast change was to increase PoPs across
southeast Oklahoma through the overnight hours. Shower and
isolated storm activity currently in the area should continue
off an on through a good chunk of the night.
There continues to be uncertainty in storm coverage this evening
and even more so since storms developed over northeast Oklahoma
this afternoon which may play a factor in limiting storm
development tonight. The latest HRRR runs have hinted at really
little development over northeast Oklahoma with only shower and
occasional storm activity over southeast Oklahoma and northwest
Arkansas. The 18Z NAMNest however shows a couple clusters of
potentially strong to severe storms over mainly northeast
Oklahoma. The latest upper air guidance is suggesting that
northeast Oklahoma may be within the favorable left exit region of
an incoming jet streak which would indicate more favorability for
synoptic lift. A little lower in the atmospheric column shows
deep moisture extending from the surface (surface dew points
currently in the mid 60s with even a few upper 60s along the Red
River) to 850mb which will continue to be advected into the region
through the night via modest southerly winds. Mid level lapse
rates should be more than sufficient to support the potential of
large hail, but hail size is not expected to be to the degree we
saw earlier today. Shear is also expected to increase through the
night as the low level jet kicks in leading to high Bulk Shear and
high SRH values. Instability should also be sufficient with over
1000J/kg of MUCAPE expected with some locations closer to 2000J/kg.
So given a storm in this environment, it is entirely possible
severe weather will occur but the question is if storms will get
going given the atmosphere across northeast Oklahoma potentially
being worked over from earlier storms.
At the moment, leaning toward the NAM Nest solution with isolated
to scattered storms across eastern Oklahoma and northwest
Arkansas with a couple of those storms possibly being severe given
a mostly favorable scenario. The primary threat being large hail
with a secondary threat for damaging wind gusts. Given that these
storms will likely be elevated, a tornado threat is not expected.
A couple of storms may also be possible over southeast Oklahoma
though the strong/severe threat is considerably lower. The best
chances for storms still appears to be over northeast Oklahoma at
this time. The best guess as to timing of any strong to severe
storms appears to be between 1AM and 5AM tonight. After 5AM,
storms should begin to weaken and will continue to slide to the
east until exiting northwest Arkansas by late morning tomorrow.
So with all that said, other than the addition of higher PoPs
across southeast Oklahoma, the forecast remains largely on track.
Snider
&&
.PRELIMINARY POINT TEMPS/POPS...
TUL 65 73 46 72 / 40 10 0 0
FSM 67 76 46 71 / 40 40 0 0
MLC 64 73 46 72 / 40 20 0 0
BVO 63 72 43 70 / 50 10 0 0
FYV 64 73 45 68 / 40 40 0 0
BYV 66 74 45 67 / 40 50 0 0
MKO 66 72 45 69 / 40 20 0 0
MIO 66 73 44 68 / 40 20 0 0
F10 64 73 45 71 / 40 10 0 0
HHW 66 73 47 72 / 30 30 0 0
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&
$$
SHORT TERM...21