Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/03/20
Area Forecast Discussion
National Weather Service Gaylord MI
1023 PM EDT Tue Jun 2 2020
Issued at 1023 PM EDT Tue Jun 2 2020
Earlier thinking still holds up. Very clearly, the strongest
convection is inbound to central/southern lower MI. Would still
not preclude a strong-ish storm in our far south. A storm due west
of MBL over the WI waters of Lake MI spiked up decently within
the past 40 min, before weakening. Some adjustments to pop
coverage (increasing) and timing (a little faster) have been made.
UPDATE Issued at 856 PM EDT Tue Jun 2 2020
Another note...00Z observed APX sounding had circa 1900j/kg of
SbCape and 1100j/kg of MlCape. Of course, we were capped at 800mb,
with 85j/kg and 145j/kg of SbCin and MlCin, respectively. The
winds also have a northerly component thru the entire column, a
clear obstacle to activity moving northward. The GRB 00Z
sounding does at least have due west winds in a portion of the
column, but no where is it outright southerly. (GRB also has a
SbCape of 4500j/kg!)
UPDATE Issued at 827 PM EDT Tue Jun 2 2020
Convection upstream is starting to take shape, with svr storms
developing due w of Manitowoc WI. That`s also due w of MBL/LDM.
Deep convection seems unlikely to migrate northward with time,
with a southward-sinking surface cold front and convection-
generated cold pool, and essentially zonal mid-level flow. So it
seems as though our svr threat is confined to the southernmost
sliver of this forecast area...at best. Most of the CAMs I have
looked at this evening keep with strong/svr convection primarily
near and south of LDM. This includes mainline HRRR and RAP runs,
along with the HRRR run at SPC.
There are plenty of types of interesting wx possible, even if
organized svr wx misses us to the south. Pressure rise and fall
couplets, and wake lows, could contribute to gusty winds well
behind and otherwise displaced from the parent convection. In
addition, the above could result in fluctuations of water levels
on Lake MI (seiches and/or meteotsunamis) - a potential problem
with very high lake levels. There`s still plenty to keep an eye on
Showers and embedded thunder are north of the svr storms, and a
good portion of northern lower MI is still getting wet tonight.
But the early returns suggest the svr threat is going to slip by
to the south.
.NEAR TERM...(Through Wednesday)
Issued at 402 PM EDT Tue Jun 2 2020
...Round of thunderstorms possible tonight...
High Impact Weather Potential: Severe thunderstorms possible later
this evening and overnight.
Pattern Synopsis/Forecast: Afternoon composite analysis reveals
broad ridging/warmth through the central CONUS into the Upper
Midwest with strong W/NW mid level flow across the western Great
Lakes. Mid-upper level speed max/short-wave trough is pressing
into the northern Plains along the North Dakota/Canadian border.
At the surface, broad low pressure is across south-central
Ontario with a with a cold front that stretches from the central
U.P. down through central Wisconsin and across southern Minnesota
with a very warm and somewhat humid airmass south of the front
across the Midwest into Michigan.
Temperatures across northern Lower Michigan have warmed through
the 80s...and touching 90 degrees in a few spots with MLCAPE
values now in the 1-2K J/KG range. But as anticipated, much of
the region remains capped this afternoon with lots of sunshine and
only a little bit of Cu across NE Lower Michigan.
Primary forecast concern: Convective development/evolution and
severe weather threat remains the main forecast concern this
Still in a wait and see mode for convection over the next several
hours. There is a narrow line of post-frontal showers/storms
sagging southward across central Minnesota. But as talked about in
earlier discussions, still anticipating additional convective
development further south along the cold front heading into the
evening hours, likely across southern Minnesota and eastward into
Wisconsin. Convection still appears likely to continue to grow
upscale/propagate eastward as a quasi MCS this evening and into
central and southern lower Michigan late this evening and through
the overnight hours, clipping the southern part of the CWA.
Severe storm parameters remain favorable with strong mid level
flow and resulting 0-6KM bulk shear values running 35 to 45 knots
through the night, supporting organized storms. Time of day is not
the greatest however with decreasing surface based instability
and storms will have to cross cold Lake Michigan. But enough
there to warrant a severe weather threat for large hail/damaging
winds, mainly south of M-72 and mainly during the overnight
Convection should exit S/E early Wednesday morning with clearing
skies and a little cooler/drier air overspreading northern
Michigan. That said, forecast soundings Wednesday afternoon
suggest enough surface heating/instability for a few showers and
possibly a thunderstorm to fire across the E/SE part of the
CWA...where northwesterly flow will intersect the marine layer off
Lake Huron. Confidence is not high, but enough so that I`ve
introduce some low end pops to the forecast for those areas.
.SHORT TERM...(Wednesday night through Friday)
Issued at 402 PM EDT Tue Jun 2 2020
High impact weather potential: Minimal.
High pressure builds into the Great Lakes region Wednesday night and
will produce precipitation-free weather through at least Thursday
afternoon...when a weak disturbance brushes the forecast area from
southern Canada. Zonal flow continues over the Great Lakes region
along with surface high pressure through Friday. Only some small
chances of a stray shower or two with some upper level disturbances
and accompanying moisture. Winds will remain fairly light Wednesday
night as aforementioned high pressure moves overhead. Winds will
become a bit breezy Thursday afternoon and become southwesterly
while veering to more northwesterly throughout the day Friday with
once again some gusty conditions during the afternoon hours with
diurnal mixing. High temperatures will be in the upper 70s to low 80s
Thursday and cool down to the low 70s to near 80 Friday...while lows
will be in the 50s.
.LONG TERM...(Friday night through Tuesday)
Issued at 402 PM EDT Tue Jun 2 2020
High Impact Weather Potential: Minimal.
Extended range features an increase in amplitude in the overall
pattern compared to the mostly zonal flow expected through the rest
of this week. Deepening Pacific trough will push heights upward
over central North America to start the weekend...along with
subsequent downstream troughing over the northeast U.S. Evolution
of this downstream trough will have potentially bigger impacts on
the upper Great Lakes heading into next week...specifically with
regard to the position of central North American ridge axis and
impacts on at least temperatures.
Looks like the weekend starts with surface ridging building into the
upper Midwest and upper Great Lakes Saturday with some northerly
component boundary layer flow. Short wave trough is forecast to
pass by Michigan in the Friday night through Saturday time frame
which could kick off a shower threat. Surface ridge axis forecast
to lie across the Great Lakes Sunday...and potential for stronger
warm advection upstream between the upper level ridge axis and the
trough over the northeast U.S. Some signal for an increased
precipitation threat by Monday as strong warm advection begins to
impinge upon the upper Great Lakes. But right now looks like the
forecast trend should be warmer heading into midweek. Will be
interesting to see what the remnants of T.C. "Cristobal" end up
doing as they get pulled into the Gulf coast region early next week
with a deep upper level trough over western North America.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 718 PM EDT Tue Jun 2 2020
SHRA/TSRA late evening and overnight.
A cold front continues to slowly settle across the northern Great
Lakes, running into warm/muggy air. Our wx is presently quiet,
but SHRA/TSRA are rapidly developing in central/northern WI. These
will move e to ese-ward, targeting central lower MI in particular.
MBL has the best chance to see strong/svr TSRA, toward and after
midnight. Chances for thunder will decrease as one heads further
north. Substantial cig/vsbys restrictions are of course possible
as active wx moves thru. Conditions will be mainly VFR and quiet
again during the day Wednesday.
Gusty westerly breezes will diminish this evening. A light nw to n
breeze on Wednesday.
Issued at 402 PM EDT Tue Jun 2 2020
No marine headlines anticipated through the middle part of the
week. Some gustiness will be found in the nearshore areas into
early evening. Winds veer northwesterly on Wednesday likely with
some gustiness again through the afternoon. But winds/waves are
expected to remain below small craft advisory criteria.
Area Forecast Discussion
National Weather Service Binghamton NY
1052 PM EDT Tue Jun 2 2020
Severe thunderstorms possible late tonight and again tomorrow
across the Twin Tiers as a couple fast moving disturbance cross
the region. Weak high pressure builds back in on Thursday with
mainly dry weather, but another front may pass Friday.
.NEAR TERM /THROUGH WEDNESDAY/...
1045 PM Update
Strong supercell thunderstorms are developing across the Niagara
Frontier and coming off of western Lake Ontario. SPC has
indicated a 40 percent chance for a severe thunderstorm watch
mainly across Yates and Steuben Counties. These storms could
approach the far western portion of our CWA over the next few
hours and will need to monitor closely. Instability, mainly
elevated is trying to advect east and south into our area.
800 PM Update
Still watching closely the potential for strong to severe
thunderstorms across the western Finger Lakes, Central Southern
Tier and into NE PA between about 11 PM and 4AM tonight into
Wednesday morning. Uncertainties remain, and thus am in
agreement with SPC`s slight risk. For much of our area the
convection looks to remain elevated overnight, generally being
lifted from around the 850mb level...however it could be closer
to surface based across Steuben and Bradford counties. Also,
current radar and satellite trends are showing storms popping up
near Georgian Bay and are heading SE...but if their direction
remains consistent these storms may end up a bit further
north/east than earlier forecast. So with this update PoPs and
chances of thunder were increased further north/east across CNY
overnight. Also added in a mention of isolated large hail,
gusty winds and heavy rain overnight in the area where SPC has
outlined in a marginal and slight risk. Otherwise, temperatures
hold rather steady tonight and may even rise late as dew points
also surge into the 60s after midnight. WPC does have a stripe
along and SW of a line from Penn Yan--Owego and Scranton
included in the marginal excessive rainfall outlook. With PWATs
surging to around 1.3 inches we could certainly see some
localized torrential downpours and plenty of lightning
Most CAMs are in good agreement that much of our CWA will see a
break in the shower/storm activity from about 4-5AM until
9-10AM...during this time it should just be partly to mostly
cloudy with perhaps some patchy fog around. Then, the Mesoscale
convective complex which is currently over Wisconsin and
Minnesota is forecast to quickly race east
overnight...potentially reaching our western zones by 10-11am
then racing across the Twin Tiers and NE PA midday. A final line
of thunderstorms then looks to develop across western NY
midday, and push east- southeast quickly across the same region
(Twin Tiers/NE PA) during the afternoon hours Wednesday. Ample
surface based instability is forecast to builds across NE PA and
perhaps the far southern tier or NY during this timeframe.
Parameters support strong gusty winds and hail once again with
these storms Wednesday afternoon. Adjusted chance for
thunderstorms up, and expanded the coverage northward a bit; as
much of CNY has at least a chance for a thunderstorm Wednesday.
High temperatures range from the low to mid-70s across CNY, with
mid-70s to lower 80s expected across NE PA. Dew points reach
the mid to upper 60s so it will be quite humid out there.
Severe storms possible late tonight and tomorrow...
320 PM Update...
Confidence is growing for severe thunderstorms to impact the
region late tonight and again tomorrow. 12Z guidance is now in
good agreement with timing of shortwave arriving late tonight
around 3Z in Western NY and exiting region by 8Z or 9Z tomorrow
morning. Forecast sounding across the Southern Tier of NY and in
NE PA, show a low level stable layer, but strong elevated
instability exists above this shallow stable layer. RAP
soundings highlighting elevated CAPE values over 1000 J/kg (NAM
is likely overdone with over 2000 J/kg) and steep mid level
lapse rates in the 700 - 500mb layer near 8C/km.
Warm air/moisture advection surges in near the 850mb level with
an approaching warm front this evening. Storms late tonight
should ride along this boundary as short wave dives SE out of
Ontario. Strong 0-6km bulk shear of 50 to 55 knots with winds
veering from SE in the low levels to NW`rly aloft support
rotating storm updrafts and possibly a few right moving
supercells overnight. With strong shear and impressive mid level
lapse rates, but stable low levels, storms will be elevated, so
thinking is that large hail will be most likely severe risk
tonight. However, depending on the strength of the low level
inversion in place, can`t rule out at least a possibility for some
damaging wind gusts. For now, have mentioned the possibility of
at least some small hail in the forecast with gusty winds, and
if confidence continues to grow later this evening, then more
enhanced wording can be added to the forecast. Again, the
greatest chance to see any severe storms late tonight will be
from the Southern Tier of NY into NE PA.
After a brief lull in the action from the storms overnight, we
will see more storms enter the region from the west around mid
to late tomorrow morning as a cold front approaches. The best
threat for severe storms tomorrow looks to be from the NY/PA
border on southward. Because of the timing, uncertainty still
exists on the amount of instability, as there will likely be
little time to destabilize before storms move into our western
counties, with the greatest destabilization likely to occur
across our NE PA counties. Strong to severe storms will exit the
area early tomorrow afternoon, but can`t rule some lingering
showers into tomorrow evening.
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
330 PM UPDATE...
Not much change to the short term with this mornings guidance.
The front is trending a little further south so PoPs were
adjusted as well as temperatures increased as clouds may try
and clear, especially for our northern zones.
Cold front stalls over southern PA and becomes the focal point
for showers and thunderstorms in the period, but mainly south of
the area. Some showers and storms are possible Wednesday
evening as an upper wave and the front trigger convection, but
they should taper off after midnight. Dry weather continues into
Thursday, however isolated showers are possible Thursday
afternoon over NEPA as the front sneaks northward a bit and
afternoon heating aids in convection.
Short wave passing through on Friday will once again work with
afternoon heating to fore convection, mainly in the afternoon,
scattered over much of the area.
.LONG TERM /FRIDAY THROUGH TUESDAY/...
230 AM UPDATE...
A cold front will sweep through the area Friday night into
Saturday triggering showers and thunderstorms over much of the
area. Long wave trough behind the front will allow for isolated
showers and storms Saturday with the cold pool aloft. Upper
heights begin to build in Sunday as the trough axis slides east
of New England and drier sir builds into the forecast area. The
dry weather will continue into Monday as a large ridge builds
into the Great Lakes by the end of the period.
.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Thunderstorms will pass over the KELM and KAVP terminals
overnight, first arriving at KELM around 03z, then at KAVP by
05z. Thunderstorms will contain hail, gusty winds, and MVFR
restrictions. Brief IFR restrictions are possible.
After showers move through the KBGM terminal overnight, ceilings
will fall to between 500 and 900 feet in low stratus.
Another round of thunderstorms could affect the KAVP, KBGM, and
KELM terminals Wednesday afternoon. We will continue to monitor
Wednesday night through Thursday night...Mainly VFR.
Friday through Friday night...Chance of showers and
thunderstorms with associated restrictions as front passes.
Saturday...Small chance of showers/restrictions, otherwise VFR.
Sunday...VFR expected at this time.
Area Forecast Discussion
National Weather Service Des Moines IA
1058 PM CDT Tue Jun 2 2020
.DISCUSSION.../Tonight through Tuesday/
Issued at 301 PM CDT Tue Jun 2 2020
Broad ridge spreads across most of the central U.S. with the axis
sliding across the Missouri River Valley this afternoon. Sharp short-
wave trough is moving through the Dakotas this morning with surface
thermal boundary placed across the Interstate 90 corridor through
the northern Plains into the upper Midwest. This feature will be the
focus for a severe weather threat later today.
On the south side of the boundary, H85 WAA will be strong today,
which along with mostly clear skies will allow temperatures to jump
into the lower to mid 90s through most of the CWA. Northern Iowa may
actually see warmer temperatures than southern Iowa this afternoon.
Expect to see moisture pooling just ahead of the boundary, which
will keep dewpoints in the mid to upper 60s across northern portions
of the forecast area later this afternoon. The amplified ridge
across the central CONUS will begin to flatten as CVA ramps up ahead
ahead of the short-wave, promoting H5 height falls across the
northern Plains and upper Midwest. This will also force the surface
boundary southward throughout the afternoon. This will be the
feature to watch with respect to the convection and severe weather
potential later this afternoon and into the evening.
CAM guidance has not been providing the best consistency for
convection and severe weather potential across the northern portions
of the forecast area for later this afternoon through the evening.
The last few cycles of the operational HRRR have backed off of
intense convection over the forecast area, focusing the threat
mainly in SE Minnesota and western Wisconsin this evening. However,
not completely sold on this operational HRRR trend. 12z NSSL-WRF and
NMM attempt to develop a cluster of multi-cells across northern Iowa
after 2z this evening (and the 18z HRRRv4 has done this as well). A
look at CAM soundings across the northern forecast area shows decent
capping, which could potentially limit updraft development. However,
these CAM soundings are generally under estimating dewpoint
temperatures, by 8-10F in some of the extreme cases. Further, the
boundary layer across the north has had plenty of time to
destabilize. Given that several of the CAMs are coming in too low
with dewpoint temperatures, the surface based CAPE values are
likely closer to the maximum of the HREF members rather than the
mean, which would place values closer to 4000 J/kg this afternoon.
Adjusting the dewpoints in CAM soundings also yields similar CAPE
values. Thus, the capping inversion noted in these soundings may
not be as much of an issue if this instability continues to
develop this afternoon, especially in the presence of strong
convergence with the synoptic boundary in place and an outflow
boundary noted on GOES satellite imagery moving southeastward from
the remnant convection over the Dakotas this morning. As for the
severe threat, the more favorable shear environment for Iowa does
not come into play until after 01z, where 0-6 km bulk shear will
be around 35-40 kts. Coupled with rather steep low and mid-level
lapse rates (assuming mixing remains robust this afternoon),
updrafts may be sustained over a considerable depth, thus looking
for hail to be the primary threat with storms over Iowa. Damaging
wind gusts up to 70 MPH could come into play, with DCAPE values
between 1000-1500 J/kg. Lapse rates look to remain near dry
adiabatic up to around 800 mb. If a rogue supercell thunderstorm
is able to develop, an isolated tornado could be possible. But
throughout this afternoon, the low-level shear environment just
does not seem to be materializing for it. HREF mean 0-1 km SRH
values barely touch 100 m^2 s^-2 close to time of CI. This may be
very reliant on storm scale processes sharply modifying the near
storm environment. Additionally, LCLs at their lowest will be
around 1500 m, with several point soundings showing over 2000 m.
Thus, will be looking mainly at a hail and wind threat. Due to the
cap that is in place, bust potential still remains medium on the
severe threat this afternoon. SE Minnesota and and western
Wisconsin will have the environment with slightly less
uncertainty. Should deep convection be inhibited late this
afternoon, can still expect some elevated showers on the backside
of the boundary, with the short-wave moving in from the Northern
Plains providing enough convergence to get things going.
Wednesday and Beyond:
Mid-level flow becomes more zonal through the middle and end of this
week. However, several small perturbations will result in modest
height falls, providing chances for light showers Wednesday and
early Thursday. Temperatures will remain warmer throughout the week
as H85 flow quickly returns southerly, leaving the forecast area in
in an area of moderate WAA. If precipitation or cloud shield remains
expansive, this will limit insolation and high temperatures some
throughout the week. Late Thursday into Friday morning, another
short-wave trough moves across the Missouri River Valley. This short-
wave will be tied better with a surface cyclone and boundary that
may bring convection to the forecast area. Ahead of the surface
boundary, GFS/NAM attempts paint an area in the western forecast
area with surface CAPE over 3000 J/kg, along with around 40 kts of 0-
6 bulk shear, may support a severe threat. This threat is currently
highlighted by the SPC Day 3 Slight Risk for severe weather. This
instability will be conditional on clearing from previous shower
Into the weekend, the synoptic picture becomes interesting. At 500
mb, a closed 5910 m contour high begins to move northeastward off
the Mexican Plateau into the southern Plains. Meanwhile, a closed
low sits off the Baja Peninsula. The high off the Plateau will act
as a block to the closed to low. GFS and ECMWF solutions diverge.
GFS depicts a short-wave at H5 that kicks off from the Rockies over
the weekend, while the ECMWF amplifies the ridge across central
CONUS. Thus for the weekend, will keep limited POPs in the forecast
to account for possible action within mid-level southwesterly flow.
Temperatures at this time for the weekend will also be kept closed
to the mean of the possible solutions, and will pinpoint better as
guidance converges to a more consistent solution.
.AVIATION.../For the 06Z TAFS through 06Z Wednesday night/
Issued at 1058 PM CDT Tue Jun 2 2020
Sct SHRA/TSRA will sink south through the TAF sites overnight but
VFR conditions are forecast to prevail. Front stalls near southern
Iowa Wednesday but latest models have precip all south of the state
thorugh the fcst pd. VFR with light and variable wind on
Area Forecast Discussion
National Weather Service Green Bay WI
1047 PM CDT Tue Jun 2 2020
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 324 PM CDT Tue Jun 2 2020
Focus is on thunderstorms development and severe potential late
this afternoon and tonight.
At 20Z surface cold front was draped from west to east across the
center of the CWA, roughly from Wausaukee to Marshfield, as
evident by the wind shift to the W/NW. Seeing a few cu trying to
develop near the front, while some higher clouds from the
convection across MN also started to stream into northern and
central WI. Further west, the main line of thunderstorms has
persisted across central MN and continues to track E/SE.
CAMs today have continually been slowing down the arrival of the
convection into the WI and the GRB CWA. Latest (18Z and 19Z) HRRR
shows a few storms getting into far northern WI around 22-23Z,
but the bulk of the thunderstorms do not arrive until 01-02Z or
so, across central and east- central WI. The 19Z sounding from
GRB shows MUCAPE of 4000 J/kg, MLCAPE of 1700 J/kg, DCAPE of 1300
J/kg, and mid level lapse rates around 8.0 C/km. This is in line
with the RAP analysis showing similar values across the southern
two-thirds of WI or so. Once thunderstorms arrive there is more
than sufficient instability for storms to produce damaging winds
and large hail. While an isolated tornado cannot be ruled out
completely, with marginal shear around 20 to 25 knots, SRH less
than 100 m2/s2, and LCL heights ranging from 1500 to 2000m do not
expect tornadoes to be a main concern. Of course, heavy downpours
and frequently lightning can be expected within any storms. With
storms arriving a couple hours later than the previous forecasts,
also expecting storms to end a couple hours later, ending between
06-09Z from NW to SE across the area.
Once storms and lingering showers clear out, clouds will also
clear out by early to mid-morning on Wednesday. Wednesday is
looking very summer-like. As sfc high builds into the area
expecting dry weather and mostly sunny skies. Afternoon highs will
range from the upper 70s in the Northwoods and along Lake
Michigan, and from 80-85 degrees across central WI and the Fox
Valley. Humidity will also fall with Tds in the mid 40s to mid 50s
with light winds.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 324 PM CDT Tue Jun 2 2020
Flattened, zonal flow remains expected to be in place across the
northern tier of the CONUS through Friday. Then as a deep trough
develops over the west coast, a building ridge across the western
Great Lakes will lead to a warmer and more humid trend this weekend
into early next week.
Wednesday night through Thursday night...Relatively quiet weather
remains expected to occur on Wednesday night as the cold front will
linger across the far southern Great Lakes. Clear skies and light
winds will lead to a relatively calm and pleasant night. The next
shortwave trough is then expected to move across south-central
Canada in the Thursday to Thursday night time period. It will push
a weak front across the region during the same time frame. Although
moisture and instability will be increasing ahead of the front,
convergence along the front looks relatively weak and upper support
will remain well to the north. So even though some thunderstorms
will be possible, severe weather is looking unlikely at this time.
Rest of the forecast...The chance of storms may continue into Friday
if the front cannot sag far enough south on Thursday night. Also
seeing evidence of a tail of a more potent shortwave moving across
the northern Great Lakes, which could provide large scale lift. But
for now, precip chances will remain low. Once this shortwave
passes, the first half of the weekend is looking quiet as high
pressure settles over the area. Then the arrival of more
humid/unstable air will lead to increasing chances of storms late in
the weekend into early next week.
.AVIATION...for 06Z TAF Issuance
Issued at 1047 PM CDT Tue Jun 2 2020
Showers will linger across far southern central and east-central
Wisconsin for a few more hours before dissipating during the
overnight hours. Clouds will clear behind the showers with mainly
clear conditions by mid Wednesday morning and lasting into
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
901 PM CDT Tue Jun 2 2020
901 PM CDT
The main focus this evening has been on the convective trends with
the MCS across WI. THe southeastward propagation has by far out
passed forecast guidance. The current timing of this convective
activity would put it at the IL state line just prior to 10 PM and
into the northern suburbs of Chicago by 11 PM. Fortunately the
threat for severe wind gusts looks to be dropping off as the
storms are becoming outflow dominate. Nevertheless, expect some
gusty winds of 30 to 40 mph over the next 1 to 2 hours over far
northern IL as the gust front and storms approach.
The main update to the forecast was to move up the time of
precipitation by 3 to 4 hours to account for the observational
trends over the past couple hours.
212 PM CDT
Through Wednesday night...
Summer like warmth is upon the region this afternoon with nearly
cloudless skies and a 850-925 thermal ridge (and associated elevated
mixed layer) nosing over the area from the west. Still 3 degrees
away from 92 record high at ORD as of this writing, MDW has
already tagged 90. The nearest forcing mechanism aloft a decent
wave/500 mb speed max across north central Minnesota on the
southern flanks of the upper level jet across the Borderland. This
wave is moving along the northern periphery of the stout CAP. The
surface front is currently draped across southern MN and
extending northeast toward Lake Superior.
Concerns center around how much of the activity associated with this
wave will make it into our area tonight, and where the effective
boundary will be tomorrow when convective initiation occurs again.
The speed max does appear to take a more W-E track which should also
keep the effective front north of the local area. MCS maintenance
parameters/as alluded to in the earlier AFD, are not super favorable
for keeping a robust MCS occurring into northern IL tonight as 850-
300 mb wind vectors/thickness fields remain oriented W-E, and
forward propogating vectors also keep a similar orientation, and
actually have somewhat of a SW-NE component. SPC has expanded the
Enhanced Risk into lower MI with more of this idea of a forward
propagating system following this W-E track.
CAM depiction of some clusters of storms upstream with potential
outflow advecting into the region tonight seems reasonable, but with
a weakening trend as any showers/storms make their way in.
Forecasted DCAPE values do support cold pool sustainability which
could act as a driver for additional storm development from elevated
and conditionally unstable parcels. It would surmise that
convection, if it were to occur, would be on the leading edge of
this outflow and favored very late evening/early overnight. Shear
profiles with this arrival time are on the lower end of the severe
spectrum in N IL which is why the severe risk, while not zero, is
focused in WI.
We will retain a healthy MUCAPE corridor overhead tomorrow which
eventually will manifest itself toward the surface given a weaker
CAP. The next upper wave across WY will make headway across the
plains and then toward our area midday into early afternoon while the
effective frontal boundary continues to nose southward across NE
IL/NW IN. We could still have some scattered storms with the MUCAPE
axis around, though the forcing initially may be weak and we could
have some capping in play. This is where guidance is initially mixed
with many of the CAMS showing weak forcing, but the HRRR/raw
NAM12/RAP are a bit more aggressive, potentially with the low level
convergence fields. The remainder of the HREF CAM suite is muted. We
are not surprised on the mixed signal as we will need to await what
the expected storm complex across WI will do tonight.
There are mixed signals with the guidance has to how
quick the convective initiation will be and therefore how far
north this will occur. Lake breeze convergence could be in play
too depending on initiation time -- so plenty of complicating factors.
During the afternoon this composite boundary should be
along/south of I-80 as most guidance members show. The cap will be
appreciably weaker than today with mixed layer CAPE forecast
upward of 1500-2500 J/kg near the boundary. Scattered mature
convective development seems probable and given effective shear of
25-30 kt and the lapse rates aloft, hail and wind would be
threats with the strongest storms. If this setup indeed pans out,
there will likely be a localized area of flooding potential near
and just south of the boundary with slower and training storm
The boundary will stall Wendesday night, and thus will maintain some
lower end PoPs for any westerly waves to incite some low level jet
response -- but confidence is low.
320 PM CDT
Thursday through Tuesday...
The large scale pattern will generally favor above normal
temperatures through the period, though the signal continues to
point toward pronounced lake cooling over the weekend and possibly
into Monday. In addition, it appears that humidity levels will be
fairly comfortable area wide over the weekend and possibly into
Monday. The main time window for a chance of isolated to widely
scattered showers and thunderstorms is Friday afternoon.
On Thursday, dry air aloft through much of the column and fairly
weak lapse rates aloft could keep destabilization more muted and
the atmosphere capped. Also, there`s not much of an apparent mid
and upper level trigger mechanism. Much of the guidance favors a
drier look, but held onto some low PoPs from NBM south of I-80
where instability could be a bit higher and capping a bit weaker.
There should be a fairly early lake breeze push inland, keeping
lakeside areas mainly in the 70s. The rest of the area should be
in the mid to upper 80s and can`t rule out a few 90 degree
Most convective activity Thursday night should be off to the
northwest, with a preference for the NAM and ECMWF, so the low NBM
PoPs may be generous. On Friday during peak heating, the forcing
is again pretty nebulous, with strongest mid and upper level
forcing generally well north of the area. Temperatures in mid to
upper 80s and dew points of 65-70 will likely yield moderate to
strong instability at peak heating and models suggest weak
capping at most. Therefore, convective temp may be reached fairly
early, with any subtle low level convergence aiding in lift for
thunderstorms. Lake breeze may be one of these sources of low
level convergence during the afternoon. With the weaker overall
forcing, NBM PoPs in lower chance range appear reasonable at this
vantage point. A belt of 35-40 kt 500 mb flow on northeast
periphery of ridging centered over the Plains could yield
effective deep layer bulk shear of 30-40 kt. Thus there is a
conditional risk for a strong to severe thunderstorms (wind/hail
risk), though coverage may be low for reasons described above.
The core of the mid and upper level ridging will gradually push
east through the weekend. Any additional convective threats
later Friday evening and overnight and shifting south. There
remains good agreement on a backdoor cold front passage by
Saturday that will bring mainly a lower humidity air mass to the
region, along with more pronounced lake cooling due to persistent
onshore winds. On Monday-Monday night, the surface high pressure
that will bring the fair weekend weather will be slowly sliding
east, so inland areas could warm a few degrees Monday PM and lake
cooling confined to the Illinois shore. There`s uncertainty on
whether convective chances will return Tuesday or primarily beyond
day 7, though humidity should be on the rise.
For the 00Z TAFs...
Aviation forecast concerns...
* Fairly low confidence in timing of potential thunderstorms late
tonight into Wednesday morning, and wind shift to north-
northeast with convective outflow.
* Chance of another period of thunderstorms mid-late Wednesday AM.
* Chance of MVFR ceilings Wednesday morning.
* Lake breezy for Chicago terminals Wednesday afternoon.
Somewhat messy, low confidence forecast with respect to
thunderstorm chances and timing late tonight into midday
Wednesday. Very but strongly capped air mass is in place across
the terminals early this evening. Thunderstorms have developed to
the northwest of the area across southern MN and into western WI
during the afternoon, along a combination of a cold front and a
pre-frontal surface trough, and within a region of weaker capping
in association with an approaching mid-level disturbance. While
individual cell movement is expected to be generally easterly, the
850-300 mb thickness field does suggest the potential for a
gradual east-southeastward movement to the developing convective
complex, which could impact parts of far northern/northeast IL
later tonight. Convective allowing models (CAMs) have quite a bit
of spread in solutions of timing and coverage of storms moving
southeast along outflow from WI storms as they attempt to spread
into the more strongly-capped air mass across our area. This leads
to somewhat low confidence in the evolution of convection into the
terminal areas. The 4km WRF appears to be doing the best in the
near term with storms building from southern MN into northern IA,
and this model depicts outflow-generated convection developing
into far northern IL in the 06-08Z time frame, though weakening
or struggling against the capping inversion south of the IL/WI
border. Operational and experimental versions of the HRRR are much
slower (though are not handling ongoing storms well), and develop
convection more notably along the cold front as it pushes across
the terminals Wednesday morning. Have generally relied on the 4km
WRF solution with the 00Z TAFs. A brief period of MVFR ceilings is
possible in/after precipitation early Wednesday.
In addition to timing complexities of storms, organized outflow
would likely disturb the wind field across the area into Wednesday
morning, with a northerly component to the surface winds for a
time, and then more firmly northerly with the passage of the cold
front by midday. Chicago terminals would likely see a lake breeze
induced northeast wind during the afternoon.
Visit us at weather.gov/chicago
Follow us on Facebook, Twitter, and YouTube at:
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
914 PM EDT Tue Jun 2 2020
Forecast for the remainder of tonight looks to be on track, with a
mostly clear sky and low temperatures a bit above normal. Will
just make a few minor tweaks mainly to temps and dew points with
00Z TAF DISCUSSION.
There will be some mainly scattered clouds around at times, but
VFR conditions are expected for the period all sites. Winds will
become lighter overnight, but will increase again closer to 10
kts from the southwest during the day Wednesday.
/ISSUED 301 PM EDT Tue Jun 2 2020/
SHORT TERM...(Tonight and Wednesday)
1. Warm and humid with very spotty afternoon/evening thunderstorms,
especially in the Plateau and mountains.
The clouds have mixed out as expected this afternoon with full
sunshine and continued WAA allowing temps to reach the upper 70`s to
low 80`s as of 18Z. The warmest spots were in the southern valley
with 84 at CHA. A very pleasant evening is on tap, although
continued southerly flow will bring dew points into the mid/upper
60`s leading to a muggy evening and overnight.
For tonight, the mid/upper ridge over much of the southern CONUS
will begin to flatten as shortwave energy moves through the lower
Great Lakes pushing a cold front gradually southward. At the same
time, a southern stream upper low, currently analyzed over N TX,
will begin to slide eastward into AR. With warm 700 mb temps between
8 and 10 C and associated strong mid level capping scene in the RAP
soundings, as well as strong Bermuda high pressure remaining in
control of the SE, the upper low to the W will only result in a
gradual increase in high clouds. Reflected a gradual increase in
clouds in the sky grids from SW to NE after 07Z. Lows will stay in
the mid/upper 60`s.
For tomorrow, the aforementioned Great Lakes mid/upper shortwave and
associated surface low will progress through the NE U.S. and SE
Ontario with its trailing cold front slowly continuing a southward
jog into the OH Valley. This will set up NW flow over the NE U.S.
while the southern CONUS ridge tries to hold on in a more suppressed
state. This will cause the front`s progression south to be very
slow, however, this system will begin to phase with the old southern
stream upper low over AR and pull it east toward our area. Subtle
cooling aloft from the lowering heights (slightly weaker cap),
continued SSW flow of warm, humid air, and added moisture from the
approaching upper low will cause spotty convection to initiate in
the Plateau and eastern mountains from late morning through the
evening. Some of this activity could move into the valley, so added
slight chance to chance PoPs for most areas except for far NE TN and
SW VA. Confidence is low on how much convection we will see due to
the aforementioned capping, but if anything does develop, an
isolated severe storm could occur. Steep mid level lapse rates above
7 C/Km will allow for MUCAPE values over 3000 J/Kg by late morning
with LI`s of -6 to -8. This combined with PWATs increasing to over
1.5 inches will cause locally heavy rainfall, as well as the
potential for isolated wet microburst, if any cells develop. Any
microburst will be very localized. Highs will reach the upper 80`s
LONG TERM...(Wednesday night through Tuesday)
The long-term period of the forecast continues to be an active with
good chances for afternoon showers/storms with increasing moisture
on Thursday into Saturday. A cold front with drier conditions
forecast Sunday into Monday and then some decent uncertainty at the
end of the forecast with the Tropical Storm Cristobal.
Upper level heights will begin to fall Wednesday night into Thursday
as an upper level trough passes to the north across the Great Lakes
into the New England. Cyclonic flow associated trough will extend
southward into the Southern Appalachians even into the northern Gulf
of Mexico. Additionally, a 80-100 kt jet will extend across eastern
Great Lakes into New England putting the forecast area in the right
entrance region of this jet. At the surface, the high will be to the
east with generally southwesterly flow. All of these variables will
add up to produce above normal PW values in the 1.5-1.7 inch range.
These values are near the 75th-90th percentile for early June. The
synoptic lift is weak but have higher confidence in precipitation
occurring than during a typical summer time pattern. Better chances
will continua to be over the higher elevations. Some precipitation
may linger into the overnight hours with the saturated atmosphere
and weak lift but expect most activity will come to an end with the
loss of daytime heating. Much of the same will continue into the day
on Friday. The troughing aloft looks a bit weaker and have slightly
lower PoPs. Surface dewpoints will be back to typical summer time
values on Thursday and Friday into the mid and upper 60s. A strong
to marginally severe storm will be possible during this timeframe.
Better chances for an isolated severe storm or two appears to be on
Thursday. SBCAPE values will be near 1000-2000 J/Kg with 0-6 km bulk
shear of 15-25 kts. The main threat with these storms would be
isolated damaging wind gusts.
The pattern begins to amplify going into the weekend. A trough will
race out of the Great Lakes to the southeast into the Mid-Atlantic.
To the west, a ridge will amplify across the Mississippi River
Valley and Great Plains. The aforementioned trough will bring a cold
front into the forecast area with showers and storms developing
along this boundary on Saturday. Models indicate the surface boundary
will stall just to the south or over southern portions of the area
with a few showers continuing across this area. This is still
several days away and the models will continue to vary on how far
south the front makes it. Precipitation chances increase some on
Tuesday as showers around the periphery of the Tropical System could
impact the area.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 66 89 69 85 68 / 0 20 30 60 40
Knoxville McGhee Tyson Airport, TN 67 89 69 85 67 / 0 20 30 50 40
Oak Ridge, TN 65 89 68 84 67 / 0 20 30 50 40
Tri Cities Airport, TN 61 86 65 83 64 / 0 10 30 50 40
Area Forecast Discussion
National Weather Service Pueblo CO
251 PM MDT Tue Jun 2 2020
.SHORT TERM...(This evening through Wednesday)
Issued at 250 PM MDT Tue Jun 2 2020
Currently...radar indicates scattered showers and thunderstorms
across the region. Storms are moving very slowly to the south. A
surface boundary is stretching from near Trinidad, northeast to
Haswell, with winds north of the to the north, while surface winds
are southerly ahead of the boundary. Temperatures have warmed into
the 80s and 90s across the Plains, while the San Luis Valley is in
the 70s and 80s.
Rest of today and tonight...high pressure is currently sitting over
the Desert Southwest, with northerly flow aloft across much of
Colorado. 500 mb vorticity fields indicate an upper disturbance
dropping south across the Plains. This will continue to spark
showers and thunderstorms over the area. The HRRR and ARW are
consistently developing activity, mainly along I-25 and south of
Highway 50 through this evening. Modest instability will allow for
gusty winds to near 45 mph, and possibly dime size hail with
stronger storms. Given the slow storm movements, locally heavy
rainfall will be possible. If one of these storms happens to move
over a burn scar, flash flooding will be possible. Models in good
agreement moving this activity south and dissipating around
midnight. After midnight, clearing skies are expected. Overnight
lows will fall into the 50s and 60s by Wednesday morning.
Wednesday...the upper level high pressure looks to remain stationary
over the Desert Southwest, with broad northwesterly flow aloft.
Models have an upper disturbance across Wyoming, moving into
northeastern Colorado by the afternoon, and into western Kansas by
evening. Southeasterly flow at the surface will keep moisture
pooled across the Plains. This will help boost instability with
CAPE values around 1500 j/kg. Expect scattered showers and
thunderstorms to develop, initially over the Mountains, and spread
east into the I-25 corridor by afternoon. Coverage is not
anticipated to be as widespread as previous days. If any spot was
going to see the potential for a couple of strong to severe storms,
it would be out of Kiowa and Prowers Counties during the afternoon,
where instability is forecast to be highest, and nearer the upper
level energy. Otherwise, main threats from thunderstorms will be
lightning, gusty outflow winds and small hail. Again, if a storm
should move over a burn scar, flash flooding will remain possible.
Afternoon highs will once again be warm with lower 90s across the
.LONG TERM...(Wednesday night through Tuesday)
Issued at 250 PM MDT Tue Jun 2 2020
.Wednesday night...Shortwave will continue moving eastward during
the evening. Threat for severe weather is greater over northeast
Colorado with severe weather threat extending into southeast
Colorado. Bufkit and models show around 1500 J/kg or higher of
CAPE in the evening with bulk shears around 30 to 40 knots. SPC
Day 2 outlook has the area defined well. LCL look to be fairly
high so the main threat from the storms will be some large hail
and strong winds. By later in the evening, the activity will move
into Kansas. Elsewhere, storms should end my mid evening.
.Thursday...Shortwave ridge remains over the region with stronger
mid level winds mostly staying to the north of the region. Mid
level moisture decreases slight, but there is still enough
moisture for some diurnal convection over the mountains. Mid level
winds remain at around 20 to 25 knots at 500mb which will allow
storms to be progressive. Low level moisture is greater near the
Kansas border, east of a dry line. SPC has marginal risk extending
southward along the Kansas/Colorado border. Increased PoPs over
the plains Thursday evening to have thunder mentioned in the
forecast for possibility of a strong to severe storm. Otherwise,
continued hot on the plains with some highs around 100F.
.Friday and Saturday...Upper low off the California coast starts
to move northeast as an open wave. Looks as if most of Friday,
during the day, will be warm and dry with best lift staying
southwest of the forecast area. By later in the afternoon, the
system may start affecting the Eastern San Juans and move
northeast during the night. The models and ensembles are
continuing to indicate the best lift and most of the convection
will be over the mountains with best chances over and near the
Continental Divide region. NBM has mostly silent PoPs over the
Interstate 25 corridor and eastern plains through midday Saturday.
By later in the afternoon Saturday, some modest convection may
develop over the plains and Interstate 25 corridor. Increased wind
speeds on Saturday as NBM under does gusty winds on the plains.
There is the potential for critical fire weather conditions in the
San Luis Valley on Friday. Threat for critical fire weather
conditons spreads eastward on Saturday with increasing winds on
.Sunday through Tuesday...Dry and warm southwest flow aloft
continues over the region with fire weather concerns each day. On
Tuesday, a weak cold front on the plains may be cooler weather
and a modest chance for some diurnal convection on the plains.
.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 250 PM MDT Tue Jun 2 2020
VFR conditions at all three terminals through the next 24 hours
outside of thunderstorms. Thunderstorms will remain possible at all
three terminals through 06z/wed this evening. Reduced CIGS and VIS
along with gusty outflow winds to near 45 mph will be possible
should a storm hit a terminal. Mid and high level clouds will
spread across the region overnight. Another round of afternoon
showers and thunderstorms is anticipated on Wednesday afternoon.