Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/09/18
Area Forecast Discussion
National Weather Service La Crosse WI
637 PM CDT Tue May 8 2018
.SHORT TERM...(Tonight through Thursday)
Issued at 226 PM CDT Tue May 8 2018
Another nice day ongoing out the office window today with enough
thinning of the cloud cover early on to allow for a very warm day
near and east of the Mississippi River, along with one more day of
elevated fire weather concerns. However, big changes are lurking
just to the west, as evidenced by thickening cloud cover making
inroads across the local area. Those come courtesy of burgeoning
warm advection and moisture transport into the region in advance of
a shortwave trough meandering east across the Dakotas, while another
upper wave is transiting eastward through southern Saskatchewan.
That latter feature is forecast to link up with the lead wave and
slow the eastward progression of an upper trough across our area
through tomorrow, with persistent warm advection ascent and moisture
transport into the region supporting increasing coverage of showers
through the evening and night, gradually exiting east into
Wednesday. Overall instability isn`t anything terribly impressive,
but elevated CAPE values pushing 500 to maybe 1000 J/kg (NAM
highest) is certainly enough to deliver some thunder, especially
across northeast Iowa into southwest Wisconsin closer to the nose of
strongest moisture transport. Severe threat very low given elevated
nature of convection and lack of any organizing shear but some small
hail isn`t totally impossible given low freezing levels of 9-10kft.
As alluded to above, the majority of precip should swing east of the
area by midday Wednesday, though can`t rule out a smattering of
additional showers and thunderstorms into the afternoon beneath the
upper trough axis, especially near and east of the Mississippi River
with sharper low level convergence along a cold front. Some of that
will also hinge on how much instability we can generate within what
should be fairly widespread lower cloud cover. Otherwise, we`ll have
to see how those clouds trend into Thursday but most of the day
should end up dry and fairly pleasant as low level ridging and drier
air briefly nose down into the region from Manitoba. With that said,
will have to watch late day shower potential possibly north of I-94
within an blossoming axis of frontogenetical forcing, though most of
that should hold off until Thursday night and beyond.
.LONG TERM...(Thursday Night through Tuesday)
Issued at 226 PM CDT Tue May 8 2018
Active period of weather set to arrive Thursday night through
Saturday as a fairly stationary frontal boundary lays out somewhere
from Nebraska through the lower Great Lakes while various pieces of
shortwave energy emanating from a cutoff western CONUS upper low get
kicked eastward. Those waves will interact with modest moisture
given a wide open Gulf of Mexico and building instability to the
south to deliver several rounds of showers and potential
thunderstorms into the first half of the weekend. As mentioned
yesterday, confidence in the exact placement of the heaviest
rainfall and timing remains on the lower side, but the general trend
for another very wet period of weather remains intact.
Highest confidence is on Thursday night-Friday with an axis of
strong and deep layer frontogenesis developing near the I-90
corridor and lifting north through the northern Great Lakes. That
strong forcing should result in a band of heavier rainfall
traversing the area, though there remain some subtle differences
among guidance regarding the actual placement of that heavier QPF
axis (GFS persistently farther north while ECMWF/NAM/GEM bullseye
near the I-90 corridor). The setup actually isn`t all that
dissimilar from the one we saw last Thursday which resulted in a
band of 2-4" of rain across northeast Iowa in an axis of strongly
sloped FGEN forcing, so we`ll have to keep a close eye on the
potential for some flooding pending where said rain band ends up.
Forcing looks to briefly wane later Friday before returning Saturday
with another wave riding along the frontal boundary just to our
south. Very tricky temperature forecast during the Friday/Saturday
timeframe, with some hints that temps may be stuck only in the 40s
(maybe even upper 30s?) in some areas north of the warm front with
clouds while areas farther south may spike into the 70s if that
boundary can briefly flex northward (a big "if). Regardless, it does
appear we`ll finally dry things out just in time for Mother`s Day
and into early next week with a return to high pressure and much
drier air working back into the region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 637 PM CDT Tue May 8 2018
Some scattered moving across the area this evening in association
with a short wave trough moving into northern Wisconsin. This
activity will continue to lift northeast through the evening and
should primarily stay north of both airports or at worst produce
some additional sprinkles at KRST. By late evening, a stronger
short wave trough will be approaching from the west. The low level
jet will form ahead of this wave and will be in position to
produce some low level shear for a short period at both airports.
It will also increase the moisture transport into the area that
will cause additional showers to form and move east across the
area through the night. There will also be enough instability to
produce a few rumbles of thunder. The main concern behind these
showers will be how low the ceilings will drop. Both the 08.18Z
NAM and 08.21Z RAP forecast sounding suggest the overnight rain
will be enough to saturate the low levels and allow IFR ceilings
to develop at KRST and MVFR at KLSE. This is a rather low
confidence forecast and will maintain continuity with previous
forecast of going to MVFR and keeping KRST just above IFR. Yet
another short wave trough will swing across the area Wednesday
afternoon and could produce a few more showers. Confidence on
placement is not high enough to include a VCSH at this point for
either airport.
&&
.HYDROLOGY...
Issued at 226 PM CDT Tue May 8 2018
Minor flooding continues along the Yellow River at Necedah (almost
done), Kickapoo River at Steuben (done later this evening) and
Mississippi River at McGregor and Guttenberg. Another round of
rain will arrive this evening and tonight, with additional showers
possible on Wednesday. In general, rainfall amounts around one-
half inch are expected, though with any convective (thunderstorm)
elements, locally heavier amounts are possible. At this time, the
threat for additional flooding tonight is low but will have to
watch to make sure storms don`t line up over the same areas for
too long (looks pretty progressive). More rounds of rain are
likely Thursday night into Saturday, with some potential for
additional heavy rainfall of 2+ inches in some areas. Right now,
the threat appears highest near and north of Interstate 90 but
will need to watch forecast trends the next few days to nail down
the details. Should those amounts be realized, additional flooding
will be possible.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Lawrence
LONG TERM...Lawrence
AVIATION...04
HYDROLOGY...Lawrence
Area Forecast Discussion
National Weather Service Green Bay WI
1104 PM CDT Tue May 8 2018
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Wednesday
Issued at 243 PM CDT Tue May 8 2018
The latest RAP analysis and satellite/radar imagery show high
pressure centered over the east coast and an area of weak low
pressure over northeast South Dakota. In addition, a shallow cold
front has dropped into far northern WI where winds have shifted to
the north. A few showers have popped up along this boundary over
Marinette county early this afternoon. A few more showers will be
possible in this general area through the rest of the afternoon
with decent low level convergence. Meanwhile, additional showers
are pushing across the Mississippi River and the latest short-
range models have some of these showers moving into north- central
WI by 5-6 pm, despite widespread relative humidities between 20
and 30 pct. As this low moves east, forecast concerns mainly
revolve around rain chances over the next 24 hours.
Tonight...The first round of showers is expected to move across
northern WI this evening as clouds increase across the rest of the
region. After a relative lull, the main area of showers,
currently over southern Minnesota, will lift northeast and into
north-central WI late tonight. Not much of a chance of thunder,
though cannot necessarily rule out an isolated storm. Warmer lows
ranging from the mid 40s over Door County to the mid 50s over
central WI.
Wednesday...The low pressure system will push a band of rain
across the region from west to east during the morning. With MU
capes upwards of 500 j/kg, some embedded thunderstorms appear
possible within the rain band. Even though this rain band is
expected to exit the NE WI shoreline in the afternoon, some
additional showers and isolated storms could also develop in its
wake if any heating can occur due to the close proximity of the
surface low and mid-level trough. Highs mainly ranging from near
60 degrees in Vilas county to the mid or upper 60s over the
southern Fox Valley.
.LONG TERM...Wednesday Night Through Tuesday
Issued at 243 PM CDT Tue May 8 2018
Precipitation trends Wednesday night, and Thursday night through
Saturday night periods, are the main forecast concerns.
Models have sped up the system a little bit for Wednesday night,
so it looks like most of the precipitation will be out of the
region by 06z/Thu. Will keep likely pops over our eastern counties
in the evening, as well a chance of thunderstorms.
Generally dry conditions are anticipated on Thursday into
Thursday evening as Canadian high pressure passes through.
Forecast confidence has increased a little bit for the end of the
week, as models generally agree on a couple rounds of moderate to
potentially heavy rainfall moving through during the Thursday
night through Saturday period. A strong frontal boundary will set
up just south of the region, with periods of moderate to strong
overrunning occurring at times. Still think that the best chance
of heavy rainfall will occur over central and east central WI, due
to the closer proximity of the 850 bm front and deeper moisture.
There will also be a small chance of thunder over our southern
counties during this period. The bottom line is that a round or
two of significant rainfall is possible later in the week, which
could cause flooding concerns to flare up again.
Temperatures will be below normal, especially Thursday night
into Friday. Cannot rule out a rain/snow mix over far northern WI
late Thursday night, though confidence is low, and temperatures
may not even reach 50 degrees in the forecast area on Friday.
Generally dry conditions are anticipated for the end of the
weekend and beginning of the next work week, along with
warming temperatures and another round of low relative humidity
over northern WI.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1104 PM CDT Tue May 8 2018
While VFR conditions should hold for most of the overnight period,
flying conditions are forecast to gradually deteriorate Wednesday
morning as an area of low pressure/associated cold front and a
mid-level shortwave trough move into the western Great Lakes
region and brings showers and a slight chance of thunderstorms to
northeast WI. Anticipate cigs/vsbys to drop into the IFR/MVFR
range pretty much for the entire day on Wednesday with little
improvement until later Wednesday night when high pressure begins
to build southeast from Canada. There may also be a brief period
of LLWS late tonight.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Kieckbusch
AVIATION.......AK
Area Forecast Discussion
National Weather Service Wichita KS
645 PM CDT Tue May 8 2018
.DISCUSSION...
Issued at 315 PM CDT Tue May 8 2018
20Z water vapor imagery shows an upper level shortwave trough moving
across the northern and central plains. At the surface a trough of
low pressure extended from the southern high plains through the
eastern Dakotas.
For this evening and overnight, models continue to bring the upper
wave through eastern KS as well as the surface trough. Forecast
soundings keep a surface parcel capped, but there is some elevated
instability progged. Models have been mixed on the idea for
convection this evening and while the HRRR has been one of the more
bullish in developing precip, the last couple runs have back off on
coverage. With the potential for some forcing and the elevated
instability, have kept a 20 to 30 percent chance POP across the
forecast area in case some isolated convection pops. Deep layer
shear is not all that impressive any storms that develop may be
multistorm with cold pools dominating. An isolated wind gust may not
be out of the question but overall conditions for severe storms do
not look favorable. Lows tonight are expected to range from the mid
50s over north central KS to the mid 60s across southeast KS.
The daytime Wednesday is shaping up to be fairly nice with mostly
sunny skies. Models keep the surface trough axis across the area and
think this may limit afternoon mixing. Additionally 850MB temps
suggest adiabatic mixing would only yield highs in the upper 80s. So
have trended highs a coupe degrees cooler, especially for central KS
where there may be an east wind through the day. For Wednesday
night, there are some signs of a vort max rounding the upper ridge
and propagating across the forecast area. This could cause some
scattered storms to develop through the night and have some 20 to 30
percent chance POPs.
For Thursday through Saturday, the pattern looks to flatten out
somewhat with energy moving mainly north of the forecast area. There
are some concerns with the placement of the surface trough over
central KS and whether convection could focus along this feature.
But GFS forecast soundings show a strong elevated mixed layer
advecting over the region and capping the boundary layer. So for now
have mainly a dry forecast save for a few slight chances skirting
the northern counties. Highs are expected to trend warmer with the
thermal ridge leaning over into central KS and we could see some
locations have highs in the mid 90s. By Sunday the the surface
trough is progged to push further south and bring cooler weather to
the area.
Monday and Tuesday are looking unsettled as an upper low moves into
the southern Rockies and eventually lifts out on Tuesday. Persistent
southerly flow in low levels is likely to bring a moist airmass into
the region. Depending on what the inhibition is like, there could be
a couple chances for showers and storms Monday and Tuesday due to
weak perturbations within the southwesterly flow aloft. Because of
this there are some chance POPs in the forecast. Have kept temps
close to seasonal normals with lows in the 50s and 60s and highs in
the 80s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 630 PM CDT Tue May 8 2018
Aviation concerns look to be minimal through the next 24 hours.
Water vapor imagery shows an impulse approaching the northern
Mississippi Valley with some of this energy extending down across
eastern KS. At the surface, a weak cold front extends from eastern
Nebraska through central KS. This front isn`t expected to progress
much further east before washing out. An isolated storm will be
possible east of the KS Turnpike but confidence in development
isn`t high enough to insert into KCNU`s TAF. Confidence is high in
mostly clear skies on Wed with light winds.
&&
.PRELIMINARY POINT TEMPS/POPS...
Wichita-KICT 62 91 64 89 / 10 0 20 10
Hutchinson 60 89 63 88 / 10 0 20 10
Newton 61 89 63 87 / 10 0 20 10
ElDorado 61 89 63 87 / 20 0 20 10
Winfield-KWLD 62 91 64 88 / 20 0 20 10
Russell 57 88 62 91 / 10 0 30 10
Great Bend 58 89 62 91 / 10 0 30 10
Salina 60 89 62 90 / 10 0 30 10
McPherson 59 89 62 88 / 10 0 30 10
Coffeyville 65 90 63 88 / 20 10 10 0
Chanute 64 89 63 86 / 20 10 10 10
Iola 63 89 63 86 / 20 10 10 10
Parsons-KPPF 65 90 63 87 / 20 10 10 0
&&
.ICT WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
AVIATION...RBL
Area Forecast Discussion
National Weather Service Jacksonville FL
752 PM EDT Tue May 8 2018
.UPDATE...Widely scattered convection diminishing just N of
our forecast area...otherwise mostly clear skies and light
winds are expected Tonight. Latest HRRR guidance suggests
potential for fog and low clouds to develop over inland areas
late Tonight, but SREF probabilistic guidance only has low
probabilities for fog/low clouds. Will include patchy fog W
of I-95 corridor late Tonight. Made just minor tweak to low
temp forecast based on latest consensus temperature guidance.
&&
.AVIATION...VFR expected next 24 hours. Patchy fog possible late
Tonight for TAF sites W of I-95 corridor...and included light fog
at KGNV/KVQQ for now.
&&
.MARINE...No significant changes planned for next CWF issuance.
High pressure will develop over the marine area by Wednesday
resulting in light winds and fairly low seas. Headline criteria is
not anticipated through the remainder of the week.
Rip Currents: Onshore winds and a persistent 8-9 second period
from an east-southeasterly ocean swell will keep a moderate risk
in place at area beaches through at least midweek.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 59 87 60 89 / 0 0 0 0
SSI 65 79 68 85 / 0 0 0 0
JAX 61 86 64 91 / 0 0 0 0
SGJ 65 80 66 82 / 0 0 0 0
GNV 59 87 59 87 / 0 0 0 0
OCF 60 89 60 91 / 0 0 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
$$
Wolf/Nelson/Bricker
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1130 PM EDT Tue May 8 2018
.UPDATE...
Issued at 1120 PM EDT TUE MAY 8 2018
Hourly grids have been updated based on recent observations which
led to colder temperatures over the next 2 to 3 hours for some of
the valley locations. Overnight lows still look on target,
however. As valleys continue to cool overnight, fog should develop
around or after 2 AM and could be dense in a few spots.
UPDATE Issued at 827 PM EDT TUE MAY 8 2018
A few showers linger mainly in Harlan and Letcher counties and
these should diminish with the loss of daytime heating and
departing trough. Otherwise, a few cumulus and ac linger. As the
ridging moves into the area tonight, these clouds may be slower
to dissipate or even linger through late evening, especially in
the east. Forecast soundings indicate some moisture remaining
between 850 and 700 mb. Chances for valley fog still look on
target at this point with some locally dense fog possible in
typically more favored locations.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 440 PM EDT TUE MAY 8 2018
19z sfc analysis shows some weakness in the pressure field over
far eastern Kentucky while high pressure controls most of the
weather through the Ohio Valley. Enough low level moisture and
cooler air aloft in the southeast again encouraged convection and
a decent cu field to develop over eastern Kentucky this afternoon
though nowhere near as extensive as yesterday with any storms so
far staying outside the state lines. Still expect a few to pop up
near the ridge lines into the first part of the evening.
Meanwhile, temperatures are running in the upper 70s to lower 80s
across the area - overachieving from guidance again this
afternoon. Dewpoints dried out a bit this afternoon with values
currently in the upper 40s to lower 50s and winds mainly light
and variable.
The models remain in good agreement aloft through the short term
portion of the forecast. They all depict a weakening trough
departing to the east with rebounding heights into Wednesday
morning as ridging passes over the state. This is in advance of a
larger trough shifting east out of the Midwest and over the Great
Lakes into Thursday morning. Plenty of energy will accompany this
trough and spread toward Kentucky early Thursday. Given this
agreement have favored a general model blend as the starting point
for the grids with emphasis on the HRRR and NAM12 in the near
term.
Sensible weather will feature another night of moderate - large
ridge to valley temperature disparity owing to good radiational
cooling conditions of light winds and clearing skies. Do expect
some patchy fog to form in the river valleys late - locally dense
but not any worse than the limited amounts we saw this morning.
Wednesday will be another warm and pleasant day, though clouds
will be on the increase in the morning with a potential for
showers and thunderstorms in the afternoon ahead of the sfc low
moving into the Upper Midwest. Western convection may be on the
wane as it spreads into our part of the state in the afternoon
keeping the activity less organized while the better mid level
support is found well off to the northwest. Expect a lull in any
activity into the evening with additional showers and storms
expected later in the night as the system`s cold front stalls out
overhead.
Again used the CONSShort and ShortBlend as the starting point for
the grids with adjustments to go a notch warmer Wednesday and
also to include terrain based differences tonight and to a lesser
extent Wednesday night. As for PoPs - beefed them up in the
southeast through early evening and also kept them a bit lower
than guidance on Wednesday.
.LONG TERM...(Thursday through Tuesday)
Issued at 435 PM EDT TUE MAY 8 2018
A bit of an unsettled pattern during the extended portion of the
forecast. Still tracking an upper level trough moving across the
lower Great Lakes on Thursday, as it continues to lose strength and
become absorbed into the larger upper level trough over Canada. A
surface cold front will be shifting SE towards the region, but
latest WPC analysis still shows the front shearing out by the time
it reaches eastern Kentucky. Soundings are also showing a very dry
airmass in place as it moves over, with generally only speed shear,
though instability during the day is still quite decent. As a
result, kept only chance pops in the forecast with isolated to
scattered thunderstorm potential during the afternoon, as any
pockets of moisture could easily result in rapid storm development.
Storms that do develop could result in some gusty conditions given
the parameters in place.
Once this system has passed, backing winds and drier air will
quickly cut off precip potential for Thursday night. More zonal
westerly flow will take hold aloft for much of the remainder of the
forecast period, with the previous frontal boundary pushing north as
a warm front, placing Kentucky in the warm sector through the
weekend. Several weather systems will move north of Kentucky,
keeping the bulk of precip potential away from the CWA. However, our
location in the warm sector will keep generally S to SW flow in
place across the JKL CWA, allowing for warm and moist air to pump
into the region. Temperatures will modify warmer each day, with mid
and upper 80s forecast for highs Friday through Sunday. Afternoon
heating will lead to some instability and the potential for isolated
or scattered showers Friday afternoon, though storm potential should
remain on the leeward side of the Appalachians away from our CWA.
By Sunday into Monday, the zonal flow will begin to break down and
allow for some height falls across the CWA. In turn, a frontal
boundary located just north of the Ohio River (oriented WSW to ENE)
will begin to propagate farther southward, impacting much of
Kentucky Sunday night into Monday as it becomes stalled. This will
provide us our next epicenter for more widespread shower and
thunderstorm chances both Sunday and Monday. Thunderstorm potential
will be best during the afternoon and evening with peak heating. The
increase in cloud cover will also limit temperatures on Monday, with
highs in the low 80s forecast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 820 PM EDT TUE MAY 8 2018
Some diurnally driven cu and lingering ac remain at this time,
with VFR observed across the area. Winds are generally light and
should remain so tonight. VFR conditions area expected to continue
at the TAF sites. However, the deeper river valleys where MVFR or
lower fog is likely to develop between 6Z and 9Z and dissipate by
13Z. The nocturnal inversion should dissipate by 15Z with
sustained winds picking up from the southwest at generally 5 to 10
KT.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...JP
SHORT TERM...GREIF
LONG TERM...JMW
AVIATION...GREIF/JP
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
811 PM CDT Tue May 8 2018
.UPDATE...
806 PM CDT
Only a few minor updates to the forecast this evening. With thick
cirrus already blanketing the area and expected to continue to
filter overhead through the night, made an upward adjustment of a
degree or two to min temps.
Regarding thunderstorm potential late tonight into Wednesday
morning, bumped up chances an hour earlier per late afternoon and
early evening high-res guidance. Start times for a one to
possibly two hour period of showers and thunderstorms should be
around 5am CDT for the western CWA, and around 7-8am CDT for the
Chicago metro. See the short term forecast for more details on
convective mode and strong/severe storm potential.
Kluber
&&
.SHORT TERM...
105 PM CDT
Through Wednesday...
Short term focus is on several rounds of thunderstorms late
tonight into early Wednesday, and then redevelopment Wednesday
afternoon. Details added focused on honing in on the more favored
times for thunderstorms by location.
Near term weather has been a continuation of the splendid spring
weather of late across the Great Lakes with plentiful sunshine and
temperatures around 80 with comfortable humidity readings. A lake
breeze has formed and will cap the warming lakeside areas to the
upper 60s. The signs of change are evident in the sky and on
satellite as higher clouds have continued to fill in from the
north and west head of a series of disturbances in the mean trough
across the central and northern Plains.
Tonight, warm air advection driven elevated showers and t-storms
are expected to blossom over Missouri and Iowa late this evening
in the vicinity of several shortwaves in the mean trough axis
upstream. As the low level jet strengthens, these will gradually
spread east into western IL after midnight and likely into our
western CWA prior to 12z. NAM and GFS and now the RAP are in good
agreement in showing strengthening shear profiles late tonight
into Wednesday morning in response to tightening height gradient
ahead of lead shortwave currently over central High Plains, and
drive an elevated instability axis and a modest to somewhat steep
lapse rate environment. MUCAPE of near 1000 J/kg per the RAP,
suggest thunderstorms with some marginally severe hail are still
possible very late tonight into early Wednesday morning and
storms move across the CWA. This convectively driven wave will
likely spread across the Chicago area in the morning, so while the
severe threat is lower, thunderstorms are likely to spread
northeastward embedded in the wave of showers.
The most likely period for a break in showers and storms will be
mid morning into the early afternoon in wake of this first wave.
Both NAM and GFS do show decent atmospheric recovery will take
place on the advection of moisture on continued southwesterly
winds, though the degree and northward extent is still a bit in
question. The weather story issued earlier today is fairly well in
line with the updated SWODY2 which brings the slight risk along
the I-57 and eastward corridor, It is this corridor that the suite
of convective allowing models initiate convection ahead of the
approaching surface trough where the highest likelihood of a moist
and unstable airmass will be. A marginal risk will continue
farther west given the uncertainty in recovery farther northwest
before the surface trough comes through, and due to the fact that
some CAMs do initiate more robust convection (briefly) farther
west over the Chicago metro area. Damaging winds are the main
driver for the Slight risk given forecast shear profiles favoring
a multicell mode, though a marginal hail and tornado risk will
exist as outlined in SWODY2.
KMD
&&
.LONG TERM...
259 PM CDT
Wednesday night through Tuesday...
The main weather concerns during the period will be temperatures
along with the chances and timing of thunderstorms across the
region, particularly Thursday night through Saturday night as a
quasi-stationary frontal boundary sets up near the area.
Thursday looks to be a nice day across the area in the wake of
Wednesdays active weather. However, this looks to be a short
break in the weather, as an upper trough begins to dig over the
northwestern CONUS Thursday night into Friday. Overall, this will
induce down stream upper-level height rises and increasing warm
air advection across the central CONUS into Friday. Meanwhile, the
surface boundary is only gradually expected to shift northward
into Central IL Friday, before possibly shifting towards the I-80
corridor on Saturday. The favored area for periods of showers and
storms will generally be on the cool side of this boundary, as the
warm sector looks to remain capped. Therefore, the exact placement
of this boundary will be important in determining where the
heaviest rainfall will occur. Given that the outflow from the
convection itself could lead to a farther south position of the
front then guidance currently suggests, just could mean that
portions of northern IL or southern Wisconsin ends up in the
strike zone for a few periods of showers and thunderstorms through
Saturday night.
At some point on Sunday it appears the surface frontal boundary
will be driven back to the south as high pressure builds over the
Great Lakes. This should bring an end to the threat for storms
over the area into early next week. After a couple of quiet and
pleasant days early next week, it then appears that the weather
pattern may turn active again by the middle of next week.
KJB
&&
.AVIATION...
For the 00Z TAFs...
The aviation forecast concerns for the Chicago airports into
Wednesday are:
- Two windows of thunder likelihood - the one with the higher
confidence being in the early morning, and the other mid-late
afternoon
- Gusty south-southeast winds Wednesday morning turning southwest
Wednesday afternoon
- Possibility of MVFR ceilings Wednesday morning
After a quiet evening locally, thunderstorms are anticipated to
increase across the Mississippi Valley region early overnight and
push east-northeast over the airports early Wednesday morning. The
thunderstorm activity may not be too wide, thus only two hour
TEMPOs for ORD and MDW, but some shower activity and possibly
thunder may linger into mid/late morning. Confidence in this first
round timing is medium-high.
These storms are not anticipated to have much effect on the
surface winds, though cannot rule out some convectively-induced
gusts. South-southwest wind speeds at 1500-3000 ft will be 40-45
kt with the low-level jet in the early morning, possibly creating
brief LLWS depending on surface conditions. The surface winds
will turn more south-southwest, and the confidence in that being
during midday/early afternoon is medium.
While MVFR ceilings are probable in the wake of the storms,
especially over northern airports, the potential for IFR looks low
for the Chicago airports.
Clouds will initially limit destabilization into Wednesday
afternoon and as such early afternoon is not expected to have
much for showers or storms. Even partial thinning of these clouds
though will likely create enough instability for redevelopment of
storms, and that is expected, especially from ORD to BMI and
eastward during the mid-late afternoon. Thunderstorms may only be
isolated/scattered in coverage near the airports and that is why
have maintained a VCTS for ORD and MDW at this time.
MTF
&&
.MARINE...
313 PM CDT
An area of low pressure will shift from the northern Plains over
Lake Michigan by Thursday evening. This will result in some
stronger Southerly winds (15 to 25 kt) on Wednesday followed by a
cold frontal passage and a period of northwest winds for Wednesday
night and Thursday. Also expect showers and thunderstorms to
impact the lake late Wednesday into Wednesday evening with the
approach of this low.
Another area of low pressure is forecast to take shape over the
central Plains on Thursday. As this occurs, the winds over the
lake will trend towards an easterly direction and increase into
Saturday. This will likely set up waves supporting small craft
advisory conditions along at least portions of the western and
southern near shores of Lake Michigan this weekend.
KJB
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory...LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-
LMZ745...9 AM Wednesday to 7 PM Wednesday.
&&
$$
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Area Forecast Discussion
National Weather Service Blacksburg VA
918 PM EDT Tue May 8 2018
.SYNOPSIS...
High pressure will be in control through Thursday before a
front passes through the region. After the front passes through
ridging over the area will bring warmer and humid conditions to
the area for the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
As of 918 PM EDT Tuesday...
High pressure will control our weather tonight into Wednesday.
Diurnal showers have ended for our forecast area this evening
with the loss of heating. Removed mention of convection from ISC
grids tonight. This evening 00z RNK raob captured the light
easterly winds from the surface up to around 3000 ft. The
combination of low level moisture and light winds will result in
patchy fog overnight into Wednesday morning. Adjusted
temperatures with the latest surface observations, their trends
and leaned toward GLAMP for overnight. Lowered low temperatures
a few degrees overnight.
As of 730 PM EDT Tuesday...
Made a quick update to adjust temperatures and cloud cover
tonight. Modified temperatures with latest surface observation
and their trends for this evening. Showers are diminishing
with the loss of heating. Thus decreased pops for this evening
into tonight. Shaped cloud cover and weather overnight to
capture river valley fog late tonight into Wednesday morning.
More changes later this evening.
As of 315 PM EDT Tuesday...
A weak 500mb low centered over the region per the 12Z analysis is
forecast to slowly move east of the region during the forecast
period. At the surface, high pressure to the north is providing a
weak, generally easterly flow. This flow is clearly visible on
METSAT where a cu field and some isolated showers are popping up
along the ridges. The past few runs of the HRRR suggest the best
chances for precip this afternoon exist mainly around the Alleghany
Highlands, but smaller chances throughout the mountains, mainly east
of I-77. Chances for showers and increased cloud cover will drop off
significantly after sunset with loss of diurnal heating. Expect
skies should be mostly clear by around midnight allowing for ample
cooling and a decent chance for fog, particularly in the valleys.
Wednesday will be similar to Tuesday as we will be in between
systems. Surface high pressure will remain the dominant player
allowing the air mass to modify a bit for slightly warmer and drier
conditions than the previous day. Chances for some afternoon showers
in the mountains will again exist, with latest GFS and Conshort
guidance indicating that the best chances will be in northwest NC
into the New River Valley.
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 315 PM EDT Tuesday...
The upper pattern will become progressive through the latter portion of
the workweek as a trof digs over the western US and we get into some
low amplitude flow in the east.
One low will move through the Great Lakes and push a trailing cold
front through the Appalachians and central mid Atlantic region on
Thursday. The best dynamics will slide by to our north but there will
be ample instability and some shear present to favor something more
that garden variety convection, but parameters do not support
widespread severe weather. The current marginal risk advertised by SPC
looks good to cover the situation and will monitor later model runs to
see how the situation evolves. A warm front will then move through on
Friday with some scattered showers/thunder possible, with perhaps some
better coverage west of the Blue Ridge due to orographic forcing.
With no significant push of cooler air behind the front on Thursday,
expect temperatures to remain above normal through the period with
highs generally in the low to mid 80s east of the Ridge, and mid/upper
70s to the west.
&&
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 315 PM EDT Tuesday...
Summer-like pattern with a flat upper ridge in the east and a Bermuda
high off the coast will bring warm and humid conditions to the region
this weekend with an isolated shower/storm in the mountains. However a
frontal boundary will sink into the region from the north later on
Sunday, then wash out just to our south. This will bring a better
chance for showers/thunderstorms to the region into the first part of
next week. Temperatures will remain above normal this weekend, though
the increase in clouds associated with the frontal boundary will bring
a moderating trend closer to seasonal norms early next week.
&&
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
As of 744 PM EDT Tuesday...
Patchy fog and isolated convection will hinder aviation
operations tonight into Wednesday.
Isolated showers in the mountains will diminish during the next
couple of hours with the loss of solar heating. Reduced
visibilities may be possible in these storms but otherwise, VFR
conditions should prevail this evening into tonight.
After sunset, skies will clear out and temperatures will be
cool, setting up a situation for some patchy fog. The best
chance for fog will be in the mountain valleys where the
greatest radiational cooling will occur.
Morning low clouds and fog will lift by mid morning. Drier air
as winds turn more southerly and the weak wedge breaks down
should allow for improvement to VFR on Wednesday.
Winds during the forecast time frame will be mostly variable,
favoring an easterly component tonight and southerly component
Wednesday.
High confidence in ceilings, visibilities and winds during the
taf period.
.Extended Aviation Discussion...
VFR conditions will continue Wednesday night. Warm front
brings another round of showers Thursday, followed by a cold
front into Friday, though best threat of sub-VFR could be
Thursday, with overall VFR for the weekend as high pressure
aloft strengthens over the region.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...None.
NC...None.
WV...None.
&&
$$
SYNOPSIS...JR
NEAR TERM...JR/KK
SHORT TERM...MBS
LONG TERM...MBS
AVIATION...KK