Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/18/17
Area Forecast Discussion
National Weather Service Columbia SC
815 PM EDT Wed May 17 2017
.SYNOPSIS...
High pressure will maintain dry weather and above normal
temperatures through the remainder of the work week. Shower and
thunderstorm chances will increase by late in the weekend as
moisture increases ahead of an approaching cold front. The front
should move across the area early next week, with unsettled
conditions continuing.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
An upper level ridge will remain over the area tonight. Low
level southeast/southerly flow combined with 20 to 30 knot low
level jet will result once again in the development of low
clouds toward morning. Some patchy fog is also possible, but
with low level jet think main concern will be the development of
stratus. Would not be surprised to see some fog at the usual
places such as AGS/OGB and in low lying areas such as river
valleys. Low temperatures will generally be close to last
night`s with most areas cooling into the middle 60s.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Upper level ridging will continue to extend across the eastern Gulf
of Mexico and the western Atlantic, as Bermuda high pressure remains
firmly in place at the surface. Subsidence and limited moisture will
result in rain-free conditions and temperatures will remain above
normal with highs in the upper 80s to lower 90s and morning lows in
the 60s.
Early morning fog/low clouds will be possible both Thursday and
Friday given increasing low level moisture.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A weak backdoor cold front will be positioned north of the area
appears to drop southward into the area during the day Saturday.
Weak convergence in vicinity of the front could support some
isolated showers, mainly across the northern/eastern Midlands
Saturday into Saturday night.
An upper level ridge over the southeastern states will shift
eastward on Sunday as an upper trough moves across the Mississippi
Valley. Southerly flow will return ahead of an approaching cold
front, and along with it a significant increase in moisture. There
is a good chance of showers and thunderstorms during the day Sunday
as a result, with the greatest coverage across the CSRA.
The deep layered moisture will remain in place Monday into
Monday night as the upper trough axis and associated cold front
at the surface move through. Showers and thunderstorms are
likely across the area during this time.
Varying model solutions on Tuesday into Wednesday give some
uncertainty with respect to how much, if any, improvement will
occur. The GFS indicated dry weather with high pressure briefly
building across the area while the ECMWF holds the front along with
a chance of showers and thunderstorms across the area into
Wednesday. Given model differences, have continued a chance for
convection both days.
Temperatures will remain above normal into the start of the weekend,
then moderate closer to normal for early next week.
&&
.AVIATION /00Z THURSDAY THROUGH MONDAY/...
High confidence in VFR conditions through 06z then possible
restrictions with stratus during the predawn hours through mid
morning.
Upper ridge remains over the area with surface high pressure
ridging in from the western Atlantic. Persistent southeasterly
flow around the surface ridge will continue to funnel low level
moisture into the region. Bufkit model time heights showing a 30
knot low level jet overnight with forecast soundings indicating
stratus redevelopment possible. Hi-res models like HRRR not
really showing much stratus in our area but rather focusing it
up in the Upstate leading to some lower confidence. Will include
a mention of IFR stratus in tempo groups during the 10z-14z time
frame. With the strong low level jet am not as confident in
visibility restrictions.
Southeast winds this evening 5 to 10 knots will persist through
the overnight then diminish during the predawn hours before
picking back up from the south by 15z around 7 to 9 knots.
EXTENDED AVIATION OUTLOOK...Low-level moisture associated with the
southerly flow on the backside of offshore high pressure plus
nocturnal cooling may help support stratus and fog during the early
morning hours each day. Flight restrictions will be possible in
scattered convection late in the weekend.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service Grand Rapids MI
940 PM EDT Wed May 17 2017
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 329 PM EDT Wed May 17 2017
The unseasonably warm temperatures are about to come to an end as
a strong cold front comes through the area during the afternoon
hours of Thursday. Till then scattered showers and thunderstorms
will be around the area. Lows tonight will be in the 60s, which is
nearly 20 degrees above normal The afternoon high Thursday will
be near 80 inland. Once the cold front comes through though it
will be much cooler. Lows Friday morning will be in the upper 30s
to mid 40s. Highs on Friday will struggle to make 60 degrees. It
will be windy this evening and again during the day Thursday.
The next threat for thunderstorms will be Saturday night into
Sunday. This storm will bring widespread rain across the area.
Beyond that we will have more spring like temperature than normal
temperatures with some scattered light rain showers from time to
time through at least Wednesday.
&&
.UPDATE...
Issued at 940 PM EDT Wed May 17 2017
It remains quiet in sw lwr MI this evening with a dry air mass in
place and little to no instability. The main item of interest is
the 60 knot low level jet spreading into the region from the
southwest over the next few hours.
Synoptic scale sfc gusts tonight should remain under advisory
criteria due to limited mixing after dark, but some ocnl/brief
gust to 40 mph will be possible. It`s possible we`ll need an
advisory however on Thursday, mainly southeast of GRR, once
deeper mixing develops by mid morning.
Latest RAP guidance shows about 500 j/kg of elevated cape coming
in toward midnight and even some sfc based cape after 06z. However
fcst soundings have a bit of a cap and stay rather dry through
the night. That said, if any convection were to move into the area
or develop, some strong wind gusts would be possible given how
strong the low level jet is.
The severe cell earlier west of MKE dissipated quickly as it moved
northeast. We`ll keep an eye on the bow echo currently approaching
Madison WI. Whatever is left of that line extrapolates into
Ludington and Muskegon toward 1 am and could bring some strong
gusts if it holds together. Suspect it will weaken considerably
before it gets here.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 329 PM EDT Wed May 17 2017
The primary question for tonight into Thursday is the risk for
thunderstorms. It will be windy this evening but not enough
widespread wind gusts over 40 mph to issue an advisory. The winds
will diminish by mid evening.
There is an upper low going negative tilt this evening as it
tracks northeast across Iowa to the western Upper Peninsula by
mid morning Thursday. Most of the strong mid level dynamics stay
west of Lake Michigan which means a significant mid level dry
layer making it hard to get any organized convection to reach
Southwest Michigan even with the strong cold front Thursday.
We have significant instability moving into the area this evening
and overnight but instability is elevated and we an elevated
mixed layer of very dry air between 750 mb over 300 mb (from
subsidence due to us being just a touch to far east of the strong
mid level dynamics) . This will make it hard for any organized
convection to impact the area tonight or Thursday. Even so, we
have a 50 to 70 knot low level jet crossing the area between 9 pm
and 2 am on a track from Benton Harbor to Alma. The other problem
is we do not have a good coupling of the upper jet lift area over
the low level convergence area tonight or Thursday. Still we do
have a strong cold front coming through the area and there will be
good surface convergence along the cold front Thursday. So I up
chance pops and will call that good.
Beyond that much cooler air moves in Thursday night into Saturday
as Canadian High pressure builds in behind the front. This air is
unseasonably chilly and that will mean highs will be at least 25
degrees cooler Friday than today. It would not be out of the
question to see patchy frost Friday morning over our northeast
CWA. I do believe the air will be dry enough that we will see some
sunshine on Friday too.
.LONG TERM...(Saturday through Wednesday)
Issued at 329 PM EDT Wed May 17 2017
Main upper low over the Central Rockies today will pivot into the
plains states later this week and move through the Great Lakes this
weekend. This system is the main feature in the long term. The
associated surface low will move through the Western Great Lakes
from Saturday into Sunday. The weekend looks to be wet as a good
surge of moisture moves into the region. PWAT values reach the 1.5
inch range which is fairly high for this time of year. CAPE values
are not overly impressive so have rain showers with a chance of
thunderstorms wording. Do not think we are looking at widespread
storms, but definitely widespread rain showers. Best chance for
precipitation will be from Saturday afternoon into Sunday morning.
Upper troughing will linger across the Great Lakes into the first
have of next week. Scattered showers look likely in a return to more
spring like weather.
High temperatures around 70 this weekend will cool slightly back
into the 60s for early next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 755 PM EDT Wed May 17 2017
The primary aviation focus over the next 24 hours continues to be
the winds as a southwesterly low level jet ahead of an
approaching cold front impacts the area.
Have included LLWS in the TAFs for much of the night since the
sfc winds will probably diminish a bit after sunset while winds at
2000 ft will be 45-50 kts.
Sfc winds will increase and become gusty again toward morning as
the cold front gets closer, and sfc gusts on Thursday could
exceed 35 kts, especially south and east of GRR.
Guidance and upstream trends suggest our thunder threat is
probably too low to put in the TAFs at this time, but will AMD if
that changes. Will keep VFR conditions going.
&&
.MARINE...
Issued at 329 PM EDT Wed May 17 2017
I will maintain the small craft advisory through Friday night but
it will likely have to be extended into at least Sunday as the
next storm moves through the area.
&&
.HYDROLOGY...
Issued at 1241 PM EDT Wed May 17 2017
Streamflow is currently normal for most sites. Although a few
storms may move through the region through Thursday, they won`t be
widespread enough to impact the main basins. Still looking at
basin average rainfall amounts this weekend of 0.50"-1.00". Can`t
rule out some locally higher amounts. That shouldn`t be enough
rain to cause more than some within bank rises, though above bank
rises can`t be ruled out. Additional rainfall is possible by the
early and middle portions of next week.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 6 AM EDT Friday for LMZ844>849.
&&
$$
UPDATE...Meade
SYNOPSIS...WDM
SHORT TERM...WDM
LONG TERM...Duke
AVIATION...Meade
HYDROLOGY...Hoving
MARINE...WDM
Area Forecast Discussion
National Weather Service Wilmington OH
958 PM EDT Wed May 17 2017
.SYNOPSIS...
The chance of showers and thunderstorms will return to the area
late tonight through Thursday as moisture increases ahead of a
cold front. The front will then sag southwards through the area
Friday morning allowing the chance of showers and thunderstorms
to continue. The front will then lift back north on Saturday
only to be followed by a stronger cold front moving in from the
west on Sunday.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Skies will stay mostly clear early tonight as high pressure
recedes slowly east. After midnight, clouds will thicken and a
few showers may develop in far western locations in moisture
convergence ahead of a cold front approaching from the
northwest. Southerly winds have subsided to around 10 knots.
The persistent low level flow of warm air will allow overnight
lows to be in the upper 60s.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...
Thursday morning the mid-level ridge axis will be pushed east
with heights falling across the region. Looking at the Ensemble
Situational Awareness table shows high PWATs and increased
moisture transport around the subtropical ridge and across the
central zones of the CWA. As this happens weak showers and
thunderstorms will move across just north of Interstate 71 in
the morning. Looking at the latest RAP there is a weak
shortwave moving across at this time and with more than
sufficient instability have kept chance PoPs in the forecast.
Later in the morning there should be brief break in
precipitation until the afternoon when high res models show pop
up showers and thunderstorms forming. PWATs on both the NAM and
GFS rise to around 1.50" Thursday with CAPE values increasing
in the afternoon. Both the NAM and GFS have an instability axis
across the central zones with the GFS slightly further north
with the higher instability values. NAM instability values are
much more robust than the GFS but think this is overdone. For
now have kept chance PoPs Thursday afternoon across the area
with higher values near Interstate 71.
Thursday evening a surface cold front will push south into the
area as the upper level low that was over Wisconsin merges into
a much bigger upper level low located over Quebec. The NAM,
GFS, and ECMWF all have the front across the northern zones
around 6z Friday and stalling north of Interstate 70 Friday
morning. Accompanying the cold front will be a weakening line of
thunderstorms. This isn`t surprising as instability will also
be waning during the evening.
&&
.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Active weather pattern through the long term forecast period.
East-west oriented front will remain stalled near the Ohio River
Friday. Will keep chance pops with best chance across the southern
counties. Highs on Friday will be a little cooler, ranging from the
the lower 70s north to the lower 80s south.
Mid level shortwave and associated surface wave of low pressure to
eject northeast into the Great Lakes Saturday. Associated warm front
to lift north across the region Saturday/Saturday night. This will
keep a continued threat of showers and thunderstorms with the best
chance west. Temperatures will warm with highs from 80 to 85.
As surface wave tracks across the Great Lakes associated cold front
to push east across the region Sunday/Sunday night. This will bring
an enhanced chance for thunderstorms. Have continued likely pops
for this period. With clouds and precipitation, temperatures will be
a little cooler, with Sundays highs ranging from the upper 70s
northwest to the lower 80s southeast.
A lingering chance of precipitation Monday across the east counties.
Cooler temperatures expected Monday with highs a little below
normal, ranging from near 70 northwest to the lower 70s southeast.
Surface high pressure to provide temporary dry period later Monday
and Monday night. Model solutions diverge on timing and amplitude
of developing mid level trof for Tuesday and Wednesday. This results
in placement and timing differences, therefore uncertainty
increases. Have chance pops west developing Tuesday afternoon and
across the region Wednesday. Highs Tuesday will be close to normal
with and generally 70 to 75, and then a little cooler Wednesday
from the upper 60s to lower 70s.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Conditions are likely to remain VFR as a weak cold front
approaches from the northwest. Under a veil of cirrus, surface
winds will decrease to around 10 knots this evening. However,
strong winds just off the surface warrant Wind Shear for the
overnight period.
A few showers may develop in the vicinity of TAF sites Thursday
morning in increasing moisture and convergence well ahead of
the front. Thunderstorms may occur in the vicinity of DAY ILN
LCK and CMH Thursday afternoon as the front moves toward an
unstable regime. Kept ceilings VFR since models suggest isolated
convection.
Winds from the southwest will gust over 20 knots Thursday
afternoon in the tight pressure gradient ahead of the front.
OUTLOOK...Thunderstorms possible Friday through Sunday.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...None.
KY...None.
IN...None.
&&
$$
SYNOPSIS...Haines
NEAR TERM...Coniglio
SHORT TERM...Haines
LONG TERM...AR
AVIATION...Coniglio
Area Forecast Discussion
National Weather Service Indianapolis IN
1158 PM EDT Wed May 17 2017
.UPDATE...
The AVIATION Section has been updated below.
&&
.SYNOPSIS...
Issued at 215 PM EDT Wed May 17 2017
A cold front is forecast to slowly move toward Indiana from the
northwest and arrive here Friday. Saturday it should turn into a
warm front and shift back north of the Hoosier State.
Another cold front is expected to cross our state Sunday. It will be
followed by high pressure Monday. Additional cold front passages are
predicted Tuesday and Wednesday.
&&
.NEAR TERM /Overnight/...
Issued at 944 PM EDT Wed May 17 2017
Surface analysis this evening shows high pressure in place over
the Carolina and Low pressure over Iowa. Indiana was firmly
entrenched within warm southwest flow in place between these two
systems. Radar shows some virga and a few isolated showers near
Bloomington and Bedford. Water vapor shows the real story. Strong
dry slot intruding into the system...spreading into Indiana. This
will quickly push any short wave energy east of Indiana for the
overnight period. With no heating and dry air arriving
aloft...rain chances overnight appear to be dwindling...and HRRR
looks overdone. Thus have trended toward a drier forecast
overnight...except for the first few hours across the south and
east as bit of the short wave energy will surge across that area
over the next 1-3 hours.
Indiana remains in the warm sector overnight with good mixing
expected. Trended toward persistence for lows.
&&
.SHORT TERM (Thursday night through Saturday)...
Issued at 215 PM EDT Wed May 17 2017
There is a lot of uncertainty about rain chances.
There is good model agreement showers and thunderstorms will occur
eventually, but poor agreement about when. Precipitation seems more
likely Friday and again Saturday than at other times, but some
chance is needed through the period.
With the persistent chance of rainfall, skies should be mostly
cloudy.
Given the uncertainty about rain, there is also uncertainty about
temperatures. Consensus should reduce errors, but they could still
be 2-4 degrees.
&&
.LONG TERM /Saturday night through Wednesday/...
Issued at 215 PM EDT Wed May 17 2017
Longer range models in pretty good agreement and blended solution
indicates upper trough in Rockies will drop into the Plains by
Friday then lift north of the Great Lakes by Sunday. This will
sweep a cold front across Indiana Sunday with precipitation near
the front. Morning timing of front at more stable time of day
suggests perhaps just isolated storms.
High pressure will build in and clear out skies Sunday night into
Monday. Another upper trough will drop down the front side of
ridge building out west and into the rear of the east canadian
upper trough on late Tuesday into Wednesday. This will renew the
threat for showers and some isolated storms late Tuesday into
Wednesday.
Temperatures will not be quite as warm...but still close to
normal during this period and a blended solution appears
reasonable.
&&
.AVIATION /Discussion for the 180600Z Tafs/...
Issued at 1159 PM EDT Wed May 17 2017
VFR Conditions expected. Brief MVFR conditions will be possible
with any storm that may strike a TAf site on THursday afternoon.
Water Vapor Imagery shows dry air working into Indiana. Lingering
convection dissipating and exiting to the east. Storms were
continuing over Northern Illinois...however HRRR Trends should
keep that activity northwest of the taf sites given the
progressive SW flow in place. Thus have removed any VCSH/VCTS
mentions during the overnight hours. Strong pressure gradient
across the area overnight will continue to provide possible llws.
Forecast soundings on Thursday suggest attainable convective
tempertures along with lower level cyclonic flow. Thus scattered
convection will be possible mainly during the peak heating
hours...but confidence for precise timing is low. Any TSRA/SHRA
that does develop on Thursday afternoon may produce brief MVFR
Conditions should it strike a TAF site.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...JK
NEAR TERM...Puma
SHORT TERM...JK
LONG TERM....Tucek
AVIATION...JP
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
947 PM CDT Wed May 17 2017
.MESOSCALE DISCUSSION...
945 PM CDT
The broken line of storms across northwest Illinois moving into
north central Illinois has shown a slight weakening over the past
hour, however, continued scattered stronger cores and punches of
wind continue via the DVN radar. The lack of a well-organized
QLCS per recent trends should help to keep the severe wind threat
scattered, with more of a widespread 40-50 mph gusts per
observations in northwest Illinois. Continue to monitor transient
low-level rotation in supercells and LCLs/LFCs have lowered per
RAP analysis and observations. With gusty southerly winds
continuing to indicate a mixed boundary and potentially effective
stout low-level shear, the isolated tornado threat does continue
in the watch area. Will monitor if any brief expansion/extension
to the watch is needed beyond 11 pm into McHenry and Kane
Counties.
MTF
&&
.SHORT TERM...
241 PM CDT
Through Thursday...
A deep low lifting across the mid-Missouri Valley this afternoon
is resulting in very windy and unsettled weather across portions
of the midwest. Main forecast challenge in the near term will be
dealing with thunderstorm chances and timing later this afternoon
and evening. Early this afternoon, water vapor imagery reveals an
upper low rotating over northeastern KS while a lead wave is
lifting across far NE MO and SE IA. Mid level echoes are noted on
radar across portions of west central Illinois in advance of this
lead disturbance and think this should be the area to keep an eye
on for any isolated to widely scattered thunderstorm development.
Special 18Z raob from DVN shows moderately strong instability is
in place but still capped, and warmer 700mb temps farther east of
around 9- 10C will be hard to overcome late this afternoon. Still
several convective allowing models indicate some thunderstorms may
be able to overcome the cap this afternoon and strong deep layer
shear of 40- 50kt will support a threat for strong to severe
thunderstorms, including discrete supercells. Veered surface flow
and high LCLs will be limiting factors as far as any tornado
threat is concerned this afternoon, but large hail and damaging
winds remain a concern.
Main upper low is progged to lift into SW WI mid to late this
evening with the mid level thermal ridge getting shunted farther
east helping to weaken convective inhibition. Corridor of better
forcing is expected to be primarily over WI but do expect some
broad ascent over northern Illinois which will result in a
second window of potential thunderstorms this evening, primarily
north of a Peru to Chicago line. Lower LCL heights will be less of
a limiting factor for tornadoes this evening and modest pressure
falls over the area may help to back surface flow. Strong low
level helicity and high STP values are progged to be in place over
northern Illinois this evening and recent runs of the WRF and
experimental HRRR show swaths of higher updraft helicity
indicative of supercellular storms. Southern extent of the
convective activity remains a big question mark this evening, but
any thunderstorms will need to be closely watched with an overall
decent setup for severe thunderstorms.
Low pressure will move east across the Great Lakes on Thursday
with a trailing cold front settling south across the local CWA.
Lack of any upper level support with broad mid level height rises
behind the departing upper wave and only modest low level ascent
in association with convergence along the cold front will be
limiting factors on thunderstorm development tomorrow. That said,
moderately strong instability is once again expected to develop
ahead of the front tomorrow afternoon with a much weaker cap in
place. Deep layer shear will be marginal, but strong enough to
support a severe weather threat for any thunderstorms that are
able to form. Temperatures out ahead of the front will warm into
the low to mid 80s once again while farther north temperatures
will top out in the 70s.
Deubelbeiss
&&
.LONG TERM...
226 PM CDT
Thursday night through Wednesday...
For the longer term forecast period, main concern will be shra/tsra
timing and coverage associated with the next the series of Northwest
Pacific coast systems to impact the region.
Little change to the current forecast for the Thursday night through
Friday night with Friday being a relatively cool day following the
passage of a cold front Thursday night. There may be a few
lingering showers Thursday night following the fropa, but expect the
night to generally be dry. PoPs will be in the increase again
during the day on Friday as the system begins to lift newd out of
the south high plains. By Friday morning, the main sfc low should
be over wrn Kansas with an associated warm front extending east
through srn Missouri and into the Ohio Valley. There is some
complication to the timing of the system lifting out of the south
high plains as a srn stream shortwave interacts with the Pacific-
origin system, leading to more stationary deepening of the sfc low,
and delaying the system ejecting newd. There is a fair amount of
model spread with the finer scale details of this system, so
confidence in timing of onset of pcpn is only moderate at best.
Confidence is relatively high in coverage and the potential for
shra/tsra, it is just lower for timing. The general trend is for
the sfc low to lift northeast into the upper Mississippi Valley by
Saturday evening, with the warm front lifting north across the area
at some point during the day. So, in addition to increasing PoPs
through the day, temperatures should also be on an upward trend
following the relatively cool Friday. If the warm front can lift
north of the CWA early enough in the day, temperatures should have
no problem rebounding back into the upper 70s to lower 80s. The
main point of concern for temps on Saturday will be along the nern
Illinois lakefront, where there is a chance for sely winds to bring
some cooler lake cooled air inland, and temps from downtown Chicago
and to the north may only reach into the 60s. However, even with
some differences in the finer scale details in the forecast for this
system, the general trend remains consistent, with periods of
showers and thunderstorms likely for early Saturday morning through
late Saturday night and possibly lingering into early Sunday morning.
For the remainder of Sunday and into mid week, the ECMWF and GFS are
relatively consistent in the trends for the larger scale pattern,
with the old upper low tracking north of the Great Lakes and a nrn
stream shortwave dropping into the nrn plains. The evolution of the
long wave pattern looks to be slowly progressive with broad, flat
ridging over the middle/lower Mississippi Valley/Ohio Valley as the
nrn stream system slowly drops into the upper Mississippi Valley by
Tuesday. The longer range guidance also suggests that more of a
split flow pattern may develop with weak srn stream energy lifting
out of the srn plains and phasing with the nrn stream shortwave over
the midwest. The ECMWF is trending much stronger with the srn
stream system and phasing while the GFS shows little, if any of the
srn stream energy and lack the deepening phased system over the
midwest by midweek. So, will carry at least chance PoPs for Tuesday
and Wednesday since the nrn stream system alone would justify carry
some pcpn mention. Should there be phasing to the extent indicated
by the ECMWF, more widespread and longer duration for shra/tsra
would be likely.
&&
.AVIATION...
For the 00Z TAFs...
Strong south winds will begin to dissipate this evening with gusts
below 30 kt expected after 01Z-02Z. While thunderstorms are
struggling to form given the strong cap, the cap will continue to
deteriorate allowing for thunderstorms to move through this
evening. Strong and isolated severe thunderstorms are expected
with the best chance near RFD. Have high confidence in
thunderstorms impacting all of the terminals this evening, but
medium confidence in timing and how many rounds of thunderstorms
there will be.
VFR conditions are expected behind the storms overnight into
Thursday morning and southwest winds will gust to 20-25 kt. Some
guidance members suggest that low end VFR/high end MVFR cigs are
psbl at RFD Thursday morning, but did not have enough confidence
to include MVFR in the TAF. Winds veer to northwest by late
Thursday afternoon, and then become northeast in the evening.
JEE
&&
.MARINE...
230 PM CDT
Main marine forecast concerns include a period of gusty south
winds tonight into early Thursday, shifting north on Thursday and
persisting through Friday. South gales remain possible over the IL
and IN nearshore waters into early this evening.
Low pressure is deepening over the central plains and will slowly
lift northeast to the Upper Mississippi Valley by this evening,
then move across the northern Lakes Thursday while trailing a cold
front pushes down the lake and eventually moves south of the lake
by Thursday evening. A broad area of gusty south winds will occur
across the lake tonight as the low lifts northeast. While stable
conditions will likely limit winds to 30 kt or so over the open
waters, winds will likely gust lower end gales over the waters
immediately adjacent to land along southern Lake Michigan. Strong
south winds will ease late tonight and shift to northerly on
Thursday as the low and trailing cold front move through. North
winds will increase into the 25-30 kt range as a fairly strong
area of high pressure builds across southern Canada and into the
northern Great Lakes into the weekend. Another low will then lift
across the western Lakes and Upper Midwest on Sunday, lingering
just north of the Lakes across Ontario into early next week.
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...Wind Advisory...ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022-
ILZ023-ILZ032-ILZ033-ILZ039 until 10 PM Wednesday.
IN...Wind Advisory...INZ001-INZ002-INZ010-INZ011-INZ019 until 10 PM
Wednesday.
LM...Small Craft Advisory...nearshore waters
until 7 AM Friday.
&&
$$
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Area Forecast Discussion...UPDATED
National Weather Service Memphis TN
1024 PM CDT Wed May 17 2017
.UPDATE...
Scattered showers and strong thunderstorms north of the I-40
earlier this evening had decreased in coverage and intensity.
Isolated showers will continue over the same general region during
the overnight, rooted in an elevated layer associated with strong
low level warm advection. 02Z HRRR model suggest some storms may
form over central AR and lift into the northeast AR during the
overnight. Will continue to carry higher (chance) PoPs over
northeast AR. Forecast remained on track at mid/late evening.
PWB
&&
.PREV DISCUSSION... /issued 625 PM CDT Wed May 17 2017/
UPDATE...
Updated to add 00Z Aviation Discussion.
PREV DISCUSSION... /issued 335 PM CDT Wed May 17 2017/
DISCUSSION...
A potent upper level low pressure system continues to lift
northeast towards the Upper Mississippi River Valley this
afternoon. Slightly lower mid level heights continue to graze
western portions of the forecast area. This has combined with
increasing instability with SBCAPE values exceeding 2000 j/kg to
support scattered showers and thunderstorms. Scattered coverage
will continue into this evening before diminishing later tonight.
Very strong and gusty winds will continue across the western half
of this area through early this evening along with continued
blowing dust. Plan to keep the wind and blowing dust advisories in
place through their 6 PM CDT expiration time. Winds will gradually
diminish through the evening. Low temperatures will remain above
average, remaining around 70 degrees areawide. Low level southerly
flow should support some late night and early morning stratus
development as well.
The upper level ridge of the southeastern U.S. states will attempt
to rebuild northwestward on Thursday behind the departing upper
low. Very warm and humid conditions will continue over the region.
Building instability and low level moisture may support a few
isolated storms by Thursday afternoon, but coverage should remain
low with storms remaining disorganized. High temperatures on
Thursday should again reach into the middle and upper 80s with
lows Thursday night around 70 degrees.
By Thursday night and Friday, another upper level low pressure
system now over the Pacific Northwest will drop southeast into the
Four Corners region. Another shortwave will rotate around this
upper low across northwest portions of the Mid South late Thursday
night into Friday morning. This feature combined with lingering
instability will support a round of scattered showers and
thunderstorms. A supporting jet max could provide enough lift and
shear to support a strong to isolated severe storm with this
system across northwest sections of the region.
The upper low over the western states will gradually lift
northeast through the weekend. A series of shortwave troughs will
rotate around the low which will bring additional chances for
showers and thunderstorms over the weekend. The greatest coverage
should be on Sunday as the strongest shortwave progresses eastward
and helps to push a cold front across the region. Moderate
instability and weak shear may support a strong storm or two with
the passage of the cold front on Sunday. Overall the threat of
organized severe storms appears low at this time.
Model guidance diverges quite a bit by early next week with low
confidence in the extended forecast period. Generally maintained
lower end pops for early next week with general upper troughing
over the region. Temperatures should remain cooler as well through
the end of the extended forecast period.
JLH
&&
.AVIATION...
00Z TAFs
MVFR and perhaps IFR conditions may develop late tonight into
Thursday morning as low stratus develops across the Lower
Mississippi Valley. Otherwise, VFR conditions should prevail
through much of the period. VCTS possible at JBR through 02Z and
again Thursday afternoon. Left out VCTS at other sites as coverage
may not justify mention at this time. Gusty south winds will
diminish this evening to 7-10 kts and increase to 10-13 kts with
a few gusts up to around 20 kts on Thursday.
CJC
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
Area Forecast Discussion
National Weather Service Miami FL
803 PM EDT Wed May 17 2017
.AVIATION...Strong and gusty east flow continues with VCSH for
all east coast sites through period. KAPF, KFXE, KOPF, and KTMB
may diminish slightly to around 10kts after 04Z tonight. All sites
seeing winds pick up to 12-17kts with gusts 20-25kts after 14Z
tomorrow. May see occasional MVFR cigs, especially along east
coast, with cloud bands/SHRA, but overall cigs are expected to
remain VFR.
&&
.UPDATE...
Latest radar trends show activity diminishing over the interior.
Meanwhile, isolated light to moderate showers continue to advect
onshore from the Atlantic. Short term guidance indicate more
showers to continue through the night, especially over the east
coast metro. Therefore, in the update, upped PoPs to chance
category over this region though not expecting much in the way
accumulation. Stagnant surface high pressure near Bermuda is still
on track to bring breezy easterly winds, generally around 15 mph,
to the east coast tonight and through the day tomorrow.
&&
.PREV DISCUSSION... /issued 447 PM EDT Wed May 17 2017/
DISCUSSION...
Through tonight: Latest water vapor imagery shows upper level
ridging over the far eastern CONUS with the axis stretching from
New England southward towards the Atlantic. A respectable 1025 mb
surface high was observed a few hundred miles west of Bermuda.
This feature has been responsible for the brisk easterly flow
experienced today. Generally, easterly winds along the east coast
metro region have been recorded at 10 to 15 mph, with occasional
higher gusts. This flow pattern has also allowed for low level
moisture to advect westward from the Atlantic, producing
isolated showers over the peninsula. The breezy east winds appear
too strong for the Gulf sea breeze to develop. Therefore, any
appreciable surface convergence appears unlikely, diminishing the
chance of stronger convection. Short term models, including the
HRRR and WRF ARW decrease shower coverage over the interior with
the loss of diurnal heating. Tonight, a moist east flow pattern
will continue the spotty showers along the east coast metro.
Thursday though mid-next week: The synoptic weather pattern over
the next several days will remain rather stagnant. Both the GFS
and ECMWF prog the upper level high pressure ridge to dominate
the eastern CONUS and surface high pressure to remain anchored
near Bermuda. Thus, the breezy and moist east and east- southeast
flow will continue the chance of showers along the east coast
during the nights and early mornings, then a chance of showers
and slight chance of thunderstorms for the western interior and
Gulf Coast. Maximum temperatures are forecast a few degrees above
average, in the lower 90s for the eastern peninsula and upper 80s
further west along the the east coast metro. By early next week,
long range models are hinting a low pressure through to deepen
over the Southern CONUS. This would shift flow across the
peninsula to more of southerly direction, increasing atmospheric
moisture from the northern Carribean. If this scenario plays out,
expect an increase in overall shower and thunderstorm activity.
MARINE...Strengthening high pressure building near Bermuda will
lead to increasing east.southeast winds across the local waters
over the next several days. This had led to a small craft advisory
for the Atlantic and Biscayne Bay waters for this afternoon into
tonight. There is also a slight chance of showers over the local
waters of South Florida today into tonight. Shower and
thunderstorms activity will increase by early to mid-next week.
BEACH FORECAST...Breezy easterly flow will lead to a High Risk of
rip currents for the Atlantic beaches through at least the end of
the work week. &&
.PRELIMINARY POINT TEMPS/POPS...
West Palm Beach 80 88 79 88 / 20 30 40 40
Fort Lauderdale 79 87 79 87 / 20 30 40 40
Miami 79 88 79 88 / 20 30 30 40
Naples 73 92 74 92 / 10 30 20 40
&&
.MFL WATCHES/WARNINGS/ADVISORIES...
FL...High Rip Current Risk through Thursday evening for FLZ168-172-
173.
AM...Small Craft Advisory until 6 AM EDT Thursday for AMZ630-650-651-
670-671.
GM...None.
&&
UPDATE...27/JT
AVIATION...88/ALM
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
951 PM EDT Wed May 17 2017
.SYNOPSIS...
High pressure centered off the coast will extend into North
Carolina through Friday. A weak cold front will push south
through the area Saturday, with a stronger system moving
through early next week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 945 PM Wednesday...
With a 500 MB ridge axis sliding just to our east this evening,
some high clouds moving through the Mid Atlantic are moving our
way. The latest run of the HRRR has this handled well and I
increased clouds a bit through 06Z over the far west. A return
to a mainly clear sky is expected after that time. Winds have
already diminished and forecast sounding indicate some
potential for patchy stratus and/or light fog development. Min
temps from 64-67 inland to around 70 coast.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
As of 330 PM Wednesday...Offshore high/inland trough pattern
will continue with models indicating only slightly better
chances for CU/SCU development. Max temps around 90 inland to
80s coast. See Climate section for record highs.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
As of 4 PM Wed...A summer-like pattern continues through the
rest of this week with above normal temperatures and mostly dry
conditions, then better precip chances arrive early next week
with slightly more seasonable temps.
Thursday Night through Friday...Summer-like Bermuda high
pressure will persist off the southeast coast with an upper
ridge over the region, bringing large scale subsidence with very
warm and dry conditions. Low level thicknesses continue around
1415-1420m with highs in the upper 80s to around 90 inland and
low 80s along the coast. Overnight lows remain in the 60s.
Friday night through Sunday...The upper ridge breaks down
toward the end of the week as a shortwave trough pushes across
the mid- Atlantic states and the attendant trailing cold front
approaches from the north. 17/12Z model suite continues in good
agreement with the backdoor front sagging into the region by
early Sat and perhaps as far south as the NC/SC border late
Sat/Sat night before lifting back north Sun. Could see some
convection advect into the northern tier of the FA as perhaps
remnant weakening MCS activity from the Central Appalachians and
VA dives southeastward, but not expecting strong storms as
upper level support, instability, and shear will be limited.
Very small chances for a storm or shower continue on Sat across
the FA with the southward advancing front. Sunday the front will
lift back north as high pres sweeps off the Mid Atlantic coast,
though only expecting clouds with very slight chances for
showers with the warm front as moisture is limited. High temps
knocked down a few degrees with the passing front with values in
the low/mid 80s over the area, with pleasant 70s OBX. Lows in
the low/mid 60s interior with upr 60s coast.
Monday through Wednesday...A strong upper trough and sfc cold
front approaches from the west early next week. Latest global
model suite in fairly good agreement with timing of the front
moving through late Mon or early Tue. Shower/storm chances
increase through the day Monday, peaking second half of Monday
into Mon night. Enough clustering amongst ensemble members to
advertise pops as highs as 60 percent this time period. Much
more uncertainty beyond Monday with regards to precip chances,
though synoptic regime favors fairly active pattern with broad
scale troughing across eastern half of the CONUS with embedded
short waves keeping shower/storm chances in the fcst. Will
advertise only 30-40 percent pops attm due to large uncertainty
in timing these shortwaves. Temps just slightly above climo with
highs in the low/mid 80s and lows in the low/mid 60s.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Short Term /through 00Z Fri/...
As of 645 PM Wednesday...Fair weather VFR conditions will
persist through the evening, then some sub-VFR conditions
possible late tonight due to winds decoupling and saturation
below inversion. Forecast soundings indicate some potential for
more widespread stratus but most Hi- res models do not, thus
confidence remains low and will indicate with SCT004 for clouds
08Z-13Z and period of 5SM BR. Fair weather VFR again after 13Z
Thursday with some 15 kt SW wind gusts by afternoon.
Long Term /Thursday Night through Monday/...
As of 4 PM Wed...Pred VFR conditions expected through the period,
though patchy sub-VFR fog/stratus possible each morning. Weak
front drops through Sat with some sub VFR cigs possible. Better
chance for lower cigs/vsbys on Monday as stronger cold front
approaches and moves through by late Mon.
&&
.MARINE...
Short Term /through Thursday/...
As of 945 PM Wednesday...No big changes to the forecast. Winds
generally 10 to 15 with seas 2 to 3 feet. Where we currently
have some stronger winds (15-20) seas are closer to 4 feet at
Diamond and 3 feet offshore of Duck. A continued offshore
high/inland trough pattern will result in typical cyclical
pattern of stronger SW winds over waters during afternoon and
evening, then lighter late night and morning in response to
warmer inland temps. Strongest winds expected to be around 15 KT
with gusts to 20 KT.
Seas will vary with wind speeds with 2-3 feet during lighter
periods and 3-4 with higher speeds.
Long Term /Thursday Night through Monday/...
As of 4 PM Wed...SW winds 10-15 kt expected through Friday,
perhaps as strong as 15-20 kt during late afternoon and evening
hours as thermal gradients tighten with very warm conditions
inland. Seas continue generally 2-4 feet. A backdoor cold front
approaches Friday night and confidence is increasing that the
front will push through the waters Saturday, stalling near the
SC/NC border late Sat/Sat night before lifting back north
Sunday. Still some uncertainty with how strong the NE surge will
be behind the front, but winds increase to 15-20 kt with gusts
possibly 25 kt or higher and seas building to 3-6 feet, highest
north of Ocracoke. A period of low end SCA conditions will be
possible Sat into Sat eve. NE winds 5-15 kt Sunday, becoming
more SE late as front lifts back to the north. SW winds on
Monday inc to 10-20 kt ahead of a cold front approaching from
the west, with seas again nearing 6 feet by late in the day.
&&
.CLIMATE...
Record High Temps today (5/17)
LOCATION TEMP/YEAR
New Bern 92/1960 (KEWN ASOS)
Cape Hatteras 86/1991 (KHSE ASOS)
Morehead City 85/1991 (COOP)
Jacksonville 93/1990 (KNCA AWOS)
Greenville 95/1915 (COOP)
Kinston 96/1941 (COOP)
Record High Temps Thursday (5/18)
LOCATION TEMP/YEAR
New Bern 95/1977 (KEWN ASOS)
Cape Hatteras 87/1991 (KHSE ASOS)
Morehead City 93/1960 (COOP)
Jacksonville 95/1977 (KNCA AWOS)
Greenville 94/1964 (COOP)
Kinston 98/1911 (COOP)
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...JBM
NEAR TERM...JBM/EH/TL
SHORT TERM...JBM
LONG TERM...TL
AVIATION...JBM/TL
MARINE...JBM/EH/TL
CLIMATE...MHX
Area Forecast Discussion
National Weather Service Marquette MI
753 PM EDT Wed May 17 2017
.SHORT TERM...(This evening through Thursday)
Issued at 352 PM EDT WED MAY 17 2017
The main forecast concern this evening will be the potential for
flooding across the west and portions of central Upper Michigan, and
then the threat for strong to severe storms this evening. The strong
to severe storms should remain confined along the Wisconsin/Michigan
border, especially across south central portions of the area. The
main threats, other than flooding, will be damaging winds and hail.
Ongoing convection that developed down across northern Iowa and
southern Minnesota has taken advantage of the instability gradient
draped across Wisconsin and up into south central Upper Michigan.
Based on the current RAP analysis and comparing it to the 1800Z GRB
RAOB, it looks like the instability may be underplayed a bit within
the RAP. Given the orientation of the CAPE gradient along the
surface trough, prefer the HRRR solution as it takes the ongoing
convection right up along the instability axis across central Upper
Michigan. While instability isn`t great, the shear is rather stout
with 0-6km shear values of 50-60 knots. Also, based on the
unidirectional shear on the GRB 1800Z hodograph, we could see a few
splitting storms, which will further complicate how convection
evolves over the next few hours. The main severe weather hazard for
this evening will be damaging winds and hail, especially across
south central portions of Upper Michigan. As the storms continue to
push northeast across the area this evening, they may still be
strong; however, they will eventually out run the better instability
and should begin weaken. With PWATs running around 1.5 inches across
the area, heavy rain will also be a threat with localized flooding
concerns based on high rain fall rates. Have not made any
adjustments to the Flash Flood Watch across the west and portions of
central Upper Michigan, as even more rainfall looks on track for
later tonight into Thursday morning as the main upper-level trough
lifts north across the area and brings another shot of widespread
heavy rain overnight into Thursday.
Overnight, with elevated instability running a couple hundred J/kg,
wouldn`t be surprised if a few strong storms develop/intensity
across central and eastern Upper Michigan. While locations across
western Upper Michigan are not expected to see strong to severe
storms tonight, precipitation will become more widespread with heavy
rain being the dominant threat. As the above mentioned upper-level
wave lifts across the area, surface troughing will slowly push
northeast across central and eastern Upper Michigan, allowing colder
air to filter south. By Thursday morning temperatures are expected
to drop into the upper 30s across the west, while only dropping into
the lower 50s across the east and south central. Lingering rain
showers will continue across much of the area through the morning
hours; however, things will continue to dry out through the
afternoon hours as the cooler, drier air mass advects south across
the area. Accompanying this drier and cooler air, will the
increasing northerly winds across the area. Momentum transport
values from BUFKIT soundings even show a few locations gusting up
into the 30-40mph range.
.LONG TERM...(Thursday night through Wednesday)
Issued at 251 PM EDT WED MAY 17 2017
Nam shows a 500 mb trough over the upper Great Lakes 00z Fri with a
closed low over the central Rockies and a ridge over the northern
plains. This ridge moves into the upper Great Lakes 00z Sat. The
closed low moves into the northern plains 00z Sun. Nam shows 850-500
mb q-vector convergence with deeper moisture moving in on Sat. Looks
to be quiet through Fri night and then have chance pops Sat morning
over the west half and have likely pops over the west half in the
afternoon and a chance of pops over the east half in the afternoon.
Overall, did not make too many changes to the going forecast.
In the extended, GFS and ECMWF show a closed 500 mb low and trough
near the upper Great Lakes 12z Sun. This trough remains over the
area through Wed with some colder air returning and a cold front
that moves through on Tue. Temperatures look to remain below normal
for this forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 751 PM EDT WED MAY 17 2017
Challenging aviation forecast tonight, especially during the
evening, as waves of shra/tsra pass across the area. While cigs at
KIWD/KCMX should hold at LIFR with wind a moist, upslope wind off
Lake Superior, KSAW may see cigs fluctuate significantly btwn LIFR
and MVFR until an upslope n to ne wind off Lake Superior locks in
this evening. There may be a lull in pcpn for the next hr or so
before the next round of heavier shra/tsra spreads n across the
area. There may be a third round later in the night. LIFR conditions
are expected at all terminals overnight with gradual improvement
from w to e during the day Thu as drier air advects into the area
under gusty n winds to 20-30kt behind departing low pres.
Improvement to VFR is expected at KIWD/KCMX by late aftn and at KSAW
near the end of the fcst period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 352 PM EDT WED MAY 17 2017
Northeast winds will increase in speed to gales of 40 to 45 knots
across the west and central tonight, before shifting over the
eastern half through the morning hours on Thursday. Winds will begin
to relax to around 10 to 20 knots across the west and central, while
20 to 30 knot winds will still be possible across the east by the
evening hours on Thursday. Winds of 10 to 20 knots are expected
through the end of the work week and beginning of the weekend. This
weekend, winds will increase to 20 to 30 knots as another storm
system lifts out of the Plains across the Upper Great Lakes. Early
next week, 10 to 20 knot winds will persist over much of the lake.
Lingering fog will begin to diminish from west to east across the
lake tonight into the morning hours on Thursday as drier air begins
to filter eastward across the lake. However, at this time dense fog
will still be possible.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
Flash Flood Watch through Thursday afternoon for MIZ002-004-009-
010-084.
Lake Superior...
Gale Warning from 8 AM to 8 PM EDT Thursday for LSZ267.
Gale Warning from 4 AM to 4 PM EDT Thursday for LSZ265-266.
Gale Warning from 11 PM EDT /10 PM CDT/ this evening to 11 AM
EDT /10 AM CDT/ Thursday for LSZ162.
Gale Warning from 11 PM this evening to 2 PM EDT Thursday for
LSZ244-245-263-264.
Gale Warning from 1 AM EDT /midnight CDT/ to 10 AM EDT /9 AM
CDT/ Thursday for LSZ240-241.
Gale Warning from 1 AM to 11 AM EDT Thursday for LSZ242-243.
Lake Michigan...
None.
&&
$$
SHORT TERM...Ritzman
LONG TERM...07
AVIATION...Rolfson
MARINE...Ritzman
Area Forecast Discussion
National Weather Service Norman OK
635 PM CDT Wed May 17 2017
.DISCUSSION...
The May 18-19, 2017 00 UTC TAF discussion is below:
&&
.AVIATION...
Unrestricted ceilings are expected to become restricted (MVFR) at
some terminals as stratus develops from south to north late
tonight. Greatest confidence for stratus is from I-44 south and
east. Opted not to include in KHBR/KCSM, where confidence is
lower; however, stratus could impact terminals this far west.
Thunderstorms--potentially strong to severe--are expected to
develop toward the end of the TAF period across central and
western Oklahoma. Gusty, eratic winds will be possible within any
thunderstorms. Otherwise, southerly winds should weaken this
evening before becoming gusty by mid-morning.
Mahale
&&
.PREV DISCUSSION... /issued 410 PM CDT Wed May 17 2017/
DISCUSSION...
Primary forecast focus is on Severe Thunderstorms Thursday and
chances on Friday.
This afternoon, stout southwest/west winds will continue into the
early evening as the surface low continues to lift north/northeast
across the Mid-Missouri valley of Nebraska/Iowa. Winds will relax
through sunset.
Briefing ridging overnight will open the plains to increasing
boundary layer return flow after midnight into Thursday morning.
GOES-16 (Formerly R) low level Water Vapor paints a fairly clear
picture, with the hefty western trough churning over the inter-
mountain west. A diffuse dry line will set up through the day,
with mid-60s, nearing 70s, dew points advecting and pooling across
portions of southern and central Oklahoma and portions of western
north Texas. I prefer not to Re-hash the excellent SPC Day Two
Outlook from Mr. Kerr, so I`ll try to keep this brief. With the
large scale trough anchored near the Four Corners, expect one or
two weak 500mb short wave perturbations to shift eastward over the
panhandles and West Texas plains by midday, with several of the
latest convective allowing models (CAMs) suggesting developing by
mid-afternoon, east of the dry line, within the warm sector,
forced by a noticable 700mb jet and subsequent trough. The latest
Experimental HRRR and Texas Tech WRF have been consistent with
this trend. Although this outcome is less certain, the fact that
it`s been consistent lends some thought to such an outcome. Better
overall certainty in initiation will be nearer the exit region of
the 500mb jet axis over the northeastern Panhandles across
northwestern Oklahoma into southwestern Kansas. The proximity to
the trough allows for greater height falls and steep low level
lapse rates focused near the dry line and frontal boundary
interaction. This suggests far western and northwestern Oklahoma
could see rapid supercell updraft growth, supported by sufficient
deep layer shear and copious amounts of instability. Large
damaging hail, up to baseballs, damaging wind gusts over 70 mph
are possible. Backing surface winds through through 00Z will
increase 0-1km helicity values over 300 m^2/s^2 through 00z, near
initiation. Paired with modest LCLs, tornadoes are possible with
this initial development.
Overnight, storms will grow upscale as the frontal boundary pushes
southeastward into the region, with a line of broken
thunderstorms developing and pushing eastward across central
Oklahoma through the early morning hours, Friday, with damaging
winds and hail the primary concerns.
Friday, not much of a reprieve, with lingering showers in the early
morning before quick recovery ahead of the deepening 500mb trough
over the southern Rockies through midday. Conditions point toward
early afternoon development along the frontal boundary across
central Oklahoma. Hail, wind, and flooding will be the big concerns,
Friday. Given the warm air advection ahead of the front and it`s
orientation, training thunderstorms could easily become an issue,
exacerbating flooding potential. Additionally, low level shear and
lapse rates, along with low LCLs could point toward a narrow window
for a few tornadoes. However, the focus is on the widespread 2 to 4
inches of rainfall that is expected across central into southern
Oklahoma and western north Texas, along with locally higher amounts
resulting in flooding.
Heavy Rainfall and Flooding don`t usually get the headlines, but
it`s nothing to scoff at, and Friday would be a good day to pay
attention to rainfall amounts and to be careful if you are
traveling. Remember, when you come to a flooded roadway, Turn Around
Don`t Drown.
Kurtz
&&
.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 64 86 66 77 / 0 20 50 60
Hobart OK 59 86 65 80 / 0 60 30 60
Wichita Falls TX 64 89 68 82 / 0 60 40 60
Gage OK 55 84 56 78 / 0 60 60 40
Ponca City OK 61 85 65 77 / 0 20 60 70
Durant OK 72 85 69 82 / 0 20 40 40
&&
.OUN WATCHES/WARNINGS/ADVISORIES...
OK...None.
TX...None.
&&
$$
30/10/10
Area Forecast Discussion
National Weather Service Paducah KY
726 PM CDT Wed May 17 2017
.SHORT TERM...(Tonight through Friday night)
Issued at 311 PM CDT Wed May 17 2017
Main near term concerns are the winds this afternoon followed by
convection chances late this afternoon through overnight. On and
off thunderstorm chances will continue through the rest of the
short term period.
Sufficient high clouds seem to have held temperatures down a few
degrees this afternoon and kept winds a tad lower. However, gusts
have still ranged from around 25 mph in west Kentucky to upwards
of 35 mph in southeast Missouri and portions of southern Illinois.
Isolated showers and even a few lightning strikes have been noted
over southeast Missouri and far southwest Illinois so far this
afternoon. Convective coverage is anticipated to ramp up through
early evening and continue through the overnight hours, with some
gradual reduction in coverage anticipated. A strong storm or two
can`t be ruled out with sufficient instability, moisture, and
shear present. However, the main concern for severe weather will
be tied closer to the surface low and shortwave moving from Iowa
into the western Great Lakes tonight.
A weak cold front will be focused to our north on Thursday. Upper
level ridging tries to build back into our area, and combined
with weak forcing, not expecting coverage of convection to be that
great. Will mainly be instability driven. PoPs will increase
Thursday night into Friday as a surface low develops off to our
west and the front to our north sags further south toward our
northern counties. Not too overly concerned with the severe
storm chances for Friday, but the potential does exist for a few.
Guidance is hinting at a lull toward Friday evening as the front
lifts further north and NVA develops across the area. As the
surface low moves northeast into the Midwest and the main trough
to our west approaches, PoP chances should gradually increase
later Friday night into the weekend.
Temperatures will remain warm through the period with highs mostly
in the 80s and lows in the mid 60s to lower 70s. Humidity levels
will also remain summer-like with dewpoints well into the 60s and
even low 70s from time to time.
.LONG TERM...(Saturday through Wednesday)
Issued at 311 PM CDT Wed May 17 2017
Forecast confidence is high and increasing through the weekend, but
drops off by next Tuesday and Wednesday.
There is much better clustering of the 12Z GFS, GEM, and ECMWF
solutions over the weekend. The upper-level storm system will lift
northeast from the northern Plains into western Ontario by 12Z
Sunday. This will push a cold front through our region early Sunday,
and the precipitation will come to an end Sunday afternoon and
evening.
The models have no problem generating enough instability to support
a full mention of thunderstorms along and ahead of the front through
the period. However, wind fields will not be strong at all, so
organized severe storms will be hard to achieve. Precipitable Water
values over 1.6" will be pushing the 99th percentile for May, so
locally heavy rainfall will be more of a concern.
The 12Z models agree that the Sunday night and Monday will be dry
throughout the area, as cooler, drier surface high pressure builds
over the region and the flow aloft relaxes and becomes nearly zonal.
More energy will be moving south on the backside of the departing
storm system the first half of the next week, but the models
disagree on how quickly it will impact our region with showers/rain.
The ECMWF is the most aggressive and would bring showers across at
least southeast Missouri overnight Monday night, while the GFS and
GEM hold it off until Tuesday night into Wednesday.
The result for the forecast will be to slowly ramp up PoPs from late
Monday night through next Wednesday. The models do not develop much
instability surface-based or otherwise, so left TS out for now. Once
a better consensus develops on the precipitation timing, we can
reconsider if/when/where to mention TS.
As for temperatures, we will see well above normal temperatures
Saturday and Saturday night and then cool to at or slightly below
normal levels Sunday through Wednesday.
&&
.AVIATION...
Issued at 726 PM CDT Wed May 17 2017
With toe 00z Thursday WFO PAH TAF routine issuance, attempted to
focus mention of visibility and ceiling restricted convective
activity close to observed and projected with the ESRL HRRR model
guidance. For the most part, attempted to keep ceilings and
visibilities in the VFR range, with isolated intrusions into IFR
category at KCGI associated with thunderstorms overnight.
There is a period in the KEVV TAF location where non-convective
wind shear was expected, so added a mention of Low Level Wind
Shear at that location between 08-12z Thursday.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
SHORT TERM...SP
LONG TERM...DRS
AVIATION...Smith