Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/28/17
Area Forecast Discussion
National Weather Service Bismarck ND
937 PM CDT Sat May 27 2017
.UPDATE...
Issued at 924 PM CDT Sat May 27 2017
Line of showers with gusty winds is about to push out of the far
southeast portion of the forecast area in the next hour. Mesoscale
models have been overdoing the precipitation associated with the
wrap around moisture dropping into the forecast area from the
north late this afternoon and tonight. Latest RAP looks to be
catching on with a dry forecast for the remainder of the night.
This is what was in our previous forecast and will continue.
Did lower min temperatures just a little tonight over the
southwest for Sunday morning. Should be a clear to partly cloudy
night with good radiational cooling, if winds diminish enough.
Appears to be a bit more of a gradient than last night so a
little hesitant to drop temperatures much lower than guidance.
Updated text products will be out shortly.
UPDATE Issued at 628 PM CDT Sat May 27 2017
Classic inverted V sounding at Bismark this evening. Small fall-
rise pressure couplet with strong subsidence behind a shortwave
trough is combining with this favored environment for strong
winds with convection, to produce gusty winds as high as 60 mph
this afternoon across central ND. These conditions will continue
through early evening from south central ND into the James River
Valley. Thunderstorms have been isolated but with a slightly more
unstable environment over the James River Valley, we could still
see an increase in thunderstorm coverage for a few hours yet this
evening before convection moves out of the area. Have updated
pops/sky cover and winds based on latest satellite and radar
imagery. Winds drop off pretty quickly behind the line of
convection moving through the area. There is a secondary surge of
higher winds pushing from Saskatchewan into northwest ND at this
time but not confident this will continue to spread much farther
south into the forecast area tonight as we lose daytime heating
and winds decouple. Updated products will be sent shortly.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 335 PM CDT Sat May 27 2017
A vigorous short wave was moving out of Southeast Saskatchewan and
into the north-central North Dakota with scattered showers and
isolated thunderstorms. Severe weather is not expected as low
level moisture is low. That dry low level (inverted V sounding) is
contributing to very gusty winds with the showers, as high as 50
mph. The subsidence behind the wave is strong and the timing would
end convection by 11 PM CDT with a quickly clearing sky to just
high cirrus. The wind was diurnally driven and too will quickly
drop off this evening.
For Sunday, similar. Diurnally driven winds increasing and under
cyclonic mid level flow look for convection again in the
afternoon. With no well defined mid level wave there should be
more distance between the showers on Sunday and they should be
more confined to the central and eastern parts of the forecast
area. temperatures, in a slightly cooler airmass, about 5 degrees
lower than today.
.LONG TERM...(Sunday night through Saturday)
Issued at 335 PM CDT Sat May 27 2017
Memorial Day looks partly sunny and cooler as the area remains
under the influences of cyclonic flow, and is deeper into the
cooler surface airmass. By mid week H5 ridging begins to nose in
over the area with temperatures back consistently into the 70s and
likely around 80 by weeks end. The ridge shows signs of breaking
down for next weekend with decent chances, we will see, of showers
and storms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 924 PM CDT Sat May 27 2017
Convection with locally gusty winds has cleared the KJMS area.
VFR conditions now expected through the forecast period.
Northwest winds diminishing this evening then increasing once
again late Sunday morning through the afternoon. Showers and
thunderstorms possible Sunday afternoon at KMOT, KBIS and KJMS.
&&
.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...TWH
SHORT TERM...JPM
LONG TERM...JPM
AVIATION...TWH
Area Forecast Discussion
National Weather Service Birmingham AL
630 PM CDT Sat May 27 2017
.UPDATE...
For 00Z Aviation.
&&
.SHORT TERM...
Tonight.
Confidence is increasing now that showers and thunderstorms will
begin to impact the area more tonight than this afternoon, so have
removed the severe potential for this afternoon but added it in
for tonight through the overnight hours as the next system moves
into the region. Again activity will develop north and west of the
area so to what extent will it hold together will determine the
extent of the strong to to isolated severe storms. The HRRR has
been hinting at this for several hourly runs and now the ARW is on
board with the activity. Still some uncertainties with the
activity as it will be outflow driven. As for the models the HRRR
does have the best handle on current activity and again has for
several runs now, so will adjust the forecast to closely represent
the HRRR.
16
.LONG TERM...
Sunday through Friday.
The forecast for Sunday will largely hinge on the MCS expected to
approach the area from the northwest late tonight. General
consensus from the latest CAMs is that a chance of isolated to
scattered showers and storms will linger for a couple hours past
12Z as an outflow boundary moves in. These would likely be in a
weakened state due to the time of day and the continued presence
of strong mid-level capping over the area associated with a strong
EML. This outflow boundary would need to be watched for additional
re-development of showers and storms later in the day, but latest
guidance suggests it will retreat north of the forecast area by
afternoon. This would leave the forecast area in a capped air
mass with a lack of forcing to break the cap during the afternoon,
as 700 mb temperatures will remain around +10-11C with dry air
also present at mid-levels and the front well off to the west. For
the late afternoon, will leave just a slight chances of an
isolated shower/storm across the northern half of Central Alabama.
If a storm develops in the afternoon, it would likely be strong
to severe with hail/wind given high CAPE, steep mid-level lapse
rates, and 35-45 kts of 0-6 km bulk shear. But, confidence in
development is too low to include in the HWO at this time.
Greater chances of showers and storms will come after sunset
Sunday night, more likely some time after the 10pm-midnight
timeframe. A decelerating cold front will move in from the
northwest, extending southwestward from low pressure over the
Great Lakes. Weak height falls will occur as the trough over the
north-central US causes the Gulf ridge to be suppressed eastward,
and the forecast area will begin to feel the influence of the
right entrance region of a jet streak over the Ohio Valley. This
upper-level forcing will result in cooling at 700 mb and allow
the cap to weaken. Will keep an eye on this late Sunday night
period for any strong to severe threat given the instability still
present, but time of day will not be particularly favorable and
bulk shear somewhat marginal.
Numerous showers and thunderstorms are expected for Memorial Day
in the southwest to northeast oriented moisture axis along and
south of the front which will have stalled. These will be aided by
weak shortwaves in the southwest flow aloft to the south of the
strong upper low over the Great Lakes. Strong storms will continue
to be possible, and an isolated severe storm cannot be ruled out.
0-6 km bulk shear values will be marginal at 25-35 kts, mid-
level lapse rates will be weakening, and profiles will be
fairly saturated. Ongoing precipitation may also hamper
destabilization. Therefore, chances of an organized threat are too
low to mention in the HWO at this time.
The forecast area will remain in the moisture axis south of the
old front Tuesday and Wednesday with continued cyclonic upper-
level flow south of the upper low lifting into Ontario. Scattered
showers and storms will continue across the area, with the best
chances around peak heating. For the rest of the week, the upper
low will continue to lift northeastward while ridging develops
over the Plains. A few southern stream waves will try to under-cut
the ridge. A warm and humid air mass will remain in place over
Central Alabama, with continued summertime afternoon scattered
showers and thunderstorms.
32/Davis
&&
.AVIATION...
00Z TAF Discussion.
A strongly capped air mass will produce rain free conditions and
minimal cloud cover across central Alabama thru 06z. A line of
strong to severe storms will push southward out of Tennessee and
into north Alabama between 04z and 06z. The convective line will
be weakening as it approaches the I-20 corridor around 08z, but
it could still produce wind gusts up to 50 mph at the northern
TAF sites. The storms will also contain frequent cloud to ground
lightning, and gradually dissipate as they push south of I-20.
MVFR cigs not associated with the convective line will likely
develop across central Alabama between 06z and 08z, with the cigs
holding thru at least 16z. After 16z, the cigs will likely rise
above 3000 feet agl, with sct TSRA developing during the heating
of the day on Sunday.
58/rose
&&
.FIRE WEATHER...
A few showers and storms will be possible across the north through
Sunday, but most areas will remain warm and dry. The best rain
chances hold off until Sunday night into Monday when the next
upper level system and surface front approach. Critical fire
weather conditions are not expected.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 68 86 69 81 65 / 40 40 60 60 40
Anniston 70 87 69 83 66 / 30 30 50 60 40
Birmingham 73 88 71 83 68 / 40 40 60 60 50
Tuscaloosa 73 89 71 84 67 / 30 30 60 70 50
Calera 72 88 71 83 67 / 20 20 60 70 50
Auburn 70 87 71 84 68 / 10 10 30 60 30
Montgomery 73 90 73 87 68 / 10 10 30 60 40
Troy 70 90 71 86 67 / 10 10 20 60 20
&&
.BMX WATCHES/WARNINGS/ADVISORIES/...
None.
&&
$$
Area Forecast Discussion
National Weather Service Brownsville TX
644 PM CDT Sat May 27 2017
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...A near-repeat of conditions from the last 24 hours to
the next 24 is anticipated. Current breezy SE winds will decrease
to moderate this evening and overnight, then pick up again Sunday
mid-morning. Wind speeds likely to be a bit lighter than today`s,
though, as the pressure gradient will be relaxed somewhat as a
front moves into central Texas.
Main challenge is onset times of MVFR ceilings overnight at the
terminals. Basically blended persistence from last night with MOS
guidance products and RUC BUFKIT time-height sections. Thinking is
that CIG`s will move inland from the coast, beginning shortly
after sunset. Only two obs from last night recorded IFR CIG at
BRO, so will not mention in this TAF set. High clouds will be in
the mix throughout the next 24 hours as well (as mentioned by
previous forecaster), courtesy of both a speed max at jet level
and anvil cirrus from thunderstorms over the Mexican plateau.
Lower cloud deck should again mix out by early afternoon Sunday.
&&
.PREV DISCUSSION... /issued 403 PM CDT Sat May 27 2017/
..Corrected for WPC risk of Excessive Rainfall category on
Monday...
SHORT TERM (Now through Sunday night ): Mid level ridging over
the northwest Gulf will remain in place initially, but will shift
slightly toward the northeast Gulf by Sunday night. Surface high
pressure will remain in control across the Gulf waters. Ample low
level moisture will remain available as moderate southeast winds
continue tonight. Low temps will range from 75 to 80, and may see
isolated convection fire over the Mexican mountains to the west.
Winds may be just slightly weaker on Sun as the upper ridge shifts
east. The heat will continue, however. High temperatures will
again rage from the mid 90s to a few degrees above the century
mark. Heat index values will be borderline for a heat advisory
Sunday, and will therefore defer to later shifts for refinement on
that point.
A front will push into south Texas Sunday, but southward progress
toward the CWA will be slowed as synoptic driven southeast to
south winds strengthen during the day. As the front moves closer
Sunday night, there may be two centers of action. The first will
be upstream over the RGV Plains, where developing convection may
drift south toward the northwest sector of the CWA. The second
will be storms developing along the Middle Texas Coast, moving
south along the coast. The models suggest that the front will
still be a bit too far north Sun night to more than just
marginally affect the northern tier counties of the CWA, but
general thunderstorms will be possible for that area nonetheless.
LONG TERM (Monday through Saturday):Models continue to trend with
an unsettled, hopefully rainy, period for Deep South Texas for the
coming week. A split flow pattern evolves across North America with
a active subtropical jet stream developing across Northern Mexico
and passing over South Texas and the Western Gulf. Atmospheric
moisture deepens significantly with several shortwave trough
moving along the west to east axis of the subtropical jet. This is
a favorable pattern for scattered to widespread, heavy at times
rainfall for Deep South Texas.
Monday-Monday night: A MCS or even MCC is forecast by the global
models to be ongoing or developing over Deep South Texas Monday
morning with widespread thunderstorm activity through much of the
day. The interaction of a cold front, an upper level disturbance
and anomalous moisture (2+inches pwat) along with increasing upper
level divergence should lead to a likely rain day. Model
guidance, GFS/ECMWF/NAM/Canadian, all pinpointing Monday and
Monday night and even Tuesday with likely to categorical rain
chances. QPF amounts are totaling 2 to 5+ inches with WPC placing
much of our CWA in a Marginal Risk of excessive rainfall. Flash
Flood Guidance remains high with 3/6hr values ranging 3.7 to 6.9
inches, so even with no definite or widespread flooding expected
at this time this bears watching due to past history of rain
events this time of year with the ingredients mentioned.
Atmosphere may become to "water logged" for severe weather but can
not rule of isolated strong to severe storms early on in the
event that may have the potential to produce hail up to one inch
and gusty winds upwards to 50+ mph with sufficient instability,
decent mid level lapse rates and some shear.
Later Tuesday and for the rest of the week: several disturbances
and sufficient moisture (pwats 1.7-2.0) should be enough to keep
at least a chance of showers and thunderstorms each day. Models
eyeing another significant shortwave approaching the Big Bend
vicinity Thursday with increasing divergence in advance of this
disturbance which might lead a bump in the pops towards the end of
the week. Temperatures are not expected to be much a factor this
week under this pattern with near to slightly below normal highs
and near normal lows.
MARINE:(Now through Sunday night): Mid level ridging and surface
high pressure will dominate, producing moderate southeast to south
winds and moderate seas. Obs from around the Laguna are near 20
knots, with the HRRR maintaining a few 20 knot wind barbs through
the afternoon, so will let the small craft advisory on the Bay ride
until its expiration at 6 pm. Winds Sunday will be a skosh less than
today. A few showers or thunderstorms may develop Sun night across
the northern sections of Lower Texas Coastal Waters as a front
approaches from the north.
Monday through Thursday...light to moderate southeast to east
winds and a low to moderate sea is expected Monday and Tuesday
with a weakening cold front over the Northwest Gulf waters.
Pressure gradient strengthen mid to late in the week with marginal
small craft advisory conditions developing by Thursday mainly for
seas and possibly for wind.
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
53-Schroeder/65
Area Forecast Discussion...UPDATED
National Weather Service Cheyenne WY
838 PM MDT Sat May 27 2017
.UPDATE...
Issued at 838 PM MDT Sat May 27 2017
Mid evening update package sent which removed PoPs for the rest of
tonight. Currently watching some showers that have developed along
a weak shortwave moving down through the Black Hills area, with
concern that we might need some PoPs across the northern Nebraska
Panhandle late tonight. However NAM and HRRR both have a decent
handle on the past and near term evolution of that activity, and
they both dissipate it as it moves south of the Black Hills with
further loss of instability. Will continue to monitor that, but
for now will continue with no showers late tonight in the
northeast.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 237 PM MDT Sat May 27 2017
With weak instability in place, will continue to see scattered
showers and isolated tstms over the next few hours, before
activity decreases around 00Z with the loss of daytime heating.
Cannot rule out pea sized hail with the heavier showers with the
low freezing levels. The shortwave wave trough axis that is
currently overhead will move southeastward into Kansas by tonight.
Northwesterly flow aloft will dominate the pattern through early
next week. Highs will rise around 10 degrees on Sunday, back into
the 60s to low 70s for areas to the east of the Laramie Range.
There will be enough aftn instability (CAPE values of 100-200
J/kg) for at least isolated to scattered showers/tstms to develop,
although the activity looks less than today across the plains. A
weak front will push across the region on Sunday night, with llvl
winds becoming more easterly/upslope along the southern Laramie
Range. All models show more storm activity in Albany/Laramie
counties by Monday aftn in an area of enhanced sfc convergence.
Thus, will show higher PoPs 30-40 percent for Monday. Outside of
some breezy northerly winds through the remainder of the aftn,
winds will be rather light in the short term period.
.LONG TERM...(Tuesday through Saturday)
Issued at 237 PM MDT Sat May 27 2017
Upper ridge over the western US at the start of the period will
migrate very slowly eastward and be positioned roughly over the
central and northern Rockies by Thursday. Temps will be gradually
warming each afternoon through Thursday with Thursday likely being
the warmest day. Chance for afternoon showers and thunderstorms
will return by Wednesday mainly over the mountains and possibly
over the plains as some mositure return gets going in S`ly to
SE`ly boundary layer flow. GFS might be a little over aggressive
with the amount of precip generated in this environment especially
in the evening/overnight hours with only weak forcing from minor
shortwaves traveling through the mean ridge and weak flow aloft.
Should be a fairly robust cap in place with 700 mb temps progged
at 10-12 C on the GFS and EC. Trimmed POPs back to slight chance
Wednesday and Thursday over much of the area outside of the
mountains. Model difference become much larger after Thursday with
the EC maintaining significant ridging aloft and warm conditions
through Sat with only slight chances for afternoon convection. GFS
allows stronger shortwave energy to flatten the ridge with much
higher chances for storms along the front range.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 631 PM MDT Sat May 27 2017
Isolated showers & t-storms persist mainly in the vcnty Laramie
Range and west-central portions of Nebraska Panhandle. Expect this
activity to continue through sunset before diminishing. Gusty
north to northwest winds will ease with sunset as well. Sunday
will see a similar pattern as today, except shower activity should
hold off until after 18Z.
&&
.FIRE WEATHER...
Issued at 237 PM MDT Sat May 27 2017
No fire weather concerns through early next week. Temperatures will
warm to back around normal over the next few days. However, minimum
afternoon humidity values will mostly remain above 25-30 percent.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
UPDATE...JG
SHORT TERM...ZF
LONG TERM...DEL
AVIATION...RJM
FIRE WEATHER...ZF
Area Forecast Discussion
National Weather Service Peachtree City GA
1015 PM EDT Sat May 27 2017
.UPDATE...
...Severe Thunderstorm Watch In Effect For Portions of North GA...
Always a tough call with these NW flow events and in this
case...WNW flow event. First wave moved through this morning as
just clouds mainly which really stabilized things longer than the
models had projected. Making up for lost time now though with CAPE
values pushing 2500 J/KG. There has also been an extensive cap to
overcome as evidenced by impressive warming on 00Z FFC sounding.
Hard to discern how far this extends into North GA and honestly
not likely to matter for the first tier of counties given momentum
of initial MCS. But certainly could see some weakening prior to
entering the southern half of the watch but enough uncertainty
there that thought it best in coordination with SPC to go another
tier of counties.
After that...depends more on further upstream convection and if
it makes a late night run at us which would have a better chance
of impacting the metro. For now have kept Atlanta area in the
chance pops except northern burbs where likely will be in place.
Will be a fluid situation with updates to pop grids likely to
continue into the overnight period.
Deese
&&
.PREV DISCUSSION... /issued 757 PM EDT Sat May 27 2017/
PREV DISCUSSION... /issued 247 PM EDT Sat May 27 2017/
SHORT TERM /Today through Monday/...
A rather complicated forecast as a series of disturbances moves
across the CWA beginning tonight and through Sunday night. The MCS
that was over TN early this morning has dissipated and has not put
out an outflow. The hi-res models eventually caught on to this, but
they still struggle with developing convection and moving it into
GA. The HRRR has flip-flop several times this morning and the
WRF/ARW continue to develop convection over TN and move it
southeast. The problem with this is that showers that have developed
over TN are moving northeast. The other issue is the strong cap over
the CWA between 800 and 700 mb. Unless there is forcing, areas in
north Georgia would need to rise to near 100 degrees before breaking
the cap. Latest models suggest the cap doesn`t break down until
Sunday morning.
Have opted to go with GFS/NAM deep moisture and associated short
waves to forecast the best areas for thunderstorms, which at this
time both the GFS/NAM agree on extreme north Georgia tonight and
Sunday with the better chances in north Georgia Sunday night. As for
severe potential, if any storms develop, there is still the risk of
isolated severe storms as CAPES continue to run high as well as 0 -
6km bulk shear.
17
LONG TERM /Monday Night through Friday/...
A largely unsettled period can be expected through the long-term.
Monday continues to exhibit the best chance for strong to severe
thunderstorm activity as a front enters the area with abundant
instability in place by Monday afternoon. The remainder of the
extended will continue to see chances for convection each day with
plentiful moisture and southwest flow aloft. Refer to the previous
long-term discussion below for additional details.
RW
PREVIOUS LONG TERM /Issued 356 AM Sat May 27 2017/
Main forecast concern in long term period is chance for
strong/severe convection on Monday. 00Z model guidance in pretty
good agreement with Monday forecast. Front progged to continue to
sag into the state Monday with above normal sfc temps and
dewpoints. SBCAPE rises to fairly high values even for late May,
GFS 2500-3500 J/kg. Deep layer shear should be sufficient for
severe convection, 0-6km bulk shear mags > 30kts over much of the
CWA, however low level shear quite weak with 0-1km bulk shear
around 5-10kts. In such environments, we typically see severe
storms with large hail and wind threats but very low risk of
tornadoes. PW will be fairly high but not too abnormally high for
this time of year (GFS values around 1.6 in). With large scale
lift not too high, QPF also less than 1 inch in most locations
Mon, so will likely see periods of heavy rain but flash flooding
risk somewhat low.
After front sags into middle or south GA, essentially washes out
Tuesday. Moisture remains plentiful but without any forcing, any
storms would be fairly isolated thru Thursday. Have kept PoPs
fairly low but unlikely we will see a dry period with weak SWly
flow aloft. By Thurs Night or Friday, warm advection should kick
in with increase in moisture as well. Have bumped up PoPs then.
SNELSON
AVIATION...
00Z UPDATE...
VFR conditions to start out in the short term although do expect
to continue with periods of mid level cigs for the next several
hours. Biggest issue will be trying to time potential TSRA
episodes with guidance all over the place with possibilities. For
now...into the overnight looks like the best chances but
confidence so low that will only include VCSH for now. Intrusion
of lower clouds from the SW overnight will require MVFR cigs aft
10Z for all sites.
//ATL CONFIDENCE...00Z UPDATE...
Medium on TSRA chances.
High on remaining elements.
Deese
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 70 89 70 87 / 30 40 30 50
Atlanta 71 87 69 84 / 30 20 20 60
Blairsville 62 84 63 79 / 70 50 60 60
Cartersville 70 86 69 83 / 60 40 50 60
Columbus 71 90 73 87 / 10 10 10 60
Gainesville 69 86 68 83 / 60 50 50 50
Macon 69 93 72 89 / 10 10 10 40
Rome 69 86 69 83 / 60 50 70 60
Peachtree City 69 88 71 85 / 20 20 20 60
Vidalia 70 93 72 92 / 5 10 10 20
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Deese
LONG TERM....20
AVIATION...Deese
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
936 PM CDT Sat May 27 2017
.UPDATE...
Several hours ago, an area of agitated cumulus/towering cu
developed to the east of a bulging segment of the dryline across
Montague, Clay, and Jefferson Counties. A portion of this cumulus
field did manage to initiate deep moist convection across portions
of Central and Southern Oklahoma, but it appears that a lingering
capping inversion present on the 00Z KFWD sounding was simply too
much to overcome to the south of the Red River. As a result, we`ve
trimmed and then relegated low-end chance PoPs to a smaller area
in the immediate vicinity of our Red River Counties through the
midnight hour, but I suspect that much of the ongoing activity in
Oklahoma will stay there for the time being as individual storms
(and occasional splits) continue to move off towards the east-
northeast.
The next forecast challenge looks to arrive near or just after
midnight into our forecast area. A pre-frontal wind shift is just
now moving into the Oklahoma City Metro region, and extends
southwestward towards Frederick at this time, with the actual cold
front lagging about 50 miles behind it. The expectation at this
time is for additional thunderstorms to develop along and ahead of
the intruding cold front over the next several hours. As some
degree of cold pool consolidation gets going and the cold front
approaches, we should begin to see a more noticeable southward-
push to this convective complex shortly. While forward-
propagating Corfidi Vectors would tend to suggest any MCS favoring
a more easterly trajectory, the presence of a significant
northeast to southwest oriented theta-e plume across the region
raises some eyebrows to the possibility that the southern extent
may attempt to build towards the southwest--into the theta-e axis.
Recent runs of the ESLR HRRRX and operational HRRR offer up some
plausible scenarios given their current handling of the convective
picture to our north. As a result, we`ve made very few changes to
the overnight portion of the inherited forecast, which paints
likely PoPs roughly north of I-20 and east of US-81, tapering
gradually to slight chances to the south and west.
Given the aforementioned stoutness of the capping inversion
overhead, we expect overall convective vigor to gradually dwindle
as activity pushes into North Texas overnight. That said, the
presence of very nearly absolutely unstable lapse rates aloft and
continued effective deep layer shear values of 35-45 kts means
this convective complex still has the potential to deliver
damaging wind gusts and large hail to portions of the region--
most notably to those areas north and east of US-81 and I-20 as
rough demarcators. There may also still be a threat for a tornado
or two across our far northeastern counties late tonight where a
sliver of low-level instability may remain.
Carlaw
&&
.AVIATION...
/ISSUED 750 PM CDT Sat May 27 2017/
/00Z TAFS/
VFR conditions prevail across the region this evening although
there is some haze trapped beneath a strong capping inversion.
This has allowed visibilities to drop to 4-5SM in some locations.
Outside of these temporary conditions, VFR conditions will prevail
with southerly winds around 15 kt. The main concern through the
remainder of the night into Sunday will be convective chances and
an approaching cold front with wind shift.
For the remainder of the evening, the 00Z FWD sounding showed a
stout capping inversion which will remain in place. The last hour
of visible satellite imagery shows the once agitated cumulus
field has eroded completely indicative of the strong cap. The
chances for isolated thunderstorms developing in North Texas
through the evening hours is very low. Later tonight, as
thunderstorms become a little better organized across southern
Oklahoma, we will have to watch the southward progression as a
cold front moves south. We think a fairly well organized cluster
of thunderstorms will head southward during the overnight hours
and should be approaching the Metroplex airports by 5-6am on
Sunday in a weakened state. We`ll prevail VFR through much of the
overnight hours and introduce a VCTS by 5 am for all airports in
the Metroplex. Confidence is still a little low on storms actually
impacting the airports, but we think they will still be ongoing
especially to the east. Storms should push south of the area by
mid morning with northerly flow prevailing and MVFR cigs remaining
in place. Cigs should improve to VFR by afternoon.
At Waco, thunderstorm chances will be tied to the cold front and
should at least be scattered in the vicinity of the airport by
midday or shortly thereafter. Northerly flow will prevail behind
the front by early afternoon with storm chances diminishing.
Dunn
&&
.PREV DISCUSSION... /ISSUED 415 PM CDT Sat May 27 2017/
The forecast today is quite complicated with regards to both heat
and severe weather headlines. Fortunately, the oppressive
conditions being experienced by a good portion of North and
Central TX should be relegated to the remainder of this afternoon.
The severe weather risk, however, looks to persist into the day
on Sunday.
Hot and very humid conditions will continue this afternoon and as
of 3 PM, many areas near and just west of the I-35 corridor are
near or just below Heat Advisory criteria. As clouds slowly thin,
temperatures will continue to climb into the mid-90s. Farther
south, the advisory may be a bit more on the marginal side,
depending on the rate of clearing, but at this time, still expect
at least a few sites on the western periphery of the advisory to
experience a couple of hours with heat index values of around 105
degrees. As we`ve stressed this week, it will remain hot and very
humid and people who spend prolonged periods of time outside
without either adequate shade or adequate hydration (water), may
experience heat exhaustion or heat stroke. Fortunately, it looks
like a reprieve from the hot conditions is on tap for a good
portion of the area starting tonight.
Early afternoon surface analysis indicated that a sharp dryline
was slowly mixing eastward from near a Lawton, OK, to Abilene, TX,
line. The dryline will continue its slow trek to the east this
afternoon before retreating back towards the west under quiescent
conditions during the early evening hours. A cold front was noted
across northwest Oklahoma and will slowly move towards the south,
eventually overtaking the dryline. The dryline, but more
importantly the cold front will be the main players for the
severe weather threat across North and Central TX over the next
24-36 hours.
For this afternoon, just about all convective allowing models are
silent for much of North and Central TX this afternoon which fits
the conceptual model for an environment characterized by strong
capping and little in the way of synoptic scale ascent. On the
smaller scale, surface winds are veered well ahead of the actual
dryline along what appears to be a broad surface trough. This
trough extends from near a Bowie to Decatur to Granbury line and
we will have to keep an eye on this surface trough as it could
provide just enough convergence to assist what should likely be
buoyant surface parcels.
The environment this afternoon will be characterized by extreme
instability values with some forecast model soundings indicating
nearly 6,000 J/kg of CAPE. While these values are quite
extraordinary, it`s plausible that little to none of it will be
realized compliments of a very strong capping inversion as sampled
by the 12 UTC FWD sounding. If a thunderstorm can manage to
develop and sustain itself, it will become severe very quickly
with a high likelihood of giant hail (perhaps near 3" in diameter
or greater), destructive straight line winds (70-80 MPH) and a
tornado or two. While the surface wind fields aren`t necessarily
overly conducive for tornadogenesis, the impressive instability
values, particularly in the low levels, will more than compensate
for the lack of strong low level shear. While the tornado hazard
IS the most conditional risk, it will be closely monitored should
storms develop as there is a potential (again, given the extreme
instability) for a robust tornado or two.
The atmosphere will be most prime for convective initiation after
about 6-7 P.M. Some of the latest suite of hi-res guidance
initiates convection across southwestern Oklahoma. This appears
plausible as surface analysis revealed a nice bulge in the dryline
across this region. Given the environment, some of these models
do take this activity east and eventually southeastward into
extreme portions of North TX. Again, this seems like a plausible
solution, but given the uncertainty as to whether or not storms
will even develop across OK, I`ve elected to only advertise 20-40
PoPs through the late afternoon into early evening hours. Storm
chances after 00 UTC should begin to increase rapidly at this
time and I do expect some sort of severe storm cluster over
southern Oklahoma. Some hi-res guidance actually depicts that this
complex will grow upscale rapidly and slide southeastward through
our northernmost row of counties against the Red River. Should
this occur, the main hazards would be large, damaging hail and
destructive straight-line winds. This complex may decay as the
onset of nocturnal cooling occurs. However, its cessation may be
tied more to the start of the low level jet, which is forecast to
become quite strong, a little later in the evening. If this
complex can survive through then, it may have some additional
forcing which would promote a greater longevity.
A potentially second, but more probable round of thunderstorms is
expected near or just after midnight as the cold front slowly
slides southward. If this line of thunderstorms can remain rooted
in the boundary layer and develop a strong cold pool, it has the
potential to morph into a forward propagating MCS as there will be
an abundance of instability as well as assistance from a 30-45
knot 925mb jet. Similar to the first round, the main hazards would
be destructive straight line winds and very large hail. The most
likely areas to be impacted would be locales east of I-35 and
north of I-20. If two rounds of convection do develop, there could
be some isolated instances of flooding or even low-end flash
flooding. At this time, I do not feel compelled to go with any
sort of short-fused/small areal coverage FFA given 1) the
antecedent conditions across North TX do not support it as most
areas missed out on the heavy rain last week and 2) the speed of
both rounds of convection should be swift enough to mitigate any
widespread concerns. We will keep an eye on areas along the Red
River, especially across more urbanized areas where flash flooding
would be more likely. All convection should be efficient at
producing brief bursts of heavy rain, however, given the high
amount of moisture in place.
Close to sunrise, there`s a great deal of uncertainty as to how
quickly this potential line of convection decays. Some guidance
suggests that this complex will plow through just about the
entire eastern half of the forecast area, while some guidance
indicates a quick and painless death of the MCS as it nears I-20.
For now, will confine PoPs to far eastern zones with slightly
lower PoPs elsewhere. The cold front will continue to slowly
trudge southward with breezy northerly winds in its wake. This
feature looks to be quite slow given that there isn`t a ton of
strong cold advection southward.
The slow progression of the front means that it`ll likely not
clear our far southern and southeastern counties by Sunday night.
While it`s likely to be mostly cloudy through the day, surface
moisture will be quite high. The mid-level flow isn`t overly
impressive, but steep lapse rates aloft coupled with modest shear
values may support multicell storm clusters capable of some
damaging downburst winds and potentially large hail. There will be
a heavy rain threat as well, again, given the high moisture
content in the atmosphere. If the front slides to the south a
little quicker than currently anticipated, it`s quite possible
that the severe weather threat also shifts to the south. For now,
we will have to simply monitor the front`s motion through the
overnight hours to get a better handle on this.
For Memorial Day, it appears that areas generally along and north
of I-20 will be mostly dry. Unfortunately, areas farther to the
south will be at greatest risk for showers and thunderstorms. At
this time, the severe weather risk is a little unclear, but
forecast soundings do not generally support widespread severe
storms on Memorial Day, but we will keep an eye on this, given
the multitude of outdoor activities.
For next week, the threat for showers and thunderstorms will
continue as low level moisture lingers across the area.
Unfortunately, there still does not appear to be any meaningful
signs of strong ascent for most days. As a result, PoPs were
broad-brushed just about each day. Towards the end of next week,
it appears that a slow moving upper low may be more of a focus for
a more concentrated area of showers and thunderstorms.
24-Bain
&&
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 75 85 65 86 66 / 40 40 20 10 5
Waco 76 87 65 83 66 / 10 50 50 40 20
Paris 71 82 62 84 62 / 80 50 10 10 5
Denton 72 84 60 86 61 / 50 40 10 10 5
McKinney 74 83 62 85 62 / 60 50 10 10 5
Dallas 76 85 66 87 67 / 40 40 20 10 5
Terrell 74 83 66 85 64 / 50 50 30 20 10
Corsicana 74 85 67 83 67 / 30 40 50 40 20
Temple 75 88 66 82 68 / 10 50 60 40 30
Mineral Wells 72 84 62 87 60 / 30 20 10 10 5
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Goodland KS
709 PM MDT Sat May 27 2017
.UPDATE...
Issued at 703 PM MDT Sat May 27 2017
Made adjustment to timing of PoPs, decrease in coverage of
thunder mention, and removed severe mention from HWO. Showers are
trending slightly faster, and instability is significantly lowered
as front remains well south of our CWA. There are some isolated
showers behind the main precip area, but with decreasing mid
level lapse rates this activity should diminish after sunset.
Timing of main area of precip associated with shortwave should be
out of our CWA by midnight.
UPDATE Issued at 254 PM MDT Sat May 27 2017
Am becoming increasingly doubtful of severe weather developing
over the southwest portion of the Tri-State Area this afternoon.
Wave clouds on visible satellite continue to be prevalent, while
the cumulus field continues to remain further south by the front.
Can`t completely rule out the possibility of severe weather along
the far southern edge over the forecast area, but am not very
confident it will occur given the front should remain to the
south.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 115 PM MDT Sat May 27 2017
Latest upper air analysis shows a trough axis over the Northern
Plains extending southwest to the Central Rockies. Satellite
imagery shows a defined line of clouds accompanying the trough axis
east with colder cloud tops at the base of the trough. Ahead of the
trough axis wave clouds indicated a stable environment. Latest
radar imagery showed a line of showers accompanying the trough axis
east. On the south end of the line a cluster of storms had developed
at the base of the trough axis. At the surface the cold front was
near the KS/OK border arcing northwest to near Denver.
Am expecting this cluster to be the focus for attention this
afternoon for the potential of strong to severe storms as the
cluster moves southeast. The better chance for severe weather will
be south of Cheyenne and Greeley/Wichita counties near the front
where the higher instability will be. Main hazard with this cluster
will be large hail up to ping-pong ball size if severe storms
develop. Have limited optimism due to CAPE of 1000j/kg or less.
However effective deep layer shear is 55kts by early evening, so if
an updraft can avoid being sheared apart large hail will be very
likely. DCAPE values and HRRR ensemble model runs both show a low
probability of severe wind gusts.
Tonight the threat for severe weather will be southeast of the
forecast area, if any is still ongoing. There may be some lingering
storm activity ahead of the approaching trough axis. Cloud cover
will exit ahead of the trough axis. Behind the trough axis a
surface high will move through.
Sunday will be warmer as northwest winds bring in WAA. Winds will
be light as a 850mb ridge moves through. A clear sky is expected
due to dry northwest flow overhead.
.LONG TERM...(Sunday night through Saturday)
Issued at 115 PM MDT Sat May 27 2017
Sunday night: Upper level ridge will build aloft bringing drier
conditions to the area. Temperatures will be near to slightly below
normal.
Monday-Tuesday: Cold front moves into the area during the day Monday
and becomes stalled with a northwest to southeast orientation across
the CWA. Showers and a few thunderstorms will be possible Monday
afternoon into Monday night for areas southwest of the front. On
Tuesday, a shortwave trough pushes into the area from the northwest
helping to provide extra lift and giving most of the area a chance
of rain and thunderstorms. Temperatures should be close to normal.
Wednesday-Thursday: Models still do not have very good agreement for
this period. GFS and ECMWF have very little continuity between them.
Tended to lean towards the GFS for this time frame. Area will see a
chance of thunderstorms on Wednesday and Thursday afternoons. 12Z
GFS soundings indicate that some of these storms could be strong or
severe.
Friday-Saturday: This period could remain wet and/or stormy as both
the GFS and ECMWF are advertising the possibility of a negatively
tilted trough or closed low approaching the CWA from the southwest.
GFS solution shows high CAPE values (~2200 J/kg) but low 0-6km shear
(~12 kt). One note, GFS is also showing PWAT values around 1.25 in.
which could result in some heavy rain through the period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 529 PM MDT Sat May 27 2017
VFR conditions should continue at KGLD and KMCK through the TAF
period. Gusty winds and showers end this evening, with winds
remaining below 12kt until sunrise Sunday. I couldn`t rule out of
a thunderstorm this evening at KGLD, but current radar trends
lower confidence and showers were favored in TAFs. KMCK has less
of a chance for showers, but a few could move within the vicinity
of the terminal early in the TAF period.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
UPDATE...DR
SHORT TERM...JTL
LONG TERM...SME
AVIATION...DR
Area Forecast Discussion
National Weather Service Huntsville AL
807 PM CDT Sat May 27 2017
.NEAR TERM...(Tonight)
Issued at 807 PM CDT Sat May 27 2017
Updated mainly concerning development and evolution of convection to
our north. This convection was basically along the I-40 corridor
from Jackson to south of Nashville to west of Cookeville. Even with
somewhat cooler conditions nearing dusk, very unstable conditions
continued with mixed layer and surface CAPE values in the 2000-3000
J/kg range. Also noticed lower level shear values increasing to our
north as the convection nears.
The HRRR continues a trend of bringing the showers across the area in
the 04-05Z timeframe. But looking at the current radar and storm
movement, think they will be here an hour or so earlier. Strong to
damaging wind gusts and large hail are the main threats. Higher shear
values keeps the possibility of a brief tornado in the picture too.
At this time, think the convection will affect mainly our southern
middle Tennessee and far northeast Alabama counties first, then the
remainder of the area in a NNW-SSE manner in the late evening and
overnight.
Update wise, sped up arrival of likely rain chances for our northern
areas a few hours earlier. Left temperatures and the remaining
parameters as is for now.
.SHORT TERM...(Sunday through Monday)
Issued at 250 PM CDT Sat May 27 2017
If the MCS does move through tonight much of the hires guidance has
it through the area shortly after sunrise Sunday. However, the cold
front will still be lingering off the NW and should spark another
round of convection that will drop S/SE through the area Sunday
afternoon/night. Timing again is very uncertain with the MCS
potentially limiting activity as we may be too worked over. Plus, the
main synoptic forcing with the front will be off to the NE. CAPE and
shear parameters are a bit lower on Sunday and the mid-level dry air
we have over the area today will be gone. So, the potential for
the stronger damaging winds may not be as great. But hail and some
stronger wind gusts are still possible with storms along the front.
The forecast uses more of a blend because of the lingering
uncertainty but if we don`t have the MCS come through we could end up
with some severe storms on Sunday with the front.
With the front losing it`s main forcing it begins to slow down as it
moves through the area Sunday into Monday. This could shift the
threat from severe to more of a heavy rain and flooding threat on
Monday. Did stick to a blend of guidance for PoPs on Monday and kept
50 to 60 PoPs for much of the area during the day. Thunderstorm
chances begin to decrease as we lose heating Monday evening. With the
increased rain chances and cloud cover temps will be a little
"cooler" on Monday compared to today and Sunday. Hoping to see some
more consistency in the guidance in the next few runs.
.LONG TERM...(Monday night through Friday)
Issued at 250 PM CDT Sat May 27 2017
A broad upper trough remains over N. MN at 00z Monday with a cold
front that will essentially be stalled across N. AL. The upper low
remains wedged between strong high pressure over the N. Atlantic and
the N. Pacific with all the energy well to our north. Locally, a mid
level ridge anchored off the SE coast will allow short waves to ride
along it SW to NE across N. AL. Continued SW flow at the surface
will keep ushering moisture into the area as well. The upper low
finally opens up and meanders eastward on Friday. At the same time,
a weak upper low develops over the midwest and will track eastward.
What this all means is that isolated to scattered thunderstorms will
essentially stay in the forecast for the entire long term period,
Monday night through Saturday night. The highest coverages will be
in the afternoon but isolated showers/storms will probably linger
each evening. Shear is non existent most of the week so would
expected convectively induced showers and maybe a strong storm
possible each afternoon. The dynamics for the weekend look stronger
with greater instability so we`ll watch that more in coming
forecasts.
Temperatures for the week will be near normal with highs in the
lower 80s and lows in the lower to mid 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 632 PM CDT Sat May 27 2017
Unsettled weather this TAF, as a series of convective systems move
NW to SE across the region. Even in the short term, there is low
confidence regarding timing of these systems. One of the models is
forecasting thunderstorm complexes now across the KY/TN border and
SE MO should move across this area in the late evening. Other output
has those systems impacting the region during the overnight. Stayed
with the quicker solution this issuance. Given an unstable atmosphere
across the region, strong erratic wind gusts are expected as storm
complex traverses the region. Have lowered VIS/CIG values into the
lower MVFR range, with IFR or lower values possible. MVFR CIGs
should continue to after sunrise Sunday, with scattered convection
into the early morning.
&&
.HUN WATCHES/WARNINGS/ADVISORIES...
AL...NONE.
TN...NONE.
&&
$$
NEAR TERM...RSB
SHORT TERM...Stumpf
LONG TERM...LN
AVIATION...RSB
For more information please visit our website
at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Lincoln IL
933 PM CDT Sat May 27 2017
.UPDATE...
Issued at 932 PM CDT Sat May 27 2017
With several convective systems off to the south of central IL
in southern MO through southern IL, KY, and TN, subsidence in
central IL has inhibited any convection so far. Although enough
instability overnight will continue that storms can`t be entirely
ruled out, looks like any significant chances will hold off until
morning when a shortwave arrives from the west. For tonight, any
significant chance for rain/thundestorms is from around I-70
southward. Severe thunderstorm outlook has been diminished to just
a marginal risk for tonight. Have sent updates for the above
mentioned featured.
&&
.SHORT TERM...(This evening through Sunday)
ISSUED AT 328 PM CDT Sat May 27 2017
20z/3pm surface analysis shows stationary frontal boundary extending
from southeast Kansas eastward into the Ohio River Valley. Dewpoints
south of the front are currently in the lower to middle 70s,
creating a highly unstable environment characterized by CAPE values
of 3000-4000J/kg along/south of the I-64 corridor. Meanwhile north
of the front, a much more stable airmass is in place across much of
central Illinois where lower to middle 60s dewpoints are yielding
CAPEs of only 1000-1500J/kg. Latest radar mosaic is showing several
clusters of thunderstorms developing along/south of the front, with
the most organized linear structure over central/southern Missouri.
This feature will race eastward along the boundary, largely
remaining south of the KILX CWA this evening. Based on radar timing
tools, the northern fringe of this system will brush the I-70
corridor between 00z and 04z...with the main widespread damaging
wind threat focusing further south across southern Illinois and
western Kentucky. HRRR appears to have a good handle on the current
situation and shows this scenario unfolding over the next several
hours. As a result, have updated PoPs to go with likely along/south
of a Jacksonville...to Taylorville...to Robinson line this evening.
Will need to closely monitor areas from Effingham and Robinson
southward, as the potential still exists for damaging wind gusts and
hail this evening. Further north, will only carry slight to chance
PoPs for showers/thunder elsewhere around central Illinois. The
main line of storms will quickly pass into southern Indiana/Kentucky
by around midnight, with only isolated showers expected overnight.
Low pressure will track across central Illinois on Sunday, keeping
rain chances alive throughout the day. Instability/shear parameters
are meager across the area, with the greatest instability developing
further southeast across the Ohio River Valley. As a result, the
latest Day 2 Convective Outlook from SPC has shifted the slight risk
out of the SE CWA. Will carry chance PoPs throughout the day, with
rain chances quickly coming to an end from west to east by late
afternoon and early evening.
.LONG TERM...(Sunday night through Saturday)
ISSUED AT 328 PM CDT Sat May 27 2017
Pronounced upper low will dig southward through Ontario into the
Great Lakes early next week, resulting in a cooling trend across
central Illinois. A weak surface trough will sink southward around
the parent low on Monday, potentially bringing a few showers.
Convergence along the boundary will be weak and with the main upper
cold core still to the north, think areal coverage of precip will
remain low. As a result, have only mentioned slight chance PoPs for
showers/thunder along and north of I-74 Monday afternoon. Cool/dry
conditions will prevail Monday night into Tuesday before the next
potential system spreads showers across south-central Illinois
Tuesday night. After that, mainly dry weather is expected until a
stronger system brings the next significant chance for rain by
Friday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 648 PM CDT Sat May 27 2017
Two areas of thunderstorms this evening appear they will likely
pass by the central IL terminals to the north and south,
respectively, with minimal impacts in central IL. At this time, no
mention of thunderstorms is warranted by current trends for this
evening, however overnight there will be slight chances of
thunderstorms too low for mention at this time, and a disturbance
late Sunday morning will bring another chance of thunderstorms. High-
res models are suggesting low clouds/fog will develop late
tonight once the convection ends, so have MVFR cigs/vsby after
10z until late morning to early afternoon Sunday, IFR at KPIA
where guidance values are lower.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...37
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...37
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1032 PM EDT Sat May 27 2017
.UPDATE...
Issued at 1032 PM EDT SAT MAY 27 2017
The watch was allowed to expire on time, as the stronger
convection has made its way further southeast into Tennessee.
Moderate stratiform rainfall, with embedded thunder, will
gradually diminish across the southwest half of the area over the
next 1 to 2 hours. Some convection has fired up across north
central Kentucky, but this will likely die out before making it
much further east. Included areas of dense fog in the valleys,
with the thicker cirrus shield likely thinning out with time.
Updates have been sent.
UPDATE Issued at 921 PM EDT SAT MAY 27 2017
Storms are gradually weakening across the area, with mainly a
heavy rainfall/flash flooding threat to continue across portions
of the Cumberland Valley over the next few hours. Will likely be
dropping the watch on time. The latest HRRR and radar mosaic
trends suggest a quieter overnight, and given the lack of forcing
and the already worked over atmosphere, this seems reasonable.
Have trended down with the POPs into Sunday morning, before a
possible re-fire occurs tomorrow afternoon, although forcing still
may be on the weaker side. Will have to take a look at fog for the
overnight as well, with only weak southerly flow remaining in
place at the low levels and thicker debris clouds gradually
thinning out with time. Updates have been sent.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 429 PM EDT SAT MAY 27 2017
The latest surface map features a stalled frontal boundary aligned
from near the Ohio River back towards Oklahoma. Aloft, a
positively tilted trough, stemming from an upper level low
spiraling across Manitoba, is positioned from the northern Plains
down across the Four Corners region. A few short wave troughs are
traversing the more zonal flow in place along and east of the
Mississippi River.
Convection has fired up along the frontal zone to our north, as
well along some leftover outflow across central Kentucky. A short
wave trough is also moving through the eastern half of TN/KY,
helping to weaken the cap, that had held back convection through
the morning hours. Deeper and more organized convection has also
fired up back towards southern Missouri, where very prominent
instability exists.
The models have been very erratic with convective initiation and
the evolution of it over the next 24 hours. As such, the forecast
is lower confidence through Sunday.
Through this evening...scattered to numerous showers and
thunderstorms will continue to develop and move off to the east
and northeast. A few of these have already reached severe limits,
along with locally heavy rainfall with some cells training in
places. An overall diminishment is expected after 01 or 02z.
Later tonight, the higher resolution short term model guidance
suggests less of a widespread wind damage threat across eastern
Kentucky, as most of the CAMs are taking organized convection well
to our southwest. This seems reasonable based on the good Theta-E
gradient set up across southeast MO and western KY/TN, where the
better instability bubble exists. There may still be some outflow
generated convection into our area on the eastern flank of this
complex, so have broad-brushed a 50 POP across the area.
Most of the CAMS suggest very little redevelopment into Sunday
afternoon in the wake of the complex; however, if we do not see
much affect from the outflow, then the atmosphere may recharge for
the afternoon. The one issue will be forcing, as upper level
heights look mainly neutral, and the surface front will still be
located to our northwest. As such, have only included chance POPs
for the afternoon, but instability will be ample once again, so
anything that does go could approach severe limits.
The front will approach from the northwest Sunday night, bringing
another round of showers and thunderstorms. The severe potential
will likely be diminishing with the loss of instability, but heavy
rain will still be a concern.
.LONG TERM...(Monday through Saturday)
Issued at 345 PM EDT SAT MAY 27 2017
Precipitation will be exiting during the day Monday as a shortwave
moves east of the region along with a surface cold front, allowing
drier air to usher in behind. A secondary cold front is projected to
develop just west of our CWA during the day Tuesday, remaining
nearly stationary over the next 24 hours. A longwave trough axis
will also begin move through the state during this time. As such,
models are not in good agreement with the mesoscale features,
specifically the location and timing of precip developing with this
system. Went ahead and kept isolated POPs in for Tuesday afternoon
as daytime heating should help kick off some convection ahead of
this frontal feature. Pops will then increase across the SE into the
day Wednesday as the front finally starts shifting eastward across
the state. Did leave out thunder late Tuesday night as latest GFS20
forecast soundings were showing a hefty llvl inversion in place that
will inhibit instability. Showers and thunderstorms that develop
during the day Wednesday will taper off through the evening as the
frontal boundary passes through and a drier airmass moves in once
more.
High pressure and dry weather will remain in place through Thursday.
By Thursday night/Friday, a stationary boundary will likely set up
just south of the state, interacting with a potential upper level
shortwave that will move through the region during this time.
Although models are overall not in very good agreement about the
timing and placement of the mesoscale features, they do generally
agree that this will bring the return of shower and thunderstorm
chances to the state Thursday night into Friday, lingering through
the end of the forecast period Saturday as the boundary to our south
remains in place. Unfortunately the GFS and ECMWF are actually not
in good agreement about this feature during this time, though both
do produce the above mentioned precip, so stuck close to the blend
for this time period.
Overall there are only minor variations in the afternoon temps
during the extended portion of the forecast, with high temps
expected to range from the mid/upper 70s to near 80. Overnight lows
will generally be in the 50s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
ISSUED AT 921 PM EDT SAT MAY 27 2017
Thunderstorms will gradually wind down across a line from KSME to
KI35. IFR or worse conditions will improve to VFR. Fog may be a
factor between 06 and 12z, but light south winds may stay up just
enough in the broader valleys to prevent it from becoming too
widespread. Scattered convection will threaten once again Sunday
afternoon and will include VCTS. Winds will remain out of south
and southwest at around 5 kts.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch through late Sunday night for KYZ050>052-
058>060-068-069-079-080-083>088-104-106>120.
&&
$$
UPDATE...GEOGERIAN
SHORT TERM...GEOGERIAN
LONG TERM...JMW
AVIATION...GEOGERIAN
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
810 PM CDT Sat May 27 2017
.UPDATE...
810 PM CDT
Changes to the forecast for the rest of tonight into Sunday
morning have been minor with just a tad higher chance for some
showers and possibly storms mentioned across north central
Illinois, with probably the best chance still looking to be very
late tonight/Sunday morning.
Across far eastern Iowa early this evening there is a short wave
impulse that was seen on earlier satellite imagery before high
clouds shrouded the area. Some light rain with isolated convection
has spread into southern Wisconsin, with one shower across Boone
County. A few showers could continue to spring up on the
eastern/southern trajectory of this short wave, so across mainly
north central Illinois and the IL/WI border region of northeast
Illinois. The 00Z DVN sounding indicated around 800 J/kg of
MUCAPE, and enough effective shear that if a storm were to pop
across north central Illinois it could have some organization to
briefly be strong. All in all though, a pretty quiet weather
evening.
A few showers, possibly a storm or two, could fester in these same
areas into overnight. In addition, it continues to look like
elevated return flow and instability also creep into the southern
CWA late tonight in response to cyclogenesis across
western/southwestern Illinois. So could also see a few storms pop
up in that area. Overall this was well covered by the forecast.
With some of the better upper level forcing ahead of the primary
trough moving over the area early Sunday, would expect then to
see an uptick in shower coverage. While a decent spread in 18Z
guidance on the rate of speed of the front Sunday afternoon, it
still looks like by peak afternoon heating it should be east of
the area, keeping the main potential for any severe storms east.
MTF
&&
.SHORT TERM...
222 PM CDT
Through Sunday...
Light winds and mostly sunny skies will continue into this evening,
except for lingering cloud cover east of I-55. The two big
factors in the forecast are the convective complexes over Iowa and
Missouri. Models have struggled to capture convection today, but
the latest run of the RAP and HRRR seem to have a better handle on
the situation. The latest RAP analysis features minimal CAPE
values and lingering CIN across the region. Ample sunshine will
certainly help erode CIN, but dewpoint depressions are mostly 10
degrees or more.
Therefore, expecting the storm complex over Iowa to dissipate before
it reaches north central IL. Lightning strikes are rapidly
decreasing in the complex, which supports the idea that the system
is weakening. In addition, a new and much more impressive
convective complex is taking shape over Missouri. The southern
convection should rob us of CAPE and moisture.
Overall have high confidence in a dry and really nice afternoon, but
confidence lowers to medium-high for overnight. Thinking the storms
over Iowa will continue northeast to Wisconsin this evening. Areas
northwest of a McHenry to DeKalb to Peru line may see showers this
evening, but only have a slight chance of showers and thunderstorms
in the forecast. There is a small chance that the southern storm
complex clips the far southern part of the forecast area after
midnight. The remainder of the night should be dry with lows
around 60.
Showers and storms may fester just west of the forecast area Sunday
morning, and expecting showers and storms to move into the Rockford
area around sunrise Sunday. Guidance differs in how quickly showers
and storms will form and move through northern IL and northwest
Indiana. The NAM is by far the slowest solution, and opted to go
with a quicker evolution ahead of the cold front. Models suggest
another band of light rain may form as the upper level vort streamer
moves through. Kept a chance of showers and storms, but have low
confidence in additional precip behind the first wave given very dry
soundings behind the front. Kept high temps lower than climo would
suggest given thick cloud cover. Highs will be in the low 70s.
JEE
&&
.LONG TERM...
222 PM CDT
Sunday night through Saturday...
An upper low is expected to be in place centered just north of the
Great Lakes through much of the upcoming week resulting in active
weather and below normal temperatures.
A blocky weather pattern will be in place over North America much
of the upcoming week as a strong ridge remains anchored over the
central and western half of the country while an upper low
meanders over the Canadian Prairies and northern Great Lakes
region with pin wheeling vort lobes rotating across the local
area. First, and one of the stronger in a series of waves, will
drop across the region on Monday with a modest surface
reflection/cold front moving across northern Illinois and
northwest Indiana primarily during the afternoon. Overall forcing
is not impressive with only modest low level convergence noted
along the front and a narrow corridor of DCVA associated with the
shortwave, but steep low to mid level lapse rates will be in
place with no CIN noted on GFS forecast soundings which should
allow for some scattered showers and possibly a thunderstorm or
two to develop.
Slight chances for precip continue Tuesday as lower amplitude
shortwaves continue to rotate through the region. Steep low level
lapse rates persist and weak diurnal instability is expected to
develop. Showers will be a possibility especially if shortwave
timing falls within peak heating. The GFS strengthens a mid level
capping inversion Wednesday as the upper low inches east and
moderately strong mid level height rises build into the Upper
Midwest resulting in subsidence aloft which should keep the area
dry midweek. This will continue on Thursday as the surface high
moves overhead. Expect a warming trend to occur late in the week
into next weekend as the upper low slowly departs east, but with
warmer temperatures will also come additional chances for showers
and thunderstorms.
Deubelbeiss
&&
.AVIATION...
For the 00Z TAFs...
642 pm...Main forecast concern is potential for thunderstorms
Sunday morning into early Sunday afternoon.
Current showers and isolated thunderstorms over northeast IA are
expected to continue to weaken/dissipate this evening. Some light
showers or sprinkles may reach rfd in the next few hours. There
remains quite a bit of uncertainty regarding precip chances late
this evening and overnight. Most recent short term guidance
suggests isolated/scattered activity may develop by 06z southwest
of the terminals. This is a change to previous runs and confidence
remains low so will maintain dry forecast overnight and monitor
trends. A cold front will move across the area Sunday and
scattered showers and thunderstorms are expected along/ahead of
this front. Timing looks on track if they occur but also low
confidence regarding coverage.
A lake breeze has moved west of ord/mdw with easterly winds
continuing tonight...diminishing to 5 kts or less. Many areas may
become light and variable. Winds will shift northwesterly behind
the cold front Sunday morning and speeds are likely to increase
to 10-15 kts with some higher gusts possible...especially by mid/
late afternoon.
Increasing mid clouds this evening will lower by morning and
possibly into high mvfr...especially at rfd. Fairly low confidence
for how prevailing mvfr cigs will become...especially after the
front passes when cigs should become vfr. cms
&&
.MARINE...
222 PM CDT
Relatively light flow will continue across Lake Michigan through
the remainder of the weekend as the Great Lakes fall between two
areas of low pressure. A northern low will meander over Manitoba
and Ontario through the weekend while a southern low will lift
from the southern Great Plains to the central Great Lakes Sunday.
As these lows merge over Ontario Sunday night into Monday, a fresh
westerly to southwest wind will develop early next week and
continue through midweek.
BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.
&&
$$
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Area Forecast Discussion...UPDATED
National Weather Service Little Rock AR
624 PM CDT Sat May 27 2017
.AVIATION...
Storm system and associated precipitation will move through
Arkansas over the next 24 hours. Timing for the highest
precipitation and thunderstorm chances will be during the
overnight hours for northern sites, in the hours either side of
sunrise over the central, and around mid to late morning in the
south. Conditions will be restricted to mvfr or lower near
thunderstorms. Winds will change around to the southwest and west,
and will be strong, variable and gusty near storms. Expect gradual
improvement from north to south late in the period. TAFS already
out.
&&
.PREV DISCUSSION...(ISSUED 237 PM CDT Sat May 27 2017)
DISCUSSION...
Main concerns in this forecast cycle are first and second period
severe storm potential. Then some lingering lighter convection on
Monday, before the entire system move out of the region and
lessens its impact on AR.
Current convection is developing over MO this afternoon with
strong to severe storms. Over AR have only seen isolated showers
this afternoon with a cap indicated in the 12z KLZK sounding
holding overall convection develop. Later tonight, this cap is
expected to break as the upper system moves through the region,
and allow plenty of convection to affect AR. Otherwise,
temperatures this afternoon were mainly in the 80s, while dew
point temperatures were in the 70s. More organized convection was
over MO and rotating around the upper ridge. Currently the main
upper lift was moving from KS to MO, while a low level jet over
eastern OK to northwest AR may develop isolated convection a bit
later.
Timing of the upper storm system appears to be late evening in
northwest AR, to midnight over more northern AR, then as the upper
lift and cold front gradually sag south, additional convection
will be seen over all of AR after midnight to Sunday morning.
Isolated to scattered strong to severe storms are expected, with
large hail, damaging winds and a tornado or two possible. Plenty
of moisture, lift and instability will be present. Euro model
appears to be the fastest to sag convection into north AR by
midnight or a bit before, with GFS catches up with Euro
overnight, while NAM is the slowest. HRRR model runs a bit
inconsistent with latest more earlier convection into northern AR,
while previous run a bit slower. Moderate risk over northern AR
to Enhance to Slight remains over AR this afternoon, evening and
tonight.
SHORT TERM...Tonight Through Monday Night
Convection chances will ramp up quickly in the evening over
northwest to northern AR, as some lift and low level jet max moves
into the area. It will take a bit long to reach more of the
northern half and central AR as the upper dynamics move into AR
later. All forms of severe weather are possible with the storms.
The convection will last into Sunday, but severe storm threat is
forecast to lower on Sunday as dynamics weaken. Rain amounts
tonight to Sunday are expected from 1 to 2 inches with a few spots
a bit heavier to 2.5 to 3 with precip water values now up to 1.5
inches. On Sunday, the cold front gradually sags to southern AR
and focuses the convection over that region. The severe storm
threat lows as the dynamics push east of AR. A lower chance of
rain is held in the forecast over the south, Sunday night and
through Monday, before ending as the upper flow becomes parallel
to the boundary and stalls it near the AR and LA state lines.
Temperatures will cool a bit behind the cold front and lows will
be below normal while highs a bit to start, then warm into
Tuesday.
LONG TERM...Tuesday Through Saturday
A large area of low pressure will be over the Great Lakes to
begin the long term period with high pressure aloft over the
southeast and western U.S. This pattern will continue through
Tuesday then the upper ridge builds over Arkansas on Wednesday.
The upper ridge weakens Friday and Saturday.
The weekend cold front will be just east of the Mississippi River
Monday night and high pressure will be building over Arkansas.
Another front will move into north Arkansas Tuesday, become
stationary, and bring small chances of showers and thunderstorms
through Thursday. The front slowly moves into southern Arkansas
Friday and should wobble to the north for Saturday. Rain chances
will continue Friday and Saturday. Will have to see how this comes
together but it could be the set up for more heavy rain...or at
least prolonged rain over multiple days. Expect temperatures to run
near to slightly below normal through the long term period.
&&
.LZK Watches/Warnings/Advisories...NONE.
&&
$$
Aviation...57
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1010 PM EDT Sat May 27 2017
.SYNOPSIS...
A frontal system will drift south into the area tonight and
become stationary through Sunday, then lift northeast Sunday
night. A cold front will drift in Monday night and become
stationary along the coast through the end of the next week.
&&
.NEAR TERM /OVERNIGHT/...
As of 1010 PM Sat...Convection moving into NE NC is currently
aided by 40+ kt deep shear and 1000+ J/KG MLCAPE. The HRRR
indicates a slow weakening trend with the MCS as it moves into
the sound counties of the FA as instability slowly wanes. Still
could see some gusty winds and heavy rain with these storms
through the next 3 hrs or so. Have retained 50-60 pops far NE
zones and diminished them elsewhere, as convection across wrn NC
will weaken well before it reaches the coastal plain overnight.
Previous discussion...As of 615 PM Sat...Convection has
initiated in ctrl VA as expected early this evening. Poor man`s
ensemble of the meso model suite indicates this activity
advecting ESE into nrn NC through this evening and potentially
impacting our nrn counties generally north of hwy 64 after 02Z
(10pm). Attm WRF_ARW is performing fairly well with this
convection and have blended more heavily with this model through
the overnight. Have inc pops across the north to 40-60 percent
with just a 20 pop far south. Most likely this convection will
move into the FA as an outflow/cold pool dominated MCS as sfc
based instability wanes late tonight, though ML CAPES still
sufficient for some strong to potentially damaging wind gusts.
Previous discussion...As of 330 PM Saturday...A few cumulus
have develop over mainly inland areas late this afternoon as
temperatures have risen to around 90 degrees well inland with
low/mid 80s coast. Latest 3km HRRR, 4 km NAM and NSSL WRF are
fairly consistent in showing line of convection associated with
approaching frontal boundary and mid-level shortwave energy to
arrive at around 02z- 03z over the Albemarle Sound region. The
highest PoPs will be over the northeastern counties/Sounds
region with only a slight chance over the far south as any
convection should wane during the late night hours. The
northwestern counties remain in a Slight Threat of severe
tonight with decent shear but diminishing instability after
midnight. Lows tonight should be in the upper 60s to lower 70s.
&&
.SHORT TERM /SUNDAY/...
As of 335 PM Saturday...Frontal boundary will drift south
through the CWA before dissipating Sunday afternoon as winds
quickly come back around to S/SW in the afternoon. Any leftover
boundaries along with heating as temperatures climb back toward
90 degrees will ignite a few scattered showers and thunderstorms
during the afternoon, mainly inland. With respectable
instability and weak low-level shear, some strong storms will be
possible, but only expect scattered coverage and will keep PoPs
at 30 percent inland and 20 percent coast. Highs Sunday will be
90-93 inland and 83-87 coast.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
As of 425 PM Saturday...An unsettled pattern will be the rule
through the extended period as shortwaves/disturbances move
through the region aloft, with weak frontal passages moving into
the area and stalling Monday night and Wednesday night. These
features will lead to continued low confidence through the period
due to timing of shortwaves/frontal boundaries across area.
Sunday night-Monday night...A weak shortwave will move through
the region Sunday evening ahead of a stronger shortwave that
will move through VA late Sunday night into Monday morning.
Trended PoPs from high chance Sunday evening to slight chance
after midnight. Models generally agree on more widespread
convective threat with a stronger shortwave trough and surface
cold front moving toward area during peak afternoon heating
Monday. GFS/NAM forecast soundings indicate MUCAPE values of
2500-3500 with deep layer shear (0-6km) increasing to near 50
KT, thus increasing concern for strong to severe storms. SPC
continues Day 3 Outlook of Slight Risk of severe for entire
area. Brought PoPs down Monday morning due to lack of moisture
and brief subsidence behind departing shortwave, then maintained
PoPs in the 40 percent range for the afternoon. Guidance
indicates low level thicknesses building to near 1430 meters,
supportive of max temps 90-94 inland, with mid to upper 80s
along the coast. Lows Monday night remaining muggy 70-74.
Tuesday-Tuesday night...The frontal boundary is expected to
stall across the area Tuesday morning, and wash out across area
with additional short wave energy resulting in another period
of mainly diurnally driven showers and thunderstorms. Tuesday
afternoon convection could be similar to or exceed Monday`s
activity, mainly because of better moisture focused along the
stalled front and channeled shortwave/vorticity over the region
coincident with peak afternoon heating. More cloud cover and
lower thicknesses will keep max temps mainly in the 80s. Lows
Tuesday night 66-70 inland to lower 70s coast.
Wednesday-Saturday...Low confidence for this forecast period
due to poor model continuity. 12Z guidance continues the wet
trend for Wednesday and Wednesday night, though the ECMWF
suggest the stalled boundary may be farther offshore than the
GFS/GEM. Drying trend for Thursday looks good with front off
coast. Higher chance PoPs for Friday with front lifting back
north, helping to focus moisture over the area through Saturday
morning. Max temps still in the mid to upper 80s for Wednesday
and Thursday, then low 80s for Friday and Saturday due to cloud
cover and showers/thunderstorms. Lows from mid 60s to lower
70s.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
Short Term /through 18Z Sunday/
As of 615 PM Saturday...VFR through the TAF PD. Thunderstorms
may impact the area after 10 pm, with KPGV seeing the best
chance of thunder tonight. Storms may tempo limit vsbys to
IFR/MFVR in heavy rain along with tempo gusty and erratic wind
gusts. May need to add a VCTS or tempo TS with later updates
after 02Z. Any storms move off and weaken late in the overnight
with benign conditions through much of Sunday.
Long Term /Sunday night through Thursday/
As of 410 PM Saturday...Sub-VFR conditions likely Sunday night
as a weak front and upper level disturbance move through the
area. Better chance for periods of sub-VFR with convective
activity each afternoon and evening from Monday through
Thursday. Less coverage for Wednesday and Thursday but sub-VFR
could linger with front stalled over area.
&&
.MARINE...
Short Term /Tonight and Sunday/
As of 345 PM Saturday...Winds continue to be SSW/SW at 10-15
knots with a few higher gusts at late afternoon with seas at
1-3 feet. Frontal boundary will enter the far northern waters
late tonight and will work its way south before dissipating
Sunday afternoon as the winds quickly become S/SW again. Expect
seas to perhaps rise to as high as 4 feet over the coastal
waters tonight but should drop back to 2-3 feet on Sunday per
latest SWAN/NWPS model.
Long Term /Sunday night through Thursday/
As of 430 PM Saturday...Zonal flow with weak disturbances aloft
will lead to several weak frontal intrusions into the area
Monday night and again Wednesday night. Southern half of waters
will mainly see SW winds 5-15 knots during period but northern
waters will see some periods of shifting winds but with speeds
less than 15 knots. Southern waters will see some periods of
seas building to 4 feet for outer portions with stronger SW
winds around 15 knots, otherwise seas mainly 2-3 feet during the
extended period. NWPS and Wavewatch in good agreement through
the medium range, with Wavewatch appearing reasonable for the
extended seas forecast.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...CTC
NEAR TERM...CTC/TL
SHORT TERM...CTC
LONG TERM...DAG
AVIATION...DAG/CTC/TL
MARINE...DAG/CTC
Area Forecast Discussion
National Weather Service Paducah KY
725 PM CDT Sat May 27 2017
.MESOSCALE DISCUSSION...
Issued at 723 PM CDT Sat May 27 2017
Dynamic and complicated convective scenario remains in play across
the WFO PAH forecast area.
In coordination with SPC, the following counties that were in
Tornado Watch # 275 that just expired were placed back into
Tornado Watch #284 until 2 am CDT Sunday morning. Locations from
south of Van Buren to New Madrid have seen scattered severe/non-
severe thunderstorm activity, but the airmass still remains primed
with ESRL HRRR CAPE of 3000-5000 J/kg2 with decent upward
vertical velocities expected between 10 pm and midnight over the
new counties included in the new Tornado Watch #284 for southern
MO.
There are still active storms moving across these southeast
Missouri counties, so additional warnings may be possible earlier
this evening.
Reference SPC`s Mesocale disussion # 878 issued earlier this
evening for more details on the storms in southeast Missouri this
evening.
The serial bowing segments moving through West Kentucky now should
work stabilize further convective activity through the remainder
of the evening.
May need to shave off part of the current PDS from some of the
Southern Illinois/Southwest Indiana counties along the Interstate
64 corridor. With boundaries still nearby, may hold these counties
in the watch until expiration.
&&
.UPDATE...
Issued at 152 PM CDT Sat May 27 2017
Rapid adjustments made to reflect current activity across the WFO
PAH Forecast area. Greatest concern at the moment will be the
convective complex moving from East Central Missouri, then along
and remnant outflow/frontal boundaries south of the Interstate 64
corridor...then again along the common borders of Southeast
Missouri, Northeast Arkansas, West Kentucky and Tennessee. |
UPDATE Issued at 1133 AM CDT Sat May 27 2017
Convection is developing along outflow boundaries and existing
warm frontal boundary over Southern Missouri and parts of Southern
Illinois and the Pennyrile of West Kentucky. Some local concern
that some of these storms along the boundary may go severe
severe before the main bowing line (developing derecho?) reaches
the WFO PAH CWA later this afternoon and this evening. Waiting to
see what SPC might do with the MDT risk area in their midday
update. Also added Flash flood Watch for Carter/Ripley counties
from 1 pm today through 7 am Sunday.(see hydro section).
&&
.SHORT TERM...(Today through Monday night)
Issued at 134 AM CDT Sat May 27 2017
New SWODY1 outlooks moderate risk for much of FA this pm/evening,
with all svr wx hazards possible. AM storms to our west are
modeled to affect western ptns FA later this morning, and may lay
out a boundary and also blow off debris clouds that could stall
development after daybreak. However, differential heating should
mix the atmos up enough to allow super charge to take place, with
high cape environ and steep mid level lapse rates revealed by
model soundings. At some point during the pm hours, cap should
break and convection become numerous to widespread, with
associated moderate risk of svr extending from late pm into/thru
the evening hours. Svr chances begin to diminish overnight as
large scale instability is lost the farther east storms push away
from source boundary/energy.
Primary cold front does not make actual passage until Sunday
evening, so until then, we`ll be continuing pops along/ahead of
the boundary, and this includes a continued slight risk of severe
again for mainly Sunday afternoon/early evening.
.LONG TERM...(Tuesday through Friday)
Issued at 134 AM CDT Sat May 27 2017
The extended period continues to be troublesome with models flip
flopping the best chances for rain. Still dealing with another
frontal boundary passage on Tuesday/Tuesday night. The GFS has
been the most consistent with the timing of this feature but not
as much on QPF. Still, believe that precip chances need to be
included for that time frame given the consistency of this signal
and the consistency of the GFS ensemble precip means. At this time
our confidence does not warrant anything more than slight
chances.
The ECMWF was never that excited about Tuesday`s rain prospects and
still isn`t. Instead, the 12Z ECMWF brings a front down into the
area on Wednesday through Thursday. That is the exact same time that
the GFS brings in a reinforcing sfc high pressure system that dries
us out. However, the 00Z ECMWF is back to looking like the GFS with
the drier weather on Wednesday with the incoming sfc high. The early
part of the extended forecast is going to be hinged on exactly what
this large upper level low over the upper Great Lakes region/eastern
Canada does and the timing and strength of impulses rotating around
it. For now, leaning toward the more consistent GFS for guidance.
Given the above discussion, POPs will be low Tuesday through
Thursday given uncertainty`s in the model signals. There has been
a stronger signal for more wet weather as we head into the latter
half of the week. However, the upper level pattern is not being
consistently resoled by the models very well at all. Yesterdays
runs indicated more of a southwesterly flow pattern setting up and
now the upper flow stays more west northwesterly through Friday.
We will continue to have POPs for late week, but work will need to
be done on fine tuning these chances as models grasp a better
handle on things.
&&
.AVIATION...
Issued at 152 PM CDT Sat May 27 2017
Current 18z Saturday TAF issuance will be a challenge with mutiple
boundaries focusing VFR to IFR changing conditions. Base forecast
includes thunderstorms in each TAF location. Main concern within
the next six ho9urs will be the KEVV, KCGI, and KPAH TAF locations
for lowered visibility.
&&
.HYDROLOGY...
Issued at 1133 AM CDT Sat May 27 2017
WPC recently upgraded parts of Southern Missouri in a Moderate
Risk of excessive rainfall through today and tonight. Given the
antecedent rainfall this morning, combined with the expected
position of the frontal boundary and outflows today, felt it was
prudent to add Carter and Ripley counties to the Flash Flood Watch
later this afternoon and tonight.
Depending on the propagation of the convection along the boundary
and the southern end of the expected wind-damaging MCS, may need
to extend the Flash Flood Watch to Wayne and Butler counties as
well. Will monitor the progression of the storms this afternoon.
Minimum rainfall of 1-1.25 inches is likely...with higher amounts
possible. Given the flashy nature of runoff and the terrain, as
well as the potential for higher public presence outdoors this
weekend, decided to go ahead with a Flash Flood Watch for Carter
and Ripley counties from 1 pm today through 7 am Sunday.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...Flash Flood Watch until 7 AM CDT Sunday for MOZ107-108.
IN...None.
KY...None.
&&
$$
MESOSCALE...Smith
UPDATE...Smith
AVIATION...Smith
HYDROLOGY...Smith
Area Forecast Discussion
National Weather Service Shreveport LA
943 PM CDT Sat May 27 2017
.DISCUSSION...
Surface low across Red River valley extending into eastern
Oklahoma generating severe thunderstorms across much of central
and eastern Oklahoma. HRRR model suggests bulk of the convection
to remain out of the ArkLaTex through 3 AM before a cold front
slides south across the I-30 corridor. As convection moves south
with the front, atmosphere becomes less conducive to maintain
severe thunderstorms as noted by an enhanced risk across McCurtain
county and a slight risk across much of northeast Texas and
Southern Arkansas. Current forecast is on track, no updates at
this time. /05/
&&
.PREV DISCUSSION... /issued 733 PM CDT Sat May 27 2017/
AVIATION...
For the ArkLaTex, VFR with a touch of haze until sunset. Winds are
S 5-15KT and will become SW for Sunday. Aloft we are SW 15-35KTS.
MVFR stratus will meet convection from the N before daybreak with
a cold front moving in our direction bringing early widespread
shwrs/tstms from 09-13Z. The cold front will move closer but not
through until Sunday night. So expect more dvlpmt of tstms for the
p.m. hrs. Fropa will shift surface winds and not much else early
Monday. The boundary will slowly lift back North into midweek./24/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 75 87 69 81 / 30 40 60 40
MLU 74 89 70 81 / 20 30 60 60
DEQ 72 82 61 85 / 80 40 40 10
TXK 73 83 65 83 / 60 40 60 20
ELD 74 84 65 81 / 50 40 60 40
TYR 75 86 68 82 / 40 40 60 30
GGG 75 85 68 81 / 30 40 60 30
LFK 77 91 72 81 / 10 30 70 60
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
05/24
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Sunday)
Issued at 316 PM CDT Sat May 27 2017
Thunderstorms moved east of the area early this afternoon which
resulted in mesoscale subsidence and drying across northeast
Kansas. This was evident on the 18Z special TOP sounding which was
dry and relatively stable. The airmass may recover enough to
support continued thunderstorm chances with a low risk of severe
weather mainly from large hail. Mid-level lapse rates were around
8.5 C which favored hail if there was enough low-level moisture to
produce storms. What storms we see will likely be slightly
elevated and not surface based. The area of extreme instability
coupled with favorable shear should remain south of our area.
Expect all of the thunderstorms to exit the area by early evening.
Model soundings suggest saturation below the frontal inversion
tonight which supports cloudiness. Recent runs of the HRRR keeps
showers together as they move out of Colorado and across Kansas
late night. Will not alter the forecast based on this due to lack
of confidence, but it is something to watch.
.LONG TERM...(Sunday night through Saturday)
Issued at 316 PM CDT Sat May 27 2017
Overall, the upper air pattern remains PNA with west coast ridging
and an upper trough over the upper Mississippi valley. Cool
Canadian air should move into Kansas tonight and Sunday in
association with a polar high pressure system building south
through the plains. This should result in dry and relatively cool
weather through the balance of the holiday weekend.
The surface ridge eventually moves east by midweek allowing for
return flow and increased moisture and instability. This along
with weak disturbances is enough to support small pops in the
extended forecast. Temperatures should slowly warm to slightly
above normal by the end of the forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 603 PM CDT Sat May 27 2017
Will keep TAFS VFR at this time with the expectation that any
precip with the southern KS overnight complex will remain south of
the sites given dry advection at 850mb. Only other potential issue
would be some MVFR VIS issues around TOP however at this time
boundary layer mixing and weak dry air advection makes fog
development uncertain at TOP and unlikely at FOE or MHK.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Johnson
LONG TERM...Johnson
AVIATION...Omitt