Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/21/18
Area Forecast Discussion...UPDATED
National Weather Service Corpus Christi TX
935 PM CDT Sun May 20 2018
.DISCUSSION...
Updated forecast based on radar trends and expected convection
overnight. Not expecting much overnight maybe closer to the coast.
Most of the activity well west of the Rio Grande should stay west
or move south of the area overnight. Still did keep a low chance
or slight chance after midnight to account for this. All forecast
parameters for tonight and portions of Monday have been updated.
Products are out. Made some adjustments to the marine forecast.
That will be issued by 10 PM.
&&
.PREVIOUS DISCUSSION... /Issued 659 PM CDT Sun May 20 2018/
DISCUSSION...
Convective line stretches from Whitsett southward to George West
with a broken line of storms extending southwestward to near
Laredo. Some of these storms may be strong to possibly severe with
strong to damaging winds being the primary threat. This threat
should continue into the evening for a few more hours. Main reason
for the update was to align pops closer to radar trends and
expected movement of the storms during the evening hours.
Additional updates will likely be needed.
PREVIOUS DISCUSSION... /Issued 630 PM CDT Sun May 20 2018/
DISCUSSION...
There will be an update coming out shortly on the evening package
based on the current radar/radar trends and expected convective
progress this evening and overnight. Also adjusting some other
parameters as-needed to fall more in line with the observations.
Update will be out shortly.
See .AVIATION discussion for 00Z TAFs.
AVIATION...
Main issue is the convection and this set of terminals is based in
part on radar and surface forcing trends (LAPS convergence),
along with meso-model "trends" (meso models cannot be relied on
for exact location of convection just that convection will likely
be around some areas). Given that, am expecting convection to move
more to the south during the evening, especially KLRD and KALI
terminals, but also possibly into the KVCT terminal. Lots of
surface moisture divergence near KCRP terminal at this time
(thus against rain), and that is the tricky terminal but given
that the models have been consistent on possibly having something
proximate to the terminal this evening did also include
convection here (weaker however). Best shot for convection is
between 02Z and 07Z at KALI, 03Z and 08Z at KCRP, 01Z to 07Z at
KLRD (possibly longer), and 01Z to 05Z at KVCT. Strongest storms
(gusts greater than 30 knots likely at all but KCRP (but not that
KCRP cannot get higher winds...cannot base on worst case
situation). After the convection, should have MVFR CIGS develop
all terminals, with some showers possibly in the vicinity of KCRP
overnight. CIGS improve to VFR before by 17Z with potential for
some convection during the afternoon again. For now, put in VCTS
at KALI and KLRD during the afternoon with much uncertainty
elsewhere. Less winds and more easterly in the forecast for
tonight and Monday outside of convection.
PREVIOUS DISCUSSION... /Issued 401 PM CDT Sun May 20 2018/
SHORT TERM (Tonight through Monday night)...
Main forecast concern is thunderstorm potential this afternoon and
evening. Convection associated with outflow boundary to the north
will slowly approach the northwest and northern parts of the region
over the next several hours. HRRR runs over the last few hours
support this, and actually bring this area of showers and storms
near the coast later this evening. MLCAPE values remain around
2000 J/kj at this time with little to no capping across South
Texas. Strong storms will be possible as this activity moves into
the area late this afternoon and early evening with primary
threats of gusty winds and small hail. An isolated severe storm or
two is not completely out of the question either. Some moderate
to heavy rains may also occur with PW values around 1.7 to 1.8
inches.
This area of showers and storms should slowly moves to the
south and east tonight. Confidence is not that great of any
redevelopment, but sufficient moisture lingering around will
warrant low pops through 12z. Overnight lows will generally be in
the lower to middle 70s inland with upper 70s along the coast.
Any remnant boundaries coupled with an approaching upper level
disturbance may result in isolated to scattered storms on Monday.
Will continue with 30 to 40 pops, with best chances along the Rio
Grande and western Brush Country. Highs tomorrow will be in the
upper 80s to low 90s.
LONG TERM (Tuesday through Sunday)...
Ridging pattern will develop overhead on Tuesday. Sufficient moisture
along the coast may allow for isolated showers or storms to develop
and stream onshore throughout the day on Tuesday. Drier air will
then push into the region Wednesday, with below normal moisture and
dry conditions persisting into late in the week as mid/upper level
ridging remains set overhead. A warming trend will continue through
the week, with highs back near 100 degrees across the Brush Country
and in the mid to upper 90s to the east by the end of the week. Over
the weekend the upper level ridge will shift further to the west as
a trough axis develops to the east of the region. Slightly higher
moisture creeping into the coastal areas and less suppressive
conditions aloft may allow for some isolated coastal convection to
pop up again by the weekend. However, most locations will remain
dry at the time.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 74 88 73 90 73 / 60 30 10 20 10
Victoria 72 90 70 91 70 / 50 30 10 20 10
Laredo 75 92 74 94 74 / 20 40 10 10 10
Alice 73 91 71 93 71 / 60 30 10 10 10
Rockport 77 86 76 88 76 / 50 30 10 20 10
Cotulla 71 92 71 94 72 / 20 40 10 10 10
Kingsville 74 92 72 93 73 / 70 30 10 20 10
Navy Corpus 78 86 78 88 77 / 40 30 10 20 10
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
GW/86...SHORT TERM
Area Forecast Discussion
National Weather Service State College PA
1154 PM EDT Sun May 20 2018
.SYNOPSIS...
A weak cold front will settle south of the area by this evening
followed by drier air that will finally work into the region.
During the day Monday, this same old frontal boundary will lift
back northward as a warm front. Showers and scattered
thunderstorms will accompany the front as it lifts north across
the Commonwealth. Most of the showers and storms will be from
late Monday into early Wednesday.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
Current fcst on track.
Earlier discussion below.
Showers and storms south of PA as of 520 PM.
Updated the grids.
Afternoon discussion below.
Satellite shows brightening skies, but with plenty of post
frontal strato-cu over northern areas. The HRRR doesn`t make me
optimistic for these clouds to mix out in time to bring much
sunshine before the afternoon is over.
Over the SE, still ahead of the weak front, a few showers are
developing. They are still fairly squat and despite the RAP
showing max CAPEs in excess of 1000J, lapse rates are not very
impressive so we expect little more than some brief showers and
maybe a rumble of thunder. The HRRR shuts things down fairly
quickly after about 5PM.
High pressure over the Upper Midwest/Northern Great Lakes will
build SE and moves across Pennsylvania late tonight and Monday
morning with fair/dry weather, lower humidity and light wind
helping to yield cool temps. Recent rains have left conditions
moist, so some late night fog looks like a fair bet.
Lows tonight will vary from the upper 40s across the Northern
Tier of PA to the lower 60s in the Southern Valleys.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
The gift that keeps on giving in the form of our cold front,
will start to make a return Monday as a warm front. The first
showers could reach my SWRN Laurel Highlands zones by mid day,
but more likely we will see the chance for showers ramp up from
SW to NE as the afternoon progresses. Ensembles show the PWATs
starting to creep up and 12Z guidance shows some erosion in the
stability, so thunderstorms will be possible.
Highs should be relatively pleasant topping 70 everywhere.
That`s a few degrees warmer than normal for the time of year.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
After being suppressed to our south early next week, the
chances for convection will increase once again Monday
afternoon and especially Monday night into Tuesday as moisture
on the northern periphery of the subtropical ridge creeps back
into the region as an old frontal boundary lifts to the NE as a
warm front, putting the west into the warn sector.
Numerous showers along with a few thunderstorms will bring a
few to several tenths of an inch of rainfall to much of the
region Monday night into Tuesday before drier air makes a push
in from the NW behind a weak cold front starting Wednesday.
Tuesday looks like the coolest day of the week, though humidity
will be highest.
From there it looks like the period form Wednesday through
Friday will feature some rare (of late) rain-free conditions,
before the chance for a pop-up shower or storm becomes returns
for Sat. Temps look to climb into the 70s each day, with
Saturday the warmest as high range from the mid 70s to the lower
80s. The coolest morning will be Friday with valleys of the
northern mountains dipping into the mid 40s.
More active weather returns for late weekend as another period
of showers and scattered thunderstorms begins.
&&
.AVIATION /04Z MONDAY THROUGH FRIDAY/...
Clearing skies, a diminishing wind and wet ground will likely
lead to areas of valley fog late tonight. The weakest pressure
gradient and lightest winds should be across the northern tier,
where SREF prob charts and NAMnest indicate the most widespread
vis reductions late tonight. However, patchy fog is possible
even into southern Pa late tonight. The one airfield least
susceptible to radiation fog will be KJST, due to its ridgetop
location.
Any fog should mix out between 12Z-14Z. After that, there is
some concern of MVFR cigs in the vicinity of KJST/KAOO later
Monday, due to a developing easterly flow ascending the higher
terrain of south central Pa. Based on an examination of varying
model guidance, believe the odds of this are slightly less than
50 pct. Much drier air working into northern Pa should ensure
VFR conditions across that part of the state Monday.
Outlook...
Tue...AM rain/low cigs possible. PM tsra impacts possible west.
Wed...AM low cigs possible W Mtns.
Thu-Fri...No sig wx expected.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...La Corte/Martin
NEAR TERM...La Corte/Martin
SHORT TERM...La Corte
LONG TERM...RXR
AVIATION...Fitzgerald
Area Forecast Discussion
National Weather Service Cheyenne WY
523 PM MDT Sun May 20 2018
.SHORT TERM...(Tonight - Monday)
Issued at 219 PM MDT Sun May 20 2018
Showers & a few thunderstorms are developing along and west of the
Laramie Range this afternoon, in response to a mid-level shortwave
lifting northeast across southwestern CO in advance of a deepening
upper low over the western US. Limited moisture & instability will
preclude a risk for strong storms, but activity may linger through
much of the evening aided by ample dynamic support. Recent runs of
the HRRR suggest at least isolated showers may persist through 06z
or so before diminishing.
Fog is possible again tonight w/ moist low-level upslope remaining
in place along/east of the Laramie Range. Moisture profiles should
not be quite as supportive of widespread dense fog tonight, but we
could see some areas of visibilities as low as 1/4 mile. Expect to
see any fog diminish by mid-morning on Monday.
Convective activity will be possible once again on Mon w/southwest
flow aloft ahead of a closed upper low over southern California. A
bit of an issue with capping/subsidence associated w/ a short-wave
ridge over the central Rockies, so expect the bulk of the activity
to be confined to the higher terrain. Highs will continue to trend
warmer as H7 temperatures climb to +8 to +12 deg C.
.LONG TERM...(Monday Night - Sunday)
Issued at 227 AM MDT Sun May 20 2018
Main highlight in the long term will be the warming temperatures
through the period and afternoon shower and thunderstorm chances.
The more significant coverage and intensity day of storms could be
Wednesday for far east WY and moreso the NE Panhandle.
By Tuesday, the H5 ridge axis will shift east in to the Central
Plains as a large western CONUS closed low pivots into the Great
Basin. Greater southwest flow aloft for western areas in the
mountains should allow for greater spatial shower and storm
coverage but instability and shear combination looks to marginal
at best. Going into mid-week on Wednesday, the closed H5 low over
the great basin will open up and shift northeast across the
Rockies. Stronger H3 diffluent flow aloft along and instability
over the High Plains (especially more so NE Panhandle) should
support stronger thunderstorm development. A negating factor is
wind shear as it continues to look meager in the 25-35 knot range.
Strong pulse to semi- organized storms could be possible
Wednesday afternoon into evening.
By late week, the base of the transiting trough axis will shift
north of the region. Stronger west winds will develop and shunt
deeper moisture farther east into the Central Plains as drying
vertical profiles occur. Friday and into the early weekend, weak
northwest flow develops as the trough axis passes east and H5
ridging shifts in just west of the Rockies. Just enough
impulse/vorticity difluence aid and meager instability could help
scattered showers and isolated thunderstorms over the higher
terrain but overall coverage will be limited and the High Plains
will likely remain rain free.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 518 PM MDT Sun May 20 2018
Mainly VFR conditions are expected at area terminals this evening
and tomorrow. One area with somewhat limited confidence is the
development of patchy fog tonight at KCYS. Models show CIGS
falling quickly with visibility under one quarter mile. While
confidence on exact visibilities are low... expect some fog and
lower ceilings to develop around 10z and continue through early
morning. A few VCTS are possible for KLAR tomorrow but elsewhere
should remain VFR through the period.
&&
.FIRE WEATHER...
Issued at 227 AM MDT Sun May 20 2018
Despite the warmer and drier conditions, fire weather concerns will
remain low as ample rain amounts have occurred over the past several
days for many areas. One areas that missed out on rainfall was Carbon
County. However, they should remain in the upper 20 to low 30 percentiles
relative humidity wise this afternoon. A few higher terrain showers and
isolated weak thunderstorms will be possible this afternoon but overall
coverage will be low to zero elsewhere.
A few isolated showers/storm could again be possible Monday across the
Laramie Range and into the NE Panhandle. Coverage again is expected to
be low. Relative humidity values will fall near 20 percent but winds
should remain below critical thresholds at 15 to 20 mph from the southwest.
Overall long range forecast appears to remain just moist enough during the
afternoons to preclude high fire concerns at this time.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...CLH
LONG TERM...JSA/CLH
AVIATION...WFOCYS
FIRE WEATHER...JSA/CLH
Please see the 00Z aviation forecast discussion below.
&&
.AVIATION...
A complex of thunderstorms will continue to shift east and south of
the region, with most activity expected to remain to the east of our
TAF sites for the remainder of this evening. However, based on
current radar trends, we did mention VCTS at SAT and TSRA at SSF
through 01Z. The wind direction at SAT and SSF will be very
complicated due to MCV formation ongoing over southern Bexar county
and a wake low over Medina county. Will go with some gusty north
winds at SAT and SSF for the next few hours given winds will
primarily be influenced by the departing convection. Winds should
then generally trend to a more east to southeast direction through
late evening. Low clouds should also re-develop given recent rains
and some brief clearing of high clouds. We expect MVFR cigs around
06Z along I-35, with IFR clouds and fog developing closer to 09Z.
Slow improvement is then in store along I-35 tomorrow afternoon. At
DRT, MVFR should develop around 09Z and continue through the morning
hours. Improvement back to VFR is then expected by early afternoon.
&&
.PREV DISCUSSION... /ISSUED 602 PM CDT Sun May 20 2018/
UPDATE...
Made some adjustments to the PoP/Wx/QPF grids through 12Z tomorrow
based off evolution of radar trends and latest HRRR runs. This
remaining line of heavy rainfall should progress east southeast
producing rainfall rates of over an inch per hour but in western
areas, a well worked over atmosphere is likely preventing re-
development. Much farther west, convection is taking place over the
Mexican mountains but just about all hi-res models keep this activity
well west of the Rio Grande. Thus lowered PoPs substantially after
00Z in the west while exiting the current system mostly out of the
CWA by 03Z.
PREV DISCUSSION... /ISSUED 308 PM CDT Sun May 20 2018/
SHORT TERM (Tonight through Monday Night)...
Showers and thunderstorms continue as a slow moving outflow boundary
continues to move southward and provide lift for further cell
development. Currently, the boundary appears to be located south of
Del Rio, to San Antonio and extended northeast to just south of La
Grange. The majority of convection has been either confined to the
boundary or developed ahead of the boundary as is the case currently.
The most significant complex, located in Uvalde county as of 245PM,
is riding the aforementioned boundary as well as producing its own
healthy outflow, which is providing focused lifting along the
interaction point of both boundaries. Ahead of this complex a
gradually increasing PWAT environment (~1.6-1.8") exists as well as
convergent 850 mb flow and moisture flux. The hi-res suite has
largely whiffed on depicting this part of the line of convection
today and only the most recent runs of the HRRR (16-17Z) have begun
to resolve this feature. While still overdoing convection, it
continues this complex along the southward moving boundary, missing
San Antonio metro to the south, and progressing southeastward into
CRPs CWA. This is largely due to a weakening low level flow regime as
well as diminishing instability availability, yet the high moisture
content and continued convergent orientation to the low level flow
regime should keep this as a heavy rainfall concern throughout the
rest of its passage through the southern CWA.
Farther east, stronger southerly 850 mb flow will continue and shift
to develop a more eastward component into the evening hours which
will continue strong convergence along the outflow oriented more
southwest to northeast in that area. Additionally, even higher PWATs
of over 2" east of the I-35 corridor will continue the possibility of
heavy rainfall well into the evening. While heavily leaning on the
recent HRRR runs for short term guidance, the ensemble precip
accumulation zeroes in on Lee/Fayette counties and eastward seeing
the most rainfall through 12Z tomorrow morning. Looking at radar
trends as of 3PM, this would seem reasonable as further cell
development continues to the southeast and trains over this area.
Ensemble guidance shows 4-5 inches for a storm total in these areas
which could produce some minor flooding concerns but should stay
below FFG values in those areas thankfully.
As a result, believe a further 1-3 inches are possible for a line
from Eagle Pass to San Antonio to Giddings with isolated amounts of
5+ inches still possible for Lee/Fayette counties as well as parts of
Dimmitt, Zavala, Frio, Medina, and Atascosa counties. North of the
boundary, the majority of the rainfall should be completed for the
evening. Some CAMs are continuing to produce convection on the
Mexican side of the Rio Grande but the well worked over environment
from the boundary passage should keep any additional development at
bay. Thus, overnight, have PoPs gradually decreasing through
midnight, and decreasing substantially after midnight with only low
end chance PoPs for the extreme southeast zones.
Also PoPs for Monday will depend on destabilization efficiency and
most likely be isolated, thus have kept in a broad brush 30 PoP with
a slight preference to the Rio Grande Plains.
LONG TERM (Tuesday through Sunday)...
A much more benign pattern is in store for the extended as a ridge
axis builds over the central United States and blocks energy from
impacting the region from a broad low out west. With afternoon highs
in the upper 80s and 90s and dewpoints in the 60s throughout the
week, can`t rule out isolated afternoon showers and thunderstorm
possibilities but chances should be pretty low as the ridge continues
to build and dry out our air mass. Only included slight chance or
sub-20 percent chances throughout the week beyond Monday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 70 88 70 90 70 / 30 20 10 10 0
Austin Bergstrom Intl Airport 70 89 69 90 68 / 30 20 10 20 0
New Braunfels Muni Airport 70 88 69 89 68 / 50 30 10 10 -
Burnet Muni Airport 67 86 67 88 68 / 20 20 10 10 0
Del Rio Intl Airport 71 88 71 89 72 / 30 30 20 10 -
Georgetown Muni Airport 68 88 68 89 69 / 20 20 10 10 0
Hondo Muni Airport 70 88 69 90 69 / 20 30 10 10 -
San Marcos Muni Airport 69 88 69 90 69 / 50 20 10 10 0
La Grange - Fayette Regional 71 89 71 90 70 / 50 20 10 20 -
San Antonio Intl Airport 71 88 71 89 71 / 50 30 10 10 -
Stinson Muni Airport 72 89 71 90 71 / 60 30 10 10 -
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Mesoscale/Aviation...24
Synoptic/Grids...09
Public Service/Data Collection...YB
Area Forecast Discussion
National Weather Service Lincoln IL
1104 PM CDT Sun May 20 2018
.UPDATE...
Issued at 830 PM CDT Sun May 20 2018
Complex of thunderstorms over central Missouri continues to track
east and northeast towards our area. Instability not that great to
its east early this evening so we expect the storms to weaken some
before they get into our area towards Midnight. The storms are
associated with a weak upper level wave over west central Missouri
and that feature will continue to track northeast towards the
lower Great Lakes on Monday. Current forecast seems to have a good
handle on the timing of the storms late this evening through the
early morning hours. May need to fine tune the arrival time over
our far west and southwest counties, but overall, the current
forecast is in good shape. Not planning on any ZFP update at this
time.
The upper level wave and the associated showers and storms should
push off to our east by afternoon but models were slow to get the
cool front to our east until tomorrow night. As a result, there is
the chance for storms to redevelop tomorrow afternoon, especially
along and east of I-55. However, if clouds and rain linger longer
than expected, any redevelopment may take place just to our east
and southeast late tomorrow afternoon.
With a weak frontal boundary stretched from west to east across
the heart of the forecast this evening, quite a contrast in
temperatures and dew points with temperatures over our far
northern counties in the low 60s while along the I-70 corridor,
temperatures were near 80 degrees. Coolest readings across the
north tonight as the front will not make any significant track
to the north overnight, with rather mild readings expected across
the south where the mercury may not get much lower than the upper
60s. Highs Monday afternoon will range from the middle 70s north
of I-74 to the middle 80s over southeast Illinois.
&&
.SHORT TERM...(This evening through Monday)
ISSUED AT 302 PM CDT Sun May 20 2018
Many mesoscale features making for a very complicated forecast in
the short term, made worse by the lack of clarity between models.
The 500mb shortwave to the west that was progged to slowly move
out over the region is slowing further still, limiting the upper
support for the MCS remnants as they drift into the region. The
same lack of support seen overnight as well as in the day time
today may continue...suppressing severe threat somewhat. A lack of
steep lapse rates in the midlevels as well as a lack of deep shear
are so far dulling convection. CAPEs even limited throughout the
day from blow off cloud cover/remnant precip from western MCS
activity. Short term models are a mess, with the HRRR providing
some of the better solutions to work with. Forecast is vague at
best, trying to follow the trend in the HRRR of a break in the
activity this evening, then the remnants of a developing MCS to
the west moving in after 06z tonight. Lack of support should keep
the thunderstorms in check, but how recharged the atmosphere is
over Central IL is a bit of a question mark considering the
moisture and warm air advection, coupled with limited daytime
heating. BUFKit soundings do not look promising, and NAMNest,
admittedly off at initiation, is marginal at best. Have several
complicating factors in place with a weak sfc low, mesoscale
boundaries, and moisture convergence...but little dynamics to
initiate or sustain. Hopefully 00Z runs will provide more detail. With
the potential for the precip not materializing before midnight,
have added a patchy fog mention as the sfc dwpts in the 60s
already, and continuity from the last couple nights.
Tomorrow is another conflict with ending precip early, but chances
continue throughout the day with boundaries and plenty of buoyant
air in place. Very vague mention of potentially higher pops to the
north as the wind fields back up a passage of a weak low to the
north and northeast in the afternoon hours.
.LONG TERM...(Monday night through Sunday)
ISSUED AT 302 PM CDT Sun May 20 2018
Once the weak upper low clears out of the region tomorrow night,
500mb ridge starts to develop over the Plains, keeping the axis
just to the east of the Miss River Valley. This results in a dry
period at least through midweek until the next low dives into a
more northerly stream aloft, skirting the US/CAN border and
driving precip slowly into the region to wrap up the week. With
the ridge axis just to the west, weak NW flow does not cut off the
region from some moderate WAA from the desert SW. Midlevels
maintain access to the warmer temps of the swrn CONUS through the
end of the forecast, keeping temps about 10F above seasonal norms.
Very low pops work into the forecast about Thursday as that open
upper wave drifts into the Upper Midwest. Higher pops in place
with approach Friday through Saturday.
&&
.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1100 PM CDT Sun May 20 2018
Timing of showers and thunderstorms into the forecast area over
the next several hours and affect on cigs and vsbys into the
early morning hours the main forecast concerns this period.
Complex of weakening showers and thunderstorms was tracking
northeast into west central Illinois and should continue to move
across the remainder of the forecast area into the early morning
hours. As the upper wave that is responsible for the precipitation
moves across the area on Monday, showers and low (mainly MVFR)
cigs and vsbys will prevail through the morning with a gradual
improvement in cigs and vsbys expected for the afternoon to low
VFR early in the afternoon, with cigs lifting or even scattering
out towards 00z.
Surface winds will be mostly easterly tonight at 8 to 13 kts with
winds veering into a southerly direction by Monday afternoon with
speeds in the 10 to 15 kt range.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Smith
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...Smith
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
901 PM CDT Sun May 20 2018
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
The day`s diurnal storms are still going tonight. At this point,
they seem to be feeding mostly off the energy from outflow
boundaries rather than diurnal heating. Some of these storms may
have some small hail in them and may be producing some gusty winds
at times, but they should all remain below strong and severe storm
criteria. This activity will persist for another few hours before
completely dissipating around midnight or so. Conditions will
remain muggy and overnight temps will fally only to the upper 60s.
Mainly just updated the pops for this forecast update. /10/
Prior discussion below:
Tonight and Monday: Convection has been slow to materialize this
afternoon, but has finally initialized in the high 0-3km theta-e
zone from northeast LA into north central MS. The HRRR is
indicating that convection will continue to fire in this zone as
it spreads to the southeast with time. Though overall convection
will begin winding down during the evening, intersecting cold pool
boundaries will keep keep some convection continuing until around
midnight.
Weak mid level ridge will continue to break down during this time
period as cold core system over the northeastern Gulf of Mexico
is absorbed by more prominent westerlies to the immediate west of
the forecast area. The resulting cool air aloft will lead to more
in the way of scattered convection Monday given expected
temps/dewpoints. Weak mid and and deep layer shear vectors
suggest slow storm movements which will lead to very localized
heavy rainfall as PWs rise to above 1.75 inches. Despite the cool
air aloft, deeper moisture looks to prevent lapse rates from
becoming too steep, keeping strong/severe potential down a
bit./26/
Monday night through Saturday: The primary focus will be for a
summer like pattern with diurnal convection through the period.
There will be some ridging followed by some troughiness with weak
flow over the forecast area through the period. Pwats will range
from 1.4 to around 1.7 inches combined with daytime heating for
scattered daytime convection, which will be followed by isolated
convection during the evening as we lose the heat of the day.
This will change some as we start to get a better inflow of moisture
for Friday night through Saturday. With all this instability we
could have some microburst potential with an isolated severe storm
with gusty winds that can not be ruled out for each day along with
some brief downpours. Where the convection develops will depend of
leftover outflow boundaries from the previous day combined with weak
disturbances that will track across the region during the heat of
the day. Daily highs will be in the upper 80s to the lower 90s.
Heat indices will creep up to the upper 90s to around 100 on
Wednesday and Thursday. Nightly lows will be around the middle 60s
to the lower 70s./17/
&&
.AVIATION...
00Z TAF discussion:
Isold to Sct TSRA wl cont in vcty of most TAF sites through 03Z
before dissipating. Away from TSRA activity, VFR conds wl cont
until after 09Z when MVFR cigs and vsbys wl be psbl over east MS.
Cigs should improve to VFR areawide by 16Z. Sct to numerous TSRA
activity is expected to develop Mon aftn and last into the
evening. /22/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 68 87 68 90 / 37 59 22 42
Meridian 67 86 66 89 / 43 47 23 42
Vicksburg 69 89 68 91 / 34 64 23 45
Hattiesburg 68 87 67 90 / 32 55 26 52
Natchez 68 89 68 90 / 26 64 24 42
Greenville 70 89 70 89 / 43 65 22 43
Greenwood 69 88 68 90 / 43 56 19 49
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1056 PM EDT Sun May 20 2018
.UPDATE...
Issued at 1056 PM EDT SUN MAY 20 2018
The last of the storms that threatened from the north have
dissipated. Expect a quiet rest of the night, with partly cloudy
to mostly clear skies and areas of fog forming once again. The
fog should be more confined to the deeper river valleys compared
to last night. Forecast lows in the low to mid 60s look on target
and have only made a few adjustments based on the latest trends
in observations. Updates have been sent.
UPDATE Issued at 805 PM EDT SUN MAY 20 2018
Eastern Kentucky remains precipitation-free at the moment, as
short wave ridging has kept most convection at bay. A cluster of
storms is moving in from around the Ohio River, but these should
dissipate as they move into a less favorable environment across
the Bluegrass, which recent runs of the HRRR supports. Will
maintain the dry forecast through the night, and have mainly
freshened up the diurnal temperature drop off through this
evening. Will assess temperatures and fog a bit later. Updates
will be out shortly.
&&
.SHORT TERM...(This evening through Monday night)
Issued at 407 PM EDT SUN MAY 20 2018
Have seen a few showers pop this afternoon across the Big Sandy
region as a summertime airmass interacts with the higher terrain.
Temperatures in the mid 80s combined with dewpoints in the mid-upper
60s have created enough instability, that when combined with even
subtle lift, is enough for a pulse type storm to quickly develop.
Have actually seen dewpoints mix down into the upper 50s to lower
60s in the Lake Cumberland region nearer the core of relatively
drier air. Additional showers and isolated storms will remain
possible this afternoon, mainly in far eastern Kentucky where
southwesterly low level winds will provide greater upslope lift.
None of these will last long given the lack of available shear for
storm-scale organization.
Upper ridging currently over much of the southeastern U.S. and
extending into eastern Kentucky will gradually flatten tonight into
Monday as a shortwave trough migrates out of the Great Plains and
toward the Great Lakes. Dry conditions should largely prevail
locally through tonight and early Monday as an overnight complex of
storms remains confined to mainly north of the Ohio River. Valley
fog will be a good bet given crossover temperatures in the mid 60s
or so, but this should be less prevalent than last night due to an
overall lack of rain today.
Rain chances will ramp back up Monday afternoon as upper heights
eventually fall southeast of the above mentioned upper impulse. A
surface low will follow a similar track, surging precipitable water
values back to the 1.5 inch range. A frontal boundary initially near
the lower Ohio Valley will lift north through the morning and
afternoon, but any height falls aloft will be enough to spark
scattered to numerous showers/storms throughout the afternoon given
abundant instability. Anemic deep layer shear will keep strong to
severe storms at bay, other than perhaps a few cell mergers and
resultant brief upticks in updraft strength. These could produce
isolated small hail and wind gusts to 40 mph or so. Rain chances
will continue into the evening and overnight as a cool front slides
southeast toward the lower Ohio Valley.
.LONG TERM...(Tuesday through Sunday)
Issued at 300 PM EDT SUN MAY 20 2018
In the extended we can expect chances for showers and storms
Tuesday through late Wednesday. The best chances for rain during
this initial round of precipitation will be Tuesday afternoon and
evening. The rain should then taper off very quickly late Tuesday
night into early Wednesday morning. The last few showers or storms
should be out of the area by late Wednesday afternoon. After that,
we should see a period of dry weather from Wednesday evening
through early Friday morning, as a ridge of high pressure
temporarily takes hold across the region. A series of low pressure
systems are then forecast to bring periods of showers and storms
back to eastern Kentucky from Friday through Saturday night.
Temperatures during the period will likely be above normal, with
daily highs in the low to mid 80s and nightly lows in the low to
mid 60s expected.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
ISSUED AT 805 PM EDT SUN MAY 20 2018
Expect VFR conditions to prevail through the majority of the
period. Fog will likely form again late tonight, but expect the
IFR or worse conditions to be more confined to the deeper river
valleys, given the lower crossover temperatures as well as lack of
precipitation coverage through the day. Have included a 2 to 4
hour window of MVFR fog at the TAF sites, generally between 09 and
13z. Storm coverage looks to be better on Monday, and will
include VCTS at all sites during the afternoon hours. Winds will
remain at around 5 kts or less through the period.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GEOGERIAN
SHORT TERM...GUSEMAN
LONG TERM...AR
AVIATION...GEOGERIAN
Area Forecast Discussion
National Weather Service Marquette MI
752 PM EDT Sun May 20 2018
.SHORT TERM...(This evening through Monday)
Issued at 346 PM EDT SUN MAY 20 2018
Water vapor imagery and RAP analysis show a split flow pattern over
the western CONUS with a wnw confluent flow aloft into the Upper
Great Lakes region and sfc high pressure dominating. Lake breezes
have kept conditions cooler this afternoon near the Great Lakes
shores (40s and lower 50s) while much farther inland under sunny
skies and deeper mixing temps have risen in the upper 60s/lower 70s
along the WI border.
Winds will diminish to calm/near calm tonight, setting the stage for
a chilly night as dry air mass (precipitable water as low as one-
quarter to one-third inch) aids radiational cooling potential. Will
continue to favored the lowest of available guidance, bias corrected
mos guidance and bias corrected CMC global which is normally a
superior performer on radiational cooling nights. Traditional
interior cold spots should fall into the upper 20s/around 30F.
Sfc high pressure will remain in control continuing the dry
conditions on Monday. With the center of the high moving east
southeast gradient winds will increase near 10 mph with gusts
reaching over 15 mph at times over the west half of the fcst area.
The winds combined with high temps reaching into the lower 70s and
minimum RHs lowering into the 20 to 25 percent range will contribute
to elevated fire weather concerns especially over the west half.
Shortwave lifting ne from the Central Plains could bring some mid-
high clouds into s central portions in the afternoon, although any
showers associated with this system should remain south on Monday.
.LONG TERM...(Monday night through Sunday)
Issued at 356 PM EDT SUN MAY 20 2018
The main weather concern through the middle of the week will be
elevated wildfire potential, especially inland from the Great Lakes
where dewpoints in the afternoon hours will drop into the 20s. A
thermal trough is expected to develop across the interior during the
afternoon hours as temperatures heat up into the 70s and lower 80s
across the interior and lake breezes dominate the low-level wind
fields. The development of this thermal trough inland of the Great
Lakes will be reinforced on Wednesday as a weakening, dry backdoor
cold front drops south. Compressional along this trough axis should
allow for another day with well-above normal temperatures on
Wednesday.
Thursday through early parts of the Memorial Day Weekend will
become much more active weather wise with increasing chances for
showers and thunderstorms. As result temperatures will be a bit more
difficult to forecast based on how cloud cover and precipitation
evolve. With the main shortwave associated with this pattern change
lifting northeast from the southwest into the northern Plains, this
track will favor good moisture transport this far north as the Gulf
of Mexico is progged to be open for days in advance. As this axis of
low to mid-level moisture gets into Upper Michigan on Thursday, we
will start to see chance for showers and storms increase across the
west half of Upper Michigan. With this convection well removed from
the main upper-level forcing, thinking the primary area of concern
will be along lake breeze boundaries and the far eastern edge of the
warm front, associated with a developing surface low in the northern
Plains. On Friday and Saturday, the surface low will track towards
the Arrowhead of Minnesota and then drop south across Wisconsin.
This should allow the warm front to gradually lift north across
Upper Michigan and allow for better chances for showers and
thunderstorms on Friday in the vicinity of the frontal boundary, as
well as lake breeze boundaries. On Saturday, as the low pressure
system tracks just to our south, this will allow for additional
chances for showers and thunderstorms. Towards the tail end of the
weekend, as the surface low continues to track south of the area we
should see a cool down, but lingering showers are not out of the
question. Right now it is difficult to say whether or not we will
see any strong to severe storms during this time period. However,
with a weakening, yet still impressive elevated mixed layer progged
to track across the region on Friday, this would favor a better
environment for stronger updrafts. Based on the current instability
axis and deep-layer shear profiles it appears that at least pesky
pulse-type thunderstorms won`t be out of the question. Overall, if
you have outdoor activities planned towards the end of the work week
and the Memorial Day Weekend you`ll definitely want to keep an eye
on the weather. Even if we don`t see stronger storms, remember
lightning is always a hazard with thunderstorms.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 750 PM EDT SUN MAY 20 2018
With high pressure and a very dry air mass dominating, VFR
conditions will prevail at KIWD/KCMX/KSAW through this forecast
period.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 346 PM EDT SUN MAY 20 2018
Sfc high pres ridge over the Upper Lakes has led to winds under 15kt
today across most of Lake Superior this afternoon. However, with the
ridge axis setting up across southern Lake Superior, sw winds over
the n central part of the lake could gust as high as 20kt late this
afternoon. High pres will then remain over the Great Lakes region
into Tue, resulting in winds mostly under 15kt. Although a cold
front will drop s across Lake Superior Tue night/Wed morning, it
will be weak, and winds will likely remain mostly under 15kt thru
Wed and into Thu.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Voss
LONG TERM...Ritzman
AVIATION...JLB
MARINE...Voss
Area Forecast Discussion
National Weather Service Nashville TN
847 PM CDT Sun May 20 2018
.DISCUSSION...
Another magical evening at the Weather Service.
Skies were mostly sunny with only isolated storms in the Mid-State
at 4 pm, then *POOF*, between 5 pm and 6 pm, thunderstorms popped
up all over the place between Clarksville, Dickson, Springfield,
Nashville and Gallatin. A few storms became severe, with damaging
winds and quarter size hail. Localized flooding was also reported.
This makes the second day in a row with that sort of *POOF*
convection in our northwest and north- central areas. Our late
afternoon LI of
-6 and -7 these last few days certainly has not been lacking in
potential, that`s for sure. and, guess what? the GFS pegs the same
general area with late afternoon LI`s of -5 to -7 late tomorrow
afternoon. So, maybe we can go for Round 3?
We should continue to see convection exhibit an evening slow down
over the next several hours. However, the HRRR keeps convective
potential running overnight across our western sections, so
believe our chance PoPs for the late night hours is certainly
warranted.
The most widespread wind damage this evening seems to have been
confined mainly to southwestern Davidson County, just southwest of
Nashville, in the Belle Meade, Green Hills and Bellevue areas.
Numerous trees were blown down, some onto houses, some onto cars
and some onto powerlines.
&&
.AVIATION...
00Z TAF DISCUSSION.
BNA/MQY/CKV/CSV...Thunderstorm complex is currently affecting the
Nashville Metro & Clarksville areas and this is reflected in the
first period of the TAF`s. Expect things to subside within the
next couple of hours. Do not expect widespread radiation fog
overnight due to a mid-level cloud deck, and also there was very
little fog reported last night. Very little air mass change is
expected during the next 24 hrs., so have included PROB30 remarks
for scattered afternoon convection again Monday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 69 86 67 86 68 / 30 50 20 40 20
Clarksville 67 83 66 84 65 / 60 50 40 40 10
Crossville 63 79 62 78 62 / 20 60 30 50 20
Columbia 66 84 65 84 65 / 30 50 20 40 20
Lawrenceburg 65 83 64 83 64 / 30 50 20 50 20
Waverly 68 83 67 85 67 / 60 50 30 40 10
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION......19
AVIATION........08
Area Forecast Discussion
National Weather Service Paducah KY
852 PM CDT Sun May 20 2018
.UPDATE...
Issued at 852 PM CDT Sun May 20 2018
Similar to last night we are expecting the convective line over
central Missouri to weaken as it approaches southeast Missouri and
southern Illinois. However, we don`t expect the line to completely
dissipate. Given the steep mid-level lapse rates over much of our
region, as revealed in LAPS soundings this evening, we should see
an increase in showers and thunderstorms over southeast Missouri
late this evening, and then farther east overnight. There will be
a weakening trend in coverage and intensity as the convection
spreads east across the region into the overnight hours. Plenty of
clouds and a persistent south wind should be enough to prevent
any significant fog formation tonight.
UPDATE Issued at 708 PM CDT Sun May 20 2018
Updated aviation discussion.
&&
.SHORT TERM...(Tonight through Tuesday night)
Issued at 312 PM CDT Sun May 20 2018
Main convective line moving through southern Illinois and the delta
region of west Kentucky being supported by 2500-5000 j2/kg2 LAPS
surface based CAPE stretching from the Mississippi River near New
Madrid, then arcing northeast into northwest Kentucky south of
KEHR and KOWB at 20z. Updraft/cold pool flow balance is episodic
with parts of the line seeing gust front extension ahead of the
line.
Cleared a few counties from Severe Thunderstorm Watch behind the
line of thunderstorms. There will be a few hours of boundary
layer stabilization before the flow returns southerly across the
area, priming the pump for later tonight into Monday over western
sections of southeast Missouri and southwest Illinois.
Although there is some timing issues for the resumption of new
showers and thunderstorms behind the current line of convection,
both the RAP and CMC model guidance suggest new convection will
fire back further west into Missouri and slowly work east back
into our area overnight and during the day on Monday. Channeled
vorticity in the southwest flow aloft will help to maintain
periodic lines of showers and thunderstorms from Monday night into
Tuesday, with the main activity shifting east with the front.
.LONG TERM...(Wednesday through Sunday)
Issued at 312 PM CDT Sun May 20 2018
Fairly high confidence of an unseasonably warm pattern Wednesday
through Friday with little if any precipitation coverage most of the
time. A nearly stationary mid/upper level high pressure ridge will
be the main weather influence through the lower and mid MS River
Valley through that time frame, with little low level
forcing/triggers. Expect daily highs well into the 80s each
afternoon. Temps will cool back into the 60s at night.
As we head into next weekend, a system over the northern Gulf of
Mexico is expected to drift slowly north into the southern Gulf
Coast states. At the same time, a mid level trof and associated weak
surface front should be working east/southeast toward the Ms River
and lower OH river Valleys. This would lead to increasing
shower/thunderstorm chances on Saturday into Sunday, especially
during the heat of the day. Conditions should also remain quite warm
and humid through the weekend. It will be interesting to see how
well, if any, the two systems can merge into one deep elongated trof
by that time.
&&
.AVIATION...
Issued at 708 PM CDT Sun May 20 2018
The stabilization of the atmosphere due to diminishing shower and
tstm activity will yield VFR cigs across the region into the
overnight hours. However, short-lived MVFR cigs are expected to be
associated directly with scattered shower/tstm activity that will
eventually pop up again during the 00Z TAF period. Best guess is
that this scattered activity may occur mainly late in the night/
early Sun morning north of the OH River, and in the late afternoon
mainly east of the MS River. Winds outside of tstms will be light
and variable overnight, picking up to less than 10 kts out of the
south-southwest after daybreak. Winds just off the surface will
lessen the likelihood of significant fog formation.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
UPDATE...DRS
SHORT TERM...Smith
LONG TERM...GM
AVIATION...DB
Area Forecast Discussion
National Weather Service Pueblo CO
329 PM MDT Sun May 20 2018
.SHORT TERM...(This evening through Monday)
Issued at 251 PM MDT Sun May 20 2018
Upper disturbance moving through the 4 corners region is helping to
spark thunderstorms across the mountains this afternoon. As these
encounter sufficient low level moisture which has penetrated
westward into the valleys due to deep upslope flow from last night,
they have been tapping around 500 to a little under 1000 j/kg of
CAPE. This has allowed a few to strengthen as they hit these
pockets of higher instability. However, shear has been the limiting
factor today and this has kept storms more on the pulsey side of
things. Thus not anticipating much in the way of a severe threat.
But could see some small hail, local wind gusts to 40 mph and brief
heavy rainfall. Will have to monitor the burn scars closely,
particularly the Hayden Pass burn scar, where there has been more
sun today to destabilize the atmosphere.
Meanwhile, persistent low clouds have remained banked up along the I-
25 corridor much of the day and expect this will continue into the
mid-late afternoon. This has delayed heating, resulting in a more
stable atmosphere across the plains. As storms develop and move
eastward, suspect they will decrease in intensity as they encounter
this cooler airmass. The exception to this will be along the Raton
Mesa region where latest HRRR runs continue to indicate the
possibility of a thunderstorm developing and moving eastward through
the evening hours. This could be forced by a developing low level
jet, so can`t discount it and have spread some isolated pops across
Las Animas and Baca counties for now.
Elsewhere, expect convection to decrease diurnally with pops
diminishing quickly towards midnight. Should be another relatively
cool night across the area, though with increasing southwest flow
aloft, do not think we will see a repeat of widespread stratus
redevelopment across the southeast plains. -KT
.LONG TERM...(Monday night through Sunday)
Issued at 251 PM MDT Sun May 20 2018
Upper level low remains over the swrn U.S. Mon night into Tues,
with rather deep sly flow ahead of the system bringing a modest
amount of moisture northward into CO through the period. As a
result, expected isolated to scattered -shra/-tsra over the
region Mon night/Tue/Tue night, as weak upper level energy
occasionally ejects from the swrn low. 0-6km wind shear remains on
the low side (30 kts or less) through the period, as wind profiles
are rather unidirectional and speeds rather light, so threat of
severe storms looks rather low. Best chance for a stronger storm
would be along the NM border Tue afternoon/evening, where
instability/shear will be greatest. Max temps Tue should drift
upward another couple degf versus Mon as sly flow continues.
Swrn low then lifts northward through the Great Basin into the nrn
Rockies Wed/Thu, with upper level ridging developing over the
western U.S. as deep low develops offshore of the Pacific Coast.
As pattern shifts, drier swly flow develops across srn CO,
shunting most moisture eastward both days. Still some low level
moisture/instability near the KS border ahead of the surface
trough/dryline, so will keep some low pops in place each afternoon
to account for this possibility. Could see some marginal critical
fire weather conditions in a few spots both days as well, though
given mix of fuels greening up and at least spotty precip, tough
to pinpoint any particular area at this point. Max temps will push
back into the 80s/90s at many lower elevations, as heights rise
and mixing deepens.
Upper wave then crests the ridge and drops into the Midwest from
Fri into next weekend, pushing a cold front south through CO Fri,
followed by surface high pressure dropping south through the
central plains. Should see at least a modest upturn in convective
chances increase through the period over the eastern mountains
and adjacent plains, as low level upslope winds develop and
transport moisture back westward into the area.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 251 PM MDT Sun May 20 2018
Residual MVFR cigs along the lower eastern slopes of the southeast
mountains will continue to lift and break late this afternoon as
evening showers and thunderstorms roll off the mountains.
Thunderstorms should decrease in intensity as they encounter cooler
more stable air east of the mountains, and have restricted
precipitation chances to a VCSH group for COS this evening to
reflect this. KALS will have a window for thunderstorms this
afternoon with erratic gusts to around 35-40 kts near thunderstorms.
Thunderstorms will diminish over the mountains after 02-03z with
clearing skies expected overnight. Increasing southwest flow aloft
should help prevent the widespread formation of stratus across the
plains so have kept TAFs VFR for now. -KT
&&
.PUB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...KT
LONG TERM...PETERSEN
AVIATION...KT
Area Forecast Discussion
National Weather Service Springfield MO
706 PM CDT Sun May 20 2018
.SHORT TERM...(This evening through Monday)
Issued at 158 PM CDT Sun May 20 2018
In a bit of a lull right now with morning convection having
stabilized conditions. Convection is firing along a distinct
outflow boundary over northeast AR. The boundary becomes less
distinct has farther to west into NW AR. Another shortwave that
extends form south central KS into central OK will shift northeast
with lift increasing over the area, especially the western cwfa
late this afternoon and this early this evening. MLCAPE values off
the HRRR reach 1000-1500 j/kg with around 30kts 0-6km bulk shear
which would support multicell or possibly supercells with a large
hail and damaging wind risk for a few hours before the wave lifts
off to the northeast. Questions still consist of how long
convection will linger into the eastern counties overnight. Have
raised rain chances using a blend of cams/short term guidance.
In general, Monday looks more quiet with weak mid level height
rises.
.LONG TERM...(Monday Night through Sunday)
Issued at 158 PM CDT Sun May 20 2018
Mid level shortwave ridging and height rises are expected through
midweek as an upstream closed upper low moves into the western
CONUS. Can`t rule out some diurnally driven isolated pulse
convection through midweek, but coverage looks limited. The
western upper trough opens up and lifts well northwest of the
area. Late in the week a blocking upper level pattern develops
with a slow moving upper low moving north out of the Gulf of
Mexico and another moving east from the western CONUS. Chaotic
upper level flow doesn`t generate much confidence in the forecast.
May see an uptick in diurnal convection late in the period, but
no major systems are expected.
&&
.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 637 PM CDT Sun May 20 2018
Pilots can expect variable flight conditions tonight into Monday.
Storms will push east of the terminal sites this evening. A front
will move across the region late tonight and Monday morning
bringing a wind shift and lowering ceilings. Expect MVFR to
potentially IFR ceilings spreading west to east late tonight and
Monday morning. Improving flight conditions can be expected by
Monday afternoon.
&&
.SGF WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&
$$
SHORT TERM...DSA
LONG TERM...DSA
AVIATION...Foster
Area Forecast Discussion
National Weather Service Shreveport LA
929 PM CDT Sun May 20 2018
.UPDATE...
Shifted likely-definite POPs to across portions of central LA
tonight, as that is where the lingering showers /with intermittent
thunderstorms/ have been occurring. Light scattered showers were
noted nearing deep east TX and across southeast OK, but all of the
precipitation activity has been waning as expected. Otherwise,
forecast is largely on track with slight/slim chances of isolated
showers developing overnight. Tweaked the surface temperatures to
reflect current trends and subsequently adjusted the dewpoint
temperatures and relative humidity values.
&&
PREV DISCUSSION... /issued 632 PM CDT Sun May 20 2018/
AVIATION...
Isolated to scattered -SHRA/-TSRA have intermittently affected the
western terminals, whilst nearing the remainder terminals early
this evening. This has caused winds to have a variable wind
direction, as well as briefly experiencing gusts when a storm
directly affects a terminal. This makes for a complicated TAF
forecast but have tried to best time when the convection will
begin and end. For the most part, should see the precipitation
taper off later this evening but will of course amend as
necessary. Otherwise, CIGS should remain VFR throughout the TAF
cycle, though there could be a brief period of MVFR CIGS and VFR-
MVFR fog at a few sites if the winds are able to drop off. Any
lingering low clouds/fog should dissipate by Monday mid-morning
and isolated -SHRA/-TSRA could make a return by the afternoon.
Felt confident enough to insert a VCTS at all but keld and kmlu
tomorrow afternoon at this time.
PREV DISCUSSION... /issued 354 PM CDT Sun May 20 2018/
SHORT TERM.../Tonight through Monday Night/
The Ewd moving outflow bndry has slowed but continues to be
reinforced by convection this afternoon, and has reached E of a
JDD/TYR/JSO/DKR line as of 2030Z. Additional sct convection has
fired ahead of this bndry over extreme Ern TX along an axis of
theta-e advection within a moderately unstable air mass
characteristic of SBCapes of 1500-2000+ J/kg, just ahead of an upper
trough axis extending from Cntrl KS S into the Srn Plains. The
ongoing convection should begin to wind down this evening with the
loss of heating, but did retain low chance pops this evening
areawide, with mid chance pops over lower E TX per the consensus
amongst the HREF and HRRR in maintaining convection a little
longer over these areas. Am reluctant to take pops out completely
after 06Z, thus did keep slight chance pops going overnight as the
tail end of the upper trough/shear axis becomes removed from the
primary shortwave over Wrn NE as it lifts NE into the Midwest
late.
This shear axis will linger over SW AR/N LA/extreme Ern TX Monday,
and will again be the focus for mainly afternoon sct convection,
especially over the Ern half of the region. Have raised pops to
mid and high chance, especially over Scntrl AR/N LA, with
additional development primarily tied to outflow interactions
within a moderately unstable but weakly sheared air mass. Did
trend max temps a little warmer than MOS given the fact that most
areas this afternoon trended a little warmer than guidance. The
convection should again gradually diminish during the evening
Monday with the loss of heating, and thus kept slight chance to
low chance pops going in the evening in VC of the shear axis. This
feature should again play a role in sct convection development Tuesday
as it become trapped beneath an amplifying dirty upper ridge over
the Srn Plains and Mid MS Valley.
15
LONG TERM.../Tuesday through Sunday/
A broad upper lvl ridge pattern with moisture in weak easterly flow
and diurnal nature of convection brought on by instability through
the workweek. Positioning of ridge will determine day by day
location of scattered, versus more isold convection, which will tend
to develop along peripheries of diffuse ridge center. Weak wind
shears will limit svr potential for storms, although gusty winds and
locally heavy rainfall will remain a possibility. An upper lvl
trough may try to organize over the central Gulf and drift nwd
towards the coast, which may enhance rainfall by the holiday wknd,
particularly if coupled by weak front which will attempt to move swd
towards the region. Increased overall cloud cover will bring aftn
temps back into upper 80s to around 90 on average, with overnight
lows expected to continue to prevail either side of 70 degrees.
Winds will remain mostly lgt and vrb for much of the week. /07/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 70 89 70 89 / 30 40 20 30
MLU 69 90 69 89 / 30 50 30 40
DEQ 65 87 66 89 / 50 30 20 20
TXK 68 88 68 87 / 40 30 20 30
ELD 67 90 67 89 / 30 50 30 30
TYR 67 89 70 88 / 20 20 10 30
GGG 67 89 69 89 / 20 20 10 30
LFK 68 90 68 89 / 30 20 10 30
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...None.
LA...None.
OK...None.
TX...None.
&&
$$
29/07/15
Area Forecast Discussion
National Weather Service Las Vegas NV
835 PM PDT Sun May 20 2018
.SYNOPSIS...A low pressure system will bring unsettled weather to
the region through Tuesday. Isolated to scattered showers and
thunderstorms will be possible for areas north of Interstate 40 on
Monday and Tuesday. Temperatures across the region will drop a
few degrees early next week. A warming trend is expected from mid
week into Memorial Day weekend.
&&
.UPDATE...Tight cyclonic circulation associated with an upper low
is presently over SW Oregon/NW California. The low is progged to
slide south into central California Monday. Some of the new 00z
guidance along with hourly rapid refresh output suggests that we may
see some light precipitation breakout around Las Vegas Monday
morning, between 8 am and 11 am. As instability increases the threat
transitions to thunderstorms after 11 am. Lower levels of the
atmosphere stay dry which means gusty winds will be the primary
concern around Las Vegas. Closer under the low over Inyo County
stronger storms could produce small hail. Updated to tweak POPs for
the rest of tonight and Monday.
&&
.AVIATION...For McCarran...Increasing clouds above 10kft are
expected through the night and on Monday, with overcast skies around
15kft by Monday morning. Winds on Monday will favor a south-
southeast direction with sustained winds up to 10 kts. There may be
light rain showers around the valley between 8 am and 11 am Monday
morning. Isolated thunderstorms, favoring the higher terrain along
the western foothills possible Monday afternoon and evening. Primary
concern at the terminal from thunderstorms will be gusty winds along
with varying wind directions.
For the rest of southern Nevada, northwest Arizona and southeast
California...Showers and a few thunderstorms are possible tonight
across Inyo County. West winds will increase overnight across
western San Bernardino County where wind gusts between 30-35 kts
will be possible. Scattered showers and thunderstorms are possible
across much of the area on Monday, with the best chances over San
Bernardino, Inyo, Esmeralda, Nye and Central Clark County...however
anticipate scattered precipitation coverage to be more widespread
and farther south than what we have seen the past few days.
&&
.SHORT TERM...Tonight through Tuesday.
Current IR and visible imagery indicates a band of cirrus moving
across southern NV and northwest arizona and another broken band of
cirrus pushing eastward over the Sierra crest. A clearing between
these cirrus decks has allowed a broader area of cumulus to develop
across Esmeralda and central Nye Counties along with the Spring
Mountains. Though moisture is limited, insolation should promote a
few showers with embedded thunderstorms possible. Per RAP guidance,
the best instability through the afternoon will be across the Sierra
and Esmeralda. Expect any convective activity that develops
quickly diminish around sunset.
Another round of unsettled weather is expected early this work week
as an upper low closes off across central California and slowly
tracks eastward across the Mojave Desert and southern Great Basin
Monday and Tuesday. As it does, mid and upper level moisture will
overspread the region. Moisture coupled with forcing will result
in precip chances mainly for areas north of Interstate 40.
Although guidance introduces marginal instability on Monday,
diurnal heating should be minimal due to a thick cirrus shield
in place. High-based showers will be favored over thunderstorms;
however, cannot rule out thunderstorms based on available
instability and associated dynamics. Clouds begin to break up more
on Tuesday as dry air works around the backside of the low. This
should allow more diurnal heating and higher a chance for
convection, especially along differential-heating boundaries. Dry
low levels will limit rain totals to a a few hundreths to half an
inch, outside of the Sierra where totals may be closer to an inch
precip. The only adjust made to the forecast was an increase to
PoPs across northwest AZ Tuesday afternoon as instability combined
with diurnal heating may lead to high chance of shower and
thunderstorm generation.
By late Tuesday the upper low will pull to the north and begin to
fill. A stable air mass will push in from the south and limit shower
activity to the far northern zones Tuesday night.
Temperatures will drop a handful of degrees Monday as a result of
limited mixing, cooling temperatures aloft, and abundant cloud
cover. Temperatures will warm slightly Tuesday with slightly less
cloud cover.
.LONG TERM...Wednesday through Sunday.
The weather pattern from the middle of the week into Memorial
Weekend is looking mostly dry for our region, but afternoon winds
could become gusty Saturday and Sunday due to an Eastern Pacific low
moving inland and lifting across northern California and northwest
Nevada. The medium range models are in fairly good agreement with
the synoptic pattern, though confidence decreases with the placement
of the upper low late in the weekend which would affect wind speeds
depending on how close the base of the system brushes it brushes our
region. The ECMWF is a little farther south and slower with it than
the GFS.
The only day where showers look possible enough to mention is
Wednesday over the southern Sierra behind the early week low
pressure system lifting away to the north. After that, a ridge
amplifies over a region ahead of the Eastern Pacific Low and
temperatures will climb each day and now highs near or in the triple
digits look likely across much of the the Mojave Desert Region
Friday through Sunday.
&&
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
procedures.
&&
$$
UPDATE...Pierce
SHORT TERM...Boothe
LONG TERM...Adair
AVIATION....Wolf
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