Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 06/25/20
Area Forecast Discussion
National Weather Service Bismarck ND
1013 PM CDT Wed Jun 24 2020
Issued at 1007 PM CDT Wed Jun 24 2020
Scattered thunderstorms continue across north central North Dakota
and will slowly move southeast overnight. Storms are producing
frequent lightning and gusty winds around 40 mph, but remain well
below severe limits. Lowered precipiation chances tomorrow with
this update as the last trends in guidance indicate less robust
thunderstorm develop along the front until the afternoon hours. By
then the front will be across east central ND and thunderstorms
will quickly move east and out of the area by the late evening.
UPDATE Issued at 623 PM CDT Wed Jun 24 2020
An isolated thunderstorm continues to trek slowly across central
ND this evening. A very weak and narrow band of low-level
convergence is likely supporting the development and maintenance
of this storm. Further northwest a complex of storms is riding
along the nose of a thermal ridge. This complex will impact
northern North Dakota through the evening hours and should slowly
dive south into the James River Valley overnight. Capping and the
time of day should limit the threat for severe storms, but gusty
winds and small hail can`t be ruled out with any storm this
evening and overnight.
.SHORT TERM...(This evening through Thursday)
Issued at 223 PM CDT Wed Jun 24 2020
This afternoon, low pressure and an associated cold front in
south central Saskatchewan is forecast to move east to Manitoba by
Thursday afternoon. The cold front will be the focus for
scattered thunderstorms tonight and Thursday.
The latest HRRR tracks a line of convection from the Sask/Mant
border south into northwest ND this evening and then southeast
from there into the Devils lake basin and the northern James
River Valley after midnight. This looks fairly reasonable. This
initial convection is not expected to be severe.
On Thursday, expectations are thunderstorms will redevelop
by mid afternoon along the cold front across eastern ND. While
deep-layer shear is not expected to be strong, decent CAPE of 2500
to 3500 will be available for strong updrafts. The are of concerns
will be the southern James river Valley in the mid to late
afternoon and the evening hours. Hail to Ping pong ball and wind
gusts to 60 mph would be possible.
.LONG TERM...(Thursday night through Wednesday)
Issued at 223 PM CDT Wed Jun 24 2020
The extended forecast will feature a more active thunderstorm
pattern, beginning Sunday, as a cold h500 upper low will become
the dominant feature across the northwest US with downstream
ridging over the western Great lakes into the central Plains.
This pattern would favor a moist flow into the northern plains
with southwest flow aloft, veering winds with height and short
wave energy to provide lift.
We do discount the 12Z GFS in the Tuesday-Wednesday time period
as it clearly has some convective feedback that causes the model
to generate an anomalous upper low over the Dakotas. We prefer
the European model projections which maintain the upper low over
the northwest US and southwest flown aloft.
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 623 PM CDT Wed Jun 24 2020
VFR at all TAF sites through the TAF period unless impacted by a
thunderstorm. Some isolated thunderstorms are possible tonight
across northern and portions of east central North Dakota and
could impact KXWA/KMOT/KJMS. A cold front will swing through the
state from west to east tomorrow and will be the focus for
scattered showers and thunderstorms. Every terminal has the
potential to see precipitation tomorrow, but due to the
uncertainty in coverage, little more than a vicinity mention was
added at this time.
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
648 PM CDT Wed Jun 24 2020
.DISCUSSION...Updated for latest aviation discussion below.
.AVIATION...Brownsville radar and surface observations indicate an
outflow boundary moving southward through the Rio Grande Valley.
As a result, winds have briefly shifted to the north-northeast at
MFE and HRL. Also, can`t rule out convection developing along the
boundary and will continue to the mention VCTS/TSRA through late
this evening. Activity diminishes late tonight before another
round of convection develops Thursday morning. Will add a PROB30
group for all aerodromes for MVFR conditions in TSRA mainly
.PREV DISCUSSION... /issued 311 PM CDT Wed Jun 24 2020/
SHORT TERM (Now through Thursday): A weak cold front continues to
slowly move across South Texas and is located just north of
Hebbronville and Falfurrias. With weakly unstable flow aloft and
little to no capping, convection has gradually increased ahead of
the boundary. Strong instability is noted in environmental
mesoanalysis data with MLCAPE on the order of 3000 to 3500 J/kg.
Shear remains fairly weak, but a few isolated severe storms will be
possible. The main threats will be damaging wind gusts, but large
hail of up to quarter-size will also be possible. High-resolution
CAMs, including the latest HRRR and the 12Z ARW, show very heavy
rainfall by this evening, with some clustering moving into the Rio
Grande Valley. With slow-moving storms and above-normal precipitable
water content, 2-inch per hour rainfall rates will be possible,
leading to localized flash flooding. In collaboration with the
Weather Prediction Center, they have expanded the marginal risk of
excessive rainfall across all of Deep South Texas for this evening.
Tonight, conditions should settle down with decreasing convection
overnight. The surface front is expected to lift northward on
Thursday, but models show a 500mb vort max moving northward and
onshore Thursday morning into the afternoon with another round of
showers and storms. Locally heavy rainfall will be possible again,
so have included such wording in the latest forecast grids. The
highest chance for rain will be along the coast and into the Lower
Rio Grande Valley.
Temperatures should be slightly below normal on Thursday with
expected increases in cloud cover and rain chances. Locations in the
Upper Valley and northern ranchlands may still reach the upper 90s
with most convection holding off until the afternoon.
LONG TERM (Friday through Wednesday): The wet and unsettled pattern
continues into Friday before the rain chances decrease and
temperatures rise this weekend and into early next week. At the
start of the long term period, Deep South Texas remains in a general
area of weakness between two ridges, with a broad inverted trough
cutting north across Mexico and into South Texas. Low level moisture
will continue to be transported into the region from Gulf with a
strong southerly-southeasterly flow on Friday. Precipitable water
values are expected to climb into the 2.00" to 2.30" on Friday. With
ample moisture in place, broad troughing and the passing of a vort
max will lead to increased rain chances on Friday. Model guidance is
now suggesting that rainfall amounts will be greater on Friday than
on Thursday. The latest WPC rainfall forecast calls for 0.25 to 1.0
inch of rain on Friday, but pockets of locally higher rainfall
amounts are likely as rain rates could climb in excess of 2 inches
per hour with any thunderstorms that develop. These thunderstorms
will likely be isolated to scattered in coverage, but with a weak
steering flow, slow moving storms could increase localized flooding
concerns. WPC has included all of Deep South Texas in a marginal
risk for excessive rain on Friday, as rainfall amounts could exceed
flash flood guidance.
Overall, forecast confidence in rainfall amounts is increasing.
However, uncertainty is increased slightly due to the arrival of
another, greater swath of the Saharan Air Layer (dust) on Friday.
This dust could have impacts that the models do not resolve well,
such as suppressing convection, or even enhancing it...thus the
Temperatures will be slightly cooler on Friday with the increased
convection and cloud cover, but will increase through the weekend
and into early next week. Heat indices are expected to reach 105-110
degrees Saturday afternoon and continue each afternoon through early
MARINE: Now through Thursday...Winds remain light as the
pressure gradient weakens ahead of the cold front. Seas have also
been subsiding to around 4 feet across the Gulf waters. Increasing
showers and thunderstorms are expected this afternoon and
evening, though, so dangerous winds and seas will be possible with
any stronger thunderstorms. Another round of thunderstorms will
be possible from the south and increasing Thursday morning and
afternoon. The gradient is also expected to increase, so a Small
Craft Advisory may be needed Thursday afternoon.
Friday through Monday...Marine conditions are expected to be
slightly adverse to hazardous through much of the long term
period. Small Craft Advisories may be needed on Friday as the
southeasterly winds strengthen and seas respond, however small
craft will need to exercise caution through the weekend and into
early next week for hazardous seas and moderate winds. Showers and
thunderstorms will be possible over the waters on Thursday and
.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL 77 88 79 89 / 40 60 50 50
BROWNSVILLE 78 89 78 90 / 50 60 50 50
HARLINGEN 76 90 76 89 / 50 60 50 60
MCALLEN 77 92 77 90 / 50 50 40 60
RIO GRANDE CITY 76 95 77 92 / 60 50 40 50
SOUTH PADRE ISLAND 80 85 82 86 / 40 60 50 50
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AREA FORECAST DISCUSSION
National Weather Service Hastings NE
638 PM CDT Wed Jun 24 2020
.SHORT TERM...(This evening through Thursday Night)
Issued at 350 PM CDT Wed Jun 24 2020
Tstm chcs/coverage main issue in the short term.
Rest of this Aftn and into Overnight: Current analysis shows pooling
moisture along a diffuse warm front running NW to SE from near
LBF to HYS. Greatest near-term risk, based on latest vis satellite
and comp radar, appears to be along I-70 from GLD to SLN. Another
area to watch will be near and N of LBF. Overall feeling is that
convection risk to GID CWA is pretty low. While CAPE/shear space
is supportive of svr (MLCAPE over 2000 J/kg and 40-50kt of deep
layer shear) over W/SW areas, there`s just not much to nudge
parcels along as there remains some displacement between most
active portion of cyclonic upper flow over upper MS Valley and
aforementioned instability axis. Also, motion vectors all are
generally NW to SE, so would need development to edge N from
central KS to northern KS to pose a risk, or for development w/in
CU field over the Sandhills. Latest couple HRRR runs show an iso
storm or two w/ the later scenario, but overall likelihood appears
low, so only 20-30 PoPs attm from around LXN-Beloit. Thus, svr
threat this eve is highly conditional and isolated.
Can`t completely rule out some iso elevated convection after
midnight given convergence w/ incr low level jet to 40- 45kt and
veering in the 06Z-12Z time frame. Nose points to areas near and S
of I-80. However, not much upper level support given subtle large
scale height rises at H5, and models actually indicate dry air
advection in the H7-H85 layer. Hi-res models don`t have any much
except near the far SE CWA, so only slgt chc PoPs near HJH.
Thu: Main story for Thu is hot/brzy. Warm front that remains from
tonight will rapidly shift N Thu AM as lee troughing deepens over
the High Plains. This will result in brzy winds. Shortwave
ridging/rising heights leads to pretty high confidence in dry
conditions for the daytime hrs. H85 temps will rise into the
23-27C range (highest W CWA), which should promote widespread 90s,
and perhaps even a run at triple digits at known "hot spots"
given ample sunshine. Deep mixing should keep Tds in check, and
along w/ brzy winds, it won`t feel terribly humid.
Thu night: Chc for rn/tstms along cold front. By Thu eve, a
positively tilted trough will extend from Desert SW to ND. An
associated SE moving cold front will extend from central SD to a low
pressure center near NW Sandhills 21Z Thu, with a diffuse trough/dry
line extending S from the low into SW Neb./E CO/W KS. Strong
diabatic heating and steep lapse rates in the presence of sfc conv
along aforementioned features should be enough to erode CIN and
spark tstms late Thu aftn, mainly N/W of the CWA. Question becomes
whether or not any of this activity will survive long enough to
move into CWA 00Z to 03Z? Models show a strengthening LLJ which
may help maintain organization, however, the front will be
outrunning the upper trough. Thus, activity will likely encounter
warmer mid level temps/incr CIN with SE extent and overall timing
is not ideal. This gives me doubt in widespread rn, but some
pockets of iso-scat tstms could hold together long enough to give
N/W portions of CWA at least some chc for rn. General evolution of
12Z HREF/18Z HRRR seems appropriate, which would place highest
chcs from ODX to LXN. Perhaps some of this could be strong w/
gusty winds and marginal hail, but agree w/ latest SPC Day 2
Outlook that greatest svr potential will be N/W of CWA, closer to
frontal position at peak heating.
.LONG TERM...(Friday through Wednesday)
Issued at 350 PM CDT Wed Jun 24 2020
Extended periods look very summer-like, w/ periodic tstm chcs, none
of which stand out as "likely", and warm/hot temps.
General overview: Models are converging on general solution in that
the Day 2 trough will shear out on Fri, w/ N energy rapidly lifting
towards Great Lakes, while SW energy gets stuck near Four Corners
region and washes out toward Sat. Whatever is left of this energy,
if anything, will then get absorbed/ejected in incr SW upper flow
ahead of deepening Pac NW trough on Sun. Models remain in good
agreement keeping the large scale trough over the Intermountain West
Sun-Mon, but then begin to diverge w/ timing and speed of eastward
Nearly every period in the extended has some sort of tstm chcs.
However, much like the last couple of weeks, think the official
forecast probably looks wetter than what it will be in reality as
we`ll be firmly within a summer pattern in which forcing is
nebulous, which results in hit and miss pcpn patterns. In theory,
the cold front that approaches Thu night and slowly moves thru CWA
on Fri could present somewhat better chcs for tstms, but again,
upper support is not great amidst neutral or slight height rises. If
something were to develop, it looks like S/SE areas would stand best
potential given model consensus of bndry position (though
confidence on this is not great). Moderate to strong instability
would argue for some svr potential, but shear immediately along
the bndry is not great (only 25-30kt on avg), so main threats
would be pulsey, marginally svr hail and iso downburst winds.
What exactly happens to this bndry remains uncertain, but in
general, looks like it could hang out just S of the area Sat, then
return N Sat night or Sun AM. As such, after briefly "cooler" temps
Fri-Sat, have temps warming well into 90s, and maybe some low 100s,
for Sun and Mon. Tds will be higher as well, but breezy S winds each
day should help offset some of the mugginess. Models ensembles
indicate slightly cooler and perhaps a bit more active by middle of
next week, but this will depend on progression of western trough,
which remains low confidence.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 627 PM CDT Wed Jun 24 2020
VFR conditions expected through the period with some passing
mid/high level clouds from convection to our west overnight...and
clear skies and wind gusts to near 25 KTS out of the south during
the afternoon hours Thursday.
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1050 PM EDT Wed Jun 24 2020
An upper level disturbance will continue to gradually lift over the
area today and Thursday, helping produce showers and thunderstorms.
Seasonable temperatures will be in store through Thursday before
drier air filters in Friday to allow for lower precipitation
chances. A noticeable uptick in temperatures occurs through the
weekend. Expect the same temperature trend and slightly wetter
conditions to enter the region early next week.
.NEAR TERM /THROUGH THURSDAY/...
As of 1030 PM EDT Wednesday: An MCV can be seen on area radar mosaic
over NW GA driving ENE toward the southern half of the FA. Mainly
just light rain within the MCV to affect the FA overnight. The
heavier QPF on the NAM and RAP seem to be overdone due to convective
feedback. In any case, will keep a chc to low-end likely PoP in the
southern portions of the FA. Plenty of mid clouds to continue thru
the night, keeping temps mainly in the upper 60s to lower 70s
overnight. Min temperatures will be around normal.
On Thursday, a stalled front will linger around the FA throughout
the day, while aloft, upper troughing will dig through the OH Valley
and slowly propagate eastward. Guidance continues to depict better
forcing with the upper feature moving through just past the fcst
period, but during the afternoon hours, with moisture in place,
support from s/w and lingering front will provide instability to
warrant the potential for another round of afternoon convection. Max
temperatures will fall just short of normal.
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 230 PM Wed: Thursday night the upper-level trough axis
moves off to our east as heights rise modestly ahead of shortwave
ridging centered over the upper Midwest. The ridge axis will stay
to our NW Friday afternoon during peak heating placing our area
in a weakly subsident regime. This will be evident by a fairly
pronounced 650-700mb warm nose which should cap most convection,
especially outside of the mountains. However, a well-mixed
boundary-layer combined with typical orographic forcing should
overcome the cap in at least a few locations over the mountains,
especially south and west. Therefore, slight chance to chance
PoPs over the Foothills and mountains prevail with the expectation
of at least a few showers and thunderstorms. Ample dry air aloft
would support a isolated damaging wind threat if convection can
fully tap into MUCAPE of 500-1000 J/kg, but limited CAPE in the
hail-growth layer suggests a negligible hail concern and shear
does not support organized convection. Model guidance is very
unenthusiastic. High temperatures will remain near normal.
The low-amplitude shortwave ridge axis will move across the
Appalachians Friday night into Saturday morning as a weak remnant
trough ejects out of the Lower Mississippi River Valley in response
to height falls across the Ohio River Valley. Weak vorticity
advection associated with the remnant trough is not expected to
overcome slightly worse lapse rates and even lower MUCAPE values
Saturday afternoon. Therefore, PoPs reflect slightly lower coverage
of showers and storms over the mountains. A frontal boundary draped
across the Rust Belt will be too far north to exert much influence
over the area outside of an increase in upper-level moisture which
will limit DCAPE values for any rogue storm that manages to develop.
High temperatures will again be near to slightly above normal.
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 200 PM Wednesday: During the beginning portion of the extended
forecast period, temperatures will be the topic of discussion as
most of the area should be slightly above climo for much of the
weekend. Shower and thunderstorm chances will be below climo
Saturday into Sunday as warmer air aloft settles in due to a flat
upper ridge, which will be the cause of this trend. If any
convection develops, most of what forms will stay confined to the
higher elevations and that is even a sparse forecast. On Sunday, the
upper ridge deepens as it develops over the Mississippi Valley,
while a strengthening upper trough begins to dive down into the
northeastern CONUS. An omega blocking pattern is evident in both the
GFS and ECWMF for the early part of next week. A frontal boundary
will likely form across the Ohio Valley and the Mid-Atlantic from
this pattern. Shortwave energy below the boundary, along with PWAT
values >1.50" for most of the area, should be enough of a spark to
allow for convection to form Monday and more widespread Tuesday as
the frontal boundary gradually sinks to the south, closer to the
cwa. Temperatures should remain around climo through Tuesday as well
before the front reaches the region during the middle part of next
week. A slight difference between the location and timing from the
two global models on the potential stalling from the front, but the
overall pattern should remain the same. With plentiful moisture and
the frontal boundary possibly becoming quasi-stationary during the
middle part of next week, a heavy rain threat and daily convection
could be in store for much of the area.
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: Convection has waned for the most part, but
additional SHRA expected to develop later this evening and patchy -
RA thru daybreak Thursday. A large cloud shield spreading across the
region will limit fog potential. Some MVFR and even IFR cigs will be
possible across northern GA that may spread to KAND. Confidence is
too low on whether these cigs will reach KGMU/KGSP. Generally 3500-
5000 ft clouds below a 10000-15000 ft deck tonight thru Thursday
morning. Guidance shows an early start to showers and tstms midday
Thursday, as a disturbance crosses the area. Winds will be mainly
out of the SW across the Piedmont, and NW at KAVL thru the period.
Outlook: Drier weather is expected Friday and Saturday, with mainly
isolated to scattered aftn/eve convection in the mountains. Low
clouds and fog will be possible around daybreak each morning,
especially in the mountain valleys. Otherwise expect VFR conditions.
03-09Z 09-15Z 15-21Z 21-00Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 88% High 98% High 100%
KAVL High 100% High 86% Med 78% High 100%
KHKY High 100% High 100% High 100% High 100%
KGMU High 100% High 85% High 100% High 100%
KAND High 100% High 90% High 98% High 100%
The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1002 PM EDT Wed Jun 24 2020
Upper level troughing will persist, providing unsettled weather
through Thursday evening. Deep layer ridging strengthens Friday,
keeping drier conditions in place into the weekend.
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
As of 1000 PM Wednesday...Current forecast remain in good shape.
No change to this update. Radar returns are showing rain showers
located over the SW section of our forecast area will gradually
move through, but most of the rain is expected to diminish
Prev dis...No major changes to the forecast
besides delaying the rain that is currently to the SW of the
forecast area. The latest HRRR and RAP is showing rain will move
into the area within the next hour or so, but diminishing as it
moves across the area. Models are showing a brief break from
the rain, before it start again after midnight.
Prev Dis..Westerly flow coupled with weak
subsidence has limited convective initiation this afternoon.
Given an area of higher CAPE values near the coast through the
next few hours, could still see some isolated showers or storms
through early evening and continued with a slight chance PoP
through dark. After midnight, axis of mid-level trough starts to
move east toward the eastern Carolinas with some decent
shortwave energy. This will kick off a few showers and possibly
a thunderstorm late tonight into Thursday morning. PoPs increase
to 30-40 percent after midnight. With scattered rain around,
rain cooled air will allow low temperatures to be slightly
cooler than recent morning, in the lower 70s for all areas.
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
As of 345 PM Wednesday...Weak shortwaves embedded in a deep
mid-level trough axis will move through the area during
Thursday. With a warm and moist environment in place, scattered
showers and some thunderstorms are possible. Timing is difficult
as the shorter range models show quite a spread in timing, with
some showing more precipitation during the morning, while other
show a more afternoon event. Most all of our area remains in a
Marginal Threat for severe weather tomorrow with strong gusty
winds being the main threat. The key will be the degree of
destabilization should morning precipitation occur. Regardless,
have continued with a 40-50 percent PoP for Thursday. Despite
cloud cover, highs should be in the low/mid 80s area-wide
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
As of 3 PM Wed...Bermuda High ridging in from the east and
inland troughing will persist through the long term period,
bringing generally seasonable conditions with day to day
variability dependent mainly on upper level synoptic trends.
Thursday...Convective activity wanes Thursday night and the
loss of daytime heating, and POPs end once the trough axis
slides offshore and heights aloft begin to rise late.
Friday and Saturday...H5 ridging builds over the area and strong
subsidence aloft keeps precip coverage well below normal.
Though a stray shower or two immediately along the sea breeze
can`t be ruled out either day, the chance is below mentionable
levels. Temps near to a couple of degrees above normal both days
with ample sunshine.
Sunday through Tuesday...Upper level low pressure will cut-off
from the background westerlies and drop over the Northeast, with
several weak shortwaves traversing the general troughing that
will extend over the Carolina Coast. Periods of unsettled
weather possible through early next week, with shower/storm
coverage not necessarily sticking to the typical diurnal trends,
depending on the timing of upper level features. Relatively
seasonable airmass prevails at the surface as Bermuda High
continues to ridge in the from east with troughing inland, and
daily temp trends will be primarily dependent on precip timing
and cloud cover.
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Short Term /through Tonight/...
As of 730 PM Wed...VFR conditions will dominate most of the TAF
period, outside of brief sub-VFR conditions due to showers and
thunderstorms. Chances of scattered showers and isolated
thunderstorms increase ahead of incoming shortwave mainly
between 0Z and 3Z with a brief sub- VFR. Afterward VFR
conditions are expected into the late morning hours, then there
can be MVFR conditions tomorrow afternoon, but confidence is
not high as models are not in good agreement as there be
additional showers and thunderstorms tomorrow afternoon. SW
winds 5kts or less overnight, then becoming 5-10kts tomorrow.
Long Term /Thursday Night through Monday/...
As of 315 PM Tue...VFR conditions prevail, with any lingering
scattered showers/storms Thursday evening the potential for
periods of flight restrictions. Friday through the weekend will
be drier with VFR expected.
Short Term /Tonight and Thursday/...
As of 1000 PM Wednesday...The latest buoy obs are showing
mostly SW 5-14 kts and seas 2-4 ft. Wind speeds at 15 knots or
less with seas 2-3 feet, with some long period swells over the
northern waters. Winds should become SW on all waters later
tonight with seas at 2-4 feet. Similar winds are expected for
Thursday, but seas may increase a bit to 3-5 feet.
Long Term /Thursday Night through Monday/...
As of 315 PM Wed...High pressure well offshore and inland
troughing will persist through the long term period bringing
persistent moderate southwesterly flow, typically a few kts
stronger each afternoon than overnight. 3 to 5 ft seas prevail
through the period as moderate SSW windswell mixes with small
medium period SE swell.
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
951 PM EDT Wed Jun 24 2020
Forecast on track this evening with little changes. Slight chance
to low-end chance POPs continue for most areas through the night as
isolated showers and storms remain possible due to the vicinity of
the frontal boundary. Past few runs of the HRRR continue to show
this as well. Will send out new zones due to the minor POP
adjustments that were made, which was mainly to increase the
central valley from slight chance POP to low-end chance POP.
00Z TAF DISCUSSION.
Current VFR conditions will give way to MVFR conditions overnight
at all terminals as additional moisture moves into the area. A
return to VFR conditions can be expected by tomorrow morning at
TYS and TRI and by mid afternoon at CHA. Don`t anticipate any fog
overnight due to increasing clouds.
/ISSUED 311 PM EDT Wed Jun 24 2020/
SHORT TERM (Tonight through Thursday)...
The short term forecast period consists of chances for showers and
thunderstorms with slightly below normal temperatures. Strong/severe
storms are currently not anticipated within the period.
Currently, a surface frontal boundary is located across southern
portions of the County Warning Area (CWA) with upper-level troughing
across the eastern U.S., generally north of TN/NC. The surface
frontal boundary has helped to provide forcing for showers with some
embedded thunder across extreme southern portions of the CWA and
into northern AL/GA. With the placement of the trough, the CWA is
within the right entrance region of a 50+ knot jet streak, which
will help to provide upper-level divergence. While the jet dynamics
further north help to provide 30+ kts of effective bulk shear, the
best instability is much further south, inhibiting chances for
severe convection. Chance PoPs were utilized through the afternoon
in the southern half of the CWA with this location of the frontal
boundary. Increased cloud cover looks to keep temperatures slightly
below normal with 80s in most locations being reasonable.
Heading into tonight, latest model guidance brings the frontal
boundary slightly further north, so slight and chance PoPs were
utilized with very isolated thunder chances due to a loss of diurnal
instability. Increasing cloud cover from the west will help to keep
temperatures somewhat moderated with 60s seeming reasonable given
the current setup. For Thursday, surface high pressure will help to
provide subsidence and suppress widespread PoP chances. However,
isentropic lift indicated by NAM data and steep low-level lapse
rates will work to produce isolated convection, mainly over higher
terrain and southern portions of the CWA. Temperatures similar to
today are expected.
LONG TERM (Thursday Night through Wednesday)...
The upper ridge that`s been dominating the weather pattern the past
several days will finally, completely, move out of the area Friday.
In it`s place a broad ridge will begin to build in from the west and
in response the front that`s been hanging around will lift out of
the area. A warming trend can be expected to wrap up the work week
with highs reaching back to near normal for this time of year on
Saturday. Under this ridging pattern diurnally driven showers and
thunderstorms can be expected in the afternoon as moisture continues
to be brought up from the Gulf of Mexico.
Over the weekend a shortwave is expected to zip across the Ohio
Valley and Tennessee Valley, which should bring an uptick in
precipitation chances and coverage of showers and thunderstorms that
do develop as the surface low and the front push through. Still not
super confident on how models are handling the Omega block next
week, especially with how poorly they`ve done with this initial
trough over the area. But there`s indications that a cut off low
will traverse back down from the northeast towards the area. Am
going to continue going slightly lower on PoPs than what the NBM
model guidance outputs for the end of the 7-day forecast as in these
situations it tends to overdo the precipitation chances.
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 67 83 68 86 69 / 40 30 30 50 20
Knoxville McGhee Tyson Airport, TN 66 82 65 87 68 / 30 20 10 30 20
Oak Ridge, TN 65 82 65 86 67 / 30 20 10 30 20
Tri Cities Airport, TN 62 80 61 84 65 / 20 20 10 20 10
Area Forecast Discussion
National Weather Service Las Vegas NV
843 PM PDT Wed Jun 24 2020
.SYNOPSIS...Hot, above average temperatures are expected to continue
through the remainder of the week and going into the weekend.
Isolated showers and thunderstorms possible this afternoon over the
Sierra, expanding to portions of the southern Great Basin on
Thursday. The end of the weekend into the start of the next work
week, a potent trough will bring a drop in temperatures and gusty
.UPDATE...No update necessary for the rest of tonight or
Thursday. Similar to yesterday, we observed only a few thunderstorms
develop over Inyo and Esmeralda County. More impressive storms were
again to the north across western/northern Nevada closer in proximity
to shortwave trough. That shortwave trough is progged to shift
southeast across central Nevada during peak heating Thursday
afternoon. With just a few degrees of cooling aloft tomorrow the
steepening lapse rates will generate a more unstable air mass for
greater coverage in thunderstorms. Concern with storms tomorrow will
be gusty winds as early afternoon forecast soundings at Bishop and
Tonopah both indicate invert-v profiles. Of course, some locally
heavy rain and hail will occur with more impressive updrafts.
.SHORT TERM...Today through Saturday.
Above average temperatures, warm overnight lows and breezy
afternoons continue this week as the ridge of high pressure over the
Baja continues. Daytime heating has resulted in a few diurnal
thunderstorms across north and central Nevada as well as portions of
the northern Sierra. The HRRR indicated the formation of a few cells
over our portion of the southern Sierra in Inyo County today.
Watching a few radar returns come to fruition over Inyo County this
afternoon - particularly just south of Bishop - though these returns
are without lightning strikes for the time being. The chance of
isolated thunderstorms along portions of the Sierra as well as
Esmeralda County lasts through the remainder of the afternoon and
into the evening hours.
This week, we have mentioned the potential for a trough to drop down
and potentially hinder our heat-causing area of high pressure. With
each model run, this trough has weakened, which is now forecast to
be a shortwave area of low pressure. This disturbance will pass
through the Desert Southwest Thursday, which will elevate afternoon
breezes and drop temperatures by a couple of degrees. The primary
impact of this disturbance, though, will be the arrival of a
relatively moist weak cold front. This cold front will materialize
in the form of isolated showers and thunderstorms again Thursday
afternoon over portions of the southern Sierra and the southern
Great Basin. Highest chances will be through the afternoon and early
evening, stretching across much of Inyo, Esmeralda, Nye and Lincoln
counties, though slight chances reach as far south as the higher
elevations of Clark and Mohave counties as well. Not much is
expected in the way of measurable rainfall, with forecast rain
totals less than a tenth of an inch.
Friday, skies will clear. The shortwave low pressure system will
push eastward out of our area, allowing ridging to meander in from
the Pacific. This increase in heights will maintain above-average
temperatures over the region going into the weekend with Saturday
shaping up to be the hottest day of the week at 6-8 degrees above
.LONG TERM...Sunday through next Wednesday.
As previously advertised, we are expecting a fairly potent trough to
drop down from the Pacific Northwest this weekend. Ensembles
continue to indicate that uncertainty lies in both timing and the
magnitude of this trough. That said, though details remain
uncertain, we have high confidence that this trough is stronger than
what is seasonally expected for this time of the year. As a result,
the gusty southwest winds with speeds 40-45 MPH on Sunday, coupled
with relative humidity values in the single-digits have warranted a
Fire Weather Watch. This watch is in effect from early Sunday
morning through late Sunday night areawide, lasting through Monday
for portions of Mohave County. A Fire Weather Watch means that
conditions are expected to be favorable for rapid wildfire starts.
Outdoor activities such as burning or fireworks may provide
additional sources of fire ignition and are not advised when near
dry brush. Though the Fire Weather Watch only encompasses portions
of Mohave County on Monday, gusts will remain elevated areawide;
they simply are not forecast to achieve "critical" speeds elsewhere.
Along with enhanced winds, this trough will drop temperatures fairly
drastically, going from effectively 6-8 degrees ABOVE average on
Saturday to 6-8 degrees BELOW average on Monday. Afternoon high
temperatures for the desert valleys including Las Vegas are forecast
to drop to the low-to-mid 90s Monday and Tuesday. The speed and exit
timing of this trough remain uncertain, though ensemble model
temperatures and upper-level heights indicate the return of a ridge
of high pressure by mid-week.
.AVIATION...For McCarran...East to northeast winds 5 to 10 knots are
expected through much of the day. A shift to a more southerly
direction is possible in the afternoon, with a few gusts as high as
20 knots possible through sunset. Winds might remain southerly all
day Thursday, or there could be a brief period of easterly winds
during the day. No operationally significant clouds expected.
For the rest of southern Nevada, northwest Arizona and southeast
California...Winds under 20 knots are expected for most of the
region through Thursday. Possible exceptions will be the usual push
of west to southwest winds into the Barstow area late in the
afternoons, and spotty thunderstorm outflow winds from the Sierra
crest across the southern Great Basin in the afternoons. Aside from
the isolated thunderstorms mentioned above, no operationally
significant clouds are expected.
.SPOTTER INFORMATION STATEMENT...Spotters are encouraged to report
any significant weather or impacts according to standard operating
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