Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 07/29/20
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
640 PM CDT Tue Jul 28 2020
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...Diminishing winds and convective cloud debris will
prevail for the overnight hours. Tomorrow, another round of
showers and thunderstorms may affect the aerodromes with winds at
the surface becoming moderate. Overall, VFR will prevail through
the next 24 hours.
&&
.PREV DISCUSSION... /issued 407 PM CDT Tue Jul 28 2020/
SHORT TERM (Now through Wednesday Night): The 12Z BRO sounding is
still quite moist and unstable with a PWAT of 2.35 inches and an
MUCAPE of 3288 J/KG. The latest HRRR run indicates that a sea breeze
boundary will the push the sct conv steadily westward clearing
through Zapata Co. around 02z. The HRRR then wants to reform some
isold coastal conv after 08z with the 12Z NAM showing some more sct
conv firing inland Wed afternoon.
Currently the KBRO radar is showing the afternoon sea breeze conv
moving into Jim Hogg/Zapata Counties. Expect this conv to persist on
for a few more hours as the sea breeze pushes west. Considering the
saturated conditions in place over the Deep South TX and RGV areas,
will maintain the FFA as is until 4 am Wed and will see if it needs
to be extended/expanded throughout the overnight hours.
Short term NAM/GFS and ECMWF maintains the conv chcs for one more
day and then start trending them down Wed Night into Thurs as 500 mb
ridging builds over TX and an inverted trough axis over the region
shifts westwards.
Temps should be on the increase as the cld cover and conv chcs
diminish over the region.
LONG TERM (Thursday through Tuesday): The subtropical ridge tries
to strengthen across the lower Texas coast on Thursday, with
slightly drier air, potentially cutting off rain chances finally
for Deep South Texas. Unfortunately, a 500mb trough deepens across
the eastern half of the CONUS, enhancing the weakness along the
coast and brings unstable weather back through the weekend. With
the lack of abundant moisture, this may lead to more sea breeze
initiated rain chances and less coverage. This may also keep
temperatures near to slightly below normal through the period. The
mid level trough axis swings east of the coast on Sunday and high
pressure builds in from the west, drying things out more for next
week.
MARINE (Now through Wednesday Night): Surface ridging over the
lower TX coastline will maintain a fairly weak PGF over the area. So
expect low to moderate SE winds to continue with moderate seas. No
SCA conditions expected through Wed Night.
Thursday through Tuesday: High pressure slowly retreats eastward
as low pressure deepens across the eastern CONUS into Friday,
keeping a weak coastal trough across the lower Texas coast. High
pressure regains control Sunday into Tuesday. Overall, the
pressure gradient may stay relatively weak, keeping favorable
marine conditions in place with light to moderate onshore flow.
The bay may build to a moderate chop during afternoon hours.
&&
.PRELIMINARY POINT TEMPS/POPS...
BAYVIEW/PORT ISABEL 77 89 78 90 / 50 40 20 10
BROWNSVILLE 77 89 78 91 / 50 40 20 10
HARLINGEN 75 90 77 92 / 40 40 20 10
MCALLEN 76 88 78 92 / 40 40 10 10
RIO GRANDE CITY 75 93 77 95 / 40 40 10 10
SOUTH PADRE ISLAND 79 85 81 86 / 50 40 20 10
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...Flash Flood Watch until 10 PM CDT this evening for TXZ248-
252>257-353.
GM...None.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
Area Forecast Discussion
National Weather Service Duluth MN
953 PM CDT Tue Jul 28 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 244 PM CDT Tue Jul 28 2020
A cold front will move south through the forecast area from Canada
this afternoon. The front is being aided by upper level short wave
energy drifting through the region and some low level
frontogenesis. This combination will lead to some scattered
showers over the Arrowhead and into northwest Wisconsin. Not
expecting any thunder as thermodynamic profiles do not support
the mention.
After frontal passage, high pressure settles overhead tonight.
With a mainly clear sky, expect some fog to form, especially in
the typical low lying areas. This fog should erode fairly quickly
after sunrise as it should not be too deep. Temps should be near
normal.
The high remains in control Wednesday and Wednesday night. A weak
northwest flow aloft will keep seasonable temps in play.
.LONG TERM...(Thursday through Tuesday)
Issued at 244 PM CDT Tue Jul 28 2020
The surface high pressure is nearby through Friday. There is a
small chance of some light rain showers in the afternoon over the
northwestern corner of Koochiching County as a frontal boundary
approaches from south central Canada.
This lead frontal boundary merges with a cold front following
quickly behind it Friday night. The cold front moves slowly
through the region Saturday into Saturday evening. There are
some timing differences amongst the global models, along with
their QPF signals. Regardless, have some pops to cover the frontal
passage. Thunderstorms are possible per the model thermodynamic
profiles. No severe storms are expected however.
High pressure returns for Sunday and Monday.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 646 PM CDT Tue Jul 28 2020
The main aviation hazard is the potential for fog overnight
tonight. High pressure will settle into the region, leading to
calm to light winds and mostly clear skies. This will allow for
ideal radiational cooling conditions and cause areas of fog to
develop. Short-range models are still all over the place on how
low visibilities may drop, and the HRRR suggests no fog
altogether. Anything that forms will likely be patchy with
a generally dry low-level airmass. For now, I opted for
prevailing MVFR for a few hours between 08 and 13Z. However,
conditions may be variable with VFR for most of the night and a
few occurrences of MVFR or possibly IFR visibilities for brief
periods. Otherwise, VFR conditions expected with high pressure in
place through the period.
&&
.MARINE...
Issued at 952 PM CDT Tue Jul 28 2020
Quiet conditions expected for the next 48 hours with high pressure
in place. Light and variable winds around 5 knots through
Wednesday night. Winds will become northeasterly Thursday, which
may increase wind speeds to around 10 knots near the head of the
lake.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 54 78 56 80 / 0 0 0 0
INL 53 76 53 82 / 0 0 0 0
BRD 55 80 56 82 / 0 0 0 0
HYR 53 78 53 81 / 0 0 0 0
ASX 56 80 55 81 / 0 0 0 0
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
SHORT TERM...GSF
LONG TERM...GSF
AVIATION...JDS
MARINE...JDS
Area Forecast Discussion
National Weather Service Goodland KS
511 PM MDT Tue Jul 28 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 330 PM MDT Tue Jul 28 2020
Overview: Small amplitude shortwave energy (situated over southern
Idaho and western Wyoming this afternoon) will progress slowly E
toward the lee of the WY/CO Front Range tonight, then ESE-SE into
the Central Plains Wed-Wed night -- on the northeast periphery of
an amplifying ridge over the Desert Southwest and Intermountain
West.
Through Tonight: With (1) small amplitude waves /DPVA/ anticipated
to remain upstream of the region, (2) low-level forcing confined
to weak (10-15 kt) southeasterly upslope flow, and (3) a
marginally unstable (100-500 J/kg mlcape) weakly capped (25-50
J/kg mlcin) airmass characterized by moist-adiabatic (5.5 C/km)
mid-level lapse rates, 10-15C H85 dewpoints, and surface
temperatures in the 80s -- in-situ convection is not anticipated
this afternoon. Diurnal convection currently developing along the
CO Front Range will progress slowly east (via 10-15 kt WSW
steering flow) toward Eastern CO this evening (00-06Z).. however..
weak forcing, an unfavorable downstream airmass, and poor diurnal
timing (i.e. by the time ongoing convection approaches western
Yuma/Kit Carson counties) suggest that said activity is likely to
weaken/dissipate with eastern extent this evening. Simulated
reflectivity forecasts via the latest runs of the HRRR and NAM
NEST support such a scenario -- indicating that ongoing convection
will not progress into Yuma/Kit Carson counties until the 01-03Z
time-frame -- and that activity will rapidly weaken thereafter,
dissipating invof the CO/KS border by ~05Z.
Wed-Wed night: As flow aloft veers to the WNW-NW on the northeast
periphery of the amplifying ridge -- small amplitude waves will
progress ESE-SE from the WY/CO Front Range into the Central Plains
Wed afternoon -- while unimpeded insolation (highs approaching
90F), a continued moist low-level airmass (H85 Td`s 12-15C).. and
steepening mid-level lapse rates (7.0-7.5 C/km).. are anticipated
to yield stronger diurnal destabilization (relatively speaking).
Simulated reflectivity forecasts via the HRRR and NAM NEST suggest
that convection will (1) develop over and (2) propagate downstream
into the Tri-State area Wed aft/eve (both of which appear
reasonable, given the pattern) -- mainly in the 20-03Z time frame.
A few instances of damaging winds and/or marginally severe hail
are possible in association with the strongest/deepest updrafts.
.LONG TERM...(Thursday through Tuesday)
Issued at 208 PM MDT Tue Jul 28 2020
For the extended period the models are showing an upper-level ridge
extending from the southern Plains over the Rockies. Thunderstorms
may develop downstream associated with a shortwave trough riding
down the ridge over the Tri-State area, only caveat is how far east
this shortwave trough manages to get with the NAM slightly quicker
than the GFS. With the presence of a stationary front near the
Kansas/Colorado border and a surface low coming off the Front Range,
I feel there is still the potential for measurable rainfall during
afternoon/evening hours on Thursday no matter the placement of the
trough. Into Friday the trough will begin to move off to the east,
while the upper level ridge begins to dominate over the area. The
amount of moisture on Friday is still forecast to be decently high
(in the 60`s) so if a surface low can move east off of the Front
Range there may be enough moisture present for some isolated storms,
confidence in this occurring as of right now is low.
The weekend and beginning of the work week, the trough looks to
continue its eastward movement towards the Great Lakes region, as
stable air associated with the surface ridge is firmly above the
region resulting in warm and dry weather for the region.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 508 PM MDT Tue Jul 28 2020
Low ceilings and fog may return once again overnight and early
Wednesday morning at both KGLD and KMCK. Air mass remains very
moist with low dew point depressions, and saturation likely as
temperatures cool. Wednesday afternoon, scattered thunderstorms
will develop across the region with brief impacts/reduced flight
categories/ possible at either terminal.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...VINCENT
LONG TERM...TT
AVIATION...024
Area Forecast Discussion
National Weather Service Grand Rapids MI
749 PM EDT Tue Jul 28 2020
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 251 PM EDT Tue Jul 28 2020
- Scattered showers and storms tonight into Wednesday
- Seasonable temperatures and dry through Saturday
&&
.DISCUSSION...(This evening through next Tuesday)
Issued at 251 PM EDT Tue Jul 28 2020
-- Scattered showers and storms tonight into Wednesday --
Low-level frontogenesis and strengthening winds above 850 mb are
occurring in Wisconsin where an upper level shortwave trough
rotating around the Ontario low is encroaching on Iowa ridging. The
boundary layer in southern Wisconsin to western Lower Michigan is
expected to be well mixed and increasingly unstable this evening as
elevated convection develops where moisture transport convergence
occurs on the nose of an 850-700 mb jet.
Convection-allowing model solutions have been pretty consistent in
depicting a west to east train of scattered cells crossing Lake
Michigan after 6 or 7 pm, moving quickly to the east-southeast into
the night as additional weaker convection develops along the rear of
the train. The vertical distribution of CAPE according to the HRRR
suggests the strongest updrafts will occur in +10 to -10 degree C
air, with updraft strength diminishing above that in colder layers.
This doesn`t favor the potential for hail, and even lightning could
be sparse in some cells. There is north/south disagreement down the
county level where exactly convection will set up, but really
anywhere between South Haven and Ludington has a chance. The initial
arrival of convection in West Michigan may be before too much
surface cooling occurs, allowing downdrafts in a nearly inverted-V,
900 J/kg DCAPE environment to easily reach the surface, mixing down
30-45 mph winds from above 850 mb. CAMs have been also showing
potential for narrow axes of 0.5 to 1 inch of rain where
showers/storms repeat. Some outlier solutions with more robust
convection and longer training are painting a swath of 3 inches in
SE Wisconsin or W Mich. But for agricultural purposes, most
locations will not see the amount of rain desired.
Scattered showers or an isolated storm may stick around in
southern/southeastern/central sections of the state on Wednesday as
the surface front slowly sinks southeast (supposedly) in
superposition with the entrance region of the upper jet streak
during solar heating.
-- Seasonable temperatures and dry through Saturday --
Probably wont hear too many complaints about the weather the next
several days as near-normal summer temperatures and fairly
comfortable humidity levels (dewpoints around 60) will be in place.
The next decent chance of rain looks to be Saturday night or Sunday
as a wave from the Southern Plains lifts northeast.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 741 PM EDT Tue Jul 28 2020
There is a band of showers and thunderstorms from offshore MKG
west into Wisconsin that will move across the TAF sites tonight.
They are weakening a bit as the lake works them over, but
lightning will still be possible with them along with wind gusts
to 40 mph.
&&
.MARINE...
Issued at 251 PM EDT Tue Jul 28 2020
Waves at the Ludington (glbuoys.glos.us/SPOT-0648) and Port Sheldon
buoys have been around 2 feet, with 3-4 feet reported at the beaches
this morning, so these are generally moderate risk swimming
conditions. Showers or storms crossing the lake this evening may
produce winds 30 to 35 knots. Low to moderate risk swimming
conditions are expected tomorrow with winds more from the north,
with the relatively higher waves affecting beaches south of Holland.
Will have to watch for upwelling of cold water at the shore the next
few days as north to northeast winds drive water below the surface
toward the west (Ekman spiral). The water temperatures at the Port
Sheldon buoy are in the 70s down to 36 ft depth, and in the 50s
below 49 ft depth, so it will be curious to see how big of an effect
the upwelling will have on the beach water temperatures.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...None.
&&
$$
SYNOPSIS...CAS
DISCUSSION...CAS
AVIATION...04
MARINE...CAS
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
835 PM CDT Tue Jul 28 2020
.UPDATE...
Issued at 835 PM CDT Tue Jul 28 2020
Radar has been pretty lethargic across wrn and north central
Nebraska this evening and the HREF and RAP models suggest just
isolated thunderstorm coverage overnight. Storm activity will
likely occur along or near a warm front across srn SD and a weak
Pacific cold front advancing slowly through the Panhandle and
northeast Colorado.
A forecast update is in place for isolated showers and
thunderstorms the rest of tonight across wrn and ncntl Nebraska.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 330 PM CDT Tue Jul 28 2020
A shortwave moving off the Front Ranges will push into western
Nebraska by Tuesday evening. Thunderstorms are expected to develop
across the Panhandle by late afternoon (4pm-6pm CDT). Storms will
then move east into the eastern Panhandle and southwest Nebraska by
early to mid evening (6pm-9pm CDT). Storms are not expected to be
severe as instability remains fairly low across the region this
evening. Any storms that do develop could be briefly strong but will
quickly weaken as they continue to move eastward and encounter
increasingly more stable air. The main threats with these storms
will be small hail and brief gusty winds.
Storms are expected to continue into the overnight hours,
transitioning over to more stratiform rain showers by late evening
and early Wednesday morning. While rainfall totals through Wednesday
night have decreased slightly with this forecast issuance, totals
across the central Sandhills and into southwest Nebraska will still
be between 1 to 2 inches. With precipitable water values of over 1.5
combined with the possibility of slow moving thunderstorms, heavy
rainfall could lead to some localized flooding. Will hold off on any
flood headlines at this time, as overall QPF has taken a significant
downward trend.
In addition to heavy rainfall possible on Wednesday due to
stratiform rain, there is also a chance of severe weather Wednesday
night. These thunderstorms, supported by a developing low pressure
system moving off the Rockies into central Nebraska, will encounter
sufficient instability across much of the Panhandle and north
central Nebraska. Thunderstorms will develop across southwest South
Dakota late Wednesday afternoon and push southeast into northern
Nebraska with widespread strong to severe thunderstorms possible.
The main threats will be very large hail and strong winds.
There is some concern with how earlier thunderstorms and rain
showers during the day Wednesday will affect the overall environment
for later in the evening. If the environment gets worked over
sufficiently, the overall severe potential will be minimal.
.LONG TERM...(Thursday through Tuesday)
Issued at 330 PM CDT Tue Jul 28 2020
Isolated thunderstorm chances continue on Thursday and Friday
afternoon/evening. Confidence in severe storms and the resulting
environment is low. Will be continuing to monitor these daily
chances over the next couple days and assess severe potential as the
event gets closer.
Quieter weather will return for the weekend and into early next week
as strong upper level ridging occurs across the western US and
resulting surface high pressure builds across the central Plains.
Plenty of clouds and continued rainfall over the next week will keep
daytime high temperatures in the upper 70s to mid 80s. The warmest
temperatures will be across the eastern Panhandle and far southwest
Nebraska. Nighttime lows will also remain cooler in the mid 50s to
low 60s. While both daytime and nighttime temperatures will be
cooler than the past several weeks, these temperatures are in line
with normal temperatures for this time of year.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 629 PM CDT Tue Jul 28 2020
VFR conditions expected at the KLBF and KVTN terminals the next 24
hours. Scattered to broken high clouds tonight, with any isolated
showers or thunderstorms expected to remain west and north of the
terminals. On Wednesday, an upper level low pressure system will
approach the area, and bring increasing chances for showers and
thunderstorms mid to late afternoon. Included a mention at KVTN
after 21Z, with no mention at KLBF. TSRA expected to impact KLBF
beyond the TAF period.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CDC
SHORT TERM...Kulik
LONG TERM...Kulik
AVIATION...Roberg
Area Forecast Discussion
National Weather Service Marquette MI
747 PM EDT Tue Jul 28 2020
.SHORT TERM...(This evening through Wednesday)
Issued at 141 PM EDT TUE JUL 28 2020
Diurnal cumulus developed right on cue late this morning,
highlighting the lake breeze boundaries well. These diurnal cumulus
become more agitated through the early afternoon hours, with a few
showers and thunderstorms having already developed across the east
along the Lake Superior lake breeze and north-central Upper
Michigan. Eastern Upper Michigan will remain the focus for better
coverage of showers and a few isolated thunderstorms through this
evening. Across west and central parts of Upper Michigan a few
isolated diurnally driven showers will be possible as well. RAP
analysis and forecast soundings show very limited, skinny
instability to work with and deep-layer shear in excess of 40
knots. The imbalance between the dynamics and thermodynamics
should keep any thunderstorms more isolated as updrafts will
likely struggle and quickly become sheared off. Outside of a quick
burst of rain with any shower activity, some gusty winds may mix
down with any collapsing updrafts due to steeper low-level lapse
rates.
Tonight, diurnally driven convection gradually diminishes after
sunset. Winds become northwest as a cold front currently northwest
of the area moves through. This will favor onshore flow tonight for
many lakeshore communities along Lake Superior, helping keep
temperatures locally warmer (upper 50s) overnight. Elsewhere, lows
will fall into the low to mid 50s, with a pocket of mid/upper 40s
possible across the interior west. Maintained the dry forecast as
moisture looks very shallow along/behind the front with sharply
drier air aloft moving in overnight. Given the good mixing in
place today, opted to hold off on any fog mentions.
Wednesday will be a few degrees cooler behind the front. Lingering
shallow moisture will lead to increased cloud cover fairly
quickly in the morning as daytime heating increases and favors the
development of stratocu. During the afternoon, as increasingly
stable air works into western and northern Upper Michigan, north-
northwest flow at the surface will favor a gradually clearing
trend for those locations later in the day. Strong subsidence
overspreading the region as high pressure builds in should keep a
lid on any shower development as the subsidence inversion and
magnitude of dry air aloft increase throughout the day.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 311 PM EDT TUE JUL 28 2020
Not much change from the previous discussion as an upper level low
will continue to move eastward into Quebec by Thursday. As the low
progresses eastward, ridging over the western US will move towards
the Upper Great Lakes for late Thursday and Friday. The ridge will
retreat back towards the western US by the weekend as another trough
will approach the Upper Great Lakes by Saturday which will bring the
next chance of some precipitation for the U.P. Troughing will
continue into early next week with persistent north-northwest flow
with more seasonable temperatures. Outside of the rain chance
Saturday, not looking at many rain chances through the forecast
period.
Temperatures will be more seasonable for this time of year with
850mb temps mostly in the 9-11C range with highs mainly in the 70s
inland, cooler by Lake Superior with upper 60s to low 70s. Saturday
looks to be the warmest day of the period with 850mb temps reaching
15C resulting in highs reaching the low 80s in spots with upper 70s
to 80 elsewhere. Some CAA will fill in across the U.P for Sunday and
Monday with highs mostly in the mid to upper 60s to low 70s and some
lows potentially reaching the low 40s across the interior west.
Enjoy these seasonable temperatures through the forecast period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 746 PM EDT TUE JUL 28 2020
VFR conditions are expected at all terminals through the forecast
period. Isolate showers may be possible near KSAW this evening where
VCSH was included.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 326 PM EDT TUE JUL 28 2020
Cold front moving across the lake tonight will switch SW winds
around 20-25 knots to more NW winds to around 15 knots. Winds should
generally be under 15 knots for the rest of the forecast period. Fog
still not expected at this time.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...Ritzman
LONG TERM...JH
AVIATION...JLB
MARINE...JH
AREA FORECAST DISCUSSION
National Weather Service Morristown TN
928 PM EDT Tue Jul 28 2020
.UPDATE...
EVENING UPDATE.
&&
.DISCUSSION...
Current radar imagery indicates sparse coverage of a few showers
across the southern Appalchians. PW values currently range from
1.7-2.0 inches as an upper level trough passes to the north
across the Great Lakes. Due to his, have continued with slight
chance PoPs into the overnight hours. Expect most locations will
remain dry but cannot rule out a few isolated showers during the
overnight period. Patchy fog will also develop tonight in the
moist boundary layer with surface dewpoints in the low 70s. Any
fog should lift shortly after sunrise on Wednesday. Overnight lows
will range from the upper 60s to low 70s.
MA
&&
.AVIATION...
00Z TAF DISCUSSION.
VFR conditions currently across the terminals with a persistent
forecast over the next 24 hours. Showers/storms are already coming
to an end across the area with a rather limited coverage of
showers/storms currently. MVFR/IFR fog will be possible at TRI
late tonight into early Wednesday morning. Isolated to scattered
showers and storms will develop after 18-20z and continue through
the end of the TAF cycle.
MA
&&
.PREV DISCUSSION...
/ISSUED 319 PM EDT Tue Jul 28 2020/
SHORT TERM...(Tonight and Wednesday)...
Upper air water vapor imagery and RAP analysis places deep
cyclonic flow across much of the Ohio valley and northeast with
ridging extending across the southwest US and western Atlantic and
GoM. A subtle perturbation moving across the TN/KY state line has
been able to allow isolated to scatter SHRA/TSRA to develop and
move generally east early this afternoon. Cloud cover today has
generally kept conditions at least somewhat cooler than yesterday.
Temperatures as of 18Z range from 90 degrees across the southern
valley to the upper 70s across southwest Virginia and northeast
Tennessee where stable air from earlier convection and continuous
cloud cover has kept conditions cooler. SPC Mesoscale Analysis
still indicates CAPE values in excess of 2500-3000 j/kg across the
entire area today. Given the relative weak synoptic scale forcing
and lack of appreciable surface boundaries, believe coverage of
convection remains isolated to scattered at best. Not anticipating
a lot of strong convection but cannot rule this possibility out
especially given the degree of thermodynamics at play today.
Low level front to the north will remain stalled out across the Ohio
river overnight and into Wednesday. Coverage of showers and
thunderstorms will drop off overnight tonight as the weak upper
level perturbation moves east of the area. Cannot rule out an
isolated shower or two given the trough to the north, but height
rises and lack of lift should keep conditions mostly rain free
tonight. Lows will range from the upper 60s to mid 70s. Wednesday,
shortwave ridging develops as a shortwave deepens across the
Mississippi river valley. Increasing heights aloft and lack of any
surface boundaries should inhibit large coverage of showers and
thunderstorms. Will continue with chance PoPs for Wednesday but
would not be surprised to see extended periods of time tomorrow with
rain-free conditions. Highs will range from the mid 80s to near 90
degrees on Wednesday.
Diegan
LONG TERM...(Wednesday Night through Monday)...
The extended fcst period kicks on Wednesday evening amidst cyclonic
flow and thus troughing across the east/northeast CONUS with a
shortwave further southwest across the Ozarks, while somewhat
quasizonal flat ridging prevails across the southeast. At the
surface, an old frontal axis looks to be laid out across the TN
Valley and southern Appalachian regions, while high pressure
prevails northward atop the OH Valley. At fcst initialization,
convection along and south of the aforementioned frontal boundary
will slowly taper with loss of heating, as heights fall across East
TN and southwest VA/NC thanks to the approaching shortwave. This
shortwave will traverse the OH Valley on Thursday while a weak
surface cyclone prevails beneath, all the while enhancing llv flow
and thus moisture advection, per latest moisture flux charts. Given
this and the upper support provided by the shortwave, will favor
another day of convection on Thursday with pops in the categorical
range given vastly improved PWATS exceeding 2.0-2.5 inches
regionwide. This will further degrade antecedent soil conditions and
work to elevate the flooding threat, especially as the old frontal
axis remains stalled in the vicinity of northeast TN and southwest
VA.
Meanwhile another upper trough will deepen westward, promoting
further height falls into Friday across the TN Valley with deep swly
flow prevailing. Thus, will keep pops elevated, albeit slightly
lower as the initial shortwave will have exited east therefore
suggesting weaker upper support overall on Friday. Moving into
Saturday, convection will extend eastward along the old stationary
boundary which continues to linger, while additional convection
prevails along a prefrontal trough extending southward across KY/TN
into MS/AL from the parent surface wave beneath the upper trough
axis. This surface wave looks to advect northeast across the OH
Valley through Saturday, lifting the pesky boundary northward into
KY, thus completely uncovering East TN and southwest VA/NC in the
warm sector. Expecting convection to be a bit more organized on
Saturday given the presence of a deep early August longwave trough
(and initial shortwave) and resultant synoptic/mesoscale
environments, which all could lead to strong/severe thunderstorms.
Moving into Sunday, the initial shortwave will eject northeast as a
cold front enters the region (possibly stalling), albeit amidst a
more stable airmass behind the surface wave, thus will favor chance
pops regionwide. For Monday, starting to focus on a second
shortwave traversing the persistent H5 trough centered over the MS
Valley which should promote reintroduction of waa amidst a deeper
swly flow regime into the southern Appalachians. This combined with
approaching height falls from the west suggests the possibility of
slightly greater coverage on Monday, however to due to range and
model uncertainty, will cap pops at chance levels.
All said, the first 72 hours of the fcst will be the most active
with flooding threats elevated Thursday into Friday, while
strong/severe convection probs increase for Saturday. Temperatures
will remain near normal levels.
CDG
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 73 88 73 86 73 / 50 60 60 90 70
Knoxville McGhee Tyson Airport, TN 72 90 73 86 73 / 30 50 50 90 80
Oak Ridge, TN 72 90 72 85 71 / 40 50 50 90 80
Tri Cities Airport, TN 68 88 69 85 69 / 20 40 40 80 70
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$