Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/13/20
Area Forecast Discussion
National Weather Service La Crosse WI
1100 PM CDT Wed Aug 12 2020
.SHORT TERM...(This evening through Thursday)
Issued at 245 PM CDT Wed Aug 12 2020
Current observations show a well formed cold pool across much of
Minnesota from earlier convection. GOES water vapor showing
moderate shortwave trough energy over central MN with another
smaller scale spin further south, now lifting into eastern MN,
both associated with the morning/early afternoon storms. There is
still an instability axis running from western IA into North
Dakota per SPC meso-a with the eastern edge near I-35. RAP
analysis of the low-level moisture transport convergence at 18Z is
above the cold pool and fairly weak into central MN. Quite dry
lower tropospheric conditions exist over WI...with some 700-850 mb
dewpoint depressions of 20C.
With the shortwave trough lifting east of instability and into
drier stable air, would expect continued downward trend to weather
as it shifts east this afternoon. Shortwave ridge building should
dominate with RAP showing low-level moisture convergence lifting
northward toward northern MN. This is where more convective
activity is expected this evening and tonight, which could
propagate southeast toward instability based on today`s activity
/and Corfidi vectors for Thursday/ and end up affecting western WI
into sern MN Thursday. With instability gradient shifting to Miss
river by morning, little bumps of lift could cause storms. While
the nose of the moisture transport shifts into nrn MN, the
eastern edge is still isentropically upgliding along I-35
overnight. Will continue the small storm chances in the
northwestern forecast area, roughly KEAU-KMCW, late tonight and
Thursday.
.LONG TERM...(Thursday night through Wednesday)
Issued at 245 PM CDT Wed Aug 12 2020
Thursday Night through Saturday...
With large scale ridging developing downstream of the trough over
the Pacific Northwest and western Canada, instability will build
east over the area through Friday with little tangible signal for
storms. Have continued the rain chances in northcentral WI through
parts of northeast Iowa until cold frontal passage Friday night.
Model guidance is in better consensus now with weekend cold front
timing and it continues to signal after midnight Friday night
through midday Saturday as the main passage time across the area.
This does not favor severe storms or heavier rainfall as it is in
the diurnal minimum. With instability growing to the northwest
Friday, healthy storms are expected over northern MN and these
will shift southeast toward the area and weaken Friday night.
There are still some slower model solutions /12.12Z NAM/ that
would suggest a slower front timing and storms in southwest WI and
far eastern IA Saturday afternoon. Weak wind shear profiles would
suggest pulse, spotty severe storms at best should this solution
verify.
Saturday Night Through Wednesday...
Good consensus on a period of pleasant weather with large scale
northwest flow, mostly clear skies, and highs in the 70s. The only
&&
.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1100 PM CDT Wed Aug 12 2020
Satellite imagery late this evening has shown an expanding area of
clouds across central and southern Minnesota where temps were held
down today. Ceilings were a mix of MVFR and VFR and looking at the
forecast soundings from the 13.01Z RAP, these clouds should
expand into KRST overnight with a period of MVFR ceilings. With
winds of 20 to 25 knots in the cloud layer, these should mix out
shortly after sunrise with VFR conditions expected into Thursday
evening. The RAP suggests there is at least a possibility the MVFR
clouds could get as far east as KLSE late tonight and have
included a short period to cover this possibility. Otherwise, VFR
conditions for KLSE through Thursday night as well.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Baumgardt
LONG TERM...Baumgardt
AVIATION...04
Area Forecast Discussion
National Weather Service State College PA
1132 PM EDT Wed Aug 12 2020
.SYNOPSIS...
A weak cold front will stall out around or just south of the
Maryland border through Friday. The presence of this front will
lead to a daily chance of thunderstorms, mainly across the
south, for the rest of the week. Some of the rain could be heavy
along and south of the stalled front. A gradual cooling trend
will be seen each day through the end of the week.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Flash Flood watch was ended early over the SE corner of CWA as
precip died out with sunset. Activity shifted to the SW portion
of the CWA this evening, with HREF/HRRR indicating blossoming
convection there this evening. Considered a short Flood Watch in
this area, but then the HRRR started to back off a bit.
Convection did develop, but heavy rains in slow moving tstms
remained isolated and were handled with a Flood Advisory.
Spotty convection does continue into the late evening, with
potential for it to linger for next several hours over the SW
and may spread back toward the E. Mrgl/Slight Excessive
Rainfall Outlook (ERO) does persist through the night across the
southern tier as any convection will be nearly stationary in
weak flow.
Elsewhere, look for mainly dry conditions across the northern
2/3rds of CWA with clouds diminishing as one moves northward.
Dewpoints around 70 in the south drop off to the mid 50s over
the north, bringing a refreshingly cool night north of I-80.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
Daytime mixing on Thursday should lower dewpoints across the
north, but dewpoints look like they could creep up a bit again
over southern half keeping mention of showers/tstms in the
forecast there. Best chance for heavier rains will continue to
be along the southern border and southward during the aftn and
evening on Thursday.
Temperatures trend a little cooler (right around normal) due to
the cloud cover to start the day in the central and south. But,
abundant sunshine across the north will help them get 5-10F
above normal for the day.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
A stationary boundary draped across the Mason-Dixon line will
drive the potential for a few lingering showers overnight on
Thursday. A small bubble of surface high pressure is expected
to develop on Friday, forcing the stationary front south &
bringing relatively tranquil weather to most of the Commonwealth
into the weekend. Low pressure off the East Coast may bring a
few showers into (where else than) southeast PA on Friday
afternoon, but going with the dry solution through Saturday.
By Saturday evening, split flow produces a weak broad upper
trough over the lingering frontal boundary to our south. This
will bring a surge of moisture into the Commonwealth during the
day on Sunday. There is still ample uncertainty in the
northward extent and amount of rainfall on Sunday with the ECENS
trending drier and the GEFS trending wetter, but the GEFS mean
produces potential for upwards of an inch of rain to much of
central and south central PA Sunday afternoon. The ECENS has
trended wetter since 24 hours ago and bolsters confidence in
higher PoPs. Will likely need to raise Pops to likely starting
in the SW Saturday night and expanding over the entire area
Sunday afternoon through Monday evening.
The weak surface trough will stick around through Monday before
a cold front sweeps through the Commonwealth, marking the end of
an unsettled stretch and ushering in cooler and drier weather.
The Climate Prediction Center 6-10 temperature outlook favors
below normal temperatures in central PA. This will be a welcome
relief after a prolonged stretch of warm weather. Additionally,
the arrival of high pressure by the middle of next week seems to
favor a drier than normal stretch for a little bit.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
Minor adjustments made as of 1130 PM.
Still a shower near AOO.
Earlier discussion below.
00Z TAFS sent.
Southeast flow of high dewpoint air across the southern part
of central PA trying to keep a few showers and storms going.
Current activity away from the TAF sites.
Backed off on low clouds overnight. For Thursday, went VCSH
across the south during the afternoon, as the cold front
stalls just to our south. This may be the case right into
Sunday. Thus the best weather may be across the north at BFD
and IPT.
Outlook...
Fri..Isold-sct t-storms possible mainly srn 1/2.
Sat-Sun...Risk of t-storms expands north and west.
Mon...Still a chance of showers and storms.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Lambert/RXR
NEAR TERM...Lambert/RXR
SHORT TERM...Lambert/Dangelo
LONG TERM...RXR/Banghoff
AVIATION...Martin
Area Forecast Discussion
National Weather Service Dodge City KS
557 PM CDT Wed Aug 12 2020
...Updated Aviation...
.SHORT TERM...(This evening through Thursday)
Issued at 136 PM CDT Wed Aug 12 2020
Early morning convection that crossed north central and portions
of south central Kansas occurred just east of a 700mb 12-16C
temperature gradient. This 700mb temperature gradient is forecast
to remain nearly stationary through this evening based on the RAP
and NAM with 700mb to 500mb lapse rates forecast to be 8C/km or
greater which will be located ahead a weak disturbance that
appears to be located over northeast Colorado based on WV loop. As
this upper wave crosses northern Kansas early tonight am
concerned convection developing early tonight in the Hays to
Larned areas, especially as the 850mb warm air advection and 850m-
700mb moisture transport begins to improve near and east of this
700mb temperature gradient. Models however are less excited with
the chance of precipitation this far west rather it keeps
developing convection overnight further east as this warm layer
moves slowly into Central Kansas. Models probably are correct with
the better chances for convection being further east but given
the location of mid level temperature gradient and developing WAA
before midnight feel there will be at least a slight chance for
thunderstorms near highway 183.
On Thursday morning the upper level disturbance will be crossing
central Kansas. An upper level trough, located over the Pacific
Northwest at 12z Wednesday, will approach the northern and
central Rockies during the day on Thursday. This upper level
trough will cross the Rockies and move out into the Western High
Plains Thursday night which will result in another chance for
thunderstorms near the northern edge of the mid level baroclinic
zone that is currently forecast to extend from southeast Wyoming
to south central Nebraska. The storms that develop ahead of this
late Thursday wave are expected to move out into the plains and
along this mid level baroclinic zone which could bring some
overnight convection to portions of Northern Kansas. At this time
however it appears that these storms Thursday night will stay well
north of the I-70 corridor and closer to the Nebraska border.
Temperatures on Thursday will be a little tricky given the
potential for a cool outflow boundary from the overnight
convection to spread across parts of western Kansas, much like
earlier today. At this time I am unsure just how far west this
cooler air will move but even given this uncertainty the highs
east of highway 183 should easily end up being 5 to near 10
degrees cooler compared to the highs near the Colorado border.
Expect afternoon temperatures to range from near 90 to around 100
degrees.
.LONG TERM...(Thursday night through Wednesday)
Issued at 136 PM CDT Wed Aug 12 2020
On Friday the upper level trough will cross the northern plains
as a surface cold front drops south across Nebraska and attempts
to move into northern Kansas. This surface boundary will briefly
become stationary Friday night as a weak upper level disturbance
embedded in a developing northwest flow approaches northwest
Kansas. There will be a chance of evening and overnight
thunderstorms near this boundary Friday night but at this time any
chance for thunderstorms currently appears to be near and north
of the I-70 corridor. Across southwest Kansas which will stay
south of the approaching cold front it will be another hot August
day with highs in the 95 to near 100 degree range.
Early this weekend the upper level trough will move into the
Mississippi Valley and an upper level ridge will build across the
Western United States. This will place western Kansas in a
northwesterly flow over the weekend as several upper level waves
embedded in this flow rotate around the upper ridge axis and
across the Central Plains. Also over the weekend a cold front will
drop south across the Northern Plains and move into southwest
Kansas on Sunday. This cold front will move into Oklahoma by early
next week as a cool dome of high pressure at the surface drops
south out of Canada and into the Upper Mississippi Valley. This
cool dome of high pressure at the surface will continue to build
south and east early next week which will keep some cooler east to
southeast flow advecting into central and western Kansas.
Currently based on the temperature trends behind the cold front
and the ongoing cool air advecting into Central and portions of
Western Kansas early next week the highs from Sunday through
Wednesday will be mainly in the 80s.
The best chance for precipitation this weekend into early next
week will be from Saturday night and Sunday as the cold front
drops into southwest Kansas as the upper level trough crosses the
Northern and Central Plains.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 555 PM CDT Wed Aug 12 2020
Main weather feature tonight will be the development of low clouds
and possible fog for all TAF sites mainly after 08Z and especially
around 10-13Z. IFR to LIFR conditions will be possible for all TAF
sites and then cloud ceilings should rise after 14-15Z back to VFR
status. Thunderstorms are possible during the overnight mainly for
central and eastern Kansas but a VCTS is possible around HYS from
04-06Z where the storms initially develop.
&&
.PRELIMINARY POINT TEMPS/POPS...
DDC 70 88 67 95 / 0 10 0 10
GCK 67 90 65 94 / 0 0 0 10
EHA 66 96 65 99 / 0 0 0 0
LBL 67 92 66 98 / 0 0 0 0
HYS 70 86 68 92 / 30 0 0 0
P28 72 89 70 94 / 10 10 0 10
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Burgert
LONG TERM...Burgert
AVIATION...Tatro
Area Forecast Discussion
National Weather Service Goodland KS
527 PM MDT Wed Aug 12 2020
.SHORT TERM...(This evening through Saturday)
Issued at 245 PM MDT Wed Aug 12 2020
Tonight...There will be a low chance of thunderstorms this evening
with the focus being on Yuma county and locations along the
Nebraska/Kansas border area where HRRR suggesting some activity
moving in from the northwest around 7 PM MDT moving southeast
through the evening then dissipating. Fog is expected to spread
northward after midnight. Dense fog is possible per model visibility
forecasts and at this time would be primarily along and south of
Interstate 70. Low temperatures are expected to range from the upper
50s to low 60s in far eastern Colorado to the low to upper 60s
elsewhere.
Thursday-Thursday night...morning fog is expected to dissipate by
14z or 15z with a sunny to mostly sunny sky in the afternoon. I`ll
be adding a slight chance of thunderstorms to the forecast near the
CO/KS border in the afternoon hours through about sunset where low
level convergence is maximized along a dry line with a weak
disturbance moving through from the northwest. High temperatures are
expected to range from the low 90s in Norton and Hill City to near
100 degrees across parts of far eastern Colorado behind the dryline
and where 850mb temperatures are near 90 degrees F. Low temperatures
are expected to be in the low to mid 60s.
Friday-Friday night...presently the forecast is dry. If the GFS
model is correct enough moisture in the 700-500mb layer moves close
to the northeast corner of the area around 00z-03z to support an
isolated thunderstorm mention. High temperatures are expected to be
in the low to upper 90s with low temperatures in the low to mid 60s.
Saturday...isolated afternoon thunderstorms will be possible as the
models bring another weather system (per 700-500mb humidity) through
the area from the northwest. East to southeast surface winds will
provide for slightly "less hot" conditions with high temperatures in
the low to mid 90s.
.LONG TERM...(Saturday night through Wednesday)
Issued at 203 PM MDT Wed Aug 12 2020
Saturday night will see the storms and showers that formed during
the afternoon and evening continue to move east and south throughout
the evening and early night hours. Lows are likely to drop to near
60 with winds out of the south around 10 to 15 mph. Winds would be
stronger with any storm that remained in the area.
Sunday has the upper level high sitting near Utah and Nevada begin
to have a ridge extend north into Canada off of it. This will not
immediately impact the Tri-State area as we would remain under
northwest flow aloft with the potential for shortwave energy to pass
through the area. While the area as a whole will see a chance for
afternoon and evening storms, the greater chances are likely to be
in the southern portion of the area based on guidance. Highs are
likely to be in the upper 80s but the GFS is suggesting that
temperatures may be a few degrees higher. Will have to see what the
conditions are after the storms and front pass through on Saturday.
Monday through Wednesday has the upper level pattern near stagnant
with the upper high in the same position as Sunday with the ridge
moving slowly east over the period. Meanwhile an upper low sits just
north of Ontario with a trough that extends slowly south across the
period. This will have the area remain in north to northwest flow
which will continue to allow shortwaves to pass and add instability.
At the surface, a stationary boundary will likely linger in Eastern
Colorado and serve as a potential focal point for storm development.
With PWAT values near or slightly above normal and 850 dewpoints
near 14C, there will be sufficient moisture for storms to
develop. Henceforth, each day will likely see a similar pattern of
storms developing in Central to Eastern Colorado and moving east
across our area during the afternoon and evening. It may be
possible for some of these storms to become severe and/or produce
heavy rainfall given the instability and moisture present but not
enough confidence to forecast it yet. Highs are likely to stay in
the mid to upper 80`s during this time period.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 525 PM MDT Wed Aug 12 2020
GLD: IFR-LIFR stratus and/or fog may develop late tonight, mainly
in the 10-14Z time frame. Otherwise, VFR conditions will prevail
through the TAF period. Light E-ESE winds will prevail this
evening -- becoming light/variable overnight -- remaining light/
variable or becoming W-SW at 5-10 knots during the day on Thu.
MCK: IFR-LIFR stratus and/or fog may develop late tonight, mainly
in the 10-13Z time frame. Otherwise, VFR conditions will prevail
through the TAF period. Light ESE-SE winds will prevail this
evening -- becoming light/variable overnight. Winds will remain
light through mid-afternoon, becoming south at 12-16 knots near
the end of the TAF period (late Thu afternoon).
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&
$$
SHORT TERM...99
LONG TERM...KAK
AVIATION...VINCENT
Area Forecast Discussion
National Weather Service Lincoln IL
750 PM CDT Wed Aug 12 2020
.SYNOPSIS...
Issued at 750 PM CDT Wed Aug 12 2020
Partly cloudy skies are expected across central and east central
Illinois into Thursday, with high temperatures rising back into
the mid 80s on Thursday. While dry conditions will prevail
overnight and Thursday morning, scattered showers and
thunderstorms are expected in areas south of I-70 by midday,
continuing into the afternoon.
&&
.UPDATE...
Issued at 750 PM CDT Wed Aug 12 2020
Isolated but persistent convection that has occurred between
Effingham and Flora has finally faded away early this
evening. However, the RAP and GFS hint at some isolated convection
lingering overnight near Flora, so some small rain chances will be
kept in the forecast there. Temperatures are largely on track, and
adjustments in the forecast were mainly for sky trends.
&&
.SHORT TERM...(This evening through Thursday)
ISSUED AT 316 PM CDT Wed Aug 12 2020
Frontal boundary still sitting over southern IL will remain semi-
active through tomorrow and might slowly lift to the north
Thursday. However, any convection will be confined to southern IL
tonight through Thursday with only a chance of precip expected in
southeast IL. A slight chance of precip is possible a little
further north of this area, but most of the CWA should be dry
through the period. Overnight lows are expected to be in the 60s
with afternoon highs, Thursday, rebounding into the middle 80s.
&&
.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 316 PM CDT Wed Aug 12 2020
A frontal boundary will be near the CWA through the first part of
the extended forecast with the chance of precip still confined to
southeast IL for Thur night and Fri. After this, as the pattern
becomes more progressive, only a slight chance of precip is
expected Sat through Sun. A cold front will then move through the
area Sun, with a small chance of precip, though will not be
mentioned at this time in the worded forecast. Beyond this, Sun
night through Wed, dry weather is expected with temps becoming
cooler.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 640 PM CDT Wed Aug 12 2020
The latest surface observations indicate a moisture gradient with
higher dew point air from about KMQB-KSPI-KDEC-KDNV and southward.
Surface high pressure in Michigan was providing an light easterly
flow across central Illinois with the drier air generally north
of the I-72 corridor. This should keep the northern TAF sites in
VFR conditions through the night and into much of Thursday.
Locations with higher moisture levels can expect light fog to
develop by daybreak with MVFR visibility from KSPI to KCMI. Lower
clouds will also develop around 14-15z, keeping the MVFR
conditions across central Il into early afternoon due to the
proximity to a weak upper level low in south central IL. Mixing
will be limited due to the morning cloud cover and light winds,
but increasing surface temperatures should allow cloud bases to
climb to VFR levels by 18z in the southern half of Illinois.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Geelhart
SYNOPSIS...Geelhart
SHORT TERM...Auten
LONG TERM...Auten
AVIATION...Miller
AREA FORECAST DISCUSSION...UPDATED
National Weather Service Jackson KY
1145 PM EDT Wed Aug 12 2020
.UPDATE...
Issued at 1145 PM EDT WED AUG 12 2020
Did an update to the forecast mainly to fine tune the sky cover
and incorporate the latest obs and trends for the T/Td grids.
These updates have been sent to the NDFD and web servers.
UPDATE Issued at 755 PM EDT WED AUG 12 2020
23z sfc analysis shows Kentucky is just south of a stalled
boundary that is helping to keep the air mass rather soupy. As
such, a few showers and storms have been able to sustain
themselves mainly in the southeast border counties with Virginia.
There remains enough instability to keep the activity going for
another couple of hours before they fade out for the bulk of the
night per the latest CAMs guidance. These are heavy rain
producers, as well, with our co-op observer outside of Whitesburg
picking up over two inches in less than an hour. Will update the
zones and HWO once the storms finally fade out. Otherwise, the
forecast is on track, with temperatures settling back into the
upper 70s and lower 80s while dewpoints remain elevated in the low
to mid 70s in most spots. The winds have been light and variable
away from any storms. The forecast grids were updated to mainly
fine tune the PoPs and add in the latest T/Td obs and trends -
capturing the extra cooling effect of the storms in the
southeast. These updates have been sent to the NDFD and web
servers.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 435 PM EDT WED AUG 12 2020
This afternoon, at mid and upper levels, much of the Conus from
the MS Valley to the eastern seaboard remained in a weakness
between ridging centered near Bermuda and ridging centered near
the southern Rockies vicinity. A weak upper level low/upper trough
continues to meander near the confluence of the OH and MS Rivers
with a couple vort maxes rotating around it across the lower OH
Valley and into IN. This upper low/trough is displaced well south
of the stronger westerlies nearer to the US/Canadian border and
Great Lakes and moving only slowly. Another weak vort/shortwave
was east of the area over the Appalachians. A min PW extends from
the southern Great Lakes south near the I 75 corridor with PW of
1.5 inches or less per mesoanalysis with PW 1.6 inches plus in
the southeast part of the CWA east into the Appalachians while a
gradient in PW resides across central KY and nearing the Lake
Cumberland Region. Some convection that had developed in the
southeast counties has mostly dissipated with additional
convection over VA. Near and east of the upper low/trough
convection continues to move across portions of IL and central and
western KY and TN with a diurnal increase having occurred across
these regions.
Overall, a relative min in instability is expected to persist
through the evening near the PW min with RAP forecasts of MLCAPE
generally peaking near or less than 1000 J/kg from the far
northwest south near I 75. Meanwhile, MLCAPE is analyzed in the
1000 to 1500 J/kg range over the southeastern counties and in the
far west in parts of Pulaski and Wayne counties. SBCAPE is
generally analyzed in the 2000 to 2500 J/kg or over these more
southeastern locations. Shear remains weak, but low level lapse
rates are in the 7 to 8C/km range or some additional pulse type
convection could still develop over the next few hours as we move
into the evening. Cumulus seems to be stunted a bit as cirrus
debris from convection to the southwest moves across the
northwest half of the area so the evolution of convection through
the evening remains uncertain. Convective allowing models for
several runs keep most of the activity through the evening in the
southeast. Some (especially recent HRRR runs) do develop more
isolated activity further north or west to just south of the Mtn
Parkway and east of I 75 as well though they have trended downward
and the cumulus trends in those areas would generally support
this. For now, we have continued to include slight chance pops to
just south of the Mtn Parkway and west to an Estill to Knox to
Bell County line. With the PW/moisture gradient near the far
southwest and the upper low to the west as well as convection in
that direction and the potential for outflows reaching the far
southwest, slight pops have been included there for the evening.
Convection is generally expected to wane across the region by late
evening into the overnight hours. Some convective cloud debris
though leads to uncertainty in fog development. In general, fog
is expected to be more confined to the valley locations.
Considering current dewpoints across the region near the 70
degree mark and lows expected to reach the upper 60s to around 70
degree mark and anticipated light winds, the pattern favors fog.
Thursday into Thursday night, the upper low/upper trough over the
lower OH Valley will slowly meander closer to eastern KY. The
current area of rather high PW to the west of the area should
gradually advect into the western and southern portions of the
region by late Thursday with PW projected to reach the 1.6 to 2
inch range there by that time with PW remaining 1.5 or less in the
northwest. A diurnal increase in convection should occur during
the day on Thursday though some convection may linger all the way
through Thursday night, especially across the west and south as
the mid and upper level system slowly nears. With rather storm
movements on Thursday and Thursday evening and the increasing
moisture, locally heavy rain cannot be ruled out along with a
storm or two with gusty winds. The airmass will remain moist with
PW increasing to 1.6 or 1.7 to 2 inches across the area.
Temperatures will again be mild on Thursday with highs mainly in
the mid and upper 80s or 2 to 3 degree above normal for this time
of year. Departures should be a bit greater with the moist airmass
in place on Thursday night as dewpoints remain near 70 along with
a fair amount of cloud cover. Lows on Thursday night will be near
the 70 degree mark.
.LONG TERM...(Friday through Wednesday)
Issued at 506 PM EDT WED AUG 12 2020
Low pressure is expected to bring a soaking rainfall Friday into
Saturday. A cold front follows for early next week, ushering in a
cooler and drier late summer air mass. Model agreement is
surprisingly good with the overall weather pattern through
Tuesday. The latest model suite shows an ~ 594 dam high centered
over the Desert Southwest Friday morning while a broad trough,
associated with a ~546 dam parent cutoff low near Great Slave
Lake, covers the northern US from the headwaters of the
Mississippi River to the West Coast. To the east of these systems,
the Ohio Valley and Great Lakes will lie within a zone of split
flow, with a ridge extending northward into in western Quebec and
a trough extending southward to near the Gulf Coast. A weak
cutoff low, rotating in the split flow pattern over the lower Ohio
Valley early Friday, is expected to slowly meander to the
northeast through Saturday. By early next week, the southwestern
high strengthens as it retrogrades toward the Great Basin and the
deep trough digs into the eastern CONUS, breaking down the split
flow pattern and lifting the remnant cutoff low circulation away
from the Ohio Valley.
The split upper level flow pattern will initially support a
quasi-stationary boundary lingering over the region into Saturday
evening as a weak low pressure lifts across the area. This system
will pull deep moisture northward across the Commonwealth,
sending PWATs to near 2 inches within a tall, skinny CAPE and
light steering flow environment. This will set the stage for
efficient warm rain processes and the potential for hydro issues
in areas which receive multiple rounds of heavy convection. The
low pressure wave and front finally pull away early Sunday,
perhaps allowing for weak surface high pressure and shortwave
ridging aloft to nose in Sunday morning. Thereafter, a Canadian
cold front, supported by the broad digging trough, will surge SE
across the Great Lakes and into the Ohio Valley Sunday night/early
Monday. This front quickly looses steam as its parent air mass
quickly modifies; even so, 850 temps aloft should still cool off
modestly into the 14-16C range by Monday evening as a noticeably
drier air mass moves into the area. A reinforcing secondary front
could follow late Tuesday into Wednesday.
Eastern Kentucky will continue to see warm and muggy conditions
Friday into Saturday, along with the threat for showers and
storms as that wave of low pressure lifts along the quasi-
stationary boundary. There is still some uncertainty with regard
to the precip timing and associated cloud cover. The UKMET and
ECMWF favor a slower arrival on Friday and linger the precip
through much of the day Saturday. On the other hand, the NAM, GFS
and Canadian are more progressive, pushing the system through
Friday into Friday night followed by the arrival of drier air
Saturday. Maintained likely to categorical PoPs on both Friday and
Saturday, but this will need to be fine-tuned as the models come
into better agreement. Nudged NBM max temps down into the low to
mid 80s on both days. However, high temps could easily be capped
in the 70s in areas which see persistent cloud cover and shower
activity. Some clearing is expected Saturday night/Sunday morning
with the surface ridging, but shower and storm chances quickly
return later Sunday or Monday with our next cold front. Slightly
drier and cooler air arrives by late Monday. A reinforcing shot of
cool air could arrive by mid-week. Mostly to partly sunny skies
should boost high temps in the low to mid 80s Sunday afternoon
ahead of the front and then cool off into the upper 70s and lower
80s for Tuesday. Lows near 70 Friday night will cool off to the
upper 50s to low 60s by Tuesday morning.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
ISSUED AT 830 PM EDT WED AUG 12 2020
Isolated to scattered showers and storms will fade out over the
first part of the evening. Later some clouds from convection west
of the area near a slow moving upper level low will lead to some
uncertainty in fog development tonight. The fog should be most
prevalent in the river valleys again, generally from 4 to 13z and
some IFR or lower is anticipated there, at times. KSJS should be
most affected with some IFR conditions probable there per trends
with generally MVFR reductions in vis for LOZ, SME, JKL, and SYM.
The fog should lift and dissipate from 13 to 14z, with convection
possibly developing in the south before the end of the period.
The threat of spotty convection will be around all day, but at
this point have chosen to not refine the placement and timing for
any TAF site potentially affected. Winds through the period will
be light and variable.
&&
.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...GREIF
SHORT TERM...JP
LONG TERM...GEERTSON
AVIATION...JP/GREIF
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
831 PM CDT Wed Aug 12 2020
.UPDATE...
Issued at 831 PM CDT Wed Aug 12 2020
Rain cooled air north of the MN River has really put the breaks on
the northward movement of the warm front, which remains parked
roughly along the Buffalo Ridge. This warm front looks to remain
more or less stationary through the night. Most models continue to
struggle as they have done all day, but the ones that update more
frequently (HRRR and HopWRFs) seem to have at least a slight grasp
of what`s happening now. Agree with their idea that scattered
showers/storms will continue to develop through the night as weak
warm advection up over the warm front/outflow boundary,
initiating from an unstable airmass where muCAPE exceeds 3000
j/kg, continues to allow storms to initiate. HRRR/HopWRFs are
favoring western WI for seeing this activity through the night,
but with showers developing clear back to the MS River in central
MN, and the farther southwest location of the warm front, think
this activity ends up a bit father west that what the HRRR has
been depicting. In the end, continued chance pops from eastern MN
into western WI through the night to start with and will update
with trends from there.
&&
.SHORT TERM...(This evening through Thursday night)
Issued at 300 PM CDT Wed Aug 12 2020
The day began with clusters of showers/thunderstorms over far
western MN, ahead of a warm front draped NW-SE over the Dakotas
into the Mid-Mississippi River Valley, high pressure over the
eastern Great Lakes, and multiple residual outflow boundaries
across MN. In addition, rounding the base of a large upper level
low over western Canada were several shortwave axes, gradually
shifting ESE within a flattening upper level ridge. With PWATs
near 1" and surface dewpoints into the mid-60s, a plentifully
moist atmosphere was in place for these storms to steadily shift
east. As they did and formed into more organized clusters and
lines, some put some heavy rain over southwestern and southern MN
(in the 2-4") range along with hail up to nickel-sized. Such
storms are no longer expected as the precipitation shield has
become far enough displaced from the surface front and into a
slightly more stable atmosphere. Nevertheless, showers/storms will
continue mainly N of I-94 and E of I-35 through this afternoon
and evening. As the warm front slowly approaches for tomorrow,
isolated/scattered showers are possible through the overnight
hours but a drier airmass is expected tomorrow as the area becomes
warm-sectored and very likely free from precipitation. As such,
PoPs have been lowered for much, if not all, of the WFO MPX
coverage area for tomorrow with multiple model solutions
indicating no precipitation for tomorrow. There is the caveat that
these same models had a very difficult time initializing the
precipitation for today but with so many solutions indicating dry
conditions for Thursday, have gone with that consensus.
Precipitation chances then increase for Thursday night as the
cold front trailing the warm sector shifts east through the
Dakotas and into northwestern MN by daybreak Friday morning. While
the heavier of the precipitation is likely beyond this short-term
period, a few isolated stronger storms in far western MN are
possible around daybreak. Better chances for severe weather on
Thursday can be expected northwest of the WFO MPX coverage area,
into northwestern MN and eastern ND.
With the area being warm-sectored through Friday night, an
associated increase in temperatures and humidity can be expected.
Lows both tonight and Thursday night will run in the 60s while
highs on Thursday climb to the mid-upper 80s. With dewpoints
into the lower 70s Thursday, heat index values will climb to the
low 90s area- wide (with some portions of far western MN into the
mid 90s.)
.LONG TERM...(Friday through Wednesday)
Issued at 300 PM CDT Wed Aug 12 2020
Friday through Friday night looks to be fairly active across the
coverage area as both the aforementioned cold front along with a
potent upper level trough moves across the region. The front will
push across MN on Friday then through WI Friday night, moving into
MI on Saturday. With PWATs climbing to 1.25" to 1.50", in
conjunction with dewpoints into the lower 70s, a rather unstable
atmosphere is expected with virtually no capping to halt
convective development. with frontal lifting and the trough aloft,
the combination will be there for fairly good coverage of
rain/thunderstorms across the area Friday through Friday night,
with some storms potentially strong to severe shifting west to
east. Bulk shear is expected to hit the 40-50kt range with MLCAPE
values around 3000 J/kg, both supportive of strong-severe
thunderstorms capable of large hail and damaging winds.
With the exit of the front on Saturday, a prolonged cooler and
drier period is then expected for the first half of next week.
Highs will drop back to the 70s with lows back into the 50s, and
potentially as low as the upper 40s by the middle of next week.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 707 PM CDT Wed Aug 12 2020
Lower than normal confidence this period, with problems abound
thanks to the warm front near the upper MN River from west central
into south central MN. Models continue to struggle mightily with
this setup. This warm front will lift north during this period,
but that northward push has been slowed considerably by cool
outflow air in the wake of clouds and rain across central MN into
western WI. North of the front, it`s beginning to look
increasingly likely that MVFR cigs will persist through the night,
especially west of I-35. In addition, more thunderstorm
development will be possible tonight as we see moist/unstable air
continually get lifted up and over the warm front and outflow
boundaries. Latest runs of the HRRR/HopWRF are favoring the Twin
Cities into western WI for seeing additional TS development
tonight. As the warm front pushes north, we will see skies clear
out (aside from a diurnal cu field), with winds becoming southerly
and gusty. Next round of TS does not look possible until Thu
night at the moment.
KMSP...With the western tail of the storms continuing to build
west/south into weak warm advection and stronger instability, MSP
is not out of the woods for seeing additional shra/tsra tonight.
Also, it looks like we`ll see clouds remain much of the night to
the north of the warm front. Lower confidence on what cloud trends
will be though through the night, so went the optimistically
vague route for this TAF, though would not be surprised if the sct
MVFR level cigs mentioned tonight into Thursday morning become a
ceiling.
/OUTLOOK FOR KMSP/
Fri...Mainly VFR. Aftn/evening TSRA lkly. Wind SSE 15G25 kts.
Sat...VFR. Wind N 5-10 kts.
Sun...VFR. Wind NW 15G25 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...None.
WI...None.
&&
$$
UPDATE...MPG
SHORT TERM...JPC
LONG TERM...JPC
AVIATION...MPG
Area Forecast Discussion
National Weather Service Shreveport LA
1027 PM CDT Wed Aug 12 2020
.UPDATE...
Convection has subsided for now, but a weak shear axis remains in
place across our eastern half so cannot completely rule out a few
shwrs or even a stray tstm redeveloping through the remainder of
tonight. In addition, patchy fog is possible in areas where heavy
rainfall fell earlier today so did add patchy fog wording across
much of SW Arkansas after midnight. Otherwise, temperatures appear
to be on track this evening so no additional forecast updates are
needed at this time.
/19/
&&
.PREV DISCUSSION... /issued 726 PM CDT Wed Aug 12 2020/
AVIATION...
For the 13/00Z TAF period, all sites begin the period with VFR
conditions despite an abundance of convective debris clouds in the
wake of a large decaying thunderstorm complex. One lone storm is
still noted near the MLU terminal, but expect a downward trend in
convection through the rest of this evening and overnight. Clouds
will linger with some lower clouds, possibly in the MVFR range,
eventually developing after midnight and toward daybreak mainly
affecting TXK/ELD along with some patchy fog due to the recent
rainfall at these sites. Otherwise, look for VFR conditions to
prevail elsewhere with cumulus/altocumulus clouds at/above 5Kft to
persist through the remainder of the period with light/varible
winds becoming more S/SW on Thursday between 5-10 kts.
/19/
PREV DISCUSSION... /issued 301 PM CDT Wed Aug 12 2020/
SHORT TERM.../Tonight through Thursday Night/
For the rest of today...continuing to watch a few lingering
showers and thunderstorms from this mornings complex that moved
through the northern portions of the area. Short range guidance
shows these slowly coming to an end as we head into the evening.
Significant cloud cover across the area in association with these
showers and thunderstorms have prevented afternoon temperatures
from reaching their full potential, with many areas in the 70s
this afternoon. That being said, I don`t think anyone will be
complaining about the rain, cloudy skies, and cooler temperatures.
Main concern heading into tonight will revolve around the ongoing
showers and thunderstorms. HREF is hinting that the MCV we saw
through the day will continue to push towards the SE into the
ArkLaMiss into the overnight hours. Often times these types of
situations hit their stride overnight, so this would increase our
potential for more heavy rain overnight. Latest HRRR model
indicate that the storms will continue to weaken through the
evening. Nonetheless will keep PoPs going through the night for
the eastern portion of the area. Overnight temperatures will range
from the lower 70s to the upper 70s. The cooler temperatures will
be in the area that saw the rainfall through the day.
The heat is on for Thursday...high pressure aloft will begin to
build towards the east and into the area. Temperatures across
portions of east Texas will climb into the upper 90s to lower 100s
by Thursday afternoon. Mixed with high humidity, heat index values
will easily reach the mid 100s for all of east Texas and portions
of northwest Louisiana. As a result, a Heat Advisory will go into
effect at noon on Thursday for all of our Texas counties, portions
of Louisiana and Miller and Lafayette counties in Arkansas. There
is a small non zero chance that a few showers or thunderstorms
will develop across portions of our eastern area during the
afternoon hours on Thursday. /33/
LONG TERM.../Friday through Monday/
The forecast period begins with a model consensus indicating that
deep mid-level ridging will be firmly in place across the Desert
Southwest with a mid-level trough centered across the Mississippi
Valley. The eastern periphery of the ridge will extend into East
Texas with the ArkLaTex wedged between the ridge and the trough. The
trough will be close enough for the ArkLaMiss to help provide
forcing to kick off more diurnally driven showers and thunderstorms
there on Friday with changes quickly drying out for the I-49
corridor and westward into East Texas.
The trough will edge eastward over the weekend and showers and
thunderstorms cannot be ruled out for the ArkLaMiss and central
Louisiana each afternoon. Otherwise, a dry and hot forecast is in
place for the weekend for southeastern Oklahoma, southwestern
Arkansas, northwestern Louisiana, East Texas, and Deep East Texas.
On Sunday night, models begin to diverge somewhat with the GFS
hinting at a short wave sliding southward and potentially kicking
off a mesoscale convective system (MCS) for the area with chances of
showers and thunderstorms continuing on Monday. With this in mind,
have chance POPs (30-40%) late Sunday afternoon and again on Monday
afternoon.
For temperatures, highs on Friday will range from the lower 90s in
SE OK/SW AR to the upper 90s and even close to triple digits in East
Texas and Deep East Texas. The trend will continue to warm as the
trough edges eastward with highs range from the mid 90s in SW AR/SE
OK to the upper 90s and near triple digits elsewhere over the
weekend. With the short wave pushing into the area and increased
cloud coverage possible Monday, highs will range from the lower 90s
in SE OK/SW AR to the upper 90s in Deep East Texas. Each day at
least portions of the forecast area will be near or above heat
advisory criteria with heat indices warming into the 105-110F range.
/04-Woodrum/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 77 96 77 96 / 20 20 10 10
MLU 75 94 75 94 / 40 50 20 30
DEQ 72 94 72 93 / 10 10 10 20
TXK 73 92 74 92 / 20 20 10 20
ELD 71 92 72 92 / 40 20 10 20
TYR 78 100 78 100 / 0 0 0 0
GGG 77 99 77 97 / 10 10 0 10
LFK 77 101 77 100 / 0 10 0 10
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Heat Advisory from noon to 8 PM CDT Thursday for ARZ070-071.
LA...Heat Advisory from noon to 8 PM CDT Thursday for LAZ001>004-
010>012-017-018.
OK...None.
TX...Heat Advisory from noon to 8 PM CDT Thursday for TXZ096-097-
108>112-124>126-136>138-149>153-165>167.
&&
$$
19/33/04
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Thursday)
Issued at 355 PM CDT Wed Aug 12 2020
20Z water vapor imagery depicts broad mid-level troughing over the
Pacific Northwest and southwestern Canada, which is working to
flatten the ridge over the southwestern CONUS. A subtle shortwave
can be seen between these features in eastern CO moving into KS,
which is one of several factors influencing tonight`s forecast. A
few very isolated thunderstorms remain possible north of I-70 the
rest of the afternoon due to isentropic lift, but the main focus is
on storms developing late this evening and especially overnight. The
trend in today`s models has been for storms in Nebraska to weaken as
they progress eastward this evening with our storms initiating in
central KS primarily after midnight, associated with an area of
isentropic lift which also happens to be on the northern edge of a
modest LLJ. We still have quite a bit of variation between the CAMs
as to exactly where storms develop, and especially how far north and
east they will spread. The area of greatest likelihood appears to be
along and south of a line from Concordia to Manhattan to Emporia,
but the latest NAM Nest keeps the entire cluster west of the CWA.
Meanwhile earlier runs of the HRRR brought storms as far east as
Topeka, while current runs struggle to bring them that far east.
Where storms do occur, these will be elevated with 1000-1500 J/kg of
CAPE and 20-30 kts of effective bulk shear. This along with steeper
mid-level lapse rates could be enough for a few storms to produce
damaging wind gusts and perhaps hail. With an increase in Pwat to
1.5-1.75 inches, some locally heavy rainfall is also possible.
Some showers and storms linger into east central KS for the morning
hours with model guidance generally drying us out by the afternoon.
Have dropped high temperatures to the mid to upper 80s across the
CWA with cloud cover and rain likely to keep conditions cooler at
least to start the day.
.LONG TERM...(Thursday night through Wednesday)
Issued at 355 PM CDT Wed Aug 12 2020
There is at least some possibility for storms to redevelop Thursday
night with strengthening WAA and isentropic lift; however, this
has shifted more toward southeastern KS. Based on some model
guidance, this could stay entirely south of the CWA or it may
barely clip the east central counties. Given the weaker forcing
and overall pattern in place, the evolution of this round will
really depend on how tonight`s system plays out and we see the
type of environment we`re left with and where outflow boundaries
end up. After this, there are a couple more chances for storms,
one on Friday night into Saturday and another on Saturday night
into Sunday ahead of a frontal boundary. This cold front looks to
bring cooler and drier conditions into the beginning of next week
with high temperatures returning to the 80s through mid-week along
with dew points in the low 60s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 640 PM CDT Wed Aug 12 2020
Light VFR showers end this evening in northeast Kansas with
renewed thunderstorm development expected after 06-09Z southwest
of a MHK to EMP line. These storms lift northeastward through the
early morning, possibly impacting TOP/FOE around sunrise.
Conditions in the heavier rain could fall below IFR at times. These
storms diminish through the morning. VFR conditions are then
expected for the rest of the period with light southeast winds.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Picha
LONG TERM...Picha
AVIATION...Skow