Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/30/20
Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
906 PM CDT Tue Sep 29 2020
Issued at 905 PM CDT Tue Sep 29 2020
Overall the forecast is in fine shape and therefore am not
planning to make any major changes this evening.
.SHORT TERM...(This Evening through Wednesday Night)
Issued at 302 PM CDT Tue Sep 29 2020
Forecast challenges primarily surround strength of winds on
Wednesday, and secondarily elevated fire danger.
Currently, skies are characterized as partly to mostly sunny.
Temperatures have warmed into the 60s and 70s. Some locations
throughout and west of the Missouri River valley will probably nose
up into the lower 80s today before it`s all said and done. A pocket
of low level moisture surging in behind the cold fropa that has
happened, is helping to keep relative humidities from bottoming out
to dangerously low values. Have noted more breezy to windy west-
northwest winds occurring today. So far, just a couple of reporting
stations have reached sustained 30 mph (or gusts to 45 mph) and not
for very long. Most locations are maintaining, generally, in the 15
to 30 mph sustained range, with gusts to 35 to 40 mph.
A cold front has pushed south through the CWA. Low level CAA will
take over now, and persist tonight, Wednesday and Wednesday night.
Some fairly strong northwest winds are expected on Wednesday while
the CWA becomes situated in a rather tight pressure gradient across
the northern plains amid the strong northwest mixing wind/caa. RAP
in BUFKIT and the 0.5km wind progs are all supportive of 20 to 35
mph sustained winds and gusts as high as 50 mph on Wednesday. A wind
advisory has been issued (15Z Wed to 01Z Thu) for Wednesday for the
CWA, except for Big Stone/Traverse Counties in MN.
The pressure gradient persists Wednesday night, which should help
keep the winds from dropping off much below 10 mph. Low temperatures
tonight (40s to near 50) near normal will be replaced with well
below normal temperatures Wednesday and Wednesday night.
Strong winds and a relatively dry airmass in place on Wednesday will
create high to very high fire danger over much of the CWA. Model-
progged relative humidity does not appear to dry out too much on
Wednesday. Fire Zone 267 (Jones/Stanley/Lyman Counties) could still
end up seeing relative humidity drop down close to 20 percent,
.LONG TERM...(Thursday through Tuesday)
Issued at 302 PM CDT Tue Sep 29 2020
The upper level flow pattern over the U.S. changes very little from
Thursday through Tuesday. We start out with a sharp 50H ridge axis
over the far western U.S/west coast into western Canada with a large
upper level low pressure trough over eastern Canada into the eastern
U.S. The only change in this pattern is a de-amplifying of the flow
Sunday night through Tuesday. Therefore, the northwest flow will
remain over our region through the entire period with several mostly
dry short wave troughs moving over. In fact, the overwhelming
consensus is for a continued dry forecast.
The main issue during this period will be the several nights of
light winds and the possibility of frost formation. Cloud cover
looks to be an issue both Thursday night and Friday night. Right
now, lower to mid 30s are expected Thursday night with mid 30s to
around 40 for Friday night. Saturday night looks to have the least
cloud cover at this time. It will all depend on the winds and cloud
cover as the nights will be long enough for good cooling. Therefore,
have several nights with patchy/areas of frost in the forecast.
Highs are expected in the 50s to the lower 60s for Thursday through
Sunday, warming into the mid 60s to the mid 70s for Monday and
Tuesday as upper level heights build some over the region.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 641 PM CDT Tue Sep 29 2020
VFR skies/vsbys are expected through tonight. Gusty winds are
again expected on Wednesday with the daytime heating.
***Construction to improve taxiways at both KABR/KPIR terminals
may cause an occasional temporary visibility reduction due
to blowing dust (bldu), mainly during daytime hours UFN.
SD...Wind Advisory from 10 AM CDT /9 AM MDT/ to 8 PM CDT /7 PM MDT/
Wednesday for SDZ003>011-015>023-033>037-045-048-051.
Area Forecast Discussion
National Weather Service Boise ID
834 PM MDT Tue Sep 29 2020
.DISCUSSION...Upper ridge axis over the PacNW coast will move
slowly eastward and reach WA/OR on Wednesday. Southeast Oregon and
southwest Idaho will remain on the eastern side of the ridge with
northwest flow aloft over the area. Wildfire smoke aloft on the
western side of the ridge will enter our area from the northwest
on Wednesday. Temperatures will be a few degrees warmer with
valley highs in the 80s (around 10 to 15 degrees above normal).
Winds will remain light and variable. No updates.
.AVIATION...VFR. Smoke layers aloft on Wednesday. Surface winds
variable 10 kts or less. Winds aloft to 10k feet MSL northwest to
SHORT TERM...Tonight through Thursday night...Upper level ridge
will remain over the region through the short term with above
normal temperatures and mostly clear skies. Wildfire smoke from CA
will eventually get wrapped around the ridge. The HRRR smoke
model has smoke increasing aloft across our area on Wednesday
LONG TERM...Friday through Tuesday...A strong upper level high
pressure ridge over the Intermountain Region will keep skies
mostly clear and temperatures around 10 degrees above normal.
Smoke from the California fires could become entrained into the
ridge circulation, increasing haze over our area this weekend.
PREV SHORT TERM...KA
PREV LONG TERM....JT
Area Forecast Discussion
National Weather Service State College PA
1122 PM EDT Tue Sep 29 2020
A change in the weather pattern will bring much needed rain to
central Pennsylvania through tonight. Scattered rain showers
are likely around Lake Erie through midweek. Temperatures will
trend noticeably cooler today and remain below average into the
.NEAR TERM /THROUGH WEDNESDAY/...
Strong fgen forcing linked to upper level jet streak will be the
focus for steady rain tonight. Band of light to moderate rain
falling across the central mountains at 00Z lines up well with
850-700mb fgen and latest RAP indicates this forcing and
associated band of steady rain will shift into the eastern part
of the forecast area late this evening, then exit the area late
Expect the back edge of the rain to pivot through the region
between 06Z-11Z, as upper level shortwave traverses the area and
large scale subsidence arrives. MRMS Bias-Corrected rain
estimates at 23Z range from around 1 inch across the central
mountains, to nothing over areas south and east of Harrisburg.
Latest near term model guidance supports storm totals by early
Wed morning ranging from as high as 1.5 inches in a few spots
across the central mountains, to around 0.5 inches over parts of
Warren County and the Lower Susq Valley.
Temperatures will fall slowly overnight under weak cold
advection with readings by dawn likely ranging from the mid 40s
over the northwest mountains, to the low and mid 50s over the
Strong subsidence and arrival of drier air mass in the wake of
departing shortwave should result in rapid clearing across most
of central Pa around dawn Wednesday. However, model soundings
indicate upslope flow could cause broken stratus to linger a
while over parts of the Allegheny Plateau. Deepening mixed
layer will allow some fairly gusty winds to reach ground level
during late morning and afternoon. Latest Bufkit soundings
support frequent gusts of 25-30kts across the northwest counties
and closer to 20kts across the Susq Valley.
A secondary shortwave is progged to swing through the base of
deepening upper trough late Wednesday, bringing increasing
clouds and the chance of showers to the northwest counties
during mid to late afternoon. NBM temperatures look reasonable
based on progged 850mb temps, with highs likely ranging from
around 60F over the Allegheny Plateau, to around 70F across the
Lower Susq Valley.
.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
Nighttime brings a secondary front across the CWA, chilling
things down to the 40s and L50s by Thursday morning. Likely
PoPs are on order for the far NW, and little to no precip is
expected downwind of the Allegheny Front. The front should be
well to the east by Thurs sunrise.
An upper trough swinging through the Great Lakes Thursday will
keep lake-enhanced rain showers in the vicinity of northwest
Pennsylvania as seasonably cool temperatures remain in place.
Rain chances will increase later Thursday into Friday,
especially across the Susquehanna Valley, as a surface low
tracks across the mid-Atlantic in tandem with approach of the
Great Lakes to Ohio Valley upper trough axis.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
All medium range guidance supports fair and cool conditions
Saturday, as surface high builds in from the Grt Lks. Both the
ECENS and NAEFS are consistent in deepening an upper level
trough over the Mississippi Valley late in the weekend,
spawning a developing surface low over the midwest. There are
timing differences and related uncertainty with regard to when
this system affects Pa. However, there appears to be a decent
chance for a period of rain sometime between Sunday evening and
Monday evening, as an increasingly moist southerly flow overruns
dome of cool/stable air east of the Appalachians associated
with high pressure over the Canadian Maritimes.
Cloud cover and possible rain will likely result in temperatures
remaining below normal into Monday with drier and likely milder
conditions likely by Tuesday.
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
A weak wave of low pressure is riding up a front along the East
Coast, bringing a wave of rain across the area through the early
At 03z, cigs are bouncing between MVFR and VFR at all central
PA TAF sites. Expect some lowering cigs and vsbys through the
early overnight hours. However, drier air will begin to arrive
from the west later as the low pressure pulls to the north
along the front, bringing an end to the steady rain from west to
east. This should lead to some eventual improvement in cigs and
vsbys for all but the western highlands /BFD and JST/ around
Expect a gradual return to VFR conds area-wide on Wednesday, as
drier air continues to filter into the region. Northwestern PA
/BFD/ could see a few rain showers redevelop later Wed.
Wed...Lingering AM restrictions giving way to VFR conds.
Thurs...NW flow. MVFR cigs and SCT SHRA NW, MVFR stratocu central
terminals. VFR SE.
Fri...MVFR w/sct SHRA NW & central. -RA and IFR poss SE.
Sat-Sun...No sig wx.
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
651 PM CDT Tue Sep 29 2020
VFR conditions will prevail through the period with clear skies
expected. Light northerly winds this evening will be variable or calm
overnight then turn out of the south tomorrow with speeds remaining
less than 7 knots.
.PREV DISCUSSION... /ISSUED 207 PM CDT Tue Sep 29 2020/
SHORT TERM (Tonight through Wednesday Night)...
High pressure has settled in across south-central TX per RAP
analysis. There`s barely a cloud in the sky on satellite imagery
over the entire state as of 18Z. After a chilly morning,
temperatures have recovered nicely into the 70s and lower 80s. Light
northerly/northwesterly flow will continue today, then winds become
light and variable to calm overnight. Ample radiational cooling will
allow for another chilly night tonight with lows in the 40s and
lower 50s. Given models generally underperformed with this morning`s
lows, have again gone closer to the low end of guidance tonight.
On Wednesday the high will shift to our east and allow for winds to
become southwesterly/southerly, though they`ll remain light. Should
see a warmer day as a result with highs into the mid 80s to lower
90s. Slightly more moisture will be able to work into the area, and
tomorrow nights lows will also be a little warmer, mainly in the
LONG TERM (Thursday through Tuesday)...
A dry and stable airmass is forecast to remain across the area for
the extended forecast period (Thursday through Tuesday of next
week). A shallow and dry cold front is forecast to push across the
area on Thursday night into Friday morning. The main feature
associated with this cold front is a wind shift to the northeast and
east. Winds shift back to the south and southeast by Friday
afternoon. Another weak cold front is forecast for Sunday night into
Monday. The GFS solution shows dry conditions across south-central
Texas while the ECMWF shows light QPF over the Hill Country and areas
mainly along and east of Highway 183. This far out, opted to go with
a dry forecast for the period. Otherwise, the first part of next
week continues dry with temperatures near climate normal values
(highs in the mid 80s and lows in the lower 60s for areas along the
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 53 89 58 88 59 / 0 0 0 0 0
Austin Bergstrom Intl Airport 51 88 55 88 58 / 0 0 0 0 0
New Braunfels Muni Airport 52 89 55 88 59 / 0 0 0 0 0
Burnet Muni Airport 51 86 57 86 57 / 0 0 0 0 0
Del Rio Intl Airport 53 90 56 90 59 / 0 0 0 0 0
Georgetown Muni Airport 52 88 57 87 57 / 0 0 0 0 0
Hondo Muni Airport 49 91 54 91 58 / 0 0 0 0 0
San Marcos Muni Airport 47 88 54 88 58 / 0 0 0 0 0
La Grange - Fayette Regional 52 86 55 87 59 / 0 0 0 0 0
San Antonio Intl Airport 53 89 57 89 61 / 0 0 0 0 0
Stinson Muni Airport 52 90 56 89 60 / 0 0 0 0 0
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1141 PM EDT Tue Sep 29 2020
Issued at 1140 PM EDT TUE SEP 29 2020
The line of showers that moved into our CWA has slowly dissipated
as it continued to edge eastward throughout the evening. Now, only
a few isolated small showers remain, mainly in the far east. Some
clouds also remain from the deteriorating line, generally VFR.
With a sharp upper level low moving over, there is enough winds
aloft that subsidence won`t be a factor tonight. So while some of
the deeper valleys could still see some patchy fog, do not expect
it to be nearly as much of an impact tonight compared to the
previous night. A new forecast package will be sent out to change
to overnight wording and reflect any changes made in the forecast.
UPDATE Issued at 833 PM EDT TUE SEP 29 2020
A line of showers and thunderstorms that formed over central
Kentucky late this afternoon continued to track eastward, and
despite all odds, has held on even into the evening as it crossed
into our CWA. The thunder has at least dissipated with the lack of
instability and cooling temps, but did update pops/weather to
show the line moving into the CWA and dissipating as it continues
eastward over the next couple of hours. Otherwise forecast seems
to be in good shape so far this evening. All updates have been
published and sent to NDFD/web.
.SHORT TERM...(This evening through Wednesday night)
Issued at 555 PM EDT TUE SEP 29 2020
Sharp trough is currently rotating through the mid Ohio Valley
this afternoon. H500 and H850 trough axis is still a bit upstream
from us, basically bisecting the Commonwealth. A weak surface
trough is reflected at the surface. These features show up well on
regional satellite and we continue to see convection firing to
our west, with an occasional lightning strike just to make things
interesting. Mesoanalysis indicates an area of very weak mixed
layer instability to our west (100-250 J/kg). Extrapolating out
the RAP suggests this area of instability weakens with time so
that activity will be just showers by the time it reaches our
forecast area...the I-75 corridor. However, high res, short term
models do try to keep this convection together, rolling through
the area during the early evening time frame. A less impressive,
but none the less second line of broken showers also continues to
push eastward across eastern Kentucky late this afternoon. Because
of trends, decided to hold onto at least a slight PoP into the
early evening. However, atmosphere stabilizes enough to leave any
mention of thunder out.
A second trough will drop southeast into the Midwest by late
Wednesday, Wednesday night. A corresponding surface cold front
will reach the Ohio River by Wednesday evening. Surface pressure
gradients tighten considerable ahead of the cold front. Steep
lapse rate through the boundary layer will set up a situation
where higher winds aloft will easily mix down through the
boundary later, causing gusty conditions to develop across the
region Wednesday. Moisture is limited with this system but there
appears to be just enough to warrant some isold PoPs Wednesday
night as the front pushes across eastern Kentucky.
.LONG TERM...(Thursday through Tuesday)
Issued at 333 PM EDT TUE SEP 29 2020
The primary themes in the extended will be well below normal
temperatures and mostly dry weather. A large trough of low
pressure, and its associated surface low, will bring increased
rain chances to eastern Kentucky Sunday and Sunday night, but
that should be the only period during which we see any rain in the
extended. This precip will be in the form of light rain showers.
Daily highs will likely max out in the 60s each day, with nightly
lows in the 40s. The coolest days will have highs in the lower
60s, and the coolest nights will see lows in the lower 40s.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
ISSUED AT 847 PM EDT TUE SEP 29 2020
Light showers are ongoing across portions of eastern KY, but
aren`t really impacting VIS at this point. There is also some
intermittent clouds, generally VFR, with some patches of MVFR
this evening. Both the clouds and the showers should be shifting
eastward through 6Z, with most sites clearing out after this
point. Clouds may hang around a bit longer in the far east,
including at KSJS. Winds will generally be light and variable
during the overnight. Heading into the daytime hours tomorrow,
another cold front will begin approaching eastern KY from the NW.
Decent mixing throughout the day will allow winds aloft to mix
down to the surface and lead to breezy conditions, especially in
the afternoon. Wind gusts between 20 and 25 knots will be possible
during the afternoon. The CWA should remain dry and mostly clear
during the day tomorrow, however can`t rule out a few clouds and
an isolated shower across the northern portion of the state
heading into tomorrow night as the front moves into the area.
Seeing an increase in the height of CIGS across our far west
this afternoon, suggesting some partial clearing. Further east
KSJS has been flirting on and off with high end IFR CIGS. While
much of the area will keep at least a mid-level deck or lower
through the bulk of the afternoon, still do expect the trend
towards higher CIGS. There will also be a slight uptick in shower
activity as well this afternoon as diurnal heating combines with a
surface wave of low pressure riding northeast over the
Appalachians along a surface frontal zone just to our east. At
present a scattered line of showers appears to be developing from
around Barbourville northeast to just east of Morehead. This
activity will push eastward with time through the afternoon. As
skies clear tonight, some river valley fog and low stratus
development will be likely again overnight, but current thinking
is that airport terminals will generally be unaffected. Winds will
remain light and variable at 5 kts or less through the overnight.
But gradient southwest winds will pick up quickly through the
day, climbing to between 10 and 15 kts with higher gusts. All this
a result of another storm front approaching from the west
Area Forecast Discussion
National Weather Service Marquette MI
721 PM EDT Tue Sep 29 2020
.SHORT TERM...(This evening through Wednesday)
Issued at 412 PM EDT TUE SEP 29 2020
WV imagery and RAP analysis indicated a mid/upper level ridge
through western North America and a broad downstream trough from
Hudson Bay through the Great Lakes into the southeast CONUS. A
shortwave trough from northwest Ontario into northwest WI supported
sct/nmrs showers through much so Upper Michigan into north central
WI. At the surface, light westerly low flow prevailed with gustier
northwest winds behind a trough through western MN. With 850 mb
temps around 3C, some lake enhancement was also helping to boost the
Tonight, expect the rain coverage to diminish from west to east this
evening per upstream radar/satellite trends. Additional showers
associated with the next upstream shrtwv over southern Manitoba are
expected to remain mainly west and south of Upper Michigan. However,
some additional isold/sct -shra or drizzle cannot be ruled out
overnight given the lingering deep moisture over the area with the
moist low level cyclonic flow.
Wednesday, a sfc trough moving through Upper Michigan along with a
weak mid level shrtwv and winds veering to the northwest will
bring another increase in sct/nmrs lake enhanced showers as 850 mb
temps drop to around 1C. Overall rainfall amounts will still
remain light with amounts of generally a few tenths at most.
Similar to today, temps will only climb into the lower to mid 50s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 358 PM EDT TUE SEP 29 2020
Not much change from the overnight shift forecast as Upper Michigan
stuck underneath an upper-level low, seen at 500mb to the northeast
of Upper Michigan. This will remain in place throughout the week and
during that time, multiple shortwaves will move along this trough
which will bring chances of precipitation through at least Friday.
Trough will slowly lift past the Hudson Bay through the weekend with
long range ensembles hinting at a gradual transition to zonal flow
by this time next week.
By Thursday morning, 850mb temps will fall between -4C and
-6C, resulting in lows mainly in the 30s with low 40s along the
lakeshores. Once again, expect scattered to numerous rain showers to
continue. These 850mb temps should not drop much as any lake-effect
precip should be remain as rain. Still looks like there could be a
small window of waterspout potential over Lake Superior with sfc
temps hovering around 10-12C. Better potential of a waterspout is
over Lake Michigan with warmer lake sfc temps around 15 to 17C and
cloud heights looking a little higher from latest model soundings.
Something that we`ll keep an eye on.
Thursday night could be interesting as some inland areas have the
potential to see their first snowflakes of the season. 850mb temps
will be between -5C and -8C which supports some snowflakes or
graupel, especially across the interior west. Latest NAM and GFS
soundings are indicating an inversion somewhere around 800mb which
is lower from the overnight sounding of near 700mb, may still be
high enough to cut off the lake-effect potential but am keeping PoPs
in the forecast over the north wind belts. We`ll see how this trends
over the next model runs. Precip should be winding down by Friday
afternoon as winds will decrease and looking at mostly dry weather
through Saturday afternoon.
Models indicate another shortwave that will approach Upper Michigan
sometime late Saturday or early Sunday. Exact track is still to be
determined however, will bring another chance of precip during that
time period. Heights rise a bit on Monday and Tuesday with the flow
almost becoming zonal. 850mb temps warm back up between 3-6C,
resulting in 50s and a few 60s before another trough moves in near
the end of this forecast period.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 721 PM EDT TUE SEP 29 2020
VFR conditions have arrived for the night at KCMX and KIWD, whereas
KSAW will remain in MVFR for another couple of hours due to
lingering -shra. Expect MVFR cigs to return at all terminals near
sunrise as thicker cloud cover moves in. While the chance for -shras
is possible at all TAF sites throughout tonight and tomorrow, short-
term model soundings seem to indicate that rain will be sporadic at
best. Therefore, most of the TAF sites are vcsh for the period.
Winds will also pick up from the nw tomorrow as caa moves down south
from Canada. VFR conditions should return to all TAF sites near the
end of the TAF period.
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 412 PM EDT TUE SEP 29 2020
Broad area of mid-level troughing will maintain a cool airmass over
the region. As this lingers over the warmer lake, creating high
instability, expect winds to remain generally in the 15-25 knot
range through mid week. Wednesday, some gusts above 25kts will be
possible, especially for higher reporting platforms as a trough
moves through. Winds in the 15 to 25 knot range till persist Thu
into Thu night will diminish Fri and remain below 15 knots this