Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/08/20
Area Forecast Discussion
National Weather Service Bismarck ND
936 PM CDT Fri Aug 7 2020
Issued at 933 PM CDT Fri Aug 7 2020
Updated to better cover current radar trends and linger pops in
the north a little longer. KMBX radar shows a few storms
developing near / north of Minot. The 00Z NAM NEST and latest HRRR
suggest that activity should gradually move northeast and
exit the forecast area around 05z.
UPDATE Issued at 808 PM CDT Fri Aug 7 2020
Made a quick update to better reflect the ongoing convection. The
line has decreased in coverage over the past hour, but the storms
that remain continue to be strong to severe. Expect them to
gradually weaken with the loss of daytime heating which is in line
with the latest HRRR.
UPDATE Issued at 637 PM CDT Fri Aug 7 2020
Late afternoon radar mosaic shows a line of storms has formed
along the eastern moving boundary in central North Dakota. The
CAMS have now generally caught on to this idea. Specifically, the
HRRR suggests the storms will continue to move east for the next
several hours before diminishing.
UPDATE Issued at 405 PM CDT Fri Aug 7 2020
A line of increasingly agitated cumulus has developed from
northern Dunn county through central Stark county. This cumulus
field is placed along a line of modest convergence, though
possibly aided by differential heating given the 10-15 degree
difference in surface dew points from east to west of the line.
While 12Z guidance had a fairly strong mid-level inversion in this
area, the early afternoon NUCAPS sounding product indicated a
substantially lesser cap in the area of the currently growing
cumulus (MLCIN of -155 J/kg from the 12Z NAM and around -40 on the
NUCAPS sounding). With current satellite trends (including
increasing glaciation seen on GOES-East Day Cloud Phase RGB)
indicating better confidence for convective initiation, an
isolated severe threat will be possible. Very steep mid-level
lapse rates of 8+ C/km on the NUCAPS sounding show ample
instability aloft for hail production, though mitigated somewhat
by just marginal effective deep layer shear of around 25 kts. The
current mid-level height rise pattern contributes additional
uncertainty in convective coverage, though clearly there is enough
convergence for convective initiation attempts in the near-term.
Given the formation of thunderstorms by this evening, severe hail
and locally damaging wind gusts will be possible.
.SHORT TERM...(This afternoon through Saturday)
Issued at 200 PM CDT Fri Aug 7 2020
The MCV that moved across southern North Dakota this morning has
now moved into the Red River valley, and any afternoon
thunderstorms that develop from its remnants will remain east of
our forecast area.
At the mid levels, we will see height rises and capping through
the rest of the day with low amplitude ridging building in. This
pattern will likely keep most of the area dry through the day. At
the surface, low pressure was centered over southeastern
Saskatchewan, with a warm front extending southeast into north
central North Dakota, and down through the James the Red River
valleys. This boundary is easily identifiable on visible satellite
imagery, marking a sharp cut off in cloud cover to its west. A
cold front was also extending south from the low, near the Montana
North Dakota border.
As an upper trough continues to approach the region this evening,
we will see some neutral to falling heights across the north after
03z, which may help to fire a couple of isolated storms in the
vicinity of the north central along the advancing cold front. Most
of the forcing stays well north of the International Border but
convergence along the wind shift and strong instability may be
enough to support a few updrafts tonight. CAMs remain meager with
developing convection, and only a couple even produce storms.
Given the strong instability in the forecast, any storms that can
mature may become strong with some small hail and gusty winds, but
the severe threat appears rather low with meager deep layer shear
in the range of 25 to 35 knots. Additionally, westerly winds at
the lower and mid levels suggest updrafts may have a hard time
sustaining themselves because of parcel detrainment, even with
strong instability present. Storms will quickly move out/diminish
after 06z, with lows in western and central North Dakota ranging
from the lower 50s northwest to the mid 60s across the southern
James River valley.
Finally, it is worth noting that near critical fire weather
conditions will be possible this afternoon across portions of the
far west. Much of this area will see minimum relative humidity
values ranging from 20 to 25 percent. Sustained winds may approach
15 to 20 mph, but these winds will only overlap the lowest
humidity values for maybe an hour or two. The west will once
again see dry conditions on Saturday, but winds will be much
lighter. Highs will be slightly cooler on Saturday, generally in
.LONG TERM...(Saturday night through Friday)
Issued at 200 PM CDT Fri Aug 7 2020
Instability and precipitation chances increase Saturday evening
and night across the southwest, expanding north and east
overnight. Severe weather will likely remain south of the state
Saturday night and east of the forecast area on Sunday. A few
stronger storms may be possible across the southern James River
valley Sunday afternoon, however.
Otherwise, after Sunday, general height rises aloft with a
return to mainly zonal flow should maintain fairly low chances
for thunderstorms through Tuesday. It is worth noting that CIPS
extended analogs have been consistent in showing a strong signal
for severe weather towards the end of the work week. We have a
very long way to go to work out any specific details, but this
will be a time period that we will be watching closely as we may
become fairly active again.
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 637 PM CDT Fri Aug 7 2020
The main concern will be the chance of thunderstorms at KBIS and
KMOT over the next couple of hours. A line of thunderstorms has
developed in parts of central North Dakota and will continue to
move east over the next several hours. Opted to carry a brief
tempo group for TS at KBIS since that location appears to have
the best chance of storms. Did not add to KMOT, but will keep an
eye on it and update if needed. Kept the other TAF locations VFR
Area Forecast Discussion
National Weather Service Cleveland OH
913 PM EDT Fri Aug 7 2020
High pressure over the Great Lakes region will remain over the
area through Saturday. A warm front will approach the area on
Monday. Low pressure over the northern Great Lakes on Monday
night will extend a cold front across the area on Tuesday.
.NEAR TERM /THROUGH SATURDAY NIGHT/...
930 pm update...
There weather is quiet and pleasant this
evening. No changes were needed with the near term forecast.
Removed PoPs in NWPA as dry air has proved too great to get any
appreciable cumulus field started in the area. Otherwise,
forecast remains on track.
Lake enhanced clouds will continue to drift southwest across
the area with areas along the lakeshore becoming mostly clear
this afternoon. In addition to these lake enhanced clouds,
starting to see some diurnally- driven cumulus across the area.
Have a short window for a slight chance of showers and
thunderstorms across NW PA this afternoon, mainly in eastern
Crawford County. This is the area where the GOES-derived fields
like LI, CAPE, in addition to the RAP fields, are showing the
most likely spot for any shower development. Otherwise,
temperatures will rise into the upper 70s to lower 80s today,
trending on the cooler side where clouds reside and vise versa.
By Saturday, drier mid-level air and coincident upper level
ridging is set to arrive as surface high pressure retains a
tight grip across the Ohio Valley. Expecting mostly sunny skies
with temperatures slightly warmer than today, into the low to
mid 80s. Lows will fall into the upper 50s to lower 60s.
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
A weak shortwave trough should exit our CWA to the east by midday
Sunday and be followed by a shortwave ridge over our region Sunday
afternoon through Sunday night, allowing fair weather to grace our
area. By Monday and Monday night, additional and weak shortwave
troughs should begin affecting our region from the west as these
disturbances revolve around a mid- to upper-level low in vicinity of
western Hudson Bay. At the surface, a high pressure ridge gradually
exits our CWA through the period as the embedded high pressure
center moves from the Upper Ohio Valley toward the southern
Appalachians. By Monday night, a cool front should begin passing
through far-western portions of Lake Erie and northern Ohio as the
front drifts eastward. This front will cause chances for isolated to
scattered showers and thunderstorms to increase from west to east
Monday and Monday night. Simultaneously, humidity will increase as a
low-level return flow of Gulf of Mexico moisture overspreads our
Temperatures trend above-normal through the period. Sunday
afternoon`s highs should reach the 80`s to 90 degrees. Overnight
lows should reach the 60`s to lower 70`s Sunday night. Monday should
be warmer, with afternoon highs reaching the mid 80`s to lower 90`s.
Monday night will be muggier, with lows in the mid 60`s to lower
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Flow aloft becomes more cyclonic Tuesday through Thursday as a
longwave trough becomes established over the eastern Great Lakes and
vicinity, and the embedded mid- to upper-level low advances from
Hudson Bay toward Labrador. Simultaneously, multiple shortwave
disturbances embedded in the longwave trough will affect our CWA. At
the surface, the aforementioned eastward-moving cool front should
exit the rest of our region by the end of Tuesday. Behind this
front, a weak surface high pressure ridge should build over our
region from the west. Multiple rounds of isolated to scattered
showers and thunderstorms remain possible, especially during the
afternoon and early evening hours of Tuesday through Thursday.
Afternoon high temperatures should reach the low to mid 80`s Tuesday
through Thursday. Lows should reach the 60`s to lower 70`s Tuesday
night and Wednesday night.
A high pressure ridge aloft may begin overspreading our CWA from the
west Thursday night and Friday. Simultaneously, a trough aloft may
begin to undercut this ridge from the Upper and Mid Mississippi
Valley region. At the surface, high pressure ridging should begin
exiting our region to the east as a surface low approaches from the
Lower Ohio Valley. This pattern should allow chances of isolated to
scattered showers and thunderstorms to persist over our region.
Thursday night lows in the 60`s to lower 70`s should be followed by
afternoon highs in the low to mid 80`s on Friday.
.AVIATION /00Z Saturday THROUGH Wednesday/...
VFR conditions across the TAF sites will prevail through the
next 24 to 30 hours with this TAF update. High pressure and
light winds will continue along with mostly clear skies. The
majority of the winds will be light and variable under 5 knots.
There may be a little bit of a lake breeze influence for CLE
and ERI tomorrow with light breeze of 5 knots from the north.
Otherwise, there are no aviation concerns at this time.
possible with afternoon showers and thunderstorms on Monday
Northeasterly winds around 10 knots this afternoon will be followed
by light and variable winds tonight through Saturday as a high
pressure center moves from Lake Huron to Lake Erie. This high
pressure center will then drift toward the southern Appalachians
Saturday night through Monday. Simultaneously, winds will become
southerly to southwesterly at about 5 to 15 knots over Lake Erie.
Southwesterly winds of about 5 to 15 knots shift to westerly
following the passage of a cool front that should drift eastward
over the lake Monday night and Tuesday. By Tuesday night and
Wednesday, winds should become light and variable over Lake Erie as
high pressure builds from the west. Waves will likely be no larger
than 1 to 3 feet through the period.
Area Forecast Discussion
National Weather Service Grand Forks ND
1025 PM CDT Fri Aug 7 2020
Issued at 1024 PM CDT Fri Aug 7 2020
MCV and associated thunderstorms finally exiting the forecast
area. Cold front in central ND moving east and there are scattered
storms with it...one area in north central ND and the other area
was near BIS but that is fading away. Still a chance of t-storms
along the front as it moves east overnight.
.SHORT TERM...(This evening through Saturday night)
Issued at 353 PM CDT Fri Aug 7 2020
Showers and thunderstorms continue in the vicinity of an MCV
moving ENE across the area this afternoon. South and east of this
feature looks to be the best area for severe storms over the next
few hours with ML CAPE at 1500-2500 J/kg and deep shear of 25-40
kts. Area of clearing southwest of MCV in area of outflow could
be the best area for redevelopment as indicated by latest HRRR
run. Severe storm threats will be mainly winds to 75 mph and 2"
hail, but also a tornado or two will be possible. Any storms that
develop have the potential to grow upscale to a line of storms in
the eastern forecast area before exiting across east-central MN.
A cold front will be pushing east across ND later tonight. Some
storms could be severe with this potential line of storms...with
the best chance along the Canadian border. Decreased chances
somewhat with this features as CAMs have trended more towards
storm that are isolated in nature. The cold front will usher in
drier air for Saturday.
Another system is expected to push east across SD and
northeastward into eastern ND and MN by late Saturday night.
Chances are mainly for the southern half of the forecast area
.LONG TERM...(Sunday through Friday)
Issued at 320 PM CDT Fri Aug 7 2020
The main chance for impactful weather is found at the beginning of
the period on Sun, followed by another chance around Thu.
During Sun an approaching surface front and upper wave will increase
chances for strong to severe convection. Current timing places this
front in the vicinity of Devils Lake by noon, progressing to the
valley by mid afternoon, then west central MN by early evening.
CAPE and shear is available and it would appear the strongest
storms would likely be proximal to the frontal position at peak heating
time. Bulk shear at 0-6km coincident with the boundary should be in
the 30 to 50 kt range, along with SB CAPES between 2 and 4K. The Red
River Valley could be the main target region, with storms moving to
northwest and west central late afternoon and early evening.
High pressure is on schedule to provide quieter weather on Mon
through Wed, with the next chance for stronger convection presenting
.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 703 PM CDT Fri Aug 7 2020
Thunderstorms moving out of Bemidji Airport area 01z. Otherwise
TAF sites will be t-storm free this evening and maybe all night as
thunderstorm coverage overnight more isolated. South winds to
become west by 09z in the RRV and toward 12z-15z BJI. Some brief
MVFR cigs psbl mainly east of the Red River for a time tonight or
early Saturday, higher chances Bemidji.
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
646 PM CDT Fri Aug 7 2020
.SHORT TERM...(This evening through Saturday night)
Issued at 400 PM CDT Fri Aug 7 2020
Upper air and satellite data showing continued generally westerly
flow across the region this afternoon, as we sit on the northern
edge of high pressure centered over TX. A subtle shortwave
disturbance embedded in the westerly flow kept pesky isolated
showers and a few rumbles of thunder around portion of the area into
the early afternoon hours...mainly between I-80 and the NE/KS state
line. The day started out with plenty of low level stratus across
the CWA...and it has been slow to diminish across areas along/east
of HWY 281. To the south/west of this area, skies are mostly
sunny/sunny...it`ll likely take a couple more hours for things to
clear further in the east. Even with the isolated precip/clouds and
with several hours yet for temps to rise along/east of HWY 281,
temperatures this afternoon have worked out pretty well...3 PM obs
are in the mid 80s to right at 90. Little change in the sfc pattern
today, with the CWA remaining in between high pressure over the
Great Lakes/Midwest and a trough of low pressure extending through
the High Plains. Speeds have topped out around 15 MPH for most, with
at least occasional gusts of 20-25 MPH.
Dry conditions remain in the forecast tonight. Models are in good
agreement showing little change overall in the pattern, with flow
remaining westerly and the CWA sitting between the departing
disturbance to the east and the next one that will be moving in
later Saturday. At the sfc, models showing low pressure sliding a
bit further east into SW NE/W KS tonight...with a weak frontal
boundary extending NNE through portions of central NE. Expecting
winds to turn more light/variable near/along this sfc boundary, and
the development of fog will again be a concern as we get into late
tonight/pre-dawn Saturday morning. Inserted a mention of patchy fog
for areas north of Phillipsburg/York line...may end up needing an
`areas` mention for I-80 north where some models show better
potential. Also increased sky cover in this area for the potential
for another round of low level stratus.
Once any morning fog/clouds dissipate, the main focus as we get
through Saturday turns to the west, and the increasing chances for
thunderstorms. Models showing the upper level ridge axis shifting a
bit east, with a shortwave disturbance emerging from the Central
Rockies later in the day. The main sfc boundary is expected to be
set up over western portions of NE/KS by mid-late afternoon,
providing a focus for thunderstorm development as the better upper
forcing moves in. Kept chances out until after 21Z, and even that
may be too soon, as models are in good agreement showing hefty
capping to overcome/mid level temps around 15-16C. It may be closer
to/after 00Z before activity moves into/develops over the western
CWA...and there are still questions with the coverage/southern
extent. The best chances for more widespread activity currently look
to slide north of the CWA. What would help bring more storms to our
CWA would be the lift along the nose of the LLJ that develops in the
evening, but there are even some questions there with its location.
Current forecast has the higher PoPs (30-40%) along/north of I-
80...but can`t completely rule out precip for any particular area,
so have 20 PoPs all the way into north central KS. For thunderstorms
that develop, certainly no shortage of instability available...and
deep layer shear is sufficient for severe weather to be a concern.
The SPC Day 2 outlook has most of our Neb counties included in the
Slight Risk area, with the Marginal south into much of our KS area.
Large hail, damaging winds and heavy rain would be the primary
hazards. Activity looks to push east of the CWA sometime during the
06-09Z time frame.
Did not make any notable changes to other weather elements for
Saturday. Expecting SSE winds around 10-15 MPH for most areas,
perhaps on the gusty side across our KS counties. Still expecting it
to be a hot day, with high temperatures reaching the lower-mid 90s
for most...and combined with dewpoints in the 60s and 70s...heat
index values across much of the CWA look to top out in the 100-105
degree range. Opted against a Heat Advisory at this time, with
current forecast heat index values below 105 (official criteria) vs
at or above that value...but it will be something for upcoming
shifts to watch.
.LONG TERM...(Sunday daytime through Friday)
Issued at 400 PM CDT Fri Aug 7 2020
General overview of this 6-day period:
As a whole, this stretch can probably be summed up as "pretty
typical summer/August weather". In the mid-upper levels, our
Central Plains area resides (generally) within a west-northwest
flow pattern, along the interface between stronger flow to our
north, and weaker flow to our south, where a large-scale ridge
will be centered over the AX/NM/west TX region much of the next
week. With the exception of Sunday-Monday (which are respectively
the overall-hottest and coolest days out of these six...more on
this below), the majority of this time looks to feature near to
slightly above normal readings for mid-August (not overly-hot,
but not nearly as cool as what we saw a few days back either).
This means highs mainly mid-80s to around 90, and overnight lows
mainly well into the 60s. As for rain/thunderstorm chances, there
are several of them scattered throughout the entire Sunday
evening-Friday time frame, but as is also typical of this
"summery" weather pattern, they will be driven by more subtle
disturbances aloft and/or nocturnal low level jet forcing. This
means that confidence in "exact" details of timing/location is
fairly low in any one particular day/night period, other than to
say that the evening through early morning hours would tend to be
more favored than the majority of the daylight hours for
precipitation (again, very typical for this time of year). For
sure, there is good reason that all rain chances (PoPs) through
this time frame have been held down in the 20-40 percent range at
most, as confidence is not there to go higher (yet).
Severe storm chances:
While no days/night currently "scream" widespread severe weather
(especially given such subtle forcing mechanisms), this weather
pattern is known for occasional bouts of at least limited
strong/severe storm activity, especially during the evening and
early-overnight hours. Have little doubt that at least a few
periods will eventually be assigned Marginal/perhaps Slight Risk
categories by SPC as they draw closer in time, but it`s just too
soon to confidently assess exactly which ones. Technically, our
extreme northern coverage area (CWA) is already "nicked" by the
southern fringes of a Marginal Risk area for Sunday evening, but
some of the latest raw model data actually suggests that our west-
southwest areas may be just as deserving of a Marginal Risk for
Sunday, so would not be surprised to see things change a bit in
later outlooks versus the current SPC Day 3.
With the "big picture" covered above, will finish up with a bit
more detail on the Sunday-Monday time frame, which are not only
the nearest-in-time of the "long term" periods, but also the most
intriguing in terms of temperature trends/contrast from one day
to the next. Not to mention that heat concerns for Sunday are
While we have been "talking up" Saturday afternoon heat concerns
for a few days now (in our Hazardous Weather Outlook etc.), Sunday
has trended upward/a bit "worse" than previous forecasts, and in
fact now looks just as hot (if not hotter) than Saturday for much
of the CWA. Needless to say, a mention of Sunday heat has now been
added to our HWO, as the afternoon looks to feature widespread
100-105 heat index values, with the overall-highest readings
favoring Nebraska counties east of Highway 281. Given that 105+
heat index is technically our Advisory criteria, this could end up
being a pretty close call to needing one for at least parts of the
area. As for actual air temperatures (Max T), most of the CWA is
now aimed into the 93-97 range, with typically-hotter southwestern
counties perhaps flirting with 100 degrees. Fortunately, there
should be at least a modest southerly breeze during the afternoon
(generally 10-15 MPH, with some higher gusts especially in KS
zones) to provide some limited relief. Turning to
precipitation/thunderstorm chances, have maintained the dry
forecast area-wide for the daytime hours (prior to 7 PM), as odds
favor any lingering Saturday night activity to be departed off to
our east by sunrise. However, have also maintained some low-
confidence PoPs/storm chances for Sunday evening-night, as latest
NAM/GFS suggest that at least limited activity could either drift
in from our west and/or form overhead late in the night as a cold
front starts to drift in from the north. As hit on above, do not
be surprised to see a bit more of our CWA eventually end up in an
SPC Marginal risk in later outlooks.
While most of the daytime is looking dry/storm-free, cannot
completely rule out some spotty activity near and behind the
aforementioned cold front working trough the area. However, this
cold front is truly the bigger story of the day, as it will bring
a period of somewhat-breezy northeast winds to the CWA (gusts 20+
MPH), and also a solid 10+ degree cool-down (versus Sunday) to
MOST of our CWA. That means highs "only" in the low-mid 80s for
most of the area. However, our KS zones will not feel this push of
cooler air quite as much, and especially Rooks-Osborne-Mitchell
counties could still manage to hit 90 (still cooler than Sunday).
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 619 PM CDT Fri Aug 7 2020
Fog is the main concern through the period are there are some
indications that vsbys could drop significantly towards
morning...but others that are conflicting.
Expect steady southerly winds this evening to diminish as they
shift and become southeasterly overnight...with hints of LLWS
focused just to our east. As winds diminish and skies remain
clear along with elevated dewpoints...the potential for fog exists
with lows forecast to be a few degrees below afternoon dewpoint
values. Therefore...do expect some fog to develop after
midnight...but density is still a bit uncertain as main supporters
are these crossover temps being exceed and SREF guidance, with
the HRRR not indicating any fog potential at all.
Otherwise...after any fog that develops burns off...expect light
southeasterly winds tomorrow with just some passing mid/high
level clouds. A chance for thunderstorms will spread from west to
east across the local area after 09/00Z.