Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/10/21
Area Forecast Discussion
National Weather Service La Crosse WI
945 PM CDT Thu Sep 9 2021
.SHORT TERM...(This evening through Friday)
Issued at 228 PM CDT Thu Sep 9 2021
A northwest flow regime continues in the region through Saturday,
allowing for smaller pops until then. The flow`s associated
shortwave troughs pass through the region this evening and will
bring increased cloud cover with it. RAP13 850-500mb lapse rates
hover from 5-6 C/km while ML CAPE is nearly non-existent in the
area. Some models show scattered precipitation from late afternoon
to evening today along the Mississippi, but due to the scattered
nature and quick dissipation, precipitation is not included in the
forecast for this evening.
Valley fog is likely Friday morning, as the light wind layer
overnight is about 5300 ft according to NAM3KM and HRRR model
soundings. Dewpoint depression also looks to be less than 4 degrees
in the models further setting the stage for a valley fog event.
Otherwise, the upper-level high pressure system over the area will
keep the area dry and increase temperatures through Saturday,
topping out in the 80s on Saturday.
.LONG TERM...(Friday night through Thursday)
Issued at 228 PM CDT Thu Sep 9 2021
Pops return late Saturday night into early Sunday morning as a
shortwave trough pushes a cold front through the area. Highest
moisture transport located in SE Iowa and SW Wisconsin late Saturday
night into early Sunday morning, so any developing showers likely to
be located in those regions. However, the exact location of the
showers will largely be determined by the location of the stationary
front to the south, which is uncertain at this time.
Higher southwesterly moisture transport ramps up again Monday
evening in the same areas. GFS MU CAPE is about 700 J/kg so severe
storms looking unlikely with this round of showers. Temperatures
will be in the 70s throughout the area.
On and off precip chances remain through Thursday as another
shortwave trough passes through the area. The location of the swt is
uncertain at this point, so best locations for showers are not
clear. Working with ensemble model data from Tuesday to Thursday to
get the best idea of any weather that will occur until then.
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 945 PM CDT Thu Sep 9 2021
Little change in thinking from previous issuance. Surface high
pressure will drift east through Friday with winds becoming
southerly. While mainly VFR conditions are expected, a period of
LIFR fog/stratus continues to look likely at KLSE between 10.09
and 10.14Z given clearing skies, light flow, and low T/Td spreads.
Boundary layer flow begins to increase slightly by sunrise, but
at this point do not expect this will significantly inhibit fog
Area Forecast Discussion...Updated
National Weather Service Billings MT
932 PM MDT Thu Sep 9 2021
The Red Flag Warning has been allowed to expire as Red Flag
conditions are no longer expected. Some light returns have
persisted the last few hours from Big Timber to Harlowton west. So
far no precipitation has been reported by any stations, but there
have been some isolated lightning strikes. These still look like
they will decrease in coverage and dissipate by around midnight.
With all of the smoke across the area, the temperatures did not
get as warm this afternoon, so have adjusted the temperature
trends this evening to reflect that. The latest runs of the HRRR
do not show the smoke changing, either near the surface or aloft,
into tomorrow. Reimer
Tonight through Friday night...
Upper ridge in control today, will get suppressed a bit tonight
and Friday. The impact of this will be felt more this weekend and
next week with cooler temperatures.
For the rest of this afternoon and tonight, weak shortwave energy
will kick across the area and trigger isolated showers and
thundestorms over the western half of the area. Inverted V
soundings suggest strong wind gusts with convection. Precipitable
water amounts start below 3/4 of an inch, but quickly rise to
around an inch this evening. Coverage of showers and storms will
be isolated (with most of the activity west and north of the area)
but those that do swing across will have potential for gusty
winds. Smoke has greatly diminished the heat and mixing potential
today. Thus, Red Flag conditions not being realized yet. Still
have potential for this late this afternoon and early this evening
Friday should be another warm day, but smoke could play a role in
this again (making things a little cooler and limiting mixing
potential). Highs are progged in the mid 80s to around 90 degrees,
but smoke could limit that. A cold front will swing into the
eastern zones late afternoon, then back into central and western
zones Friday evening. Timing of the strongest northeast to east
winds with this front looks to be during the evening hours (as
humidity levels recover). This combined with smoke limiting wind
potential with the front in the first place, and this could
decrease fire weather threat somewhat. Will leave the Red Flag in
place and will not extend it at the moment. A Red Flag may be
needed in the east for the front and the midnight crew will need
to take a closer look at that. The chance of showers and isolated
thunderstorms increases Friday afternoon and evening as a western
trough swings across. TWH
Saturday through Thursday...
Little in the way of changes for the extended forecast period.
Expect to see cooler temps through the period, with
shower/thunder potential, but little accumulating precipitation
outside of western mountains and near foothills.
Expect to see isolated shower and thunderstorm activity persist
through Saturday, as the upper trough lifts across the region.
Guidance continues to trend this system more to the north, with
best precip potential to our north.
Zonal flow will take over for next week, with weak shortwaves
sliding through the flow. This will help keep temps cooler (around
normal), and may bring some isolate showers each afternoon through
the week. Strongest waves look to cross the region Sunday night
into Tuesday, with another late Wednesday into Thursday. These
should bring better potential for showers across the CWA, but
little total precip. Although guidance has been fairly consistent
with the overall pattern, trending cooler, with this succession
of shortwaves/troughs, timing and strength of these systems has
been fluctuating significantly in guidance, so changes are
possible as we get closer in time.
Localized MVFR conditions due to heavy smoke concentrations are
possible tonight into Friday. Poor slant range visibilities can be
expected as well. Isolated high based thunderstorms are expected
west of KBIL through 06Z, with strong wind gusts to around 40kts
possible near any storm. Outside of smoke, VFR conditions will
.PRELIMINARY POINT TEMP/POPS...
Fri Sat Sun Mon Tue Wed Thu
BIL 061/091 059/078 052/081 054/071 048/072 049/079 048/069
21/K 22/T 00/U 33/W 31/U 00/U 22/W
LVM 056/090 052/075 046/080 046/071 042/072 042/077 041/068
22/T 63/T 00/U 43/T 31/U 01/U 22/W
HDN 057/093 058/080 050/082 051/072 047/072 045/080 046/070
11/K 22/T 00/U 33/W 31/U 00/U 21/B
MLS 059/092 059/075 050/079 055/071 048/071 047/078 049/070
00/K 23/T 10/U 32/W 21/U 10/U 11/B
4BQ 059/093 059/078 052/081 056/073 048/069 048/078 048/070
00/K 11/B 10/U 22/W 32/W 10/U 11/B
BHK 059/093 055/072 049/078 054/071 046/069 046/077 048/069
00/K 12/T 10/U 33/W 21/U 10/U 11/B
SHR 057/095 056/080 047/082 051/074 044/069 042/079 044/070
01/K 22/T 10/U 23/W 42/W 10/U 11/B
Area Forecast Discussion
National Weather Service Quad Cities IA IL
614 PM CDT Thu Sep 9 2021
Issued at 315 PM CDT Thu Sep 9 2021
Gorgeous early September afternoon in progress, with high pressure
providing light winds and low humidity while some scattered to
broken diurnal cumulus is leading to occasional sun breaks.
Satellite also shows a large expanse of wildfire smoke aloft through
the Plains and even some into central/western Iowa. The high will
move off to the east over the next 24 hrs. Ensuing southerly
return flow will begin the warm-up into the upcoming weekend.
.SHORT TERM...(This Evening through Friday)
ISSUED AT 315 PM CDT Thu Sep 9 2021
Another very pleasant night is on tap for the area. Lows will be
a bit tricky due to likelihood of a period of mid/high level
cloudiness late evening/overnight attendant to a passing upper level
disturbance, which is currently diving down into northern MN.
Regional radar also shows a few showers accompanying this wave.
Shower chances are non-zero for the area, but they appear far too
low for any mention with soundings depicting a rather shallow
moisture layer and considerable sub-cloud dry air. As mentioned
cloud trends will play a big role in lows for tonight, and because
of this forecast lows were kept near 50th percentile of NBM and
generally in the lower to middle 50s.
Friday will bring plentiful sunshine, albeit a bit hazy as NW flow
aloft shuttles in some western wildfire smoke. Doesn`t look to be
too thick per HRRR smoke model and should remain very high up in
the atmosphere. Southerly return flow will be developing and
strengthening during the day allowing for warmer highs generally
in the upper 70s and lower 80s. Dew points will also increase a
bit, but still comfortable to slightly noticeable humidity levels
expected with a bit of a SE trajectory on winds.
.LONG TERM...(Friday Night through Thursday)
ISSUED AT 315 PM CDT Thu Sep 9 2021
*Unseasonably warm weather is forecast into early next week.
Saturday looks to be potentially the warmest day as highs could
reach around 90F to the lower 90s although a greater uncertainty
exists on highs due to the potential for thicker wildfire smoke
*A dry pattern is anticipated for most of the outlook area through
Sunday. However, there are low chances for showers/storms across
the north Sunday afternoon into Sunday night. A cold front may
bring better chances for rain across eastern Iowa and northwest
Illinois into the middle of next week.
Friday night through Saturday
A large upper ridge over the Southwest U.S. will shift into the
Southern Plains late this week into the weekend. Models show the
upper ridge eventually breaking down with flow aloft becoming
zonal over the Midwest.
A 30-40 kt WSW LLJ juxtaposed to the north of the ridge will
advect an anomalously warm EML, characterized by 850mb temps of 24
to 28 C, across Iowa and Illinois later Friday into Saturday (NAEFS
is highlighting 850mb temps at 3+ standard deviations above
normal). Temps will warm up significantly from those of Friday
with upper 80s/lower 90s forecast for Saturday. The wildcard for
highs on Saturday will be the magnitude of western wildfire
smoke. Latest HRRR smoke model shows potentially dense smoke aloft
by Saturday AM, which if occurs and being September could be
impactful in lowering highs by a few degrees. It will also become
more humid with dewpoints reaching the low/mid 60s by Saturday.
Heat indices could potentially be in the low to mid 90s with some
areas in the upper 90s.
A weak front dropping into the northern forecast area on Sunday
will lead to highs in the upper 70s/low 80s north of highway 30.
However, to the south the very warm conditions will hang on with
highs in the mid/upper 80s. The front could kick off isolated
showers and storms from Sunday afternoon into Sunday. Right now
thinking coverage will remain low.
Warm conditions will continue through early next week with highs
in the 80s. A front lingering in our northern counties looks to
lift back as a warm front by late Monday and could take the rain
chances with it for a time while expanding the warm and humid
conditions across our north. There is a growing consensus signal
for a stronger upper level trough to move through the area heading
into the middle of next week. This will sweep a cold front through
the area, and focusing greatest rain chances by Tuesday into early
Upper level ridging looks to build in by mid to late next week
leading to dry and warm conditions.
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
ISSUED AT 613 PM CDT Thu Sep 9 2021
Clear skies may occasionally have a some mid clouds passing
through well above 10kft through Friday evening, but otherwise, a
VFR period with light winds overnight, becoming southeast during
the day Friday, and increasing to 10 to 15 kts.
Area Forecast Discussion...UPDATED
National Weather Service Fort Worth TX
716 PM CDT Thu Sep 9 2021
...New Short Term, Aviation...
.SHORT TERM... /NEW/
The only real change to the short term forecast was to bring
MinTs down a few degrees tonight into Friday morning given the
light winds, mostly clear skies and dry air at the surface.
Overnight lows will fall into the 60s, though a few of the rural
outlying/sheltered locations may briefly dip down into the upper
50s. I also introduced haze into the worded forecast based on
satellite observations and HRRR vertically integrated smoke
products. At this juncture, I don`t anticipate any substantial
reductions in visibility at the surface as most of the smoke will
remain above 5,000 feet. There may be more of an orange hue to
the sky around sunrise Friday and possibly toward sundown Friday
across parts of the area.
Otherwise, the remainder of the short term forecast remains
unchanged and appears to be on track.
A mild and beautiful day it is today! Following yesterday`s cold
front passage, temperatures are in the upper 80s with dewpoints in
the 40s across most of the region. While not exactly autumn-like,
the lower humidity is certainly appreciated. Winds are beginning
to veer out of the southeast which should allow for humidity to
increase gradually over the next few days, so today will likely be
the driest day (in terms of relative humidity) through the next
several days. The dry conditions and clear skies will mean lows
tonight should have little difficulty falling into the 60s across
the region. This morning, a few rural locations northwest of Fort
Worth even managed to drop into the upper 50s, and a repeat of
this will be likely again tonight. Friday will be slightly warmer
with highs reaching into the low to mid 90s, but low humidity will
keep it fairly pleasant overall.
.LONG TERM... /Issued 345 PM CDT Thu Sep 9 2021/
/Friday Night through Thursday/
Mid level ridging will continue to dominate the Western U.S.
through Saturday with warm and dry conditions expected across
North and Central Texas. A lack of any significant low level
moisture will lead to seasonably cool morning and warm, but dry
afternoons through Saturday.
With an increasingly active northern stream, several shortwaves
will chip away at the stronger ridging over the weekend and we
should see a general weakening of the ridge by late Saturday.
Meanwhile, a disorganized area of low pressure in the Western Gulf
and its associated 2"+ PWs will gradually meander toward the TX
Coast during this time. As zonal flow becomes established across
the Central and Northern Plains Saturday night, increasing
pressure falls in the lee of the Rockies should result in
strengthening southerly flow across Texas. This should rapidly
pull moisture northward overnight into Sunday morning with
dewpoints climbing from the 40s into the mid/upper 60s. Sunday
afternoon will feel noticeably warmer as heat indices climb back
into the upper 90s. While the ridge will try to become re-
established across the Southwest through the middle of next week,
it appears that North Texas will remain east of its stronger
influence. This should lead to at least some afternoon scattered
showers and thunderstorms, particularly across our east and
southeast counties through the middle of next week. We`ll have
20-40% PoPs each afternoon during this time with temperatures
likely to be influenced by an increase in cloud cover. The ECMWF
does show some potential for an organized coastal low in the
Monday to Wednesday timeframe which could bring significant
rainfall to Southeast Texas. We`ll keep an eye on this as some
heavy rainfall could spread into our southeast counties through
/00 UTC TAF Cycle/
VFR will prevail at all TAF sites through the end of the TAF
period. Stout ridging overhead will allow for dry conditions; with
just some high clouds. Haze from the smoke moving in from the
western US wildfires could impact slant-range visibilities, but
reductions to surface vsby is not expected. Southeasterly winds
less than 10 knots will prevail at all TAF sites throughout the
.PRELIMINARY POINT TEMPS/POPS...
Dallas-Ft. Worth 67 93 69 95 70 / 0 0 0 0 0
Waco 65 93 65 95 68 / 0 0 0 0 0
Paris 63 91 64 93 65 / 0 0 0 0 0
Denton 65 93 65 95 66 / 0 0 0 0 0
McKinney 65 93 66 94 67 / 0 0 0 0 0
Dallas 67 93 71 95 71 / 0 0 0 0 0
Terrell 63 91 64 94 65 / 0 0 0 0 0
Corsicana 64 93 64 95 68 / 0 0 0 0 0
Temple 64 94 64 94 68 / 0 0 0 0 0
Mineral Wells 62 93 64 95 64 / 0 0 0 0 0
AREA FORECAST DISCUSSION
National Weather Service Hastings NE
615 PM CDT Thu Sep 9 2021
...Short Term Update...
Issued at 614 PM CDT Thu Sep 9 2021
Some comments solely regarding high temperatures tomorrow (Fri):
The bottom line:
Have nudged down highs 1-2 degrees across the vast majority of the
coverage area (CWA) from original late afternoon "forecast
package" just issued a few hours ago, and perhaps might not have
gone quite "cool" enough.
We generally don`t "mess with" tomorrow`s (2nd period)
temperatures on an evening/swing shift, but after seeing how the
extensive smoke aloft wreaked a surprising amount of havoc with
our high temperature forecast today (our early AM forecast package
ended up 4-6 degrees too warm most areas)...and given that
confidence is high that the persistent smoke plume will remain in
place and be be very similar tomorrow based on HRRR-Smoke
(vertically integrated)...opted to proactively nudge highs down
1-2 degrees for now, and will advise upcoming night shift that
this might not have been enough. In other words, while there is
zero doubt that tomorrow will be noticeably warmer/hotter than
today based solely on a significant increase in the low-level temp
profile, feel that the majority of the CWA is probably heading
more toward low-mid 90s (at most) instead of mid-upper 90s. The
the main exception would be in a few of our extreme southwest
counties (especially Furnas/Phillips/Rooks) where upper 90s to
around 100 appears more attainable given the drier air/lower
dewpoints expected there.
.DISCUSSION...(This evening through Thursday)
Issued at 327 PM CDT Thu Sep 9 2021
Satellite continues to show smoke streaming into the area this
afternoon. The hazy sky has had an impact on temperatures with highs
not getting as warm as initially expected.
The HRRR smoke forecast continues to push the band of smoke across
the area through tonight. With the upper level ridge expected to
continue to the west during the day Friday, expect the smoke to
stream through the area tomorrow as well. The ridge drifts a little
to the east and would expect temperatures to be a little warmer. In
addition, there will be warm advection and warming temperatures at
850mb. This would all lead to temperatures in the 90s for highs
tomorrow. The only concern will be how much the smoke could reduce
the heating as it has today. Did lower temperatures a little bit,
but would not be completely surprised if temperatures were a few
degrees cooler than forecast. With that in mind, will continue to
keep mention of heat index values out of the HWO, which it is only a
small area at this time.
Friday night into Saturday the upper level ridge continues to drift
to the east and temperatures will be warm for Saturday as well.
Friday night a surface low develops to the west/northwest of the
forecast area and starts to move into the north Saturday afternoon.
Dry weather continues through the day Saturday, but as an upper
level wave moves in Saturday evening, there will be a small chance
for some showers and thunderstorms Saturday night into Sunday
morning. Most of the activity will be in Nebraska.
There will be westerly flow across the area for the period Sunday
afternoon through Thursday. There are a couple of waves that move
through during that period, but the strongest one appears to be
Tuesday and Tuesday night when the wave is a little stronger and
there is a cold front that moves through the forecast area.
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 555 PM CDT Thu Sep 9 2021
VFR expected through the period. Looking at satellite decided to
carry a FEW250 layer as smoke from western fires continues to
stream into the area.
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1125 PM EDT Thu Sep 9 2021
A slow moving cold front will produce several rounds of heavy
showers and thunderstorms through early Friday morning as
Hurricane Larry passes by well to our east producing high surf.
Fair weather gradually returns on Friday through much of the
weekend as high pressure slowly crosses the area. Drier
conditions expected over the weekend with the exception of a
chance of showers over northern areas on Sunday as a cold front
crosses the region. Canadian high pressure will build into New
England early next week.
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Update...S/WV trof is swinging into the region now...and the
greatest forcing is expected over the next several hours. This
is going to focus mainly over Penobscot Bay and parts of W
central ME before moving E. This is where all the moisture
transport will be...and localized amounts of an additional 1 to
2 inches remain possible. Slowly things will taper off from W
to E overnight.
Previous discussion...Latest mesoscale models and radar trends
continue to direct the highest moisture content and precipitable
water values towards eastern portions of our forecast area
overnight in an area of good forcing dynamics. Highest rainfall
totals will likely be over the Midcoast region and adjacent
areas through early Friday morning where Flash Flood Watches
were issued earlier this afternoon and along and ahead of a
decelerating frontal system. There has been a rather consistent
signal in the model solutions with the evolution of this event
with perhaps a slight eastward shift in the rainband maximum
The latest HREF and HRRR solutions also suggest a secondary
rainfall maximum in the foothills which will need to be
monitored closely overnight with the added effects of terrain.
Although there may be a rumble of thunder or two, limited the
threat for thunderstorms to slight chance during the overnight
It will be muggy tonight, however winds will eventually switch
to the west. Patchy fog expected in-between the moderate to
heavy showers. Coastal splash-over possible as well.
.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Heavy showers over the Midcoast region will come to an end
Friday morning as drier air pours in across the forecast area
from the west. Increasing sunshine, especially over downslope
areas will lead to temperatures in the 70s over southern and
Dry conditions will continue for Friday night as high pressure
builds towards the Mid Atlantic seaboard. It will be cooler with
overnight lows in the 40s across the north and lower to mid 50s
across the south which is still seasonably mild for this time of
.LONG TERM /SATURDAY THROUGH THURSDAY/...
Overview: High pressure to our south will result in mostly tranquil
weather for the upcoming weekend with near seasonable temperatures.
A series of weak disturbances passing mainly to our north will
introduce a few chances for scattered showers through much of next
week but there will be plenty of nice weather mixed in between.
Temperatures will remain near to slightly above normal.
Impacts: Little to no major weather related impacts are expected
through the middle of next week. Some increased surf and rip
currents may persist through at least the first half of Saturday
from distant Hurricane Larry.
Forecast Details: High pressure will be centered across the Mid-
Atlantic on Saturday as an area of low pressure approaches the Upper
Great Lakes. Our area will be under weak 500 mb ridging, which will
allow for partly to mostly sunny skies with near seasonable
temperatures into the 70s with 60s across the mountains. Skies on
Saturday night will start out mostly clear in all areas but some
increase in cloud cover is expected late, especially across the
north and mountains. Low temperatures will primarily be into the
Skies will then be partly to mostly cloudy on Sunday with the most
cloud cover over the north and mountains as a broad area of low
pressure moves across eastern Ontario and Quebec. Scattered rain
showers will be possible, especially across the north but overall am
not expecting this activity to be very widespread as we will be
sitting on the southern edge of the better dynamics and likely will
be battling dry air both at the surface and aloft. This low will
then allow for a surface cold front to cross through our area on
Monday. This front is currently looking rather dry with just an
isolated shower possible as it crosses. This front will allow for
dewpoints to fall into the 40s to low 50s in most locations on
Monday night through Tuesday and this combined with high
temperatures on Tuesday only into the 60s to near 70 it will feel
like a Fall day.
The forecast then becomes more uncertain as we approach Wednesday
through the beginning of next weekend as there are large differences
in both deterministic and ensemble guidance for both the placement
and magnitude of the upper level pattern. The ECMWF deepens a 500 mb
trough just to our east, which results in cool conditions as onshore
flow develops. On the other hand, the GFS is generally not as
amplified, which results in warmer temperatures under weak
ridging. The end of next week will feature mostly tranquil
weather with near to slightly above normal temperatures. Taking
a look at 24-hour QPF individual ensemble members, there
remains large differences in amounts but generally it looks like
the best window for measurable rainfall will be Tuesday night
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Short Term...Areas of LIFR conditions overnight in heavy
showers, low ceiling and fog. Areas of VFR conditions expected
over far northern and western portions of the forecast area,
however there will still be some fog.
Gradual clearing will commence later tonight spreading towards
the Midcoast region by mid morning on Friday. VFR conditions all
areas thereafter which will last into Friday night.
Long Term...VFR conditions expected this weekend, although some
widely scattered showers may result in brief MVFR conditions
across northern terminals late on Sunday. VFR conditions
expected next week outside of any shower activity.
Short Term...Have extended the SCAs through 12 UTC Saturday
which matches up well with our high surf advisories and adjacent
neighbors projects from long period swells from Hurricane
Larry. Rain, fog and lowered visibilities will be replaced with
gradual clearing on Friday and through the weekend along with
Long Term...Seas will gradually diminish on Saturday, although they
will remain in the 4-6 feet range through Sunday. SCA winds are
possible late Saturday afternoon or evening through Sunday as a cold
front crosses the waters. Winds will then diminish on Monday under
The anticipated lull in showers and embedded thunder today has
come and gone with more showers and scattered thunderstorms
upstream about to cross the region later this afternoon, this
evening and during the overnight hours. Precipitable water
values around 1.5" to 2.0" near the Mid-Coast combined with
additional dynamics and instability will lead to locally heavy
precipitation particularly along and east of I-95 for this
event. There could be some localized 4 inches rainfall amounts
in the Midcoast region. Any consistent training of showers and
thunderstorms could possibly lead to isolated flash flooding.
Astronomical tides top out at their highest peak for the month
for the next couple days. With building long period waves and
some contribution in water levels due to storm surge and the
effects of wave setup, expect some splash-over over the next
couple days along the vulnerable beaches of York and Rockingham
counties. These will mainly be beaches that are oriented towards
the east or southeast.
Total water levels will likely remain below flood stage. Have
noted some significant oscillations on several of the ESTOFS
runs at high tide, most likely due to the effect of wave setup.
ETSS more conservative with the average of the two models being
a most likely scenario.
ME...Flash Flood Watch until 9 AM EDT Friday for MEZ014-021-022-
High Surf Advisory until 8 AM EDT Saturday for MEZ023>028.
NH...High Surf Advisory until 8 AM EDT Saturday for NHZ014.
MARINE...Small Craft Advisory until 8 AM EDT Saturday for ANZ150>154.
...Updated Aviation Forecast Discussion...
Issued at 303 PM CDT Thu Sep 9 2021
Today through Saturday:
The narrative through the weekend is no precipitation with warming
temperatures. Record high temperatures are possible Saturday,
specifically in southeast Nebraska. An upper level ridge currently
located over the central Rocky Mountains will drift slowly to the
east. The ridge will allow for return flow at the lower levels and
theta-e advection. High temperatures this afternoon should peak in
the 80 to 85 degree range. For Friday, expect temperatures to be
10 degrees warmer than today.
Friday could serve as a signal for how the forecast will perform
Saturday. For this forecast issuance, the high temperature
forecast for Friday is near the 75th percentile of model
guidance. For return flow situations, the 75th percentile is
usually a good starting place for the forecast. If temperatures
over perform, an adjustment will be needed for Saturday.
For Saturday, the forecast is near the 50th percentile of model
guidance. This indicates that temperatures could be warmer than
expected. Furthermore, 850 hPa temperatures will be near or even
above 30 degrees Celsius. An analysis of NAEFS climatology of 850
hPa temperatures show them to be at the maximum of climatology.
Using the broad forecasting technique of bringing the 850 hPa
temperature down to the surface would result in high temperatures
near 100 degrees. All of this combined (forecast at 50th
percentile of guidance, 850 hPa temps at climatological record,
broad forecasting technique), could result in record temperatures
Smoke from the western wildfires is likely to become more visible
over the weekend. The RAP smoke model shows that smoke
particulate should increase greatly. It`s expected to remain
mostly in the upper levels of the atmosphere and would be visible
as a haze. Though, on Saturday the RAP smoke model shows an
increase in near-surface smoke particulate values.
Sunday through Monday:
The upper level ridge will breakdown over the weekend as a weak
upper level shortwave will flatten it. An attendant cold front is
also expected to encroach the forecast area and bring with it a
20% chance for precipitation. The timing of this front has slowed
from previous model runs and it doesn`t push as far south. Areas
behind the front could see a 10 to 15 degree drop in temperatures.
As the front may stall out over eastern Nebraska or western Iowa,
there could be a large difference in temperatures from the south
to the north.
Tuesday, the models are in agreement in a strong trough moving
over the northern CONUS. This will result in temperatures near the
climatic normal. There will be a few chances for precipitation
with Tuesday night and Wednesday morning being the best chance.
The cooler temperatures, or in this case, near normal
temperatures look like they`ll be short in duration. The Climate
Prediction Center has a high probability for temperatures to be
above normal for the 6 to 10 Day, 8 to 14 Day, and 3 to 4 Week
outlooks. This signal is supported by the ECMWF as it builds an
upper level ridge over the central CONUS next weekend. However,
the GFS builds one over the East Coast. As is common with extended
ranged guidance, time is needed for a consensus to be achieved.
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 621 PM CDT Thu Sep 9 2021
VFR conditions to prevail with light winds generally out of the
southeast and under 10 kts. Not expecting any smoke impacts in the
lower levels/at the surface in this period.
Area Forecast Discussion
National Weather Service Pocatello ID
222 PM MDT Thu Sep 9 2021
.SHORT TERM...Today through Saturday. High pressure breaks down
and moves east setting up warm, south southwest flow today ahead
of a trough setting up off the west coast. Expect breezy to
moderate winds for our northern areas with record to near record
temperatures for most of our area. By Friday, tomorrow, an upper
level low over OR/WA will bring scattered showers and
thunderstorms across the area by late Friday afternoon into the
early evening. Saturday expect lingering showers for our eastern
areas with breezy, cooler northwest flow behind an exiting
system. Expect well above normal temperatures today, record to
near record, before becoming below normal by Saturday.
.LONG TERM...Sunday through next Thursday. Expect mostly dry
conditions through the period with brief periods of breezy to
moderate winds. Sunday a breezy trough moves over northern ID and
Southern Canada elevating the winds over our northern areas,
especially the Central mountains. The last couple of model runs
have been showing some light precipitation mainly over the
Eastern Highlands, from Island Park down to the Bear Lake region.
Models are still indicating another mostly dry, breezy trough on
Wednesday into Thursday, again impacting mainly the Central
mountains. Fire weather highlights may be needed depending on
relative humidity recovery. Currently though relative humidity
looks to stay ABOVE critical values every afternoon. Expect 70 to
80s with cooler mountain temperatures through the period.
.AVIATION...VFR to prevail under mostly sunny skies into the early
evening. High clouds to become more prevalent ahead of an
approaching system as we get into the overnight and early morning
hours on Friday. Precip will move into the area likely by mid-
afternoon Friday at KSUN and to the other terminals around 11/00Z
so will likely need to add VCTS on the next forecast for KPIH,
KIDA, KBYI and KDIJ. Winds will become breezy out of the SW in the
15-20 mph during the afternoon hours with locally higher gusts in
and around any storms that develop.
.FIRE WEATHER...Red flag warnings remain in effect for Fire Zones
475 and 476 with critically low RHs and gusty winds expected to
continue this afternoon. A system moves into the region tomorrow,
bringing with it gusty winds but increasing humidity and rain
chances. Thunderstorms will be possible during the late afternoon
hours and into the early part of Saturday morning. Instability is
limited however and confidence in scattered coverage is less than
desired. That being said, and after coordination with surrounding
offices, have held off on Red Flag issuance at this time but one
may be needed on the next forecast package. In this systems wake,
temperatures look to be much cooler as we move into the weekend
with RHs well above critical levels which should keep fire weather
concerns at bay.
.AIR STAGNATION...Poor air quality conditions are expected
through Friday for Custer county due to wildfire smoke from local
and regional fires. There is an Air Quality Alert in effect for
Custer county through Friday from the Idaho Department of
Environmental Quality. The air quality has been determined by the
IDEQ to be unhealthy to sensitive groups, and will remain in
effect until air quality has significantly improved. The HRRR
smoke model brings regional smoke into the area through Friday,
however enhanced smoke inundation in the Central Mountains is
expected due to active localized wildfires. Precipitation Friday
and northwest flow aloft by late Saturday will help bring better
air quality conditions into the area.
Red Flag Warning until 9 PM MDT this evening for IDZ475-476.
For frequently asked questions about the Area Forecast Discussion