Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/08/23

Area Forecast Discussion

National Weather Service Des Moines IA

 538 PM CST Thu Dec 7 2023

...Updated for the 00z Aviation Discussion...

.DISCUSSION.../Tonight through Thursday/
Issued at 218 PM CST Thu Dec 7 2023

Key Messages:
- It was very warm today with record highs broken or tied in
  several places with temperatures trending a bit cooler Friday
  and thereafter more seasonal for December.
- Clouds increase on Friday with mainly rain chances Friday night into
  Saturday morning over the southeastern half of the state. There
  is a low (10%) chance of a few rumbles of thunder in southeast
  Iowa.
- Light snow moves through Saturday with the highest chances up to 40
  to 50% over northern Iowa tapering with southward extent. There
  is a 90% chance that snow accumulations will remain below an
  inch.
- Winds will be blustery on Saturday into Saturday night with an
  80% chance of wind gusts over 25 mph.

Details: Upper level ridge axis is over Iowa this afternoon and
pushing eastward with more zonal flow associated with the lead
shortwave trough in the northern stream over the Pacific Northwest
to the northern Rockies advancing eastward toward the region. GOES-
East 1.38 micron channel showed nicely the development of the cirrus
clouds that are over central Iowa, especially the northern part of
the state. This seems to not have impacted temperatures too greatly
with temperatures across much of the state having risen to forecast
highs in the upper 50s to around 60 degrees.

Attention tonight into Friday will be on the northern stream
shortwave trough that will replace our warm conditions as a cold
front moves through the state. Temperatures will not be as high on
Friday compared to today due to this front bringing in cooler low
level air, but still quite mild for December in the 50s in most
central Iowa locations. Sunshine will be fading as well on Friday as
a longwave trough zooms southwestward over the western US into the
southern Plains. A lead shortwave trough ejecting northeastward will
bring strong QG convergence over the southeastern half of the state
with an approaching jet streak adding some kinematic forcing as well
later in the day into the night. This will result in rain showers
spreading northeastward over this portion of the state Friday night
into Saturday morning. A few rumbles of thunder may be heard as well
in southeast Iowa if elevated instability does move in. On the
northwestern side of the precipitation shield, the rain may change
to snow briefly before ending early Saturday morning as the column
cools and loses saturation. Farther northwest over our forecast area
(roughly Sac County to Winnebago county and northwest), low level
dry air will prevent column saturation and despite mid-level lift,
little in the way of precipitation with this first round is forecast
for this area.

Winds will turn blustery from the northwest Saturday through
Saturday night as this shortwave trough lifts northeast into the
Great Lakes with highs mainly in the 40s. The strongest winds will
be over northern Iowa into Minnesota where the larger pressure
rise/fall couplet will reside along with stronger pressure gradient.
Latest National Blend of Models (NBM) shows over an 80% chance of
wind gusts of at least 25 mph statewide with around a 40-60% chance
of wind gusts to near 40 mph around Estherville and Algona.
Deterministic model soundings are supportive of these wind gusts in
the 30 to 40 mph range. Also on Saturday, deterministic models
continue to show a secondary shortwave trough moving through, which
will bring light snow to a portion of the state. The forcing
continues to look nebulous in the low levels in plan views, but in
forecast soundings there is a deeper depth of saturation and
omega/lift within this layer. Further, NAM, GFS, and extended RAP
soundings continue to show lapse rates steepening in the morning
with elevated instability developing as the lower levels into the
ice introduction zone and dendritic growth zone saturate, which is
especially true over northern Iowa. The NBM came in dry Saturday,
but preponderance of data from deterministic and ensemble mean QPF
shows adding PoPs and QPF prudent. Ensemble data continues to point
to a greater than 90% chance that snow accumulations will be below
an inch and the official forecast reflects that. The caveat is that
convective snow showers could produce localized areas that may near
or top an inch, which will be a detail to examine in the comings
days and tough to nail down the exact location.

As the overall longwave trough moves east on Sunday, winds will
relax and northwesterly flow will take over aloft into next week.
This favors dry conditions into the middle part of next week along
with seasonal temperatures.

&&

.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 538 PM CST Thu Dec 7 2023

VFR conditions are anticipated to continue thru the TAF period
(high confidence). Breezy southerly winds this evening/overnight
to diminish and shift to a westerly-northwesterly direction late
tonight/early Friday as a cold front moves eastward across the
state. A period of low level wind shear (LLWS) is expected across
the southeastern half of the state this evening, including OTM,
ALO, and DSM ahead of the cold front, ending as the front passes.
Friday will see increasing high cloudiness with winds remaining
from a westerly direction into Friday evening.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

DISCUSSION...Ansorge
AVIATION...Percha



Area Forecast Discussion

National Weather Service Goodland KS

 350 PM MST Thu Dec 7 2023

.SHORT TERM...(This evening through Sunday)
Issued at 200 PM MST Thu Dec 7 2023

Main concern will be potential for accumulating snow Friday and
Friday night. Light snow is still generally expected, but latest
short term CAMs suggesting a locally heavier band of snow will be
possible in northeast Colorado. Otherwise, colder and windy
conditions expected on Saturday followed by milder temperatures on
Sunday.

Upper trough axis crosses the Rockies on Friday providing synoptic
scale lift for clouds and precipitation. Light snow will start in
northeast Colorado by mid Friday morning and spread into extreme
northwest Kansas by early afternoon. Rain/snow line will set up
generally along Highway 27 and not move until Friday night. While
snow amounts generally remain on the light side, the convective
allowing models now suggesting a narrow band of locally heavy snow
may develop. This band is showing up in the HRRR, RAP and
experimental RRFS. While the exact location and timing varies
slightly, they all suggest the band would set up in Kit Carson or
Cheyenne counties of northeast Colorado, perhaps extending into
adjacent counties of northwest Kansas, primarily Friday afternoon,
less likely into Friday evening. High end amounts should this
band develop look to be around 4 inches. Some models also showing
brief gusty winds with the snow band, which may lead to a snow
squall situation, including Interstate 70. Confidence is rather
low in this scenario, but cannot be completely discounted.

Going into Friday night, areas further east will finally see a
changeover to snow but only expecting a light dusting there. Snow
will end north to south late Friday night. Winds will gradually
increase from the northwest through the night with gusts to 25 kts
by sunrise, then increase through the day Saturday with gusts to
35 kts by the afternoon. Lows Friday night will be in the 20s and
highs on Saturday in the upper 30s to lower 40s. Coldest
temperatures with this system will occur Sunday morning with lows
in the teens. Upper ridge starts to build for Sunday afternoon
with temperature rebounding into the upper 40s to lower 50s under
mostly sunny skies along with breezy west winds.

.LONG TERM...(Monday through Thursday)
Issued at 104 PM MST Thu Dec 7 2023

Longwave troughing will be in place to start the period over the
eastern CONUS, as another system is brewing in the Pacific Northwest
which will be the weather focus for later in this period.

Monday, will see a surface trough located across central Kansas with
the Tri-State area post trough. Trended winds down from what the NBM
had with a 50/50 blend with the GFS, since the GFS has been handling
longer range forecasts a bit better as of late, so currently
expecting westerly winds turning to the NW around 10 mph. Above
normal temperatures are forecasted in the 50s along with low
temperatures in the low to mid 20s.

Tuesday, will see a weak cold front moves through the area
throughout the day. Some guidance tries to get some light snow
for NW portions of the area during the afternoon, its not being
handled well by guidance has been flipping around trend wise the
last few runs so not overall optimistic in the potential at this
time. Temperatures will be cooler in the upper 30s into the 40s
for highs.

Wednesday and into the next weekend will see an increase in low
level moisture, so will need to watch for fog or stratus early in
the day. The forecast then become a little bit more complicated.
The system in the Pacific northwest as mentioned earlier moves
into the four corners region and turns into a surface low. How
exactly this evolves is still a bit uncertain, ensembles
interestingly enough also don`t agree on the strength or even any
storm developing vs overall general consensus for the most part
in the GFS/ECMWF deterministic.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 338 PM MST Thu Dec 7 2023

VFR expected to prevail at both KGLD and KMCK through the TAF
period. That being said, surface winds will increase from the
northwest this evening at both terminals with gusts to 20-25 kts
possible. Winds will begin to subside towards 12z. At KGLD... snow
is possible towards Friday afternoon, but confidence is lacking to
introduce into the TAFs at this time.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

SHORT TERM...024
LONG TERM...Trigg
AVIATION...024



Area Forecast Discussion

National Weather Service Gray ME

 1017 PM EST Thu Dec 7 2023

.SYNOPSIS...
If you thought last night was cold, well tonight will feature
temperatures as cold if not a couple degrees colder. However the
cold will be short lived, as a warming trend will begin Friday
and last through the weekend. Temperatures will climb into the
50s for many areas by Sunday, but rain will be close behind. A
strong storm will bring a combination of a soaking rain and
strong wind gusts to the area. It will be a quick moving storm
with clearing expected late Monday. Gusty winds continue and
colder temperatures return through midweek.

&&

.NEAR TERM /TONIGHT/...
1017 PM Update... Deja vu all over again as stratus continues
to bank against the Whites in blocked NW flow late this evening.
Have taken the same logic as last night... with RAP low-level
moisture depicting these clouds well, and suggesting these
clouds hang around in convergent LL flow until the ridge moves
overhead by mid-Friday-morning. This brought lows up a bit for
the Connecticut River Valley vs the inherited, although the
remainder of the area is cooling quickly with flow going calm
under clear skies.

635 PM Update...Little to report at this hour. There is some
stratus working yet again into the upper Connecticut River
Valley this evening, so have incorporated this into the sky and
temperature forecast. Overall models aren`t as persistent with
overnight stratus toward the north as they were yesterday around
this same time in the evening... so overnight lows are intact,
with hourly trends incorporating more of last night`s hourly
observations.

Previously...
High pressure remains firmly planted over the region which will
help to crash temperatures down once again under clear skies.
Up north low temperatures will fall below zero. The foothills
and interior will single digits and low teens. Across the south,
locations will see mid to upper teens. Clouds may spill over
into western New Hampshire tonight, but with a dry airmass
overhead there won`t be any worry for precipitation.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
Short wave ridging tomorrow will make for another dry day with
light winds. High temperatures will be able to warm into the
upper 20s and low 30s in the north and mountains, and mid 30s to
near 40 across the south.

Ridging moves off to the east and a trough begins to approach
the region which will increase cloudiness from west to east as
the evening goes on. This will keep temperatures much warmer
than we have seen in recent nights. Expect temperatures in the
mid to upper teens to the north and 20s to the north. With a dry
airmass still overhead and no forcing, there shouldn`t be any
concern for precipitation during this period either.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Overview: Brief ridge slips east of the area Sat and will be
followed by a deep trof that gradually flattens but remains in
place thru the end of the week. Temps remain below normal...and
while precip may average above normal over the next week it is
mostly expected to fall Sun night into Mon.

Impacts: Storm system Sun into Mon will bring a combination of
strong winds and heavy rains. The extent of either remains
uncertain. At this time a period of strong wind gusts is likely
at the coast Mon morning...potentially greater than 60 mph north
of PWM. Poor drainage and overland flooding is possible across
all of the forecast area...with snow melt determining whether
river flooding occurs. See Hydrology section for more details.

Forecast Details: S/WV ridge axis moves east of the forecast
area Sat allowing deep southwesterly flow will set up over the
Eastern Seaboard. This will advect seasonally significant PWAT
values into northern New England. At this time the system
appears progressive enough to limit QPF to between generally
0.50 to 1.50 inches. I do not see the storm speeding up any from
current forecasts...so the trend to monitor will be if it slows
down at all or pivots and allows residence time of convective
fine line to linger over any areas. The Hydrology section below
covers the threats posed by rainfall in more detail.

The southerly LLJ will also increase with time into Mon morning
and bring a period of strong wind gusts to at least coastal
areas. The inland push of milder air and low level lapse rates
will be something higher resolution model guidance will start to
glimpse over the next 12 to 24 hrs...but at this time forecast
wind speeds at 925 mb suggest coastal areas are in line for at
least a wind advisory. The LLJ peaks mostly north of Casco
Bay...and so the Midcoast zones are more at risk of seeing gusts
come closer to high wind criteria. There is far more uncertainty
southwest along the coast...where LLJ orientation is more
southerly than southeasterly. This may limit the peak gusts and
inland extent of winds...especially across the Seacoast. Much of
this will also depend on storm track...where overnight guidance
was more easterly and kept strongest winds out to sea...07.12z
guidance came back west and maintained the wind threat. For now
I kept the forecast close to the median NBM
forecast...consistent other ensemble guidance on wind
speeds/gusts.

Beyond the early week storm...CAA continues for much of the
week. This will keep winds gusty and colder than normal temps in
place. Precip chances will revolve around individual S/WV trofs
and upslope flow.

&&

.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Short Term...VFR conditions will prevail through Friday.
Ceilings thicken as our next system approaches Friday night.

Long Term...VFR conditions expected for the majority of the
area to star the period Sat. Clouds will thicken and lower thru
Sun with widespread IFR or lower conditions in low CIGs and RA
thru Mon morning. A period of LLWS is also likely for coastal
terminals at least Mon morning. Winds shift to westerly Mon
afternoon and will remain gusty into midweek. Clearing is
expected quickly Mon south of the mtns...but MVFR CIGs may
linger around LEB and HIE in upslope flow.

&&

.MARINE...
Short Term...High pressure settling over the waters will keep
winds and waves below SCA thresholds. Freezing spray is possible
tonight through early tomorrow morning.

Long Term...Southerly winds will steadily increase ahead of the
next storm system. Storm force gusts will be possible for all
waters Sun night into Mon morning. I have used the highest of
wave guidance to get seas building to near 15 ft by Mon
morning...which may end up being higher if storm force winds are
realized. Winds shift to westerly behind the storm and will
remain gusts at least SCA thresholds thru the middle of the
week.

&&

.HYDROLOGY...
A soaking rain is expected to move into the region Sunday and
increase in coverage and intensity Sunday night into Monday. The
moisture feed into the region pushes PWATs into the climatological
max territory (~1.2"), which is 3 standard deviations above normal.
Strong SW winds feeding the system will support high rainfall rates,
more comparable to the warm season. Heavy rain could result in urban
flood concerns and rapid rises on small streams, some of which have
recently grown ice. The big ? will be the snowmelt factor, which is
too uncertain to ascertain this far out. Coastal areas will
likely see a melt out, with notable loss in the coastal plains
to the foothills. System will need to be watched closely for
potential river flooding.

&&

.GYX WATCHES/WARNINGS/ADVISORIES...
ME...None.
NH...None.
MARINE...None.

&&

$$

UPDATE...Casey
NEAR/SHORT TERM...Baron
LONG TERM...Legro
AVIATION...Baron/Legro
MARINE...Baron/Legro
HYDROLOGY...Jamison



Area Forecast Discussion

National Weather Service Memphis TN

 549 PM CST Thu Dec 7 2023

...New AVIATION...

.SYNOPSIS...
Issued at 335 PM CST Thu Dec 7 2023

Showers and thunderstorms will likely impact the Mid-South on
Saturday as a strong upper level trough moves into the area.
Severe weather chances will exist through Saturday afternoon with
damaging winds as the main threat. Next week, expect a return to
seasonable temperatures with daily highs in the 50s.

&&

.DISCUSSION...
(This evening through next Wednesday)
Issued at 325 PM CST Thu Dec 7 2023

The main focus this forecast period continues to be a longwave
trough that will begin impacting the Mid-South Friday afternoon.
Ahead of this system, southerly surface winds will help transport
Gulf air to the Mid-South with dewpoints increasing to the low 60s
by Saturday morning. WAA showers are possible starting Friday
night and will likely continue through Saturday morning before
more widespread showers and thunderstorms develop.

Latest 60 hr CAMs and the 18Z HRRR depict MLCAPE values near 1000
J/kg along and south of I-40 by midday Saturday. Global models
continue to hold off on mid level height falls until around 21Z.
At this time, CAPE values will likely start to decrease, which
will limit the overall severe weather threat. However, given
plentiful shear and moderate lapse rates, a damaging wind threat
will remain until the front passes the region Saturday night. A
Marginal and Slight Risk remains in place across the Mid-South,
with areas along the Mississippi Delta at the greatest risk of
severe weather.

Showers and thunderstorms will persist through midday Sunday with
storm total rainfall upwards of 2 inches in areas of north
Mississippi. Beneficial rains will likely result in slight relief
from the current D3 and D4 drought conditions. However, there also
exists a flooding threat as heavy rains impact areas of dry soils,
which could aggravate small streams and drainage ditches.

By Monday, zonal flow aloft will be in place behind Saturday`s
system. Next week is forecast to be relatively dry with highs in
the 50s.

ANS

&&

.AVIATION...
(00Z TAFS)
Issued at 542 PM CST Thu Dec 7 2023

VFR conds will continue overnight into Friday morning with south
winds around 10 kts. A LLJ will develop across NE AR this evening
and continue through the overnight hours with LLWS likely at JBR.
Gradually lowering cigs are expected on Friday with gusty south
winds developing. MVFR cigs will push into JBR and MEM by Friday
afternoon and evening with a few SHRAs. The LLJ will redevelop and
shift a little further SE Friday evening with LLWS likely at MEM.

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&

$$

PUBLIC FORECAST...ANS
AVIATION...SJM



Area Forecast Discussion

National Weather Service Springfield MO

 531 PM CST Thu Dec 7 2023

...AVIATION UPDATE...

Key Messages:

1. Windy today with south to southwest wind gusts over 40 mph
along and west of Highway 65. A Wind Advisory continues for this
area through midnight tonight.

2. Warm today and tomorrow, then a brief cooldown over the
weekend.

3. Rain begins to move in Friday afternoon. Embedded
thunderstorms possible Friday night. Rain exits by midday
Saturday.

4. Dry and above normal temperatures next week.

.SHORT TERM...(This evening through Friday)
Issued at 106 PM CST Thu Dec 7 2023

Water vapor imagery depicts an elongated shortwave ridge
currently traversing through Missouri. Meanwhile, lee cyclogenesis
across the Great Plains is also underway as a 110+ kt upper-level
jet noses its way across the Rockies. Strong jet streak dynamics
associated with the jet is deepening a surface low across the
Dakotas. The surface pressure gradient is tightening as a result,
forcing strong SSW`ly surface winds prompting our Wind Advisory
today.

Windy Advisory continues through midnight tonight:

Windy conditions across the CWA should be peaking around now with
daytime heating promoting mixing of 55+ kt low-level jet winds
down to the surface. Gusts have been periodically reaching 35-40
mph over SW MO and 30-35 mph along the Ozark Plateau. Would not be
surprised to see a few 45-50 mph gusts just east of the KS border
where the LLJ will be strongest just before sunset. Indeed, the
NBM and HREF mean is outputting 45 mph gusts in those areas.

There is mild fire weather concern with the strong winds.
Temperatures are already 3-4 degrees higher than HREF and NBM
means and dewpoints are already a few degrees lower than forecast.
Both are bringing RH values into the 35-40% range which will
elevate fire weather risk for a short period this afternoon.

Winds will gradually decrease in speed across the CWA after
sunset as mixing ceases. A strong low-level jet will still aid in
keeping winds tonight in the 10-20 mph range with gusts up to 30
mph, especially before midnight. Model guidance has a 50-60%
chance for above 35 mph gusts across the higher terrain in the
eastern Ozarks overnight. However, given this time of year where
nocturnal inversions are quick to develop and are generally
strong, have opted for the lower-end scenario of 20-30 mph max
gusts. The NAM and RAP model soundings add confidence to this
forecast.

Warm weather continues through tomorrow:

The strong winds are also keeping warm temperatures in our region
with highs today reaching well above normal in the upper 60s.
Moderate winds tonight will keep lows mild in the lower 50s along
the moisture axis west of Highway 63. Drier air east of the
moisture gradient (within the eastern Ozarks) will see lows in
the mid 40s.

As cloud cover steadily increases overnight tonight, highs will be
slightly cooler tomorrow, but still quite warm in the lower 60s.
Low temperatures Friday night will range from 40-50F as the cold
front begins moving through.

.LONG TERM...(Friday Night through Thursday)
Issued at 106 PM CST Thu Dec 7 2023

Rain and some thunderstorms Friday afternoon to Saturday morning:

The zonal jet will break down into a deep bowl trough across the
west-central CONUS over the course of the day Friday. The initial
low-pressure system over the Dakotas will lift NE into Canada and
a new low-pressure system will begin forming along the KS/OK
border beneath the nose of the digging jet. This will force a mass
response of warm air and moisture advection into our region.
Isolated to scattered elevated light showers may form along the
warm front in our CWA Friday afternoon (15-30% chance). The system
will quickly lift NE and a cold front will dive through the CWA
overnight Friday. A quick line of showers is expected to develop
and move through with the passage of the front. Ahead of the
front, very meager elevated instability will develop which may
help force some elevated thunderstorms. Current CAMS range our CWA
between 0 and 500 J/kg of elevated CAPE (an amazing range, I
know). Model soundings depict very, very skinny CAPE profiles
hinting that any small change in the temperature/dewpoint profile
may be the difference between seeing thunderstorms and not seeing
thunderstorms Friday night.

The latest SPC Day 2 Outlook includes parts of our CWA in a
marginal risk (5% chance) for severe hail. This threat is very
conditional based on the amount of instability that can sneak in
ahead of the front. Since all of the instability will be within
the hail growth zone, and hodographs are more elongated/straight
above the inflow layer with weak shear right above the inflow
layer, it is possible (5% chance) that hail could develop.
However, with such skinny CAPE profiles, sub-severe hail appears
more likely. If there were a category below marginal and above
general thunder, I`d give our region that category for severe hail
(2-3% chance) and a 5-10% chance for sub-severe hail. In all,
though, the threat hinges on the potential for thunderstorms
(10-20% chance).

Nevertheless, the system will progress through the region quickly
with rain exiting the region by mid-day Saturday. The quick and
light nature of the rain leaves many places in our CWA with a
forecast of 0.1" of rainfall through Saturday. Areas may receive
locally higher amounts (up to 0.5") if thunderstorms form and
track across the area. Current CAMs have the highest likelihood of
this along the KS/MO border and the central MO/AR border.

Brief cooldown, then dry and above normal temperatures next week:

Following the front, the weekend will see a brief cooldown in the
lower 50s for highs Saturday and the lower 40s for highs Sunday.
Lows will be in the mid- to upper 20s during the same time. The
upper-level longwave pattern will then favor the return of above
normal temperatures next week with highs between 50-55F and lows
between 30-35F. Latest NAEFS/ECMWF ESATs have a signal for the
99.5th percentile of 700 and 850mb heights which would certainly
leave room for further warming upwards of 55-60F. Trends will
continue to be monitored for this, but bottom line is that the
signal favors for above normal temperatures.

&&

.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 523 PM CST Thu Dec 7 2023

Clear skies to begin the TAF period will turn cloudy from west to
east over the course of the night. Ceilings will steadily drop
ahead of chances for rain tomorrow with MVFR conditions by
sunrise. Widespread IFR ceilings are expected for most of the day
tomorrow with PROB30 light rain showers for the last few hours of
the period. Low level wind shear persists through about 12Z.

&&

.SGF WATCHES/WARNINGS/ADVISORIES...
MO...Wind Advisory until midnight CST tonight for MOZ055-066>068-
     077>080-088>090-093>095-101>103.

KS...Wind Advisory until midnight CST tonight for KSZ073-097-101.

&&

$$

SHORT TERM...Price
LONG TERM...Price
AVIATION...Nelson