Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/10/23
Area Forecast Discussion
National Weather Service La Crosse WI
534 PM CST Sat Dec 9 2023
.KEY MESSAGES...
- Areas of snow/reduced visibility will continue into the
evening (amounts of 1/2 to locally 2" in spots near and north
of I-90) and may create some slick roads.
- Blustery northwest winds will gust 25 to 35 mph late this
afternoon and this evening as cooler air spreads in.
- Mostly dry weather is likely over the next week with
seasonable temperatures trending back above average through
the week.
&&
.DISCUSSION...
Issued at 245 PM CST Sat Dec 9 2023
This evening-Sunday: Gusty winds, areas of snow this evening
Early this afternoon, GOES water vapor imagery showed a shortwave
trough ejecting northeast from lower Michigan while a second trough
was rotating east across Minnesota. Both of these troughs are
embedded with a broader trough that will pass across the region into
Sunday.
Observations/radar have shown areas of snow progressing into
western WI in conjunction with the stronger forcing with the
wave across MN and visibility reduced to around a mile in or
less in spots. There has been some rain/ice pellets, given the
steep low-level lapse rates and warmer surface temps at onset
for some areas. With the track of the wave and strongest lift
progressing east this evening into central Wisconsin, the
potential for snow accumulations of at least 1" exists mainly
near/north of I-90 (20-60%), highest north towards Taylor
County (locally up to 2"). Generally the potential for some
travel impacts will increase with northward extent this evening.
Overall, though, expect road impacts to be confined mostly to
areas that experience heavier snow showers (rates locally > 1/2"
per hour) as temps slowly cool this evening or colder
bridges/elevated surfaces.
Otherwise, winds will become northwest and increase through late
afternoon and evening as RAP soundings show mixed-layer winds
of 30 to 40 kts by this evening with some mixing/cold advection.
Not expecting the need for a wind advisory, but gusts of 25 to
35 mph, locally a bit higher, are likely. Any wetness on roads
could freeze as temps fall overnight, but the gusty winds/drying
could help limit impacts. Cool, seasonable temps are likely on
Sunday with some clearing potential through the day as the
trough axis slides east.
Monday-Saturday: Mainly dry and trending warmer through the week
A tranquil weather pattern will continue through the coming
work week. Both the GEFS/EPS show few, if any, precipitating
members through the work week as northwest flow aloft gives way
to broad ridging later in the week. Model guidance does indicate
a cold frontal passage late Monday, but the parent shortwave
trough and stronger forcing are expected to remain north of the
region, keeping precipitation potential quite low. After a brief
cool-down on Tuesday, temps should trend warmer later in the
week as return southerly flow develops and mid-level ridging
strengthens, suppressing any colder air well to the north. Highs
well into the 40s are likely by late in the week, and with
little snowcover and favorable south to southwest surface flow,
high temps on the warmer side of the probabilistic guidance (NBM
75-90th percentiles) near of above 50 could not be ruled out by
Thursday. Some low (~20%) precip chances return by
late Friday with a trough, but no widespread, impactful precip
systems are probable over the next week. Overall, warmer than
average temps remain strongly favored through the middle third
of December.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 533 PM CST Sat Dec 9 2023
A low pressure area will provide periods of light snow this
evening. This snow will occasionally produce MVFR visibilities.
Snow accumulations will range from a dusting to a few tenths of
an inch.
Expect sustained west winds in the 15 to 25 knot range with
gust of 20 to 30 knot range. These winds will drop to around 10
knots on Sunday morning.
With cyclonic flow continuing through Sunday, kept the MVFR
ceilings going through 11.00z.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...JM
AVIATION...KAA/Boyne
Area Forecast Discussion
National Weather Service Birmingham AL
916 PM CST Sat Dec 9 2023
...New MESOSCALE UPDATE...
.MESOSCALE UPDATE FOR SEVERE WEATHER THREAT OVERNIGHT...
Issued at 858 PM CST SAT DEC 9 2023
The threat for severe storms and tornadoes continues overnight for
all of Central Alabama. Currently, a line of strong to severe
storms stretches from Chattanooga to Cullman to Columbus MS. Ahead
of the line, a couple clusters of storms have developed, including one
near Demopolis. Counties across the west and far northeast remain
in tornado watches.
Currently, dewpoints are in the 60s areawide, with temperatures in
the mid 60s to lower 70s for much of the area. Looking at the 00Z
ROAB from BMX, surface based CAPE was around 1100J/kg with 45kts
of 0-6km shear. Little to no cap was noted on the sounding.
Current meso analysis shows surface CAPES from 500 to 1000 J/kg
with bulk shear values of 45-55kts ahead of the line. Do not see
much change in airmass over the next few hours, and expect the
Tornado watch to be expanded eastward.
Looking closer to sunrise,the latest CAM guidances shows a surge
of moisture into the southeast after 3AM with a restrengthening
low level jet. This would maintain the severe threat through the
early morning hours across the southeastern counties.
14
&&
.SHORT TERM...
(This afternoon through Sunday)
Issued at 1254 PM CST SAT DEC 9 2023
All eyes are on convection developing off to our north and west as
a dynamic system dives toward the Southeast states. Looking at
mesoscale conditions, it appears the break in the activity
advertised yesterday is in fact materializing. We`re certainly
realizing more surface-based instability than was being
advertised at this point yesterday. Breaks in the clouds are being
observed across much of western and southwestern Alabama as of
midday, with cloud streets visible across southern Mississippi and
southwestern Alabama. Current SBCAPE values based on RAP analysis
are being analyzed at 1500 J/kg within these locations.
Temperatures have already risen into the 70s at Tuscaloosa and
Demopolis, with the record high of 76 at Tuscaloosa at risk of
being broken. As 0-6km bulk shear values increase close to 50
knots late this afternoon and into this evening, we`ll have to
closely watch for convective development in central and southern
Mississippi that will move into western Alabama between 4pm and
6pm. Due to higher instability values, cores will likely form
within any discrete cell that is able to develop, with 500mb
temperatures between -14C and -16C. Therefore, we`ve added large
hail as a potential threat, especially for locations within the
Slight Risk area. Locations included are roughly along and
northwest of the I-59 corridor especially between 6pm and 10pm
tonight. Although mostly unidirectional deep-layer flow is still
expected as the cold front moves across Central Alabama overnight
tonight, SRH values will remain high enough to favor rotating
updrafts.
We`ll continue to watch for discrete cell formation out ahead of
what will become the main convective line/QLCS that forms across
central and northern Mississippi later this afternoon. All types
of severe weather will be possible across the far western and
northwestern counties through this evening, while a damaging wind
and tornado threat will continue as the QLCS moves southeastward
through Central Alabama overnight. Severe storm chances should end
between 8 and 10am in the far southeastern counties Sunday morning
with much colder and drier air advecting into the state. Most
locations will see temperatures actually fall through the day with
very cold northwesterly winds between 15 and 20mph. Temperatures
shouldn`t make it out of the 40s for many locations across the
north and northwest counties Sunday afternoon.
56/GDG
&&
.LONG TERM...
(Sunday night through next Friday)
Issued at 207 PM CST SAT DEC 9 2023
No significant changes to the extended forecast.
58/rose
Previous long-term discussion:
(Sunday night through next Friday)
Issued at 253 AM CST SAT DEC 9 2023
Quieter weather expected next week as high pressure builds in across
the Southeastern CONUS under generally zonal flow aloft. Morning
lows Monday and Tuesday mornings will be in the upper 20s to near 30
for much of the area. We`ll then see a gradual warm-up Wednesday
through Friday. There could be increasing rain chances on Friday,
but model guidance is highly variable on the evolution of the next
system. Therefore, we`ll keep low-end rain chances in the forecast
for now.
25/Owen
&&
.AVIATION...
(00Z TAFS)
Issued at 550 PM CST SAT DEC 9 2023
A line of strong to severe storms will move through Central
Alabama tonight and Sunday morning. Thunderstorms will produce
frequent lightning and strong winds. A few tornadoes are also
possible.
Ahead of the line, winds will be breezy from the south to
southeast. Isolated (becoming scattered) showers and a few
thunderstorms will be possible ahead of the line, and will carry
SHRA or vicinity wording at all terminals, to start the forecast
period. The line of storms is expected at TCL to BHM by 03-04Z
and continue eastward overnight. Will handle vis and cig
reductions from TSRA with tempos. Winds will turn to the west
behind the line of storms, then become northwest Sunday morning.
Rain will end from west to east tomorrow, with NW winds of
10-15kt.
14
&&
.FIRE WEATHER...
Showers and thunderstorms will overspread all of Central Alabama
tonight. 20-foot winds will be from the south-southwest at 8-12
mph through the evening hours. A strong cold front will track
southeast across the area after midnight, producing gusty
northwest winds. Min RHs on Sunday will be 55-65% west of I-65 and
65-75% east of I-65. The rain will end across west Alabama by the
early afternoon hours on Sunday and across east Alabama by sunset
Sunday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Gadsden 50 49 26 50 / 100 70 0 0
Anniston 52 53 28 51 / 100 80 0 0
Birmingham 49 50 29 50 / 90 70 0 0
Tuscaloosa 50 49 29 54 / 100 60 0 0
Calera 51 51 30 52 / 100 70 0 0
Auburn 58 61 31 52 / 90 90 10 0
Montgomery 57 59 31 53 / 100 80 0 0
Troy 60 62 32 54 / 90 90 0 0
&&
.BMX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...14
LONG TERM....58
AVIATION...14
Area Forecast Discussion
National Weather Service Boston/Norton MA
1036 PM EST Sat Dec 9 2023
.SYNOPSIS...
Multi-faceted, high impact storm to impact southern New England
Sunday into Monday with heavy rain, strong to damaging winds,
and perhaps a touch of snow in western MA. Otherwise, turning
drier Monday afternoon and trending colder into the middle of
next week. Then likely moderating the end of next week.
&&
.NEAR TERM /THROUGH SUNDAY/...
Just some minor tweaks to the forecast this evening. Only the
last few runs of the RAP had a clue about the light radar
returns moving across the southern coastal waters. Thus, used
that as the basis for updating rainfall chances this evening and
overnight. Not looking at a lot of precipitation, but thought
there was enough of a risk to preclude keeping the forecast dry.
The other concern overnight will be low clouds and fog as higher
humidity air moves over the relatively colder ground. Seeing
plenty of areas of fog along the south coast of New England and
portions of SE MA, but the visibility is not quite low enough to
warrant a Dense Fog Advisory just yet. Will continue to monitor.
730 PM update...
Warm front bleeding northward into MVY with wind direction now
190 degs and dew pt up to 50F, along with Buzzards Bay entrance
tower now reporting SW winds. Warm front will be slow to advance
northward overnight. As it does so, areas of fog will develop
and vsby already down to less than 2 miles at WST and GON. Fog
will become more widespread overnight and could see some patchy
dense fog too.
No appreciable rainfall overnight, but can`t rule out some
spotty mist/drizzle along and near the warm front. Despite the
warm front still south most of the region, it`s a balmy evening
across SNE with temps and dew pts in the 40s. Hence,
contributing factor to increasing areas of fog.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
Fog that forms overnight will likely have some trouble burning
off tomorrow morning due to a variety of reasons, but the two
primary mechanisms will be the low sun angle of December and
abundant cloud cover. In any case, expecting visibility to
improve by 16Z, just in time for the arrival of our next system.
As with previous updates, we continue to monitor the potential
for a multi-hazard storm beginning Sunday afternoon as low
pressure, amplified by a negatively tilting trough, ejects off
the mid- Atlantic coast before crossing eastern southern New
England and eventually moving into the Gulf of Maine. Rain will
begin between 16- 20Z tomorrow.
Strong southerly warm air advection ahead of an approaching
cold front will allow PWATs to grow to between 1 and 1.5";
extremely moist for by December standards! This increased
moisture will interact with an extremely robust 925mb LLJ, with
some guidance forecasting a strength of up to 100kt early
Monday, significantly enhancing precipitation potential with
this system. HREF LPMM, a typical, reasonable, benchmark of
maximum precipitation potential, highlights a broad area of 5-7"
of QPF across south central Connecticut, which is corroborated
by global guidance (GEFS) probabilities of exceeding 2" near
100% across western MA and probabilities of exceeding 4" between
20-30% across the same area. Thus, while position of the axis
of heaviest precipitation is up for debate and will wiggle a bit
over the next 24-36 hours as the position of the low wobbles
with each forecast cycle, we have high confidence that some
localities in the CWA will see 3-4" of rain, with locally higher
amounts. Thus, the flood watch that was in place overnight has
been expanded to encompass all of southern New England, save for
the Cape and Islands, given 6 hr FFG ranges from just 1.8" to
about 3". Urban and poor drainage flooding is expected, as well
as the potential for rapid brook and stream rises and flash
flooding in areas that receive several inches of rain in just as
many hours.
The LLJ mentioned in the above paragraph also poses a
significant threat to southern New England, with our saving
grace looking to be steep inversion below 975mb and cool ocean
temperatures, which will preclude the forecasted 80-100kt gusts
from mixing to the surface for the duration of this event. With
that said, there is still significant uncertainty in the upper
bound of gust potential across the Cape and Islands, as hi-res
guidance looks to develop a fine line between 12-16Z Monday,
which would allow for deeper mixing and stronger gusts to mix to
the surface. This uncertainty is the reason behind the High
Wind Watch being maintained through this forecast cycle, with
forecasters hoping to gain more confidence overnight before
deciding to upgrade to a warning, or to downgrade to an
advisory; noting advisory level winds of 40kt are a slam dunk in
the area outlined by the watch. NBM probabilities of 40kt
exceeding 60% across the south coast and Plymouth county, in
addition to collaboration with our neighboring WFO, have led to
the issuance of a wind advisory in the aforementioned areas,
with expected gusts of 40-55mph as far inland as Providence
overnight Sunday. To note, LLWS will be a significant concern
for the Cape and Islands, with up to 80kt of shear possible on
Nantucket early Monday!
Cold front begins to sneak into western New England Monday
morning and will be quite quick in its travel across the region.
Temperatures will fall some 20F, from the upper 50s to the 30s,
behind the front, leading to any anafrontal precipitation
transitioning to snow for a few hours Monday morning. While it
is tempting to bite on some of the deterministic guidance
outlining the potential for 6"+ of snow across western MA, snow
will have difficulty accumulating due to warm antecedent
conditions and borderline air temps in the mid 30s. Thus, relied
heavily on the positive snow depth change output rather than
raw 10:1 or Kuchera snow amounts, leading to the forecast of
perhaps a quick 1-3" of snow across the high terrain of
Franklin, Hampshire, and Hampden counties and a light dusting in
the high terrain of northern Worcester County. What does NOT
help the snow potential is the rapid departure of this system
into the Canadian maritimes, with all precip coming to an end
between 15-18Z Monday, leaving just a short window of
opportunity for accumulation.
As alluded to above, Monday will be a tale of two seasons
within one daylight period as we start out mild and rainy in the
mid 50s to near 60 and end the day with clearing skies and
temperatures in the 30s and 40s!
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
330 PM update...
* Quiet weather, no big storms or qpf events
* Temps at or cooler than normal much of this period, followed
by milder weather late next week, possibly 50+ for a day or
two
Ensembles support a northern stream dominant weather regime for
southern New England this period. Thus, temps at or colder than
normal much of the time. Also, moisture starved northern stream
short waves combined with the lack of stream phasing, not
expecting any big storms or qpf events this period. Then
beginning around the middle of next week, a Rex Block develops
out west, with a negative height anomaly over the desert
southwest and above normal heights across Alberta and
Saskatchewan. This anomalous warmth from this ridge eventually
advects ESE into the Great Lakes and into New England late next
week. Warm temps aloft combined with WNW flow may yield one or
two days of 50+ temps!
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
No major changes with this update. Warm front edging northward
from the south coast of New England with a wind shift to the S
and increased dew points. This warm front lifts very slowly
northward overnight. Earlier discussion below.
----------------------------------------------------------------
Through tonight...
MVFR across the CT River Valley will continue to spread east
this evening as any remaining VFR transitions to MVFR except for
on Nantucket. Patchy fog degrading cigs to IFR or lower likely
after 06Z at many terminals. Question mark on if fog makes it
into BOS, but minor vsby reductions possible at most terminals.
Winds generally light from the south.
Tomorrow...
Fog attempts to burn off but will be slow to do so given the
low sun angle and expansive cloud cover. Mainly MVFR with
pockets of IFR, though some guidance suggests a brief period of
VFR may break out tomorrow morning across southeast MA.
Southerly flow increasing through the day up to about 30kt by
sunset. Rain beginning from southwest to northeast between
16-20Z.
Tomorrow night...
Heavy rain expected across the region with IFR to LIFR across
the area. Embedded thunder possible. Wind shear will be a
significant issue across the Cape and Islands with up to 80kt
LLWS forecast over Nantucket. Southerly winds continue to
increase to 30-45kt, with gusts to 65kt possible, most likely
again over the Cape and Islands. Cold frontal passage begins to
work into NW MA by daybreak, shifting southerly winds to NW.
Brief transition to snow likely across the high terrain but will
not impact major terminals, perhaps ORE.
KBOS Terminal...Moderate confidence in TAF. VFR to MVFR this
evening. Fog possible at the terminal but confidence is low in
vsby reduction potential, though IFR cannot be ruled. Light
southerly flow tonight gives way to increasing gusts tomorrow;
up to 30kt by sunset. Rain begins after 20Z. LLWS around 35kt
not out of the question after 20Z Sunday.
KBDL Terminal... MVFR to IFR tonight as fog develops across the
interior. Light southerly flow tonight gives way to increasing
gusts tomorrow to near 20kt. Rain to begin around 16Z tomorrow
and persist through the end of the period.
Outlook /Monday Night through Thursday/...
Monday Night: VFR. Windy with gusts up to 35 kt.
Tuesday through Thursday: VFR. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Generally tranquil conditions tonight with south/southeast
winds 5-15kt waves 2-3ft.
Conditions deteriorate quickly Sunday into Monday as low
pressure crosses southern New England, allowing southerly winds
to build to 40kt by Sunday night and 60kt, across the outer
waters, by Monday morning. Wave heights look to approach 20ft.
Storm watches are in place for all waters and are expected to be
converted to either Gale Warnings or Storm Warnings over the
next 24 hours. Conditions will not be favorable to mariners, and
those expected to be on the waters should keep a keen eye on
the forecast.
An abrupt and significant shift in winds is expected mid to
late day Monday as a cold front crosses the waters, allowing
winds to diminish to near 20 kt overnight. Seas gradually
diminish but will still be near 15 ft overnight.
Outlook /Monday Night through Thursday/...
Monday Night: Low risk for gale force winds with gusts up to 40
kt. Rough seas up to 14 ft.
Tuesday: Winds less than 25 kt. Local rough seas.
Tuesday Night through Wednesday: Moderate risk for Small Craft
Advisory winds with gusts up to 25 kt. Seas up to 5 ft.
Wednesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Seas up to 5 ft.
Thursday: Moderate risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft.
&&
.HYDROLOGY...
330 PM update...
The risk for rapid brook and stream rises as well as poor
drainage, urban, and flash flooding is elevated from Sunday
night into Monday as some areas could see 2-4"+ of rain. Given
these elevated concerns, WPC has placed much of southern New
England in a "Slight" risk for excessive rainfall.
&&
.TIDES/COASTAL FLOODING...
330 PM update...
* Coastal Flood Watch remains in effect
12z models have trended faster with timing of strongest wind
and max surge to about 2-3 hours before high tide. Yesterday
guidance was closer to high tide, therefore the threat for
moderate/significant flooding is lower today than yesterday.
However, given the time sensitivity of only a few hours making
the difference between minor and moderate flooding, we will
continue with the Coastal Flood Watch for Narragansett Bay, as
it highlights the potential still exist. Elsewhere, the flood
threat is more minor, as the southerly flow up the bay increases
the surge do to funneling/channeling.
As of now there is moderate confidence (greater than 50%) for
minor flooding for the entire south coast from the CT/RI border,
eastward to the south coast of Cape Cod. This includes all the
towns along Narragansett and Buzzards Bays. As for moderate to
significant flooding, only a 20-30% probability of occurrence
and that is confined to Narragansett Bay. Today`s surge forecast
was based on the ETSS and PETSS 90th percentile. This yields a
storm surge of 1.5 ft to 2.5 ft, down from up to 3 ft from
yesterday`s guidance. Again, very time sensitive given high tide
and low tide are only 6 hours apart. Hence, a wind forecast
error of only 3 hours will have a big impact on storm surge and
inundation. Stay tuned!
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch from Sunday afternoon through Monday evening for
CTZ002>004.
MA...Flood Watch from Sunday afternoon through Monday evening for
MAZ002>021-026.
Wind Advisory from 8 PM Sunday to 9 AM EST Monday for
MAZ019>021.
High Wind Watch from late Sunday night through Monday
afternoon for MAZ022>024.
RI...Flood Watch from Sunday afternoon through Monday evening for
RIZ001>007.
Wind Advisory from 8 PM Sunday to 9 AM EST Monday for RIZ006-
007.
High Wind Watch from late Sunday night through Monday
afternoon for RIZ008.
Coastal Flood Watch from late Sunday night through Monday
morning for RIZ002-004>007.
MARINE...Storm Watch from late Sunday night through Monday morning for
ANZ230-236.
Storm Watch from late Sunday night through Monday afternoon
for ANZ231>235-237-250-251-254>256.
&&
$$
SYNOPSIS...Nocera/KS
NEAR TERM...Belk/Nocera/KS
SHORT TERM...KS
LONG TERM...Nocera
AVIATION...Belk/Nocera/KS
MARINE...Nocera/KS
HYDROLOGY...KS
TIDES/COASTAL FLOODING...Nocera
Area Forecast Discussion
National Weather Service Peachtree City GA
914 PM EST Sat Dec 9 2023
...Corrected to add mention of patchy dense fog...
.UPDATE...
Issued at 912 PM EST Sat Dec 9 2023
Active QLCS line moving through northern AL this evening ahead of
a cold front. This line will continue eastward overnight and
provide the potential for severe weather overnight. The QLCS is
actually out ahead of the frontal boundary and the high res models
keep the line active well into the overnight hours. Damaging wind
gusts and isolated brief tornadoes will be possible as the line
moves through. A few reports of large hail will also be possible
along with locally heavy rainfall.
Currently, a wedge is in place across NE GA. The wedge is very
well depicted within the temp field and is situated just north of
ATL. The southern end of the wedge will likely erode through the
evening and early morning hours, but far NE GA should remain
wedged until the FROPA.
Have updated temps/dewpoints to better reflect current
conditions. However, all of the changes were minor. Have also
updated the pops to reflect current radar trends. The timing was
a blend between the HRRR and the WRF. The higher res models have
wanted to slow down the FROPA by an hour or so from run to run.
Will also issue a SPS for patchy dense fog within the wedge. Do
think VSBYS will improve in areas where the wedge does erode.
&&
.SHORT TERM...
(This afternoon through Sunday)
Issued at 143 PM EST Sat Dec 9 2023
Primary forecast concerns in the short term period are likelihood
and timing of strong/severe storms and heavy rain tonight and
potential for very light snow accumulations at elevations above
3000ft in NE GA Sunday evening.
Early batch of scattered SHRA associated with warm advection
moved off this morning, while mid 60s dewpoints advecting north
into NW AL with clearing skies this afternoon leading to favorable
environment for a few severe storms and tornadoes. Line of
convection expected to approach NW GA around midnight but could
see small, fast-moving supercells ahead of the line as supported
by a few CAMs including recent HRRR runs. SBCAPE as high 1000 J/kg
as convection moves into the state but wanes overnight to no more
than 500 J/kg by 12Z, mostly in a thin "ribbon" ahead of the
convective line with greater values towards westcentral GA and SE
AL. 0-1km SRH and 0-3km line-normal shear should be sufficient for
a few mesovortices and brief/weak tornadoes within QLCS, which is
also supported by a few CAMs in 2-5km Updraft Helicity fields,
even as late as 10-12Z. After 12Z, low level shear decreases and
isolated tornado and wind threat decreases with it. Could see very
brief, strong/severe storm with damaging winds along the line
before they move out of the CWA in the mid afternoon.
Rainfall totals through Sunday expected to remain under 2 inches,
with a little more expected in the NE GA mountains. Rainfall
rates should be low enough and FF guidance sufficient to preclude
any flash flooding but will need to be monitored even with ongoing
long term drought conditions.
Front running about 6 hours behind the convective line with
steady/falling temps strong NW winds gusting to 25-30 mph, just
below wind advisory levels. Small chance for snow mixing in with
light rain at higher elevations in NE GA Sunday evening, though
cold advection will be very strong. At elevations above 3000 ft,
could see < 1/2 inch accumulation on grassy surfaces by 06Z
Monday morning. Not enough confidence in this and no impacts
expected even if it does occur, so no plans to issue any kind of
Winter or Special Weather Statement. That said, model trends have
been consistent showing temps falling rapidly and going just
below freezing as the moisture and light showers move out. Often
CAA pushes precip out in this pattern but orographic lift might
squeeze out a surprise 1/2 inch somewhere.
SNELSON
&&
.LONG TERM...
(Monday morning through next Friday)
Issued at 143 PM EST Sat Dec 9 2023
Key Messages:
- Dry weather is forecast in Georgia through Friday.
- Morning low temperatures should dip into the 20s along and north
of Interstate 85 Monday and Tuesday.
- Rain chances return to the region next weekend.
Monday through Wednesday:
Zonal flow aloft and surface high pressure should keep our weather
dry during this period. The fair weather conditions will be
favorable for chilly overnight temperatures. This will be especially
true on Monday and Tuesday mornings when limited cloud cover, light
winds, and low humidity should allow morning lows to dip into the
20s along and north of Interstate 85. With a relatively dry airmass
in place, afternoon high temperatures should recover fairly well
each day. Highs in the upper 40s and lower 50s on Monday should
trend towards upper 50s on Wednesday.
It continues to look like low relative humidity values (30-35%)
could have us flirting with near critical fire danger conditions in
the north Georgia mountains Monday, Tuesday and Wednesday
afternoons. The deciding factor may be how fuels respond to this
weekends rainfall. For now it looks like there is a roughly a 25%
chance of us issuing a Fire Danger Statement for the region each
afternoon.
Thursday and Friday:
The majority of the GEFS and EPS ensemble members favor weak upper
level ridging in our region during this period. With this in mind
our forecast remains dry for both Thursday and Friday. Overall
confidence in the precipitation forecast is lowest for Friday and
Friday night due to timing uncertainties with the next potential
trough as it moves east from Texas and/or the Gulf of Mexico.
Over the last 24 hours our temperature forecast has trended downward
slightly for this period. We now expect afternoon highs to be near
seasonal averages (low to mid 50s). This trend has shown up in both
the EPS and GEFS guidance and is linked to the strength of a surface
high (cooler airmass) shifting east from the Central Plains. Spreads
in the NBM high temperature guidance (25th to 75th percentiles)
remain large for this period as well, generally around 10 degrees.
The Outlook for Next Weekend:
Ensemble guidance leans towards weak troughing in the region next
weekend. Due to this rain chances (20 to 40%) creep back into the
NBM and subsequently our forecast Saturday and Sunday. At this time
around 75% over the GEFS and EPS members have some accumulating
precipitation in our region next weekend.
Albright
&&
.AVIATION...
(00Z TAFS)
Issued at 634 PM EST Sat Dec 9 2023
Light shra around ATL this evening, but precip should become more
widespread. Stronger storms to the SW should weaken and bypass ATL
just to the SE in the next hour or two. Precip will become
widespread overnight with a line of thunderstorms possible between
08-12Z. Models have slightly slowed the line down so extended the
tempo by an hour. SHRA likely on the backside of the front, but
think models are having a hard time resolving coverage. Gusty NW
winds behind the front. IFR
//ATL Confidence...00Z Update...
Med confidence all elements.
NListemaa
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 59 64 31 52 / 80 100 50 0
Atlanta 60 62 32 48 / 100 100 20 0
Blairsville 53 55 26 44 / 100 80 40 0
Cartersville 55 59 28 49 / 100 70 10 0
Columbus 62 65 33 53 / 80 100 20 0
Gainesville 55 60 32 50 / 100 90 40 0
Macon 61 67 33 53 / 40 100 50 0
Rome 53 58 28 51 / 100 70 10 0
Peachtree City 59 61 29 50 / 90 100 20 0
Vidalia 62 72 36 54 / 20 100 90 0
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...NListemaa
LONG TERM....Albright
AVIATION...NListemaa
Area Forecast Discussion...Updated
National Weather Service Lincoln IL
808 PM CST Sat Dec 9 2023
.UPDATE...
Issued at 808 PM CST Sat Dec 9 2023
Evening surface map indicated a sprawling low pressure system
centered at 993 mb north of the Great Lakes. Deep cyclonic flow
south of the low encompassed our area, producing a large stratocu
field across the region. Water vapor imagery showed the main
shortwave over northern WI, with subtle weaker shortwaves farther
south and west. One of these waves was producing scattered
flurries from eastern IA into northwest IL. As this translates
east over the next few hours scattered flurries are possible
mainly along and north of a Galesburg to Peoria to Bloomington
line. Otherwise west winds gusting 25-30 mph will be common
through late evening. Gusts should gradually diminish later
tonight as the low pulls farther away and the MSLP gradient
loosens somewhat. Overcast skies will offset the low level cold
advection, to keep lows in the upper 20s and lower 30s.
25
&&
.DISCUSSION...
Issued at 134 PM CST Sat Dec 9 2023
Key Messages:
* Extended period of quiet weather much of the upcoming week.
* Coolest conditions to be through Sunday night, with most of the
work week above normal temperature-wise.
Midday surface map shows the cold front has pushed well into
Indiana. A few showers continue to graze areas around
Lawrenceville, but otherwise most of the convective activity began
to take off just after the front exited our forecast area.
Large area of stratocumulus, associated with an upper trough
currently approaching the Illinois/Iowa border, will continue to
spread across much of the forecast area through this evening.
Upstream obs and radar have shown some flurries or snow showers
across Iowa, with the latest HRRR showing a of them arriving west
of the Illinois River before sunset. Will add a mention of
sprinkles/flurries across the northern CWA through early evening.
The coolest weather during the forecast period will be Sunday,
with highs only in the 30s. After that, as the broad upper trough
over the Mississippi Valley shifts eastward early next week, we
return to more of a Pacific flow, with temperatures above normal
most of the week. Highs in the 40s will be common, with some lower
50s at times south of I-70.
A large cutoff low is expected to develop over Nevada late
Tuesday, and slowly track into Texas by Friday. Longer range
models are in reasonable agreement with this scenario. However,
sprawling surface high pressure over the Midwest and mid-Atlantic
region will make it tough for this low to make a lot of headway
east. The GFS and European models suggest a second upper low
forming over the Dakotas late week, becoming the dominant feature
by Saturday. The deterministic European model is most aggressive
with the associated surface reflection, though only a handful of
its ensemble members are in agreement. In any event, the position
of the high would prevent any substantial moisture influx into the
area before Saturday morning, so the blended guidance of "silent
20" PoP`s should be sufficient for now.
Geelhart
&&
.AVIATION... (For the 00z TAFs through 00z Sunday Evening)
Issued at 505 PM CST Sat Dec 9 2023
A large area of overcast has spread across the area, wrapping
around expansive low pressure centered north of the Great Lakes.
Initially this cloud deck is at VFR levels, however guidance is
consistent in showing MVFR ceilings upstream over IA will spread
southeast across the terminals from 03-06z. This is likely to
persist until late morning to early afternoon. 20-25 kt westerly
gusts will be common this evening with gusts becoming more
sporadic overnight, then sustained at 10-15 kt Sunday.
25
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Lake Charles LA
950 PM CST Sat Dec 9 2023
...New UPDATE...
.UPDATE...
Issued at 950 PM CST Sat Dec 9 2023
Local 88Ds show the convection associated with a passing
disturbance aloft and an associated sfc cold front now moving
into the sern zones, while scattered showers/storm or two linger
behind the boundary closer to the h9/h8 fronts. The convection has
been largely behaved over the forecast area this afternoon/evening
with mainly just reports of small hail received so far. The threat
for severe weather, although fairly slim, lingers for the sern
zones where RAP guidance continues to indicate reasonable
MUCAPES/DCAPES/lapse rates/instability. The line should depart the
lower Atchafalaya Basin by 06z or so, with the lingering activity
behind it gradually diminishing in coverage through the overnight
as a drier wrly flow develops aloft. Meanwhile, brisk nrly winds
have developed behind the boundary and these should continue
through the night (and throughout Sunday as well) as CAA develops.
All in all, inherited grids/zones look in good shape per latest
obs/trends and no updates appear needed at this time.
25
&&
.SHORT TERM...
(Tonight through Monday night)
Wx map shows the southwest to northeast oriented strong cold front
continuing to move southeast, just west of ELD/SHV/LFK. Temperatures
ahead of the front, have risen into the lower 80s, with dewpoints
in the upper 60s to lower 70s. Southwest winds around 15 mph with
gusts to 25 mph common across the area this afternoon. Radar
showing scattered showers over Central and South Central
Louisiana, and across the coastal waters. 18z Lake Charles
sounding showing increased sfc based CAPE at 2718 J/kg but not
much low level directional shear anymore. The Storm Prediction
Center continues a Marginal Risk (Level 1 of 5) across parts of
Southeast Texas and most of Louisiana, with the Slight Risk (Level
2 of 5) over Central Louisiana parishes of Rapides, Avoyelles, as
well as northern Evangeline and St. Landry parishes. The greatest
threat of severe weather will be damaging winds. Areas within the
Slight Risk in Central Louisiana have the higher risk of a
possible tornado ahead and along the front.
Following the frontal passage tonight into Sunday will be very
strong cold air advection, bringing colder and drier air across
the region. Northwest winds will significantly increase by
Midnight and remain elevated through Noon Sunday with wind speed
20-25 mph and gusts over 30 mph at times. For this, issued a Wind
Advisory for areas of Central Louisiana, Southern Louisiana, and
Southeast Texas. Expect Sunday morning lows in the 40s with highs
not getting out the mid 50s Sunday afternoon.
Winds expected to diminish rapidly by late Sunday afternoon
through the overnight hours as the cold surface high over Texas
builds east over our region. With clear skies and nearly calm
winds expected for Monday morning, expect lows around 28-30 north
of I-10, and lower to mid 30s further south. Highs Monday
afternoon around 60 expected. Another clear and cold night
expected Monday night with lows 28-30 over Central Louisiana, and
mid 30s along the I-10 corridor of South Louisiana. Easterly winds
may keep temperatures up across Southeast Texas, expecting lower
40s there.
08/DML
&&
.LONG TERM...
(Tuesday through next Friday)
The start of the longterm period appears dry with high pressure
ridge moving overhead, and seasonably cool with the remnants of a
cool airmass still set in the region. Temperatures Tuesday will have
moderated into the low to mid 60s, which is typical climo for this
time of year. On Wednesday, though, northeast winds from high
pressure moving through the northeast US looks to send southward a
weak frontal boundary which should push area-wide daytime temps down
into the low 60s through Thursday. This boundary will be very weak
but can be seen by a reinforcement of low PWATs Wednesday on
northeast flow.
And like ironic clockwork, since we`re moving towards the next
weekend, that means we get to talk about the next weather system.
Early in the work week, guidance shows a shortwave trof coming
ashore in the Pacific Northwest. It slowly lumbers to the southeast
by Wednesday, with a closed upper low developing. Model agreement
continues through Thursday morning as the low moves into west Texas.
From here, we start to see some separating solutions between the
ECMWF and GFS, which lowers forecaster confidence in how next
weekend will play out. One solution takes the low to the north
across Oklahoma (ECMWF) while the other takes the low right over the
LCH CWA; each solution having each their own complications. It`s too
far out to say for sure if and how this low forms and moves across
the southeast US, and then how that will directly impact us here.
However, there is enough confidence in the active El Nino pattern
we`re in to expect some moisture return Wednesday and Thursday with
an increase in rain and potentially thunderstorm chances Friday and
Saturday with the passage of a low pressure system. Confidence in
these details should increase as we move into the work week.
11/Calhoun
&&
.AVIATION...
(00Z TAFS)
Issued at 600 PM CST Sat Dec 9 2023
This forecast period is mainly about thunder and wind across the
forecast area. Local 88Ds show scattered convection associated
with a trof axis, an embedded disturbance and sfc cold front
currently approaching KAEX and expected to impact the swrn
terminals over the next couple of hours...eventually reaching the
Acadiana terminals later this evening. All guidance slides the
rainfall west to east across the aviation forecast area by
essentially midnight, with a stiff nrly winds expected behind the
frontal passage. VFR ceilings should prevail, although forecast
soundings indicate MVFR cigs are likely for KLFT/KARA before a
drier wrly/nwrly flow develops aloft behind the trof passage and
scours out lower moisture, leaving behind generally clear skies
for Sunday.
25
&&
.MARINE...
Moderate onshore winds will continue through this evening. A
strong cold front will move through the region tonight, bringing
widespread showers and thunderstorms along with the possibility
for severe wind gusts and frequent cloud to water lightning. The
main marine concern will be after the frontal passage from late
tonight through tomorrow as strong north winds and building seas
develop in its wake. Sustained winds near 25 to 30 knots with
gusts 35 to 40 knots can be expected across the coastal waters,
with slightly lower values across the coastal lakes and bays. Gale
Warnings continue for the 0-60nm marine zones, with Small Craft
Advisories for the Inland Lakes and Bays tonight through Sunday.
With the strong offshore flow, water will be pushed away from the
coast and low water conditions of -1.0 to -2.0 Mean Lower Low
Water can be expected for the coastal lakes and bays, with a Low
Water Advisory in effect.
Conditions will begin to improve tomorrow night into Monday as
high pressure builds in behind the front with rapidly decreasing
winds and lowering seas expected as we head into the work week.
Winds and seas will increase by Tuesday night and remain elevated
through Thursday as a tightening pressure gradient produces a
prolonged and strong easterly fetch across the Northern Gulf of
Mexico.
08/DML
&&
.PRELIMINARY POINT TEMPS/POPS...
AEX 42 56 28 59 / 80 0 0 0
LCH 46 57 33 59 / 90 0 0 0
LFT 49 57 33 58 / 80 10 0 0
BPT 46 58 34 60 / 80 0 0 0
&&
.LCH WATCHES/WARNINGS/ADVISORIES...
LA...Wind Advisory until noon CST Sunday for LAZ029-032-033-044-045-
055-073-074-141>143-152>154-241>243-252>254.
TX...Wind Advisory until noon CST Sunday for TXZ515-516-615-616.
GM...Small Craft Advisory until noon CST Sunday for GMZ430-432-435-
436.
Low Water Advisory until noon CST Sunday for GMZ430-432-435-436.
Gale Warning until noon CST Sunday for GMZ450-452-455-470-472-
475.
Small Craft Advisory from noon to 9 PM CST Sunday for GMZ450-452-
455-470-472.
Small Craft Advisory from noon Sunday to midnight CST Sunday
night for GMZ475.
&&
$$
SHORT TERM...08
LONG TERM....11
AVIATION...25
Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
823 PM EST Sat Dec 9 2023
.SYNOPSIS...
Rain will overspread the region this evening and continue
through most of Sunday as a cold front approaches and crosses.
Rain will change over to snow Sunday night. A few inches may
accumulate on the ridges into Monday. It will be a chilly
Monday as temps won`t get above freezing.
&&
.NEAR TERM /THROUGH TODAY/...
Sending out a quick update to put thunder back in the forecast.
Still seeing some isolated convection on the leading edge of the
showers. Rest of the forecast is in line with current
conditions.
Previous discussion...
The main period of rainfall will still occur in the
tonight/Sunday morning period. This is associated with elongated
trough extending into the Mississippi River Valley and a cold
front crossing into the Ohio River Valley. Heavier rainfall
potential has decreased significantly due to dry air over the
Southeast and over the Great Lakes. According the grand ensemble
of Hi-Res model guidance, probability of a half inch of rain is
80% for areas southeast of Pittsburgh by Sunday evening and
only 10% for 1.00 inch of rainfall. Therefore, the Marginal risk
for Excessive Rainfall issued by the Weather Prediction Center
has been removed for our County Warning Area (CWA) and river
rises will likely not be impactful.
&&
.SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/...
Key Message: Rain changing to snow Sunday evening with few
inches of accumulation in the mountains and north of I80. A
winter weather advisory has been issued for eastern Tucker Co.
in WV.
Precipitation type will likely change from rain to snow late
Sunday evening from northeast to southwest with the passage of
the cold front. Snow character will start out as wet as model
soundings depict a deep layer stable air extending from 850mb to
500mb and temp profiles hugging the -10C isotherm. Models have
been consistent that 2 to 5 inches of snow will accumulate in
eastern Tucker over the last 48 hours. Probability of 2 inches
is over 90% for eastern Tucker, 65% for 4 inches of higher. With
low probabilities for 6 inches (33%) or higher, decided to
issue a Winter Weather Advisory opposed to a Winter Storm
Warning. If confidence increases, the ridges of the Laurel
Highlands and eastern Preston county may be included in the
Winter Weather Advisory in the next forecast update.
With prevailing northwest flow and passing upper-lvl trough over
the Great Lakes, training convection snow bands may create an
additional 1-2 inches north of Pittsburgh early Monday morning
through early Monday afternoon. Ridging and westerly flow will
like diminish the chances of snow by 7pm Monday.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
Ridging over the Central Appalachians will likely clear the sky
Monday night. Therefore early morning lows on Tuesday will
still dip into the 20s. If gusty winds remain elevated, apparent
temperatures could drop into the single digits in the higher
terrain.
Dry weather will then take hold for the remainder of the extended
period, with quasi-zonal flow Tuesday and Wednesday eventually
giving way to strong ridging over the Eastern CONUS. Temperatures
will moderate close to normal in this pattern for Tuesday. A weak
and likely dry frontal passage Wednesday may drop temps slightly
below normal again for Wednesday. The rising heights will create a
slow warming trend Thursday and Friday, perhaps to above-normal
levels.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
High confidence forecast in CIGS save for DUJ where they could
stay MVFR thru tonight into Sunday morning.
Where TAFs could go astray:
- precip may end 1-2 hours earlier than forecast, especially at
PIT to MGW and points west
- visibilities could drop to IFR briefly in heavier showers
A cold front approaches the region Sunday. Ahead of it, showers
before the main coastal low takes over and it become a rain
shield Sunday morning onward. PTYPE is forecast to be all rain.
LBE and DUJ will have rain the longest, while ZZV has it the
shortest duration and could see a period of VFR weather Sunday
morning.
Wind shear is a concern this evening with the strong southerly
flow. There have been a few PIREPS of wind shear, so will keep
that given NBM and HRRR are illustrating it.
Wind will be from the south through most of the night around 10
kts. It will switch to the west early morning Sunday. Brief
gusts to 20kts are possible this evening.
.OUTLOOK...
Restrictions in snow and rain Sunday night into Monday at
terminals close to the mountains. A return to VFR is expected
Monday night and should persist through much of next week with
building high pressure.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...Winter Weather Advisory from 7 PM Sunday to 1 PM EST Monday
for WVZ514.
&&
$$
SYNOPSIS...Hefferan
NEAR TERM...Hefferan
SHORT TERM...Hefferan
LONG TERM...Hefferan/CL
AVIATION...Cermak/McMullen