Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/22/23
Area Forecast Discussion
National Weather Service La Crosse WI
508 PM CST Sat Jan 21 2023
.DISCUSSION...(Tonight through Saturday)
Issued at 210 PM CST Sat Jan 21 2023
Key Messages:
- Light snow chances across the south tonight, perhaps freezing
drizzle
- Relatively mild temps persist for the new week with small snow
chances
* LIGHT SNOW CHANCES SOUTH TONIGHT: minor accumulations possible,
freezing drizzle?
Upper level shortwave trough currently across the southern plains is
on track to move northeast across parts of IA/northern IL tonight.
Decent slug of 700:300 mb QG convergence with this feature, although
brunt of it currently pegged to hold south of the local forecast
area. Some weak 600 mb Fgen does manage to setup across parts of
northeast IA/southwest WI tonight per the RAP. Broad isentropic
upglide along the 285:295 K sfcs also painted by the RAP across
southern parts of the forecast area tonight. While missing out on
the heart of the shortwave`s lift, this meager lift could be enough
for light pcpn chance. CAMS and the deterministic model runs all
suggest light QPF across parts of the NE IA/SW WI tonight, with
support from the GEFS/EC ensemble members.
If pcpn does stretch this far north, saturation could play a role in
what falls. RAP/HRRR/NAM12 Bufkit soundings all show a dry layer
roughly from 700:850 mb this evening. Eventually this saturates
overnight, but at least initially there would be questions of ice in
the cloud and/or if the near sfc saturation would be deep enough to
support drizzle production (freezing drizzle in this case). When it
does switch over to snow, COBB output at KDBQ in the NAM and GFS
suggest up to 1" would be possible...looking more like a few tenths
north of there.
Have increased pcpn chances for portions of NE IA/SW WI tonight,
moreso for the overnight hours. Added some freezing drizzle
potential in the evening, then snow overnight with accums generally
under 1/2 inch.
* NEW WEEK OUTLOOK: staying somewhat mild with small snow chances
The GFS and EC suggest more northwesterly flow a loft for most of the
new week. Not a big push of colder air with the bend in the flow, at
least initially, and temps look to hover at or above the late
January normals for much of the new week. As we approach the weekend
though, the GFS and EC start to shove colder air southward from
Canada...with decent consensus in the models` ensemble members. 6-10
and 8-14 day CPC temp outlooks also suggest below normal
temperatures loom on the horizon. So - perhaps one more week with
relatively mild temps before a taste of winter cold returns.
As for precipitation chances, a few shortwave troughs could drop
through the Upper Mississippi River valley. One may slide across the
north late Mon afternoon/night. The GFS is the more robust model
with pcpn chances, but only minor QPF. NAM shows a bit while the EC
keeps the bulk of any pcpn to the north. Will add some light snow
chances north of I-94 for now.
Another shortwave could come Tue night with both the EC and GFS
spinning a ripple across northern parts of the region. A stronger
and more impactful storm sits farther south, and continues to be
trended to stay there (skirting the local forecast area).
The next shortwave could track across the region Friday with most of
the EC and GEFS members pointing to some chances for light snow. The
same ensemble members disagree on how much snow would/could fall.
Another shortwave then looks to take aim on the region over the
weekend.
All in all, some spotty light snow chances for the start, with the
models trending a bit more active for the second half.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 508 PM CST Sat Jan 21 2023
Widespread IFR/LIFR stratus will likely prevail into Sunday. Areas
of fog are also expected to develop this evening and persist into
Sunday morning. Some potential for dense fog with visibility
reduced to 1/4 mile exists, especially at KRST, but trends in fog
development will be monitored this evening. Very patchy light freezing
drizzle also could not be completely ruled out overnight,
especially at KLSE, but confidence in occurrence is low. Slow
improvement is possible by Sunday afternoon, although with the
surface ridge holding just west of the region, confidence in more
substantial clearing is very low through the daytime on Sunday.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&
$$
DISCUSSION...Rieck
AVIATION...JM
Area Forecast Discussion
National Weather Service Boston/Norton MA
1033 PM EST Sat Jan 21 2023
.SYNOPSIS...
Dry and seasonable weather prevails into Sunday morning. A strong
coastal storm impacts the region late Sunday into Monday, with heavy
rain, gusty winds, possible coastal flooding and accumulating snow
for northwest Massachusetts. Drier on Tuesday, but the active
pattern continues as another system moves in for late Wednesday into
Thursday with snow and mixed precipitation changing to rain. Mainly
dry and seasonably cold conditions follow for Friday into next
Saturday.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
1015 PM Update...
Shallow moisture remains trapped beneath the subsidence
inversion. The vast majority of guidance is handling this
moisture very poorly. The only exception is the RAP relative
humidity at 925 hPa looks very good compared to the latest obs.
Have utilized this as a proxy for what will occur overnight.
Really am not anticipating much of a change with overcast in
place other than perhaps along the MA/NH border as there really
is not much to kick this moisture out. With this in mind have
increased temps to the 75th percentile of guidance for overnight
as it is going to be very difficult to radiate. The only
exception is across northern MA/NH border where temps may be
able to drop with clearing skies. In this area have lowered to
the 30th percentile of guidance as it looks reasonable, but
still may be mitigated a bit by cloudiness. Rest of the forecast
looks good at this point.
645 PM update...
Stubborn shallow moisture trapped below the low level inversion
has resulted in widespread strato-cu across SNE. Clearing noted
across far NE MA northward through SE NH and Maine but this
clearing not advancing southward. None of the guidance is
handling these lower clouds very well. HRRR soundings do show
some erosion of the shallow moisture 04-06z which would support
clearing but confidence is low as subsidence inversion remains
in place overnight as high pres builds across the region. Cloud
cover will have a significant impact on low temps as any
clearing would allow temps to fall into the teens, but 20s if
clouds persist. We blended some of the milder raw guidance to
raise temps a bit, but overall confidence is low.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY/...
Sunday will be an quiet day on the whole, as precipitation looks to
hold off until late evening into the overnight hours. The mid level
ridge early will help keep things dry, with at least partly cloud
skies. We should see more sun through the high clouds than we saw
today which, together with warm southwesterly flow, will help
temperatures moderate, reaching the upper 30s in the high elevations
and upper 40s along the southeast coast. The approaching storm
system looks to be another mixed precipitation inside runner event
as a surface low over the Carolinas deepens to sub-1000 mb off the
mid-Atlantic coast and passes over Cape Cod. At the mid levels the
positively tilted trough crosses southern New England mid day
Monday, before which we should see the bulk of the precipitation
fall. We`ve got plenty of moisture to work with as that SW flow taps
into a 0.75-1.25" PWAT plume. This again looks to be a high
elevation snow/low elevation rain event. The NAM3k is the only
guidance currently advertising a 850 mb warm nose that would spell
appreciable freezing rain with this event so have opted for a mainly
snow/rain forecast at this point. A Winter Storm Watch is in effect
for the northern slopes of the Berkshires which stands the best
chance of seeing 7 inches of snow, but confidence is not high enough
to go with a warning at this point. EPS ensemble guidance does have
a 70-80% chance of 6+ inches but GEFS isn`t nearly as excited about
the prospect. A winter Weather Advisory is in effect for Worcester
Hills and southern Berkshires where 2 to 5 inches is more likely.
This is another event where it is prudent to look at the positive
snow depth change guidance more than the 10:1 snowfall accumulation
guidance given marginal temperatures. As the low lifts northeast
colder air is pulled in so everyone may get some light snow showers
later in the day on Monday before things taper off.
Strong, potentially damaging winds are looking like less of an issue
given an offshore track of the low level jet and a fairly inverted
sounding profile. However, we will have gusty N/NE winds on Monday
morning, especially over the waters. This, in conjunction with high
astronomical tides will give us a period of some minor coastal
flooding along the MA east coast; coastal flood headlines will
likely be needed for the Monday afternoon high tide.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Highlights
* Dry and blustery Tue
* Another storm brings snow and mixed precipitation changing to rain
late Wed into Thu. Strong winds possible near the coast early Thu
* Mainly dry and seasonable Fri/Sat
Monday night into Tuesday...
Upper trough moves to the east Mon evening with ridging building in
behind it then a fast moving low amplitude trough follows for Tue.
Any lingering rain/snow showers will exit SE New Eng Mon evening,
then clearing develops overnight. Expect mainly dry weather with a
mix of clouds and sun Tue. Just a low risk for a few flurries or
snow showers over the Berkshires as the trough swings through. Temps
will average slightly above normal with highs ranging from mid 30s
higher terrain to lower 40s in the coastal plain. Decent pressure
gradient Tue will support blustery W winds, gusting to 25-35 mph at
times.
Wednesday into Thursday...
Active pattern continues with another southern stream system lifting
NE from southern Plains. As has been the case all winter, consensus
of the guidance favors an inland track with the primary low, while a
secondary low tracks across SNE so will likely be dealing with a
snow to rain scenario. However, high pres to the N across Quebec at
the onset of moisture will provide antecedent cold air for precip to
begin as snow across much of SNE Wed afternoon before changing to
rain from south to north Wed night. 850 mb temps around -4 to -6C at
the onset Wed afternoon then warm nose quickly lifts north Wed
night. Still too early for specific snow accum but minor accum
possible down to the coastal plain before changing to rain. The
highest totals will likely be across interior northern MA. GEFS/EPS
ensembles show fairly high probs of 3+ inches with low to moderate
probs of 6+ inches across far northern MA. The storm lifts out
during Thu so expect improving conditions by Thu afternoon.
There could be some wind issues near the coast sometime late Wed
night or Thu morning as a robust southerly low level jet is forecast
to develop across SE New Eng.
Coastal flood threat is marginal at this time. The high tide of
concern will be the early Thu morning (225 AM) tide which is 10.33
ft at Boston which is fairly low. Would need about a 2 ft surge for
minor flooding and this will depend on getting a period of strong
E/SE winds at high tide which is highly uncertain. Winds will be
shifting to S/SW by Thu morning.
Friday into Saturday...
Looks mainly dry and seasonably cold Fri behind the departing
storm. Then low confidence forecast for Sat as there is considerable
spread among the guidance. Followed NBM for now.
&&
.AVIATION /04Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
00z TAF update...
Tonight...
MVFR cigs should trend to VFR 04-06z as clouds scatter out but
confidence is low to moderate at best as there is uncertainty if
shallow moisture erodes below the subsidence inversion. Winds
light and variable with the high overhead.
Sunday...
Dry and VFR becoming MVFR by 00z in light rain or snow/mix
for northwest MA. Light SSW winds to start, then increasing
15-20 kts late in the day across Cape Cod and islands.
Sunday night...
IFR. Light to moderate RA for most but SN possible for a time at
BDL/BAF/ORH. NE winds 10 kt gusting to 20 kt toward 12Z; 25-30
kt for the Cape and islands.
KBOS TAF...Low to moderate confidence in TAF due to uncertainty
in MVFR cigs scattering out.
KBDL TAF...Low to moderate confidence in TAF due to uncertainty
in MVFR cigs scattering out.
Outlook /Monday Night through Thursday/...
Tuesday Night: VFR. Windy with local gusts up to 30 kt.
Wednesday: Mainly VFR, with local IFR possible. Breezy. Chance
SN, chance RA.
Wednesday Night: MVFR/IFR conditions possible. Strong winds
with gusts up to 40 kt. RA, SN.
Thursday: Mainly VFR, with local IFR possible. Strong winds
with gusts up to 40 kt. Chance RA, slight chance SN.
Thursday Night: VFR. Windy with gusts up to 35 kt.
Friday: Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Saturday night through Sunday night...High Confidence.
Sat night...1020 mb high builds over SNE, with light winds, dry
weather and good vsby. SE swells continue to erode.
Sunday...1020 mb high moves offshore, with SSW winds developing, and
increasing 15-20 kt in the afternoon. Dry weather and good vsby, but
rain possible toward 00z Monday.
Sunday night...Rain overnight. Light SE winds become gusty out
of the NE, gusting 25 to 30 kts with 3-5 ft.
Outlook /Monday Night through Thursday/...
Tuesday Night: Low risk for Small Craft Advisory winds with
gusts up to 30 kt. Local rough seas.
Wednesday: Winds less than 25 kt. Chance of rain.
Wednesday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Areas of rough seas. Rain.
Thursday: Moderate risk for gale force winds with local gusts
up to 45 kt. Rough seas up to 11 ft. Chance of rain.
Thursday Night: Low risk for gale force winds with gusts up to
35 kt. Rough seas up to 11 ft.
Friday: Moderate risk for Small Craft Advisory winds with gusts
up to 25 kt. Areas of rough seas.
&&
.TIDES/COASTAL FLOODING...
* Minor coastal flooding possible midday Monday High Tide
We are watching the late Monday morning/early afternoon high
tide for widespread minor coastal flooding along the eastern MA
coast, Cape, and Nantucket. Although the strongest winds aren`t
expected to reach the surface, winds will nevertheless be gusty
and combined with very high astro tides coastal flooding is
possible.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Winter Storm Watch from Sunday evening through Monday
afternoon for MAZ002-008.
Winter Weather Advisory from 7 PM Sunday to 4 PM EST Monday
for MAZ003-004-009-026.
RI...None.
MARINE...None.
&&
$$
SYNOPSIS...KJC/BW
NEAR TERM...KJC/BL/BW
SHORT TERM...BW
LONG TERM...KJC
AVIATION...KJC/BW
MARINE...KJC/BW
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Charleston SC
907 PM EST Sat Jan 21 2023
.SYNOPSIS...
A low pressure system will produce unsettled weather from
tonight until a cold front crosses the area late Sunday night.
High pressure will then briefly return before another low
pressure system impacts the region midweek. High pressure is
expected late week into the weekend.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
The forecast is on track. Rain is slowly expanding across the
area this evening as forcing for ascent intensifies. Rain has
been pretty very light so far with RAP soundings and the 22/00z
KCHS raob highlighting still fairly dry sub-cloud layer. This
will steadily change overnight as the column moistens and
forcing intensifies. Pops near 100% look good. Temperatures
should hold steady through the night as diabatic cooling weakens
due to a steady moistening of the column and may actually rise
a bit across the far south and along the coast as a coastal
front approaches. Lows were nudged down in a few spots given
observed temperatures at 22/02z.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday will be the most active day of the short term period. A warm
front will continue lifting into the region, while a wave of low
pressure develops and rides along the front. Rainfall will be
ongoing Sunday morning with additional showers and embedded
thunderstorms expected through the day. There could be somewhat of a
lull in the early afternoon before the next batch of rain with a
trailing cold front comes through. Rain chances will decrease
overnight with shower activity expected to be all offshore by
daybreak Monday.
Latest rainfall totals Sunday through Sunday night are forecast to
average 0.75-1.25 inches, though some locally higher amounts are
possible. The area is highlighted under a Marginal Risk in the
Excessive Rainfall Outlook, however given the relatively dry
antecedent conditions, the flood threat will largely be limited.
There is concern for decent rainfall rates around the time of high
tide (occurring ~815 AM) which would exacerbate conditions in low-
lying and urban areas along the coast. Poor mid level lapse rates
and weak instability will keep severe threat low, but wind fields
could support a couple stronger storms with damaging wind gusts if
more instability is realized. Much of the area is encompassed in a
Marginal risk for severe weather in the SPC Day 2 outlook.
Lake Winds: Gusty west winds are expected to develop behind the cold
front late Sunday night through Monday morning. A Lake Wind Advisory
will likely be needed.
Drier and cooler air will move in behind the front as high pressure
builds over the region for Monday and Tuesday. Winds will remain a
bit gusty through much of Monday before subsiding as the pressure
gradient eases. No other weather concerns are expected. High
temperatures will generally be in the upper 50s to around 60. Low
temperatures Monday night will range from around freezing/32F inland
to upper 30s/around 40 closer to the coast.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A mid level low and associated surface reflection will lift out of
the Southern Plains Tuesday night and track towards the East Coast
on Wednesday, bringing the next chance of rain to the area. Dynamics
and wind fields could support stronger storms, but the instability
will again be the question. In addition, it will get quite breezy. A
Lake Wind Advisory will be possible. Dry and quiet weather is then
expected Thursday through the end of the week as high pressure
returns. Temperatures will be warmest on Wednesday, then fall to
around or below normal behind the cold front.
&&
.AVIATION /02Z SUNDAY THROUGH THURSDAY/...
KCHS/KJZI/KSAV: Conditions will deteriorate overnight as rain
spreads in from the west and southwest. A steady rain will
dominate all terminals by late evening which will linger into
Sunday morning before a break occurs. Widespread IFR conditions
are likely overnight with cigs dropping to LIFR closer to
daybreak. The risk for LLWS will increase for all terminals by
late morning into the afternoon as wind fields increase ahead of
an approaching cold front.
Extended Aviation Outlook: Flight restrictions are likely into
Sunday night as low pressure tracks across the region bringing
showers and even a possible rumble of thunder. Sunday into early
Monday morning low level winds continue to tighten with LLWS
possible. VFR will then prevail on Monday and most of Tuesday.
Another round of flight restrictions will be possible on Wednesday.
&&
.MARINE...
Tonight: A northeast surge will persist across most local waters
early, topping out in the 15-20 kt range. A few gusts up to 25 knots
will be possible heading into early evening while the pressure
gradient is slightly enhanced. However, expect the pressure gradient
to decrease through the overnight period as low pressure passes
across the area late. Wind speeds should decrease to 10-15 kt at
this time while winds flip to east, then southeast heading into
daybreak. Seas will average between 2-4 ft, largest across offshore
Georgia waters and northern South Carolina waters off the Charleston
County coast.
Sunday through Thursday: Low pressure will pass across the region
Sunday into Sunday night. Southerly winds will increase ahead of
this system and Small Craft Advisories have been hoisted for the
Charleston county and outer Georgia waters. It is possible they will
need to be expanded to include the remaining waters as well. Winds
will turn westerly and remain elevated following passage of a cold
front overnight. Small Craft Advisory conditions will likely persist
through most of the day Monday before subsiding as the pressure
gradient eases. There is an outside chance for gale force wind gusts
Sunday night into Monday morning, mainly across the Charleston
county waters and outer Georgia waters as well, however confidence
in duration/frequency is not high enough to hoist any Watches at
this time. No additional marine concerns expected until Wednesday
when the next system impacts the area. Another round of Small Craft
Advisories are likely for most, if not all, waters.
&&
.TIDES/COASTAL FLOODING...
Sunday morning high tide (~8:15 am): The astronomical high tide is
6.31 ft MLLW at Charleston, meaning we would need to see a departure
of around 0.7 ft to reach 7.0 ft MLLW and produce minor coastal
flooding. Northeast winds will prevail through tonight, which should
be quite favorable and drive the tidal departure sufficiently high.
Also of note, an area of low pressure is expected approach and reach
the coastline of the forecast area by around the time of high tide.
Guidance is a bit varied on how high the tide will get, but there
remains a potential levels will reach moderate flood stage (7.5
ft MLLW) in the Charleston Harbor. For Fort Pulaski, the
astronomical tide is 8.23 ft MLLW and probabilitistic guidance
indicates there is a really solid chance the observed tide will
peak at or above minor flood stage (9.5 ft MLLW). A Coastal
Flood Advisory will likely be needed for Charleston and Colleton
Counties and possibly for the far southern South Carolina and
Georgia coasts. Decent rainfall rates are expected around the
time of high tide which would exacerbate any ongoing saltwater
flooding issues.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory from noon Sunday to 7 PM EST Monday for
AMZ350-374.
&&
$$
Area Forecast Discussion
National Weather Service Duluth MN
949 PM CST Sat Jan 21 2023
.DISCUSSION...(This evening through Friday)
Issued at 432 PM CST Sat Jan 21 2023
Summary...Cloud cover clearing this evening may lead to a cold
night for parts of the area, but otherwise lingering clouds to
keep us murky and moderated overnight. Our next chance of snow is
Monday as a clipper moves through the area. Additional clippers
may bring more snow chances during the work week. We may get some
colder weather next weekend as colder air moves into the region.
A steep inversion is making the cloud forecast tricky this
afternoon, with the Day Snow-Fog RGB satellite imagery showing the
western edge of the IFR stratus over most of the area this
afternoon quite clearly. The RAP appears to be getting a handle on
this stratus deck, which is trapped beneath a strong inversion at
the surface, extending to around 925mb according to the MPX and
INL soundings from this morning. The RAP continues the slow
eastward progression of the west edge of the 925mb
moisture/clearing line up until mid evening before stalling and
re-developing overnight. Wherever it clears out this evening, the
temperature is likely to drop into the single digits, with teens
where the cloud cover remains. Have played a more pessimistic
cloud forecast for now, but anticipate needing to update this
evening as the boundary layer settles back down after sunset. Fog
may re-develop, but anticipate it becoming stratus rather than
poor visibilities. On Sunday a ridge axis slides into the area,
and assuming this stratus layer does not expand extensively
overnight, we should clear out for at least parts of the area
during the morning, with some welcome sunshine for the area.
A clipper moves through the area beginning late Sunday night,
bringing light snow to the area for Monday before pulling out
Monday evening. The forcing is best for a short period of time
during the morning, followed by cold air advection showers behind
it. The f-gen band does not look very impressive, so am not
expecting a lot of snow out of this, so while I have raised pops
for this shortwave, have kept the QPF on the low side, producing
less than an inch of snow through the period.
Tuesday through Thursday we will be in northwest flow with a
series of weak clippers moving through the upper level flow. Model
agreement on these clippers is very poor, and so the model blends
have given us an effectively dry forecast through the middle part
of the week. However, experience shows that with each of those
clippers we are likely to get at least some flurries, if not a
quick dusting. For now have added in some small chance pops to
some of those periods, but we are going to have to wait and see
how these develop before making a more definitive call. These are
going to be dependent upon the behavior of a stronger system that
will affect the southern CONUS in this time frame as well. We will
also be very similar in temperatures to what we have this
weekend, with highs generally in the 20s and lows in the single
digits and teens, depending on cloud cover.
A stronger trough axis is showing up that the deterministic
models seem to be latching onto in a more consistent way but the
ensembles are showing mainly broad troughing in this time range,
so it is probably too soon to latch onto this, and have left the
blended, slight chance pops here as is. There is a consistent
signal for a shot of colder air behind this system, and we may
have some sub-zero overnight lows next weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 541 PM CST Sat Jan 21 2023
Clearing is occurring over north-central Minnesota and is likely
to bring VFR conditions to INL/BRD at least through mid this
evening. Thinking remains for fog to develop again under a
lowering inversion that continues to trap near-surface moisture
each night and result in IFR stratus cigs and patchy fog lowering
vis at area terminals. Stratus scours out and lifts to MVFR and
fog dissipates towards 18z.
&&
.MARINE...
Issued at 946 PM CST Sat Jan 21 2023
Southwest wind gusts remain generally between 10 to 20 knots
tonight and Sunday before increasing again Sunday night into
Monday as a shortwave brings snow chances into the area. Winds
turn to the northwest Monday night before diminishing again.
Small Craft Advisories may be needed for much of the Nearshore
waters Sunday night through Monday night.
&&
.PRELIMINARY POINT TEMPS/POPS...
DLH 12 24 11 29 / 0 0 10 20
INL 3 21 12 29 / 0 0 40 30
BRD 7 21 10 32 / 0 0 0 20
HYR 13 24 8 29 / 0 0 0 30
ASX 15 26 12 29 / 0 0 0 30
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
LS...None.
&&
$$
DISCUSSION...LE
AVIATION...NLY
MARINE...NLY
Area Forecast Discussion
National Weather Service Quad Cities IA IL
808 PM CST Sat Jan 21 2023
.UPDATE...
Issued at 805 PM CST Sat Jan 21 2023
Snow is on track, moving northeast with primarily visibility and
impacts shown on Iowa DOT of light snow, although some images
suggest it`s quite dendritic in nature at times, likely in the
higher reflectivity areas. For now, it`s covering our south 1/2
and about to begin snowing in the Quad Cities as of 8 PM. Thus
far, the visibility reductions to the north of I-80 in our western
areas seem more to do with fog than snow. No major changes to the
forecast at this time.
ERVIN
&&
.SYNOPSIS...
Issued at 210 PM CST Sat Jan 21 2023
An interesting day was seen, with persistent low clouds and fog
through much of the morning and into the early afternoon. Along with
the stratus/fog, we observed very fine ice crystals falling all
morning. This has lead to a dusting of snow on the ground, which
coupled with the freezing fog/mist from the morning, led to a few
slick spots. We are still seeing light radar returns from these
falling crystals, but this is fading away. While all of this is
happening, locations along and south of Highway 34 in our forecast
area have been mostly clear through the day thus far. Given much of
the area has been socked in clouds, temperatures didn`t warm as much
as initially expected. Much of the area remains in the mid to upper
20s, with our south in the low to mid 30s. Winds remain light and
variable as well, which helped keep us blanketed in the fog through
much of the morning.
&&
.SHORT TERM...(This evening through Sunday)
Issued at 210 PM CST Sat Jan 21 2023
This evening and through the night, a weak low pressure system will
pass through the area, bringing some light snow. Snow is forecast to
move in between 6PM to Midnight, and last through tomorrow morning
for most. Short-term guidance is in general agreement for a
widespread 1-2" event, with less than an inch currently expected in
our northwest. We are slowly trending lighter on precipitation
totals. Thus, we may see this decrease a little more. Some may not
even see snow in the northwest, but given a deep layer of
saturation, some light accumulations cannot be ruled out. Thus, we
have increased PoPs slightly. Guidance indicates the best lift
moving through the area tonight, which would bring the heaviest
snowfall rates. This generally looks to be around the midnight hour.
As we approach sunrise, forcing weakens and we will be left with
light snow. Heaviest axis of snow falls along a line from Fairfield
IA through the Quad Cities. Although, NBM 90th percentiles doesnt
show 3" anywhere in the area, we will stick with that as the high-
end snow amount, as some localized areas may see close to that. Best
chances to see up to 3" is in our western counties between the
Highway 34 and Interstate 80 Corridors.
Fortunately, we won`t be dealing with gusty winds with this system.
Winds are actually forecast to be light and variable, which will
make measuring the snow easier and also cut back on any blowing snow
potential. Temperatures aren`t expected to drop much tonight, as a
dense cloud canopy will help hold the "heat" in. With similar
conditions in place tonight, we have the potential to see some
patchy dense fog again tonight. Tomorrow, we will continue to see
some lingering light snow and flurries as the system exits. Much of
guidance holds the precipitation in the area until around noon, then
slowly moving it out. At this point tomorrow, the snow will be
fairly light and not much accumulation will be expected. Bulk of
snow accumulation will be tonight into the early AM tomorrow.
Temperatures tomorrow will range from the upper 20s in our northwest
to the mid 30s in the southeast.
.LONG TERM...(Sunday night through Saturday)
Issued at 210 PM CST Sat Jan 21 2023
Key Messages:
- Midweek system brings a chance for snow for portions of the area.
- Fairly seasonable temps.
Details:
Sunday night and Monday
Uncertainty with extent of any clearing of stratus during this
period. HRRR experimental ceiling plots along with RAP13 and NAMNest
are all quite bullish with low cloudiness for much of this period.
HREF ensemble mean low cloud cover does support partial clearing
possible with 40-60 percent cloud cover by 12z Monday while NBM
probs are 20-40 percent. However, given the time of year, likelihood
of light snow cover on the ground, and models showing weak surface
ridging building in by Monday it seems like a good setup for the
moisture to get trapped beneath the increasing subsidence inversion.
As a result, I`ve started trending upward on sky cover and nudging
up Mins Sunday night while leaving Max T alone for Monday for now.
Tuesday through Thursday
Medium range models continue to support a storm system ejecting from
the Southwest, reaching the Tennessee and Ohio Valleys midweek then
lifting into the Mid-Atlantic. Still some differences noted in the
track, but enough cold air exists on the north side of the storm
track for snow. The track will be critical in determining how much
of our area sees snow late Tuesday night through Wednesday, and
potential amounts. At this juncture the preponderance of the
deterministic and ensemble guidance would favor the main deformation
band and heaviest amounts south of our area, but again model changes
should be anticipated as the main energy is still offshore in the
Pacific Northwest this afternoon and will get better sampled over
the next 24 hrs. The ECMWF deterministic and 30-50 percent of ensemble
membership have trended deeper and further southwest with a northern
stream wave digging behind the departing mid-week system. As a
result, it maintains some light snow through Thursday where currently
the forecast is dry. Being still many days out and also a rather
recent slower/southwest shift from the EC on the wave, I`ve opted to
stay with the drier NBM for now but will need to keep tabs on these
trends for potentially needing to add PoPs for Thursday.
Friday and Saturday
Forecast is for dry and seasonably cooler conditions. However,
may have to watch for some precipitation chances, as the flow
pattern aloft seems to favor semi-zonal per mean of ensembles and
deterministic models, which could shuttle several disturbances
eastward ahead of a potentially western CONUS trough. Temps likely
to remain seasonable.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 514 PM CST Sat Jan 21 2023
Light winds, light snow, and fog will provide poor flying weather
through mid morning Sunday. The snow should quickly spread over
the entire area this evening, between 00z and 04z. Amounts will
not be too much, only an inch or two, but the fog and snow will
likely bring low visibility for an extended time overnight,
through mid morning, when winds will switch the to the northwest,
but only at 5 kts or so. I`ll keep TAFs pessimistic on any
improvement in cigs, but will allow visibility to move into the
2-4sm range Sunday morning.
ERVIN
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&
$$
UPDATE...Ervin
SYNOPSIS...Gunkel
SHORT TERM...Gunkel
LONG TERM...McClure
AVIATION...Ervin
Area Forecast Discussion
National Weather Service Indianapolis IN
929 PM EST Sat Jan 21 2023
.Forecast Update...
Issued at 929 PM EST Sat Jan 21 2023
GOES-16 Night Fog product and obs were indicating the clearing has
moved all the way north to near the Interstate 70 corridor, so had
to adjust cloud cover down further north as well as temperatures. In
fact, after coordinating with adjacent offices, lowered overnight
lows in this area as temperatures were at or near previous
forecasted lows. The clear skies over south central Indiana will be
very short-lived, however as clouds ahead of the Plains system will
quickly swoop in from the west.
295K Isentropic analysis continues to advertise impressive upglide
overspreading central Indiana from west to east overnight,
ahead of the Plains system. Condensation pressure deficits less than
30 millibars correlate nicely with a saturated column and they will
spread west to east across central Indiana overnight. With this in
mind, will likely see snow develop over the Wabash Valley
and spread quickly eastward 06z-12z. Look for a dusting or more by
daybreak with the bulk of the snow accumulation after 12z Sunday.
&&
.Short Term...(This evening through Sunday)
Issued at 300 PM EST Sat Jan 21 2023
- Snow arriving late tonight
- Snow ends Sunday morning; Clouds remain through Sunday afternoon
Surface analysis late this morning shows a broad area of high
pressure stretching from West Virginia and Ohio, across Indiana to
southern Illinois. A weak ridge axis over Central Illinois
stretching toward Iowa and the upper Mississippi Valley was noted as
Satellite shows clearing to the west of this axis. Clouds across
Kentucky have finally been showing some south to north erosion, with
a clearing line approaching the Ohio River. Aloft a ridge axis had
moved east of Indiana and was found over Ontario and Ohio. An upper
low was seen within water vapor imagery over SW KS and the OK
panhandle, along with a broad associated trough stretching from the
northern plains to New Mexico. Radar mosaics show snow and rain
ahead of the low over KS and eastern OK.
Tonight through Mid Day Sunday...
...Light Snow Expected Late Tonight...
...Snow covered surfaces possible late tonight and early Sunday...
Early this evening, some brief clearing will be possible over
southern parts of Central Indiana as the cloud erosion to the south
continues to make progress north. This may be the initial story this
evening, but changes will arrive overnight.
The upper trough and low are suggested to push toward Indiana and
the Ohio Valley overnight. Ample forcing aloft will allow for
precipitation ahead of the wave. 295K Isentropic surfaces show flow
nearly directly rising in on the surface...allowing for strong lift.
Specific humidity of near 4 g/kg are suggested to arrive by 09Z
before departing to the east by 15Z. As the isentropic lift departs
by late Sunday morning, The upper trough will still be over Indiana
with a poorly organized surface low over Central Kentucky. This may
result in some additional snow lingering across the area early in
the afternoon wrapping around the system. However there remains some
uncertainty as to how impactful that will be as some dry air is
shown wrapping into the system within the middle levels. Thus
overall best forcing and lift should arrive in the area after 10Z
and persist through 15Z and this will be the best window for
snowfall. HRRR appears on board with this timing. Forecast soundings
show good saturation within the mid and lower levels as these
features pass with pwats near 0.3-0.4. Inches. Although the
soundings remain below freezing, indicating snow, saturation is
mainly within the 0 to -10 degree zone rather than the dendritic
growth zone.
Overall, confidence is high for snow late tonight and ending on
Sunday morning due to good forcing features with light amounts due
to limited moisture, quick moving isentropic lift and limited
saturation within the DGZ. Ongoing amounts of 1-2 inches of
accumulation with isolated higher amounts appear reasonable. The
most favorable area for snow will be along and south of a HUF-MIE
line due to best moisture proximity. Will use highest pops here with
lesser pops to the NW. Given evaporational cooling, lows in the mid
to upper 20s will be reasonable.
Sunday afternoon...
Previously mentioned isentropic lift is lost by mid to late
afternoon as the system departs east. Isentropic surfaces show
subsidence as winds across Indiana become northwesterly in the wake
of the front. Forecast soundings at that time once again shows
trapped lower level moisture beneath a weak inversion amid cyclonic
lower level flow. Thus will trend mainly cloudy skies. Cold air
advection will be ongoing, thus little in the way of rising
temperatures will be expected and will trend highs to only the lower
30s.
&&
.Long Term...(Sunday night through Saturday)
Issued at 302 PM EST Sat Jan 21 2023
Sunday Night through Tuesday..
Any accumulating light snow from the late weekend`s rather weak
system should have tapered off by 00z Sunday evening...although
lingering flurries cannot be ruled out as the supporting trough axis
slides east across the region through the evening. Minor impacts
are possible from wet surfaces re-freezing as air temperatures
slowly drop below 32F and into the upper 20s by dawn Monday.
More of the above-normal-temperature pattern we have grown
accustomed to so far this January will resume during the early
workweek, albeit more seasonable than past weeks. A broadening
southern stream upper ridge will prevail over much of the eastern
two-thirds of the CONUS, promoting subsidence and dry conditions.
West-southwesterly breezes around surface high pressure near the
Smoky Mountains...will keep overnights mixed with lows 25-30F, and
afternoon highs slowly moderating from the upper 30s to low 40s for
most locations. At least a couple periods of partly to mostly clear
skies are expected through PM hours Monday and AM hours Tuesday...
with high clouds likely increasing from southwest to northeast by
late Tuesday.
Tuesday Night through Wednesday night...
Confidence is continuing to increase in a significant mid-latitude
winter storm system developing through the mid-week as a southern-
stream wave continues its eastward progression across Texas and
eventually into Indiana...meanwhile deepening surface low pressure
as it tracks up the lower Mississippi Valley and eventually up the
Ohio Valley while occluding around the Wednesday timeframe. The
supporting trough`s slight positive tilt will encourage an overall
split precipitation shield, with the northwestern/cold-conveyor type
section poised to cross central Indiana.
Precipitation types across the CWA would likely be free of sleet or
freezing rain with forecast soundings not suggesting any organized
elevated warm layer on this northwestern side of the progressing
system. Ensembles are suggesting rain to be more likely towards the
Ohio River for the main slug of precipitation near the daytime hours
Wednesday, yet so far it appears snow would be favored across at
least the northwestern half of the region. A rain/snow mix is
possible across the region...as well as initial rain changing to
snow as low-levels become colder through the event...yet further
forecast updates will refine these details.
A potentially limiting factor for any accumulating snowfall would be
lack of established sub-freezing air at the surface, although
temperatures would likely be close enough to 32F that any moderate
or better snowfall rates would result in accumulation. Forecast
Skew-Ts do suggest a saturated profile is possible for much/all of
the DGZ when the heaviest portions of the precip shield cross the
region. All snow should taper off around the Wednesday night
timeframe as the system continues towards the Northeastern US.
Thursday through Saturday...
The second half of the long term will feature a pattern change back
towards seasonable mid-winter cold as a broad upper trough envelops
the eastern two-thirds of the country behind the storm system`s slow
departure through the Northeast and into southeastern Canada. Broad
cyclonic flow will prevail near, if not centered over Indiana,
promoting scattered flurries. Light coatings from better organized
snow showers are certainly possible under any passing, embedded vort
maxs...which so far appears most likely around the Friday timeframe.
Considerable cloudiness should facilitate diurnal spreads around 10-
15 degrees, with highs in the 30s and lows around 20-25F...making
for perhaps the first tandem of days with seasonable temperatures
since the third week of December. The predominate broad upper
trough will be more of a southern-stream feature, with sub-normal
cold temperatures likely held well to the northwest of the region...
through at least Saturday. The normal max/min for Indianapolis
through the long term are the lowest values of the year, 36/20.
&&
.Aviation...(00Z TAF Issuance)
Issued at 641 PM EST Sat Jan 21 2023
Impacts:
- MVFR flying conditions expected to deteriorate to IFR
and worse in snow after 10z
Discussion:
Overrunning ahead of a Plains trough will bring snow showers and
deteriorating flying conditions to the terminals toward daybreak and
through Sunday morning.
Winds will be less than 10 knots and switch from SE to E toward
morning and then NW Sunday afternoon.
&&
.IND WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Update...MK
Short Term...Puma
Long Term...AGM
Aviation...MK
Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
924 PM CST Sat Jan 21 2023
...UPDATE...
.SYNOPSIS...
Issued at 245 PM CST Sat Jan 21 2023
Key Messages:
-Lingering light snow across southwest into central Nebraska will
exit the area by late this afternoon.
-Temperatures remain near to below normal into next week, with light
snow chances midweek and into the weekend.
&&
.UPDATE...
Issued at 923 PM CST Sat Jan 21 2023
A forecast update is in place for patchy fog across parts of the
panhandle and extends the fog in time across ncntl Nebraska until
18z Sunday. The RAP model shows dry air moving in aloft and this
should trigger fog as suggested by the HREF. The update uses the
short term model blend.
&&
.SHORT TERM...(This evening through Sunday night)
Issued at 245 PM CST Sat Jan 21 2023
Currently, light snow continues across portions of southwest into
central Nebraska, likely driven by an approaching subtle northern
stream H7 trough interacting with a southern stream H7 low
centered over south central Kansas. This light snow will end
quickly over the next couple of hours from north to south, as the
northern stream trough axis continues to push across the area.
Little to no accumulation is anticipated.
For tonight and tomorrow, expect partially clearing skies overnight,
as subsidence increases aloft in the wake of a departing upper level
low. For areas that do see clearing tonight, expect efficient
radiational cooling again amid the persistent deep snowpack and
light winds. Lows tonight fall to around 10 degrees where clearing
occurs, and warmer where clouds persist. This efficient cooling will
also lead to the potential for some patchy fog, especially across
north central Nebraska. Confidence wanes with southwestward extent,
though temperatures rising to near/just above freezing in some
locales may enhance the potential for patchy fog above any snowmelt.
This will need to be monitored, and further expansion in fog mention
may be needed. Surface ridging spills into the Upper Midwest into
tomorrow afternoon, with highs locally remaining near steady in the
upper 20s to low 30s. Aloft, an upper low begins to drop southward
across the Intermountain West. At the same time, a northern stream
trough begins to dive southeast out of Canada. This will drag a cold
front into the area tomorrow night along with increasing cloud cover
from west to east. Some weak CAA behind this frontal boundary will
help to offset the increasing cloudiness somewhat, and lows fall
into the upper single digits to low teens.
.LONG TERM...(Monday through Saturday)
Issued at 245 PM CST Sat Jan 21 2023
Ensemble and deterministic guidance continues to trend towards a
common solution with respect to precipitation potential on Monday. A
noted southwestward shift in the southern stream upper low has been
observed in much of the guidance suite over the last few model
cycles. As a consequence, precipitation chances have also shifted
westward, largely into portions of the western Panhandle and eastern
WY/CO. A consensus is growing for the entirety of western Nebraska
to stay dry as the best forcing remains well to our west. With this
in mind, will keep a flurry mention in place west of HWY 61, though
even this could potential be on the more aggressive side.
Regardless, little to no accumulation is expected with the passage
of this system Monday.
The upper level regime remains active into the middle of next week,
as northwest flow aloft establishes across much of the western
CONUS. This will lead to the passage of at least a few different
shortwaves in the mean flow aloft, with lingering light snow
chances midweek into the weekend. Of note, guidance drags a cold
front through the area Tuesday evening, as a surface low dives
across the Dakotas. On Wednesday, some guidance is beginning to
suggest steeping low and mid-level lapse rates in the postfrontal
environment. This looks to lead to a threat for some snow showers
(possibly convectively enhanced?) Wednesday afternoon amid diurnal
heating. This will need to be monitored going forward, with the
potential for impacts should confidence in any convective snow
showers were to grow.
Additional light snow chances continue into the weekend as
guidance continues to paint shortwaves diving into the central
CONUS. Confidence remains low with respect to any one system
beyond midweek, and trends will continue to be monitored.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 545 PM CST Sat Jan 21 2023
Watching some weakening snow showers pushing southeast out of the
Sandhills to approach the LBF terminal. Expect the weakening trend
with this activity to continue, however, have added a tempo
mention of light snow to account for potential of MVFR visibility
restriction due to -SN. Attention then turns to fog potential
mainly for north central Nebraska. VTN will likely fall on the
west edge of the expected fog coverage so will keep prevailing
MVFR with tempo mention of LIFR visibility. Confidence in this is
low so will plan to monitor and amend as needed. After sunrise
Sunday, expect a return to VFR conditions under mostly sunny
skies.
&&
.LBF WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...CDC
SYNOPSIS...Brown
SHORT TERM...Brown
LONG TERM...Brown
AVIATION...NMJ
Area Forecast Discussion
National Weather Service Louisville KY
957 PM EST Sat Jan 21 2023
.Forecast Update...
Issued at 955 PM EST Sat Jan 21 2023
At this hour, nighttime microphysics satellite imagery reveals high
clouds streaming across the region in advance of a disturbance
moving in from the central and southern Plains. With cloud bases
remaining high, temperatures have been able to cool into the low-to-
mid 30s across the region, with a few upper 20s being observed in
the typical cool spots. As we head through the overnight hours,
temperatures should remain fairly steady along and north of the
Bluegrass/Western KY Parkways, with slight warming expected to take
place across southern KY.
Precipitation will overspread the region from southwest to northeast
between 3 and 7 a.m. EST tomorrow morning. Was hoping for some high-
resolution model convergence with respect to precipitation types
tomorrow; alas, the HRRR remains obstinate with its stronger/cooler
solution, while the hi-res NAM continues with a weaker/warmer
system. In general, have continued with a solution somewhere in
between these two, with the best chances for accumulating snow north
of the Ohio River, and a messy mix of mainly rain with some snow
expected along the river. Most of central KY is still expected to
see all rain. Have slightly tweaked snowfall amounts tomorrow
morning in this update, adding a few tenths across our northernmost
row of southern IN counties where a few hours of efficient snowfall
rates are possible between 12-15Z tomorrow. Still think amounts on
average will range from a dusting to an inch.
Updated products have been sent out, with no major changes in the
near term.
&&
.Short Term...(Tonight through Sunday evening)
Issued at 330 PM EST Sat Jan 21 2023
Upper ridging and surface high pressure, currently moving off to the
east, are going to keep skies mostly clear through the evening
hours, but this nice weather won`t last long.
Early tonight, cirrus ahead of an approaching low pressure system
will begin moving from west to east across the region. Shortly after
midnight, rain showers will begin moving from central Tennessee into
south central Kentucky. Then over the next few hours, showers will
build in from the west, covering southern Indiana and central
Kentucky by around 12z. Temperatures will remain at or above
freezing at many location across the CWA, but a few locations in
southern Indiana and the northern Bluegrass region of Kentucky will
likely slip below freezing for a short period of time. This could
cause a few area residents to see the slightest amount of ice on a
metal handrail or vehicle during the rainfall. Most however will not
see this, and with ground temperatures above freezing, issues aren`t
expected.
Tomorrow during the early dawn hours into the first few hours of the
day, some of our communities, many across southern Indiana, will
likely see snow mixed in with the rain showers, but again with the
warm ground temperatures, impacts are expected to be minimal. Model
soundings across most models are keeping the DGZ fairly dry and the
low levels near freezing. This is expected to keep snow ratios low
(3-7 to 1 range). By 15-16z, believe rain will be the dominant
precip type across the CWA. Current thinking has around a dusting to
around half of an inch over our southern Indiana counties. Higher
amounts are expected to the northwest in Indianapolis` CWA. Rain
will begin to end along the western edge of the CWA during the early
afternoon hours. Rain showers will continue tapering off into
eastern Kentucky during the evening hours. High temperatures will
range from the upper 30s near Madison, Indiana to the upper 40s in
Clinton County, Kentucky in southern Kentucky.
With temperatures in sounding profiles so close to freezing, A few
degree shift cooler and increased forcing from the upper jet could
make higher snowfall amounts possible, so the forecast will be
monitored and updated if needed.
&&
.Long Term...(After midnight Sunday night through Saturday)
Issued at 300 PM EST Sat Jan 21 2023
...A Couple of Chances for Light Snow Accumulations...
Sunday Night - Monday...
A storm system will continue pushing off to the NE Sunday night into
Monday morning, however low level moisture confined mainly to the
1000-850mb layer will continue to linger. A couple of complicating
factors with the depth of the moisture and the low level thermal
profile leads to low confidence in exact p-type during this stretch.
In fact, will likely see varying p-types between snow showers when
moisture is deeper and up to the bottom of the DGZ, and periods of
drizzle or small ice pellets when moisture is shallower. There is
even a chance for some very light freezing drizzle/rain in our
eastern CWA if surface temps stay below freezing and saturation
doesn`t extend deep enough into the cold. Overall, confidence is low
in the exact low level thermal and moisture profile, so like the
idea of advertising a few p-types during this time like previous
shift. Any accums of whatever p-type would be light, but something
to watch for minor impacts Monday morning anywhere surface temps
stay at or below freezing. This would be most likely across NE
portions of the CWA.
The rest of Monday should be drying out with perhaps an improvement
in the lingering stratus deck. Will keep an optimistic forecast for
seeing some afternoon sun going, with the caveat that stratus decks
love to linger this time of year. If we do get rid of the cloud
deck, temps should be able to climb to the lower 40s for most.
Eastern spots will likely stay in the upper 30s.
Monday Night - Tuesday...
Surface high pressure, and progressive low amplitude ridging will
briefly control our weather Monday night/Tuesday. This will be a dry
stretch with cold overnight lows in the 20s, and Tuesday afternoon
highs warming notably into the 45 to 50 degree range.
Tuesday Night - Thursday...
Deep moisture from an approaching upstream system quickly
overspreads our region by Tuesday night. Although temperatures will
likely be running around 40 degrees at this time, wet bulb
temperatures look to be in the low to mid 30s once the near surface
dry layer is overcome. There is some question to just how favorable
the low level temperature profile will be, along with surface wet-
bulb temps at or just above freezing. Reasonable scenario for a snow
event across our northern CWA would be a fairly short-lived and wet
snow Tuesday night, before changing to mostly rain as the warm layer
aloft wins out thanks to LLJ increase toward dawn Wednesday. Like
what we have going now with some light accums across our north, but
under what some of the 10:1 ensemble plumes (Grand ensemble)
deterministic model snow outputs are showing.
All of that said, the ultimate track of the intensifying surface low
could place a heavier snow band across our northern CWA where
heavier rates would promote better chances for accumulation and a
prolonged favorable thermal profile. There will very likely be a
tight snowfall gradient somewhere either across our northern CWA or
displaced farther to the north out of our area of concern. Will
continue to monitor trends, but something to watch for the southern
Indiana counties that are not out of the woods for a more
significant snowfall. Think it is more probable at this point that
the heavier snow band ends up more over central IN, but overall
spread in ensembles continues to yield lower confidence for a day 4-
5 event.
As we get into Wednesday, the surface low looks to track across the
CWA, with a strong low level jet overspreading the area. If there is
a rain/snow line over our area, all indications are that the warm
layer associated with the LLJ will win out and keep p-type all rain
across the area by that point. Will continue categorical pops with
temps climbing into the 40s for most. SE CWA could get into the low
to mid 50s thanks to a tight temperature gradient.
The surface low will pass to our NE by Wednesday night, with
temperatures quickly falling again behind the front, and low level
lapse rates steepening. At some point, the thermal profile will
likely become favorable for a lingering wintry mix Wednesday night
into Thursday morning.
Thursday Night - Saturday...
We may try to briefly dry out Thursday night through Friday morning,
however a quick-hitting clipper system could dive into the region
for later Friday. Could be a rain to snow type of event, but model
solutions diverge and overall confidence is low at this time.
&&
.Aviation...(00Z TAF Issuance)
Issued at 645 PM EST Sat Jan 21 2023
Discussion:
A storm system is expected to cross the Ohio Valley late tonight and
into the day on Sunday. Precipitation types will be varied across
regional terminals, with rain expected at LEX/BWG, snow expected at
HNB, and a rain/snow mix possible at SDF, though latest guidance has
trended toward more rain at SDF. Ceilings will begin to drop from
southwest to northeast after 06Z tonight, with all sites expected to
drop to IFR/LIFR levels by Sunday morning. Once ceilings drop, only
modest recovery (IFR, maybe low-end MVFR ceilings) is expected after
18Z Sunday.
Precipitation will bring reductions in visibility, with the greatest
reductions expected at HNB where p-type will mainly be snow.
Although visibilities could drop to MVFR/IFR levels, think that CIGs
will be the primary driver of flight categories over the coming
forecast period. Precipitation is expected to taper between 18-21Z
Sunday, though lingering scattered rain/snow showers are possible
into Sunday night and Monday morning.
Confidence: Medium in ceilings; Medium in precip type at HNB, LEX,
BWG; Low-Medium in precip type at SDF; Low-Medium in visibilities.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...None.
KY...None.
&&
$$
Update...CSG
Short Term...KDW
Long Term...BJS
Aviation...CSG
Area Forecast Discussion
National Weather Service Raleigh NC
921 PM EST Sat Jan 21 2023
.SYNOPSIS...
High pressure will drift across and offshore the Mid-Atlantic
tonight, ahead of a frontal system that will cross the region Sunday
and Sunday night. High pressure will follow for Monday and Tuesday.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 900 PM Saturday...
Current analysis shows the forecast is on track, with only minor
tweaks needed for the evening update. Rain is still expected to
develop across the southern Piedmont in the next few hours, and
spread northeast overnight across the region as isentropic ascent
increases across the area. Only light rain is expected tonight, with
heavier rain possible tomorrow as a plume of Gulf moisture moves
across the Carolinas. Please see the previous discussion below for
additional details.
Previous discussion from 225 PM Saturday: A positively tilted, multi-
lobed trough axis, evident in WV imagery and 500mb RAP analysis, is
positioned from Manitoba through the southwest CONUS with a long
fetch of enhanced southwesterly from NW Mexico into the Mid-
Atlantic. At the surface, broad high pressure has filtered into the
OH Valley this afternoon promoting dry and seasonable northerly
surface flow through central NC. High clouds will persist over a
majority of the area today within the mid/upper jet directing upper
level moisture from upstream showers/storms over southern MS/AL,
although thinning with northern extent.
Conditions will rapidly deteriorate as the upper trough shifts into
the Mid-MS Valley and upper divergences aloft promotes large scale
ascent over the Mid-Atlantic and Southeast CONUS. Light to moderate
rain will start to move into the southern Piedmont and Sandhills
around 06z then spreading into the Triad and Triangle around 10z at
the nose of the deeper moisture transport where enhanced moist
isentropic ascent and a mid-level FGEN band spreads northeast.
Although it will be a raw and cold at the onset of precipitation, a
prevalent warm nose will be sufficiently strong to melt any frozen
hydrometeors and surface temperatures in the mid 30s to low 40s will
keep any frozen ptype concerns confined to the higher elevations of
NC/VA.
&&
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
As of 220 PM Saturday...
An approaching storm system will lead to cold air damming and a raw,
rainy, and chilly day on Sunday. The surface high pressure will
continue to press offshore, but will have deposited a stable and
chilly air mass over central NC. Rain will overspread the region
with the timing relatively the same as the previous forecast
cycle... between 12z and 15z Sunday. Temperatures are forecast to be
above freezing when the rain develops, but the rain will lead to
temperatures in the 30s and 40s all day Sunday.
Surface low pressure is forecast to push from the Gulf Coast NE
toward the eastern TN Valley region and weaken by 12z, with
redevelopment near the coast of SC. This will become the primary low
pressure as it tracks along the coast of SC/NC during Sunday
afternoon. It is a Miller B type scenario; however, as the primary
low fills leading to warming temps aloft ensuring an all rain event
for our region. The main mid/upper level low will push from the
Midwest through the Great Lakes Sunday and Sunday night. All this
leads to rain, possibly in a couple of waves according to most model
forecasts (one early in the day, the other later in the day).
QFP should be generous, especially in the areas in the Drought in
the south and east portions of central NC. Look for storm totals of
1.50-1.75" Slightly lower totals of 0.75-1.25" are likely further
NW. Rain will continue into the evening, finally tapering to areas
of light rain and drizzle between 06z and 12z/Mon. After highs in
the upper 30s NW ranging into the mid 50s SE, temperatures will cool
back into the mid 30s NW ranging into the lower 40s SE by Monday
morning as the steadier rain ends.
The thunder threat appears very limited inland, and for now will
continue to keep it out of the forecast.
For Sunday night into Monday, the weak surface flow within the CAD
dome will mean a lingering risk of fog, drizzle, and some light rain
well into Sunday night. A drying forecast is expected Monday as the
cold front shifts offshore and strong CAA and DAA arrive (with a
good downslope component during the afternoon). Expect gusty NW
winds at 15-25 mph with gusts to 30-35 mph Monday afternoon.
Variably cloudy to partly sunny skies will lead to highs in the
upper 40s to upper 50s NW to SE.
High pressure will then move over the region for Monday night. The
clear skies and diminishing winds will allow temperatures to drop
below freezing Monday night, slightly below normal.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 340 PM Saturday...
Wet and mild Wednesday, between otherwise seasonable and dry
conditions.
Tue-Wed night: A vigorous mid/upper-level low over the Southwest at
the start of the forecast period is forecast to deamplify from the
srn Plains and lwr MS Valley newd across the OH Valley through Wed
night. At the surface, high pressure initially over the Carolinas
will drift offshore ahead of a surface cyclone that will organize
and occlude from srn TX to the OH Valley and a secondary/triple
point low that will develop along a retreating warm front in the lee
of the srn Appalachians.
For cntl NC, the sensible weather related to this pattern will
feature near to slightly above average temperatures and dry
conditions Tue-Tue night, then rain developing ewd, while becoming
more showery in character, Wed-Wed night. Widespread low clouds and
light morning rain, into a residually-dry continental airmass
deposited by the aforementioned surface high, will favor in-situ
cold air damming and temperatures in the 40s over the wrn NC
Piedmont and Foothills Wed-Wed night, while warm frontal passage
through the rest of NC will result in warming into the 50s-60s.
Despite strong poleward moisture transport, including lwr 60s F
surface dewpoints into cntl-ern NC, weak lapse rates aloft over the
warm sector will likely yield only pockets of very weak instability.
As such, the threat of thunder and/or severe weather appears low at
this time.
Thu-Sat: On the nrn rim of a broad sub-tropical ridge from the
Bahamas to the Caribbean, and downstream of ridging forecast to
amplify across the ern N. Pacific and Gulf of Alaska, a broad trough
will encompass much of the CONUS east of the Rockies. While
uncertainties exist with amplitude and timing of individual
shortwaves within that pattern, dominant surface high pressure will
extend across the srn US, including the Carolinas, and favor
seasonable and dry conditions through at least Fri.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
As of 646 PM Saturday...
There is high confidence in VFR conditions to start the TAF period.
However, light to moderate rain and associated MVFR/IFR CIGs will
spread from the southwest to northeast early Sunday morning through
Sunday night. CIGs are expected to drop to LIFR at all terminals by
mid afternoon Sunday as additional rounds of light/moderate rain
progress from west to east across central NC. Additionally, strong
winds (30 to 40 kts) just above the sfc will promote potential low-
end LLWS conditions at KRWI early Sunday afternoon. Otherwise, sfc
winds will generally remain enerly before turning nwrly late in the
TAF period. Occasional gusts of 15 to 20 kts may be possible at KFAY
and KRWI early to mid Sunday afternoon.
Looking beyond 00z Monday, rounds of light/moderate rain will
continue over central NC before shifting east and offshore early
Monday morning. VFR conditions return Monday afternoon as high
pressure begins to filter in from the TN Valley. Another storm
system will bring a good chance of sub-VFR conditions late Tuesday
night and Wednesday.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...Swiggett/JJT
SHORT TERM...Badgett
LONG TERM...MWS
AVIATION...Luchetti/Swiggett