Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/11/24
Area Forecast Discussion
National Weather Service Columbia SC
1002 PM EDT Wed Apr 10 2024
.SYNOPSIS...
Rain will spread into the area tonight with isolated
thunderstorms possible. Thursday morning, severe thunderstorms
are possible embedded within widespread rain which may be heavy
at times. Gusty winds will increase from the south this evening
and are likely to continue Thursday and Friday. Drier, warmer
weather fills in behind the front for the upcoming weekend and
early next week.
&&
.NEAR TERM /THROUGH THURSDAY/...
An upper level trough will swing into the Southeast as the
associated surface low moves quickly across the Deep South.
Convection from Wednesday`s MCS will shift eastward tonight
into Thursday morning. The strongest convection may stay to the
south of the forecast area with the system`s rain shield
bringing widespread rain to most of the area. Strong low level
winds and a tightening surface pressure gradient will lead to
windy conditions Thursday morning. Gusts will pick up early
Thursday with gusts to 35 to 40 mph possible, so we have issued
at Wind Advisory starting at 12z Thursday morning.
The heavy rain threat appears lower than previously expected.
Over the last several runs the HRRR has consistently shown lower
QPF amounts for the Midlands while keeping the deeper convection
and higher rain totals south of the forecast area. This sort of
trend along with radar showing thunderstorms along the FL
panhandle is a typical situation that leads to lower rain
amounts for the FA.
Limited surface based instability will hinder convective
updrafts and severe potential through the near term with
sbCAPE values at most around a hundred J/kg. Damaging winds
associated with the convection will be the biggest threat. 50 to
60 kt winds just 1 km up could mix down even in deeper
shower/shallow thunderstorms. Given the weak instability the
tornado threat is limited but a brief tornado can not be ruled
out.
Later Thursday morning, the back end of showers and storms
should work into the forecast area. A prominent dry slot is
shows up on satellite and radar for the system currently moving
across the south, so we do expect a period of dry conditions
early Thursday afternoon. When the upper trough moves through,
it will bring another quick shot of moisture and daytime heating
may generate a few diurnally driven showers before the main
front moves through and alters the airmass.
Highs on Thursday should be in the 70s, with upper 70s possible
across the CSRA given that we clear out by the afternoon hours.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
Upper trough is forecast to be nearly overhead at the beginning
of the short term as is a surface front stemming south from a
low over the Great Lakes area. Winds at 850 mb are expected to
be on the stronger side as the upper trough passes through,
which will likely lead to gusty winds continuing for a few hours
at the beginning of the short term. As the axis of the trough
shifts overhead, a relative lull in the winds can be expected
for a few hours. Then, the trough axis shifts eastward through
the day on Friday. At the surface, the low pressure system
drifts off to the northeast while a surface high begins to build
into the region, keeping the pressure gradient relatively
tight. This along with the winds behind the upper trough axis
will likely lead to another day with gusty winds, but as gusty
as Thursday. That said, NBM is showing a greater than 50% chance
of gusts exceeding 30 mph in the afternoon on Friday.
In addition, there could be some lingering light showers overnight
Thursday as the upper trough moves through the region. Temperatures
on Friday are forecast to be near average.
&&
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Generally quiet weather is expected for the long term as an upper
ridge begins to build overhead and surface high pressure slowly
drifts across the region. As a result, dry conditions are
anticipated through midweek with temperatures warming into the mid
80s to begin the week ahead.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
Generally VFR conditions expected through 04-06z then
deteriorating cigs as prefrontal rain moves into the region from
the southwest. Latest runs of the HRRR are trending toward lower
rain amounts and keeping the heaviest rains and storms south of
the terminals so future updates may reflect improved conditions
but expect MVFR and eventually IFR cigs to develop during the
06z-10z time frame. Some MVFR/IFR cigs in the rainfall possible
but if trends continue will need to adjust to more optimistic
vsbys Thursday morning time frame.
Cold front will move through the region Thursday afternoon.
Ahead of the front winds should be from the southeast around 10
knots through 06z then increase to 10 to 15 knots during the
predawn hours as low pressure to the west deepens. Strongest
wind gusts are expected in the late morning through afternoon
hours with winds shifting to the south and eventually southwest
behind the front with speeds around 15 knots and gusts to 30
knots possible. Cigs should improve behind the front after
16z-18z back to VFR.
EXTENDED AVIATION OUTLOOK...Strong and gusty winds continuing
through Friday. VFR conditions return for the upcoming weekend.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
SC...Wind Advisory from 8 AM to 8 PM EDT Thursday for SCZ016-018-
020>022-025>031-035-037-038-041-115-116-135>137.
GA...Wind Advisory from 8 AM to 8 PM EDT Thursday for GAZ040-
063>065-077.
&&
$$
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1020 PM EDT Wed Apr 10 2024
.SYNOPSIS...
Showers and scattered thunderstorms, some with potentially heavy
rainfall, can be expected ahead of a cold front approaching from the
west tonight and Thursday. Very windy conditions develop Friday.
Dry and warm weather return for the weekend into early next week.
&&
.NEAR TERM /THROUGH THURSDAY/...
Evening Update...The fcst is in pretty good shape this evening. Did
make some downward adj/s to PoPs across the NC mtns and fthills
over the next few hrs as the upstream system is taking it/s time
saturating the column over the nrn zones. Still expect more moderate
rain to move in overnight and produce a good amt of rain thru Thu
across the BR escarpment due to enhanced mech lift and a few rounds
of convective activity arnd daybreak thru mid-day. The 00z HRRR has
backed off the the non-escarpment precip and actually looks a little
low with arnd a quarter to half inch storm total thru the day Thu.
For now have not made sigfnt changes to QPF and will let the mid
shift make any needed adj/s with the full fcst package.
As of 300 PM EDT Wednesday: Rain has lifted north this
afternoon, and is mainly confined to northern North Carolina.
Widespread cloud cover remains in place, with the thickest
clouds noted across the western two-thirds of the forecast area.
A brief lull in rain is expected this afternoon and early this
evening. Highs this afternoon should climb into the mid to low
to mid 70s east of the mountains thanks to 850 mb SW`ly flow.
Highs across the mountain valleys should climb into the upper
60s to lower 70s, with the mid 50s to mid 60s across the higher
elevations.
Cloud cover and rain chances ramp up again this evening into
Thursday as a low pressure system approaches out of the west. Have
high-end chance to likely PoPs across the western zones around
midnight tonight, with likely to categorical PoPs across the entire
forecast area by daybreak Thursday. Lows tonight will end up around
15-18 degrees above climo thanks to both cloud cover and rain
limiting radiational cooling. Southerly winds will gradually
increase this evening into tonight, becoming gusty, as the cold
front associated with the low pressure system approaches out of the
west. Gusty winds will linger throughout the day Thursday as the
front tracks across the western Carolinas and northeast Georgia.
Wind gusts should remain below Wind Advisory criteria across most
locations, although higher elevations along the NC/TN border and the
western North Carolina mountains may see gusts near advisory level.
Widespread rain will linger through the morning hours before
gradually tapering off from west to east Thursday afternoon.
Embedded thunderstorms may develop early Thursday morning into
Thursday afternoon thanks to both MUCAPE and SBCAPE ranging from 500-
1000 J/kg and 0-6 km bulk shear values ranging from 50-60 kts. SPC
has a Marginal Risk for severe storms on Thursday, and this seems
well placed as isolated strong to severe storms will be possible
Thursday morning into Thursday afternoon ahead of and along the cold
front. However, the overall threat continues to look low for now.
Scattered showers may redevelop behind the main line of convection
associated with the cold front thanks to wrap around moisture from
the low pressure system. With both the HRRR and NAMNest depicting
this, have chance to likely PoPs through the end of the near term.
Latest QPF guidance has come in lower than previous runs, showing 2-
3" along and near the Blue Ridge Escarpment and 0.5-1.0" elsewhere.
Locally higher amounts are possible, especially along the southern
Blue Ridge Escarpment, where rainfall totals near 4" are possible.
WPC has a Marginal Risk for Excessive Rainfall in place across the
western Carolinas and northeast Georgia for Thursday, so isolated
flooding cannot be ruled out (especially for locations along and
near the southern Blue Ridge Escarpment). Luckily, temps will remain
warm enough behind the front for all liquid precip. Highs on
Thursday should be similar to today`s but may be limited somewhat by
cloud cover and rain.
&&
.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
As of 230 PM Wednesday: The short-term period begins as a 500mb,
negatively tilted shortwave trough axis moves over the region
from the south and west. Current CAM guidance suggests that the
primary axis of heavy rain and storms will have moved well east of
the I-77 corridor by the time the period starts, and it is true
that convective complexes tend to outrun the responsible storm
as well as the guidance forecasting it. PoPs will therefore be
rapidly trending down Thursday night, with isolated to scattered
shower activity associated with the upper-level trough lingering
into the early overnight hours. A few residual upslope showers
may develop along the TN state line in the stout westerly flow
through Friday morning, but the primary story will be the strong
pressure-gradient winds behind the trough through Friday.
At this juncture, the overall meteorological setup looks favorable
for widespread 30-40mph gusts during peak mixing Friday afternoon
as the attendant surface low deepens to near 980mb over Ontario and
strong 50-75kt mid-level winds interact with a very deep (5-6kft)
mixed layer across the forecast area. Wind Advisory gust criteria
is >45mph and guidance continues to suggest that some areas may
reach this threshold, especially across the higher elevations of
the foothills and mountains, where the ground level is closer
to the stronger winds aloft and mixing will be most effective
at bringing a portion of those winds to the surface. Wind gusts
exceeding 50mph are not out of the question at elevations greater
than 4500-5000 feet from mid-morning Friday into the early overnight
hours. However, we are still four forecast periods out and blend
guidance typically overestimates the gust potential. Therefore,
we will highlight this potential threat in the HWO for now and
reevaluate our confidence in Advisory criteria for the next package.
While winds will be strong behind the departed frontal system,
they will predominantly be westerly, not northwesterly, and
therefore the source region advecting into the area will be from
the central Plains, not Canada. Therefore, we will cool down on
Friday, but modestly so, with downsloping likely to mitigate CAA
east of the mountains, where high temperatures will only be a few
degrees below normal. Across the mountains the effects of lower
thicknesses underneath the longwave trough and CAA will be a bit
more pronounced. Therefore, highs are expected to top out 7-9
degrees below normal.
An embedded shortwave trough will deepen the longwave trough
extending from the southern Appalachians north into Canada Friday
night and the longwave trough axis will quickly propagate east to
the Atlantic Coast by Saturday morning. Thicknesses will increase
during the day on Saturday as low-amplitude ridging builds east
from the Plains and surface high pressure propagates underneath
the inflection point along the Gulf Coast. Therefore, winds
will remain gusty as our area is still within a weakened pressure
gradient and mid-level winds remain strong in the NW flow aloft
behind the trough axis, but peak gusts will be lower than those
on Friday and well below Advisory criteria. Nevertheless, RH
values may bottom out in the lower to mid-20s Saturday afternoon
and combined with the remnant gusty winds fire weather may be
a concern. Temperatures will quickly rebound on Saturday, with
highs 3-5 degrees above normal area wide.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 230 PM Wednesday: The extended period looks to be mostly
quiet and warm across the forecast area as upper-level ridging
gradually amplifies into the middle of next week in response
to a strong closed low ejecting out of the southern Rockies.
This system will not directly impact our area through the period,
but its upstream effects will result in high temperatures reaching
the lower 80s in the mountain valleys and the mid-80s points east
Monday through Wednesday, which is 8-12 degrees above normal.
Low temperatures will be 12-15 degrees above normal each night,
and may not drop out of the 60s for much of the Piedmont Tuesday and
Wednesday nights as dewpoints slowly increase through the work week.
A backdoor cold front will struggle to reach our area Monday and
some of the guidance squeezes out a bit of moisture along the front,
so a slight chance of upslope showers cannot be ruled out across
the mountains and possibly the NW Piedmont Tuesday into Wednesday.
The proximity of the front will increase cloud cover, especially
overnight each day, limiting radiational cooling. Otherwise, the
forecast looks dry. Early in the period, RH values bottom out in
the upper 20s on Sunday and Monday with wind gusts of 15-20mph
possible each day. Therefore, fire weather may be a concern.
However, with increasing moisture, afternoon RH values looks to
bottom out in the mid- to upper 30s Tuesday and Wednesday so fire
weather concerns will diminish as the work week progresses.
&&
.AVIATION /02Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: An active TAF set in store with a vigorous
low pressure system tracking up the TN Valley pulling a cold front
across the Carolinas and NE GA. The first concern will be se/ly
gusty winds which develop ahead of the cold front arnd TAF issuance
or a couple hrs later. Winds will remain elevated with low-moderate
gusts as they begin to veer and become sw/ly by the early afternoon.
A strong llvl jet will traverses the area overnight and this will
lead to LLWS at 2 Kft due to speed changes on the order of 40-50 kts
beg after sunrise lasting thru noon or the early afternoon. Still
expect a chance of thunder as the main convg line passes east, which
will generally occur during a 3-4 hr window arnd sunrise thru late
morning. CIGs will also drop to IFR before midnight across most
terminals and stay down, before lifting or scattering to MVFR/VFR by
the early to mid afternoon.
Outlook: Gusty winds will linger Thursday night into Friday, with
the strongest winds expected on Friday. VFR conditions persist
Friday into the weekend as high pressure builds across the terminals.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...DEO
NEAR TERM...AR/SBK
SHORT TERM...JMP
LONG TERM...JMP
AVIATION...SBK
Area Forecast Discussion...UPDATED
National Weather Service Gray ME
1129 PM EDT Wed Apr 10 2024
.SYNOPSIS...
A series of waves will cross the region through the end of the
work week with increasing humidity, cloud cover, and showers
escalating to widespread rainfall. While some places will be
mild and humid, others toward the Gulf of Maine are likely to
remain cool and humid with onshore flow. In any case, a ripening
and melting snowpack combined with rain will lead to river and
stream rises, with a chance for minor flooding. A passing cold
front on Friday will introduce gusty winds, potentially strong
along the coast. Winds remain gusty heading into the weekend
with scattered showers.
&&
.NEAR TERM /UNTIL 7 AM THURSDAY MORNING/...
Update...Rain largely moving out of the area at this hour and I
have adjusted PoP accordingly. We will maintain WAA over the low
level cold dome...and this should result in drizzle breaking out
over time tonight. At this time this is mainly closer to the
mtns...or very near the coast...but I think expansion is likely
as the night goes on. I will continue to show a elevation
assisted pattern to the drizzle coverage.
Previous discussion...Little change expected in the near term
portion of the forecast. Latest radar imagery this afternoon
continues to indicate showers advancing into our forecast area
from southwest to northeast. The back edge as of 18Z was over
northeastern Pennsylvania. This coverage is more robust than the
latest HRRR solution.
In any case, showers will be predominantly confined to southern
portions of the forecast area overnight as the precipitation slides
south. There will be some patchy drizzle and fog overnight with a
raw southeast wind coming in off the Gulf of Maine. Overnight low
temperatures will be fairly uniform tonight, ranging from the upper
30s in the north to the lower 40s in the south.
&&
.SHORT TERM /7 AM THURSDAY MORNING THROUGH FRIDAY/...
On Thursday, a backdoor cold front will begin to turn northward
as a warm front. While the day will start out with relatively
low pops, the chance for showers will increase during the day as
a moist southerly gradient increases over the region as low
pressure tracks well to our west. Patchy drizzle and fog can be
expected once again with winds off the Gulf of Maine and plenty
of low level moisture in place. Afternoon high temperatures will
reach the 50s over southern New Hampshire and the Connecticut
River Valley with chilly 40s elsewhere.
A moist low level jet will enter the region Thursday night.
Scattered showers with patchy drizzle will switch to an all out
steady moderate rain over the region. Patchy fog will continue
during this period with temperatures bottoming out in the 40s.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
High Impact Weather Potential:
* Minor river flooding likely on Friday with overland flooding
possible as well.
* Strong southerly winds will near advisory levels along the coast
Friday. Gusty west winds continue into Saturday but not likely to
necessitate headlines.
--Pattern and Summary--
+NAO will allow for a progressive pattern across North America
through the long term forecast period. A longwave trough across the
central portion of the CONUS today will deepen as it pushes east
into the eastern United States Friday/Saturday with heights slowly
building in its wake by Sunday into early next week as west-
northwest flow remains over the region. Beyond this...troughing
over the southwestern United States will eject north and east with
building downstream heights and the potential arrival of shortwave
energy over the northeastern United States by the end of this
forecast period Wednesday. The most impactful weather of the period
looks to be as the period opens on Friday as rainfall and snowmelt
combine for a flood threat. A gradual moderating trend is expected
through the long term with high temperatures below normal for
Friday...warming to a bit above normal by the middle of next week.
--Daily Details--
Friday: Deep southerly flow continues through the day ahead of low
pressure over the Great Lakes with a 1.5" PWAT plume overhead but
rapidly pushing east ahead of triple point & associated surface cold
front. Best forcing for ascent will be early in the day until
frontal passage...with afternoon precipitation becoming showery in
the moist...cyclonic post-frontal flow. The high PWAT airmass and
good mid level forcing should allow for moderate rainfall rates
through the morning...which will bring our greatest potential for
overland flooding. See hydro section below for more details on the
flood potential.
Winds: Southerly winds at H9 reach 75-80kts with warm advection
scenario allowing for only pretty shallow mixing. This suggests a
35-40kt gust potential along the coast which nears our wind advisory
criteria. The flow trajectory suggests some downslope potential
across far northern NH and western ME as well. Mid morning-mid
afternoon appears to be the best potential for the strongest gusts.
Temperatures: Temps at H8 will be at or above 10C to start the
day...settling back to +3-5C by late afternoon in the post frontal
airmass. Highs will be determined mostly by mixing and any breaks in
the clouds which appear most likely across southern NH.
Here...expect highs to push into the middle 60s...with 50s to the
north and east of this...and coastal communities likely stuck no
higher than about 50 given the onshore flow.
Saturday/Sunday: Cold advection continues Friday night into
Saturday with the longwave trough axis overhead. Moist...cyclonic
flow and decent lapse rates below H7 suggest showery conditions to
continue on Saturday with precipitation increasingly taking the form
of snow in the mountains. The airmass dries significantly pushing
into Sunday which will allow for a drier...and somewhat warmer
day...particularly south of the mountains where highs may near 60F
as T9s rebound above +7C. We/ll have to watch a northern stream wave
that the model consensus pushes just south of our area Sunday
evening/Sunday night which may prolong the unsettled weather.
Monday/Tuesday: A weak high pressure ridge axis arrives for the
beginning of the week...which combined with a dry airmass /PWATS
around 0.25"/ should allow for a quiet start to the week with some
questions on how much temperatures moderate as the GFS/GEFS
advertises a bit more of a northerly component to the low and mid
level flow the the ECMWF/EC-EPS more northwesterly. Will follow
temperatures above seasonal norms...with 50s in the mountains and
60s elsewhere.
Wednesday: By the middle of next week...there is strong agreement on
low pressure in the western Great Lakes with warm advection ongoing
over our area with moisture also increasing. There is some spread
among the various guidance members as to the arrival of a warm front
and associated precipitation chances. At this range...mentioning
the chance for showers is prudent though at this range...ensemble
signals suggest a relatively light rainfall event which would not be
a significant flood concern. This increase in clouds and associated
shower chances will mean somewhat lower high temperatures to end the
forecast period...but likely remaining above normal.
&&
.AVIATION /04Z THURSDAY THROUGH MONDAY/...
Short Term...MVFR conditions will continue through the evening hours
with ceilings occasionally falling to IFR in showers and patchy fog.
Overnight, more widespread IFR conditions can be expected with a few
pockets of LIFR in low clouds.
Similar conditions will continue on Thursday with widespread IFR
conditions in low ceiling with drizzle and fog at times in addition
to the showers. Thursday night will continue to have IFR conditions
in moderate rain with patchy fog and localized LIFR conditions.
Long Term...LIFR CIGS/VSBYS with rain and fog along with gusty
/20G30kt/ south-southeasterly winds for the morning Friday with
improving conditions arriving from southwest to northeast
through the day. Showery conditions with occasional MVFR
restrictions will persist under moderate winds from the west for
Saturday. VFR conditions are expected to dominate Sunday-Monday
with westerly winds continuing.
&&
.MARINE...
Short Term...Moist southeast winds will continue tonight and Thursday
over the coastal waters. Areas of drizzle and fog will reduce
visibilities in addition to scattered showers. The gradient
increases Thursday night over the region as low pressure tracks well
to our west. Seas will continue to build as well.
Long Term...Southerly gales likely Friday/Friday evening as strong low pressure
moves through the Great Lakes region and north of New England. Gusty
west winds continue through Saturday with SCA conditions continuing.
Winds/waves will subside for Sunday and Monday as weak high pressure
builds towards the region.
&&
.HYDROLOGY...
A flood watch is in effect for the snow covered portions of the
Western Maine Mountains and Northern New Hampshire.
The rain through Thursday will act to compress, warm, and ripen the
snowpack, but the heavier rain Friday morning will be the catalyst
for flooding. The combination of strong winds and high dew points
(50s) over an isothermal snowpack will lead to rapid melt with
expectations up to 4” SWE loss. Complete melt-out below 2,000 ft is
likely, particularly on S/SE facing slopes.
The flood risk will be focused Friday morning as moderate to heavy
rainfall pushes through ahead of a cold front. The current QPF
forecast is for 1 to 3 inches in the mountains, less on the north
facing slopes. However, the PWATs are 2-3SD above normal, and with a
moisture feed to the Gulf we should be prepared for locally higher
amounts. Melt combined with saturated antecedent conditions sets up
ideal conditions for potential flash flooding and moderate river
flooding in the Upper Merrimack (Pemi), Saco, Androscoggin, and
Kennebec basins. Small streams draining in the steep terrain could
experience flash flooding. This melt will route downstream, causing
potential flooding impacts on low elevation rivers as well. Outside
of the snow covered areas, locally heavy rainfall may elicit poor
drainage and nuisance flooding in urban areas, especially if heavier
rainfall totals materialize.
&&
.TIDES/COASTAL FLOODING...
Very high astronomical tides will continue tonight with the
tide in Portland at 11.4` (MLLW). A southeasterly flow off the
Gulf of Maine will allow for a modest storm surge tonight, will allow
Portland to reach its 12 foot flood stage. Hampton should come
in around its 11 foot flood stage as well.
High astronomical tides will continue through the end of this
week, albeit, lowering with time. Future coastal flooding this
week will rely on whether or not significant storm systems will
line up with the higher of the high tide cycle which currently
is the overnight hours this week.
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch from late Thursday night through Friday
afternoon for MEZ007>009-012>014.
Coastal Flood Advisory from midnight tonight to 3 AM EDT
Thursday for MEZ023-024.
NH...Flood Watch from late Thursday night through Friday
afternoon for NHZ001>005.
Coastal Flood Advisory from midnight tonight to 3 AM EDT
Thursday for NHZ014.
MARINE...Gale Warning from 5 AM to 11 PM EDT Friday for
ANZ150>154.
&&
.GYX WATCHES/WARNINGS/ADVISORIES...
ME...Flood Watch from late Thursday night through Friday afternoon
for MEZ007>009-012>014.
Coastal Flood Advisory until 3 AM EDT Thursday for MEZ023-024.
NH...Flood Watch from late Thursday night through Friday afternoon
for NHZ001>005.
Coastal Flood Advisory until 3 AM EDT Thursday for NHZ014.
MARINE...Gale Warning from 5 AM to 11 PM EDT Friday for ANZ150>154.
&&
$$
NEAR TERM...Legro
Area Forecast Discussion
National Weather Service Indianapolis IN
1004 PM EDT Wed Apr 10 2024
.KEY MESSAGES...
- Rain Tonight and Thursday; Cool
- Minor Flooding possible
- Rainfall in the next 48 hours will may prolong ongoing river
flooding at a minimum, and lead to some renewed lowland flooding
along main stem rivers.
- Active weather pattern continues into next week with numerous
chances for rain and storms.
- Above normal temperatures in the 70s Sunday into most of next week.
&&
.FORECAST UPDATE...
Issued at 1002 PM EDT Wed Apr 10 2024
Periods of light/moderate rain overnight will contain embedded
heavier rates and possibly briefly training showers as was seen
earlier this evening in both Knox and Morgan/Johnson Counties.
Isolated areas of ponding of low-lying areas and minor flooding can
be expected tonight...especially if any organized rain manages to
maintain itself over the smaller region that had picked up 1.00-2.00
inches last night between Brown County and Rush County. Greatest
chances of heavier additional rainfall should be over western and
possibly northern counties where isentropic lift along approaching
system`s warm frontal zone will be focused. 12-hr rainfall through
dawn Thursday should be 1,00-1.50 inches for most locations...with
embedded areas surpassing 2.00 inches.
Easterly flow around 10KT to be maintained overnight as circulation
approaches from the SSW. Readings in mainly the 55-60F range amid
the moist environment to hold or perhaps drop slightly with lows in
the 50s. Fog development is possible in any slackening in rainfall
rates, although sustained winds should be high enough to prevent
major visibility deterioration.
Previous Mesoscale Discussion follows...
Broad area of rain continues to lift across Central Indiana this
evening. Some pockets of moderate to heavy rain is located within a
corridor of Sullivan county to Marion county, where more robust
collision and coalescence is taking place to parcels and allowing
for larger more efficient hydrometeors to reach the surface. This
area is also still seeing isentropic ascent to parcels through a
moist column, further aiding in the efficiency to the steady
rainfall. Surface OBS indicating some reduced VSBY within the
steadier rain along and south of the I-70 corridor. Satellite
imagery is indicating some cooling to cloud tops along the Ohio
River and lifting north, while underneath radar reflectivity has
some pockets of convection that has developed.
&&
.SHORT TERM (This evening through Thursday)...
Issued at 300 PM EDT Wed Apr 10 2024
Synopsis:
Surface analysis this afternoon shows a frontal boundary stretching
from north of Richmond to Columbus and then south of Vincennes.
Surface high pressure was found over Lake Huron and Lake Erie. Cool
easterly surface flow was in place across much of the forecast area
and dew points across northern Central Indiana were in the 40s,
while the southern half of the forecast areas had recovered with dew
points in the mid 50s. Radar mosaics show an area of showers over
southwest Indiana and west Central KY pushing northeast within the
flow aloft. Aloft, water vapor imagery showed a deep upper trough
over the southern plains states. This was resulting in moist
southwest flow streaming northeast into the Ohio Valley. The upper
trough was producing much stronger storms over LA and Arkansas.
Tonight...
The upper trough over the southern plains is expected to push
northeast, becoming negatively tilted in the process. Forcing
dynamics ahead of the system are suggested to push in to the Ohio
Valley and Central Indiana as the evening progresses. The lingering
lower level boundary will act as an area of lower level convergence
while the forcing provided aloft provides additional lift.
Isentropic surfaces also remain in play. The 300K GFS Isentropic
surface shows some lift surging into the area this evening and
specific humidities are over 6 g/kg. Forecast soundings also show a
saturated column through much of the night across Central Indiana
with pwats over 1.3 inches. Finally, HRRR shows a shield of rain
showers expected to develop and surge into Central Indiana this
evening and early overnight. CAPE is limited with this feature, but
given the warm and moist air and lapse rates that are marginal
unstable, a stray embedded thunderstorm cannot be ruled out. Thus
expect the main precipitation to be rain showers.
Given the clouds, precipitation and steady easterly flow, nearly
steady state or slightly cooling temps toward wet bulbs will be
expected. Expect lows in the lower to middle 50s.
Thursday...
Models show the negatively tilted upper trough slowly swinging
through Indiana and the Ohio Valley through the day. The mid levels
keep a saturated trough in place over Central Indiana through the
day, as the surface low is expected to quickly push east of the
state. This will allow the winds to become northwesterly. The
associated tight pressure gradient across the area will allow for
gusty winds of 20-30 mph also. Strong lower level cyclonic flow will
also remain in place, allowing for the development of scattered wrap
around rain showers. Forecast soundings are not as saturated on
Thursday as they were previously, as dry air begins to intrude into
the system, however still plenty of lower level moisture will still
remain present. Pwats on Thursday start over 1 inch and by late
afternoon fall to around 0.75. HRRR suggests scattered showers
through the day, gradually diminishing by late afternoon. Thus will
again use high pops on Thursday for scattered rain showers, with
lessening pops through the afternoon as dry air intrudes from the
northwest.
Given the expected clouds, rain, and cold air advection, little
temperature movement will be expected through the day. Look for high
temperatures only a few degrees warmer than the previous lows, in
the middle to lower 50s.
&&
.LONG TERM (Thursday night through Wednesday)...
Issued at 300 PM EDT Wed Apr 10 2024
An active pattern continues through the end of the work week and
into next week with numerous chances for rainfall and storms;
however temperatures remain largely above normal for this time of
year through the period.
.Thursday night and Friday...
A strengthening surface low, aided by phasing jet energy aloft,
tracks NE through the state Thursday then slowly away to the
northeast into Quebec on Friday. Guidance is in great agreement with
a strong upper wave diving SE into the state behind the departing
low Thursday night into Friday morning, keeping the chance for
convective showers around. By 12z Friday, a negatively tilted upper
trough axis is right on top of the state with Indiana in the left
exit region of an 110kt jet streak over IL and MO. Steepening low
and mid level lapse rates from CAA on the backside of the surface
low in addition to saturated low levels and 20-30 kt 0-1km and 0-3km
shear will result in an environment conducive for convective showers
late Thursday night into the first half of the day on Friday. With
such a strong 35-45 kt low level jet overhead and steep low level
lapse, expect breezy conditions during this time as well with
frequent gusts over 40 mph likely. Higher wind gusts are also
possible in any convective shower as well. Would not be surprised to
see small hail or graupel as well with the strongest showers as
freezing levels lower to around 3,000 ft by Friday morning.
Drying trend expected through the daytime hours Friday as higher
pressure and much drier air advect into the region. Friday will
likely be the coolest day over the next week with afternoon highs
struggling to even reach the 60 degree mark.
.This Weekend into Next Week...
An extended period of well above average temperatures and storm
chances arrives this weekend and persists into next week. Ridging at
the surface and aloft will expand into the Ohio Valley for the
weekend. Ridge axis remains over the Plains through Monday placing
Indiana with an upper level northwesterly flow pattern. Longer range
guidance does show the potential for waves of energy within the NW
flow to bring storm chances Late Sunday night and then again on
Monday night. This is a classic late Spring to early summertime
pattern with southerly flow and a warm, humid airmass at the surface
with waves of energy flowing NW to SE along the jet. Unfortunately,
guidance does not handle the smaller details such as timing and
placement of these waves of energy very well. While high confidence
exists in well above average temperatures in the 70s (and maybe
80s!) next week, lower confidence exists on storm track, timing, and
location. Will have to watch where the upper level storm track sets
up, which will determine where these potential clusters of storms
set up and track. Some guidance has these storm clusters pushing
into Indiana, while others keep the storms further north. For now
keeping only 20-30 POPs in the Sunday - Monday forecast and will
adjust up or down in future forecast packages as timing and location
become clearer. This will not be a wash out type event, so expect
most of these days to remain dry before and after the storms. Not
ruling out the threat for a strong to potentially severe storm
associated with these thunderstorm complexes.
Upper ridging shifts eastward mid week with numerous stronger storm
systems moving through the Plains. This places Indiana within a
warm, southwest flow pattern within the warm sector of storm systems
to the west. While much warmer, above normal temperatures continue,
the threat for more storms remains in the forecast. At the moment,
the current storm track looks to remain west of the Ohio Valley
midweek as dying frontal systems and associated storms push into the
region. There are some hints in the guidance that the storm track
does move further east over the Ohio Valley by late week bringing
more frequent and widespread chances for rain and storms, but
confidence this far out on details remains low.
For now, high confidence exists in a much warmer weather pattern
with periodic to daily chances for storms. Do not expect any
particular day to be a washout this weekend into the first half of
next week; however will keep a close eye on the weather pattern
later next week for potential repeated rounds of heavy rain and
storms. Lower confidence exists with timing and placement of daily
threats for storms. It is too early to talk about the severe or
flooding threat with storms mid to late next week, however not
ruling out the possibility.
&&
.AVIATION (00Z TAF Issuance)...
Issued at 755 PM EDT Wed Apr 10 2024
Impacts:
- IFR/possible LIFR ceilings to prevail through at least 18Z
Thursday...although MVFR at KLAF to begin period
- Mainly IFR/MVFR visibility into THursday morning...with low-IFR/
brief LIFR possible in heavier rain
- Isolated non-severe TSRA are possible overnight, with best chances
at KBMG
Discussion:
A storm system centered over the Lower Mississippo Valley early this
evening will intensify while lifting towards the Midwest tonight...
before crossing the region Thursday morning. Scattered to
widespread light to moderate rain showers will fall under mainly IFR
ceilings tonight, with generally IFR/MVFR visibility lowered in
heavier rains and any subsequent fog formation. Non-severe TSRA are
possible tonight, but chances too low outside of KBMG to include in
TAF.
Winds will remain sustained around 10 knots overnight from easterly
directions...except more norhteast at KLAF. Wind directions will
change through the early Thursday timeframe as the surface
circulation crosses the region. Gustier northwest flow will then
advance across the region from west to east Thursday afternoon
behind the deepening, departing system...with gusts to at least 20-
30KT after 18Z Thursday.
Kept VCSH for Thursday with low confidence on location and timing
for the few to scattered showers that will accompany the passing
system, although periods of steadier rain will certainly be
possible. Conditions should improve quickly from IFR to VFR during
the afternoon for KLAF/KHUF...and probably towards sundown at
KIND/KBMG.
&&
.IND WATCHES/WARNINGS/ADVISORIES...None.
&&
$$
UPDATE...AGM
SHORT TERM...Puma
LONG TERM...CM
AVIATION...AGM
Area Forecast Discussion
National Weather Service San Francisco CA
522 PM PDT Wed Apr 10 2024
...New AVIATION, MARINE...
.SYNOPSIS...
Issued at 212 PM PDT Wed Apr 10 2024
Our warming trend is well underway across the Bay Area and
Central Coast and will continue tomorrow and potentially into
Friday. The latest forecast has a delayed onset of rain showers
with locations across the North Bay being impacted first late
Friday afternoon and evening. Rain and embedded thunderstorm
chances spill southward late Friday and into the day on Saturday.
The better thunderstorm risk will be confined to the offshore
waters, though coastal areas of Santa Cruz and Monterey have a low
potential for a rumble of thunder or two. It`ll turn sharply
colder this weekend with rebounding temperatures next week.
&&
.SHORT TERM...
(This evening through Thursday)
Issued at 212 PM PDT Wed Apr 10 2024
As discussed earlier, the potential for fog/low stratus across
the coastal areas has increased a bit more tonight into Thursday
morning. As T-Td spreads diminish, mostly clear skies (except some
passing high clouds) and reduced surface-925mb flow will
encourage a bit more in the way of fog. If high clouds are really
dense, then fog may struggle to develop. Speaking of struggling,
HREF guidance yesterday didn`t appear to capture the evolution of
this morning`s fog and appears to offer low probabilities for
tonight. However, forecast soundings from afternoon RAP guidance,
along with some of the NBM guidance support inclusion of patchy
fog with visibilities of 2-4 miles across the North Bay, parts of
the SF Peninsula, and across a good portion of the Central Coast.
Guidance indicates that areas across Monterey Bay will stand the
best chance (around a 30-40% chance) to see visibility slip below
1 mile. Visibility reductions may be observed as far inland as the
Salinas Valley, but given the shallow nature of saturation (less
than 1000 feet), it`s probable that any nocturnal drainage flows
will keep the boundary layer sufficiently mixed to curb the dense
fog potential. Given that the chance for visibility to fall below
1 mile is confined to a small area, dense fog headlines are not
anticipated. Motorists are still urged to exercise caution when
commuting late tonight into early Thursday morning as sudden
changes in visibility may occur. With the shallow nature of the
marine layer, fog and low clouds should dissipate by mid-morning
Thursday, though will linger through the early afternoon hours
offshore.
As advertised earlier this week, Thursday will be one of the
warmest days we`ve seen since last Fall. Record high temperatures
are safe, but we`ll continue to see a minor heat risk for most of
the area. This means that those sensitive to the heat (elderly
and infants) may succumb to heat-related illnesses. We encourage
individuals across the area (especially interior locales such as
the Santa Clara Valley, Salinas Valley, and San Benito County) to
hydrate adequately with water and take breaks in the shade if
working outside. Never leave children or pets unattended in
vehicles. High temperatures are forecast to range between the mid
to upper 50s along the coast to upper 70s to even mid-80s across
interior sections. There`s still a bit more spread in the max
temperature forecast along coastal sections. The marine layer
isn`t overly deep and so I do anticipate mixing will erode any
low clouds/fog prior to peak heating. However, if areas stay
socked in with clouds/fog, highs along the coast may struggle to
get out of the mid 50s.
&&
.LONG TERM...
(Friday through next Tuesday)
Issued at 212 PM PDT Wed Apr 10 2024
Friday Onward....Some noteworthy alterations were made to the
PoP/QPF grids. Thanks to EKA, STO, HNX, and EKA for the
coordination. This entire week, model guidance has slowed the
progression of the upper trough that will be responsible for our
wetter and cooler conditions this weekend. Blended guidance
rain amount probabilities have trended lower and with some of the
higher resolution NWP now available, it seems prudent to update
PoP/QPF to match our IDSS messaging. These alterations result in
rain chances being confined to areas across extreme northern
portions of the North Bay during the daylight hours on Friday.
While a stray shower or two (or sprinkles/drizzle) cannot be ruled
out for locations farther south, however, confidence is
increasing that most locales will remain rain-free. While cloud
cover will inhibit heating, I did adjust temperatures upward
closer to the 75th percentile of the NBM on Friday afternoon which
means most areas away from the coast will see high temperatures
in the upper 60s to low 70s.
Forcing for ascent increase late Friday into Saturday as our main
upper storm system arrives. Upslope flow across the higher
terrain (Santa Cruz Mountains, Santa Lucia Range, and Mayacamas)
will promote some orographically enhanced precipitation, but the
primary band of showers may not enter parts of the North Bay until
closer to 10pm Friday night. Rain chances peak during the pre-
dawn hours on Saturday with values averaging between 60 and 80
percent. As the upper low attempts to scoot eastward through the
day on Saturday, this feature will slow down and the 500mb low
forecast may reside across the northern portions of our marine
zones during the afternoon hours on Saturday. This will encourage
additional onshore flow on Saturday and thus additional rounds of
precipitation. With widespread cloud cover and rain, Saturday
will not be an ideal day for outdoor activities and temperatures
will remain in the 40s and 50s which will be quite the change from
the middle portion of the week. The unidirectional flow through
the troposphere will promote training of convective cells and rain
bands over a given area, thereby increasing the potential for
minor flooding. The greatest potential for excessive rainfall, as
highlighted by the Weather Prediction Center, appears that it`ll
reside across the Big Sur coastline, however, any robust
convective cell over a more urbanized area may promote minor
flooding.
As it pertains to the potential for thunderstorms, forecast
instability values from deterministic guidance suggest that the
greater risk resides across the offshore marine areas. Some
instability does build on Saturday afternoon, however, it`s quite
meager. In fact, the potential for CAPE values over 100 J/KG are
around 30%. This translates to a low potential for a rumble of
thunder or two on Saturday afternoon. Chances for CAPE values over
100 J/kg are closer to 60% across the marine zones. 700-500mb
lapse rates do steepen around 7.5 C/km offshore and so there
remains some potential for waterspouts (beyond 40-50 miles from
the Central Coast). Snow levels do appear that they`ll fall down
sufficiently such that a few snow flakes or very light snow
showers unfold across central and southern portions of the Santa
Lucias. At this time, measurable snowfall is not expected.
With the slower progression of the upper low, 20-40 PoPs linger
through the day on Sunday. With the upper low traversing the region,
the cooler pocket of air aloft will shift overhead during peak
surface heating across southern Monterey/San Benito counties. As
such, lapse rates steepen Sunday afternoon across southern
Monterey and San Benito counties and I`ve inserted just a 20%
chance for isolated storms here. Severe weather is not expected,
but storms may be efficient at producing larger quantities of
hail.
Heading into next week, we`ll see mid-level ridging set up across
the region which should limit the opportunities for precipitation.
Temperatures will rebound and we will be well on our way to near or
above normal warmth.
&&
.AVIATION...
(00Z TAFS)
Issued at 520 PM PDT Wed Apr 10 2024
VFR with some high clouds across the area. Winds vary in direction
but mostly onshore flow with moderate to breezy speeds. Expect winds
to become light overnight. With the strong ridge and compressed
marine layer, expect another round of some low visibility and low
clouds early Thursday morning for most terminals. Moderate
confidence on ceiling heights but expect a mix of MVFR, IFR, and
LIFR conditions starting near 12-14Z. VFR will return after 18Z with
mostly clear skies.
Vicinity of SFO...Currently VFR with breezy N/NW flow before
diminishing overnight. Confidence is increasing that the terminal
will see a reduction of flight category tomorrow morning to MVFR.
Winds will be breezy with speeds up to 15-16 knots out of the west
again tomorrow afternoon.
SFO Bridge Approach...Similar to SFO.
Monterey Bay Terminals...Currently VFR with moderate northwesterly
flow. Winds will diminish overnight which will allow for some
lower visibility and ceilings causing a mix of IFR to LIFR
conditions overnight with KMRY seeing low ceilings near 07Z and
13Z for KSNS.
&&
.MARINE...
(Tonight through next Tuesday)
Issued at 520 PM PDT Wed Apr 10 2024
High pressure over the Eastern Pacific Ocean will dominate the
forecast through tomorrow, allowing for fair weather and fresh to
strong northerly breezes to prevail over the coastal waters. Long
period northwesterly swell will continue to build through the
waters through today before beginning its abating trend tomorrow.
Friday, a deep upper-level low will bring renewed chances for
rain, gusty winds, thunderstorms, and hazardous seas to the
coastal waters through the weekend.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...None.
PZ...Small Craft Advisory from 3 PM Thursday to 9 AM PDT Friday for
Pt Arena to Pt Reyes 0-10 nm-Pt Pinos to Pt Piedras Blancas
0-10 nm.
Small Craft Advisory until 9 AM PDT Friday for Pigeon Pt to Pt
Pinos 10-60 NM-Pt Arena to Pt Reyes 10-60 NM.
&&
$$
SHORT TERM...Bain
LONG TERM....Bain
AVIATION...SO
MARINE...SO
Visit us at www.weather.gov/sanfrancisco
Follow us on Facebook, Twitter, and YouTube at:
www.facebook.com/nwsbayarea
www.twitter.com/nwsbayarea
www.youtube.com/nwsbayarea
Area Forecast Discussion
National Weather Service Nashville TN
854 PM CDT Wed Apr 10 2024
...New UPDATE...
.UPDATE...
Issued at 854 PM CDT Wed Apr 10 2024
Relatively quiet evening thus far with showers clearing out of the
area for now. Will begin to see an additional wave of showers and
thunderstorms move into the area mainly after midnight, bringing
and additional half inch to inch of rain. This evening`s sounding
shows hardly any CAPE with weak lapse rates, but a PWAT at 1.23".
There does not appear to be any major concerns heading into the
overnight hours. Could see a few thunderstorms in the fix that
could lead to heavy rainfall, otherwise any strong/severe weather
does not look likely. Pressure gradient will increase overnight
and tomorrow ahead of a low pressure system moving through the
area, likely kicking winds up overnight and through much of the
day tomorrow. Some areas may flirt with Wind Advisory criteria,
but overall most should remain below 40 mph gusts. Best chance to
see gusts close to that would be across the Cumberland Plateau.
Have adjusted PoPs and temps over the next 36 hours given latest
thinking, otherwise rest of the forecast is on track and will be
updated in full here in a few hours.
&&
.SHORT TERM...
(Rest of today through Thursday)
Issued at 1200 PM CDT Wed Apr 10 2024
Chances of showers with isolated to scattered thunderstorms will
be possible across mid state region through Thursday afternoon as
surface frontal system now based across southern MS River Valley
Region pushes northeastward and associated upper level low digs
across southern MS River Valley Region northeastward into mid
state region by morning hours on Thursday before pushing
northeastward also. Leaned toward latest HRRR model solution for
rainfall coverage across our area through at least the evening
hours tonight. Total rainfall amounts this afternoon through
Thursday will generally range 0.50" - 1.0." A strong thunderstorm
here or there can not be ruled out, but stronger convection should
generally remain well to our south. Lows tonight will mainly be
in the 50s with highs on Thursday mainly mid 60s to lower 70s.
&&
.LONG TERM...
(Thursday Night through next Wednesday)
Issued at 1200 PM CDT Wed Apr 10 2024
Shower and thunderstorm chances will diminish west to east across
our area as Thursday evening progresses, with maybe some
lingering showers across northern portions of Upper Cumberland
Region after midnight Thursday and possibly lasting through the
day on Friday as continued weak shortwave passages aloft occur
across this area. Otherwise dry conditions will prevail through
Monday afternoon per prevalence of surface and generally a
pattern of building upper level ridging influences. Showers and
thunderstorm chances will return to our area as Monday afternoon
into next Wednesday afternoon progresses, as southerly low level
atmospheric flow becomes increasing established across our region
as a large synoptic frontal system takes shape across most of
eastern half of CONUS and southwesterly upper level flow becomes
increasingly progressive. After lows Thursday night generally
around seasonal normal values spanning the mid to upper 40s with
highs on Friday remaining a few degrees below seasonal normal
values mainly spanning the 60s, a significant warm air advection
pattern will begin to develop resulting overnight lows through
first part of next work week mainly in the 60s with afternoon
high values mainly in the low to mid 80s, upper 70s to around
80 Cumberland Plateau Region.
&&
.AVIATION...
(00Z TAFS)
Issued at 611 PM CDT Wed Apr 10 2024
Light showers will diminish this evening and we will get a break
in the rain for several hours. Our next line of scattered rain
will move in after 05z and a few isolated thunderstorms will also
be possible. Showers will linger during the morning with another
line of showers and thunderstorms developing from west to east
after 14z. Cigs will rise into VFR levels for a time this evening
but will return to MVFR overnight and will continue at MVFR into
tomorrow. IFR/LIFR will be possible with any thunderstorms. Things
dry out from west to east after 22z. Breezy southerly winds
gusting up to 25 knots, the strongest winds will be tomorrow
morning into the afternoon.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 60 70 48 68 / 100 100 30 10
Clarksville 57 67 47 67 / 100 100 30 10
Crossville 57 67 43 59 / 80 100 40 10
Columbia 56 67 46 67 / 100 90 30 10
Cookeville 59 68 46 61 / 80 100 40 10
Jamestown 58 69 43 59 / 80 100 50 20
Lawrenceburg 58 66 46 67 / 90 90 30 10
Murfreesboro 59 69 46 67 / 100 100 30 10
Waverly 53 65 46 67 / 90 90 20 10
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE.......Adcock
SHORT TERM...JB Wright
LONG TERM....JB Wright
AVIATION.....Mueller
Area Forecast Discussion
National Weather Service Pocatello ID
300 PM MDT Wed Apr 10 2024
.SHORT TERM...Today through Thursday Night.
Early afternoon satellite imagery shows a broad H5 ridge of high
pressure over the WRN CONUS which will continue to lead to warm
and dry conditions across CNTRL and ERN Idaho through Thursday.
Highs in the 40s/50s/60s today will increase around 5-10 degrees
for Thursday to the 50s/60s/70s as the ridge axis shifts directly
overhead. 15-20 kt 700 mb winds today supporting gusts to around
15-25 mph will increase later in the day Thursday and through the
overnight hours Friday to around 20 to 35 kts supporting wind
gusts to around 20-35 mph, especially in the mountains. Conditions
will continue to remain dry through Thursday evening as increased
cloud cover builds in out of the west as shallow moisture moves
atop the ridge. This will support some isolated shower chances
primarily in the higher terrain Thursday night as conditions
remain predominantly dry. MacKay
.LONG TERM...Friday through next Wednesday.
Well...for better or for worse...the long-term portion of the
forecast continues to feature a whole massive pile of active wx
for southeast Idaho. Over the last few days we`ve been discussing
a couple different potential scenarios for the evolution of our
next main trough/low pressure storm system for this weekend...hold
that thought, we`ll look at that momentarily. One thing that has
remained quite consistent in the forecast from model run to model
run for a couple days now though has been Friday, featuring a
weak, initial shortwave trough riding up the front/leading edge of
the main approaching trough. This feature...barely detectable in
height analysis and weakening with time...is negatively tilted,
which can be a synoptic red flag for potential strong to severe
t-storms. Despite the weakening nature of the shortwave, it should
still provide some broad ascent, and every mid-range to long-
range model IS in fact generating at least some isolated
shower/t-storm activity coincident with diurnal heating Friday
afternoon. A first look at NBM-projected SBCAPE (which we honestly
haven`t evaluated extensively yet but is based on multi-model,
ensemble-based, calibrated guidance) suggests a marginal but
adequate 200-400 J/kg SBCAPE (instability to support updrafts and
storm strength), while the NAMNest (which is often a bit
overzealous or at least falls near the upper-end of the guidance
envelope) advertises as much as 400- 900 J/kg SBCAPE...with a
sounding near Burley hinting at 30-35kts of both effective and
0-6km deep-layer bulk shear as well as very strong low-level lapse
rates. Bottom line...while we`ll need to continue to evaluate the
potential for strong t-storms as more guidance comes in...Fri
looks convective, with otherwise continued south flow ahead of the
main approaching trough continuing to support warm temps
averaging 15 degrees above normal for mid-April (highs in the
mid-60s to mid-70s for nearly all population centers).
Okay...now the main event. A main approaching trough of low
pressure will manufacture a solid-looking closed low along the
coast of CA by Sat. 500mb height cluster analysis Sat continues to
hint at the two possible scenarios we`ve been watching for this
low, with two clusters (about 45% of the ensemble membership)
supporting a slightly stronger/more anomalous closed low quite
disconnected from the remnant nrn branch of the trough that will
progress inland slower and bring a later pattern change to SE
Idaho, and two clusters (about 55% of the ensemble membership)
supporting a slightly more intact and progressive overall trough
(even with a closed low still advertised as the srn branch) that
brings cooler, wetter conditions inland to SE Idaho as much as
36-48 hours earlier. These ensemble percentages almost sound like
a flip-flop from this time yesterday when the first scenario was
more strongly favored, but we note that ALL clusters have trended
toward a much more similar timing/position solution for the closed
low compared to the differences we saw 24-48 hours ago...ALL
keeping the low well the SW of our CWA. Thus, confidence continues
to increase (and is now pretty high) that temps Sat will end up
remaining warm and almost identical to Fri with southerly flow in
place. Also, despite a first chance of precip Fri, upper-level
support associated with the low might remain far enough SW of our
region that Sat may end up leaning mostly dry for most of our
forecast area, and NBM PoPs have slowly been decreasing in line
with this conceptual expectation. Moving forward to Sun, we see
the same two scenarios, with the clusters supporting a more intact
overall trough and slightly weaker closed low behaving more
progressively with a trough axis near or already over SE Idaho
(60% support), and the clusters supporting a slightly stronger
closed low as the main player lagging back over central CA (40%
support) leading to YET ANOTHER very warm day, although perhaps
with an increasing trend in shower potential. The more progressive
solution would cool temps (and slow mid-elevation snowmelt) by
Sun with increasing showers, while the delayed solution would
support another warmer, drier day with continued snowmelt...thus
some potential implications here extending to the flood forecast
for the Portneuf River (more on that in the HYDROLOGY section
below). Interestingly, the 12z deterministic model suite seems to
be leaning toward the slower solution, despite the ensemble
percentages just mentioned. Thus, confidence remains low on
whether Sun will side with spring, or side with a pattern change
toward cooler, wetter wx.
Whether our pattern change arrives in earnest by Sun, or by Mon,
all models advertise yet another organized closed low pressure
system dropping out of Canada toward nrn Idaho, with cluster
analysis suggesting uncertainty in how quickly this system
arrives. At this time, it doesn`t look like there will be much of
any chance for a break (MAYBE Mon night?), with NBM guidance and
all long-range models showing widespread rain/snow across the
region on Tue. High temps will have already started cooling Mon,
but we take another 10 degree hit by Tue with highs only in the
40s to near 50. By this time the western half of the nation is
firmly enveloped in massive long-wave troughing, and there are
some indications that Tue`s low either slows down and lingers in
our area, or is replaced by yet another deepening low in the
region, either of which would keep cooler, wetter wx going into
Wed and likely beyond. We note that deterministic models have some
wildly conflicting solutions by mid- week as far as details are
concerned, but chances are pretty high in that cooler, wetter,
unsettled wx dominating for most of next week. By the way, breezy
conditions...first out of the south Fri/Sat and then more out of
the west thereafter...are expected each day throughout the
forecast, although so far holding below advisory criteria. -
KSmith
&&
.AVIATION...For the 18Z TAFS through 18Z Thursday.
A ridge of high pressure has finally taken hold across the nrn
Rockies and will reign as the dominant synoptic wx enforcer both
today and Thu, supporting high forecast confidence in dry, mostly
sunny/clear, VFR conditions for all terminals. Modest winds
checking in at 10kts or less today may trend just a touch higher
out of the WSW for Thursday, and sfc conditions will remain too
dry for any fog or low stratus concerns. We do carry some passing
high clouds in the TAFs over much of the period (generally FEW180)
based largely on the HRRR (which tends to pick up on high-level
cirrus the best and even perhaps over-advertises these shields)
but with some hints of support from upstream satellite
observations over the PacNW too. That said, no real impact is
expected for aviation for the next 48 hours, and there is perhaps
a 40% chance that SKC will be favored over much in the way of high
clouds. Looking ahead, an approaching shortwave trough will more
noticeably increase winds by Friday afternoon and support at least
isolated showers and thunderstorms for some terminals. - KSmith
&&
.HYDROLOGY...
As has been discussed for several days now, the Portneuf River
continues to be our only river of concern for flooding at this
early stage of our spring flood season, with very warm temps
averaging 15 degrees above normal by Fri and Sat supporting
increasing snowmelt, especially at mid-elevations in the basin.
Our latest collaborated forecast with the Northwest River Forecast
Center continues to bring the river back into minor flood stage
in the Pocatello area by early Friday morning, and then to
moderate flood stage by early Sunday morning. This potential crest
above moderate flood stage has PERHAPS trended SLIGHTLY higher in
the forecast over the past 48 hours...increasing from about 10.0
feet to about 10.3 feet...but otherwise no significant changes or
trends are noted, and resultant impacts should be approximately
the same with lowland flooding along the river, flooding into
Sacajawea Park and other trailheads in western Pocatello, and
significant flooding of agricultural land in the Blackrock area
and also down in Inkom near the confluence of the Portneuf River
and Marsh Creek. A FLOOD WARNING remains in effect until further
notice. A bit further upriver near Lava Hot Springs, the forecast
for the Portneuf River at Topaz continues to carry bankfull
conditions (action stage) with the river perhaps getting close to
that minor flood threshold. As discussed in the LONG TERM section
above, the evolution of this weekend`s approaching low pressure
system will have SOME impact on the river forecast...the more
progressive solution with the low arriving by Sun will bring
cooler temps earlier slowing snowmelt, while the delayed solution
with the low arriving Mon will extend snowmelt and may eventually
support SLIGHTLY heavier QPF, although overall QPF amounts in
either scenario look pretty modest at this juncture (with no
response on the ECMWF Extreme Forecast Index for QPF amounts),
thus runoff from snowmelt continues to be the driving factor.
Cooler and wetter wx is expected next week, and it`s uncertain
exactly how this will affect the river forecast as cooler temps
will slow snowmelt, but actively falling QPF could keep river
flows up. Stay tuned. REMEMBER... despite recent warm air
temps...the water in all of our rivers, creeks, and streams
largely originates from melting mountain snow and is dangerously
cold this time of year. Be especially careful to keep children
away from the water. - KSmith
&&
.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Area Forecast Discussion
National Weather Service Tallahassee FL
1106 PM EDT Wed Apr 10 2024
...New UPDATE, MARINE, HYDROLOGY...
...ADDITIONAL ROUNDS OF STORMS EXPECTED OVERNIGHT INTO TOMORROW MORNING WITH SEVERE WEATHER AND MORE FLASH FLOODING POSSIBLE...
.UPDATE...
Issued at 1054 PM EDT Wed Apr 10 2024
The main updates to tonight`s forecast were adjusting hourly rain
chances and corresponding wx grids to account for the latest
trends. Widespread rain (heavy at times) with embedded thunder is
ongoing across much of the Tri-State area. This activity has
flourished ahead of an energetic upper cyclone traversing the MS
Valley while aided by a robust low-level jet and localized
mesoscale lows amidst an anomalously moist airmass.
The most prominent impact the past several hrs has
been flooding for parts of the FL Panhandle into SE AL & SW GA
where Flash Flood Warnings are currently in effect. Multiple
ambient weather stations have reported amounts of 3+ inches and
some reports of flooding from Panama City, Dothan, and Rehobeth.
Secondary impacts are strong/gusty winds away from thunderstorms
with a myriad of 40+ gusts being common dating back to the
afternoon, especially along the coast. A Wind Advisory remains in
effect for most of the service area until tomorrow afternoon.
Additional convection is evident just to our west and SW ahead of
the cyclone`s attendant cold front, particularly over the Gulf
where storms are more potent. The latter will be monitored closely
for a secondary severe-weather threat round as it approaches the
coast and spreads inland in a northeastward fashion during the
overnight hrs. Our FL counties appear to be more vulnerable than
locations northward. Damaging gusts and tornadoes remain the
primary threats. Additional rainfall is a concern for areas
already affected from the 1st/ongoing round, though the
FL Big Bend looks to be in the crosshairs for potential flooding.
A Flood Watch remains in effect nearly areawide until tomorrow
afternoon. Please be sure to have ways to be awoken by any
warnings tonight.
&&
.NEAR TERM...
(Through Thursday)
Issued at 149 PM EDT Wed Apr 10 2024
Near: A large mid-upper trough will continue progressing across the
southeast with an attendant surface low currently situated over
western MS. This low should begin occluding to the northeast through
the remainder of today. Southeasterly flow is persisting and will
continue through the duration of the event advecting deep moisture
across the area. As the low occludes, a cold front will extend into
the CWA and serve as the primary forcing mechanism for storms
beginning this afternoon lasting through tomorrow afternoon. Two
rounds of severe are possible with this setup with the first being
the QLCS propagating toward our area and the second occurring
Thursday morning through the afternoon.
For the first part of this system beginning momentarily, the low-
level jet will continue strengthening as the upper trough amplifies
with 850mb winds reaching 70+kts. This will increase bulk shear
substantially across the area with values reaching 60-70kts out of
the west-southwest. Notably large looping hodographs are evident
across the area with high SRH nearing 400m2s2, perhaps higher
locally if surface winds remain out of the southeast. The main
caveat with this setup is instability with MLCAPE values seemingly
struggling to reach 500J/kg as a result of cooler midlevels. Sine
cloud breaks are evident, indicating that instability could rebound
somewhat ahead of the line. Regardless, a high-shear low-CAPE event
appears likely as low-level streamwiseness of the hodographs (0-3km)
is quite textbook, resulting in a tornado threat for the majority of
the area despite meager buoyancy. A couple strong tornadoes (EF-2+)
are also possible across our SE AL and FL Panhandle counties. A
damaging wind threat is also likely given the strong low-level wind
field with this system.
Storms will then dissipate as a brief lull in the LLJ takes place
before ramping up once again with 850mb winds in excess of 70kts as
the cold front traverses the area early tomorrow morning. Storms
will then reinvigorate along the cold front, perhaps maintaining
semi-discrete features as westerly effective shear in excess of
55kts overspreads the region. It appears that a frontal feature will
be lifting over the FL Panhandle and Big Bend as the MCS to the
north dissipates, resulting in instability increasing with MLCAPE
reaching around 1000-1500J/kg and SRH reaching around 400m2s2. This
is indicative of an increasing tornado threat, some possibly strong
(EF-2+), with a particular emphasis for our westernmost FL Panhandle
counties west of the Apalachicola River. A damaging wind threat and
perhaps some hail is also possible as lapse rates steepen with a
push of cooler air aloft steepening lapse rates.
A failure mode exists with the second round of storms. If the
antecedent convection to the north over our SE AL and SW GA counties
produce stronger outflow than forecast, the air farther south may
stabilize enough inland to inhibit convection substantially.
Regardless, an all-hazards threat exists across all of our counties
this afternoon through tomorrow afternoon, especially for our SE AL
and FL Panhandle counties.
WPC currently has all of our SE AL counties, portions of our SW
GA counties, FL Panhandle counties, and portions of our inland FL
Big Bend counties outlined in a Moderate Risk (3/4) for excessive
rainfall with nearly all of our CWA outlined in a Slight Risk
(2/4) for excessive rainfall, excluding the easternmost FL Big
Bend. More on this below in the Hydrology section.
Overnight lows will drop into the mid to upper 60s with highs
tomorrow in the upper 70s to low 80s.
&&
.SHORT TERM...
(Thursday night through Friday night)
Issued at 149 PM EDT Wed Apr 10 2024
Cold front and upper low exits eastward Thursday night with
surface high pressure translating from east Texas into southern
Alabama by Friday night. Decreasing clouds are on tap Thursday
night with sunshine plentiful Friday. Highs will be in the
mid/upper 70s Friday and lows in the upper 40s to lower 50s each
morning.
&&
.LONG TERM...
(Saturday through Tuesday)
Issued at 149 PM EDT Wed Apr 10 2024
Surface high pressure slides off the east coast this weekend while
mid level ridging builds across the eastern third of the US in
response to an upper low racing over the desert southwest at the
beginning of the next work week. Mid level flow will remain mostly
from the northwest, despite a mid level trough moving across the
midwest. The strength of the ridge will deflect the trough to the
north leaving fairly tranquil conditions in the extended. High
temperatures will reach for the mid/upper 80s early next week and
lows will bottom into the mid/upper 50s.
&&
.AVIATION...
(00Z TAFS)
Issued at 742 PM EDT Wed Apr 10 2024
Poor flying conds to continue for much of this TAF period thanks
to widespread SHRA/TSRA with embedded heavy rain, gusty winds,
and low cigs/vsbys (IFR-MVFR). Evening radar has the bulk of the
convection affecting ECP/DHN/ABY. Another round of storms is
expected overnight into the morning hrs and looks to pose a
severe threat from west to east ahead of a front. Used the latest
HRRR to help time the onset of +TSRA via tempo groups. Weather
improves tmrw after FROPA, but gusty west winds are expected.
&&
.MARINE...
Issued at 1054 PM EDT Wed Apr 10 2024
Boating conditions deteriorate overnight ahead of a strong frontal
system poised to sweep through the waters. Maritime convection
associated with this activity will continue to pose a strong wind,
and waterspout threat. Southerly gales, especially gusts, are
still expected away from thunderstorms followed by a sharp wind
shift out of the southwest to westerly in the front`s wake late
tomorrow morning to about midday. Winds should be at or near
advisory levels on Thursday despite improved weather while seas
aim to subside even more slowly. Favorable conditions arrive on
Friday as lighter northerly breezes develop in response to high
pressure building in.
&&
.FIRE WEATHER...
Issued at 149 PM EDT Wed Apr 10 2024
Storms are expected to exit the area by tomorrow afternoon
leaving a wetting rain behind. Following the passage of a cold
front, transport winds 25-30mph out of the west will overspread the
region tomorrow with mixing heights reaching up to 5000ft. This will
yield high to very high dispersions areawide tomorrow afternoon.
High dispersions areawide are also possible on Friday as elevated
transport winds persist out of the northwest. MinRH will drop to
around 40-60% tomorrow afternoon with 30-50% possible Friday.
Otherwise, there are no fire concerns at this time.
&&
.HYDROLOGY...
Issued at 1054 PM EDT Wed Apr 10 2024
Minor to moderate riverine flooding is now forecast for the
Choctawhatchee, Pea, Chipola, Flint, Apalachicola, and Ochlockonee
basins. River Flood Warnings were issued this evening where
confidence is highest based on observed rainfall dating back to
earlier this afternoon. More Flood Warnings are likely tomorrow
morning based on what additional amounts accumulate overnight.
For coastal flooding, a Coastal Flood Warning remains in effect
from Wakulla County eastward to Dixie County. The tide around 4 am
ET Thursday morning is not quite aligned with the peak surge, so
with it being a bit offset, water levels may not get quite as high
as possible, but the strong winds behind the squall line will be
sufficient to produce enough surge combined with a higher high
tide around 2 pm ET to produce water levels of 2 to 4 feet above
normally dry ground within the warning area. A coastal flood
advisory has been issued for areas in Franklin County where water
levels should be slightly less.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is requested. Spotters should safely report
significant weather conditions and/or damage by calling the
office or tweeting us @NWSTallahassee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 66 80 54 77 / 90 80 0 0
Panama City 66 74 58 74 / 90 20 0 0
Dothan 65 75 51 74 / 100 10 0 0
Albany 66 78 52 74 / 100 60 0 0
Valdosta 68 81 54 76 / 90 90 0 0
Cross City 66 77 55 77 / 90 90 0 0
Apalachicola 67 74 59 72 / 90 60 0 0
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through Thursday afternoon for FLZ007>019-026>028-
108-112-114-115-118-127-128.
Wind Advisory until 2 PM EDT /1 PM CDT/ Thursday for FLZ011-013-
016>019-026.
Wind Advisory until 11 AM EDT /10 AM CDT/ Thursday for
FLZ007>010-012-014-015-027-108-112-114-115-118-127.
Wind Advisory from 2 AM to 2 PM EDT Thursday for FLZ028-029-034-
128-134.
High Rip Current Risk through late Friday night for FLZ108-112-
114-115.
High Surf Advisory until 5 AM EDT /4 AM CDT/ Friday for FLZ108-
112-114.
Coastal Flood Advisory until 8 PM EDT Thursday for FLZ115.
High Surf Advisory from 2 AM to 2 PM EDT Thursday for FLZ115.
Coastal Flood Warning until 8 PM EDT Thursday for FLZ118-127-128-
134.
GA...Flood Watch through Thursday afternoon for GAZ120>131-142>148-
155>161.
Wind Advisory until 2 PM EDT Thursday for GAZ123-125-127>131-
142>148-155>161.
AL...Flood Watch through Thursday afternoon for ALZ065>069.
Wind Advisory until 1 PM CDT Thursday for ALZ068-069.
GM...Gale Warning until 3 PM EDT Thursday for GMZ730-755-765-775.
Gale Warning until 10 AM CDT Thursday for GMZ750-752-770-772.
&&
$$
UPDATE...IG3
NEAR TERM...Worster
SHORT TERM...Scholl
LONG TERM....Scholl
AVIATION...IG3
MARINE...Scholl/IG3
FIRE WEATHER...Worster
HYDROLOGY...Godsey/Merrifield/IG3