Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/26/23
Area Forecast Discussion
National Weather Service Boston/Norton MA
1007 PM EDT Mon Sep 25 2023
.SYNOPSIS...
The bulk of the lingering light rain showers will be coming to
an end this evening, but a few showers may linger into early
Tuesday near the southeast New England coast. Building high
pressure over Quebec will provide dry conditions with mild days
and cool nights Wednesday and Thursday. There is a low
probability for rain Friday into early Saturday if low pressure
tracks far enough north, but that remains uncertain. Above
normal temps are likely early next week with dry weather favored
too.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Rainfall continues diminish across southern New England this
evening. Looks worse on radar than it is on the ground, with
hourly rainfall reported as a few hundredths at most. Tweaked
measurable rainfall chances for the next few hours using the
latest runs of the HRRR and NationalBlend. Also made minor
tweaks to temperatures, which should not change much through
morning.
750 PM Update...
* The bulk of the lingering light showers currently south of the
MA Turnpike will come to an end through midnight
* Overnight low temps mainly in the lower to middle 50s with a
breezy NE wind along the coast
Lingering light showers mainly south of I-90 will continue to
diminish from north to south as high pressure across eastern
Canada noses drier air southward. This activity should pretty
much come to an end near or shortly after midnight, except for
a few spotty light showers near the southeast New England coast
that may persist into early Tuesday morning.
Otherwise, pressure gradient will continue to result in NE wind
gusts of 15 to 30 mph overnight with the strongest towards the
Cape and Islands. Despite most of the showers coming to an end,
the moist NE low level flow will keep an abundance of low clouds
in place overnight. The clouds will hold most overnight low
temps into the lower to middle 50s.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Not much change to the overall synoptic pattern Tuesday but the
drying trend outlined in the near term continues as high
pressure builds from north to south. Clouds will likely hang on
for the better part of the day along the south coast, Cape and
Islands, but clearing trend will allow for the development of
abundant sunshine north of the MA Turnpike by tomorrow
afternoon.
Given high pressure builds from the north, the low, and
associated LLJ, will suppress south of southern New England,
yielding a much less breezy day compared to Monday. The wind
gradient will again be from north to south, with E/NE winds
generally less than 10kt north of the Mass Pike and winds
10-20kt south of the I-90 corridor.
Clearing conditions, dropping dewpoints (falling back into the
upper 30s and 40s) and slackening winds will yield prime
radiational cooling conditions overnight Wednesday. It should be
our chilliest night of the season thus far, with upper 30s
possible across the high terrain of western MA and some of our
"radiators". Otherwise, temps will fall back into the 40s away
from the immediate coastline. Utilized a blend of the previous
forecast and consensus MOS guidance to derive overnight lows.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Key Points...
* Dry/Pleasant Wed & Thu with cool nights & mild days
* Low risk for rain sometime Fri into early Sat
* Above normal temps next Sun & Mon with dry weather likely
Details...
Wednesday and Thursday...
High pressure overhead will provide very pleasant late September
weather Wed and Thu. Dry weather will cool nights and mild days.
Lows mainly in the 40s and highs well up into the 60s to near 70.
Friday and Saturday...
Upper level shortwave energy will be approaching from the west
and probably dive southeast of us Fri into Sat. Given that the
system will be diving south of us with the limited baroclinicity
this time of year...odds favor the bulk of the rain remaining
south of our region too. We still can not rule out a period or
two of rain, especially towards the south coast. A few of the
GEFS/EPS/CMC individual ensemble members do show a more wet
scenario. The 12z operational guidance keeps most of the rain
south of our region...except for the 12z ECMWF which is quite
wet Fri into early Sat. Leaning away from the very wet ECMWF and
more dry with perhaps just a glancing blow of rain to parts of
our region. It is still too early to rule out the much wetter
scenarios depicted by the 12z ECMWF and a few individual
ensembles runs if an inverted trough to setup. Temps fairly
seasonable for this time of year with highs mainly in the 60s to
the lower 70s.
Sunday and Monday...
GEFS/EPS ensembles indicate upper level ridging building across
the Great Lakes with 2 meter temperature anomalies well above
normal. Further east into our region, it is not as extreme, but
there are above normal height fields/2 meter temps. So we do
expect above normal temps with highs probably well into the 70s
Sun and especially by Mon. The EPS does indicate some low probs
of 80+ degree highs by Mon, but the magnitude of the warmth will
be determined by how quickly an upper trough off the coast moves
further away.
&&
.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Tonight...High confidence in trends, moderate confidence in
timing.
MVFR ceilings will dominate, but some temporary improvement to
VFR may occur through 06z at some of the terminals. Expect
ceilings to lower again toward daybreak, with perhaps some
localized IFR ceilings. Lingering light showers south of the
MA Turnpike will pretty much come to an end by 06z, except for
a few spotty light showers that may linger towards the southeast
New England coast. NE wind gusts of 15 to 25 knots along the
coast and in parts of the high terrain.
Tuesday and Tuesday night... High confidence in trends,
moderate confidence in timing.
Slow but steady improving trend from mainly MVFR /localized
IFR/ to VFR, from north to south. Several northern terminals
breaking into VFR prior to 16Z, but MVFR will be holding strong
across the Cape and Islands until 20-00Z Wednesday. Mainly dry
outside a few spotty light showers towards the southeast New
England coast Tuesday morning. NE winds gradually subsiding
from gusts 20-25kt to ~15-20kt; highest winds expected along
the South Coast and Islands as LLJ shifts south.
KBOS Terminal...High confidence in trends, moderate confidence
in timing.
KBDL Terminal...High confidence in trends, moderate confidence
in timing.
Outlook /Wednesday through Saturday/...
Wednesday: VFR. Breezy.
Wednesday Night: VFR.
Thursday through Thursday Night: VFR. Breezy.
Friday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHRA.
Friday Night: Mainly VFR, with areas MVFR possible. Breezy.
Slight chance SHRA.
Saturday: Mainly VFR, with local MVFR possible. Breezy.
&&
.MARINE...
Forecaster Confidence Levels:
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Tuesday...High confidence.
NE wind gusts 25-35 kt will continue into tonight. Strongest
gusts will be over portions of the south coastal waters where
Gale warnings are in effect. SCA in place for rest of the
waters. Winds will gradually diminish later tonight into Tue
from north to south with gusts dropping below SCA over eastern
MA waters by Tue, but 25 kt gusts will continue over south
coastal waters.
Outlook /Wednesday through Saturday/...
Wednesday: Winds less than 25 kt. Seas up to 5 ft.
Wednesday Night through Thursday Night: Winds less than 25 kt.
Areas of seas approaching 5 ft.
Friday: Winds less than 25 kt. Areas of seas approaching 5 ft.
Slight chance of rain showers.
Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.
Saturday: Winds less than 25 kt. Seas up to 5 ft. Slight chance
of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 PM EDT Tuesday for ANZ230-231-236.
Small Craft Advisory until 8 PM EDT Tuesday for ANZ232>235-237-
250-251-254.
Gale Warning until 8 AM EDT Tuesday for ANZ255-256.
&&
$$
SYNOPSIS...Frank/KS
NEAR TERM...Belk/Frank
SHORT TERM...KS
LONG TERM...Frank
AVIATION...Belk/Frank/KS
MARINE...Frank/KS
Area Forecast Discussion
National Weather Service Corpus Christi TX
617 PM CDT Mon Sep 25 2023
...New AVIATION...
.SHORT TERM...
(Tonight through Tuesday night)
Issued at 250 PM CDT Mon Sep 25 2023
Key Messages:
- Marginal risk of severe storms over the Victoria Crossroads and
the northern Brush Country tonight.
- Dangerous heat index values of 105 to 110 are possible Tuesday
afternoon
Showers and thunderstorms persist in the Hill Country north of
forecast area, associated with the weak sfc low and the east-west
oriented cold front in West Texas and the Big Bend region. Models
show that the weak sfc trough moves ESE slowly sagging the front
into the Hill Country, allowing showers and thunderstorms to erupt
into the northern Brush Country and the Victoria Crossroads.
However, the models make short work of the convection with the sfc
low/500 mb trough, helping to produce the sfc low, moves to the
east, and the MCS thunderstorms moving down the Rio Grande Plains
from the Big Bend region. This would stretch the forcing out in
two directions, leaving the little support for the storms over the
Brush Country. Most of the models have this scenario, with the
something moving down the Rio Grande, and stopping around Laredo,
before diminishing. gut feeling is for the interior storms to
stop, with a few showers, and thunderstorms along the Coastal
Bend, and in the Rio Grande Plains. Although, will leave isolated
to scattered showers and thunderstorms overnight.
Tuesday, the front will still be over the region, but with the
dynamic forcing to the east over the Gulf, would only expect
isolated to scattered showers and thunderstorms during the
afternoon, and then isolated showers Tuesday night, with the
activity diminishing by Wednesday morning.
&&
.LONG TERM...
(Wednesday through next Sunday)
Issued at 250 PM CDT Mon Sep 25 2023
Key Messages:
- Isolated to scattered showers and thunderstorms possible through
the week, mainly east.
A general westward movement of the mid-level ridge is forecast
through the long term period. This allows conditions to be somewhat
unsettled here with weak shortwaves pushing through our area.
Moisture however is going to be mainly confined to marine areas and
this is where the better (30-40%) chance of rain will be daily. Will
see at least slight chance over land in a mainly typical
diurnal/seabreeze trend though. PWAT values are not impressive...~1.5
for most of the area, but closer to 1.75-2" near the coast later in
the week. NBM PoPs remain way too high for marine areas and have cut
them back quite a bit blending in some other models.
High temperatures daily will come back a bit from what we`re seeing
today, but will stay in the 90s for most of the area through the
week. Heat index values mainly up to 105 at times through the week
and we are crossing our fingers that we can make it through an
entire week without a heat advisory.
&&
.AVIATION...
(00Z TAFS)
Issued at 617 PM CDT Mon Sep 25 2023
The left over frontal boundary, from the upper Texas coast west
into the northern Brush Country to near Eagle Pass, will remain
the focus for convective development this evening. Latest MSAS
analysis shows the stronger low level convergence over the upper
Texas coast where most of the convection resides at this time.
But there is improving low level convergence along a trough axis
that extends southward from Karnes City to George West to
Hebbronville. The latest HRRR seems to be the only CAM model
that has a handle on current convection. HRRR shows convection
will develop north of the Victoria Crossroads later this evening
and move southward into the Coastal Bend. Will show TSRA in VCT
beginning at 02Z and CRP/ALI at 05/06Z respectively. Gusty winds
and MVFR vsbys expected with storms with some areas seeing vsbys
fall to IFR in heavier rain. Not as confident on the convection
reaching the western Brush Country. Will show VCTS in COT TAF this
evening and VCSH at LRD around 06Z. Expect drier air will filter
into northern areas for Tuesday. Isolated to scattered convection
could develop with the sea breeze over the Coastal Bend late
Tuesday afternoon.
&&
.MARINE...
Issued at 250 PM CDT Mon Sep 25 2023
Weak to moderate onshore flow through this evening will become weak
and shift northerly overnight as a weak surface boundary pushes
through. Weak northerly winds will persist through Tuesday before
shifting back onshore and restrengthening to weak to moderate
Tuesday evening. Mainly weak to moderate east to northeast winds
are expected through the end of this week. Isolated to scattered
showers and thunderstorms will be possible daily.
&&
.PRELIMINARY POINT TEMPS/POPS...
Corpus Christi 76 94 75 93 / 40 30 20 30
Victoria 72 93 72 94 / 40 30 20 30
Laredo 76 96 76 97 / 30 30 10 40
Alice 73 97 72 97 / 40 30 10 30
Rockport 75 93 76 92 / 40 30 30 40
Cotulla 75 96 75 97 / 40 30 10 20
Kingsville 74 97 74 96 / 40 30 20 30
Navy Corpus 78 91 78 89 / 40 30 30 40
&&
.CRP WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
SHORT TERM...JSL
LONG TERM....PH
AVIATION...TMT/89
Area Forecast Discussion
National Weather Service Des Moines IA
637 PM CDT Mon Sep 25 2023
...Updated for the 00z Aviation Discussion...
.DISCUSSION.../Tonight through Monday/
Issued at 222 PM CDT Mon Sep 25 2023
Key Messages:
- Scattered showers and thunderstorms mainly northeast linger
through Wednesday
- Warm and dry to finish out the week
Discussion:
The large low pressure system that brought thunderstorms to the area
on Saturday is taking its time exiting the area and will continue to
dominate Iowa conditions through midweek. This is easily viewed on
satellite as the large comma shaped system stands out across the
midwest. Today impacts have largely come in the form of increased
cloudiness across northeast to central Iowa into the afternoon. A
few spotty showers have developed in northeast Iowa, but given
transient nature of the cells and relatively scattered nature,
associated QPF is fairly light. As showers diminish overnight patchy
fog may develop in these areas with light winds and better
available moisture.
The low continues to churn into Tuesday with the center shifting
near to Iowa. This will result in continued scattered showers and
thunderstorms across mainly northeast Iowa. At the same time
vorticity is enhanced within the vicinity of the surface low and 0-
3km CAPE of 100-200+ J/kg is prevalent within CAM data. As such,
should be a decent funnel cloud environment in far northeast
portions of the forecast area, and especially in southern Wisconsin
to northern Illinois, tomorrow afternoon. The RAP highlights this
nicely in the non-supercell tornado product. As is usually the case
with these situations, most funnels will remain just that, but any
landspout tornado that does develop (while weak) could pose a risk
to anyone/thing nearby.
This low finally shifts east starting on Wednesday with
southernly flow cranking up warm air advection into the area.
This will send temperatures into the mid 80s by the end of the
week and weekend, around 10+ degrees above average for this time
of year. Right now the average high for both Des Moines and
Waterloo is 74 degrees. The ridge is stubborn and keeps the area
and warm and dry at least through the weekend, with hints that is
may last well into early October.
&&
.AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/
Issued at 634 PM CDT Mon Sep 25 2023
Showers and isolated thunderstorms will move across northern Iowa
early this evening before diminishing. Stratus will descend south
from Minnesota overnight and will bring lowering cigs that maybe
IFR or lower at times. Some fog is also possible. Conditions will
gradually improve during the day Tuesday though it is possible
MVFR cigs hold on much of the day over the far northern sites.
&&
.CLIMATE...
Issued at 302 AM CDT Mon Sep 25 2023
Climate Prediction Center Temp & Precip Outlooks
6-10 Day / Valid Sep 30-Oct 4
Issued Sep 24
Temp...Very likely above normal
Precip...Leaning above normal
8-14 Day / Valid Oct 2-8
Issued Sep 24
Temp...Likely above normal
Precip...Leaning slightly above normal
3-4 Week / Valid Oct 7-20
Issued Sep 22
Temp & Precip...Equal chances. No discernible trend.
&&
.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
DISCUSSION...Hagenhoff
AVIATION...Donavon
CLIMATE...Small
Area Forecast Discussion
National Weather Service Austin/San Antonio TX
916 PM CDT Mon Sep 25 2023
...New UPDATE...
.UPDATE...
Issued at 916 PM CDT Mon Sep 25 2023
Widely scattered showers and isolated thunderstorms continued near
the Coastal Plains this evening. HRRR appears to the best model this
evening and will generally follow keeping low POPs that area until
Midnight. Otherwise, have removed POPs, although cannot rule out very
isolated showers and perhaps a thunderstorm elsewhere. Re-established
trend to the sensible weather grids.
&&
.SHORT TERM...
(Tonight through Tuesday night)
Issued at 126 PM CDT Mon Sep 25 2023
Synopsis/Mesoanalysis: A highly variable surface pattern is evident
in regional surface observations early this afternoon. Influenced
heavily by both overnight and early morning convection, last night`s
front was analyzed along an approximate Del Rio - Uvalde - Seguin -
Austin line as of 1:00 PM. The Uvalde - Del Rio segment is
attempting to return northward as a warm front, though its forward
progress has been hindered by morning showers, storms, and cloud
cover over the southern Edwards Plateau. The north-south oriented
portion of the boundary running from Seguin to Austin serves as a
rough demarcation between a modestly cooler/drier air mass over Hill
Country, and a hot/muggy regime further east. This has led to the
establishment of an effective warm sector along & east of Interstate
35, where deeper cumulus agitation has been noted over the last
couple hours. Said cumulus have struggled to mature into convection
through 1:00 PM, which is a likely consequence of residual CIN
apparent in both San Antonio and Austin ACARS soundings. Said
stability is further confirmed in visible satellite imagery, which
depicts pockets of gravity waves/bores over portions of the Coastal
Plains at the current hour. This stable layer should erode given
continued daytime heating, with at least scattered convection
becoming possible along/east of I-35 and over the Coastal Plains by
mid afternoon. Additional showers and storms are possible over the
southern Edwards Plateau and Rio Grande through mid-evening, where
the western portion of the front will continue to attempt to advance
north. A few storms could become strong/severe with large hail and
damaging winds being the primary concerns. Locally heavy rainfall is
also possible. Storms should taper near and after midnight. Remnants
of the front will support additional isolated storm potential on
Tuesday, with areas over the Coastal Plains and Rio Grande being
favored. Severe weather is not currently expected in any of the
Tuesday activity.
This Afternoon & Evening: Scattered showers and storms remain
possible over the southern Edwards Plateau, Rio Grande, and
locations along/east of Interstate 35. Given weaker shear in place
across the area, organized severe weather potential is a touch lower
in today`s storms relative to yesterday. Nevertheless, CAPE values
are expected to climb into the 2000-3000+ J/kg range leading up to
storm development, which will likely support at least some hail
potential in the strongest storms that develop. Efficient mixing
will drive steep lapse rates within the boundary layer, which will
result in scattered damaging wind potential as well. We thus can`t
rule out a few strong to severe storms through this evening across
the area. The Storm Prediction Center continues to carry a marginal
(level 1/5) risk for severe weather over the majority of South-
Central Texas given this potential. Minor flooding is also possible
in any heavy downpours, particularly over the southern Edwards
Plateau, where 2-3 inches of rain have already fallen today. The
Weather Prediction Center thus continues a marginal (level 1/4) risk
of excessive rainfall over the southern Edwards Plateau, San Antonio
metro, and Coastal Plains through this evening. Apart from the
shower/storm potential, a few locations across primarily the Coastal
Plains and Rio Grande could see elevated heat indices in the 105-107
range. Practice proper heat safety if spending prolonged periods of
time outdoors in these locations through the rest of this afternoon.
Tomorrow: Anticipate modestly cooler high temperatures areawide with
a post-frontal regime firmly entrenched. Most locations should top
out in the low-mid 90s. Isolated storms will be possible along
remaining wind shifts during the afternoon hours over primarily the
Coastal Plains and Rio Grande. Severe weather is not currently
anticipated.
&&
.LONG TERM...
(Wednesday through Monday)
Issued at 126 PM CDT Mon Sep 25 2023
Any sort of convective activity over locations outside of the Coastal
Plains is unlikely beyond Wednesday afternoon. Weak northwesterly
flow aloft will result in some slight chance PoPs Wednesday
afternoon, which will be primarily driven by daytime heating, but
some weak synoptic support could result in some stronger storms with
gusty winds and small hail.
Thursday through Friday look to be mainly dry, as 500mb ridging
returns, however, not quite as strong. Temperatures will remain above
normal, but more manageable, at least compared to the torture we
endured this Summer. Lower to middle 90s will be common, with some
spots of the Hill Country actually staying below 90 degrees each
afternoon. The Coastal Plains have the best shot at any sort of
precip, with chances for seabreeze showers/isolated thunderstorms
each afternoon Thursday-Friday.
This weekend will perhaps be the start of our next shot at more
widespread precip chances, but how the overall pattern evolves beyond
Saturday is still in question. Both the GEFS and ECM ensembles
indicate southwest flow aloft as long wave troughing develops over
the western CONUS. This will result in a more active jet stream
pattern for South-Central Texas. Meanwhile, the deterministic GFS has
been fairly consistent the last few days in depicting a cutoff low
developing just outside of this forecast, next Monday-Tuesday. This
low could result in increased chances for heavy rainfall, and the WPC
Week 2 Hazards outlook does indicate a slight risk for heavy
precipitation over the Hill Country October 3rd-6th. At this time,
we will take it with a grain of salt, but know that the overall
pattern might finally be tilting more in our favor as we move into
the month of October.
&&
.AVIATION...
(00Z TAFS)
Issued at 639 PM CDT Mon Sep 25 2023
Widely SCT SHRA/ISOLD TSRA are occurring east of I-35 and over the
Edwards Plateau. Have VCSH/VCTS mention at all TAF sites for this
evening. Chances of SHRA/TSRA return Tuesday, however, too low to
mention, at this time. VFR flying conditions prevail tonight through
Tuesday evening. There could be brief lower CIGs/VSBYs in SHRA/TSRA
and a possibility of MVFR CIGs overnight into early morning, however,
chances are too low to mention, at this time. With a chaotic surface
pressure pattern, generally light at 6 KTs or less and VRBL winds
are expected tonight, except briefly gusty near SHRA/TSRA. Winds
increase a little Tuesday, though remain under 10 KTs with NE at the
I-35 sites and E at KDRT.
&&
.PRELIMINARY POINT TEMPS/POPS...
Austin Camp Mabry 72 93 69 95 / 10 10 10 10
Austin Bergstrom Intl Airport 72 92 69 94 / 10 10 10 20
New Braunfels Muni Airport 72 94 70 96 / 10 20 10 20
Burnet Muni Airport 71 92 69 93 / 10 0 0 10
Del Rio Intl Airport 74 94 73 96 / 10 20 10 20
Georgetown Muni Airport 72 92 68 92 / 10 10 0 10
Hondo Muni Airport 71 93 68 94 / 10 20 10 20
San Marcos Muni Airport 70 93 68 94 / 10 10 10 20
La Grange - Fayette Regional 73 91 70 92 / 10 20 10 30
San Antonio Intl Airport 73 93 72 94 / 10 20 10 20
Stinson Muni Airport 75 94 73 95 / 10 20 10 20
&&
.EWX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
Short-Term...04
Long-Term...Gale
Aviation...04
Area Forecast Discussion
National Weather Service Seattle WA
346 PM PDT Mon Sep 25 2023
.SYNOPSIS...A trough of low pressure over the Gulf of Alaska will
swing a series of frontal systems into the region through mid
week. Wet and occasionally breezy weather is expected. Then, a
gradual transition to drier conditions is favorable towards the
weekend as upper-level ridging builds.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY/...500mb analysis depicts a
broad trough of low pressure over the Gulf of Alaska as it ushers
strong SW flow into the region. In sharp contrast, ridging is
experienced downstream over the Intermountain West. Closer to the
surface, a stout 960mb surface low is portioned off the PNW and
BC coast over the NE PAC. Its associated front has pushed well
inland as steadier rain from this morning has become more showery
in nature. A regime of steep low-level lapse rates (6-7.5 C/km)
from the interior to the coastal waters along with upper-troughing
providing PVA/synoptic scale lift within this post-frontal
airmass will help to keep shower chances in the forecast through
tonight. RAP analysis indicates meager SBCAPE values (100-500
J/kg) in the hours ahead so can`t rule out a few thunderstorms for
the remainder of the afternoon into the evening, especially along
the coast. Along with showers, locally breezy winds are possible.
Widespread 50s are in store for overnight lows.
Rain showers and a slight chance (15%) of thunderstorms are again
in the forecast for Tuesday and the remainder of the short term.
The aforementioned upper-trough will continue to direct shortwave
disturbances into our area perturbing the environment. A strong
150 kt jet streak in the 300mb levels will lead to favorable jet
dynamics. Out of this the development of a compact low center over
the open waters will track towards the WA/OR coast by Tuesday
evening. Uncertainly exists in this low feature`s exact track
which in turn will lead to variations in wind forecasts. But,
gusts up to 30-35 mph are currently possible along the coast with
gusts up to 20-25 mph throughout the interior.
As mentioned, rain and showers are likely through Thursday. The
SPC has a general thunderstorm risk for most of western
Washington on Wednesday and with a cool upper-trough directly
overhead on Thursday, can`t rule out an additional slight chance
on this day if enough instability is present. 48-hr forecasted
rainfall totals through Wednesday evening has 2.0-4.0" for the
coast/Olympics, 0.50-1.50" throughout the lowlands and 1-3" for
the Cascades. Highs will remain in the 60s with overnight lows in
the 50s.
.LONG TERM /FRIDAY THROUGH MONDAY/...Ensemble forecasts (GEFS,
EPS, and CMC) are all in agreement of an upper-level ridge
building offshore on Friday before nosing into BC on Saturday. If
the pattern remains on track we could see its influence as
conditions may dry out over the weekend, allowing a brief
reprieve from rainfall. However, ridging may flatten going into
the beginning of next week. Here, we could see the pattern re-
amplify as rain chances return. Slightly below normal temperatures
are expected through the long term period.
McMillian
&&
.AVIATION...A deep upper level low brings strong southwesterly flow
over Western Washington that will weaken overnight. A cold front is
currently making its way across the area, bringing with it scattered
showers. A few thunderstorms are possible, especially along the
coast as the airmass is somewhat unstable.
Ceilings continue to remain around 4000 to 8000 feet this evening,
with lower ceilings along the coast. Winds are south to
southwesterly at 5-10 kt, gusty in some places A break in the rain
and gusty winds is likely overnight. Gusty southerly winds, showers,
and a possible isolated thunderstorm return again during the day
tomorrow.
KSEA...Ceiling at around 7000 ft, with southwesterly winds around 5
kt and some light showers in the area. Winds should maintain
southerly around 5-10 kt, with a break in showers overnight. Showers
and southerly winds 10-15 kt return tomorrow, with ceilings lowering
to around 3000-5000 ft tomorrow morning.
LH
&&
.MARINE...A 960 mb low is currently centered west of the region but
will begin to weaken and drift north tonight. A few isolated
thunderstorms have developed over the coastal waters, but activity
should diminish into tonight. Thunderstorms are again possible
Tuesday. These thunderstorms do have the potential to produce a
waterspout, but any should be weak and short-lived.
Another low pressure system will develop overnight Tuesday and swing
across the area Wednesday morning. Models differ on the exact track,
but gusty winds and the potential for few thunderstorms in the
coastal waters will be reinforced with this system. A weak low
swings south of the region Thursday before high pressure returns and
dominates into the weekend.
Gale force winds over the coastal waters will back down to Small
Craft Advisory levels tonight into Wednesday. Small Craft Advisory
conditions continue for the Strait of Juan de Fuca, Admiralty Inlet,
and the Northern Inland Waters until Tuesday afternoon. A brief
period of gusty winds up to Small Craft criteria are possible
Tuesday morning into the early afternoon for northern Puget Sound.
Seas ranging from 15 to 20 ft will continue tonight Tuesday, then
begin to quickly decline Wednesday into Thursday, where seas ease to
6-9 ft into the weekend.
LH
&&
.HYDROLOGY...Widespread rainfall amounts through Wednesday evening
of at least 1-2" inches possible across the lowlands, 1-3 inches
possible over the coast and Cascades, and 3-4 inches over the
Olympic mountain river basins. River flooding is not currently
forecast thanks to the dry antecedent conditions, but attention
will need to be paid to the Skokomish and also for rainfall rates
over burn scars.
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...None.
PZ...Small Craft Advisory until 6 PM PDT Tuesday for East Entrance
U.S. Waters Strait Of Juan De Fuca-Grays Harbor Bar.
Small Craft Advisory until 6 PM PDT Tuesday for Admiralty Inlet-
Central U.S. Waters Strait Of Juan De Fuca-Northern Inland
Waters Including The San Juan Islands-West Entrance U.S.
Waters Strait Of Juan De Fuca.
Gale Warning until 2 PM PDT this afternoon for East Entrance
U.S. Waters Strait Of Juan De Fuca.
Small Craft Advisory from 2 AM to 2 PM PDT Tuesday for Puget
Sound and Hood Canal.
Gale Warning until 6 PM PDT this evening for Coastal Waters From
Cape Flattery To James Island Out 10 Nm-Coastal Waters From
James Island To Point Grenville Out 10 Nm-Coastal Waters
From Point Grenville To Cape Shoalwater Out 10 Nm.
Small Craft Advisory from 6 PM this evening to 6 PM PDT Tuesday
for Coastal Waters From Cape Flattery To James Island Out
10 Nm-Coastal Waters From James Island To Point Grenville
Out 10 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater Out 10 Nm.
Gale Warning until 2 AM PDT Tuesday for Coastal Waters From Cape
Flattery To James Island 10 To 60 Nm-Coastal Waters From
James Island To Point Grenville 10 To 60 Nm-Coastal Waters
From Point Grenville To Cape Shoalwater 10 To 60 Nm.
Small Craft Advisory from 2 AM to 6 PM PDT Tuesday for Coastal
Waters From Cape Flattery To James Island 10 To 60 Nm-
Coastal Waters From James Island To Point Grenville 10 To
60 Nm-Coastal Waters From Point Grenville To Cape
Shoalwater 10 To 60 Nm.
&&
$$
Area Forecast Discussion
National Weather Service Tallahassee FL
1000 PM EDT Mon Sep 25 2023
...New UPDATE, MARINE...
.UPDATE...
Issued at 1000 PM EDT Mon Sep 25 2023
Convection will start to blossom over the Gulf waters during the
next few hours, deep moisture over the Big Bend region slowly
advances northwest. Heavy rain is expected by sunrise over the
Forgotten Coast, but recent runs of the HRRR and other CAMS
guidance point to the heavy rain potential further west along the
Emerald Coast.
&&
.NEAR TERM...
(Through Tuesday)
Issued at 356 PM EDT Mon Sep 25 2023
A PV streamer coming off the far northern periphery of the tropical
wave, currently moving westward across the Gulf, will move northward
across our region tonight into tomorrow. This will overlap with a PV
streamer coming in from the NW associated with a trough moving
across the Great Lakes region. Both of these will provide enhanced
forcing for ascent, which when coupled with PWATs near or above two
inches will lead to the possibility for heavy downpours. There
doesn`t appear to be much shear and lapse rates appear to be more on
the moist side, which makes sense given the environment. Thus,
primary concerns would be gusty winds and torrential rainfall. Areas
along the FL Big Bend and SW Georgia are currently the areas to
watch as higher PWATs lie in this region with lower PWATs to the NW.
Expect daytime highs generally in the mid to upper 80s with
overnight lows in the upper 60s to low 70s.
&&
.SHORT TERM...
(Tuesday night through Wednesday night)
Issued at 356 PM EDT Mon Sep 25 2023
An unseasonably moist airmass coupled with modest height falls aloft
and an approaching frontal boundary from the north maintains high
rain chances across the region through the short-term period.
Widespread cloud cover with areas of precipitation are expected.
Heavy rainfall leading to instances of isolated flash flooding
will continue to be the primary concern, though a few robust
thunderstorms capable of strong/gusty winds or even isolated
water- loading microbursts would not be surprising. Modeled
soundings depict long-skinny CAPE profiles, modest deep-layer
shear around 20- 25 kts, and very high Precipitable Waters of >2"
- supportive of the aforementioned threats. The latter flirts with
daily record values, per SPC sounding climo for KTLH. Greatest
potential for the wettest weather is across the FL counties,
especially in the Big Bend and near the coast. A Marginal Risk
(level 1 of 4) for excessive rainfall by the WPC remains in place
across much of the Tri-State area. Forecast temperatures have
highs in the low-mid 80s and lows ranging from the upper 60s to
low 70s.
&&
.LONG TERM...
(Thursday through Sunday)
Issued at 356 PM EDT Mon Sep 25 2023
Frontal boundary continues to sag southward late this week with
surface high pressure building in its wake. Meanwhile, large-scale
troughing scoots eastward toward the Mid-Atlantic region in response
to a building ridge across the middle of the US. This synoptic setup
supports continued elevated rain chances in the forecast, but more
focused along the Interstate corridors (especially I-10, southward)
into the weekend thanks to a likely meridional moisture gradient.
Looking ahead, details in the large-scale pattern become a bit
murky. In general, the building ridge noses into the Great Lakes
while the departing upper trough attempts to cut off over the
West/NW Atlantic. However, global models differ on the placement of
this feature. Further complicating matters is the potential for a
wave of low pressure to develop along the sagging front over the
Gulf. The deterministic 12Z GFS is a drier solution compared to the
12Z ECMWF given that the developing low tracks SW towards the GA/FL
coast and ushers reinforcing dry northeasterly flow into our area on
its left flank.
Forecast high temperatures are in the 80s with Thursday being the
coolest of the period given the expected cloud coverage and
precipitation. Overnight lows drop to the 60s. Locations north of I-
10 look to see readings down to the low 60s by Monday morning.
&&
.AVIATION...
(00Z TAFS)
Issued at 726 PM EDT Mon Sep 25 2023
Overnight, expect sub-MVFR cigs to set in 08Z-10Z at TLH and VLD,
with a period of LIFR cigs and fog at VLD around 12Z. At ECP, MVFR
cigs are forecast to begin around 12Z. There is some uncertainty
in the timing of cigs lowering, especially at ECP which is closer
to the fringe of the low clouds. Precip will overspread previously
mentioned terminals on Tuesday, with SHRA and thunder in the vcty
most of the day. Greatest coverage will be at TLH and VLD, with
lower confidence on north and west extent, especially into ABY and
DHN. For both of those terminals, we kept activity in the vcty
for now. It`s also questionable how quickly precip exits portions
of the region, especially ECP and TLH, where we end it by 21Z attm.
Another challenge is how quickly cigs rise during the morning/aftn.
While confidence in timing category transitions is low (e.g.,
MVFR to VFR), we are confident that cigs will be slow to rise
during the day. Winds generally out of an easterly direction.
&&
.MARINE...
Issued at 1000 PM EDT Mon Sep 25 2023
An inverted trough of low pressure will slowly track westward to
the south of the Panhandle waters through Tuesday, followed by
southeast breezes. Numerous thunderstorms through about Thursday
will pose the risk of gusty winds, lightning strikes, and
potential waterspouts. Around Wednesday and Wednesday night, a
cold front will back in from the northeast. Northeast winds will
freshen, possibly becoming strong at times from Thursday night
through Saturday.
&&
.FIRE WEATHER...
Issued at 356 PM EDT Mon Sep 25 2023
Moisture is on the rise over the next few days as we transition to a
wet pattern through Thursday. There are currently no fire weather
concerns.
&&
.HYDROLOGY...
Issued at 356 PM EDT Mon Sep 25 2023
Wet weather is expected for at least the next 3 days thanks to a
rapidly moistening airmass and approaching front through mid-week.
Much of the Tri-State area is under a Marginal Risk for excessive
rainfall from Tuesday AM to Thursday AM. Isolated flash flooding
is a distinct possibility in response to torrential rain rates
and/or slow-moving, backbuilding storms. The most vulnerable
locations are in the Eastern FL Big Bend (including the coast) and
South- Central GA.
Guidance has painted much of our FL counties as focal points for the
heaviest rain. Local CAMS depict 2-day high probabilities for 3"
across much of the region and 6" along the coast. There are even
some non-zero probs for 9+" south of the Apalachicola Nat`l Forest!
The 48-hr worst case scenario shows values in excess of 4" roughly
along and south of Tallahassee. Meanwhile, the current HREF places
the greatest probabilities across the Forgotten Coast for amounts of
3-5+" over the next 24 hrs. Forecast amounts through late Thursday
are 1-3" (isolated higher).
In terms of rivers, only Aucilla - Lamont (US 27) is in action
stage, but forecast to fall below 51 ft by Wednesday afternoon. The
heaviest rainfall should be spotty enough to preclude river
flooding, especially given recent dry conditions.
&&
.SPOTTER INFORMATION STATEMENT...
Spotter activation is not requested. However, spotters are always
encouraged to safely report significant weather conditions when they
occur by calling the office or tweeting us @NWSTallahassee.
&&
.PRELIMINARY POINT TEMPS/POPS...
Tallahassee 72 85 72 82 / 40 70 60 80
Panama City 72 85 73 84 / 40 70 70 70
Dothan 67 86 70 83 / 0 50 40 70
Albany 67 87 71 82 / 10 50 50 70
Valdosta 70 85 71 81 / 30 80 60 80
Cross City 71 88 72 86 / 40 90 60 80
Apalachicola 74 84 74 83 / 70 80 70 80
&&
.TAE WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AL...None.
GM...None.
&&
$$
NEAR TERM...Oliver
SHORT TERM...IG3
LONG TERM....IG3
AVIATION...LF
MARINE...IG3
FIRE WEATHER...Oliver
HYDROLOGY...IG3