Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/17/23
AREA FORECAST DISCUSSION
National Weather Service Wakefield VA
957 PM EST Sat Dec 16 2023
.SYNOPSIS...
A strong area of low pressure approaches from the Gulf of Mexico
overnight through Sunday night, tracking near the coast. This
storm system will bring widespread moderate to heavy rain,
strong winds, and coastal flooding to the area from Sunday into
early Monday. High pressure moves in behind the storm system
with drier weather expected from mid to late week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
As of 955 PM EST Saturday...
Late this evening, sfc high pressure was located over the Canadian
Maritimes. Meanwhile, sfc low pressure was over the ern Gulf of
Mexico and will continue to move NE towards central FL overnight.
Increasing and thickening high clouds were streaming nwrd into
the region. Temps were ranging from the upper 30s to the upper
40s. Clouds were thicken and lower overnight, with light rain
possibly moving into far SW counties near sunrise. Temps will
bottom out in the next couple of hours, then start to rise
toward morning.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/...
As of 400 PM EST Saturday...
Conditions deteriorate Sun into Sun night as a strong area of low
pressure tracks up the coast toward the local area. While the global
models have essentially come into agreement that the low (~985mb)
will track over NE NC and Hampton Roads and continue NNE up the
coast Sunday night, the high res models continue to take a further
inland track. However, will note that the 18z NAM and HRRR have
trended further E and are closer to the global models (which
synoptically makes more sense). Ahead of the low, deep moisture
streams into the region Sun-Sun night with PWATs increasing to 1.4-
1.8" (quite anomalous for December). This will bring widespread
moderate to locally heavy rainfall across the entire area. WPC
has the entire area in a Slight ERO for Sun-Sun night with
urban/poor drainage areas likely having the highest risk to see
localized flooding. Ensembles remain quite impressive with storm
total rainfall totals, with both the 12z GEFS and EPS QPF means
showing a widespread 2-3" of rain with the highest totals along
and E of the I- 95 corridor. Do anticipate there will be a band
of heavier precip to the NW of the low (due to F-gen) and a
band of stronger convection along and N of the occluded front.
Stronger convection along the occluded front may result in
1-2"/hr rates with total QPF of 3-4" for some. This band of
heavier QPF may set up over a similar area which saw 3-4" of
rain last week (Dec 10-11th). It is over this area where the
threat of flash flooding is highest due to a combination of more
saturated soils and collocation with urban areas with poor
drainage. As such, have issued a Flood Watch from the I-95
corridor E with the greatest threat in the Richmond Metro/Tri-
Cities and over Hampton Roads.
In addition to the heavy rain threat, the potential for very breezy
to windy conditions late Sun into Sun night exists with wind gusts
40-50 mph possible along/near the coast and 25-40 mph further
inland, as the low tracks north and deepens. As such, have expanded
Wind Advisories for the Atlantic coastal zones and for the W side of
the Ches Bay (where locations are exposed to wind off the bay).
Have also maintained a low chance for thunder Sun evening associated
with convection along the occluded front as guidance continues to
indicate elevated instability due to the fgen and occluded
front. Given the impressive wind field and large scale forcing,
the SPC has maintained the marginal risk into Hampton Roads for
isolated damaging winds with stronger storms that may develop.
Highs Sun in the low-mid 50s W to the mid 60s SE with the warmest
temps Sun evening/night as the occluded front lifts into the area.
Rain exits from SW to NE Sun night into Mon morning with lows Sun
night in the upper 40s W to mid 50s E. Remaining breezy to windy Mon
with W winds likely gusting around 30 to 40 mph inland and 40+ mph
along the coast. Highs Mon in the mid 50s W to lower 60s E. A strong
shortwave pivots into the region late Mon into Tue, but confidence
is low that we will be able to squeeze much moisture out of it due
to dry westerly flow and forecast soundings. The best chance to see
a stray rain/snow shower will be over the MD Eastern Shore with
lower chances across E VA and NE NC Mon night. Not expecting
accumulation with this activity, but we will continue to monitor the
trends. Lows Mon night in the upper 20s W to lower 30s E. A
reinforcing shot of dry, cold air arrives Tues with gusty NW winds
yet again (~30 mph gusts inland and 30-40 mph gusts along the coast)
and highs in the low-mid 40s. Lows Tue night will be very cold as
high pressure builds in with temps in the upper teens W to low-mid
20s E and mid-upper 20s along the coast.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 405 PM EST Saturday...
Dry weather returns from Wed through Sat with high pressure
dominating the local weather. Highs in the mid-upper 40s Wed, low-
mid 50s Thu, and upper 40s NE to low-mid 50s SW Fri and Sat. Lows in
the lower 20s W to upper 20s E Wed night, mid 20s W to low-mid 30s E
Thu night, upper 20s W to low-mid 30s E Fri night, and lower 30s W
to mid-upper 30s E Sat night.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
As of 715 PM EST Saturday...
Strong high pressure will slide ewrd into the nrn Atlantic
tonight into Sun morning. Meanwhile, low pressure over the ern
Gulf of Mexico will track NNE while strengthening tonight
through Sun. As such, expect increasing and lowering clouds from
this evening into Sun morning, with VFR CIGs possibly becoming
MVFR at all TAF sites but SBY. Conditions then deteriorate Sun
morning into Sun evening, as the low pressure system approaches
from the S with CIGs dropping to MVFR then IFR/LIFR with rain
moving in from S to N. Winds remain light and variable through
tonight before becoming E or SE and strengthening during Sun,
esply near/along the coast.
Low pressure will continue to impact the area Sun evening into
early Mon morning, with IFR CIGs and/or VIS due to moderate to
heavy (at times) rain. Strong low level wind shear is also
expected. High pressure returns by later Tue.
&&
.MARINE...
As of 420 PM EST Saturday...
Gale Warnings remain in effect for the entire marine area,
starting 18-21z/1-4 PM Sunday and continuing through Monday
afternoon. The strongest winds are expected Sunday evening from
the SE, with winds shifting to the SSW overnight, and then to
the W-WNW Monday. The Gale Warnings cover both of these wind
directions. Sub- advisory conditions will continue to prevail
through most of Sunday morning before conditions rapidly
deteriorate Sunday later aftn into Sunday evening. Winds will be
ENE tonight at 5-10kt, veering to the E and increasing to 10-15
kt by 12z/7 AM Sunday. Low pressure over the Gulf of Mexico will
slowly deepen this evening, and will then rapidly intensify
as it tracks NNE from Florida to SE VA/NE NC from Sunday-early
Monday AM. There is decent model consensus with respect to the
track, with some of the CAMs still farther inland but all global
models are closer to the coast. Regardless, impressive pressure
falls on the order of 12-15mb/6 hr in advance of the low will
allow for winds to rapidly increase as the low approaches later
Sunday.
Winds become ESE by late Sunday afternoon and increase to 25-30
kt (with 35-40 kt gusts) over the lower bay/srn coastal waters.
Gale force gusts will begin across the northern waters by early
Sunday evening. Winds are expected to peak between 7 PM-
midnight south/10 PM-3 AM north after the wind direction veers
to the SE. During this time, winds will average 30-35 kt with
gusts around 45 kt (slightly less on the rivers). There will
likely be a few gusts to 50 kt or higher, and will continue the
mention in the MWW after collaboration with neighboring
offices. In addition, there is a low (but non-zero) chance of
tstms which could produce 50+ kt gusts late Sun evening-early
Mon AM. Local wind probabilities have a ~2 hour period of 30-50%
probs for 48 kt gusts on the southern ocean/20-40% northern
Ocean/10-20% on the bay during the 9 PM-3 AM timeframe. As the
low pulls away to the N, winds turn to W 25-30 kt with gusts to
35-40 kt Mon morning across all the local waters. As such,
keeping the Gale Warnings through Monday in all marine zones to
account for this. Winds remain solidly SCA criteria through
Tuesday night with winds becoming NW 20-25 kt with gusts to 30
kt late Mon night- Tue. High pressure builds in by midweek with
lighter winds expected.
Waves and seas build to 4-9 ft and 12-18 ft Sun night during the
height of the event. As such, a High Surf Advisory has been issued
for coastal locations from Sun aftn-Mon aftn. Seas remain elevated
above SCA criteria through the remainder of the forecast period.
&&
.TIDES/COASTAL FLOODING...
As of 430 PM EST Saturday...
Strong low pressure approaches the area Sunday into Sunday night.
Strong east/southeast winds in advance of the low will allow water
levels to rise in the Chesapeake Bay and tidal rivers as well as the
Albemarle Sound. Given low astronomical tides, nuisance to minor
tidal flooding is expected during the high tide cycle Sunday evening
in most areas. The exception to this will be in areas along the
north side of the Albemarle Sound (Edenton- Elizabeth City) in
addition to the Back Bay area of VA Beach. Water levels may
exceed moderate flood thresholds in these areas Sunday evening
(due to the strong SE winds) before falling Sunday night as
winds become SW then W. Will maintain the Coastal Flood Watch
for these areas from Sun aftn-Sun night. Will keep water levels
relatively consistent with the previous forecast even though the
12z ETSS forecast water levels are slightly lower than the 00z
ETSS water level forecasts for most areas.
When winds become SW-W as the low passes by early Monday morning,
there will likely be a rapid increase in water levels on the bay
side of the MD Ern Shore (from Cambridge to Crisfield). These areas
(in addition to Lewisetta) have the potential to see moderate tidal
flooding during the high tide cycle early/mid Monday morning. As
such, have issued a Coastal Flood Watch for Dorchester, Wicomico,
and Somerset Counties early Monday morning-midday and for the
northern Neck including Lewisetta. No worse than minor tidal
flooding is expected in other areas adjacent to the Ches
Bay/Atlantic Ocean, but have added Coastal Flood Advisories to
areas along the Bay and the James/York/Rappahannock to include
the lower Peninsula/Peninsula/and the VA eastern shore.
Portions of southside Hampton Roads such as Sewells and Money Pt
likely stay just below flood stage.
&&
.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...Flood Watch from Sunday afternoon through late Sunday night
for MDZ021>025.
Coastal Flood Watch from late Sunday night through Monday
morning for MDZ021>023.
Wind Advisory from 7 PM Sunday to 7 AM EST Monday for MDZ024-
025.
Coastal Flood Advisory from 9 PM Sunday to 5 AM EST Monday for
MDZ024.
High Surf Advisory from 7 PM Sunday to 4 PM EST Monday for
MDZ025.
NC...Flood Watch from Sunday afternoon through late Sunday night
for NCZ012>017-030>032-102.
Coastal Flood Watch from Sunday afternoon through Monday
morning for NCZ015>017-030>032-102.
Wind Advisory from 4 PM Sunday to 7 AM EST Monday for NCZ017-
102.
High Surf Advisory from 4 PM Sunday to 4 PM EST Monday for
NCZ102.
VA...Flood Watch from Sunday afternoon through late Sunday night
for VAZ064-075>078-082>086-090-099-100-511>523.
Wind Advisory from 7 PM Sunday to 7 AM EST Monday for VAZ099-
100.
Coastal Flood Advisory from 9 PM Sunday to 5 AM EST Monday for
VAZ099-100.
High Surf Advisory from 7 PM Sunday to 4 PM EST Monday for
VAZ099-100.
Flood Watch from Sunday afternoon through late Sunday night
for VAZ079>081-087>089-092-093-095>098-524-525.
Coastal Flood Watch from Sunday afternoon through Monday
morning for VAZ098.
Wind Advisory from 4 PM Sunday to 7 AM EST Monday for VAZ095-
097-098.
High Surf Advisory from 4 PM Sunday to 4 PM EST Monday for
VAZ098.
Coastal Flood Watch from Sunday evening through Monday morning
for VAZ075-077.
Wind Advisory from 7 PM Sunday to 4 AM EST Monday for VAZ077-
078-084>086-523>525.
Coastal Flood Advisory from 11 PM Sunday to 7 AM EST Monday
for VAZ078-084>086-089-093-095>097-523>525.
MARINE...Gale Warning from 4 PM Sunday to 1 PM EST Monday for ANZ630-
631-635>637.
Gale Warning from 1 PM Sunday to 1 PM EST Monday for
ANZ632>634-638-656-658.
Gale Warning from 4 PM Sunday to 4 PM EST Monday for ANZ650-
652-654.
&&
$$
SYNOPSIS...RMM/TMG
NEAR TERM...RMM/TMG
SHORT TERM...RMM
LONG TERM...RMM
AVIATION...RMM/TMG
MARINE...AJZ/LKB
TIDES/COASTAL FLOODING...AKQ
Area Forecast Discussion
National Weather Service La Crosse WI
950 PM CST Sat Dec 16 2023
.KEY MESSAGES...
- Rain will remain mainly in WI and far eastern IA through early
evening before moving east. Fog, possibly dense in Wisconsin,
is expected overnight with such moist conditions and light
winds.
- On Sunday night a strong cold front will bring (vigorous?)
snow showers, falling temperatures, and wind gusts in the
30-45 mph range. This has trended up for impact...with lasting
effects into Monday...including single digit wind chills.
- Unusual warmth builds back into the area quickly for the
remainder of the week with Wednesday into the weekend looking
like 35-45F for highs. There are also some probabilities
(5-10%) for 50F+ on and south of I-90 as well! Rain chances
return late in the week.
&&
.DISCUSSION...
Issued at 241 PM CST Sat Dec 16 2023
Tonight: Rain ending, Fog possible, possibly dense
Moisture continues to stream into the region ahead of a low
pressure system shifting northeast out of Iowa. This moisture
stream has precipitable water values were near record (~93rd
percentile) for this time of year (KDVN, 12Z). Surface analysis
showed low pressure in east-central Iowa heading for Wisconsin
where model guidance suggests it will be more of an open trough.
Until that time, bands of precipitation will rotate northward
with a deformation band setting up on the west side of the low
center. This would target a Wisconsin Rapids to north of Cedar
Rapids IA enhanced band of rain through early evening, with
showers and drizzle to its east. Overnight, troughing will give
way to weak surface ridge building and a baggy pressure
gradient. With all of the rain and surface moisture available,
fog is likely with a reduction to visibility overnight,
persisting in Wisconsin. 16Z HREF visibility probabilities for
<1/4 mile visibility was mid-range (40-50%) over much of
northern into southwest WI. The latest NBM probabilities for IFR
suggest northern WI may be most prone to lower visibilities.
So, will need to monitor for dense fog formation overnight.
Sunday Night and Monday: Much colder, brisk, snow showers
A strong cold front and stronger shortwave trough is still forecast
to swiftly move through the area Sunday night with lasting effects
into Monday. This shortwave trough has the tropopause descending
to nearly 700mb per the latest RAP runs...good for forcing and
also enhancement of wind gusts on the southwest flank /northeast
IA/. The forecast trends for the instability depth have
steadily increased since yesterday (doubled), as 0-2km lapse
rates approach 8C/Km by late evening behind the front. MUCAPE is
also present /50-100J/Kg range/. However, there is a bit of
spread in the thermodynamics environments and instability which
mainly affects the western extent with the RAP/HRRR solutions
targeting southern MN/IA with more overall = higher shower
chances. The 16.06Z EC EPS would support that with 40-60%
chances of 0.01"+ in that area, increasing to 80%+ northeast of
I-94. Thus, have increased snow chances to the 30-40% range for
Sunday night (mainly near and north of I-90). Winds will also
increase in the mixed layer overnight with areas south and west
of La Crosse favored. 925 mb winds increase post-frontally (by
12 am Monday) into the 33-43kt range (within that mixed layer),
and with subsidence in the tropopause fold in that area and
unidirectional winds, feeling an overachieve is possible. 16.12Z
HREF CAMS have a 70-80% (30-50%) chance of 35 (40) mph+ gusts
in MN/IA and southwest WI with the main high gust timing from
3-9 am Monday.
All of these elements do raise the thought of more impact with
vigorous snow showers, gusts at least in the 30s mph, and flash
freeze. Will have to monitor this overnight period, and it
appears the snow showers will move east by 3 am or so with winds
increasing near that time or after. Accumulations have been
increased to less than 1/2" north of I-94. Wind chills Monday
will be in the single digits above zero...something we need to
message for the public to prepare for after a warm first half of
December.
An Unusually Warm Week, Dry
Large scale ridging dominates the week after Monday with unusual
warmth. While increasing spread occurs in the temperature forecast
from Wednesday on, the centered 50% of the forecast population
in the 16.00Z Grand Ensemble is in the 35-45F range roughly
through Christmas. There is agreement on a shortwave trough
ejecting eastward in the flat flow for late in the week but
considerable spread exists on the northern extent to the
precipitation schield. There are low chances of precipitation,
and temperatures would mainly be warm enough for rain. So,
travel does not look to be impacted unless a cold air source
can be found (unlikely).
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 950 PM CST Sat Dec 16 2023
CIGS: LIFR/IFR will hold through the nighttime hours with
improvement to at least MVFR by late morning (after 15z ish) Sun.
Short term guidance continues to suggest a brief period of
scattered/VFR late afternoon/early evening (perhaps a 2-4 hour
window) before next weather system returns at least MVFR cigs for
Sunday night. Will add in a period of VFR cigs late afternoon/early
afternoon with this continued signal. MVFR looks to return before
06z Mon.
WX/vsby: fog will persist through the overnight hours, but trends
favor some improvement (into MVFR) as winds increase from the west
overnight. HREF and a few of the CAMS models continue to hold
thicker (sub 1SM) fog across southwest and north-central WI, but
also across southeast MN. Will hold lower vsbys at KRST longer into
the night with this in mind. Expect VFR vsbys by mid morning Sun.
Come Sun night, an upper level shortwave trough bears down on the
region, and scattered/widespread showers looking like a decent bet
(30-60%). Temp profile would favor snow with quick, but temporary
reductions in vsby with any shower.
WINDS: generally light with a swing to the west as the night wears
on. Pressure gradient starts to tighten by Sunday night and expect
widespread strong/gusty winds northwest winds (15-25kt gusts 25-
35kt). Unidirectional in the vertical through at least 5 kft.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
DISCUSSION...Baumgardt
AVIATION.....Rieck
Area Forecast Discussion
National Weather Service Dodge City KS
513 PM CST Sat Dec 16 2023
.KEY MESSAGES...
- A mild stretch for mid December through at least early next
week.
- Limited areal coverage rain chances return Thursday and then again,
more widespread chances on Saturday.
&&
.SHORT TERM /THROUGH SUNDAY/...
Issued at 214 AM CST Sat Dec 16 2023
Multispectral GOES satellite imagery was still showing a little
snow cover over the Colorado/Kansas state line in northwest
Hamilton county and northward, and a rapidly melting patch in
southern Ford county this morning. Surface high pressure
extending deep into the Southern Plains will maintain a weak
western surface wind field across western Kansas Through Today
and Tonight. Similar overnight lows to last night can be
anticipated Tonight, generally in the mid to upper 20s area-
wide. Fog may develop across the south central Kansas counties.,
say anywhere favoring the highway 183 corridor. Locally dense
fog while not out the question, is not anticipated to become
widespread over the area based on the numerical model output
this afternoon. However, the area along the Oklahoma state line
is favored by the HRRR model, or basically the highway 160
corridor from around midnight through 8 am Sunday.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 244 AM CST Sat Dec 16 2023
Minimal modification to the airmass is seen this weekend. Highs
across the area Sunday will be marginally higher, and probably
still in the 50s for most locations – which is still 10-15 F
degrees warmer than normal for the middle of December. The mild
regime continues Monday albeit a few degrees cooler in the upper
40s/50s as the surface front of another pacific high pressure
slips into the region. The region will remain dry through at
least Thursday as the next warm conveyor belt develops, most
probably a rain episode across the Southern Plains. This episode
does not look promising for widespread wetting rains for our
area as the ecmwf ensembles offer up at least one half of the
ensemble members focusing the rains east of Barber county.
Seemingly a better opportunity for another more widespread
rainfall may come with the second westerly low that, based on
the GEFS and EC 500 mb flow ensemble means, appears to cutoff
across the southwest U.S. again as it moves toward the southern
Plains during the latter part of the weekend, with widespread
lift and moisture advection. The GFS ensembles with this even
show about half of the members supporting about a quarter to one
half inch of rain for much of the DDC forecast area. These
members also, again prefer a warm weather solution with
absolutely no supporting snow ratios large enough for any snow
at all.
&&
.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 509 PM CST Sat Dec 16 2023
Aviation weather will be very good through this TAF period with
fairly light winds and widespread VFR flight category expected
under clear skies. Patchy morning fog cannot be ruled out
briefly at DDC and/or HYS, but the greater chance of that will
be farther east across central and south central Kansas. A
slight wind shift in speed and direction is expected mid to late
morning Sunday with winds coming from the north-northwest at 10
to 15 knots.
&&
.DDC WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Russell
LONG TERM...Russell
AVIATION...Umscheid
Area Forecast Discussion
National Weather Service Duluth MN
525 PM CST Sat Dec 16 2023
.KEY MESSAGES...
- Dense fog this afternoon and overnight.
- Snow showers Sunday and Sunday evening with accumulations
generally under a half an inch.
- South Shore lake effect snow Sunday into Monday.
- Cooler Monday then warming above normal for the remainder of
the week.
&&
.DISCUSSION...
Issued at 301 PM CST Sat Dec 16 2023
Some shower activity is out there as a system depart to the east
this afternoon. In its wake, a saturated air mass is resulting
in fog near the Brainerd lakes area and spotty mixed precip
types. Visibilities are expected to improve a little this
afternoon before gelling back up overnight. Issued a Dense Fog
Advisory to cover this for now through midnight. Confidence may
increase in coverage overnight with the HRRR suggesting that the
fog begins to advect/form eastward through the night. Thus, the
area of the advisory may need to be expanded east as the night
progresses.
The next item up is a weak short wave that will increase shower
activity on Sunday into Sunday night and with cold air in place
it should be snow showers. QPF is lacking so only a nominal
amount of accumulation with most places not seeing more than an
inch. This wave will be followed quickly by another which will
drive an arctic front south on Monday morning. This will cause
some South Shore lake effect snow to develop giving locations in
Iron County 3 to 6 inches. Wind chills will also take a dip
below 0F as gusty winds accompany the cold air arrival.
High pressure builds afterwards and temperatures moderate for
another dry period for the remainder of the forecast with
temperatures running well above normal again. In fact, the
normal highs will be lower than our forecast low temperatures.
&&
.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 525 PM CST Sat Dec 16 2023
Widespread dense fog will be a mainstay through the night for much
of the Northland. Many stations are already reporting VLIFR ceilings
and visibilities. Improvements in ceilings and visibilities will
move west to east starting late tomorrow morning. However, guidance
does not suggest a return to VFR at this time, more likely MVFR
ceilings sticking around. There will also be a wave of light snow
entering from the NW tomorrow evening.
&&
.MARINE...
Issued at 301 PM CST Sat Dec 16 2023
A brief lull in the weather for the next 18 hours as high
pressure briefly crosses. The next system crosses Sunday and
will boost pressure gradients causing winds and waves to rise to
levels hazardous to small craft. A series of pressure
fluctuations will keep Lake Superior choppy through the mi part
of the week.
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...Dense Fog Advisory until midnight CST tonight for MNZ018-025-
026-033>037.
WI...None.
MARINE...None.
&&
$$
DISCUSSION...Wolfe
AVIATION...Wolfe
MARINE...Wolfe
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
611 PM EST Sat Dec 16 2023
.AVIATION...
Dry southeast flow this evening will be replaced by increasing low
level moisture as winds veer to the south. Showers will become
increasingly likely overnight and especially into Sunday as a
surface trough encroaches on the region. Cigs will drop to MVFR and
then IFR/possible LIFR Sunday morning. Winds will veer further to
the southwest and west with the passage of the trough late in the
forecast with some gradual improvement in cigs in its wake (back to
MVFR).
For DTW...Relatively quick decline from VFR to IFR Sunday morning as
a surge of moisture lifts in from the south and west. Latest model
guidance and observations over the Midwest still suggest borderline
LIFR conditions will then be possible by midday Sunday. Temperatures
remain mild enough to support all rain through Sunday.
.DTW THRESHOLD PROBABILITIES...
* High for ceiling 5000 ft or less late tonight and Sunday.
* High for all rain precipitation type late tonight and Sunday.
&&
.PREV DISCUSSION...
Issued at 355 PM EST Sat Dec 16 2023
DISCUSSION...
The final stages of gradually sloped sub 600mb isentropic downglide
will hold on through this evening. Vertical profile of modeled UVV
shows active subsidence right until midnight in a deep layer between
6.0-12.0 kft agl. Will continue to observe virga on radar
regionally, but no threat of any precipitation with very comfortable
and seasonally mild temperatures in the 40s this evening.
Meridional moisture transport axis associated with deep midlevel
trough will push into Southeast Michigan after 08Z tonight. Model
soundings show very good mid to upper level moisture and saturation
arriving abruptly, however, with conflicting data on just how good
the saturation will be in the surface to 4.0 kft agl layer through
approximately 16Z Sunday. Pops are probably in a good place with
likelies ramping up late tonight, but with latest NAM and HRRR data
very ragged and spotty with resolved precipitation. Will refrain from
categoricals tonight. Sheared but strong absolute vorticity maximum
is expected to push directly into the area between 15-18Z Sunday.
Model soundings support deep saturation throughout the troposphere
with upward vertical velocities between 700-300mb. Did go ahead an
increased Pops into categorical across the eastern forecast area
during the daytime Sunday. 24 hour expected QPF values are expected
to be 0.33 inch or less for the far eastern areas generally a tenth
for the northwest cwa. Just unpleasant weather overall, wet, damp
rainy with wind chill values of around 40 degrees.
Cold air will begin to wash across the forecast area in earnest
after 09Z Monday. Daytime temperatures Monday are forecasted to be
some 10 degrees below values reached this weekend. The initial cold
advection Monday morning will be shallow to start with, generally at
or below 5000 ft agl, which will cause for ice nucleation issues. A
mix of rain snow is good for along the front during the morning
hours on Monday. Sharp increase in surface based mixing depths due
to this caa will work in concert with strengthening surface pressure
gradient over Southeast Michigan. This will support strong northwest
winds on Monday. A couple of things that jump out in the data. 1.
EPS output suggests a little premium given on the higher elevation
areas. This suggests a more geostrophic/sustained type event. 2.
Those areas downwind of Saginaw Bay including Tuscola and Huron
(possibly Sanilac) counties stand the best potential for wind
headlines. Right now, gust potential for the Monday afternoon peak
looks to fall in the 30 to 40 mph range for many areas, a chance
for 45 mph in the northern Thumb.
The Monday evening timeframe will be monitored in subsequent model
data for any potential increase in Pops or snow coverage. A trailing
deep potential vorticity anomaly within the deep recess of the deep
mid to upper level trough is forecasted to push across the state.
Extremely low confidence exists on location/timing of the shortwave
and to what extent deep saturation will still exist because models
do show it undergoing a considerable onslaught of subsidence.
Considerable 1000-500mb height rises will then take control of the
weather during the middle of the week. A very dry air mass is
anticipated with temperatures some 3 to 7 degrees above normal
Wednesday through the end of the next week.
MARINE...
A low pressure system can be seen on satellite this afternoon
lifting out of the central plains. This system is forecast to weaken
as it moves northeast into the region with south to southeast gusts
reaching around 25 knots across Lake Huron through tonight into
tomorrow. There will be enough upper level support with this
weakening surface wave for widespread rainfall to expand across the
region beginning tonight. Southerly flow will increase wave action
across northern and eastern portions of the Thumb. This looks like a
marginal small craft event on Sunday and it possible an advisory may
be hoisted with a later forecast. The higher impact marine event
will arrive Monday morning as a strengthening nor`easter arrives
over the New England region with a potent trough and associated
strong cold front pushing through the Great Lakes. There is high
confidence in a gale event under the highly unstable post frontal
northwest flow and the Gale Watch remains in effect. The main
uncertainty is how strong the wind gusts will be. At this time,
sustained winds of 30-35 and gusts of 40 to 45 look highly probable
with a chance to exceed 45 knots at times. Occasional Waves on
Monday afternoon climb are forecast to exceed 20 feet across Lake
Huron. Cold air advection will also support a transition from rain
to scattered snow early Monday. High pressure moving in Tuesday into
Wednesday will lead to decreasing wind and wave trend Tuesday
morning into mid-week.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...None.
Lake Huron...Gale Watch from Monday morning through late Monday night for LHZ361-
422.
Gale Watch from Monday morning through Tuesday morning for LHZ362-
363-421-441>443-462>464.
Lake St Clair...None.
Michigan waters of Lake Erie...None.
&&
$$
AVIATION.....DG
DISCUSSION...CB
MARINE.......AA
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Wilmington NC
1007 PM EST Sat Dec 16 2023
.SYNOPSIS...
A nor`easter will blow through tomorrow with strong winds,
heavy rain, and coastal flooding. Cold air pours into the
region behind this system Monday night and will remain until a
return of seasonable temperatures Thursday through Saturday.
&&
.UPDATE...
Forecast updated to slow down the arrival of the rain tonight
based on latest radar trends. Also put the Storm Warning into
effect with the conditions expected about 12 hours from now.
&&
.NEAR TERM /THROUGH SUNDAY/...
The focus of course remains on the coastal storm for
Sunday and with high resolution guidance now fully available we are
nearing locked in position/status.
Good agreement on the track of the surface low moving up across the
coast or just offshore although there are still some solutions east
and west of this consensus along with timing differences. Wind
speeds and convection are the key elements of this forecast.
Guidance remains split on synoptic wind gusts nearing 50 MPH or
above along the coast as some products have come in above and below.
This is not surprising as it`s likely based at least in some part on
the embedded 70 plus jetlets at 925-850mb. These will likely
continue to wander around up and down with each suite of guidance
via noise if nothing else. Based on these developments or lack
thereof these forecast speeds remains essentially unchanged. The
wind advisory for the immediate coast still looks like a good play
as speeds exceeding this criteria are probably going to be more
convectively induced.
Turning to convection and the aforementioned high resolution
guidance. The HRRR and High Resolution NAM show dry air punching in
and around the low early Sunday afternoon and progressing to the
north as the system moves. This seems to allow just enough
instability in the lower levels to lead to more of a convective
signal/line increasing the probability of 50 knot plus gusts at the
surface. This seems reasonable although some of these fields can at
times be a little robust. SPC continues to maintain a slight risk
across mainly the coastal zones.
Lastly to address the rainfall/flooding threat. The storm total
amounts have increased slightly and certainly the highest qpf axis
gets really erratic when incorporating the high resolution guidance.
Although there may be a flood advisory or two continue to agree with
the previous shift that a FFA is not needed.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/...
Still breezy to start the period as nor`easter exits to the
northeast as it takes what will be some fairly light rain (quarter
inch or so) along with it. The strongest CAA will be held up Monday
by the next strong disturbance diving across the western Great
Lakes. This disturbance pushes a secondary shot of cold air into the
region Monday night.
&&
.LONG TERM /TUESDAY THROUGH SATURDAY/...
Impressive low level thermal trough in the east on Tuesday and the
local area is just about at its base. Highs will only manage the
mid 40s, some 10 degrees below our dead-of-winter normals. Tuesday
night turns quite cold but a few knots of wind should prevent true
radiation. Currently expected mid 20s but could def see colder. Some
low level temperature recovery is noted in guidance but surface high
overhead likely prevents any from mixing down and daytime temps very
close to Tuesday. This should change by Thursday as the high sinks to
our south and surface flow though light, acquires a southerly
component. Friday and Saturday look quiet and seasonable with a weak
pressure pattern at the surface and zonal flow aloft.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
VFR to start off the 00Z TAF period. Previous forecast remains
on track...with cigs eventually lowering to MVFR then IFR
tonight into tomorrow as strong sfc low pressure moves in from
the south. LIFR cigs possible as well at times. Meanwhile, rain
will become heavier and winds will increase, with gusts up to
30-40 kt by midday Sunday, highest along the coast. LLWS also
expected over coastal terminals due to very strong winds off
the deck, so included that in the TAFs.
Extended Outlook...Flight restrictions expected thru early Mon
along with very strong and gusty winds. This the result of the
strong storm system moving northeast across the area. Dominant
VFR conditions should return later Mon and persist thru midweek
with breezy conditions lingering into Tue.
&&
.MARINE...
Through Sunday...The main change with the latest marine
forecast is to upgrade the gale warning to a storm warning for
the same period...basically all day Sunday into early Monday
morning. Some of the more robust guidance is leaning towards storm
criteria and citing inter- office collaboration it seems
reasonable. High surf advisory remains in place as well as the
small craft advisory leading up to the storm warning.
Sunday night through Thursday... Conditions still very aggravated
following the exiting nor`easter to start the period and it`s tough
to say when the Storm Warning is lowered whether we will need a Gale
Warning for a period before things settle into Advisory realm. Wind
remains west in the late period and SCA-worthy seas will persist.
&&
.TIDES/COASTAL FLOODING...
Moderate flooding is still expected at both SC beaches and the
Lower Cape Fear. Guidance has backed off on the severity area-
wide but this seems suspicious with such a well defined and
still strengthening system. Overall the system is slower and so
too is the peak surge. This means it no longer coincides with
high tide at SC beaches but moderate flood still expected and
opted to remain closer to the upper end of PETS ensemble noting
there is considerable spread. The impressive 3 ft surge also
works its way up to NC but with even more delay after high tide.
Lowered the Watch to and Advisory but the current forecast of
7.8 at Mercer Pier still a noteworthy tide about on par with
Hurricane Ian or the nor`easter from Nov 2021.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...High Surf Advisory from 6 AM Sunday to noon EST Monday for
SCZ054-056.
Wind Advisory from 10 AM to 9 PM EST Sunday for SCZ054-056.
Coastal Flood Warning from 8 AM to 3 PM EST Sunday for SCZ054-
056.
NC...High Surf Advisory from 6 AM Sunday to noon EST Monday for
NCZ106-108-110.
Coastal Flood Advisory from 8 AM to 3 PM EST Sunday for NCZ106-
108-110.
Wind Advisory from 10 AM to 9 PM EST Sunday for NCZ106-108-110.
Coastal Flood Warning from 11 AM to 5 PM EST Sunday for NCZ107-
109.
MARINE...Storm Warning until 7 AM EST Monday for AMZ250-252-254-256.
&&
$$
SYNOPSIS...
UPDATE...MAS
NEAR TERM...SHK
SHORT TERM...MBB
LONG TERM...MBB
AVIATION...MAS
MARINE...ILM
TIDES/COASTAL FLOODING...
Area Forecast Discussion
National Weather Service Jacksonville FL
719 PM EST Sat Dec 16 2023
...New UPDATE...
.UPDATE...
Issued at 719 PM EST Sat Dec 16 2023
For the latest NE FL and SE GA Daily Key Messages please visit:
https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf
No major updates needed on the forecast this evening. Widespread
rain has moved into northeast Florida and southeast Georgia,
conditions will begin to deteriorate over the next couple hours as
heavier rain pushes inland. Convective models are indicating the
strongest thunderstorm activity to be across north central Florida
around midnight, gradually spreading northward overnight. The
highest potential for isolated severe thunderstorms will be over
northeast Florida and along the Atlantic coast, with damaging
winds, locally heavy rainfall, and an isolated tornado remaining
the main threats overnight through morning.
&&
.NEAR TERM...
(Through Tonight)
Issued at 300 PM EST Sat Dec 16 2023
For the latest NE FL and SE GA Daily Key Messages please visit:
https://www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf
The forecast for tonight shows the deepening surface low coming
at us from the southwest and moving northeast across the forecast
area Sunday morning. A triple point low expected to develop near
our coast around the 06z-12z time frame and may take over as
the primary low pres lifting to the northeast on Sunday/Sunday
afternoon. The rain forecast continues to show widespread rain,
some of it heavy with a flood watch in effect and rainfall totals
of 3-5 inches possible. Minor flooding is certainly possible in
poor drainage areas along with the threat of severe storms. Sfc
based instability does not really look good for storms until after
05z/06z, and peaks about 10z-14z over portions of northeast FL
and coastal southeast GA. Main threat from severe storms would be
a wind damage threat and a tornado threat. Significant tornado
parameter per HRRR maxes out near 1, so not too impressive from
that standpoint. SPC highlights the slight risk of severe storms
from Ocala to Jacksonville and points eastward, and marginal risk
from Trenton FL to Brunswick GA and points eastward. Winds will
ramp up to 15-25 mph with occasional gusts to 40 mph, potentially
higher in strong showers or any t-storm activity. Wind advisory
was expanded through the entire area into Sunday. Lows tonight
upper 50s northwest zones and lower/mid 60s elsewhere.
&&
.SHORT TERM...
(Sunday through Monday night)
Issued at 300 PM EST Sat Dec 16 2023
Sun & Sun Night...Widespread rainfall Sunday morning will
progressively shift ENE through midday with drying conditions into
the afternoon as the surface low crosses north-central FL, then
lifts quickly to the NNE into Sunday afternoon. Isolated morning
storms will be possible near the local Atlantic coast and over the
adjacent coastal waters, otherwise expect mainly stratiform
moderate to heavy rainfall for most locations at daybreak with
localized flooding potential. With any thunderstorm activity,
stronger wind gusts of 50-60 mph will be possible, as well some
rotating cells (tornado/waterspout) potential right at the start
of the period near the coast where higher helicity meets
instability. Strong dynamics in the morning and trailing pressure
rises from the west behind the departing surface low into Sunday
afternoon continue to support strong wind gusts of 40-50 mph along
the coast to 30-40 mph inland into the afternoon, with gradually
decreasing wind strength into Sunday evening. Precipitation
tappers off from SW to NE through the afternoon, with mainly just
trailing light showers/sprinkles into the early evening possible
across SE GA. Low clouds will linger into the evening until the
850 mb trough axis presses downstream of the area into Sunday
night. Daily high temperatures will hover in the upper 50s SE GA
to the mid 60s across NE FL during the morning with further
cooling into the afternoon as cooler NW flow develops. Sunday
night, low-mid level cold air advection drops lows in the 40s by
daybreak Monday morning, but combined with breezy winds overnight
in the 10-15 mph range, wind chills will drop into the 30s for
parts of SE GA.
Mon through Tuesday...Dry, breezy, clear and cold as deep cold
air advection occurs across the region and surface high pressure
builds to the WNW. High temps will top out in the upper 50s to low
60s Monday with lows Monday night falling into the 30s for most
locations. Lows will near freezing Tue morning across inland SE
GA, but there may be too much wind trailing the passage of a
reinforcing (dry) cold front Monday evening for a freeze event and
certainly now frost, but wind chills will fall into the mid to
upper 20s for many by daybreak Tuesday (just above Wind Chill
Advisory criteria for now). Very cold Tuesday with highs only near
50 for much of SE GA to low/mid 50s for NE FL despite full sun.
The surface high builds north of the region Tuesday night with
increasing high cirrus clouds from the west. The cold air in place
will bring a night of freezing temperatures inland, but frost
will be limited given the high clouds, and with the surface high
building NNE of the region, local onshore flow will begin to
develop which will bring warmer temps to coastal areas in the 40s.
&&
.LONG TERM...
(Tuesday through next Saturday)
Issued at 300 PM EST Sat Dec 16 2023
Wednesday through Saturday...Moderating temperatures and continued dry
weather as onshore flow develops with a surface high north of the
region and an upper ridge builds across the Gulf of Mexico and
over the local area through the end of the week. Another inland
freeze for SE GA possible Wed night, then lows rebound into the
40s into the weekend with highs in the 60s.
&&
.AVIATION...
(00Z TAFS)
Issued at 610 PM EST Sat Dec 16 2023
Light rain from the Gulf low is slowly filling across northeast
Florida and southeast Georgia. Conditions will begin to
deteriorate over the next few hours, with all TAF sites dropping
to IFR conditions around 10pm-1am due to low ceilings and heavy
rain lowering visibilities. Brief periods of LIFR visibilities
within heavy rain showers cannot be ruled out. Outside of
thunderstorms, winds will be gusty, and within thunderstorms winds
will also be gusty but variable in direction. Heavy rain and
thunderstorms will move clear of the TAF sites Sunday late morning
to early afternoon, with IFR ceilings lingering through late
afternoon to evening. Placed in AMD NOT SKED at SGJ due to
inconsistent reporting.
&&
.MARINE...
Issued at 300 PM EST Sat Dec 16 2023
As low pressure approaches, guidance has shown fairly persistent
forecast of strong to gale force winds, and gusts of storm force
offshore. Given the strength of the low and potential secondary
low development, opted to go with storm warning for the offshore
waters and maintain a gale warning for the nearshore. Storm
warning conditions develop overnight from about 05z to 14z when
the strongest winds appear to occur. Winds will shift to the west
and northwest after about 16z-20z Sunday as trough of low pressure
swings through. Gale conditions expected to linger after 18z and
into Sunday evening. The pressure gradient weakens gradually into
Monday into Tuesday but advisory level winds and seas likely to
continue, especially for offshore waters. NWPS wave guidance looks
on target for now, though with slight bump up tonight by 1-2 feet.
Rip Currents: High surf and high rip current risk extended through
at least Sunday night, and may still have elevated rip current
risk Mon and Tue despite offshore flow. Beach erosion will occur,
and could be significant in some areas.
&&
.HYDROLOGY...
Issued at 300 PM EST Sat Dec 16 2023
Flood Watch has been expanded for much of the area from this
evening into Sunday morning. Periods of heavy rainfall still
expected to spread from south to north across our area early this
evening through early Sunday with widespread 3-5 inches of storm
total rainfall. Locally higher amounts possible. HREF showing
totals exceeding 6 inches from Suwannee Valley into parts of
southeast GA. So potential for flooding in low lying and urban
locations, especially locations where ongoing coastal flooding
prevents drainage of water and also in other rural areas, as well
as secondary roads could be washed out.
Coastal Flooding:
Coastal flood advisory continues into Sunday for the Atlantic
coast, ICWW and St Johns river. Gages have been cresting into
Action stage just below minor flood these past high tide cycles.
The surge levels will increase but will peaking during the lower
of the high tides and a low tide at about 5-6AM. Nonetheless,
potential for a site to reach moderate coastal flooding levels.
At this time, will maintain the coastal flood advisory and extend
into the high tide into the afternoon, with potential extensions
in time. At this time it would be prudent for those in tidal flood
prone areas to prepare for at least minor flooding impacts this
weekend and consider early mitigation for moderate tidal flood
impacts.
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 56 60 45 58 / 100 100 0 0
SSI 59 66 47 62 / 100 90 10 0
JAX 60 68 46 62 / 100 80 0 0
SGJ 62 70 49 63 / 100 60 0 0
GNV 60 66 46 62 / 100 60 0 0
OCF 61 68 48 63 / 100 50 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...Flood Watch through Sunday morning for FLZ020-021-023-024-030-
031-033-035-038-122-124-125-132-133-136>138-140-222-225-232-
236-237-240-325-340-425.
Wind Advisory until 3 PM EST Sunday for FLZ020-021-023-024-030-
031-033-035-038-122-124-125-132-133-136>138-140-222-225-232-
236-237-240-325-340-425.
Coastal Flood Advisory until 1 PM EST Sunday for FLZ033-038-124-
125-132-133-137-138-225-325.
High Rip Current Risk through late Sunday night for FLZ124-125-
133-138.
High Surf Advisory until 8 PM EST Sunday for FLZ124-125-133-138.
GA...Flood Watch through Sunday morning for GAZ132>136-149-151>154-
162-163-165-166-250-264-350-364.
Wind Advisory until 3 PM EST Sunday for GAZ154-162-163-165-166-
264-350-364.
Coastal Flood Advisory until 1 PM EST Sunday for GAZ154-166.
High Rip Current Risk through late Sunday night for GAZ154-166.
High Surf Advisory until 8 PM EST Sunday for GAZ154-166.
Wind Advisory from 4 AM to 3 PM EST Sunday for GAZ132>136-149-
151>153-250.
AM...Gale Warning until 10 PM EST Sunday for AMZ450-452-454.
Storm Warning until 10 AM EST Sunday for AMZ470-472-474.
Gale Warning from 10 AM to 10 PM EST Sunday for AMZ470-472-474.
&&
$$
Area Forecast Discussion
National Weather Service Melbourne FL
1018 PM EST Sat Dec 16 2023
...New UPDATE, MARINE, AVIATION, HYDROLOGY...
.UPDATE...
Issued at 1015 PM EST Sat Dec 16 2023
Key Messages:
-Slight Risk of severe storms overnight, possibly a tornado
-Minor flooding from widespread moderate-locally heavy rain
continues, but is beginning to break up
-Winds increasing, both along the coast and inland
-Hazardous seas and surf continue through Sunday
-Becoming much cooler and drier early next week
After widespread moderate to occasionally heavy rain across much
of ECFL today, the stratiform shield is starting to shift north
and break up from S-N as the warm front/sector associated with
the GOMEX Gale center approaches from the south. CAMS guidance
shows convection redeveloping within the warm sector overnight
though there remains the question of whether sufficient surface
based instability will exist to support stronger updrafts
Needless to say, low level wind/shear parameters are more than
sufficient to support damaging wind gusts/isolated tornadoes.
Both SFC and MLCAPE are below 500JKG-1, however some of the
higher values lurking offshore SWFL should start to spread NE
across the western peninsula shortly.
Trends on KTBW radar will be a good harbinger on what we can
expect the rest of the tonight. HRRR guidance shows the highest
potential for severe storms between 1 and 5 AM. Persons across
ECFL are advised to remain weather-aware overnight, and have
multiple ways to receive warnings should any need to be issued.
&&
.MARINE...
Issued at 1015 PM EST Sat Dec 16 2023
Once again, no changes to sea/surf/coastal flood products this
evening. Near-gale to gale conditions ongoing with sustained
winds 25-30kt gusting into the 40s, and seas 9-12ft at all the
near shore buoys. While seas are right in line with the forecast
winds are running about 5-8kt below guidance. However since they
will likely increase some overnight, and winds just off the deck
are so strong, don`t plan on making any tweaks to speeds.
&&
.AVIATION... (00Z TAFS)
Issued at 1015 PM EST Sat Dec 16 2023
Earlier widespread IFR CIGs/VSBYs 2SM/OVC008 in RA/RA+ starting
to improve/lift into MVFR-VFR as the surface warm front approaches
the CWA. Through 12Z, lingering stratiform rain will continue to
erode with VFR becoming more prevalent, but still with areas MVFR
CIGs near BKN025 within the warm sector. Band of scattered strong
storms progged to move across the northern and central aerodromes
04Z-08Z, and possibly farther south across the MLB-SUA 08Z-12Z.
Gusts 50kt+ possible should any coherent storm cores develop.
Conditions improving after 12Z behind occluded FROPA but still
quite windy as flow veers to 270-290/15-20G30KT.
Lowered LLWS level to 1Kft per CCSFS DRWP data, which shows 50kt
just off the deck. In events of this type, even higher-res model
guidance tends to underdo the magnitude of LLWS a bit.
&&
.HYDROLOGY...
Issued at 1015 PM EST Sat Dec 16 2023
Due to ongoing heavy rainfall over the St. Johns River Basin,
the river level at Astor is now forecast to briefly rise into
Moderate Flood Stage on Sunday. The rover is forecast to fall
back into Minor Flood Stage on Monday, with level then forecast
to very slowly decline through mid week, but could remain steady
as increasing northerly winds behind the cold front impede the
downstream (northward) flow of the river.
&&
.PREVIOUS DISCUSSION...
Issued at 419 PM EST Sat Dec 16 2023
Tonight-Sunday...An unsettled weather pattern will continue across
the Florida peninsula tonight into Sunday, producing increased
coverage of showers and strong to severe storms locally. An area of
low pressure located over the Gulf of Mexico continues to strengthen
this afternoon as it moves eastward towards the peninsula, with its
associated warm front gradually moving northward and producing a
rain shield well out ahead of it this afternoon. This activity is
forecast to continue to develop over the next several hours, with
heavy downpours possible.
Current model guidance takes the center of the low across the Big
Bend/Nature Coast late tonight into early Sunday, with organized
storms forecast to develop along the warm front as it lifts
northward across east central Florida. With the low tracking just
north of east central Florida, the area will be in a fairly
favorable environment for the development of strong to severe storms
overnight. Based on model soundings, a high shear/low CAPE
environment will exist across the area, with damaging wind gusts 50
to 60 mph and a few tornadoes the main threats associated with the
strongest storms overnight. SPC has kept the entirety of east
central Florida under a Slight Risk through the remainder of the day
into tonight to highlight this threat. Additionally, heavy rainfall
will be a concern across the area with widespread totals of 2 to 4
inches and locally higher amounts of 6 inches and greater possible.
As the low moves northeastward across north Florida and away from
the area as it gets picked up by the mid-level trough sweeping
across the southeastern US, a drier air mass will begin to move in
behind it from the west. This will help diminish shower and storm
chances on Sunday, with PoPs 20 to 40 percent through Sunday morning
to account for showers associated with any lingering moisture ahead
of the dry slot. PoPs will then quickly diminish to less than 10
percent late Sunday afternoon as the drier air moves in. However, we
will not be entirely out of the clear as far as weather hazards are
concerned. 925mb winds will remain around 40 knots behind the low,
which will mix down to the surface and lead to continued gusty
conditions across east central Florida. As a result, a Wind Advisory
will remain in effect across east central Florida through 3 PM
Sunday, with wind gusts up to 40-45 mph possible. Winds will
gradually diminish through the remainder of the afternoon as the low
moves farther away from the peninsula and winds aloft decrease.
Lows tonight warmer than yesterday as the warm front lifts
northward, with temperatures in the mid 60s to low 70s. Increased
cloud coverage across the peninsula will persist into Sunday as the
drier air is slow to clear out clouds, which will keep afternoon
temperatures in the 70s across east central Florida.
Sunday Night-Tuesday...The unsettled pattern of Sat and early Sun
will transition to a more quiet period to begin the new week. The
deep low pressure will quickly exit to the Atlantic by Sunday
evening, riding along the Eastern Seaboard overnight and into Monday
morning. A cold front will trail behind this system, dropping south
of the FL Straits overnight Sunday. Drier air will slowly filter in
behind the front, dropping PWAT values to 0.30-0.50" by Monday
daybreak. This will completely wipe rain chances through the
remainder of the forecast period and returning clear blue December
skies. Breezy to windy conditions will also quickly erode overnight
on Sunday, with west to northwest winds around 10 mph for Monday.
While Sunday night will still see near normal lows in the mid 50s,
the focus will quickly shift to much cooler temperatures the
remainder of the week. Highs on Monday will struggle to reach 70
degrees, drastically falling overnight to the low to mid 40s, with
northern portions of Lake/Volusia counties reaching the upper 30s.
Wind chill readings will feel even colder as values in the mid 30s
to low 40s spread across the entire forecast area, the exception
being the barrier island south of Cape Canaveral. High pressure
drifting over the TN Valley will send even drier air to the FL
peninsula with a secondary cold front (PW below 0.30"), aiding in
the falling temperatures. Tuesday highs will look like normal lows
for this time of year, barely reaching 60 north of the I-4 corridor,
but the mid 60s for the Treasure Coast.
Wednesday-Friday...Rain chances will remain out of the forecast
through the rest of the week as high pressure settles in over the
Deep South. Daily persistence forecasting will continue, with cool
to chilly nights and dry and seasonal afternoons. Those finally
looking for a taste of Florida winter will finally see it this week,
which will certainly be one to brag about to those in the more
northern latitudes. Wednesday morning will be another cold one,
dropping again to the low 40s north of I-4 to low 50s for the
Treasure Coast. The remainder of the week will return to near normal
highs in the upper 60s/lower 70s and lows in the 50s.
&&
.MARINE...
Issued at 419 PM EST Sat Dec 16 2023
Tonight-Sunday...An area of low pressure is forecast to move
across north Florida late tonight into early Sunday, and will
continue moving offshore into Sunday. Boating conditions across
the local Atlantic waters will continue to remain hazardous
through Sunday. East winds will veer to out of the south-southeast
tonight, becoming westerly on Sunday. Wind speeds generally 25 to
35 knots, with gusts up to 45 knots. Seas will continue building
overnight, reaching 17 feet across the offshore waters tonight.
Seas will then begin to subside late Sunday as winds become
offshore. A Gale Warning remains in effect through Sunday night,
and small craft are advised to stay in port.
Showers and storms are forecast across the local Atlantic waters
through Sunday as the low moves northeastward across the peninsula.
The strongest storms will be capable of producing gusty winds, heavy
downpours, and cloud-to-water lightning strikes tonight.
Sunday Night-Wednesday...As the low pressure system quickly exits
away from the local Atlantic waters late Sunday, strong gradient
winds will slowly subside, dropping below 20 knots by midday Monday.
This drop will be brief, however, as a secondary dry cold front
drags another northwest wind surge across the waters, returning to
20-25 knots late Monday and early Tuesday. While seas will also
decline, conditions will remain hazardous, with wave heights of 6 to
9 feet lasting through most of the week. An extended SCA will be
necessary at the expiration time of the Gale Warning later this
weekend.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 73 65 73 51 / 90 100 30 10
MCO 73 66 73 54 / 90 100 30 10
MLB 74 69 77 53 / 90 100 40 10
VRB 76 71 77 54 / 90 100 40 10
LEE 72 64 71 51 / 90 100 30 10
SFB 73 66 74 53 / 90 100 30 10
ORL 72 65 73 53 / 90 100 30 10
FPR 76 71 77 54 / 90 100 40 10
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...Wind Advisory until 3 PM EST Sunday for FLZ041-044>046-053-058-
141-144-154-159-164-247-254-259-264-347-447-547-647-747.
Coastal Flood Advisory until 4 AM EST Sunday for FLZ141-154-159-
164-347-447-647-747.
High Surf Advisory until 4 AM EST Sunday for FLZ141-154-159-164-
347-447-647-747.
AM...Gale Warning until 10 PM EST Sunday for AMZ550-552-555-570-572-
575.
&&
$$
SHORT TERM...Cristaldi
LONG TERM....Watson
AVIATION...Cristaldi
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
759 PM EST Sat Dec 16 2023
...New UPDATE, DISCUSSION...
.UPDATE...
Large all day rain shield over the FL Peninsula continues over N
and C areas in cool sector of cyclone. Warm front over S FL moving
Nward as well advertised strong low pressure storm system getting
better organized in the E Gulf centered a little more than 100
miles offshore W Central and SW FL this evening as seen in
satellite and radar imagery. The system is beginning to show the
classic mid latitude cyclone coma head with convective burst and
associated dry slot moving into SW FL aiding in destabilization
and surface based instability ahead of developing squall line. 00Z
TBW sounding and radar algorithms showing very strong helicity
values in the high shear and low cape environment. Expect risk of
severe thunderstorms and possible tornadoes tonight as the system
moves ashore with a squall line and also additional discrete cells
that can produce winds around 60mph and tornadoes as the main
threats. Will coordinate shortly with SPC on the situation for the
possibility of watches as needed while we monitor the potentially
dangerous situation closely.
Winds turn onshore overnight into Sunday as the strong pressure
gradient continues to produce minor coastal flood concerns around
high tides.
Latest forecasts, grids, and briefing material on track at this
time.
&&
.AVIATION...
(00Z TAFS)
Complex forecast with Gulf storm system to move ashore overnight
with widespread MVFR/IFR CIGs and VSBY especially in heavier rain
showers that could likely become +TSRA with brief LIFR and very
strong gusty winds. General gradient winds to remain gusty as well
from the ESE turning S ahead of squall line then NW towards
morning. Wrap around moisture to keep lower cigs and RA in the
area Sunday through at least 18Z.
&&
.DISCUSSION...
Issued at 153 PM EST Sat Dec 16 2023
The surface low we have been expecting the past few days is finally
getting more organized as it approaches the eastern Gulf of Mexico.
The latest satellite imagery is showing extensive cloudiness over
the central and eastern gulf waters with building cloud tops
indicating increasing thunderstorm activity near the low center. The
latest surface observations are continuing to report steady rain
moving into the area. The latest radar and HRRR guidance has what
appears to be mostly stratiform rain streaming into the area and
continuing through the afternoon hours with the first thunderstorms
moving onshore after 6 pm and continuing through the early morning
hours on Sunday. The 12Z morning sounding is showing a definite
moistening of the atmosphere from 24 hours ago with a PWAT of 1.50
inches. The CAPE is not very impressive on the morning sounding, but
strong veering of the winds is already apparent with SFC - 3km
helicity values already exceeding 300+. This value is indicative of
the possibility of waterspouts and tornadic activity as cells move
through the area later today. This weather system will continue to
bring a multitude of weather hazards including excessive rainfall up
to 2-4 inches possible with higher amounts in stronger storms, gusty
winds up to 50 mph, hazardous marine conditions, damaging
thunderstorm gusts and even some isolated tornadoes will be
possible.
After this 24 hour weather event, models have come to an agreement
in moving this low pressure northeast of the area over the Carolinas
coastline by late Sunday evening and will continue moving northeast
along the eastern seaboard away from the area. Most of the rainfall
associated with this system will taper off as well by Sunday
evening. However, a tight pressure gradient between the area of low
pressure and high pressure building in from the northwest will
produce breezy conditions in the wake of this system making for
hazardous boating operations through at least Monday evening. Broad
high pressure builds in over the southeast U.S. by Tuesday producing
rain-free conditions for next week as well as bringing a shift in
the winds to the north and then northeast by Wednesday and remaining
around 10 to 15 knots through the end of next week.
Daytime highs will top out in the low to mid 70`s through Sunday,
then cooling into the 60`s on Monday, 50`s and 60`s on Tuesday, then
warming back into the 60`s and 70`s starting Wednesday and
continuing through the end of next week. Overnight lows tonight will
be on the warm and muggy side in the 60`s, then dropping into the
40`s and 50`s for Sunday night, 30`s and 40`s for Monday and Tuesday
nights and then back into the 40`s and 50`s starting Wednesday night
through Saturday nights.
&&
.MARINE...
Issued at 153 PM EST Sat Dec 16 2023
Dangerous boating conditions will continue through the weekend as a
robust area of low pressure develops in the central Gulf of Mexico
and moves eastward toward and across Florida. This will result in
gusty easterly winds with gusts up to 45 knots possible in our off
shore waters. By late Saturday into early Sunday morning, the low
will transit through the eastern gulf waters. This will result in a
wind shift from the east to the west with wind gusts approaching 45
knots and seas occasionally up to 11 feet. This has warranted the
continuance of a Gale Warning for the off shore waters through
Sunday morning and a Small Craft Advisory for all waters through
Monday morning. We have also issued a High Surf Advisory and High
Risk of Rip Currents for Pinellas County southward starting this
evening and continuing through Monday morning. Conditions will
slowly start to slightly improve through early next week, but winds
will still remain around 15 to 20 knots through at least Tuesday.
&&
.FIRE WEATHER...
Issued at 153 PM EST Sat Dec 16 2023
An area of low pressure moves across Florida today and Sunday with
scattered to numerous showers and storms likely. Some of these
storms could be severe with damaging winds. High pressure builds in
from the west in the wake of this low and will produce continued
gusty northwest winds on Monday, then veering to the northeast on
Tuesday. No other fire weather concerns expected during next week.
&&
.PRELIMINARY POINT TEMPS/POPS...
TPA 65 70 57 65 / 100 10 10 0
FMY 68 75 60 70 / 90 50 10 0
GIF 64 73 54 66 / 100 40 10 0
SRQ 65 73 59 68 / 100 10 10 0
BKV 61 71 51 65 / 100 30 10 0
SPG 65 69 59 64 / 100 10 10 0
&&
.TBW WATCHES/WARNINGS/ADVISORIES...
FL...Wind Advisory until 10 AM EST Sunday for Coastal Charlotte-
Coastal Citrus-Coastal Hernando-Coastal Hillsborough-
Coastal Lee-Coastal Levy-Coastal Manatee-Coastal Pasco-
Coastal Sarasota-Pinellas.
Coastal Flood Advisory until 7 AM EST Sunday for Coastal Citrus-
Coastal Hernando-Coastal Hillsborough-Coastal Levy-Coastal
Manatee-Coastal Pasco-Pinellas.
High Rip Current Risk from 1 AM EST Sunday through Monday
morning for Coastal Charlotte-Coastal Hillsborough-Coastal
Lee-Coastal Manatee-Coastal Sarasota-Pinellas.
High Surf Advisory from 1 AM Sunday to 7 AM EST Monday for
Coastal Charlotte-Coastal Hillsborough-Coastal Lee-Coastal
Manatee-Coastal Sarasota-Pinellas.
Gulf waters...Small Craft Advisory until 7 AM EST Monday for Charlotte Harbor
and Pine Island Sound-Tampa Bay waters.
Gale Warning until 7 AM EST Sunday for Coastal waters from
Bonita Beach to Englewood FL out 20 NM-Coastal waters from
Englewood to Tarpon Springs FL out 20 NM-Coastal waters
from Tarpon Springs to Suwannee River FL out 20 NM-Waters
from Bonita Beach to Englewood FL out 20 to 60 NM-Waters
from Englewood to Tarpon Springs FL out 20 to 60 NM-Waters
from Tarpon Springs to Suwannee River FL out 20 to 60 NM.
Small Craft Advisory from 7 AM Sunday to 7 AM EST Monday for
Coastal waters from Bonita Beach to Englewood FL out 20 NM-
Coastal waters from Englewood to Tarpon Springs FL out 20
NM-Coastal waters from Tarpon Springs to Suwannee River FL
out 20 NM-Waters from Bonita Beach to Englewood FL out 20
to 60 NM-Waters from Englewood to Tarpon Springs FL out 20
to 60 NM-Waters from Tarpon Springs to Suwannee River FL
out 20 to 60 NM.
&&
$$
UPDATE/AVIATION/MARINE/FIRE WEATHER...RDavis
CLIMATE/DECISION SUPPORT...Close
UPPER AIR...Anderson
RADAR...Flannery/Oglesby/Giarratana
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
421 PM MST Sat Dec 16 2023
.KEY MESSAGES...
102 PM MST Sat Dec 16 2023
- Dry clipper system moves through Sunday/Monday with gusty winds
possible Sunday afternoon
- Dry with above average temperatures into next week
&&
.DISCUSSION...(This Evening Through Saturday)
Issued at 102 PM MST Sat Dec 16 2023
Recent WV imagery and upper air analysis show deepening trough
over the midwest and a building ridge over the Rockies. Shortwave
is developing over MT/WY, moving southeast along the flow. Mostly
clear skies with a few high clouds prevail over most of the region
with light southerly winds and mild temperatures. A few stubborn
low clouds still linger over south-central SD as the clipper
system from last night slides to the southeast. Mostly clear and
dry weather will stick around through tonight, which may bode well
for those of us wishing to see the northern lights (if the sun
delivers).
Another clipper swings down from Canada late Sunday into early
Monday, passing to the north of our CWA. Most recent NAM run is
showing modest pressure rises of around 4 mb/3hrs by 00z on
Monday, hinting at a gusty afternoon for the western SD plains.
BUFKIT HRRR and NAM soundings show 40kt winds potentially mixing
down to the surface, which could translate to a brief period of
near advsy level northwest winds in our usual windy spots around
the Piedmont foothills and Rapid City.
Looking forward into next week, the upper ridge over the west
builds before troughing over Canada flattens it out. The Dakotas
will sit under largely zonal, west-southwesterly flow through the
early to mid week. This will mean above average temperatures
through most of next week. While a few weak perturbations along
the flow will cross the region through next week, these systems
will be mostly dry with breezy winds.
Cluster analysis shows a more active pattern late next week with
ensemble outputs in good agreement on the development of
troughing/an upper low over the desert southwest. However, things
get a bit murky on what the northern stream upper flow will do. It
may explain why the medium range deterministic runs are swinging
between giving us a sunny Christmas and clobbering us with a
snowstorm.
&&
.AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening)
Issued At 419 PM MST Sat Dec 16 2023
A tiny sliver of IFR stratus in/near KICR will dissipate this
evening. Otherwise, VFR conditions expected through the period.
Northwest winds will increase Sunday morning and gust to 40kts by
afternoon on the western SD plains.
&&
.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&
$$
DISCUSSION/KEY MESSAGES...Wong
AVIATION...Helgeson