Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/13/21
Area Forecast Discussion
National Weather Service La Crosse WI
502 PM CST Tue Jan 12 2021
.SHORT TERM...(This evening through Wednesday)
Issued at 204 PM CST Tue Jan 12 2021
Variable high and mid level cloudiness across the region today as
GOES water vapor imagery and RAP analysis was showing a weak mid-
level trough pushing southeast across MN into WI. Otherwise,
another mild day for mid-January with readings as of 1 pm ranging
from the upper 20s to mid 30s.
Will have to watch for fog development tonight, possibly locally
dense, mainly east of the Mississippi River given lighter winds
under a weak ridge of high pressure and very moist lower boundary
from partial snowmelt today. For now, will mention areas of fog
but will maintain a close eye for dense fog development.
Otherwise, plan on lows in the 20s.
After some areas of morning fog, may have to contend with some
low cloud/stratus mainly east of the Mississippi River in warm air
advection ahead of low pressure moving in across the Northern
Plains. These cloud may come into play with highs. Either way,
clouds or no clouds, looking like another mild mid-January day
with highs topping off well into the 30s. Could even see some
lower 40s with more sun along and west of the Mississippi River.
Typical highs for this date are in the lower/mid 20s.
.LONG TERM...(Wednesday night through Tuesday)
Issued at 204 PM CST Tue Jan 12 2021
Main concern in the long term remains the potential for wintry
precip and accumulating snow Thursday into perhaps Saturday. An
upper level trough will start digging into the Northern Plains
Wednesday night with a surface low remaining near the Canadian
border through early Thursday morning. An associated cold front
will slide through the forecast area on Thursday, marking the
beginning of precipitation chances. At the onset, warm air aloft
(especially south of I-90) will lead to some mixed precip types,
with rain or freezing rain possible pending surface temperatures.
There may also be a period of some sleet as cold air moves in
aloft and leads to only partial melting before a switch to mainly
snow. The trend has then been toward the low repositioning
somewhere over the Great Lakes Thursday night into Friday, cutting
off at 500 mb, and possibly lingering in the area into Saturday.
A cold conveyor belt (though not overly strong per NAEFS) will
ramp up while additional shortwave energy wraps around the back
side, producing continued light precipitation. Not an overly
strong frontogenesis signal in the main deterministic guidance at
this point, but still plenty of forcing for accumulating snow.
Finally, a tight pressure gradient could lead to some pretty gusty
northwest winds behind the front Friday and into Saturday.
Depending how heavy any ongoing snow is and how much snow ends up
falling, blowing and drifting could be an issue.
So while there`s pretty good agreement on the general pattern,
still quite a bit of spread in ensemble guidance regarding QPF and
snowfall amounts, owing to differences in temperatures, exact
positioning of the system, as well as overall system strength, and
in turn, strength of the cold conveyor belt and frontogenesis.
GEFS members seem to form a pretty good cluster of 3 to 6 inches
of snow for KRST, with a mean of around 4 inches, but there are
certainly outliers well above and below those values. Consensus
would place the highest amounts in the immediate region from
south- central/southeast Minnesota into north-central Wisconsin,
so leaning toward that in the forecast, though a few GEFS members
do suggest the main deformation band sets up over eastern
Wisconsin following the frontal passage. In summary, seems like
the highest snowfall rates will be along the initial cold front on
Thursday, which could bring a quick 1 or 2 inches to some. Mainly
light snow looks to follow, but it does look like it could linger
for a while, which could get totals into that 3 to 6 inch range
in spots, though overall confidence in those amounts remains
somewhat low.
Cooler, but still seasonable air will work in behind the system,
leading to highs generally in the 20s and lows in the single
digits and teens for the weekend and into early next week. Some
hints at some additional weak shortwave energy perhaps bringing
some more light precip early next week, but nothing looking too
organized or impactful at this time.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 502 PM CST Tue Jan 12 2021
Generally VFR conditions expected through the next 24 hours with
periods of mid/high clouds and S/SW winds under 10 kts. However,
fog potential exists tonigt, particularly at KLSE, but with some
cloud cover and higher winds aloft, confidence is not all that
high. Lowering VFR ceilings are expected ahead of a weak upper
level trough Wednesday morning. A few sprinkles or freezing
sprinkles are possible for a brief period, but given the dry low-
levels of the atmosphere, it is questionable whether even any
light precip would reach the surface.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...DAS
LONG TERM...CA
AVIATION...JM
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
929 PM EST Tue Jan 12 2021
.UPDATE...
Observational trends are offering a little more support to the faster
clearing offered to an extent by ARW solution. The latest RAP and
NAM low level RH progs are also suggesting that clearing of the low
stratus may come in the 09Z to 12Z time frame with the push of warmer
low level air. Will therefore update the forecast to decrease
morning cloud cover a bit.
A pocket of drizzle held along into the early evening hours across
northern Oakland, southern Lapeer and northern Macomb Counties. This
sustained a little wetter roads in this region which led to the
rapid ice up post sunset. No additional drizzle is being observed
which supports the current forecast of dry conditions overnight.
&&
.PREV DISCUSSION...
Issued at 548 PM EST Tue Jan 12 2021
AVIATION...
Observational trends have shown a slight increase in ceiling heights
over the last few hours with some improvement in visibilities. This
is indicative of a little drier air that has advected into the
boundary layer. Ample stratus does still remain trapped under a
stout low level inversion. There will be an influx of low level warm
air advecting into Se Mi late tonight into Wed morning within
southwest flow. It is this warming that will most likely drive the
clearing line now over nrn Indiana and srn Lake Mi into Se Mi late
tonight/Wed morning. There remains considerable uncertainty as to
the timing of the clearing attm. Suspect metro Detroit may clear out
prior to 12Z, while FNT and MBS take much longer into Wed morning.
With some veering of the low level flow toward the west Wed
afternoon, the low clouds may struggle to exit MBS.
For DTW...The improvement in ceiling heights to MVFR and with some
subtle increase in ceilings upstream, there is likely no additional
risk for freezing drizzle.
DTW THRESHOLD PROBABILITIES...
* High for ceilings below 5k ft tonight. Low on Wednesday.
PREV DISCUSSION...
Issued at 403 PM EST Tue Jan 12 2021
DISCUSSION...
Radar evidence of drizzle/freezing drizzle is grudgingly breaking
away from the Lake Michigan shoreline at mid afternoon, and this
diminishing trend is expected to develop into SE Michigan leading up
to sunset. Relaxation in troughiness of the surface pressure field
combines with weakening wind and shrinking moisture profiles for a
less favorable environment for DZ/FZDZ production as the evening
progresses. Surface temperatures at most locations have at least
touched the freezing mark which, combined with additional afternoon
radiative forcing on surfaces/objects, have prevented more than
sporadic trace amounts of icing during the afternoon. A few slick
spots do remain possible on elevated or untreated surfaces with the
approach of sunset.
Evidence of the shrinking moisture profile in model soundings brings
into question cloud trends late tonight through Wednesday morning.
There is a range of output in the hi-res model solutions which
generally side with the regional models that favor stratus holding
on at least through Wednesday morning. The ARW on the other hand is
one that is faster to scour out the clouds and is a viable solution
considering that low level warm advection lifts 925 mb temperatures
above 0C and deactivates Lake Michigan cloud production. Satellite
trends side with the ARW near the south end of Lake Michigan this
afternoon and this will be monitored for an additional eastward
trend tonight considering climatology and the consensus of other
model solutions.
Should a faster pace develop in scouring out stratus coverage, a
short period of partly sunny sky is possible around noon Wednesday
before high clouds thicken ahead of the next 500 mb short wave.
Steady wind in broad SW gradient flow also helps lift temperatures
well above freezing with highs near 40 reachable. The short wave of
concern moves overhead Wednesday night on the nose of a compact
upper level jet max while the primary 500 mb trough remains over
northern Ontario. Model soundings generally support more virga with
this system as dry air centered around 700 mb remains substantial.
The powerful 150 kt+ upper level jet crashing inland over the
Pacific NW tonight moves into the Rockies Wednesday and helps carve
out a long wave trough in the Plains by Thursday. The trough rapidly
closes off over the Midwest by Thursday night while reinforcing mild
air into Lower Michigan. The timing and intensity of larger scale
atmospheric features in the latest regional/global model runs show
good dprog/dt consistency across the last 24 hours of forecast
cycles. Differences in solutions arise mainly in the low level
temperature profile affecting precipitation type in the leading edge
of moisture as it advances into SE Michigan Thursday night. The
preferred forecast is for at least a warmer rain/snow mix with
surface temperatures above freezing given the mild air already in
place Thursday afternoon and likely reinforced by southerly flow
ahead of the aggressive surface pressure falls over the Midwest.
Details on the potential dry slot/occlusion process come in to
better focus by Friday when the ECMWF becomes a warm outlier
compared to the other deterministic solutions. Assuming a typical
dry slot progression into dominance of the cold core aloft leads to
scattered snow showers Friday into Saturday. The stacked pressure
features toward the surface prevent much additional cold advection
until perhaps Sunday. Even by then there are some questions on
timing as the upper air pattern becomes surprisingly progressive in
model data which may slow down in upcoming models cycles.
MARINE...
An upper level disturbance exits into the eastern Great Lakes this
afternoon with light precip in the form of rain, snow, or drizzle
tapering off heading into this evening. Another weak upper wave
moves through overnight with a low chance of additional light
precipitation. A modest southwest gradient remains resident over the
region through the midweek period with wind speeds around 15 to 20
kt. The next system moves in on Friday with southeast winds picking
up ahead of it Thursday night. The system expands and stalls over
the Great Lakes with unsettled weather likely through the weekend.
At this time, the chance for marine headlines to be needed appears
low.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
UPDATE.......SC
AVIATION.....SC
DISCUSSION...BT
MARINE.......TF
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Forks ND
1000 PM CST Tue Jan 12 2021
.UPDATE...
Issued at 957 PM CST Tue Jan 12 2021
A warm winter evening into the overnight is expected to continue
with minimal weather impacts. Temps remain unseasonably warm for
10pm in January with readings primarily in the upper 20s. Lows on
track tonight in the low 20s or upper teens.
UPDATE Issued at 543 PM CST Tue Jan 12 2021
Widespread stratus and fog not expected this evening. That being
said patchy ground fog is possible in the MN lakes region as
temps cool and winds decouple creating ideal radiative cooling
environment overnight.
&&
.SHORT TERM...(This evening through Wednesday night)
Issued at 257 PM CST Tue Jan 12 2021
Any weather impacts holding off til Wednesday evening and beyond.
An afternoon with fog and low clouds. West winds into the western
edge of the Red River valley floor boosting temps to near 40,
with widespread 30s most elsewhere. Some cirrus and bands of high
clouds will continue to move through from the west tonight. West
to southwest wind will lighten and turn a bit more south tonight.
Drier 925 mb airmass in place but will have to watch for areas
that may try to get light wind speed overnight. HRRR indicates
some patchy fog in the Park Rapids/Wadena areas late tonight and
did put some mention there.
Wednesday will see south wind in the immediate RRV and Wednesday
could end up cooler in the RRV than today and also clouds will
increase/thicken up. A cold front will move into central ND in the
aftn and move east into MN Wed evening. Some moisture near or just
ahead of the front will generate a band of rain showers. As it
moves east of the RRV Wed evening there is a risk of freezing rain
as temperatures drop to around 30/32F. Will also have to watch for
colder surface temperatures but recent day or two above 32F may
mean less impact unless actual temperature falls below 32F.
.LONG TERM...(Thursday through Tuesday)
Issued at 257 PM CST Tue Jan 12 2021
Still much uncertainty in the development of this system for Thu-
Fri. Deterministic model solutions all over the place but trend
among 12z GEFS ensembles too is lower QPF than showed in their 00z
run. ECMWF is not quite as wet either but still is the wettest of
them all with around 0.25 to 0.35 inch in parts of NW/WC MN.
Discussion with WPC is to lower ECMWF amounts some but not go as
dry as NAM. Net result is better chc of 4 inches of snow is
eastern fcst area with lower risk west. Using straight WPC QPF and
snow ratios would give around 1 inch far west to 5 far east.
Winds another issue. Main winds with 60 kts 850 mb is late Wed
night into Thursday mainly western/south central ND into SD. We
are on edge of that and appears advisory level winds likely in E
ND. During the snowfall Thu aftn/Friday winds are more north but
cold advection at that time weakens and on Friday we warm actually
at 850 mb from the north and surface low is filling to our east.
Therefore doesnt seem to be a big wind push Thu night, higher than
what most models show which is gusts in the 40 mph range in the
RRV. Uncertainty with snow leads to a less confident forecast
that we will see warning impact travel hazards. CIPS analog shows
a 40 pct risk of 3 hr blizzard conditions in the RRV. All in all
after coord will issue SPS and not do headlines as any wind/snow
event is mainly Thu night.
Northwesterly flow sticks around after that end of the week
system moves through, as does some cold air. There is a brief
period Friday night into Saturday morning where we can possibly
see some patches of blowing snow, but other than that, the
forecast is quiet and with minimal impacts. Temperatures will drop
back down into the low teens at night, and the 20s during the
day. Skies will remain mainly mostly cloudy across the northern
plains, and ridging will begin to build in once again in the
western US. This pattern gives allowance for systems to easily
move through the northern plains, so we will continue to monitor
for more possible threats.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 543 PM CST Tue Jan 12 2021
Light west winds becoming southerly overnight with VFR conditions
prevailing through the period.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...None.
MN...None.
$$
UPDATE...JK
SHORT TERM...Riddle
LONG TERM...AK/Riddle
AVIATION...JK
Area Forecast Discussion
National Weather Service Goodland KS
436 PM MST Tue Jan 12 2021
.SHORT TERM...(This evening through Wednesday night)
Issued at 157 PM MST Tue Jan 12 2021
Northwesterly flow aloft prevailed across the region early this
afternoon. 500mb RAP analysis and satellite showed a closed low over
west Texas, with a ridge along the west coast that branched eastward
towards the High Plains. Meanwhile, a shortwave progressed through
the flow above the Pacific Northwest, with cloud cover advancing out
ahead. At 1:30 PM MST, sunny skies were observed, with light west
winds, and temperatures ranging in the upper 40s to upper 50s
across the region.
The upper low moves to eastern Texas tonight, with little change in
pattern for our area. Dry weather continues as temperatures fall
into the 20s across the large majority of the region. Could see
partly cloudy skies at times as the Pacific Northwest shortwave
pushes further inland.
On Wednesday, the aforementioned Pac NW system strengthens and
enters the central and northern Rockies, becoming a closed low in
the process. Clouds increase through the day as a result, while
temperatures climb into the 60s ahead of an approaching cold front.
Overall, a warm and quiet day is expected. However, relative
humidity percentages do fall into the upper teens to upper 20s with
westerly winds gusting 20 to 30 mph. Fortunately, the gustier winds
are not collocated with the lowest relative humidity values; but,
this combination will produce elevated fire weather conditions in
the afternoon for a few hours.
For Wednesday night, the upper closed low travels eastward along the
Canadian border, just north of the Dakotas. The cold front
associated with the system enters the region around or shortly after
midnight. At that time, winds abruptly shift from west to northwest
and an initial burst of strong winds will be possible. Gusty winds
continue through the early morning hours following the frontal
passage. Gusts of 50 mph are forecast, but higher gusts may occur.
There is a slight chance of light rain across the region after
midnight as well, with a brief transition to light snow possible in
eastern Colorado. Not much moisture is anticipated. Otherwise,
temperatures fall into the mid 20s to mid 30s.
.LONG TERM...(Thursday through Tuesday)
Issued at 310 PM MST Tue Jan 12 2021
The main concern in the extended forecast will be the potential for
strong winds, near-critical fire weather conditions and the
potential for some blowing dust on Thursday and Friday.
Early Thursday morning, a cold front will move into the area from
the northwest. Precipitation is not expected at this time as the
drier and colder airmass moves into the region. Thursday morning
through the afternoon, winds are expected to be gusty due to several
factors. An upper trough will continue to dig to the southeast.
Winds aloft are expected to be in the 70-110kt range as a jet streak
comes over the Tri-State area. Questions still linger about how
strong winds will get due to mixing. The pressure gradient over the
area will also be relatively tight which will add to wind concerns.
A High Wind Watch has been issued through Thursday evening for wind
concerns through the day. Sustained winds of 25 to 35mph will be
possible with gusts from 50 to 60mph in areas.
Additionally, fire weather concerns persist for Thursday afternoon.
Relative humidity values will be in the upper teens to 20s across
the region. Wind gusts are expected to meet or exceed 50mph in
areas which brings considerable concern that any fires that pop up
will have the potential to spread quickly, especially with dry
vegetation.
Lastly for Thursday, blowing dust cannot be ruled out for the Tri-
State region. Warm and dry conditions are expected in the days
leading up to Thursday. This will allow soil to dry out and be
easier for winds to loft into the air. The front passing through
the region prior to daylight is a slight detriment to blowing dust
potential, however this does not mean that dust potential would not
be out of the question. The frontal passage and continued concern
for strong winds through the day are of enough concern to make
mention of the possibility for blowing dust issues. Those needing
to travel on Thursday will want to continue to monitor the forecast.
Winds are expected to relax slightly Thursday evening, picking up
again heading into Friday morning. A tight pressure gradient and
good mixing will result in windy conditions once again on Friday.
Combined with minimum relative humidity values in the teens and
20s, fire weather concerns will persist through the afternoon
hours. Held off on a High Wind Watch for now for the region. While
windy conditions are expected, confidence is not high enough to
issue a watch. Continue to monitor the forecast for the latest
updates.
Saturday, northwest flow aloft sets up over the Central High Plains
with a shortwave trough passing to the west and south of the Tri-
State area. The bulk of any moisture should stay out of the area,
however, portions of Eastern Colorado may get clipped by a shower.
Dry conditions are expected Sunday through Tuesday as the area
remains under northwest flow. High temperatures will remain in the
upper 30s to upper 40s. Lows will range from the mid-teens to mid-
20s.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 424 PM MST Tue Jan 12 2021
VFR conditions are expected at MCK and GLD through the 00Z TAF
period. Light west to northwest winds will continue overnight and
become gusty out of the northwest after 16Z. Scattered cirrus
clouds will continue to pass over the area in the west to
northwestflow aloft ahead of a low pressure system approaching
over the northern High Plains.
&&
.GLD WATCHES/WARNINGS/ADVISORIES...
KS...High Wind Watch from late Wednesday night through Thursday
afternoon for KSZ001>004-013>016-027>029.
CO...High Wind Watch from late Wednesday night through Thursday
afternoon for COZ090>092.
NE...High Wind Watch from late Wednesday night through Thursday
afternoon for NEZ079>081.
&&
$$
SHORT TERM...JBH
LONG TERM...AW
AVIATION...LOCKHART
Area Forecast Discussion
National Weather Service Lincoln IL
913 PM CST Tue Jan 12 2021
.SYNOPSIS...
Issued at 300 PM CST Tue Jan 12 2021
Fair weather will continue across central and southeast Illinois
through Thursday morning as clouds increase starting overnight.
Highs will be in the upper 30s and 40s through Thursday.
A winter storm system gets wound up over the Great Lakes region
late this work week. A chance of rain showers will occur in
central IL Thursday afternoon, and in southeast IL by Thursday
evening. Colder air ushering into the region will change the rain
showers to snow showers during Thursday night. Scattered light
snow showers and flurries will likely linger Friday into Saturday,
with light snow accumulations possible.
&&
.UPDATE...
Issued at 913 PM CST Tue Jan 12 2021
Skies are mostly clear with only high cirrus over the area. Winds
remain out of the southwest to south with wind speeds of 10 mph or
less. Current forecast has a good handle on this and still
expecting temps to fall into the upper 20s to around 30 during the
overnight hours. Therefore no update planned at this time.
&&
.SHORT TERM...(This evening through Wednesday)
ISSUED AT 320 PM CST Tue Jan 12 2021
IL finally enjoyed a sunny day today, with just a narrow band of
cirrus clouds pushing southeast toward I-72 at mid afternoon. 1027
mb high pressure near the TX/LA border was ridging ne into the
Ohio river valley. SW winds 8-16 mph and few gusts near 20 mph
combined with sunshine helped warm temperatures today. Temps at 3
pm ranged from 36F at Bloomington and Galesburg to, 47 in Mount
Sterling and Springfield.
Some mid/high clouds over the upper Midwest, over nw half of IA at
mid afternoon, with track se over central IL overnight, with skies
becoming partly cloudy especially over northern/ne CWA. Some of
the CAMs like HRRR were showing some fog developing during
overnight near the Wabash river and over northern CWA where snow
pack lingered. SW breezes to diminish to 5-10 mph after sunset
this evening. Lows tonight in the upper 20s to around 30 degrees,
with lower 30s from Springfield sw.
A 563 dm 500 mb low over central Texas to track east to near the
AL/GA border by 6 pm Wed, while keeping its weather well south of
IL. A northern stream short wave trof over the northern Rockies to
track into nw and west central IL by sunset Wed. This will spread
more mid/high clouds into central IL during Wed especially from
late Wed morning on. SW breezes again on Wed supports milder highs
ranging from lower 40s northern CWA, to the upper 40s over
southeast IL and sw CWA, with areas from Springfield sw around 50.
.LONG TERM...(Wednesday night through Tuesday)
ISSUED AT 320 PM CST Tue Jan 12 2021
The 12Z forecast models continue to show a strong upper level
low/trof digging into the Midwest on Thu and sending a cold front
se thru central and southeast IL during Thu. Mainly post frontal
rain showers initially with this system moving into central IL by
Thu afternoon and into southeast IL early Thu evening. Highs Thu
in the upper 30s to around 40F northern CWA and upper 40s in
Southeast IL. Temps will likely be slipping after the cold
frontal passage. Colder air ushering in Thu night to change the
rain showers to light snow showers from nw to se. Models also show
a dry wedge working into central IL overnight Thu night with pcpn
diminishing then into early Fri.
A strong cutoff upper level low (514-520 dm 500 mb low) will pivot
into northern IL Fri morning track toward the IN/OH border by dawn
Sat while sending a secondary cold front thru central IL on Fri
afternoon/evening. This will likely bring light snow showers back
into central IL during Fri into Sat morning with brisk winds,
then diminishing to flurries Sat afternoon. Highs Fri in the lower
30s northern/nw CWA and upper 30s to near 40F in southeast IL.
Highs Sat and Sunday in the mid 20s to lower 30s. Some models show
another short wave moving through the deep upper level trof over
the eastern US on Sunday and could keep flurries and more low
clouds around along with cold conditions.
Temperatures to slowly modify back to normal by next Tue (highs in
the 30s) as deep upper level trof pulls away from IL, though a
lingering trof extends from the upper MS river valley back into
northern Mexico next Tue.
&&
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 542 PM CST Tue Jan 12 2021
VFR conditions will prevail at all TAF sites next 24hrs. Clouds
will be high cirrus through the period with few clouds tonight,
becoming broken tomorrow morning. Winds will be southwest through
the period with light speeds tonight, increasing to around 10kts
tomorrow morning...continuing into the afternoon.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Auten
SYNOPSIS...07
SHORT TERM...07
LONG TERM...07
AVIATION...Auten
Area Forecast Discussion
National Weather Service Jacksonville FL
835 PM EST Tue Jan 12 2021
.UPDATE...
Cloudy conditions continue over the region under cool advection
pattern with the low clouds trapped under a strong inversion at
around 3000 ft. Additional high clouds will move over the area
tonight ahead of approaching upper level trough. Don`t see much
reason to believe that the low clouds will break up tonight so
leaned toward persistent low clouds tonight through Wednesday
morning, keeping skies mostly cloudy/cloudy in the forecast/grids.
Also, with low stratus clouds potentially lowering further, included
patchy fog in the forecast for inland areas early Wednesday morning.
Min temps tonight in the 40s, with a few upper 30s well inland,
still appear on track but favor being on the slightly warm side of
the guidance for the min temps due to the clouds.
.MARINE...
Winds and seas slightly higher tonight than models showed so just
small adjustments upwards were made based on the current conditions.
Most of the sea state in the form of long period swells rest of
tonight and Wednesday. Otherwise, forecast is on track.
&&
.PREV DISCUSSION [655 PM EST]...
.NEAR TERM.../through Wednesday/...
Cold front will continue to push to the east of the region this
afternoon, as high pressure builds from the west through Tonight
into Wednesday.
A combination of an upper trough moving over area from the west
Wednesday afternoon, and weak surface wave moving northeast from the
gulf, will provide for cloud cover across the region. For the most
part, showers from the gulf wave will stay south of the region, but
a few showers could extend into central FL counties.
Temperatures will trend near normal for Tonight. Highs Wednesday
will be limited somewhat by expected cloud cover, with readings a
little below average.
.Short Term.../Wednesday night Saturday/...
Surface high pressure will move overhead during the night Wednesday
night, as upper wave departs to the east. Clouds will break
overnight from west to east, but cloudiness is expected to clear
slowly due to the upper wave. Cooler air will advect into region
Wednesday night, with lowest temperatures forecast inland, where
better chance for clearing skies.
High pressure will become centered to the south Thursday, with ridge
extending north across area. In general, a partly to mostly sunny
day is expected for Thursday with temperatures running near to a
little above normal.
The surface ridge will push more toward the southeast Thursday
night, as a cold front moves toward the region from the northwest.
Lows will trend a little below normal.
The cold front will cross the region Friday into Friday evening.
Dynamics are fairly limited with this front, so not anticipating
much more than isolated to scattered showers with the passage. With
current frontal timing temperatures are expected to warm above
normal over eastern counties, with highs near to slowly below normal
inland. High pressure will build from the west southwest overnight
Friday night with frontal precipitation moving to the east. Cooler
air will filter in from the west Friday night, with lows a little
below seasonal averages.
For Saturday, the region will be between high pressure to the south,
and a trough of low pressure to the north. Cool advection is
expected to continue into Saturday, as cloud cover decreases.
Temperatures are anticipated to be a little below normal.
.LONG TERM.../Saturday night through Tuesday/...
High pressure will build overhead Saturday night through Sunday.
This will yield mainly clear skies Saturday night into Sunday.
Saturday night is likely to be coolest night this week, with lows
getting down to around freezing inland. Highs Sunday will remain
below seasonal averages despite expected sunshine due to a
northwest/west flow.
The high will weaken and move east Sunday night as an upper wave
draws in moisture from the gulf. This wave will then cross the area
Monday, with a low chance for showers Monday. Temperatures will be a
little milder Sunday night, but a few inland locations could still
get close to freezing. Highs Monday, will be a little below normal.
High pressure will build overhead from the west Monday night through
Tuesday. This pattern is expected to produce mainly clear skies with
near seasonal temperatures.
.AVIATION...
[Through 00Z Thursday]
Solid blanket of low clouds continues this evening across southeast
GA and northeast FL with consistent CIGS of around 1500 ft. Steered
away from any SREF guidance as it does not capture current CIG
conditions. So, based on satellite imagery and latest HRRR and NAM
model guidance will continue to go prevailing MVFR tonight, and
consistent with prior TAF forecast, trended to IFR CIGS by 07Z-10Z
at all TAF sites, with SSI possibly going as soon as 05Z-06Z to IFR,
and GNV also trending to LIFR around 10Z. The low CIGs at TAF sites
were shown to lift to MVFR by 15Z though confidence in the
transition timeframe is low. Uncertainty also in the lifting of CIGs
to VFR Wednesday afternoon and for now indicated possible VFR CIGs
around 20Z.
.Marine...
High pressure will build from the west through Wednesday. A weak
upper wave will move northeast across area Wednesday afternoon and
evening. Region will be between high pressure to the south and a
trough to the north Thursday. The high will move toward the
southeast Thursday night. A cold front will move southeast across
area Friday into Friday evening. High pressure will build from the
west Saturday, then overhead Saturday night through Sunday.
Small Craft Advisory potential Friday night and Saturday.
Rip Currents: SE GA Moderate for Wednesday
NE FL Moderate for Wednesday
&&
.PRELIMINARY POINT TEMPS/POPS...
AMG 39 57 35 59 38 / 0 0 10 0 0
SSI 44 57 40 60 42 / 0 10 10 0 0
JAX 41 59 40 62 40 / 0 10 10 0 0
SGJ 44 59 43 62 43 / 0 10 20 0 0
GNV 41 60 38 62 38 / 0 10 20 0 0
OCF 43 62 41 64 41 / 0 10 20 0 0
&&
.JAX WATCHES/WARNINGS/ADVISORIES...
FL...None.
GA...None.
AM...None.
&&
Area Forecast Discussion
National Weather Service Key West FL
1050 PM EST Tue Jan 12 2021
.DISCUSSION...
A cold front passed south across the keys earlier this evening.
Low stratus has followed by front and will present a low gray
sunrise on Wednesday.
The upper disturbance spinning over eastern Texas will eject
eastward over the next 24 hours, passing by to our north late
Wednesday. Meanwhile, our moisture will be unseasonably deep, with
PW values expected to exceed 1.7" late Wednesday. Flow in the
850-700 mb layer will shift from southwest to west as the
disturbance sails by to our north, acting on the deep moisture and
some weak elevated instability to set up a pretty hefty band of
rain with embedded convective elements near or north of the Keys
late Wed and Wed night. Once the flow aloft shifts from
southwesterly to westerly, the mid-level air mass will dry out
over the course of Thursday, and the main area of rain will move
off to the east. This will set up a drying trend on Thursday.
&&
.MARINE...
Behind a cold front earlier this evening, Sand Key Light has been
observing a north wind of about 19-20 knots. Have therefore
inserted SCEC headlines into all oceanside waters west of the
Seven Mile Bridge. Temporary easing is expected on Wed afternoon,
but then another surge of north wind is expected by early Wed
evening.
Some longer period swell westerly swell is emanating from the Gulf
right now. Both Satan Shoal and Pulley Ridge buoys have observed a
dominant wave period as long as 11 seconds in a westerly swell
this evening.
From synopsis...A cold front passed the Keys earlier this evening.
Behind the front, high pressure will move from the western Gulf on
Wednesday through the central Gulf Thursday, arriving and
weakening over South Florida on Friday. The next cold front will
plow across the Keys waters around Friday night, followed by
freshening northwest breezes. High pressure will prevail over the
western and northern Gulf on Saturday and Sunday, leading to
gentle northerly breezes on Sunday.
&&
.AVIATION...
Occasional IFR stratus will continue to stream across the
terminals at times through at least Wednesday morning, in the
shallow north wind behind a cold front earlier this evening.
Latest HRRR runs show some temporary breaks for the next few
hours, but then cigs below 010 will fill back in for several
hours around sunrise. The stratus should lift and possibly
dissipate late Wednesday morning.
&&
.KEY WATCHES/WARNINGS/ADVISORIES...
FL...None.
GM...None.
&&
$$
Public/Marine/Fire...Haner
Aviation/Nowcasts....Haner
Data Acquisition.....SDR
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