Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/03/19
Area Forecast Discussion
National Weather Service Charleston SC
937 PM EST Sat Feb 2 2019
.SYNOPSIS...
Weak upper level disturbances will affect our area the rest of
this weekend while a trough lingers along the Southeast coast.
High pressure will then build across the region Monday and
persist through late next week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Late this evening: No significant changes to the forecast
through sunrise. Made some minor adjustments to rain chances to
lower them across eastern Charleston and Berkeley counties based
on radar and model trends. Previous discussion continues below.
Early this evening: Regional radar imagery shows scattered
showers offshore within the coastal trough and isolated showers
along the lower Georgia coast. Otherwise, most of the area is
dry and should stay that way through the rest of the night. The
main source of forcing is the neutral to negatively tilted mid-
level shortwave currently moving into the Lower Mississippi
Valley. While there could be scattered showers within the
coastal trough that track northward and brush the far eastern
portions of Berkeley and Charleston counties, the best chances
for rain will likely wait until after sunrise Sunday when the
trough and its associate forcing arrives. We could start to see
the leading edge of showers move into portions of southeast
Georgia late tonight, but mostly after sunrise. Made adjustments
to rain chances based on pretty good agreement among the GFS,
NAM, HRRR, and RAP. Lows should range from the upper 40s inland
to the low 50s closer to the coast.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Sunday: Forecast models now actually show pretty good agreement
regarding the arrival of a notable mid-level shortwave beginning
in the morning. Precipitable water values are progged to
increase into the 1.25 inch range through the day, and model
time heights show a nice aligning of the best region of upward
vertical motion coinciding with the deepest moisture. There is
increasing model agreement among the GFS, NAM, HRRR, and RAP
that an expanding area of showers will spread in from the west
just ahead of the shortwave aloft right around and just after
sunrise. This area of forcing will then spread across the
forecast area through the day. There remains some timing
disagreement among the models, but confidence has increased due
to the presence of a more robust trough and the fact that the
forcing isn`t dependent on the nearby coastal trough and
developing area of low pressure. For now, have increase rain
chances into the high chance range so as to hopefully trend in
the right direction. If model trends continue much higher rain
chances will eventually be needed. Also of note, models do show
an area of negative Showalter Indices passing through tomorrow,
indicative of some possible elevated instability. So, its not
out of the question for there to be some elevated thunder, but
will not add to the forecast at this time. With widespread
cloud cover and the presence of showers, temperatures will be
tricky and lower than previously thought. Lowered highs several
degrees into the low 60s. Into the evening and overnight, the
trough and forcing will move off to the east and rain chances
come to an end.
Monday and Tuesday: The mid-levels will consist of a
strengthening low off the Southeast coast Monday morning. This
low will be pushed away by building heights within semi-zonal
flow over our area Monday afternoon. Semi-zonal flow with hints
of weak ridging are expected across the Southeast on Tuesday. At
the surface, the low/trough will be departing in the Atlantic
while high pressure persists over the Southeast. The high is
expected to gradually shift southward with time. As this is
occurring, to the distant west will be an approaching front. The
high will dominate the forecast, bringing dry conditions with a
mix of sun and clouds. A combination of rising heights, warming
850 mb temperatures, and surface wind direction will allow
temperatures to rise. Highs on Monday could be about 10 degrees
above normal while Highs on Tuesday could approach 15 degrees
above normal.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A fairly dry and warmer pattern is expected mid week as sfc
high pressure settles over the Southeast under a ridge of high
pressure building aloft. Conditions should then be even warmer
during the second half of the week as the mid/upper ridge of
high pressure becomes more amplified across the Southeast ahead
of a large trough of low pressure over the Central United
States. In general, afternoon temps should peak into the low/mid
70s Wednesday, then mid/upper 70s Thursday and Friday well
ahead of a front approaching the Southeast late next weekend.
Overnight lows will also trend warmer, from the low/mid 50s
Tuesday night to mid/upper 50s during the second half of the
week. Although a few showers are possible across inland areas
mid week, the best chances of precip appear to be next weekend
should the front shift into the region. There is also a low
threat of sea fog moving onshore and into immediate coastal
areas mid to late week as light southerly winds develop and sfc
dewpts approach 60 degrees over cooler shelf waters.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
We begin with VFR conditions at both sites, but that should
change over the next 4-6 hours. Have timed MVFR ceilings into
KSAV at 04z, and at KCHS at 06z. We could see a lowering of
ceilings into the IFR range later tonight, but confidence isn`t
high enough at this point. Then for Sunday, an area of showers
is expected to move in from the west with IFR ceilings likely.
Started this downward trend at KSAV at 14z and at 17z at KCHS.
While showers will end at first at KSAV in the afternoon, and
then in the evening at KCHS, IFR conditions could persist
through the end of the forecast period.
Extended Aviation Outlook: Rain showers associated with a
coastal trough are expected to bring flight restrictions on
Sunday. VFR Monday through Thursday.
&&
.MARINE...
A coastal trough will maintain NNE winds over the waters
through tonight. Speeds will generally be less than 15 kt and
seas 2-4 ft.
The trough should continue its movement to the northeast and
away from our area on Sunday. Inland high pressure will build
late Sunday into Monday, persisting into midweek. Winds and seas
will generally stay below Small Craft Advisory levels. However,
light southerly winds should develop over all waters heading
into mid week. These winds along with dewpt temps approaching 60
degrees, could produce a period of sea fog over cooler shelf
waters mid week and potentially until fropa occurs late week.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...None.
&&
$$
NEAR TERM...BSH
SHORT TERM...BSH/MS
LONG TERM...DPB
AVIATION...BSH/MS
MARINE...JRL/MS
Area Forecast Discussion...Updated
National Weather Service Peachtree City GA
1010 PM EST Sat Feb 2 2019
.Update...
No changes except to nudge pops up a bit after midnight for the far
southern row of counties... Increasing showers still well to our
south for now.
41
.Previous...
.SHORT TERM /Tonight through Sunday Night/...
Split-flow pattern remains in place with a shortwave pushing off
into the western Atlantic from the Southeast, with another pushing
through the ArkLaTex at AFD time. Northern stream system is
generally stationary along the U.S./Canada border, while a deep
cutoff low is working onto the Pacific Coast. Weak surface high in
the western Atlantic continues to ridge back toward the Southeast,
with E to NEly surface flow in place, and while dewpoints are
definitely drier within the ridge, there is no low-level CAA.
Moisture to our south is taking its time lifting slowly north, and
as was the concern yesterday, ended up with a bit of a temperature
bust today across north and eastern portions of the state where
basically they`ve seen full sun all day. The result has been almost
spring-like, especially after the cold weather of recent. The
ArkLaTex wave will move east overnight, with additional moisture
spreading into the region, and the increasing cloud cover will lead
to overnight lows well above-normal tonight, 10-15 degrees in some
areas. As we move toward daybreak and the shortwave pushes over the
area, there should be enough lift from the dPVA and diffluence aloft
to support weak showery activity. While new guidance keeps the idea
of low clouds in the morning, the surface saturation isn`t quite as
high, so less concerned about drizzle with this forecast. HRRR and
other CAMs indicate isolated to widely scattered showers off and on
overnight, blossoming toward daybreak with the upper lift moving
across. Without having a better handle on timing, have left pops in
the slight to at best mid-range chance category, but quite likely
pops will have to be increased (high pop/low QPF) later as we get a
better handle on shower potential.
We start losing the deeper moisture by mid-morning Sunday, but low-
levels remain saturated into the evening. Drying aloft continues to
push further down, but even by the end of the period (00z Mon) most
guidance still has pretty high RH between 925-850mb (much drier
aloft though). This wouldn`t be enough to support showers, but
certainly a continuation of the low clouds will be an issue. NAM and
GFS bufr soundings do show some slow improvement through the
evening, and as is typical the GFS is more optimistic (though still
about 1500ft at best through the end of the period, with signs of
more improvement thereafter). The thickness of the clouds and
whether or not we see any breaks will have a big impact on
temperatures...which will again be above normal either way, but as
we saw today the sunshine in a pattern like this (that is, though we
have low-level northeasterly winds, there`s no real CAA associated
with it) can make the difference between 5-7 degrees.
TDP
.LONG TERM /Monday through Saturday/...
The forecast into the coming week will be characterized by
temperatures warming well above normal with weak upper perturbations
providing chances for rain across primarily north Georgia. Late
Monday into Tuesday, a fast-weakening front will approach the
region, bringing chances for scattered showers, primarily across
northern and western portions of the area. Given unimpressive
forcing, did not mention thunder on Tuesday at this time.
By Wednesday, the upper ridge over the Gulf of Mexico begins to
amplify as the trough digs across the western U.S. Weak
disturbances in the west-southwest upper flow will keep the
chance for showers or perhaps an isolated thunderstorm on
Wednesday, especially across north Georgia. As the upper ridge
builds northward, temperatures will continue further above normal.
Widespread high temperatures in the 70s can thus be expected with
some areas of central Georgia pushing 80 degrees by Thursday.
Some record highs may be in jeopardy by midweek.
Models continue to offer conflicting conclusions regarding the
eventual cold frontal passage late week. The ECMWF remains more
progressive and sweeps the front through on Friday while the GFS
holds off.
RW
&&
.AVIATION...
00Z Update... VFR ceilings across the taf sites will gradually lower
to MVFR...then IFR before sunrise. A disturbance moving across
should be enough to allow -SHRA to form starting just before
daybreak, lifting NE through the late morning hours. Cigs should
lift slowly back to MVFR around or just after noon, remaining MVFR
through the end of the period. Winds will remain light east to
southeast.
//ATL Confidence...
00Z Update...
High on winds. Medium on all else.
41
&&
.PRELIMINARY POINT TEMPS/POPS...
Athens 46 57 41 65 / 30 30 5 10
Atlanta 48 57 45 62 / 40 40 5 20
Blairsville 41 56 39 60 / 30 40 5 30
Cartersville 47 58 43 62 / 40 40 10 30
Columbus 50 62 48 66 / 30 20 5 20
Gainesville 45 55 42 61 / 30 40 10 20
Macon 49 61 44 67 / 30 20 5 10
Rome 46 59 43 62 / 30 40 10 30
Peachtree City 48 58 43 64 / 30 20 5 20
Vidalia 51 63 47 67 / 30 40 5 5
&&
.FFC WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...41
LONG TERM....RW
AVIATION...41
Area Forecast Discussion
National Weather Service Sioux Falls SD
551 PM CST Sat Feb 2 2019
.SHORT TERM...(This evening through Sunday)
Issued at 240 PM CST Sat Feb 2 2019
Very pleasant afternoon across much of the area, with the exception
of highway 14 as they are north of the front across the area. With
the melting snow pack across the area, could see some fog develop
once again overnight. NAM not handling the near surface moisture
well, but the HRRR and RAP have been fairly consistent with patchy
fog developing in vicinity of the front sagging ever so slightly
south towards I-90 through the overnight hours. In terms of lows,
have sided with warmer guidance values, especially south of the
front.
Expect to see increasing clouds throughout the day on Sunday. South
of the front, strong warm air advection and limited snow pack will
lead to another day of above normal temperatures. Further to the
north, east to northeast winds should keep temperatures much cooler.
Low level stratus builds in depth through the afternoon into the
evening hours. With a dry layer keeping the dendritic layer from
being effective, expect drizzle/freezing drizzle to develop through
the evening hours as isentropic lift increases. Cold front quickly
moves through towards the midnight hour, with enough drying to
really limit the amount of snow behind the front. Considered issuing
a winter weather advisory for much of southwest Minnesota for icing
potential Sunday night into early Monday morning, but agreed through
collaboration to hold off for the time being.
.LONG TERM...(Sunday night through Saturday)
Issued at 240 PM CST Sat Feb 2 2019
Monday looks to be much cooler and windy with 925 hpa temperatures
falling towards -20C. Have non-diurnal temperatures by blending
superblend with SREF. Have also raised winds on Monday compared to
super blend guidance.
The middle of next week continues to look unsettled, but each model
is offering different solutions with respect to snowfall into the
Tuesday through Thursday time frame. Am confident there will likely
be some light precipitation in that time frame, but can not pin down
which wave to focus on at this point.
Late next week continues to look well below normal as second push of
arctic air looks to work into the Northern Plains. At this point,
blend values appeared to be a good starting point.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 548 PM CST Sat Feb 2 2019
Winds will continue to weaken overnight. By Sunday morning,
mostly calm winds with ample low level moisture will lead to areas
of fog. Patchy fog with increasing low level cloud cover will be
the main story throughout the daytime hours on Sunday.
Precipitation in the form of freezing drizzle and drizzle begins
Sunday late afternoon into the evening, with up to a tenth of an
inch ice accumulation for southwest Minnesota. Sites such as KFSD
are likely to see a light glaze as well overnight into Monday
morning, before changing over to brief light snow around Sunrise
Monday.
&&
.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.
&&
$$
SHORT TERM...BT
LONG TERM...BT
AVIATION...VandenBoogart
Area Forecast Discussion
National Weather Service Hastings NE
534 PM CST Sat Feb 2 2019
...AVN UPDATE...
.SHORT TERM...(This evening through Sunday)
Issued at 413 PM CST Sat Feb 2 2019
The main concern in the short term is the potential for
redevelopment of fog tonight and its impact on temperatures
Sunday.
Stratus has been extremely pesky today and slow to burn off,
especially over the E CWA as well as a narrow swath right through
the central CWA. This has resulted in cooler than expected high
temperatures this afternoon for these areas with temps largely in
the 40s to low 50s. S portions of the CWA have seen several hrs of
sun and their temps have rapidly shot up into the 60s.
The concern going forward is that without a major airmass change
we could be looking at a similar situation from last night setting
up again for tonight. Have expanded the areal coverage for fog
tonight in the forecast, but there is great uncertainty on timing
and severity. NAM probably did best with the situation today
(though still somewhat overdone) and it brings back fog the
quickest and most dense overnight. The hi-res guidance is less
aggressive with fog development overnight and actually delays
development until closer to dawn on Sun. Given the pesky nature of
fog/stratus today, felt best to trend the forecast toward more
fog and earlier development. The eastern half or so of the CWA
could see dense fog development late tonight or early Sun AM per
latest HRRR runs. Confidence is low, however, and may very well
need multiple forecast updates this eve and overnight.
With the aforementioned fog concerns tonight into Sun AM, have
also trended high temps on Sun down a few degrees and this may
still be several deg too warm if a repeat of Sat occurs. Would
not be shocked if both weekend days end of being a disappointment
for many given the once very warm/nice forecast. The W/NW has the
best chc to escape the stratus/fog on Sun and see more sun. Highs,
for now, are in the 50s to low 60s. A strong cold front is set to
move through the area after midnight Sun night, marking an end to
the mild pattern.
.LONG TERM...(Sunday night through Saturday)
Issued at 413 PM CST Sat Feb 2 2019
The long term section of the forecast is nothing like the short
term as the forecast area returns to mid-winter pattern that will
feature below to well below normal temps and at least a chc for
wintry precip.
We`ll start off the work week with a strong cold front moving
through the area Mon AM. Highs for the calendar day will likely
occur before dawn. This cold front will be forced S by a strong
shortwave working through the N Plains into the Upper Midwest.
Moisture is severely lacking with this system for local CWA per
latest model forecast soundings. In fact, may see a good amount of
sunshine on Mon, but this will do little to make it feel nice as
strong cold air advection on gusty NW winds will keep daytime
temps largely in the 20s and 30s for most.
SW upper level flow develops on Tue as a trough digs along the
West Coast. A couple weak shortwaves within the SW flow traverse
the area Mon night into Tue. Models keep the majority of any
appreciable moisture focused closer to the front that passed thru
Mon AM as by Tue it will situated over the Lower MO River Valley
/Mid-MS River Valley. Otherwise, Tue will be cold with highs in
the 20s to near 30.
The western trough will edge eastward on Wed, but latest models
suggest dry conditions continue through the daytime. Pcpn chcs
incr dramatically Wed night as lee side low pressure deepens over
SE CO. This low is forecast to shift E across the Central/Southern
Plains Wed night into Thu. At the same time, a strong 1040mb high
is forecast to drop S into the N Plains, resulting in a tight
pressure gradient and a surge of cold air. EC/GFS have not been in
great agreement lately on this system, and not surprisingly, some
differences continue, though not as drastic as 24hrs ago. GFS
remains weaker and more progressive compared to slower/stronger
EC. Both models are in agreement that pcpn should be all snow and
suggest potential for at least lgt snw accumulations. Given
potential for dry/fluffy snw, breezy winds and cold temps will
begin to message this potential in the HWO.
Below to well below normal temps are likely to continue through
the end of next week and into next weekend. Exactly how cold we
get and whether or not we make a run at wind chill advisory
criteria (wind chills -20 or colder) will depend on our
amount/depth of snow cover. The current forecast calls for highs
in the teens to 20s and lows in the single digits to low teens.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Sunday)
Issued at 534 PM CST Sat Feb 2 2019
Significant Wx: IFR fog/stratus to move back in.
Tonight: VFR to start with no clds at or below 10K ft...but patchy
fog should develop early as temps cool (by 02Z-03Z). Have seen
this scenario before...and the mdls are not quick enough to lower
CIGs/VSBYS. So deviating significantly from guidance. IFR fog
should become widespread 03Z- 06Z with CIGs/VSBYs deteriorating
rapidly. SW winds 6-10 kt. Confidence: High
Sun: IFR fog/stratus until midday. EAR should improve to VFR first
in the 17Z-19Z time frame. GRI 19Z-22Z. Went pretty pessimistic at
GRI with MVFR CIGs thru 22Z. Lgt/vrbl winds become S 5-10 kt.
Confidence: Medium (mainly due to uncertainty on timing of VFR).
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.
&&
$$
SHORT TERM...Thies
LONG TERM...Thies
AVIATION...Kelley
Area Forecast Discussion
National Weather Service Houston/Galveston TX
832 PM CST Sat Feb 2 2019
.DISCUSSION [UPDATE]...
Light to moderate showers has been affecting the western half of
the CWA this afternoon and evening and will continue to expand
eastward tonight as the shortwave moves across the region.
Expect rain activity to continue overnight and Sunday morning.
The dense sea fog that developed earlier today across the bays
and nearshore Gulf waters slowly made its way into the barrier
islands late in the afternoon, thus, a dense fog was issued for
the aforementioned locations and will continue in effect through
at least 9 AM CST Sunday. If conditions do not improve, this
advisory will likely be extended.
The rain activity inland will make it a little tricky to forecast
for fog inland, nevertheless, current model guidance and sounding
data continue to indicate fog inland overnight and early Sunday
morning...heaviest being over the bays, nearshore Gulf waters and
coastal regions. Therefore, continue to watch for patchy to
possibly dense fog in isolated areas later tonight. Exercise
caution along roadways and causeways.
The inherited POPs for today and tonight were modified to better
represent the solutions from the latest hi-res model precip
guidance as well as the current weather observations.
Temperatures were slightly increased as well. Otherwise, no
significant changes were made.
&&
.PREV DISCUSSION... /ISSUED 554 PM CST Sat Feb 2 2019/
AVIATION...
A messy 24-30 hour TAF period is expected. A weak disturbance
moving up the coast will generate periods of light rain this
evening ending between 06-08z. The disturbance will wreak havoc
with ceilings and cigs will vary between LIFR to MVFR. Sea fog
near the coast will gradually work inland in the wake of the short
wave and visibility and ceilings will likely fall to LIFR by 12z
Sunday. Fcst soundings offer a glimmer of hope with a mix of MVFR
and VFR ceilings develop after 21z and this is supported by HRRR
cigs progs and ECMWF cloud product. The respite will be short
lived as soundings and cloud progs suggest MVFR cigs will return
between 00-03z Sunday night. 43
PREV DISCUSSION... /ISSUED 400 PM CST Sat Feb 2 2019/
DISCUSSION...
Overall...not a lot of change from previous thinking that the SE
TX weather pattern will be largely dominated by the mostly zonal
flow aloft and onshore flow at the surface. For the next several
days, the main forecast issues to include the persistent sea fog
over the bays/nearshore waters along with timing the isolated to
scattered showers (via with the embedded shortwaves in the upper
flow). Activity still looks on track for tonight based on trends
over our western counties. These showers should be moving across
the CWA through this evening...with patchy fog developing in its
wake overnight/early Sun morning.
We should see a brief break with POPs Sun afternoon/evening, but
thereafter models are indicating that we`ll get a series of weak
disturbances (from increasingly SW flow aloft) for first half of
next week. And so, will be keeping with mostly isolated to wide-
ly scattered POPs during this time frame along with above normal
temperatures. The next upper trof is forecast to be deepening in
and near the Four Corners through mid week before it weakens and
ejects E/NE during the latter part of the week. This system will
then help to drag the next cold front into the state. As per the
previous runs, models are still having issues with the timing of
said cold front. Blended guidance leaning more with the slightly
faster ECMWF/UKMET and puts FROPA across SE TX late Thurs after-
noon/evening, and no real arguments with that at this time. 41
MARINE...
Given east to southeast winds tonight, sea fog should continue for
much of the upper Texas coast and bays. For now a marine weather
statement will highlight the fog threat overnight until visibility
drops to advisory levels. Dense fog advisories may be possible
tonight into tomorrow morning as moisture increases. Sunday into
Monday may be when fog is the worst. Moisture should increase more
with dewpoints in the low 60s while water temperatures remain in the
upper 50s at best. While winds may be more from the south, the
higher moisture content moving over the colder waters should support
more widespread fog and lower visibility.
Winds increase from the south gradually through the work week and
top out Wednesday into Thursday. Sea fog threat will likely continue
Monday and Tuesday depending upon moisture fields and water
temperatures. Stronger winds mid week may allow for stronger mixing
and more likely to dissipate fog.
Overpeck
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 58 73 63 76 62 / 60 20 10 20 20
Houston (IAH) 57 73 63 76 62 / 60 40 10 20 20
Galveston (GLS) 57 65 61 69 61 / 50 50 20 20 20
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Dense Fog Advisory until 9 AM CST Sunday for the following
zones: Brazoria Islands...Galveston Island and Bolivar
Peninsula...Matagorda Islands.
GM...Dense Fog Advisory until 11 AM CST Sunday for the following
zones: Coastal waters from Freeport to Matagorda Ship
Channel TX out 20 NM...Coastal waters from High Island to
Freeport TX out 20 NM...Galveston Bay...Matagorda Bay.
&&
$$
Discussion...24
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
945 PM CST Sat Feb 2 2019
.UPDATE...
Issued at 938 PM CST Sat Feb 2 2019
We are still monitoring fog potential tonight with the focus for
the better probabilities over the snow pack in northeast MO and
west central IL, and also from southeast MO across southwest IL.
Upstream cloud over has become a lot more fragmented across
western MO. In the short term this would be a positive factor for
fog development over the snow pack. However the model low level
RH fields with a nod to the RAP are also suggesting that there
will be more continuous stratus development overnight from western
MO into central and northeast MO. Predominately clear skies are
expected from southeast MO into southwest/south central IL which
would benefit radiational contributions given the lower T/Td
spreads. The gradient is stronger tonight and surface winds are
higher, and those within the lowest km above the low level
inversion are rather stout. The current forecast has fog mentioned
in both locations and we`ll keep a close eye for indicators of
more prominent dense fog potential.
Glass
&&
.SHORT TERM... (Through Late Sunday Afternoon)
Issued at 300 PM CST Sat Feb 2 2019
We remain situated beneath generally zonal upper level flow with
high pressure to our east. The resultant southerly low level flow
has helped usher plenty of warm, moist air into the region, and
scattered to overcast clouds extending west to a dryline across
central KS and OK. Forecast guidance in good agreement keeping the
zonal upper level pattern in place through the night and continuing
the low level return flow well into tomorrow. With a decrease in
mixing as the sun goes down, I expect to see the cloud coverage
trend toward overcast as we move into the early morning hours.
Per the SPC mesoanalysis, the main thrust of column moisture is
currently across eastern OK/KS. Forecast guidance is in good
agreement keeping the best low level moisture to our west, focused
on western and northern MO through the night. However, the main axis
of moist warm air advection does spill into our north and west, and
much of the guidance is painting very light QPF across those areas
tomorrow morning. Furthermore, warm, moist flow on top of snow
covered ground often times results in dense fog, and the SREF
continues to be quite bullish on widespread fog across our north.
With all that, it`s likely that we see some sort of combination of
fog and drizzle in those areas. Unfortunately these types of events
often defy expectations (see this morning), so forecast confidence
in coverage or intensity of the drizzle or fog is rather low. For
now, have gone with a low chance drizzle and areas of fog, but this
forecast will likely be updated as details become more clear. The
good news is that we will remain well above freezing.
After 12z tomorrow, a compact shortwave will eject into the northern
Plains, helping deepen a surface low over roughly the same area.
This will enhance the southerly low level flow, keeping the warm
moist air streaming into the region. Otherwise, tomorrow looks
rather similar to today, with holes to developing in the overcast
skies in the late morning and early afternoon. Despite these cloudy
skies, strong southerly flow will allow temperatures to climb well
into the 60s across much of the are tomorrow.
BSH
.LONG TERM... (Sunday Night through Next Saturday)
Issued at 300 PM CST Sat Feb 2 2019
The latest model guidance seems resolved to maintain a longwave
upper TROF over the western CONUS through the forecast period,
resulting in a W-SW flow aloft over our region. This generally
favors an active weather pattern with limited intrusions of cold
air.
The unseasonably mild air will continue through Monday, when it will
be interrupted by a cold front that will knock our temps after to
closer to seasonable values. Precipitation chances for late Sunday
night and into Monday remain low with much of the upper support
passing well to the north and a small window for other forcing to be
able to generate showers before the surface front passes through.
Morning FROPA on Monday will limit warming for areas north and west
of STL metro. For STL metro and areas S and E, an afternoon FROPA
will allow the opportunity to make a run on 70 degrees with the
airmass behind the front, despite being polar in nature, only edging
our region and never really establishing itself too firmly. This
will be key to the forecast later in the week.
Upper flow will back more SW heading into Tuesday as the old surface
frontal boundary stalls over southern MO and IL. This will create a
classic WAA precipitation setup and that is exactly what is forecast
to happen. Models have been in reasonably good agreement on the
onset time being Tuesday afternoon or early evening. By this time,
there should already be established enough warm air aloft for the
precipitation to be either all rain (for much of the forecast area)
or rain mixed with sleet becoming freezing rain for portions of
northeast MO and west-central IL.
Models also are settling on two main waves of precipitation, of
which the late Tuesday onset constitutes the first wave. The first
wave should then continue through much of Tuesday night across the
area. After a brief break or lull for much of Wednesday daytime,
the second wave looks set to move in for Wednesday night and
Thursday. A similar stratification of temperatures as with
the first wave is expected, with all rain for most of the forecast
area or freezing rain/rain transitioning back to snow for portions
of northeast MO and west-central IL.
While confidence is moderately high for the presence of warm air
aloft given the setup, confidence is less on where exactly the 32F
isotherm at the surface will be. Because it is not expected for the
low level cold air to ever be firmly established, model consensus
favors it wavering over or near northern MO and central IL
throughout this event and never really getting any further south.
Especially for interests in northern MO and central IL, this remains
a storm of concern and should be followed closely with potential for
a mixed bag of wintry weather and accumulations and associated
impacts.
It may not be all easy for areas that receive all rain, either.
There has been a signal for elevated thunderstorm potential for
areas near and south of I-70 for much of this event and finally
added it in with this forecast package. This lends greater support
also to event total QPF that could be a widespread 1-3". If
realized, this could result in impacts to area rivers or nuisance
flooding elsewhere.
There remains some discrepancy amongst the models on how this all
ends. The EC and GFS are at odds on when to bring the main
disturbance out of the southwestern CONUS, with the EC rolling it
through Thursday night and the GFS not until Saturday. A slower
rollout would maintain a precipitation threat well into next
weekend for at least some of the area. At first glance, this might
also impact when the main push of cold air at the low levels occurs,
considering the persistent SW flow aloft. The main medium range
models continue to show this push occurring Thursday night largely
thanks to good agreement with a northern stream TROF swinging
through the north-central CONUS and northern Great Lakes. This push
of cold air is also expected to be coincident with the ending of the
second wave of precipitation, probably keeping any wintry
precipitation to the N and W of STL metro before ending.
The main push of cold air looks to affect our area for next weekend
but it is not as cold as it could be and not anywhere close to the
last cold air outbreak principally because the flow aloft will
resist it making much headway south and keeping our region on the
edge. Below normal temperatures look likely here but again, not the
record breaking cold we saw last time.
TES
&&
.AVIATION... (For the 00z TAFs through 00z Sunday Evening)
Issued at 544 PM CST Sat Feb 2 2019
Low level moisture is abundant across the region and stratus
prevailed from central into western MO early this evening.
Southwesterly flow in the cloud layer should spread the stratus
back across northeast MO into west central IL this evening
impacting KUIN. Cigs heights at least this evening should
predominately be in the MVFR flight category at KUIN, but could
waver back and forth from MVFR to VFR at KCOU. A stout low level
jet will also bring LLWS to KCOU and KUIN later this evening as
winds increase dramatically above the low level inversion. Late
tonight and into Sunday morning the stratus will push east into
east central MO including the St. Louis region terminals with MVFR
flight conditions during the morning and early afternoon. KUIN
should see the lowest flight conditions on Sunday morning with a
period of IFR with fog and maybe some drizzle. Ceiling heights are
expected to rise/improve at all terminals through the afternoon
on Sunday.
SPECIFICS FOR KSTL:
VFR flight conditions are expected tonight with some bouts of
clouds from 5,000-6,000 feet. Lower based stratus will move into
the terminal on Sunday morning with flight conditions lowering to
MVFR. Ceiling heights are expected to rise/improve by mid-
afternoon on Sunday with flight conditions improving back to VFR.
Glass
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Melbourne FL
856 PM EST Sat Feb 2 2019
.DISCUSSION...
A few areas of light rain left over from showers and isolated
storms that developed over west central Florida will continue to
diminish into late evening, shifting east over the interior. No
showers are expected to redevelop over land overnight. However,
isolated to scattered showers may continue to develop over the
offshore waters after midnight. Main concern into tonight will be
with the potential for fog development across the area. Boundary
layer winds will remain relatively light and plenty of low level
moisture will exist across the area as a weak front/inverted
trough lingers across the region. This will be favorable for fog
to form, and both the HRRR and local WRF indicate areas to
widespread fog possible late tonight into early Sunday morning.
Also, MOS guidance is still indicating fog could become dense in
some spots, with visibilities a quarter of a mile or less. This
will have to be closely monitored overnight, should any Dense Fog
Advisories be needed. Expanded areas of fog mention in the
forecast over much of east central Florida for now, with rest of
the forecast looking on track.
&&
.AVIATION...VFR conditions to start this evening, except at KDAB
where IFR/MVFR cigs have already started to occur. Expect
decreasing cigs/vis as stratus and fog develop across the area
after midnight. MOS guidance indicating greatest potential and
longest duration of IFR conditions will be across northern
terminals, but HRRR/local WRF model runs show fog could be quite
widespread across the area. Some dense fog will be possible as
well, especially toward daybreak.
&&
.MARINE...Model guidance has struggled with winds/waves over the
waters late this afternoon, with speeds and wave heights being
underestimated at Buoy 41009. However, winds are starting to
diminish and generally expecting speeds to decrease to 5-10 knots
tonight out of the S/SE over much of the waters. The presence of
a weak inverted trough near the coast, should lead to weaker
northerly winds near the coast of Volusia County overnight. Will
likely continue Small Craft Exercise Caution headlines over the
offshore waters of Volusia and Brevard counties as seas up to 6
feet should linger through late tonight.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 58 72 55 68 / 10 10 10 0
MCO 60 77 58 74 / 20 10 10 0
MLB 60 75 60 71 / 10 10 10 0
VRB 60 79 59 73 / 10 10 10 0
LEE 59 76 57 73 / 20 10 10 0
SFB 59 75 56 72 / 10 10 10 0
ORL 61 76 58 73 / 20 10 10 0
FPR 60 79 59 73 / 10 10 10 0
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
Weitlich/Kelly