Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/23/18
Area Forecast Discussion...UPDATED
National Weather Service Brownsville TX
629 PM CST Thu Feb 22 2018
.DISCUSSION...Updated for latest aviation discussion below.
&&
.AVIATION...A mix of IFR/MVFR ceilings prevail across deep south Texas
early this evening. A warm front is expected to move north across the
region later tonight, with the light onshore flow maintaining the
very moist low-level conditions. LIFR ceilings should return
later this evening and overnight for all Rio Grande Valley terminals.
Patchy fog reducing visibilities to IFR/LIFR will be possible late
tonight, mainly between 08 to 13z. Conditions will gradually improve
by mid to late morning Friday with MVFR or low-end VFR conditions Friday
afternoon as southeast winds strengthen.
&&
.PREV DISCUSSION... /issued 337 PM CST Thu Feb 22 2018/
SHORT TERM (Tonight through Friday Night): Cold front which pushed all
the way through the CWA overnight has now pulled up stationary about
40 miles offshore, oriented roughly SSW-NNE. Model consensus now
gradually veers the N-NW surface flow to the west of the front back
around to onshore as the night goes on and weak coastal troughing
ejects toward the NE. NAM (which continues as the primary basis for
the first 24 hours of the forecast) is somewhat slower than the GFS
to do so, but the end result will be that temperatures and dewpoints
will creep up overnight, except over the northern/western Ranchlands
where temps will hold more steady. Will once again have to watch
convection moving off the higher terrain in Mexico in the SW flow
aloft and moving across the Rio Grande, with potential impacts for
roughly the area east of Hwy. 281/I-69C. 12Z GFS was pretty bullish
on convection in this area, with a 0.5" precip bullseye over Zapata
county driven by a weak wave aloft. HRRR has been trending weaker
with the convection in this area this evening, and forecast
soundings do not suggest a very favorable environment. But after
the past two nights, will respect the recent trend and maintain
scattered showers and isolated thunder for mainly the western three
counties.
Also will see areas of fog along the coast, with patchy fog forming
further inland with the more soupy airmass returning with the light
onshore flow. Could become dense in spots but won`t try to pin down
locations just yet.
Temperatures warm up to back up above normal Friday afternoon as SE
flow becomes breezy with a tightened pressure gradient in place.
Most areas will see 80s again during the afternoon, depending on
inland penetration of the warm front. Column RH wanes so basically
nil rain chances during the day. Models indicating another
disturbance may initiate convection over the Sierra Madre again
Friday night. Most of this activity is progged to pass north, but
could clip Zapata county again so will introduce isolated showers in
this timeframe.
LONG TERM (Saturday through Thursday): A series of deep 500 mb
troughs will dig across the southwestern and south central plains
states this weekend. This will push through another pretty mild
fropa on Sun. Surface convergence from the fropa in addition to
better moisture advection occurring ahead of the front will
increase the conv potential for this upcoming weekend. Longer
range MUCAPE values ahead of the front remain pretty unstable for
both Sat and Sun so will maintain the mention of thunder for both
days. The overall moisture levels after the fropa never decrease
that much due to pretty limited dry air advection occurring early
next week.
Another deep 500 mb trough will dig down south along the West
Coast on Mon and Tues which will rebuild the mid level ridging
over the Gulf of Mex. This will push the old cold front back
northwards as a warm front during the first half of next week with
the better moisture values shifting steadily north away from the
RGV decreasing the conv potential later in the forecast period.
This West Coast 500 mb closed low will then open up and will shift
east into the south central plains states late Wed/early Thurs
which will push another fairly mild cold front through the RGV.
Moisture advection ahead of this next fropa will be more limited
than the fropa this weekend and will maintain only some slgt chc
pops towards the end of next week.
Overall model agreement between the GFS and the ECMWF is pretty
reasonable through Day 7 in the overall timing of the 500 mb
trough progressions. The biggest disagreement shows up with the
timing and the position of the last trough axis that tracks over
the south central states. The GFS shows the trough tracking much
farther north versus the ECMWF. So overall confidence in the
longer range forecast wording is above average through Wed and
then drops to average for Thurs.
MARINE: (Now through Friday Night): Marine Weather Statement for
visibilities of 1-3 nm in fog remains in effect for the Laguna
Madre and nearshore Gulf waters through midnight tonight. If
conditions worsen this evening, it may be upgraded to a Dense Fog
Advisory. Otherwise, winds will veer onshore tonight as the old
front moves back NW as a warm front. Moderate SE winds kick in
behind the warm front for Friday, possibly increasing to SCEC
levels Friday night as the pressure gradient continues to tighten.
Seas build to near 6 ft. as well in the 20-60nm Gulf waters, with
4-5 ft. predominating until then.
Saturday through Tuesday Night: The PGF ahead of the next fropa
this weekend will increase enough on Sat to possibly push the Bay
and Gulf conditions up close to SCA levels due to the stronger
S-SE low level flow. Once the cold front moves through the region
on Sun the PGF will then weaken somewhat with the post frontal
winds allowing for fairly benign marine conditions to prevail into
Mon and Tues.
&&
.BRO WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.
&&
$$
This product is also available on the web at:
HTTP://WEATHER.GOV/RGV
63
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
939 PM EST Thu Feb 22 2018
.UPDATE...
Not planning to make any drastic changes to the forecast for
tonight. Offered thoughts in aviation discussion earlier with more
emphasis on potential freezing drizzle the latter half of the night
versus freezing rain. Even then, low confidence in timing and
coverage of drizzle exists with a lack of activity immediately
upstream. Surface temperatures are expected to be very marginal with
current surface temperatures this evening still running some 2 to 4
degrees above the freezing mark. Dewpoints are in the 20s across the
Detroit Metro area, but wet bulb cooling potential expected to be
minimal as near surface theta e content increases. From this vantage
point, not expecting any significant impacts.
&&
.PREV DISCUSSION...
Issued at 658 PM EST Thu Feb 22 2018
AVIATION...
The last few peeks of satellite imagery suggests that MVFR cloud
that initially lifted into southeastern Michigan has been thinning
and scattering out due to an increase in easterly dry air advection.
Rolled back timing on MVFR/IFR by a couple of hours, although
suspect that lowering of cig heights will be very rapid once low
level moisture advection kicks in. The big question for tonight is
both timing and overall potential for freezing rain. Looking through
a collection of forecast soundings suggests some potential for
drizzle development as early as 05-06Z tonight. Upstream,
observations over central Illinois are reporting drizzle. Given
amount of near surface saturation with IFR/LIFR conditions in central
Ohio, decided to introduce TEMPO FZDZ at all sites after 06Z. Warm
air advection is forecasted to be very strong around daybreak and the
idea is to carry a warm rain forecast once depth of moisture
increases. Confidence in areal coverage of freezing drizzle tonight
is low. IFR/LIFR cigs to remain in place early Friday before lifting
during the late afternoon.
For DTW...Pushed back timing of MVFR/IFR a couple of hours, but
suspect rapid onset of conditions late this evening. Introduced
earlier timing with TEMPO for -FZDZ between 06-10Z with warm rain
after 10Z. Low confidence in coverage of -FZDZ.
/DTW THRESHOLD PROBABILITIES...
* High for cigs aob 5kft
* Moderate for -FZDZ 06-10Z. High for rain after 10z.
PREV DISCUSSION...
Issued at 315 PM EST Thu Feb 22 2018
DISCUSSION...
Mid clouds stripped away this afternoon allowing temperatures to
reach into the upper 30s to around 40 degrees across most areas. Dew
pts are predominately in the mid 20s. Mid clouds should be returning
this evening, limiting the diurnal fall expected tonight (upper 20s
to lower 30s), as low level warm advection ramps up as well.
Strong upper wave coming out of the Four Corners region, tracking
through southern Minnesota late tonight, with max 6 hr height fall
center tracking through Lake Superior during Friday. Thus, max
forcing/better isentropic ascent displaced to our northwest, but
there looks to be adequate moisture advection/isentropic ascent
arriving close to 12z Friday to support developing precipitation. It
does not appear the surface high over Eastern Canada will put up
much of a fight, and models indicating a real good surge of warm air
in the 925-850 MB layer, rising into the upper single numbers to
near 10 C. Thus, even if surface temperatures are marginally below
freezing, it is not a given the warm drops will freeze on contact.
Either way, freezing threat looks limited/brief early Friday
morning, and certainly not enough confidence to issue an advisory.
If anything, could see a little freezing drizzle with shallow
moisture before 11z, but otherwise latest HRRR keeps it mainly dry
through 11z, and then expect dew pts to rise above freezing, with
temperatures climbing well into the 40s during the day.
Mid level dry slot arriving Friday afternoon will shut off the rain,
with low level cold air then bleeding in Friday night with northerly
drainage flow. Depth of cold air and southern placement in question
on Saturday as baroclinic zone aligns in west-east fashion, with
high pressure (1026 MB) sliding through the northern Great Lakes.
This high will tend to help maintain the low level cold feed during
the day, as precipitation potentially overspreads southern lower
Michigan (see 12z Canadian/Euro). A light wintry mix is not out of
the question, but surface temps likely well above freezing and with
the daytime timing, probably looking at mainly just a cold rain.
Strong low pressure progged to be centered over the UP of Michigan
Sunday morning will pull an occluded frontal boundary across
Southeast Michigan early Sunday. Behind this front, a much drier air
mass will quickly end precipitation as better mixing allows gusty
winds to overspread the region throughout the day on Sunday. High
pressure will then build into the region early next week as upper
level ridging slowly rebuilds over the Eastern US. This will bring a
period of dry, calm conditions to Southeast Michigan through Tuesday
as temperatures remain above average with highs in the mid 40s to
lower 50s while lows fall into the upper 20s to lower 30s. As the
high moves to the Eastern Seaboard by midweek, return southwesterly
flow will advect moisture across the region ahead of the next wave
moving into the central US. Shower chances look to increase starting
Wednesday as temperatures remain above average with highs in the mid
40s to near 50.
MARINE...
Light to moderate flow will dominate through Saturday. Strong east
to southwest wind will develop on Saturday night as a deepening low
lifts toward the Straits. Stability may be sufficient to probhit
gusts to gales on Saturday night, but the gradient will ramp up as
wind turns southwesterly on Sunday. A gale watch may eventually be
needed for the waters of Lake Huron...particularly the central axis
of the Lake including part or all of Saginaw Bay.
HYDROLOGY...
Flood warnings remain in effect for most of the primary river basins
over southeast Michigan. Additional rain on Friday is not expected
to contribute to additional flooding or prolong existing flooding as
amounts will remain generally one quarter of an inch or less.
Another round of rain will then impact the area late Saturday into
Saturday night with perhaps one half of an inch of rainfall falling
in some areas. This may impact river and stream levels to some
degree, but should not exacerbate flooding to any great degree.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
Lake Huron...NONE.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
&&
$$
UPDATE.......CB
AVIATION.....CB
DISCUSSION...SF/JD
MARINE.......JVC
HYDROLOGY....JVC
You can obtain your latest National Weather Service forecasts online
at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Forks ND
940 PM CST Thu Feb 22 2018
.UPDATE...
Issued at 940 PM CST Thu Feb 22 2018
Light to moderate snow continues to move north into the forecast
area. Regional radar shows the heavier bands have so far been
staying to our south and east, although some heavier returns
developing over northeastern SD could impact our southeastern
counties in the next few hours. The 00Z run of the RAP has some
pretty strong frontogenesis developing right over the southern
counties by 05Z or so, recent runs have backed off on that and the
negative EPV values stay mostly southeast of the CWA. Several of
the high resolution models have been pretty good about matching
current radar trends, so blended them in with the current QPF.
This lowered the evening totals a bit but bumped them up after
midnight, leaving adjusted totals fairly similar to what we had
going. Will continue to leave headlines as they are for now and
take another look in the next few hours.
&&
.SHORT TERM...(This evening through Friday)
Issued at 325 PM CST Thu Feb 22 2018
The snow is expanding on radars to the south, but is still down
and south of Watertown SD. It will lift up into the far southern
FA in the next 2 to 3 hours, then continue to expand slowly
northward tonight. The initial onset of the snow is slower than
yesterday, and also lingers a little later into Friday morning.
However, general snow totals look about the same, with areas
within the advisory expected to pick up 3-5 or 3-6 inches, with
less outside the advisory. Like the previous shift noted, there
may be a sharper northward border to the snow, which is a little
further south than the models showed yesterday. The Grand Forks to
Baudette MN corridor is along this line, so these areas may pick
up a dusting or maybe not much at all. Wind speeds still look
pretty light throughout this event, so blowing and drifting snow
are not expected to be an impact. With the slower onset and
departure times, did make some adjustments to the timing on the
winter weather advisory. The snow should exit out of the eastern
FA by late Friday morning, with Friday afternoon looking dry.
.LONG TERM...(Friday night through Thursday)
Issued at 325 PM CST Thu Feb 22 2018
The main focus for the extended outlook centers around a strong
Colorado low that is expected to develop in the central Plains
Saturday and propagate into the Great Lakes region Saturday night
and into Sunday morning. As a robust upper level trough moves out
over the Plains Saturday, lee cyclogenesis and upper level ascent
along a baroclinic zone will result in a strong surface low that is
expected to propagate to the northeast. While most deterministic
guidance agree with the development of this storm, timing and track
differences add uncertainty to the forecast. Long and medium range
ensemble guidance, along with analog guidance, suggest the greatest
risk area lies from northeast South Dakota through central/south
central Minnesota. Frontogenetical and upper level forcing signals
suggest the potential for snow banding to occur Saturday night
through Sunday across the risk area.
At this time, accumulating snowfall appears to be the biggest winter
weather threat to the FGF CWA with the best chance for accumulation
across western Minnesota and far southeastern North Dakota. Light
snow will be possible further north across northwest Minnesota and
northeast North Dakota, though there is much less confidence in
accumulation for these regions. Winds are forecast to be relatively
light until mid day Sunday when wind gusts of 20 to 25 knots will be
possible on the backside of the low in response to moderate pressure
rises.
Beyond this weekend, relatively quiet and calmer weather is
anticipated as a surface high builds over the northern Plains.
Southerly return flow should return by early next week and allow for
seasonal temperatures with highs in the mid to upper twenties and
overnight lows in the single digits and low teens.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 646 PM CST Thu Feb 22 2018
VFR across the forecast area as mid level clouds spread
northward, but conditions will deteriorate as snow and lower
stratus moves in from the south later tonight. Think snow will be
in KFAR and KBJI by mid to late evening, then move into KGFK and
KTVF around 06Z. KDVL will be spared and should be VFR throughout
the period. The other TAF sites will see ceilings drop to the
1500-4000 ft range with visibility down to 1SM, although some
2-5SM is possible on the northern fringes. The lowered vis will
continue to around 12Z before snow moves off to the east,
lingering at KBJI just a bit longer. All sites should return to
VFR conditions by afternoon, with the west and central sites
seeing the most clearing. Winds will remain fairly light, shifting
from the south to the northwest and then west, staying below 10
kts.
&&
.FGF WATCHES/WARNINGS/ADVISORIES...
ND...Winter Weather Advisory until 3 AM CST Friday for NDZ052-053.
MN...Winter Weather Advisory until 6 AM CST Friday for MNZ024-028-
030>032-040.
Winter Weather Advisory until 3 AM CST Friday for MNZ029.
&&
$$
UPDATE...JR
SHORT TERM...Godon
LONG TERM...AM
AVIATION...JR
Area Forecast Discussion
National Weather Service Hastings NE
929 PM CST Thu Feb 22 2018
.UPDATE...
Issued at 928 PM CST Thu Feb 22 2018
Regarding the rest of tonight, including the Winter Weather
Advisory:
1) Needless to say, light freezing drizzle hung on several hours
longer than originally expected this evening across much of our
coverage area (CWA), but seems to finally be letting up in
coverage per the last few radar scans. Nonetheless, with automated
airport stations within much of the eastern half of the CWA still
reporting visibilities of 3 miles or less as of 9 PM (essentially
"ground truth" that light freezing drizzle is still falling),
along with actual ground truth reports of lingering light
freezing drizzle per social media and law enforcement sources,
opted to once again extend counties along/east of Highway 281
until Midnight. This may have been "overkill" for some areas, and
some of these Advisory counties could even end up being cancelled
early, but did not want to take any chances given the slower-
than-expected trends this evening. No matter, confidence is
actually pretty high that no Advisory will be needed past Midnight
as light westerly low-level flow continues bringing light freezing
drizzle to an end from west-to-east with time.
2) Once the Winter Weather Advisory is finally gone, about the
only concern the rest of the night is whether "impactful" fog
forms in parts of the CWA. While the prevailing light west-
northwest wind direction generally strongly discourages anything
more than "light fog" in our CWA, these winds are light enough
that some models (including HRRR/RAP) continue hitting especially
our southwestern counties fairly aggressively with fog
development, mainly during the 4AM-9AM time frame. Do not have
enough confidence to formally mention "dense fog" in forecast
products, but do have 1-mile-or-less visibility mentioned for
areas mainly southwest of a Kearney-Osborne KS line, where fog
development would seem most favored.
UPDATE Issued at 644 PM CST Thu Feb 22 2018
A few comments regarding our pesky ongoing combo of light snow
and/or light freezing drizzle:
1) First and foremost, have extended the Winter Weather Advisory
for our entire coverage area (CWA) 3 more hours until 9PM (except
for the 4 northeast counties that already went until 9PM), as the
slower-than-expected exit of at least light wintry precipitation
rendered the original 6PM expiration too early. As of this
writing, the majority of light measurable snow/freezing drizzle is
within our eastern counties, but radar and ground truth suggests
pesky very light freezing drizzle extending at least as far west
as Highway 183, and did not feel it was prudent to drop the
Advisory for these western counties yet either, as even very light
freezing drizzle could pose issues. It is possible that a few of
our far eastern counties may even need extended past 9PM, but this
will be addressed in a few hours. Per RAP13 relative humidity
progs in the lowest 1 kilometer, low level saturation deep enough
to promote freezing drizzle should gradually erode from west-to-
east over the next several hours, but again, a bit slower than
earlier expected.
2) This has been an interesting/pesky event, as much of the CWA
spent nearly all day in a "lull" with little to no precipitation
in the wake of mainly light snow overnight. However, as upper
forcing increased mid-late afternoon with the arrival of a fairly
decent shortwave trough into the Central Plains, areas of wintry
mix quickly increased in coverage, with several of especially our
southern counties reporting a light glaze of ice and slick
conditions, including at least a tenth of an inch of ice
accumulation in Burr Oak KS per a NWS coop observer.
&&
.SHORT TERM...(This evening through Friday)
Issued at 328 PM CST Thu Feb 22 2018
Winter Wx Advisory remains as posted earlier.
Hazardous Weather: A little snow or frzg drzl thru early this eve.
Aloft: RAP analyses/RAOB/sat imagery show a longwave trof in the W
with SW flow over the Plns. One weak shortwave trof lifted out of
the base of the Wrn trof this AM was over Wrn Neb and was continuing
to weaken. Another moved into the base this AM and was lifting into
NM/CO. This trof will cross the CWA this eve. Heights will rise a
bit in its wake as a shortwave ridge develops and crests over the
rgn tomorrow. There is a potent shortwave trof diving down the
backside of the Wrn trof today. As it reaches the trof base tomorrow
...the Wrn trof will begin moving E.
Surface: Strong high pres over Ont/Qb extended back into the rgn. It
will lose its influence as a weak sfc trof crosses the area tonight
in response to the forcing aloft. Then Nrn Rockies high pres will
begin building in and slide into the Nrn Plns tomorrow.
Winter Wx Advisory: believe it`s shaky on verifying. It`s mainly out
for frzg drzl potential and just don`t have a good feeling that it`s
going to materialize. We`ve had a couple reports thru the day here
and there...but predicting frzg drzl is usually difficult. Fear that
we may take a hit on this Advisory...but plan is to keep it going at
least to cover the evng commute "just in case" it materializes.
Confidence is low. What appears more likely is a bit of snow here
and there and it will come and go. Not looking at anything steady
for more than 1 hr.
Tonight: Cldy to start and if any precip is occurring after 00Z it
should be done by 03Z. Then decreasing clds and that presents a fog
problem
.LONG TERM...(Friday night through Thursday)
Issued at 328 PM CST Thu Feb 22 2018
Winter Storm Watch has posted for Fri night into Sat.
Potentially Hazardous Weather: Snow and frzg drzl Fri night-Sat.
Snow: we cont to monitor potential for a swath of svrl inches (6+)
across the NW 1/4 of the CWA. This is still 36 hrs out but our
current fcst offers:
6-8" from Lexington-Loup City-Greeley
3-5" Tri-Cities (and Cambridge-Columbus)
1-3" Phillipsburg-Geneva and York
These totals are subject to further revisions.
Believe we`ll see narrow band of snow develop and blossom in a
def zone from NE CO into SW Neb Fri eve. This band will move into
Wrn CWA after midnight and spread NE mainly thru S-cntrl Neb
during the day.
Preceding the snow (SE of the watch)...frzg drzl could be a
problem due to persistent lift in the absence of deep moisture
(dry DGZ). So things could ice up first before some snow moves in.
The EC/NAM are the most emphatic about lower precip amts over the
SE 1/2 of the CWA (basically S and E of the Tri-Cities).
As always there is model variability. There can always be a narrow
swath of locally higher snowfall amts than we are advertising.
Models rarely agree with each other (or with themselves run-to-
run) on where this occurs...especially beyond 24 hrs.
So cont to monitor future fcst updates.
As for the big picture: the mean trof will remain in the W thru
next Thu...but discontinuous retrogression downstream over the
Atlantic will eventually result in a trof also developing over the
E. This will force a longwave ridge to form over the Plns. While
this is a pattern change...things could still be interesting
in early Mar as the pattern heads toward being blocked.
Temps: below normal thru Sun...then near normal Mon-Tue. Possibly
returning to below normal Wed-Thu.
Precip: above normal due to Fri night-Sat event...then no
significant precip foreseen thru next Thu.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 644 PM CST Thu Feb 22 2018
General overview:
This is a low-confidence forecast, especially with regard to
ceiling/visibility trends during the first 16 hours or so, and
precipitation trends these first 2-3 hours. Beyond the first 16
hours though, confidence is overall-higher fairly high in VFR
ceiling/visibility (especially visibility), although there are
actually hints of an MVFR ceiling during this time as well.
Surface winds will not be a big issue, with speeds averaging under
10kt throughout, and direction trending from variable this
evening, to northwesterly late tonight/early Friday, then
eventually northeasterly Friday afternoon. Read on for more
element-specific details...
Precipitation:
Any lingering very light freezing drizzle and/or snow should end
within the next 2-3 hours, with dry conditions expected
thereafter. A very light glaze of additional ice is the main
issue.
Ceiling/visibility:
Especially through these first 6 hours (and possibly beyond), both
ceiling and visibility should fluctuate between IFR/MVFR
categories, with light fog lingering even after any light
precipitation ends. One of the big question marks is whether more
persistent fog (perhaps LIFR) could develop late tonight/Friday
morning, but confidence is low on how bad fog gets (especially
with light westerly breezes) so have kept prevailing visibility
no worse than IFR for now. Am currently indicating a return to VFR
(both ceiling and visibility) by late Friday morning, but some
models/guidance suggest that even if VFR ceiling returns for a
time, an MVFR ceiling could redevelop during the day so this will
need considered in later issuances.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory until midnight CST tonight for NEZ040-
041-047>049-062>064-075>077-085>087.
Winter Storm Watch from late Friday night through Saturday
afternoon for NEZ039>041-046-047-060-061-072-073-082.
KS...Winter Weather Advisory until midnight CST tonight for KSZ006-
007-018-019.
&&
$$
UPDATES...Pfannkuch
SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Pfannkuch
Area Forecast Discussion
National Weather Service Wilmington NC
1035 PM EST Thu Feb 22 2018
.SYNOPSIS...
Strong high pressure aloft north of the Bahamas, will bring
unseasonable warmth in the days ahead, until a cold front
arrives Monday. The front will bring a chance of rain, and
temperatures closer to normal early next week. A warming trend
is expected next Wednesday and Thursday, as a low pressure
system approaches from the west.
&&
.NEAR TERM /THROUGH FRIDAY/...
As of 1000 PM Thursday...Bermuda ridge remains in place as this
atypical February pattern holds strong across the Southeast.
With little change from the past few nights, the forecast
challenge again remains the potential for fog as this
anomalously warm and humid airmass persists. Latest RAP
soundings show slightly lower moisture near the surface than the
past few nights, but less wind as well. With nearly cloudless
sky conditions and lack of any meaningful wind turbulence, fog
is again expected, although may not be as widespread as the past
few nights. Have continued with areas of fog across all areas,
and while highest moisture content will be closer to the coast,
better cooling and greater departures from crossoverT is
expected inland. May be able to avoid any dense fog tonight, but
this will be a near term challenge overnight. Do expect fog to
develop after midnight and slowly spread across the area. Mins
again will be in the upper 50s to around 60, about 20 degrees
above normal. Relevant portion of previous discussion below:
As of 332 PM Thursday...The weather pattern is nearly unchanged
tonight and Friday, the differences subtle, such as, the center
of the offshore surface high shifts slightly SW, moisture and
SW wind flow above 850 mb increases a little as the upper ridge,
is faintly dented from the NW, and local inshore water
temperatures may be a degree or two warmer. All these
differences however don`t appear crucial enough, to change the
potential for another day of record breaking warmth in late
February 2018 again Friday, where record maximums include, ILM
80 in 1975, CRE 74 in 2017, and FLO 83 in 1975.
There were wide shreds of sea fog inshore this morning, and
each morning as SSTs become a little warmer, we are seeing just
a bit less sea fog. But this is gradual and the pattern remains
highly similar, so persistence wins out, and will carry marine
fog again tonight and early Friday, impacting the coastal zones.
&&
.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 332 PM Thursday...The mid level ridge that has been
dominating conditions this week will get suppressed to the south
during this period setting the stage for some changes next
week. The center of the surface high will remain more or less in
the same position but weaken somewhat. This being said, weather
conditions will remain essentially unchanged. One small change
will be the slight chance for convective showers mostly to areas
west of the coast Saturday as the mid levels become a little
more conducive. Certainly don`t expect deep convection and even
thunder is a stretch. Overall temperature forecast remains on
track for highs in the upper 70s to possibly over 80 inland with
lows in the 60s.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 332 PM Thursday...Surface and mid-level ridging weaken
Sun as they become flatter and sink south. Stacked low tracking
across the western Great Lakes will drag a cold front into the
area, but the front is initially moisture starved and lacks
dynamics. Front moves into the area late Sun before ending up
parallel to the flow aloft. The front will be stalled in the
area Sun night but precip chances seem slim at best.
Temperatures ahead of the front Sun will be on the order of 20
degrees above normal with lows Sun night in the low 60s, right
around highs typical for late Feb. On Mon a series of
shortwaves, emerging from the base of the 5h trough over the
Southwest, move along the stalled boundary. Deep southwest flow
helps spread moisture over the southeast while the waves aid
dynamics. Anticipate an increase in precipitation in the area as
the waves move overhead. Confidence on timing is on the low
side as there is still some disagreement between the GFS/ECMWF
solutions, but the slower ECMWF might be the way to go given the
presence of a mid-level ridge. Cloud cover and precip will keep
temperatures cooler than previous days but both highs and lows
will remain above climo.
Surface high builds over the southeast Tue into Wed as flow aloft
becomes progressive at the top of a 5h ridge over the Gulf of
Mexico. Quiet period is short lived as the flat 5h flow moves the
remains of a stalled front into the area, which is then lifted north
as a warm front Wed into Thu. Subtle amplification of the mid-level
pattern late in the period will push above normal temps during the
midweek period to well above normal for the end of the period with
potential for convection late Thu or Thu night as a cold front moves
into or across the area.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
As of 00Z...Persistent pattern continues. VFR is expected at
all terminals through 06Z. Under clear skies and light winds fog
is expected to develop again overnight as the previous nights.
Have indicated IFR/MVFR after 07Z with tempo LIFR 09-13Z. Fog
should burnoff rapidly after sunrise, initially at the coastal
terminals then inland terminals by mid morning.
Extended Outlook...Morning IFR/BR possible through Sat, otherwise
VFR. SHRA/MVFR Sunday through Monday, becoming VFR Tues.
&&
.MARINE...
NEAR TERM /THROUGH FRIDAY/...
As of 1000 PM Thursday...Little change to the overall synoptic
pattern maintains a persistence type forecast for the waters
tonight. 3ft/7sec swell remains dominant as light southerly
winds of 5-10 kts continue. This swell will lengthen to 8-9 sec
overnight but seas will remain around 3 ft all waters.
Fog is again of concern again tonight, and visibilities could
be reduced in areas. A dense fog advisory for the waters cannot
be ruled out entirely late tonight and early Friday, but the
window for this seems to be closing as water temps slowly climb.
SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 332 PM Thursday...A south to southwest flow of ten knots
or less will continue across the waters through about midday
Saturday. The gradient will increase slowly from that point on
to increase winds to 15-20 knots through Sunday morning. This
will increase the seas from the 2-3 feet which will have
persisted for days to 3-5 feet by Sunday morning.
LONG TERM /SUNDAY THROUGH TUESDAY/...
As of 332 PM Thursday...Bermuda High remains off the coast Sun
with southwest flow increasing as cold front approaches from the
northwest. Pinched gradient increases winds to 15 to 20 kt Sun
and Sun night before the arrival of the front drops speeds
closer to 10 kt. Direction veers from southwest Sun night to
north-northwest by Mon morning. Surface high builds in from the
west Mon into Tue, then shifts overhead Tue afternoon. Northeast
surge Mon night will peak around 20 kt close to midnight but
then the gradient starts to weaken as the high moves closer.
Northeast flow starts to wind down after sunrise Tue with winds
slowly veering to easterly and dropping to 10 kt or less as the
period ends. Seas 3 to 5 ft Sun and Sun night drop to 2 to 4 ft
Mon. Northeast surge Mon night into Tue will push seas back to 3
to 5 ft for much of Tue before decreasing winds allow seas to
fall to 2 to 3 ft Tue night.
&&
.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...MJC
NEAR TERM...MJC/JDW
SHORT TERM...SHK
LONG TERM...III
AVIATION...MRR
MARINE...
Area Forecast Discussion
National Weather Service Lincoln IL
904 PM CST Thu Feb 22 2018
.UPDATE...
Issued at 904 PM CST Thu Feb 22 2018
One initial concern this evening is the potential for dense fog.
While most observations in our forecast area are above one quarter
mile visibility (dense fog), reports in between OBS have indicated
some dense fog has developed across central and southeast IL. HRRR
and RAP guidance are projecting that the coverage and timing of
dense fog looks to be generally spotty and shifting northward with
time. Those trends appear tied to the onset of rains and an
increase in surface winds overnight. Will not issue a dense fog
advisory at this point, and have covered the situation with an
SPS. Will monitor fog trends closely.
The rest of the night will see rains become widespread from S-SW
to N-NE, fueled by a steady stream of moisture with some tropical
sources involved. An extended period of waves of rain is setting
up for the end of the week and into the weekend, especially across
our southeast counties.
Clouds and rains tonight will limit the diurnal temperature swing,
as lows range from the mid 30s near Galesburg to the mid 40s
toward Lawrenceville. Made some updates to weather to match
expected trends, with minor adjustments to temps and winds.
The latest forecast info should be available.
&&
.SHORT TERM...(This evening through Friday)
ISSUED AT 137 PM CST Thu Feb 22 2018
Some welcome dry weather is occurring across the forecast area
early this afternoon, and temperatures in the 30s and 40s have
melted off the lingering ice. Next surge of rain is currently
approaching the western border of Missouri, with the upper wave
moving northeast from the Oklahoma area. Forecast soundings show a
dry wedge in the mid levels that lingers for a time this evening,
so PoP`s have been adjusted downward a bit to slow the onset of
the rain by a few hours. All areas will have at least categorical
PoP`s for a time, though, but rain chances by Friday morning
should be limited to areas south of I-70. A few rumbles of thunder
possible in that area after midnight, with a few hundred joules of
elevated MUCAPE.
While most of the area will be dry by morning, the clouds won`t be
in any hurry to leave, due to a persistent low level inversion.
With little cold air behind the boundary that passes by early
tomorrow, temperatures in the 50s still seem reasonable east of
I-55, with mid-upper 40s west.
.LONG TERM...(Friday night through Thursday)
ISSUED AT 137 PM CST Thu Feb 22 2018
Main focus for heavy rain into the weekend remains focused across
the southeast CWA. The frontal boundary will be hanging up from the
Ohio Valley into the southern Plains on Friday. Several waves of
energy will ride northeast, culminating in a strengthening storm
system over the central Plains this weekend. The track of the
surface low from this system will take it into Wisconsin late
Saturday evening, with the trailing cold front crossing us
Saturday night. Once that passes, a few welcome days of dry
weather are on tap.
In regards to the timing and details, rain will be spreading into
the area once again Friday evening, though locations north of
I-72 will see it arrive later in the night. With the colder
northeast surface low persisting into early Saturday, a transition
to some sleet, freezing rain or snow is possible on the northern
periphery of the rain shield. Current indications are that areas
north of a Quincy to Bloomington line are most favored for this
transition zone. Any icing there will be short lived, as
temperatures rise to near 50 degrees on Saturday. Precipitation
chances remain very high until the passage of the front.
Regarding the heavy rain, precipitable water will frequently be
in the 1-1.5 inch range across the southeast CWA into Saturday
evening. An upper wave riding northeast into the Ohio Valley will
help enhance thunder chances as well as heavy rain potential.
Current thinking is for 2-2.5 inches south of I-70 for the period
from tonight through Saturday evening. May need a flood watch down
there eventually, but will hold off for now as the rain tonight
should be an inch or less.
Temperatures through the period should remain on the milder side,
with no significant cold surges expected.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 558 PM CST Thu Feb 22 2018
Widespread IFR and LIFR ceilings have developed, with the onset of
drizzle at the TAF sites, and those cloud conditions should
continue overnight and into Friday morning. Visibility conditions
are generally IFR due to drizzle and light fog, with LIFR vis only
at PIA to this point. Forecast soundings show that vis could
become dense (VLIFR) at PIA and BMI tonight, before steady rains
arrive and help with some mixing of the boundary layer. Have kept
the forecast more pessimistic with clouds overnight, despite MAV
guidance pointing toward some MVFR cloud heights during the period
of rains later tonight. Rain/drizzle should diminish Friday
morning, with cloud ceilings rising to MVFR by early afternoon,
then VFR by late afternoon.
Winds will start out east-southeast at less than 10kt, then become
southwest by Friday morning, and eventually west Friday afternoon
after a cold frontal passage. Speeds will generally remain in the
8-12kt range.
&&
.HYDROLOGY...
Issued at 137 PM CST Thu Feb 22 2018
Many of the rivers are in flood at the moment, courtesy of the
2.5 to 5 inches of rain that has fallen this week. Danville
(Vermilion River) has crested at its 3rd highest level on record,
and the highest value since 1994. Moderate flooding is projected
on the Illinois and Wabash Rivers. The crest on the Illinois River
is currently near La Salle, with areas downstream rising into the
weekend. Heaviest precipitation over the next few days will be
focused more on the areas along and south of I-70, with potential
for 2-2.5 inches through Saturday evening. That will be more of an
impact for the Wabash, Embarras and Little Wabash Rivers.
&&
.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
UPDATE...Shimon
SHORT TERM...Geelhart
LONG TERM...Geelhart
AVIATION...Shimon
HYDROLOGY...Geelhart
Area Forecast Discussion
National Weather Service Louisville KY
837 PM EST Thu Feb 22 2018
.Forecast Update...
Issued at 835 PM EST Thu Feb 22 2018
Currently, a frontal boundary is weakly defined over southern KY,
mostly by a notable dew point gradient. Given the recent heavy
rainfall and the light and variable winds beneath a strengthening
low level inversion, we are seeing a couple spotter reports and obs
showing dense fog formation. Don`t like the idea of combining
flooded roadways and dense fog so will need to monitor this closely
over the next few hours. At this point, have only see a couple of
isolated instances, and overall think the threat will be short-lived
as the aforementioned boundary strengthens and quickly lifts north
as a warm front around and after Midnight. The mixer low levels
should improve vis at that time. Nevertheless, will keep monitoring
and issue a Special Weather Statement if dense fog reports become
more numerous/widespread.
...Axis of Heavy Rain Expected Along/North Ohio River Tonight...
The other issue will be the next round of rain set to arrive around
Midnight, lasting through the overnight hours. Already seeing a blob
of moderate to heavy rain near the Mississippi/Ohio River
confluences, which is situated on the nose of a strengthening low
level jet. Given the strong moisture transport beneath increased
lift in the right entrance region of an upper jet, feel we see a
similar setup to what we saw last night. The main difference is that
the heavy rainfall axis will be displaced more NW than last night,
putting the heaviest swath along and mainly just north of the Ohio
River. PWATs should approach 1.6 inches through the column, and
given some training think the axis of 1 to 2 inches is a good call
across the southern IN and far N central KY counties. Bumped up QPF
a bit in the southern IN counties given increased confidence offered
by hi-res models. Given the overachievement of last night, and a
similar setup in store tonight local amounts of 3 inches can`t be
ruled out. Flash Flooding will be a concern along with areal and
ongoing river flooding. If it were falling over the same heavy swath
as last night, we would be very concerned. That area does look to
get the focus of the heaviest rain later into the day on Friday so
that will need to be watched when the time comes.
&&
.Short Term...(This evening through Friday night)
Issued at 400 PM EST Thu Feb 22 2018
...MULTIPLE ROUNDS OF RAINFALL CONTINUING INTO THE WEEKEND...
...FLOOD WATCH FOR ALL OF SOUTHERN INDIANA AND MUCH OF CENTRAL
KENTUCKY THROUGH SATURDAY NIGHT...
(Tonight - Friday Night) - Rain continues and intensifies at night.
Expect river flooding.
Currently, light rain continues across southeastern Kentucky with
the northern edge of this rain stretched across a line from Logan
County through the Bluegrass. This rain is expected to continue for
the rest of the day as the low level jet continues to overrun the
stationary front. The rest of southern Indiana and central Kentucky
will continue to sit under cloudy skies. With the front running
horizontally through Kentucky, southeastern Indiana is seeing mid 40s
as southeastern Kentucky sees mid 60s.
(Tonight - Friday Night) - Rain chances increase bringing heavier
rain to southern Indiana with a gradient dropping through Kentucky.
Near 0z the stationary front in northern Tennessee will begin to
push north with a 50 knot lower level jet with precipitable water
around 1.5". During this general time the CWA will remain in the
right entrance of the upper level jet. Several global models have
the axis of heaviest rain setting up through south central Indiana.
The HRRR is showing precipitation further south. Based on recent
rainfall trends, it is believed the axis of highest rain will fall
in northwestern Kentucky near Henderson and Daviess Counties through
southern Indiana near Crawford and Perry Counties. Around an inch is
possible between 6-12z along this axis. Rain amounts will fall off
further north, south, or east. The rain is expected to move into the
area shortly after 6z from the southwest.
As the warm front continues north, the heavier rain is expect to run
into Saturday afternoon. Along that axis of heaviest rainfall
another 0.5 - 1" is expected. Winds from the south are expected to
be 10-15 mph with gusts near 25 mph in central Kentucky. The warm
front will occlude and settle across central Kentucky.
Friday night, the upper level trough axis along with a cold front
begins to move east from Utah. This will be the force that pushes
the rain chances out of the area.
Confidence is high that the area will see 1-2" near and north of the
Ohio River tonight and tomorrow. Expect local rivers to react the
this additional rainfall.
&&
.Long Term...(Saturday through Thursday)
Issued at 330 PM EST Thu Feb 22 2018
...SIGNIFICANT FLASH FLOODING POSSIBLE SATURDAY NIGHT AND SUNDAY...
...STRONG TO SEVERE THUNDERSTORMS POSSIBLE SATURDAY EVENING THROUGH
SATURDAY NIGHT...
A warm frontal boundary is likely to be draped somewhere over the
area Saturday morning. The upper pattern will continue to be
dominated by western troughing and strong ridging over the Gulf and
southwestern Atlantic. The highly anomalous and persistent stream of
Gulf moisture will continue over the Ohio Valley. The latest 12z GFS
guidance features PWATs of 1.4-1.5 during the day. Widespread
showers are likely in addition to scattered thunderstorms. Areal
flooding is certainly a possibility on Saturday, especially after
whatever rain falls Friday and Friday night. River flooding will
only continue to worsen over the weekend. 12-hour QPF looks to range
between 0.25-0.75 through 00z Sunday, with the highest totals along
the Ohio River and in southern Indiana.
Saturday night, the upper level trough slides east a bit with a
modest boost in the upper level jet. A strong 500 mb wave ejects
northeast into the Upper Midwest, taking on an increasingly negative
tilt. This will allow a surface cyclone to strengthen and track from
near Missouri/Iowa to northern Wisconsin Saturday night, shoving a
potent cold front through central Kentucky and southern Indiana.
This is a very potent system, with the latest models hinting at a 70
kt LLJ.
This LLJ may be able to push surface dewpoints into the 60s along
and just ahead of the front, with PWATs up to around 1.6. Strong
deep layer shear and marginal (but sufficient?) CAPE may result in a
squall line with a damaging wind threat. At this time, MLCAPE could
even reach 200-300 J/kg, but confidence in the details is low at
this point. However, given flooded soils, trees will be quick to
topple in the face of relatively less wind. So we could see quite a
few trees come down Saturday night.
Given our ongoing, significant prolonged rainfall/river flooding
event, flash flooding is the other primary threat Saturday night and
Sunday. Significant flash flooding is possible. Given a strong
convective environment, excessive rain rates are likely. Additional
rapid rises on small creeks and streams are also likely.
Dry weather looks to finally return Sunday and early next week.
However, the Ohio River and other rivers will continue to rise.
Additional rainfall will be possible on Wednesday and Thursday, but
details and amounts are uncertain.
&&
.Aviation...(00Z TAF Issuance)
Issued at 605 PM EST Thu Feb 22 2018
IFR ceilings across the board as we approach sunset, and LEX and HNB
are already on the edge of LIFR. Expect a slight build-down this
evening, so will be down to 400-500 ft ceilings until the low-level
jet kicks in around midnight.
With a 40 kt LLJ developing we expect wind shear as well, and that
will continue through about mid-morning. Another impulse will bring
in numerous rain showers, which will add a vis restriction to the
low ceilings.
Wind shear mixes out and we get a little stronger SSW breeze during
the day Friday, but rain and IFR cig/vis will persist. Finally look
for some lifting of ceilings and rain tapering off late in the day
as this wave pushes to our east.
&&
.Hydrology...
Updated at 335 PM EST Thu Feb 22 2018
Minor flooding continues along the Ohio River at Louisville and
Cannelton, with moderate flooding expected. Tell City is in moderate
flood.
Synoptic models continue to advertise an additional 2 to 4 inches of
rainfall through Saturday night across much of the region. This
range has been very consistent over the past few days. As with any
convective, long term event, some locally higher amounts will be
possible depending on where multiple axes of heavier precipitation
develop. The most likely geographical area to get the most rain will
be those locations along and either side of the Ohio River.
This rainfall combined with already saturated soils will lead to
excessive runoff through the period. This will result in flooding
issues in the typical low-land and flood prone areas and potentially
some flash flooding. In addition, ongoing river flooding will become
worse with time as the runoff makes its way into the rivers.
Current river forecasts are based on forecasts that contain 72 hours
of future rainfall. Thus, the current forecasts capture rainfall
through Sunday morning. The forecasts that are being issued now are
able to incorporate all of the expected rainfall for this prolonged
event.
Some of the following stage information comes from various ensemble
model packages, and is likely to change as new data are ingested by
those models. Other data is based on current official forecasts.
**Also remember that some of the rain that will be responsible for
the rises on the rivers hasn`t even fallen yet, so significant river
stage forecast changes should be expected over the coming days.**
...Ohio River...
The river from Louisville to Tell City is forecast to reach moderate
flood levels. Tell City has just reached moderate flood, and
Cannelton is expected to do so later this evening. McAlpine Upper is
expected to go into moderate flood by early Saturday morning, with
McAlpine lower going into moderate flood by Sunday afternoon. Clifty
Creek will likely enter minor flood later this evening and is
expected to get into moderate flood by Monday morning.
...Green River and Rough River...
At Dundee, minor flooding is occurring, with moderate flooding
possible.
Minor flooding is occurring at Woodbury today and expected at
Rochester by midday Friday. Munfordville and Alvaton will approach
flood stage, but are not forecast to hit flood stage at this time.
...Rolling Fork River...
Boston is forecast to rise to minor flood stage by early this
evening and has a chance to rise to moderate.
...Kentucky River...
Minor flooding may be possible at Lockport this evening and again
late this weekend. Peaks Mill on Elkhorn Creek is a smaller,
flashier stream and is more difficult to predict very far in advance
but it is in minor flood now and may go into minor flood again
late this weekend as well.
Given the consistent and consecutive heavy rainfall forecasts from
the guidance, a Flood Watch is in effect for the northwestern 2/3rds
of KY and all of southern Indiana for the duration of the overall
event, through Saturday night.
Residents of southern Indiana and central Kentucky should remain
alert this week for flooding. Stay tuned for the latest forecasts
and updates through the week.
&&
.LMK WATCHES/WARNINGS/ADVISORIES...
IN...Flood Watch through Sunday morning for INZ076>079-083-084-
089>092.
KY...Flood Watch through Sunday morning for KYZ023>043-045>049-
053>055-061>065-070>074.
&&
$$
Update...BJS
Short Term...KDW
Long Term...EBW
Aviation...RAS
Hydrology...EER/BJS
Area Forecast Discussion
National Weather Service Newport/Morehead City NC
1058 PM EST Thu Feb 22 2018
.SYNOPSIS...
A cold front will sag south into northern portions of eastern
North Carolina late tonight and early Friday then lift back
north Friday afternoon. High pressure will continue offshore
over the weekend with continued very warm temperatures. A cold
front will move through the area Sunday night into early Monday,
followed by high pressure Tuesday into Wednesday.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
As of 1030 PM Thursday...fairly major update to indicate faster
and stronger backdoor frontal push into area overnight. Latest
HRRR and NAM12 have better handle than 12Z/18Z global models and
have adjusted forecast accordingly wtih wind shift expected all
the way to southern counties by Friday morning. Temps have
dropped 10-20 degrees with frontal passage northern outer banks
and lowered min temps for mainly northern sections. Added
thicker cloud cover and fog and chance of drizzle with frontal
passage as well.
/Previous discussion/
As of 215 PM Thursday...Sct Cu inland will diminish toward
evening with loss of heating. Mostly clr skies thru the evening
will give way to increasing clouds late in combo of developing
stratus and clouds behind a backdoor cold front that will sag S
thru nrn tier. Deeper moisture looks to remain N of region so
will cont with no pops in fcst. With low lvls remaining
saturated good bet for fog to form again tonight...always tricky
to determine how widespread the fog will be...there is the
potential for some dense fog. Overnight lows will be slightly
cooler than the past 2 nights mainly cpl dgrs either side of 55.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
As of 215 PM Thursday...The backdoor front is fcst to bisect
the region early with it weakening and lifting back N later in
the day. Clouds/fog in morn shld grad diminish into the aftn.
Temps over srn tier will be similar to today around 80...bit
cooler nrn tier with front in area with highs in the 60s nrn
cst.
&&
.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
As of 315 AM Thursday...Strong high pressure at the surface and
aloft offshore will continue to provide a warm southwest flow
into the region into the weekend. An approaching cold front
coupled with deep moisture will lead to an increased rain threat
Sunday into Monday before another cold front brings a return to
dry weather Tuesday.
Friday Night and Saturday...Near-record high temperatures
expected given southwest flow and unusually high 500 mb heights
over the region. High temperatures will be well into the 70s
with a few spots reaching the lower 80s Saturday. GFS/ECMWF
show the development of a few showers Saturday given an increase
in precipitable water ahead of next front.
Sunday through Monday night...Deeper moisture will be drawn
north into the eastern Carolinas ahead of cold front as ridge to
the east weakens and moves east. Continued high chance PoPs
Sunday night and especially Monday when deepest moisture and
best lift is in place. Continued very warm Sunday in warm sector
ahead of front with highs well into the 70s, but as front moves
offshore later Sunday night, highs on Monday will range mostly
in the upper 50s to lower 60s with more widespread precipitation
expected.
Tuesday and Wednesday...Dry high pressure will build across the
region with cooler temperatures, but still above normal under
mostly clear skies. Highs will generally be in the 60s with lows
in the 40s, still about 10 degrees above normal for this time of
year.
Wednesday Night and Thursday...An increase in deep moisture
ahead of low pressure crossing the Mississippi and Ohio Valleys
will lead to another round of showers Wednesday night into
Thursday. Have high chance PoPs in the forecast. Temperatures
will remain mild, despite the precipitation however.
&&
.AVIATION /04Z FRIDAY THROUGH TUESDAY/...
Short Term /through Fri/...
As of 645 PM Thursday...Mainly VFR thru this evening with mostly
clear skies prevailing. Weak backdoor front will push in from
N-NE overnight but generally expected to stall near KPGV-KEWN
line near morning and then lift back north on Friday. Low
stratus and fog will develop ahead of and behind front at TAF
sites late tonight with IFR expected most sites poss dropping
to LIFR at times. Appears srn tier will quickly see fog/st
dissipate with VFR by mid/late morn. Nrn tier may hold onto
lower clouds and vsbys til late morn or early aftn with VFR all
areas later in aftn.
Long Term /Friday Night through Monday/...
As of 325 AM Thursday...VFR conditions will prevail Friday night and
Saturday as high pressure continues to circulate warm air into
the region on S/SW winds. Some periods of sub-VFR conditions,
likely MVFR, are expected Sunday into Monday as an approaching
frontal system will bring more numerous showers, especially
behind the cold front on Monday.
&&
.MARINE...
Short Term /through tonight/...
As of 1030 PM Thursday...Major update for overnight into Friday
morning as backdoor front pushing down stronger and faster than
previous forecast. Now expect wind shift to NE all the way down
into southern waters by morning with 10-15 KT gusting to 20 KT
at times for northern half. Still expect winds to return to
southerly during Friday but slower than previous forecast. Also
added more widespread fog and chance of drizzle in wake of front
and dense fog advisory may be needed.
/Previous discussion/
As of 215 PM Thursday...SSW winds 5 to 15 kts thru the evening
with 3 to 4 foot seas in long period swell. Late tonight a weak
cold front will cross nrn tier with winds become N to NE mainly
from about Hatteras N with light WSW winds S of the front. Once
again will likely see fog develop and will have to monitor
trends overnight for poss dense fog advisory. The front will
grad weaken and lift N Fri with winds becoming SSW below 15 kts
all waters later in the day with fog diminishing. Cont longer
period swells will keep seas mainly in the 3 to 4 foot range
Fri.
Long Term /Friday night through Monday/...
As of 325 AM Thursday...Not alot of change in the latest marine
forecast. S/SW winds will cont Friday night and Saturday.
Expect 10-15 knot winds for this period with seas of 2-4 feet.
Small Craft Advisory conditions still look like a given on
Sunday ahead of the cold front with gusty SW winds of 20-25
knots and seas building to as high as 6-7 feet, south of Oregon
Inlet. Winds subside again Monday behind the front as winds
become northerly.
&&
.MHX WATCHES/WARNINGS/ADVISORIES...
NC...None.
MARINE...None.
&&
$$
SYNOPSIS...RF
NEAR TERM...RF/JBM
SHORT TERM...RF
LONG TERM...CTC
AVIATION...CTC/JBM
MARINE...RF/CTC/JBM
CLIMATE...MHX
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
603 PM CST Thu Feb 22 2018
.SHORT TERM...(This evening through Friday)
Issued at 327 PM CST Thu Feb 22 2018
Snow is advancing northeastward into southwestern Minnesota this
afternoon. It will reach just about all of the southern half of
Minnesota and western Wisconsin by 6 or 7 PM. Light to moderate
snow will persist area wide through midnight, then begin to end
from southwest to northeast. The steady snow will end in
southwest MN around 1 AM and the I-94 corridor by around 4 AM.
During this process of drying in the mid levels, there could be a
period of freezing drizzle following the end of accumulating snow
due to continued saturation in the low levels. However, this will
be brief and little or no ice accumulation is expected.
Models are in pretty good agreement with QPF tonight. There could
be some mesoscale banding in places and hi-res guidance is hinting
at streaks of higher QPF/snowfall. However, on a widespread basis
we should expect about 3 inches across southern MN where the
period of accumulating snow will be shortest, to 4 to 6 inches
across the remainder of the forecast area. The current Winter
Weather Advisory configuration looks good, so no changes were
needed to that.
Drier air will make for a relatively pleasant day Friday with
some decrease in clouds possible.
.LONG TERM...(Friday night through Thursday)
Issued at 327 PM CST Thu Feb 22 2018
Friday night and early Saturday look good, but the next system is
fast on the heels of tonight`s system and will begin arriving
Saturday afternoon. This system will be neutrally tilted to start
Friday night over the Plains, but will trend more negative
Saturday and Saturday night as it passes across the Upper Midwest.
This lends to a higher confidence event with widespread significant
snow accumulations. 12Z GFS is most bullish/quickest with the mid
level wave closing off and results in a strong cyclone centered
over the southeast corner of MN late Saturday evening. Models have
been slowly trending toward this solution. In addition, the GFS
deterministic run is right in the middle of the spread of SLP/QPF
in the GEFS solutions, with the lowest member still showing at
least 0.6" of QPF at MSP. Thus, confidence in 6 inch amounts is
pretty high from south central MN to northwest WI and totals could
approach 12 inches somewhere in that corridor. Snowfall rates will
be impressive with an inch or two per hour possible during the
height of the event. As for wind, the rapidly deepening low
center passing by could be occurring a little too late for the
wind to respond and increase to critical levels for blizzard
conditions. Therefore, blizzard conditions are still questionable,
but certainly not impossible if gusts can increase 5 to 10 mph
above what is currently forecast.
Given that we`re within a 48 hour window of the snow beginning,
and the degree of confidence present, have issued a Winter Storm
Watch for most of the CWA except for far western MN. It`s
possible those counties will be included later if confidence
increases for greater than 6 inches. All told, it`s likely most of
the CWA will see over 12 inches between tonight`s snow and
Saturday`s, and some could exceed 15 inches.
Much more tranquil weather follows for early next week, but there
are signs of another system for late next week that will need to
be watched.
&&
.AVIATION...(For the 00Z TAFS through 00Z Friday evening)
Issued at 547 PM CST Thu Feb 22 2018
Snow has been battling the dry air this afternoon, hence it`s
later than advertised arrival, but the dry layer is quickly being
eaten away, with snow hitting the ground. Only had minor changes
to the going TAFs, with timing lined up similar to what the HRRR
is showing. Main change is looking at upstream obs, 3/4sm is the
prevailing vis, with some scattered 1/2sm vis, so trended the
TAFs that direction with prevailing 3/4sm and tempo 1/2sm vis.
Still expecting a widespread 3-5 inches, with snow mostly done by
12z. Lower confidence with cig trends behind the snow, but we
could certainly clear out faster than TAFs currently indicated,
but played the improvements a bit more conservative until we have
a better feel of how quickly skies will improve in the wake of the
snow.
KMSP...Based on the HRRR, looks like the vast majority of the
snow, along with the potential rates of around 3/4" per hour will
come between 4z and 7z. This is also the window where some vis
down to 1/2sm will be possible. Friday morning, skies may go VFR
shortly after the winds go SW and we could see VFR conditions as
early as 15z.
/OUTLOOK FOR KMSP/
Sat...VFR early. Then IFR/SN with LIFR possible in aftn and
overnight. Significant snow accums possible. Wind ENE 5-15 kts.
Sun...CHC MVFR cigs. Wind W 10-20 kts.
Mon...VFR. Win SW 5-10 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Storm Watch from Saturday afternoon through late Saturday
night for WIZ014>016-023>028.
Winter Weather Advisory until 9 AM CST Friday for WIZ014>016-
023>028.
MN...Winter Weather Advisory until 6 AM CST Friday for MNZ041-042-
047>049-051-057>060-062-066>070-076>078-085.
Winter Storm Watch from Saturday afternoon through late Saturday
night for MNZ043>045-049>053-057>063-066>070-076>078-084-
085-093.
Winter Weather Advisory until 9 AM CST Friday for MNZ043>045-050-
052-053-061-063.
Winter Weather Advisory until 3 AM CST Friday for MNZ054>056-064-
065-073>075-082>084-091>093.
Winter Storm Watch from Saturday afternoon through late Saturday
night for MNZ056-064-065-073>075-082-083-091-092.
&&
$$
SHORT TERM...BORGHOFF
LONG TERM...BORGHOFF
AVIATION...MPG
Area Forecast Discussion
National Weather Service Nashville TN
656 PM CST Thu Feb 22 2018
.UPDATE...
FOR EVENING DISCUSSION.
&&
.DISCUSSION...
Fog has developed along the frontal boundary and has been dense in
some spots. Zones were updated to include areas of fog along and
north of the current boundary position. As the boundary lifts
northward over the next few hours, fog may dissipate along the
southern fringes. Pops were also adjusted to reflect the thinking
of high res models which keeps rain concentrated in the northwest
overnight.
&&
.AVIATION...
00Z TAF DISCUSSION.
Stationary boundary is currently draped just north of CKV with
LIFR to MVFR cigs at CKV, BNA, and MQY. Cigs should improve
overnight as the boundary drifts farther north with the exception
of a period of MVFR cigs at CSV. HRRR shows rain impacting CKV
overnight while staying north of BNA and MQY. Most of the daylight
hours for BNA, MQY, and CSV will be VFR while CKV will have MVFR
cigs closer to the frontal boundary. Southerly winds will increase
overnight to the 10 kt range and turn southwesterly after 15z.
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
Flood Watch through late Saturday night for Cheatham-Davidson-
Dickson-Hickman-Houston-Humphreys-Lewis-Maury-Montgomery-Perry-
Robertson-Stewart-Sumner-Williamson.
&&
$$
DISCUSSION......Reagan
AVIATION........Reagan
Area Forecast Discussion
National Weather Service Shreveport LA
930 PM CST Thu Feb 22 2018
.UPDATE...
03z Sfc Analysis showing our returning warm front situated from
near Houston and Lufkin, Texas to near Natchitoches, Louisiana and
Vicksburg, Miss. This boundary has moved very little since 4 pm
but should at least move further north along its eastward flank,
moving north of Monroe and near or just south of El Dorado by 6 am
Friday Morning.
So far this evening, most of the activity as been going on across
Deep East Texas spreading north northeastward into NW LA and SW AR
and this is along a deformation zone which has set up across this
same general area. 00z NAM output along with the current run of
the HRRR has nailed this activity thus far and really begins to
focus renewed activity north and west of the returning warm front
or across our northwest zones for the remainder of the night. This
activity should orient itself along an elevated 850mb theta-e axis
which should be near or along a line from near TYR to TXK and LZK
later tonight. Already seeing an uptick in convective coverage
across these regions and therefore the ongoing forecast has a good
handle on this likelihood through the remainder of the overnight
hours. Did add areas of fog however through the overnight grids as
if you are void of the mixing effects of the convection, you will
likely see some fog overnight.
Overnight min temp forecast is very difficult as we could see
rising temperatures across our eastern zones and near steady to
slightly falling temperatures out west in and out of rain
activity. Therefore made only very slight adjustments to
temperatures overnight.
Prelims to follow...13.
&&
.PREV DISCUSSION... /issued 555 PM CST Thu Feb 22 2018/
AVIATION...
For the ArkLaTex, a warm front stretches from KLFK to KRSN/KMLU
and continues lifting Northward. VLIFR-IFR for most sites attm
except KMLU now well behind the boundary. Cigs/vsby issues will
linger well into daylight on Friday with models showing more TSTM
activity along the warm frontal boundary currently affecting KGGG
and soon for KTXK/KTYR. Warm front will lift past terminals with
MVFR/VFR expected late period and L/V winds. Outlook is for more
TSTMS for Sat and the next weak cold front drying us for 2/3 days.
/24/
&&
.PRELIMINARY POINT TEMPS/POPS...
SHV 53 71 63 76 / 100 70 40 90
MLU 58 78 65 81 / 40 60 40 50
DEQ 47 60 55 71 / 100 100 80 90
TXK 47 63 59 73 / 100 100 50 90
ELD 48 67 60 76 / 100 100 40 90
TYR 45 68 62 73 / 100 90 50 90
GGG 51 69 62 74 / 100 80 40 90
LFK 53 75 66 77 / 70 50 30 90
&&
.SHV WATCHES/WARNINGS/ADVISORIES...
AR...Flash Flood Watch through Friday evening for ARZ050-051-059>061-
070>073.
LA...Flash Flood Watch through Friday evening for LAZ001>006-010>014-
017>022.
OK...Flash Flood Watch through Friday evening for OKZ077.
TX...Flash Flood Watch through Friday evening for TXZ096-097-108>112-
124>126-136>138-149>153-165>167.
&&
$$
24/13
Area Forecast Discussion
National Weather Service Sacramento CA
329 PM PST Thu Feb 22 2018
.SYNOPSIS...
A cold system will bring low elevation snow to the mountains
into early Friday, which could impact travelers. A few showers are
possible in the Valley. Below normal temperatures will continue.
Additional systems likely next week.
&&
.DISCUSSION...
Vort max that was along the CA/OR coast dropping SSEwd, mainly
along the Wrn side of the CWA. Clouds and scattered showers will
spread SEwd over the CWA into this evening. Very low WBZs will
result in low snow levels dropping into the foothills. AT press
time, the snow level had dropped to Applegate around 2 kft. SPC
SREF plumes suggest the Srn portion of the CWA will be more
unstable, roughly from SMF Swd into the Nrn SJV where isolated
storms are possible through late afternoon, than the Nrn portion
of the CWA. This is due to the timing of the vort max dropping Swd
this afternoon. Effective Shear indicates the potential for some
mid level rotation/rotating storms. The limiting factor is the
elevated instability forecast in the Bufkit forecast soundings and
not surface based convection. Central Valley rotating storms are
rooted in the boundary layer with low LCLs. Dewpoints in the 30s
makes this more problematic. Can`t rule out a possible funnel
cloud, but less likely there would be an actual touchdown. Looks
as if the HRRR suggests some isolated cells in the extreme Srn
Sac, Solano Co, Nrn SJV areas this afternoon. The 12z NAM 3 km
keeps the precip in frozen form and basically out of the Valley.
Timing of the snow advisory looks good with precip winding down
around 06z.
Precip amounts will be light with this system due to a dry air mass
with PWs ranging from .13 at REV to .34 at MFR and .44 at OAK. These
values are below average. AMSU data also indicate very low PW over
the region. However, good dynamics and cold temps will result in
some brief periods of heavy showers with high snow ratios. For
example for BLU, using the max temp in the profile, a snow ratio of
16:1 to 18:1 is calculated for today. The average SLR is 9:1.
Don`t expect normal snow water equivalents with these next few
systems in the short term.
After the wx system/trof moves through the area tonite, dry Nly
winds will increase over the CWA, weakening Fri afternoon. Winds
may continue to mix the Nrn and Wrn zones overnite, while
decoupling will occur on the E side of the Valley. With clearing
skies overnite, it will be another cold nite, with a brisk Nly
wind on the W side of the Vly/lee-side of the Coastal Range.
A couple more wx systems are forecast to drop out of the GOA in
the highly amplified pattern along the W Coast of NOAM in the
short term. The next system on Sat, followed by another late Sun
into Mon. These systems will be similar, cold with relatively low
QPF. The WR US West Coast AR Landfall tool (Probability of IVT) is
virtually "bone dry" for the next 16 days. What moisture there is
will be spilling over the Pac Ridge and eroding as it hits the
Pac NW and spreads inland into our CWA. Even though Norcal will
have the continuation of a cold, showery pattern, the QPF will be
relatively low, albeit with high snow ratios. Some modest
modification in temps is expected later in the weekend and into
early next week. JHM
&&
.EXTENDED DISCUSSION (Monday THROUGH Thursday)
Models show a continuation of the wet pattern as several shortwaves
dive southward from the Gulf of Alaska. Compared to this week`s
systems, the upcoming storms have the potential to pull in some
moisture from the Pacific before spreading precipitation inland.
Given the cold nature of these systems, snow levels will remain
low.
Models are showing better agreement compared to previous
forecast runs, though differences remain in terms of timing and
precipitation amounts. The first system moves in Monday into
Tuesday. Early precipitation estimates suggest 0.10-0.30 inches
across the Valley, and around 0.25-0.65 inches over the mountains,
though these amounts will likely change as we get closer to the
event. A brief break is expected late Tuesday into Wednesday as
weak upper ridging builds in. Then, a stronger and wetter storm
will move across the area late Wednesday into Friday. Precipitation
will initially impact the northern mountains on Wednesday before
spreading across the forecast area on Thursday. Stay tuned to see
how these systems develop as model uncertainty remains.
Temperatures will remain below average as cold air continues to
filter in.
&&
.AVIATION...
VFR conditions expected next 24 hours except local MVFR vicinity
scattered showers and thunderstorms 22Z-02Z and widespread IFR
over the northern Sierra with snow showers thru about 03Z Friday.
&&
.STO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 10 PM PST this evening for Burney
Basin / Eastern Shasta County-Motherlode-Northeast
Foothills/Sacramento Valley-West Slope Northern Sierra Nevada-
Western Plumas County/Lassen Park.
&&
$$