Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/06/18
Area Forecast Discussion
National Weather Service Denver/Boulder CO
931 PM MDT Thu Apr 5 2018
.UPDATE...
Issued at 931 PM MDT Thu Apr 5 2018
Everything seems to be progressing a few hours faster than
expected, especially the development of mid level clouds and
virga/light showers as moisture overruns the incoming cooler air
on the plains. There should be a bit of a decrease in this behind
the lead trough axis later tonight as there is a patch of drier
air aloft, but it will be short lived. Colder air to the north
will be drawn southward behind this in the morning. Models
offering some different answers to the timing of the morning
events. Larger scale models show the low level winds going
southeast tonight behind the current surge of still-mild air, but
then a steady drop in temperatures with northeast winds first
thing in the morning. HRRR is more complicated holding the
southeast winds and generating convergence north of Denver, and a
Denver cyclone for the morning which keeps a pocket of warmer air
over Denver while the snow develops over northeastern Colorado.
This is a plausible scenario, but given the timing of the upper
features and the proximity of the cold air by morning, I`m leaning
toward the faster solution or at least a compromise. The earlier
solutions would lead to a sooner and longer period of overrunning
snow starting sometime in the morning, and perhaps an extra inch
of snow over what we`re forecasting. I nudged the timing a couple
hours earlier with slightly higher amounts, but this may still
need further adjustment. Either way, we should have a period of
snow in Denver in the middle of the day, but warm ground
temperatures should prevent any travel impact. Higher mountains
and maybe the northern border areas will be a different story.
&&
.SHORT TERM...(This evening through Friday)
Issued at 321 PM MDT Thu Apr 5 2018
Tonight and Friday`s storm system remains on track as radars on
the west slope are beginning to show the increasing moisture
moving in from the west. The west-northwest flow aloft will be
aided by an upper level jet in producing the rising vertical
motions necessary to generate precipitation, first over the
mountains, and then out onto the plains. The other piece of the
puzzle will be a strong cold front moving in from the northeast
during the morning hours. Upslope clouds are expected to develop
Friday morning, after the morning commute. Scattered rain shower
activity over the plains ahead of the front will quickly change
over to snow as temperatures drop into the lower 30s before
midday. Most of the precipitation with this event appears to be
headed for the mountains, so only light accumulations are expected
across the plains. The mountains will have a Winter Weather
Advisory go into effect at midnight which will continue through
midnight Friday night. East to northeast winds on the plains will
be gusty for a few hours after the cold front passes.
By late afternoon, the upper dynamics of the weather system will
be moving east of Colorado, so precipitation on the plains should
be winding down. Snowfall in the mountains will continue through
the afternoon as moist, orographic flow continues.
.LONG TERM...(Friday night through Thursday)
Issued at 321 PM MDT Thu Apr 5 2018
Areas of light snow on the plains will slowly diminish Friday
night as shallow upslope component wanes. Meanwhile, in the
mountains, orographic forcing with 25-30 knots of west/northwest
flow, sufficiently deep moisture, and neutral lapse rates will
keep snow going, and we should see another 1-4 inches and travel
impacts for the high country. As a result, we`ve extended the
advisory there until midnight Friday night.
On Saturday, warm advection kicks in as flat ridging develops
across the Central Rockies. There should still be sufficient
moisture for some rain and snow showers across the high country,
but have reduced the QPF a bit from model averages as models
typically overdo this in warm west/southwest flow. That should
change significantly, however, by Saturday evening as the remnants
of California`s atmospheric river event reach the state. Deep and
warm subtropical moisture will likely keep snow levels near 11
thousand feet early in the event, but several inches of snow
expected up high.
Cold advection finally arrives later Saturday night, dropping
snow levels down to mountain valley floors and the higher
foothills. Sufficient instability should allow some showers to
spread across the plains but overall downslope pattern is expected
to keep QPF amounts limited. In the mountains, expect snow totals
around a foot at or just above the higher passes, with
significantly lighter accumulations in lower elevations as the
duration of snow will be limited by the initially high snow
levels.
By Sunday, drier air arrives with stronger and gusty downslope
winds expected across the plains. Meanwhile, light snow showers
will linger across the high country given orographic forcing and
limited mid level moisture. There is potential for another wave
and forcing associated with an upper level speed max for Sunday
night which could bring an uptick in showers.
Then, drier and warmer weather will develop by Monday and Tuesday
with highs warming into the 70s across the plains by Tuesday. The
warm weather should remain in the forecast through Wednesday
although a passing wave could bring a few snow showers back into
the high country. Models seem to have reasonable agreement on
this. We`ll be watching potential for another storm system by next
Friday in this rather progressive weather pattern.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 931 PM MDT Thu Apr 5 2018
VFR conditions are expected overnight though there will be some
scattered light showers developing and ceilings could be low
enough to require instrument approaches to KDEN. Expecting
lowering conditions as snow develops between 13z-16z with IFR
ceilings/visibilities after that. Gradual improvement after 00z
Saturday.
&&
.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MDT Friday night for
COZ031-033-034.
&&
$$
UPDATE...Gimmestad
SHORT TERM...Dankers
LONG TERM...Barjenbruch
AVIATION...Gimmestad
Area Forecast Discussion
National Weather Service Columbia SC
1042 PM EDT Thu Apr 5 2018
.SYNOPSIS...
High pressure along the coast will move farther offshore Friday.
Low pressure and the associated frontal system will move into
the area Saturday morning with showers and a few thunderstorms
through the day. High pressure will be briefly over the region
Sunday with the next low pressure system moving in early next
week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Pressure ridge axis has shifted off the Carolina coast promoting
a weak return flow. Satellite imagery shows some high thin
clouds moving across the area tonight. Shallow low level
moisture may advect into mainly the CSRA toward morning but
given dry air mass will continue with a mostly clear sky.
Possibly more favorable radiational cooling conditions tonight
but some high clouds expected. Continued minimum temperature
forecast in the low 40s with a few sheltered areas in the upper
30s. Winds will be light and variable through the overnight
period.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
The synoptic situation will continue changing Friday as the high
pressure shifts further into the Atlantic Basin and low pressure
develops over the southern Plains. This will allow some Gulf
moisture to begin returning northward as well as westerly flow
aloft pushing additional moisture into the region. Friday night
the low will move through the central Gulf States and be just
west of the forecast area Saturday morning. Through the day
Saturday the low and associated frontal boundary will cross the
forecast area then move offshore Saturday night. Expect rain to
fall Saturday with some questions continuing in regard to
convection. Currently there is a narrow window during the day
Saturday when convection will be possible so have remained with
mainly showers with slight chance of thunderstorms with this
system. As the low moves offshore Saturday night high pressure
and drier air will begin building back into the region.
Temperatures will be in the upper 6s0 to mid 70s for daytime
highs with mid 50s for lows Friday night and mid 30s to low 40s
for Saturday night.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
Progressive upper level pattern will remain over much of the US
with systems crossing the region every couple of days. High
pressure will reside over the region Sunday then slide eastward
Sunday night as the next low pressure system moves into the
eastern US. Models have come into better agreement with this
system over the past couple of models runs however some timing
and intensity issues remain. The ECMWF and GFS do agree there
will be enough moisture as the system crosses the region Sunday
night through Tuesday for rainfall with the highest pops
currently Monday and Monday night. High pressure will return to
the region for Tuesday night and Wednesday. Temperatures through
the long term will be slightly below to near normal.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
There is some potential for strato-cu in the AGS area toward
morning due to weak onshore flow . Confidence low and given dry
air mass will continue VFR conditions.
High pressure along the coast with a weak pressure gradient
over the TAF sites tonight. Wind near calm overnight becoming
south to southwest around 10 knots by 15Z. Could see wind gusts
15 to 20 knots in the afternoon with mixing.
High clouds over the region should move east of the area after
midnight. The HRRR and Nam model suggest some low clouds may
advect into the AGS/DNL terminals late tonight, but confidence
low. Lamp guidance clear and SREF probabilities restrictions
low. Will mention scattered deck there...otherwise mostly
clear. As moisture increases...expect scattered cumulus around
5000 feet in the afternoon with increasing high clouds ahead of
an approaching low pressure system.
EXTENDED AVIATION OUTLOOK...Widespread MVFR or IFR conditions
may occur at times Friday night through Saturday night.
Convection possible. The greatest chance of most significant
restrictions is Saturday and Saturday night. Fair Sunday but
restrictions possible again Sunday night into Tuesday as
another complex low pressure system moves thru the area.
&&
.CAE WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
&&
$$
Area Forecast Discussion
National Weather Service State College PA
1059 PM EDT Thu Apr 5 2018
.SYNOPSIS...
A fast moving weather system will bring a period of light snow
to northern Pennsylvania late tonight and early Friday.
Temperatures will warm behind this system giving the region a
mild day tomorrow with any snow quickly melting. The next
weather system will quickly move south of the area late Friday
night and Saturday bringing a chance of precipitation and cold
and blustery temperatures on Saturday. The end of the weekend
will be dry but still chilly. The below average temperatures
will continue through at least the first half of next week.
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Latest GOES-16 Clear channel loop shows mid cloud increasing
over western and central PA late this evening in advance of a
weak clipper system streaking towards the commonwealth. The
weak clipper will impact mainly the northern half of the CWA
after midnight tonight. HRRR and HREFV2 supports a 1-2 inch
snowfall across the northern mountains, partly due to orographic
enhancement, while little to no accumulation is expected over
the southern counties, where surface temps are likely to remain
above freezing, and light rates to any precipitation will make
ptype either a mix of rain/snow or just light rain. Mins
overnight will range from the mid 20s north to the lower 30s
southeast.
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
Behind the clipper will be a nice but brief warmup on Friday
with temperatures rising into the 50s to near 60, though winds
will be gusty in the afternoon.
Guidance further south with next system Friday night and
early Saturday with the CWA likely missing any significant
snow. Precip rates will be low and with temperatures at or
above freezing it will not be easy to accumulate snow across
the southern CWA. As system pushes east Saturday look colder and
blustery conditions yet again.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
The second half of the weekend will be mainly dry with surface
high building in from the west. However, upper trough and
associated cold temps aloft will keep clouds and maybe a few
diurnally-driven snow showers over the northern mountains.
Another opportunity for precip early next week, as yet another
shortwave drops into base of upper trough. Air mass looks cold
enough for light snow early Monday. However, plenty of
uncertainty late Monday/Tuesday, when bulk of guidance tracks a
dying primary low west of Pa while coastal low forms along the
Carolinas coast and lifts northeast. Latest operational models
continue to lean toward snow across northwest Pa Mon night/Tue,
rain in the southeast and rain or snow over the central
counties.
Med range guidance indicating the blocking pattern at high
latitudes of the NH may begin to break down the second half of
next week, resulting in a return to milder/more settled
weather, though it still looks like we`ll fall short of seasonal
normals.
&&
.AVIATION /03Z FRIDAY THROUGH TUESDAY/...
Minor adjustments to the 03Z TAFS.
Winds have finally died down.
VFR conditions will persist for a few more hours.
The next weather system will begin to affect the area late
tonight, with light snow spreading in from the west. Have timed
restrictions into the TAFs between 07z and 10z with precip
ending after sunrise.
Weather system for Saturday trending further south.
Outlook...
Sat...Reductions psbl with more snow.
Sun...Mainly VFR. Windy.
Mon-Tue...MVFR and IFR possible in snow and rain showers.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...Ross
NEAR TERM...Ross/DeVoir
SHORT TERM...Ross
LONG TERM...Fitzgerald/RXR
AVIATION...Martin
Area Forecast Discussion
National Weather Service Hastings NE
1009 PM CDT Thu Apr 5 2018
.UPDATE...
Issued at 949 PM CDT Thu Apr 5 2018
Some of our forecast models are actually starting to diverge on
the placement of where we will see our higher snowfall totals with
this system as we near the snow start time. The 18Z GFS came in
the furthest south with the heaviest snow band running from
Gothenburg to Hastings with a more broad 2-4 inches of snow for
most areas north of Hwy 6. The 00Z NAM is the furthest north with
a 2-4 inch band running from Valley County over to Nance County
with most other areas to the south at only 1 inch or less. The
01Z HRRR is pretty close to our current forecast with the heavier
snow band running from around Grand Island to Loup City.
The 00Z NAM seems too far north and too light with snowfall and
will throw it out for now, unless future model updates start
trending that way. Believe the HRRR is probably doing the best and
expect a band of rain/snow will develop across far southern
Nebraska (south of hwy 6) between 2-4 AM and lift north as it
changes to all snow. It could snow pretty good for an hour or two
before the band lifts north, but it probably will not persist long
enough to get much snow south of Hwy 6. The snow band will
eventually stall out somewhere near or north of I-80 during the
morning and then turn around and head back south Friday afternoon.
The location where the band stalls out will see the best bet at a
few inches of snow. At this point, areas south of Hwy 6 seem like
they will see very little snow with primarily 1 inch or less,
especially less as you near the Kansas state line and head into
northern Kansas. Current forecast seems reasonable for now, but
forecast amounts will likely change some over time as we iron out
where the snow band sets up and stalls out.
&&
.SHORT TERM...(This evening through Friday)
Issued at 316 PM CDT Thu Apr 5 2018
Satellite and observations show some mid level clouds moving into
the northern part of the forecast area this afternoon. The cold
front is just through the forecast area early this afternoon.
An upper level wave will approach the area tonight. Most of the
models have the precipitation moving into the area after midnight
tonight, but there are a couple of them that bring it in before.
Have a little moving into the area a little before midnight, but the
most of it will spread across the area during the overnight hours.
Nebraska has the best chance for precipitation during the night.
During the overnight hours much of the precipitation should start as
rain, but fairly quickly mix with and change over to snow. The snow
should spread across the entire forecast area Friday morning and by
afternoon the snow should be gradually ending from north to south.
A couple other things to note with this system are the winds and
temperatures. North to northeast winds will increase on Friday. The
winds could be 15 to 25 mph with gusts of 30 to 35 mph. This could
cause a little blowing and drifting snow, especially in open areas.
High temperatures are expected to be in the mid 20s to mid 30s. The
problem is this will be in the morning and during the afternoon the
temperatures will start to fall off and are expected to be in the
lower 20s by late afternoon.
.LONG TERM...(Friday night through Thursday)
Issued at 316 PM CDT Thu Apr 5 2018
There will be a break between systems for Friday night into
Saturday. Temperatures will be cold. A surface high settles into the
area Friday night and clears out skies. The winds will be light and
with the clear skies and new snow, temperatures will drop off.
Currently there are lows around 10 degrees, but some of the models
have single digits for lows Saturday morning. The surface high moves
off to the east on Saturday and winds turn to the south, but the
temperatures will not gain too much and temperatures, especially in
snow covered areas will only get to the mid 30s.
The next upper level wave will start to affect the area Saturday
night through Sunday. Models have a few differences in how this
system moves through the area. Some of them have a single wave while
others have more of a northern/southern split in the wave. Either
way, the results are fairly similar because there is not much
distance between them. This system has a few challenges in the
precipitation type. There should be a mainly rain and snow start to
the system, but as the precipitation moves into the area, so does
some warmer air aloft. This could bring some chances for sleet or
freezing rain depending on the surface temperature. By later Sunday
morning, the surface temperatures should be warming up and gradually
the mixed precipitation will change to rain. This system should be
mostly out of the forecast area by Sunday afternoon and there will
be some clearing which will allow temperatures to warm up. Even with
the clearing have a little concern for the current forecast high, it
could be too warm.
Sunday night into Wednesday will show a return of more spring-time
temperatures. The temperatures will warm quite a bit each day. A
weak wave will move through the area Wednesday afternoon and evening
with a chance for some light rain for some locations, but not much
else going on. Temperatures remain warm for Thursday.
&&
.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Friday)
Issued at 631 PM CDT Thu Apr 5 2018
A big weather change is upon us. We will see the cloud deck
thicken and lower through the night and then eventually start
seeing some snow in the pre-dawn hours. Periods of snow are
expected through primarily Friday morning although it could linger
into the early afternoon hours. Expect visbility reductions and
low ceilings to MVFR and possibly IFR at times within the heavier
snow bands. Ceiling and visibility conditions will begin to
improve by late Friday afternoon.
&&
.GID WATCHES/WARNINGS/ADVISORIES...
NE...Winter Weather Advisory from 3 AM to 7 PM CDT Friday for
NEZ039>041-046>049-060>064.
KS...None.
&&
$$
UPDATE...Wesely
SHORT TERM...JCB
LONG TERM...JCB
AVIATION...Wesely
Area Forecast Discussion
National Weather Service Green Bay WI
1028 PM CDT Thu Apr 5 2018
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Friday
Issued at 247 PM CDT Thu Apr 5 2018
The latest RAP analysis and satellite/radar imagery show high
pressure exiting to the east over the Ohio Valley early this
afternoon. Meanwhile, a modest shortwave is bringing snow to
eastern ND and northern MN. Though moisture is rather limited,
steep mid-level lapse rates around 8.5 C/km to go along with mid-
level fgen is making snowfall production relatively efficient,
judging by the lower vsbys in moderate snow reported by the
metars in the area. As this system moves across the region
tonight, forecast concerns mainly revolve around snow amounts and
locations.
Tonight...A challenging forecast in regards to fine tuning the
details. The shortwave trough will push a weak surface low/trough across
the region. Relied heavily on the higher resolution models on
timing/snow amounts/and location of highest snowfall. These models
have slowed down the arrival of snow chances for most locations
except for far north-central WI, where light snow could start
falling very late this afternoon or early this evening. Otherwise,
most short-range guidance starts to move snow into central WI
around 02-03z before tracking it slightly north of due east into
northeast WI around midnight. Although most areas will see a
relatively high chance of light snow accumulations, most concerned
about a narrow swath of higher accums that could fall just north
of the low track. Models have shifted this swath of relatively
higher accums north over the last 12 hours, placing it from about
Marshfield to Sturgeon Bay. Because of the mesoscale nature of the
band, wouldn`t get hung up on this exact placement. But higher
amounts of 1-2 inches, locally up to 3 inches appears possible
wherever it ends up. It will be a quick hitter, so snowfall rates
could briefly reach up to an inch an hour at times. The snow is
expected to exit late tonight, and cold advection will resume.
Wind trajectories are favorable for additional accums of snow over
the snow belt of north-central WI. Highest amounts of 2-3 inches
right near the U.P. border in Vilas County.
Friday...Arctic high pressure will be building into the region
through the day. With gusty winds upwards of 25 to 30 mph driving
an unseasonably cold airmass into the region, expect partly sunny
to mostly cloudy skies and blustery conditions for much of the
day. Lake effect snow showers should continue through the morning
and trail off in the afternoon as drier low level air pushes into
western Lake Superior. Though there will be some left over
moisture in the mid-levels beneath upper troughing, saturation
depth doesn`t appear deep enough for snow shower chances away from
the snow belts. Forecast highs are expected to be a couple
degrees warmer than their record low maxes for many locations.
.LONG TERM...Friday Night Through Thursday
Issued at 247 PM CDT Thu Apr 5 2018
The main concern for the long term will be the well
below normal temperatures continuing through the beginning of
next week. The next chance for significant precipitation arrives
on Sunday night into Monday, and again Wednesday into next
Thursday.
Well below normal temperatures will cause afternoon high and
morning low temperatures to come very close to record breaking,
due to the cold air pouring in behind the system passing the area
tonight. These temperatures will continue through the beginning of
next week until a warm up begins by mid-week.
Guidance is in decent agreement for the track of the system late
Sunday afternoon through Monday, but has trended south since
yesterday. This leads to limited confidence in determining how
much accumulation will occur over our area from the possible rain
and snow showers. For the next system, Wednesday through next
Thursday, there is a large amount of uncertainty. Guidance is not
in agreement with the track of the system due a phasing and timing
problem between two streams of energy. As a result, a blend of
the models was favored for the forecast.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1028 PM CDT Thu Apr 5 2018
A short wave trough will also drag a surface cold front across
the area tonight. Scattered snow showers along and near the front
and during the short wave passage will generate brief periods of
MVFR/IFR conditions. Colder air on gusty northwest will pour into
the area for Friday. Isolated friday afternoon snow showers or
flurries are possible in the cyclonic cold flow regime. Snow
showers may be more numerous toward the Lake superior snow belt
region of far northern Wisconsin.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Hykin
AVIATION.......TDH
Area Forecast Discussion
National Weather Service Grand Rapids MI
1158 PM EDT Thu Apr 5 2018
LATEST UPDATE...
Aviation
.SYNOPSIS...
Issued at 329 PM EDT Thu Apr 5 2018
Areas of snow will spread in across the southern portion of the area
this evening, and then migrate toward Central Lower Michigan
overnight tonight and Friday morning. The heaviest accumulations
look to be toward I-94 to the South, and north of a Pentwater to Mt.
Pleasant line where 1 to 3 inches look likely. In between those
areas, an inch or so looks likely.
Snow will gradually transition to some lighter lake effect snow
showers on Friday, along with colder air filtering in. Any lake
effect will diminish on Saturday. The next noteworthy system then
will come in by Monday, bringing the potential of additional
accumulating snow to the area.
&&
.UPDATE...
Issued at 942 PM EDT Thu Apr 5 2018
No changes to the Winter Weather Advisory as the latest runs of
the HRRR/HRRRX continue to show a burst of convective snows
impacting the area for at least a few hours tonight in response to
the potent jet streak approaching from the northwest. Latest RAP
progs show the core of that jet streak to be in excess of 125
knots at 500 mb as it comes through.
It still looks like two distinct precip areas; one south of I-96
related to a 45 kt low level jet and warm advection, and another
north of M-46 linked more with the left front quad of the
approaching jetlet. Fcst of 1-3" for these two precip areas - but
only an inch or less inbetween - still looks okay. The corridor
from Muskegon and Holland through GRR to Alma may only see a
dusting, but even the lighter amounts here could slicken the
roads for the morning commute. Turning quite blustery Friday as
the winds crank up in the wake of this system.
&&
.SHORT TERM...(This evening through Saturday night)
Issued at 329 PM EDT Thu Apr 5 2018
Our main focus in the short term is the system coming through
tonight and Friday, and the headlines that are in place for it. We
will be maintaining the headline as is. We will try to add some
finer details with it, focusing the heavier amounts down South and
up North.
We have fine tuned amounts a bit with this fcst package, as it looks
like that the I-94 corridor, and north of the M-20 corridor will see
the best chance of the higher snow totals. Right now, 1 to 3 inches
still looks reasonable. The Central portion of the area looks to
miss the heavier amounts. This thinking is based on the idea that
the Srn portion of the area will see a burst of snow this evening
with the LFQ of a digging 145 knot upper jet. The band of current
pcpn SW of Chicago looks to shear out, and then redevelop, and move
over SW Lower just after 00z tonight. This will be short lived of a
few hours, but could pack a decent punch when it does move through.
That snow will move east of the area overnight, and some snow will
migrate over the nrn portion of the area by morning. This snow will
be the result of the same upper jet, but just the RRQ of the jet as
it is pushed just n of east by the ridge moving east over the
Rockies. This will not be as strong as the snow showers tonight, but
will persist a little longer until the jet moves away.
The central portion of the area is likely to not be as affected as
much by these features. It is still possible that the features could
shift a little, leaving a little bit of uncertainty with regards to
amounts.
Winds will pick up on Fri as the jet, and sfc response move east.
This will provide for wind gusts maybe up to 40 mph with cold
advection taking place and a decent gradient on the back side of the
system. H850 temps will drop down to the negative mid teens C,
providing sufficient instability over the lake for lake effect snow
showers. Moisture is not that deep, so we do not expect significant
accumulations from the lake effect before it diminishes later on
Sat. High pressure will build in Sat night to quiet things down.
.LONG TERM...(Sunday through Thursday)
Issued at 329 PM EDT Thu Apr 5 2018
It seems to me we are in for a significant warm up the second half
of next week. We get one more push of cold air early next week
before a major pattern shift midweek. The system on Monday may
bring some snow to the area and that will be followed by one final
push of cold air for Tuesday. Beyond that we will likely have a
major spring storm cross the CONUS and that may bring us severe
storms late in the week depending on how far north the warm front
gets. We have a very real chance of having our first day with
highs in the 70s late next week (with wind and storms).
As for the big warm up the second half of next week, that is
related to the re-adjustment of the upper wave pattern over North
America by the middle of next week.
One of those powerful East Asian Jet features, crossing the Pacific
around 45N, it reaches the dateline on Tuesday. With a core of winds
nearly 20 degrees of longitude long over 160 knots, it will break
through the western ridge and allow the Hudson Bay upper low to
retreat to near the North Pole by late in the week. Typically this
sort of event causes a major spring storm to cross the CONUS and
both the GFS, the ECMWF and the ensembles agree on this. Timing
will be an issue since the system now is just coming of China.
Still the models have been showing this for at least a week now.
So what this means is after the Monday system moves out of the way
by Tuesday, the polar jet retreats to north of the Canadian border.
The southern stream then becomes our main weather player into the
following weekend. Late next week as the Pacific storm progresses
through the CONUS we get into deep southerly flow and will have
our warmest temperatures of the year to date. I have little
question we will be seeing highs in the 60s late in the week,
possibly warmer. However this will be just ahead of the cold front
and the threat of storms. We will have to watch this but this is
over a week out so we have time to watch it.
As for our Monday system, this is one of those southern stream
merging with the northern stream wave deals. Where it tracks depends
on when the merge actually happens. Over the past month this has
happened too late for Michigan and these systems have tracked
south of here. With that major pattern change just behind this
that may not happen this time. That would mean Monday will be a
snowy day over the entire area. I lowered the temperature Monday
to account for this and make sure all forecast elements make
sense together. I also coordinated with nearby offices so it
works that way too.
&&
.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1140 PM EDT Thu Apr 5 2018
Conditions will deteriorate quickly from mainly VFR to a mix of
MVFR/IFR overnight as cigs lower and snow develops. The snow will
be heaviest at our southern terminals (KAZO... KBTL and KJXN)
where IFR conditions are most probable.
Cigs/visbys will improve to MVFR Friday morning and then to mainly
VFR Friday afternoon through Friday evening. However WNW winds
will increase considerably to 15 to 25 kts with gusts to around 30
kts Friday afternoon.
&&
.MARINE...
Issued at 329 PM EDT Thu Apr 5 2018
Winds will increase tonight, with the strongest winds expected
during the daylight hours on Friday with the cold air advection
behind the departing system. The mixing layer brings a good chance
of tapping 35 knot wind gusts down, so we will issue a Gale Warning
for this event.
&&
.HYDROLOGY...
Issued at 202 PM EDT Thu Apr 5 2018
Primary precipitation type through early next week will be snow.
No flooding concerns are expected until a warmer and wetter
pattern develops, which could perhaps happen toward the end of
next week.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Winter Weather Advisory until 11 AM EDT Friday for MIZ037>040-
043>046-050>052-056>059-064>067-071>074.
LM...Gale Warning from 8 AM to 8 PM EDT Friday for LMZ844>849.
&&
$$
UPDATE...Meade
SYNOPSIS...NJJ
SHORT TERM...NJJ
LONG TERM...WDM
AVIATION...Laurens
HYDROLOGY...CAS
MARINE...NJJ
Area Forecast Discussion
National Weather Service Houston/Galveston TX
827 PM CDT Thu Apr 5 2018
.UPDATE...
Radar shows a band of showers and isolated thunderstorms mainly
SW of Houston with the strongest storm over western Brazoria
County. Surface analysis shows this activity along a warm front
with higher dewpoints to the southwest and lower dewpoints/drier
air to the northeast. Latest HRRR model runs seem to have a decent
handle on the precipitation placement and have activity decreasing
the next few hours. Forecast has been updated for these trends in
the near term.
Overall think the rest of the forecast looks on track. After re-
evaluating the severe weather potential for Friday night, think
the elevated mixed layer will become too strong to overcome
especially during the day. Models do show a vorticity max moving
over the region 06-12Z Saturday in NW flow aloft but this seems to
be out of phase with the surface cold front which is also
advancing southward during this time. We will continue to message
the possibility of an isolated severe storm with hail/wind threat
since there will be steep lapse rates aloft to support that
threat. But overall thinking is the EML will be too much for
convection to overcome.
Overpeck
&&
.PREV DISCUSSION /Issued 650 PM CDT Thu Apr 5 2018/...
.AVIATION...
An ongoing band of mainly -SHRA will travel across the southern
most air fields over the next hour or two...mainly dry through
late Friday night with only a few sprinkles/a light shower not
worthy of placing within this TAF package. Confidence is highest
that areawide MVFR decks will hold through the first half of the
TAF period...with slower recovery back to VFR ceilings over the
southern hubs through early Friday afternoon. A stout southwest to
south wind will likely maintain these MVFR ceilings through the
overnight early Friday morning hours with brief periods of wind-
sheltered (rural) terminal near sunrise IFR cats. An approaching
central Texas cold front may allow for the development of late
Friday night showers...with an embedded storm or two...out ahead
of the boundary. The bulk of the thunderstorm activity will occur
overnight Saturday morning...or just beyond this 06/0Z forecast.
31
&&
.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 66 82 50 61 45 / 20 20 50 20 10
Houston (IAH) 67 82 59 68 47 / 20 20 60 40 10
Galveston (GLS) 70 80 67 70 56 / 30 20 50 50 10
&&
.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 5 AM CDT Friday for
the following zones: Coastal waters from Freeport to the
Matagorda Ship Channel out 20 NM...Coastal waters from High
Island to Freeport out 20 NM...Galveston Bay...Matagorda
Bay...Waters from Freeport to the Matagorda Ship Channel
from 20 to 60 NM...Waters from High Island to Freeport from
20 to 60 NM.
&&
$$
UPDATE...Overpeck
NEAR TERM...39
SHORT TERM...31
Area Forecast Discussion
National Weather Service Paducah KY
920 PM CDT Thu Apr 5 2018
.UPDATE...
Issued at 920 PM CDT Thu Apr 5 2018
Looking at 00z Friday mandatory upper level fields indicating the
12z Thursday Canadian, 18z GFS, and and early evening RAP
guidance are initializing the leading edge of the colder air
in the upper Midwest this evening. The earlier runs of these
models have been consistent today on weather trends.
Looking at 10.4 micron GOES-E Clean IR Window, the colder cloud
tops with the lead shortwave moving over the central Rockies
onward into KS and TX are in line with the Canadian models
trajectory of this wave. This trend would definitely place the
baroclinic zone and the developing surface low along the Red River
between northern Texas and southern OK through noon on Friday,
inhibiting the duration of significant lift along the upper level
boundary well north of the surface front by 00z Saturday (7 pm
Friday). The slower advection of a deeper cold layer into northern
parts of the WFO PAH forecast area may slow the transition to
frozen precipitation into the area in the 03z-06z Saturday (10 pm
Friday to 1 pm Saturday) time frame.
At this time, the current snowfall forecast may be at or on the
upper limit of snowfall potential for Friday night, lessening the
concern for warning level criteria snowfall for the WFO PAH
forecast area.
Plan to get all of the evening model guidance this evening before
considering any substantive changes to current winter storm watch
out for the northern part of the WFO PAH forecast area. Should the
trajectory of the shortwave out west shift markedly in the next
6-12 hours, that could change snowfall potential and areal
coverage of any wintry mix in the Quad State region. Regardless,
antecedent warmer road and soil temperatures should definitely
inhibit any significant accumulations of snow or wintry
precipitation during the next 24 hours.
UPDATE Issued at 642 PM CDT Thu Apr 5 2018
Updated Aviation Discussion for 00z TAFs.
&&
.SHORT TERM...(Tonight through Saturday night)
Issued at 320 PM CDT Thu Apr 5 2018
Well, what a difference 12-18 hours can make within the numerical
model guidance community.
Beginning with the 00Z run of the operational ECMWF...subsequent
06z and 12z runs of most deterministic and ensemble models have
trended to a solution not to phase the nrn/srn branch H50 mid lvl
short waves, leaving even more of a positive latitudinal tilt to the
system. As a result, model consensus now suppresses a weaker surface
low much farther south into Dixie, taking much of the more
significant precip with it.
Decided to cut snow amounts at least in half in the watch area
with this forecast package. This leaves us well short of winter
storm criteria. However, have chosen to keep the winter storm
watch headline going for now for the following reasons:
1. We still could see winter weather advisory needs even with the
lower snow totals now forecast. Do not want to create more
confusion to customers by dropping watch now, just to hoist and
advisory headlines in later forecasts.
2. Models may still be in flux and could flip back to a farther
north solution in future runs. Overall forecast confidence
remains quite low at this time.
In addition, will go ahead and hoist freeze warnings for much of
southeast MO for Friday night/Sat morning, where colder air will be
filtering in on north winds on the back side of the system as it
exits to the east.
Saturday is expected to be precip free as unseasonably chilly high
pressure builds into the region. In fact, will likely need to issue
another freeze warning for applicable area of the forecast area
(south half where green up has occurred). Temps should fall into the
mid/upper 20s before clouds move in after midnight.
.LONG TERM...(Sunday through Thursday)
Issued at 320 PM CDT Thu Apr 5 2018
Medium confidence in the extended. However in the short term models
are varying over the last couple of runs. This fact makes it
difficult to have a great deal of confidence in the extended
even though models are in fair agreement.
There will be a fast moving clipper type system into the area by
Sunday afternoon and should exit the region Monday morning. This
could result in a wintry mix overnight for areas along northwest of
the Ohio River. It should however be of little impact as it looks at
this time. We should have a dry period from Monday through Wednesday
with temperatures slowly rising to near normal by Wednesday.
Wednesday night into Thursday the surface high drifts off the east
coast allowing for a southerly flow to return to the region. A warm
front will lift well north of the area Wednesday night Will probably
try to avoid thunder mention at this time as Showalters are positive
but do approach zero in SEMO and K index do approach 30c as well. No
surface based instability with No CAPE and very positive LI`s.
However will wait and see what collaboration yields. As we head into
Friday we do start to see some surface based convective parameters.
We could see some scattered frost Tuesday and Wednesday mornings.
&&
.AVIATION...
Issued at 642 PM CDT Thu Apr 5 2018
VFR conditions expected into the morning hours. Light southerly
winds will be in place tonight with only some mid to high clouds.
Cold front will nudge into the northern counties by morning and
progress southward into the afternoon hours. Winds will switch
around to the north and pick up by late afternoon and just beyond
this valid TAF period. Gusts expected up around 15-20 kts by late
afternoon for KCGI and KPAH, possibly sneaking into KEVV/KOWB
toward very end of the period. Low VFR deck around 4-5kt expected
as the front moves through. Rain begins spreading northward into
southern counties during the afternoon hours, and may reach
KCGI/KPAH as early as 20z. Expect some MVFR vsbys and lowering of
cigs into MVFR category as the rain moves in.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Winter Storm Watch from Friday evening through Saturday morning
for ILZ075>078-080>091.
MO...Winter Storm Watch from Friday evening through Saturday morning
for MOZ076.
Freeze Warning from 1 AM to 8 AM CDT Saturday for MOZ086-087-100-
107>110.
IN...Winter Storm Watch from Friday evening through Saturday morning
for INZ081-082-085>088.
KY...Winter Storm Watch from Friday evening through Saturday morning
for KYZ014-015-018>020.
&&
$$
UPDATE...Smith
SHORT TERM...GM
LONG TERM...KH
AVIATION...SP