Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/05/18
Area Forecast Discussion
National Weather Service La Crosse WI
607 PM CDT Wed Apr 4 2018
.SHORT TERM...(Tonight and Thursday)
Issued at 240 PM CDT Wed Apr 4 2018
Skies were clear this afternoon as a surface ridge axis was moving
east toward the Upper Mississippi River Valley. As the high
continues to slide off to the east this evening, expect a couple
disturbances to bring small rain/snow chances to the area tonight
into Thursday.
First, a mid-level wave is forecast to move across northern Iowa
later tonight. There may be enough warm-air advection/isentropic
lift to produce some flurries or light snow, but saturating the
column will be challenging given the very dry low-level air. Low
chances for precipitation will continue with the mid-level wave as
it moves into southern Wisconsin on Thursday.
Meanwhile, a stronger shortwave currently over southwest
Saskatchewan will approach northern and central Wisconsin by
Thursday evening. Precipitation looks a little more likely with this
system. The timing of this wave in the 04.12Z Extended HRRR is much
quicker, but that solution is currently an outlier.
Temperatures will remain well below normal as the northwest flow
pattern continues. Some locations in central Wisconsin could see
lows tonight approach zero degrees Fahrenheit.
.LONG TERM...(Thursday Night through Wednesday)
Issued at 240 PM CDT Wed Apr 4 2018
Exiting short wave could still be producing a brief period of light
precipitation Thursday evening, but exiting is the key word as even
colder air advects in. Large area of high pressure /ridge/ builds in
for first part of the weekend so lowered minimum temperatures in
favored cold spots where winds could decouple and snow pack will
allow big drops.
Of far more importance is what could be very busy week ahead
according to medium range guidance. Possibility of 3 weather events
to impact region so will have to take them one at a time.
Event 1 comes in Sunday afternoon as mid level wave transverses
region. Favorable lift region ahead of this system should make for
widespread precipitation that shifts through overnight. A bit far
out for details, but thinking guidance might be too warm which would
account for more snow than rain/snow mix. Either way could see more
snow accumulations and perhaps into advisory criteria? Again,
details will need to be worked out as event approaches.
After quick revive Monday night and Tuesday, an even stronger short
wave moves through increasingly more active flow for midweek. With
warming temperatures, could see more of a precipitation mixture than
weekend event, but too far out for specifics.
With snow pack and pattern becoming more active /and warmer/ will
need to keep an eye out for flooding concerns or impacts.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 607 PM CDT Wed Apr 4 2018
Generally expecting VFR conditions through Thursday. A short wave
trough currently over the western Dakotas will slide southeast and
slip just south of both airports Thursday afternoon. Some light
precipitation should develop with this wave, but it too should
stay to the south of both airports. Another short wave trough,
currently over southern Alberta, will also slide southeast and
should be moving across central Minnesota by late Thursday
afternoon. The light precipitation associated with this wave
should still be to the northwest of the area. However, there will
be enough of an increase in moisture from these waves to bring in
a VFR ceiling for Thursday afternoon to both sites.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Hollan
LONG TERM...Shea
AVIATION...04
Area Forecast Discussion
National Weather Service Green Bay WI
1012 PM CDT Wed Apr 4 2018
Updated aviation portion for 06Z TAF issuance
.SHORT TERM...Tonight and Thursday
Issued at 304 PM CDT Wed Apr 4 2018
The latest RAP analysis and satellite/radar imagery show an area
of strong low pressure moving across northeast Ontario while a
relatively weak surface ridge axis extends north over the northern
Mississippi Valley. Skies are mostly clear except for the northern
Door Peninsula where the back edge of the cyclone`s cloud shield
is in the process of exiting. Looking upstream, a weak, channeled
shortwave is moving into the boundary waters of Minnesota early
this afternoon. Cloud bases remain relatively high with this
system, and have only seen isolated reports of flurries. As this
system moves across the northern Great Lakes tonight, and another
system approaches the region tomorrow afternoon, cloud trends and
small precip chances are the main forecast concerns.
Tonight...The surface ridge axis will shift southeast across the
state at the same time as channeled vort energy slides across far
northern WI and the Upper Peninsula. Some clouds will likely move
into northern WI during the evening, but though deep moisture is
generally lacking, models show that precip chances will remain
north of the U.P. border. This makes sense given the very low
dewpoints that moved into northern WI by early this afternoon.
Despite the ridge axis arriving, winds may struggle to decouple in
spots. Combined with some clouds, low temp forecast is tricky.
Did edge temps a degree or two lower though, mostly due to the
fall of dewpoints so far today, and believe there could be enough
clearing for temps to tank in the cold spots. Lows ranging from
around 5 above at Tomahawk to the mid teens near Lake Michigan.
Thursday...Once clouds depart far northeast WI early, should see
some sunshine for the rest of the morning. Then clouds are
expected to increase again from west to east as a slightly more
potent shortwave moves into the state during the afternoon.
Moisture will remain limited, but precip chances look to return to
central and north-central WI by late in the afternoon, which may
be slightly slower than the previous forecast. Temps will be cold
enough for mainly snow over the northwoods, and a rain/snow mix
over central WI. Winds will shift to the southwest, which should
result in warmer temps. Highs returning to the middle 30s.
.LONG TERM...Thursday Night Through Wednesday
Issued at 304 PM CDT Wed Apr 4 2018
The main concern for this period will be the well below normal
temperatures through the weekend. The system pushing through the
area beginning on Thursday will also continue into early Friday
morning with chances for snow. Another system will cross the area
Sunday night into Monday.
Guidance is in agreement for timing and p-type for the system on
Thursday continuing into Friday morning. Minor snow accumulations
are possible. Some areas in north-central and central Wisconsin
may see higher amounts of 1 to 3 inches of snow. Cold air will
drive into the area behind this system allowing temperatures on
Friday to fall well below normal. Temperatures will remain 10 to
20 degrees below normal into early next week as well. It is also
possible, if conditions become clear and calm, temperatures can
drop very quickly to the single digits below zero.
The system for Sunday night into Monday shows some uncertainty
between models for the timing of the precipitation and the axis
of the low pressure system track. This results in uncertainty in
p-type and accumulations across the area. Therefore, a standard
blend of model guidance was favored for the forecast.
&&
.AVIATION...for 06Z TAF Issuance
Issued at 1011 PM CDT Wed Apr 4 2018
VFR sct-bkn clouds will drift over northern Wisconsin overnight,
otherwise VFR conditions expected overnight into Thursday. Mid
level clouds will be on the increase Wednesday afternoon and
early evening as a short wave approaches the area from the
northwest. Scattered MVFR clouds and vsbys due to snow may spread
over the area later Thursday evening.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM.....MPC
LONG TERM......Hykin
AVIATION.......TDH
Area Forecast Discussion
National Weather Service Grand Rapids MI
937 PM EDT Wed Apr 4 2018
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 310 PM EDT Wed Apr 4 2018
One area of low pressure will track away from the region tonight
taking the snow showers and wind with it. A weak area of high
pressure will track through on Thursday resulting in mainly a dry
and less windy day. Yet another storm system quickly tracks
through Thursday night resulting in another round of snow. A cold
airmass then spreads in for the weekend.
&&
.UPDATE...
Issued at 937 PM EDT Wed Apr 4 2018
Clouds and flurries were still hanging on this evening although
much of northern and central Lwr MI has cleared out. With sfc
ridging moving in would expect to see winds diminishing and the
clearing becoming more widespread, especially inland. The latest
RAP RH guidance supports this notion. It may be tough to lose the
clouds completely however as the cold h8 temps around -13C should
continue to generate some lake effect clouds. Will lower min
temps up north where it`s already cleared out and a decent snow
pack exists. Lows around Leota could end up being in the single
digits.
&&
.SHORT TERM...(This evening through Friday night)
Issued at 310 PM EDT Wed Apr 4 2018
The snow showers will continue to diminish this evening as the
storm system pulls away and the low level convergence weakens.
Will hold onto a low risk for snow showers. Well below normal
temperatures are expected with values in the upper teens to low
20s for most places. These values are over 10 degrees below
normal. With fresh snow on the ground...even colder values are
possible...especially for the northern zones.
Above freezing highs are forecasted on Thursday as the next storm
nears from the west northwest. As the shield of precipitation
starts to move in late in the day...there could be a r/s mix at
the onset...but that should not last long. Wet bulbing should
support a mainly snow event for the region Thursday night. This
could change if the storm tracks further north than currently
forecasted. There is a convective look to some of the models with
this event...which does raise some concern as far as amounts go.
Right most of the guidance suggests a 1 to 3 inch snowfall. There
are some solutions that give the region almost no snow. The
precipitation will not last long as this storm will be moving
rather quickly. By daybreak Friday the steady area of snow should
be off to the east.
Good mixing should support windy conditions on Friday. The dgz
moistens back up in the cold airmass later in the day with the
winds veering with time. The airmass will be cold enough for lake
effect going into Friday night. Thus I bumped up POPs near the
lakeshore.
.LONG TERM...(Saturday through Wednesday)
Issued at 310 PM EDT Wed Apr 4 2018
The colder than normal and somewhat snowy weather pattern should
last till midweek, then a warming trend is likely. This change is
based on one of those Extended East Asian Jet features coming across
the Pacific and breaking through the western upper ridge next week.
That should result in a more zonal flow and hence warmer
temperatures. However that is in the Wed/Thu time frame. Till then
winter like weather will continue thanks to cross polar flow at
mid and upper levels and the upper low being displaced southward
to Hudson Bay.
On Saturday we have some of the coldest air yet coming into the area
on northwest flow and there is enough moisture and lift for Lake
Effect. So I increased the pop to likely Saturday near the lake
shore. This should be good for 1 to 3 inches of snow near the
lake shore and highs below freezing across the area.
The Mon/Tue system still looks great. We have a Pacific shortwave
that makes it through the upper ridge over the west coast and tries
to merge with a northern stream wave rotating around the Hudson Bay
Low. That should be good for another snow storm. Our forecast
shows rain by Monday afternoon but that is due to our grids having
to high of temperatures during the afternoon so really it will just
mostly be snow into Tuesday morning. Some lake effect snow showers
are possible Wed as cold air follows the system then warming begins.
&&
.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 748 PM EDT Wed Apr 4 2018
VFR conditions are expected tonight and Thursday as a dry air mass
settles in behind the departing system. The strato-cumulus clouds
with bases of 4000-6000 ft and flurries currently overhead should
mostly dissipate by 06Z. Some diurnal cumulus may reform on
Thursday, but bases will be above 3000 ft. Precipitation with the
next event should mostly hold off until after 00Z Thursday
evening, although some MVFR cigs/vsbys could impact AZO and BTL
just prior to 00Z as the snow develops/moves in.
&&
.MARINE...
Issued at 310 PM EDT Wed Apr 4 2018
The wind has fallen under gale force. Will transition this to
small craft advisories. The wind continues to decrease tonight so
right now Thursday is expected to feature no headlines. However by
Friday...the winds and waves increase again to likely small crafts
or even gales.
&&
.HYDROLOGY...
Issued at 310 PM EDT Wed Apr 4 2018
About half to three quarters of an inch of rain fell Tuesday. With
near to below normal river flows for this time of year, following a
drier than normal March, this beneficial rain may cause river levels
to rise slightly. Flooding is not expected in the next week.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...None.
LM...Small Craft Advisory until 4 AM EDT Thursday for LMZ844>849.
&&
$$
UPDATE...Meade
SYNOPSIS...MJS
SHORT TERM...MJS
LONG TERM...WDM
AVIATION...Meade
HYDROLOGY...CAS
MARINE...MJS
Area Forecast Discussion
National Weather Service Jackson MS
914 PM CDT Wed Apr 4 2018
.UPDATE...
Updated for evening discussion.
&&
.DISCUSSION...
Overnight low temperatures and frost potential were the primary
focus for this forecast update. A 1025mb surface high with origins
in the Canadian Yukon will continue to slide south and east
through the Lower Mississippi River Valley and into eastern TN and
KY by tomorrow morning. This ridge will help relax the surface
pressure gradient and will supply low 30s dewpoints across a
large portion of the area. Dry air, clear skies, and light to calm
winds will promote efficient radiational cooling across much of
the area, especially over the Golden Triangle. Have adjusted low
temps down slightly along and NE of a line from Grenada to
Meridian with lows dropping into the mid to low 30s. As such,
areas of frost can be expected during the overnight hours for
these locations and have expanded the limited risk in the
HWO/graphics accordingly. Otherwise, the rest of the forecast
remains on track and no other changes were needed. /TW/
Prior discussion below:
Tonight through Thursday: The primary concern will be the potential
for some frost over our northeast counties early Thursday morning.
Latest rap and satellite imagery showed an upper flat trough over
the Mississippi Valley Region. Under sunny skies breezy cool
northerly winds were observed across the region with cool
unseasonable readings in the 50s and 60s. A 1030 mb surface high was
noted across Southern Plains.
Quiet conditions can be expected for the period. With 30s dewpoints
and diminishing winds under clear skies expect good radiational
cooling as temps quickly drop into the 40s during the evening. With
light winds lows will range from the middle 30s northeast to the
upper 30s and lower 40s elsewhere. Conditions should favor some
patchy frost across our northeast counties. The surface high will
track toward east Tennessee by 12z Thursday. So we may not decouple
completely in the low levels. For Thursday we will start to get some
low level return flow under full insolation which will warm up temps
toward more seasonable levels. Readings will be from the middle 60s
to the lower 70s. With 30s and 40s dewpoints minimum humidity will
dip into the lower to middle 20s across portions of the east. However
lack of gusty winds should limit fire weather concerns. /17/
Thursday night through Tuesday:
An impulse in the broad upper trough over the southern plains will
move through the region Friday night into Saturday morning. With
abundant warm air advection ahead of the impulse on Friday, some
convection will break out early in the morning along the associated
warm front which will be located in the Delta and northwards. Dewpoints
will creep into the low to mid 60s during the day. There could be
some strong storms with this stuff during the day as things
continue to advect into and fester in the warm sector.
After 00Z Saturday, a surface low looks to form in northern MS and
helps to swing the cold front through the CWA. Severe weather
parameters look pretty decent with 35-45 kts of bulk shear. MUCAPE
up to 2000 j/kg during the day will wane at night but values up to
1000 j/kg will be plenty to keep strong storms in the area. Mid
level lapse rates between 6.5 and 7 C/km are good enough to to
warrant a threat of large hail too. CWAPS and helicity values are
all pretty decent too. Some limiting factors are the models don`t
quite line up on all of these ingredients. All of this
considered though, we decided to expand the slight eastward to
the Mississippi River and include the entire area in at least a
marginal threat.
The global models differ on the timing of the front`s exit to the
east. The anafrontal precip could linger through a portion of the
day on Saturday, but expect it to be east of the area by 00Z Sunday.
A surface high will follow into the mid-Mississippi Valley on Sunday
and quickly push east as an upper shortwave moves through the
Midwest. As this system moves to our north, it will trigger showers
and possibly some storms in the CWA on Monday. The system quickly
tracks east and clears the area by Tuesday. An upper ridge then
moves over the Mississippi Valley and leaves conditions near
normal for early April in the middle of next week. /10/
&&
.AVIATION...
00Z TAF discussion:
VFR conditions are expected through the next 24 hours as high
pressure nudges into the region tonight and then starts to exit to
the east during the day tomorrow. The evolution of high pressure
will result in generally light north to northeast winds,
transitioning to east and southeast morning through midday
tomorrow, and then to southerly by tomorrow afternoon. Of course
by afternoon tomorrow winds could get increase to a range of 10 to
15 mph in most areas with potential gusts up to 20 mph at GLH and
GWO. Otherwise, expect high and thin clouds to increase from the
west during the afternoon hours tomorrow with some patchy frost
possible tomorrow at daybreak, mainly at sites
GWO/GTR/CBM/NMM/MEI. /BB/
&&
.PRELIMINARY POINT TEMPS/POPS...
Jackson 39 70 52 76 / 0 2 12 46
Meridian 33 70 49 76 / 0 2 7 25
Vicksburg 40 71 54 76 / 0 2 16 52
Hattiesburg 37 72 48 77 / 0 1 5 21
Natchez 40 72 54 77 / 0 2 9 51
Greenville 40 67 54 70 / 0 4 35 67
Greenwood 36 68 52 71 / 0 2 29 68
&&
.JAN WATCHES/WARNINGS/ADVISORIES...
MS...None.
LA...None.
AR...None.
&&
$$
TW/10/17/BB