Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/15/20
Area Forecast Discussion
National Weather Service Gaylord MI
1045 PM EDT Tue Apr 14 2020
Issued at 933 PM EDT Tue Apr 14 2020
Broad cyclonic flow...cold air aloft and wrap-around moisture
continue to produce sct/nmrs snow showers across the Western Great
Lakes region late this evening. Another weak wave/convergence axis
is making its way into Northern Lower Michigan attm...resulting in
an uptick in ongoing snow shower activity. Meanwhile...another
wave/convergence axis is pivoting thru Lake Superior toward
Eastern Upper Michigan...also resulting in an enhanced line of
snow showers. Latest RAP suggest the Northern Lower Michigan wave
will slide thru our area over the next few hours...exiting our CWA
late tonight. Near term models show the Lake Superior wave will
drop into Eastern Upper Michigan overnight and will stall over
that area for a few hours. Have made some upward adjustments to
POPs and to snow amounts overnight...and have extended the Winter
Wx Advisory for Chippewa county thru 12Z Wednesday with another 2
inches or so of new snow expected for some locations.
.NEAR TERM...(Through Wednesday)
Issued at 331 PM EDT Tue Apr 14 2020
...Snow shower focus shifting to eastern upper...
High Impact Weather Potential: Locally intense snow showers
thru this evening, especially in parts of eastern upper MI.
Low pressure over nw Quebec continues to move to the ne, while
ridging into the OH Valley is edging northward. Plenty of cool and
moist low-level air is in place, with steep lapse rates already
present this morning per the 12Z APX sounding. When combined with
strong mid- April sun, we get widespread cumulus and plenty of
convective showers. In northern MI, we also have lake and synoptic
contributions to clouds/precip, resulting in something of a mess.
In particular, we have seen a series of surface trofs and wind
shifts proceed across the area. One in particular has hung up over
eastern upper MI, with resulting persistent and considerable low-
level convergence. We presently have sw winds on Beaver Isl, wsw
at Mackinac Isl, and were for time almost south at DeTour. But
across central and northern Chippewa Co, nw winds are present.
This is focusing a lot of convergence over far eastern upper MI
(that convergence is weaker to the west, with westerly winds at
Newberry and points west). There has been a substantial uptick in
snow showers as a result, somewhat hidden from view given how far
that area is from local radars. But Kinross has seen vsbys below
1SM for over 90min now, dipping to 1/4SM at times (including
So the expectation is for convergence-forced training showers, of
the sort that could produce flash flooding in the warm season.
Except of course that we`ll be getting snow instead. HRRR/Rap runs
today have pretty consistently shown a potent QPF max this
afternoon and evening in central Chip Co, somewhere between
Rudyard and Sugar Isl. Most recent Rap has a max of almost 0.50"
QPF near southern Sugar Isl. HRRR is closer to Kinross, at nearly
0.75". Will not go quite /that/ bonkers, though higher local
accums are certainly possible. Snow-liquid ratios in the high
teens will result in a (conservative?) forecast of 4 to 8" of
accums this afternoon and evening, from Trout Lk to Rudyard to
In northern lower MI, best activity presently is focused from
Charlevoix Co to sw Presque Isle Co. This is along another axis
of low-level convergence. Can`t have convergence everywhere of
course, and other parts of northern MI are seeing a relative lull
(though diurnal affects are still sustaining some showers). Plan
for numerous snow showers to be sustained thru the night in far
northern lower MI, especially south of PLN and north of Kalkaska.
But loss of diurnal instability should take a little bit of
intensity away. Will maintain the current northern lower MI
advisory I suppose (it expires at 7 pm), but most accums tonight
will be less than 2 inches. Given prevalent lake instability, some
locally higher amounts are certainly possible.
For Wednesday, inversion heights are slipping lower as 500mb
heights rebound behind the shortwave that is helping things
tonight. We do still have cool/moist low levels, a high sun angle,
and at times cyclonically curved flow (especially in northern
sections). The above will support nw-flow lake effect off of
Superior initially (with the main focus from Alger into far western
Mack Co). Diurnal components will broaden precip chances with
time, much like today, but again less intense. Suppose a stray
inch or two is possible, mainly in eastern upper MI.
Chilly min temps tonight, mainly upper teens to lower 20s. Mid 30s
to around 40f for highs Wednesday.
.SHORT TERM...(Wednesday night through Friday)
Issued at 331 PM EDT Tue Apr 14 2020
High impact weather potential: Minimal, although a few snow showers
continue to remain possible at times into at least Thursday.
Pattern synopsis/forecast: Large scale, unseasonable cool upper
level troughing is expected to remain in place for the foreseeable
future across the Great Lakes region. Primary focus revolves around
marginally supportive lake effect parameters combined with smaller
scale shortwaves embedded in aforementioned parent troughing that
may give a small boost to overall precip chances from time to time
through the forecast period.
Primary forecast concerns/challenges: PoPs and temperature trends.
Initial thermo parameters Wednesday night remain marginally
supportive for lake effect snow development given delta Ts of right
around 13 C leading to lake induced CAPE values of several hundred
J/kg. However, limited synoptic support aloft behind a quick-moving
mid-level shortwave, lots of low-level dry air and sinking
inversions heights should prove to be enough to keep any new snow
showers Wednesday night rather isolated and confined to primarily
west-northwest flow snow belts of E upper/NW lower. Not much in the
way of accumulation...perhaps a few spots pick up a new coating
overnight. Overnight lows have the potential to vary greatly across
the forecast area given light winds combined with a difference in
cloud cover. "Warmest" spots expected to be nearest the Lake
Michigan shoreline under more frequent clouds...ranging from the mid-
upper 20s. Some locations across the eastern half of the forecast
area and over parts eastern upper should easily tumble into the
upper teens, if not a bit further assuming less frequent cloud cover.
A similar story for Thursday, but with even more dry air to overcome
in the low levels per model soundings. Still expect a few snow
showers to dot the map from time to time, but expect that they`ll
transition from lake effect nature to more convectively driven given
cold air aloft leading to impressively steep mid-level lapse rates.
Wouldn`t be surprised to see any of these showers contain more of a
snow/graupel mix, but again with little in the way of accumulation
given a lack of coverage and an increasing mid-April sun angle. One
thing of note for late in the day Thursday is a more robust
shortwave passing by north of the international border - suppose
this could briefly bring an uptick in snow shower coverage across
the UP along with the chance of a minor accumulation. Afternoon high
temps expected to be some 15 or so degrees below normal at many
sites across northern MI...ranging from the upper 30s to near 40
Slightly warmer H8 air expected to spread atop the region to wrap up
the work week in advance of a compact area of low pressure progged
to pass through the mid-MS Valley into the Ohio Valley. Suppose the
chance for a rogue rain/snow shower isn`t zero, have opted to keep
the forecast dry through this time frame for now. Highs boost a few
degrees for Friday...generally in the 40s area-wide.
.LONG TERM...(Friday night through Tuesday)
Issued at 331 PM EDT Tue Apr 14 2020
High impact weather potential: Minimal for now.
A brief reprieve anticipated at the start of the extended on
Saturday as troughing aloft briefly breaks down, allowing
temperature to climb back to near normal for most (generally in the
50s). Trends beyond that would suggest cooler air pours back into
the region to wrap up the weekend into the start of next week (along
with occasional precip chances) behind a cold front tied to low
pressure that treks across southern Canada. Long range guidance
toward the end of the forecast period and beyond show at least some
positive signs for those looking for warmer spring weather as cold
air looks to retreat northward, although that`s plenty off in the
distance, so there`s certainly time for that to change.
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1045 PM EDT Tue Apr 14 2020
Broad cyclonic flow...cold air aloft and low level moisture will
continue to produce sct/nmrs snow showers across Northern Lower
Michigan thru Wednesday night...especially across far Northern
and NW Lower Michigan where some lake enhancement will be present.
Prevailing VFR conditions will occasionally drop of MVFR/IFR
within some of the heavier snow showers. West wind AOB 10 kts
overnight will strengthen to 10 to 20 kts with some higher gusts
Issued at 331 PM EDT Tue Apr 14 2020
Low pressure over northern Quebec will continue to move away from
the region, allowing weak high pressure to build into the southern
Great Lakes. Gusty westerly winds will tend to diminish with tim
thru tonight, and ongoing advisories will be spun down as well.
Those winds (w to nw) will get a little breezier again late
MI...WINTER WEATHER ADVISORY until 8 AM EDT Wednesday for MIZ086-087.
Area Forecast Discussion
National Weather Service Charleston SC
1154 PM EDT Tue Apr 14 2020
High pressure will gradually build in from the northwest
through late week. Unsettled weather is then likely late week
through early next week as several disturbances move through
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
As of 1150 PM: KCLX indicated a cluster of showers and isolated
thunderstorms across the GA and lower SC waters, moving NE at
30-35 kts. Isolated showers were also tracking across McIntosh
Co. Latest HRRR indicate that the convection will remain over
the waters for a few more hours, then develop west over the
coastal areas late tonight. Based on radar trends and latest
guidance, I will adjust PoPs through the rest of the night.
Temperatures appear on track to cool into the upper 50s to low
60s by daybreak Wednesday.
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
Moderate confidence through the period that a stalled front offshore
Wednesday will turn into a cold front and push to the southeast
farther away from the area as high pressure builds from the
northwest. The combination of deep moisture and upper lift from a
jet and possible shortwave energy will yield showers around daybreak
Wednesday, especially near the GA coast, followed by drying from the
northwest during the day. Could be a few thunderstorms near the
coast as well with even an outside chance of a strong to possibly
severe storm, especially near the GA coast and over the nearby
Atlantic. Most of the rain should be offshore Wednesday evening as
cooler and drier high pressure builds from the northwest and
continues through Friday. However, moisture will be returning Friday
with the high situated offshore and return flow in place, and can`t
rule out a few showers during the afternoon, mainly in GA.
Otherwise, temperatures will modify through the period but still
likely to remain below normal.
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A cold front could bring scattered showers and tstms to the
area Friday night and Saturday. Another system may bring a wave
of showers and tstms through the area late Sunday afternoon
.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
00Z TAFs: A cold front will move through the area overnight with
winds veering to the north toward daybreak and surging a bit.
VFR conditions will become MVFR, possibly even IFR, ceilings
develop mainly after 06Z and lasting until about 15Z at KSAV and
about 18Z at KCHS.
Extended Aviation Outlook: High confidence in VFR conditions through
Friday with an increasing risk for periodic restrictions starting
Friday night due to low clouds, showers and possible thunderstorms
from a stalling cold front over or near the area.
Tonight: A cold front will shift through with south/southwest
winds veering to southwest, except more westerly at the coast
late. Seas should average 2-4 feet through tonight, with some 5
footers 40-60 nm offshore.
Wednesday through Sunday: High confidence through Friday night with
high pressure building into the area and remaining until a cold
front begins to approach Friday night. Low confidence this weekend
as much depends on the placement of the front over or near the area.
Marginal Small Craft Advisory conditions will be possible near the
Gulf Stream Wednesday across the Charleston nearshore waters and
offshore GA waters but probably more likely over the offshore waters
Area Forecast Discussion
National Weather Service Des Moines IA
635 PM CDT Tue Apr 14 2020
.DISCUSSION.../Tonight through Tuesday/
Issued at 300 PM CDT Tue Apr 14 2020
GOES-East clean IR imagery shows a deep and expansive trough
across much of the CONUS with northerly flow over the western US
that becomes from the southwest over the northeastern US. Some
cloud enhancement over the North Dakota - South Dakota border is
associated with a PV anomaly that has started to influence our
weather this afternoon and will do so tonight as well. The day
starting off with plenty of sunshine that allowed the surface to
warm relatively speaking. With cold air in the mid-levels
fostering steep low level lapse rates, shallow cumulus clouds
developed once again by mid to late morning. With these clouds and
saturation in the dendritic growth zone (DGZ), have seen spotty
snow showers similar to yesterday, though more so over northern
Iowa versus farther south over central Iowa. Over central and
southern Iowa, there has been more more subsidence keeping the
forecast dry there. Similar to yesterday as well as last
Thursday, these spotty snow showers can bring brief reductions in
visibility with Mason City dropping to 3 miles around 1pm. In
addition, these showers can bring down stronger wind gusts from
aloft with peak gusts in the 30 to 40 mph range so far this
The aforementioned PV anomaly will reach Iowa in the cyclonic flow
this evening with associated 1-3km QG convergence increasing over
the state. Soundings at LWD and OTM and cross sections through
southern Iowa maintain quite a bit of dry air in the lowest 1.5km or
so with saturation above this and lift within the DGZ. This should
allow for a few to several hour period of light snow. The HRRR and
RAP both maintain largely subsidence within the saturation while
the coarser grid models are showing more lift within the
saturation. Overall, message is that accumulations should be
south of Highway 34 and less than an inch.
As surface high pressure slides into the region from the northwest
on Wednesday, should have a break from the afternoon spotty snow
showers as soundings show less saturation and overall subsidence.
During this time, a more significant shortwave trough will begin
to dive down the backside embedded within the longwave trough over
the western US and move over the central Rockies by midday
Thursday. A baroclinic zone will set up south of the state with
isentropic lift increasing on the 295K surface. As saturation
deepens with broad scale lift maximized over far southern Iowa
into Missouri, will see precipitation spread over southern third
of the state up to around I-80 or so. Soundings at CSQ, LWD, and
OTM show much of the profile below freezing with the exception of
the lowest 500 to 1000 feet with the wet bulb zero temperature
near or slightly above freezing during the day. So precipitation
may waver from initiation to daytime to nighttime between rain and
snow. With precipitation expected over southern Iowa, have
continued the trend of lowering highs back into the upper 30s,
which may still be too warm in the end. Any accumulation during
the daylight hours would likely be confined to grassy or elevated
surfaces. Temperatures will lower below freezing in the evening
with temperatures and wet bulb temperatures around 30 degrees or
the upper 20s. This should allow for some accumulation, even
perhaps on roadways, before subsidence spreads into the state by
12z Friday. Total accumulations from Thursday to Friday morning
could be around an inch to two inches near the Missouri border
with a slightly higher band near or south of 136 Highway in
High pressure will pass south of the state Friday into this weekend
with dry conditions and milder air returning over the region this
weekend into perhaps early next week. This will bring the first
near normal temperatures in a week to most places in Iowa. There
could be another cool shot after Monday, though this should be
more short-lived rather than a week-long cool episode that we are
currently in if it comes to fruition. The GFS and CMC, supported
by a negative trending Arctic Oscillation, would support this
cool shot while the ECMWF would support highs above normal.
.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 635 PM CDT Tue Apr 14 2020
Light snow is expected across the southern third of Iowa late this
evening into the early morning hours. This will produce MVFR to
IFR ceilings and visibilities, mainly affecting KOTM tonight. This
system will quickly depart by daybreak on Wednesday with VFR
conditions returning to southern Iowa. Elsewhere, VFR conditions
are expected for the duration of the forecast with winds becoming
light overnight and then increasing from the northwest on
Wednesday as mixing deepens.
Area Forecast Discussion
National Weather Service Goodland KS
528 PM MDT Tue Apr 14 2020
.SHORT TERM...(This evening through Wednesday night)
Issued at 125 PM MDT Tue Apr 14 2020
Satellite imagery and 500mb RAP analysis showed weak northwesterly
flow over the High Plains today, with a trough over the Upper
Midwest. A layer of cumulus clouds developed across the region this
afternoon as northwest winds blew at 15 to 25 mph, with gusts around
35 mph. At 1:00 PM MT, temperatures ranged in the upper 30s to upper
Northwest flow continues aloft tonight as temperatures fall into the
low to mid 20s. Winds relax through the evening, becoming westerly
at 10 mph or less under partly to mostly cloudy skies.
A strong shortwave digs south into the central Rockies on Thursday,
with a surface low developing in eastern Colorado. Flow aloft
becomes zonal with winds around 10 mph or less at the surface,
mitigating fire weather concerns. Temperatures reach the mid 50s to
low 60s for highs.
Cloud cover increases as rain chances move into the region from the
northwest Wednesday evening, changing to light snow overnight as
temperatures fall into the 20s. Snow amounts of a half inch or less
will be possible for locations along and north of the Nebraska
border through sunrise. However, additional light snowfall is
anticipated Thursday and Thursday night.
.LONG TERM...(Thursday through Tuesday)
Issued at 222 PM MDT Tue Apr 14 2020
Winter weather and the potential for elevated fire weather
conditions are the main concerns in the extended forecast. A
surface low over Southwestern Kansas and Southeastern Colorado will
progress east Thursday morning across the lower half of Kansas. A
cold front will drop through the region from the north. Breezy
conditions are expected with northerly winds coming in behind the
front. High temperatures will range from the mid-30s in the
northwestern part of the CWA to the mid-40s in the southeastern part
of the CWA. Timing of the cold fropa will be key in determining
high temps. Looking at thermal profiles, this appears to be mainly
a rain/snow event.
Expected snow totals have shifted southward a bit with higher
amounts expected to extend along the I-70 corridor. This is due to
the expected placement of the front and where the best frontogenesis
lies. Relatively warm ground temperatures will aid in initial
melting of snow as it begins to fall, resulting in less overall
accumulations. Precipitation will continue through the overnight
hours and into early Friday morning. Overnight lows will dip into
Friday will be a warmer day with highs ranging from the mid-40s to
low 50s across the region. The region will come under southwest
flow aloft as a split in the overall flow pattern occurs. A weak
shortwave trough will move through the region Saturday evening,
however, conditions will remain dry.
Above normal temperatures are forecasted for Saturday through
Tuesday as a gradual warming trend brings us into the 70s by Tuesday
afternoon. Through this time, elevated fire weather conditions may
be possible. Relative humidity values will range from the mid-teens
to low 20s across the southwestern part of the CWA. Winds will not
be near criteria.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 525 PM MDT Tue Apr 14 2020
VFR conditions are expected throughout the TAF period at both KGLD
and KMCK. Winds will generally be from the northwest Tuesday
evening with gusts to 20-25 kts quieting down after sunset. Light
and more variable winds are expected overnight. Light westerly
winds will continue Wednesday morning through Wednesday evening.
Scattered clouds are expected at around 10 kft for most of the TAF
period. These clouds will begin to thicken and lower Wednesday
evening as precipitation chances increase into the overnight hours
Area Forecast Discussion
National Weather Service Grand Rapids MI
738 PM EDT Tue Apr 14 2020
Issued at 330 PM EDT Tue Apr 14 2020
- Cold tonight with snow showers
- Gradually warming this week but still cool
Issued at 609 PM EDT Tue Apr 14 2020
I have updated our forecast for this evening into the day on
Wednesday by expunging all mention of rain showers in favor of
snow showers since the wet bulb zero is on the ground through
Thursday morning. Also,I increasing the pop to likely this evening
and to a high chance overnight.
I have noted over the past 40+ years of forecasting that at this
time of year, just because you have high temperature of 40
degrees, if you have dew points in the teens or 20s (which it is
today and will likely be tomorrow), when a shower moves overhead,
it just snows. That is because the snow flakes cool to the wet
bulb temperature, which is below freezing so you do not get rain.
The showers overhead are convective and some will have briefly
moderate snowfall rates associated with them. Driving to work
around 330 pm this afternoon I drove through a snow shower with
1/2 mile visibilities. We just had a similar snow shower at the
office (not has heavy on ASOS ). The latest run of the RAP model
has equilibrium heights for convection this evening to 14000 ft,
with around 100 j/kg of cape. That is decent for snow showers
There is the snow showers this evening then there is a system
largely passing south of us Wednesday morning, but the snow
showers from that may get as far north as I-96 based on the latest
run of the RAP model and that also fits well with HREF 6 hour
probability of .01" forecast which is 60 to 70 pct between 8 am
and 2 pm near and south of I-96. So I increased the pop for
Wednesday to more so allow for the snow showers to get farther
north into our CWA Wednesday.
.DISCUSSION...(This evening through next Tuesday)
Issued at 330 PM EDT Tue Apr 14 2020
-- Cold tonight with snow showers --
The main concern is whether temperatures will reach the mid to
lower 20s in the growing belts, which may begin to damage to some
crops. Some models suggest the near-surface layer decouples
overnight and winds become nearly calm for a period, allowing for
radiational cooling. While below-freezing temperatures are likely,
an anomalously deep freeze for this point in the season does not
appear to be in the cards downwind of Lake Michigan. There is a
shortwave trough approaching with a slight amount of 850 mb cold
advection overnight which may support the maintenance of
stratocumulus and scattered snow showers overnight. Water
temperatures in the low 40s at the Port Sheldon and South Haven
buoys suggest continued mixing of the boundary layer overnight at
least near the lake, with lake-effect clouds possibly maintained
despite a dry air mass. Winds 10-15 mph are available at 1000 to
2000 feet to be mixed to the surface if decoupling does not occur.
Early this morning, quick moderate bursts of snow between
Grand Rapids and Big Rapids created slick spots and travel
slowdowns along US-131. It is possible to see a repeat of that
tonight, with no particular area completely safe from a light snow
-- Gradually warming this week but still cool
Ensembles are in good agreement of cold, freezing temperatures
again Wednesday night with an isolated snow flurry. Slightly
milder temperatures are expected Thursday through Saturday, with
solutions increasingly diverging thereafter. Southern Michigan
(Kalamazoo-Jackson and south) is at risk of accumulating snow on
Friday from isentropic lift, but the greater risk is down in
.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 739 PM EDT Tue Apr 14 2020
A weak cold front is moving toward southwest Lower Michigan this
evening. It has come convective instability associated with it.
We are seeing most unstable cape values near 100 j/kg with lapse
rates near 7c, which is impressive for snow showers actually. I
have seen some of our TAF sites, like LAN, which observed 1/2SM
SHSN at 2253z. That is typical for convective snow showers to have
the visibility go from P6SM to below 1SM in a short time only to
come back quickly to P6SM. Our radar continues to show convective
snow showers across Lake Michigan into western WI. The weak cold
front pushing these snow showers along should move on shore by
06z. That should end the snow showers for our TAF sites this
However, that is not all we are watching, there is a trailing
shortwave and surface low on the front that brings an isentropic
lift event into our southern CWA Wed morning. We could see
4 to 6 hours of light snow for the I-94 TAF sites (IFR conditions)
from say 09z to 15z (give or take a few hours). Once that moves
through all of the CWA and all TAF sites should clear as much
drier mid level air moves in.
The bottom line is mostly VFR but brief periods of IFR are
possible till 06z at most of our TAF sites. It should mostly be
VFR between 06z and 09z. Then the I-94 TAF sites could see IFR in
snow from 09z till 15z. All sites should be solid VFR by 18z and
winds will be lighter than we have seen in the past few days.
Issued at 330 PM EDT Tue Apr 14 2020
Waves 4 to 5 feet were observed at the Port Sheldon buoy during
the 2 PM hour, but the trend in winds and waves will be downward
this evening. Still, it will be choppy, with 2 to 4 foot waves
expected tonight. The next chance of conditions hazardous to small
craft will be Thursday morning.
AREA FORECAST DISCUSSION
National Weather Service Jackson KY
1129 PM EDT Tue Apr 14 2020
Issued at 1113 PM EDT TUE APR 14 2020
Turning into a bit of a tricky forecast for the overnight. Snow
has moved out, but the moisture left behind, along with light
winds and cooling temps, has led to some fog across portions of
eastern Kentucky...including here at the office. However, the high
clouds are continuing to move out, and the center of a high
pressure system is now parked over central Kentucky. With the
high already built in, we may not be advecting much more of the
dry air into the eastern Kentucky. As a result, the expectation
now is that fog may first develop across portions of the far SE
where snow impacted the latest (basically JKL SEward) and
therefor haven`t had a chance to dry out, and as temperatures
continue to cool below freezing, this fog will transition to a
frost instead. Meanwhile, observed temps at 10pm were considerably
lower than forecast thanks to the cooling impact of the snow,
with some sites already at or close to the forecasted nightly
lows. With really no model guidance having a handle on this,
manipulated lows and the overnight diurnal curve by hand. That
being said, though the trend is in the right direction considering
the pattern in place and the decoupling that is likely to happen,
there may end up needing to be some more updates throughout the
night as more observations come in, especially in the deeper
UPDATE Issued at 615 PM EDT TUE APR 14 2020
A pretty potent band of snow has set up and is moving SE. Despite
moving into 40 degree air, the colder air aloft has been able to
overcome, and mostly snow is being seen along with quickly falling
temps. Tried to better show the current status of this snow band
location in the pop/weather grids, and transition that band to the
SE over the next few hours. Also increased snow amounts in some
locations, especially the higher terrain, where between a tenth
and a half an inch of snow cannot be ruled out. May have snow
lingering a bit too long in the far SE as we head into the
overnight, so will continue to monitor and update here as needed
over the next couple hours. The good news is that we are still
warm enough on the ground that after the heaviest band of snow
moves out, much if not all of the snow should begin to melt off
throughout the rest of the evening. In addition to these changes,
also updated the near term forecast for temps and winds based on
the current observations. As noted, temps are quickly dropping
along the band of snow, but may recover a bit on the backside
after the band moves out, before the sun sets. This too will help
to allow any snow accumulations to melt.
.SHORT TERM...(This evening through Wednesday night)
Issued at 405 PM EDT TUE APR 14 2020
19z sfc analysis shows high pressure edging into the state from
the west while cyclonic flow remains in place over the east.
An active pattern aloft is pushing an impulse through the area
this afternoon. As a result, plenty of clouds are found over the
state along with a few bands of light pcpn. With such cold
temperatures aloft some of this pcpn is falling as light snow over
our northwest fetches. The snow is capable of making to the sfc
even though temperatures are in the upper 30s and lower 40s north
but in the low to mid 40s southeast. Meanwhile, with northwest
winds of 5 to 10 mph dewpoints varied from the mid 20s north to
the mid and upper 30s in the southeast.
The models are in decent agreement aloft through the short term
portion of the forecast. They all depict a very deep trough
through the Great Lakes and into the Ohio Valley with bands of
energy rotating through its base. The first of these washes over
eastern Kentucky this evening and early overnight with even a drop
in heights. Another heads this way later Wednesday, though the
trough will be relaxing by that time so that heights actually
start to rebound by dawn, though northwest flow will continue.
Given the limited model spread with these features have favored
the NBM as a starting point for the grids with some adjustment
towards the HRRR and NAM12 on details.
Sensible weather will see spring`s bite tonight with an evening
of some flurries giving way to clearing skies and falling
temperatures. As a result, freezing temperatures are expected
nearly everywhere by dawn along with widespread frost.
Accordingly, a Freeze Warning is in effect for eastern Kentucky
into Wednesday morning. Temperatures will see only a limited
rebound on Wednesday, but still nearly 10 degrees warmer than
afternoon temps today. Sky cover will be more variable through the
short term making forecasting these temperatures a bit of a
challenge given uncertain solar radiation during the day and
likewise the black body night time radiation. However, it does
look cold enough for some pockets of near freezing temperatures by
Thursday morning and areas of frost - albeit somewhat dependent
on the cloud cover. The main question will be if that next batch
of upper energy will be enough for some showers for our northern
counties Wednesday evening. For now, have allowed a small chance
generally north of the Mountain Parkway as a secondary cold front
drops into the state.
Did not make much in the way of adjustments to temperatures from
the NBM through the period given the uncertainty with cloud cover
interfering with a potential ridge to valley split night
Wednesday night into Thursday morning. As for PoPs, ended up on
the high side of the NBM numbers this evening and again later
Wednesday into that night with a bit of a lean on the more `wet`
.LONG TERM...(Thursday through Tuesday)
Issued at 300 PM EDT TUE APR 14 2020
A fairly active weather pattern is on tap for the extended. A
series of weather systems will bring repeated chances of rain to
eastern Kentucky from Thursday night through Monday. Only light
rain is expected at this time across the area. The period will
start off a bit cold, with widespread frost expected across the
area early Thursday morning. After that, warmer temperatures will
lead to periods of rain and cloudy skies. The best chance for
rain will likely be Friday and Friday night, as a slow moving
frontal boundary moves through the region. Another good shot of
rain will be possible Saturday night through Sunday, as a second
front moves through the area. This second round of rain should end
by the end of the day on Monday, giving way to clearing skies and
dry conditions Monday night. Temperatures should generally be
warm, with daily highs in the 50s and 60s and nightly lows mainly
in the 40s expected.
.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
ISSUED AT 1129 PM EDT TUE APR 14 2020
Update to previous discussion: As snow moved through and then
exited, temperatures cooled quite quickly. This has coupled with
lingering moisture and KSJS and KJKL and points SE, which were the
hardest hit sites by the snow, to create a fog deck. Meanwhile,
high pressure has built in overhead, with much much drier air
located across the central portion of the state. While a large
advection of dry air into the east is not expected, just a little
would be enough to break this fog apart and clear the TAF
sites...which is what the expectation is at this point. However,
climatology is also working against us. Usually with clearing
skies and light winds, once fog is in place, we tend to keep said
fog. Another added factor is the fact that temps are falling below
freezing, and it is also a strong possibility that fog could
transition to frost across SE Kentucky. As a result, currently
have a forecast that has both KSJS and KJKL clearing out by
5Z...either by drier air, or by transition to frost. But
ultimately this is going to have to be a monitor and update if
needed situation based on how conditions actually play out
through the overnight.
A band of decent snow developed across eastern Kentucky late this
afternoon and is moving SE and now out of the state at 0Z. This
may continue to affect KSJS during the first hour of the TAF
period, but conditions are improving. For locations across SE KY
within the band, VIS could easily drop to below 1SM and CIGS could
drop to LIFR or less. Meanwhile, for the rest of the TAF sites,
the band has already cleared the sites and VFR conditions are back
in place. The exception is KJKL who is taking a little longer to
lift out of IFR CIGS after the snow went through...but should be
VFR by 1Z. VFR conditions, including clearing skies and light
winds, are then on tap for the remainder of the evening and
overnight. A few clouds may move back in from the north during the
day Monday, but all precip should remain north of the TAF sites.
Predominate winds under 10kts will be out of the WSW by the
afternoon Monday, but gusts are forecast between 15 and 20 kts.
Freeze Warning until 10 AM EDT Wednesday for KYZ044-050>052-
Freeze Warning from 3 AM to 10 AM EDT Wednesday for KYZ085>088-
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
930 PM CDT Tue Apr 14 2020
930 PM CDT
No major changes in thinking on the period of accumulating snow
overnight into Wednesday morning. The main updates were to
increase PoPs and snow amounts slightly with northward extent and
expand the expected swath of 1-2", locally higher, to portions of
our northwest Indiana counties. With temperatures falling to a few
to several degrees below freezing and likelihood that roadways are
sans residual treatments from the winter, some slippery roadways
appear to be a decent bet. With that in mind, opted to issue an
SPS from Lee County east-northeastward to all of Cook County and
Latest water vapor imagery indicates a well-defined short-wave
entering northwest Iowa. In response, radar mosaic indicates a
blossoming area of light to moderate snow across central Iowa,
extending to a bit north of the Highway 30 corridor. This would
seem to favor a northward shift of the initial snow band from the
developing f-gen circulation, in line with recent RAP/HRRR runs
and the 18z ECMWF. A fairly narrow snow band should overspread
northern Illinois I-80 and north after midnight. The best
mesoscale forcing in the band will then focusing near and a bit
south of the I-80 corridor as the whole band/area of snow
gradually drops southeastward. While the air-mass is quite dry,
the magnitude of the forcing could support localized amounts
potentially in the 2-3" range. The snow will end by mid-day in
east-central Illinois and parts of northwest Indiana, possibly
mixing with rain before ending.
The updates to the forecast inched the 1" line up to the south
side of Chicago, with amounts around a half inch perhaps as far
north as the far north side of the city. Pavement temperatures in
the city according to Chicago snow command were in the upper 30s
to mid 40s as of 9pm with air temps still 36-37F, so that may
help mitigate road impacts in the city. The swath where amounts
in the 1-2" are favored is bounded roughly on the north by a
LaSalle-Peru to Joliet to Gary line on the north and a Chenoa to
Kankakee to Kouts Indiana line on the south. Within this swath,
the aforementioned locally higher amounts are possible. The snow
that falls should quickly and fully melt by 10-11am thanks to
temperatures warming above freezing and the strong mid April sun.
Scattered snow and maybe graupel showers will be possible near
Lake Michigan during the afternoon, but no accumulation with temps
in upper 30s to lower 40s.
252 PM CDT
Through Wednesday Night...
Mother nature is evidently neither satisfied with the winter
season, nor paying attention to the date on the calendar, and
looks set to deliver a few more chances for snow to the area
through the end of the week.
For the remainder of the afternoon it`s really what you see is
what you get as convective snow (occasionally mixing with graupel)
showers continue mainly near and north of I-80 within the core of
very cold temperatures aloft with lighter showers farther to the
south. In fact, the morning DVN RAOB sampled a 700 mb temperature
of about -21C which is squarely at record levels for this time of
year. Observations and webcams have confirmed that the heaviest
showers have been dropping visibilities to around or just under 1
mile for a few minutes and see no reason that this won`t continue
for a few more hours before we lose peak heating. No accumulations
are expected but reduced visibilities and gusty winds to 40 mph
will be possible under the heavier showers this afternoon.
The next potential for wintry precipitation (likely all
snow) looks to arrive late tonight and may linger through the
morning hours on Wednesday with the arrival of a pair of
additional mid-level perturbations. These features presently show
up in moisture channel loops dropping out of the Dakotas, with a
second shortwave emerging across the Central Great Plains and
scooting east into Nebraska and Kansas. The latest suite of model
guidance supports a coating of snow for locales as far north as
I-88, but really moreso towards I-80 and points south where a very
narrow corridor of 1-2" amounts is appearing plausible. There is
still some amount of uncertainty regarding the exact placement of
any `heftier` snowfall totals as is typical with these types of
systems and given that there will be at least some modest degree
of interaction occurring between these aforementioned shortwaves
/PV-anomalies. That said, we are noting a nice degree of run-to-
run consistency in the ECMWF which has and continues to show a
localized max in QPF immediately near south of I-80 and across
parts of the Kankakee River Valley with the rest of the model
suite seemingly converging on this scenario as well.
From a synoptic/large scale forcing perspective, things look
pretty respectable upstairs with an assist from mass divergence
under the northwest extent along the cyclonic shear side of a
strengthening 150 kt jet streak across the Ohio River Valley along
with incoming DCVA from the above-mentioned shortwave. A
relatively shallow f-gen circulation is forecast to develop on
recent RAP cross sections across the sharpening baroclinic zone
which does look to result in at least modest omega into and
through the dendritic growth zone late tonight and into early
Wednesday morning. Some guidance is very close to developing
actual upright convective instability in a small corridor south of
I-80 and near I-55/57 during this period, with an attendant
notable reduction in saturated EPV* (values near -1 and lower in
places which is actually rather robust) at the top of the shallow
f-gen circulation. The ceiling on snowfall amounts will likely be
kept in check by the rather dry airmass in place with PWATs
unlikely to get much above one quarter inch, but it`s not too
surprising to see even coarse-resolution guidance developing small
pockets of 0.1-0.2" of liquid QPF given everything discussed.
snow ratios look to favor something like a 10-13:1 with this
activity With this in mind, have gently nudged snowfall amounts up
near and south of I-80 and in towards the Kankakee River Valley
late tonight through Wednesday morning. Suppose that a very
isolated total up to 3" in this vicinity can`t entirely be ruled
out, especially given the late time of night and favorable cooler
While some lingering snow will be possible in our far southeast
through about noon on Wednesday, things should quickly clear out
as the initiating shortwave/jet streak push east of the region.
Guidance then once again develops a deeply-mixed PBL up to near 10
kft through the afternoon hours with very cold temperatures
remaining in place aloft. Not seeing quite as much forcing
upstairs to get things going like today with just general cyclonic
speed shear overhead, but a developing lake breeze may provide
enough surface convergence to squeeze out some additional
snow/graupel showers with heating during the afternoon, mainly in
the vicinity of the I-90 corridor counties. Wouldn`t expect any
accumulation from this next bout of activity.
320 PM CDT
Thursday through Tuesday...
Things look pretty tranquil all things considered through the day
on Thursday with temperature rebounding into the mid and possibly
even upper 40s.
We will be quickly turning our attention off to the south and west
by Thursday evening as the next robust jet streak begins to
develop across the Southern Great Plains which should begin to
facilitate at least some degree of low-level cyclogenesis into
Friday morning. Robust isentropic upglide/WAA really looks to get
cranking more notably Thursday night and through Friday morning
and with the greatest magnitudes generally off to the south of
I-80, at least based on today`s multi-model consensus. Stout upper
level divergence and the attendant thermally direction portion of
the ageostrophic jet circulation looks to result in a low-level
mass response that should encourage an increasingly robust f-gen
circulation. This should encourage a SE-NE oriented band of
developing moderate precipitation, with it looking increasingly
likely to set up across parts of central Illinois and gradually
shifting northward with time into Friday morning. The northernmost
terminus of precipitation still remains in question, but guidance
does now seem to be honing in on I-88 or the Illinois/Wisconsin
state line. Any potential for heavier/steadier precipitation
rates now may maximize across our I-80 and south counties with
forecast QPF amounts supporting the potential for several inches
of accumulating snowfall before things taper off/mix with and
change to rain through Friday afternoon. The good news is that
with the high sun angle, any snow that does fall should melt
readily through afternoon and into Saturday.
Temps will rebound heading into the weekend, but do look to remain
near and just below normal for mid-April, although there is a
potential for temperatures to overperform a bit on Saturday and
have nudged highs just a wee bit above the blended guidance. At
this time, conditions look dry from Friday night through Saturday
as mid-level and surface ridging quickly crosses the region.
Longwave troughing will re-establish over Hudson Bay later this
weekend. An embedded trough axis and associated cold front
swinging across the Great Lakes region late Saturday night and
Sunday may bring with it chances for showers.
Looking farther ahead, active split flow looks to continue which
should keep a somewhat unsettled weather pattern going here into
the middle and end of next week.
For the 00Z TAFs...
Aviation forecast concerns:
* Snow showers ending and winds diminishing early this evening.
* Potential for a period of light snow early Wednesday morning,
and additional scattered snow showers Wednesday afternoon.
* Weak lake breeze Wednesday afternoon expect to affect KGYY.
Lowering sun angle and loss of diurnal "heating" will allow
scattered snow showers to dissipate early this evening, and gusty
west winds to diminish. VFR ceilings should also scatter out with
the loss of low-level instability. Attention then turns quickly to
the west, where a mid-level disturbance was evident in satellite
imagery across the KFSD region. This wave is expected to track
eastward tonight, with a band of light snow developing from
southern IA into northern IL after midnight. The primary axis of
snowfall with this is expected to be across the I-80 corridor and
just south, but with light snow extending as far north as the I-88
corridor across northern IL including KORD/KMDW roughly in the
08-12Z time frame. Visibility should be lower (potential IFR) at
KGYY, and somewhat better (mainly MVFR) farther north toward
KORD. KRFD may briefly get clipped after 07Z or so, but it looks
like it will mainly be south of there. Snow should end early
Wednesday morning, with VFR conditions thereafter.
Deep mixing is expected to develop with diurnal warming again
Wednesday afternoon, with scattered snow showers developing due to
deep surface-based lapse rates beneath cold air aloft. Upper level
support is a little weaker than today, so coverage and visibility
impacts are expected to be less significant than today. The deep
mixed layer should also support breezy west winds once again,
though weaker than today. Various model guidance does indicate a
lake breeze developing into KGYY with northeast winds in the
afternoon, but not pushing inland into northeast IL as far as
KORD and KMDW. Any scattered snow showers should again dissipate
by sunset Wednesday, with winds also diminishing.
Visit us at weather.gov/chicago
Follow us on Facebook, Twitter, and YouTube at:
AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
930 PM EDT Tue Apr 14 2020
A cold front will move southeast through the region overnight,
bringing a chance of showers along with colder temperatures. Chilly
high pressure will then build across the region from the Midwest
Wednesday and Thursday, as the front pushes well to our south. The
front will retreat back northward into the Carolinas over the
weekend, bringing a chance of rain as low pressure tracks eastward
along the front.
.NEAR TERM /TONIGHT/...
As of 930 PM Tuesday...
Still on track for a light precip event overnight into early Wed
morning, focused on the VA border areas and NE CWA. The latest
surface analysis shows the frontal zone having pushed northwestward
through eastern and southern sections of central NC since lunchtime,
with a surface low now just WSW of CLT tracking slowly along the
front to the NE. But the advancement of chilly/dense high pressure
through the Mid Miss Valley across the Ohio Valley/KY into WV is
tightening up the frontal zone to our NW and pushing it
southeastward into W NC/SW VA, which has helped stall the NW push of
the coastal front. Dewpoints have fallen at places like Blacksburg
and Galax in VA and Boone and Asheville in NC, with a slight
increase in speed and shift of winds to NW as the MSLP gradient has
tightened in this region. The 00z GSO sounding shows fairly steep
lapse rates (fueling a few electrical pulses within the precip band
now NW of INT) and depicts today`s good heating and mixing, but the
moisture is fairly shallow (5000-8500 ft deep) with high cloud bases
and a fairly dry subcloud layer (surface dewpoint depression over
15F) that will be tough to overcome, suggesting small precip
amounts. But with the approach of the front from the NW combined
with the now-stationary frontal zone across S and E NC and ensuing
increasing moist upglide, we should still see showers break out over
the area, focused on areas near the VA border and in NE NC down into
the central Coastal Plain overnight. Again, though, amounts will be
limited by the relatively dry low levels, and of the CAMs, the 00z
HRRR and 12z high-res WRF-ARW (which are doing the best currently)
show well this more spotty coverage. Have taken pops down just
slightly (by 5-10%) as it looks like our SW sections could stay
totally dry, but this retains the higher pops across the far N and
NE. Temps remain tricky with strengthening CAA overnight as the cold
front drops SE through the area, bringing increasing and gusty NW
winds drawn in by the departure of the surface low as it moves NE
through eastern NC. Have made minor adjustments but stayed close to
around 40 NW ranging to the upper 40s in the SE. -GIH
Early afternoon satellite imagery and surface analysis reveals the
presence of an elongated longwave trough over the lower OH valley,
which is bringing light precip to the western Appalachian mtns as of
18Z. Meanwhile across NC, the boundary that moved through the area
overnight and brought drier air into the area has started its
retreat northward as a warm front. Widespread dewpoints in the 30s
and 40s have since been replaced by upper 40s and lower 50s although
some degree of drier air has remained in place across the Triad thus
far. Similarly, temperatures have warmed into the mid 70s across the
Sandhills behind the front. Cooler temps remain in place along the
NC/VA border where WAA has been weak.
Two focus areas for the rest of the evening/overnight hours. The
front to the west will move across the Appalachians tonight,
meanwhile a weak coastal low will develop off the SC coast. Weak
ascent associated with both of these disturbances should be enough
for light showers to develop across the entire area late this
evening/overnight. Thunder chances are limited and probably too low
to include in the forecast (MLCAPES only around 100-200 J/KG) but
would be confined to the Sandhills/areas east of I-90 if it happens.
Rainfall amounts should be on the light side with nearly all flavors
of deterministic and probabilistic guidance suggesting 0.10-0.20
inches at most.
Despite the cloud cover and precip in the area, temps will drop
quite a but tonight as modest post-frontal cold advection should
commence shortly after 06Z. Lows in the low to mid 40s is the
consensus of all the better performing guidance. Winds could also be
breezy at FROPA with BL mixing supported all night long and would
not be surprised to see 10-15 mph winds through the pre-dawn hours.
.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 150 PM Tuesday...
Skies will clear out on Wednesday as surface high pressure builds in
from the north. Any lingering precip in the morning hours should
quickly taper off before noon. It will be considerably cooler
Wednesday into Wednesday night, best performing guidance is
suggesting highs in the low to mid 50s. Lows Wednesday night could
be problematic despite guidance values in the upper 30s/lower 40s.
Idealized scenario of clear skies/light winds could result in patchy
areas of frost. May need to go with a Frost Advisory Wednesday night
once we can pin down the coldest areas.
.LONG TERM /THURSDAY THROUGH TUESDAY/...
As of 256 PM Tuesday...
A +1025 mb surface high centered over the lower Ohio Valley will
build east across the southern Mid-Atlantic states through Thursday
night, before shifting offshore on Friday. This high pressure will
result in a continuation of seasonably cool, below-normal temps
through Thursday night, with some patchy frost possible across the
norther Piedmont counties Friday morning.
Weak southerly return flow will allow temps to moderate to near
normal to end the work week.
A shortwave trough ejecting east from the Central Plains through the
Ohio Valley on Friday will reach the Mid-Atlantic region late Friday
night and Saturday. This system will drag a cold front into the area
Friday night with the front forecast to slowly push south through
the area on Saturday. Showers are expected with the the front,
although convective coverage and QPF amounts are in question due to
model differences with the strength of the upper trough.
This front is forecast to briefly stall just south of the area late
Saturday, before returning north as a warm front on Sunday.
CAD conditions are likely to develop over the NC Piedmont as the
arrival of shortwave impulses embedded within the low-amplitude,
zonal flow aloft will lead to overrunning lift and precip Sunday and
Sunday night. Additionally, we will need to closely monitor the
threat for some stronger convection and destabilization across
eastern/southern portions of the area, given that a decent amount of
the NWP guidance indicates some weak low pressure wave development
along the warm front(s).
Drier, more tranquil conditions are expected to return early next
.AVIATION /00z WEDNESDAY THROUGH SUNDAY/...
As of 915 PM Tuesday...
VFR conditions currently persist across the entire area, with just
some scattered mid-level clouds around 5-7 kft. A cold front
currently just west of the Triad will make its way east across
central NC over the next several hours. At the same time, a weak low
pressure system currently over South Carolina will move east off the
Southeast US coast. These two features will result in some light
showers across parts of the area late tonight through tomorrow
morning. The best chance for this is at the eastern TAF sites
(RDU/FAY/RWI), closer to the surface low and where forecast
soundings indicate a deeper moisture layer.
In addition, as the front moves through the area, winds will shift
to a northerly direction and become gusty, reaching 10-20 kts.
Clouds will also begin to thicken. At this time keep only low VFR
ceilings at INT/GSO as upstream sites are generally staying VFR, and
the moisture layer is forecast to remain shallow. Farther east at
the remaining TAF sites, ceilings should drop to MVFR after
midnight, with a slight chance for IFR ceilings at FAY/RWI, but
confidence of the latter is low so have kept it out of the TAFs for
now. By late morning, showers will move out of the area and ceilings
will improve to VFR. Drying behind the front should allow for clear
skies by the afternoon.
Looking beyond 00z Thursday: VFR conditions will continue across the
region for Thursday and Friday as high pressure builds in. Then
forecast confidence becomes lower as an unsettled pattern returns.
An upper trough and cold front will move through the area Friday
night into Saturday, bringing more showers and sub-VFR conditions.
Additional disturbances could bring sub-VFR conditions to the area
on Sunday and Sunday night as well.