Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/23/20

Area Forecast Discussion

National Weather Service Gaylord MI

 940 PM EDT Wed Apr 22 2020

.UPDATE...
Issued at 940 PM EDT Wed Apr 22 2020

A 1002mb surface low is in n central IA, with a warm front
extending ese across northern IL and central IN. Multiple mid-
level-forced f-gen bands are evident on regional radars this
evening to the north of this system and front, across northern
WI/upper MI/central and northern lower MI. Our low levels are
on the dry side, with most surface dew points in the teens, and
are dryer as you head further north. 00Z APX sounding was
saturated as low as 3700ft or so, which is oddly plenty lower than
cloud bases (which were about 6k ft at launch). Perhaps the
balloon encountered some virga? Regardless, there was still plenty
of dry air below 835mb or so.

So a lot of the echoes out there are virga. This is especially
the case for the northernmost band, from ESC to near CVX. The
southern one, from Leelanau Co to Grayling and Tawas, could be
producing some spotty snowflakes, especially near and w of TVC.
This could be the case for another several hours, but this
activity is fizzling out over far northern WI. So do expect this
particular f-gen band to diminish overnight.

More widespread precip is further south, closer to the surface low
and warm front. Hi-res progs do develop another area of precip
over central lower MI, close to or just after midnight. Southern
Gladwin Co seems the most likely spot in the CWA to get precip
overnight, but the most recent HRRR squeezes out a touch of QPF
almost as far north as Grayling by 12Z/8am. P-type will be
tricky, as an above-freezing warm nose centered at 850mb will be
building in from the south very late tonight. It will be
accompanied by slower warm advection at the surface, and overall
surface temps won`t change too much from current values. But given
evap cooling at low levels as precip develops, there is some
potential for freezing precip. This would be mainly on elevated
surfaces, as soil temps are above freezing.

&&

.NEAR TERM...(Through Thursday)
Issued at 323 PM EDT Wed Apr 22 2020

...Scattered Rain and Snow Showers Possible South...

High Impact Weather Potential...Minimal

Synopsis: The subtle mid-level trough crossing northern Wisconsin
this afternoon will continue southeast across central Michigan this
evening. At the same time the weak surface low pressure continues
its journey into Iowa early this evening, before being absorbed by a
stronger low treking through southern MO. A remnant stationary front
will reside through the northern Ohio Valley through the night, with
any midlevel fgen sagging just to our south. This keeps the majority
of any heavier precipitation to our south. However we`ll still end
up with light rain/snow mix this evening as the midlevel theta-E
gradient pivots over our southern counties, allowing precip chances
to remain overnight. Heading into Thursday, believe the bulk of
precip still remains south, but we still may see additional light
snow/rain showers along and south of M-72.

Forecast Concerns: With a warm nose inching into our southern
sections there is a slight chance of freezing rain mixing in through
the higher terrain near Cadillac. Guidance is showing the warm nose
depth of over 3 kft with a max temp of nearly 5 C. This will be
sufficient to melt any snowflakes. However with light precip
intensity, surface temperatures hovering right around freezing, and
soil temps just above freezing, expect impacts to be minimal. Still
something to keep an eye on though.

Winds/Temperatures: Our light and variable winds will gain a more
uniform easterly component this evening in response to the
surface low. They remain easterly and become a little breezy (with
gusts mainly into the upper teens) as the gradient tightens
across the area late tonight into Thursday. Overnight lows will be
coldest in the UP where a little less cloud cover exists. South
of the bridge we`ll remain a couple degrees on either side of 30
(warmest along the coasts). Think temperatures will be similar to
today`s...even with slightly more uniform cloud cover, with highs
around 40.

&&

.SHORT TERM...(Thursday night through Saturday)
Issued at 323 PM EDT Wed Apr 22 2020

...Dry? for Most of the Area, Yes...

High Impact Weather Potential...Minimal

Pattern Synopsis/Forecast and possible outcomes...Weak high pressure
takes over the region and at least at first glance, keeps things dry
through 12z/Sat. There are a few members within the ECMWF
ensemble/SREF that shows some precipitation is possible, but with the
going forecast as dry and the deterministic run of ECMWF dry and the
GFS ensemble (and the majority of the ECMWF and SREF for that
matter) dry will continue the dry forecast. The reason why I
describe it as weak, is that the main sfc low runs along the Ohio
River on both the GFS and ECMWF. However, the 500 mb lows for both
models are in different places, and allows the precipitation to
approach M-55 and produce some slight chance pops along and south of
M-72 from 12z/Sat to 12z/Sun. So more than likely, it will remain
dry from M-55 north, but there could be an isolated shower.

.LONG TERM...(Saturday night through Wednesday)
Issued at 323 PM EDT Wed Apr 22 2020

High Impact Weather Potential...Minimal

As mentioned above, there may be some showers south of M-72
during the night, but more than likely, it will be dry for the
majority of the forecast area. It looks like it dry for Sunday, as
high pressure between systems builds into the region. There could
be some showers hanging on Sunday morning, but the majority of
the day should turn out dry, and that is expected to remain
through the night. Monday, There is a difference in timing with
the next system, as the ECMWF has NW flow that brings showers into
the region by the afternoon. The GFS has a shortwave ridge that
slows the clipper type system from getting into the forecast area,
until Monday night. This timing difference lasts into Tuesday, as
GFS has a much deeper 500 mb trough that kind of dry slots into
Tuesday evening, before sinking south and the rain showers move
into the forecast area. The ECMWF has a High over Low shortwave
block that keeps all of the showers south of the lower peninsula
through Wednesday morning. Wednesday looks dry as the GFS has us
between systems, with the next system dropping in Wednesday night.
The ECMWF puts us into a drying pattern through Thursday morning.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 726 PM EDT Wed Apr 22 2020

MVFR cigs arrive in MBL late tonight, and TVC Thu afternoon.

Low pressure is in northern IA, with a warm front extending se
into northern IL and central IN. Spotty mixed precip will continue
north of this front, perhaps impacting TVC/MBL at times tonight.
More substantially, cigs will gradually lower over central lower
MI. MVFR cigs will arrive at MBL very late tonight, and reach TVC
Thu afternoon. Otherwise VFR conditions.

Easterly breezes will increase into Thursday.


&&

.MARINE...
Issued at 323 PM EDT Wed Apr 22 2020

As surface high pressure moves off to our east, we gain an easterly
component to winds tonight. There`s a slight chance of light rain
and snow showers tonight through Thursday, especially the further
south one goes. Some advisory level winds out of the east are
possible starting Thursday morning, mainly across the northern
portions of the Lake Huron nearshore waters and the Straits.


&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...SMALL CRAFT ADVISORY from 8 AM to 5 PM EDT Thursday for
     LHZ345>348.
LM...NONE.
LS...NONE.
&&

$$

UPDATE...JZ
NEAR TERM...STJ
SHORT TERM...JL
LONG TERM...JL
AVIATION...JZ
MARINE...STJ



Area Forecast Discussion

National Weather Service La Crosse WI

 1035 PM CDT Wed Apr 22 2020

.SHORT TERM...(This evening through Thursday)
Issued at 251 PM CDT Wed Apr 22 2020

When a strong warm front lifts only about halfway through your
forecast area in late April, you know it`s going to be a fun
temperature forecast. And this warm front did not disappoint with
currently more than a 30 degree temperature spread between Medford,
WI (47F) and Charles City, IA (79F). Guidance has been pretty much
right on the money with the warm front losing its northward momentum
once it lifted into southeast MN. It currently stretches from
roughly Zumbrota, MN to Muscoda, WI with south to southwest flow on
the southern side and east to southeast flow to the north. Moisture
transport south of the front has remained rather weak, as dewpoints
are struggling to rise beyond the mid 40s across northeast IA and
far southwest WI. This is lower than the 50+ dewpoints models
originally suggested for today, so there hasn`t been as much
instability thus far as was anticipated earlier.

Through the rest of this afternoon, the warm front will slowly be
pulled southward again as the surface low (currently sitting on the
MN/IA border) drifts ever so slowly to the southeast. A strong band
of 1000-925mb frontogenesis along the front will continue to favor
development of eastward propagating showers and storms along the
front, across mainly northeast Iowa into far southwest WI. Similar
to Monday`s setup for gusty winds from the showers and storms,
today`s low levels are again exhibiting an inverted-V sounding
profile due to the drier air in place. Resultant evaporative cooling
will help to further amplify the mixing down of stronger winds aloft
with any passing showers and storms. KMCW reported a 47 mph gust
just prior to 2 PM, likely tied to the developing showers there. A
tongue of 800-900 J/kg DCAPE extends from north-central IA into a
portion of NE IA. MLCAPE profiles are not all that impressive with
only 500-1000 J/kg to work with, so any hail that develops should be
small and sub-severe. Latest CAMs keep the bulk of activity this
afternoon into early evening south of the MN border and generally
south of Vernon County in WI, with the focus gradually shifting
eastward through this evening.

Heading into tonight the main forecast concern will be increasing
low clouds developing over eastern WI, advecting into our area
overnight courtesy of easterly flow. This combined with a very stout
inversion aloft will result in mostly cloudy or overcast skies for
the area through midday Thursday before clouds begin to slowly
erode. Some guidance wants to develop some light rain across eastern
portions of the forecast area on Thursday, but forcing looks pretty
weak and moisture very shallow. Could see potential for some
drizzle, but for now have kept forecast dry through the morning. The
HRRR and RAP do try to pop some diurnal showers across
southwest/central WI in the afternoon. Lows tonight will range from
30s north of I-94 to 40s elsewhere. Highs Thursday generally in the
upper 40s and 50s, perhaps a few 60s in our far south and west.

.LONG TERM...(Thursday night through Wednesday)
Issued at 251 PM CDT Wed Apr 22 2020

Shortwave energy pushes into the area Friday into Friday night,
bringing a chance for rain. With cloudy conditions Friday, highs
look to stick to the 50s for most. For Saturday, low pressure spins
up to our south in the vicinity of southern Illinois courtesy of a
shortwave ejecting northeast out of the southern plains. There is
some question as to the extent of interaction between this southern
feature and our departing northern shortwave, and a few models try
to paint some light QPF back across our south, so we will have to
watch for perhaps some light rain.

Active northwest flow aloft continues Sunday into early next week,
with models dropping a subtle shortwave somewhere in the region from
the northwest Sunday. Precipitation amounts, if any, look fairly
light at this time. Greater chances for precipitation come later
Monday through Wednesday, as better moisture works into the area and
one or more shortwaves and associated surface features move through.
Timing/placement differences remain, so broad low PoPs from the NBM
blend were retained. Temperatures look to remain near or slightly
below normal, with highs in the 50s and 60s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1035 PM CDT Wed Apr 22 2020

VFR conditions continue for the moment at RST and LSE, but lower
stratus is beginning to blossom across central and southwest
Wisconsin, expected to spread westward overnight. Confidence has
increased that LSE will see an extended period of MVFR ceilings
developing overnight and likely continuing through much of
Thursday, though with some breaks possible at times Thursday
afternoon. Meanwhile, a much tougher call at RST as there are
questions about just how far west stratus will develop. For the
moment, will maintain a period of IFR conditions late tonight into
Thursday morning but with the latest trends suggesting any lower
stratus may erode quicker at that site (and much of southeast MN).
All in all, still a tricky forecast but winds do remain steady-
state from the east to northeast, generally 5-15 knots the next 24
hours.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...Kurz
LONG TERM...Lee
AVIATION...Lawrence



Area Forecast Discussion

National Weather Service Huntsville AL

 1000 PM CDT Wed Apr 22 2020

.NEAR TERM...(Rest of tonight)
Issued at 1000 PM CDT Wed Apr 22 2020

After further analysis, a distinct pressure fall/rise couple
continues to be progged by the NAM/HRRR overnight. In western and
central MS, there has been a rather constant south-southeast flow
with gusts earlier over 40kt. These have declined somewhat, but with
the increasing divergence aloft and increasing southwesterly LLJ,
expect these pressure falls to develop soon and lift northeast across
the area. MOS guidance is also suggestive of gusts of 25-30+ as well
late tonight and early Thursday morning. Convective clusters in
LA/southern AR will continue to evolve into a MCS overnight and
spread east- northeast into northern/central MS and into central and
northern AL. These could also influence the pressure field with a
wake low/bubble high that enhance winds in the area, especially on
the back side of this precipitation. So, main adjustments this update
are for wind fields.

.SHORT TERM...(Thursday through Friday)
Issued at 235 PM CDT Wed Apr 22 2020

Elevated storms will still be on-going during the morning hours on
Thursday due elevated instability and favorable wind shear mentioned
in the section above. While heavy rainfall will also be a threat, the
progressive nature of this activity and some of the lower progged
QPF should minimize any concerns for flash/areal flooding issues. The
big question for Thursday deals with the conditional threat for
severe thunderstorms during the afternoon hours along and ahead of a
surface cold front that will sweep into the Tennessee Valley later
that evening. The initial band of showers/storms should clear the
area by the late morning. From here on out, the main question will be
how far north does a surface warm front make it and how much heating
can occur from a late morning and early afternoon window. Models are
split on this at the moment. The NAM, in particular, favors the warm
front surging north into our south/east zones, roughly setting up
along a Cullman to Scottsboro line. The NSSL-WRF and ARW also
supports a similar set-up though they are less aggressive with the
thermodynamics compared to the NAM. Regardless, this setup would
favor an environment that would support a second round of strong to
severe storms with all modes of severe weather possible. The
GFS/ECMWF, along with extended runs of the HRRR support the Tennessee
Valley region generally getting "cut off" from the richer, more
unstable air to the south and east. As a result, it favors the
redevelopment of strong to severe storms remaining displace across
East Central Alabama into Georgia. Should this occur, our threat for
a second round of thunderstorms (let alone severe weather) will be
fairly low. As such, we`re maintaining our conditional threat
messaging. If the warm front can make back into North Alabama -- all
bets are off so to speak, and we`ll have a much better shot of at
least a few severe storms. But as it stands now, this is a lower
probability than the second scenario presented and thus this remains
a low confidence forecast.

With the front sweeping east of the region Thursday evening,
precipitation chances will quickly diminish resulting a cool and dry
night with lows in the 50s. High pressure will support a partly sunny
Friday as southerly winds help to push temperatures back into the low
to mid 70s.

.LONG TERM...(Friday night through Tuesday)
Issued at 235 PM CDT Wed Apr 22 2020

Clouds will then increase ahead of another low pressure system that
will shift into the Mid-Mississippi Valley by Friday evening.
Scattered showers and isolated storms will increase heading into the
overnight hours on Friday, but the best rain/thunder chances will
hold off until Saturday as a weak front clips the region. The best
combination of instability and forcing will be displaced to our
north and west, so think the threat for any strong to severe storms
still remains low at this time. The low pressure system and front
will clear the area on Sunday, resulting in a period of benign
weather heading into the early next week. With a cooler post frontal
air mass in place, below normal temperatures (for Late April) will
continue to be favored. Models differ on the timing of the next front
which could arrive sometime late Tuesday into Wednesday. For now,
kept with the blends with regard to PoPs during this period which
favor a later arrival time of the boundary.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1223 PM CDT Wed Apr 22 2020

VFR conditions will continue this afternoon and into this evening,
with mid to high clouds increasing in coverage ahead of an
approaching storm system. Ceilings will lower late this evening into
the overnight hours as moisture and wind shear increase ahead of this
low pressure system. Expect -SHRA/SHRA to overspread the region late
tonight into Thursday morning, with a few embedded TSRA. For now,
have handled the thunder part with a VCTS given their projected
isolated nature. SSE/S winds will also become gusty at times late in
the period as a front moves through the region.


&&

.HUN WATCHES/WARNINGS/ADVISORIES...
AL...Wind Advisory until 9 AM CDT Thursday for ALZ001>010-016.

TN...Wind Advisory until 9 AM CDT Thursday for TNZ076-096-097.

&&

$$

NEAR TERM...17
SHORT TERM...AMP.24
LONG TERM...AMP.24
AVIATION...AMP.24


For more information please visit our website
at weather.gov/huntsville.




Area Forecast Discussion

National Weather Service Little Rock AR

 852 PM CDT Wed Apr 22 2020

.UPDATE...

Latest surface analysis places surface low over eastern Oklahoma
with attendant cold front moving from the parent low through
southeast Oklahoma and across the Red River. Plume of low level
moisture has made it roughly south of a Mena to El Dorado line
characterized by 60 degree plus dew points.

Several thunderstorms that have required warnings in the past are
now encroaching upon the southwest part of the state with a
noticeable increase in lightning. This would be the preferred
area to see severe weather tonight. Latest meso analysis has CAPE
slowly increasing over the next few hours but overall conditions
remain more favorable south of the forecast area. That being said,
severe weather still remains possible over the south/southwest
until the advancing storms outrun the greater instability.

Outside of this area, precipitation earlier in the day has
stabilized the atmosphere to the point where severe weather seems
unlikely. It also does not appear that the moisture plume will
make it out of southern Arkansas before the front moves through.
Elevated convection rooted above the boundary layer still
possible across central and northern sections but overall
coverage has decreased significantly over the past few hours.

Winds still look elevated behind the front over eastern Arkansas
and will adjust the wind advisory slightly. Other changes this
evening are to adjust POPS and dew points based on current trends
and the latest hi res models.

&&

.PREV DISCUSSION...(ISSUED 626 PM CDT Wed Apr 22 2020)
UPDATE...

Updated to include the 00Z aviation discussion.

AVIATION...

Showers and thunderstorms will continue to move through Arkansas
this evening and late tonight. Some of these storms could become
strong to severe. Winds are out of the S/SE, gusting to 25kts.
VFR/MVFR ceilings are currently moving through the state, and are
expected to continue with the showers and storms through the late
night hours. By early morning, showers and storms will have moved
off to the east. Some MVFR/IFR ceilings are possible early morning
but are expected to begin lifting to VFR levels by late morning.

PREV DISCUSSION...(ISSUED 323 PM CDT Wed Apr 22 2020)
SHORT TERM...Today Through Friday

18Z subjective surface analysis showed a surface low pressure
system over southwest Oklahoma with a plume of upper 60s to lower
70s dew points east of the surface low extending from north
central Texas into south central Oklahoma. We sent up an 18Z
weather balloon and the sounding showed some steep mid-level lapse
rates but showed a pocket of dry air in the lowest 2-3 km of the
atmosphere. SPC mesoanalysis corroborated this low level dry air
showing a plume of 850 mb moisture extending from north central
Texas into south central Oklahoma in line with the higher surface
dew points. Early afternoon water vapor satellite imagery showed a
strong shortwave trough over western Oklahoma spreading large
scale forcing for ascent over central and eastern Oklahoma. The
lift associated with the shortwave trough has allowed the surface
cyclone to deepen over west central Oklahoma, and all models
indicate that this surface cyclone will move east with the
shortwave trough this afternoon through the early morning hours of
Thursday.

The 18Z LZK RAOB featured a fairly large clockwise looping
hodograph with 0-3 km helicity values over 500 m2/s2. Early
afternoon SPC mesoanalysis was in line with the LZK RAOB but also
showed a large area of nearly 1000 m2/s2 of 0-3 km helicity over
northwest Arkansas. This incredible amount of low-level
helicity/wind shear is not within the effective inflow layer of
elevated thunderstorms over Arkansas at this time, but is
indicative of strong warm air advection and low-level lift over
the northwest part of the state. This strong low-level lift should
be sufficient to allow for the continued development of widespread
rain showers with embedded thunderstorms over Arkansas from this
afternoon through midnight tonight. Steep mid-level lapse rates
will allow elevated storms to provide a hail threat from the time
of this discussion through the overnight hours...however the
threat for damaging winds and tornadoes is dependent upon the
track of the surface low and the ability for the deep plume of
moisture to make it into Arkansas after 00Z this evening.

The primary forecast challenge for late this afternoon into this
evening will be tracking the low-level moisture plume and surface
low to determine the likelihood of surface based storms initiating
over southwest Arkansas after 00Z. The RAP is the most aggressive
bringing upper 60s dew point values into southwest Arkansas and
even approaching central Arkansas with the surface low moving over
the northwest portion of the state. If this is modeled correctly,
the southwestern portion of Arkansas would be in an ideal
thermodynamic and kinematic environment for supercell
thunderstorms with all modes of severe weather possible (e.g.
large hail, damaging winds, and tornadoes). However the NAM and
HRRR bring the surface low over west central Arkansas, essentially
keeping the warm sector, and the threat for surface based storms,
generally south of Arkansas and over northern Louisiana.

Will have to keep a close eye on surface observations from this
afternoon through this evening as short term surface analysis and
mesoscale forecasting will be extremely important through 06Z
tonight. Obviously the worst case scenario is the RAP, and the
best case scenario is the NAM. By 00Z we should have a better idea
on the track of the surface low and will have a better handle on
the severe thunderstorm and tornado threat over southwest and
central Arkansas this evening through the early morning hours on
Thursday.

As precipitation exits Arkansas from west to east Thursday morning
drier air will build across the state as a pacific type cold front
moves across the state. Have a wind advisory in effect from 00Z to
12Z for eastern Arkansas as the surface low moves across the
state. Winds should diminish in intensity behind the front as the
surface low moves away from the state relaxing the pressure
gradient. Winds will generally be out of the west-northwest during
the day on Thursday, and aside from some lingering showers in the
morning, skies should clear out in the afternoon for most of the
state.

Another upper level trough will move east over Arkansas on Friday,
bringing another round of showers and thunderstorms across the
state Friday afternoon and evening. There is another conditional
threat for severe weather Friday afternoon and evening, and once
again the primary forecast challenge will be whether or not a
strong plume of low-level moisture is able to make it back into
the state Friday. The position of the surface low will once again
play an important role in the areal extent and severity of storms
Friday afternoon and evening. If the surface low tracks over
northern Arkansas and can advect mid 60s dew points into the
state, we may have enough surface based CAPE to allow for
supercell thunderstorms in another highly sheared environment.
With the pacific front moving across Arkansas on Thursday, it may
be difficult for deep moisture to make it back across the state.
Either way we will have widespread showers and thunderstorms, but
the severity of the storms will depend on the ability for the
low-level atmosphere to recover moisture during the day on Friday.
At this time due to the short period of southerly flow behind the
pacific front on Thursday, think that the most likely scenario is
for elevated thunderstorms posing a threat for damaging winds from
microbursts and large hail. If moisture return is quick to return,
the severe weather threat may be higher Friday afternoon and
evening across central and southern Arkansas.

Cavanaugh

LONG TERM...Friday Night Through Wednesday

A trough will be progressing Ewrd across AR at the beginning of the
long term, allowing for rain and thunderstorm chances Fri night into
Sat morning along a tailing cold front. Modest buoyancy and bulk
wind shear could promote stronger and at times, severe thunderstorms
over portions of Srn AR, and subsequent fcst cycles will continue to
refine the severe weather threat. The sfc low will quickly lift
towards the N/E, with cooler, drier air filtering into the state
under N/W flow. High pressure will settle over the Natural State
through the weekend, promoting settled conditions with seasonable
temperatures.

By the beginning of the new work week, Srly flow returns to the
region, promoting another warm up. Rain chances will increase in
coverage from the N/W towards the E on Tues with a few rumbles of
thunder possible in the presence of marginal buoyancy. Another front
will push through the state late in the period, cutting off rain
chances from N to S Wed evening with another settled conditions once
again returning.

&&

.LZK Watches/Warnings/Advisories...
Wind Advisory until 7 AM CDT Thursday FOR Arkansas-Independence-
Jackson-Lawrence-Lonoke-Monroe-Prairie-Randolph-Sharp-White-
Woodruff.


Flash Flood Watch until 7 AM CDT Thursday FOR Arkansas-Bradley-
Calhoun-Clark-Cleveland-Dallas-Desha-Drew-Grant-Hot Spring-
Jefferson-Lincoln-Monroe-Ouachita.

&&

$$

GOUDSWARD
Aviation...99