Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/11/21
Area Forecast Discussion
National Weather Service Amarillo TX
617 PM CDT Sat Apr 10 2021
For the 00z TAFs:
VFR conditions will prevail throughout the valid TAF period. Main
story here will be the potential for low level wind shear at KAMA
tonight, and the cold front coming in tomorrow late
afternoon/early evening. The front has slowed down somewhat from
previous runs, but it still looks to pass through KGUY late
tomorrow afternoon, and maybe edging its way towards KDHT as well.
However, it doesn`t look like it will pass through KAMA until
after sunset Sunday evening (beyond this TAF period).
.PREV DISCUSSION... /Issued 153 PM CDT Sat Apr 10 2021/
SHORT TERM...Today through Tomorrow Night...
An upper level low across Missouri will continue to swing
northeast into the Ohio Valley by Monday morning. Meanwhile, RAP
500mb analysis shows the next system in western Canada as it is
expected to dig into the northern Plains tomorrow with the
Southern Plains under weak west northwest flow aloft. By Monday
morning, this upper level low will have caught up with the
original system in the Ohio Valley and merge as one. This puts
much of the southwest and south central CONUS under zonal flow
Light winds and pleasant conditions area expected today with
temperatures warming nicely into the upper 60s to lower 70s. By
Sunday, temperatures will rise even higher with over half the
forecast area reaching the 80 degree mark. Winds will turn quickly
to the north northwest by the morning hours tomorrow due to a weak
surface trough swinging across the Panhandles. A cold front is
then expected to enter the Oklahoma Panhandle by the evening hours
tomorrow and be through the area just after midnight. Surface winds
will turn to the northeast and become windy behind the front with
some higher wind gusts possible through the evening and overnight
hours. Soundings show a decent inversion around 700mb with only a
potential for mixing of winds below that layer. A 35 to 45 knot
jet is present at 850mb with a chance for these higher wind speeds
to mix to the surface. No precipitation is expected through
tomorrow night with mostly clear skies. A few mid-level clouds may
fill into the northern Panhandles behind the front with a very
shallow layer of moisture present at 700mb.
Elevated fire weather conditions are possible tomorrow with mostly
relative humidity driven conditions. Minimum relative humidity
values will be as low as 6 to 9 percent across the southeastern
half of the combined Panhandles and below 15 percent minimum
relative humidity for the entire Panhandles. Twenty foot winds
will be around 5 to 15 knots with a few areas in the Oklahoma
Panhandle getting closer to 15 to 20 knots during the early
afternoon hours. Winds will be out of the west northwest through
the afternoon hours before turning to the north northeast during
the late afternoon and evening hours across the northern half of
the Panhandles with an incoming cold front. Twenty foot winds will
pick up to around 10 to 20 knots behind the front during the late
evening and overnight hours. Fuels remain cured fine dead fuels on
top of an underlying green base, therefore the chance for fire
weather remains at elevated or below despite the relative humidity
LONG TERM...Monday through Friday
Surface ridge builds down into the Panhandles Monday allowing for
much cooler and more moist upslope surface flow. Increasing
cloudiness expected Monday as southwesterly flow aloft continues
to bring in sub-tropical moisture across the forecast area. This
pattern continues into Monday night and Tuesday with low level
moisture advection and perturbations within the southwesterly flow
aloft resulting in the development of convection by Tuesday.
Closed upper low over the western states Tuesday will track east
across the Intermountain West and Great Basin region Wednesday
will move east across the central Plains states late next week.
The upper low will draw abundant Gulf moisture northward into the
Panhandles by the middle and end of next week. A more west
southwest upper flow will continue to to bring perturbations from
the western states across the Four Corners region and also from
the southwestern states eastward into the Panhandles. Chances for
convection, mainly showers with the possibility for some
thunderstorms, the middle and end of next week. Upslope surface
flow for most of next week as the surface ridge continue to
build into the Panhandles will allow for much cooler and more
moist conditions. A reinforcing surge of cooler air expected
Area Forecast Discussion
National Weather Service Columbia SC
1105 PM EDT Sat Apr 10 2021
Showers will move out of the area during the early morning hours
with a front moving through the area Sunday afternoon with
better precipitation chances to our east and south. Dry
conditions expected Sunday night through Tuesday with high
temperatures in the low to mid 80s. A front will slowly move
through Wednesday providing a chance of mainly light rain.
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Showers have mainly moved out of the forecast area with a few
remaining across Chesterfield County. Over the next hour these
showers will exit the forecast area with partly to mostly clear
skies into the early morning hours. Toward daybreak another push
of moisture will move northward from the eastern Gulf Coast
with a slight chance of showers mainly in the CSRA. Overnight
lows will be limited by cloud cover and elevated dewpoints with
lows ranging from the upper 50s western Midlands to lower 60s
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
A cold front moves through The Midlands and CSRA on Sunday.
Precipitable water levels decrease to below one inch during the
day which limits convective activity to isolated showers.
A flat ridge of high pressure sets up over the Lower Mississippi
River Valley early next week with the Southeast U.S. in the a
west northwest flow aloft. Temperatures will remain above
normal for mid April.
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Model ensembles depict a wide spread of solutions with regards
to the development of a closed or cut off upper level low
pressure system over New England or just off the coast. This
feature could drop a back door front into The Midlands and CSRA
later next week for a cooling trend. The ensembles also forecast
a slow increase of low level moisture from the Gulf of Mexico.
This could bring a chance of showers to the region the second
half of next week.
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
VFR expected to be dominate for the next couple hours before some
possible cig restrictions develop later tonight.
Showers and isolated thunderstorms have been progressing through
the region this evening as a cold front pushes through. These
have generally been pretty weak, and haven`t resulted in wind
gusts above what we`re seeing outside of showers. What is out
there now should push mostly to the north of OGB and should
clear the terminals between 01z and 02z this evening. Any shower
should have with it briefly gusty winds upwards of 20-25 knots
and some heavy rain. As these pass, winds should generally shift
from the south and southeast to the southwest, and drier air
above the surface will filter in.
This will set up for what will be our primary aviation question
tonight. To our west, there is currently just fair weather cumulus
and mid-high level clouds. The cumulus should begin to die off
after sunset. As this area of lesser cloud cover moves into
the area, guidance really isn`t sure what to make of how our
conditions evolve overnight. There is a wide range of
possibilities - from the HRRR which shows nothing until tomorrow
morning to the HREF which gives high probabilities of IFR cigs
developing. Low level winds are forecast to remain elevated
tonight across the CWA, so I don`t really expect fog or very low
stratus. However, there seems to be enough guidance to suggest
that at least MVFR cigs develop everywhere overnight underneath
a weak subsidence inversion. Given this, I have backed off from
previous forecasts and gone MVFR or MVFR with a TEMPO group down
to BKN007. I am hesitant to even go that low at the Midlands
sites, but will leave it up to the next forecasters to decide
what to do with that. Either way, it looks like a deck of
stratus/stratocu will develop overnight and cause at least MVFR
cigs at all terminals. As I mentioned previously, winds should
remain elevated, in the 4-8 knot range out of the southwest
By tomorrow, much drier air is forecast to filter in. Any cig
restrictions present will begin to lift around 15z, and most
clouds should be gone by the afternoon. There is a chance for
an isolated shower during the afternoon hours, but certainly not
high enough to include in the TAFs. Winds should generally be
out of the west- southwest in the 8-12 knot range.
EXTENDED AVIATION OUTLOOK...CIG and VIS restrictions aren`t
expected to remain an issue as we head into early next week.
Much drier air will filter into the region behind a cold front
on Sunday, limiting overall moisture for low clouds or fog.
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1149 PM EDT Sat Apr 10 2021
Showers will hold into the first few hours of the forecast,
especially KPTK north before mid level dry slot works north into the
region. MVFR cigs can be expected at times with this activity with
lower clouds then clearing late tonight into Sunday morning. More
scattered showers will develop on Sunday afternoon, mainly KPTK
south as secondary low pressure pivots into far southern lower
Michigan. MVFR to lower VFR cigs will return in this activity as
times with lower cigs/vsbys possible into Sunday night as low level
moisture remains trapped over the area and winds become
For DTW...Showers will end by 08z or before with MVFR cigs at times.
Another round of scattered showers will evolve Sunday afternoon as a
secondary low pivots into the vicinity.
.DTW THRESHOLD PROBABILITIES...
* High for ceiling 5000 ft or less overnight, medium again by Sunday
afternoon, high by Sunday evening/night.
Issued at 406 PM EDT Sat Apr 10 2021
A line of showers and thunderstorms have developed this afternoon
across far western Lenawee County. TDTW Z imagery shows fineline
delineating the southern edge of a lake shadow off of Lake Erie. Air
mass to the west of this lake shadow is considerably more
humid/moist with dewpoints in the lower to middle 50s. Model
soundings show this near surface moisture coupled with the lapse
rates in the 800-650mb layer is good enough for MUCAPES of 300 J/kg.
Given scaling of convective updrafts the potential does exist for
storm gusts approaching 40-50 mph. The potential for strong
thunderstorm activity should decrease moving forward this afternoon
for Southeast Michigan cwa as deep moisture arrives and lapse rates
become moist adiabatic. Easterly flow in place within the lake
shadow will provide a degree of stability which should try to prevent
surface based instability for Metro Detroit northward. Latest Swody1
has reintroduced and expanded Marginal Risk northward in Lower
Main moisture transport axis will lift south to north throughout the
cwa beginning after 20Z this afternoon. Precipitation will be slower
for the Thumb where onset time may wait until as late as 01Z. Deep
moisture axis with system relative isentropic ascent along the 314-
320 Ke surfaces. Good setup for a period of moderate to
intermittently higher rainfall rates this evening with environmental
profile supportive of elevated convective instability between 4.0-
9.0 kft agl. Latest trends suggest 0.25 to 0.75 inch QPF being
possible by 12Z Sunday. HRRR and RAP solutions have been checking in
with less QPF tonight while other model consensus remains
consistent. Latest in-house probabilistic guidance shows higher end
QPF potential is lessening but again that appears to be due to
HRRR/RAP. Plan view perspective of moisture shows very progressive
dry slot lifting south to north into Southeast Michigan between 03-
09Z which causes rain to abruptly end.
Models show heart of expansive mid to upper level dry slot over all
of Southeast Michigan to begin the day Sunday. The dry air is
expected to limit overall coverage of precipitation initially before
daytime heating occurs. Wrap around moisture within the vertically
stacked upper level low will then advect into Lower Michigan for 15-
00Z. Model soundings show favorable lapse rate structures in the
lowest 6.0 kft agl indicative of good potential for low topped
convective showers. Given the occlusion there is lack of cold upper
level air which limits convective vigor and potential for any small
Upper level low is then forecasted to stall out over the central
Great Lakes on Monday. A very interesting upper level pattern then
emerges with signs pointing to very strong blocking flanking much of
North America. What develops is a far ranging large scale shearing
deformation axis from the Atlantic Ocean clear back to the Pacific
Northwest. It is always difficult pinpointing coverage and duration
of rain activity within upper level low pressure systems
particularly within days old occlusions. Internal wave interactions
and corresponding subtle moisture advections are normally difficult
to time out. A separate wave packet and dynamic low shortwave is
expected to dive southeastward driving a geopotential height fall
region locally on Monday. Combination of daytime heating with deeper
moisture through 15.0kft should drive robust afternoon shower
development. Went against automated guidance and introduced PoPs at
likely Monday afternoon. Latest indications are that stretching
deformation may exist in a very weakened form through early
Thursday. Low confidence exists in the temperature forecast during
the early to middle of the week that will depend on opacity/coverage
Low pressure will continue tracking northeast towards lower Michigan
the remainder of today and into tonight bringing a period of
unsettled weather that will last through at least Monday. Rounds of
showers with embedded thunderstorms will accompany the low pressure
system, with the best chance for thunderstorms confined to the
southern Lake Huron basin, Lake St. Clair, and western Lake Erie.
Moderate easterly winds will veer more southeasterly into tonight,
with gusts generally holding below 25 knots. Wave runup along the
tip of the Thumb between Port Austin and Port Sanilac will allow for
choppy conditions that will lead to hazardous conditions for small
craft tonight, as waves occasionally reach 5 feet at times. The low
pressure system will begin to slowly weaken Sunday and especially
into Monday as it stalls over the central Great Lakes, with
continued light to moderate southeasterly flow in place over the
local waters. Drier weather and lighter winds veering to the
southwest will then prevail late Monday and into Tuesday as weak
surface high pressure attempts to nudge in from the northern Ohio
Daily chances for showers and thunderstorms continue through early
next week. The potential exists for rainfall amounts to
conditionally exceed a quarter of an inch at times, especially this
evening. Cumulative rainfall on the order of 0.25-0.75 inch is
expected regionally by Sunday morning. Minor rises on area rivers
and streams are possible with nuisance flooding in poor drainage
areas during the heaviest bursts of rain.
Lake Huron...Small Craft Advisory until 4 AM EDT Sunday for LHZ441-442.
Lake St Clair...NONE.
Michigan waters of Lake Erie...NONE.
You can obtain your latest National Weather Service forecasts online
Area Forecast Discussion
National Weather Service New Orleans LA
328 PM CDT Sat Apr 10 2021
The MCS from this morning has moved well out into the Gulf of
Mexico. A trailing shortwave moving across the northern Gulf, and
the cold front pushing southward has produced isolated convection
to the south of Lake Pontchartrain this afternoon, which is
rapidly moving eastward offshore as well. Looks like the effective
boundary, based on wind fields and dew points, is somewhere around
Interstate 12 at 2 PM CDT. Where we`ve lost cloud cover
sufficiently, temperatures have or will rebound to near 80
degrees, with dew points in the lower and middle 60s, compared to
the lower 70s that were widespread ahead of the front.
.SHORT TERM (through Monday night)...
Based on mid-level westerly flow, actual cold front may not make
much more southward progress. Latest HRRR solution does indicate
some threat of isolated showers overnight, so there will be a
mention in a few zones. The 00z upper air soundings will be
instructive as to whether an evening forecast update will be
Beyond tonight, high pressure will shift eastward over the next
couple of days. Low level flow will eventually turn onshore late
Monday or Monday night. Moisture increase will eventually be
sufficient for at least isolated to scattered convection by late
Monday night or Tuesday morning.
Temperature guidance is pretty well clustered through Monday, and
don`t see much of a reason to mess with it. 35
.LONG TERM (Tuesday and beyond)...
Main upper air pattern gets pretty blocky north of 35N at mid-
week, with a surface boundary getting hung up somewhere close to
the Gulf Coast. Weak shortwaves moving through the zonal flow to
the south of the block across our area will present the threat of
a few rounds of convection during the midweek period. The ECMWF
solution is a little more vigorous with one on Tuesday, the GFS
with one on Wednesday. At this point, severe weather doesn`t
appear to be as much of a concern as the potential for at least
some heavy rain at midweek. Considering that we`ve had a couple of
batches of heavy rain in the last few days, we`ll need to monitor
for any focus of heavy rain. We`ll keep to the blended PoPs and
temperatures for now. 35
.AVIATION (valid through 00z Monday)...
Currently VFR at all terminals. Threat of TSRA at any terminal
currently too low to carry in the forecast. There are currently
BKN-OVC clouds between FL030-050 to the south of the frontal
boundary, that are likely to lower into the MVFR range overnight.
At this time will keep the ceilings out of the KMCB and KBTR
forecasts. Don`t expect prime radiating conditions overnight, so,
while we can`t eliminate the possibility of fog, threat is fairly
low. Any flight restrictions that occur overnight should improve
to VFR by 15z Sunday. 35
Wind and pressure fields (especially direction) have been rather
chaotic today due to the morning convection. Winds have dropped
below Small Craft Advisory criteria, and with the pressure field
weakening somewhat, will cancel the Small Craft Advisory, which
was due to expire shortly, anyway. Outside of thunderstorms toward
midweek, don`t see any major marine issues for the majority of
this forecast package. 35
.PRELIMINARY POINT TEMPS/POPS...
MCB 52 77 52 82 / 0 0 0 10
BTR 54 79 54 84 / 0 0 0 10
ASD 57 80 54 82 / 20 0 0 10
MSY 63 79 61 82 / 10 0 0 10
GPT 59 79 57 79 / 10 0 0 10
PQL 60 79 54 79 / 10 0 0 10
Area Forecast Discussion
National Weather Service Miami FL
749 PM EDT Sat Apr 10 2021
Scattered showers and thunderstorms will continue across Palm
Beach and northern Broward counties this evening. Periods of MVFR
or IFR conditions are possible in and around any shower or
thunderstorm. A cold front will bring additional chances of
showers and thunderstorms across the region on Sunday. Winds will
remain gusty as well out of the south southwest on Sunday across
Updated the current forecast based on radar trends. Scattered
showers and thunderstorms continue this evening across portions of
Palm Beach and northern Broward counties. These storms could
contain gusty winds, small hail, and heavy downpours. An
additionalround of showers and thunderstorms associated with a
decaying MCS will start to move into the northern and western
areas this evening. These storms will continue to weaken as they
push southeastward through the rest of the evening and into the
overnight hours. A cold front will continue to push closer to the
area on Sunday. This will trigger additional chances of showers
and thunderstorms especially during the afternoon and evening
hours. There will be enough instability in place to support some
strong to possibly severe thunderstorms during this time frame.
The strongest storms could contain gusty winds, heavy downpours,
.PREV DISCUSSION... (Issued 307 PM EDT Sat Apr 10 2021)
..A Few Severe Thunderstorms Possible Sunday...
SHORT TERM (This Evening through Sunday)...
The lengthy trial of quiet weather ends today. First, we are
watching along the Atlantic sea breeze, specifically over Broward
and Palm Beach Counties where CAMs indicate some convective
development this afternoon and perhaps early evening. Mid-levels are
cool so some small hail and perhaps with shear values increasing
later a funnel cloud or two wouldn`t be impossible...along with a
damaging wind gust or two. Secondary concerns would be localized
ponding on roadways due to heavy rainfall, but this would be
concentrated only within the more urbanized locations in the metro.
Outside of the possible sea breeze generated convection, there is
currently a MCS pushing through the central Gulf Coast and Panhandle
region. Mesoscale models are in agreement that this feature will
eventually dive southward. It should arrive within our Gulf waters
sometime around 8-10pm tonight if current projections are correct. A
nice upper level impulse along with some jet dynamics will help
maintain the MCS through the day, however, as it begins to near our
area the impacts of both will decrease. Still, can`t rule out a
strong wind report or two over Collier County.
Outside of a few isolated showers and maybe a rumple of thunder
tonight, it should be mostly quiet after the MCS decays or moves
just west of our CWFA. The next round of storms will begin to
develop upstream early Sunday in closer proximity to the cold front
and where the best jet dynamics resides. Just looking over a few
parameters ahead of another possible MCS tomorrow, instability looks
moderate (in some cases around 3,000 J/KG) and bulk shear values
becoming sufficient (40-50kt), think that there will some strong to
possibly severe storms within this feature. With the upper level
heights falling/cold air advecting upstairs...hail will be possible
along with strong gusty winds and as a secondary threat localized
flooding within metro areas.
There very well could be a second round of showers and storms with
some prior model data (WRF3km) suggesting this. However, latest HRRR
guidance suggests that scenario is becoming less likely. Timing
appears to be early afternoon first impacting the Lake Okeechobee
region before settling southward through Miami-Dade and Mainland
Monroe through the end of the period.
Sunday Night and Monday...
Showers and thunderstorms may be ongoing early Sunday evening as
the first mesoscale convective system (MCS) or its remnants push
south through southern portions our area and/or the Atlantic
waters. Thereafter the weather picture becomes murkier for late
Sunday night into Monday morning. The high resolution convection
allowing models nominally suggest the development of a secondary
thunderstorm cluster over the eastern Gulf waters around 00-03z
before bringing it southeast into central/south Florida during the
overnight (generally after 10 PM) hours. That said most (but not
all) of the solutions show these storms weakening with time
leading to uncertainty in QPF/impacts across our area. So while
we can`t rule out the potential for strong thunderstorms overnight
any severe risk is highly conditional and dependent upon how
worked over the environment is from the previous convection. Keep
up with forecast changes. Rain chances should decrease from north
to south through midday on Monday as the cold front pushes towards
the Florida Straits thus allowing drier air to filter into the
Tuesday and Wednesday...
Northwesterly flow should prevail aloft as surface high pressure
centers in the Atlantic waters just north of the Bahamas. This
should result in generally quiet weather across the region. With no
really notable cold air advection behind the front temperature
readings will remain just a little above seasonal means with highs
in the 80s to around 90 (warmest towards inland SW FL) and lows in
the 60s and 70s.
Thursday through Saturday...
A progressive flow pattern evolves aloft as a series of southern
stream perturbations cross the southern CONUS. There remains low
predictability in timing when the best rain/storm chances are for
our area but with warm temperatures and increasing moisture rain
chances look to be in the cards at some point during this period.
Mainly VFR conditions expected. There could be convection develop
along the Atlantic sea breeze for Palm beach and Broward terminals
this afternoon. Additionally, APF may experience a shot at
convection later this evening as well. Covered both opportunities
with VCTS until more timing confidence is realized. Southerly winds
has picked up today with some gusts up to around 20 knots at times,
especially along the coasts.
Cautionary headlines for both the Atlantic and Gulf waters as
surface winds increase out ahead of an approaching cold front. As
the front nears and pushes through the region, scattered showers and
thunderstorms will be possible over all south Florida waters. The
strongest activity will produce frequent cloud-to-water lightning,
heavy rainfall (limiting visibility) along with perhaps small hail
and damaging wind gusts. Cautionary headlines may be needed behind
the front as well, but due to a rather lackluster pressure gradient,
SCA threshold likely will not be met. Favorable marine conditions
expected early next week through the end of the period.
There is a high risk of rip currents along the Atlantic Coast today.
Additionally, with scattered showers and thunderstorms developing
over the next day or two, lightning may become a hazard.
.PRELIMINARY POINT TEMPS/POPS...
Miami 73 87 72 89 / 30 70 70 40
West Kendall 72 88 71 90 / 30 70 70 40
Opa-Locka 73 87 70 88 / 30 70 70 40
Homestead 72 86 70 88 / 30 70 70 40
Fort Lauderdale 74 86 71 88 / 20 70 70 40
N Ft Lauderdale 72 86 70 87 / 20 70 70 40
Pembroke Pines 73 87 70 89 / 30 70 70 40
West Palm Beach 71 87 69 86 / 30 70 60 30
Boca Raton 73 85 70 88 / 30 70 60 40
Naples 71 82 70 85 / 50 50 60 20
FL...High Rip Current Risk through Sunday evening for FLZ168-172-173.
AM...Small Craft Advisory until 8 AM EDT Sunday for AMZ650-670.
Tonight/Sunday and Marine...Frye
Sunday Night through Saturday...SPM
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Area Forecast Discussion
National Weather Service Paducah KY
542 PM CDT Sat Apr 10 2021
.SHORT TERM...(Tonight through Monday night)
Issued at 318 PM CDT Sat Apr 10 2021
Strong gusty winds have developed under a dry slot associated with
the low pressure system over the mid Mississippi Valley. Abundant
sunshine has warmed temps enough to promote mixing to around 7000
feet, based on the rap model sounding for kpah. Gusts to around 30
kt will continue through sunset. These winds have been handled
with a special weather statement. Winds will be slow to subside
this evening, since the low pressure center is deepening and low
level lapse rates are forecast to remain steep well into the
The deepening surface low over northern Illinois tonight will
wrap moisture east/southeast across parts of our region. Radar
mosaics indicated the leading edge of light rain was near the I-44
corridor this afternoon. The consensus of short range guidance
pops keeps most of the rain north of a kcgi to Madisonville line
tonight. With increasing clouds and brisk winds, lows tonight will
be around 50 despite cold advection aloft.
Sunday may start out rather cloudy, with some light rain showers
continuing in sw Indiana and the I-64 corridor of Illinois. The
clouds and rain will pull away to the northeast as the storm
system lifts northeast. Highs will range from the mid 60s in parts
of sw Indiana to the lower 70s in southeast Missouri, where sun
will be prevalent.
Sunday night and Monday, a weak cold front will pass southeast
across our region with very little moisture to work with. A period
of cloudiness will accompany the front, along with a wind shift to
northwest. Highs Monday will be in the 65 to 75 degree range from
north to south.
.LONG TERM...(Tuesday through Saturday)
Issued at 318 PM CDT Sat Apr 10 2021
During the midweek period, a merged low pressure system in the Great
Lakes area is progged to eject eastward toward the Atlantic seaboard
in response to ridging building over Manitoba/western Ontario. In
addition, the medium range models suggested ridging aloft will
increase across the central Plains through the daylight hours Wed in
response to a large low pressure system moving eastward out of the
Rockies. This will keep the PAH forecast area under fairly fast west-
northwesterly flow aloft into late in the week, with high pressure
maintained at the surface.
By early Fri, measurable pcpn may flirt with westernmost parts of
the region as northern stream mid level shortwave energy merges with
part of the elongating trof out west, but measurable pcpn (mostly
just showers) appears most probable in the extended period to be on
Sat (Day 7) as deeper moist southerly flow would have increased
across the MS River valley by then.
Surface winds are forecast to have a solid northerly component
through the extended forecast period. As a result, temps near
seasonable levels, with no wild swings to above or below average,
can be expected.
Issued at 542 PM CDT Sat Apr 10 2021
For the WFO PAH 00z Sunday TAF issuance, focused on the mean VFR
ceilings this evening, after the loss of diurnal heating around
the closed surface low centered in northwest Illinois at 23z
As the surface low moves east, MVFR ceilings and vicinity showers
can be expected at KMVN, KEVV, and KOWB between 03z and 21z
VFR conditions will continue to work back north toward the end of
the forecast period as the low eventually lifts northeast away
from the WFO PAH TAF sites.
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
822 PM MDT Sat Apr 10 2021
Issued at 816 PM MDT Sat Apr 10 2021
02z surface analysis had cold front from KD50 to KBYG, moving
southeast around 30kts. Pressure rises have increased to
4-6mb/3hr. HRRR has been persistent increasing the strength of the
frontal passage/cold air advection with a rather well defined
area of 45-55kt wind gusts for a couple of hours behind the
front. This is starting to ring true looking at observations
upstream, so have hoisted High Wind Warnings to account through
the early morning hours.
.DISCUSSION...(This Evening Through Saturday)
Issued at 222 PM MDT Sat Apr 10 2021
Mean upper level troughing will dominate in the period,
supporting below normal temps with unsettled and breezy conds.
This will all ensue via an advancing clipper like system, which
will arrive tonight bringing strong winds and CAA. Clear skies and
overall light winds ongoing across the FA today with many places
seeing 60s for highs. Strong cold front will arrive late this
evening into early Sunday morning with an initial round of strong
gusty winds, strongest in the lee of the Black Hills where a
period of warning level winds will materialize via acceleration
around the hills. Gusts over 60 mph can be expected there and have
opted to upgrade the high wind watch given CAA, pressure rise
couplet, and expected flow acceleration around the hills. Also
issued a wind adv for the rest of NW into central SD, running it
through Sunday, catching the cold front and the next round of
breezy winds Sunday late morning/afternoon. There will likely be a
period of sub adv winds Sun morning, but decide to keep things
simple and just run the adv through Sunday. The high wind warning
area will need to be converted to a wind adv or extended if
stronger flow is progged. Hence, to keep things simple will defer
headline change to the mid shift. Not much moisture with this
system, but still expect some post frontal snow showers over NE WY
into NW SD, including the northern Black Hills where up to an
inch is possible. Cold pool aloft will time with diurnal heating,
Sunday, supporting convective showers Sunday afternoon, best
chance over NW SD where a little better moisture will be found.
Otherwise, cool, breezy, and increasingly unsettled weather can be
expected next week, with increasing chances for a late week storm
to affect all of a portion of the region as the western NOAM
upper trough moves east. Too much uncertainty remains in track,
timing, moisture transport, and best collocation of lift to
predict any snow/rain amounts in the Thur-Fri period at this time.
.AVIATION...(For the 00Z TAFS Through 00Z Sunday Evening)
Issued At 519 PM MDT Sat Apr 10 2021
A strong cold front will cross northeast WY 02z-06z and western SD
05z-11z. Gusty northwest winds are expected behind the front with
gusts over 35kts common and gusts around 50kts just east of the
Black Hills through early Sunday morning. A few shrasn expected
behind the front with areas of MVFR conditions, mainly from
northeast WY into far western SD.
SD...Wind Advisory from 2 AM MDT /3 AM CDT/ to 6 PM MDT /7 PM CDT/
Sunday for SDZ014-032-043-046.
High Wind Warning until 4 AM MDT Sunday for SDZ001-002-012-013-
Wind Advisory from 4 AM to 6 PM MDT Sunday for SDZ001-002-012-
High Wind Warning until 8 AM MDT Sunday for SDZ026-031-072-073.
WY...High Wind Warning until 1 AM MDT Sunday for WYZ054>058-071.