Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 05/17/20
Area Forecast Discussion
National Weather Service La Crosse WI
1043 PM CDT Sat May 16 2020
.SHORT TERM...(This evening through Sunday)
Issued at 300 PM CDT Sat May 16 2020
At 3 PM, easterly winds continue to advect dry air into the
region. Surface dew points are mainly in the 40s. This dry
air has been limiting the amount of low clouds. As a result, we
have been seeing some filtered sunshine through much of the day.
This has allowed temperatures to warm into the mid- and upper 60s
north of Interstate 94 and into the lower 70s elsewhere.
As a strengthening shortwave moves out of the Northern Plains
tonight, the 925 and 850 mb moisture transport will gradually
increase. With this system slowing as it deepens, the timing of
the showers and isolated/scattered storms gets later and later in
the RAP and HRRR. At this time, it looks like the precipitation
will move into southeast Minnesota and northeast Iowa mainly after
9 PM and for Wisconsin it looks dry until after midnight. While
the instability remains mainly less than 200 J/kg, the models
continue to show strong isentropic and synoptic lift and
precipitable water water values of 1-1.5 inches. This will promote
the development of isolated to scattered storms and the potential
of heavy rain at times. The heaviest rain continues to shift
further north and west with each progressive model run. At this
time, 1 to 2 inches is expected from north-central Iowa into east-
central Minnesota and near and north Interstate 94 in Wisconsin.
The HREF continues to suggest the highest rainfall amounts will be
in the 2 to 3 inch range. There are a few outlying models which
even suggest 4 to 5 inches. This seems a bit too high considering
the limited instability.
On Sunday, the closed low pressure area will move slowly east
through the region. This will keep the rain over the area.
However, with the strongest 925 to 850 mb moisture transport
moving east of the area, the rainfall will be on the lighter side
(0.25 to 0.75 inches).
.LONG TERM...(Sunday night through Saturday)
Issued at 300 PM CDT Sat May 16 2020
It continues to look like the low pressure system will be much
slower moving out of the region. As a result, carried some small
rain chances into Monday morning. In addition with the clouds
holding over the area into Tuesday, lowered the temperatures by at
least 5 degrees and that may not be enough yet.
In the wake of this system, a rex block develops over the eastern
US. This will keep a ridge over the area. The warmest air will
stay west of the area. Even though this will be the case, we will
still see high temperatures from the mid 70s to mid 80s. The
warmest temperatures will be late in the week.
&&
.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1043 PM CDT Sat May 16 2020
VFR conditions are prevalent along and north of I-90 at the moment
but that will change overnight and into Sunday as slow-moving low
pressure wraps bands of rain into the region. Overall conditions
will likely dip to prevailing IFR at RST and mainly MVFR at LSE
(with some IFR possible at times), as light to moderate rain comes
in waves, with even a brief period of heavy rain expected at RST
either side of sunrise. A rumble of thunder is also possible but
should be the exception for either site, while easterly winds
crank up to 15 to 25 knots with some higher gusts possible late
tonight into much of Sunday. If this storm system strengthens a
little more than currently forecast, a window of winds gusting up
to 35+ knots could occur on Sunday, though at this time,
confidence in that occurring remains a bit on the low side.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Boyne
LONG TERM...Boyne
AVIATION...Lawrence
Area Forecast Discussion
National Weather Service Charleston SC
1053 PM EDT Sat May 16 2020
.SYNOPSIS...
Tropical Storm Arthur will remain offshore of the Southeast
U.S. coast through Sunday and move near the North Carolina Outer
Banks Monday. A cold front will bring unsettled weather to the
area Monday and Tuesday before weak high pressure likely returns
later in the week.
&&
.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
Tropical Depression One has been upgraded to Tropical Storm
Arthur.
The only major change for the late evening update was to
introduce locally dense fog across the interior where the latest
NARRE-TL probabilities show a 50-70% chance for dense fog in
the Ludowici-Glennville to Allendale-Harleyville corridor. The
rest of the forecast looks on track.
The main forecast concern centers on fog and stratus
development. Guidance continues to trend a bit higher with the
fog coverage overnight along/west of I-95 where both the RAP and
NAM show very low 1000 hPA condensation pressure deficits
developing after midnight. Coastal winds look a bit too high to
support too much fog, so stratus should prevail there, while
farther inland a combination of fog/stratus will dominate. Do
not anticipate widespread dense fog issues at this time, but
locally dense fog will be possible. "Areas of fog" will be
introduced with this update mainly in the Ludowici-Glennville to
Allendale-Harleyville corridor. Lows will range from the lower
60s inland to the upper 60s/near 70 at the beaches, Downtown
Charleston around the Santee-Cooper lakes.
&&
.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
Moderate confidence this period. Tropical Depression One well
off the northeast Florida coast is expected to move generally
northward about 150 to 200 miles off the northern GA/central-
southern SC coasts as a deep upper trough approaches from the
west, likely as a tropical storm. At this point we are thinking
most of the showers will stay offshore but can`t rule out a few
into Sunday night as the low moves by, mainly near the central
SC coast. Conditions also look favorable for stratus/fog Sunday
night. By Monday the aforementioned upper trough will be pushing
a cold front toward the area and with some deeper moisture and
lift we should see a bit better risk for some showers and
thunderstorms into Monday night, possibly even a few isolated
severe storms with damaging winds. By Tuesday the deeper
moisture will likely have shifted northeast of the area but
strong forcing from the upper low and some instability along
with the sea breeze should be enough for some more showers and
thunderstorms. Temperatures should stay just above normal
through the period.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A large closed upper low will meander near the mid-Mississippi
Valley mid to late week. Weak surface high pressure is expected
to reside over the local area with dry, slightly cooler
conditions.
&&
.AVIATION /03Z SUNDAY THROUGH THURSDAY/...
The risk for IFR-LIFR cigs is the main concern at both KCHS and
KSAV overnight. Low clouds are expected to fill in after
midnight as winds tip northeast ahead of Tropical Depression
One. There looks to be too much wind to support fog, so this
stratus development is preferred.
KCHS: Expect MVFR cigs to reach KCHS by 07z then drop below
alternate minimums by 09z. Cigs look to remain just above
airfield minimums at this time. Conditions should rise above
airfield minimums by 13-14z with MVFR cigs breaking to VFR
during by mid-afternoon.
KSAV: The fog risk could be a bit higher here as low clouds
could be delayed here by 1-2 hours as winds trend a bit lighter.
MVFR cigs are expected by 08-09z with cigs dropping at/just
below airfield minimums by 10z with MVFR vsbys. Confidence in
prevailing cigs dropping solidly below airfield minimums it not
as high at KCHS, so this will be handled with a TEMPO group
10-12z. MVFR cigs will return just after daybreak with MVFR by
late morning/early afternoon.
Extended Aviation Outlook: High confidence in some restrictions
Sunday night due to low clouds/fog, possibly IFR or lower.
Additional periodic restrictions later Monday into Tuesday from
showers and thunderstorms due to a cold front. Lower confidence for
additional restrictions Wednesday and Thursday from more
showers/storms depending on how long the cold front and an area of
low pressure linger. Breezy conditions likely each afternoon through
Tuesday.
&&
.MARINE...
Tonight: Tropical Depression One currently east of Florida will
slowly lift northward through tonight. Marine users should
refer to the latest NHC advisory regarding details of this
system. Northeast winds will be 10 to 15 knots much of the
night, before increasing to a solid 15 kt towards daybreak. Wind
speeds in waters beyond 20 nm will be a bit higher, peaking in
the 15-20 kt range. Elevated seas will maintain a Small Craft
Advisory in the outer Georgia waters, with the advisory
expanding to include the Charleston county waters at 2 AM.
Sunday through Thursday: Moderate confidence this period. Low
pressure, likely a tropical or sub-tropical cyclone, is expected to
shift northward east of the local waters with the main impact being
increasing swells which will lead to slightly higher seas Sunday
before the low passes by to the northeast into Sunday night. Small
Craft Advisory conditions are expected for mainly the Charleston
County nearshore waters and offshore Georgia waters, but could be
needed for at least the rest of the SC waters Sunday into early
Sunday night. Additional marginal Small Craft Advisories may be
needed Monday into Tuesday ahead of a cold front for a portion of
the area.
Rip Currents: Swells from offshore low pressure will continue
to impact the waters into early next week leading to an enhanced
risk through at least Sunday, possibly even into Monday along
parts of the SC coast.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...None.
SC...None.
MARINE...Small Craft Advisory until 2 AM EDT Monday for AMZ374.
Small Craft Advisory from 2 AM Sunday to midnight EDT Sunday
night for AMZ350.
&&
$$
Area Forecast Discussion
National Weather Service Grand Rapids MI
812 PM EDT Sat May 16 2020
LATEST UPDATE...
Update
.SYNOPSIS...
Issued at 322 PM EDT Sat May 16 2020
- Heavy rain and flooding threat Sunday and Sunday night
- Trend toward more unsettled weather Monday and Tuesday
- Uncertainty from mid to late week
&&
.UPDATE...
Issued at 811 PM EDT Sat May 16 2020
I have updated our zone forecast to increase the wind Sunday into
Sunday night. I have noted that the NAM is forecasting 20 knot
winds at 10000 mb at 8 pm Sunday. I can honestly say that when
the 1000 mb wind at GRR on the NAM as observed at 20 knots we have
just about always needed to have a wind advisory (I have at least
20 years of data to back that up). Looking at the ECMWF, the
HRRR, HREF all of them are showing median wind gusts Sunday
evening in the 40 to 50 mph range north of I-96. My update now has
wind gusts to 40 mph and for now that should be fine. We may need
a wind advisory for this system on top of all the other headlines
we now have out.
&&
.DISCUSSION...(This evening through next Saturday)
Issued at 322 PM EDT Sat May 16 2020
-- Heavy rain and flooding threat Sunday and Sunday night --
As mentioned in the previous update, an Areal Flood Watch has been
issued for the entire area for Sunday through Monday morning.
The trend over the last 24 hours with this system has been for
heavier rain totals spread across the entire area (vs. just the
south), and for convection to be a little further south, keeping any
small severe chances limited to the very southern portion of the
area, and likely just south of the area.
It is looking like we will see the brunt of the two main forcing
mechanisms with this rain event over the region. We will see the
rain move overhead early Sunday morning and into Sunday with the
initial push of warm and rich moisture ahead of this developing
system with the 40 knot low level jet nosing in.
(I have been
forecasting for 40+ year so that is a long time)
The sfc low then translates what looks to be just south of the area
by Sunday evening. Immediately ahead of this low is when we look to
have the best chance of thunder over the southern portion of the
area. This low track is a tad further south than expected yesterday.
Right now, it seems that with the low staying just south of the
area, sfc based instability would also stay just south of the area,
and thus the best chance of severe weather Sunday afternoon and
evening. The thing to watch with this, is if the low and front comes
a little further north than expected. Then a better severe threat
would sneak into the southern counties. The convective nature of the
rain will allow for some decent local bands of rainfall.
-- Trend toward more unsettled weather Monday and Tuesday --
The sfc low and low level moisture feed were expected to clear the
area to the east early Monday morning. The latest trend now is for
the upper low to close off a little sooner, and keep the surface low
and moisture feed nearby into Monday. In addition, we will see the
band of rain associated with the deformation of the upper low hold
in, and affect the northern part of the area as the upper low
becomes nearly stationary. This is why the heavier amounts are now
also expected across the north. Right now, this is forecast to move
out by Tuesday morning. The heavier rains would diminish to more
scattered showers for Tuesday with the upper low nearby. The
movement of upper lows are difficult to forecast, and the trend has
been for this one to linger longer over the past couple of days, so
this is still subject to change.
-- Uncertainty from mid to late week --
It looks like a highly amplified pattern upstream over the western
and central portions of North America should help to push this low
out of the area, at least temporarily by Wednesday. Another strong
upper low coming on to the Pacific Coast will push the ridge over
the area, and the upper low south. This is not certain, and the
upper low could easily rotate back to the north later in the week.
This would bring back shower chances, and keep the area a bit
cooler, instead of being warmer under the possible upper ridge.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 745 PM EDT Sat May 16 2020
Expect IFR conditions with very strong winds by Sunday afternoon
at our TAF sites.
Currently at 2330z VFR conditions prevail at all of our TAF sites.
There is an area of VFR cig clouds over central lower Michigan
that look like they will drift to the west and mix out by 03z. I
did not to much with them in the TAF since I expected VFR to
prevail.
The main issue is the storm moving into our TAF sites Sunday,
during the daylight hours. The system has slowed down in the
models as to how fast it moves through the area. It looks to bring
a prolonged period of rain, heavy at times, and strong east winds
by mid afternoon Sunday. Expect showers to move in by mid morning
from the south and southwest spreading across the area by late
morning. Isolated thunderstorms are more than possible south of
I-96 in the afternoon and evening. I put VCTS for that in the
southern and eastern TAF sites.
Another aspect to this storm is very strong east winds. The ECMWF
and our high resolution models like the HREF as well as the HRRR
and NAMNEST show winds sustaining 20 to 25 knots with gusts in the
40 knot range west of Lansing and near and north of I-96. Wind is
likely to be a real issue with this storm Sunday afternoon.
&&
.MARINE...
Issued at 322 PM EDT Sat May 16 2020
We have a couple of marine related hazards expected for Sunday and
Sunday night. The first will be winds picking up with the incoming
system. The other concern will be additional lakeshore flooding and
beach erosion also for Sunday and Sunday night. We will be issuing
headlines for each of these with this afternoon`s package.
Winds will increase late tonight, and more so on Sunday. We are
looking at a solid Small Craft Advisory event for our nearshore
waters. The gale conditions and higher waves will be over mid-lake
due to the offshore component of the wind.
The other hazard expected is the lakeshore flooding and beach
erosion. Even with the expected offshore winds, lakeshore flooding
and erosion looks likely. This is the result of strong easterly
winds over the region pushing water from Lake Huron, to Lake
Michigan through the Straits of Mackinac. This will result in a
increase of water levels over the already record high levels. This
will affect the rivers near Lake Michigan, with levels rising to
over docks, nearby roads, and approaching buildings near the rivers
and inland lakes, immediately adjacent to Lake Michigan. The worst
conditions are expected over the southern lakeshore, where the water
will pile up the most.
&&
.HYDROLOGY...
Issued at 1224 PM EDT Sat May 16 2020
(I have been
forecasting for 40+ year so that is a long time)
We are looking at an increased risk for potential areal flooding,
and flooding on area rivers as a result of the rainfall that is
expected from late tonight through Monday morning.
While the details have to be worked out yet with exact placement
of heaviest rain, it appears that 1 to 2 inches of rain should
fall at most locations through this period. This is going to start
to cause issues over the south where the ground is already
quite saturated from the Wed night/Thu rains.
Also, the Grand and Kalamazoo River basins will be most affected.
Right now, contingency forecasts with up to 2 inches of rain have
many sites on the Kalamazoo and Grand River basins approaching
flood stage, with a couple of sites exceeding flood stage
(Comstock Park and Robinson Twp).
If we start to see amounts approaching 3+ inches of rainfall, much
more significant impacts will be felt with many sites going above
flood stage, and even some sites on the downstream portions of the
Muskegon River. Some locations on the Grand would be looking at
Moderate flooding with 3 inches of rain. We will continue to monitor
the latest trends.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...Lakeshore Flood Warning from 5 PM Sunday to 8 PM EDT Monday for
MIZ056-064-071.
Flood Watch from 8 AM EDT Sunday through Monday morning for
MIZ037>040-043>046-050>052-056>059-064>067-071>074.
Lakeshore Flood Advisory from 5 PM Sunday to 8 PM EDT Monday for
MIZ037-043-050.
LM...Small Craft Advisory from 6 AM Sunday to 2 AM EDT Monday for
LMZ844>849.
&&
$$
UPDATE...WDM
SYNOPSIS...NJJ
DISCUSSION...NJJ
AVIATION...WDM
HYDROLOGY...NJJ
MARINE...NJJ
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
956 PM CDT Sat May 16 2020
.UPDATE...
Issued at 956 PM CDT Sat May 16 2020
Have issued a flash flood watch through mid morning on Sunday for
the potential for additional heavy rainfall tonight.
Showers and a few thunderstorms continue to move northeast across
the area late this evening. Latest surface analysis is showing a
surface front stalled across the region with the water vapor
analysis showing a upper trough over the Central Plains. Latest
runs of the RAP/NAM are showing increasing low level moisture
convergence increasing and becoming aligned beneath this weak
ascent in the watch area late tonight. RAP soundings are very
favorable for heavy rainfall given PWATS near 1.7" and deep warm
cloud layers. Expect additional showers and scattered
thunderstorms to move across eastern Missouri and southwest
Illinois overnight into Sunday morning with some areas receive
1-2" of rainfall with locally heavier amounts. These amounts
falling on already saturated ground will likely result in flash
flooding.
Britt
&&
.SHORT TERM... (Through Late Sunday Afternoon)
Issued at 314 PM CDT Sat May 16 2020
Unsettled weather will continue through the weekend as an upper
level trough passes through the central CONUS. Two features of note
were analyzed within the broad upper trough this afternoon; a weak
negatively tilted shortwave extending from the central Plains into
Louisiana and a closed low moving ESE through the northern
Plains. A surface low was analyzed in the vicinity of the
Arklatex, with a warm front extending north and east into
southern SE MO and southern IL.
Several areas of showers and storms have developed in the mid-
Mississippi Valley along the elevated portion of the front. The most
vigorous convection is along and east of the Mississippi River,
where limited clouds have allowed for MUCAPE to build to around
2,000 J/kg. Effective bulk shear in this area is rather limited,
so individual updrafts have been fairly short-lived. Nonetheless,
at least one storm has pushed up to near severe levels and I
couldn`t rule out another storm or two following suit.
These storms have also been very efficient rainfall producers.
With PWs in the upper quartile of seasonal climatology and a
tendency for new updrafts to develop in the immediate wake of
dying convection, we`ve had reports of 1-1.5" per hour beneath the
heaviest cores, resulting in flash flooding in a few areas.
Fortunately there does not appear to be any sort of anchoring
feature to focus these storms over a particular area, so I think
additional flash flooding will be rather isolated.
As we move into the evening hours, storm coverage will wane with
the instability. Meanwhile, the previously mentioned negatively-
tilted wave will continue to the ENE, drawing the surface low and
associated warm front north into the Mid-Mississippi Valley around
midnight. The surface low will then deepen and push to our NE
tomorrow morning as it interacts with the northern upper low,
before eventually dragging a cold front through the area tomorrow
afternoon.
As larger scale forcing intensifies in the early morning hours, CAMs
are in good agreement increasing precip coverage after roughly
midnight. Scattered to widespread storms are then expected to
continue until the cold front sweeps through the area during the day
tomorrow. Instability is expected to build to around 1,000 J/kg
ahead of the ahead of the front tomorrow, supporting yet another
round of thunderstorms. Much like today, effective bulk shear
looks fairly limited, with SREF guidance showing a less than 50
percent chance of us topping even 30 kts. Nonetheless this
CAPE/shear parameter space coupled with the frontal forcing would
support a limited severe threat in southern Illinois tomorrow
afternoon.
BSH
.LONG TERM... (Monday through Next Saturday)
Issued at 427 PM CDT Sat May 16 2020
Large scale omega block still on track to take hold at the
beginning of the week while a closed low sits and spins over the
eastern third of the CONUS. Surface ridging will develop beneath
the block, kicking off an extended period of quiet weather in the
mid-Mississippi Valley. Our proximity to the eastern CONUS low
will keep things on the cloudy and cool side for the early portion
of the week. The deep moisture associated with that low will wane
as we move through the week, resulting in less overcast to broken
stratus and more broken to scattered cu. This will allow
temperatures to gradually build through the week. Some guidance is
showing a chance for diurnal showers toward the end of the week,
through the signal for this is quite weak, so have omitted it from
the forecast at this point.
BSH
&&
.AVIATION... (For the 00z TAFs through 00z Sunday Evening)
Issued at 611 PM CDT Sat May 16 2020
Showers and storms across the region will continue to decrease in
intensity and coverage this evening before picking back up around
06z as low pressure moves through the region. I think we`ll only
see isolated to perhaps scattered thunder in the overnight hours,
so have left thunder out of the TAFs until storms become more
likely after sunrise. Scattered to widespread showers and storms
will then persist until a cold front moves through the region in
the afternoon, ushering the precip out of the area. Given
questions around exact timing and coverage of tomorrow`s storms,
have just gone with VCTS and will update as details become more
clear.
Guidance in good agreement showing cigs quickly falling in the
early morning hours as ample low level moisture moves into the
region with the previously mentioned low. I`m not very confident
on exactly how low cigs will drop, but at this point much of the
guidance has all terminals dropping below 1,000 ft, so ended up
going IFR at all terminals.
BSH
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flash Flood Watch through Sunday morning for Crawford MO-
Franklin MO-Iron MO-Jefferson MO-Lincoln MO-Madison MO-
Reynolds MO-Saint Charles MO-Saint Francois MO-Saint Louis
City MO-Saint Louis MO-Sainte Genevieve MO-Warren MO-
Washington MO.
IL...Flash Flood Watch through Sunday morning for Bond IL-Calhoun IL-
Clinton IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL-
Madison IL-Marion IL-Monroe IL-Montgomery IL-Randolph IL-
Saint Clair IL-Washington IL.
&&
$$
WFO LSX
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
714 PM CDT Sat May 16 2020
.SHORT TERM...(This evening through Sunday night)
Issued at 228 PM CDT Sat May 16 2020
The overall forecast scenario hasn`t changed much, but a
persistent dry easterly flow is working to delay the arrival of
precipitation across much of the area. So, slowed progression of
PoPs a bit in line with HRRR and other CAMs. That being said, we
should still see precipitation overspread the area from late
afternoon through the evening hours. Visible imagery shows the
effect of dry air, with plenty of sunshine filtering through high
clouds from southeast Minnesota into west central Wisconsin this
afternoon. However, the upper shortwave trough is evident on water
vapor imagery across the northern high Plains, and we`ll see the
precipitation spread eastward as this feature moves south and east
through tonight. A baroclinic wave can be seen in the long wave
infrared imagery, from eastern Nebraska through northern Minnesota
and surface low development is taking place near its inflection
point near the Nebraska/Iowa border. This low will deepen some as
it lifts northeast tonight, with precipitation maximizing across
our area near the inverted trough that will extend northward from
it. It still looks like we`ll have some elevated instability in
place across the southern/eastern portion of the area, so
maintained a thunder chance. Precipitation amounts will be
heaviest where convection enhances things, but widespread amounts
in excess of an inch still appear likely. The activity will slowly
move out from west to east late Sunday afternoon and Sunday
evening.
.LONG TERM...(Monday through Saturday)
Issued at 228 PM CDT Sat May 16 2020
The large scale pattern looks to amplify in the wake of this
weekend`s system, with ridging developing across the central and
eastern US as a deep upper trough sets up over the west. Our
current system looks to cutoff beneath the upper ridge and loiter
across the Ohio and Tennessee valleys for much of the week. With
the upper ridging, we`ll see a prolonged period of dry weather
from Monday through Thursday, with temperatures warming through
the 70s to around 80 by Wednesday and Thursday. After that we`ll
start to see chances for showers and thunderstorms work into the
region from the west as impulses are ejected from the western
trough. At this point, have low PoPs for much of the period from
Thursday night through Saturday, but given the amplified pattern
would expect a somewhat slower progression of PoPs eastward, so as
we get a bit closer in time wouldn`t be surprised to see dry
weather persist a bit longer, and PoPs be more focused from late
Friday into the weekend.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 714 PM CDT Sat May 16 2020
Conditions were still VFR in many locations early this evening,
with MVFR ceilings or visibilities in just a few spots over
central into southwest MN. But this will be changing to
widespread MVFR as rain persists and intensifies later this
evening and overnight over much of southern MN and spreads more
into west central WI. Main question revolves around whether IFR
will develop, and it probably will Sunday morning from south
central MN into west central WI where the heavier rain persists
the longest. IFR is possible to develop elsewhere, and this is
something that will be watched closely. Finally, northeast winds
will strengthen somewhat tonight as surface low moving across Iowa
intensifies a bit. Gusts over 30 knots may occur over south
central MN into WI.
KMSP...
Main issue will be northeast winds. Ridge to our north will weaken
and surface low near Omaha at 00Z will move east, allowing winds
to shift from the current nne to more ne. Winds will also
intensify somewhat as low moves east due to a tighter gradient
later tonight and Sunday morning. Therefore gusts will likely be
25-30 knots Sunday morning, with sustained of 15-20 knots.
MVFR conditions will arrive with the heavier rain late tonight and
Sunday morning. There is some chance for IFR ceilings and
visibilities in the heaviest rain, and if that happens, it would
most likely occur in the 12Z-18Z time frame. But not confident
enough to include that right now.
/OUTLOOK FOR KMSP/
MON...VFR. Wind NE 10-25 kts.
TUE...VFR. Wind SE 5-10 kts.
WED...VFR. Wind S 5-15 kts.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
&&
$$
SHORT TERM...
LONG TERM...
AVIATION...TDK
Area Forecast Discussion
National Weather Service Marquette MI
715 PM EDT Sat May 16 2020
.SHORT TERM...(This evening through Sunday)
Issued at 418 PM EDT SAT MAY 16 2020
WV imagery and RAP analysis indicated a mainly zonal pattern through
the northern CONUS with a vigorous upstream shortwave trough over
Southwest South Dakota. At the surface, high pressure extended from
James Bay and northern Ontario into the northern Great Lakes
resulting in easterly winds over Upper Michigan along with local
lake breeze components. Mid level fgen and isentropic lift
associated with upper level div from the right entrance of a 300
jet stream through northern Ontario supported a band of light rain
and sprinkles over eastern MN. However, with the dry air in place
over Upper Michigan, mainly just virga into northwest WI.
Tonight, since the strongest 700-300 qvector conv, isentropic lift
and moisture advection ahead of the shrtwv remain well to the
southwest through se MN into wrn WI, expect little if any pcpn into
Upper Michigan. Increasing and thickening clouds will keep min temps
in the lower 40s.
Sunday, the models have trended significantly drier over most of
Upper Michigan as the fgen/def supported heavier rain and
strongest isentropic lift and moisture inflow will remain over
WI. So, dry weather is expected across the north half. However,
rainfall amounts along south of US-2 could still reach 0.25 inch
with amounts over 0.50 inch near MNM. With less rain over the
area, highs should be able to reach the mid 50s with readings even
to around 60 east. Readings near lake Superior where brisk
northeast winds prevail will keep temps in the 40s.
.LONG TERM...(Sunday night through Saturday)
Issued at 342 PM EDT SAT MAY 16 2020
Overall confidence in the forecast as we head through much of next
week is not high as we see a number of blocking features (cutoff
low, weak omega block, rex block...you name it, it seems to make an
appearance) progged to set up across the CONUS. This has cause some
fairly big changes in expectations for Monday, but also has
introduced some added uncertainty in how temperatures will play out
later this week. While slightly above-normal temperatures still look
to develop this week, whether we see any locations reach that 80
degree mark looks less clear.
Sunday night/Monday, shortwave energy tracking east across southern
Lake Michigan will gradually slow and keep Upper Michigan on the
northern edge of theta-e advection and deeper moisture transport
wrapping around the system. There is still some uncertainty in how
far north precipitation will be, but overall the best chance for
rain during this time period will be across the south-central. Still
doesn`t look like any instability will make it this far north, so no
mentions of thunder. The combination of the main surface low
tracking south and the Hudson Bay High starting to nudge in from the
north will create an enhanced pressure gradient, mostly across
northern parts of Lake Michigan allowing gusty east-northeast winds
to develop and persist. Models seem to be in good agreement with
these stronger winds impacting the Bay of Green Bay, but waves
heights right now look to fall right along the 5-6 foot threshold.
Thus have opted to continue to messaging the minor lakeshore
flooding concerns in the HWO. If winds/waves look to come in higher,
an advisory may be needed for Menominee County. Monday afternoon,
the above mentioned area of high pressure will gradually introduce
increasing subsidence and much drier air, favoring a dry day across
much of western and north-central Upper Michigan and a drying trend
across the south-central. Will need to keep an eye on RHs and winds
across the west half Monday afternoon for some potential fire
weather concerns, especially if no precipitation develops over the
next 24-hours makes it that far north and west.
Tuesday through Thursday, upper-level ridging builds across the
central CONUS and up in the Upper Mississippi Valley, with the
shortwave discussed above becoming cutoff and parking over
Kentucky/Tennessee. This will favor easterly flow dominating the low
to mid levels, gradually becoming southerly by mid-late week. This
pattern will still favor warm air advection moving into the region,
but not as warm as yesterday`s southwest flow showed. The forecast
could end up seeing more clouds added in as well, with a few pushes
of moisture under the east to south flow. Not expecting any
precipitation through as the western extend of high pressure
continues to impact the Upper Peninsula. RHs could end up being
lower than currently forecast later on in the week, but given the
pattern and the above mentions of low-level moisture looking to
return opted to leave the blend as is for now until confidence in
the pattern grows.
Friday into next weekend, a kicker wave looks to dig south across
the Pacific Northwest disrupting the cutoff low parked over the
western CONUS. This will help break down upper-level ridging, across
the central CONUS, but it does look like the upper-level pattern
will remain stacked up across the central and eastern CONUS, with
hints of a rex block developing. Based on the current model
depiction of where this next blocking pattern sets up, this looks to
leave us mostly dry. NBM did paint some slight/chance PoPs
Friday/Saturday, but right now confidence is very low in regards to
that panning out.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 714 PM EDT SAT MAY 16 2020
Dry air will likely persist in the low-levels thru Sun. Thus, VFR
conditions are expected at KIWD/KCMX/KSAW thru this fcst period. A
low pres system will be tracking e, well s of Upper MI. Although
bulk of associated rain will remain well s, some -shra may pass near
KIWD. Otherwise, main affect will be thickening mid-level clouds at
all terminals.
&&
.MARINE...(For the 4 PM Lake Superior forecast issuance)
Issued at 418 PM EDT SAT MAY 16 2020
Low pressure passing by well to the south of Lake Superior is
expected to boost northeast winds to around 20 kts Sunday with
stronger winds (25 kts) again possible in the western arm.
Otherwise, winds of 15 kts or less are expected through at least the
middle of next week.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
Upper Michigan...
None.
Lake Superior...
None.
Lake Michigan...
None.
&&
$$
SHORT TERM...JLB
LONG TERM...Ritzman
AVIATION...Rolfson
MARINE...JLB
Area Forecast Discussion
National Weather Service San Francisco Bay Area
857 PM PDT Sat May 16 2020
.SYNOPSIS...Rain showers will spread from north to south across
much of our forecast area from Saturday evening through Sunday
morning. Shower activity will likely decrease Sunday afternoon,
before another round of widespread shower activity develops Sunday
night and continues into Monday. There is also a slight chance of
thunderstorms on Monday. Drier conditions will develop Tuesday,
although a few showers may linger. High pressure builds Wednesday
into the Memorial Day weekend, with dry and seasonable
temperatures expected.
&&
.DISCUSSION...As of 8:55 PM PDT Saturday...Dry weather prevailed
across our area for most of today as precipitation with the
incoming system did not arrive on the North Bay Coast until early
evening. Increasing clouds in the North Bay today resulted in
slightly cooler temperatures there. Plenty of sun elsewhere
allowed for warming most everywhere else, with the most robust
warming occurring over interior Monterey and San Benito Counties,
where a few locations, such as Pinnacles National Park, warmed
into the upper 80s this afternoon.
Current satellite and radar data shows a cold frontal boundary
spreading showers across northern California. The boundary has
thus far been pressing very slowly to the south. Rain showers
began in northwest Sonoma County at about 5 pm and by 8 pm showers
had finally reach northern Marin County. Rainfall so far has been
light, with amounts less than a tenth of an inch in Sonoma
County. The greatest rain total thus far is 0.16" in Venado.
Short-term model data from the 00Z NAM and 00Z HRRR indicate
showers will continue to spread across the North Bay through
about midnight and then develop from San Francisco southward late
tonight and Sunday morning. While the 00Z NAM forecasts the
frontal boundary and associated precipitation to become steadily
more fragmented with time as the boundary moves south, the 00Z
HRRR forecasts a couple of bursts of heavier and more widespread
shower activity developing across the central and southern SF Bay
Area on Sunday morning and over the Santa Cruz, southern Diablo,
and Santa Lucia Mountain Ranges on Sunday afternoon. Precipitation
associated with the frontal boundary tonight and Sunday will be
most significant in the coastal hills due to orographic
enhancement, while lower elevation locations, including most urban
areas, will probably see only light amounts, or none at all in
rain-shadowed interior valleys like the Santa Clara Valley.
Both the NAM and GFS forecast decreasing shower activity Sunday
afternoon as the front stalls and dissipates over the southern
portion of our area. Shower activity will then increase Sunday
evening through Sunday night as the cold core of the upper low
approaches the northern California Coast. Scattered showers will
continue through Monday when isolated thunderstorms are possible
as 500 mb temperatures drop to an unseasonably cool -25 deg C.
Inland temperatures from Sunday through Tuesday are forecast to be
as much as ten degrees cooler than seasonal averages. Coastal
temps will remain near normal or be only slightly cooler than
normal.
Shower activity is expected to decrease Monday night and mostly
end by Tuesday as the upper trough axis shifts to our east.
However, isolated showers may linger into Tuesday. Dry weather
should return to nearly all areas by Wednesday, but inland
temperatures will remain cooler than normal.
Forecast rain totals through early next week are expected to be a
tenth to a half inch in most urban and lower elevation locations,
except up to an inch in the North Bay Valleys, and less than a
tenth of an inch in southern rain-shadowed valleys. In the hills,
forecast rain totals generally range from 0.5 to 1.5 inches, with
locally up to 2 inches possible along southwest-facing coastal
slopes.
Modest warming is forecast for Thursday as a weak shortwave ridge
builds temporarily over California. A trough over the Pac NW is
forecast to drop into northeast CA on Friday, which will
temporarily halt any warming trend. Precipitation with that trough
is forecast to stay to our northeast. Although details vary
between the longer range models, the general idea for the Memorial
Day Weekend is for dry weather along with a gradual warming trend.
&&
.AVIATION...as of 4:50 PM PDT Saturday...Frontal system over the
northern California coast is spreading mid level clouds into the
North Bay this afternoon. Models show rain showers into the North
Bay after 03Z spreading into the SFO Bay Area during the night
with cigs gradually lowering into MVFR range. Front will weaken
and slow down as it moves through the SFO Bay Area so rain will be
mostly light and intermittent through Sunday morning. Approaching
upper level trough will push the front into the MRY Bay Area
Sunday afternoon with improving conditions in the SFO Bay Area.
West to southwest winds 15 kt gusting to 20 kt decreasing and
switching to southerly after midnight.
Vicinity of KSFO...VFR with gradually lowering cigs tonight. Bases
lowering to 5000 ft after 03Z and 2500 ft after 06Z. Occasional
light rain begins after 09Z and continues through Sunday morning.
Onshore winds this afternoon around 15 kt will switch to
southerly after 06Z.
SFO Bridge Approach...Similar to KSFO.
Monterey Bay Terminals...A few low clouds are lingering along the
immediate coast. This is expected to expand over the MRY Bay Area
tonight. Scattered clouds at MRY and SNS after 03Z becoming MVFR
cigs after 06Z. Rain showers will remain north of the area through
Sunday morning before finally moving in Sunday afternoon. Onshore
winds decreasing and switching to southerly after 06Z.
&&
.MARINE...As of 8:45 PM PDT Saturday...A frontal system will
bring light southerly winds to the area tonight and Sunday. Winds
will increase over the southern waters and Monterey Bay Sunday as
the passing front enhances. Winds will switch back to west to
northwest on Monday. Mixed seas will persist with a longer period
west to northwest swell arriving Sunday along with a longer period
southwest swell.
&&
.MTR WATCHES/WARNINGS/ADVISORIES...
.Tngt...NONE.
&&
$$
PUBLIC FORECAST: Dykema
AVIATION: W Pi
MARINE: W Pi
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Area Forecast Discussion
National Weather Service Paducah KY
536 PM CDT Sat May 16 2020
.UPDATE...
Issued at 533 PM CDT Sat May 16 2020
Updated Aviation discussion for 00Z TAF Issuance.
&&
.SHORT TERM...(Tonight through Monday night)
Issued at 353 PM CDT Sat May 16 2020
The 18Z HRRR has a good handle on the convective evolution through
tonight. Current convection will continue its northward movement
out of the area in the early evening. Haven`t seen any gusts over
30 mph so far and would not expect much more. From late evening on
through Sunday morning the focus shift over southeast Missouri
and southern Illinois. Mainly showers are expected, but a few
thunderstorms cannot be ruled out.
The cold front will move eastward across the region Sunday
afternoon and evening, and this should provide a focus for
convection. Clouds will likely limit instability, and the better
shear will likely lag behind the front, so organized severe
weather is not likely. That said, a few stronger cells with gusty
winds and small hail cannot be ruled out.
The convection should be east of the area by 12Z Monday, but as
the upper low slides south toward the area, scattered mainly light
showers will be possible at least in the east through the day, and
possibly into Monday night.
.LONG TERM...(Tuesday through Saturday)
Issued at 353 PM CDT Sat May 16 2020
Upper level low is forecast to be over Indiana at the start of the
period. Models typically have a difficult time with these, so
confidence level is low until it finally exits the area well to
the east on Friday.
In general, the GFS and GEFS keep the upper low over east
Kentucky/Tennessee during the midweek period. The ECMWF meanders the
low around and even puts it over west Nashville at times.
The question is then how far west will the showers be Tuesday,
Wednesday, and Thursday. Deep moisture is forecast to extend to at
least the MS river through the period.
Right now going with the best chance for precipitation on Tuesday
and Wednesday in the east and will keep it dry Thursday and Friday.
Looks like a build up of clouds each day with dissipation during the
evening.
On Friday a small ridge builds over the lower Ohio Valley. There are
some indications this will be transient and we may be on the west
side of the ridge Saturday which would allow for a small chance of
storms for the start of the Memorial Day Weekend.
&&
.AVIATION...
Issued at 533 PM CDT Sat May 16 2020
Scattered showers/storms should mostly diminish near term with
the setting sun, with variable VFR clouds offering scattered to
broken bases the first half of the night. As the Low(s) drift
closer with time, we`ll see lowering bases again, and another
uptick in showers/coverage. This will begin late tonight but
be most active tmrw with diurnal assistance, with widespread
restrictions to both cigs/vsbys in showers and storms.
&&
.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&
$$
...Update to aviation forecast discussion...
.SHORT TERM...(This evening through Sunday)
Issued at 243 PM CDT Sat May 16 2020
Small chances for showers or a storm or two this afternoon before a
cold front pushes through bringing very pleasant conditions to the
area.
The upper pattern as sampled by the 12Z RAOB network shows a mid to
upper level trough over the deep south which is in response to the
MCV over the deep south from yesterday and overnight periods.
Meanwhile, the northern stream trough - in the process of closing
off - from the northern Plains has translated into the northern
Plains with the southern flank digging into Nebraska. Mid level
speed max and upper jet lag behind currently streaming out of WY into
portions of western NE. A sharp mid level ridge resides over to the
west over the intermountain west. The surface baroclinic zone has
been sharpening through the day with the cold frontal portion now
stretched from south central NE into north central portions of KS
then back into the DDC area.
This afternoon have had to lower high temps a bit due to persistent
mid to high level clouds streaming from south to north into the area
in response to the overall sharp meridional flow helping to draw
convective debris over the area. Where clearing on the backside of
these clouds has taken place, temperatures through portions of north
central KS has been rising and with mid 50s dewpoints, MLCAPE across
the area has risen to around 500 J/kg. Per SPC mesoanalysis, the
shear is below 25kts through the 0-6km layer. With overall minimal
shear and instability as well as a fairly weak cold front with weak
overall surface convergence moving into the area, it makes sense
that any showers that have tried to develop have quickly fell apart.
Most short-term CAMs have continued to trend down the threat of
storms developing with the most recent run of the HRRR backing off
even more from this mornings runs. I`ve tried to lower POPs also as
a result keeping in mind that there may be some opportunity into
this evening for some showers to develop along the cold front.
However, these POPs may still be a bit high over the area. In
short, the confidence in showers or storms developing on any
meaningful scale is low.
Into the overnight, the upper low in the northern Plains will deepen
and dig into the upper MS Valley region as the cold front tracks
through and east of the area. some wrap around stratus may linger
into part of Sunday. But, overall a breezy but pleasant day is in
store with high temperatures topping out in the low 70s.
.LONG TERM...(Sunday night through Saturday)
Issued at 243 PM CDT Sat May 16 2020
Into next week, mostly dry and pleasant weather will reign across
the central Plains with a steep mid level ridge in place.
Temperatures rise a little more each day into the 80s by Wednesday.
Perhaps as soon as Thursday and into Friday some shower and storm
chances return to the area as the ridge breaks down. A more full
return to southwest flow aloft appears to be shaping up into next
weekend with storm chances increasing again. Could see some near 90
temps if strong WAA can be established for a few days.
&&
.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 631 PM CDT Sat May 16 2020
Winds gradually become west and northwest through 04Z as a weak
frontal boundary moves through. Chances have diminished for tsra
and may only see a brief shower through 04Z. Some lower mvfr cigs
may move south into the terminals after 10Z or so as the mid
level low tracks into Missouri. Cigs are forecast to recover to
vfr by 17Z. Winds increase from the northwest to near 15 kts with
gusts to 24 kts after 15Z.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...Drake
LONG TERM...Drake
AVIATION...53