Forecast Discussions mentioning any of
"HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/13/21
Area Forecast Discussion
National Weather Service La Crosse WI
1020 PM CDT Mon Apr 12 2021
.SHORT TERM...(This evening through Tuesday)
Issued at 205 PM CDT Mon Apr 12 2021
An upper low spiraling over Minnesota through Tuesday will continue
to bring occasional shower chances as pieces of energy rotate around
it. This afternoon, we`ve already seen showers blossom across north-
central Wisconsin where not only is upper forcing strongest, but a
little frontogenesis and diurnal instability is also present.
Earlier runs of the RAP had suggested up to 200 J/kg of CAPE in this
area, which might have been enough for an isolated rumble of
thunder, but so far things have stayed tame. Elsewhere, mainly dry
conditions are expected this afternoon with perhaps an isolated
shower here and there.
Overnight, would expect isolated showers at times, especially
across our northwest closer to the upper low. Even with clouds
tonight, an additional push of cold air advection should allow
temperatures to drop into the 30s. We could start to see some
snowflakes mixing in late tonight and on Tuesday, as that
reinforcing shot of cold air drops 925 mb temperatures into the 0C
to -3C range for the day. Have lowered highs again for tomorrow
as a result, keeping things in the upper 30s to lower 40s. Some
guidance does show a few tenths of an inch of snowfall across the
area tomorrow, although with a warm ground, would expect most of
this to be on grassy/elevated surfaces where it occurs. With
surface low pressure hanging out just to our northwest, west winds
will once again be gusty (in the 25 to 30 mph range), making it
feel like a raw April day.
.LONG TERM...(Tuesday night through Monday)
Issued at 205 PM CDT Mon Apr 12 2021
Through Wednesday night, an upper level low will slowly move east
across the Upper Mississippi River Valley. This system will
provide a chance of showers mainly along and north of Interstate
90. Temperatures will be cold enough aloft for scattered snow
showers on Tuesday night and Wednesday morning. Little snowfall is
expected.
With mostly cloudy skies and 850 mb temperatures around -6C, NBM
high temperatures looked too warm on Wednesday. This was likely
due to the unseasonably warm temperatures earlier in the month. As
a result, lowered them down to the 25th NBM percentile.
More seasonable temperatures return for Friday and Saturday and
then another colder-than-normal air mass returns for Sunday and
Monday. How much cooler is still uncertain due to a large spread
in the temperature guidance.
Currently have the forecast dry from Saturday through Monday.
However, may have to add some small precipitation chances
depending on the track of yet another upper level low through the
region.
&&
.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1020 PM CDT Mon Apr 12 2021
Clouds with the occasional shower will be the rule through Wed as
the area remains under the influence of multiple upper level lows.
Cigs: With the TAF sites mostly on the southern flanks of the main
cloud mass, will bounce between VFR/MVFR cigs tonight/Tue, although
low VFR more favored at this time. MVFR should become more
widespread Tue night.
WX/vsby: low level instability and the upper level trough should
result in scattered/numerous afternoon showers Tue. Temps will
support rain and snow, although no snow accum is expected.
Winds: holding west and generally a few ticks above 10 kts. Some
gustiness also expected - in the low/mid 20s. However, enhanced
gusts (30kts) will be possible/probable with any shower Tue
afternoon.
&&
.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&
$$
SHORT TERM...Lee
LONG TERM...Boyne
AVIATION....Rieck
East Central Florida Forecast Discussion
National Weather Service Melbourne FL
823 PM EDT Mon Apr 12 2021
.DISCUSSION...
Overnight...Drier air with light NNW flow wl occur overnight after
the loss of the seabreeze. A cool night is expected with overnight
lows in the M-U50s for most but a few normally cooler spots could
see L50s. Barrier islands should realize L-M60s for mins. HRRR
suggests some patchy fog before and through daybreak across Lake
Okeechobee to Martin and Saint Lucie inland locations.
prev disc...
Tuesday...Weak high pressure continues overhead with weak
pressure gradient in place. Light early morning winds becoming
NNE/NE/ENE in the late morning and afternoon with speeds mainly
light across the interior and perhaps 10-15 mph along the
Space/Treasure coasts. After a cool start to the morning, temps
will quickly warm into the U80s over the interior and L80s at the
coast.
Tuesday night-Thursday..High pressure will continue to sit over
the southeast through Thursday morning with a weak upper-level
ridge stretching into the Northeast. Winds will become more
southerly on Wednesday and Thursday as high pressure moves
downstream with east-central Florida on the back side of high
pressure. This will allow dry conditions to continue, in addition
to warmer temperatures. Highs will reach the low-to-mid 80s along
the coast with warmer temperatures further inland with highs in
the upper 80s to low 90s. Slightly cooler temperatures are
expected north of I-4 on Thursday as clouds and precipitation move
in ahead of our next frontal system. Lows will drop down into the
upper 50s to mid 60s during the overnight hours.
The upper-level ridge will flatten by Thursday afternoon as an
upper-level trough digs southeast across eastern CONUS. This will
be the beginning of an unsettled and active weather pattern across
the southeast as a zonal upper-level longwave pattern sets up over
the country. The upper-level jet will set-up just north of east-
central Florida which will make things tricky as models appear to
be having a difficult time handling the pattern - producing
disagreement of where and when precipitation will occur. With
that said, there is some uncertainty with the forecast beyond
midweek.
Thursday afternoon-Sunday (modified previous)...Broad upper
troughing over the northern CONUS will keep a fast westerly flow
aloft across the area. This will allow a cold front to push into
the area on Thursday, but it should become parallel to the mean
flow and stall over south Florida. We`re getting into that time of
year when cold fronts have a harder time pushing cleanly through
the area. The front is forecast to remain nearly stationary across
north/central FL late week and into the weekend which should
produce unsettled weather conditions. Details remain uncertain due
to timing of ejecting southern stream impulses but have forecast
isolated to scattered showers each day from Thursday onward. At
this time, the best rain chances look to be across northern
sections on Thursday and areawide on Sunday but confidence
decreases the further out in time. Temperatures will largely
depend on how much cloud cover and precipitation we end up seeing.
Expect highs in the upper 70s to low 80s mainly north and west of
Cape Canaveral and highs in the low-to-upper 80s further south.
Lows are forecast to reach the upper 50s to upper 60s.
&&
.AVIATION...
VFR conditions through Tue.
&&
.MARINE...
Overnight-Tue...High pressure builds into the area tonight and on
Tue. Northerly winds may become variable for a bit in the evening,
eventually settling on an offshore (NW) component later in the night
due to drainage. NLY winds may gradually veer a bit more NERLY with
speeds 6-12 kts. Initial seas of around 2 ft near shore and 3-4 ft
offshore will subside to 1-2 ft near shore and 3 ft Gulf Stream by
around daybreak Tue morning.
&&
.FIRE WEATHER...
Tuesday...Dry air in place with high pressure overhead. Aftn RH
values will fall to 30-35pct for the interior and 40-45pct along the
coast. Winds will be light, increasing up to 15 mph along the coast
behind the sea breeze.
&&
.PRELIMINARY POINT TEMPS/POPS...
DAB 56 82 62 85 / 0 0 0 10
MCO 57 88 64 90 / 0 0 0 10
MLB 58 83 65 83 / 0 0 0 10
VRB 56 83 64 84 / 0 0 0 10
LEE 58 88 64 88 / 0 0 0 10
SFB 58 87 64 88 / 0 0 0 10
ORL 60 88 66 88 / 0 0 0 10
FPR 56 85 64 84 / 0 0 0 10
&&
.MLB WATCHES/WARNINGS/ADVISORIES...
FL...None.
AM...None.
&&
$$
JP/MW
Area Forecast Discussion
National Weather Service Mobile AL
1104 PM CDT Mon Apr 12 2021
.NEAR TERM /Now Through Wednesday/...Shortwave ridging aloft will
continue to build across the north central Gulf Coast region
tonight into Tuesday morning, resulting in continued mostly clear
and dry conditions across our area during this time. Surface high
pressure will shift eastward toward the FL Big Bend region and
adjacent eastern Gulf overnight into Tuesday, allowing for
continued light southerly flow across our area.
A zonal flow pattern aloft returns by Tuesday afternoon. Shortwave
impulses embedded within this flow regime will translate across
southern portions of LA/MS during the day Tuesday. Deep layer
moisture will become enhanced mainly to the west of our forecast
area across southern/southeast LA and southwestern MS, where
coverage of showers and thunderstorms are forecast to be most
numerous by Tuesday afternoon. However, precipitable water values
do improve to around 1.2-1.3" across portions of southeast MS by
the late afternoon hours as the shortwave impulses move over this
portion of the region. Scattered showers and storms could develop
and clip across parts of southeast MS, far southwest AL, and our
adjacent western Gulf zones during the afternoon and evening. We
will carry a chance (30-40%) of showers and a few thunderstorms
mainly along and to the southwest of a Richton, Lucedale, Dauphin
Island/Gulf Shores line late in the afternoon through the mid-
evening hours Tuesday. Forecast soundings indicate that instability
should be very weak and elevated across this portion of the
region, so severe weather is currently not anticipated. Highs
Tuesday are forecast to range in the lower 80s across southeast MS
and adjacent southwest AL where cloud cover gradually increases
through the day, while warmer temperatures in the mid to upper 80s
are expected into the interior northwest Florida panhandle and
adjacent south central AL. A few additional light rain showers or
possibly an isolated thunderstorm could develop across southeast
MS and adjacent southwest AL late Tuesday night, where moisture
and ascent increases slightly ahead of another shortwave trough
moving into LA and western MS. Patchy fog may otherwise develop
again in a few spots across southern portions of the area late
Tuesday night. Lows are forecast to range in the upper 50s to
lower 60s inland and in the mid 60s along the coast.
A more complex forecast unfolds on Wednesday. The slightly more
amplified shortwave trough over LA/western MS early Wednesday
morning is expected to translate eastward across our forecast area
late Wednesday morning into Wednesday afternoon. A surface cold
front will also be pushing southward into central portions of MS
and northwest AL through Wednesday afternoon. A moist S-SW surface
flow ahead of this boundary will advect increased moisture into
much of our CWA through the day Wednesday, with dewpoints rising
into the lower to mid 60s over all but perhaps interior south
central AL where dewpoints will be a bit lower in the mid to upper
50s. There is still some uncertainty on where the strongest ascent
will become focused across our forecast area during the day
Wednesday. The 12Z ECMWF, 00Z NAM, and 00Z WRF-ARW show rather
strong lift spreading across much of our CWA ahead of the approaching
front late Wednesday morning into Wednesday afternoon, while the
00Z GFS and HRRR extended runs suggest ascent will be more focused
across southeast MS and into southern portions of southwest AL
and the western FL panhandle, keeping lesser coverage over our
northeast zones. There is enough indication in multiple guidance
members to support high POPs across our entire CWA during the day
Wednesday with potential for an organized complex of showers and
thunderstorms to advance from northwest to southeast across our
region. With PWATs increasing to as high 1.6-1.8 inches and the
signal for increased ascent, this looks like a favorable set up
for heavy rainfall across portions of our CWA during the day
Wednesday. Rainfall amounts could exceed 2-3" in a short period of
time within the convective complex, which could result in
localized flash flooding Wednesday. There also remains some
variability in the guidance on the available amount of instability
Wednesday. There are indications that MLCAPE values between
800-1500 J/KG could advect into southern portions of our CWA
Wednesday afternoon, along with increased westerly low level flow,
which could bring potential for localized strong to severe storms
with localized damaging winds and hail and possibly a tornado.
This will be something to monitor closely over the next couple of
forecast periods. Highs Wednesday should otherwise range from 70-75
over northwestern portions of the area, to the upper 70s to lower
80s over our southeastern zones. /21
&&
.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&
$$
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Area Forecast Discussion
National Weather Service Tulsa OK
927 PM CDT Mon Apr 12 2021
.DISCUSSION...
Scattered showers and thunderstorms have developed this evening in the
vicinity of an elevated frontal zone. Storms remain ongoing as of mid
evening across west central Arkansas. Last few runs of the HRRR have
initialized quite poorly wrt to ongoing convection. However, this and
other CAM solutions indicate additional development later this evening
and overnight. That said, will keep pops going in the vicinity of the
elevated boundary overnight, with highest pops across NW AR.
Temperatures look reasonable for the overnight period, so will leave
those as they are.
Updated ZFP/PFM/AFM out shortly.
&&
.TSA WATCHES/WARNINGS/ADVISORIES...
OK...None.
AR...None.
&&
$$
SHORT TERM...23