River Flood Warning 59, NWS Milwaukee, WI

Area Forecast Discussion
National Weather Service Milwaukee/Sullivan WI
558 AM CDT Fri May 24 2019

.UPDATE...
Showers continue across southern Wisconsin with some areas to the
far south seeing a few rumbles of thunder. This is the start of a
very wet day with the potential for severe storms later this
evening. Forecast remains on track.

&&

.AVIATION(12Z TAFS)...
Temporary MVFR VSBYS will be possible this morning with these
showers moving through. The main concerns will come later this
morning with a period of MVFR CIGS. However, to the southeast we
should see varying extent of the MVFR CIGS with potential for a
brief period of VFR CIGS for Milwaukee and Waukesha in the
afternoon while Racine and Kenosha may remain with VFR CIGS
throughout the TAF period. Any showers will have some concerns for
brief MVFR VSBYS.

Into the late afternoon and evening we will begin to have
concerns for scattered thunderstorms, some of which may be strong
to severe with strong gusts and hail the main threat. This will
have some additional concerns for locally heavy rainfall possibly
bringing brief periods of IFR VSBYS. Into the evening we will
also have some low level wind shear of 35 kts to 2 kft from the
southwest. The main concerns will be limited into the overnight
period as lower CIGS move out, wind shear ends, with mostly rain
showers remaining, though thunder cannot be ruled out.

&&

.PREV DISCUSSION... (Issued 359 AM CDT Fri May 24 2019)

SHORT TERM...

Today and Tonight...Forecast Confidence is Medium...

A very wet day ahead is expected with showers pushing in early
this morning in association with an upper level shortwave with
moderate low level moisture. In addition, we will have some low
level frontogenesis with the approaching warm front. Later into
the morning and early afternoon lower level WAA with be the main
source of lift for any showers as the shortwave pushes out with
little to no LL jet support. There will be a little instability
with this as well that should increase throughout the day so some
thunder is certainly possible.

Lack of low level moisture should keep us dry for a period later
this morning into the early afternoon. This would help the region
to warm up and allow the environment to recover somewhat. However
with clouds likely sticking around for the most part we will have
very questionable recovery.

By the late afternoon/early evening storms should develop across
the region with threats for severe hail, wind and even tornadoes.
The primary forcing should be in association with the baroclinic
zone with some help from the LL jet strengthening in the evening. Storm
development and corresponding strength will again be heavily
dependent on the environment being able to recover from the
morning. We should be able to recover at least around 1000 J/kg of
MLCAPE with models in disagreement about MUCAPE with amounts
ranging from 1500-3500 J/kg (which would affect hail threats). Our
environment will be highly sheared both with deep shear and low
level shear. Our Effective Shear will be around 40-55kts through
the region with 0-1 km shear around 25-35 kts. This strongly
sheared environment will likely yield rotating updrafts with
storms capable of producing some larger hail as well as the
potential for a few tornadoes. Otherwise, our low to mid level
lapse rates will be around 7 C/km and will have rather low LCLs
from 500-800m AGL further enhancing our threats. The wind threat
will also exist with any storms with the environment having as
much as 1000 J/kg of Downward CAPE (DCAPE).

In addition, given long skinny CAPE profiles and precipitable
water around 2 inches we will likely have fairly efficient rain
producing storms. With rain showers/storms possible throughout
much of the day into the overnight period we will thus have
concerns for flooding with a Flash Flood Watch in effect from 0z-
12z Saturday.

LONG TERM...

Saturday and Sunday... Forecast Confidence is Medium to High.

The majority of the weekend will feature mostly quiet weather for
southern WI. Saturday is our warm day.

Showers and thunderstorms will exit southeast WI Saturday morning
as the upper jet weakens. We should be dry and warm during the
afternoon since we will still be well within the warm sector of
the system. Highs should be in the lower 80s across all of
southern WI with a westerly breeze preventing a lake breeze.

We could see another round of light showers or sprinkles across
southern WI Saturday night while we're still within the baroclinic
zone.

The surface front will finally get into southern WI by Sunday
morning which will help keep convection to our south for the day.
This will also bring easterly winds to the area which will keep
lakeshore areas cooler. Inland temps should get into the lower to
mid 70s. There may be another thunderstorm complex that will
track across IL on Sunday and that is why we are carrying a slight
chance for showers toward the IL border.

Monday... Forecast Confidence is Medium.

The next closed upper low over the southwest U.S. will start to
swing into the center of the country on Monday. Our next round of
showers and thunderstorms may arrive in southern WI late Sunday
night or first thing Monday. It looks like there is decent
synoptic support for strong thunderstorms over the Midwest on
Monday. SPC added southwest WI into a 15 percent chance for severe
in the Day 4 outlook. With precipitable water values back up over
1.5 inch, heavy rain will be possible once again.

Tuesday through Wednesday... Forecast Confidence is Medium.

Another round of showers and thunderstorms may be on the heels of
the Monday system either Tuesday or Tuesday night. This is due to
southern WI sitting within the baroclinic zone along this ring of
fire pattern. The upper low will slide across WI Wednesday and
help to temporarily break down the ridge over the southeast U.S..

Thursday through Friday... Forecast Confidence is Medium.

Our time within northwest flow will be brief and still feature
small chances for showers later in the week. Temperatures will be
cooler, with highs in the 60s.

AVIATION(09Z TAFS)...Conditions remain quiet for now however
showers will are beginning to push into the region. Initially the
only concerns with these morning showers will be temporary MVFR
VSBYS associated with heavier pockets of rain and a chance for a
rumble of thunder. Into the late morning MVFR CIGS will push in
along with continuing showers. Throughout the rest of the day
there will be concerns for MVFR VSBYS with showers and MVFR CIGS
with potential for a few periods of IFR CIGS.

Into the afternoon and evening we will have chances for
thunderstorms for southern WI, which will come with some concerns
for temporary IFR VSBYS in thunderstorms. Some of these
thunderstorms may be strong as well with wind gusts and hail as
the primary threats. Into the evening we will also have some low
level wind shear of 35 kts to 2 kft from the southwest. The main
concerns will be limited into the overnight period as lower CIGS
move out, wind shear ends, with mostly rain showers remaining,
though thunder cannot be ruled out.

MARINE... Some open lake fog may be present over parts of the
lake but this will diminish into the morning. Rain showers and
storms will persist through much of the day today with chances for
stronger storms this evening which may cause some gusty winds
over the lake. Otherwise the day should remain quiet with winds
from the southeast with some gustiness in the afternoon. Winds
will switch to the south and southwest into the evening and
overnight period. Gale force winds are not expected outside of
thunderstorm chances today and possibly again tomorrow over the
lake.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...Flash Flood Watch from this evening through Saturday morning for
     WIZ059-060-062>072.

LM...None.
&&

Update...ARK
Today/Tonight and Aviation/Marine...ARK
Saturday THROUGH Thursday...Cronce

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