Forecast Discussion for GRB NWS Office
473
FXUS63 KGRB 140334
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1034 PM CDT Thu Jun 13 2024

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Well above average temperatures are expected from Sunday into
  the middle of next week. Heat indices may surpass 90 degrees at
  times.

- Next chances for rain/storms arrive Saturday night. It is too
  soon to determine if these storms will become severe, although
  locally heavy rainfall will be possible.

- On and off chances for thunderstorms will continue through the
  middle of next week, although there is still some uncertainty
  with timing. Due to increasing heat and humidity, some stronger
  storms and locally heavy rainfall may be possible.

&&

.DISCUSSION...
Issued at 257 PM CDT Thu Jun 13 2024

Short Term...Tonight and Friday

Isolated thunderstorms are possible in far northern Wisconsin through
dusk as a jet streak moves across the region. Skies should clear
overnight, and with diminishing winds and drier air low temperatures
should be near or few degrees below normal.

A weak surface high will move into Wisconsin Friday, with cooler
and drier air. An upslope east northeast surface wind will likely
produce clouds over central Wisconsin, and perhaps isolated
showers in the afternoon. Did not include them in the forecast as
confidence is low.

Long Term...Friday Night Through Thursday

After a brief dry spell on Friday to start the extended, active
weather will then return to the region as mid-level flow amps up.
Several chances for rain/storms will be possible through the
weekend and into early next week as a persistent trough over the
western CONUS ejects several fast-moving shortwaves into the
western Great Lakes. Heavy rainfall will be a concern during this
time as the WPC highlights northeast Wisconsin for receiving
excessive rainfall Sunday and Monday. Attention will then turn to
increasing temperatures mid-week as a ring of fire pattern advects a
warm, moist airmass up into the Midwest.

Saturday through Monday precip chances... As Canadian low pressure
passes to our north Sunday and Monday, precip chances will enter
the forecast area late Saturday into early Sunday out ahead of a
warm front. Some elevated storms may be possible Saturday night
given an abundance of low-level moisture and a strong LLJ
(between 40 and 50 knots). Periods of moderate to heavy rain will
be possible Sunday morning as PWATs increase to over 1.5".
Temperatures on Sunday will be a hindrance to the forecast given
the effect of lingering convection and cloud cover. This being
said, current thinking is that temperatures on Sunday will be
slightly lower than what model guidance is currently showing.
Additional convection may develop late Sunday afternoon depending
on airmass recovery time following Saturday night`s precip.
However, main focus will be on storm chances for Monday as a cold
front moves east across the forecast area. A first glance shows a
favorable synoptic setup with placement under the right-rear quad
of an upper-level jet and a nocturnal LLJ creating a convergent
zone across western Wisconsin. Furthermore, deep Gulf moisture
ingested by the parent low will allow dewpoints to reach the low
to mid 70s across portions of central to east-central Wisconsin.
Although it is currently too soon to tell, will continue to
monitor potential for strong/severe storms as we get closer to the
event.

Rest of the extended... As the cold front departs to the southeast
Monday evening, high amplitude mid-level flow is expected to
settle in across the CONUS. A robust trough west of the Rockies will
carve out a Bermuda ridge across the eastern US, placing much of
the Midwest under a warm and moist southwesterly flow regime.
This ring of fire pattern may prove problematic as temperatures
could potentially soar into the low 90s Monday and Tuesday.
However, there is some uncertainty on whether thunderstorm
outflow from earlier in the week will act to shunt the warmer
airmass further south, resulting in cooler temperatures than what
model guidance is currently showing. Opted to go with the blended
guidance for the time being due to low confidence.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1034 PM CDT Thu Jun 13 2024

VFR conditions are expected through the TAF period as high
pressure tracks through southern Canada. Other than a few mid and
high clouds and light winds not much in the way of aviation
impacts is expected through Friday evening.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....RDM
AVIATION.......Kurimski

NWS GRB Office Area Forecast Discussion