Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 230358
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1058 PM CDT Mon Jul 22 2019

Updated aviation portion for 06Z TAF issuance

.SYNOPSIS...
Issued at 236 PM CDT Mon Jul 22 2019

Relatively quiet weather is expected for most of the work week,
along with a very gradual upward trend in temperatures and
humidity levels. The next chance for widespread significant
rainfall will be on Friday.

Large scale amplification is well underway, and will peak during
the next day or so. The main longwave features will be troughs
just off the West Coast and over eastern North America, and a
ridge over the Rockies. Fairly rapid deamplification is expected
during the middle to latter part of the week, with a return to a
nearly zonal ribbon of westerlies across the northern CONUS and
southern Canada by next weekend.

Slightly below normal temperatures resulting from northwest upper
flow at the start of the period will creep upward to modestly
above normal for the middle to latter part of the period. A
return to more humid conditions is also anticipated, though it
seems unlikely dew points will reach the levels observed late last
week. Although a round or two of scattered light precipitation
may occur during the first half of the period, precipitation
totals will depend primary on what falls during the latter half of
the period. That is difficult to assess, but amounts will
probably end up AOB normal.
&&

.SHORT TERM...Tonight and Tuesday
Issued at 236 PM CDT Mon Jul 22 2019

Mostly quiet weather will continue through the short term period.
The main focus the potential for isolated thunderstorms and
showers Tuesday afternoon as an mid level shortwave moves through
the region.

For the remainder of Monday, quiet and dry conditions are expected
to continue across the region as high pressure conditions remain
in place. Some fair weather cumulus will likely be in place
through the day, clearing again in the evening as diurnal heating
exits. Overnight, models hint at a weak shortwave moving through
the region, but given the lack of moisture/instability and
overnight timing, kept the forecast mostly dry for the period,
with the exception of far northern Wisconsin.

Tuesday, cloud cover will be on the increase as temperatures head
towards the lower 80s once more. Sufficient instability is
expected to develop in the afternoon for a few showers and
possible thunderstorms in the area. The potential for showers and
thunderstorms will be best in eastern Wisconsin during the
afternoon, as the lake breeze will provide a focus for
thunderstorm and shower development. CAPE and shear will be fairly
minimal during this time period, so although thunder is possible,
no severe development is expected. With the ample dry air and
inverted-v soundings, expect good mixing during the afternoon and
evening, increased wind gusts a bit in the afternoon. The gusts
could be a bit higher with any areas that see showers, as the rain
aids in mixing down the winds aloft. Gusts will be in the 20 to
30 mph range.

.LONG TERM...Tuesday Night Through Monday
Issued at 236 PM CDT Mon Jul 22 2019

A large anticyclone across the Plains will shift south of the
area Tuesday night and Wednesday. The scattered convection that
forms Tuesday afternoon could linger into the evening before
dissipating. A few more showers could pop up over the far
northeast during the day Wednesday,. Support is not as great as
on Tuesday, so will omit thunder for now.

Thursday through Friday, a strong shortwave will drive east
across southern Canada in the re-establishing zonal regime.
Return flow on the back side of the departing high and ahead of a
cold front approaching from the west will result in gusty south
winds, and a return of higher dew points to the area.
Thunderstorms chances will increase on Friday. The strength of the
flow aloft suggests there may be a severe risk with the storms,
though that will depend of the details of the pattern that are
uncertain this far in advance. Storms will be possible at times
through the upcoming weekend, as the frontal system crossing the
area Friday settles along the southern edge of the westerlies.

The standard forecast initialization grids seemed reasonable, so
only minor changes were needed.
&&

.AVIATION...for 06Z TAF Issuance
Issued at 1058 PM CDT Mon Jul 22 2019

Good flying weather is generally expected through the TAF period
as surface high pressure ridge dominates the weather over
Wisconsin. Generally fair skies and light NW winds will be the
rule overnight. The main exception will be across far north-
central Wisconsin where an area of showers and a few
thunderstorms associated with a weak upper level disturbance are
dying as they dive south. Models indicate these showers could
impact RHI but should dissipate before they affect the central WI
airports.

Another weak upper-level disturbance is forecast to move
southeast and impact mainly the eastern portion of the forecast
area Tuesday afternoon. Although this system will have limited
deep layer moisture to work with, surface heating, relatively cold
air aloft and weak surface convergence may be enough to generate
isolated showers or perhaps a rumble of thunder during the
afternoon. Given the limited coverage will not include in this set
of TAFs.

.KOSH...Light westerly winds will veer to a NNE direction late
Tuesday morning the back to a westerly direction late Tuesday
afternoon and into the evening hours.

A few isolated showers and perhaps a rumble of thunder is
possible Tuesday afternoon. However coverage will not be enough to
include in the TAFs at this time.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SYNOPSIS.......Skowronski
SHORT TERM.....Uhlmann
LONG TERM......Skowronski
AVIATION.......Kurimski


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