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Area forecast discussion 
National Weather Service Green Bay WI
557 am CDT Tuesday Jul 28 2015

Updated aviation portion for 12z taf issuance

Short Wednesday
issued at 315 am CDT Tuesday Jul 28 2015

A squall line across the eastern Dakotas is slowly making its way
westward towards Wisconsin this morning. evidenced by
the 00z kgrb radiosonde observation...these storms will be running into a wall of
very dry air across central Wisconsin. This is captured rather
well with the hi-res model runs as the line of thunderstorms
dissipates as it tracks into central and north central Wisconsin
this afternoon. Given the high degree of model agreement will push
back and lower probability of precipitation significantly across the County Warning Area today...limiting
probability of precipitation to the west in case some of the activity spills into the
western County Warning Area. If this activity does make it...there could be gusty
winds with the line of thunderstorms...especially across central
Wisconsin...which puts the area in the marginal risk according to
the Storm Prediction Center outlook. Given the later arrival of the activity...and
lack of activity expected across the eastern County Warning Area...will raise high
temperatures several degrees towards MOS guidance values as highs
get into the middle to upper 80s.

Precipitation chances tonight still look fairly the
likely a cold front sweeps through the western Great
Lakes region. Dry air will still be in place...with hi-res model
runs indicating the activity tonight could be spotty instead of a
solid line of showers and thunderstorms. Given the dry air in
place and the less than encouraging hi-res model runs will not
raise probability of precipitation beyond likely with this forecast issuance. Some of
these storms could produce gusty winds and small hail as MUCAPES
approach 1000 j/kg...which will continue the marginal threat for
severe weather overnight.

Clearing skies behind the cold front are expected on Wednesday as
a tight pressure gradient brings gusty westerly winds to 30 miles per hour
across the County Warning Area. Highs on Wednesday will be cooler in the upper 70s
to lower 80s as dew points falling into the 50s make conditions
more comfortable than the last few days.

Long term...Wednesday night through Monday
issued at 315 am CDT Tuesday Jul 28 2015

Upper-level low will essentially remain in place in the vicinity
of Hudson Bay...while broad upper-level ridging gradually takes
control over the intermountain west during the extended portion of
the forecast. This pattern will keep the western Great Lakes in a
general northwest flow through the upcoming weekend. Embedded
generally weak shortwave impulses traversing the northern Continental U.S.
From time to time will offer quick shots at some rather modest
precipitation especially later in the weekend. Temperatures should
remain at or above normal into the first part of next week with
evidence in some of the medium range guidance for a more notable
cool down thereafter.

As primary shortwave trough heads northeast toward Hudson Bay
Wednesday night...subsidence and a brief push of somewhat cooler
and noticeably drier Canadian air should make its way across the
western Great Lakes. Thursday looks like a breezy and seasonably
warm day with more comfortable dewpoints in the 50s.

First in series of weak upper-level impulses approaches the
western Great Lakes Friday morning. Consensus of model guidance
suggests bulk of the upper forcing will pass north of the forecast
area and moisture associated with frontal passage will be quite limited.
Thus see no reason to deviate from dry forecast for Friday. Weak
surface high pressure ridge will follow the frontal passage thus Saturday
should remain dry as per previous forecast.

More substantial shortwave disturbance begins to impact the
forecast area late Saturday night or Sunday. Both the European model (ecmwf) and
GFS were in The Ball park on timing of frontal passage in the Sunday
morning time period. Although moisture still appears rather
limited...upper forcing should be sufficienet to generate at least
scattered convection. Beyond Sunday...additional weak disturbances
within northwest flow continue thus will not deviate from model
blend which gives low end probability of precipitation for the first week of August with
temperatures trending toward below normal for early August.

Aviation...for 12z taf issuance
issued at 556 am CDT Tuesday Jul 28 2015

With the exception of patchy IFR/LIFR fog early this morning...VFR
conditions are expected to prevail today. Middle level clouds along
with scattered showers may begin to work into central Wisconsin
late this afternoon. Showers and storms will become more
widespread this evening over central Wisconsin and over the rest
of the region later tonight as a cold front slides over the
state. Adjusted rain several hours later to account for later
precipitation timing.

Grb watches/warnings/advisories...


Short term.....Kurimski
long term......esb

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