Area forecast discussion
National Weather Service Green Bay WI
107 PM CDT Tuesday may 21 2013
Updated aviation portion for 18z taf issuance
Synopsis...
issued at 351 am CDT Tuesday may 21 2013
Highly amplified/somewhat blocky flow regime will become
established across the Continental U.S. During the period. Upper trough was
currently over the northern plains...with ridges over The Rockies and
near the East Coast. Another upper low was digging southward down the West
Coast. The plains trough will phase with some energy dropping southward from
the Hudson Bay area as it slowly migrates into eastern noam. Meanwhile
back West...Ridge over The Rockies will expand to extend from the Southern
Plains...nwd...into the Canadian prairies...while the upstream
trough lingers out near the West Coast.
Temperatures will drop to below normal levels for a few days days...then
rebound this weekend and early next weak. Precipitation amnts are likely to
be at or above normal...primarily due to what falls the next couple days.
&&
Short term...today...tonight...and Wednesday
issued at 351 am CDT Tuesday may 21 2013
Various comms/equipment/connectivity issues really threw some
roadblocks into the the process of trying to put together the
forecast this morning. But here GOES...
Band of convection liftg northward across the forecast area early this
morning should eventually slow and weaken as it approaches the
deformation zone to the north. Meanwhile at the surface...west/east
boundary which likely originated as remnants of old occulusion will
linger across the north. Once the morning rains shift northward...focused probability of precipitation
near the boundary for the rest of today into tonight. Can/T rule out
isolated-scattered convection developing farther S...especially if sig sunshine
occurs across the S later today. But the more widespread rain showers/thunderstorms and rain
should be across the north. Storm Prediction Center trimmed the slight risk of severe storms to
mainly east-c WI. While severe storms would certainly be possible if sig
clearing and destablization can occur...shear will be weaker than
yesterday. Will mention possibility in the severe weather potential statement...but risk seems too
limited/conditional for explicit inclusion in grids/zones at this
point.
Surface boundary will begin to shift southward tonight. But forcing will be fairly
weak...so should get somewhat of a decreasing trend in the
convection as the atmosphere stabilizes overnight.
What seems like the best chance for sig widespread precipitation should occur
over east-c WI Wednesday as upper system approaches from the west. Models all
showed considerable qg forcing overspreading the area during the
day. Will start out with chance probability of precipitation...then take them to likely over
the southeast part of the forecast area by afternoon. Surface boundary should be well
S by then...so it will be cooler...and focus any severe threat to our
southeast.
Long term...Wednesday night through Monday
issued at 351 am CDT Tuesday may 21 2013
A return to below normal temperatures are expected through much
of the period...especially with the night time lows as Canadian
high pressure will dominate the weather pattern.
Low pressure moving across the western Great Lakes will continue
to bring chances for showers Wednesday night. The highest chances
will be across the east/Lakeshore region and will taper off
rapidly as you head northwest to Vilas County. Some uncertainty in
where axis of heavy precipitation will occur...thus later forecast
may need to adjust amounts and location of the band of heavier
rainfall. The unsettled weather will come to an end from northwest
to southeast later Thursday night. Did linger a small chance of
showers for early Thursday morning along the Lakeshore. The
biggest change on Thursday will be the clearing skies and dropping
dew points. Skies will become sunny from northwest to southeast
during the morning and early afternoon. The ample sunshine will
allow for dew points to drop into the 20s north and 30s along the
Lakeshore. It will feel cool as north/northeast winds of 15 to 25
miles per hour can be expected. Temperatures along the Bay and Lakeshore
always tricky this time of year depending if winds are due north
or have a slight easterly component. Did lower maximum temperatures a
few degrees across the east. Highs on Thursday will be in the
middle 50s to around 60 east and Vilas County... and in the lower
to middle 60s west.
The cool dry air mass...combined with clear skies and light winds
will allow temperatures to plummet by Friday morning. A widespread
frost is expected across the north with some of the typical colder
locations experiencing a hard freeze for a few hours. Areas of
frost are expected across central and northeast Wisconsin. Since
we are now well into the typical growing season...will highlight
in the hazardous weather outlook and graphicast. Despite a cool
start...temperatures will rebound into the lower to middle 60s on
Friday.
The main concern for next weekend will be position of the
Canadian high and surface warm front well southwest of the state.
The GFS was further north with the front and associated
precipitation on both days this weekend. Inkling that the best
chance for rain would be across our far southwest late Friday
night into Saturday and the remainder of the weekend would be dry.
Have removed chances for rain across the northeast two thirds of
the forecast area and confined showers to the southwest third for
both days. If models come into better agreement...may be able to
remove some more of the slight chances for showers on one or both
days. Even if the further south solution does verify... high
clouds will stream across the region over the weekend from time to
time. Hard to determine at this point if sky cover would be
partly/mostly cloudy. Best chance for mostly cloudy conditions
would be across the southwest portion of the area. Model
differences yield to a low confidence in the Memorial Day
forecast. Made little change to this period.
&&
Aviation...for 18z taf issuance
issued at 107 PM CDT Tuesday may 21 2013
Variable weather conditions expected this afternoon
and tonight as bands of showers and thunderstorms move across the
region. Conditions will generally be VFR east of a Marinette to
Shawano to Waupaca line line with MVFR conditions further west.
Brief IFR possible in showers and thunderstorms. In
addition...there is dense fog along the Lake Michigan shore. It
will probably stay just east of the Manitowoc and Sturgeon Bay
airports but it will be close.
&&
Marine...
issued at 351 am CDT Tuesday may 21 2013
Gusty north/northeast winds Wednesday night and Thursday will
create hazardous conditions for small craft. The winds and waves
will gradually subside late Thursday afternoon and evening. A
Small Craft Advisory will likely be needed Wednesday night into
Thursday evening.
&&
Grb watches/warnings/advisories...
none.
&&
$$
Synopsis.......skowronski
short term.....Skowronski
long term......eckberg
aviation.......esb
marine.........Eckberg
