Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Milwaukee/Sullivan WI
326 PM CDT Friday Mar 27 2015
Tonight...forecast confidence high
Pressure gradient will relax this evening...allowing gusty winds to
subside as surface ridging shifts southeastward from the upper
Mississippi Valley into the western Great Lakes region. Surface
ridge axis crosses southeastern Wisconsin overnight...bringing cool
and quiet conditions. Although low-level cold advection will be
weakening...and nearing neutral by midnight...clear skies and light
winds / at least away from the Lakeshore / will allow for good
radiational cooling with lows in the teens.
Saturday...forecast confidence high
High pressure slides southeast of the County Warning Area...as upstream surface
troughing advances from the northern rockies into the upper
Mississippi Valley. Winds veer southerly across the area by
afternoon with warm low-level thermal advection kicking in by
evening. This will allow some moderation in afternoon temperatures
from today...with highs climbing into the middle to upper 30s for most
areas. The exception will be along the Lakeshore...where a
northeasterly wind component will persist through midday. Highs in
this area will likely remain in the lower 30s as a result.
Saturday night through Monday...forecast confidence...medium
Expect quiet weather Saturday night...as high pressure departs ahead
of an approaching shortwave.
Widespread precipitation is then expected on Sunday as the shortwave and
cold front move through the forecast area. Between model timing and
thermal profile differences...not an easy precipitation type forecast.
Taking a general consensus of the models...it looks like precipitation
could start as snow...sleet...or freezing rain early Sunday morning.
As surface temperatures warm up...should see mainly snow/sleet/rain chances
through late morning. Kept a chance of snow along with rain into
early afternoon...since the low level warm layer is pretty shallow
on soundings. Even if temperatures get into the middle/upper 30s...still looks
cold enough aloft for snow. Best chance for prolonged snow will be
in the northeast where temperatures aloft remain below 0c the longest.
Given the expected surface temperatures and the time of year...will likely
struggle to see any frozen stuff accumulate on the
pavement...especially by late morning and early afternoon.
Looks pretty quiet Sunday night and Monday as high pressure moves
through. Attention then turns to a shortwave Monday night. Models
are all over the place with the location of this system. Farther
north GFS would be milder and completely dry...while southern European model (ecmwf)
and Canadian suggest a colder airmass along with rain/snow chances.
Went with low probability of precipitation for rain/snow for now given the uncertainty.
Tuesday through Friday...forecast confidence...medium
Should be dry weather under high pressure Tuesday. Models struggling
to agree on temperatures though...with European model (ecmwf)/Canadian holding onto a colder
airmass...while the GFS is quicker to move upper ridging and milder
temperatures into the area. Temperatures leaned a bit toward the milder GFS as it
has been a more consistent solution...though will have to keep an
eye on lowering temperatures if the European model (ecmwf)/Canadian setup eventually looks
Models in better agreement for warmer temperatures Wed/Thu. Looks like a
trough and cold front will move through by Thursday
morning...bringing a chance for rain showers to the forecast area.
Best chance for showers looks to be Wednesday night. Seeing a little
elevated instability as the cold front GOES through...so may have to
eventually consider adding thunder to the forecast.
Cooler temperatures are anticipated for Friday behind the departing trough
and cold front. The GFS is dry...while the European model (ecmwf) stalls the cold
front just south of the forecast area and keeps rain chances going
Thursday night and Friday. Put some low probability of precipitation in there for now.
VFR conditions are expected through the taf period. Scattered 3-4
kft cloud deck affecting kmke and kenw this afternoon will
dissipate by late afternoon...with clear skies tonight. Gusty
north to north- northeasterly winds will ease this evening as high
pressure builds into the region.
No changes to Small Craft Advisory with brisk north to north-
northeasterly winds continuing along the Lakeshore this afternoon
and evening. This...combined with favorable fetch...will keep waves
high. Winds will ease this evening as high pressure builds into the
region...but waves will take a few hours to subside below advisory
Northeasterly winds Saturday morning will veer southerly by
afternoon and increase Sunday morning ahead of an approaching
surface trough. Lower end gale fore gusts are possible on
Sunday...and per coordination with grb/lot have hoisted a gale watch
Lm...gale watch from late Saturday night through Sunday afternoon for
Small Craft Advisory until 1 am CDT Saturday for lmz643>646.
Tonight/Saturday and aviation/marine...spm
Saturday night through Friday...ddv