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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Thursday
• 
• High: 82 °
• Low: 55 °
• Chance of T-Storms

• Friday
• 
• High: 73 °
• Low: 50 °
• Chance of T-Storms

• Saturday
• 
• High: 72 °
• Low: 55 °
• Chance of T-Storms

• Sunday
• 
• High: 90 °
• Low: 63 °
• Partly Cloudy

• Monday
• 
• High: 90 °
• Low: 48 °
• Chance of T-Storms

Area forecast discussion 
National Weather Service Milwaukee/Sullivan WI 
1117 PM CDT Wednesday may 23 2012 




Aviation/06z tafs/... 


Recent tamdar soundings out of mke and rfd supporting low-level 
wind shear on forecast soundings....which will intensify during 
the overnight until daytime mixing brings gusty winds to the 
surface by middle morning. Some gusts to 30 to 35 knots Thursday 
with low pressure intensifying as it lifts from SW Iowa to Western 
Lake Superior during the day. 


Sky cover will be scattered-broken cirrus from convection to the west until 
a line of scattered-broken thunderstorms crosses southern Wisconsin with 
surface cold front during the late afternoon and evening. Still 
expect VFR ceilings with bases around 5k feet with thunder. Kmsn has 
best chance for severe thunderstorms with damaging wind 
gusts...but with 45 to 50 knot winds down to 925 mb/1000 feet/ and 
55 knot winds around 2500 feet...any shower or thunderstorm has the 
potential of bringing damaging winds to the surface over the 
entire forecast area. Current timing has best chance of precipitation at 
kmsn between 00z and 03z Friday...and the eastern sites seeing the 
weakening band of showers/storms between 03z and 06z. 00z NAM 
showing a period of Post-frontal MVFR ceilings...but NAM 2-meter dew 
points seem a bit high so will keep ceilings no lower than VFR for now. 




&& 


Marine... 


Keeping small craft timing as tight gradient brings strongest 
winds to the Lake Shore late in the afternoon/early evening. It 
will take mixing with maximum heating to bring criteria wind gusts 
down to the cooler lake waters. Will be a period of criteria 
westerly wind gusts just after midnight behind the front with 
winds easing...and waves subsiding below criteria between 08z and 
10z. 




&& 


Previous discussion... /issued 341 PM CDT Wednesday may 23 2012/ 


Very short term... 


Tonight and Thursday...forecast confidence...medium to high. 


Deep ridging seen across the eastern U.S. Through the period with 
strengthening low rising up out of the Central Plains toward 
Wisconsin. A few weak vorticity maxima will cross the County Warning Area in fast 
southwesterly 500mb flow so some cirrus will likely hang 
around...but significant cloud cover is not expected until cold 
front approaches Thursday afternoon. 


Strong winds will push into the area ahead of the low...and warm air 
will surge in along with them. NAM soundings show 40 to 45 knots winds 
just 1000 feet above the surface by afternoon and deep surface based 
mixed layer...with even stronger winds higher up in that layer. This 
would support a Wind Advisory...but with cloud cover increasing 
mixing could be significantly limited. Confidence is too low at this 
point to pull the trigger. Will pass along to next shift. 


NAM and European model (ecmwf) show 925mb temperatures rising to 23-25c across the County Warning Area by 
late afternoon...with the warmest temperatures from Madison westward. These 
925 temperatures support highs in the upper 80s with 90 possible in the 
area of the warmest values. Don/T think the clouds will limit 
heating too much...but kept highs a tad cooler in the west where 
convective clouds are most likely. 


Pretty good cap with over 300 j/kg of cin noted on forecast 
soundings tomorrow afternoon. This should keep thunderstorm chances 
small until cap weakens very late in the day...and even then only in 
the northwest. 


Short term...Thursday night...forecast confidence high... 


Forecast models have been consistent in dragging a cold front across 
Wisconsin Thursday night. Best dynamics remain over northern 
Wisconsin closer to a decent shortwave trough swinging through the 
Midwest. Surface dewpoints still prognosticated to get up to around 60 just 
ahead of cold front. Frontogenetic forcing weakens as front moves 
across southern Wisconsin...so will transition from a likely to 
chance of thunderstorms west to east across my County Warning 
Area. 


Friday...forecast confidence moderate... 
quiet weather with drying west-northwest low level flow at least for most of 
daytime hours. Models start to differ by late afternoon with 
location of warm front over Iowa and Illinois. Feel front should be 
far enough south of southern WI to allow for dry weather Friday 
across my County Warning Area. Models also differ on shortwave 
strength and placements for Friday across WI. So best to go dry Friday. 


Friday night...forecast confidence moderate... 
warmfront is prognosticated by models to move north to roughly central Iowa 
to northern Illinois. Increasing southwest flow above boundary layer 
coupled with isentropic lift should be enough for scattered showers 
and storms developing overnight. Models differ on rain amounts and 
placement of storms...so will keep chance going. 


Long term... 


Saturday and Saturday night...forecast confidence moderate... 
models differ on placement of northward moving warm front on 
Saturday. So have to keep chance of showers and storms going. 
Seems fair to say the front will have reached central or northern 
WI by end of Saturday night. With 850 mb temperatures rising to around 
+20c on Saturday...will take temperatures into the middle-upper 80s. 


Sunday and Sunday night...forecast confidence low to moderate... 
models suggest a dry day warm-hot south-southwest low-level 
flow...and temperatures in low 90s range over western half of my County 
Warning Area. Lack of any frontal boundary or shortwave forcing 
spells no precipitation for southern WI during the day Sunday. . 
will keep a chance of storms going Sunday night per blend of GFS and 
European model (ecmwf)...but a low chance. 


Monday through Tuesday...forecast confidence low... 
GFS has weakening cold front moving across Wisconsin on Monday as a 
trough aloft swings east through Midwest. Better chances of showers 
and storms Monday/Monday night as this happens. High pressure 
building into northern plains on Tuesday should keep the weather 
scene quiet across southern WI on Tuesday. 


Aviation/00z tafs/... 
main concern continues to be possibility of low level wind shear. 
Model forecasts still showing increasing winds in the 1 to 2 thousand 
foot layer ahead of the cold frontal passage Thursday night. Winds 
in this layer expected to be over 40 knots over most of southern 
Wisconsin by 06z tonight...nearing 50 knots from msn westward. 


VFR conditions will prevail tonight and Thursday. There is a chance 
of thunderstorms well north and west of msn Thursday afternoon. Main 
threat will be in the vicinity of the cold front...which should not 
reach msn/ues/enw until after 00z Friday. Mke taf will reflect the 
possibility of thunderstorms before 06z. 


&& 


Mkx watches/warnings/advisories... 
WI...none. 
Lm...Small Craft Advisory from 6 PM Thursday to 1 am CDT Friday for 
lmz645-646. 


Small Craft Advisory from 5 PM Thursday to 4 am CDT Friday for 
lmz643-644. 


&& 


$$ 


Update...rem 
tonight/Thursday and aviation/marine...Wimberley 
Thursday night through Wednesday...kapela