Your Weather

To update your location please enter your ZIP code, city, state, airport code or country in the field below. Weather by E-mail: Forecast storm alerts. Weather E-Mail Alert Sign Up »

Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 81 °
• Low: 52 °
• Partly Cloudy

• Thursday
• 
• High: 88 °
• Low: 55 °
• Chance of T-Storms

• Friday
• 
• High: 81 °
• Low: 48 °
• Chance of T-Storms

• Saturday
• 
• High: 84 °
• Low: 52 °
• Chance of T-Storms

• Sunday
• 
• High: 88 °
• Low: 66 °
• Partly Cloudy

Area forecast discussion...updated 
National Weather Service Milwaukee/Sullivan WI 
1152 am CDT Wednesday may 23 2012 


Aviation/18z 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. 


Cirrus have spread across the region but VFR conditions will 
prevail. Some model guidance suggesting possibility of some middle 
clouds overnight tonight and then again tomorrow afternoon over 
southwest Wisconsin. 


&& 


Previous discussion... /issued 325 am CDT Wednesday may 23 2012/ 


Very short term...today and tonight. 


Southwest 250 mb upper jet of 95 knots extends from Minnesota to 
Hudson Bay and increases to 130 knots by sunrise Thursday. Upper 
divergence stays to the northwest of the forecast area. 700 mb 50 
knot jet extends across Minnesota into southwest Ontario this 
evening with the jet pushing east a bit into northwest Wisconsin 
late tonight. 850 mb low level jet of 55 knots will extend across 
western Wisconsin and across the Lake Superior area. 850/700 mb 
convergence will stay to the north. 


Forecast soundings are very dry with a cap around 4 thousand feet. 
Therefore do not expect any cumulus today. Soundings indicate some 
altocumulus castellanus potential around midnight near The Dells. However elevated 
cape around 15 thousand feet is only 8 j/kg and still very dry below so 
will not include any chances of precipitation. 


Surface high pressure across the eastern Great Lakes will move east 
with a southeast surface wind developing. Therefore lake cooling 
should increase during the afternoon while 850 mb temperatures warm. 


Short term...Thursday through Friday night. 


Difficult to disagree with ongoing forecast for Thursday and Thursday night. 
Dry south to southeast winds in the low to middle levels will continue 
to pull warm air into southern WI for Thursday. 60-65f surface dewpoints from 
NAM and GFS likely overdone. Strong low level mixing expected to 
keep daytime dewpoints more in the 50s and possibly lower in a few eastern 
spots. Warm air aloft will act as cap as well...suppressing convection 
over most of the area. All short term guidance in good agreement on 
low pressure associated with middle-level short wave moving northeast 
along surface cold front will push into west central WI by 00z/25. 
Low level convergence and expected narrow axis of higher low level 
moisture may be able to break cap in the far west...mainly west and 
northwest of Madison by late afternoon. A few of the stronger storms 
could take on supercellular characteristics over west central WI due 
to strong bulk shear and MUCAPES approaching 2k joules and affect 
the far northwest early in the evening. 


The other concern for Thursday is the expected strong winds. 
Daytime mixing is expected to reach 850mb in the afternoon as winds at 
this level increase to 40 to 50kts while 925mb winds increase to 30 
to 40kts. 3 hour pressure falls ahead of developing low pressure of 
2-4mb are expected. Strongest low level winds are expected for 2 to 
4 hours during Thursday afternoon...and several locations may reach Wind Advisory 
thresholds. Slight onshore component at the Lakeshore should keep 
gusts slightly lower in this area. For now will highlight strong 
winds in new severe weather potential statement issuance. Dry...gusty winds will push the Mercury to 
the upper 80s to near 90 away from Lake Michigan. 


Will continue likely wording Thursday evening over western County Warning Area as surface front 
reinforced by glancing synoptic scale lift from passing middle-level 
short wave moves across central WI. Kept chance probability of precipitation in the east 
through the late night as weak front pushes through southern WI. In 
addition... axis of 10 units of q-vector convergence and low level 
fn vector response to frontogenesis pushes through eastern WI at this 
time. 


Frontal boundary still expected to sag into central Illinois for Friday with 
weak short-wave ridging moving across WI. With drier air returning 
for Friday...will remove probability of precipitation from southwest as any scattered convection in 
vicinity of front is expected to remain south of area. Front begins 
to shift northward Friday night along with the return of deeper low 
level moisture as low level jet strengthens upstream. Hence will 
continue low probability of precipitation for this period. 


Long term...Saturday through Tuesday. 


For most of this period...will lean on more consistent high resolution 
European model (ecmwf)...which also has the favor of HPC blended fields. For Sat and 
sun...all the extended guidance in reasonable agreement. Persistent 
high pressure ridge and more westerly flow slows northward progress 
of warm front across southern WI over the weekend. Warm front expected to 
move slowly northward across southern WI Sat night with main baroclinic zone 
and strongest lift shifting northward into central and northern WI. Will 
continue chance probability of precipitation on Saturday as this enhanced lift shifts northward 
and confine chance to northern County Warning Area Saturday night. This will need to be 
watched closely as daytime convection may suppress northward movement of 
elevated baroclinic zone...which would result in potential for 
higher probability of precipitation for Sat night. 


Higher amplitude high pressure over southeast Continental U.S. Expands into 
central/southern gtlakes. South winds on the west side of this 
ridge will pull warm...dry air back into southern WI. This warm...dry air 
will act as a capping inversion on Sunday...suppressing convection. 
Ridging also appears to be slowing eastward progress of approaching weak 
surface cold front until later Monday. Low level jet begins to pivot eastward 
into southern WI later Sunday night...so will continue low probability of precipitation as possibly 
mesoscale convective system may push into southern WI by early Monday. Despite differences in 
strength of low pressure system moving through northern plains...extended 
guidance in reasonable agreement on low pressure carrying weak surface 
front across southern WI on Monday/Monday night...with drier conditions 
returning on Tuesday. 


Aviation /12z tafs/...VFR conditions expected with only cirrus 
today. Main concern will be low level wind shear potential tonight 
as 15 hundred foot winds increase to 45 knots over portions of south 
central Wisconsin late this evening and 35 knots near Milwaukee late 
tonight. Surface gradient winds will increase over south central 
Wisconsin to 10 to 15 knots but remain rather light over the 
southeast. Also low areas over south central Wisconsin tonight 
should have light surface winds. 


Some middle level cloud potential later tonight mainly over south 
central Wisconsin. 


Marine...high pressure over the eastern Great Lakes will move off 
as low pressure extends from the Southern Plains to Minnesota. As a 
result southeast to south winds will increase a little late this 
afternoon and evening...with small craft advisories needed Thursday. 


Confidence... 
today and tonight...high. 
Thursday and Thursday night...medium to high. 
Friday and Friday night...medium. 
Saturday and Saturday night...low to medium. 
Sunday through Tuesday...medium. 


&& 


Mkx watches/warnings/advisories... 
WI...none. 
Lm...none. 
&& 


$$ 


Update...Wimberley 
today/tonight and aviation/marine...hentz 
Thursday through Tuesday...mbk