252 
FXUS63 KOAX 100301
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1001 PM CDT Tue Jun 9 2020

...Updated for Headlines Tonight...

.UPDATE...
Issued at 939 PM CDT Tue Jun 9 2020

Severe thunderstorms were rotating east of our area late this
evening, so have cancelled the tornado watch just a little early.

Attention then turns to strong winds and additional rains on back
side of system. Wind gusts near or over 60 mph have already been
reported in some spots, and expect widespread 50 to 60 mph gusts
much of the night as surface low works east through northern
Kansas.  

Moderate to locally heavy rain fell over parts of southeast
Nebraska and southwest Iowa with convective storms. Radar
estimates showed pockets of 2 to 3 inch amounts. Additional
rainfall could add another inch and a half as rain redevelops in
deformation zone of upper system. Therefore will continue the
flash flood watch for southeast Nebraska and southwest Iowa
overnight.

&&

.DISCUSSION...
Issued at 330 PM CDT Tue Jun 9 2020

At 330 PM, our region was experiencing a narrow band of warm 
unstable air sandwiched between a strong upper level trough over 
northern Kansas and the remnants of what was Tropical Depression 
Cristobal in eastern Iowa. At the surface temperatures were in 
the upper 80s in the Omaha and Lincoln Metros. However the winds 
of change were visible on the western horizon, with temperatures 
in the 50s and 25 to 35 mph northwest winds ongoing in central 
Nebraska. The dividing line between these two extremes, was a cold
front that stretched from Sioux City to just west of Lincoln. 
Along the cold front, thunderstorms were widespread.

The aforementioned cold front, and strong trough of low pressure 
will surge through the region tonight, resulting in severe 
thunderstorms, very strong winds and heavy rainfall. The most 
immediate threat this evening will be in southeast Nebraska and 
southwest Iowa, where storms developing along the warm front may 
produce a couple tornados, and golf ball or larger hail through 
around 10 PM. Given ample instability and 0-3 km shear in excess 
of 50 kt, any storms that form will have the potential to rotate 
and produce tornados rapidly. Due to PW values near 1.5 inches, 
the potential for several rounds of thunderstorm activity, and 
rain rates in excess of an inch per hour, there will also be a 
moderate risk for flash flooding tonight in southeast Nebraska and
southern Iowa. Most locations will see between 0.5 and 2 inches 
of rainfall through 9 AM Wednesday, but localized totals of 2 to 5
inches are possible. This evening is a good night to have the 
weather radio on and/or a TV tuned to you local news station for 
updates. 

Another aspect of this storms system (and by far the one that is
most unusual for June) will be the strength of the northwest winds
behind the cold front tonight. CAMs are suggesting suggesting a
potential for 50 to 65 mph winds gusts tonight. These gusts in the
CAMs are supported by 850 mb wind speeds of 50 to 70 kts, that 
will should offer ample opportunity for winds to mix to the 
surface (especially in regions of shower activity). Scattered 
power outages and tree damage are possible with winds of this 
magnitude. High profile vehicles will also have difficulty 
traveling along Interstate 80, and it wouldn't be surprising to 
see a couple big rigs blown over if winds really do reach 65 mph.

And now to the better, better, better part of the forecast...the 
improved weather for the rest of the week!

Wednesday will see much cooler weather (highs in the 70s), less 
humidity and ample sunshine. A great day to get outside right? 
Well that will depend on your activity of choice, as the winds 
will be gusty from the northwest (gusts of 30 to 40 mph most of 
the day). If you are trying to avoid the winds, your best chance 
will be in the evening.

A building ridge of high pressure over the south central U.S. 
will bring dry weather and a gradual warming trend Thursday 
through Sunday. Look for temperature to top out in the 80s each 
day, with lighter winds Thursday and Friday, trending toward more 
persistent south winds Saturday and Sunday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 633 PM CDT Tue Jun 9 2020

Scattered storms are popping up behind a surface that is slowly
advancing eastward, and will kick off a very busy TAF period.
Thunderstorms are expected to continue through 04/05z for KLNK and
KOFK respectively and through 07z for KOMA. The ceilings under any
storms may deteriorate to around 1500ft AGL and visibilities down
to 2SM. The general activity will then transition to rain across 
all sites, and will be accompanied by very strong wind gusts (over
45 knots) out of the northwest. With the strong surface winds, 
very strong winds above the surface may reach near 60 knots at 
1500 ft AGL, introducing wind shear into the mix as well. 

Eventually, rain will taper off and leave the TAF sites dry after
12z for KOFK and KLNK, and 13z for KOMA. In its wake, we will
still be dealing with winds 33-36 knots out of the northwest and
VFR conditions.


&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Wind Advisory until 7 AM CDT Wednesday for NEZ015-091-093.

     High Wind Warning until 7 AM CDT Wednesday for NEZ034-045-052-
     053-067-068-089-090-092.

     Flash Flood Watch until 7 AM CDT Wednesday for NEZ051>053-
     065>068-078-088>093.

     High Wind Warning until 4 AM CDT Wednesday for NEZ030>033-
     042>044-050-051-065-066-078-088.

     Wind Advisory until 4 AM CDT Wednesday for NEZ011-012-016>018.

IA...Wind Advisory until 7 AM CDT Wednesday for IAZ043-055-056-069-
     079-080-090-091.

     Flash Flood Watch until 7 AM CDT Wednesday for IAZ069-079-080-
     090-091.

&&

$$

UPDATE...Dergan
DISCUSSION...Albright
AVIATION...Petersen