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Area forecast discussion 
National Weather Service Omaha/valley NE
120 PM CDT Friday Jul 25 2014

Short term...(today through sunday)
issued at 330 am CDT Friday Jul 25 2014

Temperatures and thunderstorm chances should again be the primary forecast
concerns. Will keep heat advisory going southern zones for this
afternoon and early evening.

Convection that formed over the High Plains yesterday afternoon and
evening continued to roll eastward overnight with 40-60 knot low
level jet around 1 km above ground level. This activity was generally rooted above
the impressive cap below 750 mb from 00z koax sounding. A few things
noted from that sounding...700-500 mb lapse rate was 7.8 degrees c
per km and precipitable water was 1.38 inches. This morning was a
perfect example of how we can get overnight convection even with
700 mb temperatures of 14-15 degrees c. Cases like this though are
very hard to predict over about 24 hours in advance.

Main features noted from 00z upper air plot at 500 mb were the
closed low over southern Alberta and the ridge that stretched from
Southern California into the lower Mississippi River valley. Very
impressive 12 hour height falls...estimated at up to 140 meters...
were near the Alberta/Saskatchewan border. Weaker height falls
extended southward into western South Dakota...western Nebraska and
into Colorado.

The closed low at 500 mb will move eastward across southern Canada
through Saturday night...then open up a bit and track into the Great
Lakes region as an open shortwave trough. The 500 mb anticyclone
over New Mexico and Texas will wobble a bit through the period. An
extension of that high though will build up into central Canada
through Sunday as troughs dig over the northeast Pacific and over
the Great Lakes region...putting our area in modest to strong
northwest flow.

Today...convection should end by middle morning across southeast
Nebraska and southwest Iowa as the low level jet decreases. This
leaves our area with warm mild levels and little in the way of
large scale forcing until late afternoon. The previous forecast of
temperatures and dewpoints was not changed much. Heat index values
should peak in the 105 to 110 range in our southern zones this
afternoon. Have some concern that there may be just enough forcing
to get some isolated storms going between 6 PM and 10 PM this
evening as the weak cold front pushes across southeast Nebraska
and southwest Iowa. Otherwise...we may have to wait for storms to
again roll eastward from the High Plains north of the front late
tonight. That activity would mostly be confined to northeast
Nebraska prior to 12z Saturday. None of the models have been doing
a stellar job with the convective activity the past several
days...but this is to be expected this time of year. Recent sref
model runs have shown some weak 700-500 mb q vector convergence
moving eastward along the Nebraska/South Dakota border
tonight...then over portions of the area on Saturday. Not overly
impressed with anything...but will keep some 20-40 probability of precipitation in
northeast Nebraska and mainly 20 percent elsewhere. Storm Prediction Center day 2 outlook
does have our far southern counties in a slight risk (i think
mostly for Saturday afternoon and evening) and for now that seems
reasonable. Temperatures Saturday should not be quite as hot as
today...generally 3 to 6 degrees cooler. But cooler and drier air
will move in by Sunday as high pressure at the surface builds east
across the northern and Central Plains.

Long term...(sunday night through thursday) issued at 330 am CDT
Friday Jul 25 2014

We still look for temperatures at or below normal through this
period. Precipitation chances generally look small...with only fair model
agreement in regards to forcing strong enough to get thunderstorms going.
The 500 mb pattern is expected to amplify a bit as the ridge
retrogrades middle to late next week.


Aviation...(18z tafs for kofk...klnk and koma.)
Issued at 120 PM CDT Friday Jul 25 2014

Outflow from early morning convection continues to hold over far
eastern parts of the area at 18z with southeast winds still in
place at koma. Weak surface front expected to continue to advance
slowly southeast through 03z then stall near southern border area.
Models hint at another thunderstorm complex moving out of South
Dakota again late tonight which may impact kofk after 08z. VFR
conditions are expected outside of any thunderstorm areas.


Oax watches/warnings/advisories...
NE...heat advisory until 7 PM CDT this evening for nez065>068-078-

Iowa...heat advisory until 7 PM CDT this evening for iaz079-080-090-091.



Short term...Miller
long term...Miller

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