Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 270447
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1147 PM CDT Wed Apr 26 2017

.SHORT TERM...(Tonight through Saturday)
Issued at 329 PM CDT Wed Apr 26 2017

The chance for freezing temperatures and frost tonight, then rain
moving back into the area Thursday night through Saturday, are the
primary forecast concerns.

Temperatures this afternoon have struggled to gain much from morning
lows, with readings at mid afternoon still in the upper 30s in
northeast Nebraska, to the upper 40s in southeast Nebraska.
Widespread cloud cover and cool northwest breezes made the chilly
temperatures feel even colder. Back edge of cloud cover extended from
central South Dakota into central Nebraska, close to mid level
trough axis noted on water vapor imagery and RAP analysis. That
trough is forecast to swing northeast of eastern Nebraska and
western Iowa this evening. Subsidence in wake of trough should help
to dissipate cloud cover.

At the surface, strong low pressure is expected to move into the
northern Great Lakes region by Thursday morning, with high pressure
ridge extending from the western Dakotas into central Nebraska.
Decreasing winds are expected in our area under this scenario,
however calm winds promoting better frost formation environment is
in question.

However with temperatures already cool this afternoon, continued
cold advection this evening, clearing skis and diminishing winds,
frost formation is still possible where winds drop off
significantly. Already have Frost Advisory going for the southern
half of our area where collaboration with agricultural partners
suggests plants are vulnerable, and see no reason to pull that
advisory now. Farther north where widespread agricultural interests
indicate current plant stages suggest little vulnerability to frost
and high vulnerability to freezing temperatures, have opted to
maintain our current Freeze Warning. Expect temperatures there to
drop into the upper 20s in many spots, and remain there for
several hours overnight. Low to mid 30s are forecast farther
south.

Overall flow pattern will favor a broad trough over the middle of
the country into Friday, then sharpen into the Four Corners region
into Saturday. Impulses rotating through that flow will bring
chances for showers to the area off and on beginning Thursday night.
Dry surface air on northeast low level flow should hold precip off
until the evening, so much of Thursday should have at least some
sunshine before higher clouds begin to thicken later in the day. Mid
level impulse only slowly lifts through the area Friday morning,
bringing a break in precip potential during the afternoon. The
next shortwave is forecast into the Southern Plains Friday
evening, which spreads northeast through Saturday. Models have
trended farther south with this feature and associated
precipitation through Saturday, focusing majority of activity well
to our south. However southeast Nebraska into southwest Iowa will
still be in the likely area of rainfall, with decreasing
likelihood to only a slight chance in northeast Nebraska. Total
rainfall through Saturday is forecast from a tenth in our north to
about three-quarters of an inch in the south.

.LONG TERM...(Saturday night through Wednesday)
Issued at 329 PM CDT Wed Apr 26 2017

Mean mid level trough remains over the middle of the country through
the middle of next week, with a more significant low moving into our
region on Sunday. That low, originating from the Four Corners
region, is forecast into northeast Kansas by Sunday afternoon, then
on into the northern Great Lakes by Monday afternoon. Continued feed
of moisture from the Southern Plains north into the middle
Mississippi and Missouri River Valley regions will promote continued
precipitation chances until wrap-around section of upper low lifts
northeast of our area on Monday. So will have increased
precipitation chances for all of eastern Nebraska and southwest Iowa
Saturday night through Sunday night before decreasing Monday.

Precipitation phase is a question, especially for northeast Nebraska,
and generally for the morning hours of Sunday and Monday. A
continued feed of colder air from the north will drive temperatures
into the 30s for lows, and 850 temperatures are well below zero for
the duration of the precipitation in northeast Nebraska, and for a
time over the rest of our area. Thickness progs are borderline for
much of the period, save for Sunday night into Monday morning in
northeast Nebraska. And both GFS and ECMWF are in agreement. So
there is certainly a potential for accumulating snow in northeast
Nebraska if we can manage a full conversion to snow for a few
hours and rates can overcome warmer ground temperatures. But with
those things still in question now, have maintained our mention
of a rain and snow mix where and when temperatures are forecast to
drop to the middle 30s and below.

Beyond Monday, slightly warmer temperatures, highs in the 60s, are
forecast into mid week as heights gradually rise. However another
shortwave dropping into the region could provide another quick shot
of rain either Tuesday or Wednesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1130 PM CDT Wed Apr 26 2017

VFR conditions expected thru the fcst pc.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...Frost Advisory until 9 AM CDT Thursday for NEZ044-045-051>053-
     065>068-078-088>093.

     Freeze Warning until 9 AM CDT Thursday for NEZ011-012-015>018-
     030>034-042-043-050.

IA...Frost Advisory until 9 AM CDT Thursday for IAZ055-056-069-079-
     080-090-091.

     Freeze Warning until 9 AM CDT Thursday for IAZ043.

&&

$$

SHORT TERM...Dergan
LONG TERM...Dergan
AVIATION...DEE


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