Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 270502
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1202 AM CDT Thu Jul 27 2017

.UPDATE...
Issued at 930 PM CDT Wed Jul 26 2017

Flash flood watch was cancelled a bit earlier. Most of the showers
and storms have pushed south or weakened. Will maintain some low
POPs across our southern counties to blend in with neighbors.
Added some patchy fog wording for later tonight in parts of
eastern NE and southwest IA. Otherwise only minor changes were
made for the overnight hours.

&&

.SHORT TERM...(Tonight through Saturday)
Issued at 305 PM CDT Wed Jul 26 2017

Early-afternoon water vapor imagery and 12z upper-air data depicted
a closed upper low near James Bay with an associated trough
trailing southwest into the mid MO Valley. A weak upstream
perturbation was noted over the central High Plains tracking east.
In the low levels, 18z mesoanalysis suggests that the primary
surface boundary stretches from central IA through east-central NE
before linking with an area of low pressure over north-central
KS.

A band of slow-moving showers and thunderstorms present from
Columbus and Seward into the Omaha Metro area as of 19z appears to
be tied to a zone of deeper convergence within the frontal
circulation. The slow motion of this activity coupled with a
moist environment (i.e. PW values of 2.00-2.25") and deep warm-
cloud depths is resulting in locally heavy rainfall with Columbus
reporting a 1-hour precipitation total of 1.85" around midday.

Cloud breaks have allowed temperatures to warm to 80-85 degrees
within the pre-frontal warm sector across parts of southeast NE
as of 3 PM with estimated mlCAPE values of around 1500 J/kg.
While vertical shear will remain relatively weak, the air mass
destabilization should allow for an increase in storm coverage and
vigor through the remainder of the afternoon into evening. The
strongest storms will be capable of locally strong wind gusts and
heavy rainfall, and a Flash Flood Watch remains in effect for far
southeast NE and southwest IA.

Showers and thunderstorms will likely continue tonight across
parts of southeast NE and southwest IA as deep-layer ascent is
augmented by the above-mentioned impulse approaching from the
west. On Thursday, a surface ridge will build into the mid MO
Valley with dry and mild conditions. On Friday into Friday night,
a weak disturbance will crest the mid-level ridge axis across the
northern Plains before turning southeast into the lower MO Valley.
Any precipitation associated with this feature should remain to
the west of the area. In the low levels, we will remain under the
influence of a surface high centered over the upper Great Lakes
into Saturday with daytime highs generally in the lower to mid
80s.

.LONG TERM...(Saturday night through Wednesday)
Issued at 305 PM CDT Wed Jul 26 2017

Broad ridging aloft from the Interior West to Great Plains will
persist through the weekend into early next week before gradually
breaking down by about mid week. Model guidance does suggest that
any synoptic-scale boundary will remain to the northwest of the
area through the long-term forecast period, yielding low
confidence in precipitation potential and placement. Temperatures
will remain seasonably mild with daytime highs generally in the
80s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1149 PM CDT Wed Jul 26 2017

Visibilities will lower overnight as cloud cover shifts south.
IFR visibilities will be possible at both KOMA and KLNK through
12Z. Drier air to the north should maintain VFR conditions at
KOFK through the period. VFR conditions are anticipated at all
sites by late Thursday morning through the remainder of the
period.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

$$

UPDATE...Miller
SHORT TERM...Mead
LONG TERM...Mead
AVIATION...KG



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