Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 212014
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
314 PM CDT WED SEP 21 2016

.SHORT TERM...(This evening through Thursday)
Issued at 250 PM CDT Wed Sep 21 2016

The focus remains on the potential for thunderstorms and severe
weather this evening and tonight. The pattern aloft featured an
upper ridge axis across the southern plains, an upper trough moving
onshore in WA/OR with southwest flow across the central plains in
between the systems. A shortwave trough was evident translating
northeast out of Colorado into Nebraska. At the surface, a cool
frontal boundary was located just west of our cwa from KOGA to
KANW to KYKN.

A warm, moist unstable airmass was in place across our region with
instability parameters between 1000 and 3000 j/kg, however a
strong cap has held off convection so far. Shear parameters
increase toward evening and if storms can go ahead of the boundary
across our area, strong to severe storms are possible which may
produce hail near quarter size, damaging wind gusts as well as
locally heavy rainfall with precipitable water values averaging an
inch and a half. Chances for thunderstorms carry into the
overnight hours, aided by a 40 to 50kt low level jet.

Temperaturewise tonight, lows are forecast in the 60s again in the
mild airmass and these warm low temperature readings may set new
records for the warmest low temperature. The record high minimum
temperature for Grand Island on September 22nd is 67 degrees and the
record for Hastings is 65 degrees.

The cold frontal boundary sags into our northwest cwa late tonight
and stalls out early Thursday. Convection may linger for a time
Thursday morning on the nose of the low level jet, with conditions
drying out by afternoon. Models bring a swath of low clouds in
behind the cold front in the vicinity of our northwest zones which
would hold down high temperatures Thursday afternoon, while
farther south temperatures will remain unseasonally warm.

.LONG TERM...(Thursday night through Wednesday)
Issued at 250 PM CDT Wed Sep 21 2016

Surface low pressure deepens in eastern Colorado Thursday night
ahead of the western upper low pressure system moving into Utah. In
response, the surface boundary across our northern counties lifts
north as a warm front. Southerly flow continues to
increase/tighten heading into Friday as the upper low pressure
system moves further into the Rockies. Thursday night low
temperatures will again be very warm and may be near records for
high minimum temperatures, however the standing records are 70
degrees. Friday is shaping up to be warm but very windy in deep
mixing with the tight pressure gradient in place with south wind
gusts over 30 mph expected.

Friday night could see storms in warm air advection ahead of the
upper trough emerging onto the high plains and ahead of the
approaching cold frontal boundary pushing east from western
Nebraska and Kansas. Models continue to speed up the progression
of the trough across the plains, with the upper low center lifting
across the Dakotas and the associated cold front crossing our cwa
during the day Saturday which will lead to a drier forecast for
our area with the rain chances focused along/ahead of the boundary
in eastern Nebraska and Kansas.

Cooler air advects south behind the front over the weekend with
temps dropping below normal by Sunday and into next week. The
extended models are still having a difficult time in resolving what
to do with the upper low across the interior CONUS in a blocking
pattern with ridging to the east and suggest the potential for a
meandering cutoff low, with general cool Fall type weather with
possibly a little rain.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Thursday afternoon)
Issued at 1155 AM CDT Wed Sep 21 2016

High clouds will thicken/lower with time ahead of an approaching
cold frontal boundary and upper level disturbance. There is the
potential for convection mainly during the evening and overnight
hours and a strong to severe storm cannot be ruled out. South
winds will be steady and gusty with gusts around 25kts. A
strengthening low level jet tonight will lead to a period of low
level wind shear.

&&

.GID Watches/Warnings/Advisories...
NE...None.
KS...None.

&&

$$

SHORT TERM...Fay
LONG TERM...Fay
AVIATION...Fay



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