Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 220001

Area Forecast Discussion
National Weather Service Hastings NE
701 PM CDT Fri Jul 21 2017

.SHORT TERM...(This evening through Saturday Night)
Issued at 400 PM CDT Fri Jul 21 2017

Dry, hot conditions continue across the area this afternoon, with
the dome of upper level high pressure remaining centered over
portions of the south central/southeastern CONUS. At the surface, a
trough axis extends from west-central KS northeastward into
northeastern NE. This boundary is clipping far northwestern portions
of the CWA, with light/variable to calm winds. Across the remainder
of the CWA, winds have been south-southwesterly, helping mix out
dewpoints for mainly NC KS into the 50s and temperatures to around
105 deg. Closer to/along the boundary, dewpoints are higher, into
the mid 70s for some, with temps in the lower/mid 90s. Just another
miserable day as heat index values for most are around 105 deg.

Through the rest of this afternoon and into this evening, outside of
the heat, the main concern lies with thunderstorm chances. The
surface boundary across the northwestern areas looks to provide a
focus for development. Forcing aloft is pretty weak, and there is
plenty of warm air aloft/capping, but with peak heating of the day,
models are in pretty good agreement showing at least
isolated/scattered activity developing. Strong/severe storms remain
a concern, with portions of the CWA remaining in the SPC Day 1
Marginal Risk area. Instability certainly not an issue, but deep
layer shear is low, will keep the mention on marginally severe wx in
the HWO.

Overnight, have low PoPs continuing mainly across south central NE.
Models show the sfc/low level boundary gradually sagging south,
along with lift on the northern edge of a 30-ish kt LLJ, so could
have scattered activity around much of the night. Any severe wx
threat should wane with time.

Looking at precip chances Sat/Sat night, the sfc cool frontal
boundary continues working its way south, starting the day roughly
through the heart of the CWA. Strong/severe thunderstorms will again
be a concern, mainly across the southern half of the CWA during the
late afternoon and into the evening hours. Upper level forcing
continues to be on the weak side, but shear is a bit better. Will
keep ping pong balls/60MPH going in the HWO.

Along with helping drive thunderstorm chances tomorrow, this frontal
boundary is making the temperature forecast a bit of a headache.
Yes, forecast high temperatures are expected to be cooler than the
past several days, but still looking at highs in the 90s, perhaps
100 in far southern areas. Will be dependent on the speed of the
front pushing south and the magnitude of mixing out ahead into the
hottest air aloft. Along/south of the front, will likely see
moisture/dewpoints pooling, keeping the muggy conditions around.
Decided to keep heat headlines going across the far southeastern
portions of the CWA, where current forecast has heat index values
hitting 100-105, though it may only be briefly. Thought about
letting today`s headline expire this evening and let the mid crew
reassess, but the southeast isn`t going to have notable relief
overnight, and since we have had headlines going the past several
days, felt it would be best to just continue the headline right on
through tomorrow.

.LONG TERM...(Sunday through Friday)
Issued at 400 PM CDT Fri Jul 21 2017

Hard to have a lot of confidence in any specific details of the long
term period.

On Sunday, may start the day with a few lingering storms across far
south, but otherwise the rest of the day is currently dry. More
northwesterly flow is expected to return in the upper levels, with
the main area of high pressure/ridge axis back off to our west. Not
a lot of change in that as we get into Monday, but toward mid-week,
a more notable trough moving toward the west coast looks to push the
main ridge axis east, back onto the Plains. Through the long term,
any periodic precipitation chances would be tied to disturbances
sliding around the edge of the ridge, and confidence in timing or
location is not high at all.

As far as temperatures go, no reason to deviate from the model blend
with plenty of uncertainty, with forecast highs generally in the
upper 80s to mid 90s.


.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday)
Issued at 701 PM CDT Fri Jul 21 2017

Will continue calling for VFR ceiling/visibility through the
period, with probably the only real caveat being whether a heavier
thunderstorm just happens to pass overhead at some point. Wind-
wise, speeds should remain relatively light mainly at/below 10kt
(unless storm outflow becomes in issue), with direction
transitioning from southerly/variable this evening and tonight to
more northeasterly on Saturday behind a weak front. A few more
details follow...

Thunderstorm potential:
Although the chance of a storm during these first 6-9 hours or so
is not truly zero, they seem low enough and more focused off to
the west and north that the previous "vicinity" (VCTS) mention has
been removed from this evening/tonight, at least for now. However,
with a somewhat more favorable (albeit not likely) chance for
scattered activity in the area Saturday afternoon, have introduced
VCTS to the final 5 hours of the valid period. A marginally
severe storm cannot be ruled out, if any occur.


NE...Excessive Heat Warning until 8 PM CDT this evening for NEZ064-

     Heat Advisory until 8 PM CDT this evening for NEZ039>041-046>049-

     Heat Advisory until 7 PM CDT Saturday for NEZ086-087.

KS...Excessive Heat Warning until 8 PM CDT this evening for KSZ006.

     Heat Advisory until 8 PM CDT this evening for KSZ005.

     Heat Advisory until 7 PM CDT Saturday for KSZ006.

     Excessive Heat Warning until 7 PM CDT Saturday for KSZ007-018-

     Heat Advisory until 7 PM CDT Saturday for KSZ017.



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