Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 180000
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
700 PM CDT Wed May 17 2017

.SHORT TERM...(This evening through Thursday)
Issued at 353 PM CDT Wed May 17 2017

Aloft: A longwave trof was over the Wrn USA. A compact upr low
was embedded over Neb/KS and lifting NE...kicked out by a larger
low upstream over UT/NV/ID. The Neb/KS low will depart the rgn and
head into the upr Midwest tonight while the Wrn low slowly sags
SE through tomorrow. The tightest model clustering suggests it
will be over Wrn CO by 00/Fri.

Surface: Deep low pres was over Ern Neb at 19Z. It was moving NE
along a strong cool front that extended from Hudson Bay to KS to
another deep low over CO. Another cool front was making its way
thru the Wrn USA. The first front will sink into Srn KS with a W-E
orientation tonight and become quasi-stationary tomorrow. This
front will begin to pivot cyclonically in the afternoon as the CO
low ejects into Srn KS.

This has been a busy shift with clean-up for last night`s svr
tstms and lingering hydro issues.

A few brief shwrs will linger over the next few hrs...with patchy
steadier light rain possible well N of I-80. Rainfall amts will be
less than .10".

Windy for a time late this afternoon-eve as CAA/mixing transfers
higher winds to the sfc.

Tonight: Becoming p/cldy to even m/clr...but the consensus of
model guidance suggests low stratus will form over part of the
fcst area (FA). Used EKDMOS for low temps (mid-upr 40s).

Thu: M/cldy espcly over S-cntrl Neb. It will be windy and chilly.

Skies could turn p/cldy over N-cntrl KS. This may not have been
depicted well enough in the fcst though. Substantial heating could
occur there even though the warm front remain to the S.
Significant tstm development should occur over SW and Cntrl KS and
SW flow should bring these tstms into N-cntrl KS.

Significant low and deep layer shear will result in svr tstms with
MLCAPE 1500-2000 J/kg. Very large hodographs would support
supercells with extremely large hail. If daytime heating can erode
low-level CIN and storms can remain discrete...tornadoes will also
be possible.

The 12Z/18Z NAM large hail parameter suggests 3" hail will be
possible (conditional on supercell storms occurring). However...
due to some uncertainty of storm mode...will mention 2" in the
HWO. The concern is the number of storms may result in collisions
and mergers resulting in more multicell lines and clusters.

2-4" of R+ fell across much of the FA Tue night into this AM. This
did result in minor flooding and soils are saturated. This setup
(which begins Thu eve and conts thru Fri night) will result in
swaths of more R+.

CIPS analog guidance suggests a high probability of 1" of rain
with the mean of all the analogs suggesting 1-2" and there is
potential for swaths of more if and where storms train.

.LONG TERM...(Thursday night through Wednesday)
Issued at 353 PM CDT Wed May 17 2017

There will probably be a lull late Thu night into Fri AM before
more rain moves in. This system will move out Sat. We may have
overplayed the threat of tstms in the fcst Fri. Stability will be
increasing...but if some clearing occurs under the cold pool
aloft...more tstms will be possible.

The busyness of today combined with focus on the system Thu-Fri
did not allow for anytime to look beyond.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Thursday)
Issued at 654 PM CDT Wed May 17 2017

Although the wind direction is more west out of KGRI as of recent
observations, wind direction should soon become more north as a
low pressure system continues to pull away to the east. Visibility
should not be much of an issue despite the copious amounts of
recent rain as wind speeds should stay up. However, ceilings are
expected to lower later tonight into early Thursday morning. We
could also get a temporary scattering of ceilings later this
evening as stratus clears, before more lower stratus moves in
again, with high confidence of MVFR/IFR ceilings.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Flash Flood Watch from Thursday evening through late Friday
     night for NEZ048-049-062>064-073>077-083>087.

KS...Flash Flood Watch from Thursday evening through late Friday
     night for KSZ005>007-017>019.

&&

$$

SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Heinlein



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