789
FXUS63 KGID 182326
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
626 PM CDT Wed Sep 18 2024

.KEY MESSAGES...

- There could be a few (<20% coverage) thunderstorms mainly east
  of Hwy 281 this evening (5-11PM). A marginally severe storm is
  possible (5%).

- Warm and dry most areas Thursday and Friday with highs still
  in the mid to upper 80s.

- Showers and thunderstorms move into the region Friday night
  and especially Saturday into Sunday with widespread rainfall
  amounts over 1 inch.

- Cooler next week with highs only in the 60s for many areas
  Sunday through Tuesday.

&&

.DISCUSSION...
Issued at 326 PM CDT Wed Sep 18 2024

This Evening into Tonight...

We have a large upper level trough across the western United
States with two 500 mb low centers. The first upper low is well
to our north over Montana/North Dakota with an associated
surface front extending from the Dakotas south into Nebraska
and Kansas. This is really more of a dry line across our area
with better moisture to the east and dry high plains air to the
west. The 2nd upper low is just about to come ashore over
California and will be our weekend storm system.

The track of this first system well to our north (North Dakota)
is not providing us with much forcing and thus any showers and
thunderstorms within the moist sector will be rather isolated.
However, the SPC marginal risk does highlight a valid risk for
the possibility of a few severe thunderstorms given MLCAPE
values inching up over 1500 J/KG and 0-6 km shear values of
around 30-35 KTS. Most convective models indicate that any
thunderstorms would likely be rather isolated so again are
expecting most locations should remain dry tonight. The best
chances for catching one of those isolated storms will be east
of Highway 281.


Thursday and Friday...

Drier air will push in from the west on Thursday behind the
departing first wave with northwesterly surface winds.
Therefore, dry and warm weather with highs in the mid to upper
80s are expected on Thursday. The next upper low will slowly be
tracking east across southern California on Friday with
return southerly flow starting to take hold across the southern
and central plains ahead of this next system. We will see rising
dew points, but any rainfall should likely hold off until late
evening or overnight beginning first in Kansas and then working
north through the Friday late night hours.


Saturday and Sunday...

This appears to finally be the big rain that so many have been
waiting for, just too bad that it`s on a weekend. The latest 12Z
ECMWF ensemble average indicates over 1 inch of precipitation
for our entire forecast area with a 2 inch average across some
of our eastern counties. The GFS is also bullish with
precipitation this weekend. The brunt of the precipitation will
be Saturday afternoon through Sunday morning, but light
precipitation could linger through much of Sunday. There does
not appear to be much instability with this system so severe
weather is not much of a threat at this point in time. Can not
rule out localized flooding if we see some localized higher
amounts over 3 inches, but it has also been very dry lately.
Temperatures will start to fall on Sunday on the back side of
this next system with northwestern areas likely only in the 60s.


Monday and Tuesday...

We should dry back out and become more fall like with most highs
only in the 60s to around 70.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 625 PM CDT Wed Sep 18 2024

For KGRI/KEAR Airports:

Significant weather: None.

Tonight: Ongoing SCT clouds around 4-5K ft should dissipate by
around midnight. There`s a very slim chance for an iso storm to
pop up next few hrs at mainly GRI, but odds just too low to
include at this time. Steady S winds 7-10kt should go lgt and
vrbl with the approach of a cold front by around dawn.
Confidence: High.

Thursday: Cold front will cause lgt and vrbl winds to swing
to the NNW around 14-15Z. Some guidance suggests some FEW-SCT
stratocu around 1500ft for a few hrs immediately behind the
front, with chcs slightly higher towards GRI than EAR.
Otherwise, skies will be mostly clear by midday with steady/brzy
NNW wind continuing thru the aftn. Confidence: High.

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...None.
KS...None.

&&

$$

DISCUSSION...Wesely
AVIATION...Thies