Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 081127

National Weather Service Hastings NE
627 AM CDT Sat May 8 2021


.DISCUSSION...(Today through Friday)
Issued at 455 AM CDT Sat May 8 2021

Today`s forecast is one of the more tricky ones for numerous
reasons, the primary of which being the severe threat this afternoon
and evening. Clouds are expected to gradually fill in across the
area this morning with satellite already showing lower level cloud
cover over the northeast third of the CWA. This is also where we
could see one or two isolated showers pop up this morning, but they
are not expected to be impactful or long lived. As the morning
continues on, upper level ridging will slide off to the east as a
closed low works its way southeastward across MT. The approaching
upper level trof develops a lee low at the sfc which will strengthen
and drop farther south throughout the morning. The placement of this
low and the set up of its associated fronts will be integral in
today`s severe weather potential.

Currently models suggest that as this sfc low moves over
southwestern KS by this afternoon. A warm front looks to set up and
stretch out to the northeast across much of central and northeastern
KS. Models also depict a dry line setting up to the south running
down through southwest KS and the OK and TX panhandles, and a cold
front to the southwest of the low, arching across northern AZ and
NM. Strong diurnal heating along with steep low-level lapse rates
should help to initiate convection around the area of the triple
point this afternoon. Storms are then expected to expand
northeastward along the frontal boundary throughout the afternoon
and into the evening. SPC has placed a slight risk for severe
weather across the majority of KS for today, as models have
consistently depicted an environment capable of supporting severe
thunderstorms this afternoon and evening. While there does appear to
be modestly strong capping in place, good southerly flow should help
to advance moisture northward and help to erode the cap this
afternoon. Across northern KS (particularly along and north of the
warm front) bulk shear looks to be in the 35-45 kt range, along with
a pool of 1500-2000 j/kg of CAPE, and steep low level lapse rates.
This environment is likely to support the development of supercells
with the potential of producing large hail as the primary threat,
though an isolated tornado or two cannot be ruled out.

At the same time the tail end of a cold front is expected to drop
south through central and eastern NE. This is the reason for the
widespread PoPs across the area today since additional storms are
likely to develop along and ahead of the cold front as well. While
the severe threat looks to primarily exist across portions of north
central KS, there is a larger uncertainty regarding the severe
threat for south central NE. Where things get tricky is with the
interaction of these two boundaries, with the advancing cold front
potentially undercutting storms... this would mainly be across south
central NE (thus the uncertainty). Then as we transition later into
the evening and the cold front advances farther south, storms will
potentially evolve into a more linear structure (possibly an MCS). A
strong LLJ is expected to develop around 00Z Sunday and should help
to drive the main focus of convection to eastern KS. This would mean
a rapidly diminishing severe threat for our CWA after 00Z Sunday.
Though the existing environment may still support a wind threat for
remaining storms.

Since majority of time and effort was focused on the short term with
today`s severe threat, haven`t looked much into the long term.
Behind this system cooler air settles in with highs dipping back
down into the 50s through around midweek. Flow aloft will transition
back to being mostly zonal on Sunday and Monday as the closed low
aloft dampens and spreads out across the northern Plains. Sunday
night will likely be the coldest night of the week with the far
northwest third of the CWA hovering right around and just above
freezing. Expecting off and on rain chances throughout the remainder
of the 7-day thanks to a few waves and slight perturbations aloft
that pass through. At the sfc, high pressure gradually settles in
over the northern Midwest by Tuesday giving us mainly easterly and
southeasterly sfc flow. Highs are expected to climb back up into the
70s and 80s by Thursday as we transition to northwest flow aloft
along with generally rising heights.


.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Sunday)
Issued at 625 AM CDT Sat May 8 2021

VFR conditions expected to continue for the next several hours but
will gradually deteriorate to MVFR cigs as cloud cover increases
with an approaching frontal system. Thunderstorms are expected
this afternoon and through the evening hours with this system,
along with gusty winds that will shift to northerly late in the
evening with the frontal passage.




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