Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 151141

Area Forecast Discussion
National Weather Service Hastings NE
641 AM CDT Thu Mar 15 2018

.SHORT TERM...(Today and tonight)
Issued at 452 AM CDT Thu Mar 15 2018

After a few quiet/pleasant weather days (except for fire weather
concerns), things start turning more active during these next 24
hours. However, please note that any precipitation within our
coverage area (CWA) through sunrise Friday is now expected to stay
of the liquid/non-freezing variety. Summarizing, there are 4 main
stories/challenges of these next 24 hours: 1) A tricky high
temperature forecast today, with a roughly 20-degree gradient from
our far north to far south...2) Increasing easterly winds
especially late this afternoon-tonight, with widespread gusts to
30-35+ MPH most places...3) At least near-critical fire weather
conditions especially near and south of the state line, and
marginally-critical conditions most favored in our far southern 3
KS counties (see separate Fire Weather section below for more on
this)...4) A halfway decent chance for at least isolated (probably
not widespread) non-severe thunderstorm activity overnight,
although a few instances of small hail cannot be ruled out.

Taking a look at the current/recent weather scene as of 4 AM:
So far, things behaving pretty much as expected 24 hours ago. In
the mid-upper levels, water vapor satellite imagery and short term
model data confirm that the amplified/large scale ridge axis that
has been to our west the past few days has finally shifted almost
directly overhead. To it`s immediate west, our eyes are focused on
the leading edges of the upstream large-scale trough, whose main
parent low is still off the Pacific Northwest coast, but with
plenty of smaller-scale disturbances already moving our direction
across the Rockies. Infrared satellite imagery confirms only
limited/thin high cirrus streaming overhead locally, with skies
mostly clear. At the surface, a very weak cold front is in the
process of dropping southward across our CWA. This boundary is
rather ill-defined, but if you look closely, you can that light
breezes in northern NE are more easterly, while our southern zones
are still hanging on to more of a southerly component. Honestly
though, winds have temporarily become downright light/near-calm at
various places within this broad frontal zone this morning. Am
currently aiming low temps this morning somewhere into the 30s
most areas, but ranging from the upper 20s far north, to perhaps
low 40s far south. Given the light winds though, things could drop
a touch lower than expected yet this morning.

Now looking ahead forecast-wise through today/tonight...

Confidence remains very high that our entire CWA will make it
through at least 00Z/7PM precip-free, with only varying degrees of
passing high level clouds, providing for generally partly cloudy
skies. That leaves temperatures, fire weather (see below) and
increasing winds as the main issues. In the mid-upper levels,
increasingly strong/diffluent flow will lift toward western
portions of our region, as the aforementioned ridge axis keeps
shifting east. At the surface, the response to the upper level
forcing will be deepening low pressure centered over eastern CO,
which is expected to reach a magnitude of roughly 990 millibars
by sunset. As this low deepens, the effective west-east surface
front will settle to near the state line before stalling. North of
the front (mainly our Neb zones), easterly winds will increase
with time, with sustained speeds generally 15-25 MPH by mid-late
afternoon/gusting to around 30 MPH. Near and south of the front
(mainly our KS zones), winds probably won`t be quite as breezy
this afternoon, and will have a bit more of a south- southeast
directional component. Given that skies are expected to be no
worse than partly cloudy, and that this is not a truly intense
frontal boundary, high temps are tricky. If anything, it looks to
be a bit warmer than expected 12-24 hours ago, and have raised
highs 2-4 degrees versus previous. However, this still calls for a
decent range from upper 50s far north/mid-upper 60s Tri Cities
/mid-upper 70s in KS zones. At least one short-term model (RAP13)
suggests that highs may need nudged up a touch more yet, but will
hold firm for now with what`s in there.

The main story by far overnight is the halfway decent chance for
rain showers/isolated weak thunderstorms, especially within
roughly the northeast half of the CWA, and with lesser rain
chances farther south-southwest. Before continuing though, want to
emphasize that this does not look like a true "heavy soaker"
tonight, as even the most favored rain areas may struggle to see
more than 0.10-0.20" based on average QPF (although of course
localized downpours will surely result in some higher amounts). In
the mid-upper levels, the latest NAM/GFS are in excellent
agreement closing off a deepening/intensifying mid-level low over
northwest KS (barely west of our CWA) by sunrise Friday. At the
surface, the nearly vertically stacked system will shift the
strong surface low to roughly the same position by sunrise. As
forcing increases during the night, largely driven by an increasing
low level jet and associated low-mid level moisture advection,
most-unstable CAPE values mainly in the 850-700 millibar layer
will increase to at least a few hundred J/kg per the latest
NAM/RAP, but with effective elevated instability probably
remaining safely below 500 J/kg. At any rate, showers and at least
isolated thunderstorms (perhaps a few with small hail) will
become increasingly-likely anytime after roughly 10 PM, and
especially after roughly 1 AM. Again, the majority of activity
would seemingly favor northern zones, but even the south could see
limited activity. Whether you see rain or not, nearly the entire
area will see continued/even stronger easterly winds through the
night, with frequent gusts likely to around 35 MPH. The only
exception will be in KS zones, where the closer proximity of the
surface low will keep winds a bit lighter and perhaps more
southerly/variable in direction. Like daytime highs, overnight
lows were also nudged up a few degrees most areas, all but
ensuring that any precip through sunrise remains liquid rain. More
specifically, lows are aimed from mid 30s far north to upper 40s

.LONG TERM...(Friday through Wednesday)
Issued at 452 AM CDT Thu Mar 15 2018

A potent upper level low pressure system moving through the area
will be the primary concern right off the bat of the long term
period. Models aren`t in too bad of agreement with the placement of
the 500mb low at 12Z Friday, set up over NW KS-SW NE. Gusty easterly
winds are expected to still be in place to start the day, with the
main sfc low just outside the SWrn CWA. Through the daytime hours,
model agreement remains pretty good taking the low right across the
heart of the CWA, and into eastern NE by evening. There really
hasn`t been any significant change in the PoPs 12Z Fri-00Z Sat, with
the best chances of precipitation looking to be mainly over our
south central NE counties. Even with this being just tomorrow, there
are still some uncertainties with precipitation type, mainly in the
NNW, due to model differences with lower level/sfc temperatures.
Current forecast has rain being the primary precip type, but some
models suggest colder air aloft could work in during the afternoon
to result in some wet snow. At this point the best chances for snow
remain just off to the NNW of the CWA, but this will be something
for upcoming forecasts to monitor. The gusty easterly winds will
gradually transition to the north then northwest through the day, as
the sfc low slides across the CWA. The day starts with much of our
NE counties having sustained 20-25 MPH east winds, the day ends with
the SSW having those same speeds, only out of the NW. High
temperatures are tricky, with precip in the area and winds switching
to the NNW. Current forecast highs range from near 40 in the far
north to near 60 in the far south, but for much of the area, those
look like they`ll be earlier-in-the-day highs, with steady/falling
temps through the afternoon.

Continue to have some lingering PoPs during the evening hours,
drying out after 06Z. Some questions remain with precipitation type,
with the potential for some freezing rain across northern portions
of the area as we get toward midnight. Currently not thinking FZRA
would amount to notable amounts, as models suggest precip would be
wrapping up about the same time that would be developing. Plenty of
uncertainty still in place.

The forecast dries out for the start of the weekend, with models in
good agreement showing upper level ridging sliding through the
Plains, set up between the departing system and another moving in
from the West Coast. The gusty NW winds from Friday taper off by 12Z
Sat, thanks to a high pressure ridge moving in. Winds through the
day will be pretty light, and switching to the SSE by evening.
Expecting plenty of sun, with highs currently forecast to reach the
upper 40s to upper 50s.

The next chances for precipitation chances returns to the forecast
Sunday through Monday night. Precip looks to develop across the area
later in the day Sunday, as lift increases ahead of another upper
level low pressure system that looks to slide east across southern
KS. Though that system will be moving off to the east of the CWA
during the day on Monday, another shortwave disturbance will be
swinging east out of the Rockies through the central/nrn Plains,
keeping precip chances around. Starts out as rain Sunday, with
rain/snow possible Sun night/Mon morning and again Mon night, mainly
rain during the daytime hours Mon. Breezy/windy conditions look
favorable on Monday. Forecast highs on Sun are in the 50s/lower 60s,
with 40s for most on Mon, lower 50s in the south.

The forecast for Tues/Wed is dry, but confidence in that is lower
for Tues than Wed, as some models suggest lingering precip in the
area with another disturbance. High temps range from the 40s/low 50s
for Tues to 50s/low 60s for Wed.


.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Friday)
Issued at 641 AM CDT Thu Mar 15 2018

General overview:
Confidence is pretty high in VFR ceiling/visibility through the
first 18 hours, with fairly high confidence in at least an MVFR
ceiling settling in sometime during the final 6 hours early
Friday morning, along with chances for rain showers/a few non-
severe storms. Overall though, probably the most notable aviation
impact through most of the period will be increasing easterly
winds. Read on for more element-specific detail...

The lightest winds of the period will occur right away these first
few hours. However, as the day wears on, and especially by
evening, developing low pressure to the west will prompt a steady
increase in easterly winds. This afternoon, sustained speeds
15-20kt/gusting 20-25kt will be common, with even stronger speeds
during the night generally sustained 20-25+kt/gusting around

At least the first 15 hours or so should remain dry with only
passing high level clouds. However, anytime after 03Z, and
especially after 06Z, at least isolated to scattered rain shower
and non-severe thunderstorm activity will break out in the general
area. Did not have confidence yet to go prevailing rain, but am
carrying a multiple-hour "vicinity thunderstorm" (VCTS) mention.
Ceiling-wise, have introduced prevailing MVFR at 08Z, but some
guidance suggests that IFR could develop during the final few
hours and this will need monitored. At least for now have kept
prevailing VFR visibility, but obviously any passing showers could
promote sub-VFR. Will defer to later forecasts to attempt these
finer details.


Issued at 452 AM CDT Thu Mar 15 2018

Regarding the fire weather situation TODAY:

Was initially going to abstain from fire headlines today due to
only marginally-supportive relative humidity (RH) and wind speeds,
but several times during the last week we have seen fire
parameters get a bit worse than expected at the "zero hour" and
have ended up issuing and/or expanding existing Warnings with
minimal lead-time. With this in mind, and in coordination with
several neighboring WFOs, ended up issuing a Red Flag Warning for
our bottom row of KS zones (Rooks/Osborne/Mitchell), valid 1-8 PM.
As stated, from a purely technical standpoint, our forecasted RH
values right around 20 percent and max southeasterly wind gusts
barely expected to consistently reach 25 MPH for 3+ hours makes
this Warning a bit marginal. What is more certain is that solidly
"near-critical" parameters will extend farther north into at least
the bottom row of Nebraska zones along the state line. Obviously
fire danger will not be "zero" even north of there, but once you
get closer to I-80 and especially northward, RH values are not
expected to drop below around 30-35 percent, which is solidly
above local Warning criteria, despite the breezy easterly winds in

Closing with a quick review of our local fire weather
"Critical" means the 3+ hour overlap of relative humidity (RH) of
20- percent-or-lower and sustained winds/gusts of 20+MPH/25+MPH
(in the presence of sufficiently-dry vegetation/fuels). "Near-
critical" means the overlap of 25-percent-or-lower RH and
sustained winds/gusts of 15+MPH/20+MPH.


KS...Red Flag Warning from 1 PM this afternoon to 8 PM CDT this
     evening for KSZ017>019.



SHORT TERM...Pfannkuch
FIRE WEATHER...Pfannkuch is the U.S. government's official web portal to all federal, state and local government web resources and services.