Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 181002
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
502 AM CDT Sat Mar 18 2017

.SHORT TERM...(Today and tonight)
Issued at 502 AM CDT Sat Mar 18 2017

Another quiet afternoon is anticipated across the region today as an
upper level ridge of high pressure nudges in from the west and
southerly winds begin to increase thanks to an area of surface low
pressure developing on the lee side of the Rockies. As a
result...expect comparable temperatures to yesterdays readings,
with a bit more breezy conditions by afternoon.

As a result of the increasing winds...expect near critical fire
weather conditions to be possible by mid/late afternoon...but with
increasing dew points across our west where the winds will be
strongest, less critical fire weather conditions are possible
than otherwise would be anticipated. That said...will include a
mention of potentially near critical fire weather conditions for
the entire forecast area this afternoon in the HWO.

Beyond today, expect a seasonably warm evening across the local area
as southerly flow from the daytime hours helps advect higher
dewpoints across the region...which should help keep low temperature
10 degrees or so above normal. While there are some very low SREF
probs for fog formation to our west tonight - on the order of 10-20
percent - confidence of any fog across our local counties appears
low and did not mention in forecast grids for the time being.

.LONG TERM...(Sunday daytime through Friday)
Issued at 502 AM CDT Sat Mar 18 2017

General overview of this 6-day period:
Overall, no major changes of note from the previous forecast
package. That means that in a very basic sense, the main stories
include a very warm Sunday, a few rather "pesky" chances for rain
(and perhaps a few wet snowflakes north) mainly Monday night into
Tuesday and again Tuesday night into Wednesday, followed by the
"bigger system" we have been talking about that could feature
several rounds of rain and even a few thunderstorms during the
Wednesday night through Friday time frame. Will now cover these
various things (and a few others) in a bit more detail:

1) The "big system" Wednesday night-Friday:
This remains the big "highlight" of the entire long-term forecast,
especially for those folks (probably most) who want a decent rain.
Along these lines, while it will obviously not rain these entire
48 hours or so, there are enough differences in model
timing/discrepancies that precipitation chances (PoPs) are present
throughout Wednesday night-Friday. The potential is certainly
there for some areas to pick up a half-inch or more, but given
that there are a TON of uncertainties in the details at this Day
5-7 range, we certainly cannot "guarantee" that our entire
coverage area (CWA) sees this much. Speaking of forecast uncertainty,
if anything, the latest 00z runs of primary models such as the
GFS/ECMWF/Canadian seem to be exhibiting more differences
(especially for Wednesday-Thursday) than they were 24 hours ago
regarding the position of key features such as the main mid level
low, surface low and associated fronts, but then by Friday (Day 7)
these models tend to come into overall-better agreement. Of all
things that might not necessarily "agree" the best between the
latest raw model output and our latest official forecast, it`s
that while we are currently advertising our very highest PoPs (as
high as 60-70 percent) on Thursday, it may ultimately end up being
the case that the highest PoPs need to be delayed more-so Friday
into Friday night. As for thunderstorm chances, depending on the
model, essentially the entire Wednesay night-Friday time frame
could justify at least a slight mention of storms, but for now
have confined any thunder mention to just Thursday into Thursday
night given these periods have the overall-highest confidence in
sufficient instability. As mentioned here 24 hours ago, this
system appears to have enough instability/shear to yield our
first strong to perhaps even severe storms of 2017, but it`s still
far, far too soon to talk specific threats/details. For that
matter, at this point it`s even hard to tell whether Thursday or
Friday (or perhaps even both days) would be most favored for some
stronger storms.

2) The earlier-week precip chances Monday night-Wednesday:
Obviously before we get to the bigger late-week system we first
need to try pinning down the details of the seemingly lighter
precipitation potential here. While amounts don`t look to be
substantial by any means, at least minor accumulations of rain and
perhaps a few wet snowflakes are quite possible in parts of the
area. At least for now, have kept PoPs below "likely" percentages,
however. While rain should be the dominant precipitation type,
compared to 24 hours ago, things do look a bit more favorable for
at least a dusting of wet snow especially for some places north of
Interstate 80 and especially late Monday night into Tuesday
morning, but perhaps Tuesday night into Wednesday morning as well.

3) Temperature trends:
No major changes from previous forecast here, as Sunday is still
by far the warmest day with widespread 70s/80s before a decent
cool-down to more seasonable values in the 50s/60s arrives Monday
and especially Tuesday Wednesday, which if anything could be
trending a bit cooler than before. Technically, we then show
another modest warm-up for Thursday-Friday as, but there is
plenty of uncertainty here given the timing of the incoming system
and the coverage of widespread clouds/precipitation or lack
thereof on either day. Getting back to Sunday, while still by far
expected to be the warmest day of the long term period,
confidence has diminished a bit versus 24 hours ago that our
ENTIRE area will reach 80+ degrees (especially near/east of the
Tri Cities), as there are some possible mitigating factors here.

4) Fire weather concerns:
Fortunately, barring some pretty notable increases in forecasted
wind speeds and/or decreases in relative humidity, we are
relatively confident that we will not be dealing with outright-
critical fire weather conditions on any of these days. That being
said, at least limited parts of the CWA could see "near-critical"
conditions mainly Sunday and Monday afternoons due to the
potential for localized spatial overlaps of relative humidity
(RH) 25 percent or lower and wind gusts of 20+ MPH. Fortunately on
Sunday, the main limiting factor to fire danger will be
relatively light winds and RH staying safely above 25 percent.
However, a possible exception appears to exist especially in
Dawson County, which could lie on the far eastern fringes of a
larger area of lower RH/higher mid- late afternoon westerly winds
expected to develop across western Nebraska. As a result, will
slip this "near- critical" potential for Sunday back into our
Hazardous Weather Outlook (HWOGID). Monday is then looking very
marginal even for near-critical despite modest northeast breezes,
but because the previous HWO just introduced this mention decided
to let it ride at least one more forecast package. Beyond Monday,
the rest of the week looks "safer" from fire weather issues due to
various factors including cooler temps and/or increased
dewpoints/RH.

With the main points now covered, will end with some brief day-
details, including a few minor concerns not previously mentioned:

Sunday daytime:
While confidence remains pretty high in a dry day, there is more
concern than 24 hours ago that the day could start with a pretty
decent coverage of low stratus clouds, which could be somewhat
slow to burn off/erode from west-to-east before giving way to a
mostly sunny afternoon. In addition, there are also hints that at
least patchy fog could affect mainly our far western counties
(especially Dawson/Gosper/Furnas) right away Sunday morning.
However, with overall-better fog chances looking to focus just
west of our CWA, have collaborated with the short-term forecaster
handling Saturday night`s forecast to leave this mention out for
now. Otherwise, nudged down high temps very slightly, but still
aiming for mid-upper 70s central and east to low-mid 80s west and
south. March 19th temperature records at Grand Island/Hastings
which are in the mid-80s currently appear to be "safe" by 5+
degrees.

Sunday night:
A respectable little cold front passes southward across the entire
area, resulting in breezy north winds that will likely gust to at
least 25 MPH for at least a short time. We are maintaining a dry
forecast, as despite some modest elevated instability and the
latest SPC Day 2 outlook keeping our southeast CWA in a small
"general thunder" risk, nearly all model solutions focus any
convection at least a few hundred miles east of our domain mainly
over IA/MO.

Monday-Wednesday:
See "number 2" above for more on these days, but from a basic
meteorological standpoint, we reside under generally zonal (west-
east) flow with a few small scale disturbances sparking the
various rain/light snow chances. Markedly cooler than Sunday but
still seasonable for late-March.

Thursday-Friday:
See "number 1" above for more, but again from a basic standpoint a
large-scale trough gradually invades the Central Plains and brings
halfway decent rain/thunderstorm chances (does not look cold
enough for any snow on the backside at this time). As is often the
case, the GFS is generally faster than the ECMWF solution in
bringing in the lead energy, but timing in the passage of the main
mid level low/vort max improve by Friday, and as earlier
mentioned PoPs may very well need raised for this day.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Saturday evening)
Issued at 630 PM CDT Fri Mar 17 2017

VFR conditions expected to prevail. Surface high pressure is
building into eastern Nebraska tonight and will slide slowly
eastward throughout the next 24 hours. Winds will be light and
vary from the north to the southeast through much of the period.
Southerly winds will increase during the afternoon hours from west
to east and could be breezy at both terminals.


&&

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

$$

SHORT TERM...Rossi
LONG TERM...Pfannkuch
AVIATION...Billings Wright



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