Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 011200
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
600 AM CST Wed Mar 1 2017

.SHORT TERM...(Today and tonight)
Issued at 445 AM CST Wed Mar 1 2017

As can often be the case this time of year, a seemingly quiet
forecast with plenty of sunshine and no mentionable precip chances
is made a bit more complex with fire weather issues. See the
separate "Fire Weather" section below for all further details, but
the bottom line is that a Red Flag Warning has been issued this
afternoon for 9 of our southern-most counties. Otherwise, for
those without fire weather concerns, today will simply be a very
seasonable/cool March 1st (per long-term normals), a few degrees
cooler than yesterday but with stronger northwest winds gusting
up to around 35 MPH mainly this afternoon before subsiding around
sunset.

Taking a look at the current/recent weather picture as of
4AM/10z:
As expected 24 hours ago, the late night hours have been
very quiet in the wake of the low pressure system that promoted
quite a bit of severe thunderstorm activity in states off to our
east. Around here, frankly this system was a bit of a "dud"
precipitation-wise, as most places saw little more than a period
of sprinkles and/or flurries during the afternoon/evening, with
little-to-nothing measurable (in contrast to some models 24 hours
ago that suggested narrow bands of measurable precip). At this
time, skies over most of the CWA are crystal-clear, with the main
exception of a pesky band of low stratus brushing southward into
our far northern/northeast zones around the backside of the
departing trough. In the mid-upper levels, water vapor satellite
clearly shows the main large-scale trough axis/vort max departing
eastward out of NE/KS with broad northwest-flow moving in behind
it. At the surface, a modest pressure gradient between a strong
low centered in the MI area and a broad high centered over the
Intermountain West is promoting steady west-northwest breezes
generally 10-15 MPH across the CWA. Despite weak cold air
advection and mainly clear skies, these breezes are keeping low
temps from really tanking, and pretty much the entire CWA is
expected to bottom out somewhere in the 20s (coldest west).

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

Today:
Again, fire weather (as covered in greater detail below) is the
paramount issue. In the mid-upper levels, northwest flow becomes
firmly established as the aforementioned vort max departs well off
into the Lower Great Lakes/eastern Midwest by day`s end. For most
of the CWA for most of the day, we should see plentiful sunshine.
The one caveat is the aforementioned area of low stratus, which
based on satellite trends and also the latest 900 millibar RH
prog from the RAP, could sink southward to give areas mainly
northeast of a Loup City-GI-Geneva line a mostly cloudy start to
the day, perhaps through around mid-morning, before even these
lower clouds dissipate/vacate east and give way to quite a bit of
sun. That being said, during the peak of afternoon heating and in
the presence of deep mixing up to around 750 millibars per GFS
soundings, we could see at least a scattered area of "fair
weather" cumulus spring up especially in/near the northeast CWA.
At this time, am not expecting any "surprise" sprinkles or snow
showers out of this possible diurnal cloud development, but
suppose the chance is not necessarily zero either, and in fact
some models are spitting out some light QPF within 50-100 miles
east of the CWA this afternoon so something to keep an eye on.
Otherwise, the main story today for most folks will be the winds,
as this is likely the windiest day of the week with late morning
through late afternoon northwesterly speeds averaging sustained
20-25 MPH and frequent gusts to around 35 MPH if not slightly
higher. Temp- wise, made very little change to previous fcst,
aiming for near-40 far north, mid- 40s central and upper 40s.low
50s in KS zones.

This evening/tonight:
Once the winds die down by sunset, this should in theory should be
a very quiet night with essentially zero risk of precipitation and
mostly clear skies, with perhaps only a very slight increase in
thin high cirrus late. In response to a weakish, quick-moving low
pressure system racing southeastward across the Dakotas, our winds
locally will start out the evening generally 10-15 MPH from the
west-northwest, but quickly slacken to no more than 5-10 MPH
through the middle part of the night, and then pick up slightly
back more so to 10-15 MPH late in the night as direction turns
more southwest/westerly. Again, these modest breezes will help
temps from really falling dramatically, and lows were also altered
very little, featuring rather similar values to this morning with
most of the CWA somewhere between 22-26.

.LONG TERM...(Thursday through Tuesday)
Issued at 445 AM CST Wed Mar 1 2017

Main forecast challenge will be fire weather on Thursday and
multiple days beyond.

The entire long term is a dry forecast as northwest flow becomes
more zonal over time for the extended forecast with little in the
way of synoptic features and very little moisture to work with. I
increased wind speeds for Thursday and several other various days in
the extended. A cold front blows through Thursday and the surface
pressure gradient will be stout, with gusts of 30 mph or so
expected. I went toward CONSMOS wind speeds and MOSGuide dewpoints,
which gave me a few knots higher wind speed and a few degrees lower
dew points. This will put us near critical fire weather conditions
for areas roughly along Highway 6 and south for Thursday afternoon.
Surface pressure gradient will continue to encourage stronger wind
speeds, especially toward early next week on Monday and Tuesday, the
way it appears now. We are also expected to be quite dry, so a quick
mention in the HWO about fire weather potential on Monday and
Tuesday may be warranted on top of Thursday.

A general warming trend is on tap heading into the weekend and has
been consistently advertised by long-term numerical models. We
should easily make it into the 60s over the weekend, and will
probably top out to around 70 to the mid 70s for Sunday. Gusty winds
will blow out of the northwest on Monday and Tuesday after another
dry cold front comes through, but although high temperatures will be
cooler than the weekend, we will still likely top out near 60 to the
mid 60s early next work week.

&&

.AVIATION...(For the 12Z KGRI/KEAR TAFS through 12Z Thursday morning)
Issued at 600 AM CST Wed Mar 1 2017

General overview:
Other than a low probability that mainly KGRI sees a brief MVFR
ceiling this morning, confidence is quite high in VFR conditions
throughout the period. The main issue will be fairly strong
northwest winds during the heart of the day. Now going into a bit
more element specific detail...

Ceiling:
While KEAR carries fairly confidence in VFR throughout, there are
some signs suggesting KGRI could yet be brushed by the far
southwest edges of an area of MVFR stratus rotating southeast
through eastern Nebraska. Confidence is not high enough in this
scenario to justify a TEMPO group anymore, but will "hint" at the
possibility with a scattered MVFR mention for these first 3
hours. Otherwise, there could be at least a scattered low-end VFR
cloud field develop during the afternoon, but this is currently
not expected to breach MVFR thresholds.

Winds/Low level wind shear (LLWS):
This will be the main aviation issue. Early this morning,
generally west-northwest speeds only around 12kt will persist.
However, especially between 17-23z there will be marked increase
with sustained speeds 20-25kt and gust potential around 30kt.
During the evening speeds will decrease considerably and turn more
southwesterly with time, before picking up a touch from the west
very late in the night. Also very late in the period (mainly
after 08z), LLWS may increase enough to justify a formal TAF
inclusion. However, with this possibility not arriving until so
late in the current valid period, will defer to later forecasts to
take a closer look for possible introduction.

&&

.FIRE WEATHER...
Issued at 445 AM CST Wed Mar 1 2017

General overview:
Despite relatively cool temperatures with afternoon highs only in
the mid-40s to low-50s across the majority of the CWA, the
invasion of very dry dewpoints in the single digits-teens this
afternoon, along with gusty northwest winds and obviously the very
dry vegetation (fuels) in place will promote at least near-
critical fire weather for roughly the southwest half of the CWA,
and outright-critical levels for several counties along/south of
the state line.

Critical area:
A Red Flag Warning has been issued from 1-6 PM for all 6 KS
counties along with Furnas/Harlan/Franklin. While a few of the
northern counties are technically a little marginal on the RH
criteria, decided to be a touch liberal with Warning issuance
given that sustained northwest winds of generally 20-25 MPH and
gusts to around 35 MPH will solidly meet/exceed the wind
requirement.

Near-critical area:
Extending roughly 30 miles north of the formal Warning will be a
stripe that sees RH lower to near-critical levels, meaning they
are perilously close to meeting Warning criteria but not quite
there. This area is roughly southwest of a Gothenburg-Superior
line.

Elsewhere (including Tri Cities):
As is ALWAYS the case, especially on days like this with dry
vegetation and stronger winds, even counties well-north of the
critical/near-critical areas in Nebraska will see at least
limited (non-zero) fire danger, it`s just that RH values holding
more so into the 30-40 percent range should keep fire behavior
slightly more "in check" than farther south.

Closing with a quick review of our local fire weather definitions:
"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.

&&

.CLIMATE...
Issued at 445 AM CST Wed Mar 1 2017

A quick note about February temperatures:
Stay tuned for more details in an infographic on our social media
feed in a few hours, but at our two primary climate data sites,
Grand Island had its 6th-warmest February on record and Hastings
its 4th-warmest. In addition, based on our official cooperative
observer at Kearney airport (not the unofficial automated sensor),
Kearney registered its 5th-warmest.

More impressively, at all 3 sites, Feb. 10-23 was the record-
warmest two-week February stretch on record (based on the mean
average temperature).

&&

.GID WATCHES/WARNINGS/ADVISORIES...
NE...Red Flag Warning from 1 PM this afternoon to 6 PM CST this
     evening for NEZ082>084.

KS...Red Flag Warning from 1 PM this afternoon to 6 PM CST this
     evening for KSZ005>007-017>019.

&&

$$

SHORT TERM...Pfannkuch
LONG TERM...Heinlein
AVIATION...Pfannkuch
FIRE WEATHER...Pfannkuch
CLIMATE...Pfannkuch



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