Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 03/06/19

Area Forecast Discussion

National Weather Service Hastings NE

 549 PM CST Tue Mar 5 2019

.SHORT TERM...(This evening through Wednesday)
Issued at 334 PM CST Tue Mar 5 2019

Aloft: Moderately-amplified flow was over the CONUS per RAP
tropopause analyses and aircraft obs...with a trof over the E
Pac...a ridge over the Rckys...and a Hudson Bay low and trof over
the Ern USA. NW flow was over the Cntrl Plns with rising heights
as the ridge approaches. This ridge will crest over the rgn around
sunset tomorrow.

Surface: High pres was over KS. An Arctic front was over SA/MB.
The high will slide into AR/MO tonight on its way into the Gulf
Coast states tomorrow. The Arctic front will move SE thru
tomorrow...crossing the CWA in the afternoon. However...the
thermal contrast along tail end of the cold front will weaken. So
this front will be little more than a wind shift. Nrn Plns high
pres will build in behind the front.

Tonight: Mainly clear to start...but increasing clds espcly after
midnight. Should be m/cldy by dawn. Used consensus of all
guidance for lows which has been performing best over the last wk.

Wed: M/cldy. Not as cold...but still 15F below normal.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 334 PM CST Tue Mar 5 2019

Aloft: A weak/low-amplitude shortwave trof will move thru Wed ngt
into Thu AM. Heights will rise in its wake with the Wrn ridge
moving thru here Fri as a much deeper trof moves onshore into CA
and thru the Desert SW. The last 2 runs of the GFS/GFS-FV3/EC/
GEM/UKMET cont in unison on becoming negatively tilted with a low
forming over NEB Sat. Quite a bit of spread develops Sun. The GFS
/GFS-FV3 runs have cyclonic NW flow and troffing over NEB/KS while
the GEM/UKMET/EC runs maintain SW flow with a broad ridge as the
next deep low drops down the CA coast. This lowers fcst confidence
Sun-Tue.

Surface: Wed night the pres grad will increase as high pres drops
into the Nrn Plns and weak low pres ejects out of CO into OK.
Thu-Fri high pres will prevail over the Ern USA/Canada...and it
will extend back into NEB/KS. Lee cyclogenesis will occur Fri
afternoon. This low will cross KS from 12 AM-12 PM Sat. High pres
will build in Sun and probably slip E of the rgn Mon-Tue.

Temps: Contd much colder than normal...but not nearly as cold as
we`ve been experiencing. We will begin seeing a lot more 30s over
S- cntrl NEB and 40s over N-cntrl KS. Sat looks like temps will
finally climb above 32F at GRI...and all the other locations that
haven`t seen 32F since Feb 13th.

Precip: We are still expecting a band of 1-4" of snow mainly N of
I- 80 Wed night into Thu AM. The highest amts of 3-4" cont to be
expected from Ord-Greeley-Fullerton. Have initiated Situation
Reports (available top of our website) as probability remains high
we`ll need a Winter Wx Advisory.

Fri night-Sat: The EC/GEM/GFS cont in unison that there will be a
substantial warm nose with this sys. That means we are
advertising too much snow at the onset. Given that this sys is
still beyond 84 hrs...our fcst ptype algorithm conts to indicate
snow at the leading edge of the precip shield that moves in Fri
night. The more likely scenario is a mix of frzg rain/sleet
changing to rain Sat for most areas.

The mdl consensus is that a shield of mix precip will form and
move from SW-NE Fri night into Sat AM...with this trof rapidly
swinging thru with negative tilt. The upr low is fcst to close off
just N or E of the CWA. That means a quick shutoff to the precip
by midday Sat as the dry slot moves in. There are still a minority
of mdl runs indicating a low could close off over SE NEB. If that
occurs...that could prolong the precip into the afternoon E of
Hwy 281. But it`s doubtful there will be enough cold air around
for snow.

Rainfall amts cont to be of concern. The faster this sys moves
thru the better. Any substantive rain falling into such deep snow
will significantly increase its weight. That could stress
buildings with flat roofs to the point of partial failure/
collapse.

Snow will not be the dominant ptype this this sys. In fact...
there is potential we could see warning-level amts of frzg rain
(at least 1/4"). It has been so cold for so long...frzg rain could
even cont after air temps even climb above 32F.

Can`t rule out a couple rumbles of thunder Fri night-Sat AM over
the SE fringe of the CWA (Beloit-Hebron).

Suggest everyone cont to closely monitor this storm.

Winds: Incrsd winds above MOS Wed night. Have seen this many
times when E winds end up stronger than fcst as the pres gradient
tightens from high pres sinking into the Nrn Plns and a warm front
is stalled over KS/OK.

Sat night into Sun AM will be windy and the fcst probably doesn`t
fully reflect how windy it will be just yet. We`re probably
looking at 20-30 mph G40-50. If we get warning-level ice...this
could result in sct power outages from bringing down tree
branches.

Pattern: The EC/GFS/GEM ensemble means are all fcstg a major
pattern change in the 10-15 day time frame (Mar 15-20). The trof
that has persisted over the Wrn USA for the last 30 days appears
like it could be replaced by a ridge. That would mean temps
returning to near normal...and favoring above normal at times as
periods of downslope warming could occur.

&&

.AVIATION...(For the 00Z KGRI/KEAR TAFS through 00Z Wednesday)
Issued at 539 PM CST Tue Mar 5 2019

VFR conditions are forecast. However, ceilings will develop and
lower as a shortwave trough approaches. Any ceilings lower than
VFR should hold off until just after the valid time of the
forecast.

&&

.CLIMATE...
Issued at 526 AM CST Tue Mar 5 2019

..Various notes on our ongoing remarkably-cold snap (for Grand
Island/Hastings, our two primary long-term climate data sites)..

SECOND-COLDEST OPENING WEEK OF MARCH VERY LIKELY:
- Based on observed data through these first few days and our
  current official forecast through the 7th, both Grand
  Island/Hastings are well on their way to enduring the 2nd-
  coldest opening week of March on record. The top spot currently
  belongs to 1960, when the first week averaged an incredible 28
  degrees below normal at Grand Island, and 26 degrees below
  normal at Hastings.

LONGEST STREAK AT-OR-BELOW FREEZING IN DECADES?
- Today will mark the 19th-consecutive day that both Grand Island
  and Hastings will fail to climb above the freezing mark (32
  degrees).
- Based on our official forecast, this streak of at-or-below
  freezing days should last through at least March 8th (Friday),
  which would bring it up to 22 days.
- The last time Grand Island (GRI) had a 22+ day streak of at-or-
  below freezing was 26 years ago, with a 22-day stretch from Dec.
  9- 30, 1983. The record-longest streak is 31 days from Jan.
  22-Feb. 21, 1936.
- The last time Hastings (HSI) had a 22+ day streak of at-or-
  below freezing was actually the record-longest streak of 30
  days, way back from Jan. 23-Feb. 21, 1936.

&&

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

$$

SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Heinlein
CLIMATE...JCB/Pfannkuch