Area Forecast Discussion
Issued by NWS Hastings, NE
FXUS63 KGID 141020
Area Forecast Discussion
National Weather Service Hastings NE
420 AM CST Sat Jan 14 2017
.SHORT TERM...(Today and tonight)
Issued at 411 AM CST Sat Jan 14 2017
The main concern during the short term periods is the timing of the
onset of freezing rain tonight with the advancing winter storm
The upper low pressure system was located off the coast of Baja
early this morning with southwest flow in place across the central
and southern plains ahead of the upper system. The daytime hours
today are shaping up to be dry and quiet weather wise with light
winds under the influence of a surface high pressure ridge. The
arctic airmass has dislodged and temperatures will moderate and
have most areas rising above freezing for highs. Was hesitant to
go too warm with temperatures given the degree of cloud cover
expected and snow cover across our northern zones should hold
temperatures down several degrees.
Models are consistent with the upper low moving into old Mexico
tonight with a round of wintry precipitation developing in the
isentropic lift across the southern plains and lifting north through
Kansas toward our cwa. The timing of the onset of the precipitation
has trended slower, moving into north central Kansas between 06z and
12z Sunday. Given this trend, have lowered pops for the evening time
frame but maintained small pops in case drizzle develops ahead of
the main area of freezing rain. While the best chances for freezing
rain/sleet overnight reside across Kansas, we could see the freezing
pcpn edge into Nebraska toward daybreak.
Due to the slower start of the precipitation tonight, have delayed
the start time of the current headlines. Light icing of a few
hundredths of an inch are possible by daybreak across portions of
north central Kansas.
.LONG TERM...(Sunday through Friday)
Issued at 411 AM CST Sat Jan 14 2017
Aloft: The flow will remain split over the CONUS at 12Z Sun with a
trof over the Wrn USA and a high over the Gulf. A ridge will extend
NW from this high into the Cntrl Plns. A low will be over Nrn Mex.
This low will lift NNE across W TX...Cntrl KS and probably into SE
Neb Sun-Mon and then onto the GtLakes Mon night. Meanwhile...the Nrn
stream will amplify sending a digging shortwave trof into Nrn Plains
Sun night and down into the Cntrl Plns Mon-Tue...possibly closing
off another low. This low/trof should move E of the region Tue. Low
amplitude WNW flow will remain in its wake Wed-Thu with modest ridge
cresting over the region. SW flow develops by Fri as a deep trof
evolves over the Wrn USA.
Guidance evaluation: The 00Z GFS/CMC ensemble means are in
agreement...lifting this low across W TX Sun into Wrn OK by 12Z/Mon
and into NErn KS by 00Z/Tue. The 12Z/13 EC ensemble mean is further
W...lifting it thru the OK panhandle to near K82 (Smith Ctr) on its
way into Ern Neb. The global models and NAM are tightly clustered
until 12Z/Mon when the 18Z/00Z become SE of the consensus...are
similar to its ens mean. The 00Z EC came in further E than its prvs
2 runs...btwn the CMC/GFS and EC ensemble means...taking the low
across cntrl KS into far SE Neb. This is similar to the 00Z NAM/CMC.
Surface: High pres will be over the Midwest/GtLakes at 12Z/Sun. Low
pres will be organizing over W TX. The cold front will be quasi-
stationary from the Srn Plns into the TN Vly. A weak low will emerge
into W TX Sun and then lift NNE across OK into Srn KS by 12Z/Mon...
then across MCI into NWrn MO by 00Z/Tue. This low will then head
into the GtLakes Tue with high pres overtaking the Cntrl Plns.
Return flow develops Wed-Thu with low pres trying to form over the
Cntrl/Srn Plns Fri.
Some Sensible Wx Details...
Headlines: It was decided to not upgrade additional counties to Ice
Storm/Winter Storm Warnings just yet. It`s a little too early since
the steadiest/heaviest precip won`t move in until Sun night.
There is still a lot of uncertainty as to exactly when frzg rain
(ZR) will move in. The basic gist is periods of light frzg rain or
drizzle will gradually overtake the fcst area from S-N Sun. Precip
should be patchy and there will be lulls as waves of precip move
thru. Believe the steadiest and heaviest frzg rain will fall Sun
Expect sleet (IP) to mix with the ZR at times. If model soundings
are correct with the depth of the cold air...there could be quite a
bit of IP. Hard to know how much to acct for this...but the more IP
materializes...the lesser the amt of ice accretion from ZR. That
would be a good thing as IP is not quite as dangerous and does not
have the potential to produce sig dmg to trees/power lines etc.
Mon the dry slot will bring precip to an end for N-cntrl KS and S-
cntrl Neb S and E of the Tri-Cities. A deformation band of wrap-
around snow will develop from Wrn Neb into the Sandhills. This band
is currently expected to move into Nrn/Wrn counties from Beaver City-
Lexington-Ord. This band could deposit svrl inches of snow.
Our storm-total ice graphic/fcst currently advertise a tenth of ice
roughly from Lexington-Ord...a quarter-third of an inch thru the Tri-
Cities...and a half to three-quarters of an inch from N-Cntrl KS
thru Red Cloud to Geneva/Hebron.
These amts over 1/2 inch are very concerning. Suggest everyone
finish prepping today for potential power outages.
Storm-total snow 1-4" from the Tri-Cities N and W with the higher
totals from Beaver City-Lexington-Ord. Believe we are not high
enough yet. 4-8 inches is more likely and the only reason we`ve not
gone that high is due to the model blends averaging in the GFS runs.
12Z/00Z EC and 18Z/00Z/06Z NAM all have it.
Wind: confidence is not high due to model diff`s...but this is not
looking like an extremely windy event in the CAA behind the low.
That said we may need to adjust this expectation. NAM BUFKIT
suggests we could mix down 35 kts Mon night. That would be a
problem with as much ice as we are expecting.
Lowered high temps Mon to consensus of model 2m temps. Did not make
changes to Tue`s high temp fcst...but we are probably too warm given
the snow/ice that is expected to be over the fcst area.
Had little to no time to invest in the fcst beyond this storm.
Suffice to say turning much warmer and odds favor dry wx Tue-Thu.
Fri is iffy.
.AVIATION...(For the 06Z KGRI/KEAR TAFS through 06Z Saturday night)
Issued at 1112 PM CST Fri Jan 13 2017
Another quiet period for the tafs weatherwise as the approaching
winter storm system will begin to have impacts after this forecast
period. Winds will remain light/variable under the influence of a
weak surface ridge. Cigs are expected to remain at mid/high levels
however have introduced scattered low clouds toward the latter taf
NE...Winter Storm Watch from Sunday morning through Monday evening
Ice Storm Warning from 10 PM this evening to noon CST Monday for
KS...Ice Storm Warning from 10 PM this evening to noon CST Monday for