Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 251904
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
204 PM CDT SUN SEP 25 2016

.SHORT TERM...(This evening through Monday)
Issued at 153 PM CDT Sun Sep 25 2016

Primary concern in the short term is the expected low temps tonight
and whether or not we have any frost formation in the CWA.

Current satellite water vapor imagery along with 12Z upper air
analysis shows a wavy pattern across the northern half of the CONUS.
Looking east to west, there is a closed low over Newfoundland, with
a high amplitude ridge over the Great Lakes that extends north of
Hudson Bay. The axis of the northern Plains trough that brought us
precipitation yesterday was now over eastern SDak to northwest KS.
Good 500 mb height falls were noted on the 12Z raobs east of our
CWA, while to the west heights were building (60-70 m at UNR & DNR
in past 12 hrs) Further west, ridging was building into the coast.
Meanwhile at the surface, low pressure was situated over eastern
Manitoba with high pressure building into the Rockies. This is
setting up a tight pressure gradient over the CWA, thus the breezy
conditions. Probably the main thing to note is the drier air that has
moved in behind yesterday`s frontal passage. Surface dewpoints this
morning were running some 20 degrees F lower than the same time
Saturday.

As noted above, the question for tonight involves chances for frost.
On the plus side, high pressure is moving in from the west which
should allow winds to decrease overnight. Skies look to remain
mostly clear allowing for good radiational cooling. On the negative
side, the surface high is actually progged to slide to the west and
then south of the CWA, so winds should remain out of the west and
not go completely calm. Also with drier air continuing to move in,
may end up with a 5+ T/Td spread even in areas where the temps are
expected to fall into the 36-38 deg range. Right now we have patchy
fog in the grids for valley locations in the northwest part of the
CWA and will most likely leave them as is. Will coordinate headlines
but am leaning against it given the marginal coverage area, and
uncertainty in actually seeing frost form.

Expecting one more day of slightly cooler than average highs on
Monday as the flow remains WNW with surface high sliding to our
south. After that things warm up for a couple of days with upper
ridging building in.

.LONG TERM...(Monday night through Sunday)
Issued at 153 PM CDT Sun Sep 25 2016

Starting out Monday evening it appears the current
upper air pattern will be progressive as the trough that is over our
area now should shift east and be centered just north of Lake
Superior, and ridging building into the Rockies with a weak cut off
low over Baja. For the upcoming work week several operational models
in basic agreement in digging the cut off south towards OH/KY. This
would allow the ridge to build into the central Plains basically
keeping our CWA dry with average to slightly above average temps.
The older versions of the GFS and EC started to diverge in solutions
starting late Thu and into the weekend with the GFS kicking out the
eastern Low quicker, and bringing a weak wave through the ridge
bringing us a chance for precip late Thursday night and then
continuing chances off and on into the weekend as the ridge moves
east and a broad trough approaches. The EC was slower with all of
this, thus keeping our area dry until Sat night/Sunday.  Now the 12Z
run of the GFS seems to be coming more into line with the EC. Would
expect the Superblend to keep it dry until the weekend but will have
to wait and see what it does before deciding on minor adjustments.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Monday afternoon)
Issued at 1150 AM CDT Sun Sep 25 2016

Expect VFR conditions through the forecast period. Surface winds
will continue to be the main issue this afternoon as the terminals
lie between low pressure to the east and high pressure building
in from the west. Should remain sustained near 20 kt until around
sunset. VAD wind profile and models show winds around 30 kt at 800
mb which is where we should mix out so gusts to 30 will work.
Winds to let up after sunset as we begin to cool and pressure
gradient decreases with surface high building in.


&&

.GID Watches/Warnings/Advisories...
NE...None.
KS...None.
&&

$$

SHORT TERM...Ewald
LONG TERM...Ewald
AVIATION...Ewald


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