Area Forecast Discussion
Issued by NWS Hastings, NE

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FXUS63 KGID 222047
AFDGID

Area Forecast Discussion
National Weather Service Hastings NE
347 PM CDT FRI JUL 22 2016

...Stifling/Dangerous Heat is in Progress and Believe Today is
the Worst with Temps Returning to Normal Sunday...

.SHORT TERM...(This evening through Saturday)
Issued at 347 PM CDT Fri Jul 22 2016

Aloft: Large subtropical high pres covered most of the Srn 2/3 of
the CONUS. The Westerlies were along the US-Can border. The only
shortwave trof of significance was over the Pac NW. The high will
remain in place but weaken slightly. The Pac NW trof will head
into Canada tonight into tomorrow...but zonal flow will become
established over the Nrn 1/3 of the CONUS.

Surface: A SW-NE oriented sfc trof bisected KS/Neb...the remnants
of the last weak front to slip into the area. A cool front was
advancing thru the Pac NW. This front will cont E tonight...with a
warm front developing and lifting N and E into SD/IA. The cool
front will cont pressing E and S tonight and cross the fcst area
tomorrow afternoon/eve.

Sct elevated tstms have been a pain today from a predictability
perspective...but have provided relief to some locations in the
form of cloud cover and cooling outflow. HJH dropped to 77F at
1935Z.

Heat: this has been the worst day and do not expect tomorrow to
be as bad. NE winds have advected extremely high dwpts into
S-cntrl Neb from IA.

Peak Dwpts Today:
Aurora 81F
Kearney 79F
York 79F
Grand Island 77F
Ord 77F

What compounded these dwpts was winds were much lighter/calm near
the sfc trof.

Peak HI thus far: 115F at Aurora at 1855Z (94/81).

In this benign/barotropic environment...there is no synoptic-
scale forcing which results in virtually no confidence in the
threat of tstms. Forcing is on the low end of the mesoscale and
weak. Models don`t handle benign forcing situations well.

Tonight: The cluster of tstms along the Neb/KS border this
afternoon will cont moving E. There could be a hit-or-miss storm
...but most of them "should" dissipate this eve with loss of
heating. There will be sct tstms over the Wrn 1/3 of Neb...but SW
flow will take them into the Sandhills.

As the SW low-lvl jet develops...this will advect a plume of
drier air NE...with 850 mb dwpts dropping from +16 to +20C to +9
to +12C. This will play a role in lower sfc dwpts tomorrow.

Sat: P/cloudy. Can`t rule out an isolated tstm. SPC has most of
the fcst area outlooked in a MRGL risk for svr. Highs 95-103F with
dwpts in the 60s will result in 1500-2500 J/kg of MLCAPE...highest
N and W. Deep layer shear will be near 15 kts. This will result in
outflow dominant/brief single cells.


.LONG TERM...(Saturday night through Friday)
Issued at 347 PM CDT Fri Jul 22 2016

Aloft: Zonal flow over the Nrn USA will gradually transition to a
slight Wrn ridge/Ern trof...with WNW flow here on the Plains. The
model consensus is that the subtropical high will retrograde into
the Wrn USA. There will be svrl subtle shortwave trofs that could
affect the fcst area (modulating tstm potential)...but
predictability is low because some of these are induced by model-
generated precip that may not really exist in the future.
Nevertheless...there appears to be potential for a decent
shortwave trof to move thru late next week...but the last 2 runs
of the EC/GFS are not in agreement on timing yet.

Surface: the cool front will stall around I-70 Sun with high pres
building into the Nrn Plains. This front will oscillate N and S
across the fcst area as weak waves of low pres move E along it...
as well as from possible modification by tstm cold pools.

The transition to WNW flow will do two things:

1) Allow more shortwave trofs to influence the region...which
combined with the presence of the front and occasional upslope
flow...should increase opportunities for meaningful rain.

2) Return much cooler (actually near normal) temps.

As is usual...there are several diff mechanisms by which tstms
might develop in the long-term...all of which occur on small
space/time scales and this result in very low predictability
beyond the first day of the fcst. So confidence in tstm specifics
is nil at this point.

The 12Z EC ensemble mean QPF probabilities peg Tue night into Wed
as the next best chance for rain. And the last 2 deterministic GFS
and EC runs are supportive.

Some tstms will probably be severe next week. Be sure to follow
future fcsts as we fine-tune the potential.

&&

.AVIATION...(For the 18Z KGRI/KEAR TAFS through 18Z Saturday)
Issued at 1252 PM CDT Fri Jul 22 2016

Significant Weather: Very slight chance for a tstm.

This afternoon: VFR with SCT high-based CB and its cloud debris to
the S. Lgt and vrbl...but mainly E-NE winds. Confidence: Medium

Tonight: VFR. SCT altocu/cirrostratus at or above 12K ft.
Confidence: Medium

Sat thru 18Z: VFR. SCT altocu/cirrostratus at or above 12K ft.
Confidence: Medium

&&

.GID Watches/Warnings/Advisories...
NE...Excessive Heat Warning until 7 PM CDT Saturday for NEZ039>041-
     046>049-060>064-072>077-082>087.

KS...Excessive Heat Warning until 7 PM CDT Saturday for KSZ005>007-
     017>019.

&&

$$

SHORT TERM...Kelley
LONG TERM...Kelley
AVIATION...Kelley


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