Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 200550
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1250 AM CDT Thu Jul 20 2017

.UPDATE...
Issued at 1119 PM CDT Wed Jul 19 2017

Cancelled the Severe Thunderstorm Watch for north central Nebraska
at 0400z. A line of storms continues across the Sandhills,
generally from along Hwys 2 and 91, but primary threats are gusty
winds, small hail, frequent lightning, and heavy rain. Additional
storms are in the eastern panhandle, which are nearly stationary.
Hydro issues are not anticipated attm due to dry conditions
leading to this event and the high flood guidance of the
Sandhills. KONL has measured nearly 2.50" of rain so far with no
reported issues from spotters or law enforcement.

UPDATE Issued at 453 PM CDT Wed Jul 19 2017
Updated forecast for severe thunderstorm watch

&&

.SHORT TERM...(This evening through Thursday)
Issued at 311 PM CDT Wed Jul 19 2017

The model blend of HRRR, HRRR exp and RAP are close to the synoptic
NAM and GFS. Weakly organized MCS activity is expected this evening
across Nrn Neb which could last into Thursday morning. 500 mb winds
aloft remain weak at 25 kt or less but moisture is robust with
ambient precipitable water north of 1.5 inches. The models suggest
just an isolated heavy rain potential with the storms tonight.

The forcing is off the Black Hills and associated with a southward
propagating cold front. POPs for this forecast are limit at 30
percent. Our friendly RAP model continues to show very warm
temperatures near 15C at 700mb which could represent significant
inhibition for storm development.

The temperature forecast uses blended bias corrected guidance for
lows in the upper 60s to lower 70s tonight and blended guidance plus
bias correction Thursday for highs in the upper 80s to lower 90s
north. Upper 90s to around 100 are expected south and a heat
advisory may be necessary across Chase, Hayes and Frontier Counties.

The NAM, GFS, GEM and SREF blend suggest additional MCS activity
north of the stationary Thursday afternoon across Nrn Neb. Winds
aloft are still weak, less than 25kt in the NAM and GFS, and there
are timing differences.  The GFS is about 6 hrs faster than the NAM
which holds off on the MCS until Thursday evening.

.LONG TERM...(Thursday night through Wednesday)
Issued at 311 PM CDT Wed Jul 19 2017

The models show MCS activity growing upscale across Nrn Neb Thursday
evening. The outflow from these thunderstorms should sweep south and
cool down Swrn Neb Friday. Bias corrected model data from the NAM,
GFS, ECM and GEM models still forecast highs well into the 90s to
around 100 Friday so their is a dispute in the forecast as to how
warm it will be. Despite the outflow, h700mb temperatures in the
models appear to rebound to the 16-17C range which is very warm.

All models cool temperatures Saturday as the h500mb ridge moves into
the midsouth. The upper level ridge remains south Sunday and builds
west into the desert Southwest. This sets up northwest flow aloft
with cooler Pacific and Canadian air moving into Nebraska Sunday
through Wednesday.

The rain forecast is less predictable. The cooler temperatures aloft
and northwest flow will support thunderstorm development off of the
Black Hills and Big Horns. Scattered rain chances are in place
Friday and Saturday associated with a cold front drifting south
through the Central Plains. Moisture becomes limited Sunday and
beyond for generally isolated chances of showers and
thunderstorms.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1246 AM CDT Thu Jul 20 2017

Thunderstorms will continue along a line from KAIA through KODX
through the early morning hours of Thursday. Winds over western
Nebraska will be out of the south to the south of the thunderstorms
and to the northeast to north to the north of the line of storms.
Surface visibilities in the storms could be as low as a mile. Some
patchy fog is possible Thursday morning over western Nebraska.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 1 PM CDT /noon MDT/ this afternoon to 8 PM
CDT /7 PM MDT/ this evening for NEZ038-069>071.

&&

$$

UPDATE...Snively
SHORT TERM...CDC
LONG TERM...CDC
AVIATION...Power



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