Area Forecast Discussion
Issued by NWS North Platte, NE

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505
FXUS63 KLBF 191142
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
642 AM CDT Wed Jul 19 2017

.SHORT TERM...(Today and tonight)
Issued at 348 AM CDT Wed Jul 19 2017

Very minor mid-level height rises are expected overhead today with a
relatively flattened ridge over the Central and Southern Plains. 850
hPa thermal ridge sets up across western NEB into south central SD
this afternoon. 850 hPa temperatures expected to peak 30-34 C in
western NEB, warmest in the eastern NEB Panhandle. For context, SPC
sounding climo for LBF shows a daily average of ~23 C with the 90%
centered moving average and the daily max at ~27 C and ~30 C,
respectively. Highs are forecast to range about 98-104 with decent
insolation and a well-mixed boundary layer today. This is about 10
to 15 degrees above seasonal normal values. These temperatures
combined with surface dew points ranging from the mid 50s to upper
60s from west to east across the local forecast area should be
conducive for heat index readings at or over 100 degrees across
western NEB, peaking to 105 degrees in the extreme eastern portions.
Otherwise, there is potential again for isolated thunderstorms this
afternoon-evening. At the surface a stationary front presently lies
roughly from south central SD into northern NEB and will lift north
as a warm front today. Thereafter, a cold front will then advance
south tonight into northern NEB and the Sandhills. A decent signal
is present in the SPC SSEO spaghetti/paintball and neighborhood
probs plots thus confidence is above average. At this time the
current thinking is the best chances will be in the evening across
the NEB-SD border and more so northern NEB then decreasing south
into the Sandhills. Chances then taper off through the small hours
into early morning. Mild warmer than normal lows are anticipated
tonight -- mid 60s to around 70.

.LONG TERM...(Thursday through Tuesday)
Issued at 348 AM CDT Wed Jul 19 2017

Hot and humid weather will continue Thursday as the upper ridge
remains across the Central Plains and middle Mississippi Valley.
Something we`ll have to watch is a cold front/outflow boundary
being forced south from convection in South Dakota Wednesday
night. The NAM is the most aggressive with this feature, and if it
verifies Thursday could end up being cooler than forecasted but
still humid as 70 degree dew points pool north of the boundary.
This would also provide moist upslope easterly flow Thursday
afternoon and a possible increase in convection on the high
plains. SPC has added a slight risk for severe storms across
portions of northern and western Nebraska to account for this. The
heat advisory will remain intact due to high humidity even if the
cooler NAM is correct.

All models indicate Friday being hot, even the NAM which lifts
the front back north across the area. Highs from 95 to around
100 look good. The weekend will see somewhat of a cool down as the
upper level ridge flattens somewhat and rebuilds across the
southwest Conus. This will allow for a cold front to back in from
the northeast as a shortwave crosses the Great Lakes. Highs will
cool from the lower 90s Saturday to the 80s Sunday into the first
of next week. Slight chances for thunderstorms cannot be ruled out
as mid level Monsoonal moisture rotates around the northern
periphery of the somewhat flattened upper level ridge.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 627 AM CDT Wed Jul 19 2017

Latest surface plot and satellite imagery confirms the
development and spreading of low stratus and fog into the local
forecast area. Visibilities vary between 1/4SM to 5SM and
ceilings range from 200-800 ft across southwest NEB to the central
Sandhills and north central NEB. Current thinking is ceilings
will be primarily LIFR this morning with visibilities more
variable between LIFR-IFR, flight category improvement
expected by mid morning to VFR.

Thunderstorms possible this afternoon-evening, with best chances
during the evening across northern NEB. Confidence increasing with
respect to impacts at KVTN thus use of VCTS in the evening hours.
Don`t think thunderstorms will get farther south than the central
Sandhills. Modest southerly breezes will persist today with gusts
up to 20 kts, strongest in the Sandhills and north central NEB,
with winds lessening tonight.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 1 PM CDT /noon MDT/ this afternoon to 8 PM
CDT /7 PM MDT/ this evening for NEZ005>010-022>029-035>038-
056>059-069>071-094.

&&

$$

SHORT TERM...ET
LONG TERM...Taylor
AVIATION...ET



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