Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 161746 AAB

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1246 PM CDT Sun Jul 16 2017

Issued at 1225 PM CDT Sun Jul 16 2017

The current forecast looks good overall. Based on several hi-res
models, have increased dew points along the James River this
afternoon. Dew points mixing out into the upper 50s is more
realistic. Red flag conditions are still expected in fire weather
zone 268. Winds in the western part of zone 268 are gusting to 20
to 25 mph. Will monitor conditions in zone 267 for the possible
expansion of the Red Flag warning.


.SHORT TERM...(Today through Tuesday Afternoon)
Issued at 349 AM CDT Sun Jul 16 2017

First we will address fire weather conditions today. High pressure
is moving east, setting us up with a 10 to 12mb pressure gradient
and pressure falls at about 7mb. The only caveat is that NAM BUFKIT
soundings mixed winds are generally only on the order of upper teens
for peak mixed winds, so topping 25mph will be difficult. As for
humidity, there is a very dry layer evident in the evening sounding,
but 850mb dewpoints will be on the increase thanks to southerly
flow, suggesting that a more humid atmosphere will move up into
the Dakotas ahead of the next weather system. Deep mixing should
still get us close to Red Flag, or at the very least Very High
fire danger conditions given the state of drought most of the area
is in.

Monday, a surface front begins to move into the area. Flow aloft is
mainly unidirectional with a southwesterly component. Therefore
frontal speed will be slow in progressing east, and with
questionable upper support. 700mb temperatures are only going to be
around +12C, warm but not impossible for convection. Additionally,
there does appear to be a fetch from the Gulf of Mexico, allowing
for a deeper moisture pool and higher PWAT values compared to what
we have seen thus this spring/summer. 0-6km shear is in the 20 to
30kt, with MLCAPE values approaching 1500j/kg.

The southwest component will also aid in deep mixing, GFS BUFKIT
mixes to 9kft, deeper then the NAM and probably more representative,
which yields mixed winds around 20kts and temperatures close to the
century mark. We may approach Red Flag conditions again, although
the uptick in humidity will probably put us just above afternoon RH
criteria. Additionally, heat index values will be above 100 for
parts of the area so we may also need to look into a heat advisory.
Given headlines for today and how marginal these conditions are for
Monday, decided it best to wait and evaluate tonight.

As 500mb flow becomes more zonal and increases, a more active
pattern is expected for Tuesday and into the extended.

.LONG TERM...(Tuesday Evening through Saturday)
Issued at 349 AM CDT Sun Jul 16 2017

The long term models continue to be consistent and agree well with
the upper level flow pattern across the U.S. Broad upper level high
pressure will dominate the southern U.S. from Tuesday night into
Saturday with main jet stream extending generally from west to east
across the northern U.S. At the surface, a frontal boundary will
also extend from west to east across the northern plains. This
boundary will move back and forth in response to each short wave
trough moving across the region through the period. Thus, there will
be several periods of showers/storms through the long term.
Temperatures through the period will be mostly in the 80s and lower
90s which is near to around 5 degrees above normal.


.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
Issued at 1225 PM CDT Sun Jul 16 2017

VFR conditions will prevail across the area through tonight at all


SD...Red Flag Warning until 8 PM MDT this evening for SDZ268.



SHORT TERM...Connelly
AVIATION...SD is the U.S. government's official web portal to all federal, state and local government web resources and services.