Area Forecast Discussion
Issued by NWS Bismarck, ND

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656
FXUS63 KBIS 261749
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
1249 PM CDT TUE JUL 26 2016

.UPDATE...
Issued at 1222 PM CDT Tue Jul 26 2016

Scattered showers and thunderstorms continue across a goo portion
of western and south central ND. Very moist and moderately
unstable airmass remains across the south central. Mid level
lapse rates are sufficient to generate updrafts but shear remains
weak. Latest RAP analysis shows increasing shear spreading into
the south central this afternoon so the potential remains for a
strong to briefly severe storm here, especially if we could get a
little afternoon heating. A few areas here have also had a couple
rounds of thunderstorms with heavy rain. Will need to monitor for
possible excessive rainfall issues given the high pwats.

Farther to the north we are not quite as moist and unstable and
mid level lapse rates are less impressive, but we will see a
little more sunshine this afternoon and this area is within the
right entrance region of the upper level jet to the north. Latest
mesoscale models indicate the potential for afternoon convection
here as well so will cover the north with at least some isolated
thunderstorm activity with some higher pops around the big lake,
just ahead of current activity.

made some changes to temperatures. Needed to raise temperatures
across parts of the north and east where forecast high
temperatures have already been realized in some areas. Over the
far southwest and south central lowered temperatures a bit. Even
though we may get some afternoon sunshine, it looks like we will
have a hard time reaching forecast highs here.

UPDATE Issued at 951 AM CDT Tue Jul 26 2016

Showers and thunderstorms continue across southern north dakota
along a weak boundary. Very moist atmosphere along this boundary
with pwats around 1.4 in. A thunderstorm over Mcintosh county
created around 2.5 inches of rain in an hour. Tall skinny capes
from latest rap/hrrr verify these heavy rainfall rates. There has
been some hail and a marginally severe hail report can not be
ruled out, but the greatest threat through the morning will be
very heavy rainfall. Fortunately the thunderstorms over the
southwest have a pretty good forward movement. The storms in
mcintosh and now far western Dickey county have been training so
will need to monitor for potential of excessive rain. These storms
are tracking southeast and should be out of the state within the
next hour or so.

Made some adjustments to pops/wx based on latest radar imagery.

UPDATE Issued at 645 AM CDT Tue Jul 26 2016

Thunderstorms moving out of western Mcintosh county and my be
able to cancel the flood advisory there soon. Web cams show
widespread rain in Beach from the cluster of thunderstorms across
teh southwest. Not seeing much for gusty winds from those at this
time.

&&

.SHORT TERM...(Today and tonight)
Issued at 229 AM CDT Tue Jul 26 2016

Latest water vapor imagery shows a quasi-zonal flow into North Dakota
with multiple shortwaves seen upstream. These weaknesses/ripples
in the mid/upper level height fields will result in continued
chances for showers and thunderstorms through the short term
period. Difficult to pin down timing and location, especially
going farther out in time. However for the near term/early this
morning, isolated thunderstorms continue to develop and are nearly
forming a line in eastern Emmons into western Logan and McIntosh
counties. Also another line is forming in Dickey and extending
into LaMoure county. Shear is minimal at around 20kt and this is
confirmed with the storms nearly vertical in nature. Despite this
they are extending up to around 45kft. A special weather statement
has been issued for a portion of the thunderstorms mentioned
above. Expect more development along an existing boundary and low
level jet, but not expecting additional strengthening at this
time as shear remains marginal and mid level lapse rates weaken
to the east. Farther upstream, a shortwave in southern Montana
will continue moving east this morning, reaching southwest ND
between 12z-15z. Regional radar shows an area of showers and
thunderstorms between Billings and Miles City, Montana. A boundary
draped along the southern border will be the focusing mechanism
for low level convergence and will be enhanced as the shortwave
rides atop of the boundary during the morning hours. This should
result in the area of showers/thunderstorms from eastern Montana
to hold together, if not develop more as it moves into southwest
and south central ND through the morning hours. This has support
from the HRRR composite reflectivity over the last several hourly
runs. The SREF Calibrated Severe thunderstorms does show signs of
increasing probabilities for severe potential across the south
this afternoon into tonight. SPC maintains a Marginal or isolated
risk for Severe Thunderstorms through tonight for most of western
and south central ND. Shear does increase from around 20kt across
the south early this morning, to between 30kt and 40kt this
afternoon/evening, then wanes again later Tuesday night. Highs
today will be on average 12 degrees cooler, especially with the
added clouds and showers south. Highs will range from the upper
70s north to low/mid 80s south.

.LONG TERM...(Wednesday through Monday)
Issued at 229 AM CDT Tue Jul 26 2016

Global models depict a moderately active convective pattern in
the first half of the extended. Chances for thunderstorms will
occur in a westerly flow regime until Friday when an h500 ridge
forms over the northern plains in response to an upstream trough
over the Pacific northwest. The weekend will see suppressed
convection and warmer temperatures as the h500 ridge positions
itself over the northern plains.

Temperatures will be on the cooler side of normal Wednesday and
Thursday with highs in the 70s as surface high pressure moves
south across the eastern Dakotas. At this time the chance for
thunderstorms will be mainly across the western portions of the
region.

By Friday highs will warm into the 80s with the weekend seeing
highs in the mid to upper 80s Saturday and into the 90s by
Sunday.

The potential for severe weather this week will be tempered
somewhat buy the relative lack of shear. Both the GFS/ECMWF show
a fairly weakly sheared environment up to 6km through Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1222 PM CDT Tue Jul 26 2016

There is low confidence on when a shower/thunderstorm will impact
any one terminal through the TAF period. However the best chances
appear to be at KBIS/KJMS today. KMOT may remain completely dry, but
a few short-range models are depicting showers/thunderstorms moving
into the KMOT terminal later today, so put a mention of vicinity
thunderstorms in the TAF.

&&

.BIS Watches/Warnings/Advisories...
NONE.
&&

$$

UPDATE...TWH
SHORT TERM...KS
LONG TERM...WAA
AVIATION...AJ



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