Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 240557

Area Forecast Discussion
National Weather Service Bismarck ND
1257 AM CDT Fri Mar 24 2017

Issued at 1240 AM CDT Fri Mar 24 2017

Mesoscale short term models indicate widespread fog developing
across the forecast area over the next few hours but the official
forecast is not as pessimistic, especially on the aviation side.
Patches of fog have formed around Tioga, Williams County, and
harvey, Wells County, but lower dew point air was advecting in
from southern Saskatchewan and southern Manitoba. The expectation,
behind the rain band that moved out of the area over the past few
hours and with a clearing sky, would be for fog formation. have
opted to go patchy fog in the public forecast and not be as
pessimistic in the aviation by having mainly a tempo group for
fog rather than a prevailing group. Of course I am ready to amend
as necessary.


UPDATE Issued at 952 PM CDT Thu Mar 23 2017

Will update sky cover and POPs as the precipitation area moves
east and shrinks. Otherwise current forecast looks ok with fog
forecast to become more widespread later tonight.

UPDATE Issued at 725 PM CDT Thu Mar 23 2017

Band of steady rain now over Bismark and Mandan so updated to
likely pops for the early evening.

UPDATE Issued at 535 PM CDT Thu Mar 23 2017

Used the regional radars and the HRRR simulated DBz to refine the
POP chances this evening. This band of rain will translate
southeast slowly and diminish in areal extent and intensity with
time. Ended the thunderstorm threat as the low level lapse rates
have significantly diminished and the instability greatly
diminished as well.


.SHORT TERM...(This evening through Friday)
Issued at 242 PM CDT Thu Mar 23 2017

Precipitation this afternoon and evening with isolated
thunderstorms possible south central this afternoon highlight the
short term forecast.

Isolated convection as of 1945 UTC has developed in an area of
clearing and destabilization across far south central North
Dakota, especially along zones of differential heating on the
cloud edges. Thus, added a mention of thunderstorms for these
areas for this afternoon and early evening.

Otherwise, rain across the southwest through the upper James River
Valley in association with strong 700-600mb frontogenesis will
slowly diminish through the early evening. The 15-18 UTC high
resolution, rapidly updating suites within their visibility
forecasts do suggest the potential for fog develop tonight into
Friday morning which is plausible given the abundant low level
moisture in place across the area.

.LONG TERM...(Friday night through Thursday)
Issued at 242 PM CDT Thu Mar 23 2017

Above normal temperatures highlight the extended forecast.

The 12 UTC global models are in agreement on split flow across the
Northern Plains Friday and Saturday with an upper level ridge
potentially building across the region Monday into Tuesday, before
another potential return to split flow late next week. This
overall favors above normal temperatures with highs in the 40s and
50s and sporadic, weak precipitation events.


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1240 AM CDT Fri Mar 24 2017

The rain band has moved southeast and out of the forecast area.
A clearing sky behind would lead to the expectation of fog forming
and indeed patches have formed east of KISN and southeast of KMOT.
Enhanced short term models depict widespread fog and IFR ceilings
overnight. However, lower dew point air was working in toward
Minot, from the north, where worst conditions are depicted in
those short term models. Have opted to not be as pessimistic as
guidance and go more with TEMPO conditions rather than prevailing
for fog and low clouds.



Issued at 1245 AM CDT Fri Mar 24 2017

Lake Darling Dam increased discharges to 1200 cubic feet per
Thursday afternoon, and this has resulted in Souris River rises
between the dam and Minot. The Souris at Foxholm went into flood
at midnight when the level crossed the definition of minor flood
there, 1573.0 feet. At midnight the level was 1573.03 feet.
Additional increases in the amount of water being released at the
dam are expected in the coming days.




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