Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 211304
AFDBIS

Area Forecast Discussion
National Weather Service Bismarck ND
804 AM CDT Sun May 21 2017

.UPDATE...
Issued at 801 AM CDT Sun May 21 2017

This update will expire the frost advisory. Made some minor
adjustments to the sky grids. Otherwise expect the chances for
rain to trend down east with a few showers west this afternoon.

UPDATE Issued at 642 AM CDT Sun May 21 2017

Will let the frost advisory run its course. Widespread mid 30s
across much of western ND with a few lower 30s and upper 20s over
portions of the southwest. To the east, light rain continues over
the James River Valley but band of persistent rain overnight is
beginning to break up. Updated sky and pop grids based on latest
satellite and radar trends. Otherwise no significant changes to
the going forecast.

&&

.SHORT TERM...(Today and tonight)
Issued at 214 AM CDT Sun May 21 2017

Morning rain east and afternoon/evening thunder west highlight the
short term forecast.

A nearly stacked low pressure system will continue to lift
northeast from southern Minnesota early this morning, into
southern Ontario by late tonight. Synoptic scale forcing with this
system will continue to lift away from eastern portions of the
forecast area this morning. However, a lingering deformation zone
over far eastern portion of the forecast area will keep at least a
chance of rain through the morning with a few showers possible
into the afternoon. Another upper low over northern
Saskatchewan/Alberta will drop south today and bring scattered
showers and thunderstorms to western ND late this afternoon and
this evening. Weak instability with 21 May 00 UTC NAM indicating
afternoon ML Cape at KISN around 400 J/KG, and 0-6km bulk shear
around 25 knots with decent unidirectional speed shear. Problem
will be timing with the shortwave energy spinning around the low,
dropping south into the area, not meshing with peak daytime
heating in western ND. Still think a few thunderstorms will be
possible in the far west early this evening with some locally
gusty winds and small hail. The main upper low drops south through
western ND late this evening through early Tuesday morning,
keeping a slight chance of showers through the night mainly along
and west of the Highway 83 corridor.

.LONG TERM...(Monday through Saturday)
Issued at 214 AM CDT Sun May 21 2017

Cyclonic upper level flow will wane over the forecast area on
Monday as the upper low over the Great lakes begins to shear apart
with a portion lifting into eastern Canada and another part
dropping south into the upper Midwest. Perhaps a few lingering
showers or isolated diurnally driven thunderstorms within the
weakening cyclonic flow, but instability is even weaker than
Sunday as upper level ridging pushes in from the northwest.

A brief warm-up and dry spell Tuesday and Wednesday as shortwave
ridging traverses the forecast area. There could be an afternoon
shower over the far southeast CWA Tuesday as the remaining
remnants of the upper low mentioned above finally exits the
region. Otherwise dry conditions are expected with temperatures in
the 60s to lower 70s Tuesday, and widespread 70s on Wednesday.

During this Tuesday-Wednesday timeframe another quick moving upper
low exits the eastern Pacific and races across the southern
Canadian Rockies, only to stall over the Canadian Prairie
Provinces and U.S. Northern Plains as downstream blocking impedes
it`s progress. Thus after our quick mid-week dry spell, we once
again enter a slightly cooler and unsettled period with near daily
chances of showers and isolated thunderstorms. Highs will mainly
be in the 60s and lows in the 40s late in the work week and into
next weekend.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 642 AM CDT Sun May 21 2017

MVFR ceilings in rain at KJMS. Rain will taper early this morning
with MVFR ceilings remaining through 18-20 UTC. Otherwise VFR
conditions expected through the forecast period. Variable winds
will become northwest to north this afternoon. Isolated
thunderstorms possible west late afternoon through early evening.
Added a VCTS at KISN for this period. Otherwise confidence not
high enough to include at any other site.


&&

.BIS WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

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



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