Area Forecast Discussion
Issued by NWS Bismarck, ND

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FXUS63 KBIS 221719

Area Forecast Discussion
National Weather Service Bismarck ND
1219 PM CDT SUN MAY 22 2016

Issued at 1219 PM CDT Sun May 22 2016

The latest visible satellite imagery shows stratus beginning to
erode from west to east. The 11am cdt/16z experimental HRRR
ceiling forecast matches the visible satellite very good, and
following these trends, shows a complete erosion of the stratus
over south central ND between 3pm and 4pm. This is about the time
the HRRR and NAM12 begin to initiate convection in the west.
Right now it seems the most intense cells begin near Lemmon SD and
develop within a corridor between Dickinson and Bismarck from 4pm-
7pm cdt. This consolidates into a line of thunderstorms that
slides into the James River Valley this evening. Another area of
severe and/or heavy rain develops in south central ND between 7pm
and midnight. This is forecast to move northeast and expand into
the James River Valley with heavy rainfall late evening into the
overnight period. Large hail, damaging winds, and heavy rainfall
continue as the main threats late this afternoon through tonight.
So not much change from the previous forecast. Expect an increase
in thunderstorms and severe weather potential beginning around 4pm
cdt today.

UPDATE Issued at 909 AM CDT Sun May 22 2016

Short range models are having difficulty with the discrete fast
moving cells in the central Dakotas this morning. However, the
previous few runs of the HRRR is zeroing in on a line of storms
forming from around Minot to Hettinger in the 20 to 22 UTC time
frame ahead of the cold front. The focus through the morning and
early afternoon will be on storm initiation ahead of the cold
front and if any clearing occurs ahead of the front.

UPDATE Issued at 635 AM CDT Sun May 22 2016

Early morning convection stirring across the southern Missouri
river valley and this is somewhat anticipated by the HRRR model
runs as the low level jet gets going. Made some updates to the
pops this morning for this chance for thunderstorms. The better
chance remains this afternoon.


.SHORT TERM...(Today and tonight)
Issued at 312 AM CDT Sun May 22 2016

The main focus for the short term is potential severe weather this
afternoon and evening.

Early this morning a cold front has stalled out across eastern
Montana. This will be the focus for showers and thunderstorms this
morning. While convergence is strong along the front...instability
is limited. This has led to a mainly rain shower mode.

Further east into western North Dakota an area of low stratus has
developed. Short-term models have this area of stratus persisting
and gradually shifting eastward through the morning and early
afternoon hours. As the main upper level wave and jet streak push
into western North Dakota this afternoon this area of stratus will
begin to erode and the cold front will propagate eastward. Stratus
and a pronounced cap should limit convection through most of the
morning hours.

As forcing increases ahead of the upper level wave and peak
daytime heating take over...robust thunderstorms should develop
across portions of central North Dakota late this afternoon.
Latest guidance suggests a corridor from Minot down through
Bismarck of 1,500 to 3,000 J/Kg of CAPE this afternoon along with
50+ knots of 0-6 Km shear and lapse rates greater than 6 C/Km.
These values would indicate strong...rotating updrafts are likely.
Initially a few supercells are possible before a transition to an
MCS occurs during the evening/overnight hours.

At this time the shear profiles and higher LCLs would suggest a
very limited tornado potential...with large hail and damaging wind
the more likely hazards. Additionally with PWAT values over 1 inch
and a robust low-level jet keeping the fetch of low-level moisture
going...heavy rain with an inch or greater accumulation is
possible with stronger thunderstorms. The high-res models point
toward the southern James Valley as the most likely location for
heavy rain. An excessive rainfall outlook has been issued for
this area.

.LONG TERM...(Monday through Saturday)
Issued at 312 AM CDT Sun May 22 2016

Models are having a rather difficult time resolving individual
waves within the West Coast trough, but cyclonic flow over the
area should bring a near daily chance for scattered showers and
thunderstorms. Temperatures will remain fairly steady with
readings in the 70s and low 80s.


.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1219 PM CDT Sun May 22 2016

As a cold front moves west to east across the state thunderstorms
are expected to impact KBIS and KJMS, with a lesser chance for
storms at KDIK and KMOT this afternoon and tonight. Isolated storms
are forecast to initiate around 21Z in the west and form into a line
of storms around KBIS. There will be a chance for hail, high winds
and very heavy rain in these storms, especially at KBIS and KDIK.


.BIS Watches/Warnings/Advisories...


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