Hail and Heavy Rain in Montana, June 3, 2014

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1145 AM MDT Tue Jun 3 2014

AVIATION SECTION UPDATED

.UPDATE...
Some minor adjustments to the forecast this morning. Raised POP
across eastern portions of Central Montana as afternoon convective
activity looks best there. Sky cover is also a concern as it is
related to high temperatures, but did not make changes as there
should be a clearing move across Central Montana around mid-day.

&&

.AVIATION...
UPDATED 1745Z.
Shortwave trof currently lifting thru western half of MT is
generating scattered -SHRA from KCTB southeastward to KLWT, with
precipitation area moving ENE.  Satellite imagery shows mostly clear
skies over southwest MT behind the precip.  Expect the clear slot to
move into central MT this aftn, which should help destabilize the
atmosphere for another round of -SHRA and -TSRA starting around
20Z.  Some of these storms, mainly east of KGTF, could be strong to
severe with gusty outflow winds and hail. This second round should
move into ern MT by 00Z, with steadily decreasing cloud cover at all
local TAF sites going into this evening.  Winds generally light
across the region this aftn, but local gusts of 30-35 kts possible
near any strong storms.
Waranauskas

&&

.PREV DISCUSSION...
/ISSUED 535 AM MDT Tue Jun 3 2014/
Today through Thursday...Increasing diffluent southwest flow
aloft today as an upper trof approaches western Montana. The
airmass will become unstable by late morning with thunderstorms
developing over southwest Montana and then spreading north and
east during the afternoon. The area with the greatest threat of
thunderstorms will be Judith Basin, Fergus, Chouteau, Hill, and
Blaine counties. Afternoon CAPE for these counties approaches
2000 J/kg and LIs are -4 to -5. Additionally, an east surface
wind will advect moisture and higher dew points into the area. The
big limiting factor as to whether any of storms becomes severe
would be a lack of significant shear. Bulk shear magnitudes in the
0-6km AGL realm are generally less than 35 knots. Though an
isolated severe storm cannot be ruled out, the main threat from
these storms will likely be gusty winds and small hail. Convective
activity should decrease after midnight as the trof axis pushes
through. Lingering low level moisture and instability Wednesday
will allow for isolated afternoon thunderstorms. Conditions dry
out Wednesday night as westerly flow aloft pushes across the area.
Short wave energy and an associated surface cold front will move
across the area Thursday. Instability resulting from these features
will allow isolated afternoon thunderstorms to develop. Temperatures
will remain above seasonal averages today and Wednesday but drop
below seasonal averages Thursday in the wake of the cold frontal
passage.

Thursday night through Tuesday...The overall upper level pattern
late this week into early next week continues to feature an active
westerly flow aloft with several shortwave disturbances moving east
along the US/Canadian border. A broad trough in the upper levels
lingers over the Northern Rockies and MT Friday and Saturday while
surface high pressure shifting east into the Northern Plains States
brings a return flow from the east at the surface. This will result
in diurnal convection both days with somewhat better coverage on
Friday. Wind shear and upper level forcing looks relatively weak,
resulting in mainly terrain based convection and better chances over
the mtns. Models have come into slightly better agreement for the
next stronger wave to move into the region late this weekend/early
next week, tracking is farther north and delaying its arrival until
Sunday night or Monday with a period of mostly dry conditions
expected now on Sunday. Next trough drops into the region from the
NW Mon/Tuesday for increasing chances for precip and cooler temps.
Hoenisch

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  74  47  75  45 /  50  40  20  10
CTB  72  45  72  42 /  40  40  20  10
HLN  77  48  78  48 /  60  40  20  10
BZN  75  43  74  42 /  50  40  30  10
WEY  70  34  69  33 /  60  40  20  10
DLN  73  44  74  43 /  60  40  20  10
HVR  78  47  77  45 /  70  60  40  10
LWT  72  46  71  45 /  60  60  20  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
1027 AM MDT TUE JUN 03 2014

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0645 PM     HAIL             13 SSW BIG SANDY        48.02N 110.23W
05/28/2014  M2.00 INCH       CHOUTEAU           MT   TRAINED SPOTTER

            REPORTED 2 INCH HAIL

&&

GUSTAFSON