Mesoscale Precipitation Discussion 0919
NWS Weather Prediction Center College Park MD
913 PM EDT Tue Oct 02 2018

Areas affected...Northern Utah

Concerning...Heavy rainfall...Flash flooding possible

Valid 030112Z - 030612Z

Summary...Convection developing across northern Utah poses a
localized flash flood threat this evening with intense rainfall
rates of 1 to locally 2 inches/hour possible.

Discussion...GOES IR imagery shows cloud tops have cooled across
northwest Utah associated with a few broken lines of convection
developing. KMTX radar shows a few clusters of storms becoming
better organized, moving generally east/northeast. Dual pol
estimates show 1-hr rates of around 0.5" to locally 1.5" per hour.

The environment is characterized by broad upper level divergence
thanks to a large closed mid/upper level low off the CA coast as
well as favorable right entrance region from a shortwave moving
into the Pacific NW. Water vapor imagery hints at a vort max
moving from Nevada into Utah. PWATs are between 0.75-1.0 per
latest mesoanalysis which is between 2-3 SD above normal for the
area. Instability is sufficient but not great and generally is
running around 500-1000 J/kg of SBCAPE.

It is expected that this convection will congeal and trek eastward
over the next few hours, heading into the SLC metro area northward
to Ogden along the I-15 corridor. The NAM-Conest is performing
best with current radar trends though a consensus of the hi-res
models shows a good clustering.

With the intense rainfall rates falling over low FFGs (1-hr 0.75
to 1"), localized flash flooding will be possible this evening.

Taylor

ATTN...WFO...PIH...SLC...

ATTN...RFC...CBRFC...NWRFC...

LAT...LON   42221166 41831130 40801116 39721126 39661353
            40011378 40491389 41161389 41721389 42131378
            42131323 42221253