National Weather Service Forecast Discussion

000
FXUS65 KBOU 032110
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
310 PM MDT Sat Jun 3 2023

.SHORT TERM...(This evening through Sunday)
Issued at 146 PM MDT Sat Jun 3 2023

Waterfest!

Widespread stratiform precipitation, quite unusual this time of
the year, has been overspreading eastern Colorado throughout the
day as a very healthy plume of Gulf moisture remains anchored
under a blocking high to our north. Mostly slow and steady rain
has been the name of the game, with isolated heavier showers
embedded at times producing rainfall rates up to ~0.50"/hr. We are
beginning to see some thinning of precipitation as the water vapor
maxima moves northwest, and activity will continue to become more
intermittent as we head into the evening. There`s next to zero
instability currently so thunderstorms are unlikely (though, can`t
rule out one or two later this afternoon/evening in the northeast
plains as skies clear some).

Moisture will stick around tonight. A weak closed low hovering
over eastern Colorado/western Kansas will nudge NW overnight and
bring enhanced easterly flow across the NE corner of the state.
This should help reinvigorate shower activity late tonight into
early Sunday morning, so it may be another wet start to the day
for much of the urban corridor and plains. Some areas of fog can
be expected as well early morning. Precipitable Water values will
remain largely unchanged, or even slightly increase Sunday,
peaking between 0.9-1.0". This is well above the 90th percentile
per SPC sounding climatology and potentially in record territory
for this time of year. Easterly upslope flow looks to be a little
better defined tomorrow above 700mb, with better penetration of
showers into the foothills and eastern mountain slopes. Flash
flood risk for the Cameron Peak burn scar will thus be slightly
higher on Sunday relative to today. Still, instability will remain
very meager early in the day especially, and limit thunderstorm
potential, buffering peak rainfall rates. Some CAMs do suggest
sufficient instability creeping in later in the day to support a
few thunderstorms. Localized flooding will remain a possibility
with heavier showers/thunderstorms as steering level flow will
still be on the weak side.

.LONG TERM...(Sunday night through Saturday)
Issued at 259 PM MDT Sat Jun 3 2023

The blocking upper ridge over the northern central U.S. Sunday
night, is progged to move little through Tuesday night. There will
be weak upward vertical velocity for the CWA on the QG Omega
fields through the periods. There is low level east and
southeasterly upslope winds into the foothills through the
periods. Precipitable water values stay in the 0.50 to 1.10 inch
range, from west to east across the CWA, as well. Cape values are
fairly low. It will be more of the same, plenty of rain with
flooding issues possible, and little change of severe
thunderstorms. Temperatures look to stay a tad below seasonal
normals for the plains and foothills both Monday and Tuesday.

For the later days, Wednesday through Saturday, models show the
upper ridge to move a bit west later Wednesday into next weekend.
Precipitable water values are progged a tad lower Friday and
Saturday. There may be somewhat higher CAPE values later in the week
with temperatures a bit warmer, so the thunderstorms should be a
bit stronger.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1222 PM MDT Sat Jun 3 2023

We`ll start with the easier aspect...the winds. Should see
prevailing NE winds through early evening, followed by a period of
variable and light winds in the evening before light northwesterly
flow takes hold overnight.

Widespread moderate rain is overspreading NE Colorado and will
continue throughout the day, with CIGS primarily in the 030-060
range but with occasional lowering to 010-020 possible during
heavier showers. With limited instability, believe TS potential
will remain low today. Cannot completely rule out some VFR
conditions at times later this evening or tonight, but even then
expect periods of showers and lower CIGS. Visibility may lower to
3SM during the heaviest showers. Potential also increasing for
very low stratus and/or fog early Sun AM for KDEN, may require
including in future TAFS. Tomorrow, expect another active day
with renewed showers and likely a higher chance of a thunderstorm
in the afternoon.

&&

.HYDROLOGY...
Issued at 308 PM MDT Sat Jun 3 2023

Widespread light to moderate rain continues this afternoon with
some thinning in coverage likely over the next few hours. There is
little in the way of upslope flow, with winds along and east of
the foothills mostly northerly. Instability is also close to
nonexistent today. These factors combined are leading to a low
threat of flash flooding for the burn scars in the high country. A
few embedded heavier showers may still produce localized rainfall
rates of 0.50"-0.70"/hr for the lower elevations and may result in
minor flooding for poor drainage areas.

Showers/isolated thunderstorms will increase in coverage again
late tonight and Sunday morning for the urban corridor and
foothills. Rainfall rates may be more efficient tonight and
Sunday, with greater penetration into the mountains and some
potential for marginal instability by the afternoon. As a result,
flash flood potential for the burn scars (particularly Cameron
Peak) with trend upward, but confidence in reaching debris flow
thresholds remains too low for any Flood Watches at this time.

The flashing flooding potential will remain limited for the burn
areas west of the divide and elevated for the burn areas east of
the divide through much of next week. The chance of heavy rain is
better from mid to late next week with stronger thunderstorms
expected.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SHORT TERM...Rodriguez
LONG TERM....RPK
AVIATION.....Rodriguez
HYDROLOGY....Rodriguez/RPK

NWS BOU Office Area Forecast Discussion