Area Forecast Discussion
Issued by NWS Oklahoma City, OK

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

FXUS64 KOUN 241113

Area Forecast Discussion
National Weather Service Norman OK
613 AM CDT Sun Sep 24 2017

...Aviation Discussion...


For the 12z TAFs:

VFR conditions are expected through the period with the only
exceptions being 1.) a low probability of MVFR stratus across
western Oklahoma later this morning, and 2.) visibility reductions
in heavier showers mid morning through early afternoon in western
Oklahoma. A band of showers extends north to south across the
eastern Panhandles and is moving slowly eastward. GAG/WWR and
possibly CSM may be impacted by 14-16z. Coverage should trend
downward during the afternoon. Probability of showers and possibly
a thunderstorm increase again across western Oklahoma later


.PREV DISCUSSION... /issued 329 AM CDT Sun Sep 24 2017/

The focus for this forecast will be on a prolonged precipitation
event starting in western Oklahoma this morning and continuing
through at least the middle of next week. Determining periods of
greatest chances and when/where heavier amounts will occur will
be the main challenge. We`ll explain our current thinking and
reasoning below.

To start with, various observational data shows a band of
convection from Southwest Kansas down through the Panhandles and
West Texas. This is within a band of enhanced meridional flow and
relatively deep moisture upstream of a deep/anomalous upper
trough. Latest lightning observation shows thunder relegated to
the Permian Basin and Raton Mesa regions early this morning.
North-northeast motion of showers should bring them into far
northwest Oklahoma by around sunrise. Weak instability should
limit convective intensity and heavy rain and/or lightning should
be limited. In fact, forecast soundings exhibit very moist column
weak mid-level lapse rates (typical of meridional flow events)
throughout the duration of this rain event. Thunder coverage
should be comparatively less than showers. Furthermore,
instability will not be supportive of severe thunderstorms.

Warm cloud depth is consistently greater than 10,000 ft during
this period. Precipitable water and 850 hPa mixing ratio above
the 90th percentile and approaching the climatological max moving
average. This will support heavy rainfall amounts and the
potential for localized flooding. Highest amounts are most likely
over western Oklahoma.

Confidence in the forecast from late Tuesday onward is a little
lower. As western trough opens and pulls northeast, a period of
mid-level height rises is expected to occur. But, with weak
southerly flow atop a southward moving cold front resulting in at
least weak insentropic ascent in a very moist environment,
showers should continue through Wednesday. Confidence diminishes
further late in the weak as medium range guidance spreads. Models
vary with their handling of Southwest closed low, but it seems
likely that at some point later in the weekend, some form of at
least a weaker open/progressive wave could pass through bringing a
period of precipitation.

Temperatures were lowered considerably where the most widespread
precip/clouds are expected both Monday and Tuesday. Thereafter, a
cooler pattern should continue with highs in the 70s at most
locations for the latter half of the week.



Oklahoma City OK  88  68  84  66 /  10  10  30  50
Hobart OK         87  68  79  64 /  10  50  50  80
Wichita Falls TX  90  69  86  69 /  10  10  20  50
Gage OK           82  65  69  55 /  50  60  80  70
Ponca City OK     90  69  85  65 /  10  10  40  70
Durant OK         93  68  89  69 /  10   0  10  10




03/12 is the U.S. government's official web portal to all federal, state and local government web resources and services.